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1

A Measurement System and the TUG-EEC-Channels Database for the Aeronautical Voice Radio  

Microsoft Academic Search

A system for measuring time-variant impulse re- sponses and a database of such measurements for the aeronaut- ical voice channel are presented. Maximum length sequences (MLS) are transmitted over the voice channel with a standard aeronautical radio and the received signals are recorded. For the purpose of synchronisation, both the transmitted and received signals are recorded in parallel with a

Konrad Hofbauer; Horst Hering; Gernot Kubin

2006-01-01

2

Design of Wideband Mobile Radio Channel Simulators Based on Real-World Measurement Data  

Microsoft Academic Search

In this article, we analyze different ways to estimate the temporal autocorrelation function (TACF) and the frequency correlation function (FCF) of wideband mobile radio channels from real-world channel measurements. The way the TACF and FCF are estimated depends on whether the measured channel is autocorrelation-ergodic with respect to time and\\/or frequency. In either case, it is shown that double averaging,

Dmitry Umansky; Matthias Pätzold

2008-01-01

3

A Wideband Channel Sounder for Car-to-Car Radio Channel Measurements at 5.7 GHz and Results for an Urban Scenario  

Microsoft Academic Search

A channel sounder for wideband car-to-car 2 x 2 multiple input multiple output (MIMO) radio channel measurements at 5.7 GHz with a bandwidth of 1 GHz has been developed. With the use of highly accurate synchronization units a high degree of coherence was achieved. The HHI-channel-sounder has been used in a measurement campaign in typical urban traffic scenarios in Berlin,

Panagiotis Ch. Paschalidis; Mike Wisotzki; Andreas Kortke; Wilhelm Keusgen; Michael Peter

2008-01-01

4

Car-to-car radio channel measurements at 5 GHz: Pathloss, power-delay profile, and delay-Doppler  

E-print Network

Car-to-car radio channel measurements at 5 GHz: Pathloss, power-delay profile, and delay Contact: apaier@nt.tuwien.ac.at Abstract-- We carried out a car­to­infrastructure (C2I) and car­to­car (C2­Doppler spectra in a C2C highway scenario, where both cars were traveling in opposite directions. A pathloss

Zemen, Thomas

5

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.

2006-05-01

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

The radio system-traffic channel  

Microsoft Academic Search

A description is given of the Radio Data System (RDS) facility that allows for transmission of a silent data channel using the sidebands of existing FM radio stations. One of the features developed for RDS is the Traffic Message Channel (TMC), which will offer a low-cost means of providing motorists with digitally encoded traffic data optimized for in-car reception. Significant

P. Davies

1989-01-01

8

NONLINEAR PREDICTION OF MOBILE RADIO CHANNELS: MEASUREMENTS AND MARS MODEL DESIGNS  

E-print Network

a sequence of re­ ceived power measurements or sequences of estimates of a single or multiple coefficients systems is Takens embedding theorem [2], which allows the reconstruction of a state space represen­ tation of a dynam­ ical system in steady state motion on a finite­dimensional manifold in its state space (i

9

Achievable rates in cognitive radio channels  

Microsoft Academic Search

Cognitive radio promises a low cost, highly ?exible alternative to the classic single fre- quency band, single protocol wireless device. By sens- ing and adapting to its environment, such a device is able to flll voids in the wireless spectrum and dramat- ically increase spectral e-ciency. In this paper, the cognitive radio channel is deflned as an n-transmitter, m-receiver interference

Natasha Devroye; Patrick Mitran; Vahid Tarokh

2006-01-01

10

Limits on communications in a cognitive radio channel  

Microsoft Academic Search

In this article we review FCC secondary markets initiatives and how smart wireless devices could be used to increase spectral efficiency. We survey the current proposals for cognitive radio deployment, and present a new, potentially more spectrally efficient model for a wireless channel employing cognitive radios; the cognitive radio channel. This channel models the simplest scenario in which a cognitive

Natasha Devroye; Patrick Mitran; Vahid Tarokh

2006-01-01

11

Channel Bonding in Cognitive Radio Wireless Sensor Networks  

E-print Network

Channel Bonding in Cognitive Radio Wireless Sensor Networks Mubashir Husain Rehmani, St. In this paper, we argue that wireless sensor nodes with cognitive radio capability, to- gether with channel bonding, can help to address these challenges. In this perspective, we discuss cognitive radio wireless

Paris-Sud XI, Université de

12

Characterization of the Indoor Multiantenna Body-to-Body Radio Channel  

Microsoft Academic Search

In this paper, we investigate the wideband body-to-body radio channel with multiple antennas at both ends based on a time-domain radio channel measurement campaign. Four single-element transmitters and eight quad-element receivers were mounted on three test people. Both directional and omnidirectional antennas have been investigated. A comparison between electromagnetic antenna simulations and the measurements shows that the multipath environment reduces

Yu Wang; Ivan B. Bonev; Jesper Ø. Nielsen; IstvÁn Z. Kovacs; Gert F. Pedersen

2009-01-01

13

Analysis of Cognitive Radio Spectrum Access with Optimal Channel Reservation  

Microsoft Academic Search

A Markov chain analysis for spectrum access in licensed bands for cognitive radios is presented and forced termination probability, blocking probability and traffic throughput are derived. In addition, a channel reservation scheme for cognitive radio spectrum handoff is proposed. This scheme allows the tradeoff between forced termination and blocking according to QoS requirements. Numerical results show that the proposed scheme

Xiaorong Zhu; Lianfeng Shen; Tak-shing Yum

2007-01-01

14

Capacity of a Class of Cognitive Radio Channels: Interference Channels With Degraded Message Sets  

Microsoft Academic Search

This correspondence is motivated by two different scenarios. The first is a cognitive radio system where a cognitive radio knows a ldquodumbrdquo radio's message and the second is a sensor network in a correlated field where sensors possessing a nested message structure assist one another's information transmission. Both scenarios are modeled using the framework of discrete memoryless interference channels with

Wei Wu; Sriram Vishwanath; Ari Arapostathis

2007-01-01

15

A simplified stochastic model for the aeronautical mobile radio channel  

Microsoft Academic Search

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

Said M. Elnoubi

1992-01-01

16

Adaptive channel allocation spectrum etiquette for cognitive radio networks  

Microsoft Academic Search

In this work, we propose a game theoretic framework to analyze the behavior of cognitive radios for distributed adaptive channel allocation. We define two different objective functions for the spectrum sharing games, which capture the utility of selfish users and cooperative users, respectively. Based on the utility definition for cooperative users, we show that the channel allocation problem can be

Nie Nie; Cristina Comaniciu

2005-01-01

17

Adaptive Channel Allocation Spectrum Etiquette for Cognitive Radio Networks  

Microsoft Academic Search

In this work, we propose a game theoretic frame- work to analyze the behavior of cognitive radios for distributed adaptive channel allocation. We define two different objective functions for the spectrum sharing games, which capture the utility of selfish users and cooperative users, respectively. Based on the utility definition for cooperative users, we show that the channel allocation problem can

Nie Nie; Cristina Comaniciu

2006-01-01

18

On Channel Power Sensing in Terrestrial Spread Spectrum Packet Radio Networks  

Microsoft Academic Search

The author considers the possibility of obtaining performance gains by using channel power sensing in the channel access protocol of a terrestrial spread-spectrum packet radio network as a generalization of the CSMA (carrier-sense multiple-access) protocol of narrowband networks. Channel load sensing is viewed as a method of estimating the interference at the receiver based on the interference measured at the

Elvino S. Sousa

1989-01-01

19

Distributed computation on unreliable radio channels  

E-print Network

An important topic in wireless networking is the development of reliable algorithms for environments suffering from adversarial interference. This term captures any type of channel disruption outside the control of the ...

Newport, Calvin (Calvin Charles)

2009-01-01

20

Combined Channel Aggregation and Fragmentation Strategy in Cognitive Radio Networks  

E-print Network

In cognitive radio networks, channel aggregation (CA) and channel fragmentation (CF) techniques have been proposed to enhance the spectrum utilization. While previous literatures study them almost independently, in this paper, we combine CA and CF innovatively and present a new spectrum sharing strategy named CAF (Channel Aggregation and Fragmentation). The performance under our strategy is analyzed using a continuous time Markov chain model in terms of blocking probability, dropping probability, spectrum utilization and throughput of secondary users. Both analytical and simulation results show that our strategy lowers the blocking and dropping probabilities and enhances the spectrum utilization and throughput significantly.

Li, Lei; Wang, Kaiwei; Zhou, Wuyang

2012-01-01

21

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

ERIC Educational Resources Information Center

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

Jassem, Harvey C.

22

Development of a fast sampling system for estimation of impulse responses of mobile radio channels  

NASA Astrophysics Data System (ADS)

This paper describes the features of measurement equipment developed to measure impulse response estimates of mobile radio channels in less than a ms per measurement. The development of such equipment was required to measure mobile radio channels in realistic operating scenarios, in a normal sized vehicle moving at typical speeds in different environments. Up to speeds of 70 km/hr, the measurement period is short enough to assume the equipment is measuring the same channel during the whole sampling interval. AT the transmitter end of the measurement system, a wideband signal (10 MHz) is produced by modulating a carrier frequency with a 511 bit pseudo random sequence at 5 Mb/s and transmitted through the radio channel. The received signal is down-converted to 70 MHz and demodulated by a complex demodulator. The quadrature baseband signals at the demodulator outputs are then filtered and sampled at high speed by two fast digitizers. During this process, the data are stored in large memory banks to allow a fast sampling rate during a long period of time. Data are transferred to laser disks for further processing in the laboratory. Impulse response of radio channels are estimated by performing a software correlation between a measurement system back to back reference and real time measurements. A minivan was modified to hold the receiver, digitizers, memory banks and the computer. A shaft encoder was attached to its rear left wheel to trigger measurements while moving. Features of the system are discussed along with the effects of data block length, signal to noise ratio, sampling rate, memory size and phase stability on the design of the measurement equipment. Finally, some measurement results are presented and discussed.

Melancon, Pierre

1994-07-01

23

Fixed channel assignment algorithm for multi-radio multi-channel MESH networks  

Microsoft Academic Search

Summary Recently, multi-radio mesh technology in wireless networks has been under extensive research. This is because of its potential of overcoming the inherent wireless multi-hop throughput, scalability and latency problems caused by the half-duplex nature of the IEEE 802.11. The concept of deploying multiple radios in wireless network access points (APs) has shown a promising way to enhance the channel

Hamed M. K. Alazemi; A. Das; R. Vijaykumar; S. Roy

2008-01-01

24

47 CFR 22.757 - Channels for basic exchange telephone radio systems.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 false Channels for basic exchange telephone...Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED...Systems § 22.757 Channels for basic exchange telephone radio systems. The channels listed in §...

2010-10-01

25

QoS-guaranteed channel selection scheme for cognitive radio networks with variable channel bandwidths  

Microsoft Academic Search

Cognitive radio (CR) network allows fast deployment of wireless technologies to utilize spectrum channels, all with minimal impact on existing primary users. Another challenge in CR networks is the spectrum handoff issue when the primary user (PU) appears in the spectrum band being used by the secondary user (SU). In this paper, unlike the existing spectrum handoff schemes suitable for

Samer T. Talat; Li-Chun Wang

2009-01-01

26

Channel State Prediction in Cognitive Radio, Part I: Response Delays in Practical Hardware Platforms  

E-print Network

Channel State Prediction in Cognitive Radio, Part I: Response Delays in Practical Hardware is the cornerstone of cognitive radio. As a part of the effort toward building a cognitive radio network testbed, we. This work is a part of the effort toward building a cognitive radio network testbed. I. INTRODUCTION

Qiu, Robert Caiming

27

Adaptive and occupancy-based channel selection for unreliable cognitive radio  

E-print Network

Adaptive and occupancy-based channel selection for unreliable cognitive radio networks M. H's wireless networks, radio spectrum is used inefficiently. To counter this issue, Cognitive Radio Networks (CRNs) are designed to allow cognitive radio (CR) nodes (i) utilizing free parts of unlicensed spectrum

Paris-Sud XI, Université de

28

Propagation characteristics on microcellular urban mobile radio channels at 910 MHz  

Microsoft Academic Search

The results of measurements made to determine propagation characteristics on urban mobile radio channels with low base-station antennas and line of sight between the base and mobile units are reported. Results show that multipath propagation conditions would be significantly less severe if small-celled systems were implemented. Root-mean-square delay spread averages computed by considering all multipath signal components with powers greater

ROBERT J. C. BULTITUDE; G. KEITH BEDAL

1989-01-01

29

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

Microsoft Academic Search

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

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

2003-01-01

30

A method for measuring pulsar radio-emission energy  

NASA Astrophysics Data System (ADS)

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

Malofeev, V. M.

31

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.

32

Transmission Techniques and Channel Calibration for Spatial Interweave TDD Cognitive Radio  

E-print Network

1 Transmission Techniques and Channel Calibration for Spatial Interweave TDD Cognitive Radio the problem of beamforming design for a Cognitive Radio (CR) system in which a multiple-input multiple- output Long Term Evolution (LTE). I. INTRODUCTION AND STATE OF THE ART Cognitive Radio [1] (CR) has been

Paris-Sud XI, Université de

33

Features of the Digital Block of a Hardware Simulator for MIMO Radio Channels  

E-print Network

Features of the Digital Block of a Hardware Simulator for MIMO Radio Channels Sylvie Picol, is the realization of a hardware simulator of MIMO propagation channels for UMTS and WLAN applications. The simulator-media services. MIMO (Multiple-Input Multiple-Output) systems make use of antenna arrays at both sides of a radio

Paris-Sud XI, Université de

34

A Framework for Maximum Capacity in Multi-channel Multi-radio Wireless Networks  

E-print Network

before. In this work, we study two problems: In a specific topology, 1) what is the maximum capacity weA Framework for Maximum Capacity in Multi-channel Multi-radio Wireless Networks (Invited Paper) Wei and transmission scheduling. The capacity limit on multi-channel multi-radio wireless networks was seldom addressed

Liu, Xin

35

Measuring Ethical Sensitivity to Radio Messages.  

ERIC Educational Resources Information Center

A study examined whether ethical sensitivity can be measured in response to radio programming. The study was interested in the extent to which a person feels a program is unethical in either its substance or its presentation. Subjects, 17 undergraduates in telecommunications at a large midwestern university, received course credit for their…

Potter, Robert F.

36

Channel selection based on trust and multiarmed bandit in multiuser, multichannel cognitive radio networks.  

PubMed

This paper proposes a channel selection scheme for the multiuser, multichannel cognitive radio networks. This scheme formulates the channel selection as the multiarmed bandit problem, where cognitive radio users are compared to the players and channels to the arms. By simulation negotiation we can achieve the potential reward on each channel after it is selected for transmission; then the channel with the maximum accumulated rewards is formally chosen. To further improve the performance, the trust model is proposed and combined with multi-armed bandit to address the channel selection problem. Simulation results validate the proposed scheme. PMID:24711741

Zeng, Fanzi; Shen, Xinwang

2014-01-01

37

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.

2004-09-01

38

A load aware hybrid channel assignment for Multi-radio Wireless Mesh Network  

Microsoft Academic Search

This paper introduces an efficient solution for channel assignment in Multi-radio Wireless Mesh Network. Basing on the traffic load estimation and the characteristics of mesh routers, we perform channel assignment for their interfaces to transmit packet over multiple channels with the least of interference from others. The primary simulation results show that our algorithm outperforms others.

Tran Minh Trung; Hong Yong Geun; Park Jeong Su

2010-01-01

39

Control channel based MAC-layer configuration, routing and situation awareness for cognitive radio networks  

Microsoft Academic Search

In a cognitive radio (CR) network, MAC-layer configuration involves determining a common set of channels to facilitate communication among participating nodes. Further, the availability of multiple channels and frequent channel switches add to the complexity of route selection. Knowledge of the global network topology can be used to solve the above-described problems. In this paper, we propose a distributed algorithm

Srinivasan Krishnamurthy; Mansi Thoppian; S. Venkatesan; Ravi Prakash

2005-01-01

40

NearOptimal Data Dissemination Policies for MultiChannel, Single Radio  

E-print Network

Information Systems America 75 West Plumeria Drive San Jose, CA 95134 Email: x.qin@samsung.com Abstract We dissemination with multi­channel, single radio sensors, using expected delay as the primary optimization metric

Goldberg, Bennett

41

Radio frequency sensing measurements and methods for location classification in wireless networks  

NASA Astrophysics Data System (ADS)

The wireless radio channel is typically thought of as a means to move information from transmitter to receiver, but the radio channel can also be used to detect changes in the environment of the radio link. This dissertation is focused on the measurements we can make at the physical layer of wireless networks, and how we can use those measurements to obtain information about the locations of transceivers and people. The first contribution of this work is the development and testing of an open source, 802.11b sounder and receiver, which is capable of decoding packets and using them to estimate the channel impulse response (CIR) of a radio link at a fraction of the cost of traditional channel sounders. This receiver improves on previous implementations by performing optimized matched filtering on the field-programmable gate array (FPGA) of the Universal Software Radio Peripheral (USRP), allowing it to operate at full bandwidth. The second contribution of this work is an extensive experimental evaluation of a technology called location distinction, i.e., the ability to identify changes in radio transceiver position, via CIR measurements. Previous location distinction work has focused on single-input single-output (SISO) radio links. We extend this work to the context of multiple-input multiple-output (MIMO) radio links, and study system design trade-offs which affect the performance of MIMO location distinction. The third contribution of this work introduces the "exploiting radio windows" (ERW) attack, in which an attacker outside of a building surreptitiously uses the transmissions of an otherwise secure wireless network inside of the building to infer location information about people inside the building. This is possible because of the relative transparency of external walls to radio transmissions. The final contribution of this dissertation is a feasibility study for building a rapidly deployable radio tomographic (RTI) imaging system for special operations forces (SOF). We show that it is possible to obtain valuable tracking information using as few as 10 radios over a single floor of a typical suburban home, even without precise radio location measurements.

Maas, Dustin C.

42

A review of radio channel models for body centric communications  

NASA Astrophysics Data System (ADS)

human body is an extremely challenging environment for the operation of wireless communications systems, not least because of the complex antenna-body electromagnetic interaction effects which can occur. This is further compounded by the impact of movement and the propagation characteristics of the local environment which all have an effect upon body centric communications channels. As the successful design of body area networks (BANs) and other types of body centric system is inextricably linked to a thorough understanding of these factors, the aim of this paper is to conduct a survey of the current state of the art in relation to propagation and channel models primarily for BANs but also considering other types of body centric communications. We initially discuss some of the standardization efforts performed by the Institute of Electrical and Electronics Engineers 802.15.6 task group before focusing on the two most popular types of technologies currently being considered for BANs, namely narrowband and Ultrawideband (UWB) communications. For narrowband communications the applicability of a generic path loss model is contended, before presenting some of the scenario specific models which have proven successful. The impacts of human body shadowing and small-scale fading are also presented alongside some of the most recent research into the Doppler and time dependencies of BANs. For UWB BAN communications, we again consider the path loss as well as empirical tap delay line models developed from a number of extensive channel measurement campaigns conducted by research institutions around the world. Ongoing efforts within collaborative projects such as Committee on Science and Technology Action IC1004 are also described. Finally, recent years have also seen significant developments in other areas of body centric communications such as off-body and body-to-body communications. We highlight some of the newest relevant research in these areas as well as discussing some of the advanced topics which are currently being addressed in the field of body centric communications.

Cotton, Simon L.; D'Errico, Raffaele; Oestges, Claude

2014-06-01

43

Encoding many channels in the same frequency through radio vorticity: first experimental test  

E-print Network

We have shown experimentally that it is possible to propagate and use the properties of twisted non-monochromatic incoherent radio waves to simultaneously transmit to infinity more radio channels on the same frequency band by encoding them in different orbital angular momentum states. This novel radio technique allows the implementation of, at least in principle, an infinite number of channels on one and the same frequency, even without using polarization or dense coding techniques. An optimal combination of all these physical properties and techniques represents a solution for the problem of radio band congestion. Our experimental findings show that the vorticity of each twisted electromagnetic wave is preserved after the propagation, paving the way for entirely new paradigms in radio communication protocols.

Tamburini, Fabrizio; Sponselli, Anna; Romanato, Filippo; Thidé, Bo; Bianchini, Antonio; Palmieri, Luca; Someda, Carlo G

2011-01-01

44

Channel capacity maximization in cooperative cognitive radio networks using game theory  

Microsoft Academic Search

Cognitive radio network (CRN) has created a significant research interest due to the unique opportunistic spectrum sharing of the channels when not used by the licensed users (known as white spaces). In this paper, we make a unique endeavor in developing a Game theoretic spectrum sharing strategy to compute maximum channel capacity under the following constraints: (i) quality of an

Chittabrata Ghosh; Dharma P. Agrawal; Marepalli B. Rao

2009-01-01

45

Hardware Simulator for MIMO Radio Channels: Design and Features of the Digital Block  

E-print Network

Hardware Simulator for MIMO Radio Channels: Design and Features of the Digital Block Sylvie Picol 1 block of a hardware simulator of MIMO propagation channels for UMTS and WLAN applications. The hardware to offer to general public high-rate multi-media services. MIMO (Multiple-Input Multiple-Output) systems

Paris-Sud XI, Université de

46

Further Steps Towards the Development of a Hardware Simulator for MIMO Radio Channels  

E-print Network

. The capacity improvement of wireless networks has drawn considerable attention to MIMO (Multiple-Input Multiple1233847274 Further Steps Towards the Development of a Hardware Simulator for MIMO Radio Channels, is the realization of a hardware simulator of MIMO propagation channels for UMTS and WLAN applications. The simulator

Paris-Sud XI, Université de

47

Secure cooperative multi-channel spectrum sensing in cognitive radio networks  

Microsoft Academic Search

In this paper, two new counterattacks are proposed to combat Byzantine attacks comprising coalition head and cognitive radio as attackers which target to reduce the number of available channels for sensing in distributed multi-channel cooperative spectrum sensing. In the proposed counterattack for coalition head attack, by using statistical properties of the exchanged SNRs in coalitions, the probability of attack is

Behzad Kasiri; Jun Cai; Attahiru S. Alfa

2011-01-01

48

Measuring the radio audience by the personal interview roster method  

Microsoft Academic Search

Three methods of measuring the radio audience (telephone recall, telephone coincidental, and radio meter record) are described briefly and their advantages and disadvantages considered. The usefulness of the personal interview roster method is presented at somewhat greater length. This method consists of discovering by interview at what times during the preceding few hours the radio was on and then presenting

S. Roslow

1943-01-01

49

Programmable quantum channels and measurements  

E-print Network

We review some partial results for two strictly related problems. The first problem consists in finding the optimal joint unitary transformation on system and ancilla which is the most efficient in programming any desired channel on the system by changing the state of the ancilla. In this respect we present a solution for dimension two for both system and ancilla. The second problem consists in finding the optimal universal programmable detector, namely a device that can be tuned to perform any desired measurement on a given quantum system, by changing the state of an ancilla. With a finite dimension for the ancilla only approximate universal programmability is possible, with minimal dimension increasing function versus the precision of the approximation. We show that one can achieve a dimension growing polynomially versus the precision, and even linearly in specific cases.

Giacomo Mauro D'Ariano; Paolo Perinotti

2005-10-05

50

A digital radio processor for channel demodulation and source decoding of satellite radio programs  

Microsoft Academic Search

New satellite based digital radio standards have been developed. The advantages of these standards (CD-like sound quality, small bandwidth requirements, embedded digital data services) require considerable larger modulation and demodulation efforts because forward error correction and sophisticated data compression techniques are used. The commercial success of these radio systems is closely related to the availability of low cost receiver equipment.

F.-O. Witte; R. Backes; M. Klumpp; W. Sinnhofer; S. Arendt

1996-01-01

51

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

52

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. PMID:22346614

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

2011-01-01

53

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

54

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

55

An experimental investigation of the impact of human shadowing on temporal variation of broadband indoor radio channel characteristics and system performance  

Microsoft Academic Search

This paper reports the results of extensive measurements and analysis of the temporal variations of the indoor radio propagation channel as a result of human traffic. The broadband measurements presented were taken at 5.2 GHz and were carried out in a large laboratory environment. Four antenna configurations were considered: for three sets of measurement the receiver used an omni-directional antenna

P. Hafezi; A. Nix; M. A. Beach

2000-01-01

56

A Score-Based Opportunistic Scheduler for Fading Radio Channels  

E-print Network

transfers to increase the overall sys- tem capacity: instead of wasting radio resources in pro- viding, such as file transfers and Web browsing for instance, allows the system flexibil- ity in scheduling a user deliver high spectral efficiency by using a TDMA-like strategy (the base station (BS) transmits at full

Bonald, Thomas

57

Multichannel broadcast based on home channel for cognitive radio sensor networks.  

PubMed

Considering the limited resources and the dynamic spectrum distribution in the cognitive radio sensor networks (CRSN), a half-duplex Multichannel broadcast protocol for CRSN is presented based on the home channel. This protocol maintains the networks topology only through the home channel, so there is no need for the public channel to transmit the control information and no need for the synchronization. After network initialization, node broadcasts data via home channel in half-duplex transmission way. The simulation results show that, compared with complete broadcast, the proposed protocol effectively reduces broadcast delay and overhead. PMID:25161397

Zeng, Fanzi; Tang, Yuting; Pu, Jianjie

2014-01-01

58

The Rotation Measure Distribution of Radio Galaxies  

NASA Astrophysics Data System (ADS)

Faraday rotation allows the investigation of magnetic fields along the line of sight between an observer and a polarized source. If redshifts can be measured for sources exhibiting Faraday rotation, this would allow for a direct probe of the evolution of cosmic magnetism over time scales of up to 12.5 billion years. Previous studies of rotation measure (RM) and redshift data have been hampered by the small size of available data sets (200-300 sources at most), often drawn from highly inhomogeneous observations. We present a new catalog of over 4000 extragalactic sources with both RM and redshifts. These data were compiled using large-scale surveys and new radio-optical associations, yielding a sample size that is more than an order of magnitude larger than any previous study. Our sample includes more than 1000 sources at a redshift z>1. We present a statistical analysis of our catalog, from which we find that the variance of the RM distribution, after subtraction of the RM contribution from our own Milky Way, increases slightly with redshift at a 98.5% confidence level. Further, we show that both residual RM and redshift are correlated with fractional polarization, contributing to the RM-redshift relationship.

Robishaw, Timothy; Hammond, A.; Gaensler, B.

2012-05-01

59

SINCGARS (Single-Channel Ground/Airborne Radio System) operator performance decay  

NASA Astrophysics Data System (ADS)

The Single-Channel Ground/Airborne Radio System (SINCGARS) is scheduled to replace the Army's VRC-12 and PRC-77 radios. However, SINCGARS is more complex to operate and requires more training. This study examined the decay of operational skills and knowledge in two groups of recently trained operators who went without exposure to SINCGARS for several weeks. Performance levels were measured with the SINCGARS Learning-Retention Test (SLRT), a simulated hands-on performance test emphasizing skills and operational knowledge retention. The results provided tentative indications that operators may lose about 10 percent of their prior performance levels within the first few weeks. This figure is expected to vary considerably, depending on the type of soldier, the length of the nonexposure period, and other conditions. It was also found that performance level was correlated with soldiers' Armed Services Vocational Aptitude Battery (ASVAB) General Technical (GT) scores. Correlations between GT and SLRT scores obtained at two different times were .43 and .50, respectively. However, no relation was observed between performance decay and GT. Further evaluation of operator performance decay needs to be done to determine the effect of longer periods of nonexposure (e.g., 60 and 90 days).

Palmer, Richard L.; Buckalew, Louis W.

1988-11-01

60

Optimization-based channel constrained data aggregation routing algorithms in multi-radio wireless sensor networks.  

PubMed

In wireless sensor networks, data aggregation routing could reduce the number of data transmissions so as to achieve energy efficient transmission. However, data aggregation introduces data retransmission that is caused by co-channel interference from neighboring sensor nodes. This kind of co-channel interference could result in extra energy consumption and significant latency from retransmission. This will jeopardize the benefits of data aggregation. One possible solution to circumvent data retransmission caused by co-channel interference is to assign different channels to every sensor node that is within each other's interference range on the data aggregation tree. By associating each radio with a different channel, a sensor node could receive data from all the children nodes on the data aggregation tree simultaneously. This could reduce the latency from the data source nodes back to the sink so as to meet the user's delay QoS. Since the number of radios on each sensor node and the number of non-overlapping channels are all limited resources in wireless sensor networks, a challenging question here is to minimize the total transmission cost under limited number of non-overlapping channels in multi-radio wireless sensor networks. This channel constrained data aggregation routing problem in multi-radio wireless sensor networks is an NP-hard problem. I first model this problem as a mixed integer and linear programming problem where the objective is to minimize the total transmission subject to the data aggregation routing, channel and radio resources constraints. The solution approach is based on the Lagrangean relaxation technique to relax some constraints into the objective function and then to derive a set of independent subproblems. By optimally solving these subproblems, it can not only calculate the lower bound of the original primal problem but also provide useful information to get the primal feasible solutions. By incorporating these Lagrangean multipliers as the link arc weight, the optimization-based heuristics are proposed to get energy-efficient data aggregation tree with better resource (channel and radio) utilization. From the computational experiments, the proposed optimization-based approach is superior to existing heuristics under all tested cases. PMID:22408553

Yen, Hong-Hsu

2009-01-01

61

Ergodic Capacity of Cognitive Radio under Imperfect Channel State Information  

E-print Network

A spectrum-sharing communication system where the secondary user is aware of the instantaneous channel state information (CSI) of the secondary link, but knows only the statistics and an estimated version of the secondary transmitter-primary receiver (ST-PR) link, is investigated. The optimum power profile and the ergodic capacity of the secondary link are derived for general fading channels (with continuous probability density function) under average and peak transmit-power constraints and with respect to two different interference constraints: an interference outage constraint and a signal-to-interference outage constraint. When applied to Rayleigh fading channels, our results show, for instance, that the interference constraint is harmful at high-power regime in the sense that the capacity does not increase with the power, whereas at low-power regime, it has a marginal impact and no-interference performance corresponding to the ergodic capacity under average or peak transmit power constraint in absence of ...

Rezk, Zouheir

2012-01-01

62

AUTOMATIC RADIO TRACKING OF FISH IN EXPERIMENTAL CHANNELS  

EPA Science Inventory

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

63

Eliminating adjacent-channel interference in satellite-based General Packet Radio Service (GPRS) systems  

Microsoft Academic Search

This paper presents a method for eliminating adjacent-channel interference (ACI) in satellite-based General Packet Radio Service (GPRS) systems using a new fuzzy adaptive filters (FAF). We validate the reasons for using such a filter by analyzing the Bayesian detector in which some parameter uncertainties exist. A clustering method is used to adaptively design the parameters of the FAF. Simulation results

Qilian Liang

2002-01-01

64

Residual White Space Distribution-Based Opportunistic Channel Access for Cognitive Radio Enabled Devices  

E-print Network

(usually referred as white spaces or holes) in various spectrum bands by allow- ing secondary devicesResidual White Space Distribution-Based Opportunistic Channel Access for Cognitive Radio Enabled to use these white spaces for their communication. The OSA scheme strives to maximize the secondary node

Sahoo, Anirudha

65

High-resolution spectral analysis techniques for estimating the impulse response of indoor radio channels  

Microsoft Academic Search

The authors present a new approach for estimating the impulse response of indoor radio channels. The technique is based on the use of (1) the information theoretical criteria, (2) a high-resolution spectral analysis technique, and (3) the principal component analysis. It is shown that the new technique can be used to overcome difficulties experienced by conventional methods and, as a

Titus Lo; J. Litva; R. J. C. Bultitude

1992-01-01

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

Bluetooth radio network performance: measurement results and simulation models  

Microsoft Academic Search

When designing new communication systems, results from simulations determine a large part of the system parameters. As simulations simplify reality according to the investigated aspects, the results obtained strongly depend on the assumptions made for the simplifications. This paper now presents real-life measurement results obtained in a Bluetooth radio network testbed and compares these results with models used in radio

Kirsten Matheus; Sverker Magnusson

2004-01-01

68

A Quantitative Analysis of Spectral Occupancy Measurements for Cognitive Radio  

Microsoft Academic Search

Cognitive radio (CR) is viewed as a possible solution to the problem of radio spectrum congestion. The CR technique utilizes a temporarily unoccupied licensed band. Before investigating the technical and political implications of CR, it is necessary to know to what extent the licensed bands are temporally unoccupied. This paper describes a spectral occupancy measurement campaign conducted in the frequency

Robin I. C. Chiang; Gerard B. Rowe; Kevin W. Sowerby

2007-01-01

69

Comparasion of Energy Detection in Cognitive Radio over different fading channels  

NASA Astrophysics Data System (ADS)

With the advance of wireless communications, the problem of bandwidth scarcity has become more prominent. Cognitive radio technology has come out as a way to solve this problem by allowing the unlicensed users to use the licensed bands opportunistically. To sense the existence of licensed users, many spectrum sensing techniques have been devised. In this paper, energy detection and cyclic prefix is used for spectrum sensing.The comparison of ROC curves has been done for various wireless fading channels using squaring and cubingoperation,the improvement has gone as high as up to 0.6 times for AWGN channel and 0.4 times for Rayleigh channel as we go from squaring to cubing operation in an energy detector. Closed form expressions for Probability of detection for AWGN and Rayleigh channels are described.Nakagami fading channel shows worst results .

Buttar, Simar

2012-07-01

70

Radio frequency interference measurements in Indonesia. A survey to establish a radio astronomy observatory  

NASA Astrophysics Data System (ADS)

We report the first measurements of radio frequency spectrum occupancy performed at sites aimed to host the future radio astronomy observatory in Indonesia. The survey is intended to obtain the radio frequency interference (RFI) environment in a spectral range from low frequency 10 MHz up to 8 GHz. The measurements permit the identification of the spectral occupancy over those selected sites in reference to the allocated radio spectrum in Indonesia. The sites are in close proximity to Australia, the future host of Square Kilometre Array (SKA) at low frequency. Therefore, the survey was deliberately made to approximately adhere the SKA protocol for RFI measurements, but with lower sensitivity. The RFI environment at Bosscha Observatory in Lembang was also measured for comparison. Within the sensitivity limit of the measurement equipment, it is found that a location called Fatumonas in the surrounding of Mount Timau in West Timor has very low level of RFI, with a total spectrum occupancy in this measured frequency range being about 1 %, mostly found at low frequency below 20 MHz. More detailed measurements as well as a strategy for a radio quiet zone must be implemented in the near future.

Hidayat, Taufiq; Munir, Achmad; Dermawan, Budi; Jaelani, Anton Timur; Léon, Stéphane; Nugroho, Dading Hadi; Suksmono, Andriyan Bayu; Mahasena, Putra; Premadi, Premana Wardayanti; Herdiwijaya, Dhani; Kunjaya, Chatief; Dupe, Zadrach Ledoufij; Brahmantyo, Budi; Mandey, Denny; Yusuf, Muhammad; Tri Wulandari, Hesti Retno; Arief, Falahuddin; Irfan, Muhammad; Puri Jatmiko, Agus Triono; Akbar, Evan Irawan; Sianturi, Hery Leo; Tanesib, Jehunias Leonidas; Warsito, Ali; Utama, Judhistira Aria

2014-02-01

71

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

72

On the Spectrum Handoff for Cognitive Radio Ad Hoc Networks without Common Control Channel  

E-print Network

Cognitive radio (CR) technology is a promising solution to enhance the spectrum utilization by enabling unlicensed users to exploit the spectrum in an opportunistic manner. Since unlicensed users are temporary visitors to the licensed spectrum, they are required to vacate the spectrum when a licensed user reclaims it. Due to the randomness of the appearance of licensed users, disruptions to both licensed and unlicensed communications are often difficult to prevent. In this chapter, a proactive spectrum handoff framework for CR ad hoc networks is proposed to address these concerns. In the proposed framework, channel switching policies and a proactive spectrum handoff protocol are proposed to let unlicensed users vacate a channel before a licensed user utilizes it to avoid unwanted interference. Network coordination schemes for unlicensed users are also incorporated into the spectrum handoff protocol design to realize channel rendezvous. Moreover, a distributed channel selection scheme to eliminate collisions a...

