WorldWideScience

Sample records for relevant frequency range

  1. 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....

  2. 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.

  3. The frequency range of TMJ sounds.

    Science.gov (United States)

    Widmalm, S E; Williams, W J; Djurdjanovic, D; McKay, D C

    2003-04-01

    There are conflicting opinions about the frequency range of temporomandibular joint (TMJ) sounds. Some authors claim that the upper limit is about 650 Hz. The aim was to test the hypothesis that TMJ sounds may contain frequencies well above 650 Hz but that significant amounts of their energy are lost if the vibrations are recorded using contact sensors and/or travel far through the head tissues. Time-frequency distributions of 172 TMJ clickings (three subjects) were compared between recordings with one microphone in the ear canal and a skin contact transducer above the clicking joint and between recordings from two microphones, one in each ear canal. The energy peaks of the clickings recorded with a microphone in the ear canal on the clicking side were often well above 650 Hz and always in a significantly higher area (range 117-1922 Hz, P 375 Hz) or in microphone recordings from the opposite ear canal (range 141-703 Hz). Future studies are required to establish normative frequency range values of TMJ sounds but need methods also capable of recording the high frequency vibrations.

  4. T-ray relevant frequencies for osteosarcoma classification

    Science.gov (United States)

    Withayachumnankul, W.; Ferguson, B.; Rainsford, T.; Findlay, D.; Mickan, S. P.; Abbott, D.

    2006-01-01

    We investigate the classification of the T-ray response of normal human bone cells and human osteosarcoma cells, grown in culture. Given the magnitude and phase responses within a reliable spectral range as features for input vectors, a trained support vector machine can correctly classify the two cell types to some extent. Performance of the support vector machine is deteriorated by the curse of dimensionality, resulting from the comparatively large number of features in the input vectors. Feature subset selection methods are used to select only an optimal number of relevant features for inputs. As a result, an improvement in generalization performance is attainable, and the selected frequencies can be used for further describing different mechanisms of the cells, responding to T-rays. We demonstrate a consistent classification accuracy of 89.6%, while the only one fifth of the original features are retained in the data set.

  5. 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…

  6. Characteristics of different frequency ranges in scanning electron microscope images

    International Nuclear Information System (INIS)

    Sim, K. S.; Nia, M. E.; Tan, T. L.; Tso, C. P.; Ee, C. S.

    2015-01-01

    We demonstrate a new approach to characterize the frequency range in general scanning electron microscope (SEM) images. First, pure frequency images are generated from low frequency to high frequency, and then, the magnification of each type of frequency image is implemented. By comparing the edge percentage of the SEM image to the self-generated frequency images, we can define the frequency ranges of the SEM images. Characterization of frequency ranges of SEM images benefits further processing and analysis of those SEM images, such as in noise filtering and contrast enhancement

  7. Characteristics of different frequency ranges in scanning electron microscope images

    Energy Technology Data Exchange (ETDEWEB)

    Sim, K. S., E-mail: kssim@mmu.edu.my; Nia, M. E.; Tan, T. L.; Tso, C. P.; Ee, C. S. [Faculty of Engineering and Technology, Multimedia University, 75450 Melaka (Malaysia)

    2015-07-22

    We demonstrate a new approach to characterize the frequency range in general scanning electron microscope (SEM) images. First, pure frequency images are generated from low frequency to high frequency, and then, the magnification of each type of frequency image is implemented. By comparing the edge percentage of the SEM image to the self-generated frequency images, we can define the frequency ranges of the SEM images. Characterization of frequency ranges of SEM images benefits further processing and analysis of those SEM images, such as in noise filtering and contrast enhancement.

  8. Predicting Achievable Fundamental Frequency Ranges in Vocalization Across Species.

    Directory of Open Access Journals (Sweden)

    Ingo Titze

    2016-06-01

    Full Text Available Vocal folds are used as sound sources in various species, but it is unknown how vocal fold morphologies are optimized for different acoustic objectives. Here we identify two main variables affecting range of vocal fold vibration frequency, namely vocal fold elongation and tissue fiber stress. A simple vibrating string model is used to predict fundamental frequency ranges across species of different vocal fold sizes. While average fundamental frequency is predominantly determined by vocal fold length (larynx size, range of fundamental frequency is facilitated by (1 laryngeal muscles that control elongation and by (2 nonlinearity in tissue fiber tension. One adaptation that would increase fundamental frequency range is greater freedom in joint rotation or gliding of two cartilages (thyroid and cricoid, so that vocal fold length change is maximized. Alternatively, tissue layers can develop to bear a disproportionate fiber tension (i.e., a ligament with high density collagen fibers, increasing the fundamental frequency range and thereby vocal versatility. The range of fundamental frequency across species is thus not simply one-dimensional, but can be conceptualized as the dependent variable in a multi-dimensional morphospace. In humans, this could allow for variations that could be clinically important for voice therapy and vocal fold repair. Alternative solutions could also have importance in vocal training for singing and other highly-skilled vocalizations.

  9. 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)

  10. Radio frequency heating in the ion-cyclotron range of frequencies

    International Nuclear Information System (INIS)

    Swanson, D.G.

    1985-01-01

    Both the theory of the absorption process in the ion-cyclotron range of frequencies and some of the experiments which slow the promise and problems with radio frequency plasma heating in this range are discussed. It is shown that mode conversion is invariably involved in the process and so an extensive review of mode conversion theory, expecially as it applies to problems with back-to-back cutoff-resonance pairs, is included. This includes a discussion of the tunneling equation with and without absorption effects and with and without energy conservation. The general theory is applied to various ion-cyclotron harmonics, the two-ion hybrid resonance, and to a case where a wave converts to a Bernstein mode at the plasma edge. The results are given analytically for a variety of cases without absorption, and empirical formulas are given for the second and third harmonics of the ion-cyclotron frequency, which include effects of absorption. Various problem areas in the theory are also discussed with some of the limitations caused by the approximations involved. A number of experiments are also discussed which show effective heating, and some show the features of the mode conversion process, indicating that the general processes of absorption are reasonably well understood. Areas where further work is necessary, both in fundamental theory and in comparing theory with experiment, are also discussed

  11. 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.

  12. 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.

  13. 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 (

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

    Science.gov (United States)

    Reynolds, Nathan D.

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

  15. 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.

  16. 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

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. Cultural relevance of a fruit and vegetable food frequency questionnaire.

    Science.gov (United States)

    Paisley, Judy; Greenberg, Marlene; Haines, Jess

    2005-01-01

    Canada's multicultural population poses challenges for culturally competent nutrition research and practice. In this qualitative study, the cultural relevance of a widely used semi-quantitative fruit and vegetable food frequency questionnaire (FFQ) was examined among convenience samples of adults from Toronto's Cantonese-, Mandarin-, Portuguese-, and Vietnamese-speaking communities. Eighty-nine participants were recruited through community-based organizations, programs, and advertisements to participate in semi-structured interviews moderated in their native language. Data from the interviews were translated into English and transcribed for analysis using the constant comparative approach. Four main themes emerged from the analysis: the cultural relevance of the foods listed on the FFQ, words with multiple meanings, the need for culturally appropriate portion-size prompts, and the telephone survey as a Western concept. This research highlights the importance of investing resources to develop culturally relevant dietary assessment tools that ensure dietary assessment accuracy and, more important, reduce ethnocentric biases in food and nutrition research and practice. The transferability of findings must be established through further research.

  3. 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.

  4. Relevance feature selection of modal frequency-ambient condition pattern recognition in structural health assessment for reinforced concrete buildings

    Directory of Open Access Journals (Sweden)

    He-Qing Mu

    2016-08-01

    Full Text Available Modal frequency is an important indicator for structural health assessment. Previous studies have shown that this indicator is substantially affected by the fluctuation of ambient conditions, such as temperature and humidity. Therefore, recognizing the pattern between modal frequency and ambient conditions is necessary for reliable long-term structural health assessment. In this article, a novel machine-learning algorithm is proposed to automatically select relevance features in modal frequency-ambient condition pattern recognition based on structural dynamic response and ambient condition measurement. In contrast to the traditional feature selection approaches by examining a large number of combinations of extracted features, the proposed algorithm conducts continuous relevance feature selection by introducing a sophisticated hyperparameterization on the weight parameter vector controlling the relevancy of different features in the prediction model. The proposed algorithm is then utilized for structural health assessment for a reinforced concrete building based on 1-year daily measurements. It turns out that the optimal model class including the relevance features for each vibrational mode is capable to capture the pattern between the corresponding modal frequency and the ambient conditions.

  5. Extension of White's layered model to the full frequency range

    NARCIS (Netherlands)

    Vogelaar, Bouko; Smeulders, D.M.J.

    2007-01-01

    The low-frequency theory of the White model to predict the dispersion and intrinsic attenuation in a single porous skeleton saturated with periodic layers of two immiscible fluids is extended to the full frequency range using the Biot theory. The extension is similar to the Dutta–Odé model for

  6. 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)

  7. 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

  8. 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.

  9. 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.

  10. 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.

  11. 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

  12. 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)

  13. 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

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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)

  2. 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)

  3. 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.

  4. 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.

  5. Short-range contacts govern the performance of industry-relevant battery cathodes

    Science.gov (United States)

    Morelly, Samantha L.; Alvarez, Nicolas J.; Tang, Maureen H.

    2018-05-01

    Fundamental understanding of how processing affects composite battery electrode structure and performance is still lacking, especially for industry-relevant electrodes with low fractions of inactive material. This work combines rheology, electronic conductivity measurements, and battery rate capability tests to prove that short-range electronic contacts are more important to cathode rate capability than either ion transport or long-range electronic conductivity. LiNi0.33Mn0.33Co0.33O2, carbon black, and polyvinylidene difluoride in 1-methyl-2-pyrrolidinone represent a typical commercial electrode with films. Improvements in battery rate capability at constant electrode porosity do not correlate to electronic conductivity, but rather show an optimum fraction of free carbon. Simple comparison of rate capability in electrodes with increased total carbon loading (3 wt%) shows improvement for all fractions of free carbon. These results clearly indicate that ion transport cannot be limiting and highlight the critical importance of short-range electronic contacts for controlling battery performance.

  6. 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)

  7. 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.

  8. 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.

  9. 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

  10. 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.

  11. 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.

  12. 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.

  13. 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

  14. 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

  15. 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

  16. 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.

  17. 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.

  18. 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.

  19. Time-domain analysis of frequency dependent inertial wave forces on cylinders

    DEFF Research Database (Denmark)

    Krenk, Steen

    2013-01-01

    a simple time-domain procedure for the inertial force, in which the frequency dependence is represented via a simple explicit time filter on the wave particle acceleration or velocity. The frequency dependence of the inertia coefficient is known analytically as a function of the wave......-number, and the relevant range of waves shorter than about six times the diameter typically corresponds to deep water waves. This permits a universal non-dimensional frequency representation, that is converted to rational form to provide the relevant filter equation. Simple time-domain simulations demonstrate...... the reduction of the resonant part of the response for natural structural frequencies above the dominating wave frequency....

  20. 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

  1. 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.

  2. 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.

  3. 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.

  4. 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

  5. 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

  6. 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.

  7. 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

  8. 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

  9. 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.

  10. 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...

  11. 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.

  12. 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

  13. 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

  14. 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...

  15. 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

  16. 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)

  17. 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)

  18. 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.

  19. 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%.

  20. Trend extraction of rail corrugation measured dynamically based on the relevant low-frequency principal components reconstruction

    International Nuclear Information System (INIS)

    Li, Yanfu; Liu, Hongli; Ma, Ziji

    2016-01-01

    Rail corrugation dynamic measurement techniques are critical to guarantee transport security and guide rail maintenance. During the inspection process, low-frequency trends caused by rail fluctuation are usually superimposed on rail corrugation and seriously affect the assessment of rail maintenance quality. In order to extract and remove the nonlinear and non-stationary trends from original mixed signals, a hybrid model based ensemble empirical mode decomposition (EEMD) and modified principal component analysis (MPCA) is proposed in this paper. Compared with the existing de-trending methods based on EMD, this method first considers low-frequency intrinsic mode functions (IMFs) thought to be underlying trend components that maybe contain some unrelated components, such as white noise and low-frequency signal itself, and proposes to use PCA to accurately extract the pure trends from the IMFs containing multiple components. On the other hand, due to the energy contribution ratio between trends and mixed signals is prior unknown, and the principal components (PCs) decomposed by PCA are arranged in order of energy reduction without considering frequency distribution, the proposed method modifies traditional PCA and just selects relevant low-frequency PCs to reconstruct the trends based on the zero-crossing numbers (ZCN) of each PC. Extensive tests are presented to illustrate the effectiveness of the proposed method. The results show the proposed EEMD-PCA-ZCN is an effective tool for trend extraction of rail corrugation measured dynamically. (paper)

  1. 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....

  2. 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.

  3. 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)

  4. 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.

  5. 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.

  6. 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.

  7. 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)

  8. 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).

  9. 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.

  10. 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.

  11. Range-separated time-dependent density-functional theory with a frequency-dependent second-order Bethe-Salpeter correlation kernel

    Energy Technology Data Exchange (ETDEWEB)

    Rebolini, Elisa, E-mail: elisa.rebolini@kjemi.uio.no; Toulouse, Julien, E-mail: julien.toulouse@upmc.fr [Laboratoire de Chimie Théorique, Sorbonne Universités, UPMC Univ Paris 06, CNRS, 4 place Jussieu, F-75005 Paris (France)

    2016-03-07

    We present a range-separated linear-response time-dependent density-functional theory (TDDFT) which combines a density-functional approximation for the short-range response kernel and a frequency-dependent second-order Bethe-Salpeter approximation for the long-range response kernel. This approach goes beyond the adiabatic approximation usually used in linear-response TDDFT and aims at improving the accuracy of calculations of electronic excitation energies of molecular systems. A detailed derivation of the frequency-dependent second-order Bethe-Salpeter correlation kernel is given using many-body Green-function theory. Preliminary tests of this range-separated TDDFT method are presented for the calculation of excitation energies of the He and Be atoms and small molecules (H{sub 2}, N{sub 2}, CO{sub 2}, H{sub 2}CO, and C{sub 2}H{sub 4}). The results suggest that the addition of the long-range second-order Bethe-Salpeter correlation kernel overall slightly improves the excitation energies.

  12. Frequency specific modulation of human somatosensory cortex

    Directory of Open Access Journals (Sweden)

    Matteo eFeurra

    2011-02-01

    Full Text Available Oscillatory neuronal activities are commonly observed in response to sensory stimulation. However, their functional roles are still the subject of debate. One way to probe the roles of oscillatory neural activities is to deliver alternating current to the cortex at biologically relevant frequencies and examine whether such stimulation influences perception and cognition. In this study, we tested whether transcranial alternating current stimulation (tACS over the primary somatosensory cortex (SI could elicit tactile sensations in humans in a frequency dependent manner. We tested the effectiveness of tACS over SI at frequency bands ranging from 2 to 70 Hz. Our results show that stimulation in alpha (10-14 Hz and high gamma (52-70 Hz frequency range produces a tactile sensation in the contralateral hand. A weaker effect was also observed for beta (16-20 Hz stimulation. These findings highlight the frequency-dependency of effective tACS over SI with the effective frequencies corresponding to those observed in previous EEG/MEG studies of tactile perception. Our present study suggests that tACS could be used as a powerful online stimulation technique to reveal the causal roles of oscillatory brain activities.

  13. 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.

  14. 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.

  15. 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....

  16. Integrated, Reactor Relevant Solutions for Lower Hybrid Range of Frequencies Actuators

    Science.gov (United States)

    Shiraiwa, S.; Bonoli, P. T.; Lin, Y.; Wallace, G. M.; Wukitch, S. J.

    2017-10-01

    RF (radiofrequency) actuators with high system efficiency (wall-plug to plasma) and ability for continuous operation have long be recognized as essential tools for realizing a steady state tokamak. A number of physics and technological challenges to utilization remain including current drive efficiency and location, efficient coupling, and impurity contamination. In a reactor environment, plasma material interaction (PMI) issues associated with coupling structures are similar to the first wall and have been identified as a potential show-stopper. High field side (HFS) launch of LHRF power represents an integrated solution that both improves core wave physics and mitigates PMI/coupling issues. For HFS LHRF, wave penetration is vastly improves because wave accessibility scales as 1/B allowing for launching the wave at lower n|| (parallel refractive index). The lower n|| penetrate to higher electron temperature resulting in higher current drive efficiency (1/n||2). HFS RF launch also provides for a means to dramatically improve launcher robustness in a reactor environment. On the HFS, the SOL is quiescent; local density profile is steep and controlled through magnetic shape; fast particle, neutron, turbulent heat and particle fluxes are eliminated or minim Work supported by the U.S. DoE, Office of Science, Office of Fusion Energy Sciences, User Facility Alcator C-Mod under DE-FC02-99ER54512 and US DoE Contract No. DE-FC02-01ER54648 under a Scientific Discovery through Advanced Computing Initiative.

  17. Methodical assessment of all non-ionizing radiation sources that can provide a relevant contribution to public exposure. Final report

    International Nuclear Information System (INIS)

    Bornkessel, Christian; Schubert, Markus; Wuschek, Matthias; Brueggemeyer, Hauke; Weiskopf, Daniela

    2011-01-01

    The aim of the research project was to systematically identify artificial sources on non-ionizing radiation (electric, magnetic or electromagnetic fields in a frequency range from 0 Hz to 300 GHz, as well optical radiation in a wavelength range from 100 nm to 1 mm), that have relevant contribution to public exposure. The report includes the following chapters: (1) Concept for the relevance assessment for non-ionizing radiation sources; (2) concept for the systematic identification of sources from establishes technologies; (3) concept for the systematic identification of sources from new or foreseeable technologies; (4)overview of relevant radiation sources.

  18. 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...

  19. 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.

  20. 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…

  1. 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...

  2. Stimulus variability and the phonetic relevance hypothesis: effects of variability in speaking style, fundamental frequency, and speaking rate on spoken word identification.

    Science.gov (United States)

    Sommers, Mitchell S; Barcroft, Joe

    2006-04-01

    Three experiments were conducted to examine the effects of trial-to-trial variations in speaking style, fundamental frequency, and speaking rate on identification of spoken words. In addition, the experiments investigated whether any effects of stimulus variability would be modulated by phonetic confusability (i.e., lexical difficulty). In Experiment 1, trial-to-trial variations in speaking style reduced the overall identification performance compared with conditions containing no speaking-style variability. In addition, the effects of variability were greater for phonetically confusable words than for phonetically distinct words. In Experiment 2, variations in fundamental frequency were found to have no significant effects on spoken word identification and did not interact with lexical difficulty. In Experiment 3, two different methods for varying speaking rate were found to have equivalent negative effects on spoken word recognition and similar interactions with lexical difficulty. Overall, the findings are consistent with a phonetic-relevance hypothesis, in which accommodating sources of acoustic-phonetic variability that affect phonetically relevant properties of speech signals can impair spoken word identification. In contrast, variability in parameters of the speech signal that do not affect phonetically relevant properties are not expected to affect overall identification performance. Implications of these findings for the nature and development of lexical representations are discussed.

  3. 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.

  4. 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.

  5. 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.

  6. 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),...

  7. 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 ...

  8. 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..

  9. 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

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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

  15. 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.

  16. Low-frequency quantitative ultrasound imaging of cell death in vivo

    International Nuclear Information System (INIS)

    Sadeghi-Naini, Ali; Falou, Omar; Czarnota, Gregory J.; Papanicolau, Naum; Tadayyon, Hadi; Lee, Justin; Zubovits, Judit; Sadeghian, Alireza; Karshafian, Raffi; Al-Mahrouki, Azza; Giles, Anoja; Kolios, Michael C.

    2013-01-01

    Purpose: Currently, no clinical imaging modality is used routinely to assess tumor response to cancer therapies within hours to days of the delivery of treatment. Here, the authors demonstrate the efficacy of ultrasound at a clinically relevant frequency to quantitatively detect changes in tumors in response to cancer therapies using preclinical mouse models.Methods: Conventional low-frequency and corresponding high-frequency ultrasound (ranging from 4 to 28 MHz) were used along with quantitative spectroscopic and signal envelope statistical analyses on data obtained from xenograft tumors treated with chemotherapy, x-ray radiation, as well as a novel vascular targeting microbubble therapy.Results: Ultrasound-based spectroscopic biomarkers indicated significant changes in cell-death associated parameters in responsive tumors. Specifically changes in the midband fit, spectral slope, and 0-MHz intercept biomarkers were investigated for different types of treatment and demonstrated cell-death related changes. The midband fit and 0-MHz intercept biomarker derived from low-frequency data demonstrated increases ranging approximately from 0 to 6 dBr and 0 to 8 dBr, respectively, depending on treatments administrated. These data paralleled results observed for high-frequency ultrasound data. Statistical analysis of ultrasound signal envelope was performed as an alternative method to obtain histogram-based biomarkers and provided confirmatory results. Histological analysis of tumor specimens indicated up to 61% cell death present in the tumors depending on treatments administered, consistent with quantitative ultrasound findings indicating cell death. Ultrasound-based spectroscopic biomarkers demonstrated a good correlation with histological morphological findings indicative of cell death (r 2 = 0.71, 0.82; p < 0.001).Conclusions: In summary, the results provide preclinical evidence, for the first time, that quantitative ultrasound used at a clinically relevant frequency, in

  17. Low-frequency quantitative ultrasound imaging of cell death in vivo

    Energy Technology Data Exchange (ETDEWEB)

    Sadeghi-Naini, Ali; Falou, Omar; Czarnota, Gregory J. [Imaging Research – Physical Science, Sunnybrook Research Institute, Sunnybrook Health Sciences Centre, Toronto, Ontario M4N 3M5 (Canada); Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, Ontario M4N 3M5 (Canada); Department of Medical Biophysics, Faculty of Medicine, University of Toronto, Toronto, Ontario M4N 3M5 (Canada); Department of Radiation Oncology, Faculty of Medicine, University of Toronto, Toronto, Ontario M4N 3M5 (Canada); Papanicolau, Naum; Tadayyon, Hadi [Imaging Research – Physical Science, Sunnybrook Research Institute, Sunnybrook Health Sciences Centre, Toronto, Ontario M4N 3M5, Canada and Department of Medical Biophysics, Faculty of Medicine, University of Toronto, Toronto, Ontario M4N 3M5 (Canada); Lee, Justin [Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, Ontario M4N 3M5, Canada and Department of Radiation Oncology, Faculty of Medicine, University of Toronto, Toronto, Ontario M4N 3M5 (Canada); Zubovits, Judit [Department of Pathology, Sunnybrook Health Sciences Centre, Toronto, Ontario M4N 3M5 (Canada); Sadeghian, Alireza [Department of Computer Science, Ryerson University, Toronto, Ontario M5B 2K3 (Canada); Karshafian, Raffi [Department of Physics, Ryerson University, Toronto, Ontario M5B 2K3 (Canada); Al-Mahrouki, Azza; Giles, Anoja [Imaging Research – Physical Science, Sunnybrook Research Institute, Sunnybrook Health Sciences Centre, Toronto, Ontario M4N 3M5, Canada and Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, Ontario M4N 3M5 (Canada); Kolios, Michael C. [Department of Medical Biophysics, Faculty of Medicine, University of Toronto, Toronto, Ontario M4N 3M5, Canada and Department of Physics, Ryerson University, Toronto, Ontario M5B 2K3 (Canada)

    2013-08-15

    Purpose: Currently, no clinical imaging modality is used routinely to assess tumor response to cancer therapies within hours to days of the delivery of treatment. Here, the authors demonstrate the efficacy of ultrasound at a clinically relevant frequency to quantitatively detect changes in tumors in response to cancer therapies using preclinical mouse models.Methods: Conventional low-frequency and corresponding high-frequency ultrasound (ranging from 4 to 28 MHz) were used along with quantitative spectroscopic and signal envelope statistical analyses on data obtained from xenograft tumors treated with chemotherapy, x-ray radiation, as well as a novel vascular targeting microbubble therapy.Results: Ultrasound-based spectroscopic biomarkers indicated significant changes in cell-death associated parameters in responsive tumors. Specifically changes in the midband fit, spectral slope, and 0-MHz intercept biomarkers were investigated for different types of treatment and demonstrated cell-death related changes. The midband fit and 0-MHz intercept biomarker derived from low-frequency data demonstrated increases ranging approximately from 0 to 6 dBr and 0 to 8 dBr, respectively, depending on treatments administrated. These data paralleled results observed for high-frequency ultrasound data. Statistical analysis of ultrasound signal envelope was performed as an alternative method to obtain histogram-based biomarkers and provided confirmatory results. Histological analysis of tumor specimens indicated up to 61% cell death present in the tumors depending on treatments administered, consistent with quantitative ultrasound findings indicating cell death. Ultrasound-based spectroscopic biomarkers demonstrated a good correlation with histological morphological findings indicative of cell death (r{sup 2}= 0.71, 0.82; p < 0.001).Conclusions: In summary, the results provide preclinical evidence, for the first time, that quantitative ultrasound used at a clinically relevant frequency

  18. 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

  19. Frequency standards

    CERN Document Server

    Riehle, Fritz

    2006-01-01

    Of all measurement units, frequency is the one that may be determined with the highest degree of accuracy. It equally allows precise measurements of other physical and technical quantities, whenever they can be measured in terms of frequency.This volume covers the central methods and techniques relevant for frequency standards developed in physics, electronics, quantum electronics, and statistics. After a review of the basic principles, the book looks at the realisation of commonly used components. It then continues with the description and characterisation of important frequency standards

  20. The dielectric properties of human pineal gland tissue and RF absorption due to wireless communication devices in the frequency range 400-1850 MHz

    International Nuclear Information System (INIS)

    Schmid, Gernot; Ueberbacher, Richard; Samaras, Theodoros; Tschabitscher, Manfred; Mazal, Peter R

    2007-01-01

    In order to enable a detailed analysis of radio frequency (RF) absorption in the human pineal gland, the dielectric properties of a sample of 20 freshly removed pineal glands were measured less than 20 h after death. Furthermore, a corresponding high resolution numerical model of the brain region surrounding the pineal gland was developed, based on a real human tissue sample. After inserting this model into a commercially available numerical head model, FDTD-based computations for exposure scenarios with generic models of handheld devices operated close to the head in the frequency range 400-1850 MHz were carried out. For typical output power values of real handheld mobile communication devices, the obtained results showed only very small amounts of absorbed RF power in the pineal gland when compared to SAR limits according to international safety standards. The highest absorption was found for the 400 MHz irradiation. In this case the RF power absorbed inside the pineal gland (organ mass 96 mg) was as low as 11 μW, when considering a device of 500 mW output power operated close to the ear. For typical mobile phone frequencies (900 MHz and 1850 MHz) and output power values (250 mW and 125 mW) the corresponding values of absorbed RF power in the pineal gland were found to be lower by a factor of 4.2 and 36, respectively. These results indicate that temperature-related biologically relevant effects on the pineal gland induced by the RF emissions of typical handheld mobile communication devices are unlikely

  1. 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.

  2. 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...

  3. 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

  4. 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.

  5. 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

  6. Low-frequency noise from large wind turbines

    DEFF Research Database (Denmark)

    Møller, Henrik; Pedersen, Christian Sejer

    2011-01-01

    As wind turbines get larger, worries have emerged that the turbine noise would move down in frequency and that the low-frequency noise would cause annoyance for the neighbors. The noise emission from 48 wind turbines with nominal electric power up to 3.6 MW is analyzed and discussed. The relative...... amount of low-frequency noise is higher for large turbines (2.3–3.6 MW) than for small turbines (≤ 2 MW), and the difference is statistically significant. The difference can also be expressed as a downward shift of the spectrum of approximately one-third of an octave. A further shift of similar size...... is suggested for future turbines in the 10-MW range. Due to the air absorption, the higher low-frequency content becomes even more pronounced, when sound pressure levels in relevant neighbor distances are considered. Even when A-weighted levels are considered, a substantial part of the noise is at low...

  7. 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.

  8. 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.

  9. Frequency Constrained ShiftCP Modeling of Neuroimaging Data

    DEFF Research Database (Denmark)

    Mørup, Morten; Hansen, Lars Kai; Madsen, Kristoffer H.

    2011-01-01

    The shift invariant multi-linear model based on the CandeComp/PARAFAC (CP) model denoted ShiftCP has proven useful for the modeling of latency changes in trial based neuroimaging data[17]. In order to facilitate component interpretation we presently extend the shiftCP model such that the extracted...... components can be constrained to pertain to predefined frequency ranges such as alpha, beta and gamma activity. To infer the number of components in the model we propose to apply automatic relevance determination by imposing priors that define the range of variation of each component of the shiftCP model...

  10. Selective attention modulates human auditory brainstem responses: relative contributions of frequency and spatial cues.

    Directory of Open Access Journals (Sweden)

    Alexandre Lehmann

    Full Text Available Selective attention is the mechanism that allows focusing one's attention on a particular stimulus while filtering out a range of other stimuli, for instance, on a single conversation in a noisy room. Attending to one sound source rather than another changes activity in the human auditory cortex, but it is unclear whether attention to different acoustic features, such as voice pitch and speaker location, modulates subcortical activity. Studies using a dichotic listening paradigm indicated that auditory brainstem processing may be modulated by the direction of attention. We investigated whether endogenous selective attention to one of two speech signals affects amplitude and phase locking in auditory brainstem responses when the signals were either discriminable by frequency content alone, or by frequency content and spatial location. Frequency-following responses to the speech sounds were significantly modulated in both conditions. The modulation was specific to the task-relevant frequency band. The effect was stronger when both frequency and spatial information were available. Patterns of response were variable between participants, and were correlated with psychophysical discriminability of the stimuli, suggesting that the modulation was biologically relevant. Our results demonstrate that auditory brainstem responses are susceptible to efferent modulation related to behavioral goals. Furthermore they suggest that mechanisms of selective attention actively shape activity at early subcortical processing stages according to task relevance and based on frequency and spatial cues.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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

  18. 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.

  19. 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.

  20. Low-frequency noise from large wind turbines.

    Science.gov (United States)

    Møller, Henrik; Pedersen, Christian Sejer

    2011-06-01

    As wind turbines get larger, worries have emerged that the turbine noise would move down in frequency and that the low-frequency noise would cause annoyance for the neighbors. The noise emission from 48 wind turbines with nominal electric power up to 3.6 MW is analyzed and discussed. The relative amount of low-frequency noise is higher for large turbines (2.3-3.6 MW) than for small turbines (≤ 2 MW), and the difference is statistically significant. The difference can also be expressed as a downward shift of the spectrum of approximately one-third of an octave. A further shift of similar size is suggested for future turbines in the 10-MW range. Due to the air absorption, the higher low-frequency content becomes even more pronounced, when sound pressure levels in relevant neighbor distances are considered. Even when A-weighted levels are considered, a substantial part of the noise is at low frequencies, and for several of the investigated large turbines, the one-third-octave band with the highest level is at or below 250 Hz. It is thus beyond any doubt that the low-frequency part of the spectrum plays an important role in the noise at the neighbors. © 2011 Acoustical Society of America

  1. One-D full-wave description of plasma emission and absorption in the ion cyclotron range of frequency in tokamaks

    International Nuclear Information System (INIS)

    Fraboulet, D.; Becoulet, A.; Nguyen, F.

    1998-11-01

    To maintain the ignition state in a tokamak fusion reactor, a control must be performed on the population of alpha-products, and this implies the ability to diagnose those α-particles. It is studied here whether the detection of emission radiated in the ion cyclotron range of frequency be a reactor plasma can provide useful information concerning fusion products, especially concerning their density profile. It is shown that the detection of the radiation emitted by the fast alpha particles along their cyclotron motion can give access to moments of their distribution function. This requires to compute the phase of the emitted field, using a full-wave approach. Such a technique allows to set in a convenient way the inverse problem of the determination of the emitting α-particles distribution through the radiation detection. A brief analysis of the expected situation in a reactor-relevant plasma is given. In parallel, the 1-D full-wave code developed in this frame is also useful for studying the physics of Fast Wave plasma heating. It enables to take into account the mode conversion of the Fast Wave into the Ion Bernstein Wave that appears near each ion cyclotron resonance. Results show that higher order terms may significantly alter the energy partitioning, in hot plasma cases involving mode conversion heating and/or ion cyclotron high harmonics heating. (author)

  2. The noseleaf of Rhinolophus formosae focuses the Frequency Modulated (FM) component of the calls.

    Science.gov (United States)

    Vanderelst, Dieter; Lee, Ya-Fu; Geipel, Inga; Kalko, Elisabeth K V; Kuo, Yen-Min; Peremans, Herbert

    2013-01-01

    Bats of the family Rhinolophidae emit their echolocation calls through their nostrils and feature elaborate noseleaves shaping the directionality of the emissions. The calls of these bats consist of a long constant-frequency component preceded and/or followed by short frequency-modulated sweeps. While Rhinolophidae are known for their physiological specializations for processing the constant frequency part of the calls, previous evidence suggests that the noseleaves of these animals are tuned to the frequencies in the frequency modulated components of the calls. In this paper, we seek further support for this hypothesis by simulating the emission beam pattern of the bat Rhinolophus formosae. Filling the furrows of lancet and removing the basal lappets (i.e., two flaps on the noseleaf) we find that these conspicuous features of the noseleaf focus the emitted energy mostly for frequencies in the frequency-modulated components. Based on the assumption that this component of the call is used by the bats for ranging, we develop a qualitative model to assess the increase in performance due to the furrows and/or the lappets. The model confirms that both structures decrease the ambiguity in selecting relevant targets for ranging. The lappets and the furrows shape the emission beam for different spatial regions and frequency ranges. Therefore, we conclude that the presented evidence is in line with the hypothesis that different parts of the noseleaves of Rhinolophidae are tuned to different frequency ranges with at least some of the most conspicuous ones being tuned to the frequency modulated components of the calls-thus yielding strong evidence for the sensory importance of the component.

  3. The noseleaf of Rhinolophus formosae focuses the Frequency Modulated (FM component of the calls

    Directory of Open Access Journals (Sweden)

    Dieter eVanderelst

    2013-07-01

    Full Text Available Bats of the family Rhinolophidae emit their echolocation calls through their nostrils and feature elaborate noseleaves shaping the directionality of the emissions. The calls of these bats consist of a long constant-frequency component preceded and/or followed by short frequency-modulated sweeps. While Rhinolophidae are known for their physiological specializations for processing the constant frequency part of the calls, previous evidence suggests that the noseleaves of these animals are tuned to the frequencies in the frequency modulated components of the calls. In this paper, we seek further support for this hypothesis by simulating the emission beam pattern of the bat Rhinolophus formosae. Filling the furrows of lancet and removing the basal lappets (i.e. two flaps on the noseleaf we find that these conspicuous features of the noseleaf focus the emitted energy mostly for frequencies in the frequency-modulated components. Based on the assumption that this component of the call is used by the bats for ranging, we develop a qualitative model to assess the increase in performance due to the furrows and/or the lappets. The model confirms that both structures decrease the ambiguity in selecting relevant targets for ranging. The lappets and the furrows shape the emission beam for different spatial regions and frequency ranges. Therefore, we conclude that that the presented evidence is in line with the hypothesis that different parts of the noseleaves of Rhinolophidae are tuned to different frequency ranges with at least some of the most conspicuous ones being tuned to the frequency modulated components of the calls - thus yielding strong evidence for the sensory importance of the component.

  4. 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

  5. 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)

  6. 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.

  7. High-frequency energy in singing and speech

    Science.gov (United States)

    Monson, Brian Bruce

    While human speech and the human voice generate acoustical energy up to (and beyond) 20 kHz, the energy above approximately 5 kHz has been largely neglected. Evidence is accruing that this high-frequency energy contains perceptual information relevant to speech and voice, including percepts of quality, localization, and intelligibility. The present research was an initial step in the long-range goal of characterizing high-frequency energy in singing voice and speech, with particular regard for its perceptual role and its potential for modification during voice and speech production. In this study, a database of high-fidelity recordings of talkers was created and used for a broad acoustical analysis and general characterization of high-frequency energy, as well as specific characterization of phoneme category, voice and speech intensity level, and mode of production (speech versus singing) by high-frequency energy content. Directionality of radiation of high-frequency energy from the mouth was also examined. The recordings were used for perceptual experiments wherein listeners were asked to discriminate between speech and voice samples that differed only in high-frequency energy content. Listeners were also subjected to gender discrimination tasks, mode-of-production discrimination tasks, and transcription tasks with samples of speech and singing that contained only high-frequency content. The combination of these experiments has revealed that (1) human listeners are able to detect very subtle level changes in high-frequency energy, and (2) human listeners are able to extract significant perceptual information from high-frequency energy.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. Frequency-specific modulation of population-level frequency tuning in human auditory cortex

    Directory of Open Access Journals (Sweden)

    Roberts Larry E

    2009-01-01

    Full Text Available Abstract Background Under natural circumstances, attention plays an important role in extracting relevant auditory signals from simultaneously present, irrelevant noises. Excitatory and inhibitory neural activity, enhanced by attentional processes, seems to sharpen frequency tuning, contributing to improved auditory performance especially in noisy environments. In the present study, we investigated auditory magnetic fields in humans that were evoked by pure tones embedded in band-eliminated noises during two different stimulus sequencing conditions (constant vs. random under auditory focused attention by means of magnetoencephalography (MEG. Results In total, we used identical auditory stimuli between conditions, but presented them in a different order, thereby manipulating the neural processing and the auditory performance of the listeners. Constant stimulus sequencing blocks were characterized by the simultaneous presentation of pure tones of identical frequency with band-eliminated noises, whereas random sequencing blocks were characterized by the simultaneous presentation of pure tones of random frequencies and band-eliminated noises. We demonstrated that auditory evoked neural responses were larger in the constant sequencing compared to the random sequencing condition, particularly when the simultaneously presented noises contained narrow stop-bands. Conclusion The present study confirmed that population-level frequency tuning in human auditory cortex can be sharpened in a frequency-specific manner. This frequency-specific sharpening may contribute to improved auditory performance during detection and processing of relevant sound inputs characterized by specific frequency distributions in noisy environments.

  13. 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....

  14. 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.

  15. New generation neonatal high frequency ventilators: effect of oscillatory frequency and working principles on performance.

    Science.gov (United States)

    Grazioli, Serge; Karam, Oliver; Rimensberger, Peter C

    2015-03-01

    Several new generation neonatal ventilators that incorporate conventional as well as high frequency ventilation (HFOV) have appeared on the market. Most of them offer the possibility to use HFOV in a volume-targeted mode, despite absence of any preclinical data. With a bench test, we evaluated the performances of 4 new neonatal HFOV devices and compared them to the SensorMedics HFOV device. Expiratory tidal volumes (V(T)) were measured for various ventilator settings and lung characteristics (ie, modifications of compliance and resistance of the system), to mimic several clinical conditions of pre-term and term infants. Increasing the frequency proportionally decreased the V(T) for all the ventilators, although the magnitude of the decrease was highly variable between ventilators. At 15 Hz and a pressure amplitude of 60 cm H2O, the delivered V(T) ranged from 3.5 to 5.9 mL between devices while simulating pre-term infant conditions and from 2.6 to 6.3 mL while simulating term infant conditions. Activating the volume-targeted mode in the 3 machines that offer this mode allowed the V(T) to remain constant over the range of frequencies and with changes of lung mechanical properties, for pre-term infant settings only while targeting a V(T) of 1 mL. These new generation neonatal ventilators were able to deliver adequate V(T) under pre-term infant, but not term infant respiratory system conditions. The clinical relevance of these findings will need to be determined by further studies. Copyright © 2015 by Daedalus Enterprises.

  16. Nanoliter-droplet acoustic streaming via ultra high frequency surface acoustic waves.

    Science.gov (United States)

    Shilton, Richie J; Travagliati, Marco; Beltram, Fabio; Cecchini, Marco

    2014-08-06

    The relevant length scales in sub-nanometer amplitude surface acoustic wave-driven acoustic streaming are demonstrated. We demonstrate the absence of any physical limitations preventing the downscaling of SAW-driven internal streaming to nanoliter microreactors and beyond by extending SAW microfluidics up to operating frequencies in the GHz range. This method is applied to nanoliter scale fluid mixing. © 2014 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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)

  2. 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

  3. 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

  4. 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

  5. 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.

  6. 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...

  7. 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

  8. 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

  9. 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.

  10. Coupled quantum-classical method for long range charge transfer: relevance of the nuclear motion to the quantum electron dynamics

    International Nuclear Information System (INIS)

    Da Silva, Robson; Hoff, Diego A; Rego, Luis G C

    2015-01-01

    Charge and excitonic-energy transfer phenomena are fundamental for energy conversion in solar cells as well as artificial photosynthesis. Currently, much interest is being paid to light-harvesting and energy transduction processes in supramolecular structures, where nuclear dynamics has a major influence on electronic quantum dynamics. For this reason, the simulation of long range electron transfer in supramolecular structures, under environmental conditions described within an atomistic framework, has been a difficult problem to study. This work describes a coupled quantum mechanics/molecular mechanics method that aims at describing long range charge transfer processes in supramolecular systems, taking into account the atomistic details of large molecular structures, the underlying nuclear motion, and environmental effects. The method is applied to investigate the relevance of electron–nuclei interaction on the mechanisms for photo-induced electron–hole pair separation in dye-sensitized interfaces as well as electronic dynamics in molecular structures. (paper)

  11. 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.

