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Sample records for hf high frequency

  1. A SYNCHRONIZATION ALGORITHM FOR HF (HIGH FREQUENCY) BROADBAND OFDM SYSTEM

    Institute of Scientific and Technical Information of China (English)

    Yang Lei; Zhang You'ai

    2008-01-01

    In this letter, a kind of associated synchronization algorithm which is suitable for HF (High Frequency) broadband OFDM (Orthogonal Frequency Division Multiplexing) system is presented based on describing and constructing the GMW (Gorden, Mills and Welch) sequence. The algorithm is based on the Schmidl and Minn's symbol timing principle, the constructed GMW sequence is transmitted and disposed, and the synchronization is adjudicated using the correlation of GMW sequence. The simulation result indicates that this algorithm has high performance synchronization ability under the low SNR (Signal to Noise Ratio) at two different kinds of channel models.

  2. Tsunami Arrival Detection with High Frequency (HF Radar

    Directory of Open Access Journals (Sweden)

    Donald Barrick

    2012-05-01

    Full Text Available Quantitative real-time observations of a tsunami have been limited to deep-water, pressure-sensor observations of changes in the sea surface elevation and observations of sea level fluctuations at the coast, which are essentially point measurements. Constrained by these data, models have been used for predictions and warning of the arrival of a tsunami, but to date no system exists for local detection of an actual incoming wave with a significant warning capability. Networks of coastal high frequency (HF-radars are now routinely observing surface currents in many countries. We report here on an empirical method for the detection of the initial arrival of a tsunami, and demonstrate its use with results from data measured by fourteen HF radar sites in Japan and USA following the magnitude 9.0 earthquake off Sendai, Japan, on 11 March 2011. The distance offshore at which the tsunami can be detected, and hence the warning time provided, depends on the bathymetry: the wider the shallow continental shelf, the greater this time. We compare arrival times at the radars with those measured by neighboring tide gauges. Arrival times measured by the radars preceded those at neighboring tide gauges by an average of 19 min (Japan and 15 min (USA The initial water-height increase due to the tsunami as measured by the tide gauges was moderate, ranging from 0.3 to 2 m. Thus it appears possible to detect even moderate tsunamis using this method. Larger tsunamis could obviously be detected further from the coast. We find that tsunami arrival within the radar coverage area can be announced 8 min (i.e., twice the radar spectral time resolution after its first appearance. This can provide advance warning of the tsunami approach to the coastline locations.

  3. Wideband high frequency (HF) skywave channel parameters from narrowband measurements

    Science.gov (United States)

    Hausman, Cynthia L.; Uffelman, Donald R.; Walton, Thomas L.

    The HF wideband channel allow the use of spread-spectrum techniques to provide covert communications with low probability of intercept (LPI) and antijam protection. The objective of this work is to determine the extent to which oblique narrowband channel measurements can be used to infer effects in the wideband skywave channel. If oblique narrowband channel measurements can be used as a basis for developing wideband channel models, a large number of existing narrowband measurements can be made available for this task.

  4. High-frequency magnetoelastic measurements on Fe-Co-Hf-N/Ti-N multilayer coatings

    Science.gov (United States)

    Krüger, Kathrin; Seemann, Klaus; Leiste, Harald; Stüber, Michael; Ulrich, Sven

    2013-10-01

    Fe32Co44Hf12N12/Ti50N50 thin multilayer coatings are realized as wear resistant coatings with an integrated sensor function, in order to detect e.g. external mechanical stress. A setup was designed to monitor changes in the frequency-dependent permeability due to the mechanically induced stress in the ferromagnetic Fe32Co44Hf12N12 single layers. The change of the ferromagnetic cut-off frequency is described by an effective in-plane anisotropy field H→u,eff which accounts for a thermally induced uniaxial anisotropy field H→u and an effective biaxial magnetoelastic anisotropy field H→me. Fe32Co44Hf12N12/Ti50N50 multilayer films with seven bilayers and a total thickness of about 1 μm were grown by a sequential deposition of Fe32Co44Hf12N12 and Ti50N50 individual layers by means of reactive DC and RF magnetron sputtering, respectively. Additionally, a Fe32Co44Hf12N12 monolayer coating with a thickness of about 500 nm was deposited in order to determine the magnetic properties of the single layer. The films were investigated with respect to their static and dynamic ferromagnetic properties. A uniaxial anisotropy field of 5 mT could be induced after annealing the multilayer films for 1 h at 400 °C in vacuum in a static magnetic field of 50 mT. Additionally, magnetic softness (μ0Hc=0.6 mT) and cut-off frequencies above 2 GHz were observed. Inducing compressive stress increases the cut-off frequency of the Fe32Co44Hf12N12 single layer as well as of the Fe32Co44Hf12N12/Ti50N50 multilayer films whereas tensile stress causes a decrease in the cut-off frequency. Accordingly, the dependence of the cut-off frequency on external mechanical stress is theoretically described. Furthermore, the possibility of detecting mechanically induced stress in a ferromagnetic layer was demonstrated by the shift of the cut-off frequency with a resolution of 1.0 MPa.

  5. Wave parameters comparisons between High Frequency (HF) radar system and an in situ buoy: a case study

    Science.gov (United States)

    Fernandes, Maria; Alonso-Martirena, Andrés; Agostinho, Pedro; Sanchez, Jorge; Ferrer, Macu; Fernandes, Carlos

    2015-04-01

    The coastal zone is an important area for the development of maritime countries, either in terms of recreation, energy exploitation, weather forecasting or national security. Field measurements are in the basis of understanding how coastal and oceanic processes occur. Most processes occur over long timescales and over large spatial ranges, like the variation of mean sea level. These processes also involve a variety of factors such as waves, winds, tides, storm surges, currents, etc., that cause huge interference on such phenomena. Measurement of waves have been carried out using different techniques. The instruments used to measure wave parameters can be very different, i.e. buoys, ship base equipment like sonar and satellites. Each equipment has its own advantage and disadvantage depending on the study subject. The purpose of this study is to evaluate the behaviour of a different technology available and presently adopted in wave measurement. In the past few years the measurement of waves using High Frequency (HF) Radars has had several developments. Such a method is already established as a powerful tool for measuring the pattern of surface current, but its use in wave measurements, especially in the dual arrangement is recent. Measurement of the backscatter of HF radar wave provides the raw dataset which is analyzed to give directional data of surface elevation at each range cell. Buoys and radars have advantages, disadvantages and its accuracy is discussed in this presentation. A major advantage with HF radar systems is that they are unaffected by weather, clouds or changing ocean conditions. The HF radar system is a very useful tool for the measurement of waves over a wide area with real-time observation, but it still lacks a method to check its accuracy. The primary goal of this study was to show how the HF radar system responds to high energetic variations when compared to wave buoy data. The bulk wave parameters used (significant wave height, period and

  6. Soft Magnetic Thin Films FeCoHfO for High-Frequency Noise Suppression Applications

    Institute of Scientific and Technical Information of China (English)

    LU Guang-Duo; ZHANG Huai-Wu; TANG Xiao-Li

    2010-01-01

    @@ A series of FeCoHfO films were fabricated by dc magnetron reactive sputtering at varying partial pressure of oxygen(Po2)from 0 to 11.7%,and the electrical and magnetic properties of films have been studied.It is shown that optimal Fe43.29 Co19.51 Hf7.49O29.71 films with desired properties can be obtained when the films were prepared under Po2 = 5.1%.

  7. Approximating ambient D-region electron densities using dual-beam HF heating experiments at the high-frequency Active Auroral Research Program (HAARP)

    Science.gov (United States)

    Agrawal, Divya

    Dual-beam ELF/VLF wave generation experiments performed at the High-frequency Active Auroral Research Program (HAARP) HF transmitter in Gakona, Alaska are critically compared with the predictions of a newly developed ionospheric high frequency (HF) heating model that accounts for the simultaneous propagation and absorption of multiple HF beams. The dual-beam HF heating experiments presented herein consist of two HF beams transmitting simultaneously: one amplitude modulated (AM) HF beam modulates the conductivity of the lower ionosphere in the extremely low frequency (ELF, 30 Hz to 3 kHz) and/or very low frequency (VLF, 3 kHz to 30 kHz) band while a second HF beam broadcasts a continuous waveform (CW) signal, modifying the efficiency of ELF/VLF conductivity modulation and thereby the efficiency of ELF/VLF wave generation. Ground-based experimental observations are used together with the predictions of the theoretical model to identify the property of the received ELF/VLF wave that is most sensitive to the effects of multi-beam HF heating, and that property is determined to be the ELF/VLF signal magnitude. The dependence of the generated ELF/VLF wave magnitude on several HF transmission parameters (HF power, HF frequency, and modulation waveform) is then experimentally measured and analyzed within the context of the multi-beam HF heating model. For all cases studied, the received ELF/VLF wave magnitude as a function of transmission parameter is analyzed to identify the dependence on the ambient D-region electron density (Ne) and/or electron temperature ( Te), in turn identifying the HF transmission parameters that provide significant independent information regarding the ambient conditions of the D-region ionosphere. A theoretical analysis is performed to determine the conditions under which the effects of Ne and Te can be decoupled, and the results of this analysis are applied to identify an electron density profile that can reproduce the unusually high level of ELF

  8. Surface current measurements in Juan de Fuca Strait using the SeaSonde HF [high frequency] radar

    Energy Technology Data Exchange (ETDEWEB)

    Hodgins, D.O.

    1994-09-01

    The shore-based SeaSonde high-frequency (HF) radar was deployed for three weeks in summer 1993 to measure surface currents in the Strait of Georgia, British Columbia. Experimental objectives included documenting the complex flow regime generated by large tides and the brackish plume of the Fraser River, and determining the radar performance under low-wind, low-salinity conditions. The radar data showed that surface flows are dominated by the plume jet formed by the Fraser River outflow, giving rise to recurring, energetic eddies with scales of 8-12 km, strong flow meanders, and convergent fronts. These features were continuously modulated by the along-channel tidal flows. Comparisons with a detailed numerical model hindcast gave good correlation between observed and predicted flow fields, especially at tidal and low frequencies. Radar return was found to be correlated with local winds and radar performance was independent of salinity variations in the plume. Synthetic aperture radar (SAR) provides a map of the radar scattering characteristics of the ocean surface on a capillary wave scale. ERS-1 satellite and airborne SAR images for July 28, 1993 were obtained and surface features were examined in the context of the HF radar current fields. Results show that SAR images alone cannot reliably provide the dynamical data required in this region by oil spill models. Under certain conditions, however, the radar imagery offers valuable physical information on phenomena affecting oil slick development. Interpretation of SAR imagery in conjunction with other remote sensing information would offer more quantitative prediction data. 28 refs., 334 figs., 1 tab.

  9. 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.

  10. High frequency based detection of TIDs in the Net-TIDE project: challenges and opportunities for long HF paths

    Science.gov (United States)

    Verhulst, Tobias

    2016-07-01

    Travelling Ionospheric Disturbances (TIDs) are the ionospheric signatures of atmospheric gravity waves. TIDs carry along information about their sources of excitations which may be either natural (energy input from the auroral region, earthquakes/tsunamis, hurricanes, solar terminator, and others) or artificial (ionospheric modification experiments, nuclear explosions, and other powerful blasts like industrial accidents). TIDs contribute to the energy and momentum exchange between different regions of the ionosphere, especially during geomagnetic storms. Their tracking is important because the TIDs affect all services that rely on predictable ionospheric radio wave propagation. Although a number of methods have been proposed to measure TID characteristics, none is able to operate in real time for monitoring purposes. In the framework of a new NATO Science for Peace and Security multi-year project (2014--2017) we are exploiting for the first time the European network of high precision ionospheric DPS4D sounders and the related software to directly identify TIDs over Europe and specify in real-time the gravity wave parameters based on measuring the variations of the angles-of-arrival and Doppler frequencies of ionospherically reflected HF radio signals. The project will run until 2017 and is expected to result in a pilot network of DPS4D ionospheric sounders in Europe, enhanced with a system to process the TID observations for real-time diagnostics and issue warnings for TIDs and the potential disturbance over the area. Based on these warnings the end-users can put in action specific mitigation techniques to protect their systems. The technical challenges of operating long distance ionospheric HF radio links for the detection of TIDs will be discussed.

  11. Status and Early Results from the Axion Dark Matter eXperiment - High Frequency (ADMX-HF)

    Science.gov (United States)

    Lewis, Samantha; ADMX-HF Collaboration

    2016-03-01

    The axion was originally proposed as a solution to the Strong-CP problem of the Standard Model. A sufficiently light axion (1 - 1000 μ eV) also represents an excellent cold dark matter candidate. Such axions may be detected by their resonant conversion to photons in a high- Q microwave cavity permeated by a strong magnetic field. Previous experiments have probed the first decade in mass using this method. ADMX-HF was designed and built as an innovation test-bed and a data pathfinder for the second decade in mass range. The experiment, initially configured with a 9-tesla magnet, dilution refrigerator, 2-liter tunable copper cavity, and a Josephson Parametric Amplifier, is now operational with a system noise temperature approximately twice the Standard Quantum Limit. Preliminary data in the 25 μ eV range (on the order of 6 GHz in resonant frequency) will be presented, as well as an overview of ongoing R&D on new cavity and amplifier technologies that will be validated in situ within the next few years. This work was supported by the NSF, under Grants PHY-1067242 and PHY-1306729, the US DOE under Contract DE-AC52-07NA27344, and an award from the Heising-Simons Foundation.

  12. Influence of grain growth on the high-frequency behaviour of ferromagnetic Fe-Co-(M)-N (M=Ta, Hf) nanocomposite films

    Energy Technology Data Exchange (ETDEWEB)

    Seemann, K. [Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft, Institut fuer Material for schung I, Hermann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen (Germany)], E-mail: klaus.seemann@imf.fzk.de; Leiste, H. [Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft, Institut fuer Material for schung I, Hermann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen (Germany)

    2009-04-15

    The CMOS compatible ferromagnetic Fe-Co-(M)-N (M=Ta, Hf) films were investigated with regard to their grain size-dependent frequency behaviour. Predominantly Fe{sub 33}Co{sub 40}Ta{sub 10}N{sub 17} films were deposited by reactive r.f. magnetron sputtering. These films were compared to Fe{sub 36}Co{sub 44}Hf{sub 9}N{sub 11} films. In order to induce an in-plane uniaxial anisotropy H{sub u} as well as to investigate the grain growth behaviour, the films were annealed in a static magnetic field. The in-plane uniaxial anisotropy field of around 4 mT as well as a good soft magnetic behaviour with a saturation polarisation of approximately 1.2-1.4 T could be observed after heat treatment. Ferromagnetic resonance frequencies (FMR) of approximately up to 2.4 GHz could be achieved according to the Kittel theory. Depending on the heat treatment, high-frequency losses through energy dissipation was made conspicuous by means of the full-width at half-maximum (FWHM) {delta}f{sub eff} of the imaginary part of the frequency-dependent permeability which was between 0.4 and 1 GHz. This FWHM was basically discussed in terms of two-magnon scattering theories, in combination with the Herzer random anisotropy model. In order to correlate the resonance line broadening with a phenomenological damping parameter {alpha}{sub eff}, which ranged from about 0.0125 to 0.028, the modified Landau-Lifschitz-Gilbert equation was used to fit and describe the permeability spectra of the ferromagnetic films.

  13. Ferromagnetic resonance frequency increase and resonance line broadening of a ferromagnetic Fe-Co-Hf-N film with in-plane uniaxial anisotropy by high-frequency field perturbation

    Science.gov (United States)

    Seemann, K.; Leiste, H.; Krüger, K.

    2013-11-01

    Soft ferromagnetic Fe-Co-Hf-N films, produced by reactive r.f. magnetron sputtering, are useful to study the ferromagnetic resonance (FMR) by means of frequency domain permeability measurements up to the GHz range. Films with the composition Fe33Co43Hf10N14 exhibit a saturation polarisation Js of around 1.35 T. They are consequently considered as being uniformly magnetised due to an in-plane uniaxial anisotropy of approximately μ0Hu≈4.5 m T after annealing them, e.g., at 400 °C in a static magnetic field for 1 h. Being exposed to a high-frequency field, the precession of magnetic moments leads to a marked frequency-dependent permeability with a sharp Lorentzian shaped imaginary part at around 2.33 GHz (natural resonance peak), which is in a very good agreement with the modified Landau-Lifschitz-Gilbert (LLG) differential equation. A slightly increased FMR frequency and a clear increase in the resonance line broadening due to an increase of the exciting high-frequency power (1-25.1 mW), considered as an additional perturbation of the precessing system of magnetic moments, could be discovered. By solving the homogenous LLG differential equation with respect to the in-plane uniaxial anisotropy, it was revealed that the high-frequency field perturbation impacts the resonance peak position fFMR and resonance line broadening ΔfFMR characterised by a completed damping parameter α=αeff+Δα. Adapted from this result, the increase in fFMR and decrease in lifetime of the excited level of magnetic moments associated with ΔfFMR, similar to a spin-½ particle in a static magnetic field, was theoretically elaborated as well as compared with experimental data.

  14. High-frequency ECG

    Science.gov (United States)

    Tragardh, Elin; Schlegel, Todd T.

    2006-01-01

    The standard ECG is by convention limited to 0.05-150 Hz, but higher frequencies are also present in the ECG signal. With high-resolution technology, it is possible to record and analyze these higher frequencies. The highest amplitudes of the high-frequency components are found within the QRS complex. In past years, the term "high frequency", "high fidelity", and "wideband electrocardiography" have been used by several investigators to refer to the process of recording ECGs with an extended bandwidth of up to 1000 Hz. Several investigators have tried to analyze HF-QRS with the hope that additional features seen in the QRS complex would provide information enhancing the diagnostic value of the ECG. The development of computerized ECG-recording devices that made it possible to record ECG signals with high resolution in both time and amplitude, as well as better possibilities to store and process the signals digitally, offered new methods for analysis. Different techniques to extract the HF-QRS have been described. Several bandwidths and filter types have been applied for the extraction as well as different signal-averaging techniques for noise reduction. There is no standard method for acquiring and quantifying HF-QRS. The physiological mechanisms underlying HF-QRS are still not fully understood. One theory is that HF-QRS are related to the conduction velocity and the fragmentation of the depolarization wave in the myocardium. In a three-dimensional model of the ventricles with a fractal conduction system it was shown that high numbers of splitting branches are associated with HF-QRS. In this experiment, it was also shown that the changes seen in HF-QRS in patients with myocardial ischemia might be due to the slowing of the conduction velocity in the region of ischemia. This mechanism has been tested by Watanabe et al by infusing sodium channel blockers into the left anterior descending artery in dogs. In their study, 60 unipolar ECGs were recorded from the entire

  15. Artificial Ionization and UHF Radar Response Associated with HF Frequencies near Electron Gyro-Harmonics (Invited)

    Science.gov (United States)

    Watkins, B. J.; Fallen, C. T.; Secan, J. A.

    2013-12-01

    We present new results from O-mode ionospheric heating experiments at the HAARP facility in Alaska to demonstrate that the magnitude of artificial ionization production is critically dependent on the choice of HF frequency near gyro-harmonics. For O-mode heating in the lower F-region ionosphere, typically about 200 km altitude, artificial ionization enhancements are observed in the lower ionosphere (about 150 - 220 km) and also in the topside ionosphere above about 500 km. Lower ionosphere density enhancements are inferred from HF-enhanced ion and plasma-line signals observed with UHF radar. Upper ionospheric density enhancements have been observed with TEC (total electron content) experiments by monitoring satellite radio beacons where signal paths traverse the HF-modified ionosphere. Both density enhancements and corresponding upward plasma fluxes have also been observed in the upper ionosphere via in-situ satellite observations. The data presented focus mainly on observations near the third and fourth gyro-harmonics. The specific values of the height-dependent gyro-harmonics have been computed from a magnetic model of the field line through the HF heated volume. Experiments with several closely spaced HF frequencies around the gyro-harmonic frequency region show that the magnitude of the lower-ionosphere artificial ionization production maximizes for HF frequencies about 1.0 - 1.5 MHz above the gyro-harmonic frequency. The response is progressively larger as the HF frequency is increased in the frequency region near the gyro-harmonics. For HF frequencies that are initially greater than the gyro-harmonic value the UHF radar scattering cross-section is relatively small, and non-existent or very weak signals are observed; as the signal returns drop in altitude due to density enhancements the HF interaction region passes through lower altitudes where the HF frequency is less than the gyro-harmonic value, for these conditions the radar scattering cross-section is

  16. Challenges in comparing the acute cognitive outcomes of high-frequency repetitive transcranial magnetic stimulation (HF-rTMS) vs. electroconvulsive therapy (ECT) in major depression: A systematic review.

    Science.gov (United States)

    Kedzior, Karina Karolina; Schuchinsky, Maria; Gerkensmeier, Imke; Loo, Colleen

    2017-03-02

    The present study aimed to systematically compare the cognitive outcomes of high-frequency repetitive transcranial magnetic stimulation (HF-rTMS) and electroconvulsive therapy (ECT) in head-to-head studies with major depression (MDD) patients. A systematic literature search identified six studies with 219 MDD patients that were too heterogeneous to reliably detect meaningful differences in acute cognitive outcomes after ECT vs. HF-rTMS. Cognitive effects of brain stimulation vary depending on the timeframe and methods of assessment, stimulation parameters, and maintenance treatment. Thus, acute and longer-term differences in cognitive outcomes both need to be investigated at precisely defined timeframes and with similar instruments assessing comparable functions.

  17. Fabrication and examination of epitaxial HTSC/isolator thin films on sapphire substrates for application in high frequency devices; Herstellung und Untersuchung von epitaktischen HTSL/Isolator-Schichten auf Saphirsubstraten zur Anwendung in HF-Bauelementen

    Energy Technology Data Exchange (ETDEWEB)

    Kittel, H.

    1995-10-01

    The use of high temperature superconductors (HTSC) like YBCO with distinct lower surface resistance compared to normal conductors allows miniaturisation of high frequency (HF) circuits. The object of this work was the fabrication of YBCO thin films on low loss sapphire substrates applicable for stripline devices. To induce epitaxial growth and to avoid chemical reaction at the film-substrate boundary buffer layers were investigated. The examination of the growth properties and especially of the surface impedance has been allotted particular importance. In contrast to CaTiO{sub 3} it was possible to deposit CeO{sub 2}-buffer layers in direct growth up to a thickness of about 30 nm without cracks. The films show all growth properties required and even Laue-oscillations being a feature of high quality growth enabling the determination of film thickness distribution without destruction. The YBCO growth-, transport- and HF-properties meet the ones of YBCO films on standard substrates. A remarkable result is that the mosaic distribution of the CEO film, itself strongly dependend on film thickness, does not influence that of the YBCO film considerably. Rather it changes its shape subsequently due to YBCO deposition. A further particularity in contrast to deposition on standard substrates is the need to adjust the substrate heater tempeature for deposition of YBCO films with thicknesses {>=}300 nm needed for HF application. To demonstrate their usefullness some stripline devices like planar coils and side coupled filters have been fabricated and characterised. (orig.)

  18. Hourly surface currents measured by High Frequency (HF) Wellen radars (WERA) off western Oahu, Hawaii, from September 2002 to May 2003 (NODC Accession 0013113)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — A pair of High Frequency Wellen radars (WERA) shore-based at southwest Oahu (Ko'Olina) and northwest Oahu (Kaena), Hawaii measured surface currents over a nine-month...

  19. Ionizing wave via high-power HF acceleration

    CERN Document Server

    Mishin, Evgeny

    2010-01-01

    Recent ionospheric modification experiments with the 3.6 MW transmitter at the High Frequency Active Auroral Research Program (HAARP) facility in Alaska led to discovery of artificial ionization descending from the nominal interaction altitude in the background F-region ionosphere by ~60 km. This paper presents a physical model of an ionizing wavefront created by suprathermal electrons accelerated by the HF-excited plasma turbulence.

  20. Ionizing wave via high-power HF acceleration

    OpenAIRE

    Mishin, Evgeny; Pedersen, Todd

    2010-01-01

    Recent ionospheric modification experiments with the 3.6 MW transmitter at the High Frequency Active Auroral Research Program (HAARP) facility in Alaska led to discovery of artificial ionization descending from the nominal interaction altitude in the background F-region ionosphere by ~60 km. This paper presents a physical model of an ionizing wavefront created by suprathermal electrons accelerated by the HF-excited plasma turbulence.

  1. Textural analyses of carbon fiber materials by 2D-FFT of complex images obtained by high frequency eddy current imaging (HF-ECI)

    Science.gov (United States)

    Schulze, Martin H.; Heuer, Henning

    2012-04-01

    Carbon fiber based materials are used in many lightweight applications in aeronautical, automotive, machine and civil engineering application. By the increasing automation in the production process of CFRP laminates a manual optical inspection of each resin transfer molding (RTM) layer is not practicable. Due to the limitation to surface inspection, the quality parameters of multilayer 3 dimensional materials cannot be observed by optical systems. The Imaging Eddy- Current (EC) NDT is the only suitable inspection method for non-resin materials in the textile state that allows an inspection of surface and hidden layers in parallel. The HF-ECI method has the capability to measure layer displacements (misaligned angle orientations) and gap sizes in a multilayer carbon fiber structure. EC technique uses the variation of the electrical conductivity of carbon based materials to obtain material properties. Beside the determination of textural parameters like layer orientation and gap sizes between rovings, the detection of foreign polymer particles, fuzzy balls or visualization of undulations can be done by the method. For all of these typical parameters an imaging classification process chain based on a high resolving directional ECimaging device named EddyCus® MPECS and a 2D-FFT with adapted preprocessing algorithms are developed.

  2. HF omnidirectional spectral CW auroral radar (HF-OSCAR) at very high latitude. Part 1: Technique

    Science.gov (United States)

    Olesen, J. K.; Jacobsen, K. E.; Stauning, P.; Henriksen, S.

    1983-12-01

    An HF system for studies of very high latitude ionospheric irregularities was described. Radio aurora from field-aligned E-region irregularities of the Slant E Condition type were discussed. The complete system combines an ionosonde, a 12 MHz pulse radar and a 12 MHz bistatic CW Doppler-range set-up. The two latter units use alternately a 360 deg rotating Yagi antenna. High precision oscillators secure the frequency stability of the Doppler system in which the received signal is mixed down to a center frequency of 500 Hz. The Doppler shift range is max + or - 500 Hz. The received signal is recorded in analog form on magnetic tape and may be monitored visually and audibly. Echo range of the CW Doppler signal is obtained by a 150 Hz amplitude modulation of the transmitted signal and phase comparison with the backscattered signal.

  3. Soft magnetic properties and high frequency characteristics of FeM (M = B, Hf, Zr) and pure Fe films fabricated by oblique deposition

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Chengcheng; Zhang, Chao; Wang, Fenglong; Zhao, Zhong; Jiang, Changjun; Xue, Desheng [Lanzhou University, Key Laboratory for Magnetism and Magnetic Materials of Ministry of Education, Lanzhou (China); Lanzhou University, Key Laboratory of Special Function Materials and Structure Design of Ministry of Education, Lanzhou (China)

    2015-09-15

    To improve the high-frequency properties of Fe-based thin films, doped and pure Fe thin films were obliquely deposited on Si (100) substrate by RF-magnetron sputtering. Vibrating sample magnetometer (VSM) measurements show obvious in-plane uniaxial magnetic anisotropy in both doped and pure Fe thin films, and enhancement effects of doping on Soft magnetic properties were also observed. Microwave permeability measurements indicate that the resonance frequency and permeability of pure Fe films are much larger than those of doped Fe thin films. Damping factors of Fe thin films deposited at different oblique angles were further investigated. (orig.)

  4. Simultaneous excitement of electron and ion resonances in a magnetoplasma by a high frequency electromagnetic field low frequency modulated; Excitation simultanee des resonances electronique et ionique dans un plasma dans un champ magnetique statique, produite par un champ electromagnetique HF module a une basse frequence

    Energy Technology Data Exchange (ETDEWEB)

    Zilli, E. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1966-07-01

    A single-particle, collisionless, non-relativistic theory is exposed, in which the possibility is shown of exciting electron and ion resonances in a magnetoplasma, by means of a high frequency electromagnetic field, whose amplitude is low frequency modulated. Two solutions of this problem are given in this report. The first one rests on the possibility of exciting the ion cyclotron resonance taking into account the low frequency electromagnetic field low frequency modulated. In the second solution the possibility of exciting the electron and ion resonances is considered in an electromagnetic field, whose magnetic component parallel to vector B{sub 0} is low frequency modulated. The results are discussed in the field of a cylindrical wave guide driven in the TE{sub 01}-mode, vector B{sub 0} being parallel to the axis. (Author) [French] On montre dans l'etude du mouvement d'une particule, lorsqu'on neglige les effets relativistes et les collisions, qu'il est possible d'exciter la resonance des electrons et des ions dans un plasma place dans un champ magnetique statique et dans un champ electromagnetique HF module en amplitude a une basse frequence. Dans cette note on presente deux solutions de ce probleme. La premiere repose sur la possibilite d'exciter la resonance cyclotron des ions en prenant en consideration le champ electromagnetique BF produit par les electrons qui tournent transversalement au champ magnetique statique B{sub 0}, sous l'influence d'un champ electromagnetique HF module a basse frequence. La deuxieme est celle ou le champ BF est une modulation, appliquee de l'exterieur, de l'amplitude de la composante magnetique du champ HF. On considere le cas ou cette composante magnetique oscillante est parallele a celle du champ magnetique statique. On discute les resultats dans le cas d'un mode TE{sub 01} se propageant dans un guide circulaire en presence d'un champ magnetique statique axial. (auteur)

  5. Collisional quenching of highly rotationally excited HF

    CERN Document Server

    Yang, Benhui; Forrey, R C; Stancil, P C; Balakrishnan, N

    2015-01-01

    Collisional excitation rate coefficients play an important role in the dynamics of energy transfer in the interstellar medium. In particular, accurate rotational excitation rates are needed to interpret microwave and infrared observations of the interstellar gas for nonlocal thermodynamic equilibrium line formation. Theoretical cross sections and rate coefficients for collisional deexcitation of rotationally excited HF in the vibrational ground state are reported. The quantum-mechanical close-coupling approach implemented in the nonreactive scattering code MOLSCAT was applied in the cross section and rate coefficient calculations on an accurate 2D HF-He potential energy surface. Estimates of rate coefficients for H and H$_2$ colliders were obtained from the HF-He collisional data with a reduced-potential scaling approach. The calculation of state-to-state rotational quenching cross sections for HF due to He with initial rotational levels up to $j=20$ were performed for kinetic energies from 10$^{-5}$ to 15000...

  6. 78 FR 70567 - Nationwide Use of High Frequency and Ultra High Frequency Active SONAR Technology; Final...

    Science.gov (United States)

    2013-11-26

    ...] Nationwide Use of High Frequency and Ultra High Frequency Active SONAR Technology; Final Programmatic... Programmatic Environmental Assessment (PEA) for the Nationwide Use of High Frequency (HF) and Ultra High Frequency (UHF) Sound Navigation and Ranging (SONAR) Technology and Finding of No Significant Impact (FONSI...

  7. Creation of Artificial Ionospheric Layers Using High-Power HF Waves

    Science.gov (United States)

    2010-01-30

    Program ( HAARP ) transmitter in Gakona, Alaska. The HF- driven ionization process is initiated near the 2nd electron gyroharmonic at 220 km altitude in...the 3.6 MW High-Frequency Active Auroral Program ( HAARP ) transmitter in Gakona, Alaska. The HF-driven ionization process is initiated near the 2nd...Maine. USA. Copyright 2010 by the American Geophysical Union. 0094-8276/I0/2009GLO41895SO5.0O Research Program ( HAARP ) transmitter facility, however

  8. Nanohertz Frequency Determination for the Gravity Probe B HF SQUID Signal

    CERN Document Server

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

    2011-01-01

    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 (SQUID) signal, whose main frequency fz 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/sec resolution in its decay rate were achieved out of a succession of 1.86 second-long...

  9. High-power ELF radiation generated by modulated HF heating of the ionosphere can cause Earthquakes, Cyclones and localized heating

    OpenAIRE

    De Aquino, Fran

    2011-01-01

    The High Frequency Active Auroral Research Program (HAARP) is currently the most important facility used to generate extremely low frequency (ELF) electromagnetic radiation in the ionosphere. In order to produce this ELF radiation the HAARP transmitter radiates a strong beam of high-frequency (HF) waves modulated at ELF. This HF heating modulates the electrons' temperature in the D region ionosphere and leads to modulated conductivity and a time-varying current which then radiates at the modu...

  10. High-power ELF radiation generated by modulated HF heating of the ionosphere can cause Earthquakes, Cyclones and localized heating

    OpenAIRE

    De Aquino, Fran

    2011-01-01

    The High Frequency Active Auroral Research Program (HAARP) is currently the most important facility used to generate extremely low frequency (ELF) electromagnetic radiation in the ionosphere. In order to produce this ELF radiation the HAARP transmitter radiates a strong beam of high-frequency (HF) waves modulated at ELF. This HF heating modulates the electrons' temperature in the D region ionosphere and leads to modulated conductivity and a time-varying current which then radiates at the modu...

  11. HF Detecting Radar and Communication Frequency Selection System

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Real time communication (RTC) frequency selecting system is used to the maximum usable frequency (MUF) between two communication points, then finds the best frequency between 0. 85 MUF and 1.0MUF. Determination of electric wave delay is mostly introduced, and of MUF values, the form of frequencycontrolling code and relative interface circuits in the frequency selecting system are introduced in detail.

  12. Phenomena induced by powerful HF pumping towards magnetic zenith with a frequency near the F-region critical frequency and the third electron gyro harmonic frequency

    Directory of Open Access Journals (Sweden)

    N. F. Blagoveshchenskaya

    2009-01-01

    Full Text Available Multi-instrument observational data from an experiment on 13 October 2006 at the EISCAT/HEATING facility at Tromsø, Norway are analysed. The experiment was carried out in the evening hours when the electron density in the F-region dropped, and the HF pump frequency fH was near and then above the critical frequency of the F2 layer. The distinctive feature of this experiment is that the pump frequency was just below the third electron gyro harmonic frequency, while both the HF pump beam and UHF radar beam were directed towards the magnetic zenith (MZ. The HF pump-induced phenomena were diagnosed with several instruments: the bi-static HF radio scatter on the London-Tromsø-St. Petersburg path, the CUTLASS radar in Hankasalmi (Finland, the European Incoherent Scatter (EISCAT UHF radar at Tromsø and the Tromsø ionosonde (dynasonde. The results show thermal electron excitation of the HF-induced striations seen simultaneously from HF bi-static scatter and CUTLASS radar observations, accompanied by increases of electron temperature when the heater frequency was near and then above the critical frequency of the F2 layer by up to 0.4 MHz. An increase of the electron density up to 25% accompanied by strong HF-induced electron heating was observed, only when the heater frequency was near the critical frequency and just below the third electron gyro harmonic frequency. It is concluded that the combined effect of upper hybrid resonance and gyro resonance at the same altitude gives rise to strong electron heating, the excitation of striations, HF ray trapping and extension of HF waves to altitudes where they can excite Langmuir turbulence and fluxes of electrons accelerated to energies that produce ionization.

  13. Ionospheric modifications in high frequency heating experiments

    Energy Technology Data Exchange (ETDEWEB)

    Kuo, Spencer P. [Department of Electrical and Computer Engineering, Polytechnic School of Engineering, New York University, 5 MetroTech Center, Brooklyn, New York 11201 (United States)

    2015-01-15

    Featured observations in high-frequency (HF) heating experiments conducted at Arecibo, EISCAT, and high frequency active auroral research program are discussed. These phenomena appearing in the F region of the ionosphere include high-frequency heater enhanced plasma lines, airglow enhancement, energetic electron flux, artificial ionization layers, artificial spread-F, ionization enhancement, artificial cusp, wideband absorption, short-scale (meters) density irregularities, and stimulated electromagnetic emissions, which were observed when the O-mode HF heater waves with frequencies below foF2 were applied. The implication and associated physical mechanism of each observation are discussed and explained. It is shown that these phenomena caused by the HF heating are all ascribed directly or indirectly to the excitation of parametric instabilities which instigate anomalous heating. Formulation and analysis of parametric instabilities are presented. The results show that oscillating two stream instability and parametric decay instability can be excited by the O-mode HF heater waves, transmitted from all three heating facilities, in the regions near the HF reflection height and near the upper hybrid resonance layer. The excited Langmuir waves, upper hybrid waves, ion acoustic waves, lower hybrid waves, and field-aligned density irregularities set off subsequent wave-wave and wave-electron interactions, giving rise to the observed phenomena.

  14. High Frequency Radar Locations in the United States as of February 2016.

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This dataset show the point locations of High Frequency (HF) radar systems across the US. HF radars measure the speed and direction of ocean surface currents in near...

  15. Electrical properties of radio-frequency sputtered HfO{sub 2} thin films for advanced CMOS technology

    Energy Technology Data Exchange (ETDEWEB)

    Sarkar, Pranab Kumar; Roy, Asim, E-mail: 28.asim@gmail.com [Department of Physics, National Institute of Technology Silchar, Silchar-788010, Assam, India Phone: +91-3842-224879 (India)

    2015-08-28

    The Hafnium oxide (HfO{sub 2}) high-k thin films have been deposited by radio frequency (rf) sputtering technique on p-type Si (100) substrate. The thickness, composition and phases of films in relation to annealing temperatures have been investigated by using cross sectional FE-SEM (Field Emission Scanning Electron Microscope) and grazing incidence x-ray diffraction (GI-XRD), respectively. GI-XRD analysis revealed that at annealing temperatures of 350°C, films phases change to crystalline from amorphous. The capacitance-voltage (C-V) and current-voltage (I-V) characteristics of the annealed HfO{sub 2} film have been studied employing Al/HfO{sub 2}/p-Si metal–oxide–semiconductor (MOS) structures. The electrical properties such as dielectric constant, interface trap density and leakage current density have been also extracted from C-V and I-V Measurements. The value of dielectric constant, interface trap density and leakage current density of annealed HfO{sub 2} film is obtained as 23,7.57×1011eV{sup −1} cm{sup −2} and 2.7×10{sup −5} Acm{sup −2}, respectively. In this work we also reported the influence of post deposition annealing onto the trapping properties of hafnium oxide and optimized conditions under which no charge trapping is observed into the dielectric stack.

  16. Practical techniques for enhancing the high-frequency MASW method

    Science.gov (United States)

    For soil exploration in the vadose zone, a high-frequency multi-channel analysis of surface waves (HF-MASW) method has been developed. In the study, several practical techniques were applied to enhance the overtone image of the HF-MASW method. They included (1) the self-adaptive MASW method using a ...

  17. Effect of HF Heating Array Directivity Pattern on the Frequency Response of Generated ELF/VLF.

    Science.gov (United States)

    1983-01-01

    hhEEE|hhEE 1H ; 11:j28 111125 . mm 11111 II ll1 111 .8 MICROCOPY RESOLUTION TESI CHART I fJC ’RL_-SCI-475l I( .-cmon Numters: 1.5.1. 3.1.4, 3.2.1,.3.3...the high power HF heating facility at the Arecibo Observatory in Puerto Rico. The pattern was calculated using pattern multi- plication and method of...high power HF heating facility at the Arecibo Observatory in Puerto Rico. The pattern was calculated using pattern multiplication and method of

  18. High-frequency electric field amplification in a magnetized plasma

    Energy Technology Data Exchange (ETDEWEB)

    Timofeev, Aleksandr V [Russian Research Centre ' Kurchatov Institute' , Moscow (Russian Federation)

    2006-11-30

    In the investigation of cyclotron ion heating in systems designed for plasma isotope separation, the high-frequency (HF) electric field amplification effect was found to occur in equilibrium plasma. In the present article this effect is treated as a result of the interaction of the plasma placed in a constant external magnetic field with the HF modes of the vacuum chamber. Consistent elaboration of this approach allowed obtaining a clear interpretation of the HF electric field amplification effect and constructing a simple model of HF field excitation in a plasma column embedded in the external magnetic field. (methodological notes)

  19. High time resolution observations of HF cross-modulation within the D region ionosphere

    Science.gov (United States)

    Langston, J.; Moore, R. C.

    2013-05-01

    High-frequency cross-modulation is employed to probe the D region ionosphere during HF heating experiments at the High-frequency Active Auroral Research Program (HAARP) observatory. We have adapted Fejer's well-known cross-modulation probing method to determine the extent of ionospheric conductivity modification in the D region ionosphere with high (5 μsec) time resolution. We demonstrate that the method can be used to analyze D region conductivity changes produced by HF heating both during the initial stages of heating and under steady state conditions. The sequence of CW probe pulses used allow the separation of cross-modulation effects that occur as the probe pulse propagates upward and downward through the heated region. We discuss how this probing technique can be applied to benefit ELF/VLF wave generation experiments and ionospheric irregularities experiments at higher altitudes. We demonstrate that large phase changes equivalent to Doppler shift velocities >60 km/s can be imposed on HF waves propagating through the heated D region ionosphere.

  20. Hf-based high-k materials for Si nanocrystal floating gate memories

    Directory of Open Access Journals (Sweden)

    Sahu Bhabani

    2011-01-01

    Full Text Available Abstract Pure and Si-rich HfO2 layers fabricated by radio frequency sputtering were utilized as alternative tunnel oxide layers for high-k/Si-nanocrystals-SiO2/SiO2 memory structures. The effect of Si incorporation on the properties of Hf-based tunnel layer was investigated. The Si-rich SiO2 active layers were used as charge storage layers, and their properties were studied versus deposition conditions and annealing treatment. The capacitance-voltage measurements were performed to study the charge trapping characteristics of these structures. It was shown that with specific deposition conditions and annealing treatment, a large memory window of about 6.8 V is achievable at a sweeping voltage of ± 6 V, indicating the utility of these stack structures for low-operating-voltage nonvolatile memory devices.

  1. UHF Radar observations at HAARP with HF pump frequencies near electron gyro-harmonics and associated ionospheric effects

    Science.gov (United States)

    Watkins, Brenton; Fallen, Christopher; Secan, James

    Results for HF modification experiments at the HAARP facility in Alaska are presented for experiments with the HF pump frequency near third and fourth electron gyro-harmonics. A UHF diagnostic radar with range resolution of 600 m was used to determine time-dependent altitudes of scattering from plasma turbulence during heating experiments. Experiments were conducted with multiple HF frequencies stepped by 20 kHz above and below the gyro-harmonic values. During times of HF heating the HAARP facility has sufficient power to enhance large-scale ionospheric densities in the lower ionosphere (about 150-200 km altitude) and also in the topside ionosphere (above about 350 km). In the lower ionosphere, time-dependent decreases of the altitude of radar scatter result from electron density enhancements. The effects are substantially different even for relatively small frequency steps of 20 kHz. In all cases the time-varying altitude decrease of radar scatter stops about 5-10 km below the gyro-harmonic altitude that is frequency dependent; we infer that electron density enhancements stop at this altitude where the radar signals stop decreasing with altitude. Experiments with corresponding total electron content (TEC) data show that for HF interaction altitudes above about 170 km there is substantial topside electron density increases due to upward electron thermal conduction. For lower altitudes of HF interaction the majority of the thermal energy is transferred to the neutral gas and no significant topside density increases are observed. By selecting an appropriate HF frequency a little greater than the gyro-harmonic value we have demonstrated that the ionospheric response to HF heating is a self-oscillating mode where the HF interaction altitude moves up and down with a period of several minutes. If the interaction region is above about 170 km this also produces a continuously enhanced topside electron density and upward plasma flux. Experiments using an FM scan with the HF

  2. Automated screening for high-frequency hearing loss.

    Science.gov (United States)

    Vlaming, Marcel S M G; MacKinnon, Robert C; Jansen, Marije; Moore, David R

    2014-01-01

    Hearing loss at high frequencies produces perceptual difficulties and is often an early sign of a more general hearing loss. This study reports the development and validation of two new speech-based hearing screening tests in English that focus on detecting hearing loss at frequencies above 2000 Hz. The Internet-delivered, speech-in noise tests used closed target-word sets of digit triplets or consonant-vowel-consonant (CVC) words presented against a speech-shaped noise masker. The digit triplet test uses the digits 0 to 9 (excluding the disyllabic 7), grouped in quasi-random triplets. The CVC test uses simple words (e.g., "cat") selected for the high-frequency spectral content of the consonants. During testing, triplets or CVC words were identified in an adaptive procedure to obtain the speech reception threshold (SRT) in noise. For these new, high-frequency (HF) tests, the noise was low-pass filtered to produce greater masking of the low-frequency speech components, increasing the sensitivity of the test for HF hearing loss. Individual test tokens (digits, CVCs) were first homogenized using a group of 10 normal-hearing (NH) listeners by equalizing intelligibility across tokens at several speech-in-noise levels. Both tests were then validated and standardized using groups of 24 NH listeners and 50 listeners with hearing impairment. Performance on the new high frequency digit triplet (HF-triplet) and CVC (HF-CVC) tests was compared with audiometric hearing loss, and with that on the unfiltered, broadband digit triplet test (BB-triplet) test, and the ASL (Adaptive Sentence Lists) speech-in-noise test. The HF-triplet and HF-CVC test results (SRT) both correlated positively and highly with high-frequency audiometric hearing loss and with the ASL test. SRT for both tests as a function of high-frequency hearing loss increased at nearly three times the rate as that of the BB-triplet test. The intraindividual variability (SD) on the tests was about 2.1 (HF-triplet) and 1

  3. FInvestigation of enhancement mode HfO2 insulated N-polarity GaN/InN/GaN/In0.9Al0.1N heterostructure MISHEMT for high-frequency applications

    Science.gov (United States)

    Mohanbabu, A.; Mohankumar, N.; Godwin Raj, D.; Sarkar, Partha

    2017-08-01

    In this paper, we examined normally-OFF N-polar InN-channel Metal insulated semiconductor high-electron mobility transistors (MISHEMTs) device with a relaxed In0.9Al0.1N buffer layer. In addition, the enhancement-mode operation of the N-polar structure was investigated. The effect of scaling in N-polar MISHEMT, such as the dielectric and the channel thickness, alter the electrical behavior of the device. We have achieved a maximum drain current of 1.17 A/mm, threshold voltage (VT) =0.728 V, transconductance (gm) of 2.9 S mm-1, high ION/IOFF current ratio of 3.23×103, lowest ON-state resistance (RON) of 0.41 Ω mm and an intrinsic delay time (τ) of 1.456 Fs along with high-frequency performance with ft/ fmaxof 90 GHz/109 GHz and 180 GHz/260 GHz for TCH =0.5 nm at Vds =0.5 V and 1.0 V. The numerically simulated results of highly confined GaN/InN/GaN/In0.9Al0.1N heterostructure MISHEMT exhibits outstanding potential as one of the possibility to replace presently used N-polar MISHEMTs for delivering high power density and frequency at RF/power amplifier applications.

  4. Plant Responses to High Frequency Electromagnetic Fields

    Directory of Open Access Journals (Sweden)

    Alain Vian

    2016-01-01

    Full Text Available High frequency nonionizing electromagnetic fields (HF-EMF that are increasingly present in the environment constitute a genuine environmental stimulus able to evoke specific responses in plants that share many similarities with those observed after a stressful treatment. Plants constitute an outstanding model to study such interactions since their architecture (high surface area to volume ratio optimizes their interaction with the environment. In the present review, after identifying the main exposure devices (transverse and gigahertz electromagnetic cells, wave guide, and mode stirred reverberating chamber and general physics laws that govern EMF interactions with plants, we illustrate some of the observed responses after exposure to HF-EMF at the cellular, molecular, and whole plant scale. Indeed, numerous metabolic activities (reactive oxygen species metabolism, α- and β-amylase, Krebs cycle, pentose phosphate pathway, chlorophyll content, terpene emission, etc. are modified, gene expression altered (calmodulin, calcium-dependent protein kinase, and proteinase inhibitor, and growth reduced (stem elongation and dry weight after low power (i.e., nonthermal HF-EMF exposure. These changes occur not only in the tissues directly exposed but also systemically in distant tissues. While the long-term impact of these metabolic changes remains largely unknown, we propose to consider nonionizing HF-EMF radiation as a noninjurious, genuine environmental factor that readily evokes changes in plant metabolism.

  5. An overview of high-latitude hf induced aurora from EISCAT

    Science.gov (United States)

    Kosch, M.; Gustavsson, B.; Rietveld, M.

    The EISCAT HF facility is capable of transmitting over 200 MW into the ionosphere below 5.423 MHz using the low-gain antenna array. Over 1000 MW above 5.423 MHz is available using the high-gain antenna array. During O-mode pumping in the hours after sunset, F-region electrons can be accelerated sufficiently to excite the oxygen atoms and nitrogen molecules, resulting in observable optical emissions at 844.6 (O), 630 (O1D), 557.7 (O1S) and 427.8 (N2) nm above EISCAT. Initial success came in February 1999 with optical recordings by ALIS (Auroral Large Imaging System) from various Swedish locations south of EISCAT and DASI (Digital All-Sky Imager) from Skibotn, Norway, 50 km south-east of EISCAT. Several observations have features unique to high latitudes. Novel discoveries include: (1) Very large electron temperature enhancements of a few 1000 K, which maximise along the magnetic field line direction (2) Ion temperature enhancements of a few 100 K accompanied by large ion outflows, (3) The optical emission usually appears near the magnetic field line direction regardless of the HF transmitter beam pointing direction, (4) The optical emission appears below the HF pump reflection altitude as well as the upper-hybrid resonance height, (5) The optical emission and HF coherent radar backscatter disappears when pumping on the 3rd, 4th or 5th gyro-harmonic frequency, (6) The first artificial optical observations at 844.6 (O) and 427.8 (N2) nm and (7) Annular optical structures, which subsequently collapse into blobs.

  6. Synthesis of bulk FeHfBO soft magnetic materials and its loss characterization at megahertz frequency

    Energy Technology Data Exchange (ETDEWEB)

    Zhou Yang; Kou Xiaoming; Warsi Muhammad, Asif; Lin Shuo; Harris, Brendan S.; Parsons, Paul E.; Xiao, John Q. [Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716 (United States); Mu Mingkai; Lee, Fred C. [Center for Power Electronics System, Virginia Polytechnic and State University, Blacksburg, Virginia 24060 (United States); Zhu Hao [Spectrum Magnetics LLC, Wilmington, Delaware 19804 (United States)

    2013-05-07

    Magnetic core materials with low loss, high saturation magnetization, large permeability, and operating frequency above 1 MHz are in high demands for the next generation of miniaturized power electronics. Amorphous FeHfB ribbons with thickness around 20 {mu}m have been fabricated through melt-spinning. Different heat treatments were performed on the FeHfB ribbons, and the relations among heat treatments, microstructure, and magnetic properties have been explored. Properties such as coercivity (H{sub c}) of 2.0 Oe and saturation magnetic flux density (B{sub S}) of 1.2 T have been achieved in samples with exchange coupling. The losses can be minimized by balancing the hysteretic and eddy current losses and can be further reduced with additional magnetic field annealing. At 5 MHz with peak magnetic flux density of 20 mT, the materials show core losses comparable to the best ferrites, but with higher permeability value of about 200 and superior saturation induction of more than 1 T.

  7. Microwave Radiometer - high frequency

    Data.gov (United States)

    Oak Ridge National Laboratory — The Microwave Radiometer-High Frequency (MWRHF) provides time-series measurements of brightness temperatures from two channels centered at 90 and 150 GHz. These two...

  8. High-latitude propagation studies using a meridional chain of LF/MF/HF receivers

    Directory of Open Access Journals (Sweden)

    J. LaBelle

    2004-04-01

    Full Text Available For over a decade, Dartmouth College has operated programmable radio receivers at multiple high-latitude sites covering the frequency range 100-5000kHz with about a 1-s resolution. Besides detecting radio emissions of auroral origin, these receivers record characteristics of the ionospheric propagation of natural and man-made signals, documenting well-known effects, such as the diurnal variation in the propagation characteristics of short and long waves, and also revealing more subtle effects. For example, at auroral zone sites in equinoctial conditions, the amplitudes of distant transmissions on MF/HF frequencies are often enhanced by a few dB just before they fade away at dawn. The polarization and/or direction of the arrival of ionospherically propagating signals in the lower HF range (3-5MHz show a consistent variation between pre-midnight, post-midnight, and pre-dawn conditions. As is well known, magnetic storms and substorms dramatically affect ionospheric propagation; data from multiple stations spanning the invariant latitude range 67-79° reveal spatial patterns of propagation characteristics associated with magnetic storms and substorms. For example, in the hours preceding many isolated substorms, favorable propagation conditions occur at progressively lower latitudes as a function of time preceding the substorm onset. For some of these effects, explanations follow readily from elementary ionospheric physics, but understanding others requires further investigation.

    Key words. Magnetospheric physics (annual phenomena – Radio science (ionosphere propagation; radio-wave propagation6

  9. High frequency electromagnetic dosimetry

    CERN Document Server

    Sánchez-Hernández, David A

    2009-01-01

    Along with the growth of RF and microwave technology applications, there is a mounting concern about the possible adverse effects over human health from electromagnetic radiation. Addressing this issue and putting it into perspective, this groundbreaking resource provides critical details on the latest advances in high frequency electromagnetic dosimetry.

  10. High-spin positive-parity states in 179Hf studied by the 180Hf(τ, α) 179Hf reaction AT 32 MeV

    Science.gov (United States)

    Thorsteinsen, T. F.; Løvhøiden, G.; Vaagen, J. S.; Bjørnberg, A.; Burke, D. G.

    1981-06-01

    Full angular distributions are presented for states populated in the reaction 180Hf(τ, α) 179Hf at 32 MeV beam energy. Positive-parity states associated with the i {13}/{2} unique parity intruder orbital are given special attention. Thus, angular distributions for the five first members of the [624 {9}/{2}] groundstate sequence are given, as well as for a number of more highly excited states, some being new assignments. The distribution of l = 6 transfer strength is quite characteristic, two {13}/{2}+ states being substantially more populated than the rest. The characteristic features of the data are explained by a quasiparticle-rotor calculation employing deformed Woods-Saxon orbitals, but only if the hexadecapole shape parameter of the nuclear potential is β 4 ˜ -0.08. The often anomalous differential cross sections for I π ≠ {13}/{2}+ band members are well accounted for by a rotor model CCBA calculation employing transfer form factors extracted from the orbitals of the deformed Woods-Saxon field, and including non-adiabatic Coriolis mixing effects.

  11. Low and High-Frequency Field Potentials of Cortical Networks Exhibit Distinct Responses to Chemicals

    Science.gov (United States)

    Neural networks grown on microelectrode arrays (MEAs) have become an important, high content in vitro assay for assessing neuronal function. MEA experiments typically examine high- frequency (HF) (>200 Hz) spikes, and bursts which can be used to discriminate between differ...

  12. High frequency electromagnetic tomography

    Energy Technology Data Exchange (ETDEWEB)

    Daily, W.; Ramirez, A.; Ueng, T.; Latorre, R.

    1989-09-01

    An experiment was conducted in G Tunnel at the Nevada Test Site to evaluate high frequency electromagnetic tomography as a candidate for in situ monitoring of hydrology in the near field of a heater placed in densely welded tuff. Tomographs of 200 MHz electromagnetic permittivity were made for several planes between boreholes. Data were taken before the heater was turned on, during heating and during cooldown of the rockmass. This data is interpreted to yield maps of changes in water content of the rockmass as a function of time. This interpretation is based on laboratory measurement of electromagnetic permittivity as a function of water content for densely welded tuff. 8 refs., 6 figs.

  13. Some general effects of strong high-frequency excitation: stiffening, biasing, and smoothening

    DEFF Research Database (Denmark)

    Thomsen, Jon Juel

    2002-01-01

    Mechanical high-frequency (HF) excitation provides a working principle behind many industrial and natural applications and phenomena. This paper concerns three particular effects of HF excitation, that may change the apparent characteristics of mechanical systems: 1) stiffening, by which the appa...

  14. High-reflectivity HfO2/SiO2 ultraviolet mirrors.

    Science.gov (United States)

    Torchio, Philippe; Gatto, Alexandre; Alvisi, Marco; Albrand, Gérard; Kaiser, Norbert; Amra, Claude

    2002-06-01

    High-reflectivity dense multilayer coatings were produced for the ultraviolet spectral region. Thin-film single layers and UV mirrors were deposited by ion plating and plasma ion-assisted deposition high-energetic technologies. Optical characterizations of HfO2 and SiO2 single layers are made. The optical constants obtained for these two materials are presented. HfO2 and SiO2 mirrors with a reflectance of approximately 99% near 250 nm are reported.

  15. Basis of Ionospheric Modification by High-Frequency Waves

    Science.gov (United States)

    2007-06-01

    for conducting ionospheric heating experiments in Gakona, Alaska, as part of the High Frequency Active Auroral Research Program ( HAARP ) [5], is being...upgraded. The upgraded HAARP HF transmitting system will be a phased-array antenna of 180 elements. Each element is a cross dipole, which radiates a...supported by the High Frequency Active Auroral Research Program ( HAARP ), the Air Force Research Laboratory at Hanscom Air Force Base, MA, and by the Office

  16. Fabrication and characteristics of ZnO MOS capacitors with high-K HfO2 gate dielectrics

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    ZnO thin films are first deposited on n-type silicon by radio frequency (rf) magnetron sputtering at room temperature.And high-K HfO2 gate dielectrics thin films are deposited on ZnO films to form metal-oxide semiconductor (MOS) capacitors.The temperature to fabricate ZnO MOS capacitors is 400°C,and the low temperature process is applicable for thin film transistors,flat-panel display (FPD),flexible display,etc.The electronic availability of ZnO thin films,which serve as a semiconductor material for MOS capacitors with HfO2 gate dielectric is investigated.High frequency (1 MHz) capacitance-voltage (C-V) and current-voltage (I-V) characteristics of ZnO-based MOS capacitors are measured.The thermal stability and electronic stability of the ZnO capacitors are investigated,respectively.Experimental results indicate that good electrical characteristics can be obtained on ZnO substrates with high-K HfO2 gate dielectrics.Besides,the ZnO capacitors can exhibit high thermal and electronic stabilities.

  17. Meditation-induced changes in high-frequency heart rate variability predict smoking outcomes

    Directory of Open Access Journals (Sweden)

    Daniel J. Libby

    2012-03-01

    Full Text Available Background: High-frequency heart rate variability (HF-HRV is a measure of parasympathetic nervous system output that has been associated with enhanced self-regulation. Low resting levels of HF-HRV are associated with nicotine dependence and blunted stress-related changes in HF-HRV are associated with decreased ability to resist smoking. Meditation has been shown to increase HF-HRV. However, it is unknown whether tonic levels of HF-HRV or acute changes in HF-HRV during meditation predict treatment responses in addictive behaviors such as smoking cessation. Purpose: To investigate the relationship between HF-HRV and subsequent smoking outcomes. Methods: HF-HRV during resting baseline and during mindfulness meditation was measured within two weeks of completing a 4-week smoking cessation intervention in a sample of 31 community participants. Self-report measures of smoking were obtained at a follow up 17-weeks after the initiation of treatment. Results: Regression analyses indicated that individuals exhibiting acute increases in HF-HRV from resting baseline to meditation smoked fewer cigarettes at follow-up than those who exhibited acute decreases in HF-HRV (b=-4.94, p=.009. Conclusion: Acute changes in HF-HRV in response to meditation may be a useful tool to predict smoking cessation treatment response.

  18. Fabrication and characteristics of high-K HfO2 gate dielectrics on n-germanium

    Institute of Scientific and Technical Information of China (English)

    Han De-Dong; Kang Jin-Feng; Liu Xiao-Yan; Sun Lei; Luo Hao; Han Ru-Qi

    2007-01-01

    This paper reports that the high-K HfO2 gate dielectrics are fabricated on n-germanium substrates by sputtering Hf on Ge and following by a furnace annealing. The impacts of sputtering ambient, annealing ambient and annealing temperature on the electrical properties of high-K HfO2 gate dielectrics on germanium substrates are investigated.Experimental results indicate that high-K HfO2 gate dielectrics on germanium substrates with good electrical characteristics are obtained, the electrical properties of high-K HfO2 gate dielectrics is strongly correlated with sputtering ambient, annealing ambient and annealing temperature.

  19. SINGLE PHASE HIGH FREQUENCY AC CONVERTER FOR INDUCTION HEATING APPLICATION

    Directory of Open Access Journals (Sweden)

    M.A INAYATHULLAAH,

    2010-12-01

    Full Text Available The proposed topology reduces the total harmonic distortion (THD of a high frequency AC/AC Converter well below the acceptable limit. This paper deals with a novel single phase AC/DC/AC soft switching utility frequency AC to high frequency AC converter. In this paper a single phase full bridge inverter with Vienna rectifier as front end is used instead of conventional diode bridge rectifier to provide continuous sinusoidal input current with nearly unity power factor at the source side with extremely low distortion.. This power converter is more suitable and acceptable for cost effective high frequency (HF consumer induction heating applications.

  20. Phase Transformation and Thermal Stability of Aged Ti-Ni-Hf High Temperature Shape Memory Alloys

    Institute of Scientific and Technical Information of China (English)

    Xianglong MENG; Wei CAI; K.T.Lau; L.M.Zhou; Liancheng ZHAO

    2006-01-01

    The use of Ni-rich TiNiHf alloys as high temperature shape memory alloys(SMAs)through aging has been presented. For Ni-rich Ti80-xNixHf20 alloys, their phase transformation temperatures are averagely increased more than 100 K by aging at 823 K for 2 h. Especially for the alloys with Ni-content of 50.4 at. pct and 50.6 at. pct, their martensitic transformation start temperatures(Ms)are more than 473 K after aging. TEM observation confirmed that some fine particles precipitate from the matrix during aging. The aged Ni-rich TiNiHf SMAs show the better thermal stability of phase transformation temperatures than the solutiontreated TiNiHf alloys. The fine particles precipitated during aging should be responsible for the increase of phase transformation temperatures and its high stability.

  1. In situ studies of the atomic layer deposition of thin HfO{sub 2} dielectrics by ultra high vacuum atomic force microscope

    Energy Technology Data Exchange (ETDEWEB)

    Kolanek, Krzysztof, E-mail: kolanek@tu-cottbus.d [Brandenburg University of Technology, Department of Applied Physics and Sensors, Konrad-Wachsmann-Allee 17, 03046 Cottbus (Germany); Tallarida, Massimo; Karavaev, Konstantin; Schmeisser, Dieter [Brandenburg University of Technology, Department of Applied Physics and Sensors, Konrad-Wachsmann-Allee 17, 03046 Cottbus (Germany)

    2010-06-01

    We studied in situ the initial stages of atomic layer deposition (ALD) of HfO{sub 2} by an ultra high vacuum atomic force microscope working in frequency-modulation mode. The ALD cycles, made by using tetrakis-di-methyl-amido-Hf and water as precursors, were performed on the Si(001)/SiO{sub 2} substrate maintained at 230 {sup o}C. After each ALD cycle we studied the influence of the HfO{sub 2} growth on the surface height histogram, the root mean square roughness, the surface fractal dimension and the autocorrelation function. This detailed analysis of the surface topography allowed us to confirm the completion of the first HfO{sub 2} layer after four ALD cycles.

  2. High Frequency Oscillatory Ventilation

    Directory of Open Access Journals (Sweden)

    AC Bryan

    1996-01-01

    Full Text Available High frequency oscillatory (HFO ventilation using low tidal volume and peak airway pressures is extremely efficient at eliminating carbon dioxide and raising pH in the newborn infant with acute respiratory failure. Improvement in oxygenation requires a strategy of sustained or repetitive inflations to 25 to 30 cm H2O in order to place the lung on the deflation limb of the pressure-volume curve. This strategy has also been shown to decrease the amount of secondary lung injury in animal models. Experience of the use of HFO ventilation as a rescue therapy as well as several published controlled trials have shown improved outcomes and a decrease in the use of extracorporeal membrane oxygenation when it has been used in newborns.

  3. Development of Hf(4+)-immobilized polydopamine-coated magnetic graphene for highly selective enrichment of phosphopeptides.

    Science.gov (United States)

    Lin, Haizhu; Deng, Chunhui

    2016-01-01

    In this work, we first designed and synthesized an IMAC material with Hf(4+) immobilized on polydopamine-coated magnetic graphene and applied it to phosphopeptides enrichment successfully. The newly prepared material gathered the advantages of large specific surface area of graphene, good hydrophilicity and biocompatibility of polydopamine and superparamagnetism of Fe3O4. We investigated the performance of Hf(4+)-immobilized polydopamine-coated magnetic graphene (denoted as magG@PDA-Hf(4+)) in phosphopeptides enrichment and the results showed high selectivity and sensitivity of the new material. Finally, we successfully applied magG@PDA-Hf(4+) to phosphopeptides enrichment from non-fat milk digests and human serum, further demonstrating excellent performance of this new material in phosphopeptides enrichment. Copyright © 2015 Elsevier B.V. All rights reserved.

