Sample records for radio channel measurements

  1. Radio channel measurement and modelling for future mobile radio systems

    NASA Astrophysics Data System (ADS)

    Guerdenli, E.; Huish, P. W.

    1989-12-01

    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.

  2. Measurement and identification of mobile radio propagation channels

    Microsoft Academic Search

    R. S. Thoma; D. Hampicke; A. Richter; G. Sommerkorn

    2001-01-01

    MIMO vector radio channel sounding devices allow multidimensional analysis of wave propagation in mobile radio channels. 6-dimensions represent Doppler, TDOA, 2D DOD and 2D DOA. Antenna array architectures, calibration and K-D unitary ESPRIT parameter estimation are discussed. Parametric channel models can be derived from the estimated data

  3. Microwave line-of-sight channel measurements, channel modelling, and application of channel models to digital radio performance prediction, publications

    NASA Astrophysics Data System (ADS)

    Haeggman, S. G.

    1991-06-01

    Seven scientific papers published during 1978 to 1990 are reviewed. The papers constitute the basis for a PhD. The titles of the 7 papers are as follows: Time domain observation of microwave multipath propagation and estimation of channel model parameters; Microwave channel model parameters from pulse propagation measurements; The use of simple channel models in the analysis of 16 QAM radio links; Multipath outage probability for QAM systems with interference; Planning of propagation measurements for characterization of digital radio link channels; Measurement and statistical characterization of two 40 MHz line of sight radio channels at 6.2 GHz; and Effects on bandwidth on microwave line of sight channel modeling and digital radio performance prediction.

  4. Statistical modeling of the indoor radio channel at 10 GHz through propagation measurements .I. Narrow-band measurements and modeling

    Microsoft Academic Search

    Ayman F. Abouraddy; Said M. Elnoubi

    2000-01-01

    The aim of this paper is to report the results of a propagation measurement experiment to reach a statistical model of the indoor radio channel at 10 GHz using directive antennas at both terminals. The measurements were conducted on a floor of a university building. The distribution of the received fading envelope was tested to fit the Rayleigh and Rician

  5. 3-D DIRECTIONAL WIDEBAND DUAL-POLARIZED MEASUREMENT OF URBAN MOBILE RADIO CHANNEL WITH SYNTHETIC APERTURE TECHNIQUE

    Microsoft Academic Search

    Kimmo Kalliola; Juha Laurila; Martin Toeltsch; Klaus Hugl; Pertti Vainikainen; Ernst Bonek

    Abstract: this paper we present a novelconcept for spatial radio channel measurements at the base station site in urban environment. It combines RF switchingand synthetic aperture technique and allows the full 3-D channel characterization. A high-resolution 2-D UnitaryESPRIT algorithm is used for estimation of azimuth and elevation angles of the incoming waves, and a high delay resolutionis obtained using a

  6. Characterization of in-building UHF wireless radio communication channels using spectral energy measurements

    Microsoft Academic Search

    B. P. Donaldson; M. Fattouche; R. W. Donaldson

    1996-01-01

    A simple, cost-effective means is developed to estimate the time-invariant wireless radio channel impulse response h(t) using only the magnitude of the channel transfer function, H(jw). The Hilbert transform is used to calculate the phase of H(jw) from its magnitude. Inverse discrete Fourier transformation (IDFT) of H(jw) yields h(t). The Hilbert transform relation is applicable provided H(jw) is a minimum

  7. In-building wireless radio channel characterization based on energy measurements and the Hilbert transform

    Microsoft Academic Search

    Brian P. Donaldson; Michel Fattouche; Robert W. Donaldson

    1995-01-01

    A simple, cost-effective means is developed to estimate the impulse response h(t) for wireless radio channels using only the magnitude of the channel transfer function, H(j?). The Hilbert transform is used to calculate the phase of H(j?) from its magnitude. Inverse discrete Fourier transformation (IDFT) of H(j?) yields h(t). The Hilbert transform relation is applicable provided H(j?) is a minimum

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

    E-print Network

    Zemen, Thomas

    . As antenna system we used a 4Ã?4 MIMO circular antenna array with vertically polarized patch antenna elements University, Lund, Sweden 4 Smart Antennas Research Group, Information Systems Lab, Stanford University measurements of doubly-selective vehicle-to-vehicle MIMO radio channels in the 5.2 GHz band. Ivrlac and Nossek

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

    E-print Network

    Zemen, Thomas

    Car-to-car radio channel measurements at 5 GHz: Pathloss, power-delay profile, and delay Telekommunikation Wien (ftw.), Vienna, Austria 3mobilkom austria AG, Vienna, Austria 4Department of Electrical and Information Technology, Lund University, Lund, Sweden 5Mitsubishi Electric Research Labs, Cambridge, USA

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

    NASA Astrophysics Data System (ADS)

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

    2006-05-01

    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.

  11. Spatial characterization of urban mobile radio channels

    Microsoft Academic Search

    Martin Toeltsch; Juha Laurila; Andreas F. Molisch; K. Kalliola; P. Vainikkainen; E. Bonek

    2001-01-01

    We present statistical evaluations of wideband spatial dual-polarized radio channel measurements. Some 80 different street-level transmitter positions in downtown Helsinki, Finland, were measured. We chose three different receiver array sites below, at, and above the rooftop level of the surrounding urban environment. A super-resolution algorithm allows the determination of the directions of arrival of incident radio waves at a 16×62

  12. The indoor radio propagation channel

    Microsoft Academic Search

    HOMAYOUN HASHEMI

    1993-01-01

    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

  13. Distributed Computation on Unreliable Radio Channels

    E-print Network

    Distributed Computation on Unreliable Radio Channels by Calvin Newport Submitted to the Department on Unreliable Radio Channels by Calvin Newport Submitted to the Department of Electrical Engineering the control of the algorithm designer--from contention with unrelated devices to malicious jamming

  14. Wideband measurements and analysis of the single-floor indoor radio channel at 2.4 GHz

    Microsoft Academic Search

    Z. Blazevic; Igor Zanchi; I. Marinovid

    2007-01-01

    In this paper we present analysis of radio measurements at 2.4 GHz conducted in an indoor environment of out- faculty building. A significant correlation between coherence bandwidth and delay-spread is noticed, which is in accordance to previous results. Correlation noticed by certain authors between delay-spread and antenna separation could not be confirmed in this scenario. The analysis and comparison with

  15. Limits on communications in a cognitive radio channel

    Microsoft Academic Search

    Natasha Devroye; Patrick Mitran; Vahid Tarokh

    2006-01-01

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

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

    Microsoft Academic Search

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

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

  17. Channel Bonding in Cognitive Radio Wireless Sensor Networks

    E-print Network

    Paris-Sud XI, Université de

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

  18. Mexart Measurements of Radio Sources

    NASA Astrophysics Data System (ADS)

    González-Esparza, A.; Andrade, E.; Carrillo, A.; Jeyakumar, S.; Ananthakrishnan, S.; Praveenkumar, A.; Sankarasubramanian, G.; Sureshkumar, S.; Sierra, P.; Vazquez, S.; Perex-Enriguez, R.; Kurtz, S.

    2005-09-01

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

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

    Microsoft Academic Search

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

    2002-01-01

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

  20. Channel assignment for multicast in multi-channel multi-radio wireless mesh networks

    Microsoft Academic Search

    Hoang Lan Nguyen; Uyen Trang Nguyen

    Summary One of the most effective approaches to enhance the throughput capacity of wireless mesh networks (WMN) is to use systems with multiple channels and multiple radios per node. Multi-channel multi-radio (MCMR) networks require efficient channel assignment (CA) algorithms to determine which channel a link should use for data transmission in order to maximize network throughput. The problem of CA

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

    Microsoft Academic Search

    Wei Wu; Sriram Vishwanath; Ari Arapostathis

    2007-01-01

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

  2. Analysis of Cognitive Radio Spectrum Access with Optimal Channel Reservation

    Microsoft Academic Search

    Xiaorong Zhu; Lianfeng Shen; Tak-shing Yum

    2007-01-01

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

  3. Measurement Survey on the Antenna Configuration Impact on the Spectral Efficiency of MIMO Radio Channels: Analyzed with a Focus on Low-Mobility, Indoor Line-of-Sight Channels

    Microsoft Academic Search

    A. Knopp; C. A. Hofmann; M. Chouayakh; B. Lankl

    2010-01-01

    Typical, large-scale as well as small-scale, in-room office scenarios are analyzed by broadband measurements with a fast MIMO\\u000a channel sounder. A strong Line-of-Sight (LOS) signal component was always present, and the antenna arrays were arranged in\\u000a particular ways to construct LOS channel matrices of different channel eigenvalue profiles. In this context, we particularly\\u000a aim at investigating the practical relevance of

  4. Adaptive channel allocation spectrum etiquette for cognitive radio networks

    Microsoft Academic Search

    Nie Nie; Cristina Comaniciu

    2005-01-01

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

  5. Adaptive Channel Allocation Spectrum Etiquette for Cognitive Radio Networks

    Microsoft Academic Search

    Nie Nie; Cristina Comaniciu

    2006-01-01

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

  6. Prioritized channel assignment in a cellular radio network

    Microsoft Academic Search

    Se-Hyun Oh; Dong-Wan Tcha

    1992-01-01

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

  7. Spectrum handoff strategies for multiple channels cognitive radio network

    Microsoft Academic Search

    Adisorn Lertsinsrubtavee; Naceur Malouch; Serge Fdida

    2010-01-01

    This paper proposes a new spectrum handoff approach for multiple channels cognitive radio networks to support delay sensitive applications such as VoIP. The delay probability is estimated to determine whether and how to perform the handoff operation. Moreover, traffic prediction on licensed channels is also required in order to estimate the impairment in the delay. Since, the error of prediction

  8. Effective channel assignments in cognitive radio networks , Ying Dai a,

    E-print Network

    Wu, Jie

    Effective channel assignments in cognitive radio networks Jie Wu a , Ying Dai a, , Yanchao Zhao a this setting later in Section 3. The channel assignment (CA) problem is well-studied in tradi- tional wireless-coloring problem, which is a well-known NP-hard problem [3]. An extensive survey of CA in wireless networks

  9. A simplified stochastic model for the aeronautical mobile radio channel

    Microsoft Academic Search

    Said M. Elnoubi

    1992-01-01

    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

  10. Utilizing Multiple Channels With Fewer Radios in Wireless Mesh Networks

    Microsoft Academic Search

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

    2011-01-01

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

  11. Identification of nonlinear MIMO radio over fiber uplink channels

    Microsoft Academic Search

    Carlos A. R. Fernandes; Alain Kibangou; G. Favier; J. C. M. Mota

    2006-01-01

    This paper proposes two new methods for identifying multiple-input-multiple-output (MIMO) nonlinear systems. Specifically, we are interested in radio over fiber (ROF) uplink communications channels. The electrical optical (E\\/O) conversion in such systems introduces relevant nonlinear distortion and, consequently, the overall channel can be viewed as a convolutive post nonlinear (CPNL) mixture. The proposed techniques for system identification exploit the use

  12. Measurement incompatibility and Channel Steering

    E-print Network

    Manik Banik; Subhadipa Das; A. S. Majumdar

    2015-04-13

    Incompatible measurements in quantum theory always lead to Einstein-Podolsky-Rosen (EPR)-Schr\\"{o}dinger steering. Channel steering which is a generalized notion of EPR-Schr\\"{o}dinger steering, has been introduced recently. Here we establish a connection between lack of joint measureability and channel steering.

  13. Radio Wave Scattering from Lampposts in Microcell Urban Mobile Propagation Channel

    Microsoft Academic Search

    Mir Ghoraishi; Jun-ichi Takada; Tetsuro Imai

    2009-01-01

    The radio wave scattering from lampposts in ur- ban areas is analyzed. The lamppost is modeled as a flnite-length conducting cylinder and the approxi- mate theoretical values of its bistatic radar cross sec- tion (RCS) are compared to those experimental val- ues obtained from a propagation channel measure- ment campaign in two urban environments. In the theoretical derivation it is

  14. Optimal control of radio-signal power in channels with fadings and fluctuation noise

    NASA Astrophysics Data System (ADS)

    Sharov, A. N.; Groshikov, E. N.

    1983-05-01

    The Bellman optimality principle is used to synthesize a recursive algorithm for the closed stochastic control of radio-signal power in a channel with fadings and fluctuation noise. This algorithm minimizes a quadratic functional which is the measure of the control quality. The efficiency of this algorithm is evaluated.

  15. Evaluation of an Outdoor-to-in-Car Radio Channel with a Four-Antenna Handset and a User Phantom

    Microsoft Academic Search

    Fredrik Harrysson; Tommy Hult; Fredrik Tufvesson

    2011-01-01

    Based on static outdoor channel measurements we evaluate the influence of a vehicle on the MIMO radio channel, from a base station antenna array, to a multiple antenna handset in the hand of a user placed inside a test car. The measurement scenario is chosen to mimic a 2.6 GHz (LTE) macro-cell urban or rural scenario with two locations and

  16. Combined Channel Aggregation and Fragmentation Strategy in Cognitive Radio Networks

    E-print Network

    Li, Lei; Wang, Kaiwei; Zhou, Wuyang

    2012-01-01

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

  17. Prediction of Fast Fading Mobile Radio Channels in Wideband Communication Systems

    E-print Network

    Dong, Liang

    , TX 78712 Abstract-- The fast fading mobile radio channels place fundamental limitationsPrediction of Fast Fading Mobile Radio Channels in Wideband Communication Systems Liang Dong. Introduction The radio channel in a wireless communication system is often characterized by multipath propa

  18. Priority-based variable multi-channel MAC protocols in cognitive radio wireless network: A fair channel access strategy

    Microsoft Academic Search

    Gan Liu; Chao Chen; Yuying Li; Junfeng Guo

    2009-01-01

    This paper presents a priority-based opportunistic multi-channel medium access control (MAC) protocols in cooperative cognitive radio (CR) wireless networks, which used to promote the utilization of radio spectrum resources and to address the fairness issue of channel access among secondary users (SUs). On the one hand, we make use of Markov chain to prioritize each data channel that licensed to

  19. Evaluation of the multipath characteristics of the impulse radio channel

    Microsoft Academic Search

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

    1998-01-01

    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

  20. Spatial Dynamics of Indoor Radio Channels Invited Paper

    E-print Network

    Porrat, Dana

    Science Foundation (Grant No. 249/06), the Israeli Short Range Consortium (ISRC) and NEWCOM++ components components of wideband (2-17 GHz) non line of sight channel responses measured inside several buildings of measured channels that explicitly includes finite spatial areas of stability of the multipath components

  1. A Randomized Saturation Degree Heuristic for Channel Assignment in Cellular Radio Networks

    E-print Network

    Battiti, Roberto

    A Randomized Saturation Degree Heuristic for Channel Assignment in Cellular Radio Networks Roberto radio network so as to avoid interference and minimize the number of channels used. The problem successfully used for code assignment in Packet Radio Networks. We give a new version of this heuristic

  2. A Randomized Saturation Degree Heuristic for Channel Assignment in Cellular Radio Networks

    E-print Network

    Battiti, Roberto

    A Randomized Saturation Degree Heuristic for Channel Assignment in Cellular Radio Networks Roberto) to the cells of a cellular radio network so as to avoid interference and minimize the number of channels used was already successfully used for code assignment in Packet Radio Networks. We give a new version

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

    E-print Network

    Qiu, Robert Caiming

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

  4. Adaptive and occupancy-based channel selection for unreliable cognitive radio

    E-print Network

    Paris-Sud XI, Université de

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

  5. A Randomized Saturation Degree Heuristic for Channel Assignment in Cellular Radio Networks

    E-print Network

    Battiti, Roberto

    of a fairly flat area with no radio obstacles, such as the presence of large buildings. The cellular networkA Randomized Saturation Degree Heuristic for Channel Assignment in Cellular Radio Networks Roberto in Packet Radio Networks. We give a new version of this heuristic technique for cellular radio networks

  6. Radio Science Measurements with Suppressed Carrier

    NASA Technical Reports Server (NTRS)

    Asmar, Sami; Divsalar, Dariush; Oudrhiri, Kamal

    2013-01-01

    Radio Science started when it became apparent with early Solar missions that occultations by planetary atmospheres would affect the quality of radio communications. Since then the atmospheric properties and other aspects of planetary science, solar science, and fundamental physics were studied by scientists. Radio Science data was always extracted from a received pure residual carrier (without data modulation). For some missions, it is very desirable to obtain Radio Science data from a suppressed carrier modulation. In this paper we propose a method to extract Radio Science data when a coded suppressed carrier modulation is used in deep space communications. Type of modulation can be BPSK, QPSK, OQPSK, MPSK or even GMSK. However we concentrate mostly on BPSK modulation. The proposed method for suppressed carrier simply tries to wipe out data that acts as an interference for Radio Science measurements. In order to measure the estimation errors in amplitude and phase of the Radio Science data we use Cramer-Rao bound (CRB). The CRB for the suppressed carrier modulation with non-ideal data wiping is then compared with residual carrier modulation under the same noise condition. The method of derivation of CRB for non-ideal data wiping is an innovative method that presented here. Some numerical results are provided for coded system.

  7. Millimeter-wave channel measurements for indoor wireless communications

    Microsoft Academic Search

    G. A. Kalivas; M. El-Tanany; S. A. Mahmoud

    1992-01-01

    Propagation losses for the indoor radio channel at 21.6 GHz and 37.2 GHz are examined. The propagation measurements carried out are used to quantitatively present, through enveloped distribution, the effects of spatial fading, which is due to multipath propagation, and temporal fading, which is due to people moving in the building. Attenuation is given in the form of the exponent

  8. Propagation characteristics on microcellular urban mobile radio channels at 910 MHz

    Microsoft Academic Search

    ROBERT J. C. BULTITUDE; G. KEITH BEDAL

    1989-01-01

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

  9. Investigations of outdoor-to-indoor mobile-to-mobile radio communication channels

    Microsoft Academic Search

    Istvan Z. Kovacs; Patrick C. F. Eggers; Kim Olesen; Leif G. Petersen

    2002-01-01

    The mobile-to-mobile radio channel was investigated in different suburban outdoor-to-indoor environments. System performance parameters in terms of un-encoded BER and outage probability have been extracted from hardware and software TETRA simulations. In several scenarios, the measured signal envelope statistics were found to be a combination of single and double Rayleigh distributions. The system performances obtained in these scenarios were in

  10. Towards Cognitive Radio Networks: Spectrum Utilization Measurements in Suburb Environment

    E-print Network

    Paris-Sud XI, Université de

    Towards Cognitive Radio Networks: Spectrum Utilization Measurements in Suburb Environment Václav or more utilized licensed frequency bands that could be possibly used by cognitive radios in an opportunistic way. Cognitive radio concept for better spectrum utilization is introduced here along

  11. Antenna Devices and Measurement of Radio Emission

    E-print Network

    Erdmann, Martin

    Antenna Devices and Measurement of Radio Emission from Cosmic Ray induced Air Showers at the Pierre . . . . . . . . . . . . . . . . . . . . . . . 53 6 Antenna Theory 55 6.1 Vector Effective Length Effective Height in a Measurement Setup . . . . . . . 64 6.6.1 Thevenin Equivalent Antenna Description

  12. Adaptation of the Electra Radio to Support Multiple Receive Channels

    NASA Technical Reports Server (NTRS)

    Satorius, Edgar H.; Shah, Biren N.; Bruvold, Kristoffer N.; Bell, David J.

    2011-01-01

    Proposed future Mars missions plan communication between multiple assets (rovers). This paper presents the results of a study carried out to assess the potential adaptation of the Electra radio to a multi-channel transceiver. The basic concept is a Frequency Division multiplexing (FDM) communications scheme wherein different receiver architectures are examined. Options considered include: (1) multiple IF slices, A/D and FPGAs each programmed with an Electra baseband modem; (2) common IF but multiple A/Ds and FPGAs and (3) common IF, single A/D and single or multiple FPGAs programmed to accommodate the FDM signals. These options represent the usual tradeoff between analog and digital complexity. Given the space application, a common IF is preferable; however, multiple users present dynamic range challenges (e.g., near-far constraints) that would favor multiple IF slices (Option 1). Vice versa, with a common IF and multiple A/Ds (Option 2), individual AGC control of the A/Ds would be an important consideration. Option 3 would require a common AGC control strategy and would entail multiple digital down conversion paths within the FPGA. In this paper, both FDM parameters as well as the different Electra design options will be examined. In particular, signal channel spacing as a function of user data rates and transmit powers will be evaluated. In addition, tradeoffs between the different Electra design options will be presented with the ultimate goal of defining an augmented Electra radio architecture for potential future missions.

  13. Transmission Techniques and Channel Calibration for Spatial Interweave TDD Cognitive Radio

    E-print Network

    Paris-Sud XI, Université de

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

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

    E-print Network

    Paris-Sud XI, Université de

    of the radio propagation channel. Moreover, after the realization of a communication system, its experimental be used to compare the performance of various radio communication systems in a time-variant propagation The development of a radio communication system requires the knowledge of the main characteristics

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

    PubMed Central

    Zeng, Fanzi; Shen, Xinwang

    2014-01-01

    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

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

    PubMed

    Zeng, Fanzi; Shen, Xinwang

    2014-01-01

    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

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

    Microsoft Academic Search

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

    2005-01-01

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

  18. Land mobile satellite channel measurements and modeling

    Microsoft Academic Search

    Chun Loo; JOHN S. BUTTERWORTH

    1998-01-01

    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

  19. Channel Quality Prediction Based on Bayesian Inference in Cognitive Radio Networks

    E-print Network

    Cheng, Xiuzhen "Susan"

    , the estimated NSHMM parameters are employed to design a channel quality metric according to the predicted to investigate the effectiveness of our design. The results indicate that channel ranking based on the proposedChannel Quality Prediction Based on Bayesian Inference in Cognitive Radio Networks Xiaoshuang Xing1

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

    Microsoft Academic Search

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

    2005-01-01

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

  1. Measurements of radio pulsar braking indices

    NASA Astrophysics Data System (ADS)

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

    2010-06-01

    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.

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

    NASA Astrophysics Data System (ADS)

    Mlynarczyk, Janusz; Koperski, Piotr; Kulak, Andrzej

    2012-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Maas, Dustin C.

    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.

  4. Design and Implementation of an Underlay Control Channel for Cognitive Radios

    SciTech Connect

    Daryl Wasden; Hussein Moradi; Behrouz Farhang-Boroujeny

    2012-11-01

    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.

  5. Statistical channel impulse response models for factory and open plan building radio communicate system design

    Microsoft Academic Search

    Theodore S. Rappaport; Scott Y. Seidel; Koichiro Takamizawa

    1991-01-01

    Statistical radio channel impulse response models are presented for the analysis and design of wireless factory and open plan office communication systems. The models incorporate first- and second-order statistics to characterize the discrete impulse responses of indoor radio channels for both line-of-sight (LOS) and obstructed (OBS) topographies. The effects of large-scale transmitter-receiver separation distance, small-scale receiver movement, and models for

  6. Anti-Jamming Games in MultiChannel Cognitive Radio Networks

    Microsoft Academic Search

    Yongle Wu; Beibei Wang; K. J. Ray Liu; T. Charles Clancy

    2012-01-01

    Crucial to the successful deployment of cognitive radio networks, security issues have begun to receive research interests recently. In this paper, we focus on defending against the jamming attack, one of the major threats to cognitive radio networks. Secondary users can exploit the flexible access to multiple channels as the means of anti-jamming defense. We first investigate the situation where

  7. Multi-channel Jamming Attacks using Cognitive Radios Ashwin Sampath, Hui Dai, Haitao Zheng and Ben Y. Zhao

    E-print Network

    Zhao, Ben Y.

    Multi-channel Jamming Attacks using Cognitive Radios Ashwin Sampath, Hui Dai, Haitao Zheng and Ben explore the feasibility and im- pact of cognitive radio based jamming attacks on 802.11 networks. We show that attackers can utilize cognitive radios' fast channel switching capability to amplify their jamming impact

  8. A Framework for Radio Frequency Spectrum Measurement and Analysis

    E-print Network

    Kansas, University of

    A Framework for Radio Frequency Spectrum Measurement and Analysis V. Rory Petty ITTC-FY2008-TR frequency spectrum is utilized. The radio frequency spectrum is an important national resource that impacts allocation and the burgeoning problem of spectrum scarcity have prompted an examination of how the radio

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

    Microsoft Academic Search

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

    2000-01-01

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

  10. A FUZZY GENETIC ALGORITHM FOR AUTOMATIC CHANNEL ASSIGNMENT FOR TACTICAL HF RADIO NETWORKS

    E-print Network

    Kaminsky, Alan

    Kaminsky Harris Corporation RF Communications Division, USA ABSTRACT An innovative method for automatically in the desired pattern. The set of assigned channels is called a communication plan, or commplan. Designing. There is a set of available chan- nels the radios are allowed to use. Each channel is de- fined by its emission

  11. CHANNEL ASSIGNMENT FOR THROUGHPUT IMPROVEMENT IN MULTI-RADIO WIRELESS MESH NETWORKS

    E-print Network

    Dyer, Bill

    CHANNEL ASSIGNMENT FOR THROUGHPUT IMPROVEMENT IN MULTI-RADIO WIRELESS MESH NETWORKS by Shivaram of networking and exposed me to fiber optics and wireless networks during my early days at MSU. I thank him ...................................................... 2 Wireless Mesh Networks (WMN) .......................................... 3 Channel Assignment

  12. Residual Energy Aware Channel Assignment in Cognitive Radio Sensor Networks

    E-print Network

    Wu, Dapeng Oliver

    channel search and Optimization-based channel assignment. The last two ex- ploit R-coefficient to obtain. Optimization-based channel assignment outperforms the other two approaches with respect to network lifetime. I]. The event-driven nature often generates bursty traffic, which increases the probability of collision

  13. MIMO channel measurements for urban military applications

    Microsoft Academic Search

    Jerry R. Hampton; Manuel A. Cruz; Naim M. Merheb; A. R. Hammons; D. E. Paunil; Feng Ouyang

    2008-01-01

    This paper presents results from a measurement campaign that was conducted to characterize the multiple input multiple output (MIMO) channel characteristics in a low-rise urban environment in the military UHF frequency band. Data were collected in Baltimore, Maryland using a 2times3 MIMO testbed in June 2007. Testing consisted of transmitting orthogonal channel probes from a stationary transmit test van and

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

    PubMed Central

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

    2011-01-01

    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

  15. Analysis of GMSK with discriminator detection in mobile radio channels

    Microsoft Academic Search

    SAID M. ELNOUBI

    1986-01-01

    Discriminator detection of Gaussian minimum shift keying in a land mobile radio environment is analyzed. Simple closed-form expressions for the average probability of error are presented and evaluated for cases of practical interest.

