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1

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

2

Wideband radio channel measurement system at 2 GHz  

Microsoft Academic Search

This paper describes the wideband radio channel sounding techniques for mobile radio channel measurements. Implementation of the cross-correlation method using both a sliding correlator and a matched filter detector is presented. Limitations and accuracy of radio channel measurements are discussed. Typically, delay resolution of about 20 ns is achieved with 100 MHz bandwidth. With a sliding correlator, a dynamic range

Jarmo Kivinen; Timo O. Korhonen; Pauli Aikio; Ralf Gruber; Pertti Vainikainen; S.-G. Haggman

1999-01-01

3

SUPERRESOLUTION MEASUREMENT AND SIMULATION OF MOBILE VECTOR RADIO CHANNELS  

Microsoft Academic Search

For the simulation and design of smart antenna transmission principles in mobile radio, precise knowledge of the time-variant directional multipath structure in various radio environments is required. In this paper a new broadband multiple-input-multiple-output (MIMO) vector radio channel sounder is described which uses multiple antennas at the transmitter as well as at the receiver position. The proposed MIMO measurement principle

R. S. Thomä; D. Hampicke; A. Richter; G. Sommerkorn; U. Trautwein

2000-01-01

4

Comparison between two simulation techniques and measurement results for ultra wideband indoor radio channels  

Microsoft Academic Search

Two three-dimensional simulation techniques (Polyhedral Beam Tracing and Finite Difference Time Domain) for modeling an ultra wideband (850 MHz) indoor radio channel are compared among themselves and with experimental data. Measurements were performed within a typical hall (indoor) scenario at Pontifícia Universidade Católica do Rio de Janeiro (PUC-Rio) to extract channel parameters such as the power delay profiles. I. INTRODUCTION

F. J. B. Barros; L. A. R. Ramirez; E. Costa; F. J. V. Hasselmann; G. L. Siqueira

2011-01-01

5

Excess delay estimation from time-varying mobile radio channel impulse response measurements  

Microsoft Academic Search

This letter proposes a method for estimating the instantaneous excess delay in time-varying mobile radio channel impulse response measurement data using image processing techniques. The method is shown by example to produce more accurate mean power delay profiles than those produced assuming either constant or linearly varying excess delay

Alan J. Coulson; Ramakrishna Kakarala

1999-01-01

6

Wideband MIMO Car-to-Car Radio Channel Measurements at 5.3 GHz  

Microsoft Academic Search

Measurements of car-to-car (C2C) radio channels with 60 MHz bandwidth at 5.3 GHz have been performed in Helsinki, Finland. We focused on 30x30 multiple-input multiple- output (MIMO) measurements, conducted in four environments (urban, sub-urban, campus and highway), under quasi-realistic traffic conditions. As first results, we present in this paper the delay spread statistics for each investigated environment. The largest values

Olivier Renaudin; Veli-matti Kolmonen; Pertti Vainikainen; Claude Oestges

2008-01-01

7

FMCW channel sounder with digital processing for measuring the coherence of wideband HF radio links  

NASA Astrophysics Data System (ADS)

Multipath propagation, and in particular, the interference between the ordinary and the extraordinary waves, places a fundamental constraint on the performance of wideband HF skywave radio links. Furthermore, the dispersive nature of ionospheric propagation causes phase nonlinearity and hence distortion of narrow pulses. In this paper, an FMCW wideband sounder built for the purposes of characterizing the channel is described. Spectral analysis of the audio output of the sounder via the FFT algorithm is shown to permit measurement of thef amplitude/frequency function, the polarization bandwidth, the fade rate, the fade depth and the distortion of a narrow pulse, all for a desired isolated ionospheric propagation mode. The sounder was used to collect data over an oblique path in the UK. The results of applying the FFT processing technique to the experimental data are presented.

Salous, S.

1986-08-01

8

Radio Channel Measurements at Street Intersections for Vehicle-to-Vehicle Safety Applications  

Microsoft Academic Search

This paper presents the results of an empirical study of wireless propagation channels for vehicle-to-vehicle communications in street intersections, a scenario especially important for collision avoidance applications. The results are derived from a channel measurement campaign performed at 5.6 GHz in four different types of urban intersections. We present results on typical power delay profiles, pathloss and delay spreads and

Johan Karedal; Fredrik Tufvesson; Taimoor Abbas; Oliver Klemp; Alexander Paier; Laura Bernadó; Andreas F. Molisch

2010-01-01

9

A self-contained hydroacoustic station with radio channel for acoustic measurements on the shelf  

Microsoft Academic Search

A self-contained hydroacoustic station for long-term (up to one month) stationary measurements on the shelf of acoustic-pressure\\u000a variations in a 1- to 15 000-Hz frequency band is described. If it is necessary, for example, for arranging online monitoring\\u000a of industrial acoustic noises, the station is additionally equipped with a radiotelemetry channel, along which acoustic data\\u000a can be transmitted to a

S. V. Borisov; D. G. Kovzel; A. N. Rutenko; V. G. Ushchipovskii

2008-01-01

10

Digital Channelizing Radio Frequency Receiver  

Microsoft Academic Search

HYPRES is developing a class of digital receivers featuring direct digitization at radio frequency (RF). Such a receiver consists of a wideband analog-to-digital converter (ADC) modulator and multiple digital channelizer units to extract different frequency bands-of-interest within the broad digitized spectrum. The single-bit oversampled data, from either a lowpass delta or bandpass delta-sigma modulator, are applied to one or more

Deepnarayan Gupta; Timur V. Filippov; Alexander F. Kirichenko; Dmitri E. Kirichenko; Igor V. Vernik; Anubhav Sahu; Saad Sarwana; Pavel Shevchenko; Andrei Talalaevskii; Oleg A. Mukhanov

2007-01-01

11

Identification of time-variant directional mobile radio channels  

Microsoft Academic Search

For the identification of the time-variant, directional structure of the mobile radio channel impulse response (CIR), a broadband vector channel sounder is described. The measurement procedure relies on periodic multifrequency excitation signals, correlation processing, and joint delay-azimuth super-resolution based on the two-dimensional (2-D) unitary ESPRIT algorithm. Problems of imperfect receiver and antenna performance as well as antenna array calibration methods

Reiner S. Thomä; Dirk Hampicke; Andreas Richter; Gerd Sommerkorn; Axel Schneider; Uwe Trautwein; Walter Wirnitzer

2000-01-01

12

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

13

Radio Transmission Measurements  

Microsoft Academic Search

The paper divides naturally into three sections. The first section briefly analyses the radio transmission circuit into (a) the sending or radiating portion, (b) the transmitting portion consisting of the ether path thru which the radiated waves travel, and (c) the receiving portion. The relation of these from the standpoint of the radio transmission engineer is discussed, pointing out the

R. Bown; C. R. Englund; H. T. Friis

1923-01-01

14

Channel modeling and adaptive equalization of indoor radio channels  

Microsoft Academic Search

The authors analyze the benefits of using a decision feedback equalizer (DFE) in the indoor radio environment and examine the results of performance predictions for different channel modelings. It is found that a QPSK\\/DFE modem with second-order diversity can operate at a data rate that is an order of magnitude higher than a QPSK (quadratic-phase-shift-keying) modem without equalization. A given

T. A. Sexton; K. Pahlavan

1989-01-01

15

Measurement and Modelling of Emergency Vehicle-to-Indoor 4.9 GHz Radio Channels and Prediction of IEEE 802.16 Performance for Public Safety Applications  

Microsoft Academic Search

Work reported in this paper contributes to the characterisation of 4.9 GHz radio channels in a scenario in which emergency vehicles are parked outside a building and operate as a communications centre for communications with rescue crews and equipment inside the building. Transmission loss, rms delay spreads, equivalent CW envelope fading characteristics, and frequency correlation characteristics are reported for the

Robert J. C. Bultitude; Y. L. C. De Jong; J. A. Pugh; Sana Salous; K. Khokhar

2007-01-01

16

The importance of the multipoint-to-multipoint indoor radio channel in ad hoc networks  

Microsoft Academic Search

In the study of the multipoint-to-multipoint (M2M) radio channel, the physical backbone of wireless ad hoc networks, has direct application in the simulation and design of multi-hop routing protocols. The ad hoc network radio channel differs from the point-to-point or point-to-multipoint channels previously investigated, since each device may communicate with any other device. First, this paper presents a M2M measurement

Neal Patwari; Yanwei Wang; Robert J. O'Dea

2002-01-01

17

Increasing Channel Occupancy in Large-Scale Mobile Radio Systems: Dynamic Channel REassignment  

Microsoft Academic Search

Large-scale mobile radio systems using dynamic channel REassignment switch the channels assigned to some of the calls in progress to maintain a nearly optimum separation between coverage areas simultaneously using the same channel. Dynamic channel REassignment produces a significant increase in channel occupancy. For example, in the systems studied, which have a uniform distribution of their fixed channels and were

D. Cox; D. Reudink

1973-01-01

18

RADIO AND ELECTRICAL MEASUREMENTS ON GLACIAL STREAMS  

Microsoft Academic Search

(H. H. Wills Physics Laboratory, Universit y of Bristol, Bristol BS8 lTL, England) ABSTRACT. We discuss the suggestion that small under­ water transmitters might be used to illuminate the interior of major englacial water channels with radio waves. Once launched, the radio waves would naturally tend to be guided along the channels until att enuated by absor ption and by

M. E. R. WALFORD

1987-01-01

19

Statistics of shadowing in indoor radio channels at 900 and 1900 MHz  

Microsoft Academic Search

The authors describe measurements which were performed to characterize shadowing in indoor radio environments. They investigated the suitability of the log-normal shadowing model for indoor mobile and portable radio channels and determined how the parameters of the log-normal shadowing model are dependent on frequency and topography. They show that the correlation coefficient can be completely independent of wavelength over a

Joseph C. Liberti; Theodore S. Rappaport

1992-01-01

20

Radio occultation measurements of the lunar ionosphere  

Microsoft Academic Search

Radio occultation measurements by using interplanetary probes is a well known technique to obtain information on planetary atmospheres. To further understand the morphology of the lunar ionosphere we performed radio occultation experiments by using the radio sounding technique. This method mainly consists in the analisys of the effects produced on the radio wave transmitted from the spacecraft to the Earth

S. Pluchino; F. Schillirò; E. Salerno; G. Pupillo; G. Maccaferri; P. Cassaro

2008-01-01

21

Adaptive OFDM for wideband radio channels  

Microsoft Academic Search

An OFDM (orthogonal frequency division multiplexing) transmission system is simulated with time-variant transfer functions measured with a wideband channel sounder. The individual subcarriers are modulated with fixed and adaptive signal alphabets. Furthermore, a frequency-independent as well as the optimum power distribution are used. The simulations show that with adaptive OFDM, the required signal power for an error probability of 10-3

Andreas Czylwik

1996-01-01

22

Fading Channel Prediction for Mobile Radio Adaptive Transmission Systems  

Microsoft Academic Search

Adaptive transmission methods can potentially aid the achievement of high data rates required for mobile radio multimedia services. To realize this potential, the transmitter needs accurate channel state information (CSI) for the upcoming transmission frame. In most mobile radio systems, the CSI is estimated at the receiver and fed back to the transmitter. However, unless the mobile speed is very

Alexandra Duel-Hallen

2007-01-01

23

Channel Capacity Limits of Cognitive Radio in Asymmetric Fading Environments  

Microsoft Academic Search

Cognitive radio technology is an innovative radio design concept which aims to increase spectrum utilization by ex- ploiting unused spectrum in dynamically changing environments. By extending previous results, we investigate the capacity gains achievable with this dynamic spectrum approach in asymmetric fading channels. More specifically, we allow the secondary-to- primary and secondary-to-secondary user channels to undergo Rayleigh or Rician fading,

Himal A. Suraweera; Jason Gao; Peter J. Smith; Mansoor Shafi; Michael Faulkner

2008-01-01

24

Radio spectrum measurements at the Gauribidanur observatory  

NASA Astrophysics Data System (ADS)

During a campaign in December 2006, radio spectrum measurements over the frequency range 45-870 MHz were carried out at the Gauribidanur observatory, located about 100 km north of Bangalore. The spectrometer used for the above purpose was subsequently configured for radio spectral observations of the solar corona. This paper describes, (i) radio frequency interference over some of the frequency bands `protected' for radio astronomy; and (ii) `first' solar radio burst observation and the above instrument.

Monstein, C.; Ramesh, R.; Kathiravan, C.

2007-12-01

25

Prioritized channel assignment in a cellular radio network  

Microsoft Academic Search

Dimensioning procedures for prioritized channel assignment in a cellular radio network are considered. Under the cutoff priority discipline, the prioritized channel assignment procedures for a single cell and multicell system are formulated as nonlinear discrete capacity allocation problems. Exact incremental algorithms which efficiently solve the proposed problems are devised. They are based on the properties of the blocking probabilities of

Se-Hyun Oh; Dong-Wan Tcha

1992-01-01

26

A simplified stochastic model for the aeronautical mobile radio channel  

Microsoft Academic Search

The aeronautical mobile radio channel is analyzed. A stochastic model for the channel is proposed in terms of the transmission coefficient. The power spectrum and the correlation functions are derived for cases of practical interest. The model is useful for predicting the error rate performance of digital modulation techniques. The results from a flight test showed the validity of the

Said M. Elnoubi

1992-01-01

27

Analysis and modeling of multiple-input multiple-output (MIMO) radio channel based on outdoor measurements conducted at 2.5 GHz for fixed BWA applications  

Microsoft Academic Search

This paper summarizes our 2×2 multiple-input multiple-output (MIMO) fixed wireless outdoor propagation measurements at 2.48 GHz conducted in the suburban residential areas of San Jose, California. We report on various channel characteristics such as path loss, Ricean K-factor, cross-polarization-discrimination (XPD) and channel capacity. We present simple models for these characteristics, focusing on excess loss dependency and, derived from that, the

P. Soma; D. S. Baum; V. Erceg; R. Krishnamoorthy; A. J. Paulraj

2002-01-01

28

Computerized indoor radio channel estimation using ray tracing  

Microsoft Academic Search

\\u000a Abstract  This paper describes a computer tool for site specific indoor radio channel characterization. The behavior of the electromagnetic\\u000a fields associated with a base station and a portable radio unit is simulated by combining approximate geometric optics and\\u000a ray tracing techniques. Given a building plan and the transmitter\\/receiver locations, the set of all[attenuation \\/ time delay \\/phase] vectors, each representing an

Marc Kimpe; Harry Leib

1997-01-01

29

Performance evaluation of LOS microwave radios using a channel simulator  

Microsoft Academic Search

This paper describes a line-of-sight (LOS) channel simulator that can be used for the laboratory evaluation of microwave radios. The simulator has a unique design, utilizes state-of-the-art microwave circuitry, and is completely under computer control. The hardware and software design concepts incorporated in the simulator are described. Results from tests conducted on a military microwave radio are presented. The results

J. A. Hoffmeyer; L. E. Pratt; T. J. Riley

1986-01-01

30

Acousto-optic channel equalization for microwave digital radios.  

PubMed

Digital radio transmission systems use complex modulation schemes that require powerful signalprocessing techniques to correct channel distortions and to minimize bit error rates. Acousto-optic processors are used, in conjunction with adaptive digital equalizers, to reduce the bit error rate of the digital radio receiver. The acousto-optic processor implements an inverse channel filter that is rapidly adaptable to time-varying distortions. A specific architecture is identified and a laboratory system is tested to verify the ability of the processor to track and correct time-varying channels. Computer simulations are used to show that the hybrid acousto-optic and digital equalizer permits a fourfold increase in the modulation capacity of radio, relative to all digital equalization, while improving the bit error rate performance. PMID:20830097

Anderson, C S

1993-08-10

31

Multiple-input multiple-output fixed wireless radio channel measurements and modeling using dual-polarized antennas at 2.5 GHz  

Microsoft Academic Search

This paper presents outdoor propagation measurements together with derivative analysis, modeling, and simulation of the 2×2 fixed wireless multiple-input multiple-output (MIMO) channel. Experimental data were collected in the suburban residential areas of San Jose, CA, at 2.48 GHz by using dual-polarized antennas. Measurement results include the estimation of path loss, Rician K-factor, cross-polarization discrimination (CPD), correlation coefficients, and the MIMO

Vinko Erceg; Pitchaiah Soma; Daniel S. Baum; Severine Catreux

2004-01-01

32

Optimal radio channel recommendations with explicit and implicit feedback  

Microsoft Academic Search

The very large majority of recommender systems are running as server-side applications, and they are controlled by the content provider, i.e., who provides the recommended items. This paper focuses on a different scenario: the user is supposed to be able to access content from multiple providers, in our application they offer radio channels, and it is up to a personal

Omar Moling; Linas Baltrunas; Francesco Ricci

2012-01-01

33

Sequential and cooperative sensing for multi-channel cognitive radios  

Microsoft Academic Search

Effective spectrum sensing is a critical prerequisite for multi-channel cognitive radio (CR) networks, where multiple spectrum bands are sensed to identify transmission opportunities, while preventing interference to the primary users. The present paper develops sequential spectrum sensing algorithms which explicitly take into account the sensing time overhead, and optimize a performance metric capturing the effective average data rate of CR

Seung-Jun Kim; Georgios B. Giannakis

2010-01-01

34

The F. C. C.'s Clear Channel Radio Policies: Regulation in the Slow Lane.  

ERIC Educational Resources Information Center

In 1928, the Federal Radio Commission (the precursor of the Federal Communications Commission--FCC) noted the need for special radio channels that could carry radio across the United States free from interference from other radio stations. Many of these "clear channels" still exist as protected entities. Perhaps no other FCC policy better reflects…

Jassem, Harvey C.

35

DFVLR channel simulation equipment for mobile radio channels  

NASA Astrophysics Data System (ADS)

A simulation facility for the optimization of new systems and the comparison of promising methods in the area of satellite-aided mobile communications is described. The facility uses the stored channel method and has been used on several fading channels, including satellite to ship, emergency buoy to satellite, car mobile to fixed station and return, and satellite to car mobile. The main modes of operation are mentioned, and its functioning in combination with digital processors is discussed. Examples of its applications are given.

Papke, W.

36

A multi-channel Beacon Forwarding approach in dual radio Vehicular Ad-Hoc Networks  

Microsoft Academic Search

Dual radios in Vehicular Ad-Hoc Networks (VANETS) enable the usage of multiple communication chan- nels simultaneously. This results in a higher network capacity in contrast to single radio setups. However, using multiple channels simultaneously leads to Adjacent Channel Interference (ACI) by generating noise in nearby channels. This noise increases the packet loss probability and leads to highly unreliable communication channels.

Robert Lasowski; Robert K. Schmidt

2011-01-01

37

Adaptive equalization and diversity combining for a mobile radio channel  

Microsoft Academic Search

The feasibility of a digital cellular radio (DCR) system which uses a jointly adaptive decision-feedback equalizer and diversity combiner is discussed. The current estimates of the channel impulse response (CIR) are utilized at each diversity branch to compute the receiver parameters periodically. A block-adaptive strategy that computes the time-varying CIR by interpolating a set of CIR estimates obtained through periodic

N. W. K. Lo; D. D. Falconer; A. U. H. Sheikh

1990-01-01

38

Radio wave refractivity deduced from lidar measurements  

NASA Astrophysics Data System (ADS)

A high resolution lidar is used to backscatter light from atmospheric aerosols. The actual relative humidity is measured at altitudes corresponding to those from which the backscattered light occurs. A mathematical relationship between the two is then derived and this is used to predict atmospheric relative humidity from subsequent lidar backscatter's measurements. The predicted relative humidity is used with temperature and pressures derived from standard lapse rates to calculate the radio refractivity of the atmosphere. Radio ray coverage is then determined based upon the calculated radio refractivity.

Paulson, Merle R.; Hughes, Herbert G.

1993-12-01

39

Practical, distributed channel assignment and routing in dual-radio mesh networks  

Microsoft Academic Search

Realizing the full potential of a multi-radio mesh network involves two main challenges: how to assign channels to radios at each node to minimize interference and how to choose high throughput routing paths in the face of lossy links, variable channel conditions and external load. This paper presents ROMA, a practical, distributed channel assignment and routing protocol that achieves good

Aditya Dhananjay; Hui Zhang; Jinyang Li; Lakshminarayanan Subramanian

2009-01-01

40

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

41

Spatial correlation and capacity measurements for wideband MIMO channels in indoor office environment  

Microsoft Academic Search

This paper describes a broadband multiple input, multiple output (MIMO) channel characterization platform and capacity measurement results in indoor office environment. The MIMO testbed has been designed for broadband MIMO channel sounding, capacity measurements and for characterizing the directional-multipaths of the radio propagation channel. The MIMO channel data have been collected in 5 GHz band inside a modern office environment.

Padam L. Kafle; Apichart Intarapanich; Abu B. Sesay; John Mcrory; Robert J. Davies

2008-01-01

42

Secret Key Extraction in Ultra Wideband Channels for Unsynchronized Radios  

Microsoft Academic Search

Secure communicationsin UWB based on cryptographic keys generated from channel measurements without a trusted third party have been developed. The fine time res- olution of UWB allows high levels of mutual information to be obtained by a given A and B through independent char- acterizations of their shared communication channel. This mutual informationdetermines the maximum secret key rate available to

Masoud Ghoreishi Madiseh; Michael L. Mcguire; Stephen W. Neville; Ali Asghar Beheshti Shirazi

2008-01-01

43

A method for measuring pulsar radio-emission energy  

NASA Astrophysics Data System (ADS)

A method for the correct measurement of the mean radio-emission flux of pulsars is described which takes into account the the main characteristics of this radiation and the effect of the interstellar medium on it. It is shown that in order to measure fluxes in the meter wavelength range with an optimal sensitivity it is necessary to use a multichannel detector with a large number of channels. The observation technique used for pulsar energy measurements via the BSA and DKR-1000 telescopes is described.

Malofeev, V. M.

44

Optimum frequency of communication channel for indoor radio telemetry  

NASA Astrophysics Data System (ADS)

A major problem in application of radiotelemetry to biological research and medical practice is indoor interference caused by superposition of forward and reflected waves, with resulting signal fadeout. Avoidance of this effect requires that the radio transmitter operate at the optimum signal wavelength and the radio receiver be placed in the optimum location. A method of determining both is proposed on the basis of an experimental study and a theoretical model. Measurements are made with the Prima radiotelemetry system developed and built by A. A. Kvitka with others and V6-1 selective microvoltmeter, in an 8x5x3.5 cu m large room where the radio receiver is placed successively in three different locations (first in corner 0,0,0 m, then closer to the center 2.5,1.5,1.0 m and 1.25,0.75,1.0 m) while the radio transmitter on a dielectric post is moved around in 0.25 m steps successively in three horizontal planes 1, 1.5, 2 m, respectively, above the floor. Measurements are made at eight frequencies (60, 30, 20, 15, 12, 10, 8.89, 7.5 MHz).

Kvitka, A. A.; Podlepetskiy, B. I.; Chernysheva, S. D.

1985-10-01

45

Performance analysis of a slotted multi-channel MAC protocols for cognitive radio networks  

Microsoft Academic Search

Cognitive radio has emerged as one of effective methods to enhance utilization of radio spectrum. Main principle of cognitive radio is that the secondary users (SUs) are allowed to use the spectrum not used by primary users (PUs) without interfering PU's transmission. In this paper, we consider network system where PUs use channels under super-slot time structure and SUs content

Kyung Jae Kim; Jin Soo Park; Yun Han Bae; Bong Dae Choi

2010-01-01

46

Measurable Security through Isotropic Channels  

NASA Astrophysics Data System (ADS)

This position paper proposes the use of special broadcast networks to achieve provable and measurable confidentiality of messages. We call these networks isotropic channels, broadcast channels in which receivers cannot reliably determine whether a given message originated from any particular sender and senders cannot prevent a message from reaching any particular receiver. As long as eavesdroppers cannot reliably (i.e., with probabilistic certainty) identify the sender of a message, honest parties can efficiently exchange messages with confidentiality that asymptotically approaches and in some cases reaches perfect secrecy. Even under incorrect assumptions regarding the degree of isotropism offered by a particular channel, a high measure of confidentiality can be efficiently achieved.

Sherr, Micah; Cronin, Eric; Blaze, Matt

47

Multiple-site investigation of the properties of an HF radio channel and the ionosphere using Digital Radio Mondiale broadcasting  

NASA Astrophysics Data System (ADS)

The Digital Radio Mondiale (DRM), one of the new digital radio broadcasting standards, has been designed to overcome typical short wave radio channel difficulties, such as the multipath propagation and fast temporal changes of the received signal level, both related to the properties of the ionosphere along the path of propagation. In particular, some of the RF carriers used in the applied COFDM transmission technique serve to estimate the current state of the radio channel to enable the proper demodulation of the received signal.We have been detecting such RF carriers on select frequency channels (standard DRM broadcast) using a network of recording stations located in different parts of Poland in order to collect data on the HF radio channel. We have been also evaluating the usefulness of this procedure in providing information on the current state of the ionosphere in the refraction region between the transmitter and receivers. When the DRM system becomes more widespread, this method can supplement data that comes from the ionosondes, since it does not require much financial resources and the receivers can be easily scattered over a large area. This paper presents a set of experimental data and its analysis.

Mlynarczyk, Janusz; Koperski, Piotr; Kulak, Andrzej

2012-01-01

48

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

49

Practical, distributed channel assignment and routing in dual-radio mesh networks  

Microsoft Academic Search

Realizing the full potential of a multi-radio mesh network involves two main challenges: how to assign channels to ra- dios at each node to minimize interference and how to choose high throughput routing paths in the face of lossy links, variable channel conditions and external load. This paper presents ROMA, a practical, distributed channel assignment and routing protocol that achieves

Aditya Dhananjay; Hui Zhang; Jinyang Li; Lakshminarayanan Subramanian

2009-01-01

50

The Measurement of the Angular Diameter of Radio Stars  

Microsoft Academic Search

A new method of using interferometers to measure the diameters of radio stars is described The method is based on the use of the phase-switching system, and has several practical advantages over previous methodsMeasurements which have been made on the radio star (23 01) in Cassiopeia, indicate that the radio star has an angular diameter of about 5' arc, the

F G Smith

1952-01-01

51

Evaluation scheme RFID channel in library with wooden and metal book shelves based on measurement data  

Microsoft Academic Search

At the present time, radio frequency identification (RFID) library management system are applied in many libraries for convenience and more efficiency. Channel modeling is necessary for predicting received power and performance system. In this paper, the channel of wooden and metal book shelves are modeled for RFID library management system. The channels were measured at frequency of 2.45 GHz. The

J. Pitukwerakul; P. Supanakoon; S. Promwong

2010-01-01

52

Design and Implementation of an Underlay Control Channel for Cognitive Radios  

SciTech Connect

Implementation of any cognitive radio network requires an effective control channel that can operate under various modes of activity from the primary users. This paper reports the design and implementation of a filter bank multicarrier spread spectrum (FBMC-SS) system for use as the control channel in cognitive radio networks. The proposed design is based on a filtered multitone (FMT) implementation. Carrier and timing acquisition and tracking methods as well as a blind channel estimation method are developed for the proposed control channel. We also report an implementation of the proposed FBMC-SS system on a hardware platform; a FlexRIO FPGA module from National Instruments.

Daryl Wasden; Hussein Moradi; Behrouz Farhang-Boroujeny

2012-11-01

53

Multitone transmissions over two-user cognitive radio channel with weak interference  

Microsoft Academic Search

A transmitter with cognitive capability can sense talk between the other transmitter-receiver pairs. When this transmitter knows full or partial message of the others, it can choose an efficient strategy to access the transmission medium. This is referred to as cognitive radio channel. This work aims to investigate multi-tone transmission over two-user cognitive radio channels where cross-talk interference is weak.

Na Yi; Yi Ma; Rahim Tafazolli

2008-01-01

54

Multiflows in multi-channel multi-radio multihop wireless networks  

Microsoft Academic Search

This paper studies maximum multiflow (MMF) and maximum concurrent multiflow (MCMF) in muliti-channel multi-radio multihop wireless networks under the 802.11 inter- ference model or the protocol interference model. We introduce a fine-grained network representation of multi-channel multi-radio multihop wireless networks and present some essential topo- logical properties of its associated conflict graph. By exploiting these properties, we develop practical polynomial

Peng-Jun Wan; Yu Cheng; Zhu Wang; Frances Yao

2011-01-01

55

Channel Assignment in Multi-radio Multichannel Wireless Mesh Network by Topology Approach  

Microsoft Academic Search

Wireless mesh nodes equipping multi-radio interfaces on each node and using multi-channel for transmission can greatly enhance the network performance. In this paper, a genetic algorithm, genetic tabu search, was presented to solve the channel assignment problem. The algorithm was evaluated by simulation on NS2 and compared with greedy and multi-radio unification protocol algorithms. Simulation results showed that the performance

Li Zhang; Xinheng Wang; Caixing Liu

2009-01-01

56

OFDM for data communication over mobile radio FM channels. I. Analysis and experimental results  

Microsoft Academic Search

The performance of OFDM\\/FM modulation for digital communication over Rayleigh-fading mobile radio channels is described. The use of orthogonal frequency division multiplexing (OFDM) over mobile radio channels was proposed by Cimini (1985). OFDM transmits blocks of bits in parallel and reduces the bit error rate (BER) by averaging the effects of fading over the bits in the block. OFDM\\/FM is

Eduardo F. Casas; C. Leung

1991-01-01

57

Radio Channel Quality in Industrial Wireless Sensor Networks  

Microsoft Academic Search

Wireless mesh sensor networks are being deployed today in various monitoring and control applications. Some radio network designs, such as ZigBee, presume that radio connectivity is reasonably consistent over time. Others take the opposite approach of presuming that links are entirely unreliable, and build large degrees of physical redundancy into the network in the hope that a collection of redundant

Daniel Sexton; Michael Mahony; Michael Lapinski; Jay Werb

2005-01-01

58

An Opportunistic Spectrum Scheduling Scheme for MultiChannel Cognitive Radio Networks  

Microsoft Academic Search

In this paper, we develop an opportunistic spectrum scheduling scheme for cognitive radio networks. In the proposed scheme, the channel status (i.e., whether being occupied by primary users) and the instantaneous channel quality (SNR at the secondary receiver) are assumed to vary fast within a frame which consists of a fixed number of slots. At each scheduling epoch, each secondary

Vamsi Krishna Tumuluru; Ping Wang; Dusit Niyato

2010-01-01

59

Energy-Efficient Channel Management Scheme for Cognitive Radio Sensor Networks  

Microsoft Academic Search

In designing a cognitive radio sensor network (CRSN), we need to take account of energy both efficiency and primary user (PU) protection since the CRSN consumes additional energy to support CR functionality such as channel sensing and switching, which can shorten the network lifetime. In this paper, we propose a new channel manage- ment scheme for CRSNs, which heightens the

Jeong Ae Han; Wha Sook Jeon; Dong Geun Jeong

2011-01-01

60

A neural network parallel algorithm for channel assignment problems in cellular radio networks  

Microsoft Academic Search

The channel assignment problem involves not only assigning channels or frequencies to each radio cell. but also satisfying frequency constraints given by a compatibility matrix. The proposed parallel algorithm is based on an artificial neural network composed of nm processing elements for an n-cell-m-frequency problem. The algorithm runs not only on a sequential machine but also on a parallel machine

Nobuo Funabiki; Yoshiyasu Takefuji

1992-01-01

61

Measurements of Multipath and Its Effects on Terrestrial VHF Radio Direction Finding.  

National Technical Information Service (NTIS)

This report details the investigation of VHF radio direction finding (DF) and the effects of multipath propagation for terrestrial paths. For this investigation, an eight channel DF system was used to make field measurements of a transmitter as it was slo...

W. J. Read

1997-01-01

62

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

63

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

64

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

65

Multi-Channel Distributed Coordinated Function over Single Radio in Wireless Sensor Networks  

PubMed Central

Multi-channel assignments are becoming the solution of choice to improve performance in single radio for wireless networks. Multi-channel allows wireless networks to assign different channels to different nodes in real-time transmission. In this paper, we propose a new approach, Multi-channel Distributed Coordinated Function (MC-DCF) which takes advantage of multi-channel assignment. The backoff algorithm of the IEEE 802.11 distributed coordination function (DCF) was modified to invoke channel switching, based on threshold criteria in order to improve the overall throughput for wireless sensor networks (WSNs) over 802.11 networks. We presented simulation experiments in order to investigate the characteristics of multi-channel communication in wireless sensor networks using an NS2 platform. Nodes only use a single radio and perform channel switching only after specified threshold is reached. Single radio can only work on one channel at any given time. All nodes initiate constant bit rate streams towards the receiving nodes. In this work, we studied the impact of non-overlapping channels in the 2.4 frequency band on: constant bit rate (CBR) streams, node density, source nodes sending data directly to sink and signal strength by varying distances between the sensor nodes and operating frequencies of the radios with different data rates. We showed that multi-channel enhancement using our proposed algorithm provides significant improvement in terms of throughput, packet delivery ratio and delay. This technique can be considered for WSNs future use in 802.11 networks especially when the IEEE 802.11n becomes popular thereby may prevent the 802.15.4 network from operating effectively in the 2.4 GHz frequency band.

Campbell, Carlene E.-A.; Loo, Kok-Keong (Jonathan); Gemikonakli, Orhan; Khan, Shafiullah; Singh, Dhananjay

2011-01-01

66

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

67

A model of channel holding time in mobile radio systems  

Microsoft Academic Search

This paper deals with the analysis of channel holding time statistics in cellular mobile networks. The salient feature is that the analysis accounts also for handover initiation. For mobile terminals travelling in a lineal array of cells, the channel releasing rate is characterized in terms of the call termination rate and the crossing rate of the hysteresis band in handover

F. Graziosi; M. Pratesi; M. Nuggieri; F. Santucci

1997-01-01

68

Optimization-Based Channel Constrained Data Aggregation Routing Algorithms in Multi-Radio Wireless Sensor Networks  

PubMed Central

In wireless sensor networks, data aggregation routing could reduce the number of data transmissions so as to achieve energy efficient transmission. However, data aggregation introduces data retransmission that is caused by co-channel interference from neighboring sensor nodes. This kind of co-channel interference could result in extra energy consumption and significant latency from retransmission. This will jeopardize the benefits of data aggregation. One possible solution to circumvent data retransmission caused by co-channel interference is to assign different channels to every sensor node that is within each other's interference range on the data aggregation tree. By associating each radio with a different channel, a sensor node could receive data from all the children nodes on the data aggregation tree simultaneously. This could reduce the latency from the data source nodes back to the sink so as to meet the user's delay QoS. Since the number of radios on each sensor node and the number of non-overlapping channels are all limited resources in wireless sensor networks, a challenging question here is to minimize the total transmission cost under limited number of non-overlapping channels in multi-radio wireless sensor networks. This channel constrained data aggregation routing problem in multi-radio wireless sensor networks is an NP-hard problem. I first model this problem as a mixed integer and linear programming problem where the objective is to minimize the total transmission subject to the data aggregation routing, channel and radio resources constraints. The solution approach is based on the Lagrangean relaxation technique to relax some constraints into the objective function and then to derive a set of independent subproblems. By optimally solving these subproblems, it can not only calculate the lower bound of the original primal problem but also provide useful information to get the primal feasible solutions. By incorporating these Lagrangean multipliers as the link arc weight, the optimization-based heuristics are proposed to get energy-efficient data aggregation tree with better resource (channel and radio) utilization. From the computational experiments, the proposed optimization-based approach is superior to existing heuristics under all tested cases.

Yen, Hong-Hsu

2009-01-01

69

Frequency-domain equalization of mobile radio and terrestrial broadcast channels  

Microsoft Academic Search

For mobile radio and terrestrial broadcast applications, we compare orthogonal frequency-division multiplexing (OFDM) and single-carrier transmission with frequency-domain equalization. With respect to our earlier results, we include channel coding and frequency-domain interleaving which are necessary for OFDM systems on multipath fading channels characterized by deep notches in the signal spectrum. Our results indicate that a single-carrier system with a frequency-domain

H. Sari; G. Karam; I. Jeanclaudle

1994-01-01

70

Optimal Capacity Planning in Multi-Radio MultiChannel Wireless Networks  

Microsoft Academic Search

In this paper, we study how to compute the optimal capacity planning in a multi-radio multi-channel (MR-MC) wireless network, that is, to find solutions for a set of coupled problems including channel assignment, scheduling, and routing, with the objective to optimize network capacity. The current state of the art mainly resorts to formulation of a mixed integer programming problem, which

Yu Cheng; Hongkun Li

2010-01-01

71

Channel Estimation and Adaptive M-QAM in Cognitive Radio Links  

Microsoft Academic Search

Abstract—Cognitive radios have the ability to sense their RF environment and,adapt their transmission parameters to perform optimally in any situation. Part of this involves selecting the best modulation,type for a particular channel. In this paper we consider a variable-rate, variable-power, adaptive, M- ary Quadrature Amplitude Modulation (M-QAM) scheme in a single-user communication,scenario. The channel between the transmitter and receiver is

Alkan Soysal; Sennur Ulukus; T. Charles Clancy

2008-01-01

72

Feasibility of optimally assigning channels by exhaustive search in commercial multi-radio wireless mesh networks  

Microsoft Academic Search

Channel assignment problems in multi-radio wireless mesh networks (WMNs) have been shown to be NP-hard in various scenarios\\u000a in the literature. By far, most of research efforts have focused on developing efficient approximation algorithms that run reasonably fast and provide good quality channel assignment rather than the optimal one. However, from\\u000a the practical network design and deployment standpoint, engineers care

Wei Xie; Mihail L. Sichitiu; Liqun Fu; Yan Yao

2010-01-01

73

Adaptive equalization with RLS-MLSE for frequency-selective fast fading mobile radio channels  

Microsoft Academic Search

The authors propose a novel adaptive equalization scheme which is a combination of the recursive least squares adaptive algorithm and maximum likelihood sequence estimation (RLS-MLSE). The performance of the scheme is demonstrated in frequency-selective fast fading mobile radio channels. RLS-MLSE employs a parallel estimation scheme in which the state of the channel is estimated by the Viterbi algorithm and the

Kazuhiko Fukawa; Hiroshi Suzuki

1991-01-01

74

Dynamic Channel Sensing Management for OFDMA-Based Cognitive Radio Systems  

Microsoft Academic Search

In the cognitive radio (CR) systems, channel sensing policy to detect the presence of primary user directly affects the quality-of-service (QoS) of both primary and CR users. In this paper, we investigate the efficient channel sensing scheme for the orthogonal frequency division multiple access (OFDMA) based CR systems. To improve the overall system performance, the proposed scheme exploits the multiuser-diversity

Sang Soo Jeong; Wha Sook Jeon; Dong Geun Jeong

2007-01-01

75

Right-Wing Pirate Radio Broadcasting in Israel: The Political Discourse About Channel 7, 1993–2003  

Microsoft Academic Search

This study examines an Israeli right-wing pirate radio station, Channel 7. Channel 7 was established in 1988 as a sea-based pirate radio station of the right-wing block in the religious-Zionist movement. Three questions were posed in the research: (a) What is the social representation of right-wing pirate radio station in the Knesset (Israeli parliament) discussions? (b) Did Yitzhak Rabin (Israeli

Mira Moshe

2007-01-01

76

Broadcasting in Multi-Radio Multi-Channel Wireless Networks using Simplicial Complexes.  

National Technical Information Service (NTIS)

We consider the broadcasting problem in multi-radio multi-channel ad hoc networks. The objective is to minimize the total cost of the network-wide broadcast, where the cost can be of any form that is summable over all the transmissions (e.g., the transmis...

A. Swami J. Gao Q. Zhao R. Ramanathan W. Ren

2011-01-01

77

Performance of packet reservation multiple access protocol in a co-channel limited mobile radio environment  

Microsoft Academic Search

This paper extends the evaluation of packet protocols in a cellular mobile radio environment. Packet access protocols investigated are based on Packet Reservation Multiple Access (PRMA). The investigation was carried out for both voice and data traffic. Results were obtained by simulating a fixed channel allocation scheme based on a seven cell cluster. The authors also discuss the traffic behaviour

J. Y. Khan; J. Dunlop; S. Gormley

1993-01-01

78

Subwavelength Radio Repeater System Utilizing Miniaturized Antennas and Metamaterial Channel Isolator  

Microsoft Academic Search

Implementation of a novel high gain miniaturized radio repeater for improving wireless network connectivity in complex environment is presented in this paper. Unlike existing repeater systems, this system utilizes two closely spaced low profile miniaturized planar antennas capable of producing om- nidirectional and vertical radiation pattern as well as a channel isolator layer that serves to decouple the adjacent antennas.

Kamal Sarabandi; Young Jun Song

2011-01-01

79

Strategies for handover and dynamic channel allocation in micro-cellular mobile radio systems  

Microsoft Academic Search

Microcellular structures are the central means for increasing the network capacity of mobile radio systems. By examining existing dynamic channel allocation algorithms, the authors identify a class of adaptive algorithms best suited for such microcellular environments. Applicable algorithms of this class require intracell handover and are to a large extent decentralized. One new algorithm of this class is introduced and

Reiner Beck; Herbert Panzer

1989-01-01

80

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

81

CMOS neurostimulation ASIC with 100 channels, scaleable output, and bidirectional radio-frequency telemetry.  

PubMed

100-channel neurostimulation circuit comprising a complementary metal oxide semiconductor (CMOS), application-specific integrated circuit (ASIC) has been designed, constructed and tested. The ASIC forms a significant milestone and an integral component of a 100-electrode neurostimulation system being developed by the authors. The system comprises an externally worn transmitter and a body implantable stimulator. The purpose of the system is to communicate both data and power across tissue via radio-frequency (RF) telemetry such that externally programmable, constant current, charge balanced, biphasic stimuli may be delivered to neural tissue at 100 unique sites. An intrinsic reverse telemetry feature of the ASIC has been designed such that information pertaining to the device function, reconstruction of the stimulation voltage waveform, and the measurement of impedance may be obtained through noninvasive means. To compensate for the paucity of data pertaining to the stimulation thresholds necessary in evoking a physiological response, the ASIC has been designed with scaleable current output. The ASIC has been designed primarily as a treatment of degenerative disorders of the retina whereby the 100 channels are to be utilized in the delivery of a pattern of stimuli of varying intensity and or duty cycle to the surviving neural tissue of the retina. However, it is conceivable that other fields of neurostimulation such as cochlear prosthetics and functional electronic stimulation may benefit from the employment of the system. PMID:11296881

Suaning, G J; Lovell, N H

2001-02-01

82

AUTOMATIC RADIO TRACKING OF FISH IN EXPERIMENTAL CHANNELS  

EPA Science Inventory

An automatic tracking system controlled by an RCA 1802 microprocessor was developed to locate fish in a 400 m outdoor experimental channel at the U.S. EPA Monticello Ecological Research Station. The monitoring network consisted of 12 horizontally polarized antennas spaced at 30 m...

83

Adaptive Bayesian decision feedback equalizer for dispersive mobile radio channels  

NASA Astrophysics Data System (ADS)

The paper investigates adaptive equalization of time-dispersive mobile ratio fading channels and develops a robust high performance Bayesian decision feedback equalizer (DFE). The characteristics and implementation aspects of this Bayesian DFE are analyzed, and its performance is compared with those of the conventional symbol or fractional spaced DFE and the maximum likelihood sequence estimator (MLSE). In terms of computational complexity, the adaptive Bayesian DFE is slightly more complex than the conventional DFE but is much simpler than the adaptive MLSE. In terms of error rate in symbol detection, the adaptive Bayesian DFE outperforms the conventional DFE dramatically. Moreover, for severely fading multipath channels, the adaptive MLSE exhibits significant degradation from the theoretical optimal performance and becomes inferior to the adaptive Bayesian DFE.