Song, Yi

2011-01-01

73

Pilot symbol assisted channel estimation for OFDM-based cognitive radio systems  

NASA Astrophysics Data System (ADS)

In this article, challenges regarding the provision of channel state information (CSI) in non-contiguous orthogonal frequency division multiplexing (NC-OFDM) cognitive radio (CR) systems are addressed. We propose a novel scheme that utilizes cross entropy (CE) optimization together with an analytical pilot power distribution technique to design pilot symbols that minimizes the channel estimate mean squared error (MSE) of frequency-selective channels. The optimal selection of pilot subcarriers is a combinatorial problem that requires heavy computations. To reduce the computational complexity, the CE optimization is utilized to determine the position of pilot subcarriers. Then, for a given pilot placement obtained by the CE algorithm, a closed form expression to obtain optimal pilot power distribution is employed. Simulation results indicate that, the proposed pilot symbol design provides better channel estimate MSE as well as the bit error rate (BER) performance when compared with the conventional equal powered pilot design.

Manasseh, Emmanuel; Ohno, Shuichi; Nakamoto, Masayoshi

2013-12-01

74

Progress in Air Shower Radio Measurements: Detection of Distant Events  

E-print Network

Data taken during half a year of operation of 10 LOPES antennas (LOPES-10), triggered by EAS observed with KASCADE-Grande have been analysed. We report about the analysis of correlations of radio signals measured by LOPES-10 with extensive air shower events reconstructed by KASCADE-Grande, including shower cores at large distances. The efficiency of detecting radio signals induced by air showers up to distances of 700 m from the shower axis has been investigated. The results are discussed with special emphasis on the effects of the reconstruction accuracy for shower core and arrival direction on the coherence of the measured radio signal. In addition, the correlations of the radio pulse amplitude with the primary cosmic ray energy and with the lateral distance from the shower core are studied.

W. D. Apel; T. Asch; A. F. Badea; LOPES Collaboration

2006-07-21

75

High resolution of electromagnetic waves in time-varying radio channels  

Microsoft Academic Search

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

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

1997-01-01

76

Secured Distributed Cognitive MAC and Complexity Reduction in Channel Estimation for the Cross Layer based Cognitive Radio Networks  

E-print Network

Secured opportunistic Medium Access Control (MAC) and complexity reduction in channel estimation are proposed in the Cross layer design Cognitive Radio Networks deploying the secured dynamic channel allocation from the endorsed channel reservation. Channel Endorsement and Transmission policy is deployed to optimize the free channel selection as well as channel utilization to cognitive radio users. This strategy provide the secured and reliable link to secondary users as well as the collision free link to primary users between the physical and MAC layers which yields the better network performance. On the other hand, Complexity Reduction in Minimum Mean Square Errror (CR-MMSE) and Maximum Likelihood (CR-ML) algorithm on Decision Directed Channel Estimation (DDCE) is deployed significantly to achieve computational complexity as Least Square (LS) method. Rigorously, CR-MMSE in sample spaced channel impulse response (SS-CIR) is implemented by allowing the computationally inspired matrix inversion. Regarding CR-ML...

Shakhakarmi, Niraj

2012-01-01

77

Channel Exploration and Exploitation with Imperfect Spectrum Sensing in Cognitive Radio Networks  

E-print Network

In this paper, the problem of opportunistic channel sensing and access in cognitive radio networks when the sensing is imperfect and a secondary user has limited traffic to send at a time is investigated. Primary users' statistical information is assumed to be unknown, and therefore, a secondary user needs to learn the information online during channel sensing and access process, which means learning loss, also referred to as regret, is inevitable. In this research, the case when all potential channels can be sensed simultaneously is investigated first. The channel access process is modeled as a multi-armed bandit problem with side observation. And channel access rules are derived and theoretically proved to have asymptotically finite regret. Then the case when the secondary user can sense only a limited number of channels at a time is investigated. The channel sensing and access process is modeled as a bi-level multi-armed bandit problem. It is shown that any adaptive rule has at least logarithmic regret. Th...

Zhang, Zhou; Tan, Peng; Slevinsky, Jim

2012-01-01

78

Measurement technique of the Giotto radio science experiment  

NASA Technical Reports Server (NTRS)

The paper describes the technique used to record time delay and waveform measurements for the Giotto radio science experiment of ESA's mission to comet Halley. The data were taken by using either two-way measurements (during pre- and post-encounter) or one-way measurements (during encounter with comet Halley), the downlink of the radio signal of the Giotto spacecraft being received at 8.4 GHz by the 64 m tracking stations of NASA's Deep Space Network (DSN). The waveform measurements were obtained at a sampling frequency of 50 kHz with an open-loop receiver assembly at DSN station Canberra as recently used for the Voyager/Uranus fly-by. Performance and calibration data are given as relevant to the radio subsystems on the ground and aboard Giotto.

Edenhofer, P.; Buschert, H.; Bird, M. K.; Esposito, P. B.; Porsche, H.

1987-01-01

79

Air Shower Measurements with the LOPES Radio Antenna Array  

E-print Network

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 (LOPES-STAR) 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.

A. Haungs; for the LOPES collaboration

2008-11-12

80

Simulation studies of GPS radio occultation measurements  

NASA Astrophysics Data System (ADS)

The atmospheric propagation of GPS signals under multipath conditions and their detection are simulated. Using the multiple phase screen method, C/A-code modulated L1 signals are propagated through a spherically symmetric refractivity field derived from a high-resolution radio sonde observation. The propagated signals are tracked by a GPS receiver implemented in software and converted to refractivity profiles by the canonical transform technique and the Abel inversion. Ignoring noise and assuming an ideal receiver tracking behavior, the true refractivity profile is reproduced to better than 0.1% at altitudes above 2 km. The nonideal case is simulated by adding between 14 and 24 dB of Gaussian white noise to the signal and tracking the signal with a receiver operating at 50 and 200 Hz sampling frequency using two different carrier phase detectors. In the upper troposphere and stratosphere the fractional refractivity retrieval error is below 0.3% for 50 Hz sampling and below 0.15% for 200 Hz sampling. In the midtroposphere down to altitudes of about 2 km, phase-locked loop tracking induces negative fractional refractivity biases on the order of -1 to -2% at 50 Hz sampling frequency. Modifications to the receiver tracking algorithm significantly improve the retrieval results. In particular, replacing the carrier loop's two-quadrant phase extractor with a four-quadrant discriminator reduces the refractivity biases by a factor of 5; increasing the sampling frequency from 50 to 200 Hz gains another factor of 2.

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

2003-10-01

81

802.11s based multi-radio multi-channel mesh networking for fractionated spacecraft  

NASA Astrophysics Data System (ADS)

802.11s is a new IEEE standard for mesh networking. It defines the protocols needed to build mobile ad hoc networks that operate over 802.11a, b, g and n waveforms running on inexpensive, and high performance commercial WiFi stations. We have developed a new capability to add to the 802.11s that uses multiple directional radio links that can operate simultaneously within a single mesh node. This is the basis of our multi-channel multi-radio mesh network used in the DARPA F6 program called F6Net. We have developed an analysis and emulation facility that lets us model the F6Net and evaluate the performance in a real world experimentation setup. This paper presents an “ Over-the-Air” experimentation testbed that uses standard Commercial Off-The-Shelf (COTS) 2.4GHz WiFi dongles in an indoor environment, and a shared-code simulation testbed that uses hardware simulated drivers within NS3's channel simulation facility to test 80211s network. To the best of our knowledge, this is the first work that provides a comprehensive evaluation platform with a full-fledged COTS hardware/software prototype to evaluate 802.11s network. Furthermore, we explain the design and development of multi-radio mesh extension for 802.11s that yields a robust and scalable mesh network suitable for clusters of LEO satellites.

Michel, Tony; Thapa, Bishal; Taylor, Steve

82

Demand Assignment Multiple Access and Dynamic Channel Allocation Strategies for Integrating Radio Dispatch and Telephone Services Over Mobile Satellite Systems  

Microsoft Academic Search

The authors discuss the performance analyses of a novel demand assignment multiple access (DAMA) scheme addressing the special characteristics of the mobile radio service (MRS), and a new method for dynamically allocating a common pool of channels to both MRS and mobile telephone service (MTS) to improve channel utilization. The new DAMA scheme makes use of call queuing, batch processing,

Chris J. Powell; Victor C. M. Leung

1992-01-01

83

Path loss and matched filter gain of free space and ground reflection channels for UWB radio systems  

Microsoft Academic Search

In this paper, the path loss and matched filter gain of free space and ground reflection channels for UWB radio systems are proposed. The passband rectangular pulse with specific center frequency and bandwidth is used as the transmitted signal. The complex form Friis' transmission formula is used for the UWB channel. The received signal is evaluated. The UWB path loss

S. Promwong; J. Takada; P. Supanakoon; P. Tangtisanon

2004-01-01

84

Towards Cognitive Radio Networks: Spectrum Utilization Measurements in Suburb Environment  

E-print Network

Towards Cognitive Radio Networks: Spectrum Utilization Measurements in Suburb Environment Václav with an overall approach regarding spectrum utilization in the next generation wireless networks. Index Terms or underutilized frequency spectrum from primary licensed networks and consequently solves the spectrum utilization

Paris-Sud XI, Université de

85

ATS6-satellite radio beacon measurements at Ootacamund, India  

Microsoft Academic Search

In August 1975 the ATS6 was repositioned at 35 deg E. Radio beacon measurements of time delay, Faraday rotation and signal amplitude, made at Ootacamund, India in October 1975, are discussed with emphasis on the problem of determining the Faraday content under essentially transverse propagation conditions. It is shown that at the low geomagnetic latitude of Ootacamund the use of

K. Davies; R. F. Donnelly; R. N. Grubb; P. V. S. Rama Rao; R. G. Rastogi; M. R. Deshpande; H. Chandra; H. O. Vats; G. Sethia

1978-01-01

86

Progress in Understanding Horizontal Resolution of Radio Occultation Measurements  

Microsoft Academic Search

The meaning of high vertical resolution and the ``horizontal'' resolution of radio occultation measurements has been subject to interpretation of the Abel transform relationships between the occultation ray paths and an assumed spherically symmetric atmospheric refractivity field. For the spherically symmetric case the refractivity field is recovered exactly, within the limitations of ray optics. Only brute force methods have been

B. Ahmad; G. L. Tyler

1997-01-01

87

Distributed Multiuser Sequential Channel Sensing Schemes in Multichannel Cognitive Radio Networks  

E-print Network

Effective spectrum sensing strategies enable cognitive radios (CRs) to identify and opportunistically transmit on under-utilized spectral resources. In this paper, sequential channel sensing problems for single and multiple secondary users (SUs) cases are effectively modeled through finite state Markovian processes. More specifically, a model for single user case is introduced and validated through analytical analysis. In order to address multiple SUs, this model is extended to modified p-persistent access (MPPA) and its generalized version. While the introduced analytical framework facilitates the process of performance evaluation, these algorithms experience a high level of collision among the SUs. To mitigate this problem appropriately, p-persistent random access (PPRA) scheme is proposed, which offers higher average throughput for SUs by statistically distributing their loads among all channels. The structure and performance of the proposed schemes are discussed in detail, and a set of illustrative numeri...

Shokri-Ghadikolaei, Hossein; Nasiri-Kenari, Masoumeh

2012-01-01

88

Decametric radio measurement of Jupiter's rotation period  

NASA Technical Reports Server (NTRS)

Results of determinations of Jupiter's average decametric-wave rotation period are reported. The residual longitude drift of 18, 20 and 22.2 GHz emission observed at stations in Florida and Chile was calculated from measurements of the longitudes of source A peak centers for apparitions separated by 12 years; the drift was assumed to be the longitude shift which maximizes the cross correlation of histograms of occurence probability as a function of System III (1957.0) central meridian longitude. The weighted mean rotation period observed is 9 h 55 min 29.689 sec (standard deviation 0.005 sec), which is 0.022 sec less than the System III (1965) value. It is suggested that, if measurements are continued through the next maximum of Jovicentric earth declination, a secular drift in Jupiter's magnetic field may be observable.

May, J.; Carr, T. D.; Desch, M. D.

1979-01-01

89

Indoor radio measurement and planning for UMTS/HSDPA with antennas  

NASA Astrophysics Data System (ADS)

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

Eheduru, Marcellinus

90

Dual channel 115 and 230 GHz SIS receivers in operation at the Owens Valley Radio Observatory  

NASA Astrophysics Data System (ADS)

The Owens Valley Radio Observatory millimeter-wave interferometer array is presently operating with dual-channel SIS (superconductor-insulator--superconductor) tunnel junction receivers. The first channel covers the frequency range from 85 to 120 GHz and the second channel covers the frequency range from 200 to 300 GHz. The mixers consist of a corrugated feed horn, a single-stage circular-to-rectangular waveguide transition, a reduced-height waveguide with an SIS junction mounted across the E-plane, and a non-contacting backshort. The mixer block has a built-in RF choke for the IF (intermediate frequency) signal path which is designed to present a short circuit to the junction at frequencies above the 2-GHz IF frequency. The small-area (less than 1 sq micron) PbInAu-native oxide-PbAu SIS tunnel junctions are fabricated using a bridge lift-off technique. The receivers in the 85- to 120-GHz band have noise temperatures of less than 100 K, while the receivers in the 100- to 300-GHz band have noise temperatures in the range from 200 to 300 K. These dual-channel receivers are mounted in 4.5 K closed-cycle refrigerators and are in continuous use on the array.

Woody, D. P.; Giovanine, C. J.; Miller, R. E.

1989-03-01

91

Dual channel 115 and 230 GHz SIS receivers in operation at the Owens Valley Radio Observatory  

SciTech Connect

The Owens Valley Radio Observatory millimeter-wave interferometer array is presently operating with dual channel SIS tunnel junction receivers. The first channel covers the frequency range from 85 to 120 GHz and the second channel covers the frequency range from 200 to 300 GHz. The mixers consist of a corrugated feedhorn, single-stage circular to rectangular waveguide transition, reduced-height waveguide with an SIS junction mounted across the E-plane and a non-contacting backshort. The mixer block has a built-in RF choke for the IF signal path which is designed to present a short circuit to the junction at frequencies above the 2 GHz IF frequency. The small area (<1 ..mu..m/sup 2/) PbInAu-native oxide-PbAu SIS tunnel junctions are fabricated using a bridge lift-off technique. The LO power is provided by Gunn oscillators followed by doublers or triplers. The receivers in the 85 to 120 GHz band have noise temperatures of <100 K, while the receivers in the 200 to 300 GHz band have noise temperatures in the range from 200 to 300 K. These dual channel receivers are mounted in 4.5 K closed cycle refrigerators. They are in continuous use on the three element millimeter-wavelength interferometer array.

Woody, D.P.; Giovanine, C.J.; Miller, R.E.

1989-03-01

92

Radio Emission in Atmospheric Air Showers Measured by LOPES-30  

SciTech Connect

When Ultra High Energy Cosmic Rays (UHECR) interact with particles in the Earth's atmosphere, they produce a shower of secondary particles propagating towards the ground. These relativistic particles emit synchrotron radiation in the radio frequency range when passing the Earth's magnetic field. The LOPES (LOFAR Prototype Station) experiment investigates the radio emission from these showers in detail and will pave the way to use this detection technique for large scale applications like in LOFAR (Low Frequency Array) and the Pierre Auger Observatory. The LOPES experiment is co-located and measures in coincidence with the air shower experiment KASCADE-Grande at Forschungszentrum Karlsruhe, Germany. LOPES has an absolute amplitude calibration array of 30 dipole antennas (LOPES-30). After one year of measurements of the single East-West polarization by all 30 antennas, recently, the LOPES-30 set-up was configured to perform dual-polarization measurements. Half of the antennas have been configured for measurements of the North-South polarization. Only by measuring at the same time both, the E-W and N-S polarization components of the radio emission, the geo-synchrotron effect as the dominant emission mechanism in air showers can be verified. The status of the measurements, including the absolute calibration procedure of the dual-polarized antennas as well as analysis of dual-polarized event examples are reported.

Isar, P. G. [Institut fuer Kernphysik, Forschungszentrum Karlsruhe (Germany)

2008-01-24

93

Measurements of gravity driven granular channel flows  

NASA Astrophysics Data System (ADS)

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

Facto, Kevin

94

Weak lensing measurements in simulations of radio images  

NASA Astrophysics Data System (ADS)

We present a study of weak lensing shear measurements for simulated galaxy images at radio wavelengths. We construct a simulation pipeline into which we can input galaxy images of known shapelet ellipticity, and with which we then simulate observations with eMERLIN and the international LOFAR array. The simulations include the effects of the CLEAN algorithm, uv sampling, observing angle and visibility noise, and produce realistic restored images of the galaxies. We apply a shapelet-based shear measurement method to these images and test our ability to recover the true source shapelet ellipticities. We model and deconvolve the effective point spread function, and find suitable parameters for CLEAN and shapelet decomposition of galaxies. We demonstrate that ellipticities can be measured faithfully in these radio simulations, with no evidence of an additive bias and a modest (10 per cent) multiplicative bias on the ellipticity measurements. Our simulation pipeline can be used to test shear measurement procedures and systematics for the next generation of radio telescopes.

Patel, Prina; Abdalla, Filipe B.; Bacon, David J.; Rowe, Barnaby; Smirnov, Oleg M.; Beswick, Rob J.

2014-11-01

95

Surface measurements of radio antenna panels with white-light interferometry  

NASA Astrophysics Data System (ADS)

Typical radio telescopes have the primary reflector surface which is composed of several single panels that have dimensions of a meter a side. The manufacturing of these radio panels yield a micrometric precision over the volume on the single panel, hence the surface roughness of the panels can be measured with very high accuracy by means of the low coherence interferometry (LCI) technique which reaches micrometric spatial and depth resolution and has the advantage of being contact-less. We have developed a multi-channel partially coherent light interferometer to realize non contact 3D surface topography. The technique is based on the LCI principle, for which a bi-dimensional sensor - a CMOS - has been developed to directly acquire images. Tri-dimensional measures are recovered with a single scanning along the depth direction in a millimetric range, and every single pixel of the bi-dimensional sensor measures a point on the object, this allows a fast analysis in real time on square centimeter areas. In this paper we show the results obtained by applying the LCI technique method to analyze the surface roughness of the panels of a large radio antenna of 64 m of width and used for astronomical observations at 100 GHz; by measuring their 3D structure at micrometric resolution it is possible to verify their fabrication errors.

Chinellato, S.; Pernechele, C.; Carmignato, S.; Manzan, F.

2010-07-01

96

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

97

ATS6-satellite radio beacon measurements at Ootacamund, India  

NASA Technical Reports Server (NTRS)

In August 1975 the ATS6 was repositioned at 35 deg E. Radio beacon measurements of time delay, Faraday rotation and signal amplitude, made at Ootacamund, India in October 1975, are discussed with emphasis on the problem of determining the Faraday content under essentially transverse propagation conditions. It is shown that at the low geomagnetic latitude of Ootacamund the use of a fixed conversion coefficient gives an unreliable Faraday content. It is shown also that corrections to the measured Faraday rotation are important because of pitch and yaw of the satellite, particularly at night when the rotation on 140 MHz can be of the order of 10 to 20 deg. The shape factor shows a low predawn minimum indicating the nearly complete erosion of the F2 layer peak. Amplitude scintillation usually decreases with increase of radio frequency but exceptions are discussed.

Davies, K.; Donnelly, R. F.; Grubb, R. N.; Rama Rao, P. V. S.; Rastogi, R. G.; Deshpande, M. R.; Chandra, H.; Vats, H. O.; Sethia, G.

1978-01-01

98

Energy-Efficient Design of Sequential Channel Sensing in Cognitive Radio Networks: Optimal Sensing Strategy, Power Allocation, and Sensing Order  

Microsoft Academic Search

Energy-efficient design has become increasingly im- portant to battery-powered wireless devices. In this paper, we focus on the energy efficiency of a cognitive radio network, in which a secondary user senses the channels licensed to some primary users sequentially before it decides to transmit. Energy is consumed in both the channel sensing and transmission processes. The energy-efficient design calls for

Yiyang Pei; Ying-Chang Liang; Kah Chan Teh; Kwok Hung Li

2011-01-01

99

Radio Astronomers Set New Standard for Accurate Cosmic Distance Measurement  

NASA Astrophysics Data System (ADS)

A team of radio astronomers has used the National Science Foundation's Very Long Baseline Array (VLBA) to make the most accurate measurement ever made of the distance to a faraway galaxy. Their direct measurement calls into question the precision of distance determinations made by other techniques, including those announced last week by a team using the Hubble Space Telescope. The radio astronomers measured a distance of 23.5 million light-years to a galaxy called NGC 4258 in Ursa Major. "Ours is a direct measurement, using geometry, and is independent of all other methods of determining cosmic distances," said Jim Herrnstein, of the National Radio Astronomy Observatory (NRAO) in Socorro, NM. The team says their measurement is accurate to within less than a million light-years, or four percent. The galaxy is also known as Messier 106 and is visible with amateur telescopes. Herrnstein, along with James Moran and Lincoln Greenhill of the Harvard- Smithsonian Center for Astrophysics; Phillip Diamond, of the Merlin radio telescope facility at Jodrell Bank and the University of Manchester in England; Makato Inoue and Naomasa Nakai of Japan's Nobeyama Radio Observatory; Mikato Miyoshi of Japan's National Astronomical Observatory; Christian Henkel of Germany's Max Planck Institute for Radio Astronomy; and Adam Riess of the University of California at Berkeley, announced their findings at the American Astronomical Society's meeting in Chicago. "This is an incredible achievement to measure the distance to another galaxy with this precision," said Miller Goss, NRAO's Director of VLA/VLBA Operations. "This is the first time such a great distance has been measured this accurately. It took painstaking work on the part of the observing team, and it took a radio telescope the size of the Earth -- the VLBA -- to make it possible," Goss said. "Astronomers have sought to determine the Hubble Constant, the rate of expansion of the universe, for decades. This will in turn lead to an estimate of the age of the universe. In order to do this, you need an unambiguous, absolute distance to another galaxy. We are pleased that the NSF's VLBA has for the first time determined such a distance, and thus provided the calibration standard astronomers have always sought in their quest for accurate distances beyond the Milky Way," said Morris Aizenman, Executive Officer of the National Science Foundation's (NSF) Division of Astronomical Sciences. "For astronomers, this measurement is the golden meter stick in the glass case," Aizenman added. The international team of astronomers used the VLBA to measure directly the motion of gas orbiting what is generally agreed to be a supermassive black hole at the heart of NGC 4258. The orbiting gas forms a warped disk, nearly two light-years in diameter, surrounding the black hole. The gas in the disk includes water vapor, which, in parts of the disk, acts as a natural amplifier of microwave radio emission. The regions that amplify radio emission are called masers, and work in a manner similar to the way a laser amplifies light emission. Determining the distance to NGC 4258 required measuring motions of extremely small shifts in position of these masers as they rotate around the black hole. This is equivalent to measuring an angle one ten-thousandth the width of a human hair held at arm's length. "The VLBA is the only instrument in the world that could do this," said Moran. "This work is the culmination of a 20-year effort at the Harvard Smithsonian Center for Astrophysics to measure distances to cosmic masers," said Irwin Shapiro, Director of that institution. Collection of the data for the NGC 4258 project was begun in 1994 and was part of Herrnstein's Ph.D dissertation at Harvard University. Previous observations with the VLBA allowed the scientists to measure the speed at which the gas is orbiting the black hole, some 39 million times more massive than the Sun. They did this by observing the amount of change in the wavelength of the radio wave

1999-06-01

100

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

Microsoft Academic Search

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

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

2009-01-01

101

Fading characteristics of a 2.3 GHz radio telemetry channel in a hospital building.  

PubMed

This paper reports on radio path attenuation measurements made in a hospital complex at a spot frequency of 2.340 GHz. Power loss figures for fixed path propagation in a variety of building types have been determined for proposed telemetry use in operational ward situations. Throughout the hospital, the radio paths assessed all exhibited a loss in excess of that calculated for free-space communications. Modern buildings had external wall losses of 10-25 dB, with dividing walls in wards contributing an additional 5 dB. Received signal strength levels indicated a Rayleigh distribution for obstructed paths. Temporal testing was used to find the rate and depth of signal fades caused by the movement of personnel and equipment during normal ward usage; signal level reductions of greater than 35 dB were common during busy periods. PMID:7795861

Wang, L Q; Evans, N E; Burns, J B; Matthews, J G

1995-04-01

102

Multi-radio channel allocation in competitive wireless networks Mark Felegyhazi, Mario Cagalj, Jean-Pierre Hubaux  

E-print Network

problem using game theory. We conclude that in spite of the non-cooperative behavior of such devices present a game-theoretic analysis of fixed channel allocation strategies of devices using multi- ple researchers have considered devices using multiple radios, notably in mesh networks. In the multi

Bencsáth, Boldizsár

103

ARaCS: Educational software for radio channel characterization with swept-time delay cross-correlation sounders  

Microsoft Academic Search

In the present paper the educational software ARaCS is introduced as a tool to help in the radio channel characterization teaching field. The developed software implements an automated swept-time delay cross correlation sounder with general features. The behavior of this kind of wideband sounders can be analyzed and the influence of their main parameters stated by means of the use

Ana Vazquez Alejos; Manuel Garcia Sanchez; Iñigo Cuiñas; Felipe Gil Castiñeira

2009-01-01

104

The Possibility of Increasing the Throughput of a High-Frequency Radio-Communication Channel Using a Mimo System  

NASA Astrophysics Data System (ADS)

We consider the possibility of increasing the radio-channel throughput in the high-frequency range by using antenna arrays. The MIMO-system efficiency is studied with the help of the modified Watterson model by the simulation method. The signal parameters for which the MIMO processing yields the best results are determined.

Metelev, S. A.

2014-09-01

105

ATS-6 satellite radio beacon measurements at Ootacamund, India  

NASA Technical Reports Server (NTRS)

ATS-6 radio beacon measurements of modulation phase and Faraday rotation made at Ootacamund, India in 1975-1976 are discussed with emphasis on the measurement and analysis errors. The modulation-phase errors are insensitive to the geomagnetic field and provide an accurate determination of the total columnar electron content. Comparison of modulation-phase measurements at different frequencies shows a minor sensitivity to the ATS-6 pitch angle. For the low geomagnetic latitude and nearly transverse propagation conditions of Ootacamund, the use of a fixed conversion coefficient gives an unreliable Faraday content. However, the Faraday rotation measurements may be used to determine the shape factor F, which provides information about the electron density height profile.

Davies, K.; Donnelly, R. F.; Grubb, R. N.; Rao, P. V. S. R.; Rastogi, R. G.; Deshpande, M. R.; Chandra, H.; Vats, H. O.; Sethia, G.

1979-01-01

106

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

107

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

Microsoft Academic Search

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

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

2004-01-01

108

The Use of Extraterrestrial Radio Sources in the Measurement of Antenna Parameters  

Microsoft Academic Search

Extraterrestrial radio sources, whose emission characteristics (flux density, spectrum, angular size) and coordinates have been firmly established by careful observations, have application in the measurement of the effective area (aperture efficiency and gain) of an antenna and its radiation pattern. The radio-emission characteristics of the strong discrete (celestial) radio sources, of the sun, and of the moon are presented. Problems

D. A. Guidice; J. P. Castelli

1971-01-01

109

Radio Occultation Measurements of Jupiter's Multilayered Lower Ionosphere: New Results from Voyager and Galileo  

Microsoft Academic Search

Radio occultation measurements with Pioneer 10 provided the first evidence for the multilayered structure of Jupiter's lower ionosphere (Fjeldbo et al., Astron. Astrophys. 39, 91-96, 1975). However, radio occultation studies of this region are inherently difficult for the following reason. Radio signals propagating from spacecraft to Earth can follow a variety of paths through the ionosphere, refracting off the top

D. P. Hinson; E. T. Karayel; J. D. Twicken

1996-01-01

110

Progress in Understanding Horizontal Resolution of Radio Occultation Measurements  

NASA Astrophysics Data System (ADS)

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

Ahmad, B.; Tyler, G. L.

1997-07-01

111

Vietnam spectrum occupancy measurements and analysis for cognitive radio applications  

Microsoft Academic Search

The rapid growth of demand for wireless transmis- sion has placed great pressure on the scarce radio spectrum due to the fixed spectrum allocation policy and cognitive radio (CR) is considered as a promising solution to such the problem. The main idea behind a cognitive radio network is for the unlicensed users (also called secondary users) to exploit opportunistically the

Nguyen Quoc Bao Vo; Quoc Cuong Le; Quang Phu Le; Dinh Thuan Tran; Thien Quy Nguyen; Minh Trung Lam

2011-01-01

112

Measuring radio audiences with a PPM panel in Québec  

Microsoft Academic Search

The authors report findings from a comprehensive analysis of radio audience data captured by Arbitron's Portable People Meter (PPM). The paper compares the diary and PPM results for a common area and time period and list of stations. Comparisons, not unexpectedly, show differences in overall amount of radio use, the distribution of radio use by time periods, the relative importance

A. Pellegrini; Ken Purdye

113

Navigauge: A Disruptive Innovation to Measure Car Radio Listening  

Microsoft Academic Search

Navigauge, a start-up company that specialised in radio market research, had developed a tool that would provide high quality, accurate and location based radio market research. This new pioneering technology in radio market research was captured in a positive, albeit, reserved article in the New York Times in September of 2004. The use of this tool was in stark contrast

Srinivas K Reddy; Kevin W Sproule

2012-01-01

114

Joint routing and channel assignment protocol for multi-radio multi-channel IEEE 802.11s mesh networks  

Microsoft Academic Search

Efficient channel selection is essential in 802.11 mesh deployments, for minimizing contention and interference among co-channel devices. The IEEE 802.11 standard provides at least three non-overlapping channels and thus it's possible for a node equipped with more than one network interface card (NIC) to operate on different channels simultaneously. This may increase the aggregate bandwidth available for end users and

Sana Ghannay; Sonia Mettali Gammar

2011-01-01

115

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

116

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

117

Distributed scheduling scheme for video streaming over multi-channel multi-radio multi-hop wireless networks  

Microsoft Academic Search

An important issue of supporting multi-user video streaming over wireless networks is how to optimize the systematic scheduling by intelligently utilizing the available network resources while, at the same time, to meet each video's Quality of Service (QoS) requirement. In this work, we study the problem of video streaming over multi-channel multi-radio multihop wireless networks, and develop fully distributed scheduling

Liang Zhou; Xinbing Wang; Wei Tu; Gabriel-Miro Muntean; Benoit Geller

2010-01-01

118

Wave Normal Calculations of Chorus at Saturn Using the Cassini Radio and Plasma Wave Science Five-Channel Waveform Receiver  

Microsoft Academic Search

The Cassini spacecraft has completed the first year of its four-year prime mission to study the Saturnian system. The Cassini Radio and Plasma Wave Science (RPWS) Five-Channel Waveform Receiver (WFR) provides simultaneous waveforms from up to five separate sensors in passbands of either 1 Hz to 26 Hz, or 3 Hz to 2.5 kHz. The wave normal and Poynting vector

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

2005-01-01

119

Radio interferometer measurements of plasmasphere density structures during geomagnetic storms  

SciTech Connect

The Los Alamos plasmaspheric drift radio interferometer is a ground-based array that regularly measures periodic disturbances in the plasmasphere. These plasmaspheric density structures have been shown to depend on geomagnetic activity, as indicated by Kp. However, a direct storm time analysis of their behavior has not been done. This paper studies the amplitude, drift velocity, and location of these structures before, during, and after the onset of major geomagnetic storms. Distinct large-amplitude, storm time signatures are found during the first night after onset, continuing through the third night; there were significantly more storm time signatures during nighttime than daytime. The L shells on which the disturbances existed were found to decrease after storm onset, indicating a possible shrinking of the plasmasphere.{copyright} 1997 American Geophysical Union

Hoogeveen, G.W.; Jacobson, A.R. [Los Alamos National Laboratory, Los Alamos, New Mexico (United States)] [Los Alamos National Laboratory, Los Alamos, New Mexico (United States)

1997-07-01

120

Polarized radio emission from extensive air showers measured with LOFAR  

NASA Astrophysics Data System (ADS)

We present LOFAR measurements of radio emission from extensive air showers. We find that this emission is strongly polarized, with a median degree of polarization of nearly 99%, and that the angle between the polarization direction of the electric field and the Lorentz force acting on the particles, depends on the observer location in the shower plane. This can be understood as a superposition of the radially polarized charge-excess emission mechanism, first proposed by Askaryan and the geomagnetic emission mechanism proposed by Kahn and Lerche. We calculate the relative strengths of both contributions, as quantified by the charge-excess fraction, for 163 individual air showers. We find that the measured charge-excess fraction is higher for air showers arriving from closer to the zenith. Furthermore, the measured charge-excess fraction also increases with increasing observer distance from the air shower symmetry axis. The measured values range from (3.3± 1.0)% for very inclined air showers at 25 m to (20.3± 1.3)% for almost vertical showers at 225 m. Both dependencies are in qualitative agreement with theoretical predictions.

Schellart, P.; Buitink, S.; Corstanje, A.; Enriquez, J. E.; Falcke, H.; Hörandel, J. R.; Krause, M.; Nelles, A.; Rachen, J. P.; Scholten, O.; ter Veen, S.; Thoudam, S.; Trinh, T. N. G.

2014-10-01

121

Propagation measurements for the aeronautical satellite channel  

Microsoft Academic Search

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

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

1987-01-01

122

Radio-frequency measurement of an asymmetric single electron transistor  

NASA Astrophysics Data System (ADS)

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

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

2007-03-01

123

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

NASA Astrophysics Data System (ADS)

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

Malov, O. I.

124

Installations and methods for measurement of aircraft radio components and systems  

Microsoft Academic Search

The requirements and workings of a flight measurement system for measurement of radio frequency systems and components used in flight control and guidance are described. These systems and components consist of radio systems for communication, navigation, flight monitoring (Air Traffic Control (ATC)), and radar systems for flight monitoring (ATC); recognition and protection procedures. A range of subsystems and components for

Juergen Tetzlaff

1993-01-01

125

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

ERIC Educational Resources Information Center

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

Dombi, Andra; Tunyagi, Arthur; Neda, Zoltan

2013-01-01

126

An in situ measurement of the radio-frequency attenuation in ice at Summit Station, Greenland  

E-print Network

We report an in situ measurement of the electric field attenuation length at radio frequencies for the bulk ice at Summit Station, Greenland, made by broadcasting radio-frequency signals vertically through the ice and measuring the relative power in the return ground bounce signal. We find the depth-averaged field attenuation length to be 947 +92/-85 meters at 75 MHz. While this measurement has clear radioglaciological applications, the radio clarity of the ice also has implications for the detection of ultra-high energy (UHE) astrophysical particles via their radio emission in dielectric media such as ice. The measured attenuation length at Summit Station is comparable to previously measured radio-frequency attenuation lengths at candidate particle detector sites around the world, and strengthens the case for Summit Station as the most promising northern site for UHE neutrino detection.

Avva, J; Miki, C; Saltzberg, D; Vieregg, A G

2014-01-01

127

An in situ measurement of the radio-frequency attenuation in ice at Summit Station, Greenland  

E-print Network

We report an in situ measurement of the electric field attenuation length at radio frequencies for the bulk ice at Summit Station, Greenland, made by broadcasting radio-frequency signals vertically through the ice and measuring the relative power in the return ground bounce signal. We find the depth-averaged field attenuation length to be 947 +92/-85 meters at 75 MHz. While this measurement has clear radioglaciological applications, the radio clarity of the ice also has implications for the detection of ultra-high energy (UHE) astrophysical particles via their radio emission in dielectric media such as ice. The measured attenuation length at Summit Station is comparable to previously measured radio-frequency attenuation lengths at candidate particle detector sites around the world, and strengthens the case for Summit Station as the most promising northern site for UHE neutrino detection.

