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

Energy Technology Data Exchange (ETDEWEB)

Dowla, F

2007-03-14

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

middle range theory evaluation: bridging the theory-practice gap

African Journals Online (AJOL)

The importance underlying the practice of nursing education must continue ... describes selected middle range theory evaluation as a tool for bridging ... engaging in innovative ways of acquiring competency. ..... performances, that guides learners attitudes towards ... Reference knowledge acquired by work experience.

Dielectric characterization of materials at microwave frequency range

Directory of Open Access Journals (Sweden)

J. de los Santos

2003-01-01

Full Text Available In this study a coaxial line was used to connect a microwave-frequency Network Analyzer and a base moving sample holder for dielectric characterization of ferroelectric materials in the microwave range. The main innovation of the technique is the introduction of a special sample holder that eliminates the air gap effect by pressing sample using a fine pressure system control. The device was preliminary tested with alumina (Al2O3 ceramics and validated up to 2 GHz. Dielectric measurements of lanthanum and manganese modified lead titanate (PLTM ceramics were carried out in order to evaluate the technique for a high permittivity material in the microwave range. Results showed that such method is very useful for materials with high dielectric permittivities, which is generally a limiting factor of other techniques in the frequency range from 50 MHz to 2 GHz.

Stepped-frequency radar sensors theory, analysis and design

CERN Document Server

Nguyen, Cam

2016-01-01

This book presents the theory, analysis and design of microwave stepped-frequency radar sensors. Stepped-frequency radar sensors are attractive for various sensing applications that require fine resolution. The book consists of five chapters. The first chapter describes the fundamentals of radar sensors including applications followed by a review of ultra-wideband pulsed, frequency-modulated continuous-wave (FMCW), and stepped-frequency radar sensors. The second chapter discusses a general analysis of radar sensors including wave propagation in media and scattering on targets, as well as the radar equation. The third chapter addresses the analysis of stepped-frequency radar sensors including their principles and design parameters. Chapter 4 presents the development of two stepped-frequency radar sensors at microwave and millimeter-wave frequencies based on microwave integrated circuits (MICs), microwave monolithic integrated circuits (MMICs) and printed-circuit antennas, and discusses their signal processing....

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

International Nuclear Information System (INIS)

Hantao Ji; Russell Kulsrud; William Fox; Masaaki Yamada

2005-01-01

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

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

DEFF Research Database (Denmark)

Nielsen, Kristian; Rasmussen, Henrik K.; Adam, Aurèle J.L.

2009-01-01

structure proves that the fiber is single-moded over a wide frequency range, and we see the onset of higher-order modes at high frequencies as well as indication of microporous guiding at low frequencies and high porosity of the fiber. Transmission spectroscopy demonstrates low-loss propagation (

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

Science.gov (United States)

Sugimoto, Tsuneyoshi; Abe, Touma

2011-07-01

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

INVESTIGATION OF THE FREQUENCY-TEMPERATURE RELATIONSHIP OF THE DIELECTRIC PERMITTIVITY OF THE PZT PIEZOCERAMICS IN THE LOW FREQUENCY RANGE

Directory of Open Access Journals (Sweden)

A. I. ZOLOTAREVSKIY

2018-05-01

Full Text Available Purpose. To investigate the frequency-temperature relationship of the dielectric permittivity of PZT piezoceramics in the low frequency range. Methodology. To obtain the frequency-temperature relationship of the dielectric permittivity of the PZT piezoceramics, a technique was used to determine the capacitance of the capacitor, between which plates the sample was placed. The value of the dielectric permittivity of the sample was calculated from the capacitor capacitance obtained. Findings. The frequency-temperature relationship of the dielectric permittivity of the PZT piezoceramics in the low frequency range has been obtained by the authors. The dielectric permittivity is not practically related to the frequency of the alternating voltage at a low temperature, with increasing in temperature its value increases and frequency relationship is observed. The temperature relationship of the dielectric permittivity of the PZT piezoceramics is satisfactorily described by the exponential functional dependence in the low-temperature range. The activation energy of the PZT piezoceramics polarization is determined from the graph of the dependence of the logarithm of the dielectric permittivity upon the inverse temperature. Different values of the activation energy for the two temperature regions prove on the existence of different mechanisms of the PZT piezoceramics polarization in the temperature range being investigated. Originality. The authors investigated the frequency-temperature relationship of the dielectric permittivity of the PZT piezoceramics in the low-frequency range. It is established that the temperature relationship of the dielectric permittivity of the PZT piezoceramics is satisfactorily described by an exponential functional relationship in the lowtemperature range. The activation energy of polarization is determined for two temperature sections. Practical value. The research results can be used to study the mechanism of polarization of

Experimental Limits on Gravitational Waves in the MHz frequency Range

Energy Technology Data Exchange (ETDEWEB)

Lanza, Robert Jr. [Univ. of Chicago, IL (United States)

2015-03-01

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

Analysis of self-consistency effects in range-separated density-functional theory with Møller-Plesset perturbation theory

DEFF Research Database (Denmark)

Fromager, Emmanuel; Jensen, Hans Jørgen Aagaard

2011-01-01

Range-separated density-functional theory combines wave function theory for the long-range part of the two-electron interaction with density-functional theory for the short-range part. When describing the long-range interaction with non-variational methods, such as perturbation or coupled......-cluster theories, self-consistency effects are introduced in the density functional part, which for an exact solution requires iterations. They are generally assumed to be small but no detailed study has been performed so far. Here, the authors analyze self-consistency when using Møller-Plesset-type (MP......) perturbation theory for the long range interaction. The lowest-order self-consistency corrections to the wave function and the energy, that enter the perturbation expansions at the second and fourth order, respectively, are both expressed in terms of the one-electron reduced density matrix. The computational...

Investigation of a slot nanoantenna in optical frequency range

Science.gov (United States)

Dinesh kumar, V.; Asakawa, Kiyoshi

2009-11-01

Following the analogy of radio frequency slot antenna and its complementary dipole, we propose the implementation of a slot nanoantenna (SNA) in the optical frequency range. Using finite-difference time-domain (FDTD) method, we investigate the electromagnetic (EM) properties of a SNA formed in a thin gold film and compare the results with the properties of a gold dipole nanoantenna (DNA) of the same dimension as the slot. It is found that the response of the SNA is very similar to the DNA, like their counterparts in the radio frequency (RF) range. The SNA can enhance the near field intensity of incident field which strongly depends on its feedgap dimension. The resonance of the SNA is influenced by its slot length; for the increasing slot length, resonant frequency decreases whereas the sharpness of resonance increases. Besides, the resonance of the SNA is found sensitive to the thickness of metal film, when the latter is smaller than the skin depth. The effect of polarization of incident field on the EM response of the SNA was examined; the field enhancement is optimum when polarization is parallel to the feedgap. Finally, we calculate the radiation patterns of the DNA and SNA and compare them with those of the RF dipole antenna. The radiation pattern of the SNA is found to be independent of its slot length when excited at resonant frequency. To the best of our knowledge, this is the first study on a slot antenna in the optical frequency.

A Wide Lock-Range Referenceless CDR with Automatic Frequency Acquisition

OpenAIRE

Seon-Kyoo Lee; Young-Sang Kim; Hong-June Park; Jae-Yoon Sim

2011-01-01

A wide lock-range referenceless CDR circuit is proposed with an automatic tracking of data rate. For efficient frequency acquisition, a DLL-based loop is used with a simple phase/frequency detector to extract 1-bit period of input data stream. The CDR, implemented in a 65 nm CMOS, shows a lock range of 650 Mb/s-to-8 Gb/s and BER of less than 10-12 at 8 Gb/s with low power consumption.

A Wide Lock-Range Referenceless CDR with Automatic Frequency Acquisition

Directory of Open Access Journals (Sweden)

Seon-Kyoo Lee

2011-01-01

Full Text Available A wide lock-range referenceless CDR circuit is proposed with an automatic tracking of data rate. For efficient frequency acquisition, a DLL-based loop is used with a simple phase/frequency detector to extract 1-bit period of input data stream. The CDR, implemented in a 65 nm CMOS, shows a lock range of 650 Mb/s-to-8 Gb/s and BER of less than 10-12 at 8 Gb/s with low power consumption.

Nano-resonator frequency response based on strain gradient theory

International Nuclear Information System (INIS)

Miandoab, Ehsan Maani; Yousefi-Koma, Aghil; Pishkenari, Hossein Nejat; Fathi, Mohammad

2014-01-01

This paper aims to explore the dynamic behaviour of a nano-resonator under ac and dc excitation using strain gradient theory. To achieve this goal, the partial differential equation of nano-beam vibration is first converted to an ordinary differential equation by the Galerkin projection method and the lumped model is derived. Lumped parameters of the nano-resonator, such as linear and nonlinear springs and damper coefficients, are compared with those of classical theory and it is demonstrated that beams with smaller thickness display greater deviation from classical parameters. Stable and unstable equilibrium points based on classic and non-classical theories are also compared. The results show that, regarding the applied dc voltage, the dynamic behaviours expected by classical and non-classical theories are significantly different, such that one theory predicts the un-deformed shape as the stable condition, while the other theory predicts that the beam will experience bi-stability. To obtain the frequency response of the nano-resonator, a general equation including cubic and quadratic nonlinearities in addition to parametric electrostatic excitation terms is derived, and the analytical solution is determined using a second-order multiple scales method. Based on frequency response analysis, the softening and hardening effects given by two theories are investigated and compared, and it is observed that neglecting the size effect can lead to two completely different predictions in the dynamic behaviour of the resonators. The findings of this article can be helpful in the design and characterization of the size-dependent dynamic behaviour of resonators on small scales. (paper)

Composite Broadcasting and Ranging via a Satellite Dual-Frequency MPPSK System

Directory of Open Access Journals (Sweden)

Yu Yao

2013-01-01

Full Text Available Since digital video broadcasting via satellite (DVB-S signals are “inefficient”, regarding the amount of information they convey on the bandwidth they occupy, a joint broadcasting and ranging system would constitute a unique platform for future digital video broadcasting satellite services effecting the essential tasks of satellite navigation system and direct to home (DTH services, in terms of both spectrum efficiency and cost effectiveness. In this paper, the design of dual frequency M-ary position phase shift keying (MPPSK system which is suitable for, respectively, performing both data transmission and range measurement is proposed. The approach is based on MPPSK modulation waveforms utilized in digital video broadcasting. In particular, requirements that allow for employing such signals for range measurements with high accuracy and high range are investigated. Also, the relationship between the frequency difference of dual frequency MPPSK system and range accuracy is discussed. Moreover, the selection of MPPSK modulation parameter for data rate and ranging is considered. In addition to theoretical considerations, the paper presents system simulations and measurement results of new systems, demonstrating the high spectral utilization of integrated broadcasting and ranging applications.

PERMITTIVITY RESEARCH OF BIOLOGICAL SOLUTIONS IN GIGAHERTZ FREQUENCY RANGE

Directory of Open Access Journals (Sweden)

Anton S. Demin

2017-07-01

Full Text Available Subject of Research. We present results of permittivity research in gigahertz frequency range for saline and glucose solutions used in medical practice. Experiment results are substantiated theoretically on the basis of Debye-Cole model. Method. Researches have been carried out on blood plasma of healthy donor, water, normal saline and glucose solutions with different concentration from 3 to 12 mmol/l. Experiments have been performed by an active nearfield method based on measuring the impedance of a plane air-liquid boundary with open end of coaxial waveguide in the frequency range from 1 to 12 GHz. Measurement results have been processed with the use of vector analyzer computer system from Rohde & Schwarz. Transmittance spectra have been determined by means of IR-spectrometer from TENZOR-Bruker. Main Results. Simulation results have shown good agreement between the experimental results and the model, as well as the choice of the main parameters of the Debye-Cole model in the studied frequency range for all media. It has been shown that the range of 3-6 GHz can be considered as the main one in the development of diagnostic sensors for the non-invasive analysis of the glucose concentration in the human blood. Practical Relevance. Electrodynamic models of test fluid replacing human blood give the possibility to simulate the sensor basic characteristics for qualitative and quantitative estimation of glucose concentration in human blood and can be used to create an experimental sample of a non- invasive glucometer.

Ultrafast optical ranging using microresonator soliton frequency combs

Science.gov (United States)

Trocha, P.; Karpov, M.; Ganin, D.; Pfeiffer, M. H. P.; Kordts, A.; Wolf, S.; Krockenberger, J.; Marin-Palomo, P.; Weimann, C.; Randel, S.; Freude, W.; Kippenberg, T. J.; Koos, C.

2018-02-01

Light detection and ranging is widely used in science and industry. Over the past decade, optical frequency combs were shown to offer advantages in optical ranging, enabling fast distance acquisition with high accuracy. Driven by emerging high-volume applications such as industrial sensing, drone navigation, or autonomous driving, there is now a growing demand for compact ranging systems. Here, we show that soliton Kerr comb generation in integrated silicon nitride microresonators provides a route to high-performance chip-scale ranging systems. We demonstrate dual-comb distance measurements with Allan deviations down to 12 nanometers at averaging times of 13 microseconds along with ultrafast ranging at acquisition rates of 100 megahertz, allowing for in-flight sampling of gun projectiles moving at 150 meters per second. Combining integrated soliton-comb ranging systems with chip-scale nanophotonic phased arrays could enable compact ultrafast ranging systems for emerging mass applications.

Modal spectral analysis of piping: Determination of the significant frequency range

International Nuclear Information System (INIS)

Geraets, L.H.

1981-01-01

This paper investigates the influence of the number of modes on the response of a piping system in a dynamic modal spectral analysis. It shows how the analysis can be limited to a specific frequency range of the pipe (independent of the frequency range of the response spectrum), allowing cost reduction without loss in accuracy. The 'missing mass' is taken into account through an original technique. (orig./HP)

A Middle-Range Theory for Diabetes Self-management Mastery.

Science.gov (United States)

Fearon-Lynch, Jennifer A; Stover, Caitlin M

2015-01-01

Diabetes mellitus is the seventh leading cause of death in America and affects 382 million people worldwide. Individuals with diabetes must manage the complexity of the disease, its treatment, and complications to avert deleterious consequences associated with the illness. However, not all patients with diabetes successfully gain mastery to positively impact self-management. A new middle-range theory is proposed that merges 2 extant theories, theory of mastery and organismic integration theory, to better understand this human response. The theories' philosophical, theoretical, and conceptual perspectives were examined and relational properties synthesized to provide a conceptual representation of the phenomenon of interest.

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

Science.gov (United States)

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

2014-01-01

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

Interactive Theory of Breastfeeding: creation and application of a middle-range theory

Directory of Open Access Journals (Sweden)

Cândida Caniçali Primo

Full Text Available ABSTRACT Objective: To describe a breastfeeding theory based on King's Conceptual System. Method: Theoretical study that used analysis of concept, assertion synthesis, and derivation of theory for the creation of a new theory. Results: King's system components were associated with elements of the breastfeeding process and a middle-range theory was created, which describes, explains, predicts, and prescribes breastfeeding by analyzing factors that precede and affect it, as well as their consequences on the breastfeeding process. Conclusion: The Breastfeeding Interactive Model is abstract enough to be applied in different social, cultural, political, and economic contexts, because it conceptualizes breastfeeding in systemic, dynamic, and procedural aspects. Based on a conceptual model of nursing, it contributes to the scientific construction of the subject; however it can also potentially be applied by other professionals involved in breastfeeding assistance.

Modal density of rectangular structures in a wide frequency range

Science.gov (United States)

Parrinello, A.; Ghiringhelli, G. L.

2018-04-01

A novel approach to investigate the modal density of a rectangular structure in a wide frequency range is presented. First, the modal density is derived, in the whole frequency range of interest, on the basis of sound transmission through the infinite counterpart of the structure; then, it is corrected by means of the low-frequency modal behavior of the structure, taking into account actual size and boundary conditions. A statistical analysis reveals the connection between the modal density of the structure and the transmission of sound through its thickness. A transfer matrix approach is used to compute the required acoustic parameters, making it possible to deal with structures having arbitrary stratifications of different layers. A finite element method is applied on coarse grids to derive the first few eigenfrequencies required to correct the modal density. Both the transfer matrix approach and the coarse grids involved in the finite element analysis grant high efficiency. Comparison with alternative formulations demonstrates the effectiveness of the proposed methodology.

Low-frequency-high-intensity limit of the Keldysh-Faisal-Reiss theory

International Nuclear Information System (INIS)

Bauer, Jaroslaw

2006-01-01

When a frequency of the circularly polarized laser field approaches zero the above threshold ionization rate should approach the well-known static-field limit of tunneling ionization. In the high-intensity limit of the laser field the Keldysh-Faisal-Reiss (KFR) theory is expected to be valid. For the ground state of a hydrogen atom we study various forms of the KFR theory when both conditions: ω<<1 a.u. and γ<<1 (ω is the frequency and γ the Keldysh parameter) are satisfied. For the circularly polarized laser field ionization rate in the Keldysh theory [which utilizes the length gauge (d(vector sign)·E(vector sign)) form of the matrix element] is calculated analytically. We show numerically that if the WKB Coulomb correction in the final state of the ionized electron is included, the Keldysh theory gives the correct result in the tunneling domain. In the barrier-suppression regime the Keldysh theory without this correction gives ionization rates close to the exact static-field results. The Reiss theory [which utilizes the velocity gauge (p(vector sign)·A(vector sign)) form of the matrix element] leads to too small ionization rates in the limit ω→0, γ→0

Optimal Frequency Ranges for Sub-Microsecond Precision Pulsar Timing

Science.gov (United States)

Lam, Michael Timothy; McLaughlin, Maura; Cordes, James; Chatterjee, Shami; Lazio, Joseph

2018-01-01

Precision pulsar timing requires optimization against measurement errors and astrophysical variance from the neutron stars themselves and the interstellar medium. We investigate optimization of arrival time precision as a function of radio frequency and bandwidth. We find that increases in bandwidth that reduce the contribution from receiver noise are countered by the strong chromatic dependence of interstellar effects and intrinsic pulse-profile evolution. The resulting optimal frequency range is therefore telescope and pulsar dependent. We demonstrate the results for five pulsars included in current pulsar timing arrays and determine that they are not optimally observed at current center frequencies. We also find that arrival-time precision can be improved by increases in total bandwidth. Wideband receivers centered at high frequencies can reduce required overall integration times and provide significant improvements in arrival time uncertainty by a factor of $\\sim$$\\sqrt{2}$ in most cases, assuming a fixed integration time. We also discuss how timing programs can be extended to pulsars with larger dispersion measures through the use of higher-frequency observations.

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

International Nuclear Information System (INIS)

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

1983-03-01

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

Flight nursing expertise: towards a middle-range theory

Science.gov (United States)

Reimer, Andrew P.; Moore, Shirley M.

2010-01-01

Aim This paper presents a middle-range Theory of Flight Nursing Expertise. Background Rotary-wing (helicopter) medical transport has grown rapidly in the USA since its introduction, particularly during the past 5 years. Patients once considered too sick to transport are now being transported more frequently and over longer distances. Many limitations are imposed by the air medical transport environment and these require nurses to alter their practice. Data sources A literature search was conducted using Pubmed, Medline, CINAHL, secondary referencing and an Internet search from 1960 to 2008 for studies related to the focal concepts in flight nursing. Discussion The middle-range Theory of Flight Nursing Expertise is composed of nine concepts (experience, training, transport environment of care, psychomotor skills, flight nursing knowledge, cue recognition, pattern recognition, decision-making and action) and their relationships. Five propositions describe the relationships between those concepts and how they apply to flight nursing expertise. Implications for nursing After empirical testing, this theory may be a useful tool to assist novice flight nurses to attain the skills necessary to provide safe and competent care more efficiently, and may aid in designing curricula and programmes of research. Conclusion Research is needed to determine the usefulness of this theory in both rotary and fixed-wing medical transport settings, and to examine the similarities and differences related to expertise needed for different flight nurse team compositions. Curriculum and training innovations can result from increased understanding of the concepts and relationships proposed in this theory. PMID:20337803

Structural partitioning of complex structures in the medium-frequency range. An application to an automotive vehicle

Science.gov (United States)

Kassem, M.; Soize, C.; Gagliardini, L.

2011-02-01

In a recent work [ Journal of Sound and Vibration 323 (2009) 849-863] the authors presented an energy-density field approach for the vibroacoustic analysis of complex structures in the low and medium frequency ranges. In this approach, a local vibroacoustic energy model as well as a simplification of this model were constructed. In this paper, firstly an extension of the previous theory is performed in order to include the case of general input forces and secondly, a structural partitioning methodology is presented along with a set of tools used for the construction of a partitioning. Finally, an application is presented for an automotive vehicle.

Accuracy of finite-difference harmonic frequencies in density functional theory.

Science.gov (United States)

Liu, Kuan-Yu; Liu, Jie; Herbert, John M

2017-07-15

Analytic Hessians are often viewed as essential for the calculation of accurate harmonic frequencies, but the implementation of analytic second derivatives is nontrivial and solution of the requisite coupled-perturbed equations engenders a sizable memory footprint for large systems, given that these equations are not required for energy and gradient calculations in density functional theory. Here, we benchmark the alternative approach to harmonic frequencies based on finite differences of analytic first derivatives, a procedure that is amenable to large-scale parallelization. Not only for absolute frequencies but also for isotopic and conformer-dependent frequency shifts in flexible molecules, we find that the finite-difference approach exhibits mean errors numbers. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

RF-field generation in wide frequency range by electron beam

International Nuclear Information System (INIS)

Bogdanovich, B.; Nesterovich, A.; Minaev, S.

1996-01-01

A simple device for generating powerful RF oscillations in the frequency range of 100-250 MHz is considered. The two-gaps cavity is based on the quarter-wavelength coaxial line loaded by drift tubes. Frequency tuning is accomplished by using the movable shorting plunger. A permanent electron beam being modulated at the first gap return the energy at the second one. The additional tube with the permanent decelerating potential, introduced into the main drift tube, allows to decrease the drift tube length and keep the excitation conditions in frequency tuning. Both autogeneration and amplification modes are under consideration. RF-parameters of the cavity and experimental results are described. (author)

Statistical testing of the full-range leadership theory in nursing.

Science.gov (United States)

Kanste, Outi; Kääriäinen, Maria; Kyngäs, Helvi

2009-12-01

The aim of this study is to test statistically the structure of the full-range leadership theory in nursing. The data were gathered by postal questionnaires from nurses and nurse leaders working in healthcare organizations in Finland. A follow-up study was performed 1 year later. The sample consisted of 601 nurses and nurse leaders, and the follow-up study had 78 respondents. Theory was tested through structural equation modelling, standard regression analysis and two-way anova. Rewarding transformational leadership seems to promote and passive laissez-faire leadership to reduce willingness to exert extra effort, perceptions of leader effectiveness and satisfaction with the leader. Active management-by-exception seems to reduce willingness to exert extra effort and perception of leader effectiveness. Rewarding transformational leadership remained as a strong explanatory factor of all outcome variables measured 1 year later. The data supported the main structure of the full-range leadership theory, lending support to the universal nature of the theory.

Coherent laser radar with dual-frequency Doppler estimation and interferometric range detection

NARCIS (Netherlands)

Onori, D.; Scotti, F.; Laghezza, F.; Scaffardi, M.; Bogoni, A.

2016-01-01

The concept of a coherent interferometric dual frequency laser radar, that measures both the target range and velocity, is presented and experimentally demonstrated. The innovative architecture combines the dual frequency lidar concept, allowing a precise and robust Doppler estimation, with the

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

Science.gov (United States)

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

2016-05-01

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

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

International Nuclear Information System (INIS)

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

2016-01-01

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

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

Energy Technology Data Exchange (ETDEWEB)

Luo, Yingxin; Yeh, Hsien-Chi, E-mail: yexianji@mail.hust.edu.cn [MOE Key Laboratory of Fundamental Quantities Measurement, School of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China); Li, Hongyin [MOE Key Laboratory of Fundamental Quantities Measurement, School of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China); School of Automation, Huazhong University of Science and Technology, Wuhan 430074 (China)

2016-05-15

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

A current drive by using the fast wave in frequency range higher than two timeslower hybrid resonance frequency on tokamaks

Directory of Open Access Journals (Sweden)

Kim Sun Ho

2017-01-01

Full Text Available An efficient current drive scheme in central or off-axis region is required for the steady state operation of tokamak fusion reactors. The current drive by using the fast wave in frequency range higher than two times lower hybrid resonance (w>2wlh could be such a scheme in high density, high temperature reactor-grade tokamak plasmas. First, it has relatively higher parallel electric field to the magnetic field favorable to the current generation, compared to fast waves in other frequency range. Second, it can deeply penetrate into high density plasmas compared to the slow wave in the same frequency range. Third, parasitic coupling to the slow wave can contribute also to the current drive avoiding parametric instability, thermal mode conversion and ion heating occured in the frequency range w<2wlh. In this study, the propagation boundary, accessibility, and the energy flow of the fast wave are given via cold dispersion relation and group velocity. The power absorption and current drive efficiency are discussed qualitatively through the hot dispersion relation and the polarization. Finally, those characteristics are confirmed with ray tracing code GENRAY for the KSTAR plasmas.

Angle-dependent strong-field molecular ionization rates with tuned range-separated time-dependent density functional theory

Energy Technology Data Exchange (ETDEWEB)

Sissay, Adonay [Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803 (United States); Abanador, Paul; Mauger, François; Gaarde, Mette; Schafer, Kenneth J. [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803 (United States); Lopata, Kenneth, E-mail: klopata@lsu.edu [Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803 (United States); Center for Computation and Technology, Louisiana State University, Baton Rouge, Louisiana 70803 (United States)

2016-09-07

Strong-field ionization and the resulting electronic dynamics are important for a range of processes such as high harmonic generation, photodamage, charge resonance enhanced ionization, and ionization-triggered charge migration. Modeling ionization dynamics in molecular systems from first-principles can be challenging due to the large spatial extent of the wavefunction which stresses the accuracy of basis sets, and the intense fields which require non-perturbative time-dependent electronic structure methods. In this paper, we develop a time-dependent density functional theory approach which uses a Gaussian-type orbital (GTO) basis set to capture strong-field ionization rates and dynamics in atoms and small molecules. This involves propagating the electronic density matrix in time with a time-dependent laser potential and a spatial non-Hermitian complex absorbing potential which is projected onto an atom-centered basis set to remove ionized charge from the simulation. For the density functional theory (DFT) functional we use a tuned range-separated functional LC-PBE*, which has the correct asymptotic 1/r form of the potential and a reduced delocalization error compared to traditional DFT functionals. Ionization rates are computed for hydrogen, molecular nitrogen, and iodoacetylene under various field frequencies, intensities, and polarizations (angle-dependent ionization), and the results are shown to quantitatively agree with time-dependent Schrödinger equation and strong-field approximation calculations. This tuned DFT with GTO method opens the door to predictive all-electron time-dependent density functional theory simulations of ionization and ionization-triggered dynamics in molecular systems using tuned range-separated hybrid functionals.

Angle-dependent strong-field molecular ionization rates with tuned range-separated time-dependent density functional theory

International Nuclear Information System (INIS)

Sissay, Adonay; Abanador, Paul; Mauger, François; Gaarde, Mette; Schafer, Kenneth J.; Lopata, Kenneth

2016-01-01

Strong-field ionization and the resulting electronic dynamics are important for a range of processes such as high harmonic generation, photodamage, charge resonance enhanced ionization, and ionization-triggered charge migration. Modeling ionization dynamics in molecular systems from first-principles can be challenging due to the large spatial extent of the wavefunction which stresses the accuracy of basis sets, and the intense fields which require non-perturbative time-dependent electronic structure methods. In this paper, we develop a time-dependent density functional theory approach which uses a Gaussian-type orbital (GTO) basis set to capture strong-field ionization rates and dynamics in atoms and small molecules. This involves propagating the electronic density matrix in time with a time-dependent laser potential and a spatial non-Hermitian complex absorbing potential which is projected onto an atom-centered basis set to remove ionized charge from the simulation. For the density functional theory (DFT) functional we use a tuned range-separated functional LC-PBE*, which has the correct asymptotic 1/r form of the potential and a reduced delocalization error compared to traditional DFT functionals. Ionization rates are computed for hydrogen, molecular nitrogen, and iodoacetylene under various field frequencies, intensities, and polarizations (angle-dependent ionization), and the results are shown to quantitatively agree with time-dependent Schrödinger equation and strong-field approximation calculations. This tuned DFT with GTO method opens the door to predictive all-electron time-dependent density functional theory simulations of ionization and ionization-triggered dynamics in molecular systems using tuned range-separated hybrid functionals.

Magnetic losses of commercial REBCO coated conductors in the low frequency range

Science.gov (United States)

De Marzi, G.; Iannone, G.; Gambardella, U.

2018-05-01

We have investigated the frequency dependence of the magnetic losses of different 2 G commercial REBCO coated-conductor tapes in the low frequency range ∼1–10 mHz of applied magnetic field at 5 and 77 K. We explored high field range, well above the penetration field, with fields applied perpendicularly to the flat surface. We found that the in-field hysteresis losses increase with increasing frequencies in all the investigated high-temperature superconductor (HTS) tapes, following a power-law dependence. An electromagnetic 2D finite element method model, based on H-formulation, has also been implemented, in which the frequency dependence of the hysteretic loss is computed taking into account the measured power-law E(J) characteristic for the electric field, and the experimental J c(B). Experimental and numerical findings are in very good agreement, so an extrapolation to higher ramp rate values is possible, thus providing a useful basis for the assessment of the hysteresis losses in fusion and accelerator HTS magnets.

Frequency pulling in a low-voltage medium-power gyrotron

Science.gov (United States)

Luo, Li; Du, Chao-Hai; Huang, Ming-Guang; Liu, Pu-Kun

2018-04-01

Many recent biomedical applications use medium-power frequency-tunable terahertz (THz) sources, such as sensitivity-enhanced nuclear magnetic resonance, THz imaging, and biomedical treatment. As a promising candidate, a low-voltage gyrotron can generate watt-level, continuous THz-wave radiation. In particular, the frequency-pulling effect in a gyrotron, namely, the effect of the electron beam parameters on the oscillation frequency, can be used to tune the operating frequency. Most previous investigations used complicated and time-consuming gyrotron nonlinear theory to study the influence of many beam parameters on the interaction performance. While gyrotron linear theory investigation demonstrates the advantages of rapidly and clearly revealing the physical influence of individual key beam parameters on the overall system performance, this paper demonstrates systematically the use of gyrotron linear theory to study the frequency-pulling effect in a low-voltage gyrotron with either a Gaussian or a sinusoidal axial-field profile. Furthermore, simulations of a gyrotron operating in the first axial mode are carried out in the framework of nonlinear theory as a contrast. Close agreement is achieved between the two theories. Besides, some interesting results are obtained. In a low-current sinusoidal-profile cavity, the ranges of frequency variation for different axial modes are isolated from each other, and the frequency tuning bandwidth for each axial mode increases by increasing either the beam voltage or pitch factor. Lowering the voltage, the total tuning ranges are squeezed and become concentrated. However, the isolated frequency regions of each axial mode cannot be linked up unless the beam current is increased, meaning that higher current operation is the key to achieving a wider and continuous tuning frequency range. The results presented in this paper can provide a reference for designing a broadband low-voltage gyrotron.

Extending the Effective Ranging Depth of Spectral Domain Optical Coherence Tomography by Spatial Frequency Domain Multiplexing

Directory of Open Access Journals (Sweden)

Tong Wu

2016-11-01

Full Text Available We present a spatial frequency domain multiplexing method for extending the imaging depth range of a spectral domain optical coherence tomography (SDOCT system without any expensive device. This method uses two galvo scanners with different pivot-offset distances in two independent reference arms for spatial frequency modulation and multiplexing. The spatial frequency contents corresponding to different depth regions of the sample can be shifted to different frequency bands. The spatial frequency domain multiplexing SDOCT system provides an approximately 1.9-fold increase in the effective ranging depth compared with that of a conventional full-range SDOCT system. The reconstructed images of phantom and biological tissue demonstrate the expected increase in ranging depth. The parameters choice criterion for this method is discussed.

Modeling of high‐frequency seismic‐wave scattering and propagation using radiative transfer theory

Science.gov (United States)

Zeng, Yuehua

2017-01-01

This is a study of the nonisotropic scattering process based on radiative transfer theory and its application to the observation of the M 4.3 aftershock recording of the 2008 Wells earthquake sequence in Nevada. Given a wide range of recording distances from 29 to 320 km, the data provide a unique opportunity to discriminate scattering models based on their distance‐dependent behaviors. First, we develop a stable numerical procedure to simulate nonisotropic scattering waves based on the 3D nonisotropic scattering theory proposed by Sato (1995). By applying the simulation method to the inversion of M 4.3 Wells aftershock recordings, we find that a nonisotropic scattering model, dominated by forward scattering, provides the best fit to the observed high‐frequency direct S waves and S‐wave coda velocity envelopes. The scattering process is governed by a Gaussian autocorrelation function, suggesting a Gaussian random heterogeneous structure for the Nevada crust. The model successfully explains the common decay of seismic coda independent of source–station locations as a result of energy leaking from multiple strong forward scattering, instead of backscattering governed by the diffusion solution at large lapse times. The model also explains the pulse‐broadening effect in the high‐frequency direct and early arriving S waves, as other studies have found, and could be very important to applications of high‐frequency wave simulation in which scattering has a strong effect. We also find that regardless of its physical implications, the isotropic scattering model provides the same effective scattering coefficient and intrinsic attenuation estimates as the forward scattering model, suggesting that the isotropic scattering model is still a viable tool for the study of seismic scattering and intrinsic attenuation coefficients in the Earth.

Frequency-modulated laser ranging sensor with closed-loop control

Science.gov (United States)

Müller, Fabian M.; Böttger, Gunnar; Janeczka, Christian; Arndt-Staufenbiel, Norbert; Schröder, Henning; Schneider-Ramelow, Martin

2018-02-01

Advances in autonomous driving and robotics are creating high demand for inexpensive and mass-producible distance sensors. A laser ranging system (Lidar), based on the frequency-modulated continuous-wave (FMCW) method is built in this work. The benefits of an FMCW Lidar system are the low-cost components and the performance in comparison to conventional time-of-flight Lidar systems. The basic system consists of a DFB laser diode (λ= 1308 nm) and an asymmetric fiber-coupled Mach-Zehnder interferometer with a fixed delay line in one arm. Linear tuning of the laser optical frequency via injection current modulation creates a beat signal at the interferometer output. The frequency of the beat signal is proportional to the optical path difference in the interferometer. Since the laser frequency-to-current response is non-linear, a closed-loop feed-back system is designed to improve the tuning linearity, and consequently the measurement resolution. For fast active control, an embedded system with FPGA is used, resulting in a nearly linear frequency tuning, realizing a narrow peak in the Fourier spectrum of the beat signal. For free-space measurements, a setup with two distinct interferometers is built. The fully fiber-coupled Mach-Zehnder reference interferometer is part of the feed-back loop system, while the other - a Michelson interferometer - has a free-space arm with collimator lens and reflective target. A resolution of 2:0 mm for a 560 mm distance is achieved. The results for varying target distances show high consistency and a linear relation to the measured beat-frequency.

Real time analysis of electromagnetic radiation in a very wide frequency range

Energy Technology Data Exchange (ETDEWEB)

Peralta, J.A.; Reyes L, P.; Yepez, E. [Escuela Superior de Fisica y Matematicas, Instituto Politecnico Nacional, Edificio 9, U.P. Adolfo Lopez Mateos, Zacatenco, 07738 Mexico D.F. (Mexico)

2001-07-01

In this work, we present an electronic apparatus that facilitates the monitoring and analysis of electromagnetic radiation in a very wide frequency range. The device is a combination of real and virtual instruments, taking advantage of new hardware and software; the measurable range of frequencies depends on the speed of an analog/digital converter, reaching tens of Megahertz. The device has been successfully used to monitor the environmental electromagnetic radiation at very low frequency, a very useful parameter in the research of electromagnetic precursors of earthquakes. The apparatus is a new configuration and has advantages with respect to those previously used: when the attached computer is fast, Fourier analysis can be done in real time, can display simultaneously several bands, the digitized data allow a variety of methods of analysis, and the apparatus is very cheap. (Author)

Real time analysis of electromagnetic radiation in a very wide frequency range

International Nuclear Information System (INIS)

Peralta, J.A.; Reyes L, P.; Yepez, E.

2001-01-01

In this work, we present an electronic apparatus that facilitates the monitoring and analysis of electromagnetic radiation in a very wide frequency range. The device is a combination of real and virtual instruments, taking advantage of new hardware and software; the measurable range of frequencies depends on the speed of an analog/digital converter, reaching tens of Megahertz. The device has been successfully used to monitor the environmental electromagnetic radiation at very low frequency, a very useful parameter in the research of electromagnetic precursors of earthquakes. The apparatus is a new configuration and has advantages with respect to those previously used: when the attached computer is fast, Fourier analysis can be done in real time, can display simultaneously several bands, the digitized data allow a variety of methods of analysis, and the apparatus is very cheap. (Author)

Theories and experiments on the stiffening effect of high-frequency excitation for continuous elastic systems

DEFF Research Database (Denmark)

Thomsen, Jon Juel

2003-01-01

theories, each providing valuable insight. One of these is capable of predicting the vertical string lift due to stiffening in terms of simple expressions, with results that agree very well with experimental measurements for a wide range of conditions. It appears that resonance effects cannot be ignored...... for demonstrating and measuring the stiffening effect in a simple setting, in the form of a horizontal piano string subjected to longitudinal high-frequency excitation at the clamped base and free at the other end. A simplest possible theoretical model is set up and analyzed using a hierarchy of three approximating......, as was done in a few related studies¿¿unless the system has very low modal density or heavy damping; thus first-order consideration to resonance effects is included. Using the specific example with experimental support to put confidence on the proposed theory, expressions for predicting the stiffening effect...

Effective quantum theories with short- and long-range forces

International Nuclear Information System (INIS)

Koenig, Sebastian

2013-01-01

At low energies, nonrelativistic quantum systems are essentially governed by their wave functions at large distances. For this reason, it is possible to describe a wide range of phenomena with short- or even finite-range interactions. In this thesis, we discuss several topics in connection with such an effective description and consider, in particular, modifications introduced by the presence of additional long-range potentials. In the first part we derive general results for the mass (binding energy) shift of bound states with angular momentum L ≥ 1 in a periodic cubic box in two and three spatial dimensions. Our results have applications to lattice simulations of hadronic molecules, halo nuclei, and Feshbach molecules. The sign of the mass shift can be related to the symmetry properties of the state under consideration. We verify our analytical results with explicit numerical calculations. Moreover, we discuss the case of twisted boundary conditions that arise when one considers moving bound states in finite boxes. The corresponding finite-volume shifts in the binding energies play an important role in the study of composite-particle scattering on the lattice, where they give rise to topological correction factors. While the above results are derived under the assumption of a pure finite-range interaction - and are still true up to exponentially small correction in the short-range case - in the second part we consider primarily systems of charged particles, where the Coulomb force determines the long-range part of the potential. In quantum systems with short-range interactions, causality imposes nontrivial constraints on low-energy scattering parameters. We investigate these causality constraints for systems where a long-range Coulomb potential is present in addition to a short-range interaction. The main result is an upper bound for the Coulomb-modified effective range parameter. We discuss the implications of this bound to the effective feld theory (EFT) for

Joint time-frequency analysis of ultrasonic signal

International Nuclear Information System (INIS)

Oh, Sae Kyu; Nam, Ki Woo; Oh, Jung Hwan; Lee, Keun Chan; Jang, Hong Keun

1998-01-01

This paper examines the propagation of Lamb (or plate) waves in anisotropic laminated composite plates. The dispersion relations are explicitly derived using the classical plate theory (CLT), the first-order shear deformation theory (FSDT) and the exact solution (ES), Attention is paid to the lowest antisymmetric (flexural) and lowest symmetric(extensional) modes in the low frequency, long wavelength limit. Different values of shear correction factor were tested in FSDT and comparisons between flexural wave dispersion curves were made with exact results to asses the range of validity of approximate plate theories in the frequency domain.

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

Energy Technology Data Exchange (ETDEWEB)

Yin Jiangwei; Li Ning; Zheng Renliang; Li Wei; Ren Junyan, E-mail: lining@fudan.edu.c [State Key Laboratory of ASIC and System, Fudan University, Shanghai 201203 (China)

2009-05-01

This paper describes a divide-by-two injection-locked frequency divider (ILFD) for frequency synthesizers as used in multiband orthogonal frequency division multiplexing (OFDM) ultra-wideband (UWB) systems. By means of dual-injection technique and other conventional tuning techniques, such as DCCA and varactor tuning, the divider demonstrates a wide locking range while consuming much less power. The chip was fabricated in the Jazz 0.18 mum RF CMOS process. The measurement results show that the divider achieves a locking range of 4.85 GHz (6.23 to 11.08 GHz) at an input power of 8 dBm. The core circuit without the test buffer consumes only 3.7 mA from a 1.8 V power supply and has a die area of 0.38 x 0.28 mm{sup 2}. The wide locking range combined with low power consumption makes the ILFD suitable for its application in UWB systems.

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

International Nuclear Information System (INIS)

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

2009-01-01

This paper describes a divide-by-two injection-locked frequency divider (ILFD) for frequency synthesizers as used in multiband orthogonal frequency division multiplexing (OFDM) ultra-wideband (UWB) systems. By means of dual-injection technique and other conventional tuning techniques, such as DCCA and varactor tuning, the divider demonstrates a wide locking range while consuming much less power. The chip was fabricated in the Jazz 0.18 μm RF CMOS process. The measurement results show that the divider achieves a locking range of 4.85 GHz (6.23 to 11.08 GHz) at an input power of 8 dBm. The core circuit without the test buffer consumes only 3.7 mA from a 1.8 V power supply and has a die area of 0.38 x 0.28 mm 2 . The wide locking range combined with low power consumption makes the ILFD suitable for its application in UWB systems.

Load Frequency Control in Isolated Micro-Grids with Electrical Vehicles Based on Multivariable Generalized Predictive Theory

Directory of Open Access Journals (Sweden)

Jun Yang

2015-03-01

Full Text Available In power systems, although the inertia energy in power sources can partly cover power unbalances caused by load disturbance or renewable energy fluctuation, it is still hard to maintain the frequency deviation within acceptable ranges. However, with the vehicle-to-grid (V2G technique, electric vehicles (EVs can act as mobile energy storage units, which could be a solution for load frequency control (LFC in an isolated grid. In this paper, a LFC model of an isolated micro-grid with EVs, distributed generations and their constraints is developed. In addition, a controller based on multivariable generalized predictive control (MGPC theory is proposed for LFC in the isolated micro-grid, where EVs and diesel generator (DG are coordinated to achieve a satisfied performance on load frequency. A benchmark isolated micro-grid with EVs, DG, and wind farm is modeled in the Matlab/Simulink environment to demonstrate the effectiveness of the proposed method. Simulation results demonstrate that with MGPC, the energy stored in EVs can be managed intelligently according to LFC requirement. This improves the system frequency stability with complex operation situations including the random renewable energy resource and the continuous load disturbances.

Natural Frequency of F.G. Rectangular Plate by Shear Deformation Theory

International Nuclear Information System (INIS)

Shahrjerdi, Ali; Sapuan, S M; Shahzamanian, M M; Mustapha, F; Zahari, R; Bayat, M

2011-01-01

Natural frequency of functionally graded (F.G.) rectangular plate is carried out by using second-order shear deformation theory (SSDT). The material properties of functionally graded rectangular plates, except the Poisson's ratio, are assumed to vary continuously through the thickness of the plate in accordance with the exponential law distribution. The equations of motion are obtained by energy method. Numerical results for functionally graded plates are given in dimensionless graphical forms and the effects of material properties on natural frequency are determined.

Perron-Frobenius theory and frequency convergence for reducible substitutions

OpenAIRE

Lustig, Martin; Uyanik, Caglar

2016-01-01

We prove a general version of the classical Perron-Frobenius convergence property for reducible matrices. We then apply this result to reducible substitutions and use it to produce limit frequencies for factors and hence invariant measures on the associated subshift. The analogous results are well known for primitive substitutions and have found many applications, but for reducible substitutions the tools provided here were so far missing from the theory.

Handbook of ultra-wideband short-range sensing theory, sensors, applications

CERN Document Server

Sachs, Jürgen

2013-01-01

Ranging from the theoretical basis of UWB sensors via implementation issues to applications, this much-needed book bridges the gap between designers and appliers working in civil engineering, biotechnology, medical engineering, robotic, mechanical engineering, safety and homeland security. From the contents: * History * Signal and systems in time and frequency domain * Propagation of electromagnetic waves (in frequency and time domain) * UWB-Principles * UWB-antennas and applicators * Data processing * Applications.