  4. Extended High Frequency Audiometry in Secretory Otitis Media

    OpenAIRE

    Sharma, Deepika; Munjal, Sanjay K.; Panda, Naresh K.

    2012-01-01

    The objective of the present study was to determine the status of extended high frequencies in subjects with secretory otitis media. The study evaluated 30 ears of 20 subjects with secretory otitis media in the age group of 15–30 years. This data was compared with 20 ears of 10 volunteers of the same age group with clinically normal hearing. Pure tone air conduction thresholds were analyzed in three frequency groups: low frequency (LF: 0.25, 0.5, and 1 kHz), high frequency (HF: 2, 4, and 8 kH...

  5. Ionospheric Modification from Under-Dense Heating by High-Power HF Transmitter

    Science.gov (United States)

    2011-03-03

    Auroral Research Program ( HAARP ) is a HF transmitter, which delivers 0.36 to 3.6 GW effective isotropic radiated powers (F.IRP) for the radiation...dense heating, the EIRP of the HAARP heater can be increased significantly by increasing the heater frequency. With higher heater frequency, the loss...1304 local time) and on 13 April from 0812 to 0844 UTC (0012 to 0044 local time), using the HAARP transmitter facility at Gakona, AK, at full power

  6. Using high-frequency vibrations and non-linear inclusions to create metamaterials with adjustable effective properties

    DEFF Research Database (Denmark)

    Lazarov, Boyan Stefanov; Thomsen, Jon Juel

    2009-01-01

    We investigate how high-frequency (HF) excitation combined with strongly non-linear elasticity may influence the effective properties for low-frequency wave propagation. The HF effects are demonstrated for linear spring-mass chains with embedded non-linear parts. The investigated mechanical syste...

  7. Influence of cointercalated HF on the electrochemical behavior of highly fluorinated graphite

    Science.gov (United States)

    Nakajima, Tsuyoshi; Gupta, Vinay; Ohzawa, Yoshimi; Groult, Henri; Mazej, Zoran; Žemva, Boris

    Highly fluorinated graphite was prepared at room temperature using high oxidation state transition metal complex fluoride (K 2PdF 6, K 2MnF 6, K 2NiF 6 or KAgF 4) and elemental fluorine under pressure ((5.9-11.8) ×10 5 Pa) in anhydrous liquid HF (aHF). The composition of the fluorinated graphite samples ranged from C 1.1F to C 1.9F containing small amounts of HF. IR absorption spectra revealed that stage 1 phase of C xF contained several different phases with planar (sp 2) and puckered (sp 3) graphene layers. Electrochemical discharge of the fluorinated graphite showed that profile of discharge potential and discharge capacity varied depending on the amount of cointercalated HF. The C xF samples with less amounts of HF and HF 2δ- had relatively flat discharge potentials and large discharge capacities. The discharge capacity reached 500-600 mAh/g in 1 mol/dm 3 LiClO 4-propylene carbonate solution at 25 °C. Chemical diffusion coefficients of Li + ion in the intermediate discharge products were (4.4-13) ×10 -12 cm 2/s from impedance measurement.

  8. Current Progress of Hf (Zr)-Based High-k Gate Dielectric Thin Films

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    With the continued downscaling of complementary metal-oxide-semiconductor field effect transistor dimensions, high-dielectric constant (high-k) gate materials, as alternatives to SiO2, have been extensively investigated. Hf (Zr)-based high-k gate dielectric thin films have been regarded as the most promising candidates for high-k gate dielectric according to the International Technology Roadmap for Semiconductor due to their excellent physical properties and performance. This paper reviews the recent progress on Hf (Zr)-based high-k gate dielectrics based on PVD (physical vapor deposition) process. This article begins with a survey of various methods developed for generating Hf (Zr)-based high-k gate dielectrics, and then mainly focuses on microstructure, synthesis, characterization, formation mechanisms of interfacial layer, and optical properties of Hf (Zr)-based high-k gate dielectrics. Finally, this review concludes with personal perspectives towards future research on Hf (Zr)-based high-k gate dielectrics.

  9. Carbon nanotube transistor based high-frequency electronics

    Science.gov (United States)

    Schroter, Michael

    At the nanoscale carbon nanotubes (CNTs) have higher carrier mobility and carrier velocity than most incumbent semiconductors. Thus CNT based field-effect transistors (FETs) are being considered as strong candidates for replacing existing MOSFETs in digital applications. In addition, the predicted high intrinsic transit frequency and the more recent finding of ways to achieve highly linear transfer characteristics have inspired investigations on analog high-frequency (HF) applications. High linearity is extremely valuable for an energy efficient usage of the frequency spectrum, particularly in mobile communications. Compared to digital applications, the much more relaxed constraints for CNT placement and lithography combined with already achieved operating frequencies of at least 10 GHz for fabricated devices make an early entry in the low GHz HF market more feasible than in large-scale digital circuits. Such a market entry would be extremely beneficial for funding the development of production CNTFET based process technology. This talk will provide an overview on the present status and feasibility of HF CNTFET technology will be given from an engineering point of view, including device modeling, experimental results, and existing roadblocks. Carbon nanotube transistor based high-frequency electronics.

  10. Research on Multi-Layer Distributed HF Radio Network Structure

    Institute of Scientific and Technical Information of China (English)

    Hui Dai; Chun-Jiang Wang; Quan Yu

    2008-01-01

    High frequency (HF) transmission is an important communication techniques. However, conventional point-to-point transmission can be easily destroyed, which limits its utilization in practice. HF networking communication has the capability against demolishment. The network structure is one of the key factors for HF networking communication. In this paper, a novel analysis method of the network connectedness based on the eigenvalue is derived, and a multi-layer distributed HF radio network structure is proposed. Both the theore tical analysis and the computer simulation results verify that the application of the proposed network structure in the HF radio communication can improve the anti demolishment ability of the HF network efficiently.

  11. Propagation Impact on Modern HF (High Frequency) Communications System Design

    Science.gov (United States)

    1986-03-01

    US Gvt Printing Office, Washington DC. Piggot, W.R., Rawer, K. (1972). URSI Handbook for lonogram Interpretation and... Handbook ", Communications Research Centre Report No. 1255, 1974. Widrow B., Mantey P.E., Griffiths L.J. and Goode B.B., "Adaptive Antenna Systems...implemented in modified form by the terminal node controller (TNC). In the U.S., Amateur Radio Relay League ( ARRL ) radio amateurs have held four annual

  12. Plasma modifications induced by an X-mode HF heater wave in the high latitude F region of the ionosphere

    Science.gov (United States)

    Blagoveshchenskaya, N. F.; Borisova, T. D.; Yeoman, T. K.; Rietveld, M. T.; Häggström, I.; Ivanova, I. M.

    2013-12-01

    We presented experimental results of strong plasma modifications induced by X-mode powerful HF radio waves injected towards the magnetic zenith into the high latitude F region of the ionosphere. The experiments were conducted in 2009-2011 using the EISCAT Heating facility, UHF incoherent scatter radar and the EISCAT ionosonde at Tromsø, Norway; and the CUTLASS SuperDARN HF coherent radar at Hankasalmi, Finland. The results showed that the X-mode HF pump wave can generate strong small-scale artificial field aligned irregularities (AFAIs) in the F region of the high-latitude ionosphere. These irregularities, with spatial scales across the geomagnetic field of the order of 9-15 m, were excited when the heater frequency (fH) was above the ordinary-mode critical frequency (foF2) by 0.1-1.2 MHz. It was found that the X-mode AFAIs appeared between 10 s and 4 min after the heater is turned on. Their decay time varied over a wide range between 3 min and 30 min. The excitation of X-mode AFAIs was accompanied by electron temperature (Te) enhancements and an increase in the electron density (Ne) depending on the effective radiated power (ERP). Under ERPs of about 75-180 MW the Te enhances up to 50% above the background level and an increase in Ne of up to 30% were observed. Dramatic changes in the Te and Ne behavior occurred at effective radiated powers of about 370-840 MW, when the Ne and Te values increased up to 100% above the background ones. It was found that AFAIs, Ne and Te enhancements occurred, when the extraordinary-mode critical frequency (fxF2) lied in the frequency range fH-fce/2≤fxF2≤fH+fce/2, where fce is the electron gyrofrequency. The strong Ne enhancements were observed only in the magnetic field-aligned direction in a wide altitude range up to the upper limit of the UHF radar measurements. In addition, the maximum value of Ne is about 50 km higher than the Te enhancement peak. Such electron density enhancements (artificial ducts) cannot be explained by

  13. Extended x-ray absorption fine structure measurements on radio frequency magnetron sputtered HfO2 thin films deposited with different oxygen partial pressures.

    Science.gov (United States)

    Maidul Haque, S; Nayak, C; Bhattacharyya, Dibyendu; Jha, S N; Sahoo, N K

    2016-03-20

    Two sets of HfO2 thin film have been deposited by the radio frequency magnetron sputtering technique at various oxygen partial pressures, one set without any substrate bias and another set with a 50 W pulsed dc substrate bias. The films have been characterized by extended x-ray absorption fine structure (EXAFS) measurements at the Hf L3 edge, and the structural information obtained from analysis of the EXAFS data has been used to explain the macroscopic behavior of the refractive index obtained from spectroscopic ellipsometry measurements. It has been observed that the variation of refractive index with oxygen partial pressure depends on the Hf-Hf bond length for the set of films deposited without substrate bias, while for the other set of films deposited with pulsed dc substrate bias, it depends on the oxygen coordination of the nearest neighbor shell surrounding Hf sites.

  14. Frequency dependence of lung volume changes during superimposed high-frequency jet ventilation and high-frequency jet ventilation.

    Science.gov (United States)

    Sütterlin, R; Priori, R; Larsson, A; LoMauro, A; Frykholm, P; Aliverti, A

    2014-01-01

    Superimposed high-frequency jet ventilation (SHFJV) has proved to be safe and effective in clinical practice. However, it is unclear which frequency range optimizes ventilation and gas exchange. The aim of this study was to systematically compare high-frequency jet ventilation (HFJV) with HFJV by assessing chest wall volume variations (ΔEEV(CW)) and gas exchange in relation to variable high frequency. SHFJV or HFJV were used alternatively to ventilate the lungs of 10 anaesthetized pigs (21-25 kg). The low-frequency component was kept at 16 min(-1) in SHFJV. In both modes, high frequencies ranging from 100 to 1000 min(-1) were applied in random order and ventilation was maintained for 5 min in all modalities. Chest wall volume variations were obtained using opto-electronic plethysmography. Airway pressures and arterial blood gases were measured repeatedly. SHFJV increased ΔEEV(CW) compared with HFJV; the difference ranged from 43 to 68 ml. Tidal volume (V(T)) was always >240 ml during SHFJV whereas during HFJV ranged from 92 ml at the ventilation frequency of 100 min(-1) to negligible values at frequencies >300 min(-1). We observed similar patterns for Pa(O₂) and Pa(CO₂). SHFJV provided generally higher, frequency-independent oxygenation (Pa(O₂) at least 32.0 kPa) and CO₂ removal (Pa(CO₂) ∼5.5 kPa), whereas HFJV led to hypoxia and hypercarbia at higher rates (Pa(O₂) 10 kPa at f(HF)>300 min(-1)). In a porcine model, SHFJV was more effective in increasing end-expiratory volume than single-frequency HFJV, but both modes may provide adequate ventilation in the absence of airway obstruction and respiratory disease, except for HFJV at frequencies ≥300 min(-1).

  15. Characteristics of high-quality HfSiON gate dielectric prepared by physical vapour deposition

    Institute of Scientific and Technical Information of China (English)

    Xu Gao-Bo; Xu Qiu-Xia

    2009-01-01

    This paper presents a method using simple physical vapour deposition to form high-quality hafnium silicon oxyni-tride (HfSiON) on ultrathin SiO2 buffer layer. The gate dielectric with 10A (1/A = 0.1 nm) equivalent oxide thickness is obtained. The experimental results indicate that the prepared HfSiON gate dielectric exhibits good physical and electrical characteristics, including very good thermal stability up to 1000℃, excellent interface properties, high dielec-tric constant (k = 14) and low gate-leakage current (Ig= 1.9×10-3 A/cm2@Vg = Vfb-1V for EOT of 10A). TaN metal gate electrode is integrated with the HfSiON gate dielectric.The effective work function of TaN on HfSiON is 4.3eV, meeting the requirements of NMOS for the metal gate. And, the impacts of sputtering ambient and annealing temperature on the electrical properties of HfSiON gate dielectric are investigated.

  16. Geometric Aspects of Artificial Ionospheric Layers Driven by High-Power HF-Heating

    Science.gov (United States)

    Milikh, G. M.; Eliasson, B.; Shao, X.; Djordjevic, B.; Mishin, E. V.; Zawdie, K.; Papadopoulos, K.

    2013-12-01

    We have generalized earlier developed multi-scale dynamic model for the creation and propagation of artificial plasma layers in the ionosphere [Eliasson et al, 2012] by including two dimensional effects in the horizontal direction. Such layers were observed during high-power high frequency HF heating experiments at HAARP [Pedersen et al., 2010]. We have numerically investigated the importance of different angles of incidence of ordinary mode waves on the Langmuir turbulence and the resulting electron acceleration that leads to the formation of artificial ionospheric layers. It was shown that the most efficient electron acceleration and subsequent ionization is obtained at angles between magnetic zenith and the vertical, where strong Langmuir turbulence dominates over weak turbulence. A role played by the heating wave propagation near caustics was also investigated. Eliasson, B. et al. (2012), J. Geophys. Res. 117, A10321, doi:10.1029/2012JA018105. Pedersen, T., et al. (2010), Geophys. Res. Lett., 37, L02106, doi:10.1029/2009GL041895.

  17. High-latitude HF Doppler observations of ULF waves: 2. Waves with small spatial scale sizes

    Directory of Open Access Journals (Sweden)

    D. M. Wright

    Full Text Available The DOPE (Doppler Pulsation Experiment HF Doppler sounder located near Tromsø, Norway (geographic: 69.6°N 19.2°E; L = 6.3 is deployed to observe signatures, in the high-latitude ionosphere, of magnetospheric ULF waves. A type of wave has been identified which exhibits no simultaneous ground magnetic signature. They can be subdivided into two classes which occur in the dawn and dusk local time sectors respectively. They generally have frequencies greater than the resonance fundamentals of local field lines. It is suggested that these may be the signatures of high-m ULF waves where the ground magnetic signature has been strongly attenuated as a result of the scale size of the waves. The dawn population demonstrate similarities to a type of magnetospheric wave known as giant (Pg pulsations which tend to be resonant at higher harmonics on magnetic field lines. In contrast, the waves occurring in the dusk sector are believed to be related to the storm-time Pc5s previously reported in VHF radar data. Dst measurements support these observations by indicating that the dawn and dusk classes of waves occur respectively during geomagnetically quiet and more active intervals.

    Key words. Ionosphere (auroral ionosphere; ionosphere-magnetosphere interactions · Magnetospheric physics (MHD waves and instabilities

  18. High-temperature grain size stabilization of nanocrystalline Fe–Cr alloys with Hf additions

    Energy Technology Data Exchange (ETDEWEB)

    Li, Lulu, E-mail: lli18@ncsu.edu; Saber, Mostafa; Xu, Weizong; Zhu, Yuntian; Koch, Carl C.; Scattergood, Ronald O.

    2014-09-08

    The influence of 1–4 at% Hf additions on the thermal stability of mechanically alloyed nanocrystalline Fe–14Cr alloys was studied in this work. XRD-calculated grain size and microhardness results were reported versus isochronal annealing treatments up to 1100 °C. Microstructural evolution was investigated using channeling contrast FIB imaging and TEM. Grain size of samples with 4 at% Hf was found to be maintained in the nanoscale range at temperatures up to 1000 °C. Zener pinning was considered as a major source of high temperature grain size stabilization. By comparing the Orowan strengthening contribution to the total hardness, the deviation of grain size predictions from the actual grain size in Fe–14Cr–4Hf suggests the presence of thermodynamic stabilization by the solute segregation to grain boundaries (GBs). A predictive thermodynamic model indicates that the thermodynamic stabilization can be expected.

  19. Design and Analysis of High-Performance Smart Card with HF/UHF Dual-Band RFID Tag and Memory Functions

    OpenAIRE

    Gi-Hyun Hwang; Dae-Ki Kang

    2013-01-01

    In this paper, we introduce a novel design of high-performance smart card with HF/UHF dual-band RFID tag to overcome frequency interference problem. Firstly, we have designed and tested a UHF RFID tag using a simulation software system. In the smart card hardware design stage, we connect a HF antenna and a UHF antenna and place them in one inlay sheet. Using a spectrum analyzer, we systematically adjust the antenna pattern to detect the optimal patterns that fit the impedance of the RFID chip...

  20. High frequency nanotube oscillator

    Science.gov (United States)

    Peng, Haibing [Houston, TX; Zettl, Alexander K [Kensington, TX

    2012-02-21

    A tunable nanostructure such as a nanotube is used to make an electromechanical oscillator. The mechanically oscillating nanotube can be provided with inertial clamps in the form of metal beads. The metal beads serve to clamp the nanotube so that the fundamental resonance frequency is in the microwave range, i.e., greater than at least 1 GHz, and up to 4 GHz and beyond. An electric current can be run through the nanotube to cause the metal beads to move along the nanotube and changing the length of the intervening nanotube segments. The oscillator can operate at ambient temperature and in air without significant loss of resonance quality. The nanotube is can be fabricated in a semiconductor style process and the device can be provided with source, drain, and gate electrodes, which may be connected to appropriate circuitry for driving and measuring the oscillation. Novel driving and measuring circuits are also disclosed.

  1. High-frequency graphene voltage amplifier.

    Science.gov (United States)

    Han, Shu-Jen; Jenkins, Keith A; Valdes Garcia, Alberto; Franklin, Aaron D; Bol, Ageeth A; Haensch, Wilfried

    2011-09-14

    While graphene transistors have proven capable of delivering gigahertz-range cutoff frequencies, applying the devices to RF circuits has been largely hindered by the lack of current saturation in the zero band gap graphene. Herein, the first high-frequency voltage amplifier is demonstrated using large-area chemical vapor deposition grown graphene. The graphene field-effect transistor (GFET) has a 6-finger gate design with gate length of 500 nm. The graphene common-source amplifier exhibits ∼5 dB low frequency gain with the 3 dB bandwidth greater than 6 GHz. This first AC voltage gain demonstration of a GFET is attributed to the clear current saturation in the device, which is enabled by an ultrathin gate dielectric (4 nm HfO(2)) of the embedded gate structures. The device also shows extrinsic transconductance of 1.2 mS/μm at 1 V drain bias, the highest for graphene FETs using large-scale graphene reported to date.

  2. High-frequency Heating Behavior of Veneer-based Composites: Modelling and Validation

    Directory of Open Access Journals (Sweden)

    Peixing Wei

    2014-04-01

    Full Text Available A one-dimensional theoretical heat and mass transfer model was developed for high-frequency (HF heating of veneer-based composites, such as laminated veneer lumber (LVL and plywood. This model was based on the basic principles of energy and mass conservation, momentum conservation of gas flow, and gas thermodynamic relations. The response variables, including temperature, gas pressure, and moisture content (MC, were linked to basic material properties, such as veneer density, thermal conductivity, permeability, and dielectric properties. Initial and boundary conditions for solving the governing equations were also considered. The model was further validated by experiments with veneer HF heating and LVL HF heating. The model predictions agreed well with the experimental results. During veneer HF heating, the inner veneer core layers had lower MC than the outer surface layers. Compared to conventional hot platen heating, HF heating was proven to be an efficient and robust method for manufacturing veneer-based composites.

  3. High-Dose and High-Frequency Lanreotide Autogel in Acromegaly: A Randomized, Multicenter Study.

    Science.gov (United States)

    Giustina, Andrea; Mazziotti, Gherardo; Cannavò, Salvatore; Castello, Roberto; Arnaldi, Giorgio; Bugari, Giovanna; Cozzi, Renato; Ferone, Diego; Formenti, Anna Maria; Gatti, Enza; Grottoli, Silvia; Maffei, Pietro; Maffezzoni, Filippo; Montini, Marcella; Terzolo, Massimo; Ghigo, Ezio

    2017-07-01

    Increase in drug frequency or dose is recommended for acromegaly patients with partial response to long-acting somatostatin receptor ligands (SRLs). However, the efficacy and safety data with lanreotide (LAN) Autogel (LAN-ATG) at high dose (HD) or high frequency (HF) are still scanty. To evaluate the biochemical efficacy and safety of HF and HD LAN-ATG in patients with active acromegaly. Twenty-four-week prospective, multicenter, randomized, open-label trial. Thirty patients with active acromegaly, partial responders to SRLs, were randomized to HF (120 mg/21 days; 15 patients) or HD (180 mg/28 days; 15 patients) LAN-ATG. Normalization of serum insulin-like growth factor-I (IGF-I) and reduction in random growth hormone (GH) values < 1.0 µg/L, reduction in serum IGF-I and GH from baseline, differences in biochemical response between HF and HD LAN-ATG, adverse events. IGF-I decreased significantly (P = 0.007) during the 24-week treatment, with greater decrease in HD (P = 0.03) vs HF group (P = 0.08). Normalization in IGF-I values occurred in 27.6% of patients (P = 0.016 vs baseline), without a significant difference between HF and HD groups (P = 0.59). The decrease in serum IGF-I significantly correlated with serum LAN values (P = 0.04), and normalization of IGF-I was predicted by baseline IGF-I values (P = 0.02). Serum GH values did not change significantly (P = 0.22). Overall, 19 patients (63.3%) experienced adverse events, all being mild to moderate and transient, without differences between the two therapeutic arms. HF and HD LAN-ATG regimens are effective in normalizing IGF-I values in about one-third of patients with active acromegaly inadequately controlled by long-term conventional SRLs therapy.

  4. High-k perovskite gate oxide BaHfO3

    Directory of Open Access Journals (Sweden)

    Young Mo Kim

    2017-01-01

    Full Text Available We have investigated epitaxial BaHfO3 as a high-k perovskite dielectric. From x-ray diffraction measurement, we confirmed the epitaxial growth of BaHfO3 on BaSnO3 and MgO. We measured optical and dielectric properties of the BaHfO3 gate insulator; the optical bandgap, the dielectric constant, and the breakdown field. Furthermore, we fabricated a perovskite heterostructure field effect transistor using epitaxial BaHfO3 as a gate insulator and La-doped BaSnO3 as a channel layer on SrTiO3 substrate. To reduce the threading dislocations and enhance the electrical properties of the channel, an undoped BaSnO3 buffer layer was grown on SrTiO3 substrates before the channel layer deposition. The device exhibited a field effect mobility value of 52.7 cm2 V−1 s−1, a Ion/Ioff ratio higher than 107, and a subthreshold swing value of 0.80 V dec−1. We compare the device performances with those of other field effect transistors based on BaSnO3 channels and different gate oxides.

  5. High-frequency magnetic components

    CERN Document Server

    Kazimierczuk, Marian K

    2009-01-01

    If you are looking for a complete study of the fundamental concepts in magnetic theory, read this book. No other textbook covers magnetic components of inductors and transformers for high-frequency applications in detail. This unique text examines design techniques of the major types of inductors and transformers used for a wide variety of high-frequency applications including switching-mode power supplies (SMPS) and resonant circuits. It describes skin effect and proximity effect in detail to provide you with a sound understanding of high-frequency phenomena. As well as this, you will disco

  6. Optimum Location and System Engineering of High Power, High Frequency Transmitter-Receiver in Combat Vehicles (Short Communication

    Directory of Open Access Journals (Sweden)

    S. Sathyamurthy

    2010-04-01

    Full Text Available This paper discusses the procedure adapted after carrying out several iterations for selecting an ideal location to introduce a high power high frequency (HF transmitter-receiver in a tactical combat vehicle from electromagnetic compatibility view. This radio set contributes for very high field strength to neighbouring electronic devices and other very high frequency (VHF Tx-Rx situated in the same vehicular platform. An integrated approach was followed in deciding the optimum solution to locate the HF radio set. Leakage from HF radio set is to be minimised within the vehicle to reduce the field coupling level to neighbouring equipment. Radiation from HF antenna was maximised by careful installation of antenna, outside the vehicle environment to ensure optimum radiation of intended signal. Voltage standing wave ratio (VSWR measurement was carried out to verify this. Four different locations experimented have been reported in this paper. The vehicle penetration loss (VPL can reveal the amount of leakage from external field generated by antennas to field inside the turret. The HF, being a congested operating spectrum, due care was taken in electromagnetic interference control of HF-VHF radios and other tank electronic subsystems. High RF power of HF transmitter and very high sensitivity of HF receiver could affect systems either way. Hence, electromagnetic compatibility (EMC measures and optimum location of HF radio set are important from MIL-STD461 C, MIL6051-D/MIL-STD464A point of view.Defence Science Journal, 2010, 60(3, pp.302-306, DOI:http://dx.doi.org/10.14429/dsj.60.357

  7. Morphology and possible origins of near-range oblique HF backscatter at high and midlatitudes

    Science.gov (United States)

    Ponomarenko, Pavlo, V.; Iserhienrhien, Blessing; St.-Maurice, Jean-Pierre

    2016-06-01

    High-frequency radars (HF, ˜10-20 MHz) forming the Super Dual Auroral Radar Network (SuperDARN) regularly observe returns from very close ranges of ≤300-400 km (near-range echoes, NREs). These echoes are conventionally attributed to backscatter from meteor trails, but other sources of NRE have been invoked, including polar mesospheric summer echoes (PMSE), and non-field-aligned E region irregularities leading to high-aspect ionospheric returns. In order to relate NRE to a particular mechanism, it is essential to establish beforehand their spatiotemporal trends with respect to season, local time, and latitude. Systematic information of this kind is generally lacking from the literature, so we attempt to fill the gap by performing a statistical analysis of such echoes observed by five radars covering midlatitudes to polar latitudes over all seasons and local times. We detected two major echo populations which were observed at each radar site: (i) a nightside-early morning returns representing the well-known meteor backscatter and (ii) a midsummer population centered near the local noon. At high latitudes the summer daytime echoes are usually interpreted as PMSE, but the observed population extends to much lower latitudes and is centered well above the conventional PMSE height range. We hypothesize that this population could be related to neutral turbulence in the lower E region. In addition, there was a pronounced evening population restricted to the auroral region which we provisionally attribute to irregularities generated by the precipitating energetic particles and strong electric fields.

  8. High-frequency seafloor acoustics

    National Research Council Canada - National Science Library

    Jackson, D. R; Richardson, M. D

    2007-01-01

    This title provides access to experimental data, theory, and models relevant to high-frequency seafloor acoustics and will be of interest to sonar engineers and researchers working in underwater acoustics...

  9. Geographies of High Frequency Trading

    DEFF Research Database (Denmark)

    Grindsted, Thomas Skou

    2016-01-01

    This paper investigates the geographies of high frequency trading. Today shares shift hands within micro seconds, giving rise to a form of financial geographies termed algorithmic capitalism. This notion refers to the different spatio-temporalities produced by high frequency trading, under...... the valuation of time. As high frequency trading accelerates financial markets, the paper examines the spatio-temporalities of automated trading by the ways in which the speed of knowledge exploitation in financial markets is not only of interest, but also the expansion between different temporalities....... The paper demonstrates how the intensification of time-space compression produces radical new dynamics in the financial market and develops information rent in HFT as convertible to a time rent and a spatio-temporal rent. The final section discusses whether high frequency trading only responds to crises...

  10. Modeling and Mitigation for High Frequency Switching Transients Due to Energization in Offshore Wind Farms

    Directory of Open Access Journals (Sweden)

    Yanli Xin

    2016-12-01

    Full Text Available This paper presents a comprehensive investigation on high frequency (HF switching transients due to energization of vacuum circuit breakers (VCBs in offshore wind farms (OWFs. This research not only concerns the modeling of main components in collector grids of an OWF for transient analysis (including VCBs, wind turbine transformers (WTTs, submarine cables, but also compares the effectiveness between several mainstream switching overvoltage (SOV protection methods and a new mitigation method called smart choke. In order to accurately reproduce such HF switching transients considering the current chopping, dielectric strength (DS recovery capability and HF quenching capability of VCBs, three models are developed, i.e., a user–defined VCB model, a HF transformer terminal model and a three-core (TC frequency dependent model of submarine cables, which are validated through simulations and compared with measurements. Based on the above models and a real OWF configuration, a simulation model is built and several typical switching transient cases are investigated to analyze the switching transient process and phenomena. Subsequently, according to the characteristics of overvoltages, appropriate parameters of SOV mitigation methods are determined to improve their effectiveness. Simulation results indicate that the user–defined VCB model can satisfactorily simulate prestrikes and the proposed component models display HF characteristics, which are consistent with onsite measurement behaviors. Moreover, the employed protection methods can suppress induced SOVs, which have a steep front, a high oscillation frequency and a high amplitude, among which the smart choke presents a preferable HF damping effect.

  11. Investigation and Development of Data-Driven D-Region Model for HF Systems Impacts

    Science.gov (United States)

    Eccles, J. V.; Rice, D.; Sojka, J. J.; Hunsucker, R. D.

    2002-01-01

    Space Environment Corporation (SEC) and RP Consultants (RPC) are to develop and validate a weather-capable D region model for making High Frequency (HF) absorption predictions in support of the HF communications and radar communities. The weather-capable model will assimilate solar and earth space observations from NASA satellites. The model will account for solar-induced impacts on HF absorption, including X-rays, Solar Proton Events (SPE's), and auroral precipitation. The work plan includes: I . Optimize D-region model to quickly obtain ion and electron densities for proper HF absorption calculations. 2. Develop indices-driven modules for D-region ionization sources for low, mid, & high latitudes including X-rays, cosmic rays, auroral precipitation, & solar protons. (Note: solar spectrum & auroral modules already exist). 3. Setup low-cost monitors of existing HF beacons and add one single-frequency beacon. 4. Use PENEX HF-link database with HF monitor data to validate D-region/HF absorption model using climatological ionization drivers. 5. Develop algorithms to assimilate NASA satellite data of solar, interplanetary, and auroral observations into ionization source modules. 6. Use PENEX HF-link & HF-beacon data for skill score comparison of assimilation versus climatological D-region/HF absorption model. Only some satellites are available for the PENEX time period, thus, HF-beacon data is necessary. 7. Use HF beacon monitors to develop HF-link data assimilation algorithms for regional improvement to the D-region/HF absorption model.

  12. Trans-Ionospheric High Frequency Signal Ray Tracing

    Science.gov (United States)

    Wright, S.; Gillespie, R. J.

    2012-09-01

    All electromagnetic radiation undergoes refraction as it propagates through the atmosphere. Tropospheric refraction is largely governed by interaction of the radiation with bounded electrons; ionospheric refraction is primarily governed by free electron interactions. The latter phenomenon is important for propagation and refraction of High Frequency (HF) through Extremely High Frequency (EHF) signals. The degree to which HF to EHF signals are bent is dependent upon the integrated refractive effect of the ionosphere: a result of the signal's angle of incidence with the boundaries between adjacent ionospheric regions, the magnitude of change in electron density between two regions, as well as the frequency of the signal. In the case of HF signals, the ionosphere may bend the signal so much that it is directed back down towards the Earth, making over-the-horizon HF radio communication possible. Ionospheric refraction is a major challenge for space-based geolocation applications, where the ionosphere is typically the biggest contributor to geolocation error. Accurate geolocation requires an algorithm that accurately reflects the physical process of a signal transiting the ionosphere, and an accurate specification of the ionosphere at the time of the signal transit. Currently implemented solutions are limited by both the algorithm chosen to perform the ray trace and by the accuracy of the ionospheric data used in the calculations. This paper describes a technique for adapting a ray tracing algorithm to run on a General-Purpose Graphics Processing Unit (GPGPU or GPU), and using a physics-based model specifying the ionosphere at the time of signal transit. This technique allows simultaneous geolocation of significantly more signals than an equivalently priced Central Processing Unit (CPU) based system. Additionally, because this technique makes use of the most widely accepted numeric algorithm for ionospheric ray tracing and a timely physics-based model of the ionosphere

  13. Electrical activation to the parasternal intercostal muscles during high-frequency spinal cord stimulation in dogs

    Science.gov (United States)

    Kowalski, Krzysztof E.

    2014-01-01

    High-frequency spinal cord stimulation (HF-SCS) is a novel technique of inspiratory muscle activation involving stimulation of spinal cord pathways, which may have application as a method to provide inspiratory muscle pacing in ventilator-dependent patients with spinal cord injury. The purpose of the present study was to compare the spatial distribution of motor drive to the parasternal intercostal muscles during spontaneous breathing with that occurring during HF-SCS. In nine anesthetized dogs, HF-SCS was applied at the T2 spinal level. Fine-wire recording electrodes were used to assess single motor unit (SMU) pattern of activation in the medial bundles of the 2nd and 4th and lateral bundles of the 2nd interspaces during spontaneous breathing and HF-SCS following C1 spinal section. Stimulus amplitude during HF-SCS was adjusted such that inspired volumes matched that occurring during spontaneous breathing (protocol 1). During HF-SCS mean peak SMU firing frequency was highest in the medial bundles of the 2nd interspace (17.1 ± 0.6 Hz) and significantly lower in the lateral bundles of the 2nd interspace (13.5 ± 0.5 Hz) and medial bundles of the 4th (15.2 ± 0.7 Hz) (P intercostal muscles during HF-SCS is similar to that occurring during spontaneous breathing, and 2) differential spatial distribution of parasternal intercostal activation does not depend upon differential descending synaptic input from supraspinal centers. PMID:25342707

  14. Extended high frequency audiometry in secretory otitis media.

    Science.gov (United States)

    Sharma, Deepika; Munjal, Sanjay K; Panda, Naresh K

    2012-06-01

    The objective of the present study was to determine the status of extended high frequencies in subjects with secretory otitis media. The study evaluated 30 ears of 20 subjects with secretory otitis media in the age group of 15-30 years. This data was compared with 20 ears of 10 volunteers of the same age group with clinically normal hearing. Pure tone air conduction thresholds were analyzed in three frequency groups: low frequency (LF: 0.25, 0.5, and 1 kHz), high frequency (HF: 2, 4, and 8 kHz) and extended high frequency (EHF: 10, 12, and 16 kHz). The results showed elevated extended high frequency thresholds (EHFG) as compared to control group and comparatively better thresholds at high frequencies(HFG)s as compared to low (LFG)and extended high frequencies(EHFG) in the study group. This validates the importance of including an extended high frequency audiometry in the test battery of patients with secretory otitis media.

  15. Kr对HF(X1Σ+)基频和泛频的影响%Influence of Kr Atoms on the Fundamental and Overtone Vibrational Frequency for HF(X1Σ+)

    Institute of Scientific and Technical Information of China (English)

    谢洪平; 陈泽琴; 蒋刚; 杨迎春; 朱正和

    2000-01-01

    运用Monte-Carlo轨迹法研究了Kr(1Sg)+HF(X1Σ+;ν=1,2,3;J=4)→Kr(1Sg)+HF(X1Σ+,ν',J')的碰撞过程,从而分析Kr原子对HF基频和泛频的影响。研究表明:在初始相对平动能Et≤251.0kJ/mol时,Kr原子能够减少产生基频的粒子数反转,增加产生泛频特别是ν'=2能级的粒子数反转,并且,Kr原子有较强的弛豫高转动态(J'≥4)的能力,因此,Kr原子对HF泛频激光在提高光强和增强大气传输能力方面均有 较大的改善。%The collision reaction that Kr(1Sg)+HF(X1Σ+;ν=1,2,3;J=4)→Kr(1Sg)+HF(X1Σ+;ν',J')has been studied using Monte-Carlo trajectory method,and it has been found that Kr atoms have in fluence on the fundamental and overtone vibrational frequency for HF(X1Σ+).The studying results show that,when the initial relative translational energy Et≤251.0kJ/mol,Kr atoms can reduce the particle number reversion of the fundamental vibrational frequency,and increase it of the overtone vibrational frequency,particularly in the energy level ν'=2,and Kr atoms are more strong on relaxing the higher rotational states(J'≥4).Thus,for hydrogen fluoride(HF)overtone frequency laser Kr atoms can obviously increase the strength of light and improve the transmission property in the air.

  16. Far-Field Testing Method of Spurious Emission Produced by HF RFID

    OpenAIRE

    Nikola Gvozdenovic; Ralph Prestros; Mecklenbräuker, Christoph F.

    2016-01-01

    We present measurements of spurious emission produced by high-frequency radio frequency identification (HF RFID) using carrier frequency of 13.56 MHz. HF RFID tags produce unwanted emission due to rectification and more generally due to nonlinearity of analog front end. Depending on the conducting material of an HF RFID coil and surrounding dielectric material, the coil behaves as more or less good antenna on some harmonic frequencies. Exact characterization and analysis of unwanted emission ...

  17. Low Threshold Voltage and High Mobility N-Channel Metal-Oxide-Semiconductor Field-Effect Transistor Using Hf-Si/HfO2 Gate Stack Fabricated by Gate-Last Process

    Science.gov (United States)

    Ando, Takashi; Hirano, Tomoyuki; Tai, Kaori; Yamaguchi, Shinpei; Yoshida, Shinichi; Iwamoto, Hayato; Kadomura, Shingo; Watanabe, Heiji

    2010-01-01

    Systematic characterization of Hf-Si/HfO2 gate stacks revealed two mobility degradation modes. One is carrier scattering by fixed charges and/or trapped charges induced by the crystallization in the thick HfO2 case (inversion oxide thickness, Tinv> 1.6 nm). The other is the Hf penetration into the interfacial layer with the Si substrate in the thin HfO2 case (Tinv< 1.6 nm) for the Hf-rich electrode. It was demonstrated that careful optimization of the HfO2 thickness and the Hf-Si composition can suppress both modes. As a result, a high electron mobility equivalent to that of n+polycrystalline silicon (poly-Si)/SiO2 (248 cm2 V-1 s-1 at Eeff=1 MV/cm) was obtained at Tinv of 1.47 nm. Moreover, the effective work function of the optimized Hf-Si/HfO2 gate stack is located within 50 mV from the Si band edge (Ec). An extremely high Ion of 1165 µA/µm (at Ioff = 81 nA/µm) at Vdd=1.0 V was demonstrated for a 45 nm gate n-channel metal-oxide-semiconductor field-effect transistor (n-MOSFET) without strain enhanced technology.

  18. High-k Dielectrics for Application in Broadband Radio Frequency-Microelectromechanical System Capacitive Shunt Switch

    Science.gov (United States)

    Zhang, Yi; Lu, Jian; Ichiki, Masaaki; Onodera, Kazumasa; Maeda, Ryutaro

    130 nm-thick lead zirconate titanate(PZT)/45 nm-thick HfO2 stack and single 45 nm-thick HfO2 dielectric film were utilized as insulator layer in π-type radio frequency (RF) capacitive shunt switches for achieving high isolation performance in broadband application. Thin PZT film in perovskite structure mainly with (1 1 1) orientation was successfully prepared at low temperature (500°C) using sol-gel method. The thin PZT film exhibited excellent ferroelectric properties and high dielectric constant (k ≈ 1185). Thin HfO2 film was prepared by sputtering method in a gas mixture of O2 and Ar. The thin HfO2 film had the dielectric constant of about 17 and the dielectric strength of about 24 MV/cm. The switch of PZT/HfO2 stack dielectric showed isolation performance better than -20 dB in the frequency range of 1 ∼ 35 GHz. The switch of HfO2 had isolation performance better than -40 dB in the frequency of 5 ∼ 35 GHz, suggesting its attractive prospective in practical broadband application.

  19. Physics of the Geospace Response to Powerful HF Radio Waves

    Science.gov (United States)

    2012-10-31

    studies of the response of the Earth’s space plasma to high-power HF radio waves from the High-frequency Active Auroral Research Program ( HAARP ...of HF heating and explored to simulate artificial ducts. DMSP- HAARP experiments revealed that HF-created ion outflows and artificial density ducts...in the topside ionosphere appeared faster than predicted by the models, pointing to kinetic (suprathermal) effects. CHAMP/GRACE- HAARP experiments

  20. Coupled solitons of intense high-frequency and low-frequency waves in Zakharov-type systems

    Science.gov (United States)

    Gromov, Evgeny; Malomed, Boris

    2016-12-01

    One-parameter families of exact two-component solitary-wave solutions for interacting high-frequency (HF) and low-frequency (LF) waves are found in the framework of Zakharov-type models, which couple the nonlinear Schrödinger equation for intense HF waves to the Boussinesq (Bq) or Korteweg-de Vries (KdV) equation for the LF component through quadratic terms. The systems apply, in particular, to the interaction of surface (HF) and internal (LF) waves in stratified fluids. These solutions are two-component generalizations of the single-component Bq and KdV solitons. Perturbed dynamics and stability of the solitary waves are studied in detail by means of analytical and numerical methods. Essentially, they are stable against separation of the HF and LF components if the latter one is shaped as a potential well acting on the HF field, and unstable, against splitting of the two components, with a barrier-shaped LF one. Collisions between the solitary waves are studied by means of direct simulations, demonstrating a trend to merger of in-phase solitons, and elastic interactions of out-of-phase ones.

  1. Characterization of Stoichiometric and Aging Effects on NiTiHf High Temperature Shape Memory Alloys

    Science.gov (United States)

    Coughlin, Daniel Robert

    NiTiHf ternary alloys exhibit attractive high temperature shape memory alloy (HTSMA) properties. Material properties include moderate transformation strain, relatively high transformation temperature, stable pseudoelastic (PE) behavior, and very small irrecoverable strain during load biased tests. The addition of Hf is more attractive than Pt and Pd due to the fact that Hf has a lower cost. Four NiTiHf alloys with different chemical compositions spanning stoichiometry were used to analyze microstructure and mechanical behavior. Research will mainly be focused on the Ni-rich alloys based on that the Ni-lean alloys do not exhibit the previously mentioned HTSMA material properties. The alloys analyzed all had 20(at.)% Hf with varying Ti concentrations (29(at.)%, 29.7(at.)%, 30(at.)%, and 30.5(at.)%). All of the alloys were formed by induction melting, homogenized at 1050C for 72hrs, and then hot extruded with a diameter reduction of 7:1 at a temperature of 900C. In addition to the homogenized and extruded condition, several short-term aging cycles above 400C were completed on each of the alloys. Certain microstructure and mechanical properties are obtained when Hf is added to NiTi and a proper aging cycle is used. Results from isothermal compression tests that were executed above the austenite finish temperature determined that the Ni-rich NiTiHf alloys exhibited all the necessary properties to be considered for HTSMA applications. The test temperature range of the isothermal compression tests were chosen to characterize the transition from PE behavior to austenite plasticity and to examine the deformation behavior of the B2 phase at high temperatures. Results from compression tests showed a strengthening effect when the test temperature was increased through the PE test region. The strengthening effect is due to the yield stress and plasticity being related to the stress induced martensite that is created during the compression test executed above the austenite

  2. Additive Manufacturing of NiTiHf High Temperature Shape Memory Alloy

    Science.gov (United States)

    Benafan, Othmane; Bigelow, Glen S.; Elahinia, Mohammad; Moghaddam, Narges Shayesteh; Amerinatanzi, Amirhesam; Saedi, Soheil; Toker, Guher Pelin; Karaca, Haluk

    2017-01-01

    Additive manufacturing of a NiTi-20Hf high temperature shape memory alloy (HTSMA) was investigated. A selective laser melting (SLM) process by Phenix3D Systems was used to develop components from NiTiHf powder (of approximately 25-75 m particle fractions), and the thermomechanical response was compared to the conventionally vacuum induction skull melted counterpart. Transformation temperatures of the SLM material were found to be slightly lower due to the additional oxygen pick up from the gas atomization and melting process. The shape memory response in compression was measured for stresses up to 500 MPa, and transformation strains were found to be very comparable (Up to 1.26 for the as-extruded; up to 1.52 for SLM).

  3. Senary Refractory High-Entropy Alloy HfNbTaTiVZr

    Science.gov (United States)

    Gao, M. C.; Zhang, B.; Yang, S.; Guo, S. M.

    2016-07-01

    Discovery of new single-phase high-entropy alloys (HEAs) is important to understand HEA formation mechanisms. The present study reports computational design and experimental validation of a senary HEA, HfNbTaTiVZr, in a body-centered cubic structure. The phase diagrams and thermodynamic properties of this senary system were modeled using the CALPHAD method. Its atomic structure and diffusion constants were studied using ab initio molecular dynamics simulations. The microstructure of the as-cast HfNbTaTiVZr alloy was studied using X-ray diffraction and scanning electron microscopy, and the microsegregation in the as-cast state was found to qualitatively agree with the solidification predictions from CALPHAD. Supported by both simulation and experimental results, the HEA formation rules are discussed.

  4. High-temperature phase transitions in SrHfO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Kennedy, B.J.; Howard, C.J. [School of Chemistry, The University of Sydney, Sydney, New South Wales 2006 (Australia); Chakoumakos, B.C. [Solid State Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)

    1999-08-01

    The crystal structure of SrHfO{sub 3} has been studied at high temperatures using powder neutron diffraction and the Rietveld method. From 300 K to approximately 670 K the structure of SrHfO{sub 3} is orthorhombic ({ital Pnma}). By 870 K the material adopts a second orthorhombic structure ({ital Cmcm}). The material then undergoes a further phase transition and is tetragonal (I4/mcm) from {approximately}1000 to 1353 K. At higher temperatures ({gt}1360 K) the structure is the ideal cubic perovskite (Pm{bar 3}m). The angle of rotation of the oxygen octahedron in the tetragonal phase is taken as the order parameter and its temperature variation is consistent with a second order phase transition. {copyright} {ital 1999} {ital The American Physical Society}

  5. High-frequency Trader Subjectivity

    DEFF Research Database (Denmark)

    Borch, Christian; Lange, Ann-Christina

    2017-01-01

    In this article, we examine the recent shift in financial markets toward high-frequency trading (HFT). This turn is being legitimized with reference to how algorithms are allegedly more rational and efficient than human traders, and less prone to emotionally motivated decisions. We argue...... that although HFT does not render humans irrelevant, it is leading to a reconfiguration of both the ideal trading subject and the human–machine relations. Drawing on interviews with and ethnographic observations of high-frequency traders, as well as HFT ‘how to’ books, we analyze the subjectivity and self......-techniques of the ideal high-frequency trader. We demonstrate that these traders face the challenge of avoiding emotional interference in their algorithms and that they deploy a set of disciplinary self-techniques to curb the importance of emotional attachment....

  6. High-frequency complex pitch

    DEFF Research Database (Denmark)

    Santurette, Sébastien; Dau, Torsten

    2012-01-01

    Harmonics in a complex tone are typically considered unresolved when they interact with neighboring harmonics in the cochlea and cannot be heard out separately. Recent studies have suggested that the low pitch evoked by unresolved high-frequency harmonics may be coded via temporal fine-structure ......Harmonics in a complex tone are typically considered unresolved when they interact with neighboring harmonics in the cochlea and cannot be heard out separately. Recent studies have suggested that the low pitch evoked by unresolved high-frequency harmonics may be coded via temporal fine...

  7. 75 FR 81284 - Nationwide Use of High Frequency and Ultra High Frequency Active SONAR Technology; Draft...

    Science.gov (United States)

    2010-12-27

    ... SONAR technologies that operate at frequencies of 50 kiloHertz (kHz) and greater from mobile platforms... proposes to use HF and UHF SONAR technology from mobile platforms nationwide. Mobile platforms include...-specific, non-mobile operating scenarios or newly developed technologies fall outside of the scope of...

  8. Readout for intersatellite laser interferometry: Measuring low frequency phase fluctuations of HF signals with microradian precision

    CERN Document Server

    Gerberding, Oliver; Kullmann, Joachim; Tröbs, Michael; Bykov, Ioury; Barke, Simon; Brause, Nils Christopher; Delgado, Juan José Esteban; Schwarze, Thomas S; Reiche, Jens; Danzmann, Karsten; Rasmussen, Torben; Hansen, Torben Vendt; Engaard, Anders; Pedersen, Søren Møller; Jennrich, Oliver; Suess, Martin; Sodnik, Zoran; Heinzel, Gerhard

    2015-01-01

    Precision phase readout of optical beat note signals is one of the core techniques required for intersatellite 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, with a precision in the order of $\\mu \\textrm{rad}/\\sqrt{\\textrm{Hz}}$ at frequencies between $0.1\\,\\textrm{mHz}$ and $1\\,\\textrm{Hz}$. In this paper, we present phase readout systems, so-called phasemeters, that are able to achieve such precisions and we discuss various means that have been employed to reduce noise in the analogue circuit domain and during digitisation. We also discuss the influence of some non-linear noise sources in the analogue domain of such phasemeters. And finally, we present the performance that was achieved during testing of the elegant breadboard model of the LISA phasemeter, that was developed in the scope of an ESA technology development activity.

  9. Determining Energy Distributions of HF-Accelerated Electrons at HAARP

    Science.gov (United States)

    2015-11-18

    AFRL-AFOSR-VA-TR-2015-0383 Determining energy distributions of HF-accelerated electrons at HAARP Christopher Fallen University of Alaska Fairbanks...2012 - 11/14/2015 4. TITLE AND SUBTITLE Determining energy distributions of HF-accelerated electrons at HAARP 5a. CONTRACT NUMBER FA9550-12-1-0424...transmitted from the High-frequency Active Auroral Research Program ( HAARP ) transmitter in Alaska. For a given fixed HF-plasma interaction altitude

  10. High-frequency TRNS reduces BOLD activity during visuomotor learning.

    Directory of Open Access Journals (Sweden)

    Catarina Saiote

    Full Text Available Transcranial direct current stimulation (tDCS and transcranial random noise stimulation (tRNS consist in the application of electrical current of small intensity through the scalp, able to modulate perceptual and motor learning, probably by changing brain excitability. We investigated the effects of these transcranial electrical stimulation techniques in the early and later stages of visuomotor learning, as well as associated brain activity changes using functional magnetic resonance imaging (fMRI. We applied anodal and cathodal tDCS, low-frequency and high-frequency tRNS (lf-tRNS, 0.1-100 Hz; hf-tRNS 101-640 Hz, respectively and sham stimulation over the primary motor cortex (M1 during the first 10 minutes of a visuomotor learning paradigm and measured performance changes for 20 minutes after stimulation ceased. Functional imaging scans were acquired throughout the whole experiment. Cathodal tDCS and hf-tRNS showed a tendency to improve and lf-tRNS to hinder early learning during stimulation, an effect that remained for 20 minutes after cessation of stimulation in the late learning phase. Motor learning-related activity decreased in several regions as reported previously, however, there was no significant modulation of brain activity by tDCS. In opposition to this, hf-tRNS was associated with reduced motor task-related-activity bilaterally in the frontal cortex and precuneous, probably due to interaction with ongoing neuronal oscillations. This result highlights the potential of lf-tRNS and hf-tRNS to differentially modulate visuomotor learning and advances our knowledge on neuroplasticity induction approaches combined with functional imaging methods.

  11. The real-time HF frequency prediction service based on the development of an assimilative IRI model using the Digisonde observation in Korea.

    Science.gov (United States)

    Oh, Seung Jun; Chung, Jong-Kyun; Lee, Sungho; Lee, Jeong-Deok; Moon, Joon-Cheol

    The IRI(International Reference Ionosphere) is an international project sponsored by the Committee on Space Research (COSPAR) and the International Union of Radio Science (URSI), and it has produced an empirical standard model of the ionosphere based on all available data sources from the worldwide network of ionosonde. The model is now widely used to provide HF prediction services to HF users by the radio science-related organizations in the world. However, the accurate representation of the regional ionosphere, especially the effect of space weather, for a real-time HF prediction by using lRI, is hampered by the limitation of its performance since the model is designed as a climatological model. We have developed an assimilative IRI model using the real-time Digisonde data from two stations (Icheon and Jeju) in Korea. The data stream from the stations is ingested by the model every 30 minute to create the real-time updated CCIR/URSI maps of coefficients that are applied for the real-time usable HF frequency prediction service. Test results for the model output comparing with observed data are presented and we briefly introduce the HF prediction service operated by Korean Space Weather Center, Radio Research Agency (KSWC, RRA), Korea.

  12. High frequency QRS ECG predicts ischemic defects during myocardial perfusion imaging

    Science.gov (United States)

    Rahman, Atiar

    2006-01-01

    Background: Changes in high frequency QRS components of the electrocardiogram (HF QRS ECG) (150-250 Hz) are more sensitive than changes in conventional ST segments for detecting myocardial ischemia. We investigated the accuracy of 12-lead HF QRS ECG in detecting ischemia during adenosine tetrofosmin myocardial perfusion imaging (MPI). Methods and Results: 12-lead HF QRS ECG recordings were obtained from 45 patients before and during adenosine technetium-99 tetrofosmin MPI tests. Before the adenosine infusions, recordings of HF QRS were analyzed according to a morphological score that incorporated the number, type and location of reduced amplitude zones (RAZs) present in the 12 leads. During the adenosine infusions, recordings of HF QRS were analyzed according to the maximum percentage changes (in both the positive and negative directions) that occurred in root mean square (RMS) voltage amplitudes within the 12 leads. The best set of prospective HF QRS criteria had a sensitivity of 94% and a specificity of 83% for correctly identifying the MPI result. The sensitivity of simultaneous ST segment changes (18%) was significantly lower than that of any individual HF QRS criterion (Pperfusion defects during adenosine MPI stress tests and significantly more sensitive than analysis of conventional ST segments.

  13. High-Frequency Electron Paramagnetic Resonance Spectroscopy of Nitroxide-Functionalized Nanodiamonds in Aqueous Solution.

    Science.gov (United States)

    Akiel, R D; Stepanov, V; Takahashi, S

    2016-06-21

    Nanodiamond (ND) is an attractive class of nanomaterial for fluorescent labeling, magnetic sensing of biological molecules, and targeted drug delivery. Many of those applications require tethering of target biological molecules on the ND surface. Even though many approaches have been developed to attach macromolecules to the ND surface, it remains challenging to characterize dynamics of tethered molecule. Here, we show high-frequency electron paramagnetic resonance (HF EPR) spectroscopy of nitroxide-functionalized NDs. Nitroxide radical is a commonly used spin label to investigate dynamics of biological molecules. In the investigation, we developed a sample holder to overcome water absorption of HF microwave. Then, we demonstrated HF EPR spectroscopy of nitroxide-functionalized NDs in aqueous solution and showed clear spectral distinction of ND and nitroxide EPR signals. Moreover, through EPR spectral analysis, we investigate dynamics of nitroxide radicals on the ND surface. The demonstration sheds light on the use of HF EPR spectroscopy to investigate biological molecule-functionalized nanoparticles.

  14. High-Frequency Seafloor Acoustics

    CERN Document Server

    Jackson, Darrell R

    2007-01-01

    High-Frequency Seafloor Acoustics is the first book in a new series sponsored by the Office of Naval Research on the latest research in underwater acoustics. This exciting new title provides ready access to experimental data, theory, and models relevant to high-frequency seafloor acoustics and will be of interest to sonar engineers and researchers working in underwater acoustics. The physical characteristics of the seafloor affecting acoustic propagation and scattering are covered, including physical and geoacoustic properties and surface roughness. Current theories for acoustic propagation in sediments are presented along with corresponding models for reflection, scattering, and seafloor penetration. The main text is backed up by an extensive bibliography and technical appendices.

  15. High frequency trading and fragility

    OpenAIRE

    Cespa, Giovanni; Vives, Xavier

    2017-01-01

    We show that limited dealer participation in the market, coupled with an informational friction resulting from high frequency trading, can induce demand for liquidity to be upward sloping and strategic complementarities in traders’ liquidity consumption decisions: traders demand more liquidity when the market becomes less liquid, which in turn makes the market more illiquid, fostering the initial demand hike. This can generate market instability, where an initial dearth of liquidity degenerat...

  16. Which is the Appropriate Frequency of TENS in Managing Knee Osteoarthritis: High or Low Frequency?

    Directory of Open Access Journals (Sweden)

    Esra Erkol Ižnal

    2014-12-01

    Full Text Available Aim: To clarify the optimal Transcutaneous Electrical Nerve Stimulation (TENS frequency in managing pain and functional deficiency and the efficacy of low frequency (LF and high frequency (HF -TENS on pain and functional status in patients with knee osteoarthritis (OA. Material and Method: Ninety-three female patients with symptomatic knee OA were enrolled in this study. All the patients were randomly divided sham or LF or HF-TENS groups with five sessions/week of physical therapy as 20 minutes hot pack, 5 minutes therapeutic ultrasonography, and exercise program. Pain on the Visual Analog Scale (VAS in rest and motion, durations of walk, climbing up and down stairs and pain, stiffness, function and total scores of Western Ontario and McMaster Universities osteoarthritis index (WOMAC were assessed at baseline, after therapy and 4 weeks after the therapy. Results: The VAS pain in rest and motion were found to be significantly different for each therapy group within the three visits (p

  17. Highly ordered nanotubular film formation on Ti–25Nb–xZr and Ti–25Ta–xHf

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jeong-Jae; Byeon, In-Seop [Department of Dental Materials, Research Center of Nano-Interface Activation for Biomaterials, & Research Center for Oral Disease Regulation of the Aged, College of Dentistry, Chosun University, Gwangju (Korea, Republic of); Brantley, William A. [Division of Restorative Sciences and Prosthodontics, College of Dentistry, The Ohio State University, Columbus, OH (United States); Choe, Han-Cheol, E-mail: hcchoe@chosun.ac.kr [Department of Dental Materials, Research Center of Nano-Interface Activation for Biomaterials, & Research Center for Oral Disease Regulation of the Aged, College of Dentistry, Chosun University, Gwangju (Korea, Republic of)

    2015-12-01

    The purpose of this study was to investigate the highly ordered nanotubular film formation on Ti–25Nb–xZr and Ti–25Ta–xHf, examining the roles of niobium, zirconium, tantalum and hafnium alloying elements. The Ti–25Nb–xZr and Ti–25Ta–xHf ternary alloys contained 0, 7 and 15 wt.% of these alloying elements and were manufactured using a vacuum arc-melting furnace. Cast ingots of the alloys were homogenized in Ar atmosphere at 1050 °C for 2 h, followed by quenching into ice water. Formation of nanotubular films was achieved by an electrochemical method in 1 M H{sub 3}PO{sub 4} + 0.8 wt.% NaF at 30 V and 1 h for the Ti–25Nb–xZr alloys and 2 h for the Ti–25Ta–xHf alloys. Microstructures of the Ti–25Ta–xHf alloys transformed from α″ phase to β phase, changing from a needle-like structure to an equiaxed structure as the Hf content increased. In a similar manner, the needle-like structure of the Ti–25Nb–xZr alloys transformed to an equiaxed structure as the Zr content increased. Highly ordered nanotubes formed on the Ti–25Ta–15Hf and Ti–25Nb–15Zr alloys compared to the other alloys, and the nanotube layer thickness on Ti–25Ta–15Hf and Ti–25Nb–15Zr was greater than for the other alloys. Nanotubes formed on Ti–25Ta–15Hf and Ti–25Nb–15Zr showed two sizes of highly ordered structures. The diameters of the large nanotubes decreased and the diameters of the small nanotubes increased as Zr and Hf contents increased. It was found that the layer thickness, diameter, surface density and growth rate of nanotubes on the Ti–25Ta–xHf and Ti–25Nb–xZr alloys can be controlled by varying the Hf and Zr contents. X-ray diffraction analyses revealed only weak peaks for crystalline anatase or rutile TiO{sub 2} phases from the nanotubes on the Ti–25Nb–xZr and Ti–25Ta–xHf alloys, indicating a largely amorphous condition. - Highlights: • Nanotubular film formation on anodized Ti-25Nb-xZr and Ti-25Ta-xHf (x = 0, 7 and

  18. Improving NASICON Sinterability through Crystallization under High Frequency Electrical Fields

    Directory of Open Access Journals (Sweden)

    Ilya eLisenker

    2016-03-01

    Full Text Available The effect of high frequency (HF electric fields on the crystallization and sintering rates of a lithium aluminum germanium phosphate (LAGP ion conducting ceramic was investigated. LAGP with the nominal composition Li1.5Al0.5Ge1.5(PO43 was crystallized and sintered, both conventionally and under effect of electrical field. Electrical field application, of 300V/cm at 1MHz, produced up to a 40% improvement in sintering rate of LAGP that was crystallized and sintered under the HF field. Heat sink effect of the electrodes appears to arrest thermal runaway and subsequent flash behavior. Sintered pellets were characterized using XRD, SEM, TEM and EIS to compare conventionally and field sintered processes. The as-sintered structure appears largely unaffected by the field as the sintering curves tend to converge beyond initial stages of sintering. Differences in densities and microstructure after 1 hour of sintering were minor with measured sintering strains of 31% vs. 26% with and without field, respectively . Ionic conductivity of the sintered pellets was evaluated and no deterioration due to the use of HF field was noted, though capacitance of grain boundaries due to secondary phases was significantly increased.

  19. High-frequency submicrosecond electroporator

    Directory of Open Access Journals (Sweden)

    Vitalij Novickij

    2016-05-01

    Full Text Available In this work, we present a novel electroporator which is capable of generating single and bursts of high power (3 kV, 60 A square wave pulses of variable duration (100 ns to 1 ms with predefined repetition frequency (1 Hz to 3.5 MHz. The proposed synchronized crowbar implementation ensures a constant pulse rise and fall times, which are independent from the load, thus highly relevant in electroporation. The electroporator was successfully tested for the inactivation of the human pathogen Candida albicans. The device is compatible with standard commercial electroporation cuvettes.

  20. High-current, high-frequency capacitors

    Science.gov (United States)

    Renz, D. D.

    1983-06-01

    The NASA Lewis high-current, high-frequency capacitor development program was conducted under a contract with Maxwell Laboratories, Inc., San Diego, California. The program was started to develop power components for space power systems. One of the components lacking was a high-power, high-frequency capacitor. Some of the technology developed in this program may be directly usable in an all-electric airplane. The materials used in the capacitor included the following: the film is polypropylene, the impregnant is monoisopropyl biphenyl, the conductive epoxy is Emerson and Cuming Stycast 2850 KT, the foil is aluminum, the case is stainless steel (304), and the electrode is a modified copper-ceramic.

  1. High-spin states and lifetime measurements in sup 1 sup 7 sup 1 Hf

    CERN Document Server

    Cullen, D M; Appelbe, D E; Wilson, A N; Paul, E S; Bergström, M H; Sharpey-Schafer, J F; Baktash, C; Frosch, I; Lee, I Y; Macchiavelli, A O; MacLeod, R W; Prevost, D; Theisen, C; Curien, D

    2000-01-01

    This paper describes the results of two complementary experiments which studied the properties of the well-deformed nucleus sup 1 sup 7 sup 1 Hf. The first experiment, with a thin self-supporting target, extended the rotational bands built upon the [633]7/2, [512]5/2 and [521]1/2 configurations up to spins of 73/2-85/2 Planck constant. The configurations of these bands and observed band crossings are discussed within the framework of the cranked-shell model. The second experiment employed a backed target in order to measure the lifetimes, by the Doppler Shift Attenuation method, and thereby establish deformations for some of the states in the collective rotational bands. The extracted deformations are found to be consistent with those predicted from theoretical Total Routhian Surface calculations. These deformations provide strong evidence that the high-spin states in sup 1 sup 7 sup 1 Hf, and perhaps more importantly, in the region where the high-K (K suppi=19/2 sup + and K suppi=23/2 sup -) isomeric states ...

  2. Stress Recovery Effects of High- and Low-Frequency Amplified Music on Heart Rate Variability

    Directory of Open Access Journals (Sweden)

    Yoshie Nakajima

    2016-01-01

    Full Text Available Sounds can induce autonomic responses in listeners. However, the modulatory effect of specific frequency components of music is not fully understood. Here, we examined the role of the frequency component of music on autonomic responses. Specifically, we presented music that had been amplified in the high- or low-frequency domains. Twelve healthy women listened to white noise, a stress-inducing noise, and then one of three versions of a piece of music: original, low-, or high-frequency amplified. To measure autonomic response, we calculated the high-frequency normalized unit (HFnu, low-frequency normalized unit, and the LF/HF ratio from the heart rate using electrocardiography. We defined the stress recovery ratio as the value obtained after participants listened to music following scratching noise, normalized by the value obtained after participants listened to white noise after the stress noise, in terms of the HFnu, low-frequency normalized unit, LF/HF ratio, and heart rate. Results indicated that high-frequency amplified music had the highest HFnu of the three versions. The stress recovery ratio of HFnu under the high-frequency amplified stimulus was significantly larger than that under the low-frequency stimulus. Our results suggest that the high-frequency component of music plays a greater role in stress relief than low-frequency components.

