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1

Radio channel measurement and modelling for future mobile radio systems  

NASA Astrophysics Data System (ADS)

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

Guerdenli, E.; Huish, P. W.

1989-12-01

2

Measurement of mobile radio propagation channel in ruins  

Microsoft Academic Search

Within a running project, I-LOV1, wireless communication channel model for mobile communications is developed based on measurements in reconstructed disaster and salvage scenarios. Due to complex environment in ruins, great multipath interference can take place, which strongly impacts communication quality and localization accuracy. Besides numerous measurements investigated in environments such as urban, outdoor-to-indoor or indoor, only a few are in

Ling Chen; Thomas Ostertag; Marc Loschonsky; Leonhard M. Reindl

2010-01-01

3

Modeling of Wide-Band MIMO Radio Channels Based on NLoS Indoor Measurements  

Microsoft Academic Search

In this paper, we first verify a previously proposed Kronecker-structure-based narrow-band model for nonline-of- sight (NLoS) indoor multiple-input-multiple-output (MIMO) radio channels based on 5.2-GHz indoor MIMO channel mea- surements. It is observed that, for the narrow-band case, the measured channel coefficients are complex Gaussian distributed and, consequently, we focus on a statistical description using the first- and second-order moments of

Kai Yu; Mats Bengtsson; Björn Ottersten; Darren McNamara; Peter Karlsson; Mark Beach

2004-01-01

4

Wideband line-of-sight channel measurements and simulation: Application to digital radio links  

NASA Astrophysics Data System (ADS)

The performance of high-capacity digital radio links which is impaired by frequency-selective fading during multipath propagation, even if the signal-to-noise ratio is adequate was examined. The amplitude and group delay distortions were measured in a 40-MHz bandwidth at 4 GHz on a line-of-sight path. It is shown that the complex transfer function H(Omega) of the propagation channel can be well approximated by a two-ray model. The influence of two-path fading can be estimated if the dependence of the notch depth versus the deviation between the notch frequency and the carrier frequency f sub c for a fixed bit-error rate is known. Perfect Nyquist pulse shaping was assumed and the effects of timing and carrier recovery circuits during two-path propagation were considered. The comparison with the measured signature showed a small degradation which is attributed to modem imperfections. A two-channel simulator for two-path fading was developed, where the indirect wave which was delayed by tau = 6.3 ns relative to the direct wave was Rayleigh-distributed. By variation of the parameter-K which describes the power ratio between the indirect and the direct wave, it is possible to simulate different fading processes. The improvement by the use of an inphase diversity combiner is investigated for different values of the correlation coefficient between the two channels.

Valentin, R.; Metzger, K.

1984-10-01

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

The indoor radio propagation channel  

Microsoft Academic Search

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

HOMAYOUN HASHEMI

1993-01-01

7

Dynamic Channel Selection in Cognitive Radio Network with Channel Heterogeneity  

E-print Network

1 Dynamic Channel Selection in Cognitive Radio Network with Channel Heterogeneity Fen Hou, jwhuang}@ie.cuhk.edu.hk Abstract--We consider the channel selection problem in a cognitive radio network with heterogenous channel availabilities at different nodes. We formulate the maximum channel selection (MCS

Huang, Jianwei

8

UHF radio channel characterization for Wireless Sensor Networks within an aircraft  

Microsoft Academic Search

In this paper we present a channel model for Wireless Sensor Networks at 868 MHz within the aircraft. Door-to-cabin channel measurements have been performed in order to characterize pathloss, fading and correlation properties of the radio channel. Index Terms —Aircraft channel, UHF radio channel, Wireless Sensor Networks

Raffaele D'Errico; Lionel Rudant

2011-01-01

9

Channel-Aware Access for Cognitive Radio Networks  

Microsoft Academic Search

This paper addresses the problem of designing channel-aware access control (CAAC) algorithms for cognitive radio networks. To protect the primary transmission, the access probabilities of secondary users are adjusted based on the channel-state information and the measured interference temperature. It is shown that the proposed CAAC algorithm always converges to a fixed point. Furthermore, the CAAC algorithm can be interpreted

Bo Yang; Gang Feng; Yanyan Shen; Chengnian Long; Xinping Guan

2009-01-01

10

Impulse Response Modeling of Indoor Radio Propagation Channels  

Microsoft Academic Search

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

Homayoun Hashemi

1993-01-01

11

Multipath measurements over obstructed radio transmission paths  

Microsoft Academic Search

To provide PSTN to isolated subscribers BC TEL employs Exchange Area Radio telephone Service (EARS) in the 409 MHz\\/420 MHz UHF band. Usually LOS communication is not possible, and repeaters are used. To determine if diversity techniques could be used to improve performance and eliminate the use of repeaters, a measurement program was undertaken. The two-channel measurement system to detect

M. J. Ahmed; G. J. Garrison; W. Gosse

1993-01-01

12

Experimental comparison of indoor UHF and EHF radio channel characteristics  

Microsoft Academic Search

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

Larbi Talbi

2000-01-01

13

Radio Transmission Measurements  

Microsoft Academic Search

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

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

1923-01-01

14

Channel-Hopping Based on Available Channel Set for Rendezvous of Cognitive Radios  

E-print Network

Channel-Hopping Based on Available Channel Set for Rendezvous of Cognitive Radios Lu Yu1, Hai Liu1 the rendezvous in finite time, all existing rendezvous algorithms generate CH (channel-hopping) sequences using the whole channel set and attempt rendezvous on each of the channels (i.e., both available channels

Chu, Xiaowen

15

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

Code of Federal Regulations, 2010 CFR

... Channels for basic exchange telephone radio systems. 22.757 Section 22.757...Radiotelephone Service Basic Exchange Telephone Radio Systems § 22.757 Channels for basic exchange telephone radio systems. The channels listed...

2010-10-01

16

Measurement of Terrestrial Radio Noise  

Microsoft Academic Search

The terrestrial noise experiment on the Ariel III satellite is designed to measure the radio noise from lighting discharges, and to deduce the distribution of the sources. The measurements are made at high frequencies; at optimum frequencies the noise penetrates the ionosphere only at near vertical incidence and the sources can therefore be localized. The receivers operate in narrow bandwidths

F. Horner; R. B. Bent

1969-01-01

17

A Reconfigurable Channel Filter for Software Defined Radio Using RNS  

Microsoft Academic Search

This paper presents a high-speed FIR channel filter using residue number system (RNS) whose frequency response can be reconfigured\\u000a to adapt to a multitude of channel filtering specifications of a multi-standard software defined radio (SDR) receiver. The\\u000a channel filters in the channelizer of an SDR extract multiple narrowband channels corresponding to different communication\\u000a standards from the wideband input signal. The

K. G. Smitha; A. P. Vinod

18

Signal selection for the indoor wireless impulse radio channel  

Microsoft Academic Search

In this paper we investigate communications using quaternary pulse position data modulation over the indoor impulse radio multiple access channel disturbed with multipath. The performance of four quaternary signal sets with different correlation properties is assessed

Fernando Ramirez-Mireles; M. Z. Win; R. A. Scholtz

1997-01-01

19

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

20

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

Microsoft Academic Search

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

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

2004-01-01

21

ARQ error control for fading mobile radio channels  

Microsoft Academic Search

— In this paper, we study the correlation properties of the fading mobile radio channel. Based on these studies, we model the channel as a one-step Markov process whose transition probabilities are a function of the channel characteristics. Then we present the throughput performance of the Go-Back-N and Selective-Repeat ARQ protocols with timer control, using the Markov model for both

Michele Zorzi; Ramesh R. Rao; Laurence B. Milstein

1997-01-01

22

Multipath characteristics of impulse radio channels  

Microsoft Academic Search

We investigate the multipath characteristics of the impulse radios (IR) which have drawn much attention for future high-speed wireless communication services. For this objective, we observe the characteristics of bit error rates through computer simulations for the deterministic two-path model and the statistical indoor multipath model of Saleh and Valenzuela (1987). The simulation results indicate that the performance of the

Hojoon Lee; Byungchil Han; Yoan Shin; Sungbin Imt

2000-01-01

23

Channel Bonding in Cognitive Radio Wireless Sensor Networks  

E-print Network

Channel Bonding in Cognitive Radio Wireless Sensor Networks Mubashir Husain Rehmani, St-mail: rehmani@univ-mlv.fr, lohier@univ-mlv.fr, rachedi@univ-mlv.fr Abstract--Recently, wireless sensor networks, Wireless Multimedia Sensor Networks (WMSNs) have lot of new potential applications in different domains

Paris-Sud XI, Université de

24

Software defined radio channel simulator for wireless communications: Demonstrations of the hardware reconfiguration using DSRC and UWB channels  

Microsoft Academic Search

The software defined radio (SDR) channel simulator is designed and implemented in the FPGA for various wireless communication systems. The dedicated short range communications (DSRC) and ultra-wideband (UWB) channels are carried out to observe the characteristics of multi-path fading channels and validate the correctness of the SDR channel simulator. The hardware reconfiguration of the fading channel weighting generator circuit module

Jeich Mar; Chi-Cheng Kuo; You-Rong Lin; Ti-Han Lung

2009-01-01

25

Design of Software-Defined Radio Channel Simulator for Wireless Communications: Case Study With DSRC and UWB Channels  

Microsoft Academic Search

The software-defined radio (SDR) channel simulator is designed for testing the baseband transceiver of various wireless communication systems. The SDR architecture and the reconfiguration scheme used for changing the channel conditions and reconfiguring the hardware of the processing modules in the SDR channel simulator are presented. The simulator is capable of simulating four multipath fading channels and dedicated fading channels

Jeich Mar; Chi-Cheng Kuo; You-Rong Lin; Ti-Han Lung

2009-01-01

26

Evaluation of the multipath characteristics of the impulse radio channel  

Microsoft Academic Search

In order to estimate the performance of impulse radio communication systems, a characterization of the channel is required. In particular, knowledge of the multipath angle and time-of-arrival distributions is useful for predicting the performance of diversity reception schemes. In this paper, the CLEAN algorithm is applied to ultra-wide bandwidth (UWB) signals received on an array of sensors in order to

R. Jean-Marc Cramer; Moe Z. Win; Robert A. Scholtz

1998-01-01

27

Radio-channel characterization of an underground mine at 2.4 GHz  

Microsoft Academic Search

This paper presents comprehensive experimental results obtained from narrowband and wideband radio-channel measurements in an underground mine with narrow veins at 2.4 GHz. From continuous-wave (CW) measurement data, large-scale distance-power curves and path-loss exponents of the environment are determined. Other relevant parameters, such as the mean excess delay, the maximum excess delay, the root-mean-square (rms) delay spread, and the coherence

Chahé Nerguizian; Charles L. Despins; Sofiène Affès; Mourad Djadel

2005-01-01

28

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

Code of Federal Regulations, 2010 CFR

...radiotelephone stations and basic exchange telephone radio systems. 22.725 Section 22.725...radiotelephone stations and basic exchange telephone radio systems. The following channels are...transmitters in basic exchange telephone radio systems. These channels may be...

2010-10-01

29

Spectrum agile radio: radio resource measurements for opportunistic spectrum usage  

Microsoft Academic Search

Radio spectrum allocation is undergoing radical rethinking. Regulators, government agencies, industry, and the research community have recently established many initiatives for new spectrum policies and seek approaches to more efficiently manage the radio spectrum. In this paper, we examine new approaches, namely, spectrum agile radios, for opportunistic spectrum usage. Spectrum agile radios use parts of the radio spectrum that were

Stefan Mangold; Zhun Zhong; Kiran Challapali; Chun-Ting Chou

2004-01-01

30

Microwave indoor radio propagation measurements and modeling at 5 GHz for future wireless LAN systems  

Microsoft Academic Search

Wide-band frequency domain measurement and modeling of indoor radio channels at 5 GHz, for future HIPERLAN system are presented. Vector network analyzer is used to measure the frequency response of the channel. Impulse response profiles are obtained by using inverse Fourier transform. Empirical values of the RMS delay spread and number of multipath values are tested for normal distribution using

S. P. T. Kumar; B. Farhang-Boroiijeny; S. Uysal; C. S. Ng

1999-01-01

31

Joint channel assignment and routing for throughput optimization in multi-radio wireless mesh networks  

Microsoft Academic Search

Multi-hop infrastructure wireless mesh networks offer increased reliability, coverage and reduced equipment costs over their single-hop counterpart, wireless LANs. Equipping wireless routers with multiple radios further improves the capacity by transmitting over multiple radios simultaneously using orthogonal channels. Efficient channel assignment and routing is essential for throughput optimization of mesh clients. Efficient channel assignment schemes can greatly relieve the interference

Mansoor Alicherry; Randeep Bhatia; Erran L. Li

2005-01-01

32

Efficient Channel Assignment Under Dynamic Source Routing in Cognitive Radio Networks  

E-print Network

Efficient Channel Assignment Under Dynamic Source Routing in Cognitive Radio Networks Ying Dai: {ying.dai, jiewu}@temple.edu Abstract--The channel assignment problem is one of the most important issues in cognitive radio networks (CRNs). Under a SINR-driven model, we consider channel assignments

Wu, Jie

33

Implementation of Low Power and High-Speed Higher Order Channel Filters for Software Radio Receivers  

Microsoft Academic Search

The most computationally intensive part of the wideband receiver of a software defined radio (SDR) is the channelizer since it operates at the highest sampling rate. Higher order FIR channel filters are needed in the channelizer to meet the stringent adjacent channel attenuation specifications of wireless communications standards. In this paper, we present a coefficient-partitioning algorithm for realizing low power

A. Prasad Vinod; Edmund Ming-Kit Lai; Sabu Emmanuel

2006-01-01

34

A hybrid method for channel assignment problems in cellular radio networks  

Microsoft Academic Search

Because of the limited frequency spectrum and an increasing demand for cellular radio communication services, the problem of channel assignment becomes increasingly important. The channel assignment problem is to assign frequencies to requested calls in a cellular radio network subject to electromagnetic compatibility constraints such that required bandwidth is minimized. In this paper, we propose a new approach to solve

S. A. G. Shirazi; H. Amindavar

2006-01-01

35

Channel Selection Based on Trust and Multiarmed Bandit in Multiuser, Multichannel Cognitive Radio Networks  

PubMed Central

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

36

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

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

37

Design of a software defined radio channel simulator for mobile communications: Performance demonstration with DSRC for different vehicle speeds  

Microsoft Academic Search

The reconfiguration scheme and channel algorithms of the software defined radio (SDR) channel simulator is designed for testing the base band transceiver of various mobile radio systems. The flexibility in selecting a combination of waveform and fading channel software modules and setting the system parameters is the main feature of the SDR channel simulator. An example of the SDR channel

Jeich Mar; Ti-Han Lung; You-Rong Lin; Chi-Cheng Kuo

2008-01-01

38

Prediction of Fast Fading Mobile Radio Channels in Wideband Communication Systems  

E-print Network

Prediction of Fast Fading Mobile Radio Channels in Wideband Communication Systems Liang Dong on the performance of wireless communication systems, such that the prediction of the changing channel behaviors-frequency prediction scheme has superior performance over conducting the channel predic- tion on a single frequency. I

Dong, Liang

39

Measurements of radio pulsar braking indices  

NASA Astrophysics Data System (ADS)

A quantitative analysis of radio pulsar timing noise is presented. Our analysis employs the recently reported strong correlation (with correlation coefficient r = 0.95) between the observed second time derivative of the pulse rotation frequency (ddot?obs), obtained from fully phase-coherent timing analyses, and a timing noise statistic (?R23), used to quantify the amount of pulsar rotational fluctuations absorbed by the coefficient of the cubic term, to isolate the presumed deterministic braking index from the effects attributable to pulsar timing activity. Application of this method to a sample of 27 radio pulsars, whose timing data span 9-13 years, reveals that (i) for 22 pulsars, a sensible braking index measurement was impossible: with numerical values of the braking index either appreciably less than the corresponding uncertainty or anomalously large; (ii) save for the relatively large uncertainties, the braking index appears to be significantly measured in five pulsars. Current results are discussed in the context of the prevailing standard model for radio pulsar spin-down.

Chukwude, A. E.; Baiden, A. A.; Onuchukwu, C. C.

2010-06-01

40

Land mobile satellite channel measurements and modeling  

Microsoft Academic Search

This paper, tutorial in nature, describes the effort of many investigators who have and still are conducting channel measurements and modeling for land mobile satellite communications. Various channel measurement results, ranging from ultrahigh frequency to Ka-band, are given. Many statistical channel models and simplified models that have been developed are referred to. Some of the models are applicable to geostationary

Chun Loo; JOHN S. BUTTERWORTH

1998-01-01

41

Measurement techniques for UMTS signals radiated by radio base stations.  

PubMed

In the most European countries radio coverage for the third radio mobile generation. i.e, the UMTS (Universal Mobile Telecommunications System), will soon be started. In the past few years, national laws specifying limits on exposure to electromagnetic fields have drawn much attention on electromagnetic test bed and measurement procedures for radio mobile equipment/systems. An overview is given of the UMTS system, showing the main characteristics of the radio access network UTRAN (UMTS Terrestrial Radio Access Network). An analysis is also provided as to the measurement techniques and related instrumentation for the electric field intensity radiated by a UMTS radio station. PMID:11878424

Buscaglia, F; Gianola, P

2001-01-01

42

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.

43

A Channel Access Scheme for Large Dense Packet Radio Networks  

Microsoft Academic Search

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

Timothy J. Shepard

1996-01-01

44

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

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Channels for conventional rural radiotelephone...Radiotelephone Stations § 22.725 Channels for conventional rural radiotelephone...telephone radio systems. The following channels are allocated for paired...

2011-10-01

45

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

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Channels for conventional rural radiotelephone...Radiotelephone Stations § 22.725 Channels for conventional rural radiotelephone...telephone radio systems. The following channels are allocated for paired...

2012-10-01

46

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

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Channels for conventional rural radiotelephone...Radiotelephone Stations § 22.725 Channels for conventional rural radiotelephone...telephone radio systems. The following channels are allocated for paired...

2013-10-01

47

Design and Implementation of an Underlay Control Channel for Cognitive Radios  

SciTech Connect

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

Daryl Wasden; Hussein Moradi; Behrouz Farhang-Boroujeny

2012-11-01

48

Prediction of Channel State for Cognitive Radio Using Higher-Order Hidden Markov Model  

E-print Network

Prediction of Channel State for Cognitive Radio Using Higher-Order Hidden Markov Model Zhe Chen implementation. Prediction can be utilized to diminish the negative effect of such latency. In this paper, this latency is illustrated, and an approach for prediction of channel state using higher-order hidden Markov

Qiu, Robert Caiming

49

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

50

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

Microsoft Academic Search

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

Yue Ping Zhang; Qiang Li

2007-01-01

51

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

52

Power Control and Channel Allocation in Cognitive Radio Networks with Primary Users' Cooperation  

Microsoft Academic Search

We consider a point-to-multipoint cognitive radio network that shares a set of channels with a primary network. Within the cognitive radio network, a base station controls and supports a set of fixed-location wireless subscribers. The objective is to maximize the throughput of the cognitive network while not affecting the performance of primary users. Both downlink and uplink transmission scenarios in

Anh Tuan Hoang; Ying-Chang Liang

2010-01-01

53

Estimating channel fading statistics based on radio wave propagation predicted with deterministic MRFDPF method  

Microsoft Academic Search

The MR-FDPF (Multi-Resolution Frequency-Domain Partial Flow) method has proved to be an efficient tool for the indoor radio coverage prediction (1). In this paper, a new approach is proposed allowing extracting the fading statistics for indoor radio channels based on the electric field strength predicted with the MR-FDPF method. The performance of the proposed approach is verified both by simulations

Meiling Luo; Dmitry Umansky; Guillaume Villemaud; Marc Lafort; Jean-Marie Gorce

2011-01-01

54

Entanglement in channel discrimination with restricted measurements  

SciTech Connect

We study the power of measurements implementable with local quantum operations and classical communication (LOCC) measurements in the setting of quantum channel discrimination. More precisely, we consider discrimination procedures that attempt to identify an unknown channel, chosen uniformly from two known alternatives, that take the following form: (i) the input to the unknown channel is prepared in a possibly entangled state with an ancillary system, (ii) the unknown channel is applied to the input system, and (iii) an LOCC measurement is performed on the output and ancillary systems, resulting in a guess for which of the two channels was given. The restriction of the measurement in such a procedure to be an LOCC measurement is of interest because it isolates the entanglement in the initial input-ancillary systems as a resource in the setting of channel discrimination. We prove that there exist channel discrimination problems for which restricted procedures of this sort can be at either of the two extremes: they may be optimal within the set of all discrimination procedures (and simultaneously outperform all strategies that make no use of entanglement), or they may be no better than unentangled strategies (and simultaneously suboptimal within the set of all discrimination procedures).

Matthews, William; Piani, Marco; Watrous, John [Institute for Quantum Computing and Department of Combinatorics and Optimization, University of Waterloo, Waterloo, Ontario (Canada); Institute for Quantum Computing and Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario (Canada); Institute for Quantum Computing and School of Computer Science, University of Waterloo, Waterloo, Ontario (Canada)

2010-09-15

55

Reflector surface measurements of the IRAM 30-m radio telescope  

NASA Astrophysics Data System (ADS)

Surface measurements of the IRAM 30 m radio reflector made with a theodolite-laser-tape system are described. The results obtained with this survey system agree with holography measurements made at 22 GHz (Morris 1985).

Greve, A.

1986-01-01

56

Multichannel Broadcast Based on Home Channel for Cognitive Radio Sensor Networks  

PubMed Central

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

57

Cognitive Radio Enabled Multi-channel Access for Vehicular Communications  

E-print Network

intervals. The communi- cation device in each vehicle will stay at the control channel for negotiation area network is formed by a WAVE basic service set (WBSS) consisting two types of major architectural@ece.ucdavis.edu Abstract--The IEEE 1609.4 standard has been proposed to provide multi-channel operations in wireless access

Chuah, Chen-Nee

58

A statistical simulation model for mobile radio fading channels  

Microsoft Academic Search

Recently, a Clarke's model-based simulator was proposed for Rayleigh fading channels. However, that model, as shown in this paper, may encounter statistic deficiency. Therefore, an improved model is presented to remove the statistic deficiency. Furthermore, a new simulation model is proposed for Rician fading channels. This Rician fading simulator with finite number of sinusoids plus a zero-mean stochastic sinusoid as

Chengshan Xiao; Yahong R. Zheng

2003-01-01

59

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

60

Channel allocation and downlink beamforming in an SDMA mobile radio system  

Microsoft Academic Search

On the downlink of an SDMA mobile radio system, co-channel interference has to be kept down by beamforming. In this paper two DOA-based beamforming approaches are presented minimizing array signal power while maintaining given signal-to-noise-and-interference ratios for all users. The linear approach is computationally cheap, so that it is suited for channel allocation as well, quickly evaluating the spatial separability

Christof Farsakh; Josef A. Nossek

1995-01-01

61

Frequency-domain equalization of mobile radio and terrestrial broadcast channels  

Microsoft Academic Search

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

H. Sari; G. Karam; I. Jeanclaudle

1994-01-01

62

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

Microsoft Academic Search

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

Reiner Beck; Herbert Panzer

1989-01-01

63

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...

64

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

65

A real time downlink channel allocation scheme for an SDMA mobile radio system  

Microsoft Academic Search

In SDMA mobile radio systems where only base stations, but no mobiles are equipped with antenna arrays, co-channel interference on the downlink has to be kept down by beamforming. The performance of the beamformer is determined by the directions of arrival (DOAs) of the users operating in the same frequency\\/time\\/code slot. Thus the full capacity of an SDMA cell can

Christof Farsakh; Josef A. Nossek

1996-01-01

66

Channel parameter estimation in mobile radio environments using the SAGE algorithm  

Microsoft Academic Search

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

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

1999-01-01

67

Air shower measurements with the LOPES radio antenna array  

NASA Astrophysics Data System (ADS)

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

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

2009-06-01

68

Smart antennas for combined DOA and joint channel estimation in time-slotted CDMA mobile radio systems with joint detection  

Microsoft Academic Search

In cellular mobile radio systems, the directional inhomogeneity of the mobile radio channel can be exploited by smart antennas to increase the spectral efficiency. In this paper, a novel smart antenna concept applying receiver antenna diversity at the uplink receiver is investigated for a time-slotted code-division multiple-access (CDMA) mobile radio air interface termed time-division CDMA (TD-CDMA), which has been selected

Josef Johannes Blanz; Apostolos Papathanassiou; Martin Haardt; Ignasi Furió; Paul Walter Baier

2000-01-01

69

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

Microsoft Academic Search

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

LEONARD KLEINROCK; FOUAD A. TOBAGI

1975-01-01

70

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

71

Radio-frequency response of single pores and artificial ion channels  

NASA Astrophysics Data System (ADS)

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

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

2011-09-01

72

The Pioneer 11 radio occultation measurements of the Jovian ionosphere  

Microsoft Academic Search

Radio occultation data obtained with the Pioneer 11 spacecraft are utilized to study Jupiter's ionosphere. The ingress measurements, which were conducted by using a stable earth-based frequency reference for the tracking link, yielded ionospheric data near the morning terminator at about 79 deg south latitude. Data were also taken during egress on the evening side near 20 deg north latitude.

G. Fjeldbo; A. Kliore; B. Seidel; D. Sweetnam; P. Woiceshyn

1976-01-01

73

Galileo radio occultation measurements of lo's ionosphere and plasma wake  

Microsoft Academic Search

Six radio occultation experiments were conducted with the Galileo orbiter in 1997, yielding detailed measurements of the distribution and motion of plasma surrounding Io. This distribution has two components. One is highly asymmetric, consisting of a wake or tail that appears only on the downstream side and extends to distances as large as 10 Io radii. The other resembles a

D. P. Hinson; A. J. Kliore; F. M. Flasar; J. D. Twicken; P. J. Schinder; R. G. Herrera

1998-01-01

74

Analysis of Gravity Waves from Radio Occultation Measurements  

E-print Network

Analysis of Gravity Waves from Radio Occultation Measurements Martin Lange and Christoph Jacobi. In the height range 10-30 km atmospheric gravity waves lead to pe- riodic perturbations of the background gravity waves in the range 100-1000 km horizontal and 1-10 km vertical wavelength is investi- gated

75

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

76

Using XBee Radios for Wireless Acceleration Measurements  

NSDL National Science Digital Library

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

Ayars, Eric

2010-02-11

77

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

78

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

79

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

E-print Network

-Radio Multi-Channel Wireless Networks using Simplicial Complexes W. Ren , Q. Zhao , R. Ramanathan , J. Gao , A in multi-radio multi-channel ad hoc networks. The objective is to minimize the total cost of the network.g., the transmission and reception energy, the price for accessing a specific channel). Our technical approach is based

Islam, M. Saif

80

The atmosphere of Mars from Mariner 9 radio occultation measurements.  

NASA Technical Reports Server (NTRS)

Mariner-9 S-band radio occultation measurements conducted during November and December 1971 are described in terms of new information that was obtained about the shape and atmosphere of Mars. The arrival of the spacecraft coincided with a severely obscuring global dust storm, and the effect of the dust in the atmosphere was reflected in the reduced temperature gradients that were measured in the daytime near-equatorial atmosphere, indicating (1) heating of the atmosphere by solar radiation absorbed by dust and (2) simultaneous cooling of the surface. In general, surface atmospheric pressures measured in the equatorial regions are in very good agreement with previous radio-occultation and earth-based measurements. A global disparity in pressures strongly suggests that the physical shape of Mars is more oblate than the shape of its gravitational equipotential surface.

Kliore, A. J.; Cain, D. L.; Fjeldbo, G.; Seidel, B. L.; Sykes, M. J.; Rasool, S. I.

1972-01-01

81

The atmosphere of Io from Pioneer 10 radio occultation measurements  

Microsoft Academic Search

The occultation of the Pioneer 10 spacecraft by Io (JI) provided an opportunity to obtain two S-band radio occultation measurements of its atmosphere. The day-side entry measurements revealed an ionosphere having a peak density of about 60,000 el\\/cu cm at an altitude of about 100 km. The topside scale height indicates a plasma temperature of about 406 K if it

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

1975-01-01

82

Radio Emission in Atmospheric Air Showers Measured by LOPES-30  

NASA Astrophysics Data System (ADS)

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.

2008-01-01

83

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  

Microsoft Academic Search

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

John W. Beeman; Alec G. Maule

2001-01-01

84

Stochastic Wireless Channel Modeling, Estimation and Identification from Measurements  

SciTech Connect

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

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

2008-07-01

85

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

NASA Technical Reports Server (NTRS)

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

1984-01-01

86

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

87

Measurement of stream channel habitat using sonar  

USGS Publications Warehouse

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

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

1998-01-01

88

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

89

Initial results from radio occultation measurements with Mars Global Surveyor  

Microsoft Academic Search

A series of radio occultation experiments conducted with Mars Global Surveyor in early 1998 has yielded 88 vertical profiles of the neutral atmosphere. The measurements cover latitudes of 29°N to 64°S and local times from 0600 through midnight to 1800 during early summer in the southern hemisphere (Ls=264°-308°). Retrieved profiles of pressure and temperature versus radius and geopotential extend from

D. P. Hinson; R. A. Simpson; J. D. Twicken; G. L. Tyler; F. M. Flasar

1999-01-01

90

Measuring the kinetic power of AGN in the radio mode  

E-print Network

(Abridged) We have studied the relationship among nuclear radio and X-ray power, Bondi rate and the kinetic luminosity of sub-Eddington active galactic nuclear (AGN) jets. Besides the recently discovered correlation between jet kinetic and Bondi power, we show that a clear correlation exists also between Eddington-scaled kinetic power and bolometric luminosity, given by: Log(L_kin/L_Edd)=0.49*Log(L_bol/L_Edd)-0.78. The measured slope suggests that these objects are in a radiatively inefficient accretion mode, and has been used to put stringent constraints on the properties of the accretion flow. We found no statistically significant correlations between Bondi power and bolometric AGN luminosity, apart from that induced by their common dependence on L_kin. Analyzing the relation between kinetic power and radio core luminosity, we are then able to determine, statistically, both the probability distribution of the mean jets Lorentz factor, peaking at \\Gamma~7, and the intrinsic relation between kinetic and radio core luminosity, that we estimate as: Log(L_kin)=0.81*Log(L_R)+11.9, in good agreement with theoretical predictions of synchrotron jet models. With the aid of these findings, quantitative assessments of kinetic feedback from supermassive black holes in the radio mode will be possible based on accurate determinations of the central engine properties alone. As an example, Sgr A* may follow the correlations of radio mode AGN, based on its observed radiative output and on estimates of the accretion rate both at the Bondi radius and in the inner flow. If this is the case, the SMBH in the Galactic center is the source of ~ 5 times 10^38 ergs/s of mechanical power, equivalent to about 1.5 supernovae every 10^5 years.

