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Sample records for begets high-frequency magnetism

  1. Metamaterials and the Landau-Lifshitz permeability argument: large permittivity begets high-frequency magnetism.

    Science.gov (United States)

    Merlin, Roberto

    2009-02-10

    Homogeneous composites, or metamaterials, made of dielectric or metallic particles are known to show magnetic properties that contradict arguments by Landau and Lifshitz [Landau LD, Lifshitz EM (1960) Electrodynamics of Continuous Media (Pergamon, Oxford, UK), p 251], indicating that the magnetization and, thus, the permeability, loses its meaning at relatively low frequencies. Here, we show that these arguments do not apply to composites made of substances with Im square root(epsilon(S)) > lambda/l or Re square root(epsilon(S)) approximately lambda/l (epsilon(S) and l are the complex permittivity and the characteristic length of the particles, and lambda > l is the vacuum wavelength). Our general analysis is supported by studies of split rings, one of the most common constituents of electromagnetic metamaterials, and spherical inclusions. An analytical solution is given to the problem of scattering by a small and thin split ring of arbitrary permittivity. Results reveal a close relationship between epsilon(S) and the dynamic magnetic properties of metamaterials. For |square root(epsilon(S))| Landau-Lifshitz argument and similar to that of molecular crystals. In contrast, large values of the permittivity lead to strong diamagnetic or paramagnetic behavior characterized by susceptibilities whose magnitude is significantly larger than that of natural substances. We compiled from the literature a list of materials that show high permittivity at wavelengths in the range 0.3-3000 microm. Calculations for a system of spherical inclusions made of these materials, using the magnetic counterpart to Lorentz-Lorenz formula, uncover large magnetic effects the strength of which diminishes with decreasing wavelength.

  2. 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

  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. 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)

  5. 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.

  6. Motion behavior of non-metallic particles under high frequency magnetic field

    Institute of Scientific and Technical Information of China (English)

    ZHANG Zhong-tao; GUO Qing-tao; YU Feng-yun; LI Jie; ZHANG Jian; LI Ting-ju

    2009-01-01

    Non-metallic particles, especially alumina, are the main inclusions in aluminum and its alloys. Numerical simulation and the corresponding experiments were carried out to study the motion behavior of alumina particles in commercial pure aluminum under high frequency magnetic field. At the meantime, multi-pipe experiment was also done to discuss the prospect of continuous elimination of non-metallic particles under high frequency magnetic field. It is shown that: 1) results of numerical simulation are in good agreement with the experimental results, which certificates the rationality of the simulation model; 2) when the intensity of high frequency magnetic field is 0.06 T, the 30 μm alumina particles in melt inner could migrate to the edge and be removed within 2 s; 3) multi-pipe elimination of alumina particles under high frequency magnetic field is also effective and has a good prospect in industrial application.

  7. High frequency electromagnetic interference shielding magnetic polymer nanocomposites

    Science.gov (United States)

    He, Qingliang

    Electromagnetic interference is one of the most concerned pollution and problem right now since more and more electronic devices have been extensively utilized in our daily lives. Besides the interference, long time exposure to electromagnetic radiation may also result in severe damage to human body. In order to mitigate the undesirable part of the electromagnetic wave energy and maintain the long term sustainable development of our modern civilized society, new technology development based researches have been made to solve this problem. However, one of the major challenges facing to the electromagnetic interference shielding is the relatively low shielding efficiency and the high cost as well as the complicated shielding material manufacture. From the materials science point of view, the key solutions to these challenges are strongly depended on the breakthrough of the current limit of shielding material design and manufacture (such as hierarchical material design with controllable and predictable arrangement in nanoscale particle configuration via an easy in-situ manner). From the chemical engineering point of view, the upgrading of advanced material shielding performance and the enlarged production scale for shielding materials (for example, configure the effective components in the shielding material in order to lower their usage, eliminate the "rate-limiting" step to enlarge the production scale) are of great importance. In this dissertation, the design and preparation of morphology controlled magnetic nanoparticles and their reinforced polypropylene polymer nanocomposites will be covered first. Then, the functionalities of these polymer nanocomposites will be demonstrated. Based on the innovative materials design and synergistic effect on the performance advancement, the magnetic polypropylene polymer nanocomposites with desired multifunctionalities are designed and produced targeting to the electromagnetic interference shielding application. In addition

  8. High-frequency magnetic characteristics of Fe-Co-based nanocrystalline alloy films

    Institute of Scientific and Technical Information of China (English)

    HIHARA; Takehiko; SUMIYAMA; Kenji

    2010-01-01

    Magnetically soft Fe-Co-based nanocrystalline alloy films were produced by two preparation methods:One using a new energetic cluster deposition technique and another using a conventional magnetron sputtering technique.Their structural,static magnetic properties and high-frequency magnetic characteristics were investigated.In the energetic cluster deposition method,by applying a high-bias voltage to a substrate,positively charged clusters in a cluster beam were accelerated electrically and deposited onto a negatively biased substrate together with neutral clusters from the same cluster source,to form a high-density Fe-Co alloy cluster-assembled film with good high-frequency magnetic characteristics.In the conventional magnetron sputtering method,only by rotating substrate holder and without applying a static inducing magnetic field on the substrates,we produced Fe-Co-based nanocrystalline alloy films with a remarkable in-plane uniaxial magnetic anisotropy and a good soft magnetic property.The obtained Fe-Co-O,Fe-Co-Ti-N,and Fe-Co-Cr-N films all revealed a high real permeability exceeding 500 at a frequency up to 1.2 GHz.This makes Fe-Co-based nanocrystalline alloy films potential candidates as soft magnetic thin film materials for the high-frequency applications.

  9. Influence on cell death of high frequency motion of magnetic nanoparticles during magnetic hyperthermia experiments

    Science.gov (United States)

    Hallali, N.; Clerc, P.; Fourmy, D.; Gigoux, V.; Carrey, J.

    2016-07-01

    Studies with transplanted tumors in animals and clinical trials have provided the proof-of-concept of magnetic hyperthermia (MH) therapy of cancers using iron oxide nanoparticles. Interestingly, in several studies, the application of an alternating magnetic field (AMF) to tumor cells having internalized and accumulated magnetic nanoparticles (MNPs) into their lysosomes can induce cell death without detectable temperature increase. To explain these results, among other hypotheses, it was proposed that cell death could be due to the high-frequency translational motion of MNPs under the influence of the AMF gradient generated involuntarily by most inductors. Such mechanical actions of MNPs might cause cellular damages and participate in the induction of cell death under MH conditions. To test this hypothesis, we developed a setup maximizing this effect. It is composed of an anti-Helmholtz coil and two permanent magnets, which produce an AMF gradient and a superimposed static MF. We have measured the MNP heating power and treated tumor cells by a standard AMF and by an AMF gradient, on which was added or not a static magnetic field. We showed that the presence of a static magnetic field prevents MNP heating and cell death in standard MH conditions. The heating power of MNPs in an AMF gradient is weak, position-dependent, and related to the presence of a non-zero AMF. Under an AMF gradient and a static field, no MNP heating and cell death were measured. Consequently, the hypothesis that translational motions could be involved in cell death during MH experiments is ruled out by our experiments.

  10. Determination of the High Frequency Inductance Profile of Surface Mounted Permanent Magnet Synchronous Motors

    DEFF Research Database (Denmark)

    Lu, Kaiyuan; Rasmussen, Peter Omand; Ritchie, Ewen

    2008-01-01

    Accurate knowledge of the high frequency inductance profile plays an important role in many designs of sensorless controllers for Surface inductance. A special algorithm is used to decouple the cross-coupling effects between the d-axis and the q-axis, which allows Mounted Permanent Magnet (SMPM...

  11. Resonance of a Metal Drop under the Effect of Amplitude-Modulated High Frequency Magnetic Field

    Science.gov (United States)

    Guo, Jiahong; Lei, Zuosheng; Zhu, Hongda; Zhang, Lijie; Magnetic Hydrodynamics(Siamm) Team; Magnetic Mechanics; Engineering(Smse) Team

    2016-11-01

    The resonance of a sessile and a levitated drop under the effect of high frequency amplitude-modulated magnetic field (AMMF) is investigated experimentally and numerically. It is a new method to excite resonance of a metal drop, which is different from the case in the presence of a low-frequency magnetic field. The transient contour of the drop is obtained in the experiment and the simulation. The numerical results agree with the experimental results fairly well. At a given frequency and magnetic flux density of the high frequency AMMF, the edge deformations of the drop with an azimuthal wave numbers were excited. A stability diagram of the shape oscillation of the drop and its resonance frequency spectrum are obtained by analysis of the experimental and the numerical data. The results show that the resonance of the drop has a typical character of parametric resonance. The National Natural Science Foundation of China (No. 51274237 and 11372174).

  12. Study on technology of high-frequency pulsed magnetic field strength measurement.

    Science.gov (United States)

    Chen, Yi-Mei; Liu, Zhi-Peng; Yin, Tao

    2012-01-01

    High-frequency transient weak magnetic field is always involved in researches about biomedical engineering field while common magnetic-field sensors cannot work properly at frequencies as high as MHz. To measure the value of MHz-level weak pulsed magnetic-field strength accurately, this paper designs a measurement and calibration method for pulsed magnetic-field. In this paper, a device made of Nonferromagnetic material was independently designed and applied to pulsed magnetic field measurement. It held an accurately relative position between the magnetic field generating coil and the detecting coil. By applying a sinusoidal pulse to the generator, collecting the induced electromotive force of the detector, the final magnetic field strength was worked out through algorithms written in Matlab according to Faraday's Law. Experiments were carried out for measurement and calibration. Experiments showed that, under good stability and consistency, accurate measurement of magnetic-field strength of a sinepulse magnetic-field can be achieved, with frequency at 0.5, 1, 1.5 MHz and strength level at micro-Tesla. Calibration results carried out a measuring relative error about 2.5%.

  13. High-frequency oscillations in small magnetic elements observed with Sunrise/SuFI

    CERN Document Server

    Jafarzadeh, Shahin; Stangalini, M; Steiner, O; Cameron, R H; Danilovic, S

    2016-01-01

    We characterize waves in small magnetic elements and investigate their propagation in the lower solar atmosphere from observations at high spatial and temporal resolution. We use the wavelet transform to analyze oscillations of both horizontal displacement and intensity in magnetic bright points found in the 300 nm and the Ca II H 396.8 nm passbands of the filter imager on board the Sunrise balloon-borne solar observatory. Phase differences between the oscillations at the two atmospheric layers corresponding to the two passbands reveal upward propagating waves at high-frequencies (up to 30 mHz). Weak signatures of standing as well as downward propagating waves are also obtained. Both compressible and incompressible (kink) waves are found in the small-scale magnetic features. The two types of waves have different, although overlapping, period distributions. Two independent estimates give a height difference of approximately 450+-100 km between the two atmospheric layers sampled by the employed spectral bands. ...

  14. Determination of High-Frequency d- and q-axis Inductances for Surface-Mounted Permanent-Magnet Synchronous Machines

    DEFF Research Database (Denmark)

    Lu, Kaiyuan; Vetuschi, M.; Rasmussen, Peter Omand;

    2010-01-01

    This paper presents a reliable method for the experimental determination of high-frequency d- and q -axis inductances for surface-mounted permanent-magnet synchronous machines (SMPMSMs). Knowledge of the high-frequency d- and q-axis inductances plays an important role in the efficient design...

  15. In vitro cytotoxicity of Fe–Cr–Nb–B magnetic nanoparticles under high frequency electromagnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Chiriac, Horia, E-mail: hchiriac@phys-iasi.ro [National Institute of Research and Development for Technical Physics, Iasi (Romania); Petreus, Tudor; Carasevici, Eugen [“Gr.T. Popa” University of Medicine and Pharmacy, Iasi (Romania); Labusca, Luminita; Herea, Dumitru-Daniel; Danceanu, Camelia; Lupu, Nicoleta [National Institute of Research and Development for Technical Physics, Iasi (Romania)

    2015-04-15

    The heating potential, cytotoxicity, and efficiency of Fe{sub 68.2}Cr{sub 11.5}Nb{sub 0.3}B{sub 20} magnetic nanoparticles (MNPs), as such or coated with a chitosan layer, to decrease the cell viability in a cancer cell culture model by using high frequency alternating magnetic fields (AMF) have been studied. The specific absorption rate varied from 215 W/g for chitosan-free MNPs to about 190 W/g for chitosan-coated ones, and an equilibrium temperature of 46 °C was reached when chitosan-coated MNPs were subjected to AMF. The chitosan-free Fe{sub 68.2}Cr{sub 11.5}Nb{sub 0.3}B{sub 20} MNPs proved a good biocompatibility and low cytotoxicity in all testing conditions, while the chitosan-coated ones induced strong tumoricidal effects when a cell–particle simultaneous co-incubation approach was used. In high frequency AMF, the particle-mediated heat treatment has proved to be a critical cause for decreasing in vitro the viability of a cancer cell line.

  16. Complex high-frequency magnetization dynamics and magnetoimpedance in thin films

    Energy Technology Data Exchange (ETDEWEB)

    Silva, R.B. da [Departamento de Fisica, CCNE, Universidade Federal de Santa Maria, 97105-900 Santa Maria, RS (Brazil)]. E-mail: rbarreto1975@gmail.com; Viegas, A.D.C. [Departamento de Fisica, CCNE, Universidade Federal de Santa Maria, 97105-900 Santa Maria, RS (Brazil); Correa, M.A. [Departamento de Fisica, CCNE, Universidade Federal de Santa Maria, 97105-900 Santa Maria, RS (Brazil); Andrade, A.M.H. de [Departamento de Fisica, CCNE, Universidade Federal de Santa Maria, 97105-900 Santa Maria, RS (Brazil); Sommer, R.L. [Centro Brasileiro de Pesquisas Fisicas-CBPF, Rua Dr. Xavier Sigaud 150, Urca, 22290-180, Rio de Janeiro, RJ (Brazil)

    2006-10-01

    High-frequency differential magnetic permeability and magnetoimpedance measurements were performed in Fe{sub 73.5}Cu{sub 1}Nb{sub 3}Si{sub 13.5}B{sub 9} as-made and annealed thin films at frequencies up to 1.8 GHz. The results show complex dynamical properties characterized by multiple ferromagnetic resonance modes at relatively low frequencies for the amorphous as-made sample. After the thermal treatments, the resonance frequencies increase drastically exceeding the upper limit of 1.8 GHz for our equipment. This increase can possibly associated to higher local magnetic fields that are, in turn, associated to the formation of nanocrystalline grains randomly oriented.

  17. Nanomaterial-assisted PCR based on thermal generation from magnetic nanoparticles under high-frequency AC magnetic fields

    Science.gov (United States)

    Higashi, Toshiaki; Minegishi, Hiroaki; Echigo, Akinobu; Nagaoka, Yutaka; Fukuda, Takahiro; Usami, Ron; Maekawa, Toru; Hanajiri, Tatsuro

    2015-08-01

    Here the authors present a nanomaterial-assisted PCR technique based on the use of thermal generation from magnetic nanoparticles (MNPs) under AC magnetic fields. In this approach, MNPs work as internal nano thermal generators to realize PCR thermal cycling. In order to suppress the non-specific absorption of DNA synthetic enzymes, MNPs are decorated with bovine serum albumin (BSA), forming BSA/MNP complexes. Under high-frequency AC magnetic fields, these complexes work as internal nano thermal generators, thereby producing the typical temperature required for PCR thermal cycling, and perform all the reaction processes of PCR amplification in the place of conventional PCR thermal cyclers.

  18. Magnetic properties and high frequency characteristics of FeCoN thin films

    Directory of Open Access Journals (Sweden)

    Tae-Jong Hwang

    2016-05-01

    Full Text Available (Fe65Co35N soft magnetic thin films were prepared by reactive RF magnetron sputtering with the sputtering power of 100 W on thermally oxidized Si substrate in various nitrogen partial pressures (PN2. A strong uniaxial in-plane magnetic anisotropy with the easy-axis coercive field as low as 1∼2 Oe was observed in films grown at PN2 in the range from 3.3% to 5.5%. The saturation magnetizations for those films were about 20 KG. Outside this range, almost isotropic magnetization curves were observed. Vector network analyzer and grounded coplanar waveguide were used to measure the ferromagnetic resonance (FMR signals up to 25 GHz. The FMR signals were detected only in anisotropic films and their FMR frequencies were well fit to the Kittel formula. The obtained g-values and damping parameters at magnetic fields >20 kOe for films grown at PN2 of 3.3%, 4.8% and 5.5% were 1.96, 1.86, 1.92 and 0.0055, 0.0047, 0.0046, respectively. This low damping factor qualifies FeCoN thin films for high-frequency applications.

  19. Magnetic properties and high frequency characteristics of FeCoN thin films

    Science.gov (United States)

    Hwang, Tae-Jong; Lee, Joonsik; Kim, Ki Hyeon; Kim, Dong Ho

    2016-05-01

    (Fe65Co35)N soft magnetic thin films were prepared by reactive RF magnetron sputtering with the sputtering power of 100 W on thermally oxidized Si substrate in various nitrogen partial pressures (PN2). A strong uniaxial in-plane magnetic anisotropy with the easy-axis coercive field as low as 1˜2 Oe was observed in films grown at PN2 in the range from 3.3% to 5.5%. The saturation magnetizations for those films were about 20 KG. Outside this range, almost isotropic magnetization curves were observed. Vector network analyzer and grounded coplanar waveguide were used to measure the ferromagnetic resonance (FMR) signals up to 25 GHz. The FMR signals were detected only in anisotropic films and their FMR frequencies were well fit to the Kittel formula. The obtained g-values and damping parameters at magnetic fields >20 kOe for films grown at PN2 of 3.3%, 4.8% and 5.5% were 1.96, 1.86, 1.92 and 0.0055, 0.0047, 0.0046, respectively. This low damping factor qualifies FeCoN thin films for high-frequency applications.

  20. Effect of Additives on Magnetic Properties of High Frequency MnZn Power Ferrite

    Institute of Scientific and Technical Information of China (English)

    YU Zhong; LAN Zhongwen; WANG Jingmei; ZHANG Yidong; WANG Haocai

    2004-01-01

    The effect of additives,such as CaO and V2O5 on the magnetic properties of high frequency MnZn power ferrite is studied by the conventional ceramic process.As a result,the grain boundary resistivity increases and the power loss declines with the addition of CaO enriched at the grain boundary.By adding an optimum amount of V2O5 which acts indirectly via liquid phase formation and influences the microstructural development during sintering,the crystalline grain of ferrite was refined,the porosity decreases,the amount of grain boundary and the grain boundary resistivity increased,so the power loss is suppressed.

  1. High-frequency Oscillations in Small Magnetic Elements Observed with Sunrise/SuFI

    Science.gov (United States)

    Jafarzadeh, S.; Solanki, S. K.; Stangalini, M.; Steiner, O.; Cameron, R. H.; Danilovic, S.

    2017-04-01

    We characterize waves in small magnetic elements and investigate their propagation in the lower solar atmosphere from observations at high spatial and temporal resolution. We use the wavelet transform to analyze oscillations of both horizontal displacement and intensity in magnetic bright points found in the 300 nm and the Ca ii H 396.8 nm passbands of the filter imager on board the Sunrise balloon-borne solar observatory. Phase differences between the oscillations at the two atmospheric layers corresponding to the two passbands reveal upward propagating waves at high frequencies (up to 30 mHz). Weak signatures of standing as well as downward propagating waves are also obtained. Both compressible and incompressible (kink) waves are found in the small-scale magnetic features. The two types of waves have different, though overlapping, period distributions. Two independent estimates give a height difference of approximately 450 ± 100 km between the two atmospheric layers sampled by the employed spectral bands. This value, together with the determined short travel times of the transverse and longitudinal waves provide us with phase speeds of 29 ± 2 km s‑1 and 31 ± 2 km s‑1, respectively. We speculate that these phase speeds may not reflect the true propagation speeds of the waves. Thus, effects such as the refraction of fast longitudinal waves may contribute to an overestimate of the phase speed.

  2. 3D, LTCC-type, high-frequency magnetic sensors for the TCV Tokamak

    Energy Technology Data Exchange (ETDEWEB)

    Testa, Duccio, E-mail: duccio.testa@epfl.ch [Centre de Recherches en Physique des Plasmas, Ecole Polytechnique Fédérale de Lausanne (Switzerland); Corne, Adrien; Farine, Gaël; Jacq, Caroline; Maeder, Thomas [Laboratoire de Production Microtechnique, Ecole Polytechnique Fédérale de Lausanne (Switzerland); Toussaint, Matthieu [Centre de Recherches en Physique des Plasmas, Ecole Polytechnique Fédérale de Lausanne (Switzerland)

    2015-10-15

    High-frequency, 3D magnetic sensors have been designed and manufactured in-house for installation on the Tokamak à Configuration Variable (TCV). To optimize the in-vessel volume occupation, the sensors are based on combining the Low Temperature Co-fired Ceramic (LTCC) and the classical thick-film technologies. The target requirements for the three measurement axes are an effective area NA{sub EFF} = 100 cm{sup 2} and end-to-end resonant frequency ω{sub 0}/2π = 1 MHz. For the as-built sensors, an effective area NA{sub EFF} ∼ 220 cm{sup 2}, self-inductance L{sub SELF} ∼ 8 μH and self-resonant frequency ω{sub 0}/2π ∼ 16 MHz are obtained for the primary δB{sub NOR} measurement, while NA{sub EFF} ∼ 265 cm{sup 2}, NA{sub EFF} ∼ 300 cm{sup 2}, L{sub SELF} ∼ 150 μH and ω{sub 0}/2π ∼ 5.5 MHz are obtained for the secondary δB{sub TOR} and δB{sub POL} measurements. When including the cabling up to the front-end electronics, ω{sub 0}/2π > 2 MHz is expected for all three measurement axes. To optimize the measurement performance of this new magnetic diagnostic system while limiting the number of elements for the first phase of installation on TCV, five 3D sensors will be installed along the toroidal direction, allowing detection of magnetic perturbations with toroidal mode numbers |n| > 30, thus significantly improving on the previous detection capabilities, which were Nyquist-limited to |n| = 8.

  3. Effect of sintering process on microstructure and magnetic properties of high frequency power ferrite

    Institute of Scientific and Technical Information of China (English)

    SUN Ke; LAN Zhongwen; CHEN Shengming; SUN Yueming; YU Zhong

    2006-01-01

    An oxide ceramic process was adopted to prepare high frequency manganese-zinc (MnZn) power ferrite. In combination with the microstructure analysis of material, the influences of sintering process on initial permeability (μi) and high frequency loss in unit volume (Pcv) of MnZn power ferrite were investigated. The results show that in order to obtain fine microstructure and high frequency properties, the preferable sintering temperature and atmosphere are 1230 ℃ and oxygen partial pressure ( PO2) of 4%, respectively.

  4. Priming theta-burst repetitive transcranial magnetic stimulation with low- and high-frequency stimulation.

    Science.gov (United States)

    Todd, Gabrielle; Flavel, Stanley C; Ridding, Michael C

    2009-05-01

    Repetitive transcranial magnetic stimulation (rTMS) can be used to study metaplasticity in human motor cortex. The term metaplasticity describes a phenomenon where the prior synaptic history of a pathway can affect the subsequent induction of long-term potentiation or depression. In the current study, we investigated metaplasticity in human motor cortex with the use of inhibitory continuous theta-burst stimulation (cTBS). cTBS involves short bursts of high frequency (50 Hz) rTMS applied every 200 ms for 40 s. In the first series of experiments, cTBS was primed with 10 min of intermittent 2 or 6 Hz rTMS. Subjects (n = 20) received priming stimulation at 70% of active motor threshold or 90% of resting motor threshold. In another series of experiments, cTBS was primed with excitatory intermittent theta-burst stimulation (iTBS). iTBS involves a 2 s train of theta-burst stimulation delivered every 10 s for 190 s. Stimuli were delivered over the first dorsal interosseus motor area.. The effect of cTBS alone and primed cTBS on motor cortical excitability was investigated by recording motor-evoked potentials (MEP) in the first dorsal interosseus following single-pulse TMS. MEP area in the cTBS alone condition was not significantly different from cTBS primed with 2 or 6 Hz rTMS. However, priming cTBS with iTBS suppressed MEP area to a greater extent than in cTBS alone. Our results provide further evidence of metaplasticity in human motor cortex when appropriate priming protocols are employed.

  5. Optimized High Frequency Signal Injection Based Permanent Magnet Synchronous Motor Rotor Position Estimation Applied to Washing Machines

    Directory of Open Access Journals (Sweden)

    Olfa B.H.B. Kechiche

    2011-01-01

    Full Text Available Problem statement: This study investigates a novel optimized scheme of a High Frequency Signal Injection (HFSI based sensorless technique in order to carry out a precise and robust rotor position error estimation of a Permanent Magnet Synchronous Motor (PMSM drive designed for washing machines. The study is carried out for standstill condition, where precise position information is required for this application. Approach: In order to get rotor position error information, a PMSM high frequency model is considered in the estimated rotor reference frame (d,q. Then, the impact of the HFSI technique parameters choice on the PMSM rotor position estimation performance is studied and experimentally tested, under various injection conditions. Results: The experimental results show that the amplitude of the high frequency current, resulting from injection, is not significant to carry out high performance rotor position estimation. In order to improve rotor position estimation performance and robustness, a modified demodulation of the high frequency current resulting from injection is proposed by using a high pass filter amplifier applied to PMSM measured currents. The novel proposed rotor position error extraction scheme is implemented on a dsPIC30F6010A and is experimentally validated on a 1kW washing salient pole PMSM. Conclusion: This study presents an improved high frequency voltage injection based sensorless control for Permanent Magnet Synchronous Motor (PMSM designed for washing machines. The optimal parameters choice of the HFSI technique and the use of a high pass filter amplifier have allowed to take the most of the high frequency injected signal for extracting the rotor position error at standstill, compared to a conventional scheme.

  6. High frequency magnetic field technique: mathematical modelling and development of a full scale water fraction meter

    Energy Technology Data Exchange (ETDEWEB)

    Cimpan, Emil

    2004-09-15

    This work is concerned with the development of a new on-line measuring technique to be used in measurements of the water concentration in a two component oil/water or three component (i.e. multiphase) oil/water/gas flow. The technique is based on using non-intrusive coil detectors and experiments were performed both statically (medium at rest) and dynamically (medium flowing through a flow rig). The various coil detectors were constructed with either one or two coils and specially designed electronics were used. The medium was composed by air, machine oil, and water having different conductivity values, i.e. seawater and salt water with various conductivities (salt concentrations) such as 1 S/m, 4.9 S/m and 9.3 S/m. The experimental measurements done with the different mixtures were further used to mathematically model the physical principle used in the technique. This new technique is based on measuring the coil impedance and signal frequency at the self-resonance frequency of the coil to determine the water concentration in the mix. By using numerous coils it was found, experimentally, that generally both the coil impedance and the self-resonance frequency of the coil decreased as the medium conductivity increased. Both the impedance and the self-resonance frequency of the coil depended on the medium loss due to the induced eddy currents within the conductive media in the mixture, i.e. water. In order to detect relatively low values of the medium loss, the self-resonance frequency of the coil and also of the magnetic field penetrating the media should be relatively high (within the MHz range and higher). Therefore, the technique was called and referred to throughout the entire work as the high frequency magnetic field technique (HFMFT). To practically use the HFMFT, it was necessary to circumscribe an analytical frame to this technique. This was done by working out a mathematical model that relates the impedance and the self-resonance frequency of the coil to the

  7. 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

  8. Soft magnetic FeCoTaN film cores for new high-frequency CMOS compatible micro-inductors

    Energy Technology Data Exchange (ETDEWEB)

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

    2007-09-15

    New high-frequency micro-inductors with thin magnetic film cores where developed by R.F.-magnetron sputtering and plasma beam as well as reactive ion etching. In order to realise soft magnetic films with magnetic resonance frequencies in the GHz range determined by frequency-dependent permeability measurements, 6-inch Fe{sub 47}Co{sub 36}Ta{sub 17} and Fe{sub 37}Co{sub 46}Ta{sub 17} targets were used to deposit FeCoTaN-films by reactive R.F.-magnetron sputtering in an Ar/N{sub 2} atmosphere. To obtain soft magnetic film properties with a marked uniaxial in-plane anisotropy needed for the high-frequency suitability, the films were annealed in a static magnetic field at CMOS temperatures of around 400 deg. C. Due to the specific material composition the films possess a nanocrystalline microstructure with a low magnetocrystalline anisotropy. The film material was employed to realise different magnetic cores for new micro-inductor designs fabricated by the CMOS aluminium process.

  9. The gyrokinetic resonant theory of circular polarized high frequency wave driving charged particle in strong magnetic field

    CERN Document Server

    Zhang, Shuangxi; Kishimoto, Yasuaki

    2016-01-01

    This paper studies about circular polarized high frequency wave driving charged particle in strong magnetic field, and a new gyro resonant Lie perturbed transformation theory is given by adding a new total differential term to the original first order 1-form to remove the secularity of relevant infinitesimal generators. The time consumption of numerical simulation based on this resonant theory has an advantage over real orbit simulation if the magnetic field has almost a constant amplitude in the simulation spatial region, while the advantage disappears when the amplitude changes obviously in the simulation spatial region. A simple numerical experiment is given to test the new resonant theory and its time consumption property.

  10. High frequency, high temperature specific core loss and dynamic B-H hysteresis loop characteristics of soft magnetic alloys

    Science.gov (United States)

    Wieserman, W. R.; Schwarze, G. E.; Niedra, J. M.

    1990-01-01

    Limited experimental data exists for the specific core loss and dynamic B-H loops for soft magnetic materials for the combined conditions of high frequency and high temperature. This experimental study investigates the specific core loss and dynamic B-H loop characteristics of Supermalloy and Metglas 2605SC over the frequency range of 1 to 50 kHz and temperature range of 23 to 300 C under sinusoidal voltage excitation. The experimental setup used to conduct the investigation is described. The effects of the maximum magnetic flux density, frequency, and temperature on the specific core loss and on the size and shape of the B-H loops are examined.

  11. Influences of a High Frequency Induction Current on the Uniformity of the Magnetic Field in an Electromagnetic Casting Mould

    CERN Document Server

    Zhang, Lintao; Sienz, Johann

    2013-01-01

    An analysis of the influences of a high frequency (30 kHz) alternating current on the uniformity of the magnetic field (B) in an electromagnetic casting (EMC) mould is investigated by means of parametric numerical simulations where the induction current (Js) varies in the range of [1 to 10000 A]. The results show that values of the magnetic flux density along the casting direction (Bz) near the square mould corners are small, compared to those at the other locations where Js < 10000 A, and that the magnitude of Bz increases with an increased induction current (Js). However, it is shown that, for the EMC mould structure investigated in this paper, the variations of Js have no significant influences on the uniformity of the magnetic field, especially for the regions near molten steel level. Moreover, the effective acting region (Rbz) for the critical magnetic field (Bzc) is first introduced in this paper, which opens an interesting topic for future research.

  12. Controlling the induced anisotropy in soft magnetic films for high-frequency applications

    NARCIS (Netherlands)

    Chezan, A.R.; Craus, C.B.; Chechenin, N.G.; Vystavel, T.; Hosson, J.Th.M. De; Niesen, L.; Boerma, D.O.

    2002-01-01

    Nanocrystalline soft magnetic Fe–Zr–N films were successfully deposited by dc magnetron reactive sputtering. The nitrogen content was controlled by varying the Ar/N2 ratio and/or the substrate temperature. The films have saturation magnetization and induced uniaxial anisotropy values in the range 17

  13. Experimental and numerical results of a high frequency rotating active magnetic refrigerator

    DEFF Research Database (Denmark)

    Lozano, Jaime; Engelbrecht, Kurt; Bahl, Christian;

    2012-01-01

    Experimental results for a recently developed prototype magnetic refrigeration device at The Technical University of Denmark (DTU) were obtained and compared with numerical simulation results. A continuously rotating active magnetic regenerator (AMR) using 2.8 kg packed sphere regenerators...... as a function of cycle frequency was determined. It was found that thermal losses increase as the frequency increases. Therefore, a detailed study of these parasitic losses was carried out experimentally and numerically....

  14. The penetration of plasma clouds across magnetic boundaries the role of high frequency oscillations

    CERN Document Server

    Hurtig, T; Raadu, M A; Hurtig, Tomas; Brenning, Nils; Raadu, Michael A.

    2004-01-01

    Experiments are reported where a collisionfree plasma cloud penetrates a magnetic barrier by self-polarization. We here focus on the resulting anomalous magnetic field diffusion into the plasma cloud, two orders of magnitude faster than classical, which is one important aspect of the plasma cloud penetration mechanism. Without such fast magnetic diffusion, clouds with kinetic beta below unity would not be able to penetrate magnetic barriers at all. Tailor-made diagnostics has been used for measurements in the parameter range with the kinetic beta ? 0.5 to 10, and with normalized width w/r(gi) of the order of unity. Experimental data on hf fluctuations in density and in electric field has been combined to yield the effective anomalous transverse resistivity eta(EFF). It is concluded that they are both dominated by highly nonlinear oscillations in the lower hybrid range, driven by a strong diamagnetic current loop that is set up in the plasma in the penetration process. The anomalous magnetic diffusion rate, ca...

  15. High frequency magnetic fluctuations correlated with the inter-ELM pedestal evolution in ASDEX Upgrade

    Science.gov (United States)

    Laggner, F. M.; Wolfrum, E.; Cavedon, M.; Mink, F.; Viezzer, E.; Dunne, M. G.; Manz, P.; Doerk, H.; Birkenmeier, G.; Fischer, R.; Fietz, S.; Maraschek, M.; Willensdorfer, M.; Aumayr, F.; the EUROfusion MST1 Team; the ASDEX Upgrade Team

    2016-06-01

    In order to understand the mechanisms that determine the structure of the high confinement mode (H-mode) pedestal, the evolution of the plasma edge electron density and temperature profiles between edge localised modes (ELMs) is investigated. The onset of radial magnetic fluctuations with frequencies above 200 kHz is found to correlate with the stagnation of the electron temperature pedestal gradient. During the presence of these magnetic fluctuations the gradients of the edge electron density and temperature are clamped and stable against the ELM onset. The detected magnetic fluctuation frequency is analysed for a variety of plasma discharges with different electron pressure pedestals. It is shown that the magnetic fluctuation frequency scales with the neoclassically estimated \\text{E} × \\text{B} velocity at the plasma edge. This points to a location of the underlying instability in the gradient region. Furthermore, the magnetic signature of these fluctuations indicates a global mode structure with toroidal mode numbers of approximately 10. The fluctuations are also observed on the high field side with significant amplitude, indicating a mode structure that is symmetric on the low field side and high field side. The associated fluctuations in the current on the high field side might be attributed to either a strong peeling part or the presence of non-adiabatic electron response.

  16. Polymer Magnetic Composite Core Based Microcoils and Microtransformers for Very High Frequency Power Applications

    Directory of Open Access Journals (Sweden)

    Saravana Guru Mariappan

    2016-04-01

    Full Text Available We present a rapid prototyping and a cost effective fabrication process on batch fabricated wafer-level micro inductive components with polymer magnetic composite (PMC cores. The new PMC cores provide a possibility to bridge the gap between the non-magnetic and magnetic core inductive devices in terms of both the operating frequency and electrical performance. An optimized fabrication process of molding, casting, and demolding which uses teflon for the molding tool is presented. High permeability NiFeZn powder was mixed with Araldite epoxy to form high resistive PMC cores. Cylindrical PMC cores having a footprint of 0.79 mm 2 were fabricated with varying percentage of the magnetic powder on FR4 substrates. The core influence on the electrical performance of the inductive elements is discussed. Inductor chips having a solenoidal coil as well as transformer chips with primary and secondary coils wound around each other have been fabricated and evaluated. A core with 65% powder equipped with a solenoid made out of 25 µm thick insulated Au wire having 30 turns, yielded a constant inductance value of 2 µH up to the frequency of 50 MHz and a peak quality factor of 13. A 1:1 transformer with similar PMC core and solenoidal coils having 10 turns yielded a maximum efficiency of 84% and a coupling factor of 96%. In order to protect the solenoids and to increase the mechanical robustness and handling of the chips, a novel process was developed to encapsulate the components with an epoxy based magnetic composite. The effect on the electrical performance through the magnetic composite encapsulation is reported as well.

  17. Experimental and numerical results of a high frequency rotating active magnetic refrigerator

    DEFF Research Database (Denmark)

    Lozano, Jaime; Engelbrecht, Kurt; Bahl, Christian R.H.;

    2014-01-01

    Experimental results for a recently developed prototype magnetic refrigeration device at the Technical University of Denmark (DTU) were obtained and compared with numerical simulation results. A continuously rotating active magnetic regenerator (AMR) using 2.8 kg packed sphere regenerators...... and implemented in a one-dimensional numerical AMR model that includes also the parasitic losses from the prototype. The temperature span for a thermal load of 200 W as a function of frequency was measured and modelled. Moreover, the temperature span dependence on the cooling capacity as a function of cycle...

  18. Low and High Frequency Repetitive Transcranial Magnetic Stimulation for the Treatment of Spasticity

    Science.gov (United States)

    Valle, Angela C.; Dionisio, Karen; Pitskel, Naomi Bass; Pascual-Leone, Alvaro; Orsati, Fernanda; Ferreira, Merari J. L.; Boggio, Paulo S.; Lima, Moises C.; Rigonatti, Sergio P.; Fregni, Felipe

    2007-01-01

    The development of non-invasive techniques of cortical stimulation, such as transcranial magnetic stimulation (TMS), has opened new potential avenues for the treatment of neuropsychiatric diseases. We hypothesized that an increase in the activity in the motor cortex by cortical stimulation would increase its inhibitory influence on spinal…

  19. Static and high frequency magnetic properties of FeGa thin films deposited on convex flexible substrates

    Science.gov (United States)

    Yu, Ying; Zhan, Qingfeng; Wei, Jinwu; Wang, Jianbo; Dai, Guohong; Zuo, Zhenghu; Zhang, Xiaoshan; Liu, Yiwei; Yang, Huali; Zhang, Yao; Xie, Shuhong; Wang, Baomin; Li, Run-Wei

    2015-04-01

    Magnetostrictive FeGa thin films were deposited on the bowed flexible polyethylene terephthalate (PET) substrates, which were fixed on the convex mold. A compressive stress was induced in FeGa films when the PET substrates were shaped from convex to flat. Due to the effect of magnetostriction, FeGa films exhibit an obvious in-plane uniaxial magnetic anisotropy which could be enhanced by increasing the applied pre-strains on the substrates during growth. Consequently, the ferromagnetic resonance frequency of the films was significantly increased, but the corresponding initial permeability was decreased. Moreover, the films with pre-strains less than 0.78% exhibit a working bandwidth of microwave absorption about 2 GHz. Our investigations demonstrated a convenient method via the pre-strained substrates to tune the high frequency properties of magnetic thin films which could be applied in flexible microwave devices.

  20. Static and high frequency magnetic properties of FeGa thin films deposited on convex flexible substrates

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Ying [Key Laboratory of Magnetic Materials and Devices and Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Key Laboratory of Low Dimensional Materials and Application Technology of Ministry of Education, School of Materials Science and Engineering, Xiangtan University, Xiangtan, Hunan 411105 (China); Zhan, Qingfeng, E-mail: zhanqf@nimte.ac.cn, E-mail: runweili@nimte.ac.cn; Dai, Guohong; Zuo, Zhenghu; Zhang, Xiaoshan; Liu, Yiwei; Yang, Huali; Zhang, Yao; Wang, Baomin; Li, Run-Wei, E-mail: zhanqf@nimte.ac.cn, E-mail: runweili@nimte.ac.cn [Key Laboratory of Magnetic Materials and Devices and Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Wei, Jinwu; Wang, Jianbo [Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou 730000 (China); Xie, Shuhong [Key Laboratory of Low Dimensional Materials and Application Technology of Ministry of Education, School of Materials Science and Engineering, Xiangtan University, Xiangtan, Hunan 411105 (China)

    2015-04-20

    Magnetostrictive FeGa thin films were deposited on the bowed flexible polyethylene terephthalate (PET) substrates, which were fixed on the convex mold. A compressive stress was induced in FeGa films when the PET substrates were shaped from convex to flat. Due to the effect of magnetostriction, FeGa films exhibit an obvious in-plane uniaxial magnetic anisotropy which could be enhanced by increasing the applied pre-strains on the substrates during growth. Consequently, the ferromagnetic resonance frequency of the films was significantly increased, but the corresponding initial permeability was decreased. Moreover, the films with pre-strains less than 0.78% exhibit a working bandwidth of microwave absorption about 2 GHz. Our investigations demonstrated a convenient method via the pre-strained substrates to tune the high frequency properties of magnetic thin films which could be applied in flexible microwave devices.

  1. Diffusion and Radiation in Magnetized Collisionless Plasmas with High-Frequency Small-Scale Turbulence

    CERN Document Server

    Keenan, Brett D

    2015-01-01

    Magnetized high-energy-density plasmas can often have strong electromagnetic fluctuations whose correlation scale is smaller than the electron Larmor radius. Radiation from the electrons in such plasmas, which markedly differs from both synchrotron and cyclotron radiation, and their energy and pitch-angle diffusion are tightly related. In this paper, we present a comprehensive theoretical and numerical study of the particles' transport in both cold, "small-scale" Langmuir and Whistler-mode turbulence and its relation to the spectra of radiation simultaneously produced by these particles. We emphasize that this relation is a superb diagnostic tool of laboratory, astrophysical, interplanetary, and solar plasmas with a mean magnetic field and strong small-scale turbulence.

  2. 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%.

  3. Magnetic Fields in Evolved Stars: Imaging the Polarized Emission of High-Frequency SiO Masers

    CERN Document Server

    Vlemmings, W H T; Franco-Hernández, R

    2011-01-01

    We present Submillimeter Array observations of high frequency SiO masers around the supergiant VX Sgr and the semi-regular variable star W Hya. The J=5-4, v=1 28SiO and v=0 29SiO masers of VX Sgr are shown to be highly linearly polarized with a polarization from ~5-60%. Assuming the continuum emission peaks at the stellar position, the masers are found within ~60 mas of the star, corresponding to ~100 AU at a distance of 1.57 kpc. The linear polarization vectors are consistent with a large scale magnetic field, with position and inclination angles similar to that of the dipole magnetic field inferred in the H2O and OH maser regions at much larger distances from the star. We thus show for the first time that the magnetic field structure in a circumstellar envelope can remain stable from a few stellar radii out to ~1400 AU. This provides further evidence supporting the existence of large scale and dynamically important magnetic fields around evolved stars. Due to a lack of parallactic angle coverage, the linear...

  4. Modulation of the Left Prefrontal Cortex with High Frequency Repetitive Transcranial Magnetic Stimulation Facilitates Gait in Multiple Sclerosis

    Directory of Open Access Journals (Sweden)

    Amer M. Burhan

    2015-01-01

    Full Text Available Multiple Sclerosis (MS is a chronic central nervous system (CNS demyelinating disease. Gait abnormalities are common and disabling in patients with MS with limited treatment options available. Emerging evidence suggests a role of prefrontal attention networks in modulating gait. High-frequency repetitive transcranial magnetic stimulation (rTMS is known to enhance cortical excitability in stimulated cortex and its correlates. We investigated the effect of high-frequency left prefrontal rTMS on gait parameters in a 51-year-old Caucasian male with chronic relapsing/remitting MS with residual disabling attention and gait symptoms. Patient received 6 Hz, rTMS at 90% motor threshold using figure of eight coil centered on F3 location (using 10-20 electroencephalography (EEG lead localization system. GAITRite gait analysis system was used to collect objective gait measures before and after one session and in another occasion three consecutive daily sessions of rTMS. Two-tailed within subject repeated measure t-test showed significant enhancement in ambulation time, gait velocity, and cadence after three consecutive daily sessions of rTMS. Modulating left prefrontal cortex excitability using rTMS resulted in significant change in gait parameters after three sessions. To our knowledge, this is the first report that demonstrates the effect of rTMS applied to the prefrontal cortex on gait in MS patients.

  5. Performance of High-frequency High-flux Magnetic Cores at Cryogenic Temperatures

    Science.gov (United States)

    Gerber, Scott S.; Hammoud, Ahmad; Elbuluk, Malik E.; Patterson, Richard L.

    2002-01-01

    Three magnetic powder cores and one ferrite core, which are commonly used in inductor and transformer design for switch mode power supplies, were selected for investigation at cryogenic temperatures. The powder cores are Molypermalloy Core (MPC), High Flux Core (HFC), and Kool Mu Core (KMC). The performance of four inductors utilizing these cores has been evaluated as a function of temperature from 20 C to -180 C. All cores were wound with the same wire type and gauge to obtain equal values of inductance at room temperature. Each inductor was evaluated in terms of its inductance, quality (Q) factor, resistance, and dynamic hysteresis characteristics (B-H loop) as a function of temperature and frequency. Both sinusoidal and square wave excitations were used in these investigations. Measured data obtained on the inductance showed that both the MPC and the HFC cores maintain a constant inductance value, whereas with the KMC and ferrite core hold a steady value in inductance with frequency but decrease as temperature is decreased. All cores exhibited dependency, with varying degrees, in their quality factor and resistance on test frequency and temperature. Except for the ferrite, all cores exhibited good stability in the investigated properties with temperature as well as frequency. Details of the experimental procedures and test results are presented and discussed in the paper.

  6. Cortical excitability changes after high-frequency repetitive transcranial magnetic stimulation for central poststroke pain.

    Science.gov (United States)

    Hosomi, Koichi; Kishima, Haruhiko; Oshino, Satoru; Hirata, Masayuki; Tani, Naoki; Maruo, Tomoyuki; Yorifuji, Shiro; Yoshimine, Toshiki; Saitoh, Youichi

    2013-08-01

    Central poststroke pain (CPSP) is one of the most refractory chronic pain syndromes. Repetitive transcranial magnetic stimulation (rTMS) of the primary motor cortex has been demonstrated to provide moderate pain relief for CPSP. However, the mechanism underlying the pain relief remains unclear. The objective of this study was to assess changes in cortical excitability in patients with intractable CPSP before and after rTMS of the primary motor cortex. Subjects were 21 patients with CPSP of the hand who underwent rTMS. The resting motor threshold, the amplitude of the motor evoked potential, duration of the cortical silent period, short interval intracortical inhibition, and intracortical facilitation were measured as parameters of cortical excitability before and after navigation-guided 5 Hz rTMS of the primary motor cortex corresponding to the painful hand. Pain reduction from rTMS was assessed with a visual analog scale. The same parameters were measured in both hemispheres of 8 healthy controls. Eight of 21 patients experienced ≥ 30% pain reduction after rTMS (responders). The resting motor threshold in the patients was higher than those in the controls at baseline (P=.035). Intracortical facilitation in the responders was lower than in the controls and the nonresponders at baseline (P=.035 and P=.019), and significantly increased after rTMS (P=.039). There were no significant differences or changes in the other parameters. Our findings suggest that restoration of abnormal cortical excitability might be one of the mechanisms underlying pain relief as a result of rTMS in CPSP.

  7. Soft magnetic properties of (Ni50Fe50)SiO2 granular thin films for high frequency application

    Institute of Scientific and Technical Information of China (English)

    YANG Xiaolin; GE Shihui; RUAN Chengli

    2006-01-01

    series of (Ni50Fe50)x(SiO2)(1-x) films with different volume fraction x was fabricated by magnetron co-sputtering technique. The microstructure, magnetic and electrical properties were investigated systematically by using X-ray diffraction, transmission electronic microscope, vibrating sample magnetometer and the traditional four point measurement method of resistivity. The results show that the samples consist of nano-scaled Ni50Fe50metallic particles with fcc structure uniformly embedded in amorphous insulating SiO2 matrix, and the particle size decreases with the decrease of x . The rapid change of coercivity with x is observed, and a minimum value 160 A·m-1 of Hc was obtained for the sample of x =0.83 with film thickness of 180 nm, which can be contributed to the exchange coupling between nano-scaled Ni50Fe50 particles. At the frequency lower than 1 GHz, the real part μ' of complex permeability keeps about 110 and the image part μ" is less than 15. Besides, this film exhibits high resistivity ρ=263 μΩ·cm, high saturation magnetization 4π Ms=1.25 T, high in-plane magnetic anisotropy field Hk=6.37 kA·m-1 , and the ferromagnetic resonance (FMR) frequency is estimated to be 2.8 GHz. Therefore, this film can be used in high frequency devices operating over 2 GHz.

  8. Enhanced magnetic domain relaxation frequency and low power losses in Zn2+ substituted manganese ferrites potential for high frequency applications

    Science.gov (United States)

    Praveena, K.; Chen, Hsiao-Wen; Liu, Hsiang-Lin; Sadhana, K.; Murthy, S. R.

    2016-12-01

    Nowadays electronic industries prerequisites magnetic materials, i.e., iron rich materials and their magnetic alloys. However, with the advent of high frequency applications, the standard techniques of reducing eddy current losses, using iron cores, were no longer efficient or cost effective. Current market trends of the switched mode power supplies industries required even low energy losses in power conversion with maintenance of adequate initial permeability. From the above point of view, in the present study we aimed at the production of Manganese-Zinc ferrites prepared via solution combustion method using mixture of fuels and achieved low loss, high saturation magnetization, high permeability, and high magnetic domain relaxation frequency. The as-synthesized Zn2+ substituted MnFe2O4 were characterized by X-ray diffractometer (XRD) and transmission electron microscopy (TEM). The fractions of Mn2+, Zn2+ and Fe2+ cations occupying tetrahedral sites along with Fe occupying octahedral sites within the unit cell of all ferrite samples were estimated by Raman scattering spectroscopy. The magnetic domain relaxation was investigated by inductance spectroscopy (IS) and the observed magnetic domain relaxation frequency (fr) was increased with the increase in grain size. The real and imaginary part of permeability (μ‧ and μ″) increased with frequency and showed a maximum above 100 MHz. This can be explained on the basis of spin rotation and domain wall motion. The saturation magnetization (Ms), remnant magnetization (Mr) and magneton number (μB) decreased gradually with increasing Zn2+ concentration. The decrease in the saturation magnetization was discussed with Yafet-Kittel (Y-K) model. The Zn2+ concentration increases the relative number of ferric ions on the A sites, reduces the A-B interactions. The frequency dependent total power losses decreased as the zinc concentration increased. At 1 MHz, the total power loss (Pt) changed from 358 mW/cm3 for x=0-165 mW/cm3

  9. An air-cooled Litz wire coil for measuring the high frequency hysteresis loops of magnetic samples--a useful setup for magnetic hyperthermia applications.

    Science.gov (United States)

    Connord, V; Mehdaoui, B; Tan, R P; Carrey, J; Respaud, M

    2014-09-01

    A setup for measuring the high-frequency hysteresis loops of magnetic samples is described. An alternating magnetic field in the range 6-100 kHz with amplitude up to 80 mT is produced by a Litz wire coil. The latter is air-cooled using a forced-air approach so no water flow is required to run the setup. High-frequency hysteresis loops are measured using a system of pick-up coils and numerical integration of signals. Reproducible measurements are obtained in the frequency range of 6-56 kHz. Measurement examples on ferrite cylinders and on iron oxide nanoparticle ferrofluids are shown. Comparison with other measurement methods of the hysteresis loop area (complex susceptibility, quasi-static hysteresis loops, and calorific measurements) is provided and shows the coherency of the results obtained with this setup. This setup is well adapted to the magnetic characterization of colloidal solutions of magnetic nanoparticles for magnetic hyperthermia applications.

  10. Unusual dc electric fields induced by a high frequency alternating current in superconducting Nb films under a perpendicular magnetic field

    Science.gov (United States)

    Aliev, F. G.; Levanyuk, A. P.; Villar, R.; Sierra, J. F.; Pryadun, V. V.; Awad, A.; Moshchalkov, V. V.

    2009-06-01

    We report a systematic study of dc electric fields produced by sinusoidal high frequency ac currents in Nb superconducting films subject to a constant magnetic field perpendicular to the film plane. At frequencies in the 100 kHz to MHz range appears a new rectification effect which has not been previously observed at lower frequencies. We have observed the dc electric field generated in this regime in films without intentionally created anisotropic pinning centres, i.e. plain films, both in strip geometry as in cross-shape geometry, and also in films with symmetric periodic pinning centres. The electric field appears in both directions along and transverse to the alternating current and is essentially different at opposite film sides. It depends strongly on the intensity of the magnetic field and may exceed by nearly an order of magnitude the rectified electric fields recently reported at lower frequencies (few kHz) in systems with artificially induced anisotropic vortex pinning. The effect has a non-monotonic dependence on the drive current frequency, being maximum around a few 100 kHz to MHz, and shows a complicated temperature dependence. It is found to be different in long strips and cross shape samples. In the case of films with symmetric periodic pinning centres the rectified voltage shows a lower magnitude than in plain films, and shows an interesting structure when the applied magnetic field crosses the matching fields. We are only able to put forward tentative ideas to explain this phenomenon, which irrespective of its explanation should be taken into account in experimental studies of rectification effects in superconductors.

  11. Head and Neck Veins of the Mouse. A Magnetic Resonance, Micro Computed Tomography and High Frequency Color Doppler Ultrasound Study.

    Directory of Open Access Journals (Sweden)

    Marcello Mancini

    Full Text Available To characterize the anatomy of the venous outflow of the mouse brain using different imaging techniques. Ten C57/black male mice (age range: 7-8 weeks were imaged with high-frequency Ultrasound, Magnetic Resonance Angiography and ex-vivo Microcomputed tomography of the head and neck. Under general anesthesia, Ultrasound of neck veins was performed with a 20 MHz transducer; head and neck Magnetic Resonance Angiography data were collected on 9.4 T or 7 T scanners, and ex-vivo Microcomputed tomography angiography was obtained by filling the vessels with a radiopaque inert silicone rubber compound. All procedures were approved by the local ethical committee. The dorsal intracranial venous system is quite similar in mice and humans. Instead, the mouse Internal Jugular Veins are tiny vessels receiving the sigmoid sinuses and tributaries from cerebellum, occipital lobe and midbrain, while the majority of the cerebral blood, i.e. from the olfactory bulbs and fronto-parietal lobes, is apparently drained through skull base connections into the External Jugular Vein. Three main intra-extracranial anastomoses, absent in humans, are: 1 the petrosquamous sinus, draining into the posterior facial vein, 2 the veins of the olfactory bulb, draining into the superficial temporal vein through a foramen of the frontal bone 3 the cavernous sinus, draining in the External Jugular Vein through a foramen of the sphenoid bone. The anatomical structure of the mouse cranial venous outflow as depicted by Ultrasound, Microcomputed tomography and Magnetic Resonance Angiography is different from humans, with multiple connections between intra- and extra-cranial veins.

