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1

A new method to measure parameters of frequency-selective radio channels using power measurements  

Microsoft Academic Search

This paper describes a method of deriving channel parameters for a time-dispersive (=frequency-selective) radio channel from simple wide-band power measurements. A novel relationship is found allowing the estimation of the root-mean-square (RMS) delay spread from such data. Furthermore, we describe a set of equations that can be used for fitting the (measured) channel parameters to a mathematical model, the so-called

Klaus Witrisal; Yong-Ho Kim; Ramjee Prasad

2001-01-01

2

An improved iterative nonlinear least square approximation method for the design of measurement-based wideband mobile radio channel simulators  

Microsoft Academic Search

This paper deals with the design of measurement- based simulation models for wideband single-input single-output (SISO) mobile radio channels. We present an improved version of the iterative nonlinear least square approximation (INLSA) method for computing the parameters of measurement-based simulation models. The proposed method aims to fit the temporal- frequency correlation function (TFCF) of the simulation model to that of

Akmal Fayziyev; Matthias Patzold

2011-01-01

3

Capacity Evaluation of Measured Vehicle-to-Vehicle Radio Channels at 5.2 GHz  

Microsoft Academic Search

Reliability in Ricean multiple-input-multiple-output (MIMO) channels is crucial for safety-related vehicle-to-vehicle (V2V) applications. In Ricean channels, there is a signal-to-noise ratio-dependent critical data rate below which signaling with zero outage is possible. The link will be more reliable the higher this critical data rate is. We present results of spectral efficiency and outage probability from channel sounder measurements of V2V

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

2010-01-01

4

Peer-to-peer MIMO radio channel measurements in a rural area  

NASA Astrophysics Data System (ADS)

To demonstrate a real-time, mobile, peer-to-peer, ad-hoc networked MIMO system in a realistic tactical environment, the Defense Advanced Research Projects Agency (DARPA) has instituted a program, called Mobile Network MIMO (MNM). To assess the communication channel quality for ground level MIMO nodes, a comprehensive channel measurement and modeling effort was carried out to determine quantities such as spatial correlations, delay spread as well as propagation loss. It was found that median 8x10 MIMO capacity supported by the channel was about 8 times the corresponding 1x1 capacity, and 3.2 times the corresponding 1x10 capacity. Also conducted were wideband soundings of such channels, where it was found that the median rms delay spreads were 0.6 ?s. Reported are measurements and an empirical model of pathloss, spatial correlation scales, and crosspolarization properties of rural peer-to-peer channels.

Ling, Jonathan; Chizhik, Dmitry; Samardzija, Dragan; Valenzuela, Reinaldo A.

2006-06-01

5

The indoor radio propagation channel  

Microsoft Academic Search

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

HOMAYOUN HASHEMI

1993-01-01

6

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

7

Characteristics of a digital mobile radio channel  

Microsoft Academic Search

A field test has been made in order to better understand the digital mobile radio channel. At the mobile receiver (450 MHz, 1200 bits\\/s) recordings were made of the digital signal and the field strength. These recordings were later analyzed by a computer. Some existing models for digital channels have been tested. Theoretically motivated probability density functions for the fading

TOR AULIN

1981-01-01

8

Experimental comparison of indoor UHF and EHF radio channel characteristics  

Microsoft Academic Search

This paper reports experimental results obtained for narrowband and wideband indoor radio channels at 893 MHz and 37.2 GHz, respectively. Under LOS conditions and same scenarios, the multipath channel characteristics for both frequency bands are compared in terms of distance-power law exponents and cumulative distribution functions (CDF) of the CW measurement data, and root-mean-square (RMS) delay spreads of the impulse

Larbi Talbi

2000-01-01

9

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

10

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

11

Space and frequency diversity measurements of the 1.7 GHz indoor radio channel using a four-branch receiver  

Microsoft Academic Search

The practical space and frequency diversity performance achievable inside a building at 1.75 GHz under fading conditions due to the motion of a portable terminal and due to the movement of people are investigated. Data are collected using a four-branch dual-frequency envelope receiver positioned throughout one floor of a university building of common construction type. The measurement environment is characterized

Stephen R. Todd; Mohammed S. El-Tanany; Samy A. Mahmoud

1992-01-01

12

A UHF channel simulator for digital mobile radio  

Microsoft Academic Search

A device to simulate the channel propagation characteristics of the ground mobile environment at UHF has been designed, built, and characterized. This device provides a flexible, easily changed set of simulated channel characteristics, which allows the performance of a mobile radio unit to be evaluated in the laboratory under controlled conditions. The channel simulator was designed to simulate mobile platform

EDGAR L. CAPLES; KHALIL E. MASSAD; TIMOTHY R. MINOR

1980-01-01

13

Transient Characteristics of Wearable Antennas and Radio Propagation Channels for Ultrawideband Body-Centric Wireless Communications  

Microsoft Academic Search

This paper presents transient characterization of ultrawideband (UWB) body-worn antennas and on-body radio propagation channels for body-centric wireless communications. A novel miniaturized CPW-fed tapered slot antenna is proposed and used for transient measurements of UWB radio channels for body area network (BAN) and personal area network (PAN) scenarios. Unlike conventional UWB CPW-fed antennas, the proposed antenna employs two diverging tapered

Akram Alomainy; Andrea Sani; Atiqur Rahman; Jaime G. Santas; Yang Hao

2009-01-01

14

Utilizing Multiple Channels With Fewer Radios in Wireless Mesh Networks  

Microsoft Academic Search

Wireless mesh networking (WMN) is regarded as a low-cost technology for rapid wireless network deployment. However, in a single-channel WMN, the overlapped transmission ranges between relaying mesh points could introduce serious inter- ference. Using multiple radios over multiple channels can decrease the interference and improve the capacity of a WMN, but it increases the cost of a mesh point. One

Chia-Yu Ku; Ying-Dar Lin; Yuan-Cheng Lai

2011-01-01

15

Decision Feedback Equalization of Dispersive Radio Channels  

Microsoft Academic Search

The performance of adaptive decision feedback equalization applied to high bit rate digital radio systems in the presence of multipath propagation is analytically investigated. Minimum phase (MP) and nonminimum phase (NMP) type fades as well as the transition periods between these two states are considered. Insight is given into the IF recovered timing epoch and its consequences on the decision

ALNN LECLERT; P. Vandamme

1985-01-01

16

Channel quality estimation and rate adaptation for cellular mobile radio  

Microsoft Academic Search

We propose a technique to measure channel quality in terms of signal-to-interference plus noise ratio (SINR) for the transmission of signals over fading channels. The Euclidean distance (ED) metric, associated with the decoded information sequence or a suitable modification thereof, is used as a channel quality measure. Simulations show that the filtered or averaged metric is a reliable channel quality

Krishna Balachandran; Srinivas R. Kadaba; Sanjiv Nanda

1999-01-01

17

A stochastic MIMO radio channel model with experimental validation  

Microsoft Academic Search

Theoretical and experimental studies of multiple-input\\/multiple-output (MIMO) radio channels are presented. A simple stochastic MIMO model channel has been developed. This model uses the correlation matrices at the mobile station (MS) and base station (BS) so that results of the numerous single-input\\/multiple-output studies that have been published in the literature can be used as input parameters. The model is simplified

Jean Philippe Kermoal; Laurent Schumacher; Klaus Ingemann Pedersen; Preben Elgaard Mogensen; Frank Frederiksen

2002-01-01

18

A new nonlinear equalizer for mobile radio channels  

Microsoft Academic Search

An adaptive nonlinear equalizer for time-dispersive mobile radio channels is introduced. The resulting equations show that it can be viewed as a soft decision feedback equalizer (DFE) and as an extension of the Kalman (hard) DFE introduced by S. McLaughlin et al. (1989). However, the derivation of the equalizer follows in its essential parts different ideas. The performance of the

J. Thielecke

1990-01-01

19

Adaptive Bayesian decision feedback equalizer for dispersive mobile radio channels  

Microsoft Academic Search

The paper investigates adaptive equalization of time-dispersive mobile radio 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,

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

1995-01-01

20

Neutron Star Mass Measurements. I. Radio Pulsars  

Microsoft Academic Search

There are now about 50 known radio pulsars in binary systems, including at least five in double neutron star binaries. In some cases, the stellar masses can be directly determined from measurements of relativistic orbital effects. In others, only an indirect or statistical estimate of the masses is possible. We review the general problem of mass measurement in radio pulsar

S. E. Thorsett; Deepto Chakrabarty

1999-01-01

21

Radio Channel Characterization for Moderate Antenna Heights in Forest Areas  

Microsoft Academic Search

This paper describes the results achieved by an experimental campaign whose goal was to characterize the directional propagation channel at 1.9 GHz in forested areas for moderate antenna heights. These experimental results are useful in the context of pedestrian radio-localization systems relying on cellphone signals. Wideband experimental results, which are recorded with transmit-to-receive distances ranging from 40 to 110 m,

Claude Oestges; BelÉn Montenegro Villacieros; Danielle Vanhoenacker-Janvier

2009-01-01

22

UWB On-Body Radio Channel Modelling Using  

Microsoft Academic Search

This paper presents the ultra-wideband (UWB) on- body radio channel modelling using a sub-band Finite-Difference Time-Domain (FDTD) method and a model combining the uniform geometrical theory of diffraction (UTD) and ray tracing (RT). In the sub-band FDTD model, the frequency band (3 - 9 GHz) is uniformly divided into 12 sub-bands in order to take into account the material frequency

Yan Zhao; Yang Hao; Akram Alomainy; Clive Parini

23

Characterization of error sequences in UHF digital mobile radio channels  

Microsoft Academic Search

A statistical characterization of transmission errors for digital mobile radio links at 910 MHz in different types of urban areas is presented. Error sequences for messages of 2-s duration at a nominal rate of 20-kb\\/s for binary-phase-shift-keying (BPSK) demodulated transmissions have been obtained and characterized by Fritchman's channel model, including one error state and two to four error-free states. In

Assia Semmar; Michel Lecours; Jean-Yves Chouinard; John Ahern

1991-01-01

24

Radio Measurements of Air Showers with LOPES  

NASA Astrophysics Data System (ADS)

LOPES is a digital antenna array for the radio measurement of cosmic-ray air showers at energies around 1017 eV. It is triggered by the KASCADE-Grande air-shower array at the Karlsruhe Institute of Technology (KIT), Germany. Because of an absolute amplitude calibration and a sophisticated data analysis, LOPES can test models for the radio emission to an up-to-now unachieved level, thus improving our understanding of the radio emission mechanisms. Recent REAS simulations of the air-shower radio emission come closer to the measurements than any previously tested simulations. We have determined the radio-reconstruction precision of interesting air-shower parameters by comparing LOPES reconstructions to both REAS simulations and KASCADE-Grande measurements, and present our latest results for the angular resolution, the energy and the Xmax reconstruction based on the radio measurement of about 500 air showers. Although the precision of LOPES is limited by the high level of anthropogenic noise at KIT, it opens a promising perspective for next-generation radio arrays in regions with a lower ambient noise level.

Schröder, F. G.; Apel, W. D.; Arteaga-Velazquez, J. C.; Bähren, L.; Bekk, K.; Bertaina, M.; Biermann, P. L.; Blümer, J.; Bozdog, H.; Brancus, I. M.; Cantoni, E.; 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.; Huber, D.; 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.; Sima, O.; Toma, G.; Trinchero, G. C.; Weindl, A.; Wochele, J.; Zabierowski, J.; Zensus, J. A.

2013-02-01

25

Performance Assessment of Internet E-Mail Over Degraded High-Frequency Radio Channels.  

National Technical Information Service (NTIS)

The transmission of E-mail over high-frequency (HF) radio channels is experiencing widespread use in the Government and military communities. This ability is made possible trough the convergence of Internet and radio communication protocols, primarily by ...

C. Redding R. McLean

1998-01-01

26

Radio plasma imager simulations and measurements  

Microsoft Academic Search

The Radio Plasma Imager (RPI) will be the first-of-its kind instrument designed to use radio wave sounding techniques to perform repetitive remote sensing measurements of electron number density (Ne) structures and the dynamics of the magnetosphere and plasmasphere. RPI will fly on the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) mission to be launched early in the year 2000. The design

J. L. Green; R. F. Benson; S. F. Fung; W. W. L. Taylor; S. A. Boardsen; B. W. Reinisch; D. M. Haines; K. Bibl; G. Cheney; I. A. Galkin; X. Huang; S. H. Myers; G. S. Sales; J.-L. Bougeret; R. Manning; N. Meyer-Vernet; M. Moncuquet; D. L. Carpenter; D. L. Gallagher; P. H. Reiff

2000-01-01

27

Static Channel Assignment in Multi-radio MultiChannel 802.11 Wireless Mesh Networks: Issues, Metrics and Algorithms  

Microsoft Academic Search

The combination of multiple radio nodes in con- junction with a suitably structured multi-hop or mesh archi- tecture has the potential to solve some of the key limitations of present day wireless access networks that are based on single-radio nodes. This paper addresses the static channel assignment problem for multi-channel multi-radio static wireless mesh networks. We present four metrics based

Arindam Kumar Das; Rajiv Vijayakumar; Sumit Roy

2006-01-01

28

Radio occultation measurements of the lunar ionosphere.  

NASA Astrophysics Data System (ADS)

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 when it crosses the atmosphere. The wave amplitude and phase undergo modifications that are correlated to the physical parameters - i.e. electron density - of the crossed medium. The first data set was obtained during the lunar occultations of the European probe SMART-1 shortly before impacting the lunar soil on September 3rd, 2006. During this experiment several radio occultation measurements of the signal transmitted by the spacecraft were performed in S and X band by using the 32 meters radiotelescopes (at Medicina and Noto) of the Istituto di Radioastronomia - Istituto Nazionale di Astrofisica. Further experiments were performed during lunar occultations of Saturn and Venus. On May 22nd and June 18th 2007 the Cassini spacecraft, orbiting Saturn, and the Venus Express spacecraft, orbiting Venus, respectively were occulted by the Moon. The variation of the Total Electron Content (TEC) measured by our instruments (˜ 1013 el/m2) on this occasion is in agreement with values of the electron number density acquired by in situ measuments of the US Apollo missions and the USSR Luna 19 and 22 probes.

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

29

Channel access protocols for multihop packet radio networks  

NASA Astrophysics Data System (ADS)

We first introduce two laws which if obeyed will ensure that nodes will not interfere with one another's transmissions. We then apply these laws to the regular planar networks, i.e., the triangular, square, and hexagonal networks, and place bounds on the capacities that can be achieved by protocols obeying the laws. We also demonstrate that there exist protocols obeying one of the laws which are optimal, optimal in the sense that no other protocol similarly constrained has greater capacity. Next, we show that the application of these laws leads to new random, access protocols for multihop packet radio networks. The first of these is a class called the TREE/TDMA protocols in which two level of control are used on a shared channel: the TREE Protocol is used by nodes to feed a regular backbone of repeaters which uses avoidance, multiple access protocol (CS/CAMA) in which a single level of control used on a shared channel and in which the spatial reuse of the channel is maximized. Analytical and simulation models of the protocols are described and are used to evaluate their operating characteristics. Stability criteria, capacities, and mean packet delay times are all analyzed. We conclude the new protocols are efficient, reliable, flexible, and require hardware and software of modest complexity. Both protocols are described and are used to evaluate their operating characteristics. Stability criteria, capacities, and mean packet delay times are all analyzed.

Wang, Si-Taur

1986-11-01

30

Power Spectrum Program for Estimating the Doppler Profile of a Radio Channel.  

National Technical Information Service (NTIS)

This research memorandum describes a data processing technique for analyzing the Doppler-shift properties of a radio channel. A computer program has been developed that computes the power spectrum of power scattered by the radio channel as a function of D...

R. F. Daly

1964-01-01

31

Optimal Power Control over Fading Cognitive Radio Channels by Exploiting Primary User CSI  

Microsoft Academic Search

This paper is concerned with spectrum sharing cognitive radio networks, where a secondary user (SU) or cognitive radio link communicates simultaneously over the same frequency band with an existing primary user (PU) link. It is assumed that the SU transmitter has the perfect channel state information (CSI) on the fading channels from SU transmitter to both PU and SU receivers

Rui Zhang

2008-01-01

32

Radio-controlled model gyro measurement study  

Microsoft Academic Search

The radio-controlled model (RCM) has been used extensively for mode l tests since 1970. An assumption that has been made is that the angles measured by the RCM gyros are the Euler angles for Euler coordinate transformation. A recent study of the gyros indicates that this assumption is incorrect not only for the RCM but for most model testing instrumentation

Richard Nigon; Faria Abedin

1988-01-01

33

Decision feedback equalization of the indoor radio channel  

Microsoft Academic Search

The measured multipath profiles from five different indoor areas are used for the performance analysis of a binary phase shift keying (BPSK) modem with a decision feedback equalizer (DFE). The performance from the measured multipath profiles is compared with the performance predictions based on a computer simulated channel model. Both average probability of error and probability of outage are calculated

Kaveh Pahlavan; S. J. Howard; T. A. Sexton

1993-01-01

34

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

35

Optimization models for fixed channel assignment in wireless mesh networks with multiple radios  

Microsoft Academic Search

The combination of multiple radio nodes in conjunction with a suitably structured multi-hop or mesh architecture has the potential to solve some of the key limitations of present day wireless access networks that are based on single-radio nodes. This paper ad- dresses the channel assignment problem for multi-channel multi-interface (radio) wireless mesh networks. We focus on static wireless mesh networks

Arindam K. Das; Hamed M. K. Alazemi; Rajiv Vijayakumar; Sumit Roy

2005-01-01

36

Polarization division multiplexed photonic radio-frequency channelizer using an optical comb  

NASA Astrophysics Data System (ADS)

A polarization division multiplexed photonic radio-frequency (RF) channelizer based on an optical comb is proposed and numerically investigated. A flat optical comb with nine lines is generated using two cascaded Mach-Zehnder modulators. The input broadband signal is simultaneously multicast by the optical comb and its frequency-shifted duplicate. These two combs are polarization multiplexed, spectrally sliced by a Fabry-Pérot etalon (FPE), polarization de multiplexed and then channelized by wavelength division multiplexers (WDMs). The key advantage of the proposed approach is that it releases the trade-off between the measurement range and accuracy of a conventional optical comb based channelizer by a factor of 2. The impact of the polarization misalignment, the capability of monitoring multi-frequency RF signals with different powers and the reconfigurability of the system are also evaluated.

Xian Wang, Li; Hua Zhu, Ning; Li, Wei; Wang, Hui; Yu Zheng, Jian; Guo Liu, Jian

2013-01-01

37

Distributed Channel Assignment in Multi-Radio 802.11 Mesh Networks  

Microsoft Academic Search

To increase the utilization of the available frequency channel space in 802.11-based wireless mesh networks, recent work has explored solutions based on multi-radio stations. This paper reports on our design and experimental study of a distributed, self-stabilizing mechanism that assigns channels to multi-radio nodes in wireless mesh networks. We take a modular approach by decoupling the channel selection decision from

Bong-Jun Ko; Vishal Misra; Jitendra Padhye; Dan Rubenstein

2007-01-01

38

New approaches in cellular radio systems using dynamic radio channel management  

NASA Astrophysics Data System (ADS)

New approaches are presented to facilitate dynamic radio bandwidth management for mobile communication systems. The aim is achieve an overall high level of QoS for both handoff calls and new calls. At the same time, the utilization of wireless network resources, i.e. the revenues earned by the operator. The simultaneous satisfaction of these two conflicting interests, under varying mobility and network traffic conditions, will be difficult. However, a balanced operation could be obtained by applying two novel approaches in system management. First, apriori information about possible handoffs, in the form of cell transition probabilities could be provided by the mobile, which is based on data collected by the mobile itself. This information is used to make handoff reservation requests in neighboring cells. Second, simultaneously controlling the radio resource reservation and new call admission to the system. This approach controls both the amount of reserved channels and the number of new calls admitted in a dynamic way. A theoretical analysis and a simulation have been used to study these approaches and it has been demonstrated that these approaches perform better then other reported approaches in the literature.

Yilmaz, Nusret; Ergul, F. R.

2004-10-01

39

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

40

Equalization of digital radio channels with large multipath delay for cellular land mobile applications  

Microsoft Academic Search

A new maximum a posteriori (MAP) equalizer is proposed for digital radio links affected by large multipath delays. The “sparse” nature of the channel, where a few nonzero powerful taps are spaced by many negligible taps, is exploited to achieve a complexity proportional to the number of nonzero taps. When the channel is time-varying, an efficient nonlinear Kalman like channel

Roberto Cusani; Jari Mattila

1999-01-01

41

A Channel Access Scheme for Large Dense Packet Radio Networks  

Microsoft Academic Search

Prior work in the field of packet radio networks has often assumed a simple success-if-exclusive model of successful reception. This simple model is insufficient to model interference in large dense packet radio networks accurately. In this paper we present a model that more closely approximates communication theory and the underlying physics of radio communication. Using this model we present a

Timothy J. Shepard

1996-01-01

42

Density Structure of the Solar Corona From Radio Occultation Measurements  

Microsoft Academic Search

Starting with angular broadening measurements five decades ago, a wide variety of radio propagation and scattering phenomena have been observed when natural radio sources or spacecraft radio signals happened to pass behind or were occulted by the solar corona. While yielding information on density, velocity and magnetic fields, these unique measurements probe density most directly, and with unprecedented sensitivity, spatial

R. Woo

2003-01-01

43

Hybrid Acousto-Optic and Digital Equalization for Microwave Digital Radio Channels.  

National Technical Information Service (NTIS)

Digital radio transmission systems use complex modulation schemes that require powerful signal-processing techniques to correct channel distortions and to minimize bit error rates. We propose combining the computation power of acousto-optic processing and...

C. S. Anderson A. VanderLugt

1990-01-01

44

An Energy Efficient Channel Assignment and Routing Algorithm for Multi-Radio Wireless Mesh Networks  

Microsoft Academic Search

Endowing mesh routers with multiple radios is a recent solution to improve the performance of wireless mesh networks. The approaches proposed in the literature to solve the problem how to assign channels to radio have mainly focused so far on reducing interference or maximizing the throughput. To the best of our knowledge, none of such approaches attempted to save network

Stefano Avallone

2010-01-01

45

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

46

Comparative statistical analysis of indoor positioning using empirical data and indoor radio channel models  

Microsoft Academic Search

Indoor geolocation using maximum likelihood algorithms applied to the measured reference radio map of the received signal strength (RSS) in indoor areas has attracted tremendous attention in the recent published literature. In this paper we examine generation of reference radio maps using two different radio propagation models to replace on site measurements for calibration of these indoor geolocation systems. The

Ahmad Hatami; Kaveh Pahlavan

2006-01-01

47

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

48

Estimation of time-varying digital mobile radio channels  

Microsoft Academic Search

In packet-based communication systems using dispersive channels, training symbols are usually provided to estimate the channel response. It is demonstrated that for both simple constant and adaptive least-squares estimates, the average performance of the estimator can be computed with explicit reference to channel time variations. With these analytical results, quantitative evidence can be provided for the classification of channel time

R. A. Ziegler; J. M. Cioffi

1991-01-01

49

Estimation of time-varying digital radio channels  

Microsoft Academic Search

In the design of block-oriented digital communication systems that must operate over time-dispersive channels, it is usually assumed that the channel is constant over the duration of a data block, even if the channel fades. The authors study the degradation in receiver performance caused by actual interblock channel variation. For tractability, attention is restricted to the case in which the

Robert A. Ziegler; John M. Cioffi

1992-01-01

50

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

2012-03-01

51

Optimal parametric feedforward estimation of frequency-selective fading radio channels  

Microsoft Academic Search

Estimation of time-varying dispersive radio channels is one of the most important tasks of receiver synchronisation. State-of-the-art adaptive estimators employing decision feedback suffer from error propagation and limited robustness against faster fading. In this paper, the optimal feedforward channel estimator using only known training symbols is systematically derived. Statistical channel information is assumed to be available. For moderately rapid fading

Stefan A. Fechtel; Heinrich Meyr

1994-01-01

52

An analysis of the materiel fielding plan for the SINCGARS (Single Channel Ground and Airborne Radio System) radio  

NASA Astrophysics Data System (ADS)

This thesis is an analysis of the materiel fielding plan (MFP) for the Army's Single Channel Ground and Airborne Radio System (SINCGARS). Objectives of the study are to identify major potential problem areas in the MFP, and to generate recommendations for resolving these problems. The study involves a specific analysis of the maintenance and supply support aspects of the MFP within the context of the Major System acquisition framework. Research included extensive field interviews with personnel in the functional management areas of the Communications and Electronics Command (CECOM), the Project Office, and the Department of Army Staff. Potential problems identified concern the redistribution of VRC-12 series and PRC-77 radios, the imbedded COMSEC modification, and the issue of warranties. Recommendations include purchasing a warranty for the original production contract, improving the planning for redistribution of old radios, and providing strict control over the design of the imbedded COMSEC modification.

Tegen, C. M.

1984-12-01

53

Multi-channel distributed coordinated function over single radio in wireless sensor networks.  

PubMed

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. PMID:22346614

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

2011-01-01

54

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

55

Measurements of Ambient RadioXenon Levels Using the Automated RadioXenon Sampler/Analyzer.  

SciTech Connect

The Pacific Northwest National Laboratory has developed an Automated Radio-Xenon Sampler/Analyzer for the CTBT to measure radio-xenon isotopes. This system uses a beta-gamma coincidence counting detector to produce two-dimensional plots of gamma energy versus beta energy.

McIntyre, Justin I.; Abel, Keith H.; Hayes, James C.; Heimbigner, Tom R.; Panisko, Mark E.; Reeder, Paul L.; Thompson, Robert C.

2001-06-01

56

Spectrum Handover Mechanism Based on Channel Scheduling in Cognitive Radio Networks  

NASA Astrophysics Data System (ADS)

In this study, we address the spectrum handover mechanism for proactive-decision in cognitive radio networks. Spectrum handover occurs when the primary users suddenly appear and the secondary users are using the particular primary user's licensed channel. The proactive-sensing spectrum handover which the target channel is pre-determined. And handover avoid the sensing time, but the pre-determined target channel may not be available. So we develop a spectrum handover mechanism by using an efficient channel-scheduling algorithm to reduce disabled channel. Its basic idea is in that a new packet is scheduled by migrating some packets to other channels if none of any idle channels can accommodate it; otherwise repeating the other migrate or stay channel processes.

Ma, Bin; Xie, Xianzhong

57

Measurement of radio emission from extensive air showers with LOPES  

NASA Astrophysics Data System (ADS)

A new method is explored to detect extensive air showers: the measurement of radio waves emitted during the propagation of the electromagnetic shower component in the magnetic field of the Earth. Recent results of the pioneering experiment LOPES are discussed. It registers radio signals in the frequency range between 40 and 80 MHz. The intensity of the measured radio emission is investigated as a function of different shower parameters, such as shower energy, angle of incidence, and distance to shower axis. In addition, new antenna types are developed in the framework of LOPESstar and new methods are explored to realize a radio self-trigger algorithm in real time.

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

2011-02-01

58

MEXART Measurements of Radio Sources. Interplanetary Scintillation Array in Mexico  

NASA Astrophysics Data System (ADS)

The Mexican Array Radio Telescope (MEXART) consists of a 64x64 array of full-wave dipoles operating at 139.65 MHz. The primary aim of the array is to perform Interplanetary Scintillations (IPS) observations of radio sources to track large-scale solar wind perturbations within 1~AU. We describe the initial measurements of radio sources and the advances in the calibration of the antenna.

Gonzalez-Esparza, A.; Carrillo, A.; Andrade, E.; Jeyakumar, S.; Ananthakrishnan, S.; Praveenkumar, A.; Sankarasubramanian, G.; Sureshkumar, S.; Sierra, P.; Vazquez, S.; Perez-Enriquez, R.; Kurtz, S.

2005-12-01

59

Multiple-frequency measurement based on serial photonic channelization using optical wavelength scanning.  

PubMed

A serial photonic channelized radio frequency (RF) measurement scheme is proposed and experimentally demonstrated. This scheme can be used for instantaneous multiple-frequency measurement and capturing key parameters of linear frequency modulation signals. Based on high-speed wavelength scanning, this photonic RF channelizer works serially in time domain, and each wavelength labels a certain RF channel. With only one low-bandwidth photodetector (PD), we can implement multiple channel RF frequency measurements, which have a much simpler structure compared with parallel channelized schemes using broadband filter-bank and multiple PDs. PMID:24322131

Li, Ruiyue; Chen, Hongwei; Yu, Ying; Chen, Minghua; Yang, Sigang; Xie, Shizhong

2013-11-15

60

Zebra-multi-channel digital modular radio: architecture and performance  

Microsoft Academic Search

This paper presents the design and performance of a multi-channel SATCOM\\/LOS UHF receiver known as Zebra manufactured by Mnemonics, Inc., Melbourne, FL. The current four channel receiver debuted at the Joint Warrior Interoperability Demonstration (JWID-1996). Zebra employs an open architecture design based on commercial off-the shelf (COTS) single board computers communicating with proprietary UHF receiver modules and embedded cryptographic devices

J. D. Bard; B. J. Bryan; T. C. Colvin

1997-01-01

61

Performance analysis of spread spectrum packet radio network with channel load sensing  

Microsoft Academic Search

A continuous-time Markov-chain model for an asynchronous communication spread-spectrum code-division-multiple-access (CDMA) packet radio network is developed. The network is composed of mutually independent users. The receiver-based code is considered; a terminal with a packet to send looks up the destination's code and transmits on that code. Each user senses the channel load and refrains from transmission if the channel load

AHMED H. ABDELMONEM; TAREK N. SAADAWI

1989-01-01

62

On the Capacity Region of Multi-Radio MultiChannel Wireless Mesh Networks  

Microsoft Academic Search

Next generation fixed wireless broadband networks are being increasingly deployed as mesh networks in order to provide and extend access to the internet. These networks are characterized by the use of multiple orthogonal channels and nodes with the ability to simultaneously communicate with many neighbors using multi- ple radios (interfaces) over orthogonal channels. Networks based on the IEEE 802.11a\\/b\\/g and

Murali Kodialam; Thyaga Nandagopal

63

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

64

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

65

Application of radio channel modelling to a planning tool in a mobile radio indoor communication system  

Microsoft Academic Search

For mobile radio systems, it is very important to know how the propagation medium performs at the right frequency and within the given geographical environment. When this environment is an indoor one, that is, when a mobile system is being deployed within a building, a number of new issues appear that pose a number of constraints and restrictions to the

Gema Vallejo-Cabrejas; P. Batolome-Pascual

1993-01-01

66

On cognitive radio networks with opportunistic power control strategies in fading channels  

Microsoft Academic Search

In this paper, we consider a cognitive radio system in fading wireless channels and propose an opportunistic power control strategy for the cognitive users, which serves as an alternative way to protect the primary user's transmission and to realize spectrum sharing between the primary user and the cognitive users. The key feature of the proposed strategy is that, via opportunistically

Yan Chen; Guanding Yu; Zhaoyang Zhang; Hsiao-hwa Chen; Peiliang Qiu

2008-01-01

67

Discrete-time control analysis of transport channel synchronization in 3G radio access networks  

Microsoft Academic Search

Transport channel synchronization is a function of 3G access networks that operates in the link between Radio Network Controllers (RNCs) and Base Stations (Nodes B) and is required to support macro-diversity in the downlink direction. Its objective is to assure that every frame sent by the RNC arrives at the Node B on time to be transmitted over the air

Juan J. Alcaraz; Gaspar Pedreño; Fernando Cerdán; Joan García-Haro; Felipe Garcia-Sanchez

2009-01-01

68

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

69

Soft-decision feedback equalizer for continuous phase modulated signals in wideband mobile radio channels  

Microsoft Academic Search

A combination of a decision feedback equalizer (DFE) and a Viterbi processor for the equalization of continuous phase modulated (CPM) signals transmitted over wideband mobile radio channels is described. The equalizer structure allows soft-decision to be made and incorrect decisions to be changed in the feedback filter of the DFE. The provision of soft decisions significantly alleviates the catastrophic effect

J. C. S. Cheung; Raymond Steele

1994-01-01

70

Efficient Use of Narrowband Radio Channels for Mobile Digital Communications.  

National Technical Information Service (NTIS)

The project developed a wireless modem architecture that provides bandwidth efficient data communications in the 220 MHz ITS spectral allocations. The goal was to provide greater than 12 kbps transmission capacity on the 4 kHz channels (3 bps/Hz spectral ...

M. P. Fitz

1996-01-01

71

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

72

Simulation studies of GPS radio occultation measurements  

Microsoft Academic Search

Abstract. The atmospheric propagation of GPS signals under multipath conditions and their detection are simulated. Using the multiple phase screen method C\\/A-code modulated L1 signals are propagated through a spheri- cally symmetric refractivity field derived from a high-resolution radio sonde observation. The propagated signals are tracked by GPS receivers implemented in software and converted to refractivity profiles by the canonical

G. Beyerle; M. E. Gorbunov; C. O. Ao

2002-01-01

73

Simulation studies of GPS radio occultation measurements  

Microsoft Academic Search

The atmospheric propagation of GPS signals under multipath conditions and their detection are simulated. Using the multiple phase screen method, C\\/A-code modulated L1 signals are propagated through a spherically symmetric refractivity field derived from a high-resolution radio sonde observation. The propagated signals are tracked by a GPS receiver implemented in software and converted to refractivity profiles by the canonical transform

G. Beyerle; M. E. Gorbunov; C. O. Ao

2003-01-01

74

Radio polarisation measurements of meteor trail echoes with BRAMS  

NASA Astrophysics Data System (ADS)

BRAMS, the Belgian RAdio Meteor Stations, is a network of radio receiving stations using forward scatter techniques to detect and characterize meteors. The transmitter is a dedicated beacon located in Dourbes in the south-west of Belgium. It emits towards the zenith a purely sinusoidal wave circularly polarised, at a frequency of 49.97 MHz and with a power of 150 watts. The main goals of the project are to compute meteoroid flux rates and trajectories. Most receiving stations are using a 3 element Yagi antenna and are therefore only sensitive to one polarisation. The station located in Uccle has also a crossed 3 element Yagi antenna and therefore allows measurements of horizontal and vertical polarisations. We present the preliminary radio polarisation measurements of meteor trail echoes and compare them with the theoretical predictions of Jones & Jones (1991) for oblique scattering of radio waves from meteor trails.

Lamy, H.; Ranvier, S.; Anciaux, M.; Calders, S.; De Keyser, J.; Gamby, E.

2012-04-01

75

Information capacities of quantum measurement channels  

NASA Astrophysics Data System (ADS)

We study the relation between the unassisted and entanglement-assisted classical capacities C and Cea of entanglement-breaking channels. We argue that the gain of entanglement assistance Cea/C > 1 generically for measurement channels with unsharp observables; in particular for the measurements with pure posterior states the information loss in the entanglement-assisted protocol is zero, resulting in an arbitrarily large gain for very noisy or weak signal channels. This is illustrated by examples of continuous observables corresponding to state tomography in finite dimensions and heterodyne measurement. In contrast, state preparations are characterized by the property of having no gain of entanglement assistance, Cea/C = 1.

Holevo, A. S.

2013-03-01

76

Measuring the radio emission of cosmic ray air showers with LOPES  

NASA Astrophysics Data System (ADS)

When ultra high energy cosmic rays hit the atmosphere, they produce a shower of millions of secondary particles. Thereby the charged particles in the shower emit a radio pulse whilst deflected in the Earth's magnetic field. LOPES is a digital antenna array measuring these radio pulses in the frequency range from 40 to 80 MHz. It is located at the site of and triggered by the air shower experiment KASCADE-Grande at Karlsruhe Institute of Technology (KIT), Germany. In its present configuration, it consists of 15 east-west-polarized and 15 north-south-polarized, absolutely calibrated short dipole antennas, as well as 10 LPDAs (with two channels each). Furthermore, it serves as a test bench for technological developments, like new antenna types or a radio-based self-triggering ( LOPESSTAR). To achieve a good angular reconstruction and to digitally form a beam into the arrival direction of the shower, it has a precise time calibration.

Schröder, F. G.; Apel, W. D.; Arteaga, J. C.; Asch, T.; Badea, F.; Bähren, L.; Bekk, K.; Bertaina, M.; Biermann, P. L.; Blümer, J.; Bozdog, H.; Brancus, I. M.; Brüggemann, M.; Buchholz, P.; Buitink, S.; Cantoni, E.; Chiavassa, A.; Cossavella, F.; Daumiller, K.; de Souza, V.; Di Pierro, F.; Doll, P.; Engel, R.; Falcke, H.; Finger, M.; Fuhrmann, D.; Gemmeke, H.; Ghia, P. L.; Glasstetter, R.; Grupen, C.; Haungs, A.; Heck, D.; Hörandel, J. R.; Horneffer, A.; Huege, T.; Isar, P. G.; Kampert, K.-H.; Kang, D.; Kickelbick, D.; Krömer, O.; Kuijpers, J.; Lafebre, S.; ?uczak, P.; Ludwig, M.; Mathes, H. J.; Mayer, H. J.; Melissas, M.; Mitrica, B.; Morello, C.; Navarra, G.; Nehls, S.; Nigl, A.; Oehlschläger, J.; Over, S.; Palmieri, N.; Petcu, M.; Pierog, T.; Rautenberg, J.; Rebel, H.; Roth, M.; Saftoiu, A.; Schieler, H.; Schmidt, A.; Sima, O.; Singh, K.; Toma, G.; Trinchero, G. C.; Ulrich, H.; Weindl, A.; Wochele, J.; Wommer, M.; Zabierowski, J.; Zensus, J. A.

2010-05-01

77

Performance Evaluation of Channel Switching Scheme for Packet Data Transmission in Radio Network Controller  

Microsoft Academic Search

SUMMARY W-CDMA (Wideband-CDMA) is expected to play a sig- nificant role in the radio access technology of third-generation mobile telecommunication systems. In second-generation systems, voice traffic from each user has been transmitted mainly via the dedicated transport (ra- dio) channel. In addition, the third-generation systems will efficiently ac- commodate data traffic based on packet transmission in the shared common transport

Yoshiaki Ohta; Kenji Kawahara; Takeshi Ikenaga; Yuji Oie

2002-01-01

78

Iterative distributed channel probing for cognitive radios with power-controlled wireless links  

Microsoft Academic Search

We propose a novel scheme for cognitive radios that enables secondary users (SUs) to verify whether they can use the channel without reducing the signal to interference-noise ratio (SINR) of primary users (PUs) below a pre-specified threshold; i.e., SUs check whether they are admissible or not. Mathematically, to verify admissibility, SUs need to know whether the spectral radius of the

Jafar Mohammadi; Slawomir Stanczak; Renato L. G. Cavalcante; Jalal Etesami

2011-01-01

79

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

80

Measuring cosmic ray radio signals at the Pierre Auger Observatory  

NASA Astrophysics Data System (ADS)

The recent results of the LOPES and CODALEMA experiments open the door to a renewal of the radio technique for cosmic ray induced shower measurements. The demonstration has been done of its potential and performances at energies below 1018 eV, this upper limit being due to the small scale of the current experiments. A natural stage toward the improvement of the method is thus to install radio detectors in association with a large cosmic ray detector such as Auger. Besides surface and fluorescence detection, radio detection could be an alternative method, providing a complementary information. The Pierre Auger Collaboration has thus engaged a R&D effort which will lead to the installation of a radio engineering array covering 20 km2 on its southern site. Outline of the technique, results of the first phase of the tests and current plans for the future engineering array will be presented.