  16. ALOHA with capture over slow and fast fading radio channels with coding and diversity

    Microsoft Academic Search

    I. M. I. Habbab; M. Kavehrad; C.-E. W. Sundberg

    1989-01-01

    The effects of capture on the average system throughput and delay performance of slotted ALOHA were analyzed for slow and fast Rayleigh fading radio channels. A short-range multipoint-to-base station packet radio network is considered. It is shown that larger capture effects and thus improved network performance can be achieved with proper choice of modulation. It is also shown that the

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

    PubMed

    Zeng, Fanzi; Tang, Yuting; Pu, Jianjie

    2014-01-01

    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

  18. MEXART Measurements of Radio Sources. Interplanetary Scintillation Array in Mexico

    NASA Astrophysics Data System (ADS)

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

    2005-12-01

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

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

    Microsoft Academic Search

    Kazuhiko Fukawa; Hiroshi Suzuki

    1991-01-01

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

  20. A Quantitative Analysis of Spectral Occupancy Measurements for Cognitive Radio

    Microsoft Academic Search

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

    2007-01-01

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

  1. Adaptive DFE for GMSK in Indoor Radio Channels

    Microsoft Academic Search

    José Tellado-mourelo; Ellen Kayata Wesel; John M. Cioffi

    1996-01-01

    We simulate the performance of an equalized Gaussian MinimumShift Keying (GMSK) signal in an indoor radio environmentwith fading, noise, imperfect carrier recovery, Co-Channelinterference (CCI) and Inter Symbol Interference (ISI). We showthat data rates of 20 Mbps at Bit Error Rates (BER) 10\\\\Gamma4are possible with rms delay spreads up to 25 ns using a simpleLimiter-Discriminator-Integrator (LDI) receiver and a (6,4) DecisionFeedback

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

    Microsoft Academic Search

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

    2008-01-01

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

  3. Radio frequency channel modeling for proximity networks on the Martian surface

    Microsoft Academic Search

    Vishwanath Chukkala; Phillip Deleon; Stephen Horan; Vijayakumar Velusamy

    2005-01-01

    NASAs long-term goals for the exploration of Mars include the use of rovers and sensors which communicate through proximity wireless networks. The performance of any such wireless network depends fundamentally on the radio frequency (RF) environment. In order to evaluate and optimize the performance of such a wireless network, a basic understanding or model of the channel is important. In

  4. Analysis of GMSK with Two-Bit Differential Detection in Land Mobile Radio Channels

    Microsoft Academic Search

    S. Elnoubi

    1987-01-01

    The effect of intersymbol interference (ISI) of Gaussian filtered minimum shift keying (GMSK) on the probability of error of twobit differential detection is analyzed theoretically in fast Rayleigh fading characterizing land mobile radio channels. A closed form expression is derived for the probability of error. Numerical results are presented for cases of practical interest to researchers and designers of cellular

  5. A hybrid interleaving scheme that enables packet switching on multiple-access radio communication channels

    Microsoft Academic Search

    Donald P. Olsen

    1999-01-01

    An interleaving technique is proposed that is memory, delay, and packet efficient for demand assignment multiple-access, packet-switched transmission with frequency-hopped survivability interleaved signals over jammed or scintillated radio channels. This hybrid interleaving scheme concatenates the convolutional interleaver and the block interleaver

  6. Tracking of Time-varying Mobile Radio Channels Part II: A Case Study

    E-print Network

    Tracking of Time-varying Mobile Radio Channels Part II: A Case Study Lars Lindbom, Anders Ahl#19;en, Sweden. Anders Ahl#19;en and Mikael Sternad are with Signals and Systems, Uppsala Uni- versity, PO Box 528, SE-75120, Uppsala, Sweden. Phone +46 4713076, fax +46 18 555096, aa@signal.uu.se, ms

  7. Radiometer Calibration Using Colocated GPS Radio Occultation Measurements

    E-print Network

    Blackwell, William J.

    We present a new high-fidelity method of calibrating a cross-track scanning microwave radiometer using Global Positioning System (GPS) radio occultation (GPSRO) measurements. The radiometer and GPSRO receiver periodically ...

  8. Finite-state Markov channel-a useful model for radio communication channels

    Microsoft Academic Search

    Hong Shen Wang; Nader Moayeri

    1995-01-01

    The authors first study the behavior of a finite-state channel where a binary symmetric channel is associated with each state and Markov transitions between states are assumed. Such a channel is referred to as a finite-state Markov channel (FSMC). By partitioning the range of the received signal-to-noise ratio into a finite number of intervals, FSMC models can be constructed for

  9. Progress in Air Shower Radio Measurements: Detection of Distant Events

    E-print Network

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

    2006-07-21

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

  10. Air Shower Measurements with Radio Antennas: The LOPES Project

    SciTech Connect

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

    2008-01-24

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

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

    E-print Network

    Song, Yi

    2011-01-01

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

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

    E-print Network

    Shakhakarmi, Niraj

    2012-01-01

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

  13. Channel parameter estimation in mobile radio environments using the SAGE algorithm

    Microsoft Academic Search

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

    1999-01-01

    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

  14. Analysis of GMSK with differential detection in land mobile radio channels

    Microsoft Academic Search

    S. M. Elnoubi

    1986-01-01

    The effect of intersymbol interference (ISI) of Gaussian filtered minimum shift keying (GMSK) on the probability of error of one bit differential detection is analyzed theoretically in fast Rayleigh fading characterizing land mobile radio channels. A closed-form expression is derived for the probability of error as a function of the fading rate, IF filter bandwidth, signal-to-noise ratio (SNR) and ISI.

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

    Microsoft Academic Search

    R. Muammar

    1991-01-01

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

  16. Multipath distortion of differentially encoded GMSK with 2-b differential detection in bandlimited frequency-selective mobile radio channel

    Microsoft Academic Search

    J. Horikoshi; SHIGEO SHIMURA

    1990-01-01

    Error performance of Gaussian minimum-shift keying (GMSK) with 2-b differential detection in a frequency-selective mobile radio channel is analyzed. The two-wave model using two Rayleigh waves with constant group time-delay is adopted to describe a frequency-selective mobile radio channel. The Gaussian-type bandpass filter is introduced as a receiving filter to demonstrate the effects of band limitation at the receiver. A

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

    E-print Network

    Zhang, Zhou; Tan, Peng; Slevinsky, Jim

    2012-01-01

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

  18. Channel-estimation-based adaptive DFE for fading multipath radio channels

    NASA Astrophysics Data System (ADS)

    Shukla, P. K.; Turner, L. F.

    1991-12-01

    The performance of an adaptive decision feedback equalizer (DFE) over an HF channel when its taps are derived from an estimate of the sampled channel impulse response is examined. The conventional approach to adaptation is to adjust the equalizer taps directly to minimize a least squares error cost function. It is shown that the channel estimate approach not only yields superior performance, but also involves fewer computations than the conventional square-root-Kalman approach. The problem of channel estimation is mathematically analyzed for both the steepest descent and recursive least squares algorithms, and theoretical results are compared with simulation. It is also shown how simple theoretical predictions of the performance of the DFE can be made when using this alternative method of implementation.

  19. Indoor channel measurements and characterization at 60 GHz for wireless local area network applications

    Microsoft Academic Search

    Nektarios Moraitis; Philip Constantinou

    2004-01-01

    This work presents propagation measurement results at 60 GHz in order to determine the characteristics of indoor radio channels between fixed terminals. Path loss measurements are reported for line-of-sight (LoS) and non-line-of-sight (NLoS) cases, fading statistics in a physically stationary environment are extracted and a detailed investigation of the people movement effect on the temporal fading envelope is performed. Models

  20. OFDR based distributed temperature sensor using the three-channel simultaneous radio-frequency lock-in technique

    NASA Astrophysics Data System (ADS)

    Chen, Ke; Zhou, Xinlei; Peng, Wei; Yu, Qingxu

    2015-05-01

    Weak signal detection for single-mode fiber-optic distributed temperature sensor (DTS) is a key technology to achieve better performance. A hybrid technique combining the incoherent optical frequency domain reflectometry (IOFDR) and the three-channel simultaneous radio-frequency (RF) lock-in amplifier (LIA) is presented to improve the signal-to-noise ratio (SNR) of the measured spontaneous Raman backscattered light. The field programmable gate array (FPGA) based RF-LIA is designed with a novel and simple structure. The measurement frequency range is achieved from 1 kHz to 100 MHz. Experimental results show that the backscattered light signal of picowatt level can be detected with high SNR. With a 2.5 km single-mode fiber, a 1064 nm laser source, and the measurement time of 500 s, this sensing system can reach a spatial resolution of 0.93 m and a temperature resolution of about 0.2°C.

  1. Stochastic Wireless Channel Modeling, Estimation and Identification from Measurements

    SciTech Connect

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

    2008-07-01

    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.

  2. Wideband Propagation Measurements and Channel Implications for Indoor Broadband Wireless Local Area Networks at the 60 GHz Band

    Microsoft Academic Search

    Andreas G. Siamarou

    2003-01-01

    This paper addresses some wideband propagation characteristics for Indoor Broadband Wireless LANs at the 60 GHz band. Important system design characteristics from measured results obtained from two wideband 60 GHz LOS radio links are presented. Measurements had been undertaken using the swept frequency channel sounding method. Analysis from the complex frequency responses in a worst-case scenario have yielded to a

  3. Measurement of movements in the ionosphere using radio reflections

    Microsoft Academic Search

    J. D. Whitehead; K. L. Jones; P. E. Monro

    1983-01-01

    Movements of the ionosphere may be measured using radio reflections either by observing the movement of the diffraction, or interference, pattern along the ground; or by using the Doppler shifts of the echo as a radar beam is scanned across the sky. The two methods may use the same experimental arrangement and even the same data. The error in the

  4. Stochastic Wireless Channel Modeling, Estimation and Identification from Measurements

    Microsoft Academic Search

    Mohammed M. Olama; Yanyan Li; Seddik M. Djouadi; Charalambos D. Charalambous

    2008-01-01

    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

  5. Distributed Multiuser Sequential Channel Sensing Schemes in Multichannel Cognitive Radio Networks

    E-print Network

    Shokri-Ghadikolaei, Hossein; Nasiri-Kenari, Masoumeh

    2012-01-01

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

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

    PubMed

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

    2013-03-25

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

  7. ATS6-satellite radio beacon measurements at Ootacamund, India

    NASA Technical Reports Server (NTRS)

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

    1978-01-01

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

  8. Time Flies! Radio Signals Used for Time and Frequency Measurements

    Microsoft Academic Search

    Michael A. Lombardi NIST

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

  9. Probing the radio emission from air showers with polarization measurements

    NASA Astrophysics Data System (ADS)

    Aab, A.; Abreu, P.; Aglietta, M.; Ahlers, M.; Ahn, E. J.; Albuquerque, I. F. M.; Allekotte, I.; Allen, J.; Allison, P.; Almela, A.; Alvarez Castillo, J.; Alvarez-Muñiz, J.; Alves Batista, R.; Ambrosio, M.; Aminaei, A.; Anchordoqui, L.; Andringa, S.; Anti?i?, T.; Aramo, C.; Arqueros, F.; Asorey, H.; Assis, P.; Aublin, J.; Ave, M.; Avenier, M.; Avila, G.; Badescu, A. M.; Barber, K. B.; Bardenet, R.; Bäuml, J.; Baus, C.; Beatty, J. J.; Becker, K. H.; Bellido, J. A.; BenZvi, S.; Berat, C.; Bertou, X.; Biermann, P. L.; Billoir, P.; Blanco, F.; Blanco, M.; Bleve, C.; Blümer, H.; Bohá?ová, M.; Boncioli, D.; Bonifazi, C.; Bonino, R.; Borodai, N.; Brack, J.; Brancus, I.; Brogueira, P.; Brown, W. C.; Buchholz, P.; Bueno, A.; Buscemi, M.; Caballero-Mora, K. S.; Caccianiga, B.; Caccianiga, L.; Candusso, M.; Caramete, L.; Caruso, R.; Castellina, A.; Cataldi, G.; Cazon, L.; Cester, R.; Cheng, S. H.; Chiavassa, A.; Chinellato, J. A.; Chudoba, J.; Cilmo, M.; Clay, R. W.; Cocciolo, G.; Colalillo, R.; Collica, L.; Coluccia, M. R.; Conceição, R.; Contreras, F.; Cooper, M. J.; Coutu, S.; Covault, C. E.; Criss, A.; Cronin, J.; Curutiu, A.; Dallier, R.; Daniel, B.; Dasso, S.; Daumiller, K.; Dawson, B. R.; de Almeida, R. M.; De Domenico, M.; de Jong, S. J.; De La Vega, G.; de Mello Junior, W. J. M.; de Mello Neto, J. R. T.; De Mitri, I.; de Souza, V.; de Vries, K. D.; del Peral, L.; Deligny, O.; Dembinski, H.; Dhital, N.; Di Giulio, C.; Di Matteo, A.; Diaz, J. C.; Díaz Castro, M. L.; Diep, P. N.; Diogo, F.; Dobrigkeit, C.; Docters, W.; D'Olivo, J. C.; Dong, P. N.; Dorofeev, A.; dos Anjos, J. C.; Dova, M. T.; Ebr, J.; Engel, R.; Erdmann, M.; Escobar, C. O.; Espadanal, J.; Etchegoyen, A.; Facal San Luis, P.; Falcke, H.; Fang, K.; Farrar, G.; Fauth, A. C.; Fazzini, N.; Ferguson, A. P.; Fick, B.; Figueira, J. M.; Filevich, A.; Filip?i?, A.; Foerster, N.; Fox, B. D.; Fracchiolla, C. E.; Fraenkel, E. D.; Fratu, O.; Fröhlich, U.; Fuchs, B.; Gaior, R.; Gamarra, R. F.; Gambetta, S.; García, B.; Garcia Roca, S. T.; Garcia-Gamez, D.; Garcia-Pinto, D.; Garilli, G.; Gascon Bravo, A.; Gemmeke, H.; Ghia, P. L.; Giammarchi, M.; Giller, M.; Gitto, J.; Glaser, C.; Glass, H.; Gomez Albarracin, F.; Gómez Berisso, M.; Gómez Vitale, P. F.; Gonçalves, P.; Gonzalez, J. G.; Gookin, B.; Gorgi, A.; Gorham, P.; Gouffon, P.; Grebe, S.; Griffith, N.; Grillo, A. F.; Grubb, T. D.; Guardincerri, Y.; Guarino, F.; Guedes, G. P.; Hansen, P.; Harari, D.; Harrison, T. A.; Harton, J. L.; Haungs, A.; Hebbeker, T.; Heck, D.; Herve, A. E.; Hill, G. C.; Hojvat, C.; Hollon, N.; Holt, E.; Homola, P.; Hörandel, J. R.; Horvath, P.; Hrabovský, M.; Huber, D.; Huege, T.; Insolia, A.; Isar, P. G.; Jansen, S.; Jarne, C.; Josebachuili, M.; Kadija, K.; Kambeitz, O.; Kampert, K. H.; Karhan, P.; Kasper, P.; Katkov, I.; Kégl, B.; Keilhauer, B.; Keivani, A.; Kemp, E.; Kieckhafer, R. M.; Klages, H. O.; Kleifges, M.; Kleinfeller, J.; Knapp, J.; Krause, R.; Krohm, N.; Krömer, O.; Kruppke-Hansen, D.; Kuempel, D.; Kunka, N.; La Rosa, G.; LaHurd, D.; Latronico, L.; Lauer, R.; Lauscher, M.; Lautridou, P.; Le Coz, S.; Leão, M. S. A. B.; Lebrun, D.; Lebrun, P.; Leigui de Oliveira, M. A.; Letessier-Selvon, A.; Lhenry-Yvon, I.; Link, K.; López, R.; Lopez Agüera, A.; Louedec, K.; Lozano Bahilo, J.; Lu, L.; Lucero, A.; Ludwig, M.; Lyberis, H.; Maccarone, M. C.; Malacari, M.; Maldera, S.; Maller, J.; Mandat, D.; Mantsch, P.; Mariazzi, A. G.; Marin, V.; Mari?, I. C.; Marquez Falcon, H. R.; Marsella, G.; Martello, D.; Martin, L.; Martinez, H.; Martínez Bravo, O.; Martraire, D.; Masías Meza, J. J.; Mathes, H. J.; Matthews, J.; Matthews, J. A. J.; Matthiae, G.; Maurel, D.; Maurizio, D.; Mayotte, E.; Mazur, P. O.; Medina, C.; Medina-Tanco, G.; Melissas, M.; Melo, D.; Menichetti, E.; Menshikov, A.; Messina, S.; Meyhandan, R.; Mi?anovi?, S.; Micheletti, M. I.; Middendorf, L.; Minaya, I. A.; Miramonti, L.; Mitrica, B.; Molina-Bueno, L.; Mollerach, S.; Monasor, M.; Monnier Ragaigne, D.; Montanet, F.; Morales, B.; Morello, C.; Moreno, J. C.; Mostafá, M.; Moura, C. A.; Muller, M. A.; Müller, G.; Münchmeyer, M.; Mussa, R.; Navarra, G.; Navarro, J. L.; Navas, S.; Necesal, P.; Nellen, L.; Nelles, A.; Neuser, J.; Nhung, P. T.; Niechciol, M.; Niemietz, L.; Niggemann, T.; Nitz, D.; Nosek, D.; Nožka, L.; Oehlschläger, J.; Olinto, A.; Oliveira, M.; Ortiz, M.; Pacheco, N.; Pakk Selmi-Dei, D.; Palatka, M.; Pallotta, J.; Palmieri, N.; Parente, G.; Parra, A.; Pastor, S.; Paul, T.; Pech, M.; PeÂ?ala, J.; Pelayo, R.; Pepe, I. M.; Perrone, L.; Pesce, R.; Petermann, E.; Petrera, S.; Petrolini, A.; Petrov, Y.; Piegaia, R.; Pierog, T.; Pieroni, P.; Pimenta, M.; Pirronello, V.; Platino, M.; Plum, M.; Pontz, M.; Porcelli, A.; Preda, T.; Privitera, P.; Prouza, M.

    2014-03-01

    The emission of radio waves from air showers has been attributed to the so-called geomagnetic emission process. At frequencies around 50 MHz this process leads to coherent radiation which can be observed with rather simple setups. The direction of the electric field induced by this emission process depends only on the local magnetic field vector and on the incoming direction of the air shower. We report on measurements of the electric field vector where, in addition to this geomagnetic component, another component has been observed that cannot be described by the geomagnetic emission process. The data provide strong evidence that the other electric field component is polarized radially with respect to the shower axis, in agreement with predictions made by Askaryan who described radio emission from particle showers due to a negative charge excess in the front of the shower. Our results are compared to calculations which include the radiation mechanism induced by this charge-excess process.

  10. Spatial channel model and measurements for IMT2000 systems

    Microsoft Academic Search

    R. Michael Buehrer; S. Arunachalam; Kain H. Wu; Andrea Tonello

    2001-01-01

    This paper presents a spatial channel model for IMT-2000 systems as well as measurement results for 1.2 MHz wide wireless channels using an eight element linear array at two different frequencies. The spatial channel model is a spatial extension of the commonly known IMT-2000 temporal (i.e., delay profile) model. The measurement results are used to characterize the spatial aspects of

  11. Analytical methods to calculate the performance of a cellular mobile radio communication system with hybrid channel assignment

    Microsoft Academic Search

    Wuyi Yue

    1991-01-01

    Two approximate techniques are presented to evaluate the performance of large-scale mobile radio systems using a hybrid channel assignment scheme and a cellular structure, The two approximate analyses give the steady-state probability distributions of the system which are used to obtain expressions for the blocking probabilities. In the first method, the blocking probability is obtained by finding the interarrival time

  12. ATS-6 satellite radio beacon measurements at Ootacamund, India

    NASA Technical Reports Server (NTRS)

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

    1979-01-01

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

  13. Project 8: Using Radio Frequencies to Measure the Neutrino Mass

    E-print Network

    N. S. Oblath

    2011-10-10

    It is well known that the neutrino masses affect the shape of the energy spectrum of tritium beta-decay electrons. However, experiments have yet to measure that distortion. The Project 8 experiment proposes to measure the spectral distortion in a novel way: using radio-frequency techniques to detect and measure the energies of the beta-decay electrons. We plan on measuring the radiation created from the cyclotron motion of the electrons in a strong magnetic field. I will report on the status of a prototype that is designed to demonstrate single-electron detection at energies near the tritium endpoint, 18.6 keV. I will also discuss the possibilities for scaling up to a neutrino-mass experiment.

  14. Review on terrestrial propagation channel modelling

    Microsoft Academic Search

    M. S. Pontes; L. A. R. Silva Mello

    2010-01-01

    Design and implementation of wireless systems, comprising mobile and fixed radios, requires the knowledge of the propagation characteristics of the channel. The random nature of the radio channel parameters and the complexity of the propagation phenomena suggest that characterization of the channel can be achieved based on statistical analysis of field measurements. This approach leads to statistical and empirical models

  15. PAD-MAC: primary user activity-aware distributed MAC for multi-channel cognitive radio networks.

    PubMed

    Ali, Amjad; Piran, Md Jalil; Kim, Hansoo; Yun, Jihyeok; Suh, Doug Young

    2015-01-01

    Cognitive radio (CR) has emerged as a promising technology to solve problems related to spectrum scarcity and provides a ubiquitous wireless access environment. CR-enabled secondary users (SUs) exploit spectrum white spaces opportunistically and immediately vacate the acquired licensed channels as primary users (PUs) arrive. Accessing the licensed channels without the prior knowledge of PU traffic patterns causes severe throughput degradation due to excessive channel switching and PU-to-SU collisions. Therefore, it is significantly important to design a PU activity-aware medium access control (MAC) protocol for cognitive radio networks (CRNs). In this paper, we first propose a licensed channel usage pattern identification scheme, based on a two-state Markov model, and then estimate the future idle slots using previous observations of the channels. Furthermore, based on these past observations, we compute the rank of each available licensed channel that gives SU transmission success assessment during the estimated idle slot. Secondly, we propose a PU activity-aware distributed MAC (PAD-MAC) protocol for heterogeneous multi-channel CRNs that selects the best channel for each SU to enhance its throughput. PAD-MAC controls SU activities by allowing them to exploit the licensed channels only for the duration of estimated idle slots and enables predictive and fast channel switching. To evaluate the performance of the proposed PAD-MAC, we compare it with the distributed QoS-aware MAC (QC-MAC) and listen-before-talk MAC schemes. Extensive numerical results show the significant improvements of the PAD-MAC in terms of the SU throughput, SU channel switching rate and PU-to-SU collision rate. PMID:25831084

  16. Generalized Formalisms of the Radio Interferometer Measurement Equation

    E-print Network

    Price, Danny C

    2015-01-01

    The Radio Interferometer Measurement Equation (RIME) is a matrix-based mathematical model that describes the response of a radio interferometer. The Jones calculus it employs is not suitable for describing the analogue components of a telescope. This is because it does not consider the effect of impedance mismatches between components. This paper aims to highlight the limitations of Jones calculus, and suggests some alternative methods that are more applicable. We reformulate the RIME with a different basis that includes magnetic and mixed coherency statistics. We present a microwave network inspired 2N-port version of the RIME, and a tensor formalism based upon the electromagnetic tensor from special relativity. We elucidate the limitations of the Jones-matrix-based RIME for describing analogue components. We show how measured scattering parameters of analogue components can be used in a 2N-port version of the RIME. In addition, we show how motion at relativistic speed affects the observed flux. We present r...

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

    Microsoft Academic Search

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

    2004-01-01

    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%,

  18. Propagation measurements for the aeronautical satellite channel

    Microsoft Academic Search

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

    1987-01-01

    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

  19. Radio-Frequency Rectification on Membrane Bound Pores

    E-print Network

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

    2007-09-12

    We present measurements on direct radio-frequency pumping of ion channels and pores bound in bilipid membranes. We make use of newly developed microcoaxes, which allow delivering the high frequency signal in close proximity to the membrane bound proteins and ion channels. We find rectification of the radio-frequency signal, which is used to pump ions through the channels and pores.

  20. Measuring channel dependence in separate activation models

    Microsoft Academic Search

    Hans Colonius

    1986-01-01

    In the bimodal detection task, the observer must respond as soon as a signal is presented in either of two modalities (e.g.,\\u000a a tone or a flash). A typical finding is a facilitation of reaction time for redundant-signal trials, that is, when both signals\\u000a are presented simultaneously. Separate-activation models assume that the two signals are processed simultaneously within different\\u000a channels

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

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

  2. A compiled catalog of rotation measures of radio point sources

    NASA Astrophysics Data System (ADS)

    Xu, Jun; Han, Jin-Lin

    2014-08-01

    We compiled a catalog of Faraday rotation measures (RMs) for 4553 extragalactic radio point sources published in literature. These RMs were derived from multi-frequency polarization observations. The RM data are compared to those in the NRAO VLA Sky Survey (NVSS) RM catalog. We reveal a systematic uncertainty of about 10.0 ± 1.5 rad m-2 in the NVSS RM catalog. The Galactic foreground RM is calculated through a weighted averaging method by using the compiled RM catalog together with the NVSS RM catalog, with careful consideration of uncertainties in the RM data. The data from the catalog and the interface for the Galactic foreground RM calculations are publicly available on the webpage: http://zmtt.bao.ac.cn/RM/.

  3. Baroclinic tidal generation in the Kauai Channel inferred from high-frequency radio Doppler current meters

    NASA Astrophysics Data System (ADS)

    Zaron, Edward D.; Chavanne, Cedric; Egbert, Gary D.; Flament, Pierre

    2009-10-01

    A data-assimilating three-dimensional primitive equations model is used in conjunction with high-frequency radio Doppler current data to infer tidal conversion during two 3-month periods in Kauai Channel, Hawaii. It is estimated that the M barotropic tide loses energy at rates of 1.1 and 1.2 GW during these periods, values 25% lower than predicted with the prior model. Of this total conversion rate, approximately 85% exits the model domain to enter the deep ocean as a coherent propagating internal tide. Although the inferred tidal currents differ in detail during the 3-month periods, the domain-averaged tidal energetics do not. The tidal solutions obtained by the data-assimilative model do not exactly satisfy the primitive equations dynamics since a residual forcing is permitted in the horizontal momentum and mass conservation equations. An analysis of these residuals indicates that they are consistent with the expected amplitude of tidal-mesoscale interactions; however, the residual forcing in the mass equation, which represents refraction by the mesoscale buoyancy field, is much too small. An attempt to reconcile the forcing residuals with known processes suggests, by elimination, that tidal-mesoscale interactions are of leading-order significance and should be included in future analysis of baroclinic tidal energy budgets.

  4. Multipath Channel Models for Wireless Local and Metropolitan Area Networks

    Microsoft Academic Search

    Kyungsoo Jeong; S. H. Kim; K. M. Chung; J. C. Kim; J. H. Yu; J. S. Lee; S. H. Seo

    2005-01-01

    Wideband mobile radio channel characteristics were measured in various environments in Korea. SKT conducted impulse response measurements at 2.3 GHz with a commercial channel sounder and presents multipath channel models for wireless local and metropolitan area networks. In this paper, we describe the process to analyze the measured data and build tapped delay line channel models. The whole measurements were

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

    NASA Astrophysics Data System (ADS)

    Petrin, Allen J.

    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.

  6. Indoor Radio Communication In A Rician Channel Using Direct-sequence Spread Spectrum Multiple Access With Selection Diversity

    Microsoft Academic Search

    Ramjee Prasad; H. S. Misser; Adriaan Kegel

    1990-01-01

    The bit error probability for direct-sequence spread-spectrum multiple access (DS\\/SS-MA) communications is evaluated with differential phase-shift-keying (DPSK) modulation and selection diversity, considering the indoor radio environment as a Rician fading channel. Computed results are presented for delay spreads T, in the range of 50 ns _< T, I250 ns, and data rates of 32, 64 and 144 kbit\\/s. The effect

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

    E-print Network

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

    2014-09-30

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

  8. Dynamic impedance measurements during radio-frequency heating of cornea.

    PubMed

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

    2002-12-01

    Hyperopia affects approximately 25% of the population. The aim of different heating modalities for the treatment of hyperopia is to steepen the central curvature of the cornea. Conductive keratoplasty (CK) involves the placement of radio-frequency (RF) lesions around a 7-mm-diameter ring concentric with the pupil of the eye. Dynamics of lesion formation during CK depend on corneal electrical impedance, which is expected to change during each 600-ms-long macropulse. The purpose of this study was to measure impedance dynamics during CK. RF lesions were made in in vitro porcine eyes at different power settings. Voltage and current measurements were acquired using a high-speed computer-based data acquisition system. Root-mean-square voltages (VRMS) and curre (IRMS) were calculated for each micropulse, and impedance was determined by calculating the quotient VRMS/IRMS. Initial corneal impedance in vitro was approximately 2000 ohms. During the macropulse, impedance decreased initially due to increased mobility of conductive ions. At higher power settings (e.g., > 70%, or maximum peak-to-peak voltage of 233 V), impedance increased after the initial decrease, indicative of local water vaporization and/or tissue coagulation. Preliminary impedance data obtained for in vivo porcine eyes were similar in magnitude to the in vitro values. PMID:12549743

  9. Measuring the effective channel length of MOSFETs

    Microsoft Academic Search

    K. K. Ng; J. R. Brews

    1990-01-01

    Eleven measurement methods are outlined, and their assumptions are examined. The methods are analyzed, critiqued, and compared. Recommendations are made as to which methods are best under various conditions

  10. 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

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

    2001-01-01

    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.