  12. 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.)

  13. Frequency regulated compact screw compressors. The new solution; Drehzahlgeregelte Kompakt-Schraubenverdichter. Die neue Loesung

    Energy Technology Data Exchange (ETDEWEB)

    Juergensen, Heinz [BITZER Kuehlmaschinenbau GmbH, Sindelfingen (Germany)

    2012-07-01

    Compact screw compressors have been used for many years in liquid chilling packages for comfort air conditioners, process cooling or heat pumps with mechanical power control. Standard frequency inverters offer the possibility to adjust the performance of a conventional screw compressor, piston compressor or scroll compressor in a small range of frequency. Furthermore, frequency inverters contain a number of additional functions. This combination of existing frequency inverters and compressors - as actually offered in many cases - allows only a limited improvement of the part-load performance in the system. Due to the high cost for the frequency inverters, this combination becomes economically questionable. An integrated package of newly developed compact screw compressors and a specially developed liquid-cooled frequency inverter is required in order to come to a new level of system efficiency at part load. In addition to the increased control range of the compressor, new possibilities can be opened up in terms of application and communication. The monitoring of various values such as the compliance with the application limits for pressure and temperature and especially the early warning against exceedance facilitates a more simply implementation of a secure machine because the setting of the relevant protection functions of the integrated type-specific components already is made in the factory.

  14. The importance of individual frequencies of endogenous brain oscillations for auditory cognition - A short review.

    Science.gov (United States)

    Baltus, Alina; Herrmann, Christoph Siegfried

    2016-06-01

    Oscillatory EEG activity in the human brain with frequencies in the gamma range (approx. 30-80Hz) is known to be relevant for a large number of cognitive processes. Interestingly, each subject reveals an individual frequency of the auditory gamma-band response (GBR) that coincides with the peak in the auditory steady state response (ASSR). A common resonance frequency of auditory cortex seems to underlie both the individual frequency of the GBR and the peak of the ASSR. This review sheds light on the functional role of oscillatory gamma activity for auditory processing. For successful processing, the auditory system has to track changes in auditory input over time and store information about past events in memory which allows the construction of auditory objects. Recent findings support the idea of gamma oscillations being involved in the partitioning of auditory input into discrete samples to facilitate higher order processing. We review experiments that seem to suggest that inter-individual differences in the resonance frequency are behaviorally relevant for gap detection and speech processing. A possible application of these resonance frequencies for brain computer interfaces is illustrated with regard to optimized individual presentation rates for auditory input to correspond with endogenous oscillatory activity. This article is part of a Special Issue entitled SI: Auditory working memory. Copyright © 2015 Elsevier B.V. All rights reserved.

  15. 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.

  16. 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

  17. Saturation of subjective reward magnitude as a function of current and pulse frequency.

    Science.gov (United States)

    Simmons, J M; Gallistel, C R

    1994-02-01

    In rats with electrodes in the medial forebrain bundle, the upper portion of the function relating the experienced magnitude of the reward to pulse frequency was determined at currents ranging from 100 to 1,000 microA. The pulse frequency required to produce an asymptotic level of reward was inversely proportional to current except at the lowest currents and highest pulse frequencies. At a given current, the subjective reward magnitude functions decelerated to an asymptote over an interval in which the pulse frequency doubled or tripled. The asymptotic level of reward was approximately constant for currents between 200 and 1,000 microA but declined substantially at currents at or below 100 microA and pulse frequencies at or above 250 to 400 pulses per second. The results are consistent with the hypothesis that the magnitude of the experienced reward depends only on the number of action potentials generated by the train of pulses in the bundle of reward-relevant axons.

  18. 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...

  19. 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...

  20. 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.

  1. 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

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. Observational study of generation conditions of substorm-associated low-frequency AKR emissions

    Directory of Open Access Journals (Sweden)

    A. Olsson

    2004-11-01

    Full Text Available It has lately been shown that low-frequency bursts of auroral kilometric radiation (AKR are nearly exclusively associated with substorm expansion phases. Here we study low-frequency AKR using Polar PWI and Interball POLRAD instruments to constrain its possible generation mechanisms. We find that there are more low-frequency AKR emission events during wintertime and equinoxes than during summertime. The dot-AKR emission radial distance range coincides well with the region where the deepest density cavities are seen statistically during Kp>2. We suggest that the dot-AKR emissions originate in the deepest density cavities during substorm onsets. The mechanism for generating dot-AKR is possibly strong Alfvén waves entering the cavity from the magnetosphere and changing their character to more inertial, which causes the Alfvén wave associated parallel electric field to increase. This field may locally accelerate electrons inside the cavity enough to produce low-frequency AKR emission. We use Interball IESP low-frequency wave data to verify that in about half of the cases the dot-AKR is accompanied by low-frequency wave activity containing a magnetic component, i.e. probably inertial Alfvén waves. Because of the observational geometry, this result is consistent with the idea that inertial Alfvén waves might always be present in the source region when dot-AKR is generated. The paper illustrates once more the importance of radio emissions as a powerful remote diagnostic tool of auroral processes, which is not only relevant for the Earth's magnetosphere but may be relevant in the future in studying extrasolar planets.

  7. Direct measurements of damping rates and stability limits for low frequency MHD modes and Alfven Eigenmodes in the JET tokamak

    International Nuclear Information System (INIS)

    Fasoli, A.F.; Testa, D.; Jaun, A.; Sharapov, S.; Gormezano, C.

    2001-01-01

    The linear stability properties of global modes that can be driven by resonant energetic particles or by the bulk plasma are studied using an external excitation method based on the JET saddle coil antennas. Low toroidal mode number, stable plasma modes are driven by the saddle coils and detected by magnetic probes to measure their structure, frequency and damping rate, both in the Alfven Eigenmode (AE) frequency range and in the low frequency Magneto-Hydro-Dynamic (MHD) range. For AEs, the dominant damping mechanisms are identified for different plasma conditions of relevance for reactors. Spectra and damping rates of low frequency MHD modes that are localized at the foot of the internal transport barrier and can affect the plasma performance in advanced tokamak scenarios have been directly measured for the first time. This gives the possibility of monitoring in real time the approach to the instability boundary. (author)

  8. 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.

  9. Magnetic Frequency Response of HL-LHC Beam Screens

    Energy Technology Data Exchange (ETDEWEB)

    Morrone, M. [CERN; Martino, M. [CERN; De Maria, R. [CERN; Fitterer, M. [Fermilab; Garion, C. [CERN

    2017-10-12

    Magnetic fields used to control particle beams in accelerators are usually controlled by regulating the electrical current of the power converters. In order to minimize lifetime degradation and ultimately luminosity loss in circular colliders, current-noise is a highly critical figure of merit of power converters, in particular for magnets located in areas with high beta-function, like the High Luminosity Large Hadron Collider (HL-LHC) insertions. However, what is directly acting upon the beam is the magnetic field and not the current of the power converter, which undergoes several frequency-dependent transformations until the desired magnetic field, seen by the beam, is obtained. Beam screens are very rarely considered when assessing or specifying the noise figure of merit, but their magnetic frequency response is such that they realize relatively effective low pass filtering of the magnetic field produced by the system magnet-power converter. This work aims at filling this gap by quantifying the expected impact of different beam screen layouts for the most relevant HL-LHC insertion magnets. A welldefined post-processing technique is used to derive the frequency response of the different multipoles from multi-physics Finite Element Method (FEM) simulation results. In addition, a well approximated analytical formula for the low-frequency range of multi-layered beam screens is presented.

  10. Historical overview of Ramsey spectroscopy and its relevance on Time and Frequency Metrology

    International Nuclear Information System (INIS)

    Amaral, M M; Tarelho, L V G; De Souza, M A; Baratto, A C; Garcia, G A; Muller, S T; De Martin, J Jr; Rodriguez, A S; Bebeachibuli, A; Magalhães, D V

    2016-01-01

    A brief overview of the historical evolution of the method of successive oscillatory fields developed by Norman Ramsey, and some different implementations of the decurrent methodology are presented. We use time and frequency standards, from Cs atomic beams to optical standards, as examples. The scientific progress and the technological implementation achieved through a partnership between USP-SC and INMETRO are shown on the characterization of each time and frequency standard. (paper)

  11. Observation of vapor pressure enhancement of rare-earth metal-halide salts in the temperature range relevant to metal-halide lamps

    Energy Technology Data Exchange (ETDEWEB)

    Curry, J. J.; Henins, A.; Hardis, J. E. [National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); Estupinan, E. G. [Osram Sylvania Inc., Beverly, Massachusetts 01915 (United States); Lapatovich, W. P. [Independent Consultant, 51 Pye Brook Lane, Boxford, Massachusetts 01921 (United States); Shastri, S. D. [Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439 (United States)

    2012-02-20

    Total vapor-phase densities of Dy in equilibrium with a DyI{sub 3}/InI condensate and Tm in equilibrium with a TmI{sub 3}/TlI condensate have been measured for temperatures between 900 K and 1400 K. The measurements show strong enhancements in rare-earth vapor densities compared to vapors in equilibrium with the pure rare-earth metal-halides. The measurements were made with x-ray induced fluorescence on the sector 1-ID beam line at the Advanced Photon Source. The temperature range and salt mixtures are relevant to the operation of metal-halide high-intensity discharge lamps.

  12. 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

  13. 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.

  14. 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.))

  15. Investigating Frequency of Temporo- Mandibular Dysfunctions in Complete Denture Wearers Referring to the Prosthesis Department of Dental School during 2013-2014

    Directory of Open Access Journals (Sweden)

    MH Lotfikamran

    2016-04-01

    Results: 46 patients (46% were male, 54 patients (54% were female, and the age range was 35-64 years. The range of using denture was 1-3 years and the mean duration of using denture was 2.52 ± 1.58 years. The most common age range for the relevant disorders was 40-50 years and the frequency of TMD was more in women than in men. Moreover, there was a significant relationship between age factor and Anamnestic index (P=0.037, whereas no significant relationship was observed between frequency of these disorders, level of education and also duration of using previous denture. Conclusion: The study findings revealed that it seems that with increasing age the rate of complaints from TMD problems increases.

  16. 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.

  17. 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.

  18. Static and low frequency electric and magnetic fields

    International Nuclear Information System (INIS)

    Thommesen, G.; Tynes, T.

    1994-01-01

    The biological effects of exposure to low frequency electric and magnetic fields are reviewed with the objective of summarizing effects directly relevant to considerations of the health and safety of exposed people. Static and low frequency electric and magnetic fields may elicit biological reactions. Whether exposure to such fields may affect human health at field strengths present in everyday or occupational life is still unsettled. There is unsufficient knowledge to establish any dose concept relevant to health risk. 196 refs., 6 tabs

  19. Understanding synthesis imaging dynamic range

    Science.gov (United States)

    Braun, R.

    2013-03-01

    We develop a general framework for quantifying the many different contributions to the noise budget of an image made with an array of dishes or aperture array stations. Each noise contribution to the visibility data is associated with a relevant correlation timescale and frequency bandwidth so that the net impact on a complete observation can be assessed when a particular effect is not captured in the instrumental calibration. All quantities are parameterised as function of observing frequency and the visibility baseline length. We apply the resulting noise budget analysis to a wide range of existing and planned telescope systems that will operate between about 100 MHz and 5 GHz to ascertain the magnitude of the calibration challenges that they must overcome to achieve thermal noise limited performance. We conclude that calibration challenges are increased in several respects by small dimensions of the dishes or aperture array stations. It will be more challenging to achieve thermal noise limited performance using 15 m class dishes rather than the 25 m dishes of current arrays. Some of the performance risks are mitigated by the deployment of phased array feeds and more with the choice of an (alt,az,pol) mount, although a larger dish diameter offers the best prospects for risk mitigation. Many improvements to imaging performance can be anticipated at the expense of greater complexity in calibration algorithms. However, a fundamental limitation is ultimately imposed by an insufficient number of data constraints relative to calibration variables. The upcoming aperture array systems will be operating in a regime that has never previously been addressed, where a wide range of effects are expected to exceed the thermal noise by two to three orders of magnitude. Achieving routine thermal noise limited imaging performance with these systems presents an extreme challenge. The magnitude of that challenge is inversely related to the aperture array station diameter.

  20. 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

  1. Frequency and clinical relevance of human bocavirus infection in acute exacerbations of chronic obstructive pulmonary disease

    Directory of Open Access Journals (Sweden)

    Felix C Ringshausen

    2009-02-01

    Full Text Available Felix C Ringshausen1, Ai-Yui M Tan1, Tobias Allander2, Irmgard Borg1, Umut Arinir1, Juliane Kronsbein1, Barbara M Hauptmeier1, Gerhard Schultze-Werninghaus1, Gernot Rohde11Clinical Research Group “Significance of viral infections in chronic respiratory diseases of children and adults,” University Hospital Bergmannsheil, Department of Internal Medicine III–Pneumology, Allergology and Sleep Medicine, Bochum, Germany; 2Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, and Department of Clinical Microbiology, Karolinska University Hospital, Stockholm, SwedenObjective: Human bocavirus (HBoV is a recently discovered parvovirus associated with acute respiratory tract infections in children. The objective of the present study was to determine the frequency and clinical relevance of HBoV infection in adult patients with acute exacerbation of chronic obstructive pulmonary disease (AE-COPD.Methods: We retrospectively tested 212 COPD patients, 141 (66.5% with AE-COPD and 71 (33.5% with stable disease, of whom nasal lavage and induced sputum had been obtained for the presence of HBoV deoxyribonucleic acid (DNA. The specificity of positive polymerase chain reaction results was confirmed by sequencing.Results: Two hundred two of 212 patients for whom PCR results were available both for nasal lavage and induced sputum samples were eligible for data analysis. HBoV DNA was detected in three patients (1.5%. Of those, only one patient had AE-COPD. Thus, the frequency of HBoV infection demonstrated to be low in both AE-COPD (0.8% and stable COPD (2.9%. HBoV was found in two sputum and one nasal lavage sample in different patients, respectively. Sequencing revealed >99% sequence identity with the reference strain.Conclusion: HBoV detection was infrequent. Since we detected HBoV in both upper and lower respiratory tract specimens and in AE-COPD as well as stable disease, a major role of HBoV infection in adults with AE-COPD is unlikely

  2. 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.

  3. Some recent multi-frequency electron paramagnetic resonance results on systems relevant for dosimetry and dating.

    Science.gov (United States)

    Callens, F; Vanhaelewyn, G; Matthys, P

    2002-04-01

    Electron Paramagnetic Resonance (EPR) applications like e.g. EPR dosimetry and dating, are usually performed at X-band frequencies because of practical reasons (cost, sample size, etc.). However, it is increasingly recognized that the radiation-induced EPR signals are strongly composite, what might affect dose/age estimates. A few recent examples from both the dosimetry and dating field, illustrating the problems, will be presented. The involved spectra are mainly due to carbonate-derived radicals (CO2-, CO3(3-), etc.). Measurements at higher microwave frequencies are often recommended to improve the insight into the spectra and/or the practical signal quantification. Recent results at Q- and W-band frequencies will show that a multi-frequency approach indeed opens many interesting perspectives in this field but also that each frequency may have specific (dis)advantages depending on the EPR probe and application involved. The discussion will concern carbonate-containing apatite single crystals, shells, modern and fossil tooth enamel.

  4. 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.

  5. 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

  6. 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

  7. Astrophysical relevance of γ transition energies

    International Nuclear Information System (INIS)

    Rauscher, Thomas

    2008-01-01

    The relevant γ energy range is explicitly identified where additional γ strength must be located to have an impact on astrophysically relevant reactions. It is shown that folding the energy dependences of the transmission coefficients and the level density leads to maximal contributions for γ energies of 2≤E γ ≤4 unless quantum selection rules allow isolated states to contribute. Under this condition, electric dipole transitions dominate. These findings allow us to more accurately judge the relevance of modifications of the γ strength for astrophysics

  8. 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...

  9. Modulation of the mirror system by social relevance.

    Science.gov (United States)

    Kilner, James M; Marchant, Jennifer L; Frith, Chris D

    2006-09-01

    When we observe the actions of others, certain areas of the brain are activated in a similar manner as to when we perform the same actions ourselves. This 'mirror system' includes areas in the ventral premotor cortex and the inferior parietal lobule. Experimental studies suggest that action observation automatically elicits activity in the observer, which precisely mirrors the activity observed. In this case we would expect this activity to be independent of observer's viewpoint. Here we use whole-head magnetoencephalography (MEG) to record cortical activity of human subjects whilst they watched a series of videos of an actor making a movement recorded from different viewpoints. We show that one cortical response to action observation (oscillatory activity in the 7-12 Hz frequency range) is modulated by the relationship between the observer and the actor. We suggest that this modulation reflects a mechanism that filters information into the 'mirror system', allowing only socially relevant information to pass.

  10. [Incidence and follow-up characteristics of neurologically relevant psychogenic symptoms].

    Science.gov (United States)

    Franz, M; Schellberg, D; Reister, G; Schepank, H

    1993-06-01

    The author reports on the prevalence and stability of the course of neurologically relevant psychogenic symptoms as well as their dependence on age and sex. Altogether 240 probands from the Mannheim Cohort Study on the epidemiology of psychogenic disorders were examined for psychogenic impairment over a 10-year period during three investigation periods. On the whole, seven neurologically relevant groups of symptoms (headache, lumbar and cervical vertebral complaints, non-systematic vertigo, functional hyperkinesia, functional paresis, sleep disturbances, concentration disturbances) differ clearly in frequency, characteristics of the course and clinical relevance.

  11. 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.

  12. 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.

  13. 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.

  14. 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

  15. 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

  16. 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

  17. 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.

  18. 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.

  19. 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.

  20. 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).

  1. 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.

  2. 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.)

  3. 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

  4. 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.

  5. Comparison of High, Intermediate, and Low Frequency Shock Wave Lithotripsy for Urinary Tract Stone Disease: Systematic Review and Network Meta-Analysis.

    Science.gov (United States)

    Kang, Dong Hyuk; Cho, Kang Su; Ham, Won Sik; Lee, Hyungmin; Kwon, Jong Kyou; Choi, Young Deuk; Lee, Joo Yong

    2016-01-01

    To perform a systematic review and network meta-analysis of randomized controlled trials (RCTs) to determine the optimal shock wave lithotripsy (SWL) frequency range for treating urinary stones, i.e., high-frequency (100-120 waves/minute), intermediate-frequency (80-90 waves/minute), and low-frequency (60-70 waves/minute) lithotripsy. Relevant RCTs were identified from electronic databases for meta-analysis of SWL success and complication rates. Using pairwise and network meta-analyses, comparisons were made by qualitative and quantitative syntheses. Outcome variables are provided as odds ratios (ORs) with 95% confidence intervals (CIs). Thirteen articles were included in the qualitative and quantitative synthesis using pairwise and network meta-analyses. On pairwise meta-analyses, comparable inter-study heterogeneity was observed for the success rate. On network meta-analyses, the success rates of low- (OR 2.2; 95% CI 1.5-2.6) and intermediate-frequency SWL (OR 2.5; 95% CI 1.3-4.6) were higher than high-frequency SWL. Forest plots from the network meta-analysis showed no significant differences in the success rate between low-frequency SWL versus intermediate-frequency SWL (OR 0.87; 95% CI 0.51-1.7). There were no differences in complication rate across different SWL frequency ranges. By rank-probability testing, intermediate-frequency SWL was ranked highest for success rate, followed by low-frequency and high-frequency SWL. Low-frequency SWL was also ranked highest for low complication rate, with high- and intermediate-frequency SWL ranked lower. Intermediate- and low-frequency SWL have better treatment outcomes than high-frequency SWL when considering both efficacy and complication.

  6. 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.

  7. 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)

  8. 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

  9. 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...

  10. 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

  11. Bootstrapping agency: How control-relevant information affects motivation.

    Science.gov (United States)

    Karsh, Noam; Eitam, Baruch; Mark, Ilya; Higgins, E Tory

    2016-10-01

    How does information about one's control over the environment (e.g., having an own-action effect) influence motivation? The control-based response selection framework was proposed to predict and explain such findings. Its key tenant is that control relevant information modulates both the frequency and speed of responses by determining whether a perceptual event is an outcome of one's actions or not. To test this framework empirically, the current study examines whether and how temporal and spatial contiguity/predictability-previously established as being important for one's sense of agency-modulate motivation from control. In 5 experiments, participants responded to a cue, potentially triggering a perceptual effect. Temporal (Experiments 1a-c) and spatial (Experiments 2a and b) contiguity/predictability between actions and their potential effects were experimentally manipulated. The influence of these control-relevant factors was measured, both indirectly (through their effect on explicit judgments of agency) and directly on response time and response frequency. The pattern of results was highly consistent with the control-based response selection framework in suggesting that control relevant information reliably modulates the impact of "having an effect" on different levels of action selection. We discuss the implications of this study for the notion of motivation from control and for the empirical work on the sense of agency. (PsycINFO Database Record (c) 2016 APA, all rights reserved).

  12. 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.

  13. 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.

  14. Dynamic modulation of epileptic high frequency oscillations by the phase of slower cortical rhythms.

    Science.gov (United States)

    Ibrahim, George M; Wong, Simeon M; Anderson, Ryan A; Singh-Cadieux, Gabrielle; Akiyama, Tomoyuki; Ochi, Ayako; Otsubo, Hiroshi; Okanishi, Tohru; Valiante, Taufik A; Donner, Elizabeth; Rutka, James T; Snead, O Carter; Doesburg, Sam M

    2014-01-01

    Pathological high frequency oscillations (pHFOs) have been proposed to be robust markers of epileptic cortex. Oscillatory activity below this frequency range has been shown to be modulated by phase of lower frequency oscillations. Here, we tested the hypothesis that dynamic cross-frequency interactions involving pHFOs are concentrated within the epileptogenic cortex. Intracranial electroencephalographic recordings from 17 children with medically-intractable epilepsy secondary to focal cortical dysplasia were obtained. A time-resolved analysis was performed to determine topographic concentrations and dynamic changes in cross-frequency amplitude-to-phase coupling (CFC). CFC between pHFOs and the phase of theta and alpha rhythms was found to be significantly elevated in the seizure-onset zone compared to non-epileptic regions (pfrequency oscillations at which pHFO amplitudes were maximal was inconsistent at seizure initiation, yet consistently at the trough of the low frequency rhythm at seizure termination. Amplitudes of pHFOs were most significantly modulated by the phase of alpha-band oscillations (p<0.01). These results suggest that increased CFC between pHFO amplitude and alpha phase may constitute a marker of epileptogenic brain areas and may be relevant for understanding seizure dynamics. Copyright © 2013 Elsevier Inc. All rights reserved.

  15. Bayesian Frequency Domain Identification of LTI Systems with OBFs kernels

    NARCIS (Netherlands)

    Darwish, M.A.H.; Lataire, J.P.G.; Tóth, R.

    2017-01-01

    Regularised Frequency Response Function (FRF) estimation based on Gaussian process regression formulated directly in the frequency-domain has been introduced recently The underlying approach largely depends on the utilised kernel function, which encodes the relevant prior knowledge on the system

  16. Indoor measurements of sound at low frequencies

    DEFF Research Database (Denmark)

    Pedersen, Steffen; Møller, Henrik; Persson-Waye, Kerstin

    2006-01-01

    Due to standing waves, the sound pressure level within a room may vary as much as 20-30 dB with low-frequency tonal noise, somewhat less with noise bands. For assessment of annoyance from low-frequency noise it is relevant to measure a level close to the highest level of the room, rather than a r...

  17. 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.

  18. Low-frequency connectivity is associated with mild traumatic brain injury

    Directory of Open Access Journals (Sweden)

    B.T. Dunkley

    2015-01-01

    Full Text Available Mild traumatic brain injury (mTBI occurs from a closed-head impact. Often referred to as concussion, about 20% of cases complain of secondary psychological sequelae, such as disorders of attention and memory. Known as post-concussive symptoms (PCS, these problems can severely disrupt the patient's quality of life. Changes in local spectral power, particularly low-frequency amplitude increases and/or peak alpha slowing have been reported in mTBI, but large-scale connectivity metrics based on inter-regional amplitude correlations relevant for integration and segregation in functional brain networks, and their association with disorders in cognition and behaviour, remain relatively unexplored. Here, we used non-invasive neuroimaging with magnetoencephalography to examine functional connectivity in a resting-state protocol in a group with mTBI (n = 20, and a control group (n = 21. We observed a trend for atypical slow-wave power changes in subcortical, temporal and parietal regions in mTBI, as well as significant long-range increases in amplitude envelope correlations among deep-source, temporal, and frontal regions in the delta, theta, and alpha bands. Subsequently, we conducted an exploratory analysis of patterns of connectivity most associated with variability in secondary symptoms of mTBI, including inattention, anxiety, and depression. Differential patterns of altered resting state neurophysiological network connectivity were found across frequency bands. This indicated that multiple network and frequency specific alterations in large scale brain connectivity may contribute to overlapping cognitive sequelae in mTBI. In conclusion, we show that local spectral power content can be supplemented with measures of correlations in amplitude to define general networks that are atypical in mTBI, and suggest that certain cognitive difficulties are mediated by disturbances in a variety of alterations in network interactions which are differentially

  19. 47 CFR 87.475 - Frequencies.

    Science.gov (United States)

    2010-10-01

    ... with simultaneous radiotelephone channels and their associated glide path station frequency from the...) VHF omni-range (VOR) stations are to be assigned frequencies in the 112.050-117.950 MHz band (50 kHz channel spacing) and the following frequencies in the 108-112 MHz band: 108.200 108.250 108.400 108.450...

  20. Essays on high frequency financial econometrics

    NARCIS (Netherlands)

    Yang, X.

    2015-01-01

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

  1. Nanoelectromechanical systems: Nanodevice motion at microwave frequencies

    Science.gov (United States)

    Henry Huang, Xue Ming; Zorman, Christian A.; Mehregany, Mehran; Roukes, Michael L.

    2003-01-01

    It has been almost forgotten that the first computers envisaged by Charles Babbage in the early 1800s were mechanical and not electronic, but the development of high-frequency nanoelectromechanical systems is now promising a range of new applications, including sensitive mechanical charge detectors and mechanical devices for high-frequency signal processing, biological imaging and quantum measurement. Here we describe the construction of nanodevices that will operate with fundamental frequencies in the previously inaccessible microwave range (greater than 1 gigahertz). This achievement represents a significant advance in the quest for extremely high-frequency nanoelectromechanical systems.

  2. Measurements of crossed-field demagnetisation rate of trapped field magnets at high frequencies and below 77 K

    Science.gov (United States)

    Baskys, A.; Patel, A.; Glowacki, B. A.

    2018-06-01

    Design requirements of the next generation of electric aircraft place stringent requirements on the power density required from electric motors. A future prototype planned in the scope of the European project ‘Advanced Superconducting Motor Experimental Demonstrator’ (ASuMED) considers a permanent magnet synchronous motor, where the conventional ferromagnets are replaced with superconducting trapped field magnets, which promise higher flux densities and thus higher output power without adding weight. Previous work has indicated that stacks of tape show lower cross-field demagnetisation rates to bulk (RE)BCO whilst retaining similar performance for their size, however the crossed-field demagnetisation rate has not been studied in the temperature, the magnetic field and frequency range that are relevant for the operational prototype motor. This work investigates crossed-field demagnetisation in 2G high temperature superconducting stacks at temperatures below 77 K and a frequency range above 10 Hz. This information is crucial in developing designs and determining operational time before re-magnetisation could be required.

  3. Relationships between electroencephalographic spectral peaks across frequency bands

    Directory of Open Access Journals (Sweden)

    Sacha Jennifer Van Albada

    2013-03-01

    Full Text Available The degree to which electroenencephalographic (EEG spectral peaks are independent, and the relationships between their frequencies have been debated. A novel fitting method was used to determine peak parameters in the range 2–35 Hz from a large sample of eyes-closed spectra, and their interrelationships were investigated. Findings were compared with a mean-field model of thalamocortical activity, which predicts near-harmonic relationships between peaks. The subject set consisted of 1424 healthy subjects from the Brain Resource International Database. Peaks in the theta range occurred on average near half the alpha peak frequency, while peaks in the beta range tended to occur near twice and three times the alpha peak frequency on an individual-subject basis. Moreover, for the majority of subjects, alpha peak frequencies were significantly positively correlated with frequencies of peaks in the theta and low and high beta ranges. Such a harmonic progression agrees semiquantitatively with theoretical predictions from the mean-field model. These findings indicate a common or analogous source for different rhythms, and help to define appropriate individual frequency bands for peak identification.

  4. Relationships between Electroencephalographic Spectral Peaks Across Frequency Bands

    Science.gov (United States)

    van Albada, S. J.; Robinson, P. A.

    2013-01-01

    The degree to which electroencephalographic spectral peaks are independent, and the relationships between their frequencies have been debated. A novel fitting method was used to determine peak parameters in the range 2–35 Hz from a large sample of eyes-closed spectra, and their interrelationships were investigated. Findings were compared with a mean-field model of thalamocortical activity, which predicts near-harmonic relationships between peaks. The subject set consisted of 1424 healthy subjects from the Brain Resource International Database. Peaks in the theta range occurred on average near half the alpha peak frequency, while peaks in the beta range tended to occur near twice and three times the alpha peak frequency on an individual-subject basis. Moreover, for the majority of subjects, alpha peak frequencies were significantly positively correlated with frequencies of peaks in the theta and low and high beta ranges. Such a harmonic progression agrees semiquantitatively with theoretical predictions from the mean-field model. These findings indicate a common or analogous source for different rhythms, and help to define appropriate individual frequency bands for peak identification. PMID:23483663

  5. Dynamic range meter for radiofrequency amplifiers

    Directory of Open Access Journals (Sweden)

    Drozd S. S.

    2009-04-01

    Full Text Available The new measurement setup having increased on 20…30 dB the own dynamic range in comparison with the standard circuit of the dynamic range meter is offered and the rated value of an error bringing by setup in the worst case does not exceed ± 2,8 dB. The measurement setup can be applied also to determinate levels of intermodulation components average power amplifiers and powerful amplifiers of a low-frequency at replacement of the quartz filter on meeting low-frequency the LC-filter and the spectrum analyzer.

  6. Spatial Cognition and Range Use in Free-Range Laying Hens.

    Science.gov (United States)

    Campbell, Dana L M; Talk, Andrew C; Loh, Ziyang A; Dyall, Tim R; Lee, Caroline

    2018-02-08

    Radio-frequency identification tracking shows individual free-range laying hens vary in range use, with some never going outdoors. The range is typically more environmentally complex, requiring navigation to return to the indoor resources. Outdoor-preferring hens may have improved spatial abilities compared to indoor-preferring hens. Experiment 1 tested 32 adult ISA Brown hens in a T-maze learning task that showed exclusively-indoor birds were slowest to reach the learning success criterion ( p 0.05), the age that coincided with the onset of lay. Enriched birds that were faster to learn the maze task showed more range visits in the first 4 weeks of range access. Enriched and non-enriched birds showed no differences in telencephalon or hippocampal volume ( p > 0.05). Fear may reduce spatial abilities but further testing with more pen replicates per early rearing treatments would improve our understanding of the relationship between spatial cognitive abilities and range use.

  7. Low frequency energy scavenging using sub-wave length scale acousto-elastic metamaterial

    Directory of Open Access Journals (Sweden)

    Riaz U. Ahmed

    2014-11-01

    Full Text Available This letter presents the possibility of energy scavenging (ES utilizing the physics of acousto-elastic metamaterial (AEMM at low frequencies (<∼3KHz. It is proposed to use the AEMM in a dual mode (Acoustic Filter and Energy Harvester, simultaneously. AEMM’s are typically reported for filtering acoustic waves by trapping or guiding the acoustic energy, whereas this letter shows that the dynamic energy trapped inside the soft constituent (matrix of metamaterials can be significantly harvested by strategically embedding piezoelectric wafers in the matrix. With unit cell AEMM model, we experimentally asserted that at lower acoustic frequencies (< ∼3 KHz, maximum power in the micro Watts (∼35µW range can be generated, whereas, recently reported phononic crystal based metamaterials harvested only nano Watt (∼30nW power against 10KΩ resistive load. Efficient energy scavengers at low acoustic frequencies are almost absent due to large required size relevant to the acoustic wavelength. Here we report sub wave length scale energy scavengers utilizing the coupled physics of local, structural and matrix resonances. Upon validation of the argument through analytical, numerical and experimental studies, a multi-frequency energy scavenger (ES with multi-cell model is designed with varying geometrical properties capable of scavenging energy (power output from ∼10µW – ∼90µW between 0.2 KHz and 1.5 KHz acoustic frequencies.

  8. Low-frequency ultrasound increases non-viral gene transfer to the mouse lung.

    Science.gov (United States)

    Xenariou, Stefania; Liang, Hai-Dong; Griesenbach, Uta; Zhu, Jie; Farley, Raymond; Somerton, Lucinda; Singh, Charanjit; Jeffery, Peter K; Scheule, Ronald K; Cheng, Seng H; Geddes, Duncan M; Blomley, Martin; Alton, Eric W F W

    2010-01-01

    The aim of the study was to assess if low-frequency ultrasound (US), in the range of 30-35 kHz, increases non-viral gene transfer to the mouse lung. US is greatly attenuated in the lung due to large energy losses at the air/tissue interfaces. The advantages of low-frequency US, compared with high-frequency US are: (i) increased cavitation (responsible for the formation of transient pores in the cell membrane) and (ii) reduced energy losses during lung penetration. Cationic lipid GL67/plasmid DNA (pDNA), polyethylenimine (PEI)/pDNA and naked pDNA were delivered via intranasal instillation and the animals were then exposed to US (sonoporation) at 0.07 or 0.1 MPa for 10 min. Under these conditions, US did not enhance GL67 or PEI-mediated transfection. It did, however, increase naked pDNA gene transfer by approximately 4 folds. Importantly, this was achieved in the absence of microbubbles, which are crucial for the commonly used high-frequency (1 MHz) sonoporation but may not be able to withstand nebulization in a clinically relevant setup. Lung hemorrhage was also assessed and shown to increase with US pressure in a dose-dependent manner. We have thus, established that low-frequency US can enhance lung gene transfer with naked pDNA and this enhancement is more effective than the previously reported 1 MHz US.

  9. Radar network communication through sensing of frequency hopping

    Science.gov (United States)

    Dowla, Farid; Nekoogar, Faranak

    2013-05-28

    In one embodiment, a radar communication system includes a plurality of radars having a communication range and being capable of operating at a sensing frequency and a reporting frequency, wherein the reporting frequency is different than the sensing frequency, each radar is adapted for operating at the sensing frequency until an event is detected, each radar in the plurality of radars has an identification/location frequency for reporting information different from the sensing frequency, a first radar of the radars which senses the event sends a reporting frequency corresponding to its identification/location frequency when the event is detected, and all other radars in the plurality of radars switch their reporting frequencies to match the reporting frequency of the first radar upon detecting the reporting frequency switch of a radar within the communication range. In another embodiment, a method is presented for communicating information in a radar system.

  10. Frequency modulation drive for a piezoelectric motor

    Science.gov (United States)

    Mittas, Anthony

    2001-01-01

    A piezoelectric motor has peak performance at a specific frequency f.sub.1 that may vary over a range of frequencies. A drive system is disclosed for operating such a motor at peak performance without feedback. The drive system consists of the motor and an ac source connected to power the motor, the ac source repeatedly generating a frequency over a range from f.sub.1 -.DELTA.x to f.sub.1 +.DELTA.y.

  11. How Metastrategic Considerations Influence the Selection of Frequency Estimation Strategies

    Science.gov (United States)

    Brown, Norman R.

    2008-01-01

    Prior research indicates that enumeration-based frequency estimation strategies become increasingly common as memory for relevant event instances improves and that moderate levels of context memory are associated with moderate rates of enumeration [Brown, N. R. (1995). Estimation strategies and the judgment of event frequency. Journal of…

  12. Initiating events frequency determination

    International Nuclear Information System (INIS)

    Simic, Z.; Mikulicic, V.; Vukovic, I.

    2004-01-01

    The paper describes work performed for the Nuclear Power Station (NPS). Work is related to the periodic initiating events frequency update for the Probabilistic Safety Assessment (PSA). Data for all relevant NPS initiating events (IE) were reviewed. The main focus was on events occurring during most recent operating history (i.e., last four years). The final IE frequencies were estimated by incorporating both NPS experience and nuclear industry experience. Each event was categorized according to NPS individual plant examination (IPE) initiating events grouping approach. For the majority of the IE groups, few, or no events have occurred at the NPS. For those IE groups with few or no NPS events, the final estimate was made by means of a Bayesian update with general nuclear industry values. Exceptions are rare loss-of-coolant-accidents (LOCA) events, where evaluation of engineering aspects is used in order to determine frequency.(author)

  13. ANALISYS OF FRACTIONAL-N FREQUENCY SYNTHESIZERS

    Directory of Open Access Journals (Sweden)

    Boris I. Shakhtarin

    2018-01-01

    Full Text Available Modern information and control systems cannot be imagined without synchronization subsystems. These are the basic elements that provide tracking of the frequency and phase of reference and information signals, the evaluation of information parameters, and the synthesis of reference and clock signals. Frequency synthesizers (FS are widely used due to the high speed of frequency setting, a wide range of frequency grids and minimal phase noise in the operating frequency range. Since with the mass appearance of specialized microprocessors and with the improvement of automatic design systems, the feasibility and repeatability of products has become simpler, digital FS are increasingly being used. The most widely used are FS with a frequency divider on digital elements, which serves to convert the signal of a reference oscillator and a controlled generator. For FS using a divisor with an integer division factor in the feedback loop, there are a number of limitations, such as the lower frequency of the FS and the frequency step of the FS. To solve this problem, divisors with fractional-variable division factors in the feedback loop are used, which allow to obtain the required range and the grid frequency step of the FS. The methods of improving the quality of spectral and dynamic characteristics of digital synthesizers in a given band of frequency detuning are analyzed. The principles of the FS operation with a divisor with a fractionalvariable fission coefficient are described, and structural schemes are given. The results of imitation simulation in the Simulink system of the software package MATLAB of frequency synthesizers with a divisor with a fractional-variable fission factor implemented in various ways are presented, and a comparative analysis of the spectral characteristics of the obtained models is carried out. 

  14. radio frequency based radio frequency based water level monitor

    African Journals Online (AJOL)

    eobe

    ABSTRACT. This paper elucidates a radio frequency (RF) based transmission and reception system used to remotely monitor and .... range the wireless can cover but in this prototype, it ... power supply to the system, the sensed water level is.

  15. Frequency Hopping Transceiver Multiplexer

    Science.gov (United States)

    1983-03-01

    ATC 17 ULR IHQ OCLI CPCTR ULTRA HIGH "OQS" UP TO 4X HIGHER THAN BEST INDUS- TRY STANDARD (ATC 100). MICROWAVE POWER, CURRENT. AND 0 RATINGS5...Q"W were assigned to element (FigC-2); which will be modelled into the transformer previously ment td . The center frequencies, "Q", frequency range...of the TD 1288 system. Temperature stability, change with time or storage. Flexure Frequency, or non-linear change over bandwidth. * Humidity

  16. 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.

  17. Auditory filters at low-frequencies

    DEFF Research Database (Denmark)

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

    2009-01-01

    -ear transfer function), the asymmetry of the auditory filter changed from steeper high-frequency slopes at 1000 Hz to steeper low-frequency slopes below 100 Hz. Increasing steepness at low-frequencies of the middle-ear high-pass filter is thought to cause this effect. The dynamic range of the auditory filter...... was found to steadily decrease with decreasing center frequency. Although the observed decrease in filter bandwidth with decreasing center frequency was only approximately monotonic, the preliminary data indicates the filter bandwidth does not stabilize around 100 Hz, e.g. it still decreases below...

  18. Long-range correlated percolation

    International Nuclear Information System (INIS)

    Weinrib, A.