  12. Magnetic and High-Frequency Dielectric Parameters of Divalent Ion-Substituted W-Type Hexagonal Ferrites

    Science.gov (United States)

    Ali, Akbar; Grössinger, R.; Imran, Muhammad; Khan, M. Ajmal; Elahi, Asmat; Akhtar, Majid Niaz; Mustafa, Ghulam; Khan, Muhammad Azhar; Ullah, Hafeez; Murtaza, Ghulam; Ahmad, Mukhtar

    2017-02-01

    Polycrystalline W-type hexagonal ferrites with chemical formulae Ba0.5Sr0.5 Co2- x Me x Fe16O27 ( x = 0, 0.5, Me = Mn, Mg, Zn, Ni) have been prepared using sol-gel autocombustion. It has been reported in our earlier published work that all the samples exhibit a single-phase W-type hexagonal structure which was confirmed by x-ray diffraction (XRD) analysis. The values of bulk density lie in the range of 4.64-4.78 g/cm3 for all the samples which are quite high as compared to those for other types of hexaferrites. It was also observed that Zn-substituted ferrite reflects the highest (14.7 × 107 Ω-cm) whereas Mn-substituted ferrite has the lowest (11.3 × 107 Ω-cm) values of direct current (DC) electrical resistivity. The observed values of saturation magnetization ( M s) are found to be in the range of 62.01-68.7 emu/g depending upon the type of cation substitution into the hexagonal lattice. All the samples exhibit a typical soft magnetic character with low values of coercivity ( H c) that are in the range of 26-85 Oe. These ferrites may be promising materials for microwave absorbers due to their higher saturation magnetization and low coercivities. Both the dielectric constant and tangent loss decrease with increasing frequency in the lower frequency region and become constant in the higher frequency region. The much lower dielectric constant obtained in this study makes the investigated ferrites very useful for high-frequency applications, i.e. dielectric resonators and for camouflaging military targets such as ships, tanks and aircrafts, etc.

  13. Increasing the high-frequency magnetic permeability of MnZn ferrite in polyaniline composites by incorporating silver

    Science.gov (United States)

    Babayan, V.; Kazantseva, N. E.; Sapurina, I.; Moučka, R.; Stejskal, J.; Sáha, P.

    2013-05-01

    A hybrid composite containing 73 vol% of MnZn ferrite, 21 vol% of polyaniline, and 6 vol% of silver is obtained by oxidative polymerization of aniline with silver nitrate in the presence of ferrite powder. The hybrid composite contains ferrite particles with a size of 40-80 μm coated by an inhomogeneous layer of polyaniline in the conducting emeraldine form. Silver in the form of nano- and submicrometre -size particles is localized both on the surface of ferrite particles and in the bulk of polyaniline coating. The electrical and magnetic properties of the hybrid composite are investigated and compared with the properties of a composite with 71 vol% of MnZn ferrite coated by a conducting polyaniline layer (29 vol%). The hybrid composite containing silver exhibits an increase in the real and imaginary parts of the complex permeability in the radio-frequency band by more than one and a half times compared with those of the MnZn ferrite-polyaniline composite. The high-frequency permittivity of both composites is determined by the properties of core-shell structure: electric properties of shell as well as its composition and uniformity.

  14. Structural, dielectric and magnetic properties of Cr-Zn doped strontium hexa-ferrites for high frequency applications

    Energy Technology Data Exchange (ETDEWEB)

    Asghar, G. [Applied Thermal Physics Laboratory, Department of Physics, COMSATS Institute of Information Technology, Islamabad 44000 (Pakistan); Anis-ur-Rehman, M., E-mail: rehmananis@hotmail.com [Applied Thermal Physics Laboratory, Department of Physics, COMSATS Institute of Information Technology, Islamabad 44000 (Pakistan)

    2012-06-15

    M-type strontium hexa-ferrite nano particles with composition SrFe{sub 12-2x}Cr{sub x}Zn{sub x}O{sub 19} (X = 0.0, 0.2, 0.4, 0.6, 0.8) were prepared by co-precipitation method and are reported for the first time. X-ray diffraction analysis confirmed the successful substitution of Cr and Zn ions in the strontium hexa-ferrite lattice. Structural morphology studied by scanning electron micrographs revealed that Cr-Zn doping inhabits the grain growth. Dielectric measurements were taken as a function of frequency in the range (10 kHz to 3 MHz). Both dielectric constants and dielectric losses were found to be decreasing with the increase in Cr-Zn concentration. As Cr-Zn doping favored the decrease in dielectric losses to a large extent (0.32-0.02) so the strontium hexa-ferrite with these dopants is very useful for high frequency applications. The frequency dependent ac conductivity increases sharply at higher frequencies due to increase in hopping frequency of electrons and decrease with the increase in doping concentration and this is due to decrease in Fe{sup 2+} ions. Temperature dependent dc electrical resistivity measurements showed a decreasing trend with the increase in Cr-Zn concentration. The M-H loop indicated that both coercivity and saturation magnetization were decreased with the increase in doping concentration. The former was decreased due to increase in grain size and later was decreased due to weak and non-magnetic cations distribution on interstitial sites.

  15. Preliminary Evidence of the Effects of High-frequency Repetitive Transcranial Magnetic Stimulation (rTMS) on Swallowing Functions in Post-Stroke Individuals with Chronic Dysphagia

    Science.gov (United States)

    Cheng, Ivy K. Y.; Chan, Karen M. K.; Wong, C. S.; Cheung, Raymond T. F.

    2015-01-01

    Background: There is growing evidence of potential benefits of repetitive transcranial magnetic stimulation (rTMS) in the rehabilitation of dysphagia. However, the site and frequency of stimulation for optimal effects are not clear. Aims: The aim of this pilot study is to investigate the short-term effects of high-frequency 5 Hz rTMS applied to…

  16. Large Mn25 single-molecule magnet with spin S = 51/2: magnetic and high-frequency electron paramagnetic resonance spectroscopic characterization of a giant spin state.

    Science.gov (United States)

    Murugesu, Muralee; Takahashi, Susumu; Wilson, Anthony; Abboud, Khalil A; Wernsdorfer, Wolfgang; Hill, Stephen; Christou, George

    2008-10-20

    The synthesis and structural, spectroscopic, and magnetic characterization of a Mn25 coordination cluster with a large ground-state spin of S = 51/2 are reported. Reaction of MnCl2 with pyridine-2,6-dimethanol (pdmH2) and NaN3 in MeCN/MeOH gives the mixed valence cluster [Mn25O18(OH)2(N3)12(pdm)6(pdmH)6]Cl2 (1; 6Mn(II), 18Mn(III), Mn(IV)), which has a barrel-like cage structure. Variable temperature direct current (dc) magnetic susceptibility data were collected in the 1.8-300 K temperature range in a 0.1 T field. Variable-temperature and -field magnetization (M) data were collected in the 1.8-4.0 K and 0.1-7 T ranges and fit by matrix diagonalization assuming only the ground state is occupied at these temperatures. The fit parameters were S = 51/2, D = -0.020(2) cm(-1), and g = 1.87(3), where D is the axial zero-field splitting parameter. Alternating current (ac) susceptibility measurements in the 1.8-8.0 K range and a 3.5 G ac field oscillating at frequencies in the 50-1500 Hz range revealed a frequency-dependent out-of-phase (chi(M)'') signal below 3 K, suggesting 1 to be a single-molecule magnet (SMM). This was confirmed by magnetization vs dc field sweeps, which exhibited hysteresis loops but with no clear steps characteristic of resonant quantum tunneling of magnetization (QTM). However, magnetization decay data below 1 K were collected and used to construct an Arrhenius plot, and the fit of the thermally activated region above approximately 0.5 K gave U(eff)/k = 12 K, where U(eff) is the effective relaxation barrier. The g value and the magnitude and sign of the D value were independently confirmed by detailed high-frequency electron paramagnetic resonance (HFEPR) spectroscopy on polycrystalline samples. The combined studies confirm both the high ground-state spin S = 51/2 of complex 1 and that it is a SMM that, in addition, exhibits QTM.

  17. 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.)

  18. High-frequency electromagnetic properties of soft magnetic Nd2Co17 micron flakes fractured along c crystal plane with natural resonance frequency exceeding 10 GHz

    Science.gov (United States)

    Zhang, Yongbo; Wang, Peng; Ma, Tianyong; Wang, Ying; Qiao, Liang; Wang, Tao

    2016-02-01

    Planar anisotropy Nd2Co17 flakes fractured along c crystal plane were fabricated by surfactant-assisted high-energy ball milling technique. The magnetic flakes have a diameter range of 5-20 μm and a typical thickness of approximately 120 nm. The frequency dependence of complex permeability of Nd2Co17 epoxy resin composite has been investigated in the frequency range of 0.1-18 GHz. The measurement results show that the natural resonance frequency reaches 12.5 GHz while the initial permeability survives up to 2.26. The superior high frequency properties come from the large out-of-plane anisotropy field and the flake structure fractured along the c crystal plane of Nd2Co17. The planar anisotropic Nd2Co17 flakes have significant potential applications in the high-frequency devices working in the frequency beyond 10 GHz.

  19. 纳米高频软磁薄膜材料研究进展%Recent Progress on Nanostructured High Frequency Soft Magnetic Thin Films

    Institute of Scientific and Technical Information of China (English)

    王艺程; 张怀武; 鲁广铎; 白飞明

    2012-01-01

    Soft magnetic thin films have attracted much attention due to their great potentials in high frequency applications. The article summarizes the recent progress of nanocrystalline alloy soft magnetic films, nanogranular soft magnetic films, muhilayer films and graphical films, respectively. Special attentions were given to the film preparation techniques, the chemical composition, the microstructure and the high frequency physical properties of the different films, and the main factors affecting the magnetic and high frequency properties were also discussed. Because of the much better properties and performance, nanocrystalline alloy soft magnetic films have replaced the ferrites as the major materials used in high frequency devices. Meanwhile, nanogranular soft magnetic films, multilayer films and emerging graphical films will be the trend in future, thanks to their great freedom in designing microstructure and tailoring materials properties.%由于高频软磁薄膜材料具有巨大的应用前景因此获得了人们广泛的关注。对纳米合金软磁薄膜、纳米软磁颗粒膜、多层膜以及图形化薄膜进行了分类综述,分别介绍了各类薄膜的制备方法、化学成分、微观结构特点和高频物理性能,并对影响其性能的主要因素进行了讨论。由于纳米高频软磁薄膜材料相对于传统磁性材料具有显著优势,所以纳米合金软磁薄膜有望取代铁氧体作为制作高频磁性器件的主要应用材料。由于纳米软磁颗粒膜、多层膜以及新兴的图形化薄膜具有材料结构设计和物性剪裁的自由度,因此将是今后的重点研究方向。

  20. The impact of high-frequency magnetic stimulation of peripheral nerves: muscle hardness, venous blood flow, and motor function of upper extremity in healthy subjects.

    Science.gov (United States)

    Okudera, Yoshihiko; Matsunaga, Toshiki; Sato, Mineyoshi; Chida, Satoaki; Hatakeyama, Kazutoshi; Watanabe, Motoyuki; Shimada, Yoichi

    2015-01-01

    The purpose of this study was to investigate the impact of high-frequency peripheral nerve magnetic stimulation on the upper limb function. Twenty-five healthy adults (16 men and 9 women) participated in this study. The radial nerve of the non-dominant hand was stimulated by high-frequency magnetic stimulation device. A total of 600 impulses were applied at a frequency of 20 Hz and intensity of 1.2 resting motor threshold (rMT). At three time points (before, immediately after, and 15 min after stimulation), muscle hardness of the extensor digitorum muscle on the stimulated side was measured using a mechanical tissue hardness meter and a shear wave imaging device, cephalic venous blood flow on the stimulated side was measured using an ultrasound system, and the Box and Block test (BBT) was performed. Mechanical tissue hardness results did not show any significant differences between before, immediately after, and 15 min after stimulation. Measurements via shear wave imaging showed that muscle hardness significantly decreased both immediately and 15 min after stimulation compared to before stimulation (P nerve magnetic stimulation can achieve effects similar to electrical stimulation in a less invasive manner, and may therefore become an important element in next-generation rehabilitation.

  1. High-Frequency Repetitive Transcranial Magnetic Stimulation (rTMS) Improves Functional Recovery by Enhancing Neurogenesis and Activating BDNF/TrkB Signaling in Ischemic Rats

    Science.gov (United States)

    Luo, Jing; Zheng, Haiqing; Zhang, Liying; Zhang, Qingjie; Li, Lili; Pei, Zhong; Hu, Xiquan

    2017-01-01

    Repetitive transcranial magnetic stimulation (rTMS) has rapidly become an attractive therapeutic approach for stroke. However, the mechanisms underlying this remain elusive. This study aimed to investigate whether high-frequency rTMS improves functional recovery mediated by enhanced neurogenesis and activation of brain-derived neurotrophic factor (BDNF)/tropomyosin-related kinase B (TrkB) pathway and to compare the effect of conventional 20 Hz rTMS and intermittent theta burst stimulation (iTBS) on ischemic rats. Rats after rTMS were sacrificed seven and 14 days after middle cerebral artery occlusion (MCAO), following evaluation of neurological function. Neurogenesis was measured using specific markers: Ki67, Nestin, doublecortin (DCX), NeuN and glial fibrillary acidic protein (GFAP), and the expression levels of BDNF were visualized by Western blotting and RT-PCR analysis. Both high-frequency rTMS methods significantly improved neurological function and reduced infarct volume. Moreover, 20 Hz rTMS and iTBS significantly promoted neurogenesis, shown by an increase of Ki67/DCX, Ki67/Nestin, and Ki67/NeuN-positive cells in the peri-infarct striatum. These beneficial effects were accompanied by elevated protein levels of BDNF and phosphorylated-TrkB. In conclusion, high-frequency rTMS improves functional recovery possibly by enhancing neurogenesis and activating BDNF/TrkB signaling pathway and conventional 20 Hz rTMS is better than iTBS at enhancing neurogenesis in ischemic rats. PMID:28230741

  2. High-Frequency Repetitive Transcranial Magnetic Stimulation (rTMS Improves Functional Recovery by Enhancing Neurogenesis and Activating BDNF/TrkB Signaling in Ischemic Rats

    Directory of Open Access Journals (Sweden)

    Jing Luo

    2017-02-01

    Full Text Available Repetitive transcranial magnetic stimulation (rTMS has rapidly become an attractive therapeutic approach for stroke. However, the mechanisms underlying this remain elusive. This study aimed to investigate whether high-frequency rTMS improves functional recovery mediated by enhanced neurogenesis and activation of brain-derived neurotrophic factor (BDNF/tropomyosin-related kinase B (TrkB pathway and to compare the effect of conventional 20 Hz rTMS and intermittent theta burst stimulation (iTBS on ischemic rats. Rats after rTMS were sacrificed seven and 14 days after middle cerebral artery occlusion (MCAO, following evaluation of neurological function. Neurogenesis was measured using specific markers: Ki67, Nestin, doublecortin (DCX, NeuN and glial fibrillary acidic protein (GFAP, and the expression levels of BDNF were visualized by Western blotting and RT-PCR analysis. Both high-frequency rTMS methods significantly improved neurological function and reduced infarct volume. Moreover, 20 Hz rTMS and iTBS significantly promoted neurogenesis, shown by an increase of Ki67/DCX, Ki67/Nestin, and Ki67/NeuN-positive cells in the peri-infarct striatum. These beneficial effects were accompanied by elevated protein levels of BDNF and phosphorylated-TrkB. In conclusion, high-frequency rTMS improves functional recovery possibly by enhancing neurogenesis and activating BDNF/TrkB signaling pathway and conventional 20 Hz rTMS is better than iTBS at enhancing neurogenesis in ischemic rats.

  3. High-Frequency Repetitive Transcranial Magnetic Stimulation (rTMS) Improves Functional Recovery by Enhancing Neurogenesis and Activating BDNF/TrkB Signaling in Ischemic Rats.

    Science.gov (United States)

    Luo, Jing; Zheng, Haiqing; Zhang, Liying; Zhang, Qingjie; Li, Lili; Pei, Zhong; Hu, Xiquan

    2017-02-20

    Repetitive transcranial magnetic stimulation (rTMS) has rapidly become an attractive therapeutic approach for stroke. However, the mechanisms underlying this remain elusive. This study aimed to investigate whether high-frequency rTMS improves functional recovery mediated by enhanced neurogenesis and activation of brain-derived neurotrophic factor (BDNF)/tropomyosin-related kinase B (TrkB) pathway and to compare the effect of conventional 20 Hz rTMS and intermittent theta burst stimulation (iTBS) on ischemic rats. Rats after rTMS were sacrificed seven and 14 days after middle cerebral artery occlusion (MCAO), following evaluation of neurological function. Neurogenesis was measured using specific markers: Ki67, Nestin, doublecortin (DCX), NeuN and glial fibrillary acidic protein (GFAP), and the expression levels of BDNF were visualized by Western blotting and RT-PCR analysis. Both high-frequency rTMS methods significantly improved neurological function and reduced infarct volume. Moreover, 20 Hz rTMS and iTBS significantly promoted neurogenesis, shown by an increase of Ki67/DCX, Ki67/Nestin, and Ki67/NeuN-positive cells in the peri-infarct striatum. These beneficial effects were accompanied by elevated protein levels of BDNF and phosphorylated-TrkB. In conclusion, high-frequency rTMS improves functional recovery possibly by enhancing neurogenesis and activating BDNF/TrkB signaling pathway and conventional 20 Hz rTMS is better than iTBS at enhancing neurogenesis in ischemic rats.

  4. High frequency variations of the main magnetic field: convergence of observations and theory (Petrus Peregrinus Medal Lecture)

    Science.gov (United States)

    Jault, Dominique

    2013-04-01

    Understanding the main magnetic field variations has been hindered by the discrepancy between the periods (from months to years) of the simplest linear wave phenomena and the relatively long time intervals (10 to 100 years) over which magnetic field changes can be confidently monitored. A theoretical description of short-period waves within the Earth's fluid core is at hand. Quasi-geostrophic inertial waves (akin to Rossby waves in the atmosphere) are slightly modified in the presence of magnetic fields and torsional oscillations consist of differential motion between coaxial rigid cylindrical annuli. Torsional oscillations are sensitive to the whole magnetic field that they shear in the course of their propagation. From their modelling, we have thus gained an estimate for the magnetic field strength in the core interior. There is now ongoing work to extend the theoretical framework to longer times. Furthermore, data collected from the Swarm constellation of three satellites to be launched this year by ESA will permit to better separate the internal and external magnetic signals. We may thus dream to detect quasi-geostrophic inertial waves. As the spectral ranges of theoretical models and observations begin to overlap, we can now go beyond the understanding of the magnetic field variations as the juxtaposition of partial models, arranged as a set of nested Matryoshka dolls. This talk will give illustrations for this statement, among which the question of induction in the lower mantle.

  5. Error Analysis of High Frequency Core Loss Measurement for Low-Permeability Low-Loss Magnetic Cores

    DEFF Research Database (Denmark)

    Niroumand, Farideh Javidi; Nymand, Morten

    2016-01-01

    Magnetic components significantly contribute to the dissipated loss in power electronic converters. Measuring the true value of dissipated power in these components is highly desirable, since it can be used to verify the optimum design of these components. The common approach for measuring the loss....... The analysis has been validated by experimental measurements for relatively low-loss magnetic cores with different permeability values....... in magnetic cores is B-H loop measurement where two windings are placed on the core under test. However, this method is highly vulnerable to phase shift error, especially for low-permeability, low-loss cores. Due to soft saturation and very low core loss, low-permeability low-loss magnetic cores are favorable...

  6. Brain responses evoked by high-frequency repetitive transcranial magnetic stimulation: an event-related potential study

    NARCIS (Netherlands)

    M. Hamidi; H.A. Slagter; G. Tononi; B.R. Postle

    2010-01-01

    Background Many recent studies have used repetitive transcranial magnetic stimulation (rTMS) to study brain-behavior relationships. However, the pulse-to-pulse neural effects of rapid delivery of multiple TMS pulses are unknown largely because of TMS-evoked electrical artifacts limiting recording of

  7. Zero-field splitting in pseudotetrahedral Co(II) complexes: a magnetic, high-frequency and -field EPR, and computational study.

    Science.gov (United States)

    Idešicová, Monika; Titiš, Ján; Krzystek, J; Boča, Roman

    2013-08-19

    Six pseudotetrahedral cobalt(II) complexes of the type [CoL2Cl2], with L = heterocyclic N-donor ligand, have been studied in parallel by magnetometry, and high-frequency and -field electron paramagnetic resonance (HFEPR). HFEPR powder spectra were recorded in a 50 GHz < ν < 700 GHz range in a 17 T superconducting and 25 T resistive magnet, which allowed constructing of resonance field vs frequency diagrams from which the fitting procedure yielded the S = 3/2 spin ground state Hamiltonian parameters. The sign of the axial anisotropy parameter D was determined unambiguously; the values range between -8 and +11 cm(-1) for the given series of complexes. These data agree well with magnetometric analysis. Finally, quantum chemical ab initio calculations were performed on the whole series of complexes to probe the relationship between the magnetic anisotropy, electronic, and geometric structure.

  8. Time-of-flight measurements in atomic beam devices using adiabatic high frequency transitions and sextupole magnets

    CERN Document Server

    Baumgarten, C; Brunn, I; Court, G; Ciullo, G; Ferretti, P; Golendukhin, A; Graw, G; Haeberli, W; Henoch, M; Hertenberger, R; Koch, N; Kolster, H; Lenisa, P; Nass, A; Podyachev, S P; Reggiani, D; Rith, K; Simani, M C; Steffens, E; Stewart, J; Wise, T

    2002-01-01

    Atomic beam devices are frequently equipped with sextupole magnets to focus the beam or to act as spin filters in combination with RF-transitions for manipulating the hyperfine population within the atomic beam. A useful tool for the analysis of sextupole systems, the application of time-of-flight (TOF) measurements is presented. TOF measurements are enabled without mechanical beam chopper by utilizing adiabatic radio frequency transitions to select atoms within a certain time interval. This method is especially interesting for the use in atomic beam devices that are already equipped with RF-transitions and sextupole magnets and where space limitations or the required quality of the vacuum do not allow the installation of a mechanical chopper. The measurements presented here were performed with the atomic beam polarimeter of the HERMES polarized deuterium target and the results have been used to optimize the sextupole system of the polarimeter.

  9. High-frequency magnetic permeability of single- and multilayered (Co41Fe39B20) x (SiO2)100- x nanocomposites

    Science.gov (United States)

    Tarasova, O. S.; Sitnikov, A. V.; Kalinin, Yu. E.; Starostenko, S. N.; Granovskii, A. B.

    2016-12-01

    Thin film single-layered (Co41Fe39B20) x (SiO2)100- x nanocomposites at x = 30-80 at % and multilayered nanocomposites composed of 176 pairs of [(Co41Fe39B20)60(SiO2)40]/[(Co41Fe39B20)60(SiO2)40 + O2] have been prepared via ion-beam sputtering of the complex target. The concentration dependences of the magnetic permeability of single-layered films at a frequency of 50 MHz are characterized by maximum losses near x = 60 at %, whereas the percolation threshold with respect to the electric conductivity is x = 50 at %. The high-frequency magnetic permeability of films has been measured by the resonator method in the frequency range of 0.1—10 GHz. As is shown, while the single-layer film passes to the multilayered structure, the ferromagnetic resonance frequency shifts from 1.5 to 2.5 GHz, and the imaginary part of the magnetic permeability attains 200 that is presumably due to the inhibition of the perpendicular magnetic anisotropy component.

  10. Giant magnetoimpedance and high frequency electrical detection of magnetic transition in La{sub 0.75}Sr{sub 0.25}MnO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Barik, S K; Rebello, A; Tan, C L; Mahendiran, R [Department of Physics, Faculty of Science, National University of Singapore 2 Science Drive 3, Singapore-117542 (Singapore)

    2008-01-21

    We show that high frequency electrical transport is an efficient technique for detecting the magnetic transition hidden by the scattering of charges at grain boundaries in colossal magnetoresistive oxides, even in the absence of any external magnetic field. The dc resistivity which shows only a weak anomaly at the Curie temperature in La{sub 0.75}Sr{sub 0.25} MnO{sub 3} transforms into abrupt jumps in both resistive (Z') and reactive (Z-prime) parts of the ac impedance, Z(f, T, H) = Z'(f, T, H) + jZ-prime(f, T, H) at higher frequencies (f = 0.1-5 MHz). The anomaly in Z' and Z-prime at T{sub C} decreases as much as 19% and 15%, respectively, in a dc magnetic field of H 65 mT compared with 1% dc magnetoresistance, suggesting a possible giant low-field magnetoimpedance effect which could be exploited for room temperature practical applications. We interpret our observations due to changes in the magnetic penetration depth induced by the spontaneous ordering of spins and by the applied field. (fast track communication)

  11. A JVLA survey of the high-frequency radio emission of the massive magnetic B- and O-type stars

    Science.gov (United States)

    Kurapati, Sushma; Chandra, Poonam; Wade, Gregg; Cohen, David H.; David-Uraz, Alexandre; Gagne, Marc; Grunhut, Jason; Oksala, Mary E.; Petit, Veronique; Shultz, Matt; Sundqvist, Jon; Townsend, Richard H. D.; ud-Doula, Asif

    2017-02-01

    We conducted a survey of seven magnetic O-type stars and eleven B-type stars with masses above 8 M⊙ using the Very Large Array in the 1, 3 and 13 cm bands. The survey resulted in a detection of two O- and two B-type stars. While the detected O-type stars - HD 37742 and HD 47129 - are in binary systems, the detected B-type stars, HD 156424 and ALS 9522, are not known to be in binaries. All four stars were detected at 3 cm, whereas three were detected at 1 cm and only one star was detected at 13 cm. The detected B-type stars are significantly more radio luminous than the non-detected ones, which is not the case for O-type stars. The non-detections at 13 cm are interpreted as due to thermal free-free absorption. Mass-loss rates were estimated using 3 cm flux densities and were compared with theoretical mass-loss rates, which assume free-free emission. For HD 37742, the two values of the mass-loss rates were in good agreement, possibly suggesting that the radio emission for this star is mainly thermal. For the other three stars, the estimated mass-loss rates from radio observations were much higher than those expected from theory, suggesting either a possible contribution from non-thermal emission from the magnetic star or thermal or non-thermal emission due to interacting winds of the binary system, especially for HD 47129. All the detected stars are predicted to host centrifugal magnetospheres except HD 37742, which is likely to host a dynamical magnetosphere. This suggests that non-thermal radio emission is favoured in stars with centrifugal magnetospheres.

  12. Cortical excitability in patients with focal epilepsy: a study with high frequency repetitive transcranial magnetic stimulation (rTMS

    Directory of Open Access Journals (Sweden)

    Maria Gabriele

    2008-12-01

    Full Text Available Epileptogenesis involves an increase in excitatory synaptic strength in the brain in a manner similar to synaptic potentiation. In the present study we investigated the mechanisms of short-term synaptic potentiation in patients with focal epilepsy by using 5 Hz repetitive transcranial magnetic stimulation (rTMS, a non invasive neurophysiological technique able to investigate the mechanisms of synaptic plasticity in humans. Ten patients with focal idiopathic cortical epilepsy were studied. 5 Hz-rTMS (10 stimuli-trains, 120% of motor threshold, RMT was delivered over the first dorsal interosseus (FDI motor area of both (affected and unaffected hemispheres. Changes in the motor evoked potential (MEP size in the FDI muscle during the trains and the RMT were measured and compared between the hemispheres. 5 Hz-rTMS was also delivered in a group of healthy subjects over both hemispheres. 5 Hz-rTMS in patients elicited a reduced MEP facilitation compared to normal subjects. The reduced MEP amplitude was more evident in the affected hemisphere than in the unaffected hemisphere. RMT in the affected hemisphere was higher than in the unaffected hemisphere and in healthy subjects. Our findings showing a decreased response to 5 Hz-rTMS over the affected hemisphere, differently from the expected results suggest a reduced cortical excitability in epileptic patients. We hypothesize an altered balance between excitatory and inhibitory circuits in epileptic patients under chronic therapy.

  13. A JVLA survey of the high frequency radio emission of the massive magnetic B- and O-type stars

    CERN Document Server

    Kurapati, Sushma; Wade, Gregg; Cohen, David H; David-Uraz, Alexandre; Gagne, Marc; Grunhut, Jason; Oksala, Mary E; Petit, Veronique; Shultz, Matt; Sundqvist, Jon; Townsend, Richard H D; ud-Doula, Asif

    2016-01-01

    We conducted a survey of seven magnetic O and eleven B-type stars with masses above $8M_{\\odot}$ using the Very Large Array in the 1cm, 3cm and 13cm bands. The survey resulted in a detection of two O and two B-type stars. While the detected O-type stars - HD 37742 and HD 47129 - are in binary systems, the detected B-type stars, HD 156424 and ALS 9522, are not known to be in binaries. All four stars were detected at 3cm, whereas three were detected at 1cm and only one star was detected at 13cm. The detected B-type stars are significantly more radio luminous than the non-detected ones, which is not the case for O-type stars. The non-detections at 13cm are interpreted as due to thermal free-free absorption. Mass-loss rates were estimated using 3cm flux densities and were compared with theoretical mass-loss rates, which assume free-free emission. For HD 37742, the two values of the mass-loss rates were in good agreement, possibly suggesting that the radio emission for this star is mainly thermal. For the other th...

  14. 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...

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

    Science.gov (United States)

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

    2016-09-30

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

  16. 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.

  17. Effects of high-frequency repetitive transcranial magnetic stimulation (rTMS) on spontaneously hypertensive rats, an animal model of attention-deficit/hyperactivity disorder.

    Science.gov (United States)

    Kim, Jungyun; Park, Heamen; Yu, Seong-Lan; Jee, Sungju; Cheon, Keun-Ah; Song, Dong Ho; Kim, Seung Jun; Im, Woo-Young; Kang, Jaeku

    2016-10-01

    The current treatment of choice for attention deficit hyperactivity disorder (ADHD) is pharmacotherapy. A search for new treatment options is underway, however, as the wide application of drugs to the general population of patients with ADHD is limited by side effects and the variance of pharmacokinetic effects of the drugs in each patient. In the present study, we applied repetitive transcranial magnetic stimulation (rTMS), a non-invasive treatment used in a number of other psychiatric disorders, to spontaneously hypertensive rats (SHRs), an animal model of ADHD, in order to assess the efficacy of the treatment in modifying behavioural symptoms as well as levels of dopamine, noradrenaline, serotonin, and brain-derived neurotrophic factor (BDNF). A total of fifteen sessions of high-frequency rTMS treatment were administered. Behavioural symptoms were observed using open field, Y-maze, and elevated plus-maze tests. Upon completion of the experiments, rats were sacrificed, and the neurochemical changes in brain tissue were analysed using high performance liquid chromatography and Western blotting. The SHRs treated with rTMS tended to exhibit less locomotor activity in the open field test over the course of treatment, but there was no improvement in inattention as measured by the Y-maze test. Furthermore, BDNF concentration increased and noradrenaline concentration decreased in the prefrontal cortex of SHRs treated with rTMS. The results of the present preclinical study indicate that rTMS may constitute a new modality of treatment for patients with ADHD, through further evaluation of specific treatment parameters as well as safety and efficacy in humans are required.

  18. 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

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

    Science.gov (United States)

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

    2017-02-01

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

  20. 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.

  1. 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...

  2. Proposal of High-Frequency Magnetic Field Immunity Test for Medical Devices, and Design and Development of Coil for the Test

    Science.gov (United States)

    Yamamoto, Takahiko; Koshiji, Kohji

    Medical devices have been obliged to satisfy electromagnetic compatibility by revision of the pharmaceutical affairs law. However, even if the medical devices satisfy the electromagnetic compatibility based on the law, it is not necessarily safe. Sometimes, malfunctions of cardiac pacemaker are caused by the magnetic field leaked from an induction heating cooker. In this paper, a new method of electromagnetic susceptability (EMS) evaluation is proposed, and a loop coil for the magnetic field immunity test in the frequency range from 10kHz to 3MHz is designed and developed. As a result, the loop coil made on an experimental basis generated uniform magnetic field with a fluctuation within 3.3dB in the loop coil pane and 5.6dB along the coil axis.

  3. Analytical core loss calculations for magnetic materials used in high frequency high power converter applications. Ph.D. Thesis - Toledo Univ.

    Science.gov (United States)

    Triner, J. E.

    1979-01-01

    The basic magnetic properties under various operating conditions encountered in the state-of-the-art DC-AC/DC converters are examined. Using a novel core excitation circuit, the basic B-H and loss characteristics of various core materials may be observed as a function of circuit configuration, frequency of operation, input voltage, and pulse-width modulation conditions. From this empirical data, a mathematical loss characteristics equation is developed to analytically predict the specific core loss of several magnetic materials under various waveform excitation conditions.

  4. Fictitious Reference Iterative Tuning-Based Two-Degrees-of-Freedom Method for Permanent Magnet Synchronous Motor Speed Control Using FPGA for a High-Frequency SiC MOSFET InverterMOSFET Inverter

    Directory of Open Access Journals (Sweden)

    Charles Ronald Harahap

    2016-11-01

    Full Text Available This paper proposes proportional-integral/proportional gain controller parameter tuning in a two-degrees-of-freedom (2DOF control system using the fictitious reference iterative tuning (FRIT method for permanent magnet synchronous motor (PMSM speed control using a field-programmable gate array (FPGA for a high-frequency SiC MOSFET (metal oxide semiconductor field-effect transistor inverter. The PI-P (proportional-integral/proportional controller parameters can be tuned using the FRIT method from one-shot experimental data without using a mathematical model of the plant. Particle swarm optimization is used for FRIT optimization. An inverter that uses a SiC MOSFET is presented to achieve high-frequency operation at up to100 kHz using a switching pulse-width modulation (PWM technique. As a result, a high-responsivity and high-stability PMSM (permanent magnet synchronous motor control system is achieved, where the speed response follows the ideal response characteristic for both the step response and the disturbance response. High-responsivity and optimal disturbance rejection can be achieved using the 2DOF control system. FPGA-based digital hardware control is used to maximize the switching frequency of the SiC MOSFET inverter. Finally, an experimental system is set up, and experimental results are presented to prove the viability of the proposed method.

  5. The positive effects of high-frequency right dorsolateral prefrontal cortex repetitive transcranial magnetic stimulation on memory, correlated with increases in brain metabolites detected by proton magnetic resonance spectroscopy in recently detoxified alcohol-dependent patients

    Directory of Open Access Journals (Sweden)

    Qiao J

    2016-09-01

    Full Text Available Jun Qiao,1,2 Guixing Jin,1,2 Licun Lei,3 Lan Wang,1,2 Yaqiang Du,3 Xueyi Wang1,2 1Institute of Mental Health, The First Hospital of Hebei Medical University, 2Brain Ageing and Cognitive Neuroscience Laboratory, Hebei Medical University, 3Department of Radiology, The First Hospital of Hebei Medical University, Hebei, People’s Republic of China Objective: To explore the effect of right dorsolateral prefrontal cortex (DLPFC repetitive transcranial magnetic stimulation (rTMS on memory, and its correlation with levels of hippocampal brain metabolites detected by proton magnetic resonance spectroscopy (1H-MRS in recently detoxified alcohol-dependent patients. Materials and methods: In this randomized, double-blind sham-controlled trial, alcohol-dependent patients were enrolled and randomized into two groups: the experimental group (rTMS, 10 Hz, on right DLPFC, 20 sessions and the control group (sham stimulation. Memory function was assessed using Hopkins Verbal Learning Test-Revised (HVLT-R and Brief Visuospatial Memory Test-Revised (BVMT-R before and after treatment. 1H-MRS was used to detect the levels of N-acetyl aspartic acid (NAA, choline (Cho, and creatine (Cr in bilateral hippocampi before and after treatment. Results: Thirty-eight patients (18 in the experimental group and 20 in the control group were included in the analyses. The experimental group showed significantly greater changes in HVLT-R, BVMT-R, NAA/Cr, and Cho/Cr after rTMS from baseline than the control group. The percentage change in BVMT-R and HVLT-R correlated with the percentage change in NAA/Cr and Cho/Cr in the right brain. Conclusion: High-frequency right DLPFC rTMS was associated with improvement in memory dysfunction, which is correlated with levels of hippocampal brain metabolites detected by 1H-MRS in recently detoxified alcohol-dependent patients. Keywords: alcohol dependence, memory, repetitive transcranial magnetic stimulation, MR spectroscopy

  6. Theoretic 3-D study of the high-frequency magnetic moment dynamics in thin ferromagnetic films with in-plane uniaxial anisotropy by considering eddy-current generation

    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)

    2012-06-15

    In the present paper, theoretic investigations of polarisation vector precession trajectories represented by a macro spin in ferromagnetic films with in-plane uniaxial anisotropy were realised. For this purpose, the Landau-Lifschitz-Gilbert differential equation (LLG) in combination with the Maxwell equations were solved for three dimensions by considering a linear progression of the magnetisation or polarisation with an external field. The frequency and time dependent polarisation trajectories illustrate how a magnetic moment precesses if effective damping and eddy-currents impacts its motion. For computation, typical parameter values like the saturation polarisation J{sub s}={mu}{sub 0}{center_dot}M{sub s}=1.4 T and in-plane uniaxial anisotropy {mu}{sub 0}{center_dot}H{sub u}=4.5 mT were employed. The main focus of simulation was on the variation of the effective damping parameter {alpha}{sub eff} between 0.01 and 0.05 and ferromagnetic film thickness t{sub m} between 200 nm and 1200 nm. The frequency-dependent calculations were carried out between 50 MHz and 6 GHz. The time-dependent simulations were done for a duration between 5 and 30 ns. - Highlights: Black-Right-Pointing-Pointer Frequency- and time domain solution of the LLG and Maxwell differential equation. Black-Right-Pointing-Pointer 3D magnetic moment or macro spin trajectories by eddy-current impact. Black-Right-Pointing-Pointer Progression of a magnetic excitation field in thin ferromagnetic films. Black-Right-Pointing-Pointer Transient response evaluation of uniform magnetic moments excited by an r.f. field.

  7. 超低损耗角磁心高频损耗测量方法%High Frequency Core Loss Measurement of Low Loss Angle Magnetic Component

    Institute of Scientific and Technical Information of China (English)

    汪晶慧; 陈为

    2012-01-01

    针对传统交流功率计法测量阻抗角接近90。的磁件磁心损耗时有很大的测量误差,提出了一种新型的直流测量法,基本思想是通过一个DC.AC逆变电路将直流电压转变为矩形波电压,施加到被测磁件上,测量直流输入的有功功率得到磁心损耗。其中,为了有效扣除磁心损耗外的其他损耗,提出了用空心电感定标的方法。实验结果表明:直流测量法可用来测量小损耗角磁件磁心损耗,且不受阻抗角的影响,具有很高的精度。%The measurement error of core loss by AC meter will be very large especially when the impedance angle of magnetic component is closed to 90°. So a new DC meter method is proposed in this paper. The basic idea is to transform the input DC voltage into a square waveform on the magnetic component by a DC-AC inverter, and obtained the core loss by measuring the input active power. The method could avoid the influence of impedance angle to the measurement accuracy. However, with this method, the losses excepting for core loss should be excluded someway. A method of calibration with air core inductor is proposed to effectively calculate and take out the losses except core loss. The experimental results verify that the DC meter method is accurate to measure the core loss of low loss angle magnetic component.

  8. 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...

  9. Magnetic and high-frequency EPR studies of an octahedral Fe(III) compound with unusual zero-field splitting parameters.

    Science.gov (United States)

    Solano-Peralta, Alejandro; Saucedo-Vázquez, Juan P; Escudero, Roberto; Höpfl, Herbert; El-Mkami, Hassane; Smith, Graham M; Sosa-Torres, Martha E

    2009-03-07

    Temperature-dependent magnetic susceptibility and multi-frequency EPR (9.4, 34.5, 94 and 188 GHz) spectroscopic measurements have been carried out together with an X-ray study at 100 K to study [Fe(DMSO)(6)](NO(3))(3). The iron(III) ion remains high-spin (S = 5/2) in the temperature range studied, therefore, the EPR data were interpreted using the conventional S = 5/2 spin Hamiltonian. A full analysis of EPR spectra at 95 GHz of a powdered sample at 290 K revealed that they are extremely sensitive to D and E values. The zfs parameters were precisely determined: D = + 0.1730 cm(-1), E = 0.00 cm(-1) and lambda = |E/D| = 0.00. A sequence of the spectra neatly shows that the compound has a clear magnetic dependence on temperature. The study at 5 K, showed that the zfs parameters increase: D = + 0.1970 cm(-1), E = 0.017 cm(-1) and lambda = |E/D| = 0.086. These data indicate that as the temperature decreases the D tensor increases slightly showing an increase in the rhombicity. These results confirm that |2D| is congruent to h nu at X-band in this case. Additionally, it has been shown by X-ray crystal analysis of [Fe(DMSO)(6)](NO(3))(3) at 100 K that this is involved in a hydrogen bonding network, consisting of C-H...O interactions between the nitrate anions and the methyl groups of the coordinated DMSO molecules, thus suggesting that the differences found in the spectroscopic parameters D and E at different temperatures must be due to these supramolecular interactions.

  10. Theoretic 3-D study of the high-frequency magnetic moment dynamics in thin ferromagnetic films with in-plane uniaxial anisotropy by considering eddy-current generation

    Science.gov (United States)

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

    2012-06-01

    In the present paper, theoretic investigations of polarisation vector precession trajectories represented by a macro spin in ferromagnetic films with in-plane uniaxial anisotropy were realised. For this purpose, the Landau-Lifschitz-Gilbert differential equation (LLG) in combination with the Maxwell equations were solved for three dimensions by considering a linear progression of the magnetisation or polarisation with an external field. The frequency and time dependent polarisation trajectories illustrate how a magnetic moment precesses if effective damping and eddy-currents impacts its motion. For computation, typical parameter values like the saturation polarisation Js=μ0·Ms=1.4 T and in-plane uniaxial anisotropy μ0·Hu=4.5 mT were employed. The main focus of simulation was on the variation of the effective damping parameter αeff between 0.01 and 0.05 and ferromagnetic film thickness tm between 200 nm and 1200 nm. The frequency-dependent calculations were carried out between 50 MHz and 6 GHz. The time-dependent simulations were done for a duration between 5 and 30 ns.

  11. 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...

  12. Optimization of carbon nanotube volume percentage for enhancement of high frequency magnetic properties of SrFe{sub 8}MgCoTi{sub 2}O{sub 19}/MWCNTs

    Energy Technology Data Exchange (ETDEWEB)

    Gordani, Gholam Reza, E-mail: gordani@gmail.com [Department of Materials science and Engineering, Isfahan University of Technology, Isfahan (Iran, Islamic Republic of); Materials Engineering Department, Malek Ashtar University of Technology, Shahin Shahr (Iran, Islamic Republic of); Ghasemi, Ali [Materials Engineering Department, Malek Ashtar University of Technology, Shahin Shahr (Iran, Islamic Republic of); Saidi, Ali [Department of Materials science and Engineering, Isfahan University of Technology, Isfahan (Iran, Islamic Republic of)

    2014-08-01

    A novel magnetic nanocomposite of multiwalled carbon nanotubes decorated with SrFe{sub 8}MgCoTi{sub 2}O{sub 19} nanoparticles have been prepared by a chemical co-precipitation method. The structural, magnetic and electromagnetic properties of samples were studied as a function of volume percentage of MWCNTs by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, vibrating sample magnetometer and vector network analysis. The XRD and FTIR results showed that the nanocomposites were synthesized successfully. Field emission scanning electron microscopy micrographs demonstrated that homogeneous and high level of dispersion of MWCNTs and Sr-hexaferrite nanoparticles in nanocomposite samples were obtained. The saturation magnetization of the nanocomposite samples was found to decrease by an increase in volume percentage of MWCNTs up to 5 vol%. The vector network analysis results show that the highest value of reflection loss of nanocomposite was −42.43 dB at 11.13 GHz with an absorption bandwidth of more than of 4 GHz. The results indicate that, these novel types of nanocomposites with appropriate amount of MWCNTs hold great promise for microwave device applications. - Highlights: • We investigate the high frequency properties of Sr-hexaferrite/MWCNTs composite. • Saturation magnetization of nanocomposites is decreased with presence of MWCNTs. • The ferrite/CNTs nanocomposite sample covers whole X-band frequencies (8–12 GHz). • The ferrite/CNTs nanocomposite can be used as a potential magnetic loss material. • Nanocomposite contain 5 vol% of CNTs have shown greater than 99% of reflection loss.

  13. 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.

  14. 激磁涌流的高频信号及对应答器干扰分析%Analysis on high frequency signals of magnetizing inrush current and its interference for balise

    Institute of Scientific and Technical Information of China (English)

    刘中田; 罗丽燕; 周果; 赵会兵

    2012-01-01

    在列车自动过分相时,牵引变压器产生的激磁涌流通过母排、轮对和钢轨回流到变电所,而在这个过程中激磁涌流可能会对应答器上行链路信号产生干扰.激磁涌流对应答器上行链路干扰的途径是应答器接收天线的耦合,要清楚了解其干扰,必须了解激磁涌流4.23 MHz附近信号分量,因此对激磁涌流高频信号的分析是非常有必要的.本文用Matlab软件对激磁涌流进行了仿真得到其仿真数据.然后,用LabWindows/CVI软件进行仿真数据加载并且对激磁涌流进行短时傅里叶变换(STFT),得到激磁涌流4.23 MHz附近信号分量.最后,用FEKO软件进行激磁涌流对应答器上行链路信号的干扰仿真.研究结果表明激磁涌流含有4.23 MHz附近信号分量较小,不会对应答器上行链路信号产生干扰.%The magnetizing inrush current generated by auto-passing neutral section goes through busbar, wheel and rail back to substation. The Up-Link balise may be interfered by the magnetizing inrush current in this process. This interference way is receiving antenna coupling. To clearly understand their interference, it is necessary to get signal component near 4.23 MHz of the magnetizing inrush current. So the research on the high frequency signals of magnetizing inrush current is necessary. This paper uses MATLAB to simulate magnetizing inrush current, and data of magnetizing inrush current are acquired. And then this paper loads the simulation data with Labwindows/CVI and does STFT to get the signal component near 4.23 MHz. Finally, using FEKO does interference simulation of magnetizing inrush current to up-link balise. The research results show that the magnetizing inrush current contains small weight signals of 4.23 MHz, and it can not interfere with the Up-Link balise.

  15. Seizures beget seizures: the quest for GABA as a key player.

    Science.gov (United States)

    Ben-Ari, Yehezkel

    2006-01-01

    that has been confirmed in all developing systems and animal species studied. As a consequence, immature GABAergic synapses will excite targets and facilitate the emergence of seizures, in keeping with the well-known higher incidence of seizures in the developing brain. Using a unique preparation with two intact hippocampi placed in a three-compartment chamber in vitro, we have provided direct evidence that seizures beget seizures and that GABA signaling plays a central role in this phenomenon. Indeed, recurrent seizures triggered in one hippocampus by a convulsive agent propagate to the other hippocampus and transform the naive hippocampus into one that generates seizures once disconnected from the other hippocampus. This transformation is conditioned by the occurrence during the seizures of high-frequency oscillations (40 Hz and above). Interestingly, these oscillations are only produced when N-methyl-D-aspartate (NMDA-) and GABA receptors are operative and not blocked in the naïve hippocampus. Therefore, GABA-receptor antagonists are pro-convulsive in the developing brain but, in fact, anti-epileptic. This paradoxical conclusion has quite a few clinical implications that are discussed.

  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. Uniaxial anisotropy and high-frequency permeability of novel soft magnetic FeCoTaN and FeCoAlN films field-annealed at CMOS temperatures

    Energy Technology Data Exchange (ETDEWEB)

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

    2004-12-01

    In order to investigate the anisotropy and high-frequency behaviour, soft magnetic FeCoTaN and FeCoAlN films were fabricated by reactive RF-magnetron sputtering. Six-inch targets consisting of Fe47Co36Ta17 and Fe49Co36Al15 were used to grow the films on oxidized (100)-silicon substrates with a TiN seed layer for better film adhesion. The concentration of nitrogen was adjusted by a flow control system. For applications in, e.g., aluminium CMOS processed components the films were annealed at temperatures of about 400-bar C in a static magnetic field of 50mT to induce a uniaxial anisotropy in the film plane by activating an atomic ordering process. Controlling the anisotropy by annealing demands a specified elaboration and results in an in-plane uniaxial anisotropy between 3 and 4mT. Nitrogen in both materials caused the formation of TaN or AlN which mainly supported the suppression of polycrystalline film growth. After deposition the films showed an amorphous structure and turned to be nanocrystalline after the annealing procedure. A saturation polarization in both materials amounted to between 1.1 and 1.2T. Ferromagnetic resonance frequencies of about 1.9GHz for FeCoTaN and 1.8GHz for FeCoAlN, determined by measuring the frequency-dependent permeability by means of a strip line permeameter up to 5GHz, were observed. The experimental results where compared with a spin dynamic model based on the Landau-Lifschitz and Maxwell's eddy current equation in the total frequency range.

  18. 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.

  19. 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.

  20. The Impact of Accelerated Right Prefrontal High-Frequency Repetitive Transcranial Magnetic Stimulation (rTMS) on Cue-Reactivity: An fMRI Study on Craving in Recently Detoxified Alcohol-Dependent Patients.

    Science.gov (United States)

    Herremans, Sarah C; Van Schuerbeek, Peter; De Raedt, Rudi; Matthys, Frieda; Buyl, Ronald; De Mey, Johan; Baeken, Chris

    2015-01-01

    In alcohol-dependent patients craving is a difficult-to-treat phenomenon. It has been suggested that high-frequency (HF) repetitive transcranial magnetic stimulation (rTMS) may have beneficial effects. However, exactly how this application exerts its effect on the underlying craving neurocircuit is currently unclear. In an effort to induce alcohol craving and to maximize detection of HF-rTMS effects to cue-induced alcohol craving, patients were exposed to a block and event-related alcohol cue-reactivity paradigm while being scanned with fMRI. Hence, we assessed the effect of right dorsolateral prefrontal cortex (DLPFC) stimulation on cue-induced and general alcohol craving, and the related craving neurocircuit. Twenty-six recently detoxified alcohol-dependent patients were included. First, we evaluated the impact of one sham-controlled stimulation session. Second, we examined the effect of accelerated right DLPFC HF-rTMS treatment: here patients received 15 sessions in an open label accelerated design, spread over 4 consecutive days. General craving significantly decreased after 15 active HF-rTMS sessions. However, cue-induced alcohol craving was not altered. Our brain imaging results did not show that the cue-exposure affected the underlying craving neurocircuit after both one and fifteen active HF-rTMS sessions. Yet, brain activation changes after one and 15 HF-rTMS sessions, respectively, were observed in regions associated with the extended reward system and the default mode network, but only during the presentation of the event-related paradigm. Our findings indicate that accelerated HF-rTMS applied to the right DLPFC does not manifestly affect the craving neurocircuit during an alcohol-related cue-exposure, but instead it may influence the attentional network.

  1. 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.

  2. Magnetoencephalography Detection of High-Frequency Oscillations in the Developing Brain

    Directory of Open Access Journals (Sweden)

    Kimberly eLeiken

    2014-12-01

    Full Text Available Increasing evidence from invasive intracranial recordings suggests that the matured brain generates both physiological and pathological high-frequency signals. The present study was designed to detect high-frequency brain signals in the developing brain using newly developed magnetoencephalography (MEG methods. Twenty healthy children were studied with a high sampling rate MEG system. Functional high-frequency brain signals were evoked by electrical stimulation applied to the index fingers. To determine if the high-frequency neuromagnetic signals are true brain responses in high-frequency range, we analyzed the MEG data using the conventional averaging as well as newly developed time-frequency analysis along with beamforming. The data of healthy children showed that very high-frequency brain signals (> 1000 Hz in the somatosensory cortex in the developing brain could be detected and localized using MEG. The amplitude of very high-frequency brain signals was significantly weaker than that of the low-frequency brain signals. Very high-frequency brain signals showed a much earlier latency than those of a low-frequency. Magnetic source imaging (MSI revealed that a portion of the high-frequency signals was from the somatosensory cortex, another portion of the high-frequency signals was probably from the thalamus. Our results provide evidence that the developing brain generates high-frequency signals that can be detected with the noninvasive technique of MEG. MEG detection of high-frequency brain signals may open a new window for the study of developing brain function.

  3. 基于外加高频交变磁场下向MAG焊熔池成形控制%Downward Welding Pool Shape Control Based on Exterior High Frequency Alternative Magnetic Field

    Institute of Scientific and Technical Information of China (English)

    岳建锋; 李亮玉; 刘文吉; 王天琪

    2013-01-01

    Recent years, downward welding is used widely more and more in petrochemical, pipeline engineering and so on. However, with the increase in volume of weld pool during downward welding, weld pool becomes instable because of influence of gravity, even affecting the good bead shape. Weld pool mechanical behavior and the control strategy of the weld pool forming is analyzed and researched, on the base, a method is proposed in the welding that the Lorenz force produced to overcome bad effect of gravity component when the weld pool is exposed to exterior high frequency alternative magnetic field. The numerical simulation on electromagnetic field, eddy current field and electromagnetic force in the interior of weld pool are implemented. 45 degree and 90 degree downward welding experiments are carried out to verify the theory analysis. Experiment results show that it is feasible for using eddy current technology to overcome weld pool instable resulted by gravity component in downward metal active gas(MAG) welding.%近年来,下向熔化极活性气体保护焊(Metal active gas,MAG)在石油化工、管道工程等工业中获得广泛应用,但是下向MAG焊中当焊接熔池体积增大时由于其所处空间位置受重力因素影响较大,易产生熔池失稳问题,影响到焊缝的良好成形.针对上述问题开展下向焊熔池力学行为分析和熔池成形的控制策略研究,提出一种对下向MAG焊接熔池施加高频交变磁场,利用该磁场的电涡流效应产生电涡流力来抵消熔池液态金属重力分量的方法,达到克服重力对熔池成形的不利影响.开展熔池外加高频交变磁场熔池内部电磁场、涡流场和电涡流力的数值模拟和分析.进行45°和90°下向焊试验,对上述理论分析进行试验验证,结果表明高频交变磁场对熔池流淌具有抑制作用,采用电涡流技术用于克服下向MAG焊中的熔池失稳方案是可行的.

  4. Design and Measurement of Planar Toroidal Transformers for Very High Frequency Power Applications

    DEFF Research Database (Denmark)

    Knott, Arnold; Pejtersen, Jens

    2012-01-01

    The quest for higher power density has led to research of very high frequency (30-300 MHz) power converters. Magnetic components based on ferrite cores have limited application within this frequency range due to increased core loss. Air-core magnetics is a viable alternative as they do not exhibi...... power converters for very high frequencies. The magnetic coupling factor of both transformers is approx. 60 % and the mutual coupling inductance is dominant up to a frequency of 50 MHz....