J. Avva; J. M. Kovac; C. Miki; D. Saltzberg; A. G. Vieregg

2014-09-18

128

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

129

A new 2-cluster model for indoor UWB channel measurements  

Microsoft Academic Search

The paper describes a new model for the indoor non-line-of-sight (NLOS) UWB channel based on measurements. To date, the Saleh-Valenzuela model (Saleh, A.A. and Valenzuela, R.A., IEEE J. Selected Areas in Commun., vol.SAC-5, no.2, p.128-37, 1987) has been the standard model for indoor NLOS wireless propagation. However, we show that for our set of indoor NLOS UWB channel measurements, better

Swaroop Venkatesh; Jihad Ibrahim; R. Michael Buehrer

2004-01-01

130

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

131

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

132

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

133

Optimal throughput for cognitive radio with energy harvesting in fading wireless channel.  

PubMed

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. PMID:24574885

Vu-Van, Hiep; Koo, Insoo

2014-01-01

134

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

135

Measurement of multipath delay profile in land mobile satellite channels  

NASA Technical Reports Server (NTRS)

Mobile satellite communication channel has been evaluated mainly with fading statistics of signal. When bandwidth of transmitting signal becomes wider, frequency selectivity of fading becomes a significant factor of the channel. Channel characteristics, not only signal variation but multipath delay spread should be evaluated. A multipath measurement system is proposed and developed for mobile satellite applications. With this system and ETS-V satellite, multipath delay profiles are measured in various environments including Tokyo metropolis and Sapporo city at 1.5 GHz. Results show that the maximum excess delay is within 1 microsec and the maximum delay spread is 0.2 microsecs at elevation angles of 40 to 47 degrees. In wideband signal transmission of about 1 MHz and more, designers should consider the effect of selective fading due to the multipath of land mobile satellite channel.

Ikegami, Tetsushi; Arakaki, Yoshiya; Wakana, Hiromitsu; Suzuki, Ryutaro

1993-01-01

136

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

137

Cooperative UWB Body Area Networking: Channel Measurement and Diversity Analysis  

Microsoft Academic Search

We explore the application of cooperative commu- nications in ultra-wideband (UWB) wireless body area networks (WBANs). Firstly, time-domain UWB channel measurements are presented for a sitting human subject. Important channel para- meters such as the pathloss, power variation, power delay profile (PDP), and effective received power (ERP) cross-correlation are extracted and statistically analyzed. Armed with the model preliminaries, an intuitive

Yifan Chen; Jianqi Teo; Joshua Lai; Erry Gunawan; Kaysoon Low; Cheongboon Soh; Predrag B. Rapajic

2008-01-01

138

Dual polarized stacked microstrip patch antenna for channel measurements  

Microsoft Academic Search

A dual half-wave patch antenna for channel measurements is being developed. The polarization isolation and bandwidth are suitable for an antenna array in channel sounding. The antenna is designed for the 2154 MHz center frequency and for ±50 MHz 10dB band- width (Lret ? 10dB). The polarization isolation is planned to be comparable with other antennas designed for good polarization

Veli Voipio

1997-01-01

139

Future Trends in Solar Radio Astronomy and Coronal Magnetic-Field Measurements  

NASA Astrophysics Data System (ADS)

Solar radio astronomy has an amazingly rich, but yet largely unexploited, potential for probing the solar corona and chromosphere. Radio emission offers multiple ways of detecting and tracking electron beams, studying chromospheric and coronal thermal structure, plasma processes, particle acceleration, and measuring magnetic fields. To turn the mentioned potential into real routine diagnostics, two major components are needed: (1) well-calibrated observations with high spatial, spectral, and temporal resolutions and (2) accurate and reliable theoretical models and fast numerical tools capable of recovering the emission source parameters from the radio data. This report gives a brief overview of the new, expanded, and planned radio facilities, such as Expanded Owens Valley Solar Array (EOVSA), Jansky Very Large Array (JVLA), Chinese Solar Radio Heliograph (CSRH), Upgraded Siberian Solar Radio Telescope (USSRT), and Frequency Agile Solar Radiotelescope (FASR) with the emphasis on their ability to measure the coronal magnetic fields in active regions and flares. In particular, we emphasize the new tools for 3D modeling of the radio emission and forward fitting tools in development needed to derive the magnetic field data from the radio measurements.

Fleishman, Gregory; Nita, Gelu; Gary, Dale

140

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.

141

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. 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

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

143

Investigation of handover in distributed control channel allocation (DCCA) for microcellular radio systems  

Microsoft Academic Search

After a brief review of previous studies of dynamic channel allocation (DCA), the concept and the operation principles of distributed control channel allocation (DCCA) is described. This system can adapt to local traffic density and has good potential to reduce the number of call handovers in a microcellular system. It is shown by computer simulations that significant reductions in the

K. Madani; A. H. Aghvami

1994-01-01

144

Multi-radio Channel Allocation in Multi-hop Wireless Networks  

E-print Network

), respectively. Then, we study the existence of MMCPNE in this game and our main result, Theorem 2, shows-cooperative game and Nash equilibrium (NE) channel allocation scheme is not suitable for the multi-hop wireless networks. Thus we model the channel allocation problem as a hybrid game involving both cooperative game

Wang, Xinbing

145

Measurement of radio-frequency magnetic fluctuations in the VTF magnetic reconnection experiment  

E-print Network

In this thesis work, I designed, fabricated, and calibrated, a radio-frequency magnetic probe, subsequently used to measure magnetic turbulance in the reconnecting plasmas of the Versatile Toroidal Facility (VTF). Reconnecting ...

Whitney, John Peter, 1982-

2004-01-01

146

Handoff delay in cognitive radios — A concept paper on utilization of guard channels  

Microsoft Academic Search

In today's world of communication, everything is going wireless. The licensed and unlicensed bands of the Radio Frequency (RF) spectrum playa key role in wireless communication. Considering the tremendous growth in wireless applications and devices, the RF spectrum can be thought of as a sacred resource as it is the vital component which makes wireless communication possible. In addition, RF

Madeeha Aman; Saeed Mahfooz; Waheed ur Rehman

2011-01-01

147

Power Allocation for Multi-Antenna Multiple Access Channels in Cognitive Radio Networks  

Microsoft Academic Search

A cognitive radio network is often described as a secondary communication network operating in a frequency band originally allocated to a primary network consisting of one or multiple primary users. A fundamental challenge for realizing such a system is to ensure the quality of service of the primary users as well as to maximize the throughput of the secondary users.

Lan Zhang; Yan Xin; Ying-chang Liang

2007-01-01

148

Optimal power allocation for fading channels in cognitive radio networks: Ergodic capacity and outage capacity  

Microsoft Academic Search

A cognitive radio network (CRN) is formed by either allowing the secondary users (SUs) in a secondary communication network (SCN) to opportunistically operate in the frequency bands originally allocated to a primary communication network (PCN) or by allowing SCN to coexist with the primary users (PUs) in PCN as long as the interference caused by SCN to each PU is

Xin Kang; Ying-chang Liang; Arumugam Nallanathan; Hari Krishna Garg; Rui Zhang

2009-01-01

149

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

150

Characterizing radio channels : the science and technology of propagation and interference, 1900-1935  

E-print Network

Guglielmo Marconi's trans-Atlantic wireless experiment in 1900 marked the beginning of a communication revolution that transformed the open space above the earth into channels of information flow. This dissertation grapples ...

Yeang, Chen-Pang.

2004-01-01

151

Voice Capacity of Cognitive Radio Networks for Both Centralized and Distributed Channel Access Control  

Microsoft Academic Search

As an emerging networking technology, cognitive radio networks (CRNs) have drawn immense attention in the wireless networking community. Since multimedia services have become widely popular among wireless communication services users, supporting those services over CRNs has become an interesting research topic in recent years. However, due to the random nature of the resource availability in CRNs, providing quality-of-service (QoS) guarantees

Subodha Gunawardena; Weihua Zhuang

2010-01-01

152

Joint Beamforming and Power Allocation for Multiple Access Channels in Cognitive Radio Networks  

Microsoft Academic Search

A cognitive radio (CR) network refers to a secondary network operating in a frequency band originally licensed\\/allocated to a primary network consisting of one or multiple primary users (PUs). A fundamental challenge for realizing such a system is to ensure the quality of service (QoS) of the PUs as well as to maximize the throughput or ensure the QoS, such

Lan Zhang; Ying-chang Liang; Yan Xin

2008-01-01

153

Technique to determine location of radio sources from measurements taken on spinning spacecraft  

NASA Technical Reports Server (NTRS)

The procedure developed to extract average source direction and average source size from spin-modulated radio astronomy data measured on the IMP-6 spacecraft is described. Because all measurements are used, rather than just finding maxima or minima in the data, the method is very sensitive, even in the presence of large amounts of noise. The technique is applicable to all experiments with directivity characteristics. It is suitable for onboard processing on satellites to reduce the data flow to Earth. The application to spin-modulated nonpolarized radio astronomy data is made and includes the effects of noise, background, and second source interference. The analysis was tested with computer simulated data and the results agree with analytic predictions. Applications of this method with IMP-6 radio data have led to: (1) determination of source positions of traveling solar radio bursts at large distances from the Sun; (2) mapping of magnetospheric radio emissions by radio triangulation; and (3) detection of low frequency radio emissions from Jupiter and Saturn.

Fainberg, J.

1979-01-01

154

Water vapor and carbon dioxide species measurements in narrow channels  

Microsoft Academic Search

Classical spectroscopic techniques have been applied in a novel manner to measure the concentration of gas species, water vapor and carbon dioxide, within a narrow channel flow field non-invasively. Tunable diode laser absorption spectroscopy (TDLAS) was used in conjunction with a laser modulated at a high frequency [Wavelength Modulation Spectroscopy (WMS)] tuned to the ro-vibrational transition of the species. This

Saptarshi Basu; Derek E. Lambe; Ranganathan Kumar

2010-01-01

155

Performance of distributed control channel allocation (DCCA) under non-uniform traffic condition in microcellular radio communications  

Microsoft Academic Search

A new technique of autonomous allocation of radio resources in microcellular PCN is described. The technique uses distributed control based on carrier-to-cochannel interference-ratio measurements by the main base station located in the centre of each cell. There are six low power sub-stations surrounding the main base station, which are used to effectively change the location of the base station within

K. Madani; H. A. Aghvami

1994-01-01

156

CB Radios  

ERIC Educational Resources Information Center

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

Martin, Dick

1977-01-01

157

Global Cosmological Parameters Measured Using Classical Double Radio Sources  

E-print Network

Fourteen classical double radio galaxies with redshifts between zero and two were used to determine the cosmological parameters $\\Omega_m$, $\\Omega_{\\Lambda}$, and $\\Omega_k$, where these are the normalized values of the mean mass density, cosmological constant, and space curvature at the present epoch. A low value of $\\Omega_m$ is obtained, and $\\Omega_m = 1$ is ruled out with 97.5% confidence. The low value of $\\Omega_m$ determined using the radio source method described here is also indicated by several independent tests. Thus, it appears that either a cosmological constant, or space curvature, is significant at the present epoch. This means that the universe is undergoing, or has recently undergone, a transition away from a state of matter domination and into a state where either a cosmological constant or space curvature is determining the expansion rate of the universe. The low value of $\\Omega_m$ presented here and by Guerra & Daly (1998) means that we can state with 97.5 % confidence that the universe will continue to expand forever.

Ruth A. Daly; E. J. Guerra; Lin Wan

1998-03-23

158

Measuring bankfull channel features, bed sediment, and bed load  

NSDL National Science Digital Library

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

Clayton, Jordan

159

National Radio Astronomy Observatory Measurements of Copper Heat Straps Near 4 K  

E-print Network

National Radio Astronomy Observatory EDTN 204 Measurements of Copper Heat Straps Near 4 K measurements of the thermal resistance of heat straps used in the ALMA Band 6 cartridges. The results suggest cartridge was measured. The heat straps include Sn/Pb/Ag 62/36/2 solder joints and bolted connections

Groppi, Christopher

160

Radio spectrum measurements of artificial ball lightning and testing the hypothesis on its plasmochemical nature  

NASA Astrophysics Data System (ADS)

Spectral measurements of radiowaves emitted by artificial ball lightning are presented. The measurements were carried out using two different facilities: a pulsed power generator (PPG) and a three-contour Tesla transformer. The results of these measurements confirm the hypothesis that ball lightning is a self-oscillator of high-voltage pulses in the radio range.

Kopeikin, V. V.

2014-01-01

161

Wave propagation channel simulation by satellite-to-indoor radio link  

Microsoft Academic Search

In our paper we present the simulation of the propagation characteristics of the satellite-to-indoor propagation channel. Our first aim has been to find a correct description of the polarization state of the received inside wave. The result of our first in- vestigations is that the polarization state of the indoor wave signigicantly changes as we move further away from the

LÓRÁNT FARKAS; LAJOS NAGY; ANDREA FARKASVÖLGYI

2008-01-01

162

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

163

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

Microsoft Academic Search

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

Gregg Jørgen Suaning; Nigel H. Lovell

2001-01-01

164

Spatial equalization of a radio-mobile channel without beamforming using the constant modulus algorithm (CMA)  

Microsoft Academic Search

The author considers the problem of signal recovery by a multisensor receiver in a multipath propagation channel. She shows that a spatial filtering can recover the transmitted signals under two conditions, namely that both the number of sensors and the number of paths be larger than the length of the intersymbol interference, which is assumed to be finite. Thereby, signal

S. Mayrargue

1993-01-01

165

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

166

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

167

Application of the Rasch model to measuring the performance of cognitive radios.  

PubMed

Cognitive radios (CRs) are recent technological developments that rely on artificial intelligence to adapt a radio's performance to suit environmental demands, such as sharing radio frequencies with other radios. Measuring the performance of the cognitive engines (CEs) that underlie a CR's performance is a challenge for those developing CR technology. This simulation study illustrates how the Rasch model can be applied to the evaluation of CRs. We simulated the responses of 50 CEs to 35 performance tasks and applied the Random Coefficients Multidimensional Multinomial Logit Model (MRCMLM) to those data. Our results indicate that CEs based on different algorithms may exhibit differential performance across manipulated performance task parameters. We found that a multidimensional mixture model may provide the best fit to the simulated data and that the two algorithms simulated may respond to tasks that emphasize achieving high levels of data throughput coupled with lower emphasis on power conservation differently than they do to other combinations of performance task characteristics. PMID:24064575

Wolfe, Edward W; Dietrich, Carl B; Vanhoy, Garrett

2013-01-01

168

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

Microsoft Academic Search

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

D. Cox; R. Leck

1975-01-01

169

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

170

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

171

Measurements of LF and MF radio propagation over irregular, inhomogeneous terrain  

Microsoft Academic Search

Measurements of radio propagation path loss and local ground conductivity were made over four paths in the 100 to 2000 kHz band. The paths were of lengths up to 50 km and were chosen to represent both extreme and typical topography and conductivity conditions to the U.S. The measurements were made near Canyonlands National Park in Utah, at Highland Range

W. A. Kissick; E. J. Haakinson; G. H. Stonehocker

1978-01-01

172

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

173

Toward Epoch of Reionization Measurements with Wide-Field Radio Observations  

E-print Network

This paper explores the potential for statistical epoch of reionization (EOR) measurements using wide field radio observations. New developments in low frequency radio instrumentation and signal processing allow very sensitive EOR measurements, and the analysis techniques enabled by these advances offer natural ways of separating the EOR signal from the residual foreground emission. This paper introduces the enabling technologies and proposes an analysis technique designed to make optimal use of the capabilities of next generation low frequency radio arrays. The observations we propose can directly observe the power spectrum of the EOR using relatively short observations, and are significantly more sensitive than other techniques which have been discussed in the literature. For example, in the absence of foreground contamination the measurements we propose would produce five 3-sigma power spectrum points in 100 hours of observation with only 4 MHz bandwidth with LOFAR for simple models of the high redshift 21cm emission. The challenge of residual foreground removal may be addressed by the symmetries in the three-dimensional (two spatial frequencies and radiofrequency) radio interferometric data. These symmetries naturally separate the EOR signal from most classes of residual un-subtracted foreground contamination, including all foreground continuum sources and radio line emission from the Milky Way.

Miguel F. Morales; Jacqueline Hewitt

2003-12-17

174

Probing the Solar Corona with Radio Ranging Measurements  

NASA Technical Reports Server (NTRS)

An asymmetry in the radial variation of electron density above the east 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 are compared with the Mauna Loa Solar Observatory white-light coronagraph measurements of the underlying corona. Corona probing abilities are summarized.

Woo, R.

1995-01-01

175

Towards cognitive radio networks: Spectrum utilization measurements in suburb environment  

Microsoft Academic Search

This paper deals with spectrum utilization measurements in the frequency band from 100 MHz up to 3 GHz. The measurement is based on the energy detection principle using wideband logarithmically periodic antenna. The results point out the fact, that the frequency spectrum is not utilized in an optimal manner and that there do exist less or more utilized licensed frequency

Václav Valenta; Zbynek Fedra; R. Marsalek; G. Baudoin; M. Villegas

2009-01-01

176

Probing the Solar Corona with Radio Ranging Measurements  

NASA Technical Reports Server (NTRS)

An asymmetry in the radial variation of electron density above the east and west limbs of the Sun was inferred from centimeter wavelength ranging measurements conducted by Voyager 2 during its 1985 solar conjunction. These older data are compared with white- light coronagraph measurements of the underlying corona collected by the Mark III K-coronameter at the Mauna Loa Solar Observatory.

Woo, R.

1995-01-01

177

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

178

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

179

National Radio Astronomy Observatory Cryogenic (4K) Measurements of Some Resistors and Capacitors  

E-print Network

National Radio Astronomy Observatory EDTN 205 Cryogenic (4K) Measurements of Some Resistors capacitors and thin-film resistors at 4.2 K. The capacitors have the following dielectrics: SiO2, ATC types CA and CC, and ATC type 700A. The resistors are TaN and nichrome thin film made by Mini-Systems, Inc

Groppi, Christopher

180

Measurement of the top quark mass in the dilepton channel  

NASA Astrophysics Data System (ADS)

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

Abazov, V. M.; Abbott, B.; Abolins, M.; Acharya, B. S.; Adams, M.; Adams, T.; Agelou, M.; Aguilo, E.; Ahn, S. H.; Ahsan, M.; Alexeev, G. D.; Alkhazov, G.; Alton, A.; Alverson, G.; Alves, G. A.; Anastasoaie, M.; Andeen, T.; Anderson, S.; Andrieu, B.; Anzelc, M. S.; Arnoud, Y.; Arov, M.; Askew, A.; Åsman, B.; Assis Jesus, A. C. S.; Atramentov, O.; Autermann, C.; Avila, C.; Ay, C.; Badaud, F.; Baden, A.; Bagby, L.; Baldin, B.; Bandurin, D. V.; Banerjee, P.; Banerjee, S.; Barberis, E.; Bargassa, P.; Baringer, P.; Barnes, C.; 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.; Berntzon, L.; Bertram, I.; Besançon, M.; Beuselinck, R.; Bezzubov, V. A.; Bhat, P. C.; Bhatnagar, V.; Binder, M.; Biscarat, C.; Black, K. M.; Blackler, I.; Blazey, G.; Blekman, F.; Blessing, S.; Bloch, D.; Bloom, K.; Blumenschein, U.; Boehnlein, A.; Boeriu, O.; Boline, D.; Bolton, T. A.; Borissov, G.; Bos, K.; Bose, T.; Brandt, A.; Brock, R.; Brooijmans, G.; Bross, A.; Brown, D.; Buchanan, N. J.; Buchholz, D.; Buehler, M.; Buescher, V.; Burdin, S.; Burke, S.; Burnett, T. H.; Busato, E.; Buszello, C. P.; Butler, J. M.; Calfayan, P.; Calvet, S.; Cammin, J.; Caron, S.; Carvalho, W.; Casey, B. C. K.; Cason, N. M.; Castilla-Valdez, H.; Chakrabarti, S.; Chakraborty, D.; Chan, K. M.; Chandra, A.; Charles, F.; Cheu, E.; Chevallier, F.; Cho, D. K.; Choi, S.; Choudhary, B.; Christofek, L.; Claes, D.; Clément, B.; Clément, C.; Coadou, Y.; Cooke, M.; Cooper, W. E.; Coppage, D.; Corcoran, M.; Cousinou, M.-C.; Cox, B.; Crépé-Renaudin, S.; Cutts, D.; ?wiok, M.; da Motta, H.; Das, A.; Das, M.; Davies, B.; Davies, G.; Davis, G. A.; De, K.; de Jong, P.; de Jong, S. J.; De La Cruz-Burelo, E.; De Oliveira Martins, C.; Degenhardt, J. D.; Déliot, F.; Demarteau, M.; Demina, R.; Demine, P.; Denisov, D.; Denisov, S. P.; Desai, S.; Diehl, H. T.; Diesburg, M.; Doidge, M.; Dominguez, A.; Dong, H.; Dudko, L. V.; Duflot, L.; Dugad, S. R.; Duggan, D.; Duperrin, A.; Dyer, J.; Dyshkant, A.; Eads, M.; Edmunds, D.; Edwards, T.; Ellison, J.; Elmsheuser, J.; Elvira, V. D.; Eno, S.; Ermolov, P.; Evans, H.; Evdokimov, A.; Evdokimov, V. N.; Fatakia, S. N.; Feligioni, L.; Ferapontov, A. V.; Ferbel, T.; Fiedler, F.; Filthaut, F.; Fisher, W.; Fisk, H. E.; Fleck, I.; Ford, M.; Fortner, M.; Fox, H.; Fu, S.; Fuess, S.; Gadfort, T.; Galea, C. F.; Gallas, E.; Galyaev, E.; Garcia, C.; Garcia-Bellido, A.; Gardner, J.; Gavrilov, V.; Gay, A.; Gay, P.; Gelé, D.; Gelhaus, R.; Gerber, C. E.; Gershtein, Y.; Gillberg, D.; Ginther, G.; Gollub, N.; Gómez, B.; Goussiou, A.; Grannis, P. D.; Greenlee, H.; Greenwood, Z. D.; Gregores, E. M.; Grenier, G.; Gris, Ph.; Grivaz, J.-F.; Grünendahl, S.; Grünewald, M. W.; Guo, F.; Guo, J.; Gutierrez, G.; Gutierrez, P.; Haas, A.; Hadley, N. J.; Haefner, P.; Hagopian, S.; Haley, J.; Hall, I.; Hall, R. E.; Han, L.; Hanagaki, K.; Hansson, P.; Harder, K.; Harel, A.; Harrington, R.; Hauptman, J. M.; Hauser, R.; Hays, J.; Hebbeker, T.; Hedin, D.; Hegeman, J. G.; Heinmiller, J. M.; Heinson, A. P.; Heintz, U.; Hensel, C.; Herner, K.; Hesketh, G.; Hildreth, M. D.; Hirosky, R.; Hobbs, J. D.; Hoeneisen, B.; Hoeth, H.; Hohlfeld, M.; Hong, S. J.; Hooper, R.; Houben, P.; Hu, Y.; Hubacek, Z.; Hynek, V.; Iashvili, I.; Illingworth, R.; Ito, A. S.; Jabeen, S.; Jaffré, M.; Jain, S.; Jakobs, K.; Jarvis, C.; Jenkins, A.; Jesik, R.; Johns, K.; Johnson, C.; Johnson, M.; Jonckheere, A.; Jonsson, P.; Juste, A.; Käfer, D.; Kahn, S.; Kajfasz, E.; Kalinin, A. M.; Kalk, J. M.; Kalk, J. R.; Kappler, S.; Karmanov, D.; Kasper, J.; Kasper, P.; Katsanos, I.; Kau, D.; Kaur, R.; Kehoe, R.; Kermiche, S.; Khalatyan, N.; Khanov, A.; Kharchilava, A.; Kharzheev, Y. M.; Khatidze, D.; Kim, H.; Kim, T. J.; Kirby, M. H.; Klima, B.; Kohli, J. M.; Konrath, J.-P.; Kopal, M.; Korablev, V. M.; Kotcher, J.; Kothari, B.; Koubarovsky, A.; Kozelov, A. V.; Krop, D.; Kryemadhi, A.; Kuhl, T.; Kumar, A.; Kunori, S.; Kupco, A.; Kur?a, T.; Kvita, J.; Lammers, S.; Landsberg, G.; Lazoflores, J.; Le Bihan, A.-C.; Lebrun, P.; Lee, W. M.; Leflat, A.; Lehner, F.; Lesne, V.; Leveque, J.; Lewis, P.; Li, J.; Li, Q. Z.; Lima, J. G. R.; Lincoln, D.; Linnemann, J.; Lipaev, V. V.; Lipton, R.; Liu, Z.; Lobo, L.; Lobodenko, A.; Lokajicek, M.; Lounis, A.; Love, P.; Lubatti, H. J.; Lynker, M.; Lyon, A. L.; Maciel, A. K. A.; Madaras, R. J.; Mättig, P.; Magass, C.; Magerkurth, A.; Magnan, A.-M.; Makovec, N.; Mal, P. K.; Malbouisson, H. B.; Malik, S.; Malyshev, V. L.; Mao, H. S.; Maravin, Y.; Martens, M.; McCarthy, R.; Meder, D.; Melnitchouk, A.; Mendes, A.; Mendoza, L.; Merkin, M.; Merritt, K. W.; Meyer, A.; Meyer, J.; Michaut, M.; Miettinen, H.; Millet, T.; Mitrevski, J.; Molina, J.

181

Measurement of the top quark mass in the dilepton channel  

NASA Astrophysics Data System (ADS)

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

DØ Collaboration; Abazov, V. M.; Abbott, B.; Abolins, M.; Acharya, B. S.; Adams, M.; Adams, T.; Agelou, M.; Aguilo, E.; Ahn, S. H.; Ahsan, M.; Alexeev, G. D.; Alkhazov, G.; Alton, A.; Alverson, G.; Alves, G. A.; Anastasoaie, M.; Andeen, T.; Anderson, S.; Andrieu, B.; Anzelc, M. S.; Arnoud, Y.; Arov, M.; Askew, A.; Åsman, B.; Assis Jesus, A. C. S.; Atramentov, O.; Autermann, C.; Avila, C.; Ay, C.; Badaud, F.; Baden, A.; Bagby, L.; Baldin, B.; Bandurin, D. V.; Banerjee, P.; Banerjee, S.; Barberis, E.; Bargassa, P.; Baringer, P.; Barnes, C.; 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.; Berntzon, L.; Bertram, I.; Besançon, M.; Beuselinck, R.; Bezzubov, V. A.; Bhat, P. C.; Bhatnagar, V.; Binder, M.; Biscarat, C.; Black, K. M.; Blackler, I.; Blazey, G.; Blekman, F.; Blessing, S.; Bloch, D.; Bloom, K.; Blumenschein, U.; Boehnlein, A.; Boeriu, O.; Boline, D.; Bolton, T. A.; Borissov, G.; Bos, K.; Bose, T.; Brandt, A.; Brock, R.; Brooijmans, G.; Bross, A.; Brown, D.; Buchanan, N. J.; Buchholz, D.; Buehler, M.; Buescher, V.; Burdin, S.; Burke, S.; Burnett, T. H.; Busato, E.; Buszello, C. P.; Butler, J. M.; Calfayan, P.; Calvet, S.; Cammin, J.; Caron, S.; Carvalho, W.; Casey, B. C. K.; Cason, N. M.; Castilla-Valdez, H.; Chakrabarti, S.; Chakraborty, D.; Chan, K. M.; Chandra, A.; Charles, F.; Cheu, E.; Chevallier, F.; Cho, D. K.; Choi, S.; Choudhary, B.; Christofek, L.; Claes, D.; Clément, B.; Clément, C.; Coadou, Y.; Cooke, M.; Cooper, W. E.; Coppage, D.; Corcoran, M.; Cousinou, M.-C.; Cox, B.; Crépé-Renaudin, S.; Cutts, D.; ?wiok, M.; da Motta, H.; Das, A.; Das, M.; Davies, B.; Davies, G.; Davis, G. A.; de, K.; de Jong, P.; de Jong, S. J.; de La Cruz-Burelo, E.; de Oliveira Martins, C.; Degenhardt, J. D.; Déliot, F.; Demarteau, M.; Demina, R.; Demine, P.; Denisov, D.; Denisov, S. P.; Desai, S.; Diehl, H. T.; Diesburg, M.; Doidge, M.; Dominguez, A.; Dong, H.; Dudko, L. V.; Duflot, L.; Dugad, S. R.; Duggan, D.; Duperrin, A.; Dyer, J.; Dyshkant, A.; Eads, M.; Edmunds, D.; Edwards, T.; Ellison, J.; Elmsheuser, J.; Elvira, V. D.; Eno, S.; Ermolov, P.; Evans, H.; Evdokimov, A.; Evdokimov, V. N.; Fatakia, S. N.; Feligioni, L.; Ferapontov, A. V.; Ferbel, T.; Fiedler, F.; Filthaut, F.; Fisher, W.; Fisk, H. E.; Fleck, I.; Ford, M.; Fortner, M.; Fox, H.; Fu, S.; Fuess, S.; Gadfort, T.; Galea, C. F.; Gallas, E.; Galyaev, E.; Garcia, C.; Garcia-Bellido, A.; Gardner, J.; Gavrilov, V.; Gay, A.; Gay, P.; Gelé, D.; Gelhaus, R.; Gerber, C. E.; Gershtein, Y.; Gillberg, D.; Ginther, G.; Gollub, N.; Gómez, B.; Goussiou, A.; Grannis, P. D.; Greenlee, H.; Greenwood, Z. D.; Gregores, E. M.; Grenier, G.; Gris, Ph.; Grivaz, J.-F.; Grünendahl, S.; Grünewald, M. W.; Guo, F.; Guo, J.; Gutierrez, G.; Gutierrez, P.; Haas, A.; Hadley, N. J.; Haefner, P.; Hagopian, S.; Haley, J.; Hall, I.; Hall, R. E.; Han, L.; Hanagaki, K.; Hansson, P.; Harder, K.; Harel, A.; Harrington, R.; Hauptman, J. M.; Hauser, R.; Hays, J.; Hebbeker, T.; Hedin, D.; Hegeman, J. G.; Heinmiller, J. M.; Heinson, A. P.; Heintz, U.; Hensel, C.; Herner, K.; Hesketh, G.; Hildreth, M. D.; Hirosky, R.; Hobbs, J. D.; Hoeneisen, B.; Hoeth, H.; Hohlfeld, M.; Hong, S. J.; Hooper, R.; Houben, P.; Hu, Y.; Hubacek, Z.; Hynek, V.; Iashvili, I.; Illingworth, R.; Ito, A. S.; Jabeen, S.; Jaffré, M.; Jain, S.; Jakobs, K.; Jarvis, C.; Jenkins, A.; Jesik, R.; Johns, K.; Johnson, C.; Johnson, M.; Jonckheere, A.; Jonsson, P.; Juste, A.; Käfer, D.; Kahn, S.; Kajfasz, E.; Kalinin, A. M.; Kalk, J. M.; Kalk, J. R.; Kappler, S.; Karmanov, D.; Kasper, J.; Kasper, P.; Katsanos, I.; Kau, D.; Kaur, R.; Kehoe, R.; Kermiche, S.; Khalatyan, N.; Khanov, A.; Kharchilava, A.; Kharzheev, Y. M.; Khatidze, D.; Kim, H.; Kim, T. J.; Kirby, M. H.; Klima, B.; Kohli, J. M.; Konrath, J.-P.; Kopal, M.; Korablev, V. M.; Kotcher, J.; Kothari, B.; Koubarovsky, A.; Kozelov, A. V.; Krop, D.; Kryemadhi, A.; Kuhl, T.; Kumar, A.; Kunori, S.; Kupco, A.; Kur?a, T.; Kvita, J.; Lammers, S.; Landsberg, G.; Lazoflores, J.; Le Bihan, A.-C.; Lebrun, P.; Lee, W. M.; Leflat, A.; Lehner, F.; Lesne, V.; Leveque, J.; Lewis, P.; Li, J.; Li, Q. Z.; Lima, J. G. R.; Lincoln, D.; Linnemann, J.; Lipaev, V. V.; Lipton, R.; Liu, Z.; Lobo, L.; Lobodenko, A.; Lokajicek, M.; Lounis, A.; Love, P.; Lubatti, H. J.; Lynker, M.; Lyon, A. L.; Maciel, A. K. A.; Madaras, R. J.; Mättig, P.; Magass, C.; Magerkurth, A.; Magnan, A.-M.; Makovec, N.; Mal, P. K.; Malbouisson, H. B.; Malik, S.; Malyshev, V. L.; Mao, H. S.; Maravin, Y.; Martens, M.; McCarthy, R.; Meder, D.; Melnitchouk, A.; Mendes, A.; Mendoza, L.; Merkin, M.; Merritt, K. W.; Meyer, A.; Meyer, J.; Michaut, M.; Miettinen, H.; Millet, T.