Dallier, Richard; Pierre Auger Collaboration

2011-02-01

81

Measurement-based investigations of radio wave propagation: An expose on building corner diffraction  

NASA Astrophysics Data System (ADS)

Predicting performance metrics for the next-generation of multi-mode and multi-antenna wireless communication systems demands site-specific knowledge of the wireless channels underlying radio wave propagation mechanisms. This thesis describes the first measurement system capable of characterizing individual propagation mechanisms in situ. The measurement system merges a high-resolution spatio-temporal wireless channel sounder with a new field reconstruction technique to provide complete knowledge of the wireless channels impulse response throughout a 2-dimensional region. This wealth of data may be combined with space-time filtering techniques to isolate and characterize individual propagation mechanisms. The utility of the spatio-temporal measurement system is demonstrated through a measurement-based investigation of diffraction around building corners. These measurements are combined with space-time filtering techniques and a new linear wedge diffraction model to extract the first semi-empirical diffraction coefficient. Specific contributions of this thesis are: (1) The first ultra-wideband single-input multiple-output (SIMO) channel sounder based upon the sliding correlator architecture. (2) A quasi 2-dimensional field reconstruction technique based upon a conjoint cylindrical wave expansion of coherent perimeter measurements. (3) A wireless channel "filming" technique that records the time-domain evolution of the wireless channel throughout a 2-dimensional region. (4) High-resolution measurements of the space-time wireless channel near a right-angled brick building corner. (5) The application of space-time filtering techniques to isolate the edge diffraction problem from the overall wireless channel. (6) An approximate uniform geometrical theory of diffraction (UTD)-style linear model describing diffraction by an impedance wedge. (7) The first-ever semi-empirical diffraction coefficient extracted from in situ measurement data. This thesis paves the way for several new avenues of research. The comprehensive measurement data provided by channel "filming" will enable researchers to develop and implement powerful space-time filtering techniques that facilitate measurement-based investigations of radio wave propagation. The measurement procedure described in this thesis may be adapted to extract realistic reflection and rough-surface scattering coefficients. Finally, exhaustive measurements of individual propagation mechanisms will enable the first semi-empirical propagation model that integrates empirical descriptions of propagation mechanisms into a UTD-style mechanistic framework.

Pirkl, Ryan J.

82

GPRS radio network capacity and quality of service using fixed and on-demand channel allocation techniques  

Microsoft Academic Search

The radio network capacity needed for the General Packet Radio Service (GPRS) in coexistence with circuit switched services and the admissible quality of service for mobile Internet users is presented. Since the GPRS is to be integrated into the GSM infrastructure, a number of physical channels has to be made available to GPRS used as fixed and on-demand packet data

Peter Stuckmann; Frank Muller

2000-01-01

83

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

Microsoft Academic Search

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

LEONARD KLEINROCK; FOUAD A. TOBAGI

1975-01-01

84

Air shower measurements with the LOPES radio antenna array  

NASA Astrophysics Data System (ADS)

LOPES is set up at the location of the KASCADE-Grande extensive air shower experiment in Karlsruhe, Germany and aims to measure and investigate radio pulses from extensive air showers. Since radio waves suffer very little attenuation, radio measurements allow the detection of very distant or highly inclined showers. These waves can be recorded day and night, and provide a bolometric measure of the leptonic shower component. 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. The LOPES antennas are absolutely amplitude calibrated allowing to reconstruct the electric field strength which can be compared with predictions from detailed Monte-Carlo simulations. We report about the analysis of correlations present in the radio signals measured by the LOPES 30 antenna array. Additionally, LOPES operates antennas of a different type (LOPESSTAR) which are optimized for an application at the Pierre Auger Observatory. Status, recent results of the data analysis and further perspectives of LOPES and the possible large scale application of this new detection technique are discussed.

Lopes Collaboration; Haungs, A.; Apel, W. D.; Arteaga, J. C.; Asch, T.; Auffenberg, J.; Badea, F.; Bähren, L.; Bekk, K.; Bertaina, M.; Biermann, P. L.; Blümer, J.; Bozdog, H.; Brancus, I. M.; Brüggemann, M.; Buchholz, P.; Buitink, S.; Cantoni, E.; Chiavassa, A.; Cossavella, F.; Daumiller, K.; de Souza, V.; di Pierro, F.; Doll, P.; Engel, R.; Falcke, H.; Finger, M.; Fuhrmann, D.; Gemmeke, H.; Ghia, P. L.; Glasstetter, R.; Grupen, C.; Heck, D.; Hörandel, J. R.; Horneffer, A.; Huege, T.; Isar, P. G.; Kampert, K.-H.; Kang, D.; Kickelbick, D.; Kolotaev, Y.; Krömer, O.; Kuijpers, J.; Lafebre, S.; ?uczak, P.; Mathes, H. J.; Mayer, H. J.; Milke, J.; Mitrica, B.; Morello, C.; Navarra, G.; Nehls, S.; Nigl, A.; Oehlschläger, J.; Over, S.; Petcu, M.; Pierog, T.; Rautenberg, J.; Rebel, H.; Roth, M.; Saftoiu, A.; Schieler, H.; Schmidt, A.; Schröder, F.; Sima, O.; Singh, K.; Stümpert, M.; Toma, G.; Trinchero, G. C.; Ulrich, H.; Walkowiak, W.; Weindl, A.; Wochele, J.; Wommer, M.; Zabierowski, J.; Zensus, J. A.; LOPES Collaboration

2009-06-01

85

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

86

Propagation measurements using a digital channel sounder matched to the GSM-system bandwidth  

Microsoft Academic Search

Area coverage in the Pan-European Group Special Mobile (GSM) system requires both a specified minimum field strength and a high local probability that the length of the impulse response (IR) does not exceed a duration of about 16 ?s. Because of the lack of commercial equipment to measure and record complex IRs in mobile radio, an entirely digital channel sounder

Rudolf Werner Lorenz; Gerhard Kadel

1991-01-01

87

A stochastic multiple-input-multiple-output radio channel model for evaluation of space-time coding algorithms  

Microsoft Academic Search

A simple framework for Monte Carlo simulations of a multiple-input-multiple-output radio channel is proposed. The derived model includes the partial correlation between the paths in the channel, as well as fast fading and time dispersion. The only input parameters required for the model are the shape of the power delay spectrum and the spatial correlation functions at the transmit and

Klaus I. Pedersen; Jorgen Bach Andersen; J. P. Kermoal; Preben Mogensen

2000-01-01

88

Forecast impact experiment with GPS radio occultation measurements  

Microsoft Academic Search

Refractivity profiles from CHAMP GPS radio occultation measurements have been assimilated into the Met Office numerical weather prediction (NWP) system. A forecast impact experiment was run using 16 days of CHAMP data from May\\/June 2001, in addition to conventional and satellite observations which are used in operational forecasts. Although typically only 160 CHAMP profiles are assimilated daily, it is demonstrated

S. B. Healy; A. M. Jupp; C. Marquardt

2005-01-01

89

Chipless radio frequency identification by remote measurement of complex impedance  

Microsoft Academic Search

A novel technique for radio frequency identification devices (RFID) based on remote measurement of complex impedance at microwave frequencies is presented. The low cost read-only tags do not need semiconductor elements and can be implemented by printing a conducting pattern on a low cost dielectric substrate. Multiple tags are simultaneously illuminated by a chirped microwave signal with a bandwidth of

S. Mukherjee

2007-01-01

90

Chipless Radio Frequency Identification by Remote Measurement of Complex Impedance  

Microsoft Academic Search

A novel technique for radio frequency identification devices (RFID) based on remote measurement of complex impedance at microwave frequencies is presented. The low cost read-only tags do not need semiconductor elements and can be implemented by printing a conducting pattern on a low cost dielectric substrate. Multiple tags are simultaneously illuminated by a chirped microwave signal with a bandwidth of

S. Mukherjee

2007-01-01

91

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

92

Geometry-based channel modelling of MIMO channels in comparison with channel sounder measurements  

NASA Astrophysics Data System (ADS)

In this paper we propose a flexible geometrybased propagation model for wireless communications developed at Ilmenau University of Technology. The IlmProp comprises a geometrical representation of the environment surrounding the experiment and a precise representation of the transmitting and receiving antennas. The IlmProp is capable of simulating Multi-User MIMO scenarios and includes a complete collection of tools to analyze the synthetic channels. In order to assess the potentials as well as the limits of our channel simulator we reconstruct the scenario encountered in a recent measurement campaign at Ilmenau University of Technology leading to synthetic data sets similar to the ones actually measured. The measurements have been collected with the RUSK MIMO multi-dimensional channel sounder. From the comparisons of the two channel matrices it is possible to derive useful information to improve the model itself and to better understand the physical origins of small-scale fading. In particular the effects of the different parameters on the synthetic channel have been studied in order to assess the sensibility of the model. This analysis shows that the correct positioning of a small number of scatterers is enough to achieve frequency selectiveness as well as specific traits of the channel statistics. The size of the scattering clusters, the number of scatterers per cluster, and the Rician K-factor can be modified in order to tune the channel statistics at will. To obtain higher levels of time variance, moving scatterers or time dependent reflection coefficients must be introduced.

Del Galdo, G.; Haardt, M.; Schneider, C.

2004-05-01

93

Application of the Hardman methodology to the Single Channel Ground-Airborne Radio System (SINCGARS)  

NASA Technical Reports Server (NTRS)

The HARDMAN methodology was applied to the various configurations of employment for an emerging Army multipurpose communications system. The methodology was used to analyze the manpower, personnel and training (MPT) requirements and associated costs, of the system concepts responsive to the Army's requirement for the Single Channel Ground-Airborne Radio System (SINCGARS). The scope of the application includes the analysis of two conceptual designs Cincinnati Electronics and ITT Aerospace/Optical Division for operating and maintenance support addressed through the general support maintenance echelon.

1984-01-01

94

Radio Propagation Measurements and Modeling in Railway Viaduct Area  

Microsoft Academic Search

A network with high quality of service (QoS) is required for railway wireless communication and control systems. Research on radio-wave propagation in railway environment has great significance for the design and optimization of the railway wireless network. In this paper, measurements are taken in railway viaduct area using track side base stations of the GSM-R network. Comparison between the measured

Jinghui Lu; Gang Zhu; Bo Ai

2010-01-01

95

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

96

An 11-Channel Radio Frequency Phased Array Coil for Magnetic Resonance Guided High Intensity Focused Ultrasound of the Breast  

PubMed Central

In this study, a radio-frequency (RF) 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 RF 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 (SNR) 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 SNR, overall imaging time, and temperature measurement accuracy to that of the standard single chest-loop coil typically used in breast MRgHIFU.

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

2012-01-01

97

Rocket radio measurement of electron density in the nighttime ionosphere  

NASA Technical Reports Server (NTRS)

One experimental technique based on the Faraday rotation effect of radio waves is presented for measuring electron density in the nighttime ionosphere at midlatitudes. High frequency linearly-polarized radio signals were transmitted to a linearly-polarized receiving system located in a spinning rocket moving through the ionosphere. Faraday rotation was observed in the reference plane of the rocket as a change in frequency of the detected receiver output. The frequency change was measured and the information was used to obtain electron density data. System performance was evaluated and some sources of error were identified. The data obtained was useful in calibrating a Langmuir probe experiment for electron density values of 100/cu cm and greater. Data from two rocket flights are presented to illustrate the experiment.

Gilchrist, B. E.; Smith, L. G.

1979-01-01

98

On the ionosphere calibration in GPS radio occultation measurements  

Microsoft Academic Search

Elimination of the ionospheric contribution to atmospheric delays in GPS radio occultation measurements is a key issue in the retrieval of accurate pressure and temperature profiles above the tropopause. The traditional so-called ``ionosphere-free'' combination of the L1 and L2 phase paths, eliminating the first-order ionospheric effects, is not sufficient because of the nonnegligible bending of the two ray paths. Because

Stig Syndergaard

2000-01-01

99

Compendium of Radio Measurements of Bright Galaxies (Haynes+ 1975)  

NASA Astrophysics Data System (ADS)

This catalog contains all radio measurements of optically bright 'normal' galaxies available up until publication of this compendium in 1975. The compendium was originally intended to simplify statistical analysis of radio properties of these normal galaxies. No data processing was carried out (except to bring the data into a consistent format) and no identification was attempted. These data were originally published as Haynes R.F., Huchtmeier W.K.H., Siegman B., and Wright A.E., CSIRO Publication, 1975. The electronic version of this catalog has made small changes to the original version in an attempt to better identify positions with their source names. Where there was no entry on a line for the source name or position in the published version, data from the previous line was repeated. (2 data files).

Haynes, R. F.; Huchtmeier, W. K. H.; Siegman, B.; Wright, A. E.

1999-04-01

100

Optimization of Four Wave Mixing Effect in Radio-over-Fiber for a 32Channel 40-GBPS DWDM System  

Microsoft Academic Search

In this paper, we have discussed in detail the four wave mixing (FWM) effect of dense wavelength division multiplexing (DWDM) in Radio-over-Fiber (RoF) system. A 32-channel 40-Gbps system is considered. FWM effect for various channel spacing, input power level, effective fiber area and modulation formats are analyzed. Different schemes for minimizing these effects are discussed for the first time. Considering

Bijayananda Patnaik; P. K. Sahu

2010-01-01

101

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

102

AN/ARQ-53 Navy Shipboard Single Channel Ground and Airborne Radio System (SINCGARS). Technical Evaluation (DT-IIB).  

National Technical Information Service (NTIS)

The purpose of DT-IIB was to conduct both technical and operational testing in order to verify that the AN/ARQ-53 Navy Shipboard Single Channel Ground and Airborne Radio System (SINCGARS) is performing to the required equipment/system specifications and t...

W. Leger

1996-01-01

103

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

104

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

105

Radio-frequency probe for bubble size and velocity measurements.  

PubMed

A radio frequency (rf) probe that can provide local void fraction and interface velocity measurements in a gas-liquid two-phase flow was developed. The probe response to bubble passage was investigated with single-bubble controlled experiments. For a fixed geometry, the probe response was dependent on the dielectric constant of the medium surrounding the probe tip (air or water) and on the frequency of the carrier signal supplied to the probe. Bubble lengths (< 1 cm) and average bubble approach velocities (< 160 cm/s) were independently measured by two light sources and detectors placed at a known distance from each other and sensing the passage of each bubble. By choosing a sensitive probe tip length of 2.75-3 mm, the rf probe output provided enough information to determine the bubble length and velocity. The results obtained by the two independent methods show reasonable agreement (+/-10%). PMID:18699371

Abuaf, N; Feierabend, T P; Zimmer, G A; Jones, O C

1979-10-01

106

Recognizing magnetic structures by present and future radio telescopes with Faraday rotation measure synthesis  

NASA Astrophysics Data System (ADS)

Context. Modern radio telescopes allow us to record a large number of spectral channels. The application of a Fourier transform to spectropolarimetric data in radio continuum, Faraday rotation measure (RM) synthesis, yields the “Faraday spectrum”, which hosts valuable information about the magneto-ionic medium along the line of sight. Aims: We investigate whether the method of wavelet-based RM synthesis can help us to identify structures of regular and turbulent magnetic fields in extended magnetized objects, such as galaxies and galaxy clusters. Methods: The analysis of spectropolarimetric radio observations of multi-scale targets calls for a corresponding mathematical technique. Wavelets allow us to reformulate the RM synthesis method in a scale-dependent way and to visualize the data as a function of Faraday depth and scale. Results: We present observational tests to recognize magnetic field structures. A region with a regular magnetic field generates a broad “disk” in Faraday space, with two “horns” when the distribution of cosmic-ray electrons is broader than that of the thermal electrons. Each field reversal generates one asymmetric “horn” on top of the “disk”. A region with a turbulent field can be recognized as a “Faraday forest” of many components. These tests are applied to the spectral ranges of various synthesis radio telescopes. We argue that the ratio of maximum to minimum wavelengths determines the range of scales that can be identified in Faraday space. Conclusions: A reliable recognition of magnetic field structures in spiral galaxies or galaxy clusters requires the analysis of data cubes in position-position-Faraday depth space (“PPF cubes”), observed over a wide and continuous frequency range, allowing the recognition of a wide range of scales as well as high resolution in Faraday space. The planned Square Kilometre Array (SKA) will fulfill this condition and will be close to representing a perfect “Faraday telescope”. The combination of data from the Low Frequency Array (LOFAR, at low frequencies) and the Expanded Very Large Array (EVLA, at high frequencies) appears to be a promising approach for the recognition of magnetic structures on all scales. The addition of data at intermediate frequencies from the Westerbork Synthesis Radio Telescope (WSRT) or the Giant Meterwave Radio Telescope (GMRT) would fill the gap between the LOFAR and EVLA frequency ranges. The Global Magneto-Ionic Medium Survey (GMIMS), planned with several single-dish telescopes at low angular resolution, will also provide good scale recognition and high resolution in Faraday space.

Beck, R.; Frick, P.; Stepanov, R.; Sokoloff, D.

2012-07-01

107

Super-Sharp Radio "Vision" Measures Galaxy's Motion in Space  

NASA Astrophysics Data System (ADS)

Astronomers using the National Science Foundation's Very Long Baseline Array (VLBA) have measured the motion across the sky of a galaxy nearly 2.4 million light-years from Earth. While scientists have been measuring the motion of galaxies directly toward or away from Earth for decades, this is the first time that the transverse motion (called proper motion by astronomers) has been measured for a galaxy that is not a satellite of our own Milky Way Galaxy. M33 Radio/Optical Image of M33 CREDIT: NRAO/AUI/NSF, NOAO/AURA/NSF (Click on image for more files) An international scientific team analyzed VLBA observations made over two and a half years to detect minuscule shifts in the sky position of the spiral galaxy M33. Combined with previous measurements of the galaxy's motion toward Earth, the new data allowed the astronomers to calculate M33's movement in three dimensions for the first time. "A snail crawling on Mars would appear to be moving across the surface more than 100 times faster than the motion we measured for this galaxy," said Mark Reid, of the Harvard-Smithsonian Center for Astrophysics in Cambridge, MA. M33 is a satellite of the larger galaxy M31, the well-known Andromeda Galaxy that is the most distant object visible to the naked eye. Both are part of the Local Group of galaxies that includes the Milky Way. In addition to measuring the motion of M33 as a whole, the astronomers also were able to make a direct measurement of the spiral galaxy's rotation. Both measurements were made by observing the changes in position of giant clouds of molecules inside the galaxy. The water vapor in these clouds acts as a natural maser, strengthening, or amplifying, radio emission the same way that lasers amplify light emission. The natural masers acted as bright radio beacons whose movement could be tracked by the ultra-sharp radio "vision" of the VLBA. Reid and his colleagues plan to continue measuring M33's motion and also to make similar measurements of M31's motion. This will allow them to answer important questions about the composition, history and fates of the two galaxies as well as of the Milky Way. "We want to determine the orbits of M31 and M33. That will help us learn about their history, specifically, how close have they come in the past?" Reid explained. "If they have passed very closely, then maybe M33's small size is a result of having material pulled off it by M31 during the close encounter," he added. Accurate knowledge of the motions of both galaxies also will help determine if there's a collision in their future. In addition, orbital analysis can give astronomers valuable clues about the amount and distribution of dark matter in the galaxies. M33's motion in space M33's motion in space, relative to M31 and the Milky Way CREDIT: Bill Saxton, NRAO/AUI/NSF (Click on image for larger version) The direct measurement of M33's transverse angular spin is the first time such a measurement has been done accurately. In the 1920s, some astronomers thought they had measured the spin of spiral galaxies, but their results proved to be in error. More recently, radio astronomers have measured the Doppler shift of hydrogen gas in galaxies to determine the spin speed, which, when combined with the angular spin, gives a direct estimate of the distance of the galaxy. The astronomers' task was not simple. Not only did they have to detect an impressively tiny amount of motion across the sky, but they also had to separate the actual motion of M33 from the apparent motion caused by our Solar System's motion around the center of the Milky Way. The motion of the Solar System and the Earth around the Galactic center, some 26,000 light-years away, has been accurately measured using the VLBA over the last decade. "The VLBA is the only telescope system in the world that could do this work," Reid said. "Its extraordinary ability to resolve fine detail is unmatched and was the absolute prerequisite to making these measurements." Reid worked with Andreas Brunthaler of the Max Planck

2005-03-01

108

Potential radio frequency interference with the GPS L5 band for radio occultation measurements  

NASA Astrophysics Data System (ADS)

New Radio Occultation (RO) receivers are planned to utilize the newly implemented Global Positioning System (GPS) L5 signal centered at 1176.45 MHz. Since there are currently no operational GPS L5 receivers used for space-based RO applications, the interference environment is unclear. Distance Measuring Equipment (DME) and Tactical Air Navigation (TACAN) stations share the same frequency band as the GPS L5 signal. DME/TACAN signals have been identified to be a means of interference for any GPS L5 receiver. This study focuses on implementing a Systems Tools Kit (STK) simulation to gain insight into the power received by a RO satellite in Low Earth Orbit (LEO) from a DME/TACAN transmission. In order to confirm the validity of utilizing STK for communication purposes, a theoretical scenario was recreated as a simulation and the results were confirmed. Once the method was validated, STK was used to output a received power level aboard a RO satellite from a DME/TACAN station as well as a tool to predict the number of interfering DME/TACAN stations at any point in time. Taking a conservative approach, the signal power received was much greater than the typical power level received by a RO satellite from a GPS satellite transmission. This relatively high received power along with a high number of interfering DME/TACAN stations as an RO satellite passes over North America or Western Europe indicate that DME/TACAN interference may conflict with RO receivers.

Wolff, A. M.; Akos, D. M.; Lo, S.

2014-05-01

109

Outage probability for a frequency-selective fading digital portable radio channel with selection diversity using coding  

Microsoft Academic Search

The outage probability for a time division multiple access (TDMA) portable radio channel with diversity selection based on coding is obtained by using computer simulation. Coherent detection of a quaternary phase shift keying (QPSK) signal with spectrally raised-cosine Nyquist pulse with 0.5 roll-off factor is used as an example. Different performance criteria are used to define outage. The outage probability

Li Fung Chang; Justin C-I Chuang

1989-01-01

110

New measurements of cosmic ray air showers with the digital radio interferometer LOPES  

NASA Astrophysics Data System (ADS)

LOPES is a digital radio interferometer which measures the radio emission of extensive cosmic ray air showers. It mainly consists of 30 dipole antennas installed in co-location with KASCADE-Grande at the Karlsruhe Institute of Technology (KIT) in Germany. KASCADE-Grande measures the secondary air shower particles at ground. Whenever KASCADE-Grande detects a high-energy cosmic ray event (?1016 eV), it triggers LOPES which then digitally records the radio signal in the frequency band from 40 to 80 MHz. Using interferometric methods, LOPES is able to successfully detect air shower induced radio pulses, even in the noisy environment at the KIT. In the present studies, a considerable progress in understanding the radio emission mechanism is shown: The latest version of the "radio emission in air shower" simulation program, REAS3, seems to be the first Monte Carlo tool which is able to reproduce the magnitude and slope of most of the measured lateral distributions.

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

2011-08-01

111

Interference-mitigation measures at RATAN-600 radio telescope  

NASA Astrophysics Data System (ADS)

We report an analysis of the electromagnetic situation at RATAN-600 radio telescope over the 30-year period of operation of the complex of continuum radiometers. We analyze practical methods for mitigating radio interference ranging from the use of anti-interference adapters to incorporating fast digital signal processors into the standard data acquisition system.

Tsybulev, P. G.; Berlin, A. B.; Nizhel'Skij, N. A.; Mingaliev, M. G.; Kratov, D. V.

2007-06-01

112

Ion species mix and ion density measurements using radio frequency waves  

Microsoft Academic Search

Radio frequency wave applications have demonstrated great versatility in tokamak plasmas. Two applications, using the same diagnostic design, can make use of a fast Alfven wave to make ion species mix and ion density measurements. A discussion and derivation, using the cold plasma approximation, is given for a fast Alfven radio wave used for making an interferometry density measurement, a

George Wilder Watson III

2003-01-01

113

The atmosphere of Io from Pioneer 10 radio occultation measurements  

NASA Technical Reports Server (NTRS)

The occultation of the Pioneer 10 spacecraft by Io (JI) provided an opportunity to obtain two S-band radio occultation measurements of its atmosphere. The day-side entry measurements revealed an ionosphere having a peak density of about 60,000 el/cu cm at an altitude of about 100 km. The topside scale height indicates a plasma temperature of about 406 K if it is composed of Na(+) and 495 K if N2(+) is principal ion. A thinner and less dense ionosphere was observed on the exit (night side), having a peak density of 9,000 el/cu cm at an altitude of 50 km. The topside plasma temperature is 160 K for N2(-) and 131 K for Na(+). If the ionosphere is produced by photoionization in a manner analogous to the ionospheres of the terrestrial planets, the density of neutral particles at the surface of Io is less than 10 to 1 trillion per cu cm, corresponding to a surface pressure of less than 10 to 1 nanobars.

Kliore, A. J.; Fjeldbo, G.; Seidel, B. L.; Sweetnam, D. N.; Sesplaukis, T. T.; Woiceshyn, P. M.; Rasool, S. I.

1975-01-01

114

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

115

Measuring Ion Channels on Solid Supported Membranes  

PubMed Central

Abstract 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.

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

2009-01-01

116

Dynamic channel allocation based on the game learning in cognitive radio networks  

Microsoft Academic Search

A priority table of available channels in network is structured with the analysis of the channel usability by cooperative spectrum sensing. With this table, we design an information exchange and access mechanism based on TDMA mode. We bring in the EWA (Experience-Weight Attraction) game learning model, and propose a channel selection learning algorithm based on the channel priority and the

Wen-jiang Feng; Chao Zhou; Wei-heng Jiang

2010-01-01

117

Measurement of Geopotential Heights by GPS Radio Occultation  

NASA Technical Reports Server (NTRS)

Geopotential heights of constant pressure surfaces are retrieved from global positioning system (GPS) radio occultation data. In order to assess accuracy a subset of data obtained by GPS/MET during spring 1995 and summer 1995 are compared to the output of the European Centre for Medium-Range Weather Forecasts (ECMWF) global model. The root-mean-square measurement error is 20 m throughout the upper troposphere and lower stratosphere. Furthermore, the ECMWF global model contains enhanced errors in the southeast Pacific. In probing the data for potential utility in climate studies, a Bayesian interpolation technique is used to map the geopotential height fields in the upper troposphere during the summer. Despite limitations of the GPS/MET data set the global average 300-mbar geopotential height over a 2-week period in summer 1995 is determined with an accuracy of 7 m. By obtaining greater coverage and partially resolving synoptic variability, a future constellation of 16 orbiting receivers could obtain global average geopotential height estimates in the upper troposphere with an accuracy of 1 m each day. Accuracy would be somewhat worse for regional studies, except in the tropics where synoptic variability is depressed.

Leroy, Stephen S.

1997-01-01

118

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

119

Radio Frequency (RF) Attenuation Measurements of the Space Shuttle Vehicle  

NASA Technical Reports Server (NTRS)

Following the loss of Columbia, the Columbia Accident Investigation Board (CAIB) provided recommendations to be addressed prior to Return To Flight (RTF). As a part of CAIB Recommendation 3.4.1 - Ground Based Imagery, new C-band and X-band radars were added to the array of ground-based radars and cameras already in-situ at Kennedy Space Center. Because of higher power density considerations and new operating frequencies, the team of Subject Matter Experts (SMEs) assembled to investigate the technical details of introducing the new radars recommended a series of radio frequency (RF) attenuation tests be performed on the Space Shuttle vehicle to establish the attenuation of the vehicle outer mold line structure with respect to its external RF environment. Because of time and complex logistical constraints, it was decided to split the test into two separate efforts. The first of these would be accomplished with the assistance of the Air Force Research Laboratory (AFRL), performing RF attenuation measurements on the aft section of OV-103 (Discovery) while in-situ in Orbiter Processing Facility (OPF) 3, located at Kennedy Space Center. The second would be accomplished with the assistance of the National Institute of Standards and Technology (NIST) and the electromagnetic interference (EMI) laboratory out of the Naval Air Warfare Center, Patuxent River, Maryland (PAX River), performing RF attenuation measurements on OV-105 (Endeavour) in-situ inside the Space Shuttle Landing Facility (SLF) hangar, also located at Kennedy Space Center. This paper provides a summary description of these efforts and their results.

Scully, R. C.; Kent, B. M.; Kempf, D. R.; Johnk, R. T.

2006-01-01

120

Packet Switching in Radio Channels: Part II--The Hidden Terminal Problem in Carrier Sense Multiple-Access and the Busy-Tone Solution  

Microsoft Academic Search

We consider a population of terminals communicating with a central station over a packet-switched multiple-access radio channel. The performance of carrier sense multiple access (CSMA) [1] used as a method for multiplexing these terminals is highly dependent on the ability of each terminal to sense the carrier of any other transmission on the channel. Many situations exist in which some

F. A. Tobagi; L. Kleinrock

1975-01-01

121

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

122

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

Microsoft Academic Search

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

Peter Gorham; David Saltzberg; Allen Odian; Dawn Williams; David Besson; George Frichter; Sami Tantawi

2001-01-01

123

Measurement of galactic radio emission at frequency 37 GHz from aboard spacecraft  

Microsoft Academic Search

It is postulated that the distribution of thermal galactic radio emission is dominated by extended low-density HII regions (ELD regions), with the remaining HII regions accounting for only 16. Until now it has been impossible to measure the parameters of extended sources of thermal radio emission with sufficient accuracy. This can be done by exoatmospheric scanning at relatively high frequencies.

I. A. Strukov; D. P. Skulachev

1988-01-01

124

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

125

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

126

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

127

Evaluation of adjacent channel interference in single radio vehicular Ad-Hoc networks  

Microsoft Academic Search

VANETS extend the driver's horizon to decrease traffic accidents by utilizing IEEE 802.11p wireless networks. In high density traffic situations an overloaded communication channel leads to significant packet loss. To overcome this problem multiple channels can be used in IEEE 802.11p. This itself leads to adjacent channel interference and impacts the performance of nearby channels. In this paper we define

Robert Lasowski; Constantin Scheuermann; Florian Gschwandtner; Claudia Linnhoff-Popien

2011-01-01

128

Optimal Throughput for Cognitive Radio with Energy Harvesting in Fading Wireless Channel  

PubMed Central

Energy resource management is a crucial problem of a device with a finite capacity battery. In this paper, cognitive radio is considered to be a device with an energy harvester that can harvest energy from a non-RF energy resource while performing other actions of cognitive radio. Harvested energy will be stored in a finite capacity battery. At the start of the time slot of cognitive radio, the radio needs to determine if it should remain silent or carry out spectrum sensing based on the idle probability of the primary user and the remaining energy in order to maximize the throughput of the cognitive radio system. In addition, optimal sensing energy and adaptive transmission power control are also investigated in this paper to effectively utilize the limited energy of cognitive radio. Finding an optimal approach is formulated as a partially observable Markov decision process. The simulation results show that the proposed optimal decision scheme outperforms the myopic scheme in which current throughput is only considered when making a decision.

Vu-Van, Hiep; Koo, Insoo

2014-01-01

129

Analysis of satellite measurements of terrestrial radio noise  

NASA Technical Reports Server (NTRS)

Worldwide distributions of terrestrial radio noise as monitored by Radio Astronomy Explorer 1 (RAE 1) generated and compared with CCIR predictions. These contour maps show the global morphology of radio noise at 6.55 and 9.18 MHz for fall, winter, spring and summer during the local time blocks of 00-08 LT and 16-24 LT. These computer produced maps show general agreement with CCIR predictions over large land masses. The RAE and CCIR maps diverge at high latitudes over Asia and frequently over ocean regions. Higher noise levels observed by RAE at high latitudes are attributed to magnetospheric emission while higher noise levels observed by RAE over Asia are attributable to high power transmitters. Analysis of RAE noise observations in conjunction with various geophysical phenomena showed no obvious correlation.

Bakalyar, G.; Caruso, J. A.; Vargas-Vila, R.; Ziemba, E.

1974-01-01

130

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

131

Measurements of electronic properties of the Miyun 50 m Radio Telescope  

NASA Astrophysics Data System (ADS)

Measurement results of some properties of the Miyun 50 m radio telescope (MRT50) of the National Astronomical Observatories, such as pointing calibration, antenna beams, system noise temperature, gain and gain variations with elevation are introduced. By using a new de-convolution technique developed by our group, the broadening effect on measured beams caused by the width of an extended radio source has been removed so that we obtained higher accuracy on the measurements of MRT50 beams.

Zhang, Xi-Zhen; Zhu, Xin-Ying; Kong, De-Qing; Zheng, Lei; Yao, Cheng; Zhang, Hong-Bo; Su, Yan; Piao, Ting-Yi

2009-03-01

132

The Algebraic Measure of a Hidden Markov Quantum Memory Channel  

NASA Astrophysics Data System (ADS)

The classical product state capacity of a noisy quantum channel with memory is investigated. A forgetful noise-memory channel is constructed by Markov switching between two depolarizing channels which introduces non-Markovian noise correlations between successive channel uses. This function of a Markov process can be reformulated as an algebraic measure. This framework provides an expression for the asymptotic entropy rate and thus enables the calculation of the classical capacity. The effects of the hidden-Markovian memory on the capacity are explored. An increase in noise-correlations is found to increase the capacity.

Akhalwaya, I.; Wouters, J.; Fannes, M.; Petruccione, F.

2009-04-01

133

Effect of delay spread on a FH-FSK spread spectrum mobile radio system over frequency-selective fading channels  

NASA Astrophysics Data System (ADS)

This paper is concerned with estimating the performance of a multi-user frequency hopping (FH) spread spectrum mobile radio system with binary frequency-shift keying (BFSK) modulation over Rician and Rayleigh frequency-selective fading channels and, more specifically, with estimating the effect of time delay spread on that performance. Previous analyses of FH-BFSK communications over frequency-selective fading channels have typically assumed that the time delay spread models are symmetrical. This paper proposes the use of non-symmetrical time delay spread models, and introduces a new method to estimate average bit error probability, thus opening the way to the use of site-specific time-delay spread models in performance estimation and in mobile and personal communication system design.

Wang, X. D.; Lecours, M.

1994-02-01

134

Alternate Methods of Measuring Public Radio Audiences: A Pilot Project.  

ERIC Educational Resources Information Center

A pilot project was undertaken to explore ways to profile public radio audiences inexpensively and simply. The major effort was through use of the station's monthly programing guide mailing list. Persons found in this list were interviewed and their listening habits compared with a general survey (baseline) group. The survey showed that public…

Williams, Wenmouth, Jr.; LeRoy, David J.

135

Global Measurements of Low-Frequency Radio Noise.  

National Technical Information Service (NTIS)

This final technical report reviews progress in Stanford University's ONR-sponsored global survey of ELF'/VLF radio noise (frequencies in the range 10 Hz - 32 kliz) during the period 1 November 1989 through 31 October 1991, i.e., the period covered by ONR...

A. C. Fraser-Smith R. A. Helliwell

1995-01-01

136

On noise treatment in radio measurements of cosmic ray air showers  

NASA Astrophysics Data System (ADS)

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 influence on amplitude and time measurement of radio pulses must be studied with care. First, noise has to be determined consistently with the definition of the radio signal which typically is the maximum field strength of the radio pulse. Second, the average impact of noise on radio pulse measurements at individual antennas is studied for LOPES. It is shown that a correct treatment of noise is especially important at low signal-to-noise ratios: noise can be the dominant source of uncertainty for pulse height and time measurements, and it can systematically flatten the slope of lateral distributions. The presented method can also be transferred to other experiments in radio and acoustic detection of cosmic rays and neutrinos.

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

2012-01-01

137

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

NASA Astrophysics Data System (ADS)

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 parameters on the performance of a popular operational evaporation duct model is examined. The strengths and weaknesses of this model are evaluated under specific atmospheric conditions. The relationship between the continually varying evaporation duct height and transmitter-receiver antenna geometries is analyzed, and a range of statistics related to the implications of this relationship on the received signal strength is presented. The various issues under investigation are of direct relevance in the planning of long-range, over-sea radio systems operating in the UHF band, and have implications for the radio regulatory work carried out by organizations such as the International Telecommunication Union.

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

2010-12-01

138

Measurements and Modelling of the HF Radio Noise Environment Near an Hvdc Converter Station.  

National Technical Information Service (NTIS)

Measurements of the HF radio noise environment near an HVDC transmission line and converter station were made outside Winnipeg in July 1977. Typical levels and characteristics are presented for various combinations of mercury arc valve noise, AC hum and D...

W. R. Lauber J. M. Bertrand

1983-01-01

139

Measurements and Modelling of the HF Radio Noise Environment Near an HVDC Converter Station.  

National Technical Information Service (NTIS)

Measurements of the HF radio noise environment near an HVDC transmission line and converter station were made outside Winnipeg in July 1977. Typical levels and characteristics are presented for various combinations of mercury arc valve noise, ac hum and d...

W. R. Lauber J. M. Bertrand

1983-01-01

140

Seventy Years of Radio Science, Technology, Standards, and Measurement at the National Bureau of Standards  

NASA Astrophysics Data System (ADS)

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 for discovery and application in meteorology, navigation, and in standards of measurement and testing in electronics.The book is a bit unwieldy and some of its chapters will be of most interest to former NBS employees. For example, there is a lengthy chapter on the transfer of radio research work from Washington, D.C, to Boulder, Colo., in the early 1950s, complete with photostat of the quit claim deed to NBS from the Boulder Chamber of Commerce. On the other hand, radio research developed and flourished in this country in the early days at industrial (Bell Telephone, General Electric, Westinghouse) and government (NBS, Naval Research Laboratory) labs more than in academia, and it is very interesting to learn how the labs interacted and to read details of the organizational structure. I can attest personally to the great difficulties in locating materials concerning radio history. While we have numerous volumes devoted to certain popular radio heroes, little is available concerning government radio pioneers such as L. W. Austin, who directed the U.S. Navy's radio research for many years while situated physically at the Bureau of Standards, or J. H. Dellinger, long-time chief of the Radio Section and head spokesman on radio for the U.S. government until the 1930s.

Gillmor, C. Stewart

141

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

2011-01-01

142

Multi-Channel Multi-Radio Using 802.11 Based Media Access for Sink Nodes in Wireless Sensor Networks  

PubMed Central

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.

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

2011-01-01

143

Radio emission of energetic cosmic ray air showers: Polarization measurements with LOPES  

NASA Astrophysics Data System (ADS)

LOPES is a radio antenna array co-located with the Karlsruhe Shower Core and Array DEtector, KASCADE-Grande in Forschungszentrum Karlsruhe, Germany, which provides well-calibrated trigger information and air shower parameters for primary energies up to 10eV. By the end of 2006, the radio antennas were re-configured to perform polarization measurements of the radio signal of cosmic ray air showers, recording in the same time both, the East-West and North-South polarization directions of the radio emission. The main goal of these measurements is to reconstruct the polarization characteristics of the emitted signal. This will allow a detailed comparison with theoretical predictions. The current status of these measurements is reported here.

Lopes Collaboration; Isar, P. G.; Apel, W. D.; Arteaga, J. C.; Asch, T.; Auffenberg, J.; Badea, F.; Bähren, L.; Bekk, K.; Bertaina, M.; Biermann, P. L.; Blümer, J.; Bozdog, H.; Brancus, I. M.; Brüggemann, M.; Buchholz, P.; Buitink, S.; Cantoni, E.; Chiavassa, A.; Cossavella, F.; Daumiller, K.; de Souza, V.; di Pierro, F.; Doll, P.; Engel, R.; Falcke, H.; Finger, M.; Fuhrmann, D.; Gemmeke, H.; Ghia, P. L.; Glasstetter, R.; Grupen, C.; Haungs, A.; Heck, D.; Hörandel, J. R.; Horneffer, A.; Huang, X.; Huege, T.; Kampert, K.-H.; Kang, D.; Kickelbick, D.; Kolotaev, Y.; Krömer, O.; Kuijpers, J.; Lafebre, S.; ?uczak, P.; Mathes, H. J.; Mayer, H. J.; Milke, J.; Mitrica, B.; Morello, C.; Navarra, G.; Nehls, S.; Nigl, A.; Oehlschläger, J.; Over, S.; Petcu, M.; Pierog, T.; Rautenberg, J.; Rebel, H.; Roth, M.; Saftoiu, A.; Schieler, H.; Schmidt, A.; Schröder, F.; Sima, O.; Singh, K.; Stümpert, M.; Toma, G.; Trinchero, G. C.; Ulrich, H.; Walkowiak, W.; Weindl, A.; Wochele, J.; Wommer, M.; Zabierowski, J.; Zensus, J. A.; LOPES Collaboration

2009-06-01

144

Magellan Radio Occultation Measurements of Atmospheric Waves on Venus  

Microsoft Academic Search

Radio occultation experiments were conducted at Venus on three consecutive orbits of the Magellan spacecraft in October 1991. Each occultation occurred over the same topography (67°N, 127°E) and at the same local time (22h5m), but the data are sensitive to zonal variations because the atmosphere rotates significantly during one orbit. Through comparisons between observations and predictions of standard wave theory,

David P. Hinson; Jon M. Jenkins

1995-01-01

145

Multistage block-spreading for impulse radio multiple access through ISI channels  

Microsoft Academic Search

Transmitting digital information using ultra-short pulses, impulse radio (IR) has received increasing interest for multiple access (MA). When IRMA systems have to operate in dense multipath environments, the multiple user interference (MUI) and intersymbol interference (ISI) induced, adversely affect system capacity and performance. Analog IRMA utilizes pulse position modulation (PPM) and random time-hopping codes to mitigate ISI and suppress MUI

Liuqing Yang; Georgios B. Giannakis

2002-01-01

146

Accurate Performance Analysis of Optimum Diverity Combining and Equalization over Mobile Radio Fading Channel with CCI  

Microsoft Academic Search

This paper is devoted to the precise performance analysis of optimum diversity combining and equalization with quadrature amplitude modulation (QAM) over frequency-selective fading channels in the presence of co-channel interference (CCI). In developing the optimum receiver, a precise CCI model with taking into account the effects of symbol and carrier timing offsets between the desired signal and CCI is used.