    1984-01-01

    This paper is a study of the percolation problem with long-range correlations in the site or bond occupations. An extension of the Harris criterion for the relevance of the correlations is derived for the case that the correlations decay as x/sup -a/ for large distances x. For a d the correlations are relevant if dν-2<0. Applying this criterion to the behavior that results when the correlations are relevant, we argue that the new behavior will have ν/sub long/ = 2/a. It is shown that the correlated bond percolation problem is equivalent to a q-state Potts model with quenched disorder in the limit q→1. With the use of this result, a renormalization-group study of the problem is presented, expanding in epsilon = 6-d and in delta = 4-a. In addition to the normal percolation fixed point, we find a new long-range fixed point. The crossover to this new fixed point follows the extended Harris criterion, and the fixed point has exponents ν/sub long/ = 2/a (as predicted) and eta/sub long/ = (1/11)(delta-epsilon). Finally, several results on the percolation properties of the Ising model at its critical point are shown to be in agreement with the predictions of this paper

  19. Spectrum Management Guidelines for National and Service Test and Training Ranges

    Science.gov (United States)

    2017-07-12

    Frequency Management Group RCC 700-17 SPECTRUM MANAGEMENT GUIDELINES FOR NATIONAL AND SERVICE TEST AND TRAINING RANGES DISTRIBUTION...left blank. DOCUMENT 700-01 SPECTRUM MANAGEMENT GUIDELINES FOR NATIONAL AND SERVICE TEST AND TRAINING RANGES July 2017...Prepared by RANGE COMMANDERS COUNCIL FREQUENCY MANAGEMENT GROUP Published by Secretariat Range Commanders Council U.S. Army White

  20. Microwave Frequency Multiplier

    Science.gov (United States)

    Velazco, J. E.

    2017-02-01

    High-power microwave radiation is used in the Deep Space Network (DSN) and Goldstone Solar System Radar (GSSR) for uplink communications with spacecraft and for monitoring asteroids and space debris, respectively. Intense X-band (7.1 to 8.6 GHz) microwave signals are produced for these applications via klystron and traveling-wave microwave vacuum tubes. In order to achieve higher data rate communications with spacecraft, the DSN is planning to gradually furnish several of its deep space stations with uplink systems that employ Ka-band (34-GHz) radiation. Also, the next generation of planetary radar, such as Ka-Band Objects Observation and Monitoring (KaBOOM), is considering frequencies in the Ka-band range (34 to 36 GHz) in order to achieve higher target resolution. Current commercial Ka-band sources are limited to power levels that range from hundreds of watts up to a kilowatt and, at the high-power end, tend to suffer from poor reliability. In either case, there is a clear need for stable Ka-band sources that can produce kilowatts of power with high reliability. In this article, we present a new concept for high-power, high-frequency generation (including Ka-band) that we refer to as the microwave frequency multiplier (MFM). The MFM is a two-cavity vacuum tube concept where low-frequency (2 to 8 GHz) power is fed into the input cavity to modulate and accelerate an electron beam. In the second cavity, the modulated electron beam excites and amplifies high-power microwaves at a frequency that is a multiple integer of the input cavity's frequency. Frequency multiplication factors in the 4 to 10 range are being considered for the current application, although higher multiplication factors are feasible. This novel beam-wave interaction allows the MFM to produce high-power, high-frequency radiation with high efficiency. A key feature of the MFM is that it uses significantly larger cavities than its klystron counterparts, thus greatly reducing power density and arcing

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

    Science.gov (United States)

    Li, Ruixiao; Li, Kun; Zhao, Changming

    2018-01-01

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

  2. Dipole, quadrupole, and octupole terms in the long-range hyperfine frequency shift for hydrogen in the presence of inert gases

    International Nuclear Information System (INIS)

    Greenwood, W.G.; Tang, K.T.

    1987-01-01

    The R -6 , R -8 , and R -10 terms in the long-range expansion for the hyperfine frequency shift are calculated for hydrogen in the presence of He, Ne, Ar, Kr, and Xe. The R -6 terms are based on the dipole oscillator strength sums. For helium, the R -8 and R -10 terms are based on quadrupole and octupole oscillator strength sums. For the heavier inert gases, the results for the R -8 and R -10 terms are obtained from the sum rules and the static polarizabilities. Upper bounds are also determined for the R -8 and R -10 terms

  3. Characterizing the attenuation of coaxial and rectangular microwave-frequency waveguides at cryogenic temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Kurpiers, Philipp; Walter, Theodore; Magnard, Paul; Salathe, Yves; Wallraff, Andreas [ETH Zuerich, Department of Physics, Zuerich (Switzerland)

    2017-12-15

    Low-loss waveguides are required for quantum communication at distances beyond the chip-scale for any low-temperature solid-state implementation of quantum information processors. We measure and analyze the attenuation constant of commercially available microwave-frequency waveguides down to millikelvin temperatures and single photon levels. More specifically, we characterize the frequency-dependent loss of a range of coaxial and rectangular microwave waveguides down to 0.005 dB/m using a resonant-cavity technique. We study the loss tangent and relative permittivity of commonly used dielectric waveguide materials by measurements of the internal quality factors and their comparison with established loss models. The results of our characterization are relevant for accurately predicting the signal levels at the input of cryogenic devices, for reducing the loss in any detection chain, and for estimating the heat load induced by signal dissipation in cryogenic systems. (orig.)

  4. Frequency and Prognostic Relevance of FLT3 Mutations in Saudi Acute Myeloid Leukemia Patients

    Directory of Open Access Journals (Sweden)

    Ghaleb Elyamany

    2014-01-01

    Full Text Available The Fms-like tyrosine kinase-3 (FLT3 is a receptor tyrosine kinase that plays a key role in cell survival, proliferation, and differentiation of hematopoietic stem cells. Mutations of FLT3 were first described in 1997 and account for the most frequent molecular mutations in acute myeloid leukemia (AML. AML patients with FLT3 internal tandem duplication (ITD mutations have poor cure rates the prognostic significance of point mutations; tyrosine kinase domain (TKD is still unclear. We analyzed the frequency of FLT3 mutations (ITD and D835 in patients with AML at diagnosis; no sufficient data currently exist regarding FLT3 mutations in Saudi AML patients. This study was aimed at evaluating the frequency of FLT3 mutations in patients with AML and its significance for prognosis. The frequency of FLT3 mutations in our study (18.56% was lower than many of the reported studies, FLT3-ITD mutations were observed in 14.4%, and FLT3-TKD in 4.1%, of 97 newly diagnosed AML patients (82 adult and 15 pediatric. Our data show significant increase of FLT3 mutations in male more than female (13 male, 5 female. Our results support the view that FLT3-ITD mutation has strong prognostic factor in AML patients and is associated with high rate of relapse, and high leucocytes and blast count at diagnosis and relapse.

  5. Frequency adjustable MEMS vibration energy harvester

    Science.gov (United States)

    Podder, P.; Constantinou, P.; Amann, A.; Roy, S.

    2016-10-01

    Ambient mechanical vibrations offer an attractive solution for powering the wireless sensor nodes of the emerging “Internet-of-Things”. However, the wide-ranging variability of the ambient vibration frequencies pose a significant challenge to the efficient transduction of vibration into usable electrical energy. This work reports the development of a MEMS electromagnetic vibration energy harvester where the resonance frequency of the oscillator can be adjusted or tuned to adapt to the ambient vibrational frequency. Micro-fabricated silicon spring and double layer planar micro-coils along with sintered NdFeB micro-magnets are used to construct the electromagnetic transduction mechanism. Furthermore, another NdFeB magnet is adjustably assembled to induce variable magnetic interaction with the transducing magnet, leading to significant change in the spring stiffness and resonance frequency. Finite element analysis and numerical simulations exhibit substantial frequency tuning range (25% of natural resonance frequency) by appropriate adjustment of the repulsive magnetic interaction between the tuning and transducing magnet pair. This demonstrated method of frequency adjustment or tuning have potential applications in other MEMS vibration energy harvesters and micromechanical oscillators.

  6. Frequency adjustable MEMS vibration energy harvester

    International Nuclear Information System (INIS)

    Podder, P; Constantinou, P; Roy, S; Amann, A

    2016-01-01

    Ambient mechanical vibrations offer an attractive solution for powering the wireless sensor nodes of the emerging “Internet-of-Things”. However, the wide-ranging variability of the ambient vibration frequencies pose a significant challenge to the efficient transduction of vibration into usable electrical energy. This work reports the development of a MEMS electromagnetic vibration energy harvester where the resonance frequency of the oscillator can be adjusted or tuned to adapt to the ambient vibrational frequency. Micro-fabricated silicon spring and double layer planar micro-coils along with sintered NdFeB micro-magnets are used to construct the electromagnetic transduction mechanism. Furthermore, another NdFeB magnet is adjustably assembled to induce variable magnetic interaction with the transducing magnet, leading to significant change in the spring stiffness and resonance frequency. Finite element analysis and numerical simulations exhibit substantial frequency tuning range (25% of natural resonance frequency) by appropriate adjustment of the repulsive magnetic interaction between the tuning and transducing magnet pair. This demonstrated method of frequency adjustment or tuning have potential applications in other MEMS vibration energy harvesters and micromechanical oscillators. (paper)

  7. Frequency-dependent ultrasound-induced transformation in E. coli.

    Science.gov (United States)

    Deeks, Jeremy; Windmill, James; Agbeze-Onuma, Maduka; Kalin, Robert M; Argondizza, Peter; Knapp, Charles W

    2014-12-01

    Ultrasound-enhanced gene transfer (UEGT) is continuing to gain interest across many disciplines; however, very few studies investigate UEGT efficiency across a range of frequencies. Using a variable frequency generator, UEGT was tested in E. coli at six ultrasonic frequencies. Results indicate frequency can significantly influence UEGT efficiency positively and negatively. A frequency of 61 kHz improved UEGT efficiency by ~70 % higher, but 99 kHz impeded UEGT to an extent worse than no ultrasound exposure. The other four frequencies (26, 133, 174, and 190 kHz) enhanced transformation compared to no ultrasound, but efficiencies did not vary. The influence of frequency on UEGT efficiency was observed across a range of operating frequencies. It is plausible that frequency-dependent dynamics of mechanical and chemical energies released during cavitational-bubble collapse (CBC) are responsible for observed UEGT efficiencies.

  8. Improved optical ranging for space based gravitational wave detection

    International Nuclear Information System (INIS)

    Sutton, Andrew J; Shaddock, Daniel A; McKenzie, Kirk; Ware, Brent; De Vine, Glenn; Spero, Robert E; Klipstein, W

    2013-01-01

    The operation of 10 6  km scale laser interferometers in space will permit the detection of gravitational waves at previously unaccessible frequency regions. Multi-spacecraft missions, such as the Laser Interferometer Space Antenna (LISA), will use time delay interferometry to suppress the otherwise dominant laser frequency noise from their measurements. This is accomplished by performing sub-sample interpolation of the optical phase measurements recorded at each spacecraft for synchronization and cancellation of the otherwise dominant laser frequency noise. These sub-sample interpolation time shifts are dependent upon the inter-spacecraft range and will be measured using a pseudo-random noise ranging modulation upon the science laser. One limit to the ranging performance is mutual interference between the outgoing and incoming ranging signals upon each spacecraft. This paper reports on the demonstration of a noise cancellation algorithm which is shown to providing a factor of ∼8 suppression of the mutual interference noise. Demonstration of the algorithm in an optical test bed showed an rms ranging error of 0.06 m, improved from 0.19 m in previous results, surpassing the 1 m RMS LISA specification and potentially improving the cancellation of laser frequency noise. (paper)

  9. Development of disposable membrane hydrophones for a frequency range from 1MHz to 10MHz.

    Science.gov (United States)

    Lee, Jae-Wan; Ohm, Won-Suk; Kim, Yong-Tae

    2017-11-01

    A method for fabricating disposable membrane hydrophones is presented. The disposable hydrophones are intended for onetime use in such damaging environments as chemically contaminating fluids and high-amplitude (peak amplitude ∼100MPa) shock wave fields, where the use of commercial membrane hydrophones is not recommended. Fabrication of a hydrophone is done using only off-the-shelf components and hand tools, which translates into ease of fabrication and orders-of-magnitude reduction in unit cost. In particular, poling and sputtering, the two processes that are chiefly responsible for the cost and difficulty associated with the conventional fabrication method, are replaced with the use of pre-poled polyvinylidene fluoride (PVDF) films and polyethylene terephthalate (PET)-coated aluminum foils, respectively. Despite the seemingly crude construction, these disposable hydrophones can exhibit voltage sensitivity response that compares favorably with that of commercial hydrophones. For example, one prototype having a 2mm×2mm active element shows the end-of-cable voltage sensitivity of -270 (±1.9) dB re 1V/μPa over the frequency range of 1-10MHz. Copyright © 2017 Elsevier B.V. All rights reserved.

  10. Parametric decay below the upper hybrid frequency

    Energy Technology Data Exchange (ETDEWEB)

    Albers, E; Krause, K; Schlueter, H [Bochum Univ. (Germany, F.R.). Inst. fuer Experimentalphysik 2

    1977-03-21

    Parametric decay of the upper hybrid mode is observed between the electron cyclotron frequency and its first two harmonics. The decay products are identified as electron Bernstein and ion acoustic mode. The diagnostic results confirm the relevant dispersion relations.

  11. Accurate step-FMCW ultrasound ranging and comparison with pulse-echo signaling methods

    Science.gov (United States)

    Natarajan, Shyam; Singh, Rahul S.; Lee, Michael; Cox, Brian P.; Culjat, Martin O.; Grundfest, Warren S.; Lee, Hua

    2010-03-01

    This paper presents a method setup for high-frequency ultrasound ranging based on stepped frequency-modulated continuous waves (FMCW), potentially capable of producing a higher signal-to-noise ratio (SNR) compared to traditional pulse-echo signaling. In current ultrasound systems, the use of higher frequencies (10-20 MHz) to enhance resolution lowers signal quality due to frequency-dependent attenuation. The proposed ultrasound signaling format, step-FMCW, is well-known in the radar community, and features lower peak power, wider dynamic range, lower noise figure and simpler electronics in comparison to pulse-echo systems. In pulse-echo ultrasound ranging, distances are calculated using the transmit times between a pulse and its subsequent echoes. In step-FMCW ultrasonic ranging, the phase and magnitude differences at stepped frequencies are used to sample the frequency domain. Thus, by taking the inverse Fourier transform, a comprehensive range profile is recovered that has increased immunity to noise over conventional ranging methods. Step-FMCW and pulse-echo waveforms were created using custom-built hardware consisting of an arbitrary waveform generator and dual-channel super heterodyne receiver, providing high SNR and in turn, accuracy in detection.

  12. Two discharge modes of a repetitive nanosecond pulsed helium glow discharge under sub-atmospheric pressure in the repetition frequency range of 20 to 600 kHz

    Science.gov (United States)

    Kikuchi, Yusuke; Maegawa, Takuya; Otsubo, Akira; Nishimura, Yoshimi; Nagata, Masayoshi; Yatsuzuka, Mitsuyasu

    2018-05-01

    Two discharge modes, α and γ, of a repetitive nanosecond pulsed helium glow discharge at a gas pressure of 10 kPa in the repetition frequency range from 20 to 600 kHz are reported for the first time. The pulsed glow discharge is produced in a pair of parallel plate metal electrodes without insertion of dielectrics. The α mode discharge is volumetrically produced in the electrode gap at a low-repetition frequency, whereas the γ mode discharge is localized at the cathode surface at a high-repetition frequency. At high-repetition frequency, the time interval between voltage pulses is shorter than the lifetime of the afterglow produced by the preceding discharge. Then, the γ mode discharge is maintained by a large number of secondary electrons emitted from the cathode exposed to high-density ions and metastable helium atoms in the afterglow. In the α mode discharge with a low-repetition frequency operation, primary electrons due to gas ionization dominate the ionization process. Thus, a large discharge voltage is needed for the excitation of the α mode discharge. It is established that the bifurcation of α-γ discharge mode, accompanied by a decrease in the discharge voltage, occurs at the high-repetition frequency of ∼120 kHz.

  13. Why relevance theory is relevant for lexicography

    DEFF Research Database (Denmark)

    Bothma, Theo; Tarp, Sven

    2014-01-01

    This article starts by providing a brief summary of relevance theory in information science in relation to the function theory of lexicography, explaining the different types of relevance, viz. objective system relevance and the subjective types of relevance, i.e. topical, cognitive, situational...... that is very important for lexicography as well as for information science, viz. functional relevance. Since all lexicographic work is ultimately aimed at satisfying users’ information needs, the article then discusses why the lexicographer should take note of all these types of relevance when planning a new...... dictionary project, identifying new tasks and responsibilities of the modern lexicographer. The article furthermore discusses how relevance theory impacts on teaching dictionary culture and reference skills. By integrating insights from lexicography and information science, the article contributes to new...

  14. Resolving the range ambiguity in OFDR using digital signal processing

    International Nuclear Information System (INIS)

    Riesen, Nicolas; Lam, Timothy T-Y; Chow, Jong H

    2014-01-01

    A digitally range-gated variant of optical frequency domain reflectometry is demonstrated which overcomes the beat note ambiguity when sensing beyond a single frequency sweep. The range-gating is achieved using a spread spectrum technique involving time-stamping of the optical signal using high-frequency pseudorandom phase modulation. The reflections from different sections of fiber can then be isolated in the time domain by digitally inverting the phase modulation using appropriately-delayed copies of the pseudorandom noise code. Since the technique overcomes the range ambiguity in OFDR, it permits high sweep repetition rates without sacrificing range, thus allowing for high-bandwidth sensing over long lengths of fiber. This is demonstrated for the case of quasi-distributed sensing. (paper)

  15. Relationship between welfare and individual ranging behaviour in commercial free-range laying hens.

    Science.gov (United States)

    Larsen, H; Hemsworth, P H; Cronin, G M; Gebhardt-Henrich, S G; Smith, C L; Rault, J-L

    2018-01-24

    Laying hens housed in free-range systems have access to an outdoor range, and individual hens within a flock differ in their ranging behaviour. Whether there is a link between ranging and laying hen welfare remains unclear. We analysed the relationships between ranging by individual hens on a commercial free-range layer farm and behavioural, physiological and health measures of animal welfare. We hypothesised that hens that access the range more will be (1) less fearful in general and in response to novelty and humans, (2) have better health in terms of physical body condition and (3) have a reduced physiological stress response to behavioural tests of fear and health assessments than hens that use the range less. Using radio frequency identification tracking across two flocks, we recorded individual hens' frequency, duration and consistency of ranging. We also assessed how far hens ventured into the range based on three zones: 0 to 2.4, 2.4 to 11.4 or >11.4 m from the shed. We assessed hen welfare using a variety of measures including: tonic immobility, open field, novel object, human approach, and human avoidance (HAV) behavioural tests; stress-induced plasma corticosterone response and faecal glucocorticoid metabolites; live weight, comb colour, and beak, plumage, footpad, and keel bone condition. Range use was positively correlated with plasma corticosterone response, faecal glucocorticoid metabolites, and greater flight distance during HAV. Hens that used the range more, moved towards rather than away from the novel object more often than hens that ranged less. Distance ranged from the shed was significantly associated with comb colour and beak condition, in that hens with darker combs and more intact beaks ranged further. Overall the findings suggest that there is no strong link between outdoor range usage and laying hen welfare. Alternatively, it may be that hens that differed in their ranging behaviour showed few differences in measures of welfare because

  16. Frequency of obesity and comorbidities in medical students.

    Science.gov (United States)

    Mehmood, Yasir; Al-Swailmi, Farhan Khashim; Al-Enazi, Shehab Ahmed

    2016-01-01

    To determine the frequency of obesity disorders and their co-morbidities in medical students. This cross-sectional study was conducted in Faculty of Medicine, Northern Border University, Ar'ar, Saudi Arabia. All medical students who consented to participate were included in the study. Their relevant information was recorded on a structured proforma. Weight and height of the participants were measured using calibrated manual weighing scale and Body mass index (BMI) was calculated. The obtained results were interpreted according to classification of body weight disorders. The participants who turned out to be over-weight and obese were further assessed for hypertension, diabetes mellitus and gallstones. The collected data was analyzed using the Statistical Package for Social Science (SPSS) version 20. A total of 405 students participated in study, age range was 19-25 years. Male were 169 (41.7%) and female students were 236(58.3%). Family history of obesity was present in 34.3%. Out of 405 students, 126 were having BMI between 25 and 45.6, among them 34(8.4%) students were obese and 88 (21.7%) were overweight. Sixty two (15.3%) among them were male and 64 (15.8%) female. Fourteen (11.1%) were hypertensive and 9(7.1%) were having gall stones. The frequency of obesity among medical students was 8.4%. Increasing frequency of obesity associated with unhealthy life style needs to be controlled at national level to raise a healthy generation and to reduce burden on health economy.

  17. Incidence of milrinone blood levels outside the therapeutic range and their relevance in children after cardiac surgery for congenital heart disease.

    Science.gov (United States)

    Garcia Guerra, Gonzalo; Joffe, Ari R; Senthilselvan, Ambikaipakan; Kutsogiannis, Demetrios J; Parshuram, Christopher S

    2013-05-01

    To evaluate whether variability in milrinone blood levels (MBL) occurs during administration to critically ill children after surgical repair of congenital heart disease, and the clinical relevance of this variability. Prospective cohort study conducted in the pediatric intensive care unit of a tertiary care teaching and referral hospital. MBL were measured at three time periods after starting milrinone infusion (9-12, 18-24, 40-48 h) and at the end of the infusion. MBL were categorized as within (100-300 ng/ml) or outside the therapeutic range. Low cardiac output syndrome was defined by elevation of either lactate (>2 mmol/l) or arteriovenous oxygen difference (>30%). Five other clinical outcomes were evaluated. Regression analyses evaluated the relationships between MBL and outcomes. Sixty-three patients were included with a total of 220 MBL. Quantification of MBL was by high-performance liquid chromatography. Overall, 114 (52%) MBL were outside the therapeutic range: 78 (36%) subtherapeutic, and 36 (16%) supratherapeutic. Repeated-measures analysis found a significant association between supratherapeutic MBL and low cardiac output syndrome (p = 0.02), and supratherapeutic MBL were associated with arterial-central venous oxygen saturation difference >30% at time 3 (p = 0.007). In this cohort, nontherapeutic MBL were common. Further investigation of milrinone dosing recommendations may improve the postoperative outcomes of children.

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

    Directory of Open Access Journals (Sweden)

    V. Cuomo

    2009-07-01

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

  19. An improved broadband method to evaluate effective parameters of slab metamaterials in the microwave frequency range

    International Nuclear Information System (INIS)

    Rybin, O.; Nawaz, T.; Abbasi, T.

    2007-01-01

    An improved broadband method for determining complex effective refractive index, permittivity and permeability of an arbitrary passive metamaterial in microwave frequency range has been proposed. Evaluation of the effective parameters is realized using the reflection-transmission S-parameters obtained by simulation or experimental measurements and analytically evaluated interface reflection coefficient of the slab. Formulas for evaluation of effective permittivity and permeability which contain the square root of complex functions of S-parameters have been proposed in (1-2). But this method does not propose a way to avoid an ambiguity arising in choosing the square root branch of product of effective permittivity and permeability. Moreover the above calculation procedure requires evaluating the square root branch of function of S-parameters. Proposed way to choose the square root branch gives sometimes mistaken results. Our method is much simple as compared with the above mentioned formulas and it does not require making a choice of square root branch of complex functions of S-parameters in order to evaluate any of the parameters (refractive index, permittivity or permeability). Instead we obtain a formula for complex refractive index which is simple. On the basis of proposed model effective permittivity and permeability for rod meta-materials can be evaluated with enhanced precision and accuracy. Proposed method is easy to be implemented in engineering problems and does not require using complicated mathematical calculations. Comparison of precision of the presented method with the Nicolson-Ross techniques (1-2) has been made using the simulations for different configurations of rod meta-materials. Some discussion concerning the sensitivity of the effective parameters of meta-materials for the accuracy of the frequency dependent S -parameters is also presented in this paper. (author)

  20. Measurements with vertically viewing charge exchange analyzers during ion cyclotron range of frequencies heating in TFTR

    International Nuclear Information System (INIS)

    Kaita, R.; Hammett, G.W.; Gammel, G.; Goldston, R.J.; Medley, S.S.; Scott, S.D.; Young, K.M.

    1988-01-01

    The utility of charge exchange neutral particle analyzers for studying energetic ion distributions in high-temperature plasmas has been demonstrated in a variety of tokamak experiments. Power deposition profiles have been estimated in the Princeton large torus (PLT) from particle measurements as a function of energy and angle during heating in the ion cyclotron range of frequencies (ICRF) and extensive studies of this heating mode are planned for the upcoming operational period in the tokamak fusion test reactor (TFTR). Unlike the horizontally scanning analyzer on PLT, the TFTR system consists of vertical sightlines intersecting a poloidal cross section of the plasma. A bounce-averaged Fokker--Planck program, which includes a quasilinear operator to calculate ICRF-generated energetic ions, is used to simulate the charge exchange flux expected during fundamental hydrogen heating. These sightlines also cross the trajectory of a diagnostic neutral beam (DNB), and it may be possible to observe the fast ion tail during 3 He minority heating, if the DNB is operated in helium for double charge exchange neutralization

  1. Very-low-frequency magnetic plasma

    International Nuclear Information System (INIS)

    Pendry, J.B.; O'Brien, S.

    2002-01-01

    We show that a set of current-carrying wires can exhibit an effective magnetic permeability at very low frequencies of a few hertz. The resonant permeability, which is negative above the resonance frequency, arises from the oscillations of the wires driven by the applied magnetic field. We show that a large, frequency-specific and tunable effective permeability can be realized for a wide range of strengths of the applied field. (author)

  2. Wireless network of stand-alone end effect probes for soil in situ permittivity measurements over the 100MHZ-6GHz frequency range

    Science.gov (United States)

    Demontoux, François; Bircher, Simone; Ruffié, Gilles; Bonnaudiin, Fabrice; Wigneron, Jean-Pierre; Kerr, Yann

    2017-04-01

    Microwave remote sensing and non-destructive analysis are a powerful way to provide properties estimation of materials. Numerous applications using microwave frequency behavior of materials (remote sensing above land surfaces, non-destructive analysis…) are strongly dependent on the material's permittivity (i.e. dielectric properties). This permittivity depends on numerous parameters such as moisture, texture, temperature, frequency or bulk density. Permittivity measurements are generally carried out in the laboratory. Additionally, dielectric mixing models allow, over a restricted range of conditions, the assessment of a material's permittivity. in-situ measurements are more difficult to obtain. Some in situ measurement probes based on permittivity properties of soil exist (e.g. Time Domain Reflectometers and Transmissometers, capacitance and impedance sensors). They are dedicated to the acquisition of soil moisture data based on permittivity (mainly the real part) estimations over a range of frequencies from around 50 MHz to 1 or 2 GHz. Other Dielectric Assessment Kits exist but they are expensive and they are rather dedicated to laboratory measurements. Furthermore, the user can't address specific issues related to particular materials (e.g. organic soils) or specific measurement conditions (in situ long time records). At the IMS Laboratory we develop probes for in situ soil permittivity measurements (real and imaginary parts) in the 0.5 - 6 GHz frequency range. They are based on the end effect phenomenon of a coaxial waveguide and so are called end effect probes in this paper. The probes can be connected to a portable Vector Network Analyzer (VNA, ANRITSU MS2026A) for the S11 coefficient measurements needed to compute permittivity. It is connected to a PC to record data using an USB connection. This measurement set-up is already used for in situ measurement of soil properties in the framework of the European Space Agency's (ESA) SMOS space mission. However

  3. Fiber optics frequency comb enabled linear optical sampling with operation wavelength range extension.

    Science.gov (United States)

    Liao, Ruolin; Wu, Zhichao; Fu, Songnian; Zhu, Shengnan; Yu, Zhe; Tang, Ming; Liu, Deming

    2018-02-01

    Although the linear optical sampling (LOS) technique is powerful enough to characterize various advanced modulation formats with high symbol rates, the central wavelength of a pulsed local oscillator (LO) needs to be carefully set according to that of the signal under test, due to the coherent mixing operation. Here, we experimentally demonstrate wideband LOS enabled by a fiber optics frequency comb (FOFC). Meanwhile, when the broadband FOFC acts as the pulsed LO, we propose a scheme to mitigate the enhanced sampling error arising in the non-ideal response of a balanced photodetector. Finally, precise characterizations of arbitrary 128 Gbps PDM-QPSK wavelength channels from 1550 to 1570 nm are successfully achieved, when a 101.3 MHz frequency spaced comb with a 3 dB spectral power ripple of 20 nm is used.

  4. Band gaps in the low-frequency range based on the two-dimensional phononic crystal plates composed of rubber matrix with periodic steel stubs

    International Nuclear Information System (INIS)

    Yu, Kunpeng; Chen, Tianning; Wang, Xiaopeng

    2013-01-01

    In this paper, the numerical investigation of elastic wave propagation in two-dimensional phononic crystals composed of an array of steel stepped resonators on a thin rubber slab is presented. For the first time the rubber material is used as the matrix of the PCs. With the finite-element method, the dispersion relations of this novel PCs structure and some factors of the band structure are studied. Results show that, with the rubber material as matrix, the PC structures exhibit extremely low-frequency band gaps, in the frequency range of hundreds of Hz or even tens of Hz; the geometrical parameters and the material parameters can modulate the band gaps to different extents. Furthermore, to understand the low-frequency band gaps caused by this new structure, some resonance eigenmodes of the structure are calculated. Results show that the vibration of the unit cell of the structure can be seen as several mass–spring systems, in which the vibration of the steel stepped resonator decides the lower boundary of the first band gap and the vibration of the rubber that is not in contact with the resonator decides the upper boundary

  5. Characterization of the Mechanical Stress-Strain Performance of Aerospace Alloy Materials Using Frequency-Domain Photoacoustic Ultrasound and Photothermal Methods: An FEM Approach

    Science.gov (United States)

    Huan, Huiting; Mandelis, Andreas; Liu, Lixian

    2018-04-01

    Determining and keeping track of a material's mechanical performance is very important for safety in the aerospace industry. The mechanical strength of alloy materials is precisely quantified in terms of its stress-strain relation. It has been proven that frequency-domain photothermoacoustic (FD-PTA) techniques are effective methods for characterizing the stress-strain relation of metallic alloys. PTA methodologies include photothermal (PT) diffusion and laser thermoelastic photoacoustic ultrasound (PAUS) generation which must be separately discussed because the relevant frequency ranges and signal detection principles are widely different. In this paper, a detailed theoretical analysis of the connection between thermoelastic parameters and stress/strain tensor is presented with respect to FD-PTA nondestructive testing. Based on the theoretical model, a finite element method (FEM) was further implemented to simulate the PT and PAUS signals at very different frequency ranges as an important analysis tool of experimental data. The change in the stress-strain relation has an impact on both thermal and elastic properties, verified by FEM and results/signals from both PT and PAUS experiments.

  6. A wideband, frequency up-converting bounded vibration energy harvester for a low-frequency environment

    International Nuclear Information System (INIS)

    Ashraf, K; Md Khir, M H; Baharudin, Z; Dennis, J O

    2013-01-01

    This paper presents a bounded vibration energy harvester to effectively harvest energy from a wide band of low-frequency environmental vibrations ranging from 10 to 18 Hz. Rigid mechanical stoppers are used to confine the seismic mass movement within the elastic limits of the spring. Experimental results show the effectiveness of the proposed technique in increasing the efficiency of the energy harvester. When excited at a frequency of 10 Hz with a peak acceleration of 1 g, the harvester responds at a higher frequency of 20 Hz and gives a peak power of 2.68 mW and a peak to peak voltage of 2.62 V across a load of 220 Ω. The average power density of 65.74 μW cm −3 obtained at 10 Hz 1 g excitation monotonically increases with frequency up to 341.86 μW cm −3 at 18 Hz. An analytical model describing the nonlinear dynamics of the proposed harvester is also presented. A simple technique to estimate the energy losses during impact and thereof a method to incorporate these losses in the model are suggested. The presented model not only predicts the experimental voltage waveform and frequency response of the device with good similarity but also predicts the RMS voltage from the harvester for the whole range of operating frequencies with an RMS error of 5.2%. (paper)

  7. Transmission system for distribution of video over long-haul optical point-to-point links using a microwave photonic filter in the frequency range of 0.01-10 GHz

    Science.gov (United States)

    Zaldívar Huerta, Ignacio E.; Pérez Montaña, Diego F.; Nava, Pablo Hernández; Juárez, Alejandro García; Asomoza, Jorge Rodríguez; Leal Cruz, Ana L.

    2013-12-01

    We experimentally demonstrate the use of an electro-optical transmission system for distribution of video over long-haul optical point-to-point links using a microwave photonic filter in the frequency range of 0.01-10 GHz. The frequency response of the microwave photonic filter consists of four band-pass windows centered at frequencies that can be tailored to the function of the spectral free range of the optical source, the chromatic dispersion parameter of the optical fiber used, as well as the length of the optical link. In particular, filtering effect is obtained by the interaction of an externally modulated multimode laser diode emitting at 1.5 μm associated to the length of a dispersive optical fiber. Filtered microwave signals are used as electrical carriers to transmit TV-signal over long-haul optical links point-to-point. Transmission of TV-signal coded on the microwave band-pass windows located at 4.62, 6.86, 4.0 and 6.0 GHz are achieved over optical links of 25.25 km and 28.25 km, respectively. Practical applications for this approach lie in the field of the FTTH access network for distribution of services as video, voice, and data.

  8. Prospective observational study on assessing the hemodynamic relevance of patent ductus arteriosus with frequency domain near-infrared spectroscopy.

    Science.gov (United States)

    Schwarz, Christoph E; Preusche, Antonio; Wolf, Martin; Poets, Christian F; Franz, Axel R

    2018-02-16

    What constitutes a hemodynamically relevant patent ductus arteriosus (hrPDA) in preterm infants is unclear. Different clinical and echocardiographic parameters are used, but a gold standard definition is lacking. Our objective was to evaluate associations between regional cerebral tissue oxygen saturation (rcStO 2 ), fraction of tissue oxygen extraction (rcFtO 2 E) measured by frequency domain near-infrared spectroscopy (fd-NIRS) and their correlation to echocardiographic, Doppler-ultrasound, and clinical parameters in preterm infants with and without a hrPDA. In this prospective observational study, 22 infants standard deviation (normalised to a median Hb of 13.8 mg/dl) was 57 ±5% for rcStO 2 and 0.39 ±0.05 for rcFtO 2 E. Comparing no-hrPDA with hrPDA infants, there were no significant differences in mean rcStO 2 (58 ±5% vs. 54 ±5%; p = .102), but in mean rcFtO 2 E (0.38 ±0.05 vs. 0.43 ±0.05; p = .038). Echocardiographic parameter and Doppler indices did not correlate with cerebral oxygenation. Oxygen transport capacity of the blood may confound NIRS data interpretation. Cerebral oxygenation determined by fd-NIRS provided additional information for PDA treatment decisions not offered by routine investigations. Whether indicating PDA therapy based on echocardiography complemented by data on cerebral oxygenation results in better outcomes should be investigated in future studies.

  9. Band Width of Acoustic Resonance Frequency Relatively Natural Frequency of Fuel Rod Vibration

    Energy Technology Data Exchange (ETDEWEB)

    Proskuryakov, Konstantin Nicolaevich; Moukhine, V.S.; Novikov, K.S.; Galivets, E.Yu. [MPEI - TU, 14, Krasnokazarmennaya str., Moscow, 111250 (Russian Federation)

    2009-06-15

    In flow induced vibrations the fluid flow is the energy source that causes vibration. Acoustic resonance in piping may lead to severe problems due to over-stressing of components or significant losses of efficiency. Steady oscillatory flow in NPP primary loop can be induced by the pulsating flow introduced by reactor circulating pump or may be set up by self-excitation. Dynamic forces generated by the turbulent flow of coolant in reactor cores cause fuel rods (FR) and fuel assembly (FA) to vibrate. Flow-induced FR and FA vibrations can generally be broken into three groups: large amplitude 'resonance type' vibrations, which can cause immediate rod failure or severe damage to the rod and its support structure, middle amplitude 'within bandwidth of resonance frequency type' vibrations responsible for more gradual wear and fatigue at the contact surface between the fuel cladding and rod support and small amplitude vibrations, 'out of bandwidth of resonance frequency type' responsible for permissible wear and fatigue at the contact surface between the fuel cladding and rod support. Ultimately, these vibration types can result in a cladding breach, and therefore must be accounted for in the thermal hydraulic design of FR and FA and reactor internals. In paper the technique of definition of quality factor (Q) of acoustic contour of the coolant is presented. The value of Q defines a range of frequencies of acoustic fluctuations of the coolant within which the resonance of oscillations of the structure and the coolant is realized. Method of evaluation of so called band width (BW) of acoustic resonance frequency is worked out and presented in the paper. BW characterises the range of the frequency of coolant pressure oscillations within which the frequency of coolant pressure oscillations matches the fuel assembly's natural frequency of vibration (its resonance frequency). Paper show the way of detuning acoustic resonance from natural

  10. Method and apparatus for radio frequency ceramic sintering

    Science.gov (United States)

    Hoffman, Daniel J.; Kimrey, Jr., Harold D.

    1993-01-01

    Radio frequency energy is used to sinter ceramic materials. A coaxial waveguide resonator produces a TEM mode wave which generates a high field capacitive region in which a sample of the ceramic material is located. Frequency of the power source is kept in the range of radio frequency, and preferably between 60-80 MHz. An alternative embodiment provides a tunable radio frequency circuit which includes a series input capacitor and a parallel capacitor, with the sintered ceramic connected by an inductive lead. This arrangement permits matching of impedance over a wide range of dielectric constants, ceramic volumes, and loss tangents.

  11. Reexamining the frequency range of hearing in silver (Hypophthalmichthys molitrix) and bighead (H. nobilis) carp

    Science.gov (United States)

    Vetter, Brooke J.; Brey, Marybeth; Meninger, Allen F.

    2018-01-01

    Silver (Hypophthalmichthys molitrix) and bighead (H. nobilis) carp (collectively bigheaded carp) are invasive fish that threaten aquatic ecosystems in the upper Midwest United States and the Laurentian Great Lakes. Controlling bigheaded carp is a priority of fisheries managers and one area of focus involves developing acoustic deterrents to prevent upstream migration. For an acoustic deterrent to be effective however, the hearing ability of bigheaded carp must be characterized. A previous study showed that bigheaded carp detected sound up to 3 kHz but this range is narrower than what has been reported for other ostariophysans. Therefore, silver and bighead carp frequency detection was evaluated in response to 100 Hz to 9 kHz using auditory evoked potentials (AEPs). AEPs were recorded from 100 Hz to 5 kHz. The lowest thresholds were at 500 Hz for both species (silver carp threshold: 80.6 ± 3.29 dB re 1 μPa SPLrms, bighead carp threshold: 90.5 ± 5.75 dB re 1 μPa SPLrms; mean ± SD). These results provide fisheries managers with better insight on effective acoustic stimuli for deterrent systems, however, to fully determine bigheaded carp hearing abilities, these results need to be compared with behavioral assessments.

  12. Frequency-Dependent Properties of Magnetic Nanoparticle Crystals

    Energy Technology Data Exchange (ETDEWEB)

    Majetich, Sara [Carnegie Mellon Univ., Pittsburgh, PA (United States)

    2016-05-17

    In the proposed research program we will investigate the time- and frequency-dependent behavior of ordered nanoparticle assemblies, or nanoparticle crystals. Magnetostatic interactions are long-range and anisotropic, and this leads to complex behavior in nanoparticle assemblies, particularly in the time- and frequency-dependent properties. We hypothesize that the high frequency performance of composite materials has been limited because of the range of relaxation times; if a composite is a dipolar ferromagnet at a particular frequency, it should have the advantages of a single phase material, but without significant eddy current power losses. Arrays of surfactant-coated monodomain magnetic nanoparticles can exhibit long-range magnetic order that is stable over time. The magnetic domain size and location of domain walls is governed not by structural grain boundaries but by the shape of the array, due to the local interaction field. Pores or gaps within an assembly pin domain walls and limit the domain size. Measurements of the magnetic order parameter as a function of temperature showed that domains can exist at high temoerature, and that there is a collective phase transition, just as in an exchange-coupled ferromagnet. Dipolar ferromagnets are not merely of fundamental interest; they provide an interesting alternative to exchange-based ferromagnets. Dipolar ferromagnets made with high moment metallic particles in an insulating matrix could have high permeability without large eddy current losses. Such nanocomposites could someday replace the ferrites now used in phase shifters, isolators, circulators, and filters in microwave communications and radar applications. We will investigate the time- and frequency-dependent behavior of nanoparticle crystals with different magnetic core sizes and different interparticle barrier resistances, and will measure the magnetic and electrical properties in the DC, low frequency (0.1 Hz - 1 kHz), moderate frequency (10 Hz - 500

  13. Applicability and safety of dual-frequency ultrasonic treatment for the transdermal delivery of drugs

    Science.gov (United States)

    Schoellhammer, Carl M.; Srinivasan, Sharanya; Barman, Ross; Mo, Stacy H.; Polat, Baris E.; Langer, Robert; Blankschtein, Daniel

    2016-01-01

    Low-frequency ultrasound presents an attractive method for transdermal drug delivery. The controlled, yet nonspecific nature of enhancement broadens the range of therapeutics that can be delivered, while minimizing necessary reformulation efforts for differing compounds. Long and inconsistent treatment times, however, have partially limited the attractiveness of this method. Building on recent advances made in this area, the simultaneous use of low- and high-frequency ultrasound is explored in a physiologically relevant experimental setup to enable the translation of this treatment to testing in vivo. Dual-frequency ultrasound, utilizing 20 kHz and 1 MHz wavelengths simultaneously, was found to significantly enhance the size of localized transport regions (LTRs) in both in vitro and in vivo models while decreasing the necessary treatment time compared to 20 kHz alone. Additionally, LTRs generated by treatment with 20 kHz + 1 MHz were found to be more permeable than those generated with 20 kHz alone. This was further corroborated with pore-size estimates utilizing hindered-transport theory, in which the pores in skin treated with 20 kHz + 1 MHz were calculated to be significantly larger than the pores in skin treated with 20 kHz alone. This demonstrates for the first time that LTRs generated with 20 kHz + 1 MHz are also more permeable than those generated with 20 kHz alone, which could broaden the range of therapeutics and doses administered transdermally. With regard to safety, treatment with 20 kHz + 1 MHz both in vitro and in vivo appeared to result in no greater skin disruption than that observed in skin treated with 20 kHz alone, an FDA-approved modality. This study demonstrates that dual-frequency ultrasound is more efficient and effective than single-frequency ultrasound and is well-tolerated in vivo. PMID:25662228

  14. Radio Ranging Techniques to test Relativistic Gravitation

    OpenAIRE

    Cowsik, R.