2007-10-01

182

Measurement of the top quark mass in the dilepton channel  

E-print Network

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

Abazov, V M; Abolins, M; Acharya, B S; Adams, M; Adams, T; Agelou, M; Aguiló, E; Ahn, S H; Ahsan, M; Alexeev, G D; Alkhazov, G; Alton, A; Alverson, G; Alves, G A; Anastasoaie, M; Andeen, T; Anderson, S; Andrieu, B; Anzelc, M S; Arnoud, Y; Arov, M; Askew, A; Åsman, B; Assis-Jesus, A C S; Atramentov, O; Autermann, C; Avila, C; Ay, C; Badaud, F; Baden, A; Bagby, L; Baldin, B; Bandurin, D V; Banerjee, P; Banerjee, S; Barberis, E; Bargassa, P; Baringer, P; Barnes, C; Barreto, J; Bartlett, J F; Bassler, U; Bauer, D; Beale, S; Bean, A; Begalli, M; Begel, M; Belanger-Champagne, C; Bellantoni, L; Bellavance, A; Benítez, J A; Beri, S B; Bernardi, G; Bernhard, R; Berntzon, L; Bertram, I; Besançon, M; Beuselinck, R; Bezzubov, V A; Bhat, P C; Bhatnagar, V; Binder, M; Biscarat, C; Black, K M; Blackler, I; Blazey, G; Blekman, F; Blessing, S; Bloch, D; Bloom, K; Blumenschein, U; Böhnlein, A; Boeriu, O; Bolton, T A; Borissov, G; Bos, K; Bose, T; Brandt, A; Brock, R; Brooijmans, G; Bross, A; Brown, D; Buchanan, N J; Buchholz, D; Bühler, M; Büscher, V; Burdin, S; Burke, S; Burnett, T H; Busato, E; Buszello, C P; Butler, J M; Calfayan, P; Calvet, S; Cammin, J; Caron, S; Carvalho, W; Casey, B C K; Cason, N M; Castilla-Valdez, H; Chakrabarti, S; Chakraborty, D; Chan, K M; Chandra, A; Charles, F; Cheu, E; Chevallier, F; Cho, D K; Choi, S; Choudhary, B; Christofek, L; Claes, D; Clement, B; Clément, C; Coadou, Y; Cooke, M; Cooper, W E; Coppage, D; Corcoran, M; Cousinou, M C; Cox, B; Crepe-Renaudin, S; Cutts, D; Cwiok, M; Da Motta, H; Das, A; Das, M; Davies, B; Davies, G; Davis, G A; De, K; de Jong, P; De Jong, S J; De La Cruz-Burelo, E; De Oliveira Martins, C; Degenhardt, J D; Déliot, F; Demarteau, M; Demina, R; Demine, P; Denisov, D; Denisov, S P; Desai, S; Diehl, H T; Diesburg, M; Doidge, M; Dominguez, A; Dong, H; Dudko, L V; Duflot, L; Dugad, S R; Duggan, D; Duperrin, A; Dyer, J; Dyshkant, A; Eads, M; Edmunds, D; Edwards, T; Ellison, J; Elmsheuser, J; Elvira, V D; Eno, S; Ermolov, P; Evans, H; Evdokimov, A; Evdokimov, V N; Fatakia, S N; Feligioni, L; Ferapontov, A V; Ferbel, T; Fiedler, F; Filthaut, F; Fisher, W; Fisk, H E; Fleck, I; Ford, M; Fortner, M; Fox, H; Fu, S; Fuess, S; Gadfort, T; Galea, C F; Gallas, E; Galyaev, E; García, C; García-Bellido, A; Gardner, J; Gavrilov, V; Gay, A; Gay, P; Gelé, D; Gelhaus, R; Gerber, C E; Gershtein, Yu; Gillberg, D; Ginther, G; Gollub, N; Gómez, B; Goussiou, A; Grannis, P D; Greenlee, H; Greenwood, Z D; Gregores, E M; Grenier, G; Gris, P; Grivaz, J F; Grünendahl, S; Grünewald, M W; Guo, F; Guo, J; Gutíerrez, G; Gutíerrez, P; Haas, A; Hadley, N J; Haefner, P; Hagopian, S; Haley, J; Hall, I; Hall, R E; Han, L; Hanagaki, K; Hansson, P; Harder, K; Harel, A; Harrington, R; Hauptman, J M; Hauser, R; Hays, J; Hebbeker, T; Hedin, D; Hegeman, J G; Heinmiller, J M; Heinson, A P; Heintz, U; Hensel, C; Herner, K; Hesketh, G; Hildreth, M D; Hirosky, R; Hobbs, J D; Hoeneisen, B; Hoeth, H; Hohlfeld, M; Hong, S J; Hooper, R; Houben, P; Hu, Y; Hubacek, Z; Hynek, V; Iashvili, I; Illingworth, R; Ito, A S; Jabeen, S; Jaffré, M; Jain, S; Jakobs, K; Jarvis, C; Jenkins, A; Jesik, R; Johns, K; Johnson, C; Johnson, M; Jonckheere, A; Jonsson, P; Juste, A; Käfer, D; Kahn, S; Kajfasz, E; Kalinin, A M; Kalk, J M; Kalk, J R; Kappler, S; Karmanov, D; Kasper, J; Kasper, P; Katsanos, I; Kau, D; Kaur, R; Kehoe, R; Kermiche, S; Khalatyan, N; Khanov, A; Kharchilava, A I; Kharzheev, Yu M; Khatidze, D; Kim, H; Kim, T J; Kirby, M H; Klima, B; Kohli, J M; Konrath, J P; Kopal, M; Korablev, V M; Kotcher, J; Kothari, B; Koubarovsky, A; Kozelov, A V; Krop, D; Kryemadhi, A; Kühl, T; Kumar, A; Kunori, S; Kupco, A; Kurca, T; Kvita, J; Lammers, S; Landsberg, G L; Lazoflores, J; Le Bihan, A C; Lebrun, P; Lee, W M; Leflat, A; Lehner, F; Lesne, V; Lévêque, J; Lewis, P; Li, J; Li, Q Z; Lima, J G R; Lincoln, D; Linnemann, J; Lipaev, V V; Lipton, R; Liu, Z; Lobo, L; Lobodenko, A; Lokajícek, M; Lounis, A; Love, P; Lubatti, H J; Lynker, M; Lyon, A L; Maciel, A K A; Madaras, R J; Mättig, P; Magass, C; Magerkurth, A; Magnan, A M; Makovec, N; Mal, P K; Malbouisson, H B; Malik, S; Malyshev, V L; Mao, H S; Maravin, Y; Martens, M; McCarthy, R; Meder, D; Melnitchouk, A; Mendes, A; Mendoza, L; Merkin, M; Merritt, K W; Meyer, A; Meyer, J; Michaut, M; Miettinen, H; Millet, T; Mitrevski, J; Molina, J; Mondal, N K; Monk, J; Moore, R W; Moulik, T; Muanza, G S; Mulders, M; Mulhearn, M; Mundal, O; Mundim, L; Mutaf, Y D; Nagy, E; Naimuddin, M; Narain, M; Naumann, N A; Neal, H A; Negret, J P; Neustroev, P; Nöding, C; Nomerotski, A; Novaes, S F; Nunnemann, T; O'Dell, V; O'Neil, D C; Obrant, G; Oguri, V; Oliveira, N; Onoprienko, D; Oshima, N; Otec, R; Oteroy-Garzon, G J; Owen, M; Padley, P; Parashar, N; Park, S J; Park, S K; Parsons, J; Partridge, R; Parua, N; Patwa, A; Pawloski, G; Perea, P M; Pérez, E; Peters, K; Petroff, P; Petteni, M

2007-01-01

183

Weighted sum-rate maximization for multi-user SIMO multiple access channels in cognitive radio networks  

NASA Astrophysics Data System (ADS)

In this article, an efficient distributed and parallel algorithm is proposed to maximize the sum-rate and optimize the input distribution policy for the multi-user single input multiple output multiple access channel (MU-SIMO MAC) system with concurrent access within a cognitive radio (CR) network. The single input means that every user has a single antenna and multiple output means that base station(s) has multiple antennas. The main features are: (i) the power distribution for the users is updated by using variable scale factors which effectively and efficiently maximize the objective function at each iteration; (ii) distributed and parallel computation is employed to expedite convergence of the proposed distributed algorithm; and (iii) a novel water-filling with mixed constraints is investigated, and used as a fundamental block of the proposed algorithm. Due to sufficiently exploiting the structure of the proposed model, the proposed algorithm owns fast convergence. Numerical results verify that the proposed algorithm is effective and fast convergent. Using the proposed approach, for the simulated range, the required number of iterations for convergence is two and this number is not sensitive to the increase of the number of users. This feature is quite desirable for large scale systems with dense active users. In addition, it is also worth noting that the proposed algorithm is a monotonic feasible operator to the iteration. Thus, the stop criterion for computation could be easily set up.

He, Peter; Zhao, Lian; Lu, Jianhua

2013-12-01

184

Modeling potentiometric measurements in topological insulators including parallel channels  

NASA Astrophysics Data System (ADS)

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

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

2012-08-01

185

Lunar Dielectric Constants from Radio Thermal Emission Measurements  

Microsoft Academic Search

Thermal emission from the Moon at 21 cm was measured in all four Stokes parameters with the Very Large Array (VLA). The polarization properties of the emission are determined primarily by the dielectric constant of the regolith material, the fraction of the emergent radiation that is diffused, and the surface roughness on scales larger than the wavelength. Estimates of the

J. L. Margot; D. B. Campbell; B. A. Campbell; B. J. Butler

1996-01-01

186

Midlatitude D region variations measured from broadband radio atmospherics  

NASA Astrophysics Data System (ADS)

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

Han, Feng

187

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

188

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

189

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

NASA Astrophysics Data System (ADS)

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.; Kakati, M.

2011-10-01

190

Noise and the strong signal limit in radio astronomical measurement  

E-print Network

The random error of radioastronomical measurements is usually computed in the weak-signal limit, which assumes that the system temperature is sensibly the same on and off source, or with and without a spectral line. This assumption is often very poor. We give examples of common situations in which it is important to distinguish the system noise in signal-bearing and signal-free regions.

H. Liszt

2002-06-27

191

Effective Capacity Analysis of Cognitive Radio Channels for Quality of Service Provisioning  

E-print Network

. INTRODUCTION With the rapid growth in the wireless networks in the last two decades, the scarcity in spectrum allocated for specific applications. However, recent measurements show that the licensed spectrum has become a serious problem for spectrum sharing, since much of the prime wireless spectrum has been

Gursoy, Mustafa Cenk

192

A Fast Time-Domain Wireless Channel Simulation Tool for Radio-Wave Propagation Courses  

E-print Network

are dynamically animated and measured with precision. We have developed an educational software package testing has shown that simulations using an NVIDIA 6800 Ultra PCI/Express GPU can execute FDTD simulations up to 134Ã? faster com- pared to that of a 3.4 GHz Intel Pentium CPU [3]. Such acceleration

193

Results of refraction-angle measurement of radio waves in the Venus atmosphere on the basis of bistatic radar data  

NASA Astrophysics Data System (ADS)

Improved measurements of refraction in the Venus atmosphere using bistatic radar data have been obtained. To describe the refraction effects, a theoretical model is developed that makes it possible to determine the parameters for calculating radio communication lines in the Venus troposphere from the height dependence of the refractive index. Expressions are obtained relating the phase path length of radio waves and the integral absorption of radio waves in the atmosphere to the parameters of the theoretical model.

Salimzyanov, R. R.; Pavel'Ev, D. A.

1993-08-01

194

Educational Radio. Information Bulletin 21-B.  

ERIC Educational Resources Information Center

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

Federal Communications Commission, Washington, DC.

195

47 CFR 22.725 - Channels for conventional rural radiotelephone stations and basic exchange telephone radio systems.  

Code of Federal Regulations, 2010 CFR

... 2010-10-01 false Channels for conventional rural radiotelephone...Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED...Radiotelephone Stations § 22.725 Channels for conventional rural radiotelephone...systems. The following channels are allocated for...

2010-10-01

196

Estimating water vapour along the radio path between two LEO satellites through multifrequency differential power measurements  

NASA Astrophysics Data System (ADS)

The Normalized Differential Spectral Attenuation (NDSA) concept was proposed in 2002 by the authors for tropospheric water vapour sounding by means of a couple of LEO (Low Earth Orbit) satellites (one carrying a transmitter, the other a receiver and operating in the Ku/K bands) in limb geometry. In those years, in the course of the ACE+ mission studies (second call for proposal of the ESA Earth Explorer Opportunity Mission), the problem arose of the severe impact of scintillation due to tropospheric turbulence on the water vapour estimates provided by radio occultation measurements made in limb mode between two LEO satellites. In following ESA studies (AlmetLeo - 2004, ACTLIMB -2009) it was demonstrated that NDSA, thanks to its normalised differential approach, is effective for limiting scintillation and for estimating the Integrated Water Vapor (IWV) along the propagation path between the two LEO satellites. NDSA relies on the conversion of a spectral parameter (the spectral sensitivity S), into the IWV through IWV-S relationships. S is a finite-difference approximation of the derivative of the spectral attenuation at a given frequency fo, normalized to the spectral attenuation itself. To measure Sat fo,it is required that two tone signals with equal power at relatively close frequencies f1 and f2 (f1 > f2) symmetrically placed around fo are simultaneously transmitted. The two pertinent received powers P1 and P2 are simultaneously measured and S is provided by: S = -P2--P1- (f1 - f2 )P2 From the very beginning of the NDSA studies, it was evident that in ideal measurement conditions (no disturbance at the receiver nor propagation impairments) S is tightly correlated to the IWV. To verify this, we accounted for natural variations of the atmospheric conditions by generating simulated spherically symmetric atmospheres using real radiosonde profiles. We computed IWV along the radio path and simulated S separately obtaining IWV-S relationships at various altitudes through regression methods. In particular, the ESA-AlMetLEO study yielded a significant insight into such relationships up to 12 km using the K-Ku bands, while the ESA-ACTLIMB study offered the opportunity to investigate the potential of 179 to 182 GHz (M band) for estimates from 10 km upwards, exhibiting a significant robustness to scintillation fluctuations. However, two problems affected the reliability of the empirical IWV-S relations found and have been faced by us during the on-going ESA-ANISAP study: 1) the accuracy of the radiosonde data used to derive them was not uniform in the northern and southern hemisphere, and so their positions; 2) the number of radiosonde samples above 10 km was limited, and their reliability scarce, which affected the analysis of the IWV-S relations in the M band. To overcome both problems, instead of radiosonde data, we utilized atmospheric pro?les equally distributed on a global Earth scale as derived from ECMWF atmospheric analysis data. Such database includes pressure, temperature, humidity, liquid water, ice water and wind components in 8 global datasets in 4 days amid of each of the four seasons and at two time layers (12:00 UTC and 24:00 UTC). In this work, we show the main results of the global scale analysis of the IWV-S relations up to 20 altitude. We point out that NDSA requires a multi-frequency approach to provide reliable IWV estimates up to 20 km, and that S estimates at 17, 19 and 21 GHz are essential to provide IWV profiles in the lower troposphere through linear relationships, while the M band channels (179 and 182 GHz) can be reliably exploited still through linear relationships above 10 km where the water vapour content is smaller. We also demonstrate that an additional spectral sensitivity channel at 32 GHz is very effective both to detect the presence of liquid water along the link and to correct the IWV overestimates caused by such presence when using S measurements in the K/Ku band (17, 19 and 21 GHz).

Facheris, Luca; Cuccoli, Fabrizio

2013-04-01

197

Direction-finding measurements of type 3 radio bursts out of the ecliptic plane  

NASA Technical Reports Server (NTRS)

Direction-finding measurements with the plasma wave experiments on the HAWKEYE 1 and IMP 8 satellites are used to find the source locations of type 3 solar radio bursts in heliocentric latitude and longitude in a frequency range from 31.1 kHz to 500 kHz. Using an empirical model for the emission frequency as a function of radial distance from the sun the three-dimensional trajectory of the type 3 radio source can be determined from direction-finding measurements at different frequencies. Since the electrons which produce these radio emissions follow the magnetic field lines from the sun these measurements provide information on the three-dimensional structure of the magnetic field in the solar wind. The source locations projected into the ecliptic plane follow an Archimedian spiral. Perpendicular to the ecliptic plane the source locations usually follow a constant heliocentric latitude. With direction-finding measurements of this type it is also possible to determine the source size from the modulation factor of the received signals.

Baumback, M. M.; Kurth, W. S.; Gurnett, D. A.

1975-01-01

198

Measurement of the top quark mass in the dilepton channel  

SciTech Connect

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

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

2006-09-01

199

Radio continuum measurements of compact H II regions and other sources  

NASA Technical Reports Server (NTRS)

Results are reported for measurements of the flux densities of 33 sources at wavelengths of 13, 4, and 2 cm, which were conducted using the NASA/JPL Deep Space Network 64-m antenna at Goldstone, Calif. Besides compact H II regions, the sources included five Uhuru X-ray sources, several IR sources, an extragalactic radio source, and a H2O maser. The Lyman continuum flux is derived from the measured radio flux and the assumed distance and temperature for 10 possible H II regions; the spectra of previously known sources are extended to higher frequencies, and upper limits are placed on the flux densities for the five X-ray sources. New compact H II regions are found in the bright nebula M78, the nebula K5, and the Ophiuchus dark cloud/IR region.

Matsakis, D. N.; Evans, N. J., II; Sato, T.; Zuckerman, B.

1976-01-01

200

Channel Eigenvalue Distribution and Ergodic Capacity Analysis of Outdoor-Indoor MIMO Measured Channel  

Microsoft Academic Search

This paper analyzes the channel eigenvalue distribution and the ergodic channel capacity of correlated multiple-input multiple-output (MIMO) channels. These eigenvalue densities can be represented by complex hypergeometric functions of matrix arguments, which can be expressed in terms of complex zonal polynomials. A realistic propagation environment in the presence of spatial fading correlation under an outdoor-indoor scenario at 5.25 GHz, which

Attapongse Taparugssanagorn; Mikko Alatossava; Veli-matti Holappa; Juha Ylitalo

2007-01-01

201

Measurement of Radio Propagation Path Loss over the Sea for Wireless Multimedia  

Microsoft Academic Search

\\u000a In order to estimate the signal parameters accurately for wireless multimedia services, it is necessary to estimate a system’s\\u000a propagation characteristics through a medium. Propagation analysis provides a good initial estimate of the signal characteristics.\\u000a The ability to accurately predict radio propagation behavior for wireless multimedia services is becoming crucial to system\\u000a design. Since site measurements are costly, propagation models

Dong-you Choi

2006-01-01

202

Lunar occultation of the diffuse radio sky: LOFAR measurements between 35 and 80 MHz  

E-print Network

We present radio observations of the Moon between $35$ and $80$ MHz to demonstrate a novel technique of interferometrically measuring large-scale diffuse emission extending far beyond the primary beam (global signal) for the first time. In particular, we show that (i) the Moon appears as a negative-flux source at frequencies $35z>12$) and the Epoch of Reionization ($12>z>5$).

Vedantham, H K; de Bruyn, A G; Wijnholds, S J; Brentjens, M; Abdalla, F B; Asad, K M B; Bernardi, G; Bus, S; Chapman, E; Ciardi, B; Daiboo, S; Fernandez, E R; Ghosh, A; Harker, G; Jelic, V; Jensen, H; Kazemi, S; Lambropoulos, P; Martinez-Rubi, O; Mellema, G; Mevius, M; Offringa, A R; Pandey, V N; Patil, A H; Thomas, R M; Veligatla, V; Yatawatta, S; Zaroubi, S; Anderson, J; Asgekar, A; Bell, M E; Bentum, M J; Best, P; Bonafede, A; Breitling, F; Broderick, J; Brüggen, M; Butcher, H R; Corstanje, A; de Gasperin, F; de Geus, E; Deller, A; Duscha, S; Eislöffel, J; Engels, D; Falcke, H; Fallows, R A; Fender, R; Ferrari, C; Frieswijk, W; Garrett, M A; Grießmeier, J; Gunst, A W; Hassall, T E; Heald, G; Hoeft, M; Hörandel, J; Iacobelli, M; Juette, E; Kondratiev, V I; Kuniyoshi, M; Kuper, G; Mann, G; Markoff, S; McFadden, R; McKay-Bukowski, D; Mulcahy, D D; Munk, H; Nelles, A; Norden, M J; Orru, E; Pandey-Pommier, M; Pizzo, R; Polatidis, A G; Reich, W; Renting, A; Röttgering, H; Schwarz, D; Shulevski, A; Smirnov, O; Stappers, B W; Steinmetz, M; Swinbank, J; Tagger, M; Tang, Y; Tasse, C; ter Veen, S; Thoudam, S; Toribio, C; vocks, C; Wise, M W; Wucknitz, O; Zarka, P

2014-01-01

203

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

204

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

205

Conceptual Background to Radio  

NASA Astrophysics Data System (ADS)

The International Telecommunications Union (ITU) conceives the radio spectrum as primarily a resource for telecommunications. Indeed most applications of radio are for communications and other radio services, particularly the Radio Astronomy Service, are deemed to be `pretend'communication serviceas for spectrum amnagement purposes. The language of Radio Spectrum Management is permeated by the terminology ofcommunications, some derived from the physics of radio and some from aspects of information theory. This contribution touches on all the essential concepts of radiocommunications which the author thinks should be the common mental equipment of the Spectrum Manager. The fundamental capacity of a communication channel is discussed in terms of the degrees of freedom and bandwidth of a signal, and the signal to noise ratio. It is emphasized that an information bearing signal is inherently unpredictable, and must, at some level, be discontinuous. This has important consequences for the form of its power spectrum. The effect of inserting filters is discussed particularly with regard to constant amplitude signals and, in the context of non-linear power amplifiers, the phenomenon of`sideband recovery'. All the common generic forms of modulation are discussed including the very different case of `no-modulation' which applies in all forms of passive remote sensing. Whilst all are agreed that the radio spectrum should be used `efficiently', there is no quantitative measure of spectral efficiency which embraces all relevant aspects of spectral usage. These various aspects are dicussed. Finally a brief outline of some aspects of antennae are reviewed. It is pointed out that the recent introduction of so-called `active antennnae', which have properties unlike traditional passive antennae, has confused the interpretation of those ITU Radio Regulations which refer to antennae.

Ponsonby, J. E. B.

2004-06-01

206

Phase-Resolved Measurements of Ion Velocity in a Radio-Frequency Sheath Brett Jacobs,1,* Walter Gekelman,1  

E-print Network

Phase-Resolved Measurements of Ion Velocity in a Radio-Frequency Sheath Brett Jacobs,1,* Walter by Stern and Johnson [4]. The first experi- ments used low power cw lasers and signal averaging to study

California at Los Angles, University of

207

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

208

HF Channel Availability under Ionospheric Disturbances: Model, Method and Measurements as Contributions  

NASA Astrophysics Data System (ADS)

A small group at METU has been developing data driven models in order to forecast some critical parameters, which affect the communication and navigation systems, since 1990. The background on the subjects supports new achievements in terms of theoretical and experimental basis contributing the COST 296 WG2 activities. This work mentions the representative contributions. (i) A method has been proposed for the assessment of HF Channel Availability under ionospheric disturbances. Signal to Noise Ratio (SNR), Doppler Spread and Modified Power Delay Spread were considered. The study relates the modem performance to ionospheric disturbances. Ionospheric disturbance was characterised by Disturbance Storm Type (DST) index. Radar data including Effective Multipath Spread, Composite Doppler Spread and SNR values were obtained from the experiment conducted between Leicester UK (52.63° N; 1.08° W) and Uppsala, Sweden (59.92° N; 17.63° E) in the year 2001. First, joint probability density function (PDF) of SNR, Doppler Spread, and Effective Multipath Spread versus DST were considered. It was demonstrated by determining the conditional PDFs, and by using Bayes' Theorem, that there were dependencies between DST and the above mentioned parameters [Sari, 2006]. Thus, it is concluded that the availability of the HF channel is a function of DST. As examples of modem characterizations, Military Standards were considered. Given a magnetic condition, the modem availability was calculated. The model developed represents the ionospheric HF channel, and it is based on a stochastic approach. Depending on the new experimental data, the conditional PDFs could be updated continuously. The HF channel availability under various ionospheric Space Weather (SW) conditions can be determined using the model. The proposed method is general and can include other indices as well. The method can also be applied to a variety of other processes. (ii) The effects of space weather conditions on the variation of group range and line-of-sight Doppler velocity of the HF Radar echo signal were investigated. HF radar system under ionospheric disturbances has been identified globally and some operational suggestions have been presented. It is possible for the HF radar operator to estimate the possible skip distance and possible single hop group ranges for the given frequencies of 11 MHz and 14 MHz [Buyukpabuscu, 2007]. (iii) The measurements over the HF band during the 29 March 2006 total solar eclipse in Antalya (36° N; 30° E) Turkey was conducted from the channel occupancy and atmospheric noise points of view. The whole HF band ranging from 1 to 30 MHz has been swept using 10 kHz peak and 200 Hz average detectors of a certified EMI receiver equipped with a calibrated active monopole antenna. The changes in the atmospheric noise during the eclipse were reported [Tulunay, 2006]. The model based, theoretical and experimental works mentioned are promising and have potential for future research and developments. References Buyukpabuscu S.O. (2007), System Identification with Particular Interest On The High Frequency Radar Under Ionospheric Disturbances, MS Thesis, Electrical and Electronics Eng., Middle East Technical Univ., Ankara, Turkey, February 2007. Sari M.O. (2006), A New Approach For The Assessment Of Hf Channel Availability Under Ionospheric Disturbances, MS Thesis, Electrical and Electronics Eng., Middle East Technical Univ., Ankara, Turkey, September 2006. Tulunay E., E. M. Warrington, Y. Tulunay, Y. Bahad?rlar, A.S. Türk, R. Çaputçu, T. Yap?c? , E.T. ?enalp (2006), Propagation Related Measurements during Three Solar Eclipses in Turkey, IET 10th International Conference on Ionospheric Radio Systems & Techniques, IRST 2006, 18-21 July 2006, London, UK.

Tulunay, E.; Senalp, E. T.; Tulunay, Y.; Warrington, E. M.; Sari, M. O.

2009-04-01

209

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

Microsoft Academic Search

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

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

1989-01-01

210

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

E-print Network

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 1500 ft. (457 m) deep level of the mine on our third and most recent visit to the mine. We transmitted and received a fast, high-power, broadband pulse from within three vertical boreholes that were drilled to depths of 100 ft. (30 m) and 200 ft. below the 1500 ft. level using three different pairs of dipole antennas whose bandwidths span 125 to 900 MHz. By measuring the relative strength of the received pulses between boreholes with separations of 50 m and 169 m, we deduce the attenuation of the signal attributed to the salt medium. We fit the frequency dependence of the attenuation to a power law and find the best fit field attenuation lengths to be 93 \\pm 7 m at 150 MHz, 63 \\pm 3 m at 300 MHz, and 36 \\pm 2 m at 800 MHz. This is the most precise measurement of radio attenuation in a natural salt formation to date. We assess the implications of this measurement for a future neutrino detector in salt.

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

2008-06-12

211

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

SciTech Connect

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

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

2007-07-01

212

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

213

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

NASA Astrophysics Data System (ADS)

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

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

214

Verification by Viking landers of earlier radio occultation measurements of surface atmospheric pressure on Mars  

NASA Technical Reports Server (NTRS)

The landing of Viking 1 in Chryse Planitia on July 20, 1976 provided the first opportunity to obtain measurements of atmospheric pressure directly from the surface of Mars. A computation was conducted to predict the atmospheric pressure at the landing site before the landing itself. The relative altitude between occultation points and the Viking 1 site was obtained with the aid of earth-based planetary radar data taken in 1967. The data cover Martian latitudes from 19 deg N to 24 deg N. The investigation indicates that the radio occultation results from Mariner 9 closely correspond to the actual surface pressure on Mars.

Kliore, A. J.

1977-01-01

215

The performance of the ATS-6 radio beacon as a measurement system  

NASA Technical Reports Server (NTRS)

The overall system performance of the ATS-6 Radio Beacon transmitter in orbit and the Boulder ground receiver will be considered. In particular, the calibration accuracy and stability of the system will be described in terms of the observed difference in total content measured by the 360 to 140 MHz differential group delay and the 360 to 40 MHz differential group delay during the first year of operation. A summary of the transmitter housekeeping data and of the ground data collected on the EIRP and satellite antenna polar diagrams will also be presented.

Grubb, R. N.; Fritz, R. B.; Jones, J. E.

1976-01-01

216

Multiple Radios for Effective Rendezvous in Cognitive Radio Networks  

E-print Network

Multiple Radios for Effective Rendezvous in Cognitive Radio Networks Lu Yu1 , Hai Liu1 , Yiu in cognitive radio networks (CRNs) for establishing a communication link on a commonly-available channel, we investigate the rendezvous problem in CRNs where cognitive users are equipped with multiple radios

Chu, Xiaowen

217

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

218

Interplanetary dust detection by radio antennas: Mass calibration and fluxes measured by STEREO/WAVES  

NASA Astrophysics Data System (ADS)

We analyze dust impacts recorded by the S/WAVES radio instrument onboard the two STEREO spacecraft near 1 A.U. during the period 2007-2010. The impact of a dust particle on a spacecraft produces a plasma cloud whose associated electric field can be detected by on-board electric antennas. For this study we use the electric potential time series recorded by the waveform sampler of the instrument. The high time resolution and long sampling times of this measurement enable us to deduce considerably more information than in previous studies based on the dynamic power spectra provided by the same instrument or by radio instruments onboard other spacecraft. The large detection area compared to conventional dust detectors provides flux data with a better statistics. We show that the dust-generated signals are of two kinds, corresponding to impacts of dust from distinctly different mass ranges. We propose calibration formulas for these signals and show that we are able to use S/WAVES as a dust detector with convincing results both in the nanometer and micrometer size ranges. In the latter, the orbital motion of the spacecraft enables us to distinguish between interstellar and interplanetary dust components. Our measurements cover the mass intervals ˜10-22-10-20 kg and ˜10-17 - 5 × 10-16 kg. The flux of the larger dust agrees with measurements of other instruments on different spacecraft.

Zaslavsky, A.; Meyer-Vernet, N.; Mann, I.; Czechowski, A.; Issautier, K.; Le Chat, G.; Pantellini, F.; Goetz, K.; Maksimovic, M.; Bale, S. D.; Kasper, J. C.

2012-05-01

219

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

220

The impact of radio source structure on European geodetic VLBI measurements  

NASA Astrophysics Data System (ADS)

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

Tornatore, V.; Charlot, P.

2007-06-01

221

Frequency spectra of cosmic ray air shower radio emission measured with LOPES  

E-print Network

AIMS: We wish to study the spectral dependence of the radio emission from cosmic-ray air showers around 100 PeV (1017 eV). METHODS: We observe short radio pulses in a broad frequency band with the dipole-interferometer LOPES (LOFAR Prototype Station), which is triggered by a particle detector array named Karlsruhe Shower Core and Array Detector (KASCADE). LOFAR is the Low Frequency Array. For this analysis, 23 strong air shower events are selected using parameters from KASCADE. RESULTS: The resulting electric field spectra fall off to higher frequencies. An average electric field spectrum is fitted with an exponential, or alternatively, with a power law. The spectral slope obtained is not consistent within uncertainties and it is slightly steeper than the slope obtained from Monte Carlo simulations based on air showers simulated with CORSIKA (Cosmic Ray Simulations for KASCADE). One of the strongest events was measured during thunderstorm activity in the vicinity of LOPES and shows the longest pulse length measured of 110 ns and a spectral slope of -3.6. CONCLUSIONS: We show with two different methods that frequency spectra from air shower radio emission can be reconstructed on event-by-event basis, with only two dozen dipole antennae simultaneously over a broad range of frequencies. According to the obtained spectral slopes, the maximum power is emitted below 40 MHz. Furthermore, the decrease in power to higher frequencies indicates a loss in coherence determined by the shower disc thickness. We conclude that a broader bandwidth, larger collecting area, and longer baselines, as will be provided by LOFAR, are necessary to further investigate the relation of the coherence, pulse length, and spectral slope of cosmic ray air showers.

A. Nigl

2008-09-16

222

Contactless measurement of nonlinear conductivity in the radio-frequency range.  

PubMed

We have developed a system for contactless measurement of nonlinear conductivity in the radio-frequency band, and over a wide temperature range. A non-resonant circuit is used to electrically excite the sample, and the induced signal is detected by a resonant circuit whose natural frequency matches higher harmonics of the excitation. A simple modification of the probe allows non-resonant detection suitable for stronger signals. Two measurement procedures are proposed that allow significant excitation power variation, up to 150 W. The apparatus has been validated through the measurement of the nonlinear response at the superconducting transition of a high-Tc superconductor, and the nematic transition of an iron pnictide. PMID:25085150

Došli?, Marija; Pelc, Damjan; Požek, Miroslav

2014-07-01

223

Experimental confirmation and physical understanding of ultra-high bit rate impulse radio in the THz digital communication channels of the atmosphere  

NASA Astrophysics Data System (ADS)

We have performed highly accurate numerical calculations of high bit rate impulse propagation through the seven digital communication channels of the atmosphere at RH 58% (10 g m-3). These calculations maximized bit rates for pathlengths equal to or longer than 100 m. We have experimentally verified our calculations for three channels with a propagation pathlength of 137 m and RH 65% (11.2 g m-3). Excellent agreement between measurement and theory was obtained for Channel 3 at 252 GHz, bit rate 84 Gb s-1, FWHM bandwidth (BW) 180 GHz; Channel 6 at 672 GHz, 45 Gb s-1, BW 84 GHz; and Channel 7 at 852 GHz, 56.8 Gb s-1, BW 108 GHz.

Mandehgar, Mahboubeh; Yang, Yihong; Grischkowsky, D.

2014-09-01

224

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

Microsoft Academic Search

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

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

2004-01-01

225

Electrical Conductivity Measurements via a Low-Voltage Conductivity Channel  

Microsoft Academic Search

The electrical conductivity in combustion gases with four different compositions (2% potassium with 0%, 10%, 15%, and 20% aluminum by mass added to a hydrocarbon fuel burned in gaseous oxygen) was determined experimentally using conductivity channels with two geometrical configurations, one with a constant bore and one with a tapered bore. Electrical conductivity for these conditions was calculated using the

Robert Rhodes; Trevor Moeller; Dennis Keefer

2012-01-01

226

BEAM MEASUREMENT SYSTEM OF VEPP-2000 INJECTION CHANNELS*  

E-print Network

complex VEPP-2000 [1, 2]. Injection channels have complicated 3-dimensional geometry (figure 1) [3, 4-02-01060- D.E.Berkaev@inp.nsk.su Proceedings of ICALEPCS2009, Kobe, Japan TUP032 Operational Tools 157 #12;The time of discharge of the wire is about 10 ms because of the connecting cable capacity (200 p

Kozak, Victor R.

227

Natural convection in an inclined rectangular channel at various aspect ratios and angles - Experimental measurements  

Microsoft Academic Search

Rates of heat transfer were measured for laminar natural convection in silicone oil and air in a long rectangular channel. The aspect ratio (width\\/height) of the cross-section of the channel was varied over 1, 2, 3, 4.2, 8.4 and 15.5, and the Rayleigh number from 3,000 to 300,000. The channel was heated from below and cooled from above while the

H. Ozoe; H. Sayama; S. W. Churchill

1975-01-01

228

Optical positions of 22 radio stars measured by photoelectric astrolabe Mark-1 in Irkutsk  

NASA Astrophysics Data System (ADS)

The observation of star position for catalogue compiling had been made in Irkutsk for 5 years with the Chinese photoelectric astrolabe Mark-1 according to the agreement of scientific cooperation between CSAO and VS NIITRI. This cooperation has taken the advantage of combination of the large zenith distance (45°) of almucantar for the astrolabe Mark-1 with the high latitude (52°) for Irkutsk, which could eliminate the blind zone existing in declination measurements for all the astrolabe catalogues. Based on the cooperation, a star catalogue containing positions of 817 stars had been completed; besides, the positions of 22 radio stars had been measured precisely in both right ascension and declination, which are given in this paper.

Liu, Jin-Mei; Lu, Chun-Lin; Li, Dong-Ming; Xu, Jia-Yan

2004-06-01

229

ATS-6 radio beacon electron content measurements at Ootacamund, India, October 1975-July 1976  

SciTech Connect

An atlas of total slant-path columnar electron content data measured between the ATS-6 satellite and Ootacamund, India, a site near the magnetic Equator is presented. Although these measurements were taken during a solar minimum, the general level of flare and geomagnetic activity that occurred during the observation period is summarized. These total content (N(T)) data were derived from the modulation phase (group delay) of a carrier signal transmitted from the geostationary satellite's Radio Beacon Experiment. This atlas contains two data sets: (1) N(T) as 2-min subsamples digitally recorded between 2 October 1975 and 28 January 1976 corrected for ATS-6 pitch maneuvers and (2) N(T) as 15-min subsamples chart recorded between 21 October 1975 and 22 July 1976 but uncorrected for changes in satellite orientation.

Bouwer, S.D.; Davies, K.; Donnelly, R.F.; Grubb, R.N.; Jones, J.E.

1980-03-01

230

Reconstruction of the energy and depth of maximum of cosmic-ray air-showers from LOPES radio measurements  

E-print Network

LOPES is a digital radio interferometer located at Karlsruhe Institute of Technology (KIT), Germany, which measures radio emission from extensive air showers at MHz frequencies in coincidence with KASCADE-Grande. In this article, we explore a method (slope method) which leverages the slope of the measured radio lateral distribution to reconstruct crucial attributes of primary cosmic rays. First, we present an investigation of the method on the basis of pure simulations. Second, we directly apply the slope method to LOPES measurements. Applying the slope method to simulations, we obtain uncertainties on the reconstruction of energy and depth of shower maximum Xmax of 13% and 50 g/cm^2, respectively. Applying it to LOPES measurements, we are able to reconstruct energy and Xmax of individual events with upper limits on the precision of 20-25% for the primary energy and 95 g/cm^2 for Xmax, despite strong human-made noise at the LOPES site.

Apel, W D; 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; Schröder, F G; Sima, O; Toma, G; Trinchero, G C; Weindl, A; Wochele, J; Zabierowski, J; Zensus, J A

2014-01-01

231

Reconstruction of the energy and depth of maximum of cosmic-ray air-showers from LOPES radio measurements  

E-print Network

LOPES is a digital radio interferometer located at Karlsruhe Institute of Technology (KIT), Germany, which measures radio emission from extensive air showers at MHz frequencies in coincidence with KASCADE-Grande. In this article, we explore a method (slope method) which leverages the slope of the measured radio lateral distribution to reconstruct crucial attributes of primary cosmic rays. First, we present an investigation of the method on the basis of pure simulations. Second, we directly apply the slope method to LOPES measurements. Applying the slope method to simulations, we obtain uncertainties on the reconstruction of energy and depth of shower maximum Xmax of 13% and 50 g/cm^2, respectively. Applying it to LOPES measurements, we are able to reconstruct energy and Xmax of individual events with upper limits on the precision of 20-25% for the primary energy and 95 g/cm^2 for Xmax, despite strong human-made noise at the LOPES site.