Theory of Inpatient Circadian Care (TICC): A Proposal for a Middle-Range Theory

Science.gov (United States)

Camargo-Sanchez, Andrés; Niño, Carmen L; Sánchez, Leonardo; Echeverri, Sonia; Gutiérrez, Diana P; Duque, Andrés F; Pianeta, Oscar; Jaramillo-Gómez, Jenny A; Pilonieta, Martin A; Cataño, Nhora; Arboleda, Humberto; Agostino, Patricia V; Alvarez-Baron, Claudia P; Vargas, Rafael

2015-01-01

The circadian system controls the daily rhythms of a variety of physiological processes. Most organisms show physiological, metabolic and behavioral rhythms that are coupled to environmental signals. In humans, the main synchronizer is the light/dark cycle, although non-photic cues such as food availability, noise, and work schedules are also involved. In a continuously operating hospital, the lack of rhythmicity in these elements can alter the patient’s biological rhythms and resilience. This paper presents a Theory of Inpatient Circadian Care (TICC) grounded in circadian principles. We conducted a literature search on biological rhythms, chronobiology, nursing care, and middle-range theories in the databases PubMed, SciELO Public Health, and Google Scholar. The search was performed considering a period of 6 decades from 1950 to 2013. Information was analyzed to look for links between chronobiology concepts and characteristics of inpatient care. TICC aims to integrate multidisciplinary knowledge of biomedical sciences and apply it to clinical practice in a formal way. The conceptual points of this theory are supported by abundant literature related to disease and altered biological rhythms. Our theory will be able to enrich current and future professional practice. PMID:25767632

Theory and potentials of multi-layered plasmonic covers for multi-frequency cloaking

International Nuclear Information System (INIS)

Alu, Andrea; Engheta, Nader

2008-01-01

We have recently suggested that suitably designed plasmonic layers may cloak a given object simultaneously at multiple frequencies (Alu and Engheta 2008 Phys. Rev. Lett. 100 113901). Here, we extend our theory and fully analyze this possibility, highlighting the potentials of this plasmonic cloaking technique and its fundamental limitations dictated by the passivity and causality of the materials involved. The cloaking mechanism relies on the scattering cancellation properties of plasmonic materials. By exploiting their inherent frequency dispersion, it is possible to reduce the 'visibility' of a given object by several orders of magnitude simultaneously at multiple frequencies, such that any of the particular layers composing the cloak is responsible for noticeable reduction of scattering at each frequency of operation.

Electrodynamic properties of porous PZT-Pt films at terahertz frequency range

Energy Technology Data Exchange (ETDEWEB)

Komandin, Gennady A.; Porodinkov, Oleg E.; Spektor, Igor E.; Volkov, Alexander A. [Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation); Vorotilov, Konstantin A.; Seregin, Dmitry S.; Sigov, Alexander S. [Moscow Technological University (MIREA), Moscow (Russian Federation)

2017-01-15

Electrodynamics of Si-SiO{sub 2}-TiO{sub 2}-Pt-PZT heterostructures is studied in the frequency range from 5 to 5000 cm{sup -1} by monochromatic BWO (backward wave oscillator) and infrared Fourier-transform spectroscopy techniques to derive the dielectric characteristics of the sol-gel porous ferroelectric PbZr{sub 0.48}Ti{sub 0.52}O{sub 3} films. Broad frequency band dielectric response of PZT films with different density is constructed using the oscillator dispersion models. The main contribution to the film permittivity is found to form at frequencies below 100 cm{sup -1} depending strongly and non-linearly on the film medium density. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Ionospheric Coherence Bandwidth Measurements in the Lower VHF Frequency Range

Science.gov (United States)

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

2015-12-01

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

Frequency Diverse Array Radar Cramér-Rao Lower Bounds for Estimating Direction, Range, and Velocity

Directory of Open Access Journals (Sweden)

Yongbing Wang

2014-01-01

Full Text Available Different from phased-array radar, frequency diverse array (FDA radar offers range-dependent beampattern and thus provides new application potentials. But there is a fundamental question: what estimation performance can achieve for an FDA radar? In this paper, we derive FDA radar Cramér-Rao lower bounds (CRLBs for estimating direction, range (time delay, and velocity (Doppler shift. Two different data models including pre- and postmatched filtering are investigated separately. As the FDA radar has range-angle coupling, we use a simple transmit subaperturing strategy which divides the whole array into two subarrays, each uses a distinct frequency increment. Assuming temporally white Gaussian noise and linear frequency modulated transmit signal, extensive simulation examples are performed. When compared to conventional phased-array radar, FDA can yield better CRLBs for estimating the direction, range, and velocity. Moreover, the impacts of the element number and frequency increment are also analyzed. Simulation results show that the CRLBs decrease with the increase of the elements number and frequency increment.

Equilibrium finite-frequency noise of an interacting mesoscopic capacitor studied in time-dependent density functional theory

Science.gov (United States)

Dittmann, Niklas; Splettstoesser, Janine; Helbig, Nicole

2018-03-01

We calculate the frequency-dependent equilibrium noise of a mesoscopic capacitor in time-dependent density functional theory (TDDFT). The capacitor is modeled as a single-level quantum dot with on-site Coulomb interaction and tunnel coupling to a nearby reservoir. The noise spectra are derived from linear-response conductances via the fluctuation-dissipation theorem. Thereby, we analyze the performance of a recently derived exchange-correlation potential with time-nonlocal density dependence in the finite-frequency linear-response regime. We compare our TDDFT noise spectra with real-time perturbation theory and find excellent agreement for noise frequencies below the reservoir temperature.

Self-consistent many-body perturbation theory in range-separated density-functional theory

DEFF Research Database (Denmark)

Fromager, Emmanuel; Jensen, Hans Jørgen Aagaard

2008-01-01

effects adequately which, on the other hand, can be described by many-body perturbation theory MBPT. It is therefore of interest to develop a hybrid model which combines the best of both the MBPT and DFT approaches. This can be achieved by splitting the two-electron interaction into long-range and short...

Transformational Teaching: Connecting the Full-Range Leadership Theory and Graduate Teaching Practice

Science.gov (United States)

Kim, Won J.

2012-01-01

Reliable measurements for effective teaching are lacking. In contrast, some theories of leadership (particularly transformational leadership) have been tested and found to have efficacy in a variety of organizational settings. In this study, the full-range leadership theory, which includes transformational leadership, was applied to the…

Modelling of the dual frequency capacitive sheath in the intermediate pressure range

International Nuclear Information System (INIS)

Boyle, P C; Robiche, J; Turner, M M

2004-01-01

The nonlinearity of the plasma sheath in dual frequency capacitively coupled reactors is investigated for frequencies well above the ion plasma frequency. This work focuses on the behaviour of the voltage and the sheath width with respect to the driving current source and the collisionality regime. For typical plasma processing applications, the gas pressure ranges from a few milliTorrs to hundreds of milliTorrs, and the ion dynamics span different collisional regimes. To describe these different ion dynamics, we have used a collisionless model and a variable mobility model. The sheath widths and the voltages obtained from these two models have then been compared

Nanostructured composite layers for electromagnetic shielding in the GHz frequency range

Energy Technology Data Exchange (ETDEWEB)

Suchea, M. [Center of Materials Technology and Photonics, School of Engineering, Technological Educational Institute of Crete, Heraklion (Greece); Chemistry and Physics, “Al.I. Cuza” University of Iasi, Iasi (Romania); Tudose, I.V. [Chemistry and Physics, “Al.I. Cuza” University of Iasi, Iasi (Romania); Center of Materials Technology and Photonics, School of Engineering, Technological Educational Institute of Crete, Heraklion (Greece); Tzagkarakis, G. [Center of Materials Technology and Photonics, School of Engineering, Technological Educational Institute of Crete, Heraklion (Greece); Electrical Engineering Department, School of Engineering, Technological Educational Institute of Crete, Heraklion (Greece); Kenanakis, G. [Center of Materials Technology and Photonics, School of Engineering, Technological Educational Institute of Crete, Heraklion (Greece); Institute of Electronic Structure & Laser (IESL), Foundation for Research and Technology (FORTH) Hellas, Heraklion (Greece); Katharakis, M. [Center of Materials Technology and Photonics, School of Engineering, Technological Educational Institute of Crete, Heraklion (Greece); Drakakis, E. [Electrical Engineering Department, School of Engineering, Technological Educational Institute of Crete, Heraklion (Greece); Koudoumas, E., E-mail: koudoumas@staff.teicrete.gr [Center of Materials Technology and Photonics, School of Engineering, Technological Educational Institute of Crete, Heraklion (Greece); Electrical Engineering Department, School of Engineering, Technological Educational Institute of Crete, Heraklion (Greece)

2015-10-15

Graphical abstract: - Highlights: • Paint-like nanocomposite layers consisting of graphene nanoplatelets, PANI:HCl and PEDOT:PSS present very effective attenuation of electromagnetic radiation in the frequency range 4–20 GHz. • The shielding performance is based mostly on the graphene nanoplatelets and supported by PANI:HCl. In contrast, PEDOT:PSS plays mainly the role of the binder. • Increasing resistivity was observed to reduce the shielding effect, while increasing thickness to favor it. - Abstract: We report on preliminary results regarding the applicability of nanostructured composite layers for electromagnetic shielding in the frequency range of 4–20 GHz. Various combinations of materials were employed including poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS), polyaniline, graphene nanoplatelets, carbon nanotubes, Cu nanoparticles and Poly(vinyl alcohol). As shown, paint-like nanocomposite layers consisting of graphene nanoplatelets, polyaniline PEDOT:PSS and Poly(vinyl alcohol) can offer quite effective electromagnetic shielding, similar or even better than that of commercial products, the response strongly depending on their thickness and resistivity.

Nanostructured composite layers for electromagnetic shielding in the GHz frequency range

International Nuclear Information System (INIS)

Suchea, M.; Tudose, I.V.; Tzagkarakis, G.; Kenanakis, G.; Katharakis, M.; Drakakis, E.; Koudoumas, E.

2015-01-01

Graphical abstract: - Highlights: • Paint-like nanocomposite layers consisting of graphene nanoplatelets, PANI:HCl and PEDOT:PSS present very effective attenuation of electromagnetic radiation in the frequency range 4–20 GHz. • The shielding performance is based mostly on the graphene nanoplatelets and supported by PANI:HCl. In contrast, PEDOT:PSS plays mainly the role of the binder. • Increasing resistivity was observed to reduce the shielding effect, while increasing thickness to favor it. - Abstract: We report on preliminary results regarding the applicability of nanostructured composite layers for electromagnetic shielding in the frequency range of 4–20 GHz. Various combinations of materials were employed including poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS), polyaniline, graphene nanoplatelets, carbon nanotubes, Cu nanoparticles and Poly(vinyl alcohol). As shown, paint-like nanocomposite layers consisting of graphene nanoplatelets, polyaniline PEDOT:PSS and Poly(vinyl alcohol) can offer quite effective electromagnetic shielding, similar or even better than that of commercial products, the response strongly depending on their thickness and resistivity.

CO-ANALYSIS OF SOLAR MICROWAVE AND HARD X-RAY SPECTRAL EVOLUTIONS. I. IN TWO FREQUENCY OR ENERGY RANGES

International Nuclear Information System (INIS)

Song Qiwu; Huang Guangli; Nakajima, Hiroshi

2011-01-01

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

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

Science.gov (United States)

Li, X.

2016-12-01

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

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

International Nuclear Information System (INIS)

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

2010-01-01

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

Variables of the Theory of Planned Behavior Are Associated with Family Meal Frequency among Adolescents

Science.gov (United States)

Eto, Kumi; Koch, Pamela; Contento, Isobel R.; Adachi, Miyuki

2011-01-01

Objective: To examine associations between Theory of Planned Behavior variables and the family meal frequency. Methods: Fifth-through seventh-grade students (n = 236) completed a self-administered questionnaire in their classrooms. The relationships between Theory of Planned Behavior variables (intention, attitudes, subjective norms, and perceived…

Theory of charged particle heating by low-frequency Alfven waves

International Nuclear Information System (INIS)

Guo Zehua; Crabtree, Chris; Chen, Liu

2008-01-01

The heating of charged particles by a linearly polarized and obliquely propagating shear Alfven wave (SAW) at frequencies a fraction of the charged particle cyclotron frequency is demonstrated both analytically and numerically. Applying Lie perturbation theory, with the wave amplitude as the perturbation parameter, the resonance conditions in the laboratory frame are systematically derived. At the lowest order, one recovers the well-known linear cyclotron resonance condition k parallel v parallel -ω-nΩ=0, where v parallel is the particle velocity parallel to the background magnetic field, k parallel is the parallel wave number, ω is the wave frequency, Ω is the gyrofrequency, and n is any integer. At higher orders, however, one discovers a novel nonlinear cyclotron resonance condition given by k parallel v parallel -ω-nΩ/2=0. Analytical predictions on the locations of fixed points, widths of resonances, and resonance overlapping criteria for global stochasticity are also found to agree with those given by computed Poincare surfaces of section

Absorption properties of water-in-oil emulsions in the low THz frequency range

DEFF Research Database (Denmark)

Møller, Uffe; Folkenberg, Jacob Riis; Jepsen, Peter Uhd

We use transmission THz spectroscopy to investigate the absorption properties of water-in-oil emulsions with water content varying in the 0-20% range, relevant for a range of food products. We find that at low frequencies the effective absorption coefficient of the emulsion is suppressed compared...... to bulk water....

Intrinsic vs. spurious long-range memory in high-frequency records of environmental radioactivity

International Nuclear Information System (INIS)

Donner, R.V.; Potirakis, S.M.; Barbosa, S.M.; Matos, J.A.O.; Pereira, A.J.S.C.; Neves, L.J.M.F.

2015-01-01

The presence or absence of long-range correlations in the environmental radioactivity fluctuations has recently attracted considerable interest. Among a multiplicity of practically relevant applications, identifying and disentangling the environmental factors controlling the variable concentrations of the radioactive noble gas radon is important for estimating its effect on human health and the efficiency of possible measures for reducing the corresponding exposition. In this work, we present a critical re-assessment of a multiplicity of complementary methods that have been previously applied for evaluating the presence of long-range correlations and fractal scaling in environmental radon variations with a particular focus on the specific properties of the underlying time series. As an illustrative case study, we subsequently re-analyze two high-frequency records of indoor radon concentrations from Coimbra, Portugal, each of which spans several weeks of continuous measurements at a high temporal resolution of five minutes. Our results reveal that at the study site, radon concentrations exhibit complex multi-scale dynamics with qualitatively different properties at different time-scales: (i) essentially white noise in the high-frequency part (up to time-scales of about one hour), (ii) spurious indications of a non-stationary, apparently long-range correlated process (at time scales between some hours and one day) arising from marked periodic components, and (iii) low-frequency variability indicating a true long-range dependent process. In the presence of such multi-scale variability, common estimators of long-range memory in time series are prone to fail if applied to the raw data without previous separation of time-scales with qualitatively different dynamics. (authors)

Design of a High Linearity Four-Quadrant Analog Multiplier in Wideband Frequency Range

Directory of Open Access Journals (Sweden)

Abdul kareem Mokif Obais

2017-05-01

Full Text Available In this paper, a voltage mode four quadrant analog multiplier in the wideband frequency rangeis designed using a wideband operational amplifier (OPAMP and squaring circuits. The wideband OPAMP is designed using 10 identical NMOS transistorsand operated with supply voltages of ±12V. Two NMOS transistors and two wideband OPAMP are utilized in the design of the proposed squaring circuit. All the NMOS transistors are based on 0.35µm NMOStechnology. The multiplier has input and output voltage ranges of ±10 V, high range of linearity from -10 V to +10 V, and cutoff frequency of about 5 GHz. The proposed multiplier is designed on PSpice in Orcad 16.6

Implementation of acoustic demultiplexing with membrane-type metasurface in low frequency range

Science.gov (United States)

Chen, Xing; Liu, Peng; Hou, Zewei; Pei, Yongmao

2017-04-01

Wavelength division multiplexing technology, adopted to increase the information density, plays a significant role in optical communication. However, in acoustics, a similar function can be hardly implemented due to the weak dispersion in natural acoustic materials. Here, an acoustic demultiplexer, based on the concept of metasurfaces, is proposed for splitting acoustic waves and propagating along different trajectories in a low frequency range. An acoustic metasurface, containing multiple resonant units, is designed with various phase profiles for different frequencies. Originating from the highly dispersive properties, the resonant units are independent and merely work in the vicinity of their resonant frequencies. Therefore, by combing multiple resonant units appropriately, the phenomena of anomalous reflection, acoustic focusing, and acoustic wave bending can occur in different frequencies. The proposed acoustic demultiplexer has advantages on the subwavelength scale and the versatility in wave control, providing a strategy for separating acoustic waves with different Fourier components.

Precision improvement of frequency-modulated continuous-wave laser ranging system with two auxiliary interferometers

Science.gov (United States)

Shi, Guang; Wang, Wen; Zhang, Fumin

2018-03-01

The measurement precision of frequency-modulated continuous-wave (FMCW) laser distance measurement should be proportional to the scanning range of the tunable laser. However, the commercial external cavity diode laser (ECDL) is not an ideal tunable laser source in practical applications. Due to the unavoidable mode hopping and scanning nonlinearity of the ECDL, the measurement precision of FMCW laser distance measurements can be substantially affected. Therefore, an FMCW laser ranging system with two auxiliary interferometers is proposed in this paper. Moreover, to eliminate the effects of ECDL, the frequency-sampling method and mode hopping influence suppression method are employed. Compared with a fringe counting interferometer, this FMCW laser ranging system has a measuring error of ± 20 μm at the distance of 5.8 m.

Research on the range side lobe suppression method for modulated stepped frequency radar signals

Science.gov (United States)

Liu, Yinkai; Shan, Tao; Feng, Yuan

2018-05-01

The magnitude of time-domain range sidelobe of modulated stepped frequency radar affects the imaging quality of inverse synthetic aperture radar (ISAR). In this paper, the cause of high sidelobe in modulated stepped frequency radar imaging is analyzed first in real environment. Then, the chaos particle swarm optimization (CPSO) is used to select the amplitude and phase compensation factors according to the minimum sidelobe criterion. Finally, the compensated one-dimensional range images are obtained. Experimental results show that the amplitude-phase compensation method based on CPSO algorithm can effectively reduce the sidelobe peak value of one-dimensional range images, which outperforms the common sidelobe suppression methods and avoids the coverage of weak scattering points by strong scattering points due to the high sidelobes.

A general range-separated double-hybrid density-functional theory.

Science.gov (United States)

Kalai, Cairedine; Toulouse, Julien

2018-04-28

A range-separated double-hybrid (RSDH) scheme which generalizes the usual range-separated hybrids and double hybrids is developed. This scheme consistently uses a two-parameter Coulomb-attenuating-method (CAM)-like decomposition of the electron-electron interaction for both exchange and correlation in order to combine Hartree-Fock exchange and second-order Møller-Plesset (MP2) correlation with a density functional. The RSDH scheme relies on an exact theory which is presented in some detail. Several semi-local approximations are developed for the short-range exchange-correlation density functional involved in this scheme. After finding optimal values for the two parameters of the CAM-like decomposition, the RSDH scheme is shown to have a relatively small basis dependence and to provide atomization energies, reaction barrier heights, and weak intermolecular interactions globally more accurate or comparable to range-separated MP2 or standard MP2. The RSDH scheme represents a new family of double hybrids with minimal empiricism which could be useful for general chemical applications.

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

Science.gov (United States)

2011-02-01

providing often- needed comic relief. Mike Benjamin for his career guidance and keeping LAMSS down-to-earth. Joe Curcio for being such a great travel...of about 1% due to receiver motion . Such a shift may cause range estimate errors of about 1%, which is negligible compared to the overall expected...most cases the Doppler effect due to source/receiver motion has little effect on range-frequency striations. It also brief y mentions how to account

A Proposed Middle-Range Theory of Nursing in Hypertension Care

Directory of Open Access Journals (Sweden)

Eva Drevenhorn

2018-01-01

Full Text Available Nursing in hypertension care comprises counselling about lifestyle changes, blood pressure measurement, and being a translator for the physician. For the patient, changing lifestyle means performing self-care. As not much in the form of research and guidelines for nurses is available, a middle-range theory of nursing in hypertension care was developed to guide nurses in their practice, in order to improve the nursing of patients and design studies for investigating nursing in hypertension care. Concepts are presented related to the patient (attitude and beliefs regarding health and sickness, autonomy, personality and traits, level of perceived vulnerability, hardiness, sense of coherence, locus of control, self-efficacy, and access to social support and network and the nursing (applying theories and models for behavioural change in the consultation and using counselling skills, patient advocacy, empowerment, professional knowledge and health education, and supporting the patient. Then the concepts related to the consultation (communication, shared decision-making, concordance, coping, adherence, and self-care are integrated with Orem’s theory of nursing. Clinical and research implications of the theory are discussed.

Theory of frequency synchronization in a ring laser

Energy Technology Data Exchange (ETDEWEB)

Radina, Tatiana V., E-mail: tatiana.radina@gmail.com

2015-09-25

The self-consistent problem of the frequency synchronization of counter-propagating waves in a ring laser is rigorously solved. An intrinsic nonlinear mechanism of the phase coupling between the waves is considered for the first time. This ineradicable coupling is provided by modulation of the population difference of the energy levels of the active medium atoms in the electromagnetic field of two counter-propagating waves. The theoretical limit for the range of phase locking between the counter-propagating waves is established. The general equation of phase synchronization is obtained from the solution of a self-consistent problem. The frequency-dependent boundaries of the synchronization band calculated in the framework of this approach show good agreement with experimental results published in the literature.

High-Frequency Guided Wave Scattering by a Partly Through-Thickness Hole Based on 3D Theory

International Nuclear Information System (INIS)

Zhang Hai-Yan; Xu Jian; Ma Shi-Wei

2015-01-01

We present a theoretical investigation of the scattering of high frequency S0 Lamb mode from a circular blind hole defect in a plate based on the 3D theory. The S0 wave is incident at the frequency above the A1 mode cut-off frequency, in which the popular approximate plate theories are inapplicable. Due to the non-symmetric blind hole defect, the scattered fields will contain higher order converted modes in addition to the fundamental S0 and A0 modes. The far-field scattering amplitudes of various propagating Lamb modes for different hole sizes are inspected. The results are compared with those of lower frequencies and some different phenomena are found. Two-dimensional Fourier transform (2DFT) results of transient scattered Lamb and SH wave signals agree well with the analytical dispersion curves, which check the validity of the solutions from another point of view. (paper)

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

Science.gov (United States)

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

2017-01-01

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

Single frequency thermal wave radar: A next-generation dynamic thermography for quantitative non-destructive imaging over wide modulation frequency ranges.

Science.gov (United States)

Melnikov, Alexander; Chen, Liangjie; Ramirez Venegas, Diego; Sivagurunathan, Koneswaran; Sun, Qiming; Mandelis, Andreas; Rodriguez, Ignacio Rojas

2018-04-01

Single-Frequency Thermal Wave Radar Imaging (SF-TWRI) was introduced and used to obtain quantitative thickness images of coatings on an aluminum block and on polyetherketone, and to image blind subsurface holes in a steel block. In SF-TWR, the starting and ending frequencies of a linear frequency modulation sweep are chosen to coincide. Using the highest available camera frame rate, SF-TWRI leads to a higher number of sampled points along the modulation waveform than conventional lock-in thermography imaging because it is not limited by conventional undersampling at high frequencies due to camera frame-rate limitations. This property leads to large reduction in measurement time, better quality of images, and higher signal-noise-ratio across wide frequency ranges. For quantitative thin-coating imaging applications, a two-layer photothermal model with lumped parameters was used to reconstruct the layer thickness from multi-frequency SF-TWR images. SF-TWRI represents a next-generation thermography method with superior features for imaging important classes of thin layers, materials, and components that require high-frequency thermal-wave probing well above today's available infrared camera technology frame rates.

Single frequency thermal wave radar: A next-generation dynamic thermography for quantitative non-destructive imaging over wide modulation frequency ranges

Science.gov (United States)

Melnikov, Alexander; Chen, Liangjie; Ramirez Venegas, Diego; Sivagurunathan, Koneswaran; Sun, Qiming; Mandelis, Andreas; Rodriguez, Ignacio Rojas

2018-04-01

Single-Frequency Thermal Wave Radar Imaging (SF-TWRI) was introduced and used to obtain quantitative thickness images of coatings on an aluminum block and on polyetherketone, and to image blind subsurface holes in a steel block. In SF-TWR, the starting and ending frequencies of a linear frequency modulation sweep are chosen to coincide. Using the highest available camera frame rate, SF-TWRI leads to a higher number of sampled points along the modulation waveform than conventional lock-in thermography imaging because it is not limited by conventional undersampling at high frequencies due to camera frame-rate limitations. This property leads to large reduction in measurement time, better quality of images, and higher signal-noise-ratio across wide frequency ranges. For quantitative thin-coating imaging applications, a two-layer photothermal model with lumped parameters was used to reconstruct the layer thickness from multi-frequency SF-TWR images. SF-TWRI represents a next-generation thermography method with superior features for imaging important classes of thin layers, materials, and components that require high-frequency thermal-wave probing well above today's available infrared camera technology frame rates.

Multi-configuration time-dependent density-functional theory based on range separation

DEFF Research Database (Denmark)

Fromager, E.; Knecht, S.; Jensen, Hans Jørgen Aagaard

2013-01-01

Multi-configuration range-separated density-functional theory is extended to the time-dependent regime. An exact variational formulation is derived. The approximation, which consists in combining a long-range Multi-Configuration- Self-Consistent Field (MCSCF) treatment with an adiabatic short...... (srGGA) approximations. As expected, when modeling long-range interactions with the MCSCF model instead of the adiabatic Buijse-Baerends density-matrix functional as recently proposed by Pernal [J. Chem. Phys. 136, 184105 (2012)10.1063/1.4712019], the description of both the 1D doubly-excited state...

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

International Nuclear Information System (INIS)

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

2004-01-01

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

Frequency-Modulated Wave Dielectrophoresis of Vesicles And Cells: Periodic U-Turns at the Crossover Frequency

Science.gov (United States)

Frusawa, Hiroshi

2018-06-01

We have formulated the dielectrophoretic force exerted on micro/nanoparticles upon the application of frequency-modulated (FM) electric fields. By adjusting the frequency range of an FM wave to cover the crossover frequency f X in the real part of the Clausius-Mossotti factor, our theory predicts the reversal of the dielectrophoretic force each time the instantaneous frequency periodically traverses f X . In fact, we observed periodic U-turns of vesicles, leukemia cells, and red blood cells that undergo FM wave dielectrophoresis (FM-DEP). It is also suggested by our theory that the video tracking of the U-turns due to FM-DEP is available for the agile and accurate measurement of f X . The FM-DEP method requires a short duration, less than 30 s, while applying the FM wave to observe several U-turns, and the agility in measuring f X is of much use for not only salty cell suspensions but also nanoparticles because the electric-field-induced solvent flow is suppressed as much as possible. The accuracy of f X has been verified using two types of experiment. First, we measured the attractive force exerted on a single vesicle experiencing alternating-current dielectrophoresis (AC-DEP) at various frequencies of sinusoidal electric fields. The frequency dependence of the dielectrophoretic force yields f X as a characteristic frequency at which the force vanishes. Comparing the AC-DEP result of f X with that obtained from the FM-DEP method, both results of f X were found to coincide with each other. Second, we investigated the conductivity dependencies of f X for three kinds of cell by changing the surrounding electrolytes. From the experimental results, we evaluated simultaneously both of the cytoplasmic conductivities and the membrane capacitances using an elaborate theory on the single-shell model of biological cells. While the cytoplasmic conductivities, similar for these cells, were slightly lower than the range of previous reports, the membrane capacitances obtained

Scattering from extended targets in range-dependent fluctuating ocean-waveguides with clutter from theory and experiments.

Science.gov (United States)

Jagannathan, Srinivasan; Küsel, Elizabeth T; Ratilal, Purnima; Makris, Nicholas C

2012-08-01

Bistatic, long-range measurements of acoustic scattered returns from vertically extended, air-filled tubular targets were made during three distinct field experiments in fluctuating continental shelf waveguides. It is shown that Sonar Equation estimates of mean target-scattered intensity lead to large errors, differing by an order of magnitude from both the measurements and waveguide scattering theory. The use of the Ingenito scattering model is also shown to lead to significant errors in estimating mean target-scattered intensity in the field experiments because they were conducted in range-dependent ocean environments with large variations in sound speed structure over the depth of the targets, scenarios that violate basic assumptions of the Ingenito model. Green's theorem based full-field modeling that describes scattering from vertically extended tubular targets in range-dependent ocean waveguides by taking into account nonuniform sound speed structure over the target's depth extent is shown to accurately describe the statistics of the targets' scattered field in all three field experiments. Returns from the man-made targets are also shown to have a very different spectral dependence from the natural target-like clutter of the dominant fish schools observed, suggesting that judicious multi-frequency sensing may often provide a useful means of distinguishing fish from man-made targets.

Theory of high frequency discharge in gases under low pressures. Experimental investigation of high-frequency type ion sources; Theorie de la decharge haute frequence dans les gaz aux faibles pressions. Etude experimentale des sources d'ions du type haute frequence

Energy Technology Data Exchange (ETDEWEB)

Salmon, Jean

1955-03-02

The first part of this research thesis addresses the theory of high frequency discharge in gases under low pressures, and first proposes a calculation of the distribution function for electrons present within the gas. The author then studies the evolution of electron density within a discharge tube by assigning the governing role in electron multiplication to the secondary emission of tube walls. The second part proposes a detailed description of a source operating at 96.5 Mc/s, a discussion of measurements performed on this source, and the search for a theoretical explanation of some of its properties. The author then briefly analyses various existing types of high frequency sources, and finally discusses their use in corpuscular microscopy and in particle accelerators [French] La presente these comprend deux parties. La premiere est consacree a la theorie de la decharge haute frequence dans les gaz aux faibles pressions et comporte tout d'abord le calcul de la fonction de distribution des electrons presents au sein du gaz. Nous etudions ensuite l'evolution de la densite electronique a l'interieur d'un tube a decharge en attribuant, a l'emission secondaire des parois de ce dernier, le role essentiel dans la multiplicalion des electrons. Nous obtenons ainsi les conditions d'amorcage. Tout au long de cette etude, on doit distinguer soigneusement le cas ou le libre parcours moyen des electrons dans le gaz est inferieur aux dimensions de l'enceinte et le cas ou il leur est superieur. La deuxieme partie comprend la description detaillee d'une source fonctionnant sur 96.5 Mc/s, l'expose des mesures effectuees sur celle-ci et la recherche d'une explication theorique de certaines de ses proprietes. Nous faisons ensuite une breve analyse des divers types de sources d'ions haute frequence existant a l'heure actuelle et nous terminons en traitant de leur utilisation en microscopie corpusculaire et dans les accelerateurs de particules.

Optimized 3-D electromagnetic models of composite materials in microwave frequency range: application to EMC characterization of complex media by statistical means

Directory of Open Access Journals (Sweden)

S. Lalléchère

2017-05-01

Full Text Available The aim of this proposal is to demonstrate the ability of tridimensional (3-D electromagnetic modeling tool for the characterization of composite materials in microwave frequency band range. Indeed, an automated procedure is proposed to generate random materials, proceed to 3-D simulations, and compute shielding effectiveness (SE statistics with finite integration technique. In this context, 3-D electromagnetic models rely on random locations of conductive inclusions; results are compared with classical electromagnetic mixing theory (EMT approaches (e.g. Maxwell-Garnett formalism, and dynamic homogenization model (DHM. The article aims to demonstrate the interest of the proposed approach in various domains such as propagation and electromagnetic compatibility (EMC.

Coupled modes, frequencies and fields of a dielectric resonator and a cavity using coupled mode theory

Science.gov (United States)

Elnaggar, Sameh Y.; Tervo, Richard; Mattar, Saba M.

2014-01-01

Probes consisting of a dielectric resonator (DR) inserted in a cavity are important integral components of electron paramagnetic resonance (EPR) spectrometers because of their high signal-to-noise ratio. This article studies the behavior of this system, based on the coupling between its dielectric and cavity modes. Coupled-mode theory (CMT) is used to determine the frequencies and electromagnetic fields of this coupled system. General expressions for the frequencies and field distributions are derived for both the resulting symmetric and anti-symmetric modes. These expressions are applicable to a wide range of frequencies (from MHz to THz). The coupling of cavities and DRs of various sizes and their resonant frequencies are studied in detail. Since the DR is situated within the cavity then the coupling between them is strong. In some cases the coupling coefficient, κ, is found to be as high as 0.4 even though the frequency difference between the uncoupled modes is large. This is directly attributed to the strong overlap between the fields of the uncoupled DR and cavity modes. In most cases, this improves the signal to noise ratio of the spectrometer. When the DR and the cavity have the same frequency, the coupled electromagnetic fields are found to contain equal contributions from the fields of the two uncoupled modes. This situation is ideal for the excitation of the probe through an iris on the cavity wall. To verify and validate the results, finite element simulations are carried out. This is achieved by simulating the coupling between a cylindrical cavity's TE011 and the dielectric insert's TE01δ modes. Coupling between the modes of higher order is also investigated and discussed. Based on CMT, closed form expressions for the fields of the coupled system are proposed. These expressions are crucial in the analysis of the probe's performance.

Frequency dependence of anomalous transport in field theory and holography⋆,⋆⋆

Directory of Open Access Journals (Sweden)

Megías Eugenio

2014-01-01

Full Text Available We study the frequency dependence of anomalous transport coefficients for a relativistic gas of free chiral fermions and for a strongly coupled conformal field theory with holographic dual. We perform the computation by using the Kubo formulae for- malism, and compare with a hydrodynamic calculation of two point functions. Some implications for heavy ion physics are discussed.

Middle-Range Theory: Coping and Adaptation with Active Aging.

Science.gov (United States)

Salazar-Barajas, Martha Elba; Salazar-González, Bertha Cecilia; Gallegos-Cabriales, Esther Carlota

2017-10-01

Various disciplines focus on a multiplicity of aspects of aging: lifestyles, personal biological factors, psychological conditions, health conditions, physical environment, and social and economic factors. The aforementioned are all related to the determinants of active aging. The aim is to describe the development of a middle-range theory based on coping and adaptation with active aging. Concepts and relationships derived from Roy's model of adaptation are included. The proposed concepts are hope, health habits, coping with aging, social relations, and active aging.

An Emerging Integrated Middle-Range Theory on Asian Women's Leadership in Nursing.

Science.gov (United States)

Im, Eun-Ok; Broome, Marion E; Inouye, Jillian; Kunaviktikul, Wipada; Oh, Eui Geum; Sakashita, Reiko; Yi, Myungsun; Huang, Lian-Hua; Tsai, Hsiu-Min; Wang, Hsiu-Hung

2018-02-01

Asian cultures reflect patriarchal cultural values and attitudes, which likely have influenced women leaders in their countries differently from women in Western cultures. However, virtually no leadership theories have been developed to reflect the experiences and development of nursing leaders from Asian cultures. The purpose of this article is to present an emerging integrated middle-range theory on Asian women's leadership in nursing. Using an integrative approach, the theory was developed based on three major sources: the leadership frames of Bolman and Deal, literature reviews, and exemplars/cases from five different countries. The theory includes two main domains (leadership frames and leadership contexts). The domain of leadership frames includes human resources/networks, structure/organization, national/international politics, and symbols. The domain of leadership contexts includes cultural contexts, sociopolitical contexts, and gendered contexts. This theory will help understand nursing leadership in Asian cultures and provide directions for future nurse leaders in this ever-changing globalized world.

Surface impedance of superconductors in wide frequency ranges for wake field calculations

International Nuclear Information System (INIS)

Davidovskii, V.G.

2006-01-01

The problem of the surface impedance of superconductors in wide frequency ranges for calculations of wake fields, generated by bunches of charged particles moving axially inside a metallic vacuum chambers, is solved. The case of specular electron reflection at the superconductor surface is considered. The expression for the surface impedance of superconductors suitable for numerical computation is derived [ru

Effective theory and breakdown of conformal symmetry in a long-range quantum chain

Science.gov (United States)

Lepori, L.; Vodola, D.; Pupillo, G.; Gori, G.; Trombettoni, A.

2016-11-01

We deal with the problem of studying the symmetries and the effective theories of long-range models around their critical points. A prominent issue is to determine whether they possess (or not) conformal symmetry (CS) at criticality and how the presence of CS depends on the range of the interactions. To have a model, both simple to treat and interesting, where to investigate these questions, we focus on the Kitaev chain with long-range pairings decaying with distance as power-law with exponent α. This is a quadratic solvable model, yet displaying non-trivial quantum phase transitions. Two critical lines are found, occurring respectively at a positive and a negative chemical potential. Focusing first on the critical line at positive chemical potential, by means of a renormalization group approach we derive its effective theory close to criticality. Our main result is that the effective action is the sum of two terms: a Dirac action SD, found in the short-range Ising universality class, and an "anomalous" CS breaking term SAN. While SD originates from low-energy excitations in the spectrum, SAN originates from the higher energy modes where singularities develop, due to the long-range nature of the model. At criticality SAN flows to zero for α > 2, while for α limit α → ∞ the ELI is restored. In order to test the validity of the determined effective theory, we compared the two-fermion static correlation functions and the von Neumann entropy obtained from them with the ones calculated on the lattice, finding agreement. These results explain two observed features characteristic of long-range models, the hybrid decay of static correlation functions within gapped phases and the area-law violation for the von Neumann entropy. The proposed scenario is expected to hold in other long-range models displaying quasiparticle excitations in ballistic regime. From the effective theory one can also see that new phases emerge for α model, are not altered. This also shows

Ohmic heating of peaches in the wide range of frequencies (50 Hz to 1 MHz).

Science.gov (United States)

Shynkaryk, Mykola V; Ji, Taehyun; Alvarez, Valente B; Sastry, Sudhir K

2010-09-01

The ohmic heating (OH) rate of peaches was studied at fixed electric field strength of 60 V.cm⁻¹, square-shaped instant reversal bipolar pulses, and frequencies varying within 50 Hz to 1 MHz. Thermal damage of tissue was evaluated from electrical admittivity. It showed that the time for half disruption (τ(T)) of tissue was required more than 10 h at temperatures below 40 °C. However, cellular thermal disruption occurred almost instantly (τ(T) 90 °C). Electrical conductivity σ(o) and admittivity σ(o)* of tissue at T(o)= 0 °C and their temperature coefficients (m, m*) were calculated. For freeze-thawed tissues, σ and σ* as well as m and m* were nearly indifferent to the frequency. However, for the intact tissue, both σ(o), σ(o)* and m, m* were frequency dependent. For freeze-thawed product, the power factor (P) was approximately equal to 1 and indifferent to the frequency and temperature. On the other hand, strong frequency dependence was observed for intact tissue with the minimum P approximately equal to 0.68 in the range of tens of kHz. The time required to reach a target temperature t(f) was evaluated. The t(f) increased with frequency up to the middle of the range of tens of kHz and thereafter continuously decreased. Samples exposed to the low-frequency electric field demonstrated faster electro-thermal damage rates. The textural relaxation data supported more intense damage kinetics at low-frequency OH. It has been demonstrated that a combination of high-frequency OH with pasteurization at moderate temperature followed by rapid cooling minimizes texture degradation of peach tissue. In this study, we investigated the electric field frequency effect on the rate of OH of peaches. It was shown that the time required for reaching the target temperature is strongly dependent upon the frequency. Samples exposed to low-frequency OH demonstrated higher electro-thermal damage rates. It has been shown that the combination of high-frequency OH with

Long-range psu(2,2|4) Bethe ansatze for gauge theory and strings

International Nuclear Information System (INIS)

Beisert, Niklas; Staudacher, Matthias

2005-01-01

We generalize various existing higher-loop Bethe ansatze for simple sectors of the integrable long-range dynamic spin chain describing planar N=4 super-Yang-Mills theory to the full psu(2,2|4) symmetry and, asymptotically, to arbitrary loop order. We perform a large number of tests of our conjectured equations, such as internal consistency, comparison to direct three-loop diagonalization and expected thermodynamic behavior. In the special case of the su(1|2) subsector, corresponding to a long-range t-J model, we are able to derive, up to three loops, the S-matrix and the associated nested Bethe ansatz from the gauge theory dilatation operator. We conjecture novel all-order S-matrices for the su(1|2) and su(1,1|2) subsectors, and show that they satisfy the Yang-Baxter equation. Throughout the paper, we muse about the idea that quantum string theory on AdS 5 xS 5 is also described by a psu(2,2|4) spin chain. We propose asymptotic all-order Bethe equations for this putative ''string chain'', which differ in a systematic fashion from the gauge theory equations

Building a Middle-Range Theory of Adaptive Spirituality.

Science.gov (United States)

Dobratz, Marjorie C

2016-04-01

The purpose of this article is to describe a Roy adaptation model based- research abstraction, the findings of which were synthesized into a middle-range theory (MRT) of adaptive spirituality. The published literature yielded 21 empirical studies that investigated religion/spirituality. Quantitative results supported the influence of spirituality on quality of life, psychosocial adjustment, well-being, adaptive coping, and the self-concept mode. Qualitative findings showed the importance of spiritual expressions, values, and beliefs in adapting to chronic illness, bereavement, death, and other life transitions. These findings were abstracted into six theoretical statements, a conceptual definition of adaptive spirituality, and three hypotheses for future testing. © The Author(s) 2016.

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

Science.gov (United States)

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

1999-02-02

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

GaN-based High Power High Frequency Wide Range LLC Resonant Converter, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — SET Group will design, build and demonstrate a Gallium Nitride (GaN) based High Power High Frequency Wide Range LLC Resonant Converter capable of handling high power...

Kinetic Scale Structure of Low-frequency Waves and Fluctuations

Energy Technology Data Exchange (ETDEWEB)

López, Rodrigo A.; Yoon, Peter H. [Institute for Physical Science and Technology, University of Maryland, College Park, MD 20742 (United States); Viñas, Adolfo F. [NASA Goddard Space Flight Center, Heliophysics Science Division, Geospace Physics Laboratory, Mail Code 673, Greenbelt, MD 20771 (United States); Araneda, Jaime A., E-mail: rlopezh@umd.edu, E-mail: yoonp@umd.edu [Departamento de Física, Facultad de Ciencias Físicas y Matemáticas, Universidad de Concepción, Concepción (Chile)

2017-08-10

The dissipation of solar wind turbulence at kinetic scales is believed to be important for the heating of the corona and for accelerating the wind. The linear Vlasov kinetic theory is a useful tool for identifying various wave modes, including kinetic Alfvén, fast magnetosonic/whistler, and ion-acoustic (or kinetic slow), and their possible roles in the dissipation. However, the kinetic mode structure in the vicinity of ion-cyclotron modes is not clearly understood. The present paper aims to further elucidate the structure of these low-frequency waves by introducing discrete particle effects through hybrid simulations and Klimontovich formalism of spontaneous emission theory. The theory and simulation of spontaneously emitted low-frequency fluctuations are employed to identify and distinguish the detailed mode structures associated with ion-Bernstein modes versus quasi-modes. The spontaneous emission theory and simulation also confirm the findings of the Vlasov theory in that the kinetic Alfvén waves can be defined over a wide range of frequencies, including the proton cyclotron frequency and its harmonics, especially for high-beta plasmas. This implies that these low-frequency modes may play predominant roles even in the fully kinetic description of kinetic scale turbulence and dissipation despite the fact that cyclotron harmonic and Bernstein modes may also play important roles in wave–particle interactions.

Describing long-range charge-separation processes with subsystem density-functional theory

Energy Technology Data Exchange (ETDEWEB)

Solovyeva, Alisa; Neugebauer, Johannes, E-mail: j.neugebauer@uni-muenster.de [Theoretische Organische Chemie, Organisch-Chemisches Institut and Center for Multiscale Theory and Simulation, Westfälische Wilhelms-Universität Münster, Corrensstraße 40, 48149 Münster (Germany); Pavanello, Michele, E-mail: m.pavanello@rutgers.edu [Department of Chemistry, Rutgers University, 73 Warren St., Newark, New Jersey 07102 (United States)

2014-04-28

Long-range charge-transfer processes in extended systems are difficult to describe with quantum chemical methods. In particular, cost-effective (non-hybrid) approximations within time-dependent density functional theory (DFT) are not applicable unless special precautions are taken. Here, we show that the efficient subsystem DFT can be employed as a constrained DFT variant to describe the energetics of long-range charge-separation processes. A formal analysis of the energy components in subsystem DFT for such excitation energies is presented, which demonstrates that both the distance dependence and the long-range limit are correctly described. In addition, electronic couplings for these processes as needed for rate constants in Marcus theory can be obtained from this method. It is shown that the electronic structure of charge-separated states constructed by a positively charged subsystem interacting with a negatively charged one is difficult to converge — charge leaking from the negative subsystem to the positive one can occur. This problem is related to the delocalization error in DFT and can be overcome with asymptotically correct exchange–correlation (XC) potentials or XC potentials including a sufficiently large amount of exact exchange. We also outline an approximate way to obtain charge-transfer couplings between locally excited and charge-separated states.

Describing long-range charge-separation processes with subsystem density-functional theory

International Nuclear Information System (INIS)

Solovyeva, Alisa; Neugebauer, Johannes; Pavanello, Michele

2014-01-01

Long-range charge-transfer processes in extended systems are difficult to describe with quantum chemical methods. In particular, cost-effective (non-hybrid) approximations within time-dependent density functional theory (DFT) are not applicable unless special precautions are taken. Here, we show that the efficient subsystem DFT can be employed as a constrained DFT variant to describe the energetics of long-range charge-separation processes. A formal analysis of the energy components in subsystem DFT for such excitation energies is presented, which demonstrates that both the distance dependence and the long-range limit are correctly described. In addition, electronic couplings for these processes as needed for rate constants in Marcus theory can be obtained from this method. It is shown that the electronic structure of charge-separated states constructed by a positively charged subsystem interacting with a negatively charged one is difficult to converge — charge leaking from the negative subsystem to the positive one can occur. This problem is related to the delocalization error in DFT and can be overcome with asymptotically correct exchange–correlation (XC) potentials or XC potentials including a sufficiently large amount of exact exchange. We also outline an approximate way to obtain charge-transfer couplings between locally excited and charge-separated states

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

Science.gov (United States)

Cheong, Chin Wen; Pei, Tan Pei

2015-10-01

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

Density functional theory for prediction of far-infrared vibrational frequencies: molecular crystals of astrophysical interest

Science.gov (United States)

Ennis, C.; Auchettl, R.; Appadoo, D. R. T.; Robertson, E. G.