Andrea Merloni; Sebastian Heinz

2007-07-23

91

Indoor radio channel modeling and mitigation of fading effects using linear and circular polarized antennas in combination for smart home system at 868 MHz  

NASA Astrophysics Data System (ADS)

The markets for smart home products and services are expected to grow over the next years, driven by the increasing demands of homeowners considering energy monitoring, management, environmental controls and security. Many of these new systems will be installed in existing homes and offices and therefore using radio based systems for cost reduction. A drawback of radio based systems in indoor environments are fading effects which lead to a high variance of the received signal strength and thereby to a difficult predictability of the encountered path loss of the various communication links. For that reason it is necessary to derive a statistical path loss model which can be used to plan a reliable and cost effective radio network. This paper presents the results of a measurement campaign, which was performed in six buildings to deduce realistic radio channel models for a high variety of indoor radio propagation scenarios in the short range devices (SRD) band at 868 MHz. Furthermore, a potential concept to reduce the variance of the received signal strength using a circular polarized (CP) patch antenna in combination with a linear polarized antenna in an one-to-one communication link is presented.

Wunderlich, S.; Welpot, M.; Gaspard, I.

2014-11-01

92

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

NASA Astrophysics Data System (ADS)

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

Sakata, Ren; Tomioka, Tazuko; Kobayashi, Takahiro

93

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

Microsoft Academic Search

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

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

2010-01-01

94

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

95

The Pioneer 11 radio occultation measurements of the Jovian ionosphere  

NASA Technical Reports Server (NTRS)

Radio occultation data obtained with the Pioneer 11 spacecraft are utilized to study Jupiter's ionosphere. The ingress measurements, which were conducted by using a stable earth-based frequency reference for the tracking link, yielded ionospheric data near the morning terminator at about 79 deg south latitude. Data were also taken during egress on the evening side near 20 deg north latitude. The latter measurements were conducted in the one-way mode; i.e., an on-board crystal oscillator was employed as a frequency reference for the downlink (spacecraft-to-earth) signal. These data confirm previous results obtained with Pioneer 10 and show that Jupiter has a multilayered ionosphere extending over an altitude range of more than 3000 km. The topside scale height near 79 deg south latitude was 540 + or - 60 km. Assuming a topside electron, H(+) distribution controlled by diffusion yields a plasma temperature of 850 + or - 100 K in this region. The radio data indicate that the upper atmosphere is either warmer or more dissociated into atomic hydrogen than previously anticipated.

Fjeldbo, G.; Kliore, A.; Seidel, B.; Sweetnam, D.; Woiceshyn, P.

1976-01-01

96

Application of the SELENE radio communication system to occultation measurement  

NASA Astrophysics Data System (ADS)

The SELENE mission includes a dual frequency S- and X-band occultation experiment for the exploration of the plasma clouds above the lunar surface. The accuracy of the measurement is mainly limited by the influence of the turbulent media of the Earth's ionosphere and the solar wind plasma. The mission scenario from the other side will make accessible only the polar region along the lunar limb. Still the radio communication system of the SELENE mission, which consists of three orbiters, is able to provide other occultation configuration. The proposed types of radio occultation will allow to exclude the effect of the Earth's ionosphere and the solar wind plasma and to accomplish occultation on both sides of the Luna. The accuracy is expected to be better than 101 4 el/m2 . The occultation measurement together with the other SELENE mission experiments can present new information on the existence and the origin of the plasma clouds and the interaction of the solar wind with magnetic field anomalies on the surface of the Moon.

Nabatov, A.; Oyama, K.; Savich, N.; Imamura, T.; Noguchi, K.

97

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

98

Initial results from radio occultation measurements with Mars Global Surveyor  

NASA Astrophysics Data System (ADS)

A series of radio occultation experiments conducted with Mars Global Surveyor in early 1998 has yielded 88 vertical profiles of the neutral atmosphere. The measurements cover latitudes of 29°N to 64°S and local times from 0600 through midnight to 1800 during early summer in the southern hemisphere (Ls=264°-308°). Retrieved profiles of pressure and temperature versus radius and geopotential extend from the surface to the 10-Pa pressure level. Near-surface uncertainties in temperature and pressure are about 1 K and 2 Pa, respectively, far smaller than in previous radio occultation measurements at Mars. The profiles resolve the radiative-convective boundary layer adjacent to the surface and also reveal gravity waves, particularly at northern and equatorial latitudes, which appear to be breaking in some cases. Distinctive meridional gradients of pressure and temperature indicate the presence of a low-altitude westerly jet at latitudes of 15°-30°S at southern summer solstice. This jet appears in predictions of general circulation models in connection with the strong, seasonal, cross-equatorial Hadley circulation. The pressure gradient at ~2 km altitude implies a wind speed of 33 m s-1, stronger than predicted, which may help explain the occurrence of numerous local dust storms within this latitude band in late southern spring. These measurements also characterize the response of the atmosphere to stationary thermal forcing at midsouthern latitudes, where high terrain south of Tharsis and low terrain in Hellas Planitia produce large, zonal temperature variations in the lowest scale height above the surface. Pressure measured at constant geopotential decreases at an average rate of 0.13% per degree Ls, due primarily to condensation of CO2 at the North Pole.

Hinson, D. P.; Simpson, R. A.; Twicken, J. D.; Tyler, G. L.; Flasar, F. M.

99

Compatibility analysis of in-band digital radio systems in interference channel environment  

Microsoft Academic Search

Many countries today face converting their analog radio broadcasting to digital service. Since the in-band digital radio systems are used in the existing analog FM frequency band, compatibility and robustness is very important characteristics of the digital radio systems. In this paper, we evaluate the performances of HD-Radio and DRM+ which are in-band digital radio broadcasting techniques in the various

Myung-Sun Baek; So-Ra Park; Yong-Hoon Lee; Gun Kim; Seokhyun Yoon; Kyung-Tek Lee; Sang-Woon Lee; Soo-In Lee; Yong-Tae Lee

2010-01-01

100

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

101

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

102

An application of uncertain numbers in radio frequency power measurement  

NASA Astrophysics Data System (ADS)

The uncertain-numbers method (Hall B D 2006 Metrologia 43 L56-61) is an alternative computational procedure to the Law of Propagation of Uncertainty (LPU) described in the Guide to the Expression of Uncertainty in Measurement. One advantage of the method is that data processing can be carried out in an arbitrary series of steps and much of the mathematical analysis normally associated with the LPU can be automated by software. This has applications for measuring systems, which are modular in design and use internal data processing to apply corrections to raw data. Several scenarios involving radio frequency power measurements are used to illustrate the new method in this context. The scenarios show something of the difficulty inherent in calculating uncertainty for modern measurement systems and in particular highlight the occurrence of systematic errors arising from internal instrument correction factors. Such errors introduce correlation to a series of measurements and must be handled with care when functions of results, such as means, differences and ratios, are required.

Hall, B. D.

2009-06-01

103

CONTROL CHANNEL BASED MAC-LAYER CONFIGURATION, ROUTING AND SITUATION AWARENESS FOR COGNITIVE RADIO NETWORKS  

E-print Network

1 CONTROL CHANNEL BASED MAC-LAYER CONFIGURATION, ROUTING AND SITUATION AWARENESS FOR COGNITIVE 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

Venkatesan, S.

104

Capillary wave measurements on helically-supported capillary channels  

NASA Astrophysics Data System (ADS)

NASA is considering power generation by the Rankine cycle to save weight on long-duration manned missions to the moon or Mars. Phase separation technology is critical to this process in microgravity. Arrays of capillary channels might be useful for filtering liquid drops from a flowing vapor. The efficiency of droplet capture by a helically-supported capillary channel is being studied. A droplet impinging on the channel launches capillary waves that propagate down the channel helping to dissipate some of the drop's kinetic energy. High-speed video of the channel combined with image processing allows for measurement of the amplitude and speed of the wave packets. Increasing the pitch of the support structure decreases the wave speed. An understanding of the dynamic response of the channel to drop impact is a first step in predicting drop-capture efficiency.

Chandurwala, Fahim; Thiessen, David

2010-10-01

105

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

106

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

NASA Astrophysics Data System (ADS)

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

Petrin, Allen J.

107

Experimental comparison between centimeter- and millimeter-wave ultrawideband radio channels  

NASA Astrophysics Data System (ADS)

paper analyzes radio wave propagation phenomena at two very different frequency bands: 2-10 GHz (centimeter wave) and 57-66 GHz (millimeter wave (mm-W)). The two frequency bands have been measured using the same equipment and under similar propagation conditions, such as path loss, root-mean-square delay spread, maximum excess delay, and Rician K factor, and their respective correlations compared. Obstructed line of sight situations have also been considered by using metal and cardboard obstructions. The statistical distributions, main specular reflections, and decay factors have been found similar for the two bands. However, the measured path loss, correlation in terms of electrical distances, and the K factor are higher for the millimeter-wave frequency band. Indeed, the importance of propagation mechanism changes from one band to the other, which must be considered in the design of future mm-W systems.

Martinez-Ingles, Maria-Teresa; Molina-Garcia-Pardo, Jose-Maria; Rodríguez, José-Víctor; Pascual-García, Juan; Juan-Llácer, Leandro

2014-06-01

108

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

NASA Astrophysics Data System (ADS)

Future radio occultation (RO) receivers are planned to utilize the newly implemented Global Positioning System (GPS) L5 band centered at 1176.45 MHz. Since there are currently no operational GPS L5 receivers used for space-based RO applications, the interference environment is unclear. Distance measuring equipment (DME) and tactical air navigation (TACAN) stations share the same frequency band as GPS L5. The signals from these stations have been identified as possible sources of interference for any GPS L5 receiver, including those used in RO applications. This study utilizes Systems Tools Kit (STK) simulations to gain insight into the power received by a RO satellite in low Earth orbit (LEO) from a DME-TACAN transmission as well as the amount of interfering stations. In order to confirm the validity of utilizing STK for communication purposes, a theoretical scenario was recreated as a simulation and the results were confirmed. Once the method was validated, STK was used to output a received power level aboard a RO satellite from a DME-TACAN station as well as a tool to detail the number of interfering DME-TACAN stations witnessed by a space-based RO receiver over time. The results indicated a large number of DME-TACAN stations transmitting at similar orientations as a receiving RO satellite, thereby leading to the possibility of signal degradation in an unclear interference environment.

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

2014-11-01

109

Ion species mix and ion density measurements using radio frequency waves  

Microsoft Academic Search

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

George Wilder Watson III

2003-01-01

110

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

111

The atmosphere of Io from Pioneer 10 radio occultation measurements  

NASA Technical Reports Server (NTRS)

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

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

1975-01-01

112

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

113

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

NASA Astrophysics Data System (ADS)

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

Arkilic, Errol; Schmidt, Martin; Breuer, Kenneth

1996-11-01

114

Ionospheric wave and irregularity measurements using passive radio astronomy techniques  

NASA Technical Reports Server (NTRS)

The observation of midlatitude structures using passive radio astronomy techniques is discussed, with particular attention being given to the low-frequency radio telescope at the Clark Lake Radio Observatory. The present telescope operates in the 10-125-MHz frequency range. Observations of the ionosphere at separations of a few kilometers to a few hundreds of kilometers by the lines of sight to sources are possible, allowing the determination of the amplitude, wavelength, direction of propagation, and propagation speed of ionospheric waves. Data are considered on large-scale ionospheric gradients and the two-dimensional shapes and sizes of ionospheric irregularities.

Erickson, W. C.; Mahoney, M. J.; Jacobson, A. R.; Knowles, S. H.

1988-01-01

115

Measurement of Geopotential Heights by GPS Radio Occultation  

NASA Technical Reports Server (NTRS)

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

Leroy, Stephen S.

1997-01-01

116

Topside plasma scale height retrieved from radio occultation measurements  

NASA Astrophysics Data System (ADS)

The plasma scale height is one of the important ionospheric characteristics due to its intrinsic connection to the ionospheric plasma temperature and composition and also, to the altitudinal profile of the electron density. Therefore, the knowledge of the plasma scale height is of crucial importance when addressing several open scientific and technological issues such as the upper ionosphere temperature balance and ion composition, the estimation and correction of propagation delays in Global Navigation Satellite Systems (GNSS), the nowcast and forecast of space-weather effects on telecommunications, etc. While the plasma scale height value in the bottomside ionosphere can be deduced directly and reliably enough by vertical incidence sounding, the plasma scale height in the topside ionosphere is quite difficult to obtain. The ionospheric radio occultation (IRO) technique employed by the Low-Earth-Orbiting (LEO) satellites can deliver the valuable information on the topside plasma scale height behaviour and can provide a rich database for consequent development of new empirical models of the plasma scale height and density. Reported here is a procedure for post-processing retrieval of the topside plasma scale height values from IRO measurements by the LEO satellite CHAMP (CHAllenging Minisatellite Payload). Described also is the accumulated data base of such values. Further, presented are first results from the analysis of the topside plasma scale height's temporal and spatial variations. These preliminary results are compared with corresponding estimates from the International Reference Ionosphere (IRI) model calculations.

Stankov, S.; Jakowski, N.

117

A wireless multi-channel bioimpedance measurement system for personalized healthcare and lifestyle.  

PubMed

Miniaturized, noninvasive, wearable sensors constitute a fundamental prerequisite for pervasive, predictive, and preventive healthcare systems. In this sense, this paper presents the design, realization, and evaluation of a wireless multi-channel measurement system based on a cost-effective high-performance integrated circuit for electrical bioimpedance (EBI) measurements in the frequency range from 1 kHz to 1 MHz. The resulting on-chip spectrometer provides high measuring EBI capabilities and together with a low-cost, commercially available radio frequency transceiver device. It provides reliable wireless communication, constitutes the basic node to build EBI wireless sensor networks (EBI-WSNs). The proposed EBI-WSN behaves as a high-performance wireless multi-channel EBI spectrometer, where the number of channels is completely scalable and independently configurable to satisfy specific measurement requirements of each individual. A prototype of the EBI node leads to a very small printed circuit board of approximately 8 cm2 including chip-antenna, which can operate several years on one 3-V coin cell battery and make it suitable for long-term preventive healthcare monitoring. PMID:23739358

Ramos, Javier; Ausín, José Luis; Lorido, Antonio Manuel; Redondo, Francisco; Duque-Carrillo, Juan Francisco

2013-01-01

118

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

119

Simultaneous Multiplexing and Demultiplexing of Wavelength-Interleaved Channels in DWDM Millimeter-Wave Fiber-Radio Networks  

NASA Astrophysics Data System (ADS)

A simultaneous multiplexing and demultiplexing (MUX/DEMUX) scheme for wavelength-interleaved millimeter-wave 37.5-GHz-band fiber-radio channels spaced at 25 GHz has been proposed. The proposed MUX/DEMUX technique potentially realizes simple, compact, and low-cost central office and remote nodes by avoiding the use of wavelength-selective pre-and postprocessing hardware. The novel scheme incorporates an arrayed-waveguide grating with multiple loop-backs between the input and the output ports, in addition to multiple optical circulators and optical isolators. The multiplexing functionality of the proposed technology enables a carrier subtraction technique and consequently reduces the carrier-to-sideband ratios of the multiplexed channels. Multiplexing of the uplink channels generated via several methods is demonstrated experimentally. These techniques include generation of the channels by using the optical carriers that correspond to wavelengths spaced at the free spectral range (FSR) or multiples of the FSR from the downlink (DL) optical carriers and reuse of the DL optical carriers that are recovered by applying a wavelength reuse technique (?UL = ?DL pm n × FSR, where n = 0, 1, 2, 3, ldots). The demultiplexing functionality of the proposed scheme that separates the 37.5-GHz-band wavelength-interleaved DL channels spaced at 25 GHz is also demonstrated. In addition, the effect of optical crosstalk on the transmission performance of the demultiplexed channels is also characterized experimentally.

Bakaul, Masuduzzaman; Nirmalathas, Ampalavanapillai Thas; Lim, Christina; Novak, Dalma; Waterhouse, Rod B.

2006-09-01

120

Summary of interference measurements at selected radio observatories  

NASA Technical Reports Server (NTRS)

Results are presented from a series of RF interference (RFI) observations conducted during 1989 and 1990 at selected radio astronomy observatories in order to choose a site for the SETI, where the local and orbital RFI would be as benign as possible for observations of weak electromagnetic signals. These observatories included the DSS13 at Goldstone (California), the Arecibo Observatory (Puerto Rico), the Algonquin Radio Observatory in Ottawa (Canada), the Ohio State University Radio Observatory in Columbus (Ohio), and the NRAO in Green Bank (West Virginia). The observations characterize the RFI environment at these sites from 1 to 10 GHz, using radio astronomy antennas, feeds, and receivers; SETI signal processors; and stand-alone equipment built specifically for this purpose. The results served as part of the basis for the selection (by the NASA SETI Microwave Observing Project) of NRAO as the site of choice for SETI observations.

Tarter, Jill C.

1990-01-01

121

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

122

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

NASA Technical Reports Server (NTRS)

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

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

2006-01-01

123

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

Microsoft Academic Search

We have investigated the possibility that large rock salt formations might be suitable as target masses for detection of neutrinos of energies about 10 PeV and above. In neutrino interactions at these energies, the secondary electromagnetic cascade produces a coherent radio pulse well above ambient thermal noise via the Askaryan effect. We describe measurements of radio-frequency attenuation lengths and ambient

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

2001-01-01

124

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

125

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

USGS Publications Warehouse

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

Adams, J.; Takekawa, J.Y.

2008-01-01

126

Radio telescopes  

Microsoft Academic Search

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

J. Findlay

1964-01-01

127

A physical MIMO radio channel model for multi-element multi-polarized antenna systems  

Microsoft Academic Search

A physical multi-input multi-output (MIMO) spatio-temporal channel model for simulation of multi-element multi-polarized antenna systems is presented. The model is based on electromagnetic (EM) scattering, hence including many of the channel characteristics encountered in practice. A compact channel expression is obtained by introducing a dyad formulation of the scattering from arbitrary objects. The polarization properties of the channel and the

Thomas Svantesson

2001-01-01

128

Interference-Aware Channel Assignment in Multi-Radio Wireless Mesh Networks  

Microsoft Academic Search

The capacity problem in wireless mesh networks can be alleviated by equipping the mesh routers with multiple ra- dios tuned to non-overlapping channels. However, channel assign- ment presents a challenge because co-located wireless networks are likely to be tuned to the same channels. The resulting increase in interference can adversely affect performance. This paper presents an interference-aware channel assignment algorithm

Krishna N. Ramachandran; Elizabeth M. Belding-royer; Kevin C. Almeroth; Milind M. Buddhikot

2006-01-01

129

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

Microsoft Academic Search

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

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

2011-01-01

130

The Impact of Adjacent Channel Interference in Multi-Radio Systems using IEEE 802.11  

Microsoft Academic Search

A promising approach for improving the capacity of Wireless Mesh Networks is by making use of multiple non-overlapping RF channels. Multi-channel protocols have the advantage that several devices can transmit in parallel within a collision domain on distinct channels. When using IEEE 802.11b\\/g\\/a most protocol designers assume 3 and 12 non-overlapping channels, respectively. However, this simplified assumption does not hold.

Jens Nachtigall; Anatolij Zubow; Jens-Peter Redlich

2008-01-01

131

Galileo radio occultation measurements of Io's ionosphere and plasma wake  

NASA Astrophysics Data System (ADS)

Six radio occultation experiments were conducted with the Galileo orbiter in 1997, yielding detailed measurements of the distribution and motion of plasma surrounding Io. This distribution has two components. One is highly asymmetric, consisting of a wake or tail that appears only on the downstream side and extends to distances as large as 10 Io radii. The other resembles a bound ionosphere and is present within a few hundred kilometers of Io's surface throughout the upstream and downstream hemispheres. Motion of plasma within the wake was measured through cross correlation of data acquired simultaneously at two widely separated terrestrial antennas. Plasma near Io's equatorial plane is moving away from Io in the downstream direction. Its speed increases from 30 kms-1 at a distance of 3 Io radii from the center of Io to 57 kms-1 at 7 Io radii. The latter corresponds to corotation with Jupiter's magnetic field, which suggests that bulk plasma motion rather than wave motion is being observed. Results for the bound ionosphere include vertical profiles of electron density at 10 locations near Io's terminator. The ionosphere is substantial, with the peak density exceeding 50,000 cm-3 at 9 out of 10 locations and reaching a maximum of 277,000 cm-3. The peak density varies systematically with Io longitude, with maxima near the center of the hemispheres facing toward (0°W) and away from (180°W) Jupiter and minima near the center of the downstream (90°W) and upstream (270°W) hemispheres. This pattern may be related to the Alfvénic current system induced by Io's motion through magnetospheric plasma. The vertical extent of the bound ionosphere increases from ~200 km near the center of the upstream hemisphere to ~400 km near the boundary between the leading and trailing hemispheres. There is a close resemblance between one ionospheric profile and a Chapman layer, and the topside scale height implies a plasma temperature of 202+/-14K if Na+ is the principal ion. Two intense volcanic hot spots, Kanehekili and 9606A, may be influencing the atmospheric structure at this location.

Hinson, D. P.; Kliore, A. J.; Flasar, F. M.; Twicken, J. D.; Schinder, P. J.; Herrera, R. G.

1998-12-01

132

Holding zero switching scheme for multi-channel impedance measurement  

Microsoft Academic Search

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

Ziqiang Cui; Huaxiang Wang; Yanbin Xu; Yongbo He

2009-01-01

133

Uniplanar Wideband Quasi Yagi Antenna for Multiple Antenna Channel Measurements  

E-print Network

of arrival information, and data necessary for the design of smart antennas and spectrally efficient systemsUniplanar Wideband Quasi Yagi Antenna for Multiple Antenna Channel Measurements M. Abdalla and S antenna has gained considerable attention recently as a method of producing a broad bandwidth antenna

Haddadi, Hamed

134

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

Microsoft Academic Search

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

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

2011-01-01

135

Inverting ionospheric radio occultation measurements using maximum entropy  

Microsoft Academic Search

Practical aspects of the inversion of ionospheric radio occultation data using the Abel transform and its inverse are discussed. The linear inverse transform exhibits poor error propagation characteristics, producing significant artifacts preferentially at low altitudes where they might easily be mistaken for intermediate or sporadic layers in the ionosphere. Tikhonov regularization, which can be viewed as fixed linear filtering, reduces

D. L. Hysell

2007-01-01

136

Analysis of wireless sensor network topology and estimation of optimal network deployment by deterministic radio channel characterization.  

PubMed

One of the main challenges in the implementation and design of context-aware scenarios is the adequate deployment strategy for Wireless Sensor Networks (WSNs), mainly due to the strong dependence of the radiofrequency physical layer with the surrounding media, which can lead to non-optimal network designs. In this work, radioplanning analysis for WSN deployment is proposed by employing a deterministic 3D ray launching technique in order to provide insight into complex wireless channel behavior in context-aware indoor scenarios. The proposed radioplanning procedure is validated with a testbed implemented with a Mobile Ad Hoc Network WSN following a chain configuration, enabling the analysis and assessment of a rich variety of parameters, such as received signal level, signal quality and estimation of power consumption. The adoption of deterministic radio channel techniques allows the design and further deployment of WSNs in heterogeneous wireless scenarios with optimized behavior in terms of coverage, capacity, quality of service and energy consumption. PMID:25664434

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

2015-01-01

137

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

138

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

PubMed Central

Energy resource management is a crucial problem of a device with a finite capacity battery. In this paper, cognitive radio is considered to be a device with an energy harvester that can harvest energy from a non-RF energy resource while performing other actions of cognitive radio. Harvested energy will be stored in a finite capacity battery. At the start of the time slot of cognitive radio, the radio needs to determine if it should remain silent or carry out spectrum sensing based on the idle probability of the primary user and the remaining energy in order to maximize the throughput of the cognitive radio system. In addition, optimal sensing energy and adaptive transmission power control are also investigated in this paper to effectively utilize the limited energy of cognitive radio. Finding an optimal approach is formulated as a partially observable Markov decision process. The simulation results show that the proposed optimal decision scheme outperforms the myopic scheme in which current throughput is only considered when making a decision. PMID:24574885

Vu-Van, Hiep; Koo, Insoo

2014-01-01

139

Laser Doppler velocimetry measurement of turbulent bubbly channel flow  

Microsoft Academic Search

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

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

2002-01-01

140

Measurement of the top quark mass in the dilepton channel  

NASA Astrophysics Data System (ADS)

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

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

1999-09-01

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

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

Microsoft Academic Search

Remote sensing radio occultation measurements are used here to study magnetization of the ionospheres of Venus and Mars. For Venus, the measurements yield results on frequency of occurrence of magnetization during solar maximum that are similar to those obtained from Pioneer Venus in situ magnetic field measurements. During solar minimum, magnetization of the Venus ionosphere is more pervasive than at

Richard Woo; Arvydas J. Kliore

1991-01-01

143

The Pioneer 10 radio occultation measurements of the ionosphere of Jupiter  

Microsoft Academic Search

Data from the Pioneer 10 radio occultation measurements are utilized to study the vertical electron number density distribution in the Jovian ionosphere. The immersion measurements were made at 26 North latitude in the late afternoon local time. The solar zenith angle in this region was 81 deg. Emersion measurements were made at 58 North latitude near the morning terminator where

G. Fjeldbo; A. Kliore; B. Seidel; D. Sweetnam; D. Cain

1975-01-01

144

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

145

Electrochemical measurement of DNA in a nanofluidic channel  

NASA Astrophysics Data System (ADS)

The elongation of genomic length DNA in confining nanochannels is not only a fascinating exercise in polymer dynamics, but also is of great interest in biotechnology because the elongation of the confined molecule is directly proportional to the actual length of the molecule in basepairs. We will present a way to construct nanochannels using sacrificial PMMA ebeam lithography and to measure non-immobilized DNA molecules inside such a channel electrochemically. This kind of measurements can lead us to fast and precise electronic length measurement, which will open the door to a number of important areas in genomics such as gene exchange and evolution dynamics of single cells.

Tung, Chih-Kuan; Riehn, Robert; Austin, Robert H.

2008-03-01

146

Radio Occultation Measurements of Transient Eddies in the Northern Hemisphere of Mars  

Microsoft Academic Search

The Radio Science (RS) investigation of Mars Global Surveyor has collected more than 16,000 radio occultation profiles of the neutral atmosphere, including more than 10,000 profiles at mid-to-high latitudes of the northern hemisphere. Key attributes include fine vertical resolution and a unique measure of geopotential height on surfaces of constant pressure, which offer new insight into the behavior of transient

D. P. Hinson

2005-01-01

147

Adaptive equalization of indoor radio channels for 156Mb\\/s, QPSK data transmission  

Microsoft Academic Search

Indoor radio communication in the 20–60 GHz band using TDMA with differentially encoded QPSK is consideed. A burst-type transmission, based on a basic time slot consisting of a preamble for synchronization and equalizer training and of an information data section, is adopted. We employ fractionally spaced decision feedback equalization and give the relevant analytical and simulated performance results in terms

Ali Masoomzadeh-Fard I; Subbarayan Pasupathy

1996-01-01

148

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

149

Data detection and channel allocation on the uplink of an SDMA mobile radio system  

Microsoft Academic Search

On the uplink of an SDMA mobile radio system K>1 users are transmitting in the same frequency band and time slot. These signals are received at the base station with an array of M⩾K antennas. A complete base station receiver structure to jointly detect the bits transmitted by the K users is presented. To guarantee a good receiver performance a

C. Farsakh; J. A. Nossek

1997-01-01

150

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

151

Further improved technique for channeled stopping power measurements  

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

152

Outdoor radiolinks for 2.4 GHz-frequencies: measurement results and experiences within the radio communication network "Intermobil Region Dresden"  

NASA Astrophysics Data System (ADS)

The radio communication network "Intermobil Region Dresden" was developed and built up for data transmission of traffic videos and other traffic data. It uses Pointto- Point (PtP) and Point-to-Multipoint (PtM) bridges, forming the backbone structure. The traffic camera radio clients link up with Accesspoints, installed at the nodal points of the backbone. This paper analyses the physical and technical conditions, building up such radio communication networks. The radio channel properties (e.g. total path loss, multipath propagation) and the technical parameters (e.g. transmission power, sensitivity, antenna gain) belong to this conditions. Based on calculation and spreading measurements it is shown, that reserves have to be considered during the planning already. As well special problems, like Fresnel-zone clearance and shadowing are discussed. The choice of the antenna plays a key role for planning and building of wireless networks. It determines decisively the range and gives an important contribution to elimination of wireless disturbances (interferences). Dependent on topological facts, installation environment and wireless distance omnidirectional-, yagi-, patch- and parabol-antennas are used. Based on antenna measurements the paper discusses the use and property of decoupling. WLANs are working in the license free 2.4 GHz-band. The number of radio systems in this band increases permanently, which leads to a lot of interferences among each other. The paper makes a classification of possible interference sources and discusses their influence on transmission quality. Technical solutions are shown for increase interference robustness.