Chen, Sheng; McLaughlin, Stephen; Mulgrew, Bernard; Grant, Peter M.

1995-05-01

84

Measuring Radio Pulses from Air Showers with Lopes  

NASA Astrophysics Data System (ADS)

LOFAR is a new digital radio interferometer that is being build in The Netherlands. By sampling the radio waves with fast ADCs it can digitally store the whole waveform information and analyze transient events like air showers after they have been recorded. To demonstrate its ability to measure air showers we are building LOPES (a LOFAR Prototype Station) at the site of an existing air shower array (KASCADE-Grande). The first phase consisting of 10 antennas is already running. It has demonstrated how digital interference suppression and beamforming can overcome the problem of radio interference and pick out air shower events.

Horneffer, Andreas; Antoni, T.; Apel, W. D.; Badea, F.; Bähren, L.; Bekk, K.; Bercuci, A.; Bertaina, M.; Biermann, P. L.; Blümer, H.; Bozdog, H.; Brancus, I. M.; Brüggemann, M.; Buchholz, P.; Butcher, H.; Büttner, C.; Chiavassa, A.; Daumiller, K.; de Bruyn, G.; de Vos, C. M.; di Pierro, F.; Doll, P.; Engel, R.; Engler, J.; Falcke, H.; Feßler, F.; Gemmeke, H.; Ghia, P. L.; Gils, H. J.; Glasstetter, R.; Haungs, A.; Heck, D.; Hörandel, J. R.; Horneffer, A.; Huege, T.; Kampert, K.-H.; Kant, G. W.; Klages, H. O.; Klein, U.; Kolotaev, Y.; Koopman, Y.; Krömer, O.; Kuijpers, J.; Lafebre, S.; Maier, G.; Mathes, H. J.; Mayer, H. J.; Milke, J.; Mitrica, B.; Morello, C.; Müller, M.; Navarra, G.; Nehls, S.; Nigl, A.; Obenland, R.; Oehlschläger, J.; Ostapchenko, S.; Over, S.; Pepping, H. J.; Petcu, M.; Plewnia, S.; Rebel, H.; Risse, A.; Roth, M.; Schieler, H.; Scholz, J.; Schoonderbeek, G.; Stümpert, M.; Thouw, T.; Toma, G.; Trinchero, G. C.; Ulrich, H.; Valchierotti, S.; van Buren, J.; van Capellen, W.; Walkowiak, W.; Weindl, A.; Wijnholds, S.; Wochele, J.; Zabierowski, J.; Zagromski, S.; Zensus, J. A.; Zimmermann, D.

85

Impulsive noise measurements and characterization in a UHF digital TV channel  

Microsoft Academic Search

This paper presents the results of a study covering measurement and characterization of the wide-band impulsive noise present in a digital TV radio channel. Measurements were conducted at a frequency of 762 MHz in different outdoor and indoor environments using vertical and horizontal polarization. The measurement system was built on commercial equipment only. The calibration process, which is an important

M. G. Sanchez; L. de Haro; M. C. Ramon; A. Mansilla; C. M. Ortega; D. Oliver

1999-01-01

86

Radio frequency surface conductivity measurement apparatus for small samples  

NASA Astrophysics Data System (ADS)

We have designed and developed an apparatus for the measurement of surface conductivity on small samples of metals and superconductors used in radio frequency cavity applications. Here we present some results of surface conductivity measurements using this setup on small samples of brass and aluminum at nearly 4.06 GHz at room temperature. The measured complex surface conductivity of brass and aluminum at radio frequencies is found to be consistent with the measured values of dc conductivity on the same samples. The temperature range of the instrument will be extended down to 4.2K with the same method of measurement.

Chandra, Jagdish; Manekar, Meghmalhar

2012-06-01

87

Air Shower Measurements with Radio Antennas: The LOPES Project  

SciTech Connect

LOPES is set up at the location of the KASCADE-Grande extensive air shower experiment in Karlsruhe, Germany and aims to measure and calibrate radio pulses from Extensive Air Showers. LOPES is designed as a digital radio interferometer using high bandwidths and fast data processing and profits from the reconstructed air shower observables of KASCADE-Grande. First results of the LOPES experiment are very promising for a future large scale application of the technique to detect cosmic rays of highest energies.

Haungs, Andreas [Institut fuer Kernphysik, Forschungszentrum Karlsruhe, 76021 Karlsruhe (Germany)

2008-01-24

88

Measurement of Radio-Frequency Impedance with Networks Simulating Lines  

Microsoft Academic Search

The complex value of an impedance may be measured at radio frequencies by measuring voltage ratios on a transmission line terminated in the unknown impedance. The line may often be replaced advantageously by an equivalent network. Several new methods of carrying out the measurement have been developed and a study of the factors affecting the accuracy and the technique of

W. L. Barrow

1935-01-01

89

A concurrent access MAC protocol for cognitive radio ad hoc networks without common control channel  

NASA Astrophysics Data System (ADS)

Cognitive radio ad hoc networks (CRAHNs) consist of autonomous nodes that operate in ad hoc mode and aim at efficient utilization of spectrum resources. Usually, the cognitive nodes in a CRAHN exploit a number of available channels, but these channels are not necessarily common to all nodes. Such a network environment poses the problem of establishing a common control channel (CCC) as there might be no channel common to all the network members at all. In designing protocols, therefore, it is highly desirable to consider the network environment with no CCC. In this article, we propose a MAC protocol called concurrent access MAC (CA-MAC) that operates in the network environment with no CCC. The two devices in a communication pair can communicate with each other even if they have only one common channel available. Therefore, the problems with CCC (such as channel saturation and denial of service attacks) can also be resolved. In CA-MAC, channel accesses are distributed over communication pairs, resulting in increased network connectivity. In addition, CA-MAC allows different communication pairs to access multiple channels concurrently. According to our performance study, CA-MAC provides higher network connectivity with shorter channel access delay compared to SYN-MAC, which is the conventional key MAC protocol for the network environment with no CCC, resulting in better network throughput.

Timalsina, Sunil K.; Moh, Sangman; Chung, Ilyong; Kang, Moonsoo

2013-12-01

90

A routing protocol based on interference-aware and channel-load in multi-radio multi-channel ad hoc networks  

Microsoft Academic Search

Improving capacity and reducing delay are the most challenging topics in wireless ad hoc networks. Nodes that equip multiple\\u000a radios working on different channels simultaneously permit effective utility of frequency spectrum and can also reduce interference.\\u000a In this paper, after analyzing several current protocols in Multi-Radio Multi-Channel (MR-MC) ad hoc networks, a new multichannel\\u000a routing metric called Integrative Route Metric

Yang Lu; Feng Sheng; Hongjie Bao; Zhen Peng

2010-01-01

91

An 11-channel radio frequency phased array coil for magnetic resonance guided high-intensity focused ultrasound of the breast.  

PubMed

In this study, a radio frequency phased array coil was built to image the breast in conjunction with a magnetic resonance guided high-intensity focused ultrasound (MRgHIFU) device designed specifically to treat the breast in a treatment cylinder with reduced water volume. The MRgHIFU breast coil was comprised of a 10-channel phased array coil placed around an MRgHIFU treatment cylinder where nearest-neighbor decoupling was achieved with capacitive decoupling in a shared leg. In addition a single loop coil was placed at the chest wall making a total of 11 channels. The radio frequency coil array design presented in this work was chosen based on ease of implementation, increased visualization into the treatment cylinder, image reconstruction speed, temporal resolution, and resulting signal-to-noise ratio profiles. This work presents a dedicated 11-channel coil for imaging of the breast tissue in the MRgHIFU setup without obstruction of the ultrasound beam and, specifically, compares its performance in signal-to-noise, overall imaging time, and temperature measurement accuracy to that of the standard single chest-loop coil typically used in breast MRgHIFU. PMID:22431301

Minalga, E; Payne, A; Merrill, R; Todd, N; Vijayakumar, S; Kholmovski, E; Parker, D L; Hadley, J R

2012-03-16

92

Channel parameter estimation in mobile radio environments using the SAGE algorithm  

Microsoft Academic Search

This study investigates the application potential of the SAGE (space-alternating generalized expectation-maximization) algorithm to jointly estimate the relative delay, incidence azimuth, Doppler frequency, and complex amplitude of impinging waves in mobile radio environments. The performance, i.e., high-resolution ability, accuracy, and convergence rate of the scheme, is assessed in synthetic and real macro- and pico-cellular channels. The results indicate that the

Bernard H. Fleury; Martin Tschudin; Ralf Heddergott; Dirk Dahlhaus; Klaus Ingeman Pedersen

1999-01-01

93

Performance evaluation of a hybrid spread spectrum system in a hostile land mobile radio channel  

Microsoft Academic Search

A performance evaluation is presented for a hybrid (direct-sequence frequency-hopped) spread-spectrum (SS) operating in a hostile jamming cellular mobile radio environment. The effects of a barrage jammer, Rayleigh fading, and log-normal shadowing on the system performance are discussed. Probability of error expressions for a hybrid BDPSK (binary differential phase shift keying) SS are derived in terms of the channel parameters.

R. Muammar

1991-01-01

94

High resolution of electromagnetic waves in time-varying radio channels  

Microsoft Academic Search

The applicability of the SAGE (space-alternating generalized expectation-maximization) algorithm to the estimation of time variant radio channels is demonstrated. This algorithm allows one to separate the complex multi-dimensional optimization problem required to compute the estimate of the parameters characterizing the impinging waves, i.e. their delay, incidence azimuth, Doppler frequency, and complex amplitude, into separate one dimensional optimization processes that can

Klaus I. Pedersen; Bernard H. Fleury; Preben E. Mogensen

1997-01-01

95

Radio Frequency (RF) Measurements for Human Detection, Tracking, and Identification.  

National Technical Information Service (NTIS)

This report describes a protocol that is to be used during radio frequency measurements of humans. The purpose of the experiment is to measure the unique radar signature of walking humans so that methods of detecting and classifying dismounts can be devel...

T. J. Pizzillo

2007-01-01

96

Artificial radio-tracers in groundwater flow measurements  

Microsoft Academic Search

Single-borehole radio-indicator methods have proved to be of value in solving hydrogeological and geotechnical problems. A tracer is discharged into a screened borehole at a chosen depth and its vertical displacement or horizontal dilution is measured by a submerged detector. In the Quaternary deposits, filtration parameters were determined from measurements of natural vertical velocities and water inflows during pumping. Inactive

J. BULLA; R. RAVINGER; P. TURCEK

97

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

98

Validation of statistical channel models for 60 GHz radio systems in hospital environments.  

PubMed

Statistical channel models for 60 GHz communications systems in hospital environments are validated using channel capacity and throughput of a physical layer as figures of merit. The channel models are validated by comparing the performance figures with channels from the measurements and the channel models. The throughput evaluation is based on system specifications given by the IEEE 802.15.3 c standard for high data rate wireless personal area networks, namely orthogonal frequency division multiplexing and single carrier transmissions. The channel capacity serves as a metric of the potential of the two transmission schemes since it defines the upper bound of the throughput. The capacity is derived based on the signal formats of the transmission schemes. The capacity shows that 97 % of the measurement results are within 2? range of the modeled results. The throughput shows that the channel models predict the maximum achievable throughput of the measured channels precisely, while the mean throughput in some cases shows difference because of the interpolation effect of the small-scale fading in the statistical channel models. Due to the interpolation effect, the channel model is more suitable for a precise analysis of the outage performance than the measurements where the number of channel samples is limited and the worst faded channels are not necessarily included. PMID:23221798

Kyrö, Mikko; Takizawa, Ken-ichi; Haneda, Katsuyuki; Vainikainen, Pertti

2012-12-04

99

Verification of Secret Key Generation from UWB Channel Observations  

Microsoft Academic Search

Theoretical models of ultrawideband (UWB) radio channels indicate that pairs of UWB radio transceivers measure their common radio channel with a high degree of agreement and third parties are not be able to accurately estimate the state of the common channels. These properties allow generation of secret keys to support secure communications from UWB channels measurements. In this paper, the

Masoud Ghoreishi Madiseh; Shuai He; Michael L. McGuire; Stephen W. Neville; Xiaodai Dong

2009-01-01

100

Global Measurements of Low-Frequency Radio Noise.  

National Technical Information Service (NTIS)

We report illustrative results obtained by Stanford University's global survey of ELF/VLF radio noise (frequencies in the range 10 Hz - 32 kHz). Particular comparison is made between the noise measurements made at high (polar) latitudes with those at lowe...

A. Bernardi A. C. Fraser-Smith M. E. Ladd P. R. McGill R. A. Helliwell

1992-01-01

101

Integrated Measurement of Soil Moisture by Use of Radio Waves.  

National Technical Information Service (NTIS)

An integrated value of soil moisture can be determined by measuring the attenuation of vertically-polarized surface radio waves that are propagated over the ground between a transmitting and receiving antenna. Soil moisture values in the root-zone region ...

D. G. Chadwick

1973-01-01

102

Radio-frequency response of single pores and artificial ion channels  

NASA Astrophysics Data System (ADS)

Intercellular communication relies on ion channels and pores in cell membranes. These protein-formed channels enable the exchange of ions and small molecules to electrically and/or chemically interact with the cells. Traditionally, recordings on single-ion channels and pores are performed in the dc regime, due to the extremely high impedance of these molecular junctions. This paper is intended as an introduction to radio-frequency (RF) recordings of single-molecule junctions in bilipid membranes. First, we demonstrate how early approaches to using microwave circuitry as readout devices for ion channel formation were realized. The second step will then focus on how to engineer microwave coupling into the high-impedance channel by making use of bio-compatible micro-coaxial lines. We then demonstrate integration of an ultra-broadband microwave circuit for the direct sampling of single ?-hemolysin pores in a suspended bilipid membrane. Simultaneous direct current recordings reveal that we can monitor and correlate the RF transmission signal. This enables us to relate the open-close states of the direct current to the RF signal. Altogether, our experiments lay the ground for an RF-readout technique to perform real-time in vitro recordings of pores. The technique thus holds great promise for research and drug screening applications. The possible enhancement of sampling rates of single channels and pores by the large recording bandwidth will allow us to track the passage of single ions.

Kim, H. S.; Ramachandran, S.; Stava, E.; van der Weide, D. W.; Blick, R. H.

2011-09-01

103

Using XBee Radios for Wireless Acceleration Measurements  

NSDL National Science Digital Library

This website is a complete description of how to use XBee transducers to make wireless acceleration sensors. Other sensors can be used for measurements of pressure, temperature, or other signals. The sensors are small, rugged, and light weight. They can measure up to six analog signals simultaneously, and transmit their data reliably up to 50 meters. With other antenna and/or power options, the XBee can transmit up to 15 miles.

Ayars, Eric

2010-02-11

104

The Fadeogram, A Sonogram-Like Display of the Time-Varying Frequency Response of HF-SSB Radio Channels  

Microsoft Academic Search

A method is presented for displaying the time-varying transfer characteristic of communication channels, and is illustrated by showing in detail the behavior of an HF-SSB radio channel during one minute periods, under the various fading characteristics classified by USAEL. It is also demonstrated how this method aided study of the causes of errors in data received by digital modems.

J. Filter; B. Arazi; R. Thomson

1978-01-01

105

Bandwidth-Substitution Technique for Absolute Measurement of Power at All Radio Frequencies.  

National Technical Information Service (NTIS)

A highly sensitive technique for making absolute measurements of power at all radio frequencies is described. This technique surmounts the primary shortcomings of the other existing techniques in that it permits absolute measurement of power at all radio ...

A. Singer J. M. Minkowski

1976-01-01

106

Measurement of Black Hole Mass Radio-Loud Quasars  

NASA Astrophysics Data System (ADS)

In this work, we construct a sample of 1585 radio-loud quasars to measure their black hole masses using broad emission lines. We compare our black hole masses with the virial black hole masses measured by Shen et al. (2010). We find that there is a large deviation between them if our black hole mass is measured from the CIV broad emission line. Whereas, if our black hole mass is measured from broad emission line of Mg II or H ?, both the values are consistent.

Su, Cheng-Yue; Chen, Z.-F.; He, R.-L.; Zhang, C.-H.; Wang, T.-T.

2011-06-01

107

A novel transform domain processing based channel estimation method for OFDM radio-over-fiber systems.  

PubMed

In this paper, a transform domain processing (TDP) based channel estimation method for orthogonal frequency-division multiplexing (OFDM) Radio-over-Fiber (RoF) systems is proposed. Theoretically investigation shows that TDP can greatly reduce the number of required training symbols. An 8 x 4.65 Gb/s multi-user OFDM RoF system over 40 km fiber link and 60 GHz wireless link is experimentally demonstrated utilizing TDP scheme. Compared with conventional time domain averaging (TDA) scheme, the overhead can be reduced from several tens of training symbols to merely one symbol and the receiver sensitivity has been improved by 1.8 dB at BER of 3.8 x 10(-3). The calculated BER performance for 8 wireless users clearly validates the feasibility of this TDP-based channel estimation method. PMID:23546130

Tao, Li; Yu, Jianjun; Yang, Qi; Shao, Yufeng; Zhang, Junwen; Chi, Nan

2013-03-25

108

Seasonal variations of globally measured ELF\\/VLF radio noise  

Microsoft Academic Search

Our laboratory has been conducting a global survey of extremely low frequency (ELF) and very low frequency (VLF) radio noise since February 1985. Eight measurement stations around the world record the instantaneous noise amplitude in each of sixteen narrow-frequency bands in the 10-Hz to 32-kHz frequency range, and we have calculated the monthly averages of these amplitudes for the four

D. A. Chrissan; A. C. Fraser-Smith

1996-01-01

109

Time Flies! Radio Signals Used for Time and Frequency Measurements  

Microsoft Academic Search

The widespread use of the Global Positioning System (GPS) as a time and frequency measurement reference was discussed in the July-September 2001 issue of Cal Lab. This article describes other radio signals that serve as alternatives or backups to GPS. It describes signals used to calibrate and control frequency standards, and signals that synchronize time-of-day clocks in products including wristwatches,

Michael A. Lombardi NIST

110

Flash flood potential from channel measurements  

Microsoft Academic Search

Discharge measurements of flash floods add to hydrological knowledge and provide information needed for protection from future floods. But planning for protection cannot be postponed until a serious flood has occurred at each site. Thus methods of estimating flood potential at ungauged sites are needed. A promising method utilizes (1) a relation between a flood characteristic and stream channel size

H. C. Riggs

111

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

112

Capacity obtained from multiple-input multiple-output channel measurements in fixed wireless environments at 2.5 GHz  

Microsoft Academic Search

We present capacity, envelope correlation coefficient, and condition number statistics obtained from 2×2 multiple-input multiple-output (MIMO) fixed wireless radio channel measurements using dual-polarized antennas. To calculate the capacity, we assume that the transmitter has no knowledge about the channel. The experimental capacity results are compared to the information-theoretic channel capacity obtained from Monte Carlo simulations. Both theoretical results and experimental

Vinko Erceg; Pitchaiah Soma; Daniel S. Baum; Arogyaswami J. Paulraj

2002-01-01

113

Wideband high frequency (HF) skywave channel parameters from narrowband measurements  

NASA Astrophysics Data System (ADS)

The HF wideband channel allow the use of spread-spectrum techniques to provide covert communications with low probability of intercept (LPI) and antijam protection. The objective of this work is to determine the extent to which oblique narrowband channel measurements can be used to infer effects in the wideband skywave channel. If oblique narrowband channel measurements can be used as a basis for developing wideband channel models, a large number of existing narrowband measurements can be made available for this task.

Hausman, Cynthia L.; Uffelman, Donald R.; Walton, Thomas L.

114

Dynamic Pilot Channel Transmission with Adaptive Receive Filter Configuration for Cognitive Radio System  

NASA Astrophysics Data System (ADS)

When a cognitive radio system dynamically utilizes a frequency band, channel control information must be communicated over the network in order for the currently available carrier frequencies to be shared. In order to keep efficient spectrum utilization, this control information should also be dynamically transmitted through channels such as cognitive pilot channels based on the channel conditions. If transmitters dynamically select carrier frequencies, receivers must receive the control signal without knowledge of its carrier frequencies. A novel scheme called differential code parallel transmission (DCPT) enables receivers to receive low-rate information without any knowledge of the carrier frequency. The transmitter simultaneously transmits two signals whose carrier frequencies are separated by a predefined value. The absolute values of the carrier frequencies can be varied. When the receiver receives the DCPT signal, it multiplies the signal by a frequency-shifted version of itself; this yields a DC component that represents the data signal, which is then demodulated. However, the multiplication process results in the noise power being squared, necessitating high received signal power. In this paper, to realize a bandpass filter that passes only DCPT signals of unknown frequency and that suppresses noise and interference at other frequencies, a DCPT-adaptive bandpass filter (ABF) that employs an adaptive equalizer is proposed. In the training phase, the received signal is the filter input and the frequency-shifted signal is the training input. Then, the filter is trained to pass the higher-frequency signal of the two DCPT signals. The performance of DCPT-ABF is evaluated through computer simulations. We find that DCPT-ABF operates successfully even under strong interference.

Sakata, Ren; Tomioka, Tazuko; Kobayashi, Takahiro

115

Influence of the scatterer distribution on power delay profiles and azimuthal power spectra of mobile radio channels  

Microsoft Academic Search

We consider the distribution of scatterers that are responsible for the temporal and angular dispersion of mobile radio channel models. In a first step, we concentrate on the local scatterers around the mobile station. Various approximations for this distribution are analyzed, and their effect on the PDP (power delay profile) and APS (azimuthal power spectrum) are derived. We find that

Juha Laurila; Andreas F. Molisch; Ernst Bonek

1998-01-01

116

Gateway selection scheme for throughput optimization in multi-radio multi-channel wireless mesh networks under physical interference model  

Microsoft Academic Search

In this paper, we investigate the gateway selection problem for throughput optimization in multi-radio multichannel wireless mesh networks. In contrast to the various methodologies in the literature, we not only explicitly model the delay overhead that is incurred during channel switching, and consider this delay-related issue in the design of our mechanism but also employ the most reliable interference model

Qin Xint; Xiaolan Yao; P. E. Engelstad

2010-01-01

117

A Power-Saving Multi-Radio MultiChannel MAC Protocol for Wireless Local Area Networks  

Microsoft Academic Search

Opportunistic spectrum access and adaptive power management are effective techniques to improve throughput, delay performance, and energy efficiency for wireless netwo rks. In this paper, we consider the joint design of opportunistic spectrum access and adaptive power management under the setting of multi-radio nodes and multi-channel wireless local area networks (WLANs) under the distributed coordination function (DCF) mode. This design

Jianfeng Wang; Yuguang Fang; Dapeng Oliver Wu

2006-01-01

118

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

119

Radio Telescopes' Precise Measurements Yield Rich Scientific Payoffs  

NASA Astrophysics Data System (ADS)

Having the sharpest pictures always is a big advantage, and a sophisticated radio-astronomy technique using continent-wide and even intercontinental arrays of telescopes is yielding extremely valuable scientific results in a wide range of specialties. That's the message delivered to the American Astronomical Society's meeting in Austin, Texas, by Mark Reid of the Harvard-Smithsonian Center for Astrophysics, a leading researcher in the field of ultra-precise astronomical position measurements. Very Long Baseline Interferometry provides extremely high precision that can extend use of the parallax technique to many more celestial objects. Parallax is a direct means of measuring cosmic distances by detecting the slight shift in an object’s apparent position in the sky caused by Earth’s orbital motion. Credit: Bill Saxton, NRAO/AUI/NSF "Using radio telescopes, we are measuring distances and motions of celestial bodies with unprecedented accuracy. That's helping us better understand many processes ranging from star formation to the scale of the entire Universe," Reid said. The observing technique, called Very Long Baseline Interferometry (VLBI), was pioneered in 1967, but has come into continuous use only in the past 10-15 years. The National Science Foundation's Very Long Baseline Array (VLBA), a system of 10 radio-telescope antennas ranging from Hawaii to the Caribbean, was dedicated in 1993. There are other VLBI systems in Europe and Asia, and large radio telescopes around the world cooperate regularly to increase sensitivity. VLBI observations routinely produce images hundreds of times more detailed than those made at visible-light wavelengths by the Hubble Space Telescope. Several groups of researchers from across the globe use the VLBA to study stellar nurseries in our own Milky Way Galaxy and measure distances to regions where new stars are forming. The key has been to improve measurement accuracy to a factor of a hundred times better than that produced by the highly successful Hipparcos satellite. Using small clouds of gas in star-forming regions that strongly amplify radio waves, called cosmic masers, the astronomers measured the tiny shift in the object's position in the sky caused by the Earth's orbit around the sun. This, in turn, yielded highly-accurate distances by the simple surveying technique of triangulation, the "gold standard" of distance measuring techniques available to astronomers. Dr. Mark Reid Dr. Mark Reid Credit: CfA Click image for high-resolution file (1.02 MB) "Knowing the distance accurately means we also know the luminosities, masses and ages of the young stars much more accurately, and that is vital to understanding how star formation works," Reid said. In addition, he pointed out, the VLBA observations have shown the motions of the young stars in the Milky Way are much more complicated than simple circular motion. Massive young stars appear to be born orbiting the Milky Way considerably slower than older stars. "This might be explained by the interaction of giant molecular clouds, the ultimate sites of massive star formation, as they "surf" spiral density waves in the Milky Way." An international team of scientists led by Reid has used VLBI to detect the slight change in apparent position of the object at the Milky Way's center caused by our Solar System's orbit around that center. "It takes our Solar System more than 200 million years to circle the center of our Galaxy, and yet we can detect that motion in only a couple weeks with the VLBA -- truly astounding!" Reid said. The VLBA studies of the Galactic Center have shown that an object called Sagittarius A* is at the exact gravitational center of our Galaxy. That means, the scientists say, that the object must be incredibly massive. "The VLBA measurements, combined with infrared observations of stellar orbits around this object, provide overwhelming evidence that it's a supermassive black hole," Reid explained. "These observations are also going to make it possibl

2008-01-01

120

Jupiter's low-frequency radio spectrum from Cassini\\/Radio and Plasma Wave Science (RPWS) absolute flux density measurements  

Microsoft Academic Search

We apply the calibration method developed by Dulk et al. [2001] to the data from the Cassini\\/Radio and Plasma Wave Science (RPWS) High-Frequency Receiver in order to derive flux density measurements of six components of the Jovian low-frequency radio spectrum over the full frequency range of the instrument (3.5 kHz to 16.1 MHz). The estimated accuracy is better than 50%,

P. Zarka; B. Cecconi; W. S. Kurth

2004-01-01

121

Monitoring Voltage-Dependent Charge Displacement of Shaker B-IR K+ Ion Channels Using Radio Frequency Interrogation  

PubMed Central

Here we introduce a new technique that probes voltage-dependent charge displacements of excitable membrane-bound proteins using extracellularly applied radio frequency (RF, 500 kHz) electric fields. Xenopus oocytes were used as a model cell for these experiments, and were injected with cRNA encoding Shaker B-IR (ShB-IR) K+ ion channels to express large densities of this protein in the oocyte membranes. Two-electrode voltage clamp (TEVC) was applied to command whole-cell membrane potential and to measure channel-dependent membrane currents. Simultaneously, RF electric fields were applied to perturb the membrane potential about the TEVC level and to measure voltage-dependent RF displacement currents. ShB-IR expressing oocytes showed significantly larger changes in RF displacement currents upon membrane depolarization than control oocytes. Voltage-dependent changes in RF displacement currents further increased in ShB-IR expressing oocytes after ?120 µM Cu2+ addition to the external bath. Cu2+ is known to bind to the ShB-IR ion channel and inhibit Shaker K+ conductance, indicating that changes in the RF displacement current reported here were associated with RF vibration of the Cu2+-linked mobile domain of the ShB-IR protein. Results demonstrate the use of extracellular RF electrodes to interrogate voltage-dependent movement of charged mobile protein domains — capabilities that might enable detection of small changes in charge distribution associated with integral membrane protein conformation and/or drug–protein interactions.

Dharia, Sameera; Rabbitt, Richard D.

2011-01-01

122

31.4- and 89.6GHz flux density measurements of extragalactic radio sources  

Microsoft Academic Search

In addition to presenting measurements at 31.4 GHz for 333 radio sources from 2.7- and 5-GHz surveys, results are given of 89.6 GHz observations of selected objects that are known or suspected to have inverted radio spectra between 5 and 31.4 GHz. It is shown that while many of the sources show steepening radio spectra with radio frequency increases, the

B. J. Geldzahler; A. Witzel

1981-01-01

123

Validation of GPS Radio Occultation Measurements From Champ  

NASA Astrophysics Data System (ADS)

The ionospheric radio occultation (IRO) technique is a powerful tool for deriving vertical profiles of electron density on global scale. In this talk we report results of ionospheric radio occultation measurements carried out onboard the German CHAMP (CHAllenging Minisatellite Payload) satellite mission that contributes also to essen- tial improvements of gravity and magnetic field models of the Earth. Electron density profiles are derived from the IRO data by applying a new model assisted retrieval tech- nique that is briefly described. This retrieval technique was developed to overcome the serious upper boundary problem due to the rather low orbit height of CHAMP of less than 450 km height. Since the first IRO measurements were performed onboard CHAMP on 11 April 2001 we have retrieved more than 5000 electron density pro- files in 2001. These data are systematically compared with vertical sounding derived profiles and key parameters such as f0F2 and hmF2 to draw conclusions on reliability and accuracy of IRO derived electron density profiles. The extracted f0F2 values de- viate from corresponding ionosonde data with an absolute rms error in the order of 1 MHz. Potentials and limitations of the retrieval technique in particular for low-altitude missions like CHAMP will be addressed.

Jakowski, N.; Wehrenpfennig, A.; Heise, S.

124

A radio-optic method for measuring relative motion  

NASA Astrophysics Data System (ADS)

A radio-optic methodology for in situ monitoring of vibration or relative motion of components in engineered systems is described. The technology relies on use of light-weight radio-optic components attached to or embedded in system members to measure in real time the relative motion between the members, or between the system and the medium in which it is located, due to internal or external loads. The positions of optical fiber detector elements relative to a radiation source element as a function of time is tracked, thus measuring relative position time history from which velocity and acceleration can also be determined. The technology permits determination of critical system performance characteristics and aids in determining safety of systems that are subjected to various loads. Instruments based on this technology will have the benefits of being capable of high spatial and temporal resolution, of interfering minimally with the system under investigation, of being relatively inexpensive and of being operable either continuously or intermittently as desired. Results of Monte Carlo simulations and of limited experimental verification studies are presented.

Dunn, William L.

2004-01-01

125

Measurements of gravity driven granular channel flows  

NASA Astrophysics Data System (ADS)

This dissertation presents experiments that studied two gravity driven granular channel flows. The first experiment used magnetic resonance imaging to measure the density and displacement distributions of poppy seeds flowing in a rough walled channel. Time-averaged measurements of normalized velocity and density showed little flow speed dependence. Instantaneous measurements, however, showed marked velocity dependence in the displacement distributions. There was evidence of aperiodic starting and stopping at lower flow speeds and the onset of density waves on a continuous flow at higher speeds. The second experiment measured forces in all three spatial directions at the boundary of a flow of steel balls. The relationship between the normal and the tangential forces were examined statistically and compared to the Coulomb friction model. For both large and small forces, the tangential and normal forces are unrelated, as there appears to be a strong tendency for the tangential force to maintain a value that will bear the weight the weight of the particles in flow.

Facto, Kevin

126

Experiments on Frequency Error Compensation Using Synchronization Channel in OFDM Radio Access  

NASA Astrophysics Data System (ADS)

This paper experimentally investigates the effect of frequency error compensation provided by demodulation automatic frequency control (AFC) using the Synchronization Channel (SCH) in downlink OFDM radio access. The implemented OFDM receiver compensates for the frequency error caused by the difference in frequency between a base station (BS) and a user equipment (UE) using a time-division multiplexed SCH signal and that caused by the Doppler shift generated by the mobility of a user using reference signals with staggered multiplexing. Experimental results show that even when the standard oscillator frequency of the UE cannot be made to track the more accurate frequency of a BS, demodulation AFC can suppress the residual frequency error to a sufficiently low level, i.e., within 0.3ppm, using the SCH so that the degradation in the block error rate of the physical broadcast channel control signals is slight, i.e., within approximately 0.1dB, with respect to the case without frequency error for speeds greater than 350km/h.

Taoka, Hidekazu; Ito, Fumiaki; Takakusaki, Keiji; Sawahashi, Mamoru

127

Progress in Understanding Horizontal Resolution of Radio Occultation Measurements  

NASA Astrophysics Data System (ADS)

The meaning of high vertical resolution and the ``horizontal'' resolution of radio occultation measurements has been subject to interpretation of the Abel transform relationships between the occultation ray paths and an assumed spherically symmetric atmospheric refractivity field. For the spherically symmetric case the refractivity field is recovered exactly, within the limitations of ray optics. Only brute force methods have been available for analysis of non-spherically symmetric cases. For example, ray tracing is employed to calculate the ray asymptotes for perturbed, approximately symmetric models, followed by application of the Abel inversion to retrieve the apparent refractivity, which then can be compared with the model results. In instances where the bending angle is small a straight ray model leads to the inversion kernel for the Abel transform (Ahmad & Tyler, ``The 2-D Resolution Kernel associated with Retrieval of Ionospheric and Atmospheric Refractivity Profiles by Abelian Inversion of Radio Occultation Phase Data,'' submitted to RADIO SCIENCE, April, 1997). Weighted integrals of the 2-D refractivity field employing the inversion kernel then give the corresponding Abel inversion directly. This approach permits rapid computation of the effects of departures from spherical symmetry. Inspection of the inversion kernel provides insight into the Abel transform inversion procedure. An interesting and useful result is understanding of the artifacts created by atmospheric structures of limited horizontal extent. Transformation of the curved ray case appropriate for thick atmospheres to an equivalent straight ray case yields the kernel function for the curved rays in a spherically symmetric atmosphere. A remaining problem is to estimate the effects of ray path deviation from the background path on the analysis; for realistic cases this effect is believed to be small, however.

Ahmad, B.; Tyler, G. L.

1997-07-01

128

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

129

Car-to-car channel models based on wideband MIMO measurements at 5.3 GHz  

Microsoft Academic Search

In this paper, we describe measurement results of 30 times 30 multiple-input multiple-output (MIMO) car-to-car (C2C) radio channels at 5.3 GHz in four environments: on a campus, on a highway, in urban and sub-urban areas. We first investigate the validity of the wide-sense stationarity (WSS) assumption by using the correlation matrix distance (CMD), which is an earlier introduced metric for

Olivier Renaudin; Veli-Matti Kolmonen; Pertti Vainikainen; Claude Oestges

2009-01-01

130

Frequency-Domain Methodology for Measuring MIMO Channels Using a Generic Test Bed  

Microsoft Academic Search

A multiple-input multiple-output (MIMO) frequency-domain channel measurement methodology is pre- sented. This methodology can be implemented in any transmit\\/ receive hardware consisting of radio frequency modules and baseband digital processing units. It involves the transmission and reception of frequency and phase-optimized complex exponentials through antenna arrays, followed by an offline frequency estimation, which makes additional synchronization circuitry unnecesary. To test

Jesús Gutiérrez; Oscar Gonzalez; Jesús Pérez; David Ramírez; Luis Vielva; Jesús Ibáñez; Ignacio Santamaría

2011-01-01

131

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

132

Stochastic Wireless Channel Modeling, Estimation and Identification from Measurements  

SciTech Connect

This paper is concerned with stochastic modeling of wireless fading channels, parameter estimation, and system identification from measurement data. Wireless channels are represented by stochastic state-space form, whose parameters and state variables are estimated using the expectation maximization algorithm and Kalman filtering, respectively. The latter are carried out solely from received signal measurements. These algorithms estimate the channel inphase and quadrature components and identify the channel parameters recursively. The proposed algorithm is tested using measurement data, and the results are presented.

Olama, Mohammed M [ORNL; Djouadi, Seddik M [ORNL; Li, Yanyan [ORNL

2008-07-01

133

Maximizing the utility of radio spectrum: Broadband spectrum measurements and occupancy model for use by cognitive radio  

NASA Astrophysics Data System (ADS)

Radio spectrum is a vital national asset; proper management of this finite resource is essential to the operation and development of telecommunications, radio-navigation, radio astronomy, and passive remote sensing services. To maximize the utility of the radio spectrum, knowledge of its current usage is beneficial. As a result, several spectrum studies have been conducted in urban Atlanta, suburban Atlanta, and rural North Carolina. These studies improve upon past spectrum studies by resolving spectrum usage by nearly all its possible parameters: frequency, time, polarization, azimuth, and location type. The continuous frequency range from 400MHz to 7.2 GHz was measured with a custom-designed system. More than 8 billion spectrum measurements were taken over several months of observation. A multi-parameter spectrum usage detection method was developed and analyzed with data from the spectrum studies. This method was designed to exploit all the characteristics of spectral information that was available from the spectrum studies. Analysis of the spectrum studies showed significant levels of underuse. The level of spectrum usage in time and azimuthal space was determined to be only 6.5 % for the urban Atlanta, 5.3 % for suburban Atlanta, and 0.8 % for the rural North Carolina spectrum studies. Most of the frequencies measured never experienced usage. Interference was detected in several protected radio astronomy and sensitive radio navigation bands. A cognitive radio network architecture to share spectrum with fixed microwave systems was developed. The architecture uses a broker-based sharing method to control spectrum access and investigate interference issues.

Petrin, Allen J.

134

Measurement of stream channel habitat using sonar  

USGS Publications Warehouse

An efficient and low cost technique using a sonar system was evaluated for describing channel geometry and quantifying inundated area in a large river. The boat-mounted portable sonar equipment was used to record water depths and river width measurements for direct storage on a laptop computer. The field data collected from repeated traverses at a cross-section were evaluated to determine the precision of the system and field technique. Results from validation at two different sites showed average sample standard deviations (S.D.s) of 0.12 m for these complete cross-sections, with coefficient of variations of 10%. Validation using only the mid-channel river cross-section data yields an average sample S.D. of 0.05 m, with a coefficient of variation below 5%, at a stable and gauged river site using only measurements of water depths greater than 0.6 m. Accuracy of the sonar system was evaluated by comparison to traditionally surveyed transect data from a regularly gauged site. We observed an average mean squared deviation of 46.0 cm2, considering only that portion of the cross-section inundated by more than 0.6 m of water. Our procedure proved to be a reliable, accurate, safe, quick, and economic method to record river depths, discharges, bed conditions, and substratum composition necessary for stream habitat studies. ?? 1998 John Wiley & Sons, Ltd.

Flug, M.; Seitz, H.; Scott, J.

1998-01-01

135

Secondary fluorescence in PIXE channeling measurements  

SciTech Connect

The effect of secondary fluorescence on PIXE channeling minimum yields was studied in ZnSe/GaAs heterostructures. The secondary fluorescence enhancement of the Zn K{sub {alpha}} line was calculated as a function of proton energy for different ZnSe layer thicknesses. The corresponding yields were measured for an 1800 nm thick ZnSe layer grown on GaAs substrate. An equation for calculating the secondary fluorescence correction to the Zn minimum yield was derived and the corrections to the measured minimum yields were calculated. A notable enhancement in the Zn minimum yield due to secondary fluorescence was observed with proton energies higher than 1.5 MeV.

Seppaelae, A.; Salonen, R. [Accelerator laboratory, P.O. Box 43, FIN-00014 University of Helsinki (Finland); Raeisaenen, J. [Department of Physics, University of Jyvaeskylae, P.O. Box 35, FIN-40351 Jyvaeskylae (Finland)

1999-06-10

136

Outage Capacity of Spectrum Sharing Cognitive Radio with Channel Estimation Errors and Feedback Delay in Rayleigh Fading Environments  

NASA Astrophysics Data System (ADS)

This paper considers a spectrum sharing cognitive radio (CR) network consisting of one secondary user (SU) and one primary user (PU) in Rayleigh fading environments. The channel state information (CSI) between the secondary transmitter (STx) and the primary receiver (PRx) is assumed to be imperfect. Particularly, this CSI is assumed to be not only having channel estimation errors but also outdated due to feedback delay, which is different from existing work. We derive the closed-form expression for the outage capacity of the SU with this imperfect CSI under the average interference power constraint at the PU. Analytical results confirmed by simulations are presented to show the effect of the imperfect CSI. Particularly, it is shown that the outage capacity of the SU is robust to the channel estimation errors and feedback delay for low outage probability and high channel estimation errors and feedback delay.

Xu, D.; Feng, Z.; Zhang, P.

2013-04-01

137

Wireless platform for multi-channel analog measurements.  

PubMed

This paper describes wireless measurement platform, which uses inductive power and data transmission and provides up to four analog measurement channels. Platform is powered by inductive coupling using the 125 kHz magnetic field. Data transmission is realized by modulating the magnetic field. The platform has up to four 10-bit analog channels. The sample rate of the platform is 237 samples per second, which is divided between the used channels as needed. With 2.85 V supply voltage the measurement platform has power consumption less than 1.5 mW. Nevertheless the end application's total power consumption depends on the measurement set-up. Except for the antenna coil, the measurement platform is made using the commercially available components. Main target application for the platform is implantable electrocardiogram (ECG) measurement. At this stage ECG measurements are done with one channel. Additional channels are available for example for other ECG channels, temperature or acceleration measurements. PMID:17945918

Heinisuo, Sami; Vanhala, Jukka

2006-01-01

138

Radio-frequency measurement of an asymmetric single electron transistor  

NASA Astrophysics Data System (ADS)

Since the invention of the radio-frequency single-electron transistor (RF-SET) by Schoelkopf et al.,[1] most measurements have focused on the symmetric single electron transistor. It has been shown, however, that the symmetric SET has a rather low measurement efficiency in its normal working regime.[2][3] Recently, it has been pointed out that an asymmetric SET can be considerably more efficient than a symmetric SET as a quantum amplifier. In this case the measurement efficiency of the asymmetric SET becomes similar to that of the quantum point contact (QPC) detector which can approach the quantum limit. We investigate the asymmetric SET by fabricating Al/AlOx SETs with junction areas 40x40 nm^2 and 40x80nm^2 and total resistance of about 25k?. The results of RF and DC characterization of such asymmetric SETs will be discussed. [1] R. J. Schoelkopf, P. Wahlgren, A. A. Kozhevnikov, P. Delsing, D. E. Prober, Science, 280, 1242 (1998). [2] A. N. Korotkov, Phys. Rev. B, 63, 085312 (2001); 63, 115403 (2001). [3] D. Mozyrsky, I. Martin, and M. B. Hastings, Phys. Rev. Lett., 92, 018303 (2004). [4] S. A. Gurvitz and G. P. Berman, Phys. Rev. B, 72 , 073303(2005).

Ji, Zhongqing; Xue, Weiwei; Rimberg, A. J.