2017-11-01

Solid-state density functional theory code has been implemented for the structure optimization of crystalline methanol, acetaldehyde and acetic acid and for the calculation of infrared frequencies. The results are compared to thin film spectra obtained from low-temperature experiments performed at the Australian Synchrotron. Harmonic frequency calculations of the internal modes calculated at the B3LYP-D3/m-6-311G(d) level shows higher deviation from infrared experiment than more advanced theory applied to the gas phase. Importantly for the solid-state, the simulation of low-frequency molecular lattice modes closely resembles the observed far-infrared features after application of a 0.92 scaling factor. This allowed experimental peaks to be assigned to specific translation and libration modes, including acetaldehyde and acetic acid lattice features for the first time. These frequency calculations have been performed without the need for supercomputing resources that are required for large molecular clusters using comparable levels of theory. This new theoretical approach will find use for the rapid characterization of intermolecular interactions and bonding in crystals, and the assignment of far-infrared spectra for crystalline samples such as pharmaceuticals and molecular ices. One interesting application may be for the detection of species of prebiotic interest on the surfaces of Kuiper-Belt and Trans-Neptunian Objects. At such locations, the three small organic molecules studied here could reside in their crystalline phase. The far-infrared spectra for their low-temperature solid phases are collected under planetary conditions, allowing us to compile and assign their most intense spectral features to assist future far-infrared surveys of icy Solar system surfaces.

The technology of the ion cyclotron range of frequencies

International Nuclear Information System (INIS)

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

1988-01-01

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

The frequency dependence of friction in experiment, theory, and observations of low frequency earthquakes

Science.gov (United States)

Thomas, A.; Beeler, N. M.; Burgmann, R.; Shelly, D. R.

2011-12-01

Low frequency earthquakes (LFEs) are small amplitude, short duration events composing tectonic tremor, probably generated by shear slip on asperities downdip of the seismogenic zone. In Parkfield, Shelly and Hardebeck [2010] have identified 88 LFE families, or hypocentral locations, that contain over half a million LFEs since 2001 on a 160-km-long section of the San Andreas fault between 16 and 30 km depth. A number of studies have demonstrated the extreme sensitivity of low frequency earthquakes (LFEs) near Parkfield to stress changes ranging from contingent upon the amplitude and frequency content of the applied stress. We attempt to test this framework by comparing observations of LFEs triggered in response to stresses spanning several orders of magnitude in both frequency and amplitude (e.g. tides, teleseismic surface waves, static stress changes, etc.) to the predicted response of a single degree of freedom slider block model with rate and state dependent strength. The sensitivity of failure time in the friction model as developed in previous studies does not distinguish between shear and normal stresses; laboratory experiments show a more complicated sensitivity of failure time to normal stress change than in the published model. Because the shear and normal tidal stresses at Parkfield have different amplitudes and are not in phase, we have modified the model to include the expected sensitivity to normal stress. Our prior investigations of the response of both regular and low frequency earthquakes to tidal stresses [Thomas et al., 2009; Shelly and Johnson, 2011] are qualitatively consistent with the predictions of the friction model , as both the timing and degree (probability) of correlation are in agreement.

Spontaneous otoacoustic emissions, threshold microstructure, and psychophysical tuning over a wide frequency range in humansa

Science.gov (United States)

Baiduc, Rachael R.; Lee, Jungmee; Dhar, Sumitrajit

2014-01-01

Hearing thresholds have been shown to exhibit periodic minima and maxima, a pattern known as threshold microstructure. Microstructure has previously been linked to spontaneous otoacoustic emissions (SOAEs) and normal cochlear function. However, SOAEs at high frequencies (>4 kHz) have been associated with hearing loss or cochlear pathology in some reports. Microstructure would not be expected near these high-frequency SOAEs. Psychophysical tuning curves (PTCs), the expression of frequency selectivity, may also be altered by SOAEs. Prior comparisons of tuning between ears with and without SOAEs demonstrated sharper tuning in ears with emissions. Here, threshold microstructure and PTCs were compared at SOAE frequencies ranging between 1.2 and 13.9 kHz using subjects without SOAEs as controls. Results indicate: (1) Threshold microstructure is observable in the vicinity of SOAEs of all frequencies; (2) PTCs are influenced by SOAEs, resulting in shifted tuning curve tips, multiple tips, or inversion. High frequency SOAEs show a greater effect on PTC morphology. The influence of most SOAEs at high frequencies on threshold microstructure and PTCs is consistent with those at lower frequencies, suggesting that high-frequency SOAEs reflect the same cochlear processes that lead to SOAEs at lower frequencies. PMID:24437770

Excitation energies from Görling-Levy perturbation theory along the range-separated adiabatic connection

Science.gov (United States)

Rebolini, Elisa; Teale, Andrew M.; Helgaker, Trygve; Savin, Andreas; Toulouse, Julien

2018-06-01

A Görling-Levy (GL)-based perturbation theory along the range-separated adiabatic connection is assessed for the calculation of electronic excitation energies. In comparison with the Rayleigh-Schrödinger (RS)-based perturbation theory this GL-based perturbation theory keeps the ground-state density constant at each order and thus gives the correct ionisation energy at each order. Excitation energies up to first order in the perturbation have been calculated numerically for the helium and beryllium atoms and the hydrogen molecule without introducing any density-functional approximations. In comparison with the RS-based perturbation theory, the present GL-based perturbation theory gives much more accurate excitation energies for Rydberg states but similar excitation energies for valence states.

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

International Nuclear Information System (INIS)

Biddle, A.P.

1980-06-01

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

Numerical Investigation and Experimental Demonstration of Chaos from Two-Stage Colpitts Oscillator in the Ultrahigh Frequency Range

DEFF Research Database (Denmark)

Bumeliene, S.; Tamasevicius, A.; Mykolaitis, G.

2006-01-01

A hardware prototype of the two-stage Colpitts oscillator employing the microwave BFG520 type transistors with the threshold frequency of 9 GHz and designed to operate in the ultrahigh frequency range (300–1000 MHz) is described. The practical circuit in addition to the intrinsic two-stage oscill......A hardware prototype of the two-stage Colpitts oscillator employing the microwave BFG520 type transistors with the threshold frequency of 9 GHz and designed to operate in the ultrahigh frequency range (300–1000 MHz) is described. The practical circuit in addition to the intrinsic two......-stage oscillator contains an emitter follower acting as a buffer and minimizing the influence of the load. The circuit is investigated both numerically and experimentally. Typical phase portraits, Lyapunov exponents, Lyapunov dimension and broadband continuous power spectra are presented. The main advantage...

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

Science.gov (United States)

Revil, A

2013-01-01

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

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

International Nuclear Information System (INIS)

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

2017-01-01

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

Wide-range frequency selectivity in an acoustic sensor fabricated using a microbeam array with non-uniform thickness

International Nuclear Information System (INIS)

Shintaku, Hirofumi; Kotera, Hidetoshi; Kobayashi, Takayuki; Zusho, Kazuki; Kawano, Satoyuki

2013-01-01

In this study, we have demonstrated the fabrication of a microbeam array (MBA) with various thicknesses and investigated the suitability it for an acoustic sensor with wide-range frequency selectivity. For this, an MBA composed of 64 beams, with thicknesses varying from 2.99–142 µm, was fabricated by using single gray-scale lithography and a thick negative photoresist. The vibration of the beams in air was measured using a laser Doppler vibrometer; the resonant frequencies of the beams were measured to be from 11.5 to 290 kHz. Lastly, the frequency range of the MBA with non-uniform thickness was 10.9 times that of the MBA with uniform thickness. (paper)

Inertial-range spectrum of whistler turbulence

Directory of Open Access Journals (Sweden)

Y. Narita

2010-02-01

Full Text Available We develop a theoretical model of an inertial-range energy spectrum for homogeneous whistler turbulence. The theory is a generalization of the Iroshnikov-Kraichnan concept of the inertial-range magnetohydrodynamic turbulence. In the model the dispersion relation is used to derive scaling laws for whistler waves at highly oblique propagation with respect to the mean magnetic field. The model predicts an energy spectrum for such whistler waves with a spectral index −2.5 in the perpendicular component of the wave vector and thus provides an interpretation about recent discoveries of the second inertial-range of magnetic energy spectra at high frequencies in the solar wind.

Diversification Rates and the Evolution of Species Range Size Frequency Distribution

Directory of Open Access Journals (Sweden)

Silvia Castiglione

2017-11-01

Full Text Available The geographic range sizes frequency distribution (RFD within clades is typically right-skewed with untransformed data, and bell-shaped or slightly left-skewed under the log-transformation. This means that most species within clades occupy diminutive ranges, whereas just a few species are truly widespread. A number of ecological and evolutionary explanations have been proposed to account for this pattern. Among the latter, much attention has been given to the issue of how extinction and speciation probabilities influence RFD. Numerous accounts now convincingly demonstrate that extinction rate decreases with range size, both in living and extinct taxa. The relationship between range size and speciation rate, though, is much less obvious, with either small or large ranged species being proposed to originate more daughter taxa. Herein, we used a large fossil database including 21 animal clades and more than 80,000 fossil occurrences distributed over more than 400 million years of marine metazoans (exclusive of vertebrates evolution, to test the relationship between extinction rate, speciation rate, and range size. As expected, we found that extinction rate almost linearly decreases with range size. In contrast, speciation rate peaks at the large (but not the largest end of the range size spectrum. This is consistent with the peripheral isolation mode of allopatric speciation being the main mechanism of species origination. The huge variation in phylogeny, fossilization potential, time of fossilization, and the overarching effect of mass extinctions suggest caution must be posed at generalizing our results, as individual clades may deviate significantly from the general pattern.

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

Science.gov (United States)

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

2015-02-01

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

Flat ended steel wires, backscattering targets for calibrating over a large dynamic range

NARCIS (Netherlands)

Lubbers, Jaap; Graaff, Reindert

2006-01-01

A series of flat ended stainless steel wires was constructed and experimentally evaluated as point targets giving a calibrated backscattering over a large range (up to 72 dB) for ultrasound frequencies in the range 2 to 10 MHz. Over a range of 36 dB, theory was strictly followed (within 1 dB),

Coherent lidar modulated with frequency stepped pulse trains for unambiguous high duty cycle range and velocity sensing in the atmosphere

DEFF Research Database (Denmark)

Lindelöw, Per Jonas Petter; Mohr, Johan Jacob

2007-01-01

Range unambiguous high duty cycle coherent lidars can be constructed based on frequency stepped pulse train modulation, even continuously emitting systems could be envisioned. Such systems are suitable for velocity sensing of dispersed targets, like the atmosphere, at fast acquisition rates....... The lightwave synthesized frequency sweeper is a suitable generator yielding fast pulse repetition rates and stable equidistant frequency steps. Theoretical range resolution profiles of modulated lidars are presented....

Nanostructured composite layers for electromagnetic shielding in the GHz frequency range

Science.gov (United States)

Suchea, M.; Tudose, I. V.; Tzagkarakis, G.; Kenanakis, G.; Katharakis, M.; Drakakis, E.; Koudoumas, E.

2015-10-01

We report on preliminary results regarding the applicability of nanostructured composite layers for electromagnetic shielding in the frequency range of 4-20 GHz. Various combinations of materials were employed including poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS), polyaniline, graphene nanoplatelets, carbon nanotubes, Cu nanoparticles and Poly(vinyl alcohol). As shown, paint-like nanocomposite layers consisting of graphene nanoplatelets, polyaniline PEDOT:PSS and Poly(vinyl alcohol) can offer quite effective electromagnetic shielding, similar or even better than that of commercial products, the response strongly depending on their thickness and resistivity.

Extension of a nonlinear systems theory to general-frequency unsteady transonic aerodynamic responses

Science.gov (United States)

Silva, Walter A.

1993-01-01

A methodology for modeling nonlinear unsteady aerodynamic responses, for subsequent use in aeroservoelastic analysis and design, using the Volterra-Wiener theory of nonlinear systems is presented. The methodology is extended to predict nonlinear unsteady aerodynamic responses of arbitrary frequency. The Volterra-Wiener theory uses multidimensional convolution integrals to predict the response of nonlinear systems to arbitrary inputs. The CAP-TSD (Computational Aeroelasticity Program - Transonic Small Disturbance) code is used to generate linear and nonlinear unit impulse responses that correspond to each of the integrals for a rectangular wing with a NACA 0012 section with pitch and plunge degrees of freedom. The computed kernels then are used to predict linear and nonlinear unsteady aerodynamic responses via convolution and compared to responses obtained using the CAP-TSD code directly. The results indicate that the approach can be used to predict linear unsteady aerodynamic responses exactly for any input amplitude or frequency at a significant cost savings. Convolution of the nonlinear terms results in nonlinear unsteady aerodynamic responses that compare reasonably well with those computed using the CAP-TSD code directly but at significant computational cost savings.

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

International Nuclear Information System (INIS)

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

2015-01-01

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

Fast wave heating experiments in the ion cyclotron range of frequencies on ATF

Energy Technology Data Exchange (ETDEWEB)

Kwon, M; Shepard, T D; Goulding, R H [Oak Ridge National Lab., TN (United States); and others

1992-07-01

Fast wave heating experiments in the ion cyclotron range of frequencies (ICRF) were performed on target plasmas produced by 350 kW of electron cyclotron heating at 53 GHz and also by neutral beam injection in the Advanced Toroidal Facility (ATF). Various heating regimes were investigated in the frequency range between 9.2 MHz and 28.8 MHz with magnetic fields of 0.95 T and 1.9 T on axis. The nominal pulse lengths of up to 200 kW RF power were in the range between 100 and 400 ms. Data from spectroscopy, loading measurements, and edge RF and Langmuir probes were used to characterize the RF induced effects on the ATF plasma. In the hydrogen minority regime at low plasma density, large suprathermal ion tails were observed with a neutral particle analyser. At high density (n-bar{sub e} {>=} 5.0 x 10{sup 13} cm{sup -3}) substantial increases in antenna loading were observed, but ICRF power was insufficient to produce definitive heating results. A two-dimensional RF heating code, ORION, and a Fokker-Planck code, RFTRANS, were used to simulate these experiments. A simulation of future high power, higher density experiments in ATF indicates improved bulk heating results due to the improved loading and more efficient thermalization of the minority tail. (author). 29 refs, 16 figs, 3 tabs.

Third-harmonic entanglement and Einstein-Podolsky-Rosen steering over a frequency range of more than an octave

Science.gov (United States)

Olsen, M. K.

2018-03-01

The development of quantum technologies which use quantum states of the light field interacting with other systems creates a demand for such states over wide frequency ranges. In this work we compare the bipartite entanglement and Einstein-Podolsky-Rosen (EPR) -steering properties of the two different parametric schemes which produce third-harmonic optical fields from an input field at the fundamental frequency. The first scheme uses second harmonic cascaded with sum-frequency generation, while the second uses triply degenerate four- wave mixing, also known as direct third-harmonic generation. We find that both schemes produce continuous-variable bipartite entanglement and EPR steering over a frequency range which has previously been unobtainable. The direct scheme produces a greater degree of EPR steering, while the cascaded scheme allows for greater flexibility in having three available bipartitions, thus allowing for greater flexibility in the tailoring of light matter interfaces. There are also parameter regimes in both for which classical mean-field analyses fail to predict the mean-field solutions. Both schemes may be very useful for applications in quantum communication and computation networks, as well as providing for quantum interfaces between a wider range of light and atomic ensembles than is presently practicable.

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

Science.gov (United States)

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

2005-01-01

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

THE RELATION OF FREQUENCY TO THE PHYSIOLOGICAL EFFECTS OF ULTRA-HIGH FREQUENCY CURRENTS.

Science.gov (United States)

Christie, R V; Loomis, A L

1929-01-31

1. Biological effects of electromagnetic waves emitted by a vacuum tube oscillator have been studied at frequencis ranging from 8,300,000 to 158,000,000 cycles per second (1.9 to 38 meters wave-length). 2. The effects produced on animals can be fully explained on the basis of the heat generated by high frequency currents which are induced in them. 3. No evidence was obtained to support the theory that certain wave-lengths have a specific action on living cells. 4. At frequencies below 50,000,000 cycles, the effect of these radiations on animals is proportionate to the intensity of the electro-magnetic field. As the frequency is increased beyond this point, the amount of induced current is diminished and the apparent lethality of the radiation is decreased. This can be explained by changes occurring in the dielectric properties of tissues at low wave-lengths.

Collective Thomson scattering measurements with high frequency resolution at TEXTOR

DEFF Research Database (Denmark)

Stejner Pedersen, Morten; Nielsen, Stefan Kragh; Korsholm, Søren Bang

2010-01-01

We discuss the development and first results of a receiver system for the collective Thomson scattering (CTS) diagnostic at TEXTOR with frequency resolution in the megahertz range or better. The improved frequency resolution expands the diagnostic range and utility of CTS measurements in general ...... and is a prerequisite for measurements of ion Bernstein wave signatures in CTS spectra. The first results from the new acquisition system are shown to be consistent with theory and with simultaneous measurements by the standard receiver system. © 2010 EURATOM...

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

International Nuclear Information System (INIS)

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

2015-01-01

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

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

Science.gov (United States)

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

2015-12-01

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

Structure and dielectric properties in the radio frequency range of polymer composites based on vanadium dioxide

Directory of Open Access Journals (Sweden)

Kolbunov V.R.

2015-06-01

Full Text Available Polymer composites with active fillers are recently considered to be promising materials for the design of new functional devices with controllable properties and are intensively investigated. Dielectric studies are one of the most effective methods for studying structural features and mechanisms of conductivity formation for this type of two-component systems. The paper presents research results of the dielectric characteristics in the range of radio frequency of 50 kHz — 10 MHz and temperature range of 30—60°C of polyethylene composites of vanadium dioxide with different volume fractions of filler. Two dispersion areas were found: a high-frequency area caused by the Maxwell charge separation on the boundaries of the polyethylene matrix — conductive filler of VI2 crystallites, and a low frequency area associated with the presence of the transition layer at this boundary. The relative permittivity of the composite has a tendency to a decrease in absolute value with increasing temperature. The analysis of the low-frequency dependence of the dielectric constant of the value of the filler’s volume fraction revealed that the investigated composite belongs to two-component statistical mixtures with a transition layer between the components.

A theoretical study on directivity control of multiple-loudspeaker system with a quadrupole radiation pattern in low frequency range

Science.gov (United States)

Irwansyah, Kuse, Naoyuki; Usagawa, Tsuyoshi

2017-08-01

Directivity pattern of an ordinary loudspeaker becomes more directive at higher frequencies. However, because a single loudspeaker tends to radiate uniformly in all directions at low frequencies, reverberation from surrounding building walls may affect speech intelligibility when installing a multiple-loudspeaker system at crossroads. As an alternative, a sharply directive sound source is recommended to be used, but in many cases the directivity of an ordinary loudspeaker is less sharp at lower frequencies. Therefore, in order to overcome such a limitation, this paper discusses the possibility of using four loudspeakers under active control to realize a quadrupole radiation pattern in low frequency range. In this study, the radiation pattern of a primary loudspeaker and three secondary loudspeakers has been modelled. By placing the loudspeakers close together in the direction of 0°, 90°, 180°, and 270°, it was theoretically demonstrated that a quadrupole radiation pattern can be shaped in the target frequency range up to 600 Hz by simply controlling the directivity in three of four directions which are 45°, 135°, 225°, and 315°. Although, the radiation pattern model is far from realistic configurations and conditions, it is possible to realize a quadrupole radiation pattern in the low frequency range.

Long-range weight functions in fundamental measure theory of the non-uniform hard-sphere fluid

International Nuclear Information System (INIS)

Hansen-Goos, Hendrik

2016-01-01

We introduce long-range weight functions to the framework of fundamental measure theory (FMT) of the non-uniform, single-component hard-sphere fluid. While the range of the usual weight functions is equal to the hard-sphere radius R , the modified weight functions have range 3 R . Based on the augmented FMT, we calculate the radial distribution function g (r) up to second order in the density within Percus’ test particle theory. Consistency of the compressibility and virial routes on this level allows us to determine the free parameter γ of the theory. As a side result, we obtain a value for the fourth virial coefficient B 4 which deviates by only 0.01% from the exact result. The augmented FMT is tested for the dense fluid by comparing results for g (r) calculated via the test particle route to existing results from molecular dynamics simulations. The agreement at large distances (r   >  6 R) is significantly improved when the FMT with long-range weight functions is used. In order to improve agreement close to contact (r   =  2 R) we construct a free energy which is based on the accurate Carnahan–Starling equation of state, rather than the Percus–Yevick compressibility equation underlying standard FMT. (paper)

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

Science.gov (United States)

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

2009-01-01

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

Eigenmode frequency distribution of rapidly rotating neutron stars

International Nuclear Information System (INIS)

Boutloukos, Stratos; Nollert, Hans-Peter

2007-01-01

We use perturbation theory and the relativistic Cowling approximation to numerically compute characteristic oscillation modes of rapidly rotating relativistic stars which consist of a perfect fluid obeying a polytropic equation of state. We present a code that allows the computation of modes of arbitrary order. We focus here on the overall distribution of frequencies. As expected, we find an infinite pressure mode spectrum extending to infinite frequency. In addition we obtain an infinite number of inertial mode solutions confined to a finite, well-defined frequency range which depends on the compactness and the rotation frequency of the star. For nonaxisymmetric modes we observe how this range is shifted with respect to the axisymmetric ones, moving towards negative frequencies and thus making all m>2 modes unstable. We discuss whether our results indicate that the star's spectrum must have a continuous part, as opposed to simply containing an infinite number of discrete modes

Optimal Design of a High Efficiency LLC Resonant Converter with a Narrow Frequency Range for Voltage Regulation

Directory of Open Access Journals (Sweden)

Junhao Luo

2018-05-01

Full Text Available As a key factor in the design of a voltage-adjustable LLC resonant converter, frequency regulation range is very important to the optimization of magnetic components and efficiency improvement. This paper presents a novel optimal design method for LLC resonant converters, which can narrow the frequency variation range and ensure high efficiency under the premise of a required gain achievement. A simplified gain model was utilized to simplify the calculation and the expected efficiency was initially set as 96.5%. The restricted area of parameter optimization design can be obtained by taking the intersection of the gain requirement, the efficiency requirement, and three restrictions of ZVS (Zero Voltage Switch. The proposed method was verified by simulation and experiments of a 150 W prototype. The results show that the proposed method can achieve ZVS from full-load to no-load conditions and can reach 1.6 times the normalized voltage gain in the frequency variation range of 18 kHz with a peak efficiency of up to 96.3%. Moreover, the expected efficiency is adjustable, which means a converter with a higher efficiency can be designed. The proposed method can also be used for the design of large-power LLC resonant converters to obtain a wide output voltage range and higher efficiency.

Kinetic theory of interaction of high frequency waves with a rotating plasma

International Nuclear Information System (INIS)

Chiu, S. C.; Chan, V. S.; Chu, M. S.; Lin-Liu, Y. R.

2000-01-01

The equations of motion of charged particles of a strongly magnetized flowing plasma under the influence of high frequency waves are derived in the guiding center approximation. A quasilinear theory of the interactions of waves with rotating plasmas is formulated. This is applied to investigate the effect of radio frequency waves on a rotating tokamak plasma with a heated minority species. The angular momentum drive is mainly due to the rf-induced radial minority current. The return current by the bulk plasma gives an equal and opposite rotation drive on the bulk. Using moment equations and a small banana width approximation, the JxB drive was evaluated for the bulk plasma. Quite remarkably, although collisions are included, the net rotation drive is due to a term which can be obtained by neglecting collisions. (c) 2000 American Institute of Physics

KINETIC THEORY OF PLASMA WAVES: Part II: Homogeneous Plasma

NARCIS (Netherlands)

Westerhof, E.

2010-01-01

The theory of electromagnetic waves in a homogeneous plasma is reviewed. The linear response of the plasma to the waves is obtained in the form of the dielectric tensor. Waves ranging from the low frequency Alfven to the high frequency electron cyclotron waves are discussed in the limit of the cold

Kinetic theory of plasma waves: Part II homogeneous plasma

NARCIS (Netherlands)

Westerhof, E.

2000-01-01

The theory of electromagnetic waves in a homogeneous plasma is reviewed. The linear response of the plasma to the waves is obtained in the form of the dielectric tensor. Waves ranging from the low frequency Alfven to the high frequency electron cyclotron waves are discussed in the limit of the cold

Kinetic theory of plasma waves - Part II: Homogeneous plasma

NARCIS (Netherlands)

Westerhof, E.

2008-01-01

The theory of electromagnetic waves in a homogeneous plasma is reviewed. The linear response of the plasma to the waves is obtained in the form of the dielectric tensor. Waves ranging from the low frequency Alfven to the high frequency electron cyclotron waves axe discussed in the limit of the cold

A Technique for Real-Time Ionospheric Ranging Error Correction Based On Radar Dual-Frequency Detection

Science.gov (United States)

Lyu, Jiang-Tao; Zhou, Chen

2017-12-01

Ionospheric refraction is one of the principal error sources for limiting the accuracy of radar systems for space target detection. High-accuracy measurement of the ionospheric electron density along the propagation path of radar wave is the most important procedure for the ionospheric refraction correction. Traditionally, the ionospheric model and the ionospheric detection instruments, like ionosonde or GPS receivers, are employed for obtaining the electron density. However, both methods are not capable of satisfying the requirements of correction accuracy for the advanced space target radar system. In this study, we propose a novel technique for ionospheric refraction correction based on radar dual-frequency detection. Radar target range measurements at two adjacent frequencies are utilized for calculating the electron density integral exactly along the propagation path of the radar wave, which can generate accurate ionospheric range correction. The implementation of radar dual-frequency detection is validated by a P band radar located in midlatitude China. The experimental results present that the accuracy of this novel technique is more accurate than the traditional ionospheric model correction. The technique proposed in this study is very promising for the high-accuracy radar detection and tracking of objects in geospace.

Backreacted axion field ranges in string theory

Energy Technology Data Exchange (ETDEWEB)

Baume, Florent; Palti, Eran [Institut für Theoretische Physik, Ruprecht-Karls-Universität, Philosophenweg 19, Heidelberg, 69120 (Germany)

2016-08-05

String theory axions are interesting candidates for fields whose potential might be controllable over super-Planckian field ranges and therefore as possible candidates for inflatons in large field inflation. Axion monodromy scenarios are setups where the axion shift symmetry is broken by some effect such that the axion can traverse a large number of periods potentially leading to super-Planckian excursions. We study such scenarios in type IIA string theory where the axion shift symmetry is broken by background fluxes. In particular we calculate the backreaction of the energy density induced by the axion vacuum expectation value on its own field space metric. We find universal behaviour for all the compactifications studied where up to a certain critical axion value there is only a small backreaction effect. Beyond the critical value the backreaction is strong and implies that the proper field distance as measured by the backreacted metric increases at best logarithmically with the axion vev, thereby placing strong limitations on extending the field distance any further. The critical axion value can be made arbitrarily large by the choice of fluxes. However the backreaction of these fluxes on the axion field space metric ensures a precise cancellation such that the proper field distance up to the critical axion value is flux independent and remains sub-Planckian. We also study an axion alignment scenario for type IIA compactifications on a twisted torus with four fundamental axions mixing to leave an axion with an effective decay constant which is flux dependent. There is a choice of fluxes for which the alignment parameter controlling the effective decay constant is unconstrained by tadpoles and can in principle lead to an arbitrarily large effective decay constant. However we show that these fluxes backreact on the fundamental decay constants so as to precisely cancel any enhancement leaving a sub-Planckian effective decay constant.

Tuning Range Optimization of a Planar Inverted F Antenna for LTE Low Frequency Bands

DEFF Research Database (Denmark)

Barrio, Samantha Caporal Del; Pelosi, Mauro; Franek, Ondrej

2011-01-01

This paper presents a Planar Inverted F Antenna (PIFA) tuned with a fixed capacitor to the low frequency bands supported by the Long Term Evolution (LTE) technology. The tuning range is investigated and optimized with respect to the bandwidth and the efficiency of the resulting antenna. Simulatio...... and mock-ups are presented....

Gyrocenter-gauge kinetic theory

International Nuclear Information System (INIS)

Qin, H.; Tang, W.M.; Lee, W.W.

2000-01-01

Gyrocenter-gauge kinetic theory is developed as an extension of the existing gyrokinetic theories. In essence, the formalism introduced here is a kinetic description of magnetized plasmas in the gyrocenter coordinates which is fully equivalent to the Vlasov-Maxwell system in the particle coordinates. In particular, provided the gyroradius is smaller than the scale-length of the magnetic field, it can treat high frequency range as well as the usual low frequency range normally associated with gyrokinetic approaches. A significant advantage of this formalism is that it enables the direct particle-in-cell simulations of compressional Alfven waves for MHD applications and of RF waves relevant to plasma heating in space and laboratory plasmas. The gyrocenter-gauge kinetic susceptibility for arbitrary wavelength and arbitrary frequency electromagnetic perturbations in a homogeneous magnetized plasma is shown to recover exactly the classical result obtained by integrating the Vlasov-Maxwell system in the particle coordinates. This demonstrates that all the waves supported by the Vlasov-Maxwell system can be studied using the gyrocenter-gauge kinetic model in the gyrocenter coordinates. This theoretical approach is so named to distinguish it from the existing gyrokinetic theory, which has been successfully developed and applied to many important low-frequency and long parallel wavelength problems, where the conventional meaning of gyrokinetic has been standardized. Besides the usual gyrokinetic distribution function, the gyrocenter-gauge kinetic theory emphasizes as well the gyrocenter-gauge distribution function, which sometimes contains all the physics of the problems being studied, and whose importance has not been realized previously. The gyrocenter-gauge distribution function enters Maxwell's equations through the pull-back transformation of the gyrocenter transformation, which depends on the perturbed fields. The efficacy of the gyrocenter-gauge kinetic approach is

Main principles of passive devices based on graphene and carbon films in microwave-THz frequency range

Science.gov (United States)

Kuzhir, Polina P.; Paddubskaya, Alesia G.; Volynets, Nadezhda I.; Batrakov, Konstantin G.; Kaplas, Tommi; Lamberti, Patrizia; Kotsilkova, Rumiana; Lambin, Philippe

2017-07-01

The ability of thin conductive films, including graphene, pyrolytic carbon (PyC), graphitic PyC (GrPyC), graphene with graphitic islands (GrI), glassy carbon (GC), and sandwich structures made of all these materials separated by polymer slabs to absorb electromagnetic radiation in microwave-THz frequency range, is discussed. The main physical principles making a basis for high absorption ability of these heterostructures are explained both in the language of electromagnetic theory and using representation of equivalent electrical circuits. The idea of using carbonaceous thin films as the main working elements of passive radiofrequency (RF) devices, such as shields, filters, polarizers, collimators, is proposed theoretically and proved experimentally. The important advantage of PyC, GrI, GrPyC, and GC is that, in contrast to graphene, they either can be easily deposited onto a dielectric substrate or are strong enough to allow their transfer from the catalytic substrate without a shuttle polymer layer. This opens a new avenue toward the development of a scalable protocol for cost-efficient production of ultralight electromagnetic shields that can be transferred to commercial applications. A robust design via finite-element method and design of experiment for RF devices based on carbon/graphene films and sandwiches is also discussed in the context of virtual prototyping.

Short-range correlations in an extended time-dependent mean-field theory

International Nuclear Information System (INIS)

Madler, P.

1982-01-01

A generalization is performed of the time-dependent mean-field theory by an explicit inclusion of strong short-range correlations on a level of microscopic reversibility relating them to realistic nucleon-nucleon forces. Invoking a least action principle for correlated trial wave functions, equations of motion for the correlation functions and the single-particle model wave function are derived in lowest order of the FAHT cluster expansion. Higher order effects as well as long-range correlations are consider only to the extent to which they contribute to the mean field via a readjusted phenomenological effective two-body interaction. The corresponding correlated stationary problem is investigated and appropriate initial conditions to describe a heavy ion reaction are proposed. The singleparticle density matrix is evaluated

Manufacturing technologies for ultrasonic transducers in a broad frequency range

OpenAIRE

Gebhardt, Sylvia; Hohlfeld, Kai; Günther, Paul; Neubert, Holger

2018-01-01

According to the application field, working frequency of ultrasonic transducers needs to be tailored to a certain value. Low frequency ultrasonic transducers with working frequencies of 1 kHz to 1 MHz are especially interesting for sonar applications, whereas high frequency ultrasonic transducers with working frequencies higher than 15 MHz are favorable for high-resolution imaging in biomedical and non-destructive evaluation. Conventional non-destructive testing devices and clinical ultrasoun...

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

Science.gov (United States)

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

2007-01-01

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

Analytical determination of size-dependent natural frequencies of fully clamped rectangular microplates based on the modified couple stress theory

Energy Technology Data Exchange (ETDEWEB)

Askari, Amir R.; Tahani, Masoud [Ferdowsi University of Mashhad, Mashhad (Iran, Islamic Republic of)

2015-05-15

This paper presents an analytical and size-dependent model for vibrational analysis of fully clamped rectangular microplates. Modified couple stress theory (MCST) and the Kirchhoff plate model are considered, and Hamilton's principle is employed to derive the size dependent equation of motion that accounts for the effect of residual stresses. The natural frequencies of the microplate are extracted analytically by extended Kantorovich method. The present findings are validated with the available results in the literature, and an excellent agreement is observed between them. In addition, a parametric study is conducted to demonstrate the significant effects of couple stress components on the natural frequencies of fully clamped microplates. The ratio of MCST natural frequencies to those obtained with classical theory depends only on the Poisson's ratio of the plate and is independent of the aspect ratio of the plate for cases with no residual stresses.

Analytical determination of size-dependent natural frequencies of fully clamped rectangular microplates based on the modified couple stress theory

International Nuclear Information System (INIS)

Askari, Amir R.; Tahani, Masoud

2015-01-01

This paper presents an analytical and size-dependent model for vibrational analysis of fully clamped rectangular microplates. Modified couple stress theory (MCST) and the Kirchhoff plate model are considered, and Hamilton's principle is employed to derive the size dependent equation of motion that accounts for the effect of residual stresses. The natural frequencies of the microplate are extracted analytically by extended Kantorovich method. The present findings are validated with the available results in the literature, and an excellent agreement is observed between them. In addition, a parametric study is conducted to demonstrate the significant effects of couple stress components on the natural frequencies of fully clamped microplates. The ratio of MCST natural frequencies to those obtained with classical theory depends only on the Poisson's ratio of the plate and is independent of the aspect ratio of the plate for cases with no residual stresses.

Experimental separation of a frequency spin echo signal

International Nuclear Information System (INIS)

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

1981-01-01

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

On the universality of the long-/short-range separation in multiconfigurational density-functional theory

Science.gov (United States)

Fromager, Emmanuel; Toulouse, Julien; Jensen, Hans Jørgen Aa.

2007-02-01

In many cases, the dynamic correlation can be calculated quite accurately and at a fairly low computational cost in Kohn-Sham density-functional theory (KS-DFT), using current standard approximate functionals. However, in general, KS-DFT does not treat static correlation effects (near degeneracy) adequately which, on the other hand, can be described in wave-function theory (WFT), for example, with a multiconfigurational self-consistent field (MCSCF) model. It is therefore of high interest to develop a hybrid model which combines the best of both WFT and DFT approaches. The merge of WFT and DFT can be achieved by splitting the two-electron interaction into long-range and short-range parts. The long-range part is then treated by WFT and the short-range part by DFT. In this work the authors consider the so-called "erf" long-range interaction erf(μr12)/r12, which is based on the standard error function, and where μ is a free parameter which controls the range of the long-/short-range decomposition. In order to formulate a general method, they propose a recipe for the definition of an optimal μopt parameter, which is independent of the approximate short-range functional and the approximate wave function, and they discuss its universality. Calculations on a test set consisting of He, Be, Ne, Mg, H2, N2, and H2O yield μopt≈0.4a.u.. A similar analysis on other types of test systems such as actinide compounds is currently in progress. Using the value of 0.4a.u. for μ, encouraging results are obtained with the hybrid MCSCF-DFT method for the dissociation energies of H2, N2, and H2O, with both short-range local-density approximation and PBE-type functionals.

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

Science.gov (United States)

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

2008-01-01

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

Low-Voltage, Low-Power, and Wide-Tuning-Range Ring-VCO for Frequency ΔΣ Modulator

DEFF Research Database (Denmark)

Tuan Vu, Cao; Wisland, Dag T.; Lande, Tor Sverre

A low-voltage, low-power, and wide-tuning-range VCO which converts an analog input voltage to phase information for a frequency ΔΣ modulator is proposed in this paper. The VCO is based on a differential ring oscillator, which is improved with modified symmetric load and a positive feedback...

Synthesis strategy: building a culturally sensitive mid-range theory of risk perception using literary, quantitative, and qualitative methods.

Science.gov (United States)

Siaki, Leilani A; Loescher, Lois J; Trego, Lori L

2013-03-01

This article presents a discussion of development of a mid-range theory of risk perception. Unhealthy behaviours contribute to the development of health inequalities worldwide. The link between perceived risk and successful health behaviour change is inconclusive, particularly in vulnerable populations. This may be attributed to inattention to culture. The synthesis strategy of theory building guided the process using three methods: (1) a systematic review of literature published between 2000-2011 targeting perceived risk in vulnerable populations; (2) qualitative and (3) quantitative data from a study of Samoan Pacific Islanders at high risk of cardiovascular disease and diabetes. Main concepts of this theory include risk attention, appraisal processes, cognition, and affect. Overarching these concepts is health-world view: cultural ways of knowing, beliefs, values, images, and ideas. This theory proposes the following: (1) risk attention varies based on knowledge of the health risk in the context of health-world views; (2) risk appraisals are influenced by affect, health-world views, cultural customs, and protocols that intersect with the health risk; (3) strength of cultural beliefs, values, and images (cultural identity) mediate risk attention and risk appraisal influencing the likelihood that persons will engage in health-promoting behaviours that may contradict cultural customs/protocols. Interventions guided by a culturally sensitive mid-range theory may improve behaviour-related health inequalities in vulnerable populations. The synthesis strategy is an intensive process for developing a culturally sensitive mid-range theory. Testing of the theory will ascertain its usefulness for reducing health inequalities in vulnerable groups. © 2012 Blackwell Publishing Ltd.

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

Science.gov (United States)

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

2016-05-01

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

Multi-year high-frequency hydrothermal monitoring of selected high-threat Cascade Range volcanoes

Science.gov (United States)

Crankshaw, I. M.; Archfield, S. A.; Newman, A. C.; Bergfeld, D.; Clor, L. E.; Spicer, K. R.; Kelly, P. J.; Evans, W. C.; Ingebritsen, S. E.

2018-05-01

From 2009 to 2015 the U.S. Geological Survey (USGS) systematically monitored hydrothermal behavior at selected Cascade Range volcanoes in order to define baseline hydrothermal and geochemical conditions. Gas and water data were collected regularly at 25 sites on 10 of the highest-risk volcanoes in the Cascade Range. These sites include near-summit fumarole groups and springs/streams that show clear evidence of magmatic influence (high 3He/4He ratios and/or large fluxes of magmatic CO2 or heat). Site records consist mainly of hourly temperature and hydrothermal-flux data. Having established baseline conditions during a multiyear quiescent period, the USGS reduced monitoring frequency from 2015 to present. The archived monitoring data are housed at (doi:10.5066/F72N5088). These data (1) are suitable for retrospective comparison with other continuous geophysical monitoring data and (2) will provide context during future episodes of volcanic unrest, such that unrest-related variations at these thoroughly characterized sites will be more clearly recognizable. Relatively high-frequency year-round data are essential to achieve these objectives, because many of the time series reveal significant diurnal, seasonal, and inter-annual variability that would tend to mask unrest signals in the absence of baseline data. Here we characterize normal variability for each site, suggest strategies to detect future volcanic unrest, and explore deviations from background associated with recent unrest.

Experimental demonstrations in audible frequency range of band gap tunability and negative refraction in two-dimensional sonic crystal.

Science.gov (United States)

Pichard, Hélène; Richoux, Olivier; Groby, Jean-Philippe

2012-10-01

The propagation of audible acoustic waves in two-dimensional square lattice tunable sonic crystals (SC) made of square cross-section infinitely rigid rods embedded in air is investigated experimentally. The band structure is calculated with the plane wave expansion (PWE) method and compared with experimental measurements carried out on a finite extend structure of 200 cm width, 70 cm depth and 15 cm height. The structure is made of square inclusions of 5 cm side with a periodicity of L = 7.5 cm placed inbetween two rigid plates. The existence of tunable complete band gaps in the audible frequency range is demonstrated experimentally by rotating the scatterers around their vertical axis. Negative refraction is then analyzed by use of the anisotropy of the equi-frequency surface (EFS) in the first band and of a finite difference time domain (FDTD) method. Experimental results finally show negative refraction in the audible frequency range.

Gyrocon Radio-Frequency-Generator project for FY-78 and -79

International Nuclear Information System (INIS)

Tallerico, P.J.; Rankin, J.E.

1980-09-01

The gyrocon is a high-power, high-efficiency amplifier that operates by deflection modulation of an electron beam. The bunching is better than that in a klystron, especially for very high powers and UHF frequencies, so the overall efficiency and the maximum output power can be higher than in a klystron. The present theory includes the effects of large signals, space charge, and finite beam size. The equations of motion are relativistically correct, and the space-charge fields are correct to first order in v/c. The theory is derived and a computer code to solve these equations is discussed. The code is then used to obtain several specific examples of gyrocon designs that have significant advantages over klystrons or gridded tubes in the 0.2- to 1.0-GHz frequency range. Several embodiments of the gyrocon are possible: the radial style and the spherical style are discussed in this report. The radial style has a bender magnet to increase the deflection of the beam, whereas the spherical gyrocon does not employ the bender magnet. The optimum frequency range for the spherical gyrocon is from 1.0 to 2.5 GHz

Hyper capacity of MCM-41 supramoleculer structure in the radio- frequency range

OpenAIRE

I.I. Grygorchak; S.A. Vojtovych; Z.A. Stotsko; B.A. Seredyuk; N.K. Tovstyuk

2011-01-01

Purpose: of this paper was: 1) to synthesize supramolecular МСМ-41 structure (p-cyanogen phenyl ether of n-heptyl benzoic acid - 40%)>> with inserted guested nematic and 2) to study its dielectric properties.Design/methodology/approach: Supramolecular МСМ-41 structure has been synthesized by vacuum encapsulated method at room temperature. Dielectric properties have been studied by impedance spectroscopy method in the frequency range 10-3-106 Hz by “AUTOLAB” complex of “ECO CHEMIE” (Holland),...

Middle range theory evaluation: bridging the theory-practice gap ...

African Journals Online (AJOL)

Nurse education is being challenged to maintain quality in light of shortage of practice professionals, societal demands and rapid changes in health care delivery. The importance underlying the practice of nursing education must continue to be explored through theories to bring about refinement of educational strategies for ...

Theory of the high-frequency limiting viscosity of a dilute polymer solution. Pt. 2

Energy Technology Data Exchange (ETDEWEB)

Doi, M; Nakajima, H; Wada, Y

1976-06-01

High-frequency limiting viscosities of dilute polymer solutions are calculated on the basis of the author's previous theory for (1) necklace model of a chain with constant bond length and bond angle under a hindering rotational potential, and (2) broken rod model consisting of N rods with equal length connected by universal joints. Exact treatment is possible for a once-broken rod model, but the Monte Carlo method is used in the other calculations.

Adiabatic perturbation theory for atoms and molecules in the low-frequency regime.

Science.gov (United States)

Martiskainen, Hanna; Moiseyev, Nimrod

2017-12-14

There is an increasing interest in the photoinduced dynamics in the low frequency, ω, regime. The multiphoton absorptions by molecules in strong laser fields depend on the polarization of the laser and on the molecular structure. The unique properties of the interaction of atoms and molecules with lasers in the low-frequency regime imply new concepts and directions in strong-field light-matter interactions. Here we represent a perturbational approach for the calculations of the quasi-energy spectrum in the low-frequency regime, which avoids the construction of the Floquet operator with extremely large number of Floquet channels. The zero-order Hamiltonian in our perturbational approach is the adiabatic Hamiltonian where the atoms/molecules are exposed to a dc electric field rather than to ac-field. This is in the spirit of the first step in the Corkum three-step model. The second-order perturbation correction terms are obtained when iℏω∂∂τ serves as a perturbation and τ is a dimensionless variable. The second-order adiabatic perturbation scheme is found to be an excellent approach for calculating the ac-field Floquet solutions in our test case studies of a simple one-dimensional time-periodic model Hamiltonian. It is straightforward to implement the perturbation approach presented here for calculating atomic and molecular energy shifts (positions) due to the interaction with low-frequency ac-fields using high-level electronic structure methods. This is enabled since standard quantum chemistry packages allow the calculations of atomic and molecular energy shifts due to the interaction with dc-fields. In addition to the shift of the energy positions, the energy widths (inverse lifetimes) can be obtained at the same level of theory. These energy shifts are functions of the laser parameters (low frequency, intensity, and polarization).

