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1

CME Propagation Characteristics from Radio Observations  

NASA Astrophysics Data System (ADS)

We explore the relationship among three coronal mass ejections (CMEs), observed on 28 October 2003, 7 November 2004, and 20 January 2005, the type II burst-associated shock waves in the corona and solar wind, as well as the arrival of their related shock waves and magnetic clouds at 1 AU. Using six different coronal/interplanetary density models, we calculate the speeds of shocks from the frequency drifts observed in metric and decametric radio wave data. We compare these speeds with the velocity of the CMEs as observed in the plane-of-the-sky white-light observations and calculated with a cone model for the 7 November 2004 event. We then follow the propagation of the ejecta using Interplanetary Scintillation measurements, which were available for the 7 November 2004 and 20 January 2005 events. Finally, we calculate the travel time of the interplanetary shocks between the Sun and Earth and discuss the velocities obtained from the different data. This study highlights the difficulties in making velocity estimates that cover the full CME propagation time.

Pohjolainen, S.; van Driel-Gesztelyi, L.; Culhane, J. L.; Manoharan, P. K.; Elliott, H. A.

2007-08-01

2

Plasma plume propagation characteristics of pulsed radio frequency plasma jet  

SciTech Connect

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.

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

3

Radio wave propagation characteristics in lossy circular waveguides such as tunnels, mine shafts, and boreholes  

Microsoft Academic Search

We present the characteristics of radio propagation in a circular lossy waveguide whose walls are composed of earth soil materials with frequency-dependent properties. This type of structure is used to represent a radio link for an underground wireless communication channel such as a tunnel, mine shaft, or borehole. We present calculated results of the attenuation constant for various propagation modes

Christopher L. Holloway; David A. Hill; Roger A. Dalke; George A. Hufford

2000-01-01

4

Introducing Radio-Wave Propagation with Hypercard  

Microsoft Academic Search

An educational software developed for the introduction to radio-wave propagation is presented. Based on the HyperCard authoring system, the software is designed around the modelization of a classical radio or microwave link. Used in a continuing education program, organized for technicians and engineers involved more in the practical than in the theoretical aspects of propagation, this software greatly helps for

R. Crampagne; M. Helier; W. Tabbara

1992-01-01

5

Radio wave propagation in a multiscale inhomogeneous ionosphere  

Microsoft Academic Search

Results of an experimental study of the structure of a multiscale inhomogeneous ionosphere and statistical characteristics of signal propagation are reported. A theory is developed for the propagation of radio signals of arbitrary power and polarization in an ionosphere containing multiscale inhomogeneities. The mechanisms responsible for the formation of nonlinearities in an inhomogeneous ionosphere under the effect of oblique-incidence high-intensity

Gennadii K. Solodovnikov; Viktor I. Novozhilov; Mars N. Fatkullin

1990-01-01

6

Propagation of Radio Waves in the Lower Troposphere  

Microsoft Academic Search

The effect of tropospheric layers on the propagation of high-frequency radio waves has been experimentally investigated. A theory is proposed which is in agreement with the salient propagation characteristics observed on a nonoptical link. Fields beyond the optical horizon are governed by the layer height and the refractive index change through the layer. For low layers the higher frequencies have

J. B. Smyth; L. G. Trolese

1947-01-01

7

Huygen's principle applied to radio wave propagation  

Microsoft Academic Search

Huygen's principle, in the form of boundary integral equations, is applied to the problem of radio wave propagation. Complex propagation is analyzed by dividing the region between transmitter and receiver into a number of zones and propagating the solution between these zones by means of integral equations with simple approximate kernels. In the limit that the regions become dense, the

C. J. Coleman

2002-01-01

8

Antenna Construction and Propagation of Radio Waves.  

ERIC Educational Resources Information Center

|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…

Marine Corps Inst., Washington, DC.

9

Variations of the tropospheric propagation range of ultrashort radio waves above the sea  

Microsoft Academic Search

In connection with the development of beyond-the-horizon radar, communications and remote sensing of the atmosphere, the problem of predicting the tropospheric propagation range of ultrashort (US) radio waves has assumed great practical importance. Therefore, the dependence of radio signal characteristics on the propagation conditions has been investigated over different radio paths. Of special interest are routes over oceans, where the

A. R. Gliner; S. N. Krivonozhkin; B. M. Shevtsov

1988-01-01

10

Radio-wave propagation for space communications systems  

Microsoft Academic Search

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,

L. J. Ippolito

1981-01-01

11

Radio wave propagation below the Jovian ionosphere  

Microsoft Academic Search

The lightning and radio emission detector (LRD) instrument on board the Galileo probe measured the spectral intensity and other characteristics of radio frequency (RF) signals during descent. The measured spectra show a frequency dependent height profile with a maximum at the beginning of descent around the 1 bar level and a minimum around the 3-6 bar level [Rinnert et al.,

Klaus Rinnert; L. J. Lanzerotti

1998-01-01

12

The propagation of radio waves in the terrestrial environment  

Microsoft Academic Search

The propagation of a radio wave from a transmitter to an antenna, with one of the two imbedded in the neutral or ionized earth atmosphere, is examined. Attention is given to the propagation of radio waves through an unobstructed space, such as occurs with microwave communications and radar. The theoretical basis for radio wave propagation is reviewed, as are the

L. Boithias

1983-01-01

13

Studies of radio-wave propagation in the solar system  

Microsoft Academic Search

A review is given of studies of radio-wave propagation in the solar system that were conducted from 1963 to 1973 with the Soviet spacecraft Venera, Mars, and Luna. Results are presented for satellite radio-occultation investigations of the Martian atmosphere. Properties of radio-wave propagation in the dense atmosphere of Venus, involving a radio link with descending spacecraft, are examined along with

M. A. Kolosov; O. I. Iakovlev

1975-01-01

14

Variations of radio-wave propagation conditions in the corona during a solar activity cycle  

Microsoft Academic Search

Variations of the propagation conditions of monochromatic radio waves through the solar corona during an 11-year cycle are analyzed on the basis of space-probe (Pioneer, Mariner, Mars, Venera, Helios, Viking, and Voyager) data. It is shown that, besides short-term variations of radio-signal parameters with a characteristic time of 5-20 days, there occur long-term variations of propagation conditions with periods of

A. I. Efimov; O. I. Iakovlev; V. K. Shtrykov; V. I. Rogalskii

1984-01-01

15

800 MHz mobile radio propagation prediction using Kalman filtering techniques  

Microsoft Academic Search

A method is presented to derive a propagation model to predict the received median signal voltage for an 800-MHz mobile radio system. Results are given of an investigation into the performance of a particular model that was derived using this method. The method uses a Kalman filter that uses propagation measurements to derive a best fit for a particular propagation

LARRY M. HAWTHORNE

1989-01-01

16

On a Model for Radio Propagation in Land Mobile Communication  

Microsoft Academic Search

This article describes a study on a model for radio propagation in a land mobile communication (LMC), which differs from models based on the well-known theory for tropospheric propagation. The new propagation model has been constructed from a phenomenological paint of view for an LMC in an area where artificial or natural obstacles are present. This new model is based

Toshihiro Terada

1995-01-01

17

Radio propagation at 900 MHz in underground coal mines  

Microsoft Academic Search

This paper reports on experimental results of radio propagation in two underground coal mines. Measurements were performed at 900 MHz on horizontal and vertical polarization in typical coal mine operational zones. Values of propagation loss in dB\\/100 m are derived. Additional losses due to coal mine curvatures and common coal mining equipment obstructions are also presented. A hybrid tunnel propagation

Y. P. Zhang; G. X. Zheng; J. H. Sheng

2001-01-01

18

Precipitation in relation to radio wave propagation studies in India  

Microsoft Academic Search

In this presentation efforts have been made to highlight the research work made on precipitation characterization and its effects on radio wave propagation particularly at frequency above 10 GHz over the Indian subcontinent. The work carried out on attenuation of radio wave due to water vapour, rain and cloud has been highlighted. To evolve better formulations suitable to tropical countries

S. K. Sarkar

2007-01-01

19

HUYGEN'S PRINCIPLE APPLIED TO RADIO WAVE PROPAGATION IN ANISOTROPIC MEDIA  

Microsoft Academic Search

Huygens principle describes radio wave propagation in terms of the development of the electromagnetic field from one wavefront to another. This approach finds its mathematical expression in terms of Kirchhoff integrals. For isotropic propagation media, the necessary integrals can be derived from reciprocity relations. In the current paper, it is shown that it is possible to extend the approach to

C. J. Coleman

20

Propagation characteristics of low base-station antennas on urban road  

Microsoft Academic Search

One method of efficient spectrum utilization is to trap a radio wave in a small area. A base-station antenna that is lower than the average building height is effective for trapping radio waves. However, the propagation mode differs from conventional propagation modes for high-base-station antennas. Thus, conventional propagation characteristics do not apply. The authors propose a propagation model for low

S. Kozono; A. Taguchi

1988-01-01

21

Transpolar Propagation of Long Radio Waves  

Microsoft Academic Search

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

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

1972-01-01

22

Significance of common scatterers in multi-link indoor radio wave propagation  

Microsoft Academic Search

Correlation between different links is an essential characteristic for many of the forthcoming radio communication systems that utilize the multiple-input-multiple-output (MIMO) technology. This paper investigates the physical phenomena that cause the inter-link correlation by introducing a measure to quantify how large amount of energy propagates via similar propagation mechanisms in different links. The conditions for the so-called significance of common

Juho Poutanen; Katsuyuki Haneda; Jussi Salmi; Veli-Matti Kolmonen; Fredrik Tufvesson; Tommy Hult; Pertti Vainikainen

2010-01-01

23

Radio wave propagation in potato fields  

Microsoft Academic Search

Reliable communication is crucial for successful de- ployment of wireless sensor networks. Therefore, it is important to understand the impact of environmental conditions on the performance of the radios (Chipcon CC1000 transceivers) used in typical sensor nodes. This paper reports on an extensive set of measurements taken in a potato field, where the foliage has an important effect on the

John Thelen; Daan Goense; Koen Langendoen

2005-01-01

24

MARTIAN ATMOSPHERIC EFFECTS ON RADIO WAVE PROPAGATION  

Microsoft Academic Search

Because Mars has very low atmospheric pressure (less than 1% of Earth's), the Martian atmospheric radio refractivity is about two orders of magnitude smaller than that of Earth. Ray bending effect on microwave is not obvious. The optical depths of Martian clouds and fogs are about 1 .O at visual wavelengths. In the limiting case, the Martian clouds are expected

C. M. Ho; M. K. Sue; N. Golshan

25

A Single-Antenna Repeater for HF Radio Propagation Studies.  

National Technical Information Service (NTIS)

The purpose of the work was to develop and test a compact, portable, calibrated single-antenna repeater which has application to HF radio propagation studies. For example, high-frequency backscatter ionograms--depending on the terrain-generally show one o...

A. C. Phillips

1969-01-01

26

Nonlinear Ionospheric Propagation Effects on UHF and VLF Radio Signals  

Microsoft Academic Search

An investigation of nonlinear wave-plasma interactions in the ionosphere causing significant propagation effects on VLF and UHF radio waves has been conducted. Nonlinear scattering of VLF waves off existing density irregularities is shown to be responsible for the observed spectral broadening. When the irregularity scale size does not exceed a few tens of meters, the scattered wave is found to

Keith Michael Groves

1991-01-01

27

An Improved Recurrent Neural Network for Radio Propagation Loss Prediction  

Microsoft Academic Search

Prediction of the radio propagation loss using a numeric parabolic equation method is often accepted for its accuracy, but the large computational time is a hindrance in applications requiring real-time situation awareness. A modified Elman recurrent neural network is proposed and developed to resolve this problem. In this paper, the three dimensional parabolic equation models is used to provide the

Fang Cheng; Huairong Shen

2010-01-01

28

Radio wave propagation along mixed paths in forest environments  

Microsoft Academic Search

The propagation of radio waves is examined for communication paths that may be partly within a forest and partly in regions outside the vegetation. Analytic results are found for simple canonic geometries in which the fields can be described in terms of ray-trajectories. By viewing a realistic forest environment as a combination of such canonic cases, it is possible to

T. Tamir

1977-01-01

29

Radio wave propagation: A comparison between 900 and 1800 MHz  

Microsoft Academic Search

Extensive measurements of radio wave propagation in macro cells were performed. Two transmitters, generating 900 and 1800 MHz, respectively, were situated together. The measurements were performed for six separate transmitter locations in different terrain types. The average value of the signal strength was calculated and stored every 13.3 m over a total distance of 550 km. The difference in path

Lena Melin; Martin Ronnlund; Rickard Angbratt

1993-01-01

30

Radio-Wave Propagation between World Wars I and II  

Microsoft Academic Search

The period between World Wars I and II, 1918 to 1941, is particularly noteworthy for the significant developments that led to a comprehensive understanding of the factors that control the propagation of radio waves through the atmosphere. In slightly over two decades it became possible to identify the basic physical mechanisms with the aid and correlation of theory and experiment,

Stephen Attwood

1962-01-01

31

An Experiment Study of the Propagation of Radio Waves in a Scaled Model of Long-Wall Coal Mining Tunnels  

SciTech Connect

A long-wall coal mining tunnel is the most important working area in a coal mine. It has long been realized that radio communications can improve both productivity and safety in this dangerous area. Hence, many attempts to use radio communications in such an environment have been made. Unfortunately, no radio system has satisfactorily provided communication services there, which, we believe, is partially due to poor understanding of the propagation characteristics of radio waves in the long-wall mining tunnel. To have deeper physical insight into the propagation problem, a scaled model of the long-wall mining tunnel was built, and the propagation characteristics of UHF radio waves were measured. The experiment and the measured results are presented and discussed.

Han, G.R.; Zhang, W.M.; Zhang, Y.P. [Shanxi University, Taiyuan (China)

2009-07-01

32

Radio wave propagation experiments at the MTRS  

Microsoft Academic Search

Results of analyzing wave propagation data above 10 GHz obtained at the Main Transmit and Receive Station at Kashima since 1978 are presented. Statistics on rainfall rate and rain-induced attenuation of the beacon signal are used to determine that the effective path length was about 5 km with an elevation angle of 37 degrees. The ratio of up-link to down-link

H. Fukuchi; T. Kozu; Y. Takahashi; Y. Otsu; T. Oda

1986-01-01

33

APPLICATION OF SMALL SATELLITES FOR HIGH PRECISION MEASURING EFFECTS OF RADIO WAVE PROPAGATION  

Microsoft Academic Search

The radio holography methodology may be applied in the scientific programs for future small satellite that will use radio signals emitted by radio navigation, radio communication satellites for precise measuring effects of radio waves propagation at low elevation angles and for global monitoring of radio communication channels passed through the atmosphere and ionosphere. Another task consists in monitoring of the

K. Igarashi; N. A. Armand; A. G. Pavelyev; Ch. Reigber; J. Wickert; K. Hocke; G. Beyerle; S. S. Matyugov; O. I. Yakovlev

34

Temperature Effects on Anomalous Radio Duct Propagation in Korean Coastal Area  

NASA Astrophysics Data System (ADS)

Atmospheric radio ducts can trap VHF/UHF radio waves and propagate them over long distances. 284.4625MHz Japanese radio wave signal measurements show that the radio waves are propagated to Korea coastal regions when ground temperatures exceed 10°C. This paper discusses the reasons for the existence of this critical temperature threshold.

Kwon, Yong-Ki; Lee, Man-Seop; Kim, Hakyong

35

Propagation of Radio Waves in the Corona and Solar Wind  

NASA Astrophysics Data System (ADS)

The solar corona and solar wind are plasmas characterized by large scale MHD structures, waves, and turbulence. These introduce both systematic and random variations in the refractive index which affect the propagation of radio waves. A variety of propagation phenomena occur -- regular refraction; angular, temporal, and spectral broadening; scintillations in amplitude and phase -- widely referred to as scattering phenomena. In this tutorial I review the physical basis of these phenomena and describe a variety of techniques designed to exploit observations of scattering phenomena to deduce properties of the corona and solar wind plasma.

Bastian, T. S.

36

The prediction of radio-path characteristics  

NASA Astrophysics Data System (ADS)

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.

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

37

Ray Propagation in Ice for Radio Cherenkov Neutrino Experiments  

NASA Astrophysics Data System (ADS)

Understanding the propagation of radio signals in ice is important for existing and future south polar neutrino experiments to observe high-energy astrophysical neutrinos via radio emission from the Askaryan effect. This includes the Askaryan Radio Array (ARA), a new detector being constructed, which is planned to cover an approximately 80 km^2 area, and to detect GZK neutrinos at a rate of a few per year, with sensors placed at relatively shallow depths. In order to both simulate the behavior of the detector and reconstruct collected data, the paths of the radio signals through the ice must be accurately calculated, which involves nontrivial optics problems arising from the depth dependent properties of the naturally-occurring antarctic ice. Since analytical solutions for the ray paths are not known, it is necessary to use numerical ray-tracing. We show how existing optics results can be applied to increase the efficiency of the ray-tracing calculations, and present initial results with existing radio experiments using these tools.

Weaver, Christopher

2011-04-01

38

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

Microsoft Academic Search

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

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

39

Fade durations in satellite-path mobile radio propagation  

NASA Astrophysics Data System (ADS)

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.

Schmier, Robert G.; Bostian, Charles W.

1986-12-01

40

Conference on the Ionosphere and Radio Wave Propagation, 3rd, University of Sydney, Australia, February 11-15, 1985, Proceedings  

Microsoft Academic Search

Various papers on the ionosphere and radio wave propagation are presented. The subjects discussed include: day-to-day variability in foF2 at low latitudes over a solar cycle; semiempirical, low-latitude ionospheric model; remote sensing with the Jindalee skywave radar; photographic approach to irregularities in the 80-100 km region; interference of radio waves in a CW system; study of the F-region characteristics at

D. G. Cole; L. F. McNamara

1985-01-01

41

GPS radio occultations with CHAMP: A radio holographic analysis of GPS signal propagation in the troposphere and surface reflections  

NASA Astrophysics Data System (ADS)

Within the first nine months following the activation of the GPS radio occultation experiment aboard the low Earth orbiting satellite CHAMP, more than 25,000 occultation events have been observed. A radio holographic analysis of 3783 occultation events, recorded between 14 May 2001 and 10 June 2001, reveals that in about 20-30% of these events the received signal contains contributions from components reflected at Earth's surface. On the basis of geometrical ray tracing and multiple phase screen calculations, characteristic frequency shifts in the radio holograms' power spectral densities are analyzed quantitatively. These frequency shifts are found to be dominated by surface elevation at the reflection point location and ground-level refractivity. Using temperature and pressure profiles from European Centre for Medium-Range Weather Forecasting (ECMWF) analyses, ground-level specific humidities are derived in good agreement with ECMWF values. Complex patterns found in radio hologram spectra within a subset of observations at low latitudes are interpreted in terms of multipath propagation caused by layered structures in the refractivity field.

Beyerle, G.; Hocke, K.; Wickert, J.; Schmidt, T.; Marquardt, C.; Reigber, C.

2002-12-01

42

Radio-frequency characteristics of graphene oxide  

NASA Astrophysics Data System (ADS)

We confirm graphene oxide, a two-dimensional carbon structure at the nanoscale level can be a strong candidate for high-efficient interconnector in radio-frequency range. In this paper, we investigate high frequency characteristics of graphene oxide in range of 0.5-40 GHz. Radio-frequency transmission properties were extracted as S-parameters to determine the intrinsic ac transmission of graphene sheets, such as the impedance variation dependence on frequency. The impedance and resistance of graphene sheets drastically decrease as frequency increases. This result confirms graphene oxide has high potential for transmitting signals at gigahertz ranges.

Kim, Whan Kyun; Jung, Young Mo; Cho, Joon Hyong; Kang, Ji Yoong; Oh, Ju Yeong; Kang, Hosung; Lee, Hee-Jo; Kim, Jae Hun; Lee, Seok; Shin, H. J.; Choi, J. Y.; Lee, S. Y.; Kim, Y. C.; Han, I. T.; Kim, J. M.; Yook, Jong-Gwan; Baik, Seunghyun; Jun, Seong Chan

2010-11-01

43

Measurements of the propagation of UHF radio waves on an underground railway train  

Microsoft Academic Search

Measurements of the natural propagation of UHF radio waves on an underground train are reported. Of prime interest are the natural propagation attenuation and the median signal level behavior. The propagation attenuation rates or the median signal level behaviors are found to correlate with the train carriages and frequency. On the front carriage, the propagation attenuation rate is 54 dB\\/100

Y. P. Zhang; Z. R. Jiang; T. S. Ng; J. H. Sheng

2000-01-01

44

Characteristics of radio wave for the indoor wireless communication in Malaysian typical office environment  

Microsoft Academic Search

It is well known that the propagation characteristics are changed for wireless communication. We have investigated the characteristics of radio wave for indoor wireless communication in a typical Malaysian office environment. It is not too far when a lot of Malaysian people will use their personal computer or lab top in the office for signal transmission through an indoor wireless

M. Shahidul Islami; T. A. Rahman

2003-01-01

45

Theory of the propagation of UHF radio waves in coal mine tunnels  

Microsoft Academic Search

The theoretical study of UHF radio communication in coal mines, with particular reference to the rate of loss of signal strength along a tunnel, and from one tunnel to another around a corner is the concern of this paper. Of prime interest are the nature of the propagation mechanism and the prediction of the radio frequency that propagates with the

ALFRED G. EMSLIE; ROBERT L. LAGACE; PETER F. STRONG

1975-01-01

46

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

Microsoft Academic Search

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

Charles Burrows

1962-01-01

47

Measurements of transionospheric radio propagation parameters using the FORTE satellite  

NASA Astrophysics Data System (ADS)

We report initial measurements of ionospheric propagation parameters, particularly the total electron content (TEC), using the recently launched FORTE satellite. FORTE, which orbits the Earth at an altitude of 800 km and an inclination of 70°, contains a set of wideband radio receivers whose output is digitally recorded. A specialized triggering circuit identifies transient, broadband radio events, which include radiation from lightning, transionospheric pulse pairs, and man-made sources. Event data are transmitted to the ground station for analysis. In this paper we examine signals transmitted from an electromagnetic pulse generator operated at Los Alamos. The transmitter produces nearly impulsive signals in the VHF range. The received signal is dispersed by the ionosphere, and the received signal can be analyzed to deduce the total electron content along the path. By comparing the slant TEC thus measured with results from a ray-tracing code, we can deduce the vertical TEC to 800 km. Data from eight passes are presented. These types of data (in larger quantities) are of interest to operators of radar altimeters, who need data to corroborate their corrections for the ionospheric TEC. The combination of FORTE TEC data to 800 km and TEC measurements to 20,000 km (the Global Positioning System orbital altitude) can provide useful information for assessing the validity of models of plasmaspheric electron density. Initial estimates of the plasmaspheric density, on two daytime passes, are about 6 TECU. The signal received by FORTE, which is linearly polarized at the transmitter, is split into two magnetoionic modes by the ionosphere. The receiving antenna is also linearly polarized and therefore receives both modes. By measuring the beat frequency between the two modes, we can deduce the product of the geomagnetic field and the cosine of the angle between the field and the propagation vector. The possibility of using the measured slant TEC and the beat frequency to geolocate impulsive signals is discussed.

Massey, Robert S.; Knox, Stephen O.; Franz, Robert C.; Holden, Daniel N.; Rhodes, Charley T.

1998-11-01

48

Influence of Environmental Buildings on UHF Land Mobile Radio Propagation  

Microsoft Academic Search

This paper describes the result of measurements of the correction factor for buildings around a mobile station on UHF land mobile propagation characteristics. In order to express buildings around a mobile station quantitatively, four parameters are proposed: area factor of occupied buildings(alpha), extended-area factor of occupied buildings(alphá), buildings volume over a sampled area(beta)and buildings volume over an extended-area(betá). The examination

SHIGERU KOZONO; KUNIO WATANABE

1977-01-01

49

The application of a deterministic ray launching algorithm for the prediction of radio channel characteristics in small-cell environments  

Microsoft Academic Search

Propagation characteristics play a fundamental role in the design and implementation of radio systems. The application of broadband digital data services within the cordless environment requires close consideration of the dispersive nature of radio channels. A prediction algorithm is presented such that propagation characteristics can be estimated for small-cell high-data-rate systems. Through the use of geometric optics and geometric theory

Michael C. Lawton; J. P. McGeehan

1994-01-01

50

Radio-wave propagation investigations on a digital radio link at 2.2 GHz  

Microsoft Academic Search

Propagation measurements comprising recordings of field strength, bit error rates, and spectral characteristics of fading were carried out on two paths 73 km and 49 km long respectively, in the same geographical area. The paths were running over rugged forested terrain in the middle of Sweden. A 34 Mbit\\/sec signal was transmitted using four phase shift keying. Conventional fading statistics

A. Blomquist; F. Eklund; S. Wickerts

1979-01-01

51

Characterization of the Indoor Channel by an Optimised Simulation of the Radio Wave Propagation  

Microsoft Academic Search

This paper is based on a 3D simulation software of radio waves propagation (1)for wireless systems in indoor environments. This software (figure 1), developed in the IRCOM-SIC lab- oratory (University of Poitiers, France), allows to predict the coverage zone of a base station and the behaviour of the wide band propagation channel. Firstly, after a brief recall of our propagation

Rudolf Vauzelle; F. Escarieu

52

The Black Hole Masses and Radio Characteristics of Radio Quasars  

NASA Astrophysics Data System (ADS)

In this paper, we collect the redshift, bolometric luminosity, the full- width at half maximum of the H? emission line, the monochromatic luminosity at 5100 Å and the radio loudness for the sample of 117 quasars, including 20 radio-quiet quasars (RQQs) and 97 radio-loud quasars (RLQs). With the reverberation mapping method we calculate the black hole mass and Eddington ratio for this sample, as well as the radio luminosity from the total 5 GHz ?ux density. By analyzing the correlations among them, we obtain the following conclusions: (1) The black hole mass has weak correlations with the bolometric luminosity, radio loudness and radio luminosity for the RQQs, and has strong correlations with the bolometric luminosity, radio loudness and radio luminosity for the RLQs; (2) For the RQQs, the bolometric luminosity has weak correlations with the radio luminosity and 5 100 Å monochromatic luminosity, and for the RLQs, the bolometric luminosity has strong correlations with the radio luminosity and 5 100 Å monochromatic luminosity; (3) The RQQs and RLQs differ in the distributions of the black hole mass, emission line width and Eddington ratio. Based on these results, we suggest: the difference of emission line width between RQQs and RLQs is probably caused by the difference of black hole mass; the fundamental difference between RQQs and RLQs is caused by the difference of their intrinsic physical nature; the black hole mass, black hole spin, Eddington ratio, and host galaxy morphology are the important parameters to explain the origin of radio loudness and the double-peaked distribution; and the radio jet is closely related with the accretion rate of disk.

Xiong, Ding-rong; Zhang, Xiong; Zheng, Yong-gang; Huang, Bang-rong; Mao, Li-sheng; Liu, Wen-guang

2013-01-01

53

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

SciTech Connect

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.

Ivanov, V.B.

1995-05-01

54

Statistical modelling of radio wave propagation under sporadic E-Layer influence  

NASA Astrophysics Data System (ADS)

A technique of modelling the one-hop radio wave propagation at middle latitudes in the presence of sporadic E-Layer is presented. The technique is focused on the performance of the long-term forecast of the maximum usable frequency range and on the increase of the radio communication reliability. Examples of calculation for medium-distance paths are shown.

Sherstyukov, O. N.; Akchurin, A. D.; Ryabchenko, E. Yu.

2009-06-01

55

Modeling ELF radio atmospheric propagation and extracting lightning currents from ELF observations  

Microsoft Academic Search

Observations of extremely low frequency (ELF) radio atmospherics (sferics), the transient electromagnetic fields radiated by lightning discharges, are used to determine the current moment waveforms of vertical lighting discharges. In order to extract this information the propagation of radio atmospherics from source to receiver must be modeled accurately, especially in view of the important role played by the D and

Steven A. Cummer; Umran S. Inan

2000-01-01

56

Collaboration between URSI and CCIR in the study of tropospheric radio wave propagation problems  

Microsoft Academic Search

Topics in tropospheric radio wave propagation addressed by the International Union of Radio Science and the International Radio Consultative Committee include clear-air phenomena, precipitation effects, improvements in centimeter-wavelength space and terrestrial communications, and planning for VHF and UHF services. An example of cochannel interference between earth-space and terrestrial links operating at 4 GHz is presented. In addition, interference by precipitation

J. A. Saxton

1978-01-01

57

Plasma and radio waves from Neptune: Source mechamisms and propagation  

NASA Astrophysics Data System (ADS)

The purpose of this project was to conduct a comprehensive investigation of the radio wave emission observed by the planetary radio astronomy (PRA) instrument on board Voyager 2 as it flew by Neptune. The study has included data analysis, theoretical and numerical calculations, and ray tracing to determine the possible source mechanisms and locations of the radiation, including the narrowband bursty and smooth components of the Neptune radio emission.

Menietti, J. Douglas

1994-07-01

58

A Hybrid Model for Radio Wave Propagation Through Frequency Selective Structures (FSS)  

Microsoft Academic Search

A novel hybrid model is presented to study the radio wave propagation through frequency selective structures (FSS) used to control propagation in an outdoor to indoor building environment. This hybrid model is based on combining ray-tracing with a commercial tool, Computer Simulation Technology (CST) Microwave Studio. Numerical results of the hybrid model have been compared with those of a full

Ming Yang; Anthony K. Brown

2010-01-01

59

Measurement of building penetration loss and propagation models for radio transmission into buildings  

Microsoft Academic Search

The investigation of radio transmission into buildings is getting more and more important. Models for the propagation into buildings enable the calculation of the indoor field strength coverage based on the given outdoor coverage. In order to develop and to calibrate such propagation models several measurements of the building penetration loss with different transmitter locations were undertaken and evaluated. Additionally,

R. Hoppe; G. Wolfle; F. M. Landstorfer

1999-01-01

60

Wideband propagation modelling for indoor environments and for radio transmission into buildings  

Microsoft Academic Search

With the introduction of wireless broadband services in indoor environments there is a growing interest in propagation models for the mobile radio channel inside buildings. Because of the increasing transmission rates propagation models should be able to calculate the field strength coverage as well as the wideband properties for these indoor scenarios. This paper presents a new ray optical approach,

R. Hoppe; P. Wertz; G. Wolfle; F. M. Landstorfer

2000-01-01

61

Propagation effects on radio range and noise in earth-space telecommunications  

Microsoft Academic Search

Attention is given to the propagation effects on radio range and noise in earth-space telecommunications. The use of higher frequencies minimizes ionospheric effects on propagation, but tropospheric effects often increase or dominate. For paths of geostationary satellites, and beyond, the excess range delay caused by the ionosphere and plasmasphere is proportional to the total electron content along the path and

W. L. Flock; S. D. Slobin; E. K. Smith

1982-01-01

62

Analysis of radio wave propagation from an indoor hall to a corridor  

Microsoft Academic Search

In this paper the radio wave propagation from an indoor hall to a corridor was studied by analyzing the results from a multi-link MIMO channel sounding measurement. The results showed that despite NLOS conditions, the dominant propagation mechanisms comprised direct path through the wall and specular reflections. These findings were verified by plotting the dominant pathways with a measurement-based ray

Juho Poutanen; Katsuyuki Haneda; Jussi Salmi; Veli-Matti Kolmonen; J. Koivunen; P. Almers; P. Vainikainen

2009-01-01

63

Auroral and polar-cap ionospheric effects on radio propagation  

Microsoft Academic Search

Disturbances in the auroral and polar-cap ionosphere can have profound effects on radio signals traversing the high-latitude ionosphere (defined here as that latitudinal region poleward of approximately 55° corrected geomagnetic latitude). Some effects of the high-latitude ionosphere on polar radio paths were documented as early as the 1930s, but intensive investigations of this ionospheric global region started during the International

Robert D. Hunsucker

1992-01-01

64

Propagation characteristics of International Space Station wireless local area network  

Microsoft Academic Search

This work describes the application of the uniform geometrical theory of diffraction (UTD) for Space Station 2.4 GHz wireless local area networks (WLAN) 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

Shian U. Hwu; Yin-Chung Loh

2004-01-01

65

Event-based Transmission Line Matrix Method for Simulating Site-Specific Multipath Propagation Characteristics  

SciTech Connect

Accurate radio channel modeling is essential for deploying advanced wireless sensors in harsh industrial and urban environments. Site-specific propagation modeling tools are required to understand the channel parameters with in these environments. Multipath delay spread determines the frequency-selective fading characteristics of the channel. This paper describes a novel computationally inexpensive technique to determine multipath delay spread. Event-based transmission line matrix-based method is used to simulate the channel.

Kuruganti, Phani Teja [ORNL; Nutaro, James J [ORNL; Djouadi, Seddik M [ORNL

2012-01-01

66

38 GHz wideband point-to-multipoint radio wave propagation study for a campus environment  

Microsoft Academic Search

This article presents the results of a fixed millimeter-wave short-hop radio wave propagation study at 38 GHz. A wideband measurement campaign was performed using three cross-campus radio links from April to August 1998 at Virginia Tech. 73,963 power delay profiles (PDPs) were recorded during different weather events such as clear sky, rain, and hail. Rain\\/hail attenuation, short-term signal variation, and

Hao Xut; T. S. Rappaport; R. J. Boyle; J. H. Schaffner

1999-01-01

67

Nomograms for the calculation of propagation effects on tactical millimeter wave radio links  

Microsoft Academic Search

Description of the development and use of nomograms for calculating propagation effects on tactical millimeter-wave radio links are investigated. The principal causes of attenuation in the millimeter-wave band (35-75 GHz) are oxygen absorption, which depends on radio frequency, and rain scattering, which depends on frequency and rain rate. The nomograms display these dependencies and the range equation, and may be

W. Sollfrey

1979-01-01

68

Radio wave propagation in structured ionization for satellite and radar applications  

NASA Astrophysics Data System (ADS)

This report is an extension to DNA 5304D and DNA-IR-82-02 which presented the radio propagation algorithms recommended for use by DNA to calculate the properties of scintillated signals. This report covers effects related to antennas and extends the formalism to cover two component power spectra of plasma fluctuations. In addition, an improved representation of the total electron content power spectrum is included to support space radar and similar applications. Appendix E contains SUBROUTINE PROP which implements the radio propagation models.

Wittwer, Leon A.

1993-08-01

69

Digital Radio Link: Wave Propagation Measurements Using Narrow Band Technique.  

National Technical Information Service (NTIS)

Measurements on a 34 M Bit, 7 GHz digital radio link with a linkhop of 56 km are described. Events with flat and frequency selective fading are presented and a method using narrow band measurements to evaluate frequency selective fading is outlined. By ma...

S. Nilsson L. Ladell

1984-01-01

70

Radio wave propagation through rain forests of India  

Microsoft Academic Search

A radio wave attenuation measurement survey program was undertaken for the tropical rain forests of India. Measurements were taken at frequencies from 50 to 800 MHz, for antenna heights from 1.5 to 16.5 m above the ground with both horizontally and vertically polarized emissions, and at various separation distances varying from 40 to 4000 m. There were 96 combinations of

R. K. Tewari; S. Swarup; M. N. Roy

1990-01-01

71

Location and Propagation Status Sensing of Interference Signals in Cognitive Radio  

NASA Astrophysics Data System (ADS)

In a Cognitive Radio system, it is essential to recognize and avoid sources of interference signals. This paper describes a study on a location sensing scheme for interference signals, which utilizes multibeam phased array antenna for cognitive wireless networks. This paper also elucidates its estimation accuracy of the interference location for the radio communication link using an OFDM signal such as WiMAX. Furthermore, we use the frequency spectrum of the received OFDM interference signal, to create a method that can estimate the propagation status. This spectrum can be monitored by using a software defined radio receiver.

Kashiki, Kanshiro; Nohara, Mitsuo; Imata, Satoshi; Kishiki, Yukiko

72

The short distance propagation of LF 40 kHz radio waves and some aspects of the D-region  

NASA Astrophysics Data System (ADS)

An analysis is made of the amplitude and phase data for LF 40 kHz radio wave propagated over a surface distance of 395 km to examine its propagation characteristics, and some aspects of the D-region as inferred from them are discussed. The analysis shows that the amplitude of the sky wave remains nearly constant during daytime while the nighttime amplitude varies appreciably. It is also demonstrated that the amplitude of the skywave is enhanced during daytime on winter anomaly days and that the occurrence of a winter anomaly event can be predicted by detecting the characteristic changes in the pattern of the occurrence time of interference maxima and minima. Finally, it is inferred from the analysis of the interference pattern that a transition layer appears during the periods of sunrise and sunset. This layer has a semi-peak below 80 km and extends upward to blend with the E-layer.

Ishimine, Tsuyoshi; Echizenya, Yoshimatsu

1989-11-01

73

Radio-Wave Propagation Measurements over Sea Water.  

National Technical Information Service (NTIS)

Propagation loss was measured at three frequencies (30, 140, and 412 MHz) over various sea-water paths out to 40 nautical miles between a moderately elevated shore-based receiving site and a floating transmitter platform essentially at the water's surface...

M. M. Algor

1972-01-01

74

On radio-wave propagation in forest environments  

Microsoft Academic Search

Propagation of electromagnetic waves in forest environments at medium and high (1-100 MHz) frequencies is examined for the case where both the transmitting and receiving points are situated within the vegetation. A dissipative slab in the presence of a reflecting ionosphere is employed to describe the forest configuration. If the effect of the ground-forest interface is disregarded, the radiated field

T. Tamir; J. Fainberg

1967-01-01

75

Atmospheric, Ionospheric, Surface and Radio Propagation Studies with the Radio Science Experiment VeRa onboard Venus Express  

NASA Astrophysics Data System (ADS)

The Venus Radio Science experiment (VeRa) onboard the proposed Venus Express Orbiter will make use of the spacecraft radio carrier signals at X/S-band and an ultrastable oscillator reference frequency source (USO, Allan deviation 10 -13 ) integrated into the onboard transponder system. VeRa will perform : radio sounding of the Venusian ionosphere from 80 km up to the ionopause (300km to 600 km), radio sounding of the neutral atmosphere from the cloud deck (35km to 40 km) to 100 km altitude, measurements of dielectric constant and roughness of the Venusian surface, studies of the propagation of radio waves in the inner solar system. We shall discuss the experimental methods (spacecraft occultation and bistatic radar) and conclude on the achievable accuracies and sensitivities. We shall indicate where improvements in comparison to the Pioneer Venus and Magellan observations can be expected and examine VeRa`s contribution to the understanding of plasmaphysical processes in the solar wind and planetary ionospheric environment. Effects of the solar coronal plasma and the gravitational field of the Sun on the observables (Doppler, group delay) will also be addressed.

Haeusler, B.; Paetzold, M.; Bird, M.; Treumann, R.; Simpson, R.; Hinson, D.

76

Aperture Synthesis for HF Radio Signals Propagated Via the F Layer of the Ionosphere.  

National Technical Information Service (NTIS)

A portable high-frequency (HF) radio aperture up to 70 km in length was synthesized by receiving ionospherically propagated signals in a DC-3 airplane. By thus moving a small antenna rapidly over a long distance, a narrow receiving beam width (high azimut...

