Sample records for radio propagation characteristics

  1. Plasma plume propagation characteristics of pulsed radio frequency plasma jet

    SciTech Connect

    Liu, J. H.; Liu, X. Y.; Hu, K.; Liu, D. W.; Lu, X. P. [Advanced Electromagnetic Engineering and Technology Laboratory, Huazhong University of Science and Technology, WuHan, HuBei 430074 (China); Iza, F.; Kong, M. G. [Department of Electronic and Electrical Engineering, Loughborough University, Leicestershire LE11 3TU (United Kingdom)

    2011-04-11

    A 4 cm long helium cold atmospheric pressure plasma jet with pulsed radio frequency (rf) excitation was obtained by a copper electrode inside a quartz tube. The plasma bullet propagation characteristics common to the microseconds direct current pulse and kilohertz plasma jet is not observed in this case. The space-, time-, and wavelength-resolved optical emission profiles suggest the pulsed rf plasma channel out of the tube was strengthened by ions and metastables with longer life time than the rf period, and the plasma propagation was actually an illumination of the plasma channel caused by energetic electrons accelerated along the channel.

  2. A comparison of indoor radio propagation characteristics at 910 MHz and 1.75 GHz

    Microsoft Academic Search

    R. J. C. Bultitude; S. A. Mahmoud; W. A. Sullivan

    1989-01-01

    The results of temporally and spatially distributed wideband (impulse response) propagation experiments in the 900 MHz and 1.7 GHz radio frequency bands in two different buildings on fixed indoor radio links are reported. Results from the temporal experiments show that, for a specific location in either of the two buildings, the dynamics of indoor channels are slightly less random at

  3. Delay Doppler characteristics of multipath propagation at 910 MHz in a suburban mobile radio environment

    Microsoft Academic Search

    D. Cox

    1972-01-01

    Statistical descriptions of the time delays and Doppler shifts associated with multipath propagation in a suburban mobile radio environment obtained from bandpass impulse response measurements are presented. The measuring equipment which has0.1 mus resolution in time delay and a data output bandwidth of less than 5 kHz is also described. For the first time small scale statistics of the multipath

  4. Radio propagation by reflection from meteor trails

    Microsoft Academic Search

    G. R. Sugar

    1964-01-01

    This paper is a survey of those characteristics of meteors, and of meteor propagation, which are important to the understanding and use of meteor ionization insofar as it provides a means of radio transmission. The subjects discussed include the utility of meteor bursts for intermittent radio communication, physical properties of meteors and meteor trails, reflection properties of individual trails, short-term

  5. The indoor radio propagation channel

    Microsoft Academic Search

    HOMAYOUN HASHEMI

    1993-01-01

    In this tutorial survey the principles of radio propagation in indoor environments are reviewed. The channel is modeled as a linear time-varying filter at each location in the three-dimensional space, and the properties of the filter's impulse response are described. Theoretical distributions of the sequences of arrival times, amplitudes and phases are presented. Other relevant concepts such as spatial and

  6. Radio wave propagation and acoustic sounding

    NASA Astrophysics Data System (ADS)

    Singal, S. P.

    Radio wave propagation of the decimetric and centimetric waves depends to a large extent on the boundary layer meteorological conditions which give rise to severe fadings, very often due to multipath propagation. Sodar is one of the inexpensive remote sensing techniques which can be employed to probe the boundary layer structure. In the paper a historical perspective has been given of the simultaneously conducted studies on radio waves and sodar at various places. The radio meteorological information needed for propagation studies has been clearly spelt out and conditions of a ray path especially in the presence of a ducting layer have been defined as giving rise to fading or signal enhancement conditions. Finally the potential of the sodar studies to obtain information about the boundary layer phenomena has been stressed, clearly spelling out the use of acoustic sounding in radio wave propagation studies.

  7. Antenna Construction and Propagation of Radio Waves.

    ERIC Educational Resources Information Center

    Marine Corps Inst., Washington, DC.

    Developed as part of the Marine Corps Institute (MCI) correspondence training program, this course on antenna construction and propagation of radio waves is designed to provide communicators with instructions in the selection and/or construction of the proper antenna(s) for use with current field radio equipment. Introductory materials include…

  8. Effects of Multipath Propagation on Digital Radio

    Microsoft Academic Search

    ADOLF J. GIGER; WILLIAM T. BARNETT

    1981-01-01

    This paper summarizes experimental work at Bell Laboratories in the field of multipath propagation as it affects digital radio. Field and laboratory measurements are presented on commercial-quality high-speed digital radio systems working in the 4, 6, and 11 GHz common carrier bands. Circuits and equipment used in these systems are all state of the art, but no attempt has been

  9. Wave propagation and earth satellite radio emission studies

    NASA Technical Reports Server (NTRS)

    Yeh, K. C.; Liu, C. H.; Flaherty, B. J.

    1974-01-01

    Radio propagation studies of the ionosphere using satellite radio beacons are described. The ionosphere is known as a dispersive, inhomogeneous, irregular and sometimes even nonlinear medium. After traversing through the ionosphere the radio signal bears signatures of these characteristics. A study of these signatures will be helpful in two areas: (1) It will assist in learning the behavior of the medium, in this case the ionosphere. (2) It will provide information of the kind of signal characteristics and statistics to be expected for communication and navigational satellite systems that use the similar geometry.

  10. Coherence bandwidth loss in transionospheric radio propagation

    Microsoft Academic Search

    C. L. Rino; V. H. Gonzalez; A. R. Hessing

    1981-01-01

    In this paper a theoretical model that predicts the single-point, two-frequency coherence function for transionospheric radio waves is developed. By using an asymptotic approximation a single parameter was isolated, which gives the functional dependence on perturbation strength, propagation distance, and fractional frequency separation. The model is compared to the measured complex frequency correlation function by using data from the seven

  11. The dependence of single room indoor radio propagation on frequency

    Microsoft Academic Search

    Qin Zhou; A. K. Y. Lai

    1996-01-01

    This work focuses on the dependence of indoor radio propagation on frequency. Indoor radio propagation measurements in terms of different frequencies and positions in a single room environment were performed. A calibration technique is developed to reduce the effect contributed by the transmitting and receiving antennas. Statistical analysis of the indoor radio propagation data are reported. Fast fading was found

  12. Subionospheric VLF/LF radio waves propagation characteristics before, during and after the Sofia, Bulgaria Mw=5.6 earthquake occurred on 22 May 2012

    NASA Astrophysics Data System (ADS)

    Moldovan, Iren Adelina; Emilian Toader, Victorin; Nenovski, Petko; Biagi, Pier Francesco; Maggipinto, Tommaso; Septimiu Moldovan, Adrian; Ionescu, Constantin

    2013-04-01

    In 2009, INFREP, a network of VLF (20-60 kHz) and LF (150-300 kHz) radio receivers, was put into operation in Europe having as principal goal, the study of disturbances produced by the earthquakes on the propagation properties of these signals. On May 22nd, 2012 an earthquake with Mw=567 occurred in Bulgaria, near Sofia, inside the "sensitive" area of the INFREP VLF/LF electromagnetic network. The data collected on different frequencies, during April-May 2012 were studied using different methods of analysis: daily correlation methods, spectral approaches and terminator time techniques, in order to find out possible connections between the seismic activity and the subionospheric propagation properties of radio waves. The studies were performed with the help of a specially designed LabVIEW application, which accesses the VLF/LF receiver through internet. This program opens the receiver's web-page and automatically retrieves the list of data files to synchronize the user-side data with the receiver's data. Missing zipped files are also automatically downloaded. The application performs primary, statistical correlation and spectral analysis, appends daily files into monthly and annual files and performs 3D colour-coded maps with graphic representations of VLF and LF signals' intensities versus the minute-of-the-day and the day-of-the-month, facilitating a near real-time observation of VLF and LF electromagnetic waves' propagation. Another feature of the software is the correlation of the daily recorded files for the studied frequencies by overlaying the 24 hours radio activity and taking into account the sunrise and sunset. Data are individually processed (spectral power, correlations, differentiation, filtered using bandpass, lowpass, highpass). JTFA spectrograms (Cone-Shaped Distribution CSD, Gabor, Wavelet, short-time Fourier transform STFT, Wigner-Ville Distribution WVD, Choi-Williams Distribution CWD) are used, too.

  13. Indoor propagation characteristics in DECT band

    Microsoft Academic Search

    F. Babich; G. Lombardi; E. Valentinuzzi

    1996-01-01

    The development of personal communications systems (PCS) is a source of investigation in several fields. The aim is to guarantee a good quality connection service between users, independently from the surrounding environment and from the fact that they are fixed or mobile. Broadband measurements of indoor radio propagation channel have been performed in the office part of a factory in

  14. Radio-wave propagation for space communications systems

    NASA Technical Reports Server (NTRS)

    Ippolito, L. J.

    1981-01-01

    The most recent information on the effects of Earth's atmosphere on space communications systems is reviewed. The design and reliable operation of satellite systems that provide the many applications in space which rely on the transmission of radio waves for communications and scientific purposes are dependent on the propagation characteristics of the transmission path. The presence of atmospheric gases, clouds, fog, precipitation, and turbulence causes uncontrolled variations in the signal characteristics. These variations can result in a reduction of the quality and reliability of the transmitted information. Models and other techniques are used in the prediction of atmospheric effects as influenced by frequency, geography, elevation angle, and type of transmission. Recent data on performance characteristics obtained from direct measurements on satellite links operating to above 30 GHz have been reviewed. Particular emphasis has been placed on the effects of precipitation on the Earth/space path, including rain attenuation, and ice particle depolarization. Other factors are sky noise, antenna gain degradation, scintillations, and bandwidth coherence. Each of the various propagation factors has an effect on design criteria for communications systems. These criteria include link reliability, power margins, noise contribution, modulation and polarization factors, channel cross talk, error rate, and bandwidth limitations.

  15. Realistic radio propagation models (RPMs) for VANET simulations

    Microsoft Academic Search

    Francisco J. Martinez; Chai-Keong Toh; Juan-Carlos Cano; Carlos Miguel Tavares Calafate; Pietro Manzoni

    2009-01-01

    Deploying and testing vehicular ad hoc networks (VANETs) involves high cost and intensive labor. Hence simulation is a useful alternative prior to actual implementation. Most works found in the literature employ very simplistic radio propagation models (RPMs), ignoring the dramatic effects presented by buildings on radio signals. In this paper, we present three different RPMs that increase the level of

  16. The prediction of radio-path characteristics

    NASA Astrophysics Data System (ADS)

    Gitina, G. M.; Kalinin, Iu. K.

    The paper examines algorithms for the long-term prediction of radio-path characteristics in the ionosphere, the main characteristic being the MUF at a given distance. The proposed approach is based on long-term memories called DATA BANKS. Attention is given to the characteritics of the various banks, including the BANK OF CITIES, the BANK OF RADIO PATHS, the REFERENCE DATA BANK, and the OUTPUT DATA BANK.

  17. Transpolar Propagation of Long Radio Waves

    Microsoft Academic Search

    E. C. Field; C. Greifinger; K. Schwartz

    1972-01-01

    This report presents the results of a theoretical analysis and a laboratory simulation of certain transpolar VLF\\/ELF propagation phenomena. The calculations are based on daytime ionospheric models representative of ambient conditions and of conditions that prevail during polar-cap absorption (PCA) events. The laboratory simulation utilized a wave guide that models VLF propagation in the earth-ionosphere cavity. The influence of the

  18. Impulse Response Modeling of Indoor Radio Propagation Channels

    Microsoft Academic Search

    Homayoun Hashemi

    1993-01-01

    If indoor radio propagation channels are modeled as linear filters, they can be characterized by reporting the parameters of their equivalent impulse response functions. The measurement and modeling of estimates for such functions in two different office buildings are reported. The resulting data base consists of 12000 impulse response estimates of the channel that were obtained by inverse Fourier transforming

  19. ITS Wireless Transmission Technology. Technologies of Millimeter-Wave Inter-Vehicle Communications: Propagation Characteristics

    NASA Astrophysics Data System (ADS)

    Kato, Akihito; Sato, Katsuyoshi; Fujise, Masayuki

    2001-12-01

    In this paper, we introduce developed technologies for millimeter-wave inter-vehicle communication (IVC) system in intelligent transport systems (ITS), especially propagation characteristics of 60 GHz band for the system design of IVC. First we introduce the outline of an IVC system using millimeter wave and its research subjects. Next we show experimental results of propagation characteristics of radio wave at 60 GHz between running vehicles. The propagation model and mechanism of fading propagation are argued. The joint research activity of IVC system in Yokosuka Research Park (YRP) is also introduced.

  20. Plasma and radio waves from Neptune: Source mechanisms and propagation

    NASA Technical Reports Server (NTRS)

    Wong, H. K.

    1994-01-01

    This report summarizes results obtained through the support of NASA Grant NAGW-2412. The objective of this project is to conduct a comprehensive investigation of the radio wave emission observed by the planetary radio astronomy (PRA) instrument on board Voyager 2 as if flew by Neptune. This study has included data analysis, theoretical and numerical calculations, ray tracing, and modeling to determine the possible source mechanism(s) and locations of the Neptune radio emissions. We have completed four papers, which are included in the appendix. The paper 'Modeling of Whistler Ray Paths in the Magnetosphere of Neptune' investigated the propagation and dispersion of lighting-generated whistler in the magnetosphere of Neptune by using three dimensional ray tracing. The two papers 'Numerical Simulations of Bursty Radio Emissions from Planetary Magnetospheres' and 'Numerical Simulations of Bursty Planetary Radio Emissions' employed numerical simulations to investigate an alternate source mechanism of bursty radio emissions in addition to the cyclotron maser instability. We have also studied the possible generation of Z and whistler mode waves by the temperature anisotropic beam instability and the result was published in 'Electron Cyclotron Wave Generation by Relativistic Electrons.' Besides the aforementioned studies, we have also collaborated with members of the PRA team to investigate various aspects of the radio wave data. Two papers have been submitted for publication and the abstracts of these papers are also listed in the appendix.

  1. UWB Radio Propagation Inside Vehicle Environments

    Microsoft Academic Search

    T. Tsuboi; J. Yamada; N. Yamauchi

    2007-01-01

    This is the first study for inside vehicle wireless communication system design with UWB technology under WiMedia standard. At first, MATLAB simulator has been developed then calculated BER in AWGR channel model. And it is confirmed adequacy of channel model compared with IEEE simulation model. And wireless transmission characteristics are measured with the following? conditions such as receiver on top

  2. Coherence bandwidth loss in transionospheric radio propagation

    NASA Technical Reports Server (NTRS)

    Rino, C. L.; Gonzalez, V. H.; Hessing, A. R.

    1980-01-01

    In this report a theoretical model is developed that predicts the single-point, two-frequency coherence function for transionospheric radio waves. The theoretical model is compared to measured complex frequency correlation coefficients using data from the seven equispaced, phase-coherent UHF signals transmitted by the Wideband satellite. The theory and data are in excellent agreement. The theory is critically dependent upon the power-law index, and the frequency coherence data clearly favor the comparatively small spectral indices that have been consistently measured from the wideband satellite phase data. A model for estimating the pulse delay jitter induced by the coherence bandwidth loss is also developed and compared with the actual delay jitter observed on synthesized pulses obtained from the Wideband UFH comb. The results are in good agreement with the theory. The results presented in this report, which are based on an asymptotic theory, are compared with the more commonly used quadratic theory. The model developed and validated in this report can be used to predict the effects of coherence bandwidth loss in disturbed nuclear environments. Simple formulas for the resultant pulse delay jitter are derived that can be used in predictive codes.

  3. Radio Wave Propagation Handbook for Communication on and Around Mars

    NASA Technical Reports Server (NTRS)

    Ho, Christian; Golshan, Nasser; Kliore, Arvydas

    2002-01-01

    This handbook examines the effects of the Martian environment on radio wave propagation on Mars and in the space near the planet. The environmental effects include these from the Martian atmosphere, ionosphere, global dust storms, aerosols, clouds, and geomorphologic features. Relevant Martian environmental parameters were extracted from the measurements of Mars missions during the past 30 years, especially from Mars Pathfinder and Mars Global Surveyor. The results derived from measurements and analyses have been reviewed through an extensive literature search. The updated parameters have been theoretically analyzed to study their effects on radio propagation. This handbook also provides basic information about the entire telecommunications environment on and around Mars for propagation researchers, system engineers, and link analysts. Based on these original analyses, some important recommendations have been made, including the use of the Martian ionosphere as a reflector for Mars global or trans-horizon communication between future Martian colonies, reducing dust storm scattering effects, etc. These results have extended our wave propagation knowledge to a planet other than Earth; and the tables, models, and graphics included in this handbook will benefit telecommunication system engineers and scientific researchers.

  4. Radio Propagation Measurements Before, During, and After the Collapse of Three Large Building Structures

    Microsoft Academic Search

    Christopher L. Holloway; Galen Koepke; Dennis Camell; Kate A. Remley

    NIST is investigating various schemes for detecting emergency responders and civilians with portable radios or cell phones who may be trapped in voids in a collapsed or partially collapsed building. The first part of this effort is to understand radio propagation in collapsed structures. Buildings scheduled for implosion provide the ideal research environment for investigating radio-wave propagation issues in fully

  5. Fade durations in satellite-path mobile radio propagation

    NASA Astrophysics Data System (ADS)

    Schmier, Robert G.; Bostian, Charles W.

    1986-12-01

    Fades on satellite to land mobile radio links are caused by several factors, the most important of which are multipath propagation and vegetative shadowing. Designers of vehicular satellite communications systems require information about the statistics of fade durations in order to overcome or compensate for the fades. Except for a few limiting cases, only the mean fade duration can be determined analytically, and all other statistics must be obtained experimentally or via simulation. This report describes and presents results from a computer program developed at Virginia Tech to simulate satellite path propagation of a mobile station in a rural area. It generates rapidly-fading and slowly-fading signals by separate processes that yield correct cumulative signal distributions and then combines these to simulate the overall signal. This is then analyzed to yield the statistics of fade duration.

  6. Fade durations in satellite-path mobile radio propagation

    NASA Technical Reports Server (NTRS)

    Schmier, Robert G.; Bostian, Charles W.

    1986-01-01

    Fades on satellite to land mobile radio links are caused by several factors, the most important of which are multipath propagation and vegetative shadowing. Designers of vehicular satellite communications systems require information about the statistics of fade durations in order to overcome or compensate for the fades. Except for a few limiting cases, only the mean fade duration can be determined analytically, and all other statistics must be obtained experimentally or via simulation. This report describes and presents results from a computer program developed at Virginia Tech to simulate satellite path propagation of a mobile station in a rural area. It generates rapidly-fading and slowly-fading signals by separate processes that yield correct cumulative signal distributions and then combines these to simulate the overall signal. This is then analyzed to yield the statistics of fade duration.

  7. A SOFTWARE-DEFINED RADIO IONOSPHERIC CHIRPSOUNDER FOR HF PROPAGATION ANALYSIS

    E-print Network

    Melodia, Tommaso

    A SOFTWARE-DEFINED RADIO IONOSPHERIC CHIRPSOUNDER FOR HF PROPAGATION ANALYSIS Pradeep B. Nagaraju the flexibility of state-of-the art digital radio platforms. However, the advent of Software Defined Radio (SDR. In this paper, we report on our development of a prototype Software Defined Radio (SDR) chirpsounder system

  8. SPATIAL STABILITY IN INDOOR RADIO PROPAGATION CHANNELS Dana Porrat, Eli Kaminsky and Moshe Uziel

    E-print Network

    Porrat, Dana

    SPATIAL STABILITY IN INDOOR RADIO PROPAGATION CHANNELS Dana Porrat, Eli Kaminsky and Moshe Uziel.porrat@huji.ac.il, eli.kaminsky@mail.huji.ac.il, uzikiko@gmail.com ABSTRACT Indoor radio channel responses are composed

  9. The induced turbulence effect on propagation of radio emission in pulsar magnetospheres

    Microsoft Academic Search

    Qinghuan Luo; D. B. Melrose

    2006-01-01

    The effect of photon-beam-induced turbulence on the propagation of radio emission in a pulsar magnetosphere is discussed. Beamed radio emission with a high brightness temperature can generate low-frequency plasma waves in the pulsar magnetosphere, and these waves scatter the radio beam. We consider this effect on the propagation of radio emission both in the open field line region and in

  10. Annual report 1992/93, FOA 38. Radio systems and wave propagation

    NASA Astrophysics Data System (ADS)

    Mildh, I. M.

    1994-01-01

    The main objective of the division of Radio Systems and Wave Propagation is to carry out research and development in the field of secure and robust radio communications for Sweden's national defense. This is the Annual Report for fiscal year 1992/93 of the Division of Radio Systems and Wave Propagation. The division is responsible for research and development of secure radio communication for information transmission. We are also responsible for wave propagation research within a frequency range from LF to SHF. We carry out applied research in fields like antijamming systems, modulation, error correcting codes, wave propagation and digital signal processing. The wave propagation research is carried out by basic research so the demands from new techniques and new radio systems for accurate propagation models can be achieved.

  11. Multiple Knife-Edge Diffraction and Radio Propagation in Urban Environments

    NASA Astrophysics Data System (ADS)

    Xia, Howard Hao

    1991-05-01

    This dissertation examines multiple knife-edge diffraction problems, and their applications in radio propagation prediction in urban environments and scattering by the open-end of a parallel plate waveguide. It is argued that when computing the average received signal, scattering by buildings can be modeled as a multiple forward diffraction process past a series of absorbing screens. Therefore, we can separate the total path loss for radio signals traveling from an elevated base station antenna to a mobile at street level into the following components: (1) free space propagation; (2) multiple knife-edge diffraction due to intervening buildings, and; (3) the diffraction loss when the field travels from the rooftop of the buildings adjacent to the mobile to street level. Using the settling behavior for a plane wave incident from above the array of absorbing screens, multiple diffraction past intervening buildings can be accounted for. A theoretical model is thus developed for urban propagation, and major propagation characteristics, such as distance dependence, base station antenna height gain, mobile antenna height gain, frequency dependence, and suburban and open area correction factors, are discussed. These characteristics have a complex dependence on the environments through many parameters, such as street width, base station antenna height, distance from the transmitter to the receiver and frequency. Experimental results have been obtained in different cities, for different frequencies and with different setups, but have not previously been related through a common model. It is shown here that the multiple knife-edge diffraction process depends on the frequency, street width and the incident angle through a single characteristic parameter that can be used to relate all the experimental measurements to each other, and to compare them with the theoretical predictions.

  12. Radio-propagation model based on the combined method of ray tracing and diffraction

    Microsoft Academic Search

    Xiaoyang Huang; Bingquan Chen; Hong-Liang Cui; Jakob J. Stamnes; Robert Pastore; Mark Farwell; Wilbur Chin; Jennifer Ross

    2006-01-01

    In this paper, we consider UHF radio wave propagation in vegetated residential environments. The attenuating effects of trees as well as those due to diffraction over the buildings are investigated. A new radio wave propagation prediction model based on the combined method of ray tracing and diffraction (CMRTD) is proposed. A row of trees is modeled as a two-dimensional (2-D)

  13. The History of Radio Wave Propagation up to the End of World War I

    Microsoft Academic Search

    Charles Burrows

    1962-01-01

    Hertz in the 1880's demonstrated electromagnetic wave propagation predicted by Maxwell from his equations in 1864. Heaviside and Kennelly postulated the ionosphere to explain Marconi's historical transatlantic reception of radio waves in 1901. Austin derived the first formula for radio propagation in 1911 from experimental data in the kilometer wavelength range taken in the daytime. Much theoretical effort was expended

  14. Propagation Characteristics of International Space Station Wireless Local Area Network

    NASA Technical Reports Server (NTRS)

    Sham, Catherine C.; Hwn, Shian U.; Loh, Yin-Chung

    2005-01-01

    This paper describes the application of the Uniform Geometrical Theory of Diffraction (UTD) for Space Station Wireless Local Area Networks (WLANs) indoor propagation characteristics analysis. The verification results indicate good correlation between UTD computed and measured signal strength. It is observed that the propagation characteristics are quite different in the Space Station modules as compared with those in the typical indoor WLANs environment, such as an office building. The existing indoor propagation models are not readily applicable to the Space Station module environment. The Space Station modules can be regarded as oversized imperfect waveguides. Two distinct propagation regions separated by a breakpoint exist. The propagation exhibits the guided wave characteristics. The propagation loss in the Space Station, thus, is much smaller than that in the typical office building. The path loss model developed in this paper is applicable for Space Station WLAN RF coverage and link performance analysis.

  15. Influence of ionospheric irregularities on decameter radio wave propagation: Mathematic modeling

    SciTech Connect

    Ivanov, V.B.

    1995-05-01

    Based on numerical simulation and using the Monte Carlo method, an investigation is carried out of the influence of random irregularities in the ionospheric F-region on short-wave propagation along one-hop radio paths.

  16. Extremely Low Frequency (ELF) Ionospheric Radio Propagation Studies Using Natural Sources

    Microsoft Academic Search

    D. LLANWYN JONES

    1974-01-01

    The purpose of this paper is to describe methods of studying the propagation of radio waves over the earth's surface in the extremely low frequency (ELF) frequency band (3 Hz-3 kHz) using natural (as distinct from \\

  17. Long time scale evolution of high-power radio wave ionospheric heating 1. Beam propagation

    Microsoft Academic Search

    M. J. Keskinen; P. K. Chaturvedi; S. L. Ossakow

    1993-01-01

    The long time scale evolution, that is, for times long compared to an electron collision period of high-power radio wave ionospheric heating, is studied. Preliminary studies are made to model high-power radio wave propagation in an ionosphere containing a dynamically produced electron density cavity. We show that high-power radio wave-induced plasma density depletions in the F region ionosphere will convect

  18. Long time scale evolution of high-power radio wave ionospheric heating. 1. Beam propagation

    Microsoft Academic Search

    M. J. Keskinen; P. K. Chaturvedi; S. L. Ossakow

    1993-01-01

    The long time scale evolution, that is, for times long compared to an electron collision period of high-power radio wave ionospheric heating, is studied. Preliminary studies are made to model high-power radio wave propagation in an ionosphere containing a dynamically produced electron density cavity. We show that high-power radio wave-induced plasma density depletions in the F region ionosphere will convect

  19. Empirical formula for propagation loss in land mobile radio services

    Microsoft Academic Search

    M. Hata

    1980-01-01

    An empirical formula for propagation loss is derived from Okumura's report in order to put his propagation prediction method to computational use. The propagation loss in an urban area is presented in a simple form: A + B log10R, where A and B are frequency and antenna height functions and R is the distance. The introduced formula is applicable to

  20. Investigation of PD pulse propagation characteristics in GIS

    Microsoft Academic Search

    K. Mizuno; A. Ogawa; K. Nojima; H. Murase; H. Koyama; S. Wakabayashi; T. Sakakibara

    1996-01-01

    Concentrating on the TEM mode, damping characteristics of partial discharge (PD) pulses propagating through each GIS (gas insulated substation) component were investigated, as a result, it was discovered that frequency components above 500 MHz were damped by spacers, T-shape branches, and L-bends. Quantitative studies were undertaken on the frequency dependency of this damping characteristics. Then the equivalent circuits for analyzing

  1. COMPARING FRACTURE PROPAGATION TESTS AND RELATING TEST RESULTS TO SNOWPACK CHARACTERISTICS

    E-print Network

    Jamieson, Bruce

    COMPARING FRACTURE PROPAGATION TESTS AND RELATING TEST RESULTS TO SNOWPACK CHARACTERISTICS Cameron for a slab and weak layer combination to propagate a fracture. University of Calgary researchers performed propensity. KEYWORDS: fracture propagation, snowpack stability test, extended column test, propagation saw

  2. Characteristics of Electromagnetic Pulse Propagation in Metal

    NASA Technical Reports Server (NTRS)

    Namkung, M.; Wincheski, B.; Nath, S.; Fulton, J. P.

    2004-01-01

    It is well known that the solution of the diffusion equation for an electromagnetic field with a time harmonic term, e(sup iwt), is in the form of a traveling wave whose amplitude attenuates over distance into a conducting medium. As the attenuation is an increasing function of frequency, the high frequency components attenuate more rapidly than those of low ones upon entering a well conducting object. At the same time, the phase velocity of an individual component is also an increasing function of frequency causing a broadening of the pulse traveling inside a conductor. In the results of our previous study of numerical simulations, the problem of using a gaussian input pulse was immediately clear. First, having the dominant frequency components distributed around zero, the movement of the peak was not well defined. Second, with the amplitude of fourier components varying slowly over a wide range, the dispersion-induced blurring of the peak position was seen to be severe. For the present study, we have used a gaussian modulated single frequency sinusoidal wave, i. e., the carrier, as an input pulse in an effort to improve the issues related to the unclear movement of peak and dispersion as described above. This was based on the following two anticipated advantages: First, the packet moves in a conductor at the group velocity calculated at the carrier frequency, which means it is well controllable. Second, the amplitude of frequency components other than that of the carrier can be almost negligible, such that the effect of dispersion can be significantly reduced. A series of experiments of transmitting electromagnetic pulses through aluminum plates of various thickness was performed to test the validity of the above points. The results of numerical simulation based on wave propagation are discussed with respect to the experimental results. Finally, a simple simulation was performed based on diffusion of a continuous sine wave input and the results are compared with those of a single frequency sinusoidal wave observed over time at difference locations inside a conductor.

  3. Morphology of solar wind fluctuations and structure in the vicinity of the Sun from radio propagation measurements

    NASA Technical Reports Server (NTRS)

    Woo, R.

    1995-01-01

    Radio propagation measurements represent a powerful means for remote probing of electron density and solar wind speed in the acceleration region of the solar wind not yet explored by in situ measurements. Recent investigations based on radio propagation measurements have led to considerable progress in our knowledge of the general morphology of solar wind fluctuations and structure, especially in terms of their relationship to solar wind properties that have been observed directly by fields and particles measurements, and to coronal features observed in white-light measurements. The purpose of this paper is to present an overview of the latest results on quasi-stationary structure covering the large scale variation of solar wind speed over the streamer belt and coronal hole regions, coronal streamers (source of slow solar wind) and their associated small-scale electron density structure, plumes, density and fractional or relative density fluctuations, and the spectral characteristics of the electron density fluctuations. The radio propagation measurements not only reveal new information on the structure near the Sun, but also show that the structure appears to undergo substantial evolution on its way to 0.3 AU, the closest radial distance for which direct in situ spacecraft measurements are available.

  4. Remote sensing of the turbulence characteristics of a planetary atmosphere by radio occultation of a space probe.

    NASA Technical Reports Server (NTRS)

    Woo, R.; Ishimaru, A.

    1973-01-01

    The purpose of this paper is to analyze the effects of small-scale turbulence on radio waves propagating through a planetary atmosphere. The analysis provides a technique for inferring the turbulence characteristics of a planetary atmosphere from the radio signals received from a spacecraft as it is occulted by the planet. The planetary turbulence is assumed to be localized and smoothly varying, with the structure constant varying exponentially with altitude. Rytov's method is used to derive the variance of log-amplitude and phase fluctuations of a wave propagating through the atmosphere.

  5. MF and HF propagation characteristics of ionospheric ducts

    NASA Astrophysics Data System (ADS)

    Platt, I. G.; Dyson, P. L.

    1989-10-01

    The propagation of MF and HF radio waves along ionospheric ducts is studied in detail by developing a waveguide model of the ducts and determining power levels of ducted echoes. Distributions of returned echo power have been calculated for ducts with various cross-sections and different depletions in electron density. It is found that field aligned ducts with diameters of the order of several kilometers behave as effective waveguides for both direct and conjugate ducting modes. However, the percentage depletion required for guiding is higher than previous calculations using simplified theory. For direct ducting, there is a clear relationship between the total integrated power across a duct and the electron density gradient and propagation frequency.

  6. Long-Range Transhorizon Lunar Surface Radio Wave Propagation in the Presence of a Regolith and a Sparse Exospheric Plasma

    NASA Technical Reports Server (NTRS)

    Manning, Robert M.

    2008-01-01

    Long-range, over-the-horizon (transhorizon) radio wave propagation is considered for the case of the Moon. In the event that relay satellites are not available or otherwise unwarranted for use, transhorizon communication provides for a contingency or backup option for non line-of-sight lunar surface exploration scenarios. Two potential low-frequency propagation mechanisms characteristic of the lunar landscape are the lunar regolith and the photoelectron induced plasma exosphere enveloping the Moon. Although it was hoped that the regolith would provide for a spherical waveguide which could support a trapped surface wave phenomena, it is found that, in most cases, the regolith is deleterious to long range radio wave propagation. However, the presence of the plasma of the lunar exosphere supports wave propagation and, in fact, surpasses the attenuation of the regolith. Given the models of the regolith and exosphere adopted here, it is recommended that a frequency of 1 MHz be considered for low rate data transmission along the lunar surface. It is also recommended that further research be done to capture the descriptive physics of the regolith and the exospheric plasma so that a more complete model can be obtained. This comprehensive theoretical study is based entirely on first principles and the mathematical techniques needed are developed as required; it is self-contained and should not require the use of outside resources for its understanding.

  7. An Enhanced AODV Protocol for VANETs with Realistic Radio Propagation Model Validation

    E-print Network

    Paris-Sud XI, Université de

    An Enhanced AODV Protocol for VANETs with Realistic Radio Propagation Model Validation Jonathan for Vehicular Ad-hoc NETworks (VANETs). V-AODV is designed to run with a complex cross layered metric based for VANETs simulations. We also show that when using a routing metric based on delay and BER, the first

  8. Isotropic approximation errors in geometrical-optical description of ionospheric propagation of radio waves

    NASA Astrophysics Data System (ADS)

    Laryunin, O. A.; Kurkin, V. I.

    2014-11-01

    Isotropic approximation, i.e. neglect of magnetic field effects, is widely used to simplify the geometrical optics description of ionospheric propagation of radio waves. However, this description under certain conditions may produce a significant error. In this study, ray traycing is performed to examine an isotropic approximation error in relation to operating frequency and radiation angles.

  9. SUBMITTED TO IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION. c 2012 IEEE. 1 The LWA1 Radio Telescope

    E-print Network

    Ellingson, Steven W.

    SUBMITTED TO IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION. c 2012 IEEE. 1 The LWA1 Radio Telescope, F.K. Schinzel and K.W. Weiler Abstract-- LWA1 is a new radio telescope operating in the frequency Observatories" program. Contemporary radio telescopes which are also capable of operating in LWA1's 10­88 MHz

  10. Radio wave propagation experiments to probe the ionosphere

    NASA Technical Reports Server (NTRS)

    Schmid, P. E.

    1972-01-01

    Ionospheric bias corrections associated with radio tracking of spacecraft depend on the following measuring techniques for integrated electron content: (1) Faraday rotation measurements from an earth synchronous satellite; (2) ranging measurements at two frequencies; and (3) group and phase velocity measurements obtained from tracking data. The extraction of the integrated electron content directly from tracking data is achieved by comparison of range-rate measurements based on Doppler shift with differentiated range measurements based on tone delay. This method is most desirable because the measured corrections pertain directly to the spacecraft whose orbit is being determined and can be used in near earth as well as deep space tracking data.

  11. Spacecraft VHF Radio Propagation Analysis in Ocean Environments Including Atmospheric Effects

    NASA Technical Reports Server (NTRS)

    Hwu, Shian; Moreno, Gerardo; Desilva, Kanishka; Jih, CIndy

    2010-01-01

    The Communication Systems Simulation Laboratory (CSSL) at the National Aeronautics and Space Administration (NASA)/Johnson Space Center (JSC) is tasked to perform spacecraft and ground network communication system simulations. The CSSL has developed simulation tools that model spacecraft communication systems and the space/ground environment in which they operate. This paper is to analyze a spacecraft's very high frequency (VHF) radio signal propagation and the impact to performance when landing in an ocean. Very little research work has been done for VHF radio systems in a maritime environment. Rigorous Radio Frequency (RF) modeling/simulation techniques were employed for various environmental effects. The simulation results illustrate the significance of the environmental effects on the VHF radio system performance.

  12. The magnetoionic modes and propagation properties of auroral radio emissions

    NASA Technical Reports Server (NTRS)

    Calvert, Wynne; Hashimoto, Kozo

    1990-01-01

    The nature of the magnetoionic wave modes which accompany the aurora is clarified here by a detailed analysis, using multiple techniques, of DE 1 auroral radio observations. All four of the possible magnetoionic wave modes are found to occur, apparently emitted from two different source regions on the same auroral field line. AKR originates primarily in the X mode near the electron cyclotron frequency, and is frequently also accompanied by a weaker O-mode component from the same location. The next most prominent auroral emission is the W-mode auroral hiss originating from altitudes always well below the DE 1 satellite at frequencies below the local cyclotron frequency. The previously reported Z-mode auroral radiation was also detected, but from sources also below the satellite at the poleward edge of the cavity, and not from the expected AKR source at the cyclotron frequency.

  13. Computational strategy for modeling radio wave propagation in lossy circular waveguides

    SciTech Connect

    Moses, Ronald [Los Alamos National Laboratory; Cai, D Michael [Los Alamos National Laboratory

    2008-01-01

    The propagation of radio waves in lossy waveguides and tunnels has been researched extensively for many years as can be seen in the detailed book by Wait. The mathematics used to model waveguides for communications is essentially the same as that needed to model radio frequency (RF) propagation in simple tunnels. The presence or lack of conductors inside a waveguide or tunnel is a key driver in the nature of the solutions one will find for a particular application, Delogne. When there are conductors passing through a waveguide or tunnel, the simplest modes of propagation are surface-guided waves following the conductor and typically enabling long-range transmission. A tunnel containing a core conductor can act rather like a coaxial cable, propagating waves at a nearly constant speed, regardless of frequency. Conversely, a tunnel or waveguide without internal conductors is subject to very different wave patterns, resulting in a much more complex propagation analysis. Holloway et al. presented an exhaustive study of RF propagation in circular structures embedded in lossy surroundings. The work of Holloway et al. is the basis for this paper, where we discuss application of their computational techniques and present refinements gleaned from our work on similar problems.

  14. Global ionospheric effects of geomagnetic storm on May 2-3, 2010 and their influence on HF radio wave propagation

    NASA Astrophysics Data System (ADS)

    Kotova, Daria; Klimenko, Maxim; Klimenko, Vladimir; Zakharov, Veniamin

    2013-04-01

    In this work we have investigated the global ionospheric response to geomagnetic storm on May 2-3, 2010 using GSM TIP (Global Self-consistent Model of the Thermosphere, Ionosphere and Protonosphere) simulation results. In the GSM TIP storm time model runs, several input parameters such as cross-polar cap potential difference and R2 FAC (Region 2 Field-Aligned Currents) varied as a function of the geomagnetic activity AE-index. Current simulation also uses the empirical model of high-energy particle precipitation by Zhang and Paxton. In this model, the energy and energy flux of precipitating electrons depend on a 3 hour Kp-index. We also have included the 30 min time delay of R2 FAC variations with respect to the variations of cross-polar cap potential difference. In addition, we use the ground-based ionosonde data for comparison our model results with observations. We present an analysis of the physical mechanisms responsible for the ionospheric effects of geomagnetic storms. The obtained simulation results are used by us as a medium for HF radio wave propagation at different latitudes in quiet conditions, and during main and recovery phase of a geomagnetic storm. To solve the problem of the radio wave propagation we used Zakharov's (I. Kant BFU) model based on geometric optics. In this model the solution of the eikonal equation for each of the two normal modes is reduced using the method of characteristics to the integration of the six ray equation system for the coordinates and momentum. All model equations of this system are solved in spherical geomagnetic coordinate system by the Runge-Kutta method. This model was tested for a plane wave in a parabolic layer. In this study, the complex refractive indices of the ordinary and extraordinary waves at ionospheric heights was calculated for the first time using the global first-principal model of the thermosphere-ionosphere system that describes the parameters of an inhomogeneous anisotropic medium during a geomagnetic storm. A comparison of the ordinary and extraordinary modes of HF radio ray paths in quiet and disturbed conditions has been done. We considered in more detail the features of the radio ray paths in the presence of F3 layer in the equatorial ionosphere, the main ionospheric trough and tongue of ionization at high latitudes. It is shown that the results obtained with use of radio propagation and GSM TIP models adequately describe HF radio ray paths in the Earth's ionosphere and can be used in applications. These investigations were carried out at financial support of Russian Foundation for Basic Research (RFBR) - Grant # 12-05-31217 and RAS Program 22.

  15. Numerical modelling of VLF radio wave propagation through earth-ionosphere waveguide and its application to sudden ionospheric disturbances

    E-print Network

    Pal, Sujay

    2015-01-01

    In this thesis, we theoretically predict the normal characteristics of Very Low Frequency (3~30 kHz) radio wave propagation through Earth-ionosphere waveguide corresponding to normal behavior of the D-region ionosphere. We took the VLF narrow band data from the receivers of Indian Centre for Space Physics (ICSP) to validate our models. Detection of sudden ionospheric disturbances (SIDs) are common to all the measurements. We apply our theoretical models to infer the D-region characteristics and to reproduce the observed VLF signal behavior corresponding to such SIDs. We develop a code based on ray theory to simulate the diurnal behavior of VLF signals over short propagation paths (2000~3000 km). The diurnal variation from this code are comparable to the variation obtained from a more general Long Wave Propagation Capability (LWPC) code which is based on mode theory approach. We simulate the observational results obtained during the Total Solar Eclipse of July 22, 2009 in India. We also report and simulate a h...

  16. Propagation characteristics of a diffracted M2 beam.

    PubMed

    Amano, Sho; Mochizuki, Takayasu

    2002-10-20

    The propagation characteristics of a beam diffracted by a circular aperture are investigated. The beam-quality factor M2 defined by an 86.5% power-content radius is given theoretically and experimentally as a function of the truncation ratio. It is found that the theoretical limit of M2 is 2.37 times as great as that of an incident beam as the truncation ratio approaches 0. For a weakly diffracted beam a simple formula giving M2 is derived. Although M2 does not increase much with diffraction, the influence of diffraction should be taken into account in beam brightness. PMID:12396181

  17. Source characteristics of Jovian narrow-band kilometric radio emissions

    NASA Astrophysics Data System (ADS)

    Reiner, M. J.; Fainberg, J.; Stone, R. G.; Kaiser, M. L.; Desch, M. D.; Manning, R.; Zarka, P.; Pedersen, B.-M.

    1993-07-01

    New observations of Jovian narrow-band kilometric (nKOM) radio emissions were made by the Unified Radio and Plasma Wave (URAP) experiment on the Ulysses spacecraft during the Ulysses-Jupiter encounter in early February 1992. These observations have demonstrated the unique capability of the URAP instrument for determining both the direction and polarization of nKOM radio sources. An important result is the discovery that nKOM radio emission originates from a number of distinct sources located at different Jovian longitudes and at the inner and outermost regions of the Io plasma torus. These sources have been tracked for several Jovian rotations, yielding their corotational lags, their spatial and temporal evolution, and their radiation characteristics at both low latitudes far from Jupiter and at high latitudes near the planet. Both right-hand and left-hand circularly polarized nKOM sources were observed. The polarizations observed for sources in the outermost regions of the torus seem to favor extraordinary mode emission.

  18. Brightness, coherence, and propagation characteristics of synchrotron radiation

    SciTech Connect

    Kim, K.J.

    1985-07-01

    A formalism is presented by means of which the propagation and imaging characteristics of synchrotron radiation can be studied, taking into account the effects of diffraction, electron beam emittance, and the transverse and longitudinal extent of the source. An important quantity in this approach is the Wigner distribution of the electric fields, which can be interpreted as a phase-space distribution of photon flux, and thus can be identified with the brightness. When integrated over the angular variables, the brightness becomes the intensity distribution in the spatial variables and when integrated over the spatial variables, it becomes the intensity distribution in angular variables. The brightness so defined transforms through a general optical medium in exactly the same way as in the case of a collection of geometric rays. Finally, the brightness of different electrons adds in a simple way. Optical characteristics of various synchrotron radiation sources - bending magnets, wigglers and undulators, are analyzed using this formalism.

  19. 3D ray-tracing parallel model for radio-propagation prediction

    Microsoft Academic Search

    A. M. Cavalcante; M. J. de Sousa; J. C. W. Costa; C. R. L. Frances; G. Protasio dos Santos Cavalcante; C. de Souza Sales

    2006-01-01

    A computational parallel model based on 3D ray- tracing for radio-propagation prediction is presented. This approach considers that the main tasks in a 3D ray-tracing technique can be evaluated in an independent and\\/or parallel way. The workload distribution among the participant nodes of the parallel architecture (cluster of PC's), is performed through a random assignment of the initial rays and

  20. A New Propagation Model for Cellular Mobile Radio Communications in Urban Environments Including Tree Effects

    Microsoft Academic Search

    Reza Arablouei; Ayaz Ghorbani

    2002-01-01

    An advanced model for radio wave propagation in vegetated urban areas is proposed. The new model is based on uniform theory\\u000a of diffraction (UTD) and so appropriate for numerical calculation. We have recently proposed a new UTD-based model for multiple\\u000a diffractions by buildings and in this paper we have endeavored to extend the new model to involve tree effects. We

  1. Radio Wave Propagation for Communication on and around Mars. Part 1; Highlights: Propagation Through Mars Environment

    NASA Technical Reports Server (NTRS)

    Ho, Christian; Golshan, Nasser

    1999-01-01

    We recommend to use the dayside Martian ionosphere as a reflector for global communication, because the dayside ionosphere has stable density peak and usable critic frequency. This is very crucial for the future Mars ground to around communication. The dayside ionosphere has been well modeled as a Chapman layer. We suggest to perform the Martian nightside ionospheric modeling study. Because the nightside ionosphere has very little measurements available, we propose to drop a digital ionosond instrument into the Mars surface for data collection. Even though the Martian tropospheric radio refractivity has small value, it still can cause the ray bending and multipath effects. We recommend to perform an accurate calculation on excess phase and group delays (range and time delays). Other effects, such as range rate errors, appearance angle deviation, defocusing loss on Mars, etc. are also needed to be estimated. Ice depolarization effects due to Martian clouds on radio waves is unknown yet, which is expected to be small, because lower optical depth and thinner layer of cloud: Total Martian atmospheric gaseous attenuation is expected to be less than 1 dB on microwaves band, because the Martian atmosphere has very low concentration in uncondensed H2O and O2. An accurate calculation for zenith opacity requires the information about scale heights of H2O and O2 distribution. An accurate water vapor altitude profile at Mars is not available yet. Under the normal condition, CO2 and N2 gases do not have electric or magnetic dipoles and do not absorb electromagnetic energy from the waves. However, they may generate the dipoles through a collision and interact with waves under a high density condition and absorb electromagnetic waves in the infrared and visible band. Dust storm is most dominant factor to the radio wave attenuation. Large Martian dust storm can cause at least 3 dB or higher loss to Ka band wave. For a normal dust storm, the attenuation is about 1 dB. The attenuation much depends on dust mass loading, dust size distribution, etc. Most large dust storm occur in the southern hemisphere during later spring and early summer when the southern hemisphere become suddenly hot.

  2. Some characteristics of whistler mode waves propagating through the low-latitude ionosphere

    NASA Astrophysics Data System (ADS)

    Xu, J.-S.; Bao, Z.-T.; Liang, B.-X.

    1985-10-01

    In this paper, the propagation characteristics for rays and wave normals of VLF radio waves through the low-latitude ionosphere based on the 3-D ray tracing computation carried out for whistler mode waves are investigated by using an IGRF (1980) model. It is found that the ray path of whistlers detectable on the ground can stably remain in a region around geom. lat. 10 deg for various ionospheric profiles, and that the downcoming rays focus remarkably in the same region, with a focus gain about 10.4 dB. The results of computation also show that the lowest latitudes of nonducted whistler paths exhibit sharp cut-off near geom. lat. 6.5 deg.

  3. Antenna Construction & Propagation of Radio Waves, 5-1. Military Curriculum Materials for Vocational and Technical Education.

    ERIC Educational Resources Information Center

    Marine Corps, Washington, DC.

    These military-developed curriculum materials consist of five individualized, self-paced chapters dealing with antenna construction and propagation of radio waves. Covered in the individual lessons are the following topics: basic electricity; antenna transmission-line fundamentals; quarter-wave antennas, half-wave antennas, and associated radio…

  4. IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 48, NO. 3, MARCH 2000 345 Estimation of Radio Refractivity Structure Using

    E-print Network

    Buckingham, Michael

    IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 48, NO. 3, MARCH 2000 345 Estimation of Radio Refractivity Structure Using Matched-Field Array Processing Peter Gerstoft, Donald F. Gingras, Member, IEEE, L of the underlying "marine layer" creates elevated trapping layers in the radio refractivity structure. While direct

  5. Propagation of 2 GHz Radio Waves Over the English Channel: Analysis of Cases of SubRefraction

    Microsoft Academic Search

    E. M. Warrington; D. R. Siddle

    This paper presents details about the transhorizon propagation of 2 GHz radio waves over the sea during sub- refractive atmospheric conditions. Sub-refraction is perhaps the most rare of the four refractive conditions (ducting, super-refraction, normal refraction and sub-refraction), but nevertheless cannot be ignored when assessing the performance of a radio link. Specifically, for a 50 km, low-altitude, over-sea radio path

  6. Propagation characteristics of neutrons leaking from the accelerator facilities.

    PubMed

    Kitaichi, Masatoshi; Sawamura, Sadashi; Wakisaka, Masashi; Kaneko, Junichi H; Ochiai, Kentaro; Nishitani, Takeo; Sawamura, Teruko

    2004-01-01

    In this study spatial and time distribution of neutrons leaking from Hokkaido University 45 MeV Electron Linac facility have measured and compared with the Monte Carlo simulations. The neutron transport processes inside and outside the facility building has been simulated using MCNP. The neutrons have measured by BF3 counters and 3He counters with polyethylene moderators up to the distance of 330 m from the facility. The spatial distribution of ambient dose equivalent converted from the counts has been compared with the simulation. The distribution estimated from the counts by the BF3 counter has been shown fairly good agreement with the calculation. The spatial distribution of counts obtained at the 45 MeV Electron Linac facility has been compared with that obtained at the Fusion Neutronics Source (FNS) facility of JAERI. The difference between the propagation characteristics of neutrons leaking from those facilities has been discussed. PMID:15353739

  7. Impact of famous CEDAR, GEM and ISTP geomagnetic Storms on HF Radio Propagation

    NASA Astrophysics Data System (ADS)

    Blagoveshchensky, D.; Sergeeva, M.

    The mighty geomagnetic storms due to the extraordinary Sun s activity cause as a rule some impacts in these areas radiation effects on human and satellites commercial airlines outages electric power and other geomagnetic effects navigation and communication GPS effects ionospheric disturbances HF communication effects Therefore our scientific understanding of this activity is very important Joint efforts for example within the framework of the CAWSES enable progress in our ability to i identify critical inputs to specify the geospace environment at a level needed to minimize impacts on technology human society and life and ii support the development of robust models that predict conditions in geospace based on understanding of the Sun-Earth system and all of its interacting components In this study influence of 14 geomagnetic storms from a list of CEDAR GEM and ISTP storms within 1997-99 on radio propagation conditions have been investigated These conditions were estimated through variations of the MOF and LOF the maximum and lowest operation frequencies on each path from three high-latitude HF radio paths of North-west Russia before during and after a storm It was shown that the storm impact on the ionosphere and radio propagation for each storm has an individual character Nevertheless the common character of the certain manifestations during storm-time was revealed For example the frequency range MOF - LOF is getting wider several hours before a storm then it is sharply narrow during a storm-time and further it is expanded again several

  8. On the mean profiles of radio pulsars - I. Theory of propagation effects

    NASA Astrophysics Data System (ADS)

    Beskin, V. S.; Philippov, A. A.

    2012-09-01

    We study the influence of propagation effects on the mean profiles of radio pulsars using the method of wave propagation in inhomogeneous media described by Kravtsov & Orlov. This approach allows us first to take into consideration the transition from geometrical optics to vacuum propagation, the cyclotron absorption and the wave refraction simultaneously. In addition, the non-dipole magnetic field configuration, the drift motion of plasma particles and their realistic energy distribution are taken into account. It is confirmed that, for ordinary pulsars (period P ˜ 1 s, surface magnetic field B0 ˜ 1012 G) and typical plasma generation near the magnetic poles (multiplicity parameter ? = ne/nGJ ˜ 103), the polarization is formed inside the light cylinder at a distance resc ˜ 1000 R from the neutron star, the circular polarization being 5-20 per cent which is in agreement with observational data. A one-to-one correspondence between the signs of circular polarization and position angle (PA) derivative along the profile for both ordinary and extraordinary waves is predicted. Using numerical integration we now can model the mean profiles of radio pulsars. It is shown that the standard S-shape form of the PA swing can be realized for small enough multiplicity ? and large enough bulk Lorentz factor ? only. It is also shown that the value of the maximum derivative of PA, which is often used for determination of the angle between magnetic dipole and rotation axis, depends on the plasma parameters and could differ from the rotation vector model (RVM) prediction.

  9. A survey of various propagation models for mobile communication

    Microsoft Academic Search

    Tapan K. Sarkar; Zhong Ji; Kyungiung Kim; A. Medouri; Magdalena Salazar-Palma

    2003-01-01

    In order to estimate the signal parameters accurately for mobile systems, it is necessary to estimate a system's propagation characteristics through a medium. Propagation analysis provides a good initial estimate of the signal characteristics. The ability to accurately predict radio-propagation behavior for wireless personal communication systems, such as cellular mobile radio, is becoming crucial to system design. Since site measurements

  10. Ionospheric effects of X-ray source Scorpius XR-1. [on terrestrial radio propagation

    NASA Technical Reports Server (NTRS)

    Poppoff, I. G.; Whitten, R. C.; Willoughby, D. S.

    1975-01-01

    A simple two-ion model was employed to evaluate the ionospheric effects of various nocturnal ionization sources. The model was used to calculate the decay of the electron number density at 90 km with and without illumination by Scorpius XR-1 X rays. Reflection parameters for the determination of the effect of cosmic x-ray sources on radio wave propagation were also obtained. The results obtained in the investigation do not support the proposal made by Anathakrishnan and Ramanathan (1969) that the X-ray source in Scorpius XR-1 affects the nighttime lower ionosphere of the earth.

  11. The Relation between Type II Radio Bursts and Large-scale Coronal Propagating Fronts

    NASA Astrophysics Data System (ADS)

    Nitta, Nariaki

    2014-06-01

    Both type II radio bursts and chromospheric Moreton-Ramsey waves are believed to signify shock waves that propagate in the solar corona. Large-scale coronal propagating fronts (LCPFs), which are also called EIT waves, EUV waves or coronal bright fronts in the literature, were initially thought to be coronal counterparts of Moreton-Ramsey waves, and thus they were expected to be correlated with type II bursts. At present, the prevailing view seems to be that both type II bursts and LCPFs are more closely linked with CMEs than with flares. Here we revisit the relation between type II bursts and LCPFs, by examining radio dynamic spectra (180-25 MHz) as obtained by USAF/RSTN and analyzing EUV and white-light data from SDO and STEREO. In the sample of about 140 type II bursts and LCPFs between April 2010 and January 2013, we find the correlation of 50-60 %. Type II bursts could be associated with eruptions without significant lateral expansion, and fast LCPFs could show no presence in the metric radio spectral range. Using data from STEREO COR-1 that observed the CME as a limb event, in 42 cases we directly measure the height of the CME at the onset of the type II burst. As expected, the height tends to be lower when the type II burst starts at a higher frequency. It is found that those type II bursts that start at higher altitudes and lower frequencies tend to have weaker EUV fronts. This may indicate multiple ways of how LCPFs and type II bursts are related with CMEs.