  3. High-frequency magnetic components

    CERN Document Server

    Kazimierczuk, Marian K

    2013-01-01

    A unique text on the theory and design fundaments of inductors and transformers, updated with more coverage on the optimization of magnetic devices and many new design examples The first edition is popular among a very broad audience of readers in different areas of engineering and science. This book covers the theory and design techniques of the major types of high-frequency power inductors and transformers for a variety of applications, including switching-mode power supplies (SMPS) and resonant dc-to-ac power inverters and dc-to-dc power converters. It describes eddy-current phenomena (su

  4. Mitigating Doppler shift effect in HF multitone data modem

    Science.gov (United States)

    Sonlu, Yasar

    1989-09-01

    Digital communications over High Frequency (HF) radio channels are getting important in recent years. Current HF requirements are for data transmission at rates 2.4 kbps or more to accommodate computer data links and digital secure voice. HF modems which were produced to meet these speeds are, serial modems and parallel modems. On the other hand, the HF sky-wave communication medium, the ionosphere, has some propagation problems such as multipath and Doppler shift. The effect of Doppler shift in a parallel modem which employs Differential Quadrature Phase Shift Keying (DQPSK) modulation is considered and a correction method to mitigate the Doppler Shift effect is introduced.

  5. Magnetic Field Generation and B-Dot Sensor Characterization in the High Frequency Band

    Science.gov (United States)

    2012-03-01

    date Dr. Andrew J, Terzuoli, PhD (Member) date Dr. Michael J. Havrilla , PhD (Member) date AFIT/GE/ENG/12-20 Abstract Designing a high frequency (HF... Havrilla for their help in my research. Also, despite being deployed during the majority of my time at AFIT, Major Gooodman played an important role which

  6. MIMO High Frequency Surface Wave Radar Using Sparse Frequency FMCW Signals

    Directory of Open Access Journals (Sweden)

    Mengguan Pan

    2017-01-01

    Full Text Available The heavily congested radio frequency environment severely limits the signal bandwidth of the high frequency surface wave radar (HFSWR. Based on the concept of multiple-input multiple-output (MIMO radar, we propose a MIMO sparse frequency HFSWR system to synthesize an equivalent large bandwidth waveform in the congested HF band. The utilized spectrum of the proposed system is discontinuous and irregularly distributed between different transmitting sensors. We investigate the sparse frequency modulated continuous wave (FMCW signal and the corresponding deramping based receiver and signal processor specially. A general processing framework is presented for the proposed system. The crucial step is the range-azimuth processing and the sparsity of the carrier frequency causes the two-dimensional periodogram to fail when applied here. Therefore, we introduce the iterative adaptive approach (IAA in the range-azimuth imaging. Based on the initial 1D IAA algorithm, we propose a modified 2D IAA which particularly fits the deramping processing based range-azimuth model. The proposed processing framework for MIMO sparse frequency FMCW HFSWR with the modified 2D IAA applied is shown to have a high resolution and be able to provide an accurate and clear range-azimuth image which benefits the following detection process.

  7. High strain rate sensitivity of hardness in quinary Ti-Zr-Hf-Cu-Ni high entropy metallic glass thin films

    Science.gov (United States)

    Zhao, Shaofan; Wang, Haibin; Xiao, Lin; Guo, Nan; Zhao, Delin; Yao, Kefu; Chen, Na

    2017-10-01

    Quinary Ti-Zr-Hf-Cu-Ni high-entropy metallic glass thin films were produced by magnetron sputter deposition. Nanoindentation tests indicate that the deposited film exhibits a relatively large hardness of 10.4±0.6 GPa and a high elastic modulus of 131±11 GPa under the strain rate of 0.5 s-1. Specifically, the strain rate sensitivity of hardness measured for the thin film is 0.05, the highest value reported for metallic glasses so far. Such high strain rate sensitivity of hardness is likely due to the high-entropy effect which stabilizes the amorphous structure with enhanced homogeneity.

  8. Diaphragm activation via high frequency spinal cord stimulation in a rodent model of spinal cord injury.

    Science.gov (United States)

    Kowalski, Krzysztof E; Hsieh, Yee-Hsee; Dick, Thomas E; DiMarco, Anthony F

    2013-09-01

    As demonstrated in a canine model, high frequency spinal cord stimulation (HF-SCS) is a novel and more physiologic method of electrical activation of the inspiratory muscles compared to current techniques. The dog model, however, has significant limitations due to cost and societal concerns. Since the rodent respiratory system is also a relevant model for the study of neuronal circuitry function, the aims of the present study were to a) assess the effects of HF-SCS and b) determine the methodology of application of this technique in rats. In 9 Sprague Dawley rats, diaphragm multiunit and single motor unit EMG activity were assessed during spontaneous breathing and HF-SCS applied on the ventral epidural surface of the spinal cord at the T2 level following C1 spinal section. As in dogs, HF-SCS results in the activation of the diaphragm at physiological firing frequencies and the generation of large inspired volumes. Mean maximum firing frequencies of the diaphragm during spontaneous breathing and HF-SCS were 23.3 ± 1.4 Hz (range: 9.8-51.6 Hz) and 26.6 ± 1.3 Hz; range: 12.0-72.9 Hz, respectively, at comparable inspired volumes. Moreover, HF-SCS was successful in pacing these animals over a 60-min period without evidence of system fatigue. Our results suggest that, similar to the dog model, HF-SCS in the rat results in the activation of spinal cord tracts which synapse with the phrenic motoneuron pool, allowing the processing of the stimulus and consequent physiologic activation of the inspiratory muscles. The rat may be a useful model for further studies evaluating phrenic motoneuron physiology. Copyright © 2013 Elsevier Inc. All rights reserved.

  9. Reliability study of Zr and Al incorporated Hf based high-k dielectric deposited by advanced processing

    Science.gov (United States)

    Bhuyian, Md Nasir Uddin

    Hafnium-based high-kappa dielectric materials have been successfully used in the industry as a key replacement for SiO2 based gate dielectrics in order to continue CMOS device scaling to the 22-nm technology node. Further scaling according to the device roadmap requires the development of oxides with higher kappa values in order to scale the equivalent oxide thickness (EOT) to 0.7 nm or below while achieving low defect densities. In addition, next generation devices need to meet challenges like improved channel mobility, reduced gate leakage current, good control on threshold voltage, lower interface state density, and good reliability. In order to overcome these challenges, improvements of the high-kappa film properties and deposition methods are highly desirable. In this dissertation, a detail study of Zr and Al incorporated HfO 2 based high-kappa dielectrics is conducted to investigate improvement in electrical characteristics and reliability. To meet scaling requirements of the gate dielectric to sub 0.7 nm, Zr is added to HfO2 to form Hf1-xZrxO2 with x=0, 0.31 and 0.8 where the dielectric film is deposited by using various intermediate processing conditions, like (i) DADA: intermediate thermal annealing in a cyclical deposition process; (ii) DSDS: similar cyclical process with exposure to SPA Ar plasma; and (iii) As-Dep: the dielectric deposited without any intermediate step. MOSCAPs are formed with TiN metal gate and the reliability of these devices is investigated by subjecting them to a constant voltage stress in the gate injection mode. Stress induced flat-band voltage shift (DeltaVFB), stress induced leakage current (SILC) and stress induced interface state degradation are observed. DSDS samples demonstrate the superior characteristics whereas the worst degradation is observed for DADA samples. Time dependent dielectric breakdown (TDDB) shows that DSDS Hf1-xZrxO2 (x=0.8) has the superior characteristics with reduced oxygen vacancy, which is affiliated to

  10. Low and High-Frequency Field Potentials of Cortical Networks ...

    Science.gov (United States)

    Neural networks grown on microelectrode arrays (MEAs) have become an important, high content in vitro assay for assessing neuronal function. MEA experiments typically examine high- frequency (HF) (>200 Hz) spikes, and bursts which can be used to discriminate between different pharmacological agents/chemicals. However, normal brain activity is additionally composed of integrated low-frequency (0.5-100 Hz) field potentials (LFPs) which are filtered out of MEA recordings. The objective of this study was to characterize the relationship between HF and LFP neural network signals, and to assess the relative sensitivity of LFPs to selected neurotoxicants. Rat primary cortical cultures were grown on glass, single-well MEA chips. Spontaneous activity was sampled at 25 kHz and recorded (5 min) (Multi-Channel Systems) from mature networks (14 days in vitro). HF (spike, mean firing rate, MFR) and LF (power spectrum, amplitude) components were extracted from each network and served as its baseline (BL). Next, each chip was treated with either 1) a positive control, bicuculline (BIC, 25μM) or domoic acid (DA, 0.3μM), 2) or a negative control, acetaminophen (ACE, 100μM) or glyphosate (GLY, 100μM), 3) a solvent control (H2O or DMSO:EtOH), or 4) a neurotoxicant, (carbaryl, CAR 5, 30μM ; lindane, LIN 1, 10μM; permethrin, PERM 25, 50μM; triadimefon, TRI 5, 65μM). Post treatment, 5 mins of spontaneous activity was recorded and analyzed. As expected posit

  11. High Temperature Radio Frequency Loads

    CERN Document Server

    Federmann, S; Grudiev, A; Montesinos, E; Syratchev, I

    2011-01-01

    In the context of energy saving and recovery requirements the design of reliable and robust RF power loads which permit a high outlet temperature and high pressure of the cooling water is desirable. Cooling water arriving at the outlet withmore than 150 ◦C and high pressure has a higher value than water with 50 ◦C under low pressure. Conventional RF power loads containing dielectric and magnetic materials as well as sensitive ceramic windows usually do not permit going much higher than 90 ◦C. Here we present and discuss several design concepts for "metal only" RF high power loads. One concept is the application of magnetic steel corrugated waveguides near cutoff – this concept could find practical use above several GHz. Another solution are resonant structures made of steel to be installed in large waveguides for frequencies of 500 MHz or lower. Similar resonant structures above 100 MHz taking advantage of the rather high losses of normal steel may also be used in coaxial line geometries with large di...

  12. On the comparison of the polarisation behaviour of exchange-biased AF/F NiMn/Fe 37Co 48Hf 15 bi-layer and multi-layer films with increased ferromagnetic cut-off frequencies

    Science.gov (United States)

    Seemann, K.; Leiste, H.; Krüger, K.

    2012-03-01

    Antiferromagnetic/ferromagnetic (AF/F) NiMn/Fe37Co48Hf15 films were investigated with respect to their exchange bias, in-plane unidirectional anisotropy, polarisation and high frequency behaviour. After deposition, carried out by r.f. magnetron sputtering, the films were post-annealed for 4 h at 300 °C in a static magnetic field, in order to induce exchange-bias, which results in a unidirectional anisotropy. Dependent on the presence of a bi-layer or multi-layer sandwich structure the films show a different exchange-bias field-ferromagnetic inter-layer thickness behaviour with exchange-bias fields μ0*Heb between 2 and 10 mT. The in-plane uniaxial (single film) or unidirectional anisotropy fields μ0*HUF were between 4 and 18 mT. This results in a significant increase of the cut-off frequency in the GHz range in comparison to a single Fe37Co48Hf15 film, which is shown by frequency-dependent permeability plots. High damping in the imaginary part of the permeability, i.e., high resonance line broadening could be observed for films with high coercivity μ0*Hc of around 7 mT in the easy axis of magnetisation.

  13. Projected shell model analysis of multi-quasiparticle high-K isomers in sup 1 sup 7 sup 4 Hf

    CERN Document Server

    Zhou Xian Rong; Sun Yang; Long Gui Lu

    2002-01-01

    Multi-quasiparticle high-K states in sup 1 sup 7 sup 4 Hf are studied in the framework of the projected shell model. The calculation reproduces well the observed ground-state band as well as most of the two- and four-quasiparticle rotational bands. Some as yet unobserved high-K isomeric states in sup 1 sup 7 sup 4 Hf are predicted. Possible reasons for the existing discrepancies between calculation and experiment are discussed. It is suggested that the projected shell model may be a useful method for studying multi-quasiparticle high-K isomers and the K-mixing phenomenon in heavy deformed nuclei

  14. The use of high-frequency ultrasound imaging and biofluorescence for in vivo evaluation of gene therapy vectors

    OpenAIRE

    Ingram, N.; Macnab, SA; Marston, G; Scott, N.; Carr, IM; Markham, AF; Whitehouse, A; Coletta, PL

    2013-01-01

    Background: Non-invasive imaging of the biodistribution of novel therapeutics including gene therapy vectors in animal models is essential. Methods: This study assessed the utility of high-frequency ultrasound (HF-US) combined with biofluoresence imaging (BFI) to determine the longitudinal impact of a Herpesvirus saimiri amplicon on human colorectal cancer xenograft growth. Results: HF-US imaging of xenografts resulted in an accurate and informative xenograft volume in a longitudinal study. T...

  15. High temperature performance of Si:HfO2 based long channel Double Gate Ferroelectric Junctionless Transistors

    Science.gov (United States)

    Mehta, Hema; Kaur, Harsupreet

    2017-03-01

    In this work, we present a study that explores the suitability of Double Gate Ferroelectric Junctionless Transistor (DGFJL) incorporating Si:HfO2 for high temperature applications. At present, very few studies are focussed on Si:HfO2 to investigate its integrability in the present CMOS design space. Therefore, in the present study, using analytical modeling and TCAD simulations, it is demonstrated that Si:HfO2 based DGFJL exhibits superior performance in terms of substantial gain, reduced leakage currents, improved current drivability and high Ion/Ioff ratio at elevated temperatures as compared to the DGJL counterpart. The study, thus, highlights the fact that DGFJL is a potential candidate for device applications at high temperatures.

  16. High frequency welded (ERW) casing

    Energy Technology Data Exchange (ETDEWEB)

    Duisberg, J. (Hoesch Roehrenwerke A.G., Hamm (Germany, F.R.))

    1980-09-01

    Due to the up-to-date standard in welding and testing techniques, the significance of ERW-casing is growing rapidly. The basic items of ERW-pipe are explained in detail. The forming mechanism, the high frequency welding by induction and contact welding processes is explained in detail as well as destructive and non-destructive testing methods. Finishing the ends as threading, thread control (gauging), power tight connection, pressure test and final quality control are rounding up the picture of the production of ERW-casing. Last but not least the test results from the joint strength- and collapse tests which are of outstanding interest for casings, are compared with API requirements in order to demonstrate compliance with API requirements.

  17. Comparison of HfAlO, HfO2/Al2O3, and HfO2 on n-type GaAs using atomic layer deposition

    Science.gov (United States)

    Lu, Bin; Lv, Hongliang; Zhang, Yuming; Zhang, Yimen; Liu, Chen

    2016-11-01

    Different high-permittivity (high-k) gate dielectric structures of HfO2, HfAlO, and HfO2/Al2O3 deposited on HF-etched n-GaAs using ALD have been investigated. It has been demonstrated that the stacked structure of HfO2/Al2O3 has the lowest interface state density of 8.12 × 1012eV-1 cm-2 due to the "self-cleaning" reaction process, but the sample of HfAlO shows much better frequency dispersion and much higher dielectric permittivity extracted from the C-V curves. The investigation reveals that the electrical properties of gate dielectrics are improved by introducing alumina into HfO2.

  18. High Frequency Linacs for Hadrontherapy

    Science.gov (United States)

    Amaldi, Ugo; Braccini, Saverio; Puggioni, Paolo

    The use of radiofrequency linacs for hadrontherapy was proposed about 20 years ago, but only recently has it been understood that the high repetition rate together with the possibility of very rapid energy variations offers an optimal solution to the present challenge of hadrontherapy: "paint" a moving tumor target in three dimensions with a pencil beam. Moreover, the fact that the energy, and thus the particle range, can be electronically adjusted implies that no absorber-based energy selection system is needed, which, in the case of cyclotron-based centers, is the cause of material activation. On the other side, a linac consumes less power than a synchrotron. The first part of this article describes the main advantages of high frequency linacs in hadrontherapy, the early design studies, and the construction and test of the first high-gradient prototype which accelerated protons. The second part illustrates some technical issues relevant to the design of copper standing wave accelerators, the present developments, and two designs of linac-based proton and carbon ion facilities. Superconductive linacs are not discussed, since nanoampere currents are sufficient for therapy. In the last two sections, a comparison with circular accelerators and an overview of future projects are presented.

  19. Dynamics of the Davydov–Scott soliton with location or velocity mismatch of its high-frequency component

    Energy Technology Data Exchange (ETDEWEB)

    Blyakhman, L.G.; Gromov, E.M.; Onosova, I.V.; Tyutin, V.V., E-mail: vtyutin@hse.ru

    2017-05-03

    The dynamics of a two-component Davydov–Scott (DS) soliton with a small mismatch of the initial location or velocity of the high-frequency (HF) component was investigated within the framework of the Zakharov-type system of two coupled equations for the HF and low-frequency (LF) fields. In this system, the HF field is described by the linear Schrödinger equation with the potential generated by the LF component varying in time and space. The LF component in this system is described by the Korteweg–de Vries equation with a term of quadratic influence of the HF field on the LF field. The frequency of the DS soliton's component oscillation was found analytically using the balance equation. The perturbed DS soliton was shown to be stable. The analytical results were confirmed by numerical simulations. - Highlights: • The dynamics of the Davydov–Scott soliton with initial location or velocity mismatch of the HF component was investigated. • The study was performed within the framework of coupled linear Schrödinger and KdV equations for the HF and LF fields. • Analytical and numerical approaches were used. • The frequency of the DS soliton component oscillation was found. • Stability of the perturbed DS solitons was demonstrated.

  20. First modulation of high-frequency polar mesospheric summer echoes by radio heating of the ionosphere

    Science.gov (United States)

    Senior, A.; Mahmoudian, A.; Pinedo, H.; La Hoz, C.; Rietveld, M. T.; Scales, W. A.; Kosch, M. J.

    2014-08-01

    The first high-frequency (HF, 8 MHz) observations of the modulation of polar mesospheric summer echoes (PMSE) by artificial radio heating of the ionosphere are presented and compared to observations at 224 MHz and model predictions. The experiments were performed at the European Incoherent Scatter facility in northern Norway. It is shown that model results are in qualitative and partial quantitative agreement with the observations, supporting the prediction that with certain ranges of ice particle radii and concentration, PMSE at HF radar wavelengths can be enhanced by heating due to the dominance of dust charging over plasma diffusion.

  1. Econometrics of financial high-frequency data

    CERN Document Server

    Hautsch, Nikolaus

    2011-01-01

    This book covers major approaches in high-frequency econometrics. It discusses implementation details, provides insights into properties of high-frequency data as well as institutional settings and presents applications.

  2. First observations of electron gyro-harmonic effects under X-mode HF pumping the high latitude ionospheric F-region

    Science.gov (United States)

    Blagoveshchenskaya, N. F.; Borisova, T. D.; Kalishin, A. S.; Yeoman, T. K.; Häggström, I.

    2017-03-01

    We provide the first experimental evidence of the sensitivity of phenomena induced by extraordinary (X-mode) polarized HF high power radio waves to pump frequency stepping across the fifth electron gyro-harmonic (5fce) from below to above. The results were obtained at the EISCAT (European Incoherent Scatter Scientific Association) HF heater facility near Tromsø under effective radiated powers of 456-715 MW, when the HF pump wave was transmitted into the magnetic zenith. We have analyzed the behavior and intensities of various spectral lines in the narrowband stimulated electromagnetic emission (SEE) spectra observed far from the heater, HF-enhanced plasma and ion lines (HFPL and HFIL) from EISCAT UHF incoherent scatter radar spectra, and artificial field-aligned irregularities from CUTLASS (Co-operative UK Twin Located Auroral Sounding System) observations, depending on the frequency offset of the pump field relative to the 5fce. At pump frequencies below 5fce the narrowband SEE spectra exhibited very intense so-called stimulated ion Bernstein scatter (SIBS), accompanied by other spectral components, associated with stimulated Brillouin scatter (SBS), which are greatly suppressed and disappeared in the vicinity of 5fce and did not reappear at fH>5fce. As the pump frequency reached 5fce, the abrupt enhancements of the HFPL and HFIL power, the appearance of cascade lines in the plasma line spectra, and the onset of increasing CUTLASS backscatter power occurred. That is opposite to the ordinary mode (O-mode) effects in the vicinity of 5fce. The X-mode pumping at frequencies below and in the vicinity of the fifth electron gyro-harmonic clearly demonstrated an ascending altitude of generation of induced plasma and ion lines from the initial interaction height, whereas for O-mode heating the region of interaction descended. The observations are consistent with the coexistence of the electron acceleration along and across the geomagnetic field at fH<5fce, while only very

  3. Getting down to the Fundamentals of Hydrogen Bonding: Anharmonic Vibrational Frequencies of (HF)2 and (H2O)2 from Ab Initio Electronic Structure Computations.

    Science.gov (United States)

    Howard, J Coleman; Gray, Jessica L; Hardwick, Amanda J; Nguyen, Linh T; Tschumper, Gregory S

    2014-12-09

    This work presents a systematic investigation into the basis set convergence of harmonic vibrational frequencies of (H2O)2 and (HF)2 computed with second-order Møller-Plesset perturbation theory (MP2) and the coupled-cluster singles and doubles method with perturbative connected triples, CCSD(T), while employing correlation-consistent basis sets as large as aug-cc-pV6Z. The harmonic vibrational frequencies presented here are expected to lie within a few cm(-1) of the complete basis set (CBS) limit. For these important hydrogen-bonding prototype systems, a basis set of at least quadruple-ζ quality augmented with diffuse functions is required to obtain harmonic vibrational frequencies within 10 cm(-1) of the CBS limit. In addition, second-order vibrational perturbation theory (VPT2) anharmonic corrections yield CCSD(T) vibrational frequencies in excellent agreement with experimental spectra, differing by no more than a few cm(-1) for the intramonomer fundamental vibrations. D0 values predicted by CCSD(T) VPT2 computations with a quadruple-ζ basis set reproduce the experimental values of (HF)2 and (H2O)2 to within 2 and 21 cm(-1), respectively.

  4. High-Frequency Heart Rate Variability Linked to Affiliation with a New Group.

    Directory of Open Access Journals (Sweden)

    Baljinder K Sahdra

    Full Text Available This study tests the hypothesis that high levels of high-frequency heart rate variability (HF-HRV predisposes individuals to affiliate with new groups. Resting cardiac physiological recordings were taken before and after experimental sessions to measure trait high-frequency heart rate variability as an index of dispositional autonomic influence on heart rate. Following an experimental manipulation of priming of caring-related words, participants engaged in a minimal group paradigm, in which they imagined being a member of one of two arbitrary groups, allocated money to members of the two groups, and rated their affiliation with the groups. High levels of HF-HRV were associated with ingroup favouritism while allocating money, an effect largely attributable to a positive relationship between HF-HRV and allocation of money to the ingroup, and less due to a negative relationship between HF-HRV and money allocation to the outgroup. HF-HRV was also associated with increased self-reported affiliation feelings for the ingroup but was unrelated to feelings towards the outgroup. These effects remained substantial even after controlling for age, gender, BMI, mood, caffeine consumption, time of day of data collection, smoking and alcohol behaviour, and respiration rate. Further, the effects were observed regardless of whether participants were primed with caring-related words or not. This study is the first to bridge a long history of research on ingroup favouritism to the relatively recent body of research on cardiac vagal tone by uncovering a positive association between HF-HRV and affiliation with a novel group.

  5. Estimation of frequency wave spectrum from high frequency radar data using a parametric model

    Science.gov (United States)

    Toro, V. G.; Ocampo, F. J.; Flores-Vidal, X.; Durazo, R.; Flament, P. J.

    2011-12-01

    Models that obtain wave information from high frequency radars (HF) use information of the measured second order Doppler spectrum. The estimation is completed through an integral equation as in the case of the Barrick model, or linearly as in the Hasselmann model. For the latter, the linear form uses a parameter (α) obtained using an exclusive set of data (EuroROSE) which suggests a universal expression of such parameter. In this work we developed a methodology and better approach to extract second order information from the Doppler spectra, and a new parameterization for α was obtained by comparing with in situ measured information in the Gulf of Tehuantepec (GT), Mexico. We present frequency spectra and significant wave height obtained for a four-month data set in the GT, during the season of strong (> 10 ms-1) northerly gap winds. We found that signal strength of Doppler spectra showed a clear diurnal cycle. The time average of these spectra allowed us to select the spectra with high SNR value. The second-order information obtained was used in the mathematical model of Hasselmann, and found that α, which is a function of frequency, depends on wind speed (U10). The results suggest a good agreement between the data measured by the ASIS buoy and those obtained by the Hasselmann model. The results showed improvement in the estimation of wave frequency spectrum and pointed at the need to have a theoretical model for α to be used in any data set.

  6. High Frequency Chandler Wobble Excitation

    Science.gov (United States)

    Seitz, F.; Stuck, J.; Thomas, M.

    2003-04-01

    and OMCT forcing fields give no hint for increased excitation power in the Chandler band. Thus it is assumed, that continuous high frequency excitation due to stochastic weather phenomena is responsible for the perpetuation of the Chandler wobble.

  7. The Modulation of Ionospheric Alfvén Resonator on Heating HF Waves and the Doppler Effect

    Institute of Scientific and Technical Information of China (English)

    Ni Bin-bin; Zhao Zheng-yu; Xie Shu-guo

    2003-01-01

    Abstract: The propagation of HF waves in IAR can produce many nonlinear effects, including the modulation effect of IAR on HF waves and the Doppler effect. To start with the dependence of the ionospheric electron temperature variaof the modulation effect and lucubrate possible reasons for the field can have an observable modulation effect on HF waves while its mechanism is quite different from that of Schumann resonant field on HF waves. The depth of modulation of IAR field, which directly inspires the formation of cross-spectrum between ULF waves and HF waves and results in spectral peaks at some gyro-frequencies of IAR. With respect to the Doppler effect during the propagation of HF waves in IAR, it is mainly caused by the motion of the high-speed flyer and the drifting electrons and the frequency shift from the phase variation of the reflected waves can be neglected when the frequency of HF incident wave is high enough.

  8. The ISMAR high frequency coastal radar network: Monitoring surface currents for management of marine resources

    DEFF Research Database (Denmark)

    Carlson, Daniel Frazier

    2015-01-01

    The Institute of Marine Sciences (ISMAR) of the National Research Council of Italy (CNR) established a High Frequency (HF) Coastal Radar Network for the measurement of the velocity of surface currents in coastal seas. The network consists of four HF radar systems located on the coast of the Gargano...... of geospatial data, a netCDF architecture has been defined on the basis of the Radiowave Operators Working Group (US ROWG) recommendations and compliant to the Climate and Forecast (CF) Metadata Conventions CF-1.6. The hourly netCDF files are automatically attached to a Thematic Real-time Environmental...... by the ISMAR HF radar network are presently used in a number of applications, ranging from oil spill and SAR to fishery and coastal management applications....

  9. Nontrivial effects of high-frequency excitation for strongly damped mechanical systems

    DEFF Research Database (Denmark)

    Fidlin, Alexander; Thomsen, Jon Juel

    Some nontrivial effects are investigated, which can occur if strongly damped mechanical systems are subjected to strong high-frequency (HF) excitation. The main result is a theoretical prediction, supported by numerical simulation, that for such systems the (quasi-)equilibrium states can change...... that can be substantial (depending on the strength of the HF excitation) for finite values of the damping. The analysis is focused on the differences between the classic results for weakly damped systems, and new effects for which the strong damping terms are responsible. The analysis is based...... on a slightly modified averaging technique, and includes an elementary example of an elliptically excited pendulum for illustration, alongside with a generalization to a broader class of strongly damped dynamical systems with HF excitation. As an application example, the nontrivial behavior of a classical...

  10. Nontrivial effects of high-frequency excitation for strongly damped mechanical systems

    DEFF Research Database (Denmark)

    Fidlin, Alexander; Thomsen, Jon Juel

    2008-01-01

    Some non-trivial effects are investigated, which can occur if strongly damped mechanical systems are subjected to strong high-frequency (HF) excitation. The main result is a theoretical prediction, supported by numerical simulation, that for such systems the (quasi-)equilibrium states can change...... that can be substantial depending on the strength of the HF excitation) for finite values of the damping. The analysis is focused on the differences between the classic results for weakly damped systems, and new effects for which the strong damping terms are responsible. The analysis is based on a slightly...... modified averaging technique, and includes an elementary example of an elliptically excited pendulum for illustration, alongside with a generalization to a broader class of strongly damped dynamical systems with HF excitation. As an application example, the nontrivial behavior of a classical optimally...

  11. Systematic Comparison of HF CMOS Transconductors

    NARCIS (Netherlands)

    Klumperink, Eric A.M.; Nauta, Bram

    2003-01-01

    Transconductors are commonly used as active elements in high-frequency (HF) filters, amplifiers, mixers, and oscillators. This paper reviews transconductor design by focusing on the V-I kernel that determines the key transconductor properties. Based on bandwidth considerations, simple V-I kernels wi

  12. Longitudinal Plasmoid in High-Speed Vortex Gas Flow Created by Capacity HF Discharge

    Science.gov (United States)

    2010-10-28

    instrumentation will be used in this Project to study plasma and gas flow parameters, including new shadow device with excimer KrF laser, MW...vortex decay (attenuation) by HF plasma. The additional experiments with small helium jet injection prove the conclusion about vortex attenuation by a...equilibrium HF plasma. Plasma and airflow parameters are measured by different diagnostic instrumentation including shadow optical device with excimer

  13. Differences in clinical characteristics and prognosis of sudden low- and high-frequency hearing loss.

    Science.gov (United States)

    Choo, Oak-Sung; Yang, Suk Min; Park, Hun Yi; Lee, Jong Bin; Jang, Jeong Hun; Choi, Seong Jun; Choung, Yun-Hoon

    2017-08-01

    We compared the clinical characteristics between acute low- and high-frequency hearing loss (LF and HF, respectively) patients, and the efficacy of three different treatment protocols (systemic steroids, intratympanic steroid injection, and combination therapy). Prospective, randomized controlled study. A total of 111 patients diagnosed with LF or HF were treated on an outpatient basis. Each group was randomly divided into three equal subgroups based on therapy: oral steroid, intratympanic dexamethasone injection (IT), and combination therapy. Hearing gain was estimated by comparing pre- and post-treatment pure-tone averages. Recovery rate was assessed by Clinical Practice Guideline: Sudden Hearing Loss from the American Academy of Otolaryngology-Head and Neck Surgery. In comparison of chief complaints, ear fullness and hearing loss were more common in the LF and HF group, respectively (P = .033 and P = .001, respectively). Hearing recovery rates were significantly different between the two groups (i.e., 74.1% [40/54] in the LF group and 45.6% [26/57] in the HF group; P < .001). Oral steroid therapy was most effective in the LF group (P = .017). In the HF group, all three modalities showed similar results, although IT tended to be the most effective (P = .390). There were differences in chief complaints and treatment responses between LF and HF patients. Although they showed similar partial damage in the cochlea, the pathophysiology of LF and HF may be quite different. 1b. Laryngoscope, 127:1878-1884, 2017. © 2016 The American Laryngological, Rhinological and Otological Society, Inc.

  14. Surface ocean velocities obtained by HF radar from stations located along coastal waters of Antarctica, Hawaii, Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico and western US during April 2015 (NCEI Accession 0138389)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The archival package contains ocean surface radial velocities collected from High frequency (HF) radar stations. NDBC, which with SIO assembles data from the IOOS HF...

  15. Surface ocean velocities obtained by HF radar from stations located along coastal waters of Antarctica, Hawaii, Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico and western US during May 2015 (NCEI Accession 0138488)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The archival package contains ocean surface radial velocities collected from High frequency (HF) radar stations. NDBC, which with SIO assembles data from the IOOS HF...

  16. Surface ocean velocities obtained by HF radar from stations located along coastal waters of Antarctica, Hawaii, Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico and western US during March 2015 (NCEI Accession 0138305)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The archival package contains ocean surface radial velocities collected from High frequency (HF) radar stations. NDBC, which with SIO assembles data from the IOOS HF...

  17. Surface ocean velocities obtained by HF radar from stations located along coastal waters of Hawaii, North Slope Alaska, Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico and western US during July 2016 (NCEI Accession 0156405)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The archival package contains ocean surface radial velocities collected from High frequency (HF) radar stations. NDBC, which with SIO assembles data from the IOOS HF...

  18. Surface ocean velocities obtained by HF radar from stations located along coastal waters of Antarctica, Hawaii, Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico and western US during January 2015 (NCEI Accession 0137088)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The archival package contains ocean surface radial velocities collected from High frequency (HF) radar stations. NDBC, which with SIO assembles data from the IOOS HF...

  19. Surface ocean velocities obtained by HF radar from stations located along coastal waters of Antarctica, Hawaii, Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico and western US during May 2016 (NCEI Accession 0154390)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The archival package contains ocean surface radial velocities collected from High frequency (HF) radar stations. NDBC, which with SIO assembles data from the IOOS HF...

  20. Surface ocean velocities obtained by HF radar from stations located along coastal waters of Antarctica, Hawaii, Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico and western US during February 2016 (NCEI Accession 0145802)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The archival package contains ocean surface radial velocities collected from High frequency (HF) radar stations. NDBC, which with SIO assembles data from the IOOS HF...

  1. Surface ocean velocities obtained by HF radar from stations located along coastal waters of Antarctica, Hawaii, Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico and western US during January 2016 (NCEI Accession 0144289)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The archival package contains ocean surface radial velocities collected from High frequency (HF) radar stations. NDBC, which with SIO assembles data from the IOOS HF...

  2. Surface ocean velocities obtained by HF radar from stations located along coastal waters of Antarctica, Hawaii, Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico and western US during June 2015 (NCEI Accession 0138584)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The archival package contains ocean surface radial velocities collected from High frequency (HF) radar stations. NDBC, which with SIO assembles data from the IOOS HF...

  3. Surface ocean velocities obtained by HF radar from stations located along coastal waters of Antarctica, Hawaii, Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico and western US during December 2015 (NCEI Accession 0141107)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The archival package contains ocean surface radial velocities collected from High frequency (HF) radar stations. NDBC, which with SIO assembles data from the IOOS HF...

  4. Surface ocean velocities obtained by HF radar from stations located along coastal waters of Antarctica, Hawaii, North Slope Alaska, Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico and western US during September 2015 (NCEI Accession 0138948)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The archival package contains ocean surface radial velocities collected from High frequency (HF) radar stations. NDBC, which with SIO assembles data from the IOOS HF...

  5. Surface ocean velocities obtained by HF radar from stations located along coastal waters of Hawaii, North Slope Alaska, Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico and western US during August 2016 (NCEI Accession 0156626)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The archival package contains ocean surface radial velocities collected from High frequency (HF) radar stations. NDBC, which with SIO assembles data from the IOOS HF...

  6. Surface ocean velocities obtained by HF radar from stations located along coastal waters of Antarctica, Hawaii, Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico and western US during April 2016 (NCEI Accession 0151734)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The archival package contains ocean surface radial velocities collected from High frequency (HF) radar stations. NDBC, which with SIO assembles data from the IOOS HF...

  7. Surface ocean velocities obtained by HF radar from stations located along coastal waters of Antarctica, Hawaii, North Slope Alaska, Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico and western US during November 2015 (NCEI Accession 0139553)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The archival package contains ocean surface radial velocities collected from High frequency (HF) radar stations. NDBC, which with SIO assembles data from the IOOS HF...

  8. Surface ocean velocities obtained by HF radar from stations located along coastal waters of Antarctica, Hawaii, North Slope Alaska, Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico and western US during October 2015 (NCEI Accession 0139156)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The archival package contains ocean surface radial velocities collected from High frequency (HF) radar stations. NDBC, which with SIO assembles data from the IOOS HF...

  9. Surface ocean velocities obtained by HF radar from stations located along coastal waters of Hawaii, North Slope Alaska, Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico and western US during June 2016 (NCEI Accession 0155984)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The archival package contains ocean surface radial velocities collected from High frequency (HF) radar stations. NDBC, which with SIO assembles data from the IOOS HF...

  10. Surface ocean velocities obtained by HF radar from stations located along coastal waters of Antarctica, Hawaii, Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico and western US during February 2015 (NCEI Accession 0137265)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The archival package contains ocean surface radial velocities collected from High frequency (HF) radar stations. NDBC, which with SIO assembles data from the IOOS HF...

  11. Surface ocean velocities obtained by HF radar from stations located along coastal waters of Antarctica, Hawaii, North Slope Alaska, Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico and western US during July 2015 (NCEI Accession 0138671)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The archival package contains ocean surface radial velocities collected from High frequency (HF) radar stations. NDBC, which with SIO assembles data from the IOOS HF...

  12. Surface ocean velocities obtained by HF radar from stations located along coastal waters of Antarctica, Hawaii, North Slope Alaska, Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico and western US during August 2015 (NCEI Accession 0138776)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The archival package contains ocean surface radial velocities collected from High frequency (HF) radar stations. NDBC, which with SIO assembles data from the IOOS HF...

  13. Surface ocean velocities obtained by HF radar from stations located along coastal waters of Antarctica, Hawaii, Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico and western US during March 2016 (NCEI Accession 0148080)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The archival package contains ocean surface radial velocities collected from High frequency (HF) radar stations. NDBC, which with SIO assembles data from the IOOS HF...

  14. High frequency microseismic noise as possible earthquake precursor

    Directory of Open Access Journals (Sweden)

    Ivica Sović

    2013-08-01

    Full Text Available Before an earthquake occurs, microseismic noise in high frequency (HF range, i.e. 2-25 Hz, is being generated during preparation process. These signals change the microseismic noise and, consequently, the spectrum of microseismic noise. Time variation of spectra recorded at the same seismological station could imply the change of the state of noise source. We propose the image moment analysis approach to objectively compare microseismic noise spectra. The result could be used for earthquake precursor identification. Expected spectra change is in HF range, so the analysis has been limited to the shallow tectonic earthquakes with epicenters close, up to 15 km, the seismological stations. The method has been tested post festum using four earthquakes in Dinarides which satisfied condition for epicentral distance. The spectra were calculated for noise recorded in time intervals of 10 days before and 6 to 10 days after the earthquakes. Affine moment invariants were calculated for noise spectra which were treated as the input objects. Spectra of the first five days in the series were referent spectra. The classification parameters were Euclidean distances between referent spectra and the spectra for all days in the series, including referent ones. The results have shown that the spectra of the microseismic noise become noticeably different than the other spectra in time intervals one or two days before an earthquake.

  15. High Resolution Frequency Swept Imaging.

    Science.gov (United States)

    1980-02-14

    centers on practical targets. (iv) Greater immunity to phase fluctuations arising from turbulance and inhomogenieties in the propagation medium because...frequency swept illumination. Since the impulse reponse of a time invariant linear system can also be deduced from white noise excitation and

  16. High-frequency rTMS on leg motor area in the early phase of stroke.

    Science.gov (United States)

    Sasaki, Nobuyuki; Abo, Masahiro; Hara, Takatoshi; Yamada, Naoki; Niimi, Masachika; Kakuda, Wataru

    2017-03-01

    Although repetitive transcranial magnetic stimulation (rTMS) for upper limb motor area in stroke patients is beneficial, it has been poorly investigated in rTMS for leg motor area. Furthermore, no study has examined the usefulness of rTMS for leg motor area in patients in the early phase of stroke. Twenty-one patients with a hemispheric stroke lesion in the early phase were randomly assigned into two groups: the high-frequency (HF)-rTMS group [N = 11] and the sham stimulation group [N = 10]. Patients received rTMS for 5 consecutive days, beginning 10.9 ± 6.6 days on average after the onset. Brunnstrom Recovery Stages (BRS) for the lower limbs and the Ability for Basic Movement Scale Revised (ABMS II) were assessed before and after the intervention. The improvement in BRS for the lower limbs was significant after the intervention in the HF-rTMS group. Although both the HF-rTMS and sham stimulation groups had significant improvements in ABMS II scores, the extent of improvement in the AMBS II was significantly greater in the HF-rTMS group than in the sham stimulation group. Application of HF-rTMS over the bilateral leg motor areas has potential to be a new rehabilitation therapy for patients in the acute phase of stroke.

  17. Postural muscle atrophy prevention and recovery and bone remodelling through high frequency proprioception for astronauts

    Science.gov (United States)

    Riva, Dario; Rossitto, Franco; Battocchio, Luciano

    2009-09-01

    The difficulty in applying active exercises during space flights increases the importance of passive countermeasures, but coupling load and instability remains indispensable for generating high frequency (HF) proprioceptive flows and preventing muscle atrophy and osteoporosis. The present study, in microgravity conditions during a parabolic flight, verified whether an electronic system, composed of a rocking board, a postural reader and a bungee-cord loading apparatus creates HF postural instability comparable to that reachable on the Earth. Tracking the subject, in single stance, to real-time visual signals is necessary to obtain HF instability situations. The bungee-cord loading apparatus allowed the subject to manage the 81.5% body weight load (100% could easily be exceeded). A preliminary training programme schedule on the Earth and in space is suggested. Comparison with a pathological muscle atrophy is presented. The possibility of generating HF proprioceptive flows could complement current countermeasures for the prevention and recovery of muscle atrophy and osteoporosis in terrestrial and space environments. These exercises combine massive activation of spindles and joint receptors, applying simultaneously HF variations of pressure to different areas of the sole of the foot. This class of exercises could improve the effectiveness of current countermeasures, reducing working time and fatigue.

  18. CUTLASS HF radar observations of high-velocity E-region echoes

    Directory of Open Access Journals (Sweden)

    M. V. Uspensky

    Full Text Available A short event of high-velocity E-region echo observations by the Pykkvibaer HF radar is analysed to study echo parameters and the echo relation to the Farley-Buneman plasma instability. The echoes were detected in several beams aligned closely to the magnetic L-shell direction. Two echo groups were identified: one group corresponded to the classical type 1 echoes with velocities close to the nominal ion-acoustic speed of 400 ms1 , while the other group had significantly larger velocities, of the order of 700 ms1 . The mutual relationship between the echo power, Doppler velocity, spectral width and elevation angles for these two groups was studied. Plotting of echo parameters versus slant range showed that all ~700 ms1 echoes originated from larger heights and distances of 500–700 km, while all ~400 ms1 echoes came from lower heights and from farther distances; 700–1000 km. We argue that both observed groups of echoes occurred due to the Farley-Buneman plasma instability excited by strong ( ~70 mVm1 and uniformly distributed electric fields. We show that the echo velocities for the two groups were different because the echoes were received from different heights. Such a separation of echo heights occurred due to the differing amounts of ionospheric refraction at short and large ranges. Thus, the ionospheric refraction and related altitude modulation of ionospheric parameters are the most important factors to consider, when various characteristics of E-region decametre irregularities are derived from HF radar measurements.

    Key words. Ionosphere (ionospheric irregularities; plasma waves and instabilities; polar ionosphere

  19. Impact and Origin of Interface States in MOS Capacitor with Monolayer MoS2 and HfO2 High-k Dielectric

    Science.gov (United States)

    Xia, Pengkun; Feng, Xuewei; Ng, Rui Jie; Wang, Shijie; Chi, Dongzhi; Li, Cequn; He, Zhubing; Liu, Xinke; Ang, Kah-Wee

    2017-01-01

    Two-dimensional layered semiconductors such as molybdenum disulfide (MoS2) at the quantum limit are promising material for nanoelectronics and optoelectronics applications. Understanding the interface properties between the atomically thin MoS2 channel and gate dielectric is fundamentally important for enhancing the carrier transport properties. Here, we investigate the frequency dispersion mechanism in a metal-oxide-semiconductor capacitor (MOSCAP) with a monolayer MoS2 and an ultra-thin HfO2 high-k gate dielectric. We show that the existence of sulfur vacancies at the MoS2-HfO2 interface is responsible for the generation of interface states with a density (Dit) reaching ~7.03 × 1011 cm−2 eV−1. This is evidenced by a deficit S:Mo ratio of ~1.96 using X-ray photoelectron spectroscopy (XPS) analysis, which deviates from its ideal stoichiometric value. First-principles calculations within the density-functional theory framework further confirms the presence of trap states due to sulfur deficiency, which exist within the MoS2 bandgap. This corroborates to a voltage-dependent frequency dispersion of ~11.5% at weak accumulation which decreases monotonically to ~9.0% at strong accumulation as the Fermi level moves away from the mid-gap trap states. Further reduction in Dit could be achieved by thermally diffusing S atoms to the MoS2-HfO2 interface to annihilate the vacancies. This work provides an insight into the interface properties for enabling the development of MoS2 devices with carrier transport enhancement. PMID:28084434

  20. Impact and Origin of Interface States in MOS Capacitor with Monolayer MoS2 and HfO2 High-k Dielectric

    Science.gov (United States)

    Xia, Pengkun; Feng, Xuewei; Ng, Rui Jie; Wang, Shijie; Chi, Dongzhi; Li, Cequn; He, Zhubing; Liu, Xinke; Ang, Kah-Wee

    2017-01-01

    Two-dimensional layered semiconductors such as molybdenum disulfide (MoS2) at the quantum limit are promising material for nanoelectronics and optoelectronics applications. Understanding the interface properties between the atomically thin MoS2 channel and gate dielectric is fundamentally important for enhancing the carrier transport properties. Here, we investigate the frequency dispersion mechanism in a metal-oxide-semiconductor capacitor (MOSCAP) with a monolayer MoS2 and an ultra-thin HfO2 high-k gate dielectric. We show that the existence of sulfur vacancies at the MoS2-HfO2 interface is responsible for the generation of interface states with a density (Dit) reaching ~7.03 × 1011 cm-2 eV-1. This is evidenced by a deficit S:Mo ratio of ~1.96 using X-ray photoelectron spectroscopy (XPS) analysis, which deviates from its ideal stoichiometric value. First-principles calculations within the density-functional theory framework further confirms the presence of trap states due to sulfur deficiency, which exist within the MoS2 bandgap. This corroborates to a voltage-dependent frequency dispersion of ~11.5% at weak accumulation which decreases monotonically to ~9.0% at strong accumulation as the Fermi level moves away from the mid-gap trap states. Further reduction in Dit could be achieved by thermally diffusing S atoms to the MoS2-HfO2 interface to annihilate the vacancies. This work provides an insight into the interface properties for enabling the development of MoS2 devices with carrier transport enhancement.

  1. Semantic Priming from Letter-Searched Primes Occurs for Low- but Not High-Frequency Targets: Automatic Semantic Access May Not Be a Myth

    Science.gov (United States)

    Tse, Chi-Shing; Neely, James H.

    2007-01-01

    Letter-search (LS) within a prime often eliminates semantic priming. In 2 lexical decision experiments, the authors found that priming from LS primes occurred for low-frequency (LF) but not high-frequency (HF) targets whether the target's word frequency was manipulated between or within participants and whether the prime-target pairs were…

  2. Electrical Characterization of Metal-Insulator-Metal Capacitors with Atomic-Layer-Deposited HfO2 Dielectrics for Radio Frequency Integrated Circuit Application

    Institute of Scientific and Technical Information of China (English)

    HUANG Yu-Jian; HUANG Yue; DING Shi-Jin; ZHANG Wei; LIU Ran

    2007-01-01

    Metal-insulator-metal (MIM) capacitors with atomic-layer-deposited HfO2 dielectric and TaN electrodes are investigated for rf integrated circuit applications. For 12nm HfO2, the fabricated capacitor exhibits a high capacitance density of 15.5fF/μm2 at 100kHz, a small leakage current density of 6.4 × 10-9 A/cm2 at 1.8 V and 125℃, a breakdown electric field of 2.6 MV/cm as well as voltage coefficients of capacitance (VCCs) of 2110ppm/V2 and -824 ppm/V at 100kHz. Further, it is deduced that the conduction mechanism in the high field range is dominated by the Poole-Frenkel emission, and the conduction mechanism in the low field range is possibly related to trap-assisted tunnelling. Finally, comparison of various HfO2 MIM capacitors is present,suggesting that the present MIM capacitor is a promising candidate for future rf integrated circuit application.

  3. High frequency pressure oscillator for microcryocoolers

    NARCIS (Netherlands)

    Vanapalli, Srinivas; ter Brake, Hermanus J.M.; Jansen, Henricus V.; Zhao, Yiping; Holland, Herman J.; Burger, Johannes Faas; Elwenspoek, Michael Curt

    2008-01-01

    Microminiature pulse tube cryocoolers should operate at a frequency of an order higher than the conventional macro ones because the pulse tube cryocooler operating frequency scales inversely with the square of the pulse tube diameter. In this paper, the design and experiments of a high frequency

  4. High frequency pressure oscillator for microcryocoolers

    NARCIS (Netherlands)

    Vanapalli, Srinivas; ter Brake, Hermanus J.M.; Jansen, Henricus V.; Zhao, Yiping; Holland, Herman J.; Burger, Johannes Faas; Elwenspoek, Michael Curt

    2008-01-01

    Microminiature pulse tube cryocoolers should operate at a frequency of an order higher than the conventional macro ones because the pulse tube cryocooler operating frequency scales inversely with the square of the pulse tube diameter. In this paper, the design and experiments of a high frequency pre

  5. High frequency pressure oscillator for microcryocoolers

    NARCIS (Netherlands)

    Vanapalli, S.; Brake, ter H.J.M.; Jansen, H.V.; Zhao, Y.; Holland, H.J.; Burger, J.F.; Elwenspoek, M.C.

    2008-01-01

    Microminiature pulse tube cryocoolers should operate at a frequency of an order higher than the conventional macro ones because the pulse tube cryocooler operating frequency scales inversely with the square of the pulse tube diameter. In this paper, the design and experiments of a high frequency pre

  6. Improved Stress Reliability of Analog TiHfO Metal-Insulator-Metal Capacitors Using High-Work-Function Electrode

    Science.gov (United States)

    Cheng, Chun-Hu; Chiang, Kuo-Cheng; Pan, Han-Chang; Hsiao, Chien-Nan; Chou, Chang-Pin; McAlister, Sean P.; Chin, Albert

    2007-11-01

    We have studied the reliability of high-κ (κ ˜ 49) TixHf1-xO (x ˜ 0.67) metal-insulator-metal (MIM) capacitors after constant voltage stress induction. The use of a high-work-function Ni top electrode improves not only the leakage current, and temperature- and voltage-coefficients of capacitance, but also the long-term capacitance variation after stress induction.

  7. High vs. Low Frequency Stimulation Effects on Fine Motor Control in Chronic Hemiplegia: A Pilot Study

    Science.gov (United States)

    Doucet, Barbara M.; Griffin, Lisa

    2014-01-01

    Introduction The optimal parameters of neuromuscular electrical stimulation (NMES) for recovery of hand function following stroke are not known. This clinical pilot study examined whether higher or lower frequencies are more effective for improving fine motor control of the hand in a chronic post-stroke population. Methods A one-month, 4x/week in-home regimen of either a high frequency (40Hz) or low frequency (20Hz) NMES program was applied to the hemiplegic thenar muscles of 16 persons with chronic stroke. Participants were identified a priori as having a low level of function (LF) or a high level of function (HF). Outcome measures of strength, dexterity, and endurance were measured before and after participation in the regimen. Results LF subjects showed no significant changes with either the high or the low frequency NMES regimen. HF subjects showed significant changes in strength, dexterity and endurance. Within this group, higher frequencies of stimulation yielded strength gains and increased motor activation; lower frequencies impacted dexterity and endurance. Conclusions The results suggest that higher frequencies of stimulation could be more effective in improving strength and motor activation properties and that lower frequencies may impact coordination and endurance changes; results also indicate that persons with a higher functional level of recovery may respond more favorably to NMES regimens, but further study with larger patient groups is warranted. PMID:23893829

  8. High-frequency effects in 1D spring-mass systems with strongly non-linear inclusions

    DEFF Research Database (Denmark)

    Lazarov, Boyan Stefanov; Snaeland, S.O.; Thomsen, Jon Juel

    2010-01-01

    -like systems with embedded non-linear parts, where the masses interact with a limited set of neighbour masses. The presented analytical and numerical results show that the effective properties for LF wave propagation can be altered by establishing HF standing waves in the non-linear regions of the chain......This work generalises the possibilities to change the effective material or structural properties for low frequency (LF) wave propagation, by using high-frequency (HF) external excitation combined with strong non-linear and non-local material behaviour. The effects are demonstrated on 1D chain....... The changes affect the effective stiffness and damping of the system....

  9. Distribution of electrical activation to the external intercostal muscles during high frequency spinal cord stimulation in dogs

    Science.gov (United States)

    DiMarco, Anthony F; Kowalski, Krzysztof E

    2011-01-01

    Abstract In contrast to previous methods of electrical stimulation of the inspiratory muscles, high frequency spinal cord stimulation (HF-SCS) results in more physiological activation of these muscles. The spatial distribution of activation to the external intercostal muscles by this method is unknown. In anaesthetized dogs, multiunit and single motor unit (SMU) EMG activity was monitored in the dorsal portion of the 3rd, 5th and 7th interspaces and ventral portion of the 3rd interspace during spontaneous breathing and HF-SCS following C2 spinal section. Stimulus amplitude during HF-SCS was adjusted such that inspired volumes matched spontaneous breathing (Protocol 1). During HF-SCS, mean peak SMU firing frequency was highest in the 3rd interspace (dorsal) (18.8 ± 0.3 Hz) and significantly lower in the 3rd interspace (ventral) (12.2 ± 0.2 Hz) and 5th interspace (dorsal) (15.3 ± 0.3 Hz) (P intercostal muscles during HF-SCS is similar to that occurring during spontaneous breathing and (b) differential descending synaptic input from supraspinal centres is not a required component of the differential spatial distribution of external intercostal muscle activation. HF-SCS may provide a more physiological method of inspiratory muscle pacing. PMID:21242258

  10. Electronic and crystal structure of the high entropy TiZrHfCoNiCu intermetallics undergoing martensitic transformation

    Directory of Open Access Journals (Sweden)

    Firstov Georgiy

    2015-01-01

    Full Text Available It was shown very recently that despite high thermal stability some high entropy alloys, namely, intermetallic compounds of TiZrHfCoNiCu family, undergo martensitic transformation and exhibit shape memory effect [1]. It was also found that X-ray diffraction patterns taken from those compounds resemble qualitatively ones of B2 ordering type for austenitic state and B19` - for martensite. It is going to be shown [2] that the ordered structure of austenite phase is not B2 but is a result of group-subgroup transition down to triclinic P1 space group. Present paper reports onto the results of electron structure modelling combined with crystal structure analysis with the help of experimental data Rietveld refinement performed for TiZrHfCoNiCu intermetallics. Crystal structures of austenite and martensite phases for these high entropy intermetallics will be discussed.

  11. Temperature induced ferromagnetic resonance frequency change and resonance line broadening of a Fe-Co-Hf-N film with in-plane uniaxial anisotropy - a theoretical and experimental study

    Science.gov (United States)

    Seemann, K.; Krüger, K.; Leiste, H.

    2014-11-01

    A soft ferromagnetic Fe-Co-Hf-N film was produced by reactive r.f. magnetron sputtering, in order to study its high-frequency behaviour by means of frequency domain permeability measurements up to the GHz range. It resulted in the composition Fe33Co43Hf10N14 and exhibits a saturation polarisation Js of around 1.35 T. The film is consequently considered as being uniformly magnetised due to an in-plane uniaxial anisotropy of approximately μ0.Hu≈4.5 mT after annealing it at 400 °C in a static magnetic field for 1 h. While heating the film from room temperature to 300 °C during the high-frequency measurement procedure a marked ferromagnetic resonance peak shift (maximum of the imaginary part of the frequency-dependent permeability) from 2.35 GHz down to 1.84 GHz is conspicuous. This is in a very good agreement with the theory established by taking the “real” ferromagnetic resonance formula for ferromagnetic films into account. Simultaneously, the full width at half maximum (FWHM) ΔfFMR of the resonance line, which is a consequence of precession damping of the magnetic moments, clearly increases. This behaviour does not correlate with the ferromagnetic resonance value decrease, and is qualitatively discussed in terms of exchange interaction with the intrinsic spin-lattice relaxation process due to not totally supressed orbital momenta (≠0) of Fe2+ and Co2+ or the occupation change of their spectral levels within the induced uniaxial anisotropy field.

  12. Magnetic dipole moments of High-K isomeric states in Hf isotopes

    CERN Multimedia

    Walters, W; Nishimura, K; Bingham, C R

    2007-01-01

    It is proposed to make precision measurements of the magnetic moments of 5 multi-quasi-particle K-isomers in Hf nuclei by the Nuclear Magnetic Resonance of Oriented Nuclei (NMR/ON) technique using the NICOLE on-line nuclear orientation facility and exploiting the unique HfF$_{3}$ beams recently available at ISOLDE. Results will be used to extract single-particle and collective g-factors of the isomeric states and their excitations and to shed new light on their structure.

  13. Terrestrial bitumen analogue of orgueil organic material demonstrates high sensitivity to usual HF-HCl treatment

    Science.gov (United States)

    Korochantsev, A. V.; Nikolaeva, O. V.

    1993-01-01

    The relationship between the chemical composition and the interlayer spacing (d002) of organic materials (OM's) is known for various terrestrial OM's. We improved this general trend by correlation with corresponding trend of natural solid bitumens (asphaltite-kerite-anthraxolite) up to graphite. Using the improved trend we identified bitumen analogs of carbonaceous chondrite OM's residued after HF-HCl treatment. Our laboratory experiment revealed that these analogs and, hence, structure and chemical composition of carbonaceous chondrite OM's are very sensitive to the HF-HCl treatment. So, usual extraction of OM from carbonaceous chondrites may change significantly structural and chemical composition of extracted OM.

  14. High temperature thermal stability of the HfO{sub 2}/Ge (100) interface as a function of surface preparation studied by synchrotron radiation core level photoemission

    Energy Technology Data Exchange (ETDEWEB)

    Chellappan, Rajesh Kumar, E-mail: rajesh.chellappan2@mail.dcu.ie [School of Physical Sciences, Dublin City University, Dublin 9 (Ireland); Gajula, Durga Rao; McNeill, David [School of Electronics, Electrical Engineering and Computer Science, Queen' s University Belfast (United Kingdom); Hughes, Greg [School of Physical Sciences, Dublin City University, Dublin 9 (Ireland)

    2014-02-15

    High resolution soft x-ray photoemission spectroscopy (SXPS) have been used to study the high temperature thermal stability of ultra-thin atomic layer deposited (ALD) HfO{sub 2} layers (∼1 nm) on sulphur passivated and hydrofluoric acid (HF) treated germanium surfaces. The interfacial oxides which are detected for both surface preparations following HfO{sub 2} deposition can be effectively removed by annealing upto 700 °C without any evidence of chemical interaction at the HfO{sub 2}/Ge interface. The estimated valence and conduction band offsets for the HfO{sub 2}/Ge abrupt interface indicated that effective barriers exist to inhibit carrier injection.

  15. Multi-resonance orbital model applied to high-frequency quasi-periodic oscillations observed in Sgr A*

    CERN Document Server

    Kotrlova, Andrea; Torok, Gabriel

    2013-01-01

    The multi-resonance orbital model of high-frequency quasi-periodic oscillations (HF QPOs) enables precise determination of the black hole dimensionless spin a if observed set of oscillations demonstrates three (or more) commensurable frequencies. The black hole spin is related to the frequency ratio only, while its mass M is related to the frequency magnitude. The model is applied to the triple frequency set of HF QPOs observed in Sgr A* source with frequency ratio 3:2:1. Acceptable versions of the multi-resonance model are determined by the restrictions on the Sgr A* supermassive black hole mass. Among the best candidates the version of strong resonances related to the black hole "magic" spin a=0.983 belongs. However, the version demonstrating the best agreement with the mass restrictions predicts spin a=0.980.

  16. High-pressure synthesis and crystal structures of beta- M NX (M = Zr, Hf; X = Cl, Br, I)

    CERN Document Server

    Chen, X; Yamanaka, S

    2002-01-01

    The single crystals of six kinds of metal nitride halide, beta- M NX (M = Zr, Hf; X = Cl, Br, I), were grown in sealed Au (or Pt) tubes by the reaction of M N or M NX powders with NH sub 4 X as fluxes under high-temperature and high-pressure conditions such as 3-5 GPa at 900-1200 sup o C. The x-ray structure analysis revealed that all six kinds of compound crystallize in a rhombohedral space group R3-bar m, Z = 6. beta-ZrNCl, beta-ZrNBr, and beta-HfNCl are isotypic with SmSI, and the others isostructural with YOF.

  17. Lattice Thermal Conductivity of Ultra High Temperature Ceramics ZrB2 and HfB2 from Atomistic Simulations

    Science.gov (United States)

    Lawson, John W.; Murray, Daw S.; Bauschlicher, Charles W., Jr.

    2011-01-01

    Atomistic Green-Kubo simulations are performed to evaluate the lattice thermal conductivity for single crystals of the ultra high temperature ceramics ZrB2 and HfB2 for a range of temperatures. Recently developed interatomic potentials are used for these simulations. Heat current correlation functions show rapid oscillations which can be identified with mixed metal-Boron optical phonon modes. Agreement with available experimental data is good.

  18. High frequency epidural stimulation across the respiratory cycle evokes phrenic short-term potentiation after incomplete cervical spinal cord injury.

    Science.gov (United States)

    Gonzalez-Rothi, Elisa J; Streeter, Kristi A; Hanna, Marie H; Stamas, Anna C; Reier, Paul J; Baekey, David M; Fuller, David D

    2017-06-14

    C2 spinal hemilesion (C2Hx) paralyzes the ipsilateral diaphragm, but recovery is possible through activation of "crossed spinal" synaptic inputs to ipsilateral phrenic motoneurons. We tested the hypothesis that high frequency epidural stimulation (HF-ES) would potentiate ipsilateral phrenic output after subacute and chronic C2Hx. HF-ES (300 Hz) was applied to the ventrolateral C4 or T2 spinal cord ipsilateral to C2Hx in anesthetized and mechanically ventilated adult rats. Stimulus duration was 60-sec and currents ranged from 100-1000 µA. Bilateral phrenic nerve activity and ipsilateral hypoglossal nerve activity were recorded before and after HF-ES. Higher T2 stimulus currents potentiated ipsilateral phasic inspiratory activity at both 2- and 12-wks post-C2Hx, while higher stimulus currents delivered at C4 potentiated ipsilateral phasic phrenic activity only at 12-wks (P=0.028). Meanwhile, tonic output in the ipsilateral phrenic nerve reached 500% of baseline values at the high currents with no difference between 2- and 12-wks. HF-ES did not trigger inspiratory burst frequency changes. Similar responses occurred following T2 HF-ES. Increases in contralateral phrenic and XII nerve output were induced by C4 and T2 HF-ES at higher currents, but the relative magnitude of these changes was small compared to the ipsilateral phrenic response. We conclude that following incomplete cervical SCI, HF-ES of the ventrolateral mid-cervical or thoracic spinal cord can potentiate efferent phrenic motor output with little impact on inspiratory burst frequency. However, the substantial increases in tonic output indicate that the uninterrupted 60-sec stimulation paradigm used here is unlikely to be useful for respiratory muscle activation after spinal injury. Copyright © 2016, Journal of Neurophysiology.

  19. Surface Circulation in the Iroise Sea (W. Brittany) from High Resolution HF Radar Mapping

    Science.gov (United States)

    2013-01-01

    ratios and also a real data set from the radar experiment in Bodega Bay, northern Cal- ifornia, in the Gulf of Lion, western Mediterranean (Sentchev et...2005. HF radar observations of surface circula- tion off Bodega Bay (northern California, USA). J. Geophys. Res. 110, C10020. doi:10.1029

  20. Power-Stepped HF Cross Modulation Experiments at HAARP

    Science.gov (United States)

    Greene, S.; Moore, R. C.; Langston, J. S.

    2013-12-01

    High frequency (HF) cross modulation experiments are a well established means for probing the HF-modified characteristics of the D-region ionosphere. In this paper, we apply experimental observations of HF cross-modulation to the related problem of ELF/VLF wave generation. HF cross-modulation measurements are used to evaluate the efficiency of ionospheric conductivity modulation during power-stepped modulated HF heating experiments. The results are compared to previously published dependencies of ELF/VLF wave amplitude on HF peak power. The experiments were performed during the March 2013 campaign at the High Frequency Active Auroral Research Program (HAARP) Observatory. HAARP was operated in a dual-beam transmission format: the first beam heated the ionosphere using sinusoidal amplitude modulation while the second beam broadcast a series of low-power probe pulses. The peak power of the modulating beam was incremented in 1-dB steps. We compare the minimum and maximum cross-modulation effect and the amplitude of the resulting cross-modulation waveform to the expected power-law dependence of ELF/VLF wave amplitude on HF power.