Sheng-Chou Lin; Hung-Wen Fang

2005-01-01

147

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

148

Area spectral efficiency of a channel adaptive cellular mobile radio system in a correlated shadowed environment  

Microsoft Academic Search

In this paper, the average area spectral efficiency (ASE) in bits\\/sec\\/Hz\\/Km2 of a variable transmission rate, high capacity cellular communication system is studied in a correlated shadowed environment. The effect on average ASE of the normalised reuse distance, shadowing variance, correlation between radio signals, coverage radius and cell sectorization is investigated by computer simulations. It is shown mathematically that the

M. F. Tariq; A. Nix

1998-01-01

149

Performance evaluation of noncoherent frequency-hopped spread-spectrum cellular radio networks over fading channels  

Microsoft Academic Search

The authors characterize multiple-access for cellular mobile radio networks, in which users are assumed to be Poisson-distributed in the plane. These networks use frequency-hopped or hybrid direct-sequence\\/slow frequency-hopped spread-spectrum signaling. The Gaussian approximation technique is used to compute the symbol error probability for both types of spread-spectrum signaling with noncoherent MFSK modulation, and for a general class of dispersive fading

AmCrico M. C. Correia; A. A. Albuquerque

1991-01-01

150

Cryocooled wideband digital channelizing radio-frequency receiver based on low-pass ADC  

Microsoft Academic Search

We have demonstrated a digital receiver performing direct digitization of radio-frequency signals over a wide frequency range from kilohertz to gigahertz. The complete system, consisting of a cryopackaged superconductor all-digital receiver (ADR) chip followed by room-temperature interface electronics and a field programmable gate array (FPGA) based post-processing module, has been developed. The ADR chip comprises a low-pass analog-to-digital converter (ADC)

Igor V. Vernik; Dmitri E. Kirichenko; Vladimir V. Dotsenko; Robert Miller; Robert J. Webber; Pavel Shevchenko; Andrei Talalaevskii; Deepnarayan Gupta; Oleg A. Mukhanov

2007-01-01

151

On fractionally-spaced equalizer design for digital microwave radio channels  

Microsoft Academic Search

Advances in blind identification of fractionally-spaced models for digital communication channels and blind fractionally-spaced equalizer adaptation rely on the assumption that the time span chosen for the fractionally-spaced equalizer exceeds that of the channel. This paper considers time-domain design formulas minimizing the mean-squared symbol recovery error achieved by a finite-length FIR fractionally-spaced equalizer with a time span shorter than the

C. R. Johnson; H. J. Lee; J. P. LeBlanc; T. J. Endres; R. A. Casas; E. Tai; Z. Reznic; W. E. Meyer

1995-01-01

152

Performance evaluation of bandwidth efficient block-coded schemes on a mobile radio channel  

Microsoft Academic Search

The performance of bandwidth-efficient Reed-Solomon coded multiphase signalling schemes is evaluated on a shadowed Rician fading channel using different decoding strategies, namely, errors-only, erasures-and-errors, and soft-decision decoding. The error bounds are calculated and examined by simulation for the RS(7,5)-coded 8 PSK scheme as an example, on a shadowed Rician channel with different degrees of shadowing. It is shown that the

S. Hamidreza Jamali; Tho Le-Ngoc

1991-01-01

153

Channel capacities versus entanglement measures in multiparty quantum states  

SciTech Connect

For quantum states of two subsystems, highly entangled states have a higher capacity of transmitting classical as well as quantum information, and vice versa. We show that this is no more the case in general: Quantum capacities of multiaccess channels, motivated by communication in quantum networks, do not have any relation with genuine multiparty entanglement measures. Importantly, the statement is demonstrated for arbitrary multipartite entanglement measures. Along with revealing the structural richness of multiaccess channels, this gives us a tool to classify multiparty quantum states from the perspective of its usefulness in quantum networks, which cannot be visualized by any genuine multiparty entanglement measure.

Sen, Aditi; Sen, Ujjwal [Harish-Chandra Research Institute, Chhatnag Road, Jhunsi, Allahabad 211 019 (India)

2010-01-15

154

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

155

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

156

Ion movement through gramicidin A channels. Single-channel measurements at very high potentials.  

PubMed Central

The patch-clamp technique of Mueller (1975, Ann. N.Y. Acad. Sci., 274:247-264) and Neher and Sakmann (1976, Nature (Lond.), 260:799-802) was modified to be suitable for single-channel measurements in lipid bilayers at potentials up to 500 mV. This method was used to study gramicidin A single-channel current-voltage characteristics. It was found that the sublinear current-voltage behavior normally observed at low permeant ion concentrations and rather low potentials (V less than or equal to 200 mV) continues to be seen all the way up to 500 mV. This phenomenon is characteristic of the low permeant ion situation in which the channel is far from saturation, and implies that the overall rate constant for association between ion and channel is very weakly, if at all, voltage dependent. The magnitude of the single channel currents at 500 mV is consistent with the notion that the aqueous convergence conductance is a significant factor in determining the permeability characteristics of the gramicidin A channel.

Andersen, O S

1983-01-01

157

Measurement of laser-ion guiding channel strength  

SciTech Connect

The Advanced Test Accelerator (ATA) beam is guided in a low density ion channel produced in benzene gas by a KrF laser. The strength of the ion channel has been measured by deflecting the electron beam in a steady transverse magnetic field. After emerging from the magnetic field, the beam oscillates transversely inside the channel with a few mm amplitude. The transverse position of the beam is measured at many positions using the wall current monitors. The wavelength of the oscillation is measured from a plot of transverse position vs propagation distance. With a 0.5 J laser pulse and 4 x 10/sup -4/ Torr benzene pressure the wavelength was 1 m corresponding to 90 esu/cm/sup 3/ with ..gamma.. = 84.

Lauer, E.J.; Caporaso, G.J.; Chong, Y.P.; Prono, D.S.; Rainer, F.; Struve, K.W.; Weir, J.T.

1986-01-01

158

Performance analysis of a token based MAC protocol with asymmetric polling strategy (`TOPO') for indoor radio local area networks under channel outage conditions  

Microsoft Academic Search

A MAC (media access control)-protocol for the indoor radio environment has to be able to overcome individual link failure due to channel outage with a minimized wastage of bandwidth. `TOPO', a token based MAC protocol with asymmetric polling strategy, is suggested for a network in which the allocation of common resources, such as bandwidth, is administered by a central station.

A. Hoffmann; R. J. Haines; A. H. Aghvami

1994-01-01

159

Measuring gravitational lens time delays using low-resolution radio monitoring observations  

NASA Astrophysics Data System (ADS)

Obtaining lensing time-delay measurements requires long-term monitoring campaigns with a high enough resolution (<1 arcsec) to separate the multiple images. In the radio, a limited number of high-resolution interferometer arrays make these observations difficult to schedule. To overcome this problem, we propose a technique for measuring gravitational time delays which relies on monitoring the total flux density with low-resolution but high-sensitivity radio telescopes to follow the variation of the brighter image. This is then used to trigger high-resolution observations in optimal numbers which then reveal the variation in the fainter image. We present simulations to assess the efficiency of this method together with a pilot project observing radio lens systems with the Westerbork Synthesis Radio Telescope to trigger Very Large Array observations. This new method is promising for measuring time delays because it uses relatively small amounts of time on high-resolution telescopes. This will be important because instruments that have high sensitivity but limited resolution, together with an optimum usage of follow-up high-resolution observations from appropriate radio telescopes may in the future be useful for gravitational lensing time-delay measurements by means of this new method.

Gürkan, G.; Jackson, N.; Koopmans, L. V. E.; Fassnacht, C. D.; Berciano Alba, A.

2014-06-01

160

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

161

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

162

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

163

An adaptable radio-controlled measuring system for oceanographic research in shallow water  

Microsoft Academic Search

The scientific objective of the system presented in this paper is to conduct in situ measurements of environmental parameters and to support several marine in situ experiments which are carried out in order to investigate the interaction between the sea and the sea bottom in shallow-water ecosystems. Automated in situ measurements are carried out by means of the radio-controlled data

ULRICH PETERSOHN; P. Diekmann

1978-01-01

164

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

165

THE USE OF ELECTRICAL PROPERTIES MEASURED AT RADIO FREQUENCIES FOR PAN BOILING &BRIX CONTROL  

Microsoft Academic Search

The theory and development of a probe measuring elec­ trical properties at radio frequencies for use in sugar pro­ cessing is discussed. Basic relationships between the physical properties and the reactance and resistance of massecuites and syrupsare given. It is shown that the newsystem is less sensitive to encrustation than conductivity measurements and can be used in high purity boilings.

D. J. RADFORD; M. G. S. COX

166

CREAM-MAC: An efficient Cognitive Radio-enAbled MultiChannel MAC protocol for wireless networks  

Microsoft Academic Search

Cognitive radio technology has emerged as the novel and effective approach to improve the utilization of precious radio spectrum. Employing the cognitive radio technology, secondary (unlicensed) users can opportunistically utilize the unused licensed spectrum in a way that constrains the level of interference to the primary (licensed) users. However, there are many new challenges associated with cognitive radio based wireless

Hang Su; Xi Zhang

2008-01-01

167

Comparison of Lund'07 vehicular channel measurements with the IEEE 802.11p channel model  

Microsoft Academic Search

This paper presents a very preliminary comparison between the IEEE 802.11p channel model parameters with parameters evaluated from new high speed measurements in Lund, Sweden. Following inter- esting differences as well as similarities are observed: The measured maximum excess delay is about one fifth of the one proposed in the IEEE 802.11p model. The amplitude distribution for each tap can

Alexander Paier; Johan Karedal; Nicolai Czink; Charlotte Dumard; Thomas Zemen; Fredrik Tufvesson; Andreas F. Molisch; Christoph F. Mecklenbrauker

168

Radio-frequency analysis of carrier channels on multiconductor distribution cable networks  

SciTech Connect

The frequency-domain analysis of carrier channels on distribution cable networks is performed by means of an efficient procedure based upon the nodal approach and modal theory. The multiconductor system may present any configuration with multiple discontinuity points. The use of equivalent two-port PI-circuits allows the nodal admittance matrix to be defined in a new form. Very accurate frequency-dependent analytical models are developed to simulate systems of single-core cables or multiple-core pipe-type cables, buried or above a ground plane. In this paper the simulation and propagation models are used to compute the voltage attenuation of carrier channels on uniform line-sections and distribution networks of tree- and mesh-type configurations with different lumped loads, in a frequency range up to 200 kHz.

Celozzi, S.; D'Amore, M. (Dept. of Electrical Engineering, Univ. of Rome, Eudossiana, 18 Rome (IT))

1991-07-01

169

Noncoherently detected trellis-coded partial response CPM on mobile radio channels  

Microsoft Academic Search

A noncoherent receiver is proposed for partial response trellis-coded continuous phase modulation (TC-CPM) on interleaved flat Rician-fading channels. By using a multiple-symbol observation interval and a simple metric calculator, the power efficiency is improved over a receiver that uses a single-symbol observation interval. Performance bounds on the bit error probability are derived by defining a set of characteristic distances for

Lihbor Yiin; G. L. Stuber

1996-01-01

170

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

171

Source and event selection for radio-planetary frame-tie measurements using the Phobos Landers  

NASA Technical Reports Server (NTRS)

The Soviet Phobos Lander mission will place two spacecraft on the Martian moon Phobos in 1989. Measurements of the range from Earth-based stations to the landers will allow an accurate determination of the ephemerides of Phobos and Mars. Delta Very Long Base Interferometry (VLBI) between the landers and compact radio sources nearby on the sky will be used to obtain precise estimates of the angular offset between the radio and planetary reference frames. The accuracy of this frame-tie estimate is expected to be in the vicinity of 10 mrad, depending on how well several error sources can be controlled (calibrated or reduced). Many candidate radio sources for VLBI measurements were identified, but additional work is necessary to select those sources which have characteristics appropriate to the present application. Strategies for performing the source selection are described.

Linfield, R.; Ulvestad, J.

1988-01-01

172

Direct measurement of channel erosion by debris flows, Illgraben, Switzerland  

Microsoft Academic Search

The timing and magnitude of channel bed erosion by three debris flows was measured in 2008 at the Illgraben catchment, Switzerland, using a scour sensor which consisted of a vertical array of erodible sensor elements. During the largest debris flow, sediment was entrained progressively and stepwise at the flow head within 20 s after front arrival, and onset of erosion

C. Berger; B. W. McArdell; F. Schlunegger

2011-01-01

173

Integrated optical measurement system for fluorescence spectroscopy in microfluidic channels  

Microsoft Academic Search

A transportable miniaturized fiber-pigtailed measurement system is presented which allows quantitative fluorescence detection in microliquid handling systems. The microliquid handling chips are made in silica on silicon technology and the optical functionality is monolithically integrated with the microfluidic channel system. This results in inherent stability and photolithographic alignment precision. Permanently attached optical fibers provide a rugged connection to the light

Jorg Hubnera; Klaus B. Mogensen; Anders M. Jorgensen; Peter Friis; Pieter Telleman; Jorg P. Kutter

2001-01-01

174

Holding zero switching scheme for multi-channel impedance measurement  

Microsoft Academic Search

This paper presents a design, implementation and performance of a novel data collection scheme for multi-channel impedance measurement, which is intended for developing high performance electrical tomography systems, even without parallel processing strategy. The hardware of electrical tomography employs electrical switching parts instead of mechanically moving parts to implement object scanning, which features electrical tomography faster acquisition rate and lower

Ziqiang Cui; Huaxiang Wang; Yanbin Xu; Yongbo He

2009-01-01

175

Laser Doppler velocimetry measurement of turbulent bubbly channel flow  

Microsoft Academic Search

Measurements of the turbulence properties of gas-liquid bubbly flows with mono-dispersed 1-mm-diameter bubbles are reported for upward flow in a rectangular channel. Bubble size and liquid-phase velocity were measured using image-processing and laser Doppler velocimetry (LDV), respectively. A description is given of the special arrangements for two-dimensional LDV needed to obtain reliable bubbly flow data, in particular the configuration of

S. So; H. Morikita; S. Takagi; Y. Matsumoto

2002-01-01

176

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.

177

Ray entity based postprocessing of ray-tracing data for continuous modeling of radio channel  

NASA Astrophysics Data System (ADS)

data are usually given as angles of arrival and departure, transmitter and receiver coordinates, ray length and delay, received power level, and polarity. Usually, these values are given in raw data with some resolution that covers the area of interest where the simulation is performed. There are two main drawbacks of such approach: first, a huge amount of storage capacity is typically needed and second, although the area of interest is covered by a certain resolution, it is nearly impossible to interpolate between sample points and new time, and memory consuming simulations are necessary in order to increase the resolution of the simulations. This paper addresses the two mentioned drawbacks of ray tracing, suggesting a procedure based on the concept of ray entities both to enable continuous interpolation of ray-tracing data and reduce the memory needed for storing data. Ray entity is a set of rays that all undergo the same series of propagation phenomena (direct ray, diffraction, reflection, or scattering) on the same objects (building walls or edges). The method is given and illustrated for reflection and diffraction phenomena, and diffuse scattering was not included, but discussion is easily extended to this propagation type as well. The paper gives detailed statistics of entities' length and rays' count per simulated receiver point in few illustrative examples and provides an insight on how to interpolate angles of arrival and departure, ray length, and received power level in order to provide a continuous description of the radio environment.

Mataga, Nikola; Zentner, Radovan; Mucalo, Ana Katalini?

2014-03-01

178

Analysis of the performance of multi-channel measurement system  

NASA Astrophysics Data System (ADS)

Symmetricom's Multi-channel Measurement System (TSC MMS) is a phase measurement device based on the measurement principle of dual mixer time difference method (DMTD). TSC MMS is purchased by Time and Frequency measurement laboratory in National Time Service Center of Chinese Academy of Sciences. In order to evaluate the measurement capability of DMTD and research the improved method of performance, in this paper, the TSC MMS performance test platform is set up. We ensure the test signals have better stability than system, and the invariant environment to reduce the effect of measurement produced by external environment as much as possible. Under the same condition, three-day data are collected to measure the noise floor of a system. Finally, we analyze the reasons attributing to the measurement results and proposed a improving method in detail. The measured results demonstrate that the Allan deviation stability will reach 3E-13 per second when the frequency of the input signals is 10MHz.

Li, Yu-Wei; Liu, Ya; Li, Xiao-Hui

2010-08-01

179

Dual-channel optical phase measurement system for improved precision.  

PubMed

Developments and applications of a dual-channel phase measurement system are being proposed and experimentally studied by utilizing an optical homodyne technique. In this measurement system, the phase modulation was adopted by using a near-stable Zn-indiffused lithium niobate phase modulator. The proposed method was successfully applied on the simultaneous measurements of the phase-retardation difference between a transmitted light and a reflected light after passing through a nonpolarization beam splitter. The measured stability of the phase-retardation difference was approximately 0.0013 rad. PMID:18978910

Twu, Ruey-Ching; Hong, Hao-Yang; Lee, Hsuan-Hsien

2008-11-01

180

Measurement of the top quark mass in the dilepton channel  

NASA Astrophysics Data System (ADS)

We report a measurement of the top quark mass using six candidate events for the process pp¯-->tt¯+X-->l+?bl-?¯b¯+X, observed in the D0 experiment at the Fermilab pp¯ collider. Using maximum likelihood fits to the dynamics of the decays, we measure a mass for the top quark of mt=168.4+/-12.3(stat)+/-3.6(syst) Gev. We combine this result with our previous measurement in the tt¯-->l+jets channel to obtain mt=172.1+/-7.1 GeV as the best value of the mass of the top quark measured by D0.

Abbott, B.; Abolins, M.; Abramov, V.; Acharya, B. S.; Adam, I.; Adams, D. L.; Adams, M.; Ahn, S.; Aihara, H.; Alves, G. A.; Amos, N.; Anderson, E. W.; Astur, R.; Baarmand, M. M.; Babintsev, V. V.; Babukhadia, L.; Baden, A.; Balamurali, V.; Baldin, B.; Banerjee, S.; Bantly, J.; Barberis, E.; Baringer, P.; Bartlett, J. F.; Belyaev, A.; Beri, S. B.; Bertram, I.; Bezzubov, V. A.; Bhat, P. C.; Bhatnagar, V.; Bhattacharjee, M.; Biswas, N.; Blazey, G.; Blessing, S.; Bloom, P.; Boehnlein, A.; Bojko, N. I.; Borcherding, F.; Boswell, C.; Brandt, A.; Breedon, R.; Brock, R.; Bross, A.; Buchholz, D.; Burtovoi, V. S.; Butler, J. M.; Carvalho, W.; Casey, D.; Casilum, Z.; Castilla-Valdez, H.; Chakraborty, D.; Chang, S.-M.; Chekulaev, S. V.; Chen, L.-P.; Chen, W.; Choi, S.; Chopra, S.; Choudhary, B. C.; Christenson, J. H.; Chung, M.; Claes, D.; Clark, A. R.; Cobau, W. G.; Cochran, J.; Coney, L.; Cooper, W. E.; Cretsinger, C.; Cullen-Vidal, D.; Cummings, M. A.; Cutts, D.; Dahl, O. I.; Davis, K.; de, K.; del Signore, K.; Demarteau, M.; Denisov, D.; Denisov, S. P.; Diehl, H. T.; Diesburg, M.; di Loreto, G.; Draper, P.; Ducros, Y.; Dudko, L. V.; Dugad, S. R.; Dyshkant, A.; Edmunds, D.; Ellison, J.; Elvira, V. D.; Engelmann, R.; Eno, S.; Eppley, G.; Ermolov, P.; Eroshin, O. V.; Evdokimov, V. N.; Fahland, T.; Fatyga, M. K.; Feher, S.; Fein, D.; Ferbel, T.; Finocchiaro, G.; Fisk, H. E.; Fisyak, Y.; Flattum, E.; Forden, G. E.; Fortner, M.; Frame, K. C.; Fuess, S.; Gallas, E.; Galyaev, A. N.; Gartung, P.; Gavrilov, V.; Geld, T. L.; Genik, R. J.; Genser, K.; Gerber, C. E.; Gershtein, Y.; Gibbard, B.; Gobbi, B.; Gómez, B.; Gómez, G.; Goncharov, P. I.; González Solís, J. L.; Gordon, H.; Goss, L. T.; Gounder, K.; Goussiou, A.; Graf, N.; Grannis, P. D.; Green, D. R.; Greenlee, H.; Grinstein, S.; Grudberg, P.; Grünendahl, S.; Guglielmo, G.; Guida, J. A.; Guida, J. M.; Gupta, A.; Gurzhiev, S. N.; Gutierrez, G.; Gutierrez, P.; Hadley, N. J.; Haggerty, H.; Hagopian, S.; Hagopian, V.; Hahn, K. S.; Hall, R. E.; Hanlet, P.; Hansen, S.; Hauptman, J. M.; Hedin, D.; Heinson, A. P.; Heintz, U.; Hernández-Montoya, R.; Heuring, T.; Hirosky, R.; Hobbs, J. D.; Hoeneisen, B.; Hoftun, J. S.; Hsieh, F.; Hu, Ting; Hu, Tong; Huehn, T.; Ito, A. S.; James, E.; Jaques, J.; Jerger, S. A.; Jesik, R.; Joffe-Minor, T.; Johns, K.; Johnson, M.; Jonckheere, A.; Jones, M.; Jöstlein, H.; Jun, S. Y.; Jung, C. K.; Kahn, S.; Kalbfleisch, G.; Karmanov, D.; Karmgard, D.; Kehoe, R.; Kelly, M. L.; Kim, S. K.; Klima, B.; Klopfenstein, C.; Ko, W.; Kohli, J. M.; Koltick, D.; Kostritskiy, A. V.; Kotcher, J.; Kotwal, A. V.; Kozelov, A. V.; Kozlovsky, E. A.; Krane, J.; Krishnaswamy, M. R.; Krzywdzinski, S.; Kuleshov, S.; Kunori, S.; Landry, F.; Landsberg, G.; Lauer, B.; Leflat, A.; Li, J.; Li-Demarteau, Q. Z.; Lima, J. G.; Lincoln, D.; Linn, S. L.; Linnemann, J.; Lipton, R.; Lobkowicz, F.; Loken, S. C.; Lucotte, A.; Lueking, L.; Lyon, A. L.; Maciel, A. K.; Madaras, R. J.; Madden, R.; Magaña-Mendoza, L.; Manankov, V.; Mani, S.; Mao, H. S.; Markeloff, R.; Marshall, T.; Martin, M. I.; Mauritz, K. M.; May, B.; Mayorov, A. A.; McCarthy, R.; McDonald, J.; McKibben, T.; McKinley, J.; McMahon, T.; Melanson, H. L.; Merkin, M.; Merritt, K. W.; Miao, C.; Miettinen, H.; Mincer, A.; Mishra, C. S.; Mokhov, N.; Mondal, N. K.; Montgomery, H. E.; Mooney, P.; Mostafa, M.; da Motta, H.; Murphy, C.; Nang, F.; Narain, M.; Narasimham, V. S.; Narayanan, A.; Neal, H. A.; Negret, J. P.; Nemethy, P.; Norman, D.; Oesch, L.; Oguri, V.; Oliveira, E.; Oltman, E.; Oshima, N.; Owen, D.; Padley, P.; Para, A.; Park, Y. M.; Partridge, R.; Parua, N.; Paterno, M.; Pawlik, B.; Perkins, J.; Peters, M.; Piegaia, R.; Piekarz, H.; Pischalnikov, Y.; Pope, B. G.; Prosper, H. B.; Protopopescu, S.; Qian, J.; Quintas, P. Z.; Raja, R.; Rajagopalan, S.; Ramirez, O.; Reucroft, S.; Rijssenbeek, M.; Rockwell, T.; Roco, M.; Rubinov, P.; Ruchti, R.; Rutherfoord, J.; Sánchez-Hernández, A.; Santoro, A.; Sawyer, L.; Schamberger, R. D.; Schellman, H.; Sculli, J.; Shabalina, E.; Shaffer, C.; Shankar, H. C.; Shivpuri, R. K.; Shupe, M.; Singh, H.; Singh, J. B.; Sirotenko, V.; Smith, E.; Smith, R. P.; Snihur, R.; Snow, G. R.; Snow, J.; Snyder, S.; Solomon, J.; Sosebee, M.; Sotnikova, N.; Souza, M.; Spadafora, A. L.; Steinbrück, G.; Stephens, R. W.; Stevenson, M. L.; Stewart, D.; Stichelbaut, F.; Stoker, D.; Stolin, V.; Stoyanova, D. A.; Strauss, M.; Streets, K.; Strovink, M.; Sznajder, A.; Tamburello, P.; Tarazi, J.; Tartaglia, M.; Thomas, T. L.; Thompson, J.; Trippe, T. G.; Tuts, P. M.; Vaniev, V.; Varelas, N.; Varnes, E. W.; Vititoe, D.; Volkov, A. A.; Vorobiev, A. P.; Wahl, H. D.; Wang, G.; Warchol, J.; Watts, G.; Wayne, M.; Weerts, H.; White, A.; White, J. T.; Wightman, J. A.; Willis, S.; Wimpenny, S. J.; Wirjawan, J. V.

1999-09-01

181

Stability Measurements of the Radio Science System at the 34-M High-Efficiency Antennas.  

National Technical Information Service (NTIS)

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 meas...

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

1993-01-01

182

Measurements of radio propagation in rock salt for the detection of high-energy neutrinos  

Microsoft Academic Search

We present measurements of the transmission of radio\\/microwave pulses through salt in the Cote Blanche salt mine operated by the North American Salt Company in St. Mary Parish, Louisiana. These results are from data taken in the southwestern region of the 1500ft (457m) deep level of the mine on our third and most recent visit to the mine. We transmitted

Amy Connolly; Abigail Goodhue; Christian Miki; Ryan Nichol; David Saltzberg

2009-01-01

183

Characterizing atmospheric multipath propagation in dense atmospheres for radio occultation measurements  

Microsoft Academic Search

In a dense planetary atmosphere, atmospheric multipath is caused by inflections with vertical extent larger than the first Fresnel zone in the refractivity with height profile. When using Abelian inversion to retrieve atmospheric profiles from radio occultation measurements, atmospheric multipath effects can cause unrecoverable errors unless they are detected correctly and mapped into the ray asymptote structure. In order to

K. Kusza; G. L. Tyler

2003-01-01

184

Radio acoustic measurement of temperature profile in the troposphere and stratosphere  

Microsoft Academic Search

The radio acoustic sounding system (RASS) uses radar to measure the temperature profile in the atmosphere. In the standard technique of atmospheric radar, the radar backscatter results from electrical permittivity variations due to natural phenomena such as turbulence and precipitation. In the RASS technique, the radar backscatter results from periodical permittivity variations due to density\\/temperature variations imposed on the atmosphere

N. Matuura; Y. Masuda; H. Inuki; S. Kato; S. Fukao; T. Sato; T. Tsuda

1986-01-01

185

The Mariner 10 radio occultation measurements of the ionosphere of Venus  

Microsoft Academic Search

Data from the Mariner 10 radio occultation experiment have been utilized to determine the vertical electron density distribution in the ionosphere of Venus. The ingress measurements, which were made at latitude 1.3 deg N on the nightside of the planet, show two distinct layers. The main layer was located at 142 km altitude and had a peak density of 9000

G. Fjeldbo; B. Seidel; D. Sweetnam; T. Howard

1975-01-01

186

A Comparative Study of Radio Audience Measurement Methodology  

ERIC Educational Resources Information Center

Major differences in results obtained from three audience measurement methodologies (telephone coincidental, multi-media diaries, and personal interviews with roster recalls) confirm the need for a new methodology or technique by advertisers and their agencies. (RL)

Schultz, Don; And Others

1978-01-01

187

An analysis of source structure effects in radio interferometry measurements  

NASA Technical Reports Server (NTRS)

To begin a study of structure effects, this report presents a theoretical framework, proposes an effective position approach to structure corrections based on brightness distribution measurements, and analyzes examples of analytical and measured brightness distributions. Other topics include the effect of the frequency dependence of a brightness distribution on bandwidth synthesis (BWS) delay, the determination of the absolute location of a measured brightness distribution, and structure effects in dual frequency calibration of charged particle delays. For the 10 measured distributions analyzed, it was found that the structure effect in BWS delay at X-band (3.6 cm) can reach 30 cm, but typically falls in the range of 0 to 5 cm. A trial limit equation that is dependent on visibility was successfully tested against the 10 measured brightness distributions (seven sources). If the validity of this particular equation for an upper limit can be established for nearly all sources, the structure effect in BWS delay could be greatly reduced without supplementary measurements of brightness distributions.

Thomas, J. B.

1980-01-01

188

Measurements of time average series resonance effect in capacitively coupled radio frequency discharge plasma  

SciTech Connect

Self-excited plasma series resonance is observed in low pressure capacitvely coupled radio frequency discharges as high-frequency oscillations superimposed on the normal radio frequency current. This high-frequency contribution to the radio frequency current is generated by a series resonance between the capacitive sheath and the inductive and resistive bulk plasma. In this report, we present an experimental method to measure the plasma series resonance in a capacitively coupled radio frequency argon plasma by modifying the homogeneous discharge model. The homogeneous discharge model is modified by introducing a correction factor to the plasma resistance. Plasma parameters are also calculated by considering the plasma series resonances effect. Experimental measurements show that the self-excitation of the plasma series resonance, which arises in capacitive discharge due to the nonlinear interaction of plasma bulk and sheath, significantly enhances both the Ohmic and stochastic heating. The experimentally measured total dissipation, which is the sum of the Ohmic and stochastic heating, is found to increase significantly with decreasing pressure.

Bora, B.; Bhuyan, H.; Favre, M.; Wyndham, E.; Chuaqui, H. [Facultad de Fisica, Pontificia Universidad Catolica de Chile, Ave. Vicuna Mackenna 4860, Santiago 22 (Chile); Kakati, M. [Thermal Plasma Processed Materials Laboratory, Centre of Plasma Physics, Institute for Plasma Research, Sonapur 782 402, Assam (India)

2011-10-15

189

The polar atmosphere of Venus: Radio occultation measurements with Venus Express and Magellan  

NASA Astrophysics Data System (ADS)

The ESA Venus Express (VEx) spacecraft has been conducting radio occultation experiments since 2006. The results reported to date are based on data recorded by 35-m antennas of the ESA Tracking Station Network (e.g., Tellmann et al., J. Geophys. Res., 114, E00B36, 2009). We have recently begun to derive complementary new results through analysis of high-quality "open-loop" data recorded by a 70-m antenna of the NASA Deep Space Network. This experiment sounded the polar atmosphere in both hemispheres at latitudes greater than 75 degrees. As in previous occultation measurements in this region, there is a deep convective layer at altitudes below about 60 km. The convective layer is capped by an abrupt transition to stable stratification, and the overlying free air is modulated by vertically propagating gravity waves. These new results will be compared with Magellan radio occultation measurements acquired at comparable latitudes in the early 1990s and with the VEx results reported by Tellmann et al. (2009). Our analysis also illustrates some of the challenges that can arise in radio occultation measurements at Venus. For example, the sharp temperature minimum at the tropopause creates a thin layer that eludes radio occultation sounding owing to its peculiar refractive properties. This research is funded in part by NASA Grant NNX10AE22G of the Venus Express Participating Scientist Program.

Hinson, D. P.; Tellmann, S.; Paetzold, M.; Haeusler, B.; Bird, M. K.; Tyler, G. L.

2012-12-01

190

Radio frequency controlled synthetic wavelength sweep for absolute distance measurement by optical interferometry  

SciTech Connect

We present a new technique applied to the variable optical synthetic wavelength generation in optical interferometry. It consists of a chain of optical injection locking among three lasers: first a distributed-feedback laser is used as a master to injection lock an intensity-modulated laser that is directly modulated around 15 GHz by a radio frequency generator on a sideband. A second distributed-feedback laser is injection locked on another sideband of the intensity-modulated laser. The variable synthetic wavelength for absolute distance measurement is simply generated by sweeping the radio frequency over a range of several hundred megahertz, which corresponds to the locking range of the two slave lasers. In this condition, the uncertainty of the variable synthetic wavelength is equivalent to the radio frequency uncertainty. This latter has a relative accuracy of 10{sup -7} or better, resulting in a resolution of {+-}25 {mu}m for distances exceeding tens of meters. The radio frequency generator produces a linear frequency sweep of 1 ms duration (i.e., exactly equal to one absolute distance measurement acquisition time), with frequency steps of about 1 MHz. Finally, results of absolute distance measurements for ranges up to 10 m are presented.

Le Floch, Sebastien; Salvade, Yves; Mitouassiwou, Rostand; Favre, Patrick

2008-06-01

191

Reliable intraocular pressure measurement using automated radio-wave telemetry  

PubMed Central

Purpose To present an autonomous intraocular pressure (IOP) measurement technique using a wireless implantable transducer (WIT) and a motion sensor. Methods The WIT optical aid was implanted within the ciliary sulcus of a normotensive rabbit eye after extracapsular clear lens extraction. An autonomous wireless data system (AWDS) comprising of a WIT and an external antenna aided by a motion sensor provided continuous IOP readings. The sensitivity of the technique was determined by the ability to detect IOP changes resulting from the administration of latanoprost 0.005% or dorzolamide 2%, while the reliability was determined by the agreement between baseline and vehicle (saline) IOP. Results On average, 12 diurnal and 205 nocturnal IOP measurements were performed with latanoprost, and 26 diurnal and 205 nocturnal measurements with dorzolamide. No difference was found between mean baseline IOP (13.08±2.2 mmHg) and mean vehicle IOP (13.27±2.1 mmHg) (P=0.45), suggesting good measurement reliability. Both antiglaucoma medications caused significant IOP reduction compared to baseline; latanoprost reduced mean IOP by 10% (1.3±3.54 mmHg; P<0.001), and dorzolamide by 5% (0.62±2.22 mmHg; P<0.001). Use of latanoprost resulted in an overall twofold higher IOP reduction compared to dorzolamide (P<0.001). Repeatability was ±1.8 mmHg, assessed by the variability of consecutive IOP measurements performed in a short period of time (?1 minute), during which the IOP is not expected to change. Conclusion IOP measurements in conscious rabbits obtained without the need for human interactions using the AWDS are feasible and provide reproducible results.

Paschalis, Eleftherios I; Cade, Fabiano; Melki, Samir; Pasquale, Louis R; Dohlman, Claes H; Ciolino, Joseph B

2014-01-01

192

Dynamic wall shear stress measurements in a turbulent channel flow  

NASA Astrophysics Data System (ADS)

To quantify and understand the dynamics of near wall momentum transfer, high spatial resolution, time-resolved measurements of wall shear stress distribution are essential. In this study, a film-based shear stress sensor has been used to measure the time-resolved local wall shear stress distribution in a turbulent channel flow. Measurements have been undertaken in a turbulent channel flow at Reynolds numbers up to 130,000 based on the bulk velocity and channel height. The measured fluctuating wall shear stress distribution provides spatio-temporal information of the characteristics of near wall structures by detecting their footprints. The span-wise extent of the positive two-point correlation of the stream-wise shear stress fluctuations provides the average width in the order of 100 wall units for the near-wall coherent structures. An investigation of the topological features of the velocity gradient and rate of strain tensors enables us to show an intrinsic characteristic of the near wall flow, which follows a two-dimensional flow pattern.

Amili, Omid; Soria, Julio

2010-11-01

193

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

194

Recurrent pulse response of radio interference measuring apparatus employing an average detector  

NASA Astrophysics Data System (ADS)

Recently, the use of the average-reading measuring apparatus has been discussed in connection with the measurement of radio interference produced by computers and other similar digital equipment. These types of equipment use repeated pulses as clock pulses so that they generate pulsive radio interference of high repetition rates. Therefore, theoretical investigation has been made on the recurrent pulse response of average-reading measuring apparatus, especially in the case of high repetition rates. In addition, average-reading measuring apparatus on the market were tested for compliance with the CISPR requirements. It is concluded that some apparatus do not conform to the requirements partly because of the nonlinear response of the detector and partly because of the oscillatory envelope of the predetector stage output for an impulse input.

Nagatomo, H.; Oguchi, T.; Sugiura, A.