  11. Automatic DGD and GVD compensation at 640 Gb/s based on scalar radio-frequency spectrum measurement.

    PubMed

    Paquot, Yvan; Schröder, Jochen; Palushani, Evarist; Neo, Richard; Oxenløwe, Leif K; Madden, Steve; Choi, Duk-Yong; Luther-Davies, Barry; Pelusi, Mark D; Eggleton, Benjamin J

    2013-03-20

    We demonstrate what we believe to be the first real-time impairment-cancellation system for group-velocity dispersion (GVD) and differential group delay (DGD) for a 640 Gb/s single-channel signal. Simultaneous compensation of two independent parameters is demonstrated by feedback control of separate GVD and DGD compensators using an impairment monitor based on an integrated all-optical radio-frequency (RF) spectrum analyzer. We show that low-bandwidth measurement of only a single tone in the RF spectrum is sufficient for automatic compensation for multiple degrees of freedom using a multivariate optimization scheme. PMID:23518737

  12. 28-channel hybrid system for neuromagnetic measurements

    SciTech Connect

    Foglietti, V.; Del Gratta, C.; Pasquarelli, A.; Pizzella, V.; Torriol, G. (IESS-CNR, Via Cineto Romano 42 Roma (IT)); Roman, G.L. (Instituto Fisica Medica, Universita di Chieti (IT))

    1991-03-01

    This paper describes progress toward the development of a 28-multichannel system for neuromagnetic measurements. A novel hybrid design consisting of 16 first-order axial gradiometers and 12 first-order planar gradiometers was chosen, which optimize the use of the available cylindrical volume of the dewar tail. This configuration maintains the symmetry of the detected pattern with respect to rotation of a biomagnetic source located under the center of the array and features a localization power considerably better than an array of all first-order planar gradiometers. The detecting array permits simultaneous magnetic measurements over a circular scalp region of 16 cm diameter.

  13. High-resolution 3-D direction-of-arrival determination for urban mobile radio

    Microsoft Academic Search

    Josef Fuhl; Jean-Pierre Rossi; Ernst Bonek

    1997-01-01

    The in-depth knowledge of the mobile radio channel is particularly important for radio communication modeling and advanced technology system design. We propose an accurate method to determine jointly the azimuth and elevation angle and the delay of waves incoming at the receiver. The method is applied to measurements of the complex impulse response of the mobile radio channel, performed on

  14. The 18th Annual IEEE International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC 07) PROBABILISTIC MITIGATION OF CONTROL CHANNEL JAMMING VIA

    E-print Network

    Hochberg, Michael

    The 18th Annual IEEE International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC 07) PROBABILISTIC MITIGATION OF CONTROL CHANNEL JAMMING VIA RANDOM KEY DISTRIBUTION Patrick Tague may be able to jam control channel traffic and prevent relevant data traffic. Hence, it is of interest

  15. Marine information systems and new measuring channels for hydrophysical parameters

    NASA Astrophysics Data System (ADS)

    Smirnov, G. V.; Olenin, A. L.

    2015-03-01

    The results of the development and implementation of oceanographic information-measuring systems in the 1960s to 1970s and 1980s to 1990s are analytically treated and the basic principles of present-day systems for collecting data on oceanographic parameters are considered. We present the design of a technological platform for multichannel complexes aimed at concurrent measurements of hydrological, optical, and chemical characteristics. The platform allows one to combine the conventional and new channels for measuring oceanographic parameters.

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

    PubMed Central

    Andersen, O S

    1983-01-01

    The patch-clamp technique of Mueller (1975, Ann. N.Y. Acad. Sci., 274:247-264) and Neher and Sakmann (1976, Nature (Lond.), 260:799-802) was modified to be suitable for single-channel measurements in lipid bilayers at potentials up to 500 mV. This method was used to study gramicidin A single-channel current-voltage characteristics. It was found that the sublinear current-voltage behavior normally observed at low permeant ion concentrations and rather low potentials (V less than or equal to 200 mV) continues to be seen all the way up to 500 mV. This phenomenon is characteristic of the low permeant ion situation in which the channel is far from saturation, and implies that the overall rate constant for association between ion and channel is very weakly, if at all, voltage dependent. The magnitude of the single channel currents at 500 mV is consistent with the notion that the aqueous convergence conductance is a significant factor in determining the permeability characteristics of the gramicidin A channel. PMID:6188500

  17. Low Frequency Radio Signal Polarisation Sensor with Applications in Attitude Estimation

    E-print Network

    Maguire, Sean; Robertson, Paul

    2014-01-01

    A novel system for estimating the attitude (orientation) of a platform using measurements of Low Frequency (LF) radio signals is reported. The sensor system consists of an array of three orthogonal solenoid coil antennas, a three channel radio...

  18. Summary of interference measurements at selected radio observatories

    NASA Technical Reports Server (NTRS)

    Tarter, Jill C.

    1990-01-01

    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.

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

    E-print Network

    California at Berkeley, University of

    Interplanetary dust detection by radio antennas: Mass calibration and fluxes measured by STEREO/WAVES radio instrument onboard the two STEREO spacecraft near 1 A.U. during the period 2007­2010. The impact detection area compared to conventional dust detectors provides flux data with a better statistics. We show

  20. Magellan radio occultation measurements of atmospheric waves on Venus

    NASA Technical Reports Server (NTRS)

    Hinson, David P.; Jenkins, J. M.

    1995-01-01

    Radio occultation experiments were conducted at Venus on three consecutive orbits of the Magellan spacecraft in October 1991. Each occultation occurred over the same topography (67 deg N, 127 deg E) and at the same local time (22 hr 5 min), but the data are sensitive to zonal variations because the atmosphere rotates significantly during one orbit. Through comparisons between observations and predictions of standard wave theory, we have demonstrated that small-scale oscillations in retrieved temperature profiles as well as scintillations in received signal intensity are caused by a spectrum of vertically propagating internal gravity waves. There is a strong similarity between the intensity scintillations observed here and previous measurements, which pertain to a wide range of locations and experiment dates. This implies that the same basic phenomenon underlies all the observations and hence that gravity waves are a persistent, global feature of Venus' atmosphere. We obtained a fairly complete characterization of a gravity wave that appears above the middle cloud in temperature measurements on all three orbits. The amplitude and vertical wavelength are about 4 K and 2.5 km respectively, at 65 km. A model for radiative damping implies that the wave intrinsic frequency is approximately 2 x 10(exp 4) rad/sec, the corresponding ratio between horizontal and vertical wavelengths is approximately 100. The wave is nearly stationary relative to the surface or the Sun. Radiative attenuation limits the wave amplitude at altitudes above approximately 65 km, leading to wave drag on the mean zonal winds of about +0.4 m/sec per day (eastward). The sign, magnitude, and location of this forcing suggest a possible role in explaining the decrease with height in the zonal wind speed that is believed to occur above the cloud tops. Temperature oscillations with larger vertical wavelengths (5-10 km) were also observed on all three orbits, but we are able unable to interpret these unambiguously.

  1. MEASURING THE JET POWER OF FLAT-SPECTRUM RADIO QUASARS

    SciTech Connect

    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

    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.

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

    Microsoft Academic Search

    Timothy Jason Shepard

    1995-01-01

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

  3. Polyphase channelizer as bandpass filters in multi-standard Software Defined Radios

    Microsoft Academic Search

    Mehmood-ur-Rehman Awan; Peter Koch

    2009-01-01

    The aim of this work is to design efficient bandpass filters for multistandard software defined radios. Software defined radio (SDR) based applications which demand high sampling rate to eliminate the most of the analog components require high-performance technology and digital signal processing methods to handle and process the high sample rate data. State of the art technology such as FPGAs

  4. Optical Probe Measurements of a Plasma Channel for Fast Ignition

    NASA Astrophysics Data System (ADS)

    Ivancic, S.; Haberberger, D.; Theobald, W.; Anderson, K. S.; Froula, D. H.; Meyerhofer, D. D.; Tanaka, K.; Habara, H.; Iwawaki, T.

    2013-10-01

    The evacuation of a cavity in a plasma by a high-intensity laser beam is of practical importance to the channeling fast-ignition concept. The channel in the plasma corona of an imploded inertial confinement fusion capsule provides a clear path through the plasma so that the energy from second high-intensity laser can be deposited close to the dense core of the assembled fuel to achieve ignition. This study reports on experiments performed with the OMEGA EP Laser System using one of the short-pulse IR beams (1.25 kJ, 10 ps) to form a straight channel in a large blowoff plasma with an electron temperature of ~1.5 keV that was generated by two nanosecond, kilojoule UV laser beams. The channel was measured to reach up to half the IR critical density with a channel width of ~200 ?m. Images were taken at different times showing the radial evolution of a strong blast wave from the channel walls. Individual filaments were observed at the critical surface indicating that the laser became unstable and broke up into multiple filaments. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

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

    USGS Publications Warehouse

    Adams, J.; Takekawa, J.Y.

    2008-01-01

    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.

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

    Microsoft Academic Search

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

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

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

    Microsoft Academic Search

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

    2011-01-01

    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

  8. Integrated optical measurement system for fluorescence spectroscopy in microfluidic channels

    Microsoft Academic Search

    Jörg Hübner; Klaus B. Mogensen; Anders M. Jorgensen; Peter Friis; Pieter Telleman; Jörg P. Kutter

    2001-01-01

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

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

    Microsoft Academic Search

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

    2006-01-01

    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

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

    Microsoft Academic Search

    Jens Nachtigall; Anatolij Zubow; Jens-Peter Redlich

    2008-01-01

    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.

  11. Radio telescopes

    Microsoft Academic Search

    J. Findlay

    1964-01-01

    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

  12. Performance Analysis of Spectrum Handoff for Cognitive Radio Ad Hoc Networks without Common Control Channel under Homogeneous Primary Traffic

    E-print Network

    Song, Yi

    2011-01-01

    Cognitive radio (CR) technology is regarded as a promising solution to the spectrum scarcity problem. Due to the spectrum varying nature of CR networks, unlicensed users are required to perform spectrum handoffs when licensed users reuse the spectrum. In this paper, we study the performance of the spectrum handoff process in a CR ad hoc network under homogeneous primary traffic. We propose a novel three dimensional discrete-time Markov chain to characterize the process of spectrum handoffs and analyze the performance of unlicensed users. Since in real CR networks, a dedicated common control channel is not practical, in our model, we implement a network coordination scheme where no dedicated common control channel is needed. Moreover, in wireless communications, collisions among simultaneous transmissions cannot be immediately detected and the whole collided packets need to be retransmitted, which greatly affects the network performance. With this observation, we also consider the retransmissions of the collid...

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

    PubMed

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

    2015-01-01

    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

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

    ERIC Educational Resources Information Center

    Burgess, Vic; And Others

    1979-01-01

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

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

    E-print Network

    Whitney, John Peter, 1982-

    2004-01-01

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

  16. Aircraft measurement of radio frequency noise at 121.5 MHz, 243MHz and 406MHz

    NASA Technical Reports Server (NTRS)

    Taylor, R. E.; Hill, J. S.

    1977-01-01

    An airborne survey measurement of terrestrial radio-frequency noise over U.S. metropolitan areas has been made at 121.5, 243 and 406 MHz with horizontal-polarization monopole antennas. Flights were at 25,000 feet altitude during the period from December 30, 1976 to January 8, 1977. Radio-noise measurements, expressed in equivalent antenna-noise temperature, indicate a steady-background noise temperature of 572,000 K, at 121.5 MHz, during daylight over New York City. This data is helpful in compiling radio-noise temperature maps; in turn useful for designing satellite-aided, emergency-distress search and rescue communication systems.

  17. Aircraft measurement of radio frequency noise at 121.5 MHz, 243 MHz and 406 MHz

    NASA Technical Reports Server (NTRS)

    Taylor, R. E.; Hill, J. S.

    1977-01-01

    An airborne survey measurement of terrestrial radio-frequency noise over U.S. metropolitan areas was carried out at 121.5, 243 and 406 MHz with horizontal-polarization monopole antennas. Flights were at 25,000 feet altitude. Radio-noise measurements, expressed in equivalent antenna-noise temperature, indicate a steady-background noise temperature of 572,000 K, at 121.5 MHz, during daylight over New York City. This data is helpful in compiling radio-noise temperature maps; in turn useful for designing satellite-aided, emergency-distress search and rescue communication systems.

  18. Measurement of Radio Emission from Cosmic Ray induced Air Showers

    E-print Network

    Erdmann, Martin

    . . . . . . . . . . . . . . . . . . . 27 3.3 Low Energy Enhancements . . . . . . . . . . . . . . . . . 29 3.4 Radio Detector - AERA . . . . . . . . . . . . . . . . . . . . . . . . . . 40 4.2 AERA Data Set . . . . . . . . . . . . . . . . . . . . . 41 4.2.1 Event Rate and Antenna of the Calibration . . . . . . . . . . . . . . . . . . . . 76 6.3 Point-like Noise Sources at AERA

  19. Energy estimation for cosmic rays measured with the Auger Engineering Radio Array

    NASA Astrophysics Data System (ADS)

    Glaser, Christian; Pierre Auger Collaboration

    2013-05-01

    The Auger Engineering Radio Array (AERA) is located within the Pierre Auger Observatory and currently consists of 24 self-triggered radio stations. Observation of radio signals from cosmic rays is confirmed by the surface detector (SD) stations of the Observatory which provide well-calibrated information on the cosmic-ray energies and arrival directions. The response of the radio stations has been thoroughly calibrated to enable the reconstruction of the incoming electric field. For estimating the cosmic-ray energy we use the maximum absolute value of the measured electric field vector corrected for the incoming direction and the distance to the shower core. Performing a preliminary energy calibration using the SD information, we observe that the defined radio energy estimator provides an approximately linear dependency on the cosmic-ray energy.

  20. Wireless indoor channel modeling: statistical agreement of ray tracing simulations and channel sounding measurements

    Microsoft Academic Search

    Gus German; Quentin Spencer; Lee Swindlehurst; Reinaldo Valenzuela

    2001-01-01

    A statistical space-time model for indoor wireless propagation based on empirical measurements is compared with results from the deterministic ray-tracing simulation tool WiSE for the same environment. Excellent agreement is found in terms of the distributions of arrival times and angular spread for both modeling approaches. The WiSE package is also use to synthesize MIMO channel matrices and determine the

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

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

    This paper presents long-term statistics additional to those previously published pertaining to evaporation duct propagation of UHF radio waves in the British Channel Islands, with particular focus on a completely over-sea 50 km transhorizon path. The importance of the evaporation duct as an anomalous propagation mechanism in marine and coastal regions is highlighted. In particular, the influence of various atmospheric parameters on the performance of a popular operational evaporation duct model is examined. The strengths and weaknesses of this model are evaluated under specific atmospheric conditions. The relationship between the continually varying evaporation duct height and transmitter-receiver antenna geometries is analyzed, and a range of statistics related to the implications of this relationship on the received signal strength is presented. The various issues under investigation are of direct relevance in the planning of long-range, over-sea radio systems operating in the UHF band, and have implications for the radio regulatory work carried out by organizations such as the International Telecommunication Union.

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

    PubMed Central

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

    2011-01-01

    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

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

    PubMed

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

    2011-01-01

    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

  4. Measurement of the top quark mass in the dilepton channel

    Microsoft Academic Search

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

    2007-01-01

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

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

    Microsoft Academic Search

    Lokman Sboui; Zouheir Rezki; Mohamed-Slim Alouini

    2011-01-01

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

  6. Fundamental capacity limits of cognitive radio in fading environments with imperfect channel information

    Microsoft Academic Search

    Leila Musavian; Sonia Aïssa

    2009-01-01

    In this paper, we analyze the capacity gains of opportunistic spectrum-sharing channels in fading environments with imperfect channel information. In particular, we consider that a secondary user may access the spectrum allocated to a primary user as long as the interference power, inflicted at the primar's receiver as an effect of the transmission of the secondary user, remains below predefined

  7. The Effects of Time Delay Spread on Portable Radio Communications Channels with Digital Modulation

    Microsoft Academic Search

    J. Chuang

    1987-01-01

    Frequency-selective fading caused by multipath time delay spread degrades digital communication channels by causing intersymbol interference, thus resulting in an irreducible BER and imposing a upper limit on the data symbol rate. In this paper, a frequencyselective, slowly fading channel is studied by computer simulation. The unfiltered BPSK, QPSK, OQPSK, and MSK modulations are considered first to illustrate the physical

  8. Super resolution matrix pencil algorithm for future fading prediction of mobile radio channels

    Microsoft Academic Search

    Ali Aassie Ali; A. S. Omar

    2005-01-01

    In this paper a new application for the Matrix Pencil algorithm for the mobile channel 1 prediction is introduced. The Doppler shifts and the amplitudes of the scattered components are determined using the Matrix Pencil algorithm and the channel is then extrapolated (predicted) in the future. The movement of the mobile is assumed to be linear over the distance of

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

    NASA Technical Reports Server (NTRS)

    Fainberg, J.

    1979-01-01

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

  10. Multi-agent Q-Learning of Channel Selection in Multi-user Cognitive Radio Systems: A Two by Two Case

    Microsoft Academic Search

    Husheng Li

    2009-01-01

    Abstract— Resource allocation is an important,issue in cogni- tive radio systems. It can,be done,by carrying,out negotiation among secondary users. However, significant overhead may be incurred,by the negotiation since the negotiation needs to be done frequently,due,to the rapid change,of primary,users’ activity. In this paper, a channel selection scheme without negotiation is considered,for multi-user and,multi-channel,cognitive radio systems. To avoid collision incurred by

  11. Abel transform inversion of radio occultation measurements made with a receiver inside the Earth's atmosphere

    Microsoft Academic Search

    S. B. Healy; J. Haase; O. Lesne

    2002-01-01

    Radio occultation measurements made with a receiver inside the Earth's atmosphere can be inverted, assuming local spherical symmetry, with an Abel transform to provide an estimate of the atmospheric refractive index profile. The measurement geometry is closely related to problems encountered when inverting seismic time-travel data and solar occultation measurements, where the Abel solution is well known. The method requires

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

    E-print Network

    Combining Radio Occultation Measurements with Other Instruments to Map the Ionospheric Electron to incorporate other ionospheric measurements, such as electron-density profiles from inverted ionograms or in the individual TEC measurements contain no information about the spatial variation of the electron concentration

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

    Microsoft Academic Search

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

    2011-01-01

    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

  14. Seasonal Anomaly Observed by FORMOSAT-3\\/COSMIC Ionospheric Radio Occultation Measurements

    Microsoft Academic Search

    W. Lee; Q. Wu; S. C. Solomon; Y. Kuo; A. Coster; S. Cho

    2009-01-01

    Seasonal anomaly (winter anomaly) that the daytime electron density of F2-layer in winter is higher than in summer is observed by FORMOSAT-3\\/COSMIC ionospheric radio occultation (COSMIC RO) measurements. Ionospheric electron density profiles retrieved from RO measurements provide the global feature of ionospheric variations. COSMIC RO measurements from November 2006 to February 2009 in geomagnetic quiet conditions are used to study

  15. On the estimate and assessment of the ionospheric effects affecting low frequency radio astronomy measurements

    Microsoft Academic Search

    Biagio Forte; Marcio Aquino

    2011-01-01

    The development of the LOw Frequency telescopes ARray (LOFAR) has posed a serious issue on the calibration of those measurements in the presence of the Earth’s ionosphere. The purpose of measuring at radio frequencies as low as VHF exposes LOFAR to a number of ionospheric phenomena, capable of deteriorating the accuracy of the measurements and subsequently of the sky imaging.

  16. Theoretical investigations on site attenuation - Propagation characteristics inside the measuring site for the radio interference

    Microsoft Academic Search

    T. Kawana; S. Miyajima

    1978-01-01

    Theoretical investigations are presented on the site attenuation of the measuring site in which radio interference waves radiated from electrical equipment are measured. The general formula for calculation of site attenuation was obtained from these investigations and the reference values were calculated by this formula. Comparing these values with the site attenuation values actually measured in an open field, good

  17. High-speed digital transmission experiments in 920 MHz urban and suburban mobile radio channels

    Microsoft Academic Search

    KAZUHIRO DAIKOKU; KAZUAKI MUROTA; KOHJI MOMMA

    1982-01-01

    Field experiments have been conducted to clarify the feasibility of introducing a newly developed Gaussian filtered minimum shift keying (GMSK) modulation method into 920 MHz mobile radio systems, and have been performed in the Tokyo urban, and the Yokosuka suburban areas.

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

    Microsoft Academic Search

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

    2009-01-01

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

  19. Spectral Properties of Modulated Signal in the Doppler Domain in Urban Radio Channels With Fading

    Microsoft Academic Search

    Nathan Blaunstein; Dimitry Katz; Masashi Hayakawa

    2010-01-01

    We examine propagation of frequency modulated (FM ) radio signals in the urban environments for different elevations of base station (BS) and mobile subscriber (MS) antennas, below and above the rooftops, based on the stochastic multi-parametric approach. We concentrate our attention on the spectral properties of signal power variations in the frequency domain and describe them based on the Doppler-spread

  20. Anti-jamming communication in cognitive radio networks with unknown channel statistics

    Microsoft Academic Search

    Qian Wang; Kui Ren; Peng Ning

    2011-01-01

    Recently, many opportunistic spectrum sensing and access protocols have been proposed for cognitive radio networks (CRNs). For achieving optimized spectrum usage, existing solutions model the spectrum sensing and access problem as a partially observed Markov decision process (POMDP) and assume that the information states and\\/or the primary users' (PUs) traffic statistics are known a priori to the secondary users (SUs).

  1. A Stochastic Game Model for Jamming in MultiChannel Cognitive Radio Systems

    Microsoft Academic Search

    Quanyan Zhu; Husheng Li; Zhu Han; Tamer Basar

    2010-01-01

    The security issue in collaborative sensing in cognitive radio networks can be modeled as attackers and secondary users in a jamming and anti-jamming scenario. In this paper, we introduce a stochastic zero-sum game model to study the strategies. Primary users, secondary users and jammers are the three types of agents in the system. The primary users dictate the system states

  2. Improved radio tomography of the ionosphere using EUV\\/optical measurements from satellites

    Microsoft Academic Search

    P. A. Bernhardt; K. F. Dymond; J. M. Picone; D. M. Cotton; S. Chakrabarti; T. A. Cook; J. S. Vickers

    1997-01-01

    Computerized tomography of the ionosphere employs radio beacons on satellites and ground-based receivers that measure the integrated electron densities along line-of-sight propagation paths. The primary limitation to satellite-based ionospheric radio tomography is the lack of near-horizontal ray paths. This restricts the accuracy for the reconstruction of vertical profiles in the F region. Horizontal integration paths may be obtained using the

  3. Laser-induced fluorescence photobleaching anemometer for flow velocity measurement in sub-microscale fluidic channels

    Microsoft Academic Search

    G. R. Wang; J. Guo; Y. Lin; J. Feng; J. Wei; Y. Wang; S. Krishnamoorthy; S. Sundaram

    2006-01-01

    A non-particle tracing technique based on laser-induced fluorescence photobleaching is demonstrated for measuring the flow velocity in microfluidic channels. The technique can give high spatial and temporal resolution in the measurement of velocity in microfluidic channels

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

    SciTech Connect

    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

    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.

  5. Bit Error Simulation for pi\\/4 DQPSK Mobile Radio Communications using Two-Ray and Measurement-Based Impulse Response Models

    Microsoft Academic Search

    Victor Fung; Theodore S. Rappaport; Berthold Thoma

    1993-01-01

    An accurate software\\/hardware bit-by-bit error simulator for mobile radio communications is described. Simulation results in indoor and outdoor channels are compared with theoretical results. Bit error rate (BER) results in simulated frequency-selective fading channels generated by several channel models such as two-ray, constant amplitude, and simulated indoor radio channel impulse models (SIRCIMs) are presented. It is shown that BER is

  6. Time Varying Wireless Channel Modeling, Estimation, Identification, and Power Control from Measurements

    Microsoft Academic Search

    Mohammed M. Olama; Yanyan Li; Seddik M. Djouadi; Charalambos D. Charalambous

    2007-01-01

    This paper is concerned with a time-varying wireless channel modeling, its parameter estimation, system identification, and optimal power control from measurement data. The channel model is represented in state space form, while the Expectation Maximization algorithm and Kalman filtering are used in the channel parameter and state estimation, respectively. The inphase and quadrature components of the wireless channel and its

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

    Microsoft Academic Search

    Lan Zhang; Ying-chang Liang; Yan Xin

    2008-01-01

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

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

    PubMed

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

    2013-01-01

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

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

    Microsoft Academic Search

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

    1994-01-01

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

  10. Thermal Tides in the Northern Hemisphere of Mars with Mars Global Surveyor Radio Occultation Measurements

    Microsoft Academic Search

    Kerri L. Cahoy; D. P. Hinson; G. Tyler

    2006-01-01

    We use radio occultation measurements made by Mars Global Surveyor to study thermal tides at high northern latitudes during late spring and summer (Ls = 70-180) of Mars Year 25. We focus on how the wave structure at ionospheric altitudes (100-150 km) evolves with changing season, insolation, and local time. The local time of the measurements drifts steadily from 0300

  11. Dual-channel heterodyne measurements of atmospheric phase fluctuations.

    PubMed

    Ridley, Kevin D; Jakeman, Eric; Bryce, David; Watson, Stephen M

    2003-07-20

    A dual-channel fiber-coupled laser heterodyne system operating at a 1.55-microm wavelength is used to investigate phase fluctuations induced on a laser beam by propagation through turbulent air. Two receivers are used to characterize spatial and temporal variations produced by a turbulent layer of air in the laboratory. The system is also used for measurements through extended turbulence along an 80-m outdoor atmospheric path. Phase structure functions, power spectral densities, and cross correlations are presented. PMID:12921273

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

    Microsoft Academic Search

    Gregg Jørgen Suaning; Nigel H. Lovell

    2001-01-01

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

  13. Fundamental effective capacity limits of cognitive radio in fading environments with imperfect channel information

    Microsoft Academic Search

    Xianbin Xie; Wei Guo

    2011-01-01

    In this paper, we analyze the effective capacity gains of opportunistic spectrum-sharing with imperfect channel information. We consider that a secondary user may access the spectrum allocated to a primary user as long as the average interference power, inflicted at the primary's receiver as an effect of the transmission of the secondary user, remains below predefined power limits. We consider

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

    Microsoft Academic Search

    S. Mayrargue

    1993-01-01

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

  15. Providing survivability against jamming attack for multi-radio multi-channel wireless mesh networks

    Microsoft Academic Search

    Shanshan Jiang; Yuan Xue

    2011-01-01

    Built upon a shared wireless medium, wireless mesh network is particularly vulnerable to jamming attacks. The ability to recover from attacks and maintain an acceptable level of service degradation is a crucial aspect in the design of a wireless mesh network. To address this issue, this paper investigates the network restoration solutions via the joint design of traffic rerouting, channel

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

    SciTech Connect

    Cullen, C.