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

2014-08-11

232

Emissive sheath measurements in the afterglow of a radio frequency plasma  

NASA Astrophysics Data System (ADS)

The difference between the plasma potential and the floating potential of a highly emissive planar surface was measured in the afterglow of a radio frequency discharge. A Langmuir probe was used to measure the electron temperature and an emissive probe was used to measure the spatial distribution of the potential using the inflection point in the limit of zero emission technique. Time-resolved measurements were made using the slow-sweep method, a technique for measuring time-resolved current-voltage traces. This was the first time the inflection point in the limit of zero emission was used to make time-resolved measurements. Measurements of the potential profile of the presheath indicate that the potential penetrated approximately 50% farther into the plasma when a surface was emitting electrons. The experiments confirmed a recent kinetic theory of emissive sheaths, demonstrating that late in the afterglow as the plasma electron temperature approached the emitted electron temperature, the emissive sheath potential shrank to zero. However, the difference between the plasma potential and the floating potential of a highly emissive planar surface data appeared to be much less sensitive to the electron temperature ratio than the theory predicts.

Sheehan, J. P.; Barnat, E. V.; Weatherford, B. R.; Kaganovich, I. D.; Hershkowitz, N.

2014-01-01

233

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

234

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

235

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

236

Path-Loss Models for Wireless Communication Channel along Arm and Torso: Measurements and Simulations  

E-print Network

/health care, medicine, sports, and many other areas. An important step in the development of a WBANPath-Loss Models for Wireless Communication Channel along Arm and Torso: Measurements are connected through a wireless communication channel. A WBAN offers many promising new applications in home

237

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

E-print Network

.ijheatmasstransfer.2003.12.006 International Journal of Heat and Mass Transfer 47 (2004) 2045­2059 www merits of boiling in micro- channels are (1) very large convective heat transfer coefficients (i.e., lowMeasurement and correlation of critical heat flux in two-phase micro-channel heat sinks Weilin Qu

Qu, Weilin

238

Dense solar wind cloud geometries deduced from comparisons of radio signal delay and in situ plasma measurements  

NASA Technical Reports Server (NTRS)

The geometries of dense solar wind clouds are estimated by comparing single-location measurements of the solar wind plasma with the average of the electron density obtained by radio signal delay measurements along a radio path between earth and interplanetary spacecraft. Several of these geometries agree with the current theoretical spatial models of flare-induced shock waves. A new class of spatially limited structures that contain regions with densities greater than any observed in the broad clouds is identified. The extent of a cloud was found to be approximately inversely proportional to its density.

Landt, J. A.

1974-01-01

239

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

240

Full Mesh Channel Measurements on Body Area Networks under Walking Scenarios  

E-print Network

match the behavior of BAN communication links. We present here the results of a measurement campaign fields like sports and medical care. Capitalizing on the existing infrastructure and on-body and in communications, but the current radio commodity hard- ware is still centered on narrow-band technologies. Narrow

Boyer, Edmond

241

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

242

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

243

Radio Telescopes  

NASA Astrophysics Data System (ADS)

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

Ekers, Ron; Wilson, Thomas L.

244

Measurement of Channel Temperature in GaN High-Electron Mobility Transistors  

E-print Network

In this paper, a simple and reliable method to estimate the channel temperature of GaN high-electron mobility transistors (HEMTs) is proposed. The technique is based on electrical measurements of performance-related figures ...

Joh, Jungwoo

245

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

246

Parametric Channeling Radiation and its Application to the Measurement of Electron Beam Energy  

NASA Astrophysics Data System (ADS)

We have proposed a method for observing parametric channeling radiation (PCR) and of applying it to the measurement of electron beam energy. The PCR process occurs if the energy of the channeling radiation coincides with the energy of the parametric X-ray radiation (PXR). The PCR process can be regarded as the diffraction of "virtual channeling radiation". We developed a scheme for beam energy measurement and designed an experimental setup. We also estimated the beam parameters, and calculated the angular distributions of PXR and PCR. These considerations indicate that the observation of PCR is promising.

Takabayashi, Y.

2010-06-01

247

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

PubMed

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 photon correlation spectroscopy of particle size distributions is also discussed. PMID:15813275

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

2005-03-20

248

Revisiting the radio interferometer measurement equation. I. A full-sky Jones formalism  

NASA Astrophysics Data System (ADS)

Context. Since its formulation by Hamaker et al., the radio interferometer measurement equation (RIME) has provided a rigorous mathematical basis for the development of novel calibration methods and techniques, including various approaches to the problem of direction-dependent effects (DDEs). However, acceptance of the RIME in the radio astronomical community at large has been slow, which is partially due to the limited availability of software to exploit its power, and the sparsity of practical results. This needs to change urgently. Aims: This series of papers aims to place recent developments in the treatment of DDEs into one RIME-based mathematical framework, and to demonstrate the ease with which the various effects can be described and understood. It also aims to show the benefits of a RIME-based approach to calibration. Methods: Paper I re-derives the RIME from first principles, extends the formalism to the full-sky case, and incorporates DDEs. Paper II then uses the formalism to describe self-calibration, both with a full RIME, and with the approximate equations of older software packages, and shows how this is affected by DDEs. It also gives an overview of real-life DDEs and proposed methods of dealing with them. Finally, in Paper III some of these methods are exercised to achieve an extremely high-dynamic range calibration of WSRT observations of 3C 147 at 21 cm, with full treatment of DDEs. Results: The RIME formalism is extended to the full-sky case (Paper I), and is shown to be an elegant way of describing calibration and DDEs (Paper II). Applying this to WSRT data (Paper III) results in a noise-limited image of the field around 3C 147 with a very high dynamic range (1.6 million), and none of the off-axis artifacts that plague regular selfcal. The resulting differential gain solutions contain significant information on DDEs and errors in the sky model. Conclusions: The RIME is a powerful formalism for describing radio interferometry, and underpins the development of novel calibration methods, in particular those dealing with DDEs. One of these is the differential gains approach used for the 3C 147 reduction. Differential gains can eliminate DDE-related artifacts, and provide information for iterative improvements of sky models. Perhaps most importantly, sources as faint as 2 mJy have been shown to yield meaningful differential gain solutions, and thus can be used as potential calibration beacons in other DDE-related schemes.

Smirnov, O. M.

2011-03-01

249

1128 IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS, VOL. 9, NO. 3, MARCH 2010 Optimal Multi-Channel Cooperative Sensing in  

E-print Network

-utilization of licensed spectrum at a time or a location has been observed by measurements of wireless spectrum usage [1-Channel Cooperative Sensing in Cognitive Radio Networks Rongfei Fan and Hai Jiang, Member, IEEE Abstract--In this paper, optimal multi-channel cooperative sensing strategies in cognitive radio networks are investigated

Jiang, Hai

250

Intrinsic noise measurement of an ultra-sensitive radio-frequency single electron transistor  

NASA Astrophysics Data System (ADS)

The radio-frequency single electron transistor (rf-SET) has been the focus of intense interest since its invention in 1998[1]. Using cryogenic ultra-thin film evaporation techniques [2] and an improved on-chip superconducting matching network [3], we have consistently fabricated rf-SETs with charge sensitivity of 1.7--5?e/?Hz and uncoupled energy sensitivity 1.1--5. Using our 1GHz resonant circuit, intrinsic noise in the SET arising from a dc voltage bias was measured in the white noise limit. We measured the offset charge dependence of the intrinsic noise in the vicinity of the Josephson-quasiparticle and double Josephson-quasiparticle transport cycles. In regions for which the offset charge and resistance noise are strongly suppressed, we can determine the SET shot noise in the sup-gap regime. We discuss the effects of correlations between charge carriers on the measured Fano factor. [1] R.J.Schoelkopf et al., Science 280,1238 (1998); [2] N.A.Court et al., Cond-mat 0706.4150 (2007); [3] W.W.Xue et al., Appl.Phys.Lett. 91, 093511 (2007).

Xue, W. W.; Ji, Z.; Pan, Feng; Rimberg, A. J.

2008-03-01

251

Radio Frequency Phototube, Optical Clock and Precise Measurements in Nuclear Physics  

E-print Network

Recently a new experimental program of novel systematic studies of light hypernuclei using pionic decay was established at JLab (Study of Light Hypernuclei by Pionic Decay at JLab, JLab Experiment PR-08-012). The highlights of the proposed program include high precision measurements of binding energies of hypernuclei by using a high resolution pion spectrometer, HpiS. The average values of binding energies will be determined within an accuracy of ~10 keV or better. Therefore, the crucial point of this program is an absolute calibration of the HpiS with accuracy 10E-4 or better. The merging of continuous wave laser-based precision optical-frequency metrology with mode-locked ultrafast lasers has led to precision control of the visible frequency spectrum produced by mode-locked lasers. Such a phase-controlled mode-locked laser forms the foundation of an optical clock or femtosecond optical frequency comb (OFC) generator, with a regular comb of sharp lines with well defined frequencies. Combination of this technique with a recently developed radio frequency (RF) phototube results in a new tool for precision time measurement. We are proposing a new time-of-flight (TOF) system based on an RF phototube and OFC technique. The proposed TOF system achieves 10 fs instability level and opens new possibilities for precise measurements in nuclear physics such as an absolute calibration of magnetic spectrometers within accuracy 10E-4 - 10E-5.

Amur Margaryan

2009-10-16

252

Direction-finding measurements of type III radio bursts out of the ecliptic plane  

NASA Technical Reports Server (NTRS)

A series of two-dimensional direction-finding measurements for three type III solar radio bursts is presented which is based on spin-modulation measurements from two satellites (IMP 8 and Hawkeye I) whose spin axes were nearly perpendicular to each other. The two-dimensional direction-finding technique is combined with a model of the solar-wind plasma density in order to provide determinations of type III source locations out of the ecliptic plane as well as information on the three-dimensional structure of the solar magnetic field at radial distances of 0.2 to 1.0 AU from the sun. The direction-finding technique is described in detail, characteristics of the bursts observed by the two satellites are summarized, and the solar-wind model is outlined. The results show that the source locations follow an Archimedean spiral when projected onto the ecliptic plane but usually follow a constant heliocentric latitude perpendicular to that plane. It is also found that measured source sizes are a factor of two larger than the angular sizes of previously reported solar-flare electron emissions, that the spin-modulation factor tends to be largest near the beginning of a type III event, and that the arrival direction of the radiation varies systematically during an event.

Baumback, M. M.; Kurth, W. S.; Gurnett, D. A.

1976-01-01

253

Radio Galaxies.  

ERIC Educational Resources Information Center

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

Downes, Ann

1986-01-01

254

Measurements of reduced-density air channels produced by a double-pulsed electron beam  

SciTech Connect

Single-pulse and noncollinear double-pulse channels formed by intense relativistic electron beams were studied by using a laser deflection probe for times up to 100 ms. The first of two pulsed electron beams propagating in a 30-cm-diam tube was magnetically deflected to generate an off-axis neutral-density channel of {similar_to}40% depth in moist air at 250 Torr. Subsequently after a time delay of 1.36 ms, a similar electron beam pulse (1.2 MeV, 13 kA, 10 ns full width at half maximum) was injected along the tube axis. After injection of the second pulse, the rate of channel decay was enhanced, and a large-scale convective motion of the hot channel gas toward the second pulse ensued. Measurements of the channel motion are compared with the predictions of a simple hydrodynamic model.

Bieniosek, F.M. [Fermi National Accelerator Laboratory, P. O. Box 500, Batavia, Illinois 60510 (United States)] [Fermi National Accelerator Laboratory, P. O. Box 500, Batavia, Illinois 60510 (United States); Cartier, S.L. [Sparta, Inc., Advanced Systems Division, Phillips Laboratories, Edwards Air Force Base, California 93524 (United States)] [Sparta, Inc., Advanced Systems Division, Phillips Laboratories, Edwards Air Force Base, California 93524 (United States)

1995-05-15

255

Measurement of Properties of the Higgs Boson in Bosonic Decay Channels using the ATLAS Detector  

E-print Network

The paper reports the properties of the Higgs boson measured in bosonic decay channels (H?ZZ??4l, H???, H?WW??ll?? and H?Z??ll?) with 25 fb?1 of pp collision data from the LHC run-1 collected by the ATLAS detector. An improved mass measurement, as well as new fiducial and differential cross sections measurements are discussed.

Benhar Noccioli, E; The ATLAS collaboration

2014-01-01

256

A blind spatio-temporal equalizer for a radio-mobile channel using the constant modulus algorithm (CMA)  

Microsoft Academic Search

Discusses constant modulus signal recovery by a multi-sensor receiver in a multipath propagation channel. The author first shows that spatio-temporal filtering can recover the transmitted signal provided that the number of sensors minus one times the length of the temporal filtering be larger than the intersymbol interference length assumed to be finite. It is also shown that spatio-temporal filtering is

Sylvie MAYRARGUE

1994-01-01

257

Electrically evoked compound action potential measures for virtual channels versus physical electrodes  

PubMed Central

Objectives The number of distinct pitch percepts for cochlear implant (CI) listeners is somewhat limited by the number of physical electrodes in the array. Newer-generation CIs have the capability to potentially increase this number by stimulating areas of the cochlea between the physical electrodes. Currently this is achieved by electrically coupling adjacent electrodes or by simultaneously activating two electrodes with independent current sources (i.e., “current steering”). Presumably, either type of dual-electrode stimulation will generate neural excitation patterns that are intermediate to those generated by either physical electrode alone (henceforth termed virtual channel). However, it is not clear whether virtual-channel stimulation yields neural recruitment patterns with similar shapes and rates of growth as compared with each physical electrode alone. The purpose of this study was to compare basic electrically evoked compound action potential (ECAP) measures for physical electrodes and virtual channels to determine whether properties of the respective excitation patterns were similar. Design Data were collected for 12 adult CI recipients (N = 6 Nucleus Freedom CI24RE, N = 2 Advanced Bionics HiResolution 90K, N = 4 Advanced Bionics CII). ECAP responses were measured for a set of three adjacent physical electrodes and two corresponding intermediate virtual channels (e.g., physical electrodes 4, 5, and 6 and virtual channels 4+5 and 5+6) at three positions along the electrode array (basal, middle, and apical). Virtual channels for Nucleus subjects were produced via electrical coupling of adjacent electrode pairs (“dual-electrode mode”). For AB subjects, virtual channels were produced via simultaneous, in-phase stimulation of adjacent electrode pairs with 50 % of the total current delivered to each electrode in the pair. Specific ECAP measures were: (1) threshold and slope of the input/output (I/O) functions, (2) amplitude for a masker-probe interval of 1500 ?sec (measure of refractory recovery), and (3) the relative location of spread-of-excitation (SOE) functions among virtual channels and adjacent physical electrodes. Measures for virtual channels were compared with those for the flanking physical electrodes using a multivariate analysis of variance. Results There were no statistically significant differences between physical electrodes and virtual channels for ECAP thresholds, slope of the I/O function, or refractory recovery. On average, SOE functions for the virtual channels were spatially located approximately halfway between SOE functions for the adjacent physical electrodes. Conclusions Results from this study suggest that virtual channels produce neural recruitment patterns with properties similar to those elicited by the adjacent physical electrodes. PMID:21187752

Hughes, Michelle L.; Goulson, Adam M.

2011-01-01

258

Radio-frequency spectroscopic measurement for pairing gap in an ultracold Fermi gas  

NASA Astrophysics Data System (ADS)

The study of ultracold Fermi gases has exploded a variety of experimental and theoretical research since the achievement of degenerate quantum gases in the lab, which expands the research range over atomic physics, condensed matter physics, astrophysics and particle physics. Using the Feshbach resonance, one can tune the attractive two-body interaction from weak to strong and thereby make a smooth crossover from the BCS superfluid of cooper pairs to the Bose Einstein condensate of bound molecules. In this crossover regime, the pairing effect plays a significant role in interpreting the interaction mechanism. Whenever the localized or delocalized pairing occurs at sufficiently low temperature, the single-particle energy will shift with respect to free atoms, due to the two-body or many-body interaction. Measuring the pairing gap can improve the understanding of the thermodynamics and hydrodynamics of the phase transition from the pseudogap to the superfluid, which will make an analogue to the high-temperature superconductivity in condensed matter. In this work, we will give a brief introduction to a novel radio-frequency (RF) spectroscopic measurement for pairing gap in an ultracold Fermi gas, which is currently widely used on the ultracold atomic table in the lab. In different interaction regimes of the BEC-BCS crossover, ultracold atoms are excited with a RF pulse and the characteristic behavior can be extracted from the spectrum.

Jiang, KaiJun; Luo, Hua; Li, Kai; Zhang, DongFang; Gao, TianYou; Peng, ShiGuo

2013-03-01

259

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

260

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

261

A noise-aware combination of dual-frequency measurements from GPS radio occultation  

NASA Astrophysics Data System (ADS)

of the fundamental difficulties that arise when using GPS Radio Occultation (RO) data in exploiting the stratosphere is that the air becomes rarefied with increasing height and accentuates the ionospheric effect and noise contained in the measurement. Customarily, the conventional linear combination (CLC) is used to extract neutral atmospheric components from dual-frequency (L1 and L2) RO data. The CLC combines and magnifies measurement noises, and thus works well only for those measurements of low noise. Although the L1 data are of considerably higher quality than the L2 data, the CLC does not take this into account and treats both equally; this makes the CLC-produced data less attractive. The authors propose a new approach, named Noise-Aware Combination (NAC), which is a generalized combination that factors in the presence of measurement noise. In this NAC method, the L1 and L2 data are each regarded independently, with each contributing to the combination according to its dynamically assessed accuracy. The performance of both the CLC and NAC are tested with two sets of data: one of synthetic data and the other of real data. The tests confirm that the NAC yields significant error reductions when compared to the CLC. While the noise in the CLC-produced data stands out in high altitudes and compels the data to be blended with the a priori, the NAC relies far less on this blending. The clear advantage of the NAC over the CLC would greatly enhance the value of RO for climate research.

Wee, Tae-Kwon; Kuo, Ying-Hwa

2013-12-01

262

Indoor channel characterisation measurements with directional antennas for future high frequency ATM wireless access systems  

Microsoft Academic Search

This paper presents a selection of wideband channel sounding measurements performed as part of the ACTS AWACS (ATM Wireless Access Communications System) project. The results were obtained for two different indoor operating environments (mainly in line-of-sight conditions) at a carrier frequency of 19.37 GHz. The paper discusses the configuration of the wideband channel sounder and its connection to the prototype

Y. Sun; P. Hafezi; A. Nix; M. Beach

1997-01-01

263

Channel selection based on phase measurement in P300-based brain-computer interface.  

PubMed

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. PMID:23593261

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

2013-01-01

264

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. PMID:23593261

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

2013-01-01

265

Calibrating high-precision Faraday rotation measurements for LOFAR and the next generation of low-frequency radio telescopes  

NASA Astrophysics Data System (ADS)

Faraday rotation measurements using the current and next generation of low-frequency radio telescopes will provide a powerful probe of astronomical magnetic fields. However, achieving the full potential of these measurements requires accurate removal of the time-variable ionospheric Faraday rotation contribution. We present ionFR, a code that calculates the amount of ionospheric Faraday rotation for a specific epoch, geographic location, and line-of-sight. ionFR uses a number of publicly available, GPS-derived total electron content maps and the most recent release of the International Geomagnetic Reference Field. We describe applications of this code for the calibration of radio polarimetric observations, and demonstrate the high accuracy of its modeled ionospheric Faraday rotations using LOFAR pulsar observations. These show that we can accurately determine some of the highest-precision pulsar rotation measures ever achieved. Precision rotation measures can be used to monitor rotation measure variations - either intrinsic or due to the changing line-of-sight through the interstellar medium. This calibration is particularly important for nearby sources, where the ionosphere can contribute a significant fraction of the observed rotation measure. We also discuss planned improvements to ionFR, as well as the importance of ionospheric Faraday rotation calibration for the emerging generation of low-frequency radio telescopes, such as the SKA and its pathfinders.

Sotomayor-Beltran, C.; Sobey, C.; Hessels, J. W. T.; de Bruyn, G.; Noutsos, A.; Alexov, A.; Anderson, J.; Asgekar, A.; Avruch, I. M.; Beck, R.; Bell, M. E.; Bell, M. R.; Bentum, M. J.; Bernardi, G.; Best, P.; Birzan, L.; Bonafede, A.; Breitling, F.; Broderick, J.; Brouw, W. N.; Brüggen, M.; Ciardi, B.; de Gasperin, F.; Dettmar, R.-J.; van Duin, A.; Duscha, S.; Eislöffel, J.; Falcke, H.; Fallows, R. A.; Fender, R.; Ferrari, C.; Frieswijk, W.; Garrett, M. A.; Grießmeier, J.; Grit, T.; Gunst, A. W.; Hassall, T. E.; Heald, G.; Hoeft, M.; Horneffer, A.; Iacobelli, M.; Juette, E.; Karastergiou, A.; Keane, E.; Kohler, J.; Kramer, M.; Kondratiev, V. I.; Koopmans, L. V. E.; Kuniyoshi, M.; Kuper, G.; van Leeuwen, J.; Maat, P.; Macario, G.; Markoff, S.; McKean, J. P.; Mulcahy, D. D.; Munk, H.; Orru, E.; Paas, H.; Pandey-Pommier, M.; Pilia, M.; Pizzo, R.; Polatidis, A. G.; Reich, W.; Röttgering, H.; Serylak, M.; Sluman, J.; Stappers, B. W.; Tagger, M.; Tang, Y.; Tasse, C.; ter Veen, S.; Vermeulen, R.; van Weeren, R. J.; Wijers, R. A. M. J.; Wijnholds, S. J.; Wise, M. W.; Wucknitz, O.; Yatawatta, S.; Zarka, P.

2013-04-01

266

Reconciling models of luminous blazars with magnetic fluxes determined by radio core shift measurements  

E-print Network

Estimates of magnetic field strength in relativistic jets of active galactic nuclei (AGN), obtained by measuring the frequency-dependent radio core location, imply that the total magnetic fluxes in those jets are consistent with the predictions of the magnetically-arrested disk (MAD) scenario of jet formation. On the other hand, the magnetic field strength determines the luminosity of the synchrotron radiation, which forms the low-energy bump of the observed blazar spectral energy distribution (SED). The SEDs of the most powerful blazars are strongly dominated by the high-energy bump, which is most likely due to the external radiation Compton (ERC) mechanism. This high Compton dominance may be difficult to reconcile with the MAD scenario, unless 1) the geometry of external radiation sources (broad-line region, hot-dust torus) is quasi-spherical rather than flat, or 2) most gamma-ray radiation is produced in jet regions of low magnetization, e.g., in magnetic reconnection layers or in fast jet spines.

Nalewajko, Krzysztof; Begelman, Mitchell C

2014-01-01

267

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

268

Reconciling Models of Luminous Blazars with Magnetic Fluxes Determined by Radio Core-shift Measurements  

NASA Astrophysics Data System (ADS)

Estimates of magnetic field strength in relativistic jets of active galactic nuclei, obtained by measuring the frequency-dependent radio core location, imply that the total magnetic fluxes in those jets are consistent with the predictions of the magnetically arrested disk (MAD) scenario of jet formation. On the other hand, the magnetic field strength determines the luminosity of the synchrotron radiation, which forms the low-energy bump of the observed blazar spectral energy distribution (SED). The SEDs of the most powerful blazars are strongly dominated by the high-energy bump, which is most likely due to the external radiation Compton mechanism. This high Compton dominance may be difficult to reconcile with the MAD scenario, unless (1) the geometry of external radiation sources (broad-line region, hot-dust torus) is quasi-spherical rather than flat, or (2) most gamma-ray radiation is produced in jet regions of low magnetization, e.g., in magnetic reconnection layers or in fast jet spines.

Nalewajko, Krzysztof; Sikora, Marek; Begelman, Mitchell C.

2014-11-01

269

THE CORRELATION BETWEEN DISPERSION MEASURE AND X-RAY COLUMN DENSITY FROM RADIO PULSARS  

SciTech Connect

Pulsars are remarkable objects that emit across the entire electromagnetic spectrum, providing a powerful probe of the interstellar medium. In this study, we investigate the relation between dispersion measure (DM) and X-ray absorption column density N{sub H} using 68 radio pulsars detected at X-ray energies with the Chandra X-Ray Observatory or XMM-Newton. We find a best-fit empirical linear relation of N{sub H} (10{sup 20} cm{sup -2})= 0.30{sup +0.13}{sub -0.09} DM (pc cm{sup -3}), which corresponds to an average ionization of 10{sup +4}{sub -3}%, confirming the ratio of one free electron per 10 neutral hydrogen atoms commonly assumed in the literature. We also compare different N{sub H} estimates and note that some N{sub H} values obtained from X-ray observations are higher than the total Galactic H I column density along the same line of sight, while the optical extinction generally gives the best N{sub H} predictions.

He, C.; Ng, C.-Y.; Kaspi, V. M., E-mail: ncy@bohr.physics.hku.hk [Department of Physics, McGill University, Montreal, QC H3A 2T8 (Canada)

2013-05-01

270

A measurement of the millimetre emission and the Sunyaev-Zel'dovich effect associated with low-frequency radio sources  

NASA Astrophysics Data System (ADS)

We present a statistical analysis of the millimetre-wavelength properties of 1.4 GHz-selected sources and a detection of the Sunyaev-Zel'dovich (SZ) effect associated with the haloes that host them. We stack data at 148, 218 and 277 GHz from the Atacama Cosmology Telescope at the positions of a large sample of radio AGN selected at 1.4 GHz. The thermal SZ effect associated with the haloes that host the AGN is detected at the 5? level through its spectral signature, representing a statistical detection of the SZ effect in some of the lowest mass haloes (average M200 ? 1013 M_{{?}} h_{70}^{-1}) studied to date. The relation between the SZ effect and mass (based on weak lensing measurements of radio galaxies) is consistent with that measured by Planck for local bright galaxies. In the context of galaxy evolution models, this study confirms that galaxies with radio AGN also typically support hot gaseous haloes. Adding Herschel observations allows us to show that the SZ signal is not significantly contaminated by dust emission. Finally, we analyse the contribution of radio sources to the angular power spectrum of the cosmic microwave background.

Gralla, Megan B.; Crichton, Devin; Marriage, Tobias A.; Mo, Wenli; Aguirre, Paula; Addison, Graeme E.; Asboth, V.; Battaglia, Nick; Bock, James; Bond, J. Richard; Devlin, Mark J.; Dünner, Rolando; Hajian, Amir; Halpern, Mark; Hilton, Matt; Hincks, Adam D.; Hlozek, Renée A.; Huffenberger, Kevin M.; Hughes, John P.; Ivison, R. J.; Kosowsky, Arthur; Lin, Yen-Ting; Marsden, Danica; Menanteau, Felipe; Moodley, Kavilan; Morales, Gustavo; Niemack, Michael D.; Oliver, Seb; Page, Lyman A.; Partridge, Bruce; Reese, Erik D.; Rojas, Felipe; Sehgal, Neelima; Sievers, Jon; Sifón, Cristóbal; Spergel, David N.; Staggs, Suzanne T.; Switzer, Eric R.; Viero, Marco P.; Wollack, Edward J.; Zemcov, Michael B.

2014-11-01

271

Influence and modification of coupling device on low voltage power network channel characterization measurement  

Microsoft Academic Search

Channel characterization measurements of power line are often carried out when the power system is operation actively. So the coupling device is adopted to isolate the power frequency signal. Due to the impedance mismatch between the output of coupling device and power network, the energy of carrier signal will be attenuated, which causes much influence on the accuracy of measurement

Zheng Tao; Yang Xiaoxian; Zhang Baohui

2005-01-01

272

Prediction and measurement of incipient boiling heat flux in micro-channel heat sinks  

E-print Network

Prediction and measurement of incipient boiling heat flux in micro-channel heat sinks Weilin Qu Abstract Experiments were performed to measure the incipient boiling heat flux in a heat sink containing 21 to predict the incipient boiling heat flux, accounting for the complexities of bubble formation along

Qu, Weilin

273

A New Top Mass Measurement in The Dilepton Channel  

SciTech Connect

The top quark discovery completed the present picture of the fundamental constituents of the nature. Since then, the Collider Detector at Fermilab and D0 Collaborations have been spending great efforts to measure its properties better. About 30 times larger than the second heaviest quark, the mass of the top has been measured with increased statistic and more and more sophisticated techniques in order to reduce as much as possible its uncertainty. This is because the top is expected to play a fundamental role in the Standard Model. The value of its mass sets boundaries on the mass of the unobserved Higgs boson, and perhaps more appealing, studies of its properties might lead to the discovery of new physics.

Trovato, Marco; /INFN, Pisa /Pisa U.

2008-01-01

274

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

275

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

276

Revisiting the Dispersion Measure of Fast Radio Bursts Associated with Gamma-Ray Burst Afterglows  

NASA Astrophysics Data System (ADS)

Some fast radio bursts (FRBs) are expected to be associated with the afterglow emission of gamma-ray bursts (GRBs), while a short-lived, supermassive neutron star (NS) forms during the GRBs. I investigate the possible contributions to the dispersion measure (DM) of the FRBs from the GRB ejecta and the wind blown from the precollapsing NS. On the one hand, sometimes an internal X-ray plateau afterglow could be produced by the NS wind, which indicates that a great number of electron-positron pairs are carried by the wind. If the pair-generation radius satisfies a somewhat rigorous condition, the relativistic and dense wind would contribute a high DM to the associated FRB, which can be comparable to and even exceed the DM contributed by the intergalactic medium. On the other hand, if the wind only carries a Goldreich-Julian particle flux, its DM contribution would become negligible; meanwhile, the internal plateau afterglow would not appear. Alternatively, the FRB should be associated with a GRB afterglow produced by the GRB external shock, i.e., an energy-injection-caused shallow-decay afterglow or a normal single-power-law afterglow if the impulsive energy release of the GRB is high enough. In the latter case, the DM contributed by the high-mass GRB ejecta could be substantially important, in particular, for an environment of main-sequence stellar wind. In summary, a careful assessment on the various DM contributors could be required for the cosmological application of the expected FRB-GRB association. The future DM measurements of GRB-associated FRBs could provide a constraint on the physics of NS winds.

Yu, Yun-Wei

2014-12-01

277

Ion channel and toxin measurement using a high throughput lipid membrane platform.  

PubMed

Measurements of ion channels are important for scientific, sensing and pharmaceutical applications. Reconstitution of ion channels into lipid vesicles and planar lipid bilayers for measurement at the single molecule level is a laborious and slow process incompatible with the high throughput methods and equipment used for sensing and drug discovery. A recently published method of lipid bilayer formation mechanically combines lipid monolayers self-assembled at the interfaces of aqueous and apolar phases. We have expanded on this method by vertically orienting these phases and using gravity as the driving force to combine the monolayers. As this method only requires fluid dispensation, it is trivially integrated with high throughput automated liquid-handling robotics. In a proof-of-concept demonstration, we created over 2200 lipid bilayers in 3h. We show single molecule measurements of technologically and physiologically relevant ion channels incorporated into lipid bilayers formed with this method. PMID:18849158

Poulos, Jason L; Jeon, Tae-Joon; Damoiseaux, Robert; Gillespie, Eugene J; Bradley, Kenneth A; Schmidt, Jacob J

2009-02-15

278

Predictions of HF system performance for propagation through disturbed ionospheres measured using low-Earth-orbit satellite radio beacon tomography  

NASA Astrophysics Data System (ADS)

CERTO radio beacon on the C/NOFS satellite sends VHF/UHF radio signals at 150 and 400 MHz to provide measurements of integrated electron density or Total Electron Content (TEC) by an east-west chain of ground receivers in Peru. Computerized Ionospheric Tomography (CIT) is used to convert the TEC data into two-dimensional images of electron densities with maximum 5 × 5 km resolution in Longitude-Altitude space. These images are updated every 95 min as the C/NOFS satellite passes over the receiver network in its low-latitude orbit with an inclination of 12°. The 2-D, high-resolution images of the ionosphere are used to predict the impact of equatorial plasma structures on HF propagation of radar and radio signals. Electron density measurements from the NRL radio tomography chain across Peru are used for simulations of the performance by HF one-way links. HF rays from transmitter to receiver are traced through the electron density images produced by radio beacon tomography. Eight separate paths are found between a transmitter and ground receiver separated by 2000 km. A total of 36 backscatter echoes are found with unique group delay, Doppler frequency shift, phase delay, and echo amplitude. This multipath effect explains the range and Doppler spreading of observations for HF monostatic radar propagation through F layer irregularities. This type of analysis is useful for prediction and interpretation of range and Doppler observations from HF systems including over-the-horizon and SuperDARN radars, HF Geolocation Arrays, and HF communications networks.

Bernhardt, Paul A.; Hei, Matthew A.; Siefring, Carl L.; Wilkens, Matthew R.

2014-07-01

279

Electron temperature measurements using a 12-channel array probe  

NASA Technical Reports Server (NTRS)

The most common technique for determining the mean kinetic energy of electrons in low-temperature plasmas utilizes the so-called Langmuir probe. The present investigation is concerned with the study of the electron temperature in a pulsed high-beta plasma as a function of time by means of a miniature array of 12 planar Langmuir probes. By using a probe with many individually collecting surfaces, each biased at a different fixed voltage, an approximation to the true probe characteristic is obtained when monitoring the collected currents for each independent subprobe. The employed method, by using many points, provides enough information to reconstruct the entire I-V curve. Attention is given to the principle of operation of the new probe, calibration, accuracy, time resolution, and applications of the new method. By employing two probes it is possible to perform correlation measurements to study heat flow and temperature fluctuations.

Wild, N.; Stenzel, R. L.; Gekelman, W.

1983-01-01

280

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

NASA Astrophysics Data System (ADS)

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

Megeath, S. T.; Herter, T.; Gull, G. E.; Houck, J. R.

1990-06-01

281

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

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

282

Registration of currents of positive and negative ions in quadrupole mass spectrometer with one measuring channel  

SciTech Connect

A modernized system for registration of the ion currents of MS7302 and MS7303 quadrupole mass spectrometers is described. Charge conversion in interaction of negative ions with a metal surface is used to measure their current, which allows the currents of both positive and negative ions to be measured with a single measuring channel and permits electrical switching from one registration mode to anther without loss of vacuum or stopping of the instrument.

Gall', R.N.; Gor'kovoi, V.V.; Elokhin, V.A.; Kuz'min, A.F.; Protopopov, S.V.

1987-04-01

283

Galileo radio science investigations  

Microsoft Academic Search

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

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

1992-01-01

284

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. PMID:22156948

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

2012-01-01

285

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

SciTech Connect

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

Jayatilaka, Bodhitha A.; /Michigan U.

2006-08-01

286

A measurement of the top quark mass in the dilepton decay channel at CDF II  

NASA Astrophysics Data System (ADS)

The top quark, the most recently discovered quark, is the most massive known fundamental fermion. Precision measurements of its mass, a free parameter in the Standard Model of particle physics, can be used to constrain the mass of the Higgs Boson. In addition, deviations in the mass as measured in different channels can provide possible evidence for new physics. We describe a measurement of the top quark mass in the decay channel with two charged leptons, known as the dilepton channel, using,data collected by the CDF II detector from pp¯ collisions with s = 1.96 TeV at the Fermilab Tevatron. The likelihood in top mass is calculated for each event by convoluting the leading order matrix element describing qq¯ ? tt¯ ? b?nu?b¯?'nu ?' with detector resolution functions. The presence of background events in the data sample is modeled using similar calculations involving the matrix elements for major background processes. In a data sample with integrated luminosity of 1.0 fb-1, we observe 78 candidate events and measure Mt = 164.5 +/- 3.9(stat.) +/- 3.9(syst.) GeV/c2, the most precise measurement of the top quark mass in this channel to date.

Jayatilaka, Bodhitha A.