J. T. Lynch

1970-01-01

77

Measurements and Predictions of HF Ground Wave Radio Propagation Over Irregular, Inhomogeneous Terrain.  

National Technical Information Service (NTIS)

Measurements of radio propagation path loss were made over four paths in the 3 to 30 MHz band. The paths were of lengths up to 45 km in the Boulder, CO, area. They ranged from smooth to mountainous terrain, from open areas with few or no man-made structur...

J. E. Adams J. C. Carroll E. A. Costa D. R. Ebaugh J. R. Godwin

1984-01-01

78

MODELLING OF SHADOWING LOSS DUE TO HUGE NON-POLYGONAL STRUCTURES IN URBAN RADIO PROPAGATION  

Microsoft Academic Search

Abstract—Ray tracing algorithms rely on two dimensional or three dimensional database. They use ray optical techniques referred to as the uniform theory of diffraction (UTD) using building database given as polygons. Building geometries can also be modelled as having non-planar geometries, and this would be important in modeling of shadowing loss due to curved structures in urban radio propagation. To

Ali Kara; Erdem Yazgan

2008-01-01

79

GEOMETRICALLY BASED CHANNEL MODEL FOR INDOOR RADIO PROPAGATION WITH DIRECTIONAL ANTENNAS  

Microsoft Academic Search

A geometrically based channel model is proposed to describe radio propagation in an indoor environment with directional antennas. In conventional geometric channel models (GCMs), distribution of scatterers does not take into account the antenna properties. A difierent approach is taken here for directional channel modeling. The locations of scattering objects are deflned using non- Cartesian coordinates comprising an auxiliary geometric

Yifan Chen; Zhenrong Zhang; Tuanfa Qin

2010-01-01

80

Secure Protocols Enhancement Based on Radio-propagation Related Looser Assumptions in Mobile Ad hoc Networks  

Microsoft Academic Search

The paper presents secure protocols and new secure challenges based on looser radio propagation assumptions. According to these, a new secure enhancement mechanism for secure protocols is proposed. Then we exemplify the DoS attacks and protections as the illustration. The research indicates it will increase the usability of secure protocols in common applications.

Ruijun Yang; Qi Xia; Weinong Wang; Qunhua Pan; Xinli Huang; Minglu Li

2005-01-01

81

The Influence of the Earth's Magnetic Field on Radio Propagation by WaveGuide Modes  

Microsoft Academic Search

A general theory of radio propagation by wave-guide modes is given, which simultaneously makes allowance for the gradualness of the lowest part of the ionosphere, the earth's curvature and the earth's magnetic field. The method involves solving differential equations satisfied by the matrix admittance or matrix reflexion coefficient variables. The mode condition, excitation factor, and polarization of the waves in

K. G. Budden

1962-01-01

82

A study of VHF radio wave propagation over a water surface of variable conductivity  

Microsoft Academic Search

The ground wave propagation of VHF radio waves over an inhomogeneous sea surface of variable conductivity and under various sea roughness conditions is studied both theoretically and experimentally. Theoretical simulations predict a high sensitivity of the ground wave attenuation factor upon large variations of the surface conductivity, as can be found in an estuary. This sensitivity can be influenced appreciably

P. Forget; P. Broche

1991-01-01

83

Low frequency radio wave propagation in the Atlantic and Mediterranean areas  

Microsoft Academic Search

Data from eighteen long range aircraft flights are compared with the wave hop propagation model of Berry, and areas of agreement and disagreement noted. The field strength of low frequency radio waves from transmitting stations in Iceland, Scotland, Morocco, and Greece was measured under daytime and nighttime conditions. The nighttime waves at about 1 mm seem to oscillate with distance

F. J. Kelly; F. J. Rhoads; D. J. Baker; J. A. Murray

1982-01-01

84

Prediction of mobile radio wave propagation over buildings of irregular heights and spacings  

Microsoft Academic Search

Two models of mobile radio wave propagation over buildings are presented. The first, the flat edge model, provides a simple yet accurate representation when buildings are assumed to be of constant height and spacing. The second model combines the first with a rapid new method of calculating multiple edge diffraction to allow deterministic predictions with arbitrary buildings and spacings. This

S. R. Saunders; F. R. Bonar

1994-01-01

85

SBR image approach for radio wave propagation in tunnels with and without traffic  

Microsoft Academic Search

We propose a deterministic approach to model the radio propagation channels in tunnels with and without traffic. This technique applies the modified shooting and bouncing ray (SBR) method to find equivalent sources (images) in each launched ray tube and sums the receiving complex amplitude contributed by all images coherently. In addition, the vector effective antenna height (VEH) is introduced to

Shin-Hon Chen; Shyh-Kang Jeng

1996-01-01

86

Radio wave propagation effects in high-altitude platform systems  

Microsoft Academic Search

In modern times an intensive development of different radiocommunication systems like cellular personal systems, has been noticed. The use of stratospheric high-altitude platforms as relay stations is being discussed by the ITU-R. This short paper presents the most important propagation effects in high-altitude platform links: the free-space loss, the atmospheric gas absorption, the attenuation due to clouds and the rain

W. Pawlowski

2000-01-01

87

Channelized Coplanar Waveguide: Discontinuities, Junctions, and Propagation Characteristics.  

National Technical Information Service (NTIS)

A new variant of CPW which has been termed channelized CPW, CCPW, is presented. Measured and computed propagation characteristics are presented. Lumped equivalent circuit element values for a CCPW open circuit and right angle bend have been obtained. CCPW...

R. N. Simons G. E. Ponchak K. S. Martzaklis R. R. Romanofsky

1989-01-01

88

Set of new radio propagation models based on the measurements in Chinese environments  

NASA Astrophysics Data System (ADS)

The paper gives a set of new low power radio propagation models in the picocell environments suitable to some urban and rural conditions in China. A number of propagation measurements was taken by the authors using two antenna height of 3.2 m to 7.5 m at frequency 900 MHZ. Test settings were chosen in rural open areas, suburban streets, and urban streets, crossroads and overbridges in order to study propagation in variety of environments. Based on the obtained data in different environments, this paper takes the further steps to discuss the variations of signal strength with distance that have distinct near and far regions separated by a breakpoint and the effect of antenna height and type by analyzing the two ray model, and then gives a new propagation model, which was proved well-fitted to the measured results in some places. Moreover, this model was applied to make the radio propagation prediction for CT2 Campus Network, which is now running well. This also shows the practicality and reliability of the model in Chinese environments. Up to present, the measurement database has been established and a CAD software package which can predict the radio coverage area for rural and urban in China is going to be finished.

Shi, Jun; Zheng, Yi; Song, Junde

1995-09-01

89

Limitations and possible improvements of ionospheric models for radio propagation  

NASA Astrophysics Data System (ADS)

Factors that affect the applicability of ionospheric models used in connection with ground-to-ground HF propagation are discussed. Most such models are based on monthly medians of hourly observations by a worldwide network of ionosondes. Plots are given of diurnal variation of f0F2, ray paths for two frequencies (4.5 and 4.9 MHz) in a sunrise model ionosphere, observed and computed zenith angle during sunrise, and a comparison of overhead electron density profile with computed profile and true reflection heights for sunrise models, and other significant parameters. Sporadic E-layer tilts are considered.

Paul, A. K.

90

Building Penetration and Shadowing Characteristics of 1865 MHz Radio Waves  

Microsoft Academic Search

An in-building measurement campaign was conducted to characterize building properties pertaining to radio frequency propagation\\u000a and losses for personal communication system (PCS) applications. Measurements were made in and around seven buildings in urban\\u000a environments in three cities in The Netherlands. The mean building shadowing loss for all buildings, measured on the groundfloor,\\u000a was found to be 12.4 dB with a

Manish Panjwani; Gary Hawkins

91

Conference on the Ionosphere and Radio Wave Propagation, 3rd, University of Sydney, Australia, February 11-15, 1985, Proceedings  

NASA Astrophysics Data System (ADS)

Various papers on the ionosphere and radio wave propagation are presented. The subjects discussed include: day-to-day variability in foF2 at low latitudes over a solar cycle; semiempirical, low-latitude ionospheric model; remote sensing with the Jindalee skywave radar; photographic approach to irregularities in the 80-100 km region; interference of radio waves in a CW system; study of the F-region characteristics at Waltair; recent developments in the international reference ionosphere; research-oriented ionosonde with directional capabilities; and ionospheric forecasting for specific applications. Also addressed are: experimental and theoretical techniques for the equatorial F region; empirical models of ionospheric electron concentration; the Jindalee ionospheric sounding system; a semiempirical midlatitude ionospheric model; Es structure using an HF radar; short-term variations in f0F2 and IEC; nonreciprocity in Omega propagation observed at middle latitudes; propagation management for no acknowledge HF links; new techniques in ionospheric sounding and studies; and lunar effects in the ionospheric F region.

Cole, D. G.; McNamara, L. F.

1985-12-01

92

Propagation of VHF Radio Waves on Sea Routes in the South Polar Latitudes  

NASA Astrophysics Data System (ADS)

We present the results of meteorological and radiometeorological observations as well as the results of measurements of the attenuation factor of very-high-frequency (VHF) radio waves during the 28th Soviet Antarctic expedition in January March 1983. It is shown that radiometeorological parameters over the South ocean area in summer almost coincide with the corresponding averaged parameters over the land in winter. The main mechanism of radio-wave propagation at distances over 100 km is single scattering by turbulent fluctuations of the atmospheric refractive index. Absolute values of the running attenuation at high frequencies are low compared to those in other climatic areas.

Ivanov, V. K.; Lanovoy, V. N.; Shalyapin, V. N.; Egorova, L. A.; Vasil'Yev, A. S.; Mogila, A. A.

2005-07-01

93

New Phenomena in Propagation of Radio Polarizations due to Magnetic Fields on Cosmological Scales  

SciTech Connect

We discuss a new mechanism which could cause a rotation of polarization of electromagnetic waves due to magnetic fields on cosmological scales. The effect hinges on the geometrical phase of Pancharatnam and Berry, and causes a corkscrew twisting of the plane of polarization. The new effect represents an additional tool that allows possible intergalactic and cosmological magnetic fields to be studied using radio propagation. {copyright} {ital 1998} {ital The American Physical Society}

Ralston, J.P. [Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66044 (United States); Jain, P. [Physics Department, I. I. T., Kanpur, (India) 208016; Nodland, B. [Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627 (United States)

1998-07-01

94

Storm time, short-lived bursts of relativistic electron precipitation detected by subionospheric radio wave propagation  

Microsoft Academic Search

In this study we report on ground-based observations of short bursts of relativistic electron precipitation (REP), detected by a subionospheric propagation sensor in Sodankylä, Finland during 2005. In two ~4 hour case study periods from L = 5.2, around local midnight, several hundred short-lived radio wave perturbations were observed, covering a wide range of arrival azimuths. The vast majority (~99%)

Craig J. Rodger; Mark A. Clilverd; David Nunn; Pekka T. Verronen; Jacob Bortnik; Esa Turunen

2007-01-01

95

An SBR\\/image approach for radio wave propagation in indoor environments with metallic furniture  

Microsoft Academic Search

In this paper, we propose a deterministic approach to model the radio wave propagation channels in complex indoor environments. This technique applies the modified shooting-and-bouncing-ray (SBR) method to find the equivalent sources (images) for each launched ray tube. In addition, the first-order wedge diffraction from furniture is included and the diffracted rays also can be attributed to the corresponding images.

Shin-Hon Chen; Shyh-Kang Jeng

1997-01-01

96

Observations of the characteristics of propagation of VLF signals during meridian transits by Sco X-1  

SciTech Connect

The authors have conducted a series of studies of the VLF propagation characteristics during coordinated radio, optical, ultraviolet, and X-ray observations of the X-ray star Sco X-1. The observations were taken from 9-12 March 1989, a period when Sco X-1 was particularly active, and during a time of intense day-side solar activity. VLF sites were used to obtain phase and amplitude data from the VLF transmitter and from more remote transmitters. This paper gives preliminary results which compare the time-varying X-ray flux with the VLF phase data taken during the observation.

Beall, J.H.; Wood, K.S.; Kelly, F.J.

1990-05-03

97

Ionospheric disturbances during November 30-December 1, 1988. XI - Abnormal propagations of HF and VHF radio waves  

NASA Astrophysics Data System (ADS)

Unusual propagations of HF and VHF radio waves associated with a geomagnetic storm during the period from November 30 to December 1, 1988 are investigated using ionospheric data collected from Japan, China, and Taiwan. The increased field strength of the Japanese frequency standard signals (JJY 2.5 MHz and 5 MHz) which were received at Akita Radio Wave Observatory on the night of November 30 seem to have been caused by increased MUFs and/or scattering due to the disturbed ionosphere. The VHF-TV radio waves propagated from China were received at Kokubunji in Tokyo. One of the most probable mechanisms explaining this unusual propagation of VHF is a one-hop-F2 mode of propagation created by an ionosphere with an anomalously high f0F2. It was found out that these unusual HF and VHF propagations were attributed to unusual ionospheric conditions associated with these geomagnetic disturbances.

Ichinose, Masaru; Kamata, Mitsuhiro

1992-07-01

98

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

ERIC Educational Resources Information Center

|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

Marine Corps, Washington, DC.

99

Atmospherics in relation to source phenomena and radio wave propagation in the VHF, UHF, microwave and millimetre wave bands  

Microsoft Academic Search

Atmospherics originating from lightning flashes have been extensively studied by radio scientists for the last several decades, with a view to assessing and predicting the interfering effect on radio communication systems. Most of the earlier studies were confined to frequencies below about 30 MHz where ionospheric propagation can be exploited. The advent of satellite communication for a global coverage has,

A. K. Sen; M. K. Das Gupta

1987-01-01

100

Adaptive Radio Resource Control via Cascaded Neural Networks for Sequenced Propagation Estimation and Multi-user Detection in Third-generation Wireless Networks  

Microsoft Academic Search

A hybrid neural network approach is presented to predict radio propagation characteristics and multiuser interference and\\u000a to evaluate their combined impact on throughput, latency and information loss in third-generation (3G) wireless networks.\\u000a The three performance parameters influence the quality of service (QoS) for multimedia services for 3G networks. These networks\\u000a are based on hierarchical cell structures and operate in mobile

William S. Hortos

101

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

Microsoft Academic Search

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

E. M. Warrington; D. R. Siddle

102

Propagation characteristics of substrate integrated waveguide based on LTCC  

Microsoft Academic Search

The substrate integrated waveguide (SIW) is a new type of guided wave structure fabricated with periodic metallic via holes in a multilayered LTCC substrate. The SIW takes the advantages of both waveguide and microstrip structures, like the high-Q factor, high power capacity, small size, and the possibility of integration. In this paper, the propagation characteristics of the SIW are investigated,

Hao Li; Wei Hong; Tie Jun Cui; Ke Wu; Yu Lin Zhang; Li Yan

2003-01-01

103

Characteristics of Laser Beams Propagating in a Homogeneous Medium  

Microsoft Academic Search

Characteristics of laser beams propagating in a homogeneous medium were investigated in this paper. The wavelength, refractive index, and beam waist radius specify the divergence angles of laser beams. Based on the viewpoints of geometrical and physical optics the properties of optics field near and far from beam waist are evidently different. The main aim of this study was to

Ching-Yen Ho

104

On the usefulness of selected radio waves propagation models for designing mobile wireless systems in container terminal environment  

Microsoft Academic Search

The selected propagation models have been investigated. Results of the models' usefulness verification in terms of signal loss determination in container terminal environment have been analyzed and discussed. The applied research methodology has been described too. Future research aimed at developing new propagation model for designing mobile radio networks in the container terminal environment have been shortly presented.

Slawomir J. Ambroziak; Ryszard J. Katulski

2011-01-01

105

Application of frequency and space correlation of radio wave propagation conditions for the purpose of designing satellite communications links  

Microsoft Academic Search

The present consideration of the influence of rain effect prediction methods on 10-30 GHz frequency range satellite communications links gives attention to the possible application of the frequency and space correlation of radio wave propagation on earth-satellite paths. Different evaluation methods are discussed in light of results obtained by propagation experiments conducted under the Intercosmos program. Agreement is noted to

B. Balabanov; E. Aleksandrova; V. Sviatogor; V. Bykov; A. Kavetzki

1987-01-01

106

Long-term statistics related to evaporation duct propagation of 2 GHz radio waves in the English Channel  

Microsoft Academic Search

This paper presents long-term statistics additional to those previously published pertaining to evaporation duct propagation of UHF radio waves in the British Channel Islands, with particular focus on a completely over-sea 50 km transhorizon path. The importance of the evaporation duct as an anomalous propagation mechanism in marine and coastal regions is highlighted. In particular, the influence of various atmospheric

S. D. Gunashekar; E. M. Warrington; D. R. Siddle

2010-01-01

107

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

NASA Astrophysics Data System (ADS)

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

Blagoveshchensky, D.; Sergeeva, M.

108

A ray launching method for radio-mobile propagation in urban area  

Microsoft Academic Search

A computer code based on digitized terrain data was developed to estimate path losses and selectivity characteristics of the urban radio channel between a mobile located in a street and a base station on the roof of a high building. The principle of the program consists in a ray launching in projection on the horizontal plane supplemented by third-dimension considerations.

J. P. Rossi; J. C. Bic; A. J. Levy; Y. Gabillett; M. Rosen

1991-01-01

109

Ionospheric and Geomagnetic Activity Investigated Using Oblique Sounding Comparisons With an HF Radio Propagation Model  

NASA Astrophysics Data System (ADS)

Oblique HF sounder paths over ~2000km have been operating between New Zealand and Australia for a number of years. The maximum observed frequencies (MOF) are compared with predictions from the climatological HF radio skywave propagation model used by IPS. Variations from predicted median (MUF),lower (OWF) and upper decile frequencies may be interpreted in terms of ionospheric and geomagnetic activity and the effectiveness of parameterisation of ionospheric support for HF by the T-index examined. Closely spaced multiple paths provide opportunities to investigate small scale F2 layer structures.

Neudegg, D.; Layoun, M.; Hutchinson, S.

2008-12-01

110

Measurements and predictions of HF ground wave radio propagation over irregular, inhomogeneous terrain  

NASA Astrophysics Data System (ADS)

Measurements of radio propagation path loss were made over four paths in the 3 to 30 MHz band. The paths were of lengths up to 45 km. They ranged from smooth to mountainous terrain, from open areas with few or no man-made structures to suburban areas with building heights up to three stories, and from open spaces with little vegetation to heavily forested regions. On one path, measurements were made with and without snow cover. The measurements were made in the daytime and because of the short paths, the primary mode of propagation was ground wave. Measurements of the ground constants at each of the four measurement frequencies were made at the transmitter site using the wave-tilt measurement technique.

Adams, J. E.; Carroll, J. C.; Costa, E. A.; Ebaugh, D. R., Jr.; Godwin, J. R.; Haakinson, E. J.; Layton, D. H.; Smith, D.

1984-07-01

111

Propagation effects on radio range and noise in earth-space telecommunications  

NASA Astrophysics Data System (ADS)

Attention is given to the propagation effects on radio range and noise in earth-space telecommunications. The use of higher frequencies minimizes ionospheric effects on propagation, but tropospheric effects often increase or dominate. For paths of geostationary satellites, and beyond, the excess range delay caused by the ionosphere and plasmasphere is proportional to the total electron content along the path and inversely proportional to frequency squared. The delay due to dry air is usually of the order of a few meters while the delay due to water vapor (a few tens of centimeters) is responsible for most of the temporal variation in the range delay for clean air. For systems such as that of the Voyager spacecraft, and for attenuation values up to about 10 dB, increased sky noise degrades the received signal-to-noise ratio more than does the reduction in signal level due to attenuation.

Flock, W. L.; Slobin, S. D.; Smith, E. K.

1982-12-01

112

Source characteristics of Jovian narrow-band kilometric radio emissions  

NASA Astrophysics Data System (ADS)

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.

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

1993-07-01

113

Propagation characteristics of shock waves driven by gaseous detonation waves  

Microsoft Academic Search

We experimentally investigated propagation characteristics of the shock wave driven by a gaseous detonation wave emerging\\u000a from the open end of a cylindrical detonation tube. In the present study, we visualized the shock wave and exhaust flowfields\\u000a using a shadowgraph optical system and we obtained peak overpressure in the tube axial direction and the continuous shape\\u000a transformation of shock waves

S. Kato; S. Hashimoto; A. Uemichi; J. Kasahara; A. Matsuo

2010-01-01

114

Characteristics of Bupleurum falcatum plants propagated through somatic embryogenesis of callus cultures  

Microsoft Academic Search

Various characteristics including the saponin content in the root of Bupleurum falcatum plants propagated in vitro through somatic embryogenesis of callus cultures were compared with those of the plants propagated by seeds. The asexually propagated plants had an aerial part of more uniform characteristics than those of sexually propagated ones. However, both the mean and variance of root weight of

Noboru Hiraoka; Tomoko Kodama; Miho Oyanagi; Shihoko Nakano; Yutaka Tolnita; Nobuyuki Yamada; Osamu Iida; Motoyoshi Satake

1986-01-01

115

VHF Interferometry System for Detecting Anomalous Propagation of FM Radio Broadcasting Wave Related to Earthquake and its Preliminary Result  

NASA Astrophysics Data System (ADS)

Earthquake-related anomalous electromagnetic phenomena have been reported in various frequency ranges in a few decades. Investigation on the anomalous propagation of VHF transmitter waves is one of promising approaches on the short-term prediction and crustal activity monitoring. The anomalous propagation is considered to be generated by disturbances of the atmosphere above the epicenter or along the propagation path prior to large earthquakes. Consequently, over-horizontal propagation has been received. A recent study shows that the appearance of anomalies was significantly enhanced within 5 days before earthquakes with M ? 4.8. However, there is no information on the scattered place, that is, the direction of wave arrival. Therefore, a simple interferometer system for VHF radio wave to identify the position between space-time of earthquake-related atmospheric disturbances has been developed and installed at Chiba University. In this paper, we will show you the developed interferometer system and results of fundamental tests to evaluate the performance of developed and installed interferometer at Chiba. In addition, facts on invisible propagation of VHF radio wave obtained from 1-year continuous measurement at Chiba are described in this paper. Those are possible radio duct propagations and possible earthquake-related anomalous propagations.

Ohno, Nozomi; Tone, Yuka; Hattori, Katsumi; Yamamoto, Isao; Shimakura, Shin; Takano, Toshiaki

116

Bilateral sound propagation characteristics in electronic TMJ sound recording.  

PubMed

Temporomandibular Joint (TMJ) sounds, clicking and crepitation, are important signs of possible TM disorder or dysfunction (TMD). The sound are usually recorded and observed by stethoscope auscultation or palpation. Sound from one TMJ may propagate through head tissues and be recorded on the contra lateral side misleading the examiner to classify both joints as non-silent. Errors in localization of sound source may lead to an erroneous diagnosis. Widmalm et al. (1997) suggested a mathematical model for estimation of the sound propagation characteristics through the head tissues. A modified model applying the auto-spectral density and cross-spectral density of the signal was used to estimate the bilateral sound propagation characteristics of temporomandibular joint sounds from two subjects. The result indicates that the head tissues act as a bandpass filter causing strong attenuation in some frequency areas with little attenuation in others. The phase response of the transfer function provides a good mean to estimate the latency in time between sounds. PMID:11143344

Yang, K P; Koh, K H; Williams, W J; Widmalm, S E; Djurdjanovic, D

1999-01-01

117

Radio wave propagation in the Martian polar deposits: models and implications for radar sounding.  

NASA Astrophysics Data System (ADS)

In the present study the propagation of electromagnetic waves in the northern polar ice sheet of Mars is considered Several different scenarios of the structure of the polar deposits and composition of the ice compatible with previously published observational data are proposed Both analytical and numerical simulations of ultra wide band chirp radar pulse propagating through the cap are performed Approximate approach based on the non-coherent theory of the radiative transfer in layered media has been applied to the problem of the propagation of radar pulses in the polar caps Both 1D and 2D and 3D geometry applicable to the orbital and landed radar instruments are studied The side clutter and phase distortions of the signal are also addressed analyzed The possibilities of retrieval of the geological information depending on transparency of the polar cap for radio waves are discussed If the polar cap is relatively transparent the echo from the base of the sheet should be clearly distinctive and interpretable in terms of basal topography of the cap In the case of moderate optical thickness coherent basal echo is corrupted by strong multiple scattering in the layered structure However some conclusions about basal conditions could be made from the signals for example the subglacial lakes may be detected Finally optically thick polar caps prevent any sounding of the base so only the medium itself can be characterized by GPR measurements e g the impurity content in the ice can be found Ilyushin Y A R Seu

Ilyushin, Ya. A.

118

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

SciTech Connect

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.

Citrone, P.J.

1991-01-01

119

Characteristic Trends of Ultrastable Oscillators for Radio Science Experiments  

NASA Astrophysics Data System (ADS)

Telecommunication systems of spacecraft on deep-space missions also function as instruments for radio science experiments. Several missions augmented the radio communication system with an ultrastable oscillator (USO) in order to provide a highly stable reference signal for one-way downlink. Since the first quartz USO was flown on Voyager, the technology has advanced significantly, affording future missions higher sensitivity in reconstructing the temperature-pressure profiles of the atmospheres under study as well as the ability to study other physical phenomena of interest to radio science. The ultrastable class of oscillators has been flown on Voyagers I and II, the Galileo Orbiter, the Galileo Probe, Mars Observer, and Mars Global Surveyor. These have been quartz crystal resonators. The Cassini spacecraft will carry another quartz USO and two rubidium USOs for the Huygens Probe in support of the Doppler Wind Experiment. There are plans to fly USOs on several other future missions. This article surveys the trends in stability and spectral purity performance; design characteristics, including size and mass; and the history of these clocks in space.

Asmar, S. W.

1997-01-01

120

Light propagation characteristics of high-purity polystyrene  

NASA Astrophysics Data System (ADS)

Organic scintillation materials involve short wavelength light emitted from polymers containing aromatic ring moieties. We have characterized high-purity (>99.9%) polystyrene (PS) as a potential scintillator. It emits ultraviolet light with a 310-nm emission maximum. We demonstrate that the effective refractive index (1.67) for PS is a function of the emission spectrum. Light yield distributions generated by 137Cs and 207Bi radioactive sources were also characterized. The light attenuation length is 41.6 +/- 0.5 mm, which is ten times than expected. These results demonstrate that high-purity PS has important light propagation characteristics needed for organic scintillation materials.

Nakamura, Hidehito; Shirakawa, Yoshiyuki; Kitamura, Hisashi; Sato, Nobuhiro; Shinji, Osamu; Saito, Katashi; Takahashi, Sentaro

2013-10-01

121

The coherer: with simple demonstrations of the generation, propagation and detection of radio waves  

NASA Astrophysics Data System (ADS)

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 (tens of ohms). This state persists until the device is mechanically disturbed, whereupon the high resistance state is restored. This characteristic was employed by scientists in the 1890s to detect radio waves, and applied commercially by Marconi in his 'wireless' telegraph. It is easy to make a working coherer and directions are given for operating it from a distance with a spark transmitter based on a piezoelectric gas igniter. Incorporation of an 'aerial' and 'earth' enable a range of 7 m to be achieved and simple signals may be transmitted.

Mills, Allan

2010-03-01

122

Application of the theoretical reference ionosphere model for calculating HF-radiowave propagation characteristics  

NASA Astrophysics Data System (ADS)

We study the possibilities of the Theoretical Ionosphere Model (TIM) developed at the Institute of Solar-Terrestrial Physics, Siberian Branch, Russian Academy of Sciences, for calculating the HF-radiowave propagation characteristics. The results of simulation based on the TIM are compared with calculations based on the IRI model and data from experimental observations. Analysis of the results of calculations for the maximum usable frequency (MUF) have shown that with the same input data (coordinates of the receipt and transmission points, the route length, date, and time), the differences in the calculated MUFs (using two different models supplying radio routes with ionospheric information) amount to ˜1% in the daytime and reach 10% at night.

Kotovich, G. V.; Grozov, V. P.; Kim, A. G.; Oinats, A. V.; Romanova, E. B.; Tashchilin, A. V.

2010-08-01

123

UHF propagation prediction for wireless personal communications  

Microsoft Academic Search

Propagation characteristics of radio signals in the UHF band place fundamental limits on the design and performance of wireless personal communications systems, such as cellular mobile radio (CMR), wireless LANs, and personal communication services (PCS). Because the radio link is direct to each subscriber, the prediction of signal characteristics is most important in urban areas where subscriber density is high,

HENRY L. BERTONI; WALTER HONCHARENKO; L. R. Macel; HOWARD H. XIA

1994-01-01

124

Peer-to-peer low antenna outdoor radio wave propagation at 1.8 GHz  

Microsoft Academic Search

In this outdoor propagation study low antenna heights of 1.7 m are used at both the transmitter and the receiver to measure wideband (100 MHz baseband) power-delay profiles (PDPs) of the channel for a peer-to-peer communications system operating at 1.8 GHz. Rural and urban areas are studied in 22 different transmitter-receiver links, and the path loss and delay spread characteristics

Neal Patwari; Gregory D. Durgin; Theodore S. Rappaport; Robert J. Boyle

1999-01-01

125

Propagation characteristics of shock waves driven by gaseous detonation waves  

NASA Astrophysics Data System (ADS)

We experimentally investigated propagation characteristics of the shock wave driven by a gaseous detonation wave emerging from the open end of a cylindrical detonation tube. In the present study, we visualized the shock wave and exhaust flowfields using a shadowgraph optical system and we obtained peak overpressure in the tube axial direction and the continuous shape transformation of shock waves around the tube open end. We also obtained overpressure histories of the shock wave using piezo-pressure transducers within 201 m from the open end of the tube. We normalized and classified these results by four regions using non-dimensional pressure and distance which are independent of variety of mixture and tube diameter. In the vicinity of the open end of the tube, the shock wave is nearly planar and does not significantly attenuate, and the peak overpressure maintains approximately C-J pressure. Subsequently, the shock wave attenuates rapidly, transforming from quasi-spherical to spherical. Farther from the tube open end, the shock wave propagates with approximately sound characteristic so that the peak overpressure decreases proportional to 1/ r. Eventually, the shock wave begins to attenuate more rapidly than ideal sound attenuation, which may be due to the viscous effect.

Kato, S.; Hashimoto, S.; Uemichi, A.; Kasahara, J.; Matsuo, A.

2010-12-01

126

Radio frequency electromagnetic fields in large conducting enclosures: effects of apertures and human bodies on propagation and field-statistics  

Microsoft Academic Search

Radio frequency propagation in an electrically large resonant chamber (a screened room) was simulated by two models: a statistical combination of multiple resonant modes and a computational electromagnetic simulation [the transmission line matrix (TLM) method]. The purpose of this work was to investigate the effects of passengers and windows on electromagnetic fields (EMF) in aircraft and other vehicles. Comparison of

Martin P. Robinson; Janet Clegg; Andy C. Marvin

2006-01-01

127

Prediction of diffraction effects due to irregular terrain on radio wave propagation in the VHF and UHF bands  

Microsoft Academic Search

Many models have been proposed to represent diffraction effects on the propagation of radio waves over irregular terrain in the VHF and UHF bands. Predictions from these models have been compared with results from associated field-strength measurements available in extensive databases that also incorporate the technical parameters of thousands of VHF and UHF links. Some possible sources of the still

Emanoel Costa; Marco Aurelio Nunes da Silva; Markus Liniger

2011-01-01

128

Investigations of Angular Scattering and Multipath Properties of Tropospheric Propagation of Short Radio Waves beyond the Horizon  

Microsoft Academic Search

Experiments designed to investigate the potential communications capacity of uhf and shf tropospheric propagation beyond the radio horizon were conducted by the MIT Lincoln Laboratory on circuits of from 161 to 188 miles in length along the coastal regions of the northeastern United States. Some of these tests were made in cooperation with the Bell Telephone Laboratories and the late

J. H. Chisholm; P. A. Portmann; J. T. Debettencourt; J. F. Roche

1955-01-01

129

Utilizing a TDRS satellite for direct broadcast satellite-radio propagation experiments and demonstrations  

NASA Astrophysics Data System (ADS)

The NASA/VOA Direct Broadcast Satellite-Radio (DBS-R) Program will be using a NASA Tracking Data Relay Satellite (TDRS) satellite at 62 deg. West longitude to conduct live satellite S-band propagation experiments and demonstrations of satellite sound broadcasting over the next two years (1993-1994). The NASA/VOA DBS-R program has applied intensive effort to garner domestic and international support for the DBS-R concept. An S-band DBS-R allocation was achieved for Region 2 at WARC-92 held in Spain. With this allocation, the DBS-R program now needs to conduct S-band propagation experiments and systems demonstrations that will assist in the development of planning approaches for the use of Broadcast Satellite Service (Sound) frequency bands prior to the planning conference called for by WARC-92. These activities will also support receiver concept development applied to qualities ranging from AM to Monophonic FM, Stereophonic FM, Monophonic CD, and Stereophonic CD quality.

Hollansworth, James E.

1993-06-01

130

Utilizing a TDRS satellite for direct broadcast satellite-radio propagation experiments and demonstrations  

NASA Astrophysics Data System (ADS)

The NASA/VOA Direct Broadcast Satellite - Radio (DBS-R) Program will be using a NASA Tracking Data Relay Satellite (TDRS) satellite at 62 deg West longitude to conduct live satellite S-band propagation experiments and demonstrations of satellite sound broadcasting over the next two years (1993-1994). The NASA/VOA DBS-R program has applied intensive effort to garner domestic and international support for the DBS-R concept. An S-band DBS-R allocation was achieved for Region 2 at WARC-92 held in Spain. With this allocation, the DBS-R program now needs to conduct S-band propagation experiments and systems demonstrations that will assist in the development of planning approaches for the use of Broadcast Satellite Service (Sound) frequency bands prior to the planning conference called for by WARC-92. These activities will also support receiver concept development applied to qualities ranging from AM to Monophonic FM, Stereophonic FM, Monophonic CD, and Stereophonic CD quality.

Hollansworth, James E.

131

Utilizing a TDRS satellite for direct broadcast satellite-radio propagation experiments and demonstrations  

NASA Astrophysics Data System (ADS)

The NASA/VOA Direct Broadcast Satellite - Radio (DBS-R) Program will be using a NASA Tracking Data Relay Satellite (TDRS) at 62 deg West longitude to conduct live satellite S-band propagation experiments and demonstrations of satellite sound broadcasting over the next two years (1993-1994). The NASA/VOA DBS-R program has applied intensive effort to garner domestic and international support for the DBS-R concept. An S-band DBS-R allocation was achieved for Region 2 at WARC-92 held in Spain. With this allocation, the DBS-R program now needs to conduct S-band propagation experiments and systems demonstrations that will assist in the development of planning approaches for the use of Broadcast Satellite Service (Sound) frequency bands prior to the planning conference called for by WARC-92. These activities will also support receiver concept development applied to qualities ranging from AM to Monophonic FM, Stereophonic FM, Monophonic CD, and Stereophonic CD quality.

Hollansworth, James E.

132

GPS radio occultations with CHAMP: A radio holographic analysis of GPS signal propagation in the troposphere and surface reflections  

Microsoft Academic Search

Within the first nine months following the activation of the GPS radio occultation experiment aboard the low Earth orbiting satellite CHAMP, more than 25,000 occultation events have been observed. A radio holographic analysis of 3783 occultation events, recorded between 14 May 2001 and 10 June 2001, reveals that in about 20-30% of these events the received signal contains contributions from

G. Beyerle; K. Hocke; J. Wickert; T. Schmidt; C. Marquardt; C. Reigber

2002-01-01

133

GPS radio occultations with CHAMP: A radio holographic analysis of GPS signal propagation in the troposphere and surface reflections  

Microsoft Academic Search

Within the first nine months following the activation of the GPS radio occultation experiment aboard the low Earth orbiting satellite CHAMP, more than 25,000 occultation events have been observed. A radio holographic analysis of 3783 occultation events, recorded between 14 May 2001 and 10 June 2001, reveals that in about 20–30% of these events the received signal contains contributions from

G. Beyerle; K. Hocke; J. Wickert; T. Schmidt; C. Marquardt; C. Reigber

2002-01-01

134

Characteristics of Plane Wave Propagation in Biaxially Anisotropic Gyrotropic Media  

NASA Astrophysics Data System (ADS)

Propagation characteristics of electromagnetic waves at the interface between an isotropic regular medium and a biaxially anisotropic gyrotropic medium are investigated. The results indicate that the reflection and refraction properties of electromagnetic waves are closely dependent on the dispersion relation of the gyrotropic media, and that anomalous total reflection and negative refraction may occur. The existence conditions of total transmission are also considered. It is found that total transmission arises when the TE-polarized incident waves are normal to the interface and the physical parameters of the two media are chosen properly, which are quite different from the existence conditions of total transmission at the anisotropic left-handed material interface. Numerical results are given to validate our theoretical analysis.

Pan, Wei-Tao; Liu, Song-Hua; Qiu, Zhi-Liang

2012-03-01

135

The local characteristic function of interplanetary particle propagation  

NASA Astrophysics Data System (ADS)

An easily measurable intensity function which characterizes the interplanetary propagation of charged solar flare particles is presented. This function is nearly time invariant during a solar event despite the large variations of intensity and anisotropy, but varies from event to event. It characterizes the systematic and stochastic forces of the interplanetary magnetic field which focus and scatter the particles in pitch angle. The model of focused transport shows that this function is essentially determined by the local shape and amplitude of the pitch angle diffusion coefficient kappa (mu) and by the local value of the focusing length. The time profile of the solar particle injection is typically of negligible influence. The local characteristic function may be used as a powerful new tool for a systematic analysis of flare particle angular distributions, Examples are given.

Green, G.; Schlueter, W.

1985-08-01

136

Propagation characteristics of neutrons leaking from the accelerator facilities.  

PubMed

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

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

2004-01-01

137

Some characteristics of wave propagation observed during T-REX  

NASA Astrophysics Data System (ADS)

T-Rex observation campaign took place in Owens Valley during March and April 2006. The radiosondes launched during this campaign include profiles of the horizontal wind components, temperature, humidity and pressure. The observations are used together with analysis from the European Center of Medium Weather Forecast (ECMWF), and simulations from the Weather Research and Forecasting Model (WRF) to extend the field data to regions that were not covered by measurements. These data are then used to study some characteristics of waves observed during T-Rex. We found cases where waves are modified as they approach critical levels, or as they propagate through refractive regions. We also present cases where waves are reflected at breaking levels, and other cases which show secondary wave generation by shear instability.

Teitelbaum, Hector; Moustaoui, Mohamed; Mahalov, Alex

2010-05-01

138

Interference Characteristics Of Microwave Ovens in Indoor Radio Communications  

Microsoft Academic Search

The scarcity of suitable radio spectrum for indoor radio communications under the regulatory constraints has prompted endeavors to investigate means of utilizing the valuable channel bandwidths available within these constraints. The interference potential of the microwave oven is characterized in an attempt to render the ISM band it occupied useful for indoor radio communications. The Characterization process included an in-depth

J. Y. C. Cheah

1991-01-01

139

Radio characteristics of Broad Absorption Lines (BAL) quasars  

NASA Astrophysics Data System (ADS)

Broad absorption lines (BALs), seen in a small fraction of both the radio-quiet and radio-loud quasar populations, are probably caused by the outflow of gas with high velocities and are part of the accretion process. The presence of BALs is the geometrical effect and/or it is connected with the quasar evolution. It has been believed that BALQSO occurs only among radio-quiet galaxies. However, in 2000 Becker et al. discovered the representative sample of radio-loud objects which exhibits broad absorption troughs. The radio morphologies of radio-loud BAL quasars provide important additional information about their orientation and the direction of the outflow. Using the final release of FIRST survey combined with a A Catalog of BAL QSOs (SDSS/DR3), we have constructed a new sample of compact radio-loud BAL QSOs, which makes the majority of radio-loud BAL QSOs. The main goal of this project is to study the origin of BALs by analysis the BAL QSOs radio morphology, their orientation and jets evolution, using EVN at 1.6 GHz and VLBA at 5 and 8.4 GHz.