  5. Generation of sheet currents by high frequency fast MHD waves

    Energy Technology Data Exchange (ETDEWEB)

    Núñez, Manuel, E-mail: mnjmhd@am.uva.es

    2016-07-01

    The evolution of fast magnetosonic waves of high frequency propagating into an axisymmetric equilibrium plasma is studied. By using the methods of weakly nonlinear geometrical optics, it is shown that the perturbation travels in the equatorial plane while satisfying a transport equation which enables us to predict the time and location of formation of shock waves. For plasmas of large magnetic Prandtl number, this would result into the creation of sheet currents which may give rise to magnetic reconnection and destruction of the original equilibrium. - Highlights: • Regular solutions of quasilinear hyperbolic systems may evolve into shocks. • The shock location is found for high frequency fast MHD waves. • The result is applied to static axisymmetric equilibria. • The previous process may lead to the formation of sheet currents and destruction of the equilibrium.

  6. Non-linear high-frequency waves in the magnetosphere

    Indian Academy of Sciences (India)

    S Moolla; R Bharuthram; S V Singh; G S Lakhina

    2003-12-01

    Using fluid theory, a set of equations is derived for non-linear high-frequency waves propagating oblique to an external magnetic field in a three-component plasma consisting of hot electrons, cold electrons and cold ions. For parameters typical of the Earth’s magnetosphere, numerical solutions of the governing equations yield sinusoidal, sawtooth or bipolar wave-forms for the electric field.

  7. Effects of dislocations on small signal high frequency hot electron mobility in n-GaN at low and high temperatures under high magnetic fields including hot phonon effect

    Energy Technology Data Exchange (ETDEWEB)

    Chakraborty, A., E-mail: juimaha@yahoo.co [Department of Electronics and Telecommunication Engineering, Jadavpur University, Kolkata (India); Sarkar, C.K. [Department of Electronics and Telecommunication Engineering, Jadavpur University, Kolkata (India)

    2011-04-01

    The small signal high-frequency ac mobility of hot electrons in n-GaN in the extreme quantum limit at low- and high-temperatures has been calculated considering the non-equilibrium phonon distribution as well as the thermal phonon distributions. The energy loss rate has been calculated considering the dominance of the piezo electric coupling scattering and the polar optical phonon scattering while the momentum loss rate has been calculated considering the acoustic phonon scattering via deformation potential and the piezo electric coupling and the dislocation scattering.

  8. MHD waves generated by high-frequency photospheric vortex motions

    Directory of Open Access Journals (Sweden)

    V. Fedun

    2011-06-01

    Full Text Available In this paper, we discuss simulations of MHD wave generation and propagation through a three-dimensional open magnetic flux tube in the lower solar atmosphere. By using self-similar analytical solutions for modelling the magnetic field in Cartesian coordinate system, we have constructed a 3-D magnetohydrostatic configuration which is used as the initial condition for non-linear MHD wave simulations. For a driver we have implemented a high-frequency vortex-type motion at the footpoint region of the open magnetic flux tube. It is found that the implemented swirly source is able to excite different types of wave modes, i.e. sausage, kink and torsional Alfvén modes. Analysing these waves by magneto-seismology tools could provide insight into the magnetic structure of the lower solar atmosphere.

  9. 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.

  10. 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.

  11. 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.

  12. Skyrmion-based high-frequency signal generator

    Science.gov (United States)

    Luo, Shijiang; Zhang, Yue; Shen, Maokang; Ou-Yang, Jun; Yan, Baiqian; Yang, Xiaofei; Chen, Shi; Zhu, Benpeng; You, Long

    2017-03-01

    Many concepts for skyrmion-based devices have been proposed, and most of their possible applications are based on the motion of skyrmions driven by a dc current in an area with a constricted geometry. However, skyrmion motion driven by a pulsed current has not been investigated so far. In this work, we propose a skyrmion-based high-frequency signal generator based on the pulsed-current-driven circular motion of skyrmions in a square-shaped film by micromagnetic simulation. The results indicate that skyrmions can move in a closed curve with central symmetry. The trajectory and cycle period can be adjusted by tuning the size of the film, the current density, the Dzyaloshinskii-Moriya interaction constant, and the local in-plane magnetic anisotropy. The period can be tuned from several nanoseconds to tens of nanoseconds, which offers the possibility to prepare high-frequency signal generator based on skyrmions.

  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. 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.

  15. 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

  16. 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

  17. 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.

  18. 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

  19. 高频超声与核磁共振成像在前交叉韧带损伤诊断中的对比研究%A comparative study of high frequency ultrasound and magnetic resonance imaging in diagnosis of anterior cruciate ligament injury

    Institute of Scientific and Technical Information of China (English)

    唐盛斐; 唐基淳; 张素萍

    2015-01-01

    Objective:To investigate the value of high frequency ultrasound in diagnosis of anterior cruciate ligament (Anterior Cruciate Ligament, ACL) damage. Methods: 30 patients clinically diagnosed with ACL injury sequentially were examined with high-frequency ultrasound, magnetic resonance imaging (Magnetic Resonance Imaging, MRI) examination, and then compared with the arthroscopic examination. Results: High frequency ultrasound diagnosed accuracy of 27 cases, 2 cases of false positive and 1 case of false negative in compared with arthroscopy, the accuracy is 90% (27/30), the false positive rate is 6.67% (2/30) and the false negative rate is 3.33% (1 / 30), the accuracy of MRI matched with arthroscopy. Conclusion: High frequency ultrasound makes a high accuracy in diagnosis of ACL injuries, and it can be used as a routine diagnostic method of ACL injury.%目的:探讨高频超声在膝关节前交叉韧带(Anterior Cruciate Ligament,ACL)损伤诊断中的应用价值。方法:对30例临床拟诊为ACL损伤的患者依次行高频超声、核磁共振成像(Magnetic Resonance Imaging,MRI)检查,并与关节镜检查对比。结果:高频超声诊断符合者27例,假阳性2例,假阴性1例,诊断符合率90%(27/30),假阳性率6.67%(2/30),假阴性率3.33%(1/30),MRI诊断率与关节镜相符。结论:高频超声在ACL损伤的诊断中准确率较高,可作为ACL损伤的常规诊断方法。

  20. Very High Frequency Switch-Mode Power Supplies

    DEFF Research Database (Denmark)

    Madsen, Mickey Pierre

    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......, solenoids and toroids are considered, both for use as inductors and transformers. Two control methods are also investigated, namely burst mode control and outphasing. It is shown that a very flat efficiency curve can be achieved with burst mode. A 89.5% efficient converter is implemented and the efficiency...

  1. 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.

  2. 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.

  3. Clinical Value of High Frequency Ultrasound and 1.5T Magnetic Resonance Imaging (MRI) in the Diagnosis of Breast Cancer%高频超声、1.5T磁共振(MRI)诊断乳腺癌的临床价值

    Institute of Scientific and Technical Information of China (English)

    刘伟

    2015-01-01

    Objective To investigate the diagnostic value of high frequency ultrasound and 1.5T magnetic resonance imaging (MRI) in breast cancer.Methods The imaging data of 50 cases of patients with breast cancer confirmed by operation and pathology during January 2013 to April 2015 were retrospectively analyzed. The high frequency ultrasound and MRI imaging findings were observed and were compared with surgical and pathological results. The accuracies of high frequency ultrasound, MRI alone and combined diagnosis were analyzed.Results With the surgical and pathological results as the gold standard, the dianostic accuracy of high frequency ultrasound in breast cancer was 84.0% while of MRI was 92.0% and of the combination of the two was 98.0%. The dianostic accuracy of high frequency ultrasound combined with MRI was significantly higher than that of high frequency ultrasound and the difference was statistically significant (P<0.05).ConclusionThe accuracy of 1.5T MRI in the diagnosis of breast cancer is higher than that of high frequency ultrasound. High frequency ultrasound combined with MRI can significantly improve the dianostic accuracy in breast cancer. In clinic, it is worthy of promotion.%目的:探讨高频超声、1.5T磁共振(MRI)对乳腺癌的诊断价值。方法回顾性分析我院2013年1月-2015年4月经手术病理证实50例乳腺癌患者影像学资料,观察高频超声、MRI影像学表现,同时与手术病理结果比较,分析高频超声、MRI单独、联合诊断正确率。结果以手术病理结果为金标准,高频超声诊断乳腺癌正确率为84.0%,MRI诊断正确率为92.0%,高频超声+MRI诊断正确率为98.0%。高频超声+MRI诊断正确率明显高于高频超声检查,差异有统计学意义(P<0.05)。结论1.5T MRI诊断乳腺癌正确率比高频超声高,高频超声+MRI检查能明显提高乳腺癌诊断准确率,临床值得推广。

  4. Interannual modulation of extratropical high frequency variability

    Directory of Open Access Journals (Sweden)

    R. Caballero

    1997-06-01

    Full Text Available A simple explanation is presented for the observed interannual changes in the dominant space and time scales of Northem Hemisphere winter extratropical high frequency variability. It is found that such changes can suc- cessfully be predicted by linearizing a 2-level quasi-geostrophic mode] in spherical geometry around the ob- served zona] mean states. The mechanisms responsible for the selection of the most unstable normal mode are investigated.

  5. 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.

  6. Systemic Atherosclerotic Inflammation Following Acute Myocardial Infarction: Myocardial Infarction Begets Myocardial Infarction

    Science.gov (United States)

    Joshi, Nikhil V; Toor, Iqbal; Shah, Anoop S V; Carruthers, Kathryn; Vesey, Alex T; Alam, Shirjel R; Sills, Andrew; Hoo, Teng Y; Melville, Adam J; Langlands, Sarah P; Jenkins, William S A; Uren, Neal G; Mills, Nicholas L; Fletcher, Alison M; van Beek, Edwin J R; Rudd, James H F; Fox, Keith A A; Dweck, Marc R; Newby, David E

    2015-01-01

    Background Preclinical data suggest that an acute inflammatory response following myocardial infarction (MI) accelerates systemic atherosclerosis. Using combined positron emission and computed tomography, we investigated whether this phenomenon occurs in humans. Methods and Results Overall, 40 patients with MI and 40 with stable angina underwent thoracic 18F-fluorodeoxyglucose combined positron emission and computed tomography scan. Radiotracer uptake was measured in aortic atheroma and nonvascular tissue (paraspinal muscle). In 1003 patients enrolled in the Global Registry of Acute Coronary Events, we assessed whether infarct size predicted early (≤30 days) and late (>30 days) recurrent coronary events. Compared with patients with stable angina, patients with MI had higher aortic 18F-fluorodeoxyglucose uptake (tissue-to-background ratio 2.15±0.30 versus 1.84±0.18, P50 000] versus 3800 [1000 to 9200] ng/L, P<0.0001) and greater aortic 18F-fluorodeoxyglucose uptake (2.24±0.32 versus 2.02±0.21, P=0.03) than those with non–ST-segment elevation MI. Peak plasma troponin concentrations correlated with aortic 18F-fluorodeoxyglucose uptake (r=0.43, P=0.01) and, on multivariate analysis, independently predicted early (tertile 3 versus tertile 1: relative risk 4.40 [95% CI 1.90 to 10.19], P=0.001), but not late, recurrent MI. Conclusions The presence and extent of MI is associated with increased aortic atherosclerotic inflammation and early recurrent MI. This finding supports the hypothesis that acute MI exacerbates systemic atherosclerotic inflammation and remote plaque destabilization: MI begets MI. Clinical Trial Registration URL: https://www.clinicaltrials.gov. Unique identifier: NCT01749254. PMID:26316523

  7. 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.

  8. 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.

  9. 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...

  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 nanowir...

  11. 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...

  12. Study on GNi-WC25 Coating by High Frequency Induction Cladding

    Institute of Scientific and Technical Information of China (English)

    张增志; 韩桂泉; 付跃文; 沈立山

    2002-01-01

    Process and mechanism of high frequency were studied in this paper by means of cold-attachment for the preparation of Gni-WC25 coating . The resu lts show its special distribution law of eddy current while the magnetic transition temperature and electric-resistivity of the coating have been measured .Wear-resistance of the high-frequency induction coating has an advantage over those of laser cladding coating and oxygen-acetylene spraying-fusing coating . Moreover , the Gni-WC25 coating by high-frequency induction claddi ng has smooth surface and even microstructure.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 10 K high frequency pulse tube cryocooler with precooling

    Science.gov (United States)

    Liu, Sixue; Chen, Liubiao; Wu, Xianlin; Zhou, Yuan; Wang, Junjie

    2016-07-01

    A high frequency pulse tube cryocooler with precooling (HPTCP) has been developed and tested to meet the requirement of weak magnetic signals measurement, and the performance characteristics are presented in this article. The HPTCP is a two-stage pulse tube cryocooler with the precooling-stage replaced by liquid nitrogen. Two regenerators completely filled with stainless steel (SS) meshes are used in the cooler. Together with cold inertance tubes and cold gas reservoir, a cold double-inlet configuration is used to control the phase relationship of the HPTCP. The experimental result shows that the cold double-inlet configuration has improved the performance of the cooler obviously. The effects of operation parameters on the performance of the cooler are also studied. With a precooling temperature of 78.5 K, the maximum refrigeration capacity is 0.26 W at 15 K and 0.92 W at 20 K when the input electric power are 174 W and 248 W respectively, and the minimum no-load temperature obtained is 10.3 K, which is a new record on refrigeration temperature for high frequency pulse tube cryocooler reported with SS completely used as regenerative matrix.

  19. 78 FR 70567 - Nationwide Use of High Frequency and Ultra High Frequency Active SONAR Technology; Final...

    Science.gov (United States)

    2013-11-26

    ...] [FR Doc No: 2013-28337] DEPARTMENT OF HOMELAND SECURITY Coast Guard [Docket No. USCG-2009-0166... Programmatic Environmental Assessment (PEA) for the Nationwide Use of High Frequency (HF) and Ultra High..., recreational boating, or other maritime activities. The use of HF (50 to 999 kHz) and UHF (1,000 kHz and...

  20. 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.

  1. 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.

  2. High frequency (208 GHz) determination of the cubic spin Zeeman term for the U{sup 3+} ion in the dilute magnetic semiconductor crystals of Pb{sub 1−x}U{sub x}Te and Pb{sub 1−x}U{sub x}Se at 5 K by electron paramagnetic resonance

    Energy Technology Data Exchange (ETDEWEB)

    Misra, Sushil K., E-mail: skmisra@alcor.concordia.ca; Michaels, Adam

    2015-03-15

    A high-frequency (208 GHz) Electron Paramagnetic Resonance (EPR) study on the U{sup 3+} ion (5f{sup 3}, {sup 4}I{sub 9/2}, S=3/2) embedded with 3% concentration in the dilute magnetic semiconductor crystals of PbTe and PbSe, each characterized by cubic symmetry, has been performed at ∼5 K, especially in view to determine the value of the Zeeman cubic spin term parameter u, and the site symmetry of the U{sup 3+} ion (radius 0.089 nm), substituting for the Pb{sup 2+} ion (radius 0.119 nm). The experimental spectra reveal the presence of only one set of EPR lines from U{sup 3+} ions in these host crystals, exhibiting cubic symmetry, whose magnetic axes are oriented along the crystal axes. The spin-Hamiltonian parameters are for both crystals: g=1.9811, u=-0.0257. - Highlights: • EPR studies of U{sup 3+} ion done at 208 GHz at 5 K embedded in PbTe and PbSe crystals. • Site symmetry at U{sup 3+} ion is determined to be cubic from EPR data. • Zeeman cubic spin term parameter u=-0.0257 determined for both crystals. • g=1.9811 Determined for both crystals.

  3. Designing Magnetic Components for High Frequency DC-DC Converters

    Science.gov (United States)

    McLyman, W. T.

    1993-01-01

    The conversion process in power electronics requires the use of tranformers and inductors, components which frequenly are the heaviest and bulkiest item in the conversion circuits. They also have a significant effect upon the overall performance and efficiency of the system.

  4. EFFECT MECHANISM OF HIGH FREQUENCY ELECTRO-MAGNETIC FIELD ON THE SURFACE QUALITY AND EQUIAXED CRYSTAL RATIO OF 15CrMo BILLET%高频电磁场对15CrMo连铸坯表面质量和等轴晶率的影响机理

    Institute of Scientific and Technical Information of China (English)

    许秀杰; 邓安元; 王恩刚; 张林涛; 张永杰; 赫冀成

    2009-01-01

    An induced coil surrounding a segmented mold used in soft contact electromagnetic casting (soft-contact EMC) was used to produce a high frequency magnetic field for reducing ferrostatic pressure between the mold and melt. The distribution of magnetic field in the mold was examined using a magnetic probe of the induction coil type. Then mathematical model was developed to study the distributions of magnetic field, electromagnetic force and flowing velocity of molten steel in the mold. Finally, continuous casting experiments were conducted with alloy constructional steel 15CrMo in the laboratory caster. The surface morphologies and macrostructure were examined and analyzed. Based on the comprehension of the distributions of magnetic field, electromagnetic force and flowing velocity of molten steel in the mold through measurements and numerical simulation, the effects of electromag-netic field were systematically investigated. The results indicate that when the electromagnetic field was applied in the initially solidified area, the mold flux consumption was increased dramatically. As a result, the surface quality of continuously cast billets is greatly improved, for example, oscillation marks disappeared due to the decrease of flux pressure. Moreover, the growth of columnar grains is suppressed for two main reasons. The first one is that the mold near meniscus is heated by Joule heat generated by the high frequency electromagnetic field. The other one is that the thermal resistance between mold and the solidified shell is increased as the increase of mold flux thickness. Inhomogeneous distributions of magnetic field in the mold along the casting direction were confirmed both by measurement and numerical simulation. And the Lorentz force on the molten steel along the casting direction is uneven likewise. Under the drive of Lorentz force, two counter-rotational vortices are formed below the meniscus. Moreover, the temperature gradient in front of the solid

  5. 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.

  6. New considerations concerning the high-frequency focusing of relativistic particles and Panofsky-Wenzel theorem

    Science.gov (United States)

    Melekhin, V. N.

    1997-02-01

    It is shown that the transverse momentum imparted to a relativistic particle, passing through an accelerating cavity near and parallel to its axis ( z-axis), may be presented as a trajectory integral with an integrand being proportional to z-component of high-frequency magnetic field. The x- and y-component of this momentum are equal in value but opposite in sign. The obtained result is compared with Panofsky-Wenzel theorem. This result gives one more procedure to check the accuracy of high-frequency focusing simulation.

  7. 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

  8. 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.

  9. 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...

  10. Short-interval intracortical inhibition is modulated by high-frequency peripheral mixed nerve stimulation.

    Science.gov (United States)

    Murakami, Takenobu; Sakuma, Kenji; Nomura, Takashi; Nakashima, Kenji

    2007-06-01

    Cortical excitability can be modulated by manipulation of afferent input. We investigated the influence of peripheral mixed nerve stimulation on the excitability of the motor cortex. Motor evoked potentials (MEPs), short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF) in the right abductor pollicis brevis (APB), extensor carpi radialis (ECR) and first dorsal interosseous (FDI) muscles were evaluated using paired-pulse transcranial magnetic stimulation (TMS) before and after high-frequency peripheral mixed nerve stimulation (150 Hz, 30 min) over the right median nerve at the wrist. The MEP amplitude and SICI of the APB muscle decreased transiently 0-10 min after the intervention, whereas the ICF did not change. High-frequency peripheral mixed nerve stimulation reduced the excitability of the motor cortex. The decrement in the SICI, which reflects the function of GABA(A)ergic inhibitory interneurons, might compensate for the reduced motor cortical excitability after high-frequency peripheral mixed nerve stimulation.

  11. 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

  12. 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

  13. 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...

  14. 高频磁场下原位合成Al3(Ti0.5Zr0.5)p/6005A复合材料的显微组织与性能%Microstructure and Properties of In-Situ Synthesized Al3(Ti(0.5)Zr(0.5))p/6005A Composites under High-frequency Magnetic Field

    Institute of Scientific and Technical Information of China (English)

    祝晓辉; 赵玉涛; 李桂荣; 陈刚; 佘昌俊; 轩动华; 郑梦

    2011-01-01

    Al3 (Ti0.5 Zr0.5 )p/6005A composites were in-situ synthesized under high-frequency magnetic field by direct melt reaction using K2TiF6, K2ZrF6 and Na3A1F6 as reactants. By means of scanning electron microscopy, Xray diffraction and tensile testing machine, the microstructure and properties of the composites were investigated.The results show that the in-situ synthesized particles under magnetic field were fine Al3 (Ti0. 5 Zr0. 5 )p particles,whose average size was 1-3μm and dispersively distributed in Al substrate. At magnetic frequency of 2 MHz, the yield strength, tensile strength of the composites were 279. 4 and 305. 8 MPa, which increased by 7. 1% and 8.7%compared with that of the substrate. And the elongation was 9. 5%, which decreased by 10. 1%. The fracture characteristics of the composites transformed from ductile fracture of the substrate to mixing fracture.%以K2TiF6、K2ZrF6与Na3AlF6为反应物,在高频磁场下,采用熔体反应法原位合成了A13(Ti(0.5)Zr(0.5))p/6005A复合材料;通过扫描电镜、X射线衍射仪、拉伸试验机等对复合材料的组织与性能进行了研究.结果表明:磁场下原位生成了细小的Al3(Ti(0.5)Zr(0.5))颗粒,平均尺寸为1-3μm,且弥散分布于基体中;在磁场频率为2MHz时复合材料的屈服强度、抗拉强度分别为279.4,305.8MPa,较基体的提高了7.1%和8.7%,伸长率为9.5%,较基体的下降了10.1%;复合材料的断裂特征由基体的韧性断裂转变为混合型断裂.

  15. High-Frequency Properties of Ultracool Dwarf Star Radio Transients, or The Little Dwarfs that Could

    Science.gov (United States)

    Ravi, Vikram; Hobbs, George; Keith, Michael; Champion, David; Ferrario, Lilia; Wickramasinghe, Dayal

    2009-07-01

    Radio transients are among the most intriguing phenomena in astronomy. Numerous flaring events, some periodic, have lately surfaced, with only few identified with known objects such as magnetic stars. Periodic, non-thermal, highly circularly-polarised pulses and unusually strong quiescence have been recently detected from three late-type quickly-rotating (~2hr periods) ultracool dwarf stars (>M7) at centimetric wavelengths. This violates empirical relations and quantifiers of dwarf-star surface activity. Measurements of dwarf-star kiloGauss magnetic fields have led to emission models based on dipole fields and incoherent gyrosynchrotron or coherent electron-cyclotron maser mechanisms. We propose to observe two such similar objects at 1cm and 7mm (LP944-20 and DENIS1048-3956) that are known to flare but without detected periodicities. No observations of high-frequency emission from any magnetic star have been published. The broadband capabilities of CABB will provide extraordinary frequency-synthesised sensitivity in a search for periodicity. The obtained spectral indices, along with possible high-frequency spectral cut-offs, will greatly help constrain emission models of magnetic stars. This is the first attempt to characterise the high-frequency transient radio sky, a key science project for future telescopes such as ASKAP and the SKA.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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....

  2. 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,...

  3. 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.

  4. 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

  5. TiO2掺杂对高频MnZn功率铁氧体显微结构及磁性能的影响%Effects of TiO2 doping on the microstructure and magnetic properties of high frequency MnZn power ferrites

    Institute of Scientific and Technical Information of China (English)

    谭学谦; 余忠; 孙科; 蒋晓娜; 兰中文; 柴治

    2015-01-01

    采用氧化物陶瓷工艺制备2~4MHz高频开关电源用MnZn功率铁氧体,通过对铁氧体断面显微结构、密度和磁性能的测试,研究了TiO2掺杂量对材料微观结构、磁导率和功率损耗的影响.结果表明,随着TiO2掺杂量的增加,样品平均晶粒尺寸先减小后增大,磁导率单调减小,不同温度(25℃、100℃)下的磁心总功率损耗(激励条件3MHz,10mT、25mT)先减小后增大.说明TiO2的适量掺杂可以改善高频MnZn功率铁氧体的微观结构,降低其功耗.%MnZn power ferrites for 2-4MHz high frequency switch power supply were prepared by conventional oxide ceramic process. The influence of TiO2 doping on the microstructure, permeability and core loss of MnZn power ferrites was investigated by means of characterizing the fracture surface micrograph, density and magnetic properties. The results indicate that with increasing TiO2 doping content the average grain size decreases first and then increases, and permeability decreases monotonously, while the core loss of MnZn power ferrites decreases first and increases subsequently at 25℃ and 100℃ and different exciting condition(3MHz, 10mT and 3MHz, 25mT).The appropriate amount of TiO2 doping can improve the microstructure of MnZn power ferrites and resultantly decrease the core loss of MnZn power ferrites.

  6. 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.

  7. 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.

  8. Thermo-Mechanical Stress in High-Frequency Vacuum Electron Devices

    Science.gov (United States)

    Gamzina, Diana; Luhmann, Neville C.; Ravani, Bahram

    2016-09-01

    Analysis of the thermo-mechanical performance of high-frequency vacuum electron devices is essential to the advancement of RF sources towards high-power generation. Operation in an ultra-high vacuum environment, space restricting magnetic focusing, and limited material options are just some of the constraints that complicate thermal management in a high-power VED. An analytical method for evaluating temperature, stress, and deformation distribution in thin vacuum-to-cooling walls is presented, accounting for anisotropic material properties. Thin plate geometry is used and analytical expressions are developed for thermo-mechanical analysis that includes the microstructure effects of grain orientations. The method presented evaluates the maximum allowable heat flux that can be used to establish the power-handling limitation of high-frequency VEDs prior to full-scale design, accelerating time-to-manufacture.

  9. Thermo-Mechanical Stress in High-Frequency Vacuum Electron Devices

    Science.gov (United States)

    Gamzina, Diana; Luhmann, Neville C.; Ravani, Bahram

    2017-01-01

    Analysis of the thermo-mechanical performance of high-frequency vacuum electron devices is essential to the advancement of RF sources towards high-power generation. Operation in an ultra-high vacuum environment, space restricting magnetic focusing, and limited material options are just some of the constraints that complicate thermal management in a high-power VED. An analytical method for evaluating temperature, stress, and deformation distribution in thin vacuum-to-cooling walls is presented, accounting for anisotropic material properties. Thin plate geometry is used and analytical expressions are developed for thermo-mechanical analysis that includes the microstructure effects of grain orientations. The method presented evaluates the maximum allowable heat flux that can be used to establish the power-handling limitation of high-frequency VEDs prior to full-scale design, accelerating time-to-manufacture.

  10. Electrogravitational Resonance of a Gaussian Beam to a High-Frequency Relic Gravitational Wave

    Institute of Scientific and Technical Information of China (English)

    李芳昱; 唐孟希

    2001-01-01

    We consider the resonant response of a Gaussian beam passing through a static magnetic field to a high-frequency relic gravitational wave (GW). It is found that under the synchroresonance condition, the first-order perturbative electromagnetic energy fluxes will contain a "left circular wave" and a "right circular wave" around the symmetrical axis of the Gaussian beam, but the perturbative effects produced by the + and × polarization of the GW have a different physical behaviour. For the high-frequency relic GW with vg = 1010 Hz, h = l0-30, recently expected by the quintessential inflationary models, the corresponding perturbative photon flux passing through the region 10-2 m2 would be expected to be 104 s-1. This is the largest perturbative photon flux we have recently analysed and estimated using the typical laboratory parameters.

  11. 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.

  12. 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.

  13. 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.

  14. Effects of high frequency repetitive transcranial magnetic stimulation on emotional disorders and P300 of patients with Parkinson's disease%高频重复经颅磁刺激对帕金森病患者情绪障碍及P300电位的影响

    Institute of Scientific and Technical Information of China (English)

    郑秀琴; 于苏文; 陈升东; 蒋建波

    2013-01-01

    研究背景以往研究显示高频重复经颅磁刺激可以明显改善帕金森病患者运动功能,但帕金森病晚期非运动性症状给患者带来更为严重的影响,因此研究高频重复经颅磁刺激治疗帕金森病患者情绪和认知功能障碍等非运动性症状的临床疗效具有重要意义.方法共纳入65例诊断明确的帕金森病患者,根据统一帕金森病评价量表(UPDRS)、汉密尔顿焦虑量表(HAMA)、汉密尔顿抑郁量表(HAMD)和P300波,评价高频重复经颅磁刺激对患者精神行为和情绪、日常生活活动能力及运动功能的改善作用.结果与治疗前相比,帕金森病患者UPDRS总评分(t=10.872,P=0.000)和UPDRSⅠ(t=4.538,P:0.023)、UPDRS Ⅱ(t=8.846,P=0.012)、UPDRS Ⅲ(t=9.114,P=0.000)评分降低.患者焦虑和抑郁发生率由治疗前的52.46%(32/61)降至29.51%(18/61),认知功能障碍发生率由治疗前的42.62%(26/61)降至32.79%(20/61),HAMA(t=3.692,P=0.000)和HAMD(t=4.241,P=0.000)评分显著降低,但幻觉发生率由治疗前的18.03%(11/61)升至29.51%(18161).P300波潜伏期(t=5.924,P=0.000)和波幅(t=8.512,P=0.000)与治疗前比较,差异均有统计学意义.结论高频重复经颅磁刺激能够减轻帕金森病患者焦虑和抑郁状态,改善其认知功能.%Background Previous studies revealed that repetitive transcranial magnetic stimulation (rTMS) can obviously improve the motor function of Parkinson's disease (PD) patients. Since the non-motor symptoms of late stage PD can induce worse impacts on patients, it is important to investigate the clinical effects of high frequency rTMS on non- motor symptoms including emotional and cognitive disorders of PD patients. Methods Sixty - five patients with PD received rTMS therapy. Unified Parkinson's Disease Rating Scale (UPDRS), Hamilton Anxiety Scale (HAMA), Hamilton Depression Scale (HAMD) and P300 before and after treatment were recorded to assess the effect of rTMS on patient's emotions, abilities of

  15. Vacuum amplification of the high-frequency electromagnetic radiation

    OpenAIRE

    Vilkovisky, G. A.

    1998-01-01

    When an electrically charged source is capable of both emitting the electromagnetic waves and creating charged particles from the vacuum, its radiation gets so much amplified that only the backreaction of the vacuum makes it finite. The released energy and charge are calculated in the high-frequency approximation. The technique of expectation values is advanced and employed.

  16. 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...

  17. 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...

  18. Influence of pore roughness on high-frequency permeability

    NARCIS (Netherlands)

    Cortis, A.; Smeulders, D.M.J.; Guermond, J.L.; Lafarge, D.

    2003-01-01

    The high-frequency behavior of the fluid velocity patterns for smooth and corrugated pore channels is studied. The classical approach of Johnson et al. [J. Fluid Mech. 176, 379 (1987)] for smooth geometries is obtained in different manners, thus clarifying differences with Sheng and Zhou [Phys. Rev.

  19. Fact or friction: jumps at ultra high frequency

    NARCIS (Netherlands)

    K. Christensen; R. Oomen; M. Podolskij

    2011-01-01

    In this paper, we demonstrate that jumps in financial asset prices are not nearly as common as generally thought, and that they account for only a very small proportion of total return variation. We base our investigation on an extensive set of ultra high-frequency equity and foreign exchange rate d

  20. 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...

  1. High-frequency Trading, Algorithmic Finance, and the Flash Crash

    DEFF Research Database (Denmark)

    Borch, Christian

    2016-01-01

    The Flash Crash of 6 May 2010 has an interesting status in discussions of high-frequency trading, i.e. fully automated, superfast computerized trading: it is invoked both as an important illustration of how this field of algorithmic trading operates and, more often, as an example of how fully aut...

  2. 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...

  3. 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.

  4. 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, an...

  5. 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

  6. On the high frequency spectrum of a classical accretion disc

    CERN Document Server

    Balbus, Steven A

    2014-01-01

    We derive simple and explicit expressions for the high frequency spectrum of a classical accretion disc. Both stress-free and finite stress inner boundaries are considered. A classical accretion disc spectrum with a stress-free inner boundary departs from a Wien spectrum at large $\

  7. Piezoelectric films for high frequency ultrasonic transducers in biomedical applications.

    Science.gov (United States)

    Zhou, Qifa; Lau, Sienting; Wu, Dawei; Shung, K Kirk

    2011-02-01

    Piezoelectric films have recently attracted considerable attention in the development of various sensor and actuator devices such as nonvolatile memories, tunable microwave circuits and ultrasound transducers. In this paper, an overview of the state of art in piezoelectric films for high frequency transducer applications is presented. Firstly, the basic principles of piezoelectric materials and design considerations for ultrasound transducers will be introduced. Following the review, the current status of the piezoelectric films and recent progress in the development of high frequency ultrasonic transducers will be discussed. Then details for preparation and structure of the materials derived from piezoelectric thick film technologies will be described. Both chemical and physical methods are included in the discussion, namely, the sol-gel approach, aerosol technology and hydrothermal method. The electric and piezoelectric properties of the piezoelectric films, which are very important for transducer applications, such as permittivity and electromechanical coupling factor, are also addressed. Finally, the recent developments in the high frequency transducers and arrays with piezoelectric ZnO and PZT thick film using MEMS technology are presented. In addition, current problems and further direction of the piezoelectric films for very high frequency ultrasound application (up to GHz) are also discussed.

  8. 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...

  9. 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.

  10. Collocations of High Frequency Noun Keywords in Prescribed Science Textbooks

    Science.gov (United States)

    Menon, Sujatha; Mukundan, Jayakaran

    2012-01-01

    This paper analyses the discourse of science through the study of collocational patterns of high frequency noun keywords in science textbooks used by upper secondary students in Malaysia. Research has shown that one of the areas of difficulty in science discourse concerns lexis, especially that of collocations. This paper describes a corpus-based…

  11. Electronic Structure of ZnO Quantum Dots studied by High-frequency EPR, ESE, ENDOR and ODMR Spectroscopy

    NARCIS (Netherlands)

    Baranov, P.G.; Romanov, N.G.; Bundakova, A.P.; de Mello-Donega, Celso; Schmidt, J.

    2016-01-01

    High-frequency electron paramagnetic resonance (EPR), electron spin echo (ESE), electron-nuclear double resonance (ENDOR) and optically detected magnetic resonance (ODMR) were applied for the investigation of the electronic properties of ZnO colloidal quantum dots (QDs) which consist of a ZnO nanocr

  12. In-situ fabrication of particulate reinforced aluminum matrix composites under high-frequency pulsed electromagnetic field

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Pulsed magnetic field is generated when imposing pulse signal on high-frequency magnetic field. Distribution of the inner magnetic intensity in induction coils tends to be uniform. Furthermore oscillation and disturbance phenomena appear in the melt. Insitu Al2O3 and Al3Zr particulate reinforced aluminum matrix composites have been synthesized by direct melt reaction using Al-Zr(CO3)2 components under a foreign field. The size of reinforced particulates is 2-3 μm. They are well distributed in the matrix.Thermodynamic and kinetic analysis show that high-frequency pulsed magnetic field accelerates heat and mass transfer processes and improves the kinetic condition of in-situ fabrication.

  13. Design of Plasma Generator Driven by High-frequency High-voltage Power Supply

    Directory of Open Access Journals (Sweden)

    C. Yong-Nong

    2013-03-01

    Full Text Available In this research, a high-frequency high-voltage power supply designed for plasma generator is presented. The powersupply mainly consists of a series resonant converter with a high-frequency high-voltage boost transformer. Due to theindispensable high-voltage inheritance in the operation of plasma generator, the analysis of transformer needconsidering not only winding resistance, leakage inductance, magnetizing inductance, and core-loss resistance, butalso parasitic capacitance resulted from the insulation wrappings on the high-voltage side. This research exhibits asimple approach to measuring equivalent circuit parameters of the high-frequency, high-voltage transformer with straycapacitance being introduced into the conventional modeling. The proposed modeling scheme provides not only aprecise measurement procedure but also effective design information for series-load resonant converter. The plasmadischarging plate is designed as part of the electric circuit in the series load-resonant converter and the circuit modelof the plasma discharging plate is also conducted as well. Thus, the overall model of the high-voltage plasmagenerator is built and the designing procedures for appropriate selections of the corresponding resonant-circuitparameters can be established. Finally, a high-voltage plasma generator with 220V, 60Hz, and 1kW input, along witha 22 kHz and over 8kV output, is realized and implemented.

  14. Rapidly solidified Fe-6.5%Si alloy powders for high frequency use (abstract)

    Science.gov (United States)

    Duk Choi, Seung; Jin Yang, Choong

    1996-04-01

    Fe-(3˜6.5%) Si alloy powders having a high magnetic induction (Bs) and a low core loss value for high frequency use were obtained by an extractive melt spinning as well as a centrifugal atomization technique. Sintered core rings made by the rapidly solidified Fe-6.5% Si powders exhibited the high frequency electromagnetic properties: saturated induction (B8) of 1.23 T, coercivity (Hc) of 9.5 A/m, relative permeability (μa) of 6321, and core loss (W10/50) of 1.27 W/kg from the rings of 1.1 mm thick. The saturated induction values were found to be almost identical to those of nonoriented Fe-3% Si steel sheet and 6.5% Si sheet prepared by the CVD technique. The high frequency core loss values were measured not to be changed much up to 10 kHz (W1/10k=55 W/kg) in applied ac frequency.

  15. [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.

  16. 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.

  17. 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...

  18. Inference from high-frequency data: A subsampling approach

    DEFF Research Database (Denmark)

    Christensen, Kim; Podolskij, Mark; Thamrongrat, Nopporn;

    copies of the original statistic based on local stretches of high-frequency data, and then it studies the sampling variation of these. We show that our estimator is consistent both in frictionless markets and models with additive microstructure noise. We derive a rate of convergence for it and are also...... able to determine an optimal rate for its tuning parameters (e.g., the number of subsamples). Subsampling does not require an extra set of estimators to do inference, which renders it trivial to implement. As a variance-covariance matrix estimator, it has the attractive feature that it is positive semi...... assessment of the sampling errors inherent in high-frequency estimation of volatility. We highlight the finite sample properties of the subsampler in a Monte Carlo study, while some initial empirical work demonstrates its use to draw feasible inference about volatility in financial markets....

  19. 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.

  20. 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...

  1. 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.

  2. Ultra high frequency induction welding of powder metal compacts

    Energy Technology Data Exchange (ETDEWEB)

    Cavdar, U.; Gulsahin, I.

    2014-10-01

    The application of the iron based Powder Metal (PM) compacts in Ultra High Frequency Induction Welding (UHFIW) were reviewed. These PM compacts are used to produce cogs. This study investigates the methods of joining PM materials enforceability with UHFIW in the industry application. Maximum stress and maximum strain of welded PM compacts were determined by three point bending and strength tests. Microhardness and microstructure of induction welded compacts were determined. (Author)

  3. High-Frequency Propagation in the Ocean Waveguide

    Science.gov (United States)

    2016-06-07

    High-Frequency Propagation in the Ocean Waveguide Michael B. Porter Heat, Light, and Sound Research , Inc. 12730 High Bluff Drive, Suite 130... Research , Inc. 12730 High Bluff Drive, Suite 130 San Diego, CA 92130 phone: (858) 755-9650 fax: (858) 228-1734 email: katherine.kim...interest has a variety of applications, including mine countermeasures, tracking odontocetes in navy ranges, and bottom mapping. However, the core

  4. High-Frequency Chest Compression: A Summary of the Literature

    OpenAIRE

    Dosman, Cara F; Jones, Richard L

    2005-01-01

    The purpose of the present literature summary is to describe high-frequency chest compression (HFCC), summarize its history and outline study results on its effect on mucolysis, mucus transport, pulmonary function and quality of life. HFCC is a mechanical method of self-administered chest physiotherapy, which induces rapid air movement in and out of the lungs. This mean oscillated volume is an effective method of mucolysis and mucus clearance. HFCC can increase independence. Some studies have...

  5. Clinical Implications High Frequency Chest Wall Oscillation (HFCWO)

    OpenAIRE

    Mantellini E.; Perrero L.; Petrozzino S.; Gatta A.; Bona S.

    2012-01-01

    Purpose: patients with neuromuscular diseases presents an high incidence of respiratory infections favoured by stagnation of deep bronchial secretions and deficit of cough. The aim of the study is to evaluate the correct treatment of this condition and the role of High Frequency Chest Wall Oscillation (HFCWO) in helping the removal of bronchial secretions and reduce the incidence of infections in patients with neuromuscular disease.Methods: analysis of the current bibliography related to resp...

  6. Acoustic trapping with a high frequency linear phased array

    OpenAIRE

    Zheng, Fan; Ying LI; Hsu, Hsiu-Sheng; Liu, Changgeng; Tat Chiu, Chi; Lee, Changyang; Ham Kim, Hyung; Shung, K. Kirk

    2012-01-01

    A high frequency ultrasonic phased array is shown to be capable of trapping and translating microparticles precisely and efficiently, made possible due to the fact that the acoustic beam produced by a phased array can be both focused and steered. Acoustic manipulation of microparticles by a phased array is advantageous over a single element transducer since there is no mechanical movement required for the array. Experimental results show that 45 μm diameter polystyrene microspheres can be eas...

  7. Piezoelectric films for high frequency ultrasonic transducers in biomedical applications

    OpenAIRE

    Zhou, Qifa; Lau, Sienting; WU, DAWEI; Shung, K. Kirk

    2011-01-01

    Piezoelectric films have recently attracted considerable attention in the development of various sensor and actuator devices such as nonvolatile memories, tunable microwave circuits and ultrasound transducers. In this paper, an overview of the state of art in piezoelectric films for high frequency transducer applications is presented. Firstly, the basic principles of piezoelectric materials and design considerations for ultrasound transducers will be introduced. Following the review, the curr...

  8. 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.

  9. Strange effects of strong high-frequency excitation

    DEFF Research Database (Denmark)

    Thomsen, Jon Juel

    2003-01-01

    Three general effects of mechanical high-frequency excitation (HFE) are described: Stiffening - an apparent change in the stiffness associated with an equilibrium; Biasing - a tendency for a system to move towards a particular state which does not exist or is unstable without HFE; and Smoothening...... - a tendency for discontinuities to be apparently smeared out by HFE. Studies of specific physical systems as well as more general models are described....

  10. 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.

  11. Measurements Of High Frequency Electromagnetic Waves In Center Of Mus

    OpenAIRE

    etem, taha; ABBASOV, Teymuraz

    2016-01-01

    All electrically powered devices cause electromagnetic wave exposure onhuman body and we use them nearly every moment in a day. Mobile phones,computers, televisions, hair dryers, lighting systems, etc. they all useelectricity and naturally radiate electromagnetic waves. Effects ofelectromagnetic waves are not clear but international organizations definelimit values depending on epidemiological studies in this field. In this studywe measure high frequency electromagnetic waves in city center o...

  12. Modeling high-frequency capacitance in SOI MOS capacitors

    Science.gov (United States)

    Łukasiak, Lidia; Jasiński, Jakub; Beck, Romuald B.; Ikraiam, Fawzi A.

    2016-12-01

    This paper presents a model of high frequency capacitance of a SOI MOSCAP. The capacitance in strong inversion is described with minority carrier redistribution in the inversion layer taken into account. The efficiency of the computational process is significantly improved. Moreover, it is suitable for the simulation of thin-film SOI structures. It may also be applied to the characterization of non-standard SOI MOSCAPS e.g. with nanocrystalline body.

  13. Clinical Implications High Frequency Chest Wall Oscillation (HFCWO

    Directory of Open Access Journals (Sweden)

    Mantellini E.

    2012-01-01

    Full Text Available Purpose: patients with neuromuscular diseases presents an high incidence of respiratory infections favoured by stagnation of deep bronchial secretions and deficit of cough. The aim of the study is to evaluate the correct treatment of this condition and the role of High Frequency Chest Wall Oscillation (HFCWO in helping the removal of bronchial secretions and reduce the incidence of infections in patients with neuromuscular disease.Methods: analysis of the current bibliography related to respiratory infections and neuromuscular disease. PCEF (Peak Cough Expiratory Flow is used as a standardized indicator of efficiency of cough.Results: the High Frequency Chest Wall Oscillation (HFCWO is useful, in cases of increased production of mucus and impairment of muco-ciliary clearance, to remove the tracheobronchial secretions and reduce the incidence of infections.Conclusions: the correct approach to patients with neuromuscular disease and frequent respiratory infections is focused on treatment of cough ineffective and management of bronchial secretions. High Frequency Chest Wall Oscillation (HFCWO (VEST has a central role in treatment of cough ineffective and management of bronchial secretions reducing respiratory infections.

  14. Occupational hearing loss: tonal audiometry X high frequencies audiometry

    Directory of Open Access Journals (Sweden)

    Lauris, José Roberto Pereira

    2009-09-01

    Full Text Available Introduction: Studies on the occupational exposure show that noise has been reaching a large part of the working population around the world, and NIHL (noise-induced hearing loss is the second most frequent disease of the hearing system. Objective: To review the audiometry results of employees at the campus of the University of São Paulo, Bauru. Method: 40 audiometry results were analyzed between 2007 and 2008, whose ages comprised between 32 and 59 years, of both sexes and several professions: gardeners, maintenance technicians, drivers etc. The participants were divided into 2 groups: those with tonal thresholds within acceptable thresholds and those who presented auditory thresholds alterations, that is tonal thresholds below 25 dB (NA in any frequency (Administrative Rule no. 19 of the Ministry of Labor 1998. In addition to the Conventional Audiologic Evaluation (250Hz to 8.000Hz we also carried out High Frequencies Audiometry (9000Hz, 10000Hz, 11200Hz, 12500Hz, 14000Hz and 16000Hz. Results: According to the classification proposed by FIORINI (1994, 25.0% (N=10 they presented with NIHL suggestive audiometric configurations. The results of high frequencies Audiometry confirmed worse thresholds than those obtained in the conventional audiometry in the 2 groups evaluated. Conclusion: The use of high frequencies audiometry proved to be an important register as a hearing alteration early detection method.

  15. Development of ti-coated ferromagnetic needle, adaptable for ablation cancer therapy by high-frequency induction heating.

    Science.gov (United States)

    Naohara, Takashi; Aono, Hiromichi; Maehara, Tsunehiro; Hirazawa, Hideyuki; Matsutomo, Shinya; Watanabe, Yuji

    2012-03-06

    To develop a novel ablation therapy for human solid cancer, the heating properties of a ferromagnetic carbon steel rod and a prototype Ti-coated needle using this carbon steel rod, were investigated in several high-frequency outputs at 300 kHz. In the former, the heating property was drastically different among the three inclination angles (θ = 0°, 45° and 90°) relative to the magnetic flux direction as a result of the shape magnetic anisotropy. However, the effect of the inclination angles was completely eliminated in the latter. It is considered that the complete non-oriented heating property relative to the magnetic flux direction allows the precise control of the ablation temperature during minimally invasive thermotherapy without a lead-wire connected to a fiber-optic thermometer. This newly designed Ti-coated device will be suitable for clinical use combined with its superior biocompatibility for ablation treatments using high-frequency induction heating.

  16. 高频彩色多普勒超声与MRI在早期类风湿关节炎诊断中的价值%Value of high frequency ultrasonography and nucler magnetic resonance imaging in the early diagnosis of rheumatoid arthritis

    Institute of Scientific and Technical Information of China (English)

    王明玉; 王宪斌; 孙雪辉; 刘奉立; 黄生传

    2014-01-01

    目的 探讨高频彩色多普勒超声(HFUS)及MRI在早期类风湿关节炎(RA)患者关节病变检测中的应用价值.方法 回顾性分析2010年1-12月在山东烟台毓璜顶医院确诊的39例RA患者的临床资料,男20例,女19例,平均年龄(51.8±2.2)岁.所有患者双手、双腕均行HFUS、MR检查,重点观察有无骨侵蚀、骨髓水肿、滑膜增殖、滑膜血流、关节积液、肌腱炎等影像表现,并对两种检查方法的结果采用x2检验进行对比分析.结果 共检查关节1 248个,HFUS和MRI在观察骨侵蚀[5.1% (44/858) vs 4.1% (35/858),x2=1.075,P>0.05]、肌腱炎[4.6% (18/390) vs 1.5%(14/390),x2=0.521,P>0.05]、腱鞘水肿[9.5% (37/390) vs 7.7% (30/390),x2=0.800,P>0.05]方面的检出率差异无统计学意义;HFUS在观察关节滑膜增殖[15.4% (132/858) vs 7.7%(66/858),x2=24.870,P<0.01]、关节积液[10.4%(89/858) vs 6.1%(52/858),x2=10.578,P<0.05]方面明显的检出率优于MRI; MRI在观察骨髓水肿方面[0% (0/858)vs 5.5% (47/858),x2=48.324,P<0.05]优于HFUS.结论 HFUS在检测早期RA患者病变关节的骨侵蚀、肌腱炎、腱鞘水肿、滑膜增殖、关节积液等方面,与MRI具有等同、甚至更优异的诊断价值.%Objective To investigate the value of high frequency ultrasonography (HFUS) and nucler magnetic resonance imaging (MRI) in the early diagnosis of rheumatoid arthritis(RA).Methods The data of 39 consecutive patients with RA admitted in Yantai Yuhuangding hospital from January 2010 to December 2010 were retrospectively studied.In 39 cases of patients,males were 20 cases,female were 19 cases,the average age was (51.8 ±2.2) years.Bilateral bilateral wrist and hands jionts were examined by HFUS and MRI.Bone erosion,bone marrow edema,synovial proliferation,synovial blood flow,jiont effusion and tendinitis were received and the differences between the two examination results were compared.Chi-square test was used for statistical analysis

  17. Funding begets biodiversity

    DEFF Research Database (Denmark)

    Ahrends, Antje; Burgess, Neil David; Gereau, Roy E.

    2011-01-01

    Aim Effective conservation of biodiversity relies on an unbiased knowledge of its distribution. Conservation priority assessments are typically based on the levels of species richness, endemism and threat. Areas identified as important receive the majority of conservation investments, often...... facilitating further research that results in more species discoveries. Here, we test whether there is circularity between funding and perceived biodiversity, which may reinforce the conservation status of areas already perceived to be important while other areas with less initial funding may remain overlooked......, and variances decomposed in partial regressions. Cross-correlations are used to assess whether perceived biodiversity drives funding or vice versa. Results Funding explained 65% of variation in perceived biodiversity patterns – six times more variation than accounted for by 34 candidate environmental factors...

  18. High Frequency Cut-off and Changing of Radio Emission Mechanism in Pulsars

    CERN Document Server

    Kontorovich, V M

    2012-01-01

    Pulsars are the fast rotating neutron stars with strong magnetic field emitting over a wide frequency range. In spite of the efforts during 40 years after the discovery of pulsars, the mechanism of their radio emission remains to be unknown so far. We propose a new approach to solving this problem. The object of our study is a sample of pulsars with a high-frequency break of the spectrum from Pushchino catalogue. A theoretical explanation of the observed dependence of the high-frequency break from the pulsar period is given. The dependence of the break position from the magnetic field is predicted. This explanation is based on a new mechanism for electron emission in the inner polar gap. Radiation occurs when electrons are accelerated in the electric field rising from zero at the star surface. Acceleration passes through a maximum and tends to zero when the electron velocity approaches the velocity of light. The all radiated power is allocated to the radio band. The averaging over the polar cap, with some nat...

  19. Photospheric high-frequency acoustic power excess in sunspot umbra: signature of magneto-acoustic modes

    Directory of Open Access Journals (Sweden)

    S. Zharkov

    2013-08-01

    Full Text Available We present observational evidence for the presence of MHD (magnetohydrodynamic waves in the solar photosphere deduced from SOHO/MDI (Solar and Heliospheric Observatory/Michelson Doppler Imager Dopplergram velocity observations. The magneto-acoustic perturbations are observed as acoustic power enhancement in the sunspot umbra at high-frequency bands in the velocity component perpendicular to the magnetic field. We use numerical modelling of wave propagation through localised non-uniform magnetic field concentration along with the same filtering procedure as applied to the observations to identify the observed waves. Guided by the results of the numerical simulations we classify the observed oscillations as magneto-acoustic waves excited by the trapped sub-photospheric acoustic waves. We consider the potential application of the presented method as a diagnostic tool for magnetohelioseismology.

  20. High-resistivity nanogranular Co-Al-O films for high-frequency applications

    Science.gov (United States)

    Khalili Amiri, Pedram; Zhuang, Yan; Schellevis, Hugo; Rejaei, Behzad; Vroubel, Marina; Ma, Yue; Burghartz, Joachim N.

    2007-05-01

    This work presents a series of high-resistivity nanogranular Co-Al-O films with maximum resistivity of ˜110mΩcm. The films were deposited using pulsed dc reactive sputtering of a Co72Al28 target in an oxygen/argon ambient. The samples were characterized by scanning electron microscopy (SEM), M-H loop measurements, and s-parameter measurements on microstrip transmission lines with Co-Al-O magnetic cores. The high-frequency magnetic permeability profile was extracted from the microstrip measurements. Reduction of deposition power resulted in resistivity enhancement, as well as reduction of coercivity and permeability. SEM images reveal an average grain size of ˜80nm for films with the highest resistivity.

  1. 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.

  2. High Frequency Ground Motion from Finite Fault Rupture Simulations

    Science.gov (United States)

    Crempien, Jorge G. F.

    There are many tectonically active regions on earth with little or no recorded ground motions. The Eastern United States is a typical example of regions with active faults, but with low to medium seismicity that has prevented sufficient ground motion recordings. Because of this, it is necessary to use synthetic ground motion methods in order to estimate the earthquake hazard a region might have. Ground motion prediction equations for spectral acceleration typically have geometric attenuation proportional to the inverse of distance away from the fault. Earthquakes simulated with one-dimensional layered earth models have larger geometric attenuation than the observed ground motion recordings. We show that as incident angles of rays increase at welded boundaries between homogeneous flat layers, the transmitted rays decrease in amplitude dramatically. As the receiver distance increases away from the source, the angle of incidence of up-going rays increases, producing negligible transmitted ray amplitude, thus increasing the geometrical attenuation. To work around this problem we propose a model in which we separate wave propagation for low and high frequencies at a crossover frequency, typically 1Hz. The high-frequency portion of strong ground motion is computed with a homogeneous half-space and amplified with the available and more complex one- or three-dimensional crustal models using the quarter wavelength method. We also make use of seismic coda energy density observations as scattering impulse response functions. We incorporate scattering impulse response functions into our Green's functions by convolving the high-frequency homogeneous half-space Green's functions with normalized synthetic scatterograms to reproduce scattering physical effects in recorded seismograms. This method was validated against ground motion for earthquakes recorded in California and Japan, yielding results that capture the duration and spectral response of strong ground motion.

  3. A 300 Hz high frequency thermoacoustically driven pulse tube cooler

    Institute of Scientific and Technical Information of China (English)

    ZHU ShangLong; YU GuoYao; ZHANG XiaoDong; DAI Wei; LUO ErCang; ZHOU Yuan

    2008-01-01

    This article introduces the latest progress of a 300 Hz thermoacoustically driven pulse tube cooler. Based on the experience of former experiments, improvements have been made in the standing-wave engine, pulse tube cooler and their coupling mechanism. An inlet pressure ratio of 1.248 was obtained with the mean pressure and heating power of 4.13 MPa and 1760 W, respectively. A lowest no-load temperature of 69.5 K has been reached under this condition. This is the first time for thermoacousti-cally driven pulse tube coolers to reach the temperature below 76 K with such a high frequency.