    1999-01-01

    It is suggested that modern techniques of radio ranging when applied to study the motion of the Moon, can improve the accuracy of tests of relativistic gravitation obtained with currently operating laser ranging techniques. Other auxillary information relevant to the Solar system would also emerge from such a study.

  15. Popularity and Relevance of Science Education and Scientific Literacy

    DEFF Research Database (Denmark)

    Graeber, Wolfgang; Blonder, Ron; Bolte, Claus

    2008-01-01

    A consortium of researchers from 8 European nations has successfully applied to the EU commission for funding the PARSEL (Popularity and Relevance in Science Education for Scientific Literacy) project, which aims at raising the popularity and relevance of science teaching and enhancing students...... of a range of personal and social skills (including cognitive skills associated with investigatory scientific problem solving and socio-scientific decision making) and clarify the relevancy of science education for the 21st century. This symposium will introduce and discuss the project PARSEL ideas within...

  16. Functionally relevant microsatellites in sugarcane unigenes

    Directory of Open Access Journals (Sweden)

    Singh Nagendra K

    2010-11-01

    Full Text Available Abstract Background Unigene sequences constitute a rich source of functionally relevant microsatellites. The present study was undertaken to mine the microsatellites in the available unigene sequences of sugarcane for understanding their constitution in the expressed genic component of its complex polyploid/aneuploid genome, assessing their functional significance in silico, determining the extent of allelic diversity at the microsatellite loci and for evaluating their utility in large-scale genotyping applications in sugarcane. Results The average frequency of perfect microsatellite was 1/10.9 kb, while it was 1/44.3 kb for the long and hypervariable class I repeats. GC-rich trinucleotides coding for alanine and the GA-rich dinucleotides were the most abundant microsatellite classes. Out of 15,594 unigenes mined in the study, 767 contained microsatellite repeats and for 672 of these putative functions were determined in silico. The microsatellite repeats were found in the functional domains of proteins encoded by 364 unigenes. Its significance was assessed by establishing the structure-function relationship for the beta-amylase and protein kinase encoding unigenes having repeats in the catalytic domains. A total of 726 allelic variants (7.42 alleles per locus with different repeat lengths were captured precisely for a set of 47 fluorescent dye labeled primers in 36 sugarcane genotypes and five cereal species using the automated fragment analysis system, which suggested the utility of designed primers for rapid, large-scale and high-throughput genotyping applications in sugarcane. Pair-wise similarity ranging from 0.33 to 0.84 with an average of 0.40 revealed a broad genetic base of the Indian varieties in respect of functionally relevant regions of the large and complex sugarcane genome. Conclusion Microsatellite repeats were present in 4.92% of sugarcane unigenes, for most (87.6% of which functions were determined in silico. High level of

  17. Radio-Frequency Emissions from Streamer Collisions: Implications for High-Energy Processes.

    Science.gov (United States)

    Luque, A.

    2017-12-01

    The production of energetic particles in a discharge corona is possibly linked to the collision of streamers of opposite polarities [Cooray et al. (2009), Kochkin et al. (2012), Østgaard et al. (2016)]. There is also experimental evidence linking it to radio-frequency emissions in the UHF frequency range (300 MHz-3 GHz) [Montanyà et al. (2015), Petersen and Beasley (2014)]. Here we investigate these two links by modeling the radio-frequency emissions emanating from an encounter between two counter-propagating streamers. Our numerical model combines self-consistently a conservative, high-order Finite-Volume scheme for electron transport with a Finite-Difference Time-Domain (FDTD) method for electromagnetic propagation. We also include the most relevant reactions for streamer propagation: impact ionization, dissociative attachment and photo-ionization. Our implementation benefits from massive parallelization by running on a General-Purpose Graphical Processing Unit (GPGPU). With this code we found that streamer encounters emit electromagnetic waves predominantly in the UHF range, supporting the hypothesis that streamer collisions are essential precursors of high-energy processes in electric discharges. References Cooray, V., et al., J. Atm. Sol.-Terr. Phys., 71, 1890, doi:10.1016/j.jastp.2009.07.010 (2009). Kochkin, P. O., et al., J. Phys. D, 45, 425202, doi: 10.1088/0022-3727/45/42/425202 (2012). Montanyà, J., et al., J. Atm. Sol.-Terr. Phys., 136, 94, doi:10.1016/j.jastp.2015.06.009, (2015). Østgaard, N., et al., J. Geophys. Res. (Atmos.), 121, 2939, doi:10.1002/2015JD024394 (2016). Petersen, D., and W. Beasley, Atmospheric Research, 135, 314, doi:10.1016/j.atmosres.2013.02.006 (2014).

  18. Terahertz Frequency-Domain Spectroscopy of Low-Pressure Acetonitrile Gas by a Photomixing Terahertz Synthesizer Referenced to Dual Optical Frequency Combs

    Science.gov (United States)

    Hsieh, Yi-Da; Kimura, Hiroto; Hayashi, Kenta; Minamikawa, Takeo; Mizutani, Yasuhiro; Yamamoto, Hirotsugu; Iwata, Tetsuo; Inaba, Hajime; Minoshima, Kaoru; Hindle, Francis; Yasui, Takeshi

    2016-09-01

    A terahertz (THz) frequency synthesizer based on photomixing of two near-infrared lasers with a sub-THz to THz frequency offset is a powerful tool for spectroscopy of polar gas molecules due to its broad spectral coverage; however, its frequency accuracy and resolution are relatively low. To tune the output frequency continuously and widely while maintaining its traceability to a frequency standard, we developed a photomixing THz synthesizer phase-locked to dual optical frequency combs (OFCs). While the phase-locking to dual OFCs ensured continuous tuning within a spectral range of 120 GHz, in addition to the traceability to the frequency standard, use of a broadband uni-traveling carrier photodiode for photomixing enabled the generation of CW-THz radiation within a frequency range from 0.2 to 1.5 THz. We demonstrated THz frequency-domain spectroscopy of gas-phase acetonitrile CH3CN and its isotope CH3 13CN in the frequency range of 0.600-0.720 THz using this THz synthesizer. Their rotational transitions were assigned with a frequency accuracy of 8.42 × 10-8 and a frequency resolution of 520 kHz. Furthermore, the concentration of the CH3CN gas at 20 Pa was determined to be (5.41 ± 0.05) × 1014 molecules/cm3 by curve fitting analysis of the measured absorbance spectrum, and the mixture ratio of the mixed CH3CN/CH3 13CN gas was determined to be 1:2.26 with a gas concentration of 1014-1015 molecules/cm3. The developed THz synthesizer is highly promising for high-precision THz-FDS of low-pressure molecular gases and will enable the qualitative and quantitative analyses of multiple gases.

  19. Ultrafast and Doppler-free femtosecondoptical ranging based on dispersivefrequency-modulated interferometry.

    Science.gov (United States)

    Xia, Haiyun; Zhang, Chunxi

    2010-03-01

    An ultrafast and Doppler-free optical ranging system based on dispersive frequency-modulated interferometry is demonstrated. The principle is similar to the conventional frequency-modulated continuous-wave interferometry where the range information is derived from the beat frequency between the object signal and the reference signal. However, a passive and static frequency scanning is performed based on the chromatic dispersion of a transform-limited femtosecond pulse in the time domain. We point out that the unbalanced dispersion introduced in the Mach-Zehnder interferometer can be optimized to eliminate the frequency chirp in the temporal interferograms pertaining to the third order dispersion of the all-fiber system, if the dynamic range being considered is small. Some negative factors, such as the polarization instability of the femtosecond pulse, the power fluctuation of the optical signal and the nonuniform gain spectrum of the erbium-doped fiber amplifier lead to an obvious envelope deformation of the temporal interferograms from the Gaussian shape. Thus a new data processing method is proposed to guarantee the range resolution. In the experiment, the vibration of a speaker is measured. A range resolution of 1.59 microm is achieved with an exposure time of 394 fs at a sampling rate of 48.6 MHz.

  20. Automatic Locking of Laser Frequency to an Absorption Peak

    Science.gov (United States)

    Koch, Grady J.

    2006-01-01

    An electronic system adjusts the frequency of a tunable laser, eventually locking the frequency to a peak in the optical absorption spectrum of a gas (or of a Fabry-Perot cavity that has an absorption peak like that of a gas). This system was developed to enable precise locking of the frequency of a laser used in differential absorption LIDAR measurements of trace atmospheric gases. This system also has great commercial potential as a prototype of means for precise control of frequencies of lasers in future dense wavelength-division-multiplexing optical communications systems. The operation of this system is completely automatic: Unlike in the operation of some prior laser-frequency-locking systems, there is ordinarily no need for a human operator to adjust the frequency manually to an initial value close enough to the peak to enable automatic locking to take over. Instead, this system also automatically performs the initial adjustment. The system (see Figure 1) is based on a concept of (1) initially modulating the laser frequency to sweep it through a spectral range that includes the desired absorption peak, (2) determining the derivative of the absorption peak with respect to the laser frequency for use as an error signal, (3) identifying the desired frequency [at the very top (which is also the middle) of the peak] as the frequency where the derivative goes to zero, and (4) thereafter keeping the frequency within a locking range and adjusting the frequency as needed to keep the derivative (the error signal) as close as possible to zero. More specifically, the system utilizes the fact that in addition to a zero crossing at the top of the absorption peak, the error signal also closely approximates a straight line in the vicinity of the zero crossing (see Figure 2). This vicinity is the locking range because the linearity of the error signal in this range makes it useful as a source of feedback for a proportional + integral + derivative control scheme that

  1. The use of joint time frequency analysis to quantify the effect of ventilation on the pulse oximeter waveform.

    Science.gov (United States)

    Shelley, Kirk H; Awad, Aymen A; Stout, Robert G; Silverman, David G

    2006-04-01

    In the process of determining oxygen saturation, the pulse oximeter functions as a photoelectric plethysmograph. By analyzing how the frequency spectrum of the pulse oximeter waveform changes over time, new clinically relevant features can be extracted. Thirty patients undergoing general anesthesia for abdominal surgery had their pulse oximeter, airway pressure and CO(2) waveforms collected (50 Hz). The pulse oximeter waveform was analyzed with a short-time Fourier transform using a moving 4096 point Hann window of 82 seconds duration. The frequency signal created by positive pressure ventilation was extracted using a peak detection algorithm in the frequency range of ventilation (0.08-0.4 Hz = 5-24 breaths/minute). The respiratory rate derived in this manner was compared to the respiratory rate as determined by CO(2) detection. In total, 52 hours of telemetry data were analyzed. The respiratory rate measured from the pulse oximeter waveform was found to have a 0.89 linear correlation when compared to CO(2) detection and airway pressure change. the bias was 0.03 breath/min, SD was 0.557 breath/min and the upper and lower limits of agreement were 1.145 and -1.083 breath/min respectively. The presence of motion artifact proved to be the primary cause of failure of this technique. Joint time frequency analysis of the pulse oximeter waveform can be used to determine the respiratory rate of ventilated patients and to quantify the impact of ventilation on the waveform. In addition, when applied to the pulse oximeter waveform new clinically relevant features were observed.

  2. Pengaruh Frekuensi Pemutaran Telur terhadap Daya Tetas dan Bobot Badan DOC Ayam Kampung (The Effect of Egg Centrifugation Frequency on Hatchability and Body Weight DOC of Free-range Chicken)

    OpenAIRE

    Bachari, Irawati; Sembiring, Iskandar; Tarigan, Dedi Suranta

    2010-01-01

    The objective of research would be to assess the extent to which the effect of a good egg centrifugation frequency and interaction on hatchability of Free-range Chicken eggs.This research was conducted by using the factorial complete random sampling. The treatment was frequency of egg centrifugation with three levels of rotation, I, e., RI (4 times/day), R2 (8 times/day), R3 (12 times/day).The result of research indicated that highest hatchability was found in treatment of egg centrifuga...

  3. Broadband photosensor with a tunable frequency range, built on the basis of nanoscale carbon structure with field localization

    Science.gov (United States)

    Yakunin, Alexander N.; Akchurin, Garif G.; Aban'shin, Nikolay P.; Gorfinkel, Boris I.

    2014-03-01

    The work is devoted to the development of a new direction in creating of broadband photo sensors which distinctive feature is the possibility of dynamic adjustment of operating frequency range. The author's results of study of red threshold control of classic photoelectric effect were the basis for the work implementation. This effect was predicted theoretically and observed experimentally during irradiation of nanoscale carbon structure of planar-edge type by stream of low-energy photons. The variation of the accelerating voltage within a small range allows you to change photoelectric threshold for carbon in a wide range - from UV to IR. This is the consequence of the localization of electrostatic field at tip of the blade planar structure and of changes in the conditions of non-equilibrium electrons tunneling from the boundary surface of the cathode into the vacuum. The generation of nonequilibrium electrons in the carbon film thickness of 20 nm has a high speed which provides high performance of photodetector. The features of the use of nanoscale carbon structure photocurrent registration as in the prethreshold regime, and in the mode of field emission existence are discussed. The results of simulation and experimental examination of photosensor samples are given. It is shown that the observed effect is a single-photon tunneling. This in combination with the possibility of highspeed dynamic tuning determines the good perspectives for creation of new devices working in the mode of select multiple operating spectral bands for the signal recording. The architecture of such devices is expected to be significantly simpler than the conventional ones, based on the use of tunable filters.

  4. High quality factor gigahertz frequencies in nanomechanical diamond resonators

    OpenAIRE

    Gaidarzhy, Alexei; Imboden, Matthias; Mohanty, Pritiraj; Rankin, Janet; Sheldon, Brian W.

    2007-01-01

    We report actuation and detection of gigahertz-range resonance frequencies in nano-crystalline diamond mechanical resonators. High order transverse vibration modes are measured in coupled-beam resonators exhibiting frequencies up to 1.441 GHz. The cantilever-array design of the resonators translates the gigahertz-range resonant motion of micron-long cantilever elements to the displacement of the central supporting structure. Use of nano-crystalline diamond further increases the frequency comp...

  5. EOG feature relevance determination for microsleep detection

    Directory of Open Access Journals (Sweden)

    Golz Martin

    2017-09-01

    Full Text Available Automatic relevance determination (ARD was applied to two-channel EOG recordings for microsleep event (MSE recognition. 10 s immediately before MSE and also before counterexamples of fatigued, but attentive driving were analysed. Two type of signal features were extracted: the maximum cross correlation (MaxCC and logarithmic power spectral densities (PSD averaged in spectral bands of 0.5 Hz width ranging between 0 and 8 Hz. Generalised learn-ing vector quantisation (GRLVQ was used as ARD method to show the potential of feature reduction. This is compared to support-vector machines (SVM, in which the feature reduction plays a much smaller role. Cross validation yielded mean normalised relevancies of PSD features in the range of 1.6 – 4.9 % and 1.9 – 10.4 % for horizontal and vertical EOG, respectively. MaxCC relevancies were 0.002 – 0.006 % and 0.002 – 0.06 %, respectively. This shows that PSD features of vertical EOG are indispensable, whereas MaxCC can be neglected. Mean classification accuracies were estimated at 86.6±b 1.3 % and 92.3±b 0.2 % for GRLVQ and SVM, respectively. GRLVQ permits objective feature reduction by inclusion of all processing stages, but is not as accurate as SVM.

  6. EOG feature relevance determination for microsleep detection

    Directory of Open Access Journals (Sweden)

    Golz Martin

    2017-09-01

    Full Text Available Automatic relevance determination (ARD was applied to two-channel EOG recordings for microsleep event (MSE recognition. 10 s immediately before MSE and also before counterexamples of fatigued, but attentive driving were analysed. Two type of signal features were extracted: the maximum cross correlation (MaxCC and logarithmic power spectral densities (PSD averaged in spectral bands of 0.5 Hz width ranging between 0 and 8 Hz. Generalised learn-ing vector quantisation (GRLVQ was used as ARD method to show the potential of feature reduction. This is compared to support-vector machines (SVM, in which the feature reduction plays a much smaller role. Cross validation yielded mean normalised relevancies of PSD features in the range of 1.6 - 4.9 % and 1.9 - 10.4 % for horizontal and vertical EOG, respectively. MaxCC relevancies were 0.002 - 0.006 % and 0.002 - 0.06 %, respectively. This shows that PSD features of vertical EOG are indispensable, whereas MaxCC can be neglected. Mean classification accuracies were estimated at 86.6±b 1.3 % and 92.3±b 0.2 % for GRLVQ and SVM, respec-tively. GRLVQ permits objective feature reduction by inclu-sion of all processing stages, but is not as accurate as SVM.

  7. Ocean acidification in the coastal zone from an organism's perspective: multiple system parameters, frequency domains, and habitats.

    Science.gov (United States)

    Waldbusser, George G; Salisbury, Joseph E

    2014-01-01

    Multiple natural and anthropogenic processes alter the carbonate chemistry of the coastal zone in ways that either exacerbate or mitigate ocean acidification effects. Freshwater inputs and multiple acid-base reactions change carbonate chemistry conditions, sometimes synergistically. The shallow nature of these systems results in strong benthic-pelagic coupling, and marine invertebrates at different life history stages rely on both benthic and pelagic habitats. Carbonate chemistry in coastal systems can be highly variable, responding to processes with temporal modes ranging from seconds to centuries. Identifying scales of variability relevant to levels of biological organization requires a fuller characterization of both the frequency and magnitude domains of processes contributing to or reducing acidification in pelagic and benthic habitats. We review the processes that contribute to coastal acidification with attention to timescales of variability and habitats relevant to marine bivalves.

  8. Low frequency sound field enhancement system for rectangular rooms using multiple low frequency loudspeakers

    DEFF Research Database (Denmark)

    Celestinos, Adrian; Nielsen, Sofus Birkedal

    2006-01-01

    an enhancement system with extra loudspeakers the sound pressure level distribution along the listening area presents a significant improvement in the subwoofer frequency range. The system is simulated and implemented on the three different rooms and finally verified by measurements on the real rooms.......Rectangular rooms have strong influence on the low frequency performance of loudspeakers. Simulations of three different room sizes have been carried out using finite-difference time-domain method (FDTD) in order to predict the behaviour of the sound field at low frequencies. By using...

  9. Characterization of modulated time-of-flight range image sensors

    Science.gov (United States)

    Payne, Andrew D.; Dorrington, Adrian A.; Cree, Michael J.; Carnegie, Dale A.

    2009-01-01

    A number of full field image sensors have been developed that are capable of simultaneously measuring intensity and distance (range) for every pixel in a given scene using an indirect time-of-flight measurement technique. A light source is intensity modulated at a frequency between 10-100 MHz, and an image sensor is modulated at the same frequency, synchronously sampling light reflected from objects in the scene (homodyne detection). The time of flight is manifested as a phase shift in the illumination modulation envelope, which can be determined from the sampled data simultaneously for each pixel in the scene. This paper presents a method of characterizing the high frequency modulation response of these image sensors, using a pico-second laser pulser. The characterization results allow the optimal operating parameters, such as the modulation frequency, to be identified in order to maximize the range measurement precision for a given sensor. A number of potential sources of error exist when using these sensors, including deficiencies in the modulation waveform shape, duty cycle, or phase, resulting in contamination of the resultant range data. From the characterization data these parameters can be identified and compensated for by modifying the sensor hardware or through post processing of the acquired range measurements.

  10. Sum frequency generation image reconstruction: Aliphatic membrane under spherical cap geometry

    Energy Technology Data Exchange (ETDEWEB)

    Volkov, Victor [Bereozovaya 2A, Konstantinovo, Moscow Region 140207 (Russian Federation)

    2014-10-07

    The article explores an opportunity to approach structural properties of phospholipid membranes using Sum Frequency Generation microscopy. To establish the principles of sum frequency generation image reconstruction in such systems, at first approach, we may adopt an idealistic spherical cap uniform assembly of hydrocarbon molecules. Quantum mechanical studies for decanoic acid (used here as a representative molecular system) provide necessary information on transition dipole moments and Raman tensors of the normal modes specific to methyl terminal – a typical moiety in aliphatic (and phospholipid) membranes. Relative degree of localization and frequencies of the normal modes of methyl terminals make nonlinearities of this moiety to be promising in structural analysis using Sum Frequency Generation imaging. Accordingly, the article describes derivations of relevant macroscopic nonlinearities and suggests a mapping procedure to translate amplitudes of the nonlinearities onto microscopy image plane according to geometry of spherical assembly, local molecular orientation, and optical geometry. Reconstructed images indicate a possibility to extract local curvature of bilayer envelopes of spherical character. This may have practical implications for structural extractions in membrane systems of practical relevance.

  11. Frequency scaling of slant-path atmospheric attenuation in the absence of rain for millimeter-wave links

    Science.gov (United States)

    Lucas-Vegas, María. José; Riera, José Manuel

    2016-11-01

    Broadband satellite communications systems, either used for broadcast or fixed satellite services, have grown continuously in recent years. This has led to the use of higher frequency bands, from the Ku (14/11 GHz) to the Ka band (30/20 GHz) in the last decade, and with the expectation of using the Q/V band (50/40 GHz) and even the W band (75-110 GHz) in the future. As frequency increases, radio wave propagation effects in the slant-path within the troposphere are becoming more and more relevant. The objective of this research is the proposal of frequency scaling approximations for the total attenuation in the absence of rain, a condition that occurs during the highest percentages of time, usually more than 95% in temperate climates. There is a strong relationship between total attenuation at different frequencies, as it arises from the same physical phenomena, namely, the presence of oxygen, water vapor, and clouds in the slant path. This strong relationship allows frequency scaling estimations to be proposed. In particular, polynomials for instantaneous frequency scaling of total attenuation under these conditions have been calculated for a set of frequencies in the range 10-100 GHz, based on atmospheric profiles of 60 sites from all over the world and physical models of attenuation. Global polynomials are provided for the 72 combinations of nine significant frequencies, which can be used to estimate attenuation at a frequency band from its known value at a different one. Refined expressions have also been calculated for different climatic zones, providing more precise estimations.

  12. 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.

  13. Frequency-dependent changes in the amplitude of low-frequency fluctuations in Internet gaming disorder

    Directory of Open Access Journals (Sweden)

    Xiao eLin

    2015-09-01

    Full Text Available Neuroimaging studies have revealed that the task-related functional brain activities are impaired in Internet gaming disorder (IGD subjects. However, little is known about the alternations in spontaneous brain activities about them. Recent studies have proposed that the brain activities of different frequency ranges are generated by different nervous activities and have different physiological and psychological functions. Thus, in this study, we set to explore the spontaneous brain activities in IGD subjects by measuring the fractional amplitude of low-frequency fluctuation (fALFF, to investigate band-specific changes of resting-state fALFF. We subdivided the frequency range into five bands based on literatures. Comparing to healthy controls, the IGD group showed decreased fALFF values in the cerebellum posterior lobe and increased fALFF values in superior temporal gyrus. Significant interactions between frequency bands and groups were found in the cerebellum, the anterior cingulate, the lingual gyrus, the middle temporal gyrus and the middle frontal gyrus. Those brain regions are proved related to the executive function and decision-making. These results revealed the changed spontaneous brain activity of IGD, which contributed to understanding the underlying pathophysiology of IGD.

  14. ICRF [Ion Cyclotron Range of Frequencies] heating and antenna coupling in a high beta tokamak

    International Nuclear Information System (INIS)

    Elet, R.S.

    1988-01-01

    Maxwell's Equations are solved in two-dimensions for the electromagnetic fields in a toroidal cavity using the cold plasma fluid dielectric tensor in the Ion Cyclotron Range of Frequencies (ICRF). The Vector Wave Equation is transformed to a set of two, coupled second-order partial differential equations with inhomogeneous forcing functions which model a wave launcher. The resulting equations are finite differenced and solved numerically with a complex banded matrix algorithm on a Cray-2 computer using a code described in this report. This code is used to study power coupling characteristics of a wave launcher for low and high beta tokamaks. The low and high beta equilibrium tokamak magnetic fields applied in this model are determined from analytic solutions to the Grad-Shafranov equation. The code shows good correspondence with the results of low field side ICRF heating experiments performed on the Tokamak of Fontenay-Aux-Roses (TFR). Low field side and high field side antenna coupling properties for ICRF heating in the Columbia High Beta Tokamak (HBT) experiment are calculated with this code. Variations of antenna position in the tokamak, ionic concentration and plasma density, and volume-averaged beta have been analyzed for HBT. It is found that the location of the antenna with respect to the plasma has the dominant role in the design of an ICRF heating experiment in HBT. 10 refs., 52 figs., 13 tabs

  15. Influence of vegetation physiognomy, elevation and fire frequency on medium and large mammals in two protected areas of the Espinhaço Range

    Directory of Open Access Journals (Sweden)

    Fernando Ferreira de Pinho

    2017-05-01

    Full Text Available ABSTRACT The objectives of this study were to determine the richness of medium and large mammal species in two protected areas of the Espinhaço Mountain Range, state of Minas Gerais, Brazil; and to investigate the factors affecting the occurrence of those species. To accomplish that we placed 49 camera traps activated by heat and motion at Rio Preto State Park (RPSP and 48 at Sempre Vivas National Park (SVNP. We also collected data on three environmental variables: vegetation physiognomy, elevation and wildfire frequency, to evaluate the influence of these factors on species richness and use intensity (inferred from camera trap detection rate by large mammals. We recorded 23 large mammal species in the two parks combined. The lowest species richness was found at the rupestrian habitat of RPSP, and in the open grasslands of SVNP. The forest and savannah physiognomies were used more intensively by large mammals. Species richness was higher and use was greater at lower elevations of RPSP. In SVNP, fire frequency did not affect species richness or use intensity. The savannah habitat had very similar richness compared to the forests of the two protected areas. The high species richness and use intensity observed in these forest habitats highlights the importance of riparian environments in the Cerrado biome. The highest species richness and use intensity observed at low elevation follows patterns found in the literature, probably due to variation in the vegetation, which results in greater resource availability. Although rupestrian habitats at high elevations of the Espinhaço Range are known to have a high degree of endemism for some taxa, large mammal richness and use were not high in this habitat. These results indicate that the protection of native vegetation at lower elevations is crucial for the long-term conservation of large mammals in the Espinhaço Range.

  16. Long-time data storage: relevant time scales

    NARCIS (Netherlands)

    Elwenspoek, Michael Curt

    2011-01-01

    Dynamic processes relevant for long-time storage of information about human kind are discussed, ranging from biological and geological processes to the lifecycle of stars and the expansion of the universe. Major results are that life will end ultimately and the remaining time that the earth is

  17. Frequency-dependent complex modulus of the uterus: preliminary results

    Energy Technology Data Exchange (ETDEWEB)

    Kiss, Miklos Z [Department of Medical Physics, University of Wisconsin, Madison, WI 53706 (United States); Hobson, Maritza A [Department of Medical Physics, University of Wisconsin, Madison, WI 53706 (United States); Varghese, Tomy [Department of Medical Physics, University of Wisconsin, Madison, WI 53706 (United States); Harter, Josephine [Department of Surgical Pathology, University of Wisconsin, Madison, WI 53706 (United States); Kliewer, Mark A [Department of Radiology, University of Wisconsin, Madison, WI 53706 (United States); Hartenbach, Ellen M [Department of Obstetrics and Gynecology, University of Wisconsin, Madison, WI 53706 (United States); Zagzebski, James A [Department of Medical Physics, University of Wisconsin, Madison, WI 53706 (United States)

    2006-08-07

    The frequency-dependent complex moduli of human uterine tissue have been characterized. Quantification of the modulus is required for developing uterine ultrasound elastography as a viable imaging modality for diagnosing and monitoring causes for abnormal uterine bleeding and enlargement, as well assessing the integrity of uterine and cervical tissue. The complex modulus was measured in samples from hysterectomies of 24 patients ranging in age from 31 to 79 years. Measurements were done under small compressions of either 1 or 2%, at low pre-compression values (either 1 or 2%), and over a frequency range of 0.1-100 Hz. Modulus values of cervical tissue monotonically increased from approximately 30-90 kPa over the frequency range. Normal uterine tissue possessed modulus values over the same range, while leiomyomas, or uterine fibroids, exhibited values ranging from approximately 60-220 kPa.

  18. Frequency-dependent complex modulus of the uterus: preliminary results

    International Nuclear Information System (INIS)

    Kiss, Miklos Z; Hobson, Maritza A; Varghese, Tomy; Harter, Josephine; Kliewer, Mark A; Hartenbach, Ellen M; Zagzebski, James A

    2006-01-01

    The frequency-dependent complex moduli of human uterine tissue have been characterized. Quantification of the modulus is required for developing uterine ultrasound elastography as a viable imaging modality for diagnosing and monitoring causes for abnormal uterine bleeding and enlargement, as well assessing the integrity of uterine and cervical tissue. The complex modulus was measured in samples from hysterectomies of 24 patients ranging in age from 31 to 79 years. Measurements were done under small compressions of either 1 or 2%, at low pre-compression values (either 1 or 2%), and over a frequency range of 0.1-100 Hz. Modulus values of cervical tissue monotonically increased from approximately 30-90 kPa over the frequency range. Normal uterine tissue possessed modulus values over the same range, while leiomyomas, or uterine fibroids, exhibited values ranging from approximately 60-220 kPa

  19. Parametrically induced low-frequency waves in weakly inhomogeneous magnetized plasmas

    International Nuclear Information System (INIS)

    Pesic, S.

    1981-01-01

    The linear dispersion relation governing the parametric interaction of a lower hybrid pump wave with a weakly-inhomogeneous current carrying hot plasma confined by a helical magnetic field is derived and solved numerically. The stability boundaries are delineated over a wide range in the k-space. The frequency and growth rate of decay instabilities are calculated for plasma parameters relevant to lower hybrid plasma heating experiments. The parametric excitation of drift waves and ion cyclotron current instabilities is discussed. In the low-density plasma region low minimum thresholds and high growth rates are obtained for the pump decay into ion cyclotron and nonresonant quasimodes. The spatial amplification of hot ion Bernstein waves and nonresonant quasimodes dominate in the plasma core (ω 0 /ωsub(LH) < 2). The presented theoretical results are in qualitative agreement with current LH plasma heating experiments. (author)

  20. Frequency metrology of a photomixing source for gas phase spectroscopy

    Science.gov (United States)

    Hindle, Francis; Mouret, Gael; Yang, Chun; Cuisset, Arnaud; Bocquet, Robin; Lours, Michel; Rovera, Daniele

    2010-08-01

    The availability of frequency combs has opened new possibilities for the measurement of optical frequencies. Photomixing is an attractive solution for high resolution THz spectroscopy of gases due to the narrow spectral resolution and ability to access the 100 GHz to 3.5 THz range. One limitation of present photomixing spectrometers is the accuracy with which the THz frequency is established. Measurement of the centre frequency gas phase molecular transitions requires an accuracy better than 100 kHz in order to allow spectroscopic constants to be determined. Standard optical techniques like those employed in wavelength meters can only provide accuracies in the order of 50 MHz. We have used a turnkey fibre based frequency comb and a standard photomixing configuration to realize a THz synthesizer with an accuracy of around 50kHz. Two ECDLs used to pump the photomixer are phase locked onto the frequency comb and provide a tuning range of 10 MHz. In order to extend the tuning range an additional phase locked ECLD has been added to obtain a range in excess of 100 MHz. The absorption profiles of many Doppler limited transitions of carbonyl sulphide and formaldehyde have been measured to validate this instrument.

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

    International Nuclear Information System (INIS)

    Kawai, Hiroki; Nagaoka, Tomoaki; Watanabe, Soichi; Saito, Kazuyuki; Takahashi, Masaharu; Ito, Koichi

    2010-01-01

    This paper presents calculated specific absorption rate (SAR) dosimetry in 4 and 8 week Japanese pregnant-woman models exposed to plane waves over the frequency range of 10 MHz-1.5 GHz. Two types of 2 mm spatial-resolution pregnant-woman models comprised a woman model, which is similar to the average-sized Japanese adult female in height and weight, with a cubic (4 week) embryo or spheroidal (8 week) one. The averaged SAR in the embryos exposed to vertically and horizontally polarized plane waves at four kinds of propagation directions are calculated from 10 MHz to 1.5 GHz. The results indicate that the maximum average SAR in the embryos exposed to plane waves is lower than 0.08 W kg -1 when the incident power density is at the reference level of ICNIRP guideline for general public environment. (note)

  2. Transcranial cavitation-mediated ultrasound therapy at sub-MHz frequency via temporal interference modulation

    Science.gov (United States)

    Sun, Tao; Sutton, Jonathan T.; Power, Chanikarn; Zhang, Yongzhi; Miller, Eric L.; McDannold, Nathan J.

    2017-10-01

    Sub-megahertz transmission is not usually adopted in pre-clinical small animal experiments for focused ultrasound (FUS) brain therapy due to the large focal size. However, low frequency FUS is vital for preclinical evaluations due to the frequency-dependence of cavitation behavior. To maximize clinical relevance, a dual-aperture FUS system was designed for low-frequency (274.3 kHz) cavitation-mediated FUS therapy. Combining two spherically curved transducers provides significantly improved focusing in the axial direction while yielding an interference pattern with strong side lobes, leading to inhomogeneously distributed cavitation activities. By operating the two transducers at slightly offset frequencies to modulate this interference pattern over the period of sonication, the acoustic energy was redistributed and resulted in a spatially homogenous treatment profile. Simulation and pressure field measurements in water were performed to assess the beam profiles. In addition, the system performance was demonstrated in vivo in rats via drug delivery through microbubble-mediated blood-brain barrier disruption. This design resulted in a homogenous treatment profile that was fully contained within the rat brain at a clinically relevant acoustic frequency.

  3. High Precision Ranging and Range-Rate Measurements over Free-Space-Laser Communication Link

    Science.gov (United States)

    Yang, Guangning; Lu, Wei; Krainak, Michael; Sun, Xiaoli

    2016-01-01

    We present a high-precision ranging and range-rate measurement system via an optical-ranging or combined ranging-communication link. A complete bench-top optical communication system was built. It included a ground terminal and a space terminal. Ranging and range rate tests were conducted in two configurations. In the communication configuration with 622 data rate, we achieved a two-way range-rate error of 2 microns/s, or a modified Allan deviation of 9 x 10 (exp -15) with 10 second averaging time. Ranging and range-rate as a function of Bit Error Rate of the communication link is reported. They are not sensitive to the link error rate. In the single-frequency amplitude modulation mode, we report a two-way range rate error of 0.8 microns/s, or a modified Allan deviation of 2.6 x 10 (exp -15) with 10 second averaging time. We identified the major noise sources in the current system as the transmitter modulation injected noise and receiver electronics generated noise. A new improved system will be constructed to further improve the system performance for both operating modes.

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

    Directory of Open Access Journals (Sweden)

    Katsuya Kobayashi

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

  5. High-power non linear frequency converted laser diodes

    DEFF Research Database (Denmark)

    Jensen, Ole Bjarlin; Andersen, Peter E.; Hansen, Anders Kragh

    2015-01-01

    We present different methods of generating light in the blue-green spectral range by nonlinear frequency conversion of tapered diode lasers achieving state-of-the-art power levels. In the blue spectral range, we show results using single-pass second harmonic generation (SHG) as well as cavity enh...... enhanced sum frequency generation (SFG) with watt-level output powers. SHG and SFG are also demonstrated in the green spectral range as a viable method to generate up to 4 W output power with high efficiency using different configurations....

  6. Spatial filtering velocimeter for vehicle navigation with extended measurement range

    Science.gov (United States)

    He, Xin; Zhou, Jian; Nie, Xiaoming; Long, Xingwu

    2015-05-01

    The idea of using spatial filtering velocimeter is proposed to provide accurate velocity information for vehicle autonomous navigation system. The presented spatial filtering velocimeter is based on a CMOS linear image sensor. The limited frame rate restricts high speed measurement of the vehicle. To extend measurement range of the velocimeter, a method of frequency shifting is put forward. Theoretical analysis shows that the frequency of output signal can be reduced and the measurement range can be doubled by this method when the shifting direction is set the same with that of image velocity. The approach of fast Fourier transform (FFT) is employed to obtain the power spectra of the spatially filtered signals. Because of limited frequency resolution of FFT, a frequency spectrum correction algorithm, called energy centrobaric correction, is used to improve the frequency resolution. The correction accuracy energy centrobaric correction is analyzed. Experiments are carried out to measure the moving surface of a conveyor belt. The experimental results show that the maximum measurable velocity is about 800deg/s without frequency shifting, 1600deg/s with frequency shifting, when the frame rate of the image is about 8117 Hz. Therefore, the measurement range is doubled by the method of frequency shifting. Furthermore, experiments were carried out to measure the vehicle velocity simultaneously using both the designed SFV and a laser Doppler velocimeter (LDV). The measurement results of the presented SFV are coincident with that of the LDV, but with bigger fluctuation. Therefore, it has the potential of application to vehicular autonomous navigation.

  7. Prospects of Frequency-Time Correlation Analysis for Detecting Pipeline Leaks by Acoustic Emission Method

    International Nuclear Information System (INIS)

    Faerman, V A; Cheremnov, A G; Avramchuk, V V; Luneva, E E

    2014-01-01

    In the current work the relevance of nondestructive test method development applied for pipeline leak detection is considered. It was shown that acoustic emission testing is currently one of the most widely spread leak detection methods. The main disadvantage of this method is that it cannot be applied in monitoring long pipeline sections, which in its turn complicates and slows down the inspection of the line pipe sections of main pipelines. The prospects of developing alternative techniques and methods based on the use of the spectral analysis of signals were considered and their possible application in leak detection on the basis of the correlation method was outlined. As an alternative, the time-frequency correlation function calculation is proposed. This function represents the correlation between the spectral components of the analyzed signals. In this work, the technique of time-frequency correlation function calculation is described. The experimental data that demonstrate obvious advantage of the time-frequency correlation function compared to the simple correlation function are presented. The application of the time-frequency correlation function is more effective in suppressing the noise components in the frequency range of the useful signal, which makes maximum of the function more pronounced. The main drawback of application of the time- frequency correlation function analysis in solving leak detection problems is a great number of calculations that may result in a further increase in pipeline time inspection. However, this drawback can be partially reduced by the development and implementation of efficient algorithms (including parallel) of computing the fast Fourier transform using computer central processing unit and graphic processing unit

  8. 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

  9. Precision metrology of NSTX surfaces using coherent laser radar ranging

    International Nuclear Information System (INIS)

    Kugel, H.W.; Loesser, D.; Roquemore, A. L.; Menon, M. M.; Barry, R. E.

    2000-01-01

    A frequency modulated Coherent Laser Radar ranging diagnostic is being used on the National Spherical Torus Experiment (NSTX) for precision metrology. The distance (range) between the 1.5 microm laser source and the target is measured by the shift in frequency of the linearly modulated beam reflected off the target. The range can be measured to a precision of < 100microm at distances of up to 22 meters. A description is given of the geometry and procedure for measuring NSTX interior and exterior surfaces during open vessel conditions, and the results of measurements are elaborated

  10. A Comprehensive Evaluation of Indoor Ranging Using Ultra-Wideband Technology

    Directory of Open Access Journals (Sweden)

    Camillo Gentile

    2007-04-01

    Full Text Available Ultra-wideband technology shows promise for precision ranging due to its fine time resolution to resolve multipath fading and the presence of lower frequencies in the baseband to penetrate walls. While a concerted effort has been conducted in the extensive modeling of the indoor UWB channel in recent years, to our knowledge only two papers have reported ranging performance, but for limited range and fixed bandwidth and center frequency. In principle, boosting power can guarantee connectivity between transmitter and receiver, but not precision due to the distorting effects of walls and other objects in the direct path. In order to gauge the limits of UWB ranging, we carry out 5000 measurements up to an unprecedented 45 m in non-line-of-sight conditions in four separate buildings with dominant wall material varying from sheet rock to steel. In addition, we report performance for varying bandwidth and center frequency of the system.