Stochastic reduced-order model for an automotive vehicle in presence of numerous local elastic modes in the low-frequency range

OpenAIRE

Arnoux , A.; Batou , Anas; Soize , Christian; Gagliardini , L.

2012-01-01

International audience; This paper is devoted to the construction of a stochastic reduced-order model for dynamical structures having a high modal density in the low-frequency range, such as an automotive vehicle. This type of structure is characterized by the fact that it exhibits, in the low-frequency range, not only the classical global elastic modes but also numerous local elastic modes which cannot easily be separated from the global elastic modes. An approach has recently been proposed ...

Electromagnetic emission from terrestrial lightning in the 0.1-30 MHz frequency range

Science.gov (United States)

Karashtin, A. N.; Gurevich, A. V.

Results of measurements carried out at SURA facility of Radiophisical Research Institute and at Tien-Shan Mountain Scientific Station of Lebedev Physical Institute using specially designed installations for short electromagnetic pulse observation in the frequency range from 0.1 to 30 MHz are presented. Specific attention is paid to initial stage of the lightning discharge. It is shown that lightning can be initiated by extensive atmospheric showers caused by high energy cosmic ray particles. Analysis of emission of few thousand lightning discharges showed that • Short wave radio emission of lightning consists of a series of short pulses with duration from less than 100 nanoseconds to several microseconds separated well longer gaps. • Background noise between lightning discharges is not differ from one observed without thunderstorm activity (at given sensitivity). Usually it is the same between lightning pulses at least at the initial stage. • Each lightning discharge radio emission starts with a number of very short (less than 100 nanoseconds at 0.7 level) bi-polar pulses. Gaps between initial pulses vary from several microseconds to few hundreds of microseconds. No radio emission was observed before the first pulse during at least 500 milliseconds. Both positive and negative polarity of the first pulses occur in approximately equal proportion in different lightning discharges while the polarity was the same in any individual lightning. • First pulse amplitude, width and waveform are consistent with predicted by the theory of combined action of runaway breakdown and extensive atmospheric shower caused by cosmic ray particle of 1016 eV energy. Lightning discharges at other planets can be initiated by cosmic ray particles as well. This work was partly supported by ISTC grant # 2236p. The work of one of the authors (A. N. Karashtin) was also partly supported by INTAS grant # 03-51-5727.

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

Directory of Open Access Journals (Sweden)

Chen Xiaolong

2018-04-01

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

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

NARCIS (Netherlands)

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

2012-01-01

Two ion cyclotron range of frequencies (ICRF) heating schemes proposed for the half-field operation phase of ITER in hydrogen plasmas—fundamental H majority and second harmonic 3 He ICRF heating—were recently investigated in JET. Although the same magnetic field and RF frequencies ( f ≈ 42 MHz and f

Dielectric Properties of Marsh Vegetation in a Frequency Range of 0.1-18 GHz Under Variation of Temperature and Moisture

Science.gov (United States)

Romanov, A. N.; Kochetkova, T. D.; Suslyaev, V. I.; Shcheglova, A. S.

2017-09-01

Dielectric characteristics of some species of marsh vegetation: lichen Cladonia stellaris (Opiz) Pouzar, moss Sphagnum, and a representative of Bryidae mosses - Dicranum polysetum are studied in the frequency range from 100 MHz to 18 GHz. At a frequency of 1.41 GHz, the influence of temperature in the range from -12 to +20°C on the behavior of dielectric characteristics of mosses, lichens, and peat is studied. The dependences of the dielectric characteristics of vegetation on the volumetric wetness are established.

Low-Frequency Interlayer Breathing Modes in Few-Layer Black Phosphorus.

Science.gov (United States)

Ling, Xi; Liang, Liangbo; Huang, Shengxi; Puretzky, Alexander A; Geohegan, David B; Sumpter, Bobby G; Kong, Jing; Meunier, Vincent; Dresselhaus, Mildred S

2015-06-10

As a new two-dimensional layered material, black phosphorus (BP) is a very promising material for nanoelectronics and optoelectronics. We use Raman spectroscopy and first-principles theory to characterize and understand the low-frequency (LF) interlayer breathing modes (<100 cm(-1)) in few-layer BP for the first time. Using a laser polarization dependence study and group theory analysis, the breathing modes are assigned to Ag symmetry. Compared to the high-frequency (HF) Raman modes, the LF breathing modes are considerably more sensitive to interlayer coupling and, thus, their frequencies show a stronger dependence on the number of layers. Hence, they constitute an effective means to probe both the crystalline orientation and thickness of few-layer BP. Furthermore, the temperature dependence shows that in the temperature range -150 to 30 °C, the breathing modes have a weak anharmonic behavior, in contrast to the HF Raman modes that exhibit strong anharmonicity.

Alternative separation of exchange and correlation energies in multi-configuration range-separated density-functional theory.

Science.gov (United States)

Stoyanova, Alexandrina; Teale, Andrew M; Toulouse, Julien; Helgaker, Trygve; Fromager, Emmanuel

2013-10-07

The alternative separation of exchange and correlation energies proposed by Toulouse et al. [Theor. Chem. Acc. 114, 305 (2005)] is explored in the context of multi-configuration range-separated density-functional theory. The new decomposition of the short-range exchange-correlation energy relies on the auxiliary long-range interacting wavefunction rather than the Kohn-Sham (KS) determinant. The advantage, relative to the traditional KS decomposition, is that the wavefunction part of the energy is now computed with the regular (fully interacting) Hamiltonian. One potential drawback is that, because of double counting, the wavefunction used to compute the energy cannot be obtained by minimizing the energy expression with respect to the wavefunction parameters. The problem is overcome by using short-range optimized effective potentials (OEPs). The resulting combination of OEP techniques with wavefunction theory has been investigated in this work, at the Hartree-Fock (HF) and multi-configuration self-consistent-field (MCSCF) levels. In the HF case, an analytical expression for the energy gradient has been derived and implemented. Calculations have been performed within the short-range local density approximation on H2, N2, Li2, and H2O. Significant improvements in binding energies are obtained with the new decomposition of the short-range energy. The importance of optimizing the short-range OEP at the MCSCF level when static correlation becomes significant has also been demonstrated for H2, using a finite-difference gradient. The implementation of the analytical gradient for MCSCF wavefunctions is currently in progress.

Simple Wide Frequency Range Impedance Meter Based on AD5933 Integrated Circuit

Directory of Open Access Journals (Sweden)

Chabowski Konrad

2015-03-01

Full Text Available As it contains elements of complete digital impedance meter, the AD5933 integrated circuit is an interesting solution for impedance measurements. However, its use for measurements in a wide range of impedances and frequencies requires an additional digital and analogue circuitry. This paper presents the design and performance of a simple impedance meter based on the AD5933 IC. Apart from the AD5933 IC it consists of a clock generator with a programmable prescaler, a novel DC offset canceller for the excitation signal based on peak detectors and a current to voltage converter with switchable conversion ratios. The authors proposed a simple method for choosing the measurement frequency to minimalize errors resulting from the spectral leakage and distortion caused by a lack of an anti-aliasing filter in the DDS generator. Additionally, a novel method for the AD5933 IC calibration was proposed. It consists in a mathematical compensation of the systematic error occurring in the argument of the value returned from the AD5933 IC as a result. The performance of the whole system is demonstrated in an exemplary measurement.

Simulation of stress-modulated magnetization precession frequency in Heusler-based spin torque oscillator

International Nuclear Information System (INIS)

Huang, Houbing; Zhao, Congpeng; Ma, Xingqiao

2017-01-01

We investigated stress-modulated magnetization precession frequency in Heusler-based spin transfer torque oscillator by combining micromagnetic simulations with phase field microelasticity theory, by encapsulating the magnetic tunnel junction into multilayers structures. We proposed a novel method of using an external stress to control the magnetization precession in spin torque oscillator instead of an external magnetic field. The stress-modulated magnetization precession frequency can be linearly modulated by externally applied uniaxial in-plane stress, with a tunable range 4.4–7.0 GHz under the stress of 10 MPa. By comparison, the out-of-plane stress imposes negligible influence on the precession frequency due to the large out-of-plane demagnetization field. The results offer new inspiration to the design of spin torque oscillator devices that simultaneously process high frequency, narrow output band, and tunable over a wide range of frequencies via external stress. - Highlights: • We proposed stress-modulated magnetization precession in spin torque oscillator. • The magnetization precession frequency can be linearly modulated by in-plane stress. • The stress also can widen the magnetization frequency range 4.4–7.0 GHz. • The stress-modulated oscillation frequency can simplify STO devices.

Simulation of stress-modulated magnetization precession frequency in Heusler-based spin torque oscillator

Energy Technology Data Exchange (ETDEWEB)

Huang, Houbing, E-mail: hbhuang@ustb.edu.cn; Zhao, Congpeng; Ma, Xingqiao, E-mail: xqma@sas.ustb.edu.cn

2017-03-15

We investigated stress-modulated magnetization precession frequency in Heusler-based spin transfer torque oscillator by combining micromagnetic simulations with phase field microelasticity theory, by encapsulating the magnetic tunnel junction into multilayers structures. We proposed a novel method of using an external stress to control the magnetization precession in spin torque oscillator instead of an external magnetic field. The stress-modulated magnetization precession frequency can be linearly modulated by externally applied uniaxial in-plane stress, with a tunable range 4.4–7.0 GHz under the stress of 10 MPa. By comparison, the out-of-plane stress imposes negligible influence on the precession frequency due to the large out-of-plane demagnetization field. The results offer new inspiration to the design of spin torque oscillator devices that simultaneously process high frequency, narrow output band, and tunable over a wide range of frequencies via external stress. - Highlights: • We proposed stress-modulated magnetization precession in spin torque oscillator. • The magnetization precession frequency can be linearly modulated by in-plane stress. • The stress also can widen the magnetization frequency range 4.4–7.0 GHz. • The stress-modulated oscillation frequency can simplify STO devices.

Analysis of Weyl-affine theories of gravity in terms of the gravitational frequency shift effect

International Nuclear Information System (INIS)

Coley, A.A.; Sarmiento, G.A.

1986-01-01

A subclass of nonmetric theories of gravity, called Weyl-affine theories of gravity (WATGs), is analyzed by calculating their predictions for the gravitational frequency shift undergone by a wave signal in a planned solar probe. The analysis is carried out using a formalism in a spherically symmetric and static gravitational field. One of the advantages of the formalism is that any possible ''nonmetricity'' is contained in an arbitrary function, λ, of the Newtonian gravitational potential, U. The numerical results are calculated for a situation modeling a future experiment in the solar system. In the calculations, the metric components and the function, λ, are expanded up to third order in U. Within the limits of the gravitational redshift experiments performed to date, it is found that WATGs must coincide with their metric counterparts (i.e., λ is unity). It is hoped that the planned solar probe will test the nature of the theories under investigation to a higher degree of accuracy

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

Energy Technology Data Exchange (ETDEWEB)

Ziętek, Sławomir, E-mail: zietek@agh.edu.pl; Skowroński, Witold; Wiśniowski, Piotr; Czapkiewicz, Maciej; Stobiecki, Tomasz [Department of Electronics, AGH University of Science and Technology, Al. Mickiewicza 30, 30-059 Kraków (Poland); Ogrodnik, Piotr [Department of Electronics, AGH University of Science and Technology, Al. Mickiewicza 30, 30-059 Kraków (Poland); Faculty of Physics, Warsaw University of Technology, ul. Koszykowa 75, 00-662 Warszawa (Poland); Institute of Molecular Physics, Polish Academy of Sciences, ul. Smoluchowskiego 17, 60-179 Poznań (Poland); Barnaś, Józef [Institute of Molecular Physics, Polish Academy of Sciences, ul. Smoluchowskiego 17, 60-179 Poznań (Poland); Faculty of Physics, Adam Mickiewicz University, ul. Umultowska 85, 61-614 Poznań (Poland)

2015-09-21

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

Reflecting and Polarizing Properties of Conductive Fabrics in Ultra-High Frequency Range

Directory of Open Access Journals (Sweden)

Oleg Kiprijanovič

2015-09-01

Full Text Available The system based on ultra-wide band (UWB signals was employed for qualitative estimation of attenuating, reflecting and polarizing properties of conductive fabrics, capable to prevent local static charge accumulation. Pulsed excitation of triangle monopole antenna of 6.5 cm height by rectangular electric pulses induced radiation of UWB signals with spectral density of power having maximum in ultra-high frequency (UHF range. The same antenna was used for the radiated signal receiving. Filters and amplifiers of different passband were employed to divide UHF range into subranges of 0.3-0.55 GHz, 0.55-1 GHz, 1-2 GHz and 2-4 GHz bands. The free space method, when conductive fabric samples of 50x50 cm2 were placed between transmitting and receiving antennas, was used to imitate a practical application. Received wideband signals corresponding to the defined range were detected by unbiased detectors. The fabrics made of two types of warps, containing different threads with conductive yarns, were investigated. It was estimated attenuation and reflective properties of the fabrics when electric field is collinear or perpendicular to thread direction. In the UHF range it was revealed good reflecting properties of the fabrics containing metallic component in the threads. The system has advantages but not without a certain shortcoming. Adapting it for specific tasks should lead to more effective usage, including yet unused properties of the UWB signals.

Numerical modelisation of RF waves in the ion cyclotron range of frequency for Tokamak plasmas

International Nuclear Information System (INIS)

Edery, D.; Picq, H.; Samain, A.; Gambier, D.J.

1987-12-01

The purpose of this paper is to present the numerical code ALCYON developed to compute the RF field structure in the ion cyclotron range of frequencies. The code handles fundamental and second harmonic heating while the mode conversion onto modes of decreasing wavelength is simulated by a selective power absorption on slow waves when their wavelength reaches the mesh size

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

Directory of Open Access Journals (Sweden)

Loizos G.

2014-07-01

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

Research of resonant losses of ultrasonic sound in the deformed single crystals in temperature range 77...300 K

International Nuclear Information System (INIS)

Petchenko, A.M.; Petchenko, G.A.

2007-01-01

The damped dislocation resonance in preliminary deformed up to 1 % single crystals KBr was investigated. The measurements of a frequency dependence of a dislocation damping decrement of ultrasonic sound were conducted in range of frequencies 7,5...217,5 MHz and temperature range 77...300 K. From the analysis of frequency spectrums the temperature course of a coefficient of phonon viscosity B was determined, which is agreed both with the theory and experimental literary data. The influencing temperature changes of length of a dislocation segment on parameters of a resonant maximum and dynamic drag of dislocations by phonons was revealed and analyzed

Low profile frequency agile MIMO slot antenna with TCM characterization

KAUST Repository

Ghalib, Asim

2017-06-07

In this paper, a frequency reconfigurable multiple-input-multiple-output (MIMO) slot antenna is presented. The proposed design is low profile and compact with wide tunability range, covering several well-known frequency bands from 1800 MHz to 2450 MHz. The frequency reconfigurability is achieved by loading the annular slot with varactor diodes. The antenna system is also analyzed for MIMO performance metrics. Moreover, the effect of circular slot antenna on the chassis modes is also investigated using the theory of characteristic modes (TCM). The physical principle behind frequency reconfigurability is also investigated using TCM analysis. An interesting finding is observed using varactor diodes for frequency reconfigurability, that is the reactive impedance loading does not alter the modal significance (MS) plots but only aid in the input impedance matching at different frequency bands.

Theory of sum-frequency generation spectroscopy of adsorbed molecules using the density matrix method-broadband vibrational sum-frequency generation and applications

International Nuclear Information System (INIS)

Bonn, M; Ueba, H; Wolf, M

2005-01-01

A generalized theory of frequency- and time-resolved vibrational sum-frequency generation (SFG) spectroscopy of adsorbates at surfaces is presented using the density matrix formalism. Our theoretical treatment is specifically aimed at addressing issues that accompany the relatively novel SFG approach using broadband infrared pulses. The ultrashort duration of these pulses makes them ideally suited for time-resolved investigations, for which we present a complete theoretical treatment. A second key characteristic of these pulses is their large bandwidth and high intensity, which allow for highly non-linear effects, including vibrational ladder climbing of surface vibrations. We derive general expressions relating the density matrix to SFG spectra, and apply these expressions to specific experimental results by solving the coupled optical Bloch equations of the density matrix elements. Thus, we can theoretically reproduce recent experimentally demonstrated hot band SFG spectra using femtosecond broadband infrared excitation of carbon monoxide (CO) on a Ru(001) surface

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

Science.gov (United States)

Kono, Yoshiaki; Kohn, Joshua R.

2015-01-01

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

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...

Frequency dependence and frequency control of microbubble streaming flows

Science.gov (United States)

Wang, Cheng; Rallabandi, Bhargav; Hilgenfeldt, Sascha

2013-02-01

Steady streaming from oscillating microbubbles is a powerful actuating mechanism in microfluidics, enjoying increased use due to its simplicity of manufacture, ease of integration, low heat generation, and unprecedented control over the flow field and particle transport. As the streaming flow patterns are caused by oscillations of microbubbles in contact with walls of the set-up, an understanding of the bubble dynamics is crucial. Here we experimentally characterize the oscillation modes and the frequency response spectrum of such cylindrical bubbles, driven by a pressure variation resulting from ultrasound in the range of 1 kHz raisebox {-.9ex{stackrel{textstyle <}{˜ }} }f raisebox {-.9ex{stackrel{textstyle <}{˜ }} } 100 kHz. We find that (i) the appearance of 2D streaming flow patterns is governed by the relative amplitudes of bubble azimuthal surface modes (normalized by the volume response), (ii) distinct, robust resonance patterns occur independent of details of the set-up, and (iii) the position and width of the resonance peaks can be understood using an asymptotic theory approach. This theory describes, for the first time, the shape oscillations of a pinned cylindrical bubble at a wall and gives insight into necessary mode couplings that shape the response spectrum. Having thus correlated relative mode strengths and observed flow patterns, we demonstrate that the performance of a bubble micromixer can be optimized by making use of such flow variations when modulating the driving frequency.

Restricted numerical range: A versatile tool in the theory of quantum information

Science.gov (United States)

Gawron, Piotr; Puchała, Zbigniew; Miszczak, Jarosław Adam; Skowronek, Łukasz; Życzkowski, Karol

2010-10-01

Numerical range of a Hermitian operator X is defined as the set of all possible expectation values of this observable among a normalized quantum state. We analyze a modification of this definition in which the expectation value is taken among a certain subset of the set of all quantum states. One considers, for instance, the set of real states, the set of product states, separable states, or the set of maximally entangled states. We show exemplary applications of these algebraic tools in the theory of quantum information: analysis of k-positive maps and entanglement witnesses, as well as study of the minimal output entropy of a quantum channel. Product numerical range of a unitary operator is used to solve the problem of local distinguishability of a family of two unitary gates.

An Information Theory-Inspired Strategy for Design of Re-programmable Encrypted Graphene-based Coding Metasurfaces at Terahertz Frequencies.

Science.gov (United States)

Momeni, Ali; Rouhi, Kasra; Rajabalipanah, Hamid; Abdolali, Ali

2018-04-18

Inspired by the information theory, a new concept of re-programmable encrypted graphene-based coding metasurfaces was investigated at terahertz frequencies. A channel-coding function was proposed to convolutionally record an arbitrary information message onto unrecognizable but recoverable parity beams generated by a phase-encrypted coding metasurface. A single graphene-based reflective cell with dual-mode biasing voltages was designed to act as "0" and "1" meta-atoms, providing broadband opposite reflection phases. By exploiting graphene tunability, the proposed scheme enabled an unprecedented degree of freedom in the real-time mapping of information messages onto multiple parity beams which could not be damaged, altered, and reverse-engineered. Various encryption types such as mirroring, anomalous reflection, multi-beam generation, and scattering diffusion can be dynamically attained via our multifunctional metasurface. Besides, contrary to conventional time-consuming and optimization-based methods, this paper convincingly offers a fast, straightforward, and efficient design of diffusion metasurfaces of arbitrarily large size. Rigorous full-wave simulations corroborated the results where the phase-encrypted metasurfaces exhibited a polarization-insensitive reflectivity less than -10 dB over a broadband frequency range from 1 THz to 1.7 THz. This work reveals new opportunities for the extension of re-programmable THz-coding metasurfaces and may be of interest for reflection-type security systems, computational imaging, and camouflage technology.

Wolf, Canis lupus, visits to white-tailed deer, Odocoileus virginianus, summer ranges: Optimal foraging?

Science.gov (United States)

Demma, D.J.; Mech, L.D.

2009-01-01

We tested whether Wolf (Canis lupus) visits to individual female White-tailed Deer (Odocoileus virginianus) summer ranges during 2003 and 2004 in northeastern Minnesota were in accord with optimal-foraging theory. Using GPS collars with 10- to 30-minute location attempts on four Wolves and five female deer, plus eleven VHF-collared female deer in the Wolves' territory, provided new insights into the frequency of Wolf visits to summer ranges of female deer. Wolves made a mean 0.055 visits/day to summer ranges of deer three years and older, significantly more than their 0.032 mean visits/day to ranges of two-year-old deer, which generally produce fewer fawns, and most Wolf visits to ranges of older deer were much longer than those to ranges of younger deer. Because fawns comprise the major part of the Wolf's summer diet, this Wolf behavior accords with optimal-foraging theory.

Physics of the Brain. Prevention of the Epileptic Seizures by the Multi-photon Pulsed-operated Fiber Lasers in the Ultraviolet Range of Frequencies.

Science.gov (United States)

Stefan, V. Alexander; IAPS Team

The novel study of the epileptogenesis mechanisms is proposed. It is based on the pulsed-operated (amplitude modulation) multi-photon (frequency modulation) fiber-laser interaction with the brain epilepsy-topion (the epilepsy onset area), so as to prevent the excessive electrical discharge (epileptic seizure) in the brain. The repetition frequency, Ω, matches the low frequency (epileptic) phonon waves in the brain. The laser repetition frequency (5-100 pulses per second) enables the resonance-scanning of the wide range of the phonon (possible epileptic-to-be) activity in the brain. The tunable fiber laser frequencies, Δω (multi photon operation), are in the ultraviolet frequency range, thus enabling monitoring of the electrical charge imbalance (within the 10s of milliseconds), and the DNA-corruption in the epilepsy-topion, as the possible cause of the disease. Supported by Nikola Tesla Labs., Stefan University.

Polarizable embedding with a multiconfiguration short-range density functional theory linear response method

DEFF Research Database (Denmark)

Hedegård, Erik D.; Olsen, Jógvan Magnus Haugaard; Knecht, Stefan

2015-01-01

. To demonstrate the capabilities of PE-MC-srDFT, we also investigated the retinylidene Schiff base chromophore embedded in the channelrhodopsin protein. While using a much more compact reference wave function in terms of active space, our PE-MC-srDFT approach yields excitation energies comparable in quality......We present here the coupling of a polarizable embedding (PE) model to the recently developed multiconfiguration short-range density functional theory method (MC-srDFT), which can treat multiconfigurational systems with a simultaneous account for dynamical and static correlation effects. PE......-MC-srDFT is designed to combine efficient treatment of complicated electronic structures with inclusion of effects from the surrounding environment. The environmental effects encompass classical electrostatic interactions as well as polarization of both the quantum region and the environment. Using response theory...

Shifts in diversification rates and host jump frequencies shaped the diversity of host range among Sclerotiniaceae fungal plant pathogens

OpenAIRE

Taylor, Andrew; Clarkson, John; Raffaele, Sylvain; Navaud, Olivier; Barbacci, Adelin

2017-01-01

The range of hosts that a parasite can infect in nature is a trait determined by its own evolutionary history and that of its potential hosts. However, knowledge on host range diversity and evolution at the family level is often lacking. Here, we investigate host range variation and diversification trends within the Sclerotiniaceae , a family of Ascomycete fungi. Using a phylogenetic framework, we associate diversification rates, the frequency of host jump events, and host range variation dur...

The relationship between brightness temperature and soil moisture. Selection of frequency range for microwave remote sensing

International Nuclear Information System (INIS)

Rao, K.S.; Chandra, G.; Rao, P.V.N.

1987-01-01

The analysis of brightness temperature data acquired from field and aircraft experiments demonstrates a linear relationship between soil moisture and brightness temperature. However, the analysis of brightness temperature data acquired by the Skylab radiometer demonstrates a non-linear relationship between soil moisture and brightness temperature. In view of the above and also because of recent theoretical developments for the calculation of the dielectric constant and brightness temperature under varying soil moisture profile conditions, an attempt is made to study the theoretical relationship between brightness temperature and soil moisture as a function of frequency. Through the above analysis, the appropriate microwave frequency range for soil moisture studies is recommended

1.55-μm mode-locked quantum-dot lasers with 300 MHz frequency tuning range

Energy Technology Data Exchange (ETDEWEB)

Sadeev, T., E-mail: tagir@mailbox.tu-berlin.de; Arsenijević, D.; Bimberg, D. [Institut für Festkörperphysik, Technische Universität Berlin, 10623 Berlin (Germany); Franke, D.; Kreissl, J.; Künzel, H. [Heinrich-Hertz-Institut, Einsteinufer 37, 10587 Berlin (Germany)

2015-01-19

Passive mode-locking of two-section quantum-dot mode-locked lasers grown by metalorganic vapor phase epitaxy on InP is reported. 1250-μm long lasers exhibit a wide tuning range of 300 MHz around the fundamental mode-locking frequency of 33.48 GHz. The frequency tuning is achieved by varying the reverse bias of the saturable absorber from 0 to −2.2 V and the gain section current from 90 to 280 mA. 3 dB optical spectra width of 6–7 nm leads to ex-facet optical pulses with full-width half-maximum down to 3.7 ps. Single-section quantum-dot mode-locked lasers show 0.8 ps broad optical pulses after external fiber-based compression. Injection current tuning from 70 to 300 mA leads to 30 MHz frequency tuning.

1.55-μm mode-locked quantum-dot lasers with 300 MHz frequency tuning range

International Nuclear Information System (INIS)

Sadeev, T.; Arsenijević, D.; Bimberg, D.; Franke, D.; Kreissl, J.; Künzel, H.

2015-01-01

Passive mode-locking of two-section quantum-dot mode-locked lasers grown by metalorganic vapor phase epitaxy on InP is reported. 1250-μm long lasers exhibit a wide tuning range of 300 MHz around the fundamental mode-locking frequency of 33.48 GHz. The frequency tuning is achieved by varying the reverse bias of the saturable absorber from 0 to −2.2 V and the gain section current from 90 to 280 mA. 3 dB optical spectra width of 6–7 nm leads to ex-facet optical pulses with full-width half-maximum down to 3.7 ps. Single-section quantum-dot mode-locked lasers show 0.8 ps broad optical pulses after external fiber-based compression. Injection current tuning from 70 to 300 mA leads to 30 MHz frequency tuning

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

Energy Technology Data Exchange (ETDEWEB)

Drakakis, E. [Electrical Engineering Department, School of Engineering, Technological Educational Institute of Crete, Heraklion (Greece); Kymakis, E. [Electrical Engineering Department, School of Engineering, Technological Educational Institute of Crete, Heraklion (Greece); Center of Materials Technology and Photonics, School of Engineering, Technological Educational Institute of Crete, Heraklion (Greece); Tzagkarakis, G.; Louloudakis, D.; Katharakis, M. [Center of Materials Technology and Photonics, School of Engineering, Technological Educational Institute of Crete, Heraklion (Greece); Kenanakis, G. [Institute of Electronic Structure & Laser (IESL), Foundation for Research and Technology (FORTH) Hellas, Heraklion (Greece); Suchea, M.; Tudose, V. [Center of Materials Technology and Photonics, School of Engineering, Technological Educational Institute of Crete, Heraklion (Greece); Chemistry Faculty, “Al.I.Cuza” University of Iasi, Iasi (Romania); Koudoumas, E., E-mail: koudoumas@staff.teicrete.gr [Electrical Engineering Department, School of Engineering, Technological Educational Institute of Crete, Heraklion (Greece); Center of Materials Technology and Photonics, School of Engineering, Technological Educational Institute of Crete, Heraklion (Greece)

2017-03-15

Highlights: • Optimum paint contents should be chosen so that homogeneous and uniform nanocomposite layers exist exhibiting effective electromagnetic shielding. • The electromagnetic shielding in the frequency range studied comes mainly from absorption and increases with frequency. • Reflection reduces with increasing frequency, the decrease rate being smaller than that of the increase in absorption. • The shielding efficiency depends on both conductivity and thickness, the first dependence being more pronounced. - Abstract: We report on the mechanisms of the electromagnetic interference shielding effect of graphene based paint like composite layers. In particular, we studied the absorption and reflection of electromagnetic radiation in the 4–20 GHz frequency of various dispersions employing different amounts of graphene nanoplatelets, polyaniline, and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate), special attention given on the relative contribution of each process in the shielding effect. Moreover, the influence of the composition, the thickness and the conductivity of the composite layers on the electromagnetic shielding was also examined.

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

International Nuclear Information System (INIS)

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

2017-01-01

Highlights: • Optimum paint contents should be chosen so that homogeneous and uniform nanocomposite layers exist exhibiting effective electromagnetic shielding. • The electromagnetic shielding in the frequency range studied comes mainly from absorption and increases with frequency. • Reflection reduces with increasing frequency, the decrease rate being smaller than that of the increase in absorption. • The shielding efficiency depends on both conductivity and thickness, the first dependence being more pronounced. - Abstract: We report on the mechanisms of the electromagnetic interference shielding effect of graphene based paint like composite layers. In particular, we studied the absorption and reflection of electromagnetic radiation in the 4–20 GHz frequency of various dispersions employing different amounts of graphene nanoplatelets, polyaniline, and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate), special attention given on the relative contribution of each process in the shielding effect. Moreover, the influence of the composition, the thickness and the conductivity of the composite layers on the electromagnetic shielding was also examined.

Explanation for the temperature dependence of plasma frequencies in SrTiO3 using mixed-polaron theory

International Nuclear Information System (INIS)

Eagles, D.M.; Georgiev, M.; Petrova, P.C.

1996-01-01

A theory of mixed polarons is used to interpret the published experimental results of Gervais et al. on temperature-dependent plasma frequencies in Nb-doped SrTiO 3 . For given polaron masses before mixing, the appropriate average mixed-polaron mass at any temperature T depends on two quantities, δ and b, which are measures of the separation between the bottoms of large and nearly small polaron bands before mixing and of a mixing matrix element; δ and b are assumed to have arbitrary linear dependences on T, probably related to a T dependence of the bare mass, and a term quadratic in T is included in δ, determined from the T dependence of large-polaron binding energies. Including a constraint on the ratio δ/|b| at low T from known masses from specific-heat data, satisfactory agreement is obtained with masses determined from plasma frequencies. This gives further support for the theory of mixed polarons in SrTiO 3 in addition to that already published. copyright 1996 The American Physical Society

Gauge invariant lattice quantum field theory: Implications for statistical properties of high frequency financial markets

Science.gov (United States)

Dupoyet, B.; Fiebig, H. R.; Musgrove, D. P.

2010-01-01

We report on initial studies of a quantum field theory defined on a lattice with multi-ladder geometry and the dilation group as a local gauge symmetry. The model is relevant in the cross-disciplinary area of econophysics. A corresponding proposal by Ilinski aimed at gauge modeling in non-equilibrium pricing is implemented in a numerical simulation. We arrive at a probability distribution of relative gains which matches the high frequency historical data of the NASDAQ stock exchange index.

Combining extrapolation with ghost interaction correction in range-separated ensemble density functional theory for excited states

Science.gov (United States)

Alam, Md. Mehboob; Deur, Killian; Knecht, Stefan; Fromager, Emmanuel

2017-11-01

The extrapolation technique of Savin [J. Chem. Phys. 140, 18A509 (2014)], which was initially applied to range-separated ground-state-density-functional Hamiltonians, is adapted in this work to ghost-interaction-corrected (GIC) range-separated ensemble density-functional theory (eDFT) for excited states. While standard extrapolations rely on energies that decay as μ-2 in the large range-separation-parameter μ limit, we show analytically that (approximate) range-separated GIC ensemble energies converge more rapidly (as μ-3) towards their pure wavefunction theory values (μ → +∞ limit), thus requiring a different extrapolation correction. The purpose of such a correction is to further improve on the convergence and, consequently, to obtain more accurate excitation energies for a finite (and, in practice, relatively small) μ value. As a proof of concept, we apply the extrapolation method to He and small molecular systems (viz., H2, HeH+, and LiH), thus considering different types of excitations such as Rydberg, charge transfer, and double excitations. Potential energy profiles of the first three and four singlet Σ+ excitation energies in HeH+ and H2, respectively, are studied with a particular focus on avoided crossings for the latter. Finally, the extraction of individual state energies from the ensemble energy is discussed in the context of range-separated eDFT, as a perspective.

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

Science.gov (United States)

Park, SangWook; Kim, Minhyuk

2016-01-01

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

Relativistic runaway breakdown in low-frequency radio

Science.gov (United States)

Füllekrug, Martin; Roussel-Dupré, Robert; Symbalisty, Eugene M. D.; Chanrion, Olivier; Odzimek, Anna; van der Velde, Oscar; Neubert, Torsten

2010-01-01

The electromagnetic radiation emitted by an electron avalanche beam resulting from relativistic runaway breakdown within the Earth's atmosphere is investigated. It is found from theoretical modeling with a computer simulation that the electron beam emits electromagnetic radiation which is characterized by consecutive broadband pulses in the low-frequency radio range from ˜10 to 300 kHz at a distance of ˜800 km. Experimental evidence for the existence of consecutive broadband pulses is provided by low-frequency radio observations of sprite-producing lightning discharges at a distance of ˜550 km. The measured broadband pulses occur ˜4-9 ms after the sprite-producing lightning discharge, they exhibit electromagnetic radiation which mainly spans the frequency range from ˜50 to 350 kHz, and they exhibit complex waveforms without the typical ionospheric reflection of the first hop sky wave. Two consecutive pulses occur ˜4.5 ms and ˜3 ms after the causative lightning discharge and coincide with the sprite luminosity. It is concluded that relativistic runaway breakdown within the Earth's atmosphere can emit broadband electromagnetic pulses and possibly generates sprites. The source location of the broadband pulses can be determined with an interferometric network of wideband low-frequency radio receivers to lend further experimental support to the relativistic runaway breakdown theory.

Shifts in diversification rates and host jump frequencies shaped the diversity of host range among Sclerotiniaceae fungal plant pathogens.

Science.gov (United States)

Navaud, Olivier; Barbacci, Adelin; Taylor, Andrew; Clarkson, John P; Raffaele, Sylvain

2018-03-01

The range of hosts that a parasite can infect in nature is a trait determined by its own evolutionary history and that of its potential hosts. However, knowledge on host range diversity and evolution at the family level is often lacking. Here, we investigate host range variation and diversification trends within the Sclerotiniaceae, a family of Ascomycete fungi. Using a phylogenetic framework, we associate diversification rates, the frequency of host jump events and host range variation during the evolution of this family. Variations in diversification rate during the evolution of the Sclerotiniaceae define three major macro-evolutionary regimes with contrasted proportions of species infecting a broad range of hosts. Host-parasite cophylogenetic analyses pointed towards parasite radiation on distant hosts long after host speciation (host jump or duplication events) as the dominant mode of association with plants in the Sclerotiniaceae. The intermediate macro-evolutionary regime showed a low diversification rate, high frequency of duplication events and the highest proportion of broad host range species. Our findings suggest that the emergence of broad host range fungal pathogens results largely from host jumps, as previously reported for oomycete parasites, probably combined with low speciation rates. These results have important implications for our understanding of fungal parasites evolution and are of particular relevance for the durable management of disease epidemics. © 2018 The Authors. Molecular Ecology Published by John Wiley & Sons Ltd.

Experimental comparison of diffusional nuclear magnetic relaxation theories using ZrHsub(1.684)

International Nuclear Information System (INIS)

Korn, C.; Goren, S.

1984-01-01

The spin-lattice relaxation time of hydrogen in ZrHsub(1.684) was measured at a resonance frequency of 16.69 MHz as a function of temperature in a temperature range where the major relaxation mechanism was hydrogen diffusion. This parameter was used to calculate the hydrogen jump frequencies using the theories of Bloembergen, Purcell and Pound (BPP), of Bustard and of Barton and Sholl. A comparison shows that the BPP theory gives results closest to Arrhenius-type behaviour. The diffusional activation energy was found to be 13.3 kcal mol -1 . (Auth.)

Resonance frequency of fluid-filled and prestressed spherical shell-A model of the human eyeball.

Science.gov (United States)

Shih, Po-Jen; Guo, Yi-Ren

2016-04-01

An acoustic tonometer that measures shifts in resonance frequencies associated with intraocular pressure (IOP) could provide an opportunity for a type of tonometer that can be operated at home or worn by patients. However, there is insufficient theoretical background, especially with respect to the uncertainty in operating frequency ranges and the unknown relationships between IOPs and resonance frequencies. The purpose of this paper is to develop a frequency function for application in an acoustic tonometer. A linear wave theory is used to derive an explicit frequency function, consisting of an IOP and seven other physiological parameters. In addition, impulse response experiments are performed to measure the natural frequencies of porcine eyes to validate the provided function. From a real-time detection perspective, explicitly providing a frequency function can be the best way to set up an acoustic tonometer. The theory shows that the resonance oscillation of the eyeball is mainly dominated by liquid inside the eyeball. The experimental validation demonstrates the good prediction of IOPs and resonance frequencies. The proposed explicit frequency function supports further modal analysis not only of the dynamics of eyeballs, but also of the natural frequencies, for further development of the acoustic tonometer.

Theory and observation of compressional Alfven eigenmodes in low aspect ratio plasma

International Nuclear Information System (INIS)

Gorelenkov, N.N.

2002-01-01

A new theory of radially and poloidally localized Compressional Alfven Eigenmodes (CAE) in low aspect ratio plasma is reported. The theory is applied to identify recently observed instabilities in the MHz frequency range in National Spherical Torus experiments (NSTX). The frequency of observed CAEs is correlated with the characteristic Alfven velocity of the plasma. The observed high frequency modes are explained as CAEs driven by energetic beam ions. The CAE frequency is determined by the Alfven frequency at the mode location on the low field side of the plasma and is given approximately by ω CAE v A m=r, where m is the poloidal mode number, and r is the local minor radius. CAEs are destabilized by free energy in the energetic ion velocity space gradient via Doppler shifted cyclotron resonance with beam ions. Properties of the CAE instability driven by different NBI ion distributions are presented. (author)

A general theory on frequency and time-frequency analysis of irregularly sampled time series based on projection methods - Part 1: Frequency analysis

Science.gov (United States)

Lenoir, Guillaume; Crucifix, Michel

2018-03-01

We develop a general framework for the frequency analysis of irregularly sampled time series. It is based on the Lomb-Scargle periodogram, but extended to algebraic operators accounting for the presence of a polynomial trend in the model for the data, in addition to a periodic component and a background noise. Special care is devoted to the correlation between the trend and the periodic component. This new periodogram is then cast into the Welch overlapping segment averaging (WOSA) method in order to reduce its variance. We also design a test of significance for the WOSA periodogram, against the background noise. The model for the background noise is a stationary Gaussian continuous autoregressive-moving-average (CARMA) process, more general than the classical Gaussian white or red noise processes. CARMA parameters are estimated following a Bayesian framework. We provide algorithms that compute the confidence levels for the WOSA periodogram and fully take into account the uncertainty in the CARMA noise parameters. Alternatively, a theory using point estimates of CARMA parameters provides analytical confidence levels for the WOSA periodogram, which are more accurate than Markov chain Monte Carlo (MCMC) confidence levels and, below some threshold for the number of data points, less costly in computing time. We then estimate the amplitude of the periodic component with least-squares methods, and derive an approximate proportionality between the squared amplitude and the periodogram. This proportionality leads to a new extension for the periodogram: the weighted WOSA periodogram, which we recommend for most frequency analyses with irregularly sampled data. The estimated signal amplitude also permits filtering in a frequency band. Our results generalise and unify methods developed in the fields of geosciences, engineering, astronomy and astrophysics. They also constitute the starting point for an extension to the continuous wavelet transform developed in a companion

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

International Nuclear Information System (INIS)

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

2017-01-01

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

Laser-Bioplasma Interaction: Excitation and Suppression of the Brain Waves by the Multi-photon Pulsed-operated Fiber Lasers in the Ultraviolet Range of Frequencies

Science.gov (United States)

Stefan, V. Alexander; IAPS-team Team

2017-10-01

The novel study of the laser excitation-suppression of the brain waves is proposed. It is based on the pulsed-operated multi-photon fiber-laser interaction with the brain parvalbumin (PV) neurons. The repetition frequency matches the low frequency brain waves (5-100 Hz); enabling the resonance-scanning of the wide range of the PV neurons (the generators of the brain wave activity). The tunable fiber laser frequencies are in the ultraviolet frequency range, thus enabling the monitoring of the PV neuron-DNA, within the 10s of milliseconds. In medicine, the method can be used as an ``instantaneous-on-off anesthetic.'' Supported by Nikola Tesla Labs, Stefan University.

Memory Processes in Frequency Judgment: The impact of pre-experimental frequencies and co-occurrences on frequency estimates.

OpenAIRE

Renkewitz, Frank

2004-01-01

Contemporary theories on frequency processing have been developed in different sub-disciplines of psychology and have shown remarkable discrepancies. Thus, in judgment and decision making, frequency estimates on serially encoded events are mostly traced back to the availability heuristic (Tversky & Kahneman, 1973). Evidence for the use of this heuristic comes from several popular demonstrations of biased frequency estimates. In the area of decision making, these demonstrations led to the ...

Auditory phase and frequency discrimination: a comparison of nine procedures.

Science.gov (United States)

Creelman, C D; Macmillan, N A

1979-02-01

Two auditory discrimination tasks were thoroughly investigated: discrimination of frequency differences from a sinusoidal signal of 200 Hz and discrimination of differences in relative phase of mixed sinusoids of 200 Hz and 400 Hz. For each task psychometric functions were constructed for three observers, using nine different psychophysical measurement procedures. These procedures included yes-no, two-interval forced-choice, and various fixed- and variable-standard designs that investigators have used in recent years. The data showed wide ranges of apparent sensitivity. For frequency discrimination, models derived from signal detection theory for each psychophysical procedure seem to account for the performance differences. For phase discrimination the models do not account for the data. We conclude that for some discriminative continua the assumptions of signal detection theory are appropriate, and underlying sensitivity may be derived from raw data by appropriate transformations. For other continua the models of signal detection theory are probably inappropriate; we speculate that phase might be discriminable only on the basis of comparison or change and suggest some tests of our hypothesis.

Low frequency torsional vibration gaps in the shaft with locally resonant structures

International Nuclear Information System (INIS)

Yu Dianlong; Liu Yaozong; Wang Gang; Cai Li; Qiu Jing

2006-01-01

The propagation of torsional wave in the shaft with periodically attached local resonators is studied with the transfer matrix theory and the finite element method. The analytical dispersion relation and the complex band structure of such a structure is presented for the first time, which indicates the existence of low frequency gaps. The effect of shaft material on the vibration attenuation in band gap is investigated. The frequency response function of the shaft with finite periodic locally resonant oscillators is simulated with finite element method, which shows large vibration attenuation in the frequency range of the gap as expected. The low frequency torsional gap in shafts provides a new idea for vibration control

Simulation of electron transport in GaAs/AlAs superlattices with a small number of periods for the THz frequency range

International Nuclear Information System (INIS)

Pavelyev, D. G.; Vasilev, A. P.; Kozlov, V. A.; Koschurinov, Yu. I.; Obolenskaya, E. S.; Obolensky, S. V.; Ustinov, V. M.

2016-01-01

The electron transport in superlattices based on GaAs/AlAs heterostructures with a small number of periods (6 periods) is calculated by the Monte Carlo method. These superlattices are used in terahertz diodes for the frequency stabilization of quantum cascade lasers in the range up to 4.7 THz. The band structure of superlattices with different numbers of AlAs monolayers is considered and their current–voltage characteristics are calculated. The calculated current–voltage characteristics are compared with the experimental data. The possibility of the efficient application of these superlattices in the THz frequency range is established both theoretically and experimentally.

Transmission line theory for long plasma production by radio frequency discharges between parallel-plate electrodes

International Nuclear Information System (INIS)

Nonaka, S.

1991-01-01

In order to seek for a radio frequency (RF) eigen-mode of waves in producing a plasma between a pair of long dielectric-covered parallel-plate RF electrodes, this paper analyzed all normal modes propagating along the electrodes by solving Maxwell's equations. The result showed that only an odd surface wave mode will produce the plasma in usual experimental conditions, which will become a basic transmission line theory when use of such long electrodes for on-line mass-production of amorphous silicon solar cells

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

Energy Technology Data Exchange (ETDEWEB)

So, Jin-Kyu, E-mail: js1m10@orc.soton.ac.uk; MacDonald, Kevin F. [Optoelectronics Research Centre and Centre for Photonic Metamaterials, University of Southampton, Highfield, Southampton SO17 1BJ (United Kingdom); Zheludev, Nikolay I. [Optoelectronics Research Centre and Centre for Photonic Metamaterials, University of Southampton, Highfield, Southampton SO17 1BJ (United Kingdom); Centre for Disruptive Photonic Technologies, Nanyang Technological University, Singapore 637371 (Singapore)

2014-05-19

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

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

Directory of Open Access Journals (Sweden)

SangWook Park

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

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

Science.gov (United States)

Kim, Minhyuk

2016-01-01

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

Relativistic runaway breakdown in low-frequency radio

DEFF Research Database (Denmark)

Fullekrug, M.; Roussel-Dupre, R.; Symbalisty, E.M.D.