287

New 20-Channel Diagnostic for Angle-Resolved Fast Particles Measurements in LHD  

NASA Astrophysics Data System (ADS)

A new multi-channel diagnostic for fast particles has been developed and successfully tested on the Large Helical Device (LHD) during 2005-2006 experimental campaign. The number of simultaneously used channels was significantly improved from 2 to 20 channels and additional improvements for noise reduction have been made. Same time location of the diagnostic has been changed that allowed one to make measurements in a much wider range of pitch angles from perpendicular to tangential (90-160 degrees). All these improvements allow one to make time, energy, and angle-resolved measurements of charge exchange neutral particles in a single plasma discharge and to check the presence of fast particles loss-cones from LHD plasma in different heating regimes. This new diagnostic can be a very helpful and powerful tool in studying of fast particle distribution in such a complex helical plasma geometry like the one of LHD. Example data from plasma discharges are presented.

Veshchev, Evgeny A.; Ozaki, Tetsuo; Goncharov, Pavel R.; Sudo, Shigeru; LHD Experimental Group, Shigeru

288

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

E-print Network

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.

Apel, W D; 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; Palmieri, N; Pierog, T; Rautenberg, J; Rebel, H; Roth, M; Rühle, C; Saftoiu, A; Schieler, H; Schmid, A; Schröder, F G; Sima, O; Toma, G; Trinchero, G C; Weindl, A; Wochele, J; Wommer, M; Zabierowski, J; Zensus, J A

2013-01-01

289

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

290

Analysis of the Capability and Limitations of Relativistic Gravity Measurements Using Radio Astronomy Methods  

NASA Technical Reports Server (NTRS)

The uses of radar observations of planets and very-long-baseline radio interferometric observations of extragalactic objects to test theories of gravitation are described in detail with special emphasis on sources of error. The accuracy achievable in these tests with data already obtained, can be summarized in terms of: retardation of signal propagation (radar), deflection of radio waves (interferometry), advance of planetary perihelia (radar), gravitational quadrupole moment of sun (radar), and time variation of gravitational constant (radar). The analyses completed to date have yielded no significant disagreement with the predictions of general relativity.

Shapiro, I. I.; Counselman, C. C., III

1975-01-01

291

Measurement of the top quark pair production cross section in the all-jets decay channel  

E-print Network

We present a measurement of production in collisions at root s = 1.8 TeV from 110 pb(-1) of data collected in the all-jets decay channel with the D0 detector at Fermilab. A neural network analysis yields a cross section...

Baringer, Philip S.; Coppage, Don; Hebert, C.

1999-09-01

292

DOWNSTREAM CHANNEL CHANGES AFTER A SMALL DAM REMOVAL: USING AERIAL PHOTOS AND MEASUREMENT ERROR FOR CONTEXT;  

E-print Network

). There are a myriad of problems associated with the aging of dams: reservoir sedimentation leading to reduced storage in the reservoir and downstream after a dam removal have been established based upon studies of dam removalsDOWNSTREAM CHANNEL CHANGES AFTER A SMALL DAM REMOVAL: USING AERIAL PHOTOS AND MEASUREMENT ERROR

Tullos, Desiree

293

Laboratory measurements of wave height variations and currents along a steep-sided channel  

E-print Network

velocity. The bathymetry simulated a dredged entrance channel for a harbor. Two cases were conducted using monochromatic waves with periods of 0.73 s and 1.22 s. The instantaneous free surface oscillations were measured at 405 positions using seven...

Way, Francis

2012-06-07

294

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

295

The effect of blanking of TDMA interference on radio-astronomical correlation measurements  

E-print Network

astronomical observations are increasingly contam- inated by man-made communication signals. TDMA sig- nals.) We introduce a simplified mathemat- ical model of the problem and present a subband detection scheme. Received signal model The Westerbork Synthesis Radio Telescope (WSRT), lo- cated in the North

van der Veen, Alle-Jan

296

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

297

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

298

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

299

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

300

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

301

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

302

Radio-Frequency Measurements of Coherent Transition and Cherenkov Radiation: Implications for High-Energy Neutrino Detection  

E-print Network

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 ultra high-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 ultra high-energy neutrinos.

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

2000-04-05

303

Suspended lipid bilayer for optical and electrical measurements of single ion channel proteins.  

PubMed

Making and holding an artificial lipid bilayer horizontally in an aqueous solution within the microscopic working distance of ~100 ?m are essential for simultaneous single molecule imaging and single ion-channel electrical current recording. However, preparation of such a lipid bilayer without a solid support is technically challenging. In a typical supported lipid bilayer, the asymmetric local environments and the strong perturbation of the underneath solid or dense surface can diverge the normal behavior of membrane proteins and lipids. On the other hand, the suspended lipid bilayers can provide a native local environment for the membrane proteins and lipids by having fluids on both sides. In this technical report, we present a simple and novel methodology for making a suspended lipid bilayer that can be used for recording the single-molecule diffusion and single ion-channel electrical measurements of ion-channel proteins. Our approach has a higher validity for studying the molecular diffusions and conformational fluctuations of membrane proteins without having perturbations from supporting layers. We demonstrate the feasibility of such an approach on simultaneous single-molecule fluorescence imaging and electric current measurements of ion channel proteins. PMID:23992532

Rajapaksha, Suneth P; Wang, Xuefei; Lu, H Peter

2013-10-01

304

Single molecule measurements of channel proteins incorporated into biomimetic polymer membranes  

NASA Astrophysics Data System (ADS)

Lipid bilayer membranes have been extensively utilized to examine membrane channel and pore proteins and are the subjects of study in their own right. There has been considerable recent interest in developing technologies to substitute or strengthen lipid bilayer membranes for a number of applications, including sensing or drug delivery. In particular, biomimetic amphiphilic block co-polymers have been shown to have the capacity to form membrane structures and to contain membrane proteins within them. In this work, we describe the creation of biomimetic membranes from a 5.7 nm thick tri-block co-polymer and the investigation of the effects of the polymer environment on incorporated channel proteins (?-haemolysin, OmpG, and alamethicin) with single molecule transport measurements. We found that the polymer membranes consistently have seal resistances of tens of G? and greater, and that the conductance of single channels is reduced by approximately 10% from that measured in diphytanoyl phosphatidylcholine lipid membranes, possibly as a result of increased cohesion of the polymer compared to lipid. The voltage gating ability and threshold voltages of voltage gated channels were also found to be very similar in the lipid and polymer environments.

Wong, Denise; Jeon, Tae-Joon; Schmidt, Jacob

2006-08-01

305

High-Resolution Radio Continuum Measurements of the Nuclear Disks of Arp 220  

E-print Network

We present new Karl G. Jansky Very Large Array radio continuum images of the nuclei of Arp 220, the nearest ultra-luminous infrared galaxy. These images have both the angular resolution to study detailed morphologies of the two nuclei that power the system and sensitivity to a wide range of spatial scales. At 33 GHz, and with a resolution of 0".081 x 0".063 (29.9 x 23.3 pc), we resolve the emission surrounding both nuclei and conclude that is mostly synchrotron in nature. The spatial distributions of radio emission in both nuclei are well described by exponential profiles. These have deconvolved half-light radii of 51 and 35 pc for the eastern and western nuclei, and they match the number density profile of radio supernovae observed with very long baseline interferometry. This similarity might be due to the fast cooling of cosmic rays electrons caused by the presence of a strong (~ mG) magnetic field in this system. We estimate high luminosity surface densities of $\\mathrm{\\Sigma_{IR} \\sim 4.2^{+1.6}_{-0.7} \\...

Barcos-Muñoz, Loreto; Evans, Aaron S; Privon, George C; Armus, Lee; Condon, Jim; Mazzarella, Joseph M; Meier, David S; Momjian, Emmanuel; Murphy, Eric J; Ott, Juerguen; Reichardt, Ashely; Sakamoto, Kazushi; Sanders, David B; Schinnerer, Eva; Stierwalt, Sabrina; Surace, Jason A; Thompson, Todd A; Walter, Fabian

2014-01-01

306

Channel incision in the Rio Atenguillo, Jalisco, Mexico, defined by 36Cl measurements of bedrock  

NASA Astrophysics Data System (ADS)

The Jalisco Block of western Mexico has undergone uplift in the Tertiary, in response to subduction tectonics. The Atenguillo River, interior to the Jalisco Block, has incised the bedrock units of the Jalisco Block, including Cretaceous ash flow tuff, granite, as well as younger volcanic lava flows. To study incision rates, knickpoint propagation, and the uplift rate of the region samples from nine different points along the Atenguillo channel were collected for 36Cl exposure age dating. Exposure ages along the length of the channel are high near the head of the basin where the river meanders in a broad plain. Ages are younger at the knickpoints and downstream where the river cuts deeply and forms a canyon. Incision rates measured at different points along the channel also correlate with channel slope and age. Low incision rates are measured in the oldest part of the channel near the head (station B; 2.5 mm/year), and just above the knickpoints (station C; 0.6 mm/year and station G; 1.4 mm/year). The incision rates are highest just below the knickpoints (station F; 2.4 mm/year) and farther downstream (stations H and I; 5.6 and 2.9 mm/year, respectively). The high incision rates can be attributed to subduction-related uplift of the Jalisco Block. Other features attributable to uplift are emergent paleoshorelines and uplifted marine sediments along the coast; and relatively lower incision rates were measured north of the Jalisco Block.

Righter, K.; Caffee, M.; Rosas-Elguera, J.; Valencia, V.

2010-08-01

307

On the Capacity of Printed Planar Rectangular Patch Antenna Arrays in the MIMO Channel: Analysis and Measurements [Wireless Corner  

Microsoft Academic Search

Printed arrays of rectangular patch antennas are analyzed in terms of their MIMO performance using a full-wave channel model. These antennas are designed and manufactured in various array configurations, and their MIMO performance is measured in an indoor environment. Good agreement is achieved between the measurements and simulations performed using the full-wave channel model. Effects on the MIMO capacity of

C. A. Tunc; U. Olgun; V. B. Ertu?rk; A. Altintas

2010-01-01

308

A random point process model for atmospheric radio noises  

Microsoft Academic Search

The physical processes causing atmospheric radio noise in the very-low frequency communication channel are examined. The return strokes from lightning discharges are found to be the major source of the noise. A survey of empirical noise models is presented. The models are compared in terms of their ability to match the measured first order statistics from CCIR Report 322. While

S. D. Hettinger

1978-01-01

309

77 FR 37734 - Technical Standard Order (TSO) C-122a, Equipment That Prevent Blocked Channels Used in Two-Way...  

Federal Register 2010, 2011, 2012, 2013

...Prevent Blocked Channels Used in Two-Way Radio Communications Due to Simultaneous...Prevent Blocked Channels Used in Two-Way Radio Communications Due to Simultaneous...Prevent Blocked Channels Used in Two-Way Radio Communications Due to...

2012-06-22

310

Optimal Linear Cooperation for Spectrum Sensing in Cognitive Radio Networks  

Microsoft Academic Search

Cognitive radio technology has been proposed to improve spectrum efficiency by having the cognitive radios act as secondary users to opportunistically access under-utilized frequency bands. Spectrum sensing, as a key enabling functionality in cognitive radio networks, needs to reliably detect signals from licensed primary radios to avoid harmful interference. However, due to the effects of channel fading\\/shadowing, individual cognitive radios

Zhi Quan; Shuguang Cui; Ali H. Sayed

2008-01-01

311

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

312

Fading channel simulator  

SciTech Connect

This invention relates to high frequency (HF) radio signal propagation through fading channels and, more particularly, to simulation of fading channels in order to characterize HF radio system performance in transmitting and receiving signals through such fading channels. Fading channel effects on a transmitted communication signal are simulated with both frequency and time variations using a channel scattering function to affect the transmitted signal. A conventional channel scattering function is converted to a series of channel realizations by multiplying the square root of the channel scattering function by a complex number of which the real and imaginary parts are each independent variables. The two-dimensional inverse-FFT of this complex-valued channel realization yields a matrix of channel coefficients that provide a complete frequency-time description of the channel. The transmitted radio signal is segmented to provide a series of transmitted signal and each segment is subject to FFT to generate a series of signal coefficient matrices. The channel coefficient matrices and signal coefficient matrices are then multiplied and subjected to inverse-FFT to output a signal representing the received affected radio signal. A variety of channel scattering functions can be used to characterize the response of a transmitter-receiver system to such atmospheric effects.

Argo, P.E.; Fitzgerald, T.J.

1991-12-31

313

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

2014-07-01

314

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

315

Test of the Pioneer anomaly with the Voyager 2 radio-ranging distance measurements to Uranus and Neptune  

E-print Network

In this paper we test the hypothesis that the Pioneer anomaly can be of gravitational origin by comparing the predicted model-independent shifts Delta a/a for the semimajor axis of Uranus and Neptune with the Voyager 2 radio-technical distance measurements performed at JPL-NASA. As in the case of other tests based on different methods and data sets (secular perihelion advance, right ascension/declination residuals over about one century), the orbits of the investigated planets are not affected by any anomalous acceleration like that experienced by the Pioneer 10/11 spacecraft.

Lorenzo Iorio

2006-08-29

316

Optical Performance of Breadboard Amon-Ra Imaging Channel Instrument for Deep Space Albedo Measurement  

Microsoft Academic Search

The AmonRa instrument, the primary payload of the international EARTHSHINE mission, is designed for measurement of deep space albedo from L1 halo orbit. We report the optical design, tolerance analysis and the optical performance of the breadborad AmonRa imaging channel instrument optimized for the mission science requirements. In particular, an advanced wavefront feedback process control technique was used for the

Won Hyun Park; Seonghui Kim; Hanshin Lee; Hyun-Su Yi; Jae-Min Lee; Sun-Jung Ham; Jeeyeon Yoon; Sug-Whan Kim; Ho Soon Yang; Ki-Hyuk Choi; Zeen Chul Kim; Mike Lockwood; Nigel Morris; Ian Tosh

2007-01-01

317

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

318

Development of 200-channel mapping system for tissue oxygenation measured by near-infrared spectroscopy  

NASA Astrophysics Data System (ADS)

Near-infrared spectroscopy (NIRS) is a very useful technique for noninvasive measurement of tissue oxygenation. Among various methods of NIRS, continuous wave near-infrared spectroscopy (CW- NIRS) is especially suitable for real-time measurement and for practical use. CW-NIRS has recently been applied in vivo reflectance imaging of muscle oxygenation and brain activity. However, conventional mapping systems do not have a sufficient mapping area at present. Moreover, they do not enable quantitative measurement of tissue oxygenation because conventional NIRS is based on the inappropriate assumption that tissue is homogeneous. In this study, we developed a 200-channel mapping system that enables measurement of changes in oxygenation and blood volume and that covers a wider area (30 cm x 20 cm) than do conventional systems. The spatial resolution (source- detector separation) of this system is 15 mm. As for the effcts of tissue inhomogeneity on muscle oxygenation measurement, subcutaneous adipose tissue greatly reduces measurement sensitivity. Therefore, we also used a correction method for influence of the subcutaneous fat layer so that we could obtain quantitative changes in concentrations of oxy- and deoxy- hemoglobin. We conducted exercise tests and measured the changed in hemoglobin concentration in the thigh using the new system. The working muscles in the exercises could be imaged, and the heterogeneity of the muscles was shown. These results demonstrated the new 200-channel mapping system enables observation of the distribution of muscle metabolism and localization of muscle function.

Niwayama, Masatsugu; Kohata, Daisuke; Shao, Jun; Kudo, Nobuki; Hamaoka, Takatumi; Katsumura, Toshihito; Yamamoto, Katsuyuki

2000-07-01

319

Solar gravitational deflection of radio waves measured by very-long-baseline interferometry  

NASA Technical Reports Server (NTRS)

Utilizing a four-antenna technique, simultaneous observations were made, at each end of an 845-km baseline, of the radio sources 3C279 and 3C273B, which are 10 deg apart in the sky. Differences in interferometric phases at 3.7-cm wavelength monitored near the time of the 1972 occultation of 3C279 by the sun, yielded a gravitational deflection of 0.99 plus or minus 0.03 times the value predicted by general relativity, corresponding to gamma = 0.98 plus or minus 0.06 (standard error).

Counselman, C. C., III; Kent, S. M.; Knight, C. A.; Shapiro, I. I.; Clark, T. A.; Hinteregger, H. F.; Rogers, A. E. E.; Whitney, A. R.

1974-01-01

320

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

321

Measurement of the void fraction in a channel simulating the HANARO fuel assembly using neutron radiography  

NASA Astrophysics Data System (ADS)

A test section simulating the HANARO fuel channel was constructed and the void fraction was measured by using the high-speed neutron radiography technique. The test was performed at a beam facility of HANARO called Ex-core Neutron-irradiation Facility (ENF). D 2O was used as the working liquid and air was used to simulate the void. The measurements were made at various combinations of the liquid flow and gas flow and the result were compared with the predictions of the existing correlations.

Lim, I. C.; Sim, C. M.; Cha, J. E.; Choi, Y. S.; Takenaka, N.; Saito, Y.; Jun, B. J.

2005-04-01

322

Allometric relationships between traveltime channel networks, convex hulls, and convexity measures  

NASA Astrophysics Data System (ADS)

The channel network (S) is a nonconvex set, while its basin [C(S)] is convex. We remove open-end points of the channel connectivity network iteratively to generate a traveltime sequence of networks (Sn). The convex hulls of these traveltime networks provide an interesting topological quantity, which has not been noted thus far. We compute lengths of shrinking traveltime networks L(Sn) and areas of corresponding convex hulls C(Sn), the ratios of which provide convexity measures CM(Sn) of traveltime networks. A statistically significant scaling relationship is found for a model network in the form L(Sn) ˜ A[C(Sn)]0.57. From the plots of the lengths of these traveltime networks and the areas of their corresponding convex hulls as functions of convexity measures, new power law relations are derived. Such relations for a model network are CM(Sn) ˜ ? and CM(Sn) ˜ ?. In addition to the model study, these relations for networks derived from seven subbasins of Cameron Highlands region of Peninsular Malaysia are provided. Further studies are needed on a large number of channel networks of distinct sizes and topologies to understand the relationships of these new exponents with other scaling exponents that define the scaling structure of river networks.

Tay, Lea Tien; Sagar, B. S. Daya; Chuah, Hean Teik

2006-06-01

323

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

324

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

325

Radiation temperature measurement method for semitransparent materials using one-channel infrared pyrometer.  

PubMed

Semitransparent zinc sulfide (ZnS) crystal materials are widely used as the infrared-transmitting windows for optical instruments operating in long wavelengths. This paper describes a temperature measurement method for high-temperature ZnS materials using the one-channel optical pyrometer based on a theoretical model of radiation transfer in semitransparent plates. Numerical analyses of the radiation properties of ZnS plate are used to optimize the spectral band for the optical pyrometry. The optimized measurement spectral band is based on a trade-off between the measurement radiation intensity and the signal-to-noise ratio (SNR) for the ZnS material. The effective waveband emittance of one-dimensional (1D) ZnS plates is analyzed for various experimental conditions (temperatures, thicknesses, and direction angles) for the one-channel infrared pyrometer with the optimized measurement spectral response. The analysis can be used to improve radiation temperature measurements of semitransparent ZnS materials in applications. PMID:25322390

Fu, Tairan; Liu, Jiangfan; Zong, Anzhou

2014-10-10

326

Monitoring the width of the tropical belt with GPS radio occultation measurements  

NASA Astrophysics Data System (ADS)

GPS radio occultation data collected over the period 2002-2011 were analyzed to examine the possible expansion of the tropical belt due to climate change. By the use of high vertical-resolution temperature profiles, monthly averages of the lapse rate tropopause were obtained and used to derive a decade-long time series of the tropical edge latitude (TEL) in each hemisphere and its linear trends. Two different TEL criteria were examined. Our analysis shows that a statistically significant widening trend of ?1° latitude/decade was found in the Northern Hemisphere (NH) by either criterion. This contrasts strongly with the Southern Hemisphere (SH), where no statistically significant trends were found. Comparison with ECMWF reanalysis shows good agreement, but the agreement is worse over SH. Substantial differences in seasonal trends were found between NH and SH, with the latter showing strong widening in the austral summer countered by contraction over the austral winter and spring.

Ao, Chi O.; Hajj, Amanda J.

2013-12-01

327

Radio Journalism.  

ERIC Educational Resources Information Center

This book, a how-to-do-it guide for the novice and the professional alike, deals with several aspects of radio journalism: producing documentaries, preparing and announcing radio news, ethics and responsibility, regulation of radio journalism, and careers. It traces the history and growth of radio news, shows its impact on the public, and…

Bittner, John R.; Bittner, Denise A.

328

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

329

Radio frequency cavity analysis, measurement, and calibration of absolute Dee voltage for K-500 superconducting cyclotron at VECC, Kolkata.  

PubMed

Variable Energy Cyclotron Centre has commissioned a K-500 superconducting cyclotron for various types of nuclear physics experiments. The 3-phase radio-frequency system of superconducting cyclotron has been developed in the frequency range 9-27 MHz with amplitude and phase stability of 100 ppm and ±0.2(0), respectively. The analysis of the RF cavity has been carried out using 3D Computer Simulation Technology (CST) Microwave Studio code and various RF parameters and accelerating voltages ("Dee" voltage) are calculated from simulation. During the RF system commissioning, measurement of different RF parameters has been done and absolute Dee voltage has been calibrated using a CdTe X-ray detector along with its accessories and known X-ray source. The present paper discusses about the measured data and the simulation result. PMID:23464200

Som, Sumit; Seth, Sudeshna; Mandal, Aditya; Paul, Saikat; Duttagupta, Anjan

2013-02-01

330

Radio frequency cavity analysis, measurement, and calibration of absolute Dee voltage for K-500 superconducting cyclotron at VECC, Kolkata  

SciTech Connect

Variable Energy Cyclotron Centre has commissioned a K-500 superconducting cyclotron for various types of nuclear physics experiments. The 3-phase radio-frequency system of superconducting cyclotron has been developed in the frequency range 9-27 MHz with amplitude and phase stability of 100 ppm and {+-}0.2{sup 0}, respectively. The analysis of the RF cavity has been carried out using 3D Computer Simulation Technology (CST) Microwave Studio code and various RF parameters and accelerating voltages ('Dee' voltage) are calculated from simulation. During the RF system commissioning, measurement of different RF parameters has been done and absolute Dee voltage has been calibrated using a CdTe X-ray detector along with its accessories and known X-ray source. The present paper discusses about the measured data and the simulation result.

Som, Sumit; Seth, Sudeshna; Mandal, Aditya; Paul, Saikat; Duttagupta, Anjan [Variable Energy Cyclotron Centre, Kolkata (India)

2013-02-15

331

Radio frequency cavity analysis, measurement, and calibration of absolute Dee voltage for K-500 superconducting cyclotron at VECC, Kolkata  

NASA Astrophysics Data System (ADS)

Variable Energy Cyclotron Centre has commissioned a K-500 superconducting cyclotron for various types of nuclear physics experiments. The 3-phase radio-frequency system of superconducting cyclotron has been developed in the frequency range 9-27 MHz with amplitude and phase stability of 100 ppm and ±0.20, respectively. The analysis of the RF cavity has been carried out using 3D Computer Simulation Technology (CST) Microwave Studio code and various RF parameters and accelerating voltages ("Dee" voltage) are calculated from simulation. During the RF system commissioning, measurement of different RF parameters has been done and absolute Dee voltage has been calibrated using a CdTe X-ray detector along with its accessories and known X-ray source. The present paper discusses about the measured data and the simulation result.

Som, Sumit; Seth, Sudeshna; Mandal, Aditya; Paul, Saikat; Duttagupta, Anjan

2013-02-01

332

Automatable lipid bilayer formation and ion channel measurement using sessile droplets  

NASA Astrophysics Data System (ADS)

Artificial lipid bilayer membranes have been used to reconstitute ion channels for scientific and technological applications. Membrane formation has traditionally involved slow, labor intensive processes best suited to small scale laboratory experimentation. We have recently demonstrated a high throughput method of membrane formation using automated liquid-handling robotics. We describe here the integration of membrane formation and measurement with two methods compatible with automation and high throughput liquid-handling robotics. Both of these methods create artificial lipid bilayers by joining lipid monolayers self-assembled at the interface of aqueous and organic phases using sessile aqueous droplets in contact with a measurement electrode; one using a pin tool, commonly employed in high throughput fluid handling assays, and the other using a positive displacement pipette. Membranes formed with both methods were high quality and supported measurement of ion channels at the single molecule level. Full automation of bilayer production and measurement with the positive displacement pipette was demonstrated by integrating it with a motion control platform.

Poulos, J. L.; Portonovo, S. A.; Bang, H.; Schmidt, J. J.

2010-11-01

333

Statistically steady measurements of Rayleigh-Taylor mixing in a gas channel  

NASA Astrophysics Data System (ADS)

A novel gas channel experiment is described to study the development of high Atwood number Rayleigh-Taylor mixing. Two gas streams, one containing air and the other containing a helium-air mixture, flow parallel to each other separated by a thin splitter plate. The streams meet at the end of a splitter plate leading to the formation of an unstable interface and of buoyancy driven mixing. This buoyancy driven mixing experiment allows for long data collection times, has short transients, and is statistically steady. The facility was designed to be capable of large Atwood number studies (At˜0.75). We describe initial validation work to measure the self similar evolution of mixing at density differences (0.035channel facility and present validation results for experimental runs at Atwood numbers up to 0.1. Diagnostics include a constant temperature hot wire anemometer, and high resolution digital image analysis. The hot-wire probe gives velocity statistics of the mixing layer. A multiposition single-wire technique was used to measure the velocity fluctuations in three mutually perpendicular directions. Analysis of the measured data was used to explain the mixing as it develops to a self-similar regime in this flow. A digital image analysis procedure was used to characterize various properties of the flow and also to validate the hot wire measurements.

Banerjee, Arindam; Andrews, Malcolm J.

2006-03-01

334

Mobile set for ecological radio monitoring  

Microsoft Academic Search

Broad use of radio objects of different applications in municipal infrastructure causes the problem of ecological radio monitoring. This paper presents the results of development of a radio monitoring mobile set based on usage of home devices. The mobile set fulfils the following functions: the choice of observation channels using the locality maps; motion to the point of observation and

S. A. Zaidullin; S. A. Lavrushev; V. S. Moiseev; G. A. Morozov; Yu. E. Sedeinikov

2000-01-01

335

Effects of human shadowing, traffic and antenna movements on 62.4 GHz indoor RLAN's channels  

Microsoft Academic Search

This paper presents results of 62.4 GHz wideband propagation measurements of the indoor radio channel between fixed terminals. The impact of human shadowing, traffic and LAN's antenna movements on important channel characteristics such as coherence bandwidth, RMS delay spread and Rician K-factor are compared and evaluated

M. O. Al-Nuaimi; A. G. Siamarou

2001-01-01

336

When to Quit for A New Job: Quickest Detection of Spectrum Opportunities in Multiple Channels  

E-print Network

in cognitive radio networks where a secondary user searches for idle channels in the spectrum. A BayesianWhen to Quit for A New Job: Quickest Detection of Spectrum Opportunities in Multiple Channels Qing when its state is unlikely to change in the near future (as indicated by the measurements obtained so

Islam, M. Saif

337

Using a novel flood prediction model and GIS automation to measure the valley and channel morphology of large river networks  

EPA Science Inventory

Traditional methods for measuring river valley and channel morphology require intensive ground-based surveys which are often expensive, time consuming, and logistically difficult to implement. The number of surveys required to assess the hydrogeomorphic structure of large river n...

338

A single-channel SQUID magnetometer for measuring magnetic field of human fetal heart  

NASA Astrophysics Data System (ADS)

A non-invasive single-channel SQUID magnetometer for fetal magnetocardiography has been developed. The signal is picked-up with a wire wound third order gradiometer. The optimal configuration of the flux transformer is a trade-off between sufficient sensitivity for the magnetic field originated in fetal heart and effective immunity against the ambient magnetic noise. The over all system performance together with the measuring probe and SQUID electronics is described. The balancing of the third order flux transformer is discussed as well as the signal processing of fetal magnetocardiogram recordings.

Bachir, Wesam; Grot, Przemyslaw; Dunajski, Zbigniew

2004-07-01

339

Three dimensional profile measurement using multi-channel detector MVM-SEM  

NASA Astrophysics Data System (ADS)

In next generation lithography (NGL) for the 1x nm node and beyond, the three dimensional (3D) shape measurements such as side wall angle (SWA) and height of feature on photomask become more critical for the process control. Until today, AFM (Atomic Force Microscope), X-SEM (cross-section Scanning Electron Microscope) and TEM (Transmission Electron Microscope) tools are normally used for 3D measurements, however, these techniques require time-consuming preparation and observation. And both X-SEM and TEM are destructive measurement techniques. This paper presents a technology for quick and non-destructive 3D shape analysis using multi-channel detector MVM-SEM (Multi Vision Metrology SEM), and also reports its accuracy and precision.

Yoshikawa, Makoto; Harada, Sumito; Ito, Keisuke; Murakawa, Tsutomu; Shida, Soichi; Matsumoto, Jun; Nakamura, Takayuki

2014-07-01

340

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

341

Patch clamp measurements on Xenopus laevis oocytes: currents through endogenous channels and implanted acetylcholine receptor and sodium channels  

Microsoft Academic Search

1.Functional acetylcholine receptor (AChR) and sodium channels were expressed in the membrane ofXenopus laevis oocytes following injection with poly(A)+-mRNA extracted from denervated rat leg muscle. Wholecell currents, activated by acetylcholine or by depolarizing voltage steps had properties comparable to those observed in rat muscle. Oocytes injected with specific mRNA, transcribed from cDNA templates and coding for the AChR ofTorpedo electric

C. Methfessel; V. Witzemann; T. Takahashi; M. Mishina; S. Numa; B. Sakmann

1986-01-01

342

Effect of Ducting on Radio Occultation Measurements: An Assessment Based on High-Resolution Radiosonde Soundings  

NASA Technical Reports Server (NTRS)

Recent studies have shown that the presence of elevated ducts in the lower atmosphere has an adverse effect on the inversion of GPS radio occultation data. The problem arises because the microwave refractivity within and below an elevated duct is no longer uniquely determined by the bending angle profile. Applying Abel inversion without a priori knowledge of the duct will introduce a negative bias in the retrieved refractivity profile within and below the duct. In this work, high vertical resolution radiosonde data are used to give a quantitative assessment of the characteristics and effects of ducts, including their frequency of occurrences, heights, and thicknesses at different latitudes and seasons. The negative bias from the Abel-retrieved refractivity profiles resulting from these ducts is also computed. The results give a strong indication that ducting in the lower troposphere is a frequent phenomenon over the tropics and midlatitudes. The ducts are shown to be predominantly caused by sharp changes in the vertical structure of water vapor. The majority of the ducts are found to be below 2 km, with a median duct layer thickness of about 100 m. The negative refractivity bias is shown to be largest below 2 km, with a median value of about 0.5-1% in the tropics and 0.2-0.5% in midlatitudes. The bias is about a factor of 2-3 smaller between 2 to 3 km and is negligible above 4 km.

Ao, C. O

2007-01-01

343

The mass and internal Structure of Phobos derived from Mars Express Radio Science measurements  

NASA Astrophysics Data System (ADS)

The Mars Express spacecraft was successfully launched on 2 June 2003 and injected into its orbit around Mars on 25 December 2003. The elliptical polar orbit of Mars Express allows close flybys at the Mars moon Phobos, the first close flybys since the flybys of Viking and Phobos 2 twenty years ago. Two close flybys were performed with Mars Express in 2006 at 460 km and in 2008 at 275 km distance. The product of the gravitational constant and the mass of Phobos could be estimated using the X-band radio tracking data by evaluating the residual Doppler effect. The data of the second flyby provided a very small uncertainty of 0.3 % for the mass solution. Mars Express has changed its orbit in February 2010 which allowed a very close flyby at 62 km in March 2010. Here we report the results from the mass estimates of the flybys in 2006 and 2008 and the geophysical consequences for the internal structure of Phobos. In addition, preliminary results from the very close flyby in March 2010 regarding the estimation of the mass and the low order coefficient J2 of the gravity field of Phobos are shown.

Andert, Thomas; Paetzold, Martin; Haeusler, Bernd

344

Channel Strain Measurement in 32-nm-Node Complementary Metal-Oxide-Semiconductor Field-Effect Transistor by Raman Spectroscopy  

NASA Astrophysics Data System (ADS)

We performed a strain analysis of a 32-nm-node microprocessing unit by Raman spectroscopy in conjunction with transmission electron microscopy. The channel surface was exposed by chemical etching and mechanical polishing for Raman spectroscopy. Some defects and Ge concentration variation were observed in embedded SiGe of a p-channel metal-oxide-semiconductor field-effect transistor (pMOSFET). Uniform defects lying at the same angle were observed in the source and drain regions of an n-channel MOSFET (nMOSFET). From the Raman measurement, the Raman peak from strained Si in the pMOSFET shifted toward a higher frequency at approximately 7.5 cm-1, which corresponds to -3.75 GPa (compressive) under the assumption of uniaxial stress along the channel direction. On the other hand, the Raman peak shift from strained Si in the nMOSFET was -1.7 cm-1 corresponding to 0.85 GPa (tensile) under the assumption of uniaxial stress. From the nanobeam diffraction measurements, the compressive strain at the channel edge was larger than that at the channel center in the pMOSFET. On the other hand, the tensile strain in the nMOSFET was induced uniformly in the channel region. We think that understanding and control of channel strain introduction are indispensable in the state-of-the-art complementary MOSFET technology.

Takei, Munehisa; Hashiguchi, Hiroki; Yamaguchi, Takuya; Kosemura, Daisuke; Nagata, Kohki; Ogura, Atsushi

2012-04-01

345

Film, Radio, and Television.  

ERIC Educational Resources Information Center

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

Hardesty, Carolyn, Ed.

1990-01-01

346

Radio determination satellite service  

Microsoft Academic Search

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

Robert D. Briskman

1990-01-01

347

Division x: Radio Astronomy  

Microsoft Academic Search

Division X provides a common theme for astronomers using radio techniques to study a vast range of phenomena in the Universe, from exploring the Earth's ionosphere or making radar measurements in the Solar System, via mapping the distribution of gas and molecules in our own Galaxy and in other galaxies, to study the vast explosive processes in radio galaxies and

Luis F. Rodriguez; Ren-Dong Nan; Lucia Padrielli; Philip J. Diamond; Gloria M. Dubner; Michael Garrett; W. Miller Goss; Anne Green; Masato Ishiguro; A. Pramesh Rao; Russell A. Taylor; Jose M. Torrelles; Jean L. Turner

2007-01-01

348

Radio-frequency Attenuation Length, Basal-Reflectivity, Depth, and Polarization Measurements from Moore's Bay in the Ross Ice-Shelf  

E-print Network

Radio-glaciological parameters from Moore's Bay, in the Ross Ice Shelf, have been measured. The thickness of the ice shelf in Moore's Bay was measured from reflection times of radio-frequency pulses propagating vertically through the shelf and reflecting from the ocean. The average depth obtained is $576\\pm8$ m. The temperature-averaged attenuation length of the ice column, $\\langle L \\rangle$, is derived from the returned power assuming 100\\% reflection. A linear fit to the data yields $\\langle L(\

Barwick, S W; Besson, D; Duffin, T; Hanson, J C; Klein, S R; Kleinfelder, S A; Reed, C; Roumi, M; Stezelberger, T; Tatar, J; Walker, J; Zou, L

2014-01-01

349

Measurement of Top-Quark Polarization in t-channel Single-Top Production  

E-print Network

The measurement of the top quark polarization, sensitive to the electroweak coupling structure, in t-channel single-top production is presented. Events are analyzed corresponding to an integrated luminosity of approximately $20~\\mathrm{fb^{-1}}$ recorded with the CMS detector during pp collisions at $\\sqrt{s}=8~\\mathrm{TeV}$. By requiring one isolated lepton (muon or electron), two jets, and missing transverse energy, an angular asymmetry, sensitive to the polarization of the top quark, is reconstructed in the top-quark rest frame. The corresponding angular asymmetry at parton level is inferred from data in a phase space with enhanced single-top t-channel candidates through unfolding. Remaining background contributions are estimated through a ML-fit and subtracted. A polarization of $P_{t}=0.82\\pm0.12\\mathrm{~(stat.)}\\pm0.32\\mathrm{~(syst.)}$ is measured assuming a spin-analyzing power of the charged lepton stemming from the top decay of $100\\%$.