  4. High frequency sampling of a continuous-time ARMA process

    CERN Document Server

    Brockwell, Peter J; Klüppelberg, Claudia

    2011-01-01

    Continuous-time autoregressive moving average (CARMA) processes have recently been used widely in the modeling of non-uniformly spaced data and as a tool for dealing with high-frequency data of the form $Y_{n\\Delta}, n=0,1,2,...$, where $\\Delta$ is small and positive. Such data occur in many fields of application, particularly in finance and the study of turbulence. This paper is concerned with the characteristics of the process $(Y_{n\\Delta})_{n\\in\\bbz}$, when $\\Delta$ is small and the underlying continuous-time process $(Y_t)_{t\\in\\bbr}$ is a specified CARMA process.

  5. 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.

  6. Dynamics and sensitivity analysis of high-frequency conduction block

    Science.gov (United States)

    Ackermann, D. Michael; Bhadra, Niloy; Gerges, Meana; Thomas, Peter J.

    2011-10-01

    The local delivery of extracellular high-frequency stimulation (HFS) has been shown to be a fast acting and quickly reversible method of blocking neural conduction and is currently being pursued for several clinical indications. However, the mechanism for this type of nerve block remains unclear. In this study, we investigate two hypotheses: (1) depolarizing currents promote conduction block via inactivation of sodium channels and (2) the gating dynamics of the fast sodium channel are the primary determinate of minimal blocking frequency. Hypothesis 1 was investigated using a combined modeling and experimental study to investigate the effect of depolarizing and hyperpolarizing currents on high-frequency block. The results of the modeling study show that both depolarizing and hyperpolarizing currents play an important role in conduction block and that the conductance to each of three ionic currents increases relative to resting values during HFS. However, depolarizing currents were found to promote the blocking effect, and hyperpolarizing currents were found to diminish the blocking effect. Inward sodium currents were larger than the sum of the outward currents, resulting in a net depolarization of the nodal membrane. Our experimental results support these findings and closely match results from the equivalent modeling scenario: intra-peritoneal administration of the persistent sodium channel blocker ranolazine resulted in an increase in the amplitude of HFS required to produce conduction block in rats, confirming that depolarizing currents promote the conduction block phenomenon. Hypothesis 2 was investigated using a spectral analysis of the channel gating variables in a single-fiber axon model. The results of this study suggested a relationship between the dynamical properties of specific ion channel gating elements and the contributions of corresponding conductances to block onset. Specifically, we show that the dynamics of the fast sodium inactivation gate are

  7. High frequency chest compression therapy: a case study.

    Science.gov (United States)

    Butler, S; O'Neill, B

    1995-01-01

    A new device, the ThAIRapy Bronchial Drainage System, enables patients with cystic fibrosis to self-administer the technique of high frequency chest compression (HFCC) to assist with mucociliary clearance. We review the literature on HFCC and outline a case study of a patient currently using the ThAIRapy Bronchial Drainage System. While mucociliary clearance and lung function may be enhanced by HFCC therapy, more research is needed to determine its efficacy, cost benefits, and optimum treatment guidelines. Although our initial experience with the patient using this device has been positive, we were unable to accurately evaluate the ThAIRapy Bronchial Drainage System.

  8. Acoustic trapping with a high frequency linear phased array.

    Science.gov (United States)

    Zheng, Fan; Li, Ying; Hsu, Hsiu-Sheng; Liu, Changgeng; Tat Chiu, Chi; Lee, Changyang; Ham Kim, Hyung; Shung, K Kirk

    2012-11-19

    A high frequency ultrasonic phased array is shown to be capable of trapping and translating microparticles precisely and efficiently, made possible due to the fact that the acoustic beam produced by a phased array can be both focused and steered. Acoustic manipulation of microparticles by a phased array is advantageous over a single element transducer since there is no mechanical movement required for the array. Experimental results show that 45 μm diameter polystyrene microspheres can be easily and accurately trapped and moved to desired positions by a 64-element 26 MHz phased array.

  9. Magnetism Materials and Applications

    CERN Document Server

    Trémolet de Lacheisserie, Étienne; Schlenker, Michel

    2005-01-01

    This book treats permanent magnet (hard) materials, magnetically soft materials for low-frequency applications and for high-frequency electronics, magnetostrictive materials, superconductors, magnetic-thin films and multilayers, and ferrofluids. Chapters are dedicated to magnetic recording, the role of magnetism in magnetic resonance imaging (MRI), and instrumentation for magnetic measurements.   

  10. 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.

  11. Design of a high frequency low voltage CMOS operational amplifier

    Directory of Open Access Journals (Sweden)

    Priyanka Kakoty

    2011-03-01

    Full Text Available A method is presented in this paper for the design of a high frequency CMOS operational amplifier (Op-Amp which operates at 3V power supply using tsmc 0.18 micron CMOS technology. The OPAMPdesigned is a two-stage CMOS OPAMP followed by an output buffer. This Operational Transconductance Amplifier (OTA employs a Miller capacitor and is compensated with a current buffer compensation technique. The unique behaviour of the MOS transistors in saturation region not only allows a designer to work at a low voltage, but also at a high frequency. Designing of two-stage op-ampsis a multi-dimensional-optimization problem where optimization of one or more parameters may easily result into degradation of others. The OPAMP is designed to exhibit a unity gain frequency of 2.02GHzand exhibits a gain of 49.02dB with a 60.50 phase margin. As compared to the conventional approach, the proposed compensation method results in a higher unity gain frequency under the same load condition.Design has been carried out in Tanner tools. Simulation results are verified using S-edit and W-edit.

  12. Design of a high frequency low voltage CMOS operational amplifier

    Directory of Open Access Journals (Sweden)

    Priyanka Kakoty

    2011-03-01

    Full Text Available A method is presented in this paper for the design of a high frequency CMOS operational amplifier (Op-Amp which operates at 3V power supply using tsmc 0.18 micron CMOS technology. The OPAMPdesigned is a two-stage CMOS OPAMP followed by an output buffer. This OperationalTransconductance Amplifier (OTA employs a Miller capacitor and is compensated with a current buffercompensation technique. The unique behaviour of the MOS transistors in saturation region not onlyallows a designer to work at a low voltage, but also at a high frequency. Designing of two-stage op-ampsis a multi-dimensional-optimization problem where optimization of one or more parameters may easilyresult into degradation of others. The OPAMP is designed to exhibit a unity gain frequency of 2.02GHzand exhibits a gain of 49.02dB with a 60.50 phase margin. As compared to the conventional approach, theproposed compensation method results in a higher unity gain frequency under the same load condition.Design has been carried out in Tanner tools. Simulation results are verified using S-edit and W-edit.

  13. Planck 2013 results. VI. High Frequency Instrument data processing

    CERN Document Server

    Ade, P.A.R.; Armitage-Caplan, C.; Arnaud, M.; Ashdown, M.; Atrio-Barandela, F.; Aumont, J.; Baccigalupi, C.; Banday, A.J.; Barreiro, R.B.; Battaner, E.; Benabed, K.; Benoît, A.; Benoit-Lévy, A.; Bernard, J. -P.; Bersanelli, M.; Bielewicz, P.; Bobin, J.; Bock, J.J.; Bond, J.R.; Borrill, J.; Bouchet, F.R.; Boulanger, F.; Bowyer, J.W.; Bridges, M.; Bucher, M.; Burigana, C.; Cardoso, J. -F.; Catalano, A.; Chamballu, A.; Chary, R. -R.; Chen, X.; Chiang, L. -Y; Chiang, H.C.; Christensen, P.R.; Church, S.; Clements, D.L.; Colombi, S.; Colombo, L.P.L.; Combet, C.; Couchot, F.; Coulais, A.; Crill, B.P.; Curto, A.; Cuttaia, F.; Danese, L.; Davies, R.D.; Davis, R.J.; de Bernardis, P.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Delouis, J. -M.; Désert, F. -X.; Dickinson, C.; Diego, J.M.; Dole, H.; Donzelli, S.; Doré, O.; Douspis, M.; Dunkley, J.; Dupac, X.; Efstathiou, G.; Enßlin, T.A.; Eriksen, H.K.; Finelli, F.; Forni, O.; Frailis, M.; Fraisse, A.A.; Franceschi, E.; Galeotta, S.; Ganga, K.; Giard, M.; Giardino, G.; Girard, D.; Giraud-Héraud, Y.; González-Nuevo, J.; Górski, K.M.; Gratton, S.; Gregorio, A.; Gruppuso, A.; Gudmundsson, J.E.; Hansen, F.K.; Hanson, D.; Harrison, D.; Helou, G.; Henrot-Versillé, S.; Herent, O.; Hernández-Monteagudo, C.; Herranz, D.; Hildebrandt, S.R.; Hivon, E.; Hobson, M.; Holmes, W.A.; Hornstrup, A.; Hou, Z.; Hovest, W.; Huffenberger, K.M.; Hurier, G.; Jaffe, T.R.; Jaffe, A.H.; Jones, W.C.; Juvela, M.; Keihänen, E.; Keskitalo, R.; Kisner, T.S.; Kneissl, R.; Knoche, J.; Knox, L.; Kunz, M.; Kurki-Suonio, H.; Lagache, G.; Lamarre, J. -M.; Lasenby, A.; Laureijs, R.J.; Lawrence, C.R.; Jeune, M. Le; Leonardi, R.; Leroy, C.; Lesgourgues, J.; Liguori, M.; Lilje, P.B.; Linden-Vørnle, M.; López-Caniego, M.; Lubin, P.M.; Macías-Pérez, J.F.; MacTavish, C.J.; Maffei, B.; Mandolesi, N.; Maris, M.; Marshall, D.J.; Martin, P.G.; Martínez-González, E.; Masi, S.; Matarrese, S.; Matthai, F.; Mazzotta, P.; McGehee, P.; Meinhold, P.R.; Melchiorri, A.; Mendes, L.; Mennella, A.; Migliaccio, M.; Mitra, S.; Miville-Deschênes, M. -A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Mottet, S.; Munshi, D.; Naselsky, P.; Nati, F.; Natoli, P.; Netterfield, C.B.; Nørgaard-Nielsen, H.U.; North, C.; Noviello, F.; Novikov, D.; Novikov, I.; Orieux, F.; Osborne, S.; Oxborrow, C.A.; Paci, F.; Pagano, L.; Pajot, F.; Paladini, R.; Paoletti, D.; Pasian, F.; Patanchon, G.; Perdereau, O.; Perotto, L.; Perrotta, F.; Piacentini, F.; Piat, M.; Pierpaoli, E.; Pietrobon, D.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Ponthieu, N.; Popa, L.; Poutanen, T.; Pratt, G.W.; Prézeau, G.; Prunet, S.; Puget, J. -L.; Rachen, J.P.; Racine, B.; Reach, W.T.; Rebolo, R.; Reinecke, M.; Remazeilles, M.; Renault, C.; Ricciardi, S.; Riller, T.; Ristorcelli, I.; Rocha, G.; Rosset, C.; Roudier, G.; Rowan-Robinson, M.; Rusholme, B.; Sanselme, L.; Santos, D.; Sauvé, A.; Savini, G.; Shellard, E.P.S.; Spencer, L.D.; Starck, J. -L.; Stolyarov, V.; Stompor, R.; Sudiwala, R.; Sureau, F.; Sutton, D.; Suur-Uski, A. -S.; Sygnet, J. -F.; Tauber, J.A.; Tavagnacco, D.; Techene, S.; Terenzi, L.; Tomasi, M.; Tristram, M.; Tucci, M.; Umana, G.; Valenziano, L.; Valiviita, J.; Van Tent, B.; Vibert, L.; Vielva, P.; Villa, F.; Vittorio, N.; Wade, L.A.; Wandelt, B.D.; White, S.D.M.; Yvon, D.; Zacchei, A.; Zonca, A.

    2014-01-01

    We describe the processing of the 531 billion raw data samples from the High Frequency Instrument (hereafter 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, and 857 GHz with an angular resolution ranging from 9.7 to 4.6 arcmin. The detector noise per (effective) beam solid angle is respectively, 10, 6, 12 and 39 microKelvin in HFI four lowest frequency channel (100--353 GHz) and 13 and 14 kJy/sr for the 545 and 857 GHz channels. Using the 143 GHz channel as a reference, these two high frequency channels are intercalibrated within 5% and the 353 GHz relative calibration is at the percent level. The 100 and 217 GHz channels, which together with the 143 GHz channel determine the high-multipole part of the CMB power spectrum (50 < l <2500), are intercalibrated at better than 0.2 %.

  14. Corrosion monitoring using high-frequency guided waves

    Science.gov (United States)

    Fromme, P.

    2016-04-01

    Corrosion can develop due to adverse environmental conditions during the life cycle of a range of industrial structures, e.g., offshore oil platforms, ships, and desalination plants. Generalized corrosion leading to wall thickness loss can cause the reduction of the strength and thus degradation of the structural integrity. The monitoring of corrosion damage in difficult to access areas can be achieved using high frequency guided waves propagating along the structure from accessible areas. Using standard ultrasonic wedge transducers with single sided access to the structure, guided wave modes were selectively generated that penetrate through the complete thickness of the structure. The wave propagation and interference of the different guided wave modes depends on the thickness of the structure. Laboratory experiments were conducted for wall thickness reduction due to milling of the steel structure. From the measured signal changes due to the wave mode interference the reduced wall thickness was monitored. Good agreement with theoretical predictions was achieved. The high frequency guided waves have the potential for corrosion damage monitoring at critical and difficult to access locations from a stand-off distance.

  15. 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.

  16. 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

  17. Development of magnetodielectric materials to be used in additive manufacturing processes for high-frequency applications

    Science.gov (United States)

    Parsons, Paul Emerson, II

    Electrical devices for very-high frequency (VHF, 0.03 -- 0.3 GHz) and ultra-high frequency (UHF, 0.3 -- 3.0 GHz) are commonly used for communications. However, the wavelengths, lambda, of these frequency bands correspond to lengths between 10 and 0.1 m, resulting in prohibitively large devices. Materials with an index of refraction, n, greater than 1 can be used to effectively shrink these devices by a factor of 1/ n. In this thesis, magnetodielectric materials (MDM), where n ≥1, have been made to be used in additive manufacturing processes with strict particle size requirements and were developed using various methods, such as polyol reduction and conventional ceramic solid state processing. These materials were characterized using x-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM), vibrating sample magnetometry (VSM), to determine their crystalline, physical, and direct current (DC) magnetization properties. The techniques used to synthesize the MDM yielded particles that were chemically similar, but had drastically different physical properties which heavily influences their high-frequency electromagnetic properties. These materials were then uniformly dispersed into a non-conducting medium, such as a low-electrical loss polymer or resin, and formed into composite samples with variable volumetric loading. These composite samples were measured using several techniques to characterize the frequency-dependent electromagnetic (EM) properties, such as relative permeability, relative permittivity, and their respective losses. Finite element method (FEM) simulations were performed using these MDM-composites to design a spiral antenna to be used at approximately 585 MHz.

  18. High-frequency supersonic heating of hydrogen for propulsion

    Energy Technology Data Exchange (ETDEWEB)

    Bonneville, Jacques M.

    1963-03-15

    The possibility of increasing the specific impulse of hydrogen by supersonic heating is shown on the basis of thermodynamics. The application of high-frequency electric fields to heat the gas permits a control over the heating rates in the nozzle, and results in a reduction in energy losses to walls, electrodes, etc. The efficiencies of the various energy transfer processes are considered in some detail. A simple process of expansion and heating is presented. Results of calculations of heat transfer rates to the nozzle wall are given. A consistent set of electron densities and electric fields are also calculated and presented. Some qualitative results of experimental work previously carried out are included. It is concluded that the process should increase the specific impulse of hydrogen appreciably, in a reasonably efficient manner, and that further experimental work is indicated. (auth)

  19. High frequency nano-optomechanical disk resonators in liquids

    CERN Document Server

    Gil-Santos, E; Nguyen, D T; Hease, W; Lemaître, A; Ducci, S; Leo, G; Favero, I

    2015-01-01

    Vibrating nano- and micromechanical resonators have been the subject of research aiming at ultrasensitive mass sensors for mass spectrometry, chemical analysis and biomedical diagnosis. Unfortunately, their merits diminish dramatically in liquids due to dissipative mechanisms like viscosity and acoustic losses. A push towards faster and lighter miniaturized nanodevices would enable improved performances, provided dissipation was controlled and novel techniques were available to efficiently drive and read-out their minute displacement. Here we report on a nano-optomechanical approach to this problem using miniature semiconductor disks. These devices combine mechanical motion at high frequency above the GHz, ultra-low mass of a few picograms, and moderate dissipation in liquids. We show that high-sensitivity optical measurements allow to direct resolve their thermally driven Brownian vibrations, even in the most dissipative liquids. Thanks to this novel technique, we experimentally, numerically and analytically...

  20. Dynamical Structures of High-Frequency Financial Data

    CERN Document Server

    Kim, K; Kim, S Y; Kim, Y; Yoon, S M; Chang, Ki-Ho; Kim, Kyungsik; Kim, Soo Yong; Kim, Yup; Yoon, Seong-Min

    2005-01-01

    We study the dynamical behavior of high-frequency data from the Korean Stock Price Index (KOSPI) using the movement of returns in Korean financial markets. The dynamical behavior for a binarized series of our models is not completely random. The conditional probability is numerically estimated from a return series of KOSPI tick data. Non-trivial probability structures can be constituted from binary time series of autoregressive (AR), logit, and probit models, for which the Akaike Information Criterion shows a minimum value at the 15th order. From our results, we find that the value of the correct match ratio for the AR model is slightly larger than the findings of other models.

  1. High-Frequency Acoustic Sediment Classification in Shallow Water

    CERN Document Server

    Bentrem, F W; Kalcic, M T; Duncan, M E; Bentrem, Frank W.; Sample, John; Kalcic, Maria T.; Duncan, Michael E.

    2002-01-01

    A geoacoustic inversion technique for high-frequency (12 kHz) multibeam sonar data is presented as a means to classify the seafloor sediment in shallow water (40-300 m). The inversion makes use of backscattered data at a variety of grazing angles to estimate mean grain size. The need for sediment type and the large amounts of multibeam data being collected with the Naval Oceanographic Office's Simrad EM 121A systems, have fostered the development of algorithms to process the EM 121A acoustic backscatter into maps of sediment type. The APL-UW (Applied Physics Laboratory at the University of Washington) backscattering model is used with simulated annealing to invert for six geoacoustic parameters. For the inversion, three of the parameters are constrained according to empirical correlations with mean grain size, which is introduced as an unconstrained parameter. The four unconstrained (free) parameters are mean grain size, sediment volume interaction, and two seafloor roughness parameters. Acoustic sediment cla...

  2. High frequency techniques an introduction to RF and microwave engineering

    CERN Document Server

    White, Joseph F

    2004-01-01

    A practical guide for today's wireless engineerHigh Frequency Techniques: An Introduction to RF and Microwave Engineering is a clearly written classical circuit and field theory text illustrated with modern computer simulation software. The book's ten chapters cover: *The origins and current uses of wireless transmission *A review of AC analysis, Kirchhoff's laws, RLC elements, skin effect, and introduction to the use of computer simulation software*Resonators, Q definitions, and Q-based impedance matching *Transmission lines, waves, VSWR, reflection phenomena, Fano's reflection bandwidth limits, telegrapher, and impedance transformation equations*Development and in-depth use of the Smith Chart *Matrix algebra with Z, Y, ABCD, S, and T matrix applications*An unusually thorough introduction to electromagnetic field theory, step-by-step development of vector calculus, Maxwell's equations, waveguides, propagation, and antennas*Backward wave, branch line, rat race and Wilkinson couplers, impedance measurements, a...

  3. Electrostatic Instabilities at High Frequency in a Plasma Shock Front

    Institute of Scientific and Technical Information of China (English)

    LV Jian-Hong; HE Yong; HU Xi-Wei

    2007-01-01

    New electrostatic instabilities in the plasma shock front are reported.These instabilities are driven by the electrostatic field which is caused by charge separation and the parameter gradients in a plasma shock front.The linear analysis to the high frequency branch of electrostatic instabilities has been carried out and the dispersion relations are obtained numerically.There are unstable disturbing waves in both the parallel and perpendicular directions of shock propagation.The real frequencies of both unstable waves are similar to the electron electrostatic wave,and the unstable growth rate in the parallel direction is much greater than the one in the perpendicular direction.The dependence of growth rates on the electric field and parameter gradients is also presented.

  4. High-Frequency Cutoff in Type III Bursts

    Science.gov (United States)

    Stanislavsky, A. A.; Konovalenko, A. A.; Volvach, Ya. S.; Koval, A. A.

    In this article we report about a group of solar bursts with high-frequency cutoff, observed on 19 August of 2012 near 8:23 UT, simultaneously by three different radio telescopes: the Ukrainian decameter radio telescope (8-33 MHz), the French Nancay Decametric Array (10-70 MHz) and the Italian San Vito Solar Observatory of RSTN (25-180 MHz). Morphologically the bursts are very similar to the type III bursts. The solar activity is connected with the emergency of a new group of solar spots on the far side of the Sun with respect to observers on Earth. The solar bursts accompany many moderate flares over eastern limb. The refraction of the behind-limb radio bursts towards the Earth is favorable, if CMEs generate low-density cavities in solar corona.

  5. 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.

  6. 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.

  7. Articulated pipes conveying fluid pulsating with high frequency

    DEFF Research Database (Denmark)

    Jensen, Jakob Søndergaard

    1999-01-01

    Stability and nonlinear dynamics of two articulated pipes conveying fluid with a high-frequency pulsating component is investigated. The non-autonomous model equations are converted into autonomous equations by approximating the fast excitation terms with slowly varying terms. The downward hanging...... pipe position will lose stability if the mean flow speed exceeds a certain critical value. Adding a pulsating component to the fluid flow is shown to stabilize the hanging position for high values of the ratio between fluid and pipe-mass, and to marginally destabilize this position for low ratios....... An approximate nonlinear solution for small-amplitude flutter oscillations is obtained using a fifth-order multiple scales perturbation method, and large-amplitude oscillations are examined by numerical integration of the autonomous model equations, using a path-following algorithm. The pulsating fluid component...

  8. 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.

  9. 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.

  10. Gravitational-wave astronomy: the high-frequency window

    CERN Document Server

    Andersson, N; Andersson, Nils; Kokkotas, Kostas D

    2004-01-01

    This contribution is divided in two parts. The first part provides a text-book level introduction to gravitational radiation. The key concepts required for a discussion of gravitational-wave physics are introduced. In particular, the quadrupole formula is applied to the anticipated ``bread-and-butter'' source for detectors like LIGO, GEO600, EGO and TAMA300: inspiralling compact binaries. The second part provides a brief review of high frequency gravitational waves. In the frequency range above (say) 100Hz, gravitational collapse, rotational instabilities and oscillations of the remnant compact objects are potentially important sources of gravitational waves. Significant and unique information concerning the various stages of collapse, the evolution of protoneutron stars and the details of the supranuclear equation of state of such objects can be drawn from careful study of the gravitational-wave signal. As the amount of exciting physics one may be able to study via the detections of gravitational waves from ...

  11. High-frequency shear-horizontal surface acoustic wave sensor

    Science.gov (United States)

    Branch, Darren W

    2013-05-07

    A Love wave sensor uses a single-phase unidirectional interdigital transducer (IDT) on a piezoelectric substrate for leaky surface acoustic wave generation. The IDT design minimizes propagation losses, bulk wave interferences, provides a highly linear phase response, and eliminates the need for impedance matching. As an example, a high frequency (.about.300-400 MHz) surface acoustic wave (SAW) transducer enables efficient excitation of shear-horizontal waves on 36.degree. Y-cut lithium tantalate (LTO) giving a highly linear phase response (2.8.degree. P-P). The sensor has the ability to detect at the pg/mm.sup.2 level and can perform multi-analyte detection in real-time. The sensor can be used for rapid autonomous detection of pathogenic microorganisms and bioagents by field deployable platforms.

  12. The wave buoy analogy - estimating high-frequency wave excitations

    DEFF Research Database (Denmark)

    Nielsen, Ulrik Dam

    2008-01-01

    The paper deals with the wave buoy analogy where a ship is considered as a wave buoy, so that measured ship responses are used as a basis to estimate wave spectra and associated sea state parameters. The study presented follows up on a previous paper, Nielsen [Nielsen UD. Response-based estimation...... of sea state parameters — influence of filtering. Ocean Engineering 2007;34:1797–810.], where time series of ship responses were generated from a known wave spectrum for the purpose of the inverse process — the estimation of the underlying wave excitations. Similar response generations and vice versa...... be estimated reasonably well, even considering high-frequency wave components of a wind sea wave spectrum....

  13. High-frequency thermal processes in harmonic crystals

    CERN Document Server

    Kuzkin, Vitaly A

    2016-01-01

    We consider two high-frequency thermal processes in uniformly heated harmonic crystals relaxing towards equilibrium: (i) equilibration of kinetic and potential energies and (ii) redistribution of energy among spatial directions. Equation describing these processes with deterministic initial conditions is derived. Solution of the equation shows that characteristic time of these processes is of the order of ten periods of atomic vibrations. After that time the system practically reaches the stationary state. It is shown analytically that in harmonic crystals temperature tensor is not isotropic even in the stationary state. As an example, harmonic triangular lattice is considered. Simple formula relating the stationary value of the temperature tensor and initial conditions is derived. The function describing equilibration of kinetic and potential energies is obtained. It is shown that the difference between the energies (Lagrangian) oscillates around zero. Amplitude of these oscillations decays inversely proport...

  14. Direct current effects on high-frequency properties of patterned permalloy thin films.

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, H.; Hoffmann, A.; Divan, R.; Wang, P.; Clemson Univ.

    2009-12-01

    We have investigated experimentally direct current (dc) effects on high-frequency properties of two different permalloy (Py) submicrometer patterns of 0.24 mum and 0.55 mum width, 10 mum length, and 100 nm thickness. The natural ferromagnetic resonance (FMR) frequencies for the two samples are about 8.5 and 11.5 GHz. A 50 mA dc produces a FMR frequency reduction of about 1 GHz in both samples. We extracted susceptibility spectra for the samples from the measurement data. We studied inductance variations of Py embedded transmission lines for different dc levels. With 50 mA dc, the operational frequencies of the inductances decreased by 9% and 12.5%. We also tested effects of magnetic fields generated by external magnets on the submicrometer patterns for comparison. To obtain the same magnetization rotation angle, the external magnetic field needs to be about five times larger than the Ampere field created by the direct current. This behavior is unique and may be associated with the increased thermal energy from the Joule heating effects.

  15. Microfabricated Thin-Film Inductors for High-Frequency DC-DC Power Conversion

    Science.gov (United States)

    Yao, Di

    2011-12-01

    Microfabricated V-groove inductors targeted to operate above 10 MHz are investigated. Multilayer nano-granular Co-Zr-O/ZrO2 magnetic thin films are used as the core material of the inductors to improve the magnetic performance of the films deposited on the sidewalls of V-grooves and to control eddy-current loss in the core, which goes up very quickly as frequency increases. A loss model is developed to estimate eddy-current loss in multilayer magnetic thin films considering the effect of displacement current at high frequencies, and the model is applied in the design of V-groove inductors. V-groove inductors using multilayer magnetic thin films are co-optimized with power MOSFETs for 7-V to 3.3-V, 1-A DC-DC buck converters to maximize power handling capability per unit substrate area for given efficiencies. Prototype V-groove inductors are fabricated based on the optimization results, and measured and predicted performance of the inductors match well. The prototype inductors are a promising candidate for high-power-density high-efficiency DC-DC converters. The 7-V to 3.3-V, 1-A converters using prototype V-groove inductors are expected to exhibit power density of 2.5 W/mm2 and efficiency of 86% at 100 MHz, and power density of 0.36 W/mm2 and efficiency of 91% at 11 MHz.

  16. High-frequency underwater plasma discharge application in antibacterial activity

    Science.gov (United States)

    Ahmed, M. W.; Choi, S.; Lyakhov, K.; Shaislamov, U.; Mongre, R. K.; Jeong, D. K.; Suresh, R.; Lee, H. J.

    2017-03-01

    Plasma discharge is a novel disinfection and effectual inactivation approach to treat microorganisms in aqueous systems. Inactivation of Gram-negative Escherichia coli (E. coli) by generating high-frequency, high-voltage, oxygen (O2) injected and hydrogen peroxide (H2O2) added discharge in water was achieved. The effect of H2O2 dose and oxygen injection rate on electrical characteristics of discharge and E. coli disinfection has been reported. Microbial log reduction dependent on H2O2 addition with O2 injection was observed. The time variation of the inactivation efficiency quantified by the log reduction of the initial E. coli population on the basis of optical density measurement was reported. The analysis of emission spectrum recorded after discharge occurrence illustrated the formation of oxidant species (OH•, H, and O). Interestingly, the results demonstrated that O2 injected and H2O2 added, underwater plasma discharge had fabulous impact on the E. coli sterilization. The oxygen injection notably reduced the voltage needed for generating breakdown in flowing water and escalated the power of discharge pulses. No impact of hydrogen peroxide addition on breakdown voltage was observed. A significant role of oxidant species in bacterial inactivation also has been identified. Furthermore the E. coli survivability in plasma treated water with oxygen injection and hydrogen peroxide addition drastically reduced to zero. The time course study also showed that the retardant effect on E. coli colony multiplication in plasma treated water was favorable, observed after long time. High-frequency underwater plasma discharge based biological applications is technically relevant and would act as baseline data for the development of novel antibacterial processing strategies.

  17. 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

  18. High Frequency Plant Regeneration of Musa paradisiaca cv. Karibale Monthan

    Directory of Open Access Journals (Sweden)

    R. Shashi Kumar

    2015-06-01

    Full Text Available High frequency plant regeneration protocol has been standardized from banana cultivar Musa paradisiaca cv. Karibale Monthan, an endemic cultivar of Malnad region of Karnataka. The fruits are used as glomerular protective to solve kidney problems. To minimize the microbial contamination and to promote healthy growth, explants were treated with 70 % absolute alcohol for 6 min, 0.1 % Mercuric chloride for 10 min and 0.2 % for 10 min, 1 % Sodium hypochlorite for 15 min, 0.1 % Cefotaxime for 5 min and 0.05 % Gentamicin for 5 min. The high frequency shoot initiation (93.33 % was recorded at 5 mg/l BAP. The synergetic effect of BAP (4 to 6 mg/l, TDZ (0.1 to 1.2 mg/l and coconut water (0.1 to 0.9 ml/l induced multiple shoot buds and it was optimized at the concentration of 5 mg/l BAP, 0.5 mg/l TDZ and 0.5 ml/l coconut water with 15.90 ± 1.66 frequency of shoots per propagule. Supplementation of 1.0 mg/l IBA induced 5.33 ± 1.21 numbers of roots with a mean root length of 7.50 ± 1.87 roots. The 99% of plantlets with distinct roots and shoots were successfully acclimatized in the green house and transferred to the field to evaluate the agro-morphological variations. The weight of the bunch (kg, number of hands in a bunch, number of fingers in a hand, length of the finger (cm, girth of the finger (cm and girth of the pseudostem (cm exhibited by in vitro plants were higher than the in vivo plants.

  19. Boosting brain excitability by transcranial high frequency stimulation in the ripple range.

    Science.gov (United States)

    Moliadze, Vera; Antal, Andrea; Paulus, Walter

    2010-12-15

    Alleviating the symptoms of neurological diseases by increasing cortical excitability through transcranial stimulation is an ongoing scientific challenge. Here, we tackle this issue by interfering with high frequency oscillations (80–250 Hz) via external application of transcranial alternating current stimulation (tACS) over the human motor cortex (M1). Twenty-one subjects participated in three different experimental studies and they received on separate days tACS at three frequencies (80 Hz, 140 Hz and 250 Hz) and sham stimulation in a randomized order. tACS with 140 Hz frequency increased M1 excitability as measured by transcranial magnetic stimulation-generated motor evoked potentials (MEPs) during and for up to 1 h after stimulation. Control experiments with sham and 80 Hz stimulation were without any effect, and 250 Hz stimulation was less efficient with a delayed excitability induction and reduced duration. After-effects elicited by 140 Hz stimulation were robust against inversion of test MEP amplitudes seen normally under activation. Stimulation at 140 Hz reduced short interval intracortical inhibition, but left intracortical facilitation, long interval cortical inhibition and cortical silent period unchanged. Implicit motor learning was not facilitated by 140 Hz stimulation. High frequency stimulation in the ripple range is a new promising non-invasive brain stimulation protocol to increase human cortical excitability during and after the end of stimulation.

  20. Analysis of Excitation Characteristics of Ultra High Frequency Electromagnetic Waves Induced by PD in GIS

    Institute of Scientific and Technical Information of China (English)

    DING Dengwei; GAO Wensheng; YAO Senjing; LIU Weidong; HE Jiaxi

    2013-01-01

    The understanding of the excitation mechanism of ultra high frequency (UHF) electromagnetic waves (EW) is essential for applying UHF method to partial discharge (PD) detection.Since the EW induced by PD in gas insulated switchgear (GIS) contains not only transverse electromagnetic (TEM) wave,but also high-order transverse electric (TE) and high-order transverse magnetic (TM) waves,we analyzed the proportions between the TEM wave and the high order waves,as well as the influence of the PD position on this proportion,using the finite different time domain (FDTD) method.According to the unique characteristics of the waves,they are separated only approximately.It is found that the high-order mode is the main component,more than 70%,of the electric field around the enclosure of GIS,and that with the increasing distance between PD source and inner conductors,the low frequency (below about 800 MHz) component of EW decreases,but the high frequency component (above 1 GHz) increases,meanwhile the proportion of high-order components in EW could reach 77% from 70%.It concluded that the closer the PD source to the enclosure is,the easier high order EW may be excited.

  1. High-frequency torsional Alfvén waves as an energy source for coronal heating

    Science.gov (United States)

    Srivastava, Abhishek Kumar; Shetye, Juie; Murawski, Krzysztof; Doyle, John Gerard; Stangalini, Marco; Scullion, Eamon; Ray, Tom; Wójcik, Dariusz Patryk; Dwivedi, Bhola N.

    2017-03-01

    The existence of the Sun’s hot atmosphere and the solar wind acceleration continues to be an outstanding problem in solar-astrophysics. Although magnetohydrodynamic (MHD) modes and dissipation of magnetic energy contribute to heating and the mass cycle of the solar atmosphere, yet direct evidence of such processes often generates debate. Ground-based 1-m Swedish Solar Telescope (SST)/CRISP, Hα 6562.8 Å observations reveal, for the first time, the ubiquitous presence of high frequency (~12–42 mHz) torsional motions in thin spicular-type structures in the chromosphere. We detect numerous oscillating flux tubes on 10 June 2014 between 07:17 UT to 08:08 UT in a quiet-Sun field-of-view of 60” × 60” (1” = 725 km). Stringent numerical model shows that these observations resemble torsional Alfvén waves associated with high frequency drivers which contain a huge amount of energy (~105 W m‑2) in the chromosphere. Even after partial reflection from the transition region, a significant amount of energy (~103 W m‑2) is transferred onto the overlying corona. We find that oscillating tubes serve as substantial sources of Alfvén wave generation that provide sufficient Poynting flux not only to heat the corona but also to originate the supersonic solar wind.

  2. Identification of high-frequency resonant impedance in the CERN SPS

    CERN Document Server

    Shaposhnikova, E; Bohl, T; Caspers, F; Lasheen, A; Esteban Muller, J; Salvant, B; Timko, H; Varela, J E

    2014-01-01

    The spectrum of long bunches injected into the ring with RF switched off has been used in the SPS in the past to probe the longitudinal coupling impedance. After a large campaign of shielding of 800 inter-magnet vacuum ports in 1999 - 2001, the microwave instability threshold was significantly increased and the high-frequency spectrum of the beam became practically flat, apart from a prominent peak at around 1.4 GHz. As corresponding high-frequency impedance could potentially lead to microwave instability of high intensity bunches observed now at high energies in the SPS, a search of the source of this impedance was launched. Using a combination of impedance simulations and measurements, vacuum flanges that are present in a large quantity in the machine have been identified as a main source of impedance at this frequency. Particle simulations based on the SPS impedance model, which includes this previously unknown impedance, are able to reproduce the characteristics of the bunch spectrum and amplitude growth ...

  3. High-frequency torsional Alfvén waves as an energy source for coronal heating

    Science.gov (United States)

    Srivastava, Abhishek Kumar; Shetye, Juie; Murawski, Krzysztof; Doyle, John Gerard; Stangalini, Marco; Scullion, Eamon; Ray, Tom; Wójcik, Dariusz Patryk; Dwivedi, Bhola N.

    2017-01-01

    The existence of the Sun’s hot atmosphere and the solar wind acceleration continues to be an outstanding problem in solar-astrophysics. Although magnetohydrodynamic (MHD) modes and dissipation of magnetic energy contribute to heating and the mass cycle of the solar atmosphere, yet direct evidence of such processes often generates debate. Ground-based 1-m Swedish Solar Telescope (SST)/CRISP, Hα 6562.8 Å observations reveal, for the first time, the ubiquitous presence of high frequency (~12–42 mHz) torsional motions in thin spicular-type structures in the chromosphere. We detect numerous oscillating flux tubes on 10 June 2014 between 07:17 UT to 08:08 UT in a quiet-Sun field-of-view of 60” × 60” (1” = 725 km). Stringent numerical model shows that these observations resemble torsional Alfvén waves associated with high frequency drivers which contain a huge amount of energy (~105 W m−2) in the chromosphere. Even after partial reflection from the transition region, a significant amount of energy (~103 W m−2) is transferred onto the overlying corona. We find that oscillating tubes serve as substantial sources of Alfvén wave generation that provide sufficient Poynting flux not only to heat the corona but also to originate the supersonic solar wind. PMID:28256538

  4. High-frequency gravitational waves from magnetars and gamma-ray bursts

    CERN Document Server

    Wen, Hao; Li, Jin; Fang, Zhenyun

    2016-01-01

    Extremely powerful astrophysical electromagnetic (EM) system could lead to significant energy-momentum tensor as possible source of high-frequency gravitational waves (HFGWs). Here based on properties of magnetars and gamma-ray bursts (GRBs), we address 'Gamma-HFGWs' caused by ultra-strong EM radiations (in the radiation-dominated phase of GRBs fireball) interacting with super-high magnetar surface magnetic fields (10^{11}Tesla). By certain parameters of distance and power, the Gamma-HFGWs would have amplitude of 10^{-41} at 10^{20}Hz, and such very high frequency effectively compensate their weak amplitude and thus would cause perturbed EM waves of 10^{-20}Watt/m^2 in proposed HFGW detection system based on EM response to GWs. Particularly, predicted Gamma-HFGWs can possess distinctive pulse-like envelopes with characteristic shapes, which could be exclusive features helpful to distinguish them from background noise. Results obtained suggest that magnetars could involve in possible astrophysical EM sources o...

  5. A Generalized Heterodyne Method Incorporating a High-Frequency Integral-Type PLL for Sensorless Drives of PMSMs

    Science.gov (United States)

    Shinnaka, Shinji

    This paper proposes a new generalized heterodyne method that incorporates a high-frequency integral-type phase-locked loop (PLL) as a versatile rotor-phase estimation method from stator current caused by high-frequency voltage injection for sensorless drive of salient-pole permanent-magnet synchronous motors. The proposed method has the following characteristics that are in direct contrast to those of conventional heterodyne methods. 1) In principle, it can be applied to almost all voltage injection methods. 2) In principle, it can properly estimate the rotor phase over a wide range of speed. 3) It employs a new simple estimation structure based on the high-frequency integral-type PLL method, which does not require any additional filters. 4) An analytical method for designing the components of the structure has been established and no trial and error method is required for selecting the parameters for the components. 5) The stability of the phase-estimation system of the structure is guaranteed. 6) The high-frequency noises generated in the heterodyne process do not appear on the estimated rotor phase.

  6. High frequency lateral flow affinity assay using superparamagnetic nanoparticles

    Science.gov (United States)

    Lago-Cachón, D.; Rivas, M.; Martínez-García, J. C.; Oliveira-Rodríguez, M.; Blanco-López, M. C.; García, J. A.

    2017-02-01

    Lateral flow assay is one of the simplest and most extended techniques in medical diagnosis for point-of-care testing. Although it has been traditionally a positive/negative test, some work has been lately done to add quantitative abilities to lateral flow assay. One of the most successful strategies involves magnetic beads and magnetic sensors. Recently, a new technique of superparamagnetic nanoparticle detection has been reported, based on the increase of the impedance induced by the nanoparticles on a RF-current carrying copper conductor. This method requires no external magnetic field, which reduces the system complexity. In this work, nitrocellulose membranes have been installed on the sensor, and impedance measurements have been carried out during the sample diffusion by capillarity along the membrane. The impedance of the sensor changes because of the presence of magnetic nanoparticles. The results prove the potentiality of the method for point-of-care testing of biochemical substances and nanoparticle capillarity flow studies.

  7. Hydrodynamic description of a vibrofluidized granular bed driven at high frequency

    Science.gov (United States)

    Sheikh, Nadeem A.; Manzoor, Shehryar; Mahabat Khan, Muhammad; Ali, Muzaffar

    2016-08-01

    Results are reported for a dry granular bed vertically excited at high and low frequencies with constant peak base velocity. Previous experimental data sets using Nuclear Magnetic Resonance are used for comparison at low (~38 Hz) and high (~11 kHz) vibration frequencies. Packing fractions and granular temperatures are compared against hydrodynamic and molecular dynamics simulation models. At low frequency hydrodynamic and MD simulations results show the presence of a heat wave. Whilst at high frequencies soft sphere potential based MD simulations highlight the role of finite duration collisions between particles and the vibrating wall. In this region the timescales of vibration and collision duration are not well separated, as observed in experimental results.

  8. 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.

  9. Electromagnetic Response of High-Frequency Gravitational Waves by Coupling Open Resonant Cavity

    Institute of Scientific and Technical Information of China (English)

    LI Fang-Yu; CHEN Ying; WANG Ping

    2007-01-01

    We present a new detecting scheme of high-frequency gravitational waves(HFGWs) in the GHz band,the scheme consists of a high-quality-factor open microwave cavity,a static magnetic field passing through the cavity and an electromagnetic (EM)normal mode stored in the cavity.It is found that under the resonant condition firstand second-order perturbation EM effects have almost the same detecting sensitivity to the HFGWs in the GHz band (h~10-26,v~5GHz),but the former contains more information from the HFGWs.We akso provide a very brief review for possible improving way of the sensitivity.This scheme would be Highly complementary to other schemes of detecting the HFGWs.

  10. Utilization of Electromagnetic Detector for Selection and Detection of High-Frequency Relic Gravitational Waves

    Institute of Scientific and Technical Information of China (English)

    LI Fang-Yu; CHEN Zhen-Ya; YI Ying

    2005-01-01

    @@ It is shown that the coupling system between fractal membranes and a Gaussian beam passing through a static magnetic field has strong selection capability for the stochastic relic gravitational wave (GW) background. The relic G W components propagating along the positive direction of the symmetrical axis of the Gaussian beam might generate an optimal electromagnetic perturbation, while the perturbation produced by the relic GW components propagating along the negative and perpendicular directions to the symmetrical axis will be much less than the former, and the influence of the random fluctuation of the relic GWs to such effect can be neglected. The high-frequency relic GWs satisfying the parameters requirement (h ~ 10-31 or larger), frequency resonance and "direction coupling", in principle, would be selectable and measurable in seconds.

  11. The comparison of three high-frequency chest compression devices.

    Science.gov (United States)

    Lee, Yong W; Lee, Jongwon; Warwick, Warren J

    2008-01-01

    High-frequency chest compression (HFCC) is shown to enhance clearance of pulmonary airway secretions. Several HFCC devices have been designed to provide this therapy. Standard equipment consists of an air pulse generator attached by lengths of tubing to an adjustable, inflatable vest/jacket (V/J) garment. In this study, the V/Js were fitted over a mannequin. The three device air pulse generators produced characteristic waveform patterns. The variations in the frequency and pressure setting of devices were consistent with specific device design features. These studies suggest that a better understanding of the effects of different waveform, frequency, and pressure combinations may improve HFCC therapeutic efficacy of three different HFCC machines. The V/J component of HFCC devices delivers the compressive pulses to the chest wall to produce both airflow through and oscillatory effects in the airways. The V/J pressures of three HFCC machines were measured and analyzed to characterize the frequency, pressure, and waveform patterns generated by each of three device models. The dimensions of all V/Js were adjusted to a circumference of approximately 110% of the chest circumference. The V/J pressures were measured, and maximum, minimum, and mean pressure, pulse pressure, and root mean square of three pulse generators were calculated. Jacket pressures ranged between 2 and 34 mmHg. The 103 and 104 models' pulse pressures increased with the increase in HFCC frequency at constant dial pressure. With the ICS the pulse pressure decreased when the frequency increased. The waveforms of models 103 and 104 were symmetric sine wave and asymmetric sine wave patterns, respectively. The ICS had a triangular waveform. At 20 Hz, both the 103 and 104 were symmetric sine waveform but the ICS remained triangular. Maximum crest factors emerged in low-frequency and high-pressure settings for the ICS and in the high-frequency and low-pressure settings for models 103 and 104. Recognizing the

  12. To Recognize the Phenomenon of "Atrial Fibrillation Begets Atrial Fibrillation"%对“房颤促房颤”再认识

    Institute of Scientific and Technical Information of China (English)

    丁绍祥

    2015-01-01

    "Atrial fibrillation (AF ) begets AF" is taken as to be adaptive change for AF . However , cardiac electrophysiology is decided by its own structure characteristics to meet the need of its function .In AF ,shortening of atrial effective refractory period (AERP) is the result of the electrical remodeling ,which could induce rapid arrhythmia . But first of all ,it is a kind of compensatory mechanism to recover its function .The role of each ion channel in atrial cardiac muscle cells is different ,and its change should be combined with the specific background of time and space .The structure remodeling of AF is the cumulative result from damage effect ,as a passive process ,its essence in that the damage beyond its compensatory function causing irreversible change and directly affect the electrophysiological function of corresponding myocardial .Electrical remodeling and structural remodeling begets each other ,restoring sinus rhythm is decided by atrial structure .%“房颤促房颤”被认为是心房颤动的适应性改变。然而,心肌电生理是由其本身的结构特点决定以适应其功能的需要。心房有效不应期缩短是电重构的结果,虽可诱导快速频率,但更为重要的是恢复其生理功能的一种代偿机制:因各离子通道的作用并不相同,其变化需结合特定的时空背景。房颤结构重构是损伤效应的累积结果,其本质并非为促进房颤,而是损伤超越其代偿功能时的不可逆性改变,虽为一被动过程,但却直接影响相应心肌电生理功能。房颤的结构重构和电重构是相互促进的,心脏能否恢复窦性心律关键在于心房自身结构损伤的程度。

  13. Co/Ti-substituted M-type hexagonal ferrites for high-frequency multilayer inductors

    Energy Technology Data Exchange (ETDEWEB)

    Bierlich, S.; Reimann, T. [University of Applied Sciences Jena, Department of SciTec, Carl-Zeiss-Promenade 2, 07745 Jena (Germany); Bartsch, H. [Technical University Ilmenau, IMN MacroNano, G.-Kirchhoff-Str. 7, 98693 Ilmenau (Germany); Töpfer, J., E-mail: joerg.toepfer@fh-jena.de [University of Applied Sciences Jena, Department of SciTec, Carl-Zeiss-Promenade 2, 07745 Jena (Germany)

    2015-06-15

    The sintering behavior, microstructure and permeability of Co/Ti-substituted M-type hexagonal ferrites BaCo{sub x}Ti{sub x}Fe{sub 12−2x}O{sub 19} (1.0≤x≤1.4) was studied for applications as multilayer inductors in the high-frequency range up to 2 GHz. Single-phase M-type ferrites were obtained after calcination at 1000 °C. The saturation magnetization and coercivity decrease with x and hysteresis measurements illustrate a gradual transition of the anisotropy from uniaxial to planar. Addition of 5 wt% of a BBSZ glass allows densification at 900 °C through liquid-phase sintering. The permeability of samples sintered at 900 °C increases with the Co/Ti substitution and reaches its maximum of µ′=16 at 1 MHz at x=1.3 with a resonance frequency f{sub r}≥1 GHz. Monolithic ferrite multilayer inductors were fabricated with printed Ag coil patterns by co-firing at 900 °C. It is shown that Co/Ti-substituted hexagonal M-type ferrite is an excellent material for the high-frequency multilayer inductors. - Highlights: • Saturation magnetization and coercivity of Co–Ti substituted M-type hexaferrites BaFe{sub 12−2x}Co{sub x}Ti{sub x}O{sub 19} decrease with x. • Ferrites were sintered at low-temperature of T=900 °C using a BBSZ glass additive. • Large initial permeability of µ′=17 was obtained at x=1.3 for low-temperature sintered Co/Ti-substituted ferrites. • Monolithic ferrite multilayer inductor with Co/Ti substituted M-type ferrite layers and Ag metallization was cofired at 900 °C. • Demonstrates, that monolithic ferrite multilayer based on Co/Ti substituted hexagonal ferrites can be operated up to high frequency of 1 GHz.

  14. Low temperature high frequency coaxial pulse tube for space application

    Energy Technology Data Exchange (ETDEWEB)

    Charrier, Aurelia; Charles, Ivan; Rousset, Bernard; Duval, Jean-Marc [SBT, UMR-E CEA / UJF-Grenoble 1, INAC, 17, rue des Martyrs, Grenoble, F-38054 (France); Daniel, Christophe [CNES, 18, avenue Edouard Belin, Toulouse, F-31401 (France)

    2014-01-29

    The 4K stage is a critical step for space missions. The Hershel mission is using a helium bath, which is consumed day by day (after depletion, the space mission is over) while the Plank mission is equipped with one He4 Joule-Thomson cooler. Cryogenic chain without helium bath is a challenge for space missions and 4.2K Pulse-Tube working at high frequency (around 30Hz) is one option to take it up. A low temperature Pulse-Tube would be suitable for the ESA space mission EChO (Exoplanet Characterisation Observatory, expected launch in 2022), which requires around 30mW cooling power at 6K; and for the ESA space mission ATHENA (Advanced Telescope for High ENergy Astrophysics), to pre-cool the sub-kelvin cooler (few hundreds of mW at 15K). The test bench described in this paper combines a Gifford-McMahon with a coaxial Pulse-Tube. A thermal link is joining the intercept of the Pulse-Tube and the second stage of the Gifford-McMahon. This intercept is a separator between the hot and the cold regenerators of the Pulse-Tube. The work has been focused on the cold part of this cold finger. Coupled with an active phase shifter, this Pulse-Tube has been tested and optimized and temperatures as low as 6K have been obtained at 30Hz with an intercept temperature at 20K.

  15. Planck early results. VI. The High Frequency Instrument data processing

    Science.gov (United States)

    Planck HFI Core Team; Ade, P. A. R.; Aghanim, N.; Ansari, R.; Arnaud, M.; Ashdown, M.; Aumont, J.; Banday, A. J.; Bartelmann, M.; Bartlett, J. G.; Battaner, E.; Benabed, K.; Benoît, A.; Bernard, J.-P.; Bersanelli, M.; Bock, J. J.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Boulanger, F.; Bradshaw, T.; Bucher, M.; Cardoso, J.-F.; Castex, G.; Catalano, A.; Challinor, A.; Chamballu, A.; Chary, R.-R.; Chen, X.; Chiang, C.; Church, S.; Clements, D. L.; Colley, J.-M.; Colombi, S.; Couchot, F.; Coulais, A.; Cressiot, C.; Crill, B. P.; Crook, M.; de Bernardis, P.; Delabrouille, J.; Delouis, J.-M.; Désert, F.-X.; Dolag, K.; Dole, H.; Doré, O.; Douspis, M.; Dunkley, J.; Efstathiou, G.; Filliard, C.; Forni, O.; Fosalba, P.; Ganga, K.; Giard, M.; Girard, D.; Giraud-Héraud, Y.; Gispert, R.; Górski, K. M.; Gratton, S.; Griffin, M.; Guyot, G.; Haissinski, J.; Harrison, D.; Helou, G.; Henrot-Versillé, S.; Hernández-Monteagudo, C.; Hildebrandt, S. R.; Hills, R.; Hivon, E.; Hobson, M.; Holmes, W. A.; Huffenberger, K. M.; Jaffe, A. H.; Jones, W. C.; Kaplan, J.; Kneissl, R.; Knox, L.; Kunz, M.; Lagache, G.; Lamarre, J.-M.; Lange, A. E.; Lasenby, A.; Lavabre, A.; Lawrence, C. R.; Le Jeune, M.; Leroy, C.; Lesgourgues, J.; Macías-Pérez, J. F.; MacTavish, C. J.; Maffei, B.; Mandolesi, N.; Mann, R.; Marleau, F.; Marshall, D. J.; Masi, S.; Matsumura, T.; McAuley, I.; McGehee, P.; Melin, J.-B.; Mercier, C.; Mitra, S.; Miville-Deschênes, M.-A.; Moneti, A.; Montier, L.; Mortlock, D.; Murphy, A.; Nati, F.; Netterfield, C. B.; Nørgaard-Nielsen, H. U.; North, C.; Noviello, F.; Novikov, D.; Osborne, S.; Pajot, F.; Patanchon, G.; Peacocke, T.; Pearson, T. J.; Perdereau, O.; Perotto, L.; Piacentini, F.; Piat, M.; Plaszczynski, S.; Pointecouteau, E.; Ponthieu, N.; Prézeau, G.; Prunet, S.; Puget, J.-L.; Reach, W. T.; Remazeilles, M.; Renault, C.; Riazuelo, A.; Ristorcelli, I.; Rocha, G.; Rosset, C.; Roudier, G.; Rowan-Robinson, M.; Rusholme, B.; Saha, R.; Santos, D.; Savini, G.; Schaefer, B. M.; Shellard, P.; Spencer, L.; Starck, J.-L.; Stolyarov, V.; Stompor, R.; Sudiwala, R.; Sunyaev, R.; Sutton, D.; Sygnet, J.-F.; Tauber, J. A.; Thum, C.; Torre, J.-P.; Touze, F.; Tristram, M.; van Leeuwen, F.; Vibert, L.; Vibert, D.; Wade, L. A.; Wandelt, B. D.; White, S. D. M.; Wiesemeyer, H.; Woodcraft, A.; Yurchenko, V.; Yvon, D.; Zacchei, A.