  12. Determination of Propagation Characteristics of Crucial Planar Wave Guide Structures by Finite Difference Method

    NASA Astrophysics Data System (ADS)

    Ghosh, Prasenjit; Sarkar, Somenath

    2013-12-01

    Based on finite difference (FD) method, recently applied to investigate propagation characteristics of optical waveguides, we verify its applicability to predict the electric field and propagation parameter of planar waveguide for the entire range of normalized frequencies. As a test case, we crosscheck our FD result for symmetric step index planar waveguide and then predict the propagation characteristics of crucial planar waveguide structures like exponential index and Epstein layer model profile. Our findings show high degree of accuracy when compared with published results.

  13. Characteristics of tropopause parameters as observed with GPS radio occultation

    NASA Astrophysics Data System (ADS)

    Rieckh, T.; Scherllin-Pirscher, B.; Ladstädter, F.; Foelsche, U.

    2014-11-01

    Characteristics of the lapse rate tropopause are analyzed globally for tropopause altitude and temperature using global positioning system (GPS) radio occultation (RO) data from late 2001 to the end of 2013. RO profiles feature high vertical resolution and excellent quality in the upper troposphere and lower stratosphere, which are key factors for tropopause determination, including multiple ones. RO data provide measurements globally and allow examination of both temporal and spatial tropopause characteristics based entirely on observational measurements. To investigate latitudinal and longitudinal tropopause characteristics, the mean annual cycle, and inter-annual variability, we use tropopauses from individual profiles as well as their statistical measures for zonal bands and 5° × 10° bins. The latitudinal structure of first tropopauses shows the well-known distribution with high (cold) tropical tropopauses and low (warm) extra-tropical tropopauses. In the transition zones (20 to 40° N/S), individual profiles reveal varying tropopause altitudes from less than 7 km to more than 17 km due to variability in the subtropical tropopause break. In this region, we also find multiple tropopauses throughout the year. Longitudinal variability is strongest at northern hemispheric mid latitudes and in the Asian monsoon region. The mean annual cycle features changes in amplitude and phase, depending on latitude. This is caused by different underlying physical processes (such as the Brewer-Dobson circulation - BDC) and atmospheric dynamics (such as the strong polar vortex in the southern hemispheric winter). Inter-annual anomalies of tropopause parameters show signatures of El Niño-Southern Oscillation (ENSO), the quasi-biennial oscillation (QBO), and the varying strength of the polar vortex, including sudden stratospheric warming (SSW) events. These results are in good agreement with previous studies and underpin the high utility of the entire RO record for investigating latitudinal, longitudinal, and temporal tropopause characteristics globally.

  14. A parametric study of the propagation of auroral radio emissions through auroral cavities

    NASA Astrophysics Data System (ADS)

    Gautier, A.; Hess, S.; Cecconi, B.; Zarka, P. M.

    2013-12-01

    Auroral Kilometric Radiation is the radio counterpart of the Earth's auroral radiations, observed in a large domain of wavelength, from Infrared to UV and obviously in visible. It is generated at high latitude (~70°), mostly along the nightside magnetic field lines connecting to the Earth's magnetospheric tail. In-situ observations by numerous spacecraft show that the radio sources are embedded inside depleted cavities. The auroral cavities contain a hot tenuous plasma (ne~1 cm-3, Te~5 keV) in a strong ambient magnetic field (fp/fc < 0.1). The mechanism of emission, the Cyclotron Maser Instability (CMI), predicts an intense X mode emission near gyromagnetic frequency preferentially perpendicular to the local magnetic field. But as the radio waves are generated inside a depleted cavity, they are refracted. The apparent beaming of the source is different from that predicted by the CMI. The characteristics of the apparent beaming of the source outside of the cavity depends on several geometrical and physical parameters of the surrounding medium, as well as the frequency of the radio wave. A ray tracing code (ARTEMIS-P), which computes the trajectories of electromagnetic waves in magnetized plasma, is use to compute the path of radio ray from the source inside the hot tenuous plasma of the cavity to the outside. We model a cylindrical plasma cavity characterized by a few parameters (width, edge and parallel gradients) and we study the effect of the cavity geometry on the beaming of AKR for several frequencies. We draw conclusions about the deterministic nature of the beaming angle of the radio emissions generated in cavities. We then extend our study to emissions from giant planets.

  15. Radio-wave propagation in the non-Gaussian interstellar medium

    E-print Network

    Stanislav Boldyrev; Carl R. Gwinn

    2005-08-02

    Radio waves propagating from distant pulsars in the interstellar medium (ISM), are refracted by electron density inhomogeneities, so that the intensity of observed pulses fluctuates with time. The theory relating the observed pulse time-shapes to the electron-density correlation function has developed for 30 years, however, two puzzles have remained. First, observational scaling of pulse broadening with the pulsar distance is anomalously strong; it is consistent with the standard model only when non-uniform statistics of electron fluctuations along the line of sight are assumed. Second, the observed pulse shapes are consistent with the standard model only when the scattering material is concentrated in a narrow slab between the pulsar and the Earth. We propose that both paradoxes are resolved at once if one assumes stationary and uniform, but non-Gaussian statistics of the electron-density distribution. Such statistics must be of Levy type, and the propagating ray should exhibit a Levy flight. We propose that a natural realization of such statistics may be provided by the interstellar medium with random electron-density discontinuities. We develop a theory of wave propagation in such a non-Gaussian random medium, and demonstrate its good agreement with observations. The qualitative introduction of the approach and the resolution of the anomalous-scaling paradox was presented earlier in [PRL 91, 131101 (2003); ApJ 584, 791 (2003)].

  16. Effect of electron-density gradients on propagation of radio waves in the mid-latitude trough. Master's thesis

    SciTech Connect

    Citrone, P.J.

    1991-01-01

    Partial contents of this thesis include: (1) Radio-wave propagation and the mid-latitude trough; (2) Ionospheric measurements; (3) Modification of time-dependent ionospheric model output with latitudinal electron-density profiles from digisonde trough depictions; (4) Ray-tracing simulations to examine ground range; and (5) Effects of three-dimensional gradients in electron density on radio-wave propagation in the trough region. Data is tabulated for geophysical conditions, solar activity level, geomagnetic activity level, conditions for vertical ray refraction to surface, and ray-tracing fixed-input conditions.

  17. The Distortion Characteristics of a Pulse Wave Propagating through Fog Medium at Millimeter Wave Band

    NASA Astrophysics Data System (ADS)

    Huang, Jiying; He, Wang; Gong, Shuhong

    2007-10-01

    When a pulse wave propagates through fog, the effects of distortion, being severer at millimeter wave band, is caused by fog because of its dispersive property. The transfer function of a pulse signal is obtained by the theory of radio wave propagation; the complex envelope is deduced by the solution of Fourier integral. The broadening and compressing effects of a pulse wave are discussed. The variations of distortion effects with pulse-width, propagation distance and visibility of fog are found. As an example, the simulating and calculating results of distortion effects for Gaussian pulse at millimeter wave band are given.

  18. Characteristics of a transiently propagating crack in functionally graded materials

    Microsoft Academic Search

    Kwang Ho Lee; Young Jae Lee; Sang Bong Cho

    2009-01-01

    When a crack propagates with acceleration, deceleration and time rates of change of stress intensity factors, it is very important\\u000a for us to understand the effects of acceleration, deceleration and time rates of change of stress intensity factors on the\\u000a individual stresses and displacements at the crack tip. Therefore, the crack tip stress and displacement fields for a transiently\\u000a propagating

  19. Radio Wave Propagation through a Medium Containing Electron Density Fluctuations Described by an Anisotropic Goldreich-Sridhar Spectrum

    Microsoft Academic Search

    B. D. G. Chandran; D. C. Backer

    2002-01-01

    We study the propagation of radio waves through a medium possessing density fluctuations that are elongated along the ambient magnetic field and described by an anisotropic Goldreich-Sridhar power spectrum. We derive general formulae for the wave phase structure function Dphi, visibility, angular broadening, diffraction pattern length scales, and scintillation timescale for arbitrary distributions of turbulence along the line of sight

  20. Radio Frequency Characteristics of Printed Meander Inductors and Interdigital Capacitors

    NASA Astrophysics Data System (ADS)

    Myllymaki, Sami; Teirikangas, Merja; Nelo, Mikko; Tulppo, Joel; Soboci?ski, Maciej; Juuti, Jari; Jantunen, Heli; Sloma, Marcin; Jakubowska, Malgorzata

    2013-05-01

    Radio frequency (RF) characterizations of printed silver ink inductors manufactured at low (150 °C) and high (850 °C) temperatures and interdigital capacitors manufactured at high (850 °C) temperatures were carried out in the 500 MHz to 6 GHz range. The S-parameter responses of the components were measured with a probe station and an Agilent 8510C network analyzer. Electrical parameters such as inductance, capacitance, and a quality factor were estimated from experimental results and numerical calculation. Component parameters are dependent on physical dimensions and material properties. The components were created in a 4 ×4 mm2 area with line widths/gaps of 500/500, 250/250, and 200/200 µm. Windings in the coils varied from 2 to 5 turns and finger counts in the capacitors, from 5 to 11 within the defined area and line widths. As a result, low-T-cured (150 °C) silver ink meander line inductors achieved 8 to 18 nH inductances at 1 and 2 GHz with a quality value of 10-25. High-T-cured (850 °C) silver ink meander line inductors had 6-15 nH inductances and quality values were around 100, indicating a conductivity challenge with low-T-cured inks. Interdigital capacitors with 1 to 4 pF capacitances and sufficient quality values were created. A low-loss BaTiO3 coating was printed over the interdigital capacitors; they exhibited suitable electrical characteristics to allow decreasing the physical size of the component.

  1. Investigation on Wave Propagation Characteristics in Plates and Pipes for Identification of Structural Defect Locations

    E-print Network

    Han, Je Heon

    2013-07-31

    For successful identification of structural defects in plates and pipes, it is essential to understand structural wave propagation characteristics such as dispersion relations. Analytical approaches to identify the dispersion relations...

  2. Dynamic characteristic of intense short microwave propagation in an atmosphere

    SciTech Connect

    Yee, J.H.; Alvarez, R.A.; Mayhall, D.J.; Madsen, N.K.; Cabayan, H.S.

    1983-07-01

    The dynamic behavior of an intense microwave pulse which propagates through the atmosphere will be presented. Our theoretical results are obtained by solving Maxwell's equations, together with the electron fluid equations. Our calculations show that although large portions of the initial energy are absorbed by the electrons that are created through the avalanche process, a significant amount of energy is still able to reach the earth's surface. The amount of energy that reaches the earth's surface as a function of initial energy and wave shape after having propagated through 100 km in the atmosphere are investigated. Results for the air breakdown threshold intensity as a function of the pressure for different pulse widths and different frequencies will also be presented. In addition, we will present a comparison between the theoretical and the experimental results for the pulse shape of a short microwave pulse after it has traveled through a rectangular wave guide which contains a section of air. 23 references, 9 figures.

  3. Ionosphere-magnetosphere studies using ground based VLF radio propagation technique: an Indian example

    NASA Astrophysics Data System (ADS)

    Chakravarty, Subhas

    Since IGY period (1957-58), natural and artificially produced Very Low Frequency (VLF) elec-tromagnetic radiations are being recorded at large number of ground stations all over the world and on-board satellites to study various radio wave-thermal/energetic plasma interactive pro-cesses related to earth's ionosphere-plasmasphere-magnetosphere environment. The terrestrial propagation of these VLF radio waves are primarily enabled through the earth ionosphere wave guide (EIWG) mode to long horizontal distances around the globe and ducted along the ge-omagnetic field lines into the conjugate hemisphere through the plasmasphere-magnetosphere regions. The time frequency spectra of the received signals indicate presence of dispersion (wave/group velocities changing with frequency) and various cut-off frequencies based on the width of the EIWG, electron gyro and plasma frequencies etc., providing several types of received signals like whistlers, chorus, tweeks, hiss and hisslers which can be heard on loud-speakers/earphones with distinguishing audio structures. While the VLF technique has been a very effective tool for studying middle and high latitude phenomena, the importance of the similar and anomalous observations over the Indian low latitude stations provide potentially new challenges for their scientific interpretation and modelling. The ducted and non-ducted magnetospheric propagation, pro-longitudinal (PL) mode, low latitude TRIMPI/TLE (Tran-sient Luminous Emissions) or other effects of wave-particle/wave-wave interactions, effects due to ionospheric irregularities and electric fields, full wave solutions to D-region ionisation per-turbations due to solar and stellar energetic X-and ? ray emissions during normal and flaring conditions are a few problems which have been addressed in these low latitude studies over India. Since the conjugate points of Indian stations lie over the Indian oceanic region, the VLF propagation effects would be relatively free from sferics at least in some seasons providing a noise free environment for observing rare and new phenomena requiring better SNR to detect such changes, The VLF signals from the active seismic zones or other electro-geological sources would require high sensitivities of the system and suitable network of transmitting and receiv-ing stations designed for targeted data and applications. Some new results over Indian and other regions show evidences of earthquake related seismo-geological VLF emissions with the potential of being used as a prognostic tool, change in ozone and ion production in the night time middle atmosphere due to transit of stellar x-ray/? ray sources. Results obtained on whistlers and related studies from a number of Indian stations covering geomagnetic latitude range between 13-24 N will be mentioned and reviewed in the background of theoretical understanding of the lightning return stroke signal elements, VLF propagation through cold plasma, ionospheric wave guide mode, electron precipitation due to cyclotron resonance and production of atomic oxygen O (3 P) and ionisation in the mesosphere due to solar/stellar UV/X/?rays. Use of future VLF techniques in terms of improving ground based observations, critical analysis of available satellite data in the context and real time moni-toring/modelling of earth's geosphere and space weather conditions will be considered for a possible programme of a developing country.

  4. The Relation Between Large-Scale Coronal Propagating Fronts and Type II Radio Bursts

    NASA Astrophysics Data System (ADS)

    Nitta, Nariaki V.; Liu, Wei; Gopalswamy, Nat; Yashiro, Seiji

    2014-12-01

    Large-scale, wave-like disturbances in extreme-ultraviolet (EUV) and type II radio bursts are often associated with coronal mass ejections (CMEs). Both phenomena may signify shock waves driven by CMEs. Taking EUV full-disk images at an unprecedented cadence, the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory has observed the so-called EIT waves or large-scale coronal propagating fronts (LCPFs) from their early evolution, which coincides with the period when most metric type II bursts occur. This article discusses the relation of LCPFs as captured by AIA with metric type II bursts. We show examples of type II bursts without a clear LCPF and fast LCPFs without a type II burst. Part of the disconnect between the two phenomena may be due to the difficulty in identifying them objectively. Furthermore, it is possible that the individual LCPFs and type II bursts may reflect different physical processes and external factors. In particular, the type II bursts that start at low frequencies and high altitudes tend to accompany an extended arc-shaped feature, which probably represents the 3D structure of the CME and the shock wave around it, and not just its near-surface track, which has usually been identified with EIT waves. This feature expands and propagates toward and beyond the limb. These events may be characterized by stretching of field lines in the radial direction and may be distinct from other LCPFs, which may be explained in terms of sudden lateral expansion of the coronal volume. Neither LCPFs nor type II bursts by themselves serve as necessary conditions for coronal shock waves, but these phenomena may provide useful information on the early evolution of the shock waves in 3D when both are clearly identified in eruptive events.

  5. RADIO BURSTS WITH EXTRAGALACTIC SPECTRAL CHARACTERISTICS SHOW TERRESTRIAL ORIGINS

    SciTech Connect

    Burke-Spolaor, S.; Bailes, Matthew [Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Mail H39, P.O. Box 218, Hawthorn VIC 3122 (Australia); Ekers, Ronald [CSIRO Australia Telescope National Facility, P.O. Box 76, Epping NSW 1710 (Australia); Macquart, Jean-Pierre [ICRAR/Curtin Institute of Radio Astronomy, GPO Box U1987, Perth WA 6845 (Australia); Crawford, Fronefield III, E-mail: sburke@astro.swin.edu.au [Department of Physics and Astronomy, Franklin and Marshall College, Lancaster, PA 17604 (United States)

    2011-01-20

    Three years ago, the report of a solitary radio burst was thought to be the first discovery of a rare, impulsive event of unknown extragalactic origin. The extragalactic interpretation was based on the swept-frequency nature of the event, which followed the dispersive delay expected from an extragalactic pulse. We report here on the detection of 16 pulses, the bulk of which exhibit a frequency sweep with a shape and magnitude resembling the Lorimer Burst. These new events were detected in a sidelobe of the Parkes Telescope and are of clearly terrestrial origin, with properties unlike any known sources of terrestrial broadband radio emission. The new detections cast doubt on the extragalactic interpretation of the original burst, and call for further sophistication in radio-pulse survey techniques to identify the origin of the anomalous terrestrial signals and definitively distinguish future extragalactic pulse detections from local signals. The ambiguous origin of these seemingly dispersed, swept-frequency signals suggests that radio-pulse searches using multiple detectors will be the only experiments able to provide definitive information about the origin of new swept-frequency radio burst detections.

  6. The Relation Between Large-Scale Coronal Propagating Fronts and Type II Radio Bursts

    E-print Network

    Nitta, Nariaki V; Gopalswamy, Nat; Yashiro, Seiji

    2014-01-01

    Large-scale, wave-like disturbances in extreme-ultraviolet (EUV) and type II radio bursts are often associated with coronal mass ejections (CMEs). Both phenomena may signify shock waves driven by CMEs. Taking EUV full-disk images at an unprecedented cadence, the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory has observed the so-called EIT waves or large-scale coronal propagating fronts (LCPFs) from their early evolution, which coincides with the period when most metric type II bursts occur. This article discusses the relation of LCPFs as captured by AIA with metric type II bursts. We show examples of type II bursts without a clear LCPF and fast LCPFs without a type II burst. Part of the disconnect between the two phenomena may be due to the difficulty in identifying them objectively. Furthermore, it is possible that the individual LCPFs and type II bursts may reflect different physical processes and external factors. In particular, the type II bursts that start at low frequencies an...

  7. Tracker: A three-dimensional raytracing program for ionospheric radio propagation

    SciTech Connect

    Argo, P.E.; DeLapp, D.; Sutherland, C.D.; Farrer, R.G.

    1994-12-01

    TRACKER is an extension of a three-dimensional Hamiltonian raytrace code developed some thirty years ago by R. Michael Jones. Subsequent modifications to this code, which is commonly called the {open_quotes}Jones Code,{close_quotes} were documented by Jones and Stephensen (1975). TRACKER incorporates an interactive user`s interface, modern differential equation integrators, graphical outputs, homing algorithms, and the Ionospheric Conductivity and Electron Density (ICED) ionosphere. TRACKER predicts the three-dimensional paths of radio waves through model ionospheres by numerically integrating Hamilton`s equations, which are a differential expression of Fermat`s principle of least time. By using continuous models, the Hamiltonian method avoids false caustics and discontinuous raypath properties often encountered in other raytracing methods. In addition to computing the raypath, TRACKER also calculates the group path (or pulse travel time), the phase path, the geometrical (or {open_quotes}real{close_quotes}) pathlength, and the Doppler shift (if the time variation of the ionosphere is explicitly included). Computational speed can be traded for accuracy by specifying the maximum allowable integration error per step in the integration. Only geometrical optics are included in the main raytrace code; no partial reflections or diffraction effects are taken into account. In addition, TRACKER does not lend itself to statistical descriptions of propagation -- it requires a deterministic model of the ionosphere.

  8. Experimental simulation of beam propagation over long path lengths using radio-frequency and magnetic traps

    NASA Astrophysics Data System (ADS)

    Okamoto, H.; Endo, M.; Fukushima, K.; Higaki, H.; Ito, K.; Moriya, K.; Yamaguchi, S.; Lund, S. M.

    2014-01-01

    An overview is given of the novel beam-dynamics experiments based on compact non-neutral plasma traps at Hiroshima University. We have designed and constructed two different classes of trap systems, one of which uses a radio-frequency electric field (Paul trap) and the other uses an axial magnetic field (Penning trap) for transverse plasma confinement. These systems are called "S-POD" (Simulator for Particle Orbit Dynamics). The S-POD systems can approximately reproduce the collective motion of a charged-particle beam propagating through long alternating-gradient (AG) quadrupole focusing channels using the Paul trap and long continuous focusing channels using the Penning trap. This allows us to study various beam-dynamics issues in compact and inexpensive experiments without relying on large-scale accelerators. So far, the linear Paul traps have been applied for the study of resonance-related issues including coherent-resonance-induced stop bands and their dependence on AG lattice structures, resonance crossing in fixed-field AG accelerators, ultralow-emittance beam stability, etc. The Penning trap with multi-ring electrodes has been employed primarily for the study of beam halo formation driven by initial distribution perturbations. In this paper, we briefly overview the S-POD systems, and then summarize recent experimental results on resonance effects and halo formation.

  9. TRACKER: A three-dimensional raytracing program for ionospheric radio propagation

    NASA Astrophysics Data System (ADS)

    Argo, P. E.; Delapp, D.; Sutherland, C. D.; Farrer, R. G.

    TRACKER is an extension of a three-dimensional Hamiltonian raytrace code developed some thirty years ago by R. Michael Jones. Subsequent modifications to this code, which is commonly called the 'Jones Code' were documented by Jones and Stephensen (1975). TRACKER incorporates an interactive user's interface, modern differential equation integrators, graphical outputs, homing algorithms, and the Ionospheric Conductivity and Electron Density (ICED) ionosphere. TRACKER predicts the three-dimensional paths of radio waves through model ionospheres by numerically integrating Hamilton's equations, which are a differential expression of Fermat's principle of least time. By using continuous models, the Hamiltonian method avoids false caustics and discontinuous raypath properties often encountered in other raytracing methods. In addition to computing the raypath, TRACKER also calculates the group path (or pulse travel time), the phase path, the geometrical (or 'real') pathlength, and the Doppler shift (if the time variation of the ionosphere is explicitly included). Computational speed can be traded for accuracy by specifying the maximum allowable integration error per step in the integration. Only geometrical optics are included in the main raytrace code; no partial reflections or diffraction effects are taken into account. In addition, TRACKER does not lend itself to statistical descriptions of propagation -- it requires a deterministic model of the ionosphere.

  10. Propagation characteristics for 2.45 GHz dynamic wearable WBAN using multiport VNA

    Microsoft Academic Search

    Takahiro Aoyagi; Jun-ichi Takada; Kenichi Takizawa; Kamya Y. Yazdandoost; Huan-Bang Li; Marco Hernandez; Kiyoshi Hamaguchi; Ryu Miura; Takehiko Kobayashi; Ryuji Kohno

    2012-01-01

    In this paper, results of an indoor experiment for 2.45 GHz dynamic wearable wireless body area network (WBAN) using multiport vector network analyzer is reported. Temporal changes of propagation characteristics for two human male subjects are measured for six antenna positions on-body simultaneously. Statistical characteristics and correlations between individual receiving points are reported.

  11. Spectral Characteristic Evolution: A New Algorithm for Gravitational Wave Propagation

    E-print Network

    Casey J. Handmer; Béla Szilágyi

    2014-09-24

    We present a spectral algorithm for solving the full nonlinear vacuum Einstein field equations in the Bondi framework. Developed within the Spectral Einstein Code (SpEC), we demonstrate spectral characteristic evolution as a technical precursor to Cauchy Characteristic Extraction (CCE), a rigorous method for obtaining gauge-invariant gravitational waveforms from existing and future astrophysical simulations. We demonstrate the new algorithm's stability, convergence, and agreement with existing evolution methods. We explain how an innovative spectral approach enables a two orders of magnitude improvement in computational efficiency.

  12. Asymptotic methods of calculating the propagation of centimeter radio waves in the atmosphere in space-space paths

    Microsoft Academic Search

    M. E. Gorbunov; K. B. Lauritsen

    2007-01-01

    Asymptotic methods of calculating the propagation of centimeter radio waves in a neutral atmosphere in space-space paths are\\u000a considered. The methods are based on the technique of Fourier integral operators. The approximations that allow the representation\\u000a of the corresponding operators as compositions of nonlinear coordinate changes, multiplications by reference signals, and\\u000a Fourier transformations are constructed. The approximations are based on

  13. Propagation characteristics of laser-induced stress wave in deep tissue for gene transfer

    Microsoft Academic Search

    Takahiro Ando; Shunichi Sato; Shinta Takano; Hiroshi Ashida; Minoru Obara

    2009-01-01

    Propagation characteristics of laser-induced stress waves (LISWs) in tissue and their correlation with properties of gene transfection were investigated for targeted deep-tissue gene therapy. LISWs were generated by irradiating a laser-absorbing material with 532-nm Q-switched Nd:YAG laser pulses; a transparent plastic sheet was attached on the absorbing material for plasma confinement. Temporal pressure profiles of LISWs that were propagated through

  14. Characteristics of Radio-Frequency Circuits Utilizing Ferroelectric Capacitors

    NASA Technical Reports Server (NTRS)

    Eskridge, Michael; Gui, Xiao; MacLeod, Todd; Ho, Fat D.

    2011-01-01

    Ferroelectric capacitors, most commonly used in memory circuits and variable components, were studied in simple analog radio-frequency circuits such as the RLC resonator and Colpitts oscillator. The goal was to characterize the RF circuits in terms of frequency of oscillation, gain, etc, using ferroelectric capacitors. Frequencies of oscillation of both circuits were measured and studied a more accurate resonant frequency can be obtained using the ferroelectric capacitors. Many experiments were conducted and data collected. A model to simulate the experimental results will be developed. Discrepancies in gain and frequency in these RF circuits when conventional capacitors are replaced with ferroelectric ones were studied. These results will enable circuit designers to anticipate the effects of using ferroelectric components in their radio- frequency applications.

  15. Seismo-electromagnetic phenomenon in terms of 3D vector problem of subionospheric radio wave propagation across the solar terminator

    NASA Astrophysics Data System (ADS)

    Soloviev, O. V.; Hayakawa, M.; Molchanov, O. A.

    This paper presents a further development of mathematical model, an asymptotic theory and an appropriate numerical algorithm to study the vector VLF point source field propagation problem within the non-uniform Earth-ionosphere waveguide. It is the sequential development of our previous article [Soloviev, O.V., Hayakawa, M., Ivanov, V.I., Molchanov, O.A., 2004. Seismo-electromagnetic phenomenon in the atmosphere in terms of 3D subionospheric radio wave propagation problem. Phys. Chem. Earth 29, 639-647. doi:10.1016/j.pce.2003.10.002]. We have taken into account 3D local anisotropic ionosphere inhomogeneity over the ground of the solar terminator transition. The local ionosphere inhomogeneity, whose centre is situated above the model earthquake, is simulated by a bell-shaped tensor impedance perturbation of the ionospheric waveguide wall. The various propagation paths, which cut across the terminator line at different angles, have been investigated. Numerical results show that the emergence of the local ionosphere inhomogeneity on the radio wave propagation across the solar terminator path deforms the curves of field amplitude and phase diurnal variations in accord with the experimental observational data.

  16. Philippe Zarka Recherche de transitoires radio associs

    E-print Network

    Demoulin, Pascal

    TO GW EVENTS · RADIO PROPAGATION · TRANSIENT RADIO SKY · LOFAR TELESCOPE & OPERATING MODES · LOFAR EARLY · REFERENCES #12;· RADIO COUNTERPARTS TO GW EVENTS · RADIO PROPAGATION · TRANSIENT RADIO SKY · LOFAR TELESCOPEPhilippe Zarka LESIA Recherche de transitoires radio associés à des ondes gravitationnelles avec

  17. Guided radio-wave propagation in the equatorial ionosphere according to the topside sounding onboard Interkosmos-19

    NASA Astrophysics Data System (ADS)

    Karpachev, A. T.; Zhbankov, G. A.; Kuleshova, V. P.; Telegin, V. A.

    2014-12-01

    In addition to normal vertical-incident ionogram traces, strongly remote (up to 2000 km) traces of HF-radio-signal reflections observed on topside-sounder ionograms of the Interkosmos-19 satellite obtained in the equatorial ionosphere are presented. Such traces are connected with waveguides (ducts). These waveguides are field-aligned irregularities of the ionospheric plasma with electron density depletions of a few percent and cross-field dimension of a few to several kilometers. Ray tracing confirms this supposition and allows an estimate of typical waveguide parameters: diameter ?10-15 km and amplitude |?N/N|?10%, where N is the electron density. The waveguide traces usually start at the cutoff frequencies of the main traces. However, sometimes they begin at much lower frequencies which indicates the satellite was transitioning through an equatorial plasma bubble during the recording of the ionogram. The X-mode of ducted echoes is more distinct then the O-mode. Only one ducted trace is usually observed on the Interkosmos-19 ionograms; a second conjugate trace is rarely recorded. The same is true for combination modes which is a combination of an oblique-incidence and guided propagation. Waveguides are observed at all heights of Interkosmos-19 (500-1000 km) inside the equatorial anomaly region (from -40° to +40° Dip). Waveguides are usually associated with other irregularities of various sizes in the equatorial ionosphere, some of which cause additional traces and spread F on the topside-sounding ionograms. Ducted-echo characteristics observed with Interkosmos-19 are different from those observed earlier with the Alouette and ISIS satellites. This difference is discussed. It is shown that the ionospheric plasma irregularities responsible for the waveguides are observed much more often during nighttime than during daytime.

  18. Shock formation characteristics in the low corona from type II radio bursts

    NASA Astrophysics Data System (ADS)

    Kouloumvakos, A.; Preka-Papadema, P.; Vourlidas, A.; Moussas, X.; Hillaris, A.; Tsitsipis, P.; Kontogeorgos, A.

    2013-09-01

    In this analysis we have identified the formation of coronal shock waves from 2007 to 2011, using as proxies the type II radio bursts from radio spectrograph ARTEMIS-IV and RSTN. For the 42 events we have identified, we combined data from STEREO, SOHO/LASCO ??? SDO with the characteristics of the composite radio spectra to investigate the properties of the type II formation with the associated flares and CMEs. From the timings between the flare, the CME onset, the HXR peak and the type II start, we grouped the type IIs into separate categories. We found that in most of the cases the type II radio burst starts at the flare maximum phase and particularly in 60% of the cases at the HXR maximum. All the characteristics of the type IIs obtained from their spectrum (duration, df, df/dt). We compared the computed velocities of the type IIs, using deferent density models, with the observed speeds of the CMEs from STEREO and SOHO/LASCO. Finally, from the composite radio spectra we associated the type II with the occurrence of other transient radio emissions such as, radio bursts type III or IV.

  19. Experimental study of the relationship between the propagation distance and the polarization characteristics of whistlers

    Microsoft Academic Search

    Toshimi Okada; Yoshihito Tanaka; Masashi Hayakawa; Akira Iwai; Shin Shimakura

    1983-01-01

    Wideband measurements were performed for VLF whistlers at Moshiri in Hokkaido in January, 1983 to investigate the relationship between polarization characteristics of whistlers and their propagation distance after ionosperic transmission in the earth-ionosphere waveguide. The phase differences of the two signals of whistlers detected by orthogonal loop antennas have been measured and the following results found: (1) the polarization of

  20. Complete Analysis of the Characteristics of Propagation into Photonic Crystal Fibers, by the Finite Element Method

    Microsoft Academic Search

    F. Brechet; J. Marcou; D. Pagnoux; P. Roy

    2000-01-01

    Using the finite element method, we propose an accurate vector analysis of the lowest electromagnetic modes of photonic crystal fibers. The likeness of their propagation characteristics to those of step index fibers is emphasized. Within the determined limits of a domain of validity, an equivalent step index fiber is defined. In addition, the single-mode broadband behavior of photonic crystal fibers

  1. Asymptotic methods of calculating the propagation of centimeter radio waves in the atmosphere in space-space paths

    NASA Astrophysics Data System (ADS)

    Gorbunov, M. E.; Lauritsen, K. B.

    2007-12-01

    Asymptotic methods of calculating the propagation of centimeter radio waves in a neutral atmosphere in space-space paths are considered. The methods are based on the technique of Fourier integral operators. The approximations that allow the representation of the corresponding operators as compositions of nonlinear coordinate changes, multiplications by reference signals, and Fourier transformations are constructed. The approximations are based on a technical procedure using a linearized canonical transform. This approach makes it possible to devise fast numerical algorithms. Numerical simulations are conducted with the use of realistic global gridded fields of meteorological parameters including the turbulence. The numerical simulations show high accuracy and efficiency of the proposed methods.

  2. Operational characteristics of a radio frequency ion-source

    Microsoft Academic Search

    A. K. Ganguly; H. Bakhru

    1963-01-01

    A radiofrequency type ion source using a 30 Mc\\/s oscillator was designed ; with co-axial magnetic field and its operational characteristics are measured, ; taking oscillator power, gas pressure, magnetic field, probe voltage, and canal ; geometry as independent parameters. From these graphs, correlations were made ; with the internal phenomena of the gas discharge and of ion extraction. A

  3. Investigation of the Radio Frequency Characteristics of CMOS Electrostatic Discharge Protection Devices

    E-print Network

    Anlage, Steven

    of CMOS and many other integrated circuit technologies is determined mainly by the electrical properties-like characteristics to shunt potentially harmful static charge away from thin gate-oxide insulators. These nonlinear, and a generalized approach to predicting radio-frequency effects in CMOS with electrostatic protection is introduced

  4. Enhancement of electromagnetic propagation through complex media for Radio Frequency Identification

    E-print Network

    Marti, Uttara P

    2005-01-01

    In this thesis, I present and examine the fundamental limitations involved in Radio Frequency Identification (RFID) as well as provide a means to improve reader-tag communication in ultra high frequency RFID systems. The ...

  5. Classical radio source propagating into outer H I disc in NGC 3801

    NASA Astrophysics Data System (ADS)

    Emonts, B. H. C.; Burnett, C.; Morganti, R.; Struve, C.

    2012-04-01

    We present observations of a large-scale disc of neutral hydrogen (H I) in the nearby Fanaroff-Riley type I (FR I) radio galaxy NGC 3801 with the Westerbork Synthesis Radio Telescope. The H I disc (34 kpc in diameter and with ?) is aligned with the radio jet axis. This makes NGC 3801 an ideal system for investigating the evolution of a small radio source through its host galaxy's cold interstellar medium (ISM). The large-scale H I disc is perpendicular to a known inner CO disc and dust lane. We argue that the formation history of the large-scale H I disc is in agreement with earlier speculation that NGC 3801 was involved in a past gas-rich galaxy-galaxy merger (although other formation histories are discussed). The fact that NGC 3801 is located in an environment of several H I-rich companions, and shows indications of ongoing interaction with the nearby companion NGC 3802, strengthens this possibility. The large amounts of ambient cold ISM, combined with X-ray results by Croston, Kraft & Hardcastle on the presence of overpressured radio jets and evidence for an obscuring torus, are properties that are generally not, or no longer, associated with more evolved FR I radio sources. We do show, however, that the H I properties of NGC 3801 are comparable to those of a significant fraction of nearby low-power compact radio sources, suggesting that studies of NGC 3801 may reveal important insight into a more general phase in the evolution of at least a significant fraction of nearby radio galaxies.

  6. Analysis of radio wave propagation for ISM 2.4 GHz Wireless Sensor Networks in inhomogeneous vegetation environments.

    PubMed

    Azpilicueta, Leire; López-Iturri, Peio; Aguirre, Erik; Mateo, Ignacio; Astrain, José Javier; Villadangos, Jesús; Falcone, Francisco

    2014-01-01

    The use of wireless networks has experienced exponential growth due to the improvements in terms of battery life and low consumption of the devices. However, it is compulsory to conduct previous radio propagation analysis when deploying a wireless sensor network. These studies are necessary to perform an estimation of the range coverage, in order to optimize the distance between devices in an actual network deployment. In this work, the radio channel characterization for ISM 2.4 GHz Wireless Sensor Networks (WSNs) in an inhomogeneous vegetation environment has been analyzed. This analysis allows designing environment monitoring tools based on ZigBee and WiFi where WSN and smartphones cooperate, providing rich and customized monitoring information to users in a friendly manner. The impact of topology as well as morphology of the environment is assessed by means of an in-house developed 3D Ray Launching code, to emulate the realistic operation in the framework of the scenario. Experimental results gathered from a measurement campaign conducted by deploying a ZigBee Wireless Sensor Network, are analyzed and compared with simulations in this paper. The scenario where this network is intended to operate is a combination of buildings and diverse vegetation species. To gain insight in the effects of radio propagation, a simplified vegetation model has been developed, considering the material parameters and simplified geometry embedded in the simulation scenario. An initial location-based application has been implemented in a real scenario, to test the functionality within a context aware scenario. The use of deterministic tools can aid to know the impact of the topological influence in the deployment of the optimal Wireless Sensor Network in terms of capacity, coverage and energy consumption, making the use of these systems attractive for multiple applications in inhomogeneous vegetation environments. PMID:25513820

  7. Analysis of Radio Wave Propagation for ISM 2.4 GHz Wireless Sensor Networks in Inhomogeneous Vegetation Environments

    PubMed Central

    Azpilicueta, Leire; López-Iturri, Peio; Aguirre, Erik; Mateo, Ignacio; Astrain, José Javier; Villadangos, Jesús; Falcone, Francisco

    2014-01-01

    The use of wireless networks has experienced exponential growth due to the improvements in terms of battery life and low consumption of the devices. However, it is compulsory to conduct previous radio propagation analysis when deploying a wireless sensor network. These studies are necessary to perform an estimation of the range coverage, in order to optimize the distance between devices in an actual network deployment. In this work, the radio channel characterization for ISM 2.4 GHz Wireless Sensor Networks (WSNs) in an inhomogeneous vegetation environment has been analyzed. This analysis allows designing environment monitoring tools based on ZigBee and WiFi where WSN and smartphones cooperate, providing rich and customized monitoring information to users in a friendly manner. The impact of topology as well as morphology of the environment is assessed by means of an in-house developed 3D Ray Launching code, to emulate the realistic operation in the framework of the scenario. Experimental results gathered from a measurement campaign conducted by deploying a ZigBee Wireless Sensor Network, are analyzed and compared with simulations in this paper. The scenario where this network is intended to operate is a combination of buildings and diverse vegetation species. To gain insight in the effects of radio propagation, a simplified vegetation model has been developed, considering the material parameters and simplified geometry embedded in the simulation scenario. An initial location-based application has been implemented in a real scenario, to test the functionality within a context aware scenario. The use of deterministic tools can aid to know the impact of the topological influence in the deployment of the optimal Wireless Sensor Network in terms of capacity, coverage and energy consumption, making the use of these systems attractive for multiple applications in inhomogeneous vegetation environments. PMID:25513820

  8. Propagation characteristics of the magnetostatic surface wave in the YBCO-YIG film-layered structure

    SciTech Connect

    Tsutsumi, M.; Fukusako, T.; Yoshida, S. [Kyoto Inst. of Tech. (Japan). Faculty of Engineering and Design] [Kyoto Inst. of Tech. (Japan). Faculty of Engineering and Design

    1996-08-01

    Propagation characteristics of the magnetostatic surface wave (MSSW) in a YBa{sub 2}Cu{sub 3}O{sub 7{minus}x} (YBCO)-yttrium iron garnet (YIG) multilayered structure are investigated. Effects of the superconductor on the MSSW are discussed with regard to the dispersion characteristics of both the phase and attenuation constants as a function of the air gap between YIG and YBCO, taking into consideration the magnetic line-width of the YIG film. It was found that the nonreciprocity of MSSW is enhanced significantly by the superconductivity and depends on the magnetic line-width of the YIG film. To examine the effect of a YBCO on the MSSW propagation, experiments are carried out using a commercially available YIG film. Magnetic losses at low temperature are briefly discussed with experimentally observed nonreciprocity.

  9. Millimeter-wave propagation characteristics and channel performance for urban-suburban environments

    NASA Astrophysics Data System (ADS)

    Violette, Edmond; Espeland, Richard; Allen, Kenneth C.

    1988-12-01

    Measurements were performed in an urban-suburban environment with narrow and wideband RF probes, which included millimeter wave frequencies, in order to study propagation characteristics for street level paths. The performance of the RF channels was evaluated in these environments for both line-of-sight and non-line-of sight paths and compares a model developed for line-of-sight paths to measurements taken in Denver, CO.

  10. Characteristics of wave propagation in piezoelectric bent rods with arbitrary curvature

    Microsoft Academic Search

    Qing-tian Deng; Song-nan Luo

    2011-01-01

    The wave propagation in the piezoelectric bend rods with arbitrary curvature is studied in this paper. Basic three-dimensional equations in an orthogonal curvilinear coordinate system (r,?,s) are established. The Bessel functions in radial co-ordinate and triangle series in the angular co-ordinate are used to describe the displacements and electrical potential. Characteristics of dispersion, distributions of displacements and electrical potential over

  11. Non-detection at Venus of High-Frequency Radio Signals Characteristic of Terrestrial Lightning

    NASA Technical Reports Server (NTRS)

    Gurnett, D. A.; Zarka, P.; Manning, R.; Kurth, W. S.; Hospodarsky, G. B.; Averkamp, T. F.; Kaiser, M. L.; Farrell, W. M.

    2001-01-01

    The detection of impulsive low-frequency (10 to 80 kHz) radio signals, and separate very-low-frequency (approx. 100 Hz) radio 'whistler' signals provided the first evidence for lightning in the atmosphere of Venus. Later, a small number of impulsive high- frequency (100 kHz to 5.6 MHz) radio signals, possibly due to lightning, were also detected. The existence of lightning at Venus has, however, remained controversial. Here we report the results of a search for high-frequency (0.125 to 16 MHz) radio signals during two close fly-bys of Venus by the Cassini spacecraft. Such signals are characteristic of terrestrial lightning, and are commonly heard on AM (amplitude-modulated) radios during thunderstorms. Although the instrument easily detected signals from terrestrial lightning during a later fly-by of Earth (at a global flash rate estimated to be 70/s, which is consistent with the rate expected for terrestrial lightning), no similar signals were detected from Venus. If lightning exists in the venusian atmosphere, it is either extremely rare, or very different from terrestrial lightning.

  12. The Coherer: With Simple Demonstrations of the Generation, Propagation and Detection of Radio Waves

    ERIC Educational Resources Information Center

    Mills, Allan

    2010-01-01

    A coherer is a bistable device based on metal filings loosely confined between solid metal electrodes. This granular material normally exhibits a very high electrical resistance (tens of kilohms), but passage of the high-frequency current generated by reception of a radio signal causes it to "cohere" into a comparatively low resistance condition…

  13. Enhanced MUF propagation of HF radio waves in the auroral zone

    NASA Astrophysics Data System (ADS)

    Milan, S. E.; Jones, T. B.; Warrington, E. M.

    1997-01-01

    Four high frequency propagation paths were monitored from a transmitter located within the polar cap by four receivers located variously within the polar cap and at sub-auroral latitudes. Of these paths, one was contained entirely within the polar cap at all times, two were trans-auroral at all times, and one varied from trans-auroral during the day to polar cap during the night. Fourteen frequencies within the HF band were transmitted each hour for the duration of two 24 day experimental campaigns during the summer of 1988 and the winter of 1989. From an analysis of the received signals the confidence of signal recognition and signal strength were determined. During geomagnetically undisturbed periods the propagation behaviour resembled that of mid-latitude paths. During geomagnetically disturbed times, however, night-time propagation occurred on frequencies up to and sometimes over 10 MHz above the undisturbed night-time MUF, for periods of 2 to 6 h. These features appeared on the trans-auroral paths only and were attributed to E region (and occasionally F region) enhancement by auroral precipitation. APEs (auroral E propagation events) occurred on over 50% of nights. The occurrence of APEs also coincided with ionospheric storm periods when the HF band available for propagation was otherwise significantly narrowed due to a depletion of the F region electron density.

  14. Characteristics of radio-frequency atmospheric pressure dielectric-barrier discharge with dielectric electrodes

    SciTech Connect

    Hussain, S., E-mail: shussain@uos.edu.pk, E-mail: shussainuos@yahoo.com; Qazi, H. I. A.; Badar, M. A. [Department of Physics, University of Sargodha, 40100 Sargodha (Pakistan)] [Department of Physics, University of Sargodha, 40100 Sargodha (Pakistan)

    2014-03-15

    An experimental investigation to characterize the properties and highlight the benefits of atmospheric pressure radio-frequency dielectric-barrier discharge (rf DBD) with dielectric electrodes fabricated by anodizing aluminium substrate is presented. The current-voltage characteristics and millisecond images are used to distinguish the ? and ? modes. This atmospheric rf DBD is observed to retain the discharge volume without constriction in ? mode. Optical emission spectroscopy demonstrates that the large discharge current leads to more abundant reactive species in this plasma source.

  15. Characteristics of radio-frequency atmospheric pressure dielectric-barrier discharge with dielectric electrodes

    NASA Astrophysics Data System (ADS)

    Hussain, S.; Qazi, H. I. A.; Badar, M. A.

    2014-03-01

    An experimental investigation to characterize the properties and highlight the benefits of atmospheric pressure radio-frequency dielectric-barrier discharge (rf DBD) with dielectric electrodes fabricated by anodizing aluminium substrate is presented. The current-voltage characteristics and millisecond images are used to distinguish the ? and ? modes. This atmospheric rf DBD is observed to retain the discharge volume without constriction in ? mode. Optical emission spectroscopy demonstrates that the large discharge current leads to more abundant reactive species in this plasma source.

  16. Radio propagation measurements at microwave frequencies for microcellular mobile and personal communications

    Microsoft Academic Search

    N. Amitay; R. S. Owens; R. S. Roman

    1989-01-01

    The design and results of a propagation experiment at 900 MHz and 11 GHz to characterize microcell channels at two distinct frequencies in various environments, from rural to dense urban, are presented. The measurements were made by transmitting a continuous-wave (CW) signal from a mobile source to a fixed base and recording the signal envelope variations as a function of

  17. Characteristics of sound propagation in shallow water over an elastic seabed with a thin cap-rock layer

    E-print Network

    Characteristics of sound propagation in shallow water over an elastic seabed with a thin cap 2012; revised 15 March 2013; accepted 7 May 2013) Measurements of low-frequency sound propagation over over a lay- ered elastic seabed with a shear wave speed comparable to but lower than the water

  18. Experimental study on pulse propagation characteristics at normal dispersion region in dispersion flatted fibers

    NASA Astrophysics Data System (ADS)

    Zheng, Hongjun; Liu, Shanliang; Wu, Chongqing; Yu, Huishan; Li, Xin; Wang, Weitao; Tian, Zhen

    2012-06-01

    Pulse propagation characteristics at normal-dispersion region in dispersion-flatted-fibers are experimentally investigated by employing the second-harmonic generation frequency-resolved optical gating (SHG-FROG) method. It is found that the experimental results are consistent with the theoretical prediction. The initial optical pulse with negative chirp is compressed for nonlinear effect in the normal-dispersion fiber, and it evolves into near Gaussian pulse. Temporal width of the optical pulse decreases with the increase of the input power and propagation distance. The output pulse width for small dispersion is less than that for great dispersion at the same input power. The spectrum of the output pulse is still symmetrical about the central wavelength, and is broadened with the increase of input power. The spectral width of the output pulse is much wider than the input spectral width.

  19. Statistical Analysis and Performance Evaluation for On-Body Radio Propagation With Microstrip Patch Antennas

    Microsoft Academic Search

    Akram Alomainy; Yang Hao; Abdus Owadally; Clive G. Parini; Yuri Nechayev; Costas C. Constantinou; Peter S. Hall

    2007-01-01

    On-body propagation channel measurements using two microstrip patch antennas for various links are presented and statistically analyzed. The attenuation attributed to factors such as the body, head and clothing are: 19.2, 13.0, and 1.7 dB, respectively, when measurement performed in the anechoic chamber. Measured cumulative distribution function (CDF) of data in the chamber and lab fits to lognormal distribution with

  20. Radio-frequency common-mode noise propagation model for power-line cable

    Microsoft Academic Search

    K. Y. See; P. L. So; A. Kamarul; E. Gunawan

    2005-01-01

    Electromagnetic-interference (EMI) radiation from a power-line communications (PLC) network has been a major concern for the widespread use of broadband PLC technology. It is also well known that the dominant radiation mode of the PLC network is common mode (CM) by nature. Therefore, for electromagnetic-compatibility planning purposes, knowledge of the CM noise propagation path of the power line in the

  1. On meteor-generated infrasound. [propagation characteristics during entry into earth atmosphere

    NASA Technical Reports Server (NTRS)

    Revelle, D. O.

    1976-01-01

    The characteristics of generation and propagation of infrasonic pressure waves excited during meteor entry into the earth's atmosphere are studied. Existing line source blast wave theory is applied to infrasonic airwave data from four bright fire-balls. It is shown that the strong shock behavior of the blast wave is confined to a cylinderical region with a radius proportional to the product of the meteor Mach number and its diameter. A description of the wave form far from the source is provided. Infrasonic data reported elsewhere are analyzed. All the results should be considered as preliminary, and additional work is under way to refine the estimates obtained.

  2. The Impact of Physical Layer Frontend Characteristics on Ultra-Wideband Radio

    Microsoft Academic Search

    Wasim Q. Malik; David J. Edwards; Christopher J. Stevens

    2005-01-01

    Ultra-wideband communications systems use signals with very large bandwidths and very low power-spectral densities to achieve high data-rate communications at short ranges. The frequency-dependent characteristics of system components at such large frequency ranges pose system design challenges not encountered in narrowband communications. This paper highlights some of the distortive effects on signal propagation introduced by transceiver frontend components, and their

  3. Dielectric Effect on the Radio-Frequency Characteristics of a Rectangular Waveguide Grating Traveling Wave Tube

    NASA Astrophysics Data System (ADS)

    Lu, Zhigang; Gong, Yubin; Wei, Yanyu; Wang, Wenxiang

    2006-08-01

    A new type of partial-dielectric-loaded rectangular waveguide grating slow-wave structure (SWS) for millimeter wave traveling wave tube (TWT) is presented in this paper. The radio-frequency characteristics including the dispersion properties, the longitudinal electric field distribution and the beam-wave coupling impedance of this structure are analyzed. The results show that the dispersion of the rectangular waveguide grating circuit is weakened, the phase velocity is reduced and the position of the maximum E z is basically invariant after partially filling the dielectric materials in the rectangular waveguide grating SWS. Although the coupling impedance decreases a little, it still keeps above 40 ?.

  4. Back-propagation operation for analog neural network hardware with synapse components having hysteresis characteristics.

    PubMed

    Ueda, Michihito; Nishitani, Yu; Kaneko, Yukihiro; Omote, Atsushi

    2014-01-01

    To realize an analog artificial neural network hardware, the circuit element for synapse function is important because the number of synapse elements is much larger than that of neuron elements. One of the candidates for this synapse element is a ferroelectric memristor. This device functions as a voltage controllable variable resistor, which can be applied to a synapse weight. However, its conductance shows hysteresis characteristics and dispersion to the input voltage. Therefore, the conductance values vary according to the history of the height and the width of the applied pulse voltage. Due to the difficulty of controlling the accurate conductance, it is not easy to apply the back-propagation learning algorithm to the neural network hardware having memristor synapses. To solve this problem, we proposed and simulated a learning operation procedure as follows. Employing a weight perturbation technique, we derived the error change. When the error reduced, the next pulse voltage was updated according to the back-propagation learning algorithm. If the error increased the amplitude of the next voltage pulse was set in such way as to cause similar memristor conductance but in the opposite voltage scanning direction. By this operation, we could eliminate the hysteresis and confirmed that the simulation of the learning operation converged. We also adopted conductance dispersion numerically in the simulation. We examined the probability that the error decreased to a designated value within a predetermined loop number. The ferroelectric has the characteristics that the magnitude of polarization does not become smaller when voltages having the same polarity are applied. These characteristics greatly improved the probability even if the learning rate was small, if the magnitude of the dispersion is adequate. Because the dispersion of analog circuit elements is inevitable, this learning operation procedure is useful for analog neural network hardware. PMID:25393715

  5. Back-Propagation Operation for Analog Neural Network Hardware with Synapse Components Having Hysteresis Characteristics

    PubMed Central

    Ueda, Michihito; Nishitani, Yu; Kaneko, Yukihiro; Omote, Atsushi

    2014-01-01

    To realize an analog artificial neural network hardware, the circuit element for synapse function is important because the number of synapse elements is much larger than that of neuron elements. One of the candidates for this synapse element is a ferroelectric memristor. This device functions as a voltage controllable variable resistor, which can be applied to a synapse weight. However, its conductance shows hysteresis characteristics and dispersion to the input voltage. Therefore, the conductance values vary according to the history of the height and the width of the applied pulse voltage. Due to the difficulty of controlling the accurate conductance, it is not easy to apply the back-propagation learning algorithm to the neural network hardware having memristor synapses. To solve this problem, we proposed and simulated a learning operation procedure as follows. Employing a weight perturbation technique, we derived the error change. When the error reduced, the next pulse voltage was updated according to the back-propagation learning algorithm. If the error increased the amplitude of the next voltage pulse was set in such way as to cause similar memristor conductance but in the opposite voltage scanning direction. By this operation, we could eliminate the hysteresis and confirmed that the simulation of the learning operation converged. We also adopted conductance dispersion numerically in the simulation. We examined the probability that the error decreased to a designated value within a predetermined loop number. The ferroelectric has the characteristics that the magnitude of polarization does not become smaller when voltages having the same polarity are applied. These characteristics greatly improved the probability even if the learning rate was small, if the magnitude of the dispersion is adequate. Because the dispersion of analog circuit elements is inevitable, this learning operation procedure is useful for analog neural network hardware. PMID:25393715

  6. Self-configurable radio receiver system and method for use with signals without prior knowledge of signal defining characteristics

    NASA Technical Reports Server (NTRS)

    Hamkins, Jon (Inventor); Simon, Marvin K. (Inventor); Divsalar, Dariush (Inventor); Dolinar, Samuel J. (Inventor); Tkacenko, Andre (Inventor)

    2013-01-01

    A method, radio receiver, and system to autonomously receive and decode a plurality of signals having a variety of signal types without a priori knowledge of the defining characteristics of the signals is disclosed. The radio receiver is capable of receiving a signal of an unknown signal type and, by estimating one or more defining characteristics of the signal, determine the type of signal. The estimated defining characteristic(s) is/are utilized to enable the receiver to determine other defining characteristics. This in turn, enables the receiver, through multiple iterations, to make a maximum-likelihood (ML) estimate for each of the defining characteristics. After the type of signal is determined by its defining characteristics, the receiver selects an appropriate decoder from a plurality of decoders to decode the signal.

  7. Characteristics of the propagation of radioactive pollutants near a radiation-hazardous object

    SciTech Connect

    Romanov, V.I.

    1995-09-01

    It is well known that the radiation effect of nuclear enterprises on the environment is due mainly to gas-aerosol emissions which emanate from the object in the form of a jet flow. A characteristic feature of the propagation of radioactive impurities near such structures is that they depend on the local thermal and wind conditions at the location of the source of contamination. Transferring directly the results of laboratory investigations of the propagation and diffusion of fluxes to objects in the environment and neglecting the peculiarities of the wind and thermal interference with the underlying surface and other buildings can lead to incorrect conclusions. In this paper, we examine two examples: (1) emissions through the plant stack or other ventilation system openings, and (2) leakage of radioactive pollutants into the reactor building and from there to the atmosphere. A mathematical description on each example is provided, and data on the Archimedes number for a convective jet is given as a function of the deflecting wind velocity.