  1. Structure, optical properties and thermal stability of HfErO films deposited by simultaneous RF and VHF magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, H.Y. [Soochow University, College of Physics, Optoelectronics and Energy and Collaborative Innovation Center of Suzhou Nano Science and Technology, Suzhou (China); Nanjing University of Posts and Telecommunications, School of Tongda, Nanjing (China); Soochow University, Key Lab of Advanced Optical Manufacturing Technologies of Jiangsu Province and Key Lab of Modern Optical Technologies of Education Ministry of China, Suzhou (China); He, H.J.; Zhang, Z.; Jin, C.G.; Yang, Y.; Wang, Y.Y.; Ye, C. [Soochow University, College of Physics, Optoelectronics and Energy and Collaborative Innovation Center of Suzhou Nano Science and Technology, Suzhou (China); Soochow University, Key Lab of Advanced Optical Manufacturing Technologies of Jiangsu Province and Key Lab of Modern Optical Technologies of Education Ministry of China, Suzhou (China); Zhuge, L.J. [Soochow University, Key Lab of Advanced Optical Manufacturing Technologies of Jiangsu Province and Key Lab of Modern Optical Technologies of Education Ministry of China, Suzhou (China); Soochow University, Analysis and Testing Center, Suzhou (China); Wu, X.M. [Soochow University, College of Physics, Optoelectronics and Energy and Collaborative Innovation Center of Suzhou Nano Science and Technology, Suzhou (China); Soochow University, Key Lab of Advanced Optical Manufacturing Technologies of Jiangsu Province and Key Lab of Modern Optical Technologies of Education Ministry of China, Suzhou (China); Chinese Academy of Sciences, State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Shanghai (China)

    2015-01-23

    HfErO films are deposited on Si substrates by simultaneous radio frequency (RF) and very high frequency (VHF) magnetron sputtering technique. The content of the doped ingredient of Er and the body composition of HfO{sub x} are, respectively, controlled through the VHF and RF powers. Low content of Er doping in the HfErO films can be achieved, because the VHF source of 27.12 MHz has higher ion energy and lower ion flux than the RF source resulting in low sputtering rate in the magnetron sputtering system. The structure, optical properties and thermal stability of the HfErO films are investigated in this work. Results show that the doped content of Er is independently controlled by the VHF power. The oxygen vacancies are created by the Er incorporation. The hafnium in the HfErO films forms mixed valence of Hf{sup 2+} and Hf{sup 4+}. The HfErO films are composed with the structures of HfO{sub 2}, HfO and ErO{sub x}, which can be optimized through the VHF power. At high VHF power, the Hf-Er-O bonds are formed, which demonstrates that the Er atoms are doped into the lattice of HfO{sub 2} in the HfErO films. The HfErO films have bad thermal stability as the crystallization temperature decreases from 900 to 800 C. After thermal annealing, cubic phase of HfO{sub 2} are stabilized, which is ascribed to the oxygen vacancies creation by the Er incorporation. The optical properties such as the refractive index and the optical band gap of the HfErO films are optimized by the VHF power. (orig.)

  2. Real-Time 12-Lead High-Frequency QRS Electrocardiography for Enhanced Detection of Myocardial Ischemia and Coronary Artery Disease

    Science.gov (United States)

    Schlegel, Todd T.; Kulecz, Walter B.; DePalma, Jude L.; Feiveson, Alan H.; Wilson, John S.; Rahman, M. Atiar; Bungo, Michael W.

    2004-01-01

    Several studies have shown that diminution of the high-frequency (HF; 150-250 Hz) components present within the central portion of the QRS complex of an electrocardiogram (ECG) is a more sensitive indicator for the presence of myocardial ischemia than are changes in the ST segments of the conventional low-frequency ECG. However, until now, no device has been capable of displaying, in real time on a beat-to-beat basis, changes in these HF QRS ECG components in a continuously monitored patient. Although several software programs have been designed to acquire the HF components over the entire QRS interval, such programs have involved laborious off-line calculations and postprocessing, limiting their clinical utility. We describe a personal computer-based ECG software program developed recently at the National Aeronautics and Space Administration (NASA) that acquires, analyzes, and displays HF QRS components in each of the 12 conventional ECG leads in real time. The system also updates these signals and their related derived parameters in real time on a beat-to-beat basis for any chosen monitoring period and simultaneously displays the diagnostic information from the conventional (low-frequency) 12-lead ECG. The real-time NASA HF QRS ECG software is being evaluated currently in multiple clinical settings in North America. We describe its potential usefulness in the diagnosis of myocardial ischemia and coronary artery disease.

  3. Structure and thermoelastic martensitic transformations in ternary Ni-Ti-Hf alloys with a high-temperature shape memory effect

    Science.gov (United States)

    Pushin, V. G.; Kuranova, N. N.; Pushin, A. V.; Uksusnikov, A. N.; Kourov, N. I.

    2016-07-01

    The effect of alloying by 12-20 at % Hf on the structure, the phase composition, and the thermoelastic martensitic transformations in ternary alloys of the quasi-binary NiTi-NiHf section is studied by transmission electron microscopy, scanning electron microscopy, electron diffraction, and X-ray diffraction. The electrical resistivity is measured at various temperatures to determine the critical transformation temperatures. The data on phase composition are used to plot a full diagram for the high-temperature thermoelastic B2 ↔ B19' martensitic transformations, which occur in the temperature range 320-600 K when the hafnium content increases from 12 to 20 at %. The lattice parameters of the B2 and B19' phases are measured, and the microstructure of the B19' martensite is analyzed.

  4. Two-way shape memory effect and its stability in Ti-Ni-Hf high temperature shape memory alloy

    Institute of Scientific and Technical Information of China (English)

    MENG Xiang-long; WU Ye; CAI Wei; ZHAO Lian-cheng

    2005-01-01

    The two-way shape memory effect (TWSME) in a Ti36 Ni49 Hf15 high temperature shape memory alloy (SMA) was systematically studied by bending tests. In the TiNiHf alloy, the martensite deformation is an effective method to get two-way shape memory effect even with a small deformation strain. The results indicate that the internal stress field formed by the bending deformation is in the direction of the preferentially oriented martensite variants formed during the bending deformation. Upon cooling the preferentially oriented martensite variants form under such an oriented stress field, which should be responsible for the generation of the two-way shape memory effect.Proper training process benefits the formation of the oriented stress field, resulting in the improvement of the twoway shape memory effect. A maximum TWSME of 0.88 % is obtained in the present alloy.

  5. High-frequency Ultrasound Doppler System for Biomedical Applications with a 30 MHz Linear Array

    Science.gov (United States)

    Xu, Xiaochen; Sun, Lei; Cannata, Jonathan M.; Yen, Jesse T.; Shung, K. Kirk

    2008-01-01

    In this paper, we report the development of the first high-frequency (HF) pulsed-wave Doppler system using a 30 MHz linear array transducer to assess the cardiovascular functions in small animal. This array based pulsed-wave Doppler system included a 16-channel HF analog beamformer, a HF pulsed-wave Doppler module, timing circuits, HF bipolar pulsers, and analog front-ends. The beamformed echoes acquired by the 16 channel analog beamformer, were directly fed to the HF pulsed-wave Doppler module. Then the in-phase and quadrature-phase (IQ) audio Doppler signals were digitized by either a sound card or a Gage digitizer and stored in a PC. The Doppler spectrogram was displayed on a PC in real time. The two-way beam-widths were determined to be 160 μm to 320 μm when the array was electronically focused at different focal points at depths from 5–10 mm. A micro flow phantom, consisting of a polyimide tube with inner diameter of 127 μm, and the wire phantom were used to evaluate and calibrate the system. The results show that the system is capable of detecting motion velocity of the wire phantom as low as 0.1 mm/s, and detecting blood-mimicking flow velocity in the 127 μm tube lower than 7 mm/s. The system was subsequently used to measure the blood flow in vivo in two mouse abdominal superficial vessels with diameters of approximately 200 μm, and a mouse aorta close to the heart. These results demonstrated that this system may become an indispensable part of the current HF array based imaging systems for small animal studies. PMID:17993243

  6. High frequency group pulse electrochemical machining

    Institute of Scientific and Technical Information of China (English)

    WU Gaoyang; ZHANG Zhijing; ZHANG Weimin; TANG Xinglun

    2007-01-01

    In the process of machining ultrathin metal structure parts,the signal composition of high frequency group pulse,the influence of frequency to reverse current,and the design of the cathode in high frequency group pulse electrochemical machining (HGPECM) are discussed.The experiments on process were carried out.Results indicate that HGPECM can greatly improve the characteristics of the inter-electrode gap flow field,reduce electrode passivation,and obtain high machining quality.The machining quality is obviously improved by increasing the main pulse frequency.The dimensional accuracy reaches 30-40 pro and the roughness attained is at 0.30-0.35 μm.High frequency group pulse electrochemical machining can be successfully used in machining micro-parts.

  7. Effective market influence. An effect chain analysis of NUTEK`s high-frequency lighting campaign

    Energy Technology Data Exchange (ETDEWEB)

    Goeransson, C.; Faugert, S. [SIPU Utvaerdering, Stockholm (Sweden); Baeckman, B.; Arndt, J. [B2B AB, Stockholm (Sweden)

    1994-12-31

    This report is an evaluation of NUTEK`s `Better lighting and more energy-efficient high-frequency fluorescent tube luminaries` campaign. It is concerned with the ways in which NUTEK can influence the spread and use of high-frequency (HF) lighting devices. It also shows that NUTEK actually has affected (contributed to) development in the area. The report analyses and quantifies (as far as possible) how much NUTEK has influenced the various parties concerned in the sector, their attitudes and their actions. 14 figs, 5 tabs

  8. High performance organic nonvolatile memory transistors based on HfO2 and poly(α-methylstyrene) electret hybrid charge-trapping layers

    Science.gov (United States)

    Xu, W. C.; He, H. X.; Jing, X. S.; Wu, S. J.; Zhang, Z.; Gao, J. W.; Gao, X. S.; Zhou, G. F.; Lu, X. B.; Liu, J.-M.

    2017-08-01

    In this work, we fabricated a high performance flash-type organic nonvolatile memory transistor, which adopted polymer-electret poly(α-methylstyrene) (PαMS) and HfO2 films as hybrid charge trapping layer (CTL). Compared with a single HfO2 or PαMS CTL structure, the hybrid HfO2/PαMS CTL structure can provide enhanced charge trapping efficiency to increase the device operation speed and reduce the leakage current to boost the device reliability. The fabricated nonvolatile organic memory transistors with the hybrid CTL shows excellent electrical properties, including low operation voltage (8 V), high speed (memories.

  9. High frequency dynamics in centrifugal compressors

    NARCIS (Netherlands)

    Twerda, A.; Meulendijks, D.; Smeulers, J.P.M.; Handel, R. van den; Lier, L.J. van

    2008-01-01

    Problems with centrifugal compressors relating to high frequency, i.e. Blade passing frequency (BPF) are increasing. Pulsations and vibrations generated in centrifugal compressors can lead to nuisance, due to strong tonal noise, and even breakdown. In several cases the root cause of a failure or a

  10. High frequency dynamics in centrifugal compressors

    NARCIS (Netherlands)

    Twerda, A.; Meulendijks, D.; Smeulers, J.P.M.; Handel, R. van den; Lier, L.J. van

    2008-01-01

    Problems with centrifugal compressors relating to high frequency, i.e. Blade passing frequency (BPF) are increasing. Pulsations and vibrations generated in centrifugal compressors can lead to nuisance, due to strong tonal noise, and even breakdown. In several cases the root cause of a failure or a n

  11. Association between RR interval and high-frequency heart rate variability acquired during short-term, resting recordings with free and paced breathing.

    Science.gov (United States)

    Sandercock, Gavin; Gladwell, Valerie; Dawson, Samantha; Nunan, David; Brodie, David; Beneke, Ralph

    2008-07-01

    High-frequency (HF) oscillations in RR interval from 0.15-0.40 Hz are widely accepted as a measure of cardiac vagal outflow but the HF/RR relationship appears complex, particularly with longer RR intervals. The aim of this study was to evaluate the HF/RR interval relationship during free and paced breathing. HF power and mean RR interval length were recorded in 150 men and 120 women (mean age 34.5 +/- 11.4) during 5 min of supine rest with either free or paced (12 cycles min(-1)) breathing. Linear and quadratic models were used to assess the relationship between RR interval and the natural logarithm of HF power (lnHF). The RR interval length at which there was no further increase in lnHF was determined as the deflection point. ANCOVA was used to determine differences in the linear regression slopes for lnHF/RR with paced or free breathing. With free breathing (n = 131), the adjusted R(2) was similar between linear (15.3%) and quadratic (17.5%) fits and saturation of lnHF occurred within the recorded RR interval range (1326 ms). With paced breathing (n = 139), adjusted R(2) values were again similar between linear (22.4%) and quadratic (23.2%) fits. The deflection point was outside the range of recorded RR intervals at 1458 ms. ANCOVA showed a significant difference in the slope of the lnHF/RR regression lines between free and paced breathing. The lnHF/RR relationship is weaker when derived from between-subject recordings than from repeated within-subject samples. lnHF/RR showed evidence of saturation at approximately 45 bpm with free breathing. With paced breathing, a deflection in lnHF was found outside the recorded RR interval range ( approximately 41 bpm). Paced breathing creates a stronger lnHF/RR relationship. The slope of the lnHF/RR regression line with paced breathing is significantly different from that observed with free breathing. It appears that lnHF is a valid index of vagal outflow, except in subjects with very low heart rates. Paced breathing data

  12. Ionosonde Studies of Field-Aligned Irregularities during High-Power HF Heating at Arecibo,

    Science.gov (United States)

    1988-02-01

    September 1981 ionospheric HF heating campaign at Arecibo have been simulated using simplified ionospheric models -’ and analytic raytracing techniques. The...R given by R = ((h )2 -(V ))/6B) NR h6B is the radar range of the oblique echoes and h ERT the virtual height of the overhead ionization measured at...However, the conditions of the Arecibo experiment are such that various simplifications can be made, including the adoption of analytic raytracing

  13. A Compact High Frequency Doppler Radio Scatterometer for Coastal Oceanography

    Science.gov (United States)

    Flament, P. J.; Harris, D.; Flament, M.; Fernandez, I. Q.; Hlivak, R.; Flores-vidal, X.; Marié, L.

    2016-12-01

    A low-power High Frequency Doppler Radar has been designed for large series production. The use of commercial-off-the-shelf components is maximized to minimize overall cost. Power consumption is reduced to 130W in full duty and 20W in stand-by under 20-36 V-DC, thus enabling solar/wind and/or fuel cell operation by default. For 8 channels, commercial components and sub-assemblies cost less than k20 excluding coaxial antenna cables, and less than four man-weeks of technician suffice for integration, testing and calibration, suggesting a final cost of about k36, based on production batches of 25 units. The instrument is integrated into passively-cooled 90x60x20 cm3 field-deployable enclosures, combining signal generation, transmitter, received, A/D converter and computer, alleviating the need for additional protection such as a container or building. It uses frequency-ramped continuous wave signals, and phased-array transmissions to decouple the direct path to the receivers. Five sub-assemblies are controlled by a Linux embedded computer: (i) direct digital synthesis of transmit and orthogonal local oscillator signals, derived from a low phase noise oven-controlled crystal; (ii) distributed power amplifiers totaling 5 W, integrated into λ/8 passive transmit antenna monopoles; (iii) λ/12 compact active receive antenna monopoles with embedded out-of-band rejection filters; (iv) analog receivers based on complex demodulation by double-balanced mixers, translating the HF spectrum to the audio band; (v) 24-bit analog-to-digital sigma-delta conversion at 12 kHz with 512x oversampling, followed by decimation to a final sampling frequency of 750 Hz. Except for the HF interference rejection filters, the electronics can operate between 3 and 50 MHz with no modification. At 13.5 MHz, 5 W transmit power, 15 min integration time, the high signal-to-noise ratio permits a typical range of 120 km for currents measurements with 8-antenna beam-forming. The University of Hawaii HFR

  14. SiHf(B)CN-based ultra-high temperature ceramic nanocomposites: Single-source precursor synthesis and behavior in hostile environments

    OpenAIRE

    Yuan, Jia

    2015-01-01

    Hf-containing ultra-high-temperature ceramics (UHTCs) are being pursued for Thermal Protection Systems (TPSs) for high-temperature applications (i.e., future hypersonic vehicles) in harsh environments. Most of these ceramic composites have been prepared using traditional powder techniques; however, the grain sizes of the resulting composites are limited to the micrometer range. Furthermore, nano-sized Hf-containing materials have proven to exhibit tremendously improved structural/functional p...

  15. Overview of the Advanced High Frequency Branch

    Science.gov (United States)

    Miranda, Felix A.

    2015-01-01

    This presentation provides an overview of the competencies, selected areas of research and technology development activities, and current external collaborative efforts of the NASA Glenn Research Center's Advanced High Frequency Branch.

  16. High Energy Single Frequency Resonant Amplifier Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This SBIR phase I project proposes a single frequency high energy resonant amplifier for remote sensing. Current state-of-art technologies can not provide all...

  17. High-frequency Electrocardiogram Analysis in the Ability to Predict Reversible Perfusion Defects during Adenosine Myocardial Perfusion Imaging

    Science.gov (United States)

    Tragardh, Elin; Schlegel, Todd T.; Carlsson, Marcus; Pettersson, Jonas; Nilsson, Klas; Pahlm, Olle

    2007-01-01

    Background: A previous study has shown that analysis of high-frequency QRS components (HF-QRS) is highly sensitive and reasonably specific for detecting reversible perfusion defects on myocardial perfusion imaging (MPI) scans during adenosine. The purpose of the present study was to try to reproduce those findings. Methods: 12-lead high-resolution electrocardiogram recordings were obtained from 100 patients before (baseline) and during adenosine Tc-99m-tetrofosmin MPI tests. HF-QRS were analyzed regarding morphology and changes in root mean square (RMS) voltages from before the adenosine infusion to peak infusion. Results: The best area under the curve (AUC) was found in supine patients (AUC=0.736) in a combination of morphology and RMS changes. None of the measurements, however, were statistically better than tossing a coin (AUC=0.5). Conclusion: Analysis of HF-QRS was not significantly better than tossing a coin for determining reversible perfusion defects on MPI scans.

  18. High Frequency Resolution TOA Analysis for ELF/VLFWave Generation Experiments at HAARP

    Science.gov (United States)

    Ruddle, J. D.; Moore, R. C.

    2014-12-01

    Modulated HF heating of the ionosphere in the presence of natural ionospheric current sources has been used as a method to generate electromagnetic ELF/VLF waves since the 1970's. In the ~1-5 kHz band, the amplitude and phase of the received ELF/VLF signal depends on the amplitude and phase of the conductivity modulation generated throughout the HF-heated ionospheric body, as well as on the signal propagation parameters (i.e., the attenuation and phase constants) between each of the current sources and the receiver. Recent signal processing advances have produced an accurate ELF/VLF time-of-arrival (TOA) analysis technique that differentiates line-of-sight and ionospherically-reflected signal components, determining the amplitude and phase of each component observed at the receiver. This TOA method requires a wide bandwidth (> 2.5 kHz) and therefore is relatively insensitive to the frequency-dependent nature of ELF/VLF wave propagation. In this paper, we present an improved ELF/VLF TOA method that is capable of providing high frequency resolution. The new analysis technique is applied to experimental observations of ELF/VLF signals generated by modulated heating at HAARP. We present measurements of the amplitude and phase of the received ELF/VLF signal as a function of frequency and compare the results with the predictions of an HF heating model.

  19. Hetero-epitaxial growth of the cubic single crystalline HfO 2 film as high k materials by pulsed laser ablation

    Science.gov (United States)

    Zhang, Xinqiang; Tu, Hailing; Wang, Xiaona; Xiong, Yuhua; Yang, Mengmeng; Wang, Lei; Du, Jun

    2010-10-01

    We report a hetero-epitaxial growth of cubic single crystalline HfO 2 film on Si substrates as high k materials by pulse laser ablation (PLA) at 820 °C. To eliminate the interfacial defects, the HfO 2 film has then been annealed at 900 °C for 5 min in N 2. Reflection high-energy electron diffraction (RHEED) results indicate orientation of the HfO 2 film on Si substrates corresponding to (∥( and [∥[. An interface layer has been revealed by high-resolution transmission electron microscope (HRTEM). Through capacitance-voltage ( C- V) and current-voltage ( I- V), it has been obtained that the leakage current of the HfO 2 gate insulator with dielectric constant of 26 is 5×10 -6 A/cm 2 at -1 V.

  20. High-pressure structure prediction of Hf-C system and first-principle simulation of their electronic prop erties%Hf-C体系的高压结构预测及电子性质第一性原理模拟∗

    Institute of Scientific and Technical Information of China (English)

    彭军辉; 曾庆丰; 谢聪伟; 朱开金; 谭俊华

    2015-01-01

    Hafnium carbides (Hf-C system), known as ultra-high temperature ceramics, have attracted growing attention because of their unique features. In this paper, we carry out researches on the stable crystal structures in the Hf-C system at high pressures, using a variable-composition ab initio evolutionary algorithm implemented in the USPEX code. In addition to the ambient-pressure structures HfC (F m¯3m), there are two new compounds Hf3C2 and Hf6C5 and two high-pressure structures of HfC. When pressures are lower than 100 GPa, no new structures are found other than those at ambient pressure, and Hf3C2 and Hf6C5 become metastable at 20 GPa and 100 GPa, respectively. At 200 GPa, a new compound Hf2C is found, and the stable structure HfC has changed from F m¯3m to C2/m. At 300 GPa, another new compound HfC2 is found. At 400 GPa, the stable structure of HfC has changed again to the space group P nma. And at 500 GPa, the stable structures are Hf2C, HfC2 and HfC (P nma), no new structures are found except those at 400 GPa. The composition-pressure phase diagram that shows the pressure range of stable structures in Hf-C system is simulated by calculation of their enthalpies. When the pressures are lower than 15.5 GPa and 37.7 GPa, Hf3C2 and Hf6C5 are stable, respectively, and their space groups are both of C2/m. And Hf2C and HfC2, with space group I4/m and Immm, respectively become stable structures when the pressure is higher than 102.5 GPa and 215.5 GPa, respectively. The phase-transition route of HfC is F m¯3m → C2/m → P nma, and the two phase-transition pressures are 185.5 GPa and 322 GPa, respectively, which are different from the conclusion of Zhao. Then we will show and discuss the newly predicted high-pressure structures and their crystallographic data, such as volume, lattice constants and atom positions. The crystal structures of HfC are described in the literature. The structure of Hf2C contains 12 atoms in the conventional cell, and carbon atoms lie at the

  1. High-Frequency Link Inverter for Fuel Cells Based on Multiple-Carrier PWM

    Institute of Scientific and Technical Information of China (English)

    2004-01-01

    HIGH-FREQUENCY (I-IF) ac link inverter topologies, with or without soft switching, have important practical advantages compared to more conventional dc link inverters in terms of isolation, size of magnetics, and other properties. It is possible to obtain these basic advantages directly in a conventional PWM inverter with trans former-coupled output, but only if the transformer can handle the low modulating frequency. HF link topologies have not been common for medium power (1 to 20kW), largely because of the number of power stages and control complexity.

  2. Ion-Acoustic Instability in the Presence of High Frequency Oscillations

    DEFF Research Database (Denmark)

    Juul Rasmussen, Jens; Sandu, D.; Schrittwieser, R.

    1977-01-01

    Measurements are presented of a standing ion-acoustic wave instability, which is excited by a positively biased grid inserted perpendicularly into the plasma column of a single-ended Q-machine, under the influence of a high frequency signal superimposed onto the positive voltage at the grid....... The experimental results show that in certain regions of the frequency and amplitude of the h.f. signal the ion wave instability is stabilized or destabilized. A possible explanation of these effects is presented....

  3. High frequency conductivity in carbon nanotubes

    Directory of Open Access Journals (Sweden)

    S. S. Abukari

    2012-12-01

    Full Text Available We report on theoretical analysis of high frequency conductivity in carbon nanotubes. Using the kinetic equation with constant relaxation time, an analytical expression for the complex conductivity is obtained. The real part of the complex conductivity is initially negative at zero frequency and become more negative with increasing frequency, until it reaches a resonance minimum at ω ∼ ωB for metallic zigzag CNs and ω < ωB for armchair CNs. This resonance enhancement is indicative for terahertz gain without the formation of current instabilities induced by negative dc conductivity. We noted that due to the high density of states of conduction electrons in metallic zigzag carbon nanotubes and the specific dispersion law inherent in hexagonal crystalline structure result in a uniquely high frequency conductivity than the corresponding values for metallic armchair carbon nanotubes. We suggest that this phenomenon can be used to suppress current instabilities that are normally associated with a negative dc differential conductivity.

  4. High Precision Measurements Using High Frequency Signals

    CERN Document Server

    Jin, Aohan; Sakurai, Atsunori; Liu, Liang; Edman, Fredrik; Öwall, Viktor; Pullerits, Tonu; Karki, Khadga J

    2014-01-01

    Generalized lock-in amplifiers use digital cavities with Q-factors as high as 5X10^8. In this letter, we show that generalized lock-in amplifiers can be used to analyze microwave (giga-hertz) signals with a precision of few tens of hertz. We propose that the physical changes in the medium of propagation can be measured precisely by the ultra-high precision measurement of the signal. We provide evidence to our proposition by verifying the Newton's law of cooling by measuring the effect of change in temperature on the phase and amplitude of the signals propagating through two calibrated cables. The technique could be used to precisely measure different physical properties of the propagation medium, for example length, resistance, etc. Real time implementation of the technique can open up new methodologies of in-situ virtual metrology in material design.

  5. Surface circulation at the Strait of Gibraltar: A combined HF radar and high resolution model study

    Science.gov (United States)

    Soto-Navarro, Javier; Lorente, Pablo; Álvarez Fanjul, Enrique; Carlos Sánchez-Garrido, Jose; García-Lafuente, Jesús

    2016-03-01

    Observations from a high frequency radar system and outputs from a high resolution operational ocean model working at the Strait of Gibraltar have been analyzed and compared during the period February 2013 to September 2014 in order to evaluate their capability to resolve the surface circulation of the region. The description of the mean circulation patterns has been statistically assessed, showing good agreement, particularly in the central region of the strait corresponding with the Atlantic Jet (AJ) stream, although some short scale features are not reproduced by the model. In the frequency domain very high concordance is observed. Tidal maps of diurnal and semidiurnal constituents are in good agreement with previous observations. The analysis of the model and radar response to the wind forcing reveals that the low resolution of the model wind-forcing field and its deeper superficial level smoothes the wind effect on the simulated currents. The first three EOF modes account for the 86% of model and radar variances. The coincidence between the observed and simulated patterns is very significant for the first two modes, which account for the mean velocity field and the latitudinal shifting of the AJ consequence of the flow-topography interaction. The third mode captures the wind-induced circulation, and greater discrepancies are found in this case. Results underline the complementary character of both systems: radar observations improve the model description, resolving short scale processes, while the model completes the radar information when the time or spatial coverage is poorer.

  6. Hf-based high-k dielectrics process development, performance characterization, and reliability

    CERN Document Server

    Kim, Young-Hee

    2006-01-01

    In this work, the reliability of HfO2 (hafnium oxide) with poly gate and dual metal gate electrode (Ru-Ta alloy, Ru) was investigated. Hard breakdown and soft breakdown, particularly the Weibull slopes, were studied under constant voltage stress. Dynamic stressing has also been used. It was found that the combination of trapping and detrapping contributed to the enhancement of the projected lifetime. The results from the polarity dependence studies showed that the substrate injection exhibited a shorter projected lifetime and worse soft breakdown behavior, compared to the gate injection. The o

  7. Studies of Plasma Instability Process Excited by Ground Based High Power HF (Heating) Facilities

    Science.gov (United States)

    2007-11-02

    the altitude z = 285 km. Night time plasma line intensities were observed to be enhanced by a factor 10 ÷ 100 extended to altitude below 250 km. When HF...waves, whose wave vector is directed toward the radar, and the phase velocity vph is equal to the velocity of suprathermal electrons v vph =(1/2) λr...averaged and in final form depends on two scalar factors only: full power density P absorbed by fast electrons in the acceleration layer, and characteristic

  8. Extremely high frequency RF effects on electronics.

    Energy Technology Data Exchange (ETDEWEB)

    Loubriel, Guillermo Manuel; Vigliano, David; Coleman, Phillip Dale; Williams, Jeffery Thomas; Wouters, Gregg A.; Bacon, Larry Donald; Mar, Alan

    2012-01-01

    The objective of this work was to understand the fundamental physics of extremely high frequency RF effects on electronics. To accomplish this objective, we produced models, conducted simulations, and performed measurements to identify the mechanisms of effects as frequency increases into the millimeter-wave regime. Our purpose was to answer the questions, 'What are the tradeoffs between coupling, transmission losses, and device responses as frequency increases?', and, 'How high in frequency do effects on electronic systems continue to occur?' Using full wave electromagnetics codes and a transmission-line/circuit code, we investigated how extremely high-frequency RF propagates on wires and printed circuit board traces. We investigated both field-to-wire coupling and direct illumination of printed circuit boards to determine the significant mechanisms for inducing currents at device terminals. We measured coupling to wires and attenuation along wires for comparison to the simulations, looking at plane-wave coupling as it launches modes onto single and multiconductor structures. We simulated the response of discrete and integrated circuit semiconductor devices to those high-frequency currents and voltages, using SGFramework, the open-source General-purpose Semiconductor Simulator (gss), and Sandia's Charon semiconductor device physics codes. This report documents our findings.

  9. Effect of High-Frequency Electric Field on Propagation of Electrostatic Wave in a Non-Uniform Relativistic Plasma Waveguide

    Institute of Scientific and Technical Information of China (English)

    Kh. H. EL-SHORBAGY

    2008-01-01

    The effect of a high frequency (HF) electric field on the propagation of electrostatic wave in a 2D non-uniform relativistic plasma waveguide is investigated. A variable separation method is applied to the two-fluid plasma model. An analytical study of the reflection of electro-static wave propagation along a magnetized non-uniform relativistic plasma slab subjected to an intense HF electric field is presented and compared with the case of a non relativistic plasma. It is found that, when the frequency of the incident wave is close to the relativistic electron plasma frequency, the plasma is less reflective due to the presence of both an HF field and the effect of rel-ativistic electrons. On the other hand, for a low-frequency incident wave the reflection coefficient is directly proportional to the amplitude of the HF field. Also, it is shown that the relativistic electron plasma leads to a decrease in the value of reflection coefficient in comparison with the case of the non relativistic plasma.

  10. Modulation of auroral electrojet currents using dual HF beams with ELF phase offset

    Science.gov (United States)

    Golkowski, M.; Cohen, M.; Moore, R. C.

    2012-12-01

    The modulation of naturally occuring ionospheric currents with high power radio waves in the high frequency (HF, 3-10 MHz) band is a well known technique for generation of extremely low frequency (ELF, 3-3000 Hz) and very low frequency (VLF, 3-30 kHz) waves. We use the heating facility of the High Frequency Active Auroral Research Program (HAARP) to investigate the effect of using dual HF beams with an ELF/VLF phase offset between the modulation waveforms. Experiments with offset HF beams confirm the model of independent ELF/VLF sources. Experiments with co-located HF beams exhibit interaction between the first and second harmonics of the modulated tones when square and sine wave modulation waveforms are employed. Using ELF/VLF phase offsets for co-loacted beams is also shown to be a potential diagnostic for the D-region ionospheric profile.

  11. Evolution of Very High Frequency Power Supplies

    DEFF Research Database (Denmark)

    Knott, Arnold; Andersen, Toke Meyer; Kamby, Peter

    2013-01-01

    in radio frequency transmission equipment helps to overcome those. However those circuits were not designed to meet the same requirements as power converters. This paper summarizes the contributions in recent years in application of very high frequency (VHF) technologies in power electronics, shows results......The ongoing demand for smaller and lighter power supplies is driving the motivation to increase the switching frequencies of power converters. Drastic increases however come along with new challenges, namely the increase of switching losses in all components. The application of power circuits used...

  12. Microstructure and Room Temperature Properties of a High-Entropy TaNbHfZrTi Alloy (Postprint)

    Science.gov (United States)

    2014-04-01

    Vickers microhardness are  = 9.94 g/cm3 and Hv = 3826 MPa. The alloy has high compression yield strength (0 2 = 929 MPa) and ductility (ε > 50%). The...the BCC crystal structure, density, , Vickers microhardness, Hv, and yield strength, 0.2, of the pure metals and the studied alloy. Metal Ta Nb Hf...agreement with the random (disordered) distribution of the alloying elements in the BCC lattice of the alloy. The RT yield strength and Vickers microhardness

  13. Microstructure and properties of an HfB{sub 2}-SiC composite for ultra high temperature applications

    Energy Technology Data Exchange (ETDEWEB)

    Monteverde, F.; Bellosi, A. [National Research Council, Institute of Science and Technology for Ceramics, Via Granarolo 64, 48018 Faenza (Italy)

    2004-05-01

    An ultra-high-temperature ceramic (UHTC) based on HfB{sub 2} was produced. The microstructure consisted of fine and regular diboride grains (2 {mu}m average size), with SiC particulate distributed intergranularly, not rarely in clustered formation, and low levels of secondary phases were identified. The resulting thermo-mechanical properties proved interesting results for microhardness and fracture toughness. The microstructural alteration experienced within the explored temperature range renders the material unsuitable for service in extreme conditions of temperature and pressure. (Abstract Copyright [2004], Wiley Periodicals, Inc.)

  14. High Sensitivity, High Frequency and High Time Resolution Decimetric Spectroscope

    Science.gov (United States)

    Sawant, H. S.; Rosa, R. R.

    1990-11-01

    RESUMEN. Se ha desarrollado el primer espectroscopio decimetrico latino americano operando en una banda de 100 MHz con alta resoluci6n de fre- cuencia (100 KHz) y tiempo (10 ms), alrededor de cualquier centro de frecuencia en el intervalo de 2000-200 MHz. El prop6sito de esta nota es describir investigaciones solares y no solares que se planean, progra ma de investigaci6n y la situaci6n actual de desarrollo de este espectroscopio. ABSTRACT. First Latin American Decimetric Spectroscope operating over a band of 100 MHz with high resolution in frequency (100 KHz) and time (10 ms), around any center frequency in the range of 2000-200 MHz is being developed. The purpose of this note is to describe planned solar, and non-solar, research programmes and present status of development of this spectroscope. Keq wo : INSTRUMENTS - SPECTROSCOPY

  15. Effects of Hf and B on high temperature low stress creep behavior of a second generation Ni-based single crystal superalloy DD11

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Y.S. [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China); Science and Technology on Advanced High Temperature Structural Materials Laboratory, Beijing Institute of Aeronautical Materials, Beijing 100095 (China); Zhang, J.; Luo, Y.S. [Science and Technology on Advanced High Temperature Structural Materials Laboratory, Beijing Institute of Aeronautical Materials, Beijing 100095 (China); Li, J. [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China); NCS Testing Technology Co., Ltd., Beijing 100081 (China); Tang, D.Z., E-mail: Dingzhongtang621@163.com [Science and Technology on Advanced High Temperature Structural Materials Laboratory, Beijing Institute of Aeronautical Materials, Beijing 100095 (China)

    2016-08-30

    The as-cast and heat-treated microstructures and high temperature creep properties have been investigated in four experimental Ni-based single crystal superalloys containing various levels of Hf addition (0–0.4 wt%) and B addition (0–0.02 wt%). The experimental results indicated that the creep rupture life showed an improvement with individual addition of Hf, but it was decreased with individual addition of B. The elemental partitioning ratio and interfacial dislocation spacing of γ/γ′ were obviously changed with individual Hf or B additions. Meanwhile, the formation of secondary phases, such as the blocky MC carbide, script-like shape M{sub 3}B{sub 2} phases, was observed in the creep samples, which was also closely related to the high temperature creep behaviors. The high volume fraction of residual (γ+γ′) eutectics was mainly attributed to the significant decrease of creep rupture life for the present experimental alloy containing both Hf and B additions. This study is helpful to better understand Hf and B's role of strengthening mechanism and to optimize Hf and B additions in single crystal superalloys.

  16. Investigation of high-frequency pipe welding

    Science.gov (United States)

    Konovalov, Nikolai A.; Lakhno, Nikolay I.; Gushchin, A. G.; Putryk, N. D.; Kovalenko, Vladimir I.; Galkina, V. A.; Veselovsky, Vladimir B.; Furmanov, Valeri B.; Kovika, Nikolai D.; Novikov, Leonid V.; Shcherbina, V. N.

    1993-01-01

    For investigation of a pipe welding process at high-frequency heating aimed at increasing of pipe quality and decreasing of spoilage, the use of high-speed recording and TV-technique is considered to be effective. The authors have created a visual inspection system for pipe welding process studies at a tube mill of the Novomoskovsk Pipe Plant.

  17. High-Order Frequency-Locked Loops

    DEFF Research Database (Denmark)

    Golestan, Saeed; Guerrero, Josep M.; Quintero, Juan Carlos Vasquez

    2017-01-01

    In very recent years, some attempts for designing high-order frequency-locked loops (FLLs) have been made. Nevertheless, the advantages and disadvantages of these structures, particularly in comparison with a standard FLL and high-order phase-locked loops (PLLs), are rather unclear. This lack......) as well as a unification between FLLs and PLLs is presented....

  18. High performance top-gated indium–zinc–oxide thin film transistors with in-situ formed HfO{sub 2} gate insulator

    Energy Technology Data Exchange (ETDEWEB)

    Song, Yang, E-mail: yang_song@brown.edu [Department of Physics, Brown University, 182 Hope Street, Providence, RI 02912 (United States); Zaslavsky, A. [Department of Physics, Brown University, 182 Hope Street, Providence, RI 02912 (United States); School of Engineering, Brown University, 184 Hope Street, Providence, RI 02912 (United States); Paine, D.C. [School of Engineering, Brown University, 184 Hope Street, Providence, RI 02912 (United States)

    2016-09-01

    We report on top-gated indium–zinc–oxide (IZO) thin film transistors (TFTs) with an in-situ formed HfO{sub 2} gate dielectric insulator. Building on our previous demonstration of high-performance IZO TFTs with Al{sub 2}O{sub 3}/HfO{sub 2} gate dielectric, we now report on a one-step process, in which Hf is evaporated onto the 20 nm thick IZO channel, forming a partially oxidized HfO{sub x} layer, without any additional insulator in-between. After annealing in air at 300 °C, the in-situ reaction between partially oxidized Hf and IZO forms a high quality HfO{sub 2} gate insulator with a low interface trapped charge density N{sub TC} ~ 2.3 × 10{sup 11} cm{sup −2} and acceptably low gate leakage < 3 × 10{sup −7} A/cm{sup 2} at gate voltage V{sub G} = 1 V. The annealed TFTs with gate length L{sub G} = 50 μm have high mobility ~ 95 cm{sup 2}/V ∙ s (determined via the Y-function technique), high on/off ratio ~ 10{sup 7}, near-zero threshold voltage V{sub T} = − 0.02 V, and a subthreshold swing of 0.062 V/decade, near the theoretical limit. The on-current of our proof-of-concept TFTs is relatively low, but can be improved by reducing L{sub G}, indicating that high-performance top-gated HfO{sub 2}-isolated IZO TFTs can be fabricated using a single-step in-situ dielectric formation approach. - Highlights: • High-performance indium–zinc–oxide (IZO) thin film transistors (TFTs). • Single-step in-situ dielectric formation approach simplifies fabrication process. • During anneal, reaction between HfO{sub x} and IZO channel forms a high quality HfO{sub 2} layer. • Gate insulator HfO{sub 2} shows low interface trapped charge and small gate leakage. • TFTs have high mobility, near-zero threshold voltage, and a low subthreshold swing.

  19. A first-principles high-pressure study of Hf2PX (X=B, C, N)

    Science.gov (United States)

    Li, Hui; Luo, Zhili; Liu, Zhe; Sun, Guodong; Wang, Zhenjun

    2017-06-01

    New members of MAX family Hf2PX (X=B, C, N) were studied by first-principles calculations under pressure range of 0-100 GPa. Their structural, elastic and electronic properties were reported. The results show that they are energetically stable at zero pressure and mechanically stable under pressure range from 0 to 100 GPa. It reveals that Hf2PB>Hf2PC>Hf2PN for the structural parameters of a and V, and Hf2PBpressure environments.

  20. High frequency III-V nanowire MOSFETs

    Science.gov (United States)

    Lind, Erik

    2016-09-01

    III-V nanowire transistors are promising candidates for very high frequency electronics applications. The improved electrostatics originating from the gate-all-around geometry allow for more aggressive scaling as compared with planar field-effect transistors, and this can lead to device operation at very high frequencies. The very high mobility possible with In-rich devices can allow very high device performance at low operating voltages. GaN nanowires can take advantage of the large band gap for high voltage operation. In this paper, we review the basic physics and device performance of nanowire field- effect transistors relevant for high frequency performance. First, the geometry of lateral and vertical nanowire field-effect transistors is introduced, with special emphasis on the parasitic capacitances important for nanowire geometries. The basic important high frequency transistor metrics are introduced. Secondly, the scaling properties of gate-all-around nanowire transistors are introduced, based on geometric length scales, demonstrating the scaling possibilities of nanowire transistors. Thirdly, to model nanowire transistor performance, a two-band non-parabolic ballistic transistor model is used to efficiently calculate the current and transconductance as a function of band gap and nanowire size. The intrinsic RF metrics are also estimated. Finally, experimental state-of-the-art nanowire field-effect transistors are reviewed and benchmarked, lateral and vertical transistor geometries are explored, and different fabrication routes are highlighted. Lateral devices have demonstrated operation up to 350 GHz, and vertical devices up to 155 GHz.

  1. Consciously controlled breathing decreases the high-frequency component of heart rate variability by inhibiting cardiac parasympathetic nerve activity.

    Science.gov (United States)

    Sasaki, Konosuke; Maruyama, Ryoko

    2014-01-01

    Heart rate variability (HRV), the beat-to-beat alterations in heart rate, comprises sympathetic and parasympathetic nerve activities of the heart. HRV analysis is used to quantify cardiac autonomic regulation. Since respiration could be a confounding factor in HRV evaluation, some studies recommend consciously controlled breathing to standardize the method. However, it remains unclear whether controlled breathing affects HRV measurement. We compared the effects of controlled breathing on HRV with those of spontaneous breathing. In 20 healthy volunteers, we measured respiratory frequency (f), tidal volume, and blood pressure (BP) and recorded electrocardiograms during spontaneous breathing (14.8 ± 0.7 breaths/min) and controlled breathing at 15 (0.25 Hz) and 6 (0.10 Hz) breaths/min. Compared to spontaneous breathing, controlled breathing at 0.25 Hz showed a higher heart rate and a lower high-frequency (HF) component, an index of parasympathetic nerve activity, although the f was the same. During controlled breathing at 0.10 Hz, the ratio of the low frequency (LF) to HF components (LF/HF), an index of sympathetic nerve activity, increased greatly and HF decreased, while heart rate and BP remained almost unchanged. Thus, controlled breathing at 0.25 Hz, which requires mental concentration, might inhibit parasympathetic nerve activity. During controlled breathing at 0.10 Hz, LF/HF increases because some HF subcomponents are synchronized with f and probably move into the LF band. This increment leads to misinterpretation of the true autonomic nervous regulation. We recommend that the respiratory pattern of participants should be evaluated before spectral HRV analysis to correctly understand changes in autonomic nervous regulation.

  2. Lu Hf systematics of the ultra-high temperature Napier Metamorphic Complex in Antarctica: Evidence for the early Archean differentiation of Earth's mantle

    Science.gov (United States)

    Choi, Sung Hi; Mukasa, Samuel B.; Andronikov, Alexandre V.; Osanai, Yasuhito; Harley, Simon L.; Kelly, Nigel M.

    2006-06-01

    The Napier Complex of the East Antarctic Craton comprises some of the oldest rocks on Earth (˜ 3.8 billion years old), overprinted by an ultra-high temperature (UHT) metamorphic event near the Archean-Proterozoic boundary. Garnet, orthopyroxene, sapphirine, osumilite, rutile and a whole rock representing a fully equilibrated assemblage from this UHT granulite belt have yielded a Lu-Hf isochron age of 2403 ± 43 Ma, the first ever determined on a UHT mineral assemblage. Preservation of the UHT mineral assemblage in the rock analyzed, without any significant retrogression, suggests rapid cooling with closure likely to have occurred for the Lu-Hf system at post-peak UHT conditions near a temperature of ˜ 800 °C. This mineral-whole rock isochron yields an initial 176Hf/ 177Hf ratio corresponding to an ɛHf value of - 14 ± 1, acquired during UHT metamorphism. Such a low value demonstrates that overall UHT granulites evolved in a low Lu/Hf environment, probably formed when the rocks were first extracted from a highly depleted mantle. Zircon ɛHf values we have measured "see through" the UHT metamorphism and show that the source materials for the magmas that formed the Napier Complex were extremely depleted (> + 5.6 ɛHf at 3.85 Ga) relative to the chondritic uniform reservoir (CHUR). These results also suggest significant depletion of the early Archean mantle, in agreement with the early differentiation of the Earth that the latest core formation models require.

  3. High-frequency micromechanical columnar resonators

    Directory of Open Access Journals (Sweden)

    Jenny Kehrbusch, Elena A Ilin, Peter Bozek, Bernhard Radzio and Egbert Oesterschulze

    2009-01-01

    Full Text Available High-frequency silicon columnar microresonators are fabricated using a simple but effective technological scheme. An optimized fabrication scheme was invented to obtain mechanically protected microcolumns with lateral dimensions controlled on a scale of at least 1 μm. In this paper, we investigate the influence of the environmental conditions on the mechanical resonator properties. At ambient conditions, we observed a frequency stability δf/f of less than 10−6 during 5 h of operation at almost constant temperature. However, varying the temperature shifts the frequency by approximately −173 Hz °C− 1. In accordance with a viscous damping model of the ambient gas, we perceived that the quality factor of the first flexural mode decreased with the inverse of the square root of pressure. However, in the low-pressure regime, a linear dependence was observed. We also investigated the influence of the type of the immersing gas on the resonant frequency.

  4. The Modulation of Ionospheric Alfven Resonator on Heating HF Waves and the Doppler Effect

    Institute of Scientific and Technical Information of China (English)

    NiBin-bin; ZhaoZheng-yu; XieShu-guo

    2003-01-01

    The propagation of HF waves in IAR can produce many nonlinear effects, including the modulation effect of IAR on HF waves and the Doppler effect. To start with the dependence of the ionospheric electron temperature varia-tions on the Alfven resonant field, We discuss the mechanism of the modulation effect and lucubrate possible reasons for the Doppler effect. The results show that the Alfven resonant field can have an observable modulation effect on HF waves while its mechanism is quite different from that of Schumann resonant field on HF waves. The depth of modulation of IAR on HF waves has a quasi-quadratic relation with the Alfven field, which directly inspires the formation of cross-spectrum between ULF waves and HF waves and results in spectral peaks at some gyro-frequencies of IAR. With respect to the Doppler effect during the propagation of HF waves in IAR, it is mainly caused by the motion of the high-speed flyer and the drifting electrons and the frequency shift from the phase vari-ation of the reflected waves can be neglected when the frequency of HF incident wave is high enough.

  5. Effect of electron count and chemical complexity in the Ta-Nb-Hf-Zr-Ti high-entropy alloy superconductor

    Science.gov (United States)

    von Rohr, Fabian; Winiarski, Michał J.; Tao, Jing; Klimczuk, Tomasz; Cava, Robert Joseph

    2016-11-01

    High-entropy alloys are made from random mixtures of principal elements on simple lattices, stabilized by a high mixing entropy. The recently discovered body-centered cubic (BCC) Ta-Nb-Hf-Zr-Ti high-entropy alloy superconductor appears to display properties of both simple crystalline intermetallics and amorphous materials; e.g., it has a well-defined superconducting transition along with an exceptional robustness against disorder. Here we show that the valence electron count dependence of the superconducting transition temperature in the high-entropy alloy falls between those of analogous simple solid solutions and amorphous materials and test the effect of alloy complexity on the superconductivity. We propose high-entropy alloys as excellent intermediate systems for studying superconductivity as it evolves between crystalline and amorphous materials.

  6. High frequency and pulse scattering physical acoustics

    CERN Document Server

    Pierce, Allan D

    1992-01-01

    High Frequency and Pulse Scattering investigates high frequency and pulse scattering, with emphasis on the phenomenon of echoes from objects. Geometrical and catastrophe optics methods in scattering are discussed, along with the scattering of sound pulses and the ringing of target resonances. Caustics and associated diffraction catastrophes are also examined.Comprised of two chapters, this volume begins with a detailed account of geometrically based approximation methods in scattering theory, focusing on waves transmitted through fluid and elastic scatterers and glory scattering; surface ray r

  7. Growth and Current Leakage Characteristics of SrHfON High-k Gate Dielectric Films%SrHfON高κ栅介质薄膜的漏电特性研究

    Institute of Scientific and Technical Information of China (English)

    王雪梅; 刘正堂; 冯丽萍

    2013-01-01

    采用射频反应磁控溅射法在p-Si(100)衬底上成功制备出SrHfON高k栅介质薄膜,并研究了Au/SrHfON/Si MOS电容的漏电流机制及应力感应漏电流(SILC)效应.结果表明,MOS电容的漏电流密度随N2流量的增加而减小.在正栅压下,漏电流主要由Schottky发射机制引起;在负栅压下,漏电流机制在低、中、高栅电场区时分别为Schottky发射、F-P发射和F-N隧穿机制.同时,Au/SrHfON/Si MOS电容表现出明显的SILC效应,经恒压应力后薄膜在正栅压下的漏电流由Schouky发射和F-P发射机制共同作用,且后者占主导地位.%The SrHfON high-κ gate dielectric films,deposited by RF reactive magnetron sputtering on p-type Si (100)substrates,were used to fabricate the Au/SrHfON/Si MOS capacitor.The impacts of the growth conditions on the leakage current density were evaluated with X-ray photoelectron spectroscopy and conventional proves.The leakage current conduction mechanisms and the stress induced leakage current(SILC) effect of the MOS capacitor were studied.The leakage current density of the MOS capacitor was found to decrease with an increase of N2 flow rate.At a positive bias of the metal gate,the leakage current mainly originated from Schottky emission,but at a negative bias,the leakage current in the low-,medium-and high-gate voltage ranges resulted from Schottky emission,Poole-Franel (F-P) emission and Fowler-Nord-heim (F-N) tunneling,respectively.In addition,the SILC effect was found to dominate the Au/SrHfON/Si MOS capacitor;but after being stressel by a constant voltage,Schottky emission outperforms F-P emission in generating the leakage current.

  8. Phase and Microstructural Correlation of Spark Plasma Sintered HfB2-ZrB2 Based Ultra-High Temperature Ceramic Composites

    Directory of Open Access Journals (Sweden)

    Ambreen Nisar

    2017-07-01

    Full Text Available The refractory diborides (HfB2 and ZrB2 are considered as promising ultra-high temperature ceramic (UHTCs where low damage tolerance limits their application for the thermal protection system in re-entry vehicles. In this regard, SiC and CNT have been synergistically added as the sintering aids and toughening agents in the spark plasma sintered (SPS HfB2-ZrB2 system. Herein, a novel equimolar composition of HfB2 and ZrB2 has shown to form a solid-solution which then allows compositional tailoring of mechanical properties (such as hardness, elastic modulus, and fracture toughness. The hardness of the processed composite is higher than the individual phase hardness up to 1.5 times, insinuating the synergy of SiC and CNT reinforcement in HfB2-ZrB2 composites. The enhanced fracture toughness of CNT reinforced composite (up to a 196% increment surpassing that of the parent materials (ZrB2/HfB2-SiC is attributed to the synergy of solid solution formation and enhanced densification (~99.5%. In addition, the reduction in the analytically quantified interfacial residual tensile stress with SiC and CNT reinforcements contribute to the enhancement in the fracture toughness of HfB2-ZrB2-SiC-CNT composites, mandatory for aerospace applications.

  9. a Highly-Accurate and Fast Ray Tracing Sysyem for HF and UHF Simulations

    Science.gov (United States)

    Jones, J. C.; Richards, G. P.

    2016-12-01

    Accurate and fast ray tracing is critical for radiowave propagation tools and applications. A ray tracer needs to be accurate to reduce accumulated errors which come from the myriad of models (ionospheric electron density, magnetic field, ion density, neutral molecule density, absorption, land surface, ocean surface, and potentially others) required for accurate simulation. A ray tracer must also be fast to make the use of applications practical. Here we introduce NINJART Is Not Just Another Ray Tracer (NINJART), a highly accurate and fast ray tracing system. NINJART consists of an embarrassingly parallel algorithm rigorously solving the 3-D Hasselgrove equations with a Runge-Kutta adaptive step quadrature rule to accurately trace high frequency to ultra-high frequency radiowaves. It is capable of a wide range of propagation modes from multi-ground hops to vertical and near vertical incidence rays, chordal modes, and other esoteric paths. It is capable of using a variety of ionospheric models to include operational data assimilative or empirical models depending on the needs of the user. It can forward and backward ray trace, calculate time of flight, find the focus factor for signals near the skip zone and calculate the angle of arrival from a known transmitter to a known receiver location. Additionally NINJART uses magnetic field data from various models including the International Geomagnetic Reference Field to reduce the inaccuracies introduced by the simple dipole model, which is commonly used by other ray tracers, in calculating the effects of magneto-ionic splitting thereby allowing accurate traces of both the ordinary and extraordinary mode rays. The NINJART algorithm is a heterogeneous system utilizing the CUDA programming language to take advantage of the computing power of graphical processing units. This allows tracing of thousands of rays concurrently. NINJART achieves additional processing savings, without sacrificing accuracy, by use of an adaptive

  10. The Implementation of a High-Frequency Radio Frequency Identification System with a Battery-Free Smart Tag for Orientation Monitoring

    Directory of Open Access Journals (Sweden)

    Tilen Svete

    2017-01-01

    Full Text Available Energy-harvesting passive RFID (radio frequency identification tags provide countless possibilities as so-called smart tags. Smart tags can communicate with existing RFID readers or interrogators while providing a battery-less platform for internal and external sensors to enrich available information about the environment and smart tag it. A reduced cost and size as well as an increased lifespan and durability of battery-free smart tags offer improvements in areas such as transportation and product tracking. Battery-free smart tags can ideally support arbitrarily complex sensor measurements, but in reality energy limitations can introduce great reductions in operating range and thus application range. In this work, we present an example application of a smart tag with a passive HF (high-frequency RFID tag IC (integrated circuit and MEMS (micro electro-mechanical structure sensor. A standard HF RFID reader connected to a PC (personal computer allowed the RF (radio frequency field to power and communicate with the smart tag. A Kalman filter, implemented on a PC, was used to correct and improve the raw sensor data of smart tag orientation. Measurement results showed that the MEMS sensor on the smart tag could be powered for continuous operation and that raw smart tag orientation data could be read while in the RF field of a standard HF RFID reader, but at a limited range.

  11. High resolution low frequency ultrasonic tomography.

    Science.gov (United States)

    Lasaygues, P; Lefebvre, J P; Mensah, S

    1997-10-01

    Ultrasonic reflection tomography results from a linearization of the inverse acoustic scattering problem, named the inverse Born approximation. The goal of ultrasonic reflection tomography is to obtain reflectivity images from backscattered measurements. This is a Fourier synthesis problem and the first step is to correctly cover the frequency space of the object. For this inverse problem, we use the classical algorithm of tomographic reconstruction by summation of filtered backprojections. In practice, only a limited number of views are available with our mechanical rig, typically 180, and the frequency bandwidth of the pulses is very limited, typically one octave. The resolving power of the system is them limited by the bandwidth of the pulse. Low and high frequencies can be restored by use of a deconvolution algorithm that enhances resolution. We used a deconvolution technique based on the Papoulis method. The advantage of this technique is conservation of the overall frequency information content of the signals. The enhancement procedure was tested by imaging a square aluminium rod with a cross-section less than the wavelength. In this application, the central frequency of the transducer was 250 kHz so that the central wavelength was 6 mm whereas the cross-section of the rod was 4 mm. Although the Born approximation was not theoretically valid in this case (high contrast), a good reconstruction was obtained.

  12. High Frequency Trading, Information, and Takeovers

    NARCIS (Netherlands)

    Humphery-Jenner, M.

    2011-01-01

    This paper (1) proposes new variables to detect informed high-frequency trading (HFT), (2) shows that HFT can help to predict takeover targets, and (3) shows that HFT in uences target announcement announcement returns. Prior literature suggests that informed trade may occur before takeovers, but has

  13. Essays on high frequency financial econometrics

    NARCIS (Netherlands)

    X. Yang

    2015-01-01

    It has long been demonstrated that continuous-time methods are powerful tools in financial modeling. Yet only in recent years, their counterparts in empirical analysis—high frequency econometrics—began to emerge with the availability of intra-day data and relevant statistical tools. This dissertatio

  14. Essays on high frequency financial econometrics

    NARCIS (Netherlands)

    Yang, X.

    2015-01-01

    It has long been demonstrated that continuous-time methods are powerful tools in financial modeling. Yet only in recent years, their counterparts in empirical analysis—high frequency econometrics—began to emerge with the availability of intra-day data and relevant statistical tools. This

  15. Advanced Extremely High Frequency Satellite (AEHF)

    Science.gov (United States)

    2015-12-01

    High Frequency Satellite (AEHF) is a joint service satellite communications system that provides global , survivable, secure, protected, and jam...three satellites fully integrated into the Milstar constellation. October 2014: On October 16, 2014, the program received PEO certification for the...Combined Orbital Operation, Logistics Sustainment ( COOLS ) contract, it will be completed and coordinated in CY 2016. The AEHF system being sustained

  16. High Frequency Trading, Information, and Takeovers

    NARCIS (Netherlands)

    Humphery-Jenner, M.

    2011-01-01

    This paper (1) proposes new variables to detect informed high-frequency trading (HFT), (2) shows that HFT can help to predict takeover targets, and (3) shows that HFT in uences target announcement announcement returns. Prior literature suggests that informed trade may occur before takeovers, but has

  17. High spectral purity Kerr frequency comb radio frequency photonic oscillator.

    Science.gov (United States)

    Liang, W; Eliyahu, D; Ilchenko, V S; Savchenkov, A A; Matsko, A B; Seidel, D; Maleki, L

    2015-08-11

    Femtosecond laser-based generation of radio frequency signals has produced astonishing improvements in achievable spectral purity, one of the basic features characterizing the performance of an radio frequency oscillator. Kerr frequency combs hold promise for transforming these lab-scale oscillators to chip-scale level. In this work we demonstrate a miniature 10 GHz radio frequency photonic oscillator characterized with phase noise better than -60 dBc Hz(-1) at 10 Hz, -90 dBc Hz(-1) at 100 Hz and -170 dBc Hz(-1) at 10 MHz. The frequency stability of this device, as represented by Allan deviation measurements, is at the level of 10(-10) at 1-100 s integration time-orders of magnitude better than existing radio frequency photonic devices of similar size, weight and power consumption.

  18. Confronting models for the high-frequency QPOs with Lense-Thirring precession

    CERN Document Server

    Stefanov, Ivan Zh

    2014-01-01

    Quasiperiodic oscillations (QPOs) have been observed in the power-density spectra of some low-mass X-ray binaries(LMXB) containing a black hole. The two major groups of QPOs -- low-frequency and high-frequency -- have rather different properties. That is why they are usually studied separately. In the literature one can find a large number of models for the high-frequency QPOs but not so many for the low-frequency ones. HF QPOs have attracted significant research efforts due to their potential to provide indispensable information for the properties of the black hole, for its accretion disc and for strong field gravity in general. However, in order to interpret the data for the HF QPOs of the observed objects we have to fix a model. Here we propose a simple test which could allow us to sift the models. The test is based on five rather general assumptions concerning the nature of the central object in black-hole binaries and the mechanism for the generation of the LF QPOs observed in the PDS of such objects. In...

  19. Prompt Ion Outflows and Artificial Ducts during High-Power HF Heating at HAARP: Effect of Suprathermal Electrons?

    Science.gov (United States)

    Mishin, E. V.; Milikh, G. M.

    2014-12-01

    In situ observations from the DMSP and Demeter satellites established that high-power HF heating of the ionosphere F-region results in significant ion outflows associated with 10-30% density enhancements in the topside ionosphere magnetically-conjugate to the heated region. As follows from the SAMI2 two-fluid model calculations, their formation time should exceed 5-7 minutes. However, specially designed DMSP-HAARP experiments have shown that artificial ducts and ion outflows appear on the topside within 2 minutes. We describe the results of these observations and present a semi-quantitative explanation of the fast timescale due to suprathermal electrons accelerated by HF-induced plasma turbulence. There are two possible effects of suprathermal electrons: (1) the increase of the ambipolar electric field over the usual thermal ambipolar diffusion and (2) excitation of heat flux-driven plasma instability resulting in an anomalous electron-ion momentum exchange. Both effects result in faster upward ion flows.

  20. Mechanical competence of ovariectomy-induced compromised bone after single or combined treatment with high-frequency loading and bisphosphonates.

    Science.gov (United States)

    Camargos, G V; Bhattacharya, P; van Lenthe, G H; Del Bel Cury, A A; Naert, I; Duyck, J; Vandamme, K

    2015-06-01

    Osteoporosis leads to increased bone fragility, thus effective approaches enhancing bone strength are needed. Hence, this study investigated the effect of single or combined application of high-frequency (HF) loading through whole body vibration (WBV) and alendronate (ALN) on the mechanical competence of ovariectomy-induced osteoporotic bone. Thirty-four female Wistar rats were ovariectomized (OVX) or sham-operated (shOVX) and divided into five groups: shOVX, OVX-shWBV, OVX-WBV, ALN-shWBV and ALN-WBV. (Sham)WBV loading was applied for 10 min/day (130 to 150 Hz at 0.3g) for 14 days and ALN at 2 mg/kg/dose was administered 3x/week. Finite element analysis based on micro-CT was employed to assess bone biomechanical properties, relative to bone micro-structural parameters. HF loading application to OVX resulted in an enlarged cortex, but it was not able to improve the biomechanical properties. ALN prevented trabecular bone deterioration and increased bone stiffness and bone strength of OVX bone. Finally, the combination of ALN with HF resulted in an increased cortical thickness in OVX rats when compared to single treatments. Compared to HF loading, ALN treatment is preferred for improving the compromised mechanical competence of OVX bone. In addition, the association of ALN with HF loading results in an additive effect on the cortical thickness.

  1. High efficiency quantum cascade laser frequency comb

    Science.gov (United States)

    Lu, Quanyong; Wu, Donghai; Slivken, Steven; Razeghi, Manijeh

    2017-03-01

    An efficient mid-infrared frequency comb source is of great interest to high speed, high resolution spectroscopy and metrology. Here we demonstrate a mid-IR quantum cascade laser frequency comb with a high power output and narrow beatnote linewidth at room temperature. The active region was designed with a strong-coupling between the injector and the upper lasing level for high internal quantum efficiency and a broadband gain. The group velocity dispersion was engineered for efficient, broadband mode-locking via four wave mixing. The comb device exhibits a narrow intermode beatnote linewidth of 50.5 Hz and a maximum wall-plug efficiency of 6.5% covering a spectral coverage of 110 cm‑1 at λ ~ 8 μm. The efficiency is improved by a factor of 6 compared with previous demonstrations. The high power efficiency and narrow beatnote linewidth will greatly expand the applications of quantum cascade laser frequency combs including high-precision remote sensing and spectroscopy.

  2. High efficiency quantum cascade laser frequency comb

    Science.gov (United States)

    Lu, Quanyong; Wu, Donghai; Slivken, Steven; Razeghi, Manijeh

    2017-01-01

    An efficient mid-infrared frequency comb source is of great interest to high speed, high resolution spectroscopy and metrology. Here we demonstrate a mid-IR quantum cascade laser frequency comb with a high power output and narrow beatnote linewidth at room temperature. The active region was designed with a strong-coupling between the injector and the upper lasing level for high internal quantum efficiency and a broadband gain. The group velocity dispersion was engineered for efficient, broadband mode-locking via four wave mixing. The comb device exhibits a narrow intermode beatnote linewidth of 50.5 Hz and a maximum wall-plug efficiency of 6.5% covering a spectral coverage of 110 cm−1 at λ ~ 8 μm. The efficiency is improved by a factor of 6 compared with previous demonstrations. The high power efficiency and narrow beatnote linewidth will greatly expand the applications of quantum cascade laser frequency combs including high-precision remote sensing and spectroscopy. PMID:28262834

  3. The LASI high-frequency ellipticity system

    Energy Technology Data Exchange (ETDEWEB)

    Sternberg, B.K.; Poulton, M.M. [Univ. of Arizona, Tucson, AZ (United States)

    1995-10-01

    A high-frequency, high-resolution, electromagnetic (EM) imaging system has been developed for environmental geophysics surveys. Some key features of this system include: (1) rapid surveying to allow dense spatial sampling over a large area, (2) high-accuracy measurements which are used to produce a high-resolution image of the subsurface, (3) measurements which have excellent signal-to-noise ratio over a wide bandwidth (31 kHz to 32 MHz), (4) large-scale physical modeling to produce accurate theoretical responses over targets of interest in environmental geophysics surveys, (5) rapid neural network interpretation at the field site, and (6) visualization of complex structures during the survey.