2011-01-01

at a distance of similar to 550 km. The measured broadband pulses occur similar to 4-9 ms after the sprite-producing lightning discharge, they exhibit electromagnetic radiation which mainly spans the frequency range from similar to 50 to 350 kHz, and they exhibit complex waveforms without the typical...... electromagnetic pulses and possibly generates sprites. The source location of the broadband pulses can be determined with an interferometric network of wideband low-frequency radio receivers to lend further experimental support to the relativistic runaway breakdown theory.......The electromagnetic radiation emitted by an electron avalanche beam resulting from relativistic runaway breakdown within the Earth's atmosphere is investigated. It is found from theoretical modeling with a computer simulation that the electron beam emits electromagnetic radiation which...

Modulation of auroral electron fluxes in the frequency range 50 kHz to 10 MHz

Science.gov (United States)

Spiger, R. J.; Murphree, J. S.; Anderson, H. R.; Loewenstein, R. F.

1976-01-01

A sounding rocket-borne electron detector of high time resolution is used to search for modulation of auroral electron fluxes in the frequency range 50 kHz to 10 MHz and energy range 5-7 keV. Data were telemetered to ground via a 93-kHz subcarrier. A cross-correlation analysis of the data collected indicates low-level modulation near the detection threshold of the instrument. Two U-1 events are observed which are interpreted as indications of modulation. The two modulation events occur during a period of increasing flux for a region marking the boundary between two current sheets detected by the payload magnetometer. The strongest argument against interference contamination is the lack of any observable modulation at times other than those mentioned in the study.

Bi-Frequency Modulated Quasi-Resonant Converters: Theory and Applications

Science.gov (United States)

Zhang, Yuefeng

1995-01-01

To avoid the variable frequency operation of quasi -resonant converters, many soft-switching PWM converters have been proposed, all of them require an auxiliary switch, which will increase the cost and complexity of the power supply system. In this thesis, a new kind of technique for quasi -resonant converters has been proposed, which is called the bi-frequency modulation technique. By operating the quasi-resonant converters at two switching frequencies, this technique enables quasi-resonant converters to achieve the soft-switching, at fixed switching frequencies, without an auxiliary switch. The steady-state analysis of four commonly used quasi-resonant converters, namely, ZVS buck, ZCS buck, ZVS boost, and ZCS boost converter has been presented. Using the concepts of equivalent sources, equivalent sinks, and resonant tank, the large signal models of these four quasi -resonant converters were developed. Based on these models, the steady-state control characteristics of BFM ZVS buck, BFM ZCS buck, BFM ZVS boost, and BFM ZCS boost converter have been derived. The functional block and design consideration of the bi-frequency controller were presented, and one of the implementations of the bi-frequency controller was given. A complete design example has been presented. Both computer simulations and experimental results have verified that the bi-frequency modulated quasi-resonant converters can achieve soft-switching, at fixed switching frequencies, without an auxiliary switch. One of the application of bi-frequency modulation technique is for EMI reduction. The basic principle of using BFM technique for EMI reduction was introduced. Based on the spectral analysis, the EMI performances of the PWM, variable-frequency, and bi-frequency modulated control signals was evaluated, and the BFM control signals show the lowest EMI emission. The bi-frequency modulated technique has also been applied to the power factor correction. A BFM zero -current switching boost converter has

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

Science.gov (United States)

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

2007-01-01

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

Electroacoustic theory for concentrated colloids with overlapped DLs at arbitrary kappa alpha. I. Application to nanocolloids and nonaqueous colloids.

Science.gov (United States)

Shilov, V N; Borkovskaja, Y B; Dukhin, A S

2004-09-15

Existing theories of electroacoustic phenomena in concentrated colloids neglect the possibility of double layer overlap and are valid mostly for the "thin double layer," when the double layer thickness is much less than the particle size. In this paper we present a new electroacoustic theory which removes this restriction. This would make this new theory applicable to characterizing a variety of aqueous nanocolloids and of nonaqueous dispersions. There are two versions of the theory leading to the analytical solutions. The first version corresponds to strongly overlapped diffuse layers (so-called quasi-homogeneous model). It yields a simple analytical formula for colloid vibration current (CVI), which is valid for arbitrary ultrasound frequency, but for restricted kappa alpha range. This version of the theory, as well the Smoluchowski theory for microelectrophoresis, is independent of particle shape and polydispersity. This makes it very attractive for practical use, with the hope that it might be as useful as classical Smoluchowski theory. In order to determine the kappa alpha range of the quasi-homogeneous model validity we develop the second version that limits ultrasound frequency, but applies no restriction on kappa alpha. The ultrasound frequency should substantially exceed the Maxwell-Wagner relaxation frequency. This limitation makes active conductivity related current negligible compared to the passive dielectric displacement current. It is possible to derive an expression for CVI in the concentrated dispersion as formulae inhering definite integrals with integrands depending on equilibrium potential distribution. This second version allowed us to estimate the ranges of the applicability of the first, quasi-homogeneous version. It turns out that the quasi-homogeneous model works for kappa alpha values up to almost 1. For instance, at volume fraction 30%, the highest kappa alpha limit of the quasi-homogeneous model is 0.65. Therefore, this version of the

The initial magnetic susceptibility of polydisperse ferrofluids: A comparison between experiment and theory over a wide range of concentration

International Nuclear Information System (INIS)

Solovyova, Anna Y.; Goldina, Olga A.; Ivanov, Alexey O.; Elfimova, Ekaterina A.; Lebedev, Aleksandr V.

2016-01-01

Temperature dependencies of the static initial magnetic susceptibility for ferrofluids at various concentrations are studied using experiment and statistical-mechanical theories. Magnetic susceptibility measurements are carried out for twelve samples of magnetite-based fluids stabilized with oleic acid over a wide range of temperatures (210 K ≲T ≲ 390 K); all samples have the same granulometric composition but different volume ferroparticle concentrations (0.2 ≲ φ ≲ 0.5). Experimental results are analyzed using three theories: the second-order modified mean-field theory (MMF2) [A. O. Ivanov and O. B. Kuznetsova, Phys. Rev. E 64, 41405 (2001)]; its correction for polydisperse ferrofluids arising from Mayer-type cluster expansion and taking into account the first terms of the polydisperse second virial coefficient [A. O. Ivanov and E. A. Elfimova, J. Magn. Magn. Mater 374, 327 (2015)]; and a new theory based on MMF2 combined with the first terms of the polydisperse second and third virial contributions to susceptibility. It turns out that the applicability of each theory depends on the experimental sample density. If twelve ferrofluid samples are split into three groups of strong, moderate, and low concentrated fluids, the temperature dependences of the initial magnetic susceptibility in each group are very precisely described by one of the three theories mentioned above. The determination of a universal formula predicting a ferrofluid susceptibility over a broad range of concentrations and temperatures remains as a challenge.

Development of a spectral analyzer for radio-frequencies; Etude et realisation d'un analyseur de spectres pour radio-frequences

Energy Technology Data Exchange (ETDEWEB)

Bourbigot, J [Commission a l' Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

1967-04-01

This report describes an apparatus designed to show on the screen of a cathode ray tube the amplitude and frequency distribution of the spectral components of a given signal. The frequency range is from 5 kHz to 25 MHz. Two fundamental elements are used in the development of this apparatus, a ferrite and a ring modulator. The basic properties of these elements are studied and discussed. A theoretical study for the determination of the fundamental parameters of the analyzer is presented in the Appendix. (author) [French] On decrit un appareil qui permet de representer sur l'ecran d'un tube a rayons cathodiques la distribution en frequence et en amplitude des composantes spectrales d'un signal donne. Il fonctionne dans la gamme de frequences s'etendant de 5 kHz a 25 MHz. Deux elements interviennent fondamentalement dans la realisation de cet appareil: un echantillon de ferrite et un modulateur en anneau. Des proprietes particulieres de ces elements sont etudiees et discutees. En annexe une theorie s'appliquant a la determination de parametres fondamentaux de l'analyseur est developpee. (auteur)

Experimental studies on the high-frequency heating of a plasma in the frequency range of the ion cyclotron harmonics

International Nuclear Information System (INIS)

Laeuter, R.

1976-05-01

Experiments on the HF heating of a plasma in a cylindrical arrangement with pump frequencies ω 0 in the ion cyclotron harmonics nωsub(ci) are described. A magnetized plasma of relativily high density (approximately 10 14 cm -3 ) is generated in a pinch-like source with pulsated gas inlet, and said plasma then expands along diverging magnetic-field lines in a quasi-static homogeneous guide field B 0 = 330 G. This results in a practically fully ionized, low-impurity and more or less homogeneous plasma column of a diameter of approximately 20 cm at a variable density between 5 x 10 11 and 5 x 10 12 cm -3 and at electron temperatures of 5 to 8 eV. A standing magneto-hydrodynamic wave is excited in this plasma by means of a 1.8 m Stix coil which is part of the anode resonant circuit of a pulsated 1 MHz 500-kW transmitter. The axial wavelength is lambdasub(z) = 45 cm, the pulse duration amounts to tau = 200 μs. The degree of modulation B tilde/B 0 of the quasi-static magnetic field by the HF field is adjustable and ranges between 0.015 and 0.06. The heating at 2ωsub(ci) and 4ωsub(ci) is investigated within this study. Efficiency measurements show that a very effective energy transfer to the plasma occurs with both frequencies. Ion temperatures between 70 and 100 eV are ascertained by means of a retarding-potential spectrometer. For plasma heating, similar turbulent mechanisms seem to be responsible in both cases whereas the linear wave-particle resonance at 2ωsub(ci) seems to be of subordinated importance. The theoretically assumed parametric decay into ion-Bernstein waves, which should be possible at 4 ωsub(ci), is not observed. Measurements with compensated magnetic loops and electrostatic probes make a disturbance of the radial plasma confinement obvious, by which an anormally high pulse frequency might be explained. (orig.) [de

Zero-range effective field theory for resonant wino dark matter. Part III. Annihilation effects

OpenAIRE

Braaten, Eric; Johnson, Evan; Zhang, Hong

2018-01-01

Near a critical value of the wino mass where there is a zero-energy S-wave resonance at the neutral-wino-pair threshold, low-energy winos can be described by a zero-range effective field theory (ZREFT) in which the winos interact nonperturbatively through a contact interaction and through Coulomb interactions. The effects of wino-pair annihilation into electroweak gauge bosons are taken into account through the analytic continuation of the real parameters for the contact interaction to comple...

Priming patient safety: A middle-range theory of safety goal priming via safety culture communication.

Science.gov (United States)

Groves, Patricia S; Bunch, Jacinda L

2018-05-18

The aim of this paper is discussion of a new middle-range theory of patient safety goal priming via safety culture communication. Bedside nurses are key to safe care, but there is little theory about how organizations can influence nursing behavior through safety culture to improve patient safety outcomes. We theorize patient safety goal priming via safety culture communication may support organizations in this endeavor. According to this theory, hospital safety culture communication activates a previously held patient safety goal and increases the perceived value of actions nurses can take to achieve that goal. Nurses subsequently prioritize and are motivated to perform tasks and risk assessment related to achieving patient safety. These efforts continue until nurses mitigate or ameliorate identified risks and hazards during the patient care encounter. Critically, this process requires nurses to have a previously held safety goal associated with a repertoire of appropriate actions. This theory suggests undergraduate educators should foster an outcomes focus emphasizing the connections between nursing interventions and safety outcomes, hospitals should strategically structure patient safety primes into communicative activities, and organizations should support professional development including new skills and the latest evidence supporting nursing practice for patient safety. © 2018 John Wiley & Sons Ltd.

Mean-Field Theory of Electrical Double Layer In Ionic Liquids with Account of Short-Range Correlations

International Nuclear Information System (INIS)

Goodwin, Zachary A.H.; Feng, Guang; Kornyshev, Alexei A.

2017-01-01

We develop the theory of the electrical double layer in ionic liquids as proposed earlier by Kornyshev (2007). In the free energy function we keep the so called ‘short-range correlation terms’ which were omitted there. With some simplifying assumptions, we arrive at a modified expression for differential capacitance, which makes differential capacitance curves less sharply depending on electrode potential and having smaller values at extrema than in the previous theory. This brings the results closer to typical experimental observations, and makes it appealing to use this formalism for treatment of experimental data. Implications on Debye length and the extent of ion paring in ionic liquids are then briefly discussed.

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

International Nuclear Information System (INIS)

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

2013-01-01

We demonstrated experimentally a synchronously pumped intracavity frequency-doubled femtosecond optical parametric oscillator (OPO) using a periodically-poled lithium niobate (PPLN) as the nonlinear material in combination with a lithium triborate (LBO) as the doubling crystal. A Kerr-lens-mode-locked (KLM) Ti:sapphire oscillator at the wavelength of 790 nm was used as the pump source, which was capable of generating pulses with a duration as short as 117 fs. A tunable femtosecond laser covering the 624–672 nm range was realized by conveniently adjusting the OPO cavity length. A maximum average output power of 260 mW in the visible range was obtained at the pump power of 2.2 W, with a typical pulse duration of 205 fs assuming a sech 2 pulse profile. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

The impact research of control modes in steam turbine control system (digital electric hydraulic to the low-frequency oscillation of grid

Directory of Open Access Journals (Sweden)

Yanghai Li

2016-01-01

Full Text Available Through the analysis of the control theory for steam turbine, the transfer function of the steam turbine control modes in the parallel operation was obtained. The frequency domain analysis indicated that different control modes of turbine control system have different influence on the damping characteristics of the power system. The comparative analysis shows the direction and the degree of the influence under the different oscillation frequency range. This can provide the theory for the suppression of the low-frequency oscillation from turbine side and has a guiding significance for the stability of power system. The results of simulation tests are consistent with the theoretic analysis.

Multi-frequency excitation

KAUST Repository

Younis, Mohammad I.

2016-03-10

Embodiments of multi-frequency excitation are described. In various embodiments, a natural frequency of a device may be determined. In turn, a first voltage amplitude and first fixed frequency of a first source of excitation can be selected for the device based on the natural frequency. Additionally, a second voltage amplitude of a second source of excitation can be selected for the device, and the first and second sources of excitation can be applied to the device. After applying the first and second sources of excitation, a frequency of the second source of excitation can be swept. Using the methods of multi- frequency excitation described herein, new operating frequencies, operating frequency ranges, resonance frequencies, resonance frequency ranges, and/or resonance responses can be achieved for devices and systems.

Linear theory on temporal instability of megahertz faraday waves for monodisperse microdroplet ejection.

Science.gov (United States)

Tsai, Shirley C; Tsai, Chen S

2013-08-01

A linear theory on temporal instability of megahertz Faraday waves for monodisperse microdroplet ejection based on mass conservation and linearized Navier-Stokes equations is presented using the most recently observed micrometer- sized droplet ejection from a millimeter-sized spherical water ball as a specific example. The theory is verified in the experiments utilizing silicon-based multiple-Fourier horn ultrasonic nozzles at megahertz frequency to facilitate temporal instability of the Faraday waves. Specifically, the linear theory not only correctly predicted the Faraday wave frequency and onset threshold of Faraday instability, the effect of viscosity, the dynamics of droplet ejection, but also established the first theoretical formula for the size of the ejected droplets, namely, the droplet diameter equals four-tenths of the Faraday wavelength involved. The high rate of increase in Faraday wave amplitude at megahertz drive frequency subsequent to onset threshold, together with enhanced excitation displacement on the nozzle end face, facilitated by the megahertz multiple Fourier horns in resonance, led to high-rate ejection of micrometer- sized monodisperse droplets (>10(7) droplets/s) at low electrical drive power (<;1 W) with short initiation time (<;0.05 s). This is in stark contrast to the Rayleigh-Plateau instability of a liquid jet, which ejects one droplet at a time. The measured diameters of the droplets ranging from 2.2 to 4.6 μm at 2 to 1 MHz drive frequency fall within the optimum particle size range for pulmonary drug delivery.

A finite range pairing force for density functional theory in superfluid nuclei

International Nuclear Information System (INIS)

Tian, Y.; Ma, Z.Y.; Ring, P.

2009-01-01

The problem of pairing in the 1 S 0 channel of finite nuclei is revisited. In nuclear matter forces of separable form can be adjusted to the bare nuclear force, to any phenomenological pairing interaction such as the Gogny force or to exact solutions of the gap equation. In finite nuclei, because of translational invariance, such forces are no longer separable. Using well-known techniques of Talmi and Moshinsky we expand the matrix elements in a series of separable terms, which converges quickly preserving translational invariance and finite range. In this way the complicated problem of a cut-off at large momenta or energies inherent in other separable or zero range pairing forces is avoided. Applications in the framework of the relativistic Hartree-Bogoliubov approach show that the pairing properties are depicted on almost the same footing as by the original pairing interaction not only in nuclear matter, but also in finite nuclei. This simple separable force can be easily applied for the investigation of pairing properties in nuclei far from stability as well as for further investigations going beyond mean field theory.

Charge density fluctuation of low frequency in a dusty plasma

Institute of Scientific and Technical Information of China (English)

李芳; 吕保维; O.Havnes

1997-01-01

The charge density fluctuation of low frequency in a dusty plasma, which is derived from the longitudinal dielectric permittivity of the dusty plasma, has been studied by kinetic theory. The results show that the P value, which describes the relative charge density on the dust in the plasma, and the charging frequency of a dust particle Ωc, which describes the ratio of charge changing of the dust particles, determine the character of the charge density fluctuation of low frequency. For a dusty plasma of P<<1, when the charging frequency Ωc is much smaller than the dusty plasma frequency wd, there is a strong charge density fluctuation which is of character of dust acoustic eigen wave. For a dusty plasma of P>>1, when the frequency Ωc, is much larger than wd there are weaker fluctuations with a wide spectrum. The results have been applied to the ionosphere and the range of radius and density of dust particles is found, where a strong charge density fluctuation of low frequency should exist.

A forward model and conjugate gradient inversion technique for low-frequency ultrasonic imaging.

Science.gov (United States)

van Dongen, Koen W A; Wright, William M D

2006-10-01

Emerging methods of hyperthermia cancer treatment require noninvasive temperature monitoring, and ultrasonic techniques show promise in this regard. Various tomographic algorithms are available that reconstruct sound speed or contrast profiles, which can be related to temperature distribution. The requirement of a high enough frequency for adequate spatial resolution and a low enough frequency for adequate tissue penetration is a difficult compromise. In this study, the feasibility of using low frequency ultrasound for imaging and temperature monitoring was investigated. The transient probing wave field had a bandwidth spanning the frequency range 2.5-320.5 kHz. The results from a forward model which computed the propagation and scattering of low-frequency acoustic pressure and velocity wave fields were used to compare three imaging methods formulated within the Born approximation, representing two main types of reconstruction. The first uses Fourier techniques to reconstruct sound-speed profiles from projection or Radon data based on optical ray theory, seen as an asymptotical limit for comparison. The second uses backpropagation and conjugate gradient inversion methods based on acoustical wave theory. The results show that the accuracy in localization was 2.5 mm or better when using low frequencies and the conjugate gradient inversion scheme, which could be used for temperature monitoring.

Communication: Orbital instabilities and triplet states from time-dependent density functional theory and long-range corrected functionals

Science.gov (United States)

Sears, John S.; Koerzdoerfer, Thomas; Zhang, Cai-Rong; Brédas, Jean-Luc

2011-10-01

Long-range corrected hybrids represent an increasingly popular class of functionals for density functional theory (DFT) that have proven to be very successful for a wide range of chemical applications. In this Communication, we examine the performance of these functionals for time-dependent (TD)DFT descriptions of triplet excited states. Our results reveal that the triplet energies are particularly sensitive to the range-separation parameter; this sensitivity can be traced back to triplet instabilities in the ground state coming from the large effective amounts of Hartree-Fock exchange included in these functionals. As such, the use of standard long-range corrected functionals for the description of triplet states at the TDDFT level is not recommended.

Two-nucleon electromagnetic current in chiral effective field theory: One-pion exchange and short-range contributions

International Nuclear Information System (INIS)

Koelling, S.; Epelbaum, E.; Krebs, H.; Meissner, U.-G.

2011-01-01

We derive the leading one-loop contribution to the one-pion exchange and short-range two-nucleon electromagnetic current operator in the framework of chiral effective field theory. The derivation is carried out using the method of unitary transformation. Explicit results for the current and charge densities are given in momentum and coordinate space.

Complex permeability and permittivity variation of carbonyl iron rubber in the frequency range of 2 to 18 GHz

Directory of Open Access Journals (Sweden)

Adriana Medeiros Gama

2010-04-01

Full Text Available The complex dielectric permittivity (e and magnetic permeability (m of Radar Absorbing Materials (RAM based on metallic magnetic particles (carbonyl iron particles embedded in a dielectric matrix (silicon rubber have been studied in the frequency range of 2 to 18 GHz. The relative permeability and permittivity of carbonyl iron-silicon composites for various mass fractions are measured by the transmission/reflection method using a vector network analyzer. The concentration dependence of permittivity and permeability on the frequency is analyzed. In a general way, the results show that e´ parameter shows a more significant variation among the evaluated parameters (e”, m”, m’. The comparison of dielectric and magnetic loss tangents (e”/e” and m”/m’, respectively shows more clearly the variation of both parameters (e and m according to the frequency. It is also observed that higher carbonyl iron content fractions favor both dielectric and magnetic loss tangents.

Generalized extended Navier-Stokes theory

DEFF Research Database (Denmark)

Hansen, J. S.; Daivis, Peter J.; Dyre, Jeppe C.

2013-01-01

in molecular fluids. To discuss these phenomena in detail, molecular dynamics simulations of molecular chlorine are performed for three different state points. In general, the theory captures the behavior for small wavevector and frequencies as expected. For example, in the hydrodynamic regime......The extended Navier-Stokes theory accounts for the coupling between the translational and rotational molecular degrees of freedom. In this paper, we generalize this theory to non-zero frequencies and wavevectors, which enables a new study of spatio-temporal correlation phenomena present...... and for molecular fluids with small moment of inertia like chlorine, the theory predicts that the longitudinal and transverse intrinsic angular velocity correlation functions are almost identical, which is also seen in the molecular dynamics simulations. However, the theory fails at large wavevector and frequencies...

Travel: a long-range goal of retired women.

Science.gov (United States)

Staats, Sara; Pierfelice, Loretta

2003-09-01

The authors surveyed retired persons (predominately women) with regard to their immediate, intermediate, and long-range activities following retirement. As predicted, leisure travel emerged as a frequent long-range goal for persons retired more than 5 years. The travel activity preferences of long-retired older women present challenges and opportunities to both researchers and marketers. Length of trips and frequency of trips have been predicted from regression models, with trip length in particular being well predicted by the problem of daily life hassles. A theoretical model of continued post-retirement travel is presented as a variant of Solomon's opponent process theory of affect (R. L. Solomon, 1980). The authors suggest that to the degree that places traveled to are varied and different, older people may remain stimulated and continue to enjoy retirement.

LOW FREQUENCY DAMPER

Directory of Open Access Journals (Sweden)

Radu BOGATEANU

2009-09-01

Full Text Available The low frequency damper is an autonomous equipment for damping vibrations with the 1-20Hz range.Its autonomy enables the equipment to be located in various mechanical systems, without requiring special hydraulic installations.The low frequency damper was designed for damping the low frequency oscillations occurring in the circuit controls of the upgraded IAR-99 Aircraft.The low frequency damper is a novelty in the aerospace field ,with applicability in several areas as it can be built up in an appropriate range of dimensions meeting the requirements of different beneficiaries. On this line an equipment able to damp an extended frequency range was performed for damping oscillations in the pipes of the nuclear power plants.This damper, tested in INCAS laboratories matched the requirements of the beneficiary.The low frequency damper is patented – the patent no. 114583C1/2000 is held by INCAS.

Reaction energetics on long-range corrected density functional theory: Diels-Alder reactions.

Science.gov (United States)

Singh, Raman K; Tsuneda, Takao

2013-02-15

The possibility of quantitative reaction analysis on the orbital energies of long-range corrected density functional theory (LC-DFT) is presented. First, we calculated the Diels-Alder reaction enthalpies that have been poorly given by conventional functionals including B3LYP functional. As a result, it is found that the long-range correction drastically improves the reaction enthalpies. The barrier height energies were also computed for these reactions. Consequently, we found that dispersion correlation correction is also crucial to give accurate barrier height energies. It is, therefore, concluded that both long-range exchange interactions and dispersion correlations are essentially required in conventional functionals to investigate Diels-Alder reactions quantitatively. After confirming that LC-DFT accurately reproduces the orbital energies of the reactant and product molecules of the Diels-Alder reactions, the global hardness responses, the halves of highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) energy gaps, along the intrinsic reaction coordinates of two Diels-Alder reactions were computed. We noticed that LC-DFT results satisfy the maximum hardness rule for overall reaction paths while conventional functionals violate this rule on the reaction pathways. Furthermore, our results also show that the HOMO-LUMO gap variations are close to the reaction enthalpies for these Diels-Alder reactions. Based on these results, we foresee quantitative reaction analysis on the orbital energies. Copyright © 2012 Wiley Periodicals, Inc.

Prospects for advanced RF theory and modeling

International Nuclear Information System (INIS)

Batchelor, D. B.

1999-01-01

This paper represents an attempt to express in print the contents of a rather philosophical review talk. The charge for the talk was not to summarize the present status of the field and what we can do, but to assess what we will need to do in the future and where the gaps are in fulfilling these needs. The objective was to be complete, covering all aspects of theory and modeling in all frequency regimes, although in the end the talk mainly focussed on the ion cyclotron range of frequencies (ICRF). In choosing which areas to develop, it is important to keep in mind who the customers for RF modeling are likely to be and what sorts of tasks they will need for RF to do. This occupies the first part of the paper. Then we examine each of the elements of a complete RF theory and try to identify the kinds of advances needed. (c) 1999 American Institute of Physics

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

Science.gov (United States)

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

2017-03-09

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

A real-frequency solver for the Anderson impurity model based on bath optimization and cluster perturbation theory

Science.gov (United States)

Zingl, Manuel; Nuss, Martin; Bauernfeind, Daniel; Aichhorn, Markus

2018-05-01

Recently solvers for the Anderson impurity model (AIM) working directly on the real-frequency axis have gained much interest. A simple and yet frequently used impurity solver is exact diagonalization (ED), which is based on a discretization of the AIM bath degrees of freedom. Usually, the bath parameters cannot be obtained directly on the real-frequency axis, but have to be determined by a fit procedure on the Matsubara axis. In this work we present an approach where the bath degrees of freedom are first discretized directly on the real-frequency axis using a large number of bath sites (≈ 50). Then, the bath is optimized by unitary transformations such that it separates into two parts that are weakly coupled. One part contains the impurity site and its interacting Green's functions can be determined with ED. The other (larger) part is a non-interacting system containing all the remaining bath sites. Finally, the Green's function of the full AIM is calculated via coupling these two parts with cluster perturbation theory.

Brain states recognition during visual perception by means of artificial neural network in the different EEG frequency ranges

Science.gov (United States)

Musatov, V. Yu.; Runnova, A. E.; Andreev, A. V.; Zhuravlev, M. O.

2018-04-01

In the present paper, the possibility of classification by artificial neural networks of a certain architecture of ambiguous images is investigated using the example of the Necker cube from the experimentally obtained EEG recording data of several operators. The possibilities of artificial neural network classification of ambiguous images are investigated in the different frequency ranges of EEG recording signals.

Nonmetric theories of gravity and the gravitational frequency shift

International Nuclear Information System (INIS)

Coley, A.A.; Sarmiento G, A.F.; Universidad Nacional Autonoma de Mexico, Mexico City)

1988-01-01

A class of nonmetric theories of gravity called metric-affine theories is investigated, emphasizing a subclass of theories called Weyl-affine theories. An experimental configuration is modeled in which the gravitational redshift of light signals conecting an artificial satellite to the earth is measured. A situation in which both bodies are forced to follow circular orbits around the sun with angular speeds determined by the solar gravitational field is considered along with the more realistic situation in which the artificial satellite and the earth are both allowed to follow general coplanar orbits. The latter is found to give rise to more severe constraints. It is found that theories under investigation must coincide with their metric counterparts up to first order in the Newtonian gravitational potential U and that any nonmetric effects within the solar neighborhood can only manifest themselves at most through small contributions at the U-squared level or at the U-cubed level. 34 references

Odd-frequency pairing in superconducting heterostructures

Energy Technology Data Exchange (ETDEWEB)

Golubov, A A [Faculty of Science and Technology and MESA Institute for Nanotechnology, University of Twente, 7500 AE Enschede (Netherlands); Tanaka, Y [Department of Applied Physics, Nagoya University, Nagoya, 464-8603 (Japan); Asano, Y [Department of Applied Physics, Hokkaido University, Sapporo 060-8628 (Japan); Tanuma, Y [Institute of Physics, Kanagawa University, 3-7-1, Rokkakubashi, Kanagawa-ku, Yokohama 221-8686 (Japan)], E-mail: a.golubov@utwente.nl

2009-04-22

We review the theory of odd-frequency pairing in superconducting heterostructures, where an odd-frequency pairing component is induced near interfaces. A general description of the superconducting proximity effect in a normal metal or a ferromagnet attached to an unconventional superconductor (S) is given within quasiclassical kinetic theory for various types of symmetry state in S. Various possible symmetry classes in a superconductor are considered which are consistent with the Pauli principle: even-frequency spin-singlet even-parity (ESE) state, even-frequency spin-triplet odd-parity (ETO) state, odd-frequency spin-triplet even-parity (OTE) state and odd-frequency spin-singlet odd-parity (OSO) state. As an example, we consider a junction between a diffusive normal metal (DN) and a p-wave superconductor (even-frequency spin-triplet odd-parity symmetry), where the pairing amplitude in DN belongs to an odd-frequency spin-triplet even-parity symmetry class. We also discuss the manifestation of odd-frequency pairing in conventional superconductor/normal (S/N) proximity systems and its relation to the classical McMillan-Rowell oscillations.

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

DEFF Research Database (Denmark)

Zhao, Ying; Deng, Lei; Pang, Xiaodan

2011-01-01

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

Static electromagnetic frequency changers

CERN Document Server

Rozhanskii, L L

1963-01-01

Static Electromagnetic Frequency Changers is about the theory, design, construction, and applications of static electromagnetic frequency changers, devices that used for multiplication or division of alternating current frequency. It is originally published in the Russian language. This book is organized into five chapters. The first three chapters introduce the readers to the principles of operation, the construction, and the potential applications of static electromagnetic frequency changers and to the principles of their design. The two concluding chapters use some hitherto unpublished work

Hyperbolic equations and frequency interactions

CERN Document Server

Caffarelli, Luis

1998-01-01

The research topic for this IAS/PCMI Summer Session was nonlinear wave phenomena. Mathematicians from the more theoretical areas of PDEs were brought together with those involved in applications. The goal was to share ideas, knowledge, and perspectives. How waves, or "frequencies", interact in nonlinear phenomena has been a central issue in many of the recent developments in pure and applied analysis. It is believed that wavelet theory-with its simultaneous localization in both physical and frequency space and its lacunarity-is and will be a fundamental new tool in the treatment of the phenomena. Included in this volume are write-ups of the "general methods and tools" courses held by Jeff Rauch and Ingrid Daubechies. Rauch's article discusses geometric optics as an asymptotic limit of high-frequency phenomena. He shows how nonlinear effects are reflected in the asymptotic theory. In the article "Harmonic Analysis, Wavelets and Applications" by Daubechies and Gilbert the main structure of the wavelet theory is...

Ranging Behaviour of Commercial Free-Range Broiler Chickens 2: Individual Variation.

Science.gov (United States)

Taylor, Peta S; Hemsworth, Paul H; Groves, Peter J; Gebhardt-Henrich, Sabine G; Rault, Jean-Loup

2017-07-20

Little is known about broiler chicken ranging behaviour. Previous studies have monitored ranging behaviour at flock level but whether individual ranging behaviour varies within a flock is unknown. Using Radio Frequency Identification technology, we tracked 1200 individual ROSS 308 broiler chickens across four mixed sex flocks in two seasons on one commercial farm. Ranging behaviour was tracked from first day of range access (21 days of age) until 35 days of age in winter flocks and 44 days of age in summer flocks. We identified groups of chickens that differed in frequency of range visits: chickens that never accessed the range (13 to 67% of tagged chickens), low ranging chickens (15 to 44% of tagged chickens) that accounted for range visits and included chickens that used the range only once (6 to 12% of tagged chickens), and high ranging chickens (3 to 9% of tagged chickens) that accounted for 33 to 50% of all range visits. Males spent longer on the range than females in winter ( p ranging behaviour may help optimise ranging opportunities in free-range systems and is important to elucidate the potential welfare implications of ranging.

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

International Nuclear Information System (INIS)

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

1981-01-01

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

A Novel HBT Frequency Doubler Design for Millimeter-Wave Applications

DEFF Research Database (Denmark)

Johansen, Tom Keinicke; Krozer, Viktor; Vidkjær, Jens

2006-01-01

In this paper we presents a novel HBT frequency doubler design for millimeter-wave application. A HBT frequency doubler theory is described which leads to accurate design equations for optimal performance. The developed theory shows that an optimal HBT frequency doubler can be achieved using a no...

General covariance and quantum theory

International Nuclear Information System (INIS)

Mashhoon, B.

1986-01-01

The extension of the principle of relativity to general coordinate systems is based on the hypothesis that an accelerated observer is locally equivalent to a hypothetical inertial observer with the same velocity as the noninertial observer. This hypothesis of locality is expected to be valid for classical particle phenomena as well as for classical wave phenomena but only in the short-wavelength approximation. The generally covariant theory is therefore expected to be in conflict with the quantum theory which is based on wave-particle duality. This is explicitly demonstrated for the frequency of electromagnetic radiation measured by a uniformly rotating observer. The standard Doppler formula is shown to be valid only in the geometric optics approximation. A new definition for the frequency is proposed, and the resulting formula for the frequency measured by the rotating observer is shown to be consistent with expectations based on the classical theory of electrons. A tentative quantum theory is developed on the basis of the generalization of the Bohr frequency condition to include accelerated observers. The description of the causal sequence of events is assumed to be independent of the motion of the observer. Furthermore, the quantum hypothesis is supposed to be valid for all observers. The implications of this theory are critically examined. The new formula for frequency, which is still based on the hypothesis of locality, leads to the observation of negative energy quanta by the rotating observer and is therefore in conflict with the quantum theory

Dielectric spectroscopy in aqueous solutions of paracetamol over the frequency range of 20 Hz to 2 MHz at 293.15 K temperature

Science.gov (United States)

Pandit, T. R.; Rana, V. A.

2018-05-01

Frequency domain dielectric relaxation spectroscopy plays an important role in the study of pharmaceutical drug molecules. The complex relative dielectric permittivity ɛ*(ω) = ɛ' - j ɛ" of aqueous solutions of paracetamol in the frequency range of 20 Hz to 2 MHz at a temperature range of 293.15 K are measured with the help of Agilent precision LCR meter E4980A along with four terminal liquid test fixture Agilent 16452A. Data of complex relative permittivity are used to calculate loss tangent for all concentrations of paracetamol in distilled water. Electrode polarization relaxation time has been calculated for all solutions. Effect of variation of concentrations of paracetamol in distilled water on these dielectric parameters is discussed.

On the generation of electromagnetic waves in the terahertz frequency range

International Nuclear Information System (INIS)

Namiot, V.A.; Shchurova, L.Yu.

2011-01-01

It is shown that a thin dielectric plate, which can act as an open dielectric waveguide, it is possible to produce amplification and generation of electromagnetic waves with frequencies in the terahertz range. For this purpose, we propose using a dielectric plate with a corrugated surface, in which case the electric field of the transverse electromagnetic wave in the waveguide has a periodic spatial structure in the local area near to the corrugation. Terahertz electromagnetic waves are excited by a beam of electrons moving in vacuum along the dielectric plate at a small distance from its corrugated surface. Corrugation period is chosen in order to ensure the most effective interaction of the electron beam with the first harmonic of the electric field induced by the corrugation. Amplification and generation of electromagnetic waves propagating in a dielectric waveguide is realized as a result of deceleration of the electron beam by a wave electric field induced by a corrugated dielectric surface in the zone near the corrugation. We discuss possible ways to create electron beams with the desired characteristics. We offer a way to stabilize the beam position above the plate, avoiding the bombardment of the plate by electrons. It is shown that it is possible to significantly increase the efficiency of the device through the recovery of energy that remains in the electrons after their interaction with the wave. -- Highlights: → We propose a scheme of a generator of radio waves in the terahertz range. → This scheme includes a corrugated dielectric plate, which can act as an open waveguide. → A strip electron beam is in vacuum near the dielectric corrugated surface. → Generation is achieved by converting electrons' energy into electromagnetic energy. → The waveguide wave extends perpendicularly to electron motion.

Assessment of oscillator strengths with multiconfigurational short-range density functional theory for electronic excitations in organic molecules

DEFF Research Database (Denmark)

Hedegård, Erik Donovan

2017-01-01

considered the large collection of organic molecules whose excited states were investigated with a range of electronic structure methods by Thiel et al. As a by-product of our calculations of oscillator strengths, we also obtain electronic excitation energies, which enable us to compare the performance......We have in a series of recent papers investigated electronic excited states with a hybrid between a complete active space self-consistent field (CASSCF) wave function and density functional theory (DFT). This method has been dubbed the CAS short-range DFT method (CAS–srDFT). The previous papers...

GHz band frequency hopping PLL-based frequency synthesizers

Institute of Scientific and Technical Information of China (English)

XU Yong; WANG Zhi-gong; GUAN Yu; XU Zhi-jun; QIAO Lu-feng

2005-01-01

In this paper we describe a full-integrated circuit containing all building blocks of a completed PLL-based synthesizer except for low pass filter(LPF).The frequency synthesizer is designed for a frequency hopping (FH) transceiver operating up to 1.5 GHz as a local oscillator. The architecture of Voltage Controlled Oscillator (VCO) is optimized to get better performance, and a phase noise of -111.85-dBc/Hz @ 1 MHz and a tuning range of 250 MHz are gained at a centre frequency of 1.35 GHz.A novel Dual-Modulus Prescaler(DMP) is designed to achieve a very low jitter and a lower power.The settling time of PLL is 80 μs while the reference frequency is 400 KHz.This monolithic frequency synthesizer is to integrate all main building blocks of PLL except for the low pass filter,with a maximum VCO output frequency of 1.5 GHz,and is fabricated with a 0.18 μm mixed signal CMOS process. Low power dissipation, low phase noise, large tuning range and fast settling time are gained in this design.

Historic Frequency and Severity of Fire in Whitebark Pine Forests of the Cascade Mountain Range, USA

Directory of Open Access Journals (Sweden)

Michael P. Murray

2018-02-01

Full Text Available Whitebark pine (Pinus albicaulis Engelm. is a foundation species of high elevation forest ecosystems in the Cascade Mountain Range of Oregon, Washington, and British Columbia. We examined fire evidence on 55 fire history sites located in the Cascade Range. To estimate dates of historic fires we analyzed 57 partial cross-sections from fire-scarred trees plus 700 increment cores. The resulting 101 fire events indicate fire has been a widespread component of Cascadian whitebark pine stands. Results are site specific and vary considerably. Whitebark pine stands appear to burn in a variety of severities and frequencies. Sites where fire intervals were detected ranged from 9 to 314 years, with a median of 49 years, and averaging 67 years. Fire intervals shortened significantly with higher latitudes. In assessing the most recent fire event at each site, overall, 56 percent burned as stand replacing events. In the 20th century, the number of fires diminished significantly. Due to conservation imperatives, re-introducing fire should be undertaken with extreme care to avoid substantial mortality of this endangered species.

Microscopic theory of the phonon frequencies in BCC barium

International Nuclear Information System (INIS)

Oli, B.A.

1988-09-01

The phonon dispersion frequencies are calculated from first principles for bbc barium using a resonance pseudopotential model which incorporates the effect of s-d hybridization. It was also possible using this scheme to account for the anomalous feature of the Ba dispersion curve observed experimentally in the (ξ,0,0) direction where the frequencies of the transverse branch are higher than the frequencies of the longitudinal branch. The frequencies obtained were also used to calculate the phonon density of states by the linear-analytic tetrahedra method of zone integration. The results of these calculations are qualitatively in good agreement with experimental data, and provide further support to the interpretation of the anomalous behaviour in the (ξ,0,0) direction as arising from s-d hybridization. (author). 27 refs, 4 figs, 3 tabs

Lamb wave extraction of dispersion curves in micro/nano-plates using couple stress theories

Science.gov (United States)

Ghodrati, Behnam; Yaghootian, Amin; Ghanbar Zadeh, Afshin; Mohammad-Sedighi, Hamid

2018-01-01

In this paper, Lamb wave propagation in a homogeneous and isotropic non-classical micro/nano-plates is investigated. To consider the effect of material microstructure on the wave propagation, three size-dependent models namely indeterminate-, modified- and consistent couple stress theories are used to extract the dispersion equations. In the mentioned theories, a parameter called 'characteristic length' is used to consider the size of material microstructure in the governing equations. To generalize the parametric studies and examine the effect of thickness, propagation wavelength, and characteristic length on the behavior of miniature plate structures, the governing equations are nondimensionalized by defining appropriate dimensionless parameters. Then the dispersion curves for phase and group velocities are plotted in terms of a wide frequency-thickness range to study the lamb waves propagation considering microstructure effects in very high frequencies. According to the illustrated results, it was observed that the couple stress theories in the Cosserat type material predict more rigidity than the classical theory; so that in a plate with constant thickness, by increasing the thickness to characteristic length ratio, the results approach to the classical theory, and by reducing this ratio, wave propagation speed in the plate is significantly increased. In addition, it is demonstrated that for high-frequency Lamb waves, it converges to dispersive Rayleigh wave velocity.

Low-frequency dilatational wave propagation through unsaturated porous media containing two immiscible fluids

Energy Technology Data Exchange (ETDEWEB)

Lo, W.-C.; Sposito, G.; Majer, E.

2007-02-01

An analytical theory is presented for the low-frequency behavior of dilatational waves propagating through a homogeneous elastic porous medium containing two immiscible fluids. The theory is based on the Berryman-Thigpen-Chin (BTC) model, in which capillary pressure effects are neglected. We show that the BTC model equations in the frequency domain can be transformed, at sufficiently low frequencies, into a dissipative wave equation (telegraph equation) and a propagating wave equation in the time domain. These partial differential equations describe two independent modes of dilatational wave motion that are analogous to the Biot fast and slow compressional waves in a single-fluid system. The equations can be solved analytically under a variety of initial and boundary conditions. The stipulation of 'low frequency' underlying the derivation of our equations in the time domain is shown to require that the excitation frequency of wave motions be much smaller than a critical frequency. This frequency is shown to be the inverse of an intrinsic time scale that depends on an effective kinematic shear viscosity of the interstitial fluids and the intrinsic permeability of the porous medium. Numerical calculations indicate that the critical frequency in both unconsolidated and consolidated materials containing water and a nonaqueous phase liquid ranges typically from kHz to MHz. Thus engineering problems involving the dynamic response of an unsaturated porous medium to low excitation frequencies (e.g. seismic wave stimulation) should be accurately modeled by our equations after suitable initial and boundary conditions are imposed.

What is CPH Theory?

DEFF Research Database (Denmark)

Javadi, Hossein; Forouzbakhsh, Farshid; Daei Kasmaei, Hamed

2016-01-01

There are various theories in physics, but nature is unique. This is not nature's problem that we have various theories; nature obeys simple and unique law. We should improve our theories. Universal constancy of the speed of light undergoes the question whether the limit on the light speed...... is the mechanism of increasing in the photon energy that causes increase in its frequency growth? So, in CPH theory (Creative particles of Higgs Theory), it has been attempted to scrutinize the interface between classical mechanics, relativity and quantum mechanics through a novel approach to the established...... physical events. Emphasizing on these phenomena and presenting the relation between photon's energy and frequency, CPH Theory is to draw attention on the importance of constancy of speed in relation to the mass structure which will be scrutinized in reviewing relativistic Newton's second law. The results...

Nonlinear parametric phenomena in plasma during radio frequency heating in the ion cyclotron frequency range

International Nuclear Information System (INIS)

Stepanov, K.N.