Ceglowski, Maciej

2011-07-01

140

FURTHER STUDY OF RAINFALL EFFECT ON VHF FORESTED RADIO-WAVE PROPAGATION WITH FOUR-LAYERED MODEL  

Microsoft Academic Search

In this paper, rainfall efiect on the VHF radio-wave propagation in a tropical forest is further studied in details. Theoretical study and experimental investigations are performed with the help of a four-layered model for forested environment. It is found that the lateral wave traveling along the air-canopy interface, the direct waves, and the ground re?ected waves are the main modes

Yu Song Meng; Yee Hui Lee; Boon Chong Ng

2009-01-01

141

Mobile propagation loss and delay spread characteristics with a low base station antenna on an urban road  

Microsoft Academic Search

Propagation loss and delay spread were studied experimentally, in order to design digital mobile communication systems. For propagation loss, the results were as follows, (i) When there are no obstacles on the road, the distance over which a radio wave propagates with only free-space loss increases with frequency. (ii) When there are obstacles (trucks and buses). and when the base

Shigeru Kozono; Akira Taguchi

1993-01-01

142

Over-Water Radio Propagation in the Frequency Range from 30 MHz - 300 GHz.  

National Technical Information Service (NTIS)

Contents-- Near-Water Propagation Effects on Systems at VHF/UHF (30 MHz-3 GHz): Normal Propagation, Anomalous Propagation, Data Gaps to be Filled, Systems Applications, Systems Adaptations; Near-Water Propagation Effects on SYstems at SHF (3-30 GHz); Near...

J. H. Richter

1986-01-01

143

The effect of air bridge height on the propagation characteristics of microstrip  

Microsoft Academic Search

The air bridge is often used for lowering the effective capacitance per unit length and fabricating crossovers in monolithic microwave integrated circuits (MMICs). The static and dynamic propagation characteristics of this type of transmission line are computed by utilizing the spectral domain technique. This analysis is used to demonstrate the significant changes in the propagation characteristic as a function of

Marc E. Goldfarb; Vijai K. Tripathi

1991-01-01

144

Computation of the key parameters of radio signals propagating through a perturbed ionosphere in the land-satellite channel  

NASA Astrophysics Data System (ADS)

An analysis of the key parameters of HF/UHF radio signals was carried out for land-satellite radio channels, which determine the effects of fading in a perturbed ionosphere. Using the parameters of the perturbed plasma, the effects of the absorption and phase fluctuations of radio signals are analyzed for a channel with fading. For the evaluation of the effect of scattering of a radio signal by ionospheric inhomogeneities in an approximation of small-scale scintillations, expressions for the root-mean-square (RMS) magnitude of signal intensity and phase scintillations are presented. Scintillation index ?{/I 2} that corresponds to variations in a signal under the conditions of multipath propagation with fading is investigated by using experimental data. It is shown that roughly ˜10% of inhomogeneities of the electron concentration in the F region of the ionosphere, perturbed during a magnetic storm, yield strong quickly fading radio signals in the VHF/UHF range with significant fluctuations (up to 1%) in the intensity of the signal and phase fluctuations (up to hundreds of radians). The calculated magnitudes of the scintillation index are in good agreement with experimentally observed data.

Blaunstein, N.; Pulinets, S. A.; Cohen, Y.

2013-04-01

145

Characteristics of the amateur radio means of the Arsene satellite  

Microsoft Academic Search

The Arsene (Ariane amateur radio satellite for space education) satellite is designed to provide amateur radio telecommunications services. Its equatorial orbit (20,000\\/36,000 km\\/0 deg) provides some 50 hours of continuous visibility by a radioamateur station. This radioamateur network will transmit in Packet AX25, SSB, and TTY modes and will provide voice transmission. In addition to the usual Very High Frequencies

Andre Cuisin

1992-01-01

146

Modeling of diffraction reflection and clutter loss in UHF radio wave propagation  

Microsoft Academic Search

In the scope of a project for the development of a propagation model, to be used to forecast path losses over operational links and for off-site interfering signals, the propagation of carrier signals is studied. A set of measurements (1270 measurements over 55 paths) is used to analyze several relatively simple models for UHF-propagation over rolling hilly, agricultural and forested

J. P. G. M. Linnartz

1988-01-01

147

Theoretical studies of very long-range propagation of short radio waves  

Microsoft Academic Search

Round-the-world high-frequency propagation is of interest for terrestrial communication links and for communication with satellites and rockets, because propagation in the ionospheric waveguide is possible at frequencies above the maximum usable frequency. The global properties of long-distance propagation are analyzed with allowance for the variability of the ionosphere.

A. V. Gurevich; E. E. Tsedilina

1975-01-01

148

RADIO BURSTS WITH EXTRAGALACTIC SPECTRAL CHARACTERISTICS SHOW TERRESTRIAL ORIGINS  

SciTech Connect

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.

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

149

Radio-Wave Propagation Into Large Building Structures—Part 1: CW Signal Attenuation and Variability  

Microsoft Academic Search

We report on our investigation into radio communications problems faced by emergency responders in disaster situations. A fundamental challenge to communications into and out of large buildings is the strong attenuation of radio signals caused by losses and scattering in the building materials and structure. Another challenge is the large signal variability that occurs throughout these large structures. We designed

William F. Young; Christopher L. Holloway; Galen Koepke; Dennis Camell; Yann Becquet; Kate A. Remley

2010-01-01

150

Frequency and phase fluctuations of radio waves during propagation in the Venus atmosphere  

Microsoft Academic Search

Radio-occultation data on the Venus atmosphere obtained with the Venera-10 probe are used to analyze the effect of atmospheric irregularities on frequency and phase fluctuations of radio waves at a wavelength of 32 cm; the experiments were carried out in March 1976. It is shown that, as in the case of amplitude fluctuations, when the line of sight is removed

A. I. Efimov; V. M. Razmanov; T. S. Timofeeva; O. I. Iakovlev

1982-01-01

151

Effect of solar variability on transionospheric radio wave propagation in the equatorial region  

Microsoft Academic Search

Growth of plasma instabilities in the post-sunset equatorial ionospheric F region gives rise to irregularities known by the generic name: equatorial spread F (ESF), which scatter incident VHF or higher frequency radio waves to produce scintillations on trans-ionospheric radio waves. Changes in large scale (> 10 km) electron density distribution in the equatorial and low latitude ionosphere due to electrodynamic

A. Bhattacharyya; B. Engavale; D. Tiwari; S. Bose

2006-01-01

152

Decimeter radio wave propagation in the turbulent plasma near the sun, using Venera 10 spacecraft  

Microsoft Academic Search

The 1976 Venus superior solar conjunction resulted in the occultation of the spacecraft Venera 10 by the sun at solar minimum. At the conjunction time, decimeter radio waves passed through the solar corona. The broadening of the spectrum line, as well as amplitude and frequency fluctuations, was observed over extensive distances of the radio link from the sun. The fluctuation

M. A. Kolosov; O. I. Yakovlev; A. I. Efimov; V. I. Rogal'sky; V. M. Razmanov; V. K. Shtrykov

1982-01-01

153

Radio wave propagation measurements for land-mobile satellite systems at 2.33 GHz  

Microsoft Academic Search

The performance of a mobile satellite communications link is dominated by roadside attenuation due to vegetation or manmade structures. Previous measurement campaigns characterized land-mobile satellite channels at UHF and L bands. In 1997, the FCC allocated S-band spectrum to the Digital Audio Radio Satellite (DARS) service to provide nationwide radio services to the North American continent via satellite. This article

L. Mousselon; R. M. Barts; S. Licul; G. Joshi

2003-01-01

154

Authentication of Radio Frequency Identification Devices Using Electronic Characteristics  

ERIC Educational Resources Information Center

|Radio frequency identification (RFID) tags are low-cost devices that are used to uniquely identify the objects to which they are attached. Due to the low cost and size that is driving the technology, a tag has limited computational capabilities and resources. This limitation makes the implementation of conventional security protocols to prevent…

Chinnappa Gounder Periaswamy, Senthilkumar

2010-01-01

155

Failure initiation and propagation characteristics of honeycomb sandwich composites  

Microsoft Academic Search

The energy absorbed during the failure of a variety of structural shapes is influenced by material, geometry and the failure mode. Failure initiation and propagation of the honeycomb sandwich under loading involves not only non-linear behavior of the constituent materials, but also complex interactions between various failure mechanisms. Therefore, there is a need for an improved understanding of the material

A. R. Othman; D. C. Barton

2008-01-01

156

Laser beam propagation characteristics of incoherently added diode bars  

Microsoft Academic Search

The second moment method of laser beam propagation allows for the calculation of the beam quality factor for any laser beam, or combination of laser beams. When several laser beams are added, their effective beam quality factor is not simply the sum of the individual beam quality factors, that is, it does not act as a linear operator. In this

Andrew Forbes; Sandile Ngcobo; Daniel Esser; Dieter Preussler; Christoph Bollig

2008-01-01

157

Characteristics of electromagnetic wave propagation in uniaxially anisotropic left-handed materials  

Microsoft Academic Search

We investigate the characteristics of electromagnetic wave propagation in uniaxially anisotropic left-handed media. We discuss mainly under what conditions anomalous reflection or refraction shall occur at the interface when propagating waves pass from one isotropic regular medium into another uniaxially anistotropic left-handed medium and under what conditions anomalous transmission shall occur when an evanescent wave is transmitted through a slab

Liangbin Hu; S. T. Chui

2002-01-01

158

Radio Wave Propagation along Earth-Space Paths in the Presence of a Multilayered Anisotropic Forest  

Microsoft Academic Search

Propagation of electromagnetic waves along earth-space paths in forest environments is analyzed in this paper, where the transmitter is placed in the air region above the vegetation, while the receiver may be in the air region or within the vegetation. This propagation model considers the forest as a horizontally stratified, anisotropic medium of canopy and trunk, bounded by ground below

Le-Wei Li; Chee-Keong Lee; Tat-Soon Yeo; Mook-Seng Leong

2002-01-01

159

Application of radio ground-wave propagation theory to the tomographic imaging of ground surfaces  

Microsoft Academic Search

Radiowave propagation over ground has been historically studied for predicting the radiated fields when the ground properties are known and the field has been well covered over the past hundred years. The theory of ground-wave propagation is applied to the inverse problem of the tomographic imaging of ground surfaces. After the inverse problem is formulated, an iterative technique for solving

Zhipeng Wu

2000-01-01

160

The Attenuation vs Frequency Characteristics of VLF Radio Waves  

Microsoft Academic Search

The theoretical dependence on frequency of the attenuation of the wave guide modes in vlf propagation is discussed in some detail. It is indicated that most of the published experimental data between 1 and 30 kc was compatible with the sharply bounded model of the ionosphere with a reflecting height of about 70 km during the day and 90 km

James Wait

1957-01-01

161

Propagation characteristic of atmospheric responses to abnormal warm SST in the Kuroshio Extension in winter  

NASA Astrophysics Data System (ADS)

The propagation characteristic of atmospheric responses to the abnormal warm sea-surface temperature (SST) in the Kuroshio Extension in winter was investigated using National Centre for Atmospheric Research CAM3.0. The results show that geopotential height perturbations at 500 hPa occupy much of the mid- and high-latitude areas north of 20°N and are stronger in winter and spring than in summer. Power spectrum analysis reveals that the perturbations contain both quasi-biweekly and intraseasonal oscillations. In the latitude band with maximum perturbation amplitude, the oscillations propagate mainly eastward. The centers of dominant oscillations are situated in the mid- and higher-latitude areas north to 40°N. The perturbations in the Arctic mainly propagate meridionally, whereas those south of the Arctic propagate zonally, at a steady-phase velocity basically. The propagation characteristics of wind perturbations and temperature perturbations are similar to those of geopotential height perturbations.

Xiaodan, Wang; Zhong, Zhong; Jianwen, Liu; Linlin, Qi

2012-04-01

162

Characteristics of coronal mass ejections associated with long-wavelength type II radio bursts  

Microsoft Academic Search

We investigated the characteristics of' coronal mass ejections (CMEs) associated with long-wavelength type II radio bursts in tim near-Sun interplanetary medium. Type II radio bursts in the decameter-hectometric (DH) wavelengths indicate powerful MHD shocks leaving the inner solar corona and entering the interplanetary medium. Almost all of these bursts are associated with wider and faster than average CMEs. A large

N. Gopalswamy; S. Yashiro; M. L. Kaiser; R. A. Howard; J.-L. Bougeret

2001-01-01

163

Statistical characteristics of radio waves in a layer with strongly extended random inhomogeneities  

Microsoft Academic Search

We obtain and analyze the transport equation for the frequency correlation function and for other correlation characteristics of radio waves which have passed through a medium with strongly extended random inhomogeneities. It is shown that the correlation characteristics of the waves depend on the parameters S~ and #, where S~ is the average square of the fluctuations of the geometrical

L. M. Erukhimov; P. I. Shpiro

1981-01-01

164

End-to-End Network Simulation Using a Site-Specific Radio Wave Propagation Model  

SciTech Connect

The performance of systems that rely on a wireless network depends on the propagation environment in which that network operates. To predict how these systems and their supporting networks will perform, simulations must take into consideration the propagation environment and how this effects the performance of the wireless network. Network simulators typically use empirical models of the propagation environment. However, these models are not intended for, and cannot be used, to predict a wireless system will perform in a specific location, e.g., in the center of a particular city or the interior of a specific manufacturing facility. In this paper, we demonstrate how a site-specific propagation model and the NS3 simulator can be used to predict the end-to-end performance of a wireless network.

Djouadi, Seddik M [ORNL; Kuruganti, Phani Teja [ORNL; Nutaro, James J [ORNL

2013-01-01

165

End-to-End Network Simulation Using a Site-Specific Radio Wave Propagation Model.  

National Technical Information Service (NTIS)

The performance of systems that rely on a wireless network depends on the propagation environment in which that network operates. To predict how these systems and their supporting networks will perform, simulations must take into consideration the propaga...

J. Nutaro S. Djouadi T. Kuruganti

2013-01-01

166

Programming an Artificial Neural Network Tool for Spatial Interpolation in GIS - A Case Study for Indoor Radio Wave Propagation of WLAN  

PubMed Central

Wireless communication networks offer subscribers the possibilities of free mobility and access to information anywhere at any time. Therefore, electromagnetic coverage calculations are important for wireless mobile communication systems, especially in Wireless Local Area Networks (WLANs). Before any propagation computation is performed, modeling of indoor radio wave propagation needs accurate geographical information in order to avoid the interruption of data transmissions. Geographic Information Systems (GIS) and spatial interpolation techniques are very efficient for performing indoor radio wave propagation modeling. This paper describes the spatial interpolation of electromagnetic field measurements using a feed-forward back-propagation neural network programmed as a tool in GIS. The accuracy of Artificial Neural Networks (ANN) and geostatistical Kriging were compared by adjusting procedures. The feedforward back-propagation ANN provides adequate accuracy for spatial interpolation, but the predictions of Kriging interpolation are more accurate than the selected ANN. The proposed GIS ensures indoor radio wave propagation model and electromagnetic coverage, the number, position and transmitter power of access points and electromagnetic radiation level. Pollution analysis in a given propagation environment was done and it was demonstrated that WLAN (2.4 GHz) electromagnetic coverage does not lead to any electromagnetic pollution due to the low power levels used. Example interpolated electromagnetic field values for WLAN system in a building of Yildiz Technical University, Turkey, were generated using the selected network architectures to illustrate the results with an ANN.

Sen, Alper; Gumusay, M. Umit; Kavas, Aktul; Bulucu, Umut

2008-01-01

167

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

ERIC Educational Resources Information Center

|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…

Mills, Allan

2010-01-01

168

Propagation of VHF Radio Waves on Sea Routes in the South Polar Latitudes  

Microsoft Academic Search

We present the results of meteorological and radiometeorological observations as well as the results of measurements of the attenuation factor of very-high-frequency (VHF) radio waves during the 28th Soviet Antarctic expedition in January March 1983. It is shown that radiometeorological parameters over the South ocean area in summer almost coincide with the corresponding averaged parameters over the land in winter.

V. K. Ivanov; V. N. Lanovoy; V. N. Shalyapin; L. A. Egorova; A. S. Vasil'Yev; A. A. Mogila

2005-01-01

169

A survey of ionospheric effects upon earth-space radio propagation  

Microsoft Academic Search

The frequency dependence is derived and the order of magnitude is presented for various ionospheric effects upon radio waves which have frequencies greater than the penetration frequency of the ionosphere. Among the phenomena considered are phase-path length change, refraction, frequency change, group-path delay, polarization rotation, and absorption. A detailed discussion is given of the mean value and variability of ionospheric

R. S. Lawrence; C. G. Little; H. J. A. CHIVERSt

1964-01-01

170

Effect of solar variability on transionospheric radio wave propagation in the equatorial region  

NASA Astrophysics Data System (ADS)

Growth of plasma instabilities in the post-sunset equatorial ionospheric F region gives rise to irregularities known by the generic name: equatorial spread F (ESF), which scatter incident VHF or higher frequency radio waves to produce scintillations on trans-ionospheric radio waves. Changes in large scale (> 10 km) electron density distribution in the equatorial and low latitude ionosphere due to electrodynamic effects associated with magnetic storms, influence the generation of ESF irregularities as seen in the pattern of occurrence of nighttime equatorial scintillations that may be specifically linked with magnetic activity. Besides such effects due to transient solar events, it is well known that the probability of occurrence of ionospheric scintillations caused by ESF irregularities as well as the strength of these scintillations during different phases of the solar cycle show a significant modulation of the generation and evolution of these irregularities by solar cycle related changes in the ionosphere and thermosphere. Evolution of spatial structure in the ESF irregularities determines the spatial scales that occur in the ground scintillation pattern during different phases of a scintillation event, and these spatial scales together with the dynamics of the irregularities determine the extent of degradation of transionospheric radio signals. Solar cycle effects on the structure and dynamics of ESF irregularities and hence on degradation of transionospheic radio signals during magnetically quiet periods, as also the effect of magnetic activity on the generation of ESF irregularities are discussed here on the basis of long term spaced receiver scintillation observations at an equatorial location.

Bhattacharyya, A.; Engavale, B.; Tiwari, D.; Bose, S.

171

Two-dimensional finite-element method calculation of propagation characteristics of axially nonsymmetrical optical fibers  

Microsoft Academic Search

In an axially symmetrical single-mode optical fiber, the polarization plane of the propagated HE,, mode is subject to unstable rotation due to Might changes in ambient conditions. Such an instability can be prevented by making the refractive index distribution in the fiber axially nonsymmetrical. This paper describes a two-dimensional, vectorial-wave finite-element method calculation of the propagation characteristics of such axially

Kimiyuki Oyamada; Takanori Okoshi

1982-01-01

172

Propagation Characteristics of Infrared Pulse Waves through Windblown Sand and Dust Atmosphere  

Microsoft Academic Search

The physics characteristics of the windblown sand and dust atmosphere at the sand bench of Yellow River in China are discussed.\\u000a The pulse distortion and time delay of infrared nanosecond pulse propagating through the atmosphere having sand and dust particles\\u000a are investigated at 1.06 and 3.8 ?m, respectively. It is shown that the delay of 10 ns laser pulse propagating through 5 km

Yang Ruike; Han Xiange; Hao Yue; Sun Zhongyu

2007-01-01

173

Experimental study of propagation characteristics for wireless communications in high-speed train cars  

Microsoft Academic Search

This paper describes the measurement results of propagation loss characteristics in high-speed train cars. We focus on the propagation loss in intra-car communications using a 2-GHz band and inter-car communications using a 5-GHz band. The measurement campaign is carried out using real train cars under both running and non-running conditions. The measurement results for intra-car communications indicate a waveguide effect

N. Kita; T. Ito; S. Yokoyama; Ming-Chien Tseng; Y. Sagawa; M. Ogasawara; M. Nakatsugawa

2009-01-01

174

Propagation characteristics of coupled surface plasmon polaritons in PVDF slab waveguides at terahertz frequencies  

NASA Astrophysics Data System (ADS)

We present the propagation characteristics of y-polarized coupled surface plasmon polariton (SPP) modes supported by ferroelectric polyvinylidene fluoride (PVDF) slab waveguides at terahertz (THz) frequencies. Employing a two-dimensional (2D) finite-element method, four y-polarized coupled SPP modes are obtained, where two modes exhibit long propagation lengths (˜700 ?m) and the others provide subwavelength confinement. It is shown that PVDF is a promising material for plasmon-like excitation in the terahertz regime and results in strong confinement of THz wave propagation in SPP-based coupled waveguides.

Shruti; Sinha, Ravindra Kumar; Srivastava, Triranjita; Bhattacharyya, Ragunath

2013-03-01

175

Ionospheric heating with oblique waves. Volume 2: Applications to high-frequency radio propagation  

Microsoft Academic Search

This volume presents numerical calculations of ionospheric electron density perturbations and ground-level signal changes for several electric field distributions produced by high-frequency (HF) transmitters. This volume applies theory developed in earlier work (Vol. 1) to the problem of possible self-effects of powerful obliquely incident radio waves. Using the results from this earlier work, we use field-driven changes in ionospheric electron

R. M. Bloom; E. C. Field Jr.

1989-01-01

176

Propagation of VHF Radio Waves on Sea Routes in the South Polar Latitudes  

Microsoft Academic Search

We present the results of meteorological and radiometeorological observations as well as the results of measurements of the attenuation factor of very-high-frequency (VHF) radio waves during the 28th Soviet Antarctic expedition in January–March 1983. It is shown that radiometeorological parameters over the South ocean area in summer almost coincide with the corresponding averaged parameters over the land in winter. The

V. K. Ivanov; V. N. Lanovoy; V. N. Shalyapin; L. A. Egorova; A. S. Vasil'yev; A. A. Mogila

2005-01-01

177

Analysis of Propagation Conditions of ELF Radio Waves on the ``Zeus''-Transbaikalia Path  

NASA Astrophysics Data System (ADS)

We consider the results of measurements of the absolute values of horizontal electric and magnetic components of the electromagnetic field of the ``Zeus'' ELF radio facility at frequencies 33, 44, 82, and 188 Hz, carried out in Transbaikalia. Electromagnetic-field variations during 17 semidiurnal sessions (about 204 hours of synchronous records) are analyzed. The length of the ``Zeus''-Transbaikalia path is approximately 4000 km.

Bashkuev, Yu. B.; Khaptanov, V. B.; Khankharaev, A. V.

2003-12-01

178

High frequence and automatic link establishment (HF and ALE) radio propagation test to Antarctica  

NASA Astrophysics Data System (ADS)

Recent federal/military standards in the area of automatic link establishment (ALE) for HF radios have been developed that coordinate frequency selection between communicating terminals, allowing them to adapt to skywave conditions. This study focused on evaluating the utility of these state-of-the-art radios in the polar environment. A quick-look evaluation of this technology was demonstrated over a radio circuit between Christchurch, New Zealand, and McMurdo Station, Antarctica. This transauroral link, operated by the U.S. Navy for the National Science Foundation, is the primary link for all operational, logistical, and emergency communications for U.S. operations between the Antarctic and the outside world. Daily plots of the measured signal to noise ratio, probability of bit error, and channel quality are presented and analyzed. Because of the initial success of this technology demonstration, additional experiments were designed for deployment in FY 1993 to answer not only operational issues, but also to collect data for further scientific studies and engineering improvements.

Gilles, P. E.; Katan, J. R.; Pease, B. L.

1994-02-01

179

Interstellar Weather -- Radio Wave Propagation Through the Turbulent Ionized Interstellar Medium  

NASA Astrophysics Data System (ADS)

Turbulence, or turbulent-like structures, in the interstellar medium when combined with motions of the medium and the pulsar-Earth line of sight lead to observable changes in pulse arrival time via both dispersion measure changes and multipath propagation or pulse broadening. In the Crab (PSR B0531+21) and Vela (PSR B0833-45) pulsars the column density variations are dominated by structures within the high-density material associated with the surrounding supernova remnants and pre-stellar matter. The Crab pulsar propagation parameters have been particularly disturbed during the past two years -- including a dispersion measure ``glitch'' with an amplitude of 0.1 pc cm(-3) in 1997 October. In the millisecond pulsar B1937+21 variable propagation effects are much smaller and are associated with the general intervening interstellar medium. Daily monitoring with small telescopes at NRAO Green Bank and at Jodrell Bank allow detailed inspection of the development of these propagation effects. We learn about structures in thermal plasma, ``interstellar weather'' along the line of sight, and can assess the impact of these effects on less frequently sampled precision timing programs.

Backer, D.; Wong, T.; Valanju, J.; Lyne, A.

1998-09-01

180

Water-Wave Effects on Radio Wave Propagation in the Ocean.  

National Technical Information Service (NTIS)

A sinusoidal surface profile is used to study by an exact method the effect of water waves on an electromagnetic field propagating downwards from the surface. It is assumed that the magnetic field is directed parallel to the surface corrugations. The resu...

M. L. Burrows

1970-01-01

181

European research activities on radio-wave propagation above 10 GHz in the framework of cost  

Microsoft Academic Search

The European joint research program on the influence of atmospheric conditions on electromagnetic wave propagation above 10 GHz implemented within the framework of the Eurocop-Cost (EUROpean Cooperation and Coordination in the field of Scientific and Technical research) projects in the field of telecommunications, is illustrated. The aims, type of cooperation envisaged, and criteria governing the research program are described. The

F. Fedi

1976-01-01

182

A fast time-domain wireless channel simulation tool for radio-wave propagation courses  

Microsoft Academic Search

The application of current implementations of electromagnetic simulators to realistic wireless communication problems requires excessively large computational time. As a result, computational electromagnetic tools have not been incorporated into the electromagnetics curricula yet. Building on a recent breakthrough in FDTD technology, we developed a novel simulation environment that enables the educational study of wave propagation in wireless links

Melissa Leung; Jackie Leung; Gerard S. Baron; Costas D. Sarris

2006-01-01

183

STUDY OF EFFECT OF RAIN AND DUST ON PROPAGATION OF RADIO WAVES AT MILLIMETER WAVELENGTH  

Microsoft Academic Search

The propagation of Electromagnetic waves in millimeter band is severely affected by rain rate, drop size and dust particle size in terms of attenuation, de-polarization and noise. The vertical looking radiometers will give vertical path attenuation due to rain as well as dust and line of sight link will give horizontal path attenuation whereas the satellite link gives slant path

O. P. N. Calla; J. S. Purohit

184

Radio wave propagation studies along an Earth-space satellite link  

Microsoft Academic Search

The use of superhigh microwave frequencies for satellite communications has many advantages, but its major drawback lies in the effects of atmospheric hydrometeors on electromagnetic wave propagation. One research effort under way to investigate this problem is being conducted by the European Space Agency, which will launch the Olympus-1 communications satellite in June 1989. One of this satellite's four payloads

Jacques Albert

1990-01-01

185

A full finite difference time domain implementation for radio wave propagation in a plasma  

Microsoft Academic Search

A full finite difference time domain methodology is developed for electromagnetic wave propagation in a plasma. The finite difference grid is consistent with central difference approximation of the curl, divergence and gradient operators that appear in the joint equations of Euler and Maxwell, and the coupling effects between the fluid velocity and the electric field. To accomplish the time advancement,

J. L. Young

1994-01-01

186

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

Microsoft Academic Search

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

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

2007-01-01

187

The effect of human body on indoor radio wave propagation at 57–64 GHz  

Microsoft Academic Search

Seven GHz bandwidth around 60 GHz frequencies has been released to develop high- rate short-range wireless data communication for a small area such as an office or a research lab. A regular propagation phenomenon in such environment is the shadowing of the Line-of-Sight (LOS) link caused by moving people. One research shows this phenomenon disconnects the LOS link for 2%

M. Fakharzadeh; J. Ahmadi-Shokouh; B. Biglarbegian; M. R. Nezhad-Ahmadi; S. Safavi-Naeini

2009-01-01

188

Antennas for VHF\\/UHF personal radio: A theoretical and experimental study of characteristics and performance  

Microsoft Academic Search

A theoretical analysis of the characteristics of small personal radio antennas for the 68- to 470-MHz frequency range is given. Representing the human body by a simplified lossy dielectric structure, the influence of the body on the performance of the antenna is investigated in detail, and it is shown how antenna impedance, gain, and radiation patterns can be calculated taking

JQRGEN BACH ANDERSEN; FLEWNG HANSEN

1977-01-01

189

Characteristics of Beyond-the-Horizon Radio Transmission  

Microsoft Academic Search

This paper summarizes the principal characteristics of tropospheric transmission beyond the horizon and compares them with some of the properties of ionospheric scatter transmission. Quantitative results are given on the dependence of the average signal level on distance and frequency, fading phenomena, bandwidth capabilities and realizable antenna gain. A short historical summary of beyond-horizon tropospheric transmission is also included.

Kenneth Bullington

1955-01-01

190

Characteristics of Airplane Antennas for Radio Range Beacon Reception  

Microsoft Academic Search

This paper gives the results of an investigation on the characteristics of airplane receiving antennas to determine whether an antenna arrangement could be devised which would have all the desirable electrical properties of the vertical pole antenna and yet be free from the mechanical difficulties encountered in the use of the pole antenna. The antennas studied include the inclined antenna

H. Diamond; G. L. Davies

1932-01-01

191

Frequency characteristics of the action of powerful radio-frequency radiation on the ionospheric F layer  

SciTech Connect

The results of an investigation of the effect of artificial ionospheric nonuniformities on the characteristics of LFM signals with vertical and oblique sounding of the ionosphere are presented. A classification of the effects observed on ionograms from vertical and oblique-sounding LFM ionosonde, owing to the effect of artificial nonuniformities of different scale, is given. It was found that powerful beams of radio waves have a characteristic effect on the ionospheric plasma under conditions when moving ionospheric disturbances appear.

Erukhimov, L.M.; Ivanov, V.A.; Mityakov, N.A.; Uryadov, V.P.; Frolov, V.A.; Shumaev, V.V.

1988-03-01

192

Interplanetary Propagation of Type-III Solar Radio Bursts Associated with Near-Relativistic Electron Events  

NASA Astrophysics Data System (ADS)

We have analyzed 125 interplanetary type III radio bursts detected between 25 KHz and 1 MHz by the WAVES/RAD1 experiment on Wind between 1997 and 2006. These events were selected for association with ACE/EPAM beam-like near-relativistic solar electron events. We have argued that these highly anisotropic near- relativistic electron events are well connected via the interplanetary magnetic field (IMF) to acceleration/release sites at the Sun. Consequently the associated type III events also should have good IMF connection to their release sites from the solar corona. We have made fits to the radius vs. time histories of the interplanetary type III bursts assuming that the solar wind electron density falls off inversely with radius squared. From linear fits to the leading edge of the high-resolution WAVES radio flux density, we found the apparent velocity (along an IMF spiral computed from the solar wind velocity at 1AU) of the leading edge of the type III bursts had a median value of 0.15c. We found that a significant fraction of the type III bursts were on field lines not passing directly through the Earth (confirmed by their emission frequencies remaining above the plasma frequency at Earth and the absence of associated <1keV low energy electrons). If we had assumed that the field lines containing the bursts had passed through the Earth, we would have deduced that the burst exciter was decelerating. However, once we allowed for that effect in our analysis, we found no evidence for interplanetary deceleration of the burst exciters. We then found that although ~75% of the bursts have an approximately constant speed, ~25% of the bursts were initially accelerating between the Sun and ~0.3 AU, consistent with a numerical simulation using statistical growth theory [Li et al, 2006].

Haggerty, D. K.; Roelof, E. C.

2008-05-01

193

Numerical analysis of near-infrared wave propagation characteristics in dielectric-coated parallel planar microstructural waveguides  

Microsoft Academic Search

In this paper, the properties of electromagnetic (EM) wave propagation in layered planar microstructural waveguides are investigated. Analytical and numerical results are presented on the propagation of a 1-?m EM wave in a parallel planar waveguide. Its walls are made of Au or Si, coated with a thin layer of SiO2 and separated by a fluid. The propagation characteristics of

W. E. A. Van Petegem; C. R. James; F. E. Vermeulen; A. M. Robinson

1997-01-01

194

Lg Phase Propagation Characteristics in Northern Eurasia from Peaceful Nuclear Explosion Data  

Microsoft Academic Search

Regional phases (Pn, Pg, Sn and Lg) play a significant role in monitoring small events for Comprehensive Test-Ban Treaty (CTBT). In all the regional phases, the Lg phase is usually the strongest, which is usually used to identify nuclear explosions from earthquakes. However, the Lg is weak or disappears in some tectonic areas. Therefore, studying propagation characteristics of the Lg

H. Li; I. Morozov; S. Smithson; L. Solodilov

2003-01-01

195

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

Microsoft Academic Search

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

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

1983-01-01

196

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

Microsoft Academic Search

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

Takeshi Fujita; Kohji Toda

2004-01-01

197

Characteristic impedance and propagation of the first higher order microstrip mode in frequency and time domain  

Microsoft Academic Search

This paper experimentally and theoretically confirms the validity of the definition proposed by Das (1996) for computing the complex characteristic impedance of the first higher order (EH1) microstrip mode. The normalized complex propagation constant and complex characteristic impedance of the microstrip obtained by the rigorous full-wave integral-equation method are also presented. To better understand the circuit behavior of the leaky

Shyue-Dar Chen; Ching-Kuang C. Tzuang

2002-01-01

198

Non-detection at Venus of high-frequency radio signals characteristic of terrestrial lightning.  

PubMed

The detection of impulsive low-frequency (10 to 80 kHz) radio signals, and separate very-low-frequency (approximately 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(-1), 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. PMID:11201733

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

2001-01-18

199

Simultaneous observation of VHF radio wave transmission anomaly propagated beyond line of site prior to earthquakes in multiple sites  

NASA Astrophysics Data System (ADS)

The VHF radio wave transmission anomalies propagated beyond line of site prior to earthquakes (M>4), (hereafter termed EQ-echo) have been observed more than 20 times from 2004 at the Erimo observatory (ERM) in Hokkaido, Northern Japan. A statistical relationship between magnitude of preceding earthquake and total duration time of the EQ-echo has been proposed (Moriya et al.2009). To confirm a region where the EQ-echo simultaneously observed for each earthquake, we installed another 3 observatory with approximately 5 km spacing in the surroundings of ERM. The EQ-echoes have been observed simultaneously at two observatories prior to four earthquakes since 2008. The initial time and duration of each EQ echo were same time in several cases but different at some minutes each other in other cases. The wave forms of the EQ-echoes were similar in both records. In the Fuyushima observatory (FYS, 10km away from ERM) , three-way antennas were installed at every 120 degree to detect an arrival direction of EQ-echoes. Simultaneous observations of EQ-echoes at ERM and FYS for the preceding EQ (M=4.7) that occurred in the Hidaka mountains revealed that this EQ-echo came from direction of the epicenter based on the FYS observation and this direction was consistent with that of EQ-echo observed simultaneously in ERM. Although some of simultaneous observed EQ-echoes were observed in same time completely at both observatories, but some of them were with time rag of duration of each EQ-echo between multiple observed sites. We discussed what these time rags mean by considering possibilities of moving of scattering objects, generation of a radio duct, and so on, as in response to this fact.

Yamashita, H.; Mogi, T.; Moriya, T.; Takada, M.; Morisada, M.

2010-12-01

200

Northern Exposure 1992: An investigation of transauroral HF radio skywave propagation  

NASA Astrophysics Data System (ADS)

The primary objective of the Northern Exposure 92 campaign was to assist in the evaluation of the performance capabilities of a wideband, high frequency, Rake radio receiver on a transauroral skywave channel. A review of the data collected on the transauroral channel during the Northern Exposure 92 exercises indicates that one is likely to encounter three types of signals on the channel: (1) a strong, specularly reflected signal characterized by the usual ionospheric dispersive delay spread and negligible Doppler spread, (2) strong specular multipath signals, exhibiting extensive delay and Doppler spread, and (3) weak scatter signals, exhibiting the widest delay and Doppler spreads. The nonspread reflected signals are encountered during magnetically quiet, daytime conditions where the ionosphere may be described as laminar. The strong, specular-multipath signals occur mostly at night and are associated with reflections from large scale irregularities of electron density characterized by strong horizontal gradients capable of reflecting signals whose frequencies lie below some equivalent maximum usable frequency (MUF) defined by the path, the background ionosphere, and the maximum electron density in the irregularity region. The weak scattered signals occur at night and are associated with volume scatter from the irregular medium. The scattered signals present the greatest challenge to communication systems with amplitudes approx. 30 dB less than those of reflected signals and with 2 sigma Doppler spreads as large as 30 Hz.

Wagner, Leonard S.; Goldstein, Joseph A.; Rupar, Michael A.; Kennedy, Edward J.

1993-09-01

201

Seasonal Variations of Rain Attenuation on Radio Propagation Paths in South Africa  

Microsoft Academic Search

Seasonal statistics of rain attenuation are analyzed to investigate the characteristics and variations associated with the different seasons in various climatic zones in South Africa. A 5-year locally observed rain rate data in these climatic zones has been utilized to estimate the cumulative distributions of rain attenuation for the different seasons in each zones. From these, appropriate figures of fade

M. O. Odedina; T. J. Afullo

202

Pulsar radio-emission propagation in the interstellar medium and certain properties of observed pulses  

Microsoft Academic Search

The effect of the interstellar medium on the observed properties of pulsar emissions is investigated theoretically. In order to provide an adequate analytical representation of pulsar emission in the interstellar medium, the amplitude-modulated noise model is used. Analytical expressions are obtained for observed pulsar characteristics by means of an average correlation function of intensity, which takes into account both interstellar

A. A. Bocharov

1982-01-01

203

Characteristics of multiple filaments generated by femtosecond laser pulses in air: Prefocused versus free propagation  

SciTech Connect

The characteristics of the multiple filaments formed by prefocused and freely propagating femtosecond laser pulses are investigated and compared. It is shown in our experiments that the diameter, length, stability, and interaction for the two cases can be quite different. The filaments formed by prefocused beam indicate dynamic spatial evolution with higher laser intensity and electron density. They have a typical diameter of 100 {mu}m are of shorter length. In the free propagation case, the filaments exhibit interesting properties such as hundred-meter propagation distance and mm-size diameter. Moreover, only the interaction of the filaments with the energy background affects the evolution of the filaments. Filament-filament interactions such as the filament splitting and merging were not observed in this case.