    1996-08-01

    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.

  17. High capacity antennas for MIMO radio systems

    Microsoft Academic Search

    V. Jungnickel; V. Pohl; H. Nguyen; U. Kruger; T. Haustein; C. von Helmolt

    2002-01-01

    The capacity of radio systems with multiple-transmit and multiple-receive antennas may be improved by antenna arrangements which reduce the effective Rician factor. Channel measurements indicate that the capacity in indoor environments may then be close to the independent Rayleigh fading channel even for large numbers of antennas. High capacities may be achieved with such antennas also in outdoor environments. Experiments

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

    NASA Astrophysics Data System (ADS)

    Fraenkel, Daniël; Pierre Auger Collaboration

    2013-02-01

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

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

    NASA Astrophysics Data System (ADS)

    Woo, R.; Ishimaru, A.

    1981-01-01

    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.

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

    Microsoft Academic Search

    D. Cox; R. Leck

    1975-01-01

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

  1. A geometrically based model for line-of-sight multipath radio channels

    Microsoft Academic Search

    Joseph C. Liberti; Theodore S. Rappaport

    1996-01-01

    This paper provides a geometrically based model for single bounce multipath components in line-of-sight (LOS) microcell radiowave propagation channels. The model characterizes the excess delay, direction-of-arrival, and received power of multipath components and is particular useful for microcell and PCS systems with low transmitter and receiver antenna heights. The model includes analytical expressions for the probability density functions for all

  2. Dual-band radio-frequency device for sensing dielectric property changes in microfluidic channel

    Microsoft Academic Search

    Jin Shao; Gaurav Manandhar; Bayaner Arigong; Hualiang Zhang

    2012-01-01

    We propose a dual-band RF device to detect the dielectric changes in polydimethylsiloxane (PDMS) microfluidic channel. Such a device, which consists of two dual-band Wilkinson power dividers (working at 2Ghz and 5GHz) and two 90° dual-band microstrip lines (providing 180° phase difference at two working frequencies), is very sensitive for identifying dielectric material changes. Moreover, by operating at two frequencies

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

    Microsoft Academic Search

    E. Shelef; G. E. Hilley

    2010-01-01

    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

  4. Wide Range Neutron Flux Measuring Channel for Aerospace Application

    SciTech Connect

    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

    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.

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

    Microsoft Academic Search

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

    1973-01-01

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

  6. Measurement of the top quark mass in the dilepton channel

    SciTech Connect

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

    2006-09-01

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

  7. Measuring Neutrino Masses Using Radio-Frequency Techniques

    E-print Network

    Formaggio, Joseph A.

    We describe a new technique by which the energy spectrum of low energy electrons can be extracted. The technique relies on the detection and measurement of coherent radiation created from the cyclotron motion of charged ...

  8. Direct Sequence Spread Spectrum Digital Radio DSP Prototyping Using Xilinx FPGAs

    Microsoft Academic Search

    T. Saluvere; D. Kerek; Hannu Tenhunen

    1994-01-01

    Spread spectrum digital radio receivers and transmitters are very difficult to simulate for overall system performance evaluation. Reliable estimates for Bit Error Rates and effect of indoor and outdoor fading radio channels can be best studied via practical hardware measurements. In this work we propose a flexible CDMA spread spectrum radio architecture structure well suited for FPGA prototyping. FPGA based

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

    SciTech Connect

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

    2011-10-15

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

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

    SciTech Connect

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

    2008-06-01

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

  12. Reliable intraocular pressure measurement using automated radio-wave telemetry

    PubMed Central

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

    2014-01-01

    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

  13. Radial profile measurements of the solar wind speed using radio sounding techniques

    Microsoft Academic Search

    A. I. Efimov

    1994-01-01

    Velocity measurements of the solar wind in the region of its acceleration were carried out in 1984 with Venera Orbiters using the following specific radio sounding techniques: (i) phase and frequency correlations from two or three widely-spaced ground stations; (ii) phase and frequency correlations from two spacecraft and two widely-spaced ground stations; (iii) two station two-way coherent Doppler measurements; (iv)

  14. Spatial Capacity Estimation for Correlated MIMO Channels Based on Measured SISO Data Records

    Microsoft Academic Search

    Andreas Knopp; Christian A. Hofmann; Robert T. Schwarz; Mohamed Chouayakh; Berthold Lankl

    2007-01-01

    A novel strategy of precalculating potential MIMO spectral efficiencies of correlated channels based on single, measured or appropriately modeled SISO impulse responses is presented. Additionally, the model is capable of comprising the physical nature of the channel in form of its frequency response. The method is applied to indoor MIMO channels where the correlation is introduced by a strong Line-Of-Sight

  15. Recursive estimation and identification of wireless ad hoc channels from measurements

    Microsoft Academic Search

    M. Olama; Y. Li; S. Djouadi; T. Goodspeed; T. Kuruganti

    2007-01-01

    This paper is concerned with a time varying wireless ad hoc channel modeling, its parameter estimation and system identification from received signal measurement data. The channel model is represented in state space form, while the expectation maximization algorithm and Kalman filtering are used in the channel parameter and state estimation, respectively. The proposed algorithm is recursive, and therefore the inphase

  16. Surface figure measurements of radio telescopes with a shearing interferometer

    Microsoft Academic Search

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

    1991-01-01

    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

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

    SciTech Connect

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

    1991-07-01

    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.

  18. Self-similar solutions and their stability for the flow of relativistic fluids through channels. [model for astrophysical jets from radio galaxies

    NASA Technical Reports Server (NTRS)

    Lerche, I.; Wiita, P. J.

    1980-01-01

    The paper analyzes the flow of a perfect relativistic fluid in a circular confining channel of variable cross-section, a situation which is currently thought to be relevant for models of beams protruding from radio galaxies. Families of self-similar solutions are found, and some of their topological characteristics are illustrated. However, a perturbative investigation of the solutions indicates that all such self-similar modes are unstable and would eventually evolve into some non-self-similar form.

  19. Radio Loud AGNs Are Mergers

    NASA Astrophysics Data System (ADS)

    Chiaberge, Marco; Gilli, Roberto; Lotz, Jennifer M.; Norman, Colin

    2015-06-01

    We measure the merger fraction of Type 2 radio-loud and radio-quiet active galactic nuclei (AGNs) at z\\gt 1 using new samples. The objects have Hubble Space Telescope (HST) images taken with Wide Field Camera 3 (WFC3) in the IR channel. These samples are compared to the 3CR sample of radio galaxies at z\\gt 1 and to a sample of non-active galaxies. We also consider lower redshift radio galaxies with HST observations and previous generation instruments (NICMOS and WFPC2). The full sample spans an unprecedented range in both redshift and AGN luminosity. We perform statistical tests to determine whether the different samples are differently associated with mergers. We find that all (92%-14%+8%) radio-loud galaxies at z\\gt 1 are associated with recent or ongoing merger events. Among the radio-loud population there is no evidence for any dependence of the merger fraction on either redshift or AGN power. For the matched radio-quiet samples, only 38%-15+16 are merging systems. The merger fraction for the sample of non-active galaxies at z\\gt 1 is indistinguishable from radio-quiet objects. This is strong evidence that mergers are the triggering mechanism for the radio-loud AGN phenomenon and the launching of relativistic jets from supermassive black holes (SMBHs). We speculate that major black hole (BH)–BH mergers play a major role in spinning up the central SMBHs in these objects.

  20. Two-dimensional argon metastable density measurements in a radio frequency plasma reactor by planar laser-induced Jluorescence imaging

    E-print Network

    Zachariah, Michael R.

    Two-dimensional argon metastable density measurements in a radio frequency plasma reactor by planar American Institute of Physics. INTRODUCTION Low-pressure, radio-frequency (rf) plasmas are used ex at developing a better understanding of the chemistry and physics in these plasmas. The majority of gas

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

    Microsoft Academic Search

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

    1993-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1975-01-01

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

  3. IEEE 802.11b WLAN capacity and performance measurements in channel with large delay spreads

    Microsoft Academic Search

    A. Silvennoinen; T. Karhima; M. Hall; S. G. Haggman

    2004-01-01

    IEEE 802.11x wireless local area network (WLAN) systems are quite popular in office indoor environment and urban outdoor environments but suburban or rural environments can still offer unexploited possibilities, especially for military communication purposes. The radio channels of these environments have large delay spreads that pose limitations for IEEE 802.11b signal usage. In this study IEEE 802.11b WLAN capacity and

  4. BEAM MEASUREMENT SYSTEM OF VEPP-2000 INJECTION CHANNELS*

    E-print Network

    Kozak, Victor R.

    . Both DC and pulsed (quads and dipoles) magnets (figure 2) are used in channel's optics. Figure 1 current monitors. Figure 2: Magnetic system and beam diagnostic system of VEPP-2000 injection channelsF/m). It allows having SEM start time shift about several milliseconds to avoid the influence of pulsed systems

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

    NASA Astrophysics Data System (ADS)

    Merloni, Andrea; Heinz, Sebastian

    2007-10-01

    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.

  6. Radio-Frequency Interference from Digital Television Patrick C. Crane

    E-print Network

    Ellingson, Steven W.

    Radio-Frequency Interference from Digital Television Patrick C. Crane 29 April 2008 Digital television (DTV) signals have intermittently been observed during measurements of radio and includes the VHF television channels 2-6 (54-60, 60-66, 66-72, 76-82, and 82-88 MHz); for example

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

    NASA Astrophysics Data System (ADS)

    Arakantsev, Konstantin G.; Konyakhin, Igor A.

    2013-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

    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.

  9. Intensity-modulated fiber Bragg grating sensor system based on radio-frequency signal measurement.

    PubMed

    Dong, Xinyong; Shao, Li-Yang; Fu, H Y; Tam, H Y; Lu, C

    2008-03-01

    An intensity-modulated, fiber Bragg grating (FBG) sensor system based on radio-frequency (RF) signal measurement is presented. The RF signal is generated at a photodetector by two modulated optical signals reflected from the sensing FBG and a reference FBG. Wavelength shift of the sensing FBG changes intensity of the RF signal through changing the delay between the two optical signals, with temperature effect being compensated automatically by the reference FBG. It also exhibits important features including potentially high-speed measurement, low cost, and adjustable sensitivity. In the experiment, strain measurement with a maximum sensitivity of -0.34 microV/micro epsilon has been achieved. PMID:18311299

  10. Radio Frequency Time-of-Flight Distance Measurement for Low-Cost Wireless Sensor Localization

    Microsoft Academic Search

    Steven Lanzisera; David Zats; Kristofer S. J. Pister

    2011-01-01

    Location-aware wireless sensor networks will enable a new class of applications, and accurate range estimation is critical for this task. Low-cost location determination capability is studied almost entirely using radio frequency received signal strength (RSS) measurements, resulting in poor accuracy. More accurate systems use wide bandwidths and\\/or complex time-syn- chronized infrastructure. Low-cost, accurate ranging has proven difficult because small timing

  11. Investigation of radio channel uncertainty in distance estimation in wireless sensor networks

    Microsoft Academic Search

    Patrik Moravek; Dan Komosny; Milan Simek; Mojmir Jelinek; David Girbau; Antonio Lazaro

    The distance estimation between nodes is a crucial requirement for localization and object tracking. Received signal strength\\u000a (RSS) measurement is one of the used methods for the distance estimation in wireless networks. Its main advantage is that\\u000a there are no additional hardware requirements. This paper describes a lateration approach for localization and distance estimation\\u000a using RSS. For the purpose of

  12. Diversity selection using coding in a portable radio communications channel with frequency-selective fading

    Microsoft Academic Search

    L. F. Chang; J. C.-I. Chuang

    1989-01-01

    It is shown that the degradation in the performance of wideband digital transmission systems due to intersymbol interference can be reduced by utilizing diversity selection using coding. A BCH (31, 21, 5) double-error-correcting code and QPSK (quadrature-phase-shift-keying) modulation with coherent detection are used for this study. The probability of word error is taken to be the measure of system performance.

  13. Over-The-Air Measurements of Small Radio Terminals Using Spheroidal Coupler

    NASA Astrophysics Data System (ADS)

    Teshirogi, Tasuku; Kawamura, Takashi; Yamamoto, Aya; Sakuma, Toru; Nago, Yasuhiko; Mattori, Shigenori

    We propose a novel method for measuring the matched total radiated power (TRP) and matched total radiated sensitivity (TRS) of small radio terminals, called over-the-air (OTA) measurement, using a spheroidal coupler (SC). To measure these parameters accurately in a multiple-reflection environment, such as in an SC, we developed two key techniques, i.e. displacement method and reflection compensation method, and verified their effectiveness by several simulations and fundamental experiments on a test transmitter. We also describe an absolute method for measuring antenna radiation efficiency using the displacement method. Furthermore, we describe TRP and TRS measurements for actual UMTS (Universal Mobile Telecommunications System) terminals, and verify that the proposed method achieves quick measurements with good accuracy. The SC provides a compact, low-cost OTA measurement system with high sensitivity and high speed.

  14. The upper ionosphere of Mars: A comparison of Mariner 9 radio occultation and MARSIS measurements

    NASA Astrophysics Data System (ADS)

    Vogt, M. F.; Withers, P.

    2014-12-01

    Electron density profiles of the Martian ionosphere show that the dayside ionosphere can be divided into two regions, one controlled by diffusion where the electron density decreases exponentially with altitude, and one at lower altitudes in which electron densities follow the basic predictions of Chapman theory. Models and data generally place the transition between the two regions near 200 km, but measurements from the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) on Mars Express suggest that the transition occurs closer to 275 km. This altitude also marks the transition between the two MARSIS operational modes: the electron density above 275 km is determined from local plasma frequency measurements, while at lower altitudes it is obtained remotely from radio sounding. In this study we compare Mariner 9 radio occultation electron density profiles to the N?mec et al. (2011) empirical model based on MARSIS data to evaluate the accuracy and biases of the MARSIS measurements. We investigate whether the Mariner 9 electron density profiles can be well described by the N?mec et al. (2011) empirical model. We also identify the typical Mariner 9 transition region altitude, as measured by a change in scale height, to determine whether the transition at 275 km observed by MARSIS is a consequence of differences in the two MARSIS operational modes or is physically meaningful. The Mariner 9 radio occultation measurements of the Martian ionosphere have recently been digitized and reanalyzed and are ideal for our study because they extend as high as 400 km, spanning the transition region between the two MARSIS data types, while similar measurements from Mars Global Surveyor rarely extend beyond 200 km. Our findings will help resolve discrepancies between the two MARSIS data types and validate the MARSIS electron density measurements.

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

    USGS Publications Warehouse

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

    2007-01-01

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

  16. The New Horizons Bistatic Radio Science Experiment to Measure Pluto's Surface Properties

    NASA Astrophysics Data System (ADS)

    Linscott, I.; Hinson, D. P.; Tyler, G. L.; Vincent, M.

    2014-12-01

    The New Horizons (NH) payload includes a Radio Science Experiment (REX) for principally occultation and radiometric measurement of Pluto and Charon during the flyby in July 2015. The REX subsystem is contained, together with the NH X-Band radio, in the Integrated Electronics Module (IEM) in the New Horizons spacecraft. REX samples and records in two polarizations both total RF power in a 4.5 MHz bandwidth, and radio signal waveforms in a narrow, 1.25 kHz band. During the encounter, and at closest approach to Pluto, the spacecraft's high gain antenna (HGA) will scan Pluto's equatorial latitudes, intercepting the specular zone, a region near Pluto's limb that geometrically favors reflection from the earth's direction. At the same time, a powerful 80 kW uplink beacon will have been transmitted from earth by the DSN to arrive at Pluto during spacecraft closest approach. Reflection from the specular zone is expected to be sufficiently strong to observe the bistatic uplink in the REX narrowband record. Measurements in both polarizations will then be combined to yield surface reflectivity, roughness and limits on the dielectric constant in the specular zone.

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

    E-print Network

    Wei Zhou; Xiang-Ping Wu

    2003-09-26

    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 $\

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

    PubMed Central

    Taylor, P S

    1987-01-01

    1. The ionic selectivity of A-current K+ channels has been measured in single Helix aspersa neurones by recording the reversal potential shift in test solutions containing various monovalent cations. 2. The A-current channel is permeable to Tl+, K+, Rb+, NH4+ and Cs+. The channels may also be sparingly permeable to Na+ and Li+. Organic cations have an apparent small permeability as judged from their reversal potentials, but this may be an artifact of K+ accumulation. 3. A large patch electrode (3 microns tip) isolated a region that appeared to contain only A-current channels. This may indicate that A-current channels are found in the membrane as rafts of at least 3 microns in diameter. 4. The single-channel conductance calculated from single-channel current steps was 14 pS. PMID:2443693

  19. Radio tracking system

    NASA Technical Reports Server (NTRS)

    Breidenthal, J. C.; Komarek, T. A.

    1982-01-01

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

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

    Microsoft Academic Search

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

    1975-01-01

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

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

    Microsoft Academic Search

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

    1993-01-01

    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

  2. Sub-micrometer fluidic channel for measuring photon emitting entities

    DOEpatents

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

    2014-11-18

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2000-07-01

    An optimal estimation inverse method is presented which can be used to retrieve simultaneously vertical profiles of temperature and specific humidity, in addition to surface pressure, from satellite-to-satellite radio occultation observations of the Earth's atmosphere. The method is a nonlinear, maximum a posteriori technique which can accommodate most aspects of the real radio occultation problem and is found to be stable and to converge rapidly in most cases. The optimal estimation inverse method has two distinct advantages over the analytic inverse method in that it accounts for some of the effects of horizontal gradients and is able to retrieve optimally temperature and humidity simultaneously from the observations. It is also able to account for observation noise and other sources of error. Combined, these advantages ensure a realistic retrieval of atmospheric quantities. A complete error analysis emerges naturally from the optimal estimation theory, allowing a full characterization of the solution. Using this analysis, a quality control scheme is implemented which allows anomalous retrieval conditions to be recognized and removed, thus preventing gross retrieval errors. The inverse method presented in this paper has been implemented for bending angle measurements derived from GPS/MET radio occultation observations of the Earth. Preliminary results from simulated data suggest that these observations have the potential to improve numerical weather prediction model analyses significantly throughout their vertical range.

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

    SciTech Connect

    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

    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.

  5. Measuring Changes in the Fundamental Constants with Redshifted Radio Absorption Lines

    E-print Network

    S. J. Curran; N. Kanekar; J. K. Darling

    2004-09-07

    Strong evidence has recently emerged for a variation in the fine structure constant, $\\alpha\\equiv e^2/\\hbar c$, over the history of the Universe. This was concluded from a detailed study of the relative positions of redshifted optical quasar absorption spectra. However, {\\it radio} absorption lines at high redshift offer a much higher sensitivity to a cosmological change in $\\alpha$ than optical lines. Furthermore, through the comparison of various radio transitions, \\HI, OH and millimetre molecular (e.g. CO) lines, any variations in the proton g-factor, $g_p$, and the ratio of electron/proton masses, $\\mu\\equiv m_e/m_p$, may also be constrained. Presently, however, systems exhibiting redshifted radio lines are rare with the bias being towards those associated with optically selected QSOs. With its unprecedented sensitivity, large bandwidth and wide field of view, the SKA will prove paramount in surveying the sky for absorbers unbiased by dust extinction. This is expected to yield whole new samples of \\HI ~and OH rich systems, the latter of which will prove a useful diagnostic in finding redshifted millimetre absorbers. As well as uncovering many new systems through these blind surveys, the SKA will enable the detection of \\HI ~absorption in many more of the present optical sample -- down to column densities of $\\sim10^{17}$ \\scm, or $\\gapp2$ orders of magnitude the sensitivity of the current limits. Armed with these large samples together with the high spectral resolutions, available from the purely radio comparisons, the SKA will provide statistically sound measurements of the values of these fundamental constants in the early Universe, thus providing a physical test of Grand Unified Theories.

  6. The software radio architecture

    Microsoft Academic Search

    J. Mitola

    1995-01-01

    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,

  7. Precision measurements of the radio emission in air showers J.R. Hrandel,

    E-print Network

    Hörandel, Jörg R.

    investigations of the radio emission of air showers on larger scales, such as Tunka-Rex, AERA at the Pierre Auger-ups to detect radio emission from air showers are shown as well, namely LOPES [4], Tunka-Rex [9], and AERA Engineering Radio Array AERA 124 antennas >2000 antennas FIGURE 1. Schematic view of major radio detectors

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

    E-print Network

    Tullos, Desiree

    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

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

    Microsoft Academic Search

    Iehisa Nezu; Kouki Onitsuka

    2001-01-01

    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

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

    PubMed

    Padin, S

    2014-12-01

    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

  11. Measurement of Channel Temperature in GaN High-Electron Mobility Transistors

    E-print Network

    Joh, Jungwoo

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

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

    E-print Network

    A. Nigl

    2008-09-16

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

  13. Multiple Radios for Effective Rendezvous in Cognitive Radio Networks

    E-print Network

    Chu, Xiaowen

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

  14. RTE measurement with Xe52+ ions channeled in a Si crystal

    Microsoft Academic Search

    S. Andriamonje; M. Chevallier; C. Cohen; N. Cue; D. Dauvergne; J. Dural; R. Genre; Y. Girard; R. Kirsch; A. L'Hoir; J. C. Poizat; Y. Quéré; J. Remillieux; D. Schmaus; M. Toulemonde

    1992-01-01

    KLL resonant transfer and excitation (RTE) of 33-43 MeV\\/nucleon He-like Xe ions channeled along the axis of a thin Si crystal has been investigated in measurements of charge state distributions and of the resulting X-ray production. The resonance peaks obtained by the two methods are quite similar. The charge state measurements show that RTE appears, for well channeled ions, to

  15. Digital Broadcasting Television Channel Measurements and Characterization for SIMO Mobile Reception

    Microsoft Academic Search

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

    2006-01-01

    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

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

    SciTech Connect

    Takabayashi, Y. [SAGA Light Source, 8-7 Yayoigaoka, Tosu, Saga 841-0005 (Japan)

    2010-06-23

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

  17. The Atacama Cosmology Telescope: measuring radio galaxy bias through cross-correlation with lensing

    E-print Network

    Allison, Rupert; Sherwin, Blake D; de Bernardis, Francesco; Bond, J Richard; Calabrese, Erminia; Devlin, Mark J; Dunkley, Joanna; Gallardo, Patricio; Henderson, Shawn; Hincks, Adam D; Hlozek, Renee; Jarvis, Matt; Kosowsky, Arthur; Louis, Thibaut; Madhavacheril, Mathew; McMahon, Jeff; Moodley, Kavilan; Naess, Sigurd; Newburgh, Laura; Niemack, Michael D; Page, Lyman A; Partridge, Bruce; Sehgal, Neelima; Spergel, David N; Staggs, Suzanne T; van Engelen, Alexander; Wollack, Edward J

    2015-01-01

    We correlate the positions of radio galaxies in the FIRST survey with the CMB lensing convergence estimated from the Atacama Cosmology Telescope over 470 square degrees to determine the bias of these galaxies. We remove optically cross-matched sources below redshift $z=0.2$ to preferentially select Active Galactic Nuclei (AGN). We measure the angular cross-power spectrum $C_l^{\\kappa g}$ at $4.4\\sigma$ significance in the multipole range $100bias, the cross-spectrum is well fit by the Planck best-fit $\\Lambda$CDM cosmological model. Fixing the cosmology we fit for the overall bias model normalization, finding $b(z_{\\rm eff}) = 3.5 \\pm 0.8$ for the full galaxy sample, and $b(z_{\\rm eff})=4.0\\pm1.1 (3.0\\pm1.1)$ for sources brighter (fainter) than 2.5 mJy. This measurement characterizes the typical halo mass of radio-loud AGN: we find $\\l...

  18. The Atacama Cosmology Telescope: measuring radio galaxy bias through cross-correlation with lensing

    NASA Astrophysics Data System (ADS)

    Allison, Rupert; Lindsay, Sam N.; Sherwin, Blake D.; de Bernardis, Francesco; Bond, J. Richard; Calabrese, Erminia; Devlin, Mark J.; Dunkley, Joanna; Gallardo, Patricio; Henderson, Shawn; Hincks, Adam D.; Hlozek, Renée; Jarvis, Matt; Kosowsky, Arthur; Louis, Thibaut; Madhavacheril, Mathew; McMahon, Jeff; Moodley, Kavilan; Naess, Sigurd; Newburgh, Laura; Niemack, Michael D.; Page, Lyman A.; Partridge, Bruce; Sehgal, Neelima; Spergel, David N.; Staggs, Suzanne T.; van Engelen, Alexander; Wollack, Edward J.

    2015-07-01

    We correlate the positions of radio galaxies in the FIRST survey with the cosmic microwave background lensing convergence estimated from the Atacama Cosmology Telescope over 470 deg2 to determine the bias of these galaxies. We remove optically cross-matched sources below redshift z = 0.2 to preferentially select active galactic nuclei (AGN). We measure the angular cross-power spectrum C_l^{? g} at 4.4? significance in the multipole range 100 < l < 3000, corresponding to physical scales within ?2-60 Mpc at an effective redshift zeff = 1.5. Modelling the AGN population with a redshift-dependent bias, the cross-spectrum is well fitted by the Planck best-fitting ? cold dark matter cosmological model. Fixing the cosmology and assumed redshift distribution of sources, we fit for the overall bias model normalization, finding b(zeff) = 3.5 ± 0.8 for the full galaxy sample and b(zeff) = 4.0 ± 1.1(3.0 ± 1.1) for sources brighter (fainter) than 2.5 mJy. This measurement characterizes the typical halo mass of radio-loud AGN: we find log (M_halo / M_{?}) = 13.6^{+0.3}_{-0.4}.

  19. Adaptive channel allocation in TACS

    Microsoft Academic Search

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

    1995-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Huffenberger, K. M.; Araujo, D.; 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.; QUIET Collaboration

    2015-06-01

    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 ?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 signal-to-noise ratio > 3 significance, we detect linear polarization for seven sources in Q-band and six in W-band; only 1.3 ± 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 measurements of the same sources from the literature. For the four sources with WMAP and Planck intensity measurements >1 Jy, the polarization fractions are above 1% in both QUIET bands. At high significance, we compute polarization fractions as much as 10%–20% for some sources, but the effects of source variability may cut that level in half for contemporaneous comparisons. Our results indicate that simple models—ones that scale a fixed polarization fraction with frequency—are inadequate to model the behavior of these sources and their contributions to polarization maps.

  1. Measurement of the electronic thermal conductance channels and heat capacity of graphene at low temperature

    E-print Network

    Measurement of the electronic thermal conductance channels and heat capacity of graphene at low opto-electronics, plasmonics, and ultra-sensitive bolometry. Here we present measurements of bipolar relation, Wiedemann- Franz ratio[3, 4], and electronic specific heat[5] . Thermal transport measurements

  2. Emissive sheath measurements in the afterglow of a radio frequency plasma

    SciTech Connect

    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

    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.

  3. Channel

    NASA Technical Reports Server (NTRS)

    2006-01-01

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

    This channel is located south of Iani Chaos.