  8. Experimental Study on Surge Propagation Characteristics of Rail and Lightning Overvoltages on Level Crossing

    NASA Astrophysics Data System (ADS)

    Arai, Hideki; Matsubara, Hiroji; Miyajima, Kiyotomi; Yokoyama, Shigeru; Sato, Kazutoshi

    Lightning protection measures are required for the railway signalling system because suspension and delays of trains due to lightnings may cause social confusion. Therefore, we carried out experiments on propagation characteristics of lightning surges along a rail, and injected a lightning surge current into the rail or wayside ground to raise their potentials, in order to measure the lightning overvoltages on a level crossing for the insulation design. There are no precedents that have carried out these experiments in the field until now. We could obtain the following results. (1) The surge impedance of the rail is 56? and the surge propagation velocity in the rail is 55m/?s. (2) The surge attenuation depends only on the duration of wave tail of the traveling lightning surge along the rail and decreases as the duration of wave tail becomes longer. (3) Flashovers may occur at the terminals in the equipment of the level crossing in case 1) a 2kA lightning surge current is directly injected into the rail, or 2) a 10kA lightning surge current is injected into the wayside ground at a vertical distance of 2m from the rail. (4) We can estimate the lightning overvoltages on the terminals in the equipment of the level crossing according to the vertical distance from the rail of the lighting stroke and the level of the stroke current.

  9. Propagation characteristics of waves upstream and downstream of quasi-parallel shocks

    NASA Technical Reports Server (NTRS)

    Krauss-Varban, D.; Omidi, N.

    1993-01-01

    The propagation characteristics of waves upstream and downstream of quasi-parallel shocks are investigated by using 2D hybrid simulations. At low Alfven Mach numbers, M(A) below about 2, the shock is initially associated with upstream phase-standing whistlers. At later times, backstreaming ions excite longer-wavelength whistlers via the right-hand resonant ion/ion instability. These waves propagate along the magnetic field at a group velocity no smaller than the upstream flow speed, so that the waves remain in the upstream region. At higher MA (above about 3), these waves are convected back into the shock, causing its reformation and downstream perturbations. Shock transmitted waves mode-convert into Alfven/ion-cyclotron waves which have a wave vector along the shock normal (pointing upstream) and convect downstream. The 2D simulation results confirm our earlier suggestion that the upstream waves should be field aligned, and that their convection into the downstream is associated with linear mode conversion into the Alfven/ion-cyclotron branch.

  10. The influence of meteoroid rotation on the diffraction characteristics of underdense radio-meteors

    NASA Astrophysics Data System (ADS)

    Novikov, G. G.; Pecina, P.; Ivanov, A. V.

    2004-02-01

    We discuss the problem of meteor plasma formation and consequently of radio-wave scattering from an ionized meteor trails produced by rotating meteoroids. The problem is solved under the following approximations: the meteoroid is represented by a cube, its rotation axis is perpendicular to the velocity vector, meteoroid deceleration can be neglected, the only acting ablation mechanism is the evaporation, the deionization effects are negligibly small. In this case the ambipolar diffusion approximation applies, and, supposing that the source of free electrons is known, the distribution of free electrons inside a trail, Ne(r, t), considered as a function of position and time, can be computed. It is shown that the electron distribution along a trail axis oscillates, which is not the case with respect to the radial distribution. The function Ne(r, t) found is then used for the solution of the problem of the scattering of radio-waves on the underdense-type trails produced by rotating particles. The values for amplitude-time as well as phase-time characteristics computed under the above assumptions differ only very slightly from those computed when meteoroid rotation is not taken into consideration.

  11. Study of propagation characteristics of very low latitude whistlers by means of three-dimensional ray-tracing computations

    NASA Astrophysics Data System (ADS)

    Ohta, Kenji; Nishimura, Yasuhiro; Kitagawa, Tomomi; Hayakawa, Masashi

    1997-04-01

    The propagation mechanism of very low latitude (geomagnetic latitudes of less than 10-15°) whistlers is poorly understood. There is a controversy on their propagation; some workers using the observational facts have suggested field-aligned propagation, but some theoretical (ray tracing) works have all indicated nonducted propagation. This paper reexamines the propagation characteristics of nonducted propagation, but we use three-dimensional ray tracing (different from previous works) for realistic ionosphere/magnetosphere models (the electron density profile with latitudinal and longitudinal gradients and the International Geomagnetic Reference Field (IGRF) magnetic field model instead of the conventional dipole model). By assuming small possible tilts (in the latitudinal and longitudinal direction) of the initial wave normal angle in the input southern hemisphere, we have found that it is possible for us to detect simultaneously, at a very low latitude position in the northern ionosphere, one-hop whistler rays started from slightly spaced locations in the south with different initial wave normal angles and that some of them can penetrate through the ionosphere, but some others cannot. On the basis of systematic analysis of important parameters, we come to the general conclusion that it is possible for us to find a closely spaced set of paths to reproduce the one-hop and three-hop whistlers in the north and to have the dispersion ratio of 1:3. The echo train whistlers, as were often observed by Hayakawa et al. [1990], are realized also by this nonducted propagation without any serious requirements.

  12. How cosmic ray electron propagation affects radio-far-infrared correlations in M 31 and M 33

    NASA Astrophysics Data System (ADS)

    Berkhuijsen, E. M.; Beck, R.; Tabatabaei, F. S.

    2013-10-01

    We investigate the effect of propagation of cosmic ray electrons (CRE) on the non-thermal (NTH; synchrotron)-far-infrared correlations in M 31 and M 33. The thermal (TH) and NTH emission components of the radio continuum emission at 1.4 GHz and one higher frequency are compared with dust emission from M 31 and M 33 using Spitzer data. In both galaxies the TH emission is linearly correlated with the emission from warm dust (24 ? m, 70 ? m), but the power laws of the NTH-FIR correlations have exponents b < 1 that increase with increasing frequency. Furthermore, the values of b for M 33 are significantly smaller (b ? 0.4) than those for M 31 (b ? 0.6). We interpret the differences in b as differences in the diffusion length of the CRE. We estimate the diffusion length in two ways: (1) by smoothing the NTH emission at the higher frequency until the correlation with NTH emission at 1.4 GHz has b = 1, and (2) by smoothing the TH emission until the correlation with the NTH emission at the same frequency has b = 1, assuming that the TH emission represents the source distribution of the CRE. Our smoothing experiments show that M 31 only has a thin NTH disc with a scale height of h = 0.3-0.4 kpc at 1.4 GHz, whereas M 33 has a similar thin disc as well as a thick disc with scale height hthick ? 2 kpc. In the thin discs, the (deprojected) diffusion length at 1.4 GHz is ?1.5 kpc, yielding a diffusion coefficient of ?2 × 1028 cm2 s-1. The structure, strength and regularity of the magnetic field in a galaxy as well as the existence of a thick disc determine the diffusion of the CRE, and hence, the power-law exponent of the NTH-FIR correlations.

  13. Energetic Particle Propagation in the Inner Heliosphere as Deduced from Low Frequency (less than 100 kHz) Observations of Type III Radio Bursts

    NASA Technical Reports Server (NTRS)

    Cane, H. V.; Erickson, W. C.

    2003-01-01

    Solar energetic particle (SEP) events are well-associated with solar flares. It is observed that the delay between the time of the flare and the first-arriving particles at a spacecraft increases with increasing difference between the flare longitude and the footpoint of the field line on which the spacecraft is located. This difference we call the "connection angle" and can be as large as approximately 120 deg. Recently it has been found that all SEP events are preceded by type III radio bursts. These bursts are plasma emission caused by the propagation of 2-50 keV flare electrons through the solar corona and into the solar wind. The drift of these type III radio bursts to lower and lower frequencies enables the propagation of the flare electrons to be traced from the Sun to about 1 AU. We have made an extensive analysis of the type III bursts associated with greater than 20 MeV proton events and find that, in most cases, the radio emission extends to the local plasma frequency when the energetic particles arrive within a few hours of the flare. We conclude that this emission at the lowest possible frequency is generated close to the spacecraft. We then use the time from when the burst started at the Sun to when it reached the local plasma frequency to infer the time it took the radio producing electrons to travel to the spacecraft. We find that these delay times are organized by the connection angle and correlate with the proton delay times. We also find that the differences between the radio delays at Wind and Ulysses are matched by differences in the relative arrival times of the energetic particles at the two spacecraft. The consistent timing between the relative arrival times of energetic electrons and protons and the start of the lowest frequency radio emissions suggests that the first arriving particles of both species are accelerated as part of the flare process and that they propagate to the spacecraft along trajectories similar to those of the lower energy flare electrons. To be detected by observers at locations distant from the nominal field lines originating in the flaring regions the particles must undergo lateral transport. The continuity of the radio bursts suggests that the cross-field transport may occur in the interplanetary medium.

  14. Generation and Propagation Characteristics of Dual-Band Chorus Emissions Observed by Geotail

    NASA Astrophysics Data System (ADS)

    Yagitani, S.; Habagishi, T.; Mori, S.; Omura, Y.; Kojima, H.

    2012-12-01

    We analyze the generation and propagation characteristics of chorus emissions observed by the wave form capture (WFC) and the sweep frequency analyzer (SFA) onboard the Geotail spacecraft in the dayside outer magnetosphere (L from 9 to 10). We examine any observational evidence, which may validate the nonlinear growth theory of the chorus emissions [1]. In the nonlinear growth theory a rising-tone element is initially generated continuously in the frequency range from 0.1 to 0.7 fce, where fce is the gyrofrequency in the generation region. Because of the nonlinear damping mechanism the rising-tone element is separated into upper and lower bands at half the local gyrofrequency (1/2 fce) through propagation [2]. As the rising-tone emissions are generated in the minimum-B region and propagate toward the larger-B regions along the geomagnetic field line, the upper cutoff of the lower-band chorus corresponds to 1/2 fce in the generation region, and the lower cutoff of the upper-band chorus corresponds to 1/2 fce at the observation point. In this study, we analyze the SFA spectrum data (consecutively over several hours) and WFC waveform data (several seconds) of the dual-band chorus emissions observed by Geotail. As a result, it is found that the upper cutoff of the lower-band chorus coincides with 1/2 fce at the minimum-B region estimated from the geomagnetic field line connecting to the Geotail position by using the Tsyganenko geomagnetic field model (TS04 model), whereas the lower cutoff of the upper-band chorus coincides with 1/2 fce locally at the observation point. We also examine the amplitude of a rising-tone emission using the WFC waveform data on the basis of the nonlinear growth theory. The amplitude at the generation region is estimated from the observed frequency sweep rate of the emission, and the nonlinear growth of the amplitude through propagation toward the observation point is calculated from the nonlinear growth rate, which is found consistent with the observed amplitude. We will also discuss the observational evidence for the threshold amplitudes and the optimum amplitudes required for triggering rising-tone chorus emissions in the generation region. [1] Omura Y., Y. Katoh and D. Summers (2008), Theory and simulation of the generation of whistler-mode chorus, J. Geophys. Res., 113, A04223, doi:10.1029/2007JA012622. [2] Omura Y., M. Hikishima, Y. Katoh, D. Summers, and S. Yagitani (2009), Nonlinear mechanisms of lower-band and upper-band VLF chorus emissions in the magnetosphere, J.Geophys. Res., 114, A07217, doi:10.1029/2009JA014206. [3] Omura Y., and D. Nunn (2011), Triggering process of whistler mode chorus emissions in the magnetosphere, J. Geophys. Res., 116, A05205, doi:10.1029/2010JA016280.

  15. Propagation Characteristics of Leaky Lamb Wavesin Layered Substrate and Operation Performances of Interdigital Transducer

    NASA Astrophysics Data System (ADS)

    Fujita, Takeshi; Toda, Kohji

    Propagation characteristics of seven lowest modes of leaky Lamb waves in a layered substrate composedof a piezoelectric ceramic plate and an acrylic plate, under the condition of a liquid-solid boundaryat the acrylic plate side, are described in the relationshipwith operation performances of an interdigital transducer (IDT) for underwater ultrasound. The IDT operates effectively for radiating or detecting via a mode conversionfrom the leaky Lamb wave to a longitudinal wave in a liquid. The incorporation of a layered substrate is useful for multiple-modes operations with higher transducer efficiencies, while retaining sufficient mechanical strength. It is noticeable that the cross points of the velocity curves of the leaky Lamb wave modes and the longitudinal wave modes in two kinds of thin plates for the layered substrate are unique for the transducer operations. The transducer operations are examined in the construction of a liquid delay line. The transducers designed for operating on the cross points of three modes are well explained in comparisonbetween the calculated and experimental results.

  16. Guided radio-wave propagation in the equatorial ionosphere according to the Intercosmos-19 and Alouette/ISIS satellites

    NASA Astrophysics Data System (ADS)

    Karpachev, Alexander; Zhbankov, Gennadii; Telegin, Viktor; Kuleshova, Valentina

    In addition to normal vertical-incident ionogram traces, strongly remote (up to 2000 km), traces of HF-radio-signal reflections observed on topside-sounder ionograms of the Interkosmos-19 satellite obtained in the equatorial ionosphere are presented. Such traces are connected with waveguides (ducts). These waveguides are field-aligned irregularities of ionospheric plasma with electron density depletion of a few percent and cross-field dimension of a few to several kilometers. Ray tracing confirms this supposition and allows an estimate of the typical parameters of the waveguides. The waveguide traces usually start at the cutoff frequency of the main trace. However, sometimes they begin at much lower frequencies which indicate the waveguides are located in plasma bubbles. Only one ducted trace is usually observed on the Interkosmos-19 ionograms; a second conjugate trace is rarely recorded. Waveguides are observed at all heights of Interkosmos-19 (500-1000 km) inside the equatorial anomaly region (from -40 to +40 degrees DipLat). Ducted-echo characteristics observed with the Interkosmos-19 are different from those observed earlier with the Alouette and ISIS satellites. This difference is discussed. It is shown that the ionospheric plasma irregularities responsible for the waveguides are observed much more often during nighttime than during daytime.

  17. Static current-voltage characteristics for radio-frequency induction discharge

    SciTech Connect

    Budyansky, A.; Zykov, A. [Kharkov Univ. (Ukraine). Scientific Center of Physical Technologies

    1995-12-31

    The aim of this work was to obtain experimentally such characteristic of Radio-Frequency Induction Discharge (RFID) that can play the role of its current-voltage characteristic (CVC) and to explain the nature of current and voltage jumps arising in RF coils at exciting of discharge. Experiments were made in quartz 5.5, 11, 20 cm diam tubes with outer RF coil at pressures 10--100 mTorr, at frequency 13.56 MHz and discharge power to 500 W. In case of outer coil as analogue of discharge voltage it`s convenient to use the value of the RF voltage U{sub R}, induced around outer perimeter of discharge tube. It is evident that current and voltage jumps arising at exciting of discharge are due to low output resistance of standard generators and negative slope of initial part of CVC. Three sets of such dependencies for different pressures were obtained for each diameter of tubes. The influence of different metal electrodes placed into discharge volume on CVC`s shape has been studied also. Experimental results can explain the behavior of HFI discharge as a load of RF generator and give data for calculation of RF circuit.

  18. Effect of the initial pressure on the characteristics of the flame propagation in hydrogen-propane-air mixtures

    NASA Astrophysics Data System (ADS)

    Cheng, Guanbing; Bauer, Pascal; Zitoun, Ratiba

    2014-08-01

    This paper is aimed at an experimental investigation on effects of initial pressure on flame propagation characteristics of binary fuels hydrogen-propane-air mixtures at room temperature. The experiments are performed in a square channel equipped with perforated orifice obstacles. Four initial pressures are examined. Based on pressure transducers along the channel, the flame velocity, maximum pressure of the front peak and characteristic distances are measured. Successive stages are observed as flame propagates: (i) a velocity increase at the beginning, (ii) a velocity equal to the sound speed of combustion products and (iii) a decrease of the velocity. When the initial pressure is more important, the flame velocity and the maximal pressure of the front peak are higher, which yields a shorter characteristic distance of flame propagation. By means of a Schlieren photography technique, the physical mechanisms of flame propagation are identified in its initial stage. The physical mechanisms such as flame surface area increase and combustion product expansion as well as delayed combustion between two adjacent plates are responsible for flame acceleration upon its initial stage. The oscillations of the centerline flame velocity are due to the constrained-expanded structure of flow in reactants ahead of flame when it crosses the plates.

  19. Measurements and Modeling of Basic Propagation Characteristics for Intra-Device Communications at 60 GHz and 300 GHz

    NASA Astrophysics Data System (ADS)

    Kürner, Thomas; Fricke, Alexander; Rey, Sebastian; Le Bars, Philippe; Mounir, Achir; Kleine-Ostmann, Thomas

    2015-02-01

    Multi Gigabit wireless links using millimeter or sub millimeter waves have become of interest to replace wired connections within devices. In order to develop and simulate the corresponding systems, propagation and channel models for intra-device environments are required. This paper describes first results from measurement campaigns carried out at 60 GHz and 300 GHz in such environments. In a first step reflection and transmission properties of typical plastic materials used within devices have been measured and modeled using the Transfer Matrix Method. In a second step propagation characteristics in wave-guide like structures have been measured and modeled using ray tracing.

  20. Error propagation in time-dependent probability of occurrence for characteristic earthquakes in Italy

    NASA Astrophysics Data System (ADS)

    Peruzza, Laura; Pace, Bruno; Cavallini, Fabio

    2010-01-01

    Time-dependent models for seismic hazard and earthquake probabilities are at the leading edge of research nowadays. In the framework of a 2-year national Italian project (2005-2007), we have applied the Brownian passage time (BPT) renewal model to the recently released Database of Individual Seismogenic Sources (DISS) to compute earthquake probability in the period 2007-2036. Observed interevent times on faults in Italy are absolutely insufficient to characterize the recurrence time. We, therefore, derived mean recurrence intervals indirectly. To estimate the uncertainty of the results, we resorted to the theory of error propagation with respect to the main parameters: magnitude and slip rate. The main issue concerned the high variability of slip rate, which could hardly be reduced by exploiting geodetic constraints. We did some validation tests, and interesting considerations were derived from seismic moment budgeting on the historical earthquake catalog. In a time-dependent perspective, i.e., when the date of the last event is known, only 10-15% of the 115 sources exhibit a probability of a characteristic earthquake in the next 30 years higher than the equivalent Poissonian probabilities. If we accept the Japanese conventional choice of probability threshold greater than 3% in 30 years to define “highly probable sources,” mainly intermediate earthquake faults with characteristic M < 6, having an elapsed time of 0.7-1.2 times the recurrence interval are the most “prone” sources. The number of highly probable sources rises by increasing the aperiodicity coefficient (from 14 sources in the case of variable ? ranging between 0.22 and 0.36 to 31 sources out of 115 in the case of an ? value fixed at 0.7). On the other hand, in stationary time-independent approaches, more than two thirds of all sources are considered probabilistically prone to an impending earthquake. The performed tests show the influence of the variability of the aperiodicity factor in the BPT renewal model on the absolute probability values. However, the influence on the relative ranking of sources is small. Future developments should give priority to a more accurate determination of the date of the last seismic event for a few seismogenic sources of the DISS catalog and to a careful check on the applicability of a purely characteristic model.

  1. Remote sensing and modeling of lightning caused long recovery events within the lower ionosphere using VLF/LF radio wave propagation

    NASA Astrophysics Data System (ADS)

    Schmitter, E. D.

    2014-11-01

    On the 4 November 2012 at 3:04:27 UT a strong lightning in the midst of the North Sea affected the propagation conditions of VLF/LF transmitter radio signals from NRK (Iceland, 37.5 kHz) and GBZ (UK, 19.58 kHz) received at 5246° N 8° E (NW Germany). The amplitude and phase dips show a recovery time of 6-12 min pointing to a LOng Recovery Early VLF (LORE) event. Clear assignment of the causative return stroke in space and time was possible with data from the WWLLN (Worldwide Lightning Location Network). Based on a return stroke current model the electric field is calculated and an excess electron density distribution which decays over time in the lower ionosphere is derived. Ionization, attachment and recombination processes are modeled in detail. Entering the electron density distribution in VLF/LF radio wave propagation calculations using the LWPC (Long Wavelength Propagation Capability) code allows to model the VLF/LF amplitude and phase behavior by adjusting the return stroke current moment. The results endorse and quantify the conception of lower ionosphere EMP heating by strong - but not necessarily extremely strong - return strokes of both polarities.

  2. Performance evaluation of wireless multi-hop networks with directional antennas in an indoor radio propagation channel

    Microsoft Academic Search

    Ximing Huang; Osamu Muta; Hiroshi Furukawa

    2012-01-01

    Wireless backhaul systems have been considered as a promising candidate of beyond 3G wireless broadband system for mobile communications. The achievable transmission performance over radio relay channel depends on antenna directivity and radiation patterns of each antenna element. To improve the transmission performance and keep radio relay channel in an acceptable condition, it is effective to control the antenna directivity

  3. Multi-Band (K- Q- and E-Band) Multi-Tone Millimeter-Wave Frequency Synthesizer for Radio Wave Propagation Studies

    NASA Technical Reports Server (NTRS)

    Simons, Rainee N.; Wintucky, Edwin G.

    2014-01-01

    This paper presents the design and test results of a multi-band multi-tone millimeter-wave frequency synthesizer, based on a solid-state frequency comb generator. The intended application of the synthesizer is in a space-borne transmitter for radio wave atmospheric studies at K-band (18 to 26.5 GHz), Q-band (37 to 42 GHz), and E-band (71 to 76 GHz). These studies would enable the design of robust multi-Gbps data rate space-to-ground satellite communication links. Lastly, the architecture for a compact multi-tone beacon transmitter, which includes a high frequency synthesizer, a polarizer, and a conical horn antenna, has been investigated for a notional CubeSat based space-to-ground radio wave propagation experiment.

  4. Galileo radio science investigations

    Microsoft Academic Search

    H. T. Howard; V. R. Eshleman; D. P. Hinson; A. J. Kliore; G. F. Lindal; R. Woo; M. K. Bird; H. Volland; P. Edenhoffer; M. Paetzold; H. Porsche

    1992-01-01

    The radio science investigations planned for Galileo's 6-year flight to and 2-year orbit of Jupiter use as their instrument the dual-frequency radio system on the spacecraft operating in conjunction with various US and German tracking stations on Earth. The planned radio propagation experiments are based on measurements of absolute and differential propagation time delay, differential phase delay, Doppler shift, signal

  5. Experimental demonstration of propagation characteristics of mid-infrared photonic crystal waveguides in silicon-on-sapphire.

    PubMed

    Zou, Yi; Chakravarty, Swapnajit; Wray, Parker; Chen, Ray T

    2015-03-01

    We provide the first experimental demonstration of optical transmission characteristics of a W1 photonic crystal waveguide in silicon on sapphire at mid infrared wavelength of 3.43 ?m. Devices are studied as a function of lattice constant to tune the photonic stop band across the single wavelength of the source laser. The shift in the transmission profile as a function of temperature and refractive index is experimentally demonstrated and compared with simulations. In addition to zero transmission in the stop gap, propagation losses less than 20 dB/cm are observed for group indices greater than 20 below the light line while more than 300 dB/cm propagation losses are observed above the light line, characteristic of the waveguiding behavior of photonic crystal line defect modes. PMID:25836916

  6. Simulation of Effervescent Atomization and Nanoparticle Characteristics in Radio Frequency Suspension Plasma Spray

    NASA Astrophysics Data System (ADS)

    Xiong, Hong-Bing; Qian, Li-Juan; Lin, Jian-Zhong

    2012-03-01

    In this paper, a comprehensive model was developed to investigate the suspension spray for a radio frequency (RF) plasma torch coupled with an effervescent atomizer. Firstly, the RF plasma is simulated by solving the thermo-fluid transport equations with electromagnetic Maxwell equation. Secondly, primary atomization of the suspension is solved by a proposed one-dimensional breakup model and validated with the experimental data. Thirdly, the suspension droplets and discharged nanoparticles are modeled in Lagrangian manner, to calculate each particle tracking, acceleration, heating, melting and evaporation. Saffman lift force, Brownian force and non-continuum effect are considered for nanoparticle momentum transfer, as well as the effects of evaporation on heat transfer. This model predicts the nanoparticle trajectory, velocity, temperature and size in the RF suspension plasma spray. Effects of the torch and atomizer operating conditions on the particle characteristics are investigated. Such operating conditions include gas-to-liquid flow ratio, atomizer orifice diameter, injection pressure, power input level, plasmas gas flow rate, and powder material. The statistical distributions for the multiple particles are also discussed for different cases.

  7. Analysis of uncompensated Langmuir probe characteristics in radio-frequency discharges revisited

    NASA Astrophysics Data System (ADS)

    Oksuz, L.; Soberón, F.; Ellingboe, A. R.

    2006-01-01

    Measurements of the electron temperature, plasma density, and floating and plasma potentials with Langmuir probes in radio-frequency discharges often represent a challenge due to rf oscillations of the plasma potential. These oscillations distort the probe characteristic, resulting in wrong estimates of the plasma parameters. Both active and passive rf compensation methods have previously been used to eliminate rf fluctuation effects on the electron current drawn by an electrostatic probe. These effects on an uncompensated probe have been theoretically and experimentally studied by Garscadden and Emeleus [Proc. Phys. Soc. London 79, 535 (1962)], Boschi and Magistrelli [Nuovo Cimento 29, 487 (1963)], and Crawford [J. Appl. Phys. 34, 1897 (1963)]. They have shown theoretically that, assuming a Maxwellian distribution and sinusoidal plasma-potential oscillation, the electron temperature can be deduced directly from an uncompensated Langmuir probe trace, by taking the natural logarithm of the electron current. It is the purpose of this paper to bring back the attention onto this result, which shows that under certain discharge conditions it is not necessary to build any rf compensation in a Langmuir probe system. Here we present and reference experimental data found on the literature which support this result. Also computational data are presented.

  8. Connecting radio variability to the characteristics of gamma-ray blazars

    E-print Network

    Richards, Joseph L; Max-Moerbeck, Walter; Pavlidou, Vasiliki; Pearson, Timothy J; Readhead, Anthony C S

    2013-01-01

    We present results from four years of twice-weekly 15 GHz radio monitoring of about 1500 blazars with the Owens Valley Radio Observatory 40 m telescope. Using the intrinsic modulation index to measure variability amplitude, we find that, with $>/!6/sigma$ significance, the radio variability of radio-selected gamma-ray-loud blazars is stronger than that of gamma-ray-quiet blazars. Our extended data set also includes at least 21 months of data for all AGN with `clean' associations in the Fermi Large Area Telescope First AGN catalogue, 1LAC. With these additional data we examine the radio variability properties of a gamma-ray-selected blazar sample. Within this sample, we find no evidence for a connection between radio variability amplitude and optical classification. In contrast, for our radio-selected sample we find that the BL Lac object subpopulation is more variable than the flat spectrum radio quasar (FSRQ) subpopulation. Radio variability is found to correlate with the synchrotron peak frequency, with low...

  9. Characteristics of the SAR distributions in a head exposed to electromagnetic fields radiated by a hand-held portable radio

    Microsoft Academic Search

    Soichi Watanabe; H. Taki; Toshio Nojima; Osamu Fujiwara

    1996-01-01

    Presents characteristics of the specific absorption rate (SAR) distributions calculated by the finite-difference time-domain (FDTD) method using a heterogeneous and realistic head model and a realistic hand-held portable radio model. The difference between the SAR distributions produced by a 1\\/4-wavelength monopole antenna and those produced by a 1\\/2-wavelength dipole antenna is investigated. The dependence of the maximum local SAR on

  10. Characteristics of layers, waves and turbulence in the atmosphere and ionosphere as estimated by GPS space radio-holography

    NASA Astrophysics Data System (ADS)

    Pavelyev, Alexander; Gubenko, Vladimir; Matyugov, Stanislav; Pavelyev, Alexey

    The spatial, seasonal and geographical distrubutions of the intensity of layers, turbulence and internal waves at different altitudes in the atmosphere and ionosphere of the Earth are presented. The results have been obtained on the base of locality principle using a new phase acceleration-intensity method for analysis of the GPS radio occultation signals. This methodology has been applied to mesearements of the inclination and altitude of ionospheric layers. Obtained information has been used for estimation of the front orientation, internal frequency and phase speed of the internal waves in the ionosphere and neutral atmosphere. A new index of the ionospheric activity as measured from the phase of radio waves passed through the ionosphere is introduced and its high correlation with S4 scintillation index is established. This correlation indicates the significant influence of ionospheric layers on variations of characteristics of radio waves in transionospheric communication links. Specially for the troposphere the geographical distribution of the weak total absorption (about of 1-2 db) of the radio waves at GPS frequencies in the Earth atmosphere corresponding to influence of the oxygen and water vapor in the troposphere is measured with accuracy better than 0.1 db. Obtained results expanded the applicable domain of the GPS space radio-holography for global investigation of the natural processes in the atmosphere and ionosphere as function of solar activity and space weather effects. The new phase acceleration-intensity method is also a basic tool which can be applied for data analysis of future planetary radio occultation missions

  11. Characteristics pertinent to propagation of pulsating pressure in the channels of turbine machines

    NASA Astrophysics Data System (ADS)

    Liu, Hong; Chen, Zuoyi

    2007-01-01

    A new model describing the propagation of the pressure pulsations in the intricately shaped channels of turbine machines is presented. The proposed model was successfully used to analyze two emergency events: a failure of a steam turbine’s cast diaphragm and a failure of a rocket engine’s oxygen pump booster stage.

  12. Study on fatigue crack propagation characteristics around welded joint interface in complexed conditions

    Microsoft Academic Search

    Akihiko Ota; Naoyuki Suzuki; Yoshio Maeda; Toshio Mawari; Saburo Matsuoka; Satoshi Nishijima

    1993-01-01

    Marine structures are often constructed by welding, and they are subject to repeated loading such as waves and mechanical vibrations which can create fatigue cracks and consequently break the structures. Fatigue crack propagation properties of welded joints are studied under random loading in the air, synthetic sea water, and compressive cycling. It was found that the most crucial factor that

  13. Model of interaction between decameter-decimenter radio waves and a strongly inhomogeneous mid-latitude ionosphere

    Microsoft Academic Search

    V. A. Alimov; A. V. Rakhlin; F. I. Vybornov

    1997-01-01

    A model of decameter-decimeter radio wave propagation in a strongly inhomogeneous mid-latitude ionosphere is constructed using\\u000a a modified method of radio wave refractive scattering. The model establishes the relationship between the basic statistical\\u000a radio wave characteristics and the turbulence parameters of the upper ionosphere. Different aspects of the theory of radio\\u000a wave refractive scattering are considered in application to the

  14. Propagation characteristics of nighttime mesospheric and thermospheric waves observed by optical mesosphere thermosphere imagers at middle and low latitudes

    NASA Astrophysics Data System (ADS)

    Shiokawa, K.; Otsuka, Y.; Ogawa, T.

    2009-04-01

    We review measurements of nighttime atmospheric/ionospheric waves in the upper atmosphere in Japan, Indonesia, and Australia, using all-sky airglow imagers of optical mesosphere thermosphere imagers (OMTIs). The imagers observe two-dimensional patterns of airglow emissions from oxygen (wavelength: 557.7 nm) and hydroxyl (OH) (near-infrared band) in the mesopause region (80-100 km) and from oxygen (630.0 nm) in the thermosphere/ionosphere (200-300 km). Several statistical studies were done to investigate propagation characteristics of small-scale (less than 100 km) gravity waves in the mesopause region and medium-scale traveling ionospheric disturbances (MSTIDs, ˜100-1,000 km) in the thermosphere/ionosphere. Clear seasonal variations of occurrence and propagation directions were reported for these waves. The propagation directions in the mesopause region are controlled by wind filtering, ducting processes and relative location to the wave sources in the troposphere. Poleward-propagating waves tend to be observed in the summer in the mesopause region at several stations, suggesting that mesospheric gravity waves are generated by intense convective activity in the equatorial troposphere. On the other hand, systematic equatorward and westward motions were observed for all seasons for nighttime MSTIDs in the midlatitude ionosphere with geomagnetic conjugacy between the northern and southern hemispheres. Ionospheric instabilities may play important role for the generation and propagation of these MSTIDs. We also give an example of simultaneous observation of quasi-periodic southward-moving waves in the mesopause region and in the thermosphere at the geographic equator. From these results, we discuss mean wind acceleration by mesospheric gravity waves and penetration of gravity waves from the mesosphere to the thermosphere.

  15. ESTABLISHMENT OF BESNOITIA DARLINGI FROM OPOSSUMS (DIDELPHIS VIRGINIANA) IN EXPERIMENTAL INTERMEDIATE AND DEFINITIVE HOSTS, PROPAGATION IN CELL CULTURE, AND DESCRIPTION OF ULTRASTRUCTURAL AND GENETIC CHARACTERISTICS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Besnoitia darlingi from naturally infected opossums (Didelphis virginiana) from Mississippi, USA, was propagated experimentally in mice, cats, and cell culture and was characterised according to ultrastructural, genetic, and life-history characteristics. Cats fed tissue cysts from opossums ...

  16. Propagation Characteristics of Finite Ground Coplanar Waveguide on Si Substrates With Porous Si and Polyimide Interface Layers

    NASA Technical Reports Server (NTRS)

    Ponchak, George E.; Itotia, Isaac K.; Drayton, Rhonda Franklin

    2003-01-01

    Measured and modeled propagation characteristics of Finite Ground Coplanar (FGC) waveguide fabricated on a 15 ohm-cm Si substrate with a 23 micron thick, 68% porous Si layer and a 20 micron thick polyimide interface layer are presented for the first time. Attenuation and effective permittivity as function of the FGC geometry and the bias between the center conductor and the ground planes are presented. It is shown that the porous Si reduces the attenuation by 1 dB/cm compared to FGC lines with only polyimide interface layers, and the polyimide on porous silicon demonstrates negligible bias dependence.

  17. Interfacial fracture characteristic and crack propagation of thermal barrier coatings under tensile conditions at elevated temperatures

    Microsoft Academic Search

    W. G. Mao; C. Y. Dai; L. Yang; Y. C. Zhou

    2008-01-01

    Thermal barrier coatings (TBCs) have been extensively used in aircraft engines for improved durability and performance for\\u000a more than fifteen years. In this paper, thermal barrier coating system with plasma sprayed zirconia bonded by a MCrAlY layer\\u000a to SUS304 stainless steel substrate was performed under tensile tests at 1000°C. The crack nucleation, propagation behavior\\u000a of the ceramic coatings in as

  18. Propagation characteristics of 20/30 GHz links with a 40 deg masking angle

    NASA Technical Reports Server (NTRS)

    Davarian, Faramaz; Kantak, Anil V.; Le, Choung

    1994-01-01

    An effective means of reducing Ka-band propagation loss is the use of high elevation angle paths, i.e., a large masking angle, between earth stations and the space platform. Experimental data have shown that the signal loss associated with most atmospheric effects is inversely proportional to sin(theta), where theta denotes the path elevation angle. A large masking angle and a generous link margin are the primary tools used in the Teledesic Corporation network to minimize atmospheric-related signal outages. This report documents the results of a study sponsored by Teledesic Corporation to characterize the effect of radiowave propagation on Teledesic's links. The recent Olympus campaign in Europe and the U.S. has provided new information that is not included. Therefore, CCIR recommendations and NASA Propagation Handbook models constitute the base of this study, and, when applicable, data from other sources have been used to improve the predictions. Furthermore, attention has been given to data from the Olympus campaign. The effects investigated during this study include gas, rain, fog, sand, and cloud attenuation; diversity gain; scintillation; and depolarization.

  19. Acoustic propagation and atmosphere characteristics derived from infrasonic waves generated by the Concorde.

    PubMed

    Le, Pichon Alexis; Garcés, Milton; Blanc, Elisabeth; Barthélémy, Maud; Drob, Doug P

    2002-01-01

    Infrasonic signals generated by daily supersonic Concorde flights between North America and Europe have been consistently recorded by an array of microbarographs in France. These signals are used to investigate the effects of atmospheric variability on long-range sound propagation. Statistical analysis of wave parameters shows seasonal and daily variations associated with changes in the wind structure of the atmosphere. The measurements are compared to the predictions obtained by tracing rays through realistic atmospheric models. Theoretical ray paths allow a consistent interpretation of the observed wave parameters. Variations in the reflection level, travel time, azimuth deviation and propagation range are explained by the source and propagation models. The angular deviation of a ray's azimuth direction, due to the seasonal and diurnal fluctuations of the transverse wind component, is found to be approximately 5 degrees from the initial launch direction. One application of the seasonal and diurnal variations of the observed phase parameters is the use of ground measurements to estimate fluctuations in the wind velocity at the reflection heights. The simulations point out that care must be taken when ascribing a phase velocity to a turning height. Ray path simulations which allow the correct computation of reflection heights are essential for accurate phase identifications. PMID:11837968

  20. The AN\\/GSC10 (KATHRYN) Variable Rate Data Modem for HF Radio

    Microsoft Academic Search

    M. Zimmerman; A. Kirsch

    1967-01-01

    The AN\\/GSC-10 (KATHRYN) is a new modem equipment for digital data transmission on HF radio circuits. Its unique modulation technique provides a wide range of signal redundancy and data rate to allow optimum performance over the correspondingly wide range of propagation conditions characteristic of HF radio. Efficient detection is achieved at all levels of redundancy by utilizing a fully coherent

  1. Modelling Radio-Wave Propagation in Buildings Solving 19th Century Physics with 21st Century Computers

    E-print Network

    Sun, Jing

    -wave propagation is governed by Maxwell's equations (formulated by James Clerk Maxwell in 1861). These equations, analytical solutions to Maxwell's equations are difficult, if not impossible, to obtain for anything other numerical solutions to Maxwell's equations. Contributions of this Research This research focuses on applying

  2. Performance of UWB Impulse Radio With Planar Monopoles Over On-Human-Body Propagation Channel for Wireless Body Area Networks

    Microsoft Academic Search

    Yue Ping Zhang; Qiang Li

    2007-01-01

    Ultrawideband (UWB) is a promising technology for wireless body area networks (WBANs). This paper studied the impacts of 3.1-10.6 GHz on-human-body UWB channel on the impulse radio WBAN system. A performance evaluation method is presented for the realistic UWB WBAN systems, which observes the waveform distortion along the signal path. The measurement and characterization of the 3.1-10.6 GHz on-human-body UWB

  3. A BROKEN SOLAR TYPE II RADIO BURST INDUCED BY A CORONAL SHOCK PROPAGATING ACROSS THE STREAMER BOUNDARY

    SciTech Connect

    Kong, X. L.; Chen, Y.; Li, G.; Feng, S. W.; Song, H. Q.; Jiao, F. R. [Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment, School of Space Science and Physics, Shandong University at Weihai, Weihai 264209 (China); Guo, F., E-mail: yaochen@sdu.edu.cn [Department of Planetary Sciences and Lunar and Planetary laboratory, University of Arizona, Tucson, AZ 85721 (United States)

    2012-05-10

    We discuss an intriguing type II radio burst that occurred on 2011 March 27. The dynamic spectrum was featured by a sudden break at about 43 MHz on the well-observed harmonic branch. Before the break, the spectrum drifted gradually with a mean rate of about -0.05 MHz s{sup -1}. Following the break, the spectrum jumped to lower frequencies. The post-break emission lasted for about 3 minutes. It consisted of an overall slow drift which appeared to have a few fast-drift sub-bands. Simultaneous observations from the Solar TErrestrial RElations Observatory and the Solar Dynamics Observatory were also available and are examined for this event. We suggest that the slow-drift period before the break was generated inside a streamer by a coronal eruption driven shock, and the spectral break as well as the relatively wide spectrum after the break is a consequence of the shock crossing the streamer boundary where density drops abruptly. It is suggested that this type of radio bursts can be taken as a unique diagnostic tool for inferring the coronal density structure, as well as the radio-emitting source region.

  4. A Study on Propagation Characteristic of One-dimensional Stress Wave in Functionally Graded Armor Composites

    NASA Astrophysics Data System (ADS)

    Yang, S. Y.; Liu, X.; Cao, D. F.; Mei, H.; Lei, Z. T.; Liu, L. S.

    2013-03-01

    The development of Functionally Graded Materials (FGM) for energy-absorbing applications requires understanding of stress wave propagation in these structures in order to optimize their resistance to failure. One-dimensional stress wave in FGM composites under elastic and plastic wave loading have been investigated. The stress distributions through the thickness and stress status have been analyzed and some comparisons have been done with the materials of sharp interfaces (two-layered material). The results demonstrate that the gradient structure design greatly decreases the severity of the stress concentrations at the interfaces and there are no clear differences in stress distribution in FGM composites under elastic and plastic wave loading.

  5. Characteristics of a propagating, self-pulsing, constricted ‘?-mode-like’ discharge

    NASA Astrophysics Data System (ADS)

    Schröder, Daniel; Burhenn, Sebastian; de los Arcos, Teresa; Schulz-von der Gathen, Volker

    2015-02-01

    Investigations on the self-pulsing operation regime of a modified micro-scaled atmospheric pressure plasma jet (?-APPJ) are presented. Using a wedge-shaped electrode configuration, a self-pulsing behavior of the device is achieved, which is characterized by the repetitive ignition of a constricted ‘?-mode-like’ discharge at the gas inlet, which propagates with the gas flow towards the nozzle, where it extinguishes. The ‘?-mode-like’ feature coexists with the homogeneous alpha-glow. Synchronized voltage/current and optical emission measurements are presented in order to correlate the evolution of electrical quantities such as voltage, current, dissipated power and phase with changes in the discharge structure. First insights are gained into the underlying discharge dynamics responsible for a stable self-sustainment, propagation and extinction of the constricted discharge. The results indicate that processes induced by helium metastables play a major role. Maximal electron densities on the order of ne = 3.2 · 1012 cm?3 and dissipated power of 18.9 W are achieved in this novel operation regime.

  6. RADIO WAVE PROPAGATION IN PERPENDICULAR STREETS OF URBAN STREET GRID FOR MICROCELLULAR COMMUNICATIONS. PART I: CHANNEL MODELING - ABSTRACT

    Microsoft Academic Search

    H. M. El-Sallabi; P. Vainikainen

    2003-01-01

    This paper proposes a spatial variant wideband propaga- tion model for perpendicular street of urban street grid. Analytical expression of the spatial variant multi-ray channel transfer function is derived. The model provides characteristics of each ray in explicit expressions. The ray characteristics are given in terms of complex amplitude for both vertical and horizontal polarizations, path length, angle of arrival

  7. Measurement of the dynamic mechanical properties of high-strength steel using wave propagation characteristics

    NASA Astrophysics Data System (ADS)

    Park, Jeongwon; Kim, Do-Hyung; Kim, Hak-Sung; Park, Junhong; Yoo, Ji Woo

    2014-06-01

    The dynamic mechanical properties of different high-strength steels were measured and compared based on their respective microstructures. Beam-shaped test specimens were excited using an electric shaker while vibration responses were measured using a non-contact laser sensor. Flexural wave propagation was analyzed to precisely determine material damping. Measured properties were compared to those of carbon steels. In addition, the effects of grain size determined by optical micrographs on the dynamic properties were investigated. The influence of the tensile strength on the measured properties was analyzed. The high-strength steels exhibited smaller damping with a similar Young's modulus compared to carbon steels, although the tensile strength was much greater.

  8. Propagation characteristics of Pc 3 compressional waves generated at the dayside magnetopause

    NASA Technical Reports Server (NTRS)

    Zhang, X.; Comfort, R. H.; Musielak, Z. E.; Moore, T. E.; Gallagher, D. L.; Green, J. L.

    1993-01-01

    New, 3D ray tracing of Pc 3 compressional waves from the magnetosheath reveals that the magnetosphere can present a major propagation barrier to the penetration of these waves to the plasmasphere. This barrier is the ion-ion cutoff between the He(+) and O(+) gyroresonances. As a result of the frequency-dependent location of this cutoff, the magnetosphere behaves like a filter for Pc 3 compressional waves, and only low-frequency components of Pc 3 compressional waves can penetrate to inner magnetosphere. Results are in agreement with previous satellite observations. This 'filter action' strongly depends on the relative concentration of He(+) and O(+) and is therefore sensitive to solar and magnetic activity. Ray-tracing results are based on a cold plasma dispersion relation, a semiempirical model of plasma density, and the Mead-Fairfield (1975) magnetic field model.

  9. Performance characteristics of qualified cell lines for isolation and propagation of influenza viruses for vaccine manufacturing.

    PubMed

    Donis, Ruben O; Davis, C Todd; Foust, Angie; Hossain, M Jaber; Johnson, Adam; Klimov, Alexander; Loughlin, Rosette; Xu, Xiyan; Tsai, Theodore; Blayer, Simone; Trusheim, Heidi; Colegate, Tony; Fox, John; Taylor, Beverly; Hussain, Althaf; Barr, Ian; Baas, Chantal; Louwerens, Jaap; Geuns, Ed; Lee, Min-Shi; Venhuizen, Odewijk; Neumeier, Elisabeth; Ziegler, Thedi

    2014-11-12

    Cell culture is now available as a method for the production of influenza vaccines in addition to eggs. In accordance with currently accepted practice, viruses recommended as candidates for vaccine manufacture are isolated and propagated exclusively in hens' eggs prior to distribution to manufacturers. Candidate vaccine viruses isolated in cell culture are not available to support vaccine manufacturing in mammalian cell bioreactors so egg-derived viruses have to be used. Recently influenza A (H3N2) viruses have been difficult to isolate directly in eggs. As mitigation against this difficulty, and the possibility of no suitable egg-isolated candidate viruses being available, it is proposed to consider using mammalian cell lines for primary isolation of influenza viruses as candidates for vaccine production in egg and cell platforms. To investigate this possibility, we tested the antigenic stability of viruses isolated and propagated in cell lines qualified for influenza vaccine manufacture and subsequently investigated antigen yields of such viruses in these cell lines at pilot-scale. Twenty influenza A and B-positive, original clinical specimens were inoculated in three MDCK cell lines. The antigenicity of recovered viruses was tested by hemagglutination inhibition using ferret sera against contemporary vaccine viruses and the amino acid sequences of the hemagglutinin and neuraminidase were determined. MDCK cell lines proved to be highly sensitive for virus isolation. Compared to the virus sequenced from the original specimen, viruses passaged three times in the MDCK lines showed up to 2 amino acid changes in the hemagglutinin. Antigenic stability was also established by hemagglutination inhibition titers comparable to those of the corresponding reference virus. Viruses isolated in any of the three MDCK lines grew reasonably well but variably in three MDCK cells and in VERO cells at pilot-scale. These results indicate that influenza viruses isolated in vaccine certified cell lines may well qualify for use in vaccine production. PMID:24975811

  10. Radio Ghosts

    E-print Network

    Torsten A. Ensslin

    1999-06-11

    We investigate the possibility that patches of old radio plasma (`radio ghosts') of former radio galaxies form a second distinct phase of the inter-galactic medium (IGM), not mixed with the thermal gas. The separation of this phase from the ambient gas and its resistance against eroding turbulent forces is given by magnetic fields, which are expected to be roughly in pressure equilibrium with the surrounding medium. Since patches of this plasma are largely invisible in the radio we use the term `radio ghost' to characterize their nature. Possibilities and difficulties of different detection strategies of ghosts are discussed. These involve radio emission, cosmic microwave background (CMB) and starlight Comptonization, and Faraday rotation. Re-activation of the electron population in shock waves of cosmological structure formation, which seems to lead to the cluster radio relic phenomena. We discuss the role radio ghosts can have: They are able to store relativistic particles for cosmological times, but are also able to release them under the influence of very strong turbulence. This might happen during a major merger event of clusters of galaxies. The released relativistic proton population could produce the observed radio halos of some cluster of galaxies via hadronic reactions with the background gas leading to the production of secondary electrons and positrons. Destroyed ghosts, mixed with the IGM can help to magnetize it. Finally, the strong field strength within ghosts should have a significant impact on the propagation of extragalactic high energy cosmic rays.

  11. Characteristics of carbon incorporated BN films deposited by radio frequency PACVD

    Microsoft Academic Search

    H. S. Kim; I. H. Choi; Y.-J. Baik

    2000-01-01

    The boron nitride (BN) and carbon incorporated BN films were deposited on Si substrates by capacitively coupled radio frequency plasma assisted chemical vapor deposition (r.f. PACVD). Deposition temperatures were varied from room temperature to 500°C while deposition pressure and substrate bias were kept at 2 Pa and ?500 V, respectively. BCl3 and NH3 were chosen as source gases and Ar

  12. Source and Propagation Characteristics of Kilometric Continuum Observed with Multiple Satellites

    NASA Technical Reports Server (NTRS)

    Hashimoto, K.; Anderson, R. R.; Green, J. L.; Matsumoto, H.

    2004-01-01

    Kilometric continuum radiation was first identified with the GEOTAIL Plasma Wave Instrument (PWI) as the high frequency extension of escaping continuum emissions in the frequency range from 100 kHz to 800 kHz. It consists of from a few to many narrow-band emissions. It was observed mainly near the magnetic equator, and its source was expected to be inside of the plasmapause and the topside equatorial region. Recently, data from the IMAGE Radio Plasma Imager (RPI) and Extreme ultraviolet (EUV) experiments have been used to show that kilometric continuum is generated at the plasmapause, in or near the magnetic equator, within a notch region, and have confirmed the expectation. Data from the CRRES PWI have also identified other sources from the equatorial density irregularities. An example of CRRES observations reveals a possibility that kilometric continuum has been radiated as a wide beam emission. The IMAGE and GEOTAIL simultaneous observations are not like the previous observations since they show it has been observed to have a very broad emission cone. It could also be the highest frequency continuum enhancement so far observed since it is associated with a high energy electron injection event.

  13. Theoretical Analysis of the Optical Propagation Characteristics in a Fiber-Optic Surface Plasmon Resonance Sensor

    PubMed Central

    Liu, Linlin; Yang, Jun; Yang, Zhong; Wan, Xiaoping; Hu, Ning; Zheng, Xiaolin

    2013-01-01

    Surface plasmon resonance (SPR) sensor is widely used for its high precision and real-time analysis. Fiber-optic SPR sensor is easy for miniaturization, so it is commonly used in the development of portable detection equipment. It can also be used for remote, real-time, and online detection. In this study, a wavelength modulation fiber-optic SPR sensor is designed, and theoretical analysis of optical propagation in the optical fiber is also done. Compared with existing methods, both the transmission of a skew ray and the influence of the chromatic dispersion are discussed. The resonance wavelength is calculated at two different cases, in which the chromatic dispersion in the fiber core is considered. According to the simulation results, a novel multi-channel fiber-optic SPR sensor is likewise designed to avoid defaults aroused by the complicated computation of the skew ray as well as the chromatic dispersion. Avoiding the impact of skew ray can do much to improve the precision of this kind of sensor. PMID:23748170

  14. Propagation characteristics of coastally trapped waves on the Australian Continental Shelf

    NASA Astrophysics Data System (ADS)

    Woodham, Robert; Brassington, Gary B.; Robertson, Robin; Alves, Oscar

    2013-09-01

    Coastally trapped waves (CTWs) are investigated around the Australian coast based on their signature in the sea surface height (SSH) field, using independent data from coastal tide gauge observations and the Bluelink ocean forecasting system from 2009. A high correlation (correlation coefficients from 0.6 to 0.9) between the model and observational data is demonstrated for locations between Hillarys, in the south-west of the continent, and Cape Ferguson, in the north-east. This justifies the use of Bluelink data for the rest of the investigation and enables coastal locations between tide gauge stations to be included. Spectrum analysis shows that CTWs have periods of between 10 and 25 days, with the 10 day period dominating along the south coast, and greater energy around the 20 day period on the east coast. The greatest spectral power is located around the Great Australian Bight. After filtering to isolate these CTW frequencies, phase speeds are estimated using two methods and are consistent with earlier studies. There is a close correlation between the standard deviation of the filtered SSH data and the width of the continental shelf, indicating that CTW amplitudes are strongly modulated by the local shelf width. Contrary to earlier studies, a complex empirical orthogonal function analysis shows that the majority of the variance propagates as continuous features between the south-west and north-east, and although modulated by the shelf width, it is unaffected by the sharply changing coastline orientation, shallow Bass Strait, or wind forcing regions.

  15. Investigation on broadband propagation characteristic of terahertz electromagnetic wave in anisotropic magnetized plasma in frequency and time domain

    NASA Astrophysics Data System (ADS)

    Tian, Yuan; Ai, Xia; Han, Yiping; Liu, Xiuxiang

    2014-12-01

    In this paper, we investigate the propagation of terahertz (THz) electromagnetic wave in an anisotropic magnetized plasma by JE convolution-finite difference time domain method. The anisotropic characteristic of the plasma, which leads to right-hand circularly polarized (RCP) and right-hand circularly polarized (LCP) waves, has been taken into account. The interaction between electromagnetic waves and magnetized plasma is illustrated by reflection and transmission coefficients for both RCP and LCP THz waves. The effects of both the magnetized plasma thickness and the external magnetized field are analyzed and numerical results demonstrate that the two factors could influence the THz wave greatly. It is worthy to note that besides the reflection and transmission coefficients in the frequency domain, the waveform of the electric field in the time domain varying with thicknesses and external magnetic fields for different polarized direction has been studied.

  16. Propagation characteristics of a focused laser beam in a strontium barium niobate photorefractive crystal under reverse external electric field.

    PubMed

    Guo, Q L; Liang, B L; Wang, Y; Deng, G Y; Jiang, Y H; Zhang, S H; Fu, G S; Simmonds, P J

    2014-10-01

    The propagation characteristics of a focused laser beam in a SBN:75 photorefractive crystal strongly depend on the signal-to-background intensity ratio (R=Is/Ib) under reverse external electric field. In the range 20>R>0.05, the laser beam shows enhanced self-defocusing behavior with increasing external electric field, while it shows self-focusing in the range 0.03>R>0.01. Spatial solitons are observed under a suitable reverse external electric field for R=0.025. A theoretical model is proposed to explain the experimental observations, which suggest a new type of soliton formation due to "enhancement" not "screening" of the external electrical field. PMID:25322227

  17. Characteristics of rainfall queues for rain attenuation studies over radio links at subtropical and equatorial Africa

    NASA Astrophysics Data System (ADS)

    Alonge, Akintunde A.; Afullo, Thomas J.

    2014-08-01

    Attenuation due to precipitation remains an important design factor in the future deployment of terrestrial and earth-space communication radio links. Largely, there are concerted efforts to understand the dynamics of precipitation in attenuation occurrence at subtropical, tropical, and equatorial region of Africa. In this deliberate approach, rainfall spikes pertaining to rain cells are conceptualized as distinct rain spike traffic over radio links, by applying queueing theory concepts. The queue distributions at Durban (29°52'S, 30°58'E) and Butare (2°36'S, 29°44'E)—respectively, of subtropical and equatorial climates—are investigated from distrometer measurements. The data sets at both sites are observed over four rain regimes: drizzle, widespread, shower, and thunderstorm. The queue parameters of service time and inter-arrival of rain spikes traffic at both regions are found to be Erlang-k distributed (Ek) and exponentially distributed (M), respectively. It is established that the appearance of rain rates over radio links invariably follows a First Come, First Served (FCFS), multi-server (s), infinite queue, and semi-Markovian process, designated as M/Ek/s/?/FCFS discipline. Modeled queue parameters at both regions are found to vary significantly over different regimes. However, these queue parameters over the entire data set suggest similar queue patterns at both sites. More importantly, power law relationships describing other queue-related parameters are formulated. The paper concludes by demonstrating an application of queueing theory for rainfall synthesis. The proposed technique will provide an alternative method of estimating rain cell sizes and rain attenuation over satellite and terrestrial links.

  18. On The Propagation Characteristics and Spectral Properties of Pre-seismic ULF Signals

    NASA Astrophysics Data System (ADS)

    Vallianatos, F.; Tzanis, A.