1984-11-01

195

Measurement of the top quark mass in the dilepton channel  

Microsoft Academic Search

We present a measurement of the top quark mass in the dilepton channel based\\u000aon approximately 370\\/pb of data collected by the D0 experiment during Run II of\\u000athe Fermilab Tevatron collider. We employ two different methods to extract the\\u000atop quark mass. We show that both methods yield consistent results using\\u000aensemble tests of events generated with the D0

V. M. Abazov; B. Abbott; M. Abolins; B. S. Acharya; M. Adams; T. Adams; M. Agelou; E. Aguilo; S. H. Ahn; M. Ahsan; G. D. Alexeev; G. Alkhazov; A. Alton; G. Alverson; G. Alverson; M. Anastasoaie; C. Barnes; J. Barreto; J. F. Bartlett; D. Bauer; S. Beale; A. Bean; M. Begalli; M. Begel; C. Belanger-Champagne; L. Bellantoni; A. Bellavance; J. A. Benitez; S. B. Beri; G. Bernardi; R. Bernhard; L. Berntzon; I. Bertram; M. Besancon; V. A. Bezzubov; P. Banerjee; V. Bhatnagar; M. Binder; C. Biscarat; I. Blackler; G. Blazey; F. Blekman; S. Blessing; D. Bloch; K. Bloom; A. Boehnlein; D. Boline; T. A. Bolton; G. Borissov; K. Bos; T. Bose; A. Bellavance; R. Brock; G. Brooijmans; A. Bross; D. Brown; N. J. Buchanan; D. Buchholz; M. Besançon; V.A. Bezzubov; S. Burdin; S. Burke; T. H. Burnett; E. Busato; C. P. Buszello; J. M. Butler; S. Calvet; J. Cammin; S. Caron; W. Carvalho; B. C. K. Casey; N. M. Cason; H. Castilla-Valdez; S. Chakrabarti; D. Chakraborty; K. M. Chan; A. Chandra; F. Charles; E. Cheu; F. Chevallier; D. K. Cho; S. Choi; B. Choudhary; L. Christofek; D. Claes; B. Clement; C. Clement; Y. Coadou; M. Cooke; W. E. Cooper; D. Coppage; M. Corcoran; S. Feher; D. Fein; T. Ferbel; G. Finocchiaro; H. E. Fisk; Y. Fisyak; E. Flattum; G. E. Forden; M. Fortner; K. C. Frame; S. Fuess; E. Gallas; A. N. Galyaev; P. Gartung; V. Gavrilov; T. L. Geld; R. J. Genik; K. Genser; C. E. Gerber; Y. Gershtein; B. Gibbard; B. Gobbi; B. Gomez; G. Gomez; P. I. Goncharov; J. L. Gonzalez Solis; H. Gordon; L. T. Goss; K. Gounder; A. Goussiou; N. Graf; P. D. Grannis; H. Greenlee; S. Grinstein; P. Grudberg; G. Guglielmo; J. A. Guida; J. M. Guida; S. N. Gurzhiev; G. Gutierrez; P. Gutierrez; N. J. Hadley; H. Haggerty; S. Hagopian; V. Hagopian; K. S. Hahn; P. Hanlet; S. Hansen; J. M. Hauptman; D. Hedin; A. P. Heinson; R. Hernandez-Montoya; T. Heuring; R. Hirosky; J. D. Hobbs; B. Hoeneisen; J. S. Hoftun; F. Hsieh; T. Huehn; A. S. Ito; E. James; J. Jaques; S. A. Jerger; R. Jesik; T. Joffe-Minor; K. Johns; M. Johnson; A. Jonckheere; M. Jones; H. Jostlein; S. Y. Jun; C. K. Jung; S. Kahn; G. Kalbfleisch; D. Karmanov; D. Karmgard; R. Kehoe; M. L. Kelly; S. K. Kim; B. Klima; C. Klopfenstein; W. Ko; J. M. Kohli; D. Koltick; A. V. Kostritskiy; J. Kotcher; A. V. Kotwal; A. V. Kozelov; E. A. Kozlovsky; J. Krane; M. R. Krishnaswamy; S. Krzywdzinski; S. Kuleshov; S. Kunori; F. Landry; G. Landsberg; A. Leflat; J. Li; Q. Z. Li-Demarteau; J. G. R. Lima; D. Lincoln; S. L. Linn; J. Linnemann; R. Lipton; F. Lobkowicz; S. C. Loken; A. Lucotte; L. Lueking; A. L. Lyon; A. K. A. Maciel; R. J. Madaras; L. Magana-Mendoza; V. Manankov; S. Mani; H. S. Mao; R. Markeloff; T. Marshall; M. I. Martin; A. A. Mayorov; R. McCarthy; J. McDonald; T. McKibben; J. McKinley; T. McMahon; H. L. Melanson; M. Merkin; K. W. Merritt; C. Miao; H. Miettinen; A. Mincer; C. S. Mishra; N. Mokhov; N. K. Mondal; H. E. Montgomery; P. Mooney; M. Mostafa; H. da Motta; C. Murphy; F. Nang; M. Narain; V. S. Narasimham; A. Narayanan; H. A. Neal; J. P. Negret; P. Nemethy; D. Norman; L. Oesch; V. Oguri; E. Oliveira; E. Oltman; N. Oshima; D. Owen; P. Padley; R. Partridge; N. Parua; Anoop Gupta; Y. Hu; Z. Hubacek; V. Hynek; I. Iashvili; R. Illingworth; A. S. Ito; S. Jabeen; M. Jaffré; S. Jain; K. Jakobs; C. Jarvis; A. Jenkins; C. Johnson; P. Jonsson; A. Juste; D. Käfer; E. Kajfasz; A. M. Kalinin; J. M. Kalk; J. R. Kalk; S. Kappler; J. Kasper; P. Kasper; I. Katsanos; D. Kau; R. Kaur; R. Kehoe; S. Kermiche; N. Khalatyan; A. Khanov; A. Kharchilava; Y. M. Kharzheev; D. Khatidze; H. Kim; T. J. Kim; M. H. Kirby; J.-P. Konrath; M. Kopal; V. M. Korablev; B. Kothari; A. Koubarovsky; D. Krop; A. Kryemadhi; T. Kuhl; A. Kumar; A. Kupco; T. Kur?a; J. Kvita; S. Lammers; J. Lazoflores; A.-C. Le Bihan; P. Lebrun; W. M. Lee; A. Leflat; F. Lehner; V. Lesne; J. Leveque; P. Lewis; Q. Z. Li; D. Lincoln; V. V. Lipaev; Z. Liu; L. Lobo; A. Lobodenko; M. Lokajicek; A. Lounis; P. Love; H. J. Lubatti; M. Lynker; P. Mättig; C. Magass; A. Magerkurth; N. Makovec; P. K. Mal; H. B. Malbouisson; S. Malik; V. L. Malyshev; Y. Maravin; M. Martens; R. McCarthy; D. Meder; A. Melnitchouk; L. Mendoza; M. Merkin; A. Meyer; J. Meyer; M. Michaut; T. Millet; J. Mitrevski; J. Monk; R. W. Moore; T. Moulik; G. S. Muanza; M. Mulders; M. Mulhearn; O. Mundal; L. Mundim; Y. D. Mutaf; E. Nagy; M. Naimuddin; N. A. Naumann; H. A. Neal; P. Neustroev; C. Noeding; A. Nomerotski; S. F. Novaes; T. Nunnemann; V. O'Dell; D. C. O'Neil; G. Obrant; N. Oliveira; D. Onoprienko; R. Otec; G. J. Otero y Garzón; M. Owen; N. Parashar; S.-J. Park; J. Parsons; A. Patwa; G. Pawloski; P. M. Perea; E. Perez; K. Peters; P. Pétroff; M. Petteni; R. Piegaia; J. Piper; M.-A. Pleier; P. L. M. Podesta-Lerma; V. M. Podstavkov; Y. Pogorelov; M.-E. Pol; A. Pompoš; B. G. Pope; A. V. Popov; C. Potter; W. L. Prado da Silva; H. B. Prosper; S. Protopopescu; J. Qian

2007-01-01

196

GPS radio occultation measurements of the ionosphere from CHAMP: Early results  

Microsoft Academic Search

The paper deals with initial analyzes of radio occultation measurements of the ionosphere carried out on board the CHAMP satellite since 11 April 2001. The accuracy of the operationally retrieved electron density profiles has been estimated by comparing with independent measurements. The derived ionospheric key parameters such as f0F2 and hmF2 agree with a standard deviation of 18 and 13%,

N. Jakowski; A. Wehrenpfennig; S. Heise; Ch. Reigber; H. Lühr; L. Grunwaldt; T. K. Meehan

2002-01-01

197

Simultaneous radio and satellite optical measurements of high-altitude sprite current and lightning continuing current  

Microsoft Academic Search

We report coordinated measurements of lightning and resulting sprites using ground-level magnetic field sensors (<0.1 Hz to 30 kHz bandwidth) and the ISUAL instrument on the FORMOSAT-2 satellite. These measurements demonstrate two distinct elements of the connection between the radio and optical emissions. First, the quasi-static magnetic field signature is tightly correlated with the low-altitude optical emissions from the lightning

Steven A. Cummer; Harald U. Frey; Stephen B. Mende; Rue-Ron Hsu; Han-Tzong Su; Alfred B. Chen; Hiroshi Fukunishi; Yukihiro Takahashi

2006-01-01

198

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

199

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

200

Frame synchronization methods based on channel symbol measurements  

NASA Technical Reports Server (NTRS)

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.

1989-01-01

201

Lateral distribution of the radio signal in extensive air showers measured with LOPES  

NASA Astrophysics Data System (ADS)

The antenna array LOPES is set up at the location of the KASCADE-Grande extensive air shower experiment in Karlsruhe, Germany and aims to measure and investigate radio pulses from extensive air showers. The coincident measurements allow us to reconstruct the electric field strength at observation level in dependence of general EAS parameters. In the present work, the lateral distribution of the radio signal in air showers is studied in detail. It is found that the lateral distributions of the electric field strengths in individual EAS can be described by an exponential function. For about 20% of the events a flattening towards the shower axis is observed, preferentially for showers with large inclination angle. The estimated scale parameters R0, describing the slope of the lateral profiles range between 100 and 200 m. No evidence for a direct correlation of R0 with shower parameters like azimuth angle, geomagnetic angle, or primary energy can be found. This indicates that the lateral profile is an intrinsic property of the radio emission during the shower development which makes the radio detection technique suitable for large scale applications.

Apel, W. D.; Arteaga, J. C.; Asch, T.; Badea, A. F.; Bähren, L.; Bekk, K.; Bertaina, M.; Biermann, P. L.; Blümer, J.; Bozdog, H.; Brancus, I. M.; Brüggemann, M.; Buchholz, P.; Buitink, S.; Cantoni, E.; Chiavassa, A.; Cossavella, F.; Daumiller, K.; de Souza, V.; di Pierro, F.; Doll, P.; Engel, R.; Falcke, H.; Finger, M.; Fuhrmann, D.; Gemmeke, H.; Ghia, P. L.; Glasstetter, R.; Grupen, C.; Haungs, A.; Heck, D.; Hörandel, J. R.; Horneffer, A.; Huege, T.; Isar, P. G.; Kampert, K.-H.; Kang, D.; Kickelbick, D.; Krömer, O.; Kuijpers, J.; Lafebre, S.; ?uczak, P.; Ludwig, M.; Mathes, H. J.; Mayer, H. J.; Melissas, M.; Mitrica, B.; Morello, C.; Navarra, G.; Nehls, S.; Nigl, A.; Oehlschläger, J.; Over, S.; Palmieri, N.; Petcu, M.; Pierog, T.; Rautenberg, J.; Rebel, H.; Roth, M.; Saftoiu, A.; Schieler, H.; Schmidt, A.; Schröder, F.; Sima, O.; Singh, K.; Toma, G.; Trinchero, G. C.; Ulrich, H.; Weindl, A.; Wochele, J.; Wommer, M.; Zabierowski, J.; Zensus, J. A.; LOPES Collaboration

2010-01-01

202

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

203

Further improved technique for channeled stopping power measurements  

NASA Astrophysics Data System (ADS)

A few years ago, an ingenious method was proposed to quickly and accurately measure the difference between random and aligned stopping powers without the need for free-standing mono-crystalline thin films; the main idea was to increase the energy of the incident ion beam so that the channel numbers for a characteristic feature in the backscattering spectrum in random and aligned direction coincide, thus compensating for the difference in stopping power endured by the outgoing ions (Greco et al. 2007) [7]. A small drawback of this method is that the total length of the path that the ion travels through the thin film is slightly different in random and aligned geometries. We have improved this method by changing the measurement geometry such that the aligned and random ions travel the exact same distance through the thin film. Representative results for 0.5-3 MeV He ions channeled in <0 1 1> Si are presented and show that earlier measurements appear to overestimate slightly the reduction in stopping power for channeled ions.

Chicoine, M.; Thiebaut, B.; Roorda, S.

2014-08-01

204

Characterization of the indoor-outdoor radio propagation channel at 2.4 GHz  

Microsoft Academic Search

We present the site-specific signal strength measure- ment results for path loss, shadowing, and fading in 2.4GHz band under typical harsh environment (high temperature 40- 50 C and humidity 80-90%). We use spectrum analyzer Rohde & Schwarz FSH8 and InSSIDer (free software for WLANs). Measurements are taken in indoor and outdoor environments at various locations on different times of the

Irfan Ahmed; Sara Orfali; Tamer Khattab; Amr Mohamed

2011-01-01

205

Magnetization of the ionospheres of Venus and Mars: Results from radio occultation measurements  

SciTech Connect

In situ measurements by the Pioneer Venus orbiting spacecraft, conducted during solar maximum only, have shown that magnetization (permeation of large-scale magnetic fields) of the ionosphere of Venus occurs under high solar wind dynamic pressure and that this takes place most frequently near the subsolar region. In this paper, the authors use remote sensing radio occultation measurements to study magnetization of the ionospheres of Venus and Mars based on these characteristics. For Venus they take advantage of the unique data set consisting of 148 electron density profiles deduced from Pioneer Venus radio occultation measurements. They demonstrate that radio occultation measurements yield results on frequency of occurrence of magnetization during solar maximum that are similar to those obtained from the Pioneer Venus in situ magnetic field measurements. During solar minimum, for which direct ionospheric measurements have never been made, they find that magnetization of the Venus ionosphere is more pervasive than at solar maximum. Magnetization extends to higher solar zenith angles (SZA) and appears stronger than at solar maximum. These results confirm that during solar minimum, the high solar wind dynamic pressure state is more prevalent at Venus because the ionospheric plasma pressure is weaker than at solar maximum. Comparison of a large number of electron density profiles of Mars (deduced from radio occultation measurements by the Viking 1 and 2 and Mariner 9 spacecraft for SZA > 46{degrees}) with those of Venus shows an absence of the ledge and disturbed topside plasma observed in the Venus profiles. These results, however, do not constitute evidence against magnetization of the ionosphere of Mars, as Shinagawa and Cravens (1989) have shown on their one-dimensional MHD models that, even when the ionosphere of Mars is highly magnetized, the magnetic structure differs from that at Venus, and a ledge does not form in its electron density profiles.

Woo, R.; Kliore, A.J. (California Inst. of Tech., Pasadena (USA))

1991-07-01

206

The accuracy of radio interferometric measurements of Earth rotation  

NASA Technical Reports Server (NTRS)

The accuracy of very long base interferometry earth rotation (UT1) measurements is examined by intercomparing TEMPO and POLARIS data for 1982 and the first half of 1983. None of these data are simultaneous, and so a proper intercomparison requires accounting for the scatter introduced by the rapid, unpredictable, UT1 variations driven by exchanges of angular momentum with the atmosphere. A statistical model of these variations, based on meteorological estimates of the Atmospheric Angular Momentum is derived, and the optimal linear (Kalman) smoother for this model is constructed. The scatter between smoothed and independent raw data is consistent with the residual formal errors, which do not depend upon the actual scatter of the UT1 data. This represents the first time that an accurate prediction of the scatter between UT1 data sets were possible.

Eubanks, T. M.; Steppe, J. A.; Spieth, M. A.

1985-01-01

207

Electric field tomography: setup for single-channel measurements.  

PubMed

Results of experiments on electric field tomography, which were carried out to test the theoretical model suggested previously, are described in this paper. The theoretical foundation of the electric field tomography and substantiation of the possibility of its biomedical application are briefly presented. An experimental setup and test samples used for measurements are described. The results of experiments are presented; their comparison with the results of numerical simulation is given. Further steps towards increasing measurement accuracy and implementation of multi-channel tomographic systems are suggested. PMID:17664642

Korjenevsky, A V; Tuykin, T S

2007-07-01

208

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.

209

Coronal magnetic field strength from Type II radio emission: complementarity with Faraday rotation measurements  

NASA Astrophysics Data System (ADS)

We analyzed the band splitting of a Type II radio burst observed on 1997 May 12 by ground- and space-based radio spectrometers. Type II radio emission is the most evident signature of coronal shock waves and the observed band splitting is generally interpreted as due to plasma emission from both upstream and downstream shock regions. From the inferred compression ratio we estimated, using the magnetohydrodynamic (MHD) Rankine-Hugoniot relations, the ambient Alfvén Mach number. By means of the electron density obtained by inverting white-light polarized brightness (pB) coronagraph data and the shock speed inferred from the Type II frequency drift, we finally derived a radial profile for the magnetic field strength in the middle corona. The result was compared with the field profile obtained in May 1997 (but above ~5 R?) with Faraday rotation measurements of extragalactic radio sources occulted by the corona. The power law of the form B(r) = 3.76 r-2.29 G inferred in that work nicely describes the combined set of data in a wide range of heliocentric distances (r ? 1.8-14 R?).

Mancuso, S.; Garzelli, M. V.

2013-12-01

210

Radio tracking system  

Microsoft Academic Search

The principles and techniques of deep space radio tracking are described along with the uses of tracking data in navigation and radio science. Emphasis is placed on the measurement functions of radio tracking.

J. C. Breidenthal; T. A. Komarek

1982-01-01

211

Kelvin wave variability near the equatorial tropopause observed in GPS radio occultation measurements  

Microsoft Academic Search

Temperature fields in the equatorial upper troposphere and lower stratosphere, derived from GPS radio occultation measurements for 2001-2002, show evidence for planetary-scale Kelvin waves. These waves have a characteristic eastward phase tilt with height and typical vertical wavelengths of ~4-8 km. The Kelvin waves exhibit coherent vertical structure over ~12-25 km, with maximum amplitudes near the tropical tropopause (~17 km).

William J. Randel; Fei Wu

2005-01-01

212

New RadioIsotope technique of measuring the thickness of fine sheet materials  

Microsoft Academic Search

and V. Yanushkovskii A new continuous method of measuring the thickness of very thin materials'during their p roduction has been worked out at the Riga Scientific Research Institute for Radio-Isotope Instruments. The operation of the instrument is based on the scattering of fl-radiation from a gaseous medium. In such a case, the energy spectrum of the scattered fl-radiation becomes much

A. Muzis; B. Ol'shvanger; I. Taksar; É. Tesnavs; A. Tumul'kan; I. Fedotov; V. Shabalin; V. Yanushkovskii

1968-01-01

213

Radio propagation measurements of the solar corona and gravitational fields: Applications to Mariner 6 and 7  

NASA Technical Reports Server (NTRS)

Results from interferometric measurements of the apparent angular deflection of quasi-stellar object are examined. Some preliminary results from Mariner 6 and 7 experiments, particularly from the plasma effect viewpoint, are discussed, along with future experiments and plasma scintillation. Ray bending studies, plasma relativity separation for Mariner 6 and 7, and radio propagation test of general relativity are reviewed. First order approximations and time delay studies are appended, as well as Doppler velocity effect investigations.

Muhleman, D. O.; Anderson, J. D.; Esposito, P. B.; Martin, W. L.

1971-01-01

214

A Radio Frequency Sensor For Measurement Of Small Dielectric Property Changes  

Microsoft Academic Search

We propose a sensitive radio frequency (RF) sensor for the measurement of small dielectric property changes. Interference is used to cancel parasitic background signals to improve sensitivity. The device consists of two Wilkinson power dividers, a 180 degree reversephase and an in-phase CPW (coplanar waveguide)-slotline back-toback balun. The small dielectric property changes between de-ionize water and two sets of primary

W.-N. Liu; Y. Yang; K.-M. Huang

2012-01-01

215

In-flight calibration of the Cassini-Radio and Plasma Wave Science (RPWS) antenna system for direction-finding and polarization measurements  

NASA Astrophysics Data System (ADS)

One major objective of the Cassini mission is the analysis of Saturnian radio emissions of magnetospheric (auroral) as well as atmospheric (lightning) origin. The Radio and Plasma Wave Science (RPWS) experiment is designed to measure the full polarization and the wave vector of the incoming radio waves, allowing us to retrieve information on source locations and emission modes. For that purpose, RPWS uses a two-channel receiver, connected to two electric monopoles (selected among three), which measures the voltages induced by the electric field of the incident waves and their various correlations. The accuracy of retrieved source locations depends directly on the precise knowledge of the orientation of the three effective monopole axes and lengths, which do not coincide with the physical ones owing to interaction with the spacecraft body. Antenna calibration aims at determining the so-called effective length vector of each antenna (combining orientation and length information). For that purpose, roll maneuvers of the Cassini spacecraft were performed before and after the Jupiter flyby, at distances such that Jovian radio sources can be identified with the planet's center but still provide a high signal-to-noise ratio. The resulting modulations of the measured signals allow us to derive the orientation and length of the effective antennas. The analysis is performed in two steps: first, the Stokes parameters (wave polarization) are determined using approximate antenna orientations derived from laboratory measurements on a scale model of the spacecraft. Second, measurements with high signal-to-noise ratio and pure circular polarization are selected and used for the determination of the effective length vectors of the RPWS antennas. Two methods have been developed for inverting the system of equations relating antenna parameters, wave parameters, and measurements (least squares fit and analytical inversion), both of which provide consistent results and present different advantages and limitations which are discussed. A final set of antenna parameters to be used for direction finding studies with the RPWS experiment is obtained.

Vogl, Dieter F.; Cecconi, Baptiste; Macher, Wolfgang; Zarka, Philippe; Ladreiter, Hans Peter; FéDou, Pierre; Lecacheux, Alain; Averkamp, Terry; Fischer, Georg; Rucker, Helmut O.; Gurnett, Donald A.; Kurth, William S.; Hospodarsky, George B.

2004-09-01

216

Venus - Mass, gravity field, atmosphere, and ionosphere as measured by the Mariner 10 dual-frequency radio system  

NASA Technical Reports Server (NTRS)

The unique properties of the Mariner 10 radio system, and the preliminary scientific results obtained from the analysis of the radio signals are described. In the normal two-way communication mode, a command- and range-modulated 2115-MHz signal is transmitted to the spacecraft for reception on its omnidirectional antenna. As implemented for Mariner 10, the dual-frequency system has proven fully capable of performing interplanetary columnar electron content measurements while achieving the prime goals of the celestial mechanics and radio science team. The determination of the mass and gravitational potential of Venus is one of the major objectives of the radio science experiments. Information on Venus's atmosphere was deduced from analysis of the radio signals during occultation. Open-loop receiver differential Doppler data were used to measure the nightside and dayside ionospheres of Venus.

Howard, H. T.; Tyler, G. L.; Fjeldbo, G.; Kliore, A. J.; Levy, G. S.; Brunn, D. L.; Dickinson, R.; Edelson, R. E.; Martin, W. L.; Postal, R. B.

1974-01-01

217

Assessment of the Impacts of Radio Frequency Interference on SMAP Radar and Radiometer Measurements  

NASA Technical Reports Server (NTRS)

The NASA Soil Moisture Active and Passive (SMAP) mission will measure soil moisture with a combination of Lband radar and radiometer measurements. We present an assessment of the expected impact of radio frequency interference (RFI) on SMAP performance, incorporating projections based on recent data collected by the Aquarius and SMOS missions. We discuss the impacts of RFI on the radar and radiometer separately given the differences in (1) RFI environment between the shared radar band and the protected radiometer band, (2) mitigation techniques available for the different measurements, and (3) existing data sources available that can inform predictions for SMAP.

Chen, Curtis W.; Piepmeier, Jeffrey R.; Johnson, Joel T.; Hirad Ghaemi

2012-01-01

218

The software radio architecture  

Microsoft Academic Search

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

J. Mitola

1995-01-01

219

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

220

Ship-borne Radio and GLD360 Measurements of Intense Oceanic Lightning  

NASA Astrophysics Data System (ADS)

Recent studies with the GLD360 lightning geo-location network have shown that the peak current intensity of cloud-to-ground (CG) lightning is more powerful over the ocean than over land. This remains a poorly understood phenomenon. The Stanford VLF group has recently deployed a Very Low Frequency (1 MHz sampling rate) radio receiver system aboard the NOAA Ronald W. Brown research vessel. The goal of this transatlantic experiment is to improve our understanding of oceanic lightning and to investigate the physical difference between oceanic and land lightning. When positioned reasonably close to deep oceanic thunderstorms, the LF-VLF receiver aboard the Ronald W. Brown detects the impulsive radio emissions from the return stroke, up to 1 MHz, which enables us to estimate the return-stroke waveform shapes generated by the lightning channel. In this presentation, we present our experimental setup and a summary of the data collected during the transatlantic voyages of the NOAA ship. We process lightning-generated waveforms, compare them to LF-VLF data from land lightning over Oklahoma, extract statistical patterns, and compare the data to numerical and analytical models.

Zoghzoghy, F. G.; Cohen, M.; Said, R.; Lehtinen, N. G.; Inan, U.

2013-12-01

221

CREAM-MAC: Cognitive Radio-EnAbled MultiChannel MAC Protocol Over Dynamic Spectrum Access Networks  

Microsoft Academic Search

As the novel and effective approach to improving the utilization of the precious radio spectrum, cognitive radio technology is the key to realize the dynamic spectrum access (DSA) networks, where the secondary (unlicensed) users can opportunistically utilize the unused licensed spectrum in a way that confines the level of interference to the range the primary (licensed) users can tolerate. However,

Xi Zhang; Hang Su

2011-01-01

222

RadioAstron Measurement of High Brightness Temperature of 3C 273  

NASA Astrophysics Data System (ADS)

We report on observations of the quasar 3C 273 with the RadioAstron space to ground interferometer on projected baselines up to 173,000 km. The interferometer data at 1.3 cm between the RadioAstron Spacecraft and both the GBT and the VLA, obtained on a baseline of 7.9 x 109 ?, which achieved the highest angular resolution ever reported from any astronomical measurement, showed structure in the base of the radio jet smaller than about 30 micro arcsec. The observations at 18 cm between the spacecraft and both GBT and Arecibo on projected baselines of up to 9.6 x 108 ? give a direct measure of the brightness temperature of more than about 1014 K. This high value is greatly in excess of the 1012 K limit expected from inverse Compton cooling or the 1011 K expected if there is equilibrium between particle and magnetic energy. Such high observed brightness temperatures are difficult to understand in terms of Doppler boosting since 15 GHz VLBA monitoring of 3C 273 over the past 15 years indicate Lorentz factors of only about 10 to 15. We discuss possible explanations in terms of a continual acceleration of relativistic particles, incoherent radiation from relativistic protons, coherent radiation such as from a synchrotron maser, or a relativistic flow velocity, causing Doppler boosting, that is far in excess of the pattern velocity observed with the VLBA.

Kellermann, Kenneth I.; RadioAstron AGN Early Science Team

2014-01-01

223

Block diagrams for measuring systems of substance physicochemical composition and properties with “simple” measuring channels  

Microsoft Academic Search

Block diagrams of measuring systems for physicochemical composition and properties of substances with “simple” measuring channels\\u000a are considered. The interrelationship of technical and economic indices and their block diagrams is demonstrated, and its\\u000a features are noted.

V. A. Buzanovskii

2009-01-01

224

Near-Sun solar wind consequences of solar structure and dynamic phenomena observed by radio scintillation measurements  

NASA Technical Reports Server (NTRS)

Since radio propagation measurements using either natural or spacecraft radio signals are used for probing the solar wind in the vicinity of the sun, they represent a key tool for studying the interplanetary consequences of solar structure and dynamic phenomena. New information on the near sun consequences was obtained from radio scintillation observations of coherent spacecraft signals. The results covering density fluctuations, fractional density fluctuations, coronal streamers, heliospheric current sheets, coronal mass ejections and interplanetary shocks are reviewed. A joint ICE S-band (13 cm wavelength) Doppler scintillation measurement with the SOHO white-light coronograph (LASCO) is described.

Woo, Richard

1994-01-01

225

A System for Measurements on Radio Frequency Discharges in the Frequency Range of 20 TO 80 Mhz.  

National Technical Information Service (NTIS)

A system for measuring the basic electrical properties of radio frequency gas discharges is described. The system provides the capability for investigating discharges in air at atmospheric pressure in the frequency range of 20 to 80 MHz. The discharges ar...

E. L. Price

1968-01-01

226

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

227

VLF Radio Field Strength Measurement of power line carrier system in San Diego, California  

NASA Technical Reports Server (NTRS)

The radio frequency interference (RFI) potential was evaluated for a Powerline Carriet (PLC) installed in San Diego which monitors the performance of an electrical power system. The PLC system generated 30 amperes at 5.79 kHz. The RF radiations were measured to be (typically) 120 dBuV/m at the beginning of the 12 kV powerline and 60 dBuV/m at the end of the powerline. The RF fields varied inversely as the distance squared. Measurements were also performed with a 45 kHz PLC system. The RF fields were of similar amplitude.

Mertel, H. K.

1981-01-01

228

Measurements and modelling of the HF radio noise environment near an HVDC converter station  

NASA Astrophysics Data System (ADS)

Measurements of the HF radio noise environment near an HVDC transmission line and converter station were made outside Winnipeg in July 1977. Typical levels and characteristics are presented for various combinations of mercury arc valve noise, AC hum and DC corona from a number of sites within eight kilometers of the converter station. In addition, two sets of measurements were taken 80 km from the converter station. Values of the root-mean-square, average and quasipeak voltages were calculated from the Amplitude Probability Distribution (APDs) of the noise and were found to compare favorably with the directly measured values. Four mathematical models, the Rayleigh and three others which were developed for atmospheric noise were fitted to the measured APD data. Using inputs of v sub rms and V sub d the Log-Normal model produced the most accurate predictions of the measured APDs. The Log-Normal and the Hall models both fitted the measured Average Crossing Rate data equally well.

Lauber, W. R.; Bertrand, J. M.

1983-03-01

229

The radio waves & thermal electrostatic noise spectroscopy (SORBET) experiment on BepiColombo/MMO/PWI and the importance of radio HF measurements at Mercury  

NASA Astrophysics Data System (ADS)

SORBET (Spectroscopie des Ondes Radio & du Bruit Electrostatique Thermique) is a radio HF spectrometer designed for the radio and Plasma Waves Instrument (PWI) onboard BepiColombo/Mercury Magnetospheric Orbiter (MMO), which performs remote and in-situ measurements of waves (electromagnetic and electrostatic). Technically, SORBET includes a plasma wave spectrometer, with two E-field inputs from the two perpendicular electric antennas and one B-field input from a search coil, in the range 2.5 kHz - 640 kHz. This frequency band includes the local gyrofrequency and plasma frequency expected on most part of the MMO orbits. SORBET also includes a higher frequency radio receiver for remote sensing in the range 500kHz-10.2MHz. Owing to its capabilities, SORBET will be able to address the following scientific objectives: High resolution mapping (˜ 30 km) of electron density and temperature in the solar wind and Hermean magnetosphere and exo-ionosphere, via the technique of Quasi-Thermal Noise (QTN) spectroscopy. It is noteworthy that the QTN technique is weakly sensitive to spacecraft potential and photoelectron perturbations, a point highly in favour of this technique at Mercury. These QTN measurements will be determinant for the dynamic modeling of the magnetosphere and will provide a fundamental input for the chemistry of cold ionized species (Na, K, O ...) in Mercury's environment. Detection and study of Hermean radio emissions, including possible cyclotron emissions (up to ˜ 10-20 kHz) from mildly energetic electrons in highly magnetized (polar?) regions, and possible synchrotron radiation (up to a few MHz?) from more energetic electrons. Monitoring of solar radio emissions up to ~10 MHz, in order to create a solar activity index from the view point of Mercury, allowing to correlate it with the Hermean magnetospheric response. We propose to further discuss these scientific objectives and to underline that such radio HF measurements are a clue for understanding the structure and dynamics (regions, boundaries, acceleration, dissipation processes ...) of the Hermean magnetosphere/exo-ionosphere system and its interaction with the solar wind.

Moncuquet, M.; Matsumoto, H.; Bougeret, J.-L.; Issautier, K.; Kojima, H.; Maksimovic, M.; Meyer-Vernet, N.; Zarka, P.

230

Observation of a strong surface radar duct using helicopter acquired fine-scale radio refractivity measurements  

NASA Astrophysics Data System (ADS)

A very strong surface duct was observed near San Nicolas Island, California, using a unique helicopter-based data acquisition system developed for making fine-scale measurements of radio refractivity in the lower marine troposphere. Such fine-scale measurements are used in a computer model (TEMPER) for predicting microwave propagation in the first 400 m above the ocean surface. The helicopter system makes measurements of atmospheric temperature, pressure, relative humidity, and radar altitude. These measurements are acquired by an on-board computer, which derives and displays real-time plots of modified refractivity versus altitude. Data is stored on floppy disks for later use in the TEMPER (Tropospheric Electromagnetic Parabolic Equation Routine) computer model for microwave propagation prediction. The helicopter measurements are presented and compared with TEMPER computer model microwave propagation predictions using this helicopter data and a standard atmosphere profile.

Babin, Steven M.; Rowland, John R.

1992-05-01

231

Wide Range Neutron Flux Measuring Channel for Aerospace Application  

SciTech Connect

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.; Nunez, M. [INVAP S.E., Moreno 1089, 8400 Bariloche, Rio Negro (Argentina); Tropea, S. E. [INTI, Av. Gral. Paz 5445, 1650 San Martin, Buenos Aires (Argentina)

2008-01-21

232

Wireless Communication Systems Design for Tactical Software-Defined Radios - From Scenario-Based Analysis to Channel and Waveform Parameter.  

National Technical Information Service (NTIS)

Software defined radios and especially the associated digital waveforms for tactical wireless communication systems feature a high degree of freedom and can be tailored to completely different operational needs. In case of the development of new digital w...

A. Heuberger J. Fischer W. Felber

2010-01-01

233

Solar wind interaction with the ionosphere of Venus inferred from radio scintillation measurements  

SciTech Connect

This paper presents the first S-band (2.3 GHz) radio scintillations observed in the ionosphere of Venus and discovered when the Pioneer Venus Orbiter spacecraft traversed the ionosphere of Venus. In situ plasma measurements as well as propagation calculations confirm that the scintillations are caused by electron density irregularities in the topside ionosphere of Venus below the ionopause. While these topside plasma irregularities have not been studied before, simultaneous magnetic field measurements presented here reveal that they are associated with the penetration of large-scale magnetic fields in the ionosphere. Previous studies based on extensive magnetic field measurements have shown that the presence of large-scale magnetic fields occurs in the subsolar region when the solar wind dynamic pressure exceeds the ionospheric plasma pressure. As with the large-scale magnetic fields, the disturbed plasma and resulting scintillations are therefore a manifestation of high-dynamic solar wind interaction with the ionosphere. Since the scintillations only occur in the subsolar region of Venus, the global morphology of ionospheric scintillations at Venus is different from that of the terrestrial ionosphere, where scintillations are observed in both polar and equatorial regions, with peaks occurring during nighttime. This difference apparently stems from the fact that Venus is not a magnetic planet. The authors also demonstrate that the disturbed plasma produced by the high-dynamic solar wind interaction can be remotely sensed by scintillations during radio occultation measurements, that is, when the spacecraft is outside the ionosphere.

Woo, R.; Sjogren, W.L.; Kliore, A.J. (California Institute of Technology, Pasadena (USA)); Luhmann, J.G. (Univ. of California, Los Angeles (USA)); Brace, L.H. (NASA Goddard Space Flight Center, Greenbelt, MD (USA))

1989-02-01

234

The detection of the ionospheric irregularities by GNSS signal and the incoherent scatter radio measurements  

NASA Astrophysics Data System (ADS)

The high-latitude ionosphere has a very complicated structure and high dynamics. The ionospheric irregularities can produce scintillations of radio waves that occur predominantly in the ionosphere F-layer. The strong fluctuations can influence on the performance of the different space communication and navigation radio systems. The fluctuations of GPS/GLONASS signals are caused by the ionospheric irregularities with spatial dimensions more than 10 km. These structures can be detected by high potential incoherent scatter radars. It was proposed and carried out at the beginning of June 2012 experiment for a detailed study of the nature of the ionospheric irregularities, influencing on GPS/GLONASS signals parameters, by incoherent scatter and trans-ionospheric radio measurements simultaneously. The EISCAT facilities position provides the unique opportunity to study the ionospheric irregularities' parameters associated with TEC fluctuations and GPS/GLONASS signals scintillations. The EISCAT heating facility provides unique possibility to generate the artificial ionospheric irregularities and to estimate the impact factor of these irregularities on GPS/GLONASS signals transionospheric propagation. In order to detect the ionosphere irregularities it is used the IS radar measurements (electron density and plasma temperatures profiles) and simultaneously registered on EISCAT site amplitude and phase fluctuations in GPS/GLONASS signals by use of the Javad multi-constellation GPS/GLONASS receiver with high samples rate (100 Hz) and special scintillation GPS receiver PolaRxS PRO that dedicated to ionospheric monitoring and space weather applications and provides TEC and S4 scintillation index measurements. The low frequency fluctuations can be directly measured due to the electron density changes along the radio ray path between a GPS/GLONASS satellite and a ground-based receiver on EISCAT site. The raw data (under scintillating conditions) obtained by use of the high samples rate GPS/GLONASS receiver are processed in order to derive the scintillation parameters. The practical aspect of this investigation is a detailed study of nature and impact level of the ionospheric irregularities that can influence on the GPS/GLONASS performance especially at high latitudes and during geomagnetically disturbed period and to obtain new knowledge that may improve the reliability of the global navigation systems in Arctic and Antarctic regions. The authors are grateful to the EISCAT Scientific Association for observing time on the EISCAT facilities within the framework of Peer-reviewed Program.

Cherniak, Iurii; Shagimuratov, Irk; Krankowski, Andrzej; Sieradsky, Rafal; Zakharenkova, Irina; Rietveld, Michael; Kapcia, Jacek

2013-04-01

235

Output power distributions of mobile radio base stations based on network measurements  

NASA Astrophysics Data System (ADS)

In this work output power distributions of mobile radio base stations have been analyzed for 2G and 3G telecommunication systems. The approach is based on measurements in selected networks using performance surveillance tools part of the network Operational Support System (OSS). For the 3G network considered, direct measurements of output power levels were possible, while for the 2G networks, output power levels were estimated from measurements of traffic volumes. Both voice and data services were included in the investigation. Measurements were conducted for large geographical areas, to ensure good overall statistics, as well as for smaller areas to investigate the impact of different environments. For high traffic hours, the 90th percentile of the averaged output power was found to be below 65% and 45% of the available output power for the 2G and 3G systems, respectively.

Colombi, D.; Thors, B.; Persson, T.; Wirén, N.; Larsson, L.-E.; Törnevik, C.

2013-04-01

236

Radio frequency coupling apparatus and method for measuring minority carrier lifetimes in semiconductor materials  

DOEpatents

An apparatus for measuring the minority carrier lifetime of a semiconductor sample using radio-frequency coupling. The measuring apparatus includes an antenna that is positioned a coupling distance from a semiconductor sample which is exposed to light pulses from a laser during sampling operations. A signal generator is included to generate high frequency, such as 900 MHz or higher, sinusoidal waveform signals that are split into a reference signal and a sample signal. The sample signal is transmitted into a sample branch circuit where it passes through a tuning capacitor and a coaxial cable prior to reaching the antenna. The antenna is radio-frequency coupled with the adjacent sample and transmits the sample signal, or electromagnetic radiation corresponding to the sample signal, to the sample and receives reflected power or a sample-coupled-photoconductivity signal back. To lower impedance and speed system response, the impedance is controlled by limiting impedance in the coaxial cable and the antenna reactance. In one embodiment, the antenna is a waveguide/aperture hybrid antenna having a central transmission line and an adjacent ground flange. The sample-coupled-photoconductivity signal is then transmitted to a mixer which also receives the reference signal. To enhance the sensitivity of the measuring apparatus, the mixer is operated to phase match the reference signal and the sample-coupled-photoconductivity signal.

Johnston, Steven W. (Golden, CO); Ahrenkiel, Richard K. (Lakewood, CO)

2002-01-01

237

Measurements and Models of Radio Frequency Impulsive Noise for Indoor Wireless Communications  

Microsoft Academic Search

The authors present the results of average and impulsive noise measurements inside several office buildings and retail stores. The noise measurement system operated at 918 MHz, 2.44 GHz, and 4 GHz with a nominal 40-MHz, 3-dB RF bandwidth. Omnidirectional and directional antennas were used to investigate the characteristics and sources of RF noise in indoor channels. Statistical analyses of the

Kenneth L. Blackard; Theodore S. Rappaport; Charles W. Bostian

1993-01-01

238

Measurements of the suitability of large rock salt formations for radio detection of high-energy neutrinos  

Microsoft Academic Search

We have investigated the possibility that large rock salt formations might be suitable as target masses for detection of neutrinos of energies about 10PeV 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

Peter Gorham; David Saltzberg; Allen Odian; Dawn Williams; David Besson; George Frichter; Sami Tantawi

2002-01-01

239

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

240

Channel measurement and characterization of interference between residential femto-cell systems  

Microsoft Academic Search

Interference between femto-cell systems is a critical factor for the deployment of such systems in, e.g., resedential areas. In this paper we report on a residential channel measure- ment campaign focusing on the channel properties for femto- cell systems. We characterize basic channel properties such as delay spread and interference levels between different furnished residential houses. In addition we also

Xiang Gao; Andres Alayon Glazunov; Jialai Weng; Cheng Fang; Jie Zhang; Fredrik Tufvesson

2011-01-01

241

Portable Wireless LAN Device and Two-way Radio Threat Assessment for Aircraft Navigation Radios  

NASA Technical Reports Server (NTRS)

Measurement processes, data and analysis are provided to address the concern for Wireless Local Area Network devices and two-way radios to cause electromagnetic interference to aircraft navigation radio systems. A radiated emission measurement process is developed and spurious radiated emissions from various devices are characterized using reverberation chambers. Spurious radiated emissions in aircraft radio frequency bands from several wireless network devices are compared with baseline emissions from standard computer laptops and personal digital assistants. In addition, spurious radiated emission data in aircraft radio frequency bands from seven pairs of two-way radios are provided, A description of the measurement process, device modes of operation and the measurement results are reported. Aircraft interference path loss measurements were conducted on four Boeing 747 and Boeing 737 aircraft for several aircraft radio systems. The measurement approach is described and the path loss results are compared with existing data from reference documents, standards, and NASA partnerships. In-band on-channel interference thresholds are compiled from an existing reference document. Using these data, a risk assessment is provided for interference from wireless network devices and two-way radios to aircraft systems, including Localizer, Glideslope, Very High Frequency Omnidirectional Range, Microwave Landing System and Global Positioning System. The report compares the interference risks associated with emissions from wireless network devices and two-way radios against standard laptops and personal digital assistants. Existing receiver interference threshold references are identified as to require more data for better interference risk assessments.

Nguyen, Truong X.; Koppen, Sandra V.; Ely, Jay J.; Williams, Reuben A.; Smith, Laura J.; Salud, Maria Theresa P.