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

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

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

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

    SciTech Connect

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

    2009-07-01

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

  5. Innovative frequency measurement technique used in the design of a single channel frequency to digital converter ASIC

    Microsoft Academic Search

    Neranjen Ramalingam; Vijay K. Varadan; Vasundara V. Varadan

    1996-01-01

    The frequency to digital converter (FDC) is an application specific integrated circuit. The chip has been designed to handle one input channel but can easily be expanded to handle multiple channels of frequencies. The channel is capable of measuring frequencies from 100 Hz to 100 kHz. The power consumption of the chip is very low. The frequency measurement accuracy is

  6. Innovative frequency measurement technique used in the design of a single channel frequency to digital converter ASIC

    Microsoft Academic Search

    N. Ramalingam; V. K. Varadan; V. V. Varadan

    1999-01-01

    The frequency to digital converter (FDC) is an application specific integrated circuit (ASIC). The chip has been designed to handle one input channel but can easily be expanded to handle multiple channels of frequencies. The channel is capable of measuring frequencies from 100 Hz to 100 kHz. The power consumption of the chip is very low. The frequency measurement accuracy

  7. 1.2 GHz band wave propagation measurements in concrete building for indoor radio communications

    Microsoft Academic Search

    Jun Horikoshi; K. Tanaka; T. Morinaga

    1986-01-01

    For the design of indoor radio communication or a portable radio telephone system, 1.2 GHz band radio wave propagation characteristics are investigated in a concrete building. Penetration loss through a window, local median variations, and cumulative distributions of received signal levels in a room, reflection coefficient or equivalent dielectric constant and transmission loss of a wall\\/floor are discussed.

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

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    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.

  9. 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)

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

    2014-12-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1976-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

    We present radio observations of the Moon between 35 and 80 MHz to demonstrate a novel technique of interferometrically measuring large-scale diffuse emission extending far beyond the primary beam (global signal) for the first time. In particular, we show that (i) the Moon appears as a negative-flux source at frequencies 35 < ? < 80 MHz since it is `colder' than the diffuse Galactic background it occults, (ii) using the (negative) flux of the lunar disc, we can reconstruct the spectrum of the diffuse Galactic emission with the lunar thermal emission as a reference, and (iii) that reflected RFI (radio-frequency interference) is concentrated at the centre of the lunar disc due to specular nature of reflection, and can be independently measured. Our RFI measurements show that (i) Moon-based Cosmic Dawn experiments must design for an Earth-isolation of better than 80 dB to achieve an RFI temperature <1 mK, (ii) Moon-reflected RFI contributes to a dipole temperature less than 20 mK for Earth-based Cosmic Dawn experiments, (iii) man-made satellite-reflected RFI temperature exceeds 20 mK if the aggregate scattering cross-section of visible satellites exceeds 175 m2 at 800 km height, or 15 m2 at 400 km height. Currently, our diffuse background spectrum is limited by sidelobe confusion on short baselines (10-15 per cent level). Further refinement of our technique may yield constraints on the redshifted global 21 cm signal from Cosmic Dawn (40 > z > 12) and the Epoch of Reionization (12 > z > 5).

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

    PubMed

    Liu, Yingdi; Zhang, Jingsong

    2014-06-01

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

  13. Climate comparison of reference upper-air measurements: GPS radio occultation and GRUAN radiosondes

    NASA Astrophysics Data System (ADS)

    Ladstädter, Florian; Steiner, Andrea K.; Schwärz, Marc; Kirchengast, Gottfried

    2015-04-01

    The confidence in the vertical structure of the rate of temperature change in the upper-air region is still low. To change this, measurements of suitable quality are required. Observations from the GPS radio occultation (GPSRO) satellite technique and from the newly established GCOS Reference Upper Air Network (GRUAN) are both candidates to serve as reference observations. GPSRO is currently the only self-calibrated and SI-traceable satellite measurement system, where the observations can be traced back to precise time measurements. These observations possess the required high quality with global coverage, but common physical parameters such as temperature are only available after a sophisticated retrieval process. GRUAN on the other hand delivers data only from a sparse network of radiosonde stations (16 stations at present), with a more straight-forward measurement principle and careful bias corrections applied. Owing to the strongly differing techniques, GPSRO and GRUAN have their unique strengths and weaknesses. In this study, we compare collocated profiles from these two datasets for the time period 2011 to 2013, with a special focus on day/night biases, and use interpolated ERA-Interim data as an additional source of background information. The GRUAN effort is a vital contribution to the goal of anchoring less accurate upper-air measurements to reference data. GPSRO adds to this global coverage and more stratospheric extend, and, as an observing system independent from radiosondes, serves as another fundamentally needed source of thermodynamic reference data in the free atmosphere.

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

    Microsoft Academic Search

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

    2007-01-01

    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

  15. Broadband Permittivity of Liquids Extracted from Transmission Line Measurements of Microfluidic Channels

    Microsoft Academic Search

    Jordi Mateu; Nathan Orloff; M. Rinehart; J. C. Booth

    2007-01-01

    We present a semi-analytical procedure to extract the permittivity of fluids from measurements in our microfluidic-microelectronic platform. This platform consists of broadband coplanar waveguide transmission lines with integrated microfluidic channels for characterizing the dielectric properties of submicroliter fluid samples. On-wafer calibration techniques are used to obtain the S-parameters of the composite structure (transmission line and microfluid channel) up to 40

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

    Microsoft Academic Search

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

    1997-01-01

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

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

    PubMed

    Giri, Janhavi; Tang, John M; Wirth, Christophe; Peneff, Caroline M; Eisenberg, Bob

    2012-03-01

    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 (V (reversal) = +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

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

    SciTech Connect

    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

    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.

  19. VizieR Online Data Catalog: Radio point sources rotation measures catalog (Xu+, 2014)

    NASA Astrophysics Data System (ADS)

    Xu, J.; Han, J.-L.

    2015-04-01

    We compiled a catalog of Faraday rotation measures (RMs) for 4553 extragalactic radio point sources published in literature. These RMs were derived from multi-frequency polarization observations. The RM data are compared to those in the NRAO VLA Sky Survey (NVSS) RM catalog. We reveal a systematic uncertainty of about 10.0+/-1.5rad/m2 in the NVSS RM catalog. The Galactic foreground RM is calculated through a weighted averaging method by using the compiled RM catalog together with the NVSS RM catalog, with careful consideration of uncertainties in the RM data. The data from the catalog and the interface for the Galactic foreground RM calculations are publicly available on the webpage: http://zmtt.bao.ac.cn/RM/ . (2 data files).

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

    PubMed

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

    1999-11-01

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

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

    PubMed

    Tokuzawa, T; Ejiri, A; Kawahata, K

    2010-10-01

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

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

    SciTech Connect

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

    2010-10-15

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

  3. 47 CFR 22.725 - Channels for conventional rural radiotelephone stations and basic exchange telephone radio systems.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...2014-10-01 false Channels for conventional rural radiotelephone stations and basic exchange telephone...COMMON CARRIER SERVICES PUBLIC MOBILE SERVICES Rural Radiotelephone Service Conventional Rural Radiotelephone Stations § 22.725...

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

    E-print Network

    Athens, University of

    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

  5. Multiuser MIMO Channel Measurements and Performance in a Large Office Environment

    Microsoft Academic Search

    G. Bauch; J. Bach Andersen; C. Guthy; M. Herdin; J. Nielsen; J. A. Nossek; P. Tejera; W. Utschick

    2007-01-01

    We consider a multiuser MIMO-OFDMA scheme which exploits multiuser diversity in all dimensions: time, frequency and space. The main contribution of this paper is the evaluation and explanation of multiuser MIMO in a real world scenario, i.e. a large office room, based on measured channels. We report interesting results of a measurement campaign which suggest that significant MIMO gains are

  6. Diagnostics development for E-beam excited air channels. Conductivity measurements in air afterglows

    Microsoft Academic Search

    D. J. Eckstrom

    1983-01-01

    Nonintrusive techniques for measuring conductivity decay in the afterglow air channel of a relativistic electron beam are reviewed, and the microwave cavity perturbation technique is found to offer adequate sensitivity. A right cylindrical cavity resonating in the TM 010 mode at 1.5 GHz was fabricated, and a series of preliminary measurements in air was performed. The afterglow conductivity of laboratory

  7. Channel estimation using time multiplexed pilot symbols for coherent RAKE combining for DS-CDMA mobile radio

    Microsoft Academic Search

    H. Andoh; M. Sawahashi; F. Adachi

    1997-01-01

    Coherent DS-CDMA forward and reverse links periodically transmitting pilot symbols every data slot to estimate the fading channels are considered; Np-pilot systems are placed at the beginning of each data slot. A pilot symbol-assisted channel estimation scheme that uses weighted multi-slot averaging (WMSA) is presented for coherent RAKE combining. The BER performance achievable by WMSA coherent RAKE combining is evaluated

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

    NASA Technical Reports Server (NTRS)

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

    1986-01-01

    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.

  9. A high-frequency warm shallow water acoustic communications channel model and measurements.

    PubMed

    Chitre, Mandar

    2007-11-01

    Underwater acoustic communication is a core enabling technology with applications in ocean monitoring using remote sensors and autonomous underwater vehicles. One of the more challenging underwater acoustic communication channels is the medium-range very shallow warm-water channel, common in tropical coastal regions. This channel exhibits two key features-extensive time-varying multipath and high levels of non-Gaussian ambient noise due to snapping shrimp-both of which limit the performance of traditional communication techniques. A good understanding of the communications channel is key to the design of communication systems. It aids in the development of signal processing techniques as well as in the testing of the techniques via simulation. In this article, a physics-based channel model for the very shallow warm-water acoustic channel at high frequencies is developed, which are of interest to medium-range communication system developers. The model is based on ray acoustics and includes time-varying statistical effects as well as non-Gaussian ambient noise statistics observed during channel studies. The model is calibrated and its accuracy validated using measurements made at sea. PMID:18189549

  10. Collision model for performance analysis of coded transmission in time hopping impulse radio over multipath nakagami-m channels

    Microsoft Academic Search

    Roberto Bosisio; Luca Reggiani; Umberto Spagnolini

    2009-01-01

    Time hopping is the strategy employed in impulse radio systems to increase the communication reliability by spreading the multiple access interference (MAI) over numerous time intervals. This results in a non-stationary interference that makes the error probability performance to be dominated by the worst-case. In this paper we employ a collision model analysis for this time-varying interference that is ruled

  11. BER performance analysis of radio over free-space optical systems considering laser phase noise under Gamma-Gamma turbulence channels.

    PubMed

    Lim, Wansu; Yun, Changho; Kim, Kiseon

    2009-03-16

    This paper analytically investigates a bit error rate (BER) performance of radio over free space optical (FSO) systems considering laser phase noise under Gamma-Gamma turbulence channels. An external modulation using a dual drive Mach-Zehnder modulator (DD-MZM) and a phase shifter is employed because a DD-MZM is robust against a laser chirp and provides high spectral efficiency. We derive a closed form average BER as a function of different turbulence strengths and laser diode (LD) linewidth, and investigate its analytical behavior under practical scenario. As a result, for a given average SNR with normalized perturbation, it is shown that the difference of average BER corresponding to two LDs (with linewidth of 624 MHz and 10 MHz) under weak turbulence is almost 3 times larger than that under strong turbulence. PMID:19293875

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

    NASA Astrophysics Data System (ADS)

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

    2008-03-01

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

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

    E-print Network

    Amur Margaryan

    2009-10-24

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

  14. 12 GHz Radio-Holographic Surface Measurements of the RRI 10.4~m Telescope

    NASA Astrophysics Data System (ADS)

    Balasubramanyam, R.; Venkatesh, S.; Raju, S. B.

    2009-09-01

    A modern Q-band low noise amplifier (LNA) front-end is being fitted to the 10.4~m millimeter-wave telescope at the Raman Research Institute (RRI) to support observations in the 40-50~GHz frequency range. To assess the suitability of the surface for this purpose, we measured the deviations of the primary surface from an ideal paraboloid using radio holography. We used the 11.6996 GHz beacon signal from the GSAT3 satellite, a 1.2~m reference antenna, commercial Ku-band Low Noise Block Convereters (LNBC) as the receiver front-ends and a Stanford Research Systems (SRS) lock-in amplifier as the backend. The LNBCs had independent free-running first local oscillators (LO). Yet, we recovered the correlation by using a radiatively injected common tone that served as the second local oscillator. With this setup, we mapped the surface deviations on a 64 × 64 grid and measured an rms surface deviation of ˜ 350~?m with a measurement accuracy of ˜ 50~?m.

  15. Peak radiated power measurement of the DOE Mark II container tag with integrated ST-676 sensor radio frequency identification device.

    SciTech Connect

    Jursich, Mark

    2010-04-01

    The total peak radiated power of the Department of Energy Mark II container tag was measured in the electromagnetic reverberation chamber facility at Sandia National Laboratories. The tag's radio frequency content was also evaluated for possible emissions outside the intentional transmit frequency band. No spurious emissions of any significance were found, and the radiated power conformed to the manufacturer's specifications.

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

    E-print Network

    California at Los Angles, University of

    Phase-Resolved Measurements of Ion Velocity in a Radio-Frequency Sheath Brett Jacobs,1,* Walter plasma rotation [5] and low-frequency waves [6]. Since then, many basic plasma physics experiments have upon the ratio of the ion transit time through the sheath to the rf period (ion=rf) [11]. In the high-frequency

  17. Assessment of radiosonde temperature measurements in the upper troposphere and lower stratosphere using COSMIC radio occultation data

    Microsoft Academic Search

    Wenying He; Shu-peng Ho; Hongbin Chen; Xinjia Zhou; Doug Hunt; Ying-Hwa Kuo

    2009-01-01

    Temperature profiles derived from Global Positioning System (GPS) Radio Occultation (RO) data from the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) mission are compared with those from four types of radiosonde systems from 12 to 25 km to assess the performance of these radiosonde systems in the upper troposphere and lower stratosphere. Results show that temperature measurements from

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

    Microsoft Academic Search

    Rikard Olsson; Per-Simon Kildal; Mike Shields

    2006-01-01

    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.

  19. The New Horizons Radio Science Experiment: Expected Performance in Measurements of Pluto's Atmospheric Structure, Surface Pressure, and Surface Temperature

    NASA Astrophysics Data System (ADS)

    Hinson, D. P.; Linscott, I.; Woods, W. W.; Tyler, G. L.; Bird, M. K.; Paetzold, M.; Strobel, D. F.

    2014-12-01

    The New Horizons (NH) payload includes a Radio Science Experiment (REX) for investigating key characteristics of Pluto and Charon during the upcoming flyby in July 2015. REX flight equipment augments the NH radio transceiver used for spacecraft communications and tracking. The REX hardware implementation requires 1.6 W and 160 g. This presentation will focus on the final design and the predicted performance of two high-priority observations. First, REX will receive signals from a pair of 70-m antennas on Earth - each transmitting 20 kW at 4.2-cm wavelength - during a diametric radio occultation by Pluto. The data recorded by REX will reveal the surface pressure, the temperature structure of the lower atmosphere, and the surface radius. Second, REX will measure the thermal emission from Pluto at 4.2-cm wavelength during two linear scans across the disk at close range when both the dayside and the nightside are visible, allowing the surface temperature and its spatial variations to be determined. Both scans extend from limb to limb with a resolution of about 10 pixels; one bisects Pluto whereas the second crosses the winter pole. We will illustrate the capabilities of REX by reviewing the method of analysis and the precision achieved in a lunar occultation observed by New Horizons in May 2011. Re-analysis of radio occultation measurements by Voyager 2 at Triton is also under way. More generally, REX objectives include a radio occultation search for Pluto's ionosphere; examination of Charon through both radio occultation and radiometry; a search for a radar echo from Pluto's surface; and improved knowledge of the Pluto system mass and the Pluto-Charon mass ratio from a combination of two-way and one-way Doppler frequency measurements.

  20. Radio Occultation Measurements of Diurnal and Semidiurnal Kelvin Waves on Mars

    NASA Astrophysics Data System (ADS)

    Hinson, David P.; Pätzold, M.; Wilson, R. J.

    2006-09-01

    The Radio Science (RS) investigations of both Mars Express (MEX) and Mars Global Surveyor (MGS) include radio occultation experiments that sound the neutral atmosphere from the surface to an altitude of 40-50 km. Each experiment yields profiles of temperature and geopotential versus pressure with a vertical resolution of <1; km. We are using selected data from these RS experiments along with simulations by the GFDL Mars General Circulation Model (MGCM) to investigate thermal tides on Mars. During June-July 2004, MEX occultations sounded the atmosphere at latitudes of 40°N to 20°S during midspring of the northern hemisphere (Ls = 40°-70°) at a fixed local time of 1700. Simultaneous MGS occultations provided complementary results near 35°N at a fixed local time of 0400. Geopotential measurements at these two local times contain distinctive modulation caused by solar-asynchronous thermal tides, including both diurnal and semidiurnal components. Through MGCM simulations of the observed zonal, meridional, and vertical structure, we identify two eastward-propagating tidal modes. Both appear to be Kelvin waves. One has a diurnal period and a zonal wave number of 1 (DK1), and the other has a semidiurnal period and a zonal wave number of 2 (SK2). These are the most direct observations to date of the SK2 mode in the lower atmosphere. Its amplitude increases steadily with increasing height, resulting in large zonal variations of density at aerobraking altitudes (110-160 km) [e.g., Withers et al., Icarus, 164, 14-32, 2003].

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

    NASA Astrophysics Data System (ADS)

    Smirnov, O. M.

    2011-07-01

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

  2. Voltage-dependent gating and gating charge measurements in the Kv1.2 potassium channel.

    PubMed

    Ishida, Itzel G; Rangel-Yescas, Gisela E; Carrasco-Zanini, Julia; Islas, León D

    2015-04-01

    Much has been learned about the voltage sensors of ion channels since the x-ray structure of the mammalian voltage-gated potassium channel Kv1.2 was published in 2005. High resolution structural data of a Kv channel enabled the structural interpretation of numerous electrophysiological findings collected in various ion channels, most notably Shaker, and permitted the development of meticulous computational simulations of the activation mechanism. The fundamental premise for the structural interpretation of functional measurements from Shaker is that this channel and Kv1.2 have the same characteristics, such that correlation of data from both channels would be a trivial task. We tested these assumptions by measuring Kv1.2 voltage-dependent gating and charge per channel. We found that the Kv1.2 gating charge is near 10 elementary charges (eo), ?25% less than the well-established 13-14 eo in Shaker. Next, we neutralized positive residues in the Kv1.2 S4 transmembrane segment to investigate the cause of the reduction of the gating charge and found that, whereas replacing R1 with glutamine decreased voltage sensitivity to ?50% of the wild-type channel value, mutation of the subsequent arginines had a much smaller effect. These data are in marked contrast to the effects of charge neutralization in Shaker, where removal of the first four basic residues reduces the gating charge by roughly the same amount. In light of these differences, we propose that the voltage-sensing domains (VSDs) of Kv1.2 and Shaker might undergo the same physical movement, but the septum that separates the aqueous crevices in the VSD of Kv1.2 might be thicker than Shaker's, accounting for the smaller Kv1.2 gating charge. PMID:25779871

  3. Measurement of the top quark mass in the dilepton channel

    E-print Network

    Baringer, Philip S.; Abbott, B.; Abolins, M.; Abramov, V.; Acharya, B. S.; Adam, I.; Adams, D. L.; Adams, M.; Ahn, S.; Aihara, H.

    1999-07-14

    /c ?ee , and p0?gg decays to a precision of 0.08% at E 5M Z/2 and to 0.6% at E520 GeV @14#. The electron en- ergy scale calibration therefore does not give rise to any significant uncertainty in the top quark mass measurement.1-4 The muon and Z?mm on our... measu by varying samples of t t¯ that the rela error is given lecting dilep- mm .15 GeV ,1.7 .20 GeV ,2.5 — — .100 GeV m MEASUREMENT OF THE TOP QUARK MASS IN THE . . . PHYSICAL REVIEW D 60 052001Hence, the 2.5% uncertainty in muon momentum scale leads...

  4. 16-Channel submillimeter interferometer for measuring the plasma density profile in the T-10 device

    SciTech Connect

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

    1992-02-01

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

  5. Nasal Potential Difference Measurements to Assess CFTR Ion Channel Activity

    PubMed Central

    Clancy, Jean-Paul; Wilschanski, Michael

    2013-01-01

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

  6. Multi-Dimensional K-Factor Analysis for V2V Radio Channels in Open Sub-urban Street Crossings

    E-print Network

    Zemen, Thomas

    in a typical open sub- urban street crossing. The channel conditions vary from non line-of sight (NLOS) to line-of-sight strong fading (Rayleigh distributed), and a large K-factor value is related to less variations (Ricean

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

    E-print Network

    Liu, Xiaoqun

    2009-05-15

    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...

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

    E-print Network

    Liu, Xiaoqun

    2009-05-15

    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...

  9. Adaptive modulation and coding for WiMAX systems with vague channel state information using cognitive radio

    Microsoft Academic Search

    Hazem Shatila; Mohamed Khedr; Jeffrey H. Reed

    2010-01-01

    Adaptive modulation and coding (AMC) schemes are used in WiMAX. Higher system throughput using higher order modulation is traded for higher output. In WiMAX higher modulation tends to be used close to the base station whereas lower order modulations tends to be used at longer range. The dependency of distance might sometimes be deceiving, as channel conditions can vary considerably

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

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

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

  11. Electron temperature measurements using a 12-channel array probe

    NASA Technical Reports Server (NTRS)

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

    1983-01-01

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

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

    Microsoft Academic Search

    C. G. Little; H. Leinbach

    1958-01-01

    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

  13. Measurements of Lunar Radio Brightness Distribution and Certain Properties of Its Surface Layer

    Microsoft Academic Search

    A. E. Salomonovich

    1967-01-01

    The construction of high resolution telescopes, including the 22 m radio telescope RT 22, developed at the P. N. Lebedev Physical Institute, made it possible to investigate the distribution of lunar radio brightness in the millimetre and centimetre wavelength ranges. Such research provides information which makes it possible to deduce certain properties of the surface layer which is responsible for

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

    Microsoft Academic Search

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

    1994-01-01

    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

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

    ERIC Educational Resources Information Center

    Yahaya, Mohammed Kuta; Badiru, Olabode Idris

    2002-01-01

    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)

  16. Radio occultation measurements and MGCM simulations of Kelvin waves on Mars

    NASA Astrophysics Data System (ADS)

    Hinson, D. P.; Pätzold, M.; Wilson, R. J.; Häusler, B.; Tellmann, S.; Tyler, G. L.

    2008-01-01

    We have derived new results concerning thermal tides on Mars from a combination of radio occultation measurements and numerical simulations by a Mars General Circulation Model (MGCM). This investigation exploits a set of concurrent observations by Mars Express (MEX) and Mars Global Surveyor (MGS) in mid-2004, when the season on Mars was midspring in the northern hemisphere. The MEX occultations sampled the atmosphere near the evening terminator at latitudes ranging from 54° N to 15° S. The MGS occultations provided complementary coverage near the morning terminator at latitudes of 35° N and 71° S. The geopotential field derived from these measurements contains distinctive modulation caused by solar-asynchronous thermal tides. Through careful analysis of the combined observations, we characterized two prominent wave modes, obtaining direct solutions for some properties, such as the amplitude and phase, as well as constraints on others, such as the period, zonal wave number, and meridional structure. We supplemented these observations with MGCM simulations. After evaluating the performance of the MGCM against the measurements, we used the validated simulation to deduce the identity of the two tidal modes and to explore their behavior. One mode is a semidiurnal Kelvin wave with a zonal wave number of 2 (SK2), while the other is a diurnal Kelvin wave with a zonal wave number of 1 (DK1). Both modes are known to be close to resonance in the martian atmosphere. Our observations of the SK2 are more complete and less ambiguous than any previous measurement. The well-known DK1 is the dominant solar-asynchronous tide in the martian atmosphere, and our results confirm and extend previous observations by diverse instruments.

  17. Crosstalk measurement and reduction in dense WDM systems using subcarrier tone channel identification and linear cancellation

    Microsoft Academic Search

    Keang-Po Ho; Joseph M. Kahn

    1995-01-01

    Proposes a scheme for the monitoring and reduction of crosstalk arising front the limited stop-band rejection of optical bandpass filters in dense WDM systems. The optical carrier at each wavelength is modulated with a subcarrier tone unique to that wavelength. The crosstalk level can be determined by measuring the power of the tone. The crosstalk from other channels can be

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

    E-print Network

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

    1999-09-01

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

  19. Dual-Band Channel Measurements for an Advanced Tyre Monitoring System

    Microsoft Academic Search

    Gregor Lasser; Christoph F. Mecklenbräuker

    2010-01-01

    Due to the legal situation in some states and the beneficial effects on vehicular safety, fuel consumption and comfort issues, tyre pressure monitoring systems became very popular in the recent years. Despite this situation, few measurement data about the propagation channel between the sensor units and the vehicle's reader antenna are available, especially for frequency bands above 433MHz and for

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

    PubMed Central

    Shapovalov, George; Lester, Henry A.

    2004-01-01

    Ion channels of high conductance (>200 pS) are widespread among prokaryotes and eukaryotes. Two examples, the Escherichia coli mechanosensitive ion channels Ec-MscS and Ec-MscL, pass currents of 125–300 pA. To resolve temporal details of conductance transitions, a patch-clamp setup was optimized for low-noise recordings at a time resolution of 3 ?s (10–20 times faster than usual). Analyses of the high-resolution recordings confirm that Ec-MscL visits many subconductance states and show that most of the intersubstate transitions occur more slowly than the effective resolution of 3 ?s. There is a clear trend toward longer transition times for the larger transitions. In Ec-MscS recordings, the majority of the observed full conductance transitions are also composite. We detected a short-lived (?20 ?s) Ec-MscS substate at 2/3 of full conductance; transitions between 2/3 and full conductance did not show fine structure and had a time course limited by the achieved resolution. Opening and closing transitions in MscS are symmetrical and are not preceded or followed by smaller, rapid currents (“anticipations” or “regrets”). Compared with other, lower-conductance channels, these measurements may detect unusually early states in the transitions from fully closed to fully open. Increased temporal resolution at the single-molecule level reveals that some elementary steps of structural transitions are composite and follow several alternative pathways, while others still escape resolution. High-bandwidth, low-noise single-channel measurements may provide details about state transitions in other high-conductance channels; and similar procedures may also be applied to channel- and nanopore-based single-molecule DNA measurements. PMID:15277576

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

    Microsoft Academic Search

    Sylvie MAYRARGUE

    1994-01-01

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

  2. Predetection filtering effect on the probability of error of GMSK with discriminator detection in mobile radio channels

    Microsoft Academic Search

    S. M. Elnoubi

    1988-01-01

    Simple closed-form expressions for the probability of error of Gaussian filtered minimum-shift keying (GMSK) with discriminator detection in a fast-Rayleigh-fading channel were previously derived by the author (see ibid., vol.VT-35, p.71-6, May 1986) by assuming that the intermediate frequency filter does not distort the received signal. The effect of this filter on the probability of error is now investigated. The

  3. Pressure-sensitive channel chip for visualization measurement of micro gas flows

    Microsoft Academic Search

    Yu Matsuda; Ryota Misaki; Hiroki Yamaguchi; Tomohide Niimi

    We have developed a new pressure sensing tool named pressure-sensitive channel chip (PSCC) by combining the pressure-sensitive\\u000a paint (PSP) technique with the poly(dimethylsiloxane) (PDMS) micro-molding technique. The PSP technique based on the oxygen\\u000a quenching of luminescence is a potential diagnostic tool for pressure measurement of micro gas flows. However, the application\\u000a of PSP to micro scale measurement is very difficult,

  4. Spatial Correlation and Eigenvalue Statistics Investigation of Wideband MIMO Channel Measurements

    Microsoft Academic Search

    Attaphongse Taparugssanagorn; Tommi Jämsä; Juha Ylitalo

    2006-01-01

    Spatial correlation is one of substantial factors for multiple-input multiple-output (MIMO) wireless communication systems. The spatial correlation must be therefore taken into account in system simulations. This paper results from outdoor wideband MIMO channel measurements performed at 2.53 GHz with a bandwidth of 100 MHz in urban microcell scenario. The measurements were conducted for vehicular speed of 20 km\\/h. A

  5. Self-Calibration Methods in Measurement Channels for Linear and Non-Linear Conversion Functions Case

    Microsoft Academic Search

    Waclaw Gawedzki

    2006-01-01

    Self-calibration methods for long-term monitoring of non-electrical quantities are presented in the paper. There have been discussed the self-calibration methods of measurement channels containing integrated ratiometric output sensors and ratiometric output sensors with strong attenuation (bridge circuits). It has been shown that under certain system solutions this type sensors make measurement results independent from possible changes of the parameters of

  6. Measurements of copper and cesium telluride cathodes in a radio-frequency photoinjector

    NASA Astrophysics Data System (ADS)

    Prat, Eduard; Bettoni, Simona; Braun, Hans-Heinrich; Ganter, Romain; Schietinger, Thomas

    2015-04-01

    Radio-frequency (rf) photoinjectors are commonly used to generate intense bright electron beams for a wide range of applications, most notably as drivers for X-ray Free-Electron Lasers. The photocathode, mounted inside an rf gun and illuminated by a suitable laser, thereby plays a crucial role as the source of the electrons. The intrinsic emittance and the quantum efficiency of the electron source are determined by the properties of the photocathode's surface material. We present measurements of the intrinsic emittance and the quantum efficiency performed with copper and cesium telluride cathodes in the same rf photoinjector, thus comparing, for the first time, the performance of metal and semiconductor cathodes under the same conditions. Our results are consistent with theoretical expectations and show that the difference in intrinsic emittance for the two types of material is not significant in view of accelerator applications. We conclude that cesium telluride photocathodes provide a much higher quantum efficiency at essentially negligible degradation in beam emittance.