Komm, Matthias

2014-01-01

350

Dynamic Channel and Interface Management in MultiChannel Multi-Interface Wireless Access Networks  

Microsoft Academic Search

Availability of multiple channels and multiple radio interfaces can lead to substantial improvements in the performance of wireless access networks. The optimal allocation of available channels to the users with multiple interfaces however is not a trivial problem especially in a dynamically varying system. In this paper, we will consider the problem of channel and radio interface management in multi-channel

Hassan Halabian; Ioannis Lambadaris; Chung-Horng Lung; Anand Srinivasan

2010-01-01

351

47 CFR 95.1011 - Channel use policy.  

Code of Federal Regulations, 2011 CFR

...1011 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES PERSONAL RADIO SERVICES Low Power Radio Service (LPRS) General Provisions § 95.1011 Channel use policy. (a) The...

2011-10-01

352

47 CFR 95.1011 - Channel use policy.  

Code of Federal Regulations, 2012 CFR

...1011 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES PERSONAL RADIO SERVICES Low Power Radio Service (LPRS) General Provisions § 95.1011 Channel use policy. (a) The...

2012-10-01

353

47 CFR 95.1011 - Channel use policy.  

Code of Federal Regulations, 2010 CFR

...1011 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES PERSONAL RADIO SERVICES Low Power Radio Service (LPRS) General Provisions § 95.1011 Channel use policy. (a) The...

2010-10-01

354

47 CFR 95.1011 - Channel use policy.  

Code of Federal Regulations, 2013 CFR

...1011 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES PERSONAL RADIO SERVICES Low Power Radio Service (LPRS) General Provisions § 95.1011 Channel use policy. (a) The...

2013-10-01

355

Purity of Gaussian states: Measurement schemes and time evolution in noisy channels  

SciTech Connect

We present a systematic study of the purity for Gaussian states of single-mode continuous variable systems. We prove the connection of purity to observable quantities for these states, and show that the joint measurement of two conjugate quadratures is necessary and sufficient to determine the purity at any time. The statistical reliability and the range of applicability of the proposed measurement scheme are tested by means of Monte Carlo simulated experiments. We then consider the dynamics of purity in noisy channels. We derive an evolution equation for the purity of general Gaussian states both in thermal and in squeezed thermal baths. We show that purity is maximized at any given time for an initial coherent state evolving in a thermal bath, or for an initial squeezed state evolving in a squeezed thermal bath whose asymptotic squeezing is orthogonal to that of the input state.

Paris, Matteo G.A. [Quantum Optics and Information Group, INFM UdR di Pavia, I-27100 Pavia (Italy); Illuminati, Fabrizio; Serafini, Alessio; De Siena, Silvio [Dipartimento di Fisica 'E. R. Caianiello', Universita di Salerno, INFM UdR Salerno, INFN Sez. Napoli, Grupo Collegato Salerno, Via S. Allende, 84081 Baronissi, SA (Italy)

2003-07-01

356

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. PMID:1087643

Conti, F; Hille, B; Neumcke, B; Nonner, W; Stampfli, R

1976-01-01

357

Measurement of flow velocity and inference of liquid viscosity in a microfluidic channel by fluorescence photobleaching.  

PubMed

We present a simple, noninvasive method for simultaneous measurement of flow velocity and inference of liquid viscosity in a microfluidic channel. We track the dynamics of a sharp front of photobleached fluorescent dye using a confocal microscope and measure the intensity at a single point downstream of the initial front position. We fit an exact solution of the advection diffusion equation to the fluorescence intensity recovery curve to determine the average flow velocity and the diffusion coefficient of the tracer dye. The dye diffusivity is correlated to solute concentration to infer rheological properties of the liquid. This technique provides a simple method for simultaneous elucidation of flow velocity and liquid viscosity in microchannels. PMID:24730625

Carroll, Nick J; Jensen, Kaare H; Parsa, Shima; Holbrook, N Michele; Weitz, David A

2014-04-29

358

Precise measurement of the top quark mass in the dilepton channel at D0  

E-print Network

We measure the top quark mass (mt) in ppbar collisions at a center of mass energy of 1.96 TeV using dilepton ttbar->W+bW-bbar->l+nubl-nubarbbar events, where l denotes an electron, a muon, or a tau that decays leptonically. The data correspond to an integrated luminosity of 5.4 fb-1 collected with the D0 detector at the Fermilab Tevatron Collider. We obtain mt = 174.0 +- 1.8(stat) +- 2.4(syst) GeV, which is in agreement with the current world average mt = 173.3 +- 1.1 GeV. This is currently the most precise measurement of mt in the dilepton channel.

D0 Collaboration; V. M. Abazov; B. Abbott; B. S. Acharya; M. Adams; T. Adams; G. D. Alexeev; G. Alkhazov; A. Alton; G. Alverson; G. A. Alves; L. S. Ancu; M. Aoki; M. Arov; A. Askew; B. Åsman; O. Atramentov; C. Avila; J. BackusMayes; F. Badaud; L. Bagby; B. Baldin; D. V. Bandurin; S. Banerjee; E. Barberis; P. Baringer; J. Barreto; J. F. Bartlett; U. Bassler; V. Bazterra; S. Beale; A. Bean; M. Begalli; M. Begel; C. Belanger-Champagne; L. Bellantoni; S. B. Beri; G. Bernardi; R. Bernhard; I. Bertram; M. Besançon; R. Beuselinck; V. A. Bezzubov; P. C. Bhat; V. Bhatnagar; G. Blazey; S. Blessing; K. Bloom; A. Boehnlein; D. Boline; E. E. Boos; G. Borissov; T. Bose; A. Brandt; O. Brandt; R. Brock; G. Brooijmans; A. Bross; D. Brown; J. Brown; X. B. Bu; M. Buehler; V. Buescher; V. Bunichev; S. Burdin; T. H. Burnett; C. P. Buszello; B. Calpas; E. Camacho-Pérez; M. A. Carrasco-Lizarraga; B. C. K. Casey; H. Castilla-Valdez; S. Chakrabarti; D. Chakraborty; K. M. Chan; A. Chandra; G. Chen; S. Chevalier-Théry; D. K. Cho; S. W. Cho; S. Choi; B. Choudhary; S. Cihangir; D. Claes; J. Clutter; M. Cooke; W. E. Cooper; M. Corcoran; F. Couderc; M. -C. Cousinou; A. Croc; D. Cutts; A. Das; G. Davies; K. De; S. J. de Jong; E. De La Cruz-Burelo; F. Déliot; M. Demarteau; R. Demina; D. Denisov; S. P. Denisov; S. Desai; C. Deterre; K. DeVaughan; H. T. Diehl; M. Diesburg; A. Dominguez; T. Dorland; A. Dubey; L. V. Dudko; D. Duggan; A. Duperrin; S. Dutt; A. Dyshkant; M. Eads; D. Edmunds; J. Ellison; V. D. Elvira; Y. Enari; H. Evans; A. Evdokimov; V. N. Evdokimov; G. Facini; T. Ferbel; F. Fiedler; F. Filthaut; W. Fisher; H. E. Fisk; M. Fortner; H. Fox; S. Fuess; A. Garcia-Bellido; V. Gavrilov; P. Gay; W. Geng; D. Gerbaudo; C. E. Gerber; Y. Gershtein; G. Ginther; G. Golovanov; A. Goussiou; P. D. Grannis; S. Greder; H. Greenlee; Z. D. Greenwood; E. M. Gregores; G. Grenier; Ph. Gris; J. -F. Grivaz; A. Grohsjean; S. Grünendahl; M. W. Grünewald; T. Guillemin; F. Guo; G. Gutierrez; P. Gutierrez; A. Haas; S. Hagopian; J. Haley; L. Han; K. Harder; A. Harel; J. M. Hauptman; J. Hays; T. Head; T. Hebbeker; D. Hedin; H. Hegab; A. P. Heinson; U. Heintz; C. Hensel; I. Heredia-De La Cruz; K. Herner; G. Hesketh; M. D. Hildreth; R. Hirosky; T. Hoang; J. D. Hobbs; B. Hoeneisen; M. Hohlfeld; Z. Hubacek; N. Huske; V. Hynek; I. Iashvili; R. Illingworth; A. S. Ito; S. Jabeen; M. Jaffré; D. Jamin; A. Jayasinghe; R. Jesik; K. Johns; M. Johnson; D. Johnston; A. Jonckheere; P. Jonsson; J. Joshi; A. W. Jung; A. Juste; K. Kaadze; E. Kajfasz; D. Karmanov; P. A. Kasper; I. Katsanos; R. Kehoe; S. Kermiche; N. Khalatyan; A. Khanov; A. Kharchilava; Y. N. Kharzheev; D. Khatidze; M. H. Kirby; J. M. Kohli; A. V. Kozelov; J. Kraus; S. Kulikov; A. Kumar; A. Kupco; T. Kur?a; V. A. Kuzmin; J. Kvita; S. Lammers; G. Landsberg; P. Lebrun; H. S. Lee; S. W. Lee; W. M. Lee; J. Lellouch; L. Li; Q. Z. Li; S. M. Lietti; J. K. Lim; D. Lincoln; J. Linnemann; V. V. Lipaev; R. Lipton; Y. Liu; Z. Liu; A. Lobodenko; M. Lokajicek; R. Lopes de Sa; H. J. Lubatti; R. Luna-Garcia; A. L. Lyon; A. K. A. Maciel; D. Mackin; R. Madar; R. Magaña-Villalba; S. Malik; V. L. Malyshev; Y. Maravin; J. Martínez-Ortega; R. McCarthy; C. L. McGivern; M. M. Meijer; A. Melnitchouk; D. Menezes; P. G. Mercadante; M. Merkin; A. Meyer; J. Meyer; F. Miconi; N. K. Mondal; G. S. Muanza; M. Mulhearn; E. Nagy; M. Naimuddin; M. Narain; R. Nayyar; H. A. Neal; J. P. Negret; P. Neustroev; S. F. Novaes; T. Nunnemann; G. Obrant; J. Orduna; N. Osman; J. Osta; G. J. Otero y Garzón; M. Padilla; A. Pal; N. Parashar; V. Parihar; S. K. Park; J. Parsons; R. Partridge; N. Parua; A. Patwa; B. Penning; M. Perfilov; K. Peters; Y. Peters; K. Petridis; G. Petrillo; P. Pétroff; R. Piegaia; J. Piper; M. -A. Pleier; P. L. M. Podesta-Lerma; V. M. Podstavkov; P. Polozov; A. V. Popov; M. Prewitt; D. Price; N. Prokopenko; S. Protopopescu; J. Qian; A. Quadt; B. Quinn; M. S. Rangel; K. Ranjan; P. N. Ratoff; I. Razumov; P. Renkel; M. Rijssenbeek; I. Ripp-Baudot; F. Rizatdinova; M. Rominsky; A. Ross; C. Royon; P. Rubinov; R. Ruchti; G. Safronov; G. Sajot; P. Salcido; A. Sánchez-Hernández; M. P. Sanders; B. Sanghi; A. S. Santos; G. Savage; L. Sawyer; T. Scanlon; R. D. Schamberger; Y. Scheglov; H. Schellman; T. Schliephake; S. Schlobohm; C. Schwanenberger; R. Schwienhorst; J. Sekaric; H. Severini; E. Shabalina; V. Shary; A. A. Shchukin; R. K. Shivpuri; V. Simak; V. Sirotenko; P. Skubic; P. Slattery; D. Smirnov; K. J. Smith; G. R. Snow; J. Snow; S. Snyder; S. Söldner-Rembold; L. Sonnenschein; K. Soustruznik; J. Stark; V. Stolin; D. A. Stoyanova; M. Strauss; D. Strom; L. Stutte; L. Suter; P. Svoisky; M. Takahashi; A. Tanasijczuk; W. Taylor; M. Titov; V. V. Tokmenin; Y. -T. Tsai; D. Tsybychev; B. Tuchming; C. Tully; L. Uvarov; S. Uvarov; S. Uzunyan; R. Van Kooten; W. M. van Leeuwen; N. Varelas; E. W. Varnes

2011-05-02

359

Ultrasound Open Channel Flow-Speed Measurement Based on the Lateral Directional Echo Observations  

NASA Astrophysics Data System (ADS)

Conventional ultrasonic flowmeters have a problem in measuring the small open channel fluid flow. To solve this problem, a lateral observation technique using a single transmitter/receiver transducer attached at the bottom of the pipe was proposed. Pulse echo signals scattered from the particles in the medium were repetitively recorded with a constant time interval. From the slope of the correlation peak amplitude with the variation in pulse echo excitation time, the flow speed of the medium was estimated. The method has an advantage in that the variation in flow speed in the vertical depth direction is directly measured with a minimum measurement space. Moreover, the fluctuations caused by the turbulent water can be avoided compared with the case of a conventional method based on the time estimation method. Bubbles were generated by an aspirator and flour powder was mixed with water as scatterers in the imitated drainage water. The flow speed of water was measured with respect to the inflowing fluid volume. Moreover, vertical flow speed profiles were measured and compared with fluid flow simulation results. The results showed that the precision of the measured flow speed was satisfactory and tolerant against the turbulence of the water flow medium.

Nishimura, Ichiro; Ishigamori, Mitsuhide; Yamada, Akira

2012-07-01

360

Software Defined Radio Demonstration of MIMO-OFDM Rate Adaptation  

Microsoft Academic Search

In this paper, we present a framework for rate and power allocation in MIMO-OFDM systems using the V-BLAST and SVD techniques. The performance of these techniques are compared with one another and with waterfilling using channel measurements on our MIMO-OFDM software defined radio testbed. Specifically, we show with measured data that sub-carrier rate adaptation allows for more efficient spectral use.

John Kountouriotis; Nicholas J. Kirsch; Kapil R. Dandekar

2006-01-01

361

Detailed plasma potential measurements in a radio-frequency expanding plasma obtained from various electrostatic probes  

SciTech Connect

On-axis plasma potential measurements have been made with an emissive probe in a low pressure (0.044 Pa) rf expanding plasma containing an ion beam. The beam is detected with a retarding field energy analyzer (RFEA), and is seen to disappear at high pressure (0.39 Pa). The emissive probe measurements are in very good agreement with corresponding measurements made with two separate RFEAs, and the results indicate that the floating potential of the strongly emitting probe gives an accurate measure of the plasma potential under the present conditions.

Lafleur, T.; Charles, C.; Boswell, R. W. [Space Plasma, Power, and Propulsion Group, Research School of Physics and Engineering, Australian National University, Canberra ACT 0200 (Australia)

2009-04-15

362

The determination of parameters of the upper atmosphere by the radio-meteor measurements  

NASA Astrophysics Data System (ADS)

Study of the parameters of the upper atmosphere on the basis of amplitude-time characteristics of meteor ionization. Together with various methods meteor observations (optical, photographic, visual, spectral, television), the most effective modern method of studying meteors means is radar. The development of modern radar technology allows us to apply this tool to monitor meteors. This method allows to determine the parameters of temperature and atmospheric pressure. Actual issue is the development of methods of determining the coefficient of ambipolar diffusion, pressure, density and temperature of the atmosphere in the meteor zone. Graph of amplitude-time characteristic has the exponential form. This fact allows to determine the coefficient of ambipolar diffusion. New algorithm for estimation of the ambipolar diffusion coefficient based on a set of statistical methods and techniques of digital signal processing. There are decomposition of data on singular values and Prony's method. This method of modeling the sample data as a linear combination of exponential. Prony’s method approximates the amplitude-time characteristics of using a deterministic exponential model. Input data is amplitude-time characteristics of the meteor trail x[1]…x[N]. The method allows to estimate x[n] p-membered exponential model: begin{center} x[n]=Sigma2A_{k}exp[a _{k}(n-1)]Cos[2Pif_{k}(n-1)T+Fi_{k}] (1) end{center} 1<=n<=N, T - time range in seconds, A_{k} and a_{k} - amplitude and damping coefficient, f_{k} and Fi_{k} - frequency and initial phase. The equation describing the decay of radio signal: begin{center} A=A_{0}exp(-16Pi^{2}$D_{a}t/? (2) ). (2) lambda? - radar wavelength. The output of the algorithm - the ambipolar diffusion coefficient values D_{a}. begin{center} T=0.5lnD-T_{0}+mg/2kT_{0} (3) Last equation allows to obtain temperature values ??using the coefficient of ambipolar diffusion depends on the height.

Shamukov, Damir; Fahrutdinova, Antonina; Nugmanov, Ildus

363

A global comparative study on the ionospheric measurements between COSMIC radio occultation technique and IRI model  

NASA Astrophysics Data System (ADS)

We compare ionospheric parameters including total electron content (TEC), peak density, and height of the F2 layer (NmF2 and hmF2) between FORMOSAT-3/COSMIC (F3/C) GPS radio occultation (RO) technique retrieved and International Reference Ionosphere (IRI-2001) model predicted during different seasons in a low solar activity (LSA) year 2007. The comparison of topside TEC (tTEC, obtained by integrating electron density from hmF2 to 800 km) between IRI and F3/C shows that the IRI overestimates tTEC during both equinox seasons at around ±15° magnetic latitudes during daytime, especially in March equinox while underestimation of tTEC predicted by IRI is a dominant feature for both solstices. Further, a common finding is that the IRI overestimates tTEC from evening to prenoon hours irrespective of season at around ±20° magnetic latitudes, which is most likely due to the underestimation of hmF2 (by around 30-40 km), a key parameter on which the build of electron density profile depends in the model and inaccurate representation of the real profile by the topside electron density profiler model in IRI. The global distributions and seasonal variations of NmF2 show clear semiannual and annual asymmetry features during daytime and such features also reflected in IRI predicted peak densities with few exceptions. This high degree of agreement between tTEC comparison and the characteristic features of NmF2 global distributions indicates that the majority of contribution for tTEC has come from the F2 region. Further, it is also presented the global distributions of topside vertical scale heights (VSH) computed using electron density profiles retrieved from F3/C and predicted by IRI model during different seasons in year 2007. An important finding is that the topside VSH of F3/C profile data is meticulously following the geomagnetic equator during daytime irrespective of season and tends to increase toward higher latitudes. An appreciable latitudinal difference is found in the season averaged scale heights that derived with F3/C data during daytime while completely opposite results are found for IRI predicted scale heights. The discrepancies of topside VSH between the F3/C derived and predicted by IRI indicating that the shape of the topside electron density profile in the IRI model should desperately be revised accordingly such that it more closely resembles the real situation.

Potula, Brahmanandam Sree; Chu, Yen-Hsyang; Uma, G.; Hsia, His-Pu; Wu, Kong-Hong

2011-02-01

364

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

365

Educational Radio.  

ERIC Educational Resources Information Center

Examines the effectiveness of the radio in education and the crucial role of the radio in distance education in first half of the 20th century; dramatic social changes in the 1960s that led to a review of educational institutions and of educational media; and the radio today as a neglected but inexpensive medium of communication that should be…

Arafeh, Sousan

1999-01-01

366

Novel method to classify hemodynamic response obtained using multi-channel fNIRS measurements into two groups: exploring the combinations of channels  

PubMed Central

Near-infrared spectroscopy (NIRS) in psychiatric studies has widely demonstrated that cerebral hemodynamics differs among psychiatric patients. Recently we found that children with attention-deficit/hyperactivity disorder (ADHD) and children with autism spectrum disorders (ASD) showed different hemodynamic responses to their own mother’s face. Based on this finding, we may be able to classify the hemodynamic data into two those groups and predict to which diagnostic group an unknown participant belongs. In the present study, we proposed a novel statistical method for classifying the hemodynamic data of these two groups. By applying a support vector machine (SVM), we searched the combination of measurement channels at which the hemodynamic response differed between the ADHD and the ASD children. The SVM found the optimal subset of channels in each data set and successfully classified the ADHD data from the ASD data. For the 24-dimensional hemodynamic data, two optimal subsets classified the hemodynamic data with 84% classification accuracy, while the subset contained all 24 channels classified with 62% classification accuracy. These results indicate the potential application of our novel method for classifying the hemodynamic data into two groups and revealing the combinations of channels that efficiently differentiate the two groups. PMID:25071510

Ichikawa, Hiroko; Kitazono, Jun; Nagata, Kenji; Manda, Akira; Shimamura, Keiichi; Sakuta, Ryoichi; Okada, Masato; Yamaguchi, Masami K.; Kanazawa, So; Kakigi, Ryusuke

2014-01-01

367

Novel method to classify hemodynamic response obtained using multi-channel fNIRS measurements into two groups: exploring the combinations of channels.  

PubMed

Near-infrared spectroscopy (NIRS) in psychiatric studies has widely demonstrated that cerebral hemodynamics differs among psychiatric patients. Recently we found that children with attention-deficit/hyperactivity disorder (ADHD) and children with autism spectrum disorders (ASD) showed different hemodynamic responses to their own mother's face. Based on this finding, we may be able to classify the hemodynamic data into two those groups and predict to which diagnostic group an unknown participant belongs. In the present study, we proposed a novel statistical method for classifying the hemodynamic data of these two groups. By applying a support vector machine (SVM), we searched the combination of measurement channels at which the hemodynamic response differed between the ADHD and the ASD children. The SVM found the optimal subset of channels in each data set and successfully classified the ADHD data from the ASD data. For the 24-dimensional hemodynamic data, two optimal subsets classified the hemodynamic data with 84% classification accuracy, while the subset contained all 24 channels classified with 62% classification accuracy. These results indicate the potential application of our novel method for classifying the hemodynamic data into two groups and revealing the combinations of channels that efficiently differentiate the two groups. PMID:25071510

Ichikawa, Hiroko; Kitazono, Jun; Nagata, Kenji; Manda, Akira; Shimamura, Keiichi; Sakuta, Ryoichi; Okada, Masato; Yamaguchi, Masami K; Kanazawa, So; Kakigi, Ryusuke

2014-01-01

368

Aircraft Engine On-Line Diagnostics Through Dual-Channel Sensor Measurements: Development of a Baseline System  

NASA Technical Reports Server (NTRS)

In this paper, a baseline system which utilizes dual-channel sensor measurements for aircraft engine on-line diagnostics is developed. This system is composed of a linear on-board engine model (LOBEM) and fault detection and isolation (FDI) logic. The LOBEM provides the analytical third channel against which the dual-channel measurements are compared. When the discrepancy among the triplex channels exceeds a tolerance level, the FDI logic determines the cause of the discrepancy. Through this approach, the baseline system achieves the following objectives: (1) anomaly detection, (2) component fault detection, and (3) sensor fault detection and isolation. The performance of the baseline system is evaluated in a simulation environment using faults in sensors and components.

Kobayashi, Takahisa; Simon, Donald L.

2008-01-01

369

Measurement Based MIMO Channel Capacity in an Urban Canyon Environment at the 3.7GHz Band  

NASA Astrophysics Data System (ADS)

This paper describes the measurements made in an urban canyon environment of a relay network scenario to determine the capacity of the multiple-input-multiple-output (MIMO) channel. While varying antenna number and spacing, we measure the channel matrices in the 3.7GHz band using a 4×4 switching MIMO channel sounder. The results show that antenna spacing is shown to have less impact than signal-to-noise (SNR) on MIMO channel capacity in a line-of-sight (LOS) environment when physical antenna spacing is selected at four wavelengths. As a result, in an urban MIMO LOS scenario, a base station can provide sufficient data throughput to relay station because most links from base station to relay station have LOS environment and are free from restriction of antenna spacing.

Lim, Jae-Woo; Kwon, Se-Woong; Park, Youn-Hyun; Yoon, Hyun-Goo; Yook, Jong-Gwan; Yoon, Yong-Joong

370

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

NASA Astrophysics Data System (ADS)

Methods to detect tropical deep convective clouds and convective overshooting from measurements at the three water vapor channels (183.3 ± 1, 183.3 ± 3, and 183.3 ± 7 GHz) of the Advanced Microwave Sounding Unit-B (AMSU-B) are presented. Thresholds for the brightness temperature differences between the three channels are suggested as criterion to detect deep convective clouds, and an order relation between the differences is used to detect convective overshooting. The procedure is based on an investigation of the influence of deep convective cloud systems on the microwave brightness temperatures at frequencies from 89 to 220 GHz using simultaneous aircraft microwave and radar measurements over two tropical deep convective cloud systems, taken during the Tropical Rainfall Measuring Mission (TRMM) Large Scale Biosphere-Atmosphere Experiment (LBA) campaign. Two other aircraft cases with deep convective cloud systems observed during the Third Convection and Moisture Experiment (CAMEX-3) are used to validate the criteria. Furthermore, a microwave radiative transfer model and simulated mature tropical squall line data derived from the Goddard Cumulus Ensemble (GCE) model are used to validate the procedures and to adapt the criteria to the varying viewing angle of AMSU-B. These methods are employed to investigate the distributions of deep convective clouds and convective overshooting in the tropics (30°S to 30°N) for the four 3-month seasons from March 2003 to February 2004 using the AMSU-B data from NOAA-15, -16, and -17. The distributions show a seasonal variability of shifting from the winter hemisphere to the summer hemisphere. The distributions of deep convective clouds follow the seasonal patterns of the surface rainfall rates. The deep convective clouds over land penetrate more frequently into the tropical tropopause layer than those over ocean. The averaged deep convective cloud fraction is about 0.3% in the tropics, and convective overshooting contributes about 26% to this.

Hong, Gang; Heygster, Georg; Miao, Jungang; Kunzi, Klaus

2005-03-01

371

Electrochemical impedance measurement of prostate cancer cells using carbon nanotube array electrodes in a microfluidic channel  

NASA Astrophysics Data System (ADS)

Highly aligned multi-wall carbon nanotubes were synthesized in the shape of towers and embedded into fluidic channels as electrodes for impedance measurement of LNCaP human prostate cancer cells. Tower electrodes up to 8 mm high were grown and easily peeled off a silicon substrate. The nanotube electrodes were then successfully soldered onto patterned printed circuit boards and cast into epoxy under pressure. After polishing the top of the tower electrodes, RF plasma was used to enhance the electrocatalytic effect by removing excess epoxy and activating the open end of the nanotubes. Electrodeposition of Au particles on the plasma-treated tower electrodes was done at a controlled density. Finally, the nanotube electrodes were embedded into a polydimethylsiloxane (PDMS) channel and electrochemical impedance spectroscopy was carried out with different conditions. Preliminary electrochemical impedance spectroscopy results using deionized water, buffer solution, and LNCaP prostate cancer cells showed that nanotube electrodes can distinguish the different solutions and could be used in future cell-based biosensor development.

Heung Yun, Yeo; Dong, Zhongyun; Shanov, Vesselin N.; Schulz, Mark J.

2007-11-01

372

A study of electron density profiles in relation to ionization sources and ground-based radio wave absorption measurements, part 1  

NASA Technical Reports Server (NTRS)

An extensive set of ground-based measurements of the diurnal variation of medium frequency radio wave adsorption and virtual height is analyzed in terms of current understanding of the D- and lower E-region ion production and loss process. When this is done a gross discrepancy arises, the source of which is not known.

Gnanalingam, S.; Kane, J. A.

1973-01-01

373

Variable Temperature Rate Studies for the Reaction H3O+ Measured with a Coaxial Molecular Beam Radio Frequency Ring  

E-print Network

Beam Radio Frequency Ring Electrode Ion Trap Mark A. Smith,*,,,§ Bing Yuan, and Andrei Sanov+ are determined using a coaxial molecular beam radio frequency ring electrode ion trap (CoMB-RET). The H3O association reaction at 300 K using the Canterbury selected ion flow tube (SIFT) system in 1996,4 and the rate

Sanov, Andrei

374

Monolithic Multichannel GSa\\/s Transient Waveform Recorder for Measuring Radio Emissions from High Energy Particle Cascades  

Microsoft Academic Search

A number of particle astrophysics initiatives to exploit radio emission from high energy particle cascades require high- frequency sampling of antenna array signals. Nyquist-limited sampling of GHz frequency radio signals for an antenna array may be accomplished by commercially available test units. However, these technologies are incompatible with the size, power and cost constraints of long-duration balloon or satellite flight.

Gary S. Varner; Peter Gorham; Jing Cao

375

UC Irvine 800MHz Trunked Radio System Revised 08/16/96 UCI RADIO USE AND PROCEDURES  

E-print Network

radio identifier or radio call ]__ , reporting an emergency. " The Communications Center dispatcher channels with all other UCI radio users INCLUDING PUBLIC SAFETY AGENCIES. You do not know when emergency communications are in progress on other talk groups and your unnecessary transmission may delay another radio

Brody, James P.

376

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

377

Turning off radios to save power in 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 (WMNs). The problem how to route flows and assign channels to radios in multi-radio WMNs has attracted a lot of attention in the recent years. However, the approaches proposed so far have mainly focused on reducing interference or maximizing the throughput. Little

Stefano Avallone

2011-01-01

378

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

379

Statistically steady measurements of Rayleigh-Taylor mixing in a gas channel  

NASA Astrophysics Data System (ADS)

A novel gas channel experiment was constructed to study the development of high Atwood number Rayleigh-Taylor mixing. Two gas streams, one containing air and the other containing helium-air mixture, flow parallel to each other separated by a thin splitter plate. The streams meet at the end of a splitter plate leading to the formation of an unstable interface and of buoyancy driven mixing. This buoyancy driven mixing experiment allows for long data collection times, short transients and was statistically steady. The facility was designed to be capable of large Atwood number studies of At ˜ 0.75. We describe work to measure the self similar evolution of mixing at density differences corresponding to 0.035 < At < 0.25. Diagnostics include a constant temperature hot-wire anemometer, and high resolution digital image analysis. The hot-wire probe gives velocity, density and velocity-density statistics of the mixing layer. Two different multi-position single-wire techniques were used to measure the velocity fluctuations in three mutually perpendicular directions. Analysis of the measured data was used to explain the mixing as it develops to a self-similar regime in this flow. These measurements are to our knowledge, the first use of hot-wire anemometry in the Rayleigh-Taylor community. Since the measurement involved extensive calibration of the probes in a binary gas mixture of air and helium, a new convective heat transfer correlation was formulated to account for variable-density low Reynolds number flows past a heated cylinder. In addition to the hot-wire measurements, a digital image analysis procedure was used to characterize various properties of the flow and also to validate the hot-wire measurements. A test of statistical convergence was performed and the study revealed that the statistical convergence was a direct consequence of the number of different large three-dimensional structures that were averaged over the duration of the run.

Banerjee, Arindam

380

Noise amplitude measurements of single-mode CW lasers at radio frequencies  

NASA Technical Reports Server (NTRS)

This letter presents the results of noise measurements for a variety of single-longitudinal-mode CW lasers (Ar/+/, standing-wave-dye, and ring-dye) that are commercially available. A quantitative comparison of the total output power fluctuations detected over the 7-300 MHz region (3 dB points) is presented.

Herring, G. C.; Hillard, M. E., Jr.

1992-01-01

381

Strategies against Particle Fouling in the Channels of a Micro Heat Exchanger When Performing muPIV Flow Pattern Measurements  

Microsoft Academic Search

The measurements of flow patterns in the channels of micro devices such as mixers and heat exchangers are usually performed with the well-established ? PIV (micro Particle Imaging Velocimetry) technique. Yet, the micro particles in this technique introduce particle fouling (PF), which is observed by the inherent active imaging system. This phenomenon is enhanced during the active measurement, leading to

Volker Heinzel; Angela Jianu; Hatto Sauter

2007-01-01

382

SPATIAL DIVERSITY AND SPATIAL CORRELATION EVALUATION OF MEASURED VEHICLE-TO-VEHICLE RADIO CHANNELS AT 5.2 GHZ  

E-print Network

University, Lund, Sweden 4 Smart Antennas Research Group, Information Systems Lab, Stanford University scenario the vehicles are traveling on the highway in opposite directions with a speed of approxi- mately

Zemen, Thomas

383

MTF and PSF measurements of the CCD273-84 detector for the Euclid visible channel  

NASA Astrophysics Data System (ADS)

The European Space Agency (ESA) and e2v, together with the Euclid Imaging Consortium, have designed and manufactured pre-development models of a novel imaging detector for the visible channel of the Euclid space telescope. The new detector is an e2v back-illuminated, 4k x 4k, 12 micron square pixel CCD designated CCD273-84. The backilluminated detectors have been characterised for many critical performance parameters such as read noise, charge transfer efficiency, quantum efficiency, Modulation Transfer Function and Point Spread Function. Initial analysis of the MTF and PSF performance of the detectors has been performed by e2v and at MSSL and the results have enabled the Euclid VIS CCD project to move in to the C/D or flight phase delivery contract. This paper describes the CCD273-84 detector, the test method used for MTF measurements at e2v and the test method used for PSF measurements at MSSL. Results are presented for MTF measurements at e2v over all pre development devices. Also presented is a cross comparison of the data from the MTF and PSF measurement techniques on the same device. Good agreement between the measured PSF Full Width Half Maximum and the equivalent Full Width Half Maximum derived from the MTF images and test results is shown, with results that indicate diffusion FWHM values at or below 10 micron for the CCD273-84 detectors over the spectral range measured. At longer wavelengths the diffusion FWHM is shown to be in the 6-8 micron range.

Swindells, I.; Wheeler, R.; Darby, S.; Bowring, S.; Burt, D.; Bell, R.; Duvet, L.; Walton, D.; Cole, R.

2014-08-01

384

Combining Radio Occultation Measurements with Other Instruments to Map the Ionospheric Electron Concentration  

Microsoft Academic Search

Summary. The Multi-Instrument Data Analysis System (MIDAS) algorithm is a spatial and temporal imaging program for the atmosphere and ionosphere. This analysis algorithm can routinely use dual-frequency ground-based observations from the GPS satellites to pro- duce four-dimensional images of electron concentration over very large geographical re- gions (potentially globally). MIDAS also has the facility to incorporate other ionospheric measurements, such

Cathryn N Mitchell

385

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

386

Near-infrared surface brightness fluctuation measurements with the Hubble Space Telescope's WFC3/IR channel  

NASA Astrophysics Data System (ADS)

The surface brightness fluctuation (SBF) method at near-infrared (NIR) wavelengths is a powerful tool for estimating distances to unresolved stellar systems with high precision. The IR channel of the Wide Field Camera 3 (WFC3), installed on board the Hubble Space Telescope (HST) in 2009, has a greater sensitivity and a wider field of view than the previous generation of HST IR instruments, making it much more efficient for measuring distances to early-type galaxies in the Local Volume. To take full advantage of its capabilities, we need to empirically calibrate the SBF distance method for WFC3's NIR passbands. We present the SBF measurements for the WFC3/IR F160W bandpass filter using observations of 16 early-type galaxies in the Fornax and Virgo Clusters. These have been combined with existing (g 475-z 850) color measurements from the Advanced Camera for Surveys Virgo and Fornax Cluster Surveys to derive a space-based H 160-band SBF relation as a function of color. We have also compared the absolute SBF magnitudes to those predicted by evolutionary population synthesis models in order to study stellar population properties in the target galaxies.

Cho, Hyejeon; Jensen, Joseph B.; Blakeslee, John P.; French, Brigham S.; Lee, Hyun-chul; Lee, Young-Wook

2013-02-01

387

A multi-channel magnetic induction tomography measurement system for human brain model imaging.  