  4. Frequency dependent polarization analysis of high-frequency seismograms

    Science.gov (United States)

    Park, Jeffrey; Vernon, Frank L., III; Lindberg, Craig R.

    1987-11-01

    We present a multitaper algorithm to estimate the polarization of particle motion as a function of frequency from three-component seismic data. This algorithm is based on a singular value decomposition of a matrix of eigenspectra at a given frequency. The right complex eigenvector zˆ corresonding to the largest singular value of the matrix has the same direction as the dominant polarization of seismic motion at that frequency. The elements of the polarization vector zˆ specify the relative amplitudes and phases of motion measured along the recorded components within a chosen frequency band. The width of this frequency band is determined by the time-bandwidth product of the prolate spheroidal tapers used in the analysis. We manipulate the components of zˆ to determine the apparent azimuth and angle of incidence of seismic motion as a function of frequency. The orthogonality of the eigentapers allows one to calculate easily uncertainties in the estimated azimuth and angle of incidence. We apply this algorithm to data from the Anza Seismic Telemetered Array in the frequency band 0 ≤ ƒ ≤ 30 Hz. The polarization is not always a smooth function of frequency and can exhibit sharp jumps, suggesting the existence of scattered modes within the crustal waveguide and/or receiver site resonances.

  5. Design and Experimental Investigation for Improving the High Frequency Radio Communication Links between Benghazi-Libya and Sfax-Tunisia.

    Directory of Open Access Journals (Sweden)

    Mohamed Yousef Ahmed Abou-Hussein

    2014-02-01

    Full Text Available In this study, we have experimentally planned to replicate the positive results of the application of ionospheric prediction method to design and improve the high frequency (HF radio communication links between Benghazi-Libya and Sfax-Tunisia. The central radio propagation laboratory (CRPL method of ionospheric prediction of the National Bureau of Standards (NBS in U.S.A was used in the calculations of the optimal working frequencies for reliable HF radio communication links between Benghazi-Libya and Sfax-Tunisia. The results were drawn in the form of curves by using the computer. The computer was used to measure the received signal level variation of a frequency 17.500 Megahertz (MHz, which was transmitted with a power of 100 Kilowatt (KW from the Tunis Republic Broadcasting station in SFAX city, directed to the east region. The measurements were taken during daytime's for winter (December, January& February and summer (June, July & August seasons.

  6. Structural determination of a highly stable metal-organic framework with possible application to interim radioactive waste scavenging: Hf-UiO-66

    Science.gov (United States)

    Jakobsen, Søren; Gianolio, Diego; Wragg, David S.; Nilsen, Merete Hellner; Emerich, Hermann; Bordiga, Silvia; Lamberti, Carlo; Olsbye, Unni; Tilset, Mats; Lillerud, Karl Petter

    2012-09-01

    High-resolution synchrotron radiation x-ray powder diffraction (HR-XRPD) combined with Hf L3-edge extended x-ray absorption fine structure allowed us to determine the structure of a Hf-UiO-66 metal-organic framework (MOF) showing that it is isoreticular to Zr-UiO-66 MOF [Cavka , J. Am. Chem. Soc.JACSAT0002-786310.1021/ja8057953 130, 13850 (2008).]. Thermal gravimetric measurements (coupled with mass spectroscopy) and temperature-dependent synchrotron radiation XRPD proved the high thermal stability of the Hf-UiO-66 MOF. The Langmuir surface area (849 m2/g) combined with the high stability of the UiO-66 framework and with the high neutron absorption cross section of Hf suggest that among all microporous crystalline materials the Hf-UiO-66 MOF possesses the physical and chemical requirements for the interim storage of radioactive waste in a much safer way than is currently available. The first results proving the synthesis of a MOF material with UiO-66 topology realized by a B-containing linker are also reported, allowing a further improvement of the neutron shielding power of this class of materials.

  7. Improved thermal stability and electrical properties of atomic layer deposited HfO{sub 2}/AlN high-k gate dielectric stacks on GaAs

    Energy Technology Data Exchange (ETDEWEB)

    Cao, Yan-Qiang; Li, Xin; Zhu, Lin; Cao, Zheng-Yi; Wu, Di; Li, Ai-Dong, E-mail: adli@nju.edu.cn [National Laboratory of Solid State Microstructures and Department of Materials Science and Engineering, College of Engineering and Applied sciences, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093 (China)

    2015-01-15

    The thermal stability and electrical properties of atomic layer deposited HfO{sub 2}/AlN high-k gate dielectric stacks on GaAs were investigated. Compared to HfO{sub 2}/Al{sub 2}O{sub 3} gate dielectric, significant improvements in interfacial quality as well as electrical characteristics after postdeposition annealing are confirmed by constructing HfO{sub 2}/AlN dielectric stacks. The chemical states were carefully explored by the x-ray photoelectron spectroscopy, which indicates the AlN layers effectively prevent from the formation of defective native oxides at elevated temperatures. In addition, it is found that NH{sub 3} plasma during AlN plasma-enhanced atomic layer deposition also has the self-cleaning effect as Al(CH{sub 3}){sub 3} in removing native oxides. The passivating AlN layers suppress the formation of interfacial oxide and trap charge, leading to the decrease of capacitance equivalent thickness after annealing. Moreover, HfO{sub 2}/AlN/GaAs sample has a much lower leakage current density of 2.23 × 10{sup −4} A/cm{sup 2} than HfO{sub 2}/Al{sub 2}O{sub 3}/GaAs sample of 2.58 × 10{sup −2} A/cm{sup 2}. For the HfO{sub 2}/AlN/GaAs sample annealed at 500 °C, it has a lowest interface trap density value of 2.11 × 10{sup 11} eV{sup −1} cm{sup −2}. These results indicate that adopting HfO{sub 2}/AlN dielectric stacks may be a promising approach for the realization of high quality GaAs-based transistor devices.

  8. Polarization features of the ELF emissions excited in the outer ionosphere through modification of the ionospheric F-region by high-power HF radio emission

    Science.gov (United States)

    Belov, Alexey

    indent=1cm The results of in-situ measurements performed by the onboard equipment of the DEMETER satellite show that the guided ELF emissions can be excited through modification of the ionospheric F-region by high-power HF radio emission from the SURA heating facility. The power spectra of the excited ELF waves have a sharp upper frequency cutoff at the local proton gyrofrequency. In this work, we study the propagation and polarization characteristics of the observed ELF emissions using multicomponent measurement of electric and magnetic fields from the DEMETER satellite. For analysis we make use of singular value decomposition (SVD) technique. It is shown that the polar angle of the observed emissions wave vector with respect to ambient magnetic field is less than pi/6. The waves propagate upward in the left-hand-polarized mode. The wave polarization changes from right- to left-handed at the so-called crossover frequency. The obtained results improve the understanding of the generation mechanisms of observed ELF emissions. This work was supported by the Russian Foundation for Basic Research (project No. 12-02-00747-a), and the Government of the Russian Federation (contract No. 11.G34.31.0048).

  9. Lu-Hf systematics of the ultra-high temperature Napier Complex, East Antarctica: evidence for the early Archean formation of continental crust

    Science.gov (United States)

    Choi, S.; Mukasa, S. B.; Andronikov, A. V.; Osanai, Y.; Harley, S. L.; Kelly, N. M.

    2009-12-01

    The Napier Complex in East Antarctica comprises some of the oldest rocks on earth (~3.8 billion years old), overprinted by an ultra-high temperature (UHT) metamorphic event near the Archean-Proterozoic boundary. Garnet, orthopyroxene, sapphirine, osumilite, rutile and a whole rock representing an equilibrated assemblage from this belt yield a Lu-Hf isochron age of 2,403 ± 43 Ma. Preservation of the UHT mineral assemblage in the rock analyzed suggests rapid cooling with closure likely to have occurred for the Lu-Hf system at post-peak UHT conditions near a temperature of ~800C. Individual zircon grains from Gage Ridge within the Napier Complex yielded a remarkably uniform range of 176Hf/177Hf values between 0.280433 ± 7 and 0.280505 ± 10, corresponding to ɛHf > +5.6 at 3.85 Ga relative to the chondritic uniform reservoir (CHUR). Because of their exceedingly low Lu/Hf values (<0.001), the grains are effectively recording the initial Hf isotope composition of the magmatic systems from which the gneiss protoliths crystallized. These results indicate that (1) the source of the crustal materials that formed the Napier Complex at 3.85 Ga were depleted relative to the CHUR. The extent of depletion involved is higher than has been predicted by extrapolation from the Lu-Hf isotopic evolution inferred for the source of Proterozoic and Phanerozoic basalts, judging from an fLu/Hf value of 0.51, (2) the depleted mantle reservoir has been in existence since very early in Earth’s history, in agreement with the early differentiation of the Earth that the latest core formation models require, and (3) an extremely depleted source also mean that the bulk of continental crust was extracted from the mantle by ~3.8 Ga. Moreover, the results demonstrate that even the oldest silicic rocks in the complex are not likely to have formed from remobilized older crustal materials, but were instead juvenile products of mantle melting. In addition, zircons with metamorphic rims have a similar

  10. High-Frequency Rayleigh-Wave Method

    Institute of Scientific and Technical Information of China (English)

    Jianghai Xia; Richard D Millerg; Xu Yixian; Luo Yinhe; Chen Chao; Liu Jiangping; Julian Ivanov; Chong Zeng

    2009-01-01

    High-frequency (≥2 Hz) Rayleigh-wave data acquired with a multichannei recording sys-tem have been utilized to determine shear (S)-wave velocities in near-surface geophysics since the early 1980s. This overview article discusses the main research results of high-frequency surface-wave tech-niques achieved by research groups at the Kansas Geological Survey and China University of Geosciences in the last 15 years. The multichannel analysis of surface wave (MASW) method is a nou-iuvasive acoustic approach to estimate near-surface S-wave velocity. The differences between MASW results and direct borehole measurements are approximately 15% or less and random. Studies show that simultaneous inversion with higher modes and the fundamental mode can increase model resolution and an investigation depth. The other important seismic property, quality factor (Q), can also be estimated with the MASW method by inverting attenuation coefficients of Rayleigh waves. An inverted model (S-wave velocity or Q) obtained using a damped least-squares method can be assessed by an optimal damping vector in a vicinity of the inverted model determined by an objective function, which is the trace of a weighted sum of model-resolution and model-covariance matrices. Current developments include modeling high-frequency Rayleigh-waves in near-surface media, which builds a foundation for shallow seismic or Rayleigh-wave inversion in the time-offset domain; imaging dispersive energy with high resolution in the frequency-velocity domain and possibly with data in an arbitrary acquisition geometry, which opens a door for 3D surface-wave techniques; and successfully separating surface-wave modes, which provides a valuable tool to perform S-wave velocity profiling with high-horizontal resolution.

  11. Lattice Thermal Conductivity of Ultra High Temperature Ceramics (UHTC) ZrB2 and HfB2 from Atomistic Simulations

    Science.gov (United States)

    Lawson, JOhn W.; Daw, Murray S.; Bauschlicher, Charles W.

    2011-01-01

    Ultra high temperature ceramics (UHTC) including ZrB2 and HfB2 are candidate materials for applications in extreme environments because of their high melting point, good mechanical properties and reasonable oxidation resistance. Unlike many ceramics, these materials have high thermal conductivity which can be advantageous, for example, to reduce thermal shock. Recently, we developed Tersoff style interatomic potentials for both ZrB2 and HfB2 appropriate for atomistic simulations. As an application, Green-Kubo molecular dynamics simulations were performed to evaluate the lattice thermal conductivity for single crystals of ZrB2 and HfB2. The atomic mass difference in these binary compounds leads to oscillations in the time correlation function of the heat current. Results at room temperature and at elevated temperatures will be reported.

  12. High Temperature, High Frequency Fuel Metering Valve Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Active Signal Technologies and its subcontractor Moog propose to develop a high-frequency actuator driven valve intended to achieve TRL 6 by the end of Phase II....

  13. High-Frequency Percussive Ventilation Revisited

    Science.gov (United States)

    2010-01-01

    physiologic and clin- ical outcomes. Pediatric and adult inhalational injury studies have linked HFPV to an improvement in static lung compliance...sedation–analgesic combinations (usually fentanyl with the individual or combined use of midazolam and propofol and/or dexmedetomidine), patient...1998;84:1174–7. 34. Frantz ID III, Close RH. Alveolar pressure swings during high frequency ventilation in rabbits. Pediatr Res 1985;19:162–6. 35. Pillow

  14. Application of the Zr/Hf ratio in the determination of hafnium in geochemical samples by high-resolution inductively coupled plasma mass spectrometry.

    Science.gov (United States)

    Liu, Ya Xuan; Li, Qing Xia; Ma, Na; Sun, Xiao Ling; Bai, Jin Feng; Zhang, Qin

    2014-12-02

    Hafnium content and its change are of significance in geochemistry and cosmochemistry; however, the determination of hafnium has always been problematic in analytical chemistry. In this paper, a new idea is proposed for the determination of hafnium in geochemical samples, including rocks, soils, and stream sediments. Through the comparison of two conventional open-type acid digestion methods (HF-HNO3-HClO4 and HF-HNO3-H2SO4), it was found that although neither of these methods could fully digest the zirconium and hafnium in a sample, the zirconium and hafnium digestion behaviors in one sample were consistent in the 60 experimental geochemical reference materials with different properties, so the experimentally determined Zr/Hf ratio in solution could be used to calculate the hafnium content in a sample. In addition, possible mass spectral interferences during the determination of zirconium and hafnium by high resolution inductively coupled plasma mass spectrometry (HR-ICPMS) were studied, and it was found that the mass spectral interferences of the selected isotopes (90)Zr and (178)Hf could be neglected. The mass spectral behaviors of (90)Zr and (178)Hf were also very consistent during the determination by HR-ICPMS. Since the hafnium content was calculated using the ratio value, all of the errors (including the errors in weighing process, the accidental errors during operation and the instrument fluctuation in the determination) of the Zr/Hf ratio could be effectively reduced or even eliminated. The relative standard deviation of the actual samples was lower than 3.2%, and the detection limit of the method (considering the dilution effect and matrix effect during measurement of the Zr/Hf ratio and zirconium content) was 0.04 μg/g. The proposed method could satisfy the requirement for the determination of hafnium in geochemical samples.

  15. Constraints on Hf and Zr mobility in high-sulfidation epithermal systems: formation of kosnarite, KZr2(PO4)3, in the Chaquicocha gold deposit, Yanacocha district, Peru

    Science.gov (United States)

    Deditius, Artur P.; Utsunomiya, Satoshi; Sanchez-Alfaro, Pablo; Reich, Martin; Ewing, Rodney C.; Kesler, Stephen E.

    2015-04-01

    We report the first occurrence of Hf-rich kosnarite [K(Hf,Zr)2(PO4)3], space group R- 3c, Z = 6, in the giant Chaquicocha high-sulfidation epithermal gold deposit in the Yanacocha mining district, Peru. Kosnarite crystals are small (Yanacocha is indicative of Hf and Zr mobility under highly acidic conditions and points towards an unforeseen role of phosphates as sinks of Zr and Hf in high-sulfidation epithermal environments. Finally, potentially new geochronological applications of highly insoluble vein kosnarite, including Rb-Sr dating, may provide further age constraints in pervasively altered areas where other isotopic systems might have been reset.

  16. A tunneling current density model for ultra thin HfO2 high-k dielectric material based MOS devices

    Science.gov (United States)

    Maity, Niladri Pratap; Maity, Reshmi; Thapa, R. K.; Baishya, Srimanta

    2016-07-01

    In this paper, an analytical model for evaluation of tunneling current density of ultra thin MOS devices is presented. The impacts of the promising high-k dielectric material, HfO2 on the current density model have been carried out. In this work, improvement in the results is brought in by taking into account the barrier height lowering due to the image force effect. The considered voltage range is from 0 to ψ1/e i.e., 0 neglecting the image force effect for a MOS device consisting asymmetric barrier. Later, image force effect of ultra thin oxide layer has been introduced for practical potential barrier by superimposing the potential barrier on the trapezoidal barrier. Theoretical predictions are compared with the results obtained by the 2-D numerical device simulator ATLAS and published experimental results. Excellent agreements among the three are observed.

  17. Effects of water vapor in high vacuum chamber on the properties of HfO2 films

    Institute of Scientific and Technical Information of China (English)

    Bo Ling; Hongbo He; Jianda Shao

    2007-01-01

    The influence of water vapor content in high vacuum chamber during the coating process on physical properties of HfO2 films was investigated. Coatings were deposited on BK7 substrates by electron beam evaporation and photoelectric maximum control method. An in situ residual gas analyzer (RGA) was used to monitor the residual gas composition in the vacuum chamber. The optical properties, microstructure,absorption and laser-induced damage threshold (LIDT) of the samples were characterized by Lambda 900 spectrophotometer, X-ray diffraction (XRD), surface thermal lensing (STL) technique and 1064-nm Qswitched pulsed laser at a pulse duration of 12 ns respectively. It was found that a cold trap is an effective equipment to suppress water vapor in the vacuum chamber during the pumping process, and the coatings deposited in the vacuum atmosphere with relatively low water vapor composition show higher refractive index and smaller grain size. Meanwhile, the higher LIDT value is corresponding to lower absorbance.

  18. DIRECTIONALLY SOLIDIFIED MICROSTRUCTURE OF AN ULTRA-HIGH TEMPERATURE Nb-Si-Ti-Hf-Cr-Al ALLOY

    Institute of Scientific and Technical Information of China (English)

    P.Guan; X.P.Guo; X.Ding; J.Zhang; L.M.Gao; K.Kusabiraki

    2004-01-01

    The directionally solidified samples of an ultra-high temperature Nb-Si-Ti-Hf-Cr-Al alloy have been prepared with the use of an electron beam floating zone melting (EBFZM)furnace, and their microstructural characteristics have been analyzed. All the primary dendrites of Nb solid solution (Nbss), eutectic colonies of Nbss plus (Nb, Ti)3Si/(Nb,Ti)5Si3 and chains of (Nb, Ti)3Si/(Nb, Ti)5Si3 plates align along the growth direction of the samples. With increasing of the withdrawing rate, the microstructure is refined, and the amounts of Nbss+(Nb, Ti)3Si/(Nb, Ti)5Si3 eutectic colonies and (Nb, Ti)3Si/(Nb, Ti)5Si3 plates increase. There appear nodes in the (Nb, Ti)3Si/(Nb,Ti)5Si3 plates.

  19. How to improve reading skills in dyslexics: the effect of high frequency rTMS.

    Science.gov (United States)

    Costanzo, Floriana; Menghini, Deny; Caltagirone, Carlo; Oliveri, Massimiliano; Vicari, Stefano

    2013-12-01

    The latest progress in understanding remediation of dyslexia underlines how some changes in brain are a necessary mechanism of improvement. We wanted to determine whether high frequency repetitive transcranial magnetic stimulation (hf-rTMS) over areas that are underactive during reading in dyslexics, would improve reading of dyslexic adults. We applied 5Hz-TMS over both left and right inferior parietal lobule (IPL) and superior temporal gyrus (STG) prior to word, non-word and text reading aloud. Results show that hf-rTMS stimulation over the left IPL improves non-word reading accuracy and hf-rTMS stimulation over the left STG increases word reading speed and text reading accuracy. Moreover after right IPL stimulation, non-word reading accuracy also improves. These findings indicate that in dyslexics, L-STG and L-IPL have a differential role in word, non-word and text reading. Even if we would normally expect left-lateralized improvements only, the finding of a right IPL involvement suggests that there is additional compensatory recruitment of this region in dyslexics. In conclusion, we provide the first evidence that distinctive facilitation of neural pathways known to be underactive in dyslexics transitorily improves their reading performance. Such ameliorative effect may open new perspectives for the development of long-term specific treatments for dyslexia. © 2013 Published by Elsevier Ltd.

  20. Parametric nanomechanical amplification at very high frequency.

    Science.gov (United States)

    Karabalin, R B; Feng, X L; Roukes, M L

    2009-09-01

    Parametric resonance and amplification are important in both fundamental physics and technological applications. Here we report very high frequency (VHF) parametric resonators and mechanical-domain amplifiers based on nanoelectromechanical systems (NEMS). Compound mechanical nanostructures patterned by multilayer, top-down nanofabrication are read out by a novel scheme that parametrically modulates longitudinal stress in doubly clamped beam NEMS resonators. Parametric pumping and signal amplification are demonstrated for VHF resonators up to approximately 130 MHz and provide useful enhancement of both resonance signal amplitude and quality factor. We find that Joule heating and reduced thermal conductance in these nanostructures ultimately impose an upper limit to device performance. We develop a theoretical model to account for both the parametric response and nonequilibrium thermal transport in these composite nanostructures. The results closely conform to our experimental observations, elucidate the frequency and threshold-voltage scaling in parametric VHF NEMS resonators and sensors, and establish the ultimate sensitivity limits of this approach.

  1. Synthesis of Tetragonal and Orthorhombic Polymorphs of Hf3N4 by High-Pressure Annealing of a Prestructured Nanocrystalline Precursor

    Science.gov (United States)

    2013-01-01

    Hf3N4 in nanocrystalline form is produced by solution phase reaction of Hf(NEtMe)4 with ammonia followed by low-temperature pyrolysis in ammonia. Understanding of phase behavior in these systems is important because early transition-metal nitrides with the metal in maximum oxidation state are potential visible light photocatalysts. A combination of synchrotron powder X-ray diffraction and pair distribution function studies has been used to show this phase to have a tetragonally distorted fluorite structure with 1/3 vacancies on the anion sites. Laser heating nanocrystalline Hf3N4 at 12 GPa and 1500 K in a diamond anvil cell results in its crystallization with the same structure type, an interesting example of prestructuring of the phase during preparation of the precursor compound. This metastable pathway could provide a route to other new polymorphs of metal nitrides and to nitrogen-rich phases where they do not currently exist. Importantly it leads to bulk formation of the material rather than surface conversion as often occurs in elemental combination reactions at high pressure. Laser heating at 2000 K at a higher pressure of 19 GPa results in a further new polymorph of Hf3N4 that adopts an anion deficient cottunite-type (orthorhombic) structure. The orthorhombic Hf3N4 phase is recoverable to ambient pressure and the tetragonal phase is at least partially recoverable. PMID:23721167

  2. Ionospheric Modification by High Power, Obliquely Propagated HF Radio Wave Transmissions. Part 1. Experimental

    Science.gov (United States)

    1993-07-01

    frequency of the disturbing transmitter is greater than the i.. asma frequency in the ionospheric interaction region. In fact, with many practical radio...NY) lay in the Gulf of Mexico and it was not possible to use an oblique probe system similar to- the technique used by the Soviets in their...using a vertical incidence sounder at Albuquerque, New Mexico (35.11N, 106.8 0W) at the midpoint of the 2400 km path. This technique insures that the

  3. High-frequency electro-thermal processing of secondary nonmetallic raw materials

    Directory of Open Access Journals (Sweden)

    A. V. Livshits

    2014-01-01

    Full Text Available Despite a large number of studies in industrial waste processing, this field is still a challenge. In this regard, new processing capabilities emerging from the use of high frequency (RF and microwave (MW heat equipment are a positive factor to be researched.In HF and MW processing the heating process is determined by absorption of electromagnetic wave power through the processed material. This electromagnetic wave power is transmitted by the substance atoms and spent for heating a sample, polarization, and initiation of chemical reactions. The non-conductor (dielectric and semiconductor material heat is explained by the existing effect of dielectric losses due to losses caused by the through electrical conductivity and slow processes of polarization. The dielectric losses due to electrical conductivity result from the Joule heat released when through-current flows through the dielectric.The differences in frequency radiation of HF and microwave equipment define their different technological capabilities. HF-radiation represents almost homogeneous field between the plates of a running capacitor. With multiple reflection from the chamber walls MW-radiation is randomly distributed within the chamber. Thus, radiation partly returns to the generator, thereby affecting the equipment performance capability and life time. Microwave heating is uneven. The depth of penetration into the material is much less to HF-processing. HF heating features are high penetration of radiation and uniform heating of the material. Together with pre-pressing it can afford an opportunity to join the non-standard pieces of plastic to have the larger insulating items.The fact of the selective effect on the material is positive when processing the waste. Since the tangent of angle of dielectric losses of materials such as wood is directly proportional to humidity, the heating automatically stops as wood dries. This fact was used to produce for the fuel briquettes, which were

  4. High-performance HfO x /AlO y -based resistive switching memory cross-point array fabricated by atomic layer deposition.

    Science.gov (United States)

    Chen, Zhe; Zhang, Feifei; Chen, Bing; Zheng, Yang; Gao, Bin; Liu, Lifeng; Liu, Xiaoyan; Kang, Jinfeng

    2015-01-01

    Resistive switching memory cross-point arrays with TiN/HfO x /AlO y /Pt structure were fabricated. The bi-layered resistive switching films of 5-nm HfO x and 3-nm AlO y were deposited by atomic layer deposition (ALD). Excellent device performances such as low switching voltage, large resistance ratio, good cycle-to-cycle and device-to-device uniformity, and high yield were demonstrated in the fabricated 24 by 24 arrays. In addition, multi-level data storage capability and robust reliability characteristics were also presented. The achievements demonstrated the great potential of ALD-fabricated HfO x /AlO y bi-layers for the application of next-generation nonvolatile memory.

  5. High frequency deep brain stimulation attenuates subthalamic and cortical rhythms in Parkinson’s disease

    Directory of Open Access Journals (Sweden)

    Diane eWhitmer

    2012-06-01

    Full Text Available Parkinson’s disease (PD is marked by excessive synchronous activity in the beta (8-35 Hz band throughout the cortico-basal ganglia network. The optimal location of high frequency deep brain stimulation (HF DBS within the subthalamic nucleus (STN region and the location of maximal beta hypersynchrony are currently matters of debate. Additionally, the effect of STN HF DBS on neural synchrony in functionally connected regions of motor cortex is unknown and of great interest. Scalp EEG studies demonstrated that stimulation of the STN can activate motor cortex antidromically, but the spatial specificity of this effect has not been examined. The present study examined the effect of STN HF DBS on neural synchrony within the cortico-basal ganglia network in patients with PD. We measured local field potentials dorsal to and within the STN of PD patients, and additionally in the motor cortex in a subset of these patients. We used diffusion tensor imaging (DTI to guide the placement of subdural cortical surface electrodes over the DTI-identified origin of the hyperdirect pathway between motor cortex and the STN. The results demonstrated that local beta power was attenuated during HF DBS both dorsal to and within the STN. The degree of attenuation was monotonic with increased DBS voltages in both locations, but this voltage-dependent effect was greater in the central STN than dorsal to the STN (p < 0.05. Cortical signals over the estimated origin of the hyperdirect pathway also demonstrated attenuation of beta hypersynchrony during DBS dorsal to or within STN, whereas signals from non-specific regions of motor cortex were not attenuated. The spatially specific suppression of beta synchrony in the motor cortex support the hypothesis that DBS may treat Parkinsonism by reducing excessive synchrony in the functionally connected sensorimotor network.

  6. A High-Frequency High Frame Rate Duplex Ultrasound Linear Array Imaging System for Small Animal Imaging

    Science.gov (United States)

    Zhang, Lequan; Xu, Xiaochen; Hu, Changhong; Sun, Lei; Yen, Jesse T.; Cannata, Jonathan M.; Shung, K. Kirk

    2010-01-01

    High-frequency (HF) ultrasound imaging has been shown to be useful for non-invasively imaging anatomical structures of the eye and small animals in biological and pharmaceutical research, achieving superior spatial resolution. Cardiovascular research utilizing mice requires not only real-time B-scan imaging, but also ultrasound Doppler to evaluate both anatomy and blood flow of the mouse heart. This paper reports the development of a high frequency ultrasound duplex imaging system capable of both B-mode imaging and Doppler flow measurements, using a 64-element linear array. The system included a HF pulsed-wave Doppler module, a 32-channel HF B-mode imaging module, a PC with a 200 MS/s 14-bit A/D card, and real-time LabView software. A 50dB signal-to-noise ratio (SNR) and a depth of penetration of larger than 12 mm were achieved using a 35 MHz linear array with 50 μm pitch. The two-way beam widths were determined to be 165 μm to 260 μm and the clutter energy to total energy ratio (CTR) were 9.1 dB to 12 dB, when the array was electronically focused at different focal points at depths from 4.8 mm to 9.6 mm. The system is capable of acquiring real-time B-mode images at a rate greater than 400 frames per second (fps) for a 4.8 × 13 mm field of view, using a 30 MHz 64-element linear array with 100 μm pitch. Sample in vivo cardiac high frame rate images and duplex images of mouse hearts are shown to assess its current imaging capability and performance for small animals. PMID:20639149

  7. Advances in Very High Frequency Power Conversion

    DEFF Research Database (Denmark)

    Kovacevic, Milovan

    . Excellent performance and small size of magnetic components and capacitors at very high frequencies, along with constant advances in performance of power semiconductor devices, suggests a sizable shift in consumer power supplies market into this area in the near future. To operate dc-dc converter power...... to be applied, especially at low power levels where gating loss becomes a significant percentage of the total loss budget. Various resonant gate drive methods have been proposed to address this design challenge, with varying size, cost, and complexity. This dissertation presents a self-oscillating resonant gate...

  8. Cultures of High-frequency Trading

    DEFF Research Database (Denmark)

    Lange, Ann-Christina; Lenglet, Marc; Seyfert, Robert

    2016-01-01

    As part of ongoing work to lay a foundation for social studies of high-frequency trading (HFT), this paper introduces the culture(s) of HFT as a sociological problem relating to knowledge and practice. HFT is often discussed as a purely technological development, where all that matters is the speed...... of allocating, processing and transmitting data. Indeed, the speed at which trades are executed and data transmitted is accelerating, and it is fair to say that algorithms are now the primary interacting agents operating in the financial markets. However, we contend that HFT is first and foremost a cultural...

  9. Vertical Nanowire High-Frequency Transistors

    OpenAIRE

    Johansson, Sofia

    2014-01-01

    This thesis explores a novel transistor technology based on vertical InAs nanowires, which could be considered both for low-power high-frequency analog applications and for replacing Si CMOS in the continued scaling of digital electronics. The potential of this device - the vertical InAs nanowire MOSFET – lies in the combination of the outstanding transport properties of InAs and the improved electrostatic control of the gate-all-around geometry. Three generations of the vertical InAs nanowir...

  10. Vertical Nanowire High-Frequency Transistors

    OpenAIRE

    Johansson, Sofia

    2014-01-01

    This thesis explores a novel transistor technology based on vertical InAs nanowires, which could be considered both for low-power high-frequency analog applications and for replacing Si CMOS in the continued scaling of digital electronics. The potential of this device - the vertical InAs nanowire MOSFET – lies in the combination of the outstanding transport properties of InAs and the improved electrostatic control of the gate-all-around geometry. Three generations of the vertical InAs nano...

  11. High and low frequency subharmonic imaging of angiogenesis in a murine breast cancer model.

    Science.gov (United States)

    Dahibawkar, Manasi; Forsberg, Mark A; Gupta, Aditi; Jaffe, Samantha; Dulin, Kelly; Eisenbrey, John R; Halldorsdottir, Valgerdur G; Forsberg, Anya I; Dave, Jaydev K; Marshall, Andrew; Machado, Priscilla; Fox, Traci B; Liu, Ji-Bin; Forsberg, Flemming

    2015-09-01

    This project compared quantifiable measures of tumor vascularity obtained from contrast-enhanced high frequency (HF) and low frequency (LF) subharmonic ultrasound imaging (SHI) to 3 immunohistochemical markers of angiogenesis in a murine breast cancer model (since angiogenesis is an important marker of malignancy and the target of many novel cancer treatments). Nineteen athymic, nude, female rats were implanted with 5×10(6) breast cancer cells (MDA-MB-231) in the mammary fat pad. The contrast agent Definity (Lantheus Medical Imaging, N Billerica, MA) was injected in a tail vein (dose: 180μl/kg) and LF pulse-inversion SHI was performed with a modified Sonix RP scanner (Analogic Ultrasound, Richmond, BC, Canada) using a L9-4 linear array (transmitting/receiving at 8/4MHz in SHI mode) followed by HF imaging with a Vevo 2100 scanner (Visualsonics, Toronto, ON, Canada) using a MS250 linear array transmitting and receiving at 24MHz. The radiofrequency data was filtered using a 4th order IIR Butterworth bandpass filter (11-13MHz) to isolate the subharmonic signal. After the experiments, specimens were stained for endothelial cells (CD31), vascular endothelial growth factor (VEGF) and cyclooxygenase-2 (COX-2). Fractional tumor vascularity was calculated as contrast-enhanced pixels over all tumor pixels for SHI, while the relative area stained over total tumor area was calculated from specimens. Results were compared using linear regression analysis. Out of 19 rats, 16 showed tumor growth (84%) and 11 of them were successfully imaged. HF SHI demonstrated better resolution, but weaker signals than LF SHI (0.06±0.017 vs. 0.39±0.059; p<0.001). The strongest overall correlation in this breast cancer model was between HF SHI and VEGF (r=-0.38; p=0.03). In conclusion, quantifiable measures of tumor neovascularity derived from contrast-enhanced HF SHI appear to be a better method than LF SHI for monitoring angiogenesis in a murine xenograft model of breast cancer

  12. Implantation of Y- and Hf-ions into a F-doped Ni-base superalloy improving the oxidation resistance at high temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Zschau, H.-E. [DECHEMA-Forschungsinstitut, Theodor-Heuss-Allee 25, D-60486 Frankfurt am Main (Germany); King, F. [Goethe-Universität Frankfurt am Main, Institut für Kernphysik, Max-von-Laue-Str. 1, D-60438 Frankfurt am Main (Germany); Galetz, M.C.; Schütze, M. [DECHEMA-Forschungsinstitut, Theodor-Heuss-Allee 25, D-60486 Frankfurt am Main (Germany)

    2015-12-15

    The surface modification of Ni-base alloys with low Al-contents (between 2 and 5 wt.%) with fluorine leads to the formation of a protective alumina scale under high temperature service conditions. The combined implantation of fluorine and reactive elements (Y, Hf) can increase the adherence of this alumina scale needed for technical applications.

  13. National High Frequency Radar Network (hfrnet) and Pacific Research Efforts

    Science.gov (United States)

    Hazard, L.; Terrill, E. J.; Cook, T.; de Paolo, T.; Otero, M. P.; Rogowski, P.; Schramek, T. A.

    2016-12-01

    The U.S. High Frequency Radar Network (HFRNet) has been in operation for over ten years with representation from 31 organizations spanning academic institutions, state and local government agencies, and private organizations. HFRNet currently holds a collection from over 130 radar installations totaling over 10 million records of surface ocean velocity measurements. HFRNet is a primary example of inter-agency and inter-institutional partnerships for improving oceanographic research and operations. HF radar derived surface currents have been used in several societal applications including coastal search and rescue, oil spill response, water quality monitoring and marine navigation. Central to the operational success of the large scale network is an efficient data management, storage, access, and delivery system. The networking of surface current mapping systems is characterized by a tiered structure that extends from the individual field installations to local regional operations maintaining multiple sites and on to centralized locations aggregating data from all regions. The data system development effort focuses on building robust data communications from remote field locations (sites) for ingestion into the data system via data on-ramps (Portals or Site Aggregators) to centralized data repositories (Nodes). Centralized surface current data enables the aggregation of national surface current grids and allows for ingestion into displays, management tools, and models. The Coastal Observing Research and Development Center has been involved in international relationships and research in the Philippines, Palau, and Vietnam. CORDC extends this IT architecture of surface current mapping data systems leveraging existing developments and furthering standardization of data services for seamless integration of higher level applications. Collaborations include the Philippine Atmospheric Geophysical and Astronomical Services Administration (PAGASA), The Coral Reef Research

  14. Solar coronal observations at high frequencies

    CERN Document Server

    Katsiyannis, A C; Phillips, K J H; Williams, D R; Keenan, F P

    2001-01-01

    The Solar Eclipse Coronal Imaging System (SECIS) is a simple and extremely fast, high-resolution imaging instrument designed for studies of the solar corona. Light from the corona (during, for example, a total solar eclipse) is reflected off a heliostat and passes via a Schmidt-Cassegrain telescope and beam splitter to two CCD cameras capable of imaging at 60 frames a second. The cameras are attached via SCSI connections to a purpose-built PC that acts as the data acquisition and storage system. Each optical channel has a different filter allowing observations of the same events in both white light and in the green line (Fe XIV at 5303 A). Wavelet analysis of the stabilized images has revealed high frequency oscillations which may make a significant contribution on the coronal heating process. In this presentation we give an outline of the instrument and its future development.

  15. ELF/VLF wave generation from the beating of two HF ionospheric heating sources

    Science.gov (United States)

    Cohen, M. B.; Moore, R. C.; Golkowski, M.; Lehtinen, N. G.

    2012-12-01

    It is well established that Extremely Low Frequency (ELF, 0.3-3 kHz) and Very Low Frequency (VLF, 3-30 kHz) radio waves can be generated via modulated High Frequency (HF, 3-10 MHz) heating of the lower ionosphere (60-100 km). The ionospheric absorption of HF power modifies the conductivity of the lower ionosphere, which in the presence of natural currents such as the auroral electrojet, creates an `antenna in the sky.' We utilize a theoretical model of the HF to ELF/VLF conversion and the ELF/VLF propagation, and calculate the amplitudes of the generated ELF/VLF waves when two HF heating waves, separated by the ELF/VLF frequency, are transmitted from two adjacent locations. The resulting ELF/VLF radiation pattern exhibits a strong directional dependence (as much as 15 dB) that depends on the physical spacing of the two HF sources. This beat wave source can produce signals 10-20 dB stronger than those generated using amplitude modulation, particularly for frequencies greater than 5-10 kHz. We evaluate recent suggestions that beating two HF waves generates ELF/VLF waves in the F-region (>150 km), and conclude that those experimental results may have misinterpreted, and can be explained strictly by the much more well established D region mechanism.

  16. HF-induced airglow at magnetic zenith: theoretical considerations

    Directory of Open Access Journals (Sweden)

    E. V. Mishin

    2005-01-01

    Full Text Available Observations of airglow at 630nm (red line and 557.7nm (green line during HF modification experiments at the High Frequency Active Auroral Research Program (HAARP heating facility are analyzed. We propose a theoretical framework for understanding the generation of Langmuir and ion acoustic waves during magnetic zenith injections. We show that observations of HF-induced airglow in an underdense ionosphere as well as a decrease in the height of the emitting volume are consistent with this scenario.

  17. TEM and HRTEM study of oxide particles in an Al-alloyed high-Cr oxide dispersion strengthened ferritic steel with Hf addition

    Science.gov (United States)

    Dou, Peng; Kimura, Akihiko; Kasada, Ryuta; Okuda, Takanari; Inoue, Masaki; Ukai, Shigeharu; Ohnuki, Somei; Fujisawa, Toshiharu; Abe, Fujio; Jiang, Shan; Yang, Zhigang

    2017-03-01

    The nanoparticles in an Al-alloyed high-Cr oxide dispersion strengthened (ODS) ferritic steel with Hf addition, i.e., SOC-16 (Fe-15Cr-2W-0.1Ti-4Al-0.62Hf-0.35Y2O3), have been examined by transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). Relative to an Al-alloyed high-Cr ODS ferritic steel without Hf addition, i.e., SOC-9 (Fe-15.5Cr-2W-0.1Ti-4Al-0.35Y2O3), the dispersion morphology and coherency of the oxide nanoparticles in SOC-16 were significantly improved. Almost all the small nanoparticles (diameter anion-deficient fluorite structure and coherent with the bcc steel matrix. The larger particles (diameter >10 nm) were also mainly identified as cubic Y2Hf2O7 oxides with the anion-deficient fluorite structure. The results presented here are compared with those of SOC-9 with a brief discussion of the underlying mechanisms of the unusual thermal and irradiation stabilities of the oxides as well as the superior strength, excellent irradiation tolerance and extraordinary corrosion resistance of SOC-16.

  18. Structural characteristics of 1-ethyl-3-methylimidazolium bifluoride: HF-deficient form of a highly conductive room temperature molten salt

    Science.gov (United States)

    Matsumoto, Kazuhiko; Tsuda, Tetsuya; Hagiwara, Rika; Ito, Yasuhiko; Tamada, Osamu

    2002-01-01

    EMIF·HF, 1-ethyl-3-methylimidazolium bifluoride, has been obtained by eliminating HF from a room temperature molten salt EMIF·2.3HF at around 400 K. EMIF·HF crystallizes in space group P2 1/m with a=7.281(1) Å, b=6.762(1) Å, c=8.403(1) Å, β=107.26(1)°, V=395.09(18) Å 3, Z=2 at room temperature. The cations are stacked in pillars via the hydrogen bonding between the C4 proton and the ring π-electrons of the adjacent cation. The cations and the anions coupled by strong hydrogen bondings are co-planar.

  19. Calculation of Leakage Inductance for High Frequency Transformers

    DEFF Research Database (Denmark)

    Ouyang, Ziwei; Jun, Zhang; Hurley, William Gerard

    2015-01-01

    Frequency dependent leakage inductance is often observed. High frequency eddy current effects cause a reduction in leakage inductance. The proximity effect between adjacent layers is responsible for the reduction of leakage inductance. This paper gives a detailed analysis of high frequency leakage...... inductance and proposes an accurate prediction methodology. High frequency leakage inductances in several interleaved winding configurations are also discussed. Interleaved winding configurations actually give a smaller degree of reduction of leakage induction at high frequency. Finite Element Analysis (FEA...

  20. High-frequency transcutaneous electrical nerve stimulation alleviates spasticity after spinal contusion by inhibiting activated microglia in rats.

    Science.gov (United States)

    Hahm, Suk-Chan; Yoon, Young Wook; Kim, Junesun

    2015-05-01

    Transcutaneous electrical nerve stimulation (TENS) can be used as a physical therapy for spasticity, but the effects of TENS on spasticity and its underlying mechanisms remain unclear. The purpose of this study was to test the effects of TENS on spasticity and the role of activated microglia as underlying mechanisms of TENS treatment for spasticity in rats with a 50-mm contusive spinal cord injury (SCI). A spinal contusion was made at the T12 spinal segment in adult male Sprague-Dawley rats using the NYU impactor. Behavioral tests for motor function were conducted before and after SCI and before and after TENS application. To assess spasticity, the modified Ashworth scale (MAS) was used before and after SCI, high-frequency (HF)/low-frequency (LF) TENS application at 3 different intensities (motor threshold [MT], 50% and 90% MT) or minocycline administration. Immunohistochemistry for microglia was performed at the lumbar spinal segments. Motor recovery reached a plateau approximately 28 days after SCI. Spasticity was well developed and was sustained above the MAS grade of 3, beginning at 28 days after SCI. HF-TENS at 90% MT significantly alleviated spasticity. Motor function did not show any significant changes with LF- or HF-TENS treatment. HF-TENS significantly reduced the proportion of activated microglia observed after SCI. Minocycline, the microglia inhibitor, also significantly alleviated spasticity with the reduction of activated microglia expression. These results suggest that HF-TENS at 90% MT alleviates spasticity in rats with SCI by inhibiting activated microglia. © The Author(s) 2014.

  1. 78 FR 42102 - Termination of Radiotelephone Medium Frequency 2182 kHz Watchkeeping, 2187.5 kHz Digital...

    Science.gov (United States)

    2013-07-15

    ... SECURITY Coast Guard Termination of Radiotelephone Medium Frequency 2182 kHz Watchkeeping, 2187.5 kHz... miles from shore. Advancements in satellite, digital, very high frequency (VHF), and high frequency (HF...Hz DSC, mariners can tune their existing HF radios to other GMDSS radiotelephone distress...

  2. Frequency metrology using highly charged ions

    Science.gov (United States)

    Crespo López-Urrutia, J. R.

    2016-06-01

    Due to the scaling laws of relativistic fine structure splitting, many forbidden optical transitions appear within the ground state configurations of highly charged ions (HCI). In some hydrogen-like ions, even the hyperfine splitting of the 1s ground state gives rise to optical transitions. Given the very low polarizability of HCI, such laser-accessible transitions are extremely impervious to external perturbations and systematics that limit optical clock performance and arise from AC and DC Stark effects, such as black-body radiation and light shifts. Moreover, AC and DC Zeeman splitting are symmetric due to the much larger relativistic spin-orbit coupling and corresponding fine-structure splitting. Appropriate choice of states or magnetic sub-states with suitable total angular momentum and magnetic quantum numbers can lead to a cancellation of residual quadrupolar shifts. All these properties are very advantageous for the proposed use of HCI forbidden lines as optical frequency standards. Extremely magnified relativistic, quantum electrodynamic, and nuclear size contributions to the binding energies of the optically active electrons make HCI ideal tools for fundamental research, as in proposed studies of a possible time variation of the fine structure constant. Beyond this, HCI that cannot be photoionized by vacuum-ultraviolet photons could also provide frequency standards for future lasers operating in that range.

  3. High-frequency laser sonar system

    Science.gov (United States)

    Cray, Benjamin A.; Sarma, Ashwin; Kirsteins, Ivars P.

    2002-11-01

    A set of measurements recently completed at the Naval Undersea Warfare Center (NUWC) demonstrated that a laser-based sonar system can be used to detect acoustic particle velocity on the surface of a thin acoustically-compliant plate embedded beneath a standard acoustic window. The theoretical acoustic and measured surface particle velocity varied by less than 1 dB (reference m/s) over a wide frequency band (10 kHz to 100 kHz). However, the Polytec Model PSV-100 Scanning Laser Vibrometer System (SLVS) used in the experiments had relatively poor acoustic sensitivity, presumably due to high electronic noise, speckle noise, stand-off distance, and drifting laser focus. The laser's acoustic sensitivity appears to be inversely proportional to the backscatter signal level. The existing SLVS can sample a grid of 512 by 512 points, with each grid point having a spot size of approximately 10 mm (0.0004 in.). Such fine sampling may be used to create essentially a continuous aperture, eliminating acoustic grating lobes at all frequencies of practical sonar interest.

  4. Using strong nonlinearity and high-frequency vibrations to control effective properties of discrete elastic waveguides

    DEFF Research Database (Denmark)

    Lazarov, Boyan Stefanov; Thomsen, Jon Juel; Snaeland, Sveinn Orri

    2008-01-01

    The aim of this article is to investigate how highfrequency (HF) excitation, combined with strong nonlinear elastic material behavior, influences the effective material or structural properties for low-frequency excitation and wave propagation. The HF effects are demonstrated on discrete linear s...... spring-mass chains with non-linear inclusions. The presented analytical and numerical results suggest that the effective material properties can easily be altered by establishing finite amplitude HF standing waves in the non-linear regions of the chain....

  5. High temperature shape memory alloy Ni50.3Ti29.7Hf20 torque tube actuators

    Science.gov (United States)

    Benafan, O.; Gaydosh, D. J.

    2017-09-01

    The torsional behavior of Ni-rich Ni50.3Ti29.7Hf20 (at%) high-temperature shape memory alloy tubes was investigated under pure torsion loading. Torque tubes with varying geometry including outer diameter, wall thickness, and length were subjected to constant-torque thermal cycling at stresses ranging from 0 to 500 MPa (0-175 N m). It was found that the wall thickness had a notable effect on the transformation temperatures where thick-walled tubes transformed at lower temperatures when compared to the thin-walled form. In all tube outer diameters, shear strains were found to be in the order of 6% obtained at stresses above 300 MPa. At lower stresses, little to no effect of wall thickness was observed, but the influence increased at higher stresses where thin-walled tubes generated approximately 2% less strain when compared to the solid forms. Two-way shape memory effect was also evaluated after 20 cycles and was found to reach ˜3% strain when cycled at high stresses.

  6. Dc SQUIDs with sub-micron-sized Nb/HfTi/Nb Josephson junctions for operation in high magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Nagel, Joachim; Konovalenko, Konstantin; Kleiner, Reinhold; Koelle, Dieter [Physikalisches Institut - Experimentalphysik II, Center for Collective Quantum Phenomena and their Applications, Universitaet Tuebingen, Auf der Morgenstelle 14, D-72076 (Germany); Kieler, Oliver; Kohlmann, Johannes; Zorin, Alexander [Fachbereich 2.4 ' ' Quantenelektronik' ' , Physikalisch-Technische Bundesanstalt, 38116 Braunschweig (Germany)

    2010-07-01

    We investigate the suitability of dc superconducting quantum interference devices (SQUIDs) for operation in high magnetic fields (up to B{approx}100 mT) at temperature T=4.2 K. The micro SQUIDs with superconductor (S)-normal metal (N)-superconductor (S) sub-micrometer Josephson junctions were realized using Nb electrodes and HfTi for the normal interlayer. Our fabrication technology combines e-beam lithography and chemical-mechanical polishing which enables junction sizes down to 200 nm x 200 nm, integrated into small superconductor rings with inner dimensions down to 0.5 {mu} m x 0.5 {mu} m. The characteristic voltage of the SNS junctions is typically 30-40 {mu}V with a McCumber parameter {beta}{sub C}<0.1, and a screening parameter of the SQUIDs {beta}{sub L}{approx}0.2. The SQUIDs where characterized by measurements of electric transport and noise (using a Nb dc SQUID amplifier) in a magnetically shielded environment as well as in high magnetic fields. The SQUIDs show very low flux noise which is a major prerequisite for their application as detectors for magnetic properties of nanoparticles.

  7. High-frequency lunar teleseismic events

    Science.gov (United States)

    Nakamura, Y.; Dorman, J.; Duennebier, F.; Ewing, M.; Lammlein, D.; Latham, G.

    1974-01-01

    A small number of seismic signals, including some of the strongest observed to date, have been identified as representing a fourth principal category of natural lunar seismic events with characteristics distinct from those produced by normal meteoroid impacts, deep moonquakes, and thermal moonquakes. These signals are much richer in high frequencies than other events observed at comparable distances, and display relatively impulsive P- and S-wave beginnings, indicating negligible seismic-wave scattering near the source. Source depths of these events may range between 0 and perhaps 300 km. These and other characteristics could represent either (1) meteoroids impacting upon outcrops of competent lunar crystal rock, (2) rare impacting objects that penetrate to competent rock below a scattering zone, or (3) shallow tectonic moonquakes.

  8. Plasma effects in high frequency radiative transfer

    Science.gov (United States)

    Alonso, C. T.

    1981-02-01

    A survey of collective plasma processes which can affect the transfer of high frequency radiation in a hot dense plasma is given. For pedagogical reasons plasma processes are examined by relating them to a particular reference plasma which consists of fully ionized carbon at a temperature kT = 1 KeV (ten million degrees Kelvin) and an electron density N = 3 x 10 to the 23rd power/cu cm, (which corresponds to a mass density rho = 1 gm/cu cm) and an ion density N sub i = 5 x 10 to the 22nd power/cu cm. The transport of photons, ranging from 1 eV to 1 KeV in energy, in such plasmas is considered. Such photons are to be used as diagnostic probes of hot dense laboratory plasmas.

  9. Low Frequency Noise Degradation in 45 nm High-k nMOSFETs due to Hot Carrier and Constant Voltage Stress

    Science.gov (United States)

    Rahman, M. Shahriar; ćelik-Butler, Zeynep; Quevedo-Lopez, M. A.; Shanware, Ajit; Colombo, Luigi

    2009-04-01

    Hafnium based materials are the leading candidates to replace conventional SiON as the gate dielectric in complementary metal-oxide-semiconductor devices. Hot carrier and constant voltage stress induced 1/f noise behavior is presented for HfSiON nMOSFETs. The additional low-frequency noise introduced through stressing was evaluated on nMOSFETs with TiN metal gate and HfSiON gate dielectric. Nitridation of HfSiO was achieved either by high temperature thermal nitridation or by relatively lower temperature plasma nitridation. The difference in stress induced noise behavior is attributed to the nitrogen profile across high-k/Si interface and bulk of high-k gate oxide caused by different nitridation techniques.

  10. Relaxation phenomena of polar non-polar liquid mixtures under low and high frequency electric field

    Indian Academy of Sciences (India)

    K Dutta; S K Sit; S Acharyya

    2003-10-01

    Simultaneous calculation of the dipole moment and the relaxation time of a certain number of non-spherical rigid aliphatic polar liquid molecules () in non-polar solvents () under 9.8 GHz electric field is possible from real $'$ and imaginary $''$ parts of the complex relative permittivity $^{*}_{}$. The low frequency and infinite frequency permittivities 0 and ∞ measured by Purohit et al [1,2] and Srivastava and Srivastava [3] at 25, 35 and 30°C respectively are used to obtain static . The ratio of the individual slopes of imaginary and real $'$ parts of high frequency (hf) complex conductivity $^{*}_{}$ with weight fractions at → 0 and the slopes of $''_{}-'_{}$ curves for different s [4] are employed to obtain s. The former method is better in comparison to the existing one as it eliminates polar–polar interaction. The hf s in Coulomb metre (C m) when compared with static and reported s indicate that ss favour the monomer formations which combine to form dimers in the hf electric field. The comparison among s shows that a part of the molecule is rotating under X-band electric field [5]. The theoretical theos from available bond angles and bond moments of the substituent polar groups attached to the parent molecules differ from the measured s and s to establish the possible existence of mesomeric, inductive and electromeric effects in polar liquid molecules.

  11. Effectiveness of Haemodiafiltration with Heat Sterilized High-Flux Polyphenylene HF Dialyzer in Reducing Free Light Chains in Patients with Myeloma Cast Nephropathy.

    Directory of Open Access Journals (Sweden)

    Mathieu Rousseau-Gagnon

    Full Text Available In cases of myeloma cast nephropathy in need of haemodialysis (HD, reduction of free light chains using HD with High-Cut-Off filters (HCO-HD, in combination with chemotherapy, may be associated with better renal recovery. The aim of the present study is to evaluate the effectiveness of haemodiafiltration (HDF in reducing free light chain levels using a less expensive heat sterilized high-flux polyphenylene HF dialyzer (HF-HDF.In a single-centre prospective cohort study, 327 dialysis sessions were performed using a 2.2 m2 heat sterilized high-flux polyphenylene HF dialyzer (Phylther HF22SD, a small (1.1m2 or large (2.1 m2 high-cut-off (HCO dialyzer (HCOS and HCOL in a cohort of 16 patients presenting with dialysis-dependent acute cast nephropathy and elevated free light chains (10 kappa, 6 lambda. The outcomes of the study were the mean reduction ratio (RR of kappa and lambda, the proportion of treatments with an RR of at least 0.65, albumin loss and the description of patient outcomes. Statistical analysis was performed using linear and logistic regression through generalized estimating equation analysis so as to take into account repeated observation within subjects and adjust for session duration.There were no significant differences in the estimated marginal mean of kappa RR, which were respectively 0.67, 0.69 and 0.70 with HCOL-HD, HCOS-HDF and HF-HDF (P = 0.950. The estimated marginal mean of the proportions of treatments with a kappa RR ≥0.65 were 68%, 63% and 71% with HCOL-HD, HCOS-HDF and HF-HDF, respectively (P = 0.913. The estimated marginal mean of lambda RR were higher with HCOL-HDF (0.78, compared to HCOL-HD and HF-HDF (0.62, and 0.61 respectively. The estimated marginal mean proportion of treatments with a lambda RR ≥0.65 were higher with HCOL-HDF (81%, compared to 57% in HF-HDF (P = 0.042. The median albumin loss were 7, 21 and 63 g/session with HF-HDF, HCOL-HD and HCOL-HDF respectively (P = 0.044. Among survivors, 9 out of 10

  12. Ultrasensitive radio-frequency pseudomorphic high-electron-mobility-transistor readout for quantum devices

    Science.gov (United States)

    Oukhanski, Nikolai; Hoenig, Eckhardt

    2004-10-01

    Two versions of a cryogenic multistage pseudomorphic high-electron-mobility field-effect transistor amplifier (based on the AlGaAs/InGaAs/GaAs heterostructure) have been designed for quantum device readout and tested at an ambient temperature ˜380mK. The minimum noise temperature of the first amplifier version is below 110±25mK(˜80±20hf/kB) at 28.6 MHz, estimated from the noise of input 10 kΩ resistance and coupled input tank circuit with an active resistance at the resonant frequency RS(f0)≈17.9kΩ. Its minimum voltage spectral noise density, with respect to the input, is about 200pV/(Hz)1/2 and the corner frequency of the 1/f noise is close to 300 kHz. For the amplifier with the lowest designed back action, the minimum noise temperature below 130±30mK(˜100±25hf/kB) at 26.8 MHz was estimated when coupled to an input tank circuit with RS(f0)≈61.8kΩ. The power consumption of the amplifiers is in the range of 100-600 μW.

  13. Intercostal Muscle Pacing with High Frequency Spinal Cord Stimulation in Dogs

    Science.gov (United States)

    DiMarco, Anthony F.; Kowalski, Krzysztof E.

    2010-01-01

    High frequency spinal cord stimulation (HF-SCS) is a novel and more physiologic method of inspiratory muscle activation which involves stimulation of spinal cord pathways. In the present study, we determined if activation of the inspiratory intercostal muscles alone by this technique could be utilized to maintain artificial ventilation. In 7 anesthetized dogs, following C2 spinal cord section and bilateral phrenicotomy, trains of electrical stimulation (12 times/min) were applied at the T2 level. Eucapnea was maintained during an initial 5.5 hour period of continuous stimulation. During a subsequent 0.5 hour period, stimulus parameters were increased to induce hyperventilation resulting in a sustained fall in end-tidal PCO2 to 29.3 ± 0.4 mmHg. Single motor unit peak firing frequencies of the intercostal muscles during HF-SCS were similar to those occurring during spontaneous breathing. This technique holds promise as a method to restore ventilation in ventilator-dependent tetraplegics who do not have adequate phrenic nerve function for diaphragm pacing. PMID:20338266

  14. Effect of high-frequency excitation on natural frequencies of spinning discs

    DEFF Research Database (Denmark)

    Hansen, Morten Hartvig

    2000-01-01

    The effect of high-frequency, non-resonant parametric excitation on the low-frequency response of spinning discs is considered. The parametric excitation is obtained through a non-constant rotation speed, where the frequency of the pulsating overlay is much higher than the lowest natural frequenc...

  15. Use of GPS network data for HF Doppler measurements interpretation

    CERN Document Server

    Petrova, Inna R; Latypov, Ruslan R

    2014-01-01

    The method of measurement of Doppler frequency shift of ionospheric signal - HF Doppler technique - is one of well-known and widely used methods of ionosphere research. It allows to research various disturbances in the ionosphere. There are some sources of disturbances in the ionosphere. These are geomagnetic storms, solar flashes, metrological effects, atmospheric waves. This method allows to find out the influence of earthquakes, explosions and other processes on the ionosphere, which occur near to the Earth. HF Doppler technique has the high sensitivity to small frequency variations and the high time resolution, but interpretation of results is difficult. In this work we make an attempt to use GPS data for Doppler measurements interpretation. Modeling of Doppler frequency shift variations with use of TEC allows to separate ionosphere disturbances of medium scale.

  16. High Resolution Crossed Molecular Beams Study on the F+HD→HF+D Reaction at Collision Energy of 5.43-18.73 kJ/mol

    Institute of Scientific and Technical Information of China (English)

    Wen-rui Dong; Chun-lei Xiao; Tao Wang; Dong-xu Dai; Xiu-yan Wang; Xue-ming Yang

    2011-01-01

    The dynamics of F+HD→HF+D reaction has been studied at ten collision energies ranging from 5.43 kJ/mol to 18.73 kJ/mol using high-resolution H/D atom Rydberg tagging time-of-flight method.Product vibrational and rotational state-resolved differential cross sections have been determined.The intensity of the HF(v'=2) forward products decreases as the collision energy increases,suggesting that the resonance contribution is reduced as the collision energy increases.The forward peak of HF(v'=3) product has also been observed above the threshold of this product channel.Product energy disposals in different degrees of freedom have been analyzed.The collision energy dependence of the HF vibrational product branching was also determined.This work presents a comprehensive dynamic picture of this resonance mediated reaction in a wide collision energy regime,providing a good test ground for theoretical understandings of this interesting reaction at higher collision energies.

  17. High frequency oscillations and high frequency functional network characteristics in the intraoperative electrocorticogram in epilepsy

    NARCIS (Netherlands)

    Zweiphenning, W. J E M; van 't Klooster, M. A.; van Diessen, E.; van Klink, N. E C; Huiskamp, G. J M|info:eu-repo/dai/nl/074463640; Gebbink, T. A.; Leijten, F. S S|info:eu-repo/dai/nl/152243054; Gosselaar, P. H.|info:eu-repo/dai/nl/304813990; Otte, W. M.|info:eu-repo/dai/nl/168455706; Stam, C. J.; Braun, K. P J|info:eu-repo/dai/nl/207237239; Zijlmans, G. J M|info:eu-repo/dai/nl/304819581

    2016-01-01

    OBJECTIVE: High frequency oscillations (HFOs; > 80 Hz), especially fast ripples (FRs, 250-500 Hz), are novel biomarkers for epileptogenic tissue. The pathophysiology suggests enhanced functional connectivity within FR generating tissue. Our aim was to determine the relation between brain areas

  18. High frequency oscillations and high frequency functional network characteristics in the intraoperative electrocorticogram in epilepsy

    Directory of Open Access Journals (Sweden)

    W.J.E.M. Zweiphenning

    2016-01-01

    Significance: ‘Baseline’ high-frequency network parameters might help intra-operative recognition of epileptogenic tissue without the need for waiting for events. These findings can increase our understanding of the ‘architecture’ of epileptogenic networks and help unravel the pathophysiology of HFOs.

  19. Deformation and Phase Transformation Processes in Polycrystalline NiTi and NiTiHf High Temperature Shape Memory Alloys

    Science.gov (United States)

    Benafan, Othmane

    2012-01-01

    The deformation and transformation mechanisms of polycrystalline Ni49.9Ti50.1 and Ni50.3Ti29.7Hf20 (in at.%) shape memory alloys were investigated by combined experimental and modeling efforts aided by an in situ neutron diffraction technique at stress and temperature. The thermomechanical response of the low temperature martensite, the high temperature austenite phases, and changes between these two states during thermomechanical cycling were probed and reported. In the cubic austenite phase, stress-induced martensite, deformation twinning and slip processes were observed which helped in constructing a deformation map that contained the limits over which each of the identified mechanisms was dominant. Deformation of the monoclinic martensitic phase was also investigated where the microstructural changes (texture, lattice strains, and phase fractions) during room-temperature deformation and subsequent thermal cycling were compared to the bulk macroscopic response. When cycling between these two phases, the evolution of inelastic strains, along with the shape setting procedures were examined and used for the optimization of the transformation properties as a function of deformation levels and temperatures. Finally, this work was extended to the development of multiaxial capabilities at elevated temperatures for the in situ neutron diffraction measurements of shape memory alloys on the VULCAN Diffractometer at Oak Ridge National Laboratory.

  20. High frequency band crossings in ^168Lu.

    Science.gov (United States)

    Roux, D. G.; Li, Y.; Ma, W. C.; Amro, H.; Thompson, J.; Winger, J.; Hagemann, G.; Herskind, B.; Jensen, D.; Sletten, G.; Wilson, J.; Fallon, P.; Diamond, R.; Goergen, A.; Machiavelli, A.; Ward, D.; Hübel, H.; Domscheit, J.

    2003-10-01

    High spin states in ^168Lu were populated using the ^123Sb(^48Ca,3n) reaction at 203 MeV. The beam was provided by the 88" cyclotron at LBNL, and coincident gamma rays were detected with the Gammasphere spectrometer array. An analysis of the data which had been sorted into three- and four- dimensional histograms confirmed the four previously known (J.H.Ha et al. J. Phys. Soc. Japan 71 (2002) 1663-1671) pairs of signature partner bands and extended them to considerably higher spins (in one case up to a tentative 50 hbar). In addition, a new pair of signature partners, as well as a new doubly decoupled band were found. On the basis of the present data, the configuration of one of the known bands, previously assigned π d_3/2 øtimes ν i_13/2 was reassigned as π d_5/2 øtimes ν i_13/2. High frequency band crossings, beyond the first ν i_13/2 alignment, were observed for the first time. These results will be discussed with reference to Cranking Shell Model calculations.