1996-01-01

Parametric phenomena in plasma which occur due to varying electric fields with the ion cyclotron frequency are reviewed. Beam-like lower hybrid instability emerges in strong pumping fields provided that the transverse relative velocity of particles is larger than the ion thermal speed (υ Ti ). The resulting turbulence and the following numerous manifestations observed experimentally are addressed. The turbulence may prove important for experiments aimed at plasma production or radio frequency (RF) cleaning of metallic surfaces of vacuum chambers in stellarators, tokamaks and helicon devices. In contrast, for a weak field (U Ti ) the kinetic parametric instabilities of ion cyclotron oscillations arise due to electrons. The issues of the turbulence, mathematical modelling, its role in turbulent heating observed on the torsatron Uragan-3M, decay instabilities associated with ion cyclotron oscillations and the triggering of ion quasimodes are considered. (author)

The Frequency of Voluntary and Involuntary Autobiographical Memories across the Lifespan

Science.gov (United States)

Rubin, David C.; Berntsen, Dorthe

2011-01-01

Ratings of the memory of an important event from the last week on the frequency of voluntary and involuntary retrieval, belief in its accuracy, visual imagery, auditory imagery, setting, emotional intensity, valence, narrative coherence, and centrality to the life story were obtained from 988 adults whose age ranged from 15 to over 90. Another 992 adults provided the same ratings for a memory from their confirmation day when they were about age 14. The frequencies of involuntary and voluntary retrieval were similar. Both frequencies were predicted by emotional intensity and centrality to the life story. The results from this study, which is the first to measure the frequency of voluntary and involuntary retrieval for the same events, are counter to both cognitive and clinical theories, which consistently claim that involuntary memories are infrequent compared to voluntary memories. Age and gender differences are noted. PMID:19487759

Gauge invariant frequency splitting of the continuum Yang-Mills field

International Nuclear Information System (INIS)

Mitter, P.K.; Valent, G.

1977-01-01

Frequency splitting plays an important role in Wilson's theory of critical phenomena. Here the authors give a theory of gauge invariant frequency splitting of the Yang-Mills field in 4 dimensions. (Auth.)

Excitation and propagation of electromagnetic fluctuations with ion-cyclotron range of frequency in magnetic reconnection laboratory experiment

International Nuclear Information System (INIS)

Inomoto, Michiaki; Tanabe, Hiroshi; Ono, Yasushi; Kuwahata, Akihiro

2013-01-01

Large-amplitude electromagnetic fluctuations of ion-cyclotron-frequency range are detected in a laboratory experiment inside the diffusion region of a magnetic reconnection with a guide field. The fluctuations have properties similar to kinetic Alfvén waves propagating obliquely to the guide field. Temporary enhancement of the reconnection rate is observed during the occurrence of the fluctuations, suggesting a relationship between the modification in the local magnetic structure given by these fluctuations and the intermittent fast magnetic reconnection

Measurements on rotating ion cyclotron range of frequencies induced particle fluxes in axisymmetric mirror plasmas

International Nuclear Information System (INIS)

Hatakeyama, R.; Hershkowitz, N.; Majeski, R.; Wen, Y.J.; Brouchous, D.B.; Proberts, P.; Breun, R.A.; Roberts, D.; Vukovic, M.; Tanaka, T.

1997-01-01

A comparison of phenomenological features of plasmas is made with a special emphasis on radio-frequency induced transport, which are maintained when a set of two closely spaced dual half-turn antennas in a central cell of the Phaedrus-B axisymmetric tandem mirror [J. J. Browning et al., Phys. Fluids B 1, 1692 (1989)] is phased to excite electromagnetic fields in the ion cyclotron range of frequencies (ICRF) with m=-1 (rotating with ions) and m=+1 (rotating with electrons) azimuthal modes. Positive and negative electric currents are measured to flow axially to the end walls in the cases of m=-1 and m=+1 excitations, respectively. These parallel nonambipolar ion and electron fluxes are observed to be accompanied by azimuthal ion flows in the same directions as the antenna-excitation modes m. The phenomena are argued in terms of radial particle fluxes due to a nonambipolar transport mechanism [Hojo and Hatori, J. Phys. Soc. Jpn. 60, 2510 (1991); Hatakeyama et al., J. Phys. Soc. Jpn. 60, 2815 (1991), and Phys. Rev. E 52, 6664 (1995)], which are induced when azimuthally traveling ICRF waves are absorbed in the magnetized plasma column. copyright 1997 American Institute of Physics

Preparation, crystal structure, and dielectric characterization of Li2W2O7 ceramic at RF and microwave frequency range

Directory of Open Access Journals (Sweden)

Jinwu Chen

2017-02-01

Full Text Available Single phase Li2W2O7 with anorthic structure was prepared by the conventional solid-state reaction method at 550∘C and the anorthic structure was stable up to 660∘C. The dielectric properties at radio frequency (RF and microwave frequency range were characterized. The sample sintered at 640∘C exhibited the optimum microwave dielectric properties with a relative permittivity of 12.2, a quality factor value of 17,700GHz (at 9.8GHz, and a temperature coefficient of the resonant frequency of −232ppm/∘C as well as a high relative density ∼94.1%. Chemical compatibility measurement indicated Li2W2O7 did not react with aluminum electrodes when sintered at 640∘C for 4h.

Frequency selectivity at very low centre frequencies

DEFF Research Database (Denmark)

Orellana, Carlos Andrés Jurado; Pedersen, Christian Sejer; Marquardt, Torsten

2010-01-01

measurements based on OAE suppression techniques and notched-noise masking data psychophysically measured for centre frequencies in the range 50-125 Hz, this study examines how individual differences in frequency selectivity, as well as in masking, may occur at very low CFs due to individual differences...

Modulation of electromagnetic and absorption properties in 18-26.5 GHz frequency range of strontium hexaferrites with doping of cobalt-zirconium

Science.gov (United States)

Pubby, Kunal; Narang, Sukhleen Bindra; Kaur, Prabhjyot; Chawla, S. K.

2017-05-01

Hexaferrite nano-particles of stoichiometric composition {{Sr}}{({{CoZr}})_x}{{F}}{{{e}}_{12 - 2x}}{{{O}}_{19}}, with x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0 were prepared using sol-gel auto-combustion route owing to its advantages such as low sintering temperature requirement, homogeneity and uniformity of grains. Tartaric acid as a fuel was utilized to complete the chemical reaction. The goal of this study is to analyse the effect of co-substitution of cobalt and zirconium on the electromagnetic and absorption properties of pure {{SrF}}{{{e}}_{12}}{{{O}}_{19}} hexaferrite. The properties were measured on the rectangular pellets of thickness 2.5 mm for K-frequency band using Vector Network Analyzer. The doping of Co-Zr has resulted in increase in real as well as imaginary parts of permittivity. The values of real permittivity lie in the range 3.6-7.0 for all the composition. The real part of permeability remains in range 0.7-1.6 in the studied frequency band for all the samples and shows slightly increasing trend with frequency. The maximum values of dielectric loss tangent peak (3.04) and magnetic loss tangent peak (2.34), among all the prepared compositions, have been observed for composition x = 0.2. Compositions with x = 0.6 and x = 0.0 also have high dielectric and magnetic loss peaks. Dielectric loss peaks are attributed to dielectric resonance and magnetic loss peaks are attributed to natural resonance. Experimentally determined reflection loss results show that all six compositions of prepared series have high values of absorption to propose them as single-layer absorbers in 18-26.5 GHz frequency range. The composition with x = 0.2 has maximum absorption capacity with reflection loss peak of -37.2 dB at 24.3 GHz frequency. The undoped composition also has high absorption peak (-25.46 dB), but -10 dB absorption bandwidth is minimum (2.2 GHz) out of the present series. Maximum absorption bandwidth is obtained for x = 1.0 (4.1 GHz). Other doped compositions also

Modulation of electromagnetic and absorption properties in 18-26.5 GHz frequency range of strontium hexaferrites with doping of cobalt-zirconium

Energy Technology Data Exchange (ETDEWEB)

Pubby, Kunal; Narang, Sukhleen Bindra [Guru Nanak Dev University, Department of Electronics Technology, Amritsar (India); Kaur, Prabhjyot; Chawla, S.K. [Guru Nanak Dev University, Department of Chemistry, Centre for Advanced Studies-I, Amritsar (India)

2017-05-15

Hexaferrite nano-particles of stoichiometric composition Sr(CoZr){sub x}Fe{sub 12-2x}O{sub 19}, with x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0 were prepared using sol-gel auto-combustion route owing to its advantages such as low sintering temperature requirement, homogeneity and uniformity of grains. Tartaric acid as a fuel was utilized to complete the chemical reaction. The goal of this study is to analyse the effect of co-substitution of cobalt and zirconium on the electromagnetic and absorption properties of pure SrFe{sub 12}O{sub 19} hexaferrite. The properties were measured on the rectangular pellets of thickness 2.5 mm for K-frequency band using Vector Network Analyzer. The doping of Co-Zr has resulted in increase in real as well as imaginary parts of permittivity. The values of real permittivity lie in the range 3.6-7.0 for all the composition. The real part of permeability remains in range 0.7-1.6 in the studied frequency band for all the samples and shows slightly increasing trend with frequency. The maximum values of dielectric loss tangent peak (3.04) and magnetic loss tangent peak (2.34), among all the prepared compositions, have been observed for composition x = 0.2. Compositions with x = 0.6 and x = 0.0 also have high dielectric and magnetic loss peaks. Dielectric loss peaks are attributed to dielectric resonance and magnetic loss peaks are attributed to natural resonance. Experimentally determined reflection loss results show that all six compositions of prepared series have high values of absorption to propose them as single-layer absorbers in 18-26.5 GHz frequency range. The composition with x = 0.2 has maximum absorption capacity with reflection loss peak of -37.2 dB at 24.3 GHz frequency. The undoped composition also has high absorption peak (-25.46 dB), but -10 dB absorption bandwidth is minimum (2.2 GHz) out of the present series. Maximum absorption bandwidth is obtained for x = 1.0 (4.1 GHz). Other doped compositions also have high absorption bandwidth

Nonlinear optical response of a gold surface in the visible range: A study by two-color sum-frequency generation spectroscopy. I. Experimental determination.

Science.gov (United States)

Dalstein, L; Revel, A; Humbert, C; Busson, B

2018-04-07

We experimentally determine the effective nonlinear second-order susceptibility of gold over the visible spectral range. To reach that goal, we probe by vibrational two-color sum-frequency generation spectroscopy the methyl stretching region of a dodecanethiol self-assembled monolayer adsorbed on a gold film. The sum-frequency generation spectra show a remarkable shape reversal when the visible probe wavelength is tuned from 435 to 705 nm. After correcting from Fresnel effects, the methyl stretching vibrations serve as an internal reference, allowing to extract the dispersion of the absolute phase and relative amplitude of the effective nonlinear optical response of gold in the visible range.

Frequency Equations for the In-Plane Vibration of Circular Annular Disks

Directory of Open Access Journals (Sweden)

S. Bashmal

2010-01-01

Full Text Available This paper deals with the in-plane vibration of circular annular disks under combinations of different boundary conditions at the inner and outer edges. The in-plane free vibration of an elastic and isotropic disk is studied on the basis of the two-dimensional linear plane stress theory of elasticity. The exact solution of the in-plane equation of equilibrium of annular disk is attainable, in terms of Bessel functions, for uniform boundary conditions. The frequency equations for different modes can be obtained from the general solutions by applying the appropriate boundary conditions at the inner and outer edges. The presented frequency equations provide the frequency parameters for the required number of modes for a wide range of radius ratios and Poisson's ratios of annular disks under clamped, free, or flexible boundary conditions. Simplified forms of frequency equations are presented for solid disks and axisymmetric modes of annular disks. Frequency parameters are computed and compared with those available in literature. The frequency equations can be used as a reference to assess the accuracy of approximate methods.

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

Directory of Open Access Journals (Sweden)

Kessler Sharon E

2012-11-01

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

Radio frequency system for nuclear fusion

International Nuclear Information System (INIS)

Kozeki, Shoichiro; Sagawa, Norimoto; Takizawa, Teruhiro

1987-01-01

The importance of radio frequency waves has been increasing in the area of nuclear fusion since they are indispensable for heating of plasma, etc. This report outlines radio frequency techniques used for nuclear fusion and describes the development of radio frequency systems (radio frequency plasma heating system and current drive system). Presently, in-depth studies are underway at various research institutes to achieve plasma heating by injection of radio frequency electric power. Three ranges of frequencies, ICRF (ion cyclotron range of frequency), LHRF (lower hybrid range of frequency) and ECRF (electron cyclotron range of frequency), are considered promissing for radio frequency heating. Candidate waves for plasma current driving include ECW (electron cyclotron wave), LHW (lower hybrid wave), MSW (magnetic sound wave), ICW (ion cyclotron wave) with minority component, and FW (fast wave). FW is the greatest in terms of current drive efficiency. In general, a radio frequency system for nuclear fusion consists of a radio frequency power source, transmission/matching circuit component and plasma connection component. (Nogami, K.)

Parametric Instability, Inverse Cascade, and the 1/f Range of Solar-Wind Turbulence.

Science.gov (United States)

Chandran, Benjamin D G

2018-02-01

In this paper, weak turbulence theory is used to investigate the nonlinear evolution of the parametric instability in 3D low- β plasmas at wavelengths much greater than the ion inertial length under the assumption that slow magnetosonic waves are strongly damped. It is shown analytically that the parametric instability leads to an inverse cascade of Alfvén wave quanta, and several exact solutions to the wave kinetic equations are presented. The main results of the paper concern the parametric decay of Alfvén waves that initially satisfy e + ≫ e - , where e + and e - are the frequency ( f ) spectra of Alfvén waves propagating in opposite directions along the magnetic field lines. If e + initially has a peak frequency f 0 (at which fe + is maximized) and an "infrared" scaling f p at smaller f with -1 scaling throughout a range of frequencies that spreads out in both directions from f 0 . At the same time, e - acquires an f -2 scaling within this same frequency range. If the plasma parameters and infrared e + spectrum are chosen to match conditions in the fast solar wind at a heliocentric distance of 0.3 astronomical units (AU), then the nonlinear evolution of the parametric instability leads to an e + spectrum that matches fast-wind measurements from the Helios spacecraft at 0.3 AU, including the observed f -1 scaling at f ≳ 3 × 10 -4 Hz. The results of this paper suggest that the f -1 spectrum seen by Helios in the fast solar wind at f ≳ 3 × 10 -4 Hz is produced in situ by parametric decay and that the f -1 range of e + extends over an increasingly narrow range of frequencies as r decreases below 0.3 AU. This prediction will be tested by measurements from the Parker Solar Probe .

The mesoscopic conductance of disordered rings, its random matrix theory and the generalized variable range hopping picture

International Nuclear Information System (INIS)

Stotland, Alexander; Peer, Tal; Cohen, Doron; Budoyo, Rangga; Kottos, Tsampikos

2008-01-01

The calculation of the conductance of disordered rings requires a theory that goes beyond the Kubo-Drude formulation. Assuming 'mesoscopic' circumstances the analysis of the electro-driven transitions shows similarities with a percolation problem in energy space. We argue that the texture and the sparsity of the perturbation matrix dictate the value of the conductance, and study its dependence on the disorder strength, ranging from the ballistic to the Anderson localization regime. An improved sparse random matrix model is introduced to capture the essential ingredients of the problem, and leads to a generalized variable range hopping picture. (fast track communication)

Climate-informed flood frequency analysis based on Bayesian theory and teleconnection for the Three Gorges Dam (TGD)

Science.gov (United States)

DONG, Q.; Zhang, X.; Lall, U.; Sang, Y. F.; Xie, P.

2017-12-01

With the current global climate changing and human activities intensifying, the uncertainties and danger of floods increased significantly. However, the current flood frequency analysis is still based on the stationary assumption. This assumption not only limits the benefits of the water conservancy projects, but also brings hazard because it ignores the risk of flooding under climate change. In this paper, we relax the stationary hypothesis in the flood frequency analysis model based on the teleconnection and use the intrinsic relation of flood elements to improve the annual flood frequency results by Bayesian inference approaches. Daily discharges of the the Three Gorges Dam(TGD) in 1953-2013 years are used as an example. Firstly, according to the linear correlation between the climate indices and the distribution parameters, the prior distributions of peak and volume are established with the selected large scale climate predictors. After that, by using the copula function and predictands, the conditional probability function of peak and volume is obtained. Then, the Bayesian theory links the prior distributions and conditional distributions and get the posterior distributions. We compare the difference under different prior distributions and find the optimal flood frequency distribution model. Finally, we discuss the impact of dynamic flood frequency analysis on the plan and management of hydraulic engineering. The results show that compared with the prior probability, the posterior probability considering the correlation of the flood elements is more accurate and the uncertainty is smaller. And the dynamic flood frequency model has a great impact on the management of the existing hydraulic engineering, which can improve the engineering operation benefit and reducing its flood risk, but it nearly didn't influence the plan of hydraulic engineering. The study of this paper is helpful to the dynamic flood risk management of TGD, and provide reference for the

Optimal Tikhonov Regularization in Finite-Frequency Tomography

Science.gov (United States)

Fang, Y.; Yao, Z.; Zhou, Y.

2017-12-01

The last decade has witnessed a progressive transition in seismic tomography from ray theory to finite-frequency theory which overcomes the resolution limit of the high-frequency approximation in ray theory. In addition to approximations in wave propagation physics, a main difference between ray-theoretical tomography and finite-frequency tomography is the sparseness of the associated sensitivity matrix. It is well known that seismic tomographic problems are ill-posed and regularizations such as damping and smoothing are often applied to analyze the tradeoff between data misfit and model uncertainty. The regularizations depend on the structure of the matrix as well as noise level of the data. Cross-validation has been used to constrain data uncertainties in body-wave finite-frequency inversions when measurements at multiple frequencies are available to invert for a common structure. In this study, we explore an optimal Tikhonov regularization in surface-wave phase-velocity tomography based on minimization of an empirical Bayes risk function using theoretical training datasets. We exploit the structure of the sensitivity matrix in the framework of singular value decomposition (SVD) which also allows for the calculation of complete resolution matrix. We compare the optimal Tikhonov regularization in finite-frequency tomography with traditional tradeo-off analysis using surface wave dispersion measurements from global as well as regional studies.

Maintenance of extratropical low-frequency variabilities in the atmosphere

International Nuclear Information System (INIS)

Ting, M.

1994-01-01

The extratropical low-frequency variability is one of the most important components in extratropical dynamics. While there are some understanding of the high-frequency, synoptic scale storm track eddy development due to baroclinic instability theory, its low-frequency counterpart is poorly understood and the theory for that is slowly evolving. The main difficulty seems to be lying on the fact that the problem is three dimensional in nature

Chimera Type Behavior in Nonlocal Coupling System with Two Different Inherent Frequencies

Science.gov (United States)

Lin, Larry; Li, Ping-Cheng; Tseng, Hseng-Che

2014-03-01

From the research of Kuramoto and Strogatz, arrays of identical oscillators can display a remarkable pattern, named chimera state, in which phase-locked oscillators coexist with drifting ones in nonlocal coupling oscillator system. We consider further in this study, two groups of oscillators with different inherent frequencies and arrange them in a ring. When the difference of the inherent frequencies is within some specific parameter range, oscillators of nonlocal coupling system show two distinct chimera states. When the parameter value exceeds some threshold value, two chimera states disappear. They show different features. The statistical dynamic behavior of the system can be described by Kuramoto theory.

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.

Verification of the effects of Schumann frequency range electromagnetic fields on the human cardiovascular system

Science.gov (United States)

Tuzhilkin, D. A.; Borodin, A. S.

2017-11-01

The results of the study of variations in the electromagnetic background parameters of the Schumann resonator frequency range and the variability indices of the human heart period during its free activity are presented on the basis of 24-hour synchronous monitoring data. It is shown that the integral evaluation of the conjugacy of the heart rate variability indices from the Schumann resonance parameters is extremely weak. In this case, the differential evaluation of this dependence with separation into characteristic time intervals of the day, characterized by different motor activity of the subjects, becomes significantly higher. The number of volunteers whose conjugacy is characterized by a strong correlation in some cases reaches 35 percent of the sample.

CAMAC programmable-control frequency synthesizer

International Nuclear Information System (INIS)

Yumaguzin, T.Kh.; Vyazovkin, D.E.; Nazirov, Eh.P.; Tuktarov, R.F.

1989-01-01

Synthesizer allows to set frequency with 0.015% accuracy and to scan it with variable step. Frequency controlled divider with further summing-up of divided frequency with fundamental one is used in synthesizer, and it has allowed to use digit of the input code and to obtain 3-4 MHz frequency range. Variation of operation flowsheet in the other frequency range is possible. K-155 and K-531 series microcircuits were used during development

Intrinsic and extrinsic permeability of ferromagnetic thin films and multilayers for frequency dependence: comparison between theory and experiment

International Nuclear Information System (INIS)

Berthault, A.; Durbin, F.; Russat, J.

1992-01-01

Soft ferromagnetic thin films are attractive materials for read/write head applications because they exhibit a high magnetic permeability in the hundred MHz range. By contrast, due to their low electrical resistivity, their processability at higher frequency is somewhat limited. Using Maxwell equations and the geometry of the processed material, we have developed a theoretical model of the frequency-dependent magnetic permeability useful for multilayers design. We have distinguished different cases: - extrinsic (measured) vs intrinsic permeability in magnetic thin films and magnetic-insulator multilayers, - intrinsic vs extrinsic permeability in magnetic thin films, computes by the Newton iterative method. Using the well-know Landau-Lifshitz model for high frequency permeability, we have compared experimental and theoretical results. (orig.)

Parametric effects of word frequency effect in memory for mixed frequency lists

OpenAIRE

Lohnas, Lynn J.; Kahana, Michael J.

2013-01-01

The word frequency paradox refers to the finding that low frequency words are better recognized than high frequency words yet high frequency words are better recalled than low frequency words. Rather than comparing separate groups of low and high frequency words, we sought to quantify the functional relation between word frequency and memory performance across the broad range of frequencies typically used in episodic memory experiments. Here we report that both low frequency and high frequenc...

Frequency shifts in stimulated Raman scattering

International Nuclear Information System (INIS)

Zinth, W.; Kaiser, W.

1980-01-01

The nonresonant contributions to the nonlinear susceptibility chisup(()3) produce a frequency chirp during stimulated Raman scattering. In the case of transient stimulated Raman scattering, the spectrum of the generated Stokes pulse is found at higher frequencies than expected from spontaneous Raman data. The frequency difference can be calculated from the theory of stimulated Raman scattering. (orig.)

A Frequency-Depth Explicit Interaction Theory Formulation

DEFF Research Database (Denmark)

Ruiz, Pau Mercadé; Ferri, Francesco; Kofoed, Jens Peter

2016-01-01

An alternative definition of the usual diffraction transfer matrix defined by Kagemoto and Yue (1986) has been developed. A method is thereby presented which enables the prediction of the diffraction transfer matrix for any desired wave frequency and water depth. The method has been tested for th...

Analyses of kinetic glass transition in short-range attractive colloids based on time-convolutionless mode-coupling theory.

Science.gov (United States)

Narumi, Takayuki; Tokuyama, Michio

2017-03-01

For short-range attractive colloids, the phase diagram of the kinetic glass transition is studied by time-convolutionless mode-coupling theory (TMCT). Using numerical calculations, TMCT is shown to recover all the remarkable features predicted by the mode-coupling theory for attractive colloids: the glass-liquid-glass reentrant, the glass-glass transition, and the higher-order singularities. It is also demonstrated through the comparisons with the results of molecular dynamics for the binary attractive colloids that TMCT improves the critical values of the volume fraction. In addition, a schematic model of three control parameters is investigated analytically. It is thus confirmed that TMCT can describe the glass-glass transition and higher-order singularities even in such a schematic model.

Extending the frequency range of free-field reciprocity calibration of measurement microphones to frequencies up to 150 kHz

DEFF Research Database (Denmark)

Barrera Figueroa, Salvador; Torras Rosell, Antoni; Jacobsen, Finn

2013-01-01

Measurement microphones are typically calibrated in a free field at frequencies up to 50 kHz. This is a sufficiently high frequency for the most sound measurement applications related with noise assessment. However, other applications such as the measurement of noise emitted by ultrasound cleanin...

Morphological Parameters in Relation to the Electromagnetic Properties of Microcellular Thermoplastic Polyurethane Foam in X-Band Frequency Ranges

Directory of Open Access Journals (Sweden)

Mohammad Hassan Moeini

2017-04-01

Full Text Available Microcellular thermoplastic polyurethane foams are examined as absorbing materials in the X-band (8.2-12.4 GHz frequency range by means of experiment. In this work, we aim to establish relationships between foam morphology including cell size and air volume fraction and electromagnetic properties including absorption, transmission and reflection quality. Nanocomposites based on thermoplastic polyurethane containing carbon black were prepared by coagulation method. In this procedure 15 wt% carbon black-containing nanocomposite was converted to microcellular foams using batch foaming process and supercritical carbon dioxide as physical foaming agent. The morphology of the foams was evaluated by scanning electron microscopy. S-parameters of the samples were measured by a vector network analyzer (VNA and the effect of morphological parameters such as cell size and air volume fraction on the absorbing properties was investigated. We also established structure/properties relationships which were essential for further optimizations of the materials used in the construction of radar absorbing composites. Foaming reduced the percolation threshold of the nanocomposites due to the reduction in the average distance between nanoparticles. Foaming and dielectric constant reduction dropped the reflection percentage significantly. The increase in air volume fraction in the foam increased absorption per its weight, because of multiple scattering in composite media. The sensitivity of electromagnetic wave toward the variation of cell size is strongly weaker than that toward the variation of air volume fraction. Electromagnetic properties of the microcellular foams deviated a little from effective medium theories (EMTs. Air volume fraction of the cells was a function of cell size and smaller cells showed higher absorption.

Soliton microcomb range measurement

Science.gov (United States)

Suh, Myoung-Gyun; Vahala, Kerry J.

2018-02-01

Laser-based range measurement systems are important in many application areas, including autonomous vehicles, robotics, manufacturing, formation flying of satellites, and basic science. Coherent laser ranging systems using dual-frequency combs provide an unprecedented combination of long range, high precision, and fast update rate. We report dual-comb distance measurement using chip-based soliton microcombs. A single pump laser was used to generate dual-frequency combs within a single microresonator as counterpropagating solitons. We demonstrated time-of-flight measurement with 200-nanometer precision at an averaging time of 500 milliseconds within a range ambiguity of 16 millimeters. Measurements at distances up to 25 meters with much lower precision were also performed. Our chip-based source is an important step toward miniature dual-comb laser ranging systems that are suitable for photonic integration.

A quantum inspired model of radar range and range-rate measurements with applications to weak value measurements

Science.gov (United States)

Escalante, George

2017-05-01

Weak Value Measurements (WVMs) with pre- and post-selected quantum mechanical ensembles were proposed by Aharonov, Albert, and Vaidman in 1988 and have found numerous applications in both theoretical and applied physics. In the field of precision metrology, WVM techniques have been demonstrated and proven valuable as a means to shift, amplify, and detect signals and to make precise measurements of small effects in both quantum and classical systems, including: particle spin, the Spin-Hall effect of light, optical beam deflections, frequency shifts, field gradients, and many others. In principal, WVM amplification techniques are also possible in radar and could be a valuable tool for precision measurements. However, relatively limited research has been done in this area. This article presents a quantum-inspired model of radar range and range-rate measurements of arbitrary strength, including standard and pre- and post-selected measurements. The model is used to extend WVM amplification theory to radar, with the receive filter performing the post-selection role. It is shown that the description of range and range-rate measurements based on the quantum-mechanical measurement model and formalism produces the same results as the conventional approach used in radar based on signal processing and filtering of the reflected signal at the radar receiver. Numerical simulation results using simple point scatterrer configurations are presented, applying the quantum-inspired model of radar range and range-rate measurements that occur in the weak measurement regime. Potential applications and benefits of the quantum inspired approach to radar measurements are presented, including improved range and Doppler measurement resolution.

ICRF [ion cyclotron range of frequencies] coupling on DIII-D and the implications on ICRF technology development

International Nuclear Information System (INIS)

Hoffman, D.J.; Baity, F.W.; Mayberry, M.J.; Swain, D.W.

1987-01-01

Low-power coupling tests have been carried out with a prototype ion cyclotron range of frequencies (ICRF) compact loop antenna on the DIII-D tokamak. Plasma load resistance values higher than originally calculated are measured in ohmic and L-mode, beam-heated plasmas. Load resistance decreases by a factor of ∼2 in H-mode operation. When edge localized modes (ELMs) occur, the antenna loading increases transiently to several ohms. Results indicate that fast-wave ICRF antenna coupling characteristics are highly sensitive to changes in the edge plasma profiles associated with the H-mode regime

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

Science.gov (United States)

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

2017-02-01

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

Power Transmission Tower Series Extraction in PolSAR Image Based on Time-Frequency Analysis and A-Contrario Theory

Directory of Open Access Journals (Sweden)

Dongqing Peng

2016-11-01

Full Text Available Based on Time-Frequency (TF analysis and a-contrario theory, this paper presents a new approach for extraction of linear arranged power transmission tower series in Polarimetric Synthetic Aperture Radar (PolSAR images. Firstly, the PolSAR multidimensional information is analyzed using a linear TF decomposition approach. The stationarity of each pixel is assessed by testing the maximum likelihood ratio statistics of the coherency matrix. Then, based on the maximum likelihood log-ratio image, a Cell-Averaging Constant False Alarm Rate (CA-CFAR detector with Weibull clutter background and a post-processing operator is used to detect point-like targets in the image. Finally, a searching approach based on a-contrario theory is applied to extract the linear arranged targets from detected point-like targets. The experimental results on three sets of PolSAR data verify the effectiveness of this approach.

Simulation of a Smith-Purcell free-electron laser with sidewalls: Copious emission at the fundamental frequency

International Nuclear Information System (INIS)

Donohue, J. T.; Gardelle, J.

2011-01-01

The two-dimensional theory of the Smith-Purcell free-electron laser of Andrews and Brau [H. L. Andrews and C. A. Brau, Phys. Rev. ST Accel. Beams 7, 070701 (2004)] predicts that coherent Smith-Purcell radiation can occur only at harmonics of the frequency of the evanescent wave that is resonant with the beam. A particle-in-cell simulation shows that in a three-dimensional context, where the lamellar grating has sidewalls, coherent Smith-Purcell radiation can be copiously emitted at the fundamental frequency, for a well-defined range of beam energy.

Intensity autocorrelation measurements of frequency combs in the terahertz range

Science.gov (United States)

Benea-Chelmus, Ileana-Cristina; Rösch, Markus; Scalari, Giacomo; Beck, Mattias; Faist, Jérôme

2017-09-01

We report on direct measurements of the emission character of quantum cascade laser based frequency combs, using intensity autocorrelation. Our implementation is based on fast electro-optic sampling, with a detection spectral bandwidth matching the emission bandwidth of the comb laser, around 2.5 THz. We find the output of these frequency combs to be continuous even in the locked regime, but accompanied by a strong intensity modulation. Moreover, with our record temporal resolution of only few hundreds of femtoseconds, we can resolve correlated intensity modulation occurring on time scales as short as the gain recovery time, about 4 ps. By direct comparison with pulsed terahertz light originating from a photoconductive emitter, we demonstrate the peculiar emission pattern of these lasers. The measurement technique is self-referenced and ultrafast, and requires no reconstruction. It will be of significant importance in future measurements of ultrashort pulses from quantum cascade lasers.

Variable frequency iteration MPPT for resonant power converters

Science.gov (United States)

Zhang, Qian; Bataresh, Issa; Chen, Lin

2015-06-30

A method of maximum power point tracking (MPPT) uses an MPPT algorithm to determine a switching frequency for a resonant power converter, including initializing by setting an initial boundary frequency range that is divided into initial frequency sub-ranges bounded by initial frequencies including an initial center frequency and first and second initial bounding frequencies. A first iteration includes measuring initial powers at the initial frequencies to determine a maximum power initial frequency that is used to set a first reduced frequency search range centered or bounded by the maximum power initial frequency including at least a first additional bounding frequency. A second iteration includes calculating first and second center frequencies by averaging adjacent frequent values in the first reduced frequency search range and measuring second power values at the first and second center frequencies. The switching frequency is determined from measured power values including the second power values.

The changes of the frequency specific impedance of the human body due to the resonance in the kHz range in cancer diagnostics

Science.gov (United States)

Michalak, K. P.; Nawrocka-Bogusz, H.

2011-12-01

The frequency-specific absorption of kHz signals has been postulated for different tissues, trace elements, vitamins, toxins, pathogens, allergens etc. for low-power (μV) signals. An increase in the impedance of the human body is observed only up to the given power of the applied signal. The highest amplification of the given signal being damped by the body makes it possible to determine the intensity of the given process in the body (e.g. amount of the toxin, trace element, intensity of the allergy) being connected with a given frequency spectrum of the signal. The mechanism of frequency-specific absorption can be explained by means of the Quantum Field Theory being applied to the structure of the water. Substantially high coincidence between the frequencies of the rotation of free quasi-excited electrons in coherent domains of water and the frequencies being used in the MORA diagnostics (Med-Tronic GmbH, EN ISO 13485, EN ISO 9001) can be observed. These frequencies are located in the proximity of f = 7kHz · i (i = 1,3,5,7,...). This fact suggests that the coherent domains with the admixtures of the given substances create structure-specific coherent domains that possess frequency-specific absorption spectra. The diagnostic tool called "MORA System diagnosis" was used to investigate 102 patients with different types and stages of cancer. Many signals were observed to be absorbed by many cancer patients, e.g.: 'Cellular defense system', 'Degeneration tendencies', Manganese, Magnesium, Zinc, Selenium, Vitamin E, Glutamine, Glutathione, Cysteine, Candida albicans, Mycosis. The results confirm the role of oxidative stress, immunological system deficiency and mitochondria malfunction in the development of cancer.

A New Microwave Shield Preparation for Super High Frequency Range: Occupational Approach to Radiation Protection.

Science.gov (United States)

Zaroushani, Vida; Khavanin, Ali; Jonidi Jafari, Ahmad; Mortazavi, Seyed Bagher

2016-01-01

Widespread use of X-band frequency (a part of the super high frequency microwave) in the various workplaces would contribute to occupational exposure with potential of adverse health effects.  According to limited study on microwave shielding for the workplace, this study tried to prepare a new microwave shielding for this purpose. We used EI-403 epoxy thermosetting resin as a matrix and nickel oxide nanoparticle with the diameter of 15-35 nm as filler. The Epoxy/ Nickel oxide composites with 5, 7, 9 and 11 wt% were made in three different thicknesses (2, 4 and 6 mm). According to transmission / reflection method, shielding effectiveness (SE) in the X-band frequency range (8-12.5 GHz) was measured by scattering parameters directly given by the 2-port Vector Network Analyzer. The fabricated composites characterized by X-ray Diffraction and Field Emission Scanning Electron Microscope. The best average of shielding effectiveness in each thickness of fabricated composites obtained by 11%-2 mm, 7%-4 mm and 7%-6 mm composites with SE values of 46.80%, 66.72% and 64.52%, respectively. In addition, the 11%-6 mm, 5%-6 mm and 11%-4 mm-fabricated composites were able to attenuate extremely the incident microwave energy at 8.01, 8.51 and 8.53 GHz by SE of 84.14%, 83.57 and 81.30%, respectively. The 7%-4mm composite could be introduced as a suitable alternative microwave shield in radiation protection topics in order to its proper SE and other preferable properties such as low cost and weight, resistance to corrosion etc. It is necessary to develop and investigate the efficacy of the fabricated composites in the fields by future studies.

Anomalous high-frequency resistivity of a plasma

International Nuclear Information System (INIS)

Kruer, W.L.; Dawson, J.M.

1971-06-01

In one- and two-dimensional computer simulations we investigate anomalous high-frequency resistivity in a plasma driven by a large electric field oscillating near the electron plasma frequency. The large field excites the oscillating two-stream and the ion-acoustic decay instabilities in agreement with the linear theory. When the ion and electron fluctuations saturate, a strong anomalous heating of the plasma sets in. This strong heating is due to an efficient coupling of the externally imposed large electric field to the plasma by ion fluctuations. We determine the anomalous collision frequency and the saturation fluctuation amplitudes as a function of the external field amplitude and frequency, and the electron-ion mass ratio. A simple nonlinear theory gives results in reasonable agreement with simulations. 24 refs., 10 figs

Investigation of factors influencing the efficacy of electromagnetic shielding in X band frequency range

Directory of Open Access Journals (Sweden)

Vida Zaroushani

2016-12-01

Full Text Available Introduction: Due to the importance of engineering controls for prevention of microwave exposure, this study was conducted to design and constract a novel electromagnetic shielding and also to examine the factors influencing shielding efficacy in X band frequency range. Material and Method: This study used Resin Epoxy as matrix and nano-Nickel Oxide as filler to prepare the composite plates with three different thicknesses (2,4, and 6 mm and four different weight percentages (5,7,9 and 11. The fabricated composites characterized using X-ray diffraction and Field Emission Scanning Electron microscopy. Shielding effectiveness, percolation depth, and percolation threshold were measured using Vector Network Analyzers. Thermal Gravimetric Analysis was conducted to study the temperature influence on weight loss for fabricated composites. Result: A maximum shielding effectiveness value of 84.18% was obtained for the 11%-6mm composite at 8.01 GHz and the 7%-4mm composite exhibits a higher average of shielding effectiveness of 66.72% at X- band frequency range. The 4mm thickness was optimum and critical diameter for composite plates; and percolation depth was obtained greater than thickness of composites. However, increasing the nickel oxide content did not show noticeable effect on the shielding effectiveness. Thermal Gravimetric Analysis showed that the study shields were resistant to temperature up to 150 °C without experiencing weight loss. What is more, the results indicated that Nickel oxide Nano particles had desirable distribution and dispersion in epoxy matrix and percolation threshold was appeared in low content of nickel oxide nanoparticles. Conclusion: A novel electromagnetic shield using low thickness and few content of nanoparticle with noticeable efficacy was properly designed and constructed in the field of occupational health. In addition, this shield has low cost, easy to manufacture, resistance to wet/corrosion, and low weight. Epoxy

Sound propagation in water containing large tethered spherical encapsulated gas bubbles with resonance frequencies in the 50 Hz to 100 Hz range.

Science.gov (United States)

Lee, Kevin M; Hinojosa, Kevin T; Wochner, Mark S; Argo, Theodore F; Wilson, Preston S; Mercier, Richard S

2011-11-01

The efficacy of large tethered encapsulated gas bubbles for the mitigation of low frequency underwater noise was investigated with an acoustic resonator technique. Tethered latex balloons were used as the bubbles, which had radii of approximately 5 cm. Phase speeds were inferred from the resonances of a water and balloon-filled waveguide approximately 1.8 m in length. The Commander and Prosperetti effective-medium model [J. Acoust. Soc. Am. 85, 732-746 (1989)] quantitatively described the observed dispersion from well below to just below the individual bubble resonance frequency, and it qualitatively predicted the frequency range of high attenuation for void fractions between 2% and 5% for collections of stationary balloons within the waveguide. A finite-element model was used to investigate the sensitivity of the waveguide resonance frequencies, and hence the inferred phase speeds, to changes in individual bubble size and position. The results indicate that large tethered encapsulated bubbles could be used mitigate low frequency underwater noise and that the Commander and Prosperetti model would be useful in the design of such a system.

High-frequency spin-dependent tunnelling in magnetic nanocomposites: Magnetorefractive effect and magnetoimpedance

Energy Technology Data Exchange (ETDEWEB)

Granovsky, Alexander [Faculty of Physics, Lomonosov Moscow State University, Moscow 119992 (Russian Federation)]. E-mail: granov@magn.ru; Kozlov, Andrey [Faculty of Physics, Lomonosov Moscow State University, Moscow 119992 (Russian Federation); Nedukh, Sergey [Institute of Radiophysics and Electronics NAS of Ukraine, Kharkov 61085 (Ukraine); Tarapov, Sergey [Institute of Radiophysics and Electronics NAS of Ukraine, Kharkov 61085 (Ukraine)

2005-07-15

Since the dielectric permittivity is linear with frequency-dependent conductivity, high-frequency properties for any kind of magnetic materials with the high magnetoresistance depend on magnetization. It manifests as magnetorefractive effect (MRE) in the infrared region of spectrum and as magnetoimpedance (MI) in the frequency range between radio and microwaves. The main mechanism of both MRE and MI in nanocomposites with tunnel-type magnetoresistance is high-frequency spin-dependent tunnelling. We report on recent results of theoretical and experimental investigations of MRE and MI in nanocomposites Co{sub 51.5}Al{sub 19.5}O{sub 29}, Co{sub 50.2}Ti{sub 9.1}O{sub 40.7}, Co{sub 52.3}Si{sub 12.2}O{sub 35.5} and (Co{sub 0,4}Fe{sub 0,6}){sub 48}(MgF){sub 52}. Most of the obtained experimental data for MRE and MI are consistent with the theory based on considering the tunnel junction between adjacent granules in percolation cluster as a capacitor.

A test of the Hall-MHD model: Application to low-frequency upstream waves at Venus

Science.gov (United States)

Orlowski, D. S.; Russell, C. T.; Krauss-Varban, D.; Omidi, N.

1994-01-01

Early studies suggested that in the range of parameter space where the wave angular frequency is less than the proton gyrofrequency and the plasma beta, the ratio of the thermal to magnetic pressure, is less than 1 magnetohydrodynamics provides an adequate description of the propagating modes in a plasma. However, recently, Lacombe et al. (1992) have reported significant differences between basic wave characteristics of the specific propagation modes derived from linear Vlasov and Hall-magnetohydrodynamic (MHD) theories even when the waves are only weakly damped. In this paper we compare the magnetic polarization and normalization magnetic compression ratio of ultra low frequency (ULF) upstream waves at Venus with magnetic polarization and normalized magnetic compression ratio derived from both theories. We find that while the 'kinetic' approach gives magnetic polarization and normalized magnetic compression ratio consistent with the data in the analyzed range of beta (0.5 less than beta less than 5) for the fast magnetosonic mode, the same wave characteristics derived from the Hall-MHD model strongly depend on beta and are consistent with the data only at low beta for the fast mode and at high beta for the intermediate mode.

Investigation of Range Profiles from a Simplified Ship on Rough Sea Surface and Its Multipath Imaging Mechanisms

Directory of Open Access Journals (Sweden)

Siyuan He

2012-01-01

Full Text Available The range profiles of a two-dimension (2 D perfect electric conductor (PEC ship on a wind-driven rough sea surface are derived by performing an inverse discrete Fourier transform (IDFT on the wide band backscattered field. The rough sea surface is assuming to be a PEC surface. The back scattered field is computed based on EM numerical simulation when the frequencies are sampled between 100 MHz and 700 MHz. Considering the strong coupling interactions between the ship and sea, the complicated multipath effect to the range profile characteristics is fully analyzed based on the multipath imaging mechanisms. The coupling mechanisms could be explained by means of ray theory prediction and numerical extraction of the coupling currents. The comparison of the range profile locations between ray theory prediction and surface current simulation is implemented and analyzed in this paper. Finally, the influence of different sea states on the radar target signatures has been examined and discussed.

Dynamics of r.f. production of Stellarator plasmas in the ion cyclotron range of frequency

International Nuclear Information System (INIS)

Moiseenko, V.E.; Lysoivan, A.I.; Kasilov, S.V.; Plyusnin, V.V.

1995-01-01

The present study investigated numerically the process of r.f. production of plasma in the URAGAN-3M torsatron in the frequency range below the ion cyclotron frequency (ω ci ). The dynamics of r.f. plasma build-up at the stages of neutral gas burnout and plasma heating were studied using a zero-dimensional transport code, in which the plasma confinement law was determined by large helical device scaling. Two models for input r.f. power were used. In the first case, the r.f. power absorbed by the electrons was computed by a one-dimensional r.f. code solving Maxwell's boundary problem equations. The mechanisms of electron heating through direct excitation of the slow wave (SW) by antennae as well as the conversion of fast wave (FW) into SW in the vicinity of Alfven resonance (scenario of Alfven heating) were taken into account in the computations. In the second case, an 'ideal' model of r.f. power deposition onto the electrons as a linear function of plasma density was employed. A noticeable difference in plasma production dynamics computed for these two cases was found. Better agreement with experimental data obtained from the URAGAN-3M torsatron was found for the first case resulting from combination of the one-dimensional r.f. and zero-dimensional transport codes. ((orig.))

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

Energy Technology Data Exchange (ETDEWEB)

Michael Klopf, J. [Department of Applied Science, College of William and Mary, McGlothlin-Street Hall, Williamsburg, VA 23187 (United States); Kaufmann, Pierre; Raulin, Jean-Pierre; Szpigel, Sérgio [Centro de Rádio-Astronomia e Astrofísica Mackenzie, Escola de Engenharia, Universidade Presbiteriana Mackenzie, Rua Consolação 896, São Paulo, SP 01302-907 (Brazil)

2014-08-10

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

Quantitative theory of driven nonlinear brain dynamics.

Science.gov (United States)

Roberts, J A; Robinson, P A

2012-09-01

Strong periodic stimuli such as bright flashing lights evoke nonlinear responses in the brain and interact nonlinearly with ongoing cortical activity, but the underlying mechanisms for these phenomena are poorly understood at present. The dominant features of these experimentally observed dynamics are reproduced by the dynamics of a quantitative neural field model subject to periodic drive. Model power spectra over a range of drive frequencies show agreement with multiple features of experimental measurements, exhibiting nonlinear effects including entrainment over a range of frequencies around the natural alpha frequency f(α), subharmonic entrainment near 2f(α), and harmonic generation. Further analysis of the driven dynamics as a function of the drive parameters reveals rich nonlinear dynamics that is predicted to be observable in future experiments at high drive amplitude, including period doubling, bistable phase-locking, hysteresis, wave mixing, and chaos indicated by positive Lyapunov exponents. Moreover, photosensitive seizures are predicted for physiologically realistic model parameters yielding bistability between healthy and seizure dynamics. These results demonstrate the applicability of neural field models to the new regime of periodically driven nonlinear dynamics, enabling interpretation of experimental data in terms of specific generating mechanisms and providing new tests of the theory. Copyright © 2012 Elsevier Inc. All rights reserved.