PubMed

This paper proposes a multi-channel magnetic induction tomography measurement system for biological conductivity imaging in a human brain model. A hemispherical glass bowl filled with a salt solution is used as the human brain model; meanwhile, agar blocks of different conductivity are placed in the solution to simulate the intracerebral hemorrhage. The excitation and detection coils are fixed co-axially, and the axial gradiometer is used as the detection coil in order to cancel the primary field. On the outer surface of the glass bowl, 15 sensor units are arrayed in two circles as measurement parts, and a single sensor unit for cancelling the phase drift is placed beside the glass bowl. The phase sensitivity of our system is 0.204 degrees /S m(-1) with the excitation frequency of 120 kHz and the phase noise is in the range of -0.03 degrees to +0.05 degrees . Only the coaxial detection coil is available for each excitation coil; therefore, 15 phase data are collected in each measurement turn. Finally, the two-dimensional images of conductivity distribution are obtained using an interpolation algorithm. The frequency-varying experiment indicates that the imaging quality becomes better as the excitation frequency is increased. PMID:19491435

Xu, Zheng; Luo, Haijun; He, Wei; He, Chuanhong; Song, Xiaodong; Zahng, Zhanglong

2009-06-01

388

Holographic measurement on Medicina radio telescope using artificial satellites at 11 GHz  

NASA Astrophysics Data System (ADS)

The surface profile of the 32-m parabolic radiotelescope located in Medicina has been measured with the Misell phase-recovery technique using commercial geostationary satellites at 11 GHz and checked on H2O astronomical masers at 22 GHz as reference sources. The telescope is a parabolic reflector antenna operating in Cassegrain configuration and designed for observations up to the frequency of 23 GHz. The accuracy obtained with this technique is about 0.2 mm and the spatial resolution is 0.7 m.

Tarchi, D.; Comoretto, G.

1993-08-01

389

Adhesive-based liquid metal radio-frequency microcoil for magnetic resonance relaxometry measurement.  

PubMed

This paper reports the fabrication and characterization of an adhesive-based liquid-metal microcoil for magnetic resonance relaxometry (MRR). Conventionally, microcoils are fabricated by various techniques such as electroplating, microcontact printing and focused ion beam milling. These techniques require considerable fabrication efforts and incur high cost. In this paper, we demonstrate a novel technique to fabricate three-dimensional multilayer liquid-metal microcoils together with the microfluidic network by lamination of dry adhesive sheets. One of the unique features of the adhesive-based technique is that the detachable sample chamber can be disposed after each experiment and the microcoil can be reused without cross-contamination multiple times. The integrated microcoil has a low direct-current (DC) resistance of 0.3 ? and a relatively high inductance of 67.5 nH leading to a high quality factor of approximately 30 at 21.65 MHz. The microcoil was characterized for ?0.5 T proton MRR measurements. The optimal pulse duration, amplitude, and frequency for the 90° pulse were 131 ?s, -30 dB (1.56 W) and 21.6553 MHz, respectively. In addition, we used the liquid-metal microcoil to perform a parametric study on the transverse relaxation rate of human red blood cells at different hematocrit levels. The transverse relaxation rate increases quadratically with the hematocrit level. The results from the liquid-metal microcoil were verified by measurements with a conventional solenoid coil. PMID:22116258

Kong, Tian Fook; Peng, Weng Kung; Luong, Trung Dung; Nguyen, Nam-Trung; Han, Jongyoon

2012-01-21

390

Measurement of power transfer efficiency and ion density in various radio-frequency inductively coupled plasma  

NASA Astrophysics Data System (ADS)

The power transfer efficiency and plasma density were measured in low pressure inductive coupled argon plasma at 20--100 mTorr, 20--80 W and 13.56--60 MHz. For this experiment, a variable-frequency matching box (matcher) was developed and a modified method to determine the power transfer efficiency was used. To match 13.5MHz, 40.68MHz and 60MHz rf power source, three vacuum variable capacitors and one fixed capacitor were built in matching box to the plasma characteristic impedance. We measured the feeding line current using Rogowski coil to obtain matcher resistance and plasma resistance, so the power transfer efficiency could be obtained. The calibration process, calculations of the exact current from the voltage, is not necessary to obtain power transfer efficiency. This is the advantage of using Rogowski coil. It is clearly observed that the power transfer efficiency decrease with increasing driving frequency and decreasing pressure, whereas the ion density shows the opposite tendency compared to power efficiency.

Lee, Jae-Won; Hwang, Hye-Ju; Choi, Ik-Jin; Lee, Young-Kwang; Chung, Chin-Wook

2011-11-01

391

A survey of the application of the spherical vector wave mode expansion approach to antenna-channel interaction modeling  

NASA Astrophysics Data System (ADS)

This paper provides an overview of recent advances in the modeling, analysis, and measurements of interactions between antennas and the propagation channel in multiple antenna systems based on the spherical vector wave mode expansion of the electromagnetic field and the antenna scattering matrix. It demonstrates the importance and usefulness of this approach to gain further insights into a variety of topics such as physics-based propagation channel modeling, mean effective gain, channel correlation, propagation channel measurements, antenna measurements and testing, the number of degrees of freedom of the radio propagation channel, channel throughput, and diversity systems. The paper puts particular emphasis on the unified approach to antenna-channel analysis at the same time as the antenna and the channel influence are separated. Finally, the paper provides the first bibliography on the application of the spherical vector wave mode expansion of the electromagnetic field to antenna-channel interactions.

Alayon Glazunov, Andrés.

2014-08-01

392

Measurements and models for radio path loss and penetration loss in and around homes and trees at 5.85 GHz  

Microsoft Academic Search

This paper contains measured data and empirical models for 5.85-GHz radio propagation path loss in and around residential areas for the newly allocated U.S. National Information Infrastructure (NII) band. Three homes and two stands of trees were studied for outdoor path loss, tree loss, and house penetration loss in a narrow-band measurement campaign that included 270 local area path loss

Greg Durgin; Theodore S. Rappaport; Hao Xu

1998-01-01

393

Deriving Atmospheric Temperature of the Tropopause Region-Upper Troposphere by Combining Information from GPS Radio Occultation Refractivity and High-Spectral-Resolution Infrared Radiance Measurements  

Microsoft Academic Search

Global positioning system radio occultation (GPS\\/RO) measurements from the Challenging Minisatellite Payload (CHAMP) and Satelite de Aplicaciones Cientificas-C (SAC-C) satellites are used to improve tropospheric profile retrievals derived from the Aqua platform high-spectral-resolution Atmospheric In- frared Sounder (AIRS) and broadband Advanced Microwave Sounding Unit (AMSU) measurements under clear-sky conditions. This paper compares temperature retrievals from combined AIRS, AMSU, and CHAMP\\/SAC-C

Eva E. Borbas; W. Paul Menzel; Elisabeth Weisz; Dezso Devenyi

2008-01-01

394

Communication Channels Communication Channels  

E-print Network

Communication Channels 1/79 #12;Communication Channels Channel c is described by message script Mc extended natural variable 2/79 #12;Communication Channels Channel c is described by message script Mc extended natural variable 3/79 #12;Communication Channels Channel c is described by message script Mc

Hehner, Eric C.R.

395

Direct measurements by submersible of surge-type turbidity currents in a fjord channel, southeast Alaska  

SciTech Connect

High density, high-speed turbidity currents were observed and their properties measured in submarine channels in Queen Inlet, southeast Alaska during June, 1990 and 1991. A ROV submersible fitted with two video cameras, a CTD, an optical backscatter turbidity monitor (OBS), and electromagnetic current meter, and sidescan sonar was used to collect data from within and above the flows. Multiple flows were recorded during a ROV dive at 2.3 km from the delta front in a channel at 104 m depth. Flows were marked by sudden increases in turbidity and current velocity. In one flow, turbidity increased from 300 to 1,600 OBS units (instrument maximum) in 10 sec, and within 9.4 min, salinity (S) steadily decreased by 12.1 ppt, with only a 0.2 C temperature (T) increase. Density differences between the flow and ambient water require a minimum sediment concentration of 97 g/l. Maximum flow velocity exceeded 3.3 m/s. A vertical ROV profile indicated a flow thickness of 10 m. The upper surface was visually identified by billowing suspended sediment and by fluctuating OBS and T as ambient and flow water mixed in turbulent eddies. A faster S decrease and slower T increase with distance into and away from the flow indicate that thermal diffusive processes were less efficient than convective mass transfer. The S change indicates that flow water and ambient water mixed well beyond the flow defined by high turbidity. Warm water temperatures within the flow and low meltwater stream discharge suggest that these flows originated from the delta front and are not continuous underflows.

Cowan, E.A. (Appalachian State Univ., Boone, NC (United States). Dept. of Geology); Powell, R.D. (Illinois Univ., DeKalb, IL (United States). Geology Dept.); Lawson, D.E. (USA Cold Regions Research and Engineering Lab., Hanover, NH (United States)); Carlson, P.R. (Geological Survey, Menlo Park, CA (United States))

1992-01-01

396

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

397

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

398

3-D holographic refractive index measurement of continuously flowing cells in a microfluidic channel  

PubMed Central

Refractive index of biological specimens is a source of intrinsic contrast that can be explored without any concerns of photobleaching or harmful effects caused by extra contrast agents. In addition, RI contains rich information related to the metabolism of cells at the cellular and subcellular levels. Here, we report a no-moving parts approach that provides three-dimensional refractive index maps of biological samples continuously flowing in a microfluidic channel. Specifically, we use line illumination and off-axis digital holography to record the angular spectra of light scattered from flowing samples at high speed. Applying the scalar diffraction theory, we obtain accurate RI maps of the samples from the measured spectra. Using this method, we demonstrate label-free 3-D imaging of live RKO human colon cancer cells and RPMI8226 multiple myeloma cells, and obtain the volume, dry mass and density of these cells from the measured 3-D refractive index maps. Our results show that the reported method, alone or in combination with the existing flow cytometry techniques, promises as a quantitative tool for stain-free characterization of large number of cells.

Sung, Yongjin; Lue, Niyom; Hamza, Bashar; Martel, Joseph; Irimia, Daniel; Dasari, Ramachandra R.; Choi, Wonshik; Yaqoob, Zahid; So, Peter

2014-01-01

399

Three-Dimensional Holographic Refractive-Index Measurement of Continuously Flowing Cells in a Microfluidic Channel  

NASA Astrophysics Data System (ADS)

The refractive index of biological specimens is a source of intrinsic contrast that can be explored without any concerns of photobleaching or harmful effects caused by extra contrast agents. In addition, the refractive index contains rich information related to the metabolism of cells at the cellular and subcellular levels. Here, we report a no-moving-parts approach that provides three-dimensional refractive-index maps of biological samples continuously flowing in a microfluidic channel. Specifically, we use line illumination and off-axis digital holography to record the angular spectra of light scattered from flowing samples at high speed. Applying the scalar diffraction theory, we obtain accurate refractive-index maps of the samples from the measured spectra. Using this method, we demonstrate label-free three-dimensional imaging of live RKO human colon cancer cells and RPMI8226 multiple myeloma cells, and obtain the volume, dry mass, and density of these cells from the measured three-dimensional refractive-index maps. Our results show that the reported method, alone or in combination with the existing flow cytometry techniques, shows promise as a quantitative tool for stain-free characterization of a large number of cells.

Sung, Yongjin; Lue, Niyom; Hamza, Bashar; Martel, Joseph; Irimia, Daniel; Dasari, Ramachandra R.; Choi, Wonshik; Yaqoob, Zahid; So, Peter

2014-02-01

400

Blood viscoelasticity measurement using steady and transient flow controls of blood in a microfluidic analogue of Wheastone-bridge channel.  

PubMed

Accurate measurement of blood viscoelasticity including viscosity and elasticity is essential in estimating blood flows in arteries, arterials, and capillaries and in investigating sub-lethal damage of RBCs. Furthermore, the blood viscoelasticity could be clinically used as key indices in monitoring patients with cardiovascular diseases. In this study, we propose a new method to simultaneously measure the viscosity and elasticity of blood by simply controlling the steady and transient blood flows in a microfluidic analogue of Wheastone-bridge channel, without fully integrated sensors and labelling operations. The microfluidic device is designed to have two inlets and outlets, two side channels, and one bridge channel connecting the two side channels. Blood and PBS solution are simultaneously delivered into the microfluidic device as test fluid and reference fluid, respectively. Using a fluidic-circuit model for the microfluidic device, the analytical formula is derived by applying the linear viscoelasticity model for rheological representation of blood. First, in the steady blood flow, the relationship between the viscosity of blood and that of PBS solution (?Blood /?PBS ) is obtained by monitoring the reverse flows in the bridge channel at a specific flow-rate rate (QPBS (SS) /QBlood (L) ). Next, in the transient blood flow, a sudden increase in the blood flow-rate induces the transient behaviors of the blood flow in the bridge channel. Here, the elasticity (or characteristic time) of blood can be quantitatively measured by analyzing the dynamic movement of blood in the bridge channel. The regression formula (ABlood (t)?=?A ? ?+?A ? exp [-(t?-?t 0 )/?Blood ]) is selected based on the pressure difference (?P?=?PA ?-?PB ) at each junction (A, B) of both side channels. The characteristic time of blood (?Blood ) is measured by analyzing the area (ABlood ) filled with blood in the bridge channel by selecting an appropriate detection window in the microscopic images captured by a high-speed camera (frame rate?=?200?Hz, total measurement time?=?7?s). The elasticity of blood (GBlood ) is identified using the relationship between the characteristic time and the viscosity of blood. For practical demonstrations, the proposed method is successfully applied to evaluate the variations in viscosity and elasticity of various blood samples: (a) various hematocrits form 20% to 50%, (b) thermal-induced treatment (50?°C for 30?min), (c) flow-induced shear stress (53?±?0.5?mL/h for 120?min), and (d) normal rat versus spontaneously hypertensive rat. Based on these experimental demonstrations, the proposed method can be effectively used to monitor variations in viscosity and elasticity of bloods, even with the absence of fully integrated sensors, tedious labeling and calibrations. PMID:24396531

Jun Kang, Yang; Lee, Sang-Joon

2013-01-01

401

Blood viscoelasticity measurement using steady and transient flow controls of blood in a microfluidic analogue of Wheastone-bridge channel  

PubMed Central

Accurate measurement of blood viscoelasticity including viscosity and elasticity is essential in estimating blood flows in arteries, arterials, and capillaries and in investigating sub-lethal damage of RBCs. Furthermore, the blood viscoelasticity could be clinically used as key indices in monitoring patients with cardiovascular diseases. In this study, we propose a new method to simultaneously measure the viscosity and elasticity of blood by simply controlling the steady and transient blood flows in a microfluidic analogue of Wheastone-bridge channel, without fully integrated sensors and labelling operations. The microfluidic device is designed to have two inlets and outlets, two side channels, and one bridge channel connecting the two side channels. Blood and PBS solution are simultaneously delivered into the microfluidic device as test fluid and reference fluid, respectively. Using a fluidic-circuit model for the microfluidic device, the analytical formula is derived by applying the linear viscoelasticity model for rheological representation of blood. First, in the steady blood flow, the relationship between the viscosity of blood and that of PBS solution (?Blood/?PBS) is obtained by monitoring the reverse flows in the bridge channel at a specific flow-rate rate (QPBSSS/QBloodL). Next, in the transient blood flow, a sudden increase in the blood flow-rate induces the transient behaviors of the blood flow in the bridge channel. Here, the elasticity (or characteristic time) of blood can be quantitatively measured by analyzing the dynamic movement of blood in the bridge channel. The regression formula (ABlood (t)?=?A??+?A? exp [?(t???t0)/?Blood]) is selected based on the pressure difference (?P?=?PA???PB) at each junction (A, B) of both side channels. The characteristic time of blood (?Blood) is measured by analyzing the area (ABlood) filled with blood in the bridge channel by selecting an appropriate detection window in the microscopic images captured by a high-speed camera (frame rate?=?200?Hz, total measurement time?=?7?s). The elasticity of blood (GBlood) is identified using the relationship between the characteristic time and the viscosity of blood. For practical demonstrations, the proposed method is successfully applied to evaluate the variations in viscosity and elasticity of various blood samples: (a) various hematocrits form 20% to 50%, (b) thermal-induced treatment (50?°C for 30?min), (c) flow-induced shear stress (53?±?0.5?mL/h for 120?min), and (d) normal rat versus spontaneously hypertensive rat. Based on these experimental demonstrations, the proposed method can be effectively used to monitor variations in viscosity and elasticity of bloods, even with the absence of fully integrated sensors, tedious labeling and calibrations. PMID:24396531

Jun Kang, Yang; Lee, Sang-Joon

2013-01-01

402

Morphology of sporadic E layer retrieved from COSMIC GPS radio occultation measurements: Wind shear theory examination  

NASA Astrophysics Data System (ADS)

the basis of the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC)-measured fluctuations in the signal-to-noise ratio and excess phase of the GPS signal piercing through ionospheric sporadic E (Es) layers, the general morphologies of these layers are presented for the period from July 2006 to May 2011. It is found that the latitudinal variation in the Es layer occurrence is substantially geomagnetically controlled, most frequent in the summer hemisphere within the geomagnetic latitude region between 10° and 70° and very rare in the geomagnetic equatorial zone. Model simulations show that the summer maximum (winter minimum) in the Es layer occurrence is very likely attributed to the convergence of the Fe+ concentration flux driven by the neutral wind. In addition to seasonal and spatial distributions, the height-time variations in the Es layer occurrence in the midlatitude (>30°) region in summer and spring are primarily dominated by the semidiurnal tides, which start to appear at local time around 6 and 18 h in the height range 110-120 km and gradually descend at a rate of about 0.9-1.6 km/h. In the low-latitude (<30°) region, the diurnal tide dominates. The Horizontal Wind Model (HWM07) indicates that the height-time distribution of Es layers at middle latitude (30°-60°) is highly coincident with the zonal neutral wind shear. However, Es layer occurrences in low-latitude and equatorial regions do not correlate well with the zonal wind shear.

Chu, Y. H.; Wang, C. Y.; Wu, K. H.; Chen, K. T.; Tzeng, K. J.; Su, C. L.; Feng, W.; Plane, J. M. C.

2014-03-01

403

Impulse radio: how it works  

Microsoft Academic Search

Impulse radio, a form of ultra-wide bandwidth (UWB) spread-spectrum signaling, has properties that make it a viable candidate for short-range communications in dense multipath environments. This paper describes the characteristics of impulse radio using a modulation format that can be supported by currently available impulse signal technology and gives analytical estimates of its multiple-access capability under ideal multiple-access channel conditions

Moe Z. Win; Robert A. Scholtz

1998-01-01

404

An experimental study of condensation heat transfer inside a mini-channel with a new measurement technique  

Microsoft Academic Search

New experimental techniques were developed to measure the in-tube condensation heat transfer coefficient. In this study, very low heat dissipation rates such as several watts from the mini-channel could be estimated and low mass flow rates below the 0.2 kg\\/h could be measured with reasonable uncertainties. To the authors’ knowledge, these techniques provide a unique experimental apparatus for measuring the

Jeong Seob Shin; Moo Hwan Kim

2004-01-01

405

TECHNICAL REPORT TR-11-01, UC DAVIS, BBN, ARL, CUNY, PSU, JULY 2011. 1 Broadcasting in Multi-Radio Multi-Channel  

E-print Network

Steiner tree problem under the classic graph model. These two algorithms offer tradeoffs between Science and Engineering, Pennsylvania State University, USA Abstract We consider the broadcasting problem-channel ad hoc networks can be formulated as a minimum spanning problem in simplicial complexes. We establish

Islam, M. Saif

406

Application of the Compact Channel Thermal Noise Model of Short Channel MOSFETs to CMOS RFIC Design  

NASA Astrophysics Data System (ADS)

In this paper, a compact channel thermal noise model for short-channel MOSFETs is presented and applied to the radio frequency integrated circuit (RFIC) design. Based on the analysis of the relationship among different short-channel effects such as velocity saturation effect (VSE), channel-length modulation (CLM), and carrier heating effect (CHE), the compact model for the channel thermal noise was analytically derived as a simple form. In order to simulate MOSFET's noise characteristics in circuit simulators, an appropriate methodology is proposed. The used compact noise model is verified by comparing simulated results to the measured data at device and circuit level by using 65nm and 130nm CMOS technologies, respectively.

Jeon, Jongwook; Song, Ickhyun; Lee, Jong Duk; Park, Byung-Gook; Shin, Hyungcheol

407

Radio range measurements of coronal electron densities at 13 and 3. 6 centimeter wavelengths during the 1988 solar conjunction of Voyager 2  

SciTech Connect

Radio range measurements of total solar plasma delay obtained during the solar conjunction of the Voyager 2 spacecraft in December 1988, which occurred near solar maximum activity in the 11 yr cycle are reported. The radio range measurements were generated by the Deep Space Network at two wavelengths on the downlink from the spacecraft: 3.6 and 13 cm. A direct measurement of the integrated electron density along the ray path between the earth stations and the spacecraft was obtained by differencing the range at the two wavelengths. Coronal electron density profiles have been derived during ingress and egress of the ray path, which approached the sun to within 5 solar radii. At 10 solar radii, the derived density profiles yield 34079 {plus minus} 611/cu cm on ingress and 49688 {plus minus} 983/cu cm on egress. These density levels are significantly higher than observed near previous solar maxima. 19 refs.

Krisher, T.P.; Anderson, J.D.; Morabito, D.D.; Asmar, S.W.; Borutzki, S.E.; Delitsky, M.L.; Densmore, A.C.; Eshe, P.M.; Lewis, G.D.; Maurer, M.J. (JPL, Pasadena, CA (USA))

1991-07-01

408

Radio Ghosts  

E-print Network

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

Torsten A. Ensslin

1999-06-11

409

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

Microsoft Academic Search

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

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

2008-01-01

410

Providing hydrogen maser timing stability to orbiting VLBI radio telescope observations by post-measurement compensation of linked frequency standard imperfections  

NASA Technical Reports Server (NTRS)

Orbiting VLBI (OVLBI) astronomical observations are based upon measurements acquired simultaneously from ground-based and earth-orbiting radio telescopes. By the mid-1990s, two orbiting VLBI observatories, Russia's Radioastron and Japan's VSOP, will augment the worldwide VLBI network, providing baselines to earth radio telescopes as large as 80,000 km. The challenge for OVLBI is to effectuate space to ground radio telescope data cross-correlation (the observation) to a level of integrity currently achieved between ground radio telescopes. VLBI radio telescopes require ultrastable frequency and timing references in order that long term observations may be made without serious cross-correlation loss due to frequency source drift and phase noise. For this reason, such instruments make use of hydrogen maser frequency standards. Unfortunately, space-qualified hydrogen maser oscillators are currently not available for use on OVLBI satellites. Thus, the necessary long-term stability needed by the orbiting radio telescope may only be obtained by microwave uplinking a ground-based hydrogen maser derived frequency to the satellite. Although the idea of uplinking the frequency standard intrinsically seems simple, there are many 'contaminations' which degrade both the long and short term stability of the transmitted reference. Factors which corrupt frequency and timing accuracy include additive radio and electronic circuit thermal noise, slow or systematic phase migration due to changes of electronic circuit temporal operating conditions (especially temperature), ionosphere and troposphere induced scintillations, residual Doppler-incited components, and microwave signal multipath propagation. What is important, though, is to realize that ultimate stability does not have to be achieved in real-time. Instead, information needed to produce a high degree of coherence in the subsequent cross-correlation operation may be derived from a two-way coherent radio link, recorded and later introduced as compensations adjunct to the VLBI correlation process. Accordingly, this paper examines the technique for stable frequency/time transfer within the OVLBI system, together with a critique of the types of link degradation components which must be compensated, and the figures of merit known as coherence factors.

Springett, James C.

1994-01-01

411

The RadioAstron project: Measurements and analysis of basic parameters of space telescope in flight in 2011-2013  

NASA Astrophysics Data System (ADS)

The results of a large number of the antenna radiometric measurements at bands of 92, 18, 6.2, 1.35, and 1.7-1.2 cm are presented by the data of the standard telemetry system of the Spektr-R spacecraft. Both special sessions of calibration object observations in the mode of a single space radio telescope (SRT) operation and numerous observations of researched sources in the mode of the ground-space interferometer were used. The obtained results agree with the first results of Kardashev et al. (2013), i.e., within 10-15% at bands of 92, 18, and 6.2 cm and 20-25% at the band of 1.35 cm. In the main, the measurements for the eight subbands at wavelengths of 1.7-1.2 cm indicate a monotonic increase in the spectral system equivalent flux density (SEFD) of noise radiation with a frequency consistent with the calculated estimates for the discussed model. The sensitivity of the ground-space interferometer for the five subbands at wavelengths from 1.35 to 1.7 cm can be higher by a factor of 1.5, and for the three subbands from 1.35 to 1.2 cm lower by a factor of 1.5 than at the band of 1.35 cm. The SRT contribution to the interferometer sensitivity proportional to the square root of SEFD is close to the design one at the bands of 92 and 18 cm and decreases the design sensitivity approximately by a factor of 1.5 and 2 at the bands of 6.2 and 1.35 cm, respectively. These differences of implemented values from the design ones were not significantly affected the scientific program implementation.

Kovalev, Yu. A.; Vasil'kov, V. I.; Popov, M. V.; Soglasnov, V. A.; Voitsik, P. A.; Lisakov, M. M.; Kut'kin, A. M.; Nikolaev, N. Ya.; Nizhel'skii, N. A.; Zhekanis, G. V.; Tsybulev, P. G.

2014-09-01

412

Determination of the extragalactic-planetary frame tie from joint analysis of radio interferometric and lunar laser ranging measurements  

NASA Technical Reports Server (NTRS)

Very Long Baseline Interferometry (VLBI) observations of extragalactic radio sources provide the basis for defining an accurate non-rotating reference frame in terms of angular positions of the sources. Measurements of the distance from the Earth to the Moon and to the inner planets provide the basis for defining an inertial planetary ephemeris reference frame. The relative orientation, or frame tie, between these two reference frames is of interest for combining Earth orientation measurements, for comparing Earth orientation results with theories referred to the mean equator and equinox, and for determining the positions of the planets with respect to the extragalactic reference frame. This work presents an indirect determination of the extragalactic-planetary frame tie from a combined reduction of VLBI and Lunar Laser Ranging (LLR) observations. For this determination, data acquired by LLR tracking stations since 1969 have been analyzed and combined with 14 years of VLBI data acquired by NASA's Deep Space Network since 1978. The frame tie derived from this joint analysis, with an accuracy of 0.003 sec, is the most accurate determination obtained so far. This result, combined with a determination of the mean ecliptic (defined in the rotating sense), shows that the mean equinox of epoch J2000 is offset from the x-axis of the extragalactic frame adopted by the International Earth Rotation Service for astrometric and geodetic applications by 0.078 sec +/- 0.010 sec along the y-direction and y 0.019 sec +/- 0.001 sec. along the z-direction.

Folkner, W. M.; Charlot, P.; Finger, M. H.; Williams, J. G.; Sovers, O. J.; Newhall, XX; Standish, E. M., Jr.

1994-01-01

413

Measurement of the ttbar production cross section in the MET+jets channel at CDF  

SciTech Connect

This thesis is focused on an inclusive search of the t{bar t} {yields} E{sub T} + jets decay channel by means of neural network tools in proton antiproton collisions at {radical}s = 1.96 TeV recorded by the Collider Detector at Fermilab (CDF). At the Tevatron p{bar p} collider top quarks are mainly produced in pairs through quark-antiquark annihilation and gluon-gluon fusion processes; in the Standard Model description, the top quark then decays to a W boson and a b quark almost 100% of the times, so that its decay signatures are classified according to the W decay modes. When only one W decays leptonically, the t{bar t} event typically contains a charged lepton, missing transverse energy due to the presence of a neutrino escaping from the detector, and four high transverse momentum jets, two of which originate from b quarks. In this thesis we describe a t{bar t} production cross section measurement which uses data collected by a 'multijet' trigger, and selects this kind of top decays by requiring a high-P{sub T} neutrino signature and by using an optimized neural network to discriminate top quark pair production from backgrounds. In Chapter 1, a brief review of the Standard Model of particle physics will be discussed, focusing on top quark properties and experimental signatures. In Chapter 2 will be presented an overview of the Tevatron accelerator chain that provides p{bar p} collisions at the center-of-mass energy of {radical}s = 1.96 TeV, and proton and antiproton beams production procedure will be discussed. The CDF detector and its components and subsystems used for the study of p{bar p} collisions provided by the Tevatron will be described in Chapter 3. Chapter 4 will detail the reconstruction procedures used in CDF to detect physical objects exploiting the features of the different detector subsystems. Chapter 5 will provide an overview of the main concepts regarding Artificial Neural Networks, one of the most important tools we will use in the analysis. Chapter 6 will be devoted to the description of the main characteristics of the t{bar t} {yields} E{sub T} + jets decay channel used to train our neural network to discriminate the top pair production from background processes. We will discuss the event selection method and the technique used for background prediction, that will rely on b-jets identification rate parameterization. Finally, Chapter 7 will provide a description of the final data sample and a detailed discussion of the systematic uncertainties before determining the cross section measurement by means of a likelihood maximization.

Compostella, Gabriele; /INFN, Trento

2008-03-01

414

Measurement based satellite to outdoor channel modeling for multiple satellite systems  

Microsoft Academic Search

In this contribution we present the results of a study on satellite to outdoor channel modeling for satellite systems with multiple satellites. Our model for several satellites is based on a first order Markov channel state model for joint processes. The probability density function (PDF) of the signal amplitude within each state is fitted to the Loo distribution. The parameters

M. Milojevic; Martin Haardt; Albert Heuberger

2008-01-01

415

Performance of MIMO spatial multiplexing algorithms using indoor channel measurements and models  

Microsoft Academic Search

Summary Several algorithms have recently been proposed for multiplexing multiple users in multiple input multiple output (MIMO) downlinks. The ability of a transmitter to accomplish this using spatial methods is generally dependent on whether the users' channels are correlated. Up to this point, most of the multiplexing algorithms have been tested on uncorrelated Gaussian channels, a best-case scenario. In this

Quentin H. Spencer; Thomas Svantesson; A. Lee Swindlehurst

2004-01-01

416

Determining electrical properties based on B1 fields measured in an MR scanner using a multi-channel transmit/receive coil: a general approach  

NASA Astrophysics Data System (ADS)

Electrical properties tomography (EPT) is a recently developed noninvasive technology to image the electrical conductivity and permittivity of biological tissues at Larmor frequency in magnetic resonance scanners. The absolute phase of the complex radio-frequency magnetic field (B1) is necessary for electrical property calculation. However, due to the lack of practical methods to directly measure the absolute B1 phases, current EPT techniques have been achieved with B1 phase estimation based on certain assumptions on object anatomy, coil structure and/or electromagnetic wave behavior associated with the main magnetic field, limiting EPT from a larger variety of applications. In this study, using a multi-channel transmit/receive coil, the framework of a new general approach for EPT has been introduced, which is independent on the assumptions utilized in previous studies. Using a human head model with realistic geometry, a series of computer simulations at 7 T were conducted to evaluate the proposed method under different noise levels. Results showed that the proposed method can be used to reconstruct the conductivity and permittivity images with noticeable accuracy and stability. The feasibility of this approach was further evaluated in a phantom experiment at 7 T.

Liu, Jiaen; Zhang, Xiaotong; Van de Moortele, Pierre-Francois; Schmitter, Sebastian; He, Bin

2013-07-01

417

Determining Electrical Properties Based on B1 Fields Measured in an MR Scanner Using a Multi-channel Transmit/Receive Coil: a General Approach  

PubMed Central

Electrical Property Tomography (EPT) is a recently developed noninvasive technology to image the electrical conductivity and permittivity of biological tissues at Larmor frequency in Magnetic Resonance (MR) scanners. The absolute phase of the complex radio-frequency (RF) magnetic field (B1) is necessary for electrical property calculation. However, due to the lack of practical methods to directly measure the absolute B1 phases, current EPT techniques have been achieved with B1 phase estimation based on certain assumptions on object anatomy, coil structure and/or electromagnetic wave behavior associated with the main magnetic field, limiting EPT from a larger variety of applications. In this study, using a multi-channel transmit/receive coil, the framework of a new general approach for EPT has been introduced, which is independent on the assumptions utilized in previous studies. Using a human head model with realistic geometry, a series of computer simulations at 7T were conducted to evaluate the proposed method under different noise levels. Results showed that the proposed method can be used to reconstruct the conductivity and permittivity images with noticeable accuracy and stability. The feasibility of this approach was further evaluated in a phantom experiment at 7T. PMID:23743673

Liu, Jiaen; Zhang, Xiaotong; Van de Moortele, Pierre-Francois; Schmitter, Sebastian

2013-01-01

418

Determining electrical properties based on B(1) fields measured in an MR scanner using a multi-channel transmit/receive coil: a general approach.  

PubMed

Electrical properties tomography (EPT) is a recently developed noninvasive technology to image the electrical conductivity and permittivity of biological tissues at Larmor frequency in magnetic resonance scanners. The absolute phase of the complex radio-frequency magnetic field (B1) is necessary for electrical property calculation. However, due to the lack of practical methods to directly measure the absolute B1 phases, current EPT techniques have been achieved with B1 phase estimation based on certain assumptions on object anatomy, coil structure and/or electromagnetic wave behavior associated with the main magnetic field, limiting EPT from a larger variety of applications. In this study, using a multi-channel transmit/receive coil, the framework of a new general approach for EPT has been introduced, which is independent on the assumptions utilized in previous studies. Using a human head model with realistic geometry, a series of computer simulations at 7 T were conducted to evaluate the proposed method under different noise levels. Results showed that the proposed method can be used to reconstruct the conductivity and permittivity images with noticeable accuracy and stability. The feasibility of this approach was further evaluated in a phantom experiment at 7 T. PMID:23743673

Liu, Jiaen; Zhang, Xiaotong; Van de Moortele, Pierre-Francois; Schmitter, Sebastian; He, Bin

2013-07-01

419

Aircraft Engine On-Line Diagnostics Through Dual-Channel Sensor Measurements: Development of an Enhanced System  

NASA Technical Reports Server (NTRS)

In this paper, an enhanced on-line diagnostic system which utilizes dual-channel sensor measurements is developed for the aircraft engine application. The enhanced system is composed of a nonlinear on-board engine model (NOBEM), the hybrid Kalman filter (HKF) algorithm, and fault detection and isolation (FDI) logic. The NOBEM provides the analytical third channel against which the dual-channel measurements are compared. The NOBEM is further utilized as part of the HKF algorithm which estimates measured engine parameters. Engine parameters obtained from the dual-channel measurements, the NOBEM, and the HKF are compared against each other. When the discrepancy among the signals exceeds a tolerance level, the FDI logic determines the cause of discrepancy. Through this approach, the enhanced system achieves the following objectives: 1) anomaly detection, 2) component fault detection, and 3) sensor fault detection and isolation. The performance of the enhanced system is evaluated in a simulation environment using faults in sensors and components, and it is compared to an existing baseline system.

Kobayashi, Takahisa; Simon, Donald L.

2008-01-01

420

Measurement of light charged particles in the decay channels of medium-mass excited compound nuclei  

NASA Astrophysics Data System (ADS)

The 48Ti on 40Ca reactions have been studied at 300 and 600 MeV focusing on the fusion-evaporation (FE) and fusion-fission (FF) exit channels. Energy spectra and multiplicities of the emitted light charged particles have been compared to Monte Carlo simulations based on the statistical model. Indeed, in this mass region (A ~ 100) models predict that shape transitions can occur at high spin values and relatively scarce data exist in the literature about coincidence measurements between evaporation residues and light charged particles. Signals of shape transitions can be found in the variations of the lineshape of high energy gamma rays emitted from the de-excitation of GDR states gated on different region of angular momenta. For this purpose it is important to keep under control the FE and FF processes, to regulate the statistical model parameters and to control the onset of possible pre-equilibrium emissions from 300 to 600 MeV bombarding energy.

Valdré, S.; Barlini, S.; Casini, G.; Pasquali, G.; Piantelli, S.; Carboni, S.; Cinausero, M.; Gramegna, F.; Marchi, T.; Baiocco, G.; Bardelli, L.; Benzoni, G.; Bini, M.; Blasi, N.; Bracco, A.; Brambilla, S.; Bruno, M.; Camera, F.; Corsi, A.; Crespi, F.; D'Agostino, M.; Degerlier, M.; Kravchuk, V. L.; Leoni, S.; Million, B.; Montanari, D.; Morelli, L.; Nannini, A.; Nicolini, R.; Poggi, G.; Vannini, G.; Wieland, O.; Bednarczyk, P.; Ciema?a, M.; Dudek, J.; Fornal, B.; Kmiecik, M.; Maj, A.; Matejska-Minda, M.; Mazurek, K.; M?czy?ski, W. M.; Myalski, S.; Stycze?, J.; Zi?bli?ski, M.

2014-03-01