2003-01-01

242

A modular 31-channel SQUID system for biomagnetic measurements  

Microsoft Academic Search

A modular multichannel superconducting quantum interference device (SQUID) system, in which every channel can be optimized or replaced individually, was further improved. The number of channels was increased to 31. The noise level is better than 10 fT\\/?Hz. A novel way of RF shielding using conductive paint avoids degradation of the SQUID characteristics due to RF interference without introducing significant

O. Dossel; B. David; M. Fuchs; J. Kruger; K.-M. Ludeke; H.-A. Wischmann

1993-01-01

243

Measurement of the t-channel single top quark production cross section  

NASA Astrophysics Data System (ADS)

The D0 Collaboration reports direct evidence for electroweak production of single top quarks through the t-channel exchange of a virtual W boson. This is the first analysis to isolate an individual single top quark production channel. We select events containing an isolated electron or muon, missing transverse energy, and two, three or four jets from 2.3 fb -1 of ppbar collisions at the Fermilab Tevatron Collider. One or two of the jets are identified as containing a b hadron. We combine three multivariate techniques optimized for the t-channel process to measure the t- and s-channel cross sections simultaneously. We measure cross sections of 3.14-0.80+0.94 pb for the t-channel and 1.05±0.81 pb for the s-channel. The measured t-channel result is found to have a significance of 4.8 standard deviations and is consistent with the standard model prediction.

Abazov, V. M.; Abbott, B.; Abolins, M.; Acharya, B. S.; Adams, M.; Adams, T.; Aguilo, E.; Ahsan, M.; Alexeev, G. D.; Alkhazov, G.; Alton, A.; Alverson, G.; Alves, G. A.; Ancu, L. S.; Anzelc, M. S.; Aoki, M.; Arnoud, Y.; Arov, M.; Arthaud, M.; Askew, A.; Åsman, B.; Atramentov, O.; Avila, C.; BackusMayes, J.; Badaud, F.; Bagby, L.; Baldin, B.; Bandurin, D. V.; Banerjee, S.; Barberis, E.; Barfuss, A.-F.; Bargassa, P.; Baringer, P.; Barreto, J.; Bartlett, J. F.; Bassler, U.; Bauer, D.; Beale, S.; Bean, A.; Begalli, M.; Begel, M.; Belanger-Champagne, C.; Bellantoni, L.; Bellavance, A.; Benitez, J. A.; Beri, S. B.; Bernardi, G.; Bernhard, R.; Bertram, I.; Besançon, M.; Beuselinck, R.; Bezzubov, V. A.; Bhat, P. C.; Bhatnagar, V.; Blazey, G.; Blessing, S.; Bloom, K.; Boehnlein, A.; Boline, D.; Bolton, T. A.; Boos, E. E.; Borissov, G.; Bose, T.; Brandt, A.; Brock, R.; Brooijmans, G.; Bross, A.; Brown, D.; Bu, X. B.; Buchholz, D.; Buehler, M.; Buescher, V.; Bunichev, V.; Burdin, S.; Burnett, T. H.; Buszello, C. P.; Calfayan, P.; Calpas, B.; Calvet, S.; Cammin, J.; Carrasco-Lizarraga, M. A.; Carrera, E.; Carvalho, W.; Casey, B. C. K.; Castilla-Valdez, H.; Chakrabarti, S.; Chakraborty, D.; Chan, K. M.; Chandra, A.; Cheu, E.; Cho, D. K.; Cho, S. W.; Choi, S.; Choudhary, B.; Christoudias, T.; Cihangir, S.; Claes, D.; Clutter, J.; Coadou, Y.; Cooke, M.; Cooper, W. E.; Corcoran, M.; Couderc, F.; Cousinou, M.-C.; Cutts, D.; ?wiok, M.; Das, A.; Davies, G.; De, K.; de Jong, S. J.; De La Cruz-Burelo, E.; DeVaughan, K.; Déliot, F.; Demarteau, M.; Demina, R.; Denisov, D.; Denisov, S. P.; Desai, S.; Diehl, H. T.; Diesburg, M.; Dominguez, A.; Dorland, T.; Dubey, A.; Dudko, L. V.; Duflot, L.; Duggan, D.; Duperrin, A.; Dutt, S.; Dyshkant, A.; Eads, M.; Edmunds, D.; Ellison, J.; Elvira, V. D.; Enari, Y.; Eno, S.; Escalier, M.; Evans, H.; Evdokimov, A.; Evdokimov, V. N.; Facini, G.; Ferapontov, A. V.; Ferbel, T.; Fiedler, F.; Filthaut, F.; Fisher, W.; Fisk, H. E.; Fortner, M.; Fox, H.; Fu, S.; Fuess, S.; Gadfort, T.; Galea, C. F.; Garcia-Bellido, A.; Gavrilov, V.; Gay, P.; Geist, W.; Geng, W.; Gerber, C. E.; Gershtein, Y.; Gillberg, D.; Ginther, G.; Gómez, B.; Goussiou, A.; Grannis, P. D.; Greder, S.; Greenlee, H.; Greenwood, Z. D.; Gregores, E. M.; Grenier, G.; Gris, Ph.; Grivaz, J.-F.; Grohsjean, A.; Grünendahl, S.; Grünewald, M. W.; Guo, F.; Guo, J.; Gutierrez, G.; Gutierrez, P.; Haas, A.; Haefner, P.; Hagopian, S.; Haley, J.; Hall, I.; Hall, R. E.; Han, L.; Harder, K.; Harel, A.; Hauptman, J. M.; Hays, J.; Hebbeker, T.; Hedin, D.; Hegeman, J. G.; Heinson, A. P.; Heintz, U.; Hensel, C.; Heredia-De La Cruz, I.; Herner, K.; Hesketh, G.; Hildreth, M. D.; Hirosky, R.; Hoang, T.; Hobbs, J. D.; Hoeneisen, B.; Hohlfeld, M.; Hossain, S.; Houben, P.; Hu, Y.; Hubacek, Z.; Huske, N.; Hynek, V.; Iashvili, I.; Illingworth, R.; Ito, A. S.; Jabeen, S.; Jaffré, M.; Jain, S.; Jakobs, K.; Jamin, D.; Jesik, R.; Johns, K.; Johnson, C.; Johnson, M.; Johnston, D.; Jonckheere, A.; Jonsson, P.; Juste, A.; Kajfasz, E.; Karmanov, D.; Kasper, P. A.; Katsanos, I.; Kaushik, V.; Kehoe, R.; Kermiche, S.; Khalatyan, N.; Khanov, A.; Kharchilava, A.; Kharzheev, Y. N.; Khatidze, D.; Kirby, M. H.; Kirsch, M.; Klima, B.; Kohli, J. M.; Konrath, J.-P.; Kozelov, A. V.; Kraus, J.; Kuhl, T.; Kumar, A.; Kupco, A.; Kur?a, T.; Kuzmin, V. A.; Kvita, J.; Lacroix, F.; Lam, D.; Lammers, S.; Landsberg, G.; Lebrun, P.; Lee, H. S.; Lee, W. M.; Leflat, A.; Lellouch, J.; Li, L.; Li, Q. Z.; Lietti, S. M.; Lim, J. K.; Lincoln, D.; Linnemann, J.; Lipaev, V. V.; Lipton, R.; Liu, Y.; Liu, Z.; Lobodenko, A.; Lokajicek, M.; Love, P.; Lubatti, H. J.; Luna-Garcia, R.; Lyon, A. L.; Maciel, A. K. A.; Mackin, D.; Mättig, P.; Magaña-Villalba, R.; Mal, P. K.; Malik, S.; Malyshev, V. L.; Maravin, Y.; Martin, B.; McCarthy, R.; McGivern, C. L.; Meijer, M. M.; Melnitchouk, A.; Mendoza, L.; Menezes, D.; Mercadante, P. G.; Merkin, M.; Merritt, K. W.; Meyer, A.; Meyer, J.; Mondal, N. K.; Moore, R. W.; Moulik, T.; Muanza, G. S.; Mulhearn, M.; Mundal, O.; Mundim, L.; Nagy, E.; Naimuddin, M.; Narain, M.; Neal, H. A.; Negret, J. P.; Neustroev, P.; Nilsen, H.; Nogima, H.; Novaes, S. F.; Nunnemann, T.; O'Neil, D. C.; Obrant, G.; Ochando, C.; Onoprienko, D.; Orduna, J.; Oshima, N.; Osman, N.; Osta, J.; Otec, R.; Otero y Garzón, G. J.; Owen, M.; Padilla, M.; Padley, P.; Pangilinan, M.; Parashar, N.; Park, S.-J.; Park, S. K.; Parsons, J.; Partridge, R.; Parua, N.; Patwa, A.; Penning, B.; Perfilov, M.; Peters, K.; Peters, Y.; Pétroff, P.; Piegaia, R.; Piper, J.; Pleier, M.-A.; Podesta-Lerma, P. L. M.; Podstavkov, V. M.; Pogorelov, Y.; Pol, M.-E.; Polozov, P.; Popov, A. V.; Prewitt, M.; Prosper, H. B.; Protopopescu, S.; Qian, J.; Quadt, A.; Quinn, B.; Rakitine, A.; Rangel, M. S.; Ranjan, K.; Ratoff, P. N.; Renkel, P.

244

Measurement of the t-channel single top quark production cross section  

NASA Astrophysics Data System (ADS)

The D0 Collaboration reports direct evidence for electroweak production of single top quarks through the t-channel exchange of a virtual W boson. This is the first analysis to isolate an individual single top quark production channel. We select events containing an isolated electron or muon, missing transverse energy, and two, three or four jets from 2.3 fb-1 of pp¯ collisions at the Fermilab Tevatron Collider. One or two of the jets are identified as containing a b hadron. We combine three multivariate techniques optimized for the t-channel process to measure the t- and s-channel cross sections simultaneously. We measure cross sections of 3.14-0.80+0.94 pb for the t-channel and 1.05±0.81 pb for the s-channel. The measured t-channel result is found to have a significance of 4.8 standard deviations and is consistent with the standard model prediction.

DØ Collaboration; Abazov, V. M.; Abbott, B.; Abolins, M.; Acharya, B. S.; Adams, M.; Adams, T.; Aguilo, E.; Ahsan, M.; Alexeev, G. D.; Alkhazov, G.; Alton, A.; Alverson, G.; Alves, G. A.; Ancu, L. S.; Anzelc, M. S.; Aoki, M.; Arnoud, Y.; Arov, M.; Arthaud, M.; Askew, A.; Åsman, B.; Atramentov, O.; Avila, C.; Backusmayes, J.; Badaud, F.; Bagby, L.; Baldin, B.; Bandurin, D. V.; Banerjee, S.; Barberis, E.; Barfuss, A.-F.; Bargassa, P.; Baringer, P.; Barreto, J.; Bartlett, J. F.; Bassler, U.; Bauer, D.; Beale, S.; Bean, A.; Begalli, M.; Begel, M.; Belanger-Champagne, C.; Bellantoni, L.; Bellavance, A.; Benitez, J. A.; Beri, S. B.; Bernardi, G.; Bernhard, R.; Bertram, I.; Besançon, M.; Beuselinck, R.; Bezzubov, V. A.; Bhat, P. C.; Bhatnagar, V.; Blazey, G.; Blessing, S.; Bloom, K.; Boehnlein, A.; Boline, D.; Bolton, T. A.; Boos, E. E.; Borissov, G.; Bose, T.; Brandt, A.; Brock, R.; Brooijmans, G.; Bross, A.; Brown, D.; Bu, X. B.; Buchholz, D.; Buehler, M.; Buescher, V.; Bunichev, V.; Burdin, S.; Burnett, T. H.; Buszello, C. P.; Calfayan, P.; Calpas, B.; Calvet, S.; Cammin, J.; Carrasco-Lizarraga, M. A.; Carrera, E.; Carvalho, W.; Casey, B. C. K.; Castilla-Valdez, H.; Chakrabarti, S.; Chakraborty, D.; Chan, K. M.; Chandra, A.; Cheu, E.; Cho, D. K.; Cho, S. W.; Choi, S.; Choudhary, B.; Christoudias, T.; Cihangir, S.; Claes, D.; Clutter, J.; Coadou, Y.; Cooke, M.; Cooper, W. E.; Corcoran, M.; Couderc, F.; Cousinou, M.-C.; Cutts, D.; ?wiok, M.; Das, A.; Davies, G.; de, K.; de Jong, S. J.; de La Cruz-Burelo, E.; Devaughan, K.; Déliot, F.; Demarteau, M.; Demina, R.; Denisov, D.; Denisov, S. P.; Desai, S.; Diehl, H. T.; Diesburg, M.; Dominguez, A.; Dorland, T.; Dubey, A.; Dudko, L. V.; Duflot, L.; Duggan, D.; Duperrin, A.; Dutt, S.; Dyshkant, A.; Eads, M.; Edmunds, D.; Ellison, J.; Elvira, V. D.; Enari, Y.; Eno, S.; Escalier, M.; Evans, H.; Evdokimov, A.; Evdokimov, V. N.; Facini, G.; Ferapontov, A. V.; Ferbel, T.; Fiedler, F.; Filthaut, F.; Fisher, W.; Fisk, H. E.; Fortner, M.; Fox, H.; Fu, S.; Fuess, S.; Gadfort, T.; Galea, C. F.; Garcia-Bellido, A.; Gavrilov, V.; Gay, P.; Geist, W.; Geng, W.; Gerber, C. E.; Gershtein, Y.; Gillberg, D.; Ginther, G.; Gómez, B.; Goussiou, A.; Grannis, P. D.; Greder, S.; Greenlee, H.; Greenwood, Z. D.; Gregores, E. M.; Grenier, G.; Gris, Ph.; Grivaz, J.-F.; Grohsjean, A.; Grünendahl, S.; Grünewald, M. W.; Guo, F.; Guo, J.; Gutierrez, G.; Gutierrez, P.; Haas, A.; Haefner, P.; Hagopian, S.; Haley, J.; Hall, I.; Hall, R. E.; Han, L.; Harder, K.; Harel, A.; Hauptman, J. M.; Hays, J.; Hebbeker, T.; Hedin, D.; Hegeman, J. G.; Heinson, A. P.; Heintz, U.; Hensel, C.; Heredia-de La Cruz, I.; Herner, K.; Hesketh, G.; Hildreth, M. D.; Hirosky, R.; Hoang, T.; Hobbs, J. D.; Hoeneisen, B.; Hohlfeld, M.; Hossain, S.; Houben, P.; Hu, Y.; Hubacek, Z.; Huske, N.; Hynek, V.; Iashvili, I.; Illingworth, R.; Ito, A. S.; Jabeen, S.; Jaffré, M.; Jain, S.; Jakobs, K.; Jamin, D.; Jesik, R.; Johns, K.; Johnson, C.; Johnson, M.; Johnston, D.; Jonckheere, A.; Jonsson, P.; Juste, A.; Kajfasz, E.; Karmanov, D.; Kasper, P. A.; Katsanos, I.; Kaushik, V.; Kehoe, R.; Kermiche, S.; Khalatyan, N.; Khanov, A.; Kharchilava, A.; Kharzheev, Y. N.; Khatidze, D.; Kirby, M. H.; Kirsch, M.; Klima, B.; Kohli, J. M.; Konrath, J.-P.; Kozelov, A. V.; Kraus, J.; Kuhl, T.; Kumar, A.; Kupco, A.; Kur?a, T.; Kuzmin, V. A.; Kvita, J.; Lacroix, F.; Lam, D.; Lammers, S.; Landsberg, G.; Lebrun, P.; Lee, H. S.; Lee, W. M.; Leflat, A.; Lellouch, J.; Li, L.; Li, Q. Z.; Lietti, S. M.; Lim, J. K.; Lincoln, D.; Linnemann, J.; Lipaev, V. V.; Lipton, R.; Liu, Y.; Liu, Z.; Lobodenko, A.; Lokajicek, M.; Love, P.; Lubatti, H. J.; Luna-Garcia, R.; Lyon, A. L.; Maciel, A. K. A.; Mackin, D.; Mättig, P.; Magaña-Villalba, R.; Mal, P. K.; Malik, S.; Malyshev, V. L.; Maravin, Y.; Martin, B.; McCarthy, R.; McGivern, C. L.; Meijer, M. M.; Melnitchouk, A.; Mendoza, L.; Menezes, D.; Mercadante, P. G.; Merkin, M.; Merritt, K. W.; Meyer, A.; Meyer, J.; Mondal, N. K.; Moore, R. W.; Moulik, T.; Muanza, G. S.; Mulhearn, M.; Mundal, O.; Mundim, L.; Nagy, E.; Naimuddin, M.; Narain, M.; Neal, H. A.; Negret, J. P.; Neustroev, P.; Nilsen, H.; Nogima, H.; Novaes, S. F.; Nunnemann, T.; O'Neil, D. C.; Obrant, G.; Ochando, C.; Onoprienko, D.; Orduna, J.; Oshima, N.; Osman, N.; Osta, J.; Otec, R.; Otero Y Garzón, G. J.; Owen, M.; Padilla, M.; Padley, P.; Pangilinan, M.; Parashar, N.; Park, S.-J.; Park, S. K.; Parsons, J.; Partridge, R.; Parua, N.; Patwa, A.; Penning, B.; Perfilov, M.; Peters, K.; Peters, Y.; Pétroff, P.; Piegaia, R.; Piper, J.; Pleier, M.-A.; Podesta-Lerma, P. L. M.; Podstavkov, V. M.; Pogorelov, Y.; Pol, M.-E.; Polozov, P.; Popov, A. V.; Prewitt, M.; Prosper, H. B.; Protopopescu, S.; Qian, J.; Quadt, A.; Quinn, B.; Rakitine, A.; Rangel, M. S.; Ranjan, K.

2010-01-01

245

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

246

Cognitive Radio with Single Carrier TDCS and Multicarrier OFDM Approach with V-BLAST Receiver in Rayleigh Fading Channel  

Microsoft Academic Search

This paper presents the performance comparison of Cognitive Radio TDCS and OFDM based for MIMO system using VBLAST receiver architecture to reconstruct the transmitted data. The interference avoidance performance in terms of BER and bitrate are improved by adding multiple antennas to the system and the use of V-BLAST technique at the receiver. The results show the most promising interference

I. Budiarjo; H. Nikookar; L. P. Ligthart

2007-01-01

247

Investigation of the plasmasphere electron content on the base of radio-measurements  

NASA Astrophysics Data System (ADS)

The electron densities in plasmasphere are several orders of magnitude less than in ionosphere and the plasmasphere is often ignored at analysis and estimation of GPS TEC data, however the plasmaspheric contribution to the GPS TEC can became significant under certain conditions. This paper presents results of study of the plasmaspheric electron content variations for such cases - period of very low solar activity and during strong geomagnetic storm. Estimates of IEC can be retrieved as a result of integration of ionospheric electron density profiles (EDP). For this aim one can use EDPs derived from satellite radio occultation (RO) or ground-based radio-physical measurements. For case of the extended solar minimum of 23/24 cycle, 2009 the PEC was estimated by combination of GPS TEC observations and FORMOSAT-3/COSMIC RO measurements. It was analyzed the monthly medians of TEC and PEC for different seasons (equinoxes and solstices). Results shows that for mid-latitudinal points PEC estimates varied weakly with the time of a day and reached the value of several TECU for the condition of solar minimum. Percentage contribution of PEC to GPS TEC indicated the clear dependence from the time with maximal values (more than 50-60%) during night-time and lesser values (25-45%) during day-time. The variations of PEC during strong geomagnetic storms at November 2004 were estimated by combining of mid-latitude Kharkov Incoherent Scatter Radar observations and GPS TEC data. The comparison between two independent measurements was performed by analysis of the height-temporal distribution for specific point corresponded to the mid-latitudes of Europe. Percentage contribution of PEC to GPS TEC indicated the clear dependence from the time with maximal values (more than 70%) during night-time and smaller values (30-45%) during day-time for weak disturbance and quite time and rather high values during strong negative storm (up to 90%) with small changes in time. These changes can be explained by the competing effects of electric fields and winds which tend to raise the layer to the region with lower loss rate and movement of ionospheric plasma to protonosphere. The results of our investigations can be further used for GNSS applications as well as for long base low frequency radio astronomical facilities (like LOFAR) during high precision measurements campaigns.

Cherniak, I.; Zakharenkova, I.; Krankowski, A.

2013-12-01

248

Patch-Clamp Measurement of ICRAC and ORAI Channel Activity.  

PubMed

Depletion of internal Ca(2+) stores activates store-operated Ca(2+) channels. The most prominent members of this class of channels are Ca(2+) release-activated Ca(2+) (CRAC) channels, which are present in a variety of cell types including immune cells. CRAC channels are composed of ORAI proteins, which are activated by endoplasmic reticulum-bound STIM proteins on Ca(2+) store depletion. The underlying Ca(2+) current is called ICRAC, which is required for many cellular functions including T-cell activation, mast cell activation, Ca(2+)-dependent gene expression, and refilling of internal Ca(2+) stores. To analyze ICRAC or the Ca(2+) current through heterologously expressed ORAI channels, whole-cell patch clamp is the technique of choice. It allows the direct analysis of ion currents through CRAC/ORAI channels. The patch-clamp technique has been used to determine selectivity, permeability, rectification, inactivation, and several other biophysical and pharmacological properties of the channels, and is the most direct and reliable technique to analyze ICRAC. PMID:24890214

Alansary, Dalia; Kilch, Tatiana; Holzmann, Christian; Peinelt, Christine; Hoth, Markus; Lis, Annette

2014-01-01

249

Simulation of polar cap field-aligned electron density profiles measured with the IMAGE radio plasma imager  

Microsoft Academic Search

The radio plasma imager (RPI) on board the IMAGE satellite measured a set of field-aligned electron density profiles at polar latitudes during a weak magnetic storm on 4 March 2003. Several of those density profiles as well as a density profile measured under moderately quiet conditions are compared with those simulated by a dynamic fluid semikinetic (DyFK) model. In this

J.-N. Tu; J. L. Horwitz; P. A. Nsumei; P. Song; X.-Q. Huang; B. W. Reinisch

2004-01-01

250

A Campaign Study of Ionospheric Scintillations Using Simultaneous Formosat-3\\/COSMIC Radio Occultation Observations and AFRL SCINDA Ground Scintillation Measurements  

Microsoft Academic Search

We report preliminary results from a campaign study of ionospheric scintillations using ionospheric radio occultation measurements by Formosat-3\\/COSMIC satellites and ground scintillation measurements by the Scintillation Network Decision Aid (SCINDA) network. Under the SCINDA project, scientists at the Air Force Research Laboratory (AFRL) have developed a sensor network for the purpose of monitoring low-latitude ionospheric total electron content (TEC) and

C. S. Lin; M. J. Starks; Y. Chu; S. Syndergarrd; K. M. Groves; S. Basu

2006-01-01

251

[Electromagnetic fields emitted in radio- and microwave- frequency range: equipment and methods for the environment protection and survey measurements].  

PubMed

In the paper a review of electromagnetic field sources in radio- and microwave- frequency range is presented. The aim of the study was to analyze possibilities and methods used to survey electromagnetic field (EMF) measurements. Selective and broadband methods with examples of apparatus are described. The accuracy of typical EMF survey measurements was estimated. PMID:19388464

Bie?kowski, Pawe?

2008-01-01

252

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

Microsoft Academic Search

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

Jianjun Huang; Jianhua Yu; Zhenzhi Liu

2003-01-01

253

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

254

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

NASA Technical Reports Server (NTRS)

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 all elements in the station except for the antenna and the hydrogen maser, was measured to be 0.3 to 1.3 x 10(exp -15) when the frequency was fixed, and 0.6 to 6.0 x 10(exp -15) when the frequency was ramped (sample interval, 1000 sec). Only one measurement out of fifteen exceeded specification. In all other cases, when previous measurements on the antenna and the hydrogen maser were added, a total system stability requirement of 5.0 x 10(exp -15) as met. In addition, ambient temperature was found to cause phase variation in the measurements at a rate of 5.5 deg of phase per deg C.

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

1993-01-01

255

Ion species mix and ion density measurements using radio frequency waves  

NASA Astrophysics Data System (ADS)

Radio frequency wave applications have demonstrated great versatility in tokamak plasmas. Two applications, using the same diagnostic design, can make use of a fast Alfven wave to make ion species mix and ion density measurements. A discussion and derivation, using the cold plasma approximation, is given for a fast Alfven radio wave used for making an interferometry density measurement, a two ion species mix reflectometry measurement, and a three ion species mix reflectometry measurement. Utilizing the dependence of the fast Alfven wave upon density, the mass density evolution of a plasma can be tracked via interferometry. In addition, new antennas were installed where the graphite tiles were converted to be part of the receiving antenna, increasing reception by at least one order of magnitude. Density evolution measurements with these new antennas (˜100 MHz, 20mW) were made for the first several hundred milliseconds until tracking was lost. When tracking was successful, the density evolution observed from the new antennas shows reasonable agreement with existing diagnostics. A heterodyne reflectometer could provide a direct and inexpensive measurement of ion species mixes with different charge to mass ratios. Using the cold plasma dispersion relation for multiple ion species, the ion-ion hybrid cutoff frequency is uniquely determined by the density ratio and cyclotron frequencies of those two species. The phase of a ˜20 MHz wave that travels from the launching point to the cutoff layer to the receiving antenna provides a direct measure of the hydrogen: deuterium species mix. In the first experiment, a fast Alfven wave was launched perpendicular to a hydrogen-deuterium plasma from the low field side of the DIII-D tokamak. Quantitative measurements observed a hydrogen concentration range of 3%--67% and a maximum penetration depth of 0.60 m. Corroborative values were obtained from two independent diagnostics. In the second experiment, the fast Alfven wave was launched from the high field side during a hydrogen puffing experiment. Results again show agreement with other diagnostics. In addition, it is demonstrated that a wave launched from the high field side is able to tunnel through the resonance layer and be reflected back to the receiving antenna.

Watson, George Wilder, III

256

Field measurements of three-dimensional hydraulics in a step-pool channel  

Microsoft Academic Search

We investigated the effects of morphologic position and discharge on flow structure in a steep (0.10m\\/m) mountain channel by collecting three-dimensional measurements of time-averaged and turbulent velocity components with a SonTek FlowTracker Handheld ADV (acoustic Doppler velocimeter) on a 30-m reach of a step-pool channel in the Colorado Rockies. Velocity profiles were measured at morphologic positions characteristic of steep channels

Andrew C. Wilcox; Ellen E. Wohl

2007-01-01

257

All-digital impulse radio for MUI\\/ISI-resilient multiuser communications over frequency-selective multipath channels  

Microsoft Academic Search

Impulse radio (IR) is an ultra-wideband system with attractive features for baseband asynchronous multiple access (MA), multimedia services, and tactical wireless communications. Implemented with analog components, the continuous-time IRMA model utilizes pulse-position modulation (PPM) and random time-hopping codes to alleviate multipath effects and suppress multiuser interference (MUI). We introduce a novel continuous-time multiple input multiple output (MIMO) PPM-IRMA scheme, and

Christophe J. Le Martret; Georgios B. Giannakis

2000-01-01

258

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

SciTech Connect

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 ion transit time through the sheath to the RF period is {tau}{sub ion}/{tau}{sub RF} = 0.3). The position of the presheath/sheath edge is constant throughout the RF cycle and the time-averaged ion flux is conserved within the sheath region. The characteristic bimodal structure of the time-averaged ion distributions found in previous experiments is observed to arise from the time-dependent ion dynamics, in accord with existing theory. The large temporal variation of the IVDF has implications for the plasma chemistry and etching quality.

Jacobs, B.; Gekelman, W.; Pribyl, P. [University of California, Los Angeles, California 90095 (United States); Barnes, M. [MS Barnes Engineering, San Ramon, California 94583 (United States)

2011-05-15

259

Electric field and radio frequency measurements for rocket engine health monitoring applications  

NASA Astrophysics Data System (ADS)

Electric-field (EF) and radio-frequency (RF) emissions generated in the exhaust plumes of the diagnostic testbed facility thruster (DTFT) and the SSME are examined briefly for potential applications to plume diagnostics and engine health monitoring. Hypothetically, anomalous engine conditions could produce measurable changes in any characteristic EF and RF spectral signatures identifiable with a 'healthly' plumes. Tests to determine the presence of EF and RF emissions in the DTFT and SSME exhaust plumes were conducted. EF and RF emissions were detected using state-of-the-art sensors. Analysis of limited data sets show some apparent consistencies in spectral signatures. Significant emissions increases were detected during controlled tests using dopants injected into the DTFT.

Valenti, Elizabeth L.

1992-10-01

260

Optical measurements of paired luminous rings in capacitive radio-frequency hydrogen discharges.  

PubMed

Optical measurements of paired luminous rings separated by a narrow dark gap have been conducted in capacitive radio-frequency (rf) hydrogen discharges. The lines of molecular H(2) are strongly excited at the ring emission compared with a weaker emission of the H(alpha) line. The number of ring pairs increases with gas pressure, and the outermost ring pairs near the electrodes start to appear earlier than the inner ones. Each ring emission is turning on and off with the applied rf frequency, i.e., the left-side (right-side) ring of a paired ring is on when the left-side (right-side) electrode is biased positively. The axial light intensity profile, which is time resolved with the applied rf frequency, indicates that the emission profiles are similar to those of dc glow discharges, and the luminous rings correspond to the standing striations at the positive column. PMID:11970506

Sakawa, Y; Hori, M; Shoji, T; Sato, T

1999-11-01

261

Electric field and radio frequency measurements for rocket engine health monitoring applications  

NASA Technical Reports Server (NTRS)

Electric-field (EF) and radio-frequency (RF) emissions generated in the exhaust plumes of the diagnostic testbed facility thruster (DTFT) and the SSME are examined briefly for potential applications to plume diagnostics and engine health monitoring. Hypothetically, anomalous engine conditions could produce measurable changes in any characteristic EF and RF spectral signatures identifiable with a 'healthly' plumes. Tests to determine the presence of EF and RF emissions in the DTFT and SSME exhaust plumes were conducted. EF and RF emissions were detected using state-of-the-art sensors. Analysis of limited data sets show some apparent consistencies in spectral signatures. Significant emissions increases were detected during controlled tests using dopants injected into the DTFT.

Valenti, Elizabeth L.

1992-01-01

262

Method of measuring nitric oxide release by vascular endothelial cells grown in microfluidic channels  

NASA Astrophysics Data System (ADS)

In this paper, a simple and versatile method is presented which enables detection of nitric oxide (NO) released from vascular endothelial cells (ECs) cultured in microfluidic structures. The culturing system and NO measurement method allow cell shape to be controlled in a non-invasive manner using microfluidic structures while NO release is monitored for cell shape versus function studies. The culturing system consists of arrays of polydimethylsiloxane (PDMS) fluidic channels 120 micrometers in depth and ranging from 100 micrometers to 3 mm in width. The number of channels in each array is varied to yield a constant cell culture surface area (75 mm2) independent of channel width. The channel surfaces are collagen-coated and ECs are cultured to confluence within the channels. A cell scraper is then used to scrape extraneous cells cultured between channels, and NO measurements are made 18 to 24 hours later. A chemiluminescence-based sensor system (NOA 280i, Sievers NO Analyzer) is utilized to measure sample NO. Initial results indicate that NO concentrations can be measured from different microfluidic channel-containing samples using this method. It is shown that there is no significant difference in NO concentration derived from channels of different widths even though the degree of cell elongation varies due to physical constraint by microfluidic channel walls. However, cells treated with TNF? release more NO than untreated cells in fluidic channels, which is comparable to the function of ECs cultured in conventional culturing systems such as culturing dishes.

Hosseinpour, S.; Liu, A. C.; Barakat, A. I.; Choy, J. C.; Gray, B. L.

2014-03-01

263

Analysis of the tropopause parameters over the Iranian region using GPS radio occultation measurements  

NASA Astrophysics Data System (ADS)

Near-tropopause phenomena like upper level fronts and cyclones, penetrative cumulus convection and mesoscale mechanisms of exchange make important contributions to the mixing processes in the atmosphere. The dynamic atmospheric processes in the upper troposphere and the lower stratosphere are of significant interest due to their important role and impact on cirrus cloud formation and top of atmosphere radiative balance. Spatio-temporal monitoring of the tropopause height and its evolution over time provides important constraints on the atmospheric processes contributing to stratosphere-troposphere exchange. In this study, GPS radio occultation measurements are used to investigate the fluctuations of the tropopause heights and temperatures over the Iranian region. By applying the least-squares harmonic estimation (LS-HE) to the unevenly spaced time series of the tropopause parameters, annual and diurnal components are detected together with their higher harmonics. Multivariate LS-HE is shown to estimate the main periodic signals, particularly diurnal and semidiurnal cycles, more clearly than the univariate LS-HE. A bimodal pattern is observed in the frequency histograms of the tropopause parameters, in which the primary modes for the southern and northern parts of Iran correspond to subtropical and extra-tropical tropopause heights. 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 (above 36°) as an effect of subtropical high. Consistency of the mixing region from the radio occultation data and the total ozone measurements from the Total Ozone Mapping Spectrometer (TOMS) is also observed.

Masoumi, S.; Sharifi, M. A.; Sam-Khaniani, A.; Joghataei, M.; Schmidt, T.; Wickert, J.; McClusky, S.

2013-12-01

264

47 CFR 90.547 - Narrowband Interoperability channel capability requirement.  

Code of Federal Regulations, 2010 CFR

... Narrowband Interoperability channel capability requirement. 90.547 Section 90...SAFETY AND SPECIAL RADIO SERVICES PRIVATE LAND MOBILE RADIO SERVICES Regulations... Narrowband Interoperability channel capability requirement. (a) Except...

2009-10-01

265

47 CFR 90.547 - Narrowband Interoperability channel capability requirement.  

Code of Federal Regulations, 2010 CFR

... Narrowband Interoperability channel capability requirement. 90.547 Section 90...SAFETY AND SPECIAL RADIO SERVICES PRIVATE LAND MOBILE RADIO SERVICES Regulations... Narrowband Interoperability channel capability requirement. (a) Except...

2010-10-01

266

47 CFR 90.547 - Narrowband Interoperability channel capability requirement.  

Code of Federal Regulations, 2013 CFR

... Narrowband Interoperability channel capability requirement. 90.547 Section 90...SAFETY AND SPECIAL RADIO SERVICES PRIVATE LAND MOBILE RADIO SERVICES Regulations... Narrowband Interoperability channel capability requirement. (a) Except...

2013-10-01

267

Measuring true signal parameters in digital wireless systems in the presence of in-channel interference  

Microsoft Academic Search

A new digital signal processing method capable of measuring signals typical parameters, such as channel power, channel bandwidth, and carrier frequency, is presented hereinafter. In particular, thanks to some attractive features of the exploited MUSIC algorithm, the method allows the measurement of typical parameters of wideband signals even though they occupy, fully or partially, the same frequency range of other

L. Angrisani; Aniello Napolitano; R. S. LoMoriello

2008-01-01

268

Shallow water radio-magnetotelluric (RMT) measurements in urban environment: A case study from Stockholm city  

NASA Astrophysics Data System (ADS)

The Radio-MagnetoTelluric (RMT) method uses the electromagnetic signal from distant radio transmitters in the frequency range 15 to 250 kHz. RMT applications in near-surface studies have already been well established. Two components of electric field and three components of magnetic field are measured. These measured components are related to each other via transfer functions which contain detailed information about the variation of electrical resistivity of the subsurface. The present study is carried out in the frame of TRUST (TRansparent Underground STructure) project supported by several research and public organizations as well as industry. The study area is located close to central Stockholm in Sweden where the Swedish traffic authority has planned to construct a 21-km long motorway to bypass the city. In order to reduce the impact on natural and cultural environments, 18 km of the motorway will be located in tunnels. The main objective of this study is thus to identify potential fracture zones and faults as well as the general geological settings. The proposed path of the tunnel partly passes under the Lake Mälaren at a depth of about 60 m. Thus a challenge was posed on the applicability of RMT method in shallow water environments. Successful applications of RMT measurements using the Uppsala University's EnviroMT system on land encouraged us to modify the system to acquire data over lake water especially in urban areas. Pioneered by the Geological Survey of Sweden (SGU), RMT data were collected over the Lake Mälaren in spring 2012. The prototype acquisition system did not only turn out to be appropriate for such a challenging environment, but it was also much more efficient as compared with land surveys. Fifty two lines including 1160 stations with an average spacing of 15 m were covered in three days. Cultural noise associated with the city-related environment had to be identified and filtered out before inversion could be carried out. Reliable estimates of the impedance tensor were obtained by the parametric representation combined with a Truncated Singular Value Decomposition (TSVD) regularization of Bastani and Pedersen (2001). The processed data were then inverted to obtain 2D resistivity models. The resulting models along 23 lines correlate well and image variation of water depth, thickness of subaqueous sediments as well as the depth to crystalline bedrock. Low resistivity zones observed in the bedrock coincide well with the low velocity zones identified in refraction seismic surveys available along the RMT lines, indicating the presence of possible fracture zones in the bedrock. The experiment illustrates that the RMT methods can be well adapted to this type of environment; it is fast and cost-effective in shallow water especially in urban settings. Acknowledgments: Formas, SGU, BeFo, SBUF, Skanska, Boliden, FQM and NGI References: Bastani, M., 2001, EnviroMT - a new Controlled Source/Radio Magnetotelluric System: Ph.D. thesis, ISBN 91-554-5051-2, Uppsala University. Bastani, M. and Pedersen, L. B., 2001, Estimation of magnetotelluric transfer functions from radio transmitters. GEOPHYSICS, 66, 1038-1051.

Mehta, Suman; Bastani, Mehrdad; Malehmir, Alireza; Wang, Shunguo; Pedersen, Laust

2014-05-01

269

Rapid estimation of recharge potential in ephemeral-stream channels using electromagnetic methods, and measurements of channel and vegetation characteristics  

USGS Publications Warehouse

To classify recharge potential (RCP) in ephemeral-stream channels, a method was developed that incorporates information about channel geometry, vegetation characteristics, and bed-sediment apparent electrical conductivity (??a). Recharge potential is not independently measurable, but is instead formulated as a site-specific, qualitative parameter. We used data from 259 transects across two ephemeral-stream channels near Sierra Vista, Arizona, a location with a semiarid climate. Seven data types were collected: ??a averaged over two depth intervals (0-3 m, and 0-6 m), channel incision depth and width, diameter-at-breast-height of the largest tree, woody-plant and grass density. A two-tiered system was used to classify a transect's RCP. In the first tier, transects were categorized by estimates of near-surface-sediment hydraulic permeability as low, moderate, or high using measurements of 0-3 m-depth ??a. Each of these categories was subdivided into low, medium, or high RCP classes using the remaining six data types, thus yielding a total of nine RCP designations. Six sites in the study area were used to compare RCP and ??a with previously measured surrogates for hydraulic permeability. Borehole-averaged percent fines showed a moderate correlation with both shallow and deep ??a measurements, however, correlation of point measurements of saturated hydraulic conductivity, percent fines, and cylinder infiltrometer measurements with ??a and RCP was generally poor. The poor correlation was probably caused by the relatively large measurement volume and spatial averaging of ??a compared with the spatially-limited point measurements. Because of the comparatively large spatial extent of measurement transects and variety of data types collected, RCP estimates can give a more complete picture of the major factors affecting recharge at a site than is possible through point or borehole-averaged estimates of hydraulic permeability alone. ?? 2007 Elsevier B.V. All rights reserved.

Callegary, J. B.; Leenhouts, J. M.; Paretti, N. V.; Jones, C. A.

2007-01-01

270

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

271

Rapid Estimation of Recharge Potential in Ephemeral-Stream Channels Using Electromagnetic Methods, and Measurements of Channel and Vegetation Characteristics  

NASA Astrophysics Data System (ADS)

In order to classify recharge potential (RCP) in ephemeral-stream channels, a method was developed that incorporates information about channel geometry, vegetation characteristics, and bed-sediment apparent electrical conductivity ('a). About 400 transects along two ephemeral-stream channels near Sierra Vista, Arizona were studied. Seven data types were collected at each transect: 'a at two depth intervals, channel incision height and width, diameter-at-breast-height (DBH) of the largest tree, density of woody plants, and density of grasses. Apparent electrical conductivity was measured in the channel thalweg during the month of June, the hottest, driest month of the year. As was the case in 2005, June typically follows several months of relatively dry weather. Bed-sediment water content was expected to be at an annual minimum, maximizing the contrast between high and low clay content. Because 'a is proportional to clay content and clay is the primary factor affecting permeability during saturated flow in unconsolidated media, 'a values are inversely proportional to permeability. Apparent electrical conductivity was measured by using a low-induction-number frequency-domain electromagnetic-induction (LIN FEM) instrument at two intervals bracketing 0-3 m and 0-6 m depths. Vegetation characteristics were measured in 10 by 10 meter plots on each bank. As DBH, woody plant density and grass density increase, evapotranspiration also increases. Increases in any of these three factors, therefore, should decrease RCP. Incision height and width were measured in reference to the break in slope between the channel and floodplain or first major terrace. An increase in channel width provides greater area for infiltration, and greater incision height allows for increased flow depth. Increases in these two factors increase RCP. A two-tiered system was used to classify transect RCP. In the first tier, transects were categorized by the permeability of near-surface sediments based on measurements of 0-3 m depth 'a. Unique values of 'a were ranked, and the ranked values were divided into three categories representing low, moderate, or high permeability. Each of the permeability categories was further divided into three classes indicating low, medium, or high RCP by applying the same ranking approach to the remaining six data types. This made for a total of nine RCP designations. As expected, RCP was variable along the channels, but generally increased downstream. Local trends and variations in 'a downstream probably reflect changes in geology as the channel downcuts through sedimentary strata. Channel and vegetation did not show consistent spatial trends, but in some reaches appeared to vary with 'a. Six sites in the study area four in ephemeral-stream channels and two in detention basins were used to compare RCP with previously measured surrogates for permeability. Estimates of permeability based on a compared well except at the two detention basins where thin, low-permeability clogging layers may be present. LIN FEM instruments are not well suited for detecting layers that are thin relative to the size of the instrument. Estimates made by using this method gave a more comprehensive assessment of RCP at each site than was available through measurements of permeability alone.