2007-03-01

139

Flux density measurements and peculiarities of radio emission of pulsars at 102 and 111 MHz  

NASA Astrophysics Data System (ADS)

At present time more than 1000 pulsars are discovered. But flux density and energy measurements were basically obtained at frequencies 400, 610 and 1400 MHz. For detail consideration of pulsar spectra and its connection with pulsar parameters the multifrequency measurements of the flux densities in all radio waves are required. At frequency about 100 MHz maximum of radio emission is reached for the majority of pulsars. It is the very important point in pulsar spectrum, but we have very poor data at this frequency and at frequencies near this. In this connection the survey of more than 200 (basically weak) pulsars was conducted using the Large Phased Array telescope (PRAO, Russia). These observations were made during 1994-1999 in 25 series (4-7 days duration each). Three spectra analyzers (128 channels x 20 kHz, 32 channels x 5 kHz and 128 channels x 1.25 kHz) were used as receivers. The data-processing included searching of "zero-level" on the part of record without the signal, amplification equalizing by the basic channel (without interferences), cleaning of the channels with interferences and summation of signal in all rest channels. For calibration the discrete sources were used. In the data-processing procedure some mistakes were taken into account. For example, there were the mistakes, connected with the calculation of the mean profile, calibration signal, full energy and also with the scattering and scintillations of pulsar signal on the interstellar medium inhomogeneities. As a result, the flux densities for 235 pulsars were calculated, what is a base for calculation of the spectral indices, luminosities, etc. Now they are used to form the catalogue of pulsar spectra and carry out statistic investigations. The interesting result is the deficit of weak pulsars on distances more than 3 kpc. It may be connected with the small luminosities of non-detected pulsars, but probably it means that pulsars with luminosities less than 1026 erg/s are absent. Non-detectable pulsars must have the steep spectra, what can explain their absence in many searches at frequencies 400, 600 and 1400 MHz (these objects must be like radio pulsar in Geminga). The mean value of spectral index in range 100-400 MHz is about 1.47. As we know, the mean spectral index in range 400-1600 MHz is about 1.6 and in range 1400-4800 MHz is about 1.9. It is shown, that the mean spectral index decreases at the meter waves and increases at the centimeters. Also, the investigation of millisecond pulsars shows, that almost all these objects have approximately linear spectra. Finally, several interesting peculiarities were detected for some pulsars. For example, new interpulses were found. But now we check all of these, because we must be sure, that these interpulses are real.

Malov, O. I.

140

Digital measurements of LF radio wave absorption in the lower ionosphere and inferred gravity wave activity  

Microsoft Academic Search

Low frequency (LF) radio wave absorption in the lower ionosphere has been measured at Pruhonice (approximately 50 deg N) since 1957. A new digital computer-controlled measuring-recording-processing system was introduced in 1988. The A3 method of radio wave absorption measurement, the measuring equipment used for the digital measurements at 270 kHz, is briefly described. The digital nighttime LF A3 measurements allow

J. Lastovicka; J. Boska; D. Buresova

1993-01-01

141

Flux density measurements and peculiarities of radio emission of pulsars at 102 and 111 MHz  

Microsoft Academic Search

At present time more than 1000 pulsars are discovered. But flux density and energy measurements were basically obtained at frequencies 400, 610 and 1400 MHz. For detail consideration of pulsar spectra and its connection with pulsar parameters the multifrequency measurements of the flux densities in all radio waves are required. At frequency about 100 MHz maximum of radio emission is

O. I. Malov

2000-01-01

142

Walkie-Talkie Measurements for the Speed of Radio Waves in Air  

ERIC Educational Resources Information Center

A handheld emitter-receiver device suitable for the direct estimation of the velocity of radio waves in air is presented. The velocity of radio waves is measured using the direct time-of-flight method, without the need for any tedious and precise settings. The results for two measurement series are reported. Both sets of results give an estimate…

Dombi, Andra; Tunyagi, Arthur; Neda, Zoltan

2013-01-01

143

Walkie-Talkie Measurements for the Speed of Radio Waves in Air  

ERIC Educational Resources Information Center

|A handheld emitter-receiver device suitable for the direct estimation of the velocity of radio waves in air is presented. The velocity of radio waves is measured using the direct time-of-flight method, without the need for any tedious and precise settings. The results for two measurement series are reported. Both sets of results give an estimate…

Dombi, Andra; Tunyagi, Arthur; Neda, Zoltan

2013-01-01

144

Midlatitude daytime D region ionosphere variations measured from radio atmospherics  

NASA Astrophysics Data System (ADS)

We measured the midlatitude daytime ionospheric D region electron density profile height variations in July and August 2005 near Duke University by using radio atmospherics (or sferics for short), which are the high-power, broadband very low frequency (VLF) signals launched by lightning discharges. As expected, the measured daytime D region electron density profile heights showed temporal variations quantitatively correlated with solar zenith angle changes. In the midlatitude geographical regions near Duke University, the observed quiet time heights decreased from ˜80 km near sunrise to ˜71 km near noon when the solar zenith angle was minimum. The measured height quantitative dependence on the solar zenith angle was slightly different from the low-latitude measurement given in a previous work. We also observed unexpected spatial variations not linked to the solar zenith angle on some days, with 15% of days exhibiting regional differences larger than 0.5 km. In these 2 months, 14 days had sudden height drops caused by solar flare X-rays, with a minimum height of 63.4 km observed. The induced height change during a solar flare event was approximately proportional to the logarithm of the X-ray flux. In the long waveband (wavelength, 1-8 Å), an increase in flux by a factor of 10 resulted in 6.3 km decrease of the height at the flux peak time, nearly a perfect agreement with the previous measurement. During the rising and decaying phases of the solar flare, the height changes correlated more consistently with the short, rather than the long, wavelength X-ray flux changes.

Han, Feng; Cummer, Steven A.

2010-10-01

145

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

146

Spectroscopic Measurements of Radio Frequency Plasmas in Supercritical Fluids  

SciTech Connect

Spectroscopic measurements of radio frequency (rf) plasma were performed under high pressure CO{sub 2} conditions (5 and 7 MPa) and supercritical (sc)CO{sub 2} conditions (8-20 MPa). The temperatures evaluated from C{sub 2} Swan bands increased from 3600 K to 4600 K with increasing pressure. The broadening and shifting of the O I line profile ({approx}777 nm) of rf plasma was observed under scCO{sub 2} conditions. The width of the line profile increased with increasing pressure. The reason for the broadening and shifting is still unclear because the present theory used to explain them is not valid for such high pressure conditions. Further, the broadening of the Ar I line profile ({approx}811.5 nm) in rf plasmas was observed under atmospheric Ar (0.1 MPa), high pressure Ar conditions (1-4 MPa), and scAr condition (5 MPa); the observation of the O I line profile in CO{sub 2} plasmas is difficult in this pressure range owing to its weak intensity therein. Similar to the case of the O I line in CO{sub 2} plasmas, the reason for the broadening of the Ar I line profile at 5 MPa is unclear.

Maehara, Tsunehiro [Graduate School of Science and Engineering, Ehime University, Matsuyama 790-8577 (Japan); Iwamae, Atsushi [Graduate School of Engineering, Kyoto University, Kyoto 606-8501 (Japan); Kawashima, Ayato [Faculty of Agriculture, Ehime University, Matsuyama 790-8566 (Japan)

2010-10-29

147

MEASURING THE JET POWER OF FLAT-SPECTRUM RADIO QUASARS  

SciTech Connect

We use frequency-dependent position shifts of flat-spectrum radio cores to estimate the kinetic power of active galactic nucleus (AGN) jets. We find a correlation between the derived jet powers and AGN narrow-line luminosity, consistent with the well-known relation for radio galaxies and steep spectrum quasars. This technique can be applied to intrinsically weak jets even at high redshift.

Shabala, S. S.; Santoso, J. S. [School of Mathematics and Physics, University of Tasmania, Private Bag 37, Hobart, TAS 7001 (Australia); Godfrey, L. E. H. [International Centre for Radio Astronomy Research, Curtin University, GPO Box U1987, Perth, Western Australia 6845 (Australia)

2012-09-10

148

The principles of a special radio telescope used for atmospheric refraction measurement  

Microsoft Academic Search

A new method to measure the atmospheric refraction of centimeter waves utilizing a radio telescope to observe the sun is presented. This procedure uses a beam-switched antenna with a waiting mode to record the time by which the equivalent center of the solar radio emission passes over the zero point of the differential antenna diagram, and then to calculate out

Jingsheng Wang; Zhicai Xu; Ruijin Jia

1990-01-01

149

On noise treatment in radio measurements of cosmic ray air showers  

Microsoft Academic Search

Precise measurements of the radio emission by cosmic ray air showers require an adequate treatment of noise. Unlike to usual experiments in particle physics, where noise always adds to the signal, radio noise can in principle decrease or increase the signal if it interferes by chance destructively or constructively. Consequently, noise cannot simply be subtracted from the signal, and its

F. G. Schröder; W. D. Apel; J. C. Arteaga; T. Asch; L. Bähren; K. Bekk; M. Bertaina; P. L. Biermann; J. Blümer; H. Bozdog; I. M. Brancus; P. Buchholz; S. Buitink; E. Cantoni; A. Chiavassa; K. Daumiller; V. de Souza; P. Doll; R. Engel; H. Falcke; M. Finger; D. Fuhrmann; H. Gemmeke; C. Grupen; A. Haungs; D. Heck; J. R. Hörandel; A. Horneffer; D. Huber; T. Huege; P. G. Isar; K.-H. Kampert; D. Kang; O. Krömer; J. Kuijpers; S. Lafebre; K. Link; P. ?uczak; M. Ludwig; H. J. Mathes; M. Melissas; C. Morello; S. Nehls; J. Oehlschläger; N. Palmieri; T. Pierog; J. Rautenberg; H. Rebel; M. Roth; C. Rühle; A. Saftoiu; H. Schieler; A. Schmidt; O. Sima; G. Toma; G. C. Trinchero; A. Weindl; J. Wochele; M. Wommer; J. Zabierowski; J. A. Zensus

2010-01-01

150

Channeling and blocking measurements on quasicrystals  

NASA Astrophysics Data System (ADS)

The paper presents the first blocking experiments on quasicrystals. Channeling-RBS (with 1.5 and 2.0MeV He ions) and blocking-RBS (1.3MeV He) as well as blocking-ERDA (210 MeV I) expenments on icosahedral AlPdMn quasicrystals were performed. Good agreement of the channeling-RBS and blocking-ERDA minimum yields - as expected from the rule of reversibility for channeling and blocking - was found for Al and Pd. The RBS and ERDA minimum yields for Mn, however, show a large and unexpected difference.

Plachke, D.; Carstanjen, H. D.; Emrick, R. M.; Nolte, H.; Huber, H.; Assmann, W.; Grötzschel, R.

1998-03-01

151

Decentralized Channel Management in Scalable Multihop Spread-Spectrum Packet Radio Networks  

Microsoft Academic Search

This thesis addresses the problems of managing the transmissions of stations in aspread-spectrum packet radio network so that the system can remain effective whenscaled to millions of nodes concentrated in a metropolitan area. The principal difficultyin scaling a system of packet radio stations is interference from other stations inthe system. Interference comes both from nearby stations and from distant stations.Each

Timothy Jason Shepard

1995-01-01

152

A context-aware and Intelligent Dynamic Channel Selection scheme for cognitive radio networks  

Microsoft Academic Search

The tremendous growth in ubiquitous low-cost wireless applications that utilize the unlicensed spectrum bands has laid increasing stress on the limited and scarce radio spectrum resources. Given that the licensed or Primary Users (PUs) are oblivious to the presence of unlicensed or Secondary Users (SUs), Cognitive Radio (CR) is a new paradigm in wireless communication that allows the SUs to

Kok-Lim Alvin Yau; Peter Komisarczuk; Paul D. Teal

2009-01-01

153

Capacity of MIMO systems based on measured wireless channels  

Microsoft Academic Search

We measure the capacity of multiple-input multiple-output radio systems in microcellular environments. We use a new data evaluation method that allows to evaluate the cumulative distribution function of the capacity from a single measurement. This method is based on an extraction of the parameters of the multipath components and, thereafter, a synthetic variation of their phases. In the analyzed environments,

Andreas F. Molisch; Martin Steinbauer; Martin Toeltsch; Ernst Bonek; Reiner S. Thomä

2002-01-01

154

Measuring ion channels on solid supported membranes.  

PubMed

Application of solid supported membranes (SSMs) for the functional investigation of ion channels is presented. SSM-based electrophysiology, which has been introduced previously for the investigation of active transport systems, is expanded for the analysis of ion channels. Membranes or liposomes containing ion channels are adsorbed to an SSM and a concentration gradient of a permeant ion is applied. Transient currents representing ion channel transport activity are recorded via capacitive coupling. We demonstrate the application of the technique to liposomes reconstituted with the peptide cation channel gramicidin, vesicles from native tissue containing the nicotinic acetylcholine receptor, and membranes from a recombinant cell line expressing the ionotropic P2X2 receptor. It is shown that stable ion gradients, both inside as well as outside directed, can be applied and currents are recorded with an excellent signal/noise ratio. For the nicotinic acetylcholine receptor and the P2X2 receptor excellent assay quality factors of Z' = 0.55 and Z' = 0.67, respectively, are obtained. This technique opens up new possibilities in cases where conventional electrophysiology fails like the functional characterization of ion channels from intracellular compartments. It also allows for robust fully automatic assays for drug screening. PMID:19580777

Schulz, Patrick; Dueck, Benjamin; Mourot, Alexandre; Hatahet, Lina; Fendler, Klaus

2009-07-01

155

A New Dual Channel Pulse Wave Velocity Measurement System  

Microsoft Academic Search

Pulse wave velocity (PWV) is the most popular index to assessment the arterial stiffness. Currently, several non-invasive examination methods with single channel for PWV are announced. This paper proposes a non-invasive digital volume pulse (DVP) measuring system using a dual channel simultaneous measurement method try to meet the demands for home healthcare equipment which is easy to operate. Through synchronal

Yung-kang Chen; Hsien-tsai Wu; Chih-kai Chi; Wei-chuan Tsai; Ju-yi Chen; Ming-chun Wang

2004-01-01

156

Radio Occultation Measurements with the Mars Reconnaissance Orbiter  

NASA Astrophysics Data System (ADS)

The Mars Reconnaissance Orbiter (MRO) circles Mars in a low-altitude, sun-synchronous, polar orbit, crossing the equator at local times of about 3 and 15 h. There are frequent opportunities for radio occultation (RO) sounding of the martian atmosphere, which has been conducted routinely since January 2008. Observations are limited to one orbit per day, so as to minimize the impact on transmission of data collected by the primary scientific instruments. We are retrieving atmospheric profiles from the MRO RO data, and we are delivering the results to the NASA Planetary Data System (PDS) for archiving and public distribution. The value of these RO profiles derives from their combination of accurate absolute calibration, excellent vertical resolution (about 500 m), and accurate registration in radius. The first attribute qualifies the RO profiles as a reliable standard for cross-instrument calibration, and comparisons are underway with atmospheric observations by the MRO Mars Climate Sounder (MCS). The second attribute yields unique insight into the structure and dynamics of the lower atmosphere (0-10 km) and its interaction with surface reservoirs of dust and volatiles. The third attribute allows precise measurements of geopotential height and surface pressure, which constrain the mass distribution of the atmosphere and its seasonal variations. These attributes also enable long-term monitoring of interannual variability and climatic trends. We will characterize the spatial and seasonal coverage of the observations to date, and we will illustrate the atmospheric phenomena captured by the MRO RO profiles. This research is funded in part by Grant NNX12AL48G of the Mars Data Analysis Program.

Hinson, David P.; Asmar, S.; Kahan, D.; Akopian, V.; Maalouf, S.

2012-10-01

157

Residence times and diel passage distributions of radio-tagged juvenile spring chinook salmon and steelhead in a gatewell and fish collection channel of a Columbia River Dam  

USGS Publications Warehouse

The amount of time radio-tagged juvenile spring chinook salmon Oncorhynchus tshawytscha and juvenile steelhead O. mykiss spent within a gatewell and the juvenile collection channel at McNary Dam, Columbia River, USA, was measured to determine the diel passage behavior and residence times within these portions of the juvenile bypass system. The median gatewell residence times were 8.9 h for juvenile chinook salmon and 3.2 h for steelhead. Juvenile spring chinook salmon spent 83% of their time in the 18-m-deep gatewell at depths of 9 m or less, and juvenile steelhead spent 96% of their time in the upper 11 m. Fish released during midday and those released in the evening generally exited the gatewell in the evening, indicating that fish entering the gatewell during daylight will have prolonged residence times. Median collection-channel residence times of juvenile chinook salmon were much shorter (2.3 min) than those of steelhead (28.0 min), most likely because of the greater size of the steelhead and the high water velocities within the channel (2.1 m/s). This and other studies indicate most juvenile salmonids enter gatewells of several Columbia and Snake river dams in the evening and pass into the collection channels quickly. However, this is not consistent with the natural in-river migration patterns of these species and represents a delay in dam passage.

Beeman, J. W.; Maule, A. G.

2001-01-01

158

Radio Noise Measurements on Overhead Power Lines from 2.4 to 800 KV  

Microsoft Academic Search

This paper presents radio noise measurements made near overhead power lines from 2.4 to 345 kV in the frequency range of 60 Hz to 1 GHz and on radio noise measurements made on 7.2, 345, 525, 735, and 765-kV ac lines and on an 800-kV dc test line up to 10 GHz. The measurements and their analysis show the important

W. E. Pakala; V. L. Chartier

1971-01-01

159

At-sea distribution of radio-marked Ashy Storm-Petrels Oceanodroma homochroa captured on the California Channel Islands  

USGS Publications Warehouse

Small, rare and wide-ranging pelagic birds are difficult to locate and observe at sea; little is therefore known regarding individual movements and habitat affinities among many of the world's storm-petrels (Family Hydrobatidae). We re-located 57 of 70 radio-marked Ashy Storm-Petrels Oceanodroma homochroa captured at three colonies in the California Channel Islands: Scorpion Rocks (2004, 2005), Santa Barbara Island (2004) and Prince Island (2005). Between 23 July and 22 September 2004, and 5 July and 4 August 2005, we flew 29 telemetry surveys, covered more than 65 000 km2 (2004) and 43 000 km2 (2005) of open ocean from San Nicolas Island north to the Farallon Islands and obtained 215 locations from 57 storm-petrels at sea. In both years, radio-marked storm-petrels were aggregated over the continental slope from Point Conception to Point Buchon, within the western Santa Barbara Channel, and over the Santa Cruz Basin between Santa Cruz, San Nicolas and Santa Barbara islands. Individuals captured in the Channel Islands ranged more than 600 km and were located as far north as Gulf of the Farallones National Marine Sanctuary. This is the first study to use radiotelemetry to determine the at-sea distribution and movements for any storm-petrel species.

Adams, J.; Takekawa, J. Y.

2008-01-01

160

Trust based Fusion over Noisy Channels through Anomaly Detection in Cognitive Radio Networks.  

National Technical Information Service (NTIS)

Byzantine attacks have been identified as one of the key vulnerabilities in cognitive radio networks, where malicious nodes advertise false spectrum occupancy data in a cooperative environment. In such cases, the resultant fused data is very different fro...

K. Kwait M. Chatterjee S. Bhattacharjee S. Debroy

2011-01-01

161

Radio Frequency Hearing Aids: The Need for Complementary and Compatible Channel Allocation.  

ERIC Educational Resources Information Center

|The article discusses the use of radio frequency hearing aids, which provide a practical means of improving the signal-to-noise ratio of conventional hearing aids used by the aurally handicapped. (Author/DLS)|

Burgess, Vic; And Others

1979-01-01

162

An RF frontend circuit design of a Compass and GPS dual-mode dual-channel image rejection radio receiver  

NASA Astrophysics Data System (ADS)

This paper introduces a fully integrated low power consumption radio receiver frontend circuit for a Compass (Beidou) and GPS dual mode dual channel system with 2.5 dB NF, 1.02 mm2 areas, and 8 mA of current in 0.18 ?m TSMC CMOS process. Except for a few passive components for input matching, other components such as an off-chip low noise amplifier or a balun are not required. With a non-tunable passive image rejection filter, the receiver frontend can achieve around 60 dB gain and 34 dB image rejection.

Gong, Zhang; Honglin, Chen; Wei, Liu; Hanbing, Yang; Lijuan, Zhang; Xiangwei, Wang; Lei, Shi; Sijmg, Hu; Mingzhao, Wang; Zhuojian, Fu

2013-08-01

163

Co-Channel Interference Analysis of Point to Point mm-Wave Radio Links  

Microsoft Academic Search

Point to point mm-wave radio links are being increasingly deployed because of the expansion of commercial wireless services. Providers of wireless services continue to demand systems with higher data rate and higher carrier frequency. In order to fulfill the demand unlicensed mm-wave bands have been investigated for fixed point-to-point outdoor radio ap- plications. An analytical method is developed in this

Mingdong Xu; Peter Nuechter

2006-01-01

164

Deterministic Teleportation Channel Using Bell State Measurements Only  

Microsoft Academic Search

Teleportation schemes based on probabilistic channels usually rely heavily on the implementation of high-dimensional unitary operations. Since high-dimensional unitary operations are very difficult to directly implement in physics experiments, methods are used to avoid high-dimensional unitary operations during the teleportation process. This paper describes how to construct a deterministic teleportation channel and a control channel using Bell state measurements only

Min Jiang; Xu Huang; Yiming Zhou

2010-01-01

165

Propagation measurements for the aeronautical satellite channel  

Microsoft Academic Search

Although there is a variety of system design proposals for aeronautical satellite communications, only a few field trials have been accomplished to investigate the behaviour of the aeronautical satellite transmission channel. The German Aerospace Research Establishment (DFVLR) finished in May 86 an extensive test program to provide necessary information for a system design. Over one thousand minutes of useable test

Andreas Neul; Joachim Hagenauer; Wolfgang Papke; Frank Dolainsky; Franz Edbauer

1987-01-01

166

Side Channel Attacks: Measures and Countermeasures  

Microsoft Academic Search

The main focus of modern cryptanalysis is on break- ing the implementation of cryptographic algorithms as opposed to traditional attacks which primarily target on mathematically breaking the algorithms. For over the last decade these new trend of attacks, Side Channel Attacks (SCAs), are becoming increasingly popular and pose a serious threat to cryptographic devices. Researchers proposing countermeasures and adversaries findingout

Isuru Herath; Roshan G. Ragel

167

Radio Noise Measurements on High Voltage Lines from 2.4 to 345 kV  

Microsoft Academic Search

This paper is based on radio noise measurements made near overhead power lines operating at voltages from 2.4 kV to 345 kV inclusive. Some of the measurements made are discussed and analyzed and used in a radio noise prediction technique for determining the location of communication and electronic sites with respect to high voltage overhead power lines. This paper is

W. E. Pakala; E. R. Taylor; R. T. Harrold

1968-01-01

168

TROPOSPHERIC LIMITATIONS TO THE STABILITY OF RADIO METRIC DELAY MEASUREMENTS  

Microsoft Academic Search

Fluctuations in the index of refraction i11 both the wct and dry cornponentu of the troposphere induce timing instabilities in radio metric dat,:~ in excess of t.hnt of xrlodern frequency standards. At zenith, the wet and dry tropospl-leres rallsc fluct~iat,ions of the order of 2 x s\\/s and 7 x 10-~bs\\/s at 1000 secn~rds, rcspect~ivuly. A description of the temporal

R. N. Treuhaft

169

Dynamic impedance measurements during radio-frequency heating of cornea  

Microsoft Academic Search

Hyperopia affects approximately 25% of the population. The aim of different heating modalities for the treatment of hyperopia is to steepen the central curvature of the cornea. Conductive keratoplasty (CK) involves the placement of radio-frequency (RF) lesions around a 7-mm-diameter ring concentric with the pupil of the eye. Dynamics of lesion formation during CK depend on corneal electrical impedance, which

Bernard Choi; Jihoon Kim; Ashley J. Welch; John A. Pearce

2002-01-01

170

Measuring interstellar magnetic fields by radio synchrotron emission  

Microsoft Academic Search

Radio synchrotron emission, its polarization and its Faraday rotation are powerful tools to study the strength and structure of interstellar magnetic fields. The total intensity traces the strength and distribution of total magnetic fields. Total fields in gas-rich spiral arms and bars of nearby galaxies have strengths of 20-30 muGauss, due to the amplification of turbulent fields, and are dynamically

Rainer Beck

2009-01-01

171

Multi-channel multi-radio using 802.11 based media access for sink nodes in wireless sensor networks.  

PubMed

The next generation surveillance and multimedia systems will become increasingly deployed as wireless sensor networks in order to monitor parks, public places and for business usage. The convergence of data and telecommunication over IP-based networks has paved the way for wireless networks. Functions are becoming more intertwined by the compelling force of innovation and technology. For example, many closed-circuit TV premises surveillance systems now rely on transmitting their images and data over IP networks instead of standalone video circuits. These systems will increase their reliability in the future on wireless networks and on IEEE 802.11 networks. However, due to limited non-overlapping channels, delay, and congestion there will be problems at sink nodes. In this paper we provide necessary conditions to verify the feasibility of round robin technique in these networks at the sink nodes by using a technique to regulate multi-radio multichannel assignment. We demonstrate through simulations that dynamic channel assignment scheme using multi-radio, and multichannel configuration at a single sink node can perform close to optimal on the average while multiple sink node assignment also performs well. The methods proposed in this paper can be a valuable tool for network designers in planning network deployment and for optimizing different performance objectives. PMID:22163883

Campbell, Carlene E-A; Khan, Shafiullah; Singh, Dhananjay; Loo, Kok-Keong

2011-05-04

172

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.

173

Multi-channel liquid crystal cell parameter measurement technique  

NASA Astrophysics Data System (ADS)

We propose a novel multi-channel liquid crystal cell parameter measurement system, which combines the spectroscopic ellipsometry technique with the hyperspectral imaging spectrograph for the multi-point measurement. This system is based on PSA setup (polarizer-sample-analyzer) to measure normalized transmission spectrum for analyzing properties of homogeneous cell and MVA cell. We also develop a theoretical method to simplify the calculation of the orientation angle of liquid crystal cells for speeding up the measurement. The liquid crystal cell gap can be calculated by the measured retardation and the given refractive indices of specified wavelength. The pretilt angle is also analyzed by multi-channel measurement system. We present the analysis of hyperspectral imaging spectrograph and the orientation angle measurement by direct calculation method for high speed on-line multi-channel liquid crystal cell parameter measurement.

Liu, Chih-Shang; Chuang, Kai-Ping; Lin, Yeo-Sung; Zhuang, Ming-Yin; Chiang, Chih-Jung

2009-08-01

174

Measurement of nitrogen laser channel current, inductance, and resistance  

SciTech Connect

The laser channel current, inductance, and resistance of a nitrogen laser have been measured using a magnetic probe and have been found to have values of --42kA, 1.6 nH, and 0.1..cap omega.., respectively, for a laser channel gap of 1.6 cm operated at 10 kV and 60 torr. The results of the measurement confirm a double discharge mechanism for the nitrogen laser.

Smith, A.J.; Kwek, K.H.; Tou, T.Y.; Gholap, A.V.; Lee, S.

1987-03-01

175

Location-Based Joint Relay Selection and Channel Allocation for Cognitive Radio Networks  

Microsoft Academic Search

In cognitive radio networks (CRNs), dynamic spectrum access has been demonstrated as an effective way to improve the spectrum utilization. Spectrum holes can be exploited not only in certain time slots or frequency bands, but also at particular locations. In relay assisted CRNs, one relay at a certain location can help to identify and provide different spectrum holes over multiple

Fangyong Li; Bo Bai; Jun Zhang; Khaled Ben Letaief

2011-01-01

176

Selection diversity forwarding in a multihop packet radio network with fading channel and capture  

Microsoft Academic Search

Recent and increased interest of wireless mobile ad hoc networking motivates detailed examination of routing schemes specifically targeted for the demanding constraints that an unreliable, time varying and braodcast like wireless medium imposes. Incorporation and exploitation of radio characteristics are fundamental keys to successful and near optimal operation of routing schemes in a wireless environment. In this paper, for warding

Peter Larsson

2001-01-01

177

Capacity analysis of 802.11 multi-channel multi-radio wireless mesh networks  

Microsoft Academic Search

IEEE 802.11 based wireless mesh networks have recently attracted much attention as they provide a quick and inexpensive way to extend access to the existing wired networks. A significant problem of such networks is their limited capacity due to signal interference. A frequently proposed approach to increasing mesh network capacity is to equip each mesh node with multiple radios, which

Jinling Wang; Yong Xia; Zhengzhong Wang; Hui Wang

2007-01-01

178

Radio-telepathy: extracting a secret key from an unauthenticated wireless channel  

Microsoft Academic Search

Securing communications requires the establishment of cryptographic keys, which is challenging in mobile scenarios where a key management infrastructure is not always present. In this paper, we present a protocol that allows two users to establish a common cryptographic key by exploiting special properties of the wireless channel: the underlying channel response between any two parties is unique and decorrelates

Suhas Mathur; Wade Trappe; Narayan B. Mandayam; Chunxuan Ye; Alex Reznik

2008-01-01

179

Capacity of Cognitive Radio under imperfect secondary and cross link Channel State Information  

Microsoft Academic Search

In this paper, we study the ergodic capacity of secondary user channel in a spectrum sharing scenario in which the secondary transmitter is instantaneously aware of estimated versions of the cross link (between the secondary transmitter and the primary receiver) and the secondary link Channel State Information (CSI). The secondary link optimal power profile along with the ergodic capacity are

Lokman Sboui; Zouheir Rezki; Mohamed-Slim Alouini

2011-01-01

180

HANARO core channel flow-rate measurement.  

National Technical Information Service (NTIS)

HANARO core consists of 23 hexagonal flow tubes and 16 cylindrical flow tubes. To get the core flow distribution, we used 6 flow-rate measuring dummy fuel assemblies (instrumented dummy fuel assemblies). The differential pressures were measured and conver...

H. I. Kim H. T. Chae D. S. Im S. D. Kim

1996-01-01

181

FOREGROUND PREDICTIONS FOR THE COSMIC MICROWAVE BACKGROUND POWER SPECTRUM FROM MEASUREMENTS OF FAINT INVERTED RADIO SOURCES AT 5 GHz  

SciTech Connect

We present measurements of a population of matched radio sources at 1.4 and 5 GHz down to a flux limit of 1.5 mJy in 7 deg{sup 2} of the NOAO Deep Field South. We find a significant fraction of sources with inverted spectral indices that all have 1.4 GHz fluxes less than 10 mJy and are therefore too faint to have been detected and included in previous radio source count models that are matched at multiple frequencies. Combined with the matched source population at 1.4 and 5 GHz in 1 deg{sup -2} in the ATESP survey, we update models for the 5 GHz differential number counts and distributions of spectral indices in 5 GHz flux bins that can be used to estimate the unresolved point source contribution to the cosmic microwave background temperature anisotropies. We find a shallower logarithmic slope in the 5 GHz differential counts than in previously published models for fluxes {approx}< 100 mJy as well as larger fractions of inverted spectral indices at these fluxes. Because the Planck flux limit for resolved sources is larger than 100 mJy in all channels, our modified number counts yield at most a 10% change in the predicted Poisson contribution to the Planck temperature power spectrum. For a flux cut of 5 mJy with the South Pole Telescope and a flux cut of 20 mJy with the Atacama Cosmology Telescope, we predict a {approx}30% and {approx}10% increase, respectively, in the radio source Poisson power in the lowest frequency channels of each experiment relative to that predicted by previous models.

Schneider, Michael D. [Lawrence Livermore National Laboratory, P.O. Box 808 L-210, Livermore, CA 94551 (United States); Becker, Robert H. [Department of Physics, University of California, One Shields Avenue, Davis, CA 08991 (United States); De Vries, Willem [Lawrence Livermore National Laboratory, P.O. Box 808 L-211, Livermore, CA 94551 (United States); White, Richard L., E-mail: schneider42@llnl.gov [Space Telescope Science Institute, Baltimore, MD 21218 (United States)

2012-05-10

182

Method to measure the radio and chemosensitivity of human spheroids  

SciTech Connect

A method based on the spontaneous outgrowth of cells from spheroids was tested. Different outgrowth patterns were seen depending on the types of spheroids and on the radiation or drug doses. The method allowed dose-effect relations to be determined. Spheroid survival was defined as when the outgrowing monolayers contained at least thousand cells within five weeks. The method was used as an alternative to cloning of isolated single cells. The glioma and osteosarcoma spheroids could not be disintegrated to single cell suspensions since they resisted enzymatic and mechanical treatments for cell separation. Detection of differences in radio and chemosensitivity between different types of spheroids of human origin might be valuable for the understanding of the large variations in therapeutical response often seen between different types of tumors.

Carlsson, J.; Nederman, T.

1983-01-01

183

Adaptive transmission scheduling over fading channels for energy-efficient cognitive radio networks by reinforcement learning  

Microsoft Academic Search

In this paper, we address a cross-layer issue of long-term average utility maximization in energy-efficient cognitive radio\\u000a networks supporting packetized data traffic under the constraint of collision rate with licensed users. Utility is determined\\u000a by the number of packets transmitted successfully per consumed power and buffer occupancy. We formulate the problem by dynamic\\u000a programming method namely constrained Markov decision process

Jiang Zhu; Jun Wang; Tao Luo; Shaoqian Li

2009-01-01

184

Tangential Momentum Accommodation Coefficient (TMAC) Measurements for Silicon Micromachined Channels  

NASA Astrophysics Data System (ADS)

Flow data for Knudsen numbers ranging 0.05 to 0.1 is presented for micromachined channels which are nominally 1.33 ?m high, 52.25 ?m wide and 7500 ?m long. With high-resolution mass flow measurements (sub nanomol per second), it is found that the slip flow solutions to the Navier Stokes equations for these channels accurately describes the momentum exchange for various gases. It is also found that the Tangential Momentum Accomodation Coefficient (TMAC) of Argon and Nitrogen can be less than unity for the channel surface under consideration - prime (single crystal) silicon upon which a native oxide resides.

Arkilic, Errol; Schmidt, Martin; Breuer, Kenneth

1996-11-01

185

A new 4-state 8PSK TCM scheme for fast fading, shadowed mobile radio channels  

Microsoft Academic Search

The design of a 4-state, rate-2\\/3, 8PSK trellis-coded modulation (TCM) code, based on the design criteria for fading channels, is presented. To evaluate and compare the performance of this code with the other 4-state 8PSK TCM schemes presented in the literature, computer simulation is performed for a shadowed Rician fading channel. The simulation results show the superiority of the scheme

S. Hamidreza Jamali; Tho Le-Ngoc

1991-01-01

186

Optimal space separator of signals and noise in radio communication channels. 2. Experimental studies  

NASA Astrophysics Data System (ADS)

We present experimental results obtained for a device for signal separation with angular manipulation and separation of different types of noise in SLW-SW communication channels. We show the high efficiency of signal separation from a signal-noise mixture in almost perfect communication channels. The algorithm which we devised was tested by a real-time signal processor model under laboratory conditions. The experimental data were compared with the numerical results.

Metelev, S. A.; Lisov, A. A.

1997-04-01

187

Objective Measurement of Voice Channel Intelligibility.  

National Technical Information Service (NTIS)

Following the results of a feasibility study (Hartman and Boll, 1976) an objective intelligibility measure is developed using a large data base consisting of 8-50 word phonetically balanced word groups with twelve different kinds of distortion. Justificat...

K. J. Gamauf W. J. Hartman

1977-01-01

188

Measurements of the effects of humidity on radio-aerosol penetration through ultrafine capillaries  

SciTech Connect

The purpose of this research was to examine the effects of humidity on radio-aerosol penetration through ultrafine capillaries. A number of tests were conducted at relative humidities of 20%, 50%, and 80%, with sampling times of 20, 40, and 60 min. The radio-aerosol consisted of polystyrene particles with a diameter of 0.1 {micro}m. The ultrafine capillaries had a diameter of 250 {micro}m. The data from these tests varied significantly. These results made the identification of radio-aerosol penetration trends inconclusive. The standard deviation for all penetration data ranged from 3% to 30%. The results of this study suggest that a better control of the experimental parameters was needed to obtain more accurate data from experiments associated with radio-aerosol penetration in the presence of moisture. The experimental parameters that may have contributed to the wide variance of data, include aerosol flow, radio-aerosol generation, capillary characteristics, humidity control, and radiation measurements. It was the uncertainty of these parameters that contributed to the poor data which made conclusive deductions about radio-aerosol penetration dependence on humidity difficult. The application of this study is to ultrafine leaks resulting from stress fractures in high-level nuclear waste transportation casks under accident scenarios.

Cullen, C.

1996-08-01

189

Measurements of Ion Drifts and Thermospheric Neutral Winds at the Jicamarca Radio Observatory  

Microsoft Academic Search

Measurements of ion drifts and thermospheric neutral winds obtained simultaneously with zonal and vertical ion drift measurements of F-region plasma have been made at the Jicamarca Radio Observatory at different times during the year since August, 2009. This period is coincident with an anomalous period of extremely low solar activity. For campaigns taking place in September, 2009, March, 2010, and

J. W. Meriwether; L. Navarro; J. L. Chau; B. G. Fejer

2010-01-01

190

Stability measurements of the radio science system at the 34-m high-efficiency antennas  

Microsoft Academic Search

From 1991 to 1993 the fractional frequency stability of the operational Radio Science System was measured at DSS's 15, 45, and 65. These stations are designed to have the most stable uplink and downlink equipment in the Deep Space Network (DSN). Some measurements were performed when the antenna was moving and the frequency was ramped. The stability, including contributions of

T. T. Pham; J. C. Breidenthal; T. K. Peng; S. F. Abbate; S. T. Rockwell

1993-01-01

191

Radio occultation measurements of turbulence in the Venus atmosphere by Pioneer Venus  

Microsoft Academic Search

As in the cases of Mariner 5 and 10 and Venera 9, the Pioneer Venus radio occultation measurements of Venus show an upper region of turbulence located in the vicinity of 60 km. Estimates of the deduced intensity of turbulence are consistent with the upper bound obtained earlier from the complementary Pioneer Venus probe measurements. Comparison with the Pioneer Venus

Richard Woo; J. W. Armstrong; Akira Ishimaru

1980-01-01

192

Radio-Frequency Method for Measuring the Water Content of Liquids  

Microsoft Academic Search

The method for radio-frequency measurements of water content in nonaqueous liquids is improved, and a procedure for measuring the concentration of water emulsified in oils and diesel fuels is described. Correlations between the composition of emulsions studied and the attenuation of the energy of electromagnetic radiation passing through the emulsions are revealed.

V. A. Bannyi; A. V. Makarevich; L. S. Pinchuk; B. G. An

2002-01-01

193

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

194

Radio signals for SAW ID tags and sensors in strong electromagnetic interference  

Microsoft Academic Search

The applicability of wirelessly interrogated passive ID-tag type SAW sensors for measurements of the temperature of disc brakes of moving railway cars is shown. Here, a short radio channel allows relatively simple radio impulse processing by phase evaluation. Further, using elastic convolver measurement in large steel works, we discuss the feasibility of passive SAW sensors in a severely obstructed radio

A. Pohl; F. Seifert; L. Reindl; G. Scholl; T. Ostertag; W. Pietsch

1994-01-01

195

Measurements and polarization analysis of radio pulses from cosmic-ray-induced air showers at the Pierre Auger Observatory  

NASA Astrophysics Data System (ADS)

The Auger Engineering Radio Array (AERA) is designed to study the radio emissions from extensive air showers at the Pierre Auger Observatory. The array currently consists of a grid of 23 autonomous radio detector stations that measure the radio emissions from cosmic-ray-induced air showers since April 2011. The array is still under construction and is planned to be extended to 160 stations. The new detection technique provides an augmentation of the existing detectors, improves the sensitivity of the observatory and sheds new light on the shower physics. An analysis of the emission processes based on the polarization of the radio pulses is presented.

Fraenkel, Daniël; Pierre Auger Collaboration

2013-02-01

196

Turbulent Channel Flow Measurements Using Matched Hot-Wires  

NASA Astrophysics Data System (ADS)

We present an experimental study conducted in a turbulent channel flow facility using hot-wire probes with both constant and varying viscous-scaled wire length. The objectives of the study were threefold: first, to validate the flow produced by the channel flow facility; second, to investigate the validity of recently proposed spatial filtering corrections for Reynolds stress profiles; and third, to extend the investigation of the near-wall peak Reynolds number dependence in turbulent pipe flow conducted by Hultmark, Bailey and Smits (see J. Fluid Mech. (2010), vol. 649, pp. 103--113). We found that in channel flow, unlike in the pipe flow experiments, the near-wall peak exhibited the same Reynolds number dependence observed in turbulent boundary layer studies and channel flow DNS. Since the same measurement techniques and procedures were used in the current study as used in the pipe flow study, this demonstrated that the near-wall Reynolds number independence observed in the pipe study was not due to error introduced by measurement methodology. Furthermore, comparison of results from wires of different length verified that spatial filtering corrections work in channel flow as well as pipe and boundary layer flows. Corrected results were in good agreement with channel flow DNS, thus verifying that the flow in the facility approximates one-dimensional turbulent Poiseuille flow.

Estejab, Baraheh; Bailey, Sean

2011-11-01

197

LOPES-3D - vectorial measurements of radio emission from cosmic ray induced air showers  

NASA Astrophysics Data System (ADS)

LOPES-3D is able to measure all three components of the electric field vector of the radio emission from air showers. This allows a better comparison with emission models. The measurement of the vertical component increases the sensitivity to inclined showers. By measuring all three components of the electric field vector LOPES-3D demonstrates by how much the reconstruction accuracy of primary cosmic ray parameters increases. Thus LOPES-3D evaluates the usefulness of vectorial measurements for large scale applications.

Huber, D.; Apel, W. D.; Arteaga-Velázquez, J. C.; Bähren, L.; Bekk, K.; Bertaina, M.; Biermann, P. L.; Blümer, J.; Bozdog, H.; Brancus, I. M.; Chiavassa, A.; Daumiller, K.; de Souza, V.; Di Pierro, F.; Doll, P.; Engel, R.; Falcke, H.; Fuchs, B.; Fuhrmann, D.; Gemmeke, H.; Grupen, C.; Haungs, A.; Heck, D.; Hörandel, J. R.; Horneffer, A.; Huege, T.; Isar, P. G.; Kampert, K.-H.; Kang, D.; Krömer, O.; Kuijpers, J.; Link, K.; ?uczak, P.; Ludwig, M.; Mathes, H. J.; Melissas, M.; Morello, C.; Oehlschläger, J.; Palmieri, N.; Pierog, T.; Rautenberg, J.; Rebel, H.; Roth, M.; Rühle, C.; Saftoiu, A.; Schieler, H.; Schmidt, A.; Schröder, F. G.; Sima, O.; Toma, G.; Trinchero, G. C.; Weindl, A.; Wochele, J.; Zabierowski, J.; Zensus, J. A.

2013-05-01

198

CMOS Neurostimulation ASIC with 100 Channels, Scaleable Output, and Bidirectional Radio-Frequency Telemetry  

Microsoft Academic Search

channel neurostimulation circuit comprising a complementary metal oxide semiconductor (CMOS), application- specific integrated circuit (ASIC) has been designed, constructed and tested. The ASIC forms a significant milestone and an integral compo- nent of a 100-electrode neurostimulation system being developed by the authors. The system comprises an externally worn transmitter and a body implantable stimulator. The purpose of the system is

Gregg Jørgen Suaning; Nigel H. Lovell

2001-01-01

199

CMOS neurostimulation ASIC with 100 channels, scaleable output, and bidirectional radio-frequency telemetry  

Microsoft Academic Search

100-channel neurostimulation circuit comprising a complementary metal oxide semiconductor (CMOS), application-specific integrated circuit (ASIC) has been designed, constructed and tested. The ASIC forms a significant milestone and an integral component of a 100-electrode neurostimulation system being developed by the authors. The system comprises an externally worn transmitter and a body implantable stimulator. The purpose of the system is to communicate

Gregg Jørgen Suaning; Nigel H. Lovell

2001-01-01

200

Broadcasting in Multi-Radio Multi-Channel Wireless Networks using Simplicial Complexes.  