  11. A Comprehensive Evaluation of Indoor Ranging Using Ultra-Wideband Technology

    Directory of Open Access Journals (Sweden)

    Gentile Camillo

    2007-01-01

    Full Text Available Ultra-wideband technology shows promise for precision ranging due to its fine time resolution to resolve multipath fading and the presence of lower frequencies in the baseband to penetrate walls. While a concerted effort has been conducted in the extensive modeling of the indoor UWB channel in recent years, to our knowledge only two papers have reported ranging performance, but for limited range and fixed bandwidth and center frequency. In principle, boosting power can guarantee connectivity between transmitter and receiver, but not precision due to the distorting effects of walls and other objects in the direct path. In order to gauge the limits of UWB ranging, we carry out 5000 measurements up to an unprecedented 45 m in non-line-of-sight conditions in four separate buildings with dominant wall material varying from sheet rock to steel. In addition, we report performance for varying bandwidth and center frequency of the system.

  12. Automatic Methods in Image Processing and Their Relevance to Map-Making.

    Science.gov (United States)

    1981-02-11

    folding fre- quency = .5) and s is the "shaoing fac- tor" which controls the spatial frequency content of the signal; the signal band- width increases...ARIZONA UNIV TUCSON DIGITAL IAgE ANALYSIS LAB Iris 8/ 2AUTOMATIC METHOOS IN IMAGE PROCESSING AND THEIR RELEVANCE TO MA-.ETC~tl;FEB 1 S R HUNT DAA629

  13. 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.

  14. An algorithm for the analysis of inductive antennas of arbitrary cross-section for heating in the ion cyclotron range of frequencies

    International Nuclear Information System (INIS)

    Lehrman, I.S.; Colestock, P.L.

    1986-10-01

    The application of Ion Cyclotron Range of Frequency (ICRF) heating to near ignited plasmas will require launching structures that will be capable of withstanding the harsh plasma environment. The recessed antenna configuration is expected to provide sufficient protection for the structure, but to date no analysis has been done to determine if adequate coupling can be achieved in such a configuration. In this work we present a method for determining the current distribution for the antenna in the direction transverse to current flow and predict antenna loading in the presence of plasma. Antennas of arbitrary cross section are analyzed above ground planes of arbitrary shape. Results from ANDES, the ANtenna DESign code, are presented and compared to experimental results

  15. Analysis and applications of a frequency selective surface via a random distribution method

    International Nuclear Information System (INIS)

    Xie Shao-Yi; Huang Jing-Jian; Yuan Nai-Chang; Liu Li-Guo

    2014-01-01

    A novel frequency selective surface (FSS) for reducing radar cross section (RCS) is proposed in this paper. This FSS is based on the random distribution method, so it can be called random surface. In this paper, the stacked patches serving as periodic elements are employed for RCS reduction. Previous work has demonstrated the efficiency by utilizing the microstrip patches, especially for the reflectarray. First, the relevant theory of the method is described. Then a sample of a three-layer variable-sized stacked patch random surface with a dimension of 260 mm×260 mm is simulated, fabricated, and measured in order to demonstrate the validity of the proposed design. For the normal incidence, the 8-dB RCS reduction can be achieved both by the simulation and the measurement in 8 GHz–13 GHz. The oblique incidence of 30° is also investigated, in which the 7-dB RCS reduction can be obtained in a frequency range of 8 GHz–14 GHz. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  16. Operational characteristics of the VEC radio-frequency system

    Energy Technology Data Exchange (ETDEWEB)

    Khemka, P K; Basu Mallik, D N; Bhattacharya, D S; Mukherjee, A K; Mukherjee, B; Ramamurthy, S S [Bhabha Atomic Research Centre, Bombay (India). Variable Energy Cyclotron Project

    1979-01-01

    The operating characteristics of the 400 kW rf system of the VEC, based on the RCA 6949 oscillator tube, and covering a frequency range of 5.5 to 16.5 MHz, are described. The frequency stability of the system is measured to be 1 part in 10/sup 5/, and a dee voltage of 40 kV at 8 MHz has been achieved. The results of experimental adjustments of ratio capacitor for proper excitation and appropriate fixed dee voltage over the entire frequency range are discussed. An analysis of the multi-pactoring encountered during beam trials is presented.

  17. Operational characteristics of the VEC radio frequency system

    International Nuclear Information System (INIS)

    Khemka, P.K.; Basu Mallik, D.N.; Bhattacharya, D.S.; Mukherjee, A.K.; Mukherjee, B.; Ramamurthy, S.S.

    1979-01-01

    The operating characteristics of the 400 KW RF system of the VEC, based on the RCA 6949 oscillator tube, and covering a frequency range of 5.5 to 16.5 MHZ, are described. The frequency stability of the system is measured to be 1 part in 10 5 , and a dee voltage of 40 kV at 8 MHZ has been achieved. The results of experimental adjustments of ratio capacitor for proper excitation and appropriate fixed dee voltage over the entire frequency range are discussed. An analysis of the multi-pactoring encountered during beam trials is presented. (auth.)

  18. Ranging Behaviour of Commercial Free-Range Broiler Chickens 1: Factors Related to Flock Variability.

    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 the ranging behaviour of chickens. Understanding ranging behaviour is required to improve management and shed and range design to ensure optimal ranging opportunities. Using Radio Frequency Identification technology, we tracked 300 individual broiler chickens in each of four mixed sex ROSS 308 flocks on one commercial farm across two seasons. Ranging behaviour was tracked from the first day of range access (21 days of age) until 35 days of age in winter and 44 days of age in summer. Range use was higher than previously reported from scan sampling studies. More chickens accessed the range in summer (81%) than winter (32%; p range use was greater in summer flocks (4.4 ± 0.1 visits for a total of 26.3 ± 0.8 min/day) than winter flocks (3.2 ± 0.2 visits for a total of 7.9 ± 1.0 min/day). Seasonal differences were only marginally explained by weather conditions and may reflect the reduction in range exposure between seasons (number of days, hours per day, and time of day). Specific times of the day ( p ranging and external factors that may explain ranging preferences.

  19. A vibration energy harvesting device with bidirectional resonance frequency tunability

    International Nuclear Information System (INIS)

    Challa, Vinod R; Prasad, M G; Shi Yong; Fisher, Frank T

    2008-01-01

    Vibration energy harvesting is an attractive technique for potential powering of wireless sensors and low power devices. While the technique can be employed to harvest energy from vibrations and vibrating structures, a general requirement independent of the energy transfer mechanism is that the vibration energy harvesting device operate in resonance at the excitation frequency. Most energy harvesting devices developed to date are single resonance frequency based, and while recent efforts have been made to broaden the frequency range of energy harvesting devices, what is lacking is a robust tunable energy harvesting technique. In this paper, the design and testing of a resonance frequency tunable energy harvesting device using a magnetic force technique is presented. This technique enabled resonance tuning to ± 20% of the untuned resonant frequency. In particular, this magnetic-based approach enables either an increase or decrease in the tuned resonant frequency. A piezoelectric cantilever beam with a natural frequency of 26 Hz is used as the energy harvesting cantilever, which is successfully tuned over a frequency range of 22–32 Hz to enable a continuous power output 240–280 µW over the entire frequency range tested. A theoretical model using variable damping is presented, whose results agree closely with the experimental results. The magnetic force applied for resonance frequency tuning and its effect on damping and load resistance have been experimentally determined

  20. Brain-computer interface based on intermodulation frequency

    Science.gov (United States)

    Chen, Xiaogang; Chen, Zhikai; Gao, Shangkai; Gao, Xiaorong

    2013-12-01

    Objective. Most recent steady-state visual evoked potential (SSVEP)-based brain-computer interface (BCI) systems have used a single frequency for each target, so that a large number of targets require a large number of stimulus frequencies and therefore a wider frequency band. However, human beings show good SSVEP responses only in a limited range of frequencies. Furthermore, this issue is especially problematic if the SSVEP-based BCI takes a PC monitor as a stimulator, which is only capable of generating a limited range of frequencies. To mitigate this issue, this study presents an innovative coding method for SSVEP-based BCI by means of intermodulation frequencies. Approach. Simultaneous modulations of stimulus luminance and color at different frequencies were utilized to induce intermodulation frequencies. Luminance flickered at relatively large frequency (10, 12, 15 Hz), while color alternated at low frequency (0.5, 1 Hz). An attractive feature of the proposed method was that it would substantially increase the number of targets at a single flickering frequency by altering color modulated frequencies. Based on this method, the BCI system presented in this study realized eight targets merely using three flickering frequencies. Main results. The online results obtained from 15 subjects (14 healthy and 1 with stroke) revealed that an average classification accuracy of 93.83% and information transfer rate (ITR) of 33.80 bit min-1 were achieved using our proposed SSVEP-based BCI system. Specifically, 5 out of the 15 subjects exhibited an ITR of 40.00 bit min-1 with a classification accuracy of 100%. Significance. These results suggested that intermodulation frequencies could be adopted as steady responses in BCI, for which our system could be used as a practical BCI system.

  1. Ultra-low-power short-range radios

    CERN Document Server

    Chandrakasan, Anantha

    2015-01-01

    This book explores the design of ultra-low-power radio-frequency integrated circuits (RFICs), with communication distances ranging from a few centimeters to a few meters. Such radios have unique challenges compared to longer-range, higher-powered systems. As a result, many different applications are covered, ranging from body-area networks to transcutaneous implant communications and Internet-of-Things devices. A mix of introductory and cutting-edge design techniques and architectures which facilitate each of these applications are discussed in detail. Specifically, this book covers:.

  2. Relevance of brain lesion location to cognition in relapsing multiple sclerosis.

    Directory of Open Access Journals (Sweden)

    Francesca Rossi

    Full Text Available OBJECTIVE: To assess the relationship between cognition and brain white matter (WM lesion distribution and frequency in patients with relapsing-remitting multiple sclerosis (RR MS. METHODS: MRI-based T2 lesion probability map (LPM was used to assess the relevance of brain lesion location for cognitive impairment in a group of 142 consecutive patients with RRMS. Significance of voxelwise analyses was p<0.05, cluster-corrected for multiple comparisons. The Rao Brief Repeatable Battery was administered at the time of brain MRI to categorize the MS population into cognitively preserved (CP and cognitively impaired (CI. RESULTS: Out of 142 RRMS, 106 were classified as CP and 36 as CI. Although the CI group had greater WM lesion volume than the CP group (p = 0.001, T2 lesions tended to be less widespread across the WM. The peak of lesion frequency was almost twice higher in CI (61% in the forceps major than in CP patients (37% in the posterior corona radiata. The voxelwise analysis confirmed that lesion frequency was higher in CI than in CP patients with significant bilateral clusters in the forceps major and in the splenium of the corpus callosum (p<0.05, corrected. Low scores of the Symbol Digit Modalities Test correlated with higher lesion frequency in these WM regions. CONCLUSIONS: Overall these results suggest that in MS patients, areas relevant for cognition lie mostly in the commissural fiber tracts. This supports the notion of a functional (multiple disconnection between grey matter structures, secondary to damage located in specific WM areas, as one of the most important mechanisms leading to cognitive impairment in MS.

  3. A Rapid Subcortical Amygdala Route for Faces Irrespective of Spatial Frequency and Emotion.

    Science.gov (United States)

    McFadyen, Jessica; Mermillod, Martial; Mattingley, Jason B; Halász, Veronika; Garrido, Marta I

    2017-04-05

    There is significant controversy over the existence and function of a direct subcortical visual pathway to the amygdala. It is thought that this pathway rapidly transmits low spatial frequency information to the amygdala independently of the cortex, and yet the directionality of this function has never been determined. We used magnetoencephalography to measure neural activity while human participants discriminated the gender of neutral and fearful faces filtered for low or high spatial frequencies. We applied dynamic causal modeling to demonstrate that the most likely underlying neural network consisted of a pulvinar-amygdala connection that was uninfluenced by spatial frequency or emotion, and a cortical-amygdala connection that conveyed high spatial frequencies. Crucially, data-driven neural simulations revealed a clear temporal advantage of the subcortical connection over the cortical connection in influencing amygdala activity. Thus, our findings support the existence of a rapid subcortical pathway that is nonselective in terms of the spatial frequency or emotional content of faces. We propose that that the "coarseness" of the subcortical route may be better reframed as "generalized." SIGNIFICANCE STATEMENT The human amygdala coordinates how we respond to biologically relevant stimuli, such as threat or reward. It has been postulated that the amygdala first receives visual input via a rapid subcortical route that conveys "coarse" information, namely, low spatial frequencies. For the first time, the present paper provides direction-specific evidence from computational modeling that the subcortical route plays a generalized role in visual processing by rapidly transmitting raw, unfiltered information directly to the amygdala. This calls into question a widely held assumption across human and animal research that fear responses are produced faster by low spatial frequencies. Our proposed mechanism suggests organisms quickly generate fear responses to a wide range

  4. Josephson frequency meter for millimeter and submillimeter wavelengths

    Energy Technology Data Exchange (ETDEWEB)

    Anischenko, S.E.; Larkin, S.Y.; Chaikovsky, V.I. [State Research Center, Kiev (Ukraine)] [and others

    1994-12-31

    Frequency measurements of electromagnetic oscillations of millimeter and submillimeter wavebands with frequency growth due to a number of reasons become more and more difficult. First, these frequencies are considered to be cutoff for semiconductor converting devices and one has to use optical measurement methods instead of traditional ones with frequency transfer. Second, resonance measurement methods are characterized by using relatively narrow bands and optical ones are limited in frequency and time resolution due to the limited range and velocity of movement of their mechanical elements as well as the efficiency of these optical techniques decreases with the increase of wavelength due to diffraction losses. That requires the apriori information on the radiation frequency band of the source involved. Method of measuring frequency of harmonic microwave signals in millimeter and submillimeter wavebands based on the ac Josephson effect in superconducting contacts is devoid of all the above drawbacks. This approach offers a number of major advantages over the more traditional measurement methods, that is the one based on frequency conversion, resonance and interferrometric techniques. It can be characterized by high potential accuracy, wide range of frequencies measured, prompt measurement and the opportunity to obtain panoramic display of the results as well as full automation of the measuring process.

  5. Josephson frequency meter for millimeter and submillimeter wavelengths

    International Nuclear Information System (INIS)

    Anischenko, S.E.; Larkin, S.Y.; Chaikovsky, V.I.

    1994-01-01

    Frequency measurements of electromagnetic oscillations of millimeter and submillimeter wavebands with frequency growth due to a number of reasons become more and more difficult. First, these frequencies are considered to be cutoff for semiconductor converting devices and one has to use optical measurement methods instead of traditional ones with frequency transfer. Second, resonance measurement methods are characterized by using relatively narrow bands and optical ones are limited in frequency and time resolution due to the limited range and velocity of movement of their mechanical elements as well as the efficiency of these optical techniques decreases with the increase of wavelength due to diffraction losses. That requires the apriori information on the radiation frequency band of the source involved. Method of measuring frequency of harmonic microwave signals in millimeter and submillimeter wavebands based on the ac Josephson effect in superconducting contacts is devoid of all the above drawbacks. This approach offers a number of major advantages over the more traditional measurement methods, that is the one based on frequency conversion, resonance and interferrometric techniques. It can be characterized by high potential accuracy, wide range of frequencies measured, prompt measurement and the opportunity to obtain panoramic display of the results as well as full automation of the measuring process

  6. Free-ranging male koalas use size-related variation in formant frequencies to assess rival males.

    Directory of Open Access Journals (Sweden)

    Benjamin D Charlton

    Full Text Available Although the use of formant frequencies in nonhuman animal vocal communication systems has received considerable recent interest, only a few studies have examined the importance of these acoustic cues to body size during intra-sexual competition between males. Here we used playback experiments to present free-ranging male koalas with re-synthesised bellow vocalisations in which the formants were shifted to simulate either a large or a small adult male. We found that male looking responses did not differ according to the size variant condition played back. In contrast, male koalas produced longer bellows and spent more time bellowing when they were presented with playbacks simulating larger rivals. In addition, males were significantly slower to respond to this class of playback stimuli than they were to bellows simulating small males. Our results indicate that male koalas invest more effort into their vocal responses when they are presented with bellows that have lower formants indicative of larger rivals, but also show that males are slower to engage in vocal exchanges with larger males that represent more dangerous rivals. By demonstrating that male koalas use formants to assess rivals during the breeding season we have provided evidence that male-male competition constitutes an important selection pressure for broadcasting and attending to size-related formant information in this species. Further empirical studies should investigate the extent to which the use of formants during intra-sexual competition is widespread throughout mammals.

  7. Low-frequency characteristics extension for vibration sensors

    Institute of Scientific and Technical Information of China (English)

    杨学山; 高峰; 候兴民

    2004-01-01

    Traditional magneto-electric vibration sensors and servo accelerometers have severe shortcomings when used to measure vibration where low frequency components predominate. A low frequency characteristic extension for velocity vibration sensors is presented in this paper. The passive circuit technology, active compensation technology and the closedcycle pole compensation technology are used to extend the measurable range and to improve low frequency characteristics of sensors. Thses three types of low frequency velocity vibration sensors have been developed and widely adopted in China.

  8. Low frequency noise from large wind turbines - updated 2011; Lavfrekvent stoej fra store vindmoeller - opdateret 2011

    Energy Technology Data Exchange (ETDEWEB)

    Moeller, H.; Sejer Pedersen, C.; Pedersen, Steffen

    2011-07-01

    The study analyzed measurements of noise from 65 wind turbines, 25 large turbines (2.3 to 3.6 MW) and 40 small ones (up to 2 MW). The large mills (2.3 to 3.6 MW) emit relatively more low frequency noise than the small ones (up to 2 MW). The difference is statistically significant for the frequency range 63-250 Hz, regardless of whether calculations are performed on all the large mills or only on new wind turbines. There are no significant differences between prototype turbines and the new mills. Because of wind noise in the measurements of the small mills, it is not possible to determine whether the difference between small and large turbines continues further down in frequency. Looking at the A-weighted sound pressure in relevant neighbor distances, the lower frequencies constitute an essential part of the noise from the large mills, and there is no doubt that the low frequency noise is both audible and annoying. When the total A-weighted sound pressure level is the same, there will on average be about 3 dB more low frequency noise from large turbines than from small ones. At large distances the noise character becomes yet more low frequency because atmospheric absorption reduces the high frequencies more than the low frequencies. Depending on the sound insulation the low frequency noise can also be annoying indoors. If the total A-weighted sound pressure level outdoors is 44 dB, the low frequency noise can be heard indoors in all the houses and for all the large turbines. The sound pressure level will in many cases exceed the indoor limit for evening night at 20 dB. (ln)

  9. Radio frequency heating of fusion plasms

    International Nuclear Information System (INIS)

    Swanson, D.G.

    1983-01-01

    The electron cyclotron range of frequencies has been used successfully for plasma heating perhaps longer than any other RF plasma heating scheme and is generally well understood. The problem has always been that the strong magnetic field required for fusion devices puts the electron cyclotron frequency so high that it is at or above the high power technology limit. The development of high power gyrotrons (> 200 kW) in recent years with steadily rising frequency limits, however, has brought about a renaissance of interest in ECRH as relativistic electron energies well in excess of those required for fusion have been obtained. The relativistic electron ring stabilization of the Elmo Bumpy Torus (EBT), which was achieved with ECRF, only at one point made the EBT the most promising new fusion concept of the last decade. The results also made clear that the physical understanding of the heating processes in this frequency range, so long neglected because of the technology limitation, are not fully understood so that more basic physics is necessary before ECRF can reach the potential that technology now seems to allow

  10. 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.

  11. The vibrating reed frequency meter: digital investigation of an early cochlear model

    Directory of Open Access Journals (Sweden)

    Andrew Bell

    2015-10-01

    Full Text Available The vibrating reed frequency meter, originally employed by Békésy and later by Wilson as a cochlear model, uses a set of tuned reeds to represent the cochlea’s graded bank of resonant elements and an elastic band threaded between them to provide nearest-neighbour coupling. Here the system, constructed of 21 reeds progressively tuned from 45 to 55 Hz, is simulated numerically as an elastically coupled bank of passive harmonic oscillators driven simultaneously by an external sinusoidal force. To uncover more detail, simulations were extended to 201 oscillators covering the range 1–2 kHz. Calculations mirror the results reported by Wilson and show expected characteristics such as traveling waves, phase plateaus, and a response with a broad peak at a forcing frequency just above the natural frequency. The system also displays additional fine-grain features that resemble those which have only recently been recognised in the cochlea. Thus, detailed analysis brings to light a secondary peak beyond the main peak, a set of closely spaced low-amplitude ripples, rapid rotation of phase as the driving frequency is swept, frequency plateaus, clustering, and waxing and waning of impulse responses. Further investigation shows that each reed’s vibrations are strongly localised, with small energy flow along the chain. The distinctive set of equally spaced ripples is an inherent feature which is found to be largely independent of boundary conditions. Although the vibrating reed model is functionally different to the standard transmission line, its cochlea-like properties make it an intriguing local oscillator model whose relevance to cochlear mechanics needs further investigation.

  12. Measurements of intermediate-frequency electric and magnetic fields in households

    NARCIS (Netherlands)

    Aerts, Sam; Calderon, Carolina; Valič, Blaž; Maslanyj, Myron; Addison, Darren; Mee, Terry; Goiceanu, Cristian; Verloock, Leen; Van den Bossche, Matthias; Gajšek, Peter; Vermeulen, Roel; Röösli, Martin; Cardis, Elisabeth; Martens, Luc; Joseph, Wout

    Historically, assessment of human exposure to electric and magnetic fields has focused on the extremely-low-frequency (ELF) and radiofrequency (RF) ranges. However, research on the typically emitted fields in the intermediate-frequency (IF) range (300Hz to 1MHz) as well as potential effects of IF

  13. Contact resistance measurement structures for high frequencies

    NARCIS (Netherlands)

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

    2011-01-01

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

  14. Black Jacobin hummingbirds vocalize above the known hearing range of birds.

    Science.gov (United States)

    Olson, Christopher R; Fernández-Vargas, Marcela; Portfors, Christine V; Mello, Claudio V

    2018-03-05

    Hummingbirds are a fascinating group of birds, but some aspects of their biology are poorly understood, such as their highly diverse vocal behaviors. We show here that the predominant vocalization of black jacobins (Florisuga fusca), a hummingbird prevalent in the mountains of the Brazilian Atlantic Forest, consists of a triplet of syllables with high fundamental frequency (mean F0 ∼11.8 kHz), rapid frequency oscillations and strong ultrasonic harmonics and no detectable elements below ∼10 kHz. These are the most common vocalizations of these birds, and their frequency range is above the known hearing range of any bird species recorded to date, including hearing specialists such as owls. These observations suggest that black jacobins either have an atypically high frequency hearing range, or alternatively their primary vocalization has a yet unknown function unrelated to vocal communication. Black jacobin vocalizations challenge current notions about vocal communication in birds. Copyright © 2018 Elsevier Ltd. All rights reserved.

  15. Theta frequency background tunes transmission but not summation of spiking responses.

    Directory of Open Access Journals (Sweden)

    Dhanya Parameshwaran

    Full Text Available Hippocampal neurons are known to fire as a function of frequency and phase of spontaneous network rhythms, associated with the animal's behaviour. This dependence is believed to give rise to precise rate and temporal codes. However, it is not well understood how these periodic membrane potential fluctuations affect the integration of synaptic inputs. Here we used sinusoidal current injection to the soma of CA1 pyramidal neurons in the rat brain slice to simulate background oscillations in the physiologically relevant theta and gamma frequency range. We used a detailed compartmental model to show that somatic current injection gave comparable results to more physiological synaptically driven theta rhythms incorporating excitatory input in the dendrites, and inhibitory input near the soma. We systematically varied the phase of synaptic inputs with respect to this background, and recorded changes in response and summation properties of CA1 neurons using whole-cell patch recordings. The response of the cell was dependent on both the phase of synaptic inputs and frequency of the background input. The probability of the cell spiking for a given synaptic input was up to 40% greater during the depolarized phases between 30-135 degrees of theta frequency current injection. Summation gain on the other hand, was not affected either by the background frequency or the phasic afferent inputs. This flat summation gain, coupled with the enhanced spiking probability during depolarized phases of the theta cycle, resulted in enhanced transmission of summed inputs during the same phase window of 30-135 degrees. Overall, our study suggests that although oscillations provide windows of opportunity to selectively boost transmission and EPSP size, summation of synaptic inputs remains unaffected during membrane oscillations.

  16. Characterization of Definity™ Ultrasound Contrast Agent at Frequency Range of 5–15 MHz

    NARCIS (Netherlands)

    Faez, Telli; Goertz, David; de Jong, N.

    2011-01-01

    The status of vasa vasorum, which can be imaged using ultrasound contrast agents, is an indication for the progression of atherosclerosis. The preferred ultrasound frequency for this purpose is between 5 and 15 MHz. Therefore, it is essential to have knowledge about the acoustic properties of

  17. Clamped seismic metamaterials: ultra-low frequency stop bands

    International Nuclear Information System (INIS)

    Achaoui, Y; Enoch, S; Guenneau, S; Antonakakis, T; Brûlé, S; Craster, R V

    2017-01-01

    The regularity of earthquakes, their destructive power, and the nuisance of ground vibration in urban environments, all motivate designs of defence structures to lessen the impact of seismic and ground vibration waves on buildings. Low frequency waves, in the range 1–10 Hz for earthquakes and up to a few tens of Hz for vibrations generated by human activities, cause a large amount of damage, or inconvenience; depending on the geological conditions they can travel considerable distances and may match the resonant fundamental frequency of buildings. The ultimate aim of any seismic metamaterial, or any other seismic shield, is to protect over this entire range of frequencies; the long wavelengths involved, and low frequency, have meant this has been unachievable to date. Notably this is scalable and the effects also hold for smaller devices in ultrasonics. There are three approaches to obtaining shielding effects: bragg scattering, locally resonant sub-wavelength inclusions and zero-frequency stop-band media. The former two have been explored, but the latter has not and is examined here. Elastic flexural waves, applicable in the mechanical vibrations of thin elastic plates, can be designed to have a broad zero-frequency stop-band using a periodic array of very small clamped circles. Inspired by this experimental and theoretical observation, all be it in a situation far removed from seismic waves, we demonstrate that it is possible to achieve elastic surface (Rayleigh) wave reflectors at very large wavelengths in structured soils modelled as a fully elastic layer periodically clamped to bedrock. We identify zero frequency stop-bands that only exist in the limit of columns of concrete clamped at their base to the bedrock. In a realistic configuration of a sedimentary basin 15 m deep we observe a zero frequency stop-band covering a broad frequency range of 0–30 Hz. (paper)

  18. Rydberg-atom based radio-frequency electrometry using frequency modulation spectroscopy in room temperature vapor cells.

    Science.gov (United States)

    Kumar, Santosh; Fan, Haoquan; Kübler, Harald; Jahangiri, Akbar J; Shaffer, James P

    2017-04-17

    Rydberg atom-based electrometry enables traceable electric field measurements with high sensitivity over a large frequency range, from gigahertz to terahertz. Such measurements are particularly useful for the calibration of radio frequency and terahertz devices, as well as other applications like near field imaging of electric fields. We utilize frequency modulated spectroscopy with active control of residual amplitude modulation to improve the signal to noise ratio of the optical readout of Rydberg atom-based radio frequency electrometry. Matched filtering of the signal is also implemented. Although we have reached similarly, high sensitivity with other read-out methods, frequency modulated spectroscopy is advantageous because it is well-suited for building a compact, portable sensor. In the current experiment, ∼3 µV cm-1 Hz-1/2 sensitivity is achieved and is found to be photon shot noise limited.

  19. Current-to-frequency converter

    Energy Technology Data Exchange (ETDEWEB)

    Glowacki, S W [Institute of Nuclear Research, Warsaw (Poland)

    1981-07-15

    A current-to-frequency converter covering the range from 3 x 10/sup -10/ A up to 3 x 10/sup -5/ A of the input current is described. The circuit operates with nuclear detectors featuring a high internal resistance.

  20. Resonant long-range interactions between polar macromolecules

    International Nuclear Information System (INIS)

    Preto, Jordane; Pettini, Marco

    2013-01-01

    Motivated by its prospective biological relevance, the issue of resonant long-range interactions between two molecules displaying oscillating dipole moments is reinvestigated within the framework of classical electrodynamics. In particular, our findings shed new light on Fröhlich's theory of selective long-range interactions between biomolecules. First, terms of a very long-range kind – which have never been reported so far – are found in the interaction potential, due to field retardation. Second, at variance with a long-standing belief, it is shown that sizable resonant long-range interactions may exist only if the interacting system is out of thermal equilibrium.

  1. Frequency Adaptability of Harmonics Controllers for Grid-Interfaced Converters

    DEFF Research Database (Denmark)

    Yang, Yongheng; Zhou, Keliang; Blaabjerg, Frede

    2017-01-01

    sensitivity of the most popular harmonic controllers for grid-interfaced converters. The frequency adaptability of these harmonic controllers is evaluated in the presence of a variable grid frequency within a specified reasonable range, e.g., +-1% of the nominal grid frequency (50 Hz). Solutions...

  2. Large Amplitude Low Frequency Waves in a Magnetized Nonuniform Electron-Positron-Ion Plasma

    Institute of Scientific and Technical Information of China (English)

    Q. Haque; H. Saleem

    2004-01-01

    @@ It is shown that the large amplitude low-frequency electromagnetic drift waves in electron-positron-ion plasmas might give rise to dipolar vortices. A linear dispersion relation of several coupled electrostatic and electromagnetic low-frequency modes is obtained. The relevance of this work to both laboratory and astrophysical situations is pointed out.

  3. 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

  4. Biological effects of exposure to low frequency electric and magnetic fields

    International Nuclear Information System (INIS)

    Ahnstroem, G.

    1992-10-01

    The biological effects of exposure to low frequency electric and magnetic fields are reviewed with the objective of summarizing effects directly relevant to considerations of the health and safety of exposed people

  5. Environmental Assessment (EA) for the Comprehensive Range Plan (CRP), Melrose Air Force Range (AFR), New Mexico

    Science.gov (United States)

    2011-07-01

    intensity, frequency, and duration. Sound is created by acoustic energy, which produces minute pressure waves that travel through a medium (like air...concave plains associated with playa lake basins. Slope ranges from zero to 1 percent. Olton Loams – Consist of very deep, well-drained, moderately slow...gently sloping plains and upper side slopes of playas and draws. Slopes range from zero to 5 percent. 3.5.2.2 Water Resources Surface Water – The most

  6. Progress on radio frequency auxiliary heating system designs in ITER

    International Nuclear Information System (INIS)

    Makowski, M.; Bosia, G.; Elio, F.

    1996-09-01

    ITER will require over 100 MW of auxiliary power for heating, on- and off-axis current drive, accessing the H-mode, and plasma shut-down. The Electron Cyclotron Range of Frequencies (ECRF) and Ion Cyclotron Range of Frequencies (ICRF) are two forms of Radio Frequency (RF) auxiliary power being developed for these applications. Design concepts for both the ECRF and ICRF systems are presented, key features and critical design issues are discussed, and projected performances outlined

  7. Natural frequencies, modeshapes and modal interactions for strings vibrating against an obstacle: Relevance to Sitar and Veena

    Science.gov (United States)

    Mandal, A. K.; Wahi, P.

    2015-03-01

    We study the vibration characteristics of a string with a smooth unilateral obstacle placed at one of the ends similar to the strings in musical instruments like sitar and veena. In particular, we explore the correlation between the string vibrations and some unique sound characteristics of these instruments like less inharmonicity in the frequencies, a large number of overtones and the presence of both frequency and amplitude modulations. At the obstacle, we have a moving boundary due to the wrapping of the string and an appropriate scaling of the spatial variable leads to a fixed boundary at the cost of introducing nonlinearity in the governing equation. Reduced order system of equations has been obtained by assuming a functional form for the string displacement which satisfies all the boundary conditions and gives the free length of the string in terms of the modal coordinates. To study the natural frequencies and mode-shapes, the nonlinear governing equation is linearized about the static configuration. The natural frequencies have been found to be harmonic and they depend on the shape of the obstacle through the effective free length of the string. Expressions have been obtained for the time-varying mode-shapes as well as the variation of the nodal points. Modal interactions due to coupling have been studied which show the appearance of higher overtones as well as amplitude modulations in our theoretical model akin to the experimental observations. All the obtained results have been verified with an alternate formulation based on the assumed mode method with polynomial shape functions.

  8. Estimation of the center frequency of the highest modulation filter.

    Science.gov (United States)

    Moore, Brian C J; Füllgrabe, Christian; Sek, Aleksander

    2009-02-01

    For high-frequency sinusoidal carriers, the threshold for detecting sinusoidal amplitude modulation increases when the signal modulation frequency increases above about 120 Hz. Using the concept of a modulation filter bank, this effect might be explained by (1) a decreasing sensitivity or greater internal noise for modulation filters with center frequencies above 120 Hz; and (2) a limited span of center frequencies of the modulation filters, the top filter being tuned to about 120 Hz. The second possibility was tested by measuring modulation masking in forward masking using an 8 kHz sinusoidal carrier. The signal modulation frequency was 80, 120, or 180 Hz and the masker modulation frequencies covered a range above and below each signal frequency. Four highly trained listeners were tested. For the 80-Hz signal, the signal threshold was usually maximal when the masker frequency equaled the signal frequency. For the 180-Hz signal, the signal threshold was maximal when the masker frequency was below the signal frequency. For the 120-Hz signal, two listeners showed the former pattern, and two showed the latter pattern. The results support the idea that the highest modulation filter has a center frequency in the range 100-120 Hz.

  9. 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.

  10. Dielectric relaxation in solid collagen over a wide temperature range

    International Nuclear Information System (INIS)

    Khan, Muhammad Abdullah; Rizvi, Tasneem Zahra; Janjua, Khalid Mehmood; Zaheer, Muhammad Yar

    2001-07-01

    Dielectric constant ε' and loss factor ε'' have been measured in bovine tendon collagen in the frequency range 30 Hz - 3 MHz and temperature range 30 deg. C to 200 deg. C. Frequency dependence curve of ε'' shows a low frequency strong α-dispersion attributed to phonon assisted proton hopping between localized sites and a weak high frequency. α 2 - dispersion attributed to reorientation of polar components of collagen molecules. Temperature dependence of the dielectric data show release of bound moisture as a three step process with discrete peaks at 50 deg. C, 90 deg. C and 125 deg. C. These peaks have been attributed to release of adsorbed surface water, water bound to exposed polar sites and strongly bound internal moisture respectively. A peak observed at 160 deg. C has been attributed to thermally induced helix-coil transition of collagen molecules. (author)

  11. Relevance of randomised controlled trials in oncology.

    Science.gov (United States)

    Tannock, Ian F; Amir, Eitan; Booth, Christopher M; Niraula, Saroj; Ocana, Alberto; Seruga, Bostjan; Templeton, Arnoud J; Vera-Badillo, Francisco

    2016-12-01

    Well-designed randomised controlled trials (RCTs) can prevent bias in the comparison of treatments and provide a sound basis for changes in clinical practice. However, the design and reporting of many RCTs can render their results of little relevance to clinical practice. In this Personal View, we discuss the limitations of RCT data and suggest some ways to improve the clinical relevance of RCTs in the everyday management of patients with cancer. RCTs should ask questions of clinical rather than commercial interest, avoid non-validated surrogate endpoints in registration trials, and have entry criteria that allow inclusion of all patients who are fit to receive treatment. Furthermore, RCTs should be reported with complete accounting of frequency and management of toxicities, and with strict guidelines to ensure freedom from bias. Premature reporting of results should be avoided. The bar for clinical benefit should be raised for drug registration, which should require publication and review of mature data from RCTs, post-marketing health outcome studies, and value-based pricing. Copyright © 2016 Elsevier Ltd. All rights reserved.

  12. Novel structural flexibility identification in narrow frequency bands

    International Nuclear Information System (INIS)

    Zhang, J; Moon, F L

    2012-01-01

    A ‘Sub-PolyMAX’ method is proposed in this paper not only for estimating modal parameters, but also for identifying structural flexibility by processing the impact test data in narrow frequency bands. The traditional PolyMAX method obtains denominator polynomial coefficients by minimizing the least square (LS) errors of frequency response function (FRF) estimates over the whole frequency range, but FRF peaks in different structural modes may have different levels of magnitude, which leads to the modal parameters identified for the modes with small FRF peaks being inaccurate. In contrast, the proposed Sub-PolyMAX method implements the LS solver in each subspace of the whole frequency range separately; thus the results identified from a narrow frequency band are not affected by FRF data in other frequency bands. In performing structural identification in narrow frequency bands, not in the whole frequency space, the proposed method has the following merits: (1) it produces accurate modal parameters, even for the modes with very small FRF peaks; (2) it significantly reduces computation cost by reducing the number of frequency lines and the model order in each LS implementation; (3) it accurately identifies structural flexibility from impact test data, from which structural deflection under any static load can be predicted. Numerical and laboratory examples are investigated to verify the effectiveness of the proposed method. (paper)

  13. Laser Spectroscopy and Frequency Combs

    International Nuclear Information System (INIS)

    Hänsch, Theodor W; Picqué, Nathalie

    2013-01-01

    The spectrum of a frequency comb, commonly generated by a mode-locked femtosecond laser consists of several hundred thousand precisely evenly spaced spectral lines. Such laser frequency combs have revolutionized the art measuring the frequency of light, and they provide the long-missing clockwork for optical atomic clocks. The invention of the frequency comb technique has been motivated by precision laser spectroscopy of the simple hydrogen atom. The availability of commercial instruments is facilitating the evolution of new applications far beyond the original purpose. Laser combs are becoming powerful instruments for broadband molecular spectroscopy by dramatically improving the resolution and recording speed of Fourier spectrometers and by creating new opportunities for highly multiplexed nonlinear spectroscopy, such as two-photon spectroscopy or coherent Raman spectroscopy. Other emerging applications of frequency combs range from fundamental research in astronomy, chemistry, or attosecond science to telecommunications and satellite navigation

  14. THE IMPACT OF FREQUENCY STANDARDS ON COHERENCE IN VLBI AT THE HIGHEST FREQUENCIES

    Energy Technology Data Exchange (ETDEWEB)

    Rioja, M.; Dodson, R. [ICRAR, University of Western Australia, Perth (Australia); Asaki, Y. [Institute of Space and Astronautical Science, 3-1-1 Yoshinodai, Chuou, Sagamihara, Kanagawa 252-5210 (Japan); Hartnett, J. [School of Physics, University of Western Australia, Perth (Australia); Tingay, S., E-mail: maria.rioja@icrar.org [ICRAR, Curtin University, Perth (Australia)

    2012-10-01

    We have carried out full imaging simulation studies to explore the impact of frequency standards in millimeter and submillimeter very long baseline interferometry (VLBI), focusing on the coherence time and sensitivity. In particular, we compare the performance of the H-maser, traditionally used in VLBI, to that of ultra-stable cryocooled sapphire oscillators over a range of observing frequencies, weather conditions, and analysis strategies. Our simulations show that at the highest frequencies, the losses induced by H-maser instabilities are comparable to those from high-quality tropospheric conditions. We find significant benefits in replacing H-masers with cryocooled sapphire oscillator based frequency references in VLBI observations at frequencies above 175 GHz in sites which have the best weather conditions; at 350 GHz we estimate a 20%-40% increase in sensitivity over that obtained when the sites have H-masers, for coherence losses of 20%-10%, respectively. Maximum benefits are to be expected by using co-located Water Vapor Radiometers for atmospheric correction. In this case, we estimate a 60%-120% increase in sensitivity over the H-maser at 350 GHz.