Hao Zuoqiang; Zhang Jie; Zhang Zhe; Zheng Zhiyuan; Lu Xin; Jin Zhan; Wang Zhaohua; Liu Yunquan [Laboratory of Optical Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100080 (China); Yuan Xiaohui [Laboratory of Optical Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100080 (China); State Key Laboratory of Transient Optics and Photonics, Xi'an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi'an 710068 (China); Zhong Jiayong [Laboratory of Optical Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100080 (China); National Astronomical Observatories, Chinese Academy of Science, Beijing 100012 (China)

2006-12-15

204

Balun with passband characteristic for ultra-wideband (UWB) impulse radio transmitter  

Microsoft Academic Search

This paper presents on-chip balun with capacitors connected in series (BCCS) has three-order high pass frequency characteristic. It can be used to suppress the power spectral density (PSD) of UWB impulse radio (UWB-IR) signal within 0.96–1.61GHz. With proper value of capacitor, BCCS has sharper cutoff edge than the balun without capacitor connected, which is desired for UWB-IR transmitter. The balun

Ruibing Dong; Ramesh K. Pokharel; Haruichi Kanaya; Keiji Yoshida

2012-01-01

205

Discharge characteristics of atmospheric-pressure radio-frequency glow discharges with argon\\/nitrogen  

Microsoft Academic Search

In this letter, atmospheric-pressure glow discharges in gamma mode with argon\\/nitrogen as the plasma-forming gas using water-cooled, bare copper electrodes driven by radio-frequency power supply at 13.56 MHz are achieved. The preliminary studies on the discharge characteristics show that, induced by the alpha-gamma coexisting mode or gamma mode discharge of argon, argon-nitrogen mixture with any mixing ratios, even pure nitrogen,

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

2006-01-01

206

Characteristics of radio-frequency, atmospheric-pressure glow discharges with air using bare metal electrodes  

Microsoft Academic Search

In this letter, an induced gas discharge approach is proposed and described in detail for obtaining a uniform atmospheric-pressure glow discharge with air in a gamma mode using water-cooled, bare metal electrodes driven by radio-frequency (13.56 MHz) power supply. A preliminary study on the discharge characteristics of the air glow discharge is also presented in this study. With this induced

Hua-Bo Wang; Wen-Ting Sun; He-Ping Li; Cheng-Yu Bao; Xiao-Zhang Zhang

2006-01-01

207

Radio Polarization Characteristics and Rotation Measures for Two Vela-like Pulsars from ATCA Observations  

Microsoft Academic Search

Using data from dual-band, pulsar-gated observations conducted with the Australia Telescope Compact Array, we present radio polarization characteristics and rotation measures for two young, Vela-like pulsars, PSRs J0940-5428 and J1301-6305. Both pulsars are highly polarized, consistent with previously noted trends for energetic pulsars. PSR J0940-5428 has measured on-pulse linear, circular, and absolute circular polarization fractions of 69 ± 2%, -6

F. Crawford; B. M. Gaensler; C. Tiffany

2005-01-01

208

The evanescent and propagating wave characteristics of the photonic quantum ring laser  

NASA Astrophysics Data System (ADS)

Title : The evanescent and propagating wave characteristics of the photonic quantum ring laser B. H. Park, J. C. Ahn, J. Bae, J. Y. Kim, O'Dae Kwon Department of Electrical and Electronic Engineering, Pohang University of Science and Technology, Korea. We present the wave propagation characteristics of photonic quantum ring(PQR) lasers[Phys. Rev. Lett. 82, 536(1999)] with a clear evidence of the evanescence-propagation crossover behavior. The intensity profile was obtained in detail using a fiber tip slanted to the disk plane with an angle of about 45^o. The results show that the 3--dimensional whispering gallery nature of the PQR laser always give rise to free propagations outside the disk after tunneling through the evanescent region, with crossover ranges from 55?m ~ 80?m for device diameters of 15?m ~ 36?m. we could calculate the width of the evanescently decaying region by using the conformal transformation method. The recent PQR spectra shows emission linewidth near 0.6Åbelow the spectrum analyzer resolution of 0.8ÅHP model 70951A].

Park, Byeonghoon; Ahn, Jungchak; Bae, Joongwoo; Kim, Junyoun; Kwon, O'dae

2001-03-01

209

Effect of sea water on the fatigue crack propagation characteristics of welds for offshore structures  

Microsoft Academic Search

The fatigue crack propagation characteristics of ASTM A36 steel weldments produced by both conventional surface welding operations\\u000a and underwater repair welding techniques were evaluated in both air and seawater. The resulting fatigue crack growth rates\\u000a were shown to depend sensitively on pore density and pore distribution, factors that varied significantly with welding procedure\\u000a and environment. Variations in growth rate were

D. K. Matlock; G. R. Edwards; D. L. Olson; S. Ibarra

1987-01-01

210

Propagation characteristics of extratropical planetary waves observed in the ATSR global sea surface temperature record  

Microsoft Academic Search

This paper examines the characteristics of planetary wave signatures that have been found in the Along Track Scanning Radiometer averaged sea surface temperature (ASST) record for 1991-1996. Longitude-time plots for every latitude between 5° and 50°, north and south, reveal westward propagating wave-like patterns at many locations, whose speed decreases with latitude like baroclinic Rossby waves. A two-dimensional Radon transform

Katherine L. Hill; Ian S. Robinson; Paolo Cipollini

2000-01-01

211

Propagation characteristics of ESD-induced electromagnetic pulses measured using optical E-field sensor  

Microsoft Academic Search

This paper describes the propagation characteristics of electromagnetic pulses induced by electrostatic discharge (ESD) in the far field. ESD energy spectra measured with an electric field sensor using a Mach-Zehnder interferometer are analyzed for the frequency band DC-1 GHz by short-time Fourier transform (STFT). Analytical results show that ESD energy in high frequency band (100 MHz-1 GHz) decrease more rapidly

K. Tajima; M. Masugi; N. Kuwabara

1999-01-01

212

CHARACTERISTICS OF ELECTROMAGNETIC WAVE PROPAGATION IN BIAXIAL ANISOTROPIC LEFT-HANDED MATERIALS  

Microsoft Academic Search

Abstract—This paper investigates the characteristics of electromag- netic wave propagation in biaxially anisotropic left-handed materials (BA-LHMs) theoretically and numerically. We discuss under what con- ditions the anomalous refraction or reflection will occur at the interface when a plane wave passes from one isotropic right-handed material into another BA-LHM. Meanwhile the refraction angle of the wave vector and that of the

Wei Ding; Liang Chen; H. Liang

2007-01-01

213

Characteristics of Radio Echoes from Meteor Trails: I. The Intensity of the Radio Reflections and Electron Density in the Trails  

Microsoft Academic Search

Recent observations of radio echoes reflected from meteor trails have given a large amount of information about the electron densities in the trails and the physical processes occurring in the atmosphere after the passage of the meteor. In this paper, which is Part I of three papers dealing with the work, formulae are derived for the intensity of the radio

A C B Lovell; J A Clegg

1948-01-01

214

Discharge characteristics of atmospheric-pressure radio-frequency glow discharges with argon/nitrogen  

SciTech Connect

In this letter, atmospheric-pressure glow discharges in {gamma} mode with argon/nitrogen as the plasma-forming gas using water-cooled, bare copper electrodes driven by radio-frequency power supply at 13.56 MHz are achieved. The preliminary studies on the discharge characteristics show that, induced by the {alpha}-{gamma} coexisting mode or {gamma} mode discharge of argon, argon-nitrogen mixture with any mixing ratios, even pure nitrogen, can be employed to generate the stable {gamma} mode radio-frequency, atmospheric-pressure glow discharges and the discharge voltage rises with increasing the fraction of nitrogen in the argon-nitrogen mixture for a constant total gas flow rate.

Wang Huabo; Sun Wenting; Li Heping; Bao Chengyu; Gao Xing; Luo Huiying [Department of Engineering Physics, Tsinghua University, Beijing 100084 (China); School of Public Health and Family Medicine, Capital University of Medical Sciences, Beijing 100069 (China); Beijing Center for Diseases Control and Prevention, Beijing 100013 (China)

2006-10-16

215

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

NASA Astrophysics Data System (ADS)

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.

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

2013-08-01

216

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

NASA Astrophysics Data System (ADS)

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.

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

2013-10-01

217

Transmission characteristics of VLF\\/ELF radio waves through the Jovian ionosphere  

Microsoft Academic Search

The propagation characteristics of whistler-mode waves through the plausible profiles of the Jovian ionosphere have been investigated by means of full-wave numerical computations. There were three different profiles examined in detail: an irregular profile based on Pioneer measurements, a more-idealized smoother profile, and a smooth profile with a low-altitude ledge. The whistler transmission losses for the Pioneer profiles with several

Ken Nagai; Kenji Ohta; Yasuhide Hobara; Masashi Hayakawa

1993-01-01

218

Turbid media optical properties derived from the characteristics of propagating laser radiation beams  

NASA Astrophysics Data System (ADS)

The possibility is studied to develop a straightforward analytical approach to the determination of the optical properties of liquid turbid media having forward-peaked scattering indicatrices. The approach is based on investigating the in-depth behavior of the radius and the axial intensity of a laser radiation beam propagating through the turbid medium. Based on the small-angle approximation, the detected forward-propagating light power spatial distribution, at relatively small or large optical depths along the beam axis, is obtained asymptotically in analytical form allowing one to derive relatively simple expressions of the extinction, reduced-scattering and absorption coefficients and the anisotropy factor of the medium through the characteristics of the propagating light beam. Preliminary experiments have also been performed, using Intralipid dilutions of different relatively low concentrations and measuring the cross-sectional radial distribution of the detected light power at different depths along the beam axis. The corresponding on-axis detected light power profiles have been measured independently as well. The experimental results are consistent with the analytical expressions obtained that allow one to estimate the optical coefficients and the anisotropy factor of the investigated media on the basis of the measured beam characteristics. The values obtained are near those predicted by other researchers.

Gurdev, Ljuan; Dreischuh, Tanja; Vankov, Orlin; Bliznakova, Irina; Avramov, Lachezar; Stoyanov, Dimitar

2013-09-01

219

Self consistent radio-frequency wave propagation and peripheral direct current plasma biasing: Simplified three dimensional non-linear treatment in the 'wide sheath' asymptotic regime  

SciTech Connect

A minimal two-field fluid approach is followed to describe the radio-frequency (RF) wave propagation in the bounded scrape-off layer plasma of magnetic fusion devices self-consistently with direct current (DC) biasing of this plasma. The RF and DC parts are coupled by non-linear RF and DC sheath boundary conditions at both ends of open magnetic field lines. The physical model is studied within a simplified framework featuring slow wave (SW) only and lateral walls normal to the straight confinement magnetic field. The possibility is however kept to excite the system by any realistic 2D RF field map imposed at the outer boundary of the simulation domain. The self-consistent RF + DC system is solved explicitly in the asymptotic limit when the width of the sheaths gets very large, for several configurations of the RF excitation and of the target plasma. In the case of 3D parallelepipedic geometry, semi-analytical results are proposed in terms of asymptotic waveguide eigenmodes that can easily be implemented numerically. The validity of the asymptotic treatment is discussed and is illustrated by numerical tests against a quantitative criterion expressed from the simulation parameters. Iterative improvement of the solution from the asymptotic result is also outlined. Throughout the resolution, key physical properties of the solution are presented. The radial penetration of the RF sheath voltages along lateral walls at both ends of the open magnetic field lines can be far deeper than the skin depth characteristic of the SW evanescence. This is interpreted in terms of sheath-plasma wave excitation. Therefore, the proper choice of the inner boundary location is discussed as well as the appropriate boundary conditions to apply there. The asymptotic scaling of various quantities with the amplitude of the input RF excitation is established.

Colas, L.; Jacquot, J.; Hillairet, J.; Goniche, M. [CEA, IRFM, F-13108 Saint-Paul-lez-Durance (France); Heuraux, S.; Faudot, E. [IJL-P2M UMR 7198 CNRS, F-54506 Vandoeuvre les Nancy (France); Crombe, K. [Department of Applied Physics, Ghent University, B-9000 Ghent (Belgium); Kyrytsya, V. [LPP-ERM/KMS, Association Euratom-'Belgian State', TEC Partner, Brussels (Belgium)

2012-09-15

220

Self consistent radio-frequency wave propagation and peripheral direct current plasma biasing: Simplified three dimensional non-linear treatment in the ``wide sheath'' asymptotic regime  

NASA Astrophysics Data System (ADS)

A minimal two-field fluid approach is followed to describe the radio-frequency (RF) wave propagation in the bounded scrape-off layer plasma of magnetic fusion devices self-consistently with direct current (DC) biasing of this plasma. The RF and DC parts are coupled by non-linear RF and DC sheath boundary conditions at both ends of open magnetic field lines. The physical model is studied within a simplified framework featuring slow wave (SW) only and lateral walls normal to the straight confinement magnetic field. The possibility is however kept to excite the system by any realistic 2D RF field map imposed at the outer boundary of the simulation domain. The self-consistent RF + DC system is solved explicitly in the asymptotic limit when the width of the sheaths gets very large, for several configurations of the RF excitation and of the target plasma. In the case of 3D parallelepipedic geometry, semi-analytical results are proposed in terms of asymptotic waveguide eigenmodes that can easily be implemented numerically. The validity of the asymptotic treatment is discussed and is illustrated by numerical tests against a quantitative criterion expressed from the simulation parameters. Iterative improvement of the solution from the asymptotic result is also outlined. Throughout the resolution, key physical properties of the solution are presented. The radial penetration of the RF sheath voltages along lateral walls at both ends of the open magnetic field lines can be far deeper than the skin depth characteristic of the SW evanescence. This is interpreted in terms of sheath-plasma wave excitation. Therefore, the proper choice of the inner boundary location is discussed as well as the appropriate boundary conditions to apply there. The asymptotic scaling of various quantities with the amplitude of the input RF excitation is established.

Colas, L.; Jacquot, J.; Heuraux, S.; Faudot, E.; Crombé, K.; Kyrytsya, V.; Hillairet, J.; Goniche, M.

2012-09-01

221

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

NASA Astrophysics Data System (ADS)

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 whistlers which penetrate the ionosphere close to the observing station is right-handed over a wide frequency range; and (2) some whistlers are found to have propagated over a distance of about 500 km. These whistlers exhibit a right-handed polarization at some frequencies and a left-handed polarization at other frequencies. However, the averaging of the observed polarizations over a wide frequency results in a nearly linear polarization; this agrees qualitatively with previous theoretical calculations by Crary (1961).

Okada, T.; Tanaka, Y.; Hayakawa, M.; Iwai, A.; Shimakura, S.

1983-12-01

222

Microscopic characteristics of fatigue crack propagation in aluminum alloy based particulate reinforced metal matrix composites  

SciTech Connect

Microscopic characteristics of fatigue crack propagation in two aluminum alloy (A356 and 6061) based particulate reinforced metal matrix composites (MMCs) were investigated by carrying out three point bending fatigue tests. The impedance offered by the reinforcing particles against fatigue crack propagation has been studied by plotting the nominal and actual crack lengths vs number of cycles. Surface observation shows that fatigue cracks tend to develop along the particle-matrix interface. In the case of Al (A356) MMCs, stronger interaction of fatigue crack with Si particles, as compared to SiC particles, was evident. In both MMC materials, particle debonding was more prominent as compared to particle cracking. The attempted application of Davidson's model to calculate [Delta]K[sub th] indicated that for cast MMCs the matrix grain including the surrounding reinforcing particles has to considered as a large hard particle'', and the grain boundary particles themselves behave like a hard egg-shell'' to strengthen the material.

Wang, Zhirui; Zhang, R.J. (Univ. of Toronto, Ontario (Canada). Dept. of Metallurgy and Materials Science)

1994-04-01

223

Geometric Localization and Polarimetric Localization: Space Weather Tools to Calculate CME Propagation Characteristics  

NASA Astrophysics Data System (ADS)

The geometric localization technique [Pizzo and Biesecker, 2004] utilizes a series of lines of sight from two space-based coronagraphs to determine gross propagation characteristics of coronal mass ejections (CMEs) in three-dimensional space. The polarimetric localization technique [Moran and Davila, 2004] uses the percent polarization observed by a single coronagraph to obtain a three-dimensional reconstruction of a CME. Both techniques can be used in near-real-time within an operational space weather forecast center. When these two independent techniques are used in conjunction with each other to analyze STEREO/Secchi/COR2 beacon data, they can provide significant constraints on the three-dimensional location and velocity, including speed and direction, for any Earth-directed CME. Here, we employ these techniques to the CME of 31 December 2007 and compare results on the speed and direction of propagation for this CME.

Pizzo, V. J.; de Koning, C. A.

2008-12-01

224

Radiation characteristics of quasi-periodic radio bursts in the Jovian high-latitude region  

NASA Astrophysics Data System (ADS)

Ulysses had a "distant encounter" with Jupiter in February 2004. The spacecraft passed from north to south, and it observed Jovian radio waves from high to low latitudes (from +80° to +10°) for few months during its encounter. In this study, we present a statistical investigation of the occurrence characteristics of Jovian quasi-periodic bursts, using spectral data from the unified radio and plasma wave experiment (URAP) onboard Ulysses. The latitudinal distribution of quasi-periodic bursts is derived for the first time. The analysis suggested that the bursts can be roughly categorized into two types: one having periods shorter than 30 min and one with periods longer than 30 min, which is consistent with the results of the previous analysis of data from Ulysses' first Jovian flyby [MacDowall, R.J., Kaiser, M.L., Desch, M.D., Farrell, W.M., Hess, R.A., Stone, R.G., 1993. Quasi-periodic Jovian radio bursts: observations from the Ulysses radio and plasma wave. Experiment. Planet. Space Sci. 41, 1059-1072]. It is also suggested that the groups of quasi-periodic bursts showed a dependence on the Jovian longitude of the sub-solar point, which means that these burst groups are triggered during a particular rotational phase of the planet. Maps of the occurrence probability of these quasi-periodic bursts also showed a unique CML/MLAT dependence. We performed a 3D ray tracing analysis of the quasi-periodic burst emission to learn more about the source distribution. The results suggest that the longitudinal distribution of the occurrence probability depends on the rotational phase. The source region of quasi-periodic bursts seems to be located at an altitude between 0.4 and 1.4 Rj above the polar cap region ( L>30).

Kimura, Tomoki; Tsuchiya, Fuminori; Misawa, Hiroaki; Morioka, Akira; Nozawa, Hiromasa

2008-12-01

225

Characteristics of RF Wave Propagation in Large-Diameter Plasma with Cusp Magnetic Field Configurations  

NASA Astrophysics Data System (ADS)

RF wave propagation, in the large-diameter (45 cm) plasma produced by a planar, spiral antenna, was investigated with the cusp magnetic field configurations. Measurements of the excited magnetic field amplitude and the phase were examined by a helicon wave dispersion relation, and the obtained results were consistent with the calculated ones by Transport Analyzing System for tokamaK/Wave analysis by Finite element method (TASK/WF) code. The wave characteristics depended on the gradient and the magnitude of the magnetic field near the line cusp position, and in the neighborhood of this position, this wave showed different behavior from the helicon wave observed in a uniform field.

Takechi, Seiji; Shinohara, Shunjiro; Fukuyama, Atsushi

1999-06-01

226

Schlieren Visualization of Acoustic Propagation Characteristics in a One-Dimensional Phononic Crystal  

NASA Astrophysics Data System (ADS)

The acoustic propagation characteristics of a finite one-dimensional water-glass phononic crystal (PC) are studied using the Schlieren visualization method, which is fast and non-invasive. The band structures of this PC are measured experimentally with continuous acoustic waves incident on it using the Schlieren method, and the results are highly consistent with the theoretical calculations. The dynamic acoustic field in the PC at different frequencies is imaged and the resonance phenomena in the components of the PC are observed. The results show that the Schlieren method is an effective means of studying the interactions between acoustic waves and PCs.

Jiang, Xue-Ping; Qian, Meng-Lu; Cheng, Qian

2013-08-01

227

Effects of laser parameters on propagation characteristics of laser-induced stress wave for gene transfer  

NASA Astrophysics Data System (ADS)

Laser-based gene delivery is attractive as a new method for topical gene therapy because of the high spatial controllability of laser energy. Previously, we demonstrated that an exogenous gene can be transferred to cells both in vitro and in vivo by applying nanosecond pulsed laser-induced stress waves (LISWs) or photomechanical waves (PMWs). In this study, we investigated effects of laser parameters on the propagation characteristics of LISWs in soft tissue phantoms and depth-dependent properties of gene transfection. Temporal pressure profiles of LISWs were measured with a hydrophone, showing that with a larger laser spot diameter, LISWs can be propagated more efficiently in phantoms with keeping flat wavefront. Phantoms with various thicknesses were placed on the rat dorsal skin that had been injected with plasmid DNA coding for reporter gene, and LISWs were applied from the top of the phantom. Efficient gene expression was observed in the rat skin that had interacted with LISWs propagating through a 15-mm-thick phantom. These results would be useful to determine appropriate laser parameters for gene delivery to deep-located tissue by transcutaneous application of LISWs.

Ando, Takahiro; Sato, Shunichi; Terakawa, Mitsuhiro; Ashida, Hiroshi; Obara, Minoru

2010-02-01

228

Analysis of radio wave reflection and transmission characteristics at reinforced concrete slab by numerical simulation and scaled model experiment  

Microsoft Academic Search

The authors present the reflection and transmission characteristics of radio waves at the reinforced concrete (RC) slab of buildings. The purpose of this study is to formulate the reflection and transmission characteristics of RC slab at various realistic conditions, for the effective use of mobile communications systems inside and from outside to inside of buildings. The object frequencies for this

H. Chiba; Y. Miyazaki

1999-01-01

229

Ultra-short-wave propagation in the jungle  

Microsoft Academic Search

The predominant characteristic of propagation in the VHF frequency range is the presence of a reflected wave which tends to cancel the direct wave and results in the received field being proportional to the product of the antenna heights, and inversely proportional to the square of the distance; and the radio gain being independent of frequency. For propagation in the

C. Burrows

1966-01-01

230

Spatial and temporal distribution of the VHF\\/UHF radio waves in built-up land communication links  

Microsoft Academic Search

We present a unified approach of the description of the spatial and temporal distribution of radio signals within built-up radio communication links. This approach is based on a multiparametric stochastic model, which takes into account the characteristic features of built-up terrain and peculiarities of radio wave propagation related with multiple reflections, diffraction and scattering phenomena caused by obstructions surrounding both

Nathan Blaunstein; Nathalie Yarkoni; Dmitry Katz

2006-01-01

231

Statistical Study of Ducted Propagation Characteristics of ULF Pi1B Pulsations  

NASA Astrophysics Data System (ADS)

Previous studies of ducting in the ionospheric waveguide, both theoretical and experimental, have focused on propagation characteristics of LH polarized electromagnetic ion cyclotron waves and have attempted to quantify various characteristics such as attenuation and propagation speed. However, no such study has been carried out with regard to irregular ULF disturbances (e.g., Pi1B pulsations), despite the fact that these waves, too, appear to be ducted. We present a statistical study of approximately 90 Pi1B events,using data gathered from an induction coil magnetometer array located in Svalbard Norway, with good alignment along the magnetic meridian: Hornsund (CGM Lat. = 76.97, MLT Midnight = 21:01), Longyearbyen (CGM Lat. = 78.20, MLT Midnight = 20:50), Ny Alesund (CGM Lat. = 78.93, MLT Midnight = 20:56). We find that Pi1B waves are ducted in a manner similar to EMIC waves and we discuss effects amounting to a highpass filter effect, where waves with long wavelengths (low frequencies) are not ducted.

Young, M. A.; Lessard, M.; Engebretson, M. J.

2009-12-01

232

A 6.5-day westward propagating planetary wave: Origin and characteristics  

NASA Astrophysics Data System (ADS)

A large (10-30 m s-1) 6-7 day period westward propagating planetary wave was seen in both ground radar and satellite data within the 80-100 km height regime during August and September 1993. Previous analyses of these data argue that it was most likely a manifestation of the (1-2) Rossby planetary wave commonly referred to as the 5-day wave, perhaps shifted to longer periods by interaction with the mean zonal winds. In this study the global scale wave model (GSWM [Hagan et al., 1993]) is used to analyze the characteristics of this westward propagating wave. We propose that the observed wave is not a Doppler-shifted 5-day wave but rather an unstable mode, drawing energy from unstable regions in the upper mesosphere, whose realization is global in scale. The concept of atmospheric instability is used to determine a likely source region, and the model is used determine the characteristic period, growth rate, and perturbation fields of the instability-driven wave.

Meyer, Christian K.; Forbes, Jeffrey M.

1997-11-01

233

Analysis of laser atmospheric propagation characteristic and optimization of laser rangefinder  

NASA Astrophysics Data System (ADS)

During the process of laser propagation in free space, energy attenuation is brought by atmospheric medium. One of the major problems about laser propagation is that atmospheric component does not remain constant within the whole altitude band. So working out the relatively accurate attenuation coefficient is a research interest of many researches for several years. On this basis of analysis of the atmospheric component distributing characteristic, simple and practical simulate approach was given to meet the needs of laser rangefinder. The main work is the research on 1.06?m YAG laser transmission characteristics in the atmosphere, and the atmosphere loss of the mathematical model is investigated. The paper discussed the influence of atmospheric attenuation on ranging ability of laser rangefinder and analyzed the atmospheric attenuation theoretical. It showed that when the attenuation coefficient ? increases the detectable distance decreases rapidly. In the condition of three transmission modes, which are ground-to-ground mode, ground-to-air mode and air-to-air mode, the relationships between atmospheric transmittance and different visibility, different zenith angle were analyzed. Minimal detectable power of laser rangefinder represents ranging ability in above-mentioned three different modes was formulated with atmospheric transmittance. Based on the results, we can adjust the experimental parameters and achieve more desirable results. It has positive influence for the design of laser rangefinder.

Wang, Wen-ting; Yang, Ying-ying; Zhao, Wei-fang; Yi, Xiao-jing; Ji, Jun-wen; Lin, Xue-chun

2013-09-01

234

Radio vision of the vertical structure of the layers and a study of radio-wave propagation conditions in the atmosphere using high-stability satellite signals  

Microsoft Academic Search

From an analysis of the CHAMP (Germany) and FORMOSAT-3 (Taiwan–USA) satellite data it follows that the second-order time derivative\\u000a of the eikonal (eikonal acceleration) and the Doppler frequency shift are two most important parameters indispensable for\\u000a the radio vision of layers in the atmosphere and the ionosphere. Measurements of the temporal evolution of the Doppler shift\\u000a permit one to study

A. G. Pavelyev

2009-01-01

235

Frequency Characteristics Measurement of Overhead High-Voltage Power-Line in Low Radio-Frequency Range  

Microsoft Academic Search

This paper presents measurement results of frequency characteristics of the high-voltage power line in low radio-frequency range: amplitude and phase characteristic, group delay, and input impedance. Measurement results for the 400-kV overhead power-line under operation are presented together with the developed measurement methodology. The methodology provides a method to measure amplitude and phase characteristics, group delay and the return loss

M. Zajc; N. Suljanovic; A. Mujcic; J. F. Tasic

2007-01-01

236

Morphology and scaling characteristics of propagating drying fronts in porous media delineated by neutron radiography  

NASA Astrophysics Data System (ADS)

Improved understanding of fluid interface displacement in porous media is of considerable interest for various applications ranging from enhanced oil recovery to modeling of soil water flow and infiltration. The formation of fluid interfaces, their roughening and dynamics in porous media are influenced by the properties of the fluids and the transport properties of porous media, among other factors. We analyzed wettability effects on the dynamics and morphology of a primary drying front receding into a porous medium during stage 1 evaporation (i.e., liquid flow from drying front to evaporation plane at the surface). Neutron radiography images obtained at 300 sec intervals and at spatial resolution of 0.1 mm enabled quantifying drying front roughening and fractal and scaling characteristics in Hele-Shaw cells packed with hydrophilic and hydrophobic sand (particle size 0.3-0.9 mm). Results indicate that wettability had a minor impact on the fractal characteristics of a drying front; however the configuration, velocity and pinning-depinning of the receding front were significantly affected by wettability. The roughness exponent of the drying front was estimated by averaging over all neutron radiography images. We observed no difference in roughness exponent values obtained from fronts propagating in hydrophilic and hydrophobic sand, suggesting that wettability is negligible relative to other driving forces. The experimentally-determined roughness exponent was higher than predicted by theory which may indicate that drying front roughening is dominated by quenched disorder (generated by random packing of the sand grains). We have also calculated the height-height front correlation function. These results show fronts propagating in hydrophilic and hydrophobic sands may not be characterized by a single Hurst exponent, thus exhibiting multiaffine properties. These were further investigated by calculating different orders of the correlation function. Our results provide new insights regarding drying front dynamics and morphology including roughening and scaling characteristics for fronts in drying of hydrophilic and hydrophobic porous media.

Shokri, N.; Sahimi, M.; Or, D.

2011-12-01

237

NASA Radiowave Propagation Program.  

National Technical Information Service (NTIS)

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 dissem...

F. Davarian

1990-01-01

238

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

NASA Astrophysics Data System (ADS)

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.

Krauss-Varban, D.; Omidi, N.

1993-06-01

239

Characteristics of Frontal Waves Propagating Along the Kuroshio Near the Separation Point From the Western Boundary  

NASA Astrophysics Data System (ADS)

Direct current measurements were conducted from April 2003 to March 2004 to investigate the characteristics of frontal waves propagating along the Kuroshio near the separation point from the western boundary. During the study period, the main stream of the Kuroshio flowed northeastward in the upper layer slightly offshore from the array of four mooring systems, while a southwestward current was observed in the intermediate layer on the coastal side of the array. Downstream-propagating waves detected as significant extended empirical orthogonal functions (EEOFs) are predominant over velocity fluctuations of periods shorter than 50~days, explaining 67% of the total variance. The five apparent wave groups have periods of 7--18~days, wavelengths of 220--380~km, and phase velocities of 22--30~cm~s-1, respectively, similar to the values reported in previous studies of upstream regions. Although the phase velocity at a given wavelength in the Kuroshio is lower than that in the Gulf Stream, the dispersion tendency (i.e., that phase velocity increases with decreasing period and wavelength) is the same for both currents. The relatively low phase velocity of the Kuroshio is considered to reflect its relatively low background velocity. Data regarding growth rate, vertical phase lags, and energetics suggest that kinetic energy in this region is transferred from small to large scales mainly via eddies resulting from baroclinic instability, which is possibly related to synoptic-scale path variability and the penetration of areas of high kinetic energy into the Kuroshio Extension.

Itoh, S.; Sugimoto, T.; Yasuda, I.

2008-12-01

240

The application of GTD and ray launching techniques to channel modelling for cordless radio systems  

Microsoft Academic Search

Propagation characteristics play a fundamental role in the design and implementation of radio systems. The application of broadband digital data services within the cordless environment requires close consideration of the dispersive nature of radio channels. A prediction algorithm is presented such that the propagation characteristics can be estimated for small-cell high-data-rate systems. Through the use of geometric optics and geometric

M. C. Lawton; J. P. McGeehan

1992-01-01

241

Propagation characteristics of relativistic solar cosmic rays during current sunspot cycle  

NASA Astrophysics Data System (ADS)

The occurrence of relativistic solar cosmic ray event is a rare phenomenon recorded by ground-based detectors during intense solar flares. Unusually a large number of solar particle events have been observed during August-October 1989 in the ascending phase of current solar cycle 22. The characteristic features of 29 Sep. 1989 event, which was the most energetic solar particle event after 23 Feb. 1956, are discussed. From the examination of this solar particle event, it is found that particles of extended energy range have been released simultaneously without any preferred direction of their arrival near the earth. The source flare region along with interplanetary conditions shows that particles covered their path through diffusive propagation from flare region to the earth.

Mishra, A. P.; Nigam, S. K.; Singh, R. L.

1992-12-01

242

Application of Distributed Raman Amplifier to Improve Link Gain and Noise Characteristic of WDM Radio over Fiber Network  

Microsoft Academic Search

we study the link gain and noise characteristic of a wavelength division multiplexing (WDM) radio over fiber (RoF) network using distributed Raman amplifiers (DRAs) or Erbium doped fiber amplifier (EDFA). Experimental results indicate that using DRAs can obtain higher link gain and signal to noise ratio (SNR) simultaneously. We also study the effects of stimulated Brillouin scattering, cross-talk and linear

Zhaohui Li; Ampalavanapillai Nirmalathas; Linghao Cheng; Chao Lu; Sheel Aditya

2005-01-01

243

Role of aspect-sensitive scattering at auroral inhomogeneities in the slip mechanism of radio-wave propagation  

Microsoft Academic Search

The effect of aspect-sensitive scattering of radio waves at magnetically oriented inhomogeneities of the auroral ionosphere on the energy output from the ionospheric wave channel is investigated. A good agreement of the results of the computation of the zone of optimal reception of signals scattered at ardsotrop~c inhomogeneities of the south auroral zone is obtained with the experimental data from

S. N. Matyugin; V. P. Uryadov

1977-01-01

244

Digital Radiolaenk: Vagutbrednings-Maetningar med Smalbandsteknik (Digital Radio Link: Wave Propagation Measurements Using Narrow Band Technique).  

National Technical Information Service (NTIS)

The report describes the results from measurements on a 34 MBit, 7 GHz digital radio link. Measurements have been performed during two different periods, autumn 1982 and summer 1983. Except fading statistics a number of interesting events with flat and fr...

S. Nilsson L. Ladell

1984-01-01

245

The role of the atmosphere in satellite geodesy, radio astronomy and other applications of trans-atmospheric propagation of radio waves  

NASA Astrophysics Data System (ADS)

The influence of the atmosphere on radio waves relevant to technological applications is investigated theoretically, and the associated errors are classified and defined. Range errors are defined as the length of the phase path minus the geometric distance, and range errors are divided into those related to the troposphere and those related to the ionosphere. Ground-path error and group delay are also mentioned as important errors which can influence the angle of arrival and direct ranging. Ionospheric range errors are defined in terms of first-order and higher-order errors including the second-order refraction error, and the pulse-travel-time delay is mentioned. The parameters required to estimate ionospheric errors include slant electron content, and mean ionospheric height, and the second-order errors require knowledge of the vertical electron content, the equivalent slant thickness, the height of the F-layer peak, and the shape factor.

Leitinger, R.

246

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

Microsoft Academic Search

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

Yue Ping Zhang; Qiang Li

2007-01-01

247

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

SciTech Connect

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.

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

248

A Broken Solar Type II Radio Burst Induced by a Coronal Shock Propagating across the Streamer Boundary  

NASA Astrophysics Data System (ADS)

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-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.

Kong, X. L.; Chen, Y.; Li, G.; Feng, S. W.; Song, H. Q.; Guo, F.; Jiao, F. R.

2012-05-01

249

Transmission characteristics of VLF/ELF radio waves through the Jovian ionosphere  

NASA Astrophysics Data System (ADS)

The propagation characteristics of whistler-mode waves through the plausible profiles of the Jovian ionosphere have been investigated by means of full-wave numerical computations. There were three different profiles examined in detail: an irregular profile based on Pioneer measurements, a more-idealized smoother profile, and a smooth profile with a low-altitude ledge. The whistler transmission losses for the Pioneer profiles with several ledges are found to be extremely large in a wide frequency range from 1 to 10 kHz at both day and night, even at a high magnetic latitude. The latitudinal dependence of the transmission loss for the smooth electron density profiles corresponding approximately to the lower edge of the Pioneer profiles, is estimated such that the loss at magnetic latitude greater than 50 deg is less than 10 dB at night and day. But the transmission loss exhibits a dramatic increase with the decrease in latitude from 30 deg about 40 deg, especially at higher frequency and at day. The presence of a possible ledge in the bottom ionosphere is found to result in an oscillatory behavior of transmission loss due to the development of a standing wave pattern between relative density maxima. The possible utilization of these theoretical characteristics is suggested to study the coupling of lightning energy to whistlers in the Jovian magnetosphere and also lightning properties from the whistler observations by future deep spacecrafts.

Nagai, Ken; Ohta, Kenji; Hobara, Yasuhide; Hayakawa, Masashi

1993-11-01

250

CRACK STRENGTH AND CRACK PROPAGATION CHARACTERISTICS OF HIGH STRENGHT METALS. Period Covered August 1, 1960May 31, 1961  

Microsoft Academic Search

A program is described to obtain engineering data on the crack ; propagation and residual strength characteristics of structural materials ; suitable for use in aerospace systems. Results of a fracture testing program for ; high strength sheet metals are presented. More than 500 sheet stock panels ; ranging in width from one to 18 in. and in thickness from

R. H. Christensen; P. H. Denke

1961-01-01

251

Propagation through nonlinear time-dependent bubble clouds and the estimation of bubble populations from measured acoustic characteristics  

Microsoft Academic Search

For several decades the propagation characteristics of acoustic pulses (attenuation and sound speed) have been inverted in attempts to measure the size distributions of gas bubbles in liquids. While this has biomedical and industrial applications, most notably it has been attempted in the ocean for defence and environmental purposes, where the bubbles are predominantly generated by breaking waves. Such inversions

T. G. Leighton; S. D. Meers; P. R. White

2004-01-01

252

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

NASA Astrophysics Data System (ADS)

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.

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

2012-03-01

253

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

SciTech Connect

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.

Oksuz, L.; Soberon, F.; Ellingboe, A.R. [National Centre for Plasma Science and Technology, School of Physical Sciences, Dublin City University, Collins Avenue, Glasnevin, Dublin 9 (Ireland)

2006-01-01

254

Transfer function of multimode fiber links using an electric field propagation model: Application to Radio over Fibre Systems.  

PubMed

We present a closed-form expression for the evaluation of the transfer function of a multimode fiber (MMF) link based on the electric field propagation model. After validating the result we investigate the potential for broadband transmission in regions far from baseband. We find that MMFs offer the potential for broadband ROF transmission in the microwave and millimetre wave regions in short and middle reach distances. PMID:19529286

Gasulla, I; Capmany, J

2006-10-01

255

New field of application of the IRI modeling - Determination of ionosphere transfer characteristic for radio astronomical signals  

NASA Astrophysics Data System (ADS)

We suggest a new field of application of IRI modeling - determination of ionosphere transfer characteristic (ITC) for radio astronomical signals (RAS). VHF and HF RAS are widely used for observations of the Sun and pulsars. It is necessary to take into account possible distortions of RAS in the Earth ionosphere. However, in contrast to modern navigation systems (GPS, GLONASS, GALILEO), where very accurate reconstruction of ionosphere parameters is a built-in function, in present-day radio astronomy a retrieve of ITC has not been appropriately worked out yet. It collides with increasing requirements to accuracy of the analysis of RAS amplitude profile and to the angular and polarizing resolution of radio telescopes of new generation. We have developed a method and software for calculation of the ionosphere measure of rotation (RM) and the measure of dispersion (DM). We used the ionosphere model IRI-2001, magnetic-field model IGRF-10 and values of ionosphere total electron content as deduced from GPS measurements. The obtained values of the ionosphere DM and RM were recalculated into characteristics of phase delay, Faraday amplitude modulation and polarization changes. We made calculations for different levels of geomagnetic activity and for different angular position of radio sources as well.

Afraimovich, E. L.; Yasukevich, Yu. V.