National Technical Information Service (NTIS)

We consider the broadcasting problem in multiradio multi-channel ad hoc networks. The objective is to minimize the total broadcast cost, where the cost can be of any form that is summable over all the transmissions (e.g., the transmission and reception en...

A. Swami J. Gao Q. Zhao R. Ramanathan W. Ren

2011-01-01

201

MICROWAVE signal parametric transfer via radio channel using running wave resonator  

Microsoft Academic Search

Traveling-wave resonators (TWR) designed on the basis of directional couplers (DC), with locked up in the ring secondary arms, find a wide application in the systems of combining and decommutation of frequency channels, for example in the circuits of directed filters. A technical decision directed on a formation of a modulated signal with one adjacent frequency, for the application in

V. D. Rjabchij; V. V. Safonov; E. A. Taran

2009-01-01

202

Performance of an accessing and allocation scheme for the download channel in software radio  

Microsoft Academic Search

This paper presents an accessing and allocation scheme for a Global Pilot and Download Channel (GPDCH) on which all broadcast, signalling messages and downloading of re-configuration data are conducted between the base station and mobile software terminals. The performance of this proposed scheme is investigated by means of computer simulation to estimate the delay in the registration and downloading processes

T. H. Le; A. H. Aghvami

2000-01-01

203

47 CFR 32.2231 - Radio systems.  

Code of Federal Regulations, 2010 CFR

...original cost of radio equipment used to provide radio communication channels. Radio equipment is that equipment which is used for...reception, modulation, and demodulation of radio waves in free space over which communication...

2009-10-01

204

47 CFR 32.2231 - Radio systems.  

Code of Federal Regulations, 2010 CFR

...original cost of radio equipment used to provide radio communication channels. Radio equipment is that equipment which is used for...reception, modulation, and demodulation of radio waves in free space over which communication...

2010-10-01

205

Equivalence and Accuracy of MOSFET Channel Length Measurement Techniques  

NASA Astrophysics Data System (ADS)

It is shown that the MOSFET channel length measurement techniques of Terada and Muta, Peng et al., Whitfield, Suciu and Johnston, and De La Moneda et al. are actually equivalent, i.e. merely different expressions of the same formula for channel length in terms of measured resistance, and that some of the transresistance methods of Jain, although not equivalent, are also related to the same formula. The accuracy of this formula is evaluated for the general case and related to the error components due to source and drain resistance asymmetry, short channel geometry effect, and variation of series resistance with bias. No independent error component due to field-induced mobility degradation is found. Finally the errors in the methods of Terada and Muta, Chen et al., Sheu et al., Wordeman et al. and Jain, are determined and compared. The gate transresistance technique is found to be the most accurate method.

Jain, Sanjay

1989-02-01

206

Educational Radio. Information Bulletin 21-B.  

ERIC Educational Resources Information Center

The term "Educational Radio" includes all radio stations licensed for noncommercial operation. A history of educational radio begins with the first domestic law for control of radio in general, The Radio Act of 1912. Federal Communication Commission (FCC) regulations pertaining to educational radio or "public radio" deal with channel assignments,…

Federal Communications Commission, Washington, DC.

207

Laboratory measurements of polarization radios of wind wave surfaces  

Microsoft Academic Search

Polarization ratios (sigma_{vv}\\/sigma_{HH}) of wind-generated rough water surfaces are studied experimentally by means of radar backscatter power measurements. The measurements were made at 9.23 GHz with incidence angles between45degand55degfor wind speeds between 3 m\\/s to 10 m\\/s. Scattering surface statistics at all wind speeds were also measured by means of a wave height gauge and a laser slope gauge. The

PETER H. Y. LEE

1978-01-01

208

Correlation Bandwidth and Delay Spread Multipath Propagation Statistics for 910MHz Urban Mobile Radio Channels  

Microsoft Academic Search

Distributions of delay spread and correlation bandwidth at 0.9 and 0.5 correlation for Gaussian wide-sense stationary uncorrelated scattering (GWSSUS) channels associated with 100 small-scale areas at different locations within a 2 × 2.5 km region of New York City are presented. For delay spread the maximum value observed was3frac{1}{2};mus and l0 percent of the areas exceeded2frac{1}{2}mus; for correlation bandwidth at

D. Cox; R. Leck

1975-01-01

209

FCC (Federal Communications Commission) Methods of Measurement of Radio Noise Emissions from Computing Devices.  

National Technical Information Service (NTIS)

This standard sets forth uniform methods of measurement of radio noise emitted from computing devices defined in section 15.4 of FCC Rules. The technical standards for computing devices are set forth in Subpart J of Part 15 of FCC Rules (47 CFR Part 15J)....

1983-01-01

210

RADIO FREQUENCY MEASUREMENTS FOR SENSING MOISTURE IN SMALL SAMPLES OF PEANUTS  

Technology Transfer Automated Retrieval System (TEKTRAN)

A method developed earlier for estimating the moisture content of single peanut kernels from radio-frequency impedance measurements on a parallel-plate capacitor, holding the kernel between the plates, was used for estimating the moisture content of small samples of 6 to 8 kernels. Parallel plates...

211

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

212

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

213

The Relation of Radio SkyWave Transmission to Ionosphere Measurements  

Microsoft Academic Search

A simple, rapid, graphical method is given for obtaining maximum usable frequencies and effective reflection heights of radio waves, from vertical-incidence measurements of the critical frequencies and virtual heights of the various layers in the ionosphere. The method consists of the use of \\

N. Smith

1939-01-01

214

Numerical Studies on a Radio Frequency Hologram and Its Use in Antenna Measurements.  

National Technical Information Service (NTIS)

The objective of this thesis is to develop a numerical tool for analyzing the radio frequency hologram, and thus to advance the development of the hologram CATR for antenna measurements. An accurate simulation method is needed as the success of the hologr...

J. Ala Laurinaho

2000-01-01

215

THE ELECTRICAL PROPERTIES OF CHLORITE TREMOLITE MARBLE MEASURED FOR A RANGE OF RADIO FREQUENCIES  

Microsoft Academic Search

This article attempts to present a simple approach to measuring the electrical properties of rocks over the frequency range from 50 MHz to 950 MHz. These electrical properties, and especially the resonating frequency points, may prove useful in the transfer of radio frequency energy to rock samples for precomminution treatment of run of mine ore. The rock sample that was used consists

James Swart; Peter Mendonidis; Christo Pienaar

2009-01-01

216

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

217

A model for the tropospheric excess path length of radio waves from surface meteorological measurements  

Microsoft Academic Search

Two models are given for predicting of the excess path length of radio waves from ground-based measurements of pressure, temperature, and humidity, at zenith and at a given apparent elevation angle. The models use the same formulation for the hydrostatic component of the excess path, but use different methods for the wet component. For the hydrostatic component, the models provide

H. Berrada Baby; P. Gole; J. Lavergnat

1988-01-01

218

Measurements of rain drop size distributions and estimation of radio-wave attenuation coefficients  

NASA Astrophysics Data System (ADS)

Results of photoelectron-detector measurements of rain drop size distributions carried out near Dubna, USSR during May-September, 1987 are presented. It is shown that, for large and small drop diameters, these distributions differ from the Marshall-Palmer ones. Radio-wave attenuation coefficients are evaluated for such distributions.

Zakharian, M. V.; Kornilov, L. N.; Pozhidaev, V. N.

1989-10-01

219

Radio Transmission to and from Underground Coal Mines--Theory and Measurement  

Microsoft Academic Search

Research involved in the development of a radio communication system for use in coal mine disasters is described. Theoretically predicted field strengths for surface to mine and mine to surface propagation are compared with measurements in coal mines in Colorado and Pennsylvania. It is concluded that surface-to-mine voice communication is practical using a horizontal wire antenna operating at audio frequencies,

DAVID B. LARGE; LAWRENCE BALL; ARNOLD J. FARSTAD

1973-01-01

220

Measuring Neutrino Masses Using Radio-Frequency Techniques  

NASA Astrophysics Data System (ADS)

We describe a new technique by which the energy spectrum of low energy electrons can be extracted. The technique relies on the detection and measurement of coherent radiation created from the cyclotron motion of charged particles, such as electrons, in strong magnetic fields. The technique proposed relies on the principle that the frequency of cyclotron radiation emitted by the particle depends inversely on its Lorentz boost. Detection and measurement of the coherent radiation emitted is tantamount to measuring the kinetic energy of the electron. As the technique inherently involves the measurement of a frequency in a non-destructive manner, it can, in principle, achieve a high degree of precision and accuracy; estimated to be better than 1 part in 106 for electrons with kinetic energies between 5 and 50 keV. One immediate application of this technique is in the measurement of the endpoint spectrum from tritium beta decay, which is directly sensitive to the absolute mass scale of neutrinos.

Formaggio, J. A.; Project 8 Collaboration

2012-07-01

221

Cassini and Wind stereoscopic observations of Jovian nonthermal radio emissions: Measurement of beam widths  

NASA Astrophysics Data System (ADS)

During two intervals in 1999, simultaneous observations of Jupiter's decametric and hectometric radio emissions were made with the Cassini radio and plasma wave instrument (RPWS) and the radio and plasma wave instrument (WAVES) on the Wind spacecraft in Earth orbit. During January the Jovian longitude difference between the two spacecraft was about 5°, whereas for the August-September Earth flyby of Cassini, the angle ranged from 0° to about 2.5° (the Jovicentric latitudinal difference was <0.3° during both intervals). With these separations the instantaneous widths of the walls of the hollow conical radiation beams of some of the decametric arcs were measured by cross correlating dynamic spectra. The results suggest that the typical width is approximately 1.5°+/-0.5°. The conical beams seem to move at Io's revolution rate for Io-controlled arcs. Additionally, some of the nonarc hectometric wavelength emissions show some properties of both wide and very narrow beam widths.

Kaiser, M. L.; Zarka, P.; Kurth, W. S.; Hospodarsky, G. B.; Gurnett, D. A.

2000-07-01

222

Comprehensive measurements on body channel characteristics of Human Body Communication  

Microsoft Academic Search

Human Body Communication (HBC) is regarded as a novel transmission technology for Artificial Intelligent (AI) society. It is important to measure and analysis body channel characteristics and the results are significant for Integrated Circuit (IC) design of HBC. This paper proposed an improving electrode configuration which was used to couple signals to human body with capacitive coupling type. The body

Xinzhuo Liu; Xianqing Yang; Yuan Wang; Lei Wang

2010-01-01

223

Pressure measurements on a pitching airfoil in a water channel  

Microsoft Academic Search

Measurements of unsteady pressures over a symmetric NACA 0015 airfoil performing pitching maneuvers are reported. The tests were performed in an open-surface water channel specially constructed for this purpose. The design of the apparatus allowed the pressure measurements to be made to a very high degree of spatial and temporal resolution. Reynolds numbers in the range of 5.2 x 10(exp

Rand N. Conger; B. R. Ramaprian

1994-01-01

224

Measurement and visualization of impingement cooling in narrow channels  

NASA Astrophysics Data System (ADS)

Experimental measurement techniques such as naphthalene sublimation, liquid crystal thermography and real-time holographic interferometry are standard. Their application in narrow channels causes problems and is therefore limited. The channel width must not change too much because the naphthalene sublimation and the liquid crystal coating necessary for the thermography may cause non-negotiable variations. The interferometry fails in turbulent flow area. The diffraction along the channel edges is an additional difficulty. A comparison of the results obtained from the application of all three techniques, which has not been considered in earlier publications, is made here. The methods were used to measure and visualize the heat transfer characteristics of an array of 1.2mm diameter impinging jets in an enclosed channel (>=2.2mm) with single-sided flow-off at Reynolds numbers of about Rez 20,000. Scale-up ratios as low as 2.4 have been used in order to maintain similarity as it has not been previously reported. The naphthalene technique provided a high spatially resolved measurement of the Sherwood number along a downstream line. The liquid crystal thermography technique provided 2D contours of the Nusselt number. The temperature distribution within dead water zones was visualized with holographic interferometry. The cross-flow effects caused a shift in the stagnation point and a monotone decrease in the Nusselt number in the downstream direction.

Kaiser, E.

225

Measuring bankfull channel features, bed sediment, and bed load  

NSDL National Science Digital Library

This class exercise is an opportunity for students to gain valuable field experiences and develop fieldwork skills. The goal is to have students compare their measurements of a bankfull channel and its bed sediments with theoretical values that might imply whether the channel is 'adjusted' or is out of equilibrium with its setting. This is accomplished by having the students calculate a bankfull Shields stress value and then compare that value with both: (1) a theoretical range of values that might comprise an 'adjusted' condition, and (2) experimental values for the minimal Shields stress required to entrain bed grains of different sizes. They are then to evaluate whether the channel is stable or not. Designed for a geomorphology course

Clayton, Jordan A.

226

Accuracy in Electrical and Radio Measure- Ments and Calibrations, 1965.  

National Technical Information Service (NTIS)

NBS estimates of uncertainties associated with physical measurements, and with some NBS calibration services, are shown by 42 provisional 'accuracy charts.' Each chart is accompanied by a facing page giving a brief statement of the state of the art and te...

R. C. Powell

1965-01-01

227

G\\/T measurement errors with radio stars  

Microsoft Academic Search

This talk highlights often-overlooked or poorly treated aspects in G\\/T error analyses for satellite communication earth terminals. In particular, correction factors due to star size, differential system temperature, antenna pointing, and refractive attenuation used in G\\/T measurements are discussed in detail.

W. Daywitt; M. Kanda

1975-01-01

228

In Situ Tribocomponent Temperature Measurement Using a Radio Telemeter  

Microsoft Academic Search

A microradiotelemeter was designed and developed to measure the in situ temperature of a tribocomponent (tapered roller bearing roller). Photolithography was used to pattern a flexible circuit board for the telemeter. The overall device size was minimized by the use of surface-mount technology (SMT) components. The completed circuit board was 5 mm by 9 mm by 1.5 mm high and

David A. Nickel; Farshid Sadeghi

1997-01-01

229

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

230

Radio Sources: 3.3mm Flux and Variability Measurements.  

National Technical Information Service (NTIS)

Graphical and tabular summaries of 3.3-mm (90-GHz) flux measurements of 35 discrete galactic and extragalactic sources are presented, including results of extensive monitoring of nine sources. Variability at 3.3-mm is certain for NGC 1068, NGC 1275, 3C120...

E. E. Epstein J. W. Montgomery M. M. Dworetsky W. G. Fogarty

1971-01-01

231

Midlatitude D region variations measured from broadband radio atmospherics  

NASA Astrophysics Data System (ADS)

The high power, broadband very low frequency (VLF, 3--30 kHz) and extremely low frequency (ELF, 3--3000 Hz) electromagnetic waves generated by lightning discharges and propagating in the Earth-ionosphere waveguide can be used to measure the average electron density profile of the lower ionosphere (D region) across the wave propagation path due to several reflections by the upper boundary (lower ionosphere) of the waveguide. This capability makes it possible to frequently and even continuously monitor the D region electron density profile variations over geographically large regions, which are measurements that are essentially impossible by other means. These guided waves, usually called atmospherics (or sferics for short), are recorded by our sensors located near Duke University. The purpose of this work is to develop and implement algorithms to derive the variations of D region electron density profile which is modeled by two parameters (one is height and another is sharpness), by comparing the recorded sferic spectra to a series of model simulated sferic spectra from using a finite difference time domain (FDTD) code. In order to understand the time scales, magnitudes and sources for the midlatitude nighttime D region variations, we analyzed the sferic data of July and August 2005, and extracted both the height and sharpness of the D region electron density profile. The heights show large temporal variations of several kilometers on some nights and the relatively stable behavior on others. Statistical calculations indicate that the hourly average heights during the two months range between 82.0 km and 87.2 km with a mean value of 84.9 km and a standard deviation of 1.1 km. We also observed spatial variations of height as large as 2.0 km over 5 degrees latitudes on some nights, and no spatial variation on others. In addition, the measured height variations exhibited close correlations with local lightning occurrence rate on some nights but no correlation with local lightning or displaced lightning on others. The nighttime profile sharpness during 2.5 hours in two different nights was calculated, and the results were compared to the equivalent sharpness derived from International Reference Ionosphere (IRI) models. Both the absolute values and variation trends in IRI models are different from those in broadband measurements. Based on sferic data similar to those for nighttime, we also measured the day-time D region electron density profile variations in July and August 2005 near Duke University. As expected, the solar radiation is the dominant but not the only determinant source for the daytime D region profile height temporal variations. The observed quiet time heights showed close correlations with solar zenith angle changes but unexpected spatial variations not linked to the solar zenith angle were also observed on some days, with 15% of days exhibiting regional differences larger than 0.5 km. During the solar flare, the induced height change was approximately proportional to the logarithm of the X-ray fluxes. During the rising and decaying phases of the solar flare, the height changes correlated more consistently with the short (wavelength 0.5--4 A), rather than the long (wavelength 1--8 A) X-ray flux changes. The daytime profile sharpness during morning, noontime and afternoon periods in three different days and for the solar zenith angle range 20 to 75 degrees was calculated. These broadband measured results were compared to narrowband VLF measurements, IRI models and Faraday rotation base IRI models (called FIRI). The estimated sharpness from all these sources was more consistent when the solar zenith angle was small than when it was large. By applying the nighttime and daytime measurement techniques, we also derived the D region variations during sunrise and sunset periods. The measurements showed that both the electron density profile height and sharpness decrease during the sunrise period while increase during the sunset period.

Han, Feng

232

Radio Frequency Radiation (RFR) measurements in operational settings  

NASA Astrophysics Data System (ADS)

A detailed discussion of the principles, procedures, and instrumentation required to carry out routine RFR measurements under field or operational conditions is presented. The information herein contained comes largely from several years of experience gathered by the USAF Occupational and Environmental Health Laboratory (USAF OEHL) and its predecessor the USAF Radiological Health Laboratory (USAF RHL). Over the last 12 years the USAF OEHL have evaluated and field tested a wide variety of RFR power density instrumentation designed, developed and manufactured by a number of firms and agencies. Each of these instruments has some outstanding characteristics and some equally poor features. Based on a number of years of experience only about 15% of the RFR emitters account for about 95% of the measurement problems. There are a number of classes of emitters that may be easily and promptly dismissed from consideration as a potential hazard to personnel.

Graham, R. B.

1985-03-01

233

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

234

Record-Breaking Radio Astronomy Project to Measure Sky with Extreme Precision  

NASA Astrophysics Data System (ADS)

Astronomers will tie together the largest collection of the world's radio telescopes ever assembled to work as a single observing tool in a project aimed at improving the precision of the reference frame scientists use to measure positions in the sky. The National Science Foundation's Very Long Baseline Array (VLBA) will be a key part of the project, which is coordinated by the International VLBI Service for Geodesy and Astrometry. For 24 hours, starting Wednesday, November 18, and ending Thursday, November 19, 35 radio telescopes located on seven continents will observe 243 distant quasars. The quasars, galaxies with supermassive black holes at their cores, are profuse emitters of radio waves, and also are so distant that, despite their actual motions in space, they appear stationary as seen from Earth. This lack of apparent motion makes them ideal celestial landmarks for anchoring a grid system, similar to earthly latitude and longitude, used to mark the positions of celestial objects. Data from all the radio telescopes will be combined to make them work together as a system capable of measuring celestial positions with extremely high precision. The technique used, called very long baseline interferometry (VLBI), has been used for decades for both astronomical and geodetic research. However, no previous position-measuring observation has used as many radio telescopes or observed as many objects in a single session. The previous record was a 23-telescope observation. At a meeting in Brazil last August, the International Astronomical Union adopted a new reference frame for celestial positions that will be used starting on January 1. This new reference frame uses a set of 295 quasars to define positions, much like surveyor's benchmarks in a surburban subdivision. Because even with 35 radio telescopes around the world, there are some gaps in sky coverage, the upcoming observation will observe 243 of the 295. By observing so many quasars in a single observing session, problems of linking positions from one observing session to another can be avoided, the astronomers say. The result will be a much stronger, more precise, reference grid. Telescopes in Asia, Australia, Europe, North America, South America, Antarctica, and in the Pacific will participate. Improving the celestial positional grid will allow astronomers better to pinpoint the locations and measure the motions of objects in the sky. As astronomers increasingly study objects using multiple telescopes observing at different wavelengths, such as visible light, radio, infrared, etc., the improved positional grid will allow more accurate overlaying of the different images. The improved celestial reference frame also strengthens a terrestrial reference frame used for radio-telescope measurements that contribute to geophysical research. The precise geodetic measurements help geophysicists understand phenomena such as plate tectonics, earth tides, and processes that affect our planet's orientation in space. The VLBA is a continent-wide radio telescope system with 10, 240-ton dish antennas ranging from Hawaii to the Virgin Islands. Operated from the National Radio Astronomy Observatory's Pete V. Domenici Science Operations Center in Socorro, New Mexico, the VLBA offers the greatest resolving power, or ability to see fine detail, of any telescope in astronomy. The multi-telescope observation will be accompanied by public-outreach activities in celebration of the International Year of Astronomy. A public web page devoted to the observation will be hosted at Bordeaux Observatory, and some of the participating telescopes will have webcams available.

2009-11-01

235

Point-to-point measurement of radio frequency attenuation in South Polar ice  

NASA Astrophysics Data System (ADS)

For ultra high energy (UHE) electromagnetic showers in a dense medium, radio frequency Cherenkov emission is enhanced due to the Askaryan effect. Present and future detectors such as RICE, ANITA, ARIANNA and the Askaryan Radio Array (ARA) exploit this effect to detect UHE neutrinos interacting with Antarctic ice. The radio frequency electromagnetic wave attenuation length (the distance over which signal amplitude diminishes by a factor of 1/e due to absorption or scattering) is of tantamount importance as it determines the size scale and effective volume of these detectors. Previous attenuation measurements rely on reflections off the bedrock of signals from a surface-mounted transmitter. Using RICE in-ice transmitters and IceCube Radio Extension in-ice receivers, we are conducting a point-to-point attenuation measurement in the upper 1500 meters of South Polar ice, the region of interest for planned near-surface detectors such as ARA. We will present the analysis method as well as preliminary results.

Richman, Michael; Hoffman, Kara

2011-04-01

236

Radio observations of the planets - The importance of laboratory measurements  

NASA Astrophysics Data System (ADS)

Laboratory data on the line broadening parameters of H2S gas under Uranian/Neptunian conditions, on the far wings of the H2S and NH3 line profiles, and on the dielectric properties of CH4-, NH3-, H2S-, and NH4SH-ice are needed to constrain elemental abundances and understand the dynamics and cloud physics in the atmospheres of the giant planets. Measurements of the absorption coefficient of gaseous H2SO4 at millimeter wavelengths are needed in order to obtain a better understanding of Venus' atmosphere. To determine wind velocity fields in Venus' and Mars' atmospheres, accurate measurements of the center frequencies of the CO lines are necessary. The absorption and scattering properties of lunar soils and/or terrestrial rock powders at frequencies from approximately 1 to 200 GHz, determined in laboratory experiments, would provide a valuable addition to existing data at 450 MHz, 35 GHz, and far infrared frequencies. These data would be used to analyze the microwave spectra of planetary surfaces. Such studies may be helpful in distinguishing the effects of radiative transfer from those of nonlinear heat conduction and internal heat sources.

de Pater, I.; Mitchell, D. L.

1993-03-01

237

A proposed space mission around the Moon to measure the Moon Radio-Quiet Zone  

NASA Astrophysics Data System (ADS)

In a series of papers published since 2000 mainly in Acta Astronautica the senior author Maccone dealt with the advantages of the Farside of the Moon for future utilization Clearly the Moon Farside is free from RFI Radio Frequency Interference produced in larger and larger amounts by the increasing human exploitation of radio technologies That author suggested that crater Daedalus located at the center of the Farside was the best possible location to build up in the future one or more radiotelescopes or phased arrays to achieve the maximum sensitivity in radioastronomical and SETI searches Also a radio-quiet region of space above the Farside of the Moon exists and is called the Quiet Cone The Quiet Cone actual size however is largely unknown since it depends on the orbits of radio-emitting satellites around the Earth that are themselves largely unknown due to the military involvements In addition diffraction of electromagnetic waves grazing the surface of the Moon causes further changes in the geometrical shape of the Quiet Cone This riddle can be solved only by direct measurements of the radio attenuation above the Farside of the Moon performed by satellites orbiting the Moon itself In this paper we propose to let one or more low cost radiometers be put into orbit around the Moon to measure the RFI attenuation at different frequencies and altitudes above the Moon The opportunity of adding more payload s such as an ion detector and or a temperature sensor is evaluated also In this regard we present in this paper the experience gained by

Antonietti, N.; Pagana, G.; Pluchino, S.; Maccone, C.

238

Radio frequency rectification on membrane bound pores.  

PubMed

Probing the interaction of biological systems with radio frequencies holds great promise for research and drug screening applications. While a common assumption is that biological systems do not operate at radio frequencies, we find that currents due to ion transport through channels and pores in cell membranes are in the pA to nA range. These values translate via the average current I = ne/tau(d) = nef to frequencies in the range of 1 MHz-1 GHz, where n is the average number of ions transported and tau(d) is the dwell time of the ions in the channel. It is thus desirable to have circuitry available which facilitates radio frequency spectroscopy of ion transport. This will yield real-time in vitro information on ion channel operation. Here we present measurements on the local interaction of a radio frequency signal with single ion channels and pores. We find radio frequency rectification and pumping on the channels and pores embedded in suspended bilipid membranes, recorded in direct current measurements. This electromagnetic modulation can be used to probe the dynamics of ion channel conformational changes. PMID:20081294

Ramachandran, Sujatha; Blick, Robert H; van der Weide, Daniel W

2010-01-18

239

Ion Channel Conductance Measurements on a Silicon-Based Platform  

NASA Astrophysics Data System (ADS)

Conductance measurements of the transmembrane porin protein OmpF as a function of pH and bath concentration have been made with both a microfabricated silicon substrate device and a commercially available polystyrene aperture. Ion transport through the channel was simulated in atomic detail: the measured current was compared with theoretically calculated current, using a Brownian Dynamics kernel coupled to the Poisson equation by a P3M force field. The explicit protein structure and fixed charge distribution in the protein are calculated using the molecular dynamics code, GROMACS. Reasonable agreement is obtained in the simulated versus measured conductance over the range of experimental concentrations studied.

Wilk, S. J.; Aboud, S.; Petrossian, L.; Goryll, M.; Tang, J. M.; Eisenberg, R. S.; Saraniti, M.; Goodnick, S. M.; Thornton, T. J.

2006-05-01

240

Resource planning and packet forwarding in multi-radio, multi-mode, multi-channel, multi-rate (M4) wireless mesh networks  

Microsoft Academic Search

Most earlier works in the area of wireless mesh network assume a single interface being equipped in each node. In this paper, we consider the next-generation wireless mesh networks in which each node may be equipped with multiple radio interfaces, each capable of running in one of several modes (IEEE 802.11b\\/g 2.4GHz or 802.11a 5GHz mode), one of several channels,

Ting-yu Lin; Wai-hong Tam; Kang-lun Fan; Yu-chee Tseng

2008-01-01

241

Frame synchronization methods based on channel symbol measurements  

NASA Astrophysics Data System (ADS)

The current DSN frame synchronization procedure is based on monitoring the decoded bit stream for the appearance of a sync marker sequence that is transmitted once every data frame. The possibility of obtaining frame synchronization by processing the raw received channel symbols rather than the decoded bits is explored. Performance results are derived for three channel symbol sync methods, and these are compared with results for decoded bit sync methods reported elsewhere. It is shown that each class of methods has advantages or disadvantages under different assumptions on the frame length, the global acquisition strategy, and the desired measure of acquisition timeliness. It is shown that the sync statistics based on decoded bits are superior to the statistics based on channel symbols, if the desired operating region utilizes a probability of miss many orders of magnitude higher than the probability of false alarm. This operating point is applicable for very large frame lengths and minimal frame-to-frame verification strategy. On the other hand, the statistics based on channel symbols are superior if the desired operating point has a miss probability only a few orders of magnitude greater than the false alarm probability. This happens for small frames or when frame-to-frame verifications are required.

Dolinar, S.; Cheung, K.-M.

1989-08-01

242

Approximation of large radio telescope surface with measurement data of optic-electronic stereoscopic system  

NASA Astrophysics Data System (ADS)

The new large radio telescope RT-70 (Uzbekistan, Suffa) requires controlling the linear deformations of its primary mirror. Following issues dealing with this problem are described in this article: 1) the possibility to design measurement system based on stereoscopic scheme for the control of primary mirror's linear deformations, 2) using the approximation of a parabolic surface by the method of least squares for measurement the coordinates of control elements placed on the primary mirror. It is shown the possibility of assessing the distance to the control points using parameters in equation of a parabolic surface. Information about spatial position of special "stereoscopic" control points is used to calculate the position of all ordinary control points on primary mirror of radio telescope. The results of numerical experiments show that approximation error of paraboloid parameters proporti

Arakantsev, Konstantin G.; Konyakhin, Igor A.

2013-01-01

243

Power dissipation measurements in a low-pressure N2 radio-frequency discharge  

Microsoft Academic Search

Energy-flux density measurements using silicon substrates were performed on various parts of a parallel-plate etch reactor in contact with a low-pressure nitrogen radio-frequency discharge. The energy flux consists of contributions of ions, electrons, atoms, photons, and excited particles. Experimental results on the reaction kinetics of N+2 and atomic oxygen, and some additional model calculations of the excitation rates of molecular

J. A. G. Baggerman; R. J. Visser; E. J. H. Collart

1994-01-01

244

Power dissipation measurements in a low-pressure N2 radio-frequency discharge  

Microsoft Academic Search

Energy-flux density measurements using silicon substrates were performed on various parts of a parallel-plate etch reactor in contact with a low-pressure nitrogen radio-frequency discharge. The energy flux consists of contributions of ions, electrons, atoms, photons, and excited particles. Experimental results on the reaction kinetics of N2(+) and atomic oxygen, and some additional model calculations of the excitation rates of molecular

J. A. G. Baggerman; R. J. Visser; E. J. H. Collart

1994-01-01

245

Observations of turbulence in the atmosphere of Venus using Mariner 10 radio occultation measurements  

Microsoft Academic Search

A technique is developed for estimating the outer scale of turbulence in a planetary atmosphere using dual-frequency radio occultation measurements. This technique is based on the frequency dependence of the temporal frequency spectra for the log-amplitude fluctuations and is particularly useful when probing the upper atmosphere where the transverse velocity of the line-of-sight path is decelerating very rapidly. It is

Richard Woo

1975-01-01

246

Temporally resolved ion velocity distribution measurements in a radio-frequency plasma sheath  

Microsoft Academic Search

The ion velocity distribution function (IVDF) above and within a radio-frequency (RF) biased plasma sheath is studied experimentally with a pulsed laser-induced fluorescence diagnostic in an industrial plasma etch tool. Temporally resolved measurements taken at eight different phases of the 2.2 MHz bias waveform show that the ion dynamics vary dramatically throughout the RF cycle (the ratio of the average

B. Jacobs; W. Gekelman; P. Pribyl; M. Barnes

2011-01-01

247

Temporally-resolved ion velocity distribution measurements in a radio-frequency plasma sheath  

Microsoft Academic Search

The ion velocity distribution function (IVDF) above and within a radio-frequency (RF) biased plasma sheath is studied experimentally with a pulsed laser-induced fluorescence (LIF) diagnostic in an industrial plasma etch tool. Temporally-resolved measurements taken at 8 different phases of the 2.2 MHz bias waveform show the ion dynamics to vary dramatically throughout the RF cycle (the ratio of the average

Brett Jacobs

2010-01-01

248

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

249

Interpixel Capacitance in the IR Channel: Measurements Made On Orbit  

NASA Astrophysics Data System (ADS)

Using high signal-to-noise pixels in dark current observations, the magnitude of the inter-pixel capacitance (IPC) has been calcucated for the IR channel of WFC3. While the measured IPC magnitude of 6.3% is within 1? of the value quoted in past reports (Brown, 2008), this work also documents the difference in IPC magnitude in each of the 8 pixels surrounding a central, single pixel source. This document details the test procedure used to measure the IPC and the results, and explains possibilities for correcting users' data.

Hilbert, B.; McCullough, P.

2011-04-01

250

A Ray Launching Method For The Prediction Of Indoor Radio Channel Characteristics  

Microsoft Academic Search

Presented here is an analytical method for the prediction of power delay profiles within a room environment. The model works directly on a 3-D description of a room. Provided here is a brief discussion of the model and a presentation of both measured and modelled results for delay spread values, which are shown to be in good agreement. The model’s

M. C. Lawton; R. L. Davies; J. P. McGeehan

1991-01-01

251

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

252

PROGRESS IN MEASUREMENTS OF THE GRAVITATIONAL BENDING OF RADIO WAVES USING THE VLBA  

SciTech Connect

We have used the Very Long Baseline Array (VLBA) at 43, 23, and 15 GHz to measure the solar gravitational deflection of radio waves among four radio sources during an 18 day period in 2005 October. Using phase-referenced radio interferometry to fit the measured phase delay to the propagation equation of the parameterized post-Newtonian formalism, we have determined the deflection parameter {gamma} = 0.9998 {+-} 0.0003 (68% confidence level), in agreement with general relativity. The results come mainly from 43 GHz observations where the refraction effects of the solar corona were negligible beyond 3 deg from the Sun. The purpose of this experiment is three-fold: to improve on the previous results in the gravitational bending experiments near the solar limb; to examine and evaluate the accuracy limits of terrestrial VLBI techniques; and to determine the prospects and outcomes of future experiments. Our conclusion is that a series of improved designed experiments with the VLBA could increase the presented accuracy by at least a factor of 4.

Fomalont, E. [National Radio Astronomy Observatory, Charlottesville, VA 22903 (United States); Kopeikin, S. [Department of Physics and Astronomy, University of Missouri, Columbia, MO 65211 (United States); Lanyi, G. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Benson, J. [National Radio Astronomy Observatory, Socorro, NM 87801 (United States)], E-mail: efomalon@nrao.edu, E-mail: kopeikins@missouri.edu, E-mail: gabor.e.lanyi@jpl.nasa.gov, E-mail: jbenson@nrao.edu

2009-07-10

253

Progress in Measurements of the Gravitational Bending of Radio Waves Using the VLBA  

NASA Astrophysics Data System (ADS)

We have used the Very Long Baseline Array (VLBA) at 43, 23, and 15 GHz to measure the solar gravitational deflection of radio waves among four radio sources during an 18 day period in 2005 October. Using phase-referenced radio interferometry to fit the measured phase delay to the propagation equation of the parameterized post-Newtonian formalism, we have determined the deflection parameter ? = 0.9998 ± 0.0003 (68% confidence level), in agreement with general relativity. The results come mainly from 43 GHz observations where the refraction effects of the solar corona were negligible beyond 3 deg from the Sun. The purpose of this experiment is three-fold: to improve on the previous results in the gravitational bending experiments near the solar limb; to examine and evaluate the accuracy limits of terrestrial VLBI techniques; and to determine the prospects and outcomes of future experiments. Our conclusion is that a series of improved designed experiments with the VLBA could increase the presented accuracy by at least a factor of 4.

Fomalont, E.; Kopeikin, S.; Lanyi, G.; Benson, J.

2009-07-01

254

Ultrawideband propagation channels-theory, measurement, and modeling  

Microsoft Academic Search

This paper presents an overview of ultrawideband (UWB) propagation channels. It first demonstrates how the frequency selectivity of propagation processes causes fundamental differences between UWB channels and \\

Andreas F. Molisch

2005-01-01

255

Pressure measurements on a pitching airfoil in a water channel  

NASA Astrophysics Data System (ADS)

Measurements of unsteady pressures over a symmetric NACA 0015 airfoil performing pitching maneuvers are reported. The tests were performed in an open-surface water channel specially constructed for this purpose. The design of the apparatus allowed the pressure measurements to be made to a very high degree of spatial and temporal resolution. Reynolds numbers in the range of 5.2 x 10(exp 4) to 2.2 x 10(exp 5) were studied. Although the results qualitatively agreed with earlier studies performed at similar Reynolds numbers, the magnitudes of pressure and aerodynamic forces measured were observed to be much larger than those measured in ealier pitchup studies. They were found, in fact, to be closer to those obtained in some recent high-Reynolds-number experiments. This interesting behavior, which was suspected to be caused by the relatively high freestream turbulence level in the water channel, was explored in some detail. In addition, several issues like the quasisteady and dynamic effects of the pitching process are discussed. The experimental data are all archived and are available for use as a database.

Conger, Rand N.; Ramaprian, B. R.

1994-01-01

256

Temporal evolution of channel capacity in vehicular MIMO channels in the 5 GHz band  

Microsoft Academic Search

Reliability in Ricean multiple-input-multiple-output (MIMO) channels is crucial for safety related vehicle-to-vehicle (V2V) applications. Due to the time variability of vehicular communication channel, it is very significant to study the temporal evolution of channel characterization criteria. We present evaluation results of the temporal evolution of the spectral efficiency from channel sounder measurements of vehicle-to-vehicle MIMO radio channels in the 5.2

Arrate Alonso; Christoph Mecklenbräuker; Alexander Paier; Thomas Zemen; Nicolai Czink; Fredrik Tufvesson

2010-01-01

257

Direct measurement of neutral gas heating in a radio-frequency electrothermal plasma micro-thruster  

NASA Astrophysics Data System (ADS)

Direct measurements and modelling of neutral gas heating in a radio-frequency (13.56 MHz) electrothermal collisional plasma micro-thruster have been performed using rovibrational band matching of the second positive system of molecular nitrogen (N2) for operating pressures of 4.5 Torr down to 0.5 Torr. The temperature measured with decreasing pressure for 10 W power input ranged from 395 K to 530 K in pure N2 and from 834 K to 1090 K in argon with 1% N2. A simple analytical model was developed which describes the difference in temperatures between the argon and nitrogen discharges.

Greig, A.; Charles, C.; Hawkins, R.; Boswell, R.

2013-08-01

258

Radio Plasma Imager and Measurement of Magnetospheric Field-Aligned Electron Density  

NASA Astrophysics Data System (ADS)

The Radio Plasma Imager (RPI) aboard the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) satellite is a pioneering instrument that has made fundamental space plasma and wave observations. This paper reviews the RPI measurement techniques and measurement parameters. In particular, it focuses on RPI's capability in deducing the magnetic field-aligned electron density (FAED) profiles, which turn out to have significant contributions to (1) constructing magnetospheric density models, (2) understanding plasmaspheric refilling process, (3) understanding the source regions and generation mechanism of the kilometric continuum radiation, and (4) determining the location of electron scattering by whistler waves, a process responsible for the formation of the radiation-belt slot region.

Fung, Shing F.

2008-02-01

259

Relativistic deflection of radio signals in the solar gravitational field measured with VLBI  

NASA Astrophysics Data System (ADS)

For an observer on Earth the general theory of relativity (GR) predicts an apparent outward displacement of a star seen at the Sun's limb of 1.75 arc s. A generalized formulation for gravitational deflection of light includes a parameter ? which ranges from 1 (GR) to -1 (no deflection). Radio interferometer measurements of deflections of extragalactic objects have all been consistent with GR with increasing accuracy. The authors report the most sensitive measurement of deflection so far achieved, in which very long baseline interferometry (VLBI) observations yield a value of ? of 1.008 with a 1 ? formal standard error of ±0.005.

Robertson, D. S.; Carter, W. E.

1984-08-01

260

Measurement errors introduced by the use of co-axial cabling in the assessment of wearable antenna performance in off-body channels  

Microsoft Academic Search

This paper presents the results of an investigation into the effect of using co-axial cables in ultra-wideband off-body radio channel characterisation and performance evaluation for wearable antennas. Experiments were carefully designed to faithfully compare the use of a co-axial feed cable for a wearable antenna versus an optic fibre feed, and thus report on any errors introduced into the measurements

P. A. Catherwood; W. G. Scanlon

2011-01-01

261

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

262

Ultrasound Doppler Velocimetry Measurements in Turbulent Liquid Metal Channel Flow  

NASA Astrophysics Data System (ADS)

Control of molten metal flow using magnetic fields is important in industrial applications. The Electromagnetic Flow Control Channel (EFCO) is an experimental test facility, located at Ilmenau University of Technology, for the development of such kind of control systems. The working fluid is the low-melting liquid metal alloy GaInSn in eutectic composition. In this channel, flow control is realized by combining and coupling the non-contact flow driving technology of electromagnetic pumps based on rotating permanent magnets and the non-contact flow rate measurement technology termed Lorentz Force Velocimetry (LFV). The flow rate is adjusted by controlling the rotation rate of the permanent magnet system. Physically, LFV is based on measuring the force acting on a magnet system. This force is induced by the melt flow passing through the static magnetic field generated by the system and is proportional to the flow. To calibrate such flow meters, we apply UDV technique to measure and analyse both turbulent hydrodynamic and MHD flow profiles in EFCO at various Reynolds numbers.

Rivero, Michel; Jian, Dandan; Karcher, Christian; Cuevas, Sergio

2010-11-01

263

Microfabricated Patch Clamp Electrodes for Improved Ion Channel Protein Measurements  

NASA Astrophysics Data System (ADS)

Ion channels are trans-membrane proteins that underlie many cell functions including hormone and neurotransmitter release, muscle contraction and cell signaling cascades. Ion channel proteins are commonly characterized via the patch clamp method in which an extruded glass tube containing ionic solution, manipulated by an expert technician, is brought into contact with a living cell to record ionic current through the cell membrane. Microfabricated planar patch electrodes, micromolded in the silicone elastomer poly-dimethylsiloxane (PDMS) from microlithographically patterned structures, have been developed that improve on this method. Microfabrication techniques allow arrays of patch electrodes to be fabricated, increasing the throughput of the measurement technique. Planar patch electrodes readily allow the automation of cell sealing, further increasing throughput. Microfabricated electrode arrays may be readily integrated with microfluidic structures to allow fast, in situ solution exchange. Miniaturization of the electrode geometry should increase both the signal to noise and the bandwidth of the measurement. Microfabricated patch electrode arrays have been fabricated and measurements have been taken.

Klemic, James; Klemic, Kathryn; Reed, Mark; Sigworth, Frederick

2002-03-01

264

Modeling potentiometric measurements in topological insulators including parallel channels  

NASA Astrophysics Data System (ADS)

The discovery of spin-polarized states at the surface of three-dimensional topological insulators (TI) like Bi2Te3 and Bi2Se3 motivates intense interests in possible electrical measurements demonstrating unique signatures of these unusual states. Here we show that a three-terminal potentiometric set-up can be used to probe them by measuring the voltage change of a detecting magnet upon reversing its magnetization. We present numerical results using a nonequilibrium Green's function (NEGF)-based model to show the corresponding signal quantitatively in various transport regimes. We then provide an analytical expression for the resistance (the measured voltage difference divided by an applied current) that agrees with NEGF results well in both ballistic and diffusive limits. This expression is applicable to TI surface states, two-dimensional electrons with Rashba spin-split bands, and any combination of multiple channels, including bulk parallel states in TI, which makes it useful in analyzing experimental results.

Hong, Seokmin; Diep, Vinh; Datta, Supriyo; Chen, Yong P.