    Earlier work by Vallianatos and Tzanis (Geophys. Res. Lett, 26, 2013-2016, 1999) has proposed a model for the propagation and scaling of electric earthquake precursors, according to which the pre-seismic electric field emission is due to some precursory, time dependent polarisation, appearing in an ensemble of electrified crustal volumes within the seismogenic source, which are distributed according to a fractal power law. For simplicity, it was assumed that the hosting rock has a uniform conductivity distri- bution. Herein, we attempt to extend this formulation to the analysis of ULF magnetic precursors. We calculate the resulting transient magnetic field, which turns out to be mainly vertical and observable only if the seismogenic process generates a source with polarisation rate perpendicular to the vertical plane through the source and the receiver. Next, we proceed to investigate the spectral distribution law expected from such a set of emitters. To this effect, we assume that the evolution of the precursory polarisation process is not coherent throughout the excited ensemble, (i.e. there's no unique relaxation time), but rather, the sources emit quasi-incoherently, exhibiting a spectrum of relaxation times having energy dependence expressed by an Arrhenius law with distributed energies. We show that the macroscopic ULF field resulting from the superposition of such an ensemble of sources has power spectrum distributed ac- cording to an inverse power-law (i.e 1/fn). If the energy distribution is uniform, then the exponent n becomes equal to unity. The above theoretical predictions appear to be consistent with independent observations by other investigators, as for instance are those published by Hayakawa et al. (Geophys. Res. Lett., 27/10, 2000; Geophys. Res. Lett., 26/18, 1999), who have observed a significant increase of the intensity of the vertical magnetic field component, and an evolutionary behaviour of the ULF power spectra, which were distributed according to an inverse power-law, with the exponent decreasing to unity as a function of time to failure. Such observations and the theo- retical model presented herein, suggest that prior to failure, there is an evolutionary (progressive) homogenisation and tuning of the energy level / distribution, as well as an increase in the number of ULF emitters. In turn, this may reflect a corresponding homogenisation of the stress field distribution triggering the ULF emissions. This type 1 of behaviour (and the required physical conditions), is discussed under the perspective of Self-Organised Criticality and Critical Point systems. 2

  19. Flux pinning characteristics in cylindrical ingot niobium used in superconducting radio frequency cavity fabrication

    SciTech Connect

    Dhavale Ashavai, Pashupati Dhakal, Anatolii A Polyanskii, Gianluigi Ciovati

    2012-04-01

    We present the results of from DC magnetization and penetration depth measurements of cylindrical bulk large-grain (LG) and fine-grain (FG) niobium samples used for the fabrication of superconducting radio frequency (SRF) cavities. The surface treatment consisted of electropolishing and low temperature baking as they are typically applied to SRF cavities. The magnetization data were fitted using a modified critical state model. The critical current density Jc and pinning force Fp are calculated from the magnetization data and their temperature dependence and field dependence are presented. The LG samples have lower critical current density and pinning force density compared to FG samples which implies a lower flux trapping efficiency. This effect may explain the lower values of residual resistance often observed in LG cavities than FG cavities.

  20. Electrochemical characteristics of amorphous carbon nanorod synthesized by radio frequency magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Chang, Hsin-Yueh; Huang, Yung-Jui; Chang, Hsuan-Chen; Su, Wei-Jhih; Shih, Yi-Ting; Chen, John L.; Honda, Shin-ichi; Huang, Ying-Sheng; Lee, Kuei-Yi

    2015-01-01

    Amorphous carbon nanorods (CNRs) were deposited directly using radio frequency magnetron sputtering. The synthesized CNR electrochemical properties were investigated using graphene as the current collector for an electric double layer capacitor. The CNRs were vertically aligned to the graphene to achieve higher specific surface area. The capacitor performance was characterized using electrochemical impedance spectroscopy, cyclic voltammetry, and galvanostatic charge-discharge testing in 1 M KOH electrolyte at 30°C, 40°C, 50°C, and 60°C. The CNR specific capacitance was observed to increase with increasing measurement temperature and could reach up to 830 F/g at 60°C. Even after extensive measurements, the CNR electrode maintained good adhesion to the graphene current collector thereby suggesting electrode material stability.

  1. Electrical and optical emission characteristics of radio-frequency-driven hollow slot microplasmas operating in open air

    NASA Astrophysics Data System (ADS)

    Yalin, A. P.; Yu, Z. Q.; Stan, O.; Hoshimiya, K.; Rahman, A.; Surla, V. K.; Collins, G. J.

    2003-10-01

    We employ hollow slot electrodes, with pd values of ˜10 Torr cm and average E/N values of ˜70 Td, to create plasmas in open air. We measure the 13.56 MHz Irf-Vrf electrical characteristics of the plasma. Stable discharges, with sinusoidal currents, are obtained up to power densities of 14 kW/cm3, and root-mean-square radio-frequency (rf) currents of 1.5 A/cm of slot length, before nonsinusoidal currents and rf glow-to-arc transitions occur. We report the absolute optical emission in the vacuum ultraviolet region located between 110 and 155 nm, with a focus on the 149 nm atomic nitrogen line. For this atomic N line alone, we find an emitter efficiency of 0.0024.

  2. Shallow structure and surface wave propagation characteristics of the Juan de Fuca plate from seismic ambient noise

    NASA Astrophysics Data System (ADS)

    Tian, Y.; Shen, W.; Ritzwoller, M. H.

    2013-12-01

    Ambient noise cross-correlation analysis has been widely used to investigate the continental lithosphere, but the method has been applied much less to study the oceanic lithosphere due to the relative shortage of continuous ocean bottom seismic measurements. The Cascadia Initiative experiment possesses a total of 62 ocean bottom seismometers that spans much of the Juan de Fuca plate and provides data to investigate both the structure and evolution of the oceanic lithosphere near the Juan De Fuca ridge and the characteristics of surface waves and overtones propagating within the oceanic lithosphere. We produce ambient noise cross correlations for the first year of Cascadia OBS data for both the vertical and the horizontal components. The observed empirical Green's functions are first used to test the hypothesis that the near-ridge phase speeds can be described by a simple age-dependent formula, which we invert for an age-dependent shear wave speed model (Figure 1a). A shallow low shear velocity zone with a velocity minimum at about 20km depth is observed in Vsv and the lithosphere thickens with age faster than predicted by a half-space conductive cooling model (Figure 1b). To further understand the oceanic surface waves, we analyze the first higher mode Rayleigh waves that propagate within the Juan De Fuca plate and emerge on the North American continent and investigate the existence of radial anisotropy beneath the ridge by exploring the Rayleigh and Love wave Green's functions. The results of the study are summarized with the age-dependent shear velocity model along with some preliminary observations of both Love wave and higher mode Rayleigh waves.

  3. Determination of the time delay in the case of two-path propagation on the basis of the attenuation characteristics for two adjacent frequencies

    NASA Technical Reports Server (NTRS)

    Gilroi, H. G.

    1979-01-01

    Pronounced fading occurring in the line of sight radio links at frequencies below 10 GHz can be traced to the effects of multipath propagation. Modulation disturbances depend on travel time differences between the direct wave and the wave which is reflected at atmospheric layers. A method described for the determination of the time delay is based on an indirect approach which utilizes the difference in fading at various frequencies. The method was employed in measurements involving a distance of 181 km. The results obtained in the measurement are discussed.

  4. Case studies for solving the Saint-Venant equations using the method of characteristics: pipeline hydraulic transients and discharge propagation

    NASA Astrophysics Data System (ADS)

    Barros, R. M.; Tiago Filho, G. L.; dos Santos, I. F. S.; da Silva, F. G. B.

    2014-12-01

    Hydraulic transients occur during a change from one equilibrium state to another, for example, in flows. The pipeline project should provide the head and discharge in any operating states, e.g., sudden valve opening or closure. Among the various numerical approaches for the calculation of pipeline transients, the method of characteristics (MOC) is advantageous This study aims to present a hydraulic transitory study as MOC applications for solving the Saint- Venant equations in two case studies: 1) in a penstock of a small hydropower system as a simple pipeline in the case of valve-closure in the downstream boundary with a reservoir in the upstream boundary; and 2) for discharge propagation into a channel by velocity and depth of the flow channel along space evaluation. The main data for the first case study consisted of a design head that is 182 meters, a turbine discharge of 13.82 m3/s, a diameter of 4 meters and length pipe (penstock) of 2,152.50 meters. Regarding the second case study, the entry hydrogram was given to a rectangular channel with a width of 6.1 meters, length of 3,048 meters, slope of 0.0016 meters, and exhibited uniform flow with nominal depth of 2.44 meters. The characteristic curve of the discharge in the downstream extremity is Q = 158.(y – 3.25)32. The proposed methodology by Chaudry [5] concerning the development of hydrodynamic models was used. The obtained results for first case study showed that the simulated values for valve pressure while varying turning the valve between 4 and 12 seconds results in maximum values of pressures that oscillated between 219.97mca and 212.39 mca (4s) and 196.42mca and 190.86mca (12s). For the second case study, the values of discharge, velocity, and depth for x=0 and elapsed time of 850s were, respectively, 127.70m3/s, 3.87m/s, and 5.36m. For x=0 and an elapsed time of 1,230s, the values were 87.92m3/s, 4.49m/s, and 3.21m. Therefore, the MOC numerical approach has been confirmed to be useful for several engineering purposes, including cases of hydraulic transients and discharge propagation in hydraulic systems

  5. Radio phase characteristics of terrain from multipolarized synthetic aperture radar data

    NASA Technical Reports Server (NTRS)

    Zebker, H. A.; Held, D. N.

    1985-01-01

    Recent advances in digital data acquisition and signal processing technology permit simultaneous measurement of the complex (amplitude and phase) radar backscatter from several polarization-diverse antennas. While absolute phase mesurements remain to be analyzed in detail. The differential phase of signals polarized parallel and perpendicular to the plane of incidence provide information on the scattering mechanisms that dominate the interaction of the radio waves with the terrain. Analysis of phase backscatter maps from a typical urban area yields a bimodal distribution with the two peaks separated by approximately 180 degrees, highly indicative of a dominant simple geometric one bounce-two bounce mechanism. Some maps of agricultural areas exhibit a similar distribution, however, other agricultural areas yield a distribution that, while still bimodal, consists of two peaks separated by about 110 deg. Still other agricultural areas exhibit a more complex distribution. All of the observed phase shifts appear to be independent of incidence angle from at least 20 deg to 55 deg, therefore the 110 degree shifts are inconsistent with both the geometric model used for the urban area and with common dielectric slab models.

  6. Langmuir probe study of the charged particle characteristics in an analytical radio frequency-glow discharge. Roles of discharge conditions and sample conductivity

    Microsoft Academic Search

    Yuancai Ye; R. Kenneth Marcus

    1996-01-01

    The application of a tuned Langmuir probe to the measurement of the charged particle characteristics of electron number density, ion number density, electron energy distribution function, average electron energy and electron temperature, in an analytical radio frequency (r.f.)-glow discharge is described. Studies focus on the roles of discharge operating conditions and plasma sampling position for conductive (copper) and nonconductive (Macor)

  7. NASA Propagation Studies Website

    NASA Technical Reports Server (NTRS)

    Angkasa, Krisjani S.

    1996-01-01

    The NASA propagation studies objective is to enable the development of new commercial satellite communication systems and services by providing timely data and models about propagation of satellite radio signals through the intervening environment and to support NASA missions. In partnership with industry and academia, the program leverages unique NASA assets (currently Advanced Communications Technology Satellite) to obtain propagation data. The findings of the study are disseminated through referred journals, NASA reference publications, workshops, electronic media, and direct interface with industry.

  8. Low Pressure Radio-Frequency Oxygen Plasma Induced Oxidation of Titanium – Surface Characteristics and Biological Effects

    PubMed Central

    Tseng, Wan-Yu; Hsu, Sheng-Hao; Huang, Chieh-Hsiun; Tu, Yu-Chieh; Tseng, Shao-Chin; Chen, Hsuen-Li; Chen, Min-Huey; Su, Wei-Fang; Lin, Li-Deh

    2013-01-01

    Objective This research was designed to investigate the effects of low pressure radio-frequency (RF) oxygen plasma treatment (OPT) on the surface of commercially pure titanium (CP-Ti) and Ti6Al4V. Surface topography, elemental composition, water contact angle, cell viability, and cell morphology were surveyed to evaluate the biocompatibility of titanium samples with different lengths of OP treating time. Materials and Methods CP-Ti and Ti6Al4V discs were both classified into 4 groups: untreated, treated with OP generated by using oxygen (99.98%) for 5, 10, and 30 min, respectively. After OPT on CP-Ti and Ti6Al4V samples, scanning probe microscopy, X-ray photoelectron spectrometry (XPS), and contact angle tests were conducted to determine the surface topography, elemental composition and hydrophilicity, respectively. The change of surface morphology was further studied using sputtered titanium on silicon wafers. 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay and F-actin immunofluorescence stain were performed to investigate the viability and spreading behavior of cultivated MG-63 cells on the samples. Results The surface roughness was most prominent after 5 min OPT in both CP-Ti and Ti6Al4V, and the surface morphology of sputtered Ti sharpened after the 5 min treatment. From the XPS results, the intensity of Ti°, Ti2+, and Ti3+ of the samples’ surface decreased indicating the oxidation of titanium after OPT. The water contact angles of both CP-Ti and Ti6Al4V were increased after 5 min OPT. The results of MTT assay demonstrated MG-63 cells proliferated best on the 5 min OP treated titanium sample. The F-actin immunofluorescence stain revealed the cultivated cell number of 5 min treated CP-Ti/Ti6Al4V was greater than other groups and most of the cultivated cells were spindle-shaped. Conclusions Low pressure RF oxygen plasma modified both the composition and the morphology of titanium samples’ surface. The CP-Ti/Ti6Al4V treated with 5 min OPT displayed the roughest surface, sharpest surface profile and best biocompatibility. PMID:24386433

  9. Characteristics of atmospheric-pressure, radio-frequency glow discharges operated with argon added ethanol

    NASA Astrophysics Data System (ADS)

    Sun, Wen-Ting; Li, Guo; Li, He-Ping; Bao, Cheng-Yu; Wang, Hua-Bo; Zeng, Shi; Gao, Xing; Luo, Hui-Ying

    2007-06-01

    Rf, atmospheric-pressure glow discharge (APGD) plasmas with bare metal electrodes have promising prospects in the fields of plasma-aided etching, thin film deposition, disinfection and sterilization, etc. In this paper, the discharge characteristics are presented for the rf APGD plasmas generated with pure argon or argon-ethanol mixture as the plasma-forming gas and using water-cooled, bare copper electrodes. The experimental results show that the breakdown voltage can be reduced significantly when a small amount of ethanol is added into argon, probably due to the fact that the Penning ionization process is involved, and a pure ?-mode discharge can be produced more easily with the help of ethanol. The uniformity of the rf APGDs of pure argon or argon-ethanol mixtures using bare metallic electrodes is identified with the aid of the intensified charge coupled device images.

  10. Electrical switching dynamics and broadband microwave characteristics of VO2 radio frequency devices

    NASA Astrophysics Data System (ADS)

    Ha, Sieu D.; Zhou, You; Fisher, Christopher J.; Ramanathan, Shriram; Treadway, Jacob P.

    2013-05-01

    Vanadium dioxide (VO2) is a correlated electron system that features a metal-insulator phase transition (MIT) above room temperature and is of interest in high speed switching devices. Here, we integrate VO2 into two-terminal coplanar waveguides and demonstrate a large resistance modulation of the same magnitude (>103) in both electrically (i.e., by bias voltage, referred to as E-MIT) and thermally (T-MIT) driven transitions. We examine transient switching characteristics of the E-MIT and observe two distinguishable time scales for switching. We find an abrupt jump in conductivity with a rise time of the order of 10 ns followed by an oscillatory damping to steady state on the order of several ?s. We characterize the RF power response in the On state and find that high RF input power drives VO2 further into the metallic phase, indicating that electromagnetic radiation-switching of the phase transition may be possible. We measure S-parameter RF properties up to 13.5 GHz. Insertion loss is markedly flat at 2.95 dB across the frequency range in the On state, and sufficient isolation of over 25 dB is observed in the Off state. We are able to simulate the RF response accurately using both lumped element and 3D electromagnetic models. Extrapolation of our results suggests that optimizing device geometry can reduce insertion loss further and maintain broadband flatness up to 40 GHz.

  11. Photocatalytic characteristic and photodegradation kinetics of toluene using N-doped TiO2 modified by radio frequency plasma.

    PubMed

    Shie, Je-Lueng; Lee, Chiu-Hsuan; Chiou, Chyow-San; Chen, Yi-Hung; Chang, Ching-Yuan

    2014-01-01

    This study investigates the feasibility of applications of the plasma surface modification of photocatalysts and the removal of toluene from indoor environments. N-doped TiO2 is prepared by precipitation methods and calcined using a muffle furnace (MF) and modified by radio frequency plasma (RF) at different temperatures with light sources from a visible light lamp (VLL), a white light-emitting diode (WLED) and an ultraviolet light-emitting diode (UVLED). The operation parameters and influential factors are addressed and prepared for characteristic analysis and photo-decomposition examination. Furthermore, related kinetic models are established and used to simulate the experimental data. The characteristic analysis results show that the RF plasma-calcination method enhanced the Brunauer Emmett Teller surface area of the modified photocatalysts effectively. For the elemental analysis, the mass percentages of N for the RF-modified photocatalyst are larger than those of MF by six times. The aerodynamic diameters of the RF-modifiedphotocatalyst are all smaller than those of MF. Photocatalytic decompositions of toluene are elucidated according to the Langmuir-Hinshelwood model. Decomposition efficiencies (eta) of toluene for RF-calcined methods are all higher than those of commercial TiO2 (P25). Reaction kinetics ofphoto-decomposition reactions using RF-calcined methods with WLED are proposed. A comparison of the simulation results with experimental data is also made and indicates good agreement. All the results provide useful information and design specifications. Thus, this study shows the feasibility and potential use of plasma modification via LED in photocatalysis. PMID:24645445

  12. Characteristics of Arctic low-tropospheric humidity inversions based on radio soundings

    NASA Astrophysics Data System (ADS)

    Nygård, T.; Valkonen, T.; Vihma, T.

    2014-02-01

    Humidity inversions have a high potential importance in the Arctic climate system, especially for cloud formation and maintenance, in wide spatial and temporal scales. Here we investigate the climatology and characteristics of humidity inversions in the Arctic, including their spatial and temporal variability, sensitivity to the methodology applied and differences from the Antarctic humidity inversions. The study is based on data of the Integrated Global Radiosonde Archive (IGRA) from 36 Arctic stations between the years 2000 and 2009. The results indicate that humidity inversions are present on multiple levels nearly all the time in the Arctic atmosphere. Almost half (48%) of the humidity inversions were found at least partly within the same vertical layer with temperature inversions, whereas the existence of the other half may, at least partly, be linked to uneven vertical distribution of horizontal moisture transport. A high atmospheric surface pressure was found to increase the humidity inversion occurrence, whereas relationships between humidity inversion properties and cloud cover were generally relatively weak, although for some inversion properties they were systematic. For example, humidity inversions occurred slightly more often and were deeper under clear sky than in overcast conditions for almost all stations. The statistics of Arctic humidity inversion properties, especially inversion strength, depth and base height, proved to be very sensitive to the instruments and methodology applied. For example, the median strength of the strongest inversion in a profile was twice as large as the median of all Arctic inversions. The most striking difference between the Arctic and Antarctic humidity inversions was the much larger range of the seasonal cycle of inversion properties in the Arctic. Our results offer a baseline for validation of weather prediction and climate models and also encourage further studies on humidity inversions due to the vital, but so far poorly understood, role of humidity inversions in Arctic cloud processes.

  13. Empirical relations to determine the normalized spot size of a single-mode trapezoidal index fiber and computation of its propagation characteristics

    NASA Astrophysics Data System (ADS)

    Mallick, Aswini Kumar; Sarkar, Somenath

    2014-07-01

    Simple and complete empirical relations are presented here to determine a normalized spot size in terms of normalized frequencies over a long range and aspect ratio of a trapezoidal index single-mode fiber considering Gaussian approximation of the fundamental mode following the Marcuse method for the first time. After verification of their validity for arbitrary values of aspect ratio and normalized frequency, we calculate various propagation characteristics viz. dispersion and splice loss by using our formulations. Upon comparison, we observe an excellent match and the validity of our results with exact values and other results available in the literature. These formulas should attract the attention of experimentalists as a simple alternative to the rigorous methods of estimating the propagation characteristics of such fibers.

  14. Propagation and stability characteristics of a 500-m-long laser-based fiducial line for high-precision alignment of long-distance linear accelerators

    SciTech Connect

    Suwada, Tsuyoshi; Satoh, Masanori [Accelerator Laboratory, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan)] [Accelerator Laboratory, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan); Telada, Souichi; Minoshima, Kaoru [Length Standards Section, Metrology Institute of Japan, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Umezono, Tsukuba, Ibaraki 305-8563 (Japan)] [Length Standards Section, Metrology Institute of Japan, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Umezono, Tsukuba, Ibaraki 305-8563 (Japan)

    2013-09-15

    A laser-based alignment system with a He-Ne laser has been newly developed in order to precisely align accelerator units at the KEKB injector linac. The laser beam was first implemented as a 500-m-long fiducial straight line for alignment measurements. We experimentally investigated the propagation and stability characteristics of the laser beam passing through laser pipes in vacuum. The pointing stability at the last fiducial point was successfully obtained with the transverse displacements of ±40 ?m level in one standard deviation by applying a feedback control. This pointing stability corresponds to an angle of ±0.08 ?rad. This report contains a detailed description of the experimental investigation for the propagation and stability characteristics of the laser beam in the laser-based alignment system for long-distance linear accelerators.

  15. Packet Switching in Radio Channels: Part I--Carrier Sense Multiple-Access Modes and Their Throughput-Delay Characteristics

    Microsoft Academic Search

    LEONARD KLEINROCK; FOUAD A. TOBAGI

    1975-01-01

    Radio communication is considered as a method for providing remote terminal access to computers. Digital byte streams from each terminal are partitioned into packets (blocks) and transmitted in a burst mode over a shared radio channel. When many terminals operate in this fashion, transmissions may conflict with and destroy each other. A means for controlling this is for the terminal

  16. Effect of variations of the electric field and charged-particle precipitation on the characteristics of short-wave radio signals on an auroral radio path

    Microsoft Academic Search

    B. V. Tkachenko; A. O. Melnikov; V. K. Ridler; L. L. Lazutin; A. K. Dudakov

    1985-01-01

    Data concerning the inclined sounding of the auroral ionosphere by short waves on the Linakhamari-Umba path (400 km long) during November-December 1982 are analyzed along with measurements of variations of the electric field and hard-electron fluxes. It is shown that the effects of variations of the electric field and electron fluxes on the amplitude of scattered radio signals at different

  17. CROSS-DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY: Radio-Frequency Characteristics of a Printed Rectangular Helix Slow-Wave Structure

    Microsoft Academic Search

    Cheng-Fang Fu; Yan-Yu Wei; Wen-Xiang Wang; Yu-Bin Gong

    2008-01-01

    A new type of printed rectangular helix slow-wave structure (SWS) is investigated using the field-matching method and the electromagnetic integral equations at the boundaries. The radio-frequency characteristics including the dispersion equation and the coupling impedance for transverse antisymmetric (odd) modes of this structure are analysed. The numerical results agree well with the results obtained by the EM simulation software HFSS.

  18. Extragalactic Transients in the Era of Wide-Field Radio Surveys. I. Detection Rates and Light Curve Characteristics

    E-print Network

    Metzger, Brian D; Berger, Edo

    2015-01-01

    The impending era of wide-field radio surveys has the potential to revolutionize our understanding of astrophysical transients. Here we evaluate the prospects of a wide range of planned and hypothetical radio surveys using the properties and volumetric rates of known and hypothetical classes of extragalactic synchrotron radio transients (e.g., on- and off-axis gamma-ray bursts [GRB], supernovae, tidal disruption events [TDE], compact object mergers). Utilizing these sources and physically motivated considerations we assess the allowed phase-space of radio luminosity and peak timescale for extragalactic transients. We also include for the first time effects such as redshift evolution of the rates, K-corrections, and non-Euclidean luminosity distance, which affect the detection rates of the most sensitive surveys. The number of detected events is calculated by means of a Monte Carlo method, using the various survey properties (depth, cadence, area) and realistic detection criteria that include a cut on the mini...

  19. Radio Astronomy Radio astronomy

    E-print Network

    Metchev, Stanimir

    Effelsberg 100m telescope (Germany) Green Bank 100m telescope (National Radio Astronomy ObservatoryExperiment -10m (Chile, Europe) #12;Submillimeter radio astronomy #12;Size of telescope Snow sweep at Nobeyama 45;#12;Arecibo 300m telescope #12;Radio interferometer #12;Radio interferometer Very Large Array (VLA) (New

  20. INDOOR RADIO CHANNEL CHARACTERIZATION OF SPREAD SPECTRUM D. Dres, D. Vouyioukas, Prof. P. Constantinou

    E-print Network

    Vouyioukas, Demosthenes

    with windows placed in aluminum frame separated by concrete posts. The other outer side of the building to the design of such systems is the knowledge of radio propagation characteristics. This paper focuses is located on a specially designed movable measuring unit (cart) suitable for indoor measurements

  1. Radio Galaxies.

    ERIC Educational Resources Information Center

    Downes, Ann

    1986-01-01

    Provides background information on radio galaxies. Topic areas addressed include: what produces the radio emission; radio telescopes; locating radio galaxies; how distances to radio galaxies are found; physics of radio galaxies; computer simulations of radio galaxies; and the evolution of radio galaxies with cosmic time. (JN)

  2. Measured propagation characteristics of coplanar waveguide on semi-insulating 4H-SiC through 800 K

    Microsoft Academic Search

    George E. Ponchak; Samuel A. Alterovitz; Alan N. Downey; Jon C. Freeman; Zachary D. Schwartz

    2003-01-01

    Wireless sensors for high temperature industrial applications and jet engines require RF transmission lines and RF integrated circuits (RFICs) on wide bandgap semiconductors such as SiC. In this paper, the complex propagation constant of coplanar waveguide fabricated on semi-insulating 4H-SiC has been measured through 813 K. It is shown that the attenuation increases 3.4 dB\\/cm at 50 GHz as the

  3. New space-time perspectives on the propagation characteristics of the Black Death epidemic and its relation to bubonic plague

    Microsoft Academic Search

    George Christakos; Ricardo A. Olea

    2005-01-01

    This work presents, for the first time, a series of detailed space-time maps of Black Death mortality and infected area propagation\\u000a throughout the fourteenth century AD Europe. The maps integrate a variety of interdisciplinary knowledge bases about the devastating\\u000a epidemic and provide researchers and the interested public with an informative description of the Black Death dynamics (temporal\\u000a evolution, local and

  4. ACTS propagation experiment discussion: Ka-band propagation measurements using the ACTS propagation terminal and the CSU-CHILL and Space Communications Technology Center Florida propagation program

    NASA Technical Reports Server (NTRS)

    Bringi, V. N.; Chandrasekar, V.; Mueller, Eugene A.; Turk, Joseph; Beaver, John; Helmken, Henry F.; Henning, Rudy

    1993-01-01

    Papers on Ka-band propagation measurements using the ACTS propagation terminal and the Colorado State University CHILL multiparameter radar and on Space Communications Technology Center Florida Propagation Program are discussed. Topics covered include: microwave radiative transfer and propagation models; NASA propagation terminal status; ACTS channel characteristics; FAU receive only terminal; FAU terminal status; and propagation testbed.

  5. Amplitude fluctuations of decimeter and centimeter radio waves emmitted by the Venera-15 and Venera-16 space probes during propagation through the solar plasma

    Microsoft Academic Search

    O. I. Yakovlev; A. I. Efimov; E. P. Molotov; S. N. Rubtsov; V. P. Yakubov; A. I. Kucheryavenkov; A. S. Kaftonov

    1988-01-01

    Results are presented of investigations into the fluctuations of centimeter and decimeter radio waves in the solar plasma. The experimental dependence of the scintillation index on distance of closest point of approach in the range 2.3-100 solar radii is given. Dependence of the scintillation index on wavelength and solar activity is discussed. The dependence of the variance of the fluctuations

  6. Studies on characteristics of resistive power calculated with discrete Fourier transform in a pulse-modulated radio frequency discharge

    NASA Astrophysics Data System (ADS)

    Huo, W. G.; Zhang, H.; Ding, Z. F.

    2015-02-01

    In a pulse-modulated (PM) radio-frequency (RF) capacitively coupled plasma, the DFT (Discrete Fourier Transform)-calculated RF power and the corresponding phase shift between voltage and current measured with calibrated voltage and current probes present oscillations in the pulse rising and falling edges. The oscillating phase shift between voltage and current obtained in the falling edge is outside the expected value for a resistive-capacitive RF discharge. Numerical simulation and analytical analysis are made to interpret these abnormal characteristics and seek an approach to obtaining the reliable resistive (active) RF power. The oscillation is proved to be originated from the oscillating non-zero reactive RF power of the capacitor(s) in the load. At the time instant when the reactive RF power within an integer RF period is not zero, the reactive RF power is mistakenly regarded as the active RF power in the DFT analysis, as a result, the corresponding phase is thus incorrect and even outside the expected value for a resistive-capacitive load. The resistive RF power and the phase can be only correctly calculated at the time instant when the reactive RF power is zero. For a series (or parallel) RC (resistor-capacitor) load and a combined RC load with the dominated series (or parallel) RC impedance, the time instant of the zero reactive RF power is calculated with one of the two proposed empirical formulae. In practice, the DFT-calculated resistive RF power is obtained according to the following procedures: (1) applying DFT to the measured RF voltage and current signals to obtain the power and time instants for minimal phase shifts between voltage and current; (2) selecting the empirical formula to calculate time instants of the zero reactive RF power; (3) getting resistive powers at time instants of the zero reactive RF power. In real PM RF capacitively coupled plasmas, the empirical formula for the series RC load is selected to calculate the resistive RF power. The accuracy of DFT-calculated resistive RF power is proved to be related to two kinds of errors. The first is the error of the time instant of the zero reactive RF power calculated using the empirical formula. This error is relatively lower when the requirement that the dominated parallel or series RC impedance is met and is almost independent of the impedance phase angle of a combined RC load. The second is the error of the DFT-calculated resistive RF power compared with the corresponding time integral RF power at the real zero reactive RF power. This error is independent of the load type or the load impedance but varies with the slope of PM RF voltage amplitude vs. time. The two kinds of errors both increase in the pulse rising and falling edges.

  7. Quasar feedback and the origin of radio emission in radio-quiet quasars

    NASA Astrophysics Data System (ADS)

    Zakamska, Nadia L.; Greene, Jenny E.

    2014-07-01

    We analyse Sloan Digital Sky Survey spectra of 568 obscured luminous quasars. The [O III] ?5007 Å emission line shows blueshifts and blue excess, indicating that some of the narrow-line gas is undergoing an organized outflow. The velocity width containing 90 per cent of line power ranges from 370 to 4780 km s-1, suggesting outflow velocities up to ˜2000 km s-1, and is strongly correlated with the radio luminosity among the radio-quiet quasars. We propose that radio emission in radio-quiet quasars is due to relativistic particles accelerated in the shocks within the quasar-driven outflows; star formation in quasar hosts is insufficient to explain the observed radio emission. The median radio luminosity of the sample of ?L?[1.4 GHz] = 1040 erg s-1 suggests a median kinetic luminosity of the quasar-driven wind of Lwind = 3 × 1044 erg s-1, or about 4 per cent of the estimated median bolometric luminosity Lbol = 8 × 1045 erg s-1. Furthermore, the velocity width of [O III] is positively correlated with mid-infrared luminosity, which suggests that outflows are ultimately driven by the radiative output of the quasar. Emission lines characteristic of shocks in quasi-neutral medium increase with the velocity of the outflow, which we take as evidence of quasar-driven winds propagating into the interstellar medium of the host galaxy. Quasar feedback appears to operate above the threshold luminosity of Lbol ˜ 3 × 1045 erg s-1.

  8. Measured Propagation Characteristics of Coplanar Waveguide on Semi-Insulating 4H-SiC Through 800 K

    NASA Technical Reports Server (NTRS)

    Ponchak, George E.; Alterovitz, Samuel A.; Downey, Alan N.; Freeman, Jon C.; Schwartz, Zachary D.

    2003-01-01

    Wireless sensors for high temperature industrial applications and jet engines require RF transmission lines and RF integrated circuits (RFICs) on wide bandgap semiconductors such as SiC. In this paper, the complex propagation constant of coplanar waveguide fabricated on semiinsulating 4H-SiC has been measured through 813 K. It is shown that the attenuation increases 3.4 dB/cm at 50 GHz as the SiC temperature is increased from 300 K to 813 K. Above 500 K, the major contribution to loss is the decrease in SiC resistivity. The effective permittivity of the same line increases by approximately 5 percent at microwave frequencies and 20 percent at 1 GHz.

  9. The propagation and scattering characteristics of a forest as measured by coherent ultra-wideband foliage penetration

    NASA Astrophysics Data System (ADS)

    Gwynne, John Scott

    Coherent polarimetric synthetic aperture radar (SAR) measurements of a central Ohio forest have been collected, and it is the objective of this research to document and analyze the results. The foliage data presented in this dissertation are unique in several aspects. Primarily, the data are Ultra-Wideband (UWB) in that the bandwidth (200-1600MHz) divided by center frequency is at least 25% and are of a wavelength selected to penetrate the forest canopy. Data of this bandwidth or resolution offer the opportunity to see for the first time at these frequencies scattering components such as branches, tree trunks, and ground-tree interaction terms. Secondly, coherent apertures were collected by precisely moving the antennas within a well-known coordinate system leading to absolute phase calibration and to the generation of fully coherent SAR imagery. Much of the past work performed on foliage propagation and scattering does not include phase information which is crucial for predicting the performance of radars of this type. The underlying goals of this research are to identify the fundamental scattering mechanisms associated with the forest backscatter at these frequencies and to assess UWB usage for the concealed target detection and identification problems. To this end, methods are developed to analyze the above measurements and extract modeling parameters such as the propagation loss, phase defect, and backscatter per unit area (sigmasp{o}). The analysis of these data provide the insight needed to statistically model the forest in both forward scatter and backscatter and to determine the ability of these UWB frequencies to penetrate the forest canopy.

  10. Radiowave propagation in mobile communications: an overview of European research

    Microsoft Academic Search

    B. H. Fleury; P. E. Leuthold

    1996-01-01

    Detailed knowledge of radio propagation effects is a keystone for the development and performance assessment of mobile communication systems. Although a lot of investigations have already been carried out, there remains a need to gain deeper insight into the complex mechanisms which govern radio propagation. The authors first present a summary of the propagation mechanisms and discuss some issues related

  11. Effect of nonthermal electrons on the propagation characteristics and stability of two-dimensional nonlinear electrostatic coherent structures in relativistic electron positron ion plasmas

    SciTech Connect

    Masood, W. [Theoretical Plasma Physics Division, PINSTECH, P. O. Nilore, Islamabad (Pakistan); National Centre for Physics (NCP), Shahdara Valley Road, 44000 Islamabad (Pakistan); Rizvi, H. [Theoretical Plasma Physics Division, PINSTECH, P. O. Nilore, Islamabad (Pakistan)

    2011-06-15

    Two-dimensional propagation of nonlinear ion acoustic shock and solitary waves in an unmagnetized plasma consisting of nonthermal electrons, Boltzmannian positrons, and singly charged hot ions streaming with relativistic velocities are investigated. The system of fluid equations is reduced to Kadomtsev-Petviashvili-Burgers and Kadomtsev-Petviashvili (KP) equations in the limit of small amplitude perturbation. The dependence of the ion acoustic shock and solitary waves on various plasma parameters are explored in detail. Interestingly, it is observed that increasing the nonthermal electron population increases the wave dispersion which enervates the strength of the ion acoustic shock wave; however, the same effect leads to an enhancement of the soliton amplitude due to the absence of dissipation in the KP equation. The present investigation may be useful to understand the two-dimensional propagation characteristics of small but finite amplitude localized shock and solitary structures in planetary magnetospheres and auroral plasmas where nonthermal populations of electrons have been observed by several satellite missions.

  12. Radio Science in Africa

    NASA Astrophysics Data System (ADS)

    Lefeuvre, Francois; Mc Kinnel, Lee-Anne; Chukwuma, Victor; Amory-Mazaudier, Christine

    2010-05-01

    Radio science activities covered by URSI (International Radio Science Union) are briefly reviewed. They encompass the knowledge and study of all aspects of electromagnetic fields and waves in a wide frequency range running from micro pulsation frequencies (i.e. from ~1 mHz) to Terahertz. The topics include: electromagnetic measurements and standards, electromagnetic theory and applications, radio-communication systems and signal processing, electronics and Photonics, electromagnetic environment and interference, wave propagation and remote sensing, ionospheric radio and propagation, waves in plasmas, radio astronomy, and electromagnetics in biology and medicine. The main radio science activities conducted by the URSI national Committees of South Africa, Egypt and Nigeria, and by African radio scientists groups gathered in GIRGEA (Groupe International de Recherche en Géophysique Europe Afrique) are reviewed. The emphasis is put on the activities developed in the context of the IHY programme and of the SCINDA network for forecasting ionospheric irregularities that adversely impact communication and navigation systems in the low latitude regions.

  13. Effect of source-gate spacing on direct current and radio frequency characteristic of graphene field effect transistor

    NASA Astrophysics Data System (ADS)

    Peng, Song-ang; Jin, Zhi; Zhang, Da-yong; Shi, Jing-yuan; Wang, Xuan-yun; Wang, Shao-qing; Liu, Xin-yu; Yu, Guang-hui

    2015-01-01

    The effect of source-gate spacing on graphene filed effect transistors has been investigated. Reducing the source gate spacing allows for a significant improvement on both the direct current and radio frequency (RF) performances. Instead of the generally considered output conductance, our results suggest that the access resistances at the un-gated region contribute more to the maximum oscillation frequency (fmax). Further analysis reveals that the ratio of cut off frequency (fT) to fmax is also sensitive to the resistances at source-gate spacing. This work can be used to guide the further optimization of graphene-based RF devices.

  14. Adaptive ground implemented phased array. [evaluation to overcome radio frequency interference characteristics of TDRS VHF return link

    NASA Technical Reports Server (NTRS)

    Smith, J. M.

    1973-01-01

    Tests were conducted to determine the feasibility of using an adaptive ground implemented phased array (AGIPA) to overcome the limitations of the radio frequency interference limited low data Tracking and Data Relay Satellite VHF return link. A feasibility demonstration model of a single user channel AFIPA system was designed, developed, fabricated, and evaluated. By scaling the frequency and aperture geometry from VHF to S-band, the system performance was more easily demonstrated in the controlled environment of an anechoic chamber. The testing procedure employs an AGIPA in which received signals from each element of the array are processed on the ground to form an adaptive, independent, computer controlled beam for each user.

  15. Three-dimensional propagation characteristics of the upward connecting leaders in six negative tall-object flashes in Guangzhou

    NASA Astrophysics Data System (ADS)

    Gao, Yan; Lu, Weitao; Ma, Ying; Chen, Luwen; Zhang, Yang; Yan, Xu; Zhang, Yijun

    2014-11-01

    Six downward negative flashes terminated on tall structures in Guangzhou are analyzed. The three-dimensional (3-D) lightning channels are reconstructed from dual-station optical observations. For each reconstructed 3-D upward connecting leader (UCL) channel, its 3-D length and speed are calculated. The 3-D length values of the six positive UCLs range from 180 to 818 m. There are 38 3-D speed values which are calculated combining the 3-D UCL channel and the high-speed images for the six UCLs. The 3-D speed values range from 0.8 to 14.3 × 105 m s- 1 and four of them (11%, 4/38) are on the order of 106 m s- 1. For comparison, the corresponding two-dimensional (2-D) parameters are calculated using the single-station high-speed images. The values of the 2-D length and 2-D speed range from 147 to 610 m and 0.3 to 10.6 × 105 m s- 1, respectively. From the statistical analysis, we determine that the average value of the 3-D speed is 1.3 times that of the 2-D speed. When the time is approaching the return stroke (RS), the propagation speed of the UCL is increasing. All of the four 3-D speed values on the order of 106 m s- 1 occur less than 0.2 ms prior to the RS. When the 3-D length is shorter than 300 m, 77% (20/26) of the corresponding 3-D speed values are smaller than 5 × 105 m s- 1. When the 3-D length is longer than 300 m or the UCL tip height is higher than 650 m, all of the corresponding 3-D speed values are faster than 5 × 105 m s- 1.

  16. Characteristics of a rocket-triggered lightning flash with large stroke number and the associated leader propagation

    NASA Astrophysics Data System (ADS)

    Sun, Zhuling; Qie, Xiushu; Jiang, Rubin; Liu, Mingyuan; Wu, Xueke; Wang, Zhichao; Lu, Gaopeng; Zhang, Hongbo

    2014-12-01

    A negative lightning flash with 16 leader-return stroke sequences, triggered in the summer of 2013 using the classical rocket-and-wire triggering technique, was examined with simultaneous two-dimensional (2D) imaging of very high-frequency (VHF) radiation sources, channel-base current measurement, broadband electric field waveforms and high-speed video images. A total of 28.0 C negative charge was transferred to ground during the whole flash, and the charge transferred during the initial stage was 4.9 C, which is the weakest among the triggered lightning flashes at the SHandong Artificially Triggering Lightning Experiment (SHATLE). The peak current of 16 return strokes ranged from 5.8 to 32.5 kA with a geometric mean of 14.1 kA. The progression of upward positive leader and downward negative (dart or dart-stepped) leaders was reproduced visually by using an improved short-baseline VHF lightning location system with continuous data recording capability. The upward positive leader was mapped immediately from the tip of the metal wire during the initial stage, developing at a speed of about 104 m/s without branches. The upward positive leader and all the 14 negative leaders captured by the 2D imaging system propagated along the same channel with few branches inside the cloud, which might be the reason for the relatively small charge transfer. The 2D imaging results also show that dart leaders may transform into dart-stepped leaders after a long time interval between successive strokes.

  17. The effect of adiabatic focusing upon charged particle propagation in random magnetic fields

    NASA Technical Reports Server (NTRS)

    Earl, J. A.

    1975-01-01

    Charged particles propagating along the diverging lines of force of a spatially inhomogeneous guiding field were considered as they are scattered by random fields. Their longitudinal transport is described in terms of the eigenfunctions of a Sturm-Liouville operator incorporating the effect of adiabatic focussing along with that of scattering. The relaxation times and characteristic velocities are graphed and tabulated. The particle density is evaluated as a function of space and time for two different regimes. In the first regime (relatively weak focussing), a diffusive mode of propagation is dominant but coherent modes are also dominant. In the second regime (strong focussing), diffusion does not occur and the propagation is purely coherent. This supercoherent mode corresponds exactly to the so-called scatter-free propagation of kilovolt solar flare electrons. On a larger scale, focussed transport provides an interpretation of many observed characteristics of extragalactic radio sources.

  18. Adaptive antenna arrays with controllable spacial-polarization characteristics under conditions of the reception of partially polarized radio waves

    Microsoft Academic Search

    L. G. Kornienko; Iu. A. Kolos

    1989-01-01

    Expressions are obtained for the optimal weight coefficient vector, radiation pattern, and maximum S\\/N ratio of an adaptive antenna array with controllable three-dimensional (directional) and polarization characteristics during steady-state operation. The signals and interference radiations are assumed to be partially polarized in the general case. The characteristics of angular and polarization signal selection in the presence of interference are investigated

  19. Characteristics of atmospheric gravity waves observed using the MU (Middle and Upper atmosphere) radar and GPS (Global Positioning System) radio occultation.

    PubMed

    Tsuda, Toshitaka

    2014-01-01

    The wind velocity and temperature profiles observed in the middle atmosphere (altitude: 10-100 km) show perturbations resulting from superposition of various atmospheric waves, including atmospheric gravity waves. Atmospheric gravity waves are known to play an important role in determining the general circulation in the middle atmosphere by dynamical stresses caused by gravity wave breaking. In this paper, we summarize the characteristics of atmospheric gravity waves observed using the middle and upper atmosphere (MU) radar in Japan, as well as novel satellite data obtained from global positioning system radio occultation (GPS RO) measurements. In particular, we focus on the behavior of gravity waves in the mesosphere (50-90 km), where considerable gravity wave attenuation occurs. We also report on the global distribution of gravity wave activity in the stratosphere (10-50 km), highlighting various excitation mechanisms such as orographic effects, convection in the tropics, meteorological disturbances, the subtropical jet and the polar night jet. PMID:24492645

  20. Characteristics of atmospheric gravity waves observed using the MU (Middle and Upper atmosphere) radar and GPS (Global Positioning System) radio occultation

    PubMed Central

    TSUDA, Toshitaka

    2014-01-01

    The wind velocity and temperature profiles observed in the middle atmosphere (altitude: 10–100 km) show perturbations resulting from superposition of various atmospheric waves, including atmospheric gravity waves. Atmospheric gravity waves are known to play an important role in determining the general circulation in the middle atmosphere by dynamical stresses caused by gravity wave breaking. In this paper, we summarize the characteristics of atmospheric gravity waves observed using the middle and upper atmosphere (MU) radar in Japan, as well as novel satellite data obtained from global positioning system radio occultation (GPS RO) measurements. In particular, we focus on the behavior of gravity waves in the mesosphere (50–90 km), where considerable gravity wave attenuation occurs. We also report on the global distribution of gravity wave activity in the stratosphere (10–50 km), highlighting various excitation mechanisms such as orographic effects, convection in the tropics, meteorological disturbances, the subtropical jet and the polar night jet. PMID:24492645

  1. NASA Lunar Base Wireless System Propagation Analysis

    NASA Technical Reports Server (NTRS)

    Hwu, Shian U.; Upanavage, Matthew; Sham, Catherine C.

    2007-01-01

    There have been many radio wave propagation studies using both experimental and theoretical techniques over the recent years. However, most of studies have been in support of commercial cellular phone wireless applications. The signal frequencies are mostly at the commercial cellular and Personal Communications Service bands. The antenna configurations are mostly one on a high tower and one near the ground to simulate communications between a cellular base station and a mobile unit. There are great interests in wireless communication and sensor systems for NASA lunar missions because of the emerging importance of establishing permanent lunar human exploration bases. Because of the specific lunar terrain geometries and RF frequencies of interest to the NASA missions, much of the published literature for the commercial cellular and PCS bands of 900 and 1800 MHz may not be directly applicable to the lunar base wireless system and environment. There are various communication and sensor configurations required to support all elements of a lunar base. For example, the communications between astronauts, between astronauts and the lunar vehicles, between lunar vehicles and satellites on the lunar orbits. There are also various wireless sensor systems among scientific, experimental sensors and data collection ground stations. This presentation illustrates the propagation analysis of the lunar wireless communication and sensor systems taking into account the three dimensional terrain multipath effects. It is observed that the propagation characteristics are significantly affected by the presence of the lunar terrain. The obtained results indicate the lunar surface material, terrain geometry and antenna location are the important factors affecting the propagation characteristics of the lunar wireless systems. The path loss can be much more severe than the free space propagation and is greatly affected by the antenna height, surface material and operating frequency. The results from this paper are important for the lunar wireless system link margin analysis in order to determine the limits on the reliable communication range, achievable data rate and RF coverage performance at planned lunar base work sites.

  2. Effects of discharge frequency on plasma characteristics and etching characteristics in high density Cl2 plasma: comparison of ultrahigh-frequency plasma and radio-frequency plasma

    Microsoft Academic Search

    Seiji Samukawa; Haruaki Akashi

    1998-01-01

    We investigated the effects of discharge frequency on the characteristics of polycrystalline-silicon etching rates and on the etching selectivity on the gate oxide (SiO2). An ultrahigh-frequency (UHF) plasma excited at 500 MHz was found to possess a wider process window for highly selective polycrystalline silicon etching than did an inductively coupled plasma excited at 13.56 MHz. The ionization rate in

  3. A New Approach Towards Large Scale Soil Moisture Mapping by Radio Waves

    NASA Astrophysics Data System (ADS)

    Huebner, Christof; Kottmeier, Christoph; Brandelik, Alexander

    2011-06-01

    A new approach for obtaining integrated estimates of soil moisture content over larger regions of typically 10-50 km is described. It is based on a known correlation between propagation characteristics of low frequency radio surface waves and surface soil moisture, and provides valuable new benefits especially for meteorological prognostic models and for soil water estimation in agriculture. The paper consists of (1) a description of the theory of radio wave propagation with an extension of the classical theory of Norton (Proceedings of the Institute of Radio Engineers, Vol. 24, 1936), specifically the exploitation of the phase information, (2) demonstration of a method which guarantees the selection of reliable results from a large measurement data set, (3) a presentation of a new low cost measurement device to detect the amplitude and phase changes, and (4) results from initial measurements providing evidence that theoretical calculations are consistent with the measured change of electromagnetic signal properties due to soil moisture change.

  4. Solar Power Satellite (SPS) pilot beam and communication link subsystem investigation study, phase 1. [ionospheric propagation, radio frequency interference, and microwave transmission

    NASA Technical Reports Server (NTRS)

    1979-01-01

    A preliminary engineering model of ionospheric interactions with the pilot beam was established and used to demonstrate that the dual frequency baseline pilot beam system might not be viable in the presence of an unstable transmission path. Alternate approaches to remove this difficulty are described. Although ionospheric fluctuations will not significantly degrade beam pointing or raise the sidelobe levels, they will reduce transmission efficiency by upwards of 25%. Mitigating strategies to substantially reduce this effect are proposed. Based on the Klystron noise spectrum, the pilot beam transmitter power was determined as a function of frequency offset from the power beam carrier frequency. The RFI from the pilot beam, on the ground and at geosynchronous orbit is shown. Noise levels on the earth's surface due to the SPS are presented as a function of frequency and the number of SPS systems. Analysis of the communication subsystem indicates that a standard telemetry line of 1.544 MB/s would satisfy both voice and data link requirements. Additional links would be required for TV and radio transmissions.

  5. Ultra wideband indoor radio channel models: preliminary results

    Microsoft Academic Search

    V. Hovinen; Matti Hamalainen; Tinzo Patsi

    2002-01-01

    Knowledge of the signal propagation mechanisms in the channel is vital for the radio system design and the system performance analysis. However, currently published wideband or narrowband radio channel models do not offer spatial resolution high enough for the ultra wideband (UWB) applications and real channel measurements are needed. The preliminary UWB radio channel model for a selected radio link-configuration

  6. Radio-Frequency Characteristics of the Coaxial Step-Disk-Loaded Slow-Wave Structure for Relativistic Travelling Wave Tubes

    Microsoft Academic Search

    Ling-Na Yue; Wen-Xiang Wang; Yan-Yu Wei; Yu-Bin Gong

    2005-01-01

    We present a new periodic all-metal slow wave structure, a coaxial step-disc-loaded system and the dispersion characteristics of the structure. By using the field-matching method, the dispersion equation and the coupling impedance of this structure are obtained. The coaxial structure makes the bandwidth broader than that of the non-coaxial one. Compared with the coaxial disc-loaded and ridged-disc-loaded structures, the pass-band

  7. The back-diffusion effect of air on the discharge characteristics of atmospheric-pressure radio-frequency glow discharges using bare metal electrodes

    NASA Astrophysics Data System (ADS)

    Sun, Wen-Ting; Liang, Tian-Ran; Wang, Hua-Bo; Li, He-Ping; Bao, Cheng-Yu

    2007-05-01

    Radio-frequency (RF), atmospheric-pressure glow discharge (APGD) plasmas using bare metal electrodes have promising prospects in the fields of plasma-aided etching, deposition, surface treatment, disinfection, sterilization, etc. In this paper, the discharge characteristics, including the breakdown voltage and the discharge voltage for sustaining a stable and uniform ? mode discharge of the RF APGD plasmas are presented. The experiments are conducted by placing the home-made planar-type plasma generator in ambient and in a vacuum chamber, respectively, with helium as the primary plasma-forming gas. When the discharge processes occur in ambient, particularly for the lower plasma-working gas flow rates, the experimental measurements show that it is the back-diffusion effect of air in atmosphere, instead of the flow rate of the gas, that results in the obvious decrease in the breakdown voltage with increasing plasma-working gas flow rate. Further studies on the discharge characteristics, e.g. the luminous structures, the concentrations and distributions of chemically active species in plasmas, with different plasma-working gases or gas mixtures need to be conducted in future work.

  8. The NASA radiowave propagation program

    NASA Technical Reports Server (NTRS)

    Davarian, Faramaz

    1990-01-01

    The objectives of the NASA radiowave Propagation Program are to enable new satellite communication applications and to enhance existing satellite communication networks. These objectives are achieved by supporting radio wave propagation studies and disseminating the study results in a timely fashion. Studies initiated by this program in the 1980s enabled the infant concept of conducting mobile communications via satellite to reach a state of relative maturity in 1990. The program also supported the satellite communications community by publishing and revising two handbooks dealing with radio wave propagation effects for frequencies below and above 10 GHz, respectively. The program has served the international community through its support of the International Telecommunications Union. It supports state of the art work at universities. Currently, the program is focusing on the Advanced Communications Technology Satellite (ACTS) and its propagation needs. An overview of the program's involvement in the ACTS project is given.

  9. Radio-Frequency Characteristics of the Coaxial Step-Disk-Loaded Slow-Wave Structure for Relativistic Travelling Wave Tubes

    NASA Astrophysics Data System (ADS)

    Yue, Ling-Na; Wang, Wen-Xiang; Wei, Yan-Yu; Gong, Yu-Bin

    2005-03-01

    We present a new periodic all-metal slow wave structure, a coaxial step-disc-loaded system and the dispersion characteristics of the structure. By using the field-matching method, the dispersion equation and the coupling impedance of this structure are obtained. The coaxial structure makes the bandwidth broader than that of the non-coaxial one. Compared with the coaxial disc-loaded and ridged-disc-loaded structures, the pass-band of coaxial step-disc-loaded structure is the broadest. The calculation results show that increasing the step width and decreasing the step thickness can improve the bandwidth.

  10. Population and movement characteristics of radio-collared striped skunks in North Dakota during an epizootic of rabies

    USGS Publications Warehouse

    Greenwood, R.J.; Newton, W.E.; Pearson, G.L.; Schamber, G.J.

    1997-01-01

    We observed a total of 102 striped skunks (Mephitis mephitis) from March to July of both 1991 and 1992 in Stutsman County, North Dakota (USA) during an experiment with food supplementation. Twenty-three apparently healthy skunks in 1991 and 56 in 1992 were equipped with radio-collars. In 1991, one of 23 was tested and found to be rabid. In 1992, 50 of 56 were tested; 35 (69%) were rabid. Of skunks with ages estimated, 19 (66%) of 29 were first year animals in 1991 compared with nine (22%) of 41 first year animals in 1992. All 18 females captured in 1991 were pregnant or parous compared with 21 (60%) of 35 in 1992. The estimated survival rate of skunks was 0.85 during April to June 1991, but only 0.17 during April to July 1992. In 1992, the survival rate of first year skunks was 0.08, compared with 0.35 for older animals. Eleven (31%) of 36 skunks found dead of rabies or in late clinical stage were located below ground. We detected no differences in 1992 between healthy and rabid skunks in estimated mean (i?? SE) rate of travel (232 i?? 14 m/hr), distance traveled (2047 i?? 141 m/night), or home range size (1.6 i?? 0.4 km2) during half-month periods from April through June. Among rabid skunks, mean (i?? SE) rate of travel tended to decrease from 298 i?? 48 m/hr during the 14 days preceding the clinical period of rabies (pre-clinical) to 174 i?? 48 m/hr during the clinical period of rabies (14 days immediately before death). Similar decrease occurred in mean (i?? SE) distance traveled in a night (2318 i?? 281 m, pre-clinical; 1497 i?? 281 m, clinical). Mean (i?? SE) home range size of males (2.8 i?? 0.4) was greater than of females (1.2 i?? 0.4) during the pre-clinical period, but during the clinical period home range sizes of males (1.8 i?? 0.4) and females (1.8 i?? 0.4) were similar. Mean (i?? SE) home range size of females did not differ between pre-clinical (1.2 i?? 0.4) and clinical (1.8 i?? 0.4) periods (P = 0.22). Deaths of skunks from rabies in 1992 tended to be more spatially clumped than expected had they been random, mostly due to deaths detected before 8 May. We detected no correlation between locations of animals found dead of rabies and dates of death.