Callegary, J. B.; Leenhouts, J. M.; Paretti, N. V.; Jones, C. A.

2006-12-01

272

Measurement of the top quark mass in the dilepton channel at CDF and D0  

SciTech Connect

We present recent analyses of the top quark mass measurement in dileptonic channel. The measurements use 200-360 pb{sup -1} of data collected by CDF and D0 experiments. The future prospects are discussed as well.

Maki, Tuula; /Helsinki U. /Helsinki Inst. of Phys.

2005-10-01

273

Selectivity and patch measurements of A-current channels in Helix aspersa neurones.  

PubMed Central

1. The ionic selectivity of A-current K+ channels has been measured in single Helix aspersa neurones by recording the reversal potential shift in test solutions containing various monovalent cations. 2. The A-current channel is permeable to Tl+, K+, Rb+, NH4+ and Cs+. The channels may also be sparingly permeable to Na+ and Li+. Organic cations have an apparent small permeability as judged from their reversal potentials, but this may be an artifact of K+ accumulation. 3. A large patch electrode (3 microns tip) isolated a region that appeared to contain only A-current channels. This may indicate that A-current channels are found in the membrane as rafts of at least 3 microns in diameter. 4. The single-channel conductance calculated from single-channel current steps was 14 pS.

Taylor, P S

1987-01-01

274

Revisiting the radio interferometer measurement equation. IV. A generalized tensor formalism  

NASA Astrophysics Data System (ADS)

Context. The radio interferometer measurement equation (RIME), especially in its 2 × 2 form, has provided a comprehensive matrix-based formalism for describing classical radio interferometry and polarimetry, as shown in the previous three papers of this series. However, recent practical and theoretical developments, such as phased array feeds (PAFs), aperture arrays (AAs) and wide-field polarimetry, are exposing limitations of the formalism. Aims: This paper aims to develop a more general formalism that can be used to both clearly define the limitations of the matrix RIME, and to describe observational scenarios that lie outside these limitations. Methods: Some assumptions underlying the matrix RIME are explicated and analysed in detail. To this purpose, an array correlation matrix (ACM) formalism is explored. This proves of limited use; it is shown that matrix algebra is simply not a sufficiently flexible tool for the job. To overcome these limitations, a more general formalism based on tensors and the Einstein notation is proposed and explored both theoretically, and with a view to practical implementations. Results: The tensor formalism elegantly yields generalized RIMEs describing beamforming, mutual coupling, and wide-field polarimetry in one equation. It is shown that under the explicated assumptions, tensor equations reduce to the 2 × 2 RIME. From a practical point of view, some methods for implementing tensor equations in an optimal way are proposed and analysed. Conclusions: The tensor RIME is a powerful means of describing observational scenarios not amenable to the matrix RIME. Even in cases where the latter remains applicable, the tensor formalism can be a valuable tool for understanding the limits of such applicability.

Smirnov, O. M.

2011-07-01

275

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

276

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

277

Conductive Sphere in a Radio Frequency Field: Theory and Applications to Positioners, Heating, and Noncontact Measurements  

NASA Technical Reports Server (NTRS)

An electrically conductive spherical sample located in an electromagnetic field excited by rf (radio frequency) current in a system of coaxial coils is treated theoretically. Maxwell's equations are solved exactly and all integrals in the formulas for the fields are evaluated analytically for the case where the sphere is on the axis and the coil system is modeled by a stack of filamentary circular loops. Formulas are also derived for electromagnetic force exerted on the sphere, excess impedance in the coil system due to the presence of the sphere, and power absorbed by the sphere. All integrals in those formulas have been evaluated analytically. Force measurements are presented and they are in excellent agreement with the new theory. A low-power electromagnetic levitator that is accurately described by the theory has been demonstrated and is discussed. Experimental measurements of excess impedance are presented and compared with theory, and those results are used to demonstrate an accurate noncontact method for determining electrical conductivity. Theoretical formulas for power absorption are evaluated numerically and their usefulness in both rf heating and in making noncontact measurements of a number of thermophysical properties of materials is discussed.

Jackson, H. W.; Watkins, J. L.; Chung, S.; Wagner, P.

1996-01-01

278

An Approach to Measuring the Direction of Arrival of Radio Waves in the Presence of Wave Interference.  

National Technical Information Service (NTIS)

When two radio waves are reflected from the ionosphere and arrive at an antenna via two different elevation angles, the measurement of the angle of arrival of the stronger wave is influenced by the weaker interfering wave. This phenomenon is examined in d...

S. E. Cooper

1968-01-01

279

A nonlinear optimal estimation inverse method for radio occultation measurements of temperature, humidity, and surface pressure  

Microsoft Academic Search

An optimal estimation inverse method is presented which can be used to retrieve simultaneously vertical profiles of temperature and specific humidity, in addition to surface pressure, from satellite-to-satellite radio occultation observations of the Earth's atmosphere. The method is a nonlinear, maximum a posteriori technique which can accommodate most aspects of the real radio occultation problem and is found to be

Paul I. Palmer; J. J. Barnett; J. R. Eyre; S. B. Healy

2000-01-01

280

Reply to Comment on ‘Encoding many channels on the same frequency through radio vorticity: first experimental test’  

NASA Astrophysics Data System (ADS)

Our recent paper (Tamburini et al 2012 New J. Phys. 14 033001), which presented results from outdoor experiments that demonstrate that it is physically feasible to simultaneously transmit different states of the newly recognized electromagnetic (EM) quantity orbital angular momentum (OAM) at radio frequencies into the far zone and to identify these states there, has led to a comment (Tamagnone et al 2012 New J. Phys. 14 118001). These authors discuss whether our investigations can be regarded as a particular implementation of the multiple-input-multiple-output (MIMO) technique. Clearly, our experimental confirmation of a theoretical prediction, first made almost a century ago (Abraham 1914 Phys. Z. XV 914-8), that the total EM angular momentum (a pseudovector of dimension length × mass × velocity) can propagate over huge distances, is essentially different from—and conceptually incompatible with—the fact that there exist engineering techniques that can enhance the spectral capacity of EM linear momentum (an ordinary vector of dimension mass × velocity). Our OAM experiments (Tamburini et al 2012 New J. Phys. 14 033001; Tamburini et al 2011 Appl. Phys. Lett. 99 204102-3) confirm the availability of a new physical layer for real-world radio communications based on EM rotational degrees of freedom. The next step is to develop new protocols and techniques for high spectral density on this new physical layer. This includes MIMO-like and other, more efficient, techniques.

Tamburini, F.; Thidé, B.; Mari, E.; Sponselli, A.; Bianchini, A.; Romanato, F.

2012-11-01

281

Measurement of Attenuation Length for Radio Wave in Natural Rock Salt Samples Concerning Ultra High Energy Neutrino Detection  

NASA Astrophysics Data System (ADS)

Ultra high energy (UHE) neutrinos with the energy larger than 1015 eV, surely arrive at the earth with Greisen, Zatsepin, Kuz'min (GZK) effect, though the rate is very few. The rare call requires us to utilize a large mass (>10 Gton) of detection medium. UHE neutrino generates a huge number of unpaired electrons in rock salt. They would emit sensible radio wave by coherent Cherenkov (Askar'yan) effect. The longer attenuation length of radio wave in rock salt reduces the number of antennas required. Several rock salt samples including synthesized one are measured in attenuation length for radio wave transmission at 0.3 and 1.0 GHz. Some show attenuation length larger than 300 m, which indicate a possibility for constructing a salt neutrino detector.

Chiba, Masami; Watanabe, Yusuke; Yasuda, Osamu; Kamijo, Toshio; Chikashige, Yuichi; Kon, Tadashi; Amano, Akio; Takeoka, Yosito; Shimizu, Yutaka; Mori, Satoshi; Ninomiya, Sosuke

282

Measurement of Attenuation Length in Rock Salt and Limestone in Radio Wave for Ultra-High Energy Neutrino Detector  

NASA Astrophysics Data System (ADS)

Rock salt and limestone are studied to determine their suitability for use as a radio wave transmission medium in an ultra high energy (UHE) cosmic neutrino detector. The detector would detect radio wave generated by the Askar'yan effect (coherent Cherenkov from negative excess charges in an electromagnetic shower) in the interaction of the UHE neutrinos with the high-density medium. We have measured the radio wave attenuation lengths of the rock salt samples from the Asse mine in Germany at 9.4 GHz and found it to be longer than 3.3 m and then whereas under the assumption of constant tan? with respect to frequency, we estimate it by extrapolation to be longer than 330 m at 94 MHz.

Chiba, Masami; Kawaki, Miho; Inuzuka, Masahide; Kamijo, Toshio; Athar, H.

2002-09-01

283

Modeling of the TOA-based distance measurement error using UWB indoor radio measurements  

Microsoft Academic Search

Time of arrival (TOA) estimation used with ultra wideband (UWB) transmission is currently the most popular technique for accurate indoor geolocation. Due to severe indoor multipath conditions, these techniques often suffer from significant inaccuracy in location estimation. In this paper, we introduce a model for the error in estimated distance as measured from the estimated TOA of the direct path

Bardia Alavi; Kaveh Pahlavan

2006-01-01

284

Adaptive channel allocation in TACS  

Microsoft Academic Search

The paper describes an adaptive channel allocation, ACA, algorithm designed for an analog cellular system like TACS. The incentive to use more advanced radio resource allocation algorithms can be to eliminate frequency planning, to increase the capacity and improve the quality of the system. Specific to TACS is that measurements only are available in the uplink. Based on these limited

M. Almgren; M. Frodigh; B. Hansson; J. Lundequist; K. Wallstedt

1995-01-01

285

Refractivity coefficients used in the assimilation of GPS radio occultation measurements  

NASA Astrophysics Data System (ADS)

The sensitivity of European Centre for Medium-Range Weather Forecasts (ECMWF) numerical weather prediction analyses to the empirical refractivity coefficients used to assimilate bending angles derived from GPS radio occultation measurements has been investigated. We have compared the Smith and Weintraub (1953) coefficients with the "best average" values proposed by Rüeger (2002). The Rüeger values produce simulated bending angles in the upper troposphere and stratosphere that are larger by ˜0.115%. This produces a cooling in the troposphere by around ˜-0.1 K, which improves the fit to radiosonde geopotential height measurements in the Northern Hemisphere but degrades the fit in the tropics and Southern Hemisphere. The cooling is caused primarily by Rüeger's increase in the "k1" refractivity coefficient, which accounts for the dry air contribution to the total refractivity. It is confirmed that this cooling can be reduced by introducing nonideal gas effects in the hydrostatic integration of the forward model. However, the Rüeger k1 coefficient should also be adjusted to k1 = 77.643 K hPa-1 if it is used in a forward model that includes nonideal gas effects when evaluating the refractivity from the model state. Furthermore, if the nonideal gas effects are introduced in a consistent way, we find that the Rüeger coefficients plus nonideal gas effects produce very similar results to the Smith and Weintraub values, where nonideal gas effects are neglected.

Healy, S. B.

2011-01-01

286

Variability in the near terminator Mars Ionosphere as observed from the MGS Radio Science Measurements  

NASA Astrophysics Data System (ADS)

Mars Global Surveyor (MGS) Radio Science (RS) experiment measured 5600 electron density profiles during seven occultation seasons during the period 24 Dec. 1998 to 09 June 2005 for near terminator conditions. These profiles exhibit significant variability in the peak height (hm) and peak density (Nm) on the same day, although the other controlling parameters like solar zenith angle (SZA), local time, and latitude remain nearly constant. Most of the variability has been seen to depend on the Martian longitude and has been linked to coupling with the lower atmosphere due to nonmigrating tidal forcing from below. In this paper we revisit this variability in the Martian ionosphere by examining the observed ionospheric parameters hm, Nm and other parameters like total electron content (TEC) and neutral scale height (H) derived from the observed profiles. We also make use of the solar EUV flux measured on the Solar Heleospheric Observatory (SOHO) during the lifetime of MGS-RS experiment. We find some of variability nearly disappears when data for lower solar zenith angles are analyzed.

Kumar, Ashok; Lodhi, Neelesh; Mahajan, Kushal; Arya, Bhuwan; Singh, Sachchidanand

2012-07-01

287

Channel  

NASA Technical Reports Server (NTRS)

[figure removed for brevity, see original site] Context image for PIA03693 Channel

This channel is located south of Iani Chaos.

Image information: VIS instrument. Latitude -10.9N, Longitude 345.5E. 17 meter/pixel resolution.

Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

2006-01-01

288

Seasonal Measurement of Oceanographic Parameters in the Kaulakahi Channel, Hawaii.  

National Technical Information Service (NTIS)

Contents: Meteorology; (Shipboard measurements, Barstur climatology), Hydrological measurements; (Surface currents, wave and swell, tides, Tsunamis), Hydrological measurements; (Sound velocity, temperature, mixed layer, salinity, deep currents), Sea-floor...

J. C. Belshe

1967-01-01

289

A comparative study of charge trapping effects in LDD surface-channel and buried-channel pMOS transistors using charge profiling and threshold voltage shift measurements  

Microsoft Academic Search

Extracted charge profiles of lightly-doped drain (LDD) surface-channel and buried-channel pMOS devices stressed under hot-carrier injection conditions reveal predominant electron trapping near the gate edge at the drain region in both cases. From threshold voltage measurements, there is some evidence of hole trapping after long stress times in surface-channel pMOSFETs, but not in buried-channel devices

C. K. Kok; W. C. Chew; W. K. Chim; D. S. H. Chan; S. E. Leang

1999-01-01

290

Ion Velocity Measurements Within the Acceleration Channel of a Low-Power Hall Thruster  

Microsoft Academic Search

This paper presents axial ion velocity measurements within the acceleration channel of the 200-W Busek Company Inc. BHT-200 laboratory Hall thruster derived from laser-induced fluorescence measurements of the 5d[4]7\\/2 - 6p[3]5\\/2 xenon-ion excited-state transition. Acceleration-channel-centerline ion velocities were measured for one nominal and six related cases. These six cases were chosen to be representative of small variations of the applied

William A. Hargus; Michael R. Nakles

2008-01-01

291

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

292

1\\/ f noise measurements in n-channel MOSFETs processed in 0.25 ?m technology  

Microsoft Academic Search

Low frequency noise has been studied from the weak to strong inversion regime in n-channel MOS transistors. The 1\\/f current noise power spectrum density SID is measured as a function of the drain current and gate voltage with the gate length as a parameter. Analysis of the noise characteristics shows that the channel noise agrees with the mobility fluctuation model

Y. Akue Allogo; M. de Murcia; J. C. Vildeuil; M. Valenza; P. Llinares; D. Cottin

2002-01-01

293

Measurements of turbulent flow in a channel at low Reynolds numbers  

Microsoft Academic Search

Normal and streamwise components of the velocity fields of turbulent flow in a channel at low Reynolds numbers have been measured with laser-Doppler techniques. The experiments duplicate the conditions used in current direct numerical simulations of channel flow, and good, but not exact, agreement is found for single-point moments through fourth order. In order to eliminate LDV velocity bias and

M. A. Niederschulte; R. J. Adrian; T. J. Hanratty

1990-01-01

294

PRACTICAL REMARKS ON MEASUREMENT AND SIMULATION METHODS TO EMULATE THE WIRELESS CHANNEL IN THE REVERBERATION CHAMBER  

Microsoft Academic Search

The purpose of this paper is to provide some further observations on the use of reverberation chambers to imitate real wireless channels. It is shown, that when RMS delay spread is calculated appropriate threshold has to be chosen. Based on the threshold value the required dynamics of measurements performed for realistic wireless channels can be estimated. It is also shown,

Adam J. Pomianek; Kamil Staniec; Zbigniew Joskiewicz

2010-01-01

295

Inconsistencies in Tropical Tropopause Temperatures Between Radiosonde and GPS Radio Occultation Measurements  

NASA Astrophysics Data System (ADS)

Accurate temperature measurements at the tropical tropopause are critical to diagnosing the relationship between water vapor saturation mixing ratio and stratospheric water vapor and, accordingly, the mechanisms for stratosphere-troposphere exchange. The radiosonde network has provided the most accurate temperature record in the tropics to date, but a self-consistent temperature mapping of the tropical tropopause layer (TTL) with radiosonde data is impaired by (i) very limited spatial sampling, especially over the predominantly marine tropics, (ii) differences in radiosonde instrument packages, and (iii) solar radiation effects on reported temperatures. Global positioning system (GPS) radio occultation measurements offer a powerful approach to examining the temperature structure of the TTL that provides homogeneous spatial coverage of the tropics while still maintaining high vertical resolution. We use a GPS occultation data set obtained from the CHAMP satellite for 2001-2003 with retrievals performed at the Jet Propulsion Laboratory (JPL) and subjected to objective quality control. These occultations are compared with radiosonde measurements from the WMO global network that have been processed through the complex quality control of NCEP. GPS occultations and radiosondes show significant differences in (i) the mean cold-point tropopause temperature, (ii) the distribution of cold-point temperatures, and (iii) the height of the cold-point tropopause. We investigate differences between radiosonde and occultation climatologies of the TTL, paying special attention to the merits and deficiencies of each measurement approach. We also compare the GPS occultation retrievals of JPL to other retrieval algorithms to investigate potential biases. The temperature differences between GPS occultations and radiosondes at the cold-point tropopause could have profound implications for the water vapor budget of the stratosphere.

Spackman, J. R.; Leroy, S. S.; Moyer, E. J.; Ao, C. O.; Weinstock, E. M.; Anderson, J. G.

2004-12-01

296

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

297

Conservative Cell Load Approximation for Radio Networks with Shannon Channels and its Application to LTE Network Planning  

Microsoft Academic Search

The aim of this work is wireless network design and optimization. The well-known Shannon-Hartley formula describes the achievable bitrate of a noisy transmit channel. The downlink air-interface of UTRAN Long Term Evolution (LTE) seems to closely follow such a law, when it is modified with appropriate bandwidth and signal to noise ratio (SNR) efficiency factors. Motivated by this observation, we

Kurt Majewski; Michael Koonert

2010-01-01

298

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

299

Quantitative Measurement of Vocal Fold Vibration in Male Radio Performers and Healthy Controls Using High-Speed Videoendoscopy  

PubMed Central

Purpose Acoustic and perceptual studies show a number of differences between the voices of radio performers and controls. Despite this, the vocal fold kinematics underlying these differences are largely unknown. Using high-speed videoendoscopy, this study sought to determine whether the vocal vibration features of radio performers differed from those of non-performing controls. Method Using high-speed videoendoscopy, recordings of a mid-phonatory/i/ in 16 male radio performers (aged 25–52 years) and 16 age-matched controls (aged 25–52 years) were collected. Videos were extracted and analysed semi-automatically using High-Speed Video Program, obtaining measures of fundamental frequency (f0), open quotient and speed quotient. Post-hoc analyses of sound pressure level (SPL) were also performed (n?=?19). Pearson's correlations were calculated between SPL and both speed and open quotients. Results Male radio performers had a significantly higher speed quotient than their matched controls (t?=?3.308, p?=?0.005). No significant differences were found for f0 or open quotient. No significant correlation was found between either open or speed quotient with SPL. Discussion A higher speed quotient in male radio performers suggests that their vocal fold vibration was characterised by a higher ratio of glottal opening to closing times than controls. This result may explain findings of better voice quality, higher equivalent sound level and greater spectral tilt seen in previous research. Open quotient was not significantly different between groups, indicating that the durations of complete vocal fold closure were not different between the radio performers and controls. Further validation of these results is required to determine the aetiology of the higher speed quotient result and its implications for voice training and clinical management in performers.

Warhurst, Samantha; McCabe, Patricia; Heard, Rob; Yiu, Edwin; Wang, Gaowu; Madill, Catherine

2014-01-01

300

Observation of temporal variations in global sporadic E occurrence rates derived from GPS radio occultation measurements  

NASA Astrophysics Data System (ADS)

The GPS radio occultation (RO) technique has been established as a powerful tool for ionospheric research. With approximately one million of globally distributed profiles per year provided by the FORMOSAT-3/COSMIC satellites, our data base allows for sporadic E (Es) layer observation with a high spatial resolution and global coverage. Sporadic E layers are thin regions of enhanced electron density in the lower ionospheric E region. They cause strong amplitude scintillations in GPS occultation signals. We use Signal-to-Noise Ratio (SNR) profiles of the GPS L1 signal in order to obtain information on the sporadic E occurrence. Sudden changes in the vertical electron density gradients, which indicate the presence of a sporadic E layer, appear as strong fluctuations in the SNR above 85 km altitude. The FORMOSAT-3/COSMIC data, together with measurements collected by the satellites CHAMP and GRACE which provided continuously RO data since 2001 and 2006, respectively, enables initial trend analysis of Es occurrence. In this study we focus on the variations of sporadic E occurrence rates on different time scales. We will present the diurnal, annual and interannual variability of sporadic E layers and show their connection to other geophysical parameters like solar tides.

Arras, Christina; Wickert, Jens; Jacobi, Christoph; Heise, Stefan

2014-05-01

301

Measurement of a large deployable antenna for radio astronomy in space  

Microsoft Academic Search

A large radio astronomy antenna on Halca satellite was deployed in 1997 in space. The main reflector with the maximum diameter of 10 m is composed in a novel deployment scheme of tension truss as shown. The operating frequencies are 1.66 GHz (L-band), 4.85 GHz (C-band) and 22.15 GHz (Ka-band), all protected for radio astronomy use. If a mast is

T. Takano; S. Kuroda; H. Kobayashi; N. Kawaguch; E. Hanayama

2001-01-01

302

Remote, PCM-controlled, multi-channel radio frequency FM telemetry system for cryogenic wind tunnel application  

NASA Technical Reports Server (NTRS)

A telemetry system used in the NASA-Langley cryogenic transonic wind tunnel to obtain rotational strain and temperature data is described. The system consists of four FM transmitters allowing for a remotely controlled PCM combination. A rotating four-contact mercury slip-ring is used as an interface between the fixed and rotating mechnical structures. Over 60 channels of data on the main fan disk and blade structures have been obtained. These data are studied to verify computer predictions and mechanical life. A series of block diagrams are included.

Diamond, John K.

1989-01-01

303

Ion Implantation and Backscattering and Channeling Effect Measurements for Analysis of Semiconductor Structures.  

National Technical Information Service (NTIS)

There were two broad phases of investigation: ion implantation phenomena and evaluation of semiconductor structures by use of nuclear techniques. Both Hall and Channeling effect measurements were used to evaluate implanted layers. Evaluation of different ...

I. V. Mitchell J. Gyulai J. W. Mayer M. A. Nicolet N. G. E. Johansson

1971-01-01

304

Implementation of Elliptic Curve Cryptography with Built-In Counter Measures against Side Channel Attacks  

Microsoft Academic Search

Many software implementations of public key cryptosystems have been concerned with efficiency. The advent of side channel\\u000a attacks, such as timing and power analysis attacks, force us to reconsider the strategy of implementation of group arithmetic.\\u000a This paper presents a study of software counter measures against side channel attacks for elliptic curve cryptosystems.\\u000a \\u000a We introduce two new counter measures. The

Elena Trichina; Antonio Bellezza

2002-01-01

305

Digital Broadcasting Television Channel Measurements and Characterization for SIMO Mobile Reception  

Microsoft Academic Search

This paper presents propagation measurement results in the UHF Digital Television (DTV) band using an ATSC DTV signal as a channel sounding signal to investigate the characteristics of a wideband single-input multiple-output (SIMO) under mobile reception conditions. A series of DTV dual channel signal measurements were conducted in the Ottawa region to characterize the transmission of ATSC 8-VSB signals under

Assia Semmar; Jean-Yves Chouinard; Viet Ha Pham; Xianbin Wang; Yiyan Wu; Sébastien Laflèche

2006-01-01

306

Two-channel self-mixing laser Doppler measurement with carrier-frequency-division multiplexing  

Microsoft Academic Search

We demonstrate real-time two-channel self-mixing laser-Doppler measurement with extreme optical sensitivity using a laser-diode-pumped thin-slice LiNdP4O12 laser. Successful carrier-frequency-division-multiplexed two-channel operations are realized by using one laser, two sets of optical frequency shifters, and a two-channel frequency-modulated-wave demodulation circuit. Simultaneous independent measurements of vibrations of speakers and averaged motions of small Brownian particles in different scattering cells are demonstrated. Self-mixing

Kenju Otsuka; Kazutaka Abe; Natsumi Sano; Seiichi Sudo; Jing-Yuan Ko

2005-01-01

307

Relationship of Rain Top to the Tropopause from TRMM and COSMIC GPS radio occultation measurements  

NASA Astrophysics Data System (ADS)

Deep and penetrating convection are identified as convective clouds with rain tops above 14 km and the lapse rate tropopause height, using Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) data from June 2006 to December 2012. The tropopause derived from high vertical resolution Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) radio occultation data is utilized to examine the rain top and tropopause relationships. It is found that 0.2% of convections reach 14 km and 0.05% of them penetrate the tropopause. Deep and penetrating convection are more frequent over land than over ocean, especially over Central Africa, the Amazon, and the large islands in the West Pacific. Results also show that most of the deep and penetrating convection are detected with 2-km equivalent radii. The vertical distributions show that penetrating convection are mostly up to 4.5 km above the tropopause, while most of deep convections have rain tops at 15 km. The regional statistics illustrate that the penetrating convection is larger and higher in the Asian monsoon region and may therefore play a more important role in stratosphere-tropopause exchange. These results are important for understanding the interaction between the clouds and the thermal structure of the upper tropospheric and lower stratospheric region. Joint histogram of vertical and horizontal extents of penetrating convections over land (top panels), ocean (middle panels) and continental-oceanic boundary (bottom panels) for global and the four selected regions and seasons as labeled. The units of the extents of penetrating convections are km, while the units of contours are %. Comparison of thermal tropopause height between COSMIC RO and radiosonde measurements for the tropics (20S-20N) and midlatitudes (20N-38N and 20S-38S) during June 2006 and December 2012

Xian, T.; Fu, Y.; Li, R.; Liu, G.

2013-12-01

308

Assimilation of global positioning system radio occultation measurements into numerical weather forecast systems  

NASA Astrophysics Data System (ADS)

2004 marks the centennial of Bjerknes' conceptual solution to the problem of weather forecasting, based on the application of physical and mechanical laws to a set of initial conditions. Today many satellites observe our atmosphere to help provide these initial conditions to numerical weather forecast systems. However, there is still considerable room for improvement when it comes to weather forecasts, namely by better constraining the atmospheric initial conditions through more frequent and more accurate atmospheric observations. The radio occultation (RO) technique which observes the atmosphere from the side (instead of from above, like today's numerous weather satellites) was used for decades to study planetary atmospheres before it was finally used observe our atmosphere. The level of accuracy required in order to make RO competitive with or superior to other techniques already observing the atmosphere was achieved with the advent of the Global Positioning System (CPS) and later with advanced CPS receiver technology. We demonstrate here that useful one-dimensional (1D) vertical atmospheric temperature information can be retrieved from GPS RO refractive index measurements. We develop a first-generation system capable of retrieving that information from real CPS RO refractive index measurements, and assimilating it into a numerical weather forecast system. Resulting five day weather forecasts issued with that system show improved accuracy in the Northern hemisphere and degraded accuracy in the Southern hemisphere. Analyzing data from late CPS RO missions onboard CHAMP and SAC-C satellites, we find that improved receiver technology and processing techniques yield more CPS RO data and of better quality. We develop a two-dimensional (2D) ray-tracing iterative procedure to simulate CPS RO measurements from the three-dimensional (3D) atmospheric representation provided by a numerical weather forecast system. We demonstrate that the 2D ray-tracing results agree better with the CHAMP and SAC-C measurements than the 1D approach used in our first-generation system. In order to render the use of this type of modelling possible under the stringent time constraints of operational numerical weather prediction centers, we propose a new operator called the Fast Atmospheric Refractivity Gradient Operator (FARGO). FARGO is shown to be 250 times faster and nearly as efficient as 2D ray-tracing in fitting real observations. The work presented here will serve to implement a second-generation assimilation system of CPS RO data into numerical weather forecast systems. Also, the approach used in FARGO can be extended to simulate other refraction measurements which suffer from horizontal inhomogeneities in the Earth's lower troposphere.

Poli, Paul

309

Measurement of the t-channel single top quark production cross section  

SciTech Connect

The D0 collaboration reports direct evidence for electroweak production of single top quarks through the t-channel exchange of a virtual W boson. This is the first analysis to isolate an individual single top quark production channel. We select events containing an isolated electron or muon, missing transverse energy, and two, three or four jets from 2.3 fb{sup -1} of p{bar p} collisions at the Fermilab Tevatron Collider. One or two of the jets are identified as containing a b hadron. We combine three multivariate techniques optimized for the t-channel process to measure the t- and s-channel cross sections simultaneously. We measure cross sections of 3.14{sub -0.80}{sup +0.94} pb for the t-channel and 1.05 {+-} 0.81 pb for the s-channel. The measured t-channel result is found to have a significance of 4.8 standard deviations and is consistent with the standard model prediction.

Abazov, Victor Mukhamedovich; /Dubna, JINR; Abbott, Braden Keim; /Oklahoma U.; Abolins, Maris A.; /Michigan State U.; Acharya, Bannanje Sripath; /Tata Inst.; Adams, Mark Raymond; /Illinois U., Chicago; Adams, Todd; /Florida State U.; Aguilo, Ernest; /Alberta U. /Simon Fraser U. /York U., Canada /McGill U.; Ahsan, Mahsana; /Kansas State U.; Alexeev, Guennadi D.; /Dubna, JINR; Alkhazov, Georgiy D.; /St. Petersburg, INP; Alton, Andrew K.; /Michigan U. /Augustana Coll., Sioux Falls /Northeastern U.

2009-07-01

310

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

311

Radio-frequency measurements of coherent transition and Cherenkov radiation: Implications for high-energy neutrino detection  

Microsoft Academic Search

We report on measurements of (11-18)-cm wavelength radio emission from interactions of 15.2 MeV pulsed electron bunches at the Argonne Wakefield Accelerator. The electrons were observed both in a configuration where they produced primarily transition radiation from an aluminum foil, and in a configuration designed for the electrons to produce Cherenkov radiation in a silica sand target. Our aim was

Peter W. Gorham; David P. Saltzberg; Paul Schoessow; Wei Gai; John G. Power; Richard Konecny; M. E. Conde

2000-01-01

312

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

Microsoft Academic Search

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

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

2007-01-01

313

On-line Measurements and Control of Viable Cell Density in Cell Culture Manufacturing Processes using Radio-frequency Impedance  

Microsoft Academic Search

In this work, radio-frequency (RF) impedance is reviewed as a method for monitoring and controlling cell culture manufacturing\\u000a processes. It is clear from the many publications cited that RF Impedance is regarded as an accurate and reliable method for\\u000a measuring the live cell bio-volume both on-line and off-line and the technology is also sutable for animal cells in suspension,\\u000a attached

John P. Carvell; Jason E. Dowd

2006-01-01

314

Measurements and simulations of a channel flow powered by plasma actuators  

NASA Astrophysics Data System (ADS)

Experimental measurements and numerical simulations of a dielectric barrier discharge driven flow inside a finite length channel have been performed. Plasma actuators have been used to impart momentum to the flow in the near wall region, which diffuses throughout the height of the channel as it convects downstream. This momentum addition is found to be of sufficient magnitude to create an unsteady channel flow with exit velocities on the order of 1-3 m/s. Pressure and velocity measurements have been taken in order to quantify the effects of varying the number of symmetrically placed pairs of plasma actuators in the channel and the operating voltage applied to the actuators, showing a monotonic increase with respect to both parameters. Power law relationships have been determined for these measurements with respect to the operating voltage, with exponents of 2.0 for the exit velocity and of 5.6 for the maximum pressure differential. The pressure measurements also suggest that the pressure increase due to each actuator is independent of the bulk flow inside the channel. Numerical predictions also agree with the measured pressure and velocity distributions across the channel. The bulk velocity and pressure measurements allow for efficiency calculations of the plasma channel, which are shown to also fit into a power law relationship with respect to the operating voltage. The data collected show that the efficiency of these devices is low, less than 0.1%, but that it increases with a power law exponent of 4.09 to 4.35 indicating the possibility of using such channel for pumping small flows.

Riherd, Mark; Roy, Subrata

2012-09-01

315

Reconstructing energy and Xmax of cosmic ray air showers using the radio lateral distribution measured with LOPES  

NASA Astrophysics Data System (ADS)

The LOPES experiment, a digital radio interferometer located at KIT (Karlsruhe Institute of Technology), obtained remarkable results for the detection of radio emission from extensive air showers at MHz frequencies. Features of the radio lateral distribution function (LDF) measured by LOPES are explored in this work for a precise reconstruction of two fundamental air shower parameters: the primary energy and the shower Xmax. The method presented here has been developed on (REAS3-)simulations, and is applied to LOPES measurements. Despite the high human-made noise at the LOPES site, it is possible to reconstruct both the energy and Xmax for individual events. On the one hand, the energy resolution is promising and comparable to the one of the co-located KASCADE-Grande experiment. On the other hand, Xmax values are reconstructed with the LOPES measurements with a resolution of 90 g/cm2. A precision on Xmax better than 30 g/cm2 is predicted and achievable in a region with a lower human-made noise level.

Palmieri, N.; 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.; Huber, D.; 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.; 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

316

78 FR 27306 - Radio Broadcasting Services; Dermott, Arkansas, and Cleveland, Mississippi  

Federal Register 2010, 2011, 2012, 2013

...MB Docket No. 12-53; RM-11658] Radio Broadcasting Services; Dermott, Arkansas...Audio Division, at the request of Delta Radio Network, LLC, substitutes FM Channel...List of Subjects in 47 CFR part 73 Radio, Radio broadcasting. Federal...

2013-05-10

317

Measurements of peroxy radicals using dual-channel chemical amplification-cavity ringdown spectroscopy  

NASA Astrophysics Data System (ADS)

Peroxy radicals (hydroperoxy HO2 and organic peroxy RO2) play important roles in the photochemistry of troposphere. They are involved in the production and removal of ozone in the photochemical cycles and are closely related to atmospheric hydroxyl (OH) radical budget. In this work, a dual-channel peroxy radical chemical amplification (PERCA) instrument using diode laser cavity ring down spectroscopy (CRDS) is developed for measurements of the peroxy radicals. The ambient air is sampled into an amplification channel and a reference channel. In the amplification channel, HO2 and RO2 are first converted to NO2 via reactions with an excess amount of NO, and the OH and RO coproducts are recycled back to HO2 in subsequent reactions with an excess amount of CO and O2; the chain reactions of HO2 are repeated and amplify the level of NO2. The reference channel is for the background NO2 and O3. The NO2 concentrations from both channels are monitored simultaneously by two CRDS systems. The concentration of the amplified NO2 from HO2 and RO2 is determined as the difference between the amplification and the reference channel. The optimized amplification factor of the dual-channel PERCA-CRDS system is 180, calibrated using laboratory generated HO2 and CH3O2 radical sources. The detection sensitivity is shown to be ~4 ppt/10s (3?). The results from ambient studies and environmental chamber studies will be discussed.

Zhang, J.; Liu, Y.

2012-12-01

318

Laser measurement of H{sup -} ions in a field-effect-transistor based radio frequency ion source  

SciTech Connect

Hydrogen negative ion density measurements are required to clarify the characteristics of negative ion production and ion source performance. Both of laser photodetachment and cavity ring down (CRD) measurements have been implemented to a field-effect-transistor based radio-frequency ion source. The density ratio of negative hydrogen ions to electrons was successfully measured by laser photodetachment and effect of magnetic filter field on negative ion density was confirmed. The calculated CRD signal showed that CRD mirrors with >99.990% reflectivity are required and loss of reflectivity due to cesium contamination should be minimized.

Tanaka, N.; Matsuno, T.; Funaoi, T.; Ando, A. [Tohoku University, Aramaki 6-6-05, Aoba, Sendai, Miyagi 980-8579 (Japan); Tauchi, Y. [Yamaguchi University, Tokiwadai 2-16-1, Ube, Yamaguchi 755-8611 (Japan); Nakano, H.; Tsumori, K.; Takeiri, Y. [National Institute for Fusion Science, Oroshi-Cho 322-6, Toki, Gifu 509-5292 (Japan)

2012-02-15

319

Optical serial coherent analyzer of radio-frequency (OSCAR).  

PubMed

Optical serial coherent analyzer of radio-frequency is a novel scheme that enables fast-scanning microwave signal measurements in a large bandwidth. The measurements are performed based on serial channelization realized by using a fast scanning laser source as the local oscillator to down-convert the to-be-measured radio-frequency (RF) signals. Optical coherent detection effectively removes interferences induced by RF's self-beating and guarantees the accuracy of measurements. In the experimental demonstration, instantaneous multi-frequency measurements and vector information acquisition of RF signals can be achieved by this scheme within 2.8 ?s over 14 GHz bandwidth. PMID:24921552

Li, Ruiyue; Chen, Hongwei; Lei, Cheng; Yu, Ying; Chen, Minghua; Yang, Sigang; Xie, Shizhong

2014-06-01

320

78 FR 48626 - Private Land Mobile Radio Rules  

Federal Register 2010, 2011, 2012, 2013

...without qualification--frequencies that cover not only B/ ILT channels, but also Specialized Mobile Radio (SMR) channels, Enhanced SMR channels, and certain Public Safety Pool channels that are not part of the NPSPAC plan. MSI therefore...

2013-08-09

321

Measurement of the Top Quark Mass Simultaneously in Dilepton and Lepton + Jets Decay Channels  

SciTech Connect

The authors present the first measurement of the top quark mass using simultaneously data from two decay channels. They use a data sample of {radical}s = 1.96 TeV collisions with integrated luminosity of 1.9 fb{sup -1} collected by the CDF II detector. They select dilepton and lepton + jets channel decays of t{bar t} pairs and reconstruct two observables in each topology. They use non-parametric techniques to derive probability density functions from simulated signal and background samples. The observables are the reconstructed top quark mass and the scalar sum of transverse energy of the event in the dilepton topology and the reconstructed top quark mass and the invariant mass of jets from the W boson decay in lepton + jets channel. They perform a simultaneous fit for the top quark mass and the jet energy scale which is constrained in situ by the hadronic W boson resonance from the lepton + jets channel. Using 144 dilepton candidate events and 332 lepton + jets candidate events they measure: M{sub top} = 171.9 {+-} 1.7 (stat. + JES) {+-} 1.1 (other sys.) GeV/c{sup 2} = 171.9 {+-} 2.0 GeV/c{sup 2}. The measurement features a robust treatment of the systematic uncertainties, correlated between the two channels and develops techniques for a future top quark mass measurement simultaneously in all decay channels. Measurements of the W boson mass and the top quark mass provide a constraint on the mass of the yet unobserved Higgs boson. The Higgs boson mass implied by measurement presented here is higher than Higgs boson mass implied by previously published, most precise CDF measurements of the top quark mass in lepton + jets and dilepton channels separately.

Fedorko, Wojciech T.; /Chicago U.

2008-09-01

322

BEA Symposium: Research in Radio.  

ERIC Educational Resources Information Center

The seven articles in this journal issue examine trends and topics related to radio and other broadcast media. The articles discuss the following: (1) current trends in radio audience measurement, (2) the policy implications of radio research, (3) a research study of the relationships between age and radio usage, (4) the role of the part-time…

Finney, Robert G., Ed.; Neckowitz, Alan, Ed.