2009-06-01

256

Propagation Modes, Equivalent Circuits, and Characteristic Terminations for Multiconductor Transmission Lines with Inhomogeneous Dielectrics  

Microsoft Academic Search

The theory of wave propagation on Iossless multiconductor transmission lines with inhomogeneous dielectrics is developed using matrix analysis. The treatment is concise and complete and has the advantage of identifying propagation modes in a way that permits straightforward physical interpretation. The equivalent circuit for the general line is derived and its application to the solution of wave problems with reflections

KENNETH D. MARX

1973-01-01

257

Microwave propagation characteristics depending on base-station antenna height in an urban area  

Microsoft Academic Search

We have conducted propagation experiments assuming the environment of low base station antenna height and, hence, microcells in an urban area and have reported their results. In this report, we report the results of a propagation experiment in the microwave band that is conducted with transmission base station antennas installed at height sufficiently higher or lower than the surrounding building

K. Sakawa; H. Masui; M. Ishii; H. Shimizu; T. Kobayashi

2001-01-01

258

Propagation Characteristics of Whistlers Trapped in Field-Aligned Columns of Enhanced Ionization  

Microsoft Academic Search

Evidence from whistlers shows that the outer ionosphere contains columns or ducts of enhanced ionization. The theory of propagation in these ducts shows an upper cutoff frequency at one-half the gyrofrequency. The average propagation velocity for whistlers trapped in the ducts can be approximated by assuming that the energy follows along the ionization maximum with wave normals aligned with the

R. L. Smith

1961-01-01

259

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

Microsoft Academic Search

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

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

1996-01-01

260

Results of an investigation of conditions for long-range near-surface VHF radio-wave propagation  

NASA Astrophysics Data System (ADS)

It is noted that, in regions with sharply continental climates, significant near-surface temperature inversions can occur, leading to the appearance of large gradients of the refractive index and hence to a significant increase in the effect of refraction on the propagation of VHF waves. This phenomenon was investigated by measuring the vertical temperature in central Iakutiia in winter conditions. A high correlation was observed between the appearance of near-surface temperature inversions and the recording of anomalously long-range reflections from the earth surface.

Zlotnikov, M. F.; Olesov, L. A.

1989-08-01

261

Diagnostics of magnetic flux tube oscillations on the Sun based on fine-structure characteristics of the radio spectrum  

NASA Astrophysics Data System (ADS)

The possibility of obtaining information about oscillation processes in magnetic flux tubes on the Sun by analyzing the undulating frequency drift of the zebra pattern in the dynamic spectrum of solar radio emission is discussed. It is shown that the oscillatory variation in the frequency of zebra stripes can be associated with fast magnetoacoustic (FMA) oscillations in a flux tube, which lead to oscillations in the magnetic field strength and electron number density. The October 25, 1994 event recorded by the radio spectrograph of the Astrophysical Institute Potsdam is used as an example to demonstrate the possibility of determining the parameters of FMA oscillations and the physical conditions in coronal magnetic loops from the observed zebra-pattern characteristics.

Zlotnik, E. Ya.; Zaitsev, V. V.; Aurass, H.

2011-07-01

262

Hyperactive Chipmunk Radio  

Microsoft Academic Search

The hyperactive chipmunk radio modulates voice signals so that the radio waves behave the same in the radio medium as sound waves normally do in the acoustic medium. This is accomplished by segmenting the voice signal and compressing the segments in time before transmitting them through the radio channel. If the compression factor is correct, the distortion characteristics of the

G. H. McGibney; S. T. Nichols

263

Performance Analysis of a Built-In Planar Inverted Antenna for 800 MHz Band Portable Radio Units  

Microsoft Academic Search

The pattern averaging gain (PAG) method to estimate the average gain of mobile antennas in a multipath propagation environment is proposed. By using this method and a wire-grid model, the radiation characteristics of the planar invertedFantenna (PIFA) mounted on a portable radio case is analyzed. In particular, the variation of the antenna gain with the radio case dimensions and inclination

TOKIO TAGA; KOUICHI TSUNEKAWA

1987-01-01

264

Radiation Characteristics of Photonic Antenna for Optical Wireless Communication using Beam Propagation Method  

Microsoft Academic Search

The optical wireless communication is the only solution to the emerging next generation wireless communication. The photonic antennas play major role in the development of optical wireless communications. This photonic antenna transfers light energy from optical waveguide to free-space with high directionality and act as a matching device between optical source and channel (atmosphere). The analysis of light propagation through

L. R. D. Suresh; S. Sundaravadivelu

2007-01-01

265

Calculation of Electrical Parameters for Studies on Propagation Characteristic of PD along Transformer Winding  

Microsoft Academic Search

In order to investigate the propagation of partial discharge pulses in transformer winding, the simulation model of a 180 turns continuous disc type transformer winding based on multi-conductor transmission line (MTL) theory is constructed. According to the symmetry of windings, a 2D equivalent finite element model is set up under ANSYS environment. A modified method is proposed to calculate the

Zhiye Du; Ling Ruan; Chun Zhao; Jiangjun Ruan; Yunfei Wu; Tao Wang

2008-01-01

266

Stability and characteristic propagation speeds in superconducting cosmic and other string models  

Microsoft Academic Search

A bicharasteristic version is obtained for the differential equations of motion in a recently introduced formalism for the (fully covariant) treatment of a broad range of macroscopic ``thin'' string models, with applicability extending from ordinary (violin type) elastic strings to superconducting cosmic strings. In any locally stable state there are two bicharacteristic propagation speeds corresponding to group velocities of transverse

B. Carter

1989-01-01

267

Characteristic's of trophoblast cells migrating from first trimester chorionic villus explants and propagated in culture  

Microsoft Academic Search

We developed a method of propagating pure first trimester human trophoblast cells growing out of primary explants of mechanically derived chorionic villus fragments (Yagel et al, 1989; Graham et al, 1992). We have now extensively characterized these cells during their initial outgrowth and in long-term culture, employing a variety of markers and techniques as outlined below. By double label immunofluorescence

J. A. Irving; J. J. Lysiak; C. H. Graham; S. Hearn; V. K. M. Han; P. K. Lala

1995-01-01

268

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

NASA Astrophysics Data System (ADS)

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.

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

2009-04-01

269

Propagation studies of UWB transmission on human arm  

Microsoft Academic Search

Ultra-wideband (UWB) technology can provide very high data throughput over short distances using very low power-tens of folds lower than the best narrowband solution today. Research has proven that the UWB can be applied to realize a wireless body area network (WBANs). The combined effects of multipath and diffraction phenomena have degraded the propagation characteristics of conventional radio. In comparison,

C. T. Ong; J. Y. Hee; T. S. P. See; L. C. Ong

2008-01-01

270

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 ...

271

Source characteristics and locations of hectometric radio emissions from the northern Jovian hemisphere  

NASA Astrophysics Data System (ADS)

Northern Jovian hectometric (HOM) radio emissions, detected from high Jovian latitudes by the Unified Radio and Plasma Wave experiment on the Ulysses spacecraft, were observed at all Jovian longitudes. This emission was observed to be predominantly right-hand circularly polarized, but some left-hand circular polarization was observed implying the presence of O mode emissions from the northern Jovian hemisphere. Intense HOM emissions, with well-defined directions and polarizations, were often confined to similar longitudinal regions where intense HOM emissions were previously observed at low latitudes. The present analysis confirms that these northern HOM sources lie in the Jovian polar regions on magnetic field lines that pass through the Io plasma torus. The observations may be consistent with emission from either a filled cone beam or a longitudinal distribution of thin hollow cones.

Reiner, M. J.; Fainberg, J.; Stone, R. G.

1993-02-01

272

Microwave absorption characteristics of the clouds of Venus from Mariner 10 radio occultation  

Microsoft Academic Search

Measurements of received signal strength at S-band (13 cm) and X-band (4.8 cm) wavelengths during the radio occultation of Mariner 10 by Venus on February 5, 1974, are examined in order to study the structure and composition of the absorbing medium. The frequency excursions of the signals are determined and used to obtain the structure of the refractive index in

A. J. Kliore; C. Elachi; I. R. Patel

1977-01-01

273

Light confinement and propagation characteristics in plasmonic gap waveguides on silicon  

NASA Astrophysics Data System (ADS)

Plasmonic waveguiding structures have the ability to confine and propagate light over short distances, typically less than a hundred micrometers. This short propagation length is the price that is paid for confining light to dimensions on the order of a hundred of nanometers. With these scales in mind, several plasmonic devices can be proposed (e.g. wavelength multiplexors) and some of them have been already demonstrated such as Y junctions and directional couplers. Although the dimensions involved in such structures are below the diffraction limit, large-scale optical characterization techniques, such as transmitted power, are still employed. In this contribution, we present a characterization technique for the study of the guided modes in plasmonic gap waveguiding structures that resolves subwavelength-scale features, as it is based on atomic force microscope and on near field scattering optical microscope in guided detection.

Salas-Montiel, Rafael; Blaize, Sylvain; Bruyant, Aurélien; Apuzzo, Aniello; Lérondel, Gilles; Delacour, Cécile; Grosse, Philippe; Fédéli, Jean-Marc; Tchelnokov, Alexei

2011-02-01

274

On the longitudinal effect in whistler propagation characteristics at low latitudes  

NASA Astrophysics Data System (ADS)

The longitudinal effect of whistler propagation properties in the Chinese and Japanese meridian planes is studied using ray-tracing computations of nonducted propagation for the realistic nighttime density models at these meridian planes as deduced from satellite density measurements. A cross-over geographic latitude of 28 deg is found. A few degrees below this latitude, the ionospheric transmission condition of the downgoing whistlers in the Northern Hemisphere is easily satisfied in the Chinese meridian plane (geographic latitude = 114 deg E), whereas above this latitude the Japanese meridian plane (130 deg E) is more suitable for the ionospheric transmission. It is suggested that this longitudinal asymmetry results from the combined effect of the difference in the negative latitude gradient of the electron density in these two meridian planes and in the longitude gradient. Comparison with other studies of nighttime whistlers shows good agreement.

Zhou, H. B.; Xu, J. S.; Hayakawa, M.

1988-08-01

275

Flame propagation characteristics and flame structures of zirconium particle cloud in a small-scale chamber  

Microsoft Academic Search

Flame propagating through zirconium particle cloud in a small-scale vertical rectangle chamber was investigated experimentally.\\u000a In the experiments, the zirconium quoted 99% purity was used and the diameter of particles was distributed 1–22 ?m. The zirconium\\u000a dust was dispersed into the chamber by air flow and ignited by an electrode spark. A high-speed video camera was used to record\\u000a the

YiBin Ding; JinHua Sun; XueChao He; QiuHong Wang; Yi Yin; Yao Xu; XianFeng Chen

2010-01-01

276

Temporal propagation characteristics of ultrashort space- time Gaussian pulses in a laser satellite communication system  

Microsoft Academic Search

Tractable analytic expressions are obtained for the temporal broadening and scintillations of a narrowband, space-time Gaussian pulse propagating through clear-air weak atmospheric turbulence in a laser satellite communication system. The temporal broadening is deduced from the 1\\/e2 point of the temporal mean intensity and calculation of the temporal scintillations involves the second moment of intensity. Integral representations for the first

Deborah Eliza Tjin Tham Sjin Kelly

1998-01-01

277

Propagation characteristics of finite-width conductor-backed coplanar waveguides with periodic electromagnetic bandgap cells  

Microsoft Academic Search

Wave propagation along the finite-width conductor-backed coplanar waveguide (FW-CBCPW) with periodically loaded one-dimensional electromagnetic bandgap (EBG) cells proposed earlier by the authors is investigated theoretically and experimentally in this paper. The full-wave simulation in conjunction with Floquet's theorem is employed to find the dispersion diagram for characterizing the guided and leaky waves over a wide frequency range. For examining the

Shau-Gang Mao; Ming-Yi Chen

2002-01-01

278

Nonlinear scattering of radio waves by metal objects  

Microsoft Academic Search

Nonlinear scattering of radio waves by metal structures with resulting harmonic and intermodulation interference is analyzed from both theoretical and empirical standpoints, disregarding nonlinear effects associated with the nonlinear dependence of the electric or magnetic polarization vector on respectively the electric or magnetic field intensity in the wave propagating medium. Nonlinear characteristics of metal-oxide-metal contacts where the thin oxide film

V. B. Shteynshleyger

1984-01-01

279

Effect of Duty Cycle on the Characteristics of Pulse-Modulated Radio-Frequency Atmospheric Pressure Dielectric Barrier Discharge  

NASA Astrophysics Data System (ADS)

Using a one-dimensional fluid model, the pulse-modulated radio-frequency dielectric barrier discharge in atmospheric helium is described. The influences of the pulse duty cycle on the discharge characteristics are studied. The numerical results show that the dependence of discharge characteristics on the duty cycle is sensitive in the region of around 40% duty cycle under the given simulation parameters. In the case of a larger duty cycle, the plasma density is higher, the discharge becomes more intense, but the power consumption is higher. When the duty cycle is lower, one can get a weaker discharge, lower plasma density and higher electron temperature in the bulk plasma. In practical applications, in order to get a higher plasma density and a lower power consumption, it is more important to choose a suitable duty cycle to modulate the RF power supply.

Li, Xuechun; Wang, Huan; Ding, Zhenfeng; Wang, Younian

2012-12-01

280

Radio-Frequency, Atmospheric-Pressure Glow Discharges: Producing Methods, Characteristics and Applications in Bio-Medical Fields  

NASA Astrophysics Data System (ADS)

Radio-frequency (RF), atmospheric-pressure glow discharge (APGD) plasmas with bare metallic electrodes have shown their promising prospects in different fields. In this paper, based on the induced gas discharge approach, the discharge characteristics of RF, APGD plasmas using helium/oxygen mixture as the plasma working-gas are presented. The bio-medical effects of the helium RF APGD plasma jet acting on the gfp DNA and E. coli are also reported. Studies concerning the lethal and sub-lethal effects of the RF APGDs on the molecular and cell levels, which are related with the characteristics of the plasmas and their operation conditions are necessary in the future work based on a closer cooperation between the researchers in the field of the plasma science & technology and of the bio-medical science.

Li, He-Ping; Li, Guo; Sun, Wen-Ting; Wang, Sen; Bao, Cheng-Yu; Wang, Liyan; Huang, Ziliang; Ding, Nan; Zhao, Hongxin; Xing, Xin-Hui

2008-02-01

281

Study on the Characteristics of Sound Propagation in Shallow Underground by Air-Borne Sound  

NASA Astrophysics Data System (ADS)

Recently, the importance of type-II dilatational waves generated by air-borne sound was recognized, because it is very useful in shallow underground imaging without making contact with the ground surface. To reconfirm the existence of this wave, the propagation time of air-borne sound in sand is measured using an acryl sand tank, condenser microphones and a loudspeaker. The experimental result shows the existence of this wave and the possibility of a non-contact method of shallow underground imaging.

Moriya, Masahiro; Okamura, Tomohiro; Sugimoto, Tsuneyoshi; Shirakawa, Takashi; Nakamura, Kentaro

2003-05-01

282

Influence of radio-frequency electromagnetic field on optical characteristics of cast-iron surface  

NASA Astrophysics Data System (ADS)

Variations in spectral coefficients of specular reflection and Raman scattering spectra were detected during exposure of a cast-iron surface to an electromagnetic field in the radio-wave range. The observed variations were supposed to be caused by both field-induced changes in the surface morphological structure, density, and crystalline state and ordering of the carbon structures accompanied by a reduction in the amount of defects. Spectral reflectometry and Raman scattering methods were shown to be applicable to nondestructive remote monitoring of the morphological state of the cast-iron surface and changes in the structure and size of its microcrystalline graphite inclusions.

Azharonok, V. V.; Krat'koa, L. E.; Anisovich, A. G.; Bislukb, L. V.

2012-11-01

283

Propagation and damping characteristics of low-frequency waves in field-reversed configuration plasmas  

SciTech Connect

Propagation and damping properties of low-frequency waves in extremely high beta plasmas have been investigated in the field-reversed configuration plasma injection experiment apparatus. Two distinct wave modes were excited by different antenna geometry and the radial structures of their magnetic components were measured in detail. Due to the high beta nature of the plasma, the Alfven resonance predicted for the cold plasma vanished and the wave with small parallel wave number k{sub z}{approx}2.5 m{sup -1} propagated in a broad area across the separatrix. The wave exhibited moderate dissipation, which was suggestive of the resistive damping. The wave with large parallel wave number k{sub z}{approx}7.0 m{sup -1}, however, underwent quite strong damping inside the separatrix. Transit-time magnetic pumping, which converts the wave energy to the ion parallel kinetic energy, is most likely to be responsible for this strong damping since the wave's parallel phase velocity is close to the ion thermal velocity.

Inomoto, Michiaki; Yamamoto, Satoshi; Iwasawa, Naotaka; Kitano, Katsuhisa; Okada, Shigefumi [Center for Atomic and Molecular Technologies, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871 (Japan)

2007-10-15

284

Two dimensional photonic crystals with anisotropic constituents and their propagation characteristics  

NASA Astrophysics Data System (ADS)

Photonic crystals (PhCs) possess unique dispersion properties that can be exploited to enable novel photonic applications. These properties can also be used to significantly improve the performance of existing photonic devices. Many applications of PhCs such as waveguides, PC fibers and photonic cavities have been explored by using the presence of a photonic bandgap over a desired frequency range with a defect incorporated in the structure to allow only a desired mode to propagate. This strategy often requires a large index contrast between materials to create the band gap in the first place, which limits the materials that can be used for the photonic devices. On the other hand, many phenomena such as negative refraction, superprism, super-resolution, and slow light have been demonstrated based on unique spatial and temporal dispersion properties of a PhC and they are often observable with materials having a low index contrast. In my research we investigate self-collimation, another dispersion-related phenomenon of PhCs, that is manifested to some degree in all PhCs. In free space or homogeneous materials propagating electromagnetic waves spread due to diffraction effects, but a PhC in the region of self-collimation has essentially no diffraction and input beams spread over a range of input angles are collimated into a single direction. The phenomenon of beam-like propagation without divergence is important for many applications, including optical interconnects in an integrated circuit. Self-collimation provides a solution to beam control that does not require additional fabrication steps and can be used in conjunction with additional effects to further tailor the application needs. We develop a process to investigate the range of input angles and the degree of collimation of the beam inside the photonic crystal composed of anisotropic constituents. The optical properties of a photobleached 4-dimethylamino-N-methyl-4-stilbazolium-tosylate (DAST) crystal are used in our model to demonstrate the efficacy of the self-collimation features. In DAST we identified conditions where the divergence angle over a span of incident angles of 40 degrees can be less than 1 degree and the transmission remains high over the entire span of angles.

Siraj, Mohammad Masud

285

Observations of chorus at Saturn using the Cassini Radio and Plasma Wave Science instrument  

Microsoft Academic Search

Observations at Saturn of whistler mode chorus emissions have been obtained by the Cassini Radio and Plasma Wave Science instrument. Data from the first 45 orbits are analyzed, and the characteristics of the chorus emissions are discussed. Wave normal and Poynting vector measurements from the five-channel waveform receiver are used to examine the propagation characteristics of the chorus, and high-resolution

G. B. Hospodarsky; T. F. Averkamp; W. S. Kurth; D. A. Gurnett; J. D. Menietti; O. Santolik; M. K. Dougherty

2008-01-01

286

Propagation characteristics of lightning stepped leaders developing in charge regions and descending out of charge regions  

NASA Astrophysics Data System (ADS)

We conducted lightning observation campaign using VHF broadband digital interferometers (DITFs) in Darwin, Australia. We divided a stepped leader into two parts; the first part is a stepped leader propagating almost horizontally in the charge regions (ICR) of thunderclouds and the last part is a stepped leader descending out of the charge region (OCR). The VHF observation indicates that the channels of the stepped leaders OCR located by the DITFs were clearly broader than the channels of the stepped leaders ICR and dart leaders, indicating that the stepped leaders OCR descended in a heavily branched manner. High speed video camera images of a CG flash support the idea that stepped leaders OCR descend in a heavily branched manner.

Yoshida, Satoru; Akita, Manabu; Morimoto, Takeshi; Ushio, Tomoo; Kawasaki, Zen

2012-03-01

287

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

SciTech Connect

New, three-dimensional 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{sup +} and O{sup +} 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 {open_quotes}filter action{close_quotes} strongly depends on the relative concentration of He{sup +} and O{sup +} and is therefore sensitive to solar and magnetic activity. Ray-tracing results are based on a cold plasma dispersion relation, a semi-empirical model of plasma density, and the Mead-Fairfield magnetic field model. 43 refs., 8 figs.

Zhang, X.; Comfort, R.H.; Musielak, Z.E. [Univ. of Alabama, Huntsville, AL (United States); Moore, T.E.; Gallagher, D.L. [NASA Marshal Space Flight Center, Huntsville, AL (United States); Green, J.L. [NASA Goddard Space Flight Center, Greenbelt, MD (United States)

1993-09-01

288

Propagation Characteristics of Pc 1-2 Waves at High Latitude Ionospheric Waveguide  

NASA Astrophysics Data System (ADS)

ULF Pc1 geomagnetic pulsations have been observed from a ground array of search-coil magnetometers predominantly in the pre-noon to post-noon sector of Antarctica. With extensive coverage from geomagnetic latitudes of 62° to 87° and good alignment along the magnetic meridian, the five search-coil magnetometers operating aboard American Automated Geophysical Observatories (AGOs) and British Antarctic Survey (BAS) showed very clear ducting with spectral power attenuation of the waves in the waveguide. Halley Station, located at the lowest latitude, typically observed the highest spectral wave power and well-defined band-limited signatures with the same wave event, showing less wave power, found at the other four remote stations at higher latitudes. This is a clear implication of the ducting of the electromagnetic ion cyclotron (EMIC) waves in the ionospheric waveguide, which are generated from the equatorial magnetosphere along the geomagnetic field lines and transmitted to the ionosphere. Since the wave event was observed over a very wide range in latitude, the observation of the wave propagation will provide significant information on the ULF wave ducting in the waveguide and the source region. This study presents the observations of over 100 Pc1 events showing spectral power attenuation in the waveguide. The changes of the polarization properties such as ellipticity and polarization ellipse major axis direction during the propagation are also shown. It is shown both qualitatively and quantitatively how these behaviors are affected by specific ionospheric conditions (i.e. conductivity) and geomagnetic activity. In addition, CHAMP satellite data obtained in the ionosphere is also presented to validate the wave ducting.

Kim, H.; Young, M. A.; Lessard, M.; Engebretson, M. J.

2009-12-01

289

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

SciTech Connect

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.

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

2012-04-01

290

Characteristics of radio medical advice to fishing vessels in Scottish coastal waters.  

PubMed

We examined the emergencies arising on fishing vessels in Scottish Coastal Waters which required ship-to-shore radio medical advice. All calls to the service were identified for the 12-month period from August 2005. A total of 186 calls were received; 38% of calls were from fishing vessels. During the study period 53% of the calls were trauma-related, while 47% were medical emergencies. Our data suggest that there are many fishermen working offshore with chronic medical conditions. Overall, 85% of calls from fishing vessels resulted in evacuation as the outcome. Improved occupational health screening, compliance with health and safety legislation, and an evidence-based approach to remote medical care may improve seafarer self-care and reduce emergency evacuations. PMID:18430284

Mitchelson, Mark A; Ferguson, James; Armes, Roland; Page, J Graham

2008-01-01

291

Atmospheric propagation characteristics of highest importance to commercial free space optics  

NASA Astrophysics Data System (ADS)

There is a certain amount of disconnect between the perception and reality of Free Space Optics (FSO), both in the marketplace and in the technical community. In the marketplace, the requirement for FSO technology has not grown to even a fraction of the levels predicted a few years ago. In the technical community, proposed solutions for the limitations of FSO continue to miss the mark. The main commercial limitation for FSO is that light does not propagate very far in dense fog, which occurs a non-negligible amount of the time. There is no known solution for this problem (other than using microwave or other modality backup systems), and therefore FSO equipment has to be priced very competitively to sell in a marketplace dominated by copper wire, fiber optic cabling and increasingly lower cost and higher bandwidth wireless microwave equipment. Expensive technologies such as adaptive optics, which could potentially increase equipment range in clear weather, do not justify the added cost when expected bad weather conditions are taken into account. In this paper we present a simple equation to fit average data for probability of exceeding different atmospheric attenuation values. This average attenuation equation is then used to compare the expected availability performance as a function of link distance for representative FSO systems of different cost.

Korevaar, Eric J.; Kim, Isaac I.; McArthur, Bruce

2003-04-01

292

Optical imaging reveals characteristic seizure onsets, spread patterns, and propagation velocities in hippocampal-entorhinal cortex slices of juvenile rats.  

PubMed

We have combined recordings with extracellular microelectrodes or ion-sensitive electrodes and imaging of intrinsic optical signal changes to study the spatiotemporal pattern of seizure onset and spread during development. We have employed the entorhinal cortex-hippocampus brain slice preparation of juvenile rats at different stages of postnatal maturation. Three age groups were analyzed: 4-6 days (age group I), 10-14 days (age group II), and 20-23 days (age group III). Seizure-like events were induced by perfusion of slices with Mg(2+)-free artificial cerebrospinal fluid thereby removing the Mg(2+) block of the N-methyl-d-aspartate receptor. Seizure susceptibility was highest in age groups II and III. In age group I seizure-like events originated mainly in the hippocampus proper. Seizure-like events in age group II originated mainly in the entorhinal cortex and this tendency was even more pronounced in age group III. Invasion of the hippocampal formation via the perforant path-dentate gyrus and via the subiculum was seen in age groups I and II. In contrast, in age group III the hippocampus was invaded exclusively via the subiculum pathway. The velocity of spread at which seizure-like events propagated within different regions of the slice increased with postnatal age. The characteristics of onset, spread patterns, and propagation velocities as revealed by this study allow insight into the evolving properties of the developing brain. PMID:10964601

Weissinger, F; Buchheim, K; Siegmund, H; Heinemann, U; Meierkord, H

2000-08-01

293

The propagation and growth characteristics of rinderpest virus in HeLa cells  

Microsoft Academic Search

Summary After 95 passages in primary calf kidney cultures rinderpest virus proliferated readily in HeLa cells and produced characteristic cytopathic effects. A growth-curve experiment showed that the titre of intracellular virus was consistently 10–100 fold greater than that of free virus, thus conforming to the pattern usually described for the agents of measles and canine distemper. Whereas HeLa cultures infected

B. Liess; W. Plowright

1964-01-01

294

Radio Galaxies.  

ERIC Educational Resources Information Center

|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)|

Downes, Ann

1986-01-01

295

Monte Carlo simulation for temporal characteristics of pulse laser propagation in discrete random medium  

NASA Astrophysics Data System (ADS)

Study the laser pulses transmission time characteristics in discrete random medium using the Monte Carlo method. Firstly, the medium optical parameters have been given by OPAC software. Then, create a Monte Carlo model and Monte Carlo simulation of photon transport behavior of a large number of tracking, statistics obtain the photon average arrival time and average pulse broadening case, the calculation result with calculation results of two-frequency mutual coherence function are compared, the results are very consistent. Finally, medium impulse response function given by polynomial fitting method can be used to correct discrete random medium inter-symbol interference in optical communications and reduce the rate of system error.

Wang, Ping; Yuan, Hongwu; Mei, Haiping; Zhang, Qianghua

2013-08-01

296

CONFERENCES AND SYMPOSIA: Seventy years of the Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Waves Propagation (IZMIRAN) (Scientific session of the Physical Sciences Division of the Russian Academy of Sciences, 25 November 2009)  

NASA Astrophysics Data System (ADS)

A scientific session of the Physical Sciences Division of the Russian Academy of Sciences dedicated to the 70th anniversary of the Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation of the Russian Academy of Sciences (IZMIRAN) (Troitsk, Moscow region) was held in the conference hall of IZMIRAN on 25 November 2009. The following reports were put on the session agenda posted on the web site www.gpad.ac.ru of the Physical Sciences Division, RAS: (1) Gurevich A V (Lebedev Physical Institute RAS, Moscow) "The role of cosmic rays and runaway electron breakdown in atmospheric lightning discharges"; (2) Aleksandrov E B (Ioffe Physical Technical Institute, RAS, St. Petersburg) "Advances in quantum magnetometry for geomagnetic research"; (3) Dorman L I (IZMIRAN, Troitsk, Moscow region, CR & SWC, Israel) "Cosmic ray variations and space weather"; (4) Mareev E A (Institute of Applied Physics, RAS, Nizhnii Novgorod) "Global electric circuit research: achievements and prospects"; (5) Tereshchenko E D, Safargaleev V V (Polar Geophysical Institute, Kola Research Center, RAS, Murmansk) "Geophysical research in Spitsbergen Archipelago: status and prospects"; (6) Gulyaev Yu V, Armand N A, Efimov A I, Matyugov S S, Pavelyev A G, Savich N A, Samoznaev L N, Smirnov V V, Yakovlev O I (Kotel'nikov Institute of Radio Engineering and Electronics RAS, Fryazino Branch, Fryazino, Moscow region) "Results of solar wind and planetary ionosphere research using radiophysical methods"; (7) Kunitsyn V E (Lomonosov Moscow State University, Moscow) "Satellite radio probing and the radio tomography of the ionosphere"; (8) Kuznetsov V D (IZMIRAN, Troitsk, Moscow region) "Space Research at the Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation, Russian Academy of Sciences." Papers based on reports 2-8 are published below. The main contents of report 1 are reproduced in A V Gurevich's review, "Nonlinear effects in the ionosphere" [Phys. Usp. 50 1091 (2007)] and in the paper by A V Gurevich et al., "Nonlinear phenomena in the ionospheric plasma. Effects of cosmic rays and runaway breakdown on thunderstorm discharges" [Phys. Usp. 52 735 (2009)]. • Advances in quantum magnetometry for geomagnetic research , E B Aleksandrov Physics-Uspekhi, 2010, Volume 53, Number 5, Pages 487-496 • Cosmic ray variations and space weather, L I Dorman Physics-Uspekhi, 2010, Volume 53, Number 5, Pages 496-503 • Global electric circuit research: achievements and prospects, E A Mareev Physics-Uspekhi, 2010, Volume 53, Number 5, Pages 504-511 • Geophysical research in Spitsbergen Archipelago: status and prospects, V V Safargaleev, E D Tereshchenko Physics-Uspekhi, 2010, Volume 53, Number 5, Pages 511-517 • Results of solar wind and planetary ionosphere research using radiophysical methods, N A Armand, Yu V Gulyaev, A L Gavrik, A I Efimov, S S Matyugov, A G Pavelyev, N A Savich, L N Samoznaev, V M Smirnov, O I Yakovlev Physics-Uspekhi, 2010, Volume 53, Number 5, Pages 517-523 • Satellite radio probing and radio tomography of the ionosphere, V E Kunitsyn, E D Tereshchenko, E S Andreeva, I A Nesterov Physics-Uspekhi, 2010, Volume 53, Number 5, Pages 523-528 • Space research at the Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation, Russian Academy of Sciences , V D Kuznetsov Physics-Uspekhi, 2010, Volume 53, Number 5, Pages 528-534

2010-08-01

297

Statistical attenuation characteristics of radio waves with frequencies above 10 GHz on surface communication lines  

Microsoft Academic Search

The paper presents results of multiyear experimental studies of the statistical characteristics of microwave attenuation in the absence of rain. Experiments were conducted on a 12.65-km Dubna-Intercosmos link at frequencies of 11.5, 19.3, and 29.3 GHz, and on a 15.4-km link in Poland at a frequency of 18.6 GHz. Significant attenuation, associated with irregularities of the atmospheric refractive index, are

E. Aleksandrova; V. V. Sviatogor; V. N. Pozhidaev; A. Kavetski

1991-01-01

298

Crack Propagation through Phase-Separated Glasses: Effect of the Characteristic Size of Disorder  

NASA Astrophysics Data System (ADS)

We perform fracture experiments on nanoscale phase-separated glasses and measure crack surface roughness by atomic force microscopy. The ability of tuning the phase domain size by thermal treatment allows us to test thoroughly the predictions of crack front depinning models about the scaling properties of crack surface roughness. It appears that, in the range of validity of these depinning models developed for the fracture of brittle materials, our experimental results show a quantitative agreement with theoretical predictions: Beyond the characteristic size of disorder, the roughness of crack surfaces obeys the logarithmic scaling early predicted by Ramanathan, Erta?, and Fisher [Phys. Rev. Lett. 79, 873 (1997)PRLTAO0031-900710.1103/PhysRevLett.79.873].

Dalmas, Davy; Lelarge, Anne; Vandembroucq, Damien

2008-12-01

299

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

SciTech Connect

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 {alpha}-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.

Sun Wenting; Li Guo; Li Heping; Bao Chengyu; Wang Huabo; Zeng Shi; Gao Xing; Luo Huiying [Department of Engineering Physics, Tsinghua University, Beijing 100084 (China); School of Public Health and Family Medicine, Capital University of Medical Sciences, Beijing 100069 (China); Beijing Center for Diseases Control and Prevention, Beijing 100013 (China)

2007-06-15

300

Rolling Contact Fatigue Life and Spall Propagation Characteristics of AISI M50, M50 NiL, and AISI 52100. Part 1. Experimental Results (Preprint).  

National Technical Information Service (NTIS)

This paper is the first part of a three-part series which investigates the rolling contact fatigue (RCF) initiation and spall propagation characteristics of three bearing materials, namely AISI 52100, VIM-V AR AISI M50, and VIM-V AR M50NiL steels. Althoug...

J. W. Cooke K. L. Thompson L. Rosado N. H. Forster

2009-01-01

301

Rolling Contact Fatigue Life and Spall Propagation Characteristics of AISI M50, M50 NiL, and AISI 52100. Part 2. Stress Modeling (Preprint).  

National Technical Information Service (NTIS)

This is the second part of three-part series that investigates the rolling contact fatigue initiation and spall propagation characteristics of three bearing materials, namely AISI 52100, VIM-VAR M50, and VIM-VAR M50NiL steels. A systematic investigation o...

G. Levesque N. Branch N. H. Forster N. K. Arakere V. Svendsen

2009-01-01

302

Rolling Contact Fatigue Life and Spall Propagation Characteristics of AISI M50, M50 NiL, and AISI 52100. Part 3. Metallurgical Examination (Preprint).  

National Technical Information Service (NTIS)

This is the third part of a three-part series which investigates the rolling contact fatigue initiation and spall propagation characteristics of three bearing materials, namely AISI 52100, VIM-VAR M50, and VIM-VAR M50 NiL steels. While there is substantia...

H. K. Trivedi L. Rosado N. H. Forster W. P. Ogden

2009-01-01

303

Propagation des Fissures Courtes dans les Alliages pour Disques de Turbomachine a Hautes Caracteristiques (Crack Propagation in Heat Resistant Disk Alloys. Short Crack Propagation in Alloys for High Characteristic Turbomachine Disks).  

National Technical Information Service (NTIS)

The characterization of cast-forged Astroloy (trademark) high temperature fatigue crack propagation was addressed for small cracks and more particularly for the study of environment influence. Tests were carried on test specimens on disks. The experimenta...

P. Bernede L. Remy

1990-01-01

304

Structural characteristics of phosphorus-doped C60 thin film prepared by radio frequency-plasma assisted thermal evaporation technique.  

PubMed

Phosphorus doped C60 (P:C60) thin films were prepared by a radio frequency plasma assisted thermal evaporation technique using C60 powder as a carbon source and a mixture of argon and phosphine (PH3) gas as a dopant precursor. The effects of the plasma power on the structural characteristics of the as-prepared films were then studied using Raman spectroscopy, Auger electron spectroscopy (AES) and X-ray photo-electrons spectroscopy (XPS). XPS and Auger analysis indicated that the films were mainly composed of C and P and that the concentration of P was proportional to the plasma power. The Raman results implied that the doped films contained a more disordered carbon structure than the un-doped samples. The P:C60 films were then used as a coating layer for the Si anodes of lithium ion secondary batteries. The cyclic voltammetry (CV) analysis of the P:C60 coated Si electrodes demonstrated that the P:C60 coating layer might be used to improve the transport of Li-ions at the electrode/electrolyte interface. PMID:22630023

Arie, Arenst Andreas; Lee, Joong Kee

2012-02-01

305

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

NASA Astrophysics Data System (ADS)

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.

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

2013-05-01

306

A comparison of conventional and radio frequency defrosting of lean beef meats: Effects on water binding characteristics  

Microsoft Academic Search

The effect of defrosting rate (slow conventional air vs. fast radio frequency (RF) method) on water holding properties of lean beef meat (whole, minced and comminuted) was investigated using a conventional centrifugation method (drip loss), nuclear magnetic resonance relaxometry (NMR) and dielectric spectroscopy. Tempering by radio frequency (RF) or a conventional air method had no subsequent effect (P?0.05) on drip

K. W. Farag; E. Duggan; D. J. Morgan; D. A. Cronin; J. G. Lyng

2009-01-01

307

Fatigue crack propagation characteristics of 2 1/4 Cr-1 Mo steel in liquid lithium at 773 K  

NASA Astrophysics Data System (ADS)

The potential use of liquid lithium, in conjunction with several of the advanced energy generation systems currently under study, has led to many recent investigations of the effects of liquid lithium on the engineering properties of various materials.12 Particular emphasis has been placed on understanding the corrosion processes in liquid lithium which lead to material degradation. The mode of corrosion attack has been shown to be controlled by temperature,3 nitrogen content in the liquid lithium,3 alloy composition,4 and heat treatment.5 For example, an increase in nitrogen content in the liquid lithium accelerates both weight loss and grain boundary penetration rates in 304 L stainless steel,3 and alters the relative rates of both processes to promote grain boundary penetration at high nitrogen concentrations. The grain boundary penetration rate in pure Armco iron has been shown to be enhanced with the application of either a tensile or compressive stress.6 Furthermore, lithium penetrated grain boundaries have been shown to lack mechanical integrity.1 Thus for proper design of materials to contain liquid lithium, the interaction of stress with the various corrosion processes must be understood. In this note, the results of a study of the fatigue crack propagation characteristics of 2 1/4 Cr-1 Mo steel in liquid lithium are presented.

Spencer, Robert E.; Deweese, Steven K.; Matlock, David K.; Olson, David L.

1980-10-01

308

Comparison between two different antennas for UWB on-body propagation measurements  

Microsoft Academic Search

The effect of two different antenna types on radio propagation in ultrawideband (UWB) on-body channel measurement are analyzed. Statistical path loss parameters and time domain channel characteristics [mean delay and root mean square (rms) delay spread] are extracted from measurement data. Reduction in rms delay spread is experienced when using printed horn shaped self-complementary antennas (HSCA) for specific body area

A. Alomainy; Y. Hao; C. G. Parini; P. S. Hall

2005-01-01

309

Degradation of Base Station Radio Reception at UHF and VHF: Due to the Effects of Automobile Ignition Systems and Multipath Propagation.  

National Technical Information Service (NTIS)

The report contains the findings in the second of a two-part study on the degradation of VHF and UHF land mobile radio reception. Observations for this study on base station reception were made at 37.5 MHz, 88 MHz, 153 MHz, 459 MHz and 956 MHz. The study ...