    2011-12-01

    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 by the HFI Data Processing Centre reach our goals in terms of sensitivity, resolution, and photometric accuracy. They are already sufficiently accurate and well-characterised to allow scientific analyses which are presented in an accompanying series of early papers. At this stage, HFI data appears 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. Corresponding author: F. R. Bouchet, e-mail: bouchet@iap.fr

  16. Planck Early Results: The High Frequency Instrument data processing

    CERN Document Server

    Ade, P A R; Ansari, R; Arnaud, M; Ashdown, M; Aumont, J; Banday, A J; Bartelmann, M; Bartlett, J G; Battaner, E; Benabed, K; Benoît, A; Bernard, J -P; Bersanelli, M; Bock, J J; Bond, J R; Borrill, J; Bouchet, F R; Boulanger, F; Bradshaw, T; Bucher, M; Cardoso, J -F; Castex, G; Catalano, A; Challinor, A; Chamballu, A; Chary, R -R; Chen, X; Chiang, C; Church, S; Clements, D L; Colley, J -M; Colombi, S; Couchot, F; Coulais, A; Cressiot, C; Crill, B P; Crook, M; de Bernardis, P; Delabrouille, J; Delouis, J -M; Désert, F -X; Dolag, K; Dole, H; Doré, O; Douspis, M; Dunkley, J; Efstathiou, G; Filliard, C; Forni, O; Fosalba, P; Ganga, K; Giard, M; Girard, D; Giraud-Héraud, Y; Gispert, R; Górski, K M; Gratton, S; Griffin, M; Guyot, G; Haissinski, J; Harrison, D; Helou, G; Henrot-Versillé, S; Hernández-Monteagudo, C; Hildebrandt, S R; Hills, R; Hivon, E; Hobson, M; Holmes, W A; Huffenberger, K M; Jaffe, A H; Jones, W C; Kaplan, J; Kneissl, R; Knox, L; Kunz, M; Lagache, G; Lamarre, J -M; Lange, A E; Lasenby, A; Lavabre, A; Lawrence, C R; Jeune, M Le; Leroy, C; Lesgourgues, J; Lewis, A; Macías-Pérez, J F; MacTavish, C J; Maffei, B; Mandolesi, N; Mann, R; Marleau, F; Marshall, D J; Masi, S; Matsumura, T; McAuley, I; McGehee, P; Melin, J -B; Mercier, C; Mitra, S; Miville-Deschênes, M -A; Moneti, A; Montier, L; Mortlock, D; Murphy, A; Nati, F; Netterfield, C B; N\\orgaard-Nielsen, H U; North, C; Noviello, F; Novikov, D; Osborne, S; Pajot, F; Patanchon, G; Peacocke, T; Pearson, T J; Perdereau, O; Perotto, L; Piacentini, F; Piat, M; Plaszczynski, S; Pointecouteau, E; Ponthieu, N; Prézeau, G; Prunet, S; Puget, J -L; Reach, W T; Remazeilles, M; Renault, C; Riazuelo, A; Ristorcelli, I; Rocha, G; Rosset, C; Roudier, G; Rowan-Robinson, M; Rusholme, B; Saha, R; Santos, D; Savini, G; Schaefer, B M; Shellard, P; Spencer, L; Starck, J -L; Stolyarov, V; Stompor, R; Sudiwala, R; Sunyaev, R; Sutton, D; Sygnet, J -F; Tauber, J A; Thum, C; Torre, J -P; Touze, F; Tristram, M; Van Leeuwen, F; Vibert, L; Vibert, D; Wandelt, B D; White, S D M; Wiesemeyer, H; Woodcraft, A; Yurchenko, V; Yvon, D; Zacchei, A

    2011-01-01

    We describe the processing of the 334 billion raw data samples from the High Frequency Instrument (hereafter 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 857GHz with an angular resolution ranging from 9.9 to 4.4 arcmin. The white noise level is around 1.5 microK.degree or less in the 3 main CMB channels (100-217GHz). The photometric accuracy is better than 2% at frequencies lower or equal to 353GHz, and around 7% at the two highest frequencies. The maps created by the HFI Data Processing Centre reach our goals in terms of sensitivity, resolution, and photometric accuracy. They are already sufficiently accurate and well-characterised to allow scientific analyses which are presented in an accompanying series of early papers. At this stage, HFI data appears to be of high quality and we expect that with further refinements of the data processing we should be abl...

  17. Three-Dimensional Electromagnetic High Frequency Axisymmetric Cavity Scars.

    Energy Technology Data Exchange (ETDEWEB)

    Warne, Larry Kevin; Jorgenson, Roy Eberhardt

    2014-10-01

    This report examines the localization of high frequency electromagnetic fi elds in three-dimensional axisymmetric cavities along periodic paths between opposing sides of the cavity. The cases where these orbits lead to unstable localized modes are known as scars. This report treats both the case where the opposing sides, or mirrors, are convex, where there are no interior foci, and the case where they are concave, leading to interior foci. The scalar problem is treated fi rst but the approximations required to treat the vector fi eld components are also examined. Particular att ention is focused on the normalization through the electromagnetic energy theorem. Both projections of the fi eld along the scarred orbit as well as point statistics are examined. Statistical comparisons are m ade with a numerical calculation of the scars run with an axisymmetric simulation. This axisymmetric cas eformstheoppositeextreme(wherethetwomirror radii at each end of the ray orbit are equal) from the two -dimensional solution examined previously (where one mirror radius is vastly di ff erent from the other). The enhancement of the fi eldontheorbitaxiscanbe larger here than in the two-dimensional case. Intentionally Left Blank

  18. Advances to Dynamic Mechanical Analysis: High Frequencies and Environmental Applications

    Science.gov (United States)

    Foreman, Jonathon

    2002-03-01

    In dynamic mechanical analysis (DMA) the sample is deformed and released sinusoidally providing information about the modulus and damping behaviors with respect to temperature, time, oscillation frequency and amplitude of motion. It offers exceptional sensitivity to glass transitions and secondary relaxations. Recent developments have increased the frequency range up to 1000 Hz, which allow properties measurements under actual end-use conditions. Furthermore high frequencies enhance the ability to determine the kinetics of viscoelastic relaxations. Another recent development allows DMA measurements while samples are immersed in fluids or enveloped in gases. Most significant is the ability to alter the furnace control parameters to account for the thermal properties of the environment used. This configuration allows temperature-controlled measurements (both heating and isothermal profiles) on a wide range of sample shapes and sizes. Environmental DMA is easier to interpret than standard DMA (in air or inert gas) on preconditioned samples because such samples often lose the conditioning solvent or gas during the measurement. easy.com/dma_apps.asp>Examples will show real-time property changes from the interaction of unconditioned materials with conditioning environments and experiments on pre-conditioned materials that are heated while immersed in conditioning environments. -------------------------------------------------------------

  19. Theory of High Frequency Rectification by Silicon Crystals

    Science.gov (United States)

    Bethe, H. A.

    1942-10-29

    The excellent performance of British "red dot" crystals is explained as due to the knife edge contact against a polished surface. High frequency rectification depends critically on the capacity of the rectifying boundary layer of the crystal, C. For high conversion efficiency, the product of this capacity and of the "forward" (bulk) resistance R {sub b} of the crystal must be small. For a knife edge, this product depends primarily on the breadth of the knife edge and very little upon its length. The contact can therefore have a rather large area which prevents burn-out. For a wavelength of 10 cm. the computations show that the breadth of the knife edge should be less than about 10 {sup -3} cm. For a point contact the radius must be less than 1.5 x 10 {sup -3} cm. and the resulting small area is conducive to burn-out. The effect of "tapping" is probably to reduce the area of contact. (auth)

  20. High-Frequency Chest Compression: A Summary of the Literature

    Directory of Open Access Journals (Sweden)

    Cara F Dosman

    2005-01-01

    Full Text Available The purpose of the present literature summary is to describe high-frequency chest compression (HFCC, summarize its history and outline study results on its effect on mucolysis, mucus transport, pulmonary function and quality of life. HFCC is a mechanical method of self-administered chest physiotherapy, which induces rapid air movement in and out of the lungs. This mean oscillated volume is an effective method of mucolysis and mucus clearance. HFCC can increase independence. Some studies have shown that HFCC leads to more mucus clearance and better lung function compared with conventional chest physiotherapy. However, HFCC also decreases end-expiratory lung volume, which can lead to increased airway resistance and a decreased oscillated volume. Adding positive end-expiratory pressure to HFCC has been shown to prevent this decrease in end-expiratory lung volume and to increase the oscillated volume. It is possible that the HFCC-induced decrease in end-expiratory lung volume may result in more mucus clearance in airways that remain open by reducing airway size. Adjunctive methods, such as positive end-expiratory pressure, may not always be needed to make HFCC more effective.

  1. High frequency chest compression effects heart rate variability.

    Science.gov (United States)

    Lee, Jongwon; Lee, Yong W; Warwick, Warren J

    2007-01-01

    High frequency chest compression (HFCC) supplies a sequence of air pulses through a jacket worn by a patient to remove excessive mucus for the treatment or prevention of lung disease patients. The air pulses produced from the pulse generator propagates over the thorax delivering the vibration and compression energy. A number of studies have demonstrated that the HFCC system increases the ability to clear mucus and improves lung function. Few studies have examined the change in instantaneous heart rate (iHR) and heart rate variability (HRV) during the HFCC therapy. The purpose of this study is to measure the change of HRV with four experimental protocols: (a) without HFCC, (b) during Inflated, (c)HFCC at 6Hz, and (d) HFCC at 21Hz. The nonlinearity and regularity of HRV was assessed by approximate entropy (ApEn), a method used to quantify the complexities and randomness. To compute the ApEn, we sectioned with a total of eight epochs and displayed the ApEn over the each epoch. Our results show significant differences in the both the iHR and HRV between the experimental protocols. The iHR was elevated at both the (c) 6Hz and (d) 21Hz condition from without HFCC (10%, 16%, respectively). We also found that the HFCC system tends to increase the HRV. Our study suggests that monitoring iHR and HRV are very important physiological indexes during HFCC therapy.

  2. High-frequency chest compression: a summary of the literature.

    Science.gov (United States)

    Dosman, Cara F; Jones, Richard L

    2005-01-01

    The purpose of the present literature summary is to describe high-frequency chest compression (HFCC), summarize its history and outline study results on its effect on mucolysis, mucus transport, pulmonary function and quality of life. HFCC is a mechanical method of self-administered chest physiotherapy, which induces rapid air movement in and out of the lungs. This mean oscillated volume is an effective method of mucolysis and mucus clearance. HFCC can increase independence. Some studies have shown that HFCC leads to more mucus clearance and better lung function compared with conventional chest physiotherapy. However, HFCC also decreases end-expiratory lung volume, which can lead to increased airway resistance and a decreased oscillated volume. Adding positive end-expiratory pressure to HFCC has been shown to prevent this decrease in end-expiratory lung volume and to increase the oscillated volume. It is possible that the HFCC-induced decrease in end-expiratory lung volume may result in more mucus clearance in airways that remain open by reducing airway size. Adjunctive methods, such as positive end-expiratory pressure, may not always be needed to make HFCC more effective.

  3. 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.

  4. High frequency acoustic microscopy with Fresnel zoom lens

    Institute of Scientific and Technical Information of China (English)

    QIAO DongHai; LI ShunZhou; WANG ChengHao

    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.

  5. Tecnologia radio cognitiva en la banda ultra high frequency (UHF

    Directory of Open Access Journals (Sweden)

    Hernán Paz Penagos

    2014-01-01

    Full Text Available Mobile cellular communication companies in Colombia require more spectrum resources to expand their portfolio of services. However, additional frequency bands for that particular purpose are scarce, yet it is well known that there are many underutilized licensed bands. Therefore new radio technologies are being studied in order to solve this problem, e.g. Software Defined Radio SDR Cognitive Radio CR and Dynamic Spectrum Access DSA. These strategies recommend mobility across the radio spectrum to meet various needs and achieve greater efficiency when managing such a scarce resource. In this context, a case study is presented in an attempt to examine the require¬ments that must be met for the implementation of cognitive radio networks in Bogota. The case study includes evaluation for the possibility of migration from cellular communications to cognitive radio since the bands assigned to UltraHigh Frequency UHF television offer possible free-of-interference coexistence between the two services (i.e. Cellular and TV. The study shows feasibility to migration; however, the implementations of cognitive radio need availability of hardware, software and flexible radio platforms.

  6. Protection circuits for very high frequency ultrasound systems.

    Science.gov (United States)

    Choi, Hojong; Shung, K Kirk

    2014-04-01

    The purpose of protection circuits in ultrasound applications is to block noise signals from the transmitter from reaching the transducer and also to prevent unwanted high voltage signals from reaching the receiver. The protection circuit using a resistor and diode pair is widely used due to its simple architecture, however, it may not be suitable for very high frequency (VHF) ultrasound transducer applications (>100 MHz) because of its limited bandwidth. Therefore, a protection circuit using MOSFET devices with unique structure is proposed in this paper. The performance of the designed protection circuit was compared with that of other traditional protection schemes. The performance characteristics measured were the insertion loss (IL), total harmonic distortion (THD) and transient response time (TRT). The new protection scheme offers the lowest IL (-1.0 dB), THD (-69.8 dB) and TRT (78 ns) at 120 MHz. The pulse-echo response using a 120 MHz LiNbO3 transducer with each protection circuit was measured to validate the feasibility of the protection circuits in VHF ultrasound applications. The sensitivity and bandwidth of the transducer using the new protection circuit improved by 252.1 and 50.9 %, respectively with respect to the protection circuit using a resistor and diode pair. These results demonstrated that the new protection circuit design minimizes the IL, THD and TRT for VHF ultrasound transducer applications.

  7. Why high-frequency pulse tubes can be tipped

    Energy Technology Data Exchange (ETDEWEB)

    Swift, Gregory W092710 [Los Alamos National Laboratory; Backhaus, Scott N [Los Alamos National Laboratory

    2010-01-01

    The typical low-frequency pulse-tube refrigerator loses significant cooling power when it is tipped with the pulse tube's cold end above its hot end, because natural convection in the pulse tube loads the cold heat exchanger. Yet most high-frequency pulse-tube refrigerators work well in any orientation with respect to gravity. In such a refrigerator, natural convection is suppressed by sufficiently fast velocity oscil1ations, via a nonlinear hydrodynamic effect that tends to align the density gradients in the pulse tube parallel to the oscillation direction. Since gravity's tendency to cause convection is only linear in the pulse tube's end-to-end temperature difference while the oscillation's tendency to align density gradients with oscillating velocity is nonlinear, it is easiest to suppress convection when the end-to-end temperature difference is largest. Simple experiments demonstrate this temperature dependence, the strong dependence on the oscillating velocity, and little dependence on the magnitude or phase of the oscillating pressure. In some circumstances in this apparatus, the suppression of convection is a hysteretic function of oscillating velocity. In some other circumstances, a time-dependent convective state seems more difficult to suppress.

  8. High-frequency ultrasonic arrays for ocular imaging

    Science.gov (United States)

    Jaeger, M. D.; Kline-Schoder, R. J.; Douville, G. M.; Gagne, J. R.; Morrison, K. T.; Audette, W. E.; Kynor, D. B.

    2007-03-01

    High-resolution ultrasound imaging of the anterior portion of the eye has been shown to provide important information for sizing of intraocular lens implants, diagnosis of pathological conditions, and creation of detailed maps of corneal topography to guide refractive surgery. Current ultrasound imaging systems rely on mechanical scanning of a single acoustic element over the surface of the eye to create the three-dimensional information needed by clinicians. This mechanical scanning process is time-consuming and subject to errors caused by eye movement during the scanning period. This paper describes development of linear ultrasound imaging arrays intended to increase the speed of image acquisition and reduce problems associated with ocular motion. The arrays consist of a linear arrangement of high-frequency transducer elements designed to operate in the 50 - 75 MHz frequency range. The arrays are produced using single-crystal lithium niobate piezoelectric material, thin film electrodes, and epoxy-based acoustic layers. The array elements have been used to image steel test structures and bovine cornea.

  9. High-frequency oscillations and mesial temporal lobe epilepsy.

    Science.gov (United States)

    Lévesque, Maxime; Shiri, Zahra; Chen, Li-Yuan; Avoli, Massimo

    2017-01-20

    The interest of epileptologists has recently shifted from the macroscopic analysis of interictal spikes and seizures to the microscopic analysis of short events in the EEG that are not visible to the naked eye but are observed once the signal has been filtered in specific frequency bands. With the use of new technologies that allow multichannel recordings at high sampling rates and the development of computer algorithms that permit the automated analysis of extensive amounts of data, it is now possible to extract high-frequency oscillations (HFOs) between 80 and 500Hz from the EEG; HFOs have been further categorised as ripples (80-200Hz) and fast ripples (250-500Hz). Within the context of epileptic disorders, HFOs should reflect the pathological activity of neural networks that sustain seizure generation, and could serve as biomarkers of epileptogenesis and ictogenesis. We review here the presumptive cellular mechanisms of ripples and fast ripples in mesial temporal lobe epilepsy. We also focus on recent findings regarding the occurrence of HFOs during epileptiform activity observed in in vitro models of epileptiform synchronization, in in vivo models of mesial temporal lobe epilepsy and in epileptic patients. Finally, we address the effects of anti-epileptic drugs on HFOs and raise some questions and issues related to the definition of HFOs.

  10. 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.

  11. Planck pre-launch status: High Frequency Instrument polarization calibration

    CERN Document Server

    Rosset, C; Ponthieu, N; Ade, P; Catalano, A; Conversi, L; Couchot, F; Crill, B P; Désert, F -X; Ganga, K; Giard, M; Giraud-Héraud, Y; Haïssinski, J; Henrot-Versillé, S; Holmes, W; Jones, W C; Lamarre, J -M; Lange, A; Leroy, C; Macías-Pérez, J; Maffei, B; de Marcillac, P; Miville-Deschênes, M -A; Montier, L; Noviello, F; Pajot, F; Perdereau, O; Piacentini, F; Piat, M; Plaszczynski, S; Pointecouteau, E; Puget, J -L; Ristorcelli, I; Savini, G; Sudiwala, R; Veneziani, M; Yvon, D

    2010-01-01

    The High Frequency Instrument of Planck will map the entire sky in the millimeter and sub-millimeter domain from 100 to 857 GHz with unprecedented sensitivity to polarization ($\\Delta P/T_{\\tiny cmb} \\sim 4\\cdot 10^{-6}$) at 100, 143, 217 and 353 GHz. It will lead to major improvements in our understanding of the Cosmic Microwave Background anisotropies and polarized foreground signals. Planck will make high resolution measurements of the $E$-mode spectrum (up to $\\ell \\sim 1500$) and will also play a prominent role in the search for the faint imprint of primordial gravitational waves on the CMB polarization. This paper addresses the effects of calibration of both temperature (gain) and polarization (polarization efficiency and detector orientation) on polarization measurements. The specific requirements on the polarization parameters of the instrument are set and we report on their pre-flight measurement on HFI bolometers. We present a semi-analytical method that exactly accounts for the scanning strategy of...

  12. High-frequency acoustic for nanostructure wetting characterization.

    Science.gov (United States)

    Li, Sizhe; Lamant, Sebastien; Carlier, Julien; Toubal, Malika; Campistron, Pierre; Xu, Xiumei; Vereecke, Guy; Senez, Vincent; Thomy, Vincent; Nongaillard, Bertrand

    2014-07-01

    Nanostructure wetting is a key problem when developing superhydrophobic surfaces. Conventional methods do not allow us to draw conclusions about the partial or complete wetting of structures on the nanoscale. Moreover, advanced techniques are not always compatible with an in situ, real time, multiscale (from macro to nanoscale) characterization. A high-frequency (1 GHz) acoustic method is used for the first time to characterize locally partial wetting and the wetting transition between nanostructures according to the surface tension of liquids (the variation is obtained by ethanol concentration modification). We can see that this method is extremely sensitive both to the level of liquid imbibition and to the impalement dynamic. We thus demonstrate the possibility to evaluate the critical surface tension of a liquid for which total wetting occurs according to the aspect ratio of the nanostructures. We also manage to identify intermediate states according to the height of the nanotexturation. Finally, our measurements revealed that the drop impalement depending on the surface tension of the liquid also depends on the aspect ratio of the nanostructures. We do believe that our method may lead to new insights into nanoscale wetting characterization by accessing the dynamic mapping of the liquid imbibition under the droplet.

  13. High-frequency ultrasonic imaging of thickly sliced specimens

    Science.gov (United States)

    Miyasaka, Chiaki; Tittmann, Bernhard R.; Chandraratna, Premindra A. N.

    2003-07-01

    It has been reported that a mechanical scanning reflection acoustic microscope (hereinafter called simply "SAM"), using high frequency ultrasonic tone-burst waves, can form a horizontal cross-sectional image (i.e., c-scan image) showing a highly resolved cellular structure of biological tissue. However, the tissue prepared for the SAM has been mostly a thinly sectioned specimen. In this study, the SAM images of specimens thickly sectioned from the tissue were analyzed. Optical and scanning acoustic microscopies were used to evaluate tissues of human small intestine and esophagus. For preparing thin specimens, the tissue was embedded in paraffin, and substantially sectioned at 5-10μm by the microtome. For optical microscopy, the tissue was stained with hematoxylin and eosin, and affixed onto glass substrates. For scanning acoustic microscopy, two types of specimens were prepared: thinly sectioned specimens affixed on the glass substrate, wherein the specimens were deparaffinized in xylene, but not stained, and thickely sectioned specimens. Images of the thick specimens obtained with frequency at 200 MHz revealed cellular structures. The morphology was very similar to that seen in the thinly sectioned specimens with optical and scanning acoustic microscopy. In addition, scanning electron microscopy was used to compare the images of biological tissue. An acoustic lens with frequency at 200 MHz permitted the imaging of surface and/or subsurface of microstructures in the thick sections of small intestine and esophagus.

  14. Ultra high frequency induction welding of powder metal compacts

    Directory of Open Access Journals (Sweden)

    Çavdar, Uǧur

    2014-06-01

    Full Text Available The application of the iron based Powder Metal (PM compacts in Ultra High Frequency Induction Welding (UHFIW were reviewed. These PM compacts are used to produce cogs. This study investigates the methods of joining PM materials enforceability with UHFIW in the industry application. Maximum stress and maximum strain of welded PM compacts were determined by three point bending and strength tests. Microhardness and microstructure of induction welded compacts were determined.Soldadura por inducción de ultra alta frecuencia de polvos de metal compactados. Se ha realizado un estudio de la aplicación de polvos de metal (PM de base hierro compactados por soldadura por inducción de ultra alta frecuencia (UHFIW. Estos polvos de metal compactados se utilizan para producir engranajes. Este estudio investiga los métodos de uni.n de los materiales de PM con UHFIW en su aplicación en la industria. La máxima tensión y la máxima deformación de los polvos de metal compactados soldados fueron determinadas por flexión en tres puntos y prueba de resistencia. Se determinó la microdureza y la microestructura de los polvos compactados por soldadura por inducción.

  15. High frequency strain measurements with fiber Bragg grating sensors

    Science.gov (United States)

    Koch, J.; Angelmahr, M.; Schade, W.

    2015-05-01

    In recent years fiber Bragg grating sensors gained interest in structural health monitoring and concepts for smart structures. They are small, lightweight, and immune to electromagnetic interference. Using multiplexing techniques, several sensors can be addressed by a single fiber. Therefore, well-established structures and materials in industrial applications can be easily equipped with fiber optical sensors with marginal influence on their mechanical properties. In return, critical components can be monitored in real-time, leading to reduced maintenance intervals and a great reduction of costs. Beside of generally condition monitoring, the localization of failures in a structure is a desired feature of the condition monitoring system. Detecting the acoustic emission of a sudden event, its place of origin can be determined by analyzing the delay time of distributed sensor signals. To achieve high localization accuracies for the detection of cracks, breaks, and impacts high sampling rates combined with the simultaneous interrogation of several fiber Bragg grating sensors are required. In this article a fiber Bragg grating interrogator for high frequency measurements up to the megahertz range is presented. The interrogator is based on a passive wavelength to intensity conversion applying arrayed waveguide gratings. Light power fluctuations are suppressed by a differential data evaluation, leading to a reduced signal-to-noise ratio and a low strain detection limit. The measurement system is used to detect, inter alia, wire breaks in steel wire ropes for dockside cranes.

  16. Very high frequency plasma reactant for atomic layer deposition

    Science.gov (United States)

    Oh, Il-Kwon; Yoo, Gilsang; Yoon, Chang Mo; Kim, Tae Hyung; Yeom, Geun Young; Kim, Kangsik; Lee, Zonghoon; Jung, Hanearl; Lee, Chang Wan; Kim, Hyungjun; Lee, Han-Bo-Ram

    2016-11-01

    Although plasma-enhanced atomic layer deposition (PE-ALD) results in several benefits in the formation of high-k dielectrics, including a low processing temperature and improved film properties compared to conventional thermal ALD, energetic radicals and ions in the plasma cause damage to layer stacks, leading to the deterioration of electrical properties. In this study, the growth characteristics and film properties of PE-ALD Al2O3 were investigated using a very-high-frequency (VHF) plasma reactant. Because VHF plasma features a lower electron temperature and higher plasma density than conventional radio frequency (RF) plasma, it has a larger number of less energetic reaction species, such as radicals and ions. VHF PE-ALD Al2O3 shows superior physical and electrical properties over RF PE-ALD Al2O3, including high growth per cycle, excellent conformality, low roughness, high dielectric constant, low leakage current, and low interface trap density. In addition, interlayer-free Al2O3 on Si was achieved in VHF PE-ALD via a significant reduction in plasma damage. VHF PE-ALD will be an essential process to realize nanoscale devices that require precise control of interfaces and electrical properties.

  17. Challenges in graphene integration for high-frequency electronics

    Science.gov (United States)

    Giannazzo, F.; Fisichella, G.; Greco, G.; Roccaforte, F.

    2016-06-01

    This paper provides an overview of the state-of-the-art research on graphene (Gr) for high-frequency (RF) devices. After discussing current limitations of lateral Gr RF transistors, novel vertical devices concepts such as the Gr Base Hot Electron Transistor (GBHET) will be introduced and the main challenges in Gr integration within these architectures will be discussed. In particular, a GBHET device based on Gr/AlGaN/GaN heterostructure will be considered. An approach to the fabrication of this heterostructure by transfer of CVD grown Gr on copper to the AlGaN surface will be presented. The morphological and electrical properties of this system have been investigated at nanoscale by atomic force microscopy (AFM) and conductive atomic force microscopy (CAFM). In particular, local current-voltage measurements by the CAFM probe revealed the formation of a Schottky contact with low barrier height (˜0.41 eV) and excellent lateral uniformity between Gr and AlGaN. Basing on the electrical parameters extracted from this characterization, the theoretical performances of a GBHET formed by a metal/Al2O3/Gr/AlGaN/GaN stack have been evaluated.

  18. Contributions to modeling functionality of a high frequency damper system

    Science.gov (United States)

    Sirbu, E. A.; Horga, S.; Vrabioiu, G.

    2016-08-01

    Due to the necessity of improving the handling performances of a motor vehicle, it is imperative to understand the suspensions properties that affects ride and directional respons.The construction of a fero-magnetic shock absorber is based on two bellows interconnected by a pipe-line. Through this pipe-line the fero-magnetic fluid is carried between the two bellows. The damping characteristic of the shock absorber is affected by the viscosity of the fero-magnetic fluid. The viscosity of the fluid, is controlled through a electric coil mounted on the bellows connecting pipe-line. Modifying the electrical field of the coil, the viscosity of the fluid will change, finally affecting the damping characteristic of the shock absorber. A recent system called „CCD Pothole Suspension” is implemented on Ford vehicles. By modifying the dampning characteristic of the shock absorbers, vehicle daynamics can be improved; also the risk of damaging the suspension will be decreased. The approach of this paper is to analyze the behaviour of the fero magnetic damper, thus determining how it will affect the performances of the vehicle suspensions. The experimental research will provide a better understanding of the behavior of the fero-magnetic shock absorber, and the possible advantages of using this system.

  19. Finite beta effects on low- and high-frequency magnetosonic waves in a two-ion-species plasma

    Energy Technology Data Exchange (ETDEWEB)

    Toida, Mieko; Aota, Yukio [Department of Physics, Nagoya University, Nagoya 464-8602 (Japan)

    2013-08-15

    A magnetosonic wave propagating perpendicular to a magnetic field in a two-ion-species plasma has two branches, high-frequency and low-frequency modes. The finite beta effects on these modes are analyzed theoretically on the basis of the three-fluid model with finite ion and electron pressures. First, it is shown that the Korteweg-de Vries (KdV) equation for the low-frequency mode is valid for amplitudes ε<ε{sub max}, where the upper limit of the amplitude ε{sub max} is given as a function of β (β is the ratio of the kinetic and magnetic energy densities), the density ratio, and the cyclotron frequency ratio of two ion species. Next, the linear dispersion relation and KdV equation for the high-frequency mode are derived, including β as a factor. In addition, the theory for heavy ion acceleration by the high-frequency mode pulse and the pulse damping due to this energy transfer in a finite beta plasma are presented.

  20. Semiclassical methods for high frequency wave propagation in periodic media

    Science.gov (United States)

    Delgadillo, Ricardo A.

    We will study high-frequency wave propagation in periodic media. A typical example is given by the Schrodinger equation in the semiclassical regime with a highly oscillatory periodic potential and external smooth potential. This problem presents a numerical challenge when in the semiclassical regime. For example, conventional methods such as finite differences and spectral methods leads to high numerical cost, especially in higher dimensions. For this reason, asymptotic methods like the frozen Gaussian approximation (FGA) was developed to provide an efficient computational tool. Prior to the development of the FGA, the geometric optics and Gaussian beam methods provided an alternative asymptotic approach to solving the Schrodinger equation efficiently. Unlike the geometric optics and Gaussian beam methods, the FGA does not lose accuracy due to caustics or beam spreading. In this thesis, we will briefly review the geometric optics, Gaussian beam, and FGA methods. The mathematical techniques used by these methods will aid us in formulating the Bloch-decomposition based FGA. The Bloch-decomposition FGA generalizes the FGA to wave propagation in periodic media. We will establish the convergence of the Bloch-decomposition based FGA to the true solution for Schrodinger equation and develop a gauge-invariant algorithm for the Bloch-decomposition based FGA. This algorithm will avoid the numerical difficulty of computing the gauge-dependent Berry phase. We will show the numerical performance of our algorithm by several one-dimensional examples. Lastly, we will propose a time-splitting FGA-based artificial boundary conditions for solving the one-dimensional nonlinear Schrodinger equation (NLS) on an unbounded domain. The NLS will be split into two parts, the linear and nonlinear parts. For the linear part we will use the following absorbing boundary strategy: eliminate Gaussian functions whose centers are too distant to a fixed domain.

  1. Castration alters protein balance after high-frequency muscle contraction.

    Science.gov (United States)

    Steiner, Jennifer L; Fukuda, David H; Rossetti, Michael L; Hoffman, Jay R; Gordon, Bradley S

    2017-02-01

    Resistance exercise increases muscle mass by shifting protein balance in favor of protein accretion. Androgens independently alter protein balance, but it is unknown whether androgens alter this measure after resistance exercise. To answer this, male mice were subjected to sham or castration surgery 7-8 wk before undergoing a bout of unilateral, high-frequency, electrically induced muscle contractions in the fasted or refed state. Puromycin was injected 30 min before euthanasia to measure protein synthesis. The tibialis anterior was analyzed 4 h postcontraction. In fasted mice, neither basal nor stimulated rates of protein synthesis were affected by castration despite lower phosphorylation of mechanistic target of rapamycin in complex 1 (mTORC1) substrates [p70S6K1 (Thr389) and 4E-BP1 (Ser65)]. Markers of autophagy (LC3 II/I ratio and p62 protein content) were elevated by castration, and these measures remained elevated above sham values after contractions. Furthermore, in fasted mice, the protein content of Regulated in Development and DNA Damage 1 (REDD1) was correlated with LC3 II/I in noncontracted muscle, whereas phosphorylation of uncoordinated like kinase 1 (ULK1) (Ser757) was correlated with LC3 II/I in the contracted muscle. When mice were refed before contractions, protein synthesis and mTORC1 signaling were not affected by castration in either the noncontracted or contracted muscle. Conversely, markers of autophagy remained elevated in the muscles of refed, castrated mice even after contractions. These data suggest the castration-mediated elevation in baseline autophagy reduces the absolute positive shift in protein balance after muscle contractions in the refed or fasted states.

  2. High-frequency homogenization for travelling waves in periodic media

    Science.gov (United States)

    Harutyunyan, Davit; Milton, Graeme W.; Craster, Richard V.

    2016-07-01

    We consider high-frequency homogenization in periodic media for travelling waves of several different equations: the wave equation for scalar-valued waves such as acoustics; the wave equation for vector-valued waves such as electromagnetism and elasticity; and a system that encompasses the Schrödinger equation. This homogenization applies when the wavelength is of the order of the size of the medium periodicity cell. The travelling wave is assumed to be the sum of two waves: a modulated Bloch carrier wave having crystal wavevector k and frequency ω1 plus a modulated Bloch carrier wave having crystal wavevector m and frequency ω2. We derive effective equations for the modulating functions, and then prove that there is no coupling in the effective equations between the two different waves both in the scalar and the system cases. To be precise, we prove that there is no coupling unless ω1=ω2 and (k -m )⊙Λ ∈2 π Zd, where Λ=(λ1λ2…λd) is the periodicity cell of the medium and for any two vectors a =(a1,a2,…,ad),b =(b1,b2,…,bd)∈Rd, the product a⊙b is defined to be the vector (a1b1,a2b2,…,adbd). This last condition forces the carrier waves to be equivalent Bloch waves meaning that the coupling constants in the system of effective equations vanish. We use two-scale analysis and some new weak-convergence type lemmas. The analysis is not at the same level of rigour as that of Allaire and co-workers who use two-scale convergence theory to treat the problem, but has the advantage of simplicity which will allow it to be easily extended to the case where there is degeneracy of the Bloch eigenvalue.

  3. High-frequency homogenization for travelling waves in periodic media.

    Science.gov (United States)

    Harutyunyan, Davit; Milton, Graeme W; Craster, Richard V

    2016-07-01

    We consider high-frequency homogenization in periodic media for travelling waves of several different equations: the wave equation for scalar-valued waves such as acoustics; the wave equation for vector-valued waves such as electromagnetism and elasticity; and a system that encompasses the Schrödinger equation. This homogenization applies when the wavelength is of the order of the size of the medium periodicity cell. The travelling wave is assumed to be the sum of two waves: a modulated Bloch carrier wave having crystal wavevector [Formula: see text] and frequency ω1 plus a modulated Bloch carrier wave having crystal wavevector [Formula: see text] and frequency ω2. We derive effective equations for the modulating functions, and then prove that there is no coupling in the effective equations between the two different waves both in the scalar and the system cases. To be precise, we prove that there is no coupling unless ω1=ω2 and [Formula: see text] where Λ=(λ1λ2…λ d ) is the periodicity cell of the medium and for any two vectors [Formula: see text] the product a⊙b is defined to be the vector (a1b1,a2b2,…,adbd ). This last condition forces the carrier waves to be equivalent Bloch waves meaning that the coupling constants in the system of effective equations vanish. We use two-scale analysis and some new weak-convergence type lemmas. The analysis is not at the same level of rigour as that of Allaire and co-workers who use two-scale convergence theory to treat the problem, but has the advantage of simplicity which will allow it to be easily extended to the case where there is degeneracy of the Bloch eigenvalue.

  4. Achieving High-Frequency Optical Control of Synaptic Transmission

    Science.gov (United States)

    Jackman, Skyler L.; Beneduce, Brandon M.; Drew, Iain R.

    2014-01-01

    The optogenetic tool channelrhodopsin-2 (ChR2) is widely used to excite neurons to study neural circuits. Previous optogenetic studies of synapses suggest that light-evoked synaptic responses often exhibit artificial synaptic depression, which has been attributed to either the inability of ChR2 to reliably fire presynaptic axons or to ChR2 elevating the probability of release by depolarizing presynaptic boutons. Here, we compare light-evoked and electrically evoked synaptic responses for high-frequency stimulation at three synapses in the mouse brain. At synapses from Purkinje cells to deep cerebellar nuclei neurons (PC→DCN), light- and electrically evoked synaptic currents were remarkably similar for ChR2 expressed transgenically or with adeno-associated virus (AAV) expression vectors. For hippocampal CA3→CA1 synapses, AAV expression vectors of serotype 1, 5, and 8 led to light-evoked synaptic currents that depressed much more than electrically evoked currents, even though ChR2 could fire axons reliably at up to 50 Hz. The disparity between optical and electrical stimulation was eliminated when ChR2 was expressed transgenically or with AAV9. For cerebellar granule cell to stellate cell (grc→SC) synapses, AAV1 also led to artificial synaptic depression and AAV9 provided superior performance. Artificial synaptic depression also occurred when stimulating over presynaptic boutons, rather than axons, at CA3→CA1 synapses, but not at PC→DCN synapses. These findings indicate that ChR2 expression methods and light stimulation techniques influence synaptic responses in a neuron-specific manner. They also identify pitfalls associated with using ChR2 to study synapses and suggest an approach that allows optogenetics to be applied in a manner that helps to avoid potential complications. PMID:24872574

  5. Catchment Very-High Frequency Hydrochemistry: the Critex Chemical House

    Science.gov (United States)

    Floury, P.; Gaillardet, J.; Tallec, G.; Blanchouin, A.; Ansart, P.

    2015-12-01

    Exploring the variations of river quality at very high frequency is still a big challenge that has fundamental implications both for understanding catchment ecosystems and for water quality monitoring. Within the French Critical Zone program CRITEX, we have proposed to develop a prototype called "Chemical House", applying the "lab on field" concept to one of the stream of the Orgeval Critical Zone Observatory. The Orgeval catchment (45 km2) is part of the Critical Zone RBV ("Réseau des bassins versants") network. It is a typical temperate agricultural catchment that has been intensively monitored for the last 50 years for hydrology and nutrient chemistry. Agricultural inputs and land use are also finely monitored making Orgeval an ideal basin to test the response of the Critical Zone to agricultural forcing. Geology consists of a typical sedimentary basin of Cenozoic age with horizontal layers of limestones, silcrete and marls, covered by a thin loamy layer. Two main aquifers are present within the catchment: the Brie and the Champigny aquifers. Mean runoff is 780 mm/yr. The Chemical House is a fully automated lab and installed directly along the river, which performs measurement of all major dissolved elements such as Na, Cl, Mg, Ca, NO3, SO4 and K every half hour. It also records all physical parameters (Temperature, pH, conductivity, O2 dissolved, Turbidity) of the water every minute. Orgeval Chemical House started to measure river chemistry on June 12, 2015 and has successfully now recorded several months of data. We will present the architecture of the Chemical House and the first reproducibility and accuracy tests made during the summer drought 2015 period. Preliminary results show that the chemical house is recoding significant nychtemeral (day/night) cycles for each element. We also observe that each element has its own behaviour along a day. First results open great prospects.

  6. Recent Improvements in High-Frequency Eddy Current Conductivity Spectroscopy

    Science.gov (United States)

    Abu-Nabah, Bassam A.; Nagy, Peter B.

    2008-02-01

    Due to its frequency-dependent penetration depth, eddy current measurements are capable of mapping near-surface residual stress profiles based on the so-called piezoresistivity effect, i.e., the stress-dependence of electric conductivity. To capture the peak compressive residual stress in moderately shot-peened (Almen 4-8A) nickel-base superalloys, the eddy current inspection frequency has to go as high as 50-80 MHz. Recently, we have reported the development of a new high-frequency eddy current conductivity measuring system that offers an extended inspection frequency range up to 80 MHz. Unfortunately, spurious self- and stray-capacitance effects render the complex coil impedance variation with lift-off more nonlinear as the frequency increases, which makes it difficult to achieve accurate apparent eddy current conductivity (AECC) measurements with the standard four-point linear interpolation method beyond 25 MHz. In this paper, we will demonstrate that reducing the coil size reduces its sensitivity to capacitive lift-off variations, which is just the opposite of the better known inductive lift-off effect. Although reducing the coil size also reduces its absolute electric impedance and relative sensitivity to conductivity variations, a smaller coil still yields better overall performance for residual stress assessment. In addition, we will demonstrate the benefits of a semi-quadratic interpolation scheme that, together with the reduced lift-off sensitivity of the smaller probe coil, minimizes and in some cases completely eliminates the sensitivity of AECC measurements to lift-off uncertainties. These modifications allow us to do much more robust measurements up to as high as 80-100 MHz with the required high relative accuracy of +/-0.1%.

  7. Very high frequency plasma reactant for atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Oh, Il-Kwon; Yoo, Gilsang; Yoon, Chang Mo [School of Electrical and Electronic Engineering, Yonsei University, Seoul 120-749 (Korea, Republic of); Kim, Tae Hyung; Yeom, Geun Young [Department of Advanced Materials Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Kim, Kangsik; Lee, Zonghoon [School Materials Science and Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919 (Korea, Republic of); Jung, Hanearl; Lee, Chang Wan [School of Electrical and Electronic Engineering, Yonsei University, Seoul 120-749 (Korea, Republic of); Kim, Hyungjun, E-mail: hyungjun@yonsei.ac.kr [School of Electrical and Electronic Engineering, Yonsei University, Seoul 120-749 (Korea, Republic of); Lee, Han-Bo-Ram, E-mail: hbrlee@inu.ac.kr [Department of Materials Science and Engineering, Incheon National University, 406-840 Incheon (Korea, Republic of)

    2016-11-30

    Highlights: • Fundamental research plasma process for thin film deposition is presented. • VHF plasma source for PE-ALD Al{sub 2}O{sub 3} was employed to reduce plasma damage. • The use of VHF plasma improved all of the film qualities and growth characteristics. - Abstract: Although plasma-enhanced atomic layer deposition (PE-ALD) results in several benefits in the formation of high-k dielectrics, including a low processing temperature and improved film properties compared to conventional thermal ALD, energetic radicals and ions in the plasma cause damage to layer stacks, leading to the deterioration of electrical properties. In this study, the growth characteristics and film properties of PE-ALD Al{sub 2}O{sub 3} were investigated using a very-high-frequency (VHF) plasma reactant. Because VHF plasma features a lower electron temperature and higher plasma density than conventional radio frequency (RF) plasma, it has a larger number of less energetic reaction species, such as radicals and ions. VHF PE-ALD Al{sub 2}O{sub 3} shows superior physical and electrical properties over RF PE-ALD Al{sub 2}O{sub 3}, including high growth per cycle, excellent conformality, low roughness, high dielectric constant, low leakage current, and low interface trap density. In addition, interlayer-free Al{sub 2}O{sub 3} on Si was achieved in VHF PE-ALD via a significant reduction in plasma damage. VHF PE-ALD will be an essential process to realize nanoscale devices that require precise control of interfaces and electrical properties.

  8. Up-regulation of miR-31 in human atrial fibrillation begets the arrhythmia by depleting dystrophin and neuronal nitric oxide synthase

    Science.gov (United States)

    Carnicer, Ricardo; Recalde, Alice; Muszkiewicz, Anna; Jayaram, Raja; Carena, Maria Cristina; Wijesurendra, Rohan; Stefanini, Matilde; Surdo, Nicoletta C.; Lomas, Oliver; Ratnatunga, Chandana; Sayeed, Rana; Krasopoulos, George; Rajakumar, Timothy; Bueno-Orovio, Alfonso; Verheule, Sander; Fulga, Tudor A.; Rodriguez, Blanca; Schotten, Ulrich

    2016-01-01

    Atrial fibrillation (AF) is a growing public health burden, and its treatment remains a challenge. AF leads to electrical remodeling of the atria, which in turn promotes AF maintenance and resistance to treatment. Although remodeling has long been a therapeutic target in AF, its causes remain poorly understood. We show that atrial-specific up-regulation of microRNA-31 (miR-31) in goat and human AF depletes neuronal nitric oxide synthase (nNOS) by accelerating mRNA decay and alters nNOS subcellular localization by repressing dystrophin translation. By shortening action potential duration and abolishing rate-dependent adaptation of the action potential duration, miR-31 overexpression and/or disruption of nNOS signaling recapitulates features of AF-induced remodeling and significantly increases AF inducibility in mice in vivo. By contrast, silencing miR-31 in atrial myocytes from patients with AF restores dystrophin and nNOS and normalizes action potential duration and its rate dependency. These findings identify atrial-specific up-regulation of miR-31 in human AF as a key mechanism causing atrial dystrophin and nNOS depletion, which in turn contributes to the atrial phenotype begetting this arrhythmia. miR-31 may therefore represent a potential therapeutic target in AF. PMID:27225184

  9. Cyclokinetic models and simulations for high-frequency turbulence in fusion plasmas

    Science.gov (United States)

    Deng, Zhao; Waltz, R. E.; Wang, Xiaogang

    2016-10-01

    Gyrokinetics is widely applied in plasma physics. However, this framework is limited to weak turbulence levels and low drift-wave frequencies because high-frequency gyro-motion is reduced by the gyro-phase averaging. In order to test where gyrokinetics breaks down, Waltz and Zhao developed a new theory, called cyclokinetics [R. E. Waltz and Zhao Deng, Phys. Plasmas 20, 012507 (2013)]. Cyclokinetics dynamically follows the high-frequency ion gyro-motion which is nonlinearly coupled to the low-frequency drift-waves interrupting and suppressing gyro-averaging. Cyclokinetics is valid in the high-frequency (ion cyclotron frequency) regime or for high turbulence levels. The ratio of the cyclokinetic perturbed distribution function over equilibrium distribution function δf/ F can approach 1. This work presents, for the first time, a numerical simulation of nonlinear cyclokinetic theory for ions, and describes the first attempt to completely solve the ion gyro-phase motion in a nonlinear turbulence system. Simulations are performed [Zhao Deng and R. E. Waltz, Phys. Plasmas 22(5), 056101 (2015)] in a local flux-tube geometry with the parallel motion and variation suppressed by using a newly developed code named rCYCLO, which is executed in parallel by using an implicit time-advanced Eulerian (or continuum) scheme [Zhao Deng and R. E. Waltz, Comp. Phys. Comm. 195, 23 (2015)]. A novel numerical treatment of the magnetic moment velocity space derivative operator guarantee saccurate conservation of incremental entropy. By comparing the more fundamental cyclokinetic simulations with the corresponding gyrokinetic simulations, the gyrokinetics breakdown condition is quantitatively tested. Gyrokinetic transport and turbulence level recover those of cyclokinetics at high relative ion cyclotron frequencies and low turbulence levels, as required. Cyclokinetic transport and turbulence level are found to be lower than those of gyrokinetics at high turbulence levels and low- Ω* values

  10. High frequency electromagnetic reflection loss performance of substituted Sr-hexaferrite nanoparticles/SWCNTs/epoxy nanocomposite

    Energy Technology Data Exchange (ETDEWEB)

    Gordani, Gholam Reza, E-mail: gordani@gmail.com [Materials Engineering Department, Malek Ashtar University of Technology, Shahin Shahr (Iran, Islamic Republic of); Ghasemi, Ali [Materials Engineering Department, Malek Ashtar University of Technology, Shahin Shahr (Iran, Islamic Republic of); Saidi, Ali [Department of Materials Science and Engineering, Isfahan University of Technology, Isfahan (Iran, Islamic Republic of)

    2015-10-01

    In this study, the electromagnetic properties of a novel nanocomposite material made of substituted Sr-hexaferrite nanoparticles and different percentage of single walled carbon nanotube have been studied. The structural, magnetic and electromagnetic properties of samples were studied as a function of volume percentage of SWCNTs by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, vibrating sample magnetometer and vector network analysis. Well suitable crystallinity of hexaferrite nanoparticles was confirmed by XRD patterns. TEM and FESEM micrographs were shown the good homogenity and high level of dispersivity of SWCNTs and Sr-hexaferrite nanoparticles in nanocomposite samples. The VSM results shown that with increasing in amount of CNTs (0–6 vol%), the saturation of magnetization decreased up to 11 emu/g for nanocomposite sample contains of 6 vol% of SWCNTs. The vector network analysis results show that the maximum value of reflection loss was −36.4 dB at the frequency of 11 GHz with an absorption bandwidth of more than 4 GHz (<−20 dB). The results indicate that, this nanocomposite material with appropriate amount of SWCNTs hold great promise for microwave device applications. - Highlights: • We investigate the high frequency properties of Sr-hexaferrite/SWCNTs composite. • Saturation magnetization of nanocomposites is decreased with presence of SWCNTs. • The ferrite/CNTs nanocomposite sample covers whole X-band frequencies (8–12 GHz). • The ferrite/CNTs nanocomposite can be used as a potential magnetic loss material. • Nanocomposite contain 4 vol% of CNTs have shown greater than 99% of reflection loss.

  11. Thin-Film Microtransformer for High Frequency Power Applications

    Directory of Open Access Journals (Sweden)

    Dinulovic Dragan

    2014-07-01

    Full Text Available This paper describes a development of a microtransformer device fabricated using thin film technology. The device is designed for higher switching frequencies beyond to 50 MHz power applications. A especially by the microtransformer is a design, which allows wide flexibility of a device by choosing a different values of an inductance and of a windings ratio. The microtransformer device is integrated on silicon substrate consisting of a closed magnetic core and six coils. Both, primary and secondary device side consist three coils. Therefore, this design allows using of a device for different switching frequencies. As a magnetic material for transformer core a permalloy NiFe45/55 was chosen.

  12. Computational simulations of thermally activated magnetisation dynamics at high frequencies

    CERN Document Server

    Hannay, J D

    2001-01-01

    short time scale breakdown of the Arrhenius-Neel law for a single magnetic moment is demonstrated and explained in terms of the dynamics of the precessional motion. The variation in response as a function of the damping parameter is found to be an important factor determining the remanent magnetisation for a given pulse width. The effects of interactions between moments are described, including the apparent increase in effective damping. It is shown that interactions between grains can be described in terms of thermally excited spin waves. The most important device for today's large scale information storage is the magnetic hard disk drive. This is because it can store vast amounts of data and also provides the fastest way of accessing this valuable information. A current state of the art commercially available hard disk has data rates in excess of 1 GHz which means the magnetic bits are required to reverse in less than one nanosecond. The areal density is greater than 10 Gbits/in sup 2 which requires extreme...

  13. Variable Temperature High-Frequency Response of Heterostructure Transistors

    Science.gov (United States)

    Laskar, Joy

    1992-01-01

    The development of high performance heterostructure transistors is essential for emerging opto-electronic integrated circuits (OEICs) and monolithic microwave integrated circuits (MMICs). Applications for OEICs and MMICs include the rapidly growing telecommunications and personal communications markets. The key to successful OEIC and MMIC chip sets is the development of high performance, cost-effective technologies. In this work, several different transistor structures are investigated to determine the potential for high speed performance and the physical mechanisms controlling the ultimate device operation. A cryogenic vacuum microwave measurement system has been developed to study the high speed operation of modulation doped field-effect transistors (MODFETs), doped channel metal insulator field-effect transistors (MISFETs), and metal semiconductor field-effect transistors (MESFETs). This study has concluded that the high field velocity and not the low field mobility is what controls high frequency operation of GaAs based field-effect transistors. Both Al_{rm x} Ga_{rm 1-x}As/GaAs and InP/In_{rm y}Ga _{rm 1-y}As heterostructure bipolar transistors (HBTs) have also been studied at reduced lattice temperatures to understand the role of diffusive transport in the Al_{rm x} Ga_{rm 1-x}As/GaAs HBT and nonequilibrium transport in the InP/In _{rm y}Ga_ {rm 1-y}As HBT. It is shown that drift/diffusion formulation must be modified to accurately estimate the base delay time in the conventional Al _{rm x}Ga_ {rm 1-x}As/GaAs HBT. The reduced lattice temperature operation of the InP/In_ {rm y}Ga_{rm 1-y}As HBT demonstrates extreme nonequilibrium transport in the neutral base and collector space charge region with current gain cut-off frequency exceeding 300 GHz, which is the fastest reported transistor to date. Finally, the MODFET has been investigated as a three-terminal negative differential resistance (NDR) transistor. The existence of real space transfer is confirmed by

  14. 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...

  15. High frequency rTMS; a more effective treatment for auditory verbal hallucinations?

    Science.gov (United States)

    de Weijer, Antoin D; Sommer, Iris E C; Lotte Meijering, Anne; Bloemendaal, Mirjam; Neggers, Sebastiaan F W; Daalman, Kirstin; Boezeman, Eduard H J F

    2014-12-30

    The great majority of studies on repetitive transcranial magnetic stimulation (rTMS) as a therapeutic tool for auditory verbal hallucinations (AVH) have used 1-Hz stimulation with inconsistent results. Recently, it has been suggested that 20-Hz rTMS has strong therapeutic effects. It is conceivable that this 20-Hz stimulation is more effective than 1-Hz stimulation. The aim of this preliminary study is to investigate the efficacy of 20-Hz rTMS compared with 1-Hz rTMS as a treatment for AVH. Eighteen schizophrenia patients with medication-resistant AVH were randomized over two treatment groups. Each group received either 20 min of 1-Hz rTMS or 13 trains of 20-Hz rTMS daily over 1 week. After week 1, patients received a follow-up treatment once a week for 3 weeks. Stimulation location was based on individual AVH-related activation patterns identified with functional magnetic resonance imaging. Severity of AVH was monitored with the Auditory Hallucination Rating Scale (AHRS). Both groups showed a decrease in AVH after week 1 of rTMS. This decrease was significant for the 20-Hz group and the 1-Hz group. When the two treatment types were compared, no treatment type was superior. Based on these results we cannot conclude whether high frequency rTMS is more effective against AVH than is traditional 1-Hz rTMS. More research is needed to optimize stimulation parameters and to investigate potential target locations for stimulation.

  16. High-frequency behavior of FeN thin films fabricated by using reactive sputtering

    Science.gov (United States)

    Hwang, Tae-Jong; Lee, Joonsik; Kim, Ki Hyeon; Kim, Dong Ho

    2016-08-01

    We used ferromagnetic resonance (FMR) and its relationship with the static magnetic properties to investigate the high-frequency behavior of FeN thin films prepared by using reactive sputtering. The FMR was observed in the frequency range from 2 to 18 GHz in the FeN films fabricated at a proper nitrogen flow rate (NFR). In those FeN thin films, a decrease in the saturation magnetization and a corresponding decrease of the FMR frequency were observed as the NFR was increased during the deposition. The external field dependences of the FMR frequencies fit the Kittel formula well, and the Landé g-factors determined from the fit were found to be very close to the free electron value. The high-field damping parameters were almost insensitive to the NFR. However, the lowfield damping parameters exhibited a high sensitivity to the NFR very similar to the dependence of the hard-axis coercivity on the NFR, suggesting that extrinsic material properties, such as impurities and defect structures, could be important in deciding the low-field damping behavior.