1980-01-01

323

Nasal potential difference measurements to assess CFTR ion channel activity.  

PubMed

The Nasal potential difference measurement is used to measure the voltage across the nasal epithelium, which results from transepithelial ion transport and reflects in part CFTR function. The electrophysiologic abnormality in cystic fibrosis was first described 30 years ago and correlates with features of the CF phenotype. NPD measurement is an important in vivo research and diagnostic tool, and is used to assess the efficacy of new treatments such as gene therapy and ion transport modulators. This chapter will elaborate on the electrophysiological principles behind the test, the equipment required, the methods, and the analysis of the data. PMID:21594779

Rowe, Steven M; Clancy, John Paul; Wilschanski, Michael

2011-01-01

324

Atmospheric peroxy radical measurements using dual-channel chemical amplification cavity ringdown spectroscopy.  

PubMed

Peroxy (HO2 and RO2) radicals are important intermediates in tropospheric oxidation of hydrocarbons, and their accurate atmospheric measurements remain challenging. In this work, the peroxy radical chemical amplification (PERCA) method was combined with cavity ringdown spectroscopy (CRDS) to develop a dual-channel instrument for measurements of atmospheric peroxy radicals. In the amplification channel, the peroxy radicals were converted in an excess amount of NO and CO into a higher level of NO2 and measured along with the background NO2, while in the reference channel, only the background NO2 (ambient NO2 and NO2 converted from O3 reaction with NO) was monitored. The NO2 levels from both channels were measured simultaneously at a high time resolution (?1 s) using two identical CRDS systems with one 408.5-nm diode laser, and their difference gave the amplified NO2 from PERCA. The peroxy radical concentration was obtained from the amplified NO2 and the calibrated amplification factor or chain length (CL). The optimized CL was 190 ± 20 (1?) using laboratory-generated HO2 and CH3O2 radical sources. The detection sensitivity was 4 ppt/10 s (3?). Ambient measurements in Riverside, CA were carried out. This dual-channel diode-laser PERCA-CRDS instrument was compact and capable of providing real-time, in situ, and sensitive measurements of atmospheric peroxy radicals with fast time response. PMID:24798952

Liu, Yingdi; Zhang, Jingsong

2014-06-01

325

Electron mobility measurement in short-channel FET's using the cutoff frequency method  

Microsoft Academic Search

The cutoff frequency (FT) method is presented to measure electron mobility in short-channel field-effect transistors (FETs). This technique was used to study the electron mobilities in AlGaAs-GaAs self-aligned heterostructure insulated-gate field-effect transistors (HIGFETs), with both undoped and doped channels (E and D mode). The structures were molecular-beam-epitaxy (MBE) grown on ?100?-oriented semi-insulating GaAs substrates. All layers were undoped during the

C. C. Sun; J. M. Xu; A. Hagley; R. Surridge; A. S. Thorpe

1990-01-01

326

Decision-feedback equalization of pulse-position modulation on measured nondirected indoor infrared channels  

Microsoft Academic Search

We examine the performance of two decision-feedback equalizers (DFEs) for pulse-position modulation (PPM) on measured nondirected indoor infrared channels with intersymbol interference. PPM offers high average-power efficiency, but on ISI channels, unequalized PPM suffers severe performance penalties. We have previously examined the performance of the maximum-likelihood sequence detector (MLSD), and found that it yields significant improvements. However, the MLSD often

Malik D. Audeh; Joseph M. Kahn; John R. Barry

1999-01-01

327

Measurement and correlation of critical heat flux in two-phase micro-channel heat sinks  

Microsoft Academic Search

Critical heat flux (CHF) was measured for a water-cooled micro-channel heat sink containing 21 parallel 215×821 ?m channels. Tests were performed with deionized water over a mass velocity range of 86–368 kg\\/m2s, inlet temperatures of 30 and 60 °C, at an outlet pressure of 1.13 bar. As CHF was approached, flow instabilities induced vapor backflow into the heat sink’s upstream

Weilin Qu; Issam Mudawar

2004-01-01

328

Tropical tropopause parameters derived from GPS radio occultation measurements with CHAMP  

Microsoft Academic Search

The temperature structure in the tropical upper troposphere and lower stratosphere (UTLS) region is discussed based on Global Positioning System (GPS) radio occultation (RO) data from the German CHAMP (CHAllenging Minisatellite Payload) satellite mission. Several climatologies for tropopause parameters based on radiosonde data and model analyses have been published in recent years. Both data sources suffer either from low global

T. Schmidt; J. Wickert; G. Beyerle; C. Reigber

2004-01-01

329

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

330

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

331

Proton beam verification using RF power measurement data for a CW radio frequency quadrupole linac  

Microsoft Academic Search

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

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

1999-01-01

332

Radio frequency controlled synthetic wavelength sweep for absolute distance measurement by optical interferometry  

Microsoft Academic Search

We present a new technique applied to the variable optical synthetic wavelength generation in optical interferometry. It consists of a chain of optical injection locking among three lasers: first a distributed-feedback laser is used as a master to injection lock an intensity-modulated laser that is directly modulated around 15 GHz by a radio frequency generator on a sideband. A second

Sébastien Le Floch; Yves Salvadé; Rostand Mitouassiwou; Patrick Favre

2008-01-01

333

Two Approaches to the Identification and Measurement of Public Radio Audiences; Locating Unique Subgroups  

ERIC Educational Resources Information Center

Assesses the validity of two test samples possibly useful to the public radio station manager for determining program preferences. Results suggest that economic, valid sampling techniques can be developed, which should focus on more accessible and economic techniques than random sampling. (JEG)

Williams, Wenmouth, Jr.

1977-01-01

334

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

335

Channel Selection Based on Phase Measurement in P300-Based Brain-Computer Interface  

PubMed Central

Most EEG-based brain-computer interface (BCI) paradigms include specific electrode positions. As the structures and activities of the brain vary with each individual, contributing channels should be chosen based on original records of BCIs. Phase measurement is an important approach in EEG analyses, but seldom used for channel selections. In this paper, the phase locking and concentrating value-based recursive feature elimination approach (PLCV-RFE) is proposed to produce robust-EEG channel selections in a P300 speller. The PLCV-RFE, deriving from the phase resetting mechanism, measures the phase relation between EEGs and ranks channels by the recursive strategy. Data recorded from 32 electrodes on 9 subjects are used to evaluate the proposed method. The results show that the PLCV-RFE substantially reduces channel sets and improves recognition accuracies significantly. Moreover, compared with other state-of-the-art feature selection methods (SSNRSF and SVM-RFE), the PLCV-RFE achieves better performance. Thus the phase measurement is available in the channel selection of BCI and it may be an evidence to indirectly support that phase resetting is at least one reason for ERP generations.

Xu, Minpeng; Qi, Hongzhi; Ma, Lan; Sun, Changcheng; Zhang, Lixin; Wan, Baikun; Yin, Tao; Ming, Dong

2013-01-01

336

A flexible research platform for multi-channel auditory steady-state response measurements.  

PubMed

The possibilities of currently commercially available auditory steady-state response (ASSR) devices are mostly limited to avoid unintentional misuse and to guarantuee patient safety as such. Some setups, e.g. do not allow the application of high intensities or the use of own stimuli. Moreover, most devices generally only allow data collection using maximal two EEG channels. The freedom to modify and extend the accompagnying software and hardware is very restricted or inexistent. As a result, these devices are not suited for research and several clinically diagnostic purposes. In this paper, a research platform for multi-channel ASSR measurements is presented, referred to as SOMA (setup ORL for multi-channel ASSR). The setup allows multi-channel measurements and the use of own stimuli. It can be easily extended to facilitate new measurement protocols and real-time signal processing. The mobile setup is based on an inexpensive multi-channel RME soundcard and software is written in C++. Both hardware and software of the setup are described. An evaluation study with nine normal-hearing subjects shows no significant performance differences between a reference and the proposed platform. SOMA presents a flexible and modularly extensible mobile high-end multi-channel ASSR test platform. PMID:18215424

Van Dun, Bram; Verstraeten, Stijn; Alaerts, Jane; Luts, Heleen; Moonen, Marc; Wouters, Jan

2008-03-30

337

Fluorescence sensors for parallel measurements in multichannel microfluidic devices covering the full channel cross sections  

NASA Astrophysics Data System (ADS)

Sensitive fluorescence sensors are needed to measure single cell properties in microfluidic devices. Optimizing the parallelizability and the measurement volume are two options enabling high throughput applications. The fluorescence sensor presented is highly parallelizable and, due to MEMS micromirror arrays, several sensors can be integrated in one multichannel microfluidic system. The fluorescence sensor has a detection volume of a few thousand femtoliters, covering the full cross-sections of the microfluidic channels used and can be easily adjusted to other cross-section geometries. By measuring labeled particles with diameters below 10 ?m we qualified the applicability of the sensor with different channel geometries. The sensors have measurement volumes fitted to the channel geometries with widths from 20 ?m up to 400 ?m and reach a decision limit of less than 1790 molecules of equivalent soluble fluorophore.

Meineke, G.; Flitsch, D.; Lenenbach, A.; Noll, R.

2013-03-01

338

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

339

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

340

High resolution measurement of turbulent structure in a channel with particle image velocimetry  

Microsoft Academic Search

High resolution particle image velocimetry is used to measure the turbulent velocity field for fully developed flow ( Re = 2,872) in an enclosed channel. Photographs of particle displacement are obtained in a plane that is parallel to the flow and perpendicular to the walls. These are analyzed to give simultaneous measurements of two components of the velocity at more

Z.-C. Liu; C. C. Landreth; R. J. Adrian; T. J. Hanratty

1991-01-01

341

High resolution measurement of turbulent structure in a channel with particle image velocimetry  

Microsoft Academic Search

High resolution particle image velocimetry is used to measure the turbulent velocity field for fully developed flow (Re = 2,872) in an enclosed channel. Photographs of particle displacement are obtained in a plane that is parallel to the flow and perpendicular to the walls. These are analyzed to give simultaneous measurements of two components of the velocity at more than

Z.-C. Liu; C. C. Landreth; R. J. Adrian; T. J. Hanratty

1991-01-01

342

Measurement of heat transfer and pressure drop in rectangular channels with turbulence promoters  

NASA Technical Reports Server (NTRS)

Periodic rib turbulators were used in advanced turbine cooling designs to enhance the internal heat transfer. The objective of the present project was to investigate the combined effects of the rib angle of attack and the channel aspect ratio on the local heat transfer and pressure drop in rectangular channels with two opposite ribbed walls for Reynolds number varied from 10,000 to 60,000. The channel aspect ratio (W/H) was varied from 1 to 2 to 4. The rib angle of attack (alpha) was varied from 90 to 60 to 45 to 30 degree. The highly detailed heat transfer coefficient distribution on both the smooth side and the ribbed side walls from the channel sharp entrance to the downstream region were measured. The results showed that, in the square channel, the heat transfer for the slant ribs (alpha = 30 -45 deg) was about 30% higher that of the transverse ribs (alpha = 90 deg) for a constant pumping power. However, in the rectangular channels (W/H = 2 and 4, ribs on W side), the heat transfer at alpha = 30 -45 deg was only about 5% higher than 90 deg. The average heat transfer and friction correlations were developed to account for rib spacing, rib angle, and channel aspect ratio over the range of roughness Reynolds number.

Han, J. C.; Park, J. S.; Ibrahim, M. Y.

1986-01-01

343

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

SciTech Connect

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 Alfven eigenmode measurements.

Tokuzawa, T.; Kawahata, K. [National Institute for Fusion Science, 322-6 Oroshi-cho, Toki 509-5292 (Japan); Ejiri, A. [Graduate School of Frontier Sciences, University of Tokyo, Kashiwa 277-8561 (Japan)

2010-10-15

344

Delay spread measurements for the digital cellular channel in Toronto  

Microsoft Academic Search

The paper describes a set of measurements performed in the Toronto area, in order to assess the impact of multipath propagation on the performance of the TIA IS-54 digital standard. Five existing cells were systematically surveyed: two in downtown Toronto, two in the suburbs, and one in a suburban\\/rural area. A sweeping correlator apparatus with a 0.1 ?s resolution and

Elvino S. Sousa; V. M. Jovanovic; Christian Daigneault

1994-01-01

345

The role of helium metastable states in radio-frequency driven helium-oxygen atmospheric pressure plasma jets: measurement and numerical simulation  

NASA Astrophysics Data System (ADS)

Absolute densities of metastable He(23S1) atoms were measured line-of-sight integrated along the discharge channel of a capacitively coupled radio-frequency driven atmospheric pressure plasma jet operated in technologically relevant helium-oxygen mixtures by tunable diode-laser absorption spectroscopy. The dependences of the He(23S1) density in the homogeneous-glow-like ?-mode plasma with oxygen admixtures up to 1% were investigated. The results are compared with a one-dimensional numerical simulation, which includes a semi-kinetical treatment of the pronounced electron dynamics and the complex plasma chemistry (in total 20 species and 184 reactions). Very good agreement between measurement and simulation is found. The main formation mechanisms for metastable helium atoms are identified and analyzed, including their pronounced spatio-temporal dynamics. Penning ionization through helium metastables is found to be significant for plasma sustainment, while it is revealed that helium metastables are not an important energy carrying species into the jet effluent and therefore will not play a direct role in remote surface treatments.

Niemi, K.; Waskoenig, J.; Sadeghi, N.; Gans, T.; O'Connell, D.

2011-10-01

346

Measurement of Field Aligned Electron and Ion Densities and Ducts from the Whistler and Z Mode Radio Sounding from IMAGE  

NASA Astrophysics Data System (ADS)

We present recent results from the application of whistler mode (WM) and Z mode (ZM) radio sounding experiments from the IMAGE satellite to the magnetospheric plasma diagnostics. A recently developed WM radio sounding method [Sonwalkar et al., JGR, 116, A11210, doi:10.1029/2011JA016759, 2011] was applied to 200 cases of WM echoes observed within the plasmasphere to measure field aligned electron density (Ne) and ion densities (NH+, NHe+, NO+) for L~1.6 -4, altitude <5000 km, Kp ~1-7, and F10.7 ~ 72-110 (low solar activity). The measured plasma parameters are in general consistent with the past space borne (e.g. CHAMP, DMSP, Alouette, ISIS, AE) and ground (e.g. ionosonde) measurements, but show significant differences from those predicted by IRI-2012 and GCPM models. We believe our measurements will lead to an improved model of electron and ion densities at <5000 km within the plasmasphere. The WM radio sounding method was applied to a case study of the variation of plasma parameters at L~2 during the development of a major storm, from quiet conditions and subsequent recovery, followed by a moderate and minor storm. Our study showed that relative to the preceding quiet time: (1) There was depletion in electron density, H+, He+ and enhancement in O+ ions leading to increase in O+-H+ transition height; (2) The recovery period of electrons and individual ions was different; (3) A similar trend in the variation of electron density, H+, O+ was observed after the moderate storm and the minor storm but He+ was not affected. Following a ray tracing technique originally developed for whistler mode sounding, we analyzed the fast nonducted and ducted Z mode echoes to obtain field aligned electron density and duct parameters (duct width and enhancement) from the measured dispersion of Z mode echoes. With the help of two case studies, we illustrate that fast Z mode echoes provide measurement of electron density at altitudes <10,000 km and duct width and enhancement within an uncertainty of ~0.05 L and a few percent, respectively. Application of ZM radio sounding method presented here to a large number (~2000) case observed at low- to mid-latitudes should provide distribution of electron density and duct parameters in this latitude range for altitude <10,000 km. Our measurements will contribute towards a better understanding of the ionosphere-magnetosphere coupling.

Sonwalkar, V. S.; Hazra, S.; Mayank, K.; Reddy, A.; Liu, Y.; Carpenter, D. L.

2013-12-01

347

Radio-frequency measurements of coherent transition and Cherenkov radiation: Implications for high-energy neutrino detection  

SciTech Connect

We report on measurements of (11--18)-cm wavelength radio emission from interactions of 15.2 MeV pulsed electron bunches at the Argonne Wakefield Accelerator. The electrons were observed both in a configuration where they produced primarily transition radiation from an aluminum foil, and in a configuration designed for the electrons to produce Cherenkov radiation in a silica sand target. Our aim was to emulate the large electron excess expected to develop during an electromagnetic cascade initiated by an ultrahigh-energy particle. Such charge asymmetries are predicted to produce strong coherent radio pulses, which are the basis for several experiments to detect high-energy neutrinos from the showers they induce in Antarctic ice and in the lunar regolith. We detected coherent emission which we attribute both to transition and possibly Cherenkov radiation at different levels depending on the experimental conditions. We discuss implications for experiments relying on radio emission for detection of electromagnetic cascades produced by ultrahigh-energy neutrinos.

Gorham, Peter W.; Saltzberg, David P.; Schoessow, Paul; Gai, Wei; Power, John G.; Konecny, Richard; Conde, M. E.

2000-12-01

348

Radio-frequency measurements of coherent transition and cherenkov radiation: implications for high-energy neutrino detection  

PubMed

We report on measurements of (11-18)-cm wavelength radio emission from interactions of 15.2 MeV pulsed electron bunches at the Argonne Wakefield Accelerator. The electrons were observed both in a configuration where they produced primarily transition radiation from an aluminum foil, and in a configuration designed for the electrons to produce Cherenkov radiation in a silica sand target. Our aim was to emulate the large electron excess expected to develop during an electromagnetic cascade initiated by an ultrahigh-energy particle. Such charge asymmetries are predicted to produce strong coherent radio pulses, which are the basis for several experiments to detect high-energy neutrinos from the showers they induce in Antarctic ice and in the lunar regolith. We detected coherent emission which we attribute both to transition and possibly Cherenkov radiation at different levels depending on the experimental conditions. We discuss implications for experiments relying on radio emission for detection of electromagnetic cascades produced by ultrahigh-energy neutrinos. PMID:11138159

Gorham; Saltzberg; Schoessow; Gai; Power; Konecny; Conde

2000-12-01

349

Quantitative measurement of gas pressure drop along T-shaped micro channels by interferometry  

NASA Astrophysics Data System (ADS)

The study of gas flows in microchannels has received considerably more attention in the literature from a simulation perspective than an experimental. The majority of the experimental work has emphasis on the global measurements at the inlet or exit of the microchannel instead locally along it. In this paper some efforts were made to measure the pressure drop along T-shaped micro channel by using interferometry. The two side channels were served as gas entrances and they were both open to air and the channel outlet was being vacuumed during experiments. A Mach-Zehnder interference microscopy was built for the measurement of gas pressure drop along the mixing channel. Some points along the mixing channel were selected for interferometric measurements. Simulations were first developed in unsteady condition by using Ansys Fluent to verify the nonexistence of transient phenomena of gas flow in the defined condition and then run again in steady condition to get the theoretical pressure drop that was would be used for comparison with experimental results.

Li, Y.; Joseph, S.; Colin, S.; Baldas, L.; Barrot, C.; Orieux, S.; Newport, D.; Brandner, J. J.

2012-05-01

350

Streaming potentials in gramicidin channels measured with ion-selective microelectrodes.  

PubMed Central

Streaming potentials have been measured for gramicidin channels with a new method employing ion-selective microelectrodes. It is shown that ideally ion-selective electrodes placed at the membrane surface record the true streaming potential. Using this method for ion concentrations below 100 mM, approximately seven water molecules are transported whenever a sodium, potassium, or cesium ion, passes through the channel. This new method confirms earlier measurements (Rosenberg, P.A., and A. Finkelstein. 1978. Interaction of ions and water in gramicidin A channels. J. Gen. Physiol. 72:327-340) in which the streaming potentials were calculated as the difference between electrical potentials measured in the presence of gramicidin and in the presence of the ion carriers valinomycin and nonactin.

Tripathi, S; Hladky, S B

1998-01-01

351

High fidelity wireless network evaluation for heterogeneous cognitive radio networks  

NASA Astrophysics Data System (ADS)

We present a high fidelity cognitive radio (CR) network emulation platform for wireless system tests, measure- ments, and validation. This versatile platform provides the configurable functionalities to control and repeat realistic physical channel effects in integrated space, air, and ground networks. We combine the advantages of scalable simulation environment with reliable hardware performance for high fidelity and repeatable evaluation of heterogeneous CR networks. This approach extends CR design only at device (software-defined-radio) or lower-level protocol (dynamic spectrum access) level to end-to-end cognitive networking, and facilitates low-cost deployment, development, and experimentation of new wireless network protocols and applications on frequency- agile programmable radios. Going beyond the channel emulator paradigm for point-to-point communications, we can support simultaneous transmissions by network-level emulation that allows realistic physical-layer inter- actions between diverse user classes, including secondary users, primary users, and adversarial jammers in CR networks. In particular, we can replay field tests in a lab environment with real radios perceiving and learning the dynamic environment thereby adapting for end-to-end goals over distributed spectrum coordination channels that replace the common control channel as a single point of failure. CR networks offer several dimensions of tunable actions including channel, power, rate, and route selection. The proposed network evaluation platform is fully programmable and can reliably evaluate the necessary cross-layer design solutions with configurable op- timization space by leveraging the hardware experiments to represent the realistic effects of physical channel, topology, mobility, and jamming on spectrum agility, situational awareness, and network resiliency. We also provide the flexibility to scale up the test environment by introducing virtual radios and establishing seamless signal-level interactions with real radios. This holistic wireless evaluation approach supports a large-scale, het- erogeneous, and dynamic CR network architecture and allows developing cross-layer network protocols under high fidelity, repeatable, and scalable wireless test scenarios suitable for heterogeneous space, air, and ground networks.

Ding, Lei; Sagduyu, Yalin; Yackoski, Justin; Azimi-Sadjadi, Babak; Li, Jason; Levy, Renato; Melodia, Tammaso

2012-05-01

352

16-Channel submillimeter interferometer for measuring the plasma density profile in the T-10 device  

SciTech Connect

A description is presented of a 16-channel quasioptical interferometer of original design with a system for detecting, accumulating, and archiving experimental data. The interferometer was used in the T-10 device to study the behavior of the electron density profile in various regimes. The high spatial resolution ({triangle}x = 4.2 cm) allowed the measurements to be carried out in regimes with microwave breakdown of the plasma and revealed essential features (in comparison with 8-channel measurements) in the behavior of Ne(r) in the ohmic regimes with {open_quotes}marfe.{close_quotes} 1 ref., 4 figs.

Vasin, N.L.; Evdokimov, D.B.; Rykunov, G.V.; Chistyakov, V.V.

1992-02-01

353

Rapid Estimation of Recharge Potential in Ephemeral-Stream Channels Using Electromagnetic Methods, and Measurements of Channel and Vegetation Characteristics  

Microsoft Academic Search

In order to classify recharge potential (RCP) in ephemeral-stream channels, a method was developed that incorporates information about channel geometry, vegetation characteristics, and bed-sediment apparent electrical conductivity ('a). About 400 transects along two ephemeral-stream channels near Sierra Vista, Arizona were studied. Seven data types were collected at each transect: 'a at two depth intervals, channel incision height and width, diameter-at-breast-height

J. B. Callegary; J. M. Leenhouts; N. V. Paretti; C. A. Jones

2006-01-01

354

Instantaneous Measure of EEG Channel Importance for Improved Patient-Adaptive Neonatal Seizure Detection  

PubMed Central

A measure of bipolar channel importance is proposed for EEG-based detection of neonatal seizures. The channel weights are computed based on the integrated synchrony of classifier probabilistic outputs for the channels which share a common electrode. These estimated time-varying weights are introduced within a Bayesian probabilistic framework to provide a channel-specific and thus adaptive seizure classification scheme. Validation results on a clinical dataset of neonatal seizures confirm the utility of the proposed channel weighting for the two patient-independent seizure detectors recently developed by this research group; one based on support vector machines and the other on Gaussian mixture models. By exploiting the channel weighting, the ROC area can be significantly increased for the most difficult patients, with the average ROC area across 17 patients increased by 22% (relative) for the SVM and by 15% (relative) for the GMM-based detector, respectively. It is shown that the system developed here outperforms the recent published studies in this area.

Temko, Andriy; Lightbody, Gordon; Thomas, Eoin; Marnane, William; Boylan, Geraldine

2012-01-01

355

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

356

The Faroe Bank Channel overflow in one year of continuous current and hydrographic measurements  

NASA Astrophysics Data System (ADS)

Cold, dense water from the Nordic Seas flows out into the North Atlantic across the shallow Iceland-Scotland ridge through a few deeper passages, the deepest of which (at 840 m) is the narrow Faroe Bank Channel. The overflow is swift, with velocities exceeding 1 m/s, and associated with strong vertical mixing. Here we present results from eight hydrographic and current meter moorings that were deployed in the Faroe Bank Channel overflow region during the period 28 May 2012 to 5 June 2013, measuring current velocity, temperature, and salinity at hourly or higher sampling frequencies. One array of three moorings - the channel section - was placed at about 8° 30'W, just downstream of the sill in the channel. Another array, the slope section, with four moorings was located some 60 km further downstream, at about 9° 40'W. At the easternmost (channel) section, the cold plume was thick, with water colder than 3°C - considered as plume water - occupying the bottom 200 m at all times. At the slope section, the plume has thinned considerably as a result of entrainment of overlying warmer water. Mesoscale oscillations at periods of a few days dominated the temporal variability of velocity and temperature at both mooring sections. The mesoscale oscillation period, indicated by a peak in the energy density spectrum, was longer at the channel than the slope section (four and six days, respectively). A spectral peak at the diurnal tidal frequency is observed in the channel, but is absent on the slope. We will discuss these and other aspects of how the plume structure and variability develops along its path as the dense overflow exits the Faroe Bank Channel.

Ullgren, Jenny; Fer, Ilker; Darelius, Elin

2014-05-01

357

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

358

Propagation Issues for Cognitive Radio  

Microsoft Academic Search

Cognitive radios are expected to work in bands below about 3.5 GHz and may be used for a variety of applications, e.g., broadband fixed wireless access, mobile and nomadic access, etc. Cognitive radio system designers must have access to a wide range of channel models covering a wide span of operating frequencies, carrier bandwidths, deployment conditions, and environments. This paper

Andreas F. Molisch; Larry J. Greenstein; Mansoor Shafi

2009-01-01

359

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.

360

Beam Emittance Measurements for the Low-Energy Demonstration Accelerator Radio-Frequency Quadrupole  

Microsoft Academic Search

The Low-Energy Demonstration Accelerator (LEDA) radio-frequency quadrupole\\u000a(RFQ) is a 100% duty factor (CW) linac that delivers >100 mA of H+ beam at 6.7\\u000aMeV. The 8-m-long, 350-MHz RFQ structure accelerates a dc, 75-keV, 110-mA H+\\u000abeam from the LEDA injector with >90% transmission. LEDA [1,2] consists of a\\u000a75-keV proton injector, 6.7-MeV, 350-MHz CW RFQ with associated high-power and

J. D. Gilpatrick; W. P. Lysenko; L. J. Rybarcyk; J. D. Schneider; H. V. Smith; L. M. Young

2000-01-01

361

The BepiColombo mission to Mercury and the Italian Spring Accelerometer (ISA) role in the Radio Science Experiments measurements  

NASA Astrophysics Data System (ADS)

The BepiColombo mission to Mercury [1, 10] of the European Space Agency (ESA) aims to perform a set of experiments, the so called Radio Science Experiments (RSE), that will be devoted to the study of the gravity field and rotational state of Mercury [8] as well as to verify the theory of general relativity to an unprecedented level of accuracy [9]. One of the key ingredients in order to reach the very ambitious objectives of this mission, in the context of the RSE, is represented by the measurements of the onboard accelerometer [5, 2]. The Italian Spring Accelerometer (ISA) has been selected by ESA to measure and then allow to remove, a posteriori, the disturbing nongravitational accelerations acting on the Mercury Planetary Orbiter (MPO) surface. This paper is devoted to describe the accelerometer characteristics and performance and to introduce some of the experimental procedures in order to calibrate its measurements on ground and during the nominal phase of the mission.

Iafolla, V.; Lucchesi, D. M.; Lucente, M.; Nozzoli, S.; Peron, R.; Santoli, F.; Argada, A.; Fiorenza, E.; Lefevre, C.; Magnafico, C.

2011-10-01

362

THE RADIO-2 mm SPECTRAL INDEX OF THE CRAB NEBULA MEASURED WITH GISMO  

SciTech Connect

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 ({nu}{sub b}[GHz]) = 2.84 {+-} 0.29 or {nu}{sub b} = 695{sup +651}{sub -336} GHz. The Crab Nebula is well resolved by the {approx}16.''7 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.

Arendt, R. G. [CRESST, University of Maryland-Baltimore County, Baltimore, MD 21250 (United States); George, J. V. [Department of Astronomy, University of Maryland-College Park, College Park, MD 20742 (United States); Staguhn, J. G.; Benford, D. J.; Fixsen, D. J.; Maher, S. F.; Moseley, S. H.; Sharp, E.; Wollack, E. J. [NASA Goddard Space Flight Center, Code 665, Greenbelt, MD 20771 (United States); Devlin, M. J.; Dicker, S. R.; Korngut, P. M. [Department of Physics and Astronomy, University of Pennsylvania, Physics and Astronomy, 209 South 33rd Street, Philadelphia, PA 19104 (United States); Irwin, K. D. [NIST Quantum Devices Group, 325 Broadway Mailcode 817.03, Boulder, CO 80305 (United States); Jhabvala, C. A.; Miller, T. M. [NASA Goddard Space Flight Center, Code 553, Greenbelt, MD 20771 (United States); Kovacs, A. [Department of Astronomy, University of Minnesota, 116 Church St SE, Minneapolis, MN 55414 (United States); Mason, B. S. [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903 (United States); Navarro, S.; Sievers, A. [Instituto Radioastronomia Milimetrica (IRAM), Av. Divina Pastora 7, Nucleo Central, 18012 Granada (Spain); Sievers, J. L., E-mail: Richard.G.Arendt@nasa.gov [Canadian Institute for Theoretical Astrophysics, University of Toronto, ON M5S 3H8 (Canada)

2011-06-10

363

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

364

Measurements on the satellite-mobile channel at L and S bands  

NASA Astrophysics Data System (ADS)

An experiment is described in which measurements are made on the satellite-mobile channel at L and S bands. A light aircraft carrying a c.w. beacon is flown at elevation angles of 40, 60 and 80 degrees to a mobile receiver. The signal strength at the mobile is recorded in open, urban, suburban and tree shadowed environments. This data is then analyzed to produce statistics for the channel with respect to frequency, elevation angle, and environment. Results are presented together with a brief discussion, suggested interpretation, and conclusion.

Smith, H.; Gardiner, J. G.; Barton, S. K.

365

#EdChat Radio  

NSDL National Science Digital Library

This iTunes radio channel is available for free download by discussion or the entire database by subscription. Each podcast reflects on the Twitter #EdChat conversation of the week on a range of educational topics. Some topics of particular interest to math coaches are Mentoring New Teachers and Reinventing the Classroom.

Network, Bam R.

2013-01-01

366

Coupled Radon and Water Temperature Measurements to Characterize the Effects of Altered Stream Channel Planform  

NASA Astrophysics Data System (ADS)

In summer 2011, a 2.6 km reach of Meacham Creek, Oregon, USA, was altered from a straight, steep wall-based channel to more a sinuous, low-gradient channel. Key objectives of this restoration project were to increase the rate and magnitude of hyporheic exchange. The overarching goal was to initiate increased buffering and lagging of water temperature in the subsurface to mitigate warm surface water temperature in Meacham Creek, an important spawning and rearing stream for depressed populations of Chinook salmon and summer steelhead. To evaluate progress toward project goals and objectives, stream temperature and groundwater temperature in 22 wells have been measured hourly at the restoration site since March 2011. In addition, the radioactive isotope 222Rn was measured in each well and in the surface water on two occasions. The relative residence time of down welling stream water measured in the wells can be determined by ranked amplitude depression and lagged phase of annual temperature signals in the wells relative to that of the open channel flow. Residence times predicted by annual temperature signal dynamics are corroborated by 222Rn concentrations in each well. The data collected to date provide a foundation for developing a groundwater thermal model to predict the effects of channel reconfiguration on ground-surface water exchange and associated temperature effects at the reach scale.

Amerson, B. E.; Poole, G. C.; O'Daniel, S. J.

2013-12-01

367

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

368

Automation of Channeling Experiment for Lattice Strain Measurements Using High Energy Ion Beams  

SciTech Connect

40 MeV Si channeling studies have been performed on the strained In0.1Ga0.9As layer grown on GaAs substrate using Molecular Beam Epitaxy (MBE). Three samples with different layer thickness have been investigated in this study. Channeling experiment has been fully automated so as to minimize the radiation damage. Suitable software and hardware have been developed to control the precision goniometer using the CAMAC (Computer automation and control) based data acquisition system. In low energy He channeling, strain measurements are often misled by the beam steering effects caused due to broad critical angles if the strain is very low. Such effects can be minimized by increasing the probing beam energy as the channeling critical angle is inversely proportional to the square root of the incident energy. Hence small angular misalignments can also be resolved in the high energy channeling experiments. Heavy ions are chosen so as to have reasonably high scattering cross-section and also to avoid the nuclear reactions.

Nageswara Rao, S.V.S.; Lakshmi, G.B.V.S.; Pathak, Anand P. [School of Physics, University of Hyderabad, Central University (PO), Hyderabad 500 046 (India); Avasthi, D.K.; Subramanyam, E.T.; Singh, Kundan; Khan, S.A.; Siddiqui, Azher M.; Tripathi, A.; Srivastava, S.K. [Nuclear Science Centre, Post Box No. 10502, Aruna Asaf Ali Marg, New Delhi 110 067 (India); Kumar, Sarvesh [Department of Physics, R.B.S. College, Agra 282 002 (India); Srinivasan, T.; Tiwari, Umesh; Mehta, S.K.; Muralidharan, R.; Jain, R.K. [Solid State Physics Laboratory, Timarpur, Delhi 110 054 (India)

2003-08-26

369

Ultra-High Energy Neutrino Astrophysics from Greenland; In situ measurements of the Radio Attenuation Length at the proposed Greenland Neutrino Observatory Site  

NASA Astrophysics Data System (ADS)

Neutrino astrophysics allows us to explore the ultra-high energy universe from a unique perspective and to test our understanding of particle physics at energies greater than those achievable at particle colliders. The future of ultra-high energy neutrino detection lies with ground-based radio arrays with the sensitivity required to reach even the most pessimistic models of neutrino production. The Greenland Neutrino Observatory (GNO) is a proposed ground-based radio array located at Summit Station in Greenland. We present an in situ measurement of the radio attenuation length of the ice from 50 - 200 MHz at the Summit Station site taken in June 2013, and show that Summit Station is a world-class location for a next-generation radio detector of ultra-high energy neutrinos.

Avva, Jessica; Vieregg, Abigail

2014-08-01

370

Ultra-compact 32-channel system for time-correlated single-photon counting measurements  

NASA Astrophysics Data System (ADS)

Modern Time-Correlated Single-Photon Counting applications require to detect spectral and temporal fluorescence data simultaneously and from different areas of the analyzed sample. These rising quests have led the development of multichannel systems able to perform high count rate and high performance analysis. In this work we describe a new 32-channel TCSPC system designed to be used in modern setups. The presented module consists of four independent 8-channel TCSPC boards, each of them including two 4-channel Time-Amplitude Converter arrays. These TAC arrays are built-in 0.35 ?m Si-Ge BiCMOS technology and are characterized by low crosstalk, high resolution, high conversion rate and variable full-scale range. The 8-channel TCSPC board implements an 8-channel ADC to sample the TAC outputs, an FPGA to record and organize the measurement results and a USB 2.0 interface to enable real-time data transmission to and from an external PC. Experimental results demonstrate that the acquisition system ensures high performance TCSPC measurements, in particular: high conversion rate (5 MHz), good time resolution (down to 30 psFWHM with the full scale range set to 11 ns) and low differential non-linearity (rms value lower than 0.15% of the time bin width). We design the module to be very compact and, thanks to the reduced dimensions of the 8-channel TCSPC board (95×40 mm), the whole system can be enclosed in a small aluminum case (160×125×30 mm).

Antonioli, S.; Cuccato, A.; Miari, L.; Labanca, I.; Rech, I.; Ghioni, M.

2013-05-01

371

Transcontinental baselines and the rotation of the Earth measured by radio interferometry.  

PubMed

Nine separate very-long-baseline interferometry (VLBI) experiments, carried out in 1972 and 1973 with radio telescopes 3900 kilometers apart, yielded values for the baseline length with a root-mean-square deviation about the mean of less than 20 centitneters. The corresponding fractional spread is about five parts in 10(8). Changes in universal time and in polar motion were also detertnined accurately from these data; the root-mean-square scatter of these results with respect to those based on optical methods were 2.9 milliseconds and 1.3 meters, respectively. Solid-earth tides were apparently detected, but no useful estimate of their amplituide was extracted. PMID:17730913

Shapiro, I I; Robertson, D S; Knight, C A; Counselman, C C; Rogers, A E; Hinteregger, H F; Lippincott, S; Whitney, A R; Clark, T A; Niell, A E; Spitzmesser, D J

1974-12-01

372

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

373

Measurements of Channel Transfer Functions and Capacity Calculations for a 16X16 BLAST Array over a Ground Plane.  

National Technical Information Service (NTIS)

Wideband channel transfer function measurements were made for a 16- element transmit and 16-element receive, multiple input, multiple output (MIMO) antenna array. The measurements were conducted using the National Institute of Standards and Technology (NI...

P. B. Papazian Y. Lo J. J. Lemmon M. J. Gans

2003-01-01

374

Isothermal mass flow measurements in microfabricated rectangular channels over a very wide Knudsen range  

NASA Astrophysics Data System (ADS)

Measurement and modeling of gas flows in microelectromechanical systems (MEMS) scale channels are relevant to the fundamentals of rarefied gas dynamics (RGD) and the practical design of MEMS-based flow systems and micropumps. We describe techniques for building robust, leak-free, rectangular microchannels which are relevant to micro- and nanofluidic devices, while the channels themselves are useful for fundamental RGD studies. For the first time, we report the isothermal steady flow of helium (He) gas through these channels from the continuum to the free-molecular regime in the unprecedented Knudsen range of 0.03–1000. On the high end, our value is 20-fold larger than values previously reported by Ewart et al (2007 J. Fluid Mech. 584 337–56). We accomplished this through a dual-tank accumulation technique which enabled the monitoring of very low flow rates, below 10?14 kg s?1. The devices were prebaked under vacuum for 24 h at 100 °C in order to reduce outgassing and attain high Kn. We devised fabrication methods for controlled-depth micro-gap channels using silicon for both channel ceiling and floor, thereby allowing direct comparisons to models which utilize this simplifying assumption. We evaluated the results against a closed-form expression that accurately reproduces the continuum, slip, transition, and free-molecular regimes developed partly by using the direct simulation Monte Carlo method. The observed data were in good agreement with the expression. For Kn > ?100, we observed minor deviations between modeled and experimental flow values. Our fabrication processes and experimental data are useful to fundamental RGD studies and future MEMS microflow devices with respect to extremely low-flow measurements, model validation, and predicting optimal designs.

Anderson, John M.; Moorman, Matthew W.; Brown, Jason R.; Hochrein, James M.; Thornberg, Steven M.; Achyuthan, Komandoor E.; Gallis, Michael A.; Torczynski, John R.; Khraishi, Tariq; Manginell, Ronald P.

2014-05-01

375

Measurement of the single top quark t-channel cross section with a template fit analysis  

NASA Astrophysics Data System (ADS)

We present a measurement of the inclusive single top t-channel production cross section in proton-proton collisions at the LHC, using data collected with the CMS experiment during 2011 and 2012. The analyzed data correspond to an integrated luminosity of 1.17/1.56 fb-1 for muon/electron channel respectively at the centre-of-mass energy of 7TeV, and to 5.0 fb-1 at 8 TeV. The analysis exploits the pseudorapidity distribution of the recoil jet and reconstructed top-quark mass using background estimates determined from control samples in data. The measurement is used to determine the CKM matrix element |Vtb|.

Merola, Mario; Cms Collaboration

2013-07-01

376

The equilibrium velocity of spherical particles in rectangular microfluidic channels for size measurement.  