J. Deitz F. Lucia M. Liebman

1975-01-01

310

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

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

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

1988-01-01

311

Tools of radio astronomy  

Microsoft Academic Search

The fundamental physics of radio emission from astronomical objects and the principles of radio-telescope operation are reviewed in a textbook intended for graduate physics students. Topics examined include EM-wave propagation, wave polarization, antenna theory, filled-aperture antennas, interferometers and aperture synthesis, and receivers. Consideration is given to emission mechanisms of continuous radiation, thermal and nonthermal sources, the physics of line radiation,

Kristen Rohlfs

1986-01-01

312

Characteristics and Problems of the Gifted: neural propagation depth and flow motivation as a model of intelligence and creativity  

Microsoft Academic Search

Giftedness, the potential for exceptional achievement, is characterized by high intelligence and creativity. Gifted people exhibit a complex of cognitive, perceptual, emotional, motivational and social traits. Extending neurophysiological hypotheses about the general intelligence (g) factor, a construct is proposed to explain these traits: neural propagation depth. The hypothesis is that in more intelligent brains, activation propagates farther, reaching less directly

Francis HEYLIGHEN

313

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

Microsoft Academic Search

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 alpha mode discharge of the RF APGD plasmas are presented. The experiments are conducted

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

2007-01-01

314

Fading Characteristics and Drift and Anisotropy Parameters of the Ground Diffraction Pattern of the Radio Waves Reflected from the Equatorial Ionosphere during Spread F Conditions  

Microsoft Academic Search

The characteristics of the radio waves reflected from the ionosphere over Thumba (0.6'S dip) during the spread F conditions are discussed in relation to the normal day char- acteristics. The amplitude of the echo from the spread F ionosphere is found to fade at a much faster rate and the power spectrum anaJysis reveals two significant fading frequencies. The drift

R. K. Misra

1973-01-01

315

The 09 September 1989 gamma -ray flare - multi-site particle acceleration and shock-excited radio emission during quasiperpendicular and quasiparallel propagation  

Microsoft Academic Search

This is a case study of the location of particle acceleration sites during an impulsive flare and its subsequent coronal shock which occurred on 09 September 1989. Joint radio, hard X-ray\\/gamma -ray, and H_alpha observations of the flare impulsive emissions reveal that electron and ion acceleration results from successive energy release in different magnetic structures. In this paper we attempt

H. Aurass; A. Hofmann; H.-W. Urbarz

1998-01-01

316

Nonlinear Electrodynamics: Alternative Field Theory for Featuring Photon Propagation Over Weak Background Electromagnetic Fields and what Earth Receivers Read off Radio Signals from Interplanetary Spacecraft Transponders  

Microsoft Academic Search

A few observational and\\/or experimental results have dramatically pushed forward the research program on gravity as those from the radio-metric Doppler tracking received from the Pioneer 10 and 11 spacecrafts when the space vehicles were at heliocentric distances between 20 and 70 Astronomical Units (AU). These data have conclusively demonstrated the presence of an anomalous, tiny and blue-shifted frequency drift

Herman J. Mosquera Cuesta

2011-01-01

317

Particle model analyses of N{sub 2}O dilution with He on electrical characteristics of radio-frequency discharges  

SciTech Connect

The electrical characteristics (voltage, electric field, charged particle densities, dissipated power, particle energy, etc.) are analyzed in the case of low pressure (0.5 and 1 Torr) radio-frequency (rf) discharges in nitrous oxide (N{sub 2}O)/Helium (He) mixtures. An optimized and validated particle model has been used for these analyses in the case of gradual dilutions of N{sub 2}O with He buffer gas. A specific care is carried on the power density evolution and variation which show a complex behavior as a function of He proportion (up to 85%). These analyses are based on a microscopic approach enabling one to show the contribution of the different inelastic processes mainly between electrons and respectively N{sub 2}O and He gases. This approach enables also one to show the discharge region (the positive column or the plasma region) where the power is preferentially dissipated. The power density variation is found to be mainly proportional to the electron density variation. The latter is dependent on the different processes occurring between the charged particles [i.e., electrons, negative ions (O{sup -} and NO{sup -}), and positive ions (N{sub 2}O{sup +} and He{sup +})] and the neutral gas mixture (N{sub 2}O and He). Furthermore, the particle model shows the role of the electron-He collisions on the variation in the electron energy and distribution. This allows more particularly explaining the effects of N{sub 2}O dilution with He on the dissipated power variation in terms of creation and loss of electrons through collision processes.

Younis, G.; Yousfi, M.; Despax, B. [LAPLACE (Laboratoire Plasma et Conversion d'Energie), UPS, INP, Universite de Toulouse, 118 route de Narbonne, F-31062 Toulouse Cedex 9 (France) and LAPLACE, CNRS, F-31062 Toulouse (France)

2009-05-01

318

Maneuvering Characteristics of the YP 676 Class Seamanship Training Craft as Represented by Radio-Controlled Model 9022.  

National Technical Information Service (NTIS)

This report presents the results of maneuvering and roll experiments conducted with radio-controlled Model 9022, representing the YP 676 Class seamanship training craft. The investigaton was conducted primarily to determine the optimum rudder size for sat...

G. A. Rossignol

1983-01-01

319

Digital Radiolaenk: Vagutbredningsmaetningar Oever en 13 GHz Frisikt-Foerbindelse (Digital Radio Link: Wave Propagation Investigations on a 13 GHz Line-of-Sight Path).  

National Technical Information Service (NTIS)

Propagation investigations on two high capacity (34 Mb/s) 13 GHz-paths (28 km and 46 km) were performed during the period 1983, 1984 and 1985. The main purpose of the measurements were to examine the activity of frequency selective fading and rain attenua...

S. Mattsson

1988-01-01

320

Statistical study of Pc1–2 wave propagation characteristics in the high-latitude ionospheric waveguide  

Microsoft Academic Search

ULF wave propagation in the ionospheric waveguideAntarctic ground magnetometer array observed poleward wave power attenuationFrequency cutoff in the waveguide is dependent on the ionospheric conductivity

H. Kim; M. R. Lessard; M. J. Engebretson; M. A. Young

2011-01-01

321

The Numerical Solution of Transient Supercritical Flow by the Method of Characteristics with a Technique for Simulating Bore Propagation.  

National Technical Information Service (NTIS)

Two finite-difference schemes for the solution of unsteady, supercritical flow problems are analyzed and the results are used in proposing a method to simulate bore propagation in supercritical flow. Two nonlinear one-dimensional partial-differential equa...

J. J. Zovne

1970-01-01

322

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

PubMed

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. PMID:24089818

Suwada, Tsuyoshi; Satoh, Masanori; Telada, Souichi; Minoshima, Kaoru

2013-09-01

323

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

NASA Astrophysics Data System (ADS)

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.

Suwada, Tsuyoshi; Satoh, Masanori; Telada, Souichi; Minoshima, Kaoru

2013-09-01

324

Temperature Effects on the Propagation Characteristics of Love Waves along Multi-Guide Layers of Sio2/Su-8 on St-90?X Quartz  

PubMed Central

Theoretical calculations have been performed on the temperature effects on the propagation characteristics of Love waves in layered structures by solving the coupled electromechanical field equations, and the optimal design parameters were extracted for temperature stability improvement. Based on the theoretical analysis, excellent temperature coefficient of frequency (Tcf) of the fabricated Love wave devices with guide layers of SU-8/SiO2 on ST-90°X quartz substrate is evaluated experimentally as only 2.16 ppm.

Xu, Fangqian; Wang, Wen; Hou, Jiaoli; Liu, Minghua

2012-01-01

325

Impulsiveness and energetics in solar flares with and without type II radio bursts - a comparison of hard X-ray characteristics for over 2500 solar flares  

SciTech Connect

The hard X-ray characteristics of more than 2500 solar flares are used to study the relative size, impulsiveness, and energetics of flares with and without type II radio bursts. A quantitative definition of the hard X-ray impulsiveness is introduced, which may be applied to a large number of events unambiguously. It is found that the flares with type II bursts are generally not significantly larger, more impulsive, or more energetic than those without type II bursts. Also, no evidence is found to suggest a simple classification of the flares as either impulsive or gradual. Because type II bursts are present even in small flares with relatively unimpulsive energy releases, it is concluded that changes in the ambient conditions of the solar atmosphere causing an unusually low Alfven speed may be important in the generation of the shock wave that produces type II radio bursts. 22 references.

Pearson, D.H.; Nelson, R.; Kojoian, G.; Seal, J.

1989-01-01

326

Kinematics of ICMEs Deduced From Remote Radio Observations  

NASA Astrophysics Data System (ADS)

Low-frequency radio emissions, generated at the driven shock wave at the fundamental and harmonic of the plasma frequency, can directly reveal the kinematics of ICMEs as they propagate through the inner heliosphere. The reason is that the frequency of the radio emissions varies in a predictable way as a function of heliocentric distance. Hence, the observed frequency drift of these radio emissions is essentially a plot of the height above the Sun as a function of time. The derivative of the observed frequency-time curve at each point then gives the instantaneous speed of the propagating interplanetary shock. We have used these remote radio observations to determine the speed profiles for some 40 fast CMEs observed during solar cycle 23. The speed profiles for these fast ICMEs were found to imply an initial rapid deceleration at a constant rate, followed by a constant propagation speed to 1 AU (Reiner et al. ApJ 663, 1369, 2007), consistent with some earlier Doppler scintillation measurements (Woo et al., JGR 90, 154, 1985). Because of the large number of CME events for which this analysis was carried out, we were further able to study the correlations of the deceleration parameters of the ICME speed profiles. For most of those remote radio observations, there were no corresponding white-light observations beyond the 32 Rs (0.15 AU) limit of the LASCO coronagraph. After 2003, the all-sky camera SMEI permitted the first direct comparison between the remote radio and the white-light observations in interplanetary space (Reiner et al. JGR 110, A09S14, 2005). The STEREO spacecraft, launched in October of 2006, provide a new and unique opportunity to make direct comparisons between the radio and white-light observations of the ICME kinematics. The STEREO observations also allow the locations of the radio sources along the shock front to be directly deduced from two or three spacecraft triangulation measurement from STEREO and Wind (Reiner et al. Solar Physics 10.1007/s11207-009-9404-z, 2009). However, due to solar minimum, to date no CMEs observed by STEREO were fast enough to produce measurable radio emissions. As we approach solar maximum that situation will surely change. Nevertheless, some height-time data for fast CMEs that were observed in the Heliospheric Imagers on STEREO do seem to confirm the general characteristics of the speed profile previously deduced from radio tracking (Wood et al., ApJ 694, 707, 2009). In this talk, we will summarize our previous remote radio results, and show how they can be used to provide improved algorithms for space weather predictions.

Reiner, M. J.; MacDowall, R. J.

2009-12-01

327

Propagation Modeling and Measurement for a Multifloor Stairwell  

Microsoft Academic Search

Reliable wireless communications in stairwells are crucial to law enforcement and firefighting safety. Understanding the radio propagation in stairwells is necessary to successfully design such communications systems. In this letter, we study the radio propagation in a multifloor stairwell using measurements and simulations. Fundamental propagation mechanisms such as reflection from stairwell walls and transmission through the stair steps are investigated.

Soo Yong Lim; Zhengqing Yun; James M. Baker; Nuri Celik; Hyoun-Sun Youn; Magdy F. Iskander

2009-01-01

328

Characteristics of dust particles detected near Saturn's ring plane with the Cassini Radio and Plasma Wave instrument  

Microsoft Academic Search

During the inbound and outbound passes of the Cassini spacecraft through Saturn's ring plane on July 1, 2004, the Radio and Plasma Wave Science (RPWS) instrument detected many small particles striking the spacecraft. When a small particle strikes the spacecraft at a high velocity, it is instantly vaporized and produces a small cloud of plasma that expands radially outward from

Z. Wang; D. A. Gurnett; T. F. Averkamp; A. M. Persoon; W. S. Kurth

2006-01-01

329

The evolution of scattering equatorial F-region irregularities and resultant effects on trans-ionospheric radio waves  

Microsoft Academic Search

Results from a series of ground and airborne experiments are presented which describe spatial and temporal characteristics of equatorial F-region irregularities and the effect of these irregularities on transionospheric radio propagation. The experiments included UHF amplitude scintillation measurements from the WIDEBAND, MARISAT, and LES-9 satellites, and simultaneous ionospheric measurements from the AFGL Airborne Ionospheric Observatory and the Jicamarca Radar Observatory

H. E. Whitney; J. Aarons; J. Buchau; E. J. Weber; J. P. McClure

1978-01-01

330

Statistical study of Pc1-2 wave propagation characteristics in the high-latitude ionospheric waveguide  

NASA Astrophysics Data System (ADS)

Propagation of ULF Pc1-2 geomagnetic pulsations in the ionospheric waveguide (duct), centered around the F2 region altitude of maximum ionospheric electron density, is studied using the data obtained from a ground array of five search coil magnetometers in Antarctica distributed over a very extensive range of geomagnetic latitudes from subauroral to polar cap (-62° to -87°, spanning 2920 km geographically). A statistical study including a total of 138 Pc1-2 wave ducting events in 2007 presents wave power attenuation factors that vary between ˜10 and 14 dB/1000 km and the change of polarization during the wave propagation under different ionospheric sunlight conditions. It is also shown that the frequency cutoff of the wave events in the waveguide is dependent on the ionospheric conductivity, and the wave power attenuation increases with increasing frequency. In addition, it appears that initial propagation direction is related to attenuation, which supports the idea that meridional propagation is most efficient as predicted in previous studies. The results show the observations of ducted waves over such an unprecedented latitudinal extent along a magnetic meridian, which have rarely been measured before, and thus provide very important information in regard to wave ducting under various ionospheric conditions.

Kim, H.; Lessard, M. R.; Engebretson, M. J.; Young, M. A.

2011-07-01

331

Reconstruction of ionospheric irregularities using transionospheric radio waves  

NASA Astrophysics Data System (ADS)

Several approaches which use trans-ionospheric radio signals to study the fine structures of ionospheric irregularities are presented. Based on the theory of wave propagation in a random media, the statistical scintillation theory relates the statistics of the observed radio signal to the statistical characteristics of the irregularities; first and second order statistical quantities, such as mean square fluctuations of electron density, as well as the correlation and power spectra of the irregularities can be inferred from the data. Reconstruction by inverse propagation involves the use of simultaneous phase and amplitude information for multi-frequency coherent beacon signals to reconstruct irregularities similar to the optical synthetic holograms. Snap pictures of the fluctuating structures from this approach are provided, and examples of both approaches are given.

Liu, C. H.; Yeh, K. C.

332

Source mechanisms and radio effects of ionospheric plasma. Annual report, 1 October 1991-30 September 1992  

SciTech Connect

Since October 1, 1991 experimental and theoretical research has been conducted by Prof. Min-Chang Lee and his students at BU and MIT. This research work is aimed at investigating the ionospheric plasma disturbances which can affect significantly the radio wave propagation in communications and space surveillance. The research topics which have been investigated include: (1) A source mechanism leading to the symmetric lower hybrid sidebands and a low-frequency mode in the upper atmosphere, (2) Characteristics of lightning-induced plasmas, (3) Radio wave-produced plasmas and effects on radio communications, (4) Plasma turbulence and formation of field aligned density fluctuations as ionospheric ducts.

Lee, M.C.

1992-11-01

333

Measurement and modeling of the effects of atmospheric turbulence on coherent laser propagation characteristics and FSO system performance  

NASA Astrophysics Data System (ADS)

We investigate the random phase fluctuations of coherent laser propagate through the turbulent atmosphere, and introduce a model of its impact on optical heterodyne reception free space coherent laser optical communication (FSO) system. A polarization based shearing interferometer is used to detect the distorted laser wave-front and reconstruct the wave-front after propagate through a 1Km near-ground atmospheric channel. Further, the heterodyne efficiency of the heterodyne reception system would be given under special consideration of the mismatch between the signal field and the local oscillator. By analyzing the heterodyne efficiency data and the real-time atmospheric coherence length data, a mathematical model of the effects of atmospheric turbulence on FSO system performance is given.

Zhou, Jian; Lu, Wei; Sun, Jianfeng; Liu, Liren

2013-09-01

334

Adaptive transmission protocols for frequency-hop radio networks  

Microsoft Academic Search

ABSTRACT The focus,of this paper,is on,the,performance,of an adaptive,transmission,protocol,for,frequency-hop,(FH) radio,networks,in which,the,radios,can,adjust,the power in the transmitted,signal,and,the rate of a Reed-Solomon code,io respond,to variations,in partial-band,interfer- ence,and,propagation,loss. The adaptation,is based,on side information,from the FH receiveT and on informa- tion,derived,from,the,decoder.,The results,presented,in this paper,am,obtained,from,a simulation,of a wireless FH radio,network,in,which,the,characteristics,of the links are time-varying. These results demonstrate,that the adaptive,transmission,protocol,can,improve,the qual- ity of a link by adapting,to variations,in

J. Gass; M. Pursley; H. Russell; R. Saulitis; C Wilkins; J. Wysocarski

1998-01-01

335

Radio Band Observations of Blazar Variability  

NASA Astrophysics Data System (ADS)

The properties of blazar variability in the radio band are studied using the unique combination of temporal resolution from single dish monitoring and spatial resolution from VLBA imaging. Such measurements now available in all four Stokes parameters, together with theoretical simulations, identify the origin of radio band variability and probe the characteristics of the radio jet where the broadband blazar emission originates. Outbursts in total flux density and linear polarization in the optical-to-radio bands are attributed to shocks propagating within the jet spine, in part, based on limited modelling invoking transverse shocks; new radiative transfer simulations allowing for shocks at arbitrary angle to the flow direction confirm this picture by reproducing the observed centimeter-band variations observed more generally, and are of current interest since these shocks may play a role in the ?-ray flaring detected by Fermi. Recent UMRAO multifrequency Stokes V studies of bright blazars identify the spectral variability properties of circular polarization for the first time and demonstrate that polarity flips are relatively common. All-Stokes data are consistent with the production of circular polarization by linear-to-circular mode conversion in a region that is at least partially self-absorbed. Detailed analysis of single-epoch, multifrequency, all-Stokes VLBA observations of 3C 279 support this physical picture and are best explained by emission from an electron-proton plasma.

Aller, Margo F.; Aller, Hugh D.; Hughes, Philip A.

2011-06-01

336

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

Microsoft Academic Search

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

George Christakos; Ricardo A. Olea

2005-01-01

337

Sugarcane (Saccharum sp. Hybrid) Propagated in Headspace Renovating Systems Shows Autotrophic Characteristics and Develops Improved Anti-oxidative Response  

Microsoft Academic Search

Previous results have shown that sugarcane plantlets micropropagated in Temporary Immersion Bioreactors (TIB) demonstrated\\u000a a better morphology and physiological behaviour when compared to plantlets propagated in Gelled Medium (GM). The present work\\u000a focuses on the onset of oxidative stress symptoms at transfer to ex vitro and during acclimatization. The specific ROS being produced were identified and tissue-located by infiltrating leaves

Carlos Aragón; Luísa C. Carvalho; Justo González; Maritza Escalona; Sara Amâncio

2009-01-01

338

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

Microsoft Academic Search

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

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

2003-01-01

339

Beam wander characteristics of flat-topped, dark hollow, cos and cosh-Gaussian, J0- and I0- Bessel Gaussian beams propagating in turbulent atmosphere: a review  

NASA Astrophysics Data System (ADS)

In this paper we review our work done in the evaluations of the root mean square (rms) beam wander characteristics of the flat-topped, dark hollow, cos-and cosh Gaussian, J0-Bessel Gaussian and the I0-Bessel Gaussian beams in atmospheric turbulence. Our formulation is based on the wave-treatment approach, where not only the beam sizes but the source beam profiles are taken into account as well. In this approach the first and the second statistical moments are obtained from the Rytov series under weak atmospheric turbulence conditions and the beam size are determined as a function of the propagation distance. It is found that after propagating in atmospheric turbulence, under certain conditions, the collimated flat-topped, dark hollow, cos- and cosh Gaussian, J0-Bessel Gaussian and the I0-Bessel Gaussian beams have smaller rms beam wander compared to that of the Gaussian beam. The beam wander of these beams are analyzed against the propagation distance, source spot sizes, and against specific beam parameters related to the individual beam such as the relative amplitude factors of the constituent beams, the flatness parameters, the beam orders, the displacement parameters, the width parameters, and are compared against the corresponding Gaussian beam.

Eyyubo?lu, Halil T.; Baykal, Yahya; Çil, Celal Z.; Korotkova, Olga; Cai, Yangjian

2010-02-01

340

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

NASA Astrophysics Data System (ADS)

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.

Huebner, Christof; Kottmeier, Christoph; Brandelik, Alexander

2011-06-01

341

Neptune's radio emissions  

NASA Astrophysics Data System (ADS)

Different radio emissions observed by the Planetary Radio Astronomy (PRA) instrument during the inbound and outbound trajectories are reviewed. Two types of emissions (smooth and bursty) were recorded in the frequency range of 20 to 1300 kHz which differ in spectral, temporal, and polarization characteristics. The source location of the smooth radio emission have been determined through the observations at the closest approach when the radio source was occulted by the planet. Other types of emission detected by the PRA experiment include the fore shock of Neptune's magnetosphere and the impacts of dust at ring-crossings and different low frequency waves. It is concluded that there is at least one radio source in the auroral zone of the northern magnetic hemisphere where a good fit to the observations can be obtained when assuming an emission cone model.

Leblanc, Y.; Ladreiter, H. P.

1992-11-01

342

Statistical Study of ULF Pc 1-2 Wave Propagation Characteristics in the High Latitude Ionospheric Waveguide  

NASA Astrophysics Data System (ADS)

It is well-documented that the ionospheric cavity bounded by the E and F2 layers acts as a waveguide for geomagnetic pulsations. Using data from a five-station search-coil magnetometer array in the Antarctic (ordered poleward: Halley Bay, AGO P2, South Pole, AGO P1, AGO P5), a study is made of ULF Pc 1-2 geomagnetic pulsations in the 0.1-1.0 Hz range to examine their spectral wave power attenuation during propagation through the ionospheric waveguide. Here we present results from a statistical study of over 100 events showing that Pc 1-2 geomagnetic pulsations exhibit well-defined poleward ducting behavior in the ionospheric waveguide as well as significant spectral power loss during poleward propagation, which suggests that Pc 1-2 waves are injected into the lower latitude ionosphere and guided through the ducting layer. Through the use of spectrograms and wave power attenuation plots, we show both qualitatively and quantitatively how these behaviors are affected by specific ionospheric conditions connected to the timing of the event with regard to magnetic local time. It is also examined in a statistical way how wave spectral power attenuation is related to sunlit conditions, which are thought to contribute to the ionospheric conductivity.

Young, M.; Lessard, M.; Kim, H.; Argall, M.

2009-05-01

343

Radio channel measurement and modelling for future mobile radio systems  

NASA Astrophysics Data System (ADS)

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.

Guerdenli, E.; Huish, P. W.

1989-12-01

344

The Dynamic Radio Sky  

NASA Astrophysics Data System (ADS)

The radio band is known to be rich in variable and transient sources, but exploration of it has only begun only in the last few years. Relevant time scales are as small as a fraction of a nanosecond (giant pulses from the Crab pulsar). Short transients (less than one second, say) have signal structure in the time-frequency plane at the very least because of interstellar plasma propagation effects (dispersion and scattering), and in some cases due to emission structure. Optimal detection requires handling a range of signal types in the time-frequency plane. Short bursts by necessity have very large effective radiation brightness temperatures associated with coherent emission processes. This paper surveys relevant source classes and summarizes propagation effects that must be considered to optimize detection in large-scale surveys. Scattering horizons for the interstellar and intergalactic media are defined, and the role of the radio band in panchromatic and multimessenger studies is discussed.

Cordes, James M.

2012-04-01

345

Low Latitude Ionospheric Effects on Radiowave Propagation.  

National Technical Information Service (NTIS)

This dissertation provides experimental observations and analyses that associate low-latitude transionospheric signal scintillation with transequatorial VHF radio propagation and errors in transionospheric geopositioning. The experiment observed equatoria...

R. W. Smith

1998-01-01

346

PROPAGATION OF SOLAR ENERGETIC PARTICLES IN THREE-DIMENSIONAL INTERPLANETARY MAGNETIC FIELDS: IN VIEW OF CHARACTERISTICS OF SOURCES  

SciTech Connect

In this paper, a model of solar energetic particle (SEP) propagation in the three-dimensional Parker interplanetary magnetic field is calculated numerically. We study the effects of the different aspects of particle sources on the solar surface, which include the source location, coverage of latitude and longitude, and spatial distribution of source particle intensity, on propagation of SEPs with both parallel and perpendicular diffusion. We compute the particle flux and anisotropy profiles at different observation locations in the heliosphere. From our calculations, we find that the observation location relative to the latitudinal and longitudinal coverage of particle source has the strongest effects on particle flux and anisotropy profiles observed by a spacecraft. When a spacecraft is directly connected to the solar sources by the interplanetary magnetic field lines, the observed particle fluxes are larger than when the spacecraft is not directly connected. This paper focuses on the situations when a spacecraft is not connected to the particle sources on the solar surface. We find that when the magnetic footpoint of the spacecraft is farther away from the source, the observed particle flux is smaller and its onset and maximum intensity occur later. When the particle source covers a larger range of latitude and longitude, the observed particle flux is larger and appears earlier. There is east-west azimuthal asymmetry in SEP profiles even when the source distribution is east-west symmetric. However, the detail of particle spatial distribution inside the source does not affect the profile of the SEP flux very much. When the magnetic footpoint of the spacecraft is significantly far away from the particle source, the anisotropy of particles in the early stage of an SEP event points toward the Sun, which indicates that the first arriving particles come from outside of the observer through perpendicular diffusion at large radial distances.

He, H.-Q.; Qin, G. [State Key Laboratory of Space Weather, Center for Space Science and Applied Research, Chinese Academy of Sciences, Beijing 100190 (China); Zhang, M., E-mail: hqhe@spaceweather.ac.cn, E-mail: gqin@spaceweather.ac.cn, E-mail: mzhang@fit.edu [Department of Physics and Space Science, Florida Institute of Technology, Melbourne, FL 32901 (United States)

2011-06-20

347

Radio broadcasting via satellite  

NASA Astrophysics Data System (ADS)

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.

Helm, Neil R.; Pritchard, Wilbur L.

1990-10-01

348

Radio Control.  

National Technical Information Service (NTIS)

Radio control of the motions of aerospace vehicles of various types and purposes (missiles, spacecraft, aircraft) is examined. Chief attention is focused on the principles and methods of radio control. Current methods of analysis and synthesis of the corr...

L. S. Gutkin V. B. Pestryakov V. N. Tipugin

1971-01-01

349

Radio Days.  

ERIC Educational Resources Information Center

|Thousands of today's high school students run FM radio stations at school, carrying on a tradition that began 50 years ago. Radio helps students learn to work with others and develop a strong sense of responsibility. A sidebar gives advice on starting a high school radio station. (MLF)|

Sanderson, Neil

1998-01-01

350

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

NASA Astrophysics Data System (ADS)

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.

Masood, W.; Rizvi, H.

2011-06-01

351

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

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.

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

352

CONTROL OF LASER RADIATION PARAMETERS: Study of the spectral characteristics of a femtosecond Ti:sapphire laser after propagation of its radiation through a tapered fibre  

NASA Astrophysics Data System (ADS)

The method and results of precision measurements of the intermode frequency of a Ti:sapphire laser after the propagation of its radiation through a tapered optical fibre are described. It is shown that the stability of the intermode frequency is impaired by half at short averaging times (10 s) and by a factor of 1.1 at long averaging times (1000 s). The results of investigations of the spectrum of a femtosecond Ti:sapphire laser, which is broadened in a tapered optical fibre are presented. It is shown that, by varying the fibre parameters and the characteristics of input pulses, the envelope of the broadened spectrum can be profiled, which is important for practical applications.

Bagayev, S. N.; Denisov, V. I.; Zakharyash, Valerii F.; Klementyev, Vasilii M.; Korel', I. I.; Kuznetsov, Sergei A.; Pivtsov, V. S.; Chepurov, S. V.

2003-10-01

353

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

Microsoft Academic Search

A new approach for obtaining integrated estimates of soil moisture content over larger regions of typically 10–50 km is described.\\u000a It is based on a known correlation between propagation characteristics of low frequency radio surface waves and surface soil\\u000a moisture, and provides valuable new benefits especially for meteorological prognostic models and for soil water estimation\\u000a in agriculture. The paper consists of

Christof Huebner; Christoph Kottmeier; Alexander Brandelik

2011-01-01

354

RF Wave Propagation in Bounded Plasma under Divergent and Convergent Magnetic Field Configurations  

NASA Astrophysics Data System (ADS)

Radio frequency (RF) wave propagation in a bounded plasma (cylindrical shape with a large diameter of 45 cm) produced by a planar, spiral antenna was investigated under divergent and convergent magnetic field configurations. The measured excited magnetic field amplitude and the phase were examined based on helicon wave characteristics, and were consistent with the computed results using the Transport Analyzing System for tokamaK/Wave analysis by Finite element method (TASK/WF) code. The wave propagation region was broadened (focused) in the radial direction with increasing distance from the antenna under the divergent (convergent) field.

Takechi, Seiji; Shinohara, Shunjiro

1999-11-01

355

Propagation measurements for S-band land mobile satellite systems using highly elliptical orbits  

NASA Astrophysics Data System (ADS)

For northern European regions, the implementation of satellites placed in highly elliptical orbits (HEO) was studied for future Land Mobile Satellite (LMS) networks, (e.g., Archimedes). For the characterization of the mobile radio channel information related to the relevant propagation phenomena is needed. A collaborative research project regarding these topics was set up in order to investigate the propagation characteristics of a HEO mobile channel in S band. The diagrams and curves presented are the results of preliminary analyses of the data collected during the experimental campaign in several environmental scenarios and for three elevation angles (40, 60, and 80 degrees).

Smith, H.; Sforza, M.; Arbesser-Rastburg, B.; Baptista, J. P. V.; Barton, S. K.

1991-10-01

356

Indoor radio communications for factories of the future  

Microsoft Academic Search

The need for reliable, real-time communication for automated factories is discussed. The ability of narrowband digital radio systems to meet that need is examined. The major problems encountered in multipath propagation, resulted from multiple reflections of the transmitted signal from the building structure and surrounding inventory. Radio wave propagation experiments at 1300 MHz, which were conducted by the author in

Theodore S. Rappaport

1989-01-01

357

Fundamental and harmonic radiation in type III solar radio bursts  

Microsoft Academic Search

Type III solar radio bursts are investigated by modelling the propagation of the electron beam and the generation and subsequent propagation of waves to the observer. Predictions from this model are compared in detail with particle, Langmuir wave, and radio data from the ISEE-3 spacecraft and with other observations to clarify the roles of fundamental and harmonic emission in type

P. A. Robinson; I. H. Cairns

1994-01-01

358

Distinct propagating fast wave trains associated with flaring energy releases  

NASA Astrophysics Data System (ADS)

Context. Large-scale fast waves with perturbation of the EUV emission intensity are well resolved in both temporal and spatial scale by SDO/AIA. These waves are prone to propagate along the magnetic field line. Aims: We aim to probe the link between propagating fast wave trains and flaring energy releases. By measuring the wave parameters, we reveal their nature and investigate the potential to diagnose the energy source and waveguide. Methods: The spatial and temporal evolution of the wave amplitude and propagating speed are studied. The correlation of individual wave trains with flare-generated radio bursts is tested. Results: The propagating wave pattern comprises distinct wave trains with varying periods and wavelengths. This characteristic signature is consistent with the patterns formed by waveguide dispersion, when different spectral components propagate at different phase and group speeds. The wave train releases are found to be highly correlated in start time with the radio bursts emitted by the non-thermal electrons that were accelerated in bursty energy releases. The wave amplitude is seen to reach the maximum midway during its course. This can be caused by a combined effect of the waveguide spread in the transverse direction and density stratification. The transverse amplitude distribution perpendicular to the wave vector is found to follow approximately a Gaussian profile. The spatial structure is consistent with the kink mode that is polarised along the line-of-sight. The propagating speed is subject to deceleration from ~735-845 km s-1 to ~600 km s-1. This could be caused by the decrease in the local Alfvén speed and/or the projection effect.

Yuan, D.; Shen, Y.; Liu, Y.; Nakariakov, V. M.; Tan, B.; Huang, J.

2013-06-01

359

Impacts of Radio Channel Characteristics, Heterogeneous Traffic Intensity, and Near–Far Effect on Rate Adaptive Scheduling Algorithms  

Microsoft Academic Search

Applying adaptive modulation combined with scheduling in a shared data channel can substantially improve the spectral efficiency for wireless systems. This performance gain results from the multiuser diversity, which exploited independent channel variations across multiple users. In this paper, we present a cross-layer analysis to integrate physical-layer channel characteristics, media access control (MAC) layer scheduling strategies, and the network layer

Chiung-Jang Chen; Li-Chun Wang

2006-01-01

360

An investigation on wideband signal fluctuation characteristics in CDMA mobile radio using path and spatial diversity combination  

Microsoft Academic Search

In wideband transmission systems such as mobile CDMA, path diversity is an effective measure to reduce the degree of signal variation due to rapid fluctuation (multipath fading). In order to evaluate the path diversity effect quantitatively, this paper analyzes the characteristics of signal fluctuation width under the RAKE combination scheme based on the measured multipath delay profiles, and compares it

Hisato IWAI; Fumio WATANABE; Toshio MIZUNO

1995-01-01

361

Fast, Accurate RF Propagation Modeling and Simulation Tool for Highly Cluttered Environments  

SciTech Connect

As network centric warfare and distributed operations paradigms unfold, there is a need for robust, fast wireless network deployment tools. These tools must take into consideration the terrain of the operating theater, and facilitate specific modeling of end to end network performance based on accurate RF propagation predictions. It is well known that empirical models can not provide accurate, site specific predictions of radio channel behavior. In this paper an event-driven wave propagation simulation is proposed as a computationally efficient technique for predicting critical propagation characteristics of RF signals in cluttered environments. Convincing validation and simulator performance studies confirm the suitability of this method for indoor and urban area RF channel modeling. By integrating our RF propagation prediction tool, RCSIM, with popular packetlevel network simulators, we are able to construct an end to end network analysis tool for wireless networks operated in built-up urban areas.

Kuruganti, Phani Teja [ORNL

2007-01-01

362

Radio wave scattering in tropospheric propagation  

Microsoft Academic Search

The scattering theory of Booker and Gordo has been developed, assuming the correlation functionC(r) = C(0)exp(-r\\/l), so as to be suitable for easy numerical calculation of the transmission loss expected with this mode of transmission;C(0)denotes the variance with time of the refractive index of the atmosphere, andldenotes the scale of turbulence. In this development the parameter,[C(0)\\/l], emerges as a direct

J. W. Herbstreit; K. A. Norton; P. L. Rice; G. E. Schafer

1953-01-01

363

Radio wave loss deviation and shadow loss at 900 MHz  

Microsoft Academic Search

Radio wave propagation between base and mobile stations is normally described as being Rayleigh distributed due to multipath radio wave combining. When the number of radio wave paths are limited the variation in received signal amplitude frequently follows a more general case given by a Weibull distribution. A significant portion of the Weibull distribution is defined as the transmission loss

NEAL H. SHEPHERD

1977-01-01

364

Radio wave.  

PubMed

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

Elkin, V

365

A crack initiation and propagation simulation and the fatigue characteristics of solder joints considering the material property changes  

NASA Astrophysics Data System (ADS)

The re-working of the manufacturing process from the reliability evaluation after the production process is a significant cost and loss of energy. In-vehicle electronic devices are exposed to multiple environmental loads such as thermal and vibrational loads. The effects of the material property changes in the thermal cycle load on the fatigue life of solder joints were estimated with our fatigue simulation for the purpose of constructing a design method considering the fatigue characteristic changes in the thermal cycle. The fatigue lives were estimated with and without considering the creep property changes measured by indentation tests. The fatigue ductility index and the coefficients increased toward the reported values by considering the creep property changes.

Matsushima, M.; Shishihara, Y.; Matsunami, H.; Fukumoto, S.; Fujimoto, K.

2012-08-01

366

Nanotube radio.  

PubMed

We have constructed a fully functional, fully integrated radio receiver from a single carbon nanotube. The nanotube serves simultaneously as all essential components of a radio: antenna, tunable band-pass filter, amplifier, and demodulator. A direct current voltage source, as supplied by a battery, powers the radio. Using carrier waves in the commercially relevant 40-400 MHz range and both frequency and amplitude modulation techniques, we demonstrate successful music and voice reception. PMID:17973438

Jensen, K; Weldon, J; Garcia, H; Zettl, A

2007-10-31

367

Observations of equatorial plasma bubbles using broadcast VHF radio waves  

Microsoft Academic Search

The propagation of VHF radio waves affected by field-aligned irregularities within equatorial plasma bubbles is examined. Continuous observation of VHF radio waves at Tateyama, Japan, shows that broadcast radio waves transmitted from Southeast Asia propagate to Japan. Using a ray-tracing calculation combined with a model of scattering by field-aligned irregularities, we determined scatter points suitable for the reception of these

H. Nakata; I. Nagashima; K. Sakata; Y. Otsuka; Y. Akaike; T. Takano; S. Shimakura; K. Shiokawa; T. Ogawa

2005-01-01

368

Temperature characteristics of a Y-cut Z-propagation LiNbO3 light modulator for application to polarimeters  

NASA Astrophysics Data System (ADS)

The temperature characteristics of a Y-cut Z-propagation LiNbO3 crystal light modulator, with manufacturing errors, in the absence and presence of an electric field have been investigated by analyses and experiments. According to our analyses, when the Z-axis of the LiNbO3 crystal is at an angle of 0.22° with respect to the normal of the input surface of the crystal, we found the theoretical fluctuation of the normalized output-light intensity with temperature to be less than 7:75 × 10-6/°C. This magnitude is less than 1% of the theoretical intensity fluctuation of a conventional temperature-compensation LiNbO3 light modulator. The measured temperature characteristics of a prototype of this modulator were 2 × 10-4/°C in the absence of an electric field (OFF state) and 2:8 × 10-4/°C in the presence of an external field (ON state). During a running test of longer than 8 hours at room temperature, the intensity fluctuation of this prototype was 0.01% in the OFF state, and 0.07% in the ON state.

Takizawa, Kuniharu; Yonekura, Kazuya; Jin, Lianhua

2010-01-01

369

Propagation characteristics of medium frequency skywave signals from the continental US and Canada received at Fairbanks, Alaska  

NASA Astrophysics Data System (ADS)

Since September 1981, an F.C.C.-sponsored medium-frequency (MF) skywave monitoring program has been in continuous operation at the Geophysical Institute of the University of Alaska. The receiver frequency is automatically stepped through 16 channels every five minutes by the system programmer. Recordings are continuously made of ten or more standard broadcast stations on digital tape cassettes, which are then transferred on a weekly basis to form a data base on a VAX 11/780-785 computer. A noise source has also been provided for system calibration. Three antennas have been utilized during the program to date, a 32-meter top-loaded vertical with ground screen being the primary antenna. Measurements of the electrical characteristics and computer modeling of the antenna systems have been made, and selected results are presented, as well as daily, seasonal and sunspot variation effects on measured MF skywave signal strengths. The summer/winter and magnetic activity effects are profound on medium and long-distance paths to Fairbanks. Present plans are to continue this monitoring program until Fall 1987 at least half of a sunspot cycle.

Hunsucker, R. D.; Delana, B. S.; Wang, J. C. H.