  1. Safety and Efficacy of Eplerenone in Patients at High Risk for Hyperkalemia and/or Worsening Renal Function Analyses of the EMPHASIS-HF Study Subgroups (Eplerenone in Mild Patients Hospitalization And SurvIval Study in Heart Failure)

    NARCIS (Netherlands)

    Eschalier, Romain; McMurray, John J. V.; Swedberg, Karl; van Veldhuisen, Dirk J.; Krum, Henry; Pocock, Stuart J.; Shi, Harry; Vincent, John; Rossignol, Patrick; Zannad, Faiez; Pitt, Bertram

    2013-01-01

    Objectives The study sought to investigate the safety and efficacy of eplerenone in patients at high risk for hyperkalemia or worsening renal function (WRF) in EMPHASIS-HF, a trial that enrolled patients at least 55 years old with heart failure and reduced ejection fraction (HF-REF), in New York Hea

  2. Where is the value in high frequency trading?

    OpenAIRE

    Álvaro Cartea; José Penalva

    2011-01-01

    We analyze the impact of high frequency trading in financial markets based on a model with three types of traders: liquidity traders, market makers, and high frequency traders. Our four main findings are: i) The price impact of the liquidity trades is higher in the presence of the high frequency trader and is increasing with the size of the trade. In particular, we show that the high frequency trader reduces (increases) the prices that liquidity traders receive when selling (buying) their equ...

  3. Contact resistance measurement structures for high frequencies

    NARCIS (Netherlands)

    Roy, Deepu; Pijper, Ralf M.T.; Tiemeijer, Luuk F.; Wolters, Robertus A.M.

    2011-01-01

    Knowledge of the interfacial contact impedance offered by the device at its operating frequency range is crucial for accurate modelling and understanding of the device. In this article, a novel modified TLM test-structure has been devised to extract interfacial contact parameters at frequencies upto

  4. Development and Application of Interatomic Potentials for Ultra High Temperature Ceramics (UHTC): ZrB2 and HfB2

    Science.gov (United States)

    Lawson, John W.; Daw, Murray; Bauschlicher

    2012-01-01

    Ultra high temperature ceramics (UHTC) including ZrB2 and HfB2 are characterized by high melting point, good strength, and reasonable oxidation resistance. These materials are of interest for use as sharp leading edges for hypersonic vehicles among other applications. Progress in computational modeling of UHTCs has been limited in part due to the absence of suitable interatomic potentials. We present a Tersoff style parameterization of such potentials for ZrB2 and HfB2 appropriate for atomistic simulations. Parameters are fit to data generated from ab initio calculations. The accuracy of the potentials is assessed against further ab initio data. As a first non ]trivial application, molecular dynamics simulations are performed to evaluate the thermal conductivity of single crystals and the thermal resistance of high symmetry grain boundaries.

  5. Effect of 24 sessions of high-intensity aerobic interval training carried out at either high or moderate frequency, a randomized trial.

    Directory of Open Access Journals (Sweden)

    Håvard Hatle

    Full Text Available PURPOSE: The training response of an intensified period of high-intensity exercise is not clear. Therefore, we compared the cardiovascular adaptations of completing 24 high-intensity aerobic interval training sessions carried out for either three or eight weeks, respectively. METHODS: Twenty-one healthy subjects (23.0±2.1 years, 10 females completed 24 high-intensity training sessions throughout a time-period of either eight weeks (moderate frequency, MF or three weeks (high frequency, HF followed by a detraining period of nine weeks without any training. In both groups, maximal oxygen uptake (VO2max was evaluated before training, at the 9(th and 17(th session and four days after the final 24(th training session. In the detraining phase VO2max was evaluated after 12 days and thereafter every second week for eight weeks. Left ventricular echocardiography, carbon monoxide lung diffusion transfer factor, brachial artery flow mediated dilatation and vastus lateralis citrate maximal synthase activity was tested before and after training. RESULTS: The cardiovascular adaptation after HF training was delayed compared to training with MF. Four days after ending training the HF group showed no improvement (+3.0%, p = 0.126, whereas the MF group reached their highest VO2max with a 10.7% improvement (p<0.001: group difference p = 0.035. The HF group reached their highest VO2max (6.1% increase, p = 0.026 twelve days into the detraining period, compared to a concomitant reduction to 7.9% of VO2max (p<0.001 above baseline in the MF group (group difference p = 0.609. CONCLUSION: Both HF and MF training of high-intensity aerobic exercise improves VO2max. The cardiovascular adaptation following a HF programme of high-intensity exercise is however delayed compared to MF training. TRIAL REGISTRATION: ClinicalTrials.gov NCT00733941.

  6. Effect of 24 Sessions of High-Intensity Aerobic Interval Training Carried out at Either High or Moderate Frequency, a Randomized Trial

    Science.gov (United States)

    Hatle, Håvard; Støbakk, Per Kristian; Mølmen, Harald Edvard; Brønstad, Eivind; Tjønna, Arnt Erik; Steinshamn, Sigurd; Skogvoll, Eirik; Wisløff, Ulrik; Ingul, Charlotte Björk; Rognmo, Øivind

    2014-01-01

    Purpose The training response of an intensified period of high-intensity exercise is not clear. Therefore, we compared the cardiovascular adaptations of completing 24 high-intensity aerobic interval training sessions carried out for either three or eight weeks, respectively. Methods Twenty-one healthy subjects (23.0±2.1 years, 10 females) completed 24 high-intensity training sessions throughout a time-period of either eight weeks (moderate frequency, MF) or three weeks (high frequency, HF) followed by a detraining period of nine weeks without any training. In both groups, maximal oxygen uptake (VO2max) was evaluated before training, at the 9th and 17th session and four days after the final 24th training session. In the detraining phase VO2max was evaluated after 12 days and thereafter every second week for eight weeks. Left ventricular echocardiography, carbon monoxide lung diffusion transfer factor, brachial artery flow mediated dilatation and vastus lateralis citrate maximal synthase activity was tested before and after training. Results The cardiovascular adaptation after HF training was delayed compared to training with MF. Four days after ending training the HF group showed no improvement (+3.0%, p = 0.126), whereas the MF group reached their highest VO2max with a 10.7% improvement (pVO2max (6.1% increase, p = 0.026) twelve days into the detraining period, compared to a concomitant reduction to 7.9% of VO2max (pVO2max. The cardiovascular adaptation following a HF programme of high-intensity exercise is however delayed compared to MF training. Trial Registration ClinicalTrials.gov NCT00733941. PMID:24516645

  7. Far-Field Testing Method of Spurious Emission Produced by HF RFID

    Directory of Open Access Journals (Sweden)

    Nikola Gvozdenovic

    2016-01-01

    Full Text Available We present measurements of spurious emission produced by high-frequency radio frequency identification (HF RFID using carrier frequency of 13.56 MHz. HF RFID tags produce unwanted emission due to rectification and more generally due to nonlinearity of analog front end. Depending on the conducting material of an HF RFID coil and surrounding dielectric material, the coil behaves as more or less good antenna on some harmonic frequencies. Exact characterization and analysis of unwanted emission is important from the security perspective as well as from the perspective of interference with other systems. Consequently we measured the harmonics produced in the integrated circuitry and characterized radiation properties of the antenna. Finally we present the measurements of the spurious emission performed in a Gigahertz Transverse Electromagnetic (GTEM cell.

  8. Designing a high-frequency nutrient and biogeochemical monitoring network for the Sacramento–San Joaquin Delta, northern California

    Science.gov (United States)

    Bergamaschi, Brian A.; Downing, Bryan D.; Kraus, Tamara E.C.; Pellerin, Brian A.

    2017-07-11

    Executive SummaryThis report is the third in a series of three reports that provide information about how high-frequency (HF) nutrient monitoring may be used to assess nutrient inputs and dynamics in the Sacramento–San Joaquin Delta, California (Delta). The purpose of this report is to provide the background, principles, and considerations for designing an HF nutrient-monitoring network for the Delta to address high-priority, nutrient-management questions. The report starts with discussion of the high-priority management questions to be addressed, continues through discussion of the questions and considerations that place demands and constraints on network design, discusses the principles applicable to network design, and concludes with the presentation of three example nutrient-monitoring network designs for the Delta. For three example network designs, we assess how they would address high-priority questions that have been identified by the Delta Regional Monitoring Program (Delta Regional Monitoring Program Technical Advisory Committee, 2015).This report, along with the other two reports of this series (Kraus and others, 2017; Downing and others, 2017), was drafted in cooperation with the Delta Regional Monitoring Program to help scientists, managers, and planners understand how HF data improve our understanding of nutrient sources and sinks, drivers, and effects in the Delta. The first report in the series (Kraus and others, 2017) provides an introduction to the reasons for and fundamental concepts behind using HF monitoring measurements, including a brief summary of nutrient status and trends in the Delta and an extensive literature review showing how and where other research and monitoring programs have used HF monitoring to improve our understanding of nutrient cycling. The report covers the various technologies available for HF nutrient monitoring and presents the different ways HF monitoring instrumentation may be used for both fixed station and spatial

  9. An introduction to high-frequency nutrient and biogeochemical monitoring for the Sacramento–San Joaquin Delta, northern California

    Science.gov (United States)

    Kraus, Tamara E.C.; Bergamaschi, Brian A.; Downing, Bryan D.

    2017-07-11

    Executive SummaryThis report is the first in a series of three reports that provide information about high-frequency (HF) nutrient and biogeochemical monitoring in the Sacramento–San Joaquin Delta of northern California (Delta). This first report provides an introduction to the reasons for and fundamental concepts behind collecting HF measurements, and describes the benefits associated with a real-time, continuous, HF, multi-parameter water quality monitoring station network that is co-located with flow stations. It then provides examples of how HF nutrient measurements have improved our understating of nutrient sources and cycling in aquatic systems worldwide, followed by specific examples from the Delta. These examples describe the ways in which HF instrumentation may be used for both fixed-station and spatial assessments. The overall intent of this document is to describe how HF measurements currently (2017) are being used in the Delta to examine the relationship between nutrient concentrations, nutrient cycling, and aquatic habitat conditions.The second report in the series (Downing and others, 2017) summarizes information about HF nutrient and associated biogeochemical monitoring in the northern Delta. The report synthesizes data available from the nutrient and water quality monitoring network currently operated by the U.S. Geological Survey in this ecologically important region of the Delta. In the report, we present and discuss the available data at various timescales—first, at the monthly, seasonal, and inter-annual timescales; and, second, for comparison, at the tidal and event (for example, storms, reservoir releases, phytoplankton blooms) timescales. As expected, we determined that there is substantial variability in nitrate concentrations at short timescales within hours, but also significant variability at longer timescales such as months or years. This multi-scale, high variability affects calculation of fluxes and loads, indicating that HF

  10. High permeability-high frequency stable MnZn ferrites

    Energy Technology Data Exchange (ETDEWEB)

    Kalarus, J. [Ferroxcube Polska, 96-100 Skierniewice (Poland); Kogias, G., E-mail: kogias@cperi.certh.gr [Centre for Research and Technology-Hellas, Chemical Process Engineering Research Institute, Laboratory of Inorganic Materials, 57001 Thessaloniki (Greece); Aristotle University of Thessaloniki, Department of Chemical Engineering, Laboratory of Materials Technology, 54124 Thessaloniki (Greece); Holz, D. [Ferroxcube Polska, 96-100 Skierniewice (Poland); Zaspalis, V.T. [Centre for Research and Technology-Hellas, Chemical Process Engineering Research Institute, Laboratory of Inorganic Materials, 57001 Thessaloniki (Greece); Aristotle University of Thessaloniki, Department of Chemical Engineering, Laboratory of Materials Technology, 54124 Thessaloniki (Greece)

    2012-09-15

    Modern MnZn ferrite applications require high magnetic initial permeability and exceptional frequency stability; the former implies large grains, while the latter high grain boundary resistivity. In this article the optimization of the final firing process is described for achieving both. The optimization is based on the homogeneous dissolution of dopants under oxidative conditions and their subsequent precipitation along grain boundaries. This was accomplished by integrating isothermal plateaus at the upper stadia of the cooling stage of the final firing process. MnZn ferrites of the basic composition [Mn{sub 0.47}Zn{sub 0.47}Fe{sub 0.06}{sup 2+}]Fe{sub 2}{sup 3+}O{sub 4} were synthesized with initial permeability (measured at f=10 kHz, B<0.1 mT, T=25 Degree-Sign C) 12,600 and losses, expressed as tan({delta})/{mu}{sub i}, of 3.1 Multiplication-Sign 10{sup -6} at 10 kHz and 20.5 Multiplication-Sign 10{sup -6} at 100 kHz (B<0.1 mT, T=25 Degree-Sign C), that reflect good frequency stability. These results could be reproduced in pilot production scale. - Highlights: Black-Right-Pointing-Pointer Optimization of sintering is described for achieving high initial permeability. Black-Right-Pointing-Pointer Optimization of sintering is described for receiving frequency stability. Black-Right-Pointing-Pointer For high permeability, high densities and large grain sizes are required. Black-Right-Pointing-Pointer The achieved initial permeability is higher than 12,500. Black-Right-Pointing-Pointer The losses, tan({delta})/{mu}{sub i}, are 3.1 Multiplication-Sign 10{sup -6} at 10 kHz and 20.5 Multiplication-Sign 10{sup -6} at 100 kHz.

  11. Study on the impact of sudden stratosphere warming in the upper mesosphere-lower thermosphere regions using satellite and HF radar - [Article

    CSIR Research Space (South Africa)

    Mbatha, N

    2010-01-01

    Full Text Available The occurrence of sudden stratospheric warming (SSW) excites disturbances in the mesosphere-lower thermospheric (MLT) wind and temperature. Here, researchers have examined the high frequency (HF) radar wind data from the South African National...

  12. Highly improved resistive switching performances of the self-doped Pt/HfO2:Cu/Cu devices by atomic layer deposition

    Science.gov (United States)

    Liu, Sen; Wang, Wei; Li, QingJiang; Zhao, XiaoLong; Li, Nan; Xu, Hui; Liu, Qi; Liu, Ming

    2016-12-01

    Metal-oxide electrochemical metallization (ECM) memory is a promising candidate for the next generation nonvolatile memory. But this memory suffers from large dispersion of resistive switching parameters due to the intrinsic randomness of the conductive filament. In this work, we have proposed a self-doping approach to improve the resistive switching characteristics. The fabricated Pt/HfO2:Cu/Cu device shows outstanding nonvolatile memory properties, including high uniformity, good endurance, long retention and fast switching speed. The results demonstrate that the self-doping approach is an effective method to improve the metal-oxide ECM memory performances and the self-doped Pt/HfO2:Cu/Cu device has high potentiality for the nonvolatile memory applications in the future.

  13. Multi-resonance orbital model of high-frequency quasi-periodic oscillations: possible high-precision determination of black hole and neutron star spin

    CERN Document Server

    Stuchlik, Zdenek; Torok, Gabriel

    2013-01-01

    Using known frequencies of the twin-peak high-frequency quasiperiodic oscillations (HF QPOs) and known mass of the central black hole, the black-hole dimensionless spin can be determined by assuming a concrete version of the resonance model. However, a wide range of observationally limited values of the black hole mass implies low precision of the spin estimates. We discuss the possibility of higher precision of the black hole spin measurements in the framework of a multi-resonance model inspired by observations of more than two HF QPOs in the black hole systems, which are expected to occur at two (or more) different radii of the accretion disc. For the black hole systems we focus on the special case of duplex frequencies, when the top, bottom, or mixed frequency is common at two different radii where the resonances occur giving triple frequency sets. The sets of triple frequency ratios and the related spin are given. The strong resonance model for "magic" values of the black hole spin means that two (or more...

  14. High frequency oscillations and high frequency functional network characteristics in the intraoperative electrocorticogram in epilepsy.

    Science.gov (United States)

    Zweiphenning, W J E M; van 't Klooster, M A; van Diessen, E; van Klink, N E C; Huiskamp, G J M; Gebbink, T A; Leijten, F S S; Gosselaar, P H; Otte, W M; Stam, C J; Braun, K P J; Zijlmans, G J M

    2016-01-01

    High frequency oscillations (HFOs; > 80 Hz), especially fast ripples (FRs, 250-500 Hz), are novel biomarkers for epileptogenic tissue. The pathophysiology suggests enhanced functional connectivity within FR generating tissue. Our aim was to determine the relation between brain areas showing FRs and 'baseline' functional connectivity within EEG networks, especially in the high frequency bands. We marked FRs, ripples (80-250 Hz) and spikes in the electrocorticogram of 14 patients with refractory temporal lobe epilepsy. We assessed 'baseline' functional connectivity in epochs free of epileptiform events within these recordings, using the phase lag index. We computed the Eigenvector Centrality (EC) per channel in the FR and gamma band network. We compared EC between channels that did or did not show events at other moments in time. FR-band EC was higher in channels with than without spikes. Gamma-band EC was lower in channels with ripples and FRs. We confirmed previous findings of functional isolation in the gamma-band and found a first proof of functional integration in the FR-band network of channels covering presumed epileptogenic tissue. 'Baseline' high-frequency network parameters might help intra-operative recognition of epileptogenic tissue without the need for waiting for events. These findings can increase our understanding of the 'architecture' of epileptogenic networks and help unravel the pathophysiology of HFOs.

  15. HIGH FREQUENCY INDUCTION WELDING OF HIGH SILICON STEEL TUBES

    Directory of Open Access Journals (Sweden)

    Ricardo Miranda Alé

    2012-06-01

    Full Text Available High-Si steel is a low cost alternative for the fabrication of tubular structures resistant to atmospheric corrosion. However, the literature has often pointed out that steels presenting a higher Si content and/or a lower Mn/Si ratio have higher susceptibility to defects at the weld bond line during HFIW (High Frequency Induction Welding process, which has been widely used for manufacturing small diameter tubes. In this study the effect of the HFIW conditions on the quality of steel tubes with high-Si content and low Mn/Si ratio is investigated. The quality of welded tubes was determined by flare test and the defects in the bond line were identified by SEM. It has been found that higher welding speeds, V-convergence angles and power input should be applied in welding of high-Si steel, when compared to similar strength C-Mn steel.

  16. Optical properties and structure of HfO{sub 2} thin films grown by high pressure reactive sputtering

    Energy Technology Data Exchange (ETDEWEB)

    MartInez, F L [Departamento de Electronica y TecnologIa de Computadoras, Universidad Politecnica de Cartagena, Campus Universitario Muralla del Mar, E-30202 Cartagena (Spain); Toledano-Luque, M [Departamento de Fisica Aplicada III, Universidad Complutense de Madrid, E-28040 Madrid (Spain); GandIa, J J [Departamento de EnergIa, CIEMAT, Avda. Complutense 22, E-28040 Madrid (Spain); Carabe, J [Departamento de EnergIa, CIEMAT, Avda. Complutense 22, E-28040 Madrid (Spain); Bohne, W [Hahn-Meitner-Institut Berlin, Abteilung SF4, D-14109 Berlin (Germany); Roehrich, J [Hahn-Meitner-Institut Berlin, Abteilung SF4, D-14109 Berlin (Germany); Strub, E [Hahn-Meitner-Institut Berlin, Abteilung SF4, D-14109 Berlin (Germany); Martil, I [Departamento de Fisica Aplicada III, Universidad Complutense de Madrid, E-28040 Madrid (Spain)

    2007-09-07

    Thin films of hafnium oxide (HfO{sub 2}) have been grown by high pressure reactive sputtering on transparent quartz substrates (UV-grade silica) and silicon wafers. Deposition conditions were adjusted to obtain polycrystalline as well as amorphous films. Optical properties of the films deposited on the silica substrates were investigated by transmittance and reflectance spectroscopy in the ultraviolet, visible and near infrared range. A numerical analysis method that takes into account the different surface roughness of the polycrystalline and amorphous films was applied to calculate the optical constants (refractive index and absorption coefficient). Amorphous films were found to have a higher refractive index and a lower transparency than polycrystalline films. This is attributed to a higher density of the amorphous samples, which was confirmed by atomic density measurements performed by heavy-ion elastic recoil detection analysis. The absorption coefficient gave an excellent fit to the Tauc law (indirect gap), which allowed a band gap value of 5.54 eV to be obtained. The structure of the films (amorphous or polycrystalline) was found to have no significant influence on the nature of the band gap. The Tauc plots also give information about the structure of the films, because the slope of the plot (the Tauc parameter) is related to the degree of order in the bond network. The amorphous samples had a larger value of the Tauc parameter, i.e. more order than the polycrystalline samples. This is indicative of a uniform bond network with percolation of the bond chains, in contrast to the randomly oriented polycrystalline grains separated by grain boundaries.

  17. Comparison of the effects of high- and low-frequency repetitive transcranial magnetic stimulation on upper limb hemiparesis in the early phase of stroke.

    Science.gov (United States)

    Sasaki, Nobuyuki; Mizutani, Saneyuki; Kakuda, Wataru; Abo, Masahiro

    2013-05-01

    Recently, high-frequency repetitive transcranial magnetic stimulation (HF-rTMS) and low-frequency rTMS (LF-rTMS) are reported to improve motor function significantly in chronic hemiparetic stroke patients. However, few studies have investigated the safety and efficacy of these rTMS modalities introduced during the early phase of stroke. The purpose of this study was to clarify the rTMS modality that is more beneficial for upper limb hemiparesis in the early phase of stroke using a randomized controlled trial. Twenty-nine patients with a hemispheric stroke lesion in the early phase of stroke were examined. Patients were randomly assigned into 3 groups: the HF-rTMS group (10 Hz rTMS to the lesional hemisphere [n = 9]), the LF-rTMS group (1 Hz rTMS to the nonlesional hemisphere [n = 11]), and the sham stimulation group [n = 9]). Patients received sessions for 5 consecutive days. Grip strength and tapping frequency were assessed before and after the intervention. Motor improvement of the affected upper limb after intervention was compared among the 3 groups. All patients completed the 5-day protocol. Both the HF-rTMS and LF-rTMS groups had significant increases in both grip strength and tapping frequency. Comparison of the extent of improvement showed a more significant increase in grip strength and tapping frequency in the HF-rTMS group compared to the sham stimulation group (each P stimulation group. HF-rTMS applied to the lesional hemisphere in the early phase of stroke was more beneficial for motor improvement of the affected upper limb than LF-rTMS. Copyright © 2013 National Stroke Association. Published by Elsevier Inc. All rights reserved.

  18. Exploring the Origin of High-frequency Coherent Radiation Imaged from Back Projection, Using Stochastic Finite-fault Earthquake Rupture Models

    Science.gov (United States)

    Satriano, C.; Ruiz, J. A.; Bernard, P.; Vilotte, J. P.

    2015-12-01

    Back projection (BP) has recently emerged as a tool for imaging the spatio-temporal distribution of high-frequency (HF) emission during the earthquake rupture. BP images are typically constructed from HF-filtered, far field velocity waveforms, shifted and stacked according to the predicted travel-time from each node of a source grid. The underlying assumption is that the radiated wave field is coherent across the recording array, so that waveforms sum up constructively when the correct source point is selected. For regional arrays, at teleseismic distance, this assumption is generally valid up to 2-3 Hz. BP is an inherently HF method (resolution degrades at lower frequencies), and has been often used in conjunction with kinematic slip modeling (inherently low-frequency) to discuss the variability of rupture behavior with frequency. Many studies have evidenced that HF emissions occur at the border of large slip asperities and/or are associated with abrupt changes in rupture velocity. Here we perform a systematic investigation of the relationship between rupture properties and BP images of HF emission through the analysis of synthetic finite-source models, using a kinematic k-2 source model. This approach is based on a composite source description, with sub-events following a fractal distribution of sizes. Each elementary source is activated by the macro scale rupture front, with rupture duration proportional to its size. This approach generates, in the far-field approximation, ground displacements that follow the ω-2 model with frequency-dependent directivity effects. For a large earthquake rupture (M~9), synthetic far field recordings can be generated up to 4 Hz, with reasonable computing time. We study several scenarios, exploring the spatial variability of rupture velocity, fractal properties (slip heterogeneity) and source directivity, and analyze the effect of the relative position between the recording teleseismic array and the fault.

  19. Power-Stepped HF Cross-Modulation Experiments: Simulations and Experimental Observations

    Science.gov (United States)

    Greene, S.; Moore, R. C.

    2014-12-01

    High frequency (HF) cross modulation experiments are a well established means for probing the HF-modified characteristics of the D-region ionosphere. The interaction between the heating wave and the probing pulse depends on the ambient and modified conditions of the D-region ionosphere. Cross-modulation observations are employed as a measure of the HF-modified refractive index. We employ an optimized version of Fejer's method that we developed during previous experiments. Experiments were performed in March 2013 at the High Frequency Active Auroral Research Program (HAARP) observatory in Gakona, Alaska. During these experiments, the power of the HF heating signal incrementally increased in order to determine the dependence of cross-modulation on HF power. We found that a simple power law relationship does not hold at high power levels, similar to previous ELF/VLF wave generation experiments. In this paper, we critically compare these experimental observations with the predictions of a numerical ionospheric HF heating model and demonstrate close agreement.

  20. Hybrid Broadband Ground-Motion Simulations: Combining Long-Period Deterministic Synthetics with High-Frequency Multiple S-to-S Backscattering

    KAUST Repository

    Mai, Paul Martin

    2010-09-20

    We present a new approach for computing broadband (0-10 Hz) synthetic seismograms by combining high-frequency (HF) scattering with low-frequency (LF) deterministic seismograms, considering finite-fault earthquake rupture models embedded in 3D earth structure. Site-specific HF-scattering Green\\'s functions for a heterogeneous medium with uniformly distributed random isotropic scatterers are convolved with a source-time function that characterizes the temporal evolution of the rupture process. These scatterograms are then reconciled with the LF-deterministic waveforms using a frequency-domain optimization to match both amplitude and phase spectra around the target intersection frequency. The scattering parameters of the medium, scattering attenuation ηs, intrinsic attenuation ηi, and site-kappa, as well as frequency-dependent attenuation, determine waveform and spectral character of the HF-synthetics and thus affect the hybrid broadband seismograms. Applying our methodology to the 1994 Northridge earthquake and validating against near-field recordings at 24 sites, we find that our technique provides realistic broadband waveforms and consistently reproduces LF ground-motion intensities for two independent source descriptions. The least biased results, compared to recorded strong-motion data, are obtained after applying a frequency-dependent site-amplification factor to the broadband simulations. This innovative hybrid ground-motion simulation approach, applicable to any arbitrarily complex earthquake source model, is well suited for seismic hazard analysis and ground-motion estimation.

  1. Application of in-situ nano-scanning calorimetry and X-ray diffraction to characterize Ni–Ti–Hf high-temperature shape memory alloys

    Energy Technology Data Exchange (ETDEWEB)

    McCluskey, Patrick J., E-mail: mccluske@ge.com [GE Global Research, One Research Circle, Niskayuna, NY 12309 (United States); Xiao, Kechao [School of Engineering and Applied Sciences, Harvard University, 29 Oxford Street, Cambridge, MA 02138 (United States); Gregoire, John M. [Joint Center for Artificial Photosynthesis, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125 (United States); Dale, Darren [Cornell High Energy Synchrotron Source, Ithaca, NY 14853 (United States); Vlassak, Joost J. [School of Engineering and Applied Sciences, Harvard University, 29 Oxford Street, Cambridge, MA 02138 (United States)

    2015-03-10

    Combinatorial nanocalorimetry and synchrotron X-ray diffraction were combined to study the martensite–austenite (M–A) phase transformation behavior of Ni–Ti–Hf shape memory alloys. A thin-film library of Ni–Ti–Hf samples with a range of compositions was deposited on a parallel nano-scanning calorimeter device using sputter deposition. Crystallization of each amorphous as-deposited sample by local heating at approximately 10{sup 4} K/s produced a nanoscale grain structure of austenite and martensite. Individual samples were then cycled through the M–A transformation, while the transformation enthalpy was measured by nanocalorimetry and the low- and high-temperature phase compositions were determined by X-ray diffraction. The techniques enable correlation of the observed behavior during thermal cycling with the thermodynamic and structural properties of the samples.

  2. Lattice Thermal Conductivity of Ultra High Temperature Ceramics (UHTC) ZrB2 and HfB2 from Atomistic Simulations

    Science.gov (United States)

    Lawson, John W.; Daw, Murray S.; Bauschlicher, Charles W.

    2012-01-01

    Ultra high temperature ceramics (UHTC) including ZrB2 and HfB2 have a number of properties that make them attractive for applications in extreme environments. One such property is their high thermal conductivity. Computational modeling of these materials will facilitate understanding of fundamental mechanisms, elucidate structure-property relationships, and ultimately accelerate the materials design cycle. Progress in computational modeling of UHTCs however has been limited in part due to the absence of suitable interatomic potentials. Recently, we developed Tersoff style parameterizations of such potentials for both ZrB2 and HfB2 appropriate for atomistic simulations. As an application, Green-Kubo molecular dynamics simulations were performed to evaluate the lattice thermal conductivity for single crystals of ZrB2 and HfB2. The atomic mass difference in these binary compounds leads to oscillations in the time correlation function of the heat current, in contrast to the more typical monotonic decay seen in monoatomic materials such as Silicon, for example. Results at room temperature and at elevated temperatures will be reported.

  3. Heart rate variability changes during high frequency yoga breathingand breath awareness

    Directory of Open Access Journals (Sweden)

    Singh Nilkamal

    2011-04-01

    Full Text Available Abstract Background Pre and post comparison after one minute of high frequency yoga breathing (HFYB suggested that the HFYB modifies the autonomic status by increasing sympathetic modulation, but its effect during the practice was not assessed. Methods Thirty-eight male volunteers with group average age ± S.D., 23.3 ± 4.4 years were each assessed on two separate days in two sessions, (i HFYB and (ii breath awareness. Each session was for 35 minutes, with 3 periods, i.e., pre (5 minutes, during HFYB or breath awareness (15 minutes and post (5 minutes. Results There was a significant decrease in NN50, pNN50 and the mean RR interval during and after HFYB and after breath awareness, compared to the respective 'pre' values (p post-hoc analysis. The LF power increased and HF power decreased during and after breath awareness and LF/HF ratio increased after breath awareness (p Conclusion The results suggest that there was reduced parasympathetic modulation during and after HFYB and increased sympathetic modulation with reduced parasympathetic modulation during and after breath awareness.

  4. Physical and electrical properties of induced high-k ZrHfO crystallization with ZrN cap by high power impulse magnetron sputtering for metal-gate metal-insulator-semiconductor structures

    Science.gov (United States)

    Tsai, Jung-Ruey; Juan, Pi-Chun; Lin, Cheng-Li; Lin, Guo-Cheng

    2017-01-01

    Metal-gate TiN/ZrN/ZrHfO/p-Si metal-insulator-semiconductor (MIS) structures have been fabricated in this work. The physical and electrical properties were characterized. The crystallization of high-k ZrHfO thin-film is induced by high power impulse magnetron sputtering (HIPIMS) during the deposition of ZrN capping layer. The binding energies and depth profiles were investigated by X-ray photoelectron spectroscopy (XPS). It is found that Zr and Hf out-diffusion from high-k dielectric in samples with HIPIMS is lesser than those in samples with the conventional DC magnetron sputtering (DCMS). The dielectric constant which strongly relates to the tetragonal phase becomes higher and the flatband voltage shift shows smaller by using the HIPIMS method than by the conventional DCMS. The cation and anion vacancies have been investigated by the defect reaction model.

  5. Effects of High Intensity and Sprint Interval Training Frequency on 1.5 Mile Run Times in Air Force ROTC Cadets

    OpenAIRE

    Dahle, Jared Hill

    2016-01-01

    The effects of varying high intensity interval training (HIIT) and sprint interval training (SIT) frequency on 1.5 mile (2.4km) run performance in Air Force ROTC cadets were studied. Twenty-seven cadets (21.6 ± 2.8 years) were stratified then randomly assigned to 3 groups: a high frequency group (HF) that performed HIIT/SIT 3x week, a low frequency group (LF) that performed HIIT/SIT 2x week, and a continuous training group (CG) that performed moderate intensity training 3x week. HIIT workou...

  6. HF radiation emitted by chaotic leader processes

    Science.gov (United States)

    Mäkelä, J. S.; Edirisinghe, M.; Fernando, M.; Montaño, R.; Cooray, V.

    2007-04-01

    This paper presents direct measurements of narrowband 10 MHz HF radiation from so-called “chaotic leaders” associated with subsequent return strokes. Although the term is controversial and poorly defined, we find that more than 30% of subsequent strokes in close lightning flashes contain electric field characteristics that are best described as “chaotic”. In earlier studies, return strokes have consistently been observed to be the strongest sources of HF radiation, but the results for leader processes are less consistent. We also observe return strokes to be the main HF emitter, and the leaders before the first return stroke in a flash sequence also emit HF though somewhat less intensely. The leaders preceding subsequent strokes typically emit little or no HF radiation, whether they are dart or dart-stepped leaders. However, it was observed that the presence of a chaotic component increases the leader HF intensity dramatically Defining the HF intensity unequivocally can be problematic for processes like chaotic leaders which have a combination of continuous and impulsive phenomena. Two time-domain methods were used to measure the HF intensity, the peak energy and the RMS energy. In the frequency domain these correspond to the energy spectral density (ESD) and power spectral density (PSD), respectively. It was found that the methods are not necessarily compatible. Thus, it is suggested that to clarify future work, leader processes should be characterized by the PSD rather than the ESD.

  7. Characterization, integration and reliability of HfO{sub 2} and LaLuO{sub 3} high-κ/metal gate stacks for CMOS applications

    Energy Technology Data Exchange (ETDEWEB)

    Nichau, Alexander

    2013-07-15

    The continued downscaling of MOSFET dimensions requires an equivalent oxide thickness (EOT) of the gate stack below 1 nm. An EOT below 1.4 nm is hereby enabled by the use of high-κ/metal gate stacks. LaLuO{sub 3} and HfO{sub 2} are investigated as two different high-κ oxides on silicon in conjunction with TiN as the metal electrode. LaLuO{sub 3} and its temperature-dependent silicate formation are characterized by hard X-ray photoemission spectroscopy (HAXPES). The effective attenuation length of LaLuO{sub 3} is determined between 7 and 13 keV to enable future interface and diffusion studies. In a first investigation of LaLuO{sub 3} on germanium, germanate formation is shown. LaLuO{sub 3} is further integrated in a high-temperature MOSFET process flow with varying thermal treatment. The devices feature drive currents up to 70μA/μm at 1μm gate length. Several optimization steps are presented. The effective device mobility is related to silicate formation and thermal budget. At high temperature the silicate formation leads to mobility degradation due to La-rich silicate formation. The integration of LaLuO{sub 3} in high-T processes delicately connects with the optimization of the TiN metal electrode. Hereby, stoichiometric TiN yields the best results in terms of thermal stability with respect to Si-capping and high-κ oxide. Different approaches are presented for a further EOT reduction with LaLuO{sub 3} and HfO{sub 2}. Thereby the thermodynamic and kinetic predictions are employed to estimate the behavior on the nanoscale. Based on thermodynamics, excess oxygen in the gate stack, especially in oxidized metal electrodes, is identified to prevent EOT scaling below 1.2 nm. The equivalent oxide thickness of HfO{sub 2} gate stacks is scalable below 1 nm by the use of thinned interfacial SiO{sub 2}. The prevention of oxygen incorporation into the metal electrode by Si-capping maintains the EOT after high temperature annealing. Redox systems are employed within the

  8. On the Onset of HF-Induced Airglow at HAARP

    Science.gov (United States)

    2007-11-02

    AFRL-VS-HA-TR-2005-1061 JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 109, A02305, doi:10.1029/2003JA010205, 2004 On the onset of HF-induced airglow at HAARP ...line) during the February 2002 campaign at the High Frequency Active Auroral Research Program ( HAARP ) heating facility are analyzed. We find that... HAARP , J. Geophys. Res., 109, A02305, doi: 10.1029/2003JA010205. 1. Introduction known as the parametric decay (PDI) or oscillating two- [2] A

  9. High frequency model of stacked film capacitors

    Science.gov (United States)

    Talbert, T.; Joubert, C.; Daude, N.; Glaize, C.

    2001-11-01

    Polypropylene metallized capacitors are of general use in power electronics because of their reliability, their self-healing capabilities, and their low price. Though the behavior of metallized coiled capacitors has been discussed, no work has been carried out on stacked and flattened metallized capacitors. The purpose of this article is to suggest an analytical model of resonance frequency, stray inductance and impedance of stacked capacitors. We first solve the equation of propagation of the magnetic potential vector (A) in the dielectric of an homogeneous material. Then, we suggest an original method of resolution, like the one used for resonant cavities, in order to present an analytical solution of the problem. Finally, we give some experimental results proving that the physical knowledge of the parameters of the capacitor (dimension of the component, and material constants), enables us to calculate an analytical model of resonance frequency, stray inductance and impedance of stacked capacitors.

  10. 高压下BaHfO3电子结构与光学性质的第一性原理研究%First-principles study on the electronic structures and optical properties of BaHfO3 under high pressure

    Institute of Scientific and Technical Information of China (English)

    顾芳; 王俊锋; 陈云云; 刘清惓; 张加宏

    2012-01-01

    The cubic perovskite-type BaHfO3 has been investigated by the first-principles plane-wave pseudo-potential method based on the density function theory. The electronic structure and optical properties of BaHfO3 are calculated under high pressure. The band structure analysis indicates that BaHfO3 is a direct-band-gap insulator in the case of without pressure and imposing positive pressure, while BaHfO3 is transformed into an indirect-band-gap semiconductor under negative pressure. Besides, the band gap of BaHfO3 decreases with an increase of pressure, and it appears obvious nonlinear relationship. The optical properties calculations show that the absorption edge is blue-shifted when imposing positive pressure, while it is red-shifted and peaks of imaginary part of the dielectric function decrease when imposing negative pressure. Furthermore, the static dielectric constant and static refractive index of BaHfO3under high pressure increase. In a word, the involved results have shown that the high pressure effectively modulates the electronic structure and optical properties of BaHfO3, which will provide a theoretical basis for the design and application of BaHfO3 optoelectronic materials.%从第一性原理出发,在局域密度近似下,采用基于密度泛函理论的平面波超软赝势计算方法系统地研究了高压对BaHfO3电子结构与光学性质的影响.能带结构分析表明:无压强和施加正压强作用时,BaHfO3为直接带隙绝缘体,而施加负压强时,BaHfO3则转变为间接带隙半导体;BaHfO3的带隙随压强增加而减小,且具有明显的非线性关系.对光学性质的分析发现:施加正压强后,光学吸收带边产生蓝移;负压强作用时介电函数虚部尖峰减少,光学吸收带边产生红移;施加压强后BaHfO3的静态介电常数和静态折射率均增大.上述研究表明施加高压有效调制了BaHfO3的电子结构和光学性质,计算结果为BaHfO3光电材料的设计与应用提供了理论依据.

  11. Pressure induced novel compounds in the Hf-O system from first-principles calculations

    OpenAIRE

    2015-01-01

    Using first-principles evolutionary simulations, we have systematically investigated phase stability in the Hf-O system at pressure up to 120 GPa. New compounds Hf5O2, Hf3O2, HfO and HfO3 are discovered to be thermodynamically stable at certain pressure ranges and a new stable high-pressure phase is found for Hf2O with space group Pnnm and anti-CaCl2-type structure. Both P62m-HfO and P4m2-Hf2O3 show semimetallic character. Pnnm-HfO3 shows interesting structure, simultaneously containing oxide...

  12. The high temperature corrosion behaviour of Hf modified chromo-aluminised coatings produced by a single step process

    Energy Technology Data Exchange (ETDEWEB)

    Du, H.L. [Northumbria Univ., Newcastle-upon-Tyne (United Kingdom). Surface Eng. Res. Group; Kipkemoi, J. [Dept. of Mechanical Engineering, Aristoteles Univ., Thessaloniki (Greece); Tsipas, D.N. [Dept. of Mechanical Engineering, Aristoteles Univ., Thessaloniki (Greece); Datta, P.K. [Northumbria Univ., Newcastle-upon-Tyne (United Kingdom). Surface Eng. Res. Group

    1996-12-01

    In this paper the introduction of Cr, Al and Hf into the surface of the RENE 80, INC718 and 2.25Cr-1Mo steel by pack cementation in a single step process has been described. The coated alloys were subject to cyclic hot corrosion and cyclic oxidation test at 870 and 875 C. The surface treated alloys were also sulphidised at 750 C in an environment of H{sub 2}/H{sub 2}S/H{sub 2}O yielding P{sub S{sub 2}} = 10{sup -6} atm. and P{sub O{sub 2}} = 10{sup -23} atm. The coated and exposed specimens were characterised by optical microscope, SEM, EPMA, EDX and XRD. Cyclic hot corrosion and cyclic oxidation tests showed that the presence of the Cr-Al-Hf on the surface of the alloys enhanced their corrosion resistance. The rare earth element modified chromium aluminide coatings showed superior protectivity. However the Cr-Al-Hf coating on INC718 delayed the formation of the refractory metal sulphides in sulphidising atmosphere and thereby reduced its sulphidation resistance whilst the coating on 2.25Cr-1Mo steel only slightly increased its resistance to sulphidation attack. (orig.)

  13. Mechanisms of high-frequency song generation in brachypterous crickets and the role of ghost frequencies.

    Science.gov (United States)

    Robillard, Tony; Montealegre-Z, Fernando; Desutter-Grandcolas, Laure; Grandcolas, Philippe; Robert, Daniel

    2013-06-01

    Sound production in crickets relies on stridulation, the well-understood rubbing together of a pair of specialised wings. As the file of one wing slides over the scraper of the other, a series of rhythmic impacts causes harmonic oscillations, usually resulting in the radiation of pure tones delivered at low frequencies (2-8 kHz). In the short-winged crickets of the Lebinthini tribe, acoustic communication relies on signals with remarkably high frequencies (>8 kHz) and rich harmonic content. Using several species of the subfamily Eneopterinae, we characterised the morphological and mechanical specialisations supporting the production of high frequencies, and demonstrated that higher harmonics are exploited as dominant frequencies. These specialisations affect the structure of the stridulatory file, the motor control of stridulation and the resonance of the sound radiator. We placed these specialisations in a phylogenetic framework and show that they serve to exploit high-frequency vibrational modes pre-existing in the phylogenetic ancestor. In Eneopterinae, the lower frequency components are harmonically related to the dominant peak, suggesting they are relicts of ancestral carrier frequencies. Yet, such ghost frequencies still occur in the wings' free resonances, highlighting the fundamental mechanical constraints of sound radiation. These results support the hypothesis that such high-frequency songs evolved stepwise, by a form of punctuated evolution that could be related to functional constraints, rather than by only the progressive increase of the ancestral fundamental frequency.

  14. Low velocity target detection based on time-frequency image for high frequency ground wave radar

    Institute of Scientific and Technical Information of China (English)

    YAN Songhua; WU Shicai; WEN Biyang

    2007-01-01

    The Doppler spectral broadening resulted from non-stationary movement of target and radio-frequency interference will decrease the veracity of target detection by high frequency ground wave(HEGW)radar.By displaying the change of signal energy on two dimensional time-frequency images based on time-frequency analysis,a new mathematical morphology method to distinguish target from nonlinear time-frequency curves is presented.The analyzed results from the measured data verify that with this new method the target can be detected correctly from wide Doppler spectrum.

  15. First 100 ms of HF modification at Tromso, Norway

    Science.gov (United States)

    Djuth, F. T.; Isham, B.; Rietveld, M. T.; Hagfors, T.; La Hoz, C.

    Experiments were performed with the high-power high-frequency HF facility at Troms o Norway to test theoretical predictions for the excitation of ion and Langmuir oscillations in the ionosphere The principal diagnostic of wave-plasma interactions was the VHF radar at the European Incoherent Scatter EISCAT facility High resolution radar techniques were used to monitor the temporal development of the ion and Langmuir oscillations HF pulses 100 ms in duration were periodically transmitted into a smooth background F region plasma Measurements of the radar backscatter spectra show that all key spectral features predicted by strong Langmuir turbulence SLT theory modified Zakharov model are simultaneously present in the plasma and that their evolution is in agreement with theoretical expectations However several new features have been observed that cannot be anticipated by current theory because of limitations in the electric field strength within the simulations The experimental results reinforce the notion that new theoretical developments are needed to accommodate the large HF electric fields produced at Troms o and HAARP Gakona Alaska and to treat the electron acceleration process in a self-consistent fashion The F region response to two HF effective radiated power levels sim 58 MW and sim 125 MW was investigated at Troms o These ERP values include absorptive losses resulting from the sunlit D region In general the results at 58 MW ERP and 125 MW ERP are consistent with many of the SLT

  16. High-frequency homogenization of zero frequency stop band photonic and phononic crystals

    CERN Document Server

    Antonakakis, Tryfon; Guenneau, Sebastien

    2013-01-01

    We present an accurate methodology for representing the physics of waves, for periodic structures, through effective properties for a replacement bulk medium: This is valid even for media with zero frequency stop-bands and where high frequency phenomena dominate. Since the work of Lord Rayleigh in 1892, low frequency (or quasi-static) behaviour has been neatly encapsulated in effective anisotropic media. However such classical homogenization theories break down in the high-frequency or stop band regime. Higher frequency phenomena are of significant importance in photonics (transverse magnetic waves propagating in infinite conducting parallel fibers), phononics (anti-plane shear waves propagating in isotropic elastic materials with inclusions), and platonics (flexural waves propagating in thin-elastic plates with holes). Fortunately, the recently proposed high-frequency homogenization (HFH) theory is only constrained by the knowledge of standing waves in order to asymptotically reconstruct dispersion curves an...

  17. High-Frequency Axial Fatigue Test Procedures for Spectrum Loading

    Science.gov (United States)

    2016-07-20

    REPORT NO: NAWCADPAX/TIM-2016/49 HIGH - FREQUENCY AXIAL FATIGUE TEST PROCEEDURES FOR SPECTRUM LOADING by David T. Rusk, AIR...OF THE NAVY NAVAL AIR WARFARE CENTER AIRCRAFT DIVISION PATUXENT RIVER, MARYLAND NAWCADPAX/TIM-2016/49 20 July 2016 HIGH - FREQUENCY AXIAL...Technical Information Memorandum 3. DATES COVERED 4. TITLE AND SUBTITLE High - Frequency Axial Fatigue Test Procedures for Spectrum Loading

  18. Anomalous waiting times in high-frequency financial data

    CERN Document Server

    Scalas, E; Luckock, H; Mainardi, F; Mantelli, M; Raberto, M; Scalas, Enrico; Gorenflo, Rudolf; Luckock, Hugh; Mainardi, Francesco; Mantelli, Maurizio; Raberto, Marco

    2004-01-01

    In high-frequency financial data not only returns, but also waiting times between consecutive trades are random variables. Therefore, it is possible to apply continuous-time random walks (CTRWs) as phenomenological models of the high-frequency price dynamics. An empirical analysis performed on the 30 DJIA stocks shows that the waiting-time survival probability for high-frequency data is non-exponential. This fact imposes constraints on agent-based models of financial markets.

  19. A high frequency resonance gravity gradiometer

    Energy Technology Data Exchange (ETDEWEB)

    Bagaev, S. N.; Kvashnin, N. L.; Skvortsov, M. N. [Laser Physics Institute SB RAS, Novosibirsc (Russian Federation); Bezrukov, L. B.; Krysanov, V. A. [Institute of Nuclear Physics RAS, Moscow (Russian Federation); Oreshkin, S. I.; Motylev, A. M.; Popov, S. M.; Samoilenko, A. A.; Yudin, I. S. [Lomonosov MSU, Sternberg Astronomical Institute, Moscow (Russian Federation); Rudenko, V. N. [Institute of Nuclear Physics RAS, Moscow (Russian Federation); Lomonosov MSU, Sternberg Astronomical Institute, Moscow (Russian Federation)

    2014-06-15

    A new setup OGRAN—the large scale opto-acoustical gravitational detector is described. As distinguished from known gravitational bar detectors it uses the optical interferometrical readout for registering weak variations of gravity gradient at the kilohetz frequency region. At room temperature, its sensitivity is limited only by the bar Brownian noise at the bandwidth close to 100 Hz. It is destined for a search for rare events—gravitational pulses coincident with signals of neutrino scintillator (BUST) in the deep underground of Baksan Neutrino Observatory of INR RAS.

  20. High-Speed Low-Jitter Frequency Multiplication in CMOS

    NARCIS (Netherlands)

    van de Beek, R.C.H.

    2004-01-01

    This thesis deals with high-speed Clock and Frequency Multiplication. The term `high-speedù applies to both the output and the reference frequency of the multiplier. Much emphasis is placed on analysis and optimization of the total timing inaccuracies, and on implementing a high-speed feedback

  1. Optical Transmitter Terminal for Selective RF High Frequency Bans Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The objective of the proposal work is to investigate the highly innovative conceptual design of an optical communication selective frequency transmitter terminal...

  2. Calibration of High Frequency MEMS Microphones

    Science.gov (United States)

    Shams, Qamar A.; Humphreys, William M.; Bartram, Scott M.; Zuckewar, Allan J.

    2007-01-01

    Understanding and controlling aircraft noise is one of the major research topics of the NASA Fundamental Aeronautics Program. One of the measurement technologies used to acquire noise data is the microphone directional array (DA). Traditional direction array hardware, consisting of commercially available condenser microphones and preamplifiers can be too expensive and their installation in hard-walled wind tunnel test sections too complicated. An emerging micro-machining technology coupled with the latest cutting edge technologies for smaller and faster systems have opened the way for development of MEMS microphones. The MEMS microphone devices are available in the market but suffer from certain important shortcomings. Based on early experiments with array prototypes, it has been found that both the bandwidth and the sound pressure level dynamic range of the microphones should be increased significantly to improve the performance and flexibility of the overall array. Thus, in collaboration with an outside MEMS design vendor, NASA Langley modified commercially available MEMS microphone as shown in Figure 1 to meet the new requirements. Coupled with the design of the enhanced MEMS microphones was the development of a new calibration method for simultaneously obtaining the sensitivity and phase response of the devices over their entire broadband frequency range. Over the years, several methods have been used for microphone calibration. Some of the common methods of microphone calibration are Coupler (Reciprocity, Substitution, and Simultaneous), Pistonphone, Electrostatic actuator, and Free-field calibration (Reciprocity, Substitution, and Simultaneous). Traditionally, electrostatic actuators (EA) have been used to characterize air-condenser microphones for wideband frequency ranges; however, MEMS microphones are not adaptable to the EA method due to their construction and very small diaphragm size. Hence a substitution-based, free-field method was developed to

  3. Parametric excitation of whistler waves by HF heater

    Science.gov (United States)

    Kuo, S. P.; Lee, M. C.

    1989-01-01

    Possible generation of whistler waves by Tromso HF heater is investigated. It is shown that the HF heater wave can parametrically decay into a whistler wave and a Langmuir wave. Since whistler waves may have a broad range of frequency, the simultaneously excited Langmuir waves can have a much broader frequency bandwidth than those excited by the parametric decay instability.

  4. Microstructure, phase stability and mechanical properties of Nb–Ni–Ti–Co–Zr and Nb–Ni–Ti–Co–Zr–Hf high entropy alloys

    Directory of Open Access Journals (Sweden)

    Zhidong Han

    2015-10-01

    Full Text Available Owning to their excellent thermal stability and high strength at elevated temperature, high entropy alloys (HEAs possess great potential for the application in aviation and aerospace fields. In present work, two novel Nb–Ni–Ti–Co–Zr and Nb–Ni–Ti–Co–Zr–Hf HEAs were prepared by arc melting and copper mold suction-casting method. The microstructure, phase stability, mechanical properties at room temperature and elevated temperature of the two HEAs were studied. Both of the HEAs possess high yield stress at room temperature, especially for the Nb–Ni–Ti–Co–Zr (with 2331 Mpa. In addition, the Nb–Ni–Ti–Co–Zr HEA exhibited high yield stress of 564 Mpa at elevated temperature of 800 °C and large compressive plastic strain (more than 50% at 800 °C. Nb–Ni–Ti–Co–Zr–Hf alloy showed new phase precipitation at 800 °C, whereas the structure of Nb–Ni–Ti–Co–Zr was more stable, which is one of the reason why it possesses high strength at room temperature and elevated temperature. The high temperature properties of the Nb–Ni–Ti–Co–Zr HEA make it promising for high temperature application.

  5. Ion heating, burnout of the high-frequency field, and ion sound generation under the development of a modulation instability of an intense Langmuir wave in a plasma

    Energy Technology Data Exchange (ETDEWEB)

    Kirichok, A. V., E-mail: sandyrcs@gmail.com; Kuklin, V. M.; Pryimak, A. V. [Institute for High Technologies, V.N. Karazin Kharkiv National University, 4 Svobody Sq., Kharkiv 61022 (Ukraine); Zagorodny, A. G. [Bogolyubov Institute for Theoretical Physics, 14-b, Metrolohichna str., Kiev 03680 (Ukraine)

    2015-09-15

    The development of one-dimensional parametric instabilities of intense long plasma waves is considered in terms of the so-called hybrid models, with electrons being treated as a fluid and ions being regarded as particles. The analysis is performed for both cases when the average plasma field energy is lower (Zakharov's hybrid model—ZHM) or greater (Silin's hybrid model—SHM) than the plasma thermal energy. The efficiency of energy transfer to ions and to ion perturbations under the development of the instability is considered for various values of electron-to-ion mass ratios. The energy of low-frequency oscillations (ion-sound waves) is found to be much lower than the final ion kinetic energy. We also discuss the influence of the changes in the damping rate of the high-frequency (HF) field on the instability development. The decrease of the absorption of the HF field inhibits the HF field burnout within plasma density cavities and gives rise to the broadening of the HF spectrum. At the same time, the ion velocity distribution tends to the normal distribution in both ZHM and SHM.

  6. Ion heating, burnout of the high-frequency field, and ion sound generation under the development of a modulation instability of an intense Langmuir wave in a plasma

    Science.gov (United States)

    Kirichok, A. V.; Kuklin, V. M.; Pryimak, A. V.; Zagorodny, A. G.

    2015-09-01

    The development of one-dimensional parametric instabilities of intense long plasma waves is considered in terms of the so-called hybrid models, with electrons being treated as a fluid and ions being regarded as particles. The analysis is performed for both cases when the average plasma field energy is lower (Zakharov's hybrid model—ZHM) or greater (Silin's hybrid model—SHM) than the plasma thermal energy. The efficiency of energy transfer to ions and to ion perturbations under the development of the instability is considered for various values of electron-to-ion mass ratios. The energy of low-frequency oscillations (ion-sound waves) is found to be much lower than the final ion kinetic energy. We also discuss the influence of the changes in the damping rate of the high-frequency (HF) field on the instability development. The decrease of the absorption of the HF field inhibits the HF field burnout within plasma density cavities and gives rise to the broadening of the HF spectrum. At the same time, the ion velocity distribution tends to the normal distribution in both ZHM and SHM.

  7. On the comparison of the polarisation behaviour of exchange-biased AF/F NiMn/Fe{sub 37}Co{sub 48}Hf{sub 15} bi-layer and multi-layer films with increased ferromagnetic cut-off frequencies

    Energy Technology Data Exchange (ETDEWEB)

    Seemann, K., E-mail: klaus.seemann@kit.edu [Karlsruhe Institute of Technology KIT (Campus North), Institute for Applied Materials, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany); Leiste, H.; Krueger, K. [Karlsruhe Institute of Technology KIT (Campus North), Institute for Applied Materials, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany)

    2012-03-15

    Antiferromagnetic/ferromagnetic (AF/F) NiMn/Fe{sub 37}Co{sub 48}Hf{sub 15} films were investigated with respect to their exchange bias, in-plane unidirectional anisotropy, polarisation and high frequency behaviour. After deposition, carried out by r.f. magnetron sputtering, the films were post-annealed for 4 h at 300 Degree-Sign C in a static magnetic field, in order to induce exchange-bias, which results in a unidirectional anisotropy. Dependent on the presence of a bi-layer or multi-layer sandwich structure the films show a different exchange-bias field-ferromagnetic inter-layer thickness behaviour with exchange-bias fields {mu}{sub 0} Low-Asterisk H{sub eb} between 2 and 10 mT. The in-plane uniaxial (single film) or unidirectional anisotropy fields {mu}{sub 0}*H{sub UF} were between 4 and 18 mT. This results in a significant increase of the cut-off frequency in the GHz range in comparison to a single Fe{sub 37}Co{sub 48}Hf{sub 15} film, which is shown by frequency-dependent permeability plots. High damping in the imaginary part of the permeability, i.e., high resonance line broadening could be observed for films with high coercivity {mu}{sub 0}*H{sub c} of around 7 mT in the easy axis of magnetisation. - Highlights: Black-Right-Pointing-Pointer Static and dynamic properties of NiMn/Fe{sub 37}Co{sub 48}Hf{sub 15} bi- and multi-layer films. Black-Right-Pointing-Pointer Theoretic analysis of the H{sub eb}- field difference of bi- and multi-layer films. Black-Right-Pointing-Pointer Two-stage magnetic process in the polarisation curves of the AF/F multi-layers. Black-Right-Pointing-Pointer Damping at the ferromagnetic permeability resonance state of AF/F multi-layers. Black-Right-Pointing-Pointer Derivation of the ferromagnetic resonance of AF/F multi-layer films.

  8. DEMETER observations of the ionospheric trough over HAARP in relation to HF heating experiments

    OpenAIRE

    Piddyachiy, D.; Bell, T.F.; Berthelier, Jean-Jacques; U. S. Inan; Parrot, Michel

    2011-01-01

    International audience; Plasma density variations observed aboard the DEMETER satellite in the topside ionospheric F layer are analyzed in relation to high-frequency transmitter operations. The main interest is the high-latitude region. One hundred cases with operating and nonoperating High Frequency Active Auroral Research Program HF transmitter during day and night are examined. It is found that most large-scale variations can be attributed to the presence of the main ionospheric trough and...

  9. ExtraHF survey

    DEFF Research Database (Denmark)

    Piepoli, Massimo F; Binno, Simone; Corrà, Ugo

    2015-01-01

    AIMS: In heart failure (HF), exercise training programmes (ETPs) are a well-recognized intervention to improve symptoms, but are still poorly implemented. The Heart Failure Association promoted a survey to investigate whether and how cardiac centres in Europe are using ETPs in their HF patients...... of evidence on safety or benefit was cited. When implemented, an ETP was proposed to all HF patients in only 55% of the centres, with restriction according to severity or aetiology. CONCLUSIONS: With respect to previous surveys, there is evidence of increased availability of ETPs in HF in Europe, although too...

  10. Gender Identification Using High-Frequency Speech Energy: Effects of Increasing the Low-Frequency Limit.

    Science.gov (United States)

    Donai, Jeremy J; Halbritter, Rachel M

    The purpose of this study was to investigate the ability of normal-hearing listeners to use high-frequency energy for gender identification from naturally produced speech signals. Two experiments were conducted using a repeated-measures design. Experiment 1 investigated the effects of increasing high-pass filter cutoff (i.e., increasing the low-frequency spectral limit) on gender identification from naturally produced vowel segments. Experiment 2 studied the effects of increasing high-pass filter cutoff on gender identification from naturally produced sentences. Confidence ratings for the gender identification task were also obtained for both experiments. Listeners in experiment 1 were capable of extracting talker gender information at levels significantly above chance from vowel segments high-pass filtered up to 8.5 kHz. Listeners in experiment 2 also performed above chance on the gender identification task from sentences high-pass filtered up to 12 kHz. Cumulatively, the results of both experiments provide evidence that normal-hearing listeners can utilize information from the very high-frequency region (above 4 to 5 kHz) of the speech signal for talker gender identification. These findings are at variance with current assumptions regarding the perceptual information regarding talker gender within this frequency region. The current results also corroborate and extend previous studies of the use of high-frequency speech energy for perceptual tasks. These findings have potential implications for the study of information contained within the high-frequency region of the speech spectrum and the role this region may play in navigating the auditory scene, particularly when the low-frequency portion of the spectrum is masked by environmental noise sources or for listeners with substantial hearing loss in the low-frequency region and better hearing sensitivity in the high-frequency region (i.e., reverse slope hearing loss).

  11. Wide Frequency Band Active Damping Strategy for DFIG System High Frequency Resonance

    DEFF Research Database (Denmark)

    Song, Yipeng; Blaabjerg, Frede

    2016-01-01

    As a popular renewable power generation solution, the Doubly Fed Induction Generator (DFIG) based wind power system may suffer from High Frequency Resonance (HFR) caused by the impedance interaction between the DFIG system and the parallel compensated weak network. A wide frequency band active...... damping strategy for DFIG system HFR, including a high-pass filter and a virtual resistance, is proposed in this paper. The advantages of this active damping strategy are, 1) no resonance frequency detection unit is required, thus the control complexity can be decreased; 2) no active damping parameters...... adjustment is needed within certain wide frequency band, thus the robustness of the proposed active damping strategy can be improved. The parameter design of the high-pass filter cutoff frequency and the virtual resistance are theoretically analyzed with the purpose of satisfactory active damping. A 7.5 k...

  12. Influence of Smoking on Ultra-High-Frequency Auditory Sensitivity.

    Science.gov (United States)

    Prabhu, Prashanth; Varma, Gowtham; Dutta, Kristi Kaveri; Kumar, Prajwal; Goyal, Swati

    2017-04-01

    In this study, an attempt was made to determine the effect of smoking on ultra-high-frequency auditory sensitivity. The study also attempted to determine the relationship between the nature of smoking and ultra-high-frequency otoacoustic emissions (OAEs) and thresholds. The study sample included 25 smokers and 25 non-smokers. A detailed history regarding their smoking habits was collected. High-frequency audiometric thresholds and amplitudes of high-frequency distortion-product OAEs were analyzed for both ears from all participants. The results showed that the ultra-high-frequency thresholds were elevated and that there was reduction in the amplitudes of ultra-high-frequency OAEs in smokers. There was an increased risk of auditory damage with chronic smoking. The study results highlight the application of ultra-high-frequency OAEs and ultra-high-frequency audiometry for the early detection of auditory impairment. However, similar studies should be conducted on a larger population for better generalization of the results.

  13. Special Information on High-Frequency Radar. Part 15

    Science.gov (United States)

    1971-06-01

    NRL Memorandum Report 2265 f Special Information on High-Frequency Radar Part XV J. M. HEADRICK, W. C. HEADRICK, J. M. HUDNALL AND J. F. THOMASON...20390 3. REPORT TITLE SPECIAL INFORMATION ON HIGH-FREQUENCY RADAR, PART XV (U) 4. DESCRIPTIVE NOTES(Type of report and inclhsive dates) This is a final

  14. Electrical and structural characterization of PLD grown CeO2–HfO2 laminated high-k gate dielectrics

    NARCIS (Netherlands)

    Karakaya, K.; Barcones, B.; Rittersma, Z.M.; Berkum, van J.G.M.; Verheijen, M.A.; Rijnders, G.; Blank, D.H.A.

    2006-01-01

    The electrical and physical properties of CeO2–HfO2 nanolaminates deposited by pulsed laser deposition (PLD) are investigated. The properties of the nanolaminates are compared with binary CeO2 and HfO2 thin films. Layers were deposited using CeO2 and HfO2 targets at substrate temperatures between 22

  15. Computing effective properties of nonlinear structures exposed to strong high-frequency loading at multiple frequencies

    DEFF Research Database (Denmark)

    Thomsen, Jon Juel

    2006-01-01

    Effects of strong high-frequency excitation at multiple frequencies (multi-HFE) are analyzed for a class of generally nonlinear systems. The effects are illustrated for a simple pendulum system with a vibrating support, and for a parametrically excited flexible beam. For the latter, theoretical...

  16. Effective properties of mechanical systems under high-frequency excitation at multiple frequencies

    DEFF Research Database (Denmark)

    Thomsen, Jon Juel

    2008-01-01

    Effects of strong high-frequency excitation at multiple frequencies (multi-HFE) are analyzed for a class of generally nonlinear systems. The effects are illustrated for a simple pendulum system with a vibrating support, and for a parametrically excited flexible beam. For the latter, theoretical p...

  17. Low and high frequency fatigue tests of nodular cast irons

    Directory of Open Access Journals (Sweden)

    A. Vaško

    2017-01-01

    Full Text Available The paper deals with the comparison of fatigue properties of nodular cast iron at low and high frequency cyclic loading. The specimens from three melts of nodular cast iron with different microstructure and mechanical properties were used for experiments. Fatigue tests were carried out at low and high frequency sinusoidal cyclic push-pull loading (stress ratio R = –1 at ambient temperature (T = 20 ± 5 °C. Low frequency fatigue tests were carried out using the fatigue experimental machine Zwick/Roell Amsler 150HFP 5100 at frequency f ≈ 120 Hz; high frequency fatigue tests were carried out using the ultrasonic fatigue testing device KAUP-ZU at frequency f ≈ 20 kHz.