A theory of frequency domain invariants: spherical harmonic identities for BRDF/lighting transfer and image consistency.

Science.gov (United States)

Mahajan, Dhruv; Ramamoorthi, Ravi; Curless, Brian

2008-02-01

This paper develops a theory of frequency domain invariants in computer vision. We derive novel identities using spherical harmonics, which are the angular frequency domain analog to common spatial domain invariants such as reflectance ratios. These invariants are derived from the spherical harmonic convolution framework for reflection from a curved surface. Our identities apply in a number of canonical cases, including single and multiple images of objects under the same and different lighting conditions. One important case we consider is two different glossy objects in two different lighting environments. For this case, we derive a novel identity, independent of the specific lighting configurations or BRDFs, that allows us to directly estimate the fourth image if the other three are available. The identity can also be used as an invariant to detecttampering in the images. While this paper is primarily theoretical, it has the potential to lay the mathematical foundations for two important practical applications. First, we can develop more general algorithms for inverse rendering problems, which can directly relight and change material properties by transferring the BRDF or lighting from another object or illumination. Second, we can check the consistency of an image, to detect tampering or image splicing.

Diode-pumped dual-frequency microchip Nd : YAG laser with tunable frequency difference

Energy Technology Data Exchange (ETDEWEB)

Ren Cheng; Zhang Shulian, E-mail: ren-c06@mails.tsinghua.edu.c [State Key Laboratory of Precision Measurement Technology and Instruments, Department of Precision Instruments and Mechanology, Tsinghua University, Beijing 100084 (China)

2009-08-07

The diode-pumped dual-frequency microchip Nd : YAG laser with tunable frequency difference is presented. The gain medium used is a microchip 2 mm in thickness for miniaturized and integrated design. Two quarter-wave plates are placed into the laser cavity and the intra-cavity birefringence produces two orthogonally linearly polarized modes. The rotation of one of the two quarter-wave plates introduces a controlled and variable cavity birefringence which causes a variable frequency difference between the two orthogonally polarized modes. The frequency difference can be tuned through the whole cavity free spectral range. The obtained frequency difference ranges from 14 MHz to 1.5 GHz. The variation of the beat frequency over a period of 10 min is less than 10 kHz. The lock-in between modes is not found. Experimental results are presented, which match well with the theoretical analysis based on Jones matrices.

Low-frequency nuclear quadrupole resonance with a dc SQUID

International Nuclear Information System (INIS)

Chang, J.W.

1991-07-01

Conventional pure nuclear quadrupole resonance (NQR) is a technique well suited for the study of very large quadrupolar interactions. Numerous nuclear magnetic resonance (NMR) techniques have been developed for the study of smaller quadrupolar interactions. However, there are many nuclei which have quadrupolar interactions of intermediate strength. Quadrupolar interactions in this region have traditionally been difficult or unfeasible to detect. This work describes the development and application of a SQUID NQR technique which is capable of measuring intermediate strength quadrupolar interactions, in the range of a few hundred kilohertz to several megahertz. In this technique, a dc SQUID (Superconducting QUantum Interference Device) is used to monitor the longitudinal sample magnetization, as opposed to the transverse magnetization, as a rf field is swept in frequency. This allows the detection of low-frequency nuclear quadrupole resonances over a very wide frequency range with high sensitivity. The theory of this NQR technique is discussed and a description of the dc SQUID system is given. In the following chapters, the spectrometer is discussed along with its application to the study of samples containing half-odd-integer spin quadrupolar nuclei, in particular boron-11 and aluminum-27. The feasibility of applying this NQR technique in the study of samples containing integer spin nuclei is discussed in the last chapter. 140 refs., 46 figs., 6 tabs

The kinetic theory and stability of a stochastic plasma with respect to low frequency perturbations and magnetospheric convection

International Nuclear Information System (INIS)

Hurricane, O.A.

1994-09-01

In this dissertation, a new linear Vlasov kinetic theory is developed for calculating the plasma response to perturbing electromagnetic fields in cases where the particle dynamics are stochastic; for modes with frequencies less than the typical particle bounce frequency. A variational form is arrived at which allows one to properly perform a stability analysis for a stochastic plasma. In the case of stochastic dynamics, the authors demonstrate that the plasma responds to the flux tube volume average of the perturbing potentials as opposed to the usual case of adiabatic dynamics where plasma responds to the bounce average of the perturbed potentials. They show that for the stochastic plasma, the kinetic variational form maps into the Bernstein energy principle if the perturbation frequency is large compared to all drift frequencies, the perpendicular wavelength is large compared to the Larmor radius, and vanishing of the potentials associated with the parallel electric field are all assumed. By explicit minimization of the energy principle, it is established that the stochastic plasma is always less stable than an adiabatic plasma. Lastly, the effect of strictly enforcing the quasi-neutrality (QN) condition upon a gyro-kinetic type stability analysis is explored. From simple mathematical considerations, it is shown that when the QN condition is imposed convective type modes that are equipotentials along magnetic field lines are created that alter the stability properties of the plasma. The pertinent modifications to the Bernstein energy principle are given

Quantum theory of terahertz conductivity of semiconductor nanostructures

Science.gov (United States)

Ostatnický, T.; Pushkarev, V.; Němec, H.; Kužel, P.

2018-02-01

Efficient and controlled charge carrier transport through nanoelements is currently a primordial question in the research of nanoelectronic materials and structures. We develop a quantum-mechanical theory of the conductivity spectra of confined charge carriers responding to an electric field from dc regime up to optical frequencies. The broken translation symmetry induces a broadband drift-diffusion current, which is not taken into account in the analysis based on Kubo formula and relaxation time approximation. We show that this current is required to ensure that the dc conductivity of isolated nanostructures correctly attains zero. It causes a significant reshaping of the conductivity spectra up to terahertz or multiterahertz spectral ranges, where the electron scattering rate is typically comparable to or larger than the probing frequency.

DETAILED FIT OF 'CRITICAL BALANCE' THEORY TO SOLAR WIND TURBULENCE MEASUREMENTS

International Nuclear Information System (INIS)

Forman, Miriam A.; Wicks, Robert T.; Horbury, Timothy S.

2011-01-01

We derive the reduced spectrum of turbulent magnetic fluctuations at different frequencies f which would be observed by a single spacecraft in the solar wind when the magnetic field was at an angle θ B to the solar wind flow, if the wavevector spectrum in the solar wind frame were in anisotropic 'critical balance' (CB) as proposed by Goldreich and Sridhar in 1995 (GS95). The anisotropic power spectrum in the inertial range, P(f, θ B ), is scaled onto one curve with f- 5/3 behavior at θ B near 90 0 and f -2 behavior at small θ B . The transition between the two limiting spectra depends on the form of the GS95 wavevector spectrum and the CB scaling parameter L. Using wavelet analysis of Ulysses magnetic field data in three 30-day periods in the high-latitude solar wind in 1995, we verify that the scaling of power with angle and frequency is qualitatively consistent with GS95 theory. However, the scale length L required to fit the observed P(f, θ B ) to the original CB theory is rather less than the scale predicted by that theory for the solar wind. Part, possibly all, of this discrepancy is removed when the GS95 theory modified for imbalanced turbulence is used.

Possibility of a 4He2 bound state, effective range theory, and very low energy He--He scattering

International Nuclear Information System (INIS)

Uang, Y.; Stwalley, W.C.

1982-01-01

The best available intermolecular potential for helium by Aziz, Nain, Carley, Taylor, and McConville is shown here for the first time to have a 4 He 2 bound state. Two numerical analyses, namely, eigenvalue solution and effective range theory, are used to support this conclusion. Unlike usual chemically bound species, the binding energy of this very weakly bound level is found to be only 8.3 x 10 -4 K, which is four orders of magnitude smaller than the potential well depth epsilon = 10.8 K. The scattering length for He+He collisions, determined from effective range theory, is used to calculate the elastic cross section in the very low energy limit. The results (1.878 x 10 5 A 2 for 4 He+ 4 He and 6.035 x 10 2 A for 3 He+ 3 He) are consistent with measurements at the lowest velocities yet attained. In terms of the estimated uncertainties of the parameters of the potential of Aziz and co-workers, it is shown that it is very likely that a bound state of the 4 He 2 molecule does in fact exist

An algorithm for the calculation of 3-D ICRF [Ion Cyclotron Range of Frequencies] fields in tokamak geometry

International Nuclear Information System (INIS)

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

1987-04-01

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

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

Science.gov (United States)

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

2015-03-01

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

Magnetorefractive effect in La0.7Ca0.3MnO3 in the infrared spectral range

International Nuclear Information System (INIS)

Sukhorukov, Yu. P.; Telegin, A. V.; Granovskii, A. B.; Gan'shina, E. A.; Naumov, S. V.; Kostromitina, N. V.; Elokhina, L. V.; Gonzalez, J.

2010-01-01

The reflection and magnetic reflection spectra, magnetic resistance, electrical properties, and equatorial Kerr effect in La 0.7 Ca 0.3 MnO 3 crystals have been complexly investigated. The measurements have been performed in wide temperature and spectral ranges in magnetic fields up to 3.5 kOe. It has been found that magnetic reflection is a high-frequency response in the infrared spectral range to the colossal magnetore-sistance near the Curie temperature. Correlation between the field and temperature dependences of the magnetic reflection and colossal magnetoresistance has been revealed. The previously developed theory of the magnetorefractive effect for metallic systems makes it possible to explain the experimental data at the qualitative level. Both demerits of the theory of the magnetorefractive effect in application to the magnets and possible additional mechanisms responsible for the magnetic reflection are discussed.

Intrinsic vs. spurious long-range memory in high-frequency records of environmental radioactivity - Critical re-assessment and application to indoor 222Rn concentrations from Coimbra, Portugal

Science.gov (United States)

Donner, Reik V.; Potirakis, Stelios M.; Barbosa, Susana M.; Matos, Jose A. O.

2015-04-01

The presence or absence of long-range correlations in environmental radioactivity fluctuations has recently attracted considerable interest. Among a multiplicity of practically relevant applications, identifying and disentangling the environmental factors controlling the variable concentrations of the radioactive noble gas Radon is important for estimating its effect on human health and the efficiency of possible measures for reducing the corresponding exposition. In this work, we present a critical re-assessment of a multiplicity of complementary methods that have been previously applied for evaluating the presence of long-range correlations and fractal scaling in environmental Radon variations with a particular focus on the specific properties of the underlying time series. As an illustrative case study, we subsequently re-analyze two high-frequency records of indoor Radon concentrations from Coimbra, Portugal, each of which spans several months of continuous measurements at a high temporal resolution of five minutes. Our results reveal that at the study site, Radon concentrations exhibit complex multi-scale dynamics with qualitatively different properties at different time-scales: (i) essentially white noise in the high-frequency part (up to time-scales of about one hour), (ii) spurious indications of a non-stationary, apparently long-range correlated process (at time scales between hours and one day) arising from marked periodic components probably related to tidal frequencies, and (iii) low-frequency variability indicating a true long-range dependent process, which might be dominated by a response to meteorological drivers. In the presence of such multi-scale variability, common estimators of long-range memory in time series are necessarily prone to fail if applied to the raw data without previous separation of time-scales with qualitatively different dynamics. We emphasize that similar properties can be found in other types of geophysical time series (for

The measurement of subcritical reactivity in nuclear reactors by use of a high frequency sine-wave modulated neutron source

International Nuclear Information System (INIS)

Guppy, C.B.

1964-11-01

In this report the frequency response characteristics for phase and gain of the fundamental reactor mode of the zero power kinetics are given for various subcritical reactivities in a fast reactor and in a thermal reactor. Results, of a study on harmonic effects based on a small zero energy thermal reactor are presented which demonstrate the importance of spatial harmonic effects. A harmonic theory for thermal reactors is developed. A new method of measuring, subcritical reactivity at moderately high frequencies is suggested which circumvents the harmonic problem. It is shown that at high frequencies there is more sensitivity than at low frequencies and that this could lead to an increased range over which subcritical reactivity can be measured. (author)

Power and efficiency scaling of diode pumped Cr:LiSAF lasers: 770-1110 nm tuning range and frequency doubling to 387-463 nm.

Science.gov (United States)

Demirbas, Umit; Baali, Ilyes

2015-10-15

We report significant average power and efficiency scaling of diode-pumped Cr:LiSAF lasers in continuous-wave (cw), cw frequency-doubled, and mode-locked regimes. Four single-emitter broad-area laser diodes around 660 nm were used as the pump source, which provided a total pump power of 7.2 W. To minimize thermal effects, a 20 mm long Cr:LiSAF sample with a relatively low Cr-concentration (0.8%) was used as the gain medium. In cw laser experiments, 2.4 W of output power, a slope efficiency of 50%, and a tuning range covering the 770-1110 nm region were achieved. Intracavity frequency doubling with beta-barium borate (BBO) crystals generated up to 1160 mW of blue power and a record tuning range in the 387-463 nm region. When mode locked with a saturable absorber mirror, the laser produced 195 fs pulses with 580 mW of average power around 820 nm at a 100.3 MHz repetition rate. The optical-to-optical conversion efficiency of the system was 33% in cw, 16% in cw frequency-doubled, and 8% in cw mode-locked regimes.

Short-time dynamics of lysozyme solutions with competing short-range attraction and long-range repulsion: Experiment and theory

Science.gov (United States)

Riest, Jonas; Nägele, Gerhard; Liu, Yun; Wagner, Norman J.; Godfrin, P. Douglas

2018-02-01

Recently, atypical static features of microstructural ordering in low-salinity lysozyme protein solutions have been extensively explored experimentally and explained theoretically based on a short-range attractive plus long-range repulsive (SALR) interaction potential. However, the protein dynamics and the relationship to the atypical SALR structure remain to be demonstrated. Here, the applicability of semi-analytic theoretical methods predicting diffusion properties and viscosity in isotropic particle suspensions to low-salinity lysozyme protein solutions is tested. Using the interaction potential parameters previously obtained from static structure factor measurements, our results of Monte Carlo simulations representing seven experimental lysoyzme samples indicate that they exist either in dispersed fluid or random percolated states. The self-consistent Zerah-Hansen scheme is used to describe the static structure factor, S(q), which is the input to our calculation schemes for the short-time hydrodynamic function, H(q), and the zero-frequency viscosity η. The schemes account for hydrodynamic interactions included on an approximate level. Theoretical predictions for H(q) as a function of the wavenumber q quantitatively agree with experimental results at small protein concentrations obtained using neutron spin echo measurements. At higher concentrations, qualitative agreement is preserved although the calculated hydrodynamic functions are overestimated. We attribute the differences for higher concentrations and lower temperatures to translational-rotational diffusion coupling induced by the shape and interaction anisotropy of particles and clusters, patchiness of the lysozyme particle surfaces, and the intra-cluster dynamics, features not included in our simple globular particle model. The theoretical results for the solution viscosity, η, are in qualitative agreement with our experimental data even at higher concentrations. We demonstrate that semi

The asymmetry of the entrainment range induced by the difference in intrinsic frequencies between two subgroups within the suprachiasmatic nucleus

Science.gov (United States)

Gu, Changgui; Yang, Huijie

2017-06-01

The rhythms of physiological and behavioral activities in mammals, which are regulated by the main clock suprachiasmatic nucleus (SCN) in the brain, can not be only synchronized to the natural 24 h light-dark cycle, but also to cycles with artificial periods. The range of the artificial periods that the animal can be synchronized to is called entrainment range. In the absence of the light-dark cycle, the animal can also maintain the circadian rhythm with an endogenous period close to 24 h. Experiments found that the entrainment range is not symmetrical with respect to the endogenous period. In the present study, an explanation is given for the asymmetry based on a Kuramoto model which describes the neuronal network of the SCN. Our numerical simulations and theoretical analysis show that the asymmetry results from the difference in the intrinsic frequencies between two subgroups of the SCN, as well as the entrainment range is affected by the difference.

Examining the impact of harmonic correlation on vibrational frequencies calculated in localized coordinates

Energy Technology Data Exchange (ETDEWEB)

Hanson-Heine, Magnus W. D., E-mail: magnus.hansonheine@nottingham.ac.uk [School of Chemistry, University of Nottingham, University Park, Nottingham NG7 2RD (United Kingdom)

2015-10-28

Carefully choosing a set of optimized coordinates for performing vibrational frequency calculations can significantly reduce the anharmonic correlation energy from the self-consistent field treatment of molecular vibrations. However, moving away from normal coordinates also introduces an additional source of correlation energy arising from mode-coupling at the harmonic level. The impact of this new component of the vibrational energy is examined for a range of molecules, and a method is proposed for correcting the resulting self-consistent field frequencies by adding the full coupling energy from connected pairs of harmonic and pseudoharmonic modes, termed vibrational self-consistent field (harmonic correlation). This approach is found to lift the vibrational degeneracies arising from coordinate optimization and provides better agreement with experimental and benchmark frequencies than uncorrected vibrational self-consistent field theory without relying on traditional correlated methods.

Influence of collision frequency on neoclassical polarization current

International Nuclear Information System (INIS)

Imada, K; Wilson, H R

2009-01-01

A kinetic theory for the evolution of magnetic islands is considered in a tokamak plasma, in both the low (ν i i >> εω) collision frequency limits (ν i is the ion collision frequency, ε is the inverse aspect ratio and ω is the island propagation frequency in the E x B rest frame). The calculation of the bootstrap current perturbation in the presence of a magnetic island is reviewed, and is confirmed to be independent of ω and the collision frequency regime. The neoclassical polarization current perturbation is calculated in the two collision frequency limits (within the banana regime). The result in the collisional limit is in agreement with a fluid theory. The effect of collisions in the 'dissipation layer' at the trapped/passing boundary is also considered, for ν i i /εω] 1/2 , where r is a weak logarithmic function of √ν i /εω.

Molecular structures and vibrational frequencies of xanthine and its methyl derivatives (caffeine and theobromine) by ab initio Hartree-Fock and density functional theory calculations

Science.gov (United States)

Ucun, Fatih; Sağlam, Adnan; Güçlü, Vesile

2007-06-01

The molecular structures, vibrational frequencies and corresponding vibrational assignments of xanthine and its methyl derivatives (caffeine and theobromine) have been calculated using ab initio Hartree-Fock (HF) and density functional theory (B3LYP) methods with 6-31G(d, p) basis set level. The calculations were utilized to the CS symmetries of the molecules. The obtained vibrational frequencies and optimised geometric parameters (bond lengths and bond angles) were seen to be well agreement with the experimental data. The used scale factors which have been obtained the ratio of the frequency values of the strongest peaks in the calculated and experimental spectra seem to cause the gained vibrations well corresponding to the experimental ones. Theoretical infrared intensities and Raman activities are also reported.

Large-scale transmission-type multifunctional anisotropic coding metasurfaces in millimeter-wave frequencies

Science.gov (United States)

Cui, Tie Jun; Wu, Rui Yuan; Wu, Wei; Shi, Chuan Bo; Li, Yun Bo

2017-10-01

We propose fast and accurate designs to large-scale and low-profile transmission-type anisotropic coding metasurfaces with multiple functions in the millimeter-wave frequencies based on the antenna-array method. The numerical simulation of an anisotropic coding metasurface with the size of 30λ × 30λ by the proposed method takes only 20 min, which however cannot be realized by commercial software due to huge memory usage in personal computers. To inspect the performance of coding metasurfaces in the millimeter-wave band, the working frequency is chosen as 60 GHz. Based on the convolution operations and holographic theory, the proposed multifunctional anisotropic coding metasurface exhibits different effects excited by y-polarized and x-polarized incidences. This study extends the frequency range of coding metasurfaces, filling the gap between microwave and terahertz bands, and implying promising applications in millimeter-wave communication and imaging.

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

International Nuclear Information System (INIS)

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

2014-01-01

Measurement of specific absorption rate (SAR) of magnetic nanoparticles is crucial to assert their potential for magnetic hyperthermia. To perform this task, calorimetric methods are widely used. However, those methods are not very accurate and are difficult to standardize. In this paper, we present AC magnetometry results performed with a lab-made magnetometer that is able to obtain dynamic hysteresis-loops in the AC magnetic field frequency range from 50 kHz to 1 MHz and intensities up to 24 kA m −1 . In this work, SAR values of maghemite nanoparticles dispersed in water are measured by AC magnetometry. The so-obtained values are compared with the SAR measured by calorimetric methods. Both measurements, by calorimetry and magnetometry, are in good agreement. Therefore, the presented AC magnetometer is a suitable way to obtain SAR values of magnetic nanoparticles. - Highlights: • We propose AC magnetometry as a method to measure the specific absorption rate (SAR) of magnetic nanoparticles suitable for magnetic hyperthermia therapy. • We have built a lab-made AC magnetometer, which is able to measure magnetic dynamic hysteresis-loops of nanoparticle dispersions. • The device works with AC magnetic field intensities up to 24 kA m −1 in a frequency range from 75 kHz to 1 MHz. • The SAR values of maghemite nanoparticles around 12 nm in magnetic diameter dispersed in water are measured by the lab-made magnetometer and different calorimetric methods. • Although all methods are in good agreement, several factors (probe location, thermal inertia, losses, etc.) make calorimetric method less accurate than AC magnetometry

A study on the heating and diagnostic of a tokamak plasma by electromagnetic waves of the electron cyclotron range of frequencies

International Nuclear Information System (INIS)

Hoshino, Katsumichi

1989-09-01

A study on the heating and diagnosis of tokamak plasma by electromagnetic waves of electron cyclotron range of frequency is summarized. The main results obtained are as follows. On the engineering and technology, the technology of injecting high frequency, large power millimeter waves into tokamak plasma was established by carrying out the design, manufacture and test of a 60 GHz, 400 kW high frequency heating system, and the design, manufacture and test of a heterodyne type electron cyclotron radiation multi-channel mealsuring system were carried out, and the technology of measuring the radiation from tokamak plasma with the time resolution of 10 μs in multi-channel was established. On nuclear fusion reactor core engineering and plasma physics, the high efficiency electron heating of tokamak plasma by the incidence of fundamental irregular and regular waves at electron cyclotron frequency was verified. The discovery and analysis of the heating by electrostatic waves arising due to mode transformation from electromagnetic waves in upper hybrid resonance layer were carried out. By the incidence of second harmonic waves, the high efficiency electron heating of tokamak plasma was verified, and the heating characteristics were clarified. And others. (K.I.) 179 refs

New fractal structures for frequencies close to the visible range

DEFF Research Database (Denmark)

Malureanu, Radu; Sandru, A.; Andryieuski, Andrei

2011-01-01

In this paper we present a new type of fractal resonator to be used in the red/NIR region of the spectra. The structure presents high-transmission band in 795-825nm range. The stop band is in the 683-731 nm range. Due to the huge difference in the spectra within such a short range, the structure...

Long-range corrected density functional theory with accelerated Hartree-Fock exchange integration using a two-Gaussian operator [LC-ωPBE(2Gau)].

Science.gov (United States)

Song, Jong-Won; Hirao, Kimihiko

2015-10-14

Since the advent of hybrid functional in 1993, it has become a main quantum chemical tool for the calculation of energies and properties of molecular systems. Following the introduction of long-range corrected hybrid scheme for density functional theory a decade later, the applicability of the hybrid functional has been further amplified due to the resulting increased performance on orbital energy, excitation energy, non-linear optical property, barrier height, and so on. Nevertheless, the high cost associated with the evaluation of Hartree-Fock (HF) exchange integrals remains a bottleneck for the broader and more active applications of hybrid functionals to large molecular and periodic systems. Here, we propose a very simple yet efficient method for the computation of long-range corrected hybrid scheme. It uses a modified two-Gaussian attenuating operator instead of the error function for the long-range HF exchange integral. As a result, the two-Gaussian HF operator, which mimics the shape of the error function operator, reduces computational time dramatically (e.g., about 14 times acceleration in C diamond calculation using periodic boundary condition) and enables lower scaling with system size, while maintaining the improved features of the long-range corrected density functional theory.

Plate-type metamaterials for extremely broadband low-frequency sound insulation

Science.gov (United States)

Wang, Xiaopeng; Guo, Xinwei; Chen, Tianning; Yao, Ge

2018-01-01

A novel plate-type acoustic metamaterial with a high sound transmission loss (STL) in the low-frequency range ( ≤1000 Hz) is designed, theoretically proven and then experimentally verified. The thin plates with large modulus used in this paper mean that we do not need to apply tension to the plates, which is more applicable to practical engineering, the achievement of noise reduction is better and the installation of plates is more user-friendly than that of the membranes. The effects of different structural parameters of the plates on the sound-proofed performance at low-frequencies were also investigated by experiment and finite element method (FEM). The results showed that the STL can be modulated effectively and predictably using vibration theory by changing the structural parameters, such as the radius and thickness of the plate. Furthermore, using unit cells of different geometric sizes which are responsible for different frequency regions, the stacked panels with thickness ≤16 mm and weight ≤5 kg/m2 showed high STL below 2000 Hz. The acoustic metamaterial proposed in this study could provide a potential application in the low-frequency noise insulation.

On the Full-range β Dependence of Ion-scale Spectral Break in the Solar Wind Turbulence

Science.gov (United States)

Wang, Xin; Tu, Chuanyi; He, Jiansen; Wang, Linghua

2018-04-01

The power spectrum of magnetic fluctuations has a break at the high-frequency end of the inertial range. Beyond this break, the spectrum becomes steeper than the Kolmogorov law f ‑5/3. The break frequency was found to be associated with plasma beta (β). However, the full-range β dependence of the ion-scale spectral break has not been presented before in observational studies. Here we show the continuous variation of the break frequency on full-range β in the solar wind turbulence. By using measurements from the WIND and Ulysses spacecraft, we show the break frequency (f b ) normalized, respectively, by the frequencies corresponding to ion inertial length (f di ), ion gyroradius ({f}ρ i), and cyclotron resonance scale (f ri ) as a function of β for 1306 intervals. Their β values spread from 0.005 to 20, which nearly covers the full β range of the observed solar wind turbulence. It is found that {f}b/{f}{di} ({f}b/{f}ρ i) generally decreases (increases) with β, while {f}b/{f}{ri} is nearly a constant. We perform a linear fit on the statistical result, and obtain the empirical formulas {f}b/{f}{di}∼ {β }-1/4, {f}b/{f}ρ i∼ {β }1/4, and {f}b/{f}{ri}∼ 0.90 to describe the relation between f b and β. We also compare our observations with a numerical simulation and the prediction by ion cyclotron resonance theory. Our result favors the idea that the cyclotron resonance is an important mechanism for energy dissipation at the spectral break. When β ≪ 1 and β ≫ 1, the break at f di and {f}ρ i may also be associated with other processes.

An educational framework connecting planetary and mind frequencies (invited0

Science.gov (United States)

Gupta, V. K.; Sharma, A. S.

2015-12-01

Schumann in 1952 first predicted the existence of resonances in the Earth-Ionosphere cavity on theoretical grounds. Many studies since then have expanded the theory and determined their basic observational characteristics. Theoretically, the velocity of light divided by the earth's circumference gives 7.5 Hz to a very good approximation. Observations show that the fundamental frequency lies in the range 7 and 8 Hz. These findings define our planetary oscillator. The second oscillator is the human mind that has multiple frequencies ranging from 1 to 40 Hz, which the Electroencephalograph (EEG) can measure. Vethathiri in 1958 developed a systematic approach to reducing mind frequency to Theta (7-4 Hz) and lower. The frequencies of the two oscillators are very close to each other, which can result in entrainment, or the mutual phase locking. This can be the basis for a framework for reprograming the subconscious mind, which is programmed in the Theta and Delta (1-3 Hz) frequencies in the womb and the first six years after birth. Latest findings from Biology (B. Lipton, Biology of Belief, 2005) have shown that 95% of one's behavior after the age of six is dictated by the subconscious mind. Our proposal is to reprogram the subconscious mind so that a highly materialistic life style may be simplified and the unchecked consumption reduced. Also a mechanistic worldview of the modern science is responsible for a massive exploitation of natural resources and a growing human footprint that is pushing the 21st century towards a civilizational collapse. Through a systematic practice of lowering mind frequencies people would become aware that their existence is interconnected with the whole planet that the indigenous cultures believed and practiced. Universities may introduce the framework presented here in their undergraduate sustainability curricula that would greatly aid in reversing the current trend.

Ultrawide low frequency band gap of phononic crystal in nacreous composite material

International Nuclear Information System (INIS)

Yin, J.; Huang, J.; Zhang, S.; Zhang, H.W.; Chen, B.S.

2014-01-01

The band structure of a nacreous composite material is studied by two proposed models, where an ultrawide low frequency band gap is observed. The first model (tension-shear chain model) with two phases including brick and mortar is investigated to describe the wave propagation in the nacreous composite material, and the dispersion relation is calculated by transfer matrix method and Bloch theorem. The results show that the frequency ranges of the pass bands are quite narrow, because a special tension-shear chain motion in the nacreous composite material is formed by some very slow modes. Furthermore, the second model (two-dimensional finite element model) is presented to investigate its band gap by a multi-level substructure scheme. Our findings will be of great value to the design and synthesis of vibration isolation materials in a wide and low frequency range. Finally, the transmission characteristics are calculated to verify the results. - Highlights: • A Brick-and-Mortar structure is used to discuss wave propagation through nacreous materials. • A 1D Bloch wave solution of nacreous materials with a tension-shear chain model is obtained. • The band structure and transmission characteristics of nacreous materials with the FE model are examined. • An ultrawide low frequency band gap is found in nacreous materials with both theory and FE model

Resonance cones below the ion cyclotron frequency: theory and experiment

International Nuclear Information System (INIS)

Bellan, P.

1976-03-01

The resonance cones existing below the ion cyclotron frequency, ω/sub c/sub i//, are shown, theoretically and experimentally, to be the asymptotes of hyperbolic constant-phase surfaces of low-frequency ion acoustic waves. Above ω/sub c/sub i// the surfaces transform into ellipses that are related to the electrostatic ion cyclotron waves and ion acoustic waves

Social and emotional patterns in adulthood: support for socioemotional selectivity theory.

Science.gov (United States)

Carstensen, L L

1992-09-01

This investigation explored 2 hypotheses derived from socioemotional selectivity theory: (a) Selective reductions in social interaction begin in early adulthood and (b) emotional closeness to significant others increases rather than decreases in adulthood even when rate reductions occur. Transcribed interviews with 28 women and 22 men from the Child Guidance Study, conducted over 34 years, were reviewed and rated for frequency of interaction, satisfaction with the relationship, and degree of emotional closeness in 6 types of relationships. Interaction frequency with acquaintances and close friends declined from early adulthood on. Interaction frequency with spouses and siblings increased across the same time period and emotional closeness increased throughout adulthood in relationships with relatives and close friends. Findings suggest that individuals begin narrowing their range of social partners long before old age.

String theory or field theory?

International Nuclear Information System (INIS)

Marshakov, Andrei V

2002-01-01

The status of string theory is reviewed, and major recent developments - especially those in going beyond perturbation theory in the string theory and quantum field theory frameworks - are analyzed. This analysis helps better understand the role and place of string theory in the modern picture of the physical world. Even though quantum field theory describes a wide range of experimental phenomena, it is emphasized that there are some insurmountable problems inherent in it - notably the impossibility to formulate the quantum theory of gravity on its basis - which prevent it from being a fundamental physical theory of the world of microscopic distances. It is this task, the creation of such a theory, which string theory, currently far from completion, is expected to solve. In spite of its somewhat vague current form, string theory has already led to a number of serious results and greatly contributed to progress in the understanding of quantum field theory. It is these developments which are our concern in this review. (reviews of topical problems)

Investigations in gauge theories, topological solitons and string theories

International Nuclear Information System (INIS)

1993-01-01

This is the Final Report on a supported research project on theoretical particle physics entitled ''Investigations in Gauge Theories, Topological Solitons and String Theories.'' The major theme of particle theory pursued has been within the rubric of the standard model, particularly on the interplay between symmetries and dynamics. Thus, the research has been carried out primarily in the context of gauge with or without chiral fermions and in effective chiral lagrangian field theories. The topics studied include the physical implications of abelian and non-abelian anomalies on the spectrum and possible dynamical symmetry breaking in a wide range of theories. A wide range of techniques of group theory, differential geometry and function theory have been applied to probe topological and conformal properties of quantum field theories in two and higher dimensions, the breaking of global chiral symmetries by vector-like gauge theories such as QCD,the phenomenology of a possibly strongly interacting Higgs sector within the minimal standard model, and the relevance of solitonic ideas to non-perturbative phenomena at SSC energies

Designing double-gap linear accelerators for a wide mass range

International Nuclear Information System (INIS)

Lysenko, W.P.; Wadlinger, E.A.; Rusnak, B.; Krawczyk, F.; Saadatmand, K.; Wan, Z.

1998-01-01

For applications like ion implantation, rf linacs using double-gap structures with external resonators can be used because they are practical at low frequencies. However, since the two gaps associated with a given resonator cannot be individually phased, it is not obvious how to build a linac that can efficiently accelerate particles having different mass/charge ratios. This paper describes the beam dynamics of double-gap rf linacs and shows how to maximize the range of mass/charge ratios. The theory also tells one how to rescale a linac tune (i.e., reset the voltages and phases) so that a new particle, having a different mass or charge, will behave similarly to the original particle

Intrinsic vs. spurious long-range memory in high-frequency records of environmental radioactivity. Critical re-assessment and application to indoor 222Rn concentrations from Coimbra, Portugal

Science.gov (United States)

Donner, R. V.; Potirakis, S. M.; Barbosa, S. M.; Matos, J. A. O.; Pereira, A. J. S. C.; Neves, L. J. P. F.

2015-05-01

The presence or absence of long-range correlations in the environmental radioactivity fluctuations has recently attracted considerable interest. Among a multiplicity of practically relevant applications, identifying and disentangling the environmental factors controlling the variable concentrations of the radioactive noble gas radon is important for estimating its effect on human health and the efficiency of possible measures for reducing the corresponding exposition. In this work, we present a critical re-assessment of a multiplicity of complementary methods that have been previously applied for evaluating the presence of long-range correlations and fractal scaling in environmental radon variations with a particular focus on the specific properties of the underlying time series. As an illustrative case study, we subsequently re-analyze two high-frequency records of indoor radon concentrations from Coimbra, Portugal, each of which spans several weeks of continuous measurements at a high temporal resolution of five minutes.Our results reveal that at the study site, radon concentrations exhibit complex multi-scale dynamics with qualitatively different properties at different time-scales: (i) essentially white noise in the high-frequency part (up to time-scales of about one hour), (ii) spurious indications of a non-stationary, apparently long-range correlated process (at time scales between some hours and one day) arising from marked periodic components, and (iii) low-frequency variability indicating a true long-range dependent process. In the presence of such multi-scale variability, common estimators of long-range memory in time series are prone to fail if applied to the raw data without previous separation of time-scales with qualitatively different dynamics.

Electronic tunneling currents at optical frequencies

Science.gov (United States)

Faris, S. M.; Fan, B.; Gustafson, T. K.

1975-01-01

Rectification characteristics of nonsuperconducting metal-barrier-metal junctions as deduced from electronic tunneling theory have been observed experimentally for optical frequency irradiation of the junction.

Application of high Tc superconductors as frequency selective surfaces: Experiment and theory

International Nuclear Information System (INIS)

Dawei Zhang; Yahya Rahmat-Samii; Fetterman, H.R.

1993-01-01

YBa 2 Cu 3 O 7-x and Tl 2 CaBa 2 Cu 2 O 8 high temperature superconducting thin films were utilized to fabricate frequency selective surfaces (FSS) at millimeter-wave frequencies (75--110 GHz). An analytical/numerical model was applied, using a Floquet expansion and the Method of Moments, to analyze bandstop superconducting frequency selective surfaces. Experimental results were compared with the model, and showed a good agreement with resonant frequency prediction with an accuracy of better than 1%. The use of the superconducting frequency selective surfaces as quasi-optical millimeter-wave bandpass filters was also demonstrated

Radio Frequency Power in Plasmas: 12th Topical Conference. Proceedings

International Nuclear Information System (INIS)

Ryan, P.M.; Intrator, T.

1997-01-01

The twelfth Topical Conference on Radio Frequency Power in Plasmas was held in April, 1997, in Georgia, USA under the sponsorship of Oak Ridge National Laboratory of the US Department of Energy, the University of Wisconsin, and the American Physical Society. A large part of the conference was devoted to the ion cyclotron range of frequencies. Radio frequency contributions to the creation and maintenance of transport barriers to both particle and heat flux received a lot of attention. In addition to plasma heating, the use of RF as a versatile tool to drive current, shape profiles and stabilize plasmas was also discussed. The RF systems designs for ITER, ICRF heating advances on helical devices were among the topics of interest, so were progress in ion cyclotron codes, advanced launchers and technology, RF startup, general wave theory and the application of RF plasmas to material processing. A total of 103 papers were presented and are included in these proceedings. Out of these, 54 have been abstracted for the Energy Science and Technology database

Non-linear frequency and amplitude modulation of a nano-contact spin torque oscillator

OpenAIRE

Muduli, P. K.; Pogoryelov, Ye.; Bonetti, S.; Consolo, G.; Mancoff, Fred; Åkerman, Johan

2009-01-01

We study the current controlled modulation of a nano-contact spin torque oscillator. Three principally different cases of frequency non-linearity ($d^{2}f/dI^{2}_{dc}$ being zero, positive, and negative) are investigated. Standard non-linear frequency modulation theory is able to accurately describe the frequency shifts during modulation. However, the power of the modulated sidebands only agrees with calculations based on a recent theory of combined non-linear frequency and amplitude modulation.

Magnetic nanoparticles colourization by a mixing-frequency method

International Nuclear Information System (INIS)

Tu, Liang; Wu, Kai; Klein, Todd; Wang, Jian-Ping

2014-01-01

Brownian and Néel relaxation of magnetic nanoparticles (MNPs) can be characterized by a highly sensitive mixing-frequency method using a search-coil based detection system. The unique magnetic properties of MNPs have been used for biomarkers detection. In this paper, we present a theory and implement an experimental detection scheme using the mixing-frequency method to identify different MNPs simultaneously. A low-frequency sinusoidal magnetic field is applied to saturate the MNPs periodically. A high-frequency sinusoidal magnetic field is then applied to generate mixing-frequency signals that are highly specific to the magnetization of MNPs. The spectra of each MNP can be defined as the complex magnetization of the MNPs over the field frequency. The magnetic spectra of various MNPs and magnetic beads have been characterized and compared. The differences between the MNPs spectra enable us to identify the individual MNPs at the same time. A test has been done to verify the ratio of two different MNPs in mixed samples based on the proposed theory. The experimental results show that the mixing-frequency method is a promising method for MNPs colourization. (paper)

Increasing dynamic range of a fibre Bragg grating edge-filtering interrogator with a proportional control loop

International Nuclear Information System (INIS)

Stan, Nikola; Bailey, D C; Chadderdon, S L; Selfridge, R H; Schultz, S M; Webb, S; Zikry, M; Peters, K J

2014-01-01

We present a fibre Bragg grating (FBG) interrogator that uses a microcontroller board and a tunable optical filter in a proportional control loop to increase dynamic range and achieve high strain sensitivity. It is an edge-filtering interrogator with added proportional control loop that locks the operating wavelength to the mid-reflection point on the FBG spectrum. The interrogator separates low-frequency (LF) components of strain and measures them with extended dynamic range, while at the same time measuring high-frequency (HF) strain without loss in strain sensitivity. In this paper, we describe the implementation of the interrogator and analyse the characteristics of individual components, such as the speed and voltage resolution of the microcontroller and the tunable optical filter. We measure the performance of the proportional control loop at frequencies up to 1 kHz and characterize the system using control theory. We illustrate the limitation of the conventional interrogator to measure strains greater than 40 μϵ and demonstrate successful application of the proposed interrogator for simultaneous measurement of 450 μϵ LF strain at 50 Hz superimposed with 32 kHz HF strain. (paper)

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

Science.gov (United States)

Stutzman, Warren L.

1989-01-01

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

Effects of weak nonlinearity on dispersion relations and frequency band-gaps of periodic structures

DEFF Research Database (Denmark)

Sorokin, Vladislav; Thomsen, Jon Juel

2015-01-01

of these for nonlinear problems is impossible or cumbersome, since Floquet theory is applicable for linear systems only. Thus the nonlinear effects for periodic structures are not yet fully uncovered, while at the same time applica-tions may demand effects of nonlinearity on structural response to be accounted for....... The present work deals with analytically predicting dynamic responses for nonlinear continuous elastic periodic structures. Specifically, the effects of weak nonlinearity on the dispersion re-lation and frequency band-gaps of a periodic Bernoulli-Euler beam performing bending os-cillations are analyzed......The analysis of the behaviour of linear periodic structures can be traced back over 300 years, to Sir Isaac Newton, and still attracts much attention. An essential feature of periodic struc-tures is the presence of frequency band-gaps, i.e. frequency ranges in which waves cannot propagate...

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

International Nuclear Information System (INIS)

Ono, Masayuki.

1993-05-01

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

Simulation of beam-splitter made of metamaterials with angle spatial distribution of constitutive parameters based on transformation optics for THz frequency range

International Nuclear Information System (INIS)

Gurvitz, E A; Vozianova, A V; Khodzitsky, M K

2014-01-01

New approach to design beam splitter on basis of the transformation optics using angle constitutive parameters distribution of medium was proposed. The beam splitter was numerically simulated by COMSOL Multiphysics for terahertz frequency range. The numerical simulations were carried out for ideal and reduced constitutive parameters of medium for the case of TM plane wave

Low Frequency Space Array

International Nuclear Information System (INIS)

Dennison, B.; Weiler, K.W.; Johnston, K.J.

1987-01-01

The Low Frequency Space Array (LFSA) is a conceptual mission to survey the entire sky and to image individual sources at frequencies between 1.5 and 26 MHz, a frequency range over which the earth's ionosphere transmits poorly or not at all. With high resolution, high sensitivity observations, a new window will be opened in the electromagnetic spectrum for astronomical investigation. Also, extending observations down to such low frequencies will bring astronomy to the fundamental limit below which the galaxy becomes optically thick due to free-free absorption. A number of major scientific goals can be pursued with such a mission, including mapping galactic emission and absorption, studies of individual source spectra in a frequency range where a number of important processes may play a role, high resolution imaging of extended sources, localization of the impulsive emission from Jupiter, and a search for coherent emission processes. 19 references

Theory for the radiation at the third to fifth harmonics of the plasma frequency upstream from the Earth's bow shock

International Nuclear Information System (INIS)

Cairns, I.H.

1988-01-01

A theory is presented for the radiation at the third to fifth harmonics of the plasma frequency observed upstream from the Earth's bow shock: the radiation is produced by the process L+T'→T in the foreshock, with the initial T' radiation being the frequently observed second harmonic radiation (generated by another process) and the L waves being products of the decay L'→L+S of L' waves generated by a streaming instability. (Here L, S, and T denote Langmuir, ion acoustic, and 'transverse electromagnetic waves, respectively.) The theory can account for the observed radiation when unusually large levels (electric fields in excess of 10 mV/m) of suitable L waves are present. Such levels of L waves are possible, in principle, but have not been reported before; the radiation is observed quite infrequently, thereby implying a requirement for unusual foreshock conditions. Predictions for the characteristics of the source regions (one to each wing of the foreshock) and the bandwidth of the radiation are given. Potential problems for the theory, relating to the large levels of L waves required to account for the radiation, are discussed. copyright American Geophysical Union 1988

Frequency Selection for Multi-frequency Acoustic Measurement of Suspended Sediment

Science.gov (United States)

Chen, X.; HO, H.; Fu, X.

2017-12-01

Multi-frequency acoustic measurement of suspended sediment has found successful applications in marine and fluvial environments. Difficult challenges remain in regard to improving its effectiveness and efficiency when applied to high concentrations and wide size distributions in rivers. We performed a multi-frequency acoustic scattering experiment in a cylindrical tank with a suspension of natural sands. The sands range from 50 to 600 μm in diameter with a lognormal size distribution. The bulk concentration of suspended sediment varied from 1.0 to 12.0 g/L. We found that the commonly used linear relationship between the intensity of acoustic backscatter and suspended sediment concentration holds only at sufficiently low concentrations, for instance below 3.0 g/L. It fails at a critical value of concentration that depends on measurement frequency and the distance between the transducer and the target point. Instead, an exponential relationship was found to work satisfactorily throughout the entire range of concentration. The coefficient and exponent of the exponential function changed, however, with the measuring frequency and distance. Considering the increased complexity of inverting the concentration values when an exponential relationship prevails, we further analyzed the relationship between measurement error and measuring frequency. It was also found that the inversion error may be effectively controlled within 5% if the frequency is properly set. Compared with concentration, grain size was found to heavily affect the selection of optimum frequency. A regression relationship for optimum frequency versus grain size was developed based on the experimental results.