1985-11-01

370

Analyses of characteristics and triggering mechanisms of lahars on active volcanoes and modelling of the dynamics of propagation and deposition  

NASA Astrophysics Data System (ADS)

Lahars on active volcanoes can occur during an eruptive phase (syn-eruptive or primary lahars), during periods of reduced magmatic activity or during periods of quiescence associated to the post-eruptive remobilization of voluminous ash and tephra deposits, months or years after eruptions (post-eruptive lahars). In this research, we investigate the occurrence of lahars on Central American volcanoes (San Cristóbal and Concepción volcanoes in Nicaragua and San Miguel volcano in El Salvador) where low magnitude lahars are quite well known phenomena for the population living on the flanks. Within the last decade, lahars have occurred every year producing damages to crops and roads located in their lower flanks. On several occasions, inhabitants of the southern flanks of San Cristóbal volcano have been evacuated. Since the end of the 80's the national scientific community is making efforts to recognize and evaluate the hazard posed by these events and to improve hazard maps and evacuation plans. We present how field and instrumental seismic data have been combined with empirical data and numerical simulations, to provide a better understanding of lahars physical characteristics, triggering mechanisms, dynamics and behaviour, which are crucial for realistic hazard assessments and implementation of mitigation measures. The collection of recent lahars data allowed defining the causes that condition and trigger lahars, to preliminary assess lahar frequency and to understand the relation between lahar occurrence, rainfall, the presence of altered areas and volcanic and seismic activity. Numerical simulations helped to assess quantitatively the rheological behaviour of lahars and improve estimations of run-out distances.

Devoli, G.; de Blasio, F. V.; Tenorio, V.; Talavera, E.; Escobar, D.; Cepeda, J.

2009-04-01

371

Studying characteristics of the large-scale ionospheric irregularities induced by high-power HF radio emission with GPS diagnosis  

NASA Astrophysics Data System (ADS)

We present the results of experimental studies of artificial large-scale irregularities of the ionospheric electron number density with dual-frequency GPS diagnosis. The total electron content was analyzed in the GPS signal trajectory when the satellites passed over the heated region. Spectral composition of the observed variations was determined by wavelet analysis. Characteristic scales of artificial irregularities of the electron number density in the F layer are estimated. It is experimentally proved that the irregularities remain for at least 15-20 min after the transmitter is switched off. A more confident excitation and increased intensity of the irregularities were also confirmed when the beam was inclined south of the magnetic-zenith direction.

Ryabov, A. V.; Grach, S. M.; Shindin, A. V.; S. Kotik, D.

2011-12-01

372

Rosetta Radio Science Investigations (RSI)  

NASA Astrophysics Data System (ADS)

The Rosetta spacecraft has been successfully launched on 2nd March 2004 to its new target comet 67 P/Churyumov-Gerasimenko. The science objectives of the Rosetta Radio Science Investigations (RSI) experiment address fundamental aspects of cometary physics such as the mass and bulk density of the nucleus, its gravity field, its interplanetary orbit perturbed by nongravitational forces, its size and shape, its internal structure, the composition and roughness of the nucleus surface, the abundance of large dust grains, the plasma content in the coma and the combined dust and gas mass flux. The masses of two asteroids, Steins and Lutetia, shall be determined during flybys in 2008 and 2010, respectively. Secondary objectives are the radio sounding of the solar corona during the superior conjunctions of the spacecraft with the Sun during the cruise phase. The radio carrier links of the spacecraft Telemetry, Tracking and Command (TT&C) subsystem between the orbiter and the Earth will be used for these investigations. An Ultrastable oscillator (USO) connected to both transponders of the radio subsystem serves as a stable frequency reference source for both radio downlinks at X-band (8.4 GHz) and S-band (2.3 GHz) in the one-way mode. The simultaneous and coherent dual-frequency downlinks via the High Gain Antenna (HGA) permit separation of contributions from the classical Doppler shift and the dispersive media effects caused by the motion of the spacecraft with respect to the Earth and the propagation of the signals through the dispersive media, respectively. The investigation relies on the observation of the phase, amplitude, polarization and propagation times of radio signals transmitted from the spacecraft and received with ground station antennas on Earth. The radio signals are affected by the medium through which the signals propagate (atmospheres, ionospheres, interplanetary medium, solar corona), by the gravitational influence of the planet on the spacecraft and finally by the performance of the various systems involved both on the spacecraft and on ground.

Pätzold, Martin; Häusler, Bernd; Aksnes, Kaare; Anderson, John D.; Asmar, Sami W.; Barriot, Jean-Pierre; Bird, Michael K.; Boehnhardt, Hermann; Eidel, Werner; Grün, Eberhardt; Ip, Wing H.; Marouf, Essam; Morley, Trevor; Neubauer, Fritz M.; Rickman, Hans; Thomas, Nicolas; Tsurutani, Bruce T.; Wallis, Max K.; Wickramasinghe, N. C.; Mysen, Eirik; Olson, Oystein; Remus, Stefan; Tellmann, Silvia; Andert, Thomas; Carone, Ludmila; Fels, Markus; Stanzel, Christina; Audenrieth-Kersten, Iris; Gahr, Alexander; Müller, Anna-Liane; Stupar, Dusan; Walter, Christina

2007-02-01

373

Educational Radio.  

ERIC Educational Resources Information Center

This report summarizes information about the history, technology, and operation of educational radio in the U.S. Also presented are the Federal Communications Commission's (FCC) rules and regulations concerning the licensing and channel assignment of educational radio, and its auxiliary special broadcast services. Included are the application…

Federal Communications Commission, Washington, DC.

374

Radio Memories  

NSDL National Science Digital Library

The "Golden Age of Radio" that arguably lasted until the early 1950s may be hard to imagine today in an era of swirling iPod playlists and other genre-bending devices and technologies, but during this time the radio reigned supreme. People tuned in every week to hear the exploits of Flash Gordon, Sam Spade, and Amos n' Andy. Thanks to the Radio Memories website, many of these memories can be relived, or just experienced for the first time. Started in May 2005, the site contains a host of compelling programs, including episodes from the Interplanetary Adventures of Flash Gordon and a number of original episodes of the fabled Radio Detective Story Hour. If those types of programs fail to pique the interest of the casual visitor, the site also contains archived shows that explore the world of radio soap operas from the 1940s and the musical worlds of such stars as Tommy Dorsey and Harry James.

375

On-Body Antennas and Propagation: Recent Development  

NASA Astrophysics Data System (ADS)

The paper reviews recent advances in on-body antennas and propagation under a joint UK EPSRC research project between Queen Mary College, University of London and University of Birmingham. The study of on-body radio propagation has been extended by using various small antennas. The effect of antenna size, gain and radiation patterns on on-body channel characteristics has been studied. A practical wearable sensor antenna design is presented and it is demonstrated that a global simulation including sensor environment and human body is needed for accurate antenna characterisation. A 3D animation design software, POSER 6 has been used together with XFDTD to predict the on-body path loss variation due to changes in human postures and human motion. Finally, a preliminary study on the feasibility of a diversity scheme in an on-body environment has been carried out.

Hao, Yang; Hall, Peter S.

376

Effects of the shielding cylinder and substrate on the characteristics of an argon radio-frequency atmospheric glow discharge plasma jet  

SciTech Connect

With unique features of low breakdown voltages, large and uniform discharge areas and high concentrations of chemically reactive species, radio-frequency, atmospheric-pressure glow discharge (rf APGD) plasma sources produced with bare-metallic electrodes have shown promising prospects in the field of materials processing. In this paper, the spatial distributions (i.e., the directly measured integrated axial distribution and the radial distribution by using the inverse Abel transform) of the emission intensities of the Ar I 696.5 nm line are studied for the argon rf APGD plasma jet under different operation conditions, including variations of the rf power input or the argon flow rate, the existence of the solid shielding cylinder or the substrate. The experimental results show that, with other parameters being unchanged, the emission intensities of the Ar I 696.5 nm line increase with increasing the rf power input or the argon flow rate; and the solid shielding cylinder has more significant influences on the characteristics of the plasma impinging jet by reducing the mass flow rate of the ambient air entrained into the plasma jet region than those for the cases without the existence of the substrate at the downstream of the plasma torch nozzle exit.

Li Guo; Le Peisi; Li Heping; Bao Chengyu [Department of Engineering Physics, Tsinghua University, Beijing 100084 (China)

2010-05-15

377

Effects of the shielding cylinder and substrate on the characteristics of an argon radio-frequency atmospheric glow discharge plasma jet  

NASA Astrophysics Data System (ADS)

With unique features of low breakdown voltages, large and uniform discharge areas and high concentrations of chemically reactive species, radio-frequency, atmospheric-pressure glow discharge (rf APGD) plasma sources produced with bare-metallic electrodes have shown promising prospects in the field of materials processing. In this paper, the spatial distributions (i.e., the directly measured integrated axial distribution and the radial distribution by using the inverse Abel transform) of the emission intensities of the Ar I 696.5 nm line are studied for the argon rf APGD plasma jet under different operation conditions, including variations of the rf power input or the argon flow rate, the existence of the solid shielding cylinder or the substrate. The experimental results show that, with other parameters being unchanged, the emission intensities of the Ar I 696.5 nm line increase with increasing the rf power input or the argon flow rate; and the solid shielding cylinder has more significant influences on the characteristics of the plasma impinging jet by reducing the mass flow rate of the ambient air entrained into the plasma jet region than those for the cases without the existence of the substrate at the downstream of the plasma torch nozzle exit.

Li, Guo; Le, Pei-Si; Li, He-Ping; Bao, Cheng-Yu

2010-05-01

378

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

NASA Astrophysics Data System (ADS)

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.

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

2013-03-01

379

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 January-1 June 1980  

SciTech Connect

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 nuclear conflict. The report is composed of short contributions from selected experts in the field of nuclear propagation effects (from RDA, SRI and Rand) and is intended to provide a guide for those asked to make system procurement decisions, in a complex and specialized but critical area.

Gabbard, C.B.; LeLevier, R.E.

1980-06-01

380

Radio Emission Associated with Solar Energetic Particle Events  

NASA Astrophysics Data System (ADS)

The corona probed at meter and decimeter wavelengths is a crucial region for the acceleration and propagation of solar energetic particles (SEPs), and radio diagnostics in this plasma plays a major role in assessing the origin of SEP events. Using data from the ARTEMIS IV solar radio spectro-graph, we report the properties of the radio emission associated with several major SEP events. The association of the radio emission with the related flares and CMEs is also investigated.

Kouloumvakos, A.; Nindos, A.; Preka-Papadema, P.; Hillaris, A.; Caroubalos, C.; Moussas, X.; Alissandrakis, C.; Tsitsipis, P.; Kontogeorgos, A.

2012-01-01

381

Dynamic Characteristics of the Main Indexes of Space Weather and Their Application to the Analysis Monitoring Observations Flux Densities of Power Radio Sources on RT  

NASA Astrophysics Data System (ADS)

On radio telescope "URAN-4" of the Odessa observatory of Radio-astronomical Institute during twenty five years (since 1987 till present) monitoring of power galactic and extragalactic radio sources on frequencies 25 and 20MHz has been carried out. Data of the observation was spent in a current of the 22-23th cycles of solar activity and in the beginning of the 24th cycle. Long-term variations density fluxes of radio sources connection with change of a condition of ionosphere in a cycle of solar activity are considered. Means Fourier and Wavelet analysis determine dynamics of changes of the main indexes of space weather and the basic periods of activity are revealed. The obtained data will be used for interpretation of the observation changes flux of radio sources for during all investigated cycle of activity and periods of extreme developments of space weather.

Guglya, L.; Ryabov, M.; Panishko, S.; Suharev, A.

382

Plasma Diagnostics of the Interstellar Medium with Radio Astronomy  

NASA Astrophysics Data System (ADS)

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.

Haverkorn, Marijke; Spangler, Steven R.

2013-09-01

383

The range and frequency dependence of VHF—UHF man-made radio noise in and above metropolitan areas  

Microsoft Academic Search

The surface distribution of composite incidental man-made radio noise power in metropolitan areas displays frequency and range variations which are predictable from a knowledge of the propagation characteristics of irregular surface terrain for low-height antennas and the noise-source spectral power densities for a Poisson distributed random noise process. The observed frequency variation of composite surface noise power in the very-low-frequency

E. N. Skomal

1970-01-01

384

VHF and UHF propagation in the Canadian high Arctic  

NASA Astrophysics Data System (ADS)

Radio propagation in the Arctic maritime environment was studied. Five UHF radio paths between pairs of elevated points were selected along a 300 km east-west line which parallels a potentially important navigation route through the Arctic islands. Two VHF paths, each between an elevated site and a point near sea level were also chosen to simulate communications with a ship. Partial results from the summer to winter transition season show that propagation between the elevated points is highly reliable, but that propagation along the slanted paths appears to be strongly affected by radio wave ducting.

Butler, R. S.; Strickland, J. I.; Bilodeau, C.

1984-02-01

385

A history of radio astronomy polarisation measurements  

NASA Astrophysics Data System (ADS)

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.

Wielebinski, Richard

2012-07-01

386

Effect of surface modification of high-density polyethylene by direct current and radio frequency glow discharge on wetting and adhesion characteristics  

NASA Astrophysics Data System (ADS)

The present investigation aims to optimize the process parameters of Direct Current (DC) and Radio Frequency (RF) glow discharge treatment through air in terms of discharge power and time of exposure for the surface modification of high-density polyethylene (HDPE) sheet, for attaining best adhesive joint of the polymer to mild steel. In order to estimate the extent of surface modification, the surface energies of the polymer surfaces exposed to glow discharge have been determined by measuring contact angles using two standard test liquids of known surface energies. It is observed that at a given power level of DC glow discharge, surface energy and its polar component increase with increasing exposure time, attaining a maximum and then decreasing. In the case of RF glow discharge, surface energy and its polar component increase with increasing exposure time and then saturate. Surface modification by DC glow discharge increases the surface energy of HDPE relatively more at a lower power compared to that observed for RF glow discharge. The dispersion component of surface energy remains almost unaffected. The surfaces have also been studied by electron spectroscopy for chemical analysis (ESCA) and energy-dispersive spectra (EDS). A significant oxygen peak is observed for surface-modified polymer as detected by ESCA and EDS. Lap shear tensile test of an adhesive (Araldite AY 105) joint of HDPE with mild steel has been carried out in optimizing the parameters of DC and RF glow discharge for maximum joint strength. When HDPE is exposed to DC glow discharge, improvement of adhesive joint strength of HDPE to mild steel is found to be by a factor more than 7. On the other hand, when HDPE is exposed to RF glow discharge, results in improvement of adhesive joint strength of HDPE to mild steel by a factor nearer to 7 are found. Thus, DC glow discharge is more capable for increasing wetting and adhesion characteristics of the polymer.

Bhowmik, S.; Chaki, T. K.; Ray, S.; Hoffman, F.; Dorn, L.

2004-03-01

387

A database for propagation models  

NASA Astrophysics Data System (ADS)

The NASA Propagation Program supports academic research that models various propagation phenomena in the space research frequency bands. NASA supports such research via school and institutions prominent in the field. The products of such efforts are particularly useful for researchers in the field of propagation phenomena and telecommunications systems engineers. The systems engineer usually needs a few propagation parameter values for a system design. Published literature on the subject, such as the Cunsultative Committee for International Radio (CCIR) publications, may help somewhat, but often times, the parameter values given in such publications use a particular set of conditions which may not quite include the requirements of the system design. The systems engineer must resort to programming the propagation phenomena model of interest and to obtain the parameter values to be used in the project. Furthermore, the researcher in the propagation field must then program the propagation models either to substantiate the model or to generate a new model. The researcher or the systems engineer must either be a skillful computer programmer or hire a programmer, which of course increases the cost of the effort. An increase in cost due to the inevitable programming effort may seem particularly inappropriate if the data generated by the experiment is to be used to substantiate the already well-established models, or a slight variation thereof. To help researchers and the systems engineers, it was recommended by the participants of NASA Propagation Experimenters (NAPEX) 15 held in London, Ontario, Canada on 28-29 June 1991, that propagation software should be constructed which will contain models and prediction methods of most propagation phenomenon. Moreover, the software should be flexible enough for the user to make slight changes to the models without expending a substantial effort in programming.

Kantak, Anil V.; Suwitra, Krisjani; Le, Choung

1993-08-01

388

A Descriptive-Predictive Model of CME Propagation based on Multi-Instrument Data  

NASA Astrophysics Data System (ADS)

The space weather field has thriven in the past decades, mainly given the proliferation of space missions devoted to study the Sun and its relations to Earth. In addition, the high dependence on technology developed by society demands that a solar event, its time of arrival at Earth, and its degree of geoeffectiveness can be promptly forecasted. The accurate prediction of a CME-driven shock arrival time at Earth is therefore challenging and crucial, so as to take emergency measures when required. In this direction, we have studied 90 Earth-directed events in different stages of their propagation from Sun to Earth. A descriptive model was derived from CME height-time information from SOHO/LASCO coronagraph data, interplanetary shock approximate locations derived from Type II radio emissions detected by Wind/WAVES, and shock time of arrival at L1 as seen in-situ by the ACE and/or Wind spacecraft. The descriptive model provided a general overview of CME-driven shocks kinematics, allowing the determination of typical propagation profiles and constrains on the main parameters. On the basis of these, a predictive model was formulated, which relies on CME and low-frequency type II radio emissions. We discuss results on CME-radio emission associations, characteristics of the propagation in the interplanetary medium, and the success of the predictive model to forecast the arrival times of shocks at Earth.

Cremades, H.; Iglesias, F. A.; St Cyr, O. C.; Kaiser, M. L.; Xie, H.; Quirk, C. A.

2011-12-01

389

Analysis on Propagation Characteristics of Single-mode Step Index Linear and Nonlinear Optical Fiber with Revised Version of Improved Lorentzian Approximation for the Fundamental Mode  

NASA Astrophysics Data System (ADS)

In this paper, we approximate the fundamental mode of guided propagation by involving an extension of the previous version of Improved Lorentzian parameter for single mode step index liner and nonlinear optical fiber within the scalar variational framework. We show this version gives better performance in terms of field, propagation constants group delay and waveguide dispersion on wider scale of V-values in comparison to earlier ones and works better in low-V region.

Bandyopadhyay, Pratap Kumar; Sarkar, S. N.

2013-09-01

390

HF propagation modeling within the polar ionosphere  

NASA Astrophysics Data System (ADS)

This paper illustrates the importance of understanding and taking into account the presence of various structural features in the polar ionosphere (in particular, patches and arcs of enhanced electron density) when planning and operating HF radio links. These features result in radio waves propagating over paths well displaced from the great circle direction and impact on almost any HF communications system where the signal reflects from the ionosphere within the region poleward of the subauroral trough. The off-great circle mechanisms give rise to propagation at times that are not predicted by current prediction codes and may also suppress propagation at times that are expected. Techniques to account for this type of propagation are therefore required. A ray-tracing model that accurately reproduces many of the direction of arrival features observed in experimental measurements has been developed. Particular attention will be given in this paper to area coverage estimations undertaken by means of the ray-tracing model.

Warrington, E. M.; Zaalov, N. Y.; Naylor, J. S.; Stocker, A. J.

2012-01-01

391

Numerical characterization and modeling of subject-specific ultrawideband body-centric radio channels and systems for healthcare applications.  

PubMed

The paper presents a subject-specific radio propagation study and system modeling in wireless body area networks using a simulation tool based on the parallel finite-difference time-domain technique. This technique is well suited to model the radio propagation around complex, inhomogeneous objects such as the human body. The impact of different digital phantoms in on-body radio channel and system performance was studied. Simulations were performed at the frequency of 3-10 GHz considering a typical hospital environment, and were validated by on-site measurements with reasonably good agreement. The analysis demonstrated that the characteristics of the on-body radio channel and system performance are subject-specific and are associated with human genders, height, and body mass index. Maximum variations of almost 18.51% are observed in path loss exponent due to change of subject, which gives variations of above 50% in system bit error rate performance. Therefore, careful consideration of subject-specific parameters are necessary for achieving energy efficient and reliable radio links and system performance for body-centric wireless network. PMID:22147331

Abbasi, Qammer Hussain; Sani, Andrea; Alomainy, Akram; Hao, Yang

2011-11-29

392

Vertical propagation characteristics and seasonal variability of tidal wind oscillations in the MLT region over Trivandrum (8.5° N, 77° E): first results from SKiYMET Meteor Radar  

Microsoft Academic Search

Tidal activity in the Mesospheric Lower Thermosphere (MLT) region over Trivandrum (8.5° N, 77° E) is investigated using the observations from newly installed SKiYMET Meteor Radar. The seasonal variability and vertical propagation characteristics of atmospheric tides in the MLT region are addressed in the present communication. The observations revealed that the diurnal tide is more prominent than the semi\\/terdiurnal components

V. Deepa; G. Ramkumar; M. Antonita; K. K. Kumar; M. N. Sasi

2006-01-01

393

International Antenna and Propagation Symposium (1965). Program and Digest.  

National Technical Information Service (NTIS)

This report contains summaries of 71 presentations from the 1965 International Antennas and Propagation Symposium. The symposium covered such subjects as: (1) radar and radio astronomy; (2) arrays; (3) log periodic antennas; (4) electromagnetic scattering...

R. M. Emberson

1965-01-01

394

Adaptive equalization in TDMA digital mobile radio  

Microsoft Academic Search

In order to properly utilize NB-TDMA (narrow-band time division multiple access) digital mobile radio, it is necessary to remove both frequency-selective fading distortion caused by multipath propagation on the radio path and adjacent channel interference distortion from burst signals. It is suggested that an equalization system which combines a fractional interval equalizer and a decision feedback equalizer can solve this

M. Uesugi; K. Honma; K. Tsubaki

1989-01-01

395

Railway noise propagation models  

NASA Astrophysics Data System (ADS)

In this paper is presented a model to calculate the sound event level and thereby the energy equivalent level for short-distance railway noise propagation in a town. A model of the ground effects on the propagation from line sources, regarded as an incoherent superposition of point sources, is presented and discussed for spherical and directional sources. The influences of ground effects are calculated for short distances (15 m) and for an intermediate distance (~50 m) and are compared with frequency dependent measurements. For intermediate and long-distance railway noise propagation the sound event and the maximum sound levels are derived and calculated for spherical and directional sources. The calculations of the radiation characteristics are compared with short distance measurements of different kinds of trains, and the frequency dependent results are displayed.

Hohenwarter, D.

1990-08-01

396

Impulse radio: how it works  

Microsoft Academic Search

Impulse radio, a form of ultra-wide bandwidth (UWB) spread-spectrum signaling, has properties that make it a viable candidate for short-range communications in dense multipath environments. This paper describes the characteristics of impulse radio using a modulation format that can be supported by currently available impulse signal technology and gives analytical estimates of its multiple-access capability under ideal multiple-access channel conditions

Moe Z. Win; Robert A. Scholtz

1998-01-01

397

Wave propagation in multilayer dielectric periodic structures  

Microsoft Academic Search

The propagation characteristics in multilayered dielectric periodic structures are analyzed. The analysis extends that of R. L. Lewis and A. Hessel (1971) by introducing an additional dielectric layer. It is applied to propagation modes along the longitudinal and transverse directions of the structure's periodicity. The use of Floquet's theorem reduces the analysis to a single cell of the propagating fields

J. C. W. A. Costa; Attilio Jose Giarola

1993-01-01

398

Radio interferometry  

NASA Astrophysics Data System (ADS)

Geodetic and geophysical applications of radio interferometry are reviewed for the period 1987-1990. Emphasis is placed on geodetic very long baseline interferometry using Mark III and IIIA technology. Consideration is also given to observing campaigns and activities, data analysis techniques, and technique improvements.

Ray, Jim R.

399

Coherent Cherenkov radio pulses from hadronic showers up to EeV energies  

NASA Astrophysics Data System (ADS)

The Cherenkov radio pulse emitted by hadronic showers of energies in the EeV range in ice is calculated for the first time using full three dimensional simulations of both shower development and the coherent radio pulse emitted as the excess charge develops in the shower. A Monte Carlo, ZHAIRES, has been developed for this purpose combining the high energy hadronic interaction capabilities of AIRES, and the dense media propagation capabilities of TIERRAS, with the precise low energy tracking and specific algorithms developed to calculate the radio emission in ZHS. A thinning technique is implemented to allow the simulation of radio pulses induced by showers up to 10 EeV in ice. The code is validated comparing the results for electromagnetic and hadronic showers to those obtained with GEANT4 and ZHS codes. The contribution to the pulse of other shower particles in addition to electrons and positrons, mainly protons, pions and muons, is found to be below 3% for 10 PeV and above proton induced showers. The characteristics of hadronic showers and the corresponding Cherenkov frequency spectra are compared with those from purely electromagnetic showers. The dependence of the spectra on shower energy and high-energy hadronic model is addressed and parameterizations for the radio emission in hadronic showers in ice are given for practical applications.

Alvarez-Muñiz, Jaime; Carvalho, Washington R.; Tueros, Matías; Zas, Enrique

2012-01-01

400

Impact of radio irregularity on wireless sensor networks  

Microsoft Academic Search

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

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

2004-01-01

401

Models and solutions for radio irregularity in wireless sensor networks  

Microsoft Academic Search

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

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

2006-01-01

402

Plasmoid propagation  

SciTech Connect

A report is made on an investigation into the propagation of plasmoids. Plasmoid is the term used for a plasma moving through space as a body. Plasmoids have the potential to play important roles in target discrimination and reentry vehicle kill in the Strategic Defense Initiative. An important uncertainty regarding this potential is whether plasmas can propagate through the vacuum of space and across the earth's magnetic field without appreciable divergence or deflection. An additional concern is how deeply plasmoids can penetrate into the earth's ionosphere and upper atmosphere. Several plasma configurations are suggested that have low-divergence potential. Simple models for the plasmoid behavior are developed and the results of calculations are presented.

Lockner, T.R.; Lipinski, R.J.; Miller, R.B.

1985-12-01

403

On the Propagation of a Reaction Front Through a Porous Fuel in the Presence of an Opposed Forced Flow: Application to Mixtures Characteristic of Municipal Waste  

Microsoft Academic Search

An expression for the propagation velocity of a reaction front in a porous solid material is obtained by using a one-dimensional energy conservation equation. The reaction is divided in two distinct fronts.an ignition front where gasification of large part of the fuel occursand a flamingfront where gas phase oxidation takes place. Forced flow and reaction move in opposite directions, so,

X. ZHOU; J. L. TORERO; J. C. GOUDEAU; B. BREGEON

1995-01-01

404

Some results of measuring the characteristics of electromagnetic and plasma disturbances stimulated in the outer ionosphere by high-power high-frequency radio emission from the ``Sura'' facility  

NASA Astrophysics Data System (ADS)

We present the results of measuring the characteristics of electromagnetic and plasma disturbances at altitudes of about 700 km, obtained by using the onboard equipment of the French microsatellite DEMETER during its passage through the magnetic tube resting upon the region of intense generation of artificial ionospheric turbulence created due to modification of the ionospheric F2 region by high-power radio emission from the “Sura” facility. It is shown that an artificial density duct emerging from the disturbed region and extending to the Earth’s magnetosphere can be formed.

Rapoport, V. O.; Frolov, V. L.; Komrakov, G. P.; Markov, G. A.; Belov, A. S.; Parrot, M.; Rauch, J. L.

2007-08-01

405

Radio wave penetration into urban buildings in small cells and microcells  

Microsoft Academic Search

We performed 950 and 1800 MHz CW-measurements of radio wave propagation into various urban buildings in small-cell and microcell propagation scenarios in Vienna. We introduced a new empirical building penetration model that accounted for the power outdoors in a more detailed way than simpler previous ones. In both urban cell types, radio coverage of buildings can successfully be estimated from

Rainer Gahleitner; Emst Bonek

1994-01-01

406

Wideband Low Elevation Microwave Propagation Measurements.  

National Technical Information Service (NTIS)

A system is described that directly measures microwave propagation loss at low altitudes through the transmission of radio frequency signals. The system is designed to collect pathloss data over a 2 to 18 GHz band to better understand the phenomena that a...

J. L. Queen J. Stapleton S. Kang

1995-01-01

407

On runaway breakdown and upward propagating discharges  

Microsoft Academic Search

The origins of mysterious gamma ray and radio flashes recently detected by satellite-based instruments passing over thunderstorms are examined in the context of upward propagating discharges initiated by runaway air breakdown. Preliminary calculations normalized by the recent optical measurements of so-called sprites indicate that the runaway mechanism may well be the source of these emissions. If this is true, then

R. Roussel-Dupré; A. V. Gurevich

1996-01-01

408

Spectrum Sensing Framework for Cognitive Radio Networks  

Microsoft Academic Search

Spectrum sensing feature of cognitive radio devices represents a cornerstone characteristic facilitating real-time and accurate\\u000a spectrum occupancy measurements in cognitive radio networks. It practically enables the cognitive radio devices to detect\\u000a vacant spectrum holes and use them for their communication purposes. There are numerous spectrum sensing methods proposed\\u000a in the literature ranging from local based ones to cooperative strategies among

Liljana Gavrilovska; Vladimir Atanasovski

409

Interplanetary Shocks Lacking Type II Radio Bursts  

Microsoft Academic Search

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 (~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

N. Gopalswamy; H. Xie; P. Mäkelä; S. Akiyama; S. Yashiro; M. L. Kaiser; J.-L. Bougeret

2010-01-01

410

Unsupervised Learning of Propagation Time for Indoor Localization  

Microsoft Academic Search

Many of today's localization systems for indoor and outdoor positioning are based on propagation time measurements of radio signals. In order to achieve high positioning accuracy in presence of non line of sight (NLOS) propagation, these systems require either an expensive manual calibration or additional information. In this paper, we present a novel approach for a channel impulse response (CIR)

Andrei Szabo; Tobias Weiherer; Joachim Bamberger

2011-01-01

411

Radio holographic principle for observing natural processes in the atmosphere and retrieving meteorological parameters from radio occultation data  

Microsoft Academic Search

The radio holographic principle is briefly described and tested by using radio occultation data of the GPS\\/MET and MIR\\/GEO experiments. Sub-Fresnel spatial resolution ~12 m\\/pixel was achieved using focused synthetic aperture radio holographic approach, and direct evidence of multibeam propagation effects in the atmosphere was obtained. The achieved instrumental accuracy in angular distance measurements was near 0.004 milliradian\\/pixel, and observed

K. Igarashi; A. Pavelyev; K. Hocke; D. Pavelyev; I. A. Kucherjavenkov; S. Matyugov; A. Zakharov; O. Yakovlev

2000-01-01

412

Physical characteristics and occurrence rates of meteoric plasma layers detected in the Martian ionosphere by the Mars Global Surveyor Radio Science Experiment  

Microsoft Academic Search

Low-altitude plasma layers are present in 71 of 5600 electron density profiles from the Martian ionosphere obtained by the Mars Global Surveyor Radio Science experiment. These layers are produced by the ablation of meteoroids and subsequent ionization of meteoric atoms. The mean altitude of the meteoric layer is 91.7 +\\/- 4.8 km. The mean peak electron density in the meteoric

Paul Withers; M. Mendillo; D. P. Hinson; K. Cahoy

2008-01-01

413

Searches for radio transients  

NASA Astrophysics Data System (ADS)

Exploration of the transient Universe is an exciting and fast-emerging area within radio astronomy. Known transient phenomena range in time scales from sub-nanoseconds to years or longer, thus spanning a huge range in time domain and hinting a rich diversity in their underlying physical processes. Transient phenomena are likely locations of explosive or dynamic events and they offer tremendous potential to uncover new physics and astrophysics. A number of upcoming next-generation radio facilities and recent advances in computing and instrumentation have provided a much needed impetus for this field which has remained a relatively uncharted territory for the past several decades. In this paper we focus mainly on the class of phenomena that occur on very short time scales (i.e. from ˜milliseconds to ˜nanoseconds), known as {it fast transients}, the detections of which involve considerable signal processing and data management challenges, given the high time and frequency resolutions required in their explorations, the role of propagation effects to be considered and a multitude of deleterious effects due to radio frequency interference. We will describe the techniques, strategies and challenges involved in their detections and review the world-wide efforts currently under way, both through scientific discoveries enabled by the ongoing large-scale surveys at Parkes and Arecibo, as well as technical developments involving the exploratory use of multi-element array instruments such as VLBA and GMRT. Such developments will undoubtedly provide valuable inputs as next-generation arrays such as LOFAR and ASKAP are designed and commissioned. With their wider fields of view and higher sensitivities, these instruments, and eventually the SKA, hold great potential to revolutionise this relatively nascent field, thereby opening up exciting new science avenues in astrophysics.

Bhat, N. D. R.

2011-09-01

414

Seventy Years of Radio Science, Technology, Standards, and Measurement at the National Bureau of Standards  

Microsoft Academic Search

This large volume describes all the forms of radio research done at the National Bureau of Standards (now, National Institute of Standards and Technology) from its founding in 1901 until about 1980. The volume truly reflects its subtitle; it describes in great detail research in radio propagation and all its connections with geophysics and geospace, but also radio as instrument

C. Stewart Gillmor

1989-01-01

415

Regional seismic wave propagation  

NASA Astrophysics Data System (ADS)

In a review of studies on the seismic phase Lg, we describe its particle motion, dispersion, spectral content, mode of propagation, and magnitude-scale; we also tabulate the regional velocity, attenuation, and propagation efficiency for this seismic phase. The characteristics of Lg-wave propagation in the eastern United states are compared with those in different regions of the Soviet Union. Possible discriminants such as Lg VS. Pamplitudes, Lg/ P amplitude ratios as a function of distance, and Lg energy ratios are found, similar to attenuation and group velocity, to be highly dependent on the propagation path. The valid application of these quantities to the problem of earthquake-explosion discrimination will therefor require regional studies more detailed than previously assumed. A re-evaluation of the magnitude yield relation and an examination of physical parameters which may be relevant to the estimated yield of underground nuclear explosions were performed. The preliminary results indicate that the sub M sub b vs. yield relation shows regional differences and dependence on the source medium, and the collapse volume and the diameter of the collapsed crater are usually proportional to the estimated yield.

Chen, T. C.; Pomeroy, P. W.

1980-07-01

416

Global morphology of infrasound propagation  

Microsoft Academic Search

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,

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

2003-01-01

417

Ionospheric wave and irregularity measurements using passive radio astronomy techniques  

SciTech Connect

The observation of midlatitude structures using passive radio astronomy techniques is discussed, with particular attention being given to the low-frequency radio telescope at the Clark Lake Radio Observatory. The present telescope operates in the 10-125-MHz frequency range. Observations of the ionosphere at separations of a few kilometers to a few hundreds of kilometers by the lines of sight to sources are possible, allowing the determination of the amplitude, wavelength, direction of propagation, and propagation speed of ionospheric waves. Data are considered on large-scale ionospheric gradients and the two-dimensional shapes and sizes of ionospheric irregularities. 10 references.

Erickson, W.C.; Mahoney, M.J.; Jacobson, A.R.; Knowles, S.H.

1988-06-01

418

Demonstration of auroral radio emission mechanisms by laboratory experiment  

NASA Astrophysics Data System (ADS)

Auroral kilometric radiation occurs in regions of depleted plasma density in the polar magnetosphere. These emissions are close to the electron cyclotron frequency and appear to be connected to the formation of high pitch angle electron populations due to the conservation of the magnetic moment. This results in a horseshoe type distribution function being formed in velocity space where electrons are magnetically compressed as they descend towards the Earth's atmosphere. Satellites have observed that radio emissions occur in conjunction with the formation of this distribution and show the radiation to have propagation and polarization characteristics of the extraordinary (X-mode) plasma mode with emission efficiency observed at ~1-2%. To investigate this phenomenon a laboratory experiment, scaled to microwave frequencies and lab dimensions by increasing the cyclotron frequency, was constructed whereby an electron beam propagated through a region of increasing magnetic field created by five independently variable solenoids. Results are presented for two experimental regimes of resonant coupling, 11.7 and 4.42 GHz, achieved by varying the peak magnetic field. Measurements of the experimental radiation frequency, power and efficiency were undertaken as a function of the magnetic compression. Results showed the radiation to be polarized in the near cut-off transverse electric radiation modes, with efficiency of emission ~1-2%, peak power outputs of ~19-30 kW and frequency close to the cyclotron frequency. This represented close correlation between the laboratory radiation efficiency, spectra, polarization and propagation with that of numerical predictions and the magnetospheric observations.

McConville, S. L.; Speirs, D. C.; Ronald, K.; Phelps, A. D. R.; Cross, A. W.; Bingham, R.; Robertson, C. W.; Whyte, C. G.; He, W.; Gillespie, K. M.; Vorgul, I.; Cairns, R. A.; Kellett, B. J.

2008-07-01

419

ENG MMW TV radio-relay systems  

NASA Astrophysics Data System (ADS)

The antenna beamwidth of MMW radio-relay systems is several times lower than that of centimetric-wave radio-relay systems with aperture of antennas being equal. Besides MMW radio-relay systems have the following merits: a high degree of accuracy and noise immunity, improved resolution characteristic, lower weight and dimensions of the equipment. Despite the rather high cost of elementary components and higher atmospheric attenuation, MMW radio- relay systems advantages and features mentioned above are critical and demonstrate for the benefit of choice of MMW particularly for short-range (10 - 15) kms) systems.

Savenkov, V. A.; Kandlin, V. V.; Reshetnikov, O. N.

1994-01-01

420

Radio Direction Finding.  

National Technical Information Service (NTIS)

Discussed in the book are the theoretical principles of radio direction finding and the operating principles of the various types of radio direction finders. Questions concerned with the practical use of ground station radio direction finders are reviewed...

E. S. Goikhman M. I. Rogatkin V. A. Vartanesyan

1970-01-01

421

Amateur Radio Service.  

National Technical Information Service (NTIS)

The Amateur Radio Service data file contains data for applicants and licensees operating under the Amateur Radio Service and the primary information is obtained from FCC Form 610, Application for Individual Amateur Radio Station and/or Operator License, a...

D. P. May

1978-01-01

422

Radio Astronomy Research.  

National Technical Information Service (NTIS)

Radio astronomy research has been carried out in the fields of high resolution interferometry, radio polarimetry, solar activity, and galactic and extragalactic radio sources, details of which are given in a bibliography of references to scientific journa...

R. N. Bracewell

1968-01-01

423

Wideband Radio Wave Observations of Lightning Discharge by Maido-1 Satellite  

NASA Astrophysics Data System (ADS)

Maido-1 satellite was launched on 23 January 2009. The satellite carries the radio-frequency payload, Broadband Measurement of Waveform for VHF Lightning Impulses (VHF sensor), for research on lightning discharges. The final goal of our research is to locate sources of impulsive VHF radiation from lightning discharges and constantly monitor lightning activity from space. Maido-1 satellite has the aim of proving the functions of the sensor in space and to study the radio propagation characteristics of the ionosphere. Through the operation/observation for 5 months, more than 10, 000 VHF signals have been recorded. The locations where VHF signals are detected and the examples of the received waveforms are presented in this paper. We discuss the regional dependency of the received signals.

Kikuchi, Hiroshi; Morimoto, Takeshi; Ushio, Tomoo; Kawasaki, Zen

424

What is Radio Astronomy?  