  11. Statistical modeling of the ultra wide band propagation channel through the analysis of experimental measurements

    NASA Astrophysics Data System (ADS)

    Pagani, Pascal; Pajusco, Patrice

    2006-09-01

    For the development of future Ultra Wide Band (UWB) communication systems, realistic modeling of the propagation channel is necessary. This article presents an experimental study of the UWB radio channel, based on an extensive sounding campaign covering the indoor office environment. We consider the main characteristics of the UWB channel by studying the propagation loss and wide band parameters, such as the delay spread and the power delay profile decay. From this analysis, we propose a statistical channel model reproducing the UWB channel effects over the frequency bandwidth 3.1-10.6 GHz. To cite this article: P. Pagani, P. Pajusco, C. R. Physique 7 (2006).

  12. The IF77 electromagnetic wave propagation model

    Microsoft Academic Search

    G. D. Gierhart; M. E. Johnson

    1983-01-01

    This report provides a description of the computational details in the IF-77 radio wave propagation model. The IF-77 model is useful in estimating service coverage for radio systems operating in the 01 to 20 GHz frequency range. It is applicable to many air\\/air, air\\/ground, air\\/satellite, ground\\/ground, and ground\\/satellite systems. Irregular terrain and propagation beyond the line-of-sight range are considered in

  13. Radio telescopes

    Microsoft Academic Search

    J. Findlay

    1964-01-01

    A radio telescope is used in radio astronomy to measure the intensity of the radiation received from various parts of the sky. Such a telescope must be able both to detect and to locate faint radio sources of small angular size, and also to measure the brightness distribution across extended radio sources or over large sky areas. Ideally the telescope

  14. NASA Propagation Program Status and Propagation Needs of Satcom Industry

    NASA Technical Reports Server (NTRS)

    Golshan, Nassar

    1996-01-01

    The program objective is to enable the development of new commercial satellite systems and services and to support NASA's programs by providing timely data and models about propagation of satellite radio signals though the intervening environment. Provisions include new services, higher frequencies, higher data rates, different environments (mobile, indoors, fixed), and different orbits (geostationary, low earth orbit).

  15. Indoor radio measurement and planning for UMTS/HSDPA with antennas

    NASA Astrophysics Data System (ADS)

    Eheduru, Marcellinus

    Over the last decade, mobile communication networks have evolved tremendously with a key focus on providing high speed data services in addition to voice. The third generation of mobile networks in the form of Universal Mobile Telecommunications System (UMTS) is already offering revolutionary mobile broadband experience to its users by deploying High Speed Downlink Packet Access (HSDPA) as its packet-data technology. With data speeds up to 14.4 Mbps and ubiquitous mobility, HSDPA is anticipated to become a preferred broadband access medium for end-users via mobile phones, laptops etc. While majority of these end-users are located indoors most of the time, approximately 70-80% of the HSDPA traffic is estimated to originate from inside buildings. Thus for network operators, indoor coverage has become a necessity for technical and business reasons. Macro-cellular (outdoor) to indoor coverage is a natural inexpensive way of providing network coverage inside the buildings. However, it does not guarantee sufficient link quality required for optimal HSDPA operation. On the contrary, deploying a dedicated indoor system may be far too expensive from an operator's point of view. In this thesis, the concept is laid for the understanding of indoor radio wave propagation in a campus building environment which could be used to plan and improve outdoor-to-indoor UMTS/HSDPA radio propagation performance. It will be shown that indoor range performance depends not only on the transmit power of an indoor antenna, but also on the product's response to multipath and obstructions in the environment along the radio propagation path. An extensive measurement campaign will be executed in different indoor environments analogous to easy, medium and hard radio conditions. The effects of walls, ceilings, doors and other obstacles on measurement results would be observed. Chapter one gives a brief introduction to the evolution of UMTS and HSDPA. It goes on to talk about radio wave propagation and some important properties of antennas which must be considered when choosing an antenna for indoor radio propagation. The challenges of in-building network coverage and also the objectives of this thesis are also mentioned in this chapter. The evolution and standardization, network architecture, radio features and most importantly, the radio resource management features of UMTS/HSDPA are given in chapter two. In this chapter, the reason why Wideband Code Division Multiple Access (WCDMA) was specified and selected for 3G (UMTS) systems would be seen. The architecture of the radio access network, interfaces with the radio access network between base stations and radio network controllers (RNC), and the interface between the radio access network and the core network are also described in this chapter. The main features of HSDPA are mentioned at the end of the chapter. In chapter three the principles of the WCDMA air interface, including spreading, Rake reception, signal fading, power control and handovers are introduced. The different types and characteristics of the propagation environments and how they influence radio wave propagation are mentioned. UMTS transport, logical and physical channels are also mentioned, highlighting their significance and relationship in and with the network. Radio network planning for UMTS is discussed in chapter four. The outdoor planning process which includes dimensioning, detailed planning, optimization and monitoring is outlined. Indoor radio planning with distributed antenna systems (DAS), which is the idea and motivation behind this thesis work, is also discussed. The various antennas considered and the antenna that was selected for this thesis experiment was discussed in chapter five. The antenna radiation pattern, directivity, gain and input impedance were the properties of the antenna that were taken into consideration. The importance of the choice of the antenna for any particular type of indoor environment is also mentioned. In chapter six, the design and fabrication of the monopole antennas used for the experimental m

  16. T. Aka-Ngnui and A. Beroual: Determination of the Streamers Characteristics Propagating in Liquids 1070-9878/06/$20.00 2006 IEEE

    E-print Network

    Paris-Sud XI, Université de

    is devoted to the modeling of branching streamers propagating in transformer oil using an equivalent INTRODUCTION THE mechanisms involved in the pre-breakdown and breakdown phenomena in transformer oil have been is analyzed. Index Terms -- Oil insulation, streamer propagating, electrical network computation. 1

  17. Characteristics of high-purity Cu thin films deposited on polyimide by radio-frequency Ar/H2 atmospheric-pressure plasma jet

    NASA Astrophysics Data System (ADS)

    Zhao, P.; Zheng, W.; Meng, Y. D.; Nagatsu, M.

    2013-03-01

    With a view to fabricating future flexible electronic devices, an atmospheric-pressure plasma jet driven by 13.56 MHz radio-frequency power is developed for depositing Cu thin films on polyimide, where a Cu wire inserted inside the quartz tube was used as the evaporation source. A polyimide substrate is placed on a water-cooled copper heat sink to prevent it from being thermally damaged. With the aim of preventing oxidation of the deposited Cu film, we investigated the effect of adding H2 to Ar plasma on film characteristics. Theoretical fitting of the OH emission line in OES spectrum revealed that adding H2 gas significantly increased the rotational temperature roughly from 800 to 1500 K. The LMM Auger spectroscopy analysis revealed that higher-purity Cu films were synthesized on polyimide by adding hydrogen gas. A possible explanation for the enhancement in the Cu film deposition rate and improvement of purity of Cu films by H2 gas addition is that atomic hydrogen produced by the plasma plays important roles in heating the gas to promote the evaporation of Cu atoms from the Cu wire and removing oxygen from copper oxide components via reduction reaction.

  18. Interval analysis, constraint propagation, applications

    E-print Network

    Boyer, Edmond

    is that they are sometimes too inefficient, especially to address real-time applications like interactive control or animation. Recent advances have shown that these limitations are not intrinsic since constraint propagation three representative papers chosen from these nine presentations. The first paper on radio antennas

  19. Near-Relativistic Solar Electrons and Type III Radio Bursts

    NASA Technical Reports Server (NTRS)

    Cane, H. V.

    2003-01-01

    Recently it has been found that the inferred injection times of greater than 25 keV electrons are up to 30 minutes later than the start times of the associated type III radio bursts at the Sun. Thus it has been suggested that the electrons that produce type III bursts do not belong to the same population as those observed above 25 keV. This paper examines the characteristics and circumstances of 79 solar electron beam events measured on the ACE spacecraft. Particular attention is paid to the very low frequency emissions of the associated radio bursts and the ambient conditions at the arrival times of the electrons at the spacecraft. It is found that the inferred greater than 25 keV electron injection delays are correlated with the times required for the associated radio bursts to drift to the lowest frequencies. This suggests that the electrons responsible for the radio emission and those observed above 25 keV are part of a single population, and that the electrons both above and below 25 keV are delayed in the interplanetary medium. Further evidence for a single population is the general correspondence between electron and local radio intensities and temporal profiles. It is found that the delays increase with the ambient solar wind density consistent with the propagation times of the electrons being determined by the characteristics of the interplanetary medium. However it is known that particle arrival times at 1 AU are a linear function of inverse particle speed. Conventionally such a relationship is taken to indicate scatter-free propagation when inferred path lengths lie close to 1.2 AU, as they do for the electron events studied here. These conflicting interpretations require further investigation.

  20. Radio broadcasting via satellite

    NASA Astrophysics Data System (ADS)

    Helm, Neil R.; Pritchard, Wilbur L.

    1990-10-01

    Market areas offering potential for future narrowband broadcast satellites are examined, including international public diplomacy, government- and advertising-supported, and business-application usages. Technical issues such as frequency allocation, spacecraft types, transmission parameters, and radio receiver characteristics are outlined. Service and system requirements, advertising revenue, and business communications services are among the economic issues discussed. The institutional framework required to provide an operational radio broadcast service is studied, and new initiatives in direct broadcast audio radio systems, encompassing studies, tests, in-orbit demonstrations of, and proposals for national and international commercial broadcast services are considered.

  1. Radio channel measurement and modelling for future mobile radio systems

    NASA Astrophysics Data System (ADS)

    Guerdenli, E.; Huish, P. W.

    1989-12-01

    Digital mobile radio systems will require planning methods that provide accurate predictions of signal strength, distortion, and interference for situations ranging from very small cells in dense urban locations to large rural cells. Topographic and land usage data bases will find increasing use to enhance the accuracy of prediction models. The implications of these issues are discussed and the work in progress at British Telecommunications Research Laboratories on land mobile radio propagation modeling and wide-band channel measurements is presented.

  2. Proceedings of the Thirteenth NASA Propagation Experimenters Meeting (NAPEX 13)

    NASA Technical Reports Server (NTRS)

    Davarian, Faramaz (editor)

    1989-01-01

    The NASA Propagation Experimenters Meeting (NAPEX), supported by the NASA Propagation Program, is convened annually to discuss studies made on radio wave propagation by investigators from domestic and international organizations. The meeting was organized into three technical sessions: the first focused on mobile satellite propagation; the second examined the propagation effects for frequencies above 10 GHz; and the third addressed studies devoted exclusively to the Olympus/Advanced Communications Technology Satellite (ACTS) Program.

  3. Equatorial ionospheric disturbance observed through a transequatorial HF propagation experiment

    Microsoft Academic Search

    T. Maruyama; M. Kawamura

    2006-01-01

    A transequatorial radio-wave propagation experiment at shortwave frequencies (HF-TEP) was done between Shepparton, Australia, and Oarai, Japan, using the radio broadcasting signals of Radio Australia. The receiving facility at Oarai was capable of direction finding based on the MUSIC (Multiple Signal Classification) algorithm. The results were plotted in azimuth-time diagrams (AT plots). During the daytime, the propagation path was close

  4. Premixed Turbulent Flame Propagation in Microgravity

    NASA Technical Reports Server (NTRS)

    Menon, S.; Disseau, M.; Chakravarthy, V. K.; Jagoda, J.

    1997-01-01

    Papers included address the following topics: (1) Turbulent premixed flame propagation in microgravity; (2) The effect of gravity on turbulent premixed flame propagation - a preliminary cold flow study; and (3) Characteristics of a subgrid model for turbulent premixed combustion.

  5. Emerging high-frequency (HF) and related radio-communications concepts for enduring C(3)I roles in a nuclear war environment: Critical issues in nuclear weapons effects on propagation. Topical report, 5 January1 June 1980

    Microsoft Academic Search

    C. B. Gabbard; R. E. LeLevier

    1980-01-01

    This document summarizes the nuclear weapons effects on propagation issues that must be considered in judging the overall nuclear effects vulnerability of selected strategic C3 concepts envisioned to provide enduring C3I support in nuclear war. This document focuses on the propagation effects in bands ranging from MF to UHF, with emphasis on HF skywave propagation during and after periods of

  6. Radio Ghosts

    E-print Network

    Ensslin, T A

    1999-01-01

    We investigate the possibility that patches of old radio plasma (`radio ghosts') of former radio galaxies form a second distinct phase of the inter-galactic medium (IGM), not mixed with the thermal gas. The separation of this phase from the ambient gas and its resistance against eroding turbulent forces is given by magnetic fields, which are expected to be roughly in pressure equilibrium with the surrounding medium. Since patches of this plasma are largely invisible in the radio we use the term `radio ghost' to characterize their nature. Possibilities and difficulties of different detection strategies of ghosts are discussed. These involve radio emission, cosmic microwave background (CMB) and starlight Comptonization, and Faraday rotation. Re-activation of the electron population in shock waves of cosmological structure formation, which seems to lead to the cluster radio relic phenomena. We discuss the role radio ghosts can have: They are able to store relativistic particles for cosmological times, but are al...

  7. Propagation characteristics of Po/So in the lithosphere of the Eastern Atlantic ocean revealed from automatic incoherent ocean bottom array processing

    NASA Astrophysics Data System (ADS)

    Dahm, T.; Krueger, F.; Hannemann, K.

    2013-12-01

    Contrary to continental lithosphere, the seismic shear wave anisotropy of the uppermost oceanic mantle is rarely sampled at local scales. Local anisotropy information from ocean bottom stations are often difficult to obtain because of the rare deployments and because of poor signal to noise (SNR) ratio at these stations. In a pilot study in the North Atlantic between Portugal mainland, Madeira and the Azores, we demonstrate that an ocean bottom mid-aperture array at 4-5 km depth allows for automatic retrieval of SHo, SVo and Po velocities from data filtered between 4 and 25 Hz from regional weak earthquakes with Ml < 3 in up to 500 km distance, even if the SNR is poor. We use incoherent array analysis applied to short-term average / long-term average (STA/LTA) characteristic functions. Contrary to conventional methods the array analysis reveals local, absolute velocities beneath the array that are not averages over long travelpaths. Additionally, earthquakes can be located using the backazimuth and So-Po difference times. For instance, we observe seismicity at an aseismic segment of the Gloria transform fault. For our pilot array at 38.4 N 18.38 W we detect and study more than 900 suited earthquakes over a period of 10 months, and retrieve a strong azimuthal anisotropy of SH and SV waves of about 8% with a fast direction striking 90E in accord with the direction of plate motion. Unexpectedly, the azimuthal anisotropy of P waves is small or even absent. We study furthermore the different propagation paths and find strong attenuation of Po and So for paths crossing the Azores hotspot region and attenuation of So only for the region directly west of Portugal. This indicates that Po and So phases are blocked or not generated in the hot upper mantle of active spreading zones The project is funded by the German Research Foundation (Da478/21-1, Kr1935/13-1). DEPAS (AWI, GFZ) and University of Hamburg supported the OBS deployment.

  8. Radio Astronomy

    NSDL National Science Digital Library

    Tenenbaum, David

    This article is a Why Files short piece on how astronomers use information from radio astronomy. Contrary to popular belief, large radio telescopes are not looking for signs of life outside our solar system, but are making images of black holes, centers of galaxies, and gamma ray bursts. These phenomena cannot be seen in visible light, but emit radio waves which can be translated into images. The article discusses how this process works, and the information gathered from radio waves.

  9. Cognitive radio: Making software radios more personal

    Microsoft Academic Search

    Joseph Mitola; Gerald Quentin Maguire Jr.

    1999-01-01

    Software radios are emerging as platforms for multiband multimode personal communications systems. Radio etiquette is the set of RF bands, air interfaces, protocols, and spatial and temporal patterns that moderate the use of the radio spectrum. Cognitive radio extends the software radio with radio-domain model-based reasoning about such etiquettes. Cognitive radio enhances the flexibility of personal services through a Radio

  10. Firefighters' Radios

    NASA Technical Reports Server (NTRS)

    1976-01-01

    Public Technology Inc. asked for NASA assistance to devise the original firefighter's radio. Good short-range radio communications are essential during a fire to coordinate hose lines, rescue victims, and otherwise increase efficiency. Useful firefighting tool is lower cost, more rugged short range two-way radio. Inductorless electronic circuit replaced inductances and coils in radio circuits with combination of transistors and other low-cost components. Substitution promises reduced circuit size and cost. Enhanced electrical performance made radio more durable and improved maintainability by incorporating modular construction.

  11. Influence of the axicon characteristics and beam propagation parameter M{sup 2} on the formation of Bessel beams from semiconductor lasers

    SciTech Connect

    Sokolovskii, G S; Dyudelev, V V; Losev, S N; Butkus, M; Soboleva, K K; Sobolev, A I; Deryagin, A G; Kuchinskii, V I; Sibbet, V; Rafailov, E U

    2013-05-31

    We study the peculiarities of the formation of Bessel beams in semiconductor lasers with a high propagation parameter M{sup 2}. It is shown that the propagation distance of the Bessel beam is determined by the divergence of the quasi-Gaussian beam with high M{sup 2} rather than the geometric parameters of the optical scheme. It is demonstrated that technologically inevitable rounding of the axicon tip leads to a significant increase in the transverse dimension of the central part of the Bessel beam near the axicon. (semiconductor lasers. physics and technology)

  12. A virus spreading model for cognitive radio networks

    NASA Astrophysics Data System (ADS)

    Hou, L.; Yeung, K. H.; Wong, K. Y.

    2012-12-01

    Since cognitive radio (CR) networks could solve the spectrum scarcity problem, they have drawn much research in recent years. Artificial intelligence(AI) is introduced into CRs to learn from and adapt to their environment. Nonetheless, AI brings in a new kind of attacks specific to CR networks. The most powerful one is a self-propagating AI virus. And no spreading properties specific to this virus have been reported in the literature. To fill this research gap, we propose a virus spreading model of an AI virus by considering the characteristics of CR networks and the behavior of CR users. Several important observations are made from the simulation results based on the model. Firstly, the time taken to infect the whole network increases exponentially with the network size. Based on this result, CR network designers could calculate the optimal network size to slow down AI virus propagation rate. Secondly, the anti-virus performance of static networks to an AI virus is better than dynamic networks. Thirdly, if the CR devices with the highest degree are initially infected, the AI virus propagation rate will be increased substantially. Finally, it is also found that in the area with abundant spectrum resource, the AI virus propagation speed increases notably but the variability of the spectrum does not affect the propagation speed much.

  13. Performance of narrowband CPM systems with limiter-discriminator-integrator detection and decision feedback equalization in mobile radio channels

    Microsoft Academic Search

    Oreste Andrisano; Marco Chiani; Roberto Verdone

    1993-01-01

    A completely analytical approach is presented to achieve error probability analysis of limiter-discriminator-integrator (LDI) detection of binary continuous-phase modulation in a land mobile radio channel characterized by Rayleigh fading and Doppler effects. Optimum choice of the postdetection integration time is carried out when varying both system parameters and propagation characteristics, namely the Doppler shift. The improvements obtainable by means of

  14. Svetloe Radio Astronomical Observatory

    NASA Technical Reports Server (NTRS)

    Smolentsev, Sergey; Rahimov, Ismail

    2013-01-01

    This report summarizes information about the Svetloe Radio Astronomical Observatory activities in 2012. Last year, a number of changes took place in the observatory to improve some technical characteristics and to upgrade some units to their required status. The report provides an overview of current geodetic VLBI activities and gives an outlook for the future.

  15. Radio wave.

    PubMed

    Elkin, V

    1992-01-01

    In developing countries with high rates of poverty and illiteracy, radio is emerging as an excellent medium for delivering information on health issues, family planning, nutrition, and agricultural development. Since radio does not require wired electricity, it can reach remote rural populations. Surveys have found that between 50-75% of poor rural households in developing countries own radios, and the majority listen to educational radio at least once a week. A program that reaches the urban poor outside of Lima, Peru, has been instrumental in controlling the spread of cholera. A Bolivian station broadcasts 8 hours of literacy, health, agricultural, and cultural programming a day to an audience of more than 2 million Aymara Indians. Small village radio stations with a broadcast range of 15 miles can be established for under US$400 and can generally achieve sustainability through local fundraising events such as raffles. In many cases, listeners have become broadcasters at their local radio stations. PMID:12286181

  16. The Propagation Characteristics of Strong Ground-Motion on the Footwall of Chelungpu Fault During the 1999 Chi-Chi, Taiwan Earthquake

    NASA Astrophysics Data System (ADS)

    Huang, Y.; Huang, B.; Wang, S.

    2009-12-01

    The observation records show different ground-motion effects between the footwall and the hanging wall during the Chi-Chi earthquake, September 21, 1999 (UTC was 17:47, 20 September 1999). A series of strong ground-motion snapshots which was constructed by using near source strong motion records of the earthquake shows that: 1. The rupture velocity decreased from the south to the north progressively during Chelungpu fault ruptured, the value was from 2.69 km/sec to 2.28 km/sec and the average rupture velocity was 2.5 km/sec. 2. The propagation of seismic wave front was outstandingly different between the east site (hanging wall) and the west site (footwall) of Chelungpu fault; to follow the rupture from the south to the north of fault, a linear wave front was in an included angle about 60° with the east, and traveled toward northwest on the footwall. Based on the compare with observation records and simulations of previous studies, the seismic velocity on the foot wall side could be lower than the rupture velocity of the Chi-Chi earthquake. Herein, the linear wave front which propagated similar to shock front displayed in the strong ground-motion snapshots. The aim of this study is to find out the linear wave front from waveform data by reexamining the near source strong motion data of the Chi-Chi earthquake and try to estimate its propagated velocity. Further, to verify whether the S-wave velocity on the footwall was lower than rupture velocity or not. The result shows that the S-wave propagated as a velocity 1.92 km/sec; it was lower than rupture velocity absolutely. In sedimentary structure, S-wave velocity can be from around 3.55 km/sec to under 1.0 km/sec which depends on how hard or soft the medium is passed through. The sediment in the footwall region of Chelungpu fault is thick and solid; it is very possible that the S-wave traveled slower than fault rupture during the Chi-Chi earthquake. To have come this far, a linear S-wave front on the footwall has been figured out and its velocity was about 1.92 km/sec has been estimated by this study. These prove the velocity of S-wave propagation on the footwall was lower than rupture velocity and caused the linear wave front which propagated similar to shock front.

  17. Posterior distributions of a statistic of propagation loss inferred from radar sea clutter

    E-print Network

    Buckingham, Michael

    Posterior distributions of a statistic of propagation loss inferred from radar sea clutter L. Ted), Posterior distributions of a statistic of propagation loss inferred from radar sea clutter, Radio Sci., 40

  18. A time dependent difference theory for sound propagation in ducts with flow. [characteristic of inlet and exhaust ducts of turbofan engines

    NASA Technical Reports Server (NTRS)

    Baumeister, K. J.

    1979-01-01

    A time dependent numerical solution of the linearized continuity and momentum equation was developed for sound propagation in a two dimensional straight hard or soft wall duct with a sheared mean flow. The time dependent governing acoustic difference equations and boundary conditions were developed along with a numerical determination of the maximum stable time increments. A harmonic noise source radiating into a quiescent duct was analyzed. This explicit iteration method then calculated stepwise in real time to obtain the transient as well as the steady state solution of the acoustic field. Example calculations were presented for sound propagation in hard and soft wall ducts, with no flow and plug flow. Although the problem with sheared flow was formulated and programmed, sample calculations were not examined. The time dependent finite difference analysis was found to be superior to the steady state finite difference and finite element techniques because of shorter solution times and the elimination of large matrix storage requirements.

  19. A study on the estimation of the seaquake response of a floating structure considering the characteristics of seismic wave propagation in the ground and the water

    Microsoft Academic Search

    Hiroaki Takamura; Koichi Masuda; Hisaaki Maeda; Masatoshi Bessho

    2003-01-01

    Seaquakes, which are characterized by the propagation of vertical earthquake motion at the sea bottom as a compression (longitudinal)\\u000a wave, are reported to cause damage to ships, and their effect on floating structures is a matter of great concern. To comprehend\\u000a the basic properties of seaquakes, we first discuss a method to calculate the displacement of the seabed when it

  20. ON SUN-TO-EARTH PROPAGATION OF CORONAL MASS EJECTIONS

    SciTech Connect

    Liu, Ying D. [State Key Laboratory of Space Weather, National Space Science Center, Chinese Academy of Sciences, Beijing (China); Luhmann, Janet G.; Moestl, Christian; Bale, Stuart D.; Lin, Robert P. [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States); Lugaz, Noe [Space Science Center, University of New Hampshire, Durham, NH 03824 (United States); Davies, Jackie A., E-mail: liuxying@ssl.berkeley.edu [Space Science and Technology Department, Rutherford Appleton Laboratory, Didcot (United Kingdom)

    2013-05-20

    We investigate how coronal mass ejections (CMEs) propagate through, and interact with, the inner heliosphere between the Sun and Earth, a key question in CME research and space weather forecasting. CME Sun-to-Earth kinematics are constrained by combining wide-angle heliospheric imaging observations, interplanetary radio type II bursts, and in situ measurements from multiple vantage points. We select three events for this study, the 2012 January 19, 23, and March 7 CMEs. Different from previous event studies, this work attempts to create a general picture for CME Sun-to-Earth propagation and compare different techniques for determining CME interplanetary kinematics. Key results are obtained concerning CME Sun-to-Earth propagation: (1) the Sun-to-Earth propagation of fast CMEs can be approximately formulated into three phases: an impulsive acceleration, then a rapid deceleration, and finally a nearly constant speed propagation (or gradual deceleration); (2) the CMEs studied here are still accelerating even after the flare maximum, so energy must be continuously fed into the CME even after the time of the maximum heating and radiation has elapsed in the corona; (3) the rapid deceleration, presumably due to interactions with the ambient medium, mainly occurs over a relatively short timescale following the acceleration phase; and (4) CME-CME interactions seem a common phenomenon close to solar maximum. Our comparison between different techniques (and data sets) has important implications for CME observations and their interpretations: (1) for the current cases, triangulation assuming a compact CME geometry is more reliable than triangulation assuming a spherical front attached to the Sun for distances below 50-70 solar radii from the Sun, but beyond about 100 solar radii we would trust the latter more; (2) a proper treatment of CME geometry must be performed in determining CME Sun-to-Earth kinematics, especially when the CME propagation direction is far away from the observer; and (3) our approach to comparing wide-angle heliospheric imaging observations with interplanetary radio type II bursts provides a novel tool in investigating CME propagation characteristics. Future CME observations and space weather forecasting are discussed based on these results.

  1. On Sun-to-Earth Propagation of Coronal Mass Ejections

    NASA Astrophysics Data System (ADS)

    Liu, Ying D.; Luhmann, Janet G.; Lugaz, Noé; Möstl, Christian; Davies, Jackie A.; Bale, Stuart D.; Lin, Robert P.

    2013-05-01

    We investigate how coronal mass ejections (CMEs) propagate through, and interact with, the inner heliosphere between the Sun and Earth, a key question in CME research and space weather forecasting. CME Sun-to-Earth kinematics are constrained by combining wide-angle heliospheric imaging observations, interplanetary radio type II bursts, and in situ measurements from multiple vantage points. We select three events for this study, the 2012 January 19, 23, and March 7 CMEs. Different from previous event studies, this work attempts to create a general picture for CME Sun-to-Earth propagation and compare different techniques for determining CME interplanetary kinematics. Key results are obtained concerning CME Sun-to-Earth propagation: (1) the Sun-to-Earth propagation of fast CMEs can be approximately formulated into three phases: an impulsive acceleration, then a rapid deceleration, and finally a nearly constant speed propagation (or gradual deceleration); (2) the CMEs studied here are still accelerating even after the flare maximum, so energy must be continuously fed into the CME even after the time of the maximum heating and radiation has elapsed in the corona; (3) the rapid deceleration, presumably due to interactions with the ambient medium, mainly occurs over a relatively short timescale following the acceleration phase; and (4) CME-CME interactions seem a common phenomenon close to solar maximum. Our comparison between different techniques (and data sets) has important implications for CME observations and their interpretations: (1) for the current cases, triangulation assuming a compact CME geometry is more reliable than triangulation assuming a spherical front attached to the Sun for distances below 50-70 solar radii from the Sun, but beyond about 100 solar radii we would trust the latter more; (2) a proper treatment of CME geometry must be performed in determining CME Sun-to-Earth kinematics, especially when the CME propagation direction is far away from the observer; and (3) our approach to comparing wide-angle heliospheric imaging observations with interplanetary radio type II bursts provides a novel tool in investigating CME propagation characteristics. Future CME observations and space weather forecasting are discussed based on these results.

  2. Evaluation of CHAMP radio occultation refractivity using data assimilation office analyses and radiosondes

    E-print Network

    Joiner, Joanna

    Evaluation of CHAMP radio occultation refractivity using data assimilation office analyses occultation experiment on the CHAMP satellite has been collecting observations of the Earth's atmosphere since candidate than geometrical optics and back-propagation for generating GPS radio occultation datasets

  3. College Radio.

    ERIC Educational Resources Information Center

    Sauls, Samuel J.

    As with commercial stations, the underlying premise of the college radio station is to serve the community, whether it be the campus community or the community at large, but in unique ways often geared to underserved niches of the population. Much of college radio's charm lies in its unpredictable nature and constant mutations. The stations give…

  4. Radio Traffic

    Microsoft Academic Search

    D. Sarnoff

    1914-01-01

    The functions of the traffic department of a radio company, namely: procuring and moving traffic, procuring equipment contracts, and operating ship and shore stations economically and efficiently, are described. In connection with the work of the Marconi Company, the cooperation between the Western Union and Postal Telegraph Companies and the radio company is treated in detail. The complete routine procedure

  5. Features of Superlong-Distance and Round-the-World Propagation of HF Waves

    NASA Astrophysics Data System (ADS)

    Ponyatov, A. A.; Vertogradov, G. G.; Uryadov, V. P.; Vertogradova, E. G.; Shumaev, V. V.; Chernov, A. G.; Chaika, E. G.

    2014-11-01

    We present the results of the experimental studies of the features of superlong-distance and round-the-world propagation of the HF waves in the radio lines with different orientation and length, which were obtained in 2012-2014 using a new method of oblique ionospheric sounding. The frequency-time travel intervals of the direct round-the-world signals, their amplitude-frequency and angular-frequency characteristics are determined. The mechanism of propagation and transformation of the round-the-world signals due to the radio-wave refraction by the transverse electron-density gradients in the region of approach of two optimal paths passing via the transmitter and receiver so that each path forms the smallest angle with the terminator. It is shown that the proposed mechanism is in good agreement with the experimentally observed variation of the azimuth of the direct round-the-world signal on the Cyprus-Rostov-on-Don path and on the Alice Springs (Australia)-Rostov-on-Don path in the absence of variation of the direct round-the-world signal azimuth. For the superlong-distance propagation of the HF waves on the Virginia (USA)-Yoshkar-Ola and Puerto Rico-Yoshkar-Ola (the distances about 8000-10000 km) paths, the best propagation conditions are observed when the entire path is in the illuminated ionosphere near the terminator boundary making a small angle of 10°-25° with the terminator.

  6. Elements of Radio Waves

    E-print Network

    Frank G. Borg; Ismo Hakala; Jukka Määttälä

    2007-12-24

    We present a summary of the basic properties of the radio wave generation, propagation and reception, with a special attention to the gigahertz bandwidth region which is of interest for wireless sensor networks. We also present some measurement results which use the so-called RSSI indicator in order to track how the field strength varies with position and distance of the transceivers. We hope the paper may be useful to anyone who looks for a quick review of the fundamentals of electromagnetic theory with application to antennas.

  7. Structural exploration using longwave radio-clock time-signal

    NASA Astrophysics Data System (ADS)

    Yamazaki, S.; Mikada, H.; Onishi, K.; Konishi, N.

    2008-12-01

    VLF methods have been used for one dimensional survey that ties records of the single point measurement with subsurface structure. Since VLF electromagnetic wave is not stable due to various effects in the propagation, subsurface structural exploration using VLF methods has limitations in resolution and in the applicability depending on the place of surveys. To overcome some of the limitations, we propose to use standard-time longwaveelectromagnetic transmissions (JJY in Japan), that could be more stable than VLF, for the exploration of underground structure. Once radio time-signal receivers have become popular, we may distribute many receivers in a wide area to record continuous time signal simultaneously for estimating subsurface resistivity distribution. Continuous measurements, moreover, might improve measurement efficiency and S/N ratio. In our study, we applied numerical experiments to confirm the method to work. First, we created a test data set composed of air and heterogeneous half space earth for which JJY signal propagates. Then, we estimate the distortion of time signal on the surface of the half space to evaluate the characteristics of underground response to JJY and to see the availability of JJY standard electromagnetic wave for structural exploration as well as for a VLF method. We used electromagnetic wave of 20 kHz as a VLF wave and 40 and 60 kHz as JJY standard electromagnetic waves and evaluated the resolution of the methods derived from the skin depth and the influence of the geometry for various combination of the orientation of anomalous structure, the propagation direction of radio wave, and the orientation of two- dimentionally aligned receivers. To estimate the influence of the geometry between the orientations of structural anomaly and the propagation direction, we evaluated the characteristic response of the survey as a function of difference angle of the orientations. Our results show the following confirmation: (i) there are little influence on the attenuation of the electromagnetic radiation if observation point is located above the resistivity anomaly, (ii) - higher the frequency becomes, shallower layer the influences come from, and (iii) the smaller difference angle becomes, better the sensitivity of survey becomes. Therefore, we conclude that the structural anomaly runs in the direction of radio wave propagation, the most ideal survey would be conducted as known well for electromagnetic surveys. Our study suggests that JJY signal or any other continuous time signal could be used for the estimation of subsurface resistivity distribution. In the future, we try to extend the method to VLF-MT for subsurface structure and to apply it for field data.

  8. Plasma Diagnostics of the Interstellar Medium with Radio Astronomy

    NASA Astrophysics Data System (ADS)

    Haverkorn, Marijke; Spangler, Steven R.

    2013-10-01

    We discuss the degree to which radio propagation measurements diagnose conditions in the ionized gas of the interstellar medium (ISM). The "signal generators" of the radio waves of interest are extragalactic radio sources (quasars and radio galaxies), as well as Galactic sources, primarily pulsars. The polarized synchrotron radiation of the Galactic non-thermal radiation also serves to probe the ISM, including space between the emitting regions and the solar system. Radio propagation measurements provide unique information on turbulence in the ISM as well as the mean plasma properties such as density and magnetic field strength. Radio propagation observations can provide input to the major contemporary questions on the nature of ISM turbulence, such as its dissipation mechanisms and the processes responsible for generating the turbulence on large spatial scales. Measurements of the large scale Galactic magnetic field via Faraday rotation provide unique observational input to theories of the generation of the Galactic field.

  9. Plasma Diagnostics of the Interstellar Medium with Radio Astronomy

    NASA Astrophysics Data System (ADS)

    Haverkorn, Marijke; Spangler, Steven R.

    We discuss the degree to which radio propagation measurements diagnose conditions in the ionized gas of the interstellar medium (ISM). The "signal generators" of the radio waves of interest are extragalactic radio sources (quasars and radio galaxies), as well as Galactic sources, primarily pulsars. The polarized synchrotron radiation of the Galactic non-thermal radiation also serves to probe the ISM, including space between the emitting regions and the solar system. Radio propagation measurements provide unique information on turbulence in the ISM as well as the mean plasma properties such as density and magnetic field strength. Radio propagation observations can provide input to the major contemporary questions on the nature of ISM turbulence, such as its dissipation mechanisms and the processes responsible for generating the turbulence on large spatial scales. Measurements of the large scale Galactic magnetic field via Faraday rotation provide unique observational input to theories of the generation of the Galactic field.

  10. Proceedings of the Seventeenth NASA Propagation Experimenters Meeting (NAPEX 17) and the Advanced Communications Technology Satellite (ACTS) Propagation Studies Miniworkshop

    NASA Technical Reports Server (NTRS)

    Davarian, Faramaz (editor)

    1993-01-01

    The NASA Propagation Experimenters Meeting (NAPEX) is convened annually to discuss studies made on radio wave propagation by investors from domestic and international organizations. NAPEX 17 was held on 15 June 1993. The meeting was organized into two technical sessions. The first session was dedicated to slant path propagation studies and experiments. The second session focused on propagation studies for mobile and personal communications. Preceding NAPEX 17, the Advanced Communications Technology Satellite (ACTS) Propagation Studies Miniworkshop was held on 14 June 1993 to review ACTS propagation activities with emphasis on ACTS experiments status and data collection, processing, and exchange.

  11. Managing Mobile/Satellite Propagation Data

    NASA Technical Reports Server (NTRS)

    Kantak, Anil V.

    1990-01-01

    "Data Management System for Mobile Satellite Propagation" software package collection of FORTRAN programs and UNIX shell scripts designed to handle huge amounts of data resulting from mobile/satellite radio-propagation experiments. Data from experiments converted into standard and more useful forms. Software package contains program to convert binary format of data into standard ASCII format suitable for use with wide variety of computing-machine architectures. Written in either FORTRAN 77 or UNIX shell scripts.

  12. Radio Telescopes

    NASA Astrophysics Data System (ADS)

    Ekers, Ron; Wilson, Thomas L.

    ``Radio Telescopes" starts with a brief historical introduction from Jansky's1931 discovery of radio emission from the Milky Way through the development ofradio telescope dishes and arrays to aperture synthesis imaging. It includessufficient basics of electromagnetic radiation to provide some understanding of thedesign and operation of radio telescopes. The criteria such as frequencyrange, sensitivity, survey speed, angular resolution, and field of view thatdetermine the design of radio telescopes are introduced. Because it is soeasy to manipulate the electromagnetic waves at radio frequencies, radiotelescopes have evolved into many different forms, sometimes with "wire"structures tuned to specific wavelengths, which look very different from anykind of classical telescope. To assist astronomers more familiar with otherwavelength domains, the appendix A.1. includes a comparison of radioand optical terminology. Some of the different types of radio telescopesincluding the filled aperture dishes, electronically steered phased arrays, andaperture synthesis radio telescopes are discussed, and there is a sectioncomparing the differences between dishes and arrays. Some of the morerecent developments including hierarchical beam forming, phased arrayfeeds, mosaicing, rotation measure synthesis, digital receivers, and longbaseline interferometers are included. The problem of increasing radiofrequency interference is discussed, and some possible mitigation strategies areoutlined.

  13. A history of radio astronomy polarisation measurements

    NASA Astrophysics Data System (ADS)

    Wielebinski, Richard

    2012-07-01

    While intensity of electromagnetic radiation (radio, infrared, light, or X-ray) gives us primary information about the distribution of the baryonic matter in the Universe, polarisation is a parameter that enables us to investigate many additional details. Polarisation at radio frequencies gives us details of emission processes since the non-thermal synchrotron process dominates at low radio frequencies in emission regions. In addition, polarised radio sources can be used as probes of the intervening interstellar medium through which the radio waves are propagated. Faraday rotation effects are observed and in conjunction with known thermal emission can be used to determine magnetic fields. The Zeeman effect, a direct method of determining magnetic fields, depends on the observation of the circularpolarisation components of a spectral line. In this paper I describe the early polarisation observations of radio sources, but in addition I follow the developments through to the present day.

  14. The role of reaction temperature and cracking catalyst characteristics in determining the relative rates of protolytic cracking, chain propagation, and hydrogen transfer

    SciTech Connect

    Corma, A. (Universidad Politecnica de Valencia (Spain)); Miguel, P.J.; Orchilles, A.V. (Universitat de Valencia (Spain))

    1994-01-01

    The cracking of isobutane on USY zeolites with different unit cell size has been studied in the temperature range 400-500[degrees]C, using an experimental apparatus which makes it possible to follow the reaction at very short times on stream. By measuring product initial selectivities it has been found that protolytic cracking and bimolecular reactions take place on Broensted acid sites. In this way the contributions of bimolecular reactions involving hydride transfer have been separated from those responsible for chain transfer and those producing hydrogen transfer. Chain transfer accounts for the chain propagation in paraffin cracking, while hydrogen transfer produces the extra paraffin amounts obtained in these reactions. Hydrogen transfer reactions increase, but chain transfer reactions decrease when the unit cell size increases. From energetic considerations, the influence of the zeolite catalyst and reaction conditions on the controlling step in isobutane cracking can be suggested. 24 refs., 6 figs., 4 tabs.

  15. Global morphology of infrasound propagation

    Microsoft Academic Search

    Douglas P. Drob; J. M. Picone; M. Garcés

    2003-01-01

    Atmospheric sound waves in the 0.02–10 Hz region, also known as infrasound, exhibit long-range global propagation characteristics. Measurable infrasound is produced around the globe on a daily basis by a variety of natural and man-made sources. As a result of weak classical attenuation (?0.01 dB km?1 at 0.1 hz), these acoustic signals can propagate thousands of kilometers in tropospheric, stratospheric,

  16. CB Radios

    ERIC Educational Resources Information Center

    Martin, Dick

    1977-01-01

    Citizen band radios keep trucking across the American scene, and no doubt your students are caught in the folk craze. Provides some suggestions for channeling students' interests with a unit on CBs. (Author/RK)

  17. Radio astronomy

    Microsoft Academic Search

    Kenneth I. Kellermann; David Heeschen; Donald C. Backer; Marshall H. Cohen; Michael Davis; Imke de Pater; David De Young; George A. Dulk; J. R. Fisher; W. Miller Goss

    1991-01-01

    The following subject areas are covered: (1) scientific opportunities (millimeter and sub-millimeter wavelength astronomy; meter to hectometer astronomy; the Sun, stars, pulsars, interstellar masers, and extrasolar planets; the planets, asteroids, and comets; radio galaxies, quasars, and cosmology; and challenges for radio astronomy in the 1990's); (2) recommendations for new facilities (the millimeter arrays, medium scale instruments, and small-scale projects); (3)

  18. On Sun-to-Earth Propagation of Coronal Mass Ejections

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Luhmann, J. G.; Lugaz, N.; Moestl, C.; Bale, S. D.; Lin, R. P.

    2013-05-01

    We investigate how coronal mass ejections (CMEs) propagate through, and interact with, the inner heliosphere between the Sun and Earth, a key question in CME research and space weather forecasting. CME Sun-to-Earth kinematics are constrained by combining wide-angle heliospheric imaging observations, interplanetary radio type II bursts and in situ measurements from multiple vantage points. We select three events for this study, the 2012 January 19, 23, and March 7 CMEs, each of which has wide-angle imaging coverage from both STEREO A and B, a long-duration interplanetary type II burst and in situ signatures near the Earth. Key results are obtained concerning CME Sun-to-Earth propagation: (1) the Sun-to-Earth propagation of fast CMEs can be formulated into three phases: an impulsive acceleration, then a rapid deceleration, and finally a nearly constant speed propagation (or gradual deceleration); (2) the CMEs studied here are still accelerating even after the flare maximum, so energy must be continuously fed into the CME even after the maximum heating and radiation have elapsed in the corona; (3) the rapid deceleration, presumably due to interactions with the ambient medium, mainly occurs within a relatively short time scale following the acceleration phase; (4) CME-CME interactions seem a common phenomenon close to solar maximum. Comparison between different techniques (and data sets) gives important implications for CME observations and interpretations: (1) for the current cases triangulation with the fixed ? approximation is more reliable than triangulation with the harmonic mean approximation below 50-70 solar radii from the Sun, but beyond about 100 solar radii we would trust the harmonic mean triangulation more; (2) a proper treatment of CME geometry must be performed in determining CME Sun-to-Earth kinematics, especially when the CME propagation direction is far away from the observer; (3) our approach in comparing wide-angle heliospheric imaging observations with interplanetary radio type II bursts provides a novel tool in investigating CME propagation characteristics. Future CME observations and space weather forecasting are discussed based on the results.

  19. Indoor propagation measurements at DECT frequencies

    Microsoft Academic Search

    F. Babich; G. Lombardi; L. Tomasi; E. Valentinuzzi

    1996-01-01

    Broadband measurements of the indoor radio propagation channel, performed on the office floor of a factory, are described. The sounded frequency band has been 1.7-2.2 GHz, since several mobile and cordless telephone systems, and in particular DECT, operate within that frequency range. The frequency domain technique, proposed by Howard and Pahlavan (1990), based upon the use of a network analyzer,

  20. Cutting line determination for plant propagation

    NASA Astrophysics Data System (ADS)

    Lo, Li-Yun; Hsia, Chi-Chun; Sun, Hua-Hong; Chen, Hsiang-Ju; Wu, Xin-Ting; Hu, Min-Chun

    2014-01-01

    Investigating an efficient method for plant propagation can help not only prevent extinction of plants but also facilitate the development of botanical industries. In this paper, we propose to use image processing techniques to determine the cutting-line for the propagation of two kinds of plants, i.e. Melaleuca alternifolia Cheel and Cinnamomum kanehirai Hay, which have quite different characteristics in terms of shape, structure, and propagation way (e.g. propagation by seeding and rooting, respectively). The proposed cutting line determination methods can be further applied to develop an automatic control system to reduce labor cost and increase the effectiveness of plant propagation.

  1. Phenomenology of magnetospheric radio emissions

    NASA Technical Reports Server (NTRS)

    Carr, T. D.; Desch, M. D.; Alexander, J. K.

    1983-01-01

    Jupiter has now been observed over 24 octaves of the radio spectrum, from about 0.01 MHz to 300,000 MHz. Its radio emissions fill the entire spectral region where interplanetary electromagnetic propagation is possible at wavelengths longer than infrared. Three distinct types of radiation are responsible for this radio spectrum. Thermal emission from the atmosphere accounts for virtually all the radiation at the high frequency end. Synchrotron emission from the trapped high-energy particle belt deep within the inner magnetosphere is the dominant spectral component from about 4000 to 40 MHz. The third class of radiation consists of several distinct components of sporadic low frequency emission below 40 MHz. The decimeter wavelength emission is considered, taking into account the discovery of synchrotron emission, radiation by high-energy electrons in a magnetic field, and the present status of Jovian synchrotron phenomenology. Attention is also given to the decameter and hectometer wavelength emission, and emissions at kilometric wavelengths.

  2. Rift propagation

    NASA Technical Reports Server (NTRS)

    Parmentier, E. M.; Schubert, G.

    1989-01-01

    A model for rift propagation which treats the rift as a crack in an elastic plate which is filled from beneath by upwelling viscous asthenosphere as it lengthens and opens. Growth of the crack is driven by either remotely applied forces or the pressure of buoyant asthenosphere in the crack and is resisted by viscous stresses associated with filling the crack. The model predicts a time for a rift to form which depends primarily on the driving stress and asthenosphere viscosity. For a driving stress on the order of 10 MPa, as expected from the topography of rifted swells, the development of rifts over times of a few Myr requires an asthenosphere viscosity of 10 to the 16th Pa s (10 to the 17th poise). This viscosity, which is several orders of magnitude less than values determined by postglacial rebound and at least one order of magnitude less than that inferred for spreading center propagation, may reflect a high temperature or large amount of partial melting in the mantle beneath a rifted swell.

  3. Experimental Comparison of Bluetooth and WiFi Signal Propagation for Indoor Localisation

    E-print Network

    Braun, Torsten

    Experimental Comparison of Bluetooth and WiFi Signal Propagation for Indoor Localisation Desislava,alyafawi,braun}@iam.unibe.ch Abstract. Systems for indoor positioning using radio technologies are largely studied due coor- dinates from observed radio signals and hence good understanding of the indoor radio channel

  4. Acoustic Propagation Considerations for Underwater Acoustic Communications Network Development

    E-print Network

    Zhou, Shengli

    Acoustic Propagation Considerations for Underwater Acoustic Communications Network Development Woods Hole, MA 02543 jpreisig@whoi.edu ABSTRACT Underwater acoustic communications systems are challenged by the characteristics of acoustic propagation through the underwater environment

  5. Proceedings of the Twentieth NASA Propagation Experimenters Meeting (NAPEX XX) and the Advanced Communications Technology Satellite (ACTS) Propagation Studies Miniworkshop

    NASA Technical Reports Server (NTRS)

    Golshan, Nassar (Editor)

    1996-01-01

    The NASA Propagation Experimenters (NAPEX) Meeting and associated Advanced Communications Technology Satellite (ACTS) Propagation Studies Miniworkshop convene yearly to discuss studies supported by the NASA Propagation Program. Representatives from the satellite communications (satcom)industry, academia, and government with an interest in space-ground radio wave propagation have peer discussion of work in progress, disseminate propagation results, and interact with the satcom industry. NAPEX XX, in Fairbanks, Alaska, June 4-5, 1996, had three sessions: (1) "ACTS Propagation Study: Background, Objectives, and Outcomes," covered results from thirteen station-years of Ka-band experiments; (2) "Propagation Studies for Mobile and Personal Satellite Applications," provided the latest developments in measurement, modeling, and dissemination of propagation phenomena of interest to the mobile, personal, and aeronautical satcom industry; and (3)"Propagation Research Topics," covered a range of topics including space/ground optical propagation experiments, propagation databases, the NASA Propagation Web Site, and revision plans for the NASA propagation effects handbooks. The ACTS Miniworkshop, June 6, 1996, covered ACTS status, engineering support for ACTS propagation terminals, and the ACTS Propagation Data Center. A plenary session made specific recommendations for the future direction of the program.

  6. Models and solutions for radio irregularity in wireless sensor networks

    Microsoft Academic Search

    Gang Zhou; Tian He; Sudha Krishnamurthy; John A. Stankovic

    2006-01-01

    In this paper, we investigate the impact of radio irregularity on wireless sensor networks. Radio irregularity is a common phenomenon which arises from multiple factors, such as variance in RF sending power and dieren t path losses depending on the direction of propagation. From our experiments, we discover that the variance in received signal strength is largely random; however, it

  7. Impact of radio irregularity on wireless sensor networks

    Microsoft Academic Search

    Gang Zhou; Tian He; Sudha Krishnamurthy; John A. Stankovic

    2004-01-01

    In this paper, we investigate the impact of radio irregularity on the communication performance in wireless sensor networks. Radio irregularity is a common phenomenon which arises from multiple factors, such as variance in RF sending power and different path losses depending on the direction of propagation. From our experiments, we discover that the variance in received signal strength is largely

  8. Ultra Wideband Indoor Radio Channel Models: Preliminary Results

    Microsoft Academic Search

    Veikko Hovinen; Matti Hämäläinen; Timo Pätsi

    Knowledge of the signal propagation mechanisms in the chan- nel is vital for the radio system design and the system perform- ance analysis. However, currently published wideband or nar- rowband radio channel models do not offer spatial resolution high enough for the ultra wideband (UWB) applications and the real channel measurements are needed. In this paper is given the preliminary

  9. Tracking tropospheric radio occultation signals from low Earth orbit

    Microsoft Academic Search

    Sergey V. Sokolovskiy

    2001-01-01

    Propagation of radio occultation signals through the tropical lower troposphere with severe refractivity gradients results in significant spreading of the signal spectrum. Under such conditions a signal acquisition technique which tracks large random troposphere-induced phase accelerations more reliably than a generic phase-locked loop has to be applied. This paper discusses the results of simulations of open loop tracking of radio

  10. Measurements of the Continuous Radio Background and Comparison with Simulated

    E-print Network

    Erdmann, Martin

    . . . . . . . . . . . . . . . . . . . . . . . . 31 4.1.1. The logarithmic-periodic dipole Antenna . . . . . . . . 34 4.1.2. Signal ProcessingMeasurements of the Continuous Radio Background and Comparison with Simulated Radio Signals from . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.2. Propagation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.3. Energy Spectrum

  11. Universal scaling of forest fire propagation

    E-print Network

    Bernard, Porterie; Pierre, Clerc Jean; Nouredine, Zekri; Zekri, Lotfi

    2008-01-01

    In this paper we use a variant of the Watts-Strogatz small-world model to predict wildfire behavior near the critical propagation/nonpropagation threshold. We find that forest fire patterns are fractal and that critical exponents are universal, which suggests that the propagation/nonpropagation transition is a second-order transition. Universality tells us that the characteristic critical behaviour of propagation in real (amorphous) forest landscapes can be extracted from the simplest network model.

  12. Ultra Wideband Indoor Radio Channel Models: Preliminary Results

    Microsoft Academic Search

    Veikko Hovinen

    2002-01-01

    ULTRA WIDEBAND RADIO CHAN-NEL MEASUREMENT TECHNIQUES Knowledge of the signal propagation mechanisms in the chan-nel is vital for the radio system design and the system perform-ance analysis. However, currently published wideband or nar-rowband radio channel models do not offer spatial resolution high enough for the ultra wideband (UWB) applications and the real channel measurements are needed. In this paper is

  13. EVA Radio DRATS 2011 Report

    NASA Technical Reports Server (NTRS)

    Swank, Aaron J.; Bakula, Casey J.

    2012-01-01

    In the Fall of 2011, National Aeronautics and Space Administration (NASA) Glenn Research Center (GRC) participated in the Desert Research and Technology Studies (DRATS) field experiments held near Flagstaff, Arizona. The objective of the DRATS outing is to provide analog mission testing of candidate technologies for space exploration, especially those technologies applicable to human exploration of extra- terrestrial rocky bodies. These activities are performed at locations with similarities to extra-terrestrial conditions. This report describes the Extravehicular Activity (EVA) Dual-Band Radio Communication System which was demonstrated during the 2011 outing. The EVA radio system is designed to transport both voice and telemetry data through a mobile ad hoc wireless network and employs a dual-band radio configuration. Some key characteristics of this system include: 1. Dual-band radio configuration. 2. Intelligent switching between two different capability wireless networks. 3. Self-healing network. 4. Simultaneous data and voice communication.

  14. A Study of Type II Radio Bursts to Map the Alfvén Speed profile in the Inner Heliosphere

    NASA Astrophysics Data System (ADS)

    Martinez Oliveros, J.; Bain, H. M.; Sundkvist, D. J.; Bale, S. D.; Krucker, S.

    2013-12-01

    It is well accepted that interplanetary Type II radio bursts are the manifestations of electron acceleration in shocks driven by propagating of coronal mass ejections (CMEs) traveling faster than the characteristic local plasma speed. The slow solar wind (in the equatorial plane) becomes super-Alfvénic at the so-called 'Alfvén point', which is thought to occur at a distance of around 10 Rsun. However, observationally this has not been confirmed and furthermore, it is likely that the Alfvén point will vary considerably due to the changing conditions of the ambient medium, over the solar cycle. We present results from an investigation of coronal and interplanetary type II radio bursts to probe the changing plasma parameters in the ambient medium. A prominent feature of type II radio bursts, is the intermittency of the observed emission across the metric, decametric and kilometric frequency ranges, as the shock propagates to greater distances. This can be attributed to changes in both the shock driver and to the conditions in the ambient medium. Using radio observations from e.g. STEREO/WAVES and WIND/WAVES we will determine the distance of the observed type II emission and the speed of the associated shock. By establishing regions of the corona and interplanetary medium that are predisposed to shock formation, we map out the profile of the local Alfvén speed.