  7. Doppler spectroscopic measurements of sheath ion velocities in radio-frequency plasmas

    SciTech Connect

    Woodcock, B.K.; Busby, J.R.; Freegarde, T.G.; Hancock, G. [Physical and Theoretical Chemistry Laboratory, South Parks Road, Oxford OX1 3QZ (United Kingdom)] [Physical and Theoretical Chemistry Laboratory, South Parks Road, Oxford OX1 3QZ (United Kingdom)

    1997-05-01

    We have measured the distributions of N{sub 2}{sup +} ion velocity components parallel and perpendicular to the electrode in the sheath of a radio-frequency nitrogen reactive ion etching discharge, using pulsed laser-induced fluorescence. Parallel to the electrode, the ions have throughout a thermal distribution that is found to be consistent with the rotational temperature of 355 K. In the perpendicular direction, we see clearly the acceleration of the ions towards the electrode, and our results agree well with theoretical predictions although an unexpected peak of unaccelerated ions persists. We have also determined the absolute ion concentrations in the sheath, which we have calibrated by analyzing the decay in laser-induced fluorescence in the plasma bulk after discharge extinction. At 20 mTorr, the bulk concentration of 1.0{times}10{sup 10} cm{sup {minus}3} falls to around 2{times}10{sup 8} cm{sup {minus}3} at 2 mm from the electrode. {copyright} {ital 1997 American Institute of Physics.}

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    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].

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

    SciTech Connect

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

    2013-05-01

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

  10. A radio-polarisation and rotation measure study of the Gum Nebula and its environment

    E-print Network

    Purcell, C R; Sun, X H; Carretti, E; Bernardi, G; Haverkorn, M; Kesteven, M J; Poppi, S; Schnitzeler, D H F M; Staveley-Smith, L

    2015-01-01

    The Gum Nebula is 36 degree wide shell-like emission nebula at a distance of only 450 pc. It has been hypothesised to be an old supernova remnant, fossil HII region, wind-blown bubble, or combination of multiple objects. Here we investigate the magneto-ionic properties of the nebula using data from recent surveys: radio-continuum data from the NRAO VLA and S-band Parkes All Sky Surveys, and H-alpha data from the Southern H-Alpha Sky Survey Atlas. We model the upper part of the nebula as a spherical shell of ionised gas expanding into the ambient medium. We perform a maximum-likelihood Markov chain Monte-Carlo fit to the NVSS rotation measure data, using the H-halpha data to constrain average electron density in the shell $n_e$. Assuming a latitudinal background gradient in RM we find $n_e=1.3^{+0.4}_{-0.4} {\\rm cm}^{-3}$, angular radius $\\phi_{\\rm outer}=22.7^{+0.1}_{-0.1} {\\rm deg}$, shell thickness $dr=18.5^{+1.5}_{-1.4} {\\rm pc}$, ambient magnetic field strength $B_0=3.9^{+4.9}_{-2.2} \\mu{\\rm G}$ and warm ...

  11. Radio Galaxies.

    ERIC Educational Resources Information Center

    Downes, Ann

    1986-01-01

    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)

  12. A high performance diversity selection technique for TDMA portable radio communications

    Microsoft Academic Search

    Justin C-I Chuang; Nelson R. Sollenberger

    1989-01-01

    The authors describe and show performance results for a diversity-selection technique in a frequency-selective fading portable radio channel. Diversity selection is performed by using a quality measure obtained from the demodulation process. This technique is compared to diversity selection based on power and diversity selection after channel decoding. It is found that this diversity selection technique is more effective in

  13. Long-Range Channel Prediction Based on Nonstationary Parametric Modeling

    Microsoft Academic Search

    Ming Chen; Mats Viberg

    2009-01-01

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

  14. Revealing dissipationless chiral edge channel in magnetic topological insulator via non-local transport measurement

    NASA Astrophysics Data System (ADS)

    Lee, Wei-Li; Kou, Xufeng; Guo, Shih-Ting; Fan, Yabin; Pan, Lei; Lang, Murong; Jiang, Ying; Shao, Qiming; Nie, Tianxiao; Murata, Koichi; Tang, Jianshi; Wang, Yong; He, Liang; Lee, Ting-Kuo; Wang, Kang L.

    2015-03-01

    We observed quantum anomalous Hall effect (QAHE) in our 10-quintuple layer Cr-doped (BiSb)2Te3 film grown by MBE technique. The Hall resistance Rxy attains quantized value of h/e2 (25.8 k ?) as temperature drops below 85 mK. Unlike previous report in a thinner Cr-doped (BiSb)2Te3 film, a finite longitudinal resistance is found in the QAHE regime and remains non-zero up to 15 Tesla suggesting the coexistence of the chiral edge channel and certain dissipative conduction channel. From macroscopic non-local transport measurements with leads separated by few millimeters, we further identify the dissipationless nature of the chiral edge channel associated with the QAHE. Detailed T-dependence and field-dependence of the non-local signals will be presented and discussed.

  15. In situ measured current structures of the eddy field in the Mozambique Channel

    NASA Astrophysics Data System (ADS)

    Ternon, J. F.; Roberts, M. J.; Morris, T.; Hancke, L.; Backeberg, B.

    2014-02-01

    Circulation and the related biological production have been studied during five cruises conducted in the Mozambique Channel (MZC) between 2005 and 2010. The circulation in the MZC is known to be highly turbulent, favouring enhanced primary production as a result of mesoscale eddy dynamics, and connectivity throughout the Channel due to the variable currents associated with migrating eddies. This paper presents the results of in situ measurements that characterize the horizontal and vertical currents in the surface and subsurface layers (0-500 m). The in situ data were analysed together with the geostrophic eddy field observed from satellite altimeter measurements. Different circulation regimes were investigated, including the "classical" anticyclonic eddy generated at the Channel narrows (16°S), the enhancement of southward migrating eddies by merging with structures (both cyclonic and anticyclonic) formed in the east of the Channel, and the presence of a fully developed cyclonic eddy at the Channel narrows. Comparison between in situ measurements (S-ADCP and velocities derived from surface drifters) and the geostrophic current derived from sea surface height measurements indicated that the latter can provide a reliable, quantitative description of eddy driven circulation in the MZC, with the exception that these currents are weaker by as much 30%. It is also suggested from in situ observation (drifters) that the departure from geostrophy of the surface circulation might be linked to strong wind conditions. Finally, our observations highlight that a-geostrophic currents need to be considered in future research to facilitate a more comprehensive description of the circulation in this area.

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

    Microsoft Academic Search

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

    2010-01-01

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

  17. Effects of horizontal velocity variations on ultrasonic velocity measurements in open channels

    USGS Publications Warehouse

    Swain, E.D.

    1992-01-01

    Use of an ultrasonic velocity meter to determine discharge in open channels involves measuring the velocity in a line between transducers in the stream and relating that velocity to the average velocity in the stream. The standard method of calculating average velocity in the channel assumes that the velocity profile in the channel can be represented by the one-dimensional von Karman universal velocity profile. However, the velocity profile can be described by a two-dimensional equation that accounts for the horizontal velocity variations induced by the channel sides. An equation to calculate average velocity accounts for the two-dimensional variations in velocity within a stream. The use of this new equation to calculate average velocity was compared to the standard method in theoretical trapezoidal cross sections and in the L-31N and Snapper Creek Extension Canals near Miami, Florida. These comparisons indicate that the two-dimensional variations have the most significant effect in narrow, deep channels. Also, the two-dimensional effects may be significant in some field situations and need to be considered when determining average velocity and discharge with an ultrasonic velocity meter.

  18. Evaluation of the orbit altitude electron density estimation and its effect on the Abel inversion from radio occultation measurements

    Microsoft Academic Search

    Xinan Yue; William S. Schreiner; Christian Rocken; Ying-Hwa Kuo

    2011-01-01

    In this paper, the observations from CHAMP radio occultation (RO) and Planar Langmuir Probe (PLP) during 2002–2008 and Constellation Observing System for Meteorology Ionosphere and Climate (COSMIC) observations during 2007.090–2007.120 are used to evaluate the orbit altitude electron density estimation and its effect on the Abel inversion from RO measurements. Comparison between PLP observed and RO estimated orbit electron density

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

    Microsoft Academic Search

    Lorenzo Iorio

    2006-01-01

    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

  20. Simultaneous Transmission of Wireless and Wireline Services Using a Single 60GHz Radio-Over-Fiber Channel by Coherent Subcarrier Modulation

    Microsoft Academic Search

    Shu-Hao Fan; Hung-Chang Chien; Yu-Ting Hsueh; Arshad Chowdhury; Jianjun Yu; Gee-Kung Chang

    2009-01-01

    We proposed and experimentally demonstrated a novel hybrid subcarrier modulation (H-SCM) technique to generate a spectral-efficient 60-GHz optical millimeter-wave (mm-wave) that carries independent 2.5-Gb\\/s wireless and 10-Gb\\/s wireline signals using intensity and phase modulation, respectively. The frequency beating components of the 60-GHz channel due to interleaved and imbalanced optical path in H-SCM are numerically analyzed and experimentally measured in terms

  1. Experimental measurement of vapor density in the discharge channel of a pulsed positive streamer discharge in water

    NASA Astrophysics Data System (ADS)

    Wen, Xiao Qiong; Li, Shu Han; Liu, Jin Yuan; Niu, Zhi Wen

    2014-08-01

    Using the shadowgraph technique, we performed direct measurements of the vapor density in the discharge channel of a pulsed positive streamer discharge in water. With this experimental technique, we quantitatively measured the vapor density in the discharge channel of a pulsed positive streamer discharge in water of conductivity 100 ?S/cm. The results show that the vapor density in the discharge channel ranges from 100 to 660 kg/m3, and presents an increasing tendency along the axial direction of the discharge channel with increasing distance from the tip of the anode.

  2. Radio Astronomy Radio astronomy

    E-print Network

    Metchev, Stanimir

    ;#12;Arecibo 300m telescope #12;Radio interferometer #12;Radio interferometer Very Large Array (VLA) (New;WestVirginia) #12;Centimeter radio astronomy HI 21cm line emission traces the distribution of atomic hydrogen. Dust: far-Infrared (60-240micron) map NASA/GSFC Atomic hydrogen (HI): 21cm emission-line Dickey & Lockman

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

    NASA Technical Reports Server (NTRS)

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

    1979-01-01

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

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

    SciTech Connect

    Grinstein, S.; Mostafa, M.; Piegaia, R. [Universidad de Buenos Aires, Buenos Aires (Argentina); Alves, G.A.; Carvalho, W.; Maciel, A.K.; da Motta, H.; Santoro, A. [LAFEX, Centro Brasileiro de Pesquisas Fisicas, Rio de Janeiro (Brazil); Lima, J.G.; Oguri, V. [Universidade do Estado do Rio de Janeiro, Rio de Janeiro (Brazil); Gomez, B.; Hoeneisen, B.; Mooney, P.; Negret, J.P. [Universidad de los Andes, Bogota (Colombia); Ducros, Y. [DAPNIA/Service de Physique des Particules, CEA, Saclay (France); Beri, S.B.; Bhatnagar, V.; Kohli, J.M.; Singh, J.B. [Panjab University, Chandigarh (India); Shivpuri, R.K. [Delhi University, Delhi (India); Acharya, B.S.; Banerjee, S.; Dugad, S.R.; Gupta, A.; Krishnaswamy, M.R.; Mondal, N.K.; Narasimham, V.S.; Parua, N.; Shankar, H.C. [Tata Institute of Fundamental Research, Mumbai (India); Park, Y.M. [Kyungsung University, Pusan (Korea); Choi, S.; Kim, S.K. [Seoul National University, Seoul (Korea); Castilla-Valdez, H.; Gonzalez Solis, J.L.; Hernandez-Montoya, R.; Magana-Mendoza, L.; Sanchez-Hernandez, A. [CINVESTAV, Mexico City (Mexico); Pawlik, B. [Institute of Nuclear Physics, Krakow (Poland); Gavrilov, V.; Gershtein, Y.; Kuleshov, S. [Institute for Theoretical and Experimental Physics, Moscow (Russia); Belyaev, A.; Dudko, L.V.; Ermolov, P.; Karmanov, D.; Leflat, A.; Manankov, V.; Merkin, M.; Shabalina, E. [Moscow State University, Moscow (Russia); Abramov, V.; Babintsev, V.V.; Bezzubov, V.A.; Bojko, N.I.; Burtovoi, V.S.; Chekulaev, S.V.; Denisov, S.P.; Dyshkant, A.; Eroshin, O.V.; Evdokimov, V.N.; Galyaev, A.N.; Goncharov, P.I.; Gurzhiev, S.N.; Kostritskiy, A.V.; Kozelov, A.V.; Kozlovsky, E.A.; Mayorov, A.A. [Institute for High Energy Physics, Protvino (Russia); Babukhadia, L.; Davis, K.; Fein, D.; Forden, G.E.; Guida, J.A.; Johns, K.; Nang, F.; Narayanan, A.; Rutherfoord, J.; Shupe, M. [University of Arizona, Tucson, Arizona 85721 (United States); Barberis, E.; Clark, A.R.; Dahl, O.I.; Grudberg, P.; and others

    1999-09-01

    We present a measurement of t{ovr t} production in p{ovr p} collisions at {radical} (s) =1.8 TeV from 110 pb{sup {minus}1} of data collected in the all-jets decay channel with the D0 detector at Fermilab. A neural network analysis yields a cross section of 7.1{plus_minus}2.8(stat){plus_minus}1.5( syst) pb at a top quark mass (m{sub t}) of 172.1 GeV/c{sup 2} . Using previous D0 measurements from dilepton and single lepton channels, the combined D0 result for the t{ovr t} production cross section is 5.9{plus_minus}1.2(stat){plus_minus}1.1( syst) pb for m{sub t}=172.1 GeV /c{sup 2} . {copyright} {ital 1999} {ital The American Physical Society}

  5. Cognitive Radio: A Communications Engineering View

    Microsoft Academic Search

    FRIEDRICH K. JONDRAL

    2007-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2000-07-01

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

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

    NASA Astrophysics Data System (ADS)

    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

    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.

  8. Quantum Channel Negativity as a Measure of System-Bath Coupling and Correlation

    E-print Network

    James M. McCracken

    2013-09-10

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

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

    NASA Technical Reports Server (NTRS)

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

    2006-01-01

    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.

  10. Thermal measurements and flow visualization of heat convection in a tilted channel

    NASA Astrophysics Data System (ADS)

    Tisserand, Jean-Christophe; Creyssels, Mathieu; Riedinger, Xavier; Castaing, Bernard; Chillà, Francesca

    2010-05-01

    Convection is the most important heat transport mechanism. We can find it not only in many natural situations such as stars, planet's atmosphere but also in half-natural situations such as industrial plants. Furthermore, the Rayleigh-Benard system, in which a fluid is cooled from above and heated from below, is one of the most studied systems in thermal convection. Nevertheless, in this configuration, the neighborhood of the plates controls the heat transfer. Therefore, we have to make a system in which the flow forgets the cold and the hot plate. We have built a vertical long channel which links two chambers : the hot one at the lower end and the cold one at the upper end. Moreover, this channel, which is hanged to a structure, can be tilted from an angle of 0 degree to 90 degrees. The experimental facility used for this purpose is a square channel with an inner area of 5*5 cm² m and with a height of 20 cm. The cell is filled with water and is heated at the bottom by Joule effect. At the top, the temperature is regulated by a thermal bath and the mean temperature of the bulk is 25°C . It is worth noticing that this configuration could correspond to heat pipes (without phase transformation) used in thermalisation systems or could model a vertical access pit of an underground carry. In this paper, we want to highlight how the thermal convection in the bulk of the channel is. In the first part, the paper will be focused on the visualization of the flow into the channel thanks to particle image velocimetry (PIV) technique. We look at the mean velocity field (transverse and axial components) , the fluctuations of the mean velocity field and the shear Reynolds stress. Besides, we analyze how the influence of the power supply and the dependance of the tilt angle are. At last, we will interpret the PIV measurements in terms of turbulent viscosity and effective heat conduction and we will deduce from the PIV measurements the axial mean profile of temperature. Then, in a second part, we present new thermal measurements. Thanks to a new sensor inserted into the channel and which is not too intrusive, we have measured the axial mean profile of temperature for several tilt angle and several different power supplies. At last, in a third part, a model which allows to account for the competition between stratification and turbulence will be developed.

  11. Electro-osmosis-driven micro-channel flows: A comparative study of microscopic particle image velocimetry measurements and numerical simulations

    Microsoft Academic Search

    M. J. Kim; A. Beskok; K. D. Kihm

    2002-01-01

    This paper presents global and point-wise com- parisons of experimental measurements and numerical simulation results of electro-osmotically driven flows in two elementary micro-channel configurations, a straight chan- nel with a groove and a T-junction channel. The micro- channels are made by photolithography using poly-dim- ethylsiloxane (PDMS), a type of silicon product, which is transparent, and electro-osmotically permeable to a variety

  12. Measurement of the gravitational redshift effect with RadioAstron satellite

    E-print Network

    A. V. Birukov; V. L. Kauts; D. A. Litvinov; N. K. Porayko; V. N. Rudenko

    2015-06-07

    RadioAstron satellite admits in principle a testing the gravitational redshift effect with an accuracy of better than $10^{-5}$. It would surpass the result of Gravity Probe A mission at least an order of magnitude. However, RadioAstron's communications and frequency transfer systems are not adapted for a direct application of the non relativistic Doppler and troposphere compensation scheme used in the Gravity Probe A experiment. This leads to degradation of the redshift test accuracy approximately to the level 0.01. We discuss the way to overcome this difficulty and present preliminary results based on data obtained during special observing sessions scheduled for testing the new techniques.

  13. Measurement of the gravitational redshift effect with RadioAstron satellite

    E-print Network

    Birukov, A V; Litvinov, D A; Porayko, N K; Rudenko, V N

    2015-01-01

    RadioAstron satellite admits in principle a testing the gravitational redshift effect with an accuracy of better than $10^{-5}$. It would surpass the result of Gravity Probe A mission at least an order of magnitude. However, RadioAstron's communications and frequency transfer systems are not adapted for a direct application of the non relativistic Doppler and troposphere compensation scheme used in the Gravity Probe A experiment. This leads to degradation of the redshift test accuracy approximately to the level 0.01. We discuss the way to overcome this difficulty and present preliminary results based on data obtained during special observing sessions scheduled for testing the new techniques.

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

    NASA Technical Reports Server (NTRS)

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

    1975-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

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

  16. 33 CFR 401.63 - Radio procedures.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...DEPARTMENT OF TRANSPORTATION SEAWAY REGULATIONS AND RULES Regulations Radio Communications § 401.63 Radio procedures. Every vessel shall use the channels of communication in each control sector as listed in the table to this section....

  17. 33 CFR 401.63 - Radio procedures.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...DEPARTMENT OF TRANSPORTATION SEAWAY REGULATIONS AND RULES Regulations Radio Communications § 401.63 Radio procedures. Every vessel shall use the channels of communication in each control sector as listed in the table to this section....

  18. 33 CFR 401.63 - Radio procedures.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...DEPARTMENT OF TRANSPORTATION SEAWAY REGULATIONS AND RULES Regulations Radio Communications § 401.63 Radio procedures. Every vessel shall use the channels of communication in each control sector as listed in the table to this section....

  19. 33 CFR 401.63 - Radio procedures.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...DEPARTMENT OF TRANSPORTATION SEAWAY REGULATIONS AND RULES Regulations Radio Communications § 401.63 Radio procedures. Every vessel shall use the channels of communication in each control sector as listed in the table to this section....

  20. 33 CFR 401.63 - Radio procedures.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...DEPARTMENT OF TRANSPORTATION SEAWAY REGULATIONS AND RULES Regulations Radio Communications § 401.63 Radio procedures. Every vessel shall use the channels of communication in each control sector as listed in the table to this section....

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

    Microsoft Academic Search

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

    2006-01-01

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

  2. Four-channel ZnS scintillator measurements of escaping tritons in TFTR

    SciTech Connect

    Zweben, S.J.

    1988-10-01

    A four-channel scintillation detector capable of measuring tritons, protons, and alphas escaping from a tokamak plasma was operated during the 1986 run period of the Tokamak Fusion Test Reactor (TFTR). Signals consistent with the expected 1 MeV triton behavior have been observed during deuterium operation. Backgrounds associated with neutrons, gammas, and soft x-rays have been evaluated in situ. Such a detector should be capable of measuring escaping alphas during the D/T phase of TFTR. 16 refs., 10 figs.

  3. TEM00 mode content measurements on a passive leakage channel fiber.

    PubMed

    Steinke, Michael; Tünnermann, Henrik; Neumann, Jörg; Kracht, Dietmar; Samson, Bryce; Gu, Guancheng; Dong, Liang; Wessels, Peter

    2015-02-01

    Mode content measurements with a scanning ring cavity were performed in order to determine the TEM00 mode content of the output beam profile of a resonantly enhanced leakage channel fiber. The measurements were performed at 1.0 and 1.5 ?m. In addition, the influence of different bending diameters as well as launching conditions has been investigated. Furthermore, a numerical simulation was used to determine the maximum theoretical TEM00 overlap, if only the fundamental fiber mode is guided. The simulation was also used to analyze how the TEM00 overlap for the case of any additional higher order fiber mode can be determined consistently. PMID:25680053

  4. 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)

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

    2013-12-01

    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.

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

    E-print Network

    Boult, Terrance E.

    recognition system using two cam- eras [9]. In each channel, component-based face detector that is trainedOn 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

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

    Microsoft Academic Search

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

    1997-01-01

    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

  7. Measuring changes in the fundamental constants with redshifted radio absorption lines

    Microsoft Academic Search

    S. J. Curran; N. Kanekar; J. K. Darling

    2004-01-01

    Strong evidence has recently emerged for a variation in the fine structure constant, ??e2\\/?c, over the history of the Universe. This was concluded from a detailed study of the relative positions of redshifted optical quasar absorption spectra. However, radio absorption lines at high redshift offer a much higher sensitivity to a cosmological change in ? than optical lines. Furthermore, through

  8. Measuring changes in the fundamental constants with redshifted radio absorption lines

    Microsoft Academic Search

    S. J. Curran; N. Kanekar; J. K. Darling

    2004-01-01

    Strong evidence has recently emerged for a variation in the fine structure constant, alpha ? e2\\/ℏc, over the history of the Universe. This was concluded from a detailed study of the relative positions of redshifted optical quasar absorption spectra. However, radio absorption lines at high redshift offer a much higher sensitivity to a cosmological change in alpha than optical lines.

  9. Phase distribution measurements in narrow rectangular channels using image-processing techniques

    SciTech Connect

    Bentley, C.L.; Ruggles, A.E.

    1992-06-01

    Phase distribution of air-water flow in a narrow rectangular channel is examined using image-processing techniques. Ink is added to the water, and clear channel walls were used to allow high-speed, still photographs and video tape to be taken of the air-water flow field. Flow field images are digitized and stored in a Macintosh IIci computer using a frame grabber board. Local grey levels are related to liquid thickness in the flow channel using a calibration fixture. Image-processing shareware is used to calculate the spatially averaged liquid thickness from the image of the flow field. Time-averaged spatial liquid distributions are calculated using image calculation algorithms. The spatially averaged liquid distribution is calculated from the time-averaged spatial liquid distribution to formulate the combined temporally and spatially averaged liquid fraction values. The temporally and spatially averaged liquid fractions measured using this technique compare well to those predicted from pressure gradient measurements at zero superficial liquid velocity. 11 refs.

  10. Pressure Drop Measurements for Turbulent Channel Flow over Superhydrophobic Surfaces with Superimposed Riblets

    NASA Astrophysics Data System (ADS)

    Perkins, Richard; Prince, Joseph; Vanderhoff, Julie; Maynes, Daniel

    2012-11-01

    We consider the combined drag reducing mechanisms of riblets and superhydrophobicity. Pressure drop measurements were acquired for turbulent channel flow over riblet surfaces, superhydrophobic surfaces, and surfaces with both drag reducing mechanisms. The riblets were nominally 80 ?m tall, 16 ?m wide, and spaced with a period of 160 ?m. The superhydrophobic structuring was composed of alternating microribs (15 ?m tall and 8 ?m wide) and cavities (32 ?m wide), aligned parallel to the flow. The channel consisted of a control section and a test section comprised of smooth and patterned wafers, respectively. In all cases, the test section walls were structured on top and bottom while the side walls were left smooth. The channel had a hydraulic diameter of 7.3 mm and an aspect ratio of 10:1. Seven pressure ports were precision machined into the walls of both the control and test sections. The pressure drop measurements were acquired simultaneously over both sections to eliminate uncertainty associated with the flow rate. The drag reduction for all test sections was then computed directly and data were obtained over a Reynolds number range of 11000 to 15000.

  11. Pressure and velocity field measurements of pulsating flow in a square channel y-junction

    NASA Astrophysics Data System (ADS)

    Pastuhoff, Markus; Kalpakli, Athanasia; Alfredsson, P. Henrik

    2013-11-01

    The pressure and velocity fields in a y-junction of a square (40 × 40 mm2) cross-section channel were investigated during pulsating flow. One of the sides of the channel was covered with fast responding pressure sensitive paint (PSP) whereas the velocity field at the channel center parallel to the PSP surface was measured using particle image velocimetry (PIV). The flow conditions, in terms of mass flow rate and pulsation frequency, were selected to resemble the flow inside an exhaust manifold of a small internal combustion engine, although the gas was at room temperature. The mass flow was varied between 10 and 130 g/s with pulsations between 0 and 80 Hz. For both the PSP and the PIV measurements images were acquired unsynchronized to the pulses using a high-speed camera and phase averages were formed a posteriori. The use of PSP together with PIV demonstrates how the two techniques can be used to verify and complement each other, PIV excelling at the lower mass flow rates and PSP at the higher. It is shown that the signal-to-noise ratio for PSP at low velocities can be enhanced using a technique based on singular value decomposition.