  15. Attention-driven auditory cortex short-term plasticity helps segregate relevant sounds from noise.

    Science.gov (United States)

    Ahveninen, Jyrki; Hämäläinen, Matti; Jääskeläinen, Iiro P; Ahlfors, Seppo P; Huang, Samantha; Lin, Fa-Hsuan; Raij, Tommi; Sams, Mikko; Vasios, Christos E; Belliveau, John W

    2011-03-08

    How can we concentrate on relevant sounds in noisy environments? A "gain model" suggests that auditory attention simply amplifies relevant and suppresses irrelevant afferent inputs. However, it is unclear whether this suffices when attended and ignored features overlap to stimulate the same neuronal receptive fields. A "tuning model" suggests that, in addition to gain, attention modulates feature selectivity of auditory neurons. We recorded magnetoencephalography, EEG, and functional MRI (fMRI) while subjects attended to tones delivered to one ear and ignored opposite-ear inputs. The attended ear was switched every 30 s to quantify how quickly the effects evolve. To produce overlapping inputs, the tones were presented alone vs. during white-noise masking notch-filtered ±1/6 octaves around the tone center frequencies. Amplitude modulation (39 vs. 41 Hz in opposite ears) was applied for "frequency tagging" of attention effects on maskers. Noise masking reduced early (50-150 ms; N1) auditory responses to unattended tones. In support of the tuning model, selective attention canceled out this attenuating effect but did not modulate the gain of 50-150 ms activity to nonmasked tones or steady-state responses to the maskers themselves. These tuning effects originated at nonprimary auditory cortices, purportedly occupied by neurons that, without attention, have wider frequency tuning than ±1/6 octaves. The attentional tuning evolved rapidly, during the first few seconds after attention switching, and correlated with behavioral discrimination performance. In conclusion, a simple gain model alone cannot explain auditory selective attention. In nonprimary auditory cortices, attention-driven short-term plasticity retunes neurons to segregate relevant sounds from noise.

  16. Artificial excitation of ELF waves with frequency of Schumann resonance

    Science.gov (United States)

    Streltsov, A. V.; Guido, T.; Tulegenov, B.; Labenski, J.; Chang, C.-L.

    2014-11-01

    We report results from the experiment aimed at the artificial excitation of extremely low-frequency (ELF) electromagnetic waves with frequencies corresponding to the frequency of Schumann resonance. Electromagnetic waves with these frequencies can form a standing pattern inside the spherical cavity formed by the surface of the Earth and the ionosphere. In the experiment the ELF waves were excited by heating the ionosphere with X-mode HF electromagnetic waves generated at the High Frequency Active Auroral Research Program (HAARP) facility in Alaska. The experiment demonstrates that heating of the ionosphere can excite relatively large-amplitude electromagnetic waves with frequencies in the range 7.8-8.0 Hz when the ionosphere has a strong F layer, the frequency of the HF radiation is in the range 3.20-4.57 MHz, and the electric field greater than 5 mV/m is present in the ionosphere.

  17. Transformation Algorithm of Dielectric Response in Time-Frequency Domain

    Directory of Open Access Journals (Sweden)

    Ji Liu

    2014-01-01

    Full Text Available A transformation algorithm of dielectric response from time domain to frequency domain is presented. In order to shorten measuring time of low or ultralow frequency dielectric response characteristics, the transformation algorithm is used in this paper to transform the time domain relaxation current to frequency domain current for calculating the low frequency dielectric dissipation factor. In addition, it is shown from comparing the calculation results with actual test data that there is a coincidence for both results over a wide range of low frequencies. Meanwhile, the time domain test data of depolarization currents in dry and moist pressboards are converted into frequency domain results on the basis of the transformation. The frequency domain curves of complex capacitance and dielectric dissipation factor at the low frequency range are obtained. Test results of polarization and depolarization current (PDC in pressboards are also given at the different voltage and polarization time. It is demonstrated from the experimental results that polarization and depolarization current are affected significantly by moisture contents of the test pressboards, and the transformation algorithm is effective in ultralow frequency of 10−3 Hz. Data analysis and interpretation of the test results conclude that analysis of time-frequency domain dielectric response can be used for assessing insulation system in power transformer.

  18. Range Sidelobe Suppression Using Complementary Sets in Distributed Multistatic Radar Networks

    Science.gov (United States)

    Wang, Xuezhi; Song, Yongping; Huang, Xiaotao; Moran, Bill

    2017-01-01

    We propose an alternative waveform scheme built on mutually-orthogonal complementary sets for a distributed multistatic radar. Our analysis and simulation show a reduced frequency band requirement for signal separation between antennas with centralized signal processing using the same carrier frequency. While the scheme can tolerate fluctuations of carrier frequencies and phases, range sidelobes arise when carrier frequencies between antennas are significantly different. PMID:29295566

  19. Theoretical and experimental study of two-frequency solid-state lasers in the GHz to THz ranges. Opto-microwave applications waves

    International Nuclear Information System (INIS)

    Lai, N.D.

    2003-07-01

    We explored some new features of single- and dual-frequency solid-state lasers oscillating in continuous-wave or pulsed regimes. First, we have developed some techniques to optimise the characteristics of pulsed lasers. A weak modulation of the pump power made it possible to obtain a stable repetition rate with a relative stability of 10 -6 . The pulse duration was continuously controlled from ten nanoseconds to a few hundreds nanoseconds by three different methods: adjustment of the laser beam diameter in the absorber, adjustment of the pump beam diameter in the active medium, and, in particular, the use of forked eigenstates in a two-axis laser. Moreover, the forked eigenstates allows to increase the pulse energy by coherent addition of the pulses. A compact two-frequency Nd:YAG-Cr:YAG laser with a beat note frequency continuously adjustable up to 2,7 GHz was demonstrated. The two-frequency pulses are ideal sources to meet various needs of applications such as the Doppler lidar-radar. Moreover, we show that two-frequency pulses at 1,55 μm can be obtained by using a new c-cut Co:ASL saturable absorber in an Er-Yb:glass laser. These pulses are perfectly adapted to free-space detection systems requiring eye safety. The coherence time of the beat note in these lasers was also studied: it is limited by the pulse duration. A new technique of modulating the pump power of a solid-state laser at frequencies close to its relaxation oscillation frequency was studied and made it possible to generate a beat note coherence from pulse to pulse. Frequency conversion techniques using the nonlinear optical effects make it possible to obtain tunable two-frequency sources in the visible spectrum. Green and red two-frequency pulses were obtained by using different conversion techniques, intra-cavity or extra-cavity. A two-frequency THz source in the red spectrum was also obtained by doubling the frequencies of a two-frequency THz Er-Yb:glass laser using a mixed fan-out PPLN crystal

  20. On the frequency scalings of RF guns

    International Nuclear Information System (INIS)

    Lin, L.C.; Chen, S.C.; Wurtele, J.S.

    1995-01-01

    A frequency scaling law for RF guns is derived from the normalized Vlasov-Maxwell equations. It shows that higher frequency RF guns can generate higher brightness beams under the assumption that the accelerating gradient and all beam and structure parameters are scaled with the RF frequency. Numerical simulation results using MAGIC confirm the scaling law. A discussion of the range of applicability of the law is presented. copyright 1995 American Institute of Physics

  1. Electromagnetic fields - introduction to relevant issues

    International Nuclear Information System (INIS)

    Brueggemeyer, H.; Csicsaky, M.

    1993-01-01

    This introductory paper surveys potential sources of electric magnetic, and electro-magnetic fields. Various cases are discussed to exemplify the total frequency range: nuclear magnetic resonance tomography, high-voltage transmission lines, transformer stations, effect lighting balls, military transmitters, transmitter towers of the Postal Services and other operators, mobile radiotelephone equipment, large broadcasting transmitters, radar radiation, high-frequency heat therapy. There is evidence suggesting that electric, magnetic and electro-magnetic fields may possibly represent a certain nuisance or health hazard even at field strength occuring in equipment used for every-day-life purposes, with an emphasis on their possible actions and effects in children and adolescents. The author discusses, in conclusion, the aerial equipment ordinance issued by Lower Saxony. (Uhe) [de

  2. Deep learning relevance

    DEFF Research Database (Denmark)

    Lioma, Christina; Larsen, Birger; Petersen, Casper

    2016-01-01

    train a Recurrent Neural Network (RNN) on existing relevant information to that query. We then use the RNN to "deep learn" a single, synthetic, and we assume, relevant document for that query. We design a crowdsourcing experiment to assess how relevant the "deep learned" document is, compared...... to existing relevant documents. Users are shown a query and four wordclouds (of three existing relevant documents and our deep learned synthetic document). The synthetic document is ranked on average most relevant of all....

  3. Solid state Ka-band pulse oscillator with frequency electronic switching

    Directory of Open Access Journals (Sweden)

    Dvornichenko V. P.

    2015-08-01

    Full Text Available Transmitting devices for small radars in the millimeter wavelength range with high resolution on range and noise immunity. The work presents the results of research and development of compact pulse oscillators with digital frequency switching from pulse to pulse. The oscillator consists of a frequency synthesizer and a synchronized amplifier on the IMPATT diode. Reference oscillator of synthesizer is synchronized by crystal oscillator with digital PLL system and contains a frequency multiplier and an amplifier operating in pulse mode. Small-sized frequency synthesizer of 8 mm wave lengths provides an output power of ~1.2 W per pulse with a frequency stability of no worse than 2•10–6. Radiation frequency is controlled by three-digit binary code in OOL levels. Synchronized amplifier made on IMPATT diodes provides microwave power up to 20 W in oscillator output with microwave pulse duration of 100—300 ns in an operating band. The oscillator can be used as a driving source for the synchronization of semiconductor and electro-vacuum devices of pulsed mode, and also as a transmitting device for small-sized radar of millimeter wave range.

  4. Parental Behaviors in a Memory Relevant Setting: How Parents "Teach" Children to Remember.

    Science.gov (United States)

    Justice, Elaine M.; Coley, Denise D.

    The behavior of mothers interacting with their preschoolers in a memory-relevant situation was examined. Ten 3-year-olds and their mothers were videotaped playing a game requiring memory for the location of hidden pictures. Frequency of nine categories of parental behavior was scored: naming, verbal orienting, physical orienting, physical…

  5. Moving beyond Text Highlights: Inferring Users' Interests to Improve the Relevance of Retrieval

    Science.gov (United States)

    Balakrishnan, Vimala; Mehmood, Yasir; Nagappan, Yoganathan

    2016-01-01

    Introduction: Studies have indicated that users' text highlighting behaviour can be further manipulated to improve the relevance of retrieved results. This article reports on a study that examined users' text highlight frequency, length and users' copy-paste actions. Method: A binary voting mechanism was employed to determine the weights for the…

  6. Investigation of hopped frequency waveforms for range and velocity measurements of radar targets

    CSIR Research Space (South Africa)

    Kathree, U

    2015-10-01

    Full Text Available In the field of radar, High Range Resolution (HRR) profiles are often used to improve target tracking accuracy in range and to allow the radar system to produce an image of an object using techniques such as inverse synthetic aperture radar (ISAR...

  7. Frequency-dependent Dispersion Measures and Implications for Pulsar Timing

    Science.gov (United States)

    Cordes, J. M.; Shannon, R. M.; Stinebring, D. R.

    2016-01-01

    The dispersion measure (DM), the column density of free electrons to a pulsar, is shown to be frequency dependent because of multipath scattering from small-scale electron-density fluctuations. DMs vary between propagation paths whose transverse extent varies strongly with frequency, yielding arrival times that deviate from the high-frequency scaling expected for a cold, uniform, unmagnetized plasma (1/frequency2). Scaling laws for thin phase screens are verified with simulations; extended media are also analyzed. The rms DM difference across an octave band near 1.5 GHz is ˜ 4 × 10-5 pc cm-3 for pulsars at ˜1 kpc distance. The corresponding arrival-time variations are a few to hundreds of nanoseconds for DM ≲ 30 pc cm-3 but increase rapidly to microseconds or more for larger DMs and wider frequency ranges. Chromatic DMs introduce correlated noise into timing residuals with a power spectrum of “low pass” form. The correlation time is roughly the geometric mean of the refraction times for the highest and lowest radio frequencies used, ranging from days to years, depending on the pulsar. We discuss implications for methodologies that use large frequency separations or wide bandwidth receivers for timing measurements. Chromatic DMs are partially mitigable by including an additional chromatic term in arrival time models. Without mitigation, an additional term in the noise model for pulsar timing is implied. In combination with measurement errors from radiometer noise, an arbitrarily large increase in total frequency range (or bandwidth) will yield diminishing benefits and may be detrimental to overall timing precision.

  8. Thin Co films with tunable ferromagnetic resonance frequency

    International Nuclear Information System (INIS)

    Maklakov, Sergey S.; Maklakov, Sergey A.; Ryzhikov, Ilya A.; Rozanov, Konstantin N.; Osipov, Alexey V.

    2012-01-01

    The tailored production of thin Co films of 50 nm thick with ferromagnetic resonance frequency in a range from 2.9 to 7.3 GHz using the DC magnetron sputtering is reported. The ferromagnetic resonance frequency, coercivity, effective magnetic field and nanocrystalline structure parameters are shown to be governed by the Co deposition rate. For this investigation, FMR, VSM and TEM techniques were used. - Highlights: ► Thin Co films with FMR frequency in a range from 2.9 to 7.3 GHz are obtained. ► The films' properties are governed by the deposition rate during DC magnetron sputtering. ► FMR, VSM and TEM techniques were used during the study.

  9. Frequency of hepatitis C in obstetric cases

    International Nuclear Information System (INIS)

    Rizvi, T.J.H.; Fatima, H.

    2003-01-01

    Objective: To compare the frequency of antihepatitis C virus (HCV) after single blood transfusion, multiple blood transfusion and in non-transfused obstetric cases. Patients and methods: Patients included in the study after single transfusion were 38, after multiple transfusion 39, and controls 120. History of patients regarding all the relevant information and clinical examination were recorded on a specially-designed and coded proforma. Anti-HCV was detected by Roche HCV EIA 2nd generation kit method in all cases and controls. Descriptive statistics and frequency of anti HCV each group was calculated using SPSS version 10. Results: Frequency of anti-HCV among patients with single blood transfusion was 13.2% (5), with multiple transfusion was 15.4% (6) and 6.6% (8) in non-transfused subjects. Conclusion: Anti-HCV frequency after one pint blood was almost same (13.2%) as after multiple transfusion (15.4%). This positively provided a firm argument for the necessity of a nationwide blood donor screening for anti-HCV by most sensitive immunoassay. Equally important was the need for clear cut indication for single blood transfusion. (author)

  10. A High-Speed High-Frequency Broadband Acoustic Modem for Short-to-Medium Range Data Transmission in Ports, Very Shallow Waters and Deep Waters Using Spread-Spectrum Modulation and Decision Feedback Equalizing

    National Research Council Canada - National Science Library

    Beaujean, Pierre-Philippe; Spruance, John; Kriel, Dion

    2006-01-01

    ...: The long-term objective is the commercialization of a high-speed high-frequency acoustic modem transmitting data at true rates of up to 105,000 bps, at a maximum range of 500 m and operate between 240 kHz and 380 kHz...

  11. Preceding weak noise sharpens the frequency tuning and elevates the response threshold of the mouse inferior collicular neurons through GABAergic inhibition.

    Science.gov (United States)

    Wang, Xin; Jen, Philip H-S; Wu, Fei-Jian; Chen, Qi-Cai

    2007-09-05

    In acoustic communication, animals must extract biologically relevant signals that are embedded in noisy environment. The present study examines how weak noise may affect the auditory sensitivity of neurons in the central nucleus of the mouse inferior colliculus (IC) which receives convergent excitatory and inhibitory inputs from both lower and higher auditory centers. Specifically, we studied the frequency sensitivity and minimum threshold of IC neurons using a pure tone probe and a weak white noise masker under forward masking paradigm. For most IC neurons, probe-elicited response was decreased by a weak white noise that was presented at a specific gap (i.e. time window). When presented within this time window, weak noise masking sharpened the frequency tuning curve and increased the minimum threshold of IC neurons. The degree of weak noise masking of these two measurements increased with noise duration. Sharpening of the frequency tuning curve and increasing of the minimum threshold of IC neurons during weak noise masking were mostly mediated through GABAergic inhibition. In addition, sharpening of frequency tuning curve by the weak noise masker was more effective at the high than at low frequency limb. These data indicate that in the real world the ambient noise may improve frequency sensitivity of IC neurons through GABAergic inhibition while inevitably decrease the frequency response range and sensitivity of IC neurons.

  12. Long-range correlations of electroencephalogram in rats irradiated by millimeter wave

    International Nuclear Information System (INIS)

    Xie Taorong; Pei Jian; Li Fen; Zhang Jie; Qi Hongxing; Chen Shude; Qiao Dengjiang

    2011-01-01

    A quantitative study was conducted on stress reaction in rat induced by 35 GHz millimeter wave. Long-range correlations analysis of the rat electroencephalogram(EEG) was investigated. The scaling exponents α 1 and α 2 were calculated by de-trended fluctuation analysis (DFA) method. The exponent α 1 shows that the high frequency EEG component is characterized by Brownian noise before irradiated by 35 GHz millimeter wave while it has long-range correlations during irradiation. The exponent α 2 shows that the low frequency EEG component has long-range correlations before irradiation while it is characterized by Brownian noise during irradiation. Introducing stress parameter k(k=α 2 /α 1 ), the average change rate of k was used to evaluate the intensity of stress in rat evoked by 35 GHz millimeter wave. The k increases 49.9%±13.6% during irradiation, which indicates that the high frequency EEG component becomes more ordered and the low frequency EEG component becomes more disordered, showing the acute stress in rat induced by 35 GHz millimeter wave. (authors)

  13. Base-Level Guide for Electromagnetic Frequency Radiation

    Science.gov (United States)

    2012-12-01

    only through exposure to very powerful magnetic fields (> 4 Tesla). For the limits, the force influences on metallic objects are relevant...impractical. Nonferrous shielding materials have little or no effect upon a magnetic field. Magnetic shielding that is effective at low frequencies... detectors or area monitors in Air Force operational environments. This is noted in AFOSH 48-9. In cases where the environment may exceed ten (10

  14. Dual-etalon, cavity-ring-down, frequency comb spectroscopy.

    Energy Technology Data Exchange (ETDEWEB)

    Strecker, Kevin E.; Chandler, David W.

    2010-10-01

    The 'dual etalon frequency comb spectrometer' is a novel low cost spectometer with limited moving parts. A broad band light source (pulsed laser, LED, lamp ...) is split into two beam paths. One travels through an etalon and a sample gas, while the second arm is just an etalon cavity, and the two beams are recombined onto a single detector. If the free spectral ranges (FSR) of the two cavities are not identical, the intensity pattern at the detector with consist of a series of heterodyne frequencies. Each mode out of the sample arm etalon with have a unique frequency in RF (radio-frequency) range, where modern electronics can easily record the signals. By monitoring these RF beat frequencies we can then determine when an optical frequencies is absorbed. The resolution is set by the FSR of the cavity, typically 10 MHz, with a bandwidth up to 100s of cm{sup -1}. In this report, the new spectrometer is described in detail and demonstration experiments on Iodine absorption are carried out. Further we discuss powerful potential next generation steps to developing this into a point sensor for monitoring combustion by-products, environmental pollutants, and warfare agents.

  15. String Stretching, Frequency Modulation, and Banjo Clang

    OpenAIRE

    Politzer, David

    2014-01-01

    The banjo’s floating bridge, string break angle, and flexible drumhead all contribute to substantial audio range frequency modulation. From the world of electronic music synthesis, it is known that modulating higher frequency sounds with lower acoustic frequencies leads to metallic and bell-like tone. The mechanics of the banjo does just that quite naturally, modulating fundamentals and harmonics with the motion of the bridge. In technical terms, with a floating bridge, string stretching is f...

  16. Measurements of ion cyclotron range of frequencies mode converted wave intensity with phase contrast imaging in Alcator C-Mod and comparison with full-wave simulations

    International Nuclear Information System (INIS)

    Tsujii, N.; Porkolab, M.; Bonoli, P. T.; Lin, Y.; Wright, J. C.; Wukitch, S. J.; Jaeger, E. F.; Green, D. L.; Harvey, R. W.

    2012-01-01

    Radio frequency waves in the ion cyclotron range of frequencies (ICRF) are widely used to heat tokamak plasmas. In ICRF heating schemes involving multiple ion species, the launched fast waves convert to ion cyclotron waves or ion Bernstein waves at the two-ion hybrid resonances. Mode converted waves are of interest as actuators to optimise plasma performance through current drive and flow drive. In order to describe these processes accurately in a realistic tokamak geometry, numerical simulations are essential, and it is important that these codes be validated against experiment. In this study, the mode converted waves were measured using a phase contrast imaging technique in D-H and D- 3 He plasmas. The measured mode converted wave intensity in the D- 3 He mode conversion regime was found to be a factor of ∼50 weaker than the full-wave predictions. The discrepancy was reduced in the hydrogen minority heating regime, where mode conversion is weaker.

  17. Macroscale hydrologic modeling of ecologically relevant flow metrics

    Science.gov (United States)

    Wenger, Seth J.; Luce, Charles H.; Hamlet, Alan F.; Isaak, Daniel J.; Neville, Helen M.

    2010-09-01

    Stream hydrology strongly affects the structure of aquatic communities. Changes to air temperature and precipitation driven by increased greenhouse gas concentrations are shifting timing and volume of streamflows potentially affecting these communities. The variable infiltration capacity (VIC) macroscale hydrologic model has been employed at regional scales to describe and forecast hydrologic changes but has been calibrated and applied mainly to large rivers. An important question is how well VIC runoff simulations serve to answer questions about hydrologic changes in smaller streams, which are important habitat for many fish species. To answer this question, we aggregated gridded VIC outputs within the drainage basins of 55 streamflow gages in the Pacific Northwest United States and compared modeled hydrographs and summary metrics to observations. For most streams, several ecologically relevant aspects of the hydrologic regime were accurately modeled, including center of flow timing, mean annual and summer flows and frequency of winter floods. Frequencies of high and low flows in the summer were not well predicted, however. Predictions were worse for sites with strong groundwater influence, and some sites showed errors that may result from limitations in the forcing climate data. Higher resolution (1/16th degree) modeling provided small improvements over lower resolution (1/8th degree). Despite some limitations, the VIC model appears capable of representing several ecologically relevant hydrologic characteristics in streams, making it a useful tool for understanding the effects of hydrology in delimiting species distributions and predicting the potential effects of climate shifts on aquatic organisms.

  18. Sampling methods for low-frequency electromagnetic imaging

    International Nuclear Information System (INIS)

    Gebauer, Bastian; Hanke, Martin; Schneider, Christoph

    2008-01-01

    For the detection of hidden objects by low-frequency electromagnetic imaging the linear sampling method works remarkably well despite the fact that the rigorous mathematical justification is still incomplete. In this work, we give an explanation for this good performance by showing that in the low-frequency limit the measurement operator fulfils the assumptions for the fully justified variant of the linear sampling method, the so-called factorization method. We also show how the method has to be modified in the physically relevant case of electromagnetic imaging with divergence-free currents. We present numerical results to illustrate our findings, and to show that similar performance can be expected for the case of conducting objects and layered backgrounds

  19. Development of over 1 MW and multi-frequency gyrotrons for fusion

    International Nuclear Information System (INIS)

    Imai, T.; Kariya, T.; Minami, R.; Numakura, T.; Kato, T.; Endo, Y.; Ichimura, M.; Eguchi, T.; Mitsunaka, Y.; Shimozuma, T.; Kubo, S.; Takahashi, H.; Yoshimura, Y.; Igami, H.; Ito, S.; Mutoh, T.; Sakamoto, Keishi; Idei, H.; Zushi, H.; Nagasaki, K.; Sano, F.; Ono, M.

    2014-10-01

    The development of wide frequency range from 14 to 300 GHz of high power mega-watt gyrotron for fusion is in progress in University of Tsukuba. The strong development activity was carried out in collaboration with JAEA, NIFS, TETD and universities. Over-1 MW dual frequency gyrotron of new frequency range (14 – 35 GHz), where the reduction of diffraction loss and cathode optimization are quite important, has been developed for EC/EBW H and CD for GAMMA 10/PDX, QUEST, Heliotron J and NSTX-U. Output power of 1.25 MW at 28 GHz and estimated oscillation power of 1.2 MW at 35.45 GHz from the same tube have been achieved with the cathode angle improvement and two frequency window. This is the first demonstration of the over 1 MW dual-frequency operations in lower frequency, which contributes to the technology of wide band multi-frequency/multi-MW tube. The output power of 600 kW for 2 s at 28 GHz is also demonstrated. It is applied to the QUEST and has resulted higher EC-driven current than ever. As for higher frequency range, in the joint program of NIFS and Tsukuba for LHD ECH gyrotrons, a new frequency of 154 GHz has been successfully developed with a TE 28,8 cavity, which delivered 1.16 MW for 1 s and the total power of 4.4 MW to LHD plasma with other three 77 GHz tubes, which extended the LHD plasma to high T e region. All these gyrotron performances are new records in each frequency range. The sub-THz gyrotron development is also just begun in collaboration with JAEA for Demo-Reactor ECH system. (author)

  20. A study of three-half-turn and frame antennae for ion cyclotron range of frequency plasma heating in the URAGAN-3M torsatron

    International Nuclear Information System (INIS)

    Lysoivan, A.I.; Moiseenko, V.E.; Plyusnin, V.V.; Kasilov, S.V.; Bondarenko, V.N.; Chechkin, V.V.; Fomin, I.P.; Grigor'eva, L.I.; Konovalov, V.G.; Koval'ov, S.V.; Litvinov, A.P.; Mironov, Yu.K.; Nazarov, N.I.; Pavlichenko, O.S.; Pavlichenko, R.O.; Shapoval, A.N.; Skibenko, A.I.; Volkov, E.D.

    1995-01-01

    Numerical and experimental results of Alfven wave heating of plasmas in the frequency range below the ion cyclotron frequency (ω ci ) are presented. Two different types of antenna were used for plasma production and heating: a frame type antenna (FTA) conventionally used in the URAGAN-3M device and a three-half-turn antenna (THTA) proposed recently to avoid the deleterious effects of conversion of fast wave to slow wave in the plasma periphery and to perform plasma core heating more effectively. Numerical modeling of electromagnetic field excitation in the URAGAN-3M plasma by the FTA and THTA was performed using a one-dimensional code. The results of calculations showed better performance of the compact THTA compared with the FTA for the case of a high density plasma (approximately 10 13 cm -3 ). When using the THTA, the experiments performed showed the possibility of dense plasma production (more than 2x10 13 cm -3 ) and heating, which had not been obtained earlier in the URAGAN-3M. Shifting the power deposition profile deeper inside the plasma body with the THTA resulted in modification of the plasma density profile and an improvement in plasma confinement. ((orig.))

  1. Valve-like behavior of the magnetoimpedance in the GHz range

    International Nuclear Information System (INIS)

    Sandacci, S.I.; Makhnovskiy, D.P.; Panina, L.V.

    2004-01-01

    High-frequency modification in magneto-impedance (MI) characteristics in the frequency range of 0.5-3 GHz has been investigated in 10 μm diameter amorphous microwires with a circumferential anisotropy. As frequency is increased, the peaks in the MI behavior observed at the anisotropy field reduce and become less sharp, disappearing completely at frequencies higher than 1.6 GHz. This 'valve-like' behavior can be explained by considering the dispersion properties of the effective permeability of the AC linear response combined with the rotational DC magnetization

  2. High-frequency, high-intensity photoionization

    Science.gov (United States)

    Reiss, H. R.

    1996-02-01

    Two analytical methods for computing ionization by high-frequency fields are compared. Predicted ionization rates compare well, but energy predictions for the onset of ionization differ radically. The difference is shown to arise from the use of a transformation in one of the methods that alters the zero from which energy is measured. This alteration leads to an apparent energy threshold for ionization that can, especially in the stabilization regime, differ strongly from the laboratory measurement. It is concluded that channel closings in intense-field ionization can occur at high as well as low frequencies. It is also found that the stabilization phenomenon at high frequencies, very prominent for hydrogen, is absent in a short-range potential.

  3. Medium Range Forecasts Representation (and Long Range Forecasts?)

    Science.gov (United States)

    Vincendon, J.-C.

    2009-09-01

    The progress of the numerical forecasts urges us to interest us in more and more distant ranges. We thus supply more and more forecasts with term of some days. Nevertheless, precautions of use are necessary to give the most reliable and the most relevant possible information. Available in a TV bulletin or on quite other support (Internet, mobile phone), the interpretation and the representation of a medium range forecast (5 - 15 days) must be different from those of a short range forecast. Indeed, the "foresee-ability” of a meteorological phenomenon decreases gradually in the course of the ranges, it decreases all the more quickly that the phenomenon is of small scale. So, at the end of some days, the probability character of a forecast becomes very widely dominating. That is why in Meteo-France the forecasts of D+4 to D+7 are accompanied with a confidence index since around ten years. It is a figure between 1 and 5: the more we approach 5, the more the confidence in the supplied forecast is good. In the practice, an indication is supplied for period D+4 / D+5, the other one for period D+6 / D+7, every day being able to benefit from a different forecast, that is be represented in a independent way. We thus supply a global tendency over 24 hours with less and less precise symbols as the range goes away. Concrete examples will be presented. From now on two years, we also publish forecasts to D+8 / J+9, accompanied with a sign of confidence (" good reliability " or " to confirm "). These two days are grouped together on a single map because for us, the described tendency to this term is relevant on a duration about 48 hours with a spatial scale slightly superior to the synoptic scale. So, we avoid producing more than two zones of types of weather over France and we content with giving an evolution for the temperatures (still, in increase or in decline). Newspapers began to publish this information, it should soon be the case of televisions. It is particularly

  4. Low frequency steady-state brain responses modulate large scale functional networks in a frequency-specific means.

    Science.gov (United States)

    Wang, Yi-Feng; Long, Zhiliang; Cui, Qian; Liu, Feng; Jing, Xiu-Juan; Chen, Heng; Guo, Xiao-Nan; Yan, Jin H; Chen, Hua-Fu

    2016-01-01

    Neural oscillations are essential for brain functions. Research has suggested that the frequency of neural oscillations is lower for more integrative and remote communications. In this vein, some resting-state studies have suggested that large scale networks function in the very low frequency range (frequency characteristics of brain networks because both resting-state studies and conventional frequency tagging approaches cannot simultaneously capture multiple large scale networks in controllable cognitive activities. In this preliminary study, we aimed to examine whether large scale networks can be modulated by task-induced low frequency steady-state brain responses (lfSSBRs) in a frequency-specific pattern. In a revised attention network test, the lfSSBRs were evoked in the triple network system and sensory-motor system, indicating that large scale networks can be modulated in a frequency tagging way. Furthermore, the inter- and intranetwork synchronizations as well as coherence were increased at the fundamental frequency and the first harmonic rather than at other frequency bands, indicating a frequency-specific modulation of information communication. However, there was no difference among attention conditions, indicating that lfSSBRs modulate the general attention state much stronger than distinguishing attention conditions. This study provides insights into the advantage and mechanism of lfSSBRs. More importantly, it paves a new way to investigate frequency-specific large scale brain activities. © 2015 Wiley Periodicals, Inc.

  5. 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.

  6. Auditory DUM neurons in a bush-cricket: A filter bank for carrier frequency.

    Science.gov (United States)

    Lefebvre, Paule Chloé; Seifert, Marvin; Stumpner, Andreas

    2018-05-01

    In bush-crickets the first stage of central auditory processing occurs in the prothoracic ganglion. About 15 to 50 different auditory dorsal unpaired median neurons (DUM neurons) exist but they have not been studied in any detail. These DUM neurons may be classified into seven different morphological types, although, there is only limited correlation between morphology and physiological responses. Ninety seven percent of the stained neurons were local, 3% were intersegmental. About 90% project nearly exclusively into the auditory neuropile, and 45% into restricted areas therein. Lateral extensions overlap with the axons of primary auditory sensory neurons close to their branching point. DUM neurons are typically tuned to frequencies covering the range between 2 and 50 kHz and thereby may establish a filter bank for carrier frequency. Less than 10% of DUM neurons have their branches in adjacent and more posterior regions of the auditory neuropile and are mostly tuned to low frequencies, less sensitive than the other types and respond to vibration. Thirty five percent of DUM show indications of inhibition, either through reduced responses at higher intensities, or by hyperpolarizing responses to sound. Most DUM neurons produce phasic spike responses preferably at higher intensities. Spikes may be elicited by intracellular current injection. Preliminary data suggest that auditory DUM neurons have GABA as transmitter and therefore may inhibit other auditory interneurons. From all known local auditory neurons, only DUM neurons have frequency specific responses which appear suited for local processing relevant for acoustic communication in bush crickets. © 2018 Wiley Periodicals, Inc.

  7. FREQUENCY-DEPENDENT DISPERSION MEASURES AND IMPLICATIONS FOR PULSAR TIMING

    Energy Technology Data Exchange (ETDEWEB)

    Cordes, J. M. [Astronomy Department, Cornell University, Ithaca, NY 14853 (United States); Shannon, R. M. [CSIRO Astronomy and Space Science, Box 76, Epping, NSW 1710 (Australia); Stinebring, D. R., E-mail: cordes@astro.cornell.edu, E-mail: ryan.shannon@csiro.au, E-mail: dan.stinebring@oberlin.edu [Department of Physics and Astronomy, Oberlin College, Oberlin, OH 44074 (United States)

    2016-01-20

    The dispersion measure (DM), the column density of free electrons to a pulsar, is shown to be frequency dependent because of multipath scattering from small-scale electron-density fluctuations. DMs vary between propagation paths whose transverse extent varies strongly with frequency, yielding arrival times that deviate from the high-frequency scaling expected for a cold, uniform, unmagnetized plasma (1/frequency{sup 2}). Scaling laws for thin phase screens are verified with simulations; extended media are also analyzed. The rms DM difference across an octave band near 1.5 GHz is ∼ 4 × 10{sup −5} pc cm{sup −3} for pulsars at ∼1 kpc distance. The corresponding arrival-time variations are a few to hundreds of nanoseconds for DM ≲ 30 pc cm{sup −3} but increase rapidly to microseconds or more for larger DMs and wider frequency ranges. Chromatic DMs introduce correlated noise into timing residuals with a power spectrum of “low pass” form. The correlation time is roughly the geometric mean of the refraction times for the highest and lowest radio frequencies used, ranging from days to years, depending on the pulsar. We discuss implications for methodologies that use large frequency separations or wide bandwidth receivers for timing measurements. Chromatic DMs are partially mitigable by including an additional chromatic term in arrival time models. Without mitigation, an additional term in the noise model for pulsar timing is implied. In combination with measurement errors from radiometer noise, an arbitrarily large increase in total frequency range (or bandwidth) will yield diminishing benefits and may be detrimental to overall timing precision.

  8. Students' perceptions of the relevance of mathematics in engineering

    Science.gov (United States)

    Flegg, Jennifer; Mallet, Dann; Lupton, Mandy

    2012-09-01

    In this article, we report on the findings of an exploratory study into the experience of students as they learn first year engineering mathematics. Here we define engineering as the application of mathematics and sciences to the building and design of projects for the use of society [M. Kirschenman and B. Brenner, Education for Civil Engineering: A Profession of Practice, Leader. Manag. Eng. 10 (2010), p. 54]. Qualitative and quantitative data on students' views of the relevance of their mathematics study to their engineering studies and future careers in engineering was collected. The students described using a range of mathematics techniques (mathematics skills developed, mathematics concepts applied to engineering and skills developed relevant for engineering) for various usages (as a subject of study, a tool for other subjects or a tool for real world problems). We found a number of themes relating to the design of engineering mathematics curriculum emerged from the data. These included the relevance of mathematics within different engineering majors, the relevance of mathematics to future studies, the relevance of learning mathematical rigour and the effectiveness of problem-solving tasks in conveying the relevance of mathematics more effectively than other forms of assessment. We make recommendations for the design of engineering mathematics curriculum based on our findings.

  9. Range-separated density-functional theory for molecular excitation energies

    International Nuclear Information System (INIS)

    Rebolini, E.

    2014-01-01

    Linear-response time-dependent density-functional theory (TDDFT) is nowadays a method of choice to compute molecular excitation energies. However, within the usual adiabatic semi-local approximations, it is not able to describe properly Rydberg, charge-transfer or multiple excitations. Range separation of the electronic interaction allows one to mix rigorously density-functional methods at short range and wave function or Green's function methods at long range. When applied to the exchange functional, it already corrects most of these deficiencies but multiple excitations remain absent as they need a frequency-dependent kernel. In this thesis, the effects of range separation are first assessed on the excitation energies of a partially-interacting system in an analytic and numerical study in order to provide guidelines for future developments of range-separated methods for excitation energy calculations. It is then applied on the exchange and correlation TDDFT kernels in a single-determinant approximation in which the long-range part of the correlation kernel vanishes. A long-range frequency-dependent second-order correlation kernel is then derived from the Bethe-Salpeter equation and added perturbatively to the range-separated TDDFT kernel in order to take into account the effects of double excitations. (author)

  10. Mechanical stress-controlled tunable active frequency-selective surface

    Science.gov (United States)

    Huang, Bo-Cin; Hong, Jian-Wei; Lo, Cheng-Yao

    2017-01-01

    This study proposes a tunable active frequency-selective surface (AFSS) realized by mechanically expanding or contracting a split-ring resonator (SRR) array. The proposed AFSS transfers mechanical stress from its elastic substrate to the top of the SRR, thereby achieving electromagnetic (EM) modulation without the need for an additional external power supply, meeting the requirements for the target application: the invisibility cloak. The operating mechanism of the proposed AFSS differs from those of other AFSSs, supporting modulations in arbitrary frequencies in the target range. The proposed stress-controlled or strain-induced EM modulation proves the existence of an identical and linear relationship between the strain gradient and the frequency shift, implying its suitability for other EM modulation ranges and applications.

  11. Syllable Frequency and Spoken Word Recognition: An Inhibitory Effect.

    Science.gov (United States)

    González-Alvarez, Julio; Palomar-García, María-Angeles

    2016-08-01

    Research has shown that syllables play a relevant role in lexical access in Spanish, a shallow language with a transparent syllabic structure. Syllable frequency has been shown to have an inhibitory effect on visual word recognition in Spanish. However, no study has examined the syllable frequency effect on spoken word recognition. The present study tested the effect of the frequency of the first syllable on recognition of spoken Spanish words. A sample of 45 young adults (33 women, 12 men; M = 20.4, SD = 2.8; college students) performed an auditory lexical decision on 128 Spanish disyllabic words and 128 disyllabic nonwords. Words were selected so that lexical and first syllable frequency were manipulated in a within-subject 2 × 2 design, and six additional independent variables were controlled: token positional frequency of the second syllable, number of phonemes, position of lexical stress, number of phonological neighbors, number of phonological neighbors that have higher frequencies than the word, and acoustical durations measured in milliseconds. Decision latencies and error rates were submitted to linear mixed models analysis. Results showed a typical facilitatory effect of the lexical frequency and, importantly, an inhibitory effect of the first syllable frequency on reaction times and error rates. © The Author(s) 2016.

  12. MHD simulation of a beat frequency heated plasma

    International Nuclear Information System (INIS)

    Milroy, R.D.; Capjack, C.E.; James, C.R.; McMullin, J.N.

    1976-01-01

    The heating of a plasma in a solenoid, with a beat frequency harmonic which is excited at a frequency near to that of a Langmuir mode in a plasma, is examined. It is shown that at high temperatures the heating rate is very insensitive to changes in plasma density. The amount of energy that can be coupled to a plasma in a solenoid with this heating scheme is investigated by using a one-dimensional computer code which incorporates an exact solution of the relevant MHD equations. The absorption of energy from a high powered laser is shown to be significantly enhanced with this process. (author)

  13. Classification of hydromagnetic emissions based on frequency--time spectra

    International Nuclear Information System (INIS)

    Fukunishi, H.; Toya, T.; Koike, K.; Kuwashima, M.; Kawamura, M.

    1981-01-01

    By using 3035 hydromagnetic emission events observed in the frequency range of 0.1--2.0 Hz at Syowa (Lapprox.6), HM emissions have been classified into eight subtypes based on their spectral structures, i.e., HM whistler, periodic HM emission, HM chorus, HM emission burst, IPDP, morning IPDP, Pc 1--2 band, and irregular HM emission. It is seen that each subtype has a preferential magnetic local time interval and also a frequency range for its occurrence. Morning IPDP events and irregular HM emissions occur in the magnetic morning hours, while dispersive periodic HM emissions and HM emission bursts occur around magnetic local noon, then HM chorus emissions occur in the afternoon hours and IPDP events occur in the evening hours. Furthermore, it is noticed that the mid-frequencies of these emissions vary from high frequencies in the morning hours to low frequencies in the afternoon hours. On the basis of these results, the generation mechanisms of each subtype are discussed

  14. Phase-Amplitude Coupling and Long-Range Phase Synchronization Reveal Frontotemporal Interactions during Visual Working Memory.