  17. Artificial ionospheric layers driven by high-frequency radiowaves: An assessment

    Science.gov (United States)

    Mishin, Evgeny; Watkins, Brenton; Lehtinen, Nikolai; Eliasson, Bengt; Pedersen, Todd; Grach, Savely

    2016-04-01

    High-power ordinary mode radio waves produce artificial ionization in the F region ionosphere at the European Incoherent Scatter (Tromsø, Norway) and High Frequency Active Auroral Research Program (Gakona, Alaska, USA) facilities. We have summarized the features of the excited plasma turbulence and descending layers of freshly ionized ("artificial") plasma. The concept of an ionizing wavefront created by accelerated suprathermal electrons appears to be in accordance with the data. The strong Langmuir turbulence (SLT) regime is revealed by the specific spectral features of incoherent radar backscatter and stimulated electromagnetic emissions. Theory predicts that the SLT acceleration is facilitated in the presence of photoelectrons. This agrees with the intensified artificial plasma production and the greater speeds of descent but weaker incoherent radar backscatter in the sunlit ionosphere. Numerical investigation of propagation of O-mode waves and the development of SLT and descending layers have been performed. The greater extent of the SLT region at the magnetic zenith than that at vertical appears to make magnetic zenith injections more efficient for electron acceleration and descending layers. At high powers, anomalous absorption is suppressed, leading to the Langmuir and upper hybrid processes during the whole heater on period. The data suggest that parametric upper hybrid interactions mitigate anomalous absorption at heating frequencies far from electron gyroharmonics and also generate SLT in the upper hybrid layer. The persistence of artificial plasma at the terminal altitude depends on how close the heating frequency is to the local gyroharmonic.

  18. Evidence of high-frequency/small-scale turbulence in the Cygnus region and anomalous Faraday rotation

    Science.gov (United States)

    Medvedev, Mikhail V.

    2017-01-01

    Faraday effect - a common and useful probe of cosmic magnetic fields - is the result of magnetically-induced birefringence in plasmas causing rotation of the polarization plane of a linearly polarized electromagnetic wave. Classically, the rotation angle scales with the wavelength as Δϕ =RMλ2 , where RM is the rotation measure. Although a typical RM in the Milky Way is of the order of a few hundred to a few thousand, a famous Cygnus region shows anomalously small, even negative rotation measures. Moreover, Faraday rotation measurements seem to be inconsistent with the standard λ2-law. We argue that fast micro-turbulence can cause this anomaly. We demonstrate that electromagnetic high-frequency and/or small-scale fluctuations can lead to effective plasma collisionality by scattering electrons over pitch-angle. We show that such quasi-collisionality radically alters Faraday rotation and other radiative transport properties, e.g., absorption, transmission and reflection. Thus, we explain the Cygnus puzzle by anomalous Faraday rotation in a thin ``blanket'' of highly turbulent plasma at the front of an interstellar bubble/shock. Supported by DOE grant DE-SC0016368.

  19. Excitation and Ionisation dynamics in high-frequency plasmas

    Science.gov (United States)

    O'Connell, D.

    2008-07-01

    excitation and sustainment of the discharge. As the pressure decreases the discharge operates in so-called 'alpha-mode' where the sheath expansion is responsible for discharge sustainment. Decreasing the pressure towards the limit of operation (below 1 Pa) the discharge operates in a regime where kinetic effects dominate plasma sustainment. Wave particle interactions resulting from the flux of highly energetic electrons interacting with thermal bulk electrons give rise to a series of oscillations in the electron excitation phase space at the sheath edge. This instability is responsible for a significant energy deposit in the plasma when so-called 'ohmic heating' is no longer efficient. In addition to this an interesting electron acceleration mechanism occurs during the sheath collapse. The large sheath width, due to low plasma densities at the lower pressure, and electron inertia allows the build up of a local electric field accelerating electrons towards the electrode. Multi-frequency plasmas, provide additional process control for technological applications, and through investigating the excitation dynamics in such discharges the limitations of functional separation is observed. Non-linear frequency coupling is observed in plasma boundary sheaths governed by two frequencies simultaneously. In an alpha-operated discharge the sheath edge velocity governs the excitation and ionisation within the plasma, and it will be shown that this is determined by the time varying sheath width. The nature of the coupling effects strongly depends on the ratio of the applied voltages. Under technologically relevant conditions (low frequency voltage >> high frequency voltage) interesting phenomena depending on the phase relation of the voltages are also observed and will be discussed.

  20. Development of Ti-Coated Ferromagnetic Needle, Adaptable for Ablation Cancer Therapy by High-Frequency Induction Heating

    Directory of Open Access Journals (Sweden)

    Shinya Matsutomo

    2012-03-01

    Full Text Available To develop a novel ablation therapy for human solid cancer, the heating properties of a ferromagnetic carbon steel rod and a prototype Ti-coated needle using this carbon steel rod, were investigated in several high-frequency outputs at 300 kHz. In the former, the heating property was drastically different among the three inclination angles (θ = 0°, 45° and 90° relative to the magnetic flux direction as a result of the shape magnetic anisotropy. However, the effect of the inclination angles was completely eliminated in the latter. It is considered that the complete non-oriented heating property relative to the magnetic flux direction allows the precise control of the ablation temperature during minimally invasive thermotherapy without a lead-wire connected to a fiber-optic thermometer. This newly designed Ti-coated device will be suitable for clinical use combined with its superior biocompatibility for ablation treatments using high-frequency induction heating.

  1. Electrically tunable transport and high-frequency dynamics in antiferromagnetic S r3I r2O7

    Science.gov (United States)

    Seinige, Heidi; Williamson, Morgan; Shen, Shida; Wang, Cheng; Cao, Gang; Zhou, Jianshi; Goodenough, John B.; Tsoi, Maxim

    2016-12-01

    We report dc and high-frequency transport properties of antiferromagnetic S r3I r2O7 . Temperature-dependent resistivity measurements show that the activation energy of this material can be tuned by an applied dc electrical bias. The latter allows for continuous variations in the sample resistivity of as much as 50% followed by a reversible resistive switching at higher biases. Such a switching is of high interest for antiferromagnetic applications in high-speed memory devices. Interestingly, we found the switching behavior to be strongly affected by a high-frequency (microwave) current applied to the sample. The microwaves at 3-7 GHz suppress the dc switching and produce resonancelike features that we tentatively associated with the dissipationless magnonics recently predicted to occur in antiferromagnetic insulators subject to ac electric fields. We have characterized the effects of microwave irradiation on electronic transport in S r3I r2O7 as a function of microwave frequency and power, strength and direction of external magnetic field, strength and polarity of applied dc bias, and temperature. Our observations support the potential of antiferromagnetic materials for high-speed/high-frequency spintronic applications.

  2. A randomized, sham-controlled study of high frequency rTMS for auditory hallucination in schizophrenia.

    Science.gov (United States)

    Kimura, Hiroshi; Kanahara, Nobuhisa; Takase, Masayuki; Yoshida, Taisuke; Watanabe, Hiroyuki; Iyo, Masaomi

    2016-07-30

    Chronic auditory verbal hallucinations (AVHs) in patients with schizophrenia are sometimes resistant to standard pharmacotherapy. Repetitive transcranial magnetic stimulation (rTMS) may be a promising treatment modality for AVHs, but the best protocol has yet to be identified. We used a double-blind randomized sham-controlled design aimed at 30 patients (active group N=16 vs. sham group N=14) with chronic AVHs that persisted regardless of adequate pharmacotherapy. The protocol was a total of four sessions of high-frequency (20-Hz) rTMS targeting the left temporoparietal cortex over 2 days (total 10,400 stimulations) administered to each patient. After the rTMS session the patients were followed for 4 weeks and evaluated with the Auditory Hallucination Rating Scale (AHRS). The mean changes of AHRS score were 22.9 (baseline) to 18.4 (4th week) in the Active group and 24.2 (baseline) to 21.8 (4th week) in the Sham group, indicating no significant difference by mix model analysis. As regards other secondary end points (each subscore of AHRS, BPRS, GAF and CGI-S), none of these parameters showed a significant between-group difference. The present study's rTMS protocol was ineffective for our patients. However, several previous studies demonstrated that high-frequency rTMS is a possible strategy to ameliorate pharmacotherapy-resistant AVH. It is important to establish a high-frequency rTMS protocol with more reliability.

  3. 高频重复经颅磁刺激治疗精神分裂症难治性阴性症状的随机双盲对照试验%Effects of high frequency repetitive transcranial magnetic stimulation on refractory negative symptom of schizophrenia: A double blind, randomized controlled trial

    Institute of Scientific and Technical Information of China (English)

    任艳萍; 周东丰; 蔡焯基; 黄青; 卢芩; 陈琦

    2011-01-01

    目的:探讨双背侧前额叶高频重复经颅磁刺激(repetitive transcranial magnetic stimulation,rTMS)治疗精神分裂症难治性阴性症状的疗效和安全性,并观察不良反应.方法:本研究为双盲随机对照临床试验.研究对象来源于2002年11月1日至2003年12月31日期间就诊于北京大学第六医院和北京安定医院的门诊和住院患者,符合美国精神疾病诊断与统计手册第4版(Diagnostic and Statistical Manual of Mental Disorders,Fourth Edition,DSM.IV)中精神分裂症诊断标准.23例以难治性阴性症状为主的精神分裂症患者随机分为rTMS治疗组(n=12)和对照组(n=11),分别给予10次20Hz rTMS真刺激和伪刺激治疗,治疗期间维持原有抗精神病药种类及剂量不变.采用阳性和阴性症状量表(Positive and Negative Syndrome Scale,PANSS)评估临床症状,采用治疗中需处理的不良反应症状量表(Treatment Emergent Symptom scale,TESS)及其他检查评估不良反应.结果:23例患者均完成治疗.治疗组有效率高于对照组(34%vs.17%,P<0.05).未观察到明显不良反应.结论:抗精神病药合并20 Hz双背侧前额叶重复经颅磁刺激治疗精神分裂症难治性阴性症状有效、安全.%Objective: To examine the therapeutic effects of dual dorsolateral prefrontal repetitive transcranial magnetic stimulation ( rTMS ) on refractory negative symptom experienced by patients with schizophrenia. Methods: A double-blind, randomized controlled study was conducted. Totally 23 schizophrenic patients met the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) criteria for schizophrenia were recruited. Subjects were grouped into active treatment subgroup and sham subgroup randomly. Clinical symptom was measured with the Positive and Negative Symptom Scale (PANSS) . Side effects were valuated with the Treatment Emergent Symptom Scale (TESS). Results: Totally 23 subjects completed the trial. The treatment efficiency of

  4. Design of High Frequency Power Oscillator Board Based on Rotary Encoder Control

    Directory of Open Access Journals (Sweden)

    Jiang Shifen

    2013-06-01

    Full Text Available Accurate and stable high frequency pulse power supply is studied to improve high-speed wedm machine tool's efficiency. Regarding to the shortcomings of traditional digital circuit high frequency oscillator board, we design a high frequency power oscillator board based on rotary encoder control, control accuracy and high-frequency waveform by programming, adjusting the frequency and display. It has six brakes of processing function, it also includes feedback function of emulsification oil. The high frequency will be shutdown and the emulsification oil will be changed if there is too much metal dust in emulsification. It has been proved by practice that high-frequency circuit board is simple and reliable and can greatly increase efficiency of wire cutting.

  5. A New High Frequency Injection Method Based on Duty Cycle Shifting without Maximum Voltage Magnitude Loss

    DEFF Research Database (Denmark)

    Wang, Dong; Lu, Kaiyuan; Rasmussen, Peter Omand

    2015-01-01

    amplitude. This may be utilized to develop new position estimation algorithm without involving the inductance in the medium to high speed range. As an application example, a developed inductance independent position estimation algorithm using the proposed high frequency injection method is applied to drive......The conventional high frequency signal injection method is to superimpose a high frequency voltage signal to the commanded stator voltage before space vector modulation. Therefore, the magnitude of the voltage used for machine torque production is limited. In this paper, a new high frequency...... injection method, in which high frequency signal is generated by shifting the duty cycle between two neighboring switching periods, is proposed. This method allows injecting a high frequency signal at half of the switching frequency without the necessity to sacrifice the machine fundamental voltage...

  6. Analysis of Energy Overshoot of High Frequency Waves with Wavelet Transform

    Institute of Scientific and Technical Information of China (English)

    WEN Fan

    2000-01-01

    A study is made on the overshoot phenomena in wind-generated waves. The surface displace ments of time-growing waves are measured at four fetches in a wind wave channel. The evolution of high frequency waves is displayed with wavelet transform. The results are compared with Sutherland's. It is found that high frequency wave components experience much stronger energy overshoot in the evolution.The energy of high frequency waves decreases greatly after overshoot

  7. Sonic analogue of black holes and the effects of high frequencies on black hole evaporation

    CERN Document Server

    Unruh, W G

    1995-01-01

    The naive calculation of black hole evaporation makes the thermal emission depend on the arbitrary high frequency behaviour of the theory where the theory is certainly wrong. Using the sonic analog to black holes-- dumb holes-- I show numerically that a change in the dispersion relation at high frequencies does not seem to alter the evaporation process, lending weight to the reality of the black hole evaporation process. I also suggest a reason for the insensitivity of the process to high frequency regime.

  8. A Cold Adhesion for Self-fused Alloy Coat by High Frequency Induction

    Institute of Scientific and Technical Information of China (English)

    ZHANG Zeng-zhi; AI Bo

    2004-01-01

    In this study, a method to prepare self-fused alloy coat, which started with a cold adhesion precoating and then induction fusing plus, is presented. It also intended to analyze the mechanism, microstructure and anitwear ability of the coat. The workpiece was precoated with Ni60 powder through an adhesion agent. The oven-dried precoat was then heated by a high frequency induction generated by 100kw power with a frequency of 250kHz. The technological parameters of the method were determined through analysis of the thermal magnetism, thermal resistivity and anti-induction mechanism. By comparing the microstrucrures and properties of the coat produced by cold adhesion, thermal spraying and laser refusing, it is concluded that: (1) One side of the workpiece should be preheated to 200℃ before induction fusion, and the range of induction frequency should be 200~250kHz. (2) The microstrucrure of the coat by cold adhesion is superior to that by thermal spraying, but the particle size range should be 0.047~0.044mm (200~320 meshes) (3) The corrosion resistance of Ni60 coat by cold adhesion is better than that by thermal spraying, and the cold adhesion is the best method to prepare the antiwear coat.

  9. A Cold Adhesion for Self-fused Alloy Coat by High Frequency Induction

    Institute of Scientific and Technical Information of China (English)

    ZHANGZeng-zhi; AIBo

    2004-01-01

    In this study, a method to prepare self-fused alloy coat, which started with a cold adhesion precoating and then induction fusing plus, is presented. It also intended to analyze the mechanism, microstnlcture and anitwear ability of the coat. The workpiece was precoated with Ni60 powder through an adhesion agent. The oven-dried precoat was then heated by a high frequency induction generated by 100kw power with a frequency of 250kHz. The technological parameters of the method were determined through analysis of tbe thermal magnetism, thermal resislivity, and anti-induction mechanism. By comparing the microsLrUclures and properties of the coat produced by cold adhesion, thermal spraying and laser refusing, it is concluded that: (1) One side of the workpiece should be preheated to 200℃ before induction fusion, and the range of induction frequency should be 200-250kHz. (2) The microstructure of the coat by cold adhesion is superior to that by themal spraying, but the particle size range should be 0.047-0.044mm (200-320 meshes) (3) The corrosion resistance of Ni60 coat by cold adhesion is better than that by thermal spraying, and the cold adhesion is the best method to prepare the antiwear coat.

  10. High-Frequency QPOs and Overstable Oscillations of Black-Hole Accretion Disks

    CERN Document Server

    Lai, Dong; Tsang, David; Horak, Jiri; Yu, Cong

    2012-01-01

    The physical origin of high-frequency QPOs (HFQPOs) in black-hole X-ray binaries remains an enigma despite many years of detailed observational studies. Although there exists a number of models for HFQPOs, many of these are simply "notions" or "concepts" without actual calculation derived from fluid or disk physics. Future progress requires a combination of numerical simulations and semi-analytic studies to extract physical insights. We review recent works on global oscillation modes in black-hole accretion disks, and explain how, with the help of general relativistic effects, the energy stored in the disk differential rotation can be pumped into global spiral density modes in the disk, making these modes grow to large amplitudes under certain conditions ("corotational instability"). These modes are robust in the presence of disk magnetic fields and turbulence. The computed oscillation mode frequencies are largely consistent with the observed values for HFQPOs in BH X-ray binaries. The approximate 2:3 frequen...

  11. Relations between Strong High-Frequency Microwave Bursts and Proton Events

    Science.gov (United States)

    Grechnev, Victor V.; Meshalkina, Nataliya S.; Chertok, Ilya M.; Kiselev, Valentin I.

    2013-12-01

    Proceeding from close association between solar eruptions, flares, shock waves, and CMEs, we analyze relations between bursts at 35 GHz recorded with the Nobeyama Radio Polarimeters during 1990-2012, on the one hand, and solar energetic particle (SEP) events, on the other hand. Most west to moderately east solar events with strong bursts at 35 GHz produced near-Earth proton enhancements of J (E > 100 MeV) > 1 pfu. The strongest and hardest of those caused ground-level enhancements. There is a general, although scattered, correspondence between proton enhancements and peak fluxes at 35 GHz, especially pronounced if the 35 GHz flux exceeds 104 sfu and the microwave peak frequency is high. These properties indicate emission from numerous high-energy electrons in very strong magnetic fields suggesting a high rate of energy release in the flare-CME formation process. Flaring above the sunspot umbrae appears to be typical of such events. Irrespective of the origin of SEPs, these circumstances demonstrate significant diagnostic potential of high-frequency microwave bursts and sunspot-associated flares for space weather forecasting. Strong prolonged bursts at 35 GHz promptly alert to hazardous SEP events with hard spectra. A few exceptional events with moderate bursts at 35 GHz and strong proton fluxes look challenging, and should be investigated.

  12. Coil design considerations for a high-frequency electromagnetic induction sensing instrument

    Science.gov (United States)

    Sigman, John B.; Barrowes, Benjamin E.; Wang, Yinlin; Bennett, Hollis J.; Simms, Janet E.; Yule, Donald E.; O'Neill, Kevin; Shubitidze, Fridon

    2016-05-01

    Intermediate electrical conductivity (IEC) materials (101S/m IEC objects. Recent analytical and numerical studies have showed that these targets exhibit characteristic quadrature response peaks at high induction frequencies (100kHz - 15MHz, the High Frequency Electromagnetic Induction (HFEMI) band), and they are not detectable with traditional ultra wideband (UWB) electromagnetic induction (EMI) metal detectors operating between 100Hz - 100kHz. Using the HFEMI band for induction sensing is not so simple as driving existing instruments at higher frequencies, though. At low frequency, EMI systems use more wire turns in transmit and receive coils to boost signal-to-noise ratios (SNR), but at higher frequencies, the transmitter current has non-uniform distribution along the coil length. These non-uniform currents change the spatial distribution of the primary magnetic field and disturb axial symmetry and thwart established approaches for inferring subsurface metallic object properties. This paper discusses engineering tradeoffs for sensing with a broader band of frequencies ever used for EMI sensing, with particular focus on coil geometries.

  13. 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.

  14. Preparation of Fe3O4/MnOOH core-shell nanoparticles by a high-frequency impinging stream reactor☆

    Institute of Scientific and Technical Information of China (English)

    Dongguang Wang; Baikang Zhu; Hengcong Tao

    2015-01-01

    Well-defined Fe3O4/MnOOH nanoparticles with 61.1 emu·g−1 in magnetization intensity and 90.53 m2·g−1 in surface area have been synthesized by a new-style of high-frequency impinging stream (HFIS) reactor. In this reactor, two streams first collided together to form nano Fe3O4 suspension, which subsequently flew through an S-shaped maln channel to generate high-frequency reversing high-gravity fields. At the same time, 24 thin liquid sheets impinged into the maln channel at the frequencies higher than 100 Hz to create nano Fe3O4/MnOOH colloids. The obtalned powders were characterized by transmission electron microscopy/energy dispersive spectrometer (TEM/EDS), X-ray diffraction (XRD), Brunner–Emmet–Teller (BET) and vibrating sample magnetometer (VSM). Experimental results indicated that low coating ratio prolonged the induction period of heterogeneous nucleation. The high-frequency impingements of 24 thin liquid sheets greatly accelerated the macro-mixing and the initial dispersion. The high-frequency reversing high-gravity fields promoted the meso-and micro-mixing. As a result, nano Fe3O4 cores were fleetly and uniformly covered by MnOOH precursor. As a continuously operated and static high-gravity reactor, the high-frequency impinging stream (HFIS) reactor is being developed to the large-scaled and low-cost production of various nanocomposites.

  15. Outphasing control of gallium nitride based very high frequency resonant converters

    DEFF Research Database (Denmark)

    Madsen, Mickey Pierre; Knott, Arnold; Andersen, Michael A. E.

    2015-01-01

    In this paper an outphasing modulation control method suitable for line regulation of very high frequency resonant converters is described. The pros and cons of several control methods suitable for very high frequency resonant converters are described and compared to outphasing modulation...

  16. A rapid sample-exchange mechanism for cryogen-free dilution refrigerators compatible with multiple high-frequency signal connections

    Science.gov (United States)

    Batey, G.; Chappell, S.; Cuthbert, M. N.; Erfani, M.; Matthews, A. J.; Teleberg, G.

    2014-03-01

    Researchers attempting to study quantum effects in the solid-state have a need to characterise samples at very low-temperatures, and frequently in high magnetic fields. Often coupled with this extreme environment is the requirement for high-frequency signalling to the sample for electrical control or measurements. Cryogen-free dilution refrigerators allow the necessary wiring to be installed to the sample more easily than their wet counterparts, but the limited cooling power of the closed cycle coolers used in these systems means that the experimental turn-around time can be longer. Here we shall describe a sample loading arrangement that can be coupled with a cryogen-free refrigerator and that allows samples to be loaded from room temperature in a matter of minutes. The loaded sample is then cooled to temperatures ∼10 mK in ∼7 h. This apparatus is compatible with systems incorporating superconducting magnets and allows multiple high-frequency lines to be connected to the cold sample.

  17. High-frequency magneto-conductivity studies of low-dimensional organic conductors

    Energy Technology Data Exchange (ETDEWEB)

    Schrama, J.M

    2000-07-01

    In this thesis I present experimental studies of the millimetre-wave magneto-conductivity of the organic charge-transfer salts {kappa}-(BEDT-TTF){sub 2}Cu(NCS){sub 2}, {alpha}-(BEDT-TTF){sub 2}KHg(SCN){sub 4} and (TMTSF){sub 2}ClO{sub 4}. A rotating resonant cavity insert was developed to investigate the angle dependence of resonances in the magneto-conductivity. The technique revealed a new kind of magnetic resonance, the Fermi-surface traversal resonance (FTR), which is described by a semiclassical model. The FTRs give information about the topology of the quasi-one-dimensional (Q1D) Fermi-surface sections. The Q1D Fermi-surface sections play an important role in forming the ground states in organic conductors giving rise, for example, to nesting associated with a density-wave. Chapter 1 gives a brief historical overview of the development of organic conductors and provides basic information about crystal structures and Fermi surfaces of BEDT-TTF based systems. Chapter 2 introduces the reader to basic solid state physics used later in the thesis. In Chapter 3 I discuss the operation of the experimental techniques and apparatus, including millimetre-wave techniques. In addition, Chapter 3 contains a description of the design of the FTR rotating cavity insert which is unique of its kind. In Chapter 4 a model of oscillating real-space velocity vectors is presented. The model is used to explain the origin of the FTRs observed in the high-frequency magneto- conductivity data. In Chapter 5 I report two studies of the angle dependence of FTRs in the high-frequency magneto-conductivity. The FTRs in {kappa}-(BEDT-TTF){sub 2}Cu(NCS){sub 2} and {alpha}-(BEDT- TTF){sub 2}KHg(SCN){sub 4} show two previously unknown corrugations in the Q1D Fermi-surface sections of the two materials. The FTRs in {alpha}-(BEDT-TTF){sub 2}KHg(SCN){sub 4} are investigated both in the density-wave state and near its collapse into a high-temperature, high-field state. In Chapter 6 a study of the

  18. High-Frequency EMI Noise Suppression by Polymer-Based Composite Magnetic Materials

    Directory of Open Access Journals (Sweden)

    Rastislav Dosoudil

    2008-01-01

    Full Text Available The complex permeability and EM-wave absorption properties of hybrid polymer-based composite magneticmaterials (with MnZn and LiZn ferrite fillers and PVC matrix prepared with constant total filler content (65 vol% andparticle size (0-250 mm have been investigated in the 1-1000 MHz frequency range. Within this filler concentrationthe permeability of composites changed continuously with the change of ferrite filler content ratio between two types offerrite fillers. The observed relaxation type of permeability dispersion was due to the domain wall and natural ferromagneticresonance phenomena and was also attributed to the high damping of spin motion. Measured values of permeability wereused to determine the EM-wave absorption properties (return loss RL, matching frequency fm, matching thickness dm andbandwidth Df for RL £ -20 dB. The calculation of these properties was based on a model of single-layered absorber backedby a perfect conductor using transmission-line and EM-field theory. The composite with the volume fraction ratio of hybridMnZn:LiZn ferrite filler set to 0.5:0.5 has shown a return loss of -57 dB (> 99 % power absorption at fm = 714 MHz with the-20 dB bandwidth of Df = 232 MHz for an absorber thickness of 7.79 mm.

  19. The studies of high-frequency magnetic properties and absorption characteristics for amorphous-filler composites

    Science.gov (United States)

    Li, Z. W.; Yang, Z. H.

    2015-10-01

    Pure amorphous flake fillers and amorphous flakes coated by ferrite nanoparticles with core-shell-like structure were fabricated using mechanical ball-milling. The later with core-shell-like structure can greatly decrease permittivity and improve the absorption properties, as compared to the former. The absorption of all amorphous-filler composites has its origin in a quarter-wavelength resonator. Based on the resonator model, absorption frequency fA and the corresponding return loss RL are calculated, which are well consistent with observed values. It is also found that the resonance frequency is proportional to effective resistivity, based on William-Shockley-Kittel's eddy model.

  20. Econometric analysis of realized covariation: high frequency based covariance, regression, and correlation in financial economics

    DEFF Research Database (Denmark)

    Barndorff-Nielsen, Ole Eiler; Shephard, N.

    2004-01-01

    This paper analyses multivariate high frequency financial data using realized covariation. We provide a new asymptotic distribution theory for standard methods such as regression, correlation analysis, and covariance. It will be based on a fixed interval of time (e.g., a day or week), allowing...... the number of high frequency returns during this period to go to infinity. Our analysis allows us to study how high frequency correlations, regressions, and covariances change through time. In particular we provide confidence intervals for each of these quantities....

  1. A critical review of liquid helium temperature high frequency pulse tube cryocoolers for space applications

    Science.gov (United States)

    Wang, B.; Gan, Z. H.

    2013-08-01

    The importance of liquid helium temperature cooling technology in the aerospace field is discussed, and the results indicate that improving the efficiency of liquid helium cooling technologies, especially the liquid helium high frequency pulse tube cryocoolers, is the principal difficulty to be solved. The state of the art and recent developments of liquid helium high frequency pulse tube cryocoolers are summarized. The main scientific challenges for high frequency pulse tube cryocoolers to efficiently reach liquid helium temperatures are outlined, and the research progress addressing those challenges are reviewed. Additionally some possible solutions to the challenges are pointed out and discussed.

  2. A note for the mechanism of high-frequency oscillation instability resulted from absorbing boundary conditions

    Institute of Scientific and Technical Information of China (English)

    XIE Zhi-nan; LIAO Zhen-peng

    2008-01-01

    In this paper the explanation of the mechanism of high-frequency oscillation instability resulted from absorbing boundary conditions is further improved. And we analytically prove the proposition that for one dimensional dis- crete model of elastic wave motion, the module of reflection factor will be greater than 1 in high frequency band when artificial wave velocity is greater than 1.5 times the ratio of discrete space step to discrete time step. Based on the proof, the frequency band in which instability occurs is discussed in detail, showing such high-frequency waves are meaningless for the numerical simulation of wave motion.

  3. A novel variable polarity welding power based on high-frequency pulse modulation

    Institute of Scientific and Technical Information of China (English)

    Qiu Ling; Yang Chunli; Fan Chenglei; Lin Sanbao; Wu Yun

    2006-01-01

    A new type of variable polarity welding power modulated with high-frequency pulse current is developed.Series of high-frequency pulse current is superimposed on direct-current-electrode-negative (DCEN), which can improve the crystallization process in the weld bead as a result of the electromagnetic force generated by pulse current.Digital signal processor (DSP) is used to realize the closed-loop control of the first inverter, variable polarity output of the second inverter and high-frequency pulse current superposition.

  4. Efficacy of cumulative high-frequency rTMS on freezing of gait in Parkinson’s disease

    Science.gov (United States)

    Kim, Min Su; Hyuk Chang, Won; Cho, Jin Whan; Youn, Jinyoung; Kim, Yun Kwan; Woong Kim, Sun; Kim, Yun-Hee

    2015-01-01

    Abstract Purpose: Freezing of gait (FOG) affects mobility and balance seriously. Few reports have investigated the effects of repetitive transcranial magnetic stimulation (rTMS) on FOG in Parkinson’s disease (PD). We investigated the efficacy of high-frequency rTMS for the treatment of FOG in PD. Methods: Seventeen patients diagnosed with PD were recruited in a randomized, double-blinded, cross-over study. We applied high frequency rTMS (90% of resting motor threshold, 10 Hz, 1,000 pulses) over the lower leg primary motor cortex of the dominant hemisphere (M1-LL) for five sessions in a week. We also administered alternative sham stimulation with a two-week wash out period. The primary outcomes were measured before, immediately after, and one week after the intervention using the Standing Start 180° Turn Test (SS-180) with video analysis and the Freezing of Gait Questionnaire (FOG-Q). The secondary outcome measurements consisted of Timed Up and Go (TUG) tasks and the Unified Parkinson’s Disease Rating Scale part III (UPDRS-III). Motor cortical excitability was also evaluated. Results: There were significant improvements in the step required to complete the SS-180 and FOG-Q in the rTMS condition compared to the sham condition, and the effects continued for a week. The TUG and UPDRS-III also showed significant ameliorations over time in the rTMS condition. The MEP amplitude at 120% resting motor threshold and intracortical facilitation also increased after real rTMS condition. Conclusions: High frequency rTMS over the M1-LL may serve as an add-on therapy for improving FOG in PD. PMID:26409410

  5. 高频重复经颅磁刺激对脑梗死大鼠缺血半暗带超微结构及脑源性神经营养因子表达的影响%Effects of high-frequency repetitive transcranial magnetic stimulation on the ultrastructure of an ischemic brain penumbra and the expression of brain-derived neurotrophic factors in rats

    Institute of Scientific and Technical Information of China (English)

    黄杰; 马玉娟; 方征宇; 种玉飞; 随燕芳; 尤春景

    2011-01-01

    Objective To investigate the effects of high-frequency repetitive transcranial magnetic stimulation (rTMS) at different intensities on the ultrastructure of an ischemic brain penumbra and the expression of brainderived neurotrophic factor (BDNF) using rats with permanent middle cerebral artery occlusion (MCAO).Methods Forty-two rats were randomly divided into a blank control group,an MCAO model control group,a sham stimulation control group and an rTMS group.The rTMS group was divided further into 3 subgroups:an 80% of motor threshold (MT) subgroup,a 100% of MT subgroup and a 120% of MT subgroup.The cerebral infarction model was established by right MCAO.rTMS treatment was given 24 hours after the MCAO model was successfully established.The rTMS group and sham stimulation control group were given 20 Hz rTMS with the planned intensities.The MCAO model control group was not given any stimulation.After 14 days of treatment,transmission electron microscopy,immunohistochemical and Western blotting ( WB ) methods were used to investigate the ultrastructure of the ischemic penumbra and the expression of BDNF.Results Damage reflected in the ultrastructure in the 3 rTMS subgroups was less than in the model control group and the sham stimulation control group.Expression of BDNF protein increased significantly in 100% of the MT group and blank control group rats as compared with that in the sham stimulation control group,while the blank control group and the 3 rTMS subgroups had no statistically significant difference in comparison with the MCAO model control group.The expression of BDNF protein had no statistically significant difference between any of the groups.Conclusion 20 Hz rTMS might,especially at 100% of the MT,promote the recovery of the ultrastructure of neural tissues in the ischemic penumbra after acute cerebral infarction and enhance the expression of BDNF in the ipsilesional hemisphere.This may be one of the important mechanisms of r

  6. Computational modeling of a single microdischarge and its interactions with high frequency electromagnetic waves

    Science.gov (United States)

    PanneerChelvam, Premkumar; Raja, Laxminarayan L.; Upadhyay, Rochan R.

    2016-09-01

    We discuss the computational modeling of a single microplasma and its interaction with high frequency electromagnetic waves in a microwave regime. The work is motivated by a strong recent interest in the area of reconfigurable plasma-based metamaterials (MM) and photonic crystals (PC) where the interaction of electromagnetic waves with plasma elements (e.g. microdischarges) forms the basis for the MM/PC operation. In this work the microplasma is assumed to be driven by a 1 GHz microwave source in a parallel plate electrode configuration. Its structure and properties are described using a fluid plasma model. The interaction of the microplasma with a 100 GHz transverse magnetic (TM) and transverse electric (TE) polarized microwave propagating in a rectangular waveguide is studied. Two operational regimes of the plasma discharge are considered. One in which the peak electron density is less than the critical density (under-dense) for the interacting wave and the other in which it is higher (over-dense). The under-dense plasma with positive less than unity dielectric constant has sufficient dielectric contrast from the surrounding medium that a slight perturbation of the incident wave and bending of wave path lines through the discharge is realized. The over-dense plasma interacts strongly with the TM polarized wave because of epsilon-zero resonance at the critical density locations and the wave path lines are observed to reverse their direction near the regions of critical plasma density. The transverse electric (TE) polarized wave does not exhibit epsilon-zero resonance and the interactions are weaker than the TM wave.

  7. Magneto-dielectric properties of doped ferrite based nanosized ceramics over very high frequency range

    Directory of Open Access Journals (Sweden)

    Ashish Saini

    2016-06-01

    Full Text Available In the present study, indium doped nano sized nickel zinc cobalt based ferrite ceramics with composition Ni0.5Zn0.3Co0.2InxFe2-xO4 (x = 0.2 and 0.4 were synthesized by a co-precipitation technique. Powdered sample has been pre-sintered at 800 °C, pressed into toroids and finally sintered at 1000 °C. The single phase formation of the presintered powder has been confirmed by X ray diffraction (XRD. The average particle size of the presintered powder has been estimated by field emission scanning electron microscope (FESEM and found to be about ~60 nm for x = 0.2 and ~80 nm at x = 0.4. The electromagnetic characterization has been made using vector network analyzer. High value of permeability (17.3 and 15.2 for x = 0.2 and 0.4 respectively with low magnetic loss tangent of 10−1 order were obtained. Permittivity of 8.2 and 10, and dielectric loss tangent of the order of 10−2 were also achieved. With the measured electromagnetic parameters, miniaturization factor of 12.32 and normalized characteristic impedance close to unity (1.23 were obtained up to 100 MHz frequency. These fascinating parameters definitely propose Ni0.5Zn0.3Co0.2In0.4Fe1.6O4 ceramics as a substrate material for miniaturized antenna in very high frequency band. Possible reasons and mechanisms of electromagnetic properties for different concentrations of indium are discussed in the paper.

  8. Smart magnetodielectric nano-materials for the very high frequency applications

    Energy Technology Data Exchange (ETDEWEB)

    Thakur, Atul [Department of Physics, National Taiwan University, 1 Roosevelt Road, Sec. 4, Taipei 106, Taiwan (China); Thakur, Preeti [Physics Department, Himachal Pradesh University, Shimla 171005 (India); Hsu, Jen-Hwa, E-mail: jhhsu@phys.ntu.edu.tw [Department of Physics, National Taiwan University, 1 Roosevelt Road, Sec. 4, Taipei 106, Taiwan (China)

    2011-04-28

    Research highlights: > Ni{sub 0.4}Zn{sub 0.4}Co{sub 0.2}Cu{sub 0.02}Fe{sub 1.98}O{sub 4} nano-ferrite is prepared by a co-precipitation method. > The average crystalline size of the nano-ferrite is 38 nm. > The material shows almost constant {mu} and {epsilon} in the frequency range from 10 to 200 MHz. > Relaxation phenomenon takes place above 200 MHz. > Useful as a substrate for loading the patch antenna than pure dielectric substrates. - Abstract: Cobalt and copper doped Ni-Zn nano-ferrite with a composition of Ni{sub 0.4}Zn{sub 0.4}Co{sub 0.2}Cu{sub 0.02}Fe{sub 1.98}O{sub 4} are prepared by a coprecipitation method. The structural, electromagnetic and magnetic properties are investigated by means of X-ray diffraction, impedance analyzer and vibrating sample magnetometer, respectively. Samples are calcinated at 600 deg. C and then subjected to different sintering temperatures. After sintering at 900 deg. C for 5 h, the average crystalline size is found to be 38 nm. The material shows almost constant permeability and permittivity, in the frequency range from 10 to 200 MHz, equal to {approx}10.8 (loss tangent {approx} 0.04) and {approx}6.5 (loss tangent {approx} 0.006), respectively. Relaxation phenomenon takes place beyond 200 MHz. The refractive index n is close to 8.3, and the reduced impedance Z/Z{sub 0} is close to 1.3. The persistent and higher value of permeability than that of permittivity along with low losses enables this material useful for the very high frequency applications.

  9. High-frequency susceptibility of a multilayered ferromagnetic system with two-dimensional inhomogeneities

    Science.gov (United States)

    Mankov, Yu. I.; Tsikalov, D. S.

    2010-03-01

    This paper reports on the results of the investigation of the high-frequency susceptibility of a layered ferromagnetic structure in which, apart from a periodic change in the magnetic anisotropy parameter from layer to layer, this parameter varies along layers according to a random law (the superlattice with two-dimensional phase inhomogeneities). The evolution of the frequency dependence of the imaginary part of the averaged Green’s function in the range of the energy gap (band gap) in the spectrum of waves propagating along the superlattice axis due to the change in the relative root-mean-square fluctuations of the phase γ2 has been studied at the boundaries of the odd Brillouin zones. It has been found that, for all odd Brillouin zones, the imaginary part of the Green’s function exhibits a universal behavior: the peak corresponding to the edge of the band gap with a lower frequency remains unchanged, and the peak corresponding to the edge of the band gap with a higher frequency is smoothed with an increase in the quantity γ2. These effects, which were initially revealed at the boundary of the first Brillouin zone of the sinusoidal superlattice, have been explained, as before, by the specific features of the energy conservation laws for the incident and scattered waves in the lattice with two-dimensional inhomogeneities. It has been demonstrated that an increase in the Brillouin zone number leads to a decrease in the value of γ2 at which the peak at the edge of the band gap with a higher frequency disappears.

  10. A new type of daytime high-frequency VLF emissions at auroral latitudes ("bird emissions")

    Science.gov (United States)

    Manninen, J.; Turunen, T.; Kleimenova, N. G.; Gromova, L. I.; Kozlovskii, A. E.

    2017-01-01

    This paper is concerned with a new, previously unknown type of high-frequency (above 4 kHz) VLF emissions that were detected during winter VLF campaigns in Kannuslehto ( L 5.5), Finland. These previously unknown emissions have been discovered as a result of the application of special digital filtering: it clears the VLF records from pulse signals of intensive atmospherics, which prevent other kinds of VLF emissions in the same frequency range from being seen on spectrograms. As it appears, aside from wellknown bursts of auroral hisses and discrete quasiperiodic emissions, a previously unknown type of daytime right-hand polarized VLF waves is also present at frequencies above 4 kHz. These emissions can persist for several hours as series of separate short discrete wideband (from 4 to 10 kHz and higher) signals, each with a duration between one and several minutes. It has been found that such signals can be observed almost daily in winter. These emissions sound like bird's chirping to a human ear; for that reason, they were called "bird emissions." The dynamic spectra of individual signals often resemble flying birds. The signals are observed during daytime, more often in magnetically quiet conditions preceded by geomagnetic disturbances. As a rule, the occurrence of these bird emissions is accompanied by a slight increase in electron density in the lower ionosphere, which is evidence of the precipitation of energetic (>30 keV) electrons. This raises a number of questions as to where and how the VLF bird emissions are generated and how such emissions, at frequencies greatly exceeding half the electron equatorial gyrofrequency at L 5.5, can reach the Earth's surface.

  11. Stability Analysis of an Inverted Pendulum Subjected to Combined High Frequency Harmonics and Stochastic Excitations

    Institute of Scientific and Technical Information of China (English)

    HUANG Zhi-Long; JIN Xiao-Ling; ZHU Zi-Qi

    2008-01-01

    Stability of vertical upright position of an inverted pendulum with its suspension point subjected to high frequency harmonics and stochastic excitations is investigated. Two classes of excitations, i.e., combined high frequency harmonic excitation and Gaussian white noise excitation, and high frequency bounded noise excitation, respectively,are considered. Firstly, the terms of high frequency harmonic excitations in the equation of motion of the system can be set equivalent to nonlinear stiffness terms by using the method of direct separation of motions. Then the stochastic averaging method of energy envelope is used to derive the averaged It(o) stochastic differential equation for system energy. Finally, the stability with probability 1 of the system is studied by using the largest Lyapunov exponent obtained from the averaged It(o) stochastic differential equation. The effects of system parameters on the stability of the system are discussed, and some examples are given to illustrate the efficiency of the proposed procedure.

  12. Laser and high-frequency cauthery gingivectomy in nonperiodontal indications: assessment and comparison of techniques

    Science.gov (United States)

    Bartak, Petr; Smucler, Roman

    2003-06-01

    The authors have verified the efficiency and safety of laser and high-frequency gingivectomy in non-periodontal indications. Within a prospective, non-selective study, they treated and monitored 357 dental areas in 139 teeth.Out of the total number, 248 areas were treated wtih a diode laser, 980nm; 109 areas with high-frequency electrocautery. The following parameters were monitored: a) regeneration of the marginal gingiva; b) generation of iatrogenic recessions or periodontal pockets; c) bleeding from gingival sulcus during probing; d) changes in tooth vitality; e) patient's subjective evaluation. The authors identified a high degree of safety in both laser and high-frequency gingivectomy, with no significant difference between these two methods. Laser gingivectomy appears to have a wider indication range, while high-frequency gingivectomy requires lower financial expenses.

  13. 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...

  14. Effect of low-intensity extremely high frequency radiation on reproductive function in wistar rats.

    Science.gov (United States)

    Subbotina, T I; Tereshkina, O V; Khadartsev, A A; Yashin, A A

    2006-08-01

    The exposure to low-intensity extremely high frequency electromagnetic radiation during spermatogenesis was accompanied by pathological changes, which resulted in degeneration and polymorphism of spermatozoa. The number of newborn rats increased in the progeny of irradiated animals.

  15. High frequency wide-band transformer uses coax to achieve high turn ratio and flat response

    Science.gov (United States)

    De Parry, T.

    1966-01-01

    Center-tap push-pull transformer with toroidal core helically wound with a single coaxial cable creates a high frequency wideband transformer. This transformer has a high-turn ratio, a high coupling coefficient, and a flat broadband response.

  16. High frequency permeability and permittivity spectra of BiFeO{sub 3}/(CoTi)-BaM ferrite composites

    Energy Technology Data Exchange (ETDEWEB)

    Peng, Yun; Wu, Xiaohan; Li, Qifan; Yu, Ting; Feng, Zekun, E-mail: fengzekun@hust.edu.cn [School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074 (China); Chen, Zhongyan [School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074 (China); Jiangmen Magsource New Material CO., LTD., 529000 Guangdong (China); Su, Zhijuan; Chen, Yajie; Harris, Vincent G. [Center for Microwave Magnetic Materials and Integrated Circuits, and Department of Electrical and Computer Engineering, Northeastern University, Boston, Massachusetts 02115 (United States)

    2015-05-07

    Low magnetic loss ferrite composites consisting of Ba(CoTi){sub 1.2}Fe{sub 9.6}O{sub 19} and BiFeO{sub 3} (BFO) ferrite were investigated for permeability, permittivity, and high frequency losses at 10 MHz–1 GHz. The phase fraction of BiFeO{sub 3} was quantitatively analyzed by X-ray diffraction measurements. An effective medium approach was employed to predict the effective permeability and permittivity for the ferrite composites, which was found to be in good agreement with experimental data. The experiment demonstrated low magnetic losses (<0.128), modified by BFO phase fraction, while retaining high permeability (∼10.86) at 300 MHz. More importantly, the BFO phase resulted in a reduction of magnetic loss by 32%, as BFO phase increased from 2.7 vol. % to 12.6 vol. %. The effect of BFO phase on magnetic and dielectric properties revealed great potential for use in the miniaturization of high efficiency antennas.

  17. The Impact of Very High Frequency Surface Reverberation on Coherent Acoustic Propagation and Modeling

    Science.gov (United States)

    2015-09-30

    is to measure and model very high frequency underwater sound generated by processes at the sea surface, relevant to the high-frequency underwater...realizations generated from wave gauge data synchronized with the acoustic measurements. The curves are not generally smooth because of the limited...on Coherent Acoustic Propagation and Modeling Grant B. Deane Marine Physical Laboratory, Scripps Institution of Oceanography UCSD La Jolla, CA

  18. Conventional Audiometry, Extended High-Frequency Audiometry, and DPOAE for Early Diagnosis of NIHL

    OpenAIRE

    Mehrparvar, Amir Houshang; Mirmohammadi, Seyyed Jalil; Davari, Mohammad Hossein; MOSTAGHACI, Mehrdad; Mollasadeghi, Abolfazl; Bahaloo, Maryam; Hashemi, Seyyed Hesam

    2014-01-01

    Background: Noise most frequently affects hearing system, as it may typically cause a bilateral, progressive sensorineural hearing loss at high frequencies. Objectives: This study was designed to compare three different methods to evaluate noise-induced hearing loss (conventional audiometry, high-frequency audiometry, and distortion product otoacoustic emission). Material and Methods: This was a cross-sectional study. Data was analyzed by SPSS (ver. 19) using chi square, T test and repeated m...

  19. High-frequency vibration energy harvesting from impulsive excitation utilizing intentional dynamic instability caused by strong nonlinearity

    Science.gov (United States)

    Remick, Kevin; Dane Quinn, D.; Michael McFarland, D.; Bergman, Lawrence; Vakakis, Alexander

    2016-05-01

    The authors investigate a vibration-based energy harvesting system utilizing essential (nonlinearizable) nonlinearities and electromagnetic coupling elements. The system consists of a grounded, weakly damped linear oscillator (primary system) subjected to a single impulsive load. This primary system is coupled to a lightweight, damped oscillating attachment (denoted as nonlinear energy sink, NES) via a neodymium magnet and an inductance coil, and a piano wire, which generates an essential geometric cubic stiffness nonlinearity. Under impulsive input, the transient damped dynamics of this system exhibit transient resonance captures (TRCs) causing intentional large-amplitude and high-frequency instabilities in the response of the NES. These TRCs result in strong energy transfer from the directly excited primary system to the light-weight attachment. The energy is harvested by the electromagnetic elements in the coupling and, in the present case, dissipated in a resistive element in the electrical circuit. The primary goal of this work is to numerically, analytically, and experimentally demonstrate the efficacy of employing this type of intentional high-frequency dynamic instability to achieve enhanced vibration energy harvesting under impulsive excitation.

  20. Study on the dynamic characteristics of a high frequency brake based on giant magnetostrictive material

    Science.gov (United States)

    Xu, Ai Qun

    2016-06-01

    In order to meet the requirements of rapid and smooth braking, high-frequency braking using a giant magnetostrictive actuator is proposed, which can solve the problems in hydraulic braking, such as, it leaks easily, catches fire easily, is difficult to find failures, high cost on maintenance and repairing, etc. The main factors affecting the force of a high-frequency braking actuator are emphatically analyzed, the brakes dynamic model is established and a performance testing device for high frequency braking is constructed based on LabVIEW. The output force of the actuator increases with the excitation current of the driving coil increasing, and the increased multiple of the output force is greater than that of the excitation current; the range of the actuator force amplitude is 121.63 N ∼ 158.14 N, which changes little, while excitation frequency changes between 200 Hz ∼ 1000 Hz. In a minor range of pre-stress, the output force decreases with an increase in the axial pre-stress of the giant magnetostrictive rod, but is not obvious. It is known by finite element simulation analysis that high-frequency braking shortens the braking displacement and time effectively, which proves the feasibility and effectiveness of high frequency braking. Theoretical analysis and experimental results indicate that the output force of the actuator changes at the same frequency with excitation current; it is controllable and its mechanical properties meet the requirements of high frequency braking.

  1. High-Frequency Transcranial Random Noise Stimulation Enhances Perception of Facial Identity.

    Science.gov (United States)

    Romanska, Aleksandra; Rezlescu, Constantin; Susilo, Tirta; Duchaine, Bradley; Banissy, Michael J

    2015-11-01

    Recently, a number of studies have demonstrated the utility of transcranial current stimulation as a tool to facilitate a variety of cognitive and perceptual abilities. Few studies, though, have examined the utility of this approach for the processing of social information. Here, we conducted 2 experiments to explore whether a single session of high-frequency transcranial random noise stimulation (tRNS) targeted at lateral occipitotemporal cortices would enhance facial identity perception. In Experiment 1, participants received 20 min of active high-frequency tRNS or sham stimulation prior to completing the tasks examining facial identity perception or trustworthiness perception. Active high-frequency tRNS facilitated facial identity perception, but not trustworthiness perception. Experiment 2 assessed the spatial specificity of this effect by delivering 20 min of active high-frequency tRNS to lateral occipitotemporal cortices or sensorimotor cortices prior to participants completing the same facial identity perception task used in Experiment 1. High-frequency tRNS targeted at lateral occipitotemporal cortices enhanced performance relative to motor cortex stimulation. These findings show that high-frequency tRNS to lateral occipitotemporal cortices produces task-specific and site-specific enhancements in face perception.

  2. Perception and coding of high-frequency spectral notches: Potential implications for sound localization

    Directory of Open Access Journals (Sweden)

    Ana eAlves-Pinto

    2014-05-01

    Full Text Available The interaction of sound waves with the human pinna introduces high-frequency notches (5-10 kHz in the stimulus spectrum that are thought to be useful for vertical sound localization. A common view is that these notches are encoded as rate profiles in the auditory nerve (AN. Here, we review previously published psychoacoustical evidence in humans and computer-model simulations of inner hair cell responses to noises with and without high-frequency spectral notches that dispute this view. We also present new recordings from guinea pig AN and ‘ideal observer’ analyses of these recordings that suggest that discrimination between noises with and without high-frequency spectral notches is probably based on the information carried in the temporal pattern of AN discharges. The exact nature of the neural code involved remains nevertheless uncertain: computer model simulations suggest that high-frequency spectral notches are encoded in spike timing patterns that may be operant in the 4-7 kHz frequency regime, while ‘ideal observer’ analysis of experimental neural responses suggest that an effective cue for high-frequency spectral discrimination may be based on sampling rates of spike arrivals of AN fibers using non-overlapping time binwidths of between 4 and 9 ms. Neural responses show that sensitivity to high-frequency notches is greatest for fibers with low and medium spontaneous rates than for fibers with high spontaneous rates. Based on this evidence, we conjecture that inter-subject variability at high-frequency spectral notch detection and, consequently, at vertical sound localization may partly reflect individual differences in the available number of functional medium- and low-spontaneous-rate fibers.

  3. Distinct changes in cortical and spinal excitability following high-frequency repetitive TMS to the human motor cortex.

    Science.gov (United States)

    Quartarone, Angelo; Bagnato, Sergio; Rizzo, Vincenzo; Morgante, Francesca; Sant'angelo, Antonio; Battaglia, Fortunato; Messina, Corrado; Siebner, Hartwig Roman; Girlanda, Paolo

    2005-02-01

    It has been shown that high-frequency repetitive transcranial magnetic stimulation (rTMS) to the human primary motor hand area (M1-HAND) can induce a lasting increase in corticospinal excitability. Here we recorded motor evoked potentials (MEPs) from the right first dorsal interosseus muscle to investigate how sub-threshold high-frequency rTMS to the M1-HAND modulates cortical and spinal excitability. In a first experiment, we gave 1500 stimuli of 5 Hz rTMS. At an intensity of 90% of active motor threshold, rTMS produced no effect on MEP amplitude at rest. Increasing the intensity to 90% of resting motor threshold (RMT), rTMS produced an increase in MEP amplitude. This facilitatory effect gradually built up during the course of rTMS, reaching significance after the administration of 900 stimuli. In a second experiment, MEPs were elicited during tonic contraction using weak anodal electrical or magnetic test stimuli. 1500 (but not 600) conditioning stimuli at 90% of RMT induced a facilitation of MEPs in the contracting FDI muscle. In a third experiment, 600 conditioning stimuli were given at 90% of RMT to the M1-HAND. Using two well-established conditioning-test paradigms, we found a decrease in short-latency intracortical inhibition (SICI), and a facilitation of the first peak of facilitatory I-waves interaction (SICF). There was no correlation between the relative changes in SICI and SICF. These results demonstrate that subthreshold 5 Hz rTMS can induce lasting changes in specific neuronal subpopulations in the human corticospinal motor system, depending on the intensity and duration of rTMS. Short 5 Hz rTMS (600 stimuli) at 90% of RMT can selectively shape the excitability of distinct intracortical circuits, whereas prolonged 5 Hz rTMS (> or =900 stimuli) provokes an overall increase in excitability of the corticospinal output system, including spinal motoneurones.

  4. Adaptive high-frequency information fusion algorithm of radar and optical images

    Science.gov (United States)

    Wang, Yiding; Qin, Shuai

    2011-12-01

    An adaptive High-frequency Information Fusion Algorithm of Radar and Optical Images is proposed in this paper, in order to improve the resolution of the radar image and reserve more radar information. Firstly, Hough Transform is adopted in the process of low-resolution radar image and high-resolution optical image registration. The implicit linear information is extracted from two different heterogeneous images for better result. Then NSCT transform is used for decomposition and fusion. In different decomposition layers or in the same layer with different directions, fusion rules are adaptive for the high-frequency information of images. The ratio values of high frequency information entropy, variance, gradient and edge strength are calculated after NSCT decomposition. High frequency information entropy, variance, gradient or edge strength, which has the smallest ratio value, is selected as an optimal rule for regional fusion. High-frequency information of radar image could be better retained, at the same time the low-frequency information of optical image also could be remained. Experimental results showed that our approach performs better than those methods with single fusion rule.

  5. High-frequency profile in adolescents and its relationship with the use of personal stereo devices

    Directory of Open Access Journals (Sweden)

    Renata Almeida Araújo Silvestre

    2016-04-01

    Full Text Available Abstract Objective: To analyze and correlate the audiometric findings of high frequencies (9–16 kHz in adolescents with their hearing habits and attitudes, in order to prevent noise-induced hearing loss. Method: This was a descriptive cross-sectional study, which included 125 adolescents in a sample of normal-hearing students, at a state school. The subjects performed high-frequency audiometry testing and answered a self-administered questionnaire addressing information on sound habits concerning the use of personal stereo devices. The sample was divided according to the exposure characteristics (time, duration, intensity, etc. and the results were compared with the observed thresholds, through the difference in proportions test, chi-squared, Student's t-test, and ANOVA, all at a significance level of 0.05. Results: Average high-frequency thresholds were registered below 15 dB HL and no significant correlation was found between high frequency audiometric findings and the degree of exposure. Conclusion: The prevalence of harmful sound habits due to the use of personal stereo devices is high in the adolescent population, but there was no correlation between exposure to high sound pressure levels through personal stereos and the high-frequency thresholds in this population.