Michler, O.

2003-05-01

153

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

154

Performance analysis of ARQ Go-Back-N protocol in fading mobile radio channels  

Microsoft Academic Search

An ARQ Go-Back-N protocol with unreliable feedback and time-out mechanism is considered. Both the forward and the reverse channels are subject to fading impairments. A threshold model for successes and failures of both packets and feedback information is assumed, and the resulting success\\/failure processes are modeled as Markovian. Throughput and delay are analytically evaluated. For the fading channel model and

Michele Zorzit; Ramesh R. Rao; Laurence B. Milstein

1995-01-01

155

Orbit Determination Using TDMA Radio Navigation Data with Implicit Measurement Times  

E-print Network

Orbit Determination Using TDMA Radio Navigation Data with Implicit Measurement Times Ryan C. Dougherty and Mark L. Psiaki Cornell University, Ithaca, New York, 14853-7501 An orbit determination Kalman measurement. This algorithm will enable precise orbit determination of satellites broadcasting TDMA signals

Psiaki, Mark L.

156

Influence of Temperature in Radio Frequency Measurements of Moisture Content in Biofuel  

Microsoft Academic Search

A method that permits the determination of moisture content in biofuel in a fast and representative way is under development. The method uses radio frequency waves within the range of 310 MHz to 800 MHz and measures the reflection coefficient in samples with volume of about 0.1 m3. The influence of sample temperature in the measurements is shown in this

Ana Paz; Jenny Nyström; Eva Thorin

2006-01-01

157

Mariners 6 and 7: Radio Occultation Measurements of the Atmosphere of Mars  

Microsoft Academic Search

Radio occultation measurements with Mariners 6 and 7 provided refractivity data in the atmosphere of Mars at four points above its surface. For an atmosphere consisting predominantly of carbon dioxide, surface pressures between 6 and 7 millibars are obtained at three of the points of measurement, and 3.8 at the fourth, indicating an elevation of 5 to 6 kilometers. The

Arvydas Kliore; Gunnar Fjeldbo; Boris L. Seidel; S. I. Rasool

1969-01-01

158

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

Microsoft Academic Search

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

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

1994-01-01

159

Performance of UWB-Impulse Radio Receiver Based on Matched Filter Implementation with Imperfect Channel Estimation  

NASA Astrophysics Data System (ADS)

UWB communications have attracted considerable interest, targeting applications in high-speed data transfer wireless communication systems. This paper studies the effects of matched filter receiver in the performance of such a system. Such effects are evaluated in terms of the Bit Error Rate (BER) for a Binary Pulse Position Modulation (BPPM) scheme, considering multipath propagation channel and the presence of noise. The case of imperfect channel estimation is taken into account. Dependence of BER on parameters such as signal to noise ratio, number of estimation pulses and correletor taps is also presented.

Tatsis, Giorgos; Votis, Constantinos; Raptis, Vasilis; Christofilakis, Vasilis; Chronopoulos, Spyridon K.; Kostarakis, Panos

2010-01-01

160

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

SciTech Connect

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

Cullen, C.

1996-08-01

161

Radio measurements of constant variation, and perspectives with ALMA  

NASA Astrophysics Data System (ADS)

In the radio domain, absorption lines in front of quasars of CO, HI, OH, HCO+, HCN, up to NH3 and CII are providing interesting constraints on fundamental constant variation (? and ?). With more absorbing systems, and a wider redshift range, they could be more competitive than optical studies. This could come with ALMA, with more than one order of magnitude in sensitivity. Up to now, at intermediate and high redshift, between z = 0.25 to z = 0.89, only four absorption lines systems have been detected in the millimeter range and a fifth system at 0.765, at the OH-18cm lines (Kanekar et al. 2005). Out of these 5 systems, 3 are intervening lensing galaxies (and the background quasar is multiply imaged), and 2 correspond to an absorption of the host (PKS1413+135, B3-1504+377, for an overview see Combes & Wiklind 1996; Wiklind & Combes 1994 to 1998). A global comparison of all molecular lines observed with the HI-21cm absorption lines in PKS1413 and B0218 systems, the two narrowest line systems, have given quite stringent constraints on y = ?2 gp ?, ? y/y = (-0.20 ± 0.44) 10-5 and ? y/y = (-0.16 ± 0.54) 10-5 respectively (Murphy et al. 2001). The precision is comparable to the MM method (Murphy et al. 2003), with a limited number of absorbing systems. The high sensitivity if the NH3 inversion lines to variation in the ? ratio (Flambaum & Kozlov 2007) was used by Henkel et al. (2009) in a recent multi-line study of PKS1830 at z ~ 0.9, and Murphy et al. (2008) for B0218 at z ~ 0.7. They find a limit of ??/? < 1.4 10-6 and ??/? < 1.8 10-6 respectively. Clearly, the radio method suffers from the rarity of the objects, and the fact that they have not yet been discovered at high redshift. The main caveats are that the lines compared come from different molecules, which might have intrinsic velocity offsets, due to several reasons, chemistry, excitation, temperature, density etc. . . When very different frequencies are compared (HI to CO for instance), the background continuum source has different sizes, and the absorbing medium is not the same. Also, the continuum source varies in both intensity and shape, and the compared lines are not always observed simultaneously. Only large statistics could smooth the errors down. On the positive side, the radio domain is favoured by the high spectral resolution and the very narrow lines due to cold gas, the exquisite precision of the frequency calibration, and the well-known rest frequencies. Also, the sensitivity of the line position to the variation of constants is much higher (by a factor 100 for NH3). Fortunately, the sensitivity of ALMA will be able to detect many more continuum sources, to search for absorption lines, and at larger redshifts. ALMA will have a much wider bandwidth, allowing the search of absorption, even if not previously detected in the optical or HI-21cm. The redshift will be obtained directly in the millimeter. It is possible to predict the number of continuum sources that can be selected as targets for absorption searches with ALMA. The density of flat-spectrum quasars has been shown to follow the same curve as optical quasars, a curve peaking at z ~ 2, very similar to the star formation history (Wall et al. 2005). They are still of significant density at z ~ 3.

Combes, Françoise

2010-11-01

162

Measurements in a High Reynolds Number Deep-Channel Viscometer  

NASA Astrophysics Data System (ADS)

Experiments were conducted using a deep-channel viscometer, which consists of an annular region where the liquid is bounded by stationary inner and outer cylinders, a rotating floor, and a free surface. The deep-channel was originally devised for the low-speed, linear regime to measure the surface shear viscosity (?^s) at a given uniform surfactant surface concentration. This apparatus, when driven faster into the nonlinear regime, produces a strong secondary flow that results in a surface velocity with a significant radial component and a nonuniform distribution of surfactant at the air/water interface. A precision viscometer was constructed of glass for optical access. The application of a new boundary-fitted, digital particle image velocimetry (DPIV) technique for measurement of the surface velocity, and second-harmonic generation (SHG) for surfactant concentration will be discussed. These measurements can produce a direct determination of surface dilatational viscosity (?^s), as well as ?^s. The present experiments were conducted at Re based on radius of up to 10^4, well beyond the Stokes flow limit of order 10^2 for this flow. Additionally, a new approach for modeling ?^s based on the functional form of ?^s will also be discussed. This method does not require DPIV or SHG, but instead relies on Navier-Stokes computations in conjunction with visualization of a seeding particle on the interface.

Hirsa, A.; Korenowski, G. M.; Ringuette, M. J.; Joshi, A. A.; Lopez, J. M.

1998-11-01

163

Microfabricated Patch Clamp Electrodes for Improved Ion Channel Protein Measurements  

NASA Astrophysics Data System (ADS)

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

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

2002-03-01

164

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.

2007-10-01

165

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

166

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

NASA Technical Reports Server (NTRS)

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

Linfield, R.; Ulvestad, J.

1988-01-01

167

Eddy diffusion coefficient for the atmosphere of Venus from radio scintillation measurements  

NASA Technical Reports Server (NTRS)

Estimates are obtained of the vertical mass eddy diffusion coefficient of the Venus atmosphere in the region of turbulence near 60 km on the basis of radio scintillations observed during radio occultation by the atmosphere. The structure constant estimated from Pioneer Venus orbit 18 entrance radio occultation measurements is used, under the assumption that the turbulence is generated by wind-shear, to derive a value of 40,000 sq cm/sec for the vertical mass eddy diffusion coefficient, together with an energy dissipation rate of 20 sq cm/sec and a temperature fluctuation dissipation rate of 0.001 K-squared/sec. Results are noted to fall within the range measured for the earth's troposphere, however, indicate that small-scale turbulence is probably the dominant mechanism for vertical transport near the tropopause in the Venus atmosphere.

Woo, R.; Ishimaru, A.

1981-01-01

168

Analysis of the Temporal Structural Function of Tropospheric Delay of Radio Waves Using Radio Measurements of the Signals from Global Navigation Satellite Systems  

NASA Astrophysics Data System (ADS)

We present the results of a three-year experimental study of propagation of decimeter radio waves in the troposphere. The time analysis of the structural function of tropospheric delay of the decimeter radio waves for the three-year measurements of the GLONASS and GPS signals in a city of Kazan is given. The tropospheric contribution to the variance of the decimeter radio-wave delay is for the first time observed to significantly differ for the variations with time scales 1 to 24 h.

Khutorov, V. E.; Teptin, G. M.

2014-11-01

169

Throughput analysis of the go-back-N protocol in fading radio channels  

Microsoft Academic Search

We derive a formula for calculating the throughput efficiency of the go-back-N (GBN) protocol when error sources in the forward and backward channels are modeled by a hidden Markov model. The result is presented in the matrix form which makes it applicable to models with any number of states. We consider also the relationship between bit-level and block-level models and

William Turin

1999-01-01

170

CARMA Memorandum Series #40 Radio Pointing Measurements for CARMA  

E-print Network

the absolute azimuth and elevation, but rather the numbers on encoders attached to both axes of each antenna to convert a source hour angle and declination into the azimuth and elevation measurements on the encoders. Many of the coefficients in the pointing models are determined using optical pointing measurements

White, Stephen

171

Microwave propagation measurements for mobile digital radio application  

Microsoft Academic Search

Measurements over a variety of urban and terrain conditions were made using a spread-spectrum waveform centered at 1370 MHz. Chip rates of 10 and 20 MHz were used, giving high time-delay resolution. The transmitter end of the measurement link was elevated and fixed while the receiver was mobile. A detailed analysis of the multipath structure was made for various terrain

D. L. Nielson

1978-01-01

172

Propagation measurements on a line-of-sight over-water radio link in Norway  

NASA Astrophysics Data System (ADS)

measurements have been carried out on a 43 km long 13 GHz 128 QAM (quadrature amplitude modulation) over-water path in the coastal regions of Norway. The measurements lasted for 18 months. The intention with the measurements on this in-service radio link was to compare results with models given by the (Recommendation International Telecommunication Union) Rec. ITU-R P. 530-15. The attenuation due to combined rain and wet snow was of special interest, since the radio link is situated in an area—Trondheimsfjorden—that has a significant amount of wet snow in winter. The radio link experienced outages due to multipath, rain and wet snow, where the latter were the predominant outage cause. The fading due to combined rain and wet snow resembled the shape of the model given in Rec. ITU-R P. 530-15, but the model underpredicts the amount of fading. In addition to outages (performance degradation and unavailability) and fading, various other parameters such as fading speed, enhancement, average fade duration, and number of fade events have been measured and compared to Rec. ITU-R P. 530-15. The radio link activity has also been compared to the weather conditions at the time for the most severe fading incidents.

Thorvaldsen, Per; Henne, Ingvar

2014-07-01

173

Atmosphere and Ionosphere of Venus from the Mariner V S-Band Radio Occultation Measurement  

Microsoft Academic Search

Measurements of the frequency, phase, and amplitude of the S-band radio signal of Mariner V as it passed behind Venus were used to obtain the effects of refraction in its atmosphere and ionosphere. Profiles of refractivity, temperature, pressure, and density in the neutral atmosphere, as well as electron density in the daytime ionosphere, are presented. A constant scale height was

Arvydas Kliore; Gerald S. Levy; Dan L. Cain; Gunnar Fjeldbo; S. I. Rasool

1967-01-01

174

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

Microsoft Academic Search

This paper presents the first S-band (2.3 GHz) radio scintillations observed in the ionosphere of Venus and discovered when the Pioneer Venus Orbiter spacecraft traversed the ionosphere of Venus. In situ plasma measurements as well as propagation calculations confirm that the scintillations are caused by electron density irregularities in the topside ionosphere of Venus below the ionopause. While these topside

Richard Woo; William L. Sjogren; A. J. Kliore; J. G. Luhmann; Larry H. Brace

1989-01-01

175

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

Microsoft Academic Search

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

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

2009-01-01

176

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

E-print Network

with existing theory. The large temporal variation of the IVDF has implications for the plasma chemistry and increases the energy of ions incident upon the sub- strate. For industrial plasma processing of poorlyTemporally resolved ion velocity distribution measurements in a radio-frequency plasma sheath B

California at Los Angles, University of

177

Operation of LOPES-30 for Polarization Measurements of the Radio Emission of Cosmic Ray Air Showers  

NASA Astrophysics Data System (ADS)

The LOPES-30 experiment, located with the air shower experiment KASCADE-Grande at Forschungszentrum Karlsruhe, Germany, is an array of 30 dipole antennas set-up to investigate the pulsed radio emission from cosmic ray air showers in the Earth's atmosphere. After one year of measurements of the East-West polarization by all 30 antennas, recently, the LOPES-30 set-up was reconfigured to perform dual-polarization measurements. Half of the antennas have been configured for measurements of the North-South polarization direction. Only by measuring at the same time both, the E-W and N-S polarization components of the radio emission, the geosynchrotron effect as the dominant emission mechanism in air showers can be verified. The status of the measurements, including the absolute calibration of the antennas, the monitoring of the environmental conditions and a preliminary analysis of the dual-polarized events are reported.

Isar, P. G.; Apel, W. D.; Arteaga, J. C.; et al.

178

Reliable intraocular pressure measurement using automated radio-wave telemetry  

PubMed Central

Purpose To present an autonomous intraocular pressure (IOP) measurement technique using a wireless implantable transducer (WIT) and a motion sensor. Methods The WIT optical aid was implanted within the ciliary sulcus of a normotensive rabbit eye after extracapsular clear lens extraction. An autonomous wireless data system (AWDS) comprising of a WIT and an external antenna aided by a motion sensor provided continuous IOP readings. The sensitivity of the technique was determined by the ability to detect IOP changes resulting from the administration of latanoprost 0.005% or dorzolamide 2%, while the reliability was determined by the agreement between baseline and vehicle (saline) IOP. Results On average, 12 diurnal and 205 nocturnal IOP measurements were performed with latanoprost, and 26 diurnal and 205 nocturnal measurements with dorzolamide. No difference was found between mean baseline IOP (13.08±2.2 mmHg) and mean vehicle IOP (13.27±2.1 mmHg) (P=0.45), suggesting good measurement reliability. Both antiglaucoma medications caused significant IOP reduction compared to baseline; latanoprost reduced mean IOP by 10% (1.3±3.54 mmHg; P<0.001), and dorzolamide by 5% (0.62±2.22 mmHg; P<0.001). Use of latanoprost resulted in an overall twofold higher IOP reduction compared to dorzolamide (P<0.001). Repeatability was ±1.8 mmHg, assessed by the variability of consecutive IOP measurements performed in a short period of time (?1 minute), during which the IOP is not expected to change. Conclusion IOP measurements in conscious rabbits obtained without the need for human interactions using the AWDS are feasible and provide reproducible results. PMID:24531415

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

2014-01-01

179

Surface figure measurements of radio telescopes with a shearing interferometer  

Microsoft Academic Search

A new technique for determining the surface figure of large submillimeter wavelength telescopes is presented, which is based on measuring the telescope's focal plane diffraction pattern with a shearing interferometer. In addition to the instrumental theory, results obtained using such an interferometer on the 10.4-m diam telescope of the Caltech Submillimeter Observatory are discussed. Using wavelengths near 1 mm, a

E. Serabyn; T. G. Phillips; C. R. Masson

1991-01-01

180

Measurement and Analysis of Wireless Channel Impairments in DSRC Vehicular Communications  

Microsoft Academic Search

We present a GPS-enabled channel sounding platform for measuring both vehicle-to-vehicle and vehicle-to- roadside wireless channels. This platform was used to conduct an extensive field measurement campaign involving vehicular wireless channels across a wide variety of speeds and line-of-sight conditions. From the data, we present statistical characterizations of several classes of these channels at 5.9 GHz. This analysis suggests that

Ian L. Tan; Wanbin Tang; Kenneth P. Laberteaux; Ahmad Bahai

2008-01-01

181

Wide Range Neutron Flux Measuring Channel for Aerospace Application  

SciTech Connect

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

Cibils, R. M.; Busto, A.; Gonella, J. L.; Martinez, R.; Chielens, A. J.; Otero, J. M.; Nunez, M. [INVAP S.E., Moreno 1089, 8400 Bariloche, Rio Negro (Argentina); Tropea, S. E. [INTI, Av. Gral. Paz 5445, 1650 San Martin, Buenos Aires (Argentina)

2008-01-21

182

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

SciTech Connect

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

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

2011-01-10

183

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

SciTech Connect

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

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

1991-07-01

184

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

NASA Astrophysics Data System (ADS)

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

Richman, Michael; Hoffman, Kara

2011-04-01

185

Meridional Winds Derived from COSMIC Radio Occultation Measurements  

NASA Astrophysics Data System (ADS)

Meridional winds derived from F2 layer peak parameters (NmF2 and hmF2) measured by the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) using the servo method, are compared at multiple locations with winds derived from incoherent scatter radar (ISR) and Fabry-Perot interferometer (FPI) measurements. The National Center for Atmospheric Research Thermosphere-Ionosphere-Electrodynamics General Circulation Model (NCAR-TIEGCM) is then employed to simulate the longitudinal variations of meridional winds. Comparisons show that there is generally good agreement between COSMIC winds and ISR, FPI and TIEGCM winds, although COSMIC winds are more equatorward near sunset hours. The COSMIC winds show significant longitudinal variations at latitude 40N (local winter) and 40S (local summer). At 40N, the COSMIC winds exhibit distinct and long duration higher velocity near the midnight hours and during late morning hours within the longitude range 110W to 20W, near the negative declination sector. Similarly, at 40S, the winds are characterized by distinct larger velocity for poleward winds from sunrise to afternoon hours within the longitude range of 120°E to 110°W, near the positive declination sector. At 40°S, another notable feature for the nighttime maximum equatorward winds is seen: there is a local time shift by about 2h from longitude range of 60W to 90E within the negative declination sector to other longitudes within positive declination sector. The NCAR TIEGCM reproduces these longitudinal configurations well, except during the daytime at 40N, and there are some discrepancies in wind magnitude. Analysis of NCAR TIEGCM simulations suggests that the longitudinal variation of meridional winds is mainly controlled by the magnetic declination.

Luan, X.; Solomon, S. C.

2007-12-01

186

Meridional winds derived from COSMIC radio occultation measurements  

NASA Astrophysics Data System (ADS)

Meridional winds at the magnetic meridian in the upper thermosphere are derived from the peak height and density of the ionospheric F2 layer as retrieved by the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) satellites for 4 months from November 2006 to February 2007. These winds (referred to as COSMIC winds) are first validated by comparison at multiple locations with winds obtained from ground-based incoherent scatter radar (ISR) and Fabry-Perot interferometer (FPI) measurements. Then longitudinal variations of these winds are investigated and compared with simulations by the National Center for Atmospheric Research Thermosphere-Ionosphere-Electrodynamics General Circulation Model (NCAR TIE-GCM). The results show generally good agreement between COSMIC winds, ground-based measurements, and the simulations. Significant longitudinal variations are presented in the COSMIC winds. At 40°N (local winter), around midnight the COSMIC winds exhibit stronger and longer-duration equatorward velocities within 110°W-20°W (large negative magnetic declination sector) than those in other longitudes; during late morning hours the poleward winds show similar longitudinal variations. At 40°S (local summer), during the daytime the poleward winds are stronger within 120°E-110°W (large positive magnetic declination sector) than in 60°W-90°E (large negative magnetic declination sector), while during the nighttime the maximum equatorward winds shifts about 2 h later in 60°W-90°E than in 120°E-110°W. Analysis of the TIE-GCM simulations suggests that the longitudinal variation of meridional winds is mainly induced by magnetic declination due to the contribution of geographic zonal wind.

Luan, Xiaoli; Solomon, Stanley C.

2008-08-01

187

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

188

Magnitude Least Squares Optimization for Parallel Radio Frequency Excitation Design Demonstrated at 7 Tesla With Eight Channels  

PubMed Central

Spatially tailored radio frequency (RF) excitations accelerated with parallel transmit systems provide the opportunity to create shaped volume excitations or mitigate inhomogeneous B1 excitation profiles with clinically relevant pulse lengths. While such excitations are often designed as a least-squares optimized approximation to a target magnitude and phase profile, adherence to the target phase profile is usually not important as long as the excitation phase is slowly varying compared with the voxel dimension. In this work, we demonstrate a method for a magnitude least squares optimization of the target magnetization profile for multichannel parallel excitation to improve the magnitude profile and reduce the RF power at the cost of a less uniform phase profile. The method enables the designer to trade off the allowed spatial phase variation for the improvement in magnitude profile and reduction in RF power. We validate the method with simulation studies and demonstrate its performance in fourfold accelerated two-dimensional spiral excitations, as well as for uniform in-plane slice selective parallel excitations using an eight-channel transmit array on a 7T human MRI scanner. The experimental results are in good agreement with the simulations, which show significant improvement in the magnitude profile and reductions in the required RF power while still maintaining negligible intravoxel phase variation. PMID:18383281

Setsompop, K.; Wald, L.L.; Alagappan, V.; Gagoski, B.A.; Adalsteinsson, E.

2009-01-01

189

MIMO capacities for different antenna arrangements based on double directional wide-band channel measurements  

Microsoft Academic Search

The performance of future wireless communication systems can be highly increased by utilizing multiple antennas at both sides of a wireless communication link. A concept for MIMO double directional wide-band channel measurements is presented and high-resolution channel parameter estimation is applied. Furthermore, a procedure, where MIMO capacities are obtained by one single SISO channel transfer function, is discussed. Finally, a

Thomas Fiigen; Gerd Sommerkorn; Jürgen Maurer; Dirk Hampicke; Werner Wiesbeck; Reiner Thomä

2002-01-01

190

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

E-print Network

Measurement and correlation of critical heat flux in two-phase micro-channel heat sinks Weilin Qu-channel heat sink containing 21 parallel 215 · 821 lm channels. Tests were performed with deionized water over.13 bar. As CHF was approached, flow instabilities induced vapor backflow into the heat sink's upstream

Qu, Weilin

191

Bilayer Measurement of Endoplasmic Reticulum Ca2+ Channels  

PubMed Central

Reconstitution of ion channels into planar lipid bilayers (also called black lipid membranes or BLM) is the most widely used method to conduct physiological studies of intracellular ion channels, including endoplasmic reticulum (ER) calcium (Ca2+) channels. The two main types of Ca2+ release channels in the ER membrane are ryanodine receptors (RyanRs) and inositol(1,4,5)-trisphosphate receptors (InsP3Rs). Use of the BLM reconstitution technique enabled the initial description of the functional properties of InsP3R and RyanR at the single-channel level more than 20 years ago. Since then, BLM reconstitution methods have been used to study physiological modulation and to perform structure–function analysis of these channels, and to study pathological changes in the function of InsP3R and RyanR in various disease states. The BLM technique has also been useful for studies of other intracellular Ca2+ channels, such as ER Ca2+ leak presenilin channels and NAADP-gated lysosomal Ca2+ channels encoded by TPC2. In this article, basic protocols used for BLM studies of ER Ca2+ channels are introduced. PMID:24184754

Bezprozvanny, Ilya

2015-01-01

192

Measuring the kinetic power of active galactic nuclei in the radio mode  

NASA Astrophysics Data System (ADS)

We have studied the relationship among nuclear radio and X-ray power, Bondi rate and the kinetic luminosity of sub-Eddington active galactic nucleus (AGN) jets, as estimated from the pdV work done to inflate the cavities and bubbles observed in the hot X-ray-emitting atmospheres of their host galaxies and clusters. Besides the recently discovered correlation between jet kinetic and Bondi power, we show that a clear correlation exists also between Eddington-scaled kinetic power and bolometric luminosity, given by log(Lkin/LEdd) = (0.49 +/- 0.07) log(Lbol/LEdd) - (0.78 +/- 0.36). The measured slope suggests that these objects are in a radiatively inefficient accretion mode, and have been used to put stringent constraints on the properties of the accretion flow. Interestingly, we found no statistically significant correlations between Bondi power and bolometric AGN luminosity, apart from that induced by their common dependence on Lkin, thus confirming the idea that most of the accretion power emerges from these systems in kinetic form. We have then analysed the relation between kinetic power and radio core luminosity. Combining the measures of jet power with estimators of the unbeamed radio flux of the jet cores as, for example, the so-called Fundamental Plane of active black holes, we are able to determine, in a statistical sense, both the probability distribution of the mean jet Lorentz factor, which peaks at ?m ~ 7, and the intrinsic relationship between kinetic and radio core luminosity (and thus the jet radiative efficiency), which we estimate as logLkin = (0.81 +/- 0.11) logLR + 11.9+4.1-4.4, in good agreement with theoretical predictions of synchrotron jet models. With the aid of these findings, quantitative assessments of kinetic feedback from supermassive black holes in the radio mode (i.e. at low dimensionless accretion rates) will be possible based on accurate determinations of the central engine properties alone, such as mass, radio core and/or X-ray luminosity. As an example, we suggest that Sgr A* may follow the same correlations of radio-mode AGN, based on its observed radiative output as well as on estimates of the accretion rate both at the Bondi radius and in the inner flow. If this is the case, the supermassive black hole in the Galactic Centre is the source of ~5 × 1038 erg s-1 of mechanical power, equivalent to about 1.5 supernovae every 105 yr.

Merloni, Andrea; Heinz, Sebastian

2007-10-01

193

The application of compressive sampling to radio astronomy II: Faraday rotation measure synthesis  

E-print Network

Faraday rotation measure (RM) synthesis is an important tool to study and analyze galactic and extra-galactic magnetic fields. Since there is a Fourier relation between the Faraday dispersion function and the polarized radio emission, full reconstruction of the dispersion function requires knowledge of the polarized radio emission at both positive and negative square wavelengths $\\lambda^2$. However, one can only make observations for $\\lambda^2 > 0$. Furthermore observations are possible only for a limited range of wavelengths. Thus reconstructing the Faraday dispersion function from these limited measurements is ill-conditioned. In this paper, we propose three new reconstruction algorithms for RM synthesis based upon compressive sensing/sampling (CS). These algorithms are designed to be appropriate for Faraday thin sources only, thick sources only, and mixed sources respectively. Both visual and numerical results show that the new RM synthesis methods provide superior reconstructions of both magnitude and p...

Li, Feng; Cornwell, Tim J; de Hoog, Frank

2011-01-01

194

The application of compressive sampling to radio astronomy. II. Faraday rotation measure synthesis  

NASA Astrophysics Data System (ADS)

Faraday rotation measure (RM) synthesis is an important tool to study and analyze galactic and extra-galactic magnetic fields. Since there is a Fourier relation between the Faraday dispersion function and the polarized radio emission, full reconstruction of the dispersion function requires knowledge of the polarized radio emission at both positive and negative square wavelengths ?2. However, one can only make observations for ?2 > 0. Furthermore observations are possible only for a limited range of wavelengths. Thus reconstructing the Faraday dispersion function from these limited measurements is ill-conditioned. In this paper, we propose three new reconstruction algorithms for RM synthesis based upon compressive sensing/sampling (CS). These algorithms are designed to be appropriate for Faraday thin sources only, thick sources only, and mixed sources respectively. Both visual and numerical results show that the new RM synthesis methods provide superior reconstructions of both magnitude and phase information than RM-CLEAN.

Li, F.; Brown, S.; Cornwell, T. J.; de Hoog, F.

2011-07-01

195

Simultaneous measurements of the frequency and bearing of h.f. radio waves  

Microsoft Academic Search

The presence of traveling ionospheric disturbances (t.i.d.s) at the reflection point of h.f. radio waves, propagated at oblique incidence, has been monitored by means of a Doppler-frequency sounder. The bearing error measured by a direction finder at one end of the oblique path is shown to be correlated with the t.i.d. activity at the path mid-point. The magnitudes of the

T. B. Jones; E. Kantarizis; A. D. Morgan

1975-01-01

196

Measurements of 3-D Sunspot Coronal Magnetic Fields From Coordinated SOHO EUV and VLA Radio Observations  

Microsoft Academic Search

Three-dimensional sunspot coronal magnetograms were derived from coordinated extreme-ultraviolet (EUV) and radio observations of NOAA region 8108 (N21 E18) on 1997 November 18. The EUV spectra and images, obtained with the Coronal Diagnostic Spectrometer (CDS) and the Extreme-ultraviolet Imaging Telescope (EIT) aboard the Solar and Heliospheric Observatory (SOHO) satellite, were used to derive differential emission measure (DEM) distributions for each

J. W. Brosius; E. Landi; J. W. Cook; J. Newmark; N. Gopalswamy; A. Lara

2001-01-01

197

Satellite measurements of the HF radio environment in the topside ionosphere  

Microsoft Academic Search

Measurements made on board the orbiting Air Force meteorological satellite equipped with a high-frequency (HF) receiver have been studied in order to describe the HF radio environment at the satellite height. The satellite is in a sun-synchronous dawn-dusk orbit at a height of nearly 500 nmi (860 km) above the surface on the earth. The receiver sweeps repeatedly through the

C. M. Rush; A. L. Snyder; E. Ziemba; V. Patterson; T. Tascione; D. Nelson

1980-01-01

198

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

199

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

NASA Technical Reports Server (NTRS)

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

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

1974-01-01

200

Experimental Measurements and Modeling for Vehicle-to-Vehicle Dedicated Short Range Communication (DSRC) Wireless Channels  

Microsoft Academic Search

The dedicated short range communication (DSRC) standard (also known as IEEE 802.11p) can be used to enable a number of vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) wireless radio communication based active safety and telematics applications. In this paper, we briefly document various experimental measurement scenarios and characterize performance of the DSRC standard based radio modules in ldr Additive White Gaussian Noise

Vikas Kukshya; Hariharan Krishnan

2006-01-01

201

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

202

Contamination of Cluster Radio Sources in the Measurement of the Thermal Sunyaev-Zel'dovich Angular Power Spectrum  

E-print Network

We present a quantitative estimate of the confusion of cluster radio halos and galaxies in the measurement of the angular power spectrum of the thermal Sunyaev-Zel'dovich (SZ) effect. To achieve the goal, we use a purely analytic approach to both radio sources and dark matter of clusters by incorporating empirical models and observational facts together with some theoretical considerations. It is shown that the correction of cluster radio halos and galaxies to the measurement of the thermal SZ angular power spectrum is no more than 20% at $l>2000$ for observing frequencies $\

Wei Zhou; Xiang-Ping Wu

2003-09-26

203

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

204

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

NASA Technical Reports Server (NTRS)

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

Mertel, H. K.