  18. Integration of lead-free ferroelectric on HfO2/Si (100) for high performance non-volatile memory applications

    OpenAIRE

    Kundu, Souvik; Maurya, Deepam; Clavel, Michael; Zhou, Yuan; Nripendra N. Halder; Hudait, Mantu K.; Banerji, Pallab; Priya, Shashank

    2015-01-01

    We introduce a novel lead-free ferroelectric thin film (1-x)BaTiO3-xBa(Cu1/3Nb2/3)O3 (x = 0.025) (BT-BCN) integrated on to HfO2 buffered Si for non-volatile memory (NVM) applications. Piezoelectric force microscopy (PFM), x-ray diffraction, and high resolution transmission electron microscopy were employed to establish the ferroelectricity in BT-BCN thin films. PFM study reveals that the domains reversal occurs with 180° phase change by applying external voltage, demonstrating its effectivene...

  19. Effect of Training on Two-way Shape Memory Effect and Its Stability in a Ti-Ni-Hf High Temperature Shape Memory Alloy

    Institute of Scientific and Technical Information of China (English)

    Xianglong MENG; Wei CAI; K.T. LAU; L.M. ZHOU; Liancheng ZHAO

    2003-01-01

    The Effect of the thermal cycling training under constant strain on the two-way shape memory effect (TWSME) in a Ti36Ni49Hf15 high temperature shape memory alloy (SMA) has been investigated by bending tests. The results indicated that the training procedure is beneficial to get the better TWSME. The two-way shape memory strain increases with increasing the training strain. And it decreases with increasing the training temperature. The TWSME obtained in the present alloy shows poorer stability compared with that obtained in the TiNi alloys.

  20. Damage on HfO2/SiO2 high-reflecting coatings under single and multiple Nd:YAG laser pulse irradiation

    Institute of Scientific and Technical Information of China (English)

    Weidong Gao; Tao Wang; Yuanan Zhao; Jianda Shao

    2005-01-01

    The single- and multi-shot damage behaviors of HfO2/SiO2 high-reflecting (HR) coatings under Nd:YAG laser exposure were investigated. Fundamental aspects of multi-shot laser damage, such as the instability due to pulse-to-pulse accumulation of absorption defect and structural defect effect, and the mechanism of laser induced defect generation, are considered. It was found in multi-shot damage, the main factors influencing laser-induced damage threshold (LIDT) are accumulation of irreversible changes of structural defects and thermal stress that induced by thermal density fluctuations.

  1. Effects of high-frequency chest wall oscillation on pleural pressure and oscillated flow.

    Science.gov (United States)

    Zucker, Tal; Skjodt, Neil M; Jones, Richard L

    2008-01-01

    The effectiveness of high-frequency chest wall oscillation (HF-CWO) is directly related to the level of oscillated flow (osc) in the airways. We used the Vest system to investigate the effects of HFCWO on chest wall and pleural pressures and we correlated these pressures to the resultant osc. We also compared the latest HFCWO device with it predecessor. Different combinations of vest inflation pressure (background pressure) and oscillation frequency were randomly applied to 10 healthy volunteers. Chest wall pressure was determined using an air-filled bag under the vest and pleural pressure was estimated using an esophageal balloon. Reverse plethysmography was used to measure osc at the mouth and a spirometer was used to measure changes in end-expired lung volume. We found a significant correlation between chest wall and pleural pressure with approximately one-third of the chest wall pressure transmitted into the pleural space. Mean esophageal pressure remained negative at all background pressure/frequency combinations. There was a significant correlation (pHFCWO and since osc is dependent on esophageal pulse pressure, which in turn is dependent on chest wall pulse pressure, it follows that the effectiveness of HFCWO is influenced by the ability to generate an effective chest wall pulse pressure.

  2. A Resonantly-Excited Disk-Oscillation Model of High-Frequency QPOs of Microquasars

    CERN Document Server

    Kato, Shoji

    2012-01-01

    A possible model of twin high-frequency QPOs (HF QPOs) of microquasars is examined. The disk is assumed to have global magnetic fields and to be deformed with a two-armed pattern. In this deformed disk, set of a two-armed ($m=2$) vertical p-mode oscillation and an axisymmetric ($m=0$) g-mode oscillation are considered. They resonantly interact through the disk deformation when their frequencies are the same. This resonant interaction amplifies the set of the above oscillations in the case where these two oscillations have wave energies of opposite signs. These oscillations are assumed to be excited most efficiently in the case where the radial group velocities of these two waves vanish at the same place. The above set of oscillations is not unique, depending on the node number, $n$, of oscillations in the vertical direction. We consider that the basic two sets of oscillations correspond to the twin QPOs. The frequencies of these oscillations depend on disk parameters such as strength of magnetic fields. For o...

  3. Meeting Mr Davis vs Mr Davin: effects of name frequency on learning proper names in young and older adults.

    Science.gov (United States)

    James, Lori E; Fogler, Kethera A

    2007-05-01

    Two theoretical frameworks relevant to proper name learning in ageing make competing predictions about the effects of name frequency. Under an inhibition model, common (high-frequency; HF) proper names will be harder to learn and remember than rare (low-frequency; LF) names, whereas under a transmission deficit model, HF names will have the advantage. Young adults (ages 18-31) and two groups of healthy older adults (ages 60-74 and 75-89) learned HF (e.g., Davis) and LF (e.g., Davin) surnames in association with new faces. Young adults recalled more names than older or oldest adults, and participants of all ages recalled more HF than LF names. There was no interaction between age and name frequency: The difference favouring HF names was similar in magnitude across age groups. All evidence runs contrary to the inhibitory model's prediction that interference makes learning HF names difficult.

  4. Simulation of a birdcage and a ceramic cavity HF-resonator for high magnetic fields in magnetic resonance imaging.

    Science.gov (United States)

    Eriksen, E; Golombeck, M A; Junge, S; Dössel, O

    2002-01-01

    The aim of this work was the 3D-simulation of a dielectric resonator for high-field-MRI. A 12-rod-bird-cage-resonator was simulated in a first step, in order to verify the capability of the commercial simulation software MAFIA to simulate homogeneous, transversal B-fields in resonators. The second step was the simulation of frequency-independent dielectric ceramic resonators for static magnetic field strengths of 7 T and 12 T (294 MHz and 504 MHz respectively). The results were compared to the measured results of a manufactured TiO2- and a Al2O3-resonator. Only minor deviations showed up. These results led to the conclusion that dielectric resonators for high field MRI can be optimised using numerical field calculation software.

  5. Condenser Microphone Protective Grid Correction for High Frequency Measurements

    Science.gov (United States)

    Lee, Erik; Bennett, Reginald

    2010-01-01

    Use of a protective grid on small diameter microphones can prolong the lifetime of the unit, but the high frequency effects can complicate data interpretation. Analytical methods have been developed to correct for the grid effect at high frequencies. Specifically, the analysis pertains to quantifying the microphone protective grid response characteristics in the acoustic near field of a rocket plume noise source. A frequency response function computation using two microphones will be explained. Experimental and instrumentation setup details will be provided. The resulting frequency response function for a B&K 4944 condenser microphone protective grid will be presented, along with associated uncertainties

  6. A MEMS-based high frequency x-ray chopper.

    Science.gov (United States)

    Siria, A; Dhez, O; Schwartz, W; Torricelli, G; Comin, F; Chevrier, J

    2009-04-29

    Time-resolved x-ray experiments require intensity modulation at high frequencies (advanced rotating choppers have nowadays reached the kHz range). We here demonstrate that a silicon microlever oscillating at 13 kHz with nanometric amplitude can be used as a high frequency x-ray chopper. We claim that using micro-and nanoelectromechanical systems (MEMS and NEMS), it will be possible to achieve higher frequencies in excess of hundreds of megahertz. Working at such a frequency can open a wealth of possibilities in chemistry, biology and physics time-resolved experiments.

  7. A MEMS-based high frequency x-ray chopper

    Energy Technology Data Exchange (ETDEWEB)

    Siria, A; Schwartz, W; Chevrier, J [Institut Neel, CNRS-Universite Joseph Fourier Grenoble, BP 166, F-38042 Grenoble Cedex 9 (France); Dhez, O; Comin, F [ESRF, 6 rue Jules Horowitz, F-38043 Grenoble Cedex 9 (France); Torricelli, G [Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH (United Kingdom)

    2009-04-29

    Time-resolved x-ray experiments require intensity modulation at high frequencies (advanced rotating choppers have nowadays reached the kHz range). We here demonstrate that a silicon microlever oscillating at 13 kHz with nanometric amplitude can be used as a high frequency x-ray chopper. We claim that using micro-and nanoelectromechanical systems (MEMS and NEMS), it will be possible to achieve higher frequencies in excess of hundreds of megahertz. Working at such a frequency can open a wealth of possibilities in chemistry, biology and physics time-resolved experiments.

  8. Microstructural Response During Isothermal and Isobaric Loading of a Precipitation-Strengthened Ni-29.7Ti-20Hf High-Temperature Shape Memory Alloy

    Science.gov (United States)

    Benafan, O.; Noebe, R. D.; Padula, S. A.; Vaidyanathan, R.

    2012-12-01

    A stable Ni-rich Ni-29.7Ti-20Hf (at. pct) shape memory alloy, with relatively high transformation temperatures, was shown to exhibit promising properties at lower raw material cost when compared to typical NiTi-X (X = Pt, Pd, Au) high-temperature shape memory alloys (HTSMAs). The excellent dimensional stability and high work output for this alloy were attributed to a coherent, nanometer size precipitate phase observed using transmission electron microscopy. To establish an understanding of the role of these precipitates on the microstructure and ensuing stability of the NiTiHf alloy, a detailed study of the micromechanical and microstructural behaviors was performed. In-situ neutron diffraction at stress and temperature was used to obtain quantitative information on phase-specific internal strain, texture, and phase volume fractions during both isothermal and isobaric testing of the alloy. During isothermal testing, the alloy exhibited low isothermal strains due to limited detwinning, consistent with direct measurements of the bulk texture through neutron diffraction. This limited detwinning was attributed to the pinning of twin and variant boundaries by the dispersion of fine precipitates. During isobaric thermal cycling at 400 MPa, the high work output and near-perfect dimensional stability was attributed to the presence of the precipitates that act as homogeneous sources for the nucleation of martensite throughout the material, while providing resistance to irrecoverable processes such as plastic deformation.

  9. European coordination for coastal HF radar data in EMODnet Physics

    Science.gov (United States)

    Mader, Julien; Novellino, Antonio; Gorringe, Patrick; Griffa, Annalisa; Schulz-Stellenfleth, Johannes; Montero, Pedro; Montovani, Carlo; Ayensa, Garbi; Vila, Begoña; Rubio, Anna; Sagarminaga, Yolanda

    2015-04-01

    Historically, joint effort has been put on observing open ocean, organizing, homogenizing, sharing and reinforcing the impact of the acquired information based on one technology: ARGO with profilers Argo floats, EuroSites, ESONET-NoE, FixO3 for deep water platforms, Ferrybox for stations in ships of opportunities, and GROOM for the more recent gliders. This kind of networking creates synergies and makes easier the implementation of this source of data in the European Data exchange services like EMODnet, ROOSs portals, or any applied services in the Blue economy. One main targeted improvement in the second phase of EMODnet projects is the assembling of data along coastline. In that sense, further coordination is recommended between platform operators around a specific technology in order to make easier the implementation of the data in the platforms (4th EuroGOOS DATAMEQ WG). HF radar is today recognized internationally as a cost-effective solution to provide high spatial and temporal resolution current maps (depending on the instrument operation frequency, covering from a few kilometres offshore up to 200 km) that are needed for many applications for issues related to ocean surface drift or sea state characterization. Significant heterogeneity still exists in Europe concerning technological configurations, data processing, quality standards and data availability. This makes more difficult the development of a significant network for achieving the needed accessibility to HF Radar data for a pan European use. EuroGOOS took the initiative to lead and coordinate activities within the various observation platforms by establishing a number of Ocean Observing Task Teams such as HF-Radars. The purpose is to coordinate and join the technological, scientific and operational HF radar communities at European level. The goal of the group is on the harmonization of systems requirements, systems design, data quality, improvement and proof of the readiness and standardization of

  10. Different frequencies should be prescribed for different high frequency chest compression machines.

    Science.gov (United States)

    Milla, Carlos E; Hansen, Leland G; Warwick, Warren J

    2006-01-01

    High frequency chest compression (HFCC) is used for treatment and prevention of the lung diseases characterized by impaired mucus clearance and/or cough, where patients are at risk for acquiring acute bronchitis or pneumonia. The HFCC treatment frequencies may be prescribed according to the manufacturers' generic guidelines or may be determined for each individual patient by a "tuning" method that measures, at the mouth, the air volume displacement and the associated airflows produced at each frequency. Tuning is performed while the patient is breathing normally during the HFCC system operation. After measurements for several breaths at one frequency have been collected, the program randomly selects and measures another frequency until the entire frequency range of the machine being tuned has been sampled. Frequencies range from 6 to 21 Hz for the sine waveform machines and from 6 to 25 Hz for the square waveform machines. Each group of flow signals is digitized and analyzed by the program. For each frequency, the HFCC flow velocities and volumes are computed and averaged. These average flows and volumes are rank ordered; the three frequencies with the highest flows and the three frequencies producing the largest volumes are selected for prescription. If the same frequency is selected as one of the three best frequencies for both flow and volume, the next ranked frequency is selected randomly for flow or volume. Significant differences exist between patients and HFCC machines. In a series of 100 cystic fibrosis (CF) patients with varying degrees of lung disease, we found that the best-ranked frequencies varied from patient to patient and did not correlate with patients' age, gender, height, weight, or spirometry parameters. With the sine waveform, the highest HFCC airflows were between 13 and 20 Hz 82% of the time and the largest HFCC volumes were between 6 and 10 Hz 83% of the time. With the square waveform, both the highest average HFCC flow rates and the largest

  11. Quantum inductance and high frequency oscillators in graphene nanoribbons.

    Science.gov (United States)

    Begliarbekov, Milan; Strauf, Stefan; Search, Christopher P

    2011-04-22

    Here we investigate high frequency AC transport through narrow graphene nanoribbons with top-gate potentials that form a localized quantum dot. We show that as a consequence of the finite dwell time of an electron inside the quantum dot (QD), the QD behaves like a classical inductor at sufficiently high frequencies ω ≥ GHz. When the geometric capacitance of the top-gate and the quantum capacitance of the nanoribbon are accounted for, the admittance of the device behaves like a classical serial RLC circuit with resonant frequencies ω ∼ 100-900 GHz and Q-factors greater than 10(6). These results indicate that graphene nanoribbons can serve as all-electronic ultra-high frequency oscillators and filters, thereby extending the reach of high frequency electronics into new domains.

  12. Transient dynamics of secondary radiation from an HF pumped magnetized space plasma

    NARCIS (Netherlands)

    Norin, L.; Grach, S. M.; Thide, B.; Sergeev, E. N.; Leyser, T. B.

    2007-01-01

    In order to systematically analyze the transient wave and radiation processes that are excited when a high-frequency (HF) radio wave is injected into a magnetized space plasma, we have measured the secondary radiation, or stimulated electromagnetic emission ( SEE), from the ionosphere, preconditione

  13. Center for High-Frequency Microelectronics

    Science.gov (United States)

    1992-08-31

    H. S. Fogler , H. Etemad and M. Elta, "Enhanced Etching of Group Ill-V Semiconductors by Oscillating with Sputter Etching and Reactive Ion Etching...to SI/SiGe Modulation Doped FET," submitted for publication to IEEE Electron Dev. Lett. 17. A. Demos, H. S. Fogler , and M. Elta, "X-Ray Photoelectron... Fogler , J. Fournier and M. Elta, "High Temperature Kinetic Study of InP RIE Etched with BC1 3, Argon and Oxygen," submitted for publication to Journal of

  14. Polarization Properties of AGN at High Frequencies

    Science.gov (United States)

    Jorstad, S. G.

    2009-08-01

    I discuss variability of polarization in the core region of parsec scale radio jets and connections between 7 mm polarization in the VLBI core and polarization at shorter wavelengths from the whole source for a sample of AGN with highly relativistic jets known as blazars. The sources show pronounced diversity in polarization behavior that is not clearly understood. I discuss possible reasons for these differences as well as the role that VSOP-2 can play in exploring the magnetic field in the most compact regions of jets.

  15. Solar coronal observations at high frequencies

    OpenAIRE

    Katsiyannis, A. C.; Mathioudakis, M.; Phillips, K. J. H.; Williams, D. R.; F. P. Keenan

    2001-01-01

    The Solar Eclipse Coronal Imaging System (SECIS) is a simple and extremely fast, high-resolution imaging instrument designed for studies of the solar corona. Light from the corona (during, for example, a total solar eclipse) is reflected off a heliostat and passes via a Schmidt-Cassegrain telescope and beam splitter to two CCD cameras capable of imaging at 60 frames a second. The cameras are attached via SCSI connections to a purpose-built PC that acts as the data acquisition and storage syst...

  16. Wide Frequency Band Active Damping Strategy for DFIG System High Frequency Resonance

    DEFF Research Database (Denmark)

    Song, Yipeng; Blaabjerg, Frede

    2016-01-01

    As a popular renewable power generation solution, the Doubly Fed Induction Generator (DFIG) based wind power system may suffer from High Frequency Resonance (HFR) caused by the impedance interaction between the DFIG system and the parallel compensated weak network. A wide frequency band active...... damping strategy for DFIG system HFR, including a high-pass filter and a virtual resistance, is proposed in this paper. The advantages of this active damping strategy are, 1) no resonance frequency detection unit is required, thus the control complexity can be decreased; 2) no active damping parameters...

  17. Transient high-frequency ultrasonic water atomization

    Science.gov (United States)

    Barreras, F.; Amaveda, H.; Lozano, A.

    2002-06-01

    An experimental study was performed to improve the understanding of the characteristics of ultrasonic water atomization when excited with waves in the MHz range. In the present experiments, small volumes of water were atomized, observing the temporal evolution of the process. Typical diameters of the resulting droplets are of the order of a few microns. To visualize them, images were acquired with very high magnification. Appropriate lenses were used to enable high resolution at a distance from the flow. Droplet size distributions were also calculated with a Malvern diffractometer. Droplet exit velocity was measured using particle image velocimetry. It was noticeable that, as the remaining liquid mass deposited over the ultrasonic transducer decreased, the atomization characteristics changed, and a second peak of larger droplets appeared in the size distribution function. This phenomenon is related to the change in the curvature of the liquid surface. Although results are not conclusive, it appears that, under the conditions in this study, some observations about droplet formation are better described by cavitation phenomena rather than by the simplified surface wave theory usually invoked to explain these processes.

  18. High-frequency capillary waves excited by oscillating microbubbles

    CERN Document Server

    Pommella, Angelo; Poulichet, Vincent; Garbin, Valeria

    2013-01-01

    This fluid dynamics video shows high-frequency capillary waves excited by the volumetric oscillations of microbubbles near a free surface. The frequency of the capillary waves is controlled by the oscillation frequency of the microbubbles, which are driven by an ultrasound field. Radial capillary waves produced by single bubbles and interference patterns generated by the superposition of capillary waves from multiple bubbles are shown.

  19. High-frequency energy in singing and speech

    Science.gov (United States)

    Monson, Brian Bruce

    While human speech and the human voice generate acoustical energy up to (and beyond) 20 kHz, the energy above approximately 5 kHz has been largely neglected. Evidence is accruing that this high-frequency energy contains perceptual information relevant to speech and voice, including percepts of quality, localization, and intelligibility. The present research was an initial step in the long-range goal of characterizing high-frequency energy in singing voice and speech, with particular regard for its perceptual role and its potential for modification during voice and speech production. In this study, a database of high-fidelity recordings of talkers was created and used for a broad acoustical analysis and general characterization of high-frequency energy, as well as specific characterization of phoneme category, voice and speech intensity level, and mode of production (speech versus singing) by high-frequency energy content. Directionality of radiation of high-frequency energy from the mouth was also examined. The recordings were used for perceptual experiments wherein listeners were asked to discriminate between speech and voice samples that differed only in high-frequency energy content. Listeners were also subjected to gender discrimination tasks, mode-of-production discrimination tasks, and transcription tasks with samples of speech and singing that contained only high-frequency content. The combination of these experiments has revealed that (1) human listeners are able to detect very subtle level changes in high-frequency energy, and (2) human listeners are able to extract significant perceptual information from high-frequency energy.

  20. HF Radar observations of the Dardanelles outflow current in North Eastern Aegean using validated WERA HF radar data

    Directory of Open Access Journals (Sweden)

    Z. KOKKINI

    2015-01-01

    Full Text Available A two-site WERA HF radar station was installed in November 2009 at the eastern coast of Lemnos Island in North Aegean Sea, aiming to monitor the surface inflow of Black Sea waters exiting from the Dardanelles Strait, as well as to constitute a coastal management tool for incidents of oil-pollution or save-and-rescue operations. Strong interference by foreign transmissions is a source of noise deteriorating the quality of the backscattered signal, thus significantly reducing the HF radar’s effective data return rate. In order to ameliorate this problem, further quality-control and data gap interpolating procedures have been developed and applied, to be used in addition to the procedures incorporated and used by the manufacturer’s signal processing software. The second-level processing involves traditional despiking in the temporal domain, preceding Empirical Orthogonal Function analysis. The latter is used not only to filter high-frequency noise but also to fill data gaps in time and space. The data reconstruction procedure has been assessed via comparison of (a HF radial with CODE-type drifter radial velocities as well as (b HF-derived virtual drifter tracks with actual drifter tracks. The main circulation features and their variability, as revealed by the reconstructed fields, are presented.

  1. HF Radar observations of the Dardanelles outflow current in North Eastern Aegean using validated WERA HF radar data

    Directory of Open Access Journals (Sweden)

    Z. KOKKINI

    2014-12-01

    Full Text Available A two-site WERA HF radar station was installed in November 2009 at the eastern coast of Lemnos Island in North Aegean Sea, aiming to monitor the surface inflow of Black Sea waters exiting from the Dardanelles Strait, as well as to constitute a coastal management tool for incidents of oil-pollution or save-and-rescue operations. Strong interference by foreign transmissions is a source of noise deteriorating the quality of the backscattered signal, thus significantly reducing the HF radar’s effective data return rate. In order to ameliorate this problem, further quality-control and data gap interpolating procedures have been developed and applied, to be used in addition to the procedures incorporated and used by the manufacturer’s signal processing software. The second-level processing involves traditional despiking in the temporal domain, preceding Empirical Orthogonal Function analysis. The latter is used not only to filter high-frequency noise but also to fill data gaps in time and space. The data reconstruction procedure has been assessed via comparison of (a HF radial with CODE-type drifter radial velocities as well as (b HF-derived virtual drifter tracks with actual drifter tracks. The main circulation features and their variability, as revealed by the reconstructed fields, are presented.

  2. High-frequency multimodal atomic force microscopy

    Directory of Open Access Journals (Sweden)

    Adrian P. Nievergelt

    2014-12-01

    Full Text Available Multifrequency atomic force microscopy imaging has been recently demonstrated as a powerful technique for quickly obtaining information about the mechanical properties of a sample. Combining this development with recent gains in imaging speed through small cantilevers holds the promise of a convenient, high-speed method for obtaining nanoscale topography as well as mechanical properties. Nevertheless, instrument bandwidth limitations on cantilever excitation and readout have restricted the ability of multifrequency techniques to fully benefit from small cantilevers. We present an approach for cantilever excitation and deflection readout with a bandwidth of 20 MHz, enabling multifrequency techniques extended beyond 2 MHz for obtaining materials contrast in liquid and air, as well as soft imaging of delicate biological samples.

  3. Low-amplitude, high-frequency electromagnetic field exposure causes delayed and reduced growth in Rosa hybrida.

    Science.gov (United States)

    Grémiaux, Alexandre; Girard, Sébastien; Guérin, Vincent; Lothier, Jérémy; Baluška, František; Davies, Eric; Bonnet, Pierre; Vian, Alain

    2016-01-15

    It is now accepted that plants perceive high-frequency electromagnetic field (HF-EMF). We wondered if the HF-EMF signal is integrated further in planta as a chain of reactions leading to a modification of plant growth. We exposed whole small ligneous plants (rose bush) whose growth could be studied for several weeks. We performed exposures at two different development stages (rooted cuttings bearing an axillary bud and 5-leaf stage plants), using two high frequency (900MHz) field amplitudes (5 and 200Vm(-1)). We achieved a tight control on the experimental conditions using a state-of-the-art stimulation device (Mode Stirred Reverberation Chamber) and specialized culture-chambers. After the exposure, we followed the shoot growth for over a one-month period. We observed no growth modification whatsoever exposure was performed on the 5-leaf stage plants. When the exposure was performed on the rooted cuttings, no growth modification was observed on Axis I (produced from the elongation of the axillary bud). Likewise, no significant modification was noted on Axis II produced at the base of Axis I, that came from pre-formed secondary axillary buds. In contrast, Axis II produced at the top of Axis I, that came from post-formed secondary buds consistently displayed a delayed and significant reduced growth (45%). The measurements of plant energy uptake from HF-EMF in this exposure condition (SAR of 7.2 10(-4)Wkg(-1)) indicated that this biological response is likely not due to thermal effect. These results suggest that exposure to electromagnetic field only affected development of post-formed organs.

  4. Extraction of ULSI Interconnect Resistance at High Frequencies

    Institute of Scientific and Technical Information of China (English)

    XIAO Xia; JIAN Duanduan; YAO Suying; ZHANG Shengcai; RUAN Gang

    2005-01-01

    Correct extraction of the ultra-large-scale integrated (ULSI) interconnect components at hight frequencies is very important for evaluating electrical performances of high-speed ULSI circuits.In this paper, the extraction of the interconnect resistance at high frequencies is derived from the Ohm′s law and verified by the software FastHenry.The results are also compared with those of another resistance formula originated from the effective area of the current flowing. The applicability of these two formulae is discussed.The influence of the interconnect geometry on the resistance at high frequencies is studied.The computation indicates that the effect of frequency on the resistance is weak when the skin depth is larger than half of the short side of the rectangular interconnect cross section.With further increase of frequency, the resistance increases obviously. Results imply that conductor with a square cross section exhibits the largest resistance for rectangular conductors of constant cross section area.

  5. The Influence of High-Frequency Envelope Information on Low-Frequency Vowel Identification in Noise.

    Directory of Open Access Journals (Sweden)

    Wiebke Schubotz

    Full Text Available Vowel identification in noise using consonant-vowel-consonant (CVC logatomes was used to investigate a possible interplay of speech information from different frequency regions. It was hypothesized that the periodicity conveyed by the temporal envelope of a high frequency stimulus can enhance the use of the information carried by auditory channels in the low-frequency region that share the same periodicity. It was further hypothesized that this acts as a strobe-like mechanism and would increase the signal-to-noise ratio for the voiced parts of the CVCs. In a first experiment, different high-frequency cues were provided to test this hypothesis, whereas a second experiment examined more closely the role of amplitude modulations and intact phase information within the high-frequency region (4-8 kHz. CVCs were either natural or vocoded speech (both limited to a low-pass cutoff-frequency of 2.5 kHz and were presented in stationary 3-kHz low-pass filtered masking noise. The experimental results did not support the hypothesized use of periodicity information for aiding low-frequency perception.

  6. [High-frequency ventilation. I. Distribution of alveolar pressure amplitudes during high frequency oscillation in the lung model].

    Science.gov (United States)

    Theissen, J; Lunkenheimer, P P; Niederer, P; Bush, E; Frieling, G; Lawin, P

    1987-09-01

    The pattern of intrapulmonary pressure distribution was studied during high-frequency ventilation in order to explain the inconsistent results reported in the literature. Methods. Pressure and flow velocity (hot-wire anemometry) were measured in different lung compartments: 1. In transalveolar chambers sealed to the perforated pleural surfaces of dried pig lungs; 2. In emphysema-simulating airbags sealed to the isolated bronchial trees of dried pig lungs; and 3. In transalveolar chambers sealed to the perforated pleural surfaces of freshly excised pig lungs. Results. 1. The pressure amplitudes change from one area to another and depending on the exciting frequency. 2. High-frequency oscillation is associated with an increase in pressure amplitude when the exciting frequency rises, whereas with conventional high-frequency jet ventilation the pressure amplitude is more likely to decrease with frequency. 3. During high-frequency jet ventilation the local pressure amplitude changes with the position of the tube in the trachea rather than with the exciting frequency. 4. When the volume of the measuring chamber is doubled the resulting pressure amplitude falls to half the control value. 5. The pressure amplitude and mean pressure measured in the transalveolar chamber vary more or less independently from the peak flow velocity. High-frequency ventilation is thus seen to be a frequency-dependant, inhomogeneous mode of ventilation that can essentially be homogenized by systematically changing the exciting frequency. The frequency-dependant response to different lung areas to excitation is likely to result from an intrabronchially-localized aerodynamic effect rather than the mechanical properties of the lung parenchyma.

  7. Vibrational spectroscopy [FTIR and FTRaman] investigation, computed vibrational frequency analysis and IR intensity and Raman activity peak resemblance analysis on 4-chloro 2-methylaniline using HF and DFT [LSDA, B3LYP and B3PW91] calculations.

    Science.gov (United States)

    Ramalingam, S; Periandy, S

    2011-03-01

    In the present study, the FT-IR and FT-Raman spectra of 4-chloro-2-methylaniline (4CH2MA) have been recorded in the range of 4000-100 cm(-1). The fundamental modes of vibrational frequencies of 4CH2MA are assigned. All the geometrical parameters have been calculated by HF and DFT (LSDA, B3LYP and B3PW91) methods with 6-31G (d, p) and 6-311G (d, p) basis sets. Optimized geometries of the molecule have been interpreted and compared with the reported experimental values for aniline and some substituted aniline. The harmonic and anharmonic vibrational wavenumbers, IR intensities and Raman activities are calculated at the same theory levels used in geometry optimization. The calculated frequencies are scaled and compared with experimental values. The scaled vibrational frequencies at LSDA/B3LYP/6-311G (d, p) seem to coincide with the experimentally observed values with acceptable deviations. The impact of substitutions on the benzene structure is investigated. The molecular interactions between the substitutions (Cl, CH(3) and NH(2)) are also analyzed.

  8. High-frequency hearing in seals and sea lions.

    Science.gov (United States)

    Cunningham, Kane A; Reichmuth, Colleen

    2016-01-01

    Existing evidence suggests that some pinnipeds (seals, sea lions, and walruses) can detect underwater sound at frequencies well above the traditional high-frequency hearing limits for their species. This phenomenon, however, is not well studied: Sensitivity patterns at frequencies beyond traditional high-frequency limits are poorly resolved, and the nature of the auditory mechanism mediating hearing at these frequencies is unknown. In the first portion of this study, auditory sensitivity patterns in the 50-180 kHz range were measured for one California sea lion (Zalophus californianus), one harbor seal (Phoca vitulina), and one spotted seal (Phoca largha). Results show the presence of two distinct slope-regions at the high-frequency ends of the audiograms of all three subjects. The first region is characterized by a rapid decrease in sensitivity with increasing frequency-i.e. a steep slope-followed by a region of much less rapid sensitivity decrease-i.e. a shallower slope. In the second portion of this study, a masking experiment was conducted to investigate how the basilar membrane of a harbor seal subject responded to acoustic energy from a narrowband masking noise centered at 140 kHz. The measured masking pattern suggests that the initial, rapid decrease in sensitivity on the high-frequency end of the subject's audiogram is not due to cochlear constraints, as has been previously hypothesized, but rather to constraints on the conductive mechanism. Copyright © 2015 Elsevier B.V. All rights reserved.

  9. Factors Affecting the Benefits of High-Frequency Amplification

    Science.gov (United States)

    Horwitz, Amy R.; Ahlstrom, Jayne B.; Dubno, Judy R.

    2008-01-01

    Purpose: This study was designed to determine the extent to which high-frequency amplification helped or hindered speech recognition as a function of hearing loss, gain-frequency response, and background noise. Method: Speech recognition was measured monaurally under headphones for nonsense syllables low-pass filtered in one-third-octave steps…

  10. Free-field calibration of measurement microphones at high frequencies

    DEFF Research Database (Denmark)

    Barrera Figueroa, Salvador; Rasmussen, Knud; Torras Rosell, Antoni;

    2011-01-01

    Measurement microphones are typically calibrated in a free field at frequencies up to 50 kHz. This is a sufficiently high frequency for the most of sound measurement applications related with noise assessment. However, other applications such as assessment of the noise emitted by ultrasound clean...

  11. Synthesis of data from high-frequency nutrient and associated biogeochemical monitoring for the Sacramento–San Joaquin Delta, northern California

    Science.gov (United States)

    Downing, Bryan D.; Bergamaschi, Brian A.; Kraus, Tamara E.C.

    2017-07-11

    Executive SummaryThis report is the second in a series of three reports that provide information about high-frequency (HF) nutrient and biogeochemical monitoring in the Sacramento–San Joaquin Delta of northern California (Delta). The purpose of this report is to synthesize the data available from a nutrient and water-quality HF (about every 15 minutes) monitoring network operated by the U.S. Geological Survey in the northern Delta. In this report, we describe the network and focus on the purpose of each station. We then present and discuss the available data, at various timescales—first at the monthly, seasonal, and inter-annual timescales, and second, for comparison, at the tidal and event timescales. As expected, we determined that there is substantial variability in nitrate-N concentrations at short timescales within hours, but also significant variability at longer timescales such as months or years. Resolving this variability is made possible by the HF data, with the largest variability caused by storms, tides, and diel biological processes. Given this large temporal variability, calculations of cumulative nutrient fluxes (for example, daily, monthly, or annual loads) is difficult without HF data. For example, in the Cache Slough, calculation of the annual load without the tidal variability resulted in a 30 percent underestimation of the true annual load value. We conclude that HF measurements are important for accurate determination of fluxes and loads in tidal environments, but, more importantly, provide important insights into processes and rates of nutrient cycling.This report, along with the other two reports of this series (Bergamaschi and others, 2017; Kraus, Bergamaschi, and others, 2017), was drafted in cooperation with the Delta Regional Monitoring Program to help scientists, managers, and planners understand how HF data improve our understanding of nutrient sources and sinks, drivers, and effects in the Delta. The first report in the series

  12. Integration of lead-free ferroelectric on HfO2/Si (100) for high performance non-volatile memory applications

    Science.gov (United States)

    Kundu, Souvik; Maurya, Deepam; Clavel, Michael; Zhou, Yuan; Halder, Nripendra N.; Hudait, Mantu K.; Banerji, Pallab; Priya, Shashank

    2015-02-01

    We introduce a novel lead-free ferroelectric thin film (1-x)BaTiO3-xBa(Cu1/3Nb2/3)O3 (x = 0.025) (BT-BCN) integrated on to HfO2 buffered Si for non-volatile memory (NVM) applications. Piezoelectric force microscopy (PFM), x-ray diffraction, and high resolution transmission electron microscopy were employed to establish the ferroelectricity in BT-BCN thin films. PFM study reveals that the domains reversal occurs with 180° phase change by applying external voltage, demonstrating its effectiveness for NVM device applications. X-ray photoelectron microscopy was used to investigate the band alignments between atomic layer deposited HfO2 and pulsed laser deposited BT-BCN films. Programming and erasing operations were explained on the basis of band-alignments. The structure offers large memory window, low leakage current, and high and low capacitance values that were easily distinguishable even after ~106 s, indicating strong charge storage potential. This study explains a new approach towards the realization of ferroelectric based memory devices integrated on Si platform and also opens up a new possibility to embed the system within current complementary metal-oxide-semiconductor processing technology.

  13. High Performance Small Optically Pumped Caesium Beam Frequency Standard

    Institute of Scientific and Technical Information of China (English)

    ZHANG Jian-Wei; YANG Dong-Hai

    2007-01-01

    An experiment of a high performance small optically pumped caesium (Cs) beam frequency standard is reported. An extended cavity diode laser works as the probing laser, of which the frequency is stabilized by the Zeeman modulation method. The running parameters of the frequency standard are dynamically optimized via digital servo electronics. The experimental setup improves the frequency stability up to 1.8 × 10-12 atτ= 1 s and about 1.0 × 10~13 at τ= 105 s (Allan deviation).

  14. Ab initio Computations of the Electronic, Mechanical, and Thermal Properties of Ultra High Temperature Ceramics (UHTC) ZrB2 and HfB2

    Science.gov (United States)

    Lawson, John W.; Bauschlicher, Charles W.; Daw, Murray

    2011-01-01

    Refractory materials such as metallic borides, often considered as ultra high temperature ceramics (UHTC), are characterized by high melting point, high hardness, and good chemical inertness. These materials have many applications which require high temperature materials that can operate with no or limited oxidation. Ab initio, first principles methods are the most accurate modeling approaches available and represent a parameter free description of the material based on the quantum mechanical equations. Using these methods, many of the intrinsic properties of these material can be obtained. We performed ab initio calculations based on density functional theory for the UHTC materials ZrB2 and HfB2. Computational results are presented for structural information (lattice constants, bond lengths, etc), electronic structure (bonding motifs, densities of states, band structure, etc), thermal quantities (phonon spectra, phonon densities of states, specific heat), as well as information about point defects such as vacancy and antisite formation energies.

  15. Detection of HCl and HF by TTFMS and WMS.

    Science.gov (United States)

    De Luca, Anna Chiara; Pesce, Giuseppe; Rusciano, Giulia; Sasso, Antonio

    2006-04-01

    In this work we discuss on a compact spectrometer based on DFB diode lasers for detection of chloridric and fluoridric acids. HCl and HF concentrations are determined through optical absorption of the P(4) line (lambda=1.7 microm) and the R(3) line (lambda=1.3 microm), respectively. Both lines belong to first overtone vibrational bands and their line strengths are 7.8 x 10(-21)cm/molecule for HCl and 2.8 x 10(-20)cm/molecule for HF. We chose these lines for their relative high intensities and because they are quite far from water vapour lines which represent the main interfering gas for trace-gases analysis. To detect these species we used two different high frequency modulation techniques: two-tone frequency modulation spectroscopy (f(1)=800 MHz and f(2)=804 MHz) was used for HCl while for HF we followed a simpler approach based on wavelength modulation spectroscopy (f=600 kHz). We demonstrate that the two techniques provide comparable detection limit of about 80 ppbV at atmospheric pressure. Positive testing of our spectrometer makes it suitable for in situ measurements of exhaust gases coming from waste incinerators.

  16. Microhardness evaluation alloys Hf-Si-B; Avaliacao de microdureza de ligas Hf-Si-B

    Energy Technology Data Exchange (ETDEWEB)

    Gigolotti, Joao Carlos Janio; Costa, Eliane Fernandes Brasil [Centro Universitario de Volta Redonda (UNIFOA), Volta Redonda, RJ (Brazil); Nunes, Carlos Angelo; Rocha, Elisa Gombio; Coelho, Gilberto Carvalho, E-mail: carlosjanio@uol.com.br, E-mail: eliane-costabrasi@hotmail.com, E-mail: cnunes@demar.eel.usp.br, E-mail: elisarocha@alunos.eel.usp.br, E-mail: coelho@demar.eel.usp.br [Universidade de Sao Paulo (USP), Lorena, SP (Brazil)

    2014-08-15

    The technological advance has generated increasing demand for materials that can be used under high temperature, what includes intermetallic MR-Si-B (MR = refractory metal) alloys with multiphase structures, that can also be applied in oxide environments. Thus, this work had for objective the micro hardness study of the Hf-Si-B system alloys, heat treated at 1600 deg C, in the Hf rich region. Hf-Si-B alloys had been produced with blades of Hf (min. 99.8%), Si (min. 99.998%) and B (min. 99.5%), in the voltaic arc furnace and heat treated at 1600 deg C under argon atmosphere. The relationship of the phases had been previously identified by X-ray diffraction and contrast in backscattered electron imaging mode. The alloys had their hardness analyzed by method Vickers (micro hardness) with load of 0.05 kgf and 0.2 kgf and application time of 20 s. The results, obtained from the arithmetic mean of measurements for each alloy on the heterogeneous region, showed a mean hardness of 11.08 GPA, with small coefficient of variation of 3.8%. The borides HfB2 (19.34 GPa) e HfB - 11.76 GPa, showed the hardness higher than the silicides Hf2Si (8.57 GPa), Hf5Si3 (9.63 GPa), Hf3Si2 (11.66 GPa), Hf5Si4 (10.00 GPa), HfSi (10.02 GPa) e HfSi2 (8.61 GPa). (author)

  17. On temporal correlations in high-resolution frequency counting

    CERN Document Server

    Dunker, Tim; Rønningen, Ole Petter

    2016-01-01

    We analyze noise properties of time series of frequency data from different counting modes of a Keysight 53230A frequency counter. We use a 10 MHz reference signal from a passive hydrogen maser connected via phase-stable Huber+Suhner Sucoflex 104 cables to the reference and input connectors of the counter. We find that the high resolution gap-free (CONT) frequency counting process imposes long-term correlations in the output data, resulting in a modified Allan deviation that is characteristic of random walk phase noise. Equally important, the CONT mode results in a frequency bias. In contrast, the counter's undocumented raw continuous mode (RCON) yields unbiased frequency stability estimates with white phase noise characteristics, and of a magnitude consistent with the counter's 20 ps single-shot resolution. Furthermore, we demonstrate that a 100-point running average filter in conjunction with the RCON mode yields resolution enhanced frequency estimates with flicker phase noise characteristics. For instance,...

  18. On the high frequency polarization of pulsar radio emission

    CERN Document Server

    Von Hoensbroech, A; Krawczyk, A

    1998-01-01

    We have analyzed the polarization properties of pulsars at an observing frequency of 4.9 GHz. Together with low frequency data, we are able to trace polarization profiles over more than three octaves into an interesting frequency regime. At those high frequencies the polarization properties often undergo important changes such as significant depolarization. A detailed analysis allowed us to identify parameters, which regulate those changes. A significant correlation was found between the integrated degree of polarization and the loss of rotational energy E^dot. The data were also used to review the widely established pulsar profile classification scheme of core- and cone-type beams. We have discovered the existence of pulsars which show a strongly increasing degree of circular polarization towards high frequencies. Previously unpublished average polarization profiles, recorded at the 100m Effelsberg radio telescope, are presented for 32 radio pulsars at 4.9 GHz. The data were used to derive polarimetric param...

  19. High-Frequency Microwave Processing of Materials Laboratory

    Data.gov (United States)

    Federal Laboratory Consortium — FUNCTION: Conducts research on high-frequency microwave processing of materials using a highpower, continuous-wave (CW), 83-GHz, quasi-optical beam system for rapid,...

  20. Conditions of the Classical Transmission Line Equations at High Frequency

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    New transmission line equations are deduced applying Maxwell's equations in this paper. The conditions of the classical transmission line equations have been discussed, which is important to solve the EM problems in high frequency case.

  1. Oscillographic Chronopotentiometry with High and Low Frequency Current

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A novel electroanalytical method, oscillographic chronopotentiometry with high and low frequency current, is presented in this paper. With this method, the sensitivity of almost all kinds of oscillographic chronopotentiometry can be enhanced about one order.

  2. High frequency modeling for quantum-well laser diodes

    Institute of Scientific and Technical Information of China (English)

    GAO JianJun

    2009-01-01

    High frequency modeling of quantum-well (OW) laser diodes for optoelectronic integrated circuit (OEIC) design is discussed in this paper. Modeling of the intrinsic device and the extrinsic components is discussed by accounting for important physical effects at both de and high frequency. The concepts of equivalent circuits representing both intrinsic and extrinsic components in a QW laser diode are ana-lyzed to obtain a physics-based high frequency model. The model is based on the physical rate equa-tions, and is versatile in that it permits both small-and large-signal simulations to be performed. Sev-eral procedures of the high frequency model parameter extraction are also discussed. Emphasis here is placed on validating the model via a comparison of simulated results with measured data of the small-signal modulation response, obtained over a wide range of optical output powers.

  3. Very High Frequency Switch-Mode Power Supplies

    DEFF Research Database (Denmark)

    Madsen, Mickey Pierre

    The importance of technology and electronics in our daily life is constantly increasing. At the same time portability and energy efficiency are currently some of the hottest topics. This creates a huge need for power converters in a compact form factor and with high efficiency, which can supply...... these electronic devices. This calls for new technologies in order to miniaturize the power electronics of today. One way to do this is by increasing the switching frequency dramatically and develop very high frequency switch mode power supplies. If these converters can be designed to operate efficiently, a huge...... of technologies for very high frequency switch mode power supplies. At these highly elevated frequencies normal bulky magnetics with heavy cores consisting of rare earth materials, can be replaced by air core inductors embedded in the printed circuit board. This is investigated thoroughly and both spirals...

  4. Parametric macromodelling of linear high-frequency systems using multiple frequency scaling and sequential sampling

    OpenAIRE

    Chemmangat Manakkal Cheriya, Krishnan; Ferranti, Francesco; Dhaene, Tom; Knockaert, Luc

    2014-01-01

    An enhanced parametric macromodelling scheme is presented for linear high-frequency systems based on the use of multiple frequency scaling coefficients and a sequential sampling algorithm to fully automate the entire modelling process. The proposed method is applied on a ring resonator bandpass filter example and compared with another state-of-the-art macromodelling method to show its improved modelling capability and reduced setup time.

  5. High-frequency audibility: benefits for hearing-impaired listeners.

    Science.gov (United States)

    Hogan, C A; Turner, C W

    1998-07-01

    The present study was a systematic investigation of the benefit of providing hearing-impaired listeners with audible high-frequency speech information. Five normal-hearing and nine high-frequency hearing-impaired listeners identified nonsense syllables that were low-pass filtered at a number of cutoff frequencies. As a means of quantifying audibility for each condition, Articulation Index (AI) was calculated for each condition for each listener. Most hearing-impaired listeners demonstrated an improvement in speech recognition as additional audible high-frequency information was provided. In some cases for more severely impaired listeners, increasing the audibility of high-frequency speech information resulted in no further improvement in speech recognition, or even decreases in speech recognition. A new measure of how well hearing-impaired listeners used information within specific frequency bands called "efficiency" was devised. This measure compared the benefit of providing a given increase in speech audibility to a hearing-impaired listener to the benefit observed in normal-hearing listeners for the same increase in speech audibility. Efficiencies were calculated using the old AI method and the new AI method (which takes into account the effects of high speech presentation levels). There was a clear pattern in the results suggesting that as the degree of hearing loss at a given frequency increased beyond 55 dB HL, the efficacy of providing additional audibility to that frequency region was diminished, especially when this degree of hearing loss was present at frequencies of 4000 Hz and above. A comparison of analyses from the "old" and "new" AI procedures suggests that some, but not all, of the deficiencies of speech recognition in these listeners was due to high presentation levels.

  6. High frequency ultrasound with color Doppler in dermatology*

    Science.gov (United States)

    Barcaui, Elisa de Oliveira; Carvalho, Antonio Carlos Pires; Lopes, Flavia Paiva Proença Lobo; Piñeiro-Maceira, Juan; Barcaui, Carlos Baptista

    2016-01-01

    Ultrasonography is a method of imaging that classically is used in dermatology to study changes in the hypoderma, as nodules and infectious and inflammatory processes. The introduction of high frequency and resolution equipments enabled the observation of superficial structures, allowing differentiation between skin layers and providing details for the analysis of the skin and its appendages. This paper aims to review the basic principles of high frequency ultrasound and its applications in different areas of dermatology. PMID:27438191

  7. No More HF: Teflon-Assisted Ultrafast Removal of Silica to Generate High-Surface-Area Mesostructured Carbon for Enhanced CO2 Capture and Supercapacitor Performance.

    Science.gov (United States)

    Singh, Dheeraj Kumar; Krishna, Katla Sai; Harish, Srinivasan; Sampath, Srinivasan; Eswaramoorthy, Muthusamy

    2016-02-01

    An innovative technique to obtain high-surface-area mesostructured carbon (2545 m(2)  g(-1)) with significant microporosity uses Teflon as the silica template removal agent. This method not only shortens synthesis time by combining silica removal and carbonization in a single step, but also assists in ultrafast removal of the template (in 10 min) with complete elimination of toxic HF usage. The obtained carbon material (JNC-1) displays excellent CO2 capture ability (ca. 26.2 wt % at 0 °C under 0.88 bar CO2 pressure), which is twice that of CMK-3 obtained by the HF etching method (13.0 wt %). JNC-1 demonstrated higher H2 adsorption capacity (2.8 wt %) compared to CMK-3 (1.2 wt %) at -196 °C under 1.0 bar H2 pressure. The bimodal pore architecture of JNC-1 led to superior supercapacitor performance, with a specific capacitance of 292 F g(-1) and 182 F g(-1) at a drain rate of 1 A g(-1) and 50 A g(-1) , respectively, in 1 m H2 SO4 compared to CMK-3 and activated carbon.

  8. Posture Estimation by Using High Frequency Markers and Kernel Regressions

    Science.gov (United States)

    Ono, Yuya; Iwai, Yoshio; Ishiguro, Hiroshi

    Recently, research fields of augmented reality and robot navigation are actively investigated. Estimating a relative posture between an object and a camera is an important task in these fields. In this paper, we propose a novel method for posture estimation by using high frequency markers and kernel regressions. The markers are embedded in an object's texture in the high frequency domain. We observe the change of spatial frequency of object's texture to estimate a current posture of the object. We conduct experiments to show the effectiveness of our method.

  9. Testing the efficiency of high-frequency foreign exchange market

    Directory of Open Access Journals (Sweden)

    Václav Mastný

    2004-01-01

    Full Text Available This paper deals with the efficiency of the high-frequency foreign exchange market. The objective of this paper is to investigate whether standard statistical tests give the same results for time series resampled at intervals of 15.30 and 60 min. The data used for the purpose of this paper contain major currency pairs such as EUR/USD, GBP/USD and JPY/USD. The results of statistical tests indicate that the high frequency intervals (15-minute are not random and should not be considered independent. On the other hand, tests with lower frequency rates (30 and 60 min indicate rising randomness of the market.

  10. Tsunami Detection by High-Frequency Radar Beyond the Continental Shelf

    Science.gov (United States)

    Grilli, Stéphan T.; Grosdidier, Samuel; Guérin, Charles-Antoine

    2016-12-01

    Where coastal tsunami hazard is governed by near-field sources, such as submarine mass failures or meteo-tsunamis, tsunami propagation times may be too small for a detection based on deep or shallow water buoys. To offer sufficient warning time, it has been proposed to implement early warning systems relying on high-frequency (HF) radar remote sensing, that can provide a dense spatial coverage as far offshore as 200-300 km (e.g., for Diginext Ltd.'s Stradivarius radar). Shore-based HF radars have been used to measure nearshore currents (e.g., CODAR SeaSonde® system; http://www.codar.com/), by inverting the Doppler spectral shifts, these cause on ocean waves at the Bragg frequency. Both modeling work and an analysis of radar data following the Tohoku 2011 tsunami, have shown that, given proper detection algorithms, such radars could be used to detect tsunami-induced currents and issue a warning. However, long wave physics is such that tsunami currents will only rise above noise and background currents (i.e., be at least 10-15 cm/s), and become detectable, in fairly shallow water which would limit the direct detection of tsunami currents by HF radar to nearshore areas, unless there is a very wide shallow shelf. Here, we use numerical simulations of both HF radar remote sensing and tsunami propagation to develop and validate a new type of tsunami detection algorithm that does not have these limitations. To simulate the radar backscattered signal, we develop a numerical model including second-order effects in both wind waves and radar signal, with the wave angular frequency being modulated by a time-varying surface current, combining tsunami and background currents. In each "radar cell", the model represents wind waves with random phases and amplitudes extracted from a specified (wind speed dependent) energy density frequency spectrum, and includes effects of random environmental noise and background current; phases, noise, and background current are extracted from

  11. Targeted Metabolomic Analysis of Head and Neck Cancer Cells Using High Performance Ion Chromatography Coupled with a Q Exactive HF Mass Spectrometer.

    Science.gov (United States)

    Hu, Shen; Wang, Junhua; Ji, Eoon Hye; Christison, Terri; Lopez, Linda; Huang, Yingying

    2015-06-16

    In this study, we have demonstrated a targeted metabolomics method for analysis of cancer cells, based on high-performance ion chromatography (IC) separation, Q Exactive HF MS for high-resolution and accurate-mass (HR/AM) measurement and the use of stable isotope-labeled internal standards for absolute quantitation. Our method offers great technical advantages for metabolite analysis, including exquisite sensitivity, high speed and reproducibility, and wide dynamic range. The high-performance IC provided fast separation of cellular metabolites within 20 min and excellent resolving power for polar molecules including many isobaric metabolites. The IC/Q Exactive HF MS achieved wide dynamic ranges of 5 orders of magnitude for six targeted metabolites, pyruvate, succinic acid, malic acid, citric acid, fumaric acid, and alpha-ketoglutaric acid, with R(2) ≈ 0.99. Using this platform, metabolites can be simultaneously quantified from low fmol/μL to nmol/μL levels in cellular samples. The high flow rate IC at 380 μL/min has shown excellent reproducibility for a large set of samples (150 injections), with minimal variations of retention time (SD < ± 0.03 min). In addition, the IC-MS-based approach acquires targeted and global metabolomic data in a same analytical run, and the use of stable isotope-labeled standards facilitates accurate quantitation of targeted metabolites in large-scale metabolomics analysis. This metabolomics approach has been successfully applied to analysis of targeted metabolites in head and neck cancer cells as well as cancer stem-like cells (CSCs), and the findings indicate that the metabolic phenotypes may be distinct between high and low invasive head and neck cancer cells and between CSCs and non-SCCs.

  12. Microscale capillary wave turbulence excited by high frequency vibration.

    Science.gov (United States)

    Blamey, Jeremy; Yeo, Leslie Y; Friend, James R

    2013-03-19

    Low frequency (O(10 Hz-10 kHz)) vibration excitation of capillary waves has been extensively studied for nearly two centuries. Such waves appear at the excitation frequency or at rational multiples of the excitation frequency through nonlinear coupling as a result of the finite displacement of the wave, most often at one-half the excitation frequency in so-called Faraday waves and twice this frequency in superharmonic waves. Less understood, however, are the dynamics of capillary waves driven by high-frequency vibration (>O(100 kHz)) and small interface length scales, an arrangement ideal for a broad variety of applications, from nebulizers for pulmonary drug delivery to complex nanoparticle synthesis. In the few studies conducted to date, a marked departure from the predictions of classical Faraday wave theory has been shown, with the appearance of broadband capillary wave generation from 100 Hz to the excitation frequency and beyond, without a clear explanation. We show that weak wave turbulence is the dominant mechanism in the behavior of the system, as evident from wave height frequency spectra that closely follow the Rayleigh-Jeans spectral response η ≈ ω(-17/12) as a consequence of a period-halving, weakly turbulent cascade that appears within a 1 mm water drop whether driven by thickness-mode or surface acoustic Rayleigh wave excitation. However, such a cascade is one-way, from low to high frequencies. The mechanism of exciting the cascade with high-frequency acoustic waves is an acoustic streaming-driven turbulent jet in the fluid bulk, driving the fundamental capillary wave resonance through the well-known coupling between bulk flow and surface waves. Unlike capillary waves, turbulent acoustic streaming can exhibit subharmonic cascades from high to low frequencies; here it appears from the excitation frequency all the way to the fundamental modes of the capillary wave at some four orders of magnitude in frequency less than the excitation frequency

  13. Imaging HF-induced large-scale irregularities above HAARP

    Science.gov (United States)

    Djuth, Frank T.; Reinisch, Bodo W.; Kitrosser, David F.; Elder, John H.; Snyder, A. Lee; Sales, Gary S.

    2006-02-01

    The University of Massachusetts-Lowell digisonde is used with the HAARP high-frequency (HF), ionospheric modification facility to obtain radio images of artificially-produced, large-scale, geomagnetic field-aligned irregularities. F region irregularities generated with the HAARP beam pointed in the vertical and geomagnetic field-aligned directions are examined in a smooth background plasma. It is found that limited large-scale irregularity production takes place with vertical transmissions, whereas there is a dramatic increase in the number of source irregularities with the beam pointed parallel to the geomagnetic field. Strong irregularity production appears to be confined to within ~5° of the geomagnetic zenith and does not fill the volume occupied by the HF beam. A similar effect is observed in optical images of artificial airglow.

  14. Zircon U-Pb ages, Hf isotope data, and tectonic implications of Early-Middle Triassic granitoids in the Ailaoshan high-grade metamorphic belt of Southeast Tibet

    Science.gov (United States)

    Wu, Wenbin; Liu, Junlai; Chen, Xiaoyu; Zhang, Lisheng

    2017-04-01

    The Ailaoshan tectonic belt, where the effects of the Paleo-Tethyan ocean evolution and Indian-Eurasian plate collision are superimposed, is one of the most significant geological discontinuities in western Yunnan province of southeast Tibet. An Ailaoshan micro-block within the belt is bounded by the Ailaoshan suture zone to the west and the Red River Fault to the east, and consists of low- and high-grade metamorphic belts. Late Permian-Middle Triassic granitoids that are widely distributed to the west of the Ailaoshan suture zone and within the Ailaoshan micro-block may yield significant information on the Tethyan tectonic evolution of the Ailaoshan tectonic belt. This study reports new LA-ICP-MS zircon U-Pb geochronology and Hf isotope data of four granitoids from the Ailaoshan high-grade metamorphic belt. Zircon grains from the Yinjie granitoid do not have inherited cores and yield a weighted mean U-Pb age of 247.1 ± 2.0 Ma. The zircon ɛ Hf( t) values range from 7.8 to 12.1, and Hf model ages from 775 to 546 Ma, indicating that the granitoid was derived from juvenile crust. The rims of zircons from the Majie and Yuanjiang granitoids yield weighted mean U-Pb ages of 239.5 ± 1.8 and 237.9 ± 2.6 Ma, respectively, whereas the cores yield ages of 1608-352 Ma. The ɛ Hf( t) values of zircon rims range from -20.4 to -5.3, yielding Hf model ages from 2557 to 1606 Ma and suggesting that the source magma of the Majie and Yuanjiang granitoids was derived from ancient crust. An additional granitoid located near the Majie Village yields a zircon U-Pb age of 241.2 ± 1.0 Ma. Based on our geochronological and geochemical data, combined with geological observations, we propose that the Ailaoshan micro-block was derived from the western margin of the Yangtze block, and is comparable to the Zhongzan and Nam Co micro-blocks. The presence of late Permian mafic rocks with rift-related geochemical characteristics within the Ailaoshan micro-block, together with granitoids derived

  15. Zircon U-Pb ages, Hf isotope data, and tectonic implications of Early-Middle Triassic granitoids in the Ailaoshan high-grade metamorphic belt of Southeast Tibet

    Science.gov (United States)

    Wu, Wenbin; Liu, Junlai; Chen, Xiaoyu; Zhang, Lisheng

    2016-05-01

    The Ailaoshan tectonic belt, where the effects of the Paleo-Tethyan ocean evolution and Indian-Eurasian plate collision are superimposed, is one of the most significant geological discontinuities in western Yunnan province of southeast Tibet. An Ailaoshan micro-block within the belt is bounded by the Ailaoshan suture zone to the west and the Red River Fault to the east, and consists of low- and high-grade metamorphic belts. Late Permian-Middle Triassic granitoids that are widely distributed to the west of the Ailaoshan suture zone and within the Ailaoshan micro-block may yield significant information on the Tethyan tectonic evolution of the Ailaoshan tectonic belt. This study reports new LA-ICP-MS zircon U-Pb geochronology and Hf isotope data of four granitoids from the Ailaoshan high-grade metamorphic belt. Zircon grains from the Yinjie granitoid do not have inherited cores and yield a weighted mean U-Pb age of 247.1 ± 2.0 Ma. The zircon ɛ Hf(t) values range from 7.8 to 12.1, and Hf model ages from 775 to 546 Ma, indicating that the granitoid was derived from juvenile crust. The rims of zircons from the Majie and Yuanjiang granitoids yield weighted mean U-Pb ages of 239.5 ± 1.8 and 237.9 ± 2.6 Ma, respectively, whereas the cores yield ages of 1608-352 Ma. The ɛ Hf(t) values of zircon rims range from -20.4 to -5.3, yielding Hf model ages from 2557 to 1606 Ma and suggesting that the source magma of the Majie and Yuanjiang granitoids was derived from ancient crust. An additional granitoid located near the Majie Village yields a zircon U-Pb age of 241.2 ± 1.0 Ma. Based on our geochronological and geochemical data, combined with geological observations, we propose that the Ailaoshan micro-block was derived from the western margin of the Yangtze block, and is comparable to the Zhongzan and Nam Co micro-blocks. The presence of late Permian mafic rocks with rift-related geochemical characteristics within the Ailaoshan micro-block, together with granitoids derived

  16. Parametric Study of High Frequency Pulse Detonation Tubes

    Science.gov (United States)

    Cutler, Anderw D.

    2008-01-01

    This paper describes development of high frequency pulse detonation tubes similar to a small pulse detonation engine (PDE). A high-speed valve injects a charge of a mixture of fuel and air at rates of up to 1000 Hz into a constant area tube closed at one end. The reactants detonate in the tube and the products exit as a pulsed jet. High frequency pressure transducers are used to monitor the pressure fluctuations in the device and thrust is measured with a balance. The effects of injection frequency, fuel and air flow rates, tube length, and injection location are considered. Both H2 and C2H4 fuels are considered. Optimum (maximum specific thrust) fuel-air compositions and resonant frequencies are identified. Results are compared to PDE calculations. Design rules are postulated and applications to aerodynamic flow control and propulsion are discussed.

  17. Frequencies of inaudible high-frequency sounds differentially affect brain activity: positive and negative hypersonic effects.

    Directory of Open Access Journals (Sweden)

    Ariko Fukushima

    Full Text Available The hypersonic effect is a phenomenon in which sounds containing significant quantities of non-stationary high-frequency components (HFCs above the human audible range (max. 20 kHz activate the midbrain and diencephalon and evoke various physiological, psychological and behavioral responses. Yet important issues remain unverified, especially the relationship existing between the frequency of HFCs and the emergence of the hypersonic effect. In this study, to investigate the relationship between the hypersonic effect and HFC frequencies, we divided an HFC (above 16 kHz of recorded gamelan music into 12 band components and applied them to subjects along with an audible component (below 16 kHz to observe changes in the alpha2 frequency component (10-13 Hz of spontaneous EEGs measured from centro-parieto-occipital regions (Alpha-2 EEG, which we previously reported as an index of the hypersonic effect. Our results showed reciprocal directional changes in Alpha-2 EEGs depending on the frequency of the HFCs presented with audible low-frequency component (LFC. When an HFC above approximately 32 kHz was applied, Alpha-2 EEG increased significantly compared to when only audible sound was applied (positive hypersonic effect, while, when an HFC below approximately 32 kHz was applied, the Alpha-2 EEG decreased (negative hypersonic effect. These findings suggest that the emergence of the hypersonic effect depends on the frequencies of inaudible HFC.

  18. Frequencies of inaudible high-frequency sounds differentially affect brain activity: positive and negative hypersonic effects.

    Science.gov (United States)

    Fukushima, Ariko; Yagi, Reiko; Kawai, Norie; Honda, Manabu; Nishina, Emi; Oohashi, Tsutomu

    2014-01-01

    The hypersonic effect is a phenomenon in which sounds containing significant quantities of non-stationary high-frequency components (HFCs) above the human audible range (max. 20 kHz) activate the midbrain and diencephalon and evoke various physiological, psychological and behavioral responses. Yet important issues remain unverified, especially the relationship existing between the frequency of HFCs and the emergence of the hypersonic effect. In this study, to investigate the relationship between the hypersonic effect and HFC frequencies, we divided an HFC (above 16 kHz) of recorded gamelan music into 12 band components and applied them to subjects along with an audible component (below 16 kHz) to observe changes in the alpha2 frequency component (10-13 Hz) of spontaneous EEGs measured from centro-parieto-occipital regions (Alpha-2 EEG), which we previously reported as an index of the hypersonic effect. Our results showed reciprocal directional changes in Alpha-2 EEGs depending on the frequency of the HFCs presented with audible low-frequency component (LFC). When an HFC above approximately 32 kHz was applied, Alpha-2 EEG increased significantly compared to when only audible sound was applied (positive hypersonic effect), while, when an HFC below approximately 32 kHz was applied, the Alpha-2 EEG decreased (negative hypersonic effect). These findings suggest that the emergence of the hypersonic effect depends on the frequencies of inaudible HFC.