  15. EM PROPAGATION IN JET ENGINE TURBINES

    Microsoft Academic Search

    Eric Walton; Jonathan Young; Jim Moore; Kyle Davis

    There is interest in the propagation of EM signals inside jet engine turbines for a number of reasons. Applications include radar scattering phenomenology and jet engine plasma plume formation studies. In our research, we are interested in the communication channel characteristics for micro-size wireless sensors attached to the turbine blades that measure parameters such as strain and temperature. Propagation measurements

  16. AURORAL RADIO EMISSION FROM STARS: THE CASE OF CU VIRGINIS

    SciTech Connect

    Trigilio, Corrado; Leto, Paolo; Umana, Grazia; Buemi, Carla S. [INAF-Osservatorio Astrofisico di Catania, Via S. Sofia 78, 95123 Catania (Italy); Leone, Francesco, E-mail: ctrigilio@oact.inaf.it [Dipartimento di Fisica e Astronomia, Universita di Catania, Via Santa Sofia 78, 95123 Catania (Italy)

    2011-09-20

    CU Virginis is a rapidly rotating Magnetic Chemically Peculiar star with at present unique characteristics as a radio emitter. The most intriguing one is the presence of intense, 100% circularly polarized radiation ascribed to a cyclotron maser. Each time the star rotates, this highly beamed emission points two times toward the Earth, like a pulsar. We observed CU Vir in 2010 April with the Expanded Very Large Array in two bands centered at 1450 and 1850 MHz. We covered nearly the whole rotational period, confirming the presence of the two pulses at a flux density up to 20 mJy. Dynamical spectra, obtained with unprecedented spectral and temporal sensitivity, allow us to clearly see the different time delays as a function of frequency. We interpret this behavior as a propagation effect of the radiation inside the stellar magnetosphere. The emerging scenario suggests interesting similarities with the auroral radio emission from planets, in particular with the Auroral Kilometric Radiation from Earth, which originates at few terrestrial radii above the magnetic poles and was only recently discovered to be highly beamed. We conclude that the magnetospheres of CU Vir, Earth, and other planets, maybe also exoplanets, could have similar geometrical and physical characteristics in the regions where the cyclotron maser is generated. In addition, the pulses are perfect 'markers' of the rotation period. This has given us for the first time the possibility to measure with extraordinary accuracy the spin-down of a star on or near the main sequence.

  17. On the Connectivity and Multihop Delay of Ad Hoc Cognitive Radio Networks

    E-print Network

    Islam, M. Saif

    On the Connectivity and Multihop Delay of Ad Hoc Cognitive Radio Networks Wei Ren§, Qing Zhao cognitive radio networks, where the transmission delay of each hop consists of the propagation delay opportunities. Index Terms--Cognitive radio network, multihop delay, con- nectivity, intermittent connectivity

  18. Linearized Zverev Transform and its application for modeling radio occultations

    Microsoft Academic Search

    M. E. Gorbunov; K. B. Lauritsen

    2007-01-01

    The multiple phase screens technique is often used for modeling wave propagation and radio occultation sounding of the atmosphere. The last step of this procedure is the propagation from the last phase screen to the observation orbit of the spaceborne receiver. This step was formerly performed by the computation of multiple diffractive integrals, which impairs the numerical efficiency of the

  19. Distributed Antennas for Indoor Radio Communications

    Microsoft Academic Search

    A. Saleh; A. Rustako; R. Roman

    1987-01-01

    The idea of implementing an indoor radio communications system serving an entire building from a single central antenna appears to be an attractive proposition. However, based on various indoor propagation measurements of the signal attenuation and the multipath delay spread, such a centralized approach appears to be limited to small buildings and to narrow-band FDMA-type systems with limited reliability and

  20. Photonic Technique for Radio Frequency Measurement

    Microsoft Academic Search

    L. V. T. Nguyen; D. B. Hunter; D. J. Borg

    2005-01-01

    A novel photonic technique for radio frequency (RF) measurement utilising dispersion in a multichannel chirped fibre Bragg grating (MCFBG) is developed. The underlying principle for fast photonic RF measurement is based on amplitude comparison of the RF power fading functions of double sideband (DSB) modulated optical carriers propagating through a dispersive medium. In this paper, a demonstration of the photonic

  1. Cassini/RPWS: A low frequency radio imager at Saturn

    NASA Astrophysics Data System (ADS)

    Cecconi, B.; Lamy, L.; Zarka, P.

    2014-04-01

    The High Frequency Receiver (HFR) of the Radio and Plasma Waves Science experiment (RPWS) onboard Cassini is a sensitive, and versatile radio instrument. Although the radio antenna connected to this instrument have no intrinsic directivity, the HFR measurements can provide instantaneous direction of arrival, flux density and polarization degree of the observed radio waves. Hence, the HFR can be described as an full-sky radio imager. As the instrument provides direction of arrival, radio sources can be located with some assumption on the propagation between the source and the observer. Hence, it is possible to produce radio source maps and correlate them with observations at other wavelengths, such as UV or IR observations of the auroral regions of Saturn. The flux and polarization measurements together with the timefrequency shape of the radio emissions can also be used to identify the radio emission processes. We present a review of the results of the Cassini/RPWS/HFR observations since its arrival at Saturn in 2004: interpretation of the radio arc shapes and equatorial shadow zones; in-situ observations in the radio source region; comparison with other wavelengths and particle measurements; confirmation of the Cyclotron Maser Instability (CMI) as the main emission mechanism for auroral radio emissions; monitoring of the radio emission variability in time and location, etc.

  2. Radio frequency plasma power dependence of the moisture permeation barrier characteristics of Al{sub 2}O{sub 3} films deposited by remote plasma atomic layer deposition

    SciTech Connect

    Jung, Hyunsoo [Division of Materials Science and Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of) [Division of Materials Science and Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Samsung Display Co. Ltd., Tangjeong, Chungcheongnam-Do 336-741 (Korea, Republic of); Choi, Hagyoung; Lee, Sanghun [Division of Materials Science and Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of)] [Division of Materials Science and Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Jeon, Heeyoung [Department of Nano-scale Semiconductor Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of)] [Department of Nano-scale Semiconductor Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Jeon, Hyeongtag [Division of Materials Science and Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of) [Division of Materials Science and Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Department of Nano-scale Semiconductor Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of)

    2013-11-07

    In the present study, we investigated the gas and moisture permeation barrier properties of Al{sub 2}O{sub 3} films deposited on polyethersulfone films (PES) by capacitively coupled plasma (CCP) type Remote Plasma Atomic Layer Deposition (RPALD) at Radio Frequency (RF) plasma powers ranging from 100 W to 400 W in 100 W increments using Trimethylaluminum [TMA, Al(CH{sub 3}){sub 3}] as the Al source and O{sub 2} plasma as the reactant. To study the gas and moisture permeation barrier properties of 100-nm-thick Al{sub 2}O{sub 3} at various plasma powers, the Water Vapor Transmission Rate (WVTR) was measured using an electrical Ca degradation test. WVTR decreased as plasma power increased with WVTR values for 400 W and 100 W of 2.6 × 10{sup ?4} gm{sup ?2}day{sup ?1} and 1.2 × 10{sup ?3} gm{sup ?2}day{sup ?1}, respectively. The trends for life time, Al-O and O-H bond, density, and stoichiometry were similar to that of WVTR with improvement associated with increasing plasma power. Further, among plasma power ranging from 100 W to 400 W, the highest power of 400 W resulted in the best moisture permeation barrier properties. This result was attributed to differences in volume and amount of ion and radical fluxes, to join the ALD process, generated by O{sub 2} plasma as the plasma power changed during ALD process, which was determined using a plasma diagnosis technique called the Floating Harmonic Method (FHM). Plasma diagnosis by FHM revealed an increase in ion flux with increasing plasma power. With respect to the ALD process, our results indicated that higher plasma power generated increased ion and radical flux compared with lower plasma power. Thus, a higher plasma power provides the best gas and moisture permeation barrier properties.

  3. Over-the-Horizon Anomalous VHF Propagation and Earthquake Precursors

    NASA Astrophysics Data System (ADS)

    Devi, M.; Barbara, A. K.; Ruzhin, Ya. Yu.; Hayakawa, M.

    2012-09-01

    The purpose of this paper is to review current activities for the identification of earthquake (EQ) precursors and their epicentres. Starting with a brief description on the background to approaches using ultra-low (ULF), extremely low (ELF), very low/low (VLF/LF), medium (MF), high (HF), very high frequency (VHF) etc. radio waves for short-term EQ prediction, the paper concentrates on those characteristics of anomalous VHF reception from frequency-modulation (FM) radio transmissions and broadcast television (TV) signals in relation to EQ precursors. The possible ways to identify an impending EQ and its epicentre position as defined and observed by workers from a variety of studies fall within the purview of the paper. In attempts to find pre-EQ energy exchange and coupling processes between the lithosphere and atmosphere, the paper highlights some relevant observations of surface latent heat flux, sonic detection and ranging (SODAR) echograms and LF propagation. Explanations on possible causes leading to such anomalous reception are reviewed with reported results in association with pre-seismic induced modifications to tropospheric and ionospheric parameters.

  4. Radio Variability of Radio Quiet and Radio Loud Quasars

    E-print Network

    Richard Barvainis; Joseph Lehar; Mark Birkinshaw; Heino Falke; Katherine M. Blundell

    2004-09-22

    The majority of quasars are weak in their radio emission, with flux densities comparable to those in the optical, and energies far lower. A small fraction, about 10%, are hundreds to thousands of times stronger in the radio. Conventional wisdom holds that there are two classes of quasars, the radio quiets and radio louds, with a deficit of sources having intermediate power. Are there really two separate populations, and if so, is the physics of the radio emission fundamentally different between them? This paper addresses the second question, through a study of radio variability across the full range of radio power, from quiet to loud. The basic findings are that the root mean square amplitude of variability is independent of radio luminosity or radio-to-optical flux density ratio, and that fractionally large variations can occur on timescales of months or less in both radio quiet and radio loud quasars. Combining this with similarities in other indicators, such as radio spectral index and the presence of VLBI-scale components, leads to the suggestion that the physics of radio emission in the inner regions of all quasars is essentially the same, involving a compact, partially opaque core together with a beamed jet.

  5. Proceedings of the 16th NASA Propagation Experimenters Meeting (NAPEX 16) and the Advanced Communications Technology Satellite (ACTS) Propagation Studies Miniworkshop

    NASA Technical Reports Server (NTRS)

    Davarian, Faramaz (editor)

    1992-01-01

    The NASA Propagation Experimenters Meeting (NAPEX), supported by the NASA Propagation Program, is convened annually to discuss studies made on radio wave propagation by investigators from domestic and international organizations. NAPEX 16 was held on May 29, 1992 in Houston, Texas. The meeting was organized into two technical sessions. The first session was dedicated to slant path propagation studies and measurements. The second session focused on Olympus propagation measurements and results. Following NAPEX 16, the Advanced Communications Technology Satellite (ACTS) Miniworkshop was held to review ACTS propagation activities with emphasis on ACTS hardware development and experiment planning. Eight technical papers were presented by contributors from government agencies, private industry, and university research establishments.

  6. Telecommunications Radio Lease

    E-print Network

    Telecommunications Radio Lease 1. Fax completed form to 979.847.1111. 2. If you do not receive. Note: There is an air time charge for the use of the radios. Radio lease rates depend on the radio type to any of the radios, chargers and accessories until signed back over to the Telecommunications office

  7. ELF and VLF radio waves

    NASA Astrophysics Data System (ADS)

    Barr, R.; Jones, D. L.; Rodger, C. J.

    2000-11-01

    This review covers developments in ELF and VLF radio-wave propagation research over the last 50 years of the Journal of Atmospheric and Solar-Terrestrial Physics. A review of such a large field, over such a long period, cannot be fully comprehensive and the authors have therefore covered important areas which have they themselves have found interesting. The survey begins with a review of work on natural and man made sources of ELF and VLF radiation. This is followed by sections on experimental and theoretical studies of unperturbed (ambient) ELF and VLF radio propagation. Schumann resonance research, which is currently undergoing a renaissance, is then reviewed. A review of research into transient perturbations of ELF and VLF propagation follows, extending from the early work on nuclear explosions up to the current work on sprites. The review concludes with a brief summary of the VLF navigation systems of the USSR and USA, (Alpha and Omega) whose development and life-span covered most of the last 50 years.

  8. S-Band propagation measurements

    NASA Technical Reports Server (NTRS)

    Briskman, Robert D.

    1994-01-01

    A geosynchronous satellite system capable of providing many channels of digital audio radio service (DARS) to mobile platforms within the contiguous United States using S-band radio frequencies is being implemented. The system is designed uniquely to mitigate both multipath fading and outages from physical blockage in the transmission path by use of satellite spatial diversity in combination with radio frequency and time diversity. The system also employs a satellite orbital geometry wherein all mobile platforms in the contiguous United States have elevation angles greater than 20 deg to both of the diversity satellites. Since implementation of the satellite system will require three years, an emulation has been performed using terrestrial facilities in order to allow evaluation of DARS capabilities in advance of satellite system operations. The major objective of the emulation was to prove the feasibility of broadcasting from satellites 30 channels of CD quality programming using S-band frequencies to an automobile equipped with a small disk antenna and to obtain quantitative performance data on S-band propagation in a satellite spatial diversity system.

  9. High latitude spatially adaptive propagation experiment

    NASA Astrophysics Data System (ADS)

    Sales, G. S.; Cormier, R. J.; Greenwald, R. A.; Baker, K. B.

    1985-11-01

    A special HF phased array was used to obtain high latitude HF propagation data. The antenna located at Goose Bay, Labrador, Canada, received HF transmission (8 to 20 MHz) from Thule, Greenland. The receiving antenna at Goose Bay consisted of two parallel linear arrays each with 16 horizontal log-periodic antennas. This system was used to measure both the azimuth and elevation angle of arrival of the propagated radio wave. Comparisons are made with model calculations and the received modes are analyzed to determine the presence of ionospheric tilts.

  10. Proceedings of the Eighteenth NASA Propagation Experimenters Meeting (NAPEX 18) and the Advanced Communications Technology Satellite (ACTS) Propagation Studies Miniworkshop

    NASA Technical Reports Server (NTRS)

    Davarian, Faramaz (editor)

    1994-01-01

    The NASA Propagation Experimenters Meeting (NAPEX), supported by the NASA Propagation Program, is convened annually to discuss studies made on radio wave propagation by investigators from domestic and international organizations. Participants included representatives from Canada, the Netherlands, England, and the United States, including researchers from universities, government agencies, and private industry. The meeting was organized into two technical sessions. The first session was dedicated to slant path propagation studies and experiments. The second session focused on propagation studies for mobile, personal, and sound broadcast systems. In total, 14 technical papers and some informal contributions were presented. Preceding NAPEX_17, the Advanced Communications Technology Satellite (ACTS) Propagation Studies Miniworkshop was held to review ACTS propagation activities.

  11. Radio pulsars: the search for truth

    NASA Astrophysics Data System (ADS)

    Beskin, Vasily S.; Istomin, Yakov N.; Philippov, Aleksandr A.

    2013-02-01

    It was as early as the 1980s that A V Gurevich and his group proposed a theory to explain the magnetosphere of radio pulsars and the mechanism by which they produce coherent radio emission. The theory has been sharply criticized and is currently rarely mentioned when discussing the observational properties of radio pulsars, even though all the criticisms were in their time disproved in a most thorough and detailed manner. Recent results show even more conclusively that the theory has no internal inconsistencies. New observational data also demonstrate the validity of the basic conclusions of the theory. Based on the latest results on the effects of wave propagation in the magnetosphere of a neuron star, we show that the developed theory does indeed allow quantitative predictions of the evolution of neutron stars and the properties of the observed radio emission.

  12. The radio lighthouse CU Virginis: the spindown of a single main sequence star

    E-print Network

    C. Trigilio; P. Leto; G. Umana; C. S. Buemi; F. Leone

    2007-11-21

    The fast rotating star CU Virginis is a magnetic chemically peculiar star with an oblique dipolar magnetic field. The continuum radio emission has been interpreted as gyrosyncrotron emission arising from a thin magnetospheric layer. Previous radio observations at 1.4 GHz showed that a 100% circular polarized and highly directive emission component overlaps to the continuum emission two times per rotation, when the magnetic axis lies in the plane of the sky. This sort of radio lighthouse has been proposed to be due to cyclotron maser emission generated above the magnetic pole and propagating perpendicularly to the magnetic axis. Observations carried out with the Australia Telescope Compact Array at 1.4 and 2.5 GHz one year after this discovery show that this radio emission is still present, meaning that the phenomenon responsible for this process is steady on a timescale of years. The emitted radiation spans at least 1 GHz, being observed from 1.4 to 2.5 GHz. On the light of recent results on the physics of the magnetosphere of this star, the possibility of plasma radiation is ruled out. The characteristics of this radio lighthouse provides us a good marker of the rotation period, since the peaks are visible at particular rotational phases. After one year, they show a delay of about 15 minutes. This is interpreted as a new abrupt spinning down of the star. Among several possibilities, a quick emptying of the equatorial magnetic belt after reaching the maximum density can account for the magnitude of the breaking. The study of the coherent emission in stars like CU Vir, as well as in pre main sequence stars, can give important insight into the angular momentum evolution in young stars. This is a promising field of investigation that high sensitivity radio interferometers such as SKA can exploit.

  13. Uranus as a radio source

    NASA Technical Reports Server (NTRS)

    Desch, M. D.; Kaiser, M. L.; Zarka, P.; Lecacheux, A.; Leblanc, Y.; Aubier, M.; Ortega-Molina, A.

    1991-01-01

    The complex nature of the Uranus radio emissions, both magnetospheric and atmospheric, is reviewed, with emphasis on the identification of distinct components and the determination of their source locations. Seven radii components were discovered in addition to the RF signature of lightning in the planet's atmosphere. Six of the seven magnetospheric components are freely propagating emissions; one component, the nonthermal continuum, is trapped in the density cavity between the magnetopause and the dense inner magnetosphere. The radio components are divided into two types according to their emission signature: bursty emission and smooth emission. The inferred source location for the dominant nightside emission is above the nightside magnetic pole, largely overlapping the UV auroral region and the magnetic polar cap. The N-burst component appears to be associated with solar-wind enhancements at Uranus, consistent with the idea that the solar wind was triggering magnetospheric substormlike activity during the encounter.

  14. Nonlinear Characteristics of Wave Propagation over Vegetation

    E-print Network

    Venkattaramanan, Aravinda

    2014-04-28

    The attenuation of wave energy by submerged or near-emergent coastal vegetation is one of the prominent methods of energy dissipation in areas with significant presence of wetlands. In this thesis, the nature of this dissipation in nearshore random...

  15. Radio Jove: Jupiter Radio Astronomy for Citizens

    NASA Astrophysics Data System (ADS)

    Higgins, Charles; Thieman, J. R.; Flagg, R.; Reyes, F. J.; Sky, J.; Greenman, W.; Brown, J.; Typinski, D.; Ashcraft, T.; Mount, A.

    2014-01-01

    Radio JOVE is a hands-on educational activity that brings the radio sounds of the Sun, Jupiter, the Milky Way Galaxy, and terrestrial radio noise to students, teachers, and the general public. Participants may build a simple radio telescope kit, make scientific observations, and interact with professional radio observatories in real-time over the Internet. Our website (http://radiojove.gsfc.nasa.gov) includes science information, construction manuals, observing guides, and education resources for teachers and students. Radio Jove is continually expanding its participants with over 1800 kits sold to more than 70 countries worldwide. Recently some of our most dedicated observers have upgraded their Radio Jove antennas to semi-professional observatories. We have spectrographs and wide band antennas, some with 8 MHz bandwidth and some with dual polarization capabilities. In an effort to add to the science literature, these observers are coordinating their efforts to pursue some basic questions about Jupiter’s radio emissions (radio source locations, spectral structure, long term changes, etc.). We can compare signal and ionosphere variations using the many Radio Jove observers at different locations. Observers are also working with members of the Long Wavelength Array Station 1 (LWA1) radio telescope to coordinate observations of Jupiter; Radio Jove is planning to make coordinated observations while the Juno Mission is active beginning in 2015. The Radio Jove program is overviewed, its hardware and software are highlighted, recent sample observations are shown, and we demonstrate that we are capable of real citizen science.

  16. Proceedings of the Twenty-First NASA Propagation Experiments Meeting (NAPEX XXI) and the Advanced Communications Technology Satellite (ACTS) Propagation Studies Miniworkshop

    NASA Technical Reports Server (NTRS)

    Golshan, Nasser (Editor)

    1997-01-01

    The NASA Propagation Experimenters (NAPEX) meeting is convened each year to discuss studies supported by the NASA Propagation Program. Representatives from the satellite communications industry, academia and government who have an interest in space-ground radio wave propagation are invited to NAPEX meetings for discussions and exchange of information. The reports delivered at this meeting by program managers and investigators present recent activities and future plans. This forum provides an opportunity for peer discussion of work in progress, timely dissemination of propagation results, and close interaction with the satellite communications industry. NAPEX XXI took place in El Segundo, California on June 11-12, 1997 and consisted of three sessions. Session 1, entitled "ACTS Propagation Study Results & Outcome " covered the results of 20 station-years of Ka-band radio-wave propagation experiments. Session 11, 'Ka-band Propagation Studies and Models,' provided the latest developments in modeling, and analysis of experimental results about radio wave propagation phenomena for design of Ka-band satellite communications systems. Session 111, 'Propagation Research Topics,' covered a diverse range of propagation topics of interest to the space community, including overviews of handbooks and databases on radio wave propagation. The ACTS Propagation Studies miniworkshop was held on June 13, 1997 and consisted of a technical session in the morning and a plenary session in the afternoon. The morning session covered updates on the status of the ACTS Project & Propagation Program, engineering support for ACTS Propagation Terminals, and the Data Center. The plenary session made specific recommendations for the future direction of the program.

  17. Jet propagation through energetic materials

    SciTech Connect

    Pincosy, P; Poulsen, P

    2004-01-08

    In applications where jets propagate through energetic materials, they have been observed to become sufficiently perturbed to reduce their ability to effectively penetrate subsequent material. Analytical calculations of the jet Bernoulli flow provides an estimate of the onset and extent of such perturbations. Although two-dimensional calculations show the back-flow interaction pressure pulses, the symmetry dictates that the flow remains axial. In three dimensions the same pressure impulses can be asymmetrical if the jet is asymmetrical. The 3D calculations thus show parts of the jet having a significant component of radial velocity. On the average the downstream effects of this radial flow can be estimated and calculated by a 2D code by applying a symmetrical radial component to the jet at the appropriate position as the jet propagates through the energetic material. We have calculated the 3D propagation of a radio graphed TOW2 jet with measured variations in straightness and diameter. The resultant three-dimensional perturbations on the jet result in radial flow, which eventually tears apart the coherent jet flow. This calculated jet is compared with jet radiographs after passage through the energetic material for various material thickness and plate thicknesses. We noted that confinement due to a bounding metal plate on the energetic material extends the pressure duration and extent of the perturbation.

  18. COGNITIVE RADIO APPLICATIONS IN SOFTWARE DEFINED RADIO

    Microsoft Academic Search

    John Polson

    2004-01-01

    The topic of cognitive radios has been garnering a great deal of attention in the past several years. Opinions regarding the level of sophistication necessary to qualify a system as cognitive vary widely, and discussions have ensued regarding this technology. The software defined radio forum is also involved and has working group activity in the area of cognitive radio. Some

  19. Phenomenology of Neptune's radio emissions observed by the Voyager planetary radio astronomy experiment

    NASA Technical Reports Server (NTRS)

    Pedersen, B. M.; Lecacheux, A.; Zarka, P.; Aubier, M. G.; Kaiser, M. L.; Desch, M. D.

    1992-01-01

    The Neptune flyby in 1989 added a new planet to the known number of magnetized planets generating nonthermal radio emissions. We review the Neptunian radio emission morphology as observed by the planetary radio astronomy experiment on board Voyager 2 during a few weeks before and after closest approach. We present the characteristics of the two observed recurrent main components of the Neptunian kilometric radiation, i.e., the 'smooth' and the 'bursty' emissions, and we describe the many specific features of the radio spectrum during closest approach.

  20. Industrial interference and radio astronomy

    NASA Astrophysics Data System (ADS)

    Jessner, A.

    2013-07-01

    The interferer - victim scenario is described for the case of industrial interference affecting radio astronomical observatories. The sensitivity of radio astronomical receivers and their interference limits are outlined. EMC above 30 MHz is a serious problem for Radio Astronomy. Interferer (CISPR) and victim (ITU-R RA 769) standards are not harmonised. The emissions from the interferer and their spectral characteristics are not defined sufficiently well by CISPR standards. The required minimum coupling losses (MCL) between an industrial device and radio astronomical antenna depends on device properties but is shown to exceed 140 dB in most cases. Spatial separation of a few km is insufficient on its own, the terrain must shield > 30-40 dB, additional mitigations such as extra shielding or suppression of high frequency emissions may be necessary. A case by case compatibility analysis and tailored EMC measures are required for individual installations. Aggregation of many weak rfi emitters can become serious problem. If deployment densities are high enough, the emission constraints can even exceed those for a single interferer at a short distance from the radio observatory. Compatibility studies must account not only for the single interferer but also for many widely distributed interference sources.

  1. ATS-6 engineering performance report. Volume 5: Propagation experiments

    NASA Technical Reports Server (NTRS)

    Wales, R. O. (editor)

    1981-01-01

    Propagation experiments at 1550 MHz to 1650 MHz are reviewed, including the Integrated L-Band Experiments system and results, and the Mobile L-Band Terminals for Satellite Communication system. Experiments at 4 GHz to 6 GHz are reported, including the Radio Frequency Interferometer Measurements system and results, and Earth station antenna evaluations. Experiments above 10 GHz are discussed, including Comsat and ATS-6 millimeter wave propagation/experiments, and communication ATS-6 version at 20 and 30 GHz.

  2. A review of ionospheric effects on Earth-space propagation

    NASA Technical Reports Server (NTRS)

    Klobuchar, J. A.

    1984-01-01

    A short description is given of each ionospheric total electron content (TEC) effect upon radio waves, along with a representative value of the magnitude of each of these effects under normal ionospheric conditions. A discussion is given of the important characteristics of average ionospheric TEC behavior and the temporal and spatial variability of TEC. Radio waves undergo several effects when they pass through the Earth's ionosphere. One of the most important of these effects is a retardation, or group delay, on the modulation or information carried on the radio wave that is due to its encounter with the free, thermal electrons in the Earth's ionosphere. Other effects the ionosphere has on radio waves include: radio frequency (RF) carrier phase advance; Doppler shift of the RF carrier of the radio wave; Faraday rotation of the plane of polarization of linearly polarized waves; angular refraction or bending of the radio wave path as it travels through the ionosphere; and amplitude and phase scintillations.

  3. Tracking the CME-driven Shock Wave on 2012 March 5 and Radio Triangulation of Associated Radio Emission

    NASA Astrophysics Data System (ADS)

    Magdaleni?, J.; Marqué, C.; Krupar, V.; Mierla, M.; Zhukov, A. N.; Rodriguez, L.; Maksimovi?, M.; Cecconi, B.

    2014-08-01

    We present a multiwavelength study of the 2012 March 5 solar eruptive event, with an emphasis on the radio triangulation of the associated radio bursts. The main points of the study are reconstruction of the propagation of shock waves driven by coronal mass ejections (CMEs) using radio observations and finding the relative positions of the CME, the CME-driven shock wave, and its radio signatures. For the first time, radio triangulation is applied to different types of radio bursts in the same event and performed in a detailed way using goniopolarimetric observations from STEREO/Waves and WIND/Waves spacecraft. The event on 2012 March 5 was associated with a X1.1 flare from the NOAA AR 1429 situated near the northeast limb, accompanied by a full halo CME and a radio event comprising long-lasting interplanetary type II radio bursts. The results of the three-dimensional reconstruction of the CME (using SOHO/LASCO, STEREO COR, and HI observations), and modeling with the ENLIL cone model suggest that the CME-driven shock wave arrived at 1 AU at about 12:00 UT on March 7 (as observed by SOHO/CELIAS). The results of radio triangulation show that the source of the type II radio burst was situated on the southern flank of the CME. We suggest that the interaction of the shock wave and a nearby coronal streamer resulted in the interplanetary type II radio emission.

  4. Proceedings of the Fourteenth NASA Propagation Experimenters Meeting (NAPEX 14) and the Advanced Communications Technology Satellite (ACTS) Propagation Studies Miniworkshop

    NASA Technical Reports Server (NTRS)

    Davarian, Faramaz (editor)

    1990-01-01

    The NASA Propagation Experimenters Meeting (NAPEX), supported by the NASA Propagation Program, is convened annually to discuss studies made on radio wave propagation by investigators from domestic and international organizations. NAPEX XIV was held on May 11, 1990, at the Balcones Research Centers, University of Texas, Austin, Texas. The meeting was organized into two technical sessions: Satellite (ACTS) and the Olympus Spacecraft, while the second focused on the fixed and mobile satellite propagation studies and experiments. Following NAPEX XIV, the ACTS Miniworkshop was held at the Hotel Driskill, Austin, Texas, on May 12, 1990, to review ACTS propagation activities since the First ACTS Propagation Studies Workshop was held in Santa Monica, California, on November 28 and 29, 1989.

  5. Proceedings of the Fifteenth NASA Propagation Experimenters Meeting (NAPEX 15) and the Advanced Communications Technology Satellite (ACTS) Propagation Studies Miniworkshop

    NASA Technical Reports Server (NTRS)

    Davarian, Faramaz (editor)

    1991-01-01

    The NASA Propagation Experimenters Meeting (NAPEX), supported by the NASA Propagation Program, is convened annually to discuss studies made on radio wave propagation by investigators from domestic and international organizations. The meeting was organized into three technical sessions. The first session was dedicated to Olympus and ACTS studies and experiments, the second session was focused on the propagation studies and measurements, and the third session covered computer-based propagation model development. In total, sixteen technical papers and some informal contributions were presented. Following NAPEX 15, the Advanced Communications Technology Satellite (ACTS) miniworkshop was held on 29 Jun. 1991, to review ACTS propagation activities, with emphasis on ACTS hardware development and experiment planning. Five papers were presented.

  6. Extended Extragalactic Radio Emission

    E-print Network

    F. N. Owen; M. J. Ledlow; J. A. Eilek; N. E. Kassim; N. A. Miller; K. S. Dwarakanath; R. J. Ivison

    2000-06-11

    Extended radio emission and its relation to parent galaxy properties is briefly reviewed. Our current understanding of the relation between absolute radio and optical luminosity, radio morphology and linear size is discussed. The impact of radio jets on dense cluster cores is discussed using M87 as an example. Finally, the relation of AGN's to star-bursting galaxies at high redshift is considered.

  7. Modulate Internet Radio Into FM Using GNU Radio

    E-print Network

    Yu, Chansu

    1 Modulate Internet Radio Into FM Using GNU Radio By: Elie Salameh Outline. · Fm in gnu radio · Audio Streams in Internet Radio · Gnu & Audio Files · Sox command · Playlist ".pls" · Recording internet radio #12;2 Project description · Using gnu radio to modulate internet radio into fm. · Using usrp

  8. Telecommunications Radio Rental

    E-print Network

    Telecommunications Radio Rental 1. Fax completed form to 979.847.1111. 2. If you do not receive://telecom.tamu.edu/Accounts/Rate_Information.php). There is an air time charge for the use of the radios. Rental radios will be pro-rated per radio per daily usage of the radios, chargers and accessories until signed back over to the Telecommunications office. Amount

  9. Youth Radio

    NSDL National Science Digital Library

    With an impressive headquarters in downtown Oakland, Youth Radio is fast becoming a compelling and insightful media phenomenon that should be watched closely. Their mission is a laudable one, and as their website puts it, â??â?¦. is to promote young peopleâ??s intellectual creative and professional growth through training and access to media and to produce the highest quality original media for local and national outlets.â? Of course, the real heart of the site contains the actual programming, which is streamed 24 hours a day, 7 days a week. Along with unique mix of music, individuals can listen to a host of stories reported by young people. Visitors can also browse a list of recently added stories by topic, which include relationships, society, sports, poetry, and health. Those who are hoping to get some of the basic flavor of the offerings here would do well to take a look at the story featuring reporting from a group of Berkeley High School students at the World Social Forum in Caracas, or by listening to the commentary offered by Lauryn Silverman on the modern conundrum of multi-tasking.

  10. Theory of Type 3 and Type 2 Solar Radio Emissions

    NASA Technical Reports Server (NTRS)

    Robinson, P. A.; Cairns, I. H.

    2000-01-01

    The main features of some current theories of type III and type II bursts are outlined. Among the most common solar radio bursts, type III bursts are produced at frequencies of 10 kHz to a few GHz when electron beams are ejected from solar active regions, entering the corona and solar wind at typical speeds of 0.1c. These beams provide energy to generate Langmuir waves via a streaming instability. In the current stochastic-growth theory, Langmuir waves grow in clumps associated with random low-frequency density fluctuations, leading to the observed spiky waves. Nonlinear wave-wave interactions then lead to secondary emission of observable radio waves near the fundamental and harmonic of the plasma frequency. Subsequent scattering processes modify the dynamic radio spectra, while back-reaction of Langmuir waves on the beam causes it to fluctuate about a state of marginal stability. Theories based on these ideas can account for the observed properties of type III bursts, including the in situ waves and the dynamic spectra of the radiation. Type 11 bursts are associated with shock waves propagating through the corona and interplanetary space and radiating from roughly 30 kHz to 1 GHz. Their basic emission mechanisms are believed to be similar to those of type III events and radiation from Earth's foreshock. However, several sub-classes of type II bursts may exist with different source regions and detailed characteristics. Theoretical models for type II bursts are briefly reviewed, focusing on a model with emission from a foreshock region upstream of the shock for which observational evidence has just been reported.

  11. Radio frequency detection assembly and method for detecting radio frequencies

    DOEpatents

    Cown, Steven H. (Rigby, ID); Derr, Kurt Warren (Idaho Falls, ID)

    2010-03-16

    A radio frequency detection assembly is described and which includes a radio frequency detector which detects a radio frequency emission produced by a radio frequency emitter from a given location which is remote relative to the radio frequency detector; a location assembly electrically coupled with the radio frequency detector and which is operable to estimate the location of the radio frequency emitter from the radio frequency emission which has been received; and a radio frequency transmitter electrically coupled with the radio frequency detector and the location assembly, and which transmits a radio frequency signal which reports the presence of the radio frequency emitter.

  12. Geometric Sound Propagation

    E-print Network

    North Carolina at Chapel Hill, University of

    Some sound is absorbed Multiply bands by some absorption coefficient A[2] Coefficient is basedGeometric Sound Propagation Micah Taylor #12;Sound propagation Given a sound source in a scene arrive at the listener #12;Sound propagation Sound travels slow 344 m/s Specular reflections Perfect

  13. The universal propagator

    NASA Technical Reports Server (NTRS)

    Klauder, John R.

    1993-01-01

    For a general Hamiltonian appropriate to a single canonical degree of freedom, a universal propagator with the property that it correctly evolves the coherent-state Hilbert space representatives for an arbitrary fiducial vector is characterized and defined. The universal propagator is explicitly constructed for the harmonic oscillator, with a result that differs from the conventional propagators for this system.

  14. A novel RF-based propagation model with tissue absorption for location of the GI tract

    Microsoft Academic Search

    Lujia Wang; Li Liu; Chao Hu; M. Q.-H. Meng

    2010-01-01

    In order to accurately estimate (build) the radio signal propagation attenuation model, especially inside the gastro-intestine (GI) tract of the human body, the Radio Frequency (RF) absorption characterization in human body is investigated. This characterization provides a criterion to design the Received Signal Strength (RSS) based localization system for the objective inside the human body. In this paper, the Specific

  15. Galactic synchrotron emission with cosmic ray propagation models

    NASA Astrophysics Data System (ADS)

    Orlando, Elena; Strong, Andrew

    2013-12-01

    Cosmic ray (CR) leptons produce radio synchrotron radiation by gyrating in interstellar magnetic fields (B-fields). Details of B-fields, CR electron distributions and propagation are still uncertain. We present developments in our modelling of Galactic radio emission with the GALPROP code. It now includes calculations of radio polarization, absorption and free-free emission. Total and polarized synchrotron emission are investigated in the context of physical models of CR propagation. Predictions are compared with radio data from 22 MHz to 2.3 GHz and Wilkinson Microwave Anisotropy Probe data at 23 GHz. Spatial and spectral effects on the synchrotron modelling with different CR distribution, propagation halo size and CR propagation models are presented. We find that all-sky total intensity and polarization maps are reasonably reproduced by including an anisotropic B-field, with comparable intensity to the regular one defined by rotation measures. A halo size of 10 kpc, which is larger than usually assumed, is favoured. This work provides a basis for further studies on foreground emission with the Planck satellite and on interstellar gamma-ray emission with Fermi-Large Area Telescope.

  16. Signal Propagation Analysis and Signature Extraction for GNSS Indoor Positioning

    Microsoft Academic Search

    Marcus Andreotti; Marcio Aquino; Malcolm Woolfson; John Walker; Terry Moore

    2006-01-01

    The large popularization of GNSS (based on GPS, Glonass and forthcoming Galileo) receivers and the increased market interest for Location Based Services (LBS) have motivated interesting studies in modelling the radio channel propagation for dense urban and indoor geolocation, where two key problems need to be addressed: weak signal operation and multipath, both leading to receiver range errors and consequently

  17. Discovery of Giant Relic Radio Lobes Straddling the Classical Double Radio Galaxy 3C452

    NASA Astrophysics Data System (ADS)

    Sirothia, S. K.; Gopal-Krishna; Wiita, Paul J.

    2013-03-01

    We report the discovery of a pair of megaparsec size radio lobes of extremely steep spectrum straddling the well-known classical double radio source 3C452. The existence of such fossil lobes was unexpected since for the past several decades this powerful radio galaxy has been regarded as a textbook example of an edge-brightened double radio source of Fanaroff-Riley type II (FR II), which we now show to be a bona fide "double-double" radio galaxy (DDRG). Thus, 3C452 presents a uniquely robust example of recurrent nuclear activity in which the restarted jets are expanding non-relativistically within the relic synchrotron plasma from an earlier active phase and hence the inner double fed by them has evolved into a perfectly normal FR II radio source. This situation contrasts markedly with the strikingly narrow inner doubles observed in a few other DDRGs that have been interpreted in terms of compression of the synchrotron plasma of the relic outer lobes at the relativistic bow-shocks driven by the near ballistic propagation of the two inner jets through the relic plasma. A key ramification of this finding is that it cautions against the currently widespread use of FR II classical double radio sources for testing cosmological models and unification schemes for active galactic nuclei.

  18. DISCOVERY OF GIANT RELIC RADIO LOBES STRADDLING THE CLASSICAL DOUBLE RADIO GALAXY 3C452

    SciTech Connect

    Sirothia, S. K.; Gopal-Krishna [National Centre for Radio Astrophysics, TIFR, Post Bag No. 3, Pune University Campus, Ganeshkhind, Pune 411 007 (India); Wiita, Paul J., E-mail: sirothia@ncra.tifr.res.in, E-mail: krishna@ncra.tifr.res.in, E-mail: wiitap@tcnj.edu [Department of Physics, College of New Jersey, P.O. Box 7718, Ewing, NJ 08628 (United States)

    2013-03-01

    We report the discovery of a pair of megaparsec size radio lobes of extremely steep spectrum straddling the well-known classical double radio source 3C452. The existence of such fossil lobes was unexpected since for the past several decades this powerful radio galaxy has been regarded as a textbook example of an edge-brightened double radio source of Fanaroff-Riley type II (FR II), which we now show to be a bona fide ''double-double'' radio galaxy (DDRG). Thus, 3C452 presents a uniquely robust example of recurrent nuclear activity in which the restarted jets are expanding non-relativistically within the relic synchrotron plasma from an earlier active phase and hence the inner double fed by them has evolved into a perfectly normal FR II radio source. This situation contrasts markedly with the strikingly narrow inner doubles observed in a few other DDRGs that have been interpreted in terms of compression of the synchrotron plasma of the relic outer lobes at the relativistic bow-shocks driven by the near ballistic propagation of the two inner jets through the relic plasma. A key ramification of this finding is that it cautions against the currently widespread use of FR II classical double radio sources for testing cosmological models and unification schemes for active galactic nuclei.

  19. Possible radio emission mechanism for pulsars

    NASA Technical Reports Server (NTRS)

    Kovalev, Y. A.

    1979-01-01

    A mathematical model is presented and discussed as a possible mechanism to describe radio emission from pulsars. The model determines that the magnetic field in the neutron proton electron (npe) layer of a neutron star results from a quasistationary eddy current of superconducting and normal protons relative to normal electrons, which generates radio emission by the Josephson effect. The radiation propagates in the magnetically active medium, from the optically thick npe layer to the magnetosphere through breaks in the crust. As a result, hot radio spots form on the surface of the star, and a radiation pattern forms near the magnetic poles, the cross section of which gives the observed pulse structure. Due to the specific properties of the mechanism, variations of the quasistationary current are converted to amplitude frequency variations of the radiation spectrum. Variations of the fine structure of the spectrum pulse amplitude and spectral index, as well as their correlation are discussed.

  20. Mechanism for Radio Emission of Pulsars

    NASA Astrophysics Data System (ADS)

    Sedrakian, D. M.; Hayrapetyan, M. V.

    2015-03-01

    This is a review of work upon which a proposal for an effective mechanism for the radio emission of pulsars is based. It is shown that spin-down of a neutron star makes the system of proton vortices move toward the surface of the star's core. The magnetic energy of these vortices is released in "magnetic caps" of limited size located on the core surface and crust of neutron stars. Magnetosonic waves propagating in the crust of the star transfer this energy to its surface and form a localized source of radio emission in pulsars. Because of the star's rotation the emission from this source will pulsate. Some observed properties of the radio emission from pulsars can be explained by the proposed emission mechanism.

  1. 1420 IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATIONS, VOL. 48, NO. 9, SEPTEMBER 2000 Modeling Electromagnetic Propagation in the

    E-print Network

    Cummer, Steven A.

    to as the earth­ionosphere waveguide. At extremely low frequency (ELF: 3­3000 Hz) and very low frequency (VLF: 3--The ionosphere plays a role in radio propagation that varies strongly with frequency. At extremely low frequency (ELF: 3­3000 Hz) and very low frequency (VLF: 3­30 kHz), the ground and the ionosphere are good

  2. Propagation of electrons emitting weak type III bursts in coronal streamers

    NASA Technical Reports Server (NTRS)

    Gopalswamy, N.; Kundu, M. R.; Szabo, A.

    1987-01-01

    The observations of weak type III bursts at 73.8, 57.5, 50.0, and 38.5 MHz from Clark Lake Radio Observatory on four days are reported and their characteristics are discussed. In addition to Clark Lake data, the magnetogram and sunspot/active region data and the coronal streamer data obtained by HAO's Coronagraph/Polarimeter aboard SMM satellite are used to study the location of the burst sources with respect to the coronal streamers emanating from active regions. It is shown that the bursts occur within or close to the edge of dense coronal streamers implying that the coronal streamers contain open magnetic field lines along which the electrons generating the bursts propagate. The positional analysis of the bursts is used to estimate the variation of coronal electron density with radial distance.

  3. Energy Efficient Radio Resource

    E-print Network

    Yanikomeroglu, Halim

    Energy Efficient Radio Resource Management in a Coordinated Multi-Cell Distributed Antenna System Omer HALILOGLU Introduction System Model Performance Evaluation Conclusion References Energy Efficient Hacettepe University 5 September 2014 Omer HALILOGLU (Hacettepe University) Energy Efficient Radio Resource

  4. Resonance and Radio

    ERIC Educational Resources Information Center

    Starrett, Malin J.

    2008-01-01

    The science and technology of radio receives little attention in contemporary education. This article discusses ways to explore the basic operating principles of radio. (Contains 4 figures, 3 footnotes, and 2 notes.)

  5. Radio Diaries on National Public Radio (NPR)

    NSDL National Science Digital Library

    Radio Diaries is a nonprofit radio production company which looks "to find extraordinary stories in ordinary places, to create original and moving first-person documentaries - true radio verite - from voices that are rarely heard." And that it does. Radio Diaries staff train all kinds of people -- from teenagers to the elderly -- to become reporters. These fledgling reporters create tapes about their area of interest, tell their stories, and send their product back to Radio Diaries. A collaborative editing process then ensues, and the end product is aired as part of National Public Radio's All Things Considered. The Radio Diaries site brings together an amazing range of recorded stories divided into adult and teen areas. Two examples of diaries on the site include a piece by a teenager from New York City with Tourette's Syndrome as well as the story of the last two known remaining Civil War widows whose husbands fought on opposing sides of the war. Users can listen to the recordings using RealPlayer, or they can read transcripts; other materials are occasionally included too. The site encourages users to send in their own story ideas and will provide even more support for creative ventures with their Handbook for Teen Reporters (available in January of 2000). The site also has a store section where tapes of various radio diaries are for sale.

  6. Topological Aspects of Wave Propagation

    E-print Network

    Carlos Valero

    2014-06-13

    In the context of wave propagation on a manifold X, the characteristic functions are real valued functions on cotangent bundle of X that specify the allowable phase velocities of the waves. For certain classes of differential operators (e.g Maxwell's Equations) the associated characteristic functions have singularities. These singularities account for phenomena like conical refraction and the transformation of longitudinal waves into transversal ones (or viceversa). For a specific class of differential operators on surface, we prove that the singularities of the characteristic functions can be accounted from purely topological considerations. We also prove that there is a natural way to desingularsize the characteristic functions, and observe that this fact and Morse Theory establishes a specific connection between singularities and critical points of these functions. The relation between characteristic functions and differential operators is obtained through what is known as the symbol of the operator. We establish a connection between these symbols and holomorphic vector fields, which will provide us with symbols whose characteristic functions have interesting singularity sets.

  7. Radio Astronomy Explorer (RAE) 1 observations of terrestrial radio noise

    NASA Technical Reports Server (NTRS)

    Herman, J. R.; Caruso, J. A.

    1971-01-01

    Radio Astonomy Explorer (RAE) 1 data are analyzed to establish characteristics of HF terrestrial radio noise at an altitude of about 6000 km. Time and frequency variations in amplitude of the observed noise well above cosmic noise background are explained on the basis of temporal and spatial variations in ionospheric critical frequency coupled with those in noise source distributions. It is shown that terrestrial noise regularly breaks through the ionosphere and reaches RAE with magnitudes 15 or more db higher than cosmic noise background. Maximum terrestrial noise is observed when RAE is over the dark side of the Earth in the neighborhood of equatorial continental land masses where thunderstorms occur most frequently. The observed noise level is 30-40 db lower with RAE over oceans.

  8. Cognitive Radio Architecture Evolution

    Microsoft Academic Search

    Joseph Mitola

    2009-01-01

    The radio research community has aggressively embraced cognitive radio for dynamic radio spectrum management to enhance spectrum usage, e.g., in ISM bands and as secondary users in unused TV bands, but the needs of the mobile wireless user have not been addressed as thoroughly on the question of high quality of information (QoI) as a function of place, time, and

  9. Extragalactic Radio Sources

    ERIC Educational Resources Information Center

    Kellerman, Kenneth I.

    1973-01-01

    Discusses new problems arising from the growing observational data through radio telescope arrays, involving the origin of radio sources, apparent superluminal velocities, conversion of radio sources to relativistic particles, and the nature of compact opaque and extended transparent sources. New physics may be needed to answer these cosmological…

  10. Introduction Big Radio Data

    E-print Network

    Prodiæ, Aleksandar

    Introduction VLBI Pulsars Summary Big Radio Data Ue-Li Pen CITA, UofT, CIFAR July 3, 2014U. Pen Big Radio Data #12;Introduction VLBI Pulsars Summary Overview History VLBI Processing Future U. Pen Big signal processing U. Pen Big Radio Data #12;Introduction VLBI Pulsars Summary VLBI Current experiments

  11. The software radio architecture

    Microsoft Academic Search

    J. Mitola

    1995-01-01

    As communications technology continues its rapid transition from analog to digital, more functions of contemporary radio systems are implemented in software, leading toward the software radio. This article provides a tutorial review of software radio architectures and technology, highlighting benefits, pitfalls, and lessons learned. This includes a closer look at the canonical functional partitioning of channel coding into antenna, RF,

  12. Plants 2: Plant Propagation

    NSDL National Science Digital Library

    Science Netlinks

    2001-10-20

    This is the second (and final) Science NetLinks lesson in a series on plants. In this lesson, students will do a project in which they choose a plant and try to propagate it. The project will take about 6 to 8 weeks to complete. During this time, students will research propagation, attempt to propagate a plant, keep a journal, and write a summary when the project is finished.

  13. Sub-Fresnel-scale vertical resolution in atmospheric profiles from radio occultation

    Microsoft Academic Search

    E. Tuna Karayel; David P. Hinson

    1997-01-01

    We have investigated the vertical resolution that can be achieved in atmospheric profiles retrieved from radio occultation measurements. The results are based on forward simulations of radio wave propagation through model atmospheres using the multiple phase-screen method. We find that profiles retrieved through Abel inversion, the standard algorithm derived from geometrical optics, have a vertical resolution that is diffraction-limited, as

  14. Analysis of the Low-Frequency Radio Noise Environment at Satellite Heights from Terrestrial Sources

    Microsoft Academic Search

    M. F. Taylor; J. P. Basart; M. McCoy; E. Rios

    1996-01-01

    We have investigated the propagation of terrestrial radio sources from 1 to 30 MHz (HF spectral region) through the ionosphere for the purpose of characterizing the interference spectrum on potential space-based, low-frequency-radio telescopes. A recent survey of the HF noise environment at satellite heights from 1 to 14 MHz has been conducted using the WIND spacecraft. Radio frequencies for which

  15. Modeling and Simulation for Realistic Propagation Environments of Communications Signals at SHF Band

    NASA Technical Reports Server (NTRS)

    Ho, Christian

    2005-01-01

    In this article, most of widely accepted radio wave propagation models that have proven to be accurate in practice as well as numerically efficient at SHF band will be reviewed. Weather and terrain data along the signal's paths can be input in order to more accurately simulate the propagation environments under particular weather and terrain conditions. Radio signal degradation and communications impairment severity will be investigated through the realistic radio propagation channel simulator. Three types of simulation approaches in predicting signal's behaviors are classified as: deterministic, stochastic and attenuation map. The performance of the simulation can be evaluated under operating conditions for the test ranges of interest. Demonstration tests of a real-time propagation channel simulator will show the capabilities and limitations of the simulation tool and underlying models.

  16. Radio Observations of Supernova Remnants

    E-print Network

    W. Reich

    2002-08-28

    Supernovae release an enormous amount of energy into the interstellar medium. Their remnants can observationally be traced up to several ten-thousand years. So far more than 230 Galactic supernova remnants (SNRs) have been identified in the radio range. Detailed studies of the different types of SNRs give insight into the interaction of the blast wave with the interstellar medium. Shock accelerated particles are observed, but also neutron stars left from the supernova explosion make their contribution. X-ray observations in conjunction with radio data constrain models of supernova evolution. A brief review of the origin and evolution of SNRs is given, which are compared with supernova statistics and observational limitations. In addition the morphology and characteristics of the different types of SNRs are described, including some recent results and illustrated by SNRs images mostly obtained with the Effelsberg 100-m telescope.

  17. Impulsive radio discharges near Saturn

    NASA Technical Reports Server (NTRS)

    Evans, D. R.; Warwick, J. W.; Pearce, J. B.; Carr, T. D.; Schauble, J. J.

    1981-01-01

    Nonthermal radio emissions from the Saturn system were first detected by the Voyager planetary radio astronomy (PRA) experiment on board Voyager 1 in January 1980. Since then emission between 100 kHz and 1 MHz from the planet, termed Saturn kilometric radiation (SKR), has been received almost continuously. A description is presented of eight characteristics which have been fairly well defined by the Voyager 1 encounter. These include a very flat broadband frequency spectrum, a period of approximately 10 h 10 min, a change in the envelope shape of episodes between pre and postencounter, an intensity population structure typical of plural populations, and an episodic structure of a width of approximately 180 deg. It was found that postencounter episodes continue for about three times as long as preencounter ones, and that postencounter bursts are left-circularly polarized at high frequencies. At least one episode shows the onset of high frequency events some time before that of lower frequency ones.

  18. Further examples of seasonal variations of ELF radio propagation parameters

    NASA Astrophysics Data System (ADS)

    Bannister, Peter R.

    1999-01-01

    In this paper we use experimentally determined values of effective attenuation rate, excitation factor, and relative phase velocity, along with the theoretical expressions derived by C. and P. Greifinger, to establish the seasonal variation of representative ionospheric conductivity parameters. These parameters include the reflection heights h0 and h1 (or hE), inverse scale height ?, and reference height H. The basis for this analysis is provided by the 1990-1992 76-Hz field strength measurements taken at four land-based ELF monitoring sites established by the U.S. Navy. The source for these measurements was the U.S. Navy's dual-antenna transmitting system (WTF/MTF). The main conclusion of this paper is that the summertime and January nighttime attenuation rates are substantially lower than during other times of the year. This nighttime attenuation rate decrease appears to be mainly due to an increase in the inverse scale height ?, rather than to an increase in the reflection heights h0 and hE.

  19. Propagation measurements for satellite radio reception inside buildings

    NASA Technical Reports Server (NTRS)

    Vogel, Wolfhard J.; Torrence, Geoffrey W.

    1993-01-01

    Swept CW signals (from 700 to 1800 MHz) were received inside six buildings of brick, corrugated sheet-metal, wood-frame, mobile-home, and reinforced concrete-wall construction. A transmitter antenna was mounted outdoors on top of an 18 m tower to simulate a satellite, and a linearly scanned directional receiver antenna was used to probe the spatial, spectral, and temporal variability of the signal indoors. Levels were found to have much structure in the spatial and frequency domain, but were relatively stable in time. Typically, people moving nearby produced variations of less than 0.5 dB, whereas a person blocking the transmission path produced fades of 6 to 10 dB. Severe losses (17.5 dB) were observed in the concrete-wall building, which also exhibited the longest multipath delays (over 100 ns). Losses inside a mobile home were even larger (over 20 dB) and were independent of antenna orientation. The power-frequency distortion increased with the logarithm of the bandwidth, but could be reduced by moving to a position of higher power. Only the losses showed a clear frequency dependence, but they could be mitigated by moving the antenna.

  20. RADIO PROPAGATION IN HALLWAYS AND STREETS FOR UHF COMMUNICATIONS

    E-print Network

    Porrat, Dana

    of power level is predicted when the receiver turns a corner from a waveguide that guides high power and that, in my opinion, it is fully adequate in scope and quality as a dissertation for the degree and that, in my opinion, it is fully adequate in scope and quality as a dissertation for the degree

  1. Earth-Space Propagation Data Bases

    NASA Technical Reports Server (NTRS)

    Smith, Ernest K.

    1996-01-01

    This paper, designed for the newcomer rather than the expert, will take a rather broad view of what is meant by 'propagation data bases' in that it will take the term to mean both the actual measurements and models of Earth-space paths. The text will largely be drawn from International Radio Consultative Committee (CCIR) reports, now annexed to the Recommendations of the International Telecommunications Union-R Study Group 3, plus some experience with a course taught at the University of Colorado.

  2. Propagation of Singularities for Weak KAM Solutions and Barrier Functions

    NASA Astrophysics Data System (ADS)

    Cannarsa, Piermarco; Cheng, Wei; Zhang, Qi

    2014-10-01

    This paper studies the structure of the singular set (points of nondifferentiability) of viscosity solutions to Hamilton-Jacobi equations associated with general mechanical systems on the n-torus. First, using the level set method, we characterize the propagation of singularities along generalized characteristics. Then, we obtain a local propagation result for singularities of weak KAM solutions in the supercritical case. Finally, we apply such a result to study the propagation of singularities for barrier functions.