2012-08-01

265

Digital transmission over video channels: Teletext field measurements  

NASA Astrophysics Data System (ADS)

The results from field measurements made to evaluate the performance of digital transmission over television channels (teletext) were presented and the possible means of improvement identified. The television and teletext signal parameters and test signals used in measuring system performance were reviewed. The results of the measurements, performed across Canada, are used to indicate the teletext reception conditions for different situations. Different factors and parameters affecting teletext performance are also studied. Image grade and eye diagrams are shown to give indications about the teletext service quality to be expected. The VHF and UHF transmission of the teletext signal offered similar performances. Small bidirectional antennas are a poor choice for teletext reception. Quasi-synchronous demodulators result in performance close to those obtained with synchronous models. The study of teletext error statistics shows that a code correcting 2 single errors per line would be sufficient for the majority of cases. Possible improvements are suggested. Two ways are proposed to estimate the bit error rate.

Caron, Bernard

1986-11-01

266

Ultrawideband Propagation Channels-Theory, Measurement, and Modeling  

Microsoft Academic Search

This paper presents an overview of UWB propagation channels. It first demonstrates how the frequency selectivity of propagation processes causes fundamental differences between UWB channels and ¨ conventional¨ (narrowband) channels. The concept of pathloss has to be modified, and well-known WSSUS model is not applicable anymore. Next, describe deterministic and stochastic models for UWB channels and identify the key parameters

Andreas F. Molisch

2005-01-01

267

Measurements and modeling of radio frequency field structures in a helicon plasma  

SciTech Connect

Measurements of the radio frequency (rf) field structure, plasma density, and electron temperature are presented for a 1 kW argon helicon plasma source. The measured profiles change considerably when the equilibrium magnetic field is reversed. The measured rf fields are identified as fields of radially localized helicon waves, which propagate in the axial direction. The rf field structure is compared to the results of two-dimensional cold plasma full-wave simulations for the measured density profiles. Electron collision frequency is adjusted in the simulations to match the simulated and measured field profiles. The resulting frequency is anomalously high, which is attributed to the excitation of an ion-acoustic instability. The calculated power deposition is insensitive to the collision frequency and accounts for most of the power supplied by the rf-generator.

Lee, C. A. [University of Texas, Austin; Chen, Guangye [ORNL; Arefiev, A. V. [University of Texas, Austin; Bengtson, R. D. [University of Texas, Austin; Breizman, B. N. [University of Texas, Austin

2011-01-01

268

First simultaneous measurements of thermospheric winds and zonal ion drifts from the Jicamarca Radio Observatory  

NASA Astrophysics Data System (ADS)

The first simultaneous observations of thermospheric winds and zonal ion drifts have been ob-tained at the Jicamarca Radio Observatory using a new Fabry-Perot interferometer observatory installed on a mountain ridge overlooking the valley where the JRO radar is located. The re-sults show that the neutral winds and ion drifts generally have the same speed and temporal variation characteristics. These results illustrate the simultaneous detection of the midnight temperature maximum as well. The paper will also describe efforts to obtain common volume measurements of thermospheric winds and temperatures utilizing the FPI Arequipa observatory which is located 4 degrees south of the geomagnetic equator.

Meriwether, John; Baker, Brooke; Twork, Greg; Chau, Jorge; Veliz, Oskar; Woodman, Ronald; Hedden, Russell; Hysell, David

269

The impact of radio source structure on European geodetic VLBI measurements  

NASA Astrophysics Data System (ADS)

European geodetic very long baseline interferometry (VLBI) sessions (also known as EUROPE sessions) have been carried out on a regular basis for the past 15 years to study relative crustal motions within Europe. These sessions are based on observations of extragalactic radio sources, which serve as distant fiducial marks to establish an accurate and stable celestial reference frame for long-term geodetic measurements. The radio sources, however, are not always point-like on milliarcsecond scales, as VLBI imaging has revealed. In this work, we quantify the magnitude of the expected effect of intrinsic source structure on geodetic bandwidth synthesis delay VLBI measurements for a subset of 14 sources regularly observed during the EUROPE sessions. These sources have been imaged at both X-band (8.4 GHz) and S-band (2.3 GHz) based on dedicated observations acquired with the European VLBI Network (EVN) in November 1996. The results of this calculation indicate that the reference source 0457+024 causes significant structural effects in measurements obtained on European VLBI baselines (about 10 picoseconds on average), whereas most of the other sources produce effects that are only occasionally larger than a few picoseconds. Applying the derived source structure models to the data of the EUROPE5-96 session carried out at the same epoch as the EVN experiment shows no noticeable changes in the estimated VLBI station locations.

Tornatore, V.; Charlot, P.

2007-06-01

270

Radio-Interference Probability and Its Effect on Site-Separation Standards and Frequency Assignment of VHF and UHF Channels.  

National Technical Information Service (NTIS)

In this report equations are developed which permit computation of the probability that radio interference will occur in ATC communications. It is shown that the probability of simultaneous occurrence of desired and undesired transmissions (utilization pr...

A. J. Hoehn

1965-01-01

271

Chip-level differential encoding\\/detection of spread-spectrum signals for CDMA radio transmission over fading channels  

Microsoft Academic Search

This paper is concerned with the design and performance evaluation of a direct-sequence spread-spectrum transmission and signal-detection technique for application to code-division multiple-access mobile radio networks. Unlike the conventional differential encoding\\/detection of data symbols, such a technique envisages differential encoding\\/detection of the spreading code chips to counteract the fast time-selective fading encountered in mobile radio transmissions. Binary PSK modulation on

Alberto Cavallini; Filippo Giannetti; Marco Luise; Ruggero Reggiannini

1997-01-01

272

Wide Range Neutron Flux Measuring Channel for Aerospace Application  

NASA Astrophysics Data System (ADS)

The use of classical techniques for neutron flux measurements in nuclear reactors involves the switching between several detection chains as the power grows up to 10 decades. In space applications where mass and size constraints are of key significance, such volume of hardware represents a clear disadvantage. Instead of requiring different instruments for each reactor operating range (start-up, ramping-up, and nominal power), a single instrument chain should be desirable. A Wide Range Neutron Detector (WRND) system, combining a classic pulse Counting Channel with a Campbell's theorem based Fluctuation Channel can be implemented for the monitoring and control of a space nuclear reactor. Such an instrument will allow for a reduction in the complexity of space-based nuclear instrumentation and control systems. In this presentation we will discuss the criteria and tradeoffs involved in the development of such a system. We will focus particularly on the characteristics of the System On Chip (SOC) and the DSP board used to implement this instrument.

Cibils, R. M.; Busto, A.; Gonella, J. L.; Martinez, R.; Chielens, A. J.; Otero, J. M.; Nuñez, M.; Tropea, S. E.

2008-01-01

273

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

274

Retarding field analyzer for ion energy distribution measurements at a radio-frequency biased electrode  

SciTech Connect

A retarding field energy analyzer designed to measure ion energy distributions impacting a radio-frequency biased electrode in a plasma discharge is examined. The analyzer is compact so that the need for differential pumping is avoided. The analyzer is designed to sit on the electrode surface, in place of the substrate, and the signal cables are fed out through the reactor side port. This prevents the need for modifications to the rf electrode--as is normally the case for analyzers built into such electrodes. The capabilities of the analyzer are demonstrated through experiments with various electrode bias conditions in an inductively coupled plasma reactor. The electrode is initially grounded and the measured distributions are validated with the Langmuir probe measurements of the plasma potential. Ion energy distributions are then given for various rf bias voltage levels, discharge pressures, rf bias frequencies - 500 kHz to 30 MHz, and rf bias waveforms - sinusoidal, square, and dual frequency.

Gahan, D.; Hopkins, M. B. [National Centre for Plasma Science and Technology, Dublin City University, Glasnevin, Dublin 9 (Ireland); Dolinaj, B. [Impedans Ltd., Invent Centre, Dublin City University, Glasnevin, Dublin 9 (Ireland)

2008-03-15

275

Retarding field analyzer for ion energy distribution measurements at a radio-frequency biased electrode.  

PubMed

A retarding field energy analyzer designed to measure ion energy distributions impacting a radio-frequency biased electrode in a plasma discharge is examined. The analyzer is compact so that the need for differential pumping is avoided. The analyzer is designed to sit on the electrode surface, in place of the substrate, and the signal cables are fed out through the reactor side port. This prevents the need for modifications to the rf electrode--as is normally the case for analyzers built into such electrodes. The capabilities of the analyzer are demonstrated through experiments with various electrode bias conditions in an inductively coupled plasma reactor. The electrode is initially grounded and the measured distributions are validated with the Langmuir probe measurements of the plasma potential. Ion energy distributions are then given for various rf bias voltage levels, discharge pressures, rf bias frequencies--500 kHz to 30 MHz, and rf bias waveforms--sinusoidal, square, and dual frequency. PMID:18377005

Gahan, D; Dolinaj, B; Hopkins, M B

2008-03-01

276

Device for measurement of power and shape of radio frequency pulses in nuclear magnetic resonance  

NASA Astrophysics Data System (ADS)

A design of an instrument to measure the power and shape of radio frequency (RF) pulses operating in a broad frequency range is described. The device is capable of measuring the pulse power up to 500 W of both CW and extremely short (˜1 ?s) RF pulses of arbitrary period. The pulse envelope can be observed on a logarithmic scale on a corresponding instrument output using an inexpensive storage oscilloscope. The instrument consists of a coaxial measurement head, the RF processing circuits and an AD conversion and display unit. The whole device is based on widely available integrated circuits; thus, good reproducibility and adaptability of the design is ensured. Since the construction is intended to be used in particular (but not solely) in nuclear magnetic resonance spectroscopy, we found it useful to provide a demonstration of two typical usage scenarios. Other application fields may comprise magnetic resonance imaging, radar and laser technology, power amplifier testing, etc.

Pfeffer, M.; ?ezní?ek, R.; K?iš?an, P.; Št?pánková, H.

2012-05-01

277

Measurements of Antenna Surface for Millimeter-Wave Space Radio Telescope  

NASA Astrophysics Data System (ADS)

In the construction of a space radio telescope, it is essential to use materials with a low noise factor and high mechanical robustness for the antenna surface. We present the results of measurements of the reflection performance of two candidates for antenna surface materials for use in a radio telescope installed in a new millimeter-wave astronomical satellite, ASTRO-G. To estimate the amount of degradation caused by fluctuations in the thermal environment in the projected orbit of the satellite, a thermal cycle test was carried out for two candidates, namely, copper foil carbon fiber reinforced plastic (CFRP) and aluminum-coated CFRP. At certain points during the thermal cycle test, the reflection loss of the surfaces was measured precisely by using a radiometer in the 41-45 GHz band. In both candidates, cracks appeared on the surface after the thermal cycle test, where the number density of the cracks increased as the thermal cycle progressed. The reflection loss also increased in proportion to the number density of the cracks. Nevertheless, the loss of the copper foil surface met the requirements of ASTRO-G at the end of the equivalent life, whereas that of the aluminum-coated surface exceeded the maximal value in the requirement even before the end of the cycle.

Kamegai, Kazuhisa; Tsuboi, Masato; Doi, Akihiro; Sato, Eiichi

2011-06-01

278

Verification of RASS-measured temperature profiles using a radio-controlled model glider  

NASA Astrophysics Data System (ADS)

Potential sonic temperature profiles from a continuous electromagnetic, pulsed acoustic, radio acoustic sounding system (RASS) were compared with profiles recorded by a commercially available temperature, relative humidity and pressure recorder mounted in a radio-controlled model motor-glider. The glider profiles covered the period of the morning transition in the lowest 200 m of an initially stably stratified boundary layer. Comparison of the profiles shows that the sonic temperature can be calculated based on the average speed of sound in the boundary layer; this removes the need to correct for vertical velocity in each temperature profile, thus avoiding the possibility of contaminating the temperatures with measurement noise from the vertical velocity profiles. Further, the low-level cold bias that occurs with the spatially separated transmit and receive antennas of a bistatic RASS system was not significant for the present measurements as the separation between the antennas was minimised. The comparison of RASS and glider temperatures gives confidence in the use of RASS-derived temperatures for investigating the performance of boundary layer models.

Taylor, John R.; Segal, Nathan J.; Bradshaw, Michael R.; Low, David J.

2013-02-01

279

Measurement of the top quark mass in the dilepton channel  

SciTech Connect

We present a measurement of the top quark mass in the dilepton channel based on approximately 370 pb{sup -1} of data collected by the D0 experiment during Run II of the Fermilab Tevatron collider. We employ two different methods to extract the top quark mass. We show that both methods yield consistent results using ensemble tests of events generated with the D0 Monte Carlo simulation. We combine the results from the two methods to obtain a top quark mass m{sub t} = 178.1 {+-} 8.2 GeV. The statistical uncertainty is 6.7 GeV and the systematic uncertainty is 4.8 GeV.

Abazov, V.M.; Abbott, B.; Abolins, M.; Acharya, B.S.; Adams, M.; Adams, T.; Agelou, M.; Aguilo, E.; Ahn, S.H.; Ahsan, M.; Alexeev, G.D.; /Buenos Aires U. /Rio de Janeiro, CBPF /Rio de Janeiro State U. /Sao Paulo, IFT /Alberta U. /Simon Fraser U. /York U., Canada /McGill U. /Hefei, CUST /Andes U., Bogota /Charles U.

2006-09-01

280

Quantitative shearography: error reduction by using more than three measurement channels  

SciTech Connect

Shearography is a noncontact optical technique used to measure surface displacement derivatives. Full surface strain characterization can be achieved using shearography configurations employing at least three measurement channels. Each measurement channel is sensitive to a single displacement gradient component defined by its sensitivity vector. A matrix transformation is then required to convert the measured components to the orthogonal displacement gradients required for quantitative strain measurement. This transformation, conventionally performed using three measurement channels, amplifies any errors present in the measurement. This paper investigates the use of additional measurement channels using the results of a computer model and an experimental shearography system. Results are presented showing that the addition of a fourth channel can reduce the errors in the computed orthogonal components by up to 33% and that, by using 10 channels, reductions of around 45% should be possible.

Charrett, Tom O. H.; Francis, Daniel; Tatam, Ralph P.

2011-01-10

281

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

282

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

283

Design and Impelimentation of DSP-based MultiChannel Power Measurement System  

Microsoft Academic Search

This paper presented a DSP-based multi-channel power measurement system that can simultaneously measure and analyze power components for both supply and demand side of power system. Voltage 8-channel and current 10-channel measurements are made through voltage and current sensors connected to the developed system, and power components like as reactive power, power factor and harmonics are calculated and measured by

Jae-Guen Yoo; Sang-Ick Lee; Jeong-Chay Jeon; Gyu-Ha Choe

2006-01-01

284

Channel response measurements for diffuse non-line-of-sight (NLOS) optical communication links underwater  

Microsoft Academic Search

Presented are experimental measurements comparing the frequency (i.e. - impulse) response (up to 1GHz) for an underwater optical communications channel as a function of water clarity using collimated or diffuse laser light. The measurement technique used is adapted from a previously reported method used for measuring the channel response of collimated laser beam [1,2]. These measurements establish the bandwidth limitations

Brandon Cochenour; Linda Mullen

2011-01-01

285

Proton Beam Verification using RF Power Measurement Data for a cw Radio Frequency Quadrupole LINAC  

SciTech Connect

A cw radio frequency quadrupole (RFQ) LINAC section and klystrode based rf system was obtained from the Chalk River Laboratories and was recommissioned at LANL to conduct demonstration proton beam experiments in support of a spallation neutron source driver for tritium production. A variation of the Low Energy Demonstration Accelerator (LEDA) proton injector, modified to operate at 50 keV, was mated to the RFQ and was operated to support the high current (up to 100 mA), proton beam advance studies for the Accelerator Production of Tritium (APT) program. Detailed measurements and calibrations of the RFQ at both low and high power provided the corroborating data to other available beam measurements for verification of the accelerator design.

Bolme, G.O.; Hardek, T.W.; Hansborough, L.D.; Hodgkins, D.J.; Keffeler, D.R.; Sherman, J.D.; Smith, H.V.; Stevens, R.R.; Young, L.M.; Zaugg, T.J.; Arvin, A.H.; Bolt, A.S.; Richards, M.C.; Balleyguier, P.P.; Kamperschroer, J.H.

1999-03-29

286

Evaluation Of Radio Links And Networks  

Microsoft Academic Search

This study evaluates the performance of radio links and networks to support communication with Automatic Vehicle Control Systems (AVCS). It addresses both vehicle-to-vehicle communication and roadside-to-vehicle communication. The report contributes to the modelling of short range vehicle-to-vehicle channels, not only in terms of documenting measured results and channel parameters, but also in extending existing models to cover antenna mobility at

Jean-paul M. G. Linnartz; Rolando F. Diesta

1996-01-01

287

Measurements and simulation of ionospheric scattering on VHF and UHF radar signals: Channel scattering function  

NASA Astrophysics Data System (ADS)

The design and operation of transionospheric VHF and UHF radars requires knowledge of amplitude and phase scintillation due to ionospheric scattering. Phase coherence is of particular importance where long coherent integration periods and large bandwidths are required. A thin phase screen, parabolic equation based, Trans-Ionospheric Radio Propagation Simulator (TIRPS) is described. Modeled channel scattering functions (CSFs) are compared to experimental VHF and UHF data derived from the Advanced Research Projects Agency Long-range Tracking and Instrumentation Radar on Kwajalein Island (9.4°N, 166.8°E). TIRPS quantitatively reproduces the experimental results, including the quasi-parabolic profile observed in the measured CSFs under strong turbulence conditions. Variations in the simulated CSF with ionospheric phase screen parameters are also presented. Under conditions of high integrated strength of turbulence (CkL), a low phase spectral index (p = 1), indicating relatively dense small-scale irregularities, produces pronounced range spreading. Conversely, when the spectral index is high (p = 4), indicative of strong focusing/defocusing by large-scale irregularities, there is increased Doppler spreading and, when the outer scale of irregularities is large, a greater likelihood of asymmetry of the CSF about the zero Doppler axis.

Rogers, Neil C.; Cannon, Paul S.; Groves, Keith M.

2009-02-01

288

Polarization measurements of Jovian radio emissions at high-magnetic latitudes observed by Ulysses spacecraft  

NASA Astrophysics Data System (ADS)

In early 2004, the Unified Radio And Plasma wave (URAP) experiment onboard Ulysses measured the Stokes parameters of Jovian kilometric radiations at northern high-latitudes during the "distant encounter" flyby. Ulysses observed from more than +80 deg to less than +10 deg of Jovicentric latitude for several months. The observation indicated that quasi-periodic (QP) bursts and narrowband kilometric emissions (nKOM) have LH polarization (V~+1). Therefore, we conclude that these emissions are LO mode waves. This is consistent with several previous observations at low-latitudes (~0 deg) and mid-latitudes (~-40 deg) (e.g., Daigne and Leblanc, 1986; MacDowall et al., 1993). On the other hand, it was shown that broadband kilometric radiations (bKOM) have RH polarization (V~-1) at high-latitudes. This result does not agree with our previous study based on the combination of observed location of bKOM and ray tracing, which showed these emissions as LO mode waves (Kimura et al., 2008). We confirmed by additional ray tracing analyses that a solution can allow LO mode waves to be observed with RH polarization at high-latitudes. This result would constrain generation and propagation processes for Jovian radio components observed at high-latitudes.

Kimura, T.; MacDowall, R. J.; Hess, R. A.; Kasaba, Y.; Tsuchiya, F.; Misawa, H.; Morioka, A.

2009-04-01

289

Polarization measurements of Jovian radio emissions at high-magnetic latitudes observed by Ulysses spacecraft  

NASA Astrophysics Data System (ADS)

In early 2004, the Unified Radio And Plasma wave (URAP) experiment onboard Ulysses measured the Stokes parameters of Jovian kilometric radiations at northern high-latitudes during the "gdistant encounter"h flyby. Ulysses observed from more than +80 deg to less than +10 deg of Jovicentric latitude for several months. The observation indicated that quasi-periodic (QP) bursts and narrowband kilometric emissions (nKOM) have LH polarization (V~+1). Therefore, we conclude that these emissions are LO mode waves. This is consistent with several previous observations at low-latitudes (~0 deg) and mid-latitudes (~-40 deg) (e.g., Daigne and Leblanc, 1986; MacDowall et al., 1993). On the other hand, it was shown that broadband kilometric radiations (bKOM) have RH polarization (V~-1) at high-latitudes. This result does not agree with our previous study based on the combination of observed location of bKOM and ray tracing, which showed these emissions as LO mode waves (Kimura et al., 2008). We confirmed by additional ray tracing analyses that a solution can allow LO mode waves to be observed with RH polarization at high-latitudes. This result would constrain generation and propagation processes for Jovian radio components observed at high-latitudes.

Kimura, T.; MacDowall, R. J.; Hess, R. A.; Kasaba, Y.; Tsuchiya, F.; Misawa, H.; Morioka, A.

2008-12-01

290

Measurement and wireless transmission of embedded capacitive microsensor's output using SigmaDelta conversion and radio frequency identification (RFID) technology  

Microsoft Academic Search

This article concerns the design and post-fabrication testing of a CMOS integrated circuit (IC) for the Remote- Queried Embedded Microsensor (RQEM) system. The IC may be coupled to capacitive microsensors to measure the output of the sensors, to digitize this measured output, and to condition and encode the digital data. Wireless transmission of the code to a commercial Radio Frequency

Pavel Neuzil; Oskar Krenek; F. Michael Serry; G. Jordan Maclay

1997-01-01

291

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

292

Collision Model for Bit Error Rate analysis of Time Hopping Impulse Radio in Multipath Nakagami-m Channels  

Microsoft Academic Search

In presence of multiple access interference, the performance of impulse radio system is affected by collisions with other users. In this paper we evaluate the bit error probability by employing a collision model for describing the non-stationary interference caused by simultaneous transmissions in time hopping systems. The collision model provides a sim- ple approximation for the error probability even in

L. Reggiani; Umberto Spagnolini

2006-01-01

293

MultiLevel Standardization and Business Models for Cognitive Radio: The Case of the Cognitive Pilot Channel  

Microsoft Academic Search

This paper examines the international, inter- organizational collaboration processes for the development of cognitive radio, which will be at the basis of potentially profound changes in the telecommunications value network, as well as its functional architecture, cost and value structure and the eventual value proposition of any services deployed in such a value network. The paper will analyze the transition

Simon Delaere; Pieter Ballon

2008-01-01

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

Measurement based channel model for large concert halls  

Microsoft Academic Search

The digital dividend has the goal to achieve a more efficient utilization of the UHF broadcasting bands by permitting access to cognitive radio devices. Thus, the conventional use of analog, narrow band devices by secondary users of the same frequency range is supressed. One traditional application of this type are common Professional Wireless Microphone Systems (PWMS). To maintain the production

S. Dortmund; A. Schmidt; I. Rolfes

2010-01-01

296

Optimization of sample-chip design for stub-matched radio-frequency reflectometry measurements  

NASA Astrophysics Data System (ADS)

A radio-frequency (rf) matching circuit with an in situ tunable varactor diode used for rf reflectometry measurements in semiconductor nanostructures is investigated and used to optimize the sample-specific chip design. The samples are integrated in a 2-4 GHz stub-matching circuit consisting of a waveguide stub shunted to the terminated coplanar waveguide. Several quantum point contacts fabricated on a GaAs/AlGaAs heterostructure with different chip designs are compared. We show that the change of the reflection coefficient for a fixed change in the quantum point contact conductance can be enhanced by a factor of 3 compared to conventional designs by a suitable electrode geometry.

Hellmüller, S.; Pikulski, M.; Müller, T.; Küng, B.; Puebla-Hellmann, G.; Wallraff, A.; Beck, M.; Ensslin, K.; Ihn, T.

2012-07-01

297

Statistical analysis of CO2 supersaturation in the Martian atmosphere observed by MGS radio occultation measurements  

NASA Astrophysics Data System (ADS)

The main constituent of the Martian atmosphere is carbon dioxide (CO2). The previous literatures have shown that the extremely low temperature, which is around or even below the CO2 saturation temperature (Ts), is frequently observed in the mesosphere [1][6][7] and in the lower atmosphere [2][3][5]. The laboratory experiments [4] showed that CO2 condensation on H2O ice nuclei does not occur until the degree of supersaturation (S) attains 34% in average. This corresponds to the temperature 2-3K lower than Ts, and some of the previous literatures mentioned that the observed cold temperature was actually 2-3K lower than Ts. In the present study, we carefully analyzed pressure-temperature profiles obtained by MGS radio occultation measurements (1998-2007) [8], and we found that severer supersaturation events (S>34%) than those shown in the laboratory experiments occurred in the Martian lower atmosphere (up to ~35km) during polar nights (Fig. 1). In our analysis, we regarded CO2 partial pressure as the total pressure obtained by the radio occultation measurements. The existence of H2O vapor could increase the total pressure, but H2O saturation pressure is much smaller than CO2 saturation pressure in the extremely cold temperature domain (approximately 120-170K) focused on in the present study. Therefore, we can neglect H2O vapor pressure for the total pressure in this analysis. Those severe supersaturation events are found more frequently in the southern hemisphere (12% of all the saturation events in the southern hemisphere) than in the northern hemisphere (3% of all the saturation events in the northern hemisphere). This result might be inconsistent with the previous study, which suggested that the weaker polar vortex in the South allows H2O ice nuclei-rich air to intrude from lower latitudes into the polar region, resulting in lower amounts of convective available potential energy by supersaturation [3].

Noguchi, K.

2012-09-01

298

WCDMA Radio Interface  

Microsoft Academic Search

Understanding the WCDMA radio interface is essential for engineers dealing with UMTS radio networks. A knowledge of the structure\\u000a and usage of the physical channels in the downlink and uplink directions, together with a knowledge of spreading and modulation,\\u000a provides a good background for understanding how the WCDMA radio network works. Various kinds of services with different quality-of-service\\u000a requirements and

Matti Manninen

299

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

300

Historic Rio Grande Channel Change: Relating Channel Adjustments Measured from Aerial Photography to Human and Climate Induced Changes in Hydrology  

NASA Astrophysics Data System (ADS)

Over the last century, flow regulation, changes in land and water use, and climate change, including severe droughts, have altered geomorphic processes along the Middle Rio Grande. In association with the USACE Urban Flood Demonstration Program, we investigated changes in channel and island widths and areas as measured on 1972-2006 aerial photographs in relation to average and peak flows in the Rio Grande through Bernalillo County, NM (Albuquerque). We employed all recent (1992-2006) photographs, which were often taken annually or biannually. Digitized and georeferenced photographs were analyzed using a GIS, with particular attention paid to quantifying potential measurement error and its propagation through estimates of channel areas and bank erosion rates. Average total channel widths decreased from 169 m in 1972 to 130 m in 2006. Narrowing was concentrated in the upper and lower sections of the study reach where tributary sediment inputs and degradation related to dam operations constrict the active channel. Decreases in channel width and area coincide with periods of low flows, although the area changes are associated with large errors. Vegetated island areas have greatly increased since 1972, although islands per se were also lost during the later study period by bank attachment. Bank erosion estimates also have large associated errors. Nonetheless, erosion rates appear to be generally decreasing over time, but accelerated during the 2005 high flows. Additional research will compare geomorphic change along the Rio Grande study reach to channel adjustments along the Rio Chama, both below and above El Vado Dam, to better understand regional channel responses to dam operations and drought cycles. Initial investigations reveal that channel responses to these perturbations along the Rio Chama, a major Rio Grande tributary, are similar to the adjustments observed along the Rio Grande through Albuquerque, but the magnitude of the change is not as dramatic.

Meyer, G. A.; Swanson, B. J.; Coonrod, J.

2008-12-01

301

Radio-relay communication  

Microsoft Academic Search

In this text book, the principles of designing conventional, tropospheric, and satellite radio-relay links are discussed. Particular attention is given to frequency modulated communication lines and lines with frequency separated channels. The principles of designing radio-relay equipments are reviewed.

V. V. Markov

1979-01-01

302

Atomic nitrogen measurements in a radio-frequency atmospheric-pressure plasma jet  

NASA Astrophysics Data System (ADS)

Atmospheric-pressure plasma jets (APPJs) driven with radio-frequency voltages have the potential to be used in a range of new healthcare applications. To guarantee the safety and effectiveness of these new devices, a thorough understanding of the physics and chemistry of these plasmas is needed. The exact mechanisms through which APPJs affect biological materials like cells, bacteria and DNA are largely unknown, however, recent studies suggest the importance of reactive oxygen and nitrogen species (RONS). The starting point for the creation of many of the different RONS is the production of atomic oxygen and nitrogen in APPJs by breaking up oxygen and nitrogen gas molecules. In order to fully understand and control the production and effects of different RONS it is therforte important to measure atomic oxygen and nitrogen species in APPJs. This contribution presents the first direct measurements of atomic nitrogen species in APPJs. The measurements were performed with a two-photon absorption laser-induced fluorescence diagnostic, using 206.65 nm laser photons for the excitation of ground-state N atoms and observing fluorescence light around 744 nm. The APPJ was run with a helium gas flow of 1 slm and varying small admixtures of molecular nitrogen of 0 -- 0.7 vol%. A maximum in the measured N concentration was observed for an admixture of 0.25 vol% nitrogen gas.

Wagenaars, Erik; Gans, Timo; O'Connell, Deborah; Niemi, Kari

2012-10-01

303

Measurement of Single Channel Currents from Cardiac Gap Junctions  

NASA Astrophysics Data System (ADS)

Cardiac gap junctions consist of arrays of integral membrane proteins joined across the intercellular cleft at points of cell-to-cell contact. These junctional proteins are thought to form pores through which ions can diffuse from cytosol to cytosol. By monitoring whole-cell currents in pairs of embryonic heart cells with two independent patch-clamp circuits, the properties of single gap junction channels have been investigated. These channels had a conductance of about 165 picosiemens and underwent spontaneous openings and closings that were independent of voltage. Channel activity and macroscopic junctional conductance were both decreased by the uncoupling agent 1-octanol.

Veenstra, Richard D.; Dehaan, Robert L.

1986-08-01

304

Channel Bow in Boiling Water Reactors - Hot Cell Examination Results and Correlation to Measured Bow  

SciTech Connect

An increase in frequency of fuel channel-control blade interference has been observed in Boiling Water Reactors (BWR) in recent years. Many of the channels leading to interference were found to bow towards the control blade in a manner that was inconsistent with the expected bow due to other effects. The pattern of bow appeared to indicate a new channel bow mechanism that differed from the predominant bow mechanism caused by differential growth due to fast-fluence gradients. In order to investigate this new type of channel bow, coupons from several channels with varying degrees of bow were returned to the GE Vallecitos Nuclear Center (VNC) for Post-Irradiation Examination (PIE). This paper describes the characteristics of channel corrosion and hydrogen pickup observed, and relates the observations to the channel exposure level, control history, and measured channel bow. The channels selected for PIE had exposures in the range of 36-48 GWd/MTU and covered a wide range of measured bow. The coupons were obtained at 4 elevations from opposing channel sides adjacent and away from the control blade. The PIE performed on these coupons included visual examination, metallography, and hydrogen concentration measurements. A new mechanism of control-blade shadow corrosion-induced channel bow was found to correlate with differences in the extent of corrosion and corresponding differences in the hydrogen concentration between opposite sides of the channels. The increased corrosion on the control blade sides was found to be dependent on the level of control early in the life of the channel. The contributions of other potential factors leading to increased channel bow and channel-control blade interference are also discussed in this paper. (authors)

Mahmood, S.T. [Global Nuclear Fuel, GE Vallecitos Nuclear Center, 6705 Vallecitos Road, Sunol, CA 94586 (United States); Lin, Y.P.; Dubecky, M.A. [Global Nuclear Fuel, 3901 Castle Hayne Road, m/c H25, Wilmington, NC 28401 (United States); Edsinger, K. [Electric Power Research Institute, 3420 Hillview Avenue, Palo Alto, CA 94304 (United States); Mader, E.V. [Electric Power Research Institute, 1000 River Walk Dr. no. 340, Idaho Falls, ID 83402 (United States)

2007-07-01

305

Radio-frequency scanning tunneling microscopy: Instrumentation and applications to physical measurements  

NASA Astrophysics Data System (ADS)

The scanning tunneling microscope (STM) relies upon localized electron tunneling between a sharp probe tip and a conducting sample to attain atomic-scale spatial resolution. Perhaps the most serious obstacle in front of realizing the full potential of the STM is its inadequate temporal resolution, limited by the bandwidth of STM current detectors (˜1 kHz). To overcome this limitation, we developed a radically new approach: we embedded the tunnel junction into an inductor-capacitor resonant circuit and measured the reflection of radio-frequency waves from this circuit. Our new apparatus, which we call a radio-frequency scanning tunneling microscope (Rf-STM), allowed us to achieve 100-fold bandwidth increase upon the state-of-the-art. The bandwidth increase resulted in a number of ultrafast and sensitive measurements in nanoscale systems. First, the large bandwidth of the Rf-STM allowed acquisition of surface topography images at high speeds. In a conventional STM scan, it takes from minutes to hours to create a typical image. As the circuit bandwidth increases, one can shorten this time considerably. We showed that the Rf-STM images, collected at a rate of 100 line/s, had comparable resolution to conventional STM images taken at a rate of 1 line/s. Second, we used the Rf-STM to perform broadband electronic noise measurements. Intrinsic current fluctuations in a tunnel junction, called shot noise, gives important in formation about electron transport mechanisms. We used shot noise measurements as an absolute calibration tool for Rf-STM. Conversely, we also demonstrated how the Rf-STM could be used as a local primary thermometer. Finally, using the Rf-STM, we established the very high displacement sensitivity of a tunnel displacement detector. On a driven micro-mechanical membrane, we detected the first ten mechanical resonances, ranging in frequency from 1 MHz to 3 MHz. We also measured the displacements of a Au surface shaken by a calibrated piezoelectric actuator, ascertaining a displacement sensitivity of 15 fm/Hz--1/2, at room temperature.

Kemiktarak, Utku

306

Sirius Satellite Radio: Radio entertainment in the sky  

Microsoft Academic Search

Satellite broadcasting of radio programs is an effective means of serving large and distributed markets. A space-based radio system can provide about 100 high quality music, voice, and data channels to users spread over a vast geographic area. Employing digital technology and an elaborate system design, this approach significantly outperforms traditional AM and FM radio broadcasting in signal quality, program

F. Davarian

2002-01-01

307

Relations Between Field-surveyed Channel Networks and Map-based Geomorphometric Measures, Inez, Kentucky  

Microsoft Academic Search

Channel networks near Inez, Kentucky, were surveyed in the field within 29 small drainage basins that appeared on 1:24,000-scale maps to be unbranched (first order). The basins contained from 0 to 5 channel sources, with an average of 2.15 per basin. Many channel characteristics measured in the field are well correlated with morphometric variables measured from maps, but a substantial

David M. Mark

1983-01-01

308

Measurements of Ion Drifts and Thermospheric Neutral Winds at the Jicamarca Radio Observatory  

NASA Astrophysics Data System (ADS)

Measurements of ion drifts and thermospheric neutral winds obtained simultaneously with zonal and vertical ion drift measurements of F-region plasma have been made at the Jicamarca Radio Observatory at different times during the year since August, 2009. This period is coincident with an anomalous period of extremely low solar activity. For campaigns taking place in September, 2009, March, 2010, and September, 2010, the Jicamarca 50 MHz radar operated to measure both vertical ion drifts and horizontal neutral winds from 200 to 800 km. The Jicamarca Fabry-Perot interferometer (FPI) was installed in August, 2009, and measurements have been ongoing since first light on 15 August, 2010. The FPI instrument is located in an observatory installed on a hill overlooking the Jicamarca valley and located above the cloud inversion layer, which improved the chances of observing during local summer. This instrument after an upgrade in August 2010 is able to make zonal and meridional thermospheric wind and temperature measurements with an accuracy of 5 to 10 ms-1 and 15 to 30 K. Also obtained during the measurement campaigns with the JRO radar facility were simultaneous measurements of thermospheric winds from the FPI observatory located in Arequipa, Peru, which is located 4 degrees latitude to the south of Jicamarca. The results obtained generally showed good agreement between the observed neutral winds and ion drifts. The vertical variation of the ion drifts is significant from the early evening twilight period to midnight suggesting that the transition from the E-region dynamo to the F-region dynamo takes place rather slowly as compared with more active solar flux periods.

Meriwether, J. W.; Navarro, L.; Chau, J. L.; Fejer, B. G.

2010-12-01

309

Measurements of atomic nitrogen distributions in a radio-frequency atmospheric-pressure plasma jet  

NASA Astrophysics Data System (ADS)

Radio-frequency (RF) driven atmospheric-pressure plasma jets (APPJs) are expected to have a range of new healthcare applications. To guarantee the effectiveness and safety of these devices, a thorough understanding of the physics and chemistry of these plasmas is needed. We studied an RF-APPJ in helium with small admixtures of nitrogen and/or oxygen. The low-temperature APPJ effluent contains high concentrations of reactive species such as atomic nitrogen and oxygen. The N and O radicals play a crucial role in the plasma chemistry and discharge dynamics, but are unfortunately difficult to measure experimentally. We present a two-photon absorption laser-induced fluorescence (TALIF) technique for measuring atomic nitrogen species, which uses 207 nm photons for excitation of ground-state N atoms and observes time-resolved fluorescence at 745 nm. With this diagnostic we directly measure the spatial and temporal evolution of atomic nitrogen species, and compare these to the results of a numerical model based on hydrodynamic equations with a semi-kinetic treatment of the electrons.

Wagenaars, Erik; Niemi, Kari; O'Connell, Deborah; Gans, Timo

2011-11-01

310

FCC (Federal Communications Commission) Methods of Measurements of Radio Noise Emissions from Industrial, Scientific, and Medical Equipment.  

National Technical Information Service (NTIS)

The document sets forth uniform methods of measurements of radio noise emitted from ISM equipment, as defined in 47 CFR Section 18.107 of the FCC Rules. The technical specifications for ISM equipment are contained in Part 18 of the FCC Rules. Methods of m...

1986-01-01

311

A mathematical model for a polarisation based orientation measurement principle in time of arrival radio localisation systems  

Microsoft Academic Search

The determination of orientation within time of arrival radio localisation systems is a widely discussed matter within the scientific world. In most cases, this goal is reached by using additional navigation sensors. Some other techniques exist, which are utilising only carrier phase measurements. For that purpose, the antenna configuration has to be chosen adequately. In the case considered here, a

Andreas Eidloth; J. Thielecke

2010-01-01

312

The Measurement of Phase and Amplitude Radio Wave Interaction at University Park, Pennsylvania, for July-August-September, 1964.  

National Technical Information Service (NTIS)

The measurement of phase and amplitude radio wave interaction, to be carried out during the IQSY, comprises the contents of this report. The interaction parameters, T sub A and T sub phi are given as a function of height for the dates and times indicated....

A. J. Ferraro H. S. Lee

1965-01-01

313

Measurements of the radio refractive index structure parameter C2(n) with a microwave refractometer in tropical latitudes  

Microsoft Academic Search

The spatial and temporal variations of the radio refractive index (RRI) lead to scattering of EM energy. Modern communication systems are subject to vagaries of the turbulence due to the RRI fluctuations. Vertical resolution of radiosondes is insufficient to resolve the structures of clear-air turbulence in the atmosphere. In a tropical country like India, aircraft measurements of RRI fluctuations have

S. B. S. S. Sarma; P. K. Pasricha

1989-01-01

314

Measuring the Impact on Farmers of Agricultural Radio and Television Programs in Southwest Nigeria.  

ERIC Educational Resources Information Center

|A survey examined the effectiveness of two long-running Nigerian agricultural programs on television and radio as perceived by 198 farmers. Results indicate a positive assessment of their value for improving agricultural production. Although more listen to the radio, the television program also received high marks. (Contains 17 references.) (JOW)|

Yahaya, Mohammed Kuta; Badiru, Olabode Idris

2002-01-01

315

Some Measurements of High-Latitude Ionospheric Absorption Using Extraterrestrial Radio Waves  

Microsoft Academic Search

This paper describes the manner im which 30-mc extraterrestrial radio waves have been used to study the radio absorption characteristics of the arctic ionosphere. It opens with a brief discussion of the theory of ionospheric absorption, followed by a description of the basic principles involved in the technique. Two different types of equipment which have been used in these absorption

C. G. Little; H. Leinbach

1958-01-01

316

Measurements of Radio Star and Satellite Scintillations at a Subauroral Latitude  

Microsoft Academic Search

Observations of two radio stars, Cygnus A and Cassiopeia A, and of two satellites, Cosmos I and Transit 4A, have yielded data on lower and upper atmospheric irregularities. The frequencies studied have included 20 Mc, 40 Mc and 54 Mc for satellite transmissions, and 30 Mc to 3000 Mc for radio star signals. The antennas used have ranged from a

R. S. Allen; J. Aarons; H. Whitney

1964-01-01

317

Measurements of radio star and satellite scintillations at a subauroral latitude  

Microsoft Academic Search

Observations of two radio stars, Cygnus A and Cassiopeia A, and of two satellites, Cosmos I and Transit 4A, have yielded data on lower and upper atmospheric irregularities. The frequencies studied have included 20 Mc, 40 Mc and 54 Mc for satellite transmissions, and 30 Mc to 3000 Mc for radio star signals. The antennas used have ranged from a

R. S. ALLEN; J. Aarons; H. Whitney

1964-01-01

318

UWB for noninvasive wireless body area networks: channel measurements and results  

Microsoft Academic Search

The paper presents UWB channel measurements from 3 to 6 GHz for a body area network (BAN) in an anechoic chamber and an office room. Both, transmit and receive antenna were placed directly on the body. Channel parameters as delay spread and path loss are extracted from the measurements and the influence of the body is highlighted. We show that

Thomas Zasowski; Frank Althaus; M. Stager; A. Wittneben; G. Troster

2003-01-01

319

In situ measurement of gas composition changes in radio frequency plasmas using a quartz sensor  

NASA Astrophysics Data System (ADS)

A simple method using a quartz sensor (Q-sensor) was developed to observe gas composition changes in radio frequency (rf) plasmas. The output depends on the gases' absolute pressure, molecular weight, and viscosity. The pressure-normalized quartz sensor output depends only on the molecular weight and viscosity of the gas. Consequently, gas composition changes can be detected in the plasmas if a sensor can be used in the plasmas. Influences imparted by the plasmas on the sensor, such as those by reactive particles (e.g., radicals and ions), excited species, electrons, temperature, and electric potentials during measurements were investigated to test the applicability of this quartz sensor measurement to plasma. The Q-sensor measurement results for rf plasmas with argon, hydrogen, and their mixtures are reproducible, demonstrating that the Q-sensor measurement is applicable for plasmas. In this work, pressure- and temperature-normalized Q-sensor output (NQO) were used to obtain the gas composition information of plasma. Temperature-normalization of the Q-sensor output enabled quartz sensor measurements near plasma electrodes, where the quartz sensor temperature increases. The changes in NQO agreed with results obtained by gas analysis using a quadrupole mass spectrometer. Results confirmed that the change in NQO is mainly attributable to changes in the densities and kinds of gas molecules in the plasma gas phase, not by other extrinsic influences of plasma. For argon, hydrogen, and argon-hydrogen plasmas, these changes correspond to reduction in nitrogen, production of carbon monoxide, and dissociation of hydrogen molecules, respectively. These changes in NQO qualitatively and somewhat quantitatively agreed with results obtained using gas analysis, indicting that the measurement has a potential application to obtain the gas composition in plasmas without disturbing industrial plasma processes.