    Science.gov (United States)

    Daume, Jonathan; Gruber, Thomas; Engel, Andreas K; Friese, Uwe

    2017-01-11

    It has been suggested that cross-frequency phase-amplitude coupling (PAC), particularly in temporal brain structures, serves as a neural mechanism for coordinated working memory storage. In this magnetoencephalography study, we show that during visual working memory maintenance, temporal cortex regions, which exhibit enhanced PAC, interact with prefrontal cortex via enhanced low-frequency phase synchronization. Healthy human participants were engaged in a visual delayed match-to-sample task with pictures of natural objects. During the delay period, we observed increased spectral power of beta (20-28 Hz) and gamma (40-94 Hz) bands as well as decreased power of theta/alpha band (7-9 Hz) oscillations in visual sensory areas. Enhanced PAC between the phases of theta/alpha and the amplitudes of beta oscillations was found in the left inferior temporal cortex (IT), an area known to be involved in visual object memory. Furthermore, the IT was functionally connected to the prefrontal cortex by increased low-frequency phase synchronization within the theta/alpha band. Together, these results point to a mechanism in which the combination of PAC and long-range phase synchronization subserves enhanced large-scale brain communication. They suggest that distant brain regions might coordinate their activity in the low-frequency range to engage local stimulus-related processing in higher frequencies via the combination of long-range, within-frequency phase synchronization and local cross-frequency PAC. Working memory maintenance, like other cognitive functions, requires the coordinated engagement of brain areas in local and large-scale networks. However, the mechanisms by which spatially distributed brain regions share and combine information remain primarily unknown. We show that the combination of long-range, low-frequency phase synchronization and local cross-frequency phase-amplitude coupling might serve as a mechanism to coordinate memory processes across distant brain areas

  15. 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.

  16. Fast Hopping Frequency Generation in Digital CMOS

    CERN Document Server

    Farazian, Mohammad; Gudem, Prasad S

    2013-01-01

    Overcoming the agility limitations of conventional frequency synthesizers in multi-band OFDM ultra wideband is a key research goal in digital technology. This volume outlines a frequency plan that can generate all the required frequencies from a single fixed frequency, able to implement center frequencies with no more than two levels of SSB mixing. It recognizes the need for future synthesizers to bypass on-chip inductors and operate at low voltages to enable the increased integration and efficiency of networked appliances. The author examines in depth the architecture of the dividers that generate the necessary frequencies from a single base frequency and are capable of establishing a fractional division ratio.   Presenting the first CMOS inductorless single PLL 14-band frequency synthesizer for MB-OFDMUWB makes this volume a key addition to the literature, and with the synthesizer capable of arbitrary band-hopping in less than two nanoseconds, it operates well within the desired range on a 1.2-volt power s...

  17. Frequency-Dependent Tidal Triggering of Low Frequency Earthquakes Near Parkfield, California

    Science.gov (United States)

    Xue, L.; Burgmann, R.; Shelly, D. R.

    2017-12-01

    The effect of small periodic stress perturbations on earthquake generation is not clear, however, the rate of low-frequency earthquakes (LFEs) near Parkfield, California has been found to be strongly correlated with solid earth tides. Laboratory experiments and theoretical analyses show that the period of imposed forcing and source properties affect the sensitivity to triggering and the phase relation of the peak seismicity rate and the periodic stress, but frequency-dependent triggering has not been quantitatively explored in the field. Tidal forcing acts over a wide range of frequencies, therefore the sensitivity to tidal triggering of LFEs provides a good probe to the physical mechanisms affecting earthquake generation. In this study, we consider the tidal triggering of LFEs near Parkfield, California since 2001. We find the LFEs rate is correlated with tidal shear stress, normal stress rate and shear stress rate. The occurrence of LFEs can also be independently modulated by groups of tidal constituents at semi-diurnal, diurnal and fortnightly frequencies. The strength of the response of LFEs to the different tidal constituents varies between LFE families. Each LFE family has an optimal triggering frequency, which does not appear to be depth dependent or systematically related to other known properties. This suggests the period of the applied forcing plays an important role in the triggering process, and the interaction of periods of loading history and source region properties, such as friction, effective normal stress and pore fluid pressure, produces the observed frequency-dependent tidal triggering of LFEs.

  18. 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

  19. The Noisiness of Low Frequency Bands of Noise

    Science.gov (United States)

    Lawton, B. W.

    1975-01-01

    The relative noisiness of low frequency 1/3-octave bands of noise was examined. The frequency range investigated was bounded by the bands centered at 25 and 200 Hz, with intensities ranging from 50 to 95 db (SPL). Thirty-two subjects used a method of adjustment technique, producing comparison band intensities as noisy as 100 and 200 Hz standard bands at 60 and 72 db. The work resulted in contours of equal noisiness for 1/3-octave bands, ranging in intensity from approximately 58 to 86 db (SPL). These contours were compared with the standard equal noisiness contours; in the region of overlap, between 50 and 200 Hz, the agreement was good.

  20. Energy-range relation and mean energy variation in therapeutic particle beams

    International Nuclear Information System (INIS)

    Kempe, Johanna; Brahme, Anders

    2008-01-01

    Analytical expressions for the mean energy and range of therapeutic light ion beams and low- and high-energy electrons have been derived, based on the energy dependence of their respective stopping powers. The new mean energy and range relations are power-law expressions relevant for light ion radiation therapy, and are based on measured practical ranges or known tabulated stopping powers and ranges for the relevant incident particle energies. A practical extrapolated range, R p , for light ions was defined, similar to that of electrons, which is very closely related to the extrapolated range of the primary ions. A universal energy-range relation for light ions and electrons that is valid for all material mixtures and compounds has been developed. The new relation can be expressed in terms of the range for protons and alpha particles, and is found to agree closely with experimental data in low atomic number media and when the difference in the mean ionization energy is low. The variation of the mean energy with depth and the new energy-range relation are useful for accurate stopping power and mass scattering power calculations, as well as for general particle transport and dosimetry applications

  1. On the quantification of SSVEP frequency responses in human EEG in realistic BCI conditions.

    Directory of Open Access Journals (Sweden)

    Rafał Kuś

    Full Text Available This article concerns one of the most important problems of brain-computer interfaces (BCI based on Steady State Visual Evoked Potentials (SSVEP, that is the selection of the a-priori most suitable frequencies for stimulation. Previous works related to this problem were done either with measuring systems that have little in common with actual BCI systems (e.g., single flashing LED or were presented on a small number of subjects, or the tested frequency range did not cover a broad spectrum. Their results indicate a strong SSVEP response around 10 Hz, in the range 13-25 Hz, and at high frequencies in the band of 40-60 Hz. In the case of BCI interfaces, stimulation with frequencies from various ranges are used. The frequencies are often adapted for each user separately. The selection of these frequencies, however, was not yet justified in quantitative group-level study with proper statistical account for inter-subject variability. The aim of this study is to determine the SSVEP response curve, that is, the magnitude of the evoked signal as a function of frequency. The SSVEP response was induced in conditions as close as possible to the actual BCI system, using a wide range of frequencies (5-30 Hz, in step of 1 Hz. The data were obtained for 10 subjects. SSVEP curves for individual subjects and the population curve was determined. Statistical analysis were conducted both on the level of individual subjects and for the group. The main result of the study is the identification of the optimal range of frequencies, which is 12-18 Hz, for the registration of SSVEP phenomena. The applied criterion of optimality was: to find the largest contiguous range of frequencies yielding the strong and constant-level SSVEP response.

  2. A computer simulation of a long-range CWFM radar showing the tradeoffs of performance as a function of range

    Science.gov (United States)

    Gordy, Robert S.; Zoledziowski, Severyn

    2011-06-01

    This paper describes a study of the operation of a long range CWFM radar using "System View" software for modeling and simulation. The System View software is currently offered by Agilent. The models that were studied include: a model illustrating the basic principle of operation of the CWFM radar, the range resolution of the radar, the effect of long range processing and the resultant approach with the tradeoff of detected range resolution due to Doppler frequency shift as a function of range distance. The study was performed as part of the design of an airborne CWFM radar. The radar can be designed with a single antenna or a dual antenna. The dual antenna approach is presented in this paper.

  3. Micronuclei Frequency in Radiation Worker

    International Nuclear Information System (INIS)

    Sudprasert, Wanwisa; Jungtanasombut, Amornrat; Pakkong, Pannee

    2009-07-01

    Full text: The purpose of this study is to determine the micronuclei (MN) frequency in peripheral blood lymphocytes of 31 individuals occupationally exposed to radiation compared to 24 controls. The effect of donor gender, age, alcoholic consumption, tea/coffee consumption and radiation burden on MN frequency was studied. The results showed that MN frequencies observed for exposed employees were significantly higher than in controls (p = 0.000). The average MN frequency in control was 39.1 ± 3.7 MN/1000 BN while those of exposed group were 60.9 ± 12.3, 61.6 ± 13.0 and 62.6 ± 11.8 MN/1000 BN for the range of accumulative doses at 0.01-3.00, 3.01-6.00 and 6.01-9.00 mSv, respectively. Moreover, MN frequency showed a positive trend with increased accumulative doses as a linear-quadratic relation (R 2 = 0.4754). No correlation of MN frequency with gender, age and alcoholic consumption could be observed in both exposed and control groups. However, the effect of tea/coffee consumption on MN frequency was clearly observed in the exposed individuals (t-test = -2.018, sig. (2-tailed) = 0.030). These results indicate that the increased MN frequency, an indicator of chromosomal aberration, is associated with occupational exposure to low doses of ionizing radiation

  4. 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.

  5. A MEMS-based high frequency x-ray chopper

    Energy Technology Data Exchange (ETDEWEB)

    Siria, A; Schwartz, W; Chevrier, J [Institut Neel, CNRS-Universite Joseph Fourier Grenoble, BP 166, F-38042 Grenoble Cedex 9 (France); Dhez, O; Comin, F [ESRF, 6 rue Jules Horowitz, F-38043 Grenoble Cedex 9 (France); Torricelli, G [Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH (United Kingdom)

    2009-04-29

    Time-resolved x-ray experiments require intensity modulation at high frequencies (advanced rotating choppers have nowadays reached the kHz range). We here demonstrate that a silicon microlever oscillating at 13 kHz with nanometric amplitude can be used as a high frequency x-ray chopper. We claim that using micro-and nanoelectromechanical systems (MEMS and NEMS), it will be possible to achieve higher frequencies in excess of hundreds of megahertz. Working at such a frequency can open a wealth of possibilities in chemistry, biology and physics time-resolved experiments.

  6. Is QCD relevant to nuclear physics

    International Nuclear Information System (INIS)

    Thomas, A.W.

    1985-01-01

    A review is given of recent work on baryon structure in a number of QCD-motivated models. After establishing a prima facie case that the quark model should be relevant in a consistent description of the nucleus over a wide range of momentum transfer, the author looks for experimental confirmation. The discussion includes the search for exotic states, for a six quark component of the deuteron, and an up to date report on the interpretation of the EMC effect. (Auth.)

  7. New internal multi-range resistors for ac voltage calibration by using TVC

    International Nuclear Information System (INIS)

    Ali, Rasha S M

    2015-01-01

    Accurate calibration of ac voltages up to 1000 V by using thermal converters requires range resistors connected in series with the converter. The combination of a thermal converter and range resistor is known as the thermal voltage converter. In this paper, multi-range internal range resistors are designed and implemented in the National Institute for Standards (NIS), Egypt to cover the ac voltage ranges from 10 V to 750 V. The range resistor values are 2 kΩ, 10 kΩ, 20 kΩ, 40 kΩ, 100 kΩ, and 150 kΩ to cover the voltage ranges 10 V, 50 V, 100 V, 200 V, 500 V, and 750 V, respectively. The six range resistors are mounted in series with a single-junction thermo-element in the same box to provide a new thermal voltage converter. The required range resistor is selected by using a six-pin selector switch. Each resistor is connected to a selector pin. The new thermal voltage converter ranges are automatically calibrated against other standard thermal voltage converters at different frequencies by using a LabVIEW program to determine their ac–dc transfer difference at each range. The expanded uncertainties are estimated according to the GUM for all ranges at different frequencies. The performance of the new thermal voltage converter is also evaluated by comparing its ac–dc differences and its accuracy in measuring the ac voltage at different frequencies with a traditional thermal voltage converter. (paper)

  8. Extended parametric gain range in photonic crystal fibers with strongly frequency-dependent field distributions.

    Science.gov (United States)

    Petersen, Sidsel R; Alkeskjold, Thomas T; Olausson, Christina B; Lægsgaard, Jesper

    2014-08-15

    The parametric gain range of a degenerate four-wave mixing process is determined in the undepleted pump regime. The gain range is considered with and without taking the mode field distributions of the four-wave mixing components into account. It is found that the mode field distributions have to be included to evaluate the parametric gain correctly in dispersion-tailored speciality fibers and that mode profile engineering can provide a way to increase the parametric gain range.

  9. Contactless or High Frequency Conductometry or Oscillometry of Electrolytes

    OpenAIRE

    Kiumars Ghowsi; Hosein Ghowsi

    2013-01-01

    Circuit models are used to express the behavior of the conductometric cells in the radio frequency to microwave region .The capacitive cell has two era classic era and modern era as a detector for Capillary Zone Electrophoresis . Capacitive Cell where electrodes are outside the Cells and frequency of the electric signal is in the cell the radio frequency range is modeled. Both microscopic phenomena occurring at radio frequencies in electrolytes and macroscopic phenomena the circuit model for ...

  10. Low-frequency waves in magnetized dusty plasmas revisited

    International Nuclear Information System (INIS)

    Salimullah, M.; Khan, M.I.; Amin, R.; Nitta, H.; Shukla, P.K.

    2005-10-01

    The general dispersion relation of any wave is examined for low-frequency waves in a homogeneous dusty plasma in the presence of an external magnetic field. The low-frequency parallel electromagnetic wave propagates as a dust cyclotron wave or a whistler in the frequency range below the ion cyclotron frequency. In the same frequency regime, the transverse electromagnetic magnetosonic wave is modified with a cutoff frequency at the dust-ion lower-hybrid frequency, which reduces to the usual magnetosonic wave in absence of the dust. Electrostatic dust-lower- hybrid mode is also recovered propagating nearly perpendicular to the magnetic field with finite ion temperature and cold dust particles which for strong ion-Larmor radius effect reduces to the usual dust-acoustic wave driven by the ion pressure. (author)

  11. Application of low frequency and medium frequency currents in the management of acute and chronic pain-A narrative review

    Directory of Open Access Journals (Sweden)

    Stephen Rajan Samuel

    2015-01-01

    Full Text Available Trancutaneous electrical nerve stimulation (TENS and interferential therapy (IFT have been a regular line of treatment for various types of acute and chronic pain. This review aims to compile the latest literature in pain management using these modalities which use low-frequency and medium-frequency currents. The Cochrane Library, Scopus, PubMed, MEDLINE, and CINAHL were searched and studies were examined from their inception till October 2013. After title and abstract screening the relevant studies were included for this review. We found through this review that even though TENS and IFT are used in management of pain, there is limited amount of high quality research available in this area. Most of the studies lack methodological quality and have a low sample size.

  12. Design and Modelling of Thermostatically Controlled Loads as Frequency Controlled Reserve

    DEFF Research Database (Denmark)

    Xu, Zhao; Østergaard, Jacob; Togeby, Mikael

    2007-01-01

    Using demand as frequency controlled reserve (DFR) is beneficial to power systems in many aspects. To study the impacts of this technology on power system operation, control logics and simulation models of relevant loads should be carefully developed. Two advanced control logics for using demand...... frequency, is developed. The developed simulation model is able to represent a variety of aggregated thermostatically controlled loads, such as heaters or refrigerators. Uncertainties including customer behaviours and ambient temperature variation are also modelled. Preliminary simulation results...

  13. Quantum Frequency Conversion by Four-wave Mixing Using Bragg Scattering

    DEFF Research Database (Denmark)

    Andersen, Lasse Mejling; Rottwitt, Karsten; McKinstrie, C. J.

    2012-01-01

    Two theoretical models for frequency conversion (FC) using nondegenerate four-wave mixing are compared, and their range of validity are discussed. Quantum-statepreserving FC allows for arbitrary reshaping of states for an appropriate pump selection.......Two theoretical models for frequency conversion (FC) using nondegenerate four-wave mixing are compared, and their range of validity are discussed. Quantum-statepreserving FC allows for arbitrary reshaping of states for an appropriate pump selection....

  14. The role of high-frequency oscillatory activity in reward processing and learning.

    Science.gov (United States)

    Marco-Pallarés, Josep; Münte, Thomas F; Rodríguez-Fornells, Antoni

    2015-02-01

    Oscillatory activity has been proposed as a key mechanism in the integration of brain activity of distant structures. Particularly, high frequency brain oscillatory activity in the beta and gamma range has received increasing interest in the domains of attention and memory. In addition, a number of recent studies have revealed an increase of beta-gamma activity (20-35 Hz) after unexpected or relevant positive reward outcomes. In the present manuscript we review the literature on this phenomenon and we propose that this activity is a brain signature elicited by unexpected positive outcomes in order to transmit a fast motivational value signal to the reward network. In addition, we hypothesize that beta-gamma oscillatory activity indexes the interaction between attentional and emotional systems, and that it directly reflects the appearance of unexpected positive rewards in learning-related contexts. Copyright © 2014 Elsevier Ltd. All rights reserved.

  15. Daris, a low-frequency distributed aperture array for radio astronomy in space

    NARCIS (Netherlands)

    Boonstra, A.J.; Saks, N.; Bentum, Marinus Jan; van 't Klooster, K.; Falcke, H.

    2010-01-01

    DARIS (Distributed Aperture Array for Radio Astronomy in Space) is a radio astronomy space mission concept aimed at observing the low-frequency radio sky in the range 1-10 MHz. Because of the Earth's ionospheric disturbances and opaqueness, this frequency range can only be observed from space. The

  16. 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.

  17. 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.

  18. Development of frequency tunable gyrotrons for plasma diagnostics

    International Nuclear Information System (INIS)

    Idehara, T.; Mitsudo, S.; Sabchevski, S.; Glyavin, M.; Ogawa, I.; Sato, M.; Kawahata, K.; Brand, G.F.

    2000-01-01

    Development of two types of frequency tunable gyrotrons are described. One is frequency step-tunable gyrotrons (Gyrotron FU Series) which cover wide range from millimeter to submillimeter wavelength region. The other is a quasi-optical gyrotron operating in 90 and 180 GHz bands. Both are applicable for plasma diagnostics as power sources. (author)

  19. High resolution kilometric range optical telemetry in air by radio frequency phase measurement

    Energy Technology Data Exchange (ETDEWEB)

    Guillory, Joffray; García-Márquez, Jorge; Truong, Daniel; Wallerand, Jean-Pierre [Laboratoire Commun de Métrologie LNE-Cnam (LCM), LNE, 1 rue Gaston Boissier, 75015 Paris (France); Šmíd, Radek [Laboratoire Commun de Métrologie LNE-Cnam (LCM), LNE, 1 rue Gaston Boissier, 75015 Paris (France); Institute of Scientific Instruments of the CAS, Kralovopolska 147, 612 64 Brno (Czech Republic); Alexandre, Christophe [Centre d’Études et de Recherche en Informatique et Communications (CEDRIC), Cnam, 292 rue St-Martin, 75003 Paris (France)

    2016-07-15

    We have developed an optical Absolute Distance Meter (ADM) based on the measurement of the phase accumulated by a Radio Frequency wave during its propagation in the air by a laser beam. In this article, the ADM principle will be described and the main results will be presented. In particular, we will emphasize how the choice of an appropriate photodetector can significantly improve the telemeter performances by minimizing the amplitude to phase conversion. Our prototype, tested in the field, has proven its efficiency with a resolution better than 15 μm for a measurement time of 10 ms and distances up to 1.2 km.

  20. Mutagenic effects of carbon ions near the range end in plants

    Energy Technology Data Exchange (ETDEWEB)

    Hase, Yoshihiro, E-mail: hase.yoshihiro@jaea.go.jp [Ion Beam Mutagenesis Research Group, Quantum Beam Science Directorate, Japan Atomic Energy Agency, 1233 Watanuki, Takasaki, Gunma 370-1292 (Japan); Yoshihara, Ryouhei; Nozawa, Shigeki; Narumi, Issay [Ion Beam Mutagenesis Research Group, Quantum Beam Science Directorate, Japan Atomic Energy Agency, 1233 Watanuki, Takasaki, Gunma 370-1292 (Japan)

    2012-03-01

    To gain insight into the mutagenic effects of accelerated heavy ions in plants, the mutagenic effects of carbon ions near the range end (mean linear energy transfer (LET): 425 keV/{mu}m) were compared with the effects of carbon ions penetrating the seeds (mean LET: 113 keV/{mu}m). Mutational analysis by plasmid rescue of Escherichia coli rpsL from irradiated Arabidopsis plants showed a 2.7-fold increase in mutant frequency for 113 keV/{mu}m carbon ions, whereas no enhancement of mutant frequency was observed for carbon ions near the range end. This suggested that carbon ions near the range end induced mutations that were not recovered by plasmid rescue. An Arabidopsis DNA ligase IV mutant, deficient in non-homologous end-joining repair, showed hyper-sensitivity to both types of carbon-ion irradiation. The difference in radiation sensitivity between the wild type and the repair-deficient mutant was greatly diminished for carbon ions near the range end, suggesting that these ions induce irreparable DNA damage. Mutational analysis of the Arabidopsis GL1 locus showed that while the frequency of generation of glabrous mutant sectors was not different between the two types of carbon-ion irradiation, large deletions (>{approx}30 kb) were six times more frequently induced by carbon ions near the range end. When 352 keV/{mu}m neon ions were used, these showed a 6.4 times increase in the frequency of induced large deletions compared with the 113 keV/{mu}m carbon ions. We suggest that the proportion of large deletions increases with LET in plants, as has been reported for mammalian cells. The nature of mutations induced in plants by carbon ions near the range end is discussed in relation to mutation detection by plasmid rescue and transmissibility to progeny.

  1. Recurrent frequency-size distribution of characteristic events

    Directory of Open Access Journals (Sweden)

    S. G. Abaimov

    2009-04-01

    Full Text Available Statistical frequency-size (frequency-magnitude properties of earthquake occurrence play an important role in seismic hazard assessments. The behavior of earthquakes is represented by two different statistics: interoccurrent behavior in a region and recurrent behavior at a given point on a fault (or at a given fault. The interoccurrent frequency-size behavior has been investigated by many authors and generally obeys the power-law Gutenberg-Richter distribution to a good approximation. It is expected that the recurrent frequency-size behavior should obey different statistics. However, this problem has received little attention because historic earthquake sequences do not contain enough events to reconstruct the necessary statistics. To overcome this lack of data, this paper investigates the recurrent frequency-size behavior for several problems. First, the sequences of creep events on a creeping section of the San Andreas fault are investigated. The applicability of the Brownian passage-time, lognormal, and Weibull distributions to the recurrent frequency-size statistics of slip events is tested and the Weibull distribution is found to be the best-fit distribution. To verify this result the behaviors of numerical slider-block and sand-pile models are investigated and the Weibull distribution is confirmed as the applicable distribution for these models as well. Exponents β of the best-fit Weibull distributions for the observed creep event sequences and for the slider-block model are found to have similar values ranging from 1.6 to 2.2 with the corresponding aperiodicities CV of the applied distribution ranging from 0.47 to 0.64. We also note similarities between recurrent time-interval statistics and recurrent frequency-size statistics.

  2. Magnitudes and frequencies of earthquakes in relation to seismic risk

    International Nuclear Information System (INIS)

    Sharma, R.D.

    1989-01-01

    Estimating the frequencies of occurrence of earthquakes of different magnitudes on a regional basis is an important task in estimating seismic risk at a construction site. Analysis of global earthquake data provides an insight into the magnitudes frequency relationship in a statistical manner. It turns out that, whereas a linear relationship between the logarithm of earthquake occurrence rates and the corresponding earthquake magnitudes fits well in the magnitude range between 5 and 7, a second degree polynomial in M, the earthquake magnitude provides a better description of the frequencies of earthquakes in a much wider range of magnitudes. It may be possible to adopt magnitude frequency relation for regions, for which adequate earthquake data are not available, to carry out seismic risk calculations. (author). 32 refs., 8 tabs., 7 figs

  3. Spectral long-range interaction of temporal incoherent solitons.

    Science.gov (United States)

    Xu, Gang; Garnier, Josselin; Picozzi, Antonio

    2014-02-01

    We study the interaction of temporal incoherent solitons sustained by a highly noninstantaneous (Raman-like) nonlinear response. The incoherent solitons exhibit a nonmutual interaction, which can be either attractive or repulsive depending on their relative initial distance. The analysis reveals that incoherent solitons exhibit a long-range interaction in frequency space, which is in contrast with the expected spectral short-range interaction described by the usual approach based on the Raman-like spectral gain curve. Both phenomena of anomalous interaction and spectral long-range behavior of incoherent solitons are described in detail by a long-range Vlasov equation.

  4. Noise Measurement and Frequency Analysis of Commercially Available Noisy Toys

    Directory of Open Access Journals (Sweden)

    Shohreh Jalaie

    2005-06-01

    Full Text Available Objective: Noise measurement and frequency analysis of commercially available noisy toys were the main purposes of the study. Materials and Methods: 181 noisy toys commonly found in toy stores in different zones of Tehran were selected and categorized into 10 groups. Noise measurement were done at 2, 25, and 50 cm from toys in dBA. The noisiest toy of each group was frequency analyzed in octave bands. Results: The highest and the lowest intensity levels belonged to the gun (mean=112 dBA and range of 100-127 dBA and to the rattle-box (mean=84 dBA and range of 74-95 dBA, respectively. Noise intensity levels significantly decreased with increasing distance except for two toys. Noise frequency analysis indicated energy in effective hearing frequencies. Most of the toys energies were in the middle and high frequency region. Conclusion: As intensity level of the toys is considerable, mostly more than 90 dBA, and also their energy exist in the middle and high frequency region, toys should be considered as a cause of the hearing impairment.

  5. Flood-frequency characteristics of Wisconsin streams

    Science.gov (United States)

    Walker, John F.; Peppler, Marie C.; Danz, Mari E.; Hubbard, Laura E.

    2017-05-22

    Flood-frequency characteristics for 360 gaged sites on unregulated rural streams in Wisconsin are presented for percent annual exceedance probabilities ranging from 0.2 to 50 using a statewide skewness map developed for this report. Equations of the relations between flood-frequency and drainage-basin characteristics were developed by multiple-regression analyses. Flood-frequency characteristics for ungaged sites on unregulated, rural streams can be estimated by use of the equations presented in this report. The State was divided into eight areas of similar physiographic characteristics. The most significant basin characteristics are drainage area, soil saturated hydraulic conductivity, main-channel slope, and several land-use variables. The standard error of prediction for the equation for the 1-percent annual exceedance probability flood ranges from 56 to 70 percent for Wisconsin Streams; these values are larger than results presented in previous reports. The increase in the standard error of prediction is likely due to increased variability of the annual-peak discharges, resulting in increased variability in the magnitude of flood peaks at higher frequencies. For each of the unregulated rural streamflow-gaging stations, a weighted estimate based on the at-site log Pearson type III analysis and the multiple regression results was determined. The weighted estimate generally has a lower uncertainty than either the Log Pearson type III or multiple regression estimates. For regulated streams, a graphical method for estimating flood-frequency characteristics was developed from the relations of discharge and drainage area for selected annual exceedance probabilities. Graphs for the major regulated streams in Wisconsin are presented in the report.

  6. The isolation of low frequency impact sounds in hotel construction

    Science.gov (United States)

    LoVerde, John J.; Dong, David W.

    2002-11-01

    One of the design challenges in the acoustical design of hotels is reducing low frequency sounds from footfalls occurring on both carpeted and hard-surfaced floors. Research on low frequency impact noise [W. Blazier and R. DuPree, J. Acoust. Soc. Am. 96, 1521-1532 (1994)] resulted in a conclusion that in wood construction low frequency impact sounds were clearly audible and that feasible control methods were not available. The results of numerous FIIC (Field Impact Insulation Class) measurements performed in accordance with ASTM E1007 indicate the lack of correlation between FIIC ratings and the reaction of occupants in the room below. The measurements presented include FIIC ratings and sound pressure level measurements below the ASTM E1007 low frequency limit of 100 Hertz, and reveal that excessive sound levels in the frequency range of 63 to 100 Hertz correlate with occupant complaints. Based upon this history, a tentative criterion for maximum impact sound level in the low frequency range is presented. The results presented of modifying existing constructions to reduce the transmission of impact sounds at low frequencies indicate that there may be practical solutions to this longstanding problem.

  7. Low-Frequency Components in Rat Pial Arteriolar Rhythmic Diameter Changes.

    Science.gov (United States)

    Lapi, Dominga; Mastantuono, Teresa; Di Maro, Martina; Varanini, Maurizio; Colantuoni, Antonio

    2017-01-01

    This study aimed to analyze the frequency components present in spontaneous rhythmic diameter changes in rat pial arterioles. Pial microcirculation was visualized by fluorescence microscopy. Rhythmic luminal variations were evaluated via computer-assisted methods. Spectral analysis was carried out on 30-min recordings under baseline conditions and after administration of acetylcholine (Ach), papaverine (Pap), Nω-nitro-L-arginine (L-NNA) prior to Ach, indomethacin (INDO), INDO prior to Ach, charybdotoxin and apamin, and charybdotoxin and apamin prior to Ach. Under baseline conditions all arteriolar orders showed 3 frequency components in the ranges of 0.0095-0.02, 0.02-0.06, and 0.06-0.2 Hz, another 2 in the ranges of 0.2-2.0 and 2.5-4.5 Hz, and another ultra-low-frequency component in the range of 0.001-0.0095 Hz. Ach caused a significant increase in the spectral density of the frequency components in the range of 0.001-0.2 Hz. Pap was able to slightly increase spectral density in the ranges of 0.001-0.0095 and 0.0095-0.02 Hz. L-NNA mainly attenuated arteriolar responses to Ach. INDO prior to Ach did not affect the endothelial response to Ach. Charybdotoxin and apamin, suggested as endothelium-derived hyperpolarizing factor inhibitors, reduced spectral density in the range of 0.001-0.0095 Hz before and after Ach administration. In conclusion, regulation of the blood flow distribution is due to several mechanisms, one of which is affected by charibdotoxin and apamin, modulating the vascular tone. © 2017 S. Karger AG, Basel.

  8. Time-frequency analysis of stimulus frequency otoacoustic emissions and their changes with efferent stimulation in guinea pigs

    Science.gov (United States)

    Berezina-Greene, Maria A.; Guinan, John J.

    2015-12-01

    To aid in understanding their origin, stimulus frequency otoacoustic emissions (SFOAEs) were measured at a series of tone frequencies using the suppression method, both with and without stimulation of medial olivocochlear (MOC) efferents, in anesthetized guinea pigs. Time-frequency analysis showed SFOAE energy peaks in 1-3 delay components throughout the measured frequency range (0.5-12 kHz). One component's delay usually coincided with the phase-gradient delay. When multiple delay components were present, they were usually near SFOAE dips. Below 2 kHz, SFOAE delays were shorter than predicted from mechanical measurements. With MOC stimulation, SFOAE amplitude was decreased at most frequencies, but was sometimes enhanced, and all SFOAE delay components were affected. The MOC effects and an analysis of model data suggest that the multiple SFOAE delay components arise at the edges of the traveling-wave peak, not far basal of the peak. Comparisons with published guinea-pig neural data suggest that the short latencies of low-frequency SFOAEs may arise from coherent reflection from an organ-of-Corti motion that has a shorter group delay than the traveling wave.

  9. Frequency dependent characteristics of solar impulsive radio bursts

    International Nuclear Information System (INIS)

    Das, T.K.; Das Gupta, M.K.

    1983-01-01

    An investigation was made of the impulsive radio bursts observed in the frequency range 0.245 to 35 GHz. Important results obtained are: (i) Simple type 1 bursts with intensities 0 to 10 f.u. and simple type 2 bursts with intensities 10 to 500 f.u. are predominant in the frequency ranges 1.415 to 4.995 GHz and 4.995 to 8.8 GHz, respectively; (ii) With maxima around 2.7 GHz and 4 GHz for the first and second types respectively, the durations of the radio bursts decrease gradually both towards lower and higher frequencies; (iii) As regards occurrences, the first type dominates in the southern solar hemisphere peaking around 8.8 GHz, whereas the second type favours the north with no well-defined maximum in any frequency; (iv) Both types prefer the eastern hemisphere, the peak occurrences being around 8.8 GHz and 5 GHz for the two successive types, respectively; (c) The spectra of impulsive radio bursts are generally of the inverted U-type with the maximum emission intensity between 5 and 15 GHz. (author)

  10. Resource partitioning of sonar frequency bands in rhinolophoid bats.

    Science.gov (United States)

    Heller, Klaus-Gerhard; Helversen, Otto V

    1989-08-01

    In the Constant Frequency portions of the orientation calls of various Rhinolophus and Hipposideros species, the frequency with the strongest amplitude was studied comparatively. (1) In the five European species of the genus Rhinolophus call frequencies are either species-specific (R. ferrumequinum, R. blasii and R. euryale) or they overlap (R. hipposideros and R. mehelyi). The call frequency distributions are approximately 5-9 kHz wide, thus their ranges spead less than ±5% from the mean (Fig. 1). Frequency distributions are considerably narrower within smaller geographic areas. (2) As in other bat groups, call frequencies of the Rhinolophoidea are negatively correlated with body size (Fig. 3). Regression lines for the genera Rhinolophus and Rhinolophus, species from dryer climates have on the average higher call frequencies than species from tropical rain forests. (4) The Krau Game Reserve, a still largely intact rain forest area in Malaysia, harbours at least 12 syntopic Rhinolophus and Hipposiderso species. Their call frequencies lie between 40 and 200 kHz (Fig. 2). Distribution over the available frequency range is significantly more even than could be expected from chance alone. Two different null hypotheses to test for random character distribution were derived from frequency-size-relations and by sampling species assemblages from a species pool (Monte Carlo method); both were rejected. In particular, call frequencies lying close together are avoided (Figs. 4, 5). Conversely, the distribution of size ratios complied with a corresponding null hypothesis. This even distribution may be a consequence of resource partitioning with respect to prey type. Alternatively, the importance of these calls as social signals (e.g. recognition of conspecifics) might have necessitated a communication channel partitioning.

  11. Dense range images from sparse point clouds using multi-scale processing

    NARCIS (Netherlands)

    Do, Q.L.; Ma, L.; With, de P.H.N.

    2013-01-01

    Multi-modal data processing based on visual and depth/range images has become relevant in computer vision for 3D reconstruction applications such as city modeling, robot navigation etc. In this paper, we generate highaccuracy dense range images from sparse point clouds to facilitate such

  12. Frequencies of inaudible high-frequency sounds differentially affect brain activity: positive and negative hypersonic effects.

    Directory of Open Access Journals (Sweden)

    Ariko Fukushima

    Full Text Available The hypersonic effect is a phenomenon in which sounds containing significant quantities of non-stationary high-frequency components (HFCs above the human audible range (max. 20 kHz activate the midbrain and diencephalon and evoke various physiological, psychological and behavioral responses. Yet important issues remain unverified, especially the relationship existing between the frequency of HFCs and the emergence of the hypersonic effect. In this study, to investigate the relationship between the hypersonic effect and HFC frequencies, we divided an HFC (above 16 kHz of recorded gamelan music into 12 band components and applied them to subjects along with an audible component (below 16 kHz to observe changes in the alpha2 frequency component (10-13 Hz of spontaneous EEGs measured from centro-parieto-occipital regions (Alpha-2 EEG, which we previously reported as an index of the hypersonic effect. Our results showed reciprocal directional changes in Alpha-2 EEGs depending on the frequency of the HFCs presented with audible low-frequency component (LFC. When an HFC above approximately 32 kHz was applied, Alpha-2 EEG increased significantly compared to when only audible sound was applied (positive hypersonic effect, while, when an HFC below approximately 32 kHz was applied, the Alpha-2 EEG decreased (negative hypersonic effect. These findings suggest that the emergence of the hypersonic effect depends on the frequencies of inaudible HFC.

  13. Frequencies of inaudible high-frequency sounds differentially affect brain activity: positive and negative hypersonic effects.

    Science.gov (United States)

    Fukushima, Ariko; Yagi, Reiko; Kawai, Norie; Honda, Manabu; Nishina, Emi; Oohashi, Tsutomu

    2014-01-01

    The hypersonic effect is a phenomenon in which sounds containing significant quantities of non-stationary high-frequency components (HFCs) above the human audible range (max. 20 kHz) activate the midbrain and diencephalon and evoke various physiological, psychological and behavioral responses. Yet important issues remain unverified, especially the relationship existing between the frequency of HFCs and the emergence of the hypersonic effect. In this study, to investigate the relationship between the hypersonic effect and HFC frequencies, we divided an HFC (above 16 kHz) of recorded gamelan music into 12 band components and applied them to subjects along with an audible component (below 16 kHz) to observe changes in the alpha2 frequency component (10-13 Hz) of spontaneous EEGs measured from centro-parieto-occipital regions (Alpha-2 EEG), which we previously reported as an index of the hypersonic effect. Our results showed reciprocal directional changes in Alpha-2 EEGs depending on the frequency of the HFCs presented with audible low-frequency component (LFC). When an HFC above approximately 32 kHz was applied, Alpha-2 EEG increased significantly compared to when only audible sound was applied (positive hypersonic effect), while, when an HFC below approximately 32 kHz was applied, the Alpha-2 EEG decreased (negative hypersonic effect). These findings suggest that the emergence of the hypersonic effect depends on the frequencies of inaudible HFC.

  14. Frequency of coronary artery disease (cad) risk factors in armed forces

    International Nuclear Information System (INIS)

    Kamran, S.M.; Iftikhar, R.; Abbasi, K.

    2015-01-01

    To determine the frequency of risk factors of coronary artery disease (CAD) in apparently healthy soldiers of Pakistan Armed Forces. Study Design: Cross sectional descriptive study. Place and Duration of Study: Department of medicine, CMH Okara from July 2012 to Dec 2012. Patients and Methods: The study included 2215 male currently serving soldiers in age range of 18 to 52 years by consecutive sampling. Relevant history, body mass index (BMI), waist circumference (WC) and blood pressure (BP) of each subject were recorded. BMI > 25 kg/m/sup 2/ and WC > 90 cm was considered obesity and abdominal obesity respectively. BP > 140/90 mmHg was defined as hypertension. All the participants of study underwent blood glucose fasting, blood glucose random, ECG recording, personality assessment and lipid profile. Risk estimation was done using Eric Brittain scoring system. Results: In our study group 95.5% patients were having at least 1 risk factor of CAD, 54 % were having 2 to 4 risk factors while 3.93% had > 4 risk factors. Risk estimation of CAD using Eric Brittain scoring system showed that a large proportion of study group had high probability of developing ischemic heart disease in next 6 years. Conclusion: A large proportion of our soldiers are harboring risk of CAD due to increase in frequency of 8 conventional CAD risk factors especially obesity. (author)

  15. Loads as a Resource: Frequency Responsive Demand

    Energy Technology Data Exchange (ETDEWEB)

    Kalsi, Karanjit [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Lian, Jianming [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Marinovici, Laurentiu D. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Elizondo, Marcelo A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Zhang, Wei [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Moya, Christian [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2014-10-08

    Frequency control plays an important role in preserving the power balance of a multi-machine power system. Generators modify their power output when a non-zero frequency deviation is presented in order to restore power balance across the network. However, with plans for large-scale penetration of renewable energy resources, performing primary frequency control using only supply-side resources becomes not only prohibitively expensive, but also technically difficult. Frequency control from the demand side or load control presents a novel and viable way for providing the desired frequency response. Loads can measure frequency locally and change their power consumption after a non-zero frequency deviation is presented in order to achieve power balance between generation and consumption. The specific objectives of this project are to: •Provide a framework to facilitate large-scale deployment of frequency responsive end-use devices •Systematically design decentralized frequency-based load control strategies for enhanced stability performance •Ensure applicability over wide range of operating conditions while accounting for unpredictable end-use behavior and physical device constraints •Test and validate control strategy using large-scale simulations and field demonstrations •Create a level-playing field for smart grid assets with conventional generators

  16. Both the cutaneous sensation and phosphene perception are modulated in a frequency-specific manner during transcranial alternating current stimulation.

    Science.gov (United States)

    Turi, Zs; Ambrus, G G; Janacsek, K; Emmert, K; Hahn, L; Paulus, W; Antal, A

    2013-01-01

    Transcranial alternating current stimulation (tACS) is a non-invasive stimulation technique for shaping neuroplastic processes and possibly entraining ongoing neural oscillations in humans. Despite the growing number of studies using tACS, we know little about the procedural sensations caused by stimulation. In order to fill this gap, we explored the cutaneous sensation and phosphene perception during tACS. Twenty healthy participants took part in a randomized, single-blinded, sham-controlled study, where volunteers received short duration stimulation at 1.0 mA intensity between 2 to 250 Hz using the standard left motor cortex-contralateral supraorbital montage. We recorded the perception onset latency and the strength of the sensations assessed by visual rating scale as dependent variables. We found that tACS evoked both cutaneous sensation and phosphene perception in a frequency-dependent manner. Our results show that the most perceptible procedural sensations were induced in the beta and gamma frequency range, especially at 20 Hz, whereas minimal procedural sensations were indicated in the ripple range (140 and 250 Hz). We believe that our results provide a relevant insight into the procedural sensations caused by oscillatory currents, and will offer a basis for developing more sophisticated stimulation protocols and study designs for future investigations.