  12. Abstract--Reliability in Ricean multiple-input-multiple-output (MIMO) channels is crucial for safety related vehicle-to-

    E-print Network

    Zemen, Thomas

    -Multiple-Output (MIMO) circular antenna array with vertically polarized patch antenna elements and the measurement1 Abstract-- Reliability in Ricean multiple-input-multiple- output (MIMO) channels is crucial sounder measurements of vehicle-to-vehicle MIMO radio channels in the 5.2 GHz band. Our results show

  13. Seven-channel fabry-perot spectrum analyzer used in laser scattering measurements.

    PubMed

    John, P K; Benesch, R

    1972-01-01

    A high resolution seven-channel Fabry-Perot interferometer spectrum analyzer is described that was used in laser scattering experiments on a theta-pinch plasma where the spectral width to be measured was of the order of 1 A. The resolution of the system was 0.2 A and covered a wavelength interval of 1.4 A. The interferometer was of the pressure tuned type, using dry nitrogen gas, to center the laser radiation on any given channel for wavelength calibration of the system. The Fabry-Perot plates had to be antireflection coated for proper performance of the system. A complete profile of the Doppler broadened scattered light is obtained in a single discharge, and a typical spectral profile is shown. PMID:20111471

  14. Measurement of the top quark mass in the dilepton channel thinsp

    SciTech Connect

    Grinstein, S.; Mostafa, M.; Piegaia, R. [Universidad de Buenos Aires, Buenos Aires (Argentina); Alves, G.A.; Carvalho, W.; Maciel, A.K.; da Motta, H.; Oliveira, E.; Santoro, A. [LAFEX, Centro Brasileiro de Pesquisas Fisicas, Rio de Janeiro (Brazil); Lima, J.G.; Oguri, V. [Universidade do Estado do Rio de Janeiro, Rio de Janeiro (Brazil); Gomez, B.; Hoeneisen, B.; Mooney, P.; Negret, J.P. [Universidad de los Andes, Bogota (Colombia); Ducros, Y. [DAPNIA/Service de Physique des Particules, CEA, Saclay (France); Beri, S.B.; Bhatnagar, V.; Kohli, J.M.; Singh, J.B. [Panjab University, Chandigarh (India); Shivpuri, R.K. [Delhi University, Delhi (India); Acharya, B.S.; Banerjee, S.; Dugad, S.R.; Gupta, A.; Krishnaswamy, M.R.; Mondal, N.K.; Narasimham, V.S.; Parua, N.; Shankar, H.C. [Tata Institute of Fundamental Research, Mumbai (India); Park, Y.M. [Kyungsung University, Pusan (Korea); Choi, S.; Kim, S.K. [Seoul National University, Seoul (Korea); Castilla-Valdez, H.; Gonzalez Solis, J.L.; Hernandez-Montoya, R.; Magana-Mendoza, L.; Sanchez-Hernandez, A. [CINVESTAV, Mexico City (Mexico); Pawlik, B. [Institute of Nuclear Physics, Krakow (Poland); Gavrilov, V.; Gershtein, Y.; Kuleshov, S. [Institute for Theoretical and Experimental Physics, Moscow (Russia); Belyaev, A.; Dudko, L.V.; Ermolov, P.; Karmanov, D.; Leflat, A.; Manankov, V.; Merkin, M.; Shabalina, E. [Moscow State University, Moscow (Russia); Abramov, V.; Babintsev, V.V.; Bezzubov, V.A.; Bojko, N.I.; Burtovoi, V.S.; Chekulaev, S.V.; Denisov, S.P.; Dyshkant, A.; Eroshin, O.V.; Evdokimov, V.N.; Galyaev, A.N.; Goncharov, P.I.; Gurzhiev, S.N.; Kostritskiy, A.V.; Kozelov, A.V.; Kozlovsky, E.A.; Mayorov, A.A. [Institute for High Energy Physics, Protvino (Russia); Babukhadia, L.; Davis, K.; Fein, D.; Forden, G.E.; Guida, J.A.; James, E.; Johns, K.; Nang, F.; Narayanan, A.; Rutherfoord, J.; Shupe, M. [University of Arizona, Tucson, Arizona 85721 (United States); Aihara, H.; Barberis, E.; Chen, L.; and others

    1999-09-01

    We report a measurement of the top quark mass using six candidate events for the process p{bar p}{r_arrow}t{bar t}+X{r_arrow}l{sup +}{nu}bl{sup {minus}}{bar {nu}}{bar b}+X, observed in the D0 experiment at the Fermilab p{bar p} collider. Using maximum likelihood fits to the dynamics of the decays, we measure a mass for the top quark of m{sub t}=168.4{plus_minus}12.3(stat){plus_minus}3.6(syst) Gev. We combine this result with our previous measurement in the t{bar t}{r_arrow}l+jets channel to obtain m{sub t}=172.1{plus_minus}7.1 GeV as the best value of the mass of the top quark measured by D0. {copyright} {ital 1999} {ital The American Physical Society}

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

    PubMed

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

    2000-12-01

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

  16. Gravitational microlensing of neutron stars and radio pulsars: event rates, time-scale distributions and mass measurements

    E-print Network

    Dai, Shi; Lin, Mengxiang; Yue, Youling; Hobbs, George; Xu, Renxin

    2015-01-01

    We investigate properties of Galactic microlensing events in which a stellar object is lensed by a neutron star. For an all-sky photometric microlensing survey, we determine the number of lensing events caused by $\\sim10^{5}$ potentially-observable radio pulsars to be $\\sim0.2\\ \\rm{yr^{-1}}$ for $10^{10}$ background stellar sources. We expect a few detectable events per year for the same number of background sources from an astrometric microlensing survey. We show that such a study could lead to precise measurements of radio pulsar masses. For instance, if a pulsar distance could be constrained through radio observations, then its mass would be determined with a precision of $\\sim10\\%$. We also investigate the time-scale distributions for neutron star events, finding that they are much shorter than had been previously thought. For photometric events towards the Galactic centre that last $\\sim15$ days, around $7\\%$ will have a neutron star lens. This fraction drops rapidly for longer time-scales. Away from the...

  17. 47 CFR 73.607 - Availability of channels.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...Section 73.607 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Television Broadcast Stations § 73.607 Availability of channels. (a) Applications...

  18. 47 CFR 73.607 - Availability of channels.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...Section 73.607 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Television Broadcast Stations § 73.607 Availability of channels. (a) Applications...

  19. 47 CFR 73.607 - Availability of channels.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...Section 73.607 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Television Broadcast Stations § 73.607 Availability of channels. (a) Applications...

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

    PubMed

    Altarawneh, M M

    2012-09-01

    We present a new technique to perform radio frequency (rf) contactless conductivity measurements in pulsed magnetic fields to probe different ground states in condensed matter physics. The new method utilizes a simple analog band-stop filter circuit implemented in a radio frequency transmission setup to perform contactless conductivity measurements. The new method is more sensitive than the other methods (e.g., the tunnel diode oscillator and the proximity detector oscillator) due to more sensitive dependence of the circuit resonance frequency on the tank circuit inductance (not the transmission line). More important, the new method is more robust than other methods when used to perform measurements in very high magnetic fields, works for a wide range of temperatures (i.e., 300 K-1.4 K) and is less sensitive to noise and mechanical vibrations during pulse magnet operation. The new technique was successfully applied to measure the Shubnikov-de Haas effect in Bi(2)Se(3) in pulsed magnetic fields of up to 60 T. PMID:23020430

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

    E-print Network

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

    2007-01-15

    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.

  2. AG Channel Measurement and Modeling Results for Over-Sea Conditions

    NASA Technical Reports Server (NTRS)

    Matolak, David; Sun, Rouyu

    2014-01-01

    This report describes results from flight tests conducted in an over-sea environment, for the purpose of characterizing the air-to-ground (AG) channel, for future unmanned aircraft system (UAS) communication system analysis and design. These results are for the first of a set of several flight tests conducted in different ground site (GS) environments. An ultimate aim of all these tests is the development of models for the AG channel that can be used in communication system evaluation. In this report we provide measured results for propagation path loss, root-mean square delay spread (RMS-DS), and the correlation coefficient of the primary received signal components on the four antennas (two antennas for C-band, two for L-band). For path loss, the curved-earth two-ray model provides a reasonable fit to the measured data, altered by several dB at the shortest link distances by aircraft antenna pattern effects. This two-ray model also accounts for the majority of measured RMS-DS results of a few tens of nanoseconds, except for the occasional intermittent reflections from surface objects. These intermittent reflections yield RMS-DS values up to several hundred nanoseconds. For portions of the flight path that were over a harbor area highly populated with boats, the channel was found to be more "continuously dispersive," with RMS-DS reaching approximately 250 ns. A separate model will be developed for this over-harbor setting. The correlation coefficient results are still undergoing analysis; preliminary observations are that correlation between signals on the same-band antennas is generally large (>0.6) for the C-band straight flight paths, whereas for the L-band signals and for the oval-shaped flight paths the correlation is generally small (below 0.4). Inter-band correlations are typically very small, and are well modeled as zero-mean Gaussian in distribution, with a standard deviation less than 0.2. Hence the over-sea channel effects in the two bands can be considered uncorrelated, which will allow for good diversity gains in dual-band systems. We describe initial modeling approaches for the over-sea channel; complete models for this and the over-harbor setting will appear in a subsequent report.

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

    SciTech Connect

    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

    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.

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

    Microsoft Academic Search

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

    2001-01-01

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

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

    EPA Science Inventory

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

  6. Measured noise performance of a direct-sequence spread-spectrum system and a comparison of single vice dual-channel delay-lock loops

    Microsoft Academic Search

    Chris G. Bartone

    1987-01-01

    A direct-sequence (DS) spread spectrum system which could be used by a conventional amplitude modulated (AM) radio system was designed, built and tested. A delay-lock loop was used to provide code synchronization in the receiver. The noise performance of single-channel delay-lock loop (SCDLL) was compared with a dual channel delay lock loop (DCDLL) with no data being transmitted. When data

  7. Chandra measurements of complex X-ray emission from massive, merging, radio-halo clusters

    Microsoft Academic Search

    E. T. Million; S. W. Allen

    We report the discovery of spatially-extended, non-thermal or hot, quasi-thermal emis- sion components in Chandra X-ray spectra for ve of a sample of seven massive, merg- ing galaxy clusters with powerful radio halos: Abell 665, 2163, 2255, 2319, and 1E 0657- 56. The emission components can be tted by power-law models with mean photon indices in the range 1:4 <

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

    Microsoft Academic Search

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

    2011-01-01

    We compare ionospheric parameters including total electron content (TEC), peak density, and height of the F2 layer (NmF2 and hmF2) between FORMOSAT-3\\/COSMIC (F3\\/C) GPS radio occultation (RO) technique retrieved and International Reference Ionosphere (IRI-2001) model predicted during different seasons in a low solar activity (LSA) year 2007. The comparison of topside TEC (tTEC, obtained by integrating electron density from hmF2

  9. Optimal Linear Cooperation for Spectrum Sensing in Cognitive Radio Networks

    Microsoft Academic Search

    Zhi Quan; Shuguang Cui; Ali H. Sayed

    2008-01-01

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

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

    SciTech Connect

    Guharay, S.K.; Boyd, D.A.; Ellis, R.F.; Stauffer, F.J.; Lasnier, C.J. (Laboratory for Plasma Research, University of Maryland, College Park, Maryland 20742 (USA))

    1990-11-01

    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{degree} 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 ( {similar to} 2 {mu}{ital s}). A faster detector element, with response {lt} 100 ns, is envisioned for the remaining ten channels.

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

    SciTech Connect

    Guharay, S.K.; Boyd, D.A.; Ellis, R.F.; Stauffer, F.J.; Lasnier, C.J. (Laboratory for Plasma Research, University of Maryland, College Park, MA (USA))

    1990-10-01

    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{degree} 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 ({approximately}2 {mu}s). A faster detector element, with response {lt}100 ns, is envisioned for the remaining ten channels.

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

    E-print Network

    Lorenzo Iorio

    2006-08-29

    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.

  13. Simultaneous Measurement of Phase and Amplitude of NAA Very Low Frequency East-West and West-East Radio Transmissions at San Diego

    Microsoft Academic Search

    W. D. Westfall

    1964-01-01

    Measurements of the amplitude and phase of VLF radio waves over long paths are discussed. A system that permits the simultaneous measurement of phase and amplitude of VLF signals over complementary great circle paths is described. Phase and amplitude measurements of NAA VLF transmissions (18.6 kc\\/s) obtained simultaneously at San Diego over the two great circle paths are shown. A

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

    NASA Technical Reports Server (NTRS)

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

    2002-01-01

    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.

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

    SciTech Connect

    Odian, Allen C.

    2001-09-14

    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.

  16. 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.

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

    SciTech Connect

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

    2011-04-13

    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.

  18. CALLISTO - A new concept for solar radio

    E-print Network

    Benz, A O; Meyer, H A; Benz, Arnold O.; Monstein, Christian; Meyer, HAnsueli

    2004-01-01

    A new radio spectrometer, CALLISTO, is presented. It is a dual-channel frequency-agile receiver based on commercially available consumer electronics. Its major characteristic is the low price for hardware and software, and the short assembly time, both two or more orders of magnitude below existing spectrometers. The instrument is sensitive at the physical limit and extremely stable. The total bandwidth is 825 MHz, and the width of individual channels is 300 kHz. A total of 1000 measurements can be made per second. The spectrometer is well suited for solar low-frequency radio observations pertinent to space weather research. Five instruments of the type were constructed until now and put into operation at several sites, including Bleien (Zurich) and NRAO (USA). First results in the 45 - 870 MHz range are presented. Some of them were recorded in a preliminary setup during the time of high solar activity in October and November 2003.

  19. CALLISTO - A new concept for solar radio

    E-print Network

    Arnold O. Benz; Christian Monstein; HAnsueli Meyer

    2004-10-19

    A new radio spectrometer, CALLISTO, is presented. It is a dual-channel frequency-agile receiver based on commercially available consumer electronics. Its major characteristic is the low price for hardware and software, and the short assembly time, both two or more orders of magnitude below existing spectrometers. The instrument is sensitive at the physical limit and extremely stable. The total bandwidth is 825 MHz, and the width of individual channels is 300 kHz. A total of 1000 measurements can be made per second. The spectrometer is well suited for solar low-frequency radio observations pertinent to space weather research. Five instruments of the type were constructed until now and put into operation at several sites, including Bleien (Zurich) and NRAO (USA). First results in the 45 - 870 MHz range are presented. Some of them were recorded in a preliminary setup during the time of high solar activity in October and November 2003.

  20. Eratosthenes via Ham Radio

    ERIC Educational Resources Information Center

    Koser, John F.

    1975-01-01

    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)

  1. Assessment of radiosonde temperature measurements in the upper troposphere and lower stratosphere using COSMIC radio occultation data

    NASA Astrophysics Data System (ADS)

    He, Wenying; Ho, Shu-peng; Chen, Hongbin; Zhou, Xinjia; Hunt, Doug; Kuo, Ying-Hwa

    2009-09-01

    Temperature profiles derived from Global Positioning System (GPS) Radio Occultation (RO) data from the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) mission are compared with those from four types of radiosonde systems from 12 to 25 km to assess the performance of these radiosonde systems in the upper troposphere and lower stratosphere. Results show that temperature measurements from the Vaisala-RS92 and Shanghai radiosonde systems agree well with those of COSMIC with a close-to-zero mean difference. Large temperature biases are shown for the MRZ and VIZ-B2 radiosonde systems relative to COSMIC, which are probably caused by diurnal radiative effects. In addition, we show that the temperature measurements from a new Chinese radiosonde system are improved compared to those of an older system through a comparison with COSMIC measurements.

  2. Wireless Charge Based Capacitance Measurement Circuits with On-Chip Spiral Inductor for Radio Frequency Identification Biosensor

    NASA Astrophysics Data System (ADS)

    Kim, Boram; Uno, Shigeyasu; Nakazato, Kazuo

    2012-04-01

    A wireless measuring system of charge based capacitance measurement (CBCM) circuit has been designed and demonstrated for biomedical applications. The radio frequency identification (RFID) chip that includes on-chip spiral inductor tag antenna, and RFID circuit, and CBCM sensor chip are fabricated within standard complementary metal oxide semiconductor (CMOS) process. The capacitance change caused by DNA detection can be converted into the voltage output using capacitance-to-voltage conversion circuit. To confirm the transmission of the capacitance, the poly-capacitor of fixed capacitance and on-chip spiral inductor tag antenna were fabricated using 1.2 µm, 2-metal, 2-poly CMOS technology. As a result of measurement, three different capacitances (34, 141, 564 fF) were detected wirelessly.

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

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    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.

  4. 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

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

    2007-01-01

    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

  5. [Investigations of transient time-dependent spectral multi-channel measurement for shocked KCl crystal].

    PubMed

    Cheng, Juan; He, Ying-hong; Zuo, Hao-yi; Ran, Rui-jiang; Xue, Kang; Yang, Jing-guo; Tan, Hua; Hu, Shao-lou; Wang, Xiao-song

    2004-12-01

    In this paper, the authors reported a new method for measuring transient time-dependent spectra using multi-fiber delay coupler and optical multi-channel analysis technique. The fiber delay coupler consists of five fibers with different lengths and its time-delay between two fibers is determined by the different fiber lengths. The light beams that came from the fiber coupler were coupled by a lens system into the slit of a spectrograph and formed a spectral pattern on the focus plane of the spectrometer. A two-dimensional CCD detector converted the optical pattern into an electrical pattern, and then the transient time-dependent spectra were obtained by a personal computer. The experimental setup was constructed, and the transient time-dependent spectra were measured for KCl crystal shocked by a high speed pill. The time resolution was 20 ns, and the spectral intensity resolution reached 1/18 bit. PMID:15828310

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

    SciTech Connect

    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

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2011-06-01

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

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

    PubMed

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

    2013-02-01

    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

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

    NASA Astrophysics Data System (ADS)

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

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

  10. Frequency Allocation; The Radio Spectrum.

    ERIC Educational Resources Information Center

    Federal Communications Commission, Washington, DC.

    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…

  11. Characterization and absolute QE measurements of delta-doped N-channel and P-channel CCDs

    Microsoft Academic Search

    Blake C. Jacquot; Steve P. Monacos; Todd J. Jones; Jordana Blacksberg; Michael E. Hoenk; Shouleh Nikzad

    2010-01-01

    In this paper we present the methodology for making absolute quantum efficiency (QE) measurements from the vacuum ultraviolet (VUV) through the near infrared (NIR) on delta-doped silicon CCDs. Delta-doped detectors provide an excellent platform to validate measurements through the VUV due to their enhanced UV response. The requirements for measuring QE through the VUV are more strenuous than measurements in

  12. Frequency-hop transmission for satellite packet switching and terrestrial packet radio networks

    Microsoft Academic Search

    Michael B. Pursley

    1986-01-01

    The performance frequency-hop transmission in a packet communication network is analyzed. Satellite multiple-access broadcast channels for packet switching and terrestrial packet radio networks are the primary examples of the type of network considered. An analysis of the effects of multiple-access interference in frequency-hop radio networks is presented. New measures of 'local' performance are defined and evaluated for networks of this

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

    SciTech Connect

    Ohtomo, Takayuki; Sudo, Seiichi; Otsuka, Kenju

    2009-01-20

    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.

  14. Label-free viscosity measurement of complex fluids using reversal flow switching manipulation in a microfluidic channel

    PubMed Central

    Jun Kang, Yang; Ryu, Jeongeun; Lee, Sang-Joon

    2013-01-01

    The accurate viscosity measurement of complex fluids is essential for characterizing fluidic behaviors in blood vessels and in microfluidic channels of lab-on-a-chip devices. A microfluidic platform that accurately identifies biophysical properties of blood can be used as a promising tool for the early detections of cardiovascular and microcirculation diseases. In this study, a flow-switching phenomenon depending on hydrodynamic balancing in a microfluidic channel was adopted to conduct viscosity measurement of complex fluids with label-free operation. A microfluidic device for demonstrating this proposed method was designed to have two inlets for supplying the test and reference fluids, two side channels in parallel, and a junction channel connected to the midpoint of the two side channels. According to this proposed method, viscosities of various fluids with different phases (aqueous, oil, and blood) in relation to that of reference fluid were accurately determined by measuring the switching flow-rate ratio between the test and reference fluids, when a reverse flow of the test or reference fluid occurs in the junction channel. An analytical viscosity formula was derived to measure the viscosity of a test fluid in relation to that of the corresponding reference fluid using a discrete circuit model for the microfluidic device. The experimental analysis for evaluating the effects of various parameters on the performance of the proposed method revealed that the fluidic resistance ratio (RJL/RL, fluidic resistance in the junction channel (RJL) to fluidic resistance in the side channel (RL)) strongly affects the measurement accuracy. The microfluidic device with smaller RJL/RL values is helpful to measure accurately the viscosity of the test fluid. The proposed method accurately measured the viscosities of various fluids, including single-phase (Glycerin and plasma) and oil-water phase (oil vs. deionized water) fluids, compared with conventional methods. The proposed method was also successfully applied to measure viscosities of blood with varying hematocrits, chemically fixed RBCS, and channel sizes. Based on these experimental results, the proposed method can be effectively used to measure the viscosities of various fluids easily, without any fluorescent labeling and tedious calibration procedures. PMID:24404040

  15. The atmosphere of Neptune - Results of radio occultation measurements with the Voyager 2 spacecraft

    NASA Technical Reports Server (NTRS)

    Lindal, G. F.; Lyons, J. R.; Sweetnam, D. N.; Eshleman, V. R.; Hinson, D. P.

    1990-01-01

    This paper presents the vertical temperature and composition profiles of Neptune's troposphere and stratosphere, covering an altitude of 250 km, obtained from radio tracking data that were acquired during Voyager-2's occultation by Neptune, which began near 62 deg N planetographic latitude and ended near 45 deg S latitude. In the computations, the He/H2 abundance ratio 15/85 was adapted, which is consistent with solar abundance estimates and with recent results from Uranus. It was assumed that aerosols and heavier gases such as CH4, NH3, H2S, and H2O have a negligible effect on the microwave refractivity above the 0.5 bar pressure level.

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

    NASA Astrophysics Data System (ADS)

    Ao, Chi O.; Hajj, Amanda J.

    2013-12-01

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

  17. Density fluctuations measured by ISEE 1-2 in the Earth's magnetosheath and the resultant scattering of radio waves

    NASA Astrophysics Data System (ADS)

    Lacombe, C.; Steinberg, J.-L.; Harvey, C. C.; Hubert, D.; Mangeney, A.; Moncuquet, M.

    1997-04-01

    Radio waves undergo angular scattering when they propagate through a plasma with fluctuating density. We show how the angular scattering coefficient can be calculated as a function of the frequency spectrum of the local density fluctuations. In the Earth's magnetosheath, the ISEE 1-2 propagation experiment measured the spectral power of the density fluctuations for periods in the range 300 to 1 s, which produce most of the scattering. The resultant local angular scattering coefficient can then be calculated for the first time with realistic density fluctuation spectra, which are neither Gaussian nor power laws. We present results on the variation of the local angular scattering coefficient during two crossings of the dayside magnetosheath, from the quasi-perpendicular bow shock to the magnetopause. For a radio wave at twice the local electron plasma frequency, the scattering coefficient in the major part of the magnetosheath is b(2fp) simeq 0.5 - 4 × 10-9 rad2/m. The scattering coefficient is about ten times stronger in a thin sheet (0.1 to1RE) just downstream of the shock ramp, and close to the magnetopause.

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

    PubMed Central

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

    2014-01-01

    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

  19. Semiconductor emitter based 32-channel spectrophotometer module for real-time process measurements

    NASA Astrophysics Data System (ADS)

    Keranen, Heimo; Malinen, Jouko

    1990-08-01

    A new type of semiconductor emitter based multichannel spectrophotometer has been designed and tested. The spectrophotometer consists of a small electrically conirolled narrow band light source an optical receiver and microprocessor electronics for data processing. The light source is based on a 32-element GaAs and GaAIAs LED chip array which is connected to a diffraction grating and feedback optics. The source is capable of emitting intensity-stabilized single-beam narrow band light pulses. The wavelength of the light pulse can be selected by the electronics without using any moving parts. The optical mechanical and optoelectronic parts of the source have been integrated to form a compact hybrid construction. Main characteristics have been tested with an experimental 32-channel spectrophotometer designed for the wavelength range 810 nm - 1060 nm. Measured wavelength half-power bandwidths are 8 nm and channel separation is 7. 5 nm. A single spectrum scan can be recorded in 8 ms. 64 scans are averaged by the microprocessor electronics and data is transferred to a PC for a multicomponent spectrum analysis program. Output light power level is better than i05 times the averaged detector noise level. The wavelength range used is optimized for near infrared transmittance (NIT) analysis of agricultural products. 1.

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

    NASA Astrophysics Data System (ADS)

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

    2007-11-01

    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.

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

    E-print Network

    Bezanilla, Francisco

    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

  2. PIV flow measurements for heat transfer characterization in two-pass square channels with smooth and 90 ribbed walls

    E-print Network

    Kihm, IconKenneth David

    PIV flow measurements for heat transfer characterization in two-pass square channels with smooth the correlation between the high- Reynolds number turbulent flow and wall heat transfer characteristics in a two number (Re) of 30,000. The PIV measurement results were compared with the heat transfer experimental data

  3. Performance of a 600-channel aerodynamic pressure measurement system for turbine engine testing

    NASA Astrophysics Data System (ADS)

    Thompson, J. W., Jr.; McCarty, P. E.

    Altitude simulation testing of turbine engines in ground test facilities requires the steady-state measurement of up to 600 channels of aerodynamic pressures over the range of 0.5 to 500 psia. The time required to acquire the data and the data quality have a significant influence on total test time, hence cost, and turbine engine performance measurements, respectively. Traditionally, these large quantities of measurements have been accomplished by mechanically multiplexing 10 to 20 pneumatic signals to a single strain-gage pressure transducer. A new approach using a dedicated piezoresistive pressure transducer per cahnnel, electronic multiplexing, and rapid on-line calibration provides improved capabilities. The electronic versus pneumatic multiplexing reduces the steady-state acquisition time per test condition from a nominal 80 to 10 s and improves performance from a nominal 0.25 percent FS to 0.05 percent FS. The new system is described, with emphasis on operational characteristics, measurement uncertainty assessment, and the approach to system design and validation.

  4. Accuracy assessment of georectified aerial photographs: Implications for measuring lateral channel movement in a GIS

    E-print Network

    Marcus, W. Andrew

    change; Channel migration; Georectification; Aerial photographs; Geospatial error; GIS 0169-555X/$ - see different years so channel positions can be analyzed in overlay. Since the 1980s, the development of desktop

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

    NASA Astrophysics Data System (ADS)

    Rodriguez, Serafin P.

    1997-09-01

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

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

    NASA Astrophysics Data System (ADS)

    Hallén, Anders; Moschetti, Giuseppe

    2014-08-01

    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.