Suzuki, Atsushi; Nonaka, Hidehiko

2009-09-01

320

In situ measurement of gas composition changes in radio frequency plasmas using a quartz sensor.  

PubMed

A simple method using a quartz sensor (Q-sensor) was developed to observe gas composition changes in radio frequency (rf) plasmas. The output depends on the gases' absolute pressure, molecular weight, and viscosity. The pressure-normalized quartz sensor output depends only on the molecular weight and viscosity of the gas. Consequently, gas composition changes can be detected in the plasmas if a sensor can be used in the plasmas. Influences imparted by the plasmas on the sensor, such as those by reactive particles (e.g., radicals and ions), excited species, electrons, temperature, and electric potentials during measurements were investigated to test the applicability of this quartz sensor measurement to plasma. The Q-sensor measurement results for rf plasmas with argon, hydrogen, and their mixtures are reproducible, demonstrating that the Q-sensor measurement is applicable for plasmas. In this work, pressure- and temperature-normalized Q-sensor output (NQO) were used to obtain the gas composition information of plasma. Temperature-normalization of the Q-sensor output enabled quartz sensor measurements near plasma electrodes, where the quartz sensor temperature increases. The changes in NQO agreed with results obtained by gas analysis using a quadrupole mass spectrometer. Results confirmed that the change in NQO is mainly attributable to changes in the densities and kinds of gas molecules in the plasma gas phase, not by other extrinsic influences of plasma. For argon, hydrogen, and argon-hydrogen plasmas, these changes correspond to reduction in nitrogen, production of carbon monoxide, and dissociation of hydrogen molecules, respectively. These changes in NQO qualitatively and somewhat quantitatively agreed with results obtained using gas analysis, indicting that the measurement has a potential application to obtain the gas composition in plasmas without disturbing industrial plasma processes. PMID:19791966

Suzuki, Atsushi; Nonaka, Hidehiko

2009-09-01

321

Single channel properties of lysenin measured in artificial lipid bilayers and their applications to biomolecule detection  

PubMed Central

Single channel currents of lysenin were measured using artificial lipid bilayers formed on a glass micropipette tip. The single channel conductance for KCl, NaCl, CaCl2, and Trimethylammonium-Cl were 474 ± 87, 537 ± 66, 210 ± 14, and 274 ± 10 pS, respectively, while the permeability ratio PNa/PCl was 5.8. By adding poly(deoxy adenine) or poly(L-lysine) to one side of the bilayer, channel currents were influenced when membrane voltages were applied to pass the charged molecules through the channel pores. Current inhibition process was concentration-dependent with applied DNA. As the current fluctuations of ?-hemolysin channels is often cited as the detector in a molecular sensor, these results suggest that by monitoring channel current changes, the lysenin channel has possibilities to detect interactions between it and certain biomolecules by its current fluctuations.

AOKI, Takaaki; HIRANO, Minako; TAKEUCHI, Yuko; KOBAYASHI, Toshihide; YANAGIDA, Toshio; IDE, Toru

2010-01-01

322

First measurements of radar coherent scatter by the Radio Aurora Explorer CubeSat  

NASA Astrophysics Data System (ADS)

The Radio Aurora Explorer CubeSat detected the first radar echoes during the solar storm of March 8, 2012. The 300 s ground-to-space bi-static radar experiment was conducted in conjunction with the Poker Flat Incoherent Scatter Radar in the local morning (˜8 am) over Poker Flat, Alaska. The geomagnetic conditions for the E region field-aligned irregularity generation were optimal due to strong (about 1500 m/s) F region ion drifts and sufficient E region ionization (electron densities were ˜2 × 1011 m-3). The corresponding E region electric field of ˜80 mV/m was larger than the excitation threshold for the Farley-Buneman instability. An auto-correlation analysis resolved, for the first time, the distribution of auroral E region backscatter with 3 km resolution in altitude and sub-degree resolution in aspect angle. Moreover, the measured Doppler velocities of the UHF scatter shows the phase speed saturation of the meter-scale plasma waves. The measured Doppler velocity is in excellent agreement with the Cs cos ? formula for auroral E region irregularities.

Bahcivan, H.; Cutler, J. W.; Bennett, M.; Kempke, B.; Springmann, J. C.; Buonocore, J.; Nicolls, M.; Doe, R.

2012-07-01

323

Analysis of sporadic E variability derived from GPS radio occultation measurements and possible links to dynamics  

NASA Astrophysics Data System (ADS)

Sporadic E are thin layers of enhanced electron density, which appear usually at an altitude range between 90 and 120 km. They cause strong amplitude scintillations in GPS occultation signals. This feature is used to derive information on sporadic E occurrence from satellite based GPS radio occultation (RO) data. We intend to introduce the RO technique as a valuable method for sporadic E observation. The data base for our investigation includes RO measurements from CHAMP, GRACE-A and FORMOSAT-3/COSMIC during 2007 and 2008. This multi-satellite data set allows for global investigations with high spatial resolution. We derive global distributions of sporadic E occurrence rates as well as its daily, seasonal and spatial variations. The ionospheric E region is coupled with mesospheric/lower thermospheric wind field through the windshear (VxB) mechanism. It is expected that sporadic E layers are formed in a region of negative zonal windshear (e.g., with westward winds over eastward winds). Strong shears are provided by solar tides, in particular the diurnal tide in lower latitudes and the semidiurnal tide (SDT) in midlatitudes. With focus on the northern midlatitudes we present sporadic E occurrence rates which exhibit a dominating semidiurnal structure. Comparisons with ground-based and space-based wind measurements show excellent agreement between the phases of the sporadic E semidiurnal signal and the SDT phase.

Arras, C.; Jacobi, Ch.; Wickert, J.; Heise, S.; Schmidt, T.

2009-04-01

324

Evaluation of uncertainty in gravity wave potential energy calculations through GPS radio occultation measurements  

NASA Astrophysics Data System (ADS)

The application of the Global Positioning System (GPS) radio occultation (RO) method to the atmosphere enables the determination of height profiles of temperature, among other variables. From these measurements, gravity wave activity is usually quantified by calculating the potential energy through the integration of the ratio of perturbation and background temperatures between two given altitudes in each profile. The uncertainty in the estimation of wave activity depends on the systematic biases and random errors of the measured temperature, but also on additional factors like the selected vertical integration layer and the separation method between background and perturbation temperatures. In this study, the contributions of different parameters and variables to the uncertainty in the calculation of gravity wave potential energy in the lower stratosphere are investigated and quantified. In particular, a Monte Carlo method is used to evaluate the uncertainty that results from different GPS RO temperature error distributions. In addition, our analysis shows that RO data above 30 km height becomes dubious for gravity waves potential energy calculations.

Luna, D.; Alexander, P.; de la Torre, A.

2013-09-01

325

On-Body Measurements and Characterization of Wireless Communication Channel for Arm and Torso of Human  

Microsoft Academic Search

This paper discusses the propagation channel between two half-wavelength dipoles placed near a human body. Different parts\\u000a of the body are investigated separately. Statistical properties of the wireless on-body channel have been investigated. Path\\u000a loss parameters and time domain channel characteristics are extracted from the measurement data. Path loss models for the\\u000a arm and torso have been derived. A comparison

Elisabeth Reusens; W. Joseph; G. Vermeeren; L. Martens

326

Capacity-maximizing resource allocation for data-aided timing and channel estimation in ultra-wideband radios  

Microsoft Academic Search

The overall system performance of data-aided ultra-wideband (UWB) communications relies critically on the accuracy of synchronization and channel estimation during the training phase. The total transmission resources should be properly allocated between training and information symbols in order to strike a desired balance between performance and information rate. To this end, this paper derives optimum transmission schemes that judiciously allocate

Lin Wu; Zhi Tian

2004-01-01

327

Rip Channels, Megacusps, and Shoreline Change: Measurements and Modeling.  

National Technical Information Service (NTIS)

To investigate the relationship between alongshore rip channel migration rates and alongshore sediment transport rates, multi-year surf-zone video and wave datasets are examined at three sites along Monterey Bay, on the coast of California. Time-averaged,...

M. D. Orzech

2010-01-01

328

Noise analysis and measurements on buried channel charge coupled devices  

Microsoft Academic Search

Noise analysis of buried channel CCD by computer simulation is presented. The potential profile and signal charge distribution in potential well are obtained by solving Poisson's equation with a depletion approximation model. According to this model, it is possible to predict the volume occupied by signal charges in potential well. Thereby, the well capacitance and free carrier density are obtained.

K. C. Houng; D. C. Chen; J. Gong; H. L. Lu

1992-01-01

329

Toward Global Soundings and Atmospheric Measurements for Climate and NWP Using GNSS Radio Occultation Systems  

Microsoft Academic Search

The history of observing radio occultations [RO] using a space-borne platform and an earth-based or another space-based platform to probe an intervening planetary atmosphere, i.e. to determine atmospheric profiles and characteristics, dates back to 1964 with the sounding of the atmosphere of Mars and subsequent soundings of planetary atmospheres using a radio transmitter on a satellite and the RO technique.

S. A. Mango; D. Ector; P. Wilczynski; R. A. Fulton; D. Whitely; L. Cucurull; V. Chu; W. S. Schreiner; C. Rocken; R. A. Anthes; Y. Kuo; K. Cook

2010-01-01

330

Multi-frequency Radio Measurements of SN 1987A over 22 Years  

Microsoft Academic Search

We present extensive observations of the radio emission from the remnant of\\u000aSN 1987A made with the Australia Telescope Compact Array (ATCA), since the\\u000afirst detection of the remnant in 1990. The radio emission has evolved in time\\u000aproviding unique information on the interaction of the supernova shock with the\\u000acircumstellar medium. We particularly focus on the monitoring observations at

G. Zanardo; L. Staveley-Smith; Lewis Ball; B. M. Gaensler; M. J. Kesteven; R. N. Manchester; C.-Y. Ng; A. K. Tzioumis; T. M. Potter

2009-01-01

331

Cognitive Radio: A Communications Engineering View  

Microsoft Academic Search

Cognitive radio is an emerging technology that enables the flexible development, construction, production, shipping, and deployment of highly adaptive radios that are built upon software defined radio technology. This contribution starts with a brief section that underlines the paramount importance of the mobile radio communications channel. Then, spectrum issues are discussed to emphasize the reasons for spectrum scarcity as well

FRIEDRICH K. JONDRAL

2007-01-01

332

Investigation of non-specular scattering by comparing directional channel characteristics from microcell measurement and simulation  

Microsoft Academic Search

Channel characteristics from microcell measurement and simulation are compared. In microcell environment, the dominant propagation mechanisms are not only from reflections and diffractions from buildings but can also come from non-specular scatterings. Propagation prediction tools such as ray-tracing algorithms which calculate only reflections and diffractions are hence not enough to completely predict the channel. To address this issue, an implementation

N. Lertsirisopon; G. S. Ching; M. Ghoraishi; J.-I. Takada

2009-01-01

333

The 400-channel commutator for measurement of energy distribution in laser beam  

Microsoft Academic Search

An experimental study of a 400 channel commutator for measurement and analysis of the energy distribution over the beam cross section of pulse lasers was made for the purpose of evaluating its performance characteristics. This commutator transfers electric signals sequentially from 400 channels to the input of a digital high precision voltmeter, signals of a magnitude ranging from a few

V. L. Chereugin; A. A. Kuznetsov

1984-01-01

334

Measurement of pressure loss in the flow of polymer solutions through wavy channels  

Microsoft Academic Search

In order to examine the flow behavior of polymer solutions through porous media, the measurement of pressure loss and the experiment for flow visualization were carried out with wavy channels as one of the model channels of porous media. The test fluids used are aqueous solutions of polyacrylamide (PAA) with two different concentrations. The occurrence of the excess pressure loss,

Takashi Koshiba; N. Mori; K. Nakamura

1994-01-01

335

A system for measuring the characteristics of the ionospheric channel by digital transmissions  

Microsoft Academic Search

The increase of digital transmission rates in the decametric range, by adaptative modems was examined. The ionospheric channel is defined for its rapid fluctuations, and its slower time evolutions. The measuring system is designed to provide for two types of ionospheric medium studies. The first study estimates the main parameters of the channel transfer function, with an update process in

Y. M. Leroux; L. Bertel; J. P. Jolivet; P. Lassudrie-Duchesne; H. Rouault

1984-01-01

336

Design and implementation of a reconfigurable decimation and channel selection filter for GSM and UMTS radio standards  

Microsoft Academic Search

This work presents a low-power multistandard decimation and channel selection filter architecture. The filter is suitable after an over-sampling sigma-delta converter and performs decimation in two stages. The first stage is a modified structure of the cascade of integrators-combs (CIC) filter and allows reducing sampling rate downto only the double of the Nyquist frequency. The second stage composed of classical

Nadia Khouja; Khaled Grati; Adel Ghazel; Bertrand Le Gal

2009-01-01

337

Experimental determination of conduction channels in atomic-scale conductors based on shot noise measurements  

NASA Astrophysics Data System (ADS)

We demonstrate a general procedure for determining the conduction channels of quantum conductors from shot noise measurements. This numerical approach allows multichannel analysis which was previously limited to superconductors. Channel analysis of Ag and Au atomic contacts reveals a remarkable behavior in which the channels fully open one by one with increasing conductance. These results allow us to unambiguously distinguish between free-electron and tight-binding descriptions for the conductance of monovalent contacts. Furthermore, the channel resolution uncovers the presence of tunneling channels in parallel to the conductance through the main contact and provides a means for distinguishing between the contact conductance and tunneling contributions. Finally, unique channel distributions were found for Al and Pt contacts reflecting their distinct valence orbital structures.

Vardimon, Ran; Klionsky, Marina; Tal, Oren

2013-10-01

338

Channeling-radiation measurements at Lawrence Livermore National Laboratory  

SciTech Connect

In the last few years, the amount and quality of channeling-radiation data have increased enormously, owing largely to much improved experimental capabilities. Current results include improved interplanar potentials for diamond, the description of the effect of platelets in diamond as an average thermal vibration, an improved determination of the Debye temperature of silicon, an improved determination of the thermal-vibration amplitude of LiD, and the demonstration that LiF crystal structures can survive intense electron bombardment.

Berman, B.L.; Dahling, B.A.; Datz, S.; Kephart, J.O.; Klein, R.K.; Pantell, R.H.; Park, H.

1984-10-01

339

Measuring the full field vector of the ionospheric radio signal on a short-range path when three mutually orthogonal antennas are used  

Microsoft Academic Search

Of great interest in the context of obtaining information about ionospheric conditions, as well as of improving the effectiveness of exploitation of the radio systems' energy potential is the development of diagnostic tools based on measuring the full field vector of the radio wave (angles of arrival, and polarization parameters of the electromagnetic wave (EMW)). Morgan and Evans [l] described

E. L. Afraimovich; V. A. Kobzar; K. S. Palamatchouk; V. V. Chernukhov

1999-01-01

340

Radio wave scattering observations of the solar corona: First-order measurements of expansion velocity and turbulence spectrum using Viking and Mariner 10 spacecraft  

Microsoft Academic Search

Solar conjunction of Mars on 1976 November 25 occurred very near the beginning of solar cycle 21, about 4 months after the first Viking spacecraft arrived at the planet. Radio wave scattering data were collected at 3.6 and 13 cm wavelengths, using the radio link between the Viking orbiters and the Earth. These data allow measurements of solar wind properties

G. L. Tyler; J. F. Vesecky; M. A. Plume; H. T. Howard; A. Barnes

1981-01-01

341

The dependence of F-region electron heating on HF radio pump power: Measurements at EISCAT Tromsø  

NASA Astrophysics Data System (ADS)

Measurements of ionospheric electron temperature enhanced by the action of a powerful high-frequency radio wave on the F-region at the EISCAT facility near Tromsø, Norway are analyzed to obtain the electron heat source due to the radio wave as a function of transmitter power. The absorption of the wave in the D-region is accounted for and is found to have a significant influence on the F-region heating, especially due to variations in the D-region electron density during the experiment. It is found that the efficiency of F-region heating expressed in terms of the electron heating rate as a function of radio wave power flux is higher at higher transmitter powers. This behavior seems to be consistent with the development of geomagnetic field-aligned plasma density irregularities which are associated with the conversion of the radio wave to electrostatic upper-hybrid waves. At the highest power fluxes, the efficiency appears to be close to 100%.

Senior, A.; Rietveld, M. T.; Yeoman, T. K.; Kosch, M. J.

2012-04-01

342

Dual-spacecraft radio occultation measurement of the electron density near the lunar surface by the SELENE mission  

NASA Astrophysics Data System (ADS)

During the SELENE (Kaguya) mission the dual-spacecraft radio occultation technique was used to investigate the electron population in the vicinity of the lunar surface. One pair of coherent S-band radio signals from one spacecraft was used to probe the possible electron density enhancement near the Moon, and another signal pair from the other spacecraft measured the solar wind and the terrestrial ionosphere plasma fluctuations, which also exist in the measurement by the former signal pair. The results suggest that any stable ionosphere with densities comparable to the ones observed by the Soviet Luna 19 and 22 missions does not exist near the terminator at high latitudes, although the occurrence of temporal or localized density enhancements cannot be ruled out.

Ando, H.; Imamura, T.; Nabatov, A.; Futaana, Y.; Iwata, T.; Hanada, H.; Matsumoto, K.; Mochizuki, N.; Kono, Y.; Noda, H.; Liu, Q.; Oyama, K.-I.; Yamamoto, Z.; Saito, A.

2012-08-01

343

Infrared and radio measurements of the density structure of compact H II regions  

SciTech Connect

The density structure of compact H II regions is studied by comparing the ratio of the S III forbidden 33.47-micron and 18.71-micron emission lines and 5-GHz continuum maps. Electron densities are computed for DR 22, G29.9 - 0.0, G75.84 + 0.4, M8, M42, S158, W3, and W33. For DR 22, M42, and W3, the electron densities determined from the IR data are consistent with those derived from radio observations. The densities for S158 and M8 are quite low, implying that the S III emission is dominated by the diffuse ionized gas observed in the radio continuum. For G29.9 - 0.0, G75.84 + 0.4, and W33, the S III data give higher densities than predicted from radio observations. This implies that either these nebulae are filled with dense clumps of ionized gas which are not resolved in the radio maps, or that the S III zone is confined to the small, dense cores found in the radio maps of all three nebulae. 41 refs.

Megeath, S.T.; Herter, T.; Gull, G.E.; Houck, J.R. (Cornell Univ., Ithaca, NY (USA))

1990-06-01

344

Method and apparatus for measuring temperature of an earth formation in the presence of a radio frequency electromagnetic field  

SciTech Connect

A method and apparatus for measuring the temperature in a subsurface earth formation that is being heated in situ by subjection to a radio frequency electromagnetic field. It includes lowering a maximum registering thermometer into the formation on a non-conductive flexible line, and holding it there long enough to reach the ambient temperature at that location. Then, the thermometer is raised to the surface fast enough to avoid any significant change on the way up to read that registered maximum.

Kunetka, R.E.; Dowling, D.J.

1984-09-04

345

47 CFR 95.1211 - Channel use policy.  

Code of Federal Regulations, 2011 CFR

... FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES PERSONAL RADIO SERVICES Medical Device Radiocommunication Service (MedRadio) § 95.1211 Channel use policy. (a) The channels authorized...

2011-10-01

346

Toward Global Soundings and Atmospheric Measurements for Climate and NWP Using GNSS Radio Occultation Systems  

NASA Astrophysics Data System (ADS)

The history of observing radio occultations [RO] using a space-borne platform and an earth-based or another space-based platform to probe an intervening planetary atmosphere, i.e. to determine atmospheric profiles and characteristics, dates back to 1964 with the sounding of the atmosphere of Mars and subsequent soundings of planetary atmospheres using a radio transmitter on a satellite and the RO technique. The first use of a Global Navigation Satellite Systems (GNSS) transmitter as a signal source to sound the Earth’s intervening atmosphere utilizing the satellite RO technique was demonstrated with the transmitters on the US Global Positioning System (GPS) constellation of navigation and timing satellites (24-30 satellites) and the receiver on the GPS-MET satellite mission. Several satellite RO missions followed using GPS signal sources - i.e. CHAMP, SAC-C, Oersted, IOX, GRACE and GRAS. In April 2006 a joint USA/Taiwan mission, FORMOSAT-3/COSMIC, a constellation of 6 microsatellites, began sounding successfully the Earth’s atmosphere using GPS and RO for meteorological, ionospheric and climatic studies. Within the next two decades there will be a multiplicity of GNSS constellations flying. Several nations are now planning or initializing other full, operational GNSS missions which will significantly increase the potential number of signal source satellites for RO, to somewhere in the range of 87-125 transmitters, including: 1. GPS (USA), 2. GLONASS (Russian Federation), 3. Galileo (EU) 4. COMPASS (China), 5. IRNSS (India), 6. QZSS (Japan). The national commitments for operations and sustainment of these GNSS constellations have been made for at least the next decades. The operation and sustainment of a large constellation of RO satellites capable of handling the signals from this large multiplicity of GNSS systems would provide soundings and observations of the Earth’s atmosphere for research and operations with unparalleled spatial and temporal coverage. Such a multiplicity of RO receiver satellites would enable high spatial density, global soundings and some critical atmospheric measurements with short repeat times for NWP and some of the shorter climate time scales. The United States and Taiwan have such a new program in formulation for a constellation of 12-24 small RO satellites called COSMIC-2 or FORMOSAT-7/COSMIC-2. COSMIC-2 is a follow-on mission to the Taiwan/USA partnered mission, FORMOSAT-3/COSMIC. This paper will present new results of analyses of such a COSMIC-2 constellation of RO satellites and the multiplicities of GNSS signal sources including the spatial and temporal coverage and scales, the sounding performance in terms of the measurement range, uncertainty and resolution of the bending angle, refractivity and atmospheric density, temperature and water vapor profiles as well as the ionospheric specification, TEC, and electron density profiles.

Mango, S. A.; Ector, D.; Wilczynski, P.; Fulton, R. A.; Whitely, D.; Cucurull, L.; Chu, V.; Schreiner, W. S.; Rocken, C.; Anthes, R. A.; Kuo, Y.; Cook, K.

2010-12-01

347

Measurement of the relative probability of ? ??? decay in the ? ? ? + ? ? ? 0 channel  

Microsoft Academic Search

The relative decay probability B(? ? ??) = (1.259 0.030 0.059)% in the decay channel ? ? ?+???0 has been measured in an experiment using a spherical neutral detector in the VEPP-2M electron-positron storage ring. The\\u000a result agrees with the tabulated value and with measurements of this probability using the spherical neutral detector in other\\u000a ?-meson decay channels.

M. N. Achasov; K. I. Beloborodov; A. V. Berdyugin; A. V. Bozhenok; A. D. Bukin; D. A. Bukin; S. V. Burdin; A. V. Vasil’ev; D. I. Ganyushin; I. A. Gaponenko; V. B. Golubev; T. V. Dimova; S. I. Dolinskii; V. P. Druzhinin; M. S. Dubrovin; A. S. Zakharov; V. N. Ivanchenko; P. M. Ivanov; A. A. Korol’; S. V. Koshuba; G. A. Kukhartsev; A. A. Mamutkin; A. V. Otboev; E. V. Pakhtusova; A. A. Sal’nikov; S. I. Serednyakov; V. A. Sidorov; Z. K. Silagadze; V. V. Sharyi; Yu. M. Shatunov

2000-01-01

348

Measurements of Radio Star and Satellite Scintillations at a Subauroral Latitude.  

National Technical Information Service (NTIS)

Observations of two radio stars, Cygnus A and Cassiopeia A, and of two satellites, Cosmos I and Transit 4A, have yielded data on lower and upper atmospheric irregularities. The frequencies studied have included 20 Mc, 40 Mc and 54 Mc for satellite transmi...

R. S. Allen J. Aarons H. Whitney

1964-01-01

349

Observing Earth's atmosphere with radio occultation measurements using the Global Positioning System  

Microsoft Academic Search

The implementation of the Global Positioning System (GPS) network of satellites and the development of small, high-performance instrumentation to receive GPS signals have cre- ated an opportunity for active remote sounding of the Earth's atmosphere by radio occultation at comparatively low cost. A prototype demonstration of this capability has now been provided by the GPS\\/MET investigation. Despite using relatively immature

E. R. Kursinski; G. A. Hajj; J. T. Schofield; R. P. Linfield; K. R. Hardy

1997-01-01

350

Agesotrophic and quasi-geostrophic circulation in the Gulf of Tehuantepec, México. HF-Radio measurements  

Microsoft Academic Search

Using High Frequency Radios the ocean's surface currents in the inner Gulf of Tehuantepec GT, were mapped every half hour. The GT is characterized by wind outbursts that blow through a gap in the Mexican mountain chain. In this work we show evidence of the relationship between the wind-stress magnitude and the size of eddies excited by the wind-stress. While

X. Flores-Vidal; C. P. Chavanne; R. Durazo; P. J. Flament

2010-01-01

351

Topside ionospheric scale height analysis and modelling based on radio occultation measurements  

Microsoft Academic Search

The knowledge of the scale height in the topside ionosphere region remains rather poor due to the insufficient observations carried so far. To advance this knowledge, presented here is a new method of retrieving the topside ionospheric scale height based on radio occultation observations onboard low-earth-orbiting satellites. The scale height, well known for its dependence on the temperatures and masses

S. M. Stankov; N. Jakowski

2006-01-01

352

Venus: Ionosphere and Atmosphere as Measured by Dual-Frequency Radio Occultation of Mariner V  

Microsoft Academic Search

Venus has daytime and nighttime ionospheres at the positions probed by radio occultation. The main layers are thin by terrestrial standards, with the nighttime peak concentration of electrons being about two orders of magnitude below that of the daytime peak. Above the nighttime peak were several scale-height regimes extending to a radius of at least 7500, and probably to 9700,

1967-01-01

353

Measurement of atmospheric water vapour on the ground's surface by radio waves  

Microsoft Academic Search

Water vapour in the atmosphere and various meteorological phenomena are essential to the understanding of the mechanism of the water cycle. However, it is very difficult to observe water vapour in the atmosphere because the quantities are usually observed at a single point not over long intervals or in a specific plane or volume. Accordingly, the use of radio waves

Tokuo Kishii; Yasuhisa Kuzuha; Fumi Sugita; Michiko Hayano

2001-01-01

354

Correlation measurements in precipitation at linear polarisation using dual-channel radar  

Microsoft Academic Search

Correlation measurements at linear polarisation in dual-channel precipitation radars are investigated. It is shown that the correlation between orthogonal linearly polarised backscatter components provides information on precipitation particle orientation and shape. Thus, as in the case at circular polarisation, correlation measurements can be a useful concept for particle indentification. Preliminary results from measurements made at 9.6 GHz are presented.

Y. M. M. Antar; A. Hendry

1985-01-01

355

Poolcasting: A Social Web Radio Architecture for Group Customisation  

Microsoft Academic Search

Poolcasting is a social Web radio architecture in which groups of listeners influence in real time the music played on each channel. Poolcasting users contribute to the radio with songs they own, create radio channels and evaluate the proposed music, while an automatic intelligent technique schedules each channel with a group-customised sequence of musically associated songs. The benefits of this

Claudio Baccigalupo; Enric Plaza

2007-01-01

356

Rolling Stone Radio  

NSDL National Science Digital Library

Rolling Stone Radio is a fun and interesting site that may represent the future of Internet radio. The site provides a number of streaming audio channels that can be listened to via RealNetworks' RealPlayer G2 combined with a customized, radio-like interface to the site. Each channel features a particular genre of music, and the interface displays the artist and song title during play. The sound quality ranges from acceptable to excellent, and the sound controls and channel selectors are easy-to-use. While the site borders on the exploitative in its advertising and ability to purchase music by clicking through the interface, it does combine some of the best ideas on the Internet into a seamless entertainment package. All downloadable components of this site are free but run only on Win95/98/NT.

1999-01-01

357

A method to measure specific absorption rate of nanoparticles in colloidal suspension using different configurations of radio-frequency fields  

PubMed Central

We report a method for characterization of the efficiency of radio-frequency (rf) heating of nanoparticles (NPs) suspended in an aqueous medium. Measurements were carried out for water suspended 5?nm superparamagnetic iron-oxide NPs with 30?nm dextran matrix for three different configurations of rf electric and magnetic fields. A 30?MHz high-Q resonator was designed to measure samples placed inside a parallel plate capacitor and solenoid coil with or without an rf electric field shield. All components of rf losses were analyzed and rf electric and magnetic field induced heating of NPs and the dispersion medium was determined and discussed.

Ketharnath, Dhivya; Pande, Rohit; Xie, Leiming; Srinivasan, Srimeenakshi; Godin, Biana; Wosik, Jarek

2012-01-01

358

A method to measure specific absorption rate of nanoparticles in colloidal suspension using different configurations of radio-frequency fields.  

PubMed

We report a method for characterization of the efficiency of radio-frequency (rf) heating of nanoparticles (NPs) suspended in an aqueous medium. Measurements were carried out for water suspended 5?nm superparamagnetic iron-oxide NPs with 30?nm dextran matrix for three different configurations of rf electric and magnetic fields. A 30?MHz high-Q resonator was designed to measure samples placed inside a parallel plate capacitor and solenoid coil with or without an rf electric field shield. All components of rf losses were analyzed and rf electric and magnetic field induced heating of NPs and the dispersion medium was determined and discussed. PMID:22991480

Ketharnath, Dhivya; Pande, Rohit; Xie, Leiming; Srinivasan, Srimeenakshi; Godin, Biana; Wosik, Jarek

2012-08-24

359

Direct measurement of synchronization between femtosecond laser pulses and a 3 GHz radio frequency electric field inside a resonant cavity  

NASA Astrophysics Data System (ADS)

We demonstrate a method to measure synchronization between femtosecond laser pulses and the electric field inside a resonant 3 GHz radio frequency (RF) cavity. The method utilizes the Pockels effect in a crystal inside the RF cavity by measuring the retardation of the components of polarization as a function of RF phase. Resolution of the setup used is shown to be 29 +/- 2 fs (root-mean-square, rms), with timing jitter between the laser pulses and the RF field inside the cavity of 96 +/- 7 fs (rms). The method provides a tool to reduce jitter and improve time-resolution in ultrafast electron diffraction experiments.

Brussaard, G. J. H.; Lassise, A.; Pasmans, P. L. E. M.; Mutsaers, P. H. A.; van der Wiel, M. J.; Luiten, O. J.

2013-09-01

360

A method to measure specific absorption rate of nanoparticles in colloidal suspension using different configurations of radio-frequency fields  

NASA Astrophysics Data System (ADS)

We report a method for characterization of the efficiency of radio-frequency (rf) heating of nanoparticles (NPs) suspended in an aqueous medium. Measurements were carried out for water suspended 5 nm superparamagnetic iron-oxide NPs with 30 nm dextran matrix for three different configurations of rf electric and magnetic fields. A 30 MHz high-Q resonator was designed to measure samples placed inside a parallel plate capacitor and solenoid coil with or without an rf electric field shield. All components of rf losses were analyzed and rf electric and magnetic field induced heating of NPs and the dispersion medium was determined and discussed.

Ketharnath, Dhivya; Pande, Rohit; Xie, Leiming; Srinivasan, Srimeenakshi; Godin, Biana; Wosik, Jarek

2012-08-01

361

Non-invasive measurement of the pressure distribution in a deformable micro-channel  

NASA Astrophysics Data System (ADS)

Direct and noninvasive measurement of the pressure distribution in test sections of a micro-channel is a challenging, if not an impossible, task. Here, we present an analytical method for extracting the pressure distribution in a deformable micro-channel under flow. Our method is based on a measurement of the channel deflection profile as a function of applied \\emph{hydrostatic} pressure; this initial measurement generates "constitutive curves" for the deformable channel. The deflection profile under flow is then matched to the constitutive curves, providing the \\emph{hydrodynamic} pressure distribution. The method is validated by measurements on planar micro-fluidic channels against analytic and numerical models. The accuracy here is independent of the nature of the wall deformations and is not degraded even in the limit of large deflections, $\\zeta_{\\rm{max}}/2h_{0}= {\\cal{O}}(1)$, with $\\zeta_{\\rm{max}}$ and $2h_0$ being the maximum deflection and the unperturbed height of the channel, respectively. We discuss possible applications of the method in characterizing micro-flows, including those in biological systems.

Ozsun, Ozgur; Yakhot, Victor; Ekinci, Kamil L.

2013-11-01

362

Single-channel measurements of an N-acetylneuraminic acid-inducible outer membrane channel in Escherichia coli  

PubMed Central

NanC is an Escherichia coli outer membrane protein involved in sialic acid (Neu5Ac, i.e., N-acetylneuraminic acid) uptake. Expression of the NanC gene is induced and controlled by Neu5Ac. The transport mechanism of Neu5Ac is not known. The structure of NanC was recently solved (PDB code: 2WJQ) and includes a unique arrangement of positively charged (basic) side chains consistent with a role in acidic sugar transport. However, initial functional measurements of NanC failed to find its role in the transport of sialic acids, perhaps because of the ionic conditions used in the experiments. We show here that the ionic conditions generally preferred for measuring the function of outer-membrane porins are not appropriate for NanC. Single channels of NanC at pH 7.0 have: (1) conductance 100 pS to 800 pS in 100 mM KCl to 3 M KCl), (2) anion over cation selectivity (Vreversal = +16 mV in 250 mM KCl || 1 M KCl), and (3) two forms of voltage-dependent gating (channel closures above ±200 mV). Single-channel conductance decreases by 50% when HEPES concentration is increased from 100 ?M to 100 mM in 250 mM KCl at pH 7.4, consistent with the two HEPES binding sites observed in the crystal structure. Studying alternative buffers, we find that phosphate interferes with the channel conductance. Single-channel conductance decreases by 19% when phosphate concentration is increased from 0 mM to 5 mM in 250 mM KCl at pH 8.0. Surprisingly, TRIS in the baths reacts with Ag|AgCl electrodes, producing artifacts even when the electrodes are on the far side of agar–KCl bridges. A suitable baseline solution for NanC is 250 mM KCl adjusted to pH 7.0 without buffer.

Giri, Janhavi; Tang, John M.; Wirth, Christophe; Peneff, Caroline M.

2012-01-01

363

Channel length scaling in graphene field-effect transistors studied with pulsed current-voltage measurements.  

PubMed

We investigate current saturation at short channel lengths in graphene field-effect transistors (GFETs). Saturation is necessary to achieve low-output conductance required for device power gain. Dual-channel pulsed current-voltage measurements are performed to eliminate the significant effects of trapped charge in the gate dielectric, a problem common to all oxide-based dielectric films on graphene. With pulsed measurements, graphene transistors with channel lengths as small as 130 nm achieve output conductance as low as 0.3 mS/?m in saturation. The transconductance of the devices is independent of channel length, consistent with a velocity saturation model of high-field transport. Saturation velocities have a density dependence consistent with diffusive transport limited by optical phonon emission. PMID:21271736

Meric, Inanc; Dean, Cory R; Young, Andrea F; Baklitskaya, Natalia; Tremblay, Noah J; Nuckolls, Colin; Kim, Philip; Shepard, Kenneth L

2011-01-27

364

Detection of tropical deep convective clouds from AMSU-B water vapor channels measurements  

Microsoft Academic Search

Methods to detect tropical deep convective clouds and convective overshooting from measurements at the three water vapor channels (183.3 +\\/- 1, 183.3 +\\/- 3, and 183.3 +\\/- 7 GHz) of the Advanced Microwave Sounding Unit-B (AMSU-B) are presented. Thresholds for the brightness temperature differences between the three channels are suggested as criterion to detect deep convective clouds, and an order

Gang Hong; Georg Heygster; Jungang Miao; Klaus Kunzi

2005-01-01

365

Detection of tropical deep convective clouds from AMSU-B water vapor channels measurements  

Microsoft Academic Search

Methods to detect tropical deep convective clouds and convective overshooting from measurements at the three water vapor channels (183.3 ± 1, 183.3 ± 3, and 183.3 ± 7 GHz) of the Advanced Microwave Sounding Unit-B (AMSU-B) are presented. Thresholds for the brightness temperature differences between the three channels are suggested as criterion to detect deep convective clouds, and an order

Gang Hong; Georg Heygster; Jungang Miao; Klaus Kunzi

2005-01-01

366

Measuring and modeling the wideband mobile channel for above the sea propagation paths  

Microsoft Academic Search

This paper presents the results on mobile channel characterization for the above the sea propagation paths at 1.9 GHz. The study is based on measurement campaigns conducted in various locations, carefully selected in order to cover all kind of environments that can be met in the Aegean Sea. The purpose was to model the over-the-sea channel. This study presents conclusions

Konstantinos Maliatsos; Philip Constantinou; Panagiotis Dallas; Michail Ikonomou

2006-01-01

367

On the sensitivity of Tropical Rainfall Measuring Mission (TRMM) Microwave Imager channels to overland rainfall  

NASA Astrophysics Data System (ADS)

The response of brightness temperatures at different microwave frequencies to overland precipitation is investigated by using the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) and Microwave Imager (TMI) data. The Spearman correlation coefficients between observations at TMI channels or channel combinations and PR-measured near-surface rain are computed using 3 years of TRMM data. The results showed that the brightness temperature combinations from 19 and 37 GHz, that is, V19-V37 (the letter V denotes vertical polarization, and the numbers denote frequency in GHz) or V21-V37, can explain ˜10% more variance of near-surface rainfall rate than can the V85 brightness temperature. Also, the global distribution of the above correlation revealed that over almost all of the tropical land area covered by TRMM satellite, the V19-V37 channel has a closer response to the overland rainfall than does the V85 channel. This result is somewhat counterintuitive, because it has been long believed that the dominant signature of overland rainfall is the brightness temperature depression caused by ice scattering at high microwave frequencies (e.g., 85 GHz). To understand the underlying physics of this better low-frequency response, data analysis and radiative transfer modeling have been conducted to assess the influence on brightness temperatures from clouds with different ice and liquid water partitions. The results showed that under the condition of low frozen water and medium liquid water in the atmospheric column, the signal from the V19-V37 channel responded better to rainfall rate than did the one from the V85 channel. A plausible explanation to this result is that in addition to ice scattering signature, the V19-V37 channel contains liquid water information as well, which is more directly related to surface rain than to ice water aloft. At heavy rainfall conditions, the V19-V37, V37, and V85 channels all are correlated with near-surface rain reasonably well, and the V37 or V21 channel becomes the top responder to surface rain as the amount of hydrometeors in the atmospheric column reaches very high values. Additionally, it is found that land surface type and 2 m air temperature have significant skills in characterizing rain cloud types, so that the V19-V37 channel is more sensitive to surface rainfall for more vegetated warm surface, while the V85 channel is more sensitive to cold bare land. This finding implies that the above two parameters may be used to prioritize satellite observations at different channels, so that the channel that has the best rainfall sensitivity under a given condition receives the highest weight in retrieval algorithms.

You, Yalei; Liu, Guosheng; Wang, Yu; Cao, Jie

2011-06-01

368

Measurements of stray antenna capacitance in the STEREO/WAVES instrument: Comparison of the radio frequency voltage spectrum with models of the galactic nonthermal continuum spectrum  

NASA Astrophysics Data System (ADS)

The STEREO/WAVES instrument is designed to measure interplanetary radio emission and in situ plasma waves in the solar wind. The instrument uses three orthogonal monopole electric antennas as its sensor system in both a pseudodipole and monopole mode. At high radio frequencies, the capacitance of the antennas determines the system gain. Here we estimate the stray capacitance in the antenna system by comparing the measured voltage spectrum with a model of the galactic continuum spectrum, which is the instrument background at high frequencies. Together with the antenna free-space capacitance, these measurements provide an absolute calibration of the STEREO/WAVES experiment at radio frequencies, a prerequisite for quantitative studies of solar and astrophysical radio emission.

Eastwood, J. P.; Bale, S. D.; Maksimovic, M.; Zouganelis, I.; Goetz, K.; Kaiser, M. L.; Bougeret, J.-L.

2009-08-01

369

Measurement of single-top T-channel production using ATLAS data  

NASA Astrophysics Data System (ADS)

This document reports the measurement of the single-top t-channel cross-section using data from the ATLAS detector, located at the Large Hadron Collider on the border of France and Switzerland. The data used were collected during the first half of 2011, from proton-proton collisions with a 7 TeV center-of-mass collision energy. Single-top is electroweak top-quark production and t-channel is one of the standard model production modes. To isolate this production, selections are applied to find events with a similar final state. A cut-based analysis is used to further isolate the signal using a series of selections in several orthogonal kinematic regions. Finally, a statistical analysis is performed to determine the measured cross-section and the CKM matrix element |Vtb|. The cross-section for top and anti-top production is considered separately and the resulting cross-sections are sigmat+ = 59+18-16 pb for the positive charge channel and sigmat - = 33+13-12 pb for the negative charge channel. The total measured single-top t-channel cross-section using all kinematic channels in this analysis is 92+29-26 pb with an expected cross-section of sigmat = 62+22-20 pb. The 95% confidence level limit on the standard model | Vtb| value is determined to be |Vtb| > 0.67.

Holzbauer, Jenny Lyn

370

Measurement of charge transfer in sprite-producing lightning using ELF radio atmospherics  

Microsoft Academic Search

Transient high altitude optical emissions referred to as “sprites” are believed to occur as a result of the transfer of large amounts of charge (?100–300 C) from cloud altitudes of 5–10 km to the ground. Using a general subionospheric ELF propagation model, we quantitatively interpret magnetic field waveforms of ELF radio atmospherics originating in mid-western U.S. lightning discharges and observed

S. A. Cummer

1997-01-01

371

Measurement of charge transfer in sprite-producing lightning using ELF radio atmospherics  

Microsoft Academic Search

Transient high altitude optical emissions referred to as ``sprites'' are believed to occur as a result of the transfer of large amounts of charge (~100-300C) from cloud altitudes of 5-10 km to the ground. Using a general subionospheric ELF propagation model, we quantitatively interpret magnetic field waveforms of ELF radio atmospherics originating in mid-western U.S. lightning discharges and observed at

S. A. Cummer

1997-01-01

372

Measurements of turbulence in the Venus atmosphere deduced from Pioneer Venus multiprobe radio scintillations  

Microsoft Academic Search

The 2.3-GHz log-amplitude fluctuations observed in the radio links of the Pioneer Venus entry probes during Venus encounter have been used to study turbulence in the Venus atmosphere. The deduced estimates of the upper bound of the structure constant of the refractive index fluctuations (less than approximately 4 x 10 to the -8th\\/cu root cm) are inconsistent with similar entry

R. Woo; J. W. Armstrong; W. B. Kendall

1979-01-01

373

The structure of Mars lower atmosphere from Mars Express Radio Science (MaRS) occultation measurements  

NASA Astrophysics Data System (ADS)

The Mars Express Radio Science Experiment (MaRS) investigates the lower and middle atmosphere of Mars between the surface and about 40 km with a very high vertical resolution. More than 600 profiles of temperature, pressure, and neutral number density were retrieved between 2004 and 2011 covering four Martian years (MYs 27-30). Radio occultation experiments provide the unique possibility to retrieve geopotential height information to supplement temperature values. The temperature field in the northern winter hemisphere displays strong temperature inversions indicating a pronounced polar warming in the northern polar night (MY 27). The temperature and geopotential fields imply the presence of a strong zonal jet, with peak wind speeds of more than 170 m/s at an altitude of about 30 km (~15 Pa) and a latitude of 60-65°N. The longitudinal temperature and geopotential fields in the southern winter of Martian year 30 at latitudes between 49° and 69°S are dominated by a stationary zonal wave s = 1 structure in the lower atmosphere. Associated meridional wind fields retrieved by assuming geostrophic balance have amplitudes up to 12 m/s at the 200 Pa level. An investigation of small-scale atmospheric waves reveals enhanced gravity wave activity in the daytime atmosphere above elevated terrain and in the winter extratropics. Radio occultation experiments also provide unique insight into the structure of the planetary boundary layer. The deepest convective boundary layers, up to 10 km, are found over elevated terrain.