1981-01-01

205

Cassegrainian/Gregorian-type null correctors for surface measurements of radio telescope reflectors.  

PubMed

The (sub)millimeter wavelength radio observatory of the next generation will probably be an interferometer array of some 50 telescopes with parabolic reflectors 10-15 m in diameter. At this scale of mass production it is convenient to have at hand for workshop assembly a reflector surface measurement technique that is precise and easy to operate. We discuss the possibility of reflector measurements based on 10.6-microm CO2 laser interferometry using Cassegrainian/Gregorian-type null correctors. PMID:18259343

Greve, A

1997-08-01

206

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

207

The shape of the radio wavefront of extensive air showers as measured with LOFAR  

NASA Astrophysics Data System (ADS)

Extensive air showers, induced by high energy cosmic rays impinging on the Earth’s atmosphere, produce radio emission that is measured with the LOFAR radio telescope. As the emission comes from a finite distance of a few kilometers, the incident wavefront is non-planar. A spherical, conical or hyperbolic shape of the wavefront has been proposed, but measurements of individual air showers have been inconclusive so far. For a selected high-quality sample of 161 measured extensive air showers, we have reconstructed the wavefront by measuring pulse arrival times to sub-nanosecond precision in 200 to 350 individual antennas. For each measured air shower, we have fitted a conical, spherical, and hyperboloid shape to the arrival times. The fit quality and a likelihood analysis show that a hyperboloid is the best parameterization. Using a non-planar wavefront shape gives an improved angular resolution, when reconstructing the shower arrival direction. Furthermore, a dependence of the wavefront shape on the shower geometry can be seen. This suggests that it will be possible to use a wavefront shape analysis to get an additional handle on the atmospheric depth of the shower maximum, which is sensitive to the mass of the primary particle.

Corstanje, A.; Schellart, P.; Nelles, A.; Buitink, S.; Enriquez, J. E.; Falcke, H.; Frieswijk, W.; Hörandel, J. R.; Krause, M.; Rachen, J. P.; Scholten, O.; ter Veen, S.; Thoudam, S.; Trinh, T. N. G.; van den Akker, M.; Alexov, A.; Anderson, J.; Avruch, I. M.; Bell, M. E.; Bentum, M. J.; Bernardi, G.; Best, P.; Bonafede, A.; Breitling, F.; Broderick, J.; Brüggen, M.; Butcher, H. R.; Ciardi, B.; de Gasperin, F.; de Geus, E.; de Vos, M.; Duscha, S.; Eislöffel, J.; Engels, D.; Fallows, R. A.; Ferrari, C.; Garrett, M. A.; Grießmeier, J.; Gunst, A. W.; Hamaker, J. P.; Hoeft, M.; Horneffer, A.; Iacobelli, M.; Juette, E.; Karastergiou, A.; Kohler, J.; Kondratiev, V. I.; Kuniyoshi, M.; Kuper, G.; Maat, P.; Mann, G.; McFadden, R.; McKay-Bukowski, D.; Mevius, M.; Munk, H.; Norden, M. J.; Orru, E.; Paas, H.; Pandey-Pommier, M.; Pandey, V. N.; Pizzo, R.; Polatidis, A. G.; Reich, W.; Röttgering, H.; Scaife, A. M. M.; Schwarz, D.; Smirnov, O.; Stewart, A.; Steinmetz, M.; Swinbank, J.; Tagger, M.; Tang, Y.; Tasse, C.; Toribio, C.; Vermeulen, R.; Vocks, C.; van Weeren, R. J.; Wijnholds, S. J.; Wucknitz, O.; Yatawatta, S.; Zarka, P.

2015-02-01

208

AN INTERLABORATORY COMPARISON PROGRAMME ON RADIO FREQUENCY ELECTROMAGNETIC FIELD MEASUREMENTS: THE SECOND ROUND OF THE SCHEME.  

PubMed

The second round of an interlaboratory comparison scheme on radio frequency electromagnetic field measurements has been conducted in order to evaluate the overall performance of laboratories that perform measurements in the vicinity of mobile phone base stations and broadcast antenna facilities. The participants recorded the electric field strength produced by two high frequency signal generators inside an anechoic chamber in three measurement scenarios with the antennas transmitting each time different signals at the FM, VHF, UHF and GSM frequency bands. In each measurement scenario, the participants also used their measurements in order to calculate the relative exposure ratios. The results were evaluated in each test level calculating performance statistics (z-scores and En numbers). Subsequently, possible sources of errors for each participating laboratory were discussed, and the overall evaluation of their performances was determined by using an aggregated performance statistic. A comparison between the two rounds proves the necessity of the scheme. PMID:25205832

Nicolopoulou, E P; Ztoupis, I N; Karabetsos, E; Gonos, I F; Stathopulos, I A

2014-09-01

209

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

NASA Astrophysics Data System (ADS)

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

Lee, Charles A.; Chen, Guangye; Arefiev, Alexey V.; Bengtson, Roger D.; Breizman, Boris N.

2011-01-01

210

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

Microsoft Academic Search

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

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

1993-01-01

211

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

SciTech Connect

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

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

1989-02-01

212

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

213

Induced current measurements in whole body exposure condition to radio frequency electric fields.  

PubMed

The current induced in a human exposed to radio frequency electric fields has been studied by the use of a stripline, in which whole body exposure to vertical electric fields (3-27 MHz) can be produced. We have examined two different techniques to measure the induced current; parallel plate meters and current probes. When the subject has good connection to the ground, the choice of measurement technique is not crucial, since there are only minor differences in readings between the instruments. But when the subject is wearing shoes and/or standing on a wooden plate, the difference between the instruments increases considerably. The difference can mainly be explained by the capacitive coupling between the parallel plate meters and the ground; therefore, the current probes are preferred when the subject does not have perfect contact with the ground. Since the International Commission on Non-Ionizing Radiation Protection guidelines demand measurements of induced current in humans exposed to radio frequency fields in the range of 10-110 MHz, the importance of finding an appropriate measurement procedure becomes apparent. PMID:11748673

Wilén, J; Mild, K H; Paulsson, L E; Anger, G

2001-12-01

214

The software radio architecture  

Microsoft Academic Search

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

J. Mitola

1995-01-01

215

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

NASA Astrophysics Data System (ADS)

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

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

2006-12-01

216

Plan View and Profile Relations: Measuring Correlation Between Channel Profile and Network Morphology  

NASA Astrophysics Data System (ADS)

In this research, we explore the relationships between channel network attributes and the corresponding channel profile geometries using high-resolution digital topography and model-generated synthetic topographies. This combined analysis addresses one of the long-standing questions in geomorphology relating to the mechanistic significance of various plan-view channel network geometry measures. Statistically based numerical studies suggest that Hortonian measures of channel network architecture (e.g. bifurcation ratio, area ratio, and length ratio) describe virtually all possible network geometries, and so are not diagnostic when evaluating the origins of the geometry of a particular network. We further explore this hypothesis by examining the correlation between Hack exponent, the channel profile characteristics, and process changes (i.e debris flow vs. fluvial flows) within the landscape. Analysis of high resolution DEMs as well as modeled landscapes, suggests that the Hack exponent is likewise insensitive to changes in the channel profile concavity. In contrast, we find that changes in the concavity of channel profiles apparently impacts the spatial distribution of plan-view junction angles of joining stream segments throughout a catchment. In the context of previous work, this angle might be expected to be a function of the ratio between the slopes of the adjoined channels. Channel concavity determines downstream change in this ratio for channel segments throughout the basin, and so such a metric might be used to explicitly link profile channel geometries to plan-view network geometries. Because profile geometries may change with different advective mass transport processes, such a metric may provide a link between the processes that transport material across a landscape, the profile geometry of channels through which these flows traverse, and the overall drainage network geometry. Additional numerical and field data based analysis are required to further explore the sensitivity of the junction angle, as well as other measures, to process changes along the channel network.

Shelef, E.; Hilley, G. E.

2010-12-01

217

SUPERRESOLUTION TECHNIQUE FOR ESTIMATING MIMO WLAN CHANNELS WITH APPLICATION TO 5 GHZ CHANNEL MEASUREMENTS  

E-print Network

. The method is based on the non­stationarity of the channel impulse reponse over time. We then use the method of impulses to model the reflections from objects and a ''slow'' (f rate over a long period of time. We use the ESPRIT method, but other techniques such as MUSIC and MLE

Leshem, Amir

218

Sub-micrometer fluidic channel for measuring photon emitting entities  

DOEpatents

A nanofluidic channel fabricated in fused silica with an approximately 500 nm square cross section was used to isolate, detect and identify individual quantum dot conjugates. The channel enables the rapid detection of every fluorescent entity in solution. A laser of selected wavelength was used to excite multiple species of quantum dots and organic molecules, and the emission spectra were resolved without significant signal rejection. Quantum dots were then conjugated with organic molecules and detected to demonstrate efficient multicolor detection. PCH was used to analyze coincident detection and to characterize the degree of binding. The use of a small fluidic channel to detect quantum dots as fluorescent labels was shown to be an efficient technique for multiplexed single molecule studies. Detection of single molecule binding events has a variety of applications including high throughput immunoassays.

Stavis, Samuel M; Edel, Joshua B; Samiee, Kevan T; Craighead, Harold G

2014-11-18

219

Atmospheric channel performance measurements at 10 to 100 GHz  

NASA Astrophysics Data System (ADS)

A diagnostic probe designed to investigate propagation at millimeter wavelengths was operated on 11.8 and 27.2-km line-of-sight paths near Boulder, CO. Fully coherent carrier wave channels at 11.4, 28.8, and 96.1 GHz provide data to analyze fade mechanisms and evaluate frequency dependent performance characteristics of the link. Data during fog, snow, rain, and clear-air fade events are included with statistical analyses of event occurrence, signal levels, and bit error rates. Time delay distortion and amplitude dispersion on the channel are also examined during fading events by the wide-band digital channel operated as an impulse probe. Rain attenuation, path absorption due to water vapor content, and seasonal variations as a function of frequency are presented and described.

Espeland, R. H.; Violette, E. J.; Allen, K. C.

1984-04-01

220

Rayleigh beacon for measuring the surface profile of a radio telescope.  

PubMed

Millimeter-wavelength Rayleigh scattering from water droplets in a cloud is proposed as a means of generating a bright beacon for measuring the surface profile of a radio telescope. A ?=3??mm transmitter, with an output power of a few watts, illuminating a stratiform cloud, can generate a beacon with the same flux as Mars in 10 GHz bandwidth, but the beacon has a narrow line width, so it is extremely bright. The key advantage of the beacon is that it can be used at any time, and positioned anywhere in the sky, as long as there are clouds. PMID:25607971

Padin, S

2014-12-01

221

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

222

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

NASA Technical Reports Server (NTRS)

The observation of S-band (2.3 GHz) radio scintillations in the ionosphere of Venus by the Pioneer Venus Orbiter is reported. In situ plasma measurements and propagation calculations show that the scintillations are caused by electron density irregularities in the topside ionosphere of Venus below the ionopause. It is suggested that these topside plasma irregularities are associated with the penetration of large-scale magnetic fields in the ionosphere. It is found that the disturbed plasma and the scintillations are a manifestation of high-dynamic solar wind interaction with the ionosphere.

Woo, Richard; Sjogren, William L.; Kliore, Arvydas J.; Luhmann, Janet G.; Brace, Larry H.

1989-01-01

223

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

224

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

E-print Network

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

Gorham, P W; Odian, A; Williams, D; Besson, D; Frichter, G; Tantawi, S G; Gorham, Peter; Saltzberg, David; Odian, Allen; Williams, Dawn; Besson, David; Frichter, George; Tantawi, Sami

2002-01-01

225

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

E-print Network

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

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

2002-01-23

226

The Q/U Imaging Experiment: Polarization Measurements of Radio Sources at 43 and 95 GHz  

E-print Network

We present polarization measurements of extragalactic radio sources observed during the Cosmic Microwave Background polarization survey of the Q/U Imaging Experiment (QUIET), operating at 43 GHz (Q-band) and 95 GHz (W-band). We examine sources selected at 20 GHz from the public, $>$40 mJy catalog of the Australia Telescope (AT20G) survey. There are $\\sim$480 such sources within QUIET's four low-foreground survey patches, including the nearby radio galaxies Centaurus A and Pictor A. The median error on our polarized flux density measurements is 30--40 mJy per Stokes parameter. At S/N $> 3$ significance, we detect linear polarization for seven sources in Q-band and six in W-band; only $1.3 \\pm 1.1$ detections per frequency band are expected by chance. For sources without a detection of polarized emission, we find that half of the sources have polarization amplitudes below 90 mJy (Q-band) and 106 mJy (W-band), at 95% confidence. Finally, we compare our polarization measurements to intensity and polarization meas...

Huffenberger, K M; Bischoff, C; Buder, I; Chinone, Y; Cleary, K; Kusaka, A; Monsalve, R; Næss, S K; Newburgh, L B; Reeves, R; Ruud, T M; Wehus, I K; Zwart, J T L; Dickinson, C; Eriksen, H K; Gaier, T; Gundersen, J O; Hasegawa, M; Hazumi, M; Miller, A D; Radford, S J E; Readhead, A C S; Staggs, S T; Tajima, O; Thompson, K L

2014-01-01

227

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

Microsoft Academic Search

We have investigated the possibility that large rock salt formations might be suitable as target masses for detection of neutrinos of energies about 10PeV and above. In neutrino interactions at these energies, the secondary electromagnetic cascade produces a coherent radio pulse well above ambient thermal noise via the Askaryan effect. We describe measurements of radio-frequency attenuation lengths and ambient thermal

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

2002-01-01

228

The Pioneer 10 radio occultation measurements of the ionosphere of Jupiter  

NASA Technical Reports Server (NTRS)

Data from the Pioneer 10 radio occultation measurements are utilized to study the vertical electron number density distribution in the Jovian ionosphere. The immersion measurements were made at 26 North latitude in the late afternoon local time. The solar zenith angle in this region was 81 deg. Emersion measurements were made at 58 North latitude near the morning terminator where the solar zenith angle was 95 deg. The detectable portion of the Jovian ionosphere consists of a number of layers distributed over an altitude range of more than 3000 km. The maximum density appears to be on the order of 30,000 electrons per cu cm. Assuming that H(+) is the principal ion in the upper portion of the ionosphere yields a topside plasma temperature of 900 plus or minus 400 K.

Fjeldbo, G.; Kliore, A.; Seidel, B.; Sweetnam, D.; Cain, D.

1975-01-01

229

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

NASA Technical Reports Server (NTRS)

Remote sensing radio occultation measurements are used here to study magnetization of the ionospheres of Venus and Mars. For Venus, the measurements yield results on frequency of occurrence of magnetization during solar maximum that are similar to those obtained from Pioneer Venus in situ magnetic field measurements. During solar minimum, magnetization of the Venus ionosphere is more pervasive than at solar maximum. Magnetization extends to higher solar zenith angles and appears stronger than at solar maximum. These results confirm that during solar minimum the high solar wind dynamic pressure state is more prevalent at Venus because the ionospheric plasma pressure is weaker than at solar maximum. Comparison of a large number of electron density profiles of Mars with those of Venus shows an absence of the ledge and disturbed topside plasma observed in the Venus profiles. These results do not constitute evidence against magnetization of the ionosphere of Mars.

Woo, Richard; Kliore, Arvydas J.

1991-01-01

230

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

NASA Astrophysics Data System (ADS)

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

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

2012-05-01

231

Direction of Arrival Measurements of Auroral Medium Frequency Burst Radio Emissions at Toolik Lake, AK  

NASA Astrophysics Data System (ADS)

MF burst is an impulsive radio emission of auroral origin detected by ground-based instruments approximately between 1,300 and 3,700 kHz, and associated with substorm onsets. Its exact generation mechanism is unknown, though it has been speculated that it arises from mode conversion radiation. To discover the generation mechanism and the relation of MF burst to auroral processes, Dartmouth has deployed radio interferometers in Alaska, Northern Canada, Greenland, and Antarctica, including a three-element interferometer deployed at Toolik Lake Field Station in Alaska in 2006. This instrument measured spectra, amplitudes, and directions of arrival (DOA's) of over 47 MF burst events occurring between November 30, 2006 and May 26, 2007. These represent the first DOA measurements ever reported for the impulsive MF burst phenomenon. Preliminary analysis shows that the events originated from a wide range of directions in the sky, with all azimuths represented in the distribution of DOA's. The DOA of each individual event is well-defined, however. Many events show apparent motion, with southward motions more common than northward among the subset of events analyzed so far. Some of the events were detected simultaneously on an interferometer deployed at Kaktovik, Alaska, 400 km away. The all-sky imager at Toolik Lake was also operational for some events. Further analysis of these data promises to reveal first information about the locations and motions of MF burst sources, a first step towards discovering the generation mechanism of this mysterious radio emission and its relation to auroral processes.

Bunch, N. L.; Labelle, J. W.; Hughes, J. M.; Weatherwax, A. T.; Ye, S.; Lummerzheim, D.

2007-12-01

232

The helium to hydrogen ratio in Saturn's atmosphere from Cassini CIRS and radio science measurement  

NASA Astrophysics Data System (ADS)

The determination of the He H 2 ratio in Jupiter and Saturn is a key parameter for modeling the internal structure of the planets and understanding their evolution It may be determined from two methods In the first approach the thermal profile of the atmosphere of the planet is retrieved from occultations of the radio signal emitted by a spacecraft This profile is very sensitive to the assumed He H 2 ratio As a consequence the calculated thermal infrared spectrum also depends upon this ratio The best fit of the measured spectrum in the region where the opacity is due only to H 2 and He then provides the value of the helium abundance in the troposphere of the planet This method was employed by Conrath et al 1984 for Saturn using Voyager data to derive a very low He H 2 ratio 0 034 per volume that is difficult to reconcile with plausible theories of the evolution of the planet The second method uses an inversion algorithm for the simultaneous retrieval of temperature the para H 2 fraction and the helium abundance from measured infrared spectra alone Conrath and Gautier 2000 This method requires well-calibrated spectra such as those obtained by the IRIS instrument aboard Voyager Conrath and Gautier 2000 derived from IRIS spectra of Saturn a He H 2 ratio between 0 11 and 0 16 corresponding to a helium mass fraction of Y 0 18-0 25 The Radio Science experiment aboard Cassini has acquired several radio occultation profiles near the equator We present here the preliminary results of a combined

Gautier, D.; Conrath, B.; Flasar, M.; Achterberg, R.; Schinder, P.; Kliore, A.; Cassini Cirs; Radio Science Teams

233

BEAM MEASUREMENT SYSTEM OF VEPP-2000 INJECTION CHANNELS*  

E-print Network

. Kozak, I. Ostanin, V. Repkov, Budker Institute of Nuclear Physics, Lavrentev av. 11, 630090, Novosibirsk]. They have 15 m length and 12Ã?6 mm2 physical aperture. Beams, stored in the booster, are injected. Both DC and pulsed (quads and dipoles) magnets (figure 2) are used in channel's optics. Figure 1

Kozak, Victor R.

234

Measurement and prediction of pressure drop in two-phase micro-channel heat sinks  

E-print Network

Measurement and prediction of pressure drop in two-phase micro-channel heat sinks Weilin Qu, Issam be eliminated simply by throttling the flow upstream of the heat sink. Different methods for predicting two-phase pressure drop are assessed for suitability to micro-channel heat-sink design. First, generalized two

Qu, Weilin

235

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

E-print Network

DOWNSTREAM CHANNEL CHANGES AFTER A SMALL DAM REMOVAL: USING AERIAL PHOTOS AND MEASUREMENT ERROR and Ecological Engineering, Oregon State University, Corvallis, OR, USA ABSTRACT Dam removal is often implemented to assess downstream channel changes associated with a small dam removal. The Brownsville Dam, a 2.1 m tall

Tullos, Desiree

236

Turbulent structures in partly vegetated open-channel flows with LDA and PI V measurements  

Microsoft Academic Search

The effects of vegetation growing in rivers in and at ihe edge of the water on turbulent structures and the associated sediment transport are not claritied yet. in spite of their importance for hydraulics and river engineering. In this study, turbulence measurements of open-channel flows with a vegetated zone at a half channel width were conducted by making use of

Iehisa Nezu; Kouki Onitsuka

2001-01-01

237

CDF Note 11025 Measurement of Single Top s-channel Cross Section  

E-print Network

strategy and background model method as the WH analysis [6] at CDF. II. DATA SAMPLE AND EVENT SELECTIONCDF Note 11025 Measurement of Single Top s-channel Cross Section in Lepton plus Jet Channel Using Ldt = 9.4 fb-1 CDF Data The CDF Collaboration URL http://www-cdf.fnal.gov (Dated: August 9, 2013) We

Quigg, Chris

238

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

NASA Astrophysics Data System (ADS)

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. The radio data are digitally beam-formed before the spectra are determined by sub-band filtering and fast Fourier transformation. Results: The resulting electric field spectra fall off to higher frequencies. An average electric field spectrum is fitted with an exponential E?=K\\cdotexp (?/MHz/?) and ?=-0.017±0.004, or alternatively, with a power law ??=K\\cdot?? and a spectral index of ?=-1±0.2. 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). For the analyzed sample of LOPES events, we do not find any significant dependence of the spectral slope on the electric field amplitude, the azimuth angle, the zenith angle, the curvature radius, nor on the average distance of the antennae from the shower core position. But 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. Table 2 and Fig. 14 are only available in electronic form at http://www.aanda.org

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

2008-09-01

239

Measuring a Cherenkov ring in the radio emission from air showers at 110-190 MHz with LOFAR  

NASA Astrophysics Data System (ADS)

Measuring radio emission from air showers offers a novel way to determine properties of the primary cosmic rays such as their mass and energy. Theory predicts that relativistic time compression effects lead to a ring of amplified emission which starts to dominate the emission pattern for frequencies above ? 100 MHz. In this article we present the first detailed measurements of this structure. Ring structures in the radio emission of air showers are measured with the LOFAR radio telescope in the frequency range of 110-190 MHz. These data are well described by CoREAS simulations. They clearly confirm the importance of including the index of refraction of air as a function of height. Furthermore, the presence of the Cherenkov ring offers the possibility for a geometrical measurement of the depth of shower maximum, which in turn depends on the mass of the primary particle.

Nelles, A.; Schellart, P.; Buitink, S.; Corstanje, A.; de Vries, K. D.; Enriquez, J. E.; Falcke, H.; Frieswijk, W.; Hörandel, J. R.; Scholten, O.; ter Veen, S.; Thoudam, S.; van den Akker, M.; Anderson, J.; Asgekar, A.; Bell, M. E.; Bentum, M. J.; Bernardi, G.; Best, P.; Bregman, J.; Breitling, F.; Broderick, J.; Brouw, W. N.; Brüggen, M.; Butcher, H. R.; Ciardi, B.; Deller, A.; Duscha, S.; Eislöffel, J.; Fallows, R. A.; Garrett, M. A.; Gunst, A. W.; Hassall, T. E.; Heald, G.; Horneffer, A.; Iacobelli, M.; Juette, E.; Karastergiou, A.; Kondratiev, V. I.; Kramer, M.; Kuniyoshi, M.; Kuper, G.; Maat, P.; Mann, G.; Mevius, M.; Norden, M. J.; Paas, H.; Pandey-Pommier, M.; Pietka, G.; Pizzo, R.; Polatidis, A. G.; Reich, W.; Röttgering, H.; Scaife, A. M. M.; Schwarz, D.; Smirnov, O.; Stappers, B. W.; Steinmetz, M.; Stewart, A.; Tagger, M.; Tang, Y.; Tasse, C.; Vermeulen, R.; Vocks, C.; van Weeren, R. J.; Wijnholds, S. J.; Wucknitz, O.; Yatawatta, S.; Zarka, P.

2015-05-01

240

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

NASA Astrophysics Data System (ADS)

LOPES is a digital radio interferometer located at Karlsruhe Institute of Technology (KIT), Germany, that measures radio emission from extensive air showers at MHz frequencies in coincidence with KASCADE-Grande. In this article, we explore a method (slope method) that 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 /cm2, 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 /cm2 for Xmax, despite strong human-made noise at the LOPES site.

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

2014-09-01

241

Measuring a Cherenkov ring in the radio emission from air showers at 110-190 MHz with LOFAR  

E-print Network

Measuring radio emission from air showers offers a novel way to determine properties of the primary cosmic rays such as their mass and energy. Theory predicts that relativistic time compression effects lead to a ring of amplified emission which starts to dominate the emission pattern for frequencies above ~100 MHz. In this article we present the first detailed measurements of this structure. Ring structures in the radio emission of air showers are measured with the LOFAR radio telescope in the frequency range of 110 - 190 MHz. These data are well described by CoREAS simulations. They clearly confirm the importance of including the index of refraction of air as a function of height. Furthermore, the presence of the Cherenkov ring offers the possibility for a geometrical measurement of the depth of shower maximum, which in turn depends on the mass of the primary particle.

Nelles, A; Buitink, S; Corstanje, A; de Vries, K D; Enriquez, J E; Falcke, H; Frieswijk, W; Hörandel, J R; Scholten, O; ter Veen, S; Thoudam, S; Akker, M van den; Anderson, J; Asgekar, A; Bell, M E; Bentum, M J; Bernardi, G; Best, P; Bregman, J; Breitling, F; Broderick, J; Brouw, W N; Brüggen, M; Butcher, H R; Ciardi, B; Deller, A; Duscha, S; Eislöffel, J; Fallows, R A; Garrett, M A; Gunst, A W; Hassall, T E; Heald, G; Horneffer, A; Iacobelli, M; Juette, E; Karastergiou, A; Kondratiev, V I; Kramer, M; Kuniyoshi, M; Kuper, G; Maat, P; Mann, G; Mevius, M; Norden, M J; Paas, H; Pandey-Pommier, M; Pietka, G; Pizzo, R; Polatidis, A G; Reich, W; Röttgering, H; Scaife, A M M; Schwarz, D; Smirnov, O; Stapper, B W; Steinmetz, M; Stewart, A; Tagger, M; Tang, Y; Tasse, C; Vermeulen, R; Vocks, C; van Weeren, R J; Wijnholds, S J; Wucknitz, O; Yatawatta, S; Zarka, P

2014-01-01

242

Emissive sheath measurements in the afterglow of a radio frequency plasma  

SciTech Connect

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., E-mail: sheehanj@umich.edu; Hershkowitz, N. [Nuclear Engineering and Engineering Physics, University of Wisconsin—Madison, Madison, Wisconsin 53706 (United States)] [Nuclear Engineering and Engineering Physics, University of Wisconsin—Madison, Madison, Wisconsin 53706 (United States); Barnat, E. V.; Weatherford, B. R. [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)] [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States); Kaganovich, I. D. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540 (United States)] [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540 (United States)

2014-01-15

243

The occultation of Mariner 10 by Mercury. [planetary radius and atmospheric radio measurements  

NASA Technical Reports Server (NTRS)

Analysis of Mariner 10 dual-frequency radio-occultation recordings has yielded new information on the radius and atmosphere of Mercury. The ingress measurements, which were conducted near 1.1 deg north latitude and 67.4 deg east longitude on the night side of the planet, gave a value for the radius of 2439.5 + or - 1 km. Egress near 67.6 deg north latitude and 258.4 deg east longitude on the sunlit side yielded a radius of 2439.0 + or - 1 km. The atmospheric measurements showed the electron density to be less than 1000 per cu cm on both sides of the planet. From the latter result one may infer an upper limit to the dayside surface gas density of 1 million molecules per cu cm.

Fjeldbo, G.; Kliore, A.; Sweetnam, D.; Esposito, P.; Seidel, B.; Howard, T.

1976-01-01

244

An Improved Method for the Evaluation of Uncertainty of Channel Power Measurement With a Spectrum Analyzer  

Microsoft Academic Search

This paper discusses issues in the uncertainty of power measurement performed with a superheterodyne spectrum analyzer. In particular, the channel power technique is considered, and an original and effective method is proposed based on the \\

Matteo Bertocco; Alessandro Sona; Piero Zanchetta

2007-01-01

245

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

246

Digital Broadcasting Television Channel Measurements and Characterization for SIMO Mobile Reception  

Microsoft Academic Search

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

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

2006-01-01

247

Mariners 6 and 7: radio occultation measurements of the atmosphere of Mars.  