The Development of a Tactical-Level Full Range Leadership Measurement Instrument

Science.gov (United States)

2010-03-01

full range leadership theory has become established as the predominant and most widely researched theory on leadership . The most commonly used survey...instrument to assess full range leadership theory is the Multifactor Leadership Questionnaire, originally developed by Bass in 1985. Although much...existing literature to develop a new full range leadership theory measurement instrument that effectively targets low- to mid-level supervisors, or

Absolute distance measurement with extension of nonambiguity range using the frequency comb of a femtosecond laser

Science.gov (United States)

Jang, Yoon-Soo; Lee, Keunwoo; Han, Seongheum; Lee, Joohyung; Kim, Young-Jin; Kim, Seung-Woo

2014-12-01

We revisit the method of synthetic wavelength interferometry (SWI) for absolute measurement of long distances using the radio-frequency harmonics of the pulse repetition rate of a mode-locked femtosecond laser. Our intention here is to extend the nonambiguity range (NAR) of the SWI method using a coarse virtual wavelength synthesized by shifting the pulse repetition rate. The proposed concept of NAR extension is experimentally verified by measuring a ˜13-m distance with repeatability of 9.5 μm (root-mean-square). The measurement precision is estimated to be 31.2 μm in comparison with an incremental He-Ne laser interferometer. This extended SWI method is found to be well suited for long-distance measurements demanded in the fields of large-scale precision engineering, geodetic survey, and future space missions.

Simulation of Heating with the Waves of Ion Cyclotron Range of Frequencies in Experimental Advanced Superconducting Tokamak

International Nuclear Information System (INIS)

Yang Cheng; Zhu Sizheng; Zhang Xinjun

2010-01-01

Simulation on the heating scenarios in experimental advanced superconducting tokamak (EAST) was performed by using a full wave code TORIC. The locations of resonance layers for these heating schemes are predicted and the simulations for different schemes in ICRF experiments in EAST, for example, ion heating (both fundamental and harmonic frequency) or electron heating (by direct fast waves or by mode conversion waves), on-axis or off-axis heating, and high-field-side (HFS) launching or low-field-side (LFS) launching, etc, were conducted. For the on-axis minority ion heating of 3 He in D( 3 He) plasma, the impacts of both density and temperature on heating were discussed in the EAST parameter ranges.

Study of blood plasma optical properties in mice grafted with Ehrlich carcinoma in the frequency range 0.1-1.0 THz

Science.gov (United States)

Smolyanskaya, O. A.; Kravtsenyuk, O. V.; Panchenko, A. V.; Odlyanitskiy, E. L.; Guillet, J. P.; Cherkasova, O. P.; Khodzitsky, M. K.

2017-12-01

In the course of in vitro studies of blood of laboratory animals with progressing Ehrlich carcinoma, we have revealed the change of the blood plasma optical properties in the THz range, which can be used for developing the express diagnostics of the presence of oncological diseases. An applied software package is elaborated that allows the phantoms of biological samples having a complex structure to be numerically simulated and the parameters of the electromagnetic wave reflected from these samples in the THz frequency range to be calculated. Presented at the Fundamentals of Laser Micro- and Nanotechnologies (FLAMN-16) International Symposium (Pushkin, Leningrad oblast, 27 June to 1 July 2016).

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

Science.gov (United States)

Arthur, Steve M.; Schwartz, Charles C.

1999-01-01

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

Acoustic emission source location in plates using wavelet analysis and cross time frequency spectrum.

Science.gov (United States)

Mostafapour, A; Davoodi, S; Ghareaghaji, M

2014-12-01

In this study, the theories of wavelet transform and cross-time frequency spectrum (CTFS) are used to locate AE source with frequency-varying wave velocity in plate-type structures. A rectangular array of four sensors is installed on the plate. When an impact is generated by an artificial AE source such as Hsu-Nielsen method of pencil lead breaking (PLB) at any position of the plate, the AE signals will be detected by four sensors at different times. By wavelet packet decomposition, a packet of signals with frequency range of 0.125-0.25MHz is selected. The CTFS is calculated by the short-time Fourier transform of the cross-correlation between considered packets captured by AE sensors. The time delay is calculated when the CTFS reaches the maximum value and the corresponding frequency is extracted per this maximum value. The resulting frequency is used to calculate the group velocity of wave velocity in combination with dispersive curve. The resulted locating error shows the high precision of proposed algorithm. Copyright © 2014 Elsevier B.V. All rights reserved.

Evidence of resonant mode coupling and the relationship between low and high frequencies in a rapidly rotating a star

International Nuclear Information System (INIS)

Breger, M.; Montgomery, M. H.

2014-01-01

In the theory of resonant mode coupling, the parent and child modes are directly related in frequency and phase. The oscillations present in the fast rotating δ Sct star KIC 8054146 allow us to test the most general and generic aspects of such a theory. The only direct way to separate the parent and coupled (child) modes is to examine the correlations in amplitude variability between the different frequencies. For the dominant family of related frequencies, only a single mode and a triplet are the origins of nine dominant frequency peaks ranging from 2.93 to 66.30 cycles day –1 (as well as dozens of small-amplitude combination modes and a predicted and detected third high-frequency triplet). The mode-coupling model correctly predicts the large amplitude variations of the coupled modes as a product of the amplitudes of the parent modes, while the phase changes are also correctly modeled. This differs from the behavior of 'normal' combination frequencies in that the amplitudes are three orders of magnitude larger and may exceed even the amplitudes of the parent modes. We show that two dominant low frequencies at 5.86 and 2.93 cycles day –1 in the gravity-mode region are not harmonics of each other, and their properties follow those of the almost equidistant high-frequency triplet. We note that the previously puzzling situation of finding two strong peaks in the low-frequency region related by nearly a factor of two in frequency has been seen in other δ Sct stars as well.

Evidence of resonant mode coupling and the relationship between low and high frequencies in a rapidly rotating a star

Energy Technology Data Exchange (ETDEWEB)

Breger, M.; Montgomery, M. H. [Department of Astronomy, University of Texas, Austin, TX 78712 (United States)

2014-03-10

In the theory of resonant mode coupling, the parent and child modes are directly related in frequency and phase. The oscillations present in the fast rotating δ Sct star KIC 8054146 allow us to test the most general and generic aspects of such a theory. The only direct way to separate the parent and coupled (child) modes is to examine the correlations in amplitude variability between the different frequencies. For the dominant family of related frequencies, only a single mode and a triplet are the origins of nine dominant frequency peaks ranging from 2.93 to 66.30 cycles day{sup –1} (as well as dozens of small-amplitude combination modes and a predicted and detected third high-frequency triplet). The mode-coupling model correctly predicts the large amplitude variations of the coupled modes as a product of the amplitudes of the parent modes, while the phase changes are also correctly modeled. This differs from the behavior of 'normal' combination frequencies in that the amplitudes are three orders of magnitude larger and may exceed even the amplitudes of the parent modes. We show that two dominant low frequencies at 5.86 and 2.93 cycles day{sup –1} in the gravity-mode region are not harmonics of each other, and their properties follow those of the almost equidistant high-frequency triplet. We note that the previously puzzling situation of finding two strong peaks in the low-frequency region related by nearly a factor of two in frequency has been seen in other δ Sct stars as well.

Electric current - frequency converter

International Nuclear Information System (INIS)

Kumahara, Tadashi; Kinbana, Setsuro.

1967-01-01

Herein disclosed is an improved simple electric current-frequency converter, the input current and output frequency linearity of which is widened to a range of four to five figures while compensating, for temperature. The converter may be used for computor processing and for telemetering the output signals from a nuclear reactor. The converter is an astable multivibrator which includes charging circuits comprising emitter-voltage compensated NPN transistors, a charged voltage detecting circuit of temperature compensated field effect transistors, and a transistor switching circuit for generating switching pulses independent of temperature. The converter exhibited a 0.7% frequency change within a range of 5 - 45 0 C and less than a 0.1% frequency drift after six hours of operation when the input current was maintained constant. (Yamaguchi, T.)

Application of a renormalization-group treatment to the statistical associating fluid theory for potentials of variable range (SAFT-VR).

Science.gov (United States)

Forte, Esther; Llovell, Felix; Vega, Lourdes F; Trusler, J P Martin; Galindo, Amparo

2011-04-21

An accurate prediction of phase behavior at conditions far and close to criticality cannot be accomplished by mean-field based theories that do not incorporate long-range density fluctuations. A treatment based on renormalization-group (RG) theory as developed by White and co-workers has proven to be very successful in improving the predictions of the critical region with different equations of state. The basis of the method is an iterative procedure to account for contributions to the free energy of density fluctuations of increasing wavelengths. The RG method has been combined with a number of versions of the statistical associating fluid theory (SAFT), by implementing White's earliest ideas with the improvements of Prausnitz and co-workers. Typically, this treatment involves two adjustable parameters: a cutoff wavelength L for density fluctuations and an average gradient of the wavelet function Φ. In this work, the SAFT-VR (variable range) equation of state is extended with a similar crossover treatment which, however, follows closely the most recent improvements introduced by White. The interpretation of White's latter developments allows us to establish a straightforward method which enables Φ to be evaluated; only the cutoff wavelength L then needs to be adjusted. The approach used here begins with an initial free energy incorporating only contributions from short-wavelength fluctuations, which are treated locally. The contribution from long-wavelength fluctuations is incorporated through an iterative procedure based on attractive interactions which incorporate the structure of the fluid following the ideas of perturbation theories and using a mapping that allows integration of the radial distribution function. Good agreement close and far from the critical region is obtained using a unique fitted parameter L that can be easily related to the range of the potential. In this way the thermodynamic properties of a square-well (SW) fluid are given by the same

Improved real-time dynamics from imaginary frequency lattice simulations

Directory of Open Access Journals (Sweden)

Pawlowski Jan M.

2018-01-01

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

Improved real-time dynamics from imaginary frequency lattice simulations

Science.gov (United States)

Pawlowski, Jan M.; Rothkopf, Alexander

2018-03-01

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

Quantum mechanical analysis on faujasite-type molecular sieves by using fermi dirac statistics and quantum theory of dielectricity

International Nuclear Information System (INIS)

Jabeen, S.; Raza, S.M.; Ahmed, M.A.; Zai, M.Y.; Akbar, S.; Jafri, Y.Z.

2012-01-01

We studied Faujasite type molecular sieves by using Fermi Dirac statistics and the quantum theory of dielectricity. We developed an empirical relationship for quantum capacitance which follows an inverse Gaussian profile in the frequency range of 66 Hz - 3 MHz. We calculated quantum capacitance, sample crystal momentum, charge quantization and quantized energy of Faujasite type molecular sieves in the frequency range of 0.1 Hz - 10/sup 4/ MHz. Our calculations for diameter of sodalite and super-cages of Faujasite type molecular sieves are in agreement with experimental results reported in this manuscript. We also calculated quantum polarizability, quantized molecular field, orientational polarizability and deformation polarizability by using experimental results of Ligia Frunza etal. The phonons are over damped in the frequency range 0.1 Hz - 10 kHz and become a source for producing cages in the Faujasite type molecular sieves. Ion exchange recovery processes occur due to over damped phonon excitations in Faujasite type molecular sieves and with increasing temperatures. (author)

Fourier domain optical coherence tomography achieves full range complex imaging in vivo by introducing a carrier frequency during scanning

International Nuclear Information System (INIS)

Wang, Ruikang K

2007-01-01

The author describes a Fourier domain optical coherence tomography (FDOCT) system that is capable of full range complex imaging in vivo. This is achieved by introducing a constant carrier frequency into the OCT spectral interferograms at the time when imaging is performed. The complex functions of the spatial interferograms formed by each single wavelength are constructed before performing the Fourier transformation to localize the scatters within a sample. Two algorithms, based on Fourier filtering and Hilbert transformation, respectively, are described to achieve the full range complex FDOCT imaging. It is shown that the Hilbert transformation approach delivers better performance than the Fourier filtering method does in terms of tolerating the sample movement in vivo. The author finally demonstrates experimentally the system and algorithms for true in vivo imaging at a rate of 20 000 axial scans per second

Photonic filtering of microwave signals in the frequency range of 0.01-20 GHz using a Fabry-Perot filter

Energy Technology Data Exchange (ETDEWEB)

Aguayo-Rodriguez, G; Zaldivar-Huerta, I E [Instituto Nacional de Astrofisica, Optica y Electronica (INAOE). Sta. Maria Tonantzintla, Pue. Mexico (Mexico); GarcIa-Juarez, A [Depto. de Investigacion en Fisica, Universidad de Sonora (UNISON) Hermosillo, Son. Mexico (Mexico); Rodriguez-Asomoza, J [Depto. de Ingenieria Electronica, Universidad de las Americas-Puebla (UDLA). San Andres Cholula, Pue. Mexico (Mexico); Larger, L; Courjal, N [Laboratoire d' Optique P. M. Duffieux, UMR 6603 CNRS, Institut des Microtechiques de Franche-Comte, FRW 0067, UFR Sciences et Techniques, Universite de Franche-Comte (UFC), Besancon cedex (France)

2011-01-01

We demonstrate experimentally the efficiency of tuning of a photonic filter in the frequency range of 0.01 to 20 GHz. The presented work combines the use of a multimode optical source associated with a dispersive optical fiber to obtain the filtering effect. Tunability effect is achieved by the use of a Fabry-Perot filter that allows altering the spectral characteristics of the optical source. Experimental results are validated by means of numerical simulations. The scheme here proposed has a potential application in the field of optical telecommunications.

Analysing collaboration among HIV agencies through combining network theory and relational coordination.

Science.gov (United States)

Khosla, Nidhi; Marsteller, Jill Ann; Hsu, Yea Jen; Elliott, David L

2016-02-01

Agencies with different foci (e.g. nutrition, social, medical, housing) serve people living with HIV (PLHIV). Serving needs of PLHIV comprehensively requires a high degree of coordination among agencies which often benefits from more frequent communication. We combined Social Network theory and Relational Coordination theory to study coordination among HIV agencies in Baltimore. Social Network theory implies that actors (e.g., HIV agencies) establish linkages amongst themselves in order to access resources (e.g., information). Relational Coordination theory suggests that high quality coordination among agencies or teams relies on the seven dimensions of frequency, timeliness and accuracy of communication, problem-solving communication, knowledge of agencies' work, mutual respect and shared goals. We collected data on frequency of contact from 57 agencies using a roster method. Response options were ordinal ranging from 'not at all' to 'daily'. We analyzed data using social network measures. Next, we selected agencies with which at least one-third of the sample reported monthly or more frequent interaction. This yielded 11 agencies whom we surveyed on seven relational coordination dimensions with questions scored on a Likert scale of 1-5. Network density, defined as the proportion of existing connections to all possible connections, was 20% when considering monthly or higher interaction. Relational coordination scores from individual agencies to others ranged between 1.17 and 5.00 (maximum possible score 5). The average scores for different dimensions across all agencies ranged between 3.30 and 4.00. Shared goals (4.00) and mutual respect (3.91) scores were highest, while scores such as knowledge of each other's work and problem-solving communication were relatively lower. Combining theoretically driven analyses in this manner offers an innovative way to provide a comprehensive picture of inter-agency coordination and the quality of exchange that underlies

High frequency asymptotic methods

International Nuclear Information System (INIS)

Bouche, D.; Dessarce, R.; Gay, J.; Vermersch, S.

1991-01-01

The asymptotic methods allow us to compute the interaction of high frequency electromagnetic waves with structures. After an outline of their foundations with emphasis on the geometrical theory of diffraction, it is shown how to use these methods to evaluate the radar cross section (RCS) of complex tri-dimensional objects of great size compared to the wave-length. The different stages in simulating phenomena which contribute to the RCS are reviewed: physical theory of diffraction, multiple interactions computed by shooting rays, research for creeping rays. (author). 7 refs., 6 figs., 3 insets

Magnonic Crystal Theory of the Spin-Wave Frequency Gap in Low-Doped $La_{1-x}Ca_{x}MnO_{3}$ Manganites

OpenAIRE

Krawczyk, M.; Puszkarski, H.

2005-01-01

A theory of three-dimensional (3D) hypothetical magnonic crystal (conceived as the magnetic counterpart of the well-known photonic crystal) is developed and applied to explain the existence of a spin-wave frequency gap recently revealed in low-doped manganites $La_{1-x}Ca_{x}MnO_{3}$ by neutron scattering. A successful confrontation with the experimental results allows us to formulate a working hypothesis that certain manganites could be regarded as 3D magnonic crystals existing in nature.

Interaction range perturbation theory for three-particle problem

International Nuclear Information System (INIS)

Simenog, I.V.; Shapoval, D.V.

1988-01-01

The limit of zero interaction range is correctly defined for a system of three spinless particles and three particles in a doublet state. The scattering amplitude is expanded with respect to the interaction range r, and the corrections of order r ln r, r, and r 2 ln2 r are found. An explicit model-independent asymptotic expression is obtained for the scattering amplitude in terms of the scattering length, and its accuracy is established

A small-form-factor piezoelectric vibration energy harvester using a resonant frequency-down conversion

Energy Technology Data Exchange (ETDEWEB)

Sun, Kyung Ho; Kim, Young-Cheol [Department of System Dynamics, Korea Institute of Machinery and Materials, 156 Gajeongbuk-Ro, Yuseong-Gu, Daejeon 305-343 (Korea, Republic of); Kim, Jae Eun, E-mail: jekim@cu.ac.kr [School of Mechanical and Automotive Engineering, Catholic University of Daegu, 13-13 Hayang-Ro, Hayang-Eup, Gyeongsan-Si, Gyeongsangbuk-Do 712-702 (Korea, Republic of)

2014-10-15

While environmental vibrations are usually in the range of a few hundred Hertz, small-form-factor piezoelectric vibration energy harvesters will have higher resonant frequencies due to the structural size effect. To address this issue, we propose a resonant frequency-down conversion based on the theory of dynamic vibration absorber for the design of a small-form-factor piezoelectric vibration energy harvester. The proposed energy harvester consists of two frequency-tuned elastic components for lowering the first resonant frequency of an integrated system but is so configured that an energy harvesting beam component is inverted with respect to the other supporting beam component for a small form factor. Furthermore, in order to change the unwanted modal characteristic of small separation of resonant frequencies, as is the case with an inverted configuration, a proof mass on the supporting beam component is slightly shifted toward a second proof mass on the tip of the energy harvesting beam component. The proposed small-form-factor design capability was experimentally verified using a fabricated prototype with an occupation volume of 20 × 39 × 6.9 mm{sup 3}, which was designed for a target frequency of as low as 100 Hz.

A small-form-factor piezoelectric vibration energy harvester using a resonant frequency-down conversion

Directory of Open Access Journals (Sweden)

Kyung Ho Sun

2014-10-01

Full Text Available While environmental vibrations are usually in the range of a few hundred Hertz, small-form-factor piezoelectric vibration energy harvesters will have higher resonant frequencies due to the structural size effect. To address this issue, we propose a resonant frequency-down conversion based on the theory of dynamic vibration absorber for the design of a small-form-factor piezoelectric vibration energy harvester. The proposed energy harvester consists of two frequency-tuned elastic components for lowering the first resonant frequency of an integrated system but is so configured that an energy harvesting beam component is inverted with respect to the other supporting beam component for a small form factor. Furthermore, in order to change the unwanted modal characteristic of small separation of resonant frequencies, as is the case with an inverted configuration, a proof mass on the supporting beam component is slightly shifted toward a second proof mass on the tip of the energy harvesting beam component. The proposed small-form-factor design capability was experimentally verified using a fabricated prototype with an occupation volume of 20 × 39 × 6.9 mm3, which was designed for a target frequency of as low as 100 Hz.

Extension and applications of switching model: Range theory, multiple scattering model of Goudsmit-Saunderson, and lateral spread treatment of Marwick-Sigmund

Science.gov (United States)

Ikegami, Seiji

2017-09-01

The switching model (PSM) developed in the previous paper is extended to obtain an ;extended switching model (ESM). In the ESM, the mixt electronic-and-nuclear energy-loss region, in addition to the electronic and nuclear energy-loss regions in PSM, is taken into account analytically and appropriately. This model is combined with a small-angle multiple scattering range theory considering both nuclear and electronic stopping effects developed by Marwick-Sigmund and Valdes-Arista to formulate a improved range theory. The ESM is also combined with the multiple scattering theory with non-small angle approximation by Goudsmit-Saunderson. Furthermore, we applied ESM to lateral spread model of Marwick-Sigmund. Numerical calculations of the entire distribution functions including one of the mixt region are roughly and approximately possible. However, exact numerical calculation may be impossible. Consequently, several preliminary numerical calculations of the electronic, mixt, and nuclear regions are performed to examine their underlying behavior with respect to the incident energy, the scattering angle, the outgoing projectile intensity, and the target thickness. We show the numerical results not only of PSM and but also of ESM. Both numerical results are shown in the present paper for the first time. Since the theoretical relations are constructed using reduced variables, the calculations are made only on the case of C colliding on C.

Radar meteors range distribution model. I. Theory

Czech Academy of Sciences Publication Activity Database

Pecinová, Drahomíra; Pecina, Petr

2007-01-01

Roč. 37, č. 2 (2007), s. 83-106 ISSN 1335-1842 R&D Projects: GA ČR GA205/03/1405 Institutional research plan: CEZ:AV0Z10030501 Keywords : physics of meteors * radar meteors * range distribution Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics

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

Energy Technology Data Exchange (ETDEWEB)

Leger, Joel D.; Nyby, Clara M.; Varner, Clyde; Tang, Jianan; Rubtsova, Natalia I.; Yue, Yuankai; Kireev, Victor V.; Burtsev, Viacheslav D.; Qasim, Layla N.; Rubtsov, Igor V., E-mail: irubtsov@tulane.edu [Department of Chemistry, Tulane University, New Orleans, Louisiana 70118 (United States); Rubtsov, Grigory I. [Institute for Nuclear Research of the Russian Academy of Sciences, Moscow 117312 (Russian Federation)

2014-08-15

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

Compact frequency-modulation Q-switched single-frequency fiber laser at 1083 nm

International Nuclear Information System (INIS)

Zhang, Yuanfei; Feng, Zhouming; Xu, Shanhui; Mo, Shupei; Yang, Changsheng; Li, Can; Gan, Jiulin; Chen, Dongdan; Yang, Zhongmin

2015-01-01

A compact frequency-modulation Q-switched single-frequency fiber laser is demonstrated at 1083 nm. The short linear resonant cavity consists of a 12 mm long homemade Yb 3+ -doped phosphate fiber and a pair of fiber Bragg gratings (FBGs) in which the Q-switching and the frequency excursion is achieved by a tensile-induced period modulation. Over 375 MHz frequency-tuning range is achieved with a modulation frequency varying from tens to hundreds of kilohertz. The highest peak power of the output pulse reaching 6.93 W at the repetition rate of 10 kHz is obtained. (paper)

An Extended System Frequency Response Model Considering Wind Power Participation in Frequency Regulation

Directory of Open Access Journals (Sweden)

Yi Tang

2017-11-01

Full Text Available With increasing penetration of wind power into the power system, wind power participation in frequency regulation is regarded as a beneficial strategy to improve the dynamic frequency response characteristics of power systems. The traditional power system frequency response (SFR model, which only includes synchronous generators, is no longer suitable for power systems with high penetrated wind power. An extended SFR model, based on the reduced-order model of wind turbine generator (WTG and the traditional SFR model, is presented in this paper. In the extended SFR model, the reduced-order model of WTG with combined frequency control is deduced by employing small signal analysis theory. Afterwards, the stability analysis of a closed-loop control system for the extended SFR model is carried out. Time-domain simulations using a test system are performed to validate the effectiveness of the extended SFR model; this model can provide a simpler, clearer and faster way to analyze the dynamic frequency response characteristic for a high-wind integrated power systems. The impact of additional frequency control parameters and wind speed disturbances on the system dynamic frequency response characteristics are investigated.

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

International Nuclear Information System (INIS)

Schmid, Gernot; Ueberbacher, Richard

2005-01-01

In order to identify possible age-dependent dielectric properties of brain and eye tissues in the frequency range of 400 MHz to 18 GHz, measurements on bovine grey and white matter as well as on cornea, lens (cortical) and the vitreous body were performed using a commercially available open-ended coaxial probe and a computer-controlled vector network analyser. Freshly excised tissues of 52 animals of two age groups (42 adult animals, i.e. 16-24 month old and 10 young animals, i.e. 4-6 month old calves) were examined within 8 min (brain tissue) and 15 min (eye tissue), respectively, of the animals' death. Tissue temperatures for the measurements were 32 ± 1 0 C and 25 ± 1 0 C for brain and eye tissues, respectively. Statistical analysis of the measured data revealed significant differences in the dielectric properties of white matter and cortical lens tissue between the adult and the young group. In the case of white matter the mean values of conductivity and permittivity of young tissue were 15%-22% and 12%-15%, respectively, higher compared to the adult tissue in the considered frequency range. Similarly, young cortical lens tissue was 25%-76% higher in conductivity and 27%-39% higher in permittivity than adult cortical lens tissue

Frequency Comb Driven Raman Transitions in the THz Range: High Precision Isotope Shift Measurements in Ca+

DEFF Research Database (Denmark)

Meyer, Steffen

2017-01-01

and frequency resolved optical gating (FROG) are used, and the two frequency comb systems used for the experiments are thoroughly characterized, a Coherent Mira Ti:sapph oscillator and a MenloSystems fiber based frequency comb system. The potential of frequency comb driven Raman transitions is shown...... transition frequencies typically are on the order of a few THz. High precision measurements on these ions have many intriguing applications, for example the test of time-variations of fundamental constants, ultracold chemistry on the quantum level, and quantum information and computing, to name just a few...

Analysis of Dynamic Fracture Compliance Based on Poroelastic Theory - Part II: Results of Numerical and Experimental Tests

Science.gov (United States)

Wang, Ding; Ding, Pin-bo; Ba, Jing

2018-03-01

In Part I, a dynamic fracture compliance model (DFCM) was derived based on the poroelastic theory. The normal compliance of fractures is frequency-dependent and closely associated with the connectivity of porous media. In this paper, we first compare the DFCM with previous fractured media theories in the literature in a full frequency range. Furthermore, experimental tests are performed on synthetic rock specimens, and the DFCM is compared with the experimental data in the ultrasonic frequency band. Synthetic rock specimens saturated with water have more realistic mineral compositions and pore structures relative to previous works in comparison with natural reservoir rocks. The fracture/pore geometrical and physical parameters can be controlled to replicate approximately those of natural rocks. P- and S-wave anisotropy characteristics with different fracture and pore properties are calculated and numerical results are compared with experimental data. Although the measurement frequency is relatively high, the results of DFCM are appropriate for explaining the experimental data. The characteristic frequency of fluid pressure equilibration calculated based on the specimen parameters is not substantially less than the measurement frequency. In the dynamic fracture model, the wave-induced fluid flow behavior is an important factor for the fracture-wave interaction process, which differs from the models at the high-frequency limits, for instance, Hudson's un-relaxed model.

LOW-FREQUENCY OSCILLATIONS IN GLOBAL SIMULATIONS OF BLACK HOLE ACCRETION

International Nuclear Information System (INIS)

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

2011-01-01

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

OLFAR - Orbiting low frequency antennas for radio astronomy

NARCIS (Netherlands)

Bentum, Marinus Jan

2013-01-01

One of the last unexplored frequency ranges in radio astronomy is the frequency band below 30 MHz. New interesting astronomical science drivers for low frequency radio astronomy have emerged, ranging from studies of the astronomical dark ages, the epoch of reionization, exoplanets, to ultra-high

Phase-coherence transitions and communication in the gamma range between delay-coupled neuronal populations.

Directory of Open Access Journals (Sweden)

Alessandro Barardi

2014-07-01

Full Text Available Synchronization between neuronal populations plays an important role in information transmission between brain areas. In particular, collective oscillations emerging from the synchronized activity of thousands of neurons can increase the functional connectivity between neural assemblies by coherently coordinating their phases. This synchrony of neuronal activity can take place within a cortical patch or between different cortical regions. While short-range interactions between neurons involve just a few milliseconds, communication through long-range projections between different regions could take up to tens of milliseconds. How these heterogeneous transmission delays affect communication between neuronal populations is not well known. To address this question, we have studied the dynamics of two bidirectionally delayed-coupled neuronal populations using conductance-based spiking models, examining how different synaptic delays give rise to in-phase/anti-phase transitions at particular frequencies within the gamma range, and how this behavior is related to the phase coherence between the two populations at different frequencies. We have used spectral analysis and information theory to quantify the information exchanged between the two networks. For different transmission delays between the two coupled populations, we analyze how the local field potential and multi-unit activity calculated from one population convey information in response to a set of external inputs applied to the other population. The results confirm that zero-lag synchronization maximizes information transmission, although out-of-phase synchronization allows for efficient communication provided the coupling delay, the phase lag between the populations, and the frequency of the oscillations are properly matched.

Spectropolarimetric Observations of Solar Noise Storms at Low Frequencies

Science.gov (United States)

Mugundhan, V.; Ramesh, R.; Kathiravan, C.; Gireesh, G. V. S.; Hegde, Aathira

2018-03-01

A new high-resolution radio spectropolarimeter instrument operating in the frequency range of 15 - 85 MHz has recently been commissioned at the Radio Astronomy Field Station of the Indian Institute of Astrophysics at Gauribidanur, 100 km north of Bangalore, India. We describe the design and construction of this instrument. We present observations of a solar radio noise storm associated with Active Region (AR) 12567 in the frequency range of {≈} 15 - 85 MHz during 18 and 19 July 2016, observed using this instrument in the meridian-transit mode. This is the first report that we are aware of in which both the burst and continuum properties are derived simultaneously. Spectral indices and degree of polarization of both the continuum radiation and bursts are estimated. It is found that i) Type I storm bursts have a spectral index of {≈} {+}3.5, ii) the spectral index of the background continuum is ≈+2.9, iii) the transition frequency between Type I and Type III storms occurs at ≈55 MHz, iv) Type III bursts have an average spectral index of ≈-2.7, v) the spectral index of the Type III continuum is ≈-1.6, and vi) the degree of circular polarization of all Type I (Type III) bursts is ≈90% (30%). The results obtained here indicate that the continuum emission is due to bursts occurring in rapid succession. We find that the derived parameters for Type I bursts are consistent with suprathermal electron acceleration theory and those of Type III favor fundamental plasma emission.

Radio-frequency integrated-circuit engineering

CERN Document Server

Nguyen, Cam

2015-01-01

Radio-Frequency Integrated-Circuit Engineering addresses the theory, analysis and design of passive and active RFIC's using Si-based CMOS and Bi-CMOS technologies, and other non-silicon based technologies. The materials covered are self-contained and presented in such detail that allows readers with only undergraduate electrical engineering knowledge in EM, RF, and circuits to understand and design RFICs. Organized into sixteen chapters, blending analog and microwave engineering, Radio-Frequency Integrated-Circuit Engineering emphasizes the microwave engineering approach for RFICs. Provide

Design of multi-frequency CW radars

CERN Document Server

Jankiraman, Mohinder

2007-01-01

This book deals with the basic theory for design and analysis of Low Probability of Intercept (LPI) radar systems. The design of one such multi-frequency high resolution LPI radar, PANDORA, is covered.

A novel method for determining calibration and behavior of PVDF ultrasonic hydrophone probes in the frequency range up to 100 MHz.

Science.gov (United States)

Bleeker, H J; Lewin, P A

2000-01-01

A new calibration technique for PVDF ultrasonic hydrophone probes is described. Current implementation of the technique allows determination of hydrophone frequency response between 2 and 100 MHz and is based on the comparison of theoretically predicted and experimentally determined pressure-time waveforms produced by a focused, circular source. The simulation model was derived from the time domain algorithm that solves the non linear KZK (Khokhlov-Zabolotskaya-Kuznetsov) equation describing acoustic wave propagation. The calibration technique data were experimentally verified using independent calibration procedures in the frequency range from 2 to 40 MHz using a combined time delay spectrometry and reciprocity approach or calibration data provided by the National Physical Laboratory (NPL), UK. The results of verification indicated good agreement between the results obtained using KZK and the above-mentioned independent calibration techniques from 2 to 40 MHz, with the maximum discrepancy of 18% at 30 MHz. The frequency responses obtained using different hydrophone designs, including several membrane and needle probes, are presented, and it is shown that the technique developed provides a desirable tool for independent verification of primary calibration techniques such as those based on optical interferometry. Fundamental limitations of the presented calibration method are also examined.

Electron spin resonance for the detection of long-range spin nematic order

Science.gov (United States)

Furuya, Shunsuke C.; Momoi, Tsutomu

2018-03-01

Spin nematic phase is a quantum magnetic phase characterized by a quadrupolar order parameter. Since the quadrupole operators are directly coupled to neither the magnetic field nor the neutron, currently, it is an important issue to develop a method for detecting the long-range spin nematic order. In this paper, we propose that electron spin resonance (ESR) measurements enable us to detect the long-range spin nematic order. We show that the frequency of the paramagnetic resonance peak in the ESR spectrum is shifted by the ferroquadrupolar order parameter together with other quantities. The ferroquadrupolar order parameter is extractable from the angular dependence of the frequency shift. In contrast, the antiferroquadrupolar order parameter is usually invisible in the frequency shift. Instead, the long-range antiferroquadrupolar order yields a characteristic resonance peak in the ESR spectrum, which we call a magnon-pair resonance peak. This resonance corresponds to the excitation of the bound magnon pair at the wave vector k =0 . Reflecting the condensation of bound magnon pairs, the field dependence of the magnon-pair resonance frequency shows a singular upturn at the saturation field. Moreover, the intensity of the magnon-pair resonance peak shows a characteristic angular dependence and it vanishes when the magnetic field is parallel to one of the axes that diagonalize the weak anisotropic interactions. We confirm these general properties of the magnon-pair resonance peak in the spin nematic phase by studying an S =1 bilinear-biquadratic model on the square lattice in the linear flavor-wave approximation. In addition, we argue applications to the S =1/2 frustrated ferromagnets and also the S =1/2 orthogonal dimer spin system SrCu2(BO3)2, both of which are candidate materials of spin nematics. Our theory for the antiferroquadrupolar ordered phase is consistent with many features of the magnon-pair resonance peak experimentally observed in the low

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

Science.gov (United States)

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

2016-12-01

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

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

Experimental evidence of the role of viscosity in the molecular kinetic theory of dynamic wetting.

Science.gov (United States)

Duvivier, D; Seveno, D; Rioboo, R; Blake, T D; De Coninck, J

2011-11-01

We report an experimental study of the dynamics of spontaneous spreading of aqueous glycerol drops on glass. For a range of glycerol concentrations, we follow the evolution of the radius and contact angle over several decades of time and investigate the influence of solution viscosity. The application of the molecular kinetic theory to the resulting data allows us to extract the coefficient of contact-line friction ζ, the molecular jump frequency κ(0), and the jump length λ for each solution. Our results show that the modified theory, which explicitly accounts for the effect of viscosity, can successfully be applied to droplet spreading. The viscosity affects the jump frequency but not the jump length. In combining these data, we confirm that the contact-line friction of the solution/air interface against the glass is proportional to the viscosity and exponentially dependent on the work of adhesion.

Regularization of Instantaneous Frequency Attribute Computations

Science.gov (United States)

Yedlin, M. J.; Margrave, G. F.; Van Vorst, D. G.; Ben Horin, Y.

2014-12-01

We compare two different methods of computation of a temporally local frequency:1) A stabilized instantaneous frequency using the theory of the analytic signal.2) A temporally variant centroid (or dominant) frequency estimated from a time-frequency decomposition.The first method derives from Taner et al (1979) as modified by Fomel (2007) and utilizes the derivative of the instantaneous phase of the analytic signal. The second method computes the power centroid (Cohen, 1995) of the time-frequency spectrum, obtained using either the Gabor or Stockwell Transform. Common to both methods is the necessity of division by a diagonal matrix, which requires appropriate regularization.We modify Fomel's (2007) method by explicitly penalizing the roughness of the estimate. Following Farquharson and Oldenburg (2004), we employ both the L curve and GCV methods to obtain the smoothest model that fits the data in the L2 norm.Using synthetic data, quarry blast, earthquakes and the DPRK tests, our results suggest that the optimal method depends on the data. One of the main applications for this work is the discrimination between blast events and earthquakesFomel, Sergey. " Local seismic attributes." , Geophysics, 72.3 (2007): A29-A33.Cohen, Leon. " Time frequency analysis theory and applications." USA: Prentice Hall, (1995).Farquharson, Colin G., and Douglas W. Oldenburg. "A comparison of automatic techniques for estimating the regularization parameter in non-linear inverse problems." Geophysical Journal International 156.3 (2004): 411-425.Taner, M. Turhan, Fulton Koehler, and R. E. Sheriff. " Complex seismic trace analysis." Geophysics, 44.6 (1979): 1041-1063.

Modulated convection at high frequencies and large modulation amplitudes

International Nuclear Information System (INIS)

Swift, J.B.; Hohenberg, P.C.

1987-01-01

Modulated Rayleigh-Benard convection is analyzed for high frequencies and large modulation amplitudes. The linear theory of Gershuni and Zhukhovitskii is generalized to the nonlinear domain, and a subcritical bifurcation to convection is found in agreement with the experiments of Niemela and Donnelly. The crossover between the high-frequency (''Stokes layer'') regime and the low-frequency regime studied previously is analyzed

High and low spatial frequencies in website evaluations.

Science.gov (United States)

Thielsch, Meinald T; Hirschfeld, Gerrit

2010-08-01

Which features of websites are important for users' perceptions regarding aesthetics or usability? This study investigates how evaluations of aesthetic appeal and usability depend on high vs. low spatial frequencies. High spatial frequencies convey information on fine details, whereas low spatial frequencies convey information about the global layout. Participants rated aesthetic appeal and usability of 50 website screenshots from different domains. Screenshots were presented unfiltered, low-pass filtered with blurred targets or high-pass filtered with high-pass filtered targets. The main result is that low spatial frequencies can be seen to have a unique contribution in perceived website aesthetics, thus confirming a central prediction from processing fluency theory. There was no connection between low spatial frequencies and usability evaluations, whereas strong correlations were found between ratings of high-pass filtered websites and those of unfiltered websites in aesthetics and usability. This study thus offers a new perspective on the biological basis of users' website perceptions. This research links ergonomics to neurocognitive models of visual processing. This paper investigates how high and low spatial frequencies, which are neurologically processed in different visual pathways, independently contribute to users' perceptions of websites. This is very relevant for theories of website perceptions and for practitioners of web design.

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

Science.gov (United States)

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

2012-12-01

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

Effective field theories

International Nuclear Information System (INIS)

Mack, G.; Kalkreuter, T.; Palma, G.; Speh, M.

1992-05-01

Effective field theories encode the predictions of a quantum field theory at low energy. The effective theory has a fairly low utraviolet cutoff. As a result, loop corrections are small, at least if the effective action contains a term which is quadratic in the fields, and physical predictions can be read straight from the effective Lagrangean. Methods will be discussed how to compute an effective low energy action from a given fundamental action, either analytically or numerically, or by a combination of both methods. Basically, the idea is to integrate out the high frequency components of fields. This requires the choice of a 'blockspin', i.e. the specification af a low frequency field as a function of the fundamental fields. These blockspins will be fields of the effective field theory. The blockspin need not be a field of the same type as one of the fundamental fields, and it may be composite. Special features of blockspin in nonabelian gauge theories will be discussed in some detail. In analytical work and in multigrid updating schemes one needs interpolation kernels A from coarse to fine grid in addition to the averaging kernels C which determines the blockspin. A neural net strategy for finding optimal kernels is presented. Numerical methods are applicable to obtain actions of effective theories on lattices of finite volume. The special case of a 'lattice' with a single site (the constraint effective potential) is of particular interest. In a higgs model, the effective action reduces in this case to the free energy, considered as a function of a gauge covariant magnetization. Its shape determines the phase structure of the theory. Its loop expansion with and without gauge fields can be used to determine finite size corrections to numerical data. (orig.)

Atomic theories

CERN Document Server

Loring, FH

2014-01-01

Summarising the most novel facts and theories which were coming into prominence at the time, particularly those which had not yet been incorporated into standard textbooks, this important work was first published in 1921. The subjects treated cover a wide range of research that was being conducted into the atom, and include Quantum Theory, the Bohr Theory, the Sommerfield extension of Bohr's work, the Octet Theory and Isotopes, as well as Ionisation Potentials and Solar Phenomena. Because much of the material of Atomic Theories lies on the boundary between experimentally verified fact and spec

Characterizing short-range vs. long-range spatial correlations in dislocation distributions

International Nuclear Information System (INIS)

Chevy, Juliette; Fressengeas, Claude; Lebyodkin, Mikhail; Taupin, Vincent; Bastie, Pierre; Duval, Paul

2010-01-01

Hard X-ray diffraction experiments have provided evidence of a strongly heterogeneous distribution of dislocation densities along the axis of cylindrical ice single crystals oriented for basal slip in torsion creep. The dislocation arrangements showed a complex scale-invariant character, which was analyzed by means of statistical and multifractal techniques. A trend to decreasing autocorrelation of the dislocation distribution was observed as deformation proceeds. At low strain levels, long-range spatial correlations control the distribution, but short-range correlations in relation with cross-slip progressively prevail when strain increases. This trend was reproduced by a model based on field dislocation dynamics, a theory accounting for both long-range elastic interactions and short-range interactions through transport of dislocation densities.

Characterizing short-range vs. long-range spatial correlations in dislocation distributions

Energy Technology Data Exchange (ETDEWEB)

Chevy, Juliette, E-mail: juliette.chevy@gmail.com [Laboratoire de Glaciologie et Geophysique de l' Environnement-CNRS, 54 rue Moliere, 38402 St. Martin d' Heres (France)] [Laboratoire Science et Ingenierie des Materiaux et Procedes, Grenoble INP-CNRS-UJF, BP 75, 38402 St. Martin d' Heres Cedex (France); Fressengeas, Claude; Lebyodkin, Mikhail; Taupin, Vincent [Laboratoire de Physique et Mecanique des Materiaux, Universite Paul Verlaine-Metz/CNRS, Ile du Saulcy, 57045 Metz Cedex (France); Bastie, Pierre [Laboratoire de Spectrometrie Physique, BP 87, 38402 St. Martin d' Heres Cedex (France)] [Institut Laue Langevin, BP 156, 38042 Grenoble Cedex 9 (France); Duval, Paul [Laboratoire de Glaciologie et Geophysique de l' Environnement-CNRS, 54 rue Moliere, 38402 St. Martin d' Heres (France)

2010-03-15

Hard X-ray diffraction experiments have provided evidence of a strongly heterogeneous distribution of dislocation densities along the axis of cylindrical ice single crystals oriented for basal slip in torsion creep. The dislocation arrangements showed a complex scale-invariant character, which was analyzed by means of statistical and multifractal techniques. A trend to decreasing autocorrelation of the dislocation distribution was observed as deformation proceeds. At low strain levels, long-range spatial correlations control the distribution, but short-range correlations in relation with cross-slip progressively prevail when strain increases. This trend was reproduced by a model based on field dislocation dynamics, a theory accounting for both long-range elastic interactions and short-range interactions through transport of dislocation densities.

Efficient estimation for ergodic diffusions sampled at high frequency

DEFF Research Database (Denmark)

Sørensen, Michael

A general theory of efficient estimation for ergodic diffusions sampled at high fre- quency is presented. High frequency sampling is now possible in many applications, in particular in finance. The theory is formulated in term of approximate martingale estimating functions and covers a large class...

A succession of theories: purging redundancy from disturbance theory.

Science.gov (United States)

Pulsford, Stephanie A; Lindenmayer, David B; Driscoll, Don A

2016-02-01

The topics of succession and post-disturbance ecosystem recovery have a long and convoluted history. There is extensive redundancy within this body of theory, which has resulted in confusion, and the links among theories have not been adequately drawn. This review aims to distil the unique ideas from the array of theory related to ecosystem change in response to disturbance. This will help to reduce redundancy, and improve communication and understanding between researchers. We first outline the broad range of concepts that have developed over the past century to describe community change in response to disturbance. The body of work spans overlapping succession concepts presented by Clements in 1916, Egler in 1954, and Connell and Slatyer in 1977. Other theories describing community change include state and transition models, biological legacy theory, and the application of functional traits to predict responses to disturbance. Second, we identify areas of overlap of these theories, in addition to highlighting the conceptual and taxonomic limitations of each. In aligning each of these theories with one another, the limited scope and relative inflexibility of some theories becomes apparent, and redundancy becomes explicit. We identify a set of unique concepts to describe the range of mechanisms driving ecosystem responses to disturbance. We present a schematic model of our proposed synthesis which brings together the range of unique mechanisms that were identified in our review. The model describes five main mechanisms of transition away from a post-disturbance community: (i) pulse events with rapid state shifts; (ii) stochastic community drift; (iii) facilitation; (iv) competition; and (v) the influence of the initial composition of a post-disturbance community. In addition, stabilising processes such as biological legacies, inhibition or continuing disturbance may prevent a transition between community types. Integrating these six mechanisms with the functional

Radio-Frequency-Controlled Cold Collisions and Universal Properties of Unitary Bose Gases

Science.gov (United States)

Ding, Yijue

This thesis investigates two topics: ultracold atomic collisions in a radio-frequency field and universal properties of a degenerate unitary Bose gas. One interesting point of the unitary Bose gas is that the system has only one length scale, that is, the average interparticle distance. This single parameter determines all properties of the gas, which is called the universality of the system. We first introduce a renormalized contact interaction to extend the validity of the zero-range interaction to large scattering lengths. Then this renormalized interaction is applied to many-body theories to determined those universal relations of the system. From the few-body perspective, we discuss the scattering between atoms in a single-color radio-frequency field. Our motivation is proposing the radio-frequency field as an effective tool to control interactions between cold atoms. Such a technique may be useful in future experiments such as creating phase transitions in spinor condensates. We also discuss the formation of ultracold molecules using radio-freqency fields from a time-dependent approach.

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

Science.gov (United States)

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

2011-12-01

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

Short-range and long-range forces in quantum theory: selected topics