NSDL National Science Digital Library

This website contains information on radio astronomy, the NRAO, how telescopes work, the history and discovery of radio astronomy, and the radio communication process. This website has activites like "Make your own Radio Image", and visual aids on topics such as: free-free emission, spectral lines, synchrotron emission, masers, and how radio communication works. The site is also a resource for blackbody radiation, the Cosmic Microwave Backround, and the mechanisms of radio wave emission.

2004-07-14

425

AURORAL RADIO EMISSION FROM STARS: THE CASE OF CU VIRGINIS  

SciTech Connect

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.

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

426

Locomotive to Caboose Radio Communication  

Microsoft Academic Search

Although the characteristics of ultra-high frequency radio communication between fixed points have been established Fairly well, the utilization of these frequencies in communication between front and rear of moving railway trains presented problems of which little was known. This paper reports the results of extensive tests made to determine the practical value of these frequencies for such service, and describes

S. G. Ellis

1936-01-01

427

A low cost multi-media radio system  

NASA Astrophysics Data System (ADS)

An alternative, or supplemental, approach to automatic link establishment (ALE) radios is to combine modern, commercially available packet radio technology with an understanding of channel requirements to produce a low-cost multimedia radio (MMR). A prototype unit has been demonstrated to provide two-way, half-duplex packetized message communication via skywave propagation when the operating frequency is below the maximum usable frequency (MUF) and meteor burst (MB) propagation when the operating frequency exceeds the MUF. The prototype MMR uses off-the-shelf commercial radio equipment, including packet radio controller, HF transceiver, 1 kW power amplifier (HPA), Yagi antennas, and PC-controller for a total cost below $4000.

Merrill, Steven C.; McDonough, Anne K.; Symes, Steven W.; Desourdis, Robert I., Jr.

428

Learning radio astronomy by doing radio astronomy  

NASA Astrophysics Data System (ADS)

PARTNeR (Proyecto Académico con el Radio Telescopio de NASA en Robledo, Academic Project with the NASA Radio Telescope at Robledo) is an educational program that allows high school and undergraduate students to control a 34 meter radio telescope and conduct radio astronomical observations via the internet. High-school teachers who join the project take a course to learn about the science of radio astronomy and how to use the antenna as an educational resource. Also, teachers are provided with learning activities they can do with their students and focused on the classroom implementation of the project within an interdisciplinary framework. PARTNeR provides students with firsthand experience in radio astronomy science. Thus, remote radio astronomical observations allow students to learn with a first rate scientific equipment the basics of radio astronomy research, aiming to arouse scientific careers and positive attitudes toward science. In this contribution we show the current observational programs and some recent results.

Vaquerizo Gallego, J. A.

2011-11-01

429

Concomitant chemo-radio-immunotherapy has a lethal therapeutic effect on tongue carcinomas independent of the clinical stage and histological characteristics of the tumor.  

PubMed

We examined the effect of concomitant chemo-radio-immunotherapy on 80 patients with tongue carcinoma. Disappearance of the tumor without recurrence was observed in 21 patients (38.9%) in intravenous infusion chemotherapy group (A) and in 20 patients (76.9%) in intra-arterial infusion chemotherapy group (B) (P<0.005). A total of 41 patients (51.3%) were free from the tumor after the combined therapy. Along with the good therapeutic effect, oral function was preserved with minimal impairment of speech and mastication. Tumor stage, the mode of tumor cell invasion and tumor cell differentiation were not correlated with the therapeutic effect. In addition, the expression of p53, p21(Cip1/WAF1) and proliferating cell nuclear antigen did not differ between the patients with lethal and non-lethal effects. The 5-year-survival rate was 56.8% in Group A, 76.9% in Group B and 59.6% overall. Thus, combined chemo-radio-immunotherapy, especially intra-arterial infusion, may bring a universal therapeutic effect in tongue carcinoma regardless of the tumor stage and the expression of cell phase-regulating proteins. PMID:16730473

Yamamoto, Tetsuya; Oku, Naohisa; Tatemoto, Yukihiro; Ueta, Eisaku; Kamatani, Takaaki; Sasabe, Eri; Osaki, Tokio

2006-05-26

430

Radio frequency interference  

Microsoft Academic Search

The article consists of a Powerpoint presentation on radio frequency interference. The areas discussed include: radio frequency interference; electromagnetic interference; mobile Internet device and wireless sensitivity requirement.

H. Skinner; K. Slattery

2008-01-01

431

Radio pulsars: the search for truth  

NASA Astrophysics Data System (ADS)

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.

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

2013-02-01

432

Faint solar radio structures from decametric observations  

NASA Astrophysics Data System (ADS)

Aims: Decameter radio observations of the solar corona reveal the presence of numerous faint frequency drifting emissions, similar to “solar S bursts” which are reported in the literature. We present a statistical analysis of the characteristics of these emissions and propose a mechanism to excite the Langmuir waves thought to be at the origin of these emissions. Methods: The observations were performed between 1998 and 2002 with the Digital Spectro Polarimeter (DSP) receivers operated at the UTR-2 and Nançay decameter radio telescopes in the frequency range 15-30 MHz. Our theoretical explanation is based on Vlasov-Ampère simulations. Results: Based on the frequency drift rate, three populations of structures can be identified. The largest population presents an average negative frequency drift of -0.9 MHz s-1 and a lifetime up to 11 s (median value of 2.72 s). A second population shows a very small frequency drift of -0.1 MHz s-1 and a short lifetime of about 1 s. The third population presents an average positive frequency drift of +0.95 MHz s-1 and a lifetime of up to 3 s. Also, the frequency drift as a function of frequency is consistent with the former results, which present results in higher frequency range. No specific relationship was found between the occurrence of these emissions and the solar cycle or presence of flares. Assuming that these emissions are produced by “electron clouds” propagating the solar corona, we deduce electron velocities of about 3-5 times the electron thermal velocity. As previously shown, a localized, time-dependent modulation of the electron distribution function (heating) leads to low velocity electron clouds (consistent with observations), which, in turn, can generate Langmuir waves and electromagnetic signals by nonlinear processes.

Briand, C.; Zaslavsky, A.; Maksimovic, M.; Zarka, P.; Lecacheux, A.; Rucker, H. O.; Konovalenko, A. A.; Abranin, E. P.; Dorovsky, V. V.; Stanislavsky, A. A.; Melnik, V. N.

2008-10-01

433

Near earth propagation: physics revealed  

NASA Astrophysics Data System (ADS)

Both the military and consumer sectors are pursuing distributed networked systems and sensors. A major stumbling block to deployment of these sensors will be the radio frequency (RF) propagation environment within a few wavelengths of the earth. Increasing transmit power (battery consumption) is not a practical solution to the problem. This paper will discuss some of the physical phenomena related to the near earth propagation (NEP) problem. When radiating near the earth the communications link is subjected to a list of physical impairments. On the list are the expected Fresnel region encroachment and multipath reflections. Additionally, radiation pattern changes and near earth boundary layer perturbations exist. A significant amount of data has been collected on NEP. Disturbances in the NEP atmosphere can have a time varying attenuation related to the time of day and these discoveries will be discussed. Solutions, or workarounds, to the near earth propagation problem hinge on dynamic adaptive RF elements. Adaptive RF elements will allow the distributed sensor to direct energy, beam form, impedance correct, increase communication efficiency, and decrease battery consumption. Small electrically controllable elements are under development to enable antenna impedance matching in a dynamic environment. Additionally, small dynamic beam forming arrays are under development to focus RF energy in the direction of need. With an increased understanding of the near earth propagation problem, distributed autonomous networked sensors can become a reality within a few centimeters of the earth.

Wert, R.; Goroch, A.; Worthington, E.; Wong, V.

2007-05-01

434

Rosetta Radio Science Investigations (RSI)  

NASA Astrophysics Data System (ADS)

The Rosetta Radio Science Investigations (RSI) experiment addresses fundamental aspects of cometary physics such as the mass and bulk density of the nucleus, its gravity field, nucleus size and shape, internal structure, composition and roughness of the nucleus surface, the abundance of large dust grains, the plasma content in the coma and the combined dust and gas mass flux. RSI does not have a dedicated instrument on the Rosetta spacecraft but makes use of the onboard radio subsystem which is responsible for communication between the spacecraft and the ground stations on Earth. The Rosetta radio subsystem is specially equipped with an Ultra-Stable Oscillator (USO) which significantly improves the sensitivity and accuracy of the measurements. The spacecraft is capable of receiving two uplink signals non-simultaneously at either X-band (7100 MHz) or S-band via the High Gain Antenna (HGA). The downlink transmission via the HGA can occur simultaneously at S-band and X-band. RSI is interested in the nondispersive frequency shifts (classical Doppler) and dispersive frequency shifts (due to the ionized propagation medium), the signal power and the polarization of the radio carrier waves. Variations in these parameters will yield information on the motion of the spacecraft, the perturbing forces acting on the spacecraft and the propagation medium. The RSI science objectives are divided into the primary science objectives (a) cometary gravity field investigations, (b) comet nucleus investigations, (c) cometary coma investigations, (d) asteroid mass and bulk density and the secondary science objectives (e) solar corona sounding, (f) a search for gravitational waves at the comet, the asteroids flybys and during cruise.

Paetzold, M.

435

Shock Waves and Radio Continuum in Miras  

NASA Astrophysics Data System (ADS)

We report a search for radio continuum emission from a sample of 34 Mira and semi-regular variable stars. The main aim of this survey was to look for thermal free-free emission from post-shock ionised gas. The stars were observed on November 3-5, 1995, at 4.8 and 8.6 GHz using the Australia Telescope Compact Array. Radio continuum emission was detected from one source only, the symbiotic Mira R Aqr, which is a well-known radio continuum source. No continuum emission was detected from the other sources with 3 sigma upper limits of typically 0.3 mJy. We have not either detected the Miras previously known to display radio continuum, including o Cet, R Aql and W Hya. Upper limits to radio brightness temperatures are determined. We discuss a simple model for strong shocks propagating in the inner envelopes of long-period variable stars and we derive simple formulae allowing to estimate the shock velocity from the observed radio continuum flux. From the upper limits to the radio flux densities we find no direct evidence for strong shocks with velocities above 25 km/s near two stellar radii, and we infer that the pulsation-driven stellar shocks generated in the stellar photospheres are strongly damped within a short radial distance from the stellar surface.

Chapman, J. M.; Rudnitskij, G. M.

436

Extraction Method for Substrate-Related Components of Vertical Junctionless Silicon Nanowire Field-Effect Transistors and Its Verification on Radio Frequency Characteristics  

NASA Astrophysics Data System (ADS)

In this paper, we propose a radio-frequency (RF) model and parameter extraction method for vertical junctionless silicon nanowire (VJL SNW) field-effect transistors (FETs) using three-dimensional (3D) device simulation. We introduce the substrate-related components such as the substrate resistance (Rsub) and drain-to-substrate capacitance (Csub), and evaluate the RF performance such as ft, fmax, gate input capacitance, and transport time delay. A quasi-static (QS) RF model has been used in simulation program with integrated circuit emphasis (SPICE) circuit simulator to simulate VJL SNW FETs with RF parameters extracted from 3D device simulated Y-parameters. We confirmed the validity of our RF model by the well-matched results between HSPICE and 3D device simulation in terms of the Y-parameters and the S22-parameter up to 100 GHz.

Shin, Sunhae; Kang, In Man; Kim, Kyung Rok

2012-06-01

437

Consideration on the scatter of cod and fatigue crack propagation characteristics of heavy section C-Mn-V forged steel for offshore structure  

SciTech Connect

A 197-mm thick C-Mn-V forged steel plate including welds was subjected to mechanical and corrosion-fatigue tests and several engineering data useful for the design of offshore structures were obtained. The chemical and mechanical properties of base metal and welds satisfy typical current requirements in the North Sea projects and the heavy wall forged tubular is proved to be applicable to the offshore structures. The scatter of critical cod in the transition temperature range was studied and a new statistical method was presented for estimating the lowest critical cod value. Corrosion-fatigure tests in seawater were conducted on the base metal and heat affected zone (HAZ) of submerged arc welding at a cyclic frequency corresponding to sea wave frequency. No difference in fatigue crack propagation rate was observed between the base metal and HAZ.

Fukuda, T.; Iwadate, T.; Shimazaki, M.

1982-01-01

438

Monitoring the lower ionosphere with a small scale interferometric network of radio receivers  

NASA Astrophysics Data System (ADS)

Sprites, gigantic jets and relativistic electron beams above thunderclouds attracted significant attention in the last decades. These natural transient events are caused by lightning discharges and they are associated with characteristic low frequency radio emissions from a certain height above thunderclouds. The altitudes of these sources can be inferred from their radio waves which are reflected by the lower ionosphere along their propagation path. The ionospheric conditions vary with time and location which makes it important to monitor the lower ionosphere during the observation period. This work uses 100 kHz radio emissions from the LOng Range Navigation (LORAN) transmitters in Western Europe to monitor the height of the reflecting lower ionosphere. The pulsed LORAN transmissions are synced with high precision to atomic time and they are therefore particularly suitable for monitoring the lower ionosphere. The vertical electric field strengths of the LORAN transmissions are recorded with a small scale interferometric network of eight wide band digital radio receivers which are separated by distances ranging from ~3 km up to ~30 km. The network was deployed in southern France during the summer months from July to September in 2011 and 2012 when numerous thunderstorms occur. The ionospheric monitoring with the network reveals the dynamics of the lower ionosphere at different locations throughout the observation period. Results of the ionospheric monitoring for different meteorological conditions will be presented.

Mezentsev, Andrey; Fullekrug, Martin

2013-04-01

439

Jovian non-thermal radio emission observed by STEREO/WAVES  

NASA Astrophysics Data System (ADS)

Solar TErrestrial RElations Observatory (STEREO) consists of two 3-axis-stabilized identical spacecraft (STEREO-A and STEREO-B), launched on Oct. 25, 2006. The WAVES experiment onboard STEREO is a radio burst tracer which observes the generation and evolution of the radio disturbances from the Sun to the orbit of Earth. Being mainly dedicated for measuring solar radio bursts, SWAVES also provided unique observations of the Jovian planetary radio emission. For the first time Jovian radiation is observed stereoscopically by two identical spacecraft in a frequency range from few kHz up to 16 MHz. The data recorded during more than two years (Nov 2006 - Dec 2008) of mission operations is analyzed. A big amount of the events of non-Io and Io controlled "arc-like" decametric components of the Jovian radiation (DAM) as well as hectometric emission (HOM) has been recorded. The unique stereoscopic observations by STEREO provide the opportunity to determine the propagation characteristics of the Jovian non-thermal radiation such as directivity and beam width of the emission cone. First results will be presented.

Rucker, H. O.; Panchenko, M.; Shaposhnikov, V. E.; Melnik, V. N.; Boudjada, M. Y.; Stereo Team

2009-04-01

440

Stress Induced Effects on the Propagation of Surface Waves.  

National Technical Information Service (NTIS)

It is known that the propagation characteristics of elastic waves are influenced by the nature of biasing stress distributions in the propagating medium. A knowledge of the magnitude of such effects plays an important role in improving the performance and...

B. K. Sinha W. J. Tanski T. Lukaszek A. Ballato

1983-01-01

441

Propagation of Bending Waves in a Periodically Stiffened Panel.  

National Technical Information Service (NTIS)

The wave propagation characteristics of a semi-infinite, simply supported, periodically stiffened plate were analyzed using the propagation constant approach. The stiffeners were modeled as line forces with the impedance calculated from energy principles....

P. Goeransson

1984-01-01

442

The Radio Sonde  

Microsoft Academic Search

The radio sonde has been developed in recent years as a practical instrument for transmitting information from the stratosphere. This paper discusses some of the problems connected with the application of the radio-sonde principle to the radio meteorograph and also to the cosmic-ray radio sonde.

W. H. Pickering

1943-01-01

443

The Radio Amateur's Handbook.  

ERIC Educational Resources Information Center

|The objectives of this basic reference work for the radio amateur are to present radio theory and practice in terms of application and to reflect both the fundamentals and the rapidly-advancing technology of radio communications so that the radio amateur will have a guide to what is practical, meaningful, proven, and useful. Twenty-three chapters…

Blakeslee, Douglas, Ed.

444

Propagation 1: State of the act of modelling and prediction in HF propagation  

NASA Astrophysics Data System (ADS)

The lecture reviews the state of the art in HF propagation modelling and describes the principles of radio frequency predictions. As a basis for the discussions, a brief introduction is given to the ionospheric parameters of importance to HF-propagation. Current methods for frequency prediction are semi-empirical, that is they depend upon a large data base of ionospheric physical models of the ionosphere and of radio wave propagation through the medium. In addition models of the noise and interference environment must be included. The lecture discusses the principles on which the methods are based, as well as their limitations. Examples are given of the use of predictions in system planning and communications. The relative importance of skywave and ground wave communications in the HF-band is discussed.

Thrane, E. V.

1986-03-01

445

The radio lighthouse CU Virginis: the spin-down of a single main-sequence star  

NASA Astrophysics Data System (ADS)

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 gyrosynchrotron emission arising from a thin magnetospheric layer. Previous radio observations at 1.4 GHz showed that a 100 per cent 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 time-scale 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 provide 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 min. 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 Square Kilometre Array can exploit.

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

2008-03-01

446

Radio Quiet Zones (RQZ) - Working with national communication administrations  

NASA Astrophysics Data System (ADS)

Radio Astronomy detects extremely faint radio signals from space, and hence is very susceptible to Radio Frequency Interference (RFI) from other radio communication services. Although radio astronomy has been allocated some radio bands by the International Telecommunications Union (ITU), cosmic radio emissions occur over the whole of the electromagnetic spectrum. Thus, there is a need for radio telescopes to operate over very wide radio bands and avoid RFI. Radio Quiet Zones (RQZ) in various forms have been implemented around many radio astronomy observatories, to minimise the impact of RFI on radio astronomy observations by coordinating with nearby radiocommunication services. The history and characteristics of such RQZ around the world will be reviewed, with emphasis on recent experience. For the next generation radio astronomy telescopes such as the Square Kilometre Array (SKA), it will be of critical importance to minimise RFI over the whole operating frequency range 200 MHz - 25 GHz. Progress towards establishing strict RQZ for the SKA will be reviewed. The main experience and lesson learned is that it is critical to work closely with national communication administrations. Work on RQZ in international bodies and the implications for radio sciences will also be discussed.

Tzioumis, Anastasios

447

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, ÂÂ. is to promote young peopleÂs intellectual creative and professional growth through training and access to media and to produce the highest quality original media for local and national outlets. 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.

448

Study on method to simulate light propagation on tissue with characteristics of radial-beam LED based on Monte-carlo method.  

PubMed

In biomedical, Monte-carlo simulation is commonly used for simulation of light diffusion in tissue. But, most of previous studies did not consider a radial beam LED as light source. Therefore, we considered characteristics of a radial beam LED and applied them on MC simulation as light source. In this paper, we consider 3 characteristics of radial beam LED. The first is an initial launch area of photons. The second is an incident angle of a photon at an initial photon launching area. The third is the refraction effect according to contact area between LED and a turbid medium. For the verification of the MC simulation, we compared simulation and experimental results. The average of the correlation coefficient between simulation and experimental results is 0.9954. Through this study, we show an effective method to simulate light diffusion on tissue with characteristics for radial beam LED based on MC simulation. PMID:24109615

Song, Sangha; Elgezua, Inko; Kobayashi, Yo; Fujie, Masakatsu G

2013-07-01

449

HF groundwave and skywave propagation  

NASA Astrophysics Data System (ADS)

The principles of HF ground- and skywave propagation are reviewed with regard to regular conditions as well as anomalous phenomena which may effect the signal characteristics and thus may have an influence on the performance of digital communication systems. Particular consideration is given to the statistics of signal fading as a basis for system design.

Hortenbach, Klaus-Juergen

1986-10-01

450

Over-the-Horizon Anomalous VHF Propagation and Earthquake Precursors  

NASA Astrophysics Data System (ADS)

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.

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

2012-09-01

451

A genealogical database for plant propagation records  

Microsoft Academic Search

A CODASYL type database has been created for plant propagation records. The existence and history of plants can be recorded in such a way that details of parentage and offspring can be traced. Plants that have undergone similar treatments and events or that have similar characteristics can be located and other information assisting the management of the propagation experiments is

P. A. Clarke; B. Casiero

1979-01-01

452

Technical evaluation report on the ElectromagneticWave Propagation Panel Symposium on Propagation Effects on Military Systems in the High Latitude Region  

NASA Astrophysics Data System (ADS)

Propagation effects on military systems in the high latitude region were examined. Topics discussed include: experimental studies of ionospheric irregularities and regular structure, results of ionospheric modification (HF heating) experiments,theoretical studies of ionospheric irregularity formation, global survey of ground conductivities,disturbance modeling studies, high latitude effects on HF radio communicaton, transionospheric communications, satellite synthetic aperture radar (SAR), MF radio broadcasting, spatially adaptive propagation, HF digital, Skywave HF sea state radar, and meteor burst communication.

Hunsucker, R. D.

1985-11-01

453

Satellite communications and amateur radio  

Microsoft Academic Search

Amateur radio use of Radio-1 and Radio-2 satellite communications is described since its beginning in October, 1978, which involves cooperation between DOSAAF and engineering and student design bodies. Second generation satellites Radio-3 and Radio-8 offered the possibility of an expanded system, and much work was done to increase useful life and reliability of space radio communications. Soviet and foreign radio

A. Abolits

1985-01-01

454

Structure-guided engineering of Anticalins with improved binding behavior and biochemical characteristics for application in radio-immuno imaging and/or therapy.  

PubMed

Modern strategies in radio-immuno therapy and in vivo imaging require robust, small, and specific ligand-binding proteins. In this context we have previously developed artificial lipocalins, so-called Anticalins, with high binding activity toward rare-earth metal-chelate complexes using combinatorial protein design. Here we describe further improvement of the Anticalin C26 via in vitro affinity maturation to yield CL31, which has a fourfold slower dissociation half-life above 2h. Also, we present the crystallographic analyses of both the initial and the improved Anticalin, providing insight into the molecular mechanism of chelated metal binding and the role of amino acid substitutions during the step-wise affinity maturation. Notably, one of the four structurally variable loops that form the ligand pocket in the lipocalin scaffold undergoes a significant conformational change from C26 to CL31, acting as a lid that closes over the accommodated metal-chelate ligand. A systematic mutational study indicated that further improvement of ligand affinity is difficult to achieve while providing clues on the contribution of relevant side chains in the engineered binding pocket. Unexpectedly, some of the amino acid replacements led to strong increases - more then 10-fold - in the yield of soluble protein from periplasmic secretion in Escherichia coli. PMID:23542582

Eggenstein, E; Eichinger, A; Kim, H-J; Skerra, A

2013-03-27

455

Developments in Jovian Radio Emissions Tomography and Observations Techniques  

NASA Astrophysics Data System (ADS)

Jupiter radio emission is known to be the most powerful nonthermal planetary radiation. In recent years specifically space-based observations allow us to permanently cover a large frequency band(from 100 kHz up to 40 MHz combined with ground-based telescopes)of the Jovian spectrum. The Plasma and Wave Science experiment onboard Galileo enables the observation of Jovian kilometric and hectometric emissions; Wind/WAVES and ground-based telescopes (mainly Decametric Array in Nancay, France, and UTR-2 in Kharkov, Ukraine) cover also hectometric and mainly decametric emissions. Specific geometrical configurations between Cassini approaching Jupiter and Wind spacecraft orbiting Earth, with Galileo orbiting Jupiter and Wind, in combination with ground-based observations provide a new approach to perform Jovian radio tomography. The tomography technique is used to analyze ray paths of Jovian radio emission observed in different directions (e.g. solar and anti-solar direction) and for different declination of Earth. The developments of Jovian radio emission tomography in recent years treated refraction effects and its connection to the local magnetic field in the radio source as well as the radio wave propagation through the Io torus and the terrestrial ionosphere. Most recently ground-based multi-site and simultaneous Jupiter decametric radio observations by means of digital spectropolarimeter and waveform receiver provide the basis of a new data analysis treatment. The above addressed topics are without exemption deeply connected to the plasma structures the radio waves are generated in and propagating through.

Rucker, H. O.; Boudjada, M. Y.; Leitner, M.; Lecacheux, A.; Aubier, M.; Konovalenko, A.; Galopeau, P. H. M.; Shaposhnikov, V.

2001-06-01

456

Vertical Laser Beam Propagation Through the Troposphere.  

National Technical Information Service (NTIS)

The characteristics of the earth's atmosphere and its effects upon laser beams was investigated in a series of balloon borne, optical propagation experiments. These experiments were designed to simulate the space to ground laser link. An experiment to det...

P. O. Minott J. L. Bufton W. H. Schaefer D. A. Grolemund

1974-01-01

457

HF (High Frequencies) Groundwave and Skywave Propagation.  

National Technical Information Service (NTIS)

The principles of HF ground- and skywave propagation are reviewed with regard to regular conditions as well as anomalous phenomena which may effect the signal characteristics and thus may have an influence on the performance of digital communication syste...

K. Hortenbach

1986-01-01

458

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

NASA Astrophysics Data System (ADS)

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.

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

2013-03-01

459

Astrometry and geodesy with radio interferometry: experiments, models, results  

Microsoft Academic Search

Summarizes current status of radio interferometry at radio frequencies\\u000abetween Earth-based receivers, for astrometric and geodetic applications.\\u000aEmphasizes theoretical models of VLBI observables that are required to extract\\u000aresults at the present accuracy levels of 1 cm and 1 nanoradian. Highlights the\\u000aachievements of VLBI during the past two decades in reference frames, Earth\\u000aorientation, atmospheric effects on microwave propagation,

Ojars J. Sovers; John L. Fanselow; Christopher S. Jacobs

1998-01-01

460

Radio frequency picosecond phototube  

SciTech Connect

We propose a photon detector for recording low-level and ultra-fast optical signals, based on radio frequency (RF) analysis of low-energy photoelectrons (PEs). By using currently developed 500 MHz RF deflector, it is possible to scan circularly and detect single PEs, amplified in multi-channel plates (MCPs). The operation of the tube is investigated by means of thermionic electron source. It is demonstrated that the signals generated in the MCP can be processed event by event; by using available nanosecond electronics and that time resolution better than 20 ps can be achieved. Timing characteristics of the Cherenkov detector with RF phototube in a ''head-on'' geometry is investigated by means of Monte Carlo simulation.

A. Margaryan; R. Carlini; R. Ent; N. Grigoryan; K. Gyunashyan; O. Hashimoto; K. Hovater; M. Ispiryan; S. Knyazyan; B. Kross; S. Majewski; G. Marikyan; M. Mkrtchyan; L. Parlakyan; V. Popov; L. Tang; H. Vardanyan; C. Yan; S. Zhamkochyan; C. Zorn

2006-10-01

461

Midlatitude propagation of VLF to MF waves through nighttime ionosphere above powerful VLF transmitters  

NASA Astrophysics Data System (ADS)

nighttime observations made by the DEMETER satellite in the very low frequency (VLF) to medium frequency (MF) bands (3 kHz to 3 MHz) have demonstrated the propagation of radio waves from the bottom of ionosphere up to the satellite altitude (~700 km). Propagation characteristics derived from the magneto-ionic theory [Budden, ] are used to explain the absence of wave observations between ~1 and 2 MHz. Under hypotheses made for the Appleton and Hartree (or Appleton and Lassen) formula, studies of the vertical variations of the real and imaginary parts of the refractive index are performed to point out modifications in the propagation characteristics of the waves: (i) at the crossing of the plasma cutoffs regions, (ii) at the crossing of the ordinary and extraordinary mode resonance regions, and (iii) in the region where the product of the collision frequency (?) and the electronic density (Ne) is maximum. It is shown that enhancements in the collision frequencies, produced by powerful VLF transmitters in the region where the product of ? and Ne is maximum, open the half angle of the MF wave transmission cones and increase the power densities of those waves at the DEMETER altitude.

Lefeuvre, F.; PinçOn, J. L.; Parrot, M.

2013-03-01

462

Principles of Radio Navigation.  

National Technical Information Service (NTIS)

The textbook for radio engineering higher institutions of learning and departments explains the operating principles of radio navigational aids used to navigate flying vehicles. General questions concerned with the accuracy of navigational fixes obtained ...

O. V. Belavin

1970-01-01

463

ITSY Handheld Software Radio.  

National Technical Information Service (NTIS)

Software radio technology promises to eliminate existing radio interoperability problems, provide a path for rapidly incorporating advances in digital communications, and enable new applications and waveforms that take advantage of the tremendous flexibil...

V. G. Bose

2001-01-01

464

Modeling electromagnetic propagation in the Earth-ionosphere waveguide  

Microsoft Academic Search

The ionosphere plays a role in radio propagation that varies strongly with frequency. At extremely low frequency (ELF: 3-3000 Hz) and very low frequency (VLF: 3-30 kHz), the ground and the ionosphere are good electrical conductors and form a spherical Earth-ionosphere waveguide. Many giants of the electromagnetics (EMs) community studied ELF-VLF propagation in the Earth-ionosphere waveguide, a topic which was

Steven A. Cummer

2000-01-01

465

A Kinetic Model for the Radio CME  

NASA Astrophysics Data System (ADS)

Current studies on Coronal Mass Ejections (CMEs) are mostly concentrated on their macroscopic properties as measured on White-Light images. On the other hand, radio emissions from CMEs carry the information of high energy particles associated with them, but usually without spatial information. In this regard, the rare radio maps of the 1998 April 20 CME obtained with the Nancay radioheliograph between 164 and 432 MHz (called a radio CME by Bastian et al. in 2001) offer an exceptional opportunity to explore the spatial distribution of high energy electrons inside the CME loop. We present a detailed kinetic model for the radio CME employing the lower hybrid (LH) waves excited by the CME shock as the primary electron acceleration mechanism, and magnetic mirroring and Coulomb collisions as the propagation effects inside the expanding loop. The main constraint in this modeling comes from the fact that the LH waves accelerate electrons parallel to the magnetic field and the accelerated electrons should gain, during propagation, sufficient amount of the perpendicular momentum to emit the synchrotron radiation as observed. The relative magnetic field variation responsible for the magnetic mirroring is inferred from the geometrical shape of the CME on the images of the Large Angle and Spectrometric Coronagraph Experiment (LASCO), and the field strength and the amplitude of the LH waves are determined from the observed radio spectra. The modeling is focused on the spatial distribution of the LH waves most plausible to explain the radio maps, and the result is discussed in relation to the associated shock property.

Lee, Jeongwoo; Gary, D. E.

2009-05-01

466

Atmospheric Sensitivity and Validation Study of the Variable Terrain Radio Parabolic Equation Model (VTRPE).  

National Technical Information Service (NTIS)

The Variable Terrain Radio Parabolic Equation (VTRPE) computer model is a powerful and flexible program that provides calculations of the radar propagation conditions of the atmosphere. This study quantifies the sensitivity of the VTRPE model to the accur...

M. K. Doggett

1997-01-01

467

Attenuation of Radio Wave Signals Coupled Into Twelve Large Building Structures.  

National Technical Information Service (NTIS)

This is the fourth in a series of NIST technical notes (TN) on propagation and detection of radio signals in large building structures (apartment complex, hotel, office buildings, sports stadium, shopping mall, etc.). The first, second, and third NIST Tec...

C. L. Holloway D. Camell G. Koepke K. A. Remley W. F. Young

2008-01-01

468

Cognitive Radio Architecture Evolution  

Microsoft Academic Search

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

Joseph Mitola

2009-01-01

469

Commercial Radio as Communication.  

ERIC Educational Resources Information Center

|Compares the day-to-day work routines of commercial radio with the principles of a theoretical communication model. Illuminates peculiarities of the conduct of communication by commercial radio. Discusses the application of theoretical models to the evaluation of practicing institutions. Offers assessments of commercial radio deriving from…

Rothenbuhler, Eric W.

1996-01-01

470

Introduction to Radio Astronomy  

Microsoft Academic Search

A general description of the nature of radio astronomy, its differences from optical astronomy, a review of the earliest beginnings of galactic and solar radio astronomy, and a listing of other important observational discoveries is given. A nearly complete bibliography of these early publications and of the principal review books and papers on Radio Astronomy is given. Some practical aspects

F. T. Haddock

1958-01-01

471

Electromagnetic wave propagation in multilayer dielectric periodic structures  

Microsoft Academic Search

The propagation characteristics in multilayer dielectric periodic structures, that extends a previous analysis by introducing additional dielectric layers, is presented. It is applied to propagating electromagnetic modes along the longitudinal and transverse directions of the structure's periodicity. The use of Floquet's theorem reduces the analysis to a single cell of the propagating fields for both, TE and TM polarizations. Results

J. Crisostomo; W. A. Costa; A. J. Giarola

1993-01-01

472

Perpendicular propagation of magnetosonic waves  

NASA Astrophysics Data System (ADS)

Azimuthal and radial propagation characteristics of perpendicularly propagating fast magnetosonic waves in an axis-symmetrical medium with the presence of plasmapause is investigated analytically based on Snell's law. We find that Q = nr sin ? is conserved during the propagation, where n is wave refractive index, r is geo-centered distance, and ? is wave azimuthal angle with zero pointing radially outward. The radial range of wave propagation can be determined by comparing Q and the radial profile of nr.Trapped waves, which are bounded in a narrow radial range but migrate azimuthally and even circularly, are identified inside the plasmapause over a broad range of wave azimuthal angles and over a broad range of wave frequencies from the proton gyrofrequency to the lower hybrid resonance frequency. In contrast untrapped waves launched inside and outside the plasmasphere can travel azimuthally 0-4 hrs and 0-7 hrs in local times respectively. The substantial radial and azimuthal propagation may account for the presence of magnetosonic waves away from the source region.

Chen, Lunjin; Thorne, Richard M.

2012-07-01

473

Clamping of time scales and collation of frequencies in the frequency range of super-long radio waves  

Microsoft Academic Search

The frequency range of super-long radio waves was historically the first frequency range used for radio communication. Fifty to 55 years ago, almost all of radio (mainly spark transmitters and the corresponding receiving equipment) worked on frequencies below 60 kHz. The theory of propagation of super-long radio waves around the earth reached at that time a rather high development stage

M. V. Bolotnikov; A. D. Klykov

1972-01-01

474

Acousto-optical and SAW propagation characteristics of temperature stable multilayered structures based on LiNbO3 and diamond  

NASA Astrophysics Data System (ADS)

Theoretical studies on the surface acoustic wave (SAW) properties of c-axis oriented LiNbO3/IDT/diamond and diamond/IDT/128° rotated Y-X cut LiNbO3 multilayered structures have been considered. Both layered structures exhibit a positive temperature coefficient of delay (TCD) characteristic, and a zero TCD device is obtained after integrating with an over-layer of either tellurium dioxide (TeO2) or silicon dioxide (SiO2). The presence of a TeO2 over-layer enhanced the electromechanical coupling coefficients of both multilayered structures, which acts as a better temperature compensation layer than SiO2. The temperature stable TeO2/LiNbO3/IDT/diamond layered structure exhibits good electromechanical coefficient and higher phase velocity for SAW device applications. On the other hand, a high acousto-optical (AO) figure of merit (30-37) × 10-15 s3 kg-1 has been obtained for the temperature stable SiO2/diamond/IDT/LiNbO3 layered structure indicating a promising device structure for AO applications.

Shandilya, Swati; Sreenivas, K.; Gupta, Vinay

2008-01-01

475

Primary analysis of CMEs associated with the radio emission during October 22 to November 03, 2002  

NASA Astrophysics Data System (ADS)

Based on data of eight solar radio emissions associated with the coronal mass ejection (CME) in the period of October 22, 2003 to November 3, 2003 observed with the solar radio broad band spectrometer of National Astronomical Observatories of China (NAOC), and combined with image data obtained from Nobeyama Radioheliograph (NoRH) and Siberian Solar Radio Telescope (SSRT), spectral data from Culgoora and Waves/Wind, and the fixed frequency data from Nobeyama Radio Polarimeter (NoRP), characteristics of radio emission of these 8 radio bursts are analyzed primarily in order to find the relationship between the CMEs and the radio emissions.

Yao, Yin-Bo; Shao, Cheng-Wen; Shi, Shuo-Biao; Li, Wei-Hua; Xu, Chun; Liu, Yu-Ying

2005-06-01

476

Gear Crack Propagation Investigations.  

National Technical Information Service (NTIS)

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 ...

D. G. Lewicki R. Ballarini

1996-01-01

477

Examining Titan’s atmospheric conductivity profile using Cassini radio occultations  

NASA Astrophysics Data System (ADS)

We present a study investigating the atmosphere of Titan using radio occultation measurements from Cassini’s Radio Science Subsystem (RSS). While previous studies have examined the ionospheric profile above 400 km using Cassini RSS observations, and below 80 km using observations from the Huygens probe, a definitive conductivity profile at all altitudes and representing several latitudes and local times has yet to be published. There are challenges in processing Cassini radio occultation data below 400 km to study conductivity that include resolving and removing the effect of the neutral atmosphere, since the ratio of neutral to charged particles increases below that altitude. We will be surveying the multi-frequency radio occultations at Titan in search of the dispersive behavior characteristic of charged particles in the lower atmosphere. Our work employs a method previously used on Magellan data at Venus to extend processing of available Cassini occultation data to the surface. This will provide better atmospheric Schumann resonance cavity model constraints, as well as enable more complete studies of the structure of the ionosphere, its interactions with Saturn's magnetosphere, and further our understanding of the role and distribution of aerosols in Titan’s atmosphere. Schumann resonance consists of EM radiation propagating at the atmospheric cavity's resonant frequencies and it was observed for the first time on another planetary body during Huygens' descent on Titan. Modeling of Titan's cavity can shed light on characterizing a suspected underground liquid ocean and a possible radiative source, such as interactions between ionosphere and Saturn's magnetosphere. Also, characteristics of charged particles associated with the thick organic aerosol haze in Titan's atmosphere can be better constrained by a full atmospheric conductivity profile.

Ionita, D.; Paty, C. S.; Steffes, P. G.

2009-12-01

478

Extra Low-Frequency Terrestrial Radio-Wave Field Calculations with the Zonal Harmonics Series.  

National Technical Information Service (NTIS)

Use of the zonal harmonics series for calculating the terrestrial wave guide fields directly is described. The analysis is extended to include radio waves propagating into sea water or below the earth's surface. A sample calculation of ELF radio waves is ...

J. R. Johler R. L. Lewis

1968-01-01

479

Extra Low-Frequency Terrestrial Radio-Wave Field Calculations with the Zonal Harmonics Series  

Microsoft Academic Search

Use of the zonal harmonics series for calculating the terrestrial wave guide fields directly is described. The analysis is extended to include radio waves propagating into sea water or below the earth's surface. A sample calculation of ELF radio waves is analyzed into a direct wave and a wave that has traveled the circumference of the earth. The location of

J. Ralph Johler; Richard L. Lewis

1969-01-01

480

Alzheimer's disease as a defect of neuronal autotrophism: a hypothetical analogy with amateur radio operation  

Microsoft Academic Search

Amyloid precursor protein appears to be a signaling protein that plays a role in neuronal autotrophism, indicating integrity of the nerve terminal and synapse. Analogous to amateur radio operation with a damaged antenna in which further attempts to improve signal propagation can result in damage to the radio equipment, abnormal signaling by the secreted amyloid precursor protein stimulates compensatory metabolic

T.-K. Baik; R. W. Leech; R. A. Brumback

1998-01-01