PubMed

Radio occultation measurements with Mariners 6 and 7 provided refractivity data in the atmosphiere of Mars at four points above its surface. For an atmosphere consisting predominantly of carbon dioxide, surface pressures between 6 and 7 millibars are obtained at three of the points of measurement, and 3.8 at the fourth, indicating an elevation of 5 to 6 kilometers. The temperature profile measured by Mariner 6 near the equator in the daytime indicates temperatures in the stratosphere about 100 degrees K warmer than those predicted by theory. The measurements of Mariner 6 taken at 79 degrees N at the beginning of polar night indicate that conditions are favorable for the condensation of carbon dioxide at almost all altitudes. Mariner 7 measurements taken at 58 degrees S in daytime and 38 degrees N at night also show that carbon dioxide condensation is possible at altitudes above about 25 kilometers. Measurements of the electron density in the ionosphere show that the upper atmosphere is substantially warmer than it was in 1965, possibly because of increased solar activity and closer proximity to the sun. PMID:17744965

Kliore, A; Fjeldbo, G; Seidel, B L; Rasool, S I

1969-12-12

248

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

NASA Technical Reports Server (NTRS)

From 1991 to 1993 the fractional frequency stability of the operational Radio Science System was measured at DSS's 15, 45, and 65. These stations are designed to have the most stable uplink and downlink equipment in the Deep Space Network (DSN). Some measurements were performed when the antenna was moving and the frequency was ramped. The stability, including contributions of all elements in the station except for the antenna and the hydrogen maser, was measured to be 0.3 to 1.3 x 10(exp -15) when the frequency was fixed, and 0.6 to 6.0 x 10(exp -15) when the frequency was ramped (sample interval, 1000 sec). Only one measurement out of fifteen exceeded specification. In all other cases, when previous measurements on the antenna and the hydrogen maser were added, a total system stability requirement of 5.0 x 10(exp -15) as met. In addition, ambient temperature was found to cause phase variation in the measurements at a rate of 5.5 deg of phase per deg C.

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

1993-01-01

249

Structure of the atmosphere of Jupiter from Pioneer 10 and 11 radio occultation measurements  

NASA Technical Reports Server (NTRS)

A technique for incorporating effects of the oblateness of Jupiter's atmosphere into the data analysis procedure for radio-occultation measurements is described which makes use of a spherical harmonic representation of the gravity field to compute the shape of the planet. With this technique, the center of refraction is located by the radius of curvature and the normal direction at the closest approach point of the ray. The present technique, a subsequent approximation involving the use of a constant center of refraction, and the Abel integral transform inversion method for spherical planets are applied to Pioneer 10 and 11 data. All the intermediate results obtained show a temperature inversion between 10 and 100 mb, with temperatures from 130 to 170 K at 10 mb and from 80 to 120 K at 100 mb. Comparison of the radio-occultation profiles with radiative-convective equilibrium models and the temperature profile based on Pioneer 10 IR radiometer data indicates good agreement between the models and the occultation results.

Kliore, A. J.; Woiceshyn, P. M.

1976-01-01

250

On Equalization and Beamforming for Mobile Radio  

E-print Network

On Equalization and Beamforming for Mobile Radio Applications Erik Lindskog Systems and Control decision feedback equal­ izers, for IIR channels with colored noise. Given a probabilistic measure of model equations define a large class of equalizers, with DFE's and linear equalizers based on nominal models being

251

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

NASA Astrophysics Data System (ADS)

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 new images have both the angular resolution to study the detailed morphologies of the two nuclei that power the galaxy merger and sensitivity to a wide range of spatial scales. At 33 GHz, we achieve a resolution of 0.''081 × 0.''063 (29.9 × 23.3 pc) and resolve the radio emission surrounding both nuclei. We conclude from the decomposition of the radio spectral energy distribution that a majority of the 33 GHz emission is synchrotron radiation. The spatial distributions of radio emission in both nuclei are well described by exponential profiles. These have deconvolved half-light radii (R 50d ) of 51 and 35 pc for the eastern and western nuclei, respectively, 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 extremely high molecular gas surface densities of 2.2+2.1-1.0 × 10^5 (east) and 4.5+4.5-1.9 × 10^5 (west) M ? pc-2, corresponding to total hydrogen column densities of N H = 2.7+2.7-1.2 × 1025 (east) and 5.6+5.5-2.4 × 1025 cm-2 (west). The implied gas volume densities are similarly high, {nH_{_2} ˜ 3.8+3.8-1.6 × 10^4} (east) and {˜ } 11+12-4.5 × 10^4 cm-3 (west). We also estimate very high luminosity surface densities of ? _IR ˜ 4.2+1.6-0.7 × 1013 (east) and ? _IR ˜ 9.7+3.7-2.4 × 1013 (west) L? kpc-2, and star formation rate surface densities of ?SFR ~ 103.7 ± 0.1 (east) and ?SFR ~ 104.1 ± 0.1(west) M ? yr-1kpc-2. These values, especially for the western nucleus are, to our knowledge, the highest luminosity surface densities and star formation rate surface densities measured for any star-forming system. Despite these high values, the nuclei appear to lie below the dusty Eddington limit in which radiation pressure is balanced only by self-gravity. The small measured sizes also imply that at wavelengths shorter than ? = 1 mm, dust absorption effects must play an important role in the observed light distribution while below 5 GHz free-free absorption contributes substantial opacity. According to these calculations, the nuclei of Arp 220 are only transparent in the frequency range ~5-350 GHz. Our results offer no clear evidence that an active galactic nucleus dominates the emission from either nucleus at 33 GHz.

Barcos-Muñoz, L.; Leroy, A. K.; Evans, A. S.; Privon, G. C.; Armus, L.; Condon, J.; Mazzarella, J. M.; Meier, D. S.; Momjian, E.; Murphy, E. J.; Ott, J.; Reichardt, A.; Sakamoto, K.; Sanders, D. B.; Schinnerer, E.; Stierwalt, S.; Surace, J. A.; Thompson, T. A.; Walter, F.

2015-01-01

252

Quantitative prediction of radio frequency induced local heating derived from measured magnetic field maps in magnetic resonance imaging: A phantom validation at 7 T  

NASA Astrophysics Data System (ADS)

Electrical Properties Tomography (EPT) technique utilizes measurable radio frequency (RF) coil induced magnetic fields (B1 fields) in a Magnetic Resonance Imaging (MRI) system to quantitatively reconstruct the local electrical properties (EP) of biological tissues. Information derived from the same data set, e.g., complex numbers of B1 distribution towards electric field calculation, can be used to estimate, on a subject-specific basis, local Specific Absorption Rate (SAR). SAR plays a significant role in RF pulse design for high-field MRI applications, where maximum local tissue heating remains one of the most constraining limits. The purpose of the present work is to investigate the feasibility of such B1-based local SAR estimation, expanding on previously proposed EPT approaches. To this end, B1 calibration was obtained in a gelatin phantom at 7 T with a multi-channel transmit coil, under a particular multi-channel B1-shim setting (B1-shim I). Using this unique set of B1 calibration, local SAR distribution was subsequently predicted for B1-shim I, as well as for another B1-shim setting (B1-shim II), considering a specific set of parameter for a heating MRI protocol consisting of RF pulses plaid at 1% duty cycle. Local SAR results, which could not be directly measured with MRI, were subsequently converted into temperature change which in turn were validated against temperature changes measured by MRI Thermometry based on the proton chemical shift.

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

2014-12-01

253

Measurement of Flow Velocity and Inference of Liquid Viscosity in a Microfluidic Channel by Fluorescence Photobleaching  

E-print Network

(FRAP) has been used to measure the flow velocity in lymphatic capillaries of mice8 and in straight or curved microchannels.9,10 In addition to velocity measurements, FRAP analysis is an effective method channels.11 Perhaps the most powerful feature of FRAP-based fluidic measurements in biological

254

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

Microsoft Academic Search

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

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

2007-01-01

255

Atmosphere and ionosphere of venus from the mariner v s-band radio occultation measurement.  

PubMed

Measurements of the frequency, phase, and amplitude of the S-band radio signal of Mariner V as it passed behind Venus were used to obtain the effects of refraction in its atmosphere and ionosphere. Profiles of refractivity, temperature, pressure, and density in the neutral atmosphere, as well as electron density in the daytime ionosphere, are presented. A constant scale height was observed above the tropopause, and the temperature increased with an approximately linear lapse rate below the tropopause to the level at which signal was lost, presumably because heavy defocusing attenuation occurred as critical refraction was approached. An ionosphere having at least two maxima was observed at only 85 kilometers above the tropopause. PMID:17749791

Kliore, A; Levy, G S; Cain, D L; Fjeldbo, G; Rasool, S I

1967-12-29

256

The atmosphere of Titan - an analysis of the Voyager 1 radio occultation measurements  

NASA Astrophysics Data System (ADS)

The equatorial atmosphere of Titan was probed by means of two coherently related radio signals transmitted from Voyager 1 at 13.0 and 3.6 cm wavelengths during the November 12, 1980 occultation of the spacecraft by the Saturn satellite. An analysis of the differential dispersive frequency measurements did not reveal any ionization layers in the upper atmosphere of Titan. The gas refractivity data, which extend from the surface to about 200 km altitude, were interpreted in two different ways. In the first, it is assumed that N2 makes up virtually all of the atmosphere, with small amounts of CH4 and other hydrocarbons present. In the second interpretation of the refractivity data, it is assumed that the 3.5 km altitude level corresponds to the bottom of a CH4 cloud layer and that N2 and CH4 were perfectly mixed below this level.

Lindal, G. F.; Wood, G. E.; Hotz, H. B.; Sweetnam, D. N.; Eshleman, V. R.; Tyler, G. L.

1983-02-01

257

Quantum correlation evolution of GHZ and states under noisy channels using ameliorated measurement-induced disturbance  

NASA Astrophysics Data System (ADS)

We study quantum correlation of Greenberger-Horne-Zeilinger (GHZ) and W states under various noisy channels using measurement-induced disturbance approach and its optimized version. Although these inequivalent maximal entangled states represent the same quantum correlation in the absence of noise, it is shown that the W state is more robust than the GHZ state through most noisy channels. Also, using measurement-induced disturbance measure, we obtain the analytical relations for the time evolution of quantum correlations in terms of the noisy parameter and remove its overestimating quantum correlations upon implementing the ameliorated measurement-induced disturbance.

Espoukeh, Pakhshan; Pedram, Pouria

2015-01-01

258

Measurements and models of radio frequency impulsive noise for indoor wireless communications  

NASA Astrophysics Data System (ADS)

This paper presents the results of average and impulsive noise measurements inside several office buildings and retail stores. The noise measurement system operated at 918 MHz, 2.44 GHz, and 4 GHz with a nominal 40 MHz 3 dB RF bandwidth. Omnidirectional and directional antennas were used to investigate the characteristics and sources of RF noise in indoor channels. Statistical analyses of the measurements are presented in the form of peak amplitude probability distributions, pulse duration distributions, and interarrival time distributions. Simple first-order mathematical models for these statistical characterizations are also presented. These analyses indicate that photocopiers, printers (both line printers and cash register receipt printers), elevators, and microwave ovens are significant sources of impulsive noise in office and retail environments.

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

1993-09-01

259

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

PubMed Central

NanC is an Escherichia coli outer membrane protein involved in sialic acid (Neu5Ac, i.e., N-acetylneuraminic acid) uptake. Expression of the NanC gene is induced and controlled by Neu5Ac. The transport mechanism of Neu5Ac is not known. The structure of NanC was recently solved (PDB code: 2WJQ) and includes a unique arrangement of positively charged (basic) side chains consistent with a role in acidic sugar transport. However, initial functional measurements of NanC failed to find its role in the transport of sialic acids, perhaps because of the ionic conditions used in the experiments. We show here that the ionic conditions generally preferred for measuring the function of outer-membrane porins are not appropriate for NanC. Single channels of NanC at pH 7.0 have: (1) conductance 100 pS to 800 pS in 100 mM KCl to 3 M KCl), (2) anion over cation selectivity (Vreversal = +16 mV in 250 mM KCl || 1 M KCl), and (3) two forms of voltage-dependent gating (channel closures above ±200 mV). Single-channel conductance decreases by 50% when HEPES concentration is increased from 100 ?M to 100 mM in 250 mM KCl at pH 7.4, consistent with the two HEPES binding sites observed in the crystal structure. Studying alternative buffers, we find that phosphate interferes with the channel conductance. Single-channel conductance decreases by 19% when phosphate concentration is increased from 0 mM to 5 mM in 250 mM KCl at pH 8.0. Surprisingly, TRIS in the baths reacts with Ag|AgCl electrodes, producing artifacts even when the electrodes are on the far side of agar–KCl bridges. A suitable baseline solution for NanC is 250 mM KCl adjusted to pH 7.0 without buffer. PMID:22246445

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

2012-01-01

260

Time division of the channels of the measuring circuits of capacitive and inductive sensors  

Microsoft Academic Search

The principle of time division of the channels for converting passive quantities and methods of achieving it are described.\\u000a Measuring circuits of capacitive and inductive sensors, which employ switching methods and phase and polyharmonic division\\u000a of the channels are considered. Each of these circuits enables the error due to the finite value of the amplifier gain to\\u000a be eliminated, and

V. P. Arbuzov

2009-01-01

261

Second order statistics of NLOS indoor MIMO channels based on 5.2 GHz measurements  

Microsoft Academic Search

Herein, results from measurements conducted by the University of Bristol are presented. The channel characteristics of multiple input multiple output (MIMO) indoor systems at 5.2 GHz are studied. Our investigation shows that the envelope of the channel for non-line-of-sight (NLOS) indoor situations are approximately Rayleigh distributed and consequently we focus on a statistical description of the first and second order

Kai Yu; Mats Bengtsson; Björn Ottersten; Darren McNamara; Peter Karlsson; Mark Beach

2001-01-01

262

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

Microsoft Academic Search

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

Weilin Qu; Issam Mudawar

2004-01-01

263

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

NASA Technical Reports Server (NTRS)

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

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

1996-01-01

264

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

265

Performance of ultra-wideband time-shift-modulated signals in the indoor wireless impulse radio channel  

Microsoft Academic Search

Impulse radio (IR) is a spread spectrum (SS) wireless technique in which ultra-wideband (UWB) communication waveforms that consist of trains of time-shifted sub-nanosecond pulses are modulated to convey information exclusively in the relative time position of the pulses. We make an assessment of the performance of non-binary IR modulation in the presence of multipath with detection using a RAKE receiver

Fernando Ramirez-Mireles; M. Z. Win; R. A. Scholtz

1997-01-01

266

Measurement of Superluminal Motion of Radio-Loud AGNs at 43 GHz with the VLBA  

NASA Astrophysics Data System (ADS)

We present the results of bi-monthly VLBA observations at 7mm in 1998-1999 of 15 radio-bright AGNs. These include 5 BL Lac objects (3C 66A, OJ 287, 1803+784, 1823+568, and BL Lac), 8 quasars (0420-014, 0528+134, 3C 273, 3C 279, PKS 1510-089, 3C 345, CTA 102, and 3C 454.3), and 2 radio galaxies (3C 111 and 3C 120). This is part of a mm-wave polarization monitoring program with the VLBA, JCMT, and (starting in February 1999) Steward Observatory, plus total flux density monitoring at BIMA and OVRO (mm array calibration data). Several of the sources (BL Lac, 3C 279, PKS 1510-089, and 3C 120) are being monitored weekly or semi-weekly with RXTE. The regular monitoring with high angular resolution allows us to identify components across different epochs with high confidence, and to determine with to high accuracy the extrapolated times of zero separation from the core. We will show the VLBA images and measurements of proper motions. For a number of sources the values of proper motions of components in the jets will be compared with the results of our previous program of VLBA monitoring of gamma -ray bright blazars at high frequencies in 1994--1997. This research is supported in part by the National Science Foundation through grant AST-9802941. The gamma -ray blazar VLBA monitoring was supported in part by various NASA guest investigator grants (RXTE and CGRO).

Marchenko, S. G.; Marscher, A. P.; Cawthorne, T. V.; Stevens, J. A.; Gear, W. K.; Lister, M. L.; Robson, E. I.; Smith, P. S.; Forster, J. R.; Gabuzda, D. C.

1999-05-01

267

Temperature and Pressure Measurements and Visualization of He II Cavitation Flow through Venturi Channel  

SciTech Connect

He II cavitation flow through a Venturi channel was experimentally investigated through temperature and pressure measurements and optical visualization. So far some distinctive features of cavitation between He II and He I flows were clarified. Then, detailed measurements were added for further investigation, such as the measurements of the temperature drop distribution throughout the flow channel and the void fraction. Further considerations were given on the cavitation inception with emphasis on the superheating of liquid helium, and the effect of the flow separation on cavitation.

Ishii, T.; Murakami, M.; Harada, K. [Institute of Engineering Mechanics and Systems, University of Tsukuba, Tennodai 1-1-1, Tsukuba 305-8573 (Japan)

2004-06-23

268

Measurements of a 150 to 1700 MHz low loss Eleven feed for the 42 m radio telescope at Green Bank  

Microsoft Academic Search

We present measured results for a dual polarized 150 to 1700 MHz Eleven feed for use in the 42 m radio telescope in Green Bank. The feed is manufactured from a 3 mm thick aluminium plate and located inside a steel container with a soft radome over its opening. The feed provides dual polarization and more than a decade bandwidth.

Rikard Olsson; Per-Simon Kildal; Mike Shields

2006-01-01

269

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

270

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

271

Neuromotor channel capacity as an outcome and tracking measure in Parkinson's Disease  

Microsoft Academic Search

Motion quality is an important issue in movement disorders. We have developed and extensively studied neuromotor channel capacity, derived in part from Fitts' Law, as an objective coordination measure. We now use it to characterize subjects receiving deep brain stimulation (DBS) therapy. NMCC was measured (different conditions, medications and stimulation \\

George V. Kondraske; R. Malcolm Stewart

2002-01-01

272

A Specific Multi-channel Photon-Counting Unit for Air-Pollution Measurement  

E-print Network

A Specific Multi-channel Photon-Counting Unit for Air-Pollution Measurement Papageorgas P.1.g. confocal microscopy), air pollution optical measurements, laser sounding of the atmosphere the development of appropriate laser light sources. The corresponding development of portable multichannel Raman

Athens, University of

273

RADIO PLASMA IMAGER SIMULATIONS AND MEASUREMENTS J. L. GREEN1, R. F. BENSON1, S. F. FUNG1, W. W. L. TAYLOR2, S. A. BOARDSEN2,  

E-print Network

instrument designed to use radio wave sounding techniques to perform repetitive remote sensing measurements waves that travel great distances in the magnetosphere, reflect within magnetospheric plasmasRADIO PLASMA IMAGER SIMULATIONS AND MEASUREMENTS J. L. GREEN1, R. F. BENSON1, S. F. FUNG1, W. W. L

Demoulin, Pascal

274

A 27 channels, 1 MHz fibre-optic measuring system  

NASA Astrophysics Data System (ADS)

The Kapitza facility is a pulse forming network consisting of an energy source, semiconductor opening switch, pulse transformer and a load. To characterize the Kapitza facility, there is a need for a measurement system where the sensors are completely separated electrically from the Data Acquisition System. A measurement system based upon fiber-optic data transmission was finally chosen. This fiber-optic system, with a bandwidth of 1 MHz, uses FM transmission techniques; the data input is used to frequency modulate the optical carrier that is coupled to the fiber, and subsequently demodulated at the receiver to recover the analog signal. In this report the operation of the optical measurement system, the components that have been used and the calibration of the transmitter/receiver units are some of the subjects that are discussed. In the appendix, schematics, print layouts, lists with the used components, wave forms of the input output signals and specifications are given.

Kaanders, M. A.

1993-03-01

275

Radio Astronomy Radio astronomy  

E-print Network

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

Metchev, Stanimir

276

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

Microsoft Academic Search

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

C. G. Little; H. Leinbach

1958-01-01

277

A proposed space mission around the Moon to measure the Moon RadioQuiet Zone  

Microsoft Academic Search

In a series of papers published since 2000 mainly in Acta Astronautica the senior author Maccone dealt with the advantages of the Farside of the Moon for future utilization Clearly the Moon Farside is free from RFI Radio Frequency Interference produced in larger and larger amounts by the increasing human exploitation of radio technologies That author suggested that crater Daedalus

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

2006-01-01

278

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

ERIC Educational Resources Information Center

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

Yahaya, Mohammed Kuta; Badiru, Olabode Idris

2002-01-01

279

Design parameters and measured performance of the IRAM 30-m Millimeter Radio Telescope  

Microsoft Academic Search

The “Millimeter Radio Telescope” (MRT) is operated by the Institute for Radio Astronomy in the millimeter range (IRAM) and is located at 2850-m altitude in the Sierra Nevada, near Granada, Spain. It is a reflector antenna of 30-m diameter with a surface accuracy of 0.08 mm and a pointing accuracy of better than 2 arcsec. The telescope is equipped with

JACOB W. M. BAARS; ALBERT GREVE; HAUKE HEIN; DAVE MORRIS; JUAN PENALVER; CLEMENS THUM

1994-01-01

280

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

281

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 measuremen...

Connolly, Amy; Miki, Christian; Nichol, Ryan; Saltzberg, David

2008-01-01

282

In-vivo measurement of distal radio-ulnar joint translation.  

PubMed

Distal radio-ulnar joint (DRUJ) instability is increasingly recognised and assessment can be subjective and difficult. Previous research has used cadaveric models or in-vivo with CT, with variable results. A test device was designed to establish normal values of in-vivo DRUJ dorso-palmar translation. Twenty volunteers were recruited. Those with previous wrist/forearm injuries were excluded. The device held the elbow at 90° flexion and neutral forearm rotation, with the distal ulna secured. A dorso-palmar shear force was applied to the distal radius and displacement measured three times on each wrist alternately by the same operator. The mean translation of the DRUJ is 5.5 mm. Same-sided mean measurements for two subjects taken days apart varied by 1 mm. The intra-class correlation coefficient was 0.93. The device is reliable, reproducible and appears to be a simple valid test. Contralateral sides were comparable. It will primarily be a research device to guide clinical practice in DRUJ instability. PMID:23413844

Nagata, H; Hosny, S; Giddins, G E B

2013-01-01

283

A Measurement of the Millimeter Emission and the Sunyaev-zel'dovich Effect Associated with Low-frequency Radio Sources  

NASA Technical Reports Server (NTRS)

We present a statistical analysis of the millimeter-wavelength properties of 1.4 GHz-selected sources and a detection of the Sunyaev-Zel'dovich Effect associated with the halos that host them. The Atacama Cosmology Telescope (ACT) has conducted a survey at 148 GHz, 218 GHz and 277 GHz along the celestial equator. Using samples of radio sources selected at 1.4 GHz from the Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) Survey and the National Radio Astronomy Observatory Very Large Array Sky Survey (NVSS), we measure the stacked 148, 218 and 277 GHz flux densities for sources with 1.4 GHz flux densities ranging from 5 to 200 mJy. At these flux densities, the radio source population is dominated by active galactic nuclei (AGN), with both steep and at spectrum populations, which have combined radio-to-millimeter spectral indices ranging from 0.5 to 0.95, reecting the prevalence of steep spectrum sources at high flux densities and the presence of at spectrum sources at lower flux densities. The thermal Sunyaev-Zelapos;dovich (SZ) eect associated with the halos that host the AGN is detected at the 5 level through its spectral signature. When we compare the SZ eect with weak lensing measurements of radio galaxies, we find that the relation between the two is consistent with that measured by Planck for local bright galaxies. We present a detection of the SZ eect in some of the lowest mass halos (average M(sub 200) approx. equals 10(exp 13) solar M h(sup-1) (sub 70) ) studied to date. This detection is particularly important in the context of galaxy evolution models, as it confirms that galaxies with radio AGN also typically support hot gaseous halos. With Herschel* observations, we show that the SZ detection is not significantly contaminated by dusty galaxies or by dust associated with the AGN or galaxies hosting the AGN. We show that 5 mJy < S(sub 1:4) < 200 mJy radio sources contribute l(l +1)C(sub l)/(2 pi ) = 0:37+/- 0:03 micro K(exp 2) to the angular power spectrum at l = 3000 at 148 GHz, after accounting for the SZ effect associated with their host halos.

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.; Duenner, Rolando; Hajian, Amir; Halpern, Mark; Hilton, Matt; Hincks, Adam D.; Hlozek Renee A.; Huffenberger, Kevin M.; Hughes, John P.; Ivison, R. J.; Kosowsky, Arthur; Lin, Yen-Ting; Switzer, Eric R.; Wollack, Edward J.; Zemcov, Michael B.

2013-01-01

284

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

NASA Astrophysics Data System (ADS)

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

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

2012-05-01

285

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

286

Design of multi-channel radio-frequency front-end for 200mhz parallel magnetic resonance imaging  

E-print Network

can be dramatically reduced by designing a whole receiver front-end even multiple receiver front-ends on a single chip using CMOS technology, and multiplexing the output signal of each receiver front-end into one channel so that as much hardware...

Liu, Xiaoqun

2009-05-15

287

Measurements of the random and channeled stopping powers for He ions in InP  

NASA Astrophysics Data System (ADS)

Measurements of the ratio of channeled to random stopping powers for He ions in InP [1] have been revised and extended over a wider energy range. Values for both <110> and <111> channels are found to be the same as for He ions in silicon in the range 0.6 to 3.5 MeV. The random stopping power for He in InP has been measured to be 1.10 ± 0.03 times the values in the Ziegler-Biersack-Littmark (ZBL) tables in the range 0.5 to 4.5 MeV.

Hetherington, D. W.

1996-07-01

288

A Measurement of the Millimeter Emission and the Sunyaev-Zel'dovich Effect Associated with Low-Frequency Radio Sources  

NASA Technical Reports Server (NTRS)

We present a statistical analysis of the millimeter-wavelength properties of 1.4 GHz-selected sources and a detection of the Sunyaev-Zel'dovich effect associated with the halos 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 Sunyaev-Zel'dovich (SZ) effect associated with the halos that host the AGN is detected at the 5 sigma level through its spectral signature, representing a statistical detection of the SZ effect in some of the lowest mass halos (average M(sub 200) approximately equals 10(sup 13) solar mass h(sub 70)(exp -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 halos. Adding Herschel observations allows us to show that the SZ signal is not significantly contaminated by dust emission. Finally, we analyze the contribution of radio sources to the angular power spectrum of the cosmic microwave background.

Gralla, Megan B.; Crichton, Devin; Marriage, Tobias; Mo, Wenli; Aguirre, Paula; Addison, Graeme E.; Asboth, V.; Battaglia, Nick; Bock, James; Bond, J. Richard; Devlin, Mark; Dunner, Rolando; Hajian, Amir; Halpern, Mark; Hilton, Matt; Hincks, Adam D.; Hlozek, Renee A.; Huffenberger, Kevin M.; Hughes, John P.; Ivison, R.J.; Kosowsky, Arthur; Lin, Yen-Ting; Marsden, Danica; Menanteau, Felipe; Wollack, Edward J.

2014-01-01

289

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

PubMed Central

Purpose Acoustic and perceptual studies show a number of differences between the voices of radio performers and controls. Despite this, the vocal fold kinematics underlying these differences are largely unknown. Using high-speed videoendoscopy, this study sought to determine whether the vocal vibration features of radio performers differed from those of non-performing controls. Method Using high-speed videoendoscopy, recordings of a mid-phonatory/i/ in 16 male radio performers (aged 25–52 years) and 16 age-matched controls (aged 25–52 years) were collected. Videos were extracted and analysed semi-automatically using High-Speed Video Program, obtaining measures of fundamental frequency (f0), open quotient and speed quotient. Post-hoc analyses of sound pressure level (SPL) were also performed (n?=?19). Pearson's correlations were calculated between SPL and both speed and open quotients. Results Male radio performers had a significantly higher speed quotient than their matched controls (t?=?3.308, p?=?0.005). No significant differences were found for f0 or open quotient. No significant correlation was found between either open or speed quotient with SPL. Discussion A higher speed quotient in male radio performers suggests that their vocal fold vibration was characterised by a higher ratio of glottal opening to closing times than controls. This result may explain findings of better voice quality, higher equivalent sound level and greater spectral tilt seen in previous research. Open quotient was not significantly different between groups, indicating that the durations of complete vocal fold closure were not different between the radio performers and controls. Further validation of these results is required to determine the aetiology of the higher speed quotient result and its implications for voice training and clinical management in performers. PMID:24971625

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

2014-01-01

290

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

291

A generalised Measurement Equation and van Cittert-Zernike theorem for wide-field radio astronomical interferometry  

E-print Network

We derive a generalised van Cittert-Zernike (vC-Z) theorem for radio astronomy that is valid for partially polarized sources over an arbitrarily wide field-of-view (FoV). The classical vC-Z theorem is the theoretical foundation of radio astronomical interferometry, and its application is the basis of interferometric imaging. Existing generalised vC-Z theorems in radio astronomy assume, however, either paraxiality (narrow FoV) or scalar (unpolarized) sources. Our theorem uses neither of these assumptions, which are seldom fulfilled in practice in radio astronomy, and treats the full electromagnetic field. To handle wide, partially polarized fields, we extend the two-dimensional electric field (Jones vector) formalism of the standard "Measurement Equation" of radio astronomical interferometry to the full three-dimensional formalism developed in optical coherence theory. The resulting vC-Z theorem enables all-sky imaging in a single telescope pointing, and imaging using not only standard dual-polarized interferometers (that measure 2-D electric fields), but also electric tripoles and electromagnetic vector-sensor interferometers. We show that the standard 2-D Measurement Equation is easily obtained from our formalism in the case of dual-polarized antenna element interferometers. We find, however, that such dual-polarized interferometers can have polarimetric aberrations at the edges of the FoV that are often correctable. Our theorem is particularly relevant to proposed and recently developed wide FoV interferometers such as LOFAR and SKA, for which direction-dependent effects will be important.