  17. Extended parametric gain range in photonic crystal fibers with strongly frequency-dependent field distributions

    DEFF Research Database (Denmark)

    Petersen, Sidsel Rübner; Alkeskjold, Thomas Tanggaard; Olausson, Christina Bjarnal Thulin

    2014-01-01

    The parametric gain range of a degenerate four-wave mixing process is determined in the undepleted pump regime. The gain range is considered with and without taking the mode field distributions of the four-wave mixing components into account. It is found that the mode field distributions have...

  18. Face Recognition Is Affected by Similarity in Spatial Frequency Range to a Greater Degree Than Within-Category Object Recognition

    Science.gov (United States)

    Collin, Charles A.; Liu, Chang Hong; Troje, Nikolaus F.; McMullen, Patricia A.; Chaudhuri, Avi

    2004-01-01

    Previous studies have suggested that face identification is more sensitive to variations in spatial frequency content than object recognition, but none have compared how sensitive the 2 processes are to variations in spatial frequency overlap (SFO). The authors tested face and object matching accuracy under varying SFO conditions. Their results…

  19. Sub-Frequency Interval Approach in Electromechanical Impedance Technique for Concrete Structure Health Monitoring

    Directory of Open Access Journals (Sweden)

    Bahador Sabet Divsholi

    2010-12-01

    Full Text Available The electromechanical (EM impedance technique using piezoelectric lead zirconate titanate (PZT transducers for structural health monitoring (SHM has attracted considerable attention in various engineering fields. In the conventional EM impedance technique, the EM admittance of a PZT transducer is used as a damage indicator. Statistical analysis methods such as root mean square deviation (RMSD have been employed to associate the damage level with the changes in the EM admittance signatures, but it is difficult to determine the location of damage using such methods. This paper proposes a new approach by dividing the large frequency (30–400 kHz range into sub-frequency intervals and calculating their respective RMSD values. The RMSD of the sub-frequency intervals (RMSD-S will be used to study the severity and location of damage. An experiment is carried out on a real size concrete structure subjected to artificial damage. It is observed that damage close to the PZT changes the high frequency range RMSD-S significantly, while the damage far away from the PZT changes the RMSD-S in the low frequency range significantly. The relationship between the frequency range and the PZT sensing region is also presented. Finally, a damage identification scheme is proposed to estimate the location and severity of damage in concrete structures.

  20. Complex magnetic susceptibility setup for spectroscopy in the extremely low-frequency range

    NARCIS (Netherlands)

    Kuipers, B.W.M.; Bakelaar, I.A.; Klokkenburg, M.; Erne, B.H.

    2008-01-01

    A sensitive balanced differential transformer was built to measure complex initial parallel magnetic susceptibility spectra in the 0.01–1000 Hz range. The alternating magnetic field can be chosen sufficiently weak that the magnetic structure of the samples is only slightly perturbed and the low

  1. Metamaterial near-field sensor for deep-subwavelength thickness measurements and sensitive refractometry in the terahertz frequency range

    Energy Technology Data Exchange (ETDEWEB)

    Reinhard, Benjamin; Schmitt, Klemens M.; Neu, Jens [Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, 67663 Kaiserslautern (Germany); Wollrab, Viktoria; Beigang, Rene; Rahm, Marco [Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, 67663 Kaiserslautern (Germany); Fraunhofer Institute for Physical Measurement Techniques IPM, 79110 Freiburg (Germany)

    2012-05-28

    We present a metamaterial-based terahertz (THz) sensor for thickness measurements of subwavelength-thin materials and refractometry of liquids and liquid mixtures. The sensor operates in reflection geometry and exploits the frequency shift of a sharp Fano resonance minimum in the presence of dielectric materials. We obtained a minimum thickness resolution of 12.5 nm (1/16 000 times the wavelength of the THz radiation) and a refractive index sensitivity of 0.43 THz per refractive index unit. We support the experimental results by an analytical model that describes the dependence of the resonance frequency on the sample material thickness and the refractive index.

  2. Metamaterial near-field sensor for deep-subwavelength thickness measurements and sensitive refractometry in the terahertz frequency range

    International Nuclear Information System (INIS)

    Reinhard, Benjamin; Schmitt, Klemens M.; Neu, Jens; Wollrab, Viktoria; Beigang, Rene; Rahm, Marco

    2012-01-01

    We present a metamaterial-based terahertz (THz) sensor for thickness measurements of subwavelength-thin materials and refractometry of liquids and liquid mixtures. The sensor operates in reflection geometry and exploits the frequency shift of a sharp Fano resonance minimum in the presence of dielectric materials. We obtained a minimum thickness resolution of 12.5 nm (1/16 000 times the wavelength of the THz radiation) and a refractive index sensitivity of 0.43 THz per refractive index unit. We support the experimental results by an analytical model that describes the dependence of the resonance frequency on the sample material thickness and the refractive index.

  3. Test site experiments with a reconfigurable stepped frequency GPR

    Science.gov (United States)

    Persico, Raffaele; Matera, Loredana; Piro, Salvatore; Rizzo, Enzo; Capozzoli, Luigi

    2016-04-01

    In this contribution, some new possibilities offered by a reconfigurable stepped frequency GPR system are exposed. In particular, results achieved from a prototypal system achieved in two scientific test sites will be shown together with the results achieved in the same test sites with traditional systems. Moreover a novel technique for the rejection of undesired interferences is shown, with the use of interferences caused on purpose. Key words GPR, reconfigurable stepped frequency. Introduction A reconfigurable GPR system is meant as a GPR where some parameter can be changed vs. the frequency (if the system is stepped frequency) or vs. the time (if the system is pulsed) in a programmable way. The programming should then account for the conditions met in the scenario at hand [1]. Within the research project AITECH (http://www.aitechnet.com/ibam.html), the Institute for Archaeological and Monumental Heritage, together with the University of Florence and the IDS corporation have implemented a prototype, that has been used in sites of cultural interest in Italy [2], but also abroad in Norway and Malta. The system is a stepped frequency GPR working in the frequency range 50-1000 MHz, and its reconfigurability consists in three properties. The first one is the fact that the length of the antennas can be modulated by the aperture and closure of two electronic switches present along the arms of the antennas, so that the antennas can become electrically (and electronically) longer or shorter, so becoming more suitable to radiate some frequencies rather than some other. In particular, the system can radiate three different bands in the comprehensive range between 50-1000 MHz, so being suitable for different depth range of the buried targets, and the three bands are gathered in a unique "going through" because for each measurement point the system can sweep the entire frequency range trhee times, one for each configuration of the switchres on the arms. The second property is

  4. Relevance of metric-free interactions in flocking phenomena.

    Science.gov (United States)

    Ginelli, Francesco; Chaté, Hugues

    2010-10-15

    We show that the collective properties of self-propelled particles aligning with their topological (Voronoi) neighbors are qualitatively different from those of usual models where metric interaction ranges are used. This relevance of metric-free interactions, shown in a minimal setting, indicate that realistic models for the cohesive motion of cells, bird flocks, and fish schools may have to incorporate them, as suggested by recent observations.

  5. Configuration Considerations for Low Frequency Arrays

    Science.gov (United States)

    Lonsdale, C. J.

    2005-12-01

    The advance of digital signal processing capabilities has spurred a new effort to exploit the lowest radio frequencies observable from the ground, from ˜10 MHz to a few hundred MHz. Multiple scientifically and technically complementary instruments are planned, including the Mileura Widefield Array (MWA) in the 80-300 MHz range, and the Long Wavelength Array (LWA) in the 20-80 MHz range. The latter instrument will target relatively high angular resolution, and baselines up to a few hundred km. An important practical question for the design of such an array is how to distribute the collecting area on the ground. The answer to this question profoundly affects both cost and performance. In this contribution, the factors which determine the anticipated performance of any such array are examined, paying particular attention to the viability and accuracy of array calibration. It is argued that due to the severity of ionospheric effects in particular, it will be difficult or impossible to achieve routine, high dynamic range imaging with a geographically large low frequency array, unless a large number of physically separate array stations is built. This conclusion is general, is based on the need for adequate sampling of ionospheric irregularities, and is independent of the calibration algorithms and techniques that might be employed. It is further argued that array configuration figures of merit that are traditionally used for higher frequency arrays are inappropriate, and a different set of criteria are proposed.

  6. EOG feature relevance determination for microsleep detection

    OpenAIRE

    Golz Martin; Wollner Sebastian; Sommer David; Schnieder Sebastian

    2017-01-01

    Automatic relevance determination (ARD) was applied to two-channel EOG recordings for microsleep event (MSE) recognition. 10 s immediately before MSE and also before counterexamples of fatigued, but attentive driving were analysed. Two type of signal features were extracted: the maximum cross correlation (MaxCC) and logarithmic power spectral densities (PSD) averaged in spectral bands of 0.5 Hz width ranging between 0 and 8 Hz. Generalised learn-ing vector quantisation (GRLVQ) was used as ARD...

  7. Frequency of aneuploidy related to age in porcine oocytes.

    Directory of Open Access Journals (Sweden)

    Miroslav Hornak

    Full Text Available It is generally accepted that mammalian oocytes are frequently suffering from chromosome segregation errors during meiosis I, which have severe consequences, including pregnancy loss, developmental disorders and mental retardation. In a search for physiologically more relevant model than rodent oocytes to study this phenomenon, we have employed comparative genomic hybridization (CGH, combined with whole genome amplification (WGA, to study the frequency of aneuploidy in porcine oocytes, including rare cells obtained from aged animals. Using this method, we were able to analyze segregation pattern of each individual chromosome during meiosis I. In contrast to the previous reports where conventional methods, such as chromosome spreads or FISH, were used to estimate frequency of aneuploidy, our results presented here show, that the frequency of this phenomenon was overestimated in porcine oocytes. Surprisingly, despite the results from human and mouse showing an increase in the frequency of aneuploidy with advanced maternal age, our results obtained by the most accurate method currently available for scoring the aneuploidy in oocytes indicated no increase in the frequency of aneuploidy even in oocytes from animals, whose age was close to the life expectancy of the breed.

  8. Temperature dependence of the resonance frequency of thermogravimetric devices

    NARCIS (Netherlands)

    Iervolino, E.; Riccio, M.; Van Herwaarden, A.W.; Irace, A.; Breglio, G.; Van der Vlist, W.; Sarro, P.M.

    2010-01-01

    This paper investigates the temperature dependence of the resonance frequency of thermogravimetric (TG) devices for tip heating over the temperature range of View the MathML source 25–600?C. The resonance frequency of a fabricated TG device shows to be temperature independent for tip heating up to

  9. High-frequency response and the possibilities of frequency-tunable narrow-band terahertz amplification in resonant tunneling nanostructures

    International Nuclear Information System (INIS)

    Kapaev, V. V.; Kopaev, Yu. V.; Savinov, S. A.; Murzin, V. N.

    2013-01-01

    The characteristics of the high-frequency response of single- and double-well resonant tunneling structures in a dc electric field are investigated on the basis of the numerical solution of a time-dependent Schrödinger equation with open boundary conditions. The frequency dependence of the real part of high frequency conductivity (high-frequency response) in In 0.53 Ga 0.47 As/AlAs/InP structures is analyzed in detail for various values of the dc voltage V dc in the negative differential resistance (NDR) region. It is shown that double-well three-barrier structures are promising for the design of terahertz-band oscillators. The presence of two resonant states with close energies in such structures leads to a resonant (in frequency) response whose frequency is determined by the energy difference between these levels and can be controlled by varying the parameters of the structure. It is shown that, in principle, such structures admit narrow-band amplification, tuning of the amplification frequency, and a fine control of the amplification (oscillation) frequency in a wide range of terahertz frequencies by varying a dc electric voltage applied to the structure. Starting from a certain width of the central intermediate barrier in double-well structures, one can observe a collapse of resonances, where the structure behaves like a single-well system. This phenomenon imposes a lower limit on the oscillation frequency in three-barrier resonant tunneling structures.

  10. Increased frequency and range of sexual behavior in a patient with Parkinson's disease after use of pramipexole: a case report.

    Science.gov (United States)

    Munhoz, Renato P; Fabiani, Giorgio; Becker, Nilson; Teive, Hélio A G

    2009-04-01

    Several recent reports have linked the use of dopamine agonists (DAs) to a variety of compulsive behaviors in patients with Parkinson's disease (PD). These inappropriate behaviors may include pathological gambling, compulsive shopping, and hypersexuality. To report the case of a patient with increased range of sexual behavior after use of pramipexole, a DA. A 67-year-old man with a 7-year diagnosis of PD treated with levodopa and pramipexole presented with a dramatic change in sexual behavior after an increase in DA dose. The patient, who historically was a very shy and conservative person, started to present increased frequency of sexual intercourse with his wife, during which he began speaking obscenities with an extreme preference for anal intercourse, preferences never requested before. After pramipexole was withdrawn, complete remission was observed with return to his usual sexual behavior. Hypersexuality and paraphilias are complications not uncommonly found in patients with PD under dopaminergic treatment. Further studies are needed for the understanding of this complex complication, and particularly the most prevalent relationship between pathological hypersexuality and use of DAs.

  11. 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.

  12. Equivalent magnetic noise reduction at high frequency range due to polarized direction optimization in Terfenol-D/Pb(Mg{sub 1/3}Nb{sub 2/3})O{sub 3}-PbTiO{sub 3} magnetoelectric laminate sensors

    Energy Technology Data Exchange (ETDEWEB)

    Fang, Cong, E-mail: fangcong86@gmail.com [Key Laboratory of Inorganic Functional Material and Device, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 201800 (China); University of Chinese Academy of Sciences, Beijing, 100049 (China); Ma, Jiashuai; Yao, Meng [Key Laboratory of Inorganic Functional Material and Device, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 201800 (China); University of Chinese Academy of Sciences, Beijing, 100049 (China); Di, Wenning; Lin, Di; Xu, Haiqing; Wang, Wei [Key Laboratory of Inorganic Functional Material and Device, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 201800 (China); Luo, Haosu, E-mail: hsluo@mail.sic.ac.cn [Key Laboratory of Inorganic Functional Material and Device, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 201800 (China)

    2017-02-01

    In this paper, we investigate the responsivities and output voltage noise power spectral densities of magnetoelectric (ME) laminate sensors, consisting of length magnetized Terfenol-D alloys and transverse/width poled Pb(Mg{sub 1/3}Nb{sub 2/3})O{sub 3}-PbTiO{sub 3} (PMNT) crystals (i.e. L-T mode and L-W mode respectively), which are directly integrated with custom-build low noise charge amplifier circuits. Both the theoretical analyses and experimental results prove that the L-W mode sensor with the optimized polarized direction of the PMNT plate possesses lower magnetic detection limit at the interested high frequency range of 10 kHz≤f≤50 kHz. The equivalent magnetic noise (EMN) of the L-W mode sensor is 0.78 pT/Hz{sup 1/2} at 30 kHz, which is about 1.7 times lower than the 1.35 pT/Hz{sup 1/2} for conventional L-T mode sensor. Furthermore, an effective method of using operational amplifiers with low equivalent input noise voltage and employing ME laminate composites with high voltage coefficient to reduce the EMNs of the ME laminate sensors at high frequency range has been established. - Highlights: • We present fabrications and properties of the L-T and L-T mode ME composites. • The equivalent magnetic noise levels at high frequency are measured. • The equivalent magnetic noise of the L-W mode sensor is 0.78 pT/Hz{sup 1/2} at 30 kHz. • The dominated noise source can be confirmed from OPA at high frequency range.

  13. Time domain acoustic contrast control implementation of sound zones for low-frequency input signals

    DEFF Research Database (Denmark)

    Schellekens, Daan H. M.; Møller, Martin Bo; Olsen, Martin

    2016-01-01

    Sound zones are two or more regions within a listening space where listeners are provided with personal audio. Acoustic contrast control (ACC) is a sound zoning method that maximizes the average squared sound pressure in one zone constrained to constant pressure in other zones. State......-of-the-art time domain broadband acoustic contrast control (BACC) methods are designed for anechoic environments. These methods are not able to realize a flat frequency response in a limited frequency range within a reverberant environment. Sound field control in a limited frequency range is a requirement...... to accommodate the effective working range of the loudspeakers. In this paper, a new BACC method is proposed which results in an implementation realizing a flat frequency response in the target zone. This method is applied in a bandlimited low-frequency scenario where the loudspeaker layout surrounds two...

  14. Low-frequency scaling applied to stochastic finite-fault modeling

    Science.gov (United States)

    Crane, Stephen; Motazedian, Dariush

    2014-01-01

    Stochastic finite-fault modeling is an important tool for simulating moderate to large earthquakes. It has proven to be useful in applications that require a reliable estimation of ground motions, mostly in the spectral frequency range of 1 to 10 Hz, which is the range of most interest to engineers. However, since there can be little resemblance between the low-frequency spectra of large and small earthquakes, this portion can be difficult to simulate using stochastic finite-fault techniques. This paper introduces two different methods to scale low-frequency spectra for stochastic finite-fault modeling. One method multiplies the subfault source spectrum by an empirical function. This function has three parameters to scale the low-frequency spectra: the level of scaling and the start and end frequencies of the taper. This empirical function adjusts the earthquake spectra only between the desired frequencies, conserving seismic moment in the simulated spectra. The other method is an empirical low-frequency coefficient that is added to the subfault corner frequency. This new parameter changes the ratio between high and low frequencies. For each simulation, the entire earthquake spectra is adjusted, which may result in the seismic moment not being conserved for a simulated earthquake. These low-frequency scaling methods were used to reproduce recorded earthquake spectra from several earthquakes recorded in the Pacific Earthquake Engineering Research Center (PEER) Next Generation Attenuation Models (NGA) database. There were two methods of determining the stochastic parameters of best fit for each earthquake: a general residual analysis and an earthquake-specific residual analysis. Both methods resulted in comparable values for stress drop and the low-frequency scaling parameters; however, the earthquake-specific residual analysis obtained a more accurate distribution of the averaged residuals.

  15. Dissemination of optical-comb-based ultra-broadband frequency reference through a fiber network.

    Science.gov (United States)

    Nagano, Shigeo; Kumagai, Motohiro; Li, Ying; Ido, Tetsuya; Ishii, Shoken; Mizutani, Kohei; Aoki, Makoto; Otsuka, Ryohei; Hanado, Yuko

    2016-08-22

    We disseminated an ultra-broadband optical frequency reference based on a femtosecond (fs)-laser optical comb through a kilometer-scale fiber link. Its spectrum ranged from 1160 nm to 2180 nm without additional fs-laser combs at the end of the link. By employing a fiber-induced phase noise cancellation technique, the linewidth and fractional frequency instability attained for all disseminated comb modes were of order 1 Hz and 10-18 in a 5000 s averaging time. The ultra-broad optical frequency reference, for which absolute frequency is traceable to Japan Standard Time, was applied in the frequency stabilization of an injection-seeded Q-switched 2051 nm pulse laser for a coherent light detection and ranging LIDAR system.

  16. Frequency effects in silane plasmas for PECVD

    International Nuclear Information System (INIS)

    Howling, A.A.; Dorier, J.L.; Hollenstein, C.; Finger, F.; Kroll, U.

    1991-09-01

    It is generally recognised that the excitation frequency is an important parameter in rf plasma-assisted deposition. VHF silane plasmas (50-100 MHz) have been shown to produce high quality amorphous silicon films up to 20 A/s, and therefore the aim of this work is to compare the VHF range with the 13.56 MHz industrial frequency in the same reactor. The principal diagnostics used are electrical measurements and a CCD camera for spatially-resolved plasma-induced emission with Abel inversion of the plasma image. We present a comparative study of key discharge parameters such as deposition rates, plasma uniformity, ion impact energy, power transfer efficiency and powder formation for the rf range 13-70 MHz. (author) 5 figs., 19 refs

  17. Bayesian Ranging for Radio Localization with and without Line-of-Sight Detection

    DEFF Research Database (Denmark)

    Jing, Lishuai; Pedersen, Troels; Fleury, Bernard Henri

    2015-01-01

    We consider Bayesian ranging methods for local- ization in wireless communication systems. Based on a channel model and given priors for the range and the line-of-sight (LOS) condition, we propose range estimators with and without LOS detection. Since the pdf of the received frequency...

  18. Voice Range Profiles of Singing Students: The Effects of Training Duration and Institution.

    Science.gov (United States)

    Lycke, Hugo; Siupsinskiene, Nora

    2016-01-01

    The aim of the study was to assess differences in voice parameters measured by the physiological voice range profile (VRP) in groups of vocally healthy subjects differentiated by the duration of vocal training and the training institution. Six basic frequency- and intensity-related VRP parameters and the frequency dip of the register transition zone were determined from VRP recordings of 162 females studying in individual singing lessons (1st-5th level) in Dutch, Belgian, English, and French public or private training facilities. Sixty-seven nonsinging female students served as controls. Singing students in more advanced singing classes demonstrated a significantly greater frequency range, particularly at high frequencies, than did first-year students. Students with private training showed a significantly increased mean intensity range in comparison to those in group classes, while students with musical theater training exhibited significantly increased frequency- and intensity-related VRP parameters in comparison to the students with classical training. When compared to nonsingers, all singing student subgroups showed significant increases in all basic VRP parameters. However, the register transition parameter was not influenced by training duration or institution. Our study suggests that the extension of physiological vocal limits might depend on training duration and institution. © 2016 S. Karger AG, Basel.

  19. Frequency and temperature dependence of high damping elastomers

    International Nuclear Information System (INIS)

    Kulak, R.F.; Hughes, T.H.

    1993-01-01

    High damping steel-laminated elastomeric seismic isolation bearings are one of the preferred devices for isolating large buildings and structures. In the US, the current reference design for the Advanced Liquid Metal Reactor (ALMR) uses laminated bearings for seismic isolation. These bearings are constructed from alternating layers of high damping rubber and steel plates. They are typically designed for shear strains between 50 and 100% and are expected to sustain two to three times these levels for beyond design basis loading conditions. Elastomeric bearings are currently designed to provide a system frequency between 0.4 and 0.8 Hz and expected to operate between -20 and 40 degrees Centigrade. To assure proper performance of isolation bearings, it is necessary to characterize the elastomer's response under expected variations of frequency and temperature. The dynamic response of the elastomer must be characterized within the frequency range that spans the bearing acceptance test frequency, which may be as low as 0.005 Hz, and the design frequency. Similarly, the variation in mechanical characteristics of the elastomer must be determined over the design temperature range, which is between -20 and 40 degrees Centigrade. This paper reports on (1) the capabilities of a testing facility at ANL for testing candidate elastomers, (2) the variation with frequency and temperature of the stiffness and damping of one candidate elastomer, and (3) the effect of these variations on bearing acceptance testing criteria and on the choice of bearing design values for stiffness and damping

  20. Frequency-agile dual-comb spectroscopy

    Science.gov (United States)

    Millot, Guy; Pitois, Stéphane; Yan, Ming; Hovhannisyan, Tatevik; Bendahmane, Abdelkrim; Hänsch, Theodor W.; Picqué, Nathalie

    2016-01-01

    Spectroscopic gas sensing and its applications to, for example, trace detection or chemical kinetics, require ever more demanding measurement times, acquisition rates, sensitivities, precisions and broad tuning ranges. Here, we propose a new approach to near-infrared molecular spectroscopy, utilizing advanced concepts of optical telecommunications and supercontinuum photonics. We generate, without mode-locked lasers, two frequency combs of slightly different repetition frequencies and moderate, but rapidly tunable, spectral span. The output of a frequency-agile continuous-wave laser is split and sent into two electro-optic intensity modulators. Flat-top low-noise frequency combs are produced by wave-breaking in a nonlinear optical fibre of normal dispersion. With a dual-comb spectrometer, we record Doppler-limited spectra spanning 60 GHz within 13 μs and an 80 kHz refresh rate, at a tuning speed of 10 nm s-1. The sensitivity for weak absorption is enhanced by a long gas-filled hollow-core fibre. New opportunities for real-time diagnostics may be opened up, even outside the laboratory.

  1. Iodine frequency references for space

    International Nuclear Information System (INIS)

    Schuldt, Thilo; Braxmaier, Claus; Döringshoff, Klaus; Peters, Achim; Oswald, Markus; Johann, Ulrich

    2017-01-01

    Optical frequency references are a key element for the realization of future space missions. They are needed for missions related to tests of fundamental physics, gravitational wave detection, Earth observation and navigation and ranging. In missions such as GRACE follow-on or LISA the optical frequency reference is used as light source for high-sensitivity inter-satellite distance metrology. While cavity-based systems are current baseline e.g. for LISA, frequency stabilization on a hyperfine transition in molecular iodine near 532 nm is a promising alternative. Due to its absolute frequency, iodine standards crucially simplify the initial spacecraft acquisition procedures. Current setups fulfill the GRACE-FO and LISA frequency stability requirements and are realized near Engineering Model level. We present the current status of our developments on Elegant Breadboard (EBB) and Engineering Model (EM) level taking into account specific design criteria for space compatibility such as compactness (size iodine spectroscopy EM: 38 × 18 × 10 cm 3 ) and robustness. Both setups achieved similar frequency stabilities of ∼ 1 · 10 −14 at an integration time of 1 s and below 5 · 10 −15 at integration times between 10 s and 1000 s. Furthermore, we present an even more compact design currently developed for a sounding rocket mission with launch in 2017. (paper)

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

    KAUST Repository

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

    2017-01-01

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

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

    KAUST Repository

    Alsaif, Bidoor

    2017-11-02

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

  4. Heart rate, multiple body temperature, long-range and long-life telemetry system for free-ranging animals

    Science.gov (United States)

    Lund, G. F.; Westbrook, R. M.; Fryer, T. B.

    1980-01-01

    The design details and rationale for a versatile, long-range, long-life telemetry data acquisition system for heart rates and body temperatures at multiple locations from free-ranging animals are presented. The design comprises an implantable transmitter for short to medium range transmission, a receiver retransmitter collar to be worn for long-range transmission, and a signal conditioner interface circuit to assist in signal discrimination and demodulation of receiver or tape-recorded audio outputs. Implanted electrodes are used to obtain an ECG, from which R-wave characteristics are selected to trigger a short RF pulse. Pulses carrying heart rate information are interrupted periodically by a series of pulse interval modulated RF pulses conveying temperature information sensed at desired locations by thermistors. Pulse duration and pulse sequencing are used to discriminate between heart rate and temperature pulses as well as radio frequency interference. The implanted transmitter may be used alone for medium and short-range tracking, or with a receiver-transmitter collar that employs commercial tracking equipment for transmissions of up to 12 km. A system prototype has been tested on a dog.

  5. Near-Field Three-Dimensional Planar Millimeter-Wave Holographic Imaging by Using Frequency Scaling Algorithm

    Directory of Open Access Journals (Sweden)

    Ye Zhang

    2017-10-01

    Full Text Available In this paper, a fast three-dimensional (3-D frequency scaling algorithm (FSA with large depth of focus is presented for near-field planar millimeter-wave (MMW holographic imaging. Considering the cross-range range coupling term which is neglected in the conventional range migration algorithm (RMA, we propose an algorithm performing the range cell migration correction for de-chirped signals without interpolation by using a 3-D frequency scaling operation. First, to deal with the cross-range range coupling term, a 3-D frequency scaling operator is derived to eliminate the space variation of range cell migration. Then, a range migration correction factor is performed to compensate for the residual range cell migration. Finally, the imaging results are obtained by matched filtering in the cross-range direction. Compared with the conventional RMA, the proposed algorithm is comparable in accuracy but more efficient by using only chirp multiplications and fast Fourier transforms (FFTs. The algorithm has been tested with satisfying results by both simulation and experiment.

  6. Low power fast settling multi-standard current reusing CMOS fractional-N frequency synthesizer

    Institute of Scientific and Technical Information of China (English)

    Lou Wenfeng; Feng Peng; Wang Haiyong; Wu Nanjian

    2012-01-01

    A low power fast settling multi-standard CMOS fractional-N frequency synthesizer is proposed.The current reusing and frequency presetting techniques are adopted to realize the low power fast settling multi-standard fractional-N frequency synthesizer.An auxiliary non-volatile memory (NVM) is embedded to avoid the repetitive calibration process and to save power in practical application.This PLL is implemented in a 0.18μm technology.The frequency range is 0.3 to 2.54 GHz and the settling time is less than 5μs over the entire frequency range.The LC-VCO with the stacked divide-by-2 has a good figure of merit of-193.5 dBc/Hz.The measured phase noise of frequency synthesizer is about -115 dBc/Hz at 1 MHz offset when the carrier frequency is 2.4 GHz and the reference spurs are less than -52 dBc.The whole frequency synthesizer consumes only 4.35 mA @ 1.8 V.

  7. Single and multi-frequency impedance characterization of symmetric activated carbon single capacitor cells

    Directory of Open Access Journals (Sweden)

    Suzana Sopčić

    2018-05-01

    Full Text Available Electrochemical impedance spectroscopy (EIS technique is used for characterization of single cell symmetric capacitors having different mass loadings of activated carbon (AC. Relevant values of charge storage capacitance (CT and internal resistance (ESR were evaluated by the single frequency and multi-frequency analyses of measured impedance spectra. Curve fittings were based on the non-ideal R-C model that takes into account the parasitic inductance, contributions from electrode materials/contacts and the effects of AC porosity. Higher CT and lower ESR values were obtained not only for the cell with higher mass of AC, but also using the single vs. multi-frequency approach. Lower CT and higher values of ESR that are generally obtained using the multi-frequency method and curve fittings should be related to the not ideal capacitive response of porous AC material and too high frequency chosen in applying the single frequency analysis.

  8. Spatial-frequency spectrum of patterns changes the visibility of spatial-phase differences

    Science.gov (United States)

    Lawton, T. B.

    1985-01-01

    It is shown that spatial-frequency components over a 4-octave range affected the visibility of spatial-phase differences. Contrast thresholds were measured for discrimination between two (+45- and -45-deg) spatial phases of a sinusoidal test grating added to a background grating. The background could contain one or several sinusoidal components, all in 0-deg phase. Phase differences between the test and the background were visible at lower contrasts when test and background frequencies were harmonically related than when they were not, when test and background frequencies were within 1 octave than when they were farther apart, when the fundamental frequency of the background was low than when it was high, and for some discriminations more than for others, after practice. The visibility of phase differences was not affected by additional components in the background if the fundamental and difference frequencies of the background remained unchanged. Observers' reports of their strategies gave information about the types of attentive processing that were used to discriminate phase differences. Attentive processing facilitated phase discrimination for multifrequency gratings spanning a much wider range of spatial frequencies than would be possible by using only local preattentive processing. These results were consistent with the visibility of phase differences being processed by some combination of even- and odd-symmetric simple cells tuned to a wide range of different spatial frequencies.

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

    Science.gov (United States)

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

    2015-12-01

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

  10. Infrared frequency-tunable coherent thermal sources

    International Nuclear Information System (INIS)

    Wang, Hao; Yang, Yue; Wang, Liping

    2015-01-01

    In this work, we numerically demonstrate an infrared (IR) frequency-tunable selective thermal emitter made of graphene-covered silicon carbide (SiC) gratings. Rigorous coupled-wave analysis shows temporally-coherent emission peaks associated with magnetic polariton (MP), whose resonance frequency can be dynamically tuned within the phonon absorption band of SiC by varying graphene chemical potential. An analytical inductor–capacitor circuit model is introduced to quantitatively predict the resonance frequency and further elucidate the mechanism for the tunable emission peak. The effects of grating geometric parameters, such as grating height, groove width and grating period, on the selective emission peak are explored. The direction-independent behavior of MP and associated coherent emission are also demonstrated. Moreover, by depositing four layers of graphene sheets onto the SiC gratings, a large tunability of 8.5% in peak frequency can be obtained to yield the coherent emission covering a broad frequency range from 820 to 890 cm −1 . The novel tunable metamaterial could pave the way to a new class of tunable thermal sources in the IR region. (paper)

  11. Radio frequency system of the RIKEN ring cyclotron

    International Nuclear Information System (INIS)

    Fujisawa, T.; Ogiwara, K.; Kohara, S.; Oikawa, Y.; Yokoyama, I.; Nagase, M.; Takeshita, I.; Chiba, Y.; Kumata, Y.

    1987-01-01

    The radio-frequency(RF) system of the RIKEN ring cyclotron(K = 540) is required to work in a frequency range of 20 to 45 MHz and to generate the maximum acceleration voltage 250 kV. A new movable box type variable frequency resonator was designed for that purpose. The final amplifier is capable to deliver 300 kW. The resonators and the amplifiers have been installed at RIKEN and the performances are studied. The result shows the movable box type resonator and the power amplifier system satisfy the design aim. (author)

  12. A Fixed-Frequency Bidirectional Resonant DC-DC Converter Suitable for Wide Voltage Gain Range

    DEFF Research Database (Denmark)

    Shen, Yanfeng; Wang, Huai; Blaabjerg, Frede

    2017-01-01

    This paper proposes a new bidirectional resonant dc-dc converter suitable for wide voltage gain range applications (e.g., energy storage systems). The proposed converter overcomes the narrow voltage gain range of conventional resonant DC-DC converters, and meanwhile achieves high efficiency...... and characteristics of the proposed converter are analyzed. Finally, a 1-kW converter prototype is built and the experimental results verify the theoretical analyses....

  13. Extending electronic length frequency analysis in R

    DEFF Research Database (Denmark)

    Taylor, M. H.; Mildenberger, Tobias K.

    2017-01-01

    VBGF (soVBGF) requires a more intensive search due to two additional parameters. This work describes the implementation of two optimisation approaches ("simulated annealing" and "genetic algorithm") for growth function fitting using the open-source software "R." Using a generated LFQ data set......Electronic length frequency analysis (ELEFAN) is a system of stock assessment methods using length-frequency (LFQ) data. One step is the estimation of growth from the progression of LFQ modes through time using the von Bertalanffy growth function (VBGF). The option to fit a seasonally oscillating...... of the asymptotic length parameter (L-infinity) are found to have significant effects on parameter estimation error. An outlook provides context as to the significance of the R-based implementation for further testing and development, as well as the general relevance of the method for data-limited stock assessment....

  14. Digital instantaneous frequency measurement technique utilising high-speed ADC’s and FPGA’s

    CSIR Research Space (South Africa)

    Herselman, PL

    2006-02-27

    Full Text Available This paper presents the Digital Instantaneous Frequency Measurement (DIFM) technique, which can measure the carrier frequency of a received waveform within a fraction of a microsecond. The resulting frequency range, resolution and accuracy...

  15. Bulk plasma rotation in the presence of waves in the ion cyclotron range of frequencies

    International Nuclear Information System (INIS)

    Eriksson, L.G.; Noterdaeme, J.M.; Kirov, K.

    2003-01-01

    Experiments with directed ICRF waves have for the first time in JET demonstrated the influence of absorbed wave momentum on bulk plasma rotation. Resonating fast ions acted as an intermediary in this process, and the experiments therefore provided evidence for the effect of fast ions on the plasma rotation. Results from these experiments are reviewed together with results from ICRF heated plasmas with symmetric spectra in JET and Tore Supra. The relevance of different theoretical models is briefly considered. (author)

  16. Combining agreement and frequency rating scales to optimize psychometrics in measuring behavioral health functioning.

    Science.gov (United States)

    Marfeo, Elizabeth E; Ni, Pengsheng; Chan, Leighton; Rasch, Elizabeth K; Jette, Alan M

    2014-07-01

    The goal of this article was to investigate optimal functioning of using frequency vs. agreement rating scales in two subdomains of the newly developed Work Disability Functional Assessment Battery: the Mood & Emotions and Behavioral Control scales. A psychometric study comparing rating scale performance embedded in a cross-sectional survey used for developing a new instrument to measure behavioral health functioning among adults applying for disability benefits in the United States was performed. Within the sample of 1,017 respondents, the range of response category endorsement was similar for both frequency and agreement item types for both scales. There were fewer missing values in the frequency items than the agreement items. Both frequency and agreement items showed acceptable reliability. The frequency items demonstrated optimal effectiveness around the mean ± 1-2 standard deviation score range; the agreement items performed better at the extreme score ranges. Findings suggest an optimal response format requires a mix of both agreement-based and frequency-based items. Frequency items perform better in the normal range of responses, capturing specific behaviors, reactions, or situations that may elicit a specific response. Agreement items do better for those whose scores are more extreme and capture subjective content related to general attitudes, behaviors, or feelings of work-related behavioral health functioning. Copyright © 2014 Elsevier Inc. All rights reserved.

  17. Equivalent distributed capacitance model of oxide traps on frequency dispersion of C – V curve for MOS capacitors

    International Nuclear Information System (INIS)

    Lu Han-Han; Xu Jing-Ping; Liu Lu; Lai Pui-To; Tang Wing-Man

    2016-01-01

    An equivalent distributed capacitance model is established by considering only the gate oxide-trap capacitance to explain the frequency dispersion in the C – V curve of MOS capacitors measured for a frequency range from 1 kHz to 1 MHz. The proposed model is based on the Fermi–Dirac statistics and the charging/discharging effects of the oxide traps induced by a small ac signal. The validity of the proposed model is confirmed by the good agreement between the simulated results and experimental data. Simulations indicate that the capacitance dispersion of an MOS capacitor under accumulation and near flatband is mainly caused by traps adjacent to the oxide/semiconductor interface, with negligible effects from the traps far from the interface, and the relevant distance from the interface at which the traps can still contribute to the gate capacitance is also discussed. In addition, by excluding the negligible effect of oxide-trap conductance, the model avoids the use of imaginary numbers and complex calculations, and thus is simple and intuitive. (paper)

  18. Membrane voltage fluctuations reduce spike frequency adaptation and preserve output gain in CA1 pyramidal neurons in a high conductance state

    Science.gov (United States)

    Fernandez, Fernando R.; Broicher, Tilman; Truong, Alan; White, John A.

    2011-01-01

    Modulating the gain of the input-output function of neurons is critical for processing of stimuli and network dynamics. Previous gain control mechanisms have suggested that voltage fluctuations play a key role in determining neuronal gain in vivo. Here we show that, under increased membrane conductance, voltage fluctuations restore Na+ current and reduce spike frequency adaptation in rat hippocampal CA1 pyramidal neurons in vitro. As a consequence, membrane voltage fluctuations produce a leftward shift in the f-I relationship without a change in gain, relative to an increase in conductance alone. Furthermore, we show that these changes have important implications for the integration of inhibitory inputs. Due to the ability to restore Na+ current, hyperpolarizing membrane voltage fluctuations mediated by GABAA-like inputs can increase firing rate in a high conductance state. Finally, our data show that the effects on gain and synaptic integration are mediated by voltage fluctuations within a physiologically relevant range of frequencies (10–40 Hz). PMID:21389243

  19. Multiple spatial frequency channels in human visual perceptual memory.

    Science.gov (United States)

    Nemes, V A; Whitaker, D; Heron, J; McKeefry, D J

    2011-12-08

    Current models of short-term visual perceptual memory invoke mechanisms that are closely allied to low-level perceptual discrimination mechanisms. The purpose of this study was to investigate the extent to which human visual perceptual memory for spatial frequency is based upon multiple, spatially tuned channels similar to those found in the earliest stages of visual processing. To this end we measured how performance on a delayed spatial frequency discrimination paradigm was affected by the introduction of interfering or 'memory masking' stimuli of variable spatial frequency during the delay period. Masking stimuli were shown to induce shifts in the points of subjective equality (PSE) when their spatial frequencies were within a bandwidth of 1.2 octaves of the reference spatial frequency. When mask spatial frequencies differed by more than this value, there was no change in the PSE from baseline levels. This selective pattern of masking was observed for different spatial frequencies and demonstrates the existence of multiple, spatially tuned mechanisms in visual perceptual memory. Memory masking effects were also found to occur for horizontal separations of up to 6 deg between the masking and test stimuli and lacked any orientation selectivity. These findings add further support to the view that low-level sensory processing mechanisms form the basis for the retention of spatial frequency information in perceptual memory. However, the broad range of transfer of memory masking effects across spatial location and other dimensions indicates more long range, long duration interactions between spatial frequency channels that are likely to rely contributions from neural processes located in higher visual areas. Copyright © 2011 Elsevier Ltd. All rights reserved.

  20. Frequency spectrum of Calder Hall reactor noise

    International Nuclear Information System (INIS)

    Cummins, J.D.

    1960-01-01

    The frequency spectrum of the noise power of Calder Hall reactor No. 1 has been obtained by analysing a tape recording of the backed off power. The root mean square noise power due to all frequencies above 0.001 cycles per second was found to be 0.13%. The noise power for this reactor, is due mainly to modulations of the power level by reactivity variations caused in turn by gas temperature changes. These gas temperature changes are caused by a Cyclic variation in the feedwater regulator to the heat exchanger. The apparatus and method used to determine the noise power are described in this memorandum. It is shown that for frequencies in the range 0.001 to 0.030 cycles per second the noise spectrum falls at 60 decibels per decade of frequency. (author)