PubMed

According to the Segré-Silberberg effect, spherical particles migrate to a lateral equilibrium position in parabolic flow profiles. Here, for the first time, the corresponding equilibrium velocity is studied experimentally for micro particles in channels with rectangular cross section. Micro channels are fabricated in PMMA substrate based on a hot embossing process. To measure individual particle velocities at very high precision, the technique of spatially modulated emission is applied. It is found that the equilibrium velocity is size-dependent and the method offers a new way to measure particle size in microfluidic systems. The method is of particular interest for microfluidic flow cytometry as it delivers an alternative to the scatter signal for cell size determination. PMID:24829932

Sommer, Christian; Quint, Stephan; Spang, Peter; Walther, Thomas; Baßler, Michael

2014-06-01

377

Measurements of mixed convective heat transfer to low temperature helium in a horizontal channel  

NASA Technical Reports Server (NTRS)

A horizontal 2.85 m long, 19 mm i.d. stainless steel heated circular channel was employed to measure coefficients of heat transfer to low temperature helium flow. Experimental parameters range from 6.5 to 15 K, from 0.12 to 0.3 MPa at heat fluxes up to 1000 W/m square and Reynolds numbers from 9,000 to 20,000. A significantly nonuniform distribution of heat transfer coefficients over the tube periphery is observed. Difference between temperatures on the upper and lower surfaces of the stainless steel channel wall was found to reach 9 K. It was noted that the highest temperature on the wall outer surface is displaced from its uppermost point. Measurements of local flow temperatures revealed vortical structure of the flow. The displacement of the point with the highest temperature is attributable to the effect of vortices. The relationships for calculating local and averaged coefficients of heat transfer are proposed.

Yeroshenko, V. M.; Kuznetsov, Y. V.; Shevchenko, O. A.; Hendricks, R. C.; Daney, D. E.

1979-01-01

378

Narrow-band measurement and analysis of the inter-vehicle transmission channel at 5.2 GHz  

Microsoft Academic Search

The inter-vehicle transmission channel is characterised based on narrow-band measurements at 5.2 GHz. The measurement setup consists of a transmitter and a receiver, which are installed in two different vehicles. While measuring the transmission channel, both vehicles are manoeuvred in realistic road traffic scenarios. Measurements are obtained for four different classes of environments: urban, suburban (village), motorway and highway. Statistical

J. Maurer; T. Fugen; W. Wiesbeck

2002-01-01

379

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

380

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

381

Measurements of jet flows impinging into a channel containing a rod bundle using dynamic PIV  

Microsoft Academic Search

In this investigation, full-field velocity profiles of jet flows impinging into a rod bundle were measured using Particle Image Velocimetry (PIV) technique in a facility with Matched-Index of Refraction. The test section consisted of a 1m long rectangular channel with a cross-sectional area of 76.2×76.2mm2. Water was pumped through either single or double jets located on the top wall of

Noushin Amini; Yassin A. Hassan

2009-01-01

382

Quantum channel negativity as a measure of system-bath coupling and correlation  

NASA Astrophysics Data System (ADS)

Complete positivity is a ubiquitous assumption in the study of quantum systems interacting with the environment, but the lack of complete positivity of a quantum evolution (called the “negativity”) can be used as a measure of the system-bath coupling and correlation. The negativity can be computed from the Choi representation of a channel, is always defined and bounded, and contains some information about environmentally induced noise in a quantum system.

McCracken, James M.

2013-09-01

383

Channeling measurements of the trapping efficiencies of solute atoms for self-interstitial atoms in metals  

Microsoft Academic Search

Channeling techniques were used to measure the concentration of mixed dumbbells as a function of irradiation fluence in crystals of Al-0.10 at.% Ag, Cu-0.25 at.% Be and Mg-0.18 at.% Ag. From the experimentally observed production rates of mixed dumbbells from alpha or deuteron irradiations at temperatures where self-interstitials were mobile, it was concluded that the dominant trapping configuration was the

M. L. Swanson; L. M. Howe

1979-01-01

384

Lightning Return-Stroke Current Waveforms Aloft, from Measured Field Change, Current, and Channel Geometry  

NASA Technical Reports Server (NTRS)

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 kilometers for 24 return strokes in these channels. Streak photographs of 14 of the same strokes are analyzed to determine the rise times, 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% rise time of the stroke current increased by about a factor of seven in our sample, from an observed 0.31 plus or minus 0.17 microseconds at the surface to an inferred 2.2 plus or minus 0.5 microcseconds at 1 kilometer path length above the surface. 3) The three-dimensional propagation speed of the current front averaged 1.80 plus or minus 0.24 X 10(exp 8) meters per second over channel lengths typically greater than 1 kilometer. 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, at least in such cases. 5) Peak return-stroke currents decreased by approximately 37 plus or minus 12% from 100 meters to 1 kilometer of path length above the surface. Because of uncertainty about how to partition the measured current between leader and return stroke, we are unable to infer the variation of current amplitude near the ground.

Willett, J. C.; LeVine, D. M.; Idone, V. P.

2006-01-01

385

Undersea Acoustic Propagation Channel Estimation.  

National Technical Information Service (NTIS)

This research concerns the continuing development of Seaweb underwater networking. In this type of wireless network the radio channel is replaced by an underwater acoustic channel which is strongly dependent on the physical properties of the ocean medium ...

S. Dessalermos

2005-01-01

386

USING RADIO HALOS AND MINIHALOS TO MEASURE THE DISTRIBUTIONS OF MAGNETIC FIELDS AND COSMIC RAYS IN GALAXY CLUSTERS  

SciTech Connect

Some galaxy clusters show diffuse radio emission in the form of giant halos (GHs) on Mpc scales or minihalos (MHs) on smaller scales. Comparing Very Large Array and XMM-Newton radial profiles of several such clusters, we find a universal linear correlation between radio and X-ray surface brightness, valid in both types of halos. It implies a halo central emissivity {nu}j{sub {nu}} = 10{sup -31.4{+-}0.2}(n/10{sup -2}cm{sup -3}){sup 2}(T/T{sub 0}){sup 0.2{+-}0.5}ergs{sup -1}cm{sup -3}, where T and T{sub 0} are the local and central temperatures, respectively, and n is the electron number density. We argue that the tight correlation and the scaling of j{sub {nu}}, combined with morphological and spectral evidence, indicate that both GHs and MHs arise from secondary electrons and positrons, produced in cosmic-ray ion (CRI) collisions with a strongly magnetized B {approx}> 3{mu}G intracluster gas. When the magnetic energy density drops below that of the microwave background, the radio emission weakens considerably, producing halos with a clumpy morphology (e.g., RXC J2003.5 - 2323 and A2255) or a distinct radial break. We thus measure a magnetic field B = 3{mu}G at a radius r {approx_equal} 110kpc in A2029 and r {approx_equal} 50kpc in Perseus. The spectrum of secondaries, produced from hadronic collisions of {approx}20GeV CRIs, reflects the energy dependence of the collision cross section. We use the observed spectra of halos, in particular where they steepen with increasing radius or frequency, to (1) measure B {approx_equal} 10({nu}/700MHz){mu}G with {nu} the spectral break frequency, (2) identify a correlation between the average spectrum and the central magnetic field, and (3) infer a CRI spectral index s {approx}< -2.7 and energy fraction {xi}{sub p} {approx} 10{sup -3.6{+-}0.2} at particle energies above 10 GeV. Our results favor a model where CRIs diffuse away from their sources (which are probably supernovae, according to a preliminary correlation with star formation), whereas the magnetic fields are generated by mergers in GHs and by core sloshing in MHs.

Keshet, Uri; Loeb, Abraham [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

2010-10-10

387

Measurement of Attenuation Length for UHF Radio Wave in Natural Rock Salt Samples Concerning Ultra High Energy Neutrino Detection  

NASA Astrophysics Data System (ADS)

Ultra high energy (UHE ) neutrinos (E > 1015 eV) exist at any rate due to presence of the cosmic microwave background and UHE cosmic rays implied by Greisen, Zatsepin and Kuz'min (GZK). The low rate of GZK neutrinos requires us to utilize a large mass (> 50 Gton) of detection medium. The UHE neutrino generates a huge number of unpaired electrons in rock salt. They would emit sensible radio wave by coherent Cherenkov effect (Askar'yan effect). Attenuation lengths of natural rock salt samples including synthesized one at 0.3 and 1.0 GHz were measured to find a suitable site constructing a salt neutrino detector. The result indicates a possibility for constructing the salt neutrino detector with economical antenna spacing.

Chiba, Masami; Watanabe, Yusuke; Takayama, Yasuhiro; Fujii, Masatoshi; Yasuda, Osamu; Yabuki, Fumiaki; Shibasaki, Yuji; Kamijo, Toshio; Chikashige, Yuichi; Kon, Tadashi; Amano, Akio; Takeoka, Yoshito; Shimizu, Yutaka; Mori, Satoshi; Ninomiya, Sosuke; Utsumi, Michiaki

2007-03-01

388

Noninvasive Imaging and Measurement of Accommodation Using Dual-Channel SD-OCT.  

PubMed

Abstract Purpose: To investigate the feasibility and practicality of real-time noninvasive imaging and measurement of ocular accommodation (0-5D with one diopter step) using dual-channel, dual-focus spectral domain optical coherence tomography (SD-OCT). Materials and Methods: A custom-built, dual-channel, dual-focus SD-OCT was used to image the anterior segment, including the cornea, iris, and anterior and posterior lens surfaces. Three consecutive measurements were taken in each accommodative session for each subject. Changes in ocular dimensions during accommodation were calculated based on the acquired SD-OCT images. A Friedman test was used to test sensitivity of ocular dimension changes per diopter of accommodation. Results: With accommodation, anterior chamber depth (ACD), curvature radius of both anterior (RAL) and posterior (RPL) lens surfaces, and pupil diameter (PD) decreased significantly, whereas lens thickness (LT) increased significantly (p?channel, dual-focus approach, is a feasible and practical modality for noninvasive imaging and measurement of ocular accommodation. PMID:24206216

Sun, Yong; Fan, Shanhui; Zheng, Haihua; Dai, Cuixia; Ren, Qiushi; Zhou, Chuanqing

2014-06-01

389

Measuring flood discharge in unstable stream channels using ground-penetrating radar  

USGS Publications Warehouse

Field experiments were conducted to test the ability of ground-penetrating radar (GPR) to measure stream-channel cross sections at high flows without the necessity of placing instruments in the water. Experiments were conducted at four U.S. Geological Survey gaging stations in southwest Washington State. With the GPR antenna suspended above the water surface from a bridge or cableway, traverses were made across stream channels to collect radar profile plots of the streambed. Subsequent measurements of water depth were made using conventional depth-measuring equipment (weight and tape) and were used to calculate radar signal velocities. Other streamflow-parameter data were collected to examine their relation to radar signal velocity and to claritv of streambed definition. These initial tests indicate that GPR is capable of producing a reasonably accurate (??20%) stream-channel profile and discharge far more quickly than conventional stream-gaging procedures, while avoiding the problems and hazards associated with placing instruments in the water.

Spicer, K. R.; Costa, J. E.; Placzek, G.

1997-01-01

390

High-frequency noise and spectrum occupancy measurements for Virginia and Texas with comparisons to International Radio Consultative Committee predictions  

NASA Astrophysics Data System (ADS)

There is ongoing interest in the high-frequency (HF) band of the spectrum, both in terms of the noise levels and the available spectrum bandwidth. In particular, current HF radar systems such as the U.S. Navy's Relocatable Over-the-Horizon Radar (ROTHR) or the Australian Jindalee radar must operate against the external noise and share the spectrum with other HF band users. Current estimates of external noise levels are based on International Radio Consultative Committee (CCIR) [1988]. These predictions are based primarily on measurements made several decades ago at a few sites around the world. There are no current generally accepted estimates for available spectrum bandwidth. The Radar Division at the Naval Research Laboratory, in support of the U.S. Navy's ROTHR, developed a semiportable HF spectrum monitoring system to make HF noise and available bandwidth measurements. HF measurements were made over the 5- to 28-MHz frequency range at three locations. Measurements were made in Virginia at the end of August 1994, in Texas at the end of November 1994, and aboard the U.S.S. Ashland off the coast of Virginia in May 1995. These measurements are presented, as well as comparisons with CCIR predictions for the same period.

Rodriguez, Serafin P.

1997-09-01

391

A practical DCA implementation for GSM networks: dynamic frequency and channel assignment  

Microsoft Academic Search

A new dynamic channel assignment (DCA) scheme specifically adapted for the GSM system is introduced and evaluated. This functionality is fully compatible with the existing GSM standards and therefore it can be implemented in existing GSM networks with legacy handsets. The channel assignment decisions are based on the downlink measurement and radio resource usage data that are already available in

Matti Salmenkaita; Jose Gimenez; Pablo Tapia

2001-01-01

392

Firefighters' Radios  

NASA Technical Reports Server (NTRS)

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

1976-01-01

393

Direct measurement of electron channeling in a crystal using scanning transmission electron microscopy  

SciTech Connect

Self-focusing of an atomic-scale high-energy electron wave packet by channeling along a zone axis in crystalline silicon is directly measured by scanning transmission electron microscopy using thin epitaxial SrTiO{sub 3}(100) islands grown on Si(100) as test objects. As the electron probe propagates down a silicon atom column, it is progressively focused onto the column, resulting in a fourfold increase in the scattered signal at the channeling maximum. This results in an enhancement of the visibility of the SrTiO{sub 3} islands, which is lost if the sample is flipped upside down and the channeling occurs only after the probe scatters off the SrTiO{sub 3} layer. The evolution of the probe wave function calculated by the multislice method accurately predicts the trends in the channeling signal on an absolute thickness scale. We find that while electron channeling enhances the visibility of on-column atoms, it suppresses the contribution from off-column atoms. It can therefore be used as a filter to selectively image the atoms that are most aligned with the atomic columns of the substrate. By using this technique, coherent islands can be distinguished from relaxed islands. For SrTiO{sub 3} films formed in a topotactic reaction on Si(100), we show that only {approx}55% of the SrTiO{sub 3} is aligned with the Si atom columns. The fraction of coherent SrTiO{sub 3} islands on Si(100) can be increased by choosing growth conditions away from equilibrium.

Kourkoutis, L. Fitting; Parker, M. K. [School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853 (United States); Vaithyanathan, V. [Department of Material Science and Engineering, Pennsylvania State University, University Park, Pennsylvania 16802-5055 (United States); Schlom, D. G. [Department of Material Science and Engineering, Cornell University, Ithaca, New York 14853 (United States); Kavli Institute at Cornell for Nanoscale Science, Ithaca, New York 14853 (United States); Muller, D. A. [School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853 (United States); Kavli Institute at Cornell for Nanoscale Science, Ithaca, New York 14853 (United States)

2011-08-15

394

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

395

Measurement of 15 N relaxation in the detergent-solubilized tetrameric KcsA potassium channel  

Microsoft Academic Search

A set of TROSY-HNCO (tHNCO)-based 3D experiments is presented for measuring 15N relaxation parameters in large, membrane-associated proteins, characterized by slow tumbling times and significant spectral\\u000a overlap. Measurement of backbone 15N R\\u000a 1, R\\u000a 1?, 15N–{1H} NOE, and 15N CSA\\/dipolar cross correlation is demonstrated and applied to study the dynamic behavior of the homotetrameric KcsA potassium\\u000a channel in SDS micelles

Jordan H. Chill; John M. Louis; James L. Baber; Ad Bax

2006-01-01

396

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

397

An intercomparison technique for measuring thermal attachment cross sections and rate constants in distinct final channels  

NASA Technical Reports Server (NTRS)

A new technique is introduced for comparing negative-ion signal rates in which a common ion is produced by dissociative attachment in a series of molecules. Measurements are carried out at electron energies less than 100 MeV and at resolutions of 6-8 MeV (FWHM). The technique is demonstrated by detection of the Cl(-) signal in CFCl3, CCl4, CF2Cl2, 1,1,2-C2Cl3F3, 1,1,1-C2Cl3F3 and C2Cl4. Measurements for 1,1,1-C2Cl3F3 show that there is a significant open channel, other than Cl(-) formation, which accounts for about 60 percent of negative-ion formation in thermal-multiple-collision (swarm) experiments. Channel cross sections and rate constants are given for the process Cl(-)/1,1,1-Cl2Cl3F3, as well as in C2Cl4, for the separate channels Cl(-)/C2Cl4 and C2Cl4(-)/C2Cl4.

Alajajian, S. H.; Chutjian, A.

1987-01-01

398

Measurements of Shear Lift Force on a Bubble in Channel Flow in Microgravity  

NASA Technical Reports Server (NTRS)

Under microgravity conditions, the shear lift force acting on bubbles, droplets or solid particles in multiphase flows becomes important because under normal gravity, this hydrodynamic force is masked by buoyancy. This force plays an important role in furnishing the detachment process of bubbles in a setting where a bubble suspension is needed in microgravity. In this work, measurements of the shear lift force acting on a bubble in channel flow are performed. The shear lift force is deduced from the bubble kinematics using scaling and then compared with predictions from models in literature that address different asymptotic and numerical solutions. Basic trajectory calculations are then performed and the results are compared with experimental data of position of the bubble in the channel. A direct comparison of the lateral velocity of the bubbles is also made with the lateral velocity prediction from investigators, whose work addressed the shear lift on a sphere in different two-dimensional shear flows including Poiseuille flow.

Nahra, Henry K.; Motil, Brian J.; Skor, Mark

2003-01-01

399

Genetic interactions found between calcium channel genes modulate amyloid load measured by positron emission tomography.  

PubMed

Late-onset Alzheimer's disease (LOAD) is known to have a complex, oligogenic etiology, with considerable genetic heterogeneity. We investigated the influence of genetic interactions between genes in the Alzheimer's disease (AD) pathway on amyloid-beta (A?) deposition as measured by PiB or AV-45 ligand positron emission tomography (PET) to aid in understanding LOAD's genetic etiology. Subsets of the Alzheimer's Disease Neuroimaging Initiative (ADNI) cohorts were used for discovery and for two independent validation analyses. A significant interaction between RYR3 and CACNA1C was confirmed in all three of the independent ADNI datasets. Both genes encode calcium channels expressed in the brain. The results shown here support previous animal studies implicating interactions between these calcium channels in amyloidogenesis and suggest that the pathological cascade of this disease may be modified by interactions in the amyloid-calcium axis. Future work focusing on the mechanisms of such relationships may inform targets for clinical intervention. PMID:24026422

Koran, Mary Ellen I; Hohman, Timothy J; Thornton-Wells, Tricia A

2014-01-01

400

LDV measurements of periodic fully developed main and secondary flows in a channel with rib-disturbed walls  

Microsoft Academic Search

Laser-Doppler velocimeter measurements of mean velocities, turbulence intensities, and Reynolds stresses are presented for periodic fully developed flows in a channel with square rib-disturbed walls on two opposite sides. Quantities such as the vorticity thickness and turbulent kinetic energy are used to characterize the flow. The investigated flow was periodic in space. The Reynolds number based on the channel hydraulic

T.-M. Liou; Y.-Y. Wu; Y. Chang

1993-01-01

401

X-Ray Measurement of the Spin-down of Calvera: A Radio- and Gamma-Ray-Quiet Pulsar  

NASA Astrophysics Data System (ADS)

We measure spin-down of the 59 ms X-ray pulsar Calvera by comparing the XMM-Newton discovery data from 2009 with new Chandra timing observations taken in 2013. Its period derivative is \\dot{P}=(3.19+/- \\,0.08)\\times 10^{-15}, which corresponds to spin-down luminosity \\dot{E}=6.1\\times 10^{35} erg s-1, characteristic age \\tau _c\\equiv P/2\\dot{P}=2.9\\times 10^5 yr, and surface dipole magnetic field strength Bs = 4.4 × 1011 G. These values rule out a mildly recycled pulsar, but Calvera could be an orphaned central compact object (anti-magnetar), with a magnetic field that was initially buried by supernova debris and is now reemerging and approaching normal strength. We also performed unsuccessful searches for high-energy ?-rays from Calvera in both imaging and timing of >100 MeV Fermi photons. Even though the distance to Calvera is uncertain by an order of magnitude, an upper limit of d < 2 kpc inferred from X-ray spectra implies a ?-ray luminosity limit of <3.3 × 1032 erg s-1, which is less than that of any pulsar of comparable \\dot{E}. Calvera shares some properties with PSR J1740+1000, a young radio pulsar that we show by virtue of its lack of proper motion was born outside of the Galactic disk. As an energetic, high-Galactic-latitude pulsar, Calvera is unique in being undetected in both radio and ?-rays to faint limits, which should place interesting constraints on models for particle acceleration and beam patterns in pulsar magnetospheres.

Halpern, J. P.; Bogdanov, S.; Gotthelf, E. V.

2013-12-01

402

POLE-TO-POLE SOLAR WIND DENSITY FROM ULYSSES RADIO MEASUREMENTS  

Microsoft Academic Search

We present new in situ measurements of solar wind electron density as a function of heliolatitude. The data were obtained on Ulysses during its fast transit from south solar pole to north solar pole, at heliocentric distance about 1.5 AU, near the 1996 solar activity minimum. The density is measured accurately using the method of quasi-thermal noise spectroscopy with the

K. Issautier; N. Meyer-Vernet; M. Moncuquet; S. Hoang

1997-01-01

403

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

404

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

405

1985 Voyager 2 Radio Ranging Measurements of Coronal Density: Asymmetry in the Radial Profiles Explained  

NASA Technical Reports Server (NTRS)

An asymmetry in the radial variation of electron density above the cast and west limbs of the Sun was inferred from centimeter wavelength ranging measurements conducted by Voyager 2 during its 1985 solar conjunction. The Voyager 2 ranging measurements, which took place in the heliocentric distance range of 7-40 solar radius, have been compared with the white-light coronagraph measurements of the underlying corona collected by the Mark 3 K-coronameter located at the Mauna Loa Solar Observatory. It is shown that the disparity in radial profiles is not real but is instead caused by longitudinal variations stemming from the probing of significantly different source regions its revealed in the white-light measurements. These results improve our understanding of the probing abilities of ranging measurements and their relationship to white-light measurements. They reinforce the notion that the high-precision and high-sensitivity features of ranging measurements are more fully exploited in the investigation of density variations across the ubiquitous low-contrast raylike structures that permit the corona, rather than in determining radial density profiles.

Woo, Richard

1996-01-01

406

Measuring High-Frequency Humidity, Temperature and Radio Refractive Index in the Surface Layer.  

National Technical Information Service (NTIS)

Three different instrument systems are compared in their ability to either directly measure humidity, temperature, and refractive-index fluctuations. Each system consists of a basic instrument--a Lyman-alpha hygrometer, an infrared absorption hygrometer o...

J. T. Priestley R. J. Hill

1985-01-01

407

Radio-frequency impedance measurements using a tunnel-diode oscillator technique  

NASA Astrophysics Data System (ADS)

A resonant method based on a tunnel-diode oscillator for precision measurements of relative impedance changes in materials is described. The system consists of an effective self-resonant LC tank circuit driven by a forward-biased tunnel diode operating in its negative resistance region. Samples under investigation are placed in the core of an inductive coil and impedance changes are determined directly from the measured shift in resonance frequency. A customized low temperature insert is used to integrate this experiment with a commercial Model 6000 Physical Property Measurement System (Quantum Design). Test measurements on a manganese-based perovskite sample exhibiting colossal magnetoresistance indicate that this method is well suited to study the magnetoimpedance in these materials.

Srikanth, H.; Wiggins, J.; Rees, H.

1999-07-01

408

Proposal of radio modulation level controlled VPC is ATM networks and its call blocking improvement  

Microsoft Academic Search

This paper proposes radio modulation controlled level VPC in ATM networks. This technique combines the modulation level controlled radio (MLCR) and virtual path capacity control (VPC) method. The traffic fluctuation can be absorbed flexibly when applying the MLCR system to the radio channel of ATM networks which consist of wired and radio channels. We theoretically analyze the call blocking probability

Masahiro Nishi; Katsutoshi Tsukamoto; Minoru Okada; Shozo Komaki

1996-01-01

409

The 'Brick Wall' radio loss approximation and the performance of strong channel codes for deep space applications at high data rates  

NASA Technical Reports Server (NTRS)

In order to evaluate performance of strong channel codes in presence of imperfect carrier phase tracking for residual carrier BPSK modulation in this paper an approximate 'brick wall' model is developed which is independent of the channel code type for high data rates. It is shown that this approximation is reasonably accurate (less than 0.7dB for low FERs for (1784,1/6) code and less than 0.35dB for low FERs for (5920,1/6) code). Based on the approximation's accuracy, it is concluded that the effects of imperfect carrier tracking are more or less independent of the channel code type for strong channel codes. Therefore, the advantage that one strong channel code has over another with perfect carrier tracking translates to nearly the same advantage under imperfect carrier tracking conditions. This will allow the link designers to incorporate projected channel code performance of strong channel codes into their design tables without worrying about their behavior in the face of imperfect carrier phase tracking.

Shambayati, Shervin

2001-01-01

410

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

411

Direct thrust measurements and modelling of a radio-frequency expanding plasma thruster  

SciTech Connect

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{sup -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{sup -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.; Charles, C.; Boswell, R. W. [Space Plasma, Power and Propulsion Group, Research School of Physics and Engineering, The Australian National University, Canberra ACT 0200 (Australia); Takahashi, K. [Space Plasma, Power and Propulsion Group, Research School of Physics and Engineering, The Australian National University, Canberra ACT 0200 (Australia); Department of Electrical Engineering and Computer Science, Iwate University, Morioka 020-8551 (Japan)

2011-08-15

412

In situ measurements of subsurface contaminants with a multi-channel laser-induced fluorescence system  

NASA Astrophysics Data System (ADS)

A new multi-channel laser-induced fluorescence (LIF) probe with novel optical fiber probe geometry has been designed and integrated into a cone penetrometer testing (CPT) system for in situ contamination detection. The system is capable of collecting excitation and emission matrices (EEMs) of subsurface contaminants as a function of depth in seconds. Compared to our previous multi-channel LIF-CPT system, the new system is faster and more compact, with reduced probe size and sampling area. This article describes the first field demonstration of the system at Hanscom Air Force Base, Massachusetts. One contaminated site within the base was characterized through in situ measurements of 26 LIF-CPT pushes. To validate the LIF results, core samples taken at five locations were analyzed by both on-site LIF measurements and by off-site laboratory analyses with EPA methods. The comparison of the LIF and laboratory results is presented, along with the results of the in situ measurements.

Wu Pepper, Jane; Wright, Andrew O.; Kenny, Jonathan E.

2002-01-01

413

Radio sociology  

NASA Astrophysics Data System (ADS)

A work was conducted, using radio telemetry, to locate a migrating, radio-tagged, sharp-shinned hawk. The hawk was monitored through the noise radiation it created. The hawk was found. During this study, it was found that the concentration of population corresponds with areas of increased noise temperature. Through this study, a bigger study was planned. The study would involved the relationship between a place's radiation signature and its other attributes, such as economic type, population, geographic concentration. The method of radio sociology would be used to track the sources of radio noise.

Swenson, George W., Jr.

1996-04-01

414

Satellite-to-indoor broadband channel measurements at 1.51 GHz and 5.2 GHz  

Microsoft Academic Search

To investigate the satellite-to-indoor wave propagation channel for navigation applications the German Aerospace Center conducted broadband channel sounder measurements using a mobile crane as transmitter platform with the receiver being placed indoors. Using this setup, measurements were performed for L-band at 1.51 GHz and C-band at 5.2 GHz with a broadband signal of 100 MHz bandwidth. Results are given in

Thomas Jost; Wei Wang; Armin Dammann; Uwe-Carsten Fiebig; Michael Walter; Frank Schubert

2009-01-01

415

Acetylcholine Receptor (from Electrophorus electricus): A Comparison of Single-Channel Current Recordings and Chemical Kinetic Measurements  

Microsoft Academic Search

We report a direct comparison between two types of measurements of the dynamic properties of the acetylcholine receptor: single-channel currents recorded using the patch-clamp technique and chemical kinetic measurements. Electrophorus electricus electroplax cells, and membrane vesicles prepared from these cells, were used. Such a comparison, and single-channel currents recorded from these cells, have not previously been reported. We first give

George P. Hess; Hans-Albert Kolb; Peter Lauger; Ernest Schoffeniels; Werner Schwarze

1984-01-01

416

Millimeter-Wave Schottky Mixer Receivers for Applications in Antenna Measurements and Radio Astronomy.  

National Technical Information Service (NTIS)

The document contains 6 individual papers. In paper 1, an embedding network for a single-ended whisker-contacted millimeter wave mixer is developed. This is based on scaled model measurements at 2.5-12 GHz (from the fundamental to the third harmonic band)...

A. O. Lehto

1990-01-01

417

Results of Sun Measurements at the Metsaehovi Radio Research Station at 37 Ghz (Autumn 1978).  

National Technical Information Service (NTIS)

Results of Sun radiation measurements at 8mm (37 GHz), performed with a 13.7m radome covered dish, are presented. Several high resolution maps of the whole Sun were drawn by computer plotter. The development of typical active areas over the course of seve...

S. Urpo

1979-01-01

418

Increasing fluxes of S5 1044+71 measured with RATAN-600 radio telescope  

NASA Astrophysics Data System (ADS)

We report about the growing fluxes of the quasar S5 1044+71, identified with the FERMI source 2FGL J1048.3+714, since detection of the high state in the rest of January 2014 (ATEL #5792). We continue measurements and again detect the increase of the flux densities at frequencies 8.2-21.7 GHz in February.

Trushkin, S. T.; Mingaliev, M. G.; Sotnikova, Yu. V.; Erkenov, A.; Udovitskij, R. Yu.; Mufakharov, T. V.

2014-02-01

419

Inconsistencies in Tropical Tropopause Temperatures Between Radiosonde and GPS Radio Occultation Measurements  

Microsoft Academic Search

Accurate temperature measurements at the tropical tropopause are critical to diagnosing the relationship between water vapor saturation mixing ratio and stratospheric water vapor and, accordingly, the mechanisms for stratosphere-troposphere exchange. The radiosonde network has provided the most accurate temperature record in the tropics to date, but a self-consistent temperature mapping of the tropical tropopause layer (TTL) with radiosonde data is

J. R. Spackman; S. S. Leroy; E. J. Moyer; C. O. Ao; E. M. Weinstock; J. G. Anderson

2004-01-01

420

Acoustical Noise Measurements as Well as Radio and TV Interferences around the Nibe Wind Turbines.  

National Technical Information Service (NTIS)

During 1982-1983 a number of noise measurements around the two wind turbines, mill A and mill B, at Nibe was carried out under the Wind Program of the Danish Ministry of Energy and the Research Association of the Danish Electricity Supply Undertakings. Th...

1984-01-01

421

A new emissive-probe method for electron temperature measurement in radio-frequency plasmas  

SciTech Connect

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{sup 11}-2.8x10{sup 12} cm{sup -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.

Kusaba, Kouta; Shindo, Haruo [Department of Information Telecommunication and Electronics, Tokai University, Kita-kaname 1117, Hiratsuka 259-1292 (Japan)

2007-12-15

422

Direct thrust measurements and modelling of a radio-frequency expanding plasma thruster  

Microsoft Academic Search

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

T. Lafleur; K. Takahashi; C. Charles; R. W. Boswell

2011-01-01

423

Solar wind electron densities from Viking dual-frequency radio measurements  

SciTech Connect

Simultaneous phase coherent, two-frequency measurements of the time delay between the Earth station and the Viking spacecraft have been analyzed in terms of the electron density profiles from 4 solar radii (R/sub sun/) to 200 R/sub sun/. The measurements were made during a period of solar activity minimum (1976--1977) and show a strong solar latitude effect. The data were analyzed with both a model independent, direct numerical inversion technique and with model fitting, yielding essentially the same results. It is shown that the solar wind density can be represented by two power laws near the solar equator proportional to r/sup -2.7/ and r/sup -2.04/. However, the more rapidly falling term quickly disappears at moderate latitudes (approx.20/sup 0/), leaving only the inverse-square behavior.

Muhleman, D.O.; Anderson, J.D.

1981-08-01

424

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

425

Precise measurements of radio-frequency magnetic susceptibility in (anti)ferromagnetic materials  

Microsoft Academic Search

Dynamic magnetic susceptibility, $\\\\chi$, was studied in several intermetallic\\u000amaterials exhibiting ferromagnetic, antiferromagnetic and metamagnetic\\u000atransitions. Precise measurements by using a 14 MHz tunnel diode oscillator\\u000a(TDO) allow detailed insight into the field and temperature dependence of\\u000a$\\\\chi$. In particular, local moment ferromagnets show a sharp peak in $\\\\chi(T)$\\u000anear the Curie temperature, $T_c$. The peak amplitude decreases and shifts

M. D. Vannette; A. Safa-Sefat; S. Jia; S. A. Law; G. Lapertot; S. L. Bud; P. C. Canfield; J. Schmalian; R. Prozorov

2007-01-01

426

Radio wave propagation measurements in tunnel entrance environment for intelligent transportation systems applications  

Microsoft Academic Search

Underground environments are of great interest to intelligent transportation system (ITS) applications, since they occur frequently in both urban and rural situations, and have peculiar propagation characteristics. This investigation includes two of the major fields in ITS applications: road-to-vehicle, and vehicle-to-vehicle communications. Besides that, the propagation measurements presented also focus on the transition effects when moving between the regions outside

A. V. B. da Silva; M. Nakagawa

2001-01-01

427

Precise measurements of radio-frequency magnetic susceptibility in ferromagnetic and antiferromagnetic materials  

NASA Astrophysics Data System (ADS)

Dynamic magnetic susceptibility, ?, was studied in several intermetallic materials exhibiting ferromagnetic, antiferromagnetic and metamagnetic transitions. Precise measurements by using a 14 MHz tunnel diode oscillator (TDO) allow detailed insight into the field and temperature dependence of ?. In particular, local moment ferromagnets show a sharp peak in ?(T) near the Curie temperature, TC. The peak amplitude decreases and shifts to higher temperatures with very small applied dc fields. Anisotropic measurements of CeVSb3 show that this peak is present provided the magnetic easy axis is aligned with the excitation field. In a striking contrast, small moment, itinerant ferromagnets (i.e., ZrZn2) show a broad maximum in ?(T) that responds differently to applied field. We believe that TDO measurements provide a very sensitive way to distinguish between local and itinerant moment magnetic orders. Local moment antiferromagnets do not show a peak at the Néel temperature, TN, but only a sharp decrease of ? below TN due to the loss of spin-disorder scattering changing the penetration depth of the ac excitation field. Furthermore, we show that the TDO is capable of detecting changes in spin order as well as metamagnetic transitions. Finally, critical scaling of ?(T,H) in the vicinity of TC is discussed in CeVSb3 and CeAgSb2.

Vannette, M. D.; Sefat, A. S.; Jia, S.; Law, S. A.; Lapertot, G.; Bud'ko, S. L.; Canfield, P. C.; Schmalian, J.; Prozorov, R.

428

Analysis of single pulse radio flux measurements of PSR B1133+16 at 4.85 and 8.35 GHz  

NASA Astrophysics Data System (ADS)

We show the results of microsecond resolution radio data analysis focused on flux measurements of single pulses of PSR B1133+16. The data were recorded at 4.85 and 8.35 GHz with 0.5- and 1.1-GHz bandwidth, respectively, using Radio Telescope Effelsberg (Max-Planck-Institut für Radioastronomie). The most important conclusion of the analysis is that the strongest single pulse emission at 4.85 and 8.35 GHz contributes almost exclusively to the trailing part of the leading component of the pulsar mean profile, whereas studies at lower frequencies report that the contribution is spread almost uniformly, covering all phases of the pulsar mean profile. We also estimate the radio emission heights to be around 1-2 per cent of the light-cylinder radius, which is in agreement with previous studies. Additionally, these observations allowed us to add two more measurements of the flux density to the PSR B1133+16 broad-band radio spectrum, covering frequencies from 16.7 MHz up to 32 GHz. We fit two different models to the spectrum: a broken power law and a spectrum based on the flicker-noise model, which represents the spectrum in a simpler, but similarly accurate, way.

Krzeszowski, K.; Maron, O.; S?owikowska, A.; Dyks, J.; Jessner, A.

2014-05-01

429

Experimental measurements in a radio frequency discharge heated supersonic flow: Evaluation of a potential electric propulsion thruster.  

National Technical Information Service (NTIS)

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 ...

P. J. Wantuck D. E. Hull

1991-01-01

430

Autonomous Measurements of Bridge Pier and Abutment Scour using Motion-Sensing Radio Transmitters, Tech Transfer Summary.  

National Technical Information Service (NTIS)

The main objective of this study is to evaluate the capabilities of Radio Frequency IDentification (RFID) technology in collecting field data and remotely monitoring bridge scour. RFID is a wireless automated identification technology that utilizes waves ...

M. Elhakeem T. N. Papanicolaou

2010-01-01

431

A Comparative Study of Measured Amplitude and Phase Perturbations of VLF and LF Radio Signals Induced by Solar Flares  

NASA Astrophysics Data System (ADS)

Very Low Frequency (VLF) and Low Frequency (LF) signal perturbations were examined to study ionospheric disturbances induced by solar X-ray flares in order to understand processes involved in propagation of VLF/LF radio signals over short paths and to estimate specific characteristics of each short path. The receiver at the Belgrade station is constantly monitoring the amplitude and phase of a coherent and subionospherically propagating LF signal operated in Sicily NSC at 45.90 kHz, and a VLF signal operated in Isola di Tavolara ICV at 20.27 kHz, with the great circle distances of 953 km and 976 km, respectively. A significant number of similarities between these short paths is a direct result of both transmitters and the receiver's geographic location. The main difference is in transmitter frequencies. From July 2008 to February 2014 there were about 200 events that were chosen for further examination. All selected examples showed that the amplitude and phase of VLF and LF signals were perturbed by solar X-ray flares occurrence. This six-year period covers both minimum and maximum of solar activity. Simultaneous measurement of amplitude and phase of the VLF/LF signals during a solar flare occurrence was applied to evaluate the electron density profile versus altitude, to carry out the function of time over the middle Europe.

Sulic, D. M.; Sreckovic, V. A.

2014-06-01

432

Modification of a whole-body NMR imager into a radio frequency EPR spectrometer suitable for in vivo measurements  

NASA Astrophysics Data System (ADS)

We report the modification of a low-field whole-body NMR imager to allow radio frequency EPR spectroscopy. The instrument is designed to give optimum sensitivity for in vivo detection of free radicals. The RF circuit is able to operate over a wide frequency range (240 - 320 MHz) and is designed to handle input power levels of up to 12.5 W. The EPR resonator is of the loop - gap type suitable for samples up to 400 ml. A remote resonator coupling method has been developed enabling convenient matching adjustment. An automatic frequency control circuit is able to adjust for frequency deviations caused by animal motion. Where possible, existing imager hardware and commercially available instruments have been used. The instrument is controlled from a central computer via an IEEE 488 instrumentation bus. Here we present sensitivity measurements obtained from a variety of large aqueous samples containing nitroxide free radicals. We show that the instrument is suitable for the detection of exogenous free radicals in 200 g rats.

McCallum, S. J.; Alecci, M.; Lurie, D. J.

1996-07-01

433

Radio-Frequency Illuminated Superconductive Disks: Reverse Josephson Effects and Implications for Precise Measuring of Proposed Gravity Effects  

NASA Technical Reports Server (NTRS)

We have previously reported results using a high precision gravimeter to probe local gravity changes in the neighborhood of large bulk-processed high-temperature superconductors. It have been indicated three essential components to achieve anomalous gravity effects, namely large, two-layer high-temperature YBCO superconductors, magnetic levitation and AC input in the form of radio-frequency (RF) electromagnetic fields. We report experiments on RF-illuminated (1-15 MHz) superconducting disks with corresponding gravity readings indicating an apparent increase in observed gravity of approximately 3-5 x l0(exp -5)cm/sq s, above and to the side of the superconductor. In this preliminary study, RF- illumination is achieved using a series of large radius (15 cm) spiral antenna with RF power inputs equal to or greater than 90 W. The observed gravitational modification range is significantly lower than the 2.1% gravity modification. The error analyses of thermal and electromagnetic interference in a magnetically shielded gravimeter with vacuum enclosures, Faraday cages and shielded instrument leads, are outlined both experimentally and theoretically. The nearly exact correspondence between the peak gravity effects reported and the well-known peak in AC resistance in superconductors (2-7 MHz, owing to reverse Josephson quantum effects) suggests that electrical resistance will arise in this frequency range and subsequently any trapped magnetic fields in the superconductor may disperse partially into the measuring instrument's local environment. Implications for propulsion initiatives and RF-heating in superconductors will be discussed.

Noever, David A.; Koczor, Ronald J.

1998-01-01

434

College Radio.  

ERIC Educational Resources Information Center

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

Sauls, Samuel J.

435