T. D. Carozzi; G. Woan

2008-11-30

292

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

293

Error analysis for intrinsic quality factor measurement in superconducting radio frequency resonators  

NASA Astrophysics Data System (ADS)

In this paper, we discuss error analysis for intrinsic quality factor (Q0) and accelerating gradient (Eacc) measurements in superconducting radio frequency (SRF) resonators. The analysis is applicable for cavity performance tests that are routinely performed at SRF facilities worldwide. We review the sources of uncertainties along with the assumptions on their correlations and present uncertainty calculations with a more complete procedure for treatment of correlations than in previous publications [T. Powers, in Proceedings of the 12th Workshop on RF Superconductivity, SuP02 (Elsevier, 2005), pp. 24-27]. Applying this approach to cavity data collected at Vertical Test Stand facility at Fermilab, we estimated total uncertainty for both Q0 and Eacc to be at the level of approximately 4% for input coupler coupling parameter ?1 in the [0.5, 2.5] range. Above 2.5 (below 0.5) Q0 uncertainty increases (decreases) with ?1 whereas Eacc uncertainty, in contrast with results in Powers [in Proceedings of the 12th Workshop on RF Superconductivity, SuP02 (Elsevier, 2005), pp. 24-27], is independent of ?1. Overall, our estimated Q0 uncertainty is approximately half as large as that in Powers [in Proceedings of the 12th Workshop on RF Superconductivity, SuP02 (Elsevier, 2005), pp. 24-27].

Melnychuk, O.; Grassellino, A.; Romanenko, A.

2014-12-01

294

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

295

Error analysis for intrinsic quality factor measurement in superconducting radio frequency resonators.  

PubMed

In this paper, we discuss error analysis for intrinsic quality factor (Q0) and accelerating gradient (Eacc) measurements in superconducting radio frequency (SRF) resonators. The analysis is applicable for cavity performance tests that are routinely performed at SRF facilities worldwide. We review the sources of uncertainties along with the assumptions on their correlations and present uncertainty calculations with a more complete procedure for treatment of correlations than in previous publications [T. Powers, in Proceedings of the 12th Workshop on RF Superconductivity, SuP02 (Elsevier, 2005), pp. 24-27]. Applying this approach to cavity data collected at Vertical Test Stand facility at Fermilab, we estimated total uncertainty for both Q0 and Eacc to be at the level of approximately 4% for input coupler coupling parameter ?1 in the [0.5, 2.5] range. Above 2.5 (below 0.5) Q0 uncertainty increases (decreases) with ?1 whereas Eacc uncertainty, in contrast with results in Powers [in Proceedings of the 12th Workshop on RF Superconductivity, SuP02 (Elsevier, 2005), pp. 24-27], is independent of ?1. Overall, our estimated Q0 uncertainty is approximately half as large as that in Powers [in Proceedings of the 12th Workshop on RF Superconductivity, SuP02 (Elsevier, 2005), pp. 24-27]. PMID:25554312

Melnychuk, O; Grassellino, A; Romanenko, A

2014-12-01

296

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.

297

Galvanomagnetic Channel Mobility Measurements of low-k and high-k Transistors.  

NASA Astrophysics Data System (ADS)

This paper reports a different diagnostic technique for SiO2 and HfSiO gate stacks which can determine true mobility (?) regardless of trap characteristics. It can be used in the wafer fab to give workers greater insight into determining the true drift mobility. Effective mobility (?eff) measurements in high-k transistors are ambiguous as a diagnostic technique because there are two different mechanisms by which ?eff can be degraded: (1) Enhanced scattering of carriers by phonons and by charged defects at or near the interface, and (2) Reduction of the channel carrier density by trapping. Conventional measurements cannot distinguish between the two mechanisms of mobility degradation, hence their contributions cannot be determined. The trapping can cause ?eff to underestimate ?. The potential use of new materials for the conducting channel compounds the uncertainty about what the true ? should be. So, it is highly desirable to measure both ? and ?eff to understand what is limiting the channel current. Our method employs galvanomagnetic (Hall effect and magnetoresistance) measurements on SiO2 and HfSiO transistors to determine the drift velocity of carriers in the channel, even in the presence of carrier trapping. We will report on Hall and magnetoresistance measurements using specially designed and fabricated low-k and high-k transistors.

Agrawal, R.; Mahajan, R.; Bate, R. T.; Kirk, W. P.; Pant, G.; Gnade, B. E.; Wallace, R. M.

2006-10-01

298

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

299

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

300

Coupling interactions between voltage sensors of the sodium channel as revealed by site-specific measurements.  

PubMed

The voltage-sensing S4 segments in the sodium channel undergo conformational rearrangements in response to changes in the electric field. However, it remains unclear whether these structures move independently or in a coordinated manner. Previously, site-directed fluorescence measurements were shown to track S4 transitions in each of the four domains. Here, using a similar technique, we provide direct evidence of coupling interactions between voltage sensors in the sodium channel. Pairwise interactions between S4s were evaluated by comparing site-specific conformational changes in the presence and absence of a gating perturbation in a distal domain. Reciprocity of effect, a fundamental property of thermodynamically coupled systems, was measured by generating converse mutants. The magnitude of a local gating perturbation induced by a remote S4 mutation depends on the coupling strength and the relative equilibrium positions of the two voltage sensors. In general, our data indicates that the movement of all four voltage sensors in the sodium channel are coupled to a varying extent. Moreover, a gating perturbation in S4-DI has the largest effect on the activation of S4-DIV and vice versa, demonstrating an energetic linkage between S4-DI and S4-DIV. This result suggests a physical mechanism by which the activation and inactivation process may be coupled in voltage-gated sodium channels. In addition, we propose that cooperative interactions between voltage sensors may be the mechanistic basis for the fast activation kinetics of the sodium channel. PMID:14981134

Chanda, Baron; Asamoah, Osei Kwame; Bezanilla, Francisco

2004-03-01

301

Measurement and scaling of hydrodynamic interactions in the presence of draining channels.  

PubMed

Central to the adhesion and locomotion of tree frogs are their structured toe pads, which consist of an array of 10 ?m hexagonal epithelial cells separated by interconnected channels that are 1 ?m wide and 10 ?m deep. It has been proposed that the channels facilitate the drainage of excess fluid trapped between the toe pads and the contacting surface, and thus reduce the hydrodynamic repulsion during approach. We performed direct force measurement of the normal hydrodynamic interactions during the drainage of fluid from the gap between a structured and a smooth surface using surface force apparatus. The structured surface consisted of a hexagonal array of cylindrical posts to represent the network of interconnected channels. The measured hydrodynamic drainage forces agree with the predictions from Reynolds' theory for smooth surfaces at large separations. Deviations from theory, characterized by a reduction in the hydrodynamic repulsion, are observed below some critical separation (h(c)), which is independent of drive velocity. We employ a scaling analysis to establish the relationship between structural features (channel depth, width, and post diameter) and the critical separation for the onset of deviations. We find agreement between our experiments and the scaling analysis, which allows us to estimate a characteristic length scale that corresponds to the transition from the fluid being radially squeezed out of the nominal contact area to being squeezed out through the network of interconnected channels. PMID:23009050

Gupta, Rohini; Fréchette, Joëlle

2012-10-16

302

Experimental measurements of traffic and radio disturbances in Ente Nazionale per l'Energia Elettrica's (ENEL) mobile radio networks  

NASA Astrophysics Data System (ADS)

To help redesign the Italian national communication network, a telephone traffic analyzer was implemented using a 8086 microprocessor. Results show that the peak load is double the average load in working hours; that the average peak load is 0.115 Erlang for each network; and that the average conversation length is 19 sec. Electromagnetic disturbances were measured in 50 Italian localities, finding and average reduction of receiver sensibility of 11 dB at 450 MHz and 24 dB at 160 MHz in urban areas with a high noise level.

Farinetti, A.; Manin, A.

1983-06-01

303

Class of algorithms for decoding block codes with channel measurement information  

Microsoft Academic Search

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

DAVID CHASE

1972-01-01

304

A generalized measurement equation and van Cittert-Zernike theorem for wide-field radio astronomical interferometry  

NASA Astrophysics Data System (ADS)

We derive a generalized van Cittert-Zernike (vC-Z) theorem for radio astronomy that is valid for partially polarized sources over an arbitrarily wide field of view (FoV). The classical vC-Z theorem is the theoretical foundation of radio astronomical interferometry, and its application is the basis of interferometric imaging. Existing generalized vC-Z theorems in radio astronomy assume, however, either paraxiality (narrow FoV) or scalar (unpolarized) sources. Our theorem uses neither of these assumptions, which are seldom fulfiled in practice in radio astronomy, and treats the full electromagnetic field. To handle wide, partially polarized fields, we extend the two-dimensional (2D) electric field (Jones vector) formalism of the standard `Measurement Equation' (ME) of radio astronomical interferometry to the full three-dimensional (3D) formalism developed in optical coherence theory. The resulting vC-Z theorem enables full-sky imaging in a single telescope pointing, and imaging based not only on standard dual-polarized interferometers (that measure 2D electric fields) but also electric tripoles and electromagnetic vector-sensor interferometers. We show that the standard 2D ME is easily obtained from our formalism in the case of dual-polarized antenna element interferometers. We also exploit an extended 2D ME to determine that dual-polarized interferometers can have polarimetric aberrations at the edges of a wide FoV. Our vC-Z theorem is particularly relevant to proposed, and recently developed, wide FoV interferometers such as Low Frequency Array (LOFAR) and Square Kilometer Array (SKA), for which direction-dependent effects will be important.

Carozzi, T. D.; Woan, G.

2009-05-01

305

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

306

Multi-channel transimpedance measurement of a planar electromagnetic sensor array  

NASA Astrophysics Data System (ADS)

Planar electromagnetic sensor arrays have advantages such as nice coherence, fast response speed and high sensitivity, which can be used for micro damage inspection of crucial parts in equipment, and the key point in improving the inspection performance is to achieve a precise measurement of multi-channel transimpedances (the inductive voltages divided by the exciting current of the sensor). The principle and characteristics of planar electromagnetic sensor arrays are introduced in this paper, and a digital lock-in impedance measurement algorithm was investigated, with which the interference and noise in inductive voltage signals can be restrained effectively and the amplitude and phase of the transimpedance can be obtained with good repeatability. An eight channel impedance measurement system was established based on a field programmable gate array and utilized to inspect the micro damage in metal materials, and the experimental data were analyzed. The experimental results show that the impedance measurement has excellent repeatability when the sensor array is placed in air, and the maximum measurement error of the complete transimpedance measurement system is lower than 10%. A micro crack with a size of 1?mm (length) × 0.1?mm (width) × 1?mm (depth) can be detected through the measurement of multi-channel transimpedance in the planar electromagnetic sensor array.

Chen, Dixiang; Xie, Ruifang; Zhou, Weihong; Hu, Hengjiang; Pan, Mengchun

2015-02-01

307

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

NASA Technical Reports Server (NTRS)

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

Diamond, John K.

1989-01-01

308

A Fluorometric Approach to Local Electric Field Measurements in a Voltage-Gated Ion Channel  

Microsoft Academic Search

Site-specific electrostatic measurements have been limited to soluble proteins purified for in vitro spectroscopic characterization or proteins of known structure; however, comparable measurements have not been made for functional membrane bound proteins. Here, using an electrochromic fluorophore, we describe a method to monitor localized electric field changes in a voltage-gated potassium channel. By coupling the novel probe Di-1-ANEPIA to cysteines

Osei Kwame Asamoah; Joseph P. Wuskell; Leslie M. Loew; Francisco Bezanilla

2003-01-01

309

Reduction of flow-measurement uncertainties in laser velocimeters with nonorthogonal channels  

NASA Technical Reports Server (NTRS)

An analysis of certain geometrical limitations inherent in the application of laser velocimeters with nonorthogonal channels has led to the development of advanced-LDA-calibration and data-acquisition techniques that minimize systematic and statistical errors, respectively. The data-acquisition technique optimizes the number of velocity samples collected from three velocimeter channels as a function of local turbulence intensity, vector direction, and prescribed confidence interval. Linear velocity surveys and streamline traces measured in a turbulent flow field with a three-dimensional laser velocimeter are presented and the validity and accuracy of the theoretical analysis are discussed.

Snyder, P. K.; Orloff, K. L.; Reinath, M. S.

1983-01-01

310

In situ measurements of particle friction angles in steep, narrow channels  

NASA Astrophysics Data System (ADS)

The persistent observation that sediment requires increased fluid stresses to move on steeper channels has inspired a wide range of explanations, which can loosely be divided into those that invoke increased grain stability (friction angle, ?) and those that require altered flow hydraulics in steep channels. Measurements of bulk fluid forces over a wide range of channel slopes (? ? 22°) have been obtained using laboratory flume experiments that can control for grain stability and show that altered flow hydraulics do play a role in increased critical shear stress. However, measurements of grain stability are almost all limited to channel slopes less than a few degrees. These friction angle studies have been conducted by tilting a fixed gravel bed with a single loose particle until dislodgment, or by directly measuring the forces required to dislodge a particle using a load cell. The latter methodology is less common but offers the advantage of quickly measuring the friction angles of in situ grains in natural river channels. Indeed, it has enabled the collection of extremely large datasets at low slopes [e.g., Johnston et al., 1998]. We are adding to this dataset with measurements from several natural steep channels in the San Gabriel Mountains, CA to test if the particle friction angle changes systematically as a function of slope or width-to-grain size ratio (W/D50), which is thought to determine the propensity for particle jamming. Using a load cell that records peak forces we measure the minimum force required to pull a particle from its pocket in the downstream direction and the particle weight. Particles are sampled over a regular grid and we record the percentage of the particle buried by fines and the qualitative degree of interlocking. Preliminary results from three sites with bed slopes of ? = 2.9°, 3.2°, and 9.0° suggest that the at-a-site variability in friction angle is much higher than between-site variability, and that median values do not vary in a consistent manner with bed slope (? = 51°, 67°, and 65°, respectively). At an individual site the degree of interlocking is the primary control on particle friction angle. However, the degree of interlocking was not higher in the steep (? = 9.0°), narrow (W/D50 = 12.5) channel. This indicates that increased grain stability may not play a crucial role in increasing the threshold shear stresses required for sediment motion on very steep slopes.

Prancevic, J.; Lamb, M. P.

2013-12-01

311

Single channel and ensemble hERG conductance measured in droplet bilayers.  

PubMed

The human ether-a-go-go related gene (hERG) encodes the potassium channel Kv11.1, which plays a key role in the cardiac action potential and has been implicated in cardiac disorders as well as a number of off-target pharmaceutical interactions. The electrophysiology of this channel has been predominantly studied using patch clamp, but lipid bilayers have the potential to offer some advantages, including apparatus simplicity, ease of use, and the ability to control the membrane and solution compositions. We made membrane preparations from hERG-expressing cells and measured them using droplet bilayers, allowing measurement of channel ensemble currents and 13.5 pS single channel currents. These currents were ion selective and were blockable by E-4031 and dofetilide in a dose-dependent manner, allowing determination of IC50 values of 17 nM and 9.65 ?M for E-4031 and dofetilide, respectively. We also observed time- and voltage- dependent currents following step changes in applied potential that were similar to previously reported patch clamp measurements. PMID:25653065

Vijayvergiya, Viksita; Acharya, Shiv; Poulos, Jason; Schmidt, Jacob

2015-02-01

312

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

313

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

314

Small vertical movement of a K+ channel voltage sensor measured with luminescence energy transfer.  

PubMed

Voltage-gated ion channels open and close in response to voltage changes across electrically excitable cell membranes. Voltage-gated potassium (Kv) channels are homotetramers with each subunit constructed from six transmembrane segments, S1-S6 (ref. 2). The voltage-sensing domain (segments S1-S4) contains charged arginine residues on S4 that move across the membrane electric field, modulating channel open probability. Understanding the physical movements of this voltage sensor is of fundamental importance and is the subject of controversy. Recently, the crystal structure of the KvAP channel motivated an unconventional 'paddle model' of S4 charge movement, indicating that the segments S3b and S4 might move as a unit through the lipid bilayer with a large (15-20-A) transmembrane displacement. Here we show that the voltage-sensor segments do not undergo significant transmembrane translation. We tested the movement of these segments in functional Shaker K+ channels by using luminescence resonance energy transfer to measure distances between the voltage sensors and a pore-bound scorpion toxin. Our results are consistent with a 2-A vertical displacement of S4, not the large excursion predicted by the paddle model. This small movement supports an alternative model in which the protein shapes the electric field profile, focusing it across a narrow region of S4 (ref. 6). PMID:16094368

Posson, David J; Ge, Pinghua; Miller, Christopher; Bezanilla, Francisco; Selvin, Paul R

2005-08-11

315

47 CFR 76.609 - Measurements.  

Code of Federal Regulations, 2010 CFR

...COMMISSION (CONTINUED) BROADCAST RADIO SERVICES MULTICHANNEL VIDEO AND CABLE TELEVISION SERVICE Technical Standards § 76...the channel under measurement and to substitute therefor a matching resistance termination. Other antennas and inputs should...

2010-10-01

316

78 FR 48626 - Private Land Mobile Radio Rules  

Federal Register 2010, 2011, 2012, 2013, 2014

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

2013-08-09

317

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

318

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

319

A dual-channel cooled GaAsFET receiver for the Dominion Radio Astrophysical Observatory 26-metre radio telescope covering 1.35 to 1.75 GHz  

NASA Astrophysics Data System (ADS)

A low-noise receiver for a radio telescope is described. Two identical three-stage GaAsFET amplifiers were built which give excess noise temperatures of less than 28 K with at least 34 dB gain between 1.35 and 1.75 GHz when operated at a physical temperature of 12 K. This noise temperature is measured at the cryostat input connectors. The physical temperature is maintained by a closed cycle helium refrigerator. Source-inductance feedback is used to allow optimum noise performance combined with good input match. Return loss is better than 15 dB across the band. Construction details of the amplifiers and their mounting in the cryostat are provided. Sample observational results are presented.

Walker, G.; Vaneldik, J. F.; Routledge, D.; Landecker, T. L.; Galt, J. A.

1988-01-01

320

Highly sensitive FBG temperature measurement based on a wavelength pumped multiplexing filter and two optical channels  

NASA Astrophysics Data System (ADS)

An improved demodulation system for fiber Bragg grating (FBG) sensors based on the wavelength pumped multiplexing (WPM) filter is presented. Double photoelectric measurement channels are exploited to compensate the surrounding and light source interference including temperature influence. Temperature testing is employed to prove the demodulation system capacity and characteristics. The digital thermometer and one free FBG are simultaneously introduced in the constant-temperature water tank for the comparison study. The results show that the demodulation scheme can measure temperature with a high resolution, stability and reliability. Its sensitivity of temperature measurement can reach 0.05 °C in repeated testing.

Jiang, Qi; Kang, Yan-Shen

2010-07-01

321

Distributed-feedback fiber laser sensor for simultaneous strain and temperature measurements operating in the radio-frequency domain.  

PubMed

Radio-frequency (rf) beat frequencies between two longitudinal modes and two polarization modes of a birefringent dual-longitudinal-mode moiré distributed-feedback fiber laser are employed to measure strain and temperature simultaneously. Operating entirely in the rf domain, this approach potentially allows one to employ low-cost and precise rf measuring techniques. A strain-temperature cross sensitivity of the strain- and the thermo-optic coefficients, which can be neglected in wavelength-based grating sensors, has been observed. The achieved sensor accuracy was +/-15 microepsilon and +/-0.2 degrees C. PMID:11958255

Hadeler, O; Ibsen, M; Zervas, M N

2001-07-01

322

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

NASA Astrophysics Data System (ADS)

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

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

2012-08-01

323

Sensitivity analysis of a new SWIR-channel measuring tropospheric CH 4 and CO from space  

NASA Astrophysics Data System (ADS)

In preparation for future atmospheric space missions a consortium of Dutch organizations is performing design studies on a nadir viewing grating-based imaging spectrometer using OMI and SCIAMACHY heritage. The spectrometer measures selected species (O 3, NO II, HCHO, H IIO, SO II, aerosols (optical depth, type and absorption index), CO and CH4) with sensitivity down to the Earth's surface, thus addressing science issues on air quality and climate. It includes 3 UV-VIS channels continuously covering the 270-490 nm range, a NIR-channel covering the 710-775 nm range, and a SWIR-channel covering the 2305-2385 nm range. This instrument concept is, named TROPOMI, part of the TRAQ-mission proposal to ESA in response to the Call for Earth Explorer Ideas 2005, and, named TROPI, part of the CAMEO-proposal prepared for the US NRC decadal study-call on Earth science and applications from space. The SWIR-channel is optional in the TROPOMI/TRAQ instrument and included as baseline in the TROPI/CAMEO instrument. This paper focuses on derivation of the instrument requirements of the SWIR-channel by presenting the results of retrieval studies. Synthetic detector spectra are generated by the combination of a forward model and an instrument simulator that includes the properties of state-of-the-art detector technology. The synthetic spectra are input to the CO and CH 4 IMLM retrieval algorithm originally developed for SCIAMACHY. The required accuracy of the Level-2 SWIR data products defines the main instrument parameters like spectral resolution and sampling, telescope aperture, detector temperature, and optical bench temperature. The impact of selected calibration and retrieval errors on the Level-2 products has been characterized. The current status of the SWIR-channel optical design with its demanding requirements on ground-pixel size, spectral resolution, and signal-to-noise ratio will be presented.

Jongma, Rienk T.; Gloudemans, Annemieke M. S.; Hoogeveen, Ruud W. M.; Aben, Ilse; de Vries, Johan; Escudero-Sanz, Isabel; van den Oord, Gijsbertus; Levelt, Pieternel F.

2006-08-01

324

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

Federal Register 2010, 2011, 2012, 2013, 2014

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

2013-05-10

325

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

326

Measurement of the Top Quark Pair Production Cross Section in the All-Jets Decay Channel  

NASA Astrophysics Data System (ADS)

We present a measurement of tt¯ production in pp¯ collisions at 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 of 7.1+/-2.8\\(stat\\)+/-1.5\\(syst\\) pb at a top quark mass \\(mt\\) of 172.1 GeV/c2. Using previous D0 measurements from dilepton and single lepton channels, the combined D0 result for the tt¯ production cross section is 5.9+/-1.2\\(stat\\)+/-1.1\\(syst\\) pb for mt = 172.1 GeV/c2.

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

1999-09-01

327

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

328

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

329

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

Microsoft Academic Search

Experiments were performed to measure the incipient boiling heat flux in a heat sink containing 21 rectangular (231 ?m wide and 713 ?m deep) micro-channels. Tests were performed using deionized water with inlet liquid velocities of 0.13–1.44 m\\/s, inlet temperatures of 30, 60 and 90 °C, and an outlet pressure of 1.2 bar. Using a microscope, boiling incipience was identified

Weilin Qu; Issam Mudawar

2002-01-01

330

Coupling Interactions between Voltage Sensors of the Sodium Channel as Revealed by Site-specific Measurements  

Microsoft Academic Search

The voltage-sensing S4 segments in the sodium channel undergo conformational rearrangements in response to changes in the electric field. However, it remains unclear whether these structures move indepen- dently or in a coordinated manner. Previously, site-directed fluorescence measurements were shown to track S4 transitions in each of the four domains (Chanda, B., and F. Bezanilla. 2002. J. Gen. Physiol. 120:629-645).

Baron Chanda; Osei Kwame Asamoah; Francisco Bezanilla

2004-01-01

331

Plasma Potential Measurements in the Discharge Channel of a 6kW Hall Thruster  

Microsoft Academic Search

In an effort to understand the role of neutral flow dynamics in the operation of Hall thrusters, a floating emissive probe was used to measure the plasma potential, electric field, and electron temperature in the discharge channel of a 6-kW Hall thruster operating at 300 V and anode flow rates of 10, 20, and 30 mg\\/s. To isolate the effect

Bryan M. Reid; Alec D. Gallimore

332

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

333

Harmonic Analysis of Time Variations Observed in the Solar Radio Flux Measured at 810 MHz from 1957 to 2004  

E-print Network

Long-running measurements of the solar radio flux density at 810 MHz were processed. Based on the least-squares method and using modified periodograms and an iterative technique of fitting and subtracting sinusoids in the time domain, frequency, amplitude, and phase characteristics of any analyzed time series were obtained. Solar cycles 20, 21, and 22 and shorter segments around solar minima and maxima were examined separately. Also, dynamic studies with 405, 810, and 1620 day windows were undertaken. The harmonic representations obtained for all these time series indicate large differences among solar cycles and their segments. We show that the solar radio flux at 810 MHz violates the Gnevyshev-Ohl rule for the pair of cycles 22-23. Analyzing the period 1957-2004, the following spectral periods longer than 1350 days were detected: 10.6, 8.0, 28.0, 5.3, 55.0, 3.9, 6.0, 4.4, and 14.6 yr. For spectral periods between 270 and 1350 days the 11 yr cycle is not recognized. We think that these harmonics form ``impulses of activity'' or a quasi-biennial cycle defined in the Benevolenskaya model of the ``double magnetic cycle.'' The value of about 0.09 is proposed for the interaction parameter (between the low- and high-frequency components) of this model. We confirm the intermittent behavior of the periodicity near 155 days. Correlation coefficients between the radio emission at 810 MHz and sunspot numbers, as well as the radio emission at 2800 MHz calculated for 540 day intervals, depend on the solar cycle phase.

S. Zieba; J. Maslowski; A. Michalec; G. Michalek; A. Kulak

2007-01-15

334

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

335

Ground-based measurement of gradients in the “wet” radio refractivity of air  

Microsoft Academic Search

order of 0.1-1 N km - . These gradients are larger, by 1-2 orders of magnitude, than gradients determined by others by averaging over long (.,100-km) distances. This result implies that for applications that are sensitive to local gradients, such as wet propagation-delay models for radio-interferometric geodetic studies, the use of meteorological data from widely spread stations may be inadequate.

James L. Davis; Gunnar Elgered; Arthur E. Niell; Clara E. Kuehn

1993-01-01

336

National Radio Astronomy Observatory Electronics Division Technical Note No. 219  

E-print Network

1 National Radio Astronomy Observatory Electronics Division Technical Note No. 219 Measurements of Automotive Radar Emissions received by a Radio Astronomy Observatory Darrel Emerson (National Radio Astronomy upon radio astronomy observations, measurements sponsored by the National Science Foundation were

Groppi, Christopher

337

High fidelity wireless network evaluation for heterogeneous cognitive radio networks  

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

338

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

339

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

340

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

341

Rolling Stone Radio  

NSDL National Science Digital Library

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

342

Eratosthenes via Ham Radio  

ERIC Educational Resources Information Center

A secondary geology class used Eratosthenes' method for measuring the circumference of the earth by comparing their measurements of the shadow of a vertical rod to the measurements made by another person contacted by ham radio. (MLH)

Koser, John F.

1975-01-01

343

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

Microsoft Academic Search

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

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

2000-01-01

344

A 19-channel fast grating polychromator for ECE measurements in the MTX tokamak  

NASA Astrophysics Data System (ADS)

A 19-channel grating polychromator is developed to measure the temporal evolution of the electron cyclotron emission spectrum in the second and third harmonics in MTX tokamak with an aim to determine the electron temperature in ohmically heated thermal plasmas as well as the electron energy distribution function in gyrotron and free-electron laser-pumped nonthermal plasmas. The spectrometer can cover a spectral range of about 0.3 to 1.4 mm and deliver a maximum spatial resolution of about 1 cm radially. A combination of a 90° off-axis paraboloidal mirror as the collimating element and a toroidal mirror to focus the diffracted beam yields images on the exit slits with a modest astigmatic distortion. Liquid-helium-cooled InSb detectors are installed in nine channels and associated electronics are optimized for a very low noise and fast response time ( ˜ 2 ?s). A faster detector element, with response < 100 ns, is envisioned for the remaining ten channels.

Guharay, S. K.; Boyd, D. A.; Ellis, R. F.; Stauffer, F. J.; Lasnier, C. J.

1990-11-01

345

A 19-channel fast grating polychromator for ECE measurements in the MTX tokamak (abstract)  

NASA Astrophysics Data System (ADS)

A 19-channel grating polychromator is developed to measure the temporal evolution of the electron cyclotron emission spectrum in the second and third harmonics in the MTX tokamak with an aim to determine the electron temperature in ohmically heated thermal plasmas as well as the electron energy distribution function in gyrotron and free-electron laser-pumped nonthermal plasmas. The spectrometer can cover a spectral range of about 0.3 to 1.4 mm and deliver a maximum spatial resolution of about 1 cm radially. A combination of a 90° off-axis paraboloidal mirror as the collimating element and a toroidal mirror to focus the diffracted beam yields images on the exit slits with a modest astigmatic distortion. Liquid-helium-cooled InSb detectors are installed in nine channels and associated electronics are optimized for a very low noise and fast response time (˜2 ?s). A faster detector element, with response <100 ns, is envisioned for the remaining ten channels.

Guharay, S. K.; Boyd, D. A.; Ellis, R. F.; Stauffer, F. J.; Lasnier, C. J.

1990-10-01

346

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

NASA Technical Reports Server (NTRS)

Direct current measurements are available near the attachment point from both natural cloud-to-ground lightning and rocket-triggered lightning, but little is known about the rise time and peak amplitude of return-stroke currents aloft. We present, as functions of height, current amplitudes, rise times, and effective propagation velocities that have been estimated with a novel remote-sensing technique from data on 24 subsequent return strokes in six different lightning flashes that were triggering at the NASA Kennedy Space Center, FL, during 1987. The unique feature of this data set is the stereo pairs of still photographs, from which three-dimensional channel geometries were determined previously. This has permitted us to calculate the fine structure of the electric-field-change (E) waveforms produced by these strokes, using the current waveforms measured at the channel base together with physically reasonable assumptions about the current distributions aloft. The computed waveforms have been compared with observed E waveforms from the same strokes, and our assumptions have been adjusted to maximize agreement. In spite of the non-uniqueness of solutions derived by this technique, several conclusions seem inescapable: 1) The effective propagation speed of the current up the channel is usually significantly (but not unreasonably) faster than the two-dimensional velocity measured by a streak camera for 14 of these strokes. 2) Given the deduced propagation speed, the peak amplitude of the current waveform often must decrease dramatically with height to prevent the electric field from being over-predicted. 3) The rise time of the current wave front must always increase rapidly with height in order to keep the fine structure of the calculated field consistent with the observations.