Tellmann, Silvia; PäTzold, Martin; HäUsler, Bernd; Hinson, D. P.; Tyler, G. Leonard

2013-02-01

374

Computer modeling of the optic-electronic system for deformation measurement of radio-telescope counter-reflector  

NASA Astrophysics Data System (ADS)

The metrological support of many measurement tasks requires measuring spatial position of some objects in respect to rigid base. The microwave radio-telescope development requires high-precision control of the position of the counterreflector. The construction elements weight and thermal deformation leads to changes of position and linear shift of each planar section in respect to ideal parabolic shape. In this case it is necessary to implement control system for measuring these deformations of the reflector. For determination of the actual shape of the reflector control objects (light-emitting diodes, LED) placed on the reflector, and their coordinates in respect to motionless construction element (base ring placed on the top main mirror) are measured by triangulation method using CCD camera, which determines vision angles of LEDs. Analysis of relations of primary errors of measurements and errors of determinations of actual coordinates of the reflectors confirm feasibility of the whole system of control of the shape of counter-reflector.

Kaliteevskiy, Ilya; Konyakhin, Igor

2008-10-01

375

Quantitative measurement of strain field in strained-channel-transistor arrays by scanning moiré fringe imaging  

NASA Astrophysics Data System (ADS)

We have applied scanning moiré fringe (SMF) imaging in scanning transmission electron microscopy (STEM) to the quantitative measurement of a strain field introduced in p-type channels of transistors with an embedded Si1-xGex source and drain. The compressive strain field parallel to the channels was revealed by the SMF image. We showed that the quantitative strain profile extracted from the SMF image was coincident with the independent measurement by a high-resolution STEM image. In addition, we demonstrated that the strain measurement by SMF imaging can be performed for an extended field of view that is larger than half a micrometer.

Kim, Suhyun; Kondo, Yukihito; Lee, Kyungwoo; Byun, Gwangsun; Jung Kim, Joong; Lee, Sunyoung; Lee, Kyupil

2013-07-01

376

Note: Radio frequency inductance-capacitance band-stop filter circuit to perform contactless conductivity measurements in pulsed magnetic fields  

NASA Astrophysics Data System (ADS)

We present a new technique to perform radio frequency (rf) contactless conductivity measurements in pulsed magnetic fields to probe different ground states in condensed matter physics. The new method utilizes a simple analog band-stop filter circuit implemented in a radio frequency transmission setup to perform contactless conductivity measurements. The new method is more sensitive than the other methods (e.g., the tunnel diode oscillator and the proximity detector oscillator) due to more sensitive dependence of the circuit resonance frequency on the tank circuit inductance (not the transmission line). More important, the new method is more robust than other methods when used to perform measurements in very high magnetic fields, works for a wide range of temperatures (i.e., 300 K-1.4 K) and is less sensitive to noise and mechanical vibrations during pulse magnet operation. The new technique was successfully applied to measure the Shubnikov-de Haas effect in Bi2Se3 in pulsed magnetic fields of up to 60 T.

Altarawneh, M. M.

2012-09-01

377

Two channel laser speckle instrument for biological microflow localization and velocity measurements  

Microsoft Academic Search

Laser speckle instrument for real-time capillary flow velocity measurements is described. The instrument is developed for investigation of lymph flow dynamics in transillumination geometry simultaneously with microscopic examination of rat lymfangions. The use of two independent channels of laser speckle registration allows both to measure flow velocity and to localize centerline flow along the probing beam direction with several micrometers

Ivan V. Fedosov; Valery V. Tuchin

2005-01-01

378

A spatial diversity system to measure optical fading in an underwater communications channel  

Microsoft Academic Search

A two transmitter two receiver spatial diversity system was built for measuring and characterizing fading in underwater optical communication channels. The system allows the collection of laboratory generated interruptions of the optical beam from turbulence, particles, and bubbles. The data collected is characterized using fading metrics developed for atmospheric measurements. Spatial diversity is shown to decrease the amount of fading

Jim A. Simpson; Brian L. Hughes; John F. Muth

2009-01-01

379

tau polarisation measurement in the tau yields pi nu channel.  

National Technical Information Service (NTIS)

A measurement of the polarisation of (tau)'s produced by Z(sup 0) yields (tau)(sup +) (tau)(sup -) using the decay mode (tau) yields (pi) (nu) (sub (tau)) is presented. The present experiment was carried out using the ALEPH detector at the LEP collider at...

F. Zomer

1991-01-01

380

Multifrequency channel microwave reflectometer with frequency hopping operation for density fluctuation measurements in Large Helical Device.  

PubMed

In order to measure the internal structure of density fluctuations using a microwave reflectometer, the broadband frequency tunable system, which has the ability of fast and stable hopping operation, has been improved in the Large Helical Device. Simultaneous multipoint measurement is the key issue of this development. For accurate phase measurement, the system utilizes a single sideband modulation technique. Currently, a dual channel heterodyne frequency hopping reflectometer system has been constructed and applied to the Alfve?n eigenmode measurements. PMID:21033938

Tokuzawa, T; Ejiri, A; Kawahata, K

2010-10-01

381

Multifrequency channel microwave reflectometer with frequency hopping operation for density fluctuation measurements in Large Helical Device  

NASA Astrophysics Data System (ADS)

In order to measure the internal structure of density fluctuations using a microwave reflectometer, the broadband frequency tunable system, which has the ability of fast and stable hopping operation, has been improved in the Large Helical Device. Simultaneous multipoint measurement is the key issue of this development. For accurate phase measurement, the system utilizes a single sideband modulation technique. Currently, a dual channel heterodyne frequency hopping reflectometer system has been constructed and applied to the Alfvén eigenmode measurements.

Tokuzawa, T.; Ejiri, A.; Kawahata, K.

2010-10-01

382

Transatlantic Radio Telephone Transmission  

Microsoft Academic Search

The paper reports upon measurements of trans-Atlantic radio transmission which had been made during the past two years in a study of the possibilities of trans-Atlantic radio telephony. These measurements cover several different frequencies in the range below 60 kilocycles in both directions across the Atlantic and represent probably the most comprehensive study yet made of any transmission path. An

L. Espenschied; C. N. Anderson; A. Bailey

1926-01-01

383

Ultra-wideband channel model for communication around the human body  

Microsoft Academic Search

Using ultra-wideband (UWB) wireless sensors placed on a person to continuously monitor health information is a promising new application. However, there are currently no detailed models describing the UWB radio channel around the human body making it difficult to design a suitable communication system. To address this problem, we have measured radio propagation around the body in a typical indoor

Andrew Fort; Julien Ryckaert; Claude Desset; Philippe De Doncker; Piet Wambacq; Leo Van Biesen

2006-01-01

384

Radio-frequency measurements of UNiX compounds (X= Al, Ga, Ge) in high magnetic fields  

SciTech Connect

We performed radio-frequency (RF) skin-depth measurements of antiferromagnetic UNiX compounds (X=Al, Ga, Ge) in magnetic fields up to 60 T and at temperatures between 1.4 to {approx}60 K. Magnetic fields are applied along different crystallographic directions and RF penetration-depth was measured using a tunnel-diode oscillator (TDO) circuit. The sample is coupled to the inductive element of a TDO resonant tank circuit, and the shift in the resonant frequency {Delta}f of the circuit is measured. The UNiX compounds exhibit field-induced magnetic transitions at low temperatures, and those transitions are accompanied by a drastic change in {Delta}f. The results of our skin-depth measurements were compared with previously published B-T phase diagrams for these three compounds.

Mielke, Charles H [Los Alamos National Laboratory; Mcdonald, David R [Los Alamos National Laboratory; Zapf, Vivien [Los Alamos National Laboratory; Altarawneh, Moaz M [Los Alamos National Laboratory; Lacerda, Alex H [Los Alamos National Laboratory; Adak, Sourav [Los Alamos National Laboratory; Karunakar, Kothapalli [Los Alamos National Laboratory; Nakotte, Heinrich [Los Alamos National Laboratory; Chang, S [NIST; Alsmadi, A M [HASHEMITE UNIV; Alyones, S [HASHEMIT UNIV

2009-01-01

385

Frequency Allocation; The Radio Spectrum.  

ERIC Educational Resources Information Center

|The Federal Communications Commission (FCC) assigns segments of the radio spectrum to categories of users, and specific frequencies within each segment to individual users. Since demand for channel space exceeds supply, the process is complex. The radio spectrum can be compared to a long ruler: the portion from 10-540 kiloHertz has been set aside…

Federal Communications Commission, Washington, DC.

386

Measurements of the Suitability of Large Rock Salt Formations for Radio Detection of High-Energy Neutrinos  

SciTech Connect

We have investigated the possibility that large rock salt formations might be suitable as target masses for detection of neutrinos of energies about 10 PeV and above. In neutrino interactions at these energies, the secondary electromagnetic cascade produces a coherent radio pulse well above ambient thermal noise via the Askaryan effect. We describe measurements of radio-frequency attenuation lengths and ambient thermal noise in two salt formations. Measurements in the Waste Isolation Pilot Plant (WIPP), located in an evaporite salt bed in Carlsbad, NM yielded short attenuation lengths, 3-7 m over 150-300 MHz. However, measurements at United Salt's Hockley mine, located in a salt dome near Houston, Texas yielded attenuation lengths in excess of 250 m at similar frequencies. We have also analyzed early ground-penetrating radar data at Hockley mine and have found additional evidence for attenuation lengths in excess of several hundred meters at 440 MHz. We conclude that salt domes, which may individually contain several hundred cubic kilometer water-equivalent mass, provide attractive sites for next-generation high-energy neutrino detectors.

Odian, Allen C.

2001-09-14

387

Polarized foreground removal at low radio frequencies using rotation measure synthesis: uncovering the signature of hydrogen reionization  

NASA Astrophysics Data System (ADS)

Measurement of redshifted 21-cm emission from neutral hydrogen promises to be the most effective method for studying the reionization history of hydrogen and, indirectly, the first galaxies. These studies will be limited not by raw sensitivity to the signal, but rather, by bright foreground radiation from Galactic and extragalactic radio sources and the Galactic continuum. In addition, leakage due to gain errors and non-ideal feeds conspire to further contaminate low-frequency radio observations. This leakage leads to a portion of the complex linear polarization signal finding its way into Stokes I, and inhibits the detection of the non-polarized cosmological signal from the epoch of reionization. In this work, we show that rotation measure synthesis can be used to recover the signature of cosmic hydrogen reionization in the presence of contamination by polarized foregrounds. To achieve this, we apply the rotation measure synthesis technique to the Stokes I component of a synthetic data cube containing Galactic foreground emission, the effect of instrumental polarization leakage and redshifted 21-cm emission by neutral hydrogen from the epoch of reionization. This produces an effective Stokes I Faraday dispersion function for each line of sight, from which instrumental polarization leakage can be fitted and subtracted. Our results show that it is possible to recover the signature of reionization in its late stages (z? 7) by way of the 21-cm power spectrum, as well as through tomographic imaging of ionized cavities in the intergalactic medium.

Geil, Paul M.; Gaensler, B. M.; Wyithe, J. Stuart B.

2011-11-01

388

Radio determination satellite service  

NASA Astrophysics Data System (ADS)

The capabilities and measured performance of a geosynchronous satellite-based service called the radio determination satellite service (RDSS), which operates at radio frequencies allocated by the International Telecommunications Union (ITU) and is licensed in the United States by the Federal Communications Commission (FCC), are discussed. Plans for both improvement in capability and expansion to nearly global coverage are described. Since RDSS can also provide radio navigation, some comparisons of this service with the Global Positioning System (GPS) are made.

Briskman, Robert D.

1990-07-01

389

Long-Range Channel Prediction Based on Nonstationary Parametric Modeling  

Microsoft Academic Search

Motivated by the analysis of measured radio channels and recently published physics-based scattering SISO and MIMO channel models, a new approach of long-range channel prediction based on nonstationary multicomponent polynomial phase signals (MC-PPS) is proposed. An iterative and recursive method for detecting the number of signals and the orders of the polynomial phases is proposed. The performance of these detectors

Ming Chen; Mats Viberg

2009-01-01

390

The Radio-2 mm Spectral Index of the Crab Nebula Measured with Gismo  

NASA Astrophysics Data System (ADS)

We present results of 2 mm observations of the Crab Nebula, obtained using the Goddard-IRAM Superconducting 2 Millimeter Observer (GISMO) bolometer camera on the IRAM 30 m telescope. Additional 3.3 mm observations with the MUSTANG bolometer array on the Green Bank Telescope are also presented. The integrated 2 mm flux density of the Crab Nebula provides no evidence for the emergence of a second synchrotron component that has been proposed. It is consistent with the radio power-law spectrum, extrapolated up to a break frequency of log (? b [GHz]) = 2.84 ± 0.29 or ? b = 695+651 - 336 GHz. The Crab Nebula is well resolved by the ~16farcs7 beam (FWHM) of GISMO. Comparison to radio data at comparable spatial resolution enables us to confirm significant spatial variation of the spectral index between 21 cm and 2 mm. The main effect is a spectral flattening in the inner region of the Crab Nebula, correlated with the toroidal structure at the center of the nebula that is prominent in the near-IR through X-ray regime. Based on observations carried out with the IRAM 30 m Telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain).

Arendt, R. G.; George, J. V.; Staguhn, J. G.; Benford, D. J.; Devlin, M. J.; Dicker, S. R.; Fixsen, D. J.; Irwin, K. D.; Jhabvala, C. A.; Korngut, P. M.; Kovács, A.; Maher, S. F.; Mason, B. S.; Miller, T. M.; Moseley, S. H.; Navarro, S.; Sievers, A.; Sievers, J. L.; Sharp, E.; Wollack, E. J.

2011-06-01

391

System integration and radiation pattern measurements of a phased array antenna employing an integrated photonic beamformer for radio astronomy applications.  

PubMed

In this paper we describe the system integration and the experimental demonstration of a photonically beamformed four-element receiving array antenna for radio astronomy applications. To our knowledge, the work described here is the first demonstration of the squint-free, continuously tunable beamsteering capability offered by an integrated photonic beamformer based on optical ring resonator true-time-delay units, with measured radiation patterns. The integrated beamformer is realized in a low loss, complementary metal-oxide-semiconductor (CMOS) compatible optical waveguide technology. The measurements show a wideband, continuous beamsteering operation over a steering angle of 23.5 degrees and an instantaneous bandwidth of 500 MHz limited only by the measurement setup. PMID:22410879

Burla, Maurizio; Roeloffzen, Chris G H; Zhuang, Leimeng; Marpaung, David; Khan, Muhammad Rezaul; Maat, Peter; Dijkstra, Klaas; Leinse, Arne; Hoekman, Marcel; Heideman, René

2012-03-01

392

An experimental electrical parameter measuring system for an asymmetric capacitive radio frequency discharge excited copper ion laser  

NASA Astrophysics Data System (ADS)

An experimental system has been designed and built to study the electrical characteristics in an asymmetric capacitive coupled radio frequency (RF) discharge excited copper ion laser at moderate gas pressures. The system consists of laser chamber, thru-line integrated voltage and current probe, matching circuit and electrical measurement system. There are some results of electrical measurements carried out in a helium discharge at 13.56 MHz. Although this system has been specifically designed and built to measure the discharge parameter of the capacitive RF-excited copper ion laser in moderate-pressure helium gas, it can operate over a wide range of gas pressure and a wide range of driving frequency and gas components. It is simple, cheap, accurate and real-time.

Huang, Jianjun; Yu, Jianhua; Liu, Zhenzhi

2003-06-01

393

Confirmatory measurement channels for LIF-based bioaerosol instrumentation  

NASA Astrophysics Data System (ADS)

As part of the U.S. Department of Homeland Security Detect-to-Protect (DTP) program, a multilab [Sandia National Laboratories (SNL), Lawrence Livermore National Laboratories (LLNL), Pacific Northwest National Laboratory (PNNL), Oak Ridge National Laboratory (ORNL), and Los Alamos National Laboratory (LANL)] effort is addressing the need for useable detect-to-warn bioaerosol sensors for public facility protection. Towards this end, the SNL team is investigating the use of rapid fluorogenic staining to infer the protein content of bioaerosols. This is being implemented in a flow cytometer wherein each particle detected generates coincident signals of correlated forward scatter, side scatter, and fluorescence. Several thousand such coincident signal sets are typically collected to generate a distribution describing the probability of observing a particle with certain scattering and fluorescence values. These data are collected for sample particles in both a stained and unstained state. A linear unmixing analysis is performed to differentiate components in the mixture. In this paper, we discuss the implementation of the staining process and the cytometric measurement, the results of their application to the analysis of known and blind samples, and a potential instrumental implementations that would use staining.

Bisson, Scott E.; Crocker, Robert W.; Kulp, Thomas J.; Reichardt, Thomas A.; Reilly, Peter T. A.; Whitten, William B.

2008-05-01

394

A Measurement of the Top Quark Mass in the Dilepton Decay Channel at CDF II  

SciTech Connect

The top quark, the most recently discovered quark, is the most massive known fundamental fermion. Precision measurements of its mass, a free parameter in the Standard Model of particle physics, can be used to constrain the mass of the Higgs Boson. In addition, deviations in the mass as measured in different channels can provide possible evidence for new physics. We describe a measurement of the top quark mass in the decay channel with two charged leptons, known as the dilepton channel, using data collected by the CDF II detector from p{bar p} collisions with {radical}s = 1.96 TeV at the Fermilab Tevatron. The likelihood in top mass is calculated for each event by convolving the leading order matrix element describing q{bar q} {yields} t{bar t} {yields} b{ell}{nu}{sub {ell}}{bar b}{ell}'{nu}{sub {ell}'} with detector resolution functions. The presence of background events in the data sample is modeled using similar calculations involving the matrix elements for major background processes. In a data sample with integrated luminosity of 1.0 fb{sup -1}, we observe 78 candidate events and measure M{sub t} = 164.5 {+-} 3.9(stat.) {+-} 3.9(syst.) GeV/c{sup 2}, the most precise measurement of the top quark mass in this channel to date.

Jayatilaka, Bodhitha A.; /Michigan U.

2006-08-01

395

INVESTIGATING TECHNOLOGIES TO MONITOR OPEN-CHANNEL DISCHARGE BY DIRECT MEASUREMENT OF CROSS SECTIONAL AREA AND VELOCITY OF FLOW  

Microsoft Academic Search

The U.S. Geological Survey is investigating technologies that may enable the direct, continuous, noncontact measurement of open-channel discharge. Measurement of open-channel discharge could be achieved by monitoring bottom and surface elevation and flow velocity of open channels. These parameters have been individually measured using particle-image velocimetry, lasers, radar, and acoustics in related applications. The U.S. Geological Survey is planning research

N. B. MELCHER; R. T. CHENG; F. P. HAENI

396

Lightning return stroke current waveforms aloft from measured field change, current, and channel geometry  

NASA Astrophysics Data System (ADS)

Three-dimensional reconstructions of six rocket-triggered lightning channels are derived from stereo photographs. These reconstructed channels are used to infer the behavior of the current in return strokes above the ground from current waveforms measured at the channel base and electric field change waveforms measured at a range of 5.2 km for 24 return strokes in these channels. Streak photographs of 14 of the same strokes are analyzed to determine the risetimes, propagation speeds, and amplitudes of relative light intensity for comparison with the electrical inferences. Results include the following: (1) The fine structure of the field change waveforms that were radiated by these subsequent return strokes can be explained, in large part, by channel geometry. (2) The average 10-90% risetime of the stroke current increased by about a factor of seven in our sample, from an observed 0.31 ± 0.17 ?s at the surface to an inferred 2.2 ± 0.5 ?s at 1 km path length above the surface. (3) The three-dimensional propagation speed of the current front averaged 1.80 ± 0.24 × 108 m/s over channel lengths typically greater than 1 km. (4) Assuming that the measured current was entirely due to the return stroke forced an unreasonably large and abrupt reduction in inferred current amplitude over the first few tens of meters above the surface, especially in cases when the leader was bright relative to its stroke. Therefore a significant fraction of the current at the surface was probably due to the leader in such cases. (5) Independent of the above, peak return stroke currents decreased by approximately 37 ± 12% between 100 m and 1 km of path length above the surface. Because of uncertainty about how to partition the measured current between leader and return stroke, however, we are unable to infer the variation of current amplitude near the ground.

Willett, J. C.; Le Vine, D. M.; Idone, V. P.

2008-04-01

397

Magnetic induction measurements with a six channel coil array for vital parameter monitoring.  

PubMed

Vital parameter monitoring on neonatal intensive care units is essential but very stressful for patients during daily routine care. For contact-less monitoring of breathing and heart activity, magnetic induction measurements are applicable in research scenarios. For monitoring both vital parameters in newborn intensive care wards, we developed a Multi Channel Simultaneous Magnetic Induction Measurement System (MUSIMITOS2+). In this article we now evaluate the technical requirements of a coil array for vital parameter monitoring and finally present a multichannel coil array with 6 excitation and measurement channels combined as axial gradiometers for the specific measurement scenario. This array will be stored underneath the child. As a test case we will present data of a animal trial with the described coil array and the measurement device MUSIMITOS2+. PMID:23365964

Cordes, Axel; Heimann, Konrad; Leonhardt, Steffen

2012-01-01

398

Real human body measurements, model, and simulations of a 2.45 GHz wireless body area network communication channel  

Microsoft Academic Search

In this paper, the propagation channel between two half-wavelength dipoles at 2.45 GHz, placed near a human body is studied. Measurements are performed on a real human, considering different parts of the body separately. The measurement results are compared with FDTD simulations, using an anatomically correct model of the human body. Channel characteristics are extracted from the measurement and simulation

E. Reusens; W. Joseph; G. Vermeeren; D. Kurup; L. Martens

2008-01-01

399

A micromachined Kelvin probe for surface potential measurements in microfluidic channels and solid-state applications  

Microsoft Academic Search

This paper reports on a micromachined Kelvin probe structure with integrated scanning tip and dither actuation mechanism. It is fabricated by a modified micro electro-discharge machining process which allows electrical isolation within the micromachined structure using epoxy plugs. The device is used to measure changes in the external surface potential of a parylene microfluidic channel as a function of varying

L. L. Chu; K. Takahata; P. Selvaganapathy; J. L. Shohet; Y. B. Gianchandani

2003-01-01

400

Measurements of MIMO Indoor Channels at 1800 MHz with Multiple Indoor and Outdoor Base Stations  

Microsoft Academic Search

This paper proposes several configurations for multiple base stations in indoor MIMO systems and compares their performance. The results are based on channel measurements realized with a MIMO testbed. The receiver was moved along several routes and floors on an office building. Both outdoor and indoor locations are considered for the transmitters or base stations, which allows the analysis of

Laura García; Niklas Jalden; Björn Lindmark; Per Zetterberg; Leandro de Haro-Ariet

2007-01-01

401

A Measure of Distributive Justice in Distribution Channels: Scale Development and Validation  

Microsoft Academic Search

The construct of distributive justice has been conceptualized largely along the three allocation rules of equity, equality, and need. Extant empirical research in the marketing channels area, however, treats distributive justice as a unidimensional, global construct focusing almost exclusively on the allocation rule of equity. As a result, the measurement of equality and need, two distinct and significant allocation rules,

Vishal Kashyap; Chris Manolis; Thomas G. Brashear

2008-01-01

402

Class of algorithms for decoding block codes with channel measurement information  

Microsoft Academic Search

A class of decoding algorithms that utilizes channel measurement information, in addition to the conventional use of the algebraic properties of the code, is presented. The maximum number of errors that can, with high probability, be corrected is equal to one less thand, the minimum Hamming distance of the code. This two-fold increase over the error-correcting capability of a conventional

DAVID CHASE

1972-01-01

403

Implications of the Measured Image Size for the Radio Afterglow of GRB 030329  

SciTech Connect

We use data on the image size of the radio afterglow of GRB 030329 (Taylor et al. 2004) to constrain the physical parameters of this explosion. Together with the observed broad band spectrum, this data over-constrains the physical parameters, thus enabling to test different GRB jet models for consistency. We consider two extreme models for the lateral spreading of the jet: model 1 with relativistic expansion in the local rest frame, and model 2 with little lateral expansion as long as the jet is highly relativistic. We find that both models are consistent with the data for a uniform external medium, while for a stellar wind environment model 1 is consistent with the data but model 2 is disfavored by the data. Our derivations can be used to place tighter constraints on the dynamics and structure of GRB jets in future afterglows, following a denser monitoring campaign for the temporal evolution of their image size.

Granot, J.

2005-01-05

404

Gating Transitions in Bacterial Ion Channels Measured at 3 ?s Resolution  

PubMed Central

Ion channels of high conductance (>200 pS) are widespread among prokaryotes and eukaryotes. Two examples, the Escherichia coli mechanosensitive ion channels Ec-MscS and Ec-MscL, pass currents of 125–300 pA. To resolve temporal details of conductance transitions, a patch-clamp setup was optimized for low-noise recordings at a time resolution of 3 ?s (10–20 times faster than usual). Analyses of the high-resolution recordings confirm that Ec-MscL visits many subconductance states and show that most of the intersubstate transitions occur more slowly than the effective resolution of 3 ?s. There is a clear trend toward longer transition times for the larger transitions. In Ec-MscS recordings, the majority of the observed full conductance transitions are also composite. We detected a short-lived (?20 ?s) Ec-MscS substate at 2/3 of full conductance; transitions between 2/3 and full conductance did not show fine structure and had a time course limited by the achieved resolution. Opening and closing transitions in MscS are symmetrical and are not preceded or followed by smaller, rapid currents (“anticipations” or “regrets”). Compared with other, lower-conductance channels, these measurements may detect unusually early states in the transitions from fully closed to fully open. Increased temporal resolution at the single-molecule level reveals that some elementary steps of structural transitions are composite and follow several alternative pathways, while others still escape resolution. High-bandwidth, low-noise single-channel measurements may provide details about state transitions in other high-conductance channels; and similar procedures may also be applied to channel- and nanopore-based single-molecule DNA measurements.

Shapovalov, George; Lester, Henry A.

2004-01-01

405

Measurements of energetic helium-3 minority distributions during ion cyclotron radio-frequency heating in the Princeton Large Torus  

SciTech Connect

Ion cyclotron radio-frequency heating experiments were performed with a /sup 3/He minority ion species in a /sup 4/He majority plasma in the Princeton Large Torus. The energetic /sup 3/He ion ''tail'' was measured directly with a charge exchange neutral analyzer for the first time. Comparisons with bounce-averaged quasi-linear calculations suggest a modestly peaked radi-frequency power deposition profile. The double charge exchange process /sup 3/He/sup + +/ )plus) /sup 4/He/sup 0/ )plus) /sup 3/He/sup 0/ )plus) /sup 4/He/sup + +/ demonstrated in these measurements may be useful as part of an alpha particle diagnostic in a fusion reactor experiment. 18 refs., 4 figs.

Hammett, G.W.; Kaita, R.; Wilson, J.R.

1988-03-01

406

Direct measurement of single-channel Ca2+ currents in bullfrog hair cells reveals two distinct channel subtypes  

PubMed Central

To confer their acute sensitivity to mechanical stimuli, hair cells employ Ca2+ ions to mediate sharp electrical tuning and neurotransmitter release. We examined the diversity and properties of voltage-gated Ca2+ channels in bullfrog saccular hair cells by means of perforated and cell-attached patch-clamp techniques. Whole-cell Ca2+ current records provided hints that hair cells express L-type as well as dihydropyridine-insensitive Ca2+ currents.Single Ca2+ channel records confirmed the presence of L-type channels, and a distinct Ca2+ channel, which has sensitivity towards ?-conotoxin GVIA. Despite its sensitivity towards ?-conotoxin GVIA, the non-L-type channel cannot necessarily be considered as an N-type channel because of its distinct voltage-dependent gating properties.Using 65 mm Ca2+ as the charge carrier, the L-type channels were recruited at about –40 mV and showed a single-channel conductance of 13 pS. Under similar recording conditions, the non-L-type channels were activated at ?–60 mV and had a single-channel conductance of ?16 pS.The non-L-type channel exhibited at least two fast open time constants (?o = 0.2 and 5 ms). In contrast, the L-type channels showed long openings (?o =?23 ms) that were enhanced by Bay K 8644, in addition to the brief openings (?o = 0.3 and 10 ms).The number of functional channels observed in patches of similar sizes suggests that Ca2+ channels are expressed singly, in low-density clusters (2–15 channels) and in high-density clusters (20–80 channels). Co-localization of the two channel subtypes was observed in patches containing low-density clusters, but was rare in patches containing high-density clusters.Finally, we confirmed the existence of two distinct Ca2+ channel subtypes by using immunoblot and immunohistochemical techniques.

Rodriguez-Contreras, Adrian; Yamoah, Ebenezer N

2001-01-01

407

Radio interferometric geolocation  

Microsoft Academic Search

We present a novel radio interference based sensor localization method for wireless sensor networks. The technique relies on a pair of nodes emitting radio waves simultaneously at slightly different frequencies. The carrier frequency of the composite signal is between the two frequencies, but has a very low frequency envelope. Neighboring nodes can measure the energy of the envelope signal as

Miklós Maróti; Péter Völgyesi; Sebestyén Dóra; Branislav Kusý; András Nádas; Ákos Lédeczi; György Balogh; Károly Molnár

2005-01-01

408

Film, Radio, and Television.  

ERIC Educational Resources Information Center

|This journal issue covers the history of film, radio, and television in Iowa. The first article, "When Pictures and Sound Came to Iowa," summarizes the origin of movies and radio and their early beginnings in Iowa. Using old photographs and measurement charts, the viewing, reading, and listening habits of young people in 1950 and 1958 are…

Hardesty, Carolyn, Ed.

1990-01-01

409

Characterization of Ionospheric Scintillation Using Simultaneous Formosat-3/COSMIC Radio Occultation Observations and AFRL SCINDA Ground Scintillation Measurements  

NASA Astrophysics Data System (ADS)

Ionospheric scintillation at low latitudes has been studied using ionospheric radio occultation (RO) measurements by the FORMOSAT-3/COSMIC micro-satellites in conjunction with ground-based data from the Scintillation Network Decision Aid (SCINDA) station at Kwajalein Atoll. The Air Force Research Laboratory has developed the SCINDA network for monitoring low-latitude ionospheric total electron content (TEC) and scintillation associated with equatorial spread F. The network currently consists of sixteen stations distributed around the globe and the data have been used to conduct numerous studies on the characteristics and climatology of equatorial scintillation. The present study focuses on COSMIC RO and SCINDA data during the three COSMIC campaigns in 2006. Radio occultation events are selected by requiring that ionospheric scintillation was detected by the SCINDA VHF scintillation monitor at Kwajalein, and that the occultation ray path intersected the Kwajalein longitude below the satellite altitude, which varied from 500 to 800 km for the six FORMOSAT-3 satellites. In order to exclude tropospheric effects, only GPS signal amplitudes from FORMOSAT-3 with ray path tangent altitudes above 100 km are considered. Locations of ionospheric scintillation are estimated by triangulation using the satellites and the SCINDA ground station. Airglow images at Kwajalein are also used to confirm occurrence of equatorial ionospheric scintillations. For the selected events, large amplitude L1 and L2 scintillations tend to occur at altitudes below 200 km at frequencies around 0.5 Hz. The results are discussed as a potential path toward better specifying the occurrence of equatorial scintillations.

Starks, M. J.; Lin, C. S.; Groves, K. M.; Pedersen, T. R.; Basu, S.; Syndergaard, S.; Rocken, C.

2007-05-01

410

Design and measurements of 64-channel ASIC for neural signal recording.  

PubMed

This paper presents the design and measurements of a low noise multi-channel front-end electronics for recording extra-cellular neuronal signals using microelectrode arrays. The integrated circuit contains 64 readout channels and was fabricated in CMOS 0.18 microm technology. A single readout channel is built of an AC coupling circuit at the input, a low noise preamplifier, a band-pass filter and a second amplifier. In order to reduce the number of output lines, the 64 analog signals from readout channels are multiplexed to a single output by an analog multiplexer. The chip is optimized for low noise and matching performance with the possibility of cut-off frequencies tuning. The low cut-off frequency can be tuned in the 1 Hz-60 Hz range and the high cut-off frequency can be tuned in the 3.5 kHz-15 kHz range. For the nominal gain setting at 44 dB and power dissipation per single channel of 220 microW the equivalent input noise is in the range from 6 microV-11 microV rms depending on the band-pass filter settings. The chip has good uniformity concerning the spread of its electrical parameters from channel to channel. The spread of gain calculated as standard deviation to mean value is about 4.4% and the spread of the low cut-off frequency is on the same level. The chip occupies 5x2.3 mm(2) of silicon area. PMID:19964226

Kmon, P; Zoladz, M; Grybos, P; Szczygiel, R

2009-01-01

411

Dust particle size measurement by the multi-channel laser light scattering method  

Microsoft Academic Search

The measurement of the spatial distribution of dust particle size was performed by the multi-channel laser light scattering method. To self-consistently determine the time evolution of the particle size, in-situ polarization-sensitive laser light scattering was used using a 30 mW He-Ne laser. Polarization light intensities (incident and scattered light intensities with the same polarization) were measured at 71 . Before

W. Choe; C. R. Seon; K. B. Chai; H. Y. Park; Y. H. Shin; K. H. Chung

2006-01-01

412

Measurement and research of channel noise distributed characterization in low voltage networks  

Microsoft Academic Search

In this paper, measurement and research of noise characterizations in three-phase four-wire low voltage power network channels are carried out. The power networks have overhead conductor structures. Measurement frequency is from 1 kHz to 1 MHz. The studies include noise classification and load characterizations, noise distribution characterization along the power lines and noise distribution characterization when coupling across different phases.

Yang Xiaoxian; Zheng Tao; Zhang Baohui

2005-01-01

413

Current Perception Threshold Measurement via Single Channel Electroencephalogram Based on Confidence Algorithm  

Microsoft Academic Search

\\u000a A new algorithm for pattern recognition for current perception threshold measurement is proposed. Because of risk-sensitiveness\\u000a of medical diagnosis, the current perception threshold requires the prediction to be qualified with confidence. Using confidence\\u000a support vector machine, the current perception threshold measurement via single channel electroencephalogram is confident\\u000a and credible. Experimental results demonstrate the proposed algorithm is effective.

You Wang; Yi Qiu; Yuping Miao; Guiping Dai; Guang Li

2010-01-01

414

Calcium Cooperativity of Exocytosis as a Measure of Ca2+ Channel Domain Overlap  

PubMed Central

The number of Ca2+ channels contributing to the exocytosis of a single neurotransmitter vesicle in a presynaptic terminal has been a question of significant interest and debate, and is important for a full understanding of localized Ca2+ signaling in general, and synaptic physiology in particular. This is usually estimated by measuring the sensitivity of the neurotransmitter release rate to changes in the synaptic Ca2+ current, which is varied using appropriate voltage-clamp protocols or via pharmacological Ca2+ channel block under the condition of constant single-channel Ca2+ current. The slope of the resulting log-log plot of transmitter release rate versus presynaptic Ca2+ current is termed Ca2+ current cooperativity of exocytosis, and provides indirect information about the underlying presynaptic morphology. In this review, we discuss the relationship between the Ca2+ current cooperativity and the average number of Ca2+ channels participating in the exocytosis of a single vesicle, termed the Ca2+ channel cooperativity. We relate these quantities to the morphology of the presynaptic active zone. We also review experimental studies of Ca2+ current cooperativity and its modulation during development in different classes of synapses.

Matveev, Victor; Bertram, Richard; Sherman, Arthur

2011-01-01

415

Effects of horizontal velocity variations on ultrasonic velocity measurements in open channels  

USGS Publications Warehouse

Use of an ultrasonic velocity meter to determine discharge in open channels involves measuring the velocity in a line between transducers in the stream and relating that velocity to the average velocity in the stream. The standard method of calculating average velocity in the channel assumes that the velocity profile in the channel can be represented by the one-dimensional von Karman universal velocity profile. However, the velocity profile can be described by a two-dimensional equation that accounts for the horizontal velocity variations induced by the channel sides. An equation to calculate average velocity accounts for the two-dimensional variations in velocity within a stream. The use of this new equation to calculate average velocity was compared to the standard method in theoretical trapezoidal cross sections and in the L-31N and Snapper Creek Extension Canals near Miami, Florida. These comparisons indicate that the two-dimensional variations have the most significant effect in narrow, deep channels. Also, the two-dimensional effects may be significant in some field situations and need to be considered when determining average velocity and discharge with an ultrasonic velocity meter.

Swain, E. D.

1992-01-01

416

Fading channel simulator  

DOEpatents

This invention relates to high frequency (HF) radio signal propagation through fading channels and, more particularly, to simulation of fading channels in order to characterize HF radio system performance in transmitting and receiving signals through such fading channels. Fading channel effects on a transmitted communication signal are simulated with both frequency and time variations using a channel scattering function to affect the transmitted signal. A conventional channel scattering function is converted to a series of channel realizations by multiplying the square root of the channel scattering function by a complex number of which the real and imaginary parts are each independent variables. The two-dimensional inverse-FFT of this complex-valued channel realization yields a matrix of channel coefficients that provide a complete frequency-time description of the channel. The transmitted radio signal is segmented to provide a series of transmitted signal and each segment is subject to FFT to generate a series of signal coefficient matrices. The channel coefficient matrices and signal coefficient matrices are then multiplied and subjected to inverse-FFT to output a signal representing the received affected radio signal. A variety of channel scattering functions can be used to characterize the response of a transmitter-receiver system to such atmospheric effects.

Argo, P.E.; Fitzgerald, T.J.

1991-12-31

417

Accurate Permittivity Measurement Using the Cavity Perturbation Technique at ISM 5.8GHz Radio Band  

Microsoft Academic Search

In this paper, a new calibration method with two-filling factors for the permittivity measurement is proposed. With this calibration method, it is not necessary to measure the volume of the small sample, which not only eliminates the measurement error of the sample volume, but also simplifies the measurement procedure. To improve the measurement accuracy, the Cursor method, the resonance curve

Yan Ye; Taijun Liu; Xingbin Zeng; Jiaming He; C. Akyel

2007-01-01

418

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

419

On the occurrence of equatorial F-region irregularities during solar minimum using radio occultation measurements  

NASA Astrophysics Data System (ADS)

The technique of radio occultation (RO) is demonstrated to be a powerful tool for studying equatorial F-region irregularities (EFIs) associated with equatorial plasma bubbles. The extensive 4.9 year RO dataset of the Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) satellites was employed in this study and contains EFI observations under a wide variety of solar and geomagnetic conditions. From an analysis of the EFI occurrence dependence on season/longitude, it is found that the EFI occurrence statistics largely match those reported previously, with the exception of an equinoctial EFI occurrence maximum in the American sector that is absent from previous studies. It is revealed that this maximum is due to enhanced EFI occurrence near the South Atlantic anomaly, where EFIs are expected to be suppressed by particle precipitation. An investigation into the solar activity dependence of the EFI occurrence characteristics revealed significant increases in the range of local times and latitudes with solar activity for most longitude sectors and seasons. Finally, the EFI suppression and enhancement effects of storm-time electric fields are also investigated using the COSMIC data.

Carter, B. A.; Zhang, K.; Norman, R.; Kumar, V. V.; Kumar, Sushil

2013-02-01

420

Least-squares harmonic estimation of the tropopause parameters using GPS radio occultation measurements  

NASA Astrophysics Data System (ADS)

In order to investigate temporal variations of the tropopause parameters, Least-Squares Harmonic Estimation (LS-HE) is applied to the time series of the tropopause temperatures and heights derived from Global Positioning System Radio Occultation (GPS RO) atmospheric profiles of CHAMP, GRACE and COSMIC missions from January 2006 until May 2010 in different regions of Iran. By applying the univariate LS-HE to the completely unevenly spaced time series of the tropopause temperatures and heights, annual and diurnal components are detected together with their higher harmonics. The multivariate LS-HE estimates the main periodic signals, particularly diurnal and semidiurnal cycles, more clearly than the univariate LS-HE. Mixing in the values of the tropopause height and temperature is seen to occur in winter at lower latitudes (around 30°) as a result of subtropical jet, and in summer at higher latitudes (36°-42°) as an effect of subtropical high. A bimodal pattern is observed in the frequency histograms of the tropopause heights, in which the primary modes for the southern and northern parts of Iran correspond to subtropical and extratropical heights, respectively.

Sharifi, Mohammad Ali; Sam Khaniani, Ali; Masoumi, Salim; Schmidt, Torsten; Wickert, Jens

2013-04-01

421

Measuring kinetics of complex single ion channel data using mean-variance histograms.  

PubMed Central

The measurement of single ion channel kinetics is difficult when those channels exhibit subconductance events. When the kinetics are fast, and when the current magnitudes are small, as is the case for Na+, Ca2+, and some K+ channels, these difficulties can lead to serious errors in the estimation of channel kinetics. I present here a method, based on the construction and analysis of mean-variance histograms, that can overcome these problems. A mean-variance histogram is constructed by calculating the mean current and the current variance within a brief "window" (a set of N consecutive data samples) superimposed on the digitized raw channel data. Systematic movement of this window over the data produces large numbers of mean-variance pairs which can be assembled into a two-dimensional histogram. Defined current levels (open, closed, or sublevel) appear in such plots as low variance regions. The total number of events in such low variance regions is estimated by curve fitting and plotted as a function of window width. This function decreases with the same time constants as the original dwell time probability distribution for each of the regions. The method can therefore be used: 1) to present a qualitative summary of the single channel data from which the signal-to-noise ratio, open channel noise, steadiness of the baseline, and number of conductance levels can be quickly determined; 2) to quantify the dwell time distribution in each of the levels exhibited. In this paper I present the analysis of a Na+ channel recording that had a number of complexities. The signal-to-noise ratio was only about 8 for the main open state, open channel noise, and fast flickers to other states were present, as were a substantial number of subconductance states. "Standard" half-amplitude threshold analysis of these data produce open and closed time histograms that were well fitted by the sum of two exponentials, but with apparently erroneous time constants, whereas the mean-variance histogram technique provided a more credible analysis of the open, closed, and subconductance times for the patch. I also show that the method produces accurate results on simulated data in a wide variety of conditions, whereas the half-amplitude method, when applied to complex simulated data shows the same errors as were apparent in the real data. The utility and the limitations of this new method are discussed. Images FIGURE 2 FIGURE 4 FIGURE 8 FIGURE 9

Patlak, J B

1993-01-01

422

State-of-the-Art Survey of Radio Frequencies Available for Tactical Battlefield Radios in Frequency Bands Above 30 MHz.  

National Technical Information Service (NTIS)

The combat radio used by the fighting units (battalion and below) of the U.S. Army is the Single Channel Ground/Air Radio System (SINCGARS). This radio system operates effectively except that the available bandwidth is insufficient to avoid channel conges...