  6. High-frequency gamblers show increased resistance to extinction following partial reinforcement.

    Science.gov (United States)

    Horsley, Rachel R; Osborne, Matthew; Norman, Christine; Wells, Timothy

    2012-04-15

    Behaviours that have been rewarded intermittently persist for longer during periods of non-reward than behaviours that have been rewarded continuously. This classic phenomenon is known as the partial reinforcement extinction effect. For decades it has been generally understood that this phenomenon is fundamental to the persistence of gambling in the absence of winning. One obvious, yet untested hypothesis arising from this is that persistent (here, high-frequency) gamblers might be more sensitive to partial reinforcement contingencies. Therefore, our aim was to test the hypothesis that compared to low-frequency gamblers, high-frequency gamblers would show greater resistance to extinction following partial reinforcement in a computer based experiment. Participants were 19 high-frequency gamblers and 21 low-frequency gamblers, all healthy non-smokers aged between 18 and 52. Following partial or continuous reinforcement, persistence of responding in extinction was measured as the number of times a target response was made. After partial reinforcement, high-frequency gamblers made the target response a greater number of times in extinction (compared to low-frequency gamblers). Moreover, the partial reinforcement extinction effect was larger in high-frequency gamblers than in low-frequency gamblers. It remains to be seen whether increased sensitivity to partial reinforcement is a cause or effect of persistent gambling. Nevertheless, the present study represents an important first step in investigating the role of simple partial reinforcement contingencies in determining resistance to extinction in gamblers, the importance of which, whilst hitherto recognised, has never been demonstrated experimentally.

  7. The high frequency characteristics of laser reflection and visible light during solid state disk laser welding

    Science.gov (United States)

    Gao, Xiangdong; You, Deyong; Katayama, Seiji

    2015-07-01

    Optical properties are related to weld quality during laser welding. Visible light radiation generated from optical-induced plasma and laser reflection is considered a key element reflecting weld quality. An in-depth analysis of the high-frequency component of optical signals is conducted. A combination of a photoelectric sensor and an optical filter helped to obtain visible light reflection and laser reflection in the welding process. Two groups of optical signals were sampled at a high sampling rate (250 kHz) using an oscilloscope. Frequencies in the ranges 1-10 kHz and 10-125 kHz were investigated respectively. Experimental results showed that there was an obvious correlation between the high-frequency signal and the laser power, while the high-frequency signal was not sensitive to changes in welding speed. In particular, when the defocus position was changed, only a high frequency of the visible light signal was observed, while the high frequency of the laser reflection signal remained unchanged. The basic correlation between optical features and welding status during the laser welding process is specified, which helps to provide a new research focus for investigating the stability of welding status.

  8. High Frequency Tan Delta Measurement Method for 132kV Transmission Underground Cables

    Directory of Open Access Journals (Sweden)

    A.R. Avinash

    2015-07-01

    Full Text Available Tangent Delta is a measurement technique to investigate cables insulation strength. Current techniques utilize Very Low Frequency (VLF at 0.1 Hz and power frequency at 50 Hz. However, high voltages are required, thus requiring larger space and cost. Proposed method of tangent delta testing utilizes High frequency Low voltage diagnoses. The phase between the current and the voltage is utilized to determine the tangent delta (tan δ. The aim of this study is to develop a low voltage high frequency tangent delta measurement method and test if it can discriminate manufactured 132 kV good conditioned cable sample from defect induced cables with void, scotched and contamination in its insulation. Impurities are clearly discriminated using this method. Comparison of Tangent Delta of cables manufactured simultaneously in good condition and defect induced is performed using High Frequency Tangent Delta method and in 50 Hz conventional method to validate the effectiveness of the measurement technique. The High Frequency AC setup utilizes a small testing environment which can sample small lengths with minimum 1 m length of cable. The small lengths will result in the reduction of total capacitance of the cable but using High Frequency induces high electric stress on XLPE layer thus resulting in measureable dielectric current.

  9. Influence of zinc concentration on structure, complex permittivity and permeability of Ni–Zn ferrites at high frequency

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Nan-Nan; Yang, Yang; Zhang, Yu-Xiang [School of Physics and Information Technology, Shaanxi Normal University, Xi' an 710119 (China); Zhou, Jian-Ping, E-mail: zhoujp@snnu.edu.cn [School of Physics and Information Technology, Shaanxi Normal University, Xi' an 710119 (China); Liu, Peng [School of Physics and Information Technology, Shaanxi Normal University, Xi' an 710119 (China); Deng, Chao-Yong [Department of Electronic Science, Key Laboratory of Functional Composite Materials of Guizhou Province, Guizhou University, Guiyang 550025 (China)

    2016-03-01

    Polycrystalline soft magnetic nickel–zinc ferrites with chemical composition Ni{sub 1−x}Zn{sub x}Fe{sub 2}O{sub 4}, where x=0, 0.2, 0.4, 0.6, 0.65, 0.7, 0.75, and 0.8, were prepared by solid state reaction method. We researched the effect of zinc concentration on the lattice parameter, crystal morphology and electromagnetic properties at high frequency. Results show that ε′ and ε″ decline with increasing frequency until they reach almost constants over 3 MHz to 1 GHz. The dielectric constant achieves a maximum when the Zn concentration is 0.8. The value of ε′ slightly declines with increasing frequency in the range of 2–18 GHz. The spectra of the permeability displays a relaxation resonance for the ferrites with x=0, 0.2, and 0.4 in 3 MHz to 1 GHz frequency range. The permeability is ruled by Snoek's law, which results in the values of μ′ decreased fast below 2 GHz and smaller than 1 above 2 GHz. The value of μ′ reaches maximum and μ″ shows minimum for the samples around x=0.75 in 2–18 GHz range. The magnetic permeability μ′ decreases in an external magnetic field, and shows two resonance peaks corresponding to domain wall and spin rotation resonance. The resonance peaks shift to higher frequency with increasing the external magnetic field. But the permeability has no clear response for magnetic field when zinc concentration is much higher. - Graphical abstract: (a) Resonance frequencies for the domain wall and spin components as a function of external magnetic field and (b) illustration of magnetization process. - Highlights: • A detailed study on permittivity and permeability of Ni–Zn ferrites in 3 MHz to 18 GHz. • Magnetic field inspires two resonance peaks in permeability. • The resonance peaks shift to higher frequency with the magnetic field.

  10. Effect of ischemia and cooling on the response to high frequency stimulation in rat tail nerves

    DEFF Research Database (Denmark)

    Andersen, Henning; Feldbæk Nielsen, Jørgen; Sørensen, Bodil

    2000-01-01

    In normal rat tail nerves the effect of temperature and ischemia on the response to long-term high frequency stimulation (HFS) (143 Hz) was studied. The effect of temperature was studied in two consecutive tests at 14 degrees C and 35 degrees C. Prior to the HFS the peak-to-peak amplitude (PP-amp...... ischemia to the rat tail, an additional fall of the PP-amp was seen after 15-20 min of HFS at both low (20 Hz) and high (143 Hz) stimulation frequencies. In conclusion, ischemia and cooling result in an impaired ability to transmit high frequency impulses.......In normal rat tail nerves the effect of temperature and ischemia on the response to long-term high frequency stimulation (HFS) (143 Hz) was studied. The effect of temperature was studied in two consecutive tests at 14 degrees C and 35 degrees C. Prior to the HFS the peak-to-peak amplitude (PP...

  11. High Frequency Resonance Damping of DFIG based Wind Power System under Weak Network

    DEFF Research Database (Denmark)

    Song, Yipeng; Wang, Xiongfei; Blaabjerg, Frede

    2017-01-01

    When operating in a micro or weak grid which has a relatively large network impedance, the Doubly Fed Induction Generator (DFIG) based wind power generation system is prone to suffer high frequency resonance due to the impedance interaction between DFIG system and the parallel compensated network...... (series RL + shunt C). In order to improve the performance of the DFIG system as well as other units and loads connected to the weak grid, the high frequency resonance needs to be effectively damped. In this paper, the proposed active damping control strategy is able to implement effective damping either...... in the Rotor Side Converter (RSC) or in the Grid Side Converter (GSC), through the introduction of virtual positive capacitor or virtual negative inductor to reshape the DFIG system impedance and mitigate the high frequency resonance. A detailed theoretical explanation on the virtual positive capacitor...

  12. Influence of high frequency pulse on electrode wear in micro-EDM

    Directory of Open Access Journals (Sweden)

    Xiao-peng Li

    2014-09-01

    Full Text Available An electromagnetic coupling mathematical model is established by finite element method and is verified by the contrastive experiments of copper matrix Ni–TiN cylindrical coating electrode, copper electrode and Cu50W electrode. The wear mechanism of Ni–TiN/Cu composite electrode in the case of high-frequency pulse current is studied, and the influence of the fluctuation frequency of discharge current on electrode wear in micro-EDM is found out. Compared with the electrode made from homogeneous material, the high frequency electromagnetic properties of Ni–TiN composite layer can be used effectively to inhibit the effect of high frequency pulse on the electrode and improve the distribution trend of current density.

  13. Influence of high frequency pulse on electrode wear in micro-EDM

    Institute of Scientific and Technical Information of China (English)

    Xiao-peng LI; Yuan-gang WANG; Fu-ling ZHAO; Meng-hua WU; Yu LIU

    2014-01-01

    An electromagnetic coupling mathematical model is established by finite element method and is verified by the contrastive experiments of copper matrix NieTiN cylindrical coating electrode, copper electrode and Cu50W electrode. The wear mechanism of NieTiN/Cu composite electrode in the case of high-frequency pulse current is studied, and the influence of the fluctuation frequency of discharge current on electrode wear in micro-EDM is found out. Compared with the electrode made from homogeneous material, the high frequency electromagnetic properties of NieTiN composite layer can be used effectively to inhibit the effect of high frequency pulse on the electrode and improve the distribution trend of current density.

  14. Extended high-frequency audiometry (9,000-20,000 Hz). Usefulness in audiological diagnosis.

    Science.gov (United States)

    Rodríguez Valiente, Antonio; Roldán Fidalgo, Amaya; Villarreal, Ithzel M; García Berrocal, José R

    2016-01-01

    Early detection and appropriate treatment of hearing loss are essential to minimise the consequences of hearing loss. In addition to conventional audiometry (125-8,000 Hz), extended high-frequency audiometry (9,000-20,000 Hz) is available. This type of audiometry may be useful in early diagnosis of hearing loss in certain conditions, such as the ototoxic effect of cisplatin-based treatment, noise exposure or oral misunderstanding, especially in noisy environments. Eleven examples are shown in which extended high-frequency audiometry has been useful in early detection of hearing loss, despite the subject having a normal conventional audiometry. The goal of the present paper was to highlight the importance of the extended high-frequency audiometry examination for it to become a standard tool in routine audiological examinations.

  15. 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.

  16. Applications of High-Frequency Gravitational Waves to the Global War on Terror

    Science.gov (United States)

    Baker, Robert M. L.

    2010-01-01

    Applications of high-frequency gravitational waves or HFGWs to the global war on terror are now realistic because technology developed by GravWave® LLC and other institutions overseas can lead to devices, some already constructed, that can generate and detect HFGWs. In fact, three HFGW detectors have been built outside the United States and an ultra high-sensitive Li-Baker HFGW Detector has been proposed. HFGW generators have been proposed theoretically by the Russians, Germans, Italians and Chinese. Because of their unique characteristics, such as their ability to pass through all material without attenuation, HFGWs could be utilized for uninterruptible, very low-probability-of-intercept (LPI), high-bandwidth communications among and between anti-terrorist assets. One such communications system, which can be constructed from off-the-shelf elements, is discussed. The HFGW generation device or transmitter alternative selected is based upon bands of piezoelectric crystal, film-bulk acoustic resonators or FBARs energized by conventional Magnetrons. The system is theoretically capable of transmitting and detecting, through use of the Li-Baker HFGW detector, a signal generated on the opposite side of the Earth. Although HFGWs do not interact with and are not absorbed by ordinary matter, their presence can be detected by their distortion of spacetime as measured by the Laser Interferometer Gravitational Observatory (LIGO), Virgo, GEO600, et al., by detection photons generated from electromagnetic beams having the same frequency, direction and phase as the HFGWs in a superimposed magnetic field (Li-Baker HFGW Detector), by the change in polarization HFGWs produce in a microwave guide (Birmingham University Detector) and by other such instruments. Potential theoretical applications, which may or may not be practical yet theoretically possible, are propulsion, including "moving" space objects such as missiles, anti-missiles and warheads in flight; surveillance through

  17. High frequency hearing thresholds and product distortion otoacoustic emissions in cystic fibrosis patients,

    Directory of Open Access Journals (Sweden)

    Lucia Bencke Geyer

    2015-12-01

    Full Text Available ABSTRACT INTRODUCTION: The treatment of patients with cystic fibrosis involves the use of ototoxic drugs, mainly aminoglycoside antibiotics. Due to the use of these drugs, fibrocystic patients are at risk of developing hearing loss. OBJECTIVE: To evaluate the hearing of patients with cystic fibrosis by High Frequency Audiometry and Distortion Product Otoacoustic Emissions. METHODS: Cross-sectional study. The study group consisted of 39 patients (7-20 years of age with cystic fibrosis and a control group of 36 individuals in the same age group without otologic complaints, with normal audiometric thresholds and type A tympanometric curves. High Frequency Audiometry and Distortion Product Otoacoustic Emissions tests were conducted. RESULTS: The study group had significantly higher thresholds at 250, 1000, 8000, 9000, 10,000, 12,500, and 16,000 Hz (p = 0.004 as well as higher prevalence of otoacoustic emission alterations at 1000 and 6000 Hz (p = 0.001, with significantly lower amplitudes at 1000, 1400, and 6000 Hz. There was a significant association between alterations in hearing thresholds in High Frequency Audiometry with the number of courses of aminoglycosides administered (p = 0.005. Eighty-three percent of patients who completed more than ten courses of aminoglycosides had hearing loss in High Frequency Audiometry. CONCLUSION: A significant number of patients with cystic fibrosis who received repeated courses of aminoglycosides showed alterations in High Frequency Audiometry and Distortion Product Otoacoustic Emissions. The implementation of ten or more aminoglycoside cycles was associated with alterations in High Frequency Audiometry.

  18. Technogical Researching for High Frequency Induction Hardening of the Slippery Seats%滑座高频淬火工艺研究

    Institute of Scientific and Technical Information of China (English)

    张艾丽; 王淑新; 刘志斌; 张涛

    2001-01-01

    根据滑座高频淬火表面结构特点,设计专用感应器并加导磁体来提高感应器电效率及解决尖角效应问题。经反复试验,确定高频淬火参数,攻克滑座高频淬火工艺难关。%Accoding to structure features of the slippery seats, we design a special induction utensil and increase electric efficiency of the induction utensil with adding some conduct magnets, so we solve the problem of the sharp angle effect. The technological parameter of high frequency induction hardening is determined by testing over and over again,and the difficult technological problem for high frequency induction hardening of the slippery seats is overcomed .

  19. Casimir force between $\\delta-\\delta^{\\prime}$ mirrors transparent at high frequencies

    CERN Document Server

    Braga, Alessandra N; Alves, Danilo T

    2016-01-01

    We investigate, in the context of a real massless scalar field in $1+1$ dimensions, models of partially reflecting mirrors simulated by Dirac $\\delta-\\delta^{\\prime}$ 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 $\\delta-\\delta^{\\prime}$ point interaction that enables to achieve full transparency in the limit of high frequencies. Taking this modified $\\delta-\\delta^{\\prime}$ model into account, we investigate the Casimir force, comparing our results with those found in the literature.

  20. Passive ultrasonics using sub-Nyquist sampling of high-frequency thermal-mechanical noise.

    Science.gov (United States)

    Sabra, Karim G; Romberg, Justin; Lani, Shane; Degertekin, F Levent

    2014-06-01

    Monolithic integration of capacitive micromachined ultrasonic transducer arrays with low noise complementary metal oxide semiconductor electronics minimizes interconnect parasitics thus allowing the measurement of thermal-mechanical (TM) noise. This enables passive ultrasonics based on cross-correlations of diffuse TM noise to extract coherent ultrasonic waves propagating between receivers. However, synchronous recording of high-frequency TM noise puts stringent requirements on the analog to digital converter's sampling rate. To alleviate this restriction, high-frequency TM noise cross-correlations (12-25 MHz) were estimated instead using compressed measurements of TM noise which could be digitized at a sampling frequency lower than the Nyquist frequency.

  1. Adaptive control of linear multivariable systems with high frequency gain matrix hurwitz

    Institute of Scientific and Technical Information of China (English)

    Ying ZHOU; Yuqiang WU; Shumin FEI

    2005-01-01

    A new adaptive control scheme is proposed for multivariable model reference adaptive control(MRAC) systems based on the nonlinear backstepping approach with vector form.The assumption on a priori knowledge of the high frequency gain matrix in existing results is relaxed and the new required condition for the high frequency gain matrix can be easily checked for certain plants so that the proposed method is widely applicable.This control scheme guarantees the global stability of the closed-loop systems and the tracking error can be arbitrary small.The simulation result for an application example shows the validity of the proposed nonlinear adaptive scheme.

  2. High aspect ratio MEMS capacitor for high frequency impedance matching applications

    DEFF Research Database (Denmark)

    Yalcinkaya, Arda Deniz; Jensen, Søren; Hansen, Ole

    2003-01-01

    We present a microelectromechanical tunable capacitor with a low control voltage, a wide tuning range and adequate electrical quality factor. The device is fabricated in a single-crystalline silicon layer using deep reactive ion etching (DRIE) for obtaining high-aspect ratio (> 20) parallel comb-...... response and it was found that the device is a suitable passive component to be used in impedance matching applications, band-pass filtering or voltage controlled oscillators in the Very High Frequency (VHF) and Ultra High Frequency (UHF) bands....

  3. Effectiveness of treatment with high-frequency chest wall oscillation in patients with bronchiectasis

    OpenAIRE

    Nicolini, Antonello; Cardini, Federica; Landucci, Norma; Lanata, Sergio; Ferrari-Bravo, Maura; Barlascini, Cornelius

    2013-01-01

    Background High-frequency airway clearance (HFCWC) assist devices generate either positive or negative trans-respiratory pressure excursions to produce high-frequency, small-volume oscillations in the airways. HFCWC can lead to changes in volume of 15–57 ml and in flow up to 1.6 L/s, which generate minimal coughing to mobilize secretions. The typical treatment lasts 20–30 minutes, and consists of short periods of compression at different frequencies, separated by coughing. The aim of this stu...

  4. Adaptive Piezoelectric Circuitry Sensor Network with High-Frequency Harmonics Interrogation for Structural Damage Detection

    Science.gov (United States)

    2014-09-17

    AFRL-OSR-VA-TR-2014-0255 ADAPTIVE PIEZOELECTRIC CIRCUITRY SENSOR NETWORK KON-WELL WANG MICHIGAN UNIV ANN ARBOR Final Report 09/17/2014 DISTRIBUTION A...by ANSI Std. Z39.18 09-09-2014 Final Performance Report 06-01-2011 - 05-31-2014 Adaptive Piezoelectric Circuitry Sensor Network with High-Frequency...approach. Specifically, we propose to create a new concept of adaptive high-frequency piezoelectric self-sensing interrogation by means of tunable

  5. A Pitch Extraction Method with High Frequency Resolution for Singing Evaluation

    Science.gov (United States)

    Takeuchi, Hideyo; Hoguro, Masahiro; Umezaki, Taizo

    This paper proposes a pitch estimation method suitable for singing evaluation incorporable in KARAOKE machines. Professional singers and musicians have sharp hearing for music and singing voice. They recognize that singer's voice pitch is “a little off key” or “be in tune”. In the same way, the pitch estimation method that has high frequency resolution is necessary in order to evaluate singing. This paper proposes a pitch estimation method with high frequency resolution utilizing harmonic characteristic of autocorrelation function. The proposed method can estimate a fundamental frequency in the range 50 ∼ 1700[Hz] with resolution less than 3.6 cents in light processing.

  6. Required changes in emission standards for high-frequency noise in power systems

    Energy Technology Data Exchange (ETDEWEB)

    Lundmark, C.M.; Larsson, E.O.A. [Lulea Univ. of Technology, Skelleftea (Sweden); Bollen, M.H.J. [STRI AB, Ludvika (Sweden)

    2006-07-01

    This paper discusses some recent developments that make the existing standards on the emission of high-frequency noise in power systems due for reconsideration. It is shown that it is possible for an equipment to remain below the emission limits while at the same time the disturbance level increases beyond what was intended by the standard document. Further, the change from analog to digital communication and the use of communication via the power system, make that the permitted disturbance levels need to be reconsidered. This paper also contains an example of measured high-frequency noise and proposes a framework for re-coordination of emission and immunity levels. (Author)

  7. Interference Dynamics of Hydrogen Atoms in High-Frequency Dichromatic Laser Fields

    Science.gov (United States)

    Cheng, Tai-Wang; Li, Xiao-Feng; Fu, Pan-Ming; Chen, Shi-Gang

    2002-08-01

    We investigate the ionization and high-order harmonic generation of a hydrogen atom in high-frequency (several atomic units) super strong (up to several tens of atomic units) dichromatic laser fields. An effective iterative method in the framework of high-frequency Floquet theory is used in the calculations. We have considered two kinds of dichromatic laser field, i.e. 1ω-2ω and 1ω-3ω. We find that, in both the cases, the ionization and high-order harmonic generation show evident dependence on the relative phase and strength of the additional harmonic field. The dynamical origin of these interference effects is also discussed.

  8. Interference Dynamics of Hydrogen Atoms in High-Frequency Dichromatic Laser Fields

    Institute of Scientific and Technical Information of China (English)

    程太旺; 李晓峰; 傅盘铭; 陈式刚

    2002-01-01

    We investigate the ionization and high-order harmonic generation of a hydrogen atom in high-frequency (several atomic units) super strong (up to several tens of atomic units) dichromatic laser fields. An effective iterative method in the framework of high-frequency Floquet theory is used in the calculations. We have considered two kinds of dichromatic laser field, i.e. 1ω - 2ω and lω - 3ω. We find that, in both the cases, the ionization and high-order harmonic generation show evident dependence on the relative phase and strength of the additional harmonic field. The dynamical origin of these interference effects is also discussed.

  9. A Realized Variance for the Whole Day Based on Intermittent High-Frequency Data

    DEFF Research Database (Denmark)

    Hansen, Peter Reinhard; Lunde, Asger

    2005-01-01

    We consider the problem of deriving an empirical measure of daily integrated variance (IV) in the situation where high-frequency price data are unavailable for part of the day. We study three estimators in this context and characterize the assumptions that justify their use. We show that the opti......We consider the problem of deriving an empirical measure of daily integrated variance (IV) in the situation where high-frequency price data are unavailable for part of the day. We study three estimators in this context and characterize the assumptions that justify their use. We show...

  10. Designing All-Pole Filters for High-Frequency Phase-Locked Loops

    Directory of Open Access Journals (Sweden)

    Ricardo Bressan Pinheiro

    2014-01-01

    signals exchanged between the nodes of the networks and detected by PLLs. The necessity to improve clock precision that follows the bandwidth increase provoked the improvement of the filter component of the PLLs, avoiding instability and high-frequency components in the reference signals. Here, a technique of designing this kind of filter is presented, considering second-order filters, implying third-order PLLs. Simulations show that following this technique produces very fast tracking processes, enabling precise operation even for very high frequencies.

  11. 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

  12. Spontaneous breathing during high-frequency oscillatory ventilation improves regional lung characteristics in experimental lung injury

    NARCIS (Netherlands)

    van Heerde, M.; Roubik, K.; Kopelent, V.; Kneyber, M. C. J.; Markhorst, D. G.

    2010-01-01

    Background Maintenance of spontaneous breathing is advocated in mechanical ventilation. This study evaluates the effect of spontaneous breathing on regional lung characteristics during high-frequency oscillatory (HFO) ventilation in an animal model of mild lung injury. Methods Lung injury was induce

  13. Finite-element modeling of viscoelastic cells during high-frequency cyclic strain.

    Science.gov (United States)

    Milner, Jaques S; Grol, Matthew W; Beaucage, Kim L; Dixon, S Jeffrey; Holdsworth, David W

    2012-03-22

    Mechanotransduction refers to the mechanisms by which cells sense and respond to local loads and forces. The process of mechanotransduction plays an important role both in maintaining tissue viability and in remodeling to repair damage; moreover, it may be involved in the initiation and progression of diseases such as osteoarthritis and osteoporosis. An understanding of the mechanisms by which cells respond to surrounding tissue matrices or artificial biomaterials is crucial in regenerative medicine and in influencing cellular differentiation. Recent studies have shown that some cells may be most sensitive to low-amplitude, high-frequency (i.e., 1-100 Hz) mechanical stimulation. Advances in finite-element modeling have made it possible to simulate high-frequency mechanical loading of cells. We have developed a viscoelastic finite-element model of an osteoblastic cell (including cytoskeletal actin stress fibers), attached to an elastomeric membrane undergoing cyclic isotropic radial strain with a peak value of 1,000 µstrain. The results indicate that cells experience significant stress and strain amplification when undergoing high-frequency strain, with peak values of cytoplasmic strain five times higher at 45 Hz than at 1 Hz, and peak Von Mises stress in the nucleus increased by a factor of two. Focal stress and strain amplification in cells undergoing high-frequency mechanical stimulation may play an important role in mechanotransduction.

  14. High Frequency Combustion Instabilities of LOx/CH4 Spray Flames in Rocket Engine Combustion Chambers

    NARCIS (Netherlands)

    Sliphorst, M.

    2011-01-01

    Ever since the early stages of space transportation in the 1940’s, and the related liquid propellant rocket engine development, combustion instability has been a major issue. High frequency combustion instability (HFCI) is the interaction between combustion and the acoustic field in the combustion c

  15. Analysis on the Behavior of Undamped and Unstable High Frequency Resonance in DFIG System

    DEFF Research Database (Denmark)

    Song, Yipeng; Blaabjerg, Frede

    2017-01-01

    As the wind power generation develops, the Doubly Fed Induction Generator (DFIG) based wind power system may suffer Sub Synchronous Resonance (SSR) and High Frequency Resonance (HFR) in the series and parallel compensated weak network. The principle and frequency of HFR have been discussed using ...

  16. Automatic detection of high frequency oscillations during epilepsy surgery predicts seizure outcome

    NARCIS (Netherlands)

    Fedele, Tommaso; van 't Klooster, Maryse; Burnos, Sergey; Zweiphenning, Willemiek; van Klink, Nicole; Leijten, Frans; Zijlmans, Maeike; Sarnthein, Johannes

    2016-01-01

    OBJECTIVE: High frequency oscillations (HFOs) and in particular fast ripples (FRs) in the post-resection electrocorticogram (ECoG) have recently been shown to be highly specific predictors of outcome of epilepsy surgery. FR visual marking is time consuming and prone to observer bias. We validate her

  17. 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.

  18. Neural correlates of heterotopic facilitation induced after high frequency electrical stimulation of nociceptive pathways

    NARCIS (Netherlands)

    Broeke, E.N. van den; Heck, C.H. van; Rijn, C.M. van; Wilder-Smith, O.H.G.

    2011-01-01

    Background High frequency electrical stimulation (HFS) of primary nociceptive afferents in humans induce a heightened sensitivity in the surrounding non-stimulated skin area. Several studies suggest that this heterotopic effect is the result of central (spinal) plasticity. The aim of this study is t

  19. The Sensitivity of Adolescent School-Based Hearing Screens Is Significantly Improved by Adding High Frequencies.

    Science.gov (United States)

    Sekhar, Deepa L; Zalewski, Thomas R; Beiler, Jessica S; Czarnecki, Beth; Barr, Ashley L; King, Tonya S; Paul, Ian M

    2016-12-01

    High frequency hearing loss (HFHL), often related to hazardous noise, affects one in six U.S. adolescents. Yet, only 20 states include school-based hearing screens for adolescents. Only six states test multiple high frequencies. Study objectives were to (1) compare the sensitivity of state school-based hearing screens for adolescents to gold standard sound-treated booth testing and (2) consider the effect of adding multiple high frequencies and two-step screening on sensitivity/specificity. Of 134 eleventh-grade participants (2013-2014), 43 of the 134 (32%) did not pass sound-treated booth testing, and 27 of the 43 (63%) had HFHL. Sensitivity/specificity of the most common protocol (1,000, 2,000, 4,000 Hz at 20 dB HL) for these hearing losses was 25.6% (95% confidence interval [CI] = [13.5, 41.2]) and 85.7% (95% CI [76.8, 92.2]), respectively. A protocol including 500, 1,000, 2,000, 4,000, 6,000 Hz at 20 dB HL significantly improved sensitivity to 76.7% (95% CI [61.4, 88.2]), p < .001. Two-step screening maintained specificity (84.6%, 95% CI [75.5, 91.3]). Adolescent school-based hearing screen sensitivity improves with high frequencies.

  20. High-frequency ultrasound for monitoring changes in liver tissue during preservation

    Energy Technology Data Exchange (ETDEWEB)

    Vlad, Roxana M [Department of Medical Biophysics, University of Toronto, Toronto, Ontario (Canada); Czarnota, Gregory J [Department of Radiation Oncology, University of Toronto, Toronto, Ontario (Canada); Giles, Anoja [Department of Medical Biophysics, University of Toronto, Toronto, Ontario (Canada); Sherar, Michael D [Department of Medical Biophysics, University of Toronto, Toronto, Ontario (Canada); Hunt, John W [Department of Medical Biophysics, University of Toronto, Toronto, Ontario (Canada); Kolios, Michael C [Department of Medical Biophysics, University of Toronto, Toronto, Ontario (Canada)

    2005-01-21

    Currently the only method to assess liver preservation injury is based on liver appearance and donor medical history. Previous work has shown that high-frequency ultrasound could detect ischemic cell death due to changes in cell morphology. In this study, we use high-frequency ultrasound integrated backscatter to assess liver damage in experimental models of liver ischemia. Ultimately, our goal is to predict organ suitability for transplantation using high-frequency imaging and spectral analysis techniques. To examine the effects of liver ischemia at different temperatures, livers from Wistar rats were surgically excised, immersed in phosphate buffer saline and stored at 4 and 20 deg. C for 24 h. To mimic organ preservation, livers were excised, flushed with University of Wisconsin (UW) solution and stored at 4 deg. C for 24 h. Preservation injury was simulated by either not flushing livers with UW solution or, before scanning, allowing livers to reach room temperature. Ultrasound images and corresponding radiofrequency data were collected over the ischemic period. No significant increase in integrated backscatter ({approx}2.5 dBr) was measured for the livers prepared using standard preservation conditions. For all other ischemia models, the integrated backscatter increased by 4-9 dBr demonstrating kinetics dependent on storage conditions. The results provide a possible framework for using high-frequency imaging to non-invasively assess liver preservation injury.

  1. Low power very high frequency resonant converter with high step down ratio

    DEFF Research Database (Denmark)

    Madsen, Mickey Pierre; Knott, Arnold; Andersen, Michael A. E.

    2013-01-01

    This paper presents the design of a resonant converter with a switching frequency in the very high frequency range (30-300MHz), a large step down ratio and low output power. This gives the designed converters specifications which are far from previous results. The class E inverter and rectifier h...

  2. Finite-Element Modeling of Viscoelastic Cells During High-Frequency Cyclic Strain

    Directory of Open Access Journals (Sweden)

    David W. Holdsworth

    2012-03-01

    Full Text Available Mechanotransduction refers to the mechanisms by which cells sense and respond to local loads and forces. The process of mechanotransduction plays an important role both in maintaining tissue viability and in remodeling to repair damage; moreover, it may be involved in the initiation and progression of diseases such as osteoarthritis and osteoporosis. An understanding of the mechanisms by which cells respond to surrounding tissue matrices or artificial biomaterials is crucial in regenerative medicine and in influencing cellular differentiation. Recent studies have shown that some cells may be most sensitive to low-amplitude, high-frequency (i.e., 1–100 Hz mechanical stimulation. Advances in finite-element modeling have made it possible to simulate high-frequency mechanical loading of cells. We have developed a viscoelastic finite-element model of an osteoblastic cell (including cytoskeletal actin stress fibers, attached to an elastomeric membrane undergoing cyclic isotropic radial strain with a peak value of 1,000 µstrain. The results indicate that cells experience significant stress and strain amplification when undergoing high-frequency strain, with peak values of cytoplasmic strain five times higher at 45 Hz than at 1 Hz, and peak Von Mises stress in the nucleus increased by a factor of two. Focal stress and strain amplification in cells undergoing high-frequency mechanical stimulation may play an important role in mechanotransduction.

  3. Surfactant nebulization versus instillation during high frequency ventilation in surfactant-deficient rabbits

    NARCIS (Netherlands)

    Dijk, Peter H.; Heikamp, A; Bambang Oetomo, Sidarto

    1998-01-01

    Surfactant nebulization improves lung function at low alveolar doses of surfactant. However, efficiency of nebulization is low, and lung deposition seems to depend on lung aeration. High frequency ventilation (HFV) has been shown to improve lung aeration. We hypothesize that the combination of HFV a

  4. [Design of a high-voltage insulation testing system of X-ray high frequency generators].

    Science.gov (United States)

    Huang, Yong; Mo, Guo-Ming; Wang, Yan; Wang, Hong-Zhi; Yu, Jie-Ying; Dai, Shu-Guang

    2007-09-01

    In this paper, we analyze the transformer of X-ray high-voltage high-frequency generators and, have designed and implemented a high-voltage insulation testing system for its oil tank using full-bridge series resonant soft switching PFM DC-DC converter.

  5. What middle ear parameters tell about impedance matching and high frequency hearing.

    Science.gov (United States)

    Hemilä, S; Nummela, S; Reuter, T

    1995-05-01

    Acoustic energy enters the mammalian cochlea aided by an anatomical impedance matching performed by the middle ear. The purpose of this paper is to analyse the functional consequences of changes in scale of the middle ear when going from the smallest mammals to the largest. Our anatomical measurements in mammals of different sizes ranging from bats to elephants indicate that middle ear proportions are largely isometric. Thus the calculated transformer ratio is basically independent of animal size, a typical value lying between 30 and 80. Similarly, the calculated specific acoustic input impedance of the inner ear is independent of animal size, the average value being about 140 kPa s/m. We show that if the high frequency hearing limit of isometric ears is limited by ossicle inertia, it should be inversely proportional to the cubic root of the ossicular mass. This prediction is in reasonable agreement with published audiogram data. We then present a three-parameter model of the middle ear where some obvious deviations from perfect isometry are taken into account. The high frequency hearing limits of different species generally agree well with the predictions of this simple model. However, the hearing limits of small rodents clearly deviate from the model calculation. We interpret this observation as indicating that the hearing limit towards very high frequencies may be set by cochlear transduction mechanisms. Further we discuss the exceptional high frequency hearing of the cat and the amphibious hearing of seals.

  6. 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...

  7. Fabrication of High-Frequency pMUT Arrays on Silicon Substrates

    DEFF Research Database (Denmark)

    Pedersen, Thomas; Zawada, Tomasz; Hansen, Karsten;

    2010-01-01

    A novel technique based on silicon micromachining for fabrication of linear arrays of high-frequency piezoelectric micromachined ultrasound transducers (pMUT) is presented. Piezoelectric elements are formed by deposition of lead zirconia titanate into etched features of a silicon substrate...

  8. Planck early results. IV. First assessment of the High Frequency Instrument in-flight performance

    DEFF Research Database (Denmark)

    Bréelle, E.; Bucher, M.; Cressiot, C.;

    2011-01-01

    The Planck High Frequency Instrument (HFI) is designed to measure the temperature and polarization anisotropies of the cosmic microwave background and Galactic foregrounds in six ~30% bands centered at 100, 143, 217, 353, 545, and 857 GHz at an angular resolution of 10′ (100 GHz), 7′ (143 GHz), a...

  9. Planck 2015 results: VII. High Frequency Instrument data processing: Time-ordered information and beams

    DEFF Research Database (Denmark)

    Adam, R.; Ade, P. A R; Aghanim, N.;

    2016-01-01

    The Planck High Frequency Instrument (HFI) has observed the full sky at six frequencies (100, 143, 217, 353, 545, and 857 GHz) in intensity and at four frequencies in linear polarization (100, 143, 217, and 353 GHz). In order to obtain sky maps, the time-ordered information (TOI) containing the d...

  10. New technique for fabrication of high frequency piezoelectric Micromachined Ultrasound Transducers

    DEFF Research Database (Denmark)

    Pedersen, T; Thomsen, Erik Vilain; Zawada, T;

    2008-01-01

    A novel technique for fabrication of linear arrays of high frequency piezoelectric Micromachined Ultrasound Transducers (pMUT) on silicon substrates is presented. Piezoelectric elements are formed by deposition of PZT ((PbZrxTi1-x)O3) into etched features of the silicon substrate...

  11. High frequency pulse anodising of magnetron sputtered Al–Zr and Al–Ti Coatings

    DEFF Research Database (Denmark)

    Gudla, Visweswara Chakravarthy; Bordo, Kirill; Engberg, Sara

    2016-01-01

    High frequency pulse anodising of Al–Zr and Al–Ti coatings is studied as a surface finishing technique and compared to conventional decorative DC anodising. The Al–Zr and Al–Ti coatings were deposited using DC magnetron sputtering and were heat treated after deposition to generate a multiphase mi...

  12. High Frequency AC Inductor Analysis and Design for Dual Active Bridge (DAB) Converters

    DEFF Research Database (Denmark)

    Zhang, Zhe; Andersen, Michael A. E.

    2016-01-01

    The dual active bridge (DAB) converter is an isolated bidirectional dc-dc topology which is the most critical part for the power conversion systems such as solid-state transformers (SST). This paper focuses on analysis and design of high frequency ac inductors which are the power interfacing...

  13. Effectiveness of a prolonged incarceration and rehabilitation measure for high-frequency offenders

    NARCIS (Netherlands)

    Tollenaar, N.; van der Laan, A. M.; van der Heijden, P. G M

    2014-01-01

    Objectives: To estimate the incapacitation effect and the impact on post-release recidivism of a measure combining prolonged incarceration and rehabilitation, the ISD measure for high frequency offenders (HFOs) was compared to the standard practice of short-term imprisonment. Methods: We applied a q

  14. A Markov Chain Estimator of Multivariate Volatility from High Frequency Data

    DEFF Research Database (Denmark)

    Hansen, Peter Reinhard; Horel, Guillaume; Lunde, Asger;

    We introduce a multivariate estimator of financial volatility that is based on the theory of Markov chains. The Markov chain framework takes advantage of the discreteness of high-frequency returns. We study the finite sample properties of the estimation in a simulation study and apply...

  15. A numerical and experimental investigation of the performance of sound intensity probes at high frequencies

    DEFF Research Database (Denmark)

    Jacobsen, Finn; Cutanda, Vicente; Juhl, Peter Møller

    1998-01-01

    The high-frequency performance of a p-p intensity probe with a solid spacer between the two microphones is examined. It is shown theoretically and verified experimentally that with a spacer length that equals the diameter of the microphones, the finite difference error is almost perfectly cancelled...

  16. Cluster observations of high-frequency waves in the exterior cusp

    Directory of Open Access Journals (Sweden)

    Y. Khotyaintsev

    2004-07-01

    Full Text Available We study wave emissions, in the frequency range from above the lower hybrid frequency up to the plasma frequency, observed during one of the Cluster crossings of a high-beta exterior cusp region on 4 March 2003. Waves are localized near narrow current sheets with a thickness a few times the ion inertial length; currents are strong, of the order of 0.1-0.5μA/m2 (0.1-0.5mA/m2 when mapped to ionosphere. The high frequency part of the waves, frequencies above the electron-cyclotron frequency, is analyzed in more detail. These high frequency waves can be broad-band, can have spectral peaks at the plasma frequency or spectral peaks at frequencies below the plasma frequency. The strongest wave emissions usually have a spectral peak near the plasma frequency. The wave emission intensity and spectral character change on a very short time scale, of the order of 1s. The wave emissions with strong spectral peaks near the plasma frequency are usually seen on the edges of the narrow current sheets. The most probable generation mechanism of high frequency waves are electron beams via bump-on-tail or electron two-stream instability. Buneman and ion-acoustic instability can be excluded as a possible generation mechanism of waves. We suggest that high frequency waves are generated by electron beams propagating along the separatrices of the reconnection region.

  17. Investigation into high-frequency-vibration assisted micro-blanking of pure copper foils

    Directory of Open Access Journals (Sweden)

    Wang Chunju

    2015-01-01

    Full Text Available The difficulties encountered during the manufacture of microparts are often associated with size effects relating to material, process and tooling. Utilizing acoustoplastic softening, achieved through a high-frequency vibration assisted micro-blanking process, was introduced to improve the surface finish in micro-blanking. A frequency of 1.0 kHz was chosen to activate the longitudinal vibration mode of the horn tip, using a piezoelectric actuator. A square hole with dimensions of 0.5 mm × 0.5 mm was made, successfully, from a commercial rolled T2 copper foil with 100 μm in thickness. It was found that the maximum blanking force could be reduced by 5% through utilizing the high-frequency vibration. Proportion of the smooth, burnished area in the cut cross-section increases with an increase of the plasticity to fracture, under the high-frequency vibration, which suggests that the vibration introduced is helpful for inhibiting evolution of the crack due to its acoustoplastic softening effect. During blanking, roughness of the burnished surface could be reduced by increasing the vibration amplitude of the punch, which played a role as surface polishing. The results obtained suggest that the high-frequency vibration can be adopted in micro-blanking in order to improve quality of the microparts.

  18. Mitigation of high-frequency pulsations, using Multi Bore Restriction Orifices

    NARCIS (Netherlands)

    Lier, L.J. van; Korst, H.J.C.

    2007-01-01

    In reciprocating fluid displacement systems, a trend toward high-speed machinery and application of stepless reverse-flow capacity control system is observed. Badly designed compression systems may cause excessive high-frequency noise and vibration levels, which are a risk from a structural integrit

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

    Science.gov (United States)

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

    1999-01-01

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

  20. High-Frequency Oscillatory Ventilation in Pediatric Acute Lung Injury : A Multicenter International Experience

    NARCIS (Netherlands)

    Rettig, Jordan S; Smallwood, Craig D; Walsh, Brian K; Rimensberger, Peter C; Bachman, Thomas E; Bollen, Casper W.; Duval, Els L; Gebistorf, Fabienne; Markhorst, Dick G; Tinnevelt, Marcel; Todd, Mark; Zurakowski, David; Arnold, John H

    2015-01-01

    OBJECTIVE: We aim to describe current clinical practice, the past decade of experience and factors related to improved outcomes for pediatric patients receiving high-frequency oscillatory ventilation. We have also modeled predictive factors that could help stratify mortality risk and guide future hi

  1. Single phase AC-DC power factor corrected converter with high frequency isolation using buck converter

    Directory of Open Access Journals (Sweden)

    R. Ramesh,

    2014-03-01

    Full Text Available Single phase ac-dc converters having high frequency isolation are implemented in buck, boost, buck-boost configuration with improving the power quality in terms of reducing the harmonics of input current. The paperpropose the circuit configuration, control mechanism, and simulation result for the single phase ac-dc converter.

  2. 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...

  3. 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...

  4. Lab-chip HPLC with integrated droplet-based microfluidics for separation and high frequency compartmentalisation.

    Science.gov (United States)

    Kim, Jin-Young; Cho, Soong-Won; Kang, Dong-Ku; Edel, Joshua B; Chang, Soo-Ik; deMello, Andrew J; O'Hare, Danny

    2012-09-21

    We demonstrate the integration of a droplet-based microfluidic device with high performance liquid chromatography (HPLC) in a monolithic format. Sequential operations of separation, compartmentalisation and concentration counter were conducted on a monolithic chip. This describes the use of droplet-based microfluidics for the preservation of chromatographic separations, and its potential application as a high frequency fraction collector.

  5. Reflections on Pediatric High-Frequency Oscillatory Ventilation From a Physiologic Perspective

    NARCIS (Netherlands)

    Kneyber, Martin C. J.; van Heerde, Marc; Markhorst, Dick G.

    2012-01-01

    Mechanical ventilation using low tidal volumes has become universally accepted to prevent ventilator-induced lung injury. High-frequency oscillatory ventilation (HFOV) allows pulmonary gas exchange using very small tidal volume (1-2 mL/kg) with concomitant decreased risk of atelectrauma. However, it

  6. High Frequency Discharge Plasma Induced Grafting of Polystyrene onto Titanium Dioxide Powder

    Institute of Scientific and Technical Information of China (English)

    ZHONG Shaofeng; OU Qiongrong; MENG Yuedong

    2007-01-01

    Grafting of polystyrene (PS) onto titanium dioxide powder was investigated. The graft polymerization reaction was induced by high frequency discharge produced N2 plasma treatment of the surfaces of titanium dioxide. IR , XPS and TGA results show that PS was grafted on the titanium dioxide powder. And the crystal structure of the titanium dioxide powder observed by XRD was unchanged after plasma treatment.

  7. Self-adaptive method for high frequency multi-channel analysis of surface wave method

    Science.gov (United States)

    When the high frequency multi-channel analysis of surface waves (MASW) method is conducted to explore soil properties in the vadose zone, existing rules for selecting the near offset and spread lengths cannot satisfy the requirements of planar dominant Rayleigh waves for all frequencies of interest ...

  8. 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...

  9. Effect of a low voltage with a high frequency electrical stunning on unconsciousness in slaughter pigs

    NARCIS (Netherlands)

    Lambooij, B.; Merkus, G.S.M.; Voorst, van N.; Pieterse, C.

    1996-01-01

    Effects of low voltage and high frequency electrical stunning of slaughter pigs was examined. Forty slaughter pigs were positioned for stunning while lying on a beam in a cage and stunned with 240 V with 800 Hz during 3 s passing the brain and 125 V with 50 Hz during 3 s passing the heart. Before th

  10. Statistical properties of short term price trends in high frequency stock market data

    CERN Document Server

    Sieczka, P; Sieczka, Pawe{\\l}; Ho{\\l}yst, Janusz A.

    2007-01-01

    We investigated distributions of short term price trends for high frequency stock market data. A number of trends as a function of their lengths was measured. We found that such a distribution does not fit to results following from an uncorrelated stochastic process. We proposed a simple model with a memory that gives a qualitative agreement with real data.

  11. Synthesis and properties of Pr-substituted MgZn ferrites for core materials and high frequency applications

    Energy Technology Data Exchange (ETDEWEB)

    Mukhtar, Muhammad Waqas; Irfan, Muhammad [Department of Physics, Federal Urdu University of Arts, Science and Technology, Islamabad 44000 (Pakistan); Ahmad, Ishtiaq; Ali, Ihsan [Department of Physics, Bahauddin Zakariya University, Multan 60800 (Pakistan); Akhtar, Majid Niaz [Department of Physics, COMSATS Institute of Information Technology, Lahore (Pakistan); Khan, Muhammad Azhar [Department of Physics, Islamia University, Bahawalpur (Pakistan); Abbas, Ghazanfar [Department of Physics, COMSATS Institute of Information Technology, Islamabad 44000 (Pakistan); Rana, M.U. [Center of Excellence in Solid State Physics, University of the Punjab, Lahore (Pakistan); Ali, Akbar [Department of Basic Sciences, Riphah International University, Islamabad-44000 (Pakistan); Ahmad, Mukhtar, E-mail: ahmadmr25@yahoo.com [Department of Physics, COMSATS Institute of Information Technology, Islamabad 44000 (Pakistan)

    2015-05-01

    A series of single phase spinel ferrites having chemical formula Mg{sub 0.5}Zn{sub 0.5}Pr{sub x}Fe{sub 2−x}O{sub 4} (x=0.00, 0.05, 0.10, 0.15, 0.20, 0.25) were prepared using the sol–gel technique after sintering at 700 °C. The thermal decomposition behavior of an as prepared powder was investigated by means of DTA/TGA analyses. The sintered powders were then characterized by Fourier transform infrared spectroscope, X-ray diffraction, scanning electron microscope, energy dispersive X-ray spectroscope and vibrating sample magnetometer. X-ray diffraction patterns confirm the single phase spinel structure of prepared ferrites without the presence of any impurity phase. The value of lattice parameter (a) increases with the increase of Pr contents (x) into the spinel lattice. The grain size estimated from electron microscope images is in the range of 2.75–5.4 µm which confirms the spinel crystalline nature of the investigated samples. The saturation magnetization (M{sub s}) decreases whereas coercivity (H{sub c}) increases with the increase of Pr contents (x). The measured parameters suggest that these materials are favorable for high frequency applications and as core materials. - Highlights: • Pr-substituted spinel ferrites synthesized by autocombustion route have been investigated. • The average grain size was in the range of 2.75–5.4 µm estimated by SEM technique. • The (M{sub s}) decreases whereas (H{sub c}) increases with the increase of Pr contents (x). • These parameters are favorable for high frequency applications and as core materials.

  12. Ictal high frequency oscillations distinguish two types of seizure territories in humans.

    Science.gov (United States)

    Weiss, Shennan A; Banks, Garrett P; McKhann, Guy M; Goodman, Robert R; Emerson, Ronald G; Trevelyan, Andrew J; Schevon, Catherine A

    2013-12-01

    High frequency oscillations have been proposed as a clinically useful biomarker of seizure generating sites. We used a unique set of human microelectrode array recordings (four patients, 10 seizures), in which propagating seizure wavefronts could be readily identified, to investigate the basis of ictal high frequency activity at the cortical (subdural) surface. Sustained, repetitive transient increases in high gamma (80-150 Hz) amplitude, phase-locked to the low-frequency (1-25 Hz) ictal rhythm, correlated with strong multi-unit firing bursts synchronized across the core territory of the seizure. These repetitive high frequency oscillations were seen in recordings from subdural electrodes adjacent to the microelectrode array several seconds after seizure onset, following ictal wavefront passage. Conversely, microelectrode recordings demonstrating only low-level, heterogeneous neural firing correlated with a lack of high frequency oscillations in adjacent subdural recording sites, despite the presence of a strong low-frequency signature. Previously, we reported that this pattern indicates a failure of the seizure to invade the area, because of a feedforward inhibitory veto mechanism. Because multi-unit firing rate and high gamma amplitude are closely related, high frequency oscillations can be used as a surrogate marker to distinguish the core seizure territory from the surrounding penumbra. We developed an efficient measure to detect delayed-onset, sustained ictal high frequency oscillations based on cross-frequency coupling between high gamma amplitude and the low-frequency (1-25 Hz) ictal rhythm. When applied to the broader subdural recording, this measure consistently predicted the timing or failure of ictal invasion, and revealed a surprisingly small and slowly spreading seizure core surrounded by a far larger penumbral territory. Our findings thus establish an underlying neural mechanism for delayed-onset, sustained ictal high frequency oscillations, and

  13. On the Importance of High Frequency Gravity Waves for Ice Nucleation in the Tropical Tropopause Layer

    Science.gov (United States)

    Jensen, Eric J.

    2016-01-01

    Recent investigations of the influence of atmospheric waves on ice nucleation in cirrus have identified a number of key processes and sensitivities: (1) ice concentrations produced by homogeneous freezing are strongly dependent on cooling rates, with gravity waves dominating upper tropospheric cooling rates; (2) rapid cooling driven by high-frequency waves are likely responsible for the rare occurrences of very high ice concentrations in cirrus; (3) sedimentation and entrainment tend to decrease ice concentrations as cirrus age; and (4) in some situations, changes in temperature tendency driven by high-frequency waves can quench ice nucleation events and limit ice concentrations. Here we use parcel-model simulations of ice nucleation driven by long-duration, constant-pressure balloon temperature time series, along with an extensive dataset of cold cirrus microphysical properties from the recent ATTREX high-altitude aircraft campaign, to statistically examine the importance of high-frequency waves as well as the consistency between our theoretical understanding of ice nucleation and observed ice concentrations. The parcel-model simulations indicate common occurrence of peak ice concentrations exceeding several hundred per liter. Sedimentation and entrainment would reduce ice concentrations as clouds age, but 1-D simulations using a wave parameterization (which underestimates rapid cooling events) still produce ice concentrations higher than indicated by observations. We find that quenching of nucleation events by high-frequency waves occurs infrequently and does not prevent occurrences of large ice concentrations in parcel simulations of homogeneous freezing. In fact, the high-frequency variability in the balloon temperature data is entirely responsible for production of these high ice concentrations in the simulations.

  14. MAGNET

    CERN Multimedia

    by B. Curé

    2011-01-01

    The magnet operation was very satisfactory till the technical stop at the end of the year 2010. The field was ramped down on 5th December 2010, following the successful regeneration test of the turbine filters at full field on 3rd December 2010. This will limit in the future the quantity of magnet cycles, as it is no longer necessary to ramp down the magnet for this type of intervention. This is made possible by the use of the spare liquid Helium volume to cool the magnet while turbines 1 and 2 are stopped, leaving only the third turbine in operation. This obviously requires full availability of the operators to supervise the operation, as it is not automated. The cryogenics was stopped on 6th December 2010 and the magnet was left without cooling until 18th January 2011, when the cryoplant operation resumed. The magnet temperature reached 93 K. The maintenance of the vacuum pumping was done immediately after the magnet stop, when the magnet was still at very low temperature. Only the vacuum pumping of the ma...

  15. Magnetic microwires a magneto-optical study

    CERN Document Server

    Chizhik, Alexander

    2014-01-01

    PrefaceKerr Effect as Method of Investigation of Magnetization Reversal in Magnetic Wires Cold-Drawn Fe-Rich Amorphous Wire Conventional Co-Rich Amorphous WireInteraction Between Glass-Covered MicrowiresCircular Magnetic Bistability in Co-Rich Amorphous Microwires Effect of High-Frequency Driving Current on Magnetization Reversal in Co-Rich Amorphous MicrowiresRelation Between Surface Magnetization Reversal and Magnetoimpedance Helical Magnetic Structure Magnetization Reversal in Crossed Magnetic Field Visualization of Barkhausen Jump Magnetizatio

  16. MAGNET

    CERN Multimedia

    B. Curé

    2012-01-01

      Following the unexpected magnet stops last August due to sequences of unfortunate events on the services and cryogenics [see CMS internal report], a few more events and initiatives again disrupted the magnet operation. All the magnet parameters stayed at their nominal values during this period without any fault or alarm on the magnet control and safety systems. The magnet was stopped for the September technical stop to allow interventions in the experimental cavern on the detector services. On 1 October, to prepare the transfer of the liquid nitrogen tank on its new location, several control cables had to be removed. One cable was cut mistakenly, causing a digital input card to switch off, resulting in a cold-box (CB) stop. This tank is used for the pre-cooling of the magnet from room temperature down to 80 K, and for this reason it is controlled through the cryogenics control system. Since the connection of the CB was only allowed for a field below 2 T to avoid the risk of triggering a fast d...