Willett, J. C.; LeVine, D. M.

2002-01-01

347

SARAS: a precision system for measurement of the cosmic radio background and signatures from the epoch of reionization  

NASA Astrophysics Data System (ADS)

SARAS is a correlation spectrometer purpose designed for precision measurements of the cosmic radio background and faint features in the sky spectrum at long wavelengths that arise from redshifted 21-cm from gas in the reionization epoch. SARAS operates in the octave band 87.5-175 MHz. We present herein the system design arguing for a complex correlation spectrometer concept. The SARAS design concept provides a differential measurement between the antenna temperature and that of an internal reference termination, with measurements in switched system states allowing for cancellation of additive contaminants from a large part of the signal flow path including the digital spectrometer. A switched noise injection scheme provides absolute spectral calibration. Additionally, we argue for an electrically small frequency-independent antenna over an absorber ground. Various critical design features that aid in avoidance of systematics and in providing calibration products for the parametrization of other unavoidable systematics are described and the rationale discussed. The signal flow and processing is analyzed and the response to noise temperatures of the antenna, reference termination and amplifiers is computed. Multi-path propagation arising from internal reflections are considered in the analysis, which includes a harmonic series of internal reflections. We opine that the SARAS design concept is advantageous for precision measurement of the absolute cosmic radio background spectrum; therefore, the design features and analysis methods presented here are expected to serve as a basis for implementations tailored to measurements of a multiplicity of features in the background sky at long wavelengths, which may arise from events in the dark ages and subsequent reionization era.

Patra, Nipanjana; Subrahmanyan, Ravi; Raghunathan, A.; Udaya Shankar, N.

2013-08-01

348

A fluorometric approach to local electric field measurements in a voltage-gated ion channel.  

PubMed

Site-specific electrostatic measurements have been limited to soluble proteins purified for in vitro spectroscopic characterization or proteins of known structure; however, comparable measurements have not been made for functional membrane bound proteins. Here, using an electrochromic fluorophore, we describe a method to monitor localized electric field changes in a voltage-gated potassium channel. By coupling the novel probe Di-1-ANEPIA to cysteines in Shaker and tracking field-induced optical changes, in vivo electrostatic measurements were recorded with submillisecond resolution. This technique reports dynamic changes in the electric field during the gating process and elucidates the electric field profile within Shaker. The extension of this method to other membrane bound proteins, including transporters, will yield insight into the role of electrical forces on protein function. PMID:12526775

Asamoah, Osei Kwame; Wuskell, Joseph P; Loew, Leslie M; Bezanilla, Francisco

2003-01-01

349

Multi-channel optical pyrometer for sub-nanosecond temperature measurements at NDCX-I/II  

SciTech Connect

We present a detailed technical description of a fast multi-channel pyrometer designed for warm-dense-matter (WDM) experiments with intense heavy ion beams at the neutralized-drift-compression-experiment linear accelerator (NDCX-I/II) at Lawrence Berkeley National Laboratory (LBNL). The unique features of the described instrument are its sub-nanosecond temporal resolution (100 ps rise-time) and a broad range, 1,500 K - 12,000 K of measurable brightness temperatures in the visible and near-infrared regions of the spectrum. The working scheme, calibration procedure, experimental data obtained with the pyrometer and future applications are presented.

Ni, P.A.; Bieniosek, F.M.; Waldron, W.L.

2011-04-13

350

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

351

Channel and Traffic based Adaptive Radio Resource Management strategies for the return link of Ka\\/Q\\/V band Communication Satellite systems employing Fade Mitigation Techniques  

Microsoft Academic Search

Efficient utilization of the satellite radio resource is of paramount importance to a satellite system's performance and economic competitiveness. The likely use of Ka band and above frequencies for future satellite systems and the need for a better quality of service (QoS) complicate the radio resource management process especially in the return link of a satellite system, one that connects

A. Aroumont; J. Radzik; M. Bousquet; L. Castanet

2007-01-01

352

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

353

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

354

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

355

Time domain measures of inter-channel EEG correlations: a comparison of linear, nonparametric and nonlinear measures.  

PubMed

Correlations between ten-channel EEGs obtained from thirteen healthy adult participants were investigated. Signals were obtained in two behavioral states: eyes open no task and eyes closed no task. Four time domain measures were compared: Pearson product moment correlation, Spearman rank order correlation, Kendall rank order correlation and mutual information. The psychophysiological utility of each measure was assessed by determining its ability to discriminate between conditions. The sensitivity to epoch length was assessed by repeating calculations with 1, 2, 3, …, 8 s epochs. The robustness to noise was assessed by performing calculations with noise corrupted versions of the original signals (SNRs of 0, 5 and 10 dB). Three results were obtained in these calculations. First, mutual information effectively discriminated between states with less data. Pearson, Spearman and Kendall failed to discriminate between states with a 1 s epoch, while a statistically significant separation was obtained with mutual information. Second, at all epoch durations tested, the measure of between-state discrimination was greater for mutual information. Third, discrimination based on mutual information was more robust to noise. The limitations of this study are discussed. Further comparisons should be made with frequency domain measures, with measures constructed with embedded data and with the maximal information coefficient. PMID:24465281

Bonita, J D; Ambolode, L C C; Rosenberg, B M; Cellucci, C J; Watanabe, T A A; Rapp, P E; Albano, A M

2014-02-01

356

Frequency Allocation; The Radio Spectrum.  

ERIC Educational Resources Information Center

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

Federal Communications Commission, Washington, DC.

357

Viking radio occultation measurements of the atmosphere and topography of Mars - Data acquired during 1 Martian year of tracking  

NASA Technical Reports Server (NTRS)

The results of one Martian year of radio occultation measurements of the atmosphere and topography of Mars obtained using the Viking Orbiters are briefly summarized. Determinations of the vertical distribution of tropospheric gas refractivity and ionospheric electron density obtained from atmospheric Doppler frequency perturbations of the S and X band radio tracking frequencies indicate large meteorological variations, with near-surface temperatures ranging from 150 to 250 K, 5-km atmospheric pressure ranging from 3.5 to 4.8 mbar, inversion layers over the polar caps and dust storms, and seasonal pressure variations. Double- and single-layered upper atmospheric electron density profiles were observed on the sunlit and dark sides of the planet, respectively. A topographic map of the Martian surface, obtained from the limb diffraction effects observed at ingress and egress, is found to agree well with the elevation contours of US Geological survey map M 25M 3 RMC, with the exception of the south polar and Alba Patera regions.

Lindal, G. F.; Hotz, H. B.; Sweetnam, D. N.; Shippony, Z.; Brenkle, J. P.; Hartsell, G. V.; Spear, R. T.

1979-01-01

358

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

359

The ^3He(e,e'n) Channel in Ay and GE^n Measurements  

NASA Astrophysics Data System (ADS)

Experiments E05-102 and E08-005 involved measurements of electron scattering from polarized ^3He reactions that have been conducted in Jefferson Lab's Hall A this past year. E08-005 measured the Target Single-Spin Asymmetry Ay in the quasi-elastic ^3He^(e,e'n) reaction. Plane wave impulse approximation (PWIA) predicts that Ay should be exactly zero. A previous experiment at Q^2 of 0.2 (GeV/c)^2, where Laget and Nagorny predict Ay to be small, showed a large asymmetry as predicted by Faddeev calculations. The recent experiment measured this asymmetry at Q^2 of 0.1 (GeV/c)^2, 0.5 (GeV/c)^2 and 1.0 (GeV/c)^2. This is the first measurement of Ay at large Q^2, which is another region where Ay is expected to be small. Any non-zero result is an indication of effects beyond impulse approximation. During E05-102, a parasitic measurement of the electric form factor of the neutron (GE^n) was taken using the ^3He(e,e'n) channel at Q^2 of 0.4 (GeV/c)^2, 0.5 (GeV/c)^2 and 1.0 (GeV/c)^2. An overview of these measurements will be presented.

Long, Elena

2009-10-01

360

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

361

Bulk velocity measurements by video analysis of dye tracer in a macro-rough channel  

NASA Astrophysics Data System (ADS)

Steep mountain rivers have hydraulic and morphodynamic characteristics that hinder velocity measurements. The high spatial variability of hydraulic parameters, such as water depth (WD), river width and flow velocity, makes the choice of a representative cross-section to measure the velocity in detail challenging. Additionally, sediment transport and rapidly changing bed morphology exclude the utilization of standard and often intrusive velocity measurement techniques. The limited technical choices are further reduced in the presence of macro-roughness elements, such as large, relatively immobile boulders. Tracer tracking techniques are among the few reliable methods that can be used under these conditions to evaluate the mean flow velocity. However, most tracer tracking techniques calculate bulk flow velocities between two or more fixed cross-sections. In the presence of intense sediment transport resulting in an important temporal variability of the bed morphology, dead water zones may appear in the few selected measurement sections. Thus a technique based on the analysis of an entire channel reach is needed in this study. A dye tracer measurement technique in which a single camcorder visualizes a long flume reach is described and developed. This allows us to overcome the problem of the presence of dead water zones. To validate this video analysis technique, velocity measurements were carried out on a laboratory flume simulating a torrent, with a relatively gentle slope of 1.97% and without sediment transport, using several commonly used velocity measurement instruments. In the absence of boulders, salt injections, WD and ultrasonic velocity profiler measurements were carried out, along with dye injection technique. When boulders were present, dye tracer technique was validated only by comparison with salt tracer. Several video analysis techniques used to infer velocities were developed and compared, showing that dye tracking is a valid technique for bulk velocity measurements. RGB Euclidean distance was identified as being the best measure of the average flow velocity.

Ghilardi, T.; Franca, M. J.; Schleiss, A. J.

2014-03-01

362

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

363

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; Stämpfli, R

1976-01-01

364

Simultaneously measured lightning return stroke channel-base current and luminosity  

NASA Astrophysics Data System (ADS)

time delay between lightning return stroke current and the resultant luminosity was measured for 22 return strokes in eight lightning flashes triggered by the rocket-and-wire technique during the summer of 2014 in Florida. The current-to-luminosity delay measured at the channel base at the 20% amplitude level ranged from 30 to 200 ns with an average of 90 ns and at the 50% amplitude level ranged from 30 to 180 ns with an average of 94 ns. The delays are significantly shorter than that predicted by Liang et al. (2014) from theory. The current-to-luminosity delays increase with increasing current risetime, current risetime varying from 190 ns to 570 ns, but the delay appears not to depend on the peak current value.

Carvalho, F. L.; Jordan, D. M.; Uman, M. A.; Ngin, T.; Gamerota, W. R.; Pilkey, J. T.

2014-11-01

365

Field intercomparison of channel master ADCP with RiverSonde Radar for measuring river discharge  

USGS Publications Warehouse

The RiverSonde radar makes non-contact measurement of a horizontal swath of surface velocity across a river section. This radar, which has worked successfully at several rivers in the Western USA, has shown encouraging correlation with simultaneous measurements of average currents at one level recorded by an acoustic travel-time system. This work reports a field study intercomparing data sets from a 600 kHz Channel Master ADCP with the RiverSonde radar. The primary goal was to begin to explore the robustness of the radar data as a reliable index of discharge. This site Is at Three Mile Slough in Northern California, USA. The larger intent of the work is to examine variability in space and time of the radar's surface currents compared with subsurface flows across the river section. Here we examine data from a couple of periods with strong winds. ?? 2005 IEEE.

Spain, P.; Marsden, R.; Barrick, D.; Teague, C.; Ruhl, C.

2005-01-01

366

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

PubMed

We measure the top quark mass (m(t)) in p ?p collisions at a center of mass energy ?s = 1.96 TeV using dilepton t ?t?W(+)bW(-) ?b??(+)?(?)b?(-) ??(?) ?b events, where ? 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 m(t)=174.0±1.8(stat)±2.4(syst) GeV, which is in agreement with the current world average m(t)=173.3±1.1 GeV. This is currently the most precise measurement of m(t) in the dilepton channel. PMID:21929164

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

2011-08-19

367

Channel Steering  

E-print Network

We introduce and study the notion of steerability for channels. This generalizes the notion of steerability of bipartite quantum states. We discuss a key conceptual difference between the case of states and the case of channels: while state steering deals with the notion of "hidden" states, steerability in the channel case is better understood in terms of coherence of channel extensions, rather than in terms of "hidden" channels. This distinction vanishes in the case of states. We further argue how the proposed notion of lack of coherence of channel extensions coincides with the notion of channel extensions realized via local operations and classical communication. We also discuss how the Choi-Jamiolkowski isomorphism allows the direct application of many results about states to the case of channels. We introduce measures for the steerability of channel extensions.

Marco Piani

2014-11-03

368

Radio determination satellite service  

NASA Astrophysics Data System (ADS)

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

Briskman, Robert D.

1990-07-01

369

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

370

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

371

#EdChat Radio  

NSDL National Science Digital Library

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

BAM Radio Network

2013-01-01

372

Three-channel three-dimensional self-mixing thin-slice solid-state laser-Doppler measurements.  

PubMed

We report successful real-time three-channel self-mixing laser-Doppler measurements with extreme optical sensitivity using a laser-diode-pumped thin-slice Nd:GdVO(4) laser in the carrier-frequency-division-multiplexing scheme with three pairs of acoustic optical modulators (i.e., frequency shifters) and a three-channel FM-wave demodulation circuit. We demonstrate (1) simultaneous independent measurement of three different nanometer-vibrating targets, (2) simultaneous measurements of small particles in Brownian motion from three directions, and (3) identification of the velocity vector of small particles moving in water flowing in a small-diameter glass pipe. PMID:19151832

Ohtomo, Takayuki; Sudo, Seiichi; Otsuka, Kenju

2009-01-20

373

Three-channel three-dimensional self-mixing thin-slice solid-state laser-Doppler measurements  

SciTech Connect

We report successful real-time three-channel self-mixing laser-Doppler measurements with extreme optical sensitivity using a laser-diode-pumped thin-slice Nd:GdVO4 laser in the carrier-frequency-division-multiplexing scheme with three pairs of acoustic optical modulators (i.e., frequency shifters) and a three-channel FM-wave demodulation circuit. We demonstrate (1) simultaneous independent measurement of three different nanometer-vibrating targets, (2) simultaneous measurements of small particles in Brownian motion from three directions, and (3) identification of the velocity vector of small particles moving in water flowing in a small-diameter glass pipe.

Ohtomo, Takayuki; Sudo, Seiichi; Otsuka, Kenju

2009-01-20

374

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

375

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

376

in the lipid bilayer Distance measurements reveal a common topology of prokaryotic voltage-gated ion channels  

E-print Network

in the lipid bilayer Distance measurements reveal a common topology of prokaryotic voltage.pnas.org/misc/reprints.shtml To order reprints, see: Notes: #12;Distance measurements reveal a common topology of prokaryotic voltage conformations in a mem- brane environment. The validity of the crystal structure for the prokaryotic K channel

Bezanilla, Francisco

377

The R-609 radio set  

NASA Astrophysics Data System (ADS)

The R-609 radio set is intended for simplex telephone communication in the frequency range from 100 to 150 MHz with the setting of the operating frequencies of the transmitter and receiver by interchangeable crystals. The set can be preliminary tuned in this range on any four operating frequencies and search-free communication carried out on them. Switching from one communication channel to another is realized automatically by pressing the appropriate button on the control panel or on the measuring unit, for which no more than three seconds are required. Thirty crystals each for the transmitter and the receiver are usually attached to the operating set of the station. The radio set utilizes a wide-band discone antenna, ensuring communication in the entire range of frequencies, or a half-wave vibrator. The radio set is powered from an alternating current network with a voltage of 110, 127 ro 220 V, and also from an on-board direct current network through a voltage converter of the types OP-120 and AMG-3.

Ronzhin, S.

1985-02-01

378

Application of left- and right-looking SAR stereo to depth measurements of the Ammavaru outflow channel, Lada Terra, Venus  

NASA Technical Reports Server (NTRS)

Venusian channels are too narrow to be resolved by Magellan's radar altimeter, so they are not visible in the standard topographic data products. Stereo image data, in addition to their benefit to geologic mapping of Venus structures as a whole, are indispensible in measuring the topography across the channels. These measurements can then be used in conjunction with the regional topographic maps based on the altimeter data to produce cross-sectional areas for the channels and estimate the fluid discharge through them. As an example of the application of the stereo image data to venusian channels, a number of test depth and profile measurements were made of the large outflow channel system in Lada Terra, centered at 50 deg S latitude, 21 deg E longitude (F-MIDR 50S021). These measurements were made by viewing the cycle 1 and 2 digital FMIDRs in stereo on a display monitor, so as to minimize the errors in measuring parallax displacement as much as possible. The MIDRs are produced at a scale of 75 m/pixel. This corresponds to a vertical scale of about 17 m/pixel, when calculating the height of a feature from its parallax displacement. An error in placement determination of 1 pixel was assumed to characterize the vertical accuracy as plus or minus 17 m. When this technique was applied to the outflow channel, it was noted that the walls of the collapsed terrain source and 'trough reach' of the channel are laid over in both the cycle 1 and 2 images. This is evident when examining the distance between features on the plateau and the cliff walls in the two images. The layover 'shifts' the features closer to the apparent edge of the wall relative to the oppositely illuminated image.

Parker, T. J.

1992-01-01

379

RBS channeling measurement of damage annealing in InAs/AlSb HEMT structures  

NASA Astrophysics Data System (ADS)

Electrical isolation of InAs/AlSb high electron mobility transistors has been achieved by the ion implantation isolation technique. The multilayered structures are grown by molecular beam epitaxy on GaAs substrates. The optimal isolation is provided by damaging patterned areas by 100 keV Ar ions implanted at room temperature using fluence of 2 × 1015 cm-2, and then annealing the samples in 365 °C for 30 min. The damage build-up and annealing is studied by channeling Rutherford backscattering spectrometry (RBS) and compared to sheet resistance measurements. Only a low level of damage annealing can be seen in RBS for the post-implant annealed samples, but for Ar fluence higher than 2 × 1014 cm-2, a strong electrical resistivity increase can still be achieved.

Hallén, Anders; Moschetti, Giuseppe

2014-08-01

380

UNDERSTANDING HF CHANNEL SIMULATOR REQUIREMENTS IN ORDER TO REDUCE HF MODEM PERFORMANCE MEASUREMENT VARIABILITY  

Microsoft Academic Search

SUMMARY This paper begins with a brief overview of the HF channel and the mechanisms that hinder both analog and digital communications. Next the paper examines the Watterson channel model and describes the constituent parts common to most channel simulator implementations. This is followed by an overview of standards and documents which address various aspects of simulator implementations utilized for

W. N. Furman; J. W. Nieto

381

On the mobile radio capacity increase through SDMA  

Microsoft Academic Search

In a cellular mobile radio system an SDMA component can be implemented for the reuse of radio channels physically incorporated by time, frequency or code slots. In this paper we will present simulation results on an SDMA downlink channel allocation scheme operating in a typical urban mobile radio cell. Based on the resulting blocking probabilities we will give estimations on

C. Farsakh; J. A. Nossek

1998-01-01

382

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

383

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

384

Performance of a DFE modem evaluated from measured indoor radio multipath profiles  

Microsoft Academic Search

Measured multipath profiles from five different indoor areas are used for the performance analysis of a binary phase-shift-keying modem, with and without a decision feedback equalizer. Both the average bit error rate and outage probability are calculated as the performance criteria. The average probability of error from the measured multipath profiles is compared with the performance predictions based on theoretical

Steven J. Howard; K. Pahlavan

1990-01-01

385

On the stability of fiber-optic quantum cryptography at arbitrary losses in a communication channel: Exclusion of unambiguous measurements  

NASA Astrophysics Data System (ADS)

Since a source of quantum states is not strictly single-photon and losses exist in a communication channel, an attack with unambiguous measurements is possible, leading to loss of security. The problem of the stability of quantum key distribution protocols in a channel with large losses is still unsolved. A radical solution of this problem has been proposed by completely excluding unambiguous measurements by an eavesdropper. The problem is solved by means of counting of classical reference pulses. The conservation of the number of classical sync pulses results in the impossibility of unambiguous measurements. In this case, losses in the communication channel are considered as a priori unknown and can vary during a series of messages.

Molotkov, S. N.

2014-11-01

386

Velocity measurement of particulate flow in microfluidic channels using single point confocal fluorescence detection.  

PubMed

This article presents a non-invasive, optical technique for measuring particulate flow within microfluidic channels. Confocal fluorescence detection is used to probe single fluorescently labeled microspheres (0.93 microm diameter) passing through a focused laser beam at a variety of flow rates (50 nL min(-1)-8 microL min(-1)). Simple statistical methods are subsequently used to investigate the resulting fluorescence bursts and generate velocity data for the flowing particles. Fluid manipulation is achieved by hydrodynamically pumping fluid through microchannels (150 microm wide and 50 microm deep) structured in a polydimethylsiloxane (PDMS) substrate. The mean fluorescence burst frequency is shown to be directly proportional to flow speed. Furthermore, the Poisson recurrence time and width of recovered autocorrelation curves is demonstrated to be inversely proportional to flow speed. The component-based confocal fluorescence detection system is simple and can be applied to a diversity of planar chip systems. In addition, velocity measurement only involves interrogation of the fluidic system at a single point along the flow stream, as opposed to more normal multiple-point measurements. PMID:11763073

Edel, J B; Hill, E K; de Mello, A J

2001-11-01

387

Measurement of a phase of a radio wave reflected from rock salt and ice irradiated by an electron beam for detection of ultra-high-energy neutrinos  

NASA Astrophysics Data System (ADS)

We have found a radio-wave-reflection effect in rock salt for the detection of ultra-high energy neutrinos (UHE?'s) which are expected to be generated in Greisen, Zatsepin, and Kuzmin (GZK) processes in the universe. When an UHE? interacts with rock salt or ice as a detection medium, a shower is generated. That shower is formed by hadronic and electromagnetic avalanche processes. The energy of the UHE? shower converts to thermal energy through ionization processes. Consequently, the temperature rises along the shower produced by the UHE?. The refractive index of the medium rises with temperature. The irregularity of the refractive index in the medium leads to a reflection of radio waves. This reflection effect combined with the long attenuation length of radio waves in rock salt and ice would yield a new method to detect UHE?'s. We measured the phase of the reflected radio wave under irradiation with an electron beam on ice and rock salt powder. The measured phase showed excellent consistence with the power reflection fraction which was measured directly. A model taking into account the temperature change explained the phase and the amplitude of the reflected wave. Therefore the reflection mechanism was confirmed. The power reflection fraction was compared with that calculated with the Fresnel equations, the ratio between the measured result and that obtained with the Fresnel equations in ice was larger than that of rock salt.

Chiba, Masami; Kamijo, Toshio; Tanikawa, Takahiro; Yano, Hiroyuki; Yabuki, Fumiaki; Yasuda, Osamu; Chikashige, Yuichi; Kon, Tadashi; Shimizu, Yutaka; Watanabe, Souichirou; Utsumi, Michiaki; Fujii, Masatoshi

2013-05-01

388

Channel probe measurements for the American sector clutter experiment, January, 1994  

SciTech Connect

The ionospheric phenomenon called Equatorial Spread F encompasses a variety of effects associated with plasma irregularities occurring in the post-sunset and nighttime ionosphere near the magnetic equator. These irregularities can seriously degrade the performance of systems which involve either of necessity or inadvertently radio propagation through the equatorial ionosphere. One such system is Over-the-Horizon (OTH) radars which operate in the high-frequency (hf) band and use ionospheric reflection for forward and backscatter propagation to ranges of thousands of kilometers. When such radars are directed towards the equator, Spread F irregularities can cause scintillation effects which may be aliased into the ranges of interest and have the effect of causing, excess clutter in which targets may be hidden. In January, 1994 Los Alamos participated in a campaign to measure Spread F effects on OTH propagation from the United States looking towards South America in conjunction with local diagnostics in Peru. During the campaign Los Alamos fielded a 1600 km bistatic path between Piura, Peru, and Arequipa, Peru-, the one-hop reflection region for this path was near the magnetic equator, We obtained four types of measurements: an oblique ionogram between Piura and Arequipa every three minutes; Doppler spread and spatial correlation for a single frequency cw path between Piura and Arequipa; Doppler spread, time-delay spread, and spatial coherence for a 10 kHz bandwidth path between Piura and Arequipa-, and Doppler spread and time-delay spread for the one-way path between the AVA radar in New York and Arequipa, Peru. This report describes the diagnostic experiments that we carried out and gives a brief description of some of the data we obtained.

Fitzgerald, T.J.

1994-05-20

389

Measurement of the quenching and channeling effects in a CsI crystal used for a WIMP search  

E-print Network

We have studied channeling effects in a Cesium Iodide (CsI) crystal that is similar in composition to the ones being used in a search for Weakly Interacting Massive Particles (WIMPs) dark matter candidates, and measured its energy-dependent quenching factor, the relative scintillation yield for electron and nuclear recoils. The experimental results are reproduced with a GEANT4 simulation that includes a model of the scintillation efficiency as a function of electronic stopping power. We present the measured and simulated quenching factors and the estimated effects of channeling.

Lee, J H; Seong, I S; Kim, B H; Kim, J H; Li, J; Park, J W; Lee, J K; Kim, K W; Bhang, H; Kim, S C; Choi, Seonho; Choi, J H; Joo, H W; Lee, S J; Olsen, S L; Myung, S S; Kim, S K; Kim, Y D; Kang, W G; So, J H; Kim, H J; Lee, H S; Hahn, I S; Leonard, D S; Li, Y J; Yue, Q; Li, X R

2015-01-01

390

Measurement of the quenching and channeling effects in a CsI crystal used for a WIMP search  

E-print Network

We have studied channeling effects in a Cesium Iodide (CsI) crystal that is similar in composition to the ones being used in a search for Weakly Interacting Massive Particles (WIMPs) dark matter candidates, and measured its energy-dependent quenching factor, the relative scintillation yield for electron and nuclear recoils. The experimental results are reproduced with a GEANT4 simulation that includes a model of the scintillation efficiency as a function of electronic stopping power. We present the measured and simulated quenching factors and the estimated effects of channeling.

J. H. Lee; G. B. Kim; I. S. Seong; B. H. Kim; J. H. Kim; J. Li; J. W. Park; J. K. Lee; K. W. Kim; H. Bhang; S. C. Kim; Seonho Choi; J. H. Choi; H. W. Joo; S. J. Lee; S. L. Olsen; S. S. Myung; S. K. Kim; Y. D. Kim; W. G. Kang; J. H. So; H. J. Kim; H. S. Lee; I. S. Hahn; D. S. Leonard; J. Li; Y. J. Li; Q. Yue; X. R. Li

2015-02-12

391

HF radio field strength and total propagation invariants  

NASA Astrophysics Data System (ADS)

This paper investigates the relationship between measured field strengths, observed over two midlatitude long-distance paths, and total adiabatic invariants calculated for all possible propagation channels, for equinoxes and for low and high solar activity. Communication channel invariants or channel volumes of all types of channels have been calculated for a frequency of 15 MHz using the EMI-81 ionospheric model for both simple channels (F, E, FE) made up of conventional hop trajectories (Fh, Eh) refracted by ionospheric layers, and ricochet, or chordal, trajectories (Fr, Er, FE) which propagate in stratification ducts within the ionospheric layers, or combinations of these channels. It is shown that under night and twilight (day-night) conditions the field strength, in general, is proportional to the total channel volume: E approximately = (I(sub Sigma))(sup n), where n = 0.5 to 2. This indicates the strong influence of multiple scattering by irregularities on the processes of capture, loss, and radio wave propagation in ionospheric waveguide channels. This is in accordance with the results of using ray diffusion theory and adiabatic approximation, where the horizontal character of the waveguide channel varies slowly in relation to the oscillation of the ray within the duct. Greater field strengths observed during sunset, when the terminator was moving along the path, are explained by the influence of the larger wave channel volumes at this time in comparison with other periods.

Tsedilina, E. E.

1994-01-01

392

Measurement of radio wave reflection due to temperature rising from rock salt and ice irradiated by an electron beam for an ultra-high-energy neutrino detector  

SciTech Connect

An ultra-high-energy neutrino (UHE{nu}) gives temperature rise along the hadronic and electromagnetic shower when it enters into rock salt or ice. Permittivities of them arise with respect the temperatures at ionization processes of the UHE{nu} shower. It is expected by Fresnel's formula that radio wave reflects at the irregularity of the permittivity in the medium. We had found the radio wave reflection effect in rock salt. The reflection effect and long attenuation length of radio wave in rock salt and ice would yield a new UHE{nu} detection method. An experiment for ice was performed to study the reflection effect. A coaxial tube was filled with rock salt powder or ice. Open end of the coaxial tube was irradiated by a 2 MeV electron beam. Radio wave of 435 MHz was introduced to the coaxial tube. We measured the reflection wave from the open end. We found the radio wave reflection effect due to electron beam irradiation in ice as well as in rock salt.