A. R. Downs

1997-01-01

423

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

424

Experimental measurements in a radio frequency discharge heated supersonic flow: Evaluation of a potential electric propulsion thruster  

SciTech Connect

An operational radio frequency discharge-driven supersonic flow system, which utilizes an inductively and capacitively coupled plasma (ICCP) tube to produce high enthalpy source gas, is described. The ICCP coupled to a properly designed nozzle represents a potential electric propulsion device. The high gas temperatures achieved in the plasma discharge (> 5000 K) and the electrodeless nature of the tube's operation offers potentially high thruster performance coupled and long operational lifetime. A preliminary characterization of the current system was established using emission and probe-based measurements. A nominal peak specific impulse of 155 s was estimated for operation with argon. The calculated thrust based upon the peak velocity and mass flow through the device is 1.1 N. 14 refs., 10 figs.

Wantuck, P.J.; Hull, D.E.

1991-01-01

425

Precision mass measurements of very short-lived, neutron-rich Na isotopes using a radio-frequency spectrometer  

NASA Astrophysics Data System (ADS)

Mass measurements of high precision have been performed on sodium isotopes out to 30Na using a new technique of radio-frequency excitation of ion trajectories in a homogeneous magnetic field. This method, especially suited to very short-lived nuclides, has allowed us to significantly reduce the uncertainty in mass of the most exotic Na isotopes: a relative error of 5×10-7 was achieved for 28Na having a half-life of only 30.5 ms and 9×10-7 for the weakly produced 30Na. Verifying and minimizing binding energy uncertainties in this region of the nuclear chart is important for clarification of a long-standing problem concerning the strength of the N=20 magic shell closure. These results are the fruit of the commissioning of the new experimental program MISTRAL.

Lunney, D.; Audi, G.; Doubre, H.; Henry, S.; Monsanglant, C.; de Saint Simon, M.; Thibault, C.; Toader, C.; Borcea, C.; Bollen, G.; ISOLDE Collaboration

2001-11-01

426

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

427

Sensitivity analysis of a new SWIR-channel measuring tropospheric CH4 and CO from space  

NASA Astrophysics Data System (ADS)

In preparation for future atmospheric space missions a consortium of Dutch organizations is performing design studies on a nadir viewing grating-based imaging spectrometer using OMI and SCIAMACHY heritage. The spectrometer measures selected species (O3, NO2, HCHO, H2O, SO2, aerosols (optical depth, type and absorption index), CO and CH4) with sensitivity down to the Earth's surface, thus addressing science issues on air quality and climate. It includes 3 UV-VIS channels continuously covering the 270-490 nm range, a NIR-channel covering the 710-775 nm range, and a SWIR-channel covering the 2305-2385 nm range. This instrument concept is, named TROPOMI, part of the TRAQ-mission proposal to ESA in response to the Call for Earth Explorer Ideas 2005, and, named TROPI, part of the CAMEO-proposal prepared for the US NRC decadal study-call on Earth science and applications from space. The SWIR-channel is optional in the TROPOMI/TRAQ instrument and included as baseline in the TROPI/CAMEO instrument. This paper focuses on derivation of the instrument requirements of the SWIR-channel by presenting the results of retrieval studies. Synthetic detector spectra are generated by the combination of a forward model and an instrument simulator that includes the properties of state-of-the-art detector technology. The synthetic spectra are input to the CO and CH4 IMLM retrieval algorithm originally developed for SCIAMACHY. The required accuracy of the Level-2 SWIR data products defines the main instrument parameters like spectral resolution and sampling, telescope aperture, detector temperature, and optical bench temperature. The impact of selected calibration and retrieval errors on the Level-2 products has been characterized. The current status of the SWIR-channel optical design with its demanding requirements on ground-pixel size, spectral resolution, and signal-to-noise ratio will be presented.

Jongma, Rienk T.; Gloudemans, Annemieke M. S.; Hoogeveen, Ruud W. M.; Aben, Ilse; de Vries, Johan; Escudero-Sanz, Isabel; van den Oord, Gijsbertus; Levelt, Pieternel F.

2006-09-01

428

Highly sensitive FBG temperature measurement based on a wavelength pumped multiplexing filter and two optical channels  

NASA Astrophysics Data System (ADS)

An improved demodulation system for fiber Bragg grating (FBG) sensors based on the wavelength pumped multiplexing (WPM) filter is presented. Double photoelectric measurement channels are exploited to compensate the surrounding and light source interference including temperature influence. Temperature testing is employed to prove the demodulation system capacity and characteristics. The digital thermometer and one free FBG are simultaneously introduced in the constant-temperature water tank for the comparison study. The results show that the demodulation scheme can measure temperature with a high resolution, stability and reliability. Its sensitivity of temperature measurement can reach 0.05 °C in repeated testing.

Jiang, Qi; Kang, Yan-Shen

2010-07-01

429

Capacity of the mobile MIMO channel for a small wireless handset and user influence  

Microsoft Academic Search

We obtained results on the capacity of a mobile MIMO channel and on the influence of the user. Measurements were done in a configuration with three distributed transmitters equipped with single antennas and with a small wireless handset with four antennas, creating a 4Rx × 3Tx configuration. We express the quality of the radio channel in terms of the effective

W. A. T. Kotterman; G. F. Pedersen; K. Olesen

2002-01-01

430

Measurement of the Top Quark Pair Production Cross Section in the All-Jets Decay Channel  

SciTech Connect

We present a measurement of t{ovr t} production in p{ovr p} collisions at {radical} (s) =1.8 TeV from 110 pb{sup {minus}1} of data collected in the all-jets decay channel with the D0 detector at Fermilab. A neural network analysis yields a cross section of 7.1{plus_minus}2.8(stat){plus_minus}1.5( syst) pb at a top quark mass (m{sub t}) of 172.1 GeV/c{sup 2} . Using previous D0 measurements from dilepton and single lepton channels, the combined D0 result for the t{ovr t} production cross section is 5.9{plus_minus}1.2(stat){plus_minus}1.1( syst) pb for m{sub t}=172.1 GeV /c{sup 2} . {copyright} {ital 1999} {ital The American Physical Society}

Grinstein, S.; Mostafa, M.; Piegaia, R. [Universidad de Buenos Aires, Buenos Aires (Argentina); Alves, G.A.; Carvalho, W.; Maciel, A.K.; da Motta, H.; Santoro, A. [LAFEX, Centro Brasileiro de Pesquisas Fisicas, Rio de Janeiro (Brazil); Lima, J.G.; Oguri, V. [Universidade do Estado do Rio de Janeiro, Rio de Janeiro (Brazil); Gomez, B.; Hoeneisen, B.; Mooney, P.; Negret, J.P. [Universidad de los Andes, Bogota (Colombia); Ducros, Y. [DAPNIA/Service de Physique des Particules, CEA, Saclay (France); Beri, S.B.; Bhatnagar, V.; Kohli, J.M.; Singh, J.B. [Panjab University, Chandigarh (India); Shivpuri, R.K. [Delhi University, Delhi (India); Acharya, B.S.; Banerjee, S.; Dugad, S.R.; Gupta, A.; Krishnaswamy, M.R.; Mondal, N.K.; Narasimham, V.S.; Parua, N.; Shankar, H.C. [Tata Institute of Fundamental Research, Mumbai (India); Park, Y.M. [Kyungsung University, Pusan (Korea); Choi, S.; Kim, S.K. [Seoul National University, Seoul (Korea); Castilla-Valdez, H.; Gonzalez Solis, J.L.; Hernandez-Montoya, R.; Magana-Mendoza, L.; Sanchez-Hernandez, A. [CINVESTAV, Mexico City (Mexico); Pawlik, B. [Institute of Nuclear Physics, Krakow (Poland); Gavrilov, V.; Gershtein, Y.; Kuleshov, S. [Institute for Theoretical and Experimental Physics, Moscow (Russia); Belyaev, A.; Dudko, L.V.; Ermolov, P.; Karmanov, D.; Leflat, A.; Manankov, V.; Merkin, M.; Shabalina, E. [Moscow State University, Moscow (Russia); Abramov, V.; Babintsev, V.V.; Bezzubov, V.A.; Bojko, N.I.; Burtovoi, V.S.; Chekulaev, S.V.; Denisov, S.P.; Dyshkant, A.; Eroshin, O.V.; Evdokimov, V.N.; Galyaev, A.N.; Goncharov, P.I.; Gurzhiev, S.N.; Kostritskiy, A.V.; Kozelov, A.V.; Kozlovsky, E.A.; Mayorov, A.A. [Institute for High Energy Physics, Protvino (Russia); Babukhadia, L.; Davis, K.; Fein, D.; Forden, G.E.; Guida, J.A.; Johns, K.; Nang, F.; Narayanan, A.; Rutherfoord, J.; Shupe, M. [University of Arizona, Tucson, Arizona 85721 (United States); Barberis, E.; Clark, A.R.; Dahl, O.I.; Grudberg, P.; and others

1999-09-01

431

Analysis of Global Positioning System (GPS) radio occultation measurement errors based on Satellite de Aplicaciones Cientificas-C (SAC-C) GPS radio occultation data recorded in open-loop and phase-locked-loop mode  

NASA Astrophysics Data System (ADS)

The error characteristics of Global Positioning System (GPS) radio occultation (RO) measurement errors are studied based on Satellite de Aplicaciones Cientificas-C (SAC-C) GPS radio occultation data tracked in both open-loop (OL) and phase-locked-loop (PLL) mode. The error characteristics are derived by applying dynamical error estimation, i.e., without using any external data. The computed error profiles show that the mean measurement errors are the smallest in the height range between about 5-7 km and 20-25 km, about 0.2-1% for bending angles and 0.1-0.2% for refractivity at all latitudes. The largest measurement errors are found in the lower troposphere, where the mean bending angle measurement errors are within the range from 1 to 6%, whereas the mean refractivity measurement errors are within the range from 0.2% to 1%. From the error distributions, it is found that the occultation-to-occultation variability of the measurement errors generally spans one order of magnitude. The bending angle error correlation length is about 1 km and 100 m, at high and low altitudes, respectively, corresponding approximately to the cutoff frequency of the applied noise filters. The widths of the refractivity error autocorrelation functions are notably broader. The variability and the magnitude of the OL measurement errors are larger than for the PLL measurement errors. This is mainly attributed to the ability of OL tracking to track RO signals under atmospheric conditions for which PLL tracking fails.

Lohmann, Martin S.

2007-05-01

432

Strain measurements in heteroepitaxial yttria-stabilized zirconia on Si by ion beam channeling  

Microsoft Academic Search

Yttria-stabilized zirconia (YSZ) films have been epitaxially grown on Si(100) substrates at 800 °C by vacuum evaporation. By post-annealing in dry O2 at 800 °C, SiO2 layer was formed at the YSZ\\/Si interface. Strain in heteroepitaxial cubic YSZ films has been measured by ion beam channeling. The strain was found to be tensile. This tensile strain is caused as the

Hirofumi Fukumoto; Masateru Yamamoto; Yukio Osaka; Fumitaka Nishiyama

1990-01-01

433

Twenty-channel grating polychromator for millimeter wave plasma emission measurements  

Microsoft Academic Search

A 20-channel grating instrument based on the Ebert–Fastie grating monochromator has been built to measure electron temperature profiles and electron temperature fluctuations in TFTR (tokamak fusion test reactor). Second-harmonic electron cyclotron emission for the plasma over the frequency range of 120–400 GHz is utilized; this corresponds to a central tokamak magnetic field of 2.9–5 T. System sensitivity is typically 10-eV

A. Cavallo; R. C. Cutler; M. P. McCarthy

1988-01-01

434

Twenty-channel grating polychromator for millimeter wave plasma emission measurements  

Microsoft Academic Search

A 20-channel grating instrument based on the Ebert--Fastie grating monochromator has been built to measure electron temperature profiles and electron temperature fluctuations in TFTR (tokamak fusion test reactor). Second-harmonic electron cyclotron emission for the plasma over the frequency range of 120--400 GHz is utilized; this corresponds to a central tokamak magnetic field of 2.9--5 T. System sensitivity is typically 10-eV

A. Cavallo; R. C. Cutler; M. P. McCarthy

1988-01-01

435

Prediction and measurement of incipient boiling heat flux in micro-channel heat sinks  

Microsoft Academic Search

Experiments were performed to measure the incipient boiling heat flux in a heat sink containing 21 rectangular (231 ?m wide and 713 ?m deep) micro-channels. Tests were performed using deionized water with inlet liquid velocities of 0.13–1.44 m\\/s, inlet temperatures of 30, 60 and 90 °C, and an outlet pressure of 1.2 bar. Using a microscope, boiling incipience was identified

Weilin Qu; Issam Mudawar

2002-01-01

436

The 400-channel commutator for measurement of energy distribution in laser beam  

NASA Astrophysics Data System (ADS)

An experimental study of a 400 channel commutator for measurement and analysis of the energy distribution over the beam cross section of pulse lasers was made for the purpose of evaluating its performance characteristics. This commutator transfers electric signals sequentially from 400 channels to the input of a digital high precision voltmeter, signals of a magnitude ranging from a few microvolts to tens of volts and remaining constant during the switching period. Each commutator element is a step-by-step switch and the effect of its performance on the accuracy of voltmeter readings depends on the switching cycle as well as the commutation characteristics. These were tracked through a set of three relays and a digital voltmeter continuously selecting one of two strobe signals. The voltmeter readings were analyzed by equipment including a start-stop cycle setter, a shaper of control pulses for a control module, with two amplifiers and two commutator control windings, and were also printed out after passage through a matching circuit. Calculations based on the voltmeter output data and on the equivalent electrical circuit of the commutator elements, with a high ratio of open resistance to closed resistance, yield an error of 5 x .0001 to 5 x .001 at temperatures of 20 to 65 C or one channel operating alone with crosstalk from the other 399 channels.

Chereugin, V. L.; Kuznetsov, A. A.

1984-11-01

437

47 CFR 95.1211 - Channel use policy.  

Code of Federal Regulations, 2012 CFR

... FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES PERSONAL RADIO SERVICES Medical Device Radiocommunication Service (MedRadio) § 95.1211 Channel use policy. Link to an amendment published...

2012-10-01

438

Development of 200-channel mapping system for tissue oxygenation measured by near-infrared spectroscopy  

NASA Astrophysics Data System (ADS)

Near-infrared spectroscopy (NIRS) is a very useful technique for noninvasive measurement of tissue oxygenation. Among various methods of NIRS, continuous wave near-infrared spectroscopy (CW- NIRS) is especially suitable for real-time measurement and for practical use. CW-NIRS has recently been applied in vivo reflectance imaging of muscle oxygenation and brain activity. However, conventional mapping systems do not have a sufficient mapping area at present. Moreover, they do not enable quantitative measurement of tissue oxygenation because conventional NIRS is based on the inappropriate assumption that tissue is homogeneous. In this study, we developed a 200-channel mapping system that enables measurement of changes in oxygenation and blood volume and that covers a wider area (30 cm x 20 cm) than do conventional systems. The spatial resolution (source- detector separation) of this system is 15 mm. As for the effcts of tissue inhomogeneity on muscle oxygenation measurement, subcutaneous adipose tissue greatly reduces measurement sensitivity. Therefore, we also used a correction method for influence of the subcutaneous fat layer so that we could obtain quantitative changes in concentrations of oxy- and deoxy- hemoglobin. We conducted exercise tests and measured the changed in hemoglobin concentration in the thigh using the new system. The working muscles in the exercises could be imaged, and the heterogeneity of the muscles was shown. These results demonstrated the new 200-channel mapping system enables observation of the distribution of muscle metabolism and localization of muscle function.

Niwayama, Masatsugu; Kohata, Daisuke; Shao, Jun; Kudo, Nobuki; Hamaoka, Takatumi; Katsumura, Toshihito; Yamamoto, Katsuyuki

2000-07-01

439

Detailed plasma potential measurements in a radio-frequency expanding plasma obtained from various electrostatic probes  

SciTech Connect

On-axis plasma potential measurements have been made with an emissive probe in a low pressure (0.044 Pa) rf expanding plasma containing an ion beam. The beam is detected with a retarding field energy analyzer (RFEA), and is seen to disappear at high pressure (0.39 Pa). The emissive probe measurements are in very good agreement with corresponding measurements made with two separate RFEAs, and the results indicate that the floating potential of the strongly emitting probe gives an accurate measure of the plasma potential under the present conditions.

Lafleur, T.; Charles, C.; Boswell, R. W. [Space Plasma, Power, and Propulsion Group, Research School of Physics and Engineering, Australian National University, Canberra ACT 0200 (Australia)

2009-04-15

440

Measurement of a phase of a radio wave reflected from rock salt and ice irradiated by an electron beam for detection of ultra-high-energy neutrinos  

NASA Astrophysics Data System (ADS)

We have found a radio-wave-reflection effect in rock salt for the detection of ultra-high energy neutrinos (UHE?'s) which are expected to be generated in Greisen, Zatsepin, and Kuzmin (GZK) processes in the universe. When an UHE? interacts with rock salt or ice as a detection medium, a shower is generated. That shower is formed by hadronic and electromagnetic avalanche processes. The energy of the UHE? shower converts to thermal energy through ionization processes. Consequently, the temperature rises along the shower produced by the UHE?. The refractive index of the medium rises with temperature. The irregularity of the refractive index in the medium leads to a reflection of radio waves. This reflection effect combined with the long attenuation length of radio waves in rock salt and ice would yield a new method to detect UHE?'s. We measured the phase of the reflected radio wave under irradiation with an electron beam on ice and rock salt powder. The measured phase showed excellent consistence with the power reflection fraction which was measured directly. A model taking into account the temperature change explained the phase and the amplitude of the reflected wave. Therefore the reflection mechanism was confirmed. The power reflection fraction was compared with that calculated with the Fresnel equations, the ratio between the measured result and that obtained with the Fresnel equations in ice was larger than that of rock salt.

Chiba, Masami; Kamijo, Toshio; Tanikawa, Takahiro; Yano, Hiroyuki; Yabuki, Fumiaki; Yasuda, Osamu; Chikashige, Yuichi; Kon, Tadashi; Shimizu, Yutaka; Watanabe, Souichirou; Utsumi, Michiaki; Fujii, Masatoshi

2013-05-01

441

Polar cap electron density distribution from IMAGE radio plasma imager measurements: Empirical model with the effects of solar illumination and geomagnetic activity  

Microsoft Academic Search

We present a statistical study of the relative importance of solar illumination and geomagnetic activity dependences of the electron density (Ne) distribution in the polar cap magnetosphere based on 5 years of electron density measurements made by the radio plasma imager (RPI) on board the IMAGE spacecraft. This study covers a geocentric distance of R = 1.4–5.0 RE, and the

Patrick A. Nsumei; Bodo W. Reinisch; Paul Song; Jiannan Tu; Xueqin Huang

2008-01-01

442

Correlation between the Jovian Polar cusps FUV emissions and low frequency radio emissions of Jupiter measured by the Cassini spacecraft  

Microsoft Academic Search

During its flyby of Jupiter at the end of 2000, the Cassini spacecraft have recorded strong LF radio emissions with the RPWS instrument. This radio bursts have been preceded by the arrival of a strong interplanetary schock at Jupiter. We have examined the FUV emissions associated to the Jovian polar cusps in the images archive taken at the same period

L. Pallier; R. Prangé; P. Zarka; B. Cecconi; D. Gurnett

2003-01-01

443

Measurement of interior ballistic performance using FM\\/FM radio telemetry techniques  

Microsoft Academic Search

The continuous measurement of ballistic performance during the interior ballistic cycle of cannon launched projectiles is important to on-going research programs being conducted at the Ballistic Research Laboratory (BRL). These measurements, such as propelling gas pressure, projectile acceleration, and projectile-bore interactions, are necessary to evaluate existing weapon systems and validate newly formulated interior ballistic models. Of particular interest is the

J. W. Evans

1985-01-01

444

Measurement of radio wave reflection due to temperature rising from rock salt and ice irradiated by an electron beam for an ultra-high-energy neutrino detector  

SciTech Connect

An ultra-high-energy neutrino (UHE{nu}) gives temperature rise along the hadronic and electromagnetic shower when it enters into rock salt or ice. Permittivities of them arise with respect the temperatures at ionization processes of the UHE{nu} shower. It is expected by Fresnel's formula that radio wave reflects at the irregularity of the permittivity in the medium. We had found the radio wave reflection effect in rock salt. The reflection effect and long attenuation length of radio wave in rock salt and ice would yield a new UHE{nu} detection method. An experiment for ice was performed to study the reflection effect. A coaxial tube was filled with rock salt powder or ice. Open end of the coaxial tube was irradiated by a 2 MeV electron beam. Radio wave of 435 MHz was introduced to the coaxial tube. We measured the reflection wave from the open end. We found the radio wave reflection effect due to electron beam irradiation in ice as well as in rock salt.

Tanikawa, Takahiro; Chiba, Masami; Kamijo, Toshio; Yabuki, Fumiaki; Yasuda, Osamu; Akiyama, Hidetoshi; Chikashige, Yuichi; Kon, Tadashi; Shimizu, Yutaka; Utsumi, Michiaki; Fujii, Masatoshi [Graduate School of Science and Engineering, Tokyo Metropolitan University, 1-1 Minami-Ohsawa, Hachioji-shi, Tokyo 192-0397 (Japan); Faculty of Science and Technology, Seikei University, Musashino-shi, Tokyo 180-8633 (Japan); Department of Applied Science and Energy Engineering, School of Engineering, Tokai University, Hiratsuka-shi, Kanagawa 259-1292 (Japan); School of Medicine, Shimane University, Izumo-shi, Shimane 693-8501 (Japan)

2012-11-12

445

Measurements and simulation of Faraday rotation across the Coma radio relic  

NASA Astrophysics Data System (ADS)

The aim of this work is to probe the magnetic field properties in relics and infall regions of galaxy clusters using Faraday rotation measures. We present Very Large Array multifrequency observations of seven sources in the region south-west of the Coma cluster, where the infalling group NGC 4839 and the relic 1253+275 are located. The Faraday rotation measure maps for the observed sources are derived and analysed to study the magnetic field in the south-west region of Coma. We discuss how to interpret the data by comparing observed and mock rotation measure maps that are produced simulating different three-dimensional magnetic field models. The magnetic field model that gives the best fit to the Coma central region underestimates the rotation measure in the south-west region by a factor of ˜6, and no significant jump in the rotation measure data is found at the position of the relic. We explore different possibilities to reconcile observed and mock rotation measure trends, and conclude that an amplification of the magnetic field along the south-west sector is the most plausible solution. Our data together with recent X-ray estimates of the gas density obtained with Suzaku suggest that a magnetic field amplification by a factor of ˜3 is required throughout the entire south-west region in order to reconcile real and mock rotation measure trends. The magnetic field in the relic region is inferred to be ˜ 2 ?G, consistent with inverse Compton limits.

Bonafede, A.; Vazza, F.; Brüggen, M.; Murgia, M.; Govoni, F.; Feretti, L.; Giovannini, G.; Ogrean, G.

2013-08-01

446

Low temperature radio-frequency transverse susceptibility measurements using a CMOS oscillator circuit  

NASA Astrophysics Data System (ADS)

A transverse susceptibility (TS) measurement system based on a simple inverter CMOS cell oscillator cross-coupled to a LC tank is presented. The system has been implemented to operate at a Quantum Design Physical Properties Measurement System (PPMS). We introduce several improvements with respect to similar currently operating TS measurement equipments. The electronics have been redesigned to use CMOS transistors as active devices, which simplifies the circuit design and enlarge the tuning range, thus making the proposed electronic block more feasible, predictable, and precise. Additionally, we propose a newly designed sample holder, which facilitates the procedure to change a sample and improves reproducibility of the circuit. Our design minimizes the thermal leak of the measuring probe by one order of magnitude, allowing to measure from 1.8 K in standard PPMS systems, thanks to the use of a low temperature beryllium-copper coaxial cable instead of the conventional RG402 Cu coaxial cable employed in the insert for the PPMS in similar systems. The data acquisition method is also simplified, so that the measuring sequences are implemented directly in the PPMS controller computer by programming them in the Quantum Design MultiVu software that controls the PPMS. We present the test measurements performed on the system without sample to study the background signal and stability of the circuit. Measurements on a Gd2O3 calibrating sample yield to the estimation of the system sensitivity, which is found to be on the order of 10-6 emu. Finally, measurements on a TmCo2 Laves phase sample with a ferrimagnetic transition temperature around 4 K are described, demonstrating that the developed system is well suited to explore interesting magnetic phenomena at this temperature scale.

Figueroa, A. I.; Bartolomé, J.; García del Pozo, J. M.; Arauzo, A.; Guerrero, E.; Téllez, P.; Bartolomé, F.; García, L. M.

2012-08-01

447

Four-channel ZnS scintillator measurements of escaping tritons in TFTR  

SciTech Connect

A four-channel scintillation detector capable of measuring tritons, protons, and alphas escaping from a tokamak plasma was operated during the 1986 run period of the Tokamak Fusion Test Reactor (TFTR). Signals consistent with the expected 1 MeV triton behavior have been observed during deuterium operation. Backgrounds associated with neutrons, gammas, and soft x-rays have been evaluated in situ. Such a detector should be capable of measuring escaping alphas during the D/T phase of TFTR. 16 refs., 10 figs.

Zweben, S.J.

1988-10-01

448

Measurement of the void fraction in a channel simulating the HANARO fuel assembly using neutron radiography  

NASA Astrophysics Data System (ADS)

A test section simulating the HANARO fuel channel was constructed and the void fraction was measured by using the high-speed neutron radiography technique. The test was performed at a beam facility of HANARO called Ex-core Neutron-irradiation Facility (ENF). D2O was used as the working liquid and air was used to simulate the void. The measurements were made at various combinations of the liquid flow and gas flow and the result were compared with the predictions of the existing correlations.

Lim, I. C.; Sim, C. M.; Cha, J. E.; Choi, Y. S.; Takenaka, N.; Saito, Y.; Jun, B. J.

2005-04-01

449

Measurement of the conductance of the sodium channel from current fluctuations at the node of Ranvier.  

PubMed Central

Single myelinated nerve fibres of Rana esculenta were investigated under voltage clamp conditions at 13 degrees C. Fluctuations of steady-state membrane current were measured during the last 152 msec of 190-225 msec pulses depolarizing the membrane by 8-48 mV. Noise power spectral densities were calculated in the frequency range of 6-6-6757 Hz. 2. External application of 150 nM tetrodotoxin (TTX) and/or 10 mM tetraethylammonium (TEA) ion reduced the current fluctuations. The difference of current noise spectra measured in the presence and absence of TTX (TEA) was not changed by the presence of TEA (TTX) during both measurements, and was taken as the spectrum of the Na (K) current fluctuations. 3. Residual current noise during application of both TTX and TEA was, except for some excess noise at the low and high frequency ends of the spectrum, similar to the noise measured from a passive nerve model and could be understood in terms of Nyquist noise of the known resistances and the amplifier noise. 4. Na current fluctuation spectra were interpreted as the sum N/f+SNa(f) where SNa(F) represents the spectrum expected for a set of equal, independent Na channels with only two conductance states (open or closed) which follow Hodgkin-Huxley kinetics. With values of hinfinity, tauh and minfinity measured from macroscopic Na currents, the measured spectra were fitted well by optimizing N, SNa(0) and taum. Values of taum obtained by this method were in fair agreement with values found from macroscopic currents. 5. The 1/f component of Na current noise was roughly proportional to the square of the steady-state Na current, I2. The mean value of N/I2 was (1-1 +/- 0-3) X 10(-4). 6. The current carried by a single Na channel was calculated from fitted spectra and steady-state Na currents measured simultaneously with the current fluctuations. The single channel conductance gamma normalized to zero absolute membrane potential was calculated. The average gamma from twelve measurements at depolarizations of 8-40 mV was 7-9 +/- 0-9 pS (S.E. of mean). The apparent value of gamma was smallest with small depolarizations. Variations of the assumed kinetic properties of the model did not drastically affect the single channel conductance. 7. External application of 0-1 mM-Ni ion lengthened taum in the macroscopic currents and in the fluctuation spectra and enhanced both the steady-state Na current and the current fluctuations. In Ni-treated nodes gamma was smaller than in normal nodes.

Conti, F; Hille, B; Neumcke, B; Nonner, W; Stampfli, R

1976-01-01

450

Systematic Ground-Based Measurements of Mesospherc Water Vapor and Radio Wave Absorption  

Microsoft Academic Search

Ground-based microwave radiometry has been used to remotely measure mesospheric water vapor during the late winter and spring of 1983-1984 and through the winter of 1984 and spring of 1985. The 22.235-GHz spectral emission line has been observed with a cryogenically cooled MASER low-noise receiver. A simple measure of the emission feature is obtained by fitting a best fit exponential

CHARLES L. CROSKEY; JOHN J. OLIVERO; Leslie Hale; P. J. Moser

1987-01-01

451

Faraday Rotation Measurements in a Laser Initiated Discharge Channel for Ion Beam Transport  

NASA Astrophysics Data System (ADS)

The neutralized beam transport in high-current plasma channels makes them interesting for the final focusing of high-intensity beams in an inertial confinement fusion reactor. The current-density distribution inside the channel is of great interest, since it determines the focusing properties. A Faraday polarimeter is currently under construction for the laser-channel experiment at the Lawrence Berkeley National Laboratory. The setup consists of a high power cw CO2 laser and a detector of two ambient temperature HgCdTe photodetectors working in the half shadow angle principle. Expected peak rotation for 40 kA discharge current is about half a degree. The polarimeter is designed to achieve a sensitivity of 0.01^circ and a contrast of 10-3 with a risetime better than 1 ? s. Tests of the detector - amplifier system will be presented as well as first time- and space-resolved measurements of the rotation. The polarimeter will be used in conjunction with a Michelson interferometer to determine the magnetic field. Measurements will be compared with numerical simulations (CYCLOPS).

Niemann, C.; Ponce, D. M.; Yu, S. S.; Leemans, W.; Fessenden, T. J.; Dahlbacka, G.; Vandersloot, K.; Sharp, W. M.; Tauschwitz, A.

1999-11-01

452

Phase distribution measurements in narrow rectangular channels using image-processing techniques  

SciTech Connect

Phase distribution of air-water flow in a narrow rectangular channel is examined using image-processing techniques. Ink is added to the water, and clear channel walls were used to allow high-speed, still photographs and video tape to be taken of the air-water flow field. Flow field images are digitized and stored in a Macintosh IIci computer using a frame grabber board. Local grey levels are related to liquid thickness in the flow channel using a calibration fixture. Image-processing shareware is used to calculate the spatially averaged liquid thickness from the image of the flow field. Time-averaged spatial liquid distributions are calculated using image calculation algorithms. The spatially averaged liquid distribution is calculated from the time-averaged spatial liquid distribution to formulate the combined temporally and spatially averaged liquid fraction values. The temporally and spatially averaged liquid fractions measured using this technique compare well to those predicted from pressure gradient measurements at zero superficial liquid velocity. 11 refs.

Bentley, C.L.; Ruggles, A.E.

1992-06-01

453

O18+Pd110: Measurements and realistic coupled-channel analysis in a transitional region  

NASA Astrophysics Data System (ADS)

The inelastic, two-neutron and ? transfer and quasielastic cross sections for the O18+Pd110 system have been measured in the near barrier region (40 MeV ?Elab?58 MeV). The experiments were performed in the São Paulo Pelletron laboratory. Coupled-channel analysis of the experimental data was performed using the São Paulo potential as a microscopic bare interaction. In the calculations, low-lying inelastic excitations, one- and two-neutron and ? transfers to the target were considered as the main couplings, with no extra surface absorption. The agreement between the theoretical results and the experimental data is good. The role played by the coupled channels is very different in comparison with similar data analyses for the closed-shell region around Ni58.

Pereira, D.; Rossi, E. S., Jr.; Nobre, G. P. A.; Chamon, L. C.; Silva, C. P.; Gasques, L. R.; Alvarez, M. A. G.; Ribas, R. V.; Oliveira, J. R. B.; Medina, N. H.; Rao, M. N.; Cybulska, E. W.; Seale, W. A.; Carlin, N.; Gomes, P. R. S.; Lubian, J.; Anjos, R. M.

2006-09-01

454

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

455

Dielectric spectroscopy of thin films by dual-channel impedance measurements on differential interdigitated electrode arrays  

NASA Astrophysics Data System (ADS)

We report a new approach to measuring the dielectric behavior of thin films by means of differential interdigitated electrode (IDE) cells coupled with a dual-channel impedance measurement setup. The differential IDE cell consists of two identical IDE's on a common substrate. With one IDE loaded with sample and the other one empty, the complex permittivities of both capacitors are measured simultaneously by means of a dual-channel impedance measurement setup. The net dielectric response of the material under study is then obtained by the difference of the two permittivities, which corrects for the substrate contribution. The applicability of this approach is examined with bulk glycerol and a 600 nm indomethacin film and is evidenced by the results being consistent with those measured by conventional methods. The main advantages of this new approach include a simplified preparation technique for thin film samples and a straightforward correction for the substrate contribution by subtracting the empty IDE signal obtained at the same temperature and thermal history.

Chen, Z.; Sepúlveda, A.; Ediger, M. D.; Richert, R.

2012-08-01

456

Multiaccess quantum channels  

Microsoft Academic Search

Shared communication channels are subject to multiple-access interference. Transmitter and receiver design techniques that explicitly deal with this interference have been shown to improve substantially the performance of communication systems over radio-frequency and other \\

Julio I. Concha; H. Vincent Poor

2004-01-01

457

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

458

Project 8: Using Radio-Frequency Techniques to Measure Neutrino Mass  

NASA Astrophysics Data System (ADS)

The shape of the beta decay energy distribution is sensitive to the mass of the electron neutrino. Attempts to measure the endpoint shape of tritium decay have so far seen no distortion from the zero-mass form. Here we show that a new type of electron energy spectroscopy could improve future measurements of this spectrum and therefore of the neutrino mass. We propose to detect the coherent cyclotron radiation emitted by an energetic electron in a magnetic field. For mildly relativistic electrons, like those in tritium decay, the relativistic shift of the cyclotron frequency allows us to extract the electron energy from the emitted radiation. As the technique inherently involves the measurement of a frequency in a non-destructive manner, it can, in principle, achieve a high degree of resolution and accuracy.

Project 8 Collaboration; Formaggio, J. A.

2012-08-01

459

Direct thrust measurements and modelling of a radio-frequency expanding plasma thruster  

NASA Astrophysics Data System (ADS)

It is shown analytically that the thrust from a simple plasma thruster (in the absence of a magnetic field) is given by the maximum upstream electron pressure, even if the plasma diverges downstream. Direct thrust measurements of a thruster are then performed using a pendulum thrust balance and a laser displacement sensor. A maximum thrust of about 2 mN is obtained at 700 W for a thruster length of 17.5 cm and a flow rate of 0.9 mg s-1, while a larger thrust of 4 mN is obtained at a similar power for a length of 9.5 cm and a flow rate of 1.65 mg s-1. The measured thrusts are in good agreement with the maximum upstream electron pressure found from measurements of the plasma parameters and in fair agreement with a simple global approach used to model the thruster.

Lafleur, T.; Takahashi, K.; Charles, C.; Boswell, R. W.

2011-08-01

460

Phase-Resolved Measurements of Ion Velocity in a Radio-Frequency Sheath  

SciTech Connect

The time-dependent argon-ion velocity distribution function above and within the plasma sheath of an rf-biased substrate has been measured using laser-induced fluorescence in a commercial plasma processing tool. Discharge parameters were such that the 2.2 MHz rf-bias period was on the order of the ion transit time through the sheath ({tau}{sub ion}/{tau}{sub rf}=0.3). This work embodies the first time-resolved measurement of ion velocity distribution functions within an rf-biased sheath over a large area (30 cm diameter) silicon wafer substrate.

Jacobs, Brett; Gekelman, Walter; Pribyl, Pat [Department of Physics and Astronomy, University of California--Los Angeles, Los Angeles, California 90024 (United States); Barnes, Michael [MS Barnes Engineering, San Ramon, California 94583 (United States)

2010-08-13

461

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

462

A new emissive-probe method for electron temperature measurement in radio-frequency plasmas.  

PubMed

A new method to measure electron temperature by an emissive probe has been proposed. The method is based on measurement of the functional relationship between the floating potential and the heating voltage of emissive probe. From the measured data of the floating potential change as a function of the heating voltage, the electron temperature could be determined by comparing with the theoretical curve obtained under the assumption of Maxwellian distribution. The overall characteristic of the floating potential change could be explained as a function of the heating voltage. The electron temperatures obtained by the present method were consistent with those measured by the rf-compensated Langmuir probe within the error. These experimental verifications were made in the electron density range of 2.6x10(11)-2.8x10(12) cm(-3). It was stressed that the present method is advantageous in that the probe is operated in a floating condition, hence applicable to plasmas produced in an insulated container. PMID:18163728

Kusaba, Kouta; Shindo, Haruo

2007-12-01

463

Radio Frequency Interference (RFI)\\/Electromagnetic Interference (EMI) measurements air route traffic control centers  

Microsoft Academic Search

Electromagnetic interference tests conducted at three air route traffic control centers are described. The tests included measurement of radiated and conducted emission from both the automated system and nonautomated equipments, and radiated and conducted susceptibility of the automated system. Conducted and radiated emission from most of the automated system equipments exceeded the established limits, but was not sufficiently high to

M. V. Stone

1975-01-01

464

Absolute reflectivities and aspect sensitivities of VHF radio wave scatterers measured with the SOUSY radar  

Microsoft Academic Search

By accurately calibrating the SOUSY radar in West Germany it has been made possible to measure absolute values of effective reflection coefficients and turbulence structure constants. Some typical values of these parameters as a function of altitude are presented. Such profiles are presented for both a vertically directed beam, and also for two beams directed 7 deg off-vertical. Comparisons of

W. K. Hocking; R. Ruester; P. Czechowsky

1986-01-01

465

Measurement of interior ballistic performance using FM/FM radio telemetry techniques  

NASA Astrophysics Data System (ADS)

The continuous measurement of ballistic performance during the interior ballistic cycle of cannon launched projectiles is important to on-going research programs being conducted at the Ballistic Research Laboratory (BRL). These measurements, such as propelling gas pressure, projectile acceleration, and projectile-bore interactions, are necessary to evaluate existing weapon systems and validate newly formulated interior ballistic models. Of particular interest is the resistance to projectile motion and the behavior of the projectile during the engraving process. The measurement of forces on projectiles and projectile-bore interactions requires that transducers be located on-board the projectile. In-bore measurements of ballistic performance are made at the BRL using an FM/FM, S-band telemeter. Standard artillery projectiles are modified and instrumented with telemetry transmitting systems. These projectiles are test fired and data extracted via the real time telemetry link. The projectile systems are expendable free-flight rounds and those modified for recovery in the BRL Large Caliber Soft Recovery System (LCSRS). The instrumentation package for the recoverable rounds is configured so it can be removed from the projectile, recalibrated after exposure to the launch environment, and used on subsequent rounds.

Evans, J. W.

1985-12-01

466

Automatable lipid bilayer formation and ion channel measurement using sessile droplets  

NASA Astrophysics Data System (ADS)

Artificial lipid bilayer membranes have been used to reconstitute ion channels for scientific and technological applications. Membrane formation has traditionally involved slow, labor intensive processes best suited to small scale laboratory experimentation. We have recently demonstrated a high throughput method of membrane formation using automated liquid-handling robotics. We describe here the integration of membrane formation and measurement with two methods compatible with automation and high throughput liquid-handling robotics. Both of these methods create artificial lipid bilayers by joining lipid monolayers self-assembled at the interface of aqueous and organic phases using sessile aqueous droplets in contact with a measurement electrode; one using a pin tool, commonly employed in high throughput fluid handling assays, and the other using a positive displacement pipette. Membranes formed with both methods were high quality and supported measurement of ion channels at the single molecule level. Full automation of bilayer production and measurement with the positive displacement pipette was demonstrated by integrating it with a motion control platform.

Poulos, J. L.; Portonovo, S. A.; Bang, H.; Schmidt, J. J.

2010-11-01

467

Radio frequency resonator structure and diagnostic measurements for a laboratory simulation of Auroral Kilometric Radiation  

SciTech Connect

Auroral Kilometric Radiation is emitted from regions of depleted plasma density in the Earth's polar magnetosphere. The radiation frequency is close to the local electron cyclotron frequency, polarized in the X-mode with an efficiency of {approx}1%, with power up to 1 GW. Kinetic analysis of the instability in the descending auroral flux indicated that the phenomena scaled with the cyclotron frequency. Therefore, an experimental reproduction of the auroral geometry has been created scaled to laboratory dimensions by raising the radiation frequency to the microwave range. The experiment transports a 75-85 keV electron beam through a region of increasing magnetic flux density, with a mirror ratio of up to 30. The experiments measured the mode, spectrum, power, and conversion efficiency of the emitted radiation as a function of the mirror ratio in two resonance regimes, with frequencies of 4.42 and 11.7 GHz. The microwave diagnostics and measurements will be presented in this paper.

Ronald, K.; Speirs, D. C.; McConville, S. L.; Phelps, A. D. R.; Robertson, C. W.; Whyte, C. G.; He, W.; Gillespie, K. M.; Cross, A. W. [Scottish Universities Physics Alliance and Department of Physics, John Anderson Building, 107 Rottenrow, University of Strathclyde, Glasgow G4 0NG (United Kingdom); Bingham, R. [Scottish Universities Physics Alliance and Department of Physics, John Anderson Building, 107 Rottenrow, University of Strathclyde, Glasgow G4 0NG (United Kingdom); Space Science and Technology Department, Science and Technology Facility Council, Rutherford Appleton Laboratory, Didcot OX11 0QX (United Kingdom)

2008-05-15

468

Plasma resistivity profile measurement from an external radio-frequency magnetic coil  

SciTech Connect

Plasma resistivity is obtained by measuring the change in circuit behavior from a simple loop placed externally to the plasma. The loop is part of a series-driven oscillator that can be tuned over a wide range of frequencies with a very low internal impedance. By varying the frequency, and observing both the detuning and loading of this circuit, the location and resistance of the screening currents can be determined. A two-dimensional resistive magnetohydrodynamic code calculation is performed to obtain both the plasma interaction with the oscillating field as well as the effects of nearby conductors. The plasma resistance in the numerical calculations is adjusted to match the data from the experiment and, in this way, obtain a measure of the plasma resistivity profile.

Slough, John T.; Andreason, Samuel P.; Milroy, Richard D. [University of Washington Seattle, Washington 98105 (United States)

2004-10-01

469

Measurement of Spread-Spectrum Radio Signals by Means of Wideband Field Probes  

Microsoft Academic Search

Field probes have been widely used, in the literature, for electromagnetic compatibility measurements and electromagnetic interference estimation. In the last two decades, these instruments have been exploited for open-space electric field exposure assessment, thanks to their ergonomics and capability to adapt to any scenario. This paper analyses the behaviour of field probes, in presence of digital spread-spectrum signals: OFDM (802.11a,

Daniele Trinchero; Federico Longobardi; Riccardo Stefanelli; Benedetta Fiorelli; Laura Anglesio; Alberto Benedetto; G. d'Amore; S. Trinchero; M. Borsero; G. Vizio

2009-01-01

470

Measurements and models for radio path loss and penetration loss in and around homes and trees at 5.85 GHz  

Microsoft Academic Search

This paper contains measured data and empirical models for 5.85-GHz radio propagation path loss in and around residential areas for the newly allocated U.S. National Information Infrastructure (NII) band. Three homes and two stands of trees were studied for outdoor path loss, tree loss, and house penetration loss in a narrow-band measurement campaign that included 270 local area path loss

Greg Durgin; Theodore S. Rappaport; Hao Xu

1998-01-01

471