  17. MAGNET

    CERN Multimedia

    Benoit Curé

    2010-01-01

    Operation of the magnet has gone quite smoothly during the first half of this year. The magnet has been at 4.5K for the full period since January. There was an unplanned short stop due to the CERN-wide power outage on May 28th, which caused a slow dump of the magnet. Since this occurred just before a planned technical stop of the LHC, during which access in the experimental cavern was authorized, it was decided to leave the magnet OFF until 2nd June, when magnet was ramped up again to 3.8T. The magnet system experienced a fault also resulting in a slow dump on April 14th. This was triggered by a thermostat on a filter choke in the 20kA DC power converter. The threshold of this thermostat is 65°C. However, no variation in the water-cooling flow rate or temperature was observed. Vibration may have been the root cause of the fault. All the thermostats have been checked, together with the cables, connectors and the read out card. The tightening of the inductance fixations has also been checked. More tem...

  18. MAGNET

    CERN Multimedia

    B. Curé

    2012-01-01

      The magnet was energised at the beginning of March 2012 at a low current to check all the MSS safety chains. Then the magnet was ramped up to 3.8 T on 6 March 2012. Unfortunately two days later an unintentional switch OFF of the power converter caused a slow dump. This was due to a misunderstanding of the CCC (CERN Control Centre) concerning the procedure to apply for the CMS converter control according to the beam-mode status at that time. Following this event, the third one since 2009, a discussion was initiated to define possible improvement, not only on software and procedures in the CCC, but also to evaluate the possibility to upgrade the CMS hardware to prevent such discharge from occurring because of incorrect procedure implementations. The magnet operation itself was smooth, and no power cuts took place. As a result, the number of magnetic cycles was reduced to the minimum, with only two full magnetic cycles from 0 T to 3.8 T. Nevertheless the magnet suffered four stops of the cryogeni...

  19. High frequency guided waves for hidden fatigue crack growth monitoring in multi-layer aerospace structures

    Science.gov (United States)

    Chan, Henry; Fromme, Paul

    2015-03-01

    Varying loading conditions of aircraft structures result in stress concentration at fastener holes, where multi-layered components are connected, possibly leading to the development of fatigue cracks. High frequency guided waves propagating along the structure allow for the non-destructive testing of such components, e.g., aircraft wings. However, the sensitivity for the detection of small, potentially hidden, fatigue cracks has to be ascertained. The type of multi-layered model structure investigated consists of two adhesively bonded aluminium plate-strips. Fatigue experiments were carried out. The sensitivity of the high frequency guided wave modes to monitor fatigue crack growth at a fastener hole during cyclic loading was investigated, using both standard pulse-echo equipment and laser interferometry. The sensitivity and repeatability of the measurements were ascertained, having the potential for fatigue crack growth monitoring at critical and difficult to access fastener locations from a stand-off distance.

  20. Defect Detection in Multi-Layered Structures Using High Frequency Guided Waves

    Science.gov (United States)

    Masserey, B.; Kostson, E.; Fromme, P.

    2011-06-01

    Aircraft structures contain multi-layered components connected by fasteners, where fatigue cracks and disbonds can develop due to cyclic loading conditions and stress concentration. High frequency guided waves propagating along the structure allow for the efficient non-destructive testing of components, such as aircraft wings. However, the sensitivity for the detection of small defects has to be ascertained. The type of multi-layered model structure investigated consists of two adhesively bonded aluminium plate-strips. High frequency ultrasonic wave propagation along the structure and the sensitivity to disbonds and small defects in the metallic layers was investigated and verified experimentally. Preliminary fatigue experiments were carried out and the sensitivity of the guided waves to monitor fatigue crack growth at a fastener hole during cyclic loading was investigated. The measurement setup has the potential for fatigue crack growth monitoring at critical and difficult to access fastener locations from a stand-off distance.

  1. Investigations of high-frequency induction hardening process for piston rod of shock absorber

    Institute of Scientific and Technical Information of China (English)

    Xianhua Cheng; Qianqian Shangguan

    2005-01-01

    The microhardness of piston rods treated with different induction hardening processes was tested. The experimental results reveal that the depth of the hardened zone is proportional to the ratio of the moving speed of the piston rod to the output power of the induction generator. This result is proved correct through the Finite Element Method (FEM) simulation of the thermal field of induction heating. From tensile and impact tests, an optimized high frequency induction hardening process for piston rods has been obtained, where the output power was 82%×80 kW and the moving speed of workpiece was 5364 mm/min. The piston rods, treated by the optimized high frequency induction hardening process, show the best comprehensive mechanical performance.

  2. High frequency PMN-PT single crystal focusing transducer fabricated by a mechanical dimpling technique.

    Science.gov (United States)

    Chen, Y; Lam, K H; Zhou, D; Cheng, W F; Dai, J Y; Luo, H S; Chan, H L W

    2013-02-01

    High frequency (∼30MHz and ∼80MHz) focusing ultrasound transducers were fabricated using a PMN-0.28PT single crystal by a mechanical dimpling technique. The dimpled single crystal was used as an active element for the focusing transducer. Compared with a plane transducer, the focusing transducer fabricated with a dimpled active element exhibits much broader bandwidth and higher sensitivity. Besides, a high quality image can be obtained by the 30MHz focusing transducer, in which the -6dB axial and lateral resolution is 27μm and 139μm, respectively. These results prove that the dimpling technique is capable to fabricate the high frequency focusing transducers with excellent performance for imaging applications.

  3. High frequency optoelectronic oscillators based on the optical feedback of semiconductor mode-locked laser diodes.

    Science.gov (United States)

    Haji, Mohsin; Hou, Lianping; Kelly, Anthony E; Akbar, Jehan; Marsh, John H; Arnold, John M; Ironside, Charles N

    2012-01-30

    Optical self seeding feedback techniques can be used to improve the noise characteristics of passively mode-locked laser diodes. External cavities such as fiber optic cables can increase the memory of the phase and subsequently improve the timing jitter. In this work, an improved optical feedback architecture is proposed using an optical fiber loop delay as a cavity extension of the mode-locked laser. We investigate the effect of the noise reduction as a function of the loop length and feedback power. The well known composite cavity technique is also implemented for suppressing supermode noise artifacts presented due to harmonic mode locking effects. Using this method, we achieve a record low radio frequency linewidth of 192 Hz for any high frequency (>1 GHz) passively mode-locked laser to date (to the best of the authors' knowledge), making it promising for the development of high frequency optoelectronic oscillators.

  4. Dependence structure of the Korean stock market in high frequency data

    Science.gov (United States)

    Kim, Min Jae; Kwak, Young Bin; Kim, Soo Yong

    2011-03-01

    This paper analyzes the evolution of the dependence structure for various time window intervals, known as Epps effect, using the Trade and Quote data of 663 actively traded stocks in Korean stock market. It is found that the random matrix theory analysis could not represent the dependence structure of the stock market in the microstructure regime. The Cook-Johnson copula is introduced as a parsimonious alternative method to handle this problem, and the existence of the Epps effect is confirmed for the 663 stocks using high frequency data. It was also found that large capitalization companies tend to have a stronger dependence structure, except for the largest capitalization group, since the phenomenon of price level resistance leads to the weak dependence structure in the largest capitalization group. In addition, grouping the industry as a sub-portfolio is an appropriate approach for hour interval traders, whereas this approach is not a strategy recommended for high frequency traders.

  5. High-frequency guided ultrasonic waves for hidden defect detection in multi-layer aircraft structures

    Science.gov (United States)

    Masserey, B.; Raemy, C.; Fromme, P.

    2012-05-01

    Aerospace structures contain multi-layer components subjected to cyclic loading conditions; fatigue cracks and disbonds can develop, often at fastener holes. High-frequency guided waves have the potential for non-destructive damage detection at critical and difficult to access locations from a stand-off distance. Using commercially available ultrasonic transducers, high frequency guided waves were generated that penetrate through the complete thickness of a model structure, consisting of two adhesively bonded aluminum plates. The wave propagation along the specimen was measured and quantified using a laser interferometer. The wave propagation and scattering at internal defects was simulated using Finite Element (FE) models and good agreement with the measurement results found. The detection sensitivity using standard pulse-echo measurements was verified and the influence of the stand-off distance predicted from the FE simulation results.

  6. Vast Volatility Matrix Estimation using High Frequency Data for Portfolio Selection

    CERN Document Server

    Fan, Jianqing; Yu, Ke

    2010-01-01

    Portfolio allocation with gross-exposure constraint is an effective method to increase the efficiency and stability of selected portfolios among a vast pool of assets, as demonstrated in Fan et al (2008). The required high-dimensional volatility matrix can be estimated by using high frequency financial data. This enables us to better adapt to the local volatilities and local correlations among vast number of assets and to increase significantly the sample size for estimating the volatility matrix. This paper studies the volatility matrix estimation using high-dimensional high-frequency data from the perspective of portfolio selection. Specifically, we propose the use of "pairwise-refresh time" and "all-refresh time" methods proposed by Barndorff-Nielsen et al (2008) for estimation of vast covariance matrix and compare their merits in the portfolio selection. We also establish the concentration inequalities of the estimates, which guarantee desirable properties of the estimated volatility matrix in vast asset ...

  7. Compressive inverse scattering: I. High-frequency SIMO/MISO and MIMO measurements

    Science.gov (United States)

    Fannjiang, Albert C.

    2010-03-01

    Inverse scattering from discrete targets with the single-input-multiple-output (SIMO), multiple-input-single-output (MISO) or multiple-input-multiple-output (MIMO) measurements is analyzed by compressed sensing theory with and without the Born approximation. High-frequency analysis of (probabilistic) recoverability by the L1-based minimization/regularization principles is presented. In the absence of noise, it is shown that the L1-based solution can recover exactly the target of sparsity up to the dimension of the data either with the MIMO measurement for the Born scattering or with the SIMO/MISO measurement for the exact scattering. The stability with respect to noisy data is proved for weak or widely separated scatterers. Reciprocity between the SIMO and MISO measurements is analyzed. Finally a coherence bound (and the resulting recoverability) is proved for diffraction tomography with high-frequency, few-view and limited-angle SIMO/MISO measurements.

  8. High-frequency manipulation of few-electron double quantum dots-toward spin qubits

    Science.gov (United States)

    Kodera, T.; van der Wiel, W. G.; Ono, K.; Sasaki, S.; Fujisawa, T.; Tarucha, S.

    2004-04-01

    We use a photon-assisted tunneling (PAT) technique to study the high-frequency response of one- and two-electron states in a semiconductor vertically coupled double-dot system. In particular, PAT associated with two-electron spin states in the spin-blockade regime is observed up to the absorption of 10 photons, indicating the preservation of long relaxation times and hence the robustness of our electron spin device under strong microwave irradiation. An alternative double-dot structure with greater flexibility in tuning the inter-dot coupling is presented and its transport characteristics are discussed. This structure is proposed for high-frequency control of two-electron spin states, as required for quantum computation schemes using electron spins in quantum dots.

  9. Self-oscillating Galvanic Isolated Bidirectional Very High Frequency DC-DC Converter

    DEFF Research Database (Denmark)

    Pedersen, Jeppe Arnsdorf; Madsen, Mickey Pierre; Knott, Arnold;

    2015-01-01

    This paper describes a galvanic isolated bidirectional Very High Frequency (VHF = 30 MHz - 300MHz) ClassE converter. The reason for increasing the switching frequency is to minimize the passive components in the converter. To make the converter topology bidirectional the rectifier has to be synch......This paper describes a galvanic isolated bidirectional Very High Frequency (VHF = 30 MHz - 300MHz) ClassE converter. The reason for increasing the switching frequency is to minimize the passive components in the converter. To make the converter topology bidirectional the rectifier has...... conduction mode. The designed converter operates at a switching frequency of 35.6 MHz, which is well within the VHF range. The same converter is also implemented with PCB embedded inductors to minimize cost and the physical volume of the total converter....

  10. Detection of a high frequency break in the X-ray power spectrum of Ark 564

    CERN Document Server

    Papadakis, I E; Negoro, H; Gliozzi, M

    2001-01-01

    We present a power spectrum analysis of the long ASCA observation of Ark 564 in June/July 2001. The observed power spectrum covers a frequency range of ~ 3.5 decades. We detect a high frequency break at ~ 0.002 Hz. The power spectrum has an rms of ~30% and a slope of ~ -1 and ~ -2 below and above the break frequency. When combined with the results from a long RXTE observation (Pounds et al. 2001), the observed power spectra of Ark 564 and Cyg X-1 (in the low/hard state) are almost identical, showing a similar shape and rms amplitude. However, the ratio of the high frequency breaks is very small (~ 10e{3-4}), implying that these characteristic frequencies are not indicative of the black hole mass. This result supports the idea of a small black hole mass/high accretion rate in Ark 564.

  11. Method for detecting moment connection fracture using high-frequency transients in recorded accelerations

    Science.gov (United States)

    Rodgers, J.E.; Elebi, M.

    2011-01-01

    The 1994 Northridge earthquake caused brittle fractures in steel moment frame building connections, despite causing little visible building damage in most cases. Future strong earthquakes are likely to cause similar damage to the many un-retrofitted pre-Northridge buildings in the western US and elsewhere. Without obvious permanent building deformation, costly intrusive inspections are currently the only way to determine if major fracture damage that compromises building safety has occurred. Building instrumentation has the potential to provide engineers and owners with timely information on fracture occurrence. Structural dynamics theory predicts and scale model experiments have demonstrated that sudden, large changes in structure properties caused by moment connection fractures will cause transient dynamic response. A method is proposed for detecting the building-wide level of connection fracture damage, based on observing high-frequency, fracture-induced transient dynamic responses in strong motion accelerograms. High-frequency transients are short (Elsevier B.V. All rights reserved.

  12. Energy conservation and high-frequency damping in numerical time-integration

    DEFF Research Database (Denmark)

    Krenk, Steen

    2007-01-01

    Momentum and energy conserving time integration procedures are receiving increased interest due to the central role of conservation properties in relation to the problems under investigation. However, most problems in structural dynamics are based on models that are first discretized in space, en...... this often leads to a fairly large number of high-frequency modes, that are not represented well - and occasionally directly erroneously - by the model. It is desirable to cure this problem by devising algorithms that include the possibility of introducing algorithmic energy dissipation of the high......-frequency modes. The problem is well known from classic collocation based algorithms - notably various forms of the Newmark algorithm where the equation of motion is supplemented by approximate relations between displacement, velocity and acceleration. Here adjustment of the algorithmic parameters can be used...

  13. Energy conservation and high-frequency damping in numerical time integration

    DEFF Research Database (Denmark)

    Krenk, Steen

    2008-01-01

    Momentum and energy conserving time integration procedures are receiving increased interest due to the central role of conservation properties in relation to the problems under investigation. However, most problems in structural dynamics are based on models that are first discretized in space, en...... this often leads to a fairly large number of high-frequency modes, that are not represented well – and occasionally directly erroneously – by the model. It is desirable to cure this problem by devising algorithms that include the possibility of introducing algorithmic energy dissipation of the high......-frequency modes. The problem is well known from classic collocation based algorithms – notably various forms of the Newmark algorithm – where the equation of motion is supplemented by approximate relations between displacement, velocity and acceleration. Here adjustment of the algorithmic parameters can be used...

  14. Research on High Frequency Amplitude Attenuation of Electric Fast Transient Generator

    Directory of Open Access Journals (Sweden)

    Huafu Zhang

    2013-01-01

    Full Text Available In order to solve the amplitude attenuation of electric fast transient (EFT generator operating in high frequency, the charging and discharging process of energy storage capacitor in EFT generator are analyzed, the main circuit voltage variation mathematical model is established, the parameters of main loop circuit and the parameters of switch driving waveform which affect burst amplitude are discussed. Through the simulation, this paper puts forward effective methods to overcome burst amplitude attenuation in high frequency. The simulation results show that when the frequency is low, the duty ratio of drive signal have little effect on energy storage capacitor voltage amplitude attenuation. when the charging resistance is less than 500 Ω, the duty ratio of drive signal is less than 0.125, the repetition frequency of burst reaches 1.2 MHz, the amplitude attenuation of energy storage capacitor voltage is less than 9%, the amplitude of burst satisfies IEC61000-4-4 standards.

  15. The value of high-frequency and color Doppler ultrasonography in diagnosing congenital muscular torticollis

    Directory of Open Access Journals (Sweden)

    Wang Lei

    2012-10-01

    Full Text Available Abstract Background Congenital muscular torticollis (CMT is a relatively common neck deformity in infancy. The aim of our research was to determine the value of high-frequency and color Doppler ultrasonography in diagnosing CMT. Methods Patients with a clinical suspicion of CMT underwent an ultrasound examination before diagnosis, and the sonographic characteristics were analyzed and compared with the clinical findings. Results The sensitivity and specificity of an ultrasound diagnosis for CMT was 95.83% and 83.33%, respectively. The patients were divided into 2 groups based on the stage of the disease: the early-stage group (age Conclusions Different stage of CMT patients had different sonographic characteristics. High-frequency and color Doppler ultrasonography can serve as adjunct confirmation tool for the diagnosis of CMT.

  16. High frequency A-type pulsators discovered using SuperWASP

    CERN Document Server

    Holdsworth, Daniel L; Gillon, M; Clubb, K I; Southworth, J; Maxted, P F L; Anderson, D R; Barros, S C C; Cameron, A Collier; Delrez, L; Faedi, F; Haswell, C A; Hellier, C; Horne, K; Jehin, E; Norton, A J; Pollacco, D; Skillen, I; Smith, A M S; West, R G; Wheatley, P J

    2014-01-01

    We present the results of a survey using the WASP archive to search for high frequency pulsations in F-, A- and B-type stars. Over 1.5 million targets have been searched for pulsations with amplitudes greater than 0.5 millimagnitude. We identify over 350 stars which pulsate with periods less than 30 min. Spectroscopic follow-up of selected targets has enabled us to confirm 10 new rapidly oscillating Ap stars, 13 pulsating Am stars and the fastest known $\\delta$ Scuti star. We also observe stars which show pulsations in both the high-frequency domain and in the low-frequency $\\delta$ Scuti range. This work shows the power of the WASP photometric survey to find variable stars with amplitudes well below the nominal photometric precision per observation.

  17. High Frequency Characteristics Of Ferrite Materials And Applications To Microstrip Circuits

    OpenAIRE

    Moataza A. Hindy

    1999-01-01

    Dispersion behavior of the parameters of microstrip lines printed on ferrite substrate is presented. The characteristic impedance for lines on magnetized ferrite substrates are obtained for partially magnetized substrates in the direction of wave propagation and vertically magnetized substrates with variable DC magnetic field. The obtained results are applied to analyze variable phase shifters, controlled resonators, and impedance matching.

  18. Noninvasive Quantitative Imaging of Collagen Microstructure in Three-Dimensional Hydrogels Using High-Frequency Ultrasound

    OpenAIRE

    Mercado, Karla P.; Helguera, María; Hocking, Denise C.; Dalecki, Diane

    2015-01-01

    Collagen I is widely used as a natural component of biomaterials for both tissue engineering and regenerative medicine applications. The physical and biological properties of fibrillar collagens are strongly tied to variations in collagen fiber microstructure. The goal of this study was to develop the use of high-frequency quantitative ultrasound to assess collagen microstructure within three-dimensional (3D) hydrogels noninvasively and nondestructively. The integrated backscatter coefficient...

  19. Design and Fabrication of Nanoscale IDTs Using Electron Beam Technology for High-Frequency SAW Devices

    Directory of Open Access Journals (Sweden)

    Wei-Che Shih

    2014-01-01

    Full Text Available High-frequency Rayleigh-mode surface acoustic wave (SAW devices were fabricated for 4G mobile telecommunications. The RF magnetron sputtering method was adopted to grow piezoelectric aluminum nitride (AlN thin films on the Si3N4/Si substrates. The influence of sputtering parameters on the crystalline characteristics of AlN thin films was investigated. The interdigital transducer electrodes (IDTs of aluminum (Al were then fabricated onto the AlN surfaces by using the electron beam (e-beam direct write lithography method to form the Al/AlN/Si3N4/Si structured SAW devices. The Al electrodes were adopted owing to its low resistivity, low cost, and low density of the material. For 4G applications in mobile telecommunications, the line widths of 937 nm, 750 nm, 562 nm, and 375 nm of IDTs were designed. Preferred orientation and crystalline properties of AlN thin films were determined by X-ray diffraction using a Siemens XRD-8 with CuKα radiation. Additionally, the cross-sectional images of AlN thin films were obtained by scanning electron microscope. Finally, the frequency responses of high-frequency SAW devices were measured using the E5071C network analyzer. The center frequencies of the high-frequency Rayleigh-mode SAW devices of 1.36 GHz, 1.81 GHz, 2.37 GHz, and 3.74 GHz are obtained. This study demonstrates that the proposed processing method significantly contributes to high-frequency SAW devices for wireless communications.

  20. Environmental Assessment for the Advanced Extremely High Frequency Satellite Beddown and Deployment Program

    Science.gov (United States)

    2010-07-01

    Fish and Wildlife Service Advanced Extremely High Frequency Satellite Final Environmental Assessment v VIF Vehicle Integration Facility WMO World...Vehicle Mate Operations Upon arrival on CCAFS, the transporter would take the encapsulated payload to the Vehicle Integration Facility ( VIF ), which...is located just south of LC-41 (Figure 2-2). At the VIF , the encapsulated payload would be mated to the Atlas V Launch Vehicle (LV) using a mobile

  1. 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.

  2. Data mining neocortical high-frequency oscillations in epilepsy and controls.

    Science.gov (United States)

    Blanco, Justin A; Stead, Matt; Krieger, Abba; Stacey, William; Maus, Douglas; Marsh, Eric; Viventi, Jonathan; Lee, Kendall H; Marsh, Richard; Litt, Brian; Worrell, Gregory A

    2011-10-01

    Transient high-frequency (100-500 Hz) oscillations of the local field potential have been studied extensively in human mesial temporal lobe. Previous studies report that both ripple (100-250 Hz) and fast ripple (250-500 Hz) oscillations are increased in the seizure-onset zone of patients with mesial temporal lobe epilepsy. Comparatively little is known, however, about their spatial distribution with respect to seizure-onset zone in neocortical epilepsy, or their prevalence in normal brain. We present a quantitative analysis of high-frequency oscillations and their rates of occurrence in a group of nine patients with neocortical epilepsy and two control patients with no history of seizures. Oscillations were automatically detected and classified using an unsupervised approach in a data set of unprecedented volume in epilepsy research, over 12 terabytes of continuous long-term micro- and macro-electrode intracranial recordings, without human preprocessing, enabling selection-bias-free estimates of oscillation rates. There are three main results: (i) a cluster of ripple frequency oscillations with median spectral centroid = 137 Hz is increased in the seizure-onset zone more frequently than a cluster of fast ripple frequency oscillations (median spectral centroid = 305 Hz); (ii) we found no difference in the rates of high frequency oscillations in control neocortex and the non-seizure-onset zone neocortex of patients with epilepsy, despite the possibility of different underlying mechanisms of generation; and (iii) while previous studies have demonstrated that oscillations recorded by parenchyma-penetrating micro-electrodes have higher peak 100-500 Hz frequencies than penetrating macro-electrodes, this was not found for the epipial electrodes used here to record from the neocortical surface. We conclude that the relative rate of ripple frequency oscillations is a potential biomarker for epileptic neocortex, but that larger prospective studies correlating high-frequency

  3. Impedance-Based High Frequency Resonance Analysis of DFIG System in Weak Grids

    OpenAIRE

    Song, Yipeng; Wang, Xiongfei; Blaabjerg, Frede

    2017-01-01

    The impedance-based model of Doubly Fed Induction Generator (DFIG) systems, including the rotor part (Rotor Side Converter (RSC) and induction machine), and the grid part (Grid Side Converter (GSC) and its output filter), has been developed for analysis and mitigation of the Sub- Synchronous Resonance (SSR). However, the High Frequency Resonance (HFR) of DFIG systems due to the impedance interaction between DFIG system and parallel compensated weak network is often overlooked. This paper thus...

  4. High Frequency Model of Electrified Railway Propulsion System for EMC Analysis

    OpenAIRE

    Jia, Kelin

    2012-01-01

    A model of the electrified railway propulsion system working in a wide frequency range is studied in this thesis. The high frequency modeling is the first stage to study and predict the Electromagnetic compatibility (EMC) problems in the electrified railway propulsion system, which are safety and reliability issues of high concern. Modeling methods and models for the line converter, motor power supply module, and the traction motor are developed. These models can work individually or be combi...

  5. The high frequency acoustic radiation from the boundary layer of an axisymmetric body

    Institute of Scientific and Technical Information of China (English)

    LI Fuxin; MA Lin; MA Zhiming

    2001-01-01

    The mechanism of acoustic radiation from the boundary layer of an axisymmetric body is analyzed, and its sound pressure spectrum is predicted. It is shown that the acoustic radiation results from the transition region and the turbulent boundary layer; and that the acoustic radiation from transition region is predominant at low frequencies; while the turbulent boundary layer has the decisive effect on acoustic radiation at high frequencies. The calculated values are in good agreement with the experimental data.

  6. Profiling the high frequency wine consumer by price segmentation in the US market

    OpenAIRE

    Liz Thach; Janeen Olsen

    2015-01-01

    Heavy users of consumer products are important to marketers as a profitable target segment. This is equally true in the wine industry, but with the added precaution of encouraging responsible consumption. This study examines the attributes and behaviors of 681 high frequency (heavy-user) wine consumers in the US, based on a price segmentation of High, Moderate, and Low Spenders. For this study, price segmentation was defined as the price typically paid for a bottle of wine for home consumptio...

  7. Contrast validation test for retrieval method of high frequency ground wave radar

    Institute of Scientific and Technical Information of China (English)

    WANG Hailong; GUO Peifang; HAN Shuzong; XIE Qiang; ZHOU Liangming

    2005-01-01

    In this paper, on the basis of the working principles of high frequency ground wave radar for retrieval of ocean wave and sea wind elements were used to systematically study the data obtained from contrast validation test in Zhoushan sea area of Zhejiang Province on Oct. 2000, to validate the accuracy of OSMAR2000for wave and wind parameters, and to analyze the possible error caused when using OSMAR2000 to retrieve ocean parameters.

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

    OpenAIRE

    Lee Jongwon; Lee Yong W; Warwick Warren J; Sohn Kiwon; Holte James E

    2005-01-01

    Abstract Background High frequency chest compression (HFCC) is a useful and popular therapy for clearing bronchial airways of excessive or thicker mucus. Our observation of respiratory airflow of a subject during use of HFCC showed the airflow oscillation by HFCC was strongly influenced by the nonlinearity of the respiratory system. We used a computational model-based approach to analyse the respiratory airflow during use of HFCC. Methods The computational model, which is based on previous ph...

  9. High Frequency Combustion Instabilities of LOx/CH4 Spray Flames in Rocket Engine Combustion Chambers

    OpenAIRE

    Sliphorst, M.

    2011-01-01

    Ever since the early stages of space transportation in the 1940’s, and the related liquid propellant rocket engine development, combustion instability has been a major issue. High frequency combustion instability (HFCI) is the interaction between combustion and the acoustic field in the combustion chamber. It destroys the thermal boundary layer wall increasing heat transfer and could lead to compromised performance, and ultimately to destruction of the engine and mission loss. The main object...

  10. A study of the high-frequency hearing thresholds of dentistry professionals

    Directory of Open Access Journals (Sweden)

    Lopes, Andréa Cintra

    2012-01-01

    Full Text Available Introduction: In the dentistry practice, dentists are exposed to harmful effects caused by several factors, such as the noise produced by their work instruments. In 1959, the American Dental Association recommended periodical hearing assessments and the use of ear protectors. Aquiring more information regarding dentists', dental nurses', and prosthodontists' hearing abilities is necessary to propose prevention measures and early treatment strategies. Objective: To investigate the auditory thresholds of dentists, dental nurses, and prosthodontists. Method: In this clinical and experimental study, 44 dentists (Group I; GI, 36 dental nurses (Group II; GII, and 28 prosthodontists (Group III; GIII were included, , with a total of 108 professionals. The procedures that were performed included a specific interview, ear canal inspection, conventional and high-frequency threshold audiometry, a speech reception threshold test, and an acoustic impedance test. Results: In the 3 groups that were tested, the comparison between the mean hearing thresholds provided evidence of worsened hearing ability relative to the increase in frequency. For the tritonal mean at 500 to 2,000 Hz and 3,000 to 6,000 Hz, GIII presented the worst thresholds. For the mean of the high frequencies (9,000 and 16,000 Hz, GII presented the worst thresholds. Conclusion: The conventional hearing threshold evaluation did not demonstrate alterations in the 3 groups that were tested; however, the complementary tests such as high-frequency audiometry provided greater efficacy in the early detection of hearing problems, since this population's hearing loss impaired hearing ability at frequencies that are not tested by the conventional tests. Therefore, we emphasize the need of utilizing high-frequency threshold audiometry in the hearing assessment routine in combination with other audiological tests.

  11. High-frequency audiometry: A means for early diagnosis of noise-induced hearing loss

    OpenAIRE

    Amir H Mehrparvar; Seyyed J Mirmohammadi; Abbas Ghoreyshi; Abolfazl Mollasadeghi; Ziba Loukzadeh

    2011-01-01

    Noise-induced hearing loss (NIHL), an irreversible disorder, is a common problem in industrial settings. Early diagnosis of NIHL can help prevent the progression of hearing loss, especially in speech frequencies. For early diagnosis of NIHL, audiometry is performed routinely in conventional frequencies. We designed this study to compare the effect of noise on high-frequency audiometry (HFA) and conventional audiometry. In a historical cohort study, we compared hearing threshold and prevalence...

  12. Generation of high frequency photons with sub-Poissonian statistics at consecutive interactions

    CERN Document Server

    Chirkin, A S

    2003-01-01

    The process of parametric amplification at high frequency pumping, which is accompanied by optical frequency mixing in the same nonlinear crystal (NC), is considered. It is shown that if a signal wave is in a coherent state at the input of the NC, then the radiation with signal and summary frequencies can have sub-Poissonian photon statistics at the output of the NC in the deamplification regime. The Fano factors as functions of parameters of the problem are studied.

  13. Comparing the Robustness of High-Frequency Traveling-Wave Tube Slow-Wave Circuits

    Science.gov (United States)

    Chevalier, Christine T.; Wilson, Jeffrey D.; Kory, Carol L.

    2007-01-01

    A three-dimensional electromagnetic field simulation software package was used to compute the cold-test parameters, phase velocity, on-axis interaction impedance, and attenuation, for several high-frequency traveling-wave tube slow-wave circuit geometries. This research effort determined the effects of variations in circuit dimensions on cold-test performance. The parameter variations were based on the tolerances of conventional micromachining techniques.

  14. Analysis of Results from ASIAEX East China Sea: Mid to High Frequency Bottom Loss

    Science.gov (United States)

    2016-06-07

    Analysis of Results from ASIAEX East China Sea : Mid to High Frequency Bottom Loss Peter H. Dahl phone: (206) 543-2667 fax: (206) 543-6785...during the Asian Seas International Acoustics Experiment (ASIAEX) conducted in the East China Sea (May-June 2001). APPROACH The bottom loss...measurements are interpreted as estimates of the modulus of the plane wave reflection coefficient, and data are compared to predicted values using a

  15. Research Initiatives for Materials State Sensing (RIMSS) Task Order 0020: High Frequency Eddy Current NDE

    Science.gov (United States)

    2014-10-01

    coatings using eddy current techniques”, AIP Conference Proceedings , Vol. 1430, 2012, pp 441. 7. F. M. Smits, “Measurement of sheet resistivities with... Conference 2014: 27 October - 30 October, Charleston, SC, USA. “High-Frequency Eddy Current System for Analyzing Wet Conductive Coatings during...Processing”. 3. QNDE 2014 (ORAL PRESENTATION), 41st Annual Review of Progress in Quantitative Nondestructive Evaluation: Conference Boise Centre

  16. Increased Low- and High-Frequency Oscillatory Activity in the Prefrontal Cortex of Fibromyalgia Patients

    Science.gov (United States)

    Lim, Manyoel; Kim, June Sic; Kim, Dajung J.; Chung, Chun Kee

    2016-01-01

    Recent human neuroimaging studies have suggested that fibromyalgia (FM), a chronic widespread pain disorder, exhibits altered thalamic structure and function. Since the thalamus has extensive reciprocal connection with the cortex, structural and functional thalamic alterations in FM might be linked to aberrant thalamocortical oscillation. This study investigated the presence of abnormal brain rhythmicity in low- and high-frequency bands during resting state in patients with FM and their relationship to clinical pain symptom. Spontaneous magnetoencephalography (MEG) activity was recorded in 18 females with FM and 18 age- and sex-matched healthy control (HC) subjects. The most remarkable finding was that FM patients had general increases in theta, beta and gamma power along with a slowing of the dominant alpha peak. Increased spectral powers in the theta-band were primarily localized to the left dorsolateral prefrontal (DLPFC) and orbitofrontal cortex (OFC). Beta and gamma over-activation were localized to insular, primary motor and primary and secondary somatosensory (S2) cortices, as well as the DLPFC and OFC. Furthermore, enhanced high-frequency oscillatory activities in the DLPFC and OFC were associated with higher affective pain scores in patients with FM. Our results demonstrate that FM patients feature enhanced low- and high-frequency oscillatory activity in the brain areas related to cognitive and emotional modulation of pain. Increased low- and high-frequency activity of the prefrontal cortex may contribute to persistent perception of pain in FM. Therapeutic intervention based on manipulating neural oscillation to restore normal thalamocortical rhythmicity may be beneficial to pain relief in FM. PMID:27014041

  17. Single-phase vs. Three-phase High Power High Frequency Transformers

    OpenAIRE

    Xue, Jing

    2010-01-01

    This thesis proposes one comparison methodology for single and three-phase high power high frequency transformers in power conversion systems. The objective is to compare the volume of the transformers. And single and three-phase Dual Active Bridge Converter (DAB1 and DAB3) topologies with single and three-phase isolating transformers are selected for the transformer comparison. Design optimization of power transformer has been studied and simplified models have been built for the single and ...

  18. High-frequency cranial electrostimulation (CES) in patients with probable Alzheimer's disease.

    Science.gov (United States)

    Scherder, Erik J A; van Tol, M J; Swaab, D F

    2006-07-01

    In a previous study, low-frequency cranial electrostimulation did not improve cognition and (affective) behavior in patients with probable Alzheimer's disease. In the present study, 21 Alzheimer's disease patients, divided into an experimental (n = 11) and a control group (n = 10), were treated for 30 mins/day, 5 days/wk, for 6 wks with high-frequency cranial electrostimulation. Similar to the previous study, no improvements on cognition and (affective) behavior were found.

  19. High-Frequency Sound Interaction in Ocean Sediments: Modeling Environmental Controls

    Science.gov (United States)

    2016-06-07

    experiments is testing the various acoustic models proposed to account for the anomalous penetration of high-frequency energy at subcritical angles...frequency bottom interaction models to sites of naval interest . OBJECTIVES The objectives for the current year were to conduct surveys of the proposed sites...survey rectangle was fine to medium sand. Depth ranged between 15-18 meters with a uniform acoustic backscatter strength throughout most of the area

  20. Control of extracellular cleavage of ProBDNF by high frequency neuronal activity

    OpenAIRE

    Nagappan, Guhan; Zaitsev, Eugene; Senatorov, Vladimir V.; Yang, Jianmin; Hempstead, Barbara L.; Lu, Bai

    2009-01-01

    Pro- and mature neurotrophins often elicit opposing biological effects. For example, mature brain-derived neurotrophic factor (mBDNF) is critical for long-term potentiation induced by high-frequency stimulation, whereas proBDNF facilitate long-term depression induced by low-frequency stimulation. Because mBDNF is derived from proBDNF by endoproteolytic cleavage, mechanisms regulating the cleavage of proBDNF may control the direction of BDNF regulation. Using methods that selectively detect pr...

  1. High-Frequency Percussive Ventilation: Pneumotachograph Validation and Tidal Volume Analysis

    Science.gov (United States)

    2010-06-01

    Meredith Pride for their invaluable research efforts. Table 3. Mean Difference in High-Frequency VT* Relative to Test- Lung VT† Difference in High...respiratory gas on pneumotachographic measurement of ventilation in newborn infants. Biomed Tech 1994;39(4):85-92. 15. Jackson AC, Vinegar A. A technique...for measuring frequency re- sponse of pressure, volume, and flow transducers. J Appl Physiol 1979;47(2):462-467. 16. Finucane KE, Egan BA, Dawson SV

  2. Iloprost drug delivery during infant conventional and high-frequency oscillatory ventilation

    OpenAIRE

    Robert M. DiBlasi; Crotwell, Dave N.; Shen, Shuijie; Zheng, Jiang; Fink, James B.; Yung, Delphine

    2016-01-01

    Iloprost is a selective pulmonary vasodilator approved for inhalation by the Food and Drug Administration. Iloprost has been increasingly used in the management of critically ill neonates with hypoxic lung disease. This in vitro study was designed to test the hypothesis that aerosol drug delivery could be effectively administered to infants with both conventional ventilation and high-frequency oscillatory ventilation (HFOV). A neonatal test lung model configured with newborn lung mechanics wa...

  3. High-frequency averaging in semi-classical Hartree-type equations

    CERN Document Server

    Giannoulis, Johannes; Sparber, Christof

    2009-01-01

    We investigate the asymptotic behavior of solutions to semi-classical Schroedinger equations with nonlinearities of Hartree type. For a weakly nonlinear scaling, we show the validity of an asymptotic superposition principle for slowly modulated highly oscillatory pulses. The result is based on a high-frequency averaging effect due to the nonlocal nature of the Hartree potential, which inhibits the creation of new resonant waves. In the proof we make use of the framework of Wiener algebras.

  4. B-2 Extremely High Frequency SATCOM and Computer Increment 1 (B-2 EHF Inc 1)

    Science.gov (United States)

    2015-12-01

    Selected Acquisition Report (SAR) RCS: DD-A&T(Q&A)823-224 B-2 Extremely High Frequency SATCOM and Computer Increment 1 (B-2 EHF Inc 1) As of FY...10 Track to Budget 11 Cost and Funding 13 Low Rate Initial Production 19 Foreign Military Sales 20 Nuclear Costs 20 Unit Cost...Document CLIN - Contract Line Item Number CPD - Capability Production Document CY - Calendar Year DAB - Defense Acquisition Board DAE - Defense

  5. Fatigue behaviour of welded joints treated by high frequency hammer peening: Part 1 , experimental study

    OpenAIRE

    LE QUILLIEC, Guenhael; LIEURADE, Henri Paul; BOUSSEAU, Marc; DRISSI-HABTI, Monssef; INGLEBERT, Geneviève; MACQUET, Pascal; JUBIN, Laurent

    2011-01-01

    High frequency hammer peening is a recent improvement method which is probably one of the most effective for treating welded assemblies. A number of experimental results relating to this process are presented in this article. These results lead to better understand the mechanisms of the process, to outline the influence of the operating parameters and to confirm the role played by the initial quality of the welds. In the long run, the aim of this study is to propose an industrially applicable...

  6. Mechanics and modelling of high frequency mechanical impact and its effect on fatigue

    OpenAIRE

    LE QUILLIEC, Guenhael; LIEURADE, Henri Paul; DRISSI-HABTI, Monssef; INGLEBERT, Geneviève; MACQUET, Pascal; JUBIN, Laurent; BOUSSEAU, Marc

    2013-01-01

    High frequency mechanical impact is a recent improvement method which is probably one of the most effective for treating welded assemblies. A number of experimental results relating to this process are presented in this article. These results lead to better understand the mechanisms of the process, to outline the influence of the operating parameters and to confirm the role played by the initial quality of treated welds. In addition, a process is proposed in order to numerically estimate the ...

  7. Fatigue Behaviour of Welded Joints Treated by High Frequency Hammer Peening: Part I , Experimental Study

    OpenAIRE

    LE QUILLIEC, Guenhael; Lieurade, Henri-Paul; BOUSSEAU, Marc; DRISSI-HABTI, Monssef; INGLEBERT, Geneviève; MACQUET, Pascal; JUBIN, Laurent

    2011-01-01

    International audience; High frequency hammer peening is a recent improvement method which is probably one of the most effective for treating welded assemblies. A number of experimental results relating to this process are presented in this article. These results lead to better understand the mechanisms of the process, to outline the influence of the operating parameters and to confirm the role played by the initial quality of the welds. In the long run, the aim of this study is to propose an...

  8. Design aspects of high strength steel welded structures improved by high frequency mechanical impact (HFMI) treatment

    OpenAIRE

    Yildirim, Halid Can

    2013-01-01

    This doctoral study is concerned with the fatigue strength of welded steel structures which are improved by high frequency mechanical impact (HFMI) treatment. A comprehensive evaluation of 417 HFMI test data obtained from the literature and 24 HFMI fatigue data tested as a part of this work are studied. According to the statistical analyses an S-N slope of five (5) is proposed. A yield strength correction procedure which relates the material yield strength (fy) to fatigue is presented and ver...

  9. Self-stabilization of high-frequency oscillations in semiconductor superlattices by time-delay autosynchronization.

    Science.gov (United States)

    Schlesner, J; Amann, A; Janson, N B; Just, W; Schöll, E

    2003-12-01

    We present a scheme to stabilize high-frequency domain oscillations in semiconductor superlattices by a time-delayed feedback loop. Applying concepts from chaos control theory we propose to control the spatiotemporal dynamics of fronts of accumulation and depletion layers which are generated at the emitter and may collide and annihilate during their transit, and thereby suppress chaos. The proposed method only requires the feedback of internal global electrical variables, viz., current and voltage, which makes the practical implementation very easy.

  10. The Relevance of the High Frequency Audiometry in Tinnitus Patients with Normal Hearing in Conventional Pure-Tone Audiometry

    Directory of Open Access Journals (Sweden)

    Veronika Vielsmeier

    2015-01-01

    Full Text Available Objective. The majority of tinnitus patients suffer from hearing loss. But a subgroup of tinnitus patients show normal hearing thresholds in the conventional pure-tone audiometry (125 Hz–8 kHz. Here we explored whether the results of the high frequency audiometry (>8 kHz provide relevant additional information in tinnitus patients with normal conventional audiometry by comparing those with normal and pathological high frequency audiometry with respect to their demographic and clinical characteristics. Subjects and Methods. From the database of the Tinnitus Clinic at Regensburg we identified 75 patients with normal hearing thresholds in the conventional pure-tone audiometry. We contrasted these patients with normal and pathological high-frequency audiogram and compared them with respect to gender, age, tinnitus severity, pitch, laterality and duration, comorbid symptoms and triggers for tinnitus onset. Results. Patients with pathological high frequency audiometry were significantly older and had higher scores on the tinnitus questionnaires in comparison to patients with normal high frequency audiometry. Furthermore, there was an association of high frequency audiometry with the laterality of tinnitus. Conclusion. In tinnitus patients with normal pure-tone audiometry the high frequency audiometry provides useful additional information. The association between tinnitus laterality and asymmetry of the high frequency audiometry suggests a potential causal role for the high frequency hearing loss in tinnitus etiopathogenesis.

  11. Monitoring of hidden damage in multi-layered aerospace structures using high-frequency guided waves

    Science.gov (United States)

    Semoroz, A.; Masserey, B.; Fromme, P.

    2011-04-01

    Aerospace structures contain multi-layered components connected by fasteners, where fatigue cracks and disbonds or localized lack of sealant can develop due to cyclic loading conditions and stress concentration. High frequency guided waves propagating along such a structure allow for the efficient non-destructive testing of large components, such as aircraft wings. The type of multi-layered model structure investigated in this contribution consists of two aluminium plates adhesively bonded with an epoxy based sealant layer. Using commercially available transducer equipment, specific high frequency guided ultrasonic wave modes that penetrate through the complete thickness of the structure were excited. The wave propagation along the structure was measured experimentally using a laser interferometer. Two types of hidden damage were considered: a localized lack of sealant and small surface defects in the metallic layer facing the sealant. The detection sensitivity using standard pulse-echo measurement equipment has been quantified and the detection of small hidden defects from significant stand-off distances has been shown. Fatigue experiments were carried out and the potential of high frequency guided waves for the monitoring of fatigue crack growth at a fastener hole during cyclic loading was discussed.

  12. Application of High-frequency Electrosurgical Scalpel and Methylene Blue Staining in Endonasal Dacryocystorhinostomy

    Institute of Scientific and Technical Information of China (English)

    Zhongling Luo; Lixin Zhang; Yueguang Qiu; Xiaofang Luo

    2014-01-01

    Purpose:.To evaluate the application of a high-frequency electrosurgical scalpel and methylene blue staining in the en-donasal dacryocystorhinostomy. Methods:.This retrospective study included 37 patients (43 eyes).undergoing endonasal dacryocystorhinostomy in our hospital between 2011 and 2013 using methylene blue staining of the lacrimal sac and a high-frequency electrosurgical scalpel for cutting nasal mucosa, intraoperative stanch, and fixation of lacrimal sac and nasal mucosal flaps. Surgical efficacy, in-traoperative challenges,.and corresponding handling methods were evaluated and summarized. Results:.Among 43 eyes,.42 were successfully cured (97.7%) and the symptoms in 1 eye were improved (2.3%). Total effi-cacy rate was 100%. All surgeries were successfully performed.. No severe intraoperative complications were observed. Conclusion:.A high-frequency electrosurgical scalpel,.com-bined with methylene blue staining of the lacrimal sac, is effi-cacious for nasal mucosal cutting,.intraoperative stanch,.and fixation of mucosal flap by cauterization,.which significantly alleviates intraoperative complications and enhances surgical success rate..It deserves widespread application in clinical practice. .(Eye Science 2014; 29:25-29).

  13. A Switched Capacitor Based AC/DC Resonant Converter for High Frequency AC Power Generation

    Directory of Open Access Journals (Sweden)

    Cuidong Xu

    2015-09-01

    Full Text Available A switched capacitor based AC-DC resonant power converter is proposed for high frequency power generation output conversion. This converter is suitable for small scale, high frequency wind power generation. It has a high conversion ratio to provide a step down from high voltage to low voltage for easy use. The voltage conversion ratio of conventional switched capacitor power converters is fixed to n, 1/n or −1/n (n is the switched capacitor cell. In this paper, A circuit which can provide n, 1/n and 2n/m of the voltage conversion ratio is presented (n is stepping up the switched capacitor cell, m is stepping down the switching capacitor cell. The conversion ratio can be changed greatly by using only two switches. A resonant tank is used to assist in zero current switching, and hence the current spike, which usually exists in a classical switching switched capacitor converter, can be eliminated. Both easy operation and efficiency are possible. Principles of operation, computer simulations and experimental results of the proposed circuit are presented. General analysis and design methods are given. The experimental result verifies the theoretical analysis of high frequency AC power generation.

  14. Inactivation of bacteria and yeast using high-frequency ultrasound treatment.

    Science.gov (United States)

    Gao, Shengpu; Hemar, Yacine; Ashokkumar, Muthupandian; Paturel, Sara; Lewis, Gillian D

    2014-09-01

    High-frequency (850 kHz) ultrasound was used to inactivate bacteria and yeast at different growth phases under controlled temperature conditions. Three species of bacteria, Enterobacter aerogenes, Bacillus subtilis and Staphylococcus epidermidis as well as a yeast, Aureobasidium pullulans were considered. The study shows that high-frequency ultrasound is highly efficient in inactivating the bacteria in both their exponential and stationary growth phases, and inactivation rates of more than 99% were achieved. TEM observation suggests that the mechanism of bacteria inactivation is mainly due to acoustic cavitation generated free radicals and H2O2. The rod-shaped bacterium B. subtilis was also found to be sensitive to the mechanical effects of acoustic cavitation. The study showed that the inactivation process continued even after ultrasonic processing cessed due to the presence of H2O2, generated during acoustic cavitation. Compared to bacteria, the yeast A. pullulans was found to be more resistant to high-frequency ultrasound treatment.

  15. Potential Sources of High Frequency and Biphonic Vocalization in the Dhole (Cuon alpinus.

    Directory of Open Access Journals (Sweden)

    Roland Frey

    Full Text Available Biphonation, i.e. two independent fundamental frequencies in a call spectrum, is a prominent feature of vocal activity in dog-like canids. Dog-like canids can produce a low (f0 and a high (g0 fundamental frequency simultaneously. In contrast, fox-like canids are only capable of producing the low fundamental frequency (f0. Using a comparative anatomical approach for revealing macroscopic structures potentially responsible for canid biphonation, we investigated the vocal anatomy for 4 (1 male, 3 female captive dholes (Cuon alpinus and for 2 (1 male, 1 female wild red fox (Vulpes vulpes. In addition, we analyzed the acoustic structure of vocalizations in the same dholes that served postmortem as specimens for the anatomical investigation. All study dholes produced both high-frequency and biphonic calls. The anatomical reconstructions revealed that the vocal morphologies of the dhole are very similar to those of the red fox. These results suggest that the high-frequency and biphonic calls in dog-like canids can be produced without specific anatomical adaptations of the sound-producing structures. We discuss possible production modes for the high-frequency and biphonic calls involving laryngeal and nasal structures.

  16. A comprehensive inversion approach for feedforward compensation of piezoactuator system at high frequency

    Science.gov (United States)

    Tian, Lizhi; Xiong, Zhenhua; Wu, Jianhua; Ding, Han

    2016-09-01

    Motion control of the piezoactuator system over broadband frequencies is limited due to its inherent hysteresis and system dynamics. One of the suggested ways is to use feedforward controller to linearize the input-output relationship of the piezoactuator system. Although there have been many feedforward approaches, it is still a challenge to develop feedforward controller for the piezoactuator system at high frequency. Hence, this paper presents a comprehensive inversion approach in consideration of the coupling of hysteresis and dynamics. In this work, the influence of dynamics compensation on the input-output relationship of the piezoactuator system is investigated first. With system dynamics compensation, the input-output relationship of the piezoactuator system will be further represented as rate-dependent nonlinearity due to the inevitable dynamics compensation error, especially at high frequency. Base on this result, the feedforward controller composed by a cascade of linear dynamics inversion and rate-dependent nonlinearity inversion is developed. Then, the system identification of the comprehensive inversion approach is proposed. Finally, experimental results show that the proposed approach can improve the performance on tracking of both periodic and non-periodic trajectories at medium and high frequency compared with the conventional feedforward approaches.

  17. High frequency switched-mode stimulation can evoke postsynaptic responses in cerebellar principal neurons

    Directory of Open Access Journals (Sweden)

    Marijn Van Dongen

    2015-03-01

    Full Text Available This paper investigates the efficacy of high frequency switched-mode neural stimulation. Instead of using a constant stimulation amplitude, the stimulus is switched on and off repeatedly with a high frequency (up to 100kHz duty cycled signal. By means of tissue modeling that includes the dynamic properties of both the tissue material as well as the axon membrane, it is first shown that switched-mode stimulation depolarizes the cell membrane in a similar way as classical constant amplitude stimulation.These findings are subsequently verified using in vitro experiments in which the response of a Purkinje cell is measured due to a stimulation signal in the molecular layer of the cerebellum of a mouse. For this purpose a stimulator circuit is developed that is able to produce a monophasic high frequency switched-mode stimulation signal. The results confirm the modeling by showing that switched-mode stimulation is able to induce similar responses in the Purkinje cell as classical stimulation using a constant current source. This conclusion opens up possibilities for novel stimulation designs that can improve the performance of the stimulator circuitry. Care has to be taken to avoid losses in the system due to the higher operating frequency.

  18. Automotive Interior Noise Reduction in High Frequency Using Statistical Energy Analysis

    Institute of Scientific and Technical Information of China (English)

    CHEN Xin; WANG Deng-feng; ZHU Lei; MA Zheng-dong

    2009-01-01

    Statistical energy analysis (SEA) is an effective method for predicting high frequency vibro-acoustic performance of automobiles. A full vehicle SEA model is presented for interior noise reduction. It is composed of a number of subsystems based on a 3D model with all parameters for each subsystem. The excitation inputs are measured through road tests in different conditions, including inputs from the engine vibration and the sound pressure of the engine bay. The accuracy in high frequency of SEA model is validated, by comparing the analysis results with the testing pressure level data at driver's right ear. Noise contribution and sensitivity of key subsystems are analyzed. Finally, the effectiveness of noise reduction is verified. Based on the SEA model, an approach combining test and simulation is proposed for the noise vibration and harshness (NVH) design in vehicle development. It contains building the SEA model, testing for subsystem parameter identification, validating the simulation model, identifying subsystem power inputs, analyzing the design sensitivity. An example is given to demonstrate the interior noise reduction in high frequency.

  19. High-Frequency Deep Brain Stimulation of the Putamen Improves Bradykinesia in Parkinson’s Disease

    Science.gov (United States)

    Montgomery, Erwin B.; Huang, He; Walker, Harrison C.; Guthrie, Barton L.; Watts, Ray L.

    2014-01-01

    Deep brain stimulation is effective for a wide range of neurological disorders; however, its mechanisms of action remain unclear. With respect to Parkinson’s disease, the existence of multiple effective targets suggests that putamen stimulation also may be effective and raises questions as to the mechanisms of action. Are there as many mechanisms of action as there are effective targets or some single or small set of mechanisms common to all effective targets? During the course of routine surgery of the globus pallidus interna in patients with Parkinson’s disease, the deep brain stimulation lead was placed in the putamen en route to the globus pallidus interna. Recordings of hand opening and closing during high-frequency and no stimulation were made. Speed of the movements, based on the amplitude and frequency of the repetitive hand movements as well as the decay in amplitude, were studied. Hand speed in 6 subjects was statistically significantly faster during active deep brain stimulation than the no-stimulation condition. There were no statistically significant differences in decay in the amplitude of hand movements. High-frequency deep brain stimulation of the putamen improves bradykinesia in a hand-opening and -closing task in patients with Parkinson’s disease. Consequently, high-frequency deep brain stimulation of virtually every structure in the basal ganglia-thalamic-cortical system improves bradykinesia. These observations, together with microelectrode recordings reported in the literature, argue that deep brain stimulation effects may be system specific and not structure specific. PMID:21714010

  20. Zero-voltage switching converter absorbing parasitic parameters for super high frequency induction heating

    Institute of Scientific and Technical Information of China (English)

    Zheng-shi WANG; Hui-ming CHEN

    2008-01-01

    This paper presents a novel mega-Hz-level super high frequency zero-voltage soft-switching converter for induction heating power supplies. The prominent advantage of this topology is that it can absorb both inductive and capacitive parasitic components in the converter. The switch devices operate in a zero-voltage soft-switching mode. Consequently, the high voltage and high current spikes caused by parasitic inductors or capacitors oscillation do not occur in this circuit, and the high power loss caused by high frequency switching can be greatly reduced. A large value inductor is adopted between the input capacitor and the switches, thus, this novel converter shares the benefits of both voltage-type and current-type circuits simultaneously, and there are no needs of dead time between two switches. The working principles in different modes are introduced, Results of simulation and experiments operated at around 1 MHz frequency verify the validity of parasitic components absorption and show that this converter is competent for super high frequency applications.