Tanikawa, Takahiro; Chiba, Masami; Kamijo, Toshio; Yabuki, Fumiaki; Yasuda, Osamu; Akiyama, Hidetoshi; Chikashige, Yuichi; Kon, Tadashi; Shimizu, Yutaka; Utsumi, Michiaki; Fujii, Masatoshi [Graduate School of Science and Engineering, Tokyo Metropolitan University, 1-1 Minami-Ohsawa, Hachioji-shi, Tokyo 192-0397 (Japan); Faculty of Science and Technology, Seikei University, Musashino-shi, Tokyo 180-8633 (Japan); Department of Applied Science and Energy Engineering, School of Engineering, Tokai University, Hiratsuka-shi, Kanagawa 259-1292 (Japan); School of Medicine, Shimane University, Izumo-shi, Shimane 693-8501 (Japan)

2012-11-12

393

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

394

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.

395

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

396

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

397

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

PubMed

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. PMID:25419536

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

2014-02-27

398

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

E-print Network

and Capacitors A. R. Kerr and M. Lambeth 5 March 2007 Abstract: This note describes measurements of some chip capacitors and thin-film resistors at 4.2 K. The capacitors have the following dielectrics: SiO2, ATC types. Resistors and capacitors specified for operation in the standard military temperature range (&55EC to +125EC

Groppi, Christopher

399

Diurnal radio aurora variations at 50 MHz measured by the Bistatic Auroral Radar System radars  

Microsoft Academic Search

The Bistatic Auroral Radar System (BARS), which is a part of the Canopus program, was employed to measure typical morphological characteristics and diurnal variations in the backscatter. Mean Doppler velocity and intensity data, obtained from the normal operating mode of the BARS radars for selected intervals between March 1986 and July 1987, were used. The Canopus magnetometers at Gillam and

Dieter Andre; Allen G. McNamara; Don D. Wallis; Bruce A. McIntosh; Terry J. Hughes

1988-01-01

400

A novel approach to joint flexion/extension angles measurement based on wearable UWB radios.  

PubMed

In this paper, a new method for measuring and monitoring human body joint angles, which uses wearable ultrawideband (UWB) transceivers mounted on body segments, is proposed and investigated. The model is based on providing a high ranging accuracy (intersensor distance) between a pair of transceivers placed on the adjacent segments of the joint center of rotation. The measured distance is then used to compute the joint angles based on the law of cosines. The performance of the method was compared with a flexible goniometer by simultaneously measuring joint flexion-extension angles at different angular velocities, ranging between 8 and 90(°) /s. The measurement errors were evaluated by the average differences between two sets of data (ranging from 0.8(°) for slow movement to 2.8(°) for fast movement), by standard deviation (ranging from 1.2(°) to 4.2(°) for various movement speeds) and by the Pearson correlation coefficient (greater than 0.99) which demonstrates the very good performance of the UWB-based approach. The experimental results have shown that the system has sufficient accuracy for clinical applications, such as rehabilitation. PMID:24403428

Qi, Yongbin; Soh, Cheong Boon; Gunawan, Erry; Low, Kay-Soon; Maskooki, Arash

2014-01-01

401

Absolute reflectivities and aspect sensitivities of VHF radio wave scatterers measured with the SOUSY radar  

Microsoft Academic Search

By accurately calibrating the SOUSY radar in West Germany it has been made possible to measure absolute values of effective reflection coefficients and turbulence structure constants. Some typical values of these parameters as a function of altitude are presented. Such profiles are presented for both a vertically directed beam, and also for two beams directed 7 deg off-vertical. Comparisons of

W. K. Hocking; R. Ruester; P. Czechowsky

1986-01-01

402

Measurement and prediction of pressure drop in two-phase micro-channel heat sinks  

Microsoft Academic Search

This study explores hydrodynamic instability and pressure drop in a water-cooled two-phase micro-channel heat sink containing 21 parallel 231×713 ?m micro-channels. Two types of two-phase hydrodynamic instability were identified: severe pressure drop oscillation and mild parallel channel instability. It is shown the severe pressure drop oscillation, which can trigger pre-mature critical heat flux, can be eliminated simply by throttling the

Weilin Qu; Issam Mudawar

2003-01-01

403

Small vertical movement of a K+ channel voltage sensor measured with luminescence energy transfer  

Microsoft Academic Search

Voltage-gated ion channels open and close in response to voltage changes across electrically excitable cell membranes. Voltage-gated potassium (Kv) channels are homotetramers with each subunit constructed from six transmembrane segments, S1-S6 (ref. 2). The voltage-sensing domain (segments S1-S4) contains charged arginine residues on S4 that move across the membrane electric field, modulating channel open probability. Understanding the physical movements of

David J. Posson; Pinghua Ge; Christopher Miller; Francisco Bezanilla; Paul R. Selvin

2005-01-01

404

IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL. 54, NO. 4, APRIL 2006 1827 UWB On-Body Radio Channel Modeling Using  

E-print Network

are essen- tial. The idea of a number of nodes scattered around the human body and communicating wirelessly wearable entertainment systems and high performance mobile PCs. For low-power, reliable, and robust on-body of the on-body radio propagation and its behavior with regards to different environments and system

Hao, Yang

405

S Band Radio Occultation Measurements of the Atmosphere and Topography of Mars with Mariner 9: Extended Mission Coverage of Polar and Intermediate Latitudes  

Microsoft Academic Search

A set of significant S band radio occultation measurements was obtained with Mariner 9 during May and June of 1972, for the first time yielding extensive occultation data on the north and south polar regions. The daytime temperature profiles, representative of a clear atmosphere, exhibit gradients (averaging -2.3øK\\/km) far smaller than those expected under conditions of radiativeconvective balance. The measured

A. J. Kliore; G. Fjeldbo; B. L. Seidel; M. J. Sykes; P. M. Woiceshyn

1973-01-01

406

Two-photon absorption laser-induced fluorescence measurements of atomic nitrogen in a radio-frequency atmospheric-pressure plasma jet  

Microsoft Academic Search

The first direct measurements of atomic nitrogen species in a radio-frequency atmospheric-pressure plasma jet (APPJ) are presented. Atomic nitrogen radicals play a key role in new plasma medicine applications of 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

E Wagenaars; T Gans; D O'Connell; K Niemi

2012-01-01

407

1. VIEW TO NORTHWEST WITH RADIO CONTROL HOUSE (RIGHT), TRANSMITTER ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

1. VIEW TO NORTHWEST WITH RADIO CONTROL HOUSE (RIGHT), TRANSMITTER TOWER (CENTER), AND NORTH BREAKWATER LIGHT IN DISTANCE AT LEFT - Frankfort Coast Guard Station, Radio Control House, Second Street at ship channel, Frankfort, Benzie County, MI

408

The use of transversal filters for measuring the frequency characteristics of single microwave radio pulses  

NASA Astrophysics Data System (ADS)

A new approach to the problem of measuring the instantaneous frequency of single microwave pulses is proposed which provides high accuracy over a wide frequency range and is superior to the known methods based on dispersion delay lines, characterized by low accuracy, and narrow-band multichannel resonance systems, which do not provide complete phase spectrum information. The approach proposed here can be implemented by using transversal filters. Results of an experimental verification of this method are presented.

Guliaev, Iu. V.; Ermolenko, A. V.; Zaitsev, B. D.; Sinitsyn, N. I.; Fedorenko, V. A.

409

Direction finding and antenna calibration through analytical inversion of radio measurements performed using a system of two or three electric dipole antennas on a three-axis stabilized spacecraft  

Microsoft Academic Search

We present an analytical inversion method to achieve direction-finding (DF) (i.e., retrieve the direction of arrival of an incoming electromagnetic wave, its flux, and its full polarization state) using radio measurements performed using a system of two or three electric dipole antennas on a three-axis stabilized spacecraft. The Radio and Plasma Wave Science (RPWS) radio receiver on board Cassini includes

B. Cecconi; P. Zarka

2005-01-01

410

Radio frequency pressure transducer  

Microsoft Academic Search

A novel system is reported here for the pressure measurement at microwave and millimetre-wave frequencies. This method consists in using a radio frequency transducer based on RF resonator. Accurate determination of the pressure is expected.

M. M. Jatlaoui; P. Pons; H. Aubert

2007-01-01

411

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

412

On Channel Reliability Measure Training for Multi-Camera Face Recognition Binglong Xie, Visvanathan Ramesh, Ying Zhu Terry Boult  

E-print Network

On Channel Reliability Measure Training for Multi-Camera Face Recognition Binglong Xie, Visvanathan-camera face recognition has severe limitations when the subject is not cooperative, or there are pose changes and different illumination conditions. Face recognition us- ing multiple synchronized cameras is proposed

Boult, Terrance E.

413

Design and Testing of A Closed Stirring-respirometer for Measuring Oxygen Consumption of Channel Catfish Eggs  

Technology Transfer Automated Retrieval System (TEKTRAN)

A closed stirring-respirometer was designed to allow for agitation of small samples of channel catfish egg masses while measuring oxygen consumption. Egg mass samples ranging in size from 15-46 g were placed on a platform above a magnetic spin bar; the degree of agitation was controlled with a magne...

414

CDF note 9950 Measurement of the tt Cross Section in the Lepton Plus Jets Channel Using Neural  

E-print Network

detector is described in detail in [7]. This analysis uses the standard CDF lepton+jets event selectionCDF note 9950 Measurement of the t¯t Cross Section in the Lepton Plus Jets Channel Using Neural Networks in 4.6 fb-1 of CDF data. The CDF Collaboration URL http://www-cdf.fnal.gov (Dated: September 25

Quigg, Chris

415

CDF/PHYS/TOP/PUBLIC/8369 Measurement of the Top Quark Mass in the Dilepton Channel using a Matrix  

E-print Network

, using #12;2 additional data collected at the CDF II detector. II. EVENT SELECTION This analysis is based. The CDF II detector is a general purpose detector described elsewhere [10]. For this analysis, we selectCDF/PHYS/TOP/PUBLIC/8369 Measurement of the Top Quark Mass in the Dilepton Channel using a Matrix

Quigg, Chris

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

Radio Astronomy  

NSDL National Science Digital Library

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

Tenenbaum, David

418

Measurement of a Phase of a Radio Wave Reflected from Rock Salt and Ice Irradiated by an Electron Beam for Detection of Ultra-High-Energy Neutrinos  

E-print Network

We have found a radio-wave-reflection effect in rock salt for the detection of ultra-high energy neutrinos which are expected to be generated in Greisen, Zatsepin, and Kuzmin (GZK) processes in the universe. When an UHE neutrino interacts with rock salt or ice as a detection medium, a shower is generated. That shower is formed by hadronic and electromagnetic avalanche processes. The energy of the UHE neutrino shower converts to thermal energy through ionization processes. Consequently, the temperature rises along the shower produced by the UHE neutrino. The refractive index of the medium rises with temperature. The irregularity of the refractive index in the medium leads to a reflection of radio waves. This reflection effect combined with the long attenuation length of radio waves in rock salt and ice would yield a new method to detect UHE neutrinos. We measured the phase of the reflected radio wave under irradiation with an electron beam on ice and rock salt powder. The measured phase showed excellent consis...

Chiba, Masami; Tanikawa, Takahiro; Yano, Hiroyuki; Yabuki, Fumiaki; Yasuda, Osamu; Chikashige, Yuichi; Kon, Tadashi; Shimizu, Yutaka; Watanabe, Souichirou; Utsumi, Michiaki; Fujii, Masatoshi

2013-01-01

419

GPS Integrity Channel RTCA Working Group recommendations  

NASA Astrophysics Data System (ADS)

Recommendations made by a working group established by the Radio Technical Commission for Aeronautics are presented for the design of a wide-area broadcast service to provide indications on the status of GPS satellites. The integrity channel requirements and operational goals are outlined. Six integrity channel system concepts are considered and system design and time-to-alarm considerations are examined. The recommended system includes the broadcast of a coarse range measurement for each satellite which will enable the on-board GPS receiver to determine whether or not the navigation accuracy is within prescribed limits.

Kalafus, Rudolph M.

420

Cognitive radio: Making software radios more personal  

Microsoft Academic Search

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

Joseph Mitola; Gerald Quentin Maguire Jr.

1999-01-01

421

Improving satisfaction with bank service offerings: measuring the contribution of each delivery channel  

Microsoft Academic Search

This article presents the results of a qualitative study of a Portuguese bank regarding customer use of Internet banking integrated in a multi-channel offering that includes high street branches, telephone banking, and automatic teller machines. The results show that performance evaluation is a key factor influencing channel use. Customers tend to use the different service delivery systems in a complementary

Lia Patrício; Raymond P. Fisk; João Falcão e Cunha

2003-01-01

422

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

423

Automatic Measurement of Water Levels by Using Image Identification Method in Open Channel  

NASA Astrophysics Data System (ADS)

Water level data is indispensable to hydrology research, and it is important information for hydraulic engineering and overall utilization of water resources. The information of water level can be transmitted to management office by the network so that the management office may well understand whether the river level is exceeding the warning line. The existing water level measurement method can only present water levels in a form of data without any of images, the methods which make data just be a data and lack the sense of reality. Those images such as the rising or overflow of river level that the existing measurement method cannot obtain simultaneously. Therefore, this research employs a newly, improved method for water level measurement. Through the Video Surveillance System to record the images on site, an image of water surface will be snapped, and then the snapped image will be pre-processed and be compared with its altitude reference value to obtain a water level altitude value. With the ever-growing technology, the application scope of image identification is widely in increase. This research attempts to use image identification technology to analyze water level automatically. The image observation method used in this research is one of non-contact water level gage but it is quite different from other ones; the image observation method is cheap and the facilities can be set up beside an embankment of river or near the houses, thus the impact coming from external factors will be significantly reduced, and a real scene picture will be transmitted through wireless transmission. According to the dynamic water flow test held in an indoor experimental channel, the results of the research indicated that all of error levels of water level identification were less than 2% which meant the image identification could achieve identification result at different water levels. This new measurement method can offer instant river level figures and on-site video so that a disaster prevention measures can be made accordingly. Keywords: Image identification; Water Level; Video surveillance system.

Chung Yang, Han; Xue Yang, Jia

2014-05-01

424

Mass Flow Rate Measurements in a MicroChannel: from Hydrodynamic to Free Molecular Regime  

NASA Astrophysics Data System (ADS)

Mass flow rate measurements in a single silicon micro channel were carried out for various gases in isothermal steady flows. The results obtained, from hydrodynamic to near free molecular regime by using a powerful experimental platform, allowed us to deduce interesting information, notably about the reflection/accommodation process at the wall. In the 0-0.3 Knudsen range, a continuum approximated analytic approach was derived from NS equations, associated to first or second order slip boundary conditions. Identifying the experimental mass flow rate curves to the theoretical ones the TMAC of various gases were extracted. Over all the Knudsen range [0-50] the experimental results were compared with theoretical values calculated from kinetic approaches: using variable TMAC values as fitting parameter, the theoretical curves were fitted to the experimental ones. Whatever the Knudsen range and the theoretical approach, the TMAC values are found decreasing when the molecular weights of the gas considered increase (as long as the different gases are compared using the same approach). Moreover, the values of the various accommodation coefficients are rather close one to other but sufficiently smaller than unity to conclude that the full accommodation modelling is not satisfactory to describe the gas/wall interaction.

Graur, I. A.; Perrier, P.; Ghozlani, W.; Méolans, J. G.

2008-12-01

425

Measurement of the Electronic Thermal Conductance Channels and Heat Capacity of Graphene at Low Temperature  

NASA Astrophysics Data System (ADS)

The ability to transport energy is a fundamental property of the two-dimensional Dirac fermions in graphene. Electronic thermal transport in this system is relatively unexplored and is expected to show unique fundamental properties and to play an important role in future applications of graphene, including optoelectronics, plasmonics, and ultrasensitive bolometry. Here, we present measurements of bipolar thermal conductances due to electron diffusion and electron-phonon coupling and infer the electronic specific heat, with a minimum value of 10kB (10-22J/K) per square micron. We test the validity of the Wiedemann-Franz law and find that the Lorenz number equals 1.32×(?2/3)(kB/e)2. The electron-phonon thermal conductance has a temperature power law T2 at high doping levels, and the coupling parameter is consistent with recent theory, indicating its enhancement by impurity scattering. We demonstrate control of the thermal conductance by electrical gating and by suppressing the diffusion channel using NbTiN superconducting electrodes, which sets the stage for future graphene-based single-microwave photon detection.

Fong, Kin Chung; Wollman, Emma E.; Ravi, Harish; Chen, Wei; Clerk, Aashish A.; Shaw, M. D.; Leduc, H. G.; Schwab, K. C.

2013-10-01

426

Determination of the manning coefficient from measured bed roughness in natural channels  

USGS Publications Warehouse

This report presents the results of a study to test the hypothesis that basic values of the Manning roughness coefficient of stream channels may be related to (1) some characteristic size of the streambed particles and to (2) the distribution of particle size. These two elements involving particle size can be combined into a single element by weighting characteristic particle sizes. The investigation was confined to channels with coarse bed material to avoid the complication of bed-form roughness that is associated with alluvial channels composed of fine bed material. Fifty current-meter measurements of discharge and appropriate field surveys were made at 11 sites on California streams for the purpose of computing the roughness coefficient, n, by the Manning formula. The test sites were selected to give a wide range in average size of bed material, and the discharge measurements and surveys were made at such times as to provide data covering a suitable range in stream depth. The sites selected were relatively free of the extraneous flow-retarding effects associated with irregular channel conformation and streambank vegetation. The characteristic bed-particle sizes used in the analyses were the 16,- 50,- and 84-percentile sizes as obtained from a cumulative frequency distribution of the diameters of randomly sampled surficial bed material. Separate distributions were computed for the minimum and intermediate values of the three diameters of a particle. The minimum diameters of the streambed particles were used in the study because a particle at rest on the bed invariably has its minimum diameter in the vertical position; this diameter is, therefore, the most representative measure of roughness height. The intermediate diameter was also studied because this is the diameter most easily measurable-either by sieve analysis or by photographic techniques--and--because it is the diameter that had been used in previous studies by other investigators. No significant difference in reliability was found between the results obtained using minimum diameters and those obtained using intermediate diameters. In analyzing the field data, the roughness parameter, n/R1/6 (where R is hydraulic radius), was related to relative smoothness, R/d (where d is a characteristic, or weighted characteristic, particle size). The parameter n/R1/6, rather than n, was used because it is directly proportional to the square root of the Darcy-Weisbach friction factor, f, which is more widely used in theoretical studies of hydraulic friction. If the transformation of n/R1/6 to vf is made, the relations obtained in this study are of a form that is identical with that of the theoretical friction equation obtained by several investigators and that derived from field data by Leopold and Wolman (1957). The constants in the equation vary, of course, with the characteristic particle size used. The relations best fitting the field data for this study were obtained by using either a characteristic particle diameter equal to the 84-percentile size (d84, the size equal to, or exceeding, that of 84 percent of the streambed particles), or a diameter obtained by weighting three characteristic particle sizes (dw, the size obtained by assigning a weight of 0.1 to d16 , a weight of 0.3 to d50 , and a weight of 0.6 to d84). The use of d84 alone gave slightly better results than the use of dw, and, in addition, the use of d84 alone is attractive from a standpoint of simplicity. It is difficult, however, to rationalize the use of d84 alone because of the implication that the distribution of sizes is irrelevant, and it matters not at all whether 84 percent of the bed material is sand or whether it is large cobbles, as long as 16 percent of the material is of greater size. Consequently, the author recommends the use of dw rather than d84 , although there was no unanimity of opinion on this recommendation among his colleagues who reviewed this paper. The reader is free to

Limerinos, John Thomas

1970-01-01

427

Range difference multilateration for obtaining precision geodetic and trajectory measurements. [by radio interferometry  

NASA Technical Reports Server (NTRS)

The theoretical aspects of a new multilateration technique suitable for precision geodesy and orbit determination applications are examined. The multilateration technique considered herein makes use of the differential time of arrival of signals at an ensemble of ground stations from a spacecraft or aircraft as the fundamental data type. It is demonstrated that simultaneous measurements give rise to a system of equations which upon solution permits the determination of the three-dimensional vehicle coordinates plus the three-dimensional coordinates of the station net relative to an arbitrarily adopted origin (which may be taken to be one of the stations). A solution to these equations can be obtained without any a priori knowledge of the locations of the stations and vehicle. The necessary conditions for obtaining all of these coordinates in the same solution are discussed, and it is indicated that at least five stations are required in the station ensemble.

Escobal, P. R.; Ong, K. M.; Von Roos, O. H.

1975-01-01

428

Multicolor Photometric Observation of Lightning from Space: Comparison with Radio Measurements  

NASA Technical Reports Server (NTRS)

This study evaluates the effectiveness of spectrophotometric measurements from space in revealing properties of lightning flash. The multicolor optical waveform data obtained by FORMOSAT-2/Imager of Sprites and Upper Atmospheric Lightning (ISUAL) were analyzed in relation to National Lightning Detection Network (NLDN), North Alabama Lightning Mapping Array (LMA). As of July 2011, we found six lightning events which were observed by ISUAL and North Alabama LMA. In two of these events, NLDN showed clear positive cloud-to-ground (CG) discharges with peak current of +139.9 kA and +41.6 kA and, around that time, LMA showed continuous intra-cloud (IC) leader activities at 4-6 km altitudes. ISUAL also observed consistent optical waveforms of the IC and CG components and, interestingly, it was found that the blue/red spectral ratio clearly decreased by a factor of 1.5-2.5 at the time of CG discharges. Other four lightning events in which NLDN did not detect any CG discharges were also investigated, but such a feature was not found in any of these cases. These results suggest that the optical color of CG component is more reddish than that of IC component and we explain this as a result of more effective Rayleigh scattering in blue light emissions coming from lower-altitude light source. This finding suggests that spectral measurements could be a new useful technique to characterize ICs and CGs from space. In this talk, we will also present a result from lightning statistical analysis of ISUAL spectrophotometric data and ULF magnetic data.

Adachi, Toru; Cohen, Morris; Said, Ryan; Blakeslee, Richard J.; Cummer, Steven A.; Li, Jingbo; Lu, Geopeng; Hsu, Rue-Ron; Su, Han-Tzong; Chen, Alfred Bing-Chih; Takahashi, Yukihiro; Frey, Harald U.; Mende, Stephen B.

2011-01-01

429

Terahertz Optical Subcarrier Radio Frequency Generation  

NASA Astrophysics Data System (ADS)

There is interest to develop optically generated radio frequency signals for systems such as radar, microwave-over-fiber, and high-frequency wireless communication. Because such systems have the potential for multi-channel broadband communication. We demonstrate the generation of terahertz optical subcarrier radio frequencies in a semiconductor optical amplifier. The circuit arrangement consists of a 1550 nm pigtailed laser diode driven below its lasing threshold to generate a spectrum of spontaneous emission. The spontaneous emissions signalsare passed through a semiconductor amplifier driveninto saturation. A fraction of the output signal emerging from theamplifier is fed back into the input of the amplifier. By appropriately arranging the phases of the input and the feedback signals, optical subcarrier frequencies of up to 3.75 terahertzwere generated and measured.

Sanchez, Sonia; Donkor, Eric

2000-11-01

430

The First measurement of the top quark mass at CDF II in the lepton+jets and dilepton channels simultaneously  

SciTech Connect

The authors present a measurement of the mass of the top quark using data corresponding to an integrated luminosity of 1.9 fb{sup -1} of p{bar p} collisions collected at {radical}s = 1.96 TeV with the CDF II detector at Fermilab's Tevatron. This is the first measurement of the top quark mass using top-antitop pair candidate events in the lepton + jets and dilepton decay channels simultaneously. They reconstruct two observables in each channel and use a non-parametric kernel density estimation technique to derive two-dimensional probability density functions from simulated signal and background samples. The observables are the top quark mass and the invariant mass of two jets from the W decay in the lepton + jets channel, and the top quark mass and the scalar sum of transverse energy of the event in the diletpon 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 mass. using 332 lepton + jets candidate events and 144 diletpon candidate events, they measure the top quark mass to be 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}.

Aaltonen, T.; /Helsinki Inst. of Phys.; Adelman, J.; /Chicago U., EFI; Akimoto, T.; /Tsukuba U.; Albrow, Michael G.; /Fermilab; Alvarez Gonzalez, B.; /CSIC, Catalunya; Amerio, S.; /INFN, Padua; Amidei, Dante E.; /Michigan U.; Anastassov, A.; /Northwestern U.; Annovi, Alberto; /Frascati; Antos, J.; /Comenius U.; Apollinari, G.; /Fermilab /Purdue U.

2008-09-01

431

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

432

Comparison of channel impulse response measurements and calculations in indoor environments  

Microsoft Academic Search

Emerging radio systems are established in the UHF to EHF. They are also intended for short ranges like in a single building or a scenario of a few buildings. A wave propagation tool for indoor environments is required in order to plan these systems. The wavelength above 1 GHz is small with respect to the dimensions of the physical environment,

T. Zwick; F. Demmerle; W. Wiesbeck

1996-01-01

433

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

434

Wuhan Atmosphere Radio Exploration (WARE) radar: System design and online winds measurements  

NASA Astrophysics Data System (ADS)

The basic configuration of the Wuhan MST (mesosphere-stratosphere-troposphere) radar, which was designed and constructed by the School of Electronic Information, Wuhan University, is preliminarily described in this paper. The Wuhan MST radar operates at very high frequency (VHF) band (53.8 MHz) by observing the real-time characteristics of turbulence and the wind field vector in the height range of 3.5-90 km (not including 25-60 km) with high temporal and height resolutions. This all-solid-state, all-coherent pulse Doppler radar is China's first independent development of an MST radar focusing on atmospheric observation. The subsystems of the Wuhan MST radar include an antenna system, a feeder line system, all-solid-state radar transmitters, digital receivers, a beam control system, a signal processing system, a data processing system, a product generation system, and a user terminal. Advanced radar technologies are used, including highly reliable all-solid-state transmitters, low-noise large dynamic range digital receivers, an active phased array, high-speed digital signal processing, and real-time graphic terminals. This paper describes the design and implementation of the radar. Preliminary online wind measurements and results of the comparison to simultaneous observations by a GPS rawinsonde are presented as well.

Zhengyu, Zhao; Chen, Zhou; Haiyin, Qing; Guobin, Yang; Yuannong, Zhang; Gang, Chen; Yaogai, Hu

2013-05-01

435

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

436

Measuring and Evaluating the Role of ATP-Sensitive K+ Channels in Cardiac Muscle  

PubMed Central

Since ion channels move electrical charge during their activity, they have traditionally been studied using electrophysiological approaches. This was sometimes combined with mathematical models, for example with the description of the ionic mechanisms underlying the initiation and propagation of action potentials in the squid giant axon by Hodgkin and Huxley. The methods for studying ion channels also have strong roots in protein chemistry (limited proteolysis, the use of antibodies, etc). The advent of the molecular cloning and the identification of genes coding for specific ion channel subunits in the late 1980’s introduced a multitude of new techniques with which to study ion channels and the field has been rapidly expanding ever since (e.g. antibody development against specific peptide sequences, mutagenesis, the use of gene targeting in animal models, determination of their protein structures) and new methods are still in development. This review focuses on techniques commonly employed to examine ion channel function in a electrophysiological laboratory. The focus is on the KATP channel, but many of the techniques described are also used to study other ion channels. PMID:22245446

Kefaloyianni, Eirini; Bao, Li; Rindler, Michael J.; Hong, Miyoun; Patel, Tejaskumar; Taskin, Eylem; Coetzee, William A.

2012-01-01

437

Multiplexing of Radio-Frequency Single Electron Transistors  

NASA Technical Reports Server (NTRS)

We present results on wavelength division multiplexing of radio-frequency single electron transistors. We use a network of resonant impedance matching circuits to direct applied rf carrier waves to different transistors depending on carrier frequency. A two-channel demonstration of this concept using discrete components successfully reconstructed input signals with small levels of cross coupling. A lithographic version of the rf circuits had measured parameters in agreement with electromagnetic modeling, with reduced cross capacitance and inductance, and should allow 20 to 50 channels to be multiplexed.

Stevenson, Thomas R.; Pellerano, F. A.; Stahle, C. M.; Aidala, K.; Schoelkopf, R. J.; Krebs, Carolyn (Technical Monitor)

2001-01-01

438

Second order statistics of selection combining receiver over ?-? fading channels subject to co-channel interferences  

NASA Astrophysics Data System (ADS)

Radio propagation performances in interference-limited faded environment are studied in this paper. Selection combining (SC) based on signal-to-interference ratio (SIR) over?-?fading channels is performed. Probability density function (PDF) and cumulative distribution function (CDF) of the received SIR are determined. Based on the results obtained for PDF and CDF, infinite-series expressions are derived for the output level crossing rate (LCR) and average fade duration (AFD). These second order statistical measures are regarded as necessary for supporting technical documentation in every radio communication link design. Influences of various system parameters such as fading severity and the number of co-channel interferences affecting these measures are graphically presented and discussed.

Stefanovi?, Mihajlo; Pani?, Stefan R.; Stefanovi?, DušAn; Nikoli?, Bojana; Cvetkovi?, Aleksandra

2012-12-01

439

A parameterization for the radio emission of air showers as predicted by CoREAS simulations and applied to LOFAR measurements  

NASA Astrophysics Data System (ADS)

Measuring radio emission from air showers provides excellent opportunities to directly measure all air shower properties, including the shower development. To exploit this in large-scale experiments, a simple and analytic parameterization of the distribution of the radio signal at ground level is needed. Data taken with the Low-Frequency Array (LOFAR) show a complex two-dimensional pattern of pulse powers, which is sensitive to the shower geometry. Earlier parameterizations of the lateral signal distribution have proven insufficient to describe these data. In this article, we present a parameterization derived from air-shower simulations. We are able to fit the two-dimensional distribution with a double Gaussian, requiring five fit parameters. All parameters show strong correlations with air shower properties, such as the energy of the shower, the arrival direction, and the shower maximum. We successfully apply the parameterization to data taken with LOFAR and discuss implications for air shower experiments.

Nelles, Anna; Buitink, Stijn; Falcke, Heino; Hörandel, Jörg R.; Huege, Tim; Schellart, Pim

2015-01-01

440

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