  3. Hf propagation through actively modified ionospheres

    SciTech Connect

    Argo, P.E.; Fitzgerald, T.J.; Wolcott, J.H.; Simons, D.J. (Los Alamos National Lab., NM (USA)); Warshaw, S.; Carlson, R. (Lawrence Livermore National Lab., CA (USA))

    1990-01-01

    We have developed a computer modeling capability to predict the effect of localized electron density perturbations created by chemical releases or high-power radio frequency heating upon oblique, one-hop hf propagation paths. We have included 3-d deterministic descriptions of the depleted or enhanced ionization, including formation, evolution, and drift. We have developed a homing ray trace code to calculate the path of energy propagation through the modified ionosphere in order to predict multipath effects. We also consider the effect of random index of refraction variations using a formalism to calculate the mutual coherence functions for spatial and frequency separations based upon a path integral solution of the parabolic wave equation for a single refracted path through an ionosphere which contains random electron density fluctuations. 5 refs., 8 figs.

  4. Proceedings of the Twenty-First NASA Propagation Experimenters Meeting (NAPEX XXI) and the Advanced Communications Technology Satellite (ACTS) Propagation Studies Miniworkshop

    NASA Technical Reports Server (NTRS)

    Golshan, Nasser (Editor)

    1997-01-01

    The NASA Propagation Experimenters (NAPEX) meeting is convened each year to discuss studies supported by the NASA Propagation Program. Representatives from the satellite communications industry, academia and government who have an interest in space-ground radio wave propagation are invited to NAPEX meetings for discussions and exchange of information. The reports delivered at this meeting by program managers and investigators present recent activities and future plans. This forum provides an opportunity for peer discussion of work in progress, timely dissemination of propagation results, and close interaction with the satellite communications industry.

  5. Profile and polarization characteristics of energetic pulsars

    E-print Network

    Patrick Weltevrede; Simon Johnston

    2008-09-16

    In this paper we compare the characteristics of pulsars with a high spin-down energy loss rate (Edot) against those with a low Edot. We show that the differences in the total intensity pulse morphology between the two classes are in general rather subtle. A much more significant difference is the fractional polarization which is very high for high Edot pulsars and low for low Edot pulsars. The Edot at the transition is very similar to the death line predicted for curvature radiation. This suggests a possible link between high energy and radio emission in pulsars and could imply that gamma-ray efficiency is correlated with the degree of linear polarization in the radio band. The degree of circular polarization is in general higher in the second component of doubles, which is possibly caused by the effect of co-rotation on the curvature of the field lines in the inertial observer frame. The most direct link between the high energy emission and the radio emission could be the sub-group of pulsars which we call the energetic wide beam pulsars. These young pulsars have very wide profiles with steep edges and are likely to be emitted from a single magnetic pole. The similarities with the high energy profiles suggest that both types of emission are produced at the same extended height range in the magnetosphere. Alternatively, the beams of the energetic wide beam pulsars could be magnified by propagation effects in the magnetosphere. This would naturally lead to decoupling of the wave modes, which could explain the high degree of linear polarization. As part of this study, we have discovered three previous unknown interpulse pulsars (and we detected one for the first time at 20 cm). We also obtained rotation measures for 18 pulsars whose values had not previously been measured.

  6. Longitudinal wave propagation in piezoelectric coupled rods

    Microsoft Academic Search

    Q. Wang; V. K. Varadan

    2002-01-01

    This paper presents the results of longitudinal wave propagation in piezoelectric coupled rod structures. The deduction of non-dispersive or dispersive characteristics of the structures is based on a classical rod model and the Mindlin-Herrmann rod model. In the classical model, correction factors for piezoelectric effects are introduced to provide remedy for the discontinuity of the normal stress at the interface

  7. Propagation of Significant Figures.

    ERIC Educational Resources Information Center

    Schwartz, Lowell M.

    1985-01-01

    Shows that the rules of thumb for propagating significant figures through arithmetic calculations frequently yield misleading results. Also describes two procedures for performing this propagation more reliably than the rules of thumb. However, both require considerably more calculational effort than do the rules. (JN)

  8. Vegetative propagation of jojoba

    Microsoft Academic Search

    C. B. Low; W. P. Hackett

    1981-01-01

    Development of jojoba as an economically viable crop requires improved methods of propagation and culture. Rooting experiments were performed on cutting material collected from wild jojoba plants. A striking seasonal fluctuation in rooting potential was found. Jojoba plants can be successfully propagated from stem cuttings made during spring, summer, and, to some extent, fall. Variability among jojoba plants may also

  9. Desynchronisation between coexisting radio local loop systems based on DECT

    Microsoft Academic Search

    Jordi Casademont; Josep Paradells; M. I. L. Carrillo

    1997-01-01

    The Digital Enhanced Cordless Telecommunication System (DECT) is gaining acceptance in environments different from those for which the system was designed, in particular outdoors environments such as radio local loop (RLL) and public cordless systems. The main difference between indoors and outdoors is that in this latter environment the signal propagation is not limited between walls, and therefore, is more

  10. Intermittent activity of radio sources. Accretion instabilities and jet precession

    Microsoft Academic Search

    M. Kunert-Bajraszewska; A. Janiuk; A. Siemiginowska; M. Gawronski

    2011-01-01

    We consider the radiation pressure instability operating on short timescales (103 - 106 years) in the accretion disk around a supermassive black hole as the origin of the intermittent activity of radio sources. We test whether this instability can be responsible for short ages (<104 years) of Compact Steep Spectrum sources measured by hot spots propagation velocities in VLBI observations

  11. Environmental constraints in earth-space propagation

    NASA Astrophysics Data System (ADS)

    Goodman, J. M.

    1980-11-01

    The advantages of utilizing space for telecommunications is well known in both the commercial and military arenas. A small complement of satellites at synchronous orbit, for example, may provide nearly global coverage and may be designed to support small disadvantaged customers as well as those characterized by large antenna structures and sophisticated acquisition and processing capabilities. Modern navigational and timing needs can also be satisfied through exploitation of space platforms and NAVSTAR/GPS is a system which exemplifies the utilization of space for those purposes. Applications of space in surveillance and kindred areas also exist and spaceborne instruments for monitoring the exoatmospheric environment and transmissions from the Sun abound. There is an obvious charm in the utilization of space for various purposes, however, most applications require the transmission of intelligence or data between space platforms and other space segments or a ground terminal. Thus the channel or the propagation path clearly becomes a part of the total system as a perturbation source. The nuisance value of the propagation path derives from the extent to which it does not duplicate free space at a specified frequency. This paper reviews the general utilization of space to introduce the importance of Earth-space radio propagation with special emphasis directed toward DoD mission areas. An outline of the basic properties of Earth-space RF propagation follows and finally an assessment of the major effects is given.

  12. Precision calibration of radio interferometers using redundant baselines

    E-print Network

    Liu, Adrian

    Growing interest in 21-cm tomography has led to the design and construction of broad-band radio interferometers with low noise, moderate angular resolution, high spectral resolution and wide fields of view. With characteristics ...

  13. Simulator for general-type beam propagation in turbulent atmosphere

    Microsoft Academic Search

    Çaglar Arpali; Canan Yazicioglu; Halil T. Eyyuboglu; Serap A. Arpali; Yahya Baykal

    2006-01-01

    A simulator is designed in MATLAB code which gives the propagation characteristics of a general-type beam in turbulent atmosphere. When the required source and medium parameters are entered, the simulator yields the average intensity profile along the propagation axis in a video format. In our simulator, the user can choose the option of a ``user defined beam'' in which the

  14. Propagation of electromagnetic ion cyclotron wave energy in the magnetosphere

    Microsoft Academic Search

    T. M. Loto'aniu; B. J. Fraser; C. L. Waters

    2005-01-01

    Recent satellite and conjugate observations of Pc 1 electromagnetic ion cyclotron (EMIC) waves have cast doubt on the validity of the long-standing bouncing wave packet (BWP) model that describes their propagation in the magnetosphere. A study was undertaken using the Combined Release and Radiation Effects Satellite (CRRES) E and B field data to further the understanding of the propagation characteristics

  15. The earth as a radio source. [noting auroral kilometric radiation

    NASA Technical Reports Server (NTRS)

    Gurnett, D. A.

    1975-01-01

    The primary characteristics of radio emission from the earth's magnetosphere are summarized, the origins of these missions are considered and similarities to other astronomical radio sources discussed. The auroral kilometric radiation has features very similar to Io-related decametric radiation from Jupiter and from Saturn. The radiation at fp and 2 fp upstream of the bow shock appears to be generated by the same mechanism as type III solar radio bursts. The beaming of the auroral kilometric radiation into a cone shaped region over the polar cap has some similarity to the angular distribution of radiation from Io and to the beaming of radio emission from pulsars.

  16. Talk Radio: Predictors of Use and Effects on Attitudes about Government

    Microsoft Academic Search

    Barry A. Hollander

    1996-01-01

    Early studies portrayed the talk radio listener, and the caller in particular, as more alienated and less politically and socially active. The research here, using national survey data, finds that the portrait of the talk radio audience has changed to one more positive in terms of socio-demographic characteristics and political participation. However, talk radio is also found to be associated

  17. Ionospheric Sounding Using Real-Time Amateur Radio Reporting Networks

    NASA Astrophysics Data System (ADS)

    Frissell, N. A.; Miller, E. S.; Kaeppler, S. R.; Ceglia, F.; Pascoe, D.; Sinanis, N.; Smith, P.; Williams, R.; Shovkoplyas, A.

    2014-12-01

    Amateur radio reporting networks, such as the Reverse Beacon Network (RBN), PSKReporter, and the Weak Signal Propagation Network, are powerful tools for remote sensing the ionosphere. These voluntarily constructed and operated networks provide real-time and archival data that could be used for space weather operations, forecasting, and research. The potential exists for the study of both global and localized effects. The capability of one such network to detect space weather disturbances is demonstrated by examining the impacts on RBN-observed HF propagation paths of an X2.9 class solar flare detected by the GOES 15 satellite. Prior to the solar flare, the RBN observed strong HF propagation conditions between multiple continents, primarily Europe, North America, and South America. Immediately following the GOES 15 detection of the solar flare, the number of reported global RBN propagation paths dropped to less than 35% that of prior observations. After the flare, the RBN showed the gradual recovery of HF propagation conditions.

  18. Tracking by Identification Using Computer Vision and Radio

    PubMed Central

    Mandeljc, Rok; Kova?i?, Stanislav; Kristan, Matej; Perš, Janez

    2013-01-01

    We present a novel system for detection, localization and tracking of multiple people, which fuses a multi-view computer vision approach with a radio-based localization system. The proposed fusion combines the best of both worlds, excellent computer-vision-based localization, and strong identity information provided by the radio system, and is therefore able to perform tracking by identification, which makes it impervious to propagated identity switches. We present comprehensive methodology for evaluation of systems that perform person localization in world coordinate system and use it to evaluate the proposed system as well as its components. Experimental results on a challenging indoor dataset, which involves multiple people walking around a realistically cluttered room, confirm that proposed fusion of both systems significantly outperforms its individual components. Compared to the radio-based system, it achieves better localization results, while at the same time it successfully prevents propagation of identity switches that occur in pure computer-vision-based tracking. PMID:23262485

  19. High Energy Astrophysics: Radio Galaxies Geoffrey V. Bicknell Radio Galaxies

    E-print Network

    Bicknell, Geoff

    High Energy Astrophysics: Radio Galaxies © Geoffrey V. Bicknell Radio Galaxies 1 Fanaroff Laing #12;High Energy Astrophysics: Radio Galaxies 2/56 The prototype FR 2 radio galaxy, Cygnus A Energy Astrophysics: Radio Galaxies 3/56 Cygnus A at 850 microns. Only the hot spots and core are visible

  20. Spectrum agile radio: radio resource measurements for opportunistic spectrum usage

    Microsoft Academic Search

    Stefan Mangold; Zhun Zhong; Kiran Challapali; Chun-Ting Chou

    2004-01-01

    Radio spectrum allocation is undergoing radical rethinking. Regulators, government agencies, industry, and the research community have recently established many initiatives for new spectrum policies and seek approaches to more efficiently manage the radio spectrum. In this paper, we examine new approaches, namely, spectrum agile radios, for opportunistic spectrum usage. Spectrum agile radios use parts of the radio spectrum that were

  1. PROPAGATING WAVES ALONG SPICULES

    SciTech Connect

    Okamoto, Takenori J. [National Astronomical Observatory, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); De Pontieu, Bart, E-mail: joten.okamoto@nao.ac.jp [Lockheed Martin Solar and Astrophysics Laboratory, B/252, 3251 Hanover Street, Palo Alto, CA 94304 (United States)

    2011-08-01

    Alfvenic waves are thought to play an important role in coronal heating and acceleration of solar wind. Here we investigate the statistical properties of Alfvenic waves along spicules (jets that protrude into the corona) in a polar coronal hole using high-cadence observations of the Solar Optical Telescope on board Hinode. We developed a technique for the automated detection of spicules and high-frequency waves. We detected 89 spicules and found (1) a mix of upward propagating, downward propagating, as well as standing waves (occurrence rates of 59%, 21%, and 20%, respectively); (2) the phase speed gradually increases with height; (3) upward waves dominant at lower altitudes, standing waves at higher altitudes; (4) standing waves dominant in the early and late phases of each spicule, while upward waves were dominant in the middle phase; (5) in some spicules, we find waves propagating upward (from the bottom) and downward (from the top) to form a standing wave in the middle of the spicule; and (6) the medians of the amplitude, period, and velocity amplitude were 55 km, 45 s, and 7.4 km s{sup -1}, respectively. We speculate that upward propagating waves are produced near the solar surface (below the spicule) and downward propagating waves are caused by reflection of (initially) upward propagating waves off the transition region at the spicule top. The mix of upward and downward propagating waves implies that exploiting these waves to perform seismology of the spicular environment requires careful analysis and may be problematic.

  2. Gear crack propagation investigations

    NASA Technical Reports Server (NTRS)

    Lewicki, David G.; Ballarini, Roberto

    1996-01-01

    Analytical and experimental studies were performed to investigate the effect of gear rim thickness on crack propagation life. The FRANC (FRacture ANalysis Code) computer program was used to simulate crack propagation. The FRANC program used principles of linear elastic fracture mechanics, finite element modeling, and a unique re-meshing scheme to determine crack tip stress distributions, estimate stress intensity factors, and model crack propagation. Various fatigue crack growth models were used to estimate crack propagation life based on the calculated stress intensity factors. Experimental tests were performed in a gear fatigue rig to validate predicted crack propagation results. Test gears were installed with special crack propagation gages in the tooth fillet region to measure bending fatigue crack growth. Good correlation between predicted and measured crack growth was achieved when the fatigue crack closure concept was introduced into the analysis. As the gear rim thickness decreased, the compressive cyclic stress in the gear tooth fillet region increased. This retarded crack growth and increased the number of crack propagation cycles to failure.

  3. Modeling of laser beam propagation through turbulence

    NASA Astrophysics Data System (ADS)

    Shugaev, Fedor V.; Shtemenko, Ludmila S.; Nikolaeva, Oksana A.; Arsenyan, Tatiana I.; Suhareva, Natalia A.; Sukhorukov, Anatoly P.

    2014-10-01

    Our approach for modeling laser beam propagation through turbulence involves parabolic equation method and results of experimental investigation in laboratory. The analytic solution to the problem of the Gaussian beam propagation through non-uniform gas has been derived. The solution depends on the refracted index, i.e. on the gas density. The density distribution can be found from the Navier-Stokes system. The appropriate solution may be constructed by two ways : (i) as a series in powers of vorticity which is supposed to be small; (ii) with the aid of the parametrix method which includes an iterative procedure. It follows from the solution that acoustic radiation of vortex rings arises. Statistical properties of the propagating beam were found from the solution to the parabolic equation as average over time. In experiments the propagation path was equal to 7 m. The laser beam propagation was accompanied by convection and lateral wind. The frequency of turbulent fluctuations was equal to 2-10 Hz. Phase trajectories were found as well as statistical properties of the beam intensity in turbulent gas flow. The conclusion is as follows. Statistical characteristics traditionally used for the estimation of the laser beam special distortions in the open space transmission channels are to be complemented by the dynamic parameters such as the space of embeddings dimension, characteristic frequencies for the phase trajectories and so on.

  4. Some Comments On Fast Radio Burst

    E-print Network

    Luan, Jing

    2014-01-01

    Fast Radio Bursts (FRBs) are single $\\mathrm{ms}$ radio pulses with dispersion measures (DM) ranging up to $\\sim 10^3\\mathrm{pc cm^{-3}}$. It has been proposed that they originate from galactic flare stars, and that their DMs come from propagation through the stellar corona. We disapprove this hypothesis by showing that free-free absorption would conceal any radio signal emitted from below the corona. It appears that FRBs come from extragalactic sources. FRB 110220 has a scattering tail of several $\\mathrm{ms}$ Propagation through the intergalactic plasma is unlikely to account for scattering of this magnitude unless the intergalactic magnetic field is as large as $2.4\\times 10^{-9}\\mathrm{G}$. This suggests that this burst originated in the central region of an external galaxy. Extrapolated to cosmological distances and sources sizes of order $c\\Delta t$, the electric fields of FRBs are strong in the sense that they would accelerate thermal electrons to relativistic energies in less than a nanosecond.

  5. US Radio Broadcasting Past

    NSDL National Science Digital Library

    White, Thomas W.

    Thomas H. White discusses the history of United States radio in detail from the late 1800�s to the 1940�s in this informative site featuring a compilation of materials and articles. The site features 24 different sections arranged by title and year for users to browse, each section allows the user to discover the beginnings of radio in the United States. Sections include some that outline the changes of radio in relation to U.S. history, including but not limited to the World Wars, as well as discussions of big business and radio, and early government regulation to name only a few. For anyone interested in the history of radio and how radio got to where it is today, this site is an excellent resource.

  6. American RadioWorks

    NSDL National Science Digital Library

    Radio documentaries have been around almost since the beginning of regularly scheduled radio programming, but not all are created equal (or with great aplomb), and the American Radio Works is certainly one of the finer documentary production units in the field. Based at Minnesota Public Radio in St. Paul, Minnesota, Radio Works' primary themes include public affairs documentaries on major social and economic issues, investigative reporting, and the Living History series, which seeks to document the 20th century American experience "through the lives of those who witnessed it." The web-browsing public will be glad to know that all of the radio projects are available online here, and can be listened to in their entirety. Visitors can listen to close to 40 of their productions, including their most recent production which deals with the extensive phone conversations recorded by Presidents Johnson, Kennedy, and Nixon during their terms in the White House

  7. Gear Crack Propagation Investigation

    NASA Technical Reports Server (NTRS)

    1995-01-01

    Reduced weight is a major design goal in aircraft power transmissions. Some gear designs incorporate thin rims to help meet this goal. Thin rims, however, may lead to bending fatigue cracks. These cracks may propagate through a gear tooth or into the gear rim. A crack that propagates through a tooth would probably not be catastrophic, and ample warning of a failure could be possible. On the other hand, a crack that propagates through the rim would be catastrophic. Such cracks could lead to disengagement of a rotor or propeller from an engine, loss of an aircraft, and fatalities. To help create and validate tools for the gear designer, the NASA Lewis Research Center performed in-house analytical and experimental studies to investigate the effect of rim thickness on gear-tooth crack propagation. Our goal was to determine whether cracks grew through gear teeth (benign failure mode) or through gear rims (catastrophic failure mode) for various rim thicknesses. In addition, we investigated the effect of rim thickness on crack propagation life. A finite-element-based computer program simulated gear-tooth crack propagation. The analysis used principles of linear elastic fracture mechanics, and quarter-point, triangular elements were used at the crack tip to represent the stress singularity. The program had an automated crack propagation option in which cracks were grown numerically via an automated remeshing scheme. Crack-tip stress-intensity factors were estimated to determine crack-propagation direction. Also, various fatigue crack growth models were used to estimate crack-propagation life. Experiments were performed in Lewis' Spur Gear Fatigue Rig to validate predicted crack propagation results. Gears with various backup ratios were tested to validate crack-path predictions. Also, test gears were installed with special crack-propagation gages in the tooth fillet region to measure bending-fatigue crack growth. From both predictions and tests, gears with backup ratios (rim thickness divided by tooth height) of 3.3 and 1.0 produced tooth fractures, whereas a backup ratio of 0.3 produced rim fractures. For a backup ratio of 0.5, the experiments produced rim fractures and the predictions produced both rim and tooth fractures, depending on the initial geometry of the crack. Good correlation between predicted and measured crack growth was achieved when the fatigue crack-closure concept was introduced into the analysis. As the gear rim thickness decreased, the compressive cyclic stress in the gear-tooth fillet region increased. This retarded crack growth and increased the number of crack-propagation cycles to failure.

  8. Apparent Faster-Than-Light Pulse Propagation in Interstellar Space: A New Probe of the Interstellar Medium

    Microsoft Academic Search

    F. A. Jenet; D. Fleckenstein; A. Ford; A. Garcia; R. Miller; J. Rivera; K. Stovall

    2010-01-01

    Radio pulsars emit regular bursts of radio radiation that propagate through the interstellar medium (ISM), the tenuous gas and plasma between the stars. Previously known dispersive properties of the ISM cause low-frequency pulses to be delayed in time with respect to high frequency ones. This effect can be explained by the presence of free electrons in the medium. The ISM

  9. Radio Surveys: an Overview

    NASA Astrophysics Data System (ADS)

    Morganti, Raffaella

    2015-03-01

    Radio astronomy has provided important surveys that have made possible key (and sometimes serendipitous) discoveries. I will briefly mention some of the past continuum and line (HI) radio surveys as well as new, on-going surveys and surveys planned for the near future. This new generation of large radio surveys is bringing extra challenges in terms of data handling but also great new possibilities thanks to the wider range of data products that they will provide.

  10. National Radio Observatory

    NSDL National Science Digital Library

    The National Radio Astronomy Observatory (NRAO) "operates powerful, advanced radio telescopes spanning the western hemisphere." The website is nicely divided into information for the general public, astronomers, and teachers and students. Users can learn all about NRAO's many telescopes located throughout the United States. Researchers can find out about meetings, conferences, software resources, and surveys. Amateur radio astronomers can find links describing how to build antennas and interferometers. Everyone will enjoy the numerous images of astronomical phenomena and NRAO's telescopes and facilities.

  11. Radio-Locator

    NSDL National Science Digital Library

    Radio-Locator is a comprehensive database of radio stations throughout the United States and Canada. Stations can be searched by location and format, or even more specifically with the site's advanced search. Users can even search for vacant frequencies on the dial. The bulk of their information come from the FCC's public databases, but is also updated and corrected. Radio-Locator also provides links to individual stations website and internet streams if available.

  12. Radio data transmission for SCADA

    SciTech Connect

    Frasier, W.E. (Enron Corp., Houston, TX (US))

    1989-09-01

    Enron has used such wireless systems as meteor burst radio, 952 MHz multiple address radio, VSAT and L-band satellite, cellular radio and ACSB radio. The company's experience with meteor burst radio communications is discussed in this paper. It indicates good system reliability and consequently all back-up telephone lines have been removed from sites using this system.

  13. Radio emission of RRAT pulsars at 111 MHz

    NASA Astrophysics Data System (ADS)

    Losovsky, B. Ya.; Dumsky, D. V.

    2014-08-01

    Observations of the RRAT pulsars J0627+16, J0628+09, J1819-1458, J1826-1419, J1839-01, J1840-1419, J1846-0257, J1848-12, J1850+15, J1854+0306, J1919+06, J1913+1330, J1919+17, J1946+24, and J2033+00 observed earlier on the 64-m Parkes telescope (Australia) and the 300-m Arecibo radio telescope (Puerto Rico) at 1400 MHz were conducted at 111 MHz on the LSA radio telescope of the Pushchino Radio Astronomy observatory in 2010-2012. A characteristic feature of these pulsars is their sporadic radio emission during rare active epochs and the absence of radio emission during long time intervals. No appreciable flare activity of these pulsars was detected in the Pushchino observations. However, processing the observations using the Fast Folding Algorithm taking into account known information about the pulsar dispersion measures and periods shows that, even during quiescent intervals, the majority of the studied pulsars generate weak radio pulses with a period corresponding to that of the radio emission of the sporadic pulses observed at active epochs. The flux of this radio emission does not exceed 100 mJy at the pulse peak, even at the low frequency of 111 MHz. This considerably hinders detection of the radio emission of RRAT pulsars at high frequencies, since the radio fluxes of RRAT pulsars decreases with increasing frequency.

  14. Radio Properties of AGN

    NASA Astrophysics Data System (ADS)

    Abrahamyan, Hayk V.; Mickaelian, Areg M.

    2014-07-01

    To study the radio properties of AGN, we cross-correlate and investigate Veron-Cetty & Veron catalog of QSOs and Active Galaxies (v.13, 2010) with a number of radio catalogs: NVSS, FIRST, GB6, 87GB, SUMSS, WISH, WENSS, and 7C. This catalog contains 168,940 objects with positional accuracy of mostly 1 arcsec, though many positions have larger errors. We use new cross-correlation software based on accuracy of each object independently. In this software we take into account errors for each source and take identifications with errors within 3 sigma. Altogether, we find ~16,000 AGN having radio detection in any of the listed catalogs. Using all data from radio catalogs, we derive a homogeneous sample of radio AGN. The sample allows accomplish several tasks, including study of the distribution of radio sources by activity types, differences in physical properties of radio-loud and radio-quiet AGN, luminosity functions for various types of radio AGN, study of the q parameter by AGN types and its evolution, etc.

  15. STEM on the radio

    NASA Astrophysics Data System (ADS)

    Showstack, Randy

    2011-10-01

    Looking for an Internet radio station focusing on programing about science, technology, engineering, and math (STEM)? The U.S. National Science Foundation (NSF) announced on 26 September the launch of Science360 Radio, which it says is the first Internet radio stream dedicated to STEM programing. Science360 includes more than 100 radio shows and podcasts that are available on the Web as well as on iPhone and Android devices. The shows originate from a variety of sources, including NSF, other U.S. government agencies, science organizations, universities, and media outlets. For more information, see http://science360.gov/files/.

  16. Radio continuum properties of luminous infrared galaxies. Identifying the presence of an AGN in the radio

    NASA Astrophysics Data System (ADS)

    Vardoulaki, E.; Charmandaris, V.; Murphy, E. J.; Diaz-Santos, T.; Armus, L.; Evans, A. S.; Mazzarella, J. M.; Privon, G. C.; Stierwalt, S.; Barcos-Muñoz, L.

    2015-02-01

    Context. Luminous infrared galaxies (LIRGs) are systems enshrouded in dust, which absorbs most of their optical/UV emission and radiates it again in the mid- and far-infrared. Radio observations are largely unaffected by dust obscuration, enabling us to study the central regions of LIRGs in an unbiased manner. Aims: The main goal of this project is to examine how the radio properties of local LIRGs relate to their infrared spectral characteristics. Here we present an analysis of the radio continuum properties of a subset of the Great Observatories All-sky LIRG Survey (GOALS), which consists of 202 nearby systems (z< 0.088). Our radio sample consists of 35 systems, containing 46 individual galaxies, that were observed at both 1.49 and 8.44 GHz with the VLA with a resolution of about 1 arcsec (FWHM). The aim of the project is to use the radio imagery to probe the central kpc of these LIRGs in search of active galactic nuclei (AGN). Methods: We used the archival data at 1.49 and 8.44 GHz to create radio-spectral-index maps using the standard relation between flux density S? and frequency ?, S? ~ ?- ?, where ? is the radio spectral index. By studying the spatial variations in ?, we classified the objects as radio-AGN, radio-SB, and AGN/SB (a mixture). We identified the presence of an active nucleus using the radio morphology, deviations from the radio/infrared correlation, and spatially resolved spectral index maps, and then correlated this to the usual mid-infrared ([NeV]/[NeII] and [OIV]/[NeII] line ratios and equivalent width of the 6.2 ?m PAH feature) and optical (BPT diagram) AGN diagnostics. Results: We find that 21 out of the 46 objects in our sample (~45%) are radio-AGN, 9 out of the 46 (~20%) are classified as starbursts (SB) based on the radio analysis, and 16 (~35%) are AGN/SB. After comparing to other AGN diagnostics we find 3 objects out of the 46 (~7%) that are identified as AGN based on the radio analysis, but are not classified as such based on the mid-infrared and optical AGN diagnostics presented in this study. Appendix A is available in electronic form at http://www.aanda.orgVLA images as FITS files are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/574/A4

  17. 75 FR 10439 - Cognitive Radio Technologies and Software Defined Radios

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-08

    ...10-12] Cognitive Radio Technologies and Software Defined Radios AGENCY: Federal Communications...proceeding concerning the use of open source software to implement security features in software defined radios (SDRs). While, the...

  18. Signalling characteristics in satellite-aided land mobile communications

    NASA Technical Reports Server (NTRS)

    Anderson, R. E.

    1982-01-01

    The feasibility of land mobile radio communications has been demonstrated by a large number of experiments with NASA's ATS satellites. Significant differences in the propagation characteristics of satellite and terrestrial mobile signal paths were observed in the experiments. Terrestrial paths are best in cities where they can provide frequency reuse and assure communication by bouncing signals around obstructions. Satellites may be best in thinly populated areas because they eliminate the need for many tower mounted relays. The satellite paths do not have the severe Rayleigh fading that limits the range and signal quality of terrestrial paths if the satellite is above approximately ten degrees elevation, a value easily achieved for the United States. The experiments verified that high quality voice communications and other functions, such as data transmission and vehicle position surveillance, are easily accomplished through geostationary satellites with vehicle transmitter power and antenna gain no different than those of terrestrial mobile communications.

  19. Propagation of sound in turbulent media

    NASA Technical Reports Server (NTRS)

    Wenzel, A. R.

    1976-01-01

    Perturbation methods commonly used to study the propagation of acoustic waves in turbulent media are reviewed. Emphasis is on those techniques which are applicable to problems involving long-range propagation in the atmosphere and ocean. Characteristic features of the various methods are illustrated by applying them to particular problems. It is shown that conventional perturbation techniques, such as the Born approximation, yield solutions which contain secular terms, and which therefore have a relatively limited range of validity. In contrast, it is found that solutions obtained with the aid of the Rytov method or the smoothing method do not contain secular terms, and consequently have a much greater range of validity.

  20. Gluon Propagators in QCD.

    NASA Astrophysics Data System (ADS)

    Li, Sai-Ping

    Two currently interesting problems in QCD that tie with gluon propagation are studied here. (1) At finite temperatures, the gluon propagator develops masses from theoretical fluctuations in the infrared limit. We reexamine a recent calculation of the magnetic mass m(,mag) in the temporal gauge and show that there is not necessary a g('3)T('2) term in. (DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI). (2) Recent studies of the infrared behavior of the propagator in the infrared limit suggest a momentum singularity of 1/q('4) behavior for the gluon propagator which corresponds to a linear quark-antiquark potential. Lattice calculations however show an approximate 1/q('2) (instead of 1/q('4)) behavior. There is thus a discrepancy between the continum limit analytical and numerical lattice calculations.

  1. Proceedings of the 19th NASA Propagation Experimenters Meeting (NAPEX 19) and the 7th Advanced Communications Technology Satellite (ACTS) Propagation Studies Workshop (APSW 7)

    NASA Technical Reports Server (NTRS)

    Davarian, Faramaz (editor)

    1995-01-01

    The NASA Propagation Experimenters Meeting (NAPEX), supported by the NASA Propagation Program, is convened annually to discuss studies made on radio wave propagation by investigators from domestic and international organizations. NAPEX 19 was held on 14 Jun. 1995, in Fort Collins, Colorado. Participants included representatives from Canada, Japan, and the United States, including researchers from universities, government agencies, and private industry. The meeting focused on mobile personal satellite systems and the use of 20/30-GHz band for fixed and mobile satellite applications. In total, 18 technical papers were presented. Following NAPEX 19, the Advanced Communications Technology Satellite (ACTS) Propagation Studies Workshop 7 (APSW 7) was held on 15-16 Jun. 1995, to review ACTS propagation activities with emphasis on the experimenters' status reports and dissemination of propagation data to industry.

  2. The Deep Space Network as an instrument for radio science research

    NASA Technical Reports Server (NTRS)

    Asmar, S. W.; Renzetti, N. A.

    1993-01-01

    Radio science experiments use radio links between spacecraft and sensor instrumentation that is implemented in the Deep Space Network. The deep space communication complexes along with the telecommunications subsystem on board the spacecraft constitute the major elements of the radio science instrumentation. Investigators examine small changes in the phase and/or amplitude of the radio signal propagating from a spacecraft to study the atmospheric and ionospheric structure of planets and satellites, planetary gravitational fields, shapes, masses, planetary rings, ephemerides of planets, solar corona, magnetic fields, cometary comae, and such aspects of the theory of general relativity as gravitational waves and gravitational redshift.

  3. TACTICAL RADIO OPERATIONS August 2009

    E-print Network

    US Army Corps of Engineers

    FM 6-02.53 TACTICAL RADIO OPERATIONS August 2009 DISTRIBUTION RESTRICTION. Approved for public August 2009 TACTICAL RADIO OPERATIONS Contents Page PREFACE ...........................................................................................................viii Chapter 1 APPLICATIONS FOR TACTICAL RADIO DEPLOYMENT.............................. 1-1 Modularity

  4. Radio Emission from Exoplanets

    E-print Network

    Samuel J. George; Ian R. Stevens

    2008-04-24

    We present results from new low frequency observations of two extrasolar planetary systems (Epsilon Eridani and HD128311) taken at 150 MHz with the Giant Metrewave Radio Telescope (GMRT). We do not detect either system, but are able to place tight upper limits on their low frequency radio emission.

  5. Writing for Radio.

    ERIC Educational Resources Information Center

    Tupper, Marianna S.

    1995-01-01

    Describes a 24-hour commercial radio station simulation class project for eighth-grade language arts. Students wrote their own scripts, chose music and were disc jockeys on their own music and talk shows, and prepared news and traffic reports. Guest speakers from actual commercial radio came in to discuss issues such as advertising, censorship,…

  6. Film, Radio, and Television.

    ERIC Educational Resources Information Center

    Hardesty, Carolyn, Ed.

    1990-01-01

    This journal issue covers the history of film, radio, and television in Iowa. The first article, "When Pictures and Sound Came to Iowa," summarizes the origin of movies and radio and their early beginnings in Iowa. Using old photographs and measurement charts, the viewing, reading, and listening habits of young people in 1950 and 1958 are…

  7. Stabilized radio frequency quadrupole

    DOEpatents

    Lancaster, Henry D. (Orinda, CA); Fugitt, Jock A. (Berkeley, CA); Howard, Donald R. (Danville, CA)

    1984-01-01

    A long-vane stabilized radio frequency resonator for accelerating charged particles and including means defining a radio frequency resonator cavity, a plurality of long vanes mounted in the defining means for dividing the cavity into sections, and means interconnecting opposing ones of the plurality of vanes for stabilizing the resonator.

  8. A refracting radio telescope

    Microsoft Academic Search

    Paul Bernhardt; A. V. da Rosa

    1977-01-01

    Observations of extraterrestrial radio sources at the lower end of the radio frequency spectrum are limited by reflection of waves from the topside ionosphere and by the large size of antenna apertures necessary for the realization of narrow beamwidths. The use of the ionosphere as a lens is considered. The lens is formed by the release of chemicals such as

  9. Radio Halo Sources in Clusters of Galaxies.

    NASA Astrophysics Data System (ADS)

    Hanisch, Robert James

    A series of observations have been made of clusters of galaxies in search of radio halo emission. The observations are of several types: (1) a survey at 430 MHz using the 305-meter telescope at Arecibo of 72 rich clusters, (2) a survey at 50-120 MHz using the high frequency array of the University of Tasmania in Llanherne of 30 rich, X-ray emitting clusters, (3) detailed maps of the Coma cluster, Abell 1367, and Abell 399/401 at 430 and 1400 MHz, again using the Arecibo telescope, and (4) low-frequency fan -beam maps of several clusters (Coma, Perseus, Virgo, Abell 1367, and Abell 399/401) made at the University of Maryland's Clark Lake Radio Observatory. The surveys had two goals: first, to determine just how common or uncommon radio halo sources are, and second, to determine if radio halo sources occur preferentially in one type of cluster. The more detailed mapping was intended to determine the extent and size-frequency dependence of the radio halo sources and thereby to learn more about particle propagation rates and modes of diffusion in astrophysical plasmas. Our observations corroborate previous indications that radio halo sources similar to the one in the Coma cluster are quite uncommon. Our results indicate that this is not because it requires some unusual history of radio frequency activity to produce a radio halo, but rather because ratio halos can exist only in clusters that are highly evolved dynamically, i.e., that have a deep and wide central potential capable of containing a large amount of hot gas. This type of cluster, which is also characterized by a high degree of central concentration and an unusually low fraction of spiral galaxies, is itself rather uncommon and thus can account for the rarity of radio halo sources. Given the most tenable models for halo formation, it is reasonable to find halos only in this type of cluster. If halos are formed by relativistic electrons diffusing away from cluster radio galaxies, the electrons must propagate at speeds much greater than the Alfven speed if they are to reach the observed distances from the cluster center without suffering overwhelming energy losses. Super-Alfvenic streaming speeds can only occur, however, if the background plasma is hot. Thus, those clusters which are most dynamically evolved and contain a widespread distribution of hot intracluster gas will be capable of maintaining the largest halo sources. On the other hand, if radio halos are formed by a population of secondary relativistic electrons, which is produced through proton-proton collisions between cosmic ray protons originating in active galaxies and thermal protons in the intracluster medium, it is clear that a rich intracluster medium is necessary so that the cross-section for proton -proton collisions is high.

  10. Smart Radio Spectrum Management for Cognitive Radio

    E-print Network

    Bhattacharya, Partha Pratim; Gera, Rishita; Agarwal, Anjali

    2011-01-01

    Today's wireless networks are characterized by fixed spectrum assignment policy. The limited available spectrum and the inefficiency in the spectrum usage necessitate a new communication paradigm to exploit the existing wireless spectrum opportunistically. Cognitive radio is a paradigm for wireless communication in which either a network or a wireless node changes its transmission or reception parameters to communicate efficiently avoiding interference with licensed or unlicensed users. In this work, a fuzzy logic based system for spectrum management is proposed where the radio can share unused spectrum depending on some parameters like distance, signal strength, node velocity and availability of unused spectrum. The system is simulated and is found to give satisfactory results.

  11. Worldwide monitoring of VLF-LF propagation and atmospheric noise

    NASA Astrophysics Data System (ADS)

    Tomko, A. A.; Hepner, T.

    2001-03-01

    A joint effort is underway between The Johns Hopkins University Applied Physics Laboratory and the Space and Naval Warfare (SPAWAR) Systems Center, San Diego, to deploy monitoring equipment capable of characterizing worldwide VLF-LF radio wave propagation and atmospheric noise levels. The monitoring equipment consists of a PC-based spectrum analyzer and orthogonal ferrite core magnetic loop antennas. The analyzer performs continuous measurements of the radio spectrum from 12 to 62 kHz and records time histories of VLF-LF signals (equivalent vertical electric field strength), noise amplitude probability distribution, noise impulsiveness, and average noise field strength. Data are downloaded via the Internet to a central database server. The Internet connection also provides for system reconfiguration and clock synchronization. Data collected by the monitoring network will be used to improve communication coverage forecasts and to analyze transient and long-term propagation effects. This paper provides an overview of the monitoring network and samples of data collected by it.

  12. Propagation Effects of Wind and Temperature on Acoustic Ground Contour Levels

    NASA Technical Reports Server (NTRS)

    Heath, Stephanie L.; McAninch, Gerry L.

    2006-01-01

    Propagation characteristics for varying wind and temperature atmospheric conditions are identified using physically-limiting propagation angles to define shadow boundary regions. These angles are graphically illustrated for various wind and temperature cases using a newly developed ray-tracing propagation code.

  13. Wave propagation into the middle atmosphere

    NASA Technical Reports Server (NTRS)

    Hirota, I.

    1989-01-01

    Recent observations of various types of waves propagating into the middle atmosphere are reviewed. Emphasis is made on the excitation processes in the lower atmosphere and their vertical propagation through the background flow as a function of the latitude, height and season. The following subjects are discussed: (1) Vertical propagation of quasi-stationary forced Rossby waves into the winter stratosphere in connection with the sudden warming; (2) Spectral distribution and seasonal characteristics of normal mode (free) Rossby waves and the asymmetry of the Northern and Southern Hemispheres; and (3) Seasonal variation of internal gravity waves in the middle atmosphere. Further discussions are presented for future studies based on accumulated observational data during the MAP period.

  14. Prsentation de la radio Badr Benmammar

    E-print Network

    Paris-Sud XI, Université de

    combinant anciennes et nouvelles techniques, on parle alors de radio logicielle restreinte (software defined-25Mar2012 #12;2 Plan Radio logicielle (software radio) Radio logicielle restreinte (SDR) Radio cognitive spectre (Spectrum mobility) cel-00680189,version2-25Mar2012 #12;3 Radio logicielle (software radio)Radio

  15. Intergalactic Propagation of UHE Cosmic Rays

    E-print Network

    Abraham Achterberg; Yves A. Gallant; Colin A. Norman; Donald B. Melrose

    1999-07-05

    We discuss the intergalactic propagation of ultra-high-energy cosmic rays (UHECRs) with energies E \\geq 10^{18.5} eV. We consider the propagation of UHECRs under the influence of the energy-dependent deflection by a weak random magnetic field in the intergalactic medium and energy losses by photo-pion and pair production. We calculate arrival spectra taking full account of the kinematics of photo-pion production and the Poisson statistics of the photo-pion interaction rate. We give estimates for the deflection of UHECRs from the line of sight to the source, time delays with respect to photons from the same source, arrival spectra and source statistics. These estimates are confirmed by numerical simulations of the propagation in energy evolution of UHECRs. These simulations demonstrate that the often-used continuous approximation in the treatment of energy losses due to photo-pion production on the cosmic microwave background (CMWB) cannot be justified for UHECRs. We discuss the implications of these results for the observed flux of particles above the Greisen-Zatsepin-Kuz'min cut-off in two of the scenarios that have been proposed for the production of these particles: continuous production in the large shock waves associated with powerful radio galaxies, or possibly large-scale structure formation, and the impulsive production at relativistic blast waves associated with cosmological gamma-ray bursts.

  16. Urban millimeter wave propagation studies

    NASA Astrophysics Data System (ADS)

    Violette, E. J.; Espeland, R. H.; Allen, K. C.; Schwering, F.

    1983-04-01

    Measurements of millimeter wave propagation in urban areas at 9.6, 28.8 and 57.6 GHz, and a determination of signal levels reflected from several building surfaces, were made to study wave propagation characteristics in a city environment. Principal emphasis was on the evaluation of communications link reliability, detectability and usable bandwidth as a function of position of terminals. Reflected signal level measurements were performed on building surfaces of concrete aggregate, painted smooth concrete with protruding ribs, brick, and metal siding. Multipath measurements were recorded as a function of distance for several runs over paths of about 1 kilometer in the center of the Denver metro area. Non-line-of-sight observations showed a large number of substantial signals arriving from a wide range of angles. This report contains the results and analysis from single-path and multipath and multipath reflections recorded for the study. Included are an evaluation of multipath effects for both urban and non-urban line-of-sight path and measurements of signals received on non-line-of-sight paths, using edge diffraction effects.

  17. Propagation of Rhizopus javanicus Biosorbent

    PubMed Central

    Treen-Sears, Margaret E.; Martin, Stanley M.; Volesky, Bohumil

    1984-01-01

    After propagation of Rhizopus javanicus in defined media containing glucose, urea, and mineral salts in deionized distilled water, the ability of the nonliving biomass to sequester cupric ion was assayed. Growth, uptake capacity (saturation uptake at >1 mM Cu2+ concentration in solution), and biosorptive yield (biomass concentration × uptake capacity) were increased by augmentation of the growth medium with mineral salts once growth was under way. In the stationary phase, the uptake capacity of mycelia, which were normally a poor biosorbent, was improved within 4 h of trace metal addition to the growth medium. Growth of the culture was inhibited by excessive concentrations (0.04 to 40 ?M) of metals in the medium in the following order: Cu > Co ? Ni > Mn > Mo; zinc was not inhibitory at 40 ?M, and chromium was stimulatory at 0.53 ?M but slightly inhibitory at higher levels. Iron and potassium phosphate stimulated growth at levels of 0.53 and 40 mM, respectively. When R. javanicus was propagated in a medium with a high salt concentration, exponential growth (0.23 h?1) to a biomass concentration of >3 g/liter and a biosorptive yield of >500 ?mol/liter was achieved. It is evident that the powerful biosorbent characteristics of Rhizopus biomass led to depletion of available trace minerals in suspension culture, which in turn limited growth. PMID:16346580

  18. Canal de Propagation 3me anne Tlcom-Rseaux

    E-print Network

    Dobigeon, Nicolas

    1 Canal de Propagation 3ème année Télécom-Réseaux 2007-2008 Martial COULON #12;2 #12;3 Chap. I VHF/UHF Pico-Cellules : qques m, haut débit. #12;5 I.2. Définition du Canal Radio Mobile · Canal de ( entre 100km et 1mm) Canal montant (Reverse Channel ou Uplink Channel) Mobiles vers BS Transmissions

  19. Radio Emission From EAS - Coherent Geosynchrotron Radiation

    E-print Network

    Tim Huege; Heino Falcke

    2003-05-19

    Extensive air showers (EAS) have been known for over 30 years to emit pulses of radio emission at frequencies from a few to a few hundred MHz, an effect that offers great opportunities for the study of EAS with the next generation of "software radio interferometers" such as LOFAR and LOPES. The details of the emission mechanism, however, remain rather uncertain to date. Following past suggestions that the bulk of the emission is of geomagnetic origin, we model the radio pulses as "coherent geosynchrotron radiation" arising from the deflection of electrons and positrons in the earth's magnetic field. We analytically develop our model in a step-by-step procedure to disentangle the coherence effects arising from different scales present in the shower structure and infer which shower characteristics govern the frequency spectrum and radial dependence of the emission. The effect is unavoidable and our predictions are in good agreement with the available experimental data within their large margins of error.

  20. Project CLEA: Radio Astronomy of Pulsars

    NSDL National Science Digital Library

    This software for Windows, from Project CLEA -- Contemporary Laboratory Experiences In Astronomy, presents students with a radio telescope. The default operating characteristics (beam width, receiver noise, steerability) can be set by the instructor. Students can point the telescope at a source in the sky, viewing the output of the radio receiver on a graphic display that resembles a digital oscilloscope. The student manual describes exercises in which students acquaint themselves with the operation of the radio telescope, measure the signals from several pulsars at various frequencies, learn about pulsar signals, and then estimate the distance to the pulsar. The site includes student and instructor manuals as well as a pre- and posttest. The software is available for Windows only.

  1. HOST GALAXIES OF X-SHAPED RADIO SOURCES

    SciTech Connect

    Springmann, A.; Cheung, C.

    2007-01-01

    Most radiation from galaxies containing active galactic nuclei (AGNs) is emitted not by the stars composing the galaxy, but from an active source at the galactic center, most likely a supermassive black hole. Of particular interest are radio galaxies, active galaxies that emit much of their radiation at radio wavelengths. Within each radio galaxy, an AGN powers a pair of collimated jets of relativistic particles, forming a pair of giant lobes at the end of the jets and thus giving a characteristic double-lobed appearance. A particular class of radio galaxies has an “X”-or winged-shaped morphology: in these, two pairs of lobes appear to originate from the galactic center, producing a distinctive X-shape. Two main mechanisms have been proposed to explain the X-shape morphology: one being a realignment of the black hole within the AGN and the second positing that the radio jets are expanding into an asymmetric medium, causing backflow and producing secondary wings. By analyzing radio host galaxy shapes, the distribution of the stellar mass is compared to the differing model expectations regarding the distribution of the surrounding gas and stellar material about the AGN. Results show elliptical host galaxies with an orthogonal offset between the semi-major axis of the host galaxy and the secondary radio wings, which lends support to the hydrodynamical model. However, results also show circular host galaxies with radio wings, making the realignment scenario a more likely model to describe the formation of these X-shaped radio sources.

  2. Elevated Temperature Crack Propagation

    NASA Technical Reports Server (NTRS)

    Orange, Thomas W.

    1994-01-01

    This paper is a summary of two NASA contracts on high temperature fatigue crack propagation in metals. The first evaluated the ability of fairly simple nonlinear fracture parameters to correlate crack propagation. Hastelloy-X specimens were tested under isothermal and thermomechanical cycling at temperatures up to 980 degrees C (1800 degrees F). The most successful correlating parameter was the crack tip opening displacement derived from the J-integral. The second evaluated the ability of several path-independent integrals to correlate crack propagation behavior. Inconel 718 specimens were tested under isothermal, thermomechanical, temperature gradient, and creep conditions at temperatures up to 650 degrees C (1200 degrees F). The integrals formulated by Blackburn and by Kishimoto correlated the data reasonably well under all test conditions.

  3. RADIO SIGNATURES OF CORONAL-MASS-EJECTION-STREAMER INTERACTION AND SOURCE DIAGNOSTICS OF TYPE II RADIO BURST

    SciTech Connect

    Feng, S. W.; Chen, Y.; Kong, X. L.; Li, G.; Song, H. Q. [Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment, School of Space Science and Physics, Shandong University at Weihai, Weihai 264209 (China); Feng, X. S. [SIGMA Weather Group, State Key laboratory for Space Weather, Center for Space Science and Applied Research, Chinese Academy of Sciences, Beijing 100190 (China); Liu Ying, E-mail: yaochen@sdu.edu.cn [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States)

    2012-07-01

    It has been suggested that type II radio bursts are due to energetic electrons accelerated at coronal shocks. Radio observations, however, have poor or no spatial resolutions to pinpoint the exact acceleration locations of these electrons. In this paper, we discuss a promising approach to infer the electron acceleration location by combining radio and white light observations. The key assumption is to relate specific morphological features (e.g., spectral bumps) of the dynamic spectra of type II radio bursts to imaging features (e.g., coronal mass ejection (CME) going into a streamer) along the CME (and its driven shock) propagation. In this study, we examine the CME-streamer interaction for the solar eruption dated on 2003 November 1. The presence of spectral bump in the relevant type II radio burst is identified, which is interpreted as a natural result of the shock-radio-emitting region entering the dense streamer structure. The study is useful for further determinations of the location of type II radio burst and the associated electron acceleration by CME-driven shock.

  4. Cognitive Radio An Integrated Agent Architecture for Software Defined Radio

    E-print Network

    Maguire Jr., Gerald Q.

    Cognitive Radio An Integrated Agent Architecture for Software Defined Radio Dissertation Doctor learning and natural language processing technology into software radio. The thesis defines and develops-based control, natural language processing, and machine learning technology into software-defined radio

  5. Multiple Radios for Effective Rendezvous in Cognitive Radio Networks

    E-print Network

    Chu, Xiaowen

    Multiple Radios for Effective Rendezvous in Cognitive Radio Networks Lu Yu1 , Hai Liu1 , Yiu in cognitive radio networks (CRNs) for establishing a communication link on a commonly-available channel, we investigate the rendezvous problem in CRNs where cognitive users are equipped with multiple radios

  6. Multiple Radios for Fast Rendezvous in Cognitive Radio Networks

    E-print Network

    Chu, Xiaowen

    1 Multiple Radios for Fast Rendezvous in Cognitive Radio Networks Lu Yu, Hai Liu, Yiu-Wing Leung, Xiaowen Chu, and Zhiyong Lin Abstract--Rendezvous is a fundamental operation in cognitive radio networks. The existing work on rendezvous implicitly assumes that each cognitive user is equipped with one radio (i

  7. Techniques and Technology Article Optimizing Radio Retention and Minimizing Radio

    E-print Network

    Sandercock, Brett K.

    Techniques and Technology Article Optimizing Radio Retention and Minimizing Radio Impacts the duration of transmitter attachment and minimizing the impacts of radios on the behavior and demography of the study animal. We tested 4 methods of radio attachment for a breeding population of upland sandpipers

  8. OneWorldRadio

    NSDL National Science Digital Library

    A number of media commentators have been complaining lately about the lack of ideological viewpoints within the vast sea of radio programming, something that has not been lost on the people at OneWorldRadio. Funded by the Department for International Development, OneWorld Radio is part of an international network of over 1200 partner organizations that are utilizing the internet "to promote human rights and sustainable development worldwide." With online audio content from member organizations (such as radio stations) available in French, Spanish, and a number of other languages, visitors can listen or download any one of hundreds of programs archived here. Additionally, visitors can elect to search their impressive archive by language, region, or topic. Persons interested in the use of radio for development and human rights will want to examine the news and events section as it contains important updates about events dealing with conferences on media freedom throughout the world and links to important radio broadcasts of note. Finally, visitors (and all who sign up for the free membership) can elect to receive the helpful OneWorldRadio e-newsletter.

  9. Vegetative Propagation Project

    NSDL National Science Digital Library

    Nancy Iversen (Cooperstown High School REV)

    1995-06-30

    Students select a healthy plant to be propagated, do some reading about that plant, and determine what type of vegetative reproduction is suitable for that plant. Students vegetatively reproduce plant, keeping a journal of observations of the plant and the process. The journal entries should include a description of the procedure used to propagate, the amount of water given the plant, the date and numbers of roots that appear, when plant was transferred to soil, a description of soil and pot used and sketches drawn 'every so often' --the works!

  10. Turbofan Duct Propagation Model

    NASA Technical Reports Server (NTRS)

    Lan, Justin H.; Posey, Joe W. (Technical Monitor)

    2001-01-01

    The CDUCT code utilizes a parabolic approximation to the convected Helmholtz equation in order to efficiently model acoustic propagation in acoustically treated, complex shaped ducts. The parabolic approximation solves one-way wave propagation with a marching method which neglects backwards reflected waves. The derivation of the parabolic approximation is presented. Several code validation cases are given. An acoustic lining design process for an example aft fan duct is discussed. It is noted that the method can efficiently model realistic three-dimension effects, acoustic lining, and flow within the computational capabilities of a typical computer workstation.

  11. Riding the Radio Waves

    NSDL National Science Digital Library

    2014-09-18

    Students learn how AM radios work through basic concepts about waves and magnetic fields. Waves are first introduced by establishing the difference between transverse and longitudinal waves, as well as identifying the amplitude and frequency of given waveforms. Then students learn general concepts about magnetic fields, leading into how radio waves are created and transmitted. Several demonstrations are performed to help students better understand these concepts. This prepares students to be able to comprehend the functionig of the AM radios they will build during the associated activity.

  12. A Database for Propagation Models and Conversion to C++ Programming Language

    NASA Technical Reports Server (NTRS)

    Kantak, Anil V.; Angkasa, Krisjani; Rucker, James

    1996-01-01

    In the past few years, a computer program was produced to contain propagation models and the necessary prediction methods of most propagation phenomena. The propagation model database described here creates a user friendly environment that makes using the database easy for experienced users and novices alike. The database is designed to pass data through the desired models easily and generate relevant results quickly. The database already contains many of the propagation phenomena models accepted by the propagation community and every year new models are added. The major sources of models included are the NASA Propagation Effects Handbook or the International Radio Consultive Committee (CCIR) or publications such as the Institute for Electrical and Electronic Engineers (IEEE).

  13. 2011 Tsunami Propagation

    NSDL National Science Digital Library

    Julie Martin

    This activity uses data collected from DART (Deep-ocean Assessment and Reporting of Tsunamis) stations in the Pacific following the 2011 tsunami generated off the coast of Japan. Students are required to map the wave front after 5, 10, and 15 hours to better understand the speed and propagation of the tsunami wave.

  14. GRC RF Propagation Studies

    NASA Technical Reports Server (NTRS)

    Nessel, James

    2013-01-01

    NASA Glenn Research Center has been involved in the characterization of atmospheric effects on space communications links operating at Ka-band and above for the past 20 years. This presentation reports out on the most recent activities of propagation characterization that NASA is currently involved in.