  19. TID measurement using oblique transmissions of HF pulses

    Science.gov (United States)

    Galkin, Ivan; Reinisch, Bodo; Huang, Xueqin; Paznukhov, Vadym; Hamel, Ryan; Kozlov, Alexander; Belehaki, Anna

    2017-04-01

    The Traveling Ionospheric Disturbance (TID), a wave-like signature of moving plasma density modulation in the ionosphere, is widely acknowledged for its utility in backtracking the anomalous events responsible for the TID generation, and as a major inconvenience to high-frequency (HF) operational systems because of its deleterious impact on the accuracy of navigation and geolocation. The pilot project "Net-TIDE" for the real-time detection and evaluation of TIDs began its operation in 2016 based on the remote-sensing data from synchronized, network-coordinated HF sounding between pairs of DPS4D ionosondes at five participating observatories in Europe. Measurement of all signal properties (Doppler frequency, angle of arrival, and time-of-flight from transmitter to receiver) proved to be instrumental in detecting the TID and deducing the TID parameters: amplitude, wavelength, phase velocity, and direction of propagation. Processing of the measured HF signal data required a specialized signal processing technique that is capable of consistently extracting different signals that have propagated along different ionospheric paths. The multi-path signal environment proved to be the greatest challenge for the reliable TID specification by Net-TIDE, demanding the development of an intelligent system for "signal tracking". The intelligent system is based on a neural network model of a pre-attentive vision capable of extracting continuous signal tracks from the multi-path signal ensemble. Specific examples of the Net-TIDE algorithm suite operation and its suitability for a fully automated TID warning service are discussed.

  20. Forecasting Value-at-Risk Using High-Frequency Information

    Directory of Open Access Journals (Sweden)

    Huiyu Huang

    2013-06-01

    Full Text Available in the prediction of quantiles of daily Standard&Poor’s 500 (S&P 500 returns we consider how to use high-frequency 5-minute data. We examine methods that incorporate the high frequency information either indirectly, through combining forecasts (using forecasts generated from returns sampled at different intraday interval, or directly, through combining high frequency information into one model. We consider subsample averaging, bootstrap averaging, forecast averaging methods for the indirect case, and factor models with principal component approach, for both direct and indirect cases. We show that in forecasting the daily S&P 500 index return quantile (Value-at-Risk or VaR is simply the negative of it, using high-frequency information is beneficial, often substantially and particularly so, in forecasting downside risk. Our empirical results show that the averaging methods (subsample averaging, bootstrap averaging, forecast averaging, which serve as different ways of forming the ensemble average from using high-frequency intraday information, provide an excellent forecasting performance compared to using just low-frequency daily information.

  1. Advanced waveforms and frequency with spinal cord stimulation: burst and high-frequency energy delivery.

    Science.gov (United States)

    Pope, Jason E; Falowski, Steven; Deer, Tim R

    2015-07-01

    In recent years, software development has been key to the next generation of neuromodulation devices. In this review, we will describe the new strategies for electrical waveform delivery for spinal cord stimulation. A systematic literature review was performed using bibliographic databases, limited to the English language and human data, between 2010 and 2014. The literature search yielded three articles on burst stimulation and four articles on high-frequency stimulation. High-frequency and burst stimulation may offer advantages over tonic stimulation, as data suggest improved patient tolerance, comparable increase in function and possible success with a subset of patients refractory to tonic spinal cord stimulation. High-frequency and burst stimulation are new ways to deliver energy to the spinal cord that may offer advantages over tonic stimulation. These may offer new salvage strategies to mitigate spinal cord stimulation failure and improve cost-effectiveness by reducing explant rate.

  2. A novel three-phase UPS system with a single-phase resonant HF link

    OpenAIRE

    Darwish, MK

    2006-01-01

    This paper presents a new three-phase uninterruptible power supply (UPS) system based on a single-phase resonant high frequency (HF) link and a single-phase transformer. The three-phase output voltage is constructed and regulated from a three-phase cycloconverter fed from the constant amplitude, constant frequency link voltage. The generation of a novel switching stategy for the three-phase cycloconverter is presented. The simulation of the proposed system is carried out and verified with exp...

  3. High-speed optical frequency-domain imaging

    OpenAIRE

    Yun, S. H.; Tearney, G. J.; Boer; Iftimia, N. V.; Bouma, B. E.

    2003-01-01

    We demonstrate high-speed, high-sensitivity, high-resolution optical imaging based on optical frequency-domain interferometry using a rapidly-tuned wavelength-swept laser. We derive and show experimentally that frequency-domain ranging provides a superior signal-to-noise ratio compared with conventional time-domain ranging as used in optical coherence tomography. A high sensitivity of −110 dB was obtained with a 6 mW source at an axial resolution of 13.5 µm and an A-line rate of 15.7 kHz, rep...

  4. High density THz frequency comb produced by coherent synchrotron radiation

    CERN Document Server

    Tammaro, S; Roy, P; Lampin, J -F; Ducournau, G; Cuisset, A; Hindle, F; Mouret, G

    2014-01-01

    Frequency combs (FC) have radically changed the landscape of frequency metrology and high-resolution spectroscopy investigations extending tremendously the achievable resolution while increasing signal to noise ratio. Initially developed in the visible and near-IR spectral regions, the use of FC has been expanded to mid-IR, extreme ultra-violet and X-ray. Significant effort is presently dedicated to the generation of FC at THz frequencies. One solution based on converting a stabilized optical frequency comb using a photoconductive terahertz emitter, remains hampered by the low available THz power. Another approach is based on active mode locked THz quantum-cascade-lasers providing intense FC over a relatively limited spectral extension. Alternatively, here we show that dense powerful THz FC is generated over one decade of frequency by coherent synchrotron radiation (CSR). In this mode, the entire ring behaves in a similar fashion to a THz resonator wherein electron bunches emit powerful THz pulses quasi-synch...

  5. High Frequency Stochastic Resonance in Periodically Driven Systems

    CERN Document Server

    Dykman, M I

    1993-01-01

    Abstract: High frequency stochastic resonance (SR) phenomena, associated with fluctuational transitions between coexisting periodic attractors, have been investigated experimentally in an electronic model of a single-well Duffing oscillator bistable in a nearly resonant field of frequency $\\omega_F$. It is shown that, with increasing noise intensity, the signal/noise ratio (SNR) for a signal due to a weak trial force of frequency $\\Omega decreases again at higher noise intensities: behaviour similar to that observed previously for conventional (low frequency) SR in systems with static bistable potentials. The stochastic enhancement of the SNR of an additional signal at the mirror-reflected frequency $\\vert Ømega - 2 ømega_F \\vert$ is also observed, in accordance with theoretical predictions. Relationships with phenomena in nonlinear optics are discussed.

  6. High frequency acoustic microscopy with Fresnel zoom lens

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The acoustic field distributions and the convergent beams generated by the planar-structure Fresnel zone transducers on solid surface are investigated. Because only 0 and 180 degree phase transducers are used, an imaging system with the Fresnel zoom lens could work at very high frequency, which overcomes the frequency limit of the traditional phased array acoustic imaging system. Simulation results are given to illustrate the acoustic field distributions along the focal axis and the whole plane as well. Based on the principle of scanning of the focus with the change of frequency for the excited signal, an experimental imaging system is also built. Acoustic Fresnel zone transducers are fabricated at center frequency of 400 MHz. Measurements and detections of the known hole flaws at different depths of the fused quartz sample are presented to show that the imaging system with Fresnel zoom lens could move its focus by only changing the frequency of the excited signal.

  7. Adequacy of Frequency Reserves for High Wind Power Generation

    DEFF Research Database (Denmark)

    Das, Kaushik; Litong-Palima, Marisciel; Maule, Petr

    2016-01-01

    In this article, a new methodology is developed to assess the adequacy of frequency reserves to handle power imbalances caused by wind power forecast errors. The goal of this methodology is to estimate the adequate volume and speed of activation of frequency reserves required to handle power...... imbalances caused due to high penetration of wind power. An algorithm is proposed and developed to estimate the power imbalances due to wind power forecast error following activation of different operating reserves. Frequency containment reserve requirements for mitigating these power imbalances...... are developed through this methodology. Furthermore, the probability of reducing this frequency containment reserve requirement is investigated through this methodology with activation of different volumes and speed of frequency restoration reserve. Wind power generation for 2020 and 2030 scenarios...

  8. Quantum-state resolved reactive scattering at the gas-liquid interface: F +squalane (C30H62) dynamics via high-resolution infrared absorption of nascent HF(v,J)

    Science.gov (United States)

    Zolot, Alexander M.; Dagdigian, Paul J.; Nesbitt, David J.

    2008-11-01

    Exothermic chemical reaction dynamics at the gas-liquid interface have been investigated by colliding a supersonic beam of F atoms [Ecom=0.7(3)kcal/mol] with a continuously refreshed liquid hydrocarbon (squalane) surface under high vacuum conditions. Absolute HF(v,J) product densities are determined by infrared laser absorption spectroscopy, with velocity distributions along the probe axis derived from high resolution Dopplerimetry. Nascent HF(v ⩽3) products are formed in a highly nonequilibrium (inverted) vibrational distribution [⟨Evib⟩=13.2(2)kcal/mol], reflecting insufficient time for complete thermal accommodation with the surface prior to desorption. Colder, but still non-Boltzmann, rotational state populations [⟨Erot⟩=1.0(1)kcal/mol] indicate that some fraction of molecules directly scatter into the gas phase without rotationally equilibrating with the surface. Nascent HF also recoils from the liquid surface with excess translational energy, resulting in Doppler broadened linewidths that increase systematically with internal HF excitation. The data are consistent with microscopic branching in HF-surface dynamics following the reactive event, with (i) a direct reactive scattering fraction of newly formed product molecules leaving the surface promptly and (ii) a trapping desorption fraction that accommodates rotationally (though still not vibrationally) with the bulk liquid. Comparison with analogous gas phase F +hydrocarbon processes reveals that the liquid acts as a partial "heat sink" for vibrational energy flow on the time scale of the chemical reaction event.

  9. High-throughput identification of higher-κ dielectrics from an amorphous N{sub 2}-doped HfO{sub 2}–TiO{sub 2} library

    Energy Technology Data Exchange (ETDEWEB)

    Chang, K.-S., E-mail: kschang@mail.ncku.edu.tw [Department of Materials Science and Engineering, National Cheng Kung University (NCKU), Tainan, Taiwan (China); Promotion Center for Global Materials Research (PCGMR), National Cheng Kung University (NCKU), Tainan, Taiwan (China); Lu, W.-C. [Department of Materials Science and Engineering, National Cheng Kung University (NCKU), Tainan, Taiwan (China); Institute of Nanotechnology and Microsystems Engineering, National Cheng Kung University (NCKU), Tainan, Taiwan (China); Wu, C.-Y.; Feng, H.-C. [Department of Materials Science and Engineering, National Cheng Kung University (NCKU), Tainan, Taiwan (China)

    2014-12-05

    Highlights: • Amorphous N{sub 2}-doped HfO{sub 2}–TiO{sub 2} libraries were fabricated using sputtering. • Structure and quality of the dielectric and interfacial layers were investigated. • κ (54), J{sub L} < 10{sup −6} A/cm{sup 2}, and equivalent oxide thickness (1 nm) were identified. - Abstract: High-throughput sputtering was used to fabricate high-quality, amorphous, thin HfO{sub 2}–TiO{sub 2} and N{sub 2}-doped HfO{sub 2}–TiO{sub 2} (HfON–TiON) gate dielectric libraries. Electron probe energy dispersive spectroscopy was used to investigate the structures, compositions, and qualities of the dielectric and interfacial layers of these libraries to determine their electrical properties. A κ value of approximately 54, a leakage current density <10{sup −6} A/cm{sup 2}, and an equivalent oxide thickness of approximately 1 nm were identified in an HfON–TiON library within a composition range of 68–80 at.% Ti. This library exhibits promise for application in highly advanced metal–oxide–semiconductor (higher-κ) gate stacks.

  10. Analysis of the operation of a diffraction-radiation generator with preliminary HF modulation

    Science.gov (United States)

    Pivovarova, A. G.

    1991-05-01

    The excitation conditions and output characteristics of a diffraction-radiation generator with preliminary HF modulation are determined. Attention is given to the effects of the modulation parameter, the phase shift, and the aiming distance on the displacement of the generation zone, variations of the minimum starting current, the frequency shift, the oscillation amplitude, and the efficiency of the generator. It is shown that the efficiency of a generator with preliminary HF modulation can be twice as high as that of a generator without modulation.

  11. Design & Implementation of High Switching & Low Phase Noise Frequency Synthesizer

    Directory of Open Access Journals (Sweden)

    Ali M. N. Hassan

    2006-01-01

    Full Text Available This research describes the design & implementation of frequency synthesizer using single loop Phase lock loop with the following specifications: Frequency range (1.5 – 2.75 GHz,Step size (1 MHz, Switching time 36.4 µs, & phase noise @10 kHz = -92dBc & spurious -100 dBc The development in I.C. technology provide the simplicity in the design of frequency synthesizer because it implements the phase frequency detector(PFD , prescalar & reference divider in single chip. Therefore our system consists of a single chip contains (low phase noise PFD, charge pump, prescalar & reference divider, voltage controlled oscillator , loop filter & reference oscillator. The single chip is used to provide the following properties :•Low power consumptionSmall size, light weight.Flexibility in selecting crystal oscillator frequencies to fit into the system frequency planning.•High reliability.The application of this synthesizer in frequency hopping systems, satellite communications & radar because it has high switching speed ,low phase noise & low spurious level.

  12. Slow high-frequency effects in mechanics: problems, solutions, potentials

    DEFF Research Database (Denmark)

    Thomsen, Jon Juel

    Strong high-frequency excitation (HFE) may change the ‘slow’ (i.e. effective or average) properties of mechanical systems, e.g. their stiffness, natural frequencies, equilibriums, equilibrium stability, and bifurcation paths. This tutorial describes three general HFE effects: Stiffening – an appa......Strong high-frequency excitation (HFE) may change the ‘slow’ (i.e. effective or average) properties of mechanical systems, e.g. their stiffness, natural frequencies, equilibriums, equilibrium stability, and bifurcation paths. This tutorial describes three general HFE effects: Stiffening...... and compared: The Method of Direct Separation of Motions, the Method of Averaging, and the Method of Multiple Scales. The tutorial concludes by suggesting that more vibration experts, researchers and students should know about HFE effects, for the benefit not only of general vibration troubleshooting, but also...

  13. Propagation of high frequency waves in the quiet solar atmosphere

    Directory of Open Access Journals (Sweden)

    Andić A.

    2008-01-01

    Full Text Available High-frequency waves (5 mHz to 20 mHz have previously been suggested as a source of energy accounting for partial heating of the quiet solar atmosphere. The dynamics of previously detected high-frequency waves is analyzed here. Image sequences were taken by using the German Vacuum Tower Telescope (VTT, Observatorio del Teide, Izana, Tenerife, with a Fabry-Perot spectrometer. The data were speckle reduced and analyzed with wavelets. Wavelet phase-difference analysis was performed to determine whether the waves propagate. We observed the propagation of waves in the frequency range 10 mHz to 13 mHz. We also observed propagation of low-frequency waves in the ranges where they are thought to be evanescent in the regions where magnetic structures are present.

  14. Propagation of High Frequency Waves in the Quiet Solar Atmosphere

    Directory of Open Access Journals (Sweden)

    Andić, A.

    2008-12-01

    Full Text Available High-frequency waves (5 mHz to 20 mHz have previously been suggested as a source of energy accounting for partial heating of the quiet solar atmosphere. The dynamics of previously detected high-frequency waves is analysed here. Image sequences were taken by using the German Vacuum Tower Telescope (VTT, Observatorio del Teide, Izana, Tenerife, with a Fabry-Perot spectrometer. The data were speckle reduced and analysed with wavelets. Wavelet phase-difference analysis was performed to determine whether the waves propagate. We observed the propagation of waves in the frequency range 10 mHz to 13 mHz. We also observed propagation of low-frequency waves in the ranges where they are thought to be evanescent in the regions where magnetic structures are present.

  15. Propagation of High Frequency Waves in the Quiet Solar Atmosphere

    CERN Document Server

    Andić, Aleksandra

    2008-01-01

    High-frequency waves (5 mHz to 20mHz) have previously been suggested as a source of energy accounting partial heating of the quiet solar atmosphere. The dynamics of previously detected high-frequency waves is analysed here. Image sequences are taken using the German Vacuum Tower Telescope (VTT), Observatorio del Teide, Izana, Tenerife, with a Fabry-Perot spectrometer. The data were speckle reduced and analyzed with wavelets. Wavelet phase-difference analysis is performed to determine whether the waves propagate. We observe the propagation of waves in the frequency range 10mHz to 13mHz. We also observe propagation of low-frequency waves in the ranges where they are thought to be evanescent in regions where magnetic structures are present.

  16. On the Ongoing Evolution of Very High Frequency Power Supplies

    DEFF Research Database (Denmark)

    Knott, Arnold; Andersen, Toke Meyer; Kamby, Peter

    2013-01-01

    in radio frequency transmission equipment helps to overcome those. However those circuits were not designed to meet the same requirements as power converters. This paper summarizes the contributions in recent years in application of very high frequency (VHF) technologies in power electronics, describes......The ongoing demand for smaller and lighter power supplies is driving the motivation to increase the switching frequencies of power converters. Drastic increases however come along with new challenges, namely the increase of switching losses in all components. The application of power circuits used...

  17. High-Frequency-Induced Cathodic Breakdown during Plasma Electrolytic Oxidation

    Science.gov (United States)

    Nominé, A.; Nominé, A. V.; Braithwaite, N. St. J.; Belmonte, T.; Henrion, G.

    2017-09-01

    The present communication shows the possibility of observing microdischarges under cathodic polarization during plasma electrolytic oxidation at high frequency. Cathodic microdischarges can ignite beyond a threshold frequency found close to 2 kHz. The presence (respectively, absence) of an electrical double layer is put forward to explain how the applied voltage can be screened, which therefore prevents (respectively, promotes) the ignition of a discharge. Interestingly, in the conditions of the present study, the electrical double layer requires between 175 and 260 μ s to form. This situates the expected threshold frequency between 1.92 and 2.86 kHz, which is in good agreement with the value obtained experimentally.

  18. High-frequency magnetoelastic measurements on Fe–Co–Hf–N/Ti–N multilayer coatings

    Energy Technology Data Exchange (ETDEWEB)

    Krüger, Kathrin, E-mail: kathrin.krueger@kit.edu; Seemann, Klaus; Leiste, Harald; Stüber, Michael; Ulrich, Sven

    2013-10-15

    Fe{sub 32}Co{sub 44}Hf{sub 12}N{sub 12}/Ti{sub 50}N{sub 50} thin multilayer coatings are realized as wear resistant coatings with an integrated sensor function, in order to detect e.g. external mechanical stress. A setup was designed to monitor changes in the frequency-dependent permeability due to the mechanically induced stress in the ferromagnetic Fe{sub 32}Co{sub 44}Hf{sub 12}N{sub 12} single layers. The change of the ferromagnetic cut-off frequency is described by an effective in-plane anisotropy field H{sup →}{sub u,eff} which accounts for a thermally induced uniaxial anisotropy field H{sup →}{sub u} and an effective biaxial magnetoelastic anisotropy field H{sup →}{sub me}. Fe{sub 32}Co{sub 44}Hf{sub 12}N{sub 12}/Ti{sub 50}N{sub 50} multilayer films with seven bilayers and a total thickness of about 1 μm were grown by a sequential deposition of Fe{sub 32}Co{sub 44}Hf{sub 12}N{sub 12} and Ti{sub 50}N{sub 50} individual layers by means of reactive DC and RF magnetron sputtering, respectively. Additionally, a Fe{sub 32}Co{sub 44}Hf{sub 12}N{sub 12} monolayer coating with a thickness of about 500 nm was deposited in order to determine the magnetic properties of the single layer. The films were investigated with respect to their static and dynamic ferromagnetic properties. A uniaxial anisotropy field of 5 mT could be induced after annealing the multilayer films for 1 h at 400 °C in vacuum in a static magnetic field of 50 mT. Additionally, magnetic softness (μ{sub 0}H{sub c}=0.6 mT) and cut-off frequencies above 2 GHz were observed. Inducing compressive stress increases the cut-off frequency of the Fe{sub 32}Co{sub 44}Hf{sub 12}N{sub 12} single layer as well as of the Fe{sub 32}Co{sub 44}Hf{sub 12}N{sub 12}/Ti{sub 50}N{sub 50} multilayer films whereas tensile stress causes a decrease in the cut-off frequency. Accordingly, the dependence of the cut-off frequency on external mechanical stress is theoretically described. Furthermore, the possibility of

  19. Engineering Graphene Conductivity for Flexible and High-Frequency Applications.

    Science.gov (United States)

    Samuels, Alexander J; Carey, J David

    2015-10-14

    Advances in lightweight, flexible, and conformal electronic devices depend on materials that exhibit high electrical conductivity coupled with high mechanical strength. Defect-free graphene is one such material that satisfies both these requirements and which offers a range of attractive and tunable electrical, optoelectronic, and plasmonic characteristics for devices that operate at microwave, terahertz, infrared, or optical frequencies. Essential to the future success of such devices is therefore the ability to control the frequency-dependent conductivity of graphene. Looking to accelerate the development of high-frequency applications of graphene, here we demonstrate how readily accessible and processable organic and organometallic molecules can efficiently dope graphene to carrier densities in excess of 10(13) cm(-2) with conductivities at gigahertz frequencies in excess of 60 mS. In using the molecule 3,6-difluoro-2,5,7,7,8,8-hexacyanoquinodimethane (F2-HCNQ), a high charge transfer (CT) of 0.5 electrons per adsorbed molecule is calculated, resulting in p-type doping of graphene. n-Type doping is achieved using cobaltocene and the sulfur-containing molecule tetrathiafulvalene (TTF) with a CT of 0.41 and 0.24 electrons donated per adsorbed molecule, respectively. Efficient CT is associated with the interaction between the π electrons present in the molecule and in graphene. Calculation of the high-frequency conductivity shows dispersion-less behavior of the real component of the conductivity over a wide range of gigahertz frequencies. Potential high-frequency applications in graphene antennas and communications that can exploit these properties and the broader impacts of using molecular doping to modify functional materials that possess a low-energy Dirac cone are also discussed.

  20. Extended High Frequency Audiometry in Polycystic Ovary Syndrome

    Directory of Open Access Journals (Sweden)

    Cuneyt Kucur

    2013-01-01

    and BMI of PCOS and control groups were comparable. Each subject was tested with low (250–2000 Hz, high (4000–8000 Hz, and extended high frequency audiometry (8000–20000. Hormonal and biochemical values including LH, LH/FSH, testosterone, fasting glucose, fasting insulin, HOMA-I, and CRP were calculated. Results. PCOS patients showed high levels of LH, LH/FSH, testosterone, fasting insulin, glucose, HOMA-I, and CRP levels. The hearing thresholds of the groups were similar at frequencies of 250, 500, 1000, 2000, and 4000 Hz; statistically significant difference was observed in 8000–14000 Hz in PCOS group compared to control group. Conclusion. PCOS patients have hearing impairment especially in extended high frequencies. Further studies are needed to help elucidate the mechanism behind hearing impairment in association with PCOS.

  1. Efficient estimation for ergodic diffusions sampled at high frequency

    DEFF Research Database (Denmark)

    Sørensen, Michael

    A general theory of efficient estimation for ergodic diffusions sampled at high fre- quency is presented. High frequency sampling is now possible in many applications, in particular in finance. The theory is formulated in term of approximate martingale estimating functions and covers a large class...

  2. Occupational exposure to anaesthetic gases and high-frequency audiometry.

    Science.gov (United States)

    Giorgianni, Concetto; Gangemi, Silvia; Tanzariello, Maria Giuseppina; Barresi, Gaetano; Miceli, Ludovica; D'Arrigo, Graziella; Spatari, Giovanna

    2015-09-01

    Occupational exposure to anaestethic gases has been suggested to induce auditory damages. The aim of this study is to investigate high-frequency audiometric responses in subjects exposed to anaesthetic gases, in order to highlight the possible effects on auditory system. The study was performed on a sample of 30 medical specialists of Messina University Anaesthesia and Intensive care. We have used tonal audiometry as well as high-frequency one. We have compared the responses with those obtained in a similar control group not exposed to anaesthetic gases. Results were compared statistically. Results show a strong correlation (p = 0.000) between left and right ear responses to all the audiometric tests. The exposed and the control group run though the standard audiometry analysis plays different audiometric responses up only to higher frequencies (2000 HZ p = 0.009 and 4000 Hz p = 0.04); in high-frequency audiometry, as all other frequencies, the attention is drew to the fact that the sample groups distinguish themselves in a significantly statistic way (10,000 Hz p = 0.025, 12,000 Hz p = 0.008, 14,000 Hz p = 0.026, 16,000 Hz p = 0.08). The highest values are the ones related to exposed subjects both in standard (2000 Hz p = 0.01, 4000 Hz p = 0.02) and in high-frequency audiometry (10,000 Hz p = 0.011, 12,000 Hz p = 0.004, 14,000 Hz p = 0.012, 16,000 Hz p = 0.004). Results, even if preliminary and referred to a low-range sample, show an involvement of the anatomic structure responsible for the perception of high-frequency audiometric responses in subjects exposed to anaesthetic gases. © The Author(s) 2012.

  3. Determination of the density of the defect states in Hf0.5Zr0.5O2 high-k film Deposited by using rf-magnetron sputtering technique

    Directory of Open Access Journals (Sweden)

    W. Lu

    2014-08-01

    Full Text Available A memory structure Pt/Al2O3/Hf0.5Zr0.5O2/Al2O3/p-Si was fabricated by using atomic layer deposition and rf-magnetron sputtering techniques, and its microstructure has been investigated by using the high resolution transmission electron microscopy (HRTEM. By measuring the applied gate voltage dependence of the capacitance for the memory structure, the planar density of the trapped charges in Hf0.5Zr0.5O2 high-k film was estimated as 6.63 × 1012 cm−2, indicating a body defect density of larger than 2.21 × 1019 cm−3. It is observed that the post-annealing in N2 can reduces the defect density in Hf0.5Zr0.5O2 film, which was ascribed to the occupancy of oxygen vacancies by nitrogen atoms.

  4. Lipa, B. et al. Tsunami Arrival Detection with High Frequency (HF Radar. Remote Sens. 2012, 4, 1448-1461

    Directory of Open Access Journals (Sweden)

    Donald Barrick

    2012-11-01

    Full Text Available We neglected to state that the radar data from Tokushima and Anan is owned by the Ministry of Land, Infrastructure, Transport and Tourism, Shikoku Regional Development Bureau, Komatsushima port and airport office, Japan. Lipa et al. [1] describe results on tsunami detection using data measured by two radars located at Tokushima and Anan on the Kii channel. This data is owned by the Ministry of Land, Infrastructure, Transport and Tourism, Shikoku Regional Development Bureau, Komatsushima port and airport office, Japan. Locations of the radars are shown in Figure 4(a,c [1]. Results of the data analysis are given in Section 3.1.2, plotted in Figure 6 and listed in Table 1 [1].

  5. Dimensioning of the cooling system of the capacitors operating in a high frequency antenna, through a finite element method; Dimensionnement du systeme de refroidissement des condensateurs d'une antenne a haute frequence, par la methode des elements finis

    Energy Technology Data Exchange (ETDEWEB)

    Tenza, A. [Association Euratom-CEA Cadarache, 13 - Saint-Paul-lez-Durance (France). Dept. de Recherches sur la Fusion Controlee]|[Ecole Superieure d' Ingenieurs de Marseille (ESIM), 13 - Marseille (France)

    2003-07-01

    The aim of this work is the study of the heat transfer and of thermal behaviour of the HF (high frequency) components (in fact capacitors) of the ITER-proto-2005-FCI antenna. Preliminary results carried out with the Castem software show that it is possible to cool the hottest part of the antenna efficiently. A water flow (1 bar, 25 Celsius degrees) or an helium flow (10 bars, 50 Celsius degrees) permit to limit the maximal value of the temperature to 270 Celsius degrees. A second software Ansys has allowed the author to simulate capacitors with more complicated shapes. (A.C.)

  6. Mechanical properties of ZrB2- and HfB2-based ultra-high temperature ceramics fabricated by spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Zapata-Solvas, E. [Imperial College, London; Jayaseelan, D. [Imperial College, London; Lin, Hua-Tay [ORNL; Brown, P. [DSTL, Porton Down, Salisbury, Wiltshire, UK; Lee, W.E. [Imperial College, London

    2013-01-01

    Flexural strengths at room temperature, at 1400 C in air and at room temperature after 1 h oxidation at 1400 C were determined for ZrB2- and HfB2-based ultra-high temperature ceramics (UHTCs). Defects caused by electrical discharge machining (EDM) lowered measured strengths significantly and were used to calculate fracture toughness via a fracture mechanics approach. ZrB2 with 20 vol.% SiC had room temperature strength of 700 90 MPa, fracture toughness of 6.4 0.6 MPa, Vickers hardness at 9.8 N load of 21.1 0.6 GPa, 1400 C strength of 400 30 MPa and room temperature strength after 1 h oxidation at 1400 C of 678 15 MPa with an oxide layer thickness of 45 5 m. HfB2 with 20 vol.% SiC showed room temperature strength of 620 50 MPa, fracture toughness of 5.0 0.4 MPa, Vickers hardness at 9.8 N load of 27.0 0.6 GPa, 1400 C strength of 590 150 MPa and room temperature strength after 1 h oxidation at 1400 C of 660 25 MPa with an oxide layer thickness of 12 1 m. 2 wt.% La2O3 addition to UHTCs slightly reduced mechanical performance while increasing tolerance to property degradation after oxidation and effectively aided internal stress relaxation during spark plasma sintering (SPS) cooling, as quantified by X-ray diffraction (XRD). Slow crack growth was suggested as the failure mechanism at high temperatures as a consequence of sharp cracks formation during oxidation.

  7. Fuzzy and conventional control of high-frequency ventilation.

    Science.gov (United States)

    Noshiro, M; Matsunami, T; Takakuda, K; Ryumae, S; Kagawa, T; Shimizu, M; Fujino, T

    1994-07-01

    A high-frequency ventilator was developed, consisting of a single-phase induction motor, an unbalanced mass and a mechanical vibration system. Intermittent positive pressure respiration was combined with high-frequency ventilation to measure end-tidal pCO2. Hysteresis was observed between the rotational frequency of the high-frequency ventilator and end-tidal pCO2. A fuzzy proportional plus integral control system, designed on the basis of the static characteristics of the controlled system and a knowledge of respiratory physiology, successfully regulated end-tidal pCO2. The characteristics of gas exchange under high-frequency ventilation was approximated by a first-order linear model. A conventional PI control system, designed on the basis of the approximated model, regulated end-tidal pCO2 with a performance similar to that of the fuzzy PI control system. The design of the fuzzy control system required less knowledge about the controlled system than that of the conventional control system.

  8. High frequency optical pulse generation by frequency doubling using polarization rotation

    Science.gov (United States)

    Liu, Yang

    2016-05-01

    In this work, we propose and experimentally characterize a stable 40 GHz optical pulse generation by frequency doubling using polarization rotation in a phase modulator (PM). Only half the electrical driving frequency is required (i.e. 20 GHz); hence the deployment cost can be reduced. Besides, precise control of the bias of the PM is not required. The generated optical pulses have a high center-mode-suppression-ratio (CMSR) of  >  28 dB. The single sideband (SSB) noise spectrum is also measured, and the time-domain waveforms under different CMSRs are also analyzed and discussed.

  9. Planck 2013 results. VI. High Frequency Instrument data processing

    DEFF Research Database (Denmark)

    Ade, P. A. R.; Aghanim, N.; Armitage-Caplan, C.

    2013-01-01

    We describe the processing of the 531 billion raw data samples from the High Frequency Instrument (HFI), which we performed to produce six temperature maps from the first 473 days of Planck-HFI survey data. These maps provide an accurate rendition of the sky emission at 100, 143,217, 353, 545......, these two high frequency channels are calibrated to within 5% and the 353 GHz channel to the percent level. The 100 and217 GHz channels, which together with the 143 GHz channel determine the high-multipole part of the CMB power spectrum (50 ..., and 857 GHz with an angular resolution ranging from 9.07 to 4.06. The detector noise per (effective) beam solid angle is respectively,10, 6 , 12, and 39 µK in the four lowest HFI frequency channels (100-353 GHz) and 13 and 14 kJy sr-1 in the 545 and 857 GHz channels. Relativeto the 143 GHz channel...

  10. High Frequency Amplitude Detector for GMI Magnetic Sensors

    Directory of Open Access Journals (Sweden)

    Aktham Asfour

    2014-12-01

    Full Text Available A new concept of a high-frequency amplitude detector and demodulator for Giant-Magneto-Impedance (GMI sensors is presented. This concept combines a half wave rectifier, with outstanding capabilities and high speed, and a feedback approach that ensures the amplitude detection with easily adjustable gain. The developed detector is capable of measuring high-frequency and very low amplitude signals without the use of diode-based active rectifiers or analog multipliers. The performances of this detector are addressed throughout the paper. The full circuitry of the design is given, together with a comprehensive theoretical study of the concept and experimental validation. The detector has been used for the amplitude measurement of both single frequency and pulsed signals and for the demodulation of amplitude-modulated signals. It has also been successfully integrated in a GMI sensor prototype. Magnetic field and electrical current measurements in open- and closed-loop of this sensor have also been conducted.

  11. Development and in vivo testing of a high frequency endoscopic Raman spectroscopy system for potential applications in the detection of early colonic neoplasia.

    Science.gov (United States)

    Short, Michael A; Wang, Wenbo; Tai, Isabella T; Zeng, Haishan

    2016-01-01

    The objective of this study was to build and test an adjunct system to a colonoscope for in vivo measurement of Raman spectra from colon tissue for potentially improving the detection of early cancers. The novelty of this system was that low cost fibre optic probes were used, without the addition of expensive optical filters. Good quality in vivo Raman spectra were successfully obtained with a 1 s integration time in the high frequency (HF) range from normal tissue and polyps of patients during a colonoscopy. The polyps were subsequently removed, and their pathology determined. The acquired in vivo Raman spectra showed clear changes between tissue with normal and tubular adenoma pathology. Further clinical study with this low cost HF Raman probe is warranted to fully test its clinical utility. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Efficient Design of Sierpinski Fractal Antenna for High Frequency Applications

    Directory of Open Access Journals (Sweden)

    Rajdeep Singh

    2014-08-01

    Full Text Available A wideband published slot antenna appropriate for wireless code division multiple access (WCDMA and sustaining the international interoperability for microwave access (WiMAX applications is planned here. The antenna is fractal line fed and its construction is based on fractal geometry where the resonance frequency of antenna is dropped by applying iteration methods. Fractal antennas are the most suited for aerospace and UWB applications because of their low profile, light weight and low power handling capacity. They can be designed in a variety of shapes in order to obtain enhanced gain and bandwidth, dual band and circular polarization to even ultra-wideband operation. For the simulation process ANSOFT HFSS (high frequency structure simulator has been used. The effect of antenna dimensions and substrate parameters on the performance of antenna have been discussed. The antenna has been designed using the Arlon substrate with relative permittivity of 1.3 and a substrate of Sierpinski Carpet shaped placed on it. Feed used is the fractal line feed. The designed antenna is a low profile, small size and multiband antenna since it can be operated at different frequencies within the frequency range of 4.3GHz to 11GHz. It includes the frequencies used for wireless WCDMA application and used to receive and transmit a high-frequency signal.

  13. High frequency conductivity of hot electrons in carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Amekpewu, M., E-mail: mamek219@gmail.com [Department of Applied Physics, University for Development Studies, Navrongo (Ghana); Mensah, S.Y. [Department of Physics, College of Agriculture and Natural Sciences, U.C.C. (Ghana); Musah, R. [Department of Applied Physics, University for Development Studies, Navrongo (Ghana); Mensah, N.G. [Department of Mathematics, College of Agriculture and Natural Sciences, U.C.C. (Ghana); Abukari, S.S.; Dompreh, K.A. [Department of Physics, College of Agriculture and Natural Sciences, U.C.C. (Ghana)

    2016-05-01

    High frequency conductivity of hot electrons in undoped single walled achiral Carbon Nanotubes (CNTs) under the influence of ac–dc driven fields was considered. We investigated semi-classically Boltzmann's transport equation with and without the presence of the hot electrons’ source by deriving the current densities in CNTs. Plots of the normalized current density versus frequency of ac-field revealed an increase in both the minimum and maximum peaks of normalized current density at lower frequencies as a result of a strong injection of hot electrons. The applied ac-field plays a twofold role of suppressing the space-charge instability in CNTs and simultaneously pumping an energy for lower frequency generation and amplification of THz radiations. These have enormous promising applications in very different areas of science and technology.

  14. High frequency conductivity of hot electrons in carbon nanotubes

    Science.gov (United States)

    Amekpewu, M.; Mensah, S. Y.; Musah, R.; Mensah, N. G.; Abukari, S. S.; Dompreh, K. A.

    2016-05-01

    High frequency conductivity of hot electrons in undoped single walled achiral Carbon Nanotubes (CNTs) under the influence of ac-dc driven fields was considered. We investigated semi-classically Boltzmann's transport equation with and without the presence of the hot electrons' source by deriving the current densities in CNTs. Plots of the normalized current density versus frequency of ac-field revealed an increase in both the minimum and maximum peaks of normalized current density at lower frequencies as a result of a strong injection of hot electrons. The applied ac-field plays a twofold role of suppressing the space-charge instability in CNTs and simultaneously pumping an energy for lower frequency generation and amplification of THz radiations. These have enormous promising applications in very different areas of science and technology.

  15. Realistic simulations of tsunami detection by High-Frequency Radar in British Columbia, Canada

    Science.gov (United States)

    Grilli, Stéphan; Shelby, Michael; Grilli, Annette; Lado Insua, Tania; Guérin, Charles-Antoine

    2016-04-01

    A promising technique for long-range detection of tsunamis is the use of shore-based High Frequency (HF) surface wave radars, also simply referred to as oceanographic radars. These over-the-horizon radars are routinely used for real-time monitoring of ocean surface currents up to a 70-80 km range, based on the Doppler shift the latter cause in ocean waves at the radar Bragg frequency. Quite recently there has been convincing numerical and experimental evidence that oceanographic radars can also be used to detect tsunami-induced surface currents. However, these need to be at least 0.15-0.20 m/s to be detectable, when considering environmental noise and background currents (from tide and mesoscale circulation). This limits the actual detection of tsunami currents to the near range, that is essentially to the continental shelf over which tsunami currents become strong enough; in many cases this does not leave enough time to issue an efficient warning, unless there is a wide shelf. In recent work, some of the authors have proposed a detection algorithm that does not have this limitation and can detect an approaching tsunami in deeper water, beyond the continental shelf. This algorithm does not require "inverting" currents, but instead is based on spatial correlations of the raw signals recorded at two distant radar cells along the same wave ray, shifted in time by the tsunami propagation time along the ray. An elevated correlation would indicate the presence of a tsunami. We apply this algorithm to a realistic tsunami case study conducted, using a state-of-the-art long wave model, for sources (both seismic and landslide) and bathymetry off of Vancouver Island, BC. The propagation time between different radar cells is calculated with a Geometrical Optics approach using the Eikonal equation. This requires first determining wave rays' intersections with radar cells and computing a connectivity matrix between the latter. A model simulating the radar backscattered signal in

  16. General concepts of modern HF communications

    Science.gov (United States)

    Aarons, Jules

    Both conceptual and hardware advancements have led to substantial systems developments in military HF communications; the former encompass coding and error correction techniques for security, in order to minimize propagation and interference, while the latter prominently include digital equipment permitting the selection of a frequency for a particular path and propagation mode, as well as modulation selection. Propagation-related advancements involve better statistical models as well as advancements in short-term forecasting methods responsive to changes in solar-geophysical parameters. Adaptive HF systems have been developed for meteor-scatter radio communications.

  17. Casimir force between δ -δ' mirrors transparent at high frequencies

    Science.gov (United States)

    Braga, Alessandra N.; Silva, Jeferson Danilo L.; Alves, Danilo T.

    2016-12-01

    We investigate, in the context of a real massless scalar field in 1 +1 dimensions, models of partially reflecting mirrors simulated by Dirac δ -δ' point interactions. In the literature, these models do not exhibit full transparency at high frequencies. In order to provide a more realistic feature for these models, we propose a modified δ -δ' point interaction that enables full transparency in the limit of high frequencies. Taking this modified δ -δ' model into account, we investigate the Casimir force, comparing our results with those found in the literature.

  18. Morphology of hydroxyapatite coated nanotube surface of Ti-35Nb-xHf alloys for implant materials

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jae-Un [Functional Coatings Group, Materials Processing Division, Korea Institute of Materials Science (KIMS), Changwon, Kyungnam (Korea, Republic of); Jeong, Yong-Hoon [Department of Dental Materials, Research Center of Nano-Interface Activation for Biomaterials and Research Center for Oral Disease Regulation of the Aged, Chosun University, Gwangju (Korea, Republic of); Division of Restorative and Prosthetic Dentistry, College of Dentistry, The Ohio State University, 305 W. 12th Ave. Columbus, OH (United States); Choe, Han-Cheol, E-mail: hcchoe@chosun.ac.kr [Department of Dental Materials, Research Center of Nano-Interface Activation for Biomaterials and Research Center for Oral Disease Regulation of the Aged, Chosun University, Gwangju (Korea, Republic of)

    2011-11-01

    The purpose of this research is to study the morphology of hydroxyapatite coated nanotube surface of Ti-35Nb-xHf for implant materials using various experiments. For this study, Ti-35Nb-xHf (x = 0, 3, 7 and 15 wt.%) alloys were prepared by arc melting and heat treated for 12 h at 1000 Degree-Sign C in an argon atmosphere and then water quenching. Nanotube formation on the Ti-35Nb-xHf alloys was achieved by anodizing in H{sub 3}PO{sub 4} electrolytes containing 0.8 wt.% NaF at room temperature. Anodization was carried out using an electrochemical method and all experiments were conducted at room temperature. Hydroxyapatite (HA) was deposited on the nanotubular Ti-35Nb-xHf alloys surface for the biomaterials by radio-frequency (RF) magnetron sputtering method. The morphologies of nanotubular and HA coated surface were characterized by X-ray diffractometer (XRD), optical microscopy (OM), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and scanning transmission electron microscopy (STEM). The wettability of HA coated surface was measured by contact angle goniometer. The microstructure of Ti-35Nb-xHf alloys was transformed needle-like to equiaxed structure with Hf content and {alpha} Double-Prime phase decreased, whereas {beta} phase increased as Hf content increased. HA coating surface was affected by microstructure of bulk and morphology of nanotube formation. In case of low Hf content, tip of nanotube formed at {beta} phase was coated with HA film, whereas {alpha} Double-Prime phase was not coated with HA film. In case of high Hf content, nanotube surface was coated uniformly with HA film. The wettability of HA coated nanotubular surface was higher than that of non coated samples.

  19. A Novel Soft Switching PWM Power Frequency Converter with Non DC Smoothing Filter Link for Consumer High Frequency Induction Heating

    Science.gov (United States)

    Sugimura, Hisayuki; Muraoka, Hidekazu; Hiraki, Eiji; Hirota, Izuo; Yasui, Kenji; Omori, Hideki; Lee, Hyun-Woo; Nakaoka, Mutsuo

    In this paper, high frequency power converter without DC smoothing electrolytic capacitor filter link which convert the 100V/200Vrms and 60Hz single phase utility frequency AC power into a high frequency AC. This proposed high frequency AC power converter without electrolytic capacitor filter can operate under a principle of soft switching PWM based on a lossless capacitor snubber is proposed and demonstrated for consumer high frequency induction heating (IH). In particular, this high frequency power converter capable of producing a high frequency AC more than 20kHz is developed for consumer IH applications as hot water producer and steamer based on the specially designed spiral type IH-Dual Packs Heater (DPH), which includes the dual mode pulse modulation control scheme based on soft switching PWM for high output power setting and commercial frequency AC zero voltage soft switching pulse density modulation (PDM) for low output power settings. This developed high frequency power frequency converter using trench gate IGBTs is clarified on the basis of experimental and simulation results for its circuit operation of the utility frequency AC to high frequency AC frequency PWM power converter without the electrolytic capacitor bank DC filter link for the IH hot water and IH steamer. These IH appliances are based upon an innovative electromagnetic IH-DPH for fluid heating as heat exchanger in consumer pipeline. Finally, its power regulation characteristics, power conversion efficiency and harmonic current components characteristics including power factor in utility AC grid side are evaluated and discussed from an experimental point of view. The practical effectiveness of this utility frequency AC to high frequency AC soft switching high power frequency converter defined conveniently as high frequency soft switching cyclo-inverter is proved as one of the important products effective for next generation IH application all electricity power utilizations.

  20. HfO{sub 2}/SiO{sub 2} multilayer enhanced aluminum alloy-based dual-wavelength high reflective optics

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Angela Q. [Johns Hopkins University, The Zanvyl Krieger School of Arts and Sciences, Baltimore, MD 21218 (United States); Corning Advanced Optics, Fairport, NY 14450-1376 (United States); Wang, Jue [Corning Advanced Optics, Fairport, NY 14450-1376 (United States); D' lallo, Michael J.; Platten, Jim E. [Corning Advanced Optics, Fairport, NY 14450-1376 (United States); Crifasi, Joseph C.; Roy, Brian P. [Corning Advanced Optics, Keene, NH 03431 (United States)

    2015-10-01

    Laser durable multiband high reflective optics can be attained by depositing HfO{sub 2}/SiO{sub 2} stacks on diamond-turned and optically polished aluminum alloy substrates. HfO{sub 2} and SiO{sub 2} single layers were prepared using modified plasma-ion assisted deposition. Ellipsometric measurements were performed using two types of variable angle spectroscopic ellipsometry with a combined spectral range of 150 nm to 14 μm. Optical constants were generated in the entire spectral range. Scatter loss as a function of surface roughness was calculated at 1064 nm, 1572 nm, and 4.1 μm, representing a primary wavelength, a secondary wavelength, and a middle wave infrared band selected for a dual-wavelength laser beam expander, respectively. The surface requirement of the aluminum alloy substrates was determined. Calculated and measured spectral reflectances were compared. Laser-induced damage threshold tests were performed at 1064 nm, 20 ns, and 20 Hz. A laser-induced damage threshold of 47 J/cm{sup 2} was determined. Post-damage analysis suggests that nodule defects are the limiting factor for the laser-induced damage threshold. Surface modification of the aluminum alloy was identified as a potential technical solution that may further increase the laser damage resistance of the dielectric enhanced dual-wavelength reflective optics. - Highlights: • A dual-wavelength was considered on dielectric enhanced mirrors. • A modified plasma-ion assisted deposition enabled in-situ plasma smoothing. • Optical constants were derived from deep ultraviolet to long-wave infrared. • Laser-induced damage mechanism was discussed.

  1. Frequencies and amplitudes of high-degree solar oscillations

    Science.gov (United States)

    Kaufman, James Morris

    Measurements of some of the properties of high-degree solar p- and f-mode oscillations are presented. Using high-resolution velocity images from Big Bear Solar Observatory, we have measured mode frequencies, which provide information about the composition and internal structure of the Sun, and mode velocity amplitudes (corrected for the effects of atmospheric seeing), which tell us about the oscillation excitation and damping mechanisms. We present a new and more accurate table of the Sun's acoustic vibration frequencies, nunl, as a function of radial order n and spherical harmonic degree l. These frequencies are averages over azimuthal order m and approximate the normal mode frequencies of a nonrotating spherically symmetric Sun near solar minimum. The frequencies presented here are for solar p- and f-modes with 180 less than or = l less than or = 1920, 0 less than or = n less than or = 8, and 1.7 mHz less than or = nunl less than or = 5.3 mHz. The uncertainties, sigmanl, in the frequencies areas are as low as 3.1 micro-Hz. The theoretically expected f-mode frequencies are given by omega squared = gkh approx. = gl/R, where g is the gravitational acceleration at the surface, kh is the horizontal component of the wave vector, and R is the radius of the Sun. We find that the observed frequencies are significantly less than expected for l greater than 1000, for which we have no explanation. Observations of high-degree oscillations, which have very small spatial features, suffer from the effects of atmospheric image blurring and image motion (or 'seeing'), thereby reducing the amplitudes of their spatial-frequency components. In an attempt to correct the velocity amplitudes for these effects, we simultaneously measured the atmospheric modulation transfer function (MTF) by looking at the effects of seeing on the solar limb. We are able to correct the velocity amplitudes using the MTF out to l approx. = 1200. We find that the frequency of the peak velocity power (as a

  2. Note: High precision measurements using high frequency gigahertz signals

    Science.gov (United States)

    Jin, Aohan; Fu, Siyuan; Sakurai, Atsunori; Liu, Liang; Edman, Fredrik; Pullerits, Tõnu; Öwall, Viktor; Karki, Khadga Jung

    2014-12-01

    Generalized lock-in amplifiers use digital cavities with Q-factors as high as 5 × 108 to measure signals with very high precision. In this Note, we show that generalized lock-in amplifiers can be used to analyze microwave (giga-hertz) signals with a precision of few tens of hertz. We propose that the physical changes in the medium of propagation can be measured precisely by the ultra-high precision measurement of the signal. We provide evidence to our proposition by verifying the Newton's law of cooling by measuring the effect of change in temperature on the phase and amplitude of the signals propagating through two calibrated cables. The technique could be used to precisely measure different physical properties of the propagation medium, for example, the change in length, resistance, etc. Real time implementation of the technique can open up new methodologies of in situ virtual metrology in material design.

  3. Computation of High-Frequency Waves with Random Uncertainty

    KAUST Repository

    Malenova, Gabriela

    2016-01-06

    We consider the forward propagation of uncertainty in high-frequency waves, described by the second order wave equation with highly oscillatory initial data. The main sources of uncertainty are the wave speed and/or the initial phase and amplitude, described by a finite number of random variables with known joint probability distribution. We propose a stochastic spectral asymptotic method [1] for computing the statistics of uncertain output quantities of interest (QoIs), which are often linear or nonlinear functionals of the wave solution and its spatial/temporal derivatives. The numerical scheme combines two techniques: a high-frequency method based on Gaussian beams [2, 3], a sparse stochastic collocation method [4]. The fast spectral convergence of the proposed method depends crucially on the presence of high stochastic regularity of the QoI independent of the wave frequency. In general, the high-frequency wave solutions to parametric hyperbolic equations are highly oscillatory and non-smooth in both physical and stochastic spaces. Consequently, the stochastic regularity of the QoI, which is a functional of the wave solution, may in principle below and depend on frequency. In the present work, we provide theoretical arguments and numerical evidence that physically motivated QoIs based on local averages of |uE|2 are smooth, with derivatives in the stochastic space uniformly bounded in E, where uE and E denote the highly oscillatory wave solution and the short wavelength, respectively. This observable related regularity makes the proposed approach more efficient than current asymptotic approaches based on Monte Carlo sampling techniques.

  4. Nonlinear Conte-Zbilut-Federici (CZF Method of Computing LF/HF Ratio: A More Reliable Index of Changes in Heart Rate Variability

    Directory of Open Access Journals (Sweden)

    Vernon Bond Jr

    2016-09-01

    Full Text Available Objectives: Acupuncture treatments are safe and effective for a wide variety of diseases involving autonomic dysregulation. Heart rate variability (HRV is a noninvasive method for assessing sympathovagal balance. The low frequency/high frequency (LF/HF spectral power ratio is an index of sympathovagal influence on heart rate and of cardi

  5. Planck early results. VI. The High Frequency Instrument data processing

    DEFF Research Database (Denmark)

    Bucher, M.; Castex, G.; Colley, J.-M.

    2011-01-01

    We describe the processing of the 336 billion raw data samples from the High Frequency Instrument (HFI) which we performed to produce six temperature maps from the first 295 days of Planck-HFI survey data. These maps provide an accurate rendition of the sky emission at 100, 143, 217, 353, 545...... and 857 GHz with an angular resolution ranging from 9.9 to 4.4′. The white noise level is around 1.5 μK degree or less in the 3 main CMB channels (100-217 GHz). The photometric accuracy is better than 2% at frequencies between 100 and 353 GHz and around 7% at the two highest frequencies. The maps created...... to be of high quality and we expect that with further refinements of the data processing we should be able to achieve, or exceed, the science goals of the Planck project. © ESO, 2011....

  6. SAFETY AND EFFICACY OF EPLERENONE IN PATIENTS AT HIGH RISK FOR HYPERKALEMIA AND/OR WORSENING RENAL FUNCTION. ANALYSES OF THE EMPHASIS-HF STUDY SUBGROUPS (EPLERENONE IN MILD PATIENTS HOSPITALIZATION AND SURVIVAL STUDY IN HEART FAILURE

    Directory of Open Access Journals (Sweden)

    R. Eschalier

    2014-01-01

    Full Text Available Translation articles:R. Eschalier, J.J.V. McMurray, K. Swedberg, D.J. van Veldhuisen, H. Krum, S.J. Pocock, H. Shi, J. Vincent, P. Rossignol, F. Zannad, B. Pitt, for the EMPHASIS-HF Investigators “Safety and Efficacy of Eplerenone in Patients at High Risk for Hyperkalemia and/or Worsening Renal Function. Analyses of the EMPHASIS-HF Study Subgroups (Eplerenone in Mild Patients Hospitalization And SurvIval Study in Heart Failure”  J Am Coll Cardiol 2013;62(17:1585-93; http://dx.doi.org/10.1016/j.jacc.2013.04.086

  7. The influence of age and high-frequency hearing loss on sensitivity to temporal fine structure at low frequencies (L).

    Science.gov (United States)

    Moore, Brian C J; Glasberg, Brian R; Stoev, Martin; Füllgrabe, Christian; Hopkins, Kathryn

    2012-02-01

    Sensitivity to temporal fine structure (TFS) at low frequencies may be adversely affected by hearing loss at high frequencies even when absolute thresholds at low frequencies are within the normal range. However, in several studies suggesting this, the effects of hearing loss and age were confounded. Here, interaural phase discrimination (IPD) thresholds for pure tones at 500 and 750 Hz were measured for 39 subjects with ages from 61 to 83 yr. All subjects had near-normal audiometric thresholds at low frequencies, but thresholds varied across subjects at high frequencies. IPD thresholds were correlated with age. IPD thresholds for the test frequency of 750 Hz were weakly correlated with absolute thresholds at high frequencies, but these correlations became non-significant when the effect of age was partialed out. The results do not confirm that sensitivity to TFS at low frequencies is influenced by hearing loss at high frequencies, independently of age.

  8. Non trivial effect of strong high-frequency excitation on a nonlinear controlled system

    DEFF Research Database (Denmark)

    Fidlin, A.; Thomsen, Jon Juel

    2004-01-01

    due to control is usually high compared to uncontrolled systems. A standard optimal controller for a standard nonlinear system (a movable cart used to balance a pendulum vertically) is shown to exhibit pronounced bias error in presence of HF-excitation. The bias increases with increased excitation...

  9. High frequency modeling of power transformers. Stresses and diagnostics

    Energy Technology Data Exchange (ETDEWEB)

    Bjerkan, Eilert

    2005-05-15

    In this thesis a reliable, versatile and rigorous method for high frequency power transformer modeling is searched and established. The purpose is to apply this model to sensitivity analysis of FRA (Frequency Response Analysis) which is a quite new diagnostic method for assessing the mechanical integrity of power transformer windings on-site. The method should be versatile in terms of being able to estimate internal and external over voltages and resonances. Another important aspect is that the method chosen is suitable for real transformer geometries. In order to verify the suitability of the model for real transformers, a specific test-object is used. This is a 20MVA transformer, and details are given in chapter 1.4. The high frequency power transformer model is established from geometrical and constructional information from the manufacturer, together with available material characteristics. All circuit parameters in the lumped circuit representation are calculated based on these data. No empirical modifications need to be performed. Comparison shows capability of reasonable accuracy in the range from 10 khz to 1 MHz utilizing a disc-to-disc representation. A compromise between accuracy of model due to discretization and complexity of the model in a turn-to-turn representation is inevitable. The importance of the iron core is emphasized through a comparison of representations with/without the core included. Frequency-dependent phenomena are accurately represented using an isotropic equivalent for windings and core, even with a coarse mesh for the FEM-model. This is achieved through a frequency-dependent complex permeability representation of the materials. This permeability is deduced from an analytical solution of the frequency-dependent magnetic field inside the conductors and the core. The importance of dielectric losses in a transformer model is also assessed. Since published data on the high frequency properties of press board are limited, some initial

  10. Ionosphere research with a HF/MF cubesat radio instrument

    Science.gov (United States)

    Kallio, Esa; Aikio, Anita; Alho, Markku; Fontell, Mathias; Harri, Ari-Matti; Kauristie, Kirsti; Kestilä, Antti; Koskimaa, Petri; Mäkelä, Jakke; Mäkelä, Miika; Turunen, Esa; Vanhamäki, Heikki; Verronen, Pekka

    2017-04-01

    New technology provides new possibilities to study geospace and 3D ionosphere by using spacecraft and computer simulations. A type of nanosatellites, CubeSats, provide a cost effective possibility to provide in-situ measurements in the ionosphere. Moreover, combined CubeSat observations with ground-based observations gives a new view on auroras and associated electromagnetic phenomena. Especially joint and active CubeSat - ground based observation campaigns enable the possibility of studying the 3D structure of the ionosphere. Furthermore using several CubeSats to form satellite constellations enables much higher temporal resolution. At the same time, increasing computation capacity has made it possible to perform simulations where properties of the ionosphere, such as propagation of the electromagnetic waves in the medium frequency, MF (0.3-3 MHz) and high frequency, HF (3-30 MHz), ranges is based on a 3D ionospheric model and on first-principles modelling. Electromagnetic waves at those frequencies are strongly affected by ionospheric electrons and, consequently, those frequencies can be used for studying the plasma. On the other hand, even if the ionosphere originally enables long-range telecommunication at MF and HF frequencies, the frequent occurrence of spatiotemporal variations in the ionosphere disturbs communication channels, especially at high latitudes. Therefore, study of the MF and HF waves in the ionosphere has both a strong science and technology interests. We introduce recently developed simulation models as well as measuring principles and techniques to investigate the arctic ionosphere by a polar orbiting CubeSat whose novel AM radio instrument measures HF and MF waves. The cubesat, which contains also a white light aurora camera, is planned to be launched in late 2017 (http://www.suomi100satelliitti.fi/eng). The new models are (1) a 3D ray tracing model and (2) a 3D full kinetic electromagnetic simulation. We also introduce how combining of the

  11. High-frequency Pulse-tube Refrigerator for 4 K

    Science.gov (United States)

    Tanaeva, I. A.; Klaasse Bos, C. G.; de Waele, A. T. A. M.

    2006-04-01

    At present pulse-tube refrigerators (PTRs), used for the important temperature region of 4 K, are of the Gifford-McMahon (GM)-type. The main sources of losses in GM-type PTRs are the compressor and the rotary valve. The efficiency of the combination of the compressor and the rotary valve is only about 30%. In addition to that GM-type compressors are heavy and need periodic maintenance. The main goal of this research is to develop a Stirling-type 4-K pulse-tube refrigerator. This implies higher operating frequencies, compared to the usual 1-2 Hz. At higher frequencies a number of properties of a pulse-tube system, such as length-to-diameter ratios of the pulse tubes and the regenerator, volume and configuration of a regenerator material, phase-shift control method, etc., change significantly, and, therefore, require detailed study. The interactions between various parameters of the pulse tube and of the linear compressor are very complicated. Therefore, as a first part of this research, we study the pulse tube at high frequencies, independent of the compressor. We generate high-frequency pressure oscillations, using a GM-type compressor and a special type of rotary valve, which enables us to operate at frequencies up to 20 Hz. Results of this work are described in this contribution.

  12. Extremely high-frequency micro-Doppler measurements of humans

    Science.gov (United States)

    Hedden, Abigail S.; Silvious, Jerry L.; Dietlein, Charles R.; Green, Jeremy A.; Wikner, David A.

    2014-05-01

    The development of sensors that are capable of penetrating smoke, dust, fog, clouds, and rain is critical for maintaining situational awareness in degraded visual environments and for providing support to the Warfighter. Atmospheric penetration properties, the ability to form high-resolution imagery with modest apertures, and available source power make the extremely high-frequency (EHF) portion of the spectrum promising for the development of radio frequency (RF) sensors capable of penetrating visual obscurants. Comprehensive phenomenology studies including polarization and backscatter properties of relevant targets are lacking at these frequencies. The Army Research Laboratory (ARL) is developing a fully-polarimetric frequency-modulated continuous-wave (FMCW) instrumentation radar to explore polarization and backscatter properties of in-situ rain, scattering from natural and man-made surfaces, and the radar cross section and micro-Doppler signatures of humans at EHF frequencies, specifically, around the 220 GHz atmospheric window. This work presents an overview of the design and construction of the radar system, hardware performance, data acquisition software, and initial results including an analysis of human micro-Doppler signatures.

  13. Modelling financial high frequency data using point processes

    DEFF Research Database (Denmark)

    Hautsch, Nikolaus; Bauwens, Luc

    In this chapter written for a forthcoming Handbook of Financial Time Series to be published by Springer-Verlag, we review the econometric literature on dynamic duration and intensity processes applied to high frequency financial data, which was boosted by the work of Engle and Russell (1997...

  14. Very High Frequency Interleaved Self-Oscillating Resonant SEPIC Converter

    DEFF Research Database (Denmark)

    Kovacevic, Milovan; Knott, Arnold; Andersen, Michael A. E.

    2013-01-01

    This paper describes analysis and design procedure of an interleaved, self-oscillating resonant SEPIC converter, suitable for operation at very high frequencies (VHF) ranging from 30 MHz to 300 MHz. The presented circuit consists of two resonant SEPIC DC-DC converters, and a capacitive...

  15. Very High Frequency Half Bridge DC/DC Converter

    DEFF Research Database (Denmark)

    Madsen, Mickey Pierre; Knott, Arnold; Andersen, Michael A. E.

    2014-01-01

    This paper presents the first, off chip, class DE (resonant half bridge) converter working in the Very High Frequency (VHF) range. The benefits of using half bridge circuits both in the inverter and rectifier part of a VHF resonant dc/dc converter are analyzed and design equations for all...

  16. Current barriers to confine high frequency common mode currents

    NARCIS (Netherlands)

    Moonen, Dominicus Johannes Guilielmus; Buesink, Frederik Johannes Karel; Leferink, Frank Bernardus Johannes

    2016-01-01

    A commercially produced three phase power line filter is submitted to a Current Barrier (CB) Electro-Magnetic Compatibility (EMC) zoning strategy as an attempt to confine high frequency common mode currents. The intent of the paper is not to show how to build a ’perfect’ filter, since this is known.

  17. High Frequency State-Variable Biquadratic Active Filters

    Directory of Open Access Journals (Sweden)

    T. Dostal

    1998-04-01

    Full Text Available The state-variable (KHN active RC biquadratic filters with good performance in high frequency range , flexibility of outputs (LP, HP, BP, low sensitivities in novel current and hybrid modes, using current conveyors, transimpedance, trans-admittance and current operational amplifiers, are given in this paper.

  18. Modelling financial high frequency data using point processes

    DEFF Research Database (Denmark)

    Hautsch, Nikolaus; Bauwens, Luc

    In this chapter written for a forthcoming Handbook of Financial Time Series to be published by Springer-Verlag, we review the econometric literature on dynamic duration and intensity processes applied to high frequency financial data, which was boosted by the work of Engle and Russell (1997......) on autoregressive duration models...

  19. Piping system subjected to seismic hard rock high frequencies

    Energy Technology Data Exchange (ETDEWEB)

    Rydell, Cecilia, E-mail: cecilia.rydell@byv.kth.se [KTH Royal Institute of Technology, SE-100 44 Stockholm (Sweden); Vattenfall AB, SE-169 92 Stockholm (Sweden); Malm, Richard; Ansell, Anders [KTH Royal Institute of Technology, SE-100 44 Stockholm (Sweden)

    2014-10-15

    Highlights: • A study of the influence of support gaps in the analysis of a piping system. • Piping system located within a nuclear power plant reactor containment building. • Piping system subjected to a seismic hard rock high-frequency load. • Comparison of low- and high-frequency seismic loads. • The influence on the stress response of piping and acceleration response of valves. - Abstract: This paper addresses the influence of support gaps in the analyses of a piping system when subjected to a seismic hard rock high-frequency load. The system is located within the reactor containment building of a nuclear power plant and is assessed to be susceptible to high-frequency loads. The stress response of the pipe and the acceleration response of the valves are evaluated for different support gap sizes. It is shown that the inclusion of the support gaps in the analyses reduces the stress response for almost all pipe elements. On the other hand, the acceleration response of the valves is not necessarily reduced by the consideration of the gaps.

  20. High frequency ultrasound imaging of a single-species biofilm

    NARCIS (Netherlands)

    Shemesh, H.; Goertz, D. E.; van der Sluis, L. W. M.; de Jong, N.; Wu, M. K.; Wesselink, P. R.

    2007-01-01

    Objective: This study evaluated the feasibility of a high frequency ultrasound scan to examine the 3D morphology of Streptococcus mutans biofilms grown in vitro. Methods: Six 2-day S. mutans biofilms and six 7-day biofilms were grown on tissue culture membranes and on bovine dentine discs. A sterile