  15. Phtodetection Characteristics of Metamorphic HEMT and its Application

    E-print Network

    Choi, Woo-Young

    Phtodetection Characteristics of Metamorphic HEMT and its Application for Radio-on-fiber systems Engineering #12;Phtodetection Characteristics of Metamorphic HEMT and its Application for Radio.............................................................................5 A. InP-based high-electron-mobility transistor .......................5 B. Metamorphic high

  16. NationalRadio Observatory

    E-print Network

    Groppi, Christopher

    exhibits and displays in our exhibit hall where you will discover what radio astronomers are learning about, at least 48 hours before the tour. 15 participants max. No photography. A high-tech tour through telescope

  17. Multiband propagation experiment for narrowband characterisation of high elevation angle land mobile-satellite channels

    NASA Astrophysics Data System (ADS)

    Butt, G.; Evans, B. G.; Richharia, M.

    1992-07-01

    Results of a recent multiband propagation measurement campaign for the high elevation angle land mobile satellite channel are reported. Simultaneous narrowband sounding of the channel has been carried out in suburban, wooded and open areas of the UK using a helicopter-mounted platform to simulate the satellite signal at various elevation angles. Propagation related link degradations in the land mobile-satellite channel have been observed to be less severe when the path elevation angle is increased or radio frequency decreases.

  18. Constraints on cosmic ray propagation in the galaxy

    NASA Technical Reports Server (NTRS)

    Cordes, James M.

    1992-01-01

    The goal was to derive a more detailed picture of magnetohydrodynamic turbulence in the interstellar medium and its effects on cosmic ray propagation. To do so, radio astronomical observations (scattering and Faraday rotation) were combined with knowledge of solar system spacecraft observations of MHD turbulence, simulations of wave propagation, and modeling of the galactic distribution to improve the knowledge. A more sophisticated model was developed for the galactic distribution of electron density turbulence. Faraday rotation measure data was analyzed to constrain magnetic field fluctuations in the ISM. VLBI observations were acquired of compact sources behind the supernova remnant CTA1. Simple calculations were made about the energies of the turbulence assuming a direct link between electron density and magnetic field variations. A simulation is outlined of cosmic ray propagation through the galaxy using the above results.

  19. The cosmic evolution of radio-AGN feedback to z = 1

    NASA Astrophysics Data System (ADS)

    Best, P. N.; Ker, L. M.; Simpson, C.; Rigby, E. E.; Sabater, J.

    2014-11-01

    This paper presents the first measurement of the radio luminosity function of `jet-mode' (radiatively inefficient) radio-AGN out to z = 1, in order to investigate the cosmic evolution of radio-AGN feedback. Eight radio source samples are combined to produce a catalogue of 211 radio-loud AGN with 0.5 < z < 1.0, which are spectroscopically classified into jet-mode and radiative-mode (radiatively efficient) AGN classes. Comparing with large samples of local radio-AGN from the Sloan Digital Sky Survey, the cosmic evolution of the radio luminosity function of each radio-AGN class is independently derived. Radiative-mode radio-AGN show an order of magnitude increase in space density out to z ? 1 at all luminosities, consistent with these AGN being fuelled by cold gas. In contrast, the space density of jet-mode radio-AGN decreases with increasing redshift at low radio luminosities (L1.4 GHz ? 1024 W Hz-1) but increases at higher radio luminosities. Simple models are developed to explain the observed evolution. In the best-fitting models, the characteristic space density of jet-mode AGN declines with redshift in accordance with the declining space density of massive quiescent galaxies, which fuel them via cooling of gas in their hot haloes. A time delay of 1.5-2 Gyr may be present between the quenching of star formation and the onset of jet-mode radio-AGN activity. The behaviour at higher radio luminosities can be explained either by an increasing characteristic luminosity of jet-mode radio-AGN activity with redshift (roughly as (1 + z)3) or if the jet-mode radio-AGN population also includes some contribution of cold-gas-fuelled sources seen at a time when their accretion rate was low. Higher redshifts measurements would distinguish between these possibilities.

  20. The Radio JOVE Project

    NASA Astrophysics Data System (ADS)

    Garcia, L.; Thieman, J.; Higgins, C.

    1999-09-01

    Radio JOVE is an interactive educational activity which brings the radio sounds of Jupiter and the Sun to students, teachers, and the general public. This is accomplished through the construction of a simple radio telescope kit and the use of a real-time radio observatory on the Internet. Our website (http://radiojove.gsfc.nasa.gov/) will contain science information, instruction manuals, observing guides, and education resources for students and teachers. Our target audience is high school science classes, but subjects can be tailored to college undergraduate physics and astronomy courses or even to middle school science classes. The goals of the project are: 1) Educate people about planetary and solar radio astronomy, space physics, and the scientific method 2) Provide teachers and students with a hands-on radio astronomy exercise as a science curriculum support activity by building and using a simple radio telescope receiver/antenna kit 3) Create the first ever online radio observatory which provides real-time data for those with internet access 4) Allow interactions among participating schools by facilitating exchanges of ideas, data, and observing experiences. Our current funding will allow us to impact 100 schools by partially subsidizing their participation in the program. We expect to expand well beyond this number as publicity and general interest increase. Additional schools are welcome to fully participate, but we will not be able to subsidize their kit purchases. We hope to make a wide impact among the schools by advertising through appropriate newsletters, space grant consortia, the INSPIRE project (http://image.gsfc.nasa.gov/poetry/inspire/), electronic links, and science and education meetings. We would like to acknoledge support from the NASA/GSFC Director's Discretionary Fund, the STScI IDEAS grant program and the NASA/GSFC Space Science Data Operations Office.

  1. Magnetic-azimuth dependence of D-layer radio reflectivity, using lightning sferics as radio transmitters

    NASA Astrophysics Data System (ADS)

    Jacobson, A. R.; Shao, X.; Holzworth, R. H.; Lay, E. H.

    2011-12-01

    The Very Low Frequency (3-30 kHz) and Low-Frequency (30-300 kHz) radiation from lightning strokes provides a convenient intense source for studying radio propagation in the ionospheric D-region [Cheng and Cummer, 2005; Cheng et al., 2006; Cheng et al., 2007; Cummer et al., 1998; Jacobson et al., 2010; Shao and Jacobson, 2009]. In this poster we present a new study of the magnetic-azimuth dependence of D-layer radio reflectivity at relatively short ranges (r < 1000 km). This range regime is poorly adapted to a waveguide approach but is well treated by our discrete-reflection approach [Jacobson et al., 2009]. We use cloud-to-ground strokes, which are ~100X more numerous than the Narrow Bipolar Pulse sferics to which our method had previously been confined. Cheng, Z., and S. A. Cummer (2005), Broadband VLF measurements of lightning-induced ionospheric perturbations, Geophys. Res. Lett., 32, L08804, doi:08810.01029/02004GL022187. Cheng, Z., S. A. Cummer, D. N. Baker, and S. G. Kanekal (2006), Nighttime D region electron density profiles and variabilities inferred from broadband measurements using VLF radio emissions from lightning, J. Geophys. Res., 111, A05302, doi:05310.01029/02005JA011308. Cheng, Z., S. A. Cummer, H.-T. Su, and R.-R. Hsu (2007), Broadband very low frequency measurement of D region ionospheric perturbations caused by lightning electromagnetic pulses, J. Geophys. Res., 112, A06318. Cummer, S. A., U. S. Inan, and T. F. Bell (1998), Ionospheric D region remote sensing using VLF radio atmospherics, Radio Sci., 33, 1781-1792. Jacobson, A. R., X. Shao, and R. H. Holzworth (2009), Full-wave reflection of lightning long-wave radio pulses from the ionospheric D-region: Numerical model, J. Geophys. Res.- Space, 114, A03303, doi:03310.01029/02008JA013642. Jacobson, A. R., R. Holzworth, and X.-M. Shao (2010), Full-wave reflection of lightning long-wave radio pulses from the ionospheric D-region: Comparison with midday observations of broadband lightning signals, J. Geophys. Res. -Space, 115, A00E27, doi:10.1029/2009JA014540. Shao, X.-M., and A. R. Jacobson (2009), Model simulation of Very-Low-Frequency and Low-Frequency lightning signal propagation over intermediate ranges, IEEE Trans. Electromag. Compat., 51(3), 519-525.

  2. Astrometry of southern radio sources.

    PubMed

    White, G L; Jauncey, D L; Harvey, B R; Savage, A; Gulkis, S; Preston, R A; Peterson, B A; Reynolds, J E; Nicolson, G D; Malin, D F

    1991-01-01

    An overview is presented of a number of astrometry and astrophysics programs based on radio sources from the Parkes 2.7 GHz catalogues. The programs cover the optical identification and spectroscopy of flat-spectrum Parkes sources and the determination of their milliarc-second radio structures and positions. Work is also in progress to tie together the radio and Hipparcos positional reference frames. A parallel program of radio and optical astrometry of southern radio stars is also under way. PMID:11538705

  3. An Analogue Front-End Architecture for Software Defined Radio

    Microsoft Academic Search

    Vincent J. Arkesteijn; Eric A. M. Klumperink; Bram Nauta

    2002-01-01

    A Software Defined Radio (SDR) is a radio receiver and\\/or transmitter, whose characteristics can to a large extent be defined by software. Thus, an SDR can receive and\\/or transmit a wide variety of signals, supporting many different standards. In our research, we currently focus on a demonstrator that is able to receive both Bluetooth and HiperLAN\\/2. This helps us to

  4. An Analogue Front-End Architecture for Software Defined Radio

    Microsoft Academic Search

    Vincent J. Arkesteijn; Eric A. M. Klumperink; Bram Nauta

    A Software Defined Radio (SDR) is a radio receiver and\\/or transmitter, whose characteristics can to a large extent be defined by software. Thus, an SDR can re- ceive and\\/or transmit a wide variety of signals, supporting many different standards. In our research, we currently focus on a demonstrator that is able to receive both Bluetooth and HiperLAN\\/2. This helps us

  5. Interplanetary scintillation observations with the Cocoa Cross radio telescope

    NASA Technical Reports Server (NTRS)

    Cronyn, W. M.; Shawhan, S. D.; Erskine, F. T.; Huneke, A. H.; Mitchell, D. G.

    1976-01-01

    Physical and electrical parameters for the 34.3-MHz Cocoa Cross radio telescope are given. The telescope is dedicated to the determination of solar-wind characteristics in and out of the ecliptic plane through measurement of electron-density irregularity structure as determined from IPS (interplanetary scintillation) of natural radio sources. The collecting area (72,000 sq m), angular resolution (0.4 deg EW by 0.6 deg NS), and spatial extent (1.3 km EW by 0.8 km NS) make the telescope well suited for measurements of IPS index and frequency scale for hundreds of weak radio sources without serious confusion effects.

  6. Proceedings of the laser beam propagation in the atmosphere

    SciTech Connect

    Leader, J.C.

    1983-01-01

    Among the topics discussed are the atmospheric attenuation of laser radiation, the determination of atmospheric properties from lidar measurements, laser transmission measurement limitations due to correlated atmospheric effects, high spatial resolution studies of propagation, multiple scattering of laser beam propagation in clouds, the probability density of the irradiance in atmospheric turbulence, source statistics effects on irradiance scintillations in turbulence, and numerical solutions of the fourth-moment equation. Also discussed are the characteristics and effects of speckle propagation through turbulence, the application of random medium propagation theory to communication and radar system analyses, multiple scattering corrections to the Beer-Lambert Law, millimeter wave propagation through a clear atmosphere, endoatmospheric laser arrays for thermal blooming environments, the wavelength dependence of adaptive optics compensation, time-dependent thermal blooming in axial pipe flow, and turbulence-induced adaptive optics performance degradation.

  7. Pilot study of the radio-emitting AGN population: the emerging new class of FR 0 radio-galaxies

    NASA Astrophysics Data System (ADS)

    Baldi, Ranieri D.; Capetti, Alessandro; Giovannini, Gabriele

    2015-04-01

    We present the results of a pilot JVLA project aimed at studying the bulk of the radio-emitting AGN population, that was unveiled by the NVSS/FIRST and SDSS surveys. The key questions are related to the origin of their radio-emission and to its connection with the properties of their hosts. We obtained A-array observations at the JVLA at 1.4, 4.5, and 7.5 GHz for 12 sources, a small but representative subsample. The radio maps reveal compact unresolved or only slightly resolved radio structures on a scale of 1-3 kpc, with the one exception of a hybrid FR I/FR II source extended over ~40 kpc. Thanks to either the new high-resolution maps or to the radio spectra, we isolated the radio core component in most of them. We split the sample into two groups. Four sources have low black hole (BH) masses (mostly ~107 M?) and are hosted by blue galaxies, often showing evidence of a contamination from star formation to their radio emission, and are associated with radio-quiet (RQ) AGN. The second group consists in seven radio-loud (RL) AGN, which are located in red massive (~1011 M?) early-type galaxies, have high BH masses (?108 M?), and are spectroscopically classified as low excitation galaxies (LEG). These are all characteristics typical of FR I radio galaxies. They also lie on the correlation between radio core power and [O III] line luminosity defined by FR Is. However, they are more core-dominated (by a factor of ~30) than FR Is and show a deficit of extended radio emission. We dub these sources "FR 0" to emphasize their lack of prominent extended radio emission, which is their single distinguishing feature with respect to FR Is. The differences in radio properties between FR 0s and FR Is might be ascribed to an evolutionary effect, with the FR 0 sources undergoing rapid intermittency that prevents the growth of large-scale structures. However, this contrasts with the scenario in which low-luminosity radio-galaxies are fed by continuous accretion of gas from their hot coronae. In our preferred scenario the lack of extended radio emission in FR 0s is due to their lower jet Lorentz ? factor with respect to FR Is. The slower jets in FR 0s are more subject to instabilities and entrainment, which causes their premature disruption.

  8. Tesla's contribution to radiowave propagation

    Microsoft Academic Search

    Aleksandar Marincic; Djuradj Budimir

    2001-01-01

    We review Nikola Tesla's contribution to radiowave propagation and wireless power transmission. Tesla's patents, published and unpublished notes about radiowave propagation and wireless power transmission are less known, and if known to some extent, they are usually wrongly interpreted

  9. Ray Tracing Jupiter`s HOM Radio Emission

    NASA Astrophysics Data System (ADS)

    Higgins, C.; West, C.

    2007-05-01

    Cassini, Galileo, and Voyager spacecraft observations show well-defined attenuation features in the hectometer (HOM) spectrum of Jupiter's radio emission. The features are best displayed as frequency versus time spectrograms of HOM intensity between 500 - 3000 kHz. The bands have been shown by Gurnett et al. (1998) to be the result of propagation processes involving these emissions from opposite hemispheres. Enhancements in the HOM intensity and occurrence are seen along the edges of the observed attenuation features which may indicate caustic surfaces due to refraction along the propagation path. Using magnetic field and density models of the Jovian magnetosphere, we present some ray tracing analyses to show that radio wave refraction from density enhancements in the Io flux tube can produce the attenuation structures seen in the observations. This can provide boundaries to the electron density within the Io flux tube.

  10. Propagator for finite range potentials: The case of reflection

    SciTech Connect

    Cacciari, Ilaria; Moretti, Paolo [Istituto di Fisica Applicata 'Nello Carrara', CNR, via Madonna del Piano 10, 50019 Sesto Fiorentino, Florence (Italy); Istituto dei Sistemi Complessi, CNR, Sezione di Firenze, via Madonna del Piano 10, Sesto Fiorentino, Florence 50019 (Italy)

    2007-04-15

    Following a previous study on the transmission propagator for a finite range potential, the problem of reflection is considered. It is found that the Laplace transform of the reflection propagator can be expressed in terms of the usual Fredholm determinant {delta} and of a new similar determinant {gamma}, containing the peculiar characteristics of reflection. As an example, an array of delta potentials is considered. Moreover, a possible application to the calculation of quantum traversal time is shown.

  11. Vegetative propagation of jojoba

    SciTech Connect

    Low, C.B.; Hackett, W.P.

    1981-03-01

    Development of jojoba as an economically viable crop requires improved methods of propagation and culture. Rooting experiments were performed on cutting material collected from wild jojoba plants. A striking seasonal fluctuation in rooting potential was found. Jojoba plants can be successfully propagated from stem cuttings made during spring, summer, and, to some extent, fall. Variability among jojoba plants may also play a role in rooting potential, although it is not as important as season. In general, the use of auxin (4,000 ppm indolebutyric acid) on jojoba cuttings during periods of high rooting potential promotes adventitious root formation, but during periods of low rooting potential it has no effect or is even slightly inhibitory. In the greenhouse, cutting-grown plants apparently reproductively matured sooner than those grown from seed. If this observation holds true for plants transplanted into the field, earlier fruit production by cutting--grown plants would mean earlier return of initial planting and maintenance costs.

  12. Florida's propagation report

    NASA Technical Reports Server (NTRS)

    Helmken, Henry; Henning, Rudolf

    1994-01-01

    One of the key goals of the Florida Center is to obtain a maximum of useful information on propagation behavior unique to its subtropical weather and subtropical climate. Such weather data is of particular interest when it is (or has the potential to become) useful for developing and implementing techniques to compensate for adverse weather effects. Also discussed are data observations, current challenges, CDF's, sun movement, and diversity experiments.

  13. Transionospheric Propagation Code (TIPC)

    SciTech Connect

    Roussel-Dupre, R.; Kelley, T.A.

    1990-10-01

    The Transionospheric Propagation Code is a computer program developed at Los Alamos National Lab to perform certain tasks related to the detection of vhf signals following propagation through the ionosphere. The code is written in Fortran 77, runs interactively and was designed to be as machine independent as possible. A menu format in which the user is prompted to supply appropriate parameters for a given task has been adopted for the input while the output is primarily in the form of graphics. The user has the option of selecting from five basic tasks, namely transionospheric propagation, signal filtering, signal processing, DTOA study, and DTOA uncertainty study. For the first task a specified signal is convolved against the impulse response function of the ionosphere to obtain the transionospheric signal. The user is given a choice of four analytic forms for the input pulse or of supplying a tabular form. The option of adding Gaussian-distributed white noise of spectral noise to the input signal is also provided. The deterministic ionosphere is characterized to first order in terms of a total electron content (TEC) along the propagation path. In addition, a scattering model parameterized in terms of a frequency coherence bandwidth is also available. In the second task, detection is simulated by convolving a given filter response against the transionospheric signal. The user is given a choice of a wideband filter or a narrowband Gaussian filter. It is also possible to input a filter response. The third task provides for quadrature detection, envelope detection, and three different techniques for time-tagging the arrival of the transionospheric signal at specified receivers. The latter algorithms can be used to determine a TEC and thus take out the effects of the ionosphere to first order. Task four allows the user to construct a table of delta-times-of-arrival (DTOAs) vs TECs for a specified pair of receivers.

  14. Passive turbulent flamelet propagation

    NASA Technical Reports Server (NTRS)

    Ashurst, William T.; Ruetsch, G. R.; Lund, T. S.

    1994-01-01

    We analyze results of a premixed constant density flame propagating in three-dimensional turbulence, where a flame model developed by Kerstein, et al. (1988) has been used. Simulations with constant and evolving velocity fields are used, where peculiar results were obtained from the constant velocity field runs. Data from the evolving flow runs with various flame speeds are used to determine two-point correlations of the fluctuating scalar field and implications for flamelet modeling are discussed.

  15. Forward-backward squeezing propagator

    NASA Astrophysics Data System (ADS)

    Daboul, Jamil

    1996-02-01

    I show that a usual propagator cannot be defined for the pseudo-diffusion equation of Q functions. Instead, a forward-backward propagator is defined, which motivated a generalization of the Cahill-Glauber interpolating operator. An algorithm is also given for squeezing Q functions directly, using one-dimensional propagators.

  16. Effects of antenna length and material on output power and detection of miniature radio transmitters

    Microsoft Academic Search

    John W. Beeman; Neil Bower; Steve Juhnke; Laura Dingmon; Mike van den Tillaart; Tom Thomas

    The optimal antenna of transmitters used in small aquatic animals is often a compromise between efficient radio wave propagation\\u000a and effects on animal behavior. Radio transmission efficiency generally increases with diameter and length of the conductor,\\u000a but increased antenna length or weight can adversely affect animal behavior. We evaluated the effects of changing antenna\\u000a length and material on the subsequent

  17. Effects of antenna length and material on output power and detection of miniature radio transmitters

    Microsoft Academic Search

    John W. Beeman; Neil Bower; Steve Juhnke; Laura Dingmon; Mike van den Tillaart; Tom Thomas

    2007-01-01

    The optimal antenna of transmitters used in small aquatic animals is often a compromise between efficient radio wave propagation\\u000a and effects on animal behavior. Radio transmission efficiency generally increases with diameter and length of the conductor,\\u000a but increased antenna length or weight can adversely affect animal behavior. We evaluated the effects of changing antenna\\u000a length and material on the subsequent

  18. Radio science investigations by VeRa onboard the Venus Express spacecraft

    Microsoft Academic Search

    B. Häusler; M. Pätzold; G. L. Tyler; R. A. Simpson; M. K. Bird; V. Dehant; J.-P. Barriot; W. Eidel; R. Mattei; S. Remus; J. Selle; S. Tellmann; T. Imamura

    2006-01-01

    The Venus Express Radio Science Experiment (VeRa) uses radio signals at wavelengths of 3.6 and 13cm (“X”- and “S”-band, respectively) to investigate the Venus surface, neutral atmosphere, ionosphere, and gravity field, as well as the interplanetary medium. An ultrastable oscillator (USO) provides a high quality onboard reference frequency source; instrumentation on Earth is used to record amplitude, phase, propagation time,

  19. Propagators in Lagrangian space

    E-print Network

    Francis Bernardeau; Patrick Valageas

    2008-05-06

    It has been found recently that propagators, e.g. the cross-correlation spectra of the cosmic fields with the initial density field, decay exponentially at large-k in an Eulerian description of the dynamics. We explore here similar quantities defined for a Lagrangian space description. We find that propagators in Lagrangian space do not exhibit the same properties: they are found not to be monotonic functions of time, and to track back the linear growth rate at late time (but with a renormalized amplitude). These results have been obtained with a novel method which we describe alongside. It allows the formal resummation of the same set of diagrams as those that led to the known results in Eulerian space. We provide a tentative explanation for the marked differences seen between the Eulerian and the Lagrangian cases, and we point out the role played by the vorticity degrees of freedom that are specific to the Lagrangian formalism. This provides us with new insights into the late-time behavior of the propagators.

  20. Olympus propagation experiments

    NASA Technical Reports Server (NTRS)

    Arbesser-Rastburg, Bertram

    1994-01-01

    A summary of the activities of the OPEX (Olympus Propagation EXperimenters) group is given and some of the recent findings are presented. OLYMPUS, a telecommunication satellite owned by the European Space Agency, was launched on 12 June 1989. After the in-orbit tests were completed (in September 1989) the first propagation experiments started. Throughout 1990 the spacecraft functioned very well and a large number of experimenters received the beacon signals. On 29 May 1991 the spacecraft became inoperational after a major technical problem. With a series of complicated procedures OLYMPUS was recovered on 15 August 1991 - the first time in history that a civilian telecommunications satellite was brought back to service after losing power and telemetry. The propagation experiments were back on track. However, the recovery had used up so much fuel that the North-South station keeping had to be abandoned, which led to a natural increase of inclination at a rate of about 0.8 deg per year. On 10 October 1992 the second 30 GHz beacon tube failed, causing a loss of this beacon signal. The other two beacon frequencies continued to deliver a stable signal for more than two years. On 12 August 1993 the spacecraft experienced another problem with the altitude control, but this time there was not enough fuel left for a recovery maneuver and thus the mission came to an end.

  1. Propagators and topology

    NASA Astrophysics Data System (ADS)

    Maas, Axel

    2015-03-01

    Two popular perspectives on the non-perturbative domain of Yang-Mills theories are either in terms of the gluons themselves or in terms of collective gluonic excitations, i.e. topological excitations. If both views are correct, then they are only two different representations of the same underlying physics. One possibility to investigate this connection is by the determination of gluon correlation functions in topological background fields, as created by the smearing of lattice configurations. This is performed here for the minimal Landau gauge gluon propagator, ghost propagator, and running coupling, both in momentum and position space for SU(2) Yang-Mills theory. The results show that the salient low-momentum features of the propagators are qualitatively retained under smearing at sufficiently small momenta, in agreement with an equivalence of both perspectives. However, the mid-momentum behavior is significantly affected. These results are also relevant for the construction of truncations in functional methods, as they provide hints on necessary properties to be retained in truncations.

  2. Escaping radio emission from pulsars: Possible role of velocity shear

    SciTech Connect

    Mahajan, S.M. [Univ. of Texas, Austin, TX (United States). Inst. for Fusion Studies]|[International Centre for Theoretical Physics, Trieste (Italy); Machabeli, G.Z. [Abastumani Astrophysical Observatory, Tbilisi (Georgia). Dept. of Theoretical Astrophysics; Rogava, A.D. [Abastumani Astrophysical Observatory, Tbilisi (Georgia). Dept. of Theoretical Astrophysics]|[Tbilisi State Univ. (Georgia). Dept. of Physics

    1997-01-01

    It is demonstrated that the velocity shear, intrinsic to the e{sup +}e{sup {minus}} plasma present in the pulsar magnetosphere, can efficiently convert the nonescaping longitudinal Langmuir waves (produced by some kind of a beam or stream instability) into propagating (escaping) electromagnetic waves. It is suggested that this shear induced transformation may be the basic mechanism needed for the eventual generation of the observed pulsar radio emission.

  3. BSA Radio Merit Badge

    NSDL National Science Digital Library

    Mr. Hjorten

    2006-02-03

    The radio merit badge is one of many elective merit badges a Boy Scout can earn while on his path to completing the rank of Eagle Scout. One of the purposes of this merit badge is to inform, educate, and train Scouts in radio communication. It is also designed to help each young man develop additional skills and increase their enjoyment and expand their adventures. This instructional module is aimed at providing a structured beginning to any Boy Scout wishing to achieve the radio merit badge. This instruction in no way replaces the merit badge booklet of which I highly recommend reviewing while working through the requirement and a merit badge counselor; both of which are necessary in completing the requirement. I recommend that you contact your radio merit badge counselor for guidance and instruction prior to working through the requirements and beginning this instruction. OBJECTIVES: After completing this instructional module, you will have the knowledge base and skills to complete all the requirements of the Boy Scouts of America Radio Merit Badge. MATERIALS: To complete this learning activity, each student will need: Access to a computer with internet connection capabilities. A contact name and number of your nearest ...

  4. Premixed Turbulent Flame Propagation in Microgravity

    NASA Technical Reports Server (NTRS)

    Menon, Suresh

    1999-01-01

    A combined numerical-experimental study has been carried out to investigate the structure and propagation characteristics of turbulent premixed flames with and without the influence of buoyancy. Experimentally, the premixed flame characteristics are studied in the wrinkled regime using a Couette flow facility and an isotropic flow facility in order to resolve the scale of flame wrinkling. Both facilities were chosen for their ability to achieve sustained turbulence at low Reynolds number. This implies that conventional diagnostics can be employed to resolve the smallest scales of wrinkling. The Couette facility was also built keeping in mind the constraints imposed by the drop tower requirements. Results showed that the flow in this Couette flow facility achieves full-developed turbulence at low Re and all turbulence statistics are in good agreement with past measurements on large-scale facilities. Premixed flame propagation studies were then carried out both using the isotropic box and the Couette facility. Flame imaging showed that fine scales of wrinkling occurs during flame propagation. Both cases in Ig showed significant buoyancy effect. To demonstrate that micro-g can remove this buoyancy effect, a small drop tower was built and drop experiments were conducted using the isotropic box. Results using the Couette facility confirmed the ability to carry out these unique reacting flow experiments at least in 1g. Drop experiments at NASA GRC were planned but were not completed due to termination of this project.

  5. Simulation studies of GPS radio occultation measurements

    NASA Astrophysics Data System (ADS)

    Beyerle, G.; Gorbunov, M. E.; Ao, C. O.

    2003-10-01

    The atmospheric propagation of GPS signals under multipath conditions and their detection are simulated. Using the multiple phase screen method, C/A-code modulated L1 signals are propagated through a spherically symmetric refractivity field derived from a high-resolution radio sonde observation. The propagated signals are tracked by a GPS receiver implemented in software and converted to refractivity profiles by the canonical transform technique and the Abel inversion. Ignoring noise and assuming an ideal receiver tracking behavior, the true refractivity profile is reproduced to better than 0.1% at altitudes above 2 km. The nonideal case is simulated by adding between 14 and 24 dB of Gaussian white noise to the signal and tracking the signal with a receiver operating at 50 and 200 Hz sampling frequency using two different carrier phase detectors. In the upper troposphere and stratosphere the fractional refractivity retrieval error is below 0.3% for 50 Hz sampling and below 0.15% for 200 Hz sampling. In the midtroposphere down to altitudes of about 2 km, phase-locked loop tracking induces negative fractional refractivity biases on the order of -1 to -2% at 50 Hz sampling frequency. Modifications to the receiver tracking algorithm significantly improve the retrieval results. In particular, replacing the carrier loop's two-quadrant phase extractor with a four-quadrant discriminator reduces the refractivity biases by a factor of 5; increasing the sampling frequency from 50 to 200 Hz gains another factor of 2.

  6. eRadio : empowerment through community Web radio

    E-print Network

    Gomez-Monroy, Carla, 1977-

    2004-01-01

    The eRadio project proposes to be an effective aid to increase interaction and reduce alienation among the members of dispersed communities by using a holistic approach to participatory and interactive web radio-production, ...

  7. A Challenging Solar Eruptive Event of 18 November 2003 and the Causes of the 20 November Geomagnetic Superstorm. II. CMEs, Shock Waves, and Drifting Radio Bursts

    NASA Astrophysics Data System (ADS)

    Grechnev, V. V.; Uralov, A. M.; Chertok, I. M.; Slemzin, V. A.; Filippov, B. P.; Egorov, Y. I.; Fainshtein, V. G.; Afanasyev, A. N.; Prestage, N. P.; Temmer, M.

    2014-04-01

    We continue our study (Grechnev et al., 2013, doi:10.1007/s11207-013-0316-6; Paper I) on the 18 November 2003 geoffective event. To understand possible impact on geospace of coronal transients observed on that day, we investigated their properties from solar near-surface manifestations in extreme ultraviolet, LASCO white-light images, and dynamic radio spectra. We reconcile near-surface activity with the expansion of coronal mass ejections (CMEs) and determine their orientation relative to the earthward direction. The kinematic measurements, dynamic radio spectra, and microwave and X-ray light curves all contribute to the overall picture of the complex event and confirm an additional eruption at 08:07 - 08:20 UT close to the solar disk center presumed in Paper I. Unusual characteristics of the ejection appear to match those expected for a source of the 20 November superstorm but make its detection in LASCO images hopeless. On the other hand, none of the CMEs observed by LASCO seem to be a promising candidate for a source of the superstorm being able to produce, at most, a glancing blow on the Earth's magnetosphere. Our analysis confirms free propagation of shock waves revealed in the event and reconciles their kinematics with "EUV waves" and dynamic radio spectra up to decameters.

  8. Low Frequency Radio Signals from Sprite Streamers

    NASA Astrophysics Data System (ADS)

    Qin, J.; Celestin, S. J.; Pasko, V. P.

    2013-12-01

    Sprites are mesospheric discharges that carry significant electrical currents and produce radio signals observed typically in the extremely low (ELF) to very low (VLF) frequency bands [Cummer et al., GRL, 25, 1281, 1998]. Recently, Low-Frequency (LF) radio observations of sprite-producing lightning discharges have shown the existence of consecutive broadband pulses exhibiting EM radiation that spans in the LF range, and it has been suggested that this LF radio signals may stem from non-luminous relativistic electron beams above thunderstorms [Fullekrug et al., JGR, 115, A00E09, 2010]. In this talk, we present the first theoretical estimates of the radio signals produced by individual sprite streamers using simulation results from a plasma fluid model. It is demonstrated that the spectral content of the radiation produced by sprite streamers is a function of the air density N and the lightning-induced quasi-static ambient electric field E in the regions of space where the sprite streamers are propagating. We demonstrate that the exponential growth of the current in sprite streamers at 75 km would be preferentially associated with electromagnetic radiation in the frequency range from 0 and up to ˜3 kHz, whereas the growth of the streamer current at 40 km could produce radiation with frequencies up to ˜300 kHz, consistently with the scaling of atmospheric air density [Kosar et al., JGR, 117, A08328, 2012]. We further conjecture that the periodic branching of streamers may lead to a radiation spectrum enhancement in the VLF to LF range. The present study shows that sprite streamers could be responsible for at least part of the LF radiation associated with sprite-producing lightning discharges that was detected recently by Fullekrug et al. [2010].

  9. Rolling Stone Radio

    NSDL National Science Digital Library

    Rolling Stone Radio is a fun and interesting site that may represent the future of Internet radio. The site provides a number of streaming audio channels that can be listened to via RealNetworks' RealPlayer G2 combined with a customized, radio-like interface to the site. Each channel features a particular genre of music, and the interface displays the artist and song title during play. The sound quality ranges from acceptable to excellent, and the sound controls and channel selectors are easy-to-use. While the site borders on the exploitative in its advertising and ability to purchase music by clicking through the interface, it does combine some of the best ideas on the Internet into a seamless entertainment package. All downloadable components of this site are free but run only on Win95/98/NT.

  10. New American Radio

    NSDL National Science Digital Library

    It's quite unusual that a long-defunct radio program would garner a new website, but this is the case with the New American Radio (NAR) show. During its 10-year run, NAR commissioned and distributed over 300 original works, including conceptual new drama works, language explorations, sonic meditations, and works that "pioneer new dimensions in acoustic space." On the site's homepage, visitors can peruse a list of full-length works, excerpts, and even a set of meditative essays on the creative process. A good work to start with here is "O Little Town of East New York" by Shelley Hirsch. It's a compelling autobiographical "docu-musical" about growing up in this diverse neighborhood in the 1960s. The site could be used by any number of students studying communication, drama, theater, radio production, and related subjects.

  11. The radio structure of radio-quiet quasars

    E-print Network

    Christian Leipski; Heino Falcke; Nicola Bennert; Susanne Huettemeister; ;

    2006-06-21

    We investigate the radio emitting structures of radio-quiet active galactic nuclei with an emphasis on radio-quiet quasars to study their connection to Seyfert galaxies. We present and analyse high-sensitivity VLA radio continuum images of 14 radio-quiet quasars and six Seyfert galaxies. Many of the low redshift radio-quiet quasars show radio structures that can be interpreted as jet-like outflows. However, the detection rate of extended radio structures on arcsecond scales among our sample decreases with increasing redshift and luminosity, most likely due to a lack of resolution. The morphologies of the detected radio emission indicate strong interactions of the jets with the surrounding medium. We also compare the radio data of seven quasars with corresponding HST images of the [OIII] emitting narrow-line region (NLR). We find that the scenario of interaction between the radio jet and the NLR gas is confirmed in two sources by structures in the NLR gas distribution as previously known for Seyfert galaxies. The extended radio structures of radio-quiet quasars at sub-arcsecond resolution are by no means different from that of Seyferts. Among the luminosities studied here, the morphological features found are similar in both types of objects while the overall size of the radio structures increases with luminosity. This supports the picture where radio-quiet quasars are the scaled-up versions of Seyfert galaxies. In addition to known luminosity relations we find a correlation of the NLR size and the radio size shared by quasars and Seyferts.

  12. Temporal scaling in information propagation

    PubMed Central

    Huang, Junming; Li, Chao; Wang, Wen-Qiang; Shen, Hua-Wei; Li, Guojie; Cheng, Xue-Qi

    2014-01-01

    For the study of information propagation, one fundamental problem is uncovering universal laws governing the dynamics of information propagation. This problem, from the microscopic perspective, is formulated as estimating the propagation probability that a piece of information propagates from one individual to another. Such a propagation probability generally depends on two major classes of factors: the intrinsic attractiveness of information and the interactions between individuals. Despite the fact that the temporal effect of attractiveness is widely studied, temporal laws underlying individual interactions remain unclear, causing inaccurate prediction of information propagation on evolving social networks. In this report, we empirically study the dynamics of information propagation, using the dataset from a population-scale social media website. We discover a temporal scaling in information propagation: the probability a message propagates between two individuals decays with the length of time latency since their latest interaction, obeying a power-law rule. Leveraging the scaling law, we further propose a temporal model to estimate future propagation probabilities between individuals, reducing the error rate of information propagation prediction from 6.7% to 2.6% and improving viral marketing with 9.7% incremental customers. PMID:24939414

  13. Temporal scaling in information propagation.

    PubMed

    Huang, Junming; Li, Chao; Wang, Wen-Qiang; Shen, Hua-Wei; Li, Guojie; Cheng, Xue-Qi

    2014-01-01

    For the study of information propagation, one fundamental problem is uncovering universal laws governing the dynamics of information propagation. This problem, from the microscopic perspective, is formulated as estimating the propagation probability that a piece of information propagates from one individual to another. Such a propagation probability generally depends on two major classes of factors: the intrinsic attractiveness of information and the interactions between individuals. Despite the fact that the temporal effect of attractiveness is widely studied, temporal laws underlying individual interactions remain unclear, causing inaccurate prediction of information propagation on evolving social networks. In this report, we empirically study the dynamics of information propagation, using the dataset from a population-scale social media website. We discover a temporal scaling in information propagation: the probability a message propagates between two individuals decays with the length of time latency since their latest interaction, obeying a power-law rule. Leveraging the scaling law, we further propose a temporal model to estimate future propagation probabilities between individuals, reducing the error rate of information propagation prediction from 6.7% to 2.6% and improving viral marketing with 9.7% incremental customers. PMID:24939414

  14. Imaging Interplanetary CMEs at Radio Frequency From Solar Polar Orbit

    NASA Astrophysics Data System (ADS)

    Wu, Ji; Sun, Weiying; Zheng, Jianhua; Zhang, Cheng; Wang, Chi; Wang, C. B.; Wang, S.

    Coronal mass ejections (CMEs) are violent discharges of plasma and magnetic fields from the Sun's corona. They have come to be recognized as the major driver of physical conditions in the Sun-Earth system. Consequently, the detection of CMEs is important for un-derstanding and ultimately predicting space weather conditions. The Solar Polar Orbit Radio Telescope (SPORT) is a proposed mission to observe the propagation of interplanetary CMEs from solar polar orbit. The main payload (radio telescope) on board SPORT will be an in-terferometric imaging radiometer working at the meter wavelength band, which will follow the propagation of interplanetary CMEs from a distance of a few solar radii to near 1 AU from solar polar orbit. The SPORT spacecraft will also be equipped with a set of optical and in situ measurement instruments such as a EUV solar telescope, a solar wind plasma experiment, a solar wind ion composition instrument, an energetic particle detector, a wave detector, a mag-netometer and an interplanetary radio burst tracker. In this paper, we first describe the current shortage of interplanetary CME observations. Next, the scientific motivation and objectives of SPORT are introduced. We discuss the basic specifications of the main radio telescope of SPORT with reference to the radio emission mechanisms and the radio frequency band to be observed. Finally, we discuss the key technologies of the SPORT mission, including the con-ceptual design of the main telescope, the image retrieval algorithm and the solar polar orbit injection. Other payloads and their respective observation objectives are also briefly discussed. Key words: Interplanetary CMEs; Interferometric imaging; Solar polar orbit; Radiometer.

  15. Direct calculation of coherence bandwidth in urban microcells using a ray-tracing propagation model

    Microsoft Academic Search

    H. R. Anderson; J. P. McGeehan

    1994-01-01

    An important parameter in characterizing radio communications channels is the coherence bandwidth. This paper presents an analysis of the coherence bandwidth in a urban microcell environment where the dynamic channel response is determined by a site-specific ray-tracing propagation model. Such an analytical model provides a direct calculation of signal fading envelope correlation as a function of frequency and location. The

  16. An Empirical Model for Propagation Loss Through Tropical Woodland in Urban Areas at UHF

    Microsoft Academic Search

    Maurício Henrique Costa Dias; Mauro Soares de Assis

    2011-01-01

    Vegetation attenuation is a significant source of signal degradation in radio systems, particularly the loss associated with the propagation through trees and foliage. Modeling such loss, however, is quite complex, with parameters to consider as diverse as taxonomy, seasonal variations, foliage shapes, etc. An important feature usually considered, at either empirical [1]–[3] or theoretical models [4]–[6], is how trees are

  17. Propagation predictions and studies using a ray tracing program combined with a theoretical ionospheric model

    Microsoft Academic Search

    M. K. Lee; J. S. Nisbet

    1975-01-01

    Radio wave propagation predictions are described in which modern comprehensive theoretical ionospheric models are coupled with ray-tracing programs. In the computer code described, a network of electron density and collision frequency parameters along a band about the great circle path is calculated by specifying the transmitter and receiver geographic coordinates, time, the day number, and the 2800-MHz solar flux. The

  18. The analytical method of characteristics

    NASA Astrophysics Data System (ADS)

    Kluwick, A.

    The paper examines applications of the analytical method of characteristics to wave propagation phenomena in fluid dynamics, with emphasis on unsteady flows. The applications include unsteady one-dimensional flows, weak shocks, one-dimensional simple waves, the propagation of plane sound waves through an elastically embedded rigid wall, one-dimensional interacting waves in gases, plane finite-amplitude waves in homogeneous elastic solids, spherical and cylindrical sound waves, transonic flows, and short waves in dissipative systems. Consideration is also given to comparison with other perturbation techniques, generalization of the method to three-dimensional flows, and combination of the analytical method of characteristics and the method of multiple scales.

  19. Observations of Radio Giant Pulses with GAVRT

    NASA Astrophysics Data System (ADS)

    Jones, Glenn

    2011-08-01

    Radio giant pulses provide a unique opportunity to study the pulsar radio emission mechanism in exquisite detail. Previous studies have revealed a wide range of properties and phenomena, including extraordinarily high brightness temperatures, sub-nanosecond emission features, and banded dynamic spectra. New measurements of giant pulse characteristics can help guide and test theoretical emission models. To this end, an extensive observation campaign has begun which will provide more than 500 hours on the Crab with a 34-meter antenna located in California, USA. The observations are being done as part of an educational outreach program called the Goldstone-Apple Valley Radio Telescope (GAVRT). This antenna has a novel wide bandwidth receiver which provides up to 8 GHz of instantaneous bandwidth in the range of 2.5 to 14 GHz. These observations will provide detailed information about the variability, amplitude distribution, and detailed frequency structure of radio giant pulses. In addition, a database of pulses from these observations and others of the Crab pulsar is being created which will simplify multiwavelength correlation analysis.

  20. Isla Earth Radio Series

    NSDL National Science Digital Library

    This radio series explores environmental issues of local, national, and global importance, with the intent to increase ecological awareness, deepen understanding, and encourage environmentally sustainable choices. Topics include alternative fuels, endangered species, energy conservation, wetlands, and similar issues. Each program is accompanied by a written transcript and links to additional information from other web sites. Other materials include image galleries, puzzles and games with environmental themes, and the e-Digest--a series of written features on environmental topics. There is also information on the show's sponsor and information for radio stations that wish to carry the program.

  1. INTERPLANETARY SHOCKS LACKING TYPE II RADIO BURSTS

    SciTech Connect

    Gopalswamy, N.; Kaiser, M. L. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Xie, H.; Maekelae, P.; Akiyama, S. [Catholic University of America, Washington, DC 20064 (United States); Yashiro, S. [Interferometrics, Herndon, VA 20170 (United States); Howard, R. A. [Naval Research Laboratory, Washington, DC 20375 (United States); Bougeret, J.-L., E-mail: nat.gopalswamy@nasa.go [Paris Observatory, Meudon (France)

    2010-02-20

    We report on the radio-emission characteristics of 222 interplanetary (IP) shocks detected by spacecraft at Sun-Earth L1 during solar cycle 23 (1996 to 2006, inclusive). A surprisingly large fraction of the IP shocks ({approx}34%) was radio quiet (RQ; i.e., the shocks lacked type II radio bursts). We examined the properties of coronal mass ejections (CMEs) and soft X-ray flares associated with such RQ shocks and compared them with those of the radio-loud (RL) shocks. The CMEs associated with the RQ shocks were generally slow (average speed {approx}535 km s{sup -1}) and only {approx}40% of the CMEs were halos. The corresponding numbers for CMEs associated with RL shocks were 1237 km s{sup -1} and 72%, respectively. Thus, the CME kinetic energy seems to be the deciding factor in the radio-emission properties of shocks. The lower kinetic energy of CMEs associated with RQ shocks is also suggested by the lower peak soft X-ray flux of the associated flares (C3.4 versus M4.7 for RL shocks). CMEs associated with RQ CMEs were generally accelerating within the coronagraph field of view (average acceleration {approx}+6.8 m s{sup -2}), while those associated with RL shocks were decelerating (average acceleration {approx}-3.5 m s{sup -2}). This suggests that many of the RQ shocks formed at large distances from the Sun, typically beyond 10 Rs, consistent with the absence of metric and decameter-hectometric (DH) type II radio bursts. A small fraction of RL shocks had type II radio emission solely in the kilometric (km) wavelength domain. Interestingly, the kinematics of the CMEs associated with the km type II bursts is similar to those of RQ shocks, except that the former are slightly more energetic. Comparison of the shock Mach numbers at 1 AU shows that the RQ shocks are mostly subcritical, suggesting that they were not efficient in accelerating electrons. The Mach number values also indicate that most of these are quasi-perpendicular shocks. The radio-quietness is predominant in the rise phase and decreases through the maximum and declining phases of solar cycle 23. About 18% of the IP shocks do not have discernible ejecta behind them. These shocks are due to CMEs moving at large angles from the Sun-Earth line and hence are not blast waves. The solar sources of the shock-driving CMEs follow the sunspot butterfly diagram, consistent with the higher-energy requirement for driving shocks.

  2. 46 CFR 129.395 - Radio installations.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...2014-10-01 2014-10-01 false Radio installations. 129.395 Section 129...and Distribution Systems § 129.395 Radio installations. A separate circuit...switchboard, must be provided for at least one radio installation. Additional radios,...

  3. 46 CFR 129.395 - Radio installations.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...2012-10-01 2012-10-01 false Radio installations. 129.395 Section 129...and Distribution Systems § 129.395 Radio installations. A separate circuit...switchboard, must be provided for at least one radio installation. Additional radios,...

  4. 46 CFR 129.395 - Radio installations.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...2013-10-01 2013-10-01 false Radio installations. 129.395 Section 129...and Distribution Systems § 129.395 Radio installations. A separate circuit...switchboard, must be provided for at least one radio installation. Additional radios,...

  5. Some Fundamental Limitations for Cognitive Radio

    E-print Network

    Sahai, Anant

    ' & $ % Some Fundamental Limitations for Cognitive Radio Anant Sahai Wireless Foundations, UCB EECS program November 1 at BWRC Cognitive Radio Workshop #12;' & $ % Outline 1. Why cognitive radios? 2 November 1 at BWRC Cognitive Radio Workshop #12;' & $ % Apparent spectrum allocations · Traditional

  6. 46 CFR 129.395 - Radio installations.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...2010-10-01 2010-10-01 false Radio installations. 129.395 Section 129...and Distribution Systems § 129.395 Radio installations. A separate circuit...switchboard, must be provided for at least one radio installation. Additional radios,...

  7. 46 CFR 129.395 - Radio installations.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...2011-10-01 2011-10-01 false Radio installations. 129.395 Section 129...and Distribution Systems § 129.395 Radio installations. A separate circuit...switchboard, must be provided for at least one radio installation. Additional radios,...

  8. Land mobile satellite propagation measurements in Japan using ETS-V satellite

    NASA Technical Reports Server (NTRS)

    Obara, Noriaki; Tanaka, Kenji; Yamamoto, Shin-Ichi; Wakana, Hiromitsu

    1993-01-01

    Propagation characteristics of land mobile satellite communications channels have been investigated actively in recent years. Information of propagation characteristics associated with multipath fading and shadowing is required to design commercial land mobile satellite communications systems, including protocol and error correction method. CRL (Communications Research Laboratory) has carried out propagation measurements using the Engineering Test Satellite-V (ETS-V) at L band (1.5 GHz) through main roads in Japan by a medium gain antenna with an autotracking capability. This paper presents the propagation statistics obtained in this campaign.

  9. Experiments on the propagation of plasma filaments.

    PubMed

    Katz, Noam; Egedal, Jan; Fox, Will; Le, Ari; Porkolab, Miklos

    2008-07-01

    We investigate experimentally the motion and structure of isolated plasma filaments propagating through neutral gas. Plasma filaments, or "blobs," arise from turbulent fluctuations in a range of plasmas. Our experimental geometry is toroidally symmetric, and the blobs expand to a larger major radius under the influence of a vertical electric field. The electric field, which is caused by nabla B and curvature drifts in a 1/R magnetic field, is limited by collisional damping on the neutral gas. The blob's electrostatic potential structure and the resulting E x B flow field give rise to a vortex pair and a mushroom shape, which are consistent with nonlinear plasma simulations. We observe experimentally this characteristic mushroom shape for the first time. We also find that the blob propagation velocity is inversely proportional to the neutral density and decreases with time as the blob cools. PMID:18764120

  10. Propagating phonons coupled to an artificial atom

    NASA Astrophysics Data System (ADS)

    Gustafsson, Martin V.; Aref, Thomas; Kockum, Anton Frisk; Ekström, Maria K.; Johansson, Göran; Delsing, Per

    2014-10-01

    Quantum information can be stored in micromechanical resonators, encoded as quanta of vibration known as phonons. The vibrational motion is then restricted to the stationary eigenmodes of the resonator, which thus serves as local storage for phonons. In contrast, we couple propagating phonons to an artificial atom in the quantum regime and reproduce findings from quantum optics, with sound taking over the role of light. Our results highlight the similarities between phonons and photons but also point to new opportunities arising from the characteristic features of quantum mechanical sound. The low propagation speed of phonons should enable new dynamic schemes for processing quantum information, and the short wavelength allows regimes of atomic physics to be explored that cannot be reached in photonic systems.

  11. Ionic wave propagation along actin filaments.

    PubMed

    Tuszy?ski, J A; Portet, S; Dixon, J M; Luxford, C; Cantiello, H F

    2004-04-01

    We investigate the conditions enabling actin filaments to act as electrical transmission lines for ion flows along their lengths. We propose a model in which each actin monomer is an electric element with a capacitive, inductive, and resistive property due to the molecular structure of the actin filament and viscosity of the solution. Based on Kirchhoff's laws taken in the continuum limit, a nonlinear partial differential equation is derived for the propagation of ionic waves. We solve this equation in two different regimes. In the first, the maximum propagation velocity wave is found in terms of Jacobi elliptic functions. In the general case, we analyze the equation in terms of Fisher-Kolmogoroff modes with both localized and extended wave characteristics. We propose a new signaling mechanism in the cell, especially in neurons. PMID:15041636

  12. SECURING RADIO FREQUENCY IDENTIFICATION (RFID)

    E-print Network

    May 2007 SECURING RADIO FREQUENCY IDENTIFICATION (RFID) SYSTEMS SECURING RADIO FREQUENCY IDENTIFICATION (RFID) SYSTEMS Karen Scarfone, EditorKaren Scarfone, Editor Computer Security Division of Standards and Technology National Institute of Standards and Technology RFID is a form of automatic

  13. Radio-frequency radiation energy transfer in an ionospheric layer with random small-scale inhomogeneities

    SciTech Connect

    Zabotin, N.A.

    1994-06-01

    The equation of radiation energy balance in a randomly inhomogeneous plane-stratified plasma layer was derived based on the phenomenological approach. The use of the small-angle scattering approximation in the invariate ray coordinates allows it to be transformed into a drift-type equation. The latter describes the deformation of the spatial distribution of the radio-frequency radiation energy due to multiple scattering by anisotropic inhomogeneities. Two effects are investigated numerically: shift of the radio wave arrival angles under a slightly oblique propagation, and variation of the intensity of the radio-frequency radiation reflected from a plasma layer.

  14. Transport with Feynman propagators

    SciTech Connect

    White, R.H.

    1990-11-06

    Richard Feynman's formulation of quantum electrodynamics suggests a Monte Carlo algorithm for calculating wave propagation. We call this the Sum Over All Paths (SOAP) method. The method is applied to calculate diffraction by double slits of finite width and by a reflection grating. Calculations of reflection by plane and parabolic mirrors of finite aperture and from several figured surfaces are shown. An application to a one-dimensional scattering problem is discussed. A variation of SOAP can be applied to the diffusion equation. 2 refs., 8 figs.

  15. Modeling the vehicle-to-vehicle propagation channel: A review

    NASA Astrophysics Data System (ADS)

    Matolak, David W.

    2014-09-01

    In this paper we provide a review of the vehicle-to-vehicle (V2V) wireless propagation channel. This "car-to-car" application will be used to improve roadway efficiency, provide unique traveler services, and can also enable safety applications that can save lives. We briefly review some currently envisioned applications and the initial V2V radio technology, then address the V2V propagation channel. Propagation basics germane to the V2V setting are described, followed by a discussion of channel dispersion and time variation. The channel impulse response and its Fourier transform, the channel transfer function, are described in detail, and their common statistical characterizations are also reviewed. The most common models for the V2V channel—the tapped delay line and geometry-based stochastic channel models—are covered in some detail. We highlight key differences between the V2V channel and the well-known cellular radio channel. These differences are the more rapid time variation and the higher probability of obstruction of the direct line of sight component; modeling of these effects has required some novel approaches. The V2V channel's nonstationary statistical behavior is addressed, as is the use of multiple-antenna systems. The remaining areas for future work are also described.

  16. Intelligence artificielle et radio cognitive

    E-print Network

    Paris-Sud XI, Université de

    Intelligence artificielle et radio cognitive Badr Benmammar badr.benmammar@gmail.com cel-00680196,version2-25Mar2012 #12;2 Plan Intelligence artificielle et radio cognitive Algorithmes intelligents Réseaux de neurones Logique floue Processus de décision de Markov Langages de la radio cognitive Domaines

  17. Spectrum Sensing for Cognitive Radio

    Microsoft Academic Search

    Simon Haykin; David J. Thomson; Jeffrey H. Reed

    2009-01-01

    Spectrum sensing is the very task upon which the entire operation of cognitive radio rests. For cognitive radio to fulfill the potential it offers to solve the spectrum underutilization problem and do so in a reliable and computationally feasible manner, we require a spectrum sensor that detects spectrum holes (i.e., underutilized subbands of the radio spectrum), provides high spectral-resolution capability,

  18. Mathematical Foundations of Cognitive Radios

    E-print Network

    Paris-Sud XI, Université de

    Mathematical Foundations of Cognitive Radios Romain Couillet and M´erouane Debbah Abstract. In this paper, we intro- duce a fundamental vision of cognitive radios from a physical layer viewpoint -- Recently, much interest has been directed towards software defined radios and embedded intelligence

  19. Language Issues for Cognitive Radio

    E-print Network

    Kokar, Mieczyslaw M.

    INVITED P A P E R Language Issues for Cognitive Radio Computer languages that may be useful for expressing cognitive radio concepts are identified and evaluated in this tutorial paper. By Mieczyslaw M aspects of formal languages in the context of cognitive radio. A bottom up approach is taken in which

  20. Radio Interferometric Geolocation Miklos Maroti

    E-print Network

    Maróti, Miklós

    Radio Interferometric Geolocation Mikl´os Mar´oti P´eter V¨olgyesi Sebesty´en D´ora Branislav.kusy, akos.ledeczi}@vanderbilt.edu ABSTRACT We present a novel radio interference based sensor local- ization method for wireless sensor networks. The technique relies on a pair of nodes emitting radio waves