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

    Microsoft Academic Search

    W. N. Furman; J. W. Nieto

    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

  8. A conceptual model of channel choice: measuring online and offline shopping value perceptions

    Microsoft Academic Search

    Thijs L. J. Broekhuizen; Wander Jager

    2004-01-01

    This study tries to understand how consumers evaluate channels for their purchasing. Specifically, it develops a conceptual model that addresses consumer value perceptions of using the Internet versus the traditional (physical) channel. Previous research showed that perceptions of price, product quality, service quality and risk strongly influence perceived value and purchase intentions in the offline and online channel. Perceptions of

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

    E-print Network

    Qu, Weilin

    the desired cooling performance. These include pool boiling thermosyphons, channel flow boiling, jet, Issam Mudawar * Boiling and Two-phase Flow Laboratory, School of Mechanical Engineering, 1288 Mechanical, and sprays. Two-phase micro-channel heat sinks are a special class of channel flow boiling systems

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

    Microsoft Academic Search

    S. T. Mahmood; Y. P. Lin; M. A. Dubecky; K. Edsinger; E. V. Mader

    2007-01-01

    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

  11. Radio Communication in Tunnels

    Microsoft Academic Search

    JIRO CHIBA; TATSUO INABA; YOSHITOMO KUWAMOTO; OSAMU BANNO; RISABURO SATO

    1978-01-01

    The attenuation constant of radio waves in tunnels was obtained experimentally and theoretically. According to this study, the tunnel is a transmission channel of high-pass type. It is found that the higher the frequency, the smaller the attenuation constant. The experimental values of attenuation constants are similar to the theoretical values of the the TE01 and EH11 and modes when

  12. Experimental measurements in a radio frequency discharge heated supersonic flow: Evaluation of a potential electric propulsion thruster

    SciTech Connect

    Wantuck, P.J.; Hull, D.E.

    1991-01-01

    An operational radio frequency discharge-driven supersonic flow system, which utilizes an inductively and capacitively coupled plasma (ICCP) tube to produce high enthalpy source gas, is described. The ICCP coupled to a properly designed nozzle represents a potential electric propulsion device. The high gas temperatures achieved in the plasma discharge (> 5000 K) and the electrodeless nature of the tube's operation offers potentially high thruster performance coupled and long operational lifetime. A preliminary characterization of the current system was established using emission and probe-based measurements. A nominal peak specific impulse of 155 s was estimated for operation with argon. The calculated thrust based upon the peak velocity and mass flow through the device is 1.1 N. 14 refs., 10 figs.

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

    SciTech Connect

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

    2010-10-10

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

  14. Evaluating the use of drone photogrammetry for measurement of stream channel morphology and response to high flow events

    NASA Astrophysics Data System (ADS)

    Price, Katie; Ballow, William

    2015-04-01

    Traditional high-precision survey methods for stream channel measurement are labor-intensive and require wadeability or boat access to streams. These conditions limit the number of sites researchers are able to study and generally prohibit the possibility of repeat channel surveys to evaluate short-term fluctuations in channel morphology. In recent years, unmanned aerial vehicles (drones) equipped with photo and video capabilities have become widely available and affordable. Concurrently, developments in photogrammetric software offer unprecedented mapping and 3D rendering capabilities of drone-captured photography. In this study, we evaluate the potential use of drone-mounted cameras for detailed stream channel morphometric analysis. We used a relatively low-cost drone (DJI Phantom 2+ Vision) and commercially available, user friendly software (Agisoft Photscan) for photogrammetric analysis of drone-captured stream channel photography. Our test study was conducted on Proctor Creek, a highly responsive urban stream in Atlanta, Georgia, within the crystalline Piedmont region of the southeastern United States. As a baseline, we performed traditional high-precision survey methods to collect morphological measurements (e.g., bankfull and wetted width, bankfull and wetted thalweg depth) at 11 evenly-spaced transects, following USGS protocols along reaches of 20 times average channel width. We additionally used the drone to capture 200+ photos along the same reaches, concurrent with the channel survey. Using the photogrammetry software, we generated georeferenced 3D models of the stream channel, from which morphological measurements were derived from the 11 transects and compared with measurements from the traditional survey method. We additionally explored possibilities for novel morphometric characterization available from the continuous 3D surface, as an improvement on the limited number of detailed cross-sections available from standard methods. These results showed great promise for the drone photogrammetry methods, which encouraged the exploration of the possibility of repeat aerial surveys to evaluate channel response to high flow events. Repeat drone surveys were performed following a sequence of high-flow events in Proctor Creek to evaluate the possibility of using these methods for assessment of stream channel response to flooding.

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

    NASA Technical Reports Server (NTRS)

    Ao, C. O

    2007-01-01

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

  16. A New Floating-Probe for Measurement of Insulated Plasma Produced by Radio-Frequency Power

    NASA Astrophysics Data System (ADS)

    Taniuchi, Yasuyuki; Yamada, Toshinori; Tokieda, Takanori; Utsumi, Michiaki; Isomura, Masao; Shindo, Haruo

    2012-11-01

    The paper provides a new probe method which enables us to measure parameters of plasmas produced in insulated vessel. In particular, the measurements of electron temperature and density are all made in floating condition of probe, so that there is no need to draw net current from plasma. The method is based on measurement of the functional relationship between the floating potential and the heating voltage of emissive probe. In the first place, the measured parameters of plasma produced in the metal vessel are shown, demonstrating how a new probe works. In the second place, the measurement in the quartz discharge tube is shown, and the measured data by the present method are compared with those obtained by the conventional double probe, demonstrating that they are consistent. It is emphasized that the present new method is a first success in floating probe to be able to measure all plasma parameters.

  17. Defending Wireless Sensor Networks from Radio Interference through

    E-print Network

    Xu, Wenyuan

    of a jammed region act as radio relays between different spectral zones. For coordinated channel switching, we Terms: Security, Reliability, Experimentation Additional Key Words and Phrases: Jamming, Radio18 Defending Wireless Sensor Networks from Radio Interference through Channel Adaptation WENYUAN XU

  18. A neutron scatterometer for void-fraction measurement in heated rod-bundle channels under CANDU LOCA conditions

    Microsoft Academic Search

    J. R. Buell; D. P Byskal; M. R. Desrosiers; E. M. A. Hussein; P. J. Ingham; R. S. Swartz

    2005-01-01

    The difficult problem of directly measuring the void fraction of rapidly boiling water in rod-bundle channels, such as those simulating a large loss-of-coolant accident (LOCA) in a nuclear reactor, is overcome by using a fast-neutron scattering device (scatterometer). The neutron scatterometer measures the number of neutrons scattered from a test section exposed to fast neutrons, and relates these measurements to

  19. Characterization and Absolute QE Measurements of Delta-Doped N-Channel and P-Channel CCDs

    NASA Technical Reports Server (NTRS)

    Jacquot, Blake C.; Monacos, Steve P.; Jones, Todd J.; Blacksberg, Jordana; Hoenk, Michael E.; Nikzad, Shouleh

    2010-01-01

    In this paper we present the methodology for making absolute quantum efficiency (QE) measurements from the vacuum ultraviolet (VUV) through the near infrared (NIR) on delta-doped silicon CCDs. Delta-doped detectors provide an excellent platform to validate measurements through the VUV due to their enhanced UV response. The requirements for measuring QE through the VUV are more strenuous than measurements in the near UV and necessitate, among other things, the use of a vacuum monochromator, and good camera vacuum to prevent chip condensation, and more stringent handling requirements. The system used for these measurements was originally designed for deep UV characterization of CCDs for the WF/PC instrument on Hubble and later for Cassini CCDs.

  20. Functional reconstitution and channel activity measurements of purified wildtype and mutant CFTR protein.

    PubMed

    Eckford, Paul D W; Li, Canhui; Bear, Christine E

    2015-01-01

    The Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) is a unique channel-forming member of the ATP Binding Cassette (ABC) superfamily of transporters. The phosphorylation and nucleotide dependent chloride channel activity of CFTR has been frequently studied in whole cell systems and as single channels in excised membrane patches. Many Cystic Fibrosis-causing mutations have been shown to alter this activity. While a small number of purification protocols have been published, a fast reconstitution method that retains channel activity and a suitable method for studying population channel activity in a purified system have been lacking. Here rapid methods are described for purification and functional reconstitution of the full-length CFTR protein into proteoliposomes of defined lipid composition that retains activity as a regulated halide channel. This reconstitution method together with a novel flux-based assay of channel activity is a suitable system for studying the population channel properties of wild type CFTR and the disease-causing mutants F508del- and G551D-CFTR. Specifically, the method has utility in studying the direct effects of phosphorylation, nucleotides and small molecules such as potentiators and inhibitors on CFTR channel activity. The methods are also amenable to the study of other membrane channels/transporters for anionic substrates. PMID:25867140

  1. HF radio field strength and total propagation invariants

    NASA Astrophysics Data System (ADS)

    Tsedilina, E. E.

    1994-01-01

    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.

  2. Measurement of the effect of electric field on lipid ion channel conformation

    SciTech Connect

    Osman, P.D.; Cornell, B. (CSIRO, Lindfield, New South Wales (Australia) CSIRO, North Ryde, New South Wales (Australia))

    1992-01-01

    This presentation reports on results from a new technique for measuring conformational changes by solid state NMR, in lipid membranes and membrane spanning ion channels, in response to the direct application of electrical field. An apparatus for applying biphasic electric field pulses of up to 20 MV/m to samples of aligned lipids held in an NMR probe, together with methods for the improvement of field homogeneity, will be described. In particular it has been found possible to obtain aligned lipid bilayers of very high impedance by substituting anhydrous glycerol for water. Measurements have been carried out on cholestric liquid crystals, on dilauryl phosphatidylcholine (DLPC) and dioleoyl phosphatidylethanolamine (DOPE) and on melittin in DLPC. The interaction of electric fields with aligned bilayers and powdered samples of DLPC and DOPE will be described, showing elongation of vesicles in response to the field and showing electric field induced Lalpha to powder to Hexll conversion in DOPE. The effect of electric fields on melittin incorporated into aligned lipid bilayers of DLPC will also be reported.

  3. Turbulence Measurements from a Moored Platform at Mid-Depth in a Swift Tidal Channel

    NASA Astrophysics Data System (ADS)

    Hay, Alex; Lueck, Rolf; Wolk, Fabian; McMillan, Justine

    2014-05-01

    Results are presented from a turbulence experiment with a 3-m long streamlined floatation body, instrumented with velocity shear probes, fast-response thermistors, a 1 MHz Acoustic Doppler Current Profiler (AD2CP), and an Acoustic Doppler Velocimeter (ADV). The system was deployed over seven tidal cycles at mid-depth in a 30-m deep tidal channel in the lower Bay of Fundy, Canada. Peak flow speeds exceeded 2 m s-1, and while 10-min time scale average speeds were similar between ebb and flood, the variances were markedly higher during flood. Turbulent kinetic energy (TKE) dissipation rates measured with the shear probes exhibit a pronounced flood/ebb contrast: O(10-4) W kg-1 peak values during flood, but lower by an order of magnitude during ebb. Dissipation rates follow u3 scaling over a wide range of flow speeds between 0.5 and 2.5 m s-1. Below 0.5 m s-1 an asymmetry in the mounting arrangement caused the floatation body to pitch upward, biasing the measured dissipation values high. The ADV on the platform registered mean speed - used to implement Taylor's hypothesis - which was corroborated with the platform-mounted ADCP. Additional ADCPs were also deployed on a nearby bottom pod, sampling at turbulence resolving rates - up to 8 Hz. Comparisons between the shear probe and acoustic estimates of the TKE spectrum and dissipation rate - at comparable depths - are presented.

  4. Passive mixing in micro-channels with geometric variations through µPIV and µLIF measurements

    NASA Astrophysics Data System (ADS)

    Hsieh, Shou-Shing; Huang, Yi-Cheng

    2008-06-01

    Five passive micro-mixers were designed, fabricated and tested, and were compared to that of the conventional T-shaped channel in order to examine the mixing performance by increasing the lateral convection/or related mixing mechanisms. Electro-osmotic pumping was used to generate fluid velocities in the creeping flow regime (Re Lt 1) in order to achieve the mixing enhancement by chaotic advection. Iodine dye (qualitative) and rhodamine B (quantitative) mixing experiments were visualized and measured through conventional microscopes and with µLIF techniques. µPIV measurements were used for 2D velocity vectors and stretching calculations. Steady-state results show that the alternating wavy-regime (chaotic mixers) micro-channels and inline aligned elements (which alter the flow direction laterally) in micro-channels can induce stirring and improve the mixing significantly even at extremely low Reynolds numbers.

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

    Microsoft Academic Search

    Steven J. Howard; K. Pahlavan

    1990-01-01

    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

  6. Modified UWB channel estimation

    Microsoft Academic Search

    Xiangning Fan; Bing Leng; Zaichen Zhang; Guangguo Bi

    2005-01-01

    Ultra wideband (UWB) wireless communication is a new type of radio communication. One of the main applications of UWB in the future focuses on wireless personal area networks (WPAN). Channel estimation is very important for OFDM based UWB system because of its coherent demodulation. In this paper, a new improved channel estimation method is proposed based on the characteristics of

  7. 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)

    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

    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.

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

    NASA Technical Reports Server (NTRS)

    Gnanalingam, S.; Kane, J. A.

    1973-01-01

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

  9. On the Modeling of GMSK Binary Transmission over Time-Variant TDMA\\/FDD Macrocellular Radio Channels with Derotation-Based Coherent Demodulation

    Microsoft Academic Search

    E. Baccarelli; R. Cusani; G. Di Blasio; S. Galli

    1997-01-01

    GMSK is an efficient modulation technique for digital mobile communications. In this paper a simple solution to the modeling and simulation of GMSK systems impaired by fading channels and additive white Gaussian noise is given, and its effects on the channel characteristics are also considered. The modeling is based on the well-known linearized representation of phase-modulated signals. The analysis is

  10. Vector channels for smart antennas. Measurements, statistical modeling, and directional properties in outdoor environments

    Microsoft Academic Search

    Adnan Kavak; Murat Torlak; Wolfhard J. Vogel; Guanghan Xu

    2000-01-01

    In wireless communications, smart antenna systems that employ antenna arrays coupled with adaptive signal-processing techniques at the basestation improve capacity, coverage, and trunking efficiency. However, design and performance analysis of smart antenna systems strongly depend on channel propagation characteristics of signals present at the antenna array, the so-called vector channels. Here, variation of narrow-band vector channels (spatial signatures) due to

  11. Measurements and simulation of Faraday rotation across the Coma radio relic

    NASA Astrophysics Data System (ADS)

    Bonafede, A.; Vazza, F.; Brüggen, M.; Murgia, M.; Govoni, F.; Feretti, L.; Giovannini, G.; Ogrean, G.

    2013-08-01

    The aim of this work is to probe the magnetic field properties in relics and infall regions of galaxy clusters using Faraday rotation measures. We present Very Large Array multifrequency observations of seven sources in the region south-west of the Coma cluster, where the infalling group NGC 4839 and the relic 1253+275 are located. The Faraday rotation measure maps for the observed sources are derived and analysed to study the magnetic field in the south-west region of Coma. We discuss how to interpret the data by comparing observed and mock rotation measure maps that are produced simulating different three-dimensional magnetic field models. The magnetic field model that gives the best fit to the Coma central region underestimates the rotation measure in the south-west region by a factor of ˜6, and no significant jump in the rotation measure data is found at the position of the relic. We explore different possibilities to reconcile observed and mock rotation measure trends, and conclude that an amplification of the magnetic field along the south-west sector is the most plausible solution. Our data together with recent X-ray estimates of the gas density obtained with Suzaku suggest that a magnetic field amplification by a factor of ˜3 is required throughout the entire south-west region in order to reconcile real and mock rotation measure trends. The magnetic field in the relic region is inferred to be ˜ 2 ?G, consistent with inverse Compton limits.

  12. CRAM ´ ER-RAO LOWER BOUND AS A PERFORMANCE MEASURE FOR HIGH RESOLUTION MULTIDIMENSIONAL CHANNEL PARAMETER ESTIMATION SCHEMES

    Microsoft Academic Search

    Martin Tschudin; Ralf Heddergott

    The Cramer-Rao lower bound (CRLB) is derived as a perfor- mance measure for multidimensional channel parameter estima- tion schemes. A compact formulation of the CRLB is given, revealing its dependence on the given wave parameters. More- over, the SAGE algorithm is presented to yield a high resolution of the impinging electromagnetic field with respect to delay, az- imuth and elevation.

  13. 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...

  14. Enhancing the Precision of Infrared Thermodetector for Medicine by Two-Channel Measuring Technique and Mulriple Linear Interpolation Algorithm

    Microsoft Academic Search

    Ye Shu-ming; Jiang Kai; Chen Hang; Pan Jie

    2005-01-01

    The best way to control the spread of severe acute respiratory syndrome (SARS) is measuring the body temperature precisely, therefore, it is very important to develop a set of high-precision infrared thermodetector for medicine. The ambient temperature signal and the object temperature signal were collected with two channel AD gates of thermopile infrared sensor unit. The values were calculated by

  15. Measurement of tt Cross Section in the Lepton Plus Jets Channel Using Neural Networks in 4.6 fb-1

    E-print Network

    Quigg, Chris

    Measurement of t¯t Cross Section in the Lepton Plus Jets Channel Using Neural Networks in 4.6 fb-1 , Including the Ratio Over the Z Cross Section fb-1 A. Lister University of Geneva J. Conway, R. Erbacher, W.6 fb-1 of CDF data (corresponding to data up to period 23). The changes with respect to the previous

  16. Comparison of Self-Calibration Methods for Measurement Channels in Respect of a Method of Conversion Functions Interpolation

    Microsoft Academic Search

    W. Gawedzki

    2008-01-01

    The paper suggests algorithms enabling self-calibration of measurement channels with linear as well as nonlinear conversion functions. To approximate conversion characteristics, interpolation methods are used. They are widely known; however, the essence of the suggested self-calibration method is the current modernization of interpolating functions parameters due to a suitable procedure. It enables correction of the two essential error components which

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

    SciTech Connect

    Compostella, Gabriele; /INFN, Trento

    2008-03-01

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

  18. Imaging algorithms in radio interferometry

    Microsoft Academic Search

    R. J. Sault; T. A. Oosterloo

    2007-01-01

    The paper reviews progress in imaging in radio interferometry for the period 1993-1996. Unlike an optical telescope, the basic measurements of a radio interferometer (correlations between antennas) are indirectly related to a sky brightness image. In a real sense, algorithms and computers are the lenses of a radio interferometer. In the last 20 years, whereas interferometer hardware advances have resulted

  19. ELEC6014 (EZ412/612) Radio Communications Networks and Systems S Chen ELEC6014 Radio Communications Networks and Systems

    E-print Network

    Chen, Sheng

    , Fundamentals of Wireless Communication. Cambridge University Press, 2005. 1 #12;ELEC6014 (EZ412/612) Radio;ELEC6014 (EZ412/612) Radio Communications Networks and Systems S Chen Channel Fundamentals · IdealELEC6014 (EZ412/612) Radio Communications Networks and Systems S Chen ELEC6014 Radio Communications

  20. 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

    NASA Astrophysics Data System (ADS)

    Tanikawa, Takahiro; Chiba, Masami; Kamijo, Toshio; Yabuki, Fumiaki; Yasuda, Osamu; Akiyama, Hidetoshi; Chikashige, Yuichi; Kon, Tadashi; Shimizu, Yutaka; Utsumi, Michiaki; Fujii, Masatoshi

    2012-11-01

    An ultra-high-energy neutrino (UHE?) 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? 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? 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.

  1. 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

    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

    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.

  2. Spatial Dynamics of Indoor Radio Wideband Dana Porrat, Aawatif Hayar and Yuval Serfaty

    E-print Network

    Porrat, Dana

    of the multipath. The spatial stability of measured responses, i.e. the size of the typical area of visibility of a multipath component is a frequency domain concept; it is manifested in the impulse response by a location1 Spatial Dynamics of Indoor Radio Wideband Channels Dana Porrat, Aawatif Hayar and Yuval Serfaty

  3. Effect of Optical Loss and Antenna Separation in 2 2 MIMO Fiber-Radio Systems

    Microsoft Academic Search

    Andrey Kobyakov; Michael Sauer; Anthony Ng'oma; Jack H. Winters

    2010-01-01

    We study the impact of fiber-optic loss due to realistic cable deployment and optical connector loss variation and distance between the transmitter antennas in a radio-over-fiber transmission system with 2 ?? 2 MIMO. We evaluate an upper bound on the system capacity based on measured values of the error vector magnitude and the condition number of the channel matrix. For

  4. Atmospheric anisotropy and its effect on the delay power spectra of tropospheric scatter radio signals

    Microsoft Academic Search

    H. M. Ibrahim

    1982-01-01

    The atmospheric anisotropy and its effect on the delay power spectra of signals received on troposcatter radio links were studied. A simplified model for determining an anisotropy coefficient is suggested. Theoretical and measured anisotropy profiles are utilized in the calculations of the delay power spectra of tropospheric links. The impact of the anisotropy on the troposcatter channel as a communication

  5. Integrating field measurements and flume experiments for analysing fluvial bedload transport and channel morphodynamics in steep mountain streams

    NASA Astrophysics Data System (ADS)

    Beylich, Achim A.; Laute, Katja; Liermann, Susan

    2013-04-01

    Fluvial bedload transport, temporal storage of material and channel morphodynamics have high importance for sedimentary budgets of steep catchments and steep mountain streams. In addition, headwater catchments and steep mountain streams can be relevant sediment sources for lowland river systems. Since 2004 extended and interdisciplinary field investigations on fluvial bedload transport and channel morphodynamics have been conducted in a number of selected stream segments in supply-limited fluvial systems in the inner Nordfjord (Erdalen and Bødalen drainage basins) in western Norway. A range of different methods and techniques have been used. Field studies in the Erdalen drainage basin (79.5 km2) and the Bødalen drainage basin (60.1 km2) have included (i) continuous channel discharge monitoring, (ii) frequently repeated surveys of channel morphometry and granulometric analyses, (iii) different tracer techniques (painted stones, magnetic tracers), (iv) Helley-Smith and other basket measurements, (v) horizontally installed impact sensors, (vi) underwater video filming and (vii) extended biofilm analyses, including also controlled biofilm growing experiments with fixed baskets in selected channel segments. Additional field studies with impact sensors were carried out in selected transport-limited fluvial systems in the Coast Mountains of British Columbia (Canada) in 2010 and 2011. The field studies have been combined with flume experiments for calibration of field measurements, especially for the calibration of the measurements that have been carried out with impact sensors in Norway and Canada. As a key achievement, the entire range of different bedload component grain sizes can be covered by the applied combination of techniques. The flux of bedload material can be quantified and is related to the spatio-temporal variability of sediment supply / availability within the drainage basins and to temporal sediment storage within the channel systems.

  6. Project 8: Using Radio-Frequency Techniques to Measure Neutrino Mass

    E-print Network

    J. A. Formaggio; for the Project 8 Collaboration

    2011-01-31

    The shape of the beta decay energy distribution is sensitive to the mass of the electron neutrino. Attempts to measure the endpoint shape of tritium decay have so far seen no distortion from the zero-mass form. Here we show that a new type of electron energy spectroscopy could improve future measurements of this spectrum and therefore of the neutrino mass. We propose to detect the coherent cyclotron radiation emitted by an energetic electron in a magnetic field. For mildly relativistic electrons, like those in tritium decay, the relativistic shift of the cyclotron frequency allows us to extract the electron energy from the emitted radiation. As the technique inherently involves the measurement of a frequency in a non-destructive manner, it can, in principle, achieve a high degree of resolution and accuracy.

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

    SciTech Connect

    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

    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.

  8. Measurement based satellite to outdoor channel modeling for multiple satellite systems

    Microsoft Academic Search

    M. Milojevic; Martin Haardt; Albert Heuberger

    2008-01-01

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

  9. Measurement and modeling of an ultra-wide bandwidth indoor channel

    Microsoft Academic Search

    Saeed S. Ghassemzadeh; Rittwik Jana; Christopher W. Rice; William Turin; Vahid Tarokh

    2004-01-01

    This paper describes the results of frequency domain channel sounding in residential environments. It consists of detailed characterization of complex frequency responses of Ultra-Wideband Band (UWB) signals having a nominal center frequency of 5 GHz. A path loss model as well as a second-order Autoregressive (AR) model is proposed for frequency response generation of the UWB indoor channel. Probability distributions

  10. Stochastic UWB wireless channel modeling and estimation from received signal measurements

    Microsoft Academic Search

    Yanyan Li; Mohammed Olama; Seddik Djouadi; Aly Fathy; Teja Kuruganti

    2009-01-01

    In this paper, stochastic differential equations (SDEs) are used to model ultra-wideband (UWB) indoor channels. We show that the impulse responses for time-varying wireless channels can be approximated in a mean square sense as close as desired by impulse responses that can be realized by SDEs. The Expected Maximization and Extended Kalman Filter are employed to recursively identify and estimate

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

    NASA Astrophysics Data System (ADS)

    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

    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.

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

    USGS Publications Warehouse

    Limerinos, John Thomas

    1970-01-01

    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

  13. Four-Wave Mixing Crosstalk Measurement in a Highly Doped L-Band Erbium-Doped Fiber Amplifier by Using Half of the Signal Channels

    Microsoft Academic Search

    Hirotaka Ono; Makoto Yamada

    2008-01-01

    We propose a four-wave mixing (FWM) crosstalk measurement method for a signal with 50 GHz spaced wavelength channels in a highly doped L-band erbium-doped fiber amplifier (EDFA). The method uses the crosstalk measured by using a signal with 100 GHz spaced wavelength channels. This approach is based on analyses of the channel spacing dependence of FWM signal generation and the

  14. Project 8: Using Radio-Frequency Techniques to Measure Neutrino Mass

    E-print Network

    N. S. Oblath; for the Project 8 Collaboration

    2013-10-01

    The Project 8 experiment aims to measure the neutrino mass using tritium beta decays. Beta-decay electron energies will be measured with a novel technique: as the electrons travel in a uniform magnetic field their cyclotron radiation will be detected. The frequency of each electron's cyclotron radiation is inversely proportional to its total relativistic energy; therefore, by observing the cyclotron radiation we can make a precise measurement of the electron energies. The advantages of this technique include scalability, excellent energy resolution, and low backgrounds. The collaboration is using a prototype experiment to study the feasibility of the technique with a $^{83m}$Kr source. Demonstrating the ability to see the 17.8 keV and 30.2 keV conversion electrons from $^{83m}$Kr will show that it may be possible to measure tritium beta-decay electron energies ($Q \\approx 18.6$ keV) with their cyclotron radiation. Progress on the prototype, analysis and signal-extraction techniques, and an estimate of the potential future of the experiment will be discussed.

  15. THE HUYGENS DOPPLER WIND EXPERIMENT Titan Winds Derived from Probe Radio Frequency Measurements

    E-print Network

    ) will be performed during the Titan atmospheric des- cent of the ESA Huygens Probe. The direction and strength of Titan's zonal winds will be determined with an accuracy better than 1 m s-1 from the start of mission Probe, as well as its position and attitude after Titan touchdown. The DWE measurement strategy relies

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

    Microsoft Academic Search

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

    1986-01-01

    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

  17. Dielectric measurements of water in the radio microwave frequencies by time domain reflectometry

    Microsoft Academic Search

    M. Merabet; T. K. Bose

    1988-01-01

    The time domain reflectometric method is used with success to measure the dielectric properties of water from 10 MHz to 8 GHz. It is shown that special precautions must be taken into account in order to determine the dielectric properties of a substance with high dielectric constant in the microwave region.

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

    E-print Network

    Groppi, Christopher

    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

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

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

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

  20. First simultaneous measurement of the top quark mass in the lepton+jets and dilepton channels at CDF

    SciTech Connect

    Aaltonen, T.; Maki, T.; Mehtala, P.; Orava, R.; Remortel, N. van [Division of High Energy Physics, Department of Physics, University of Helsinki and Helsinki Institute of Physics, FIN-00014, Helsinki (Finland); Adelman, J.; Brubaker, E.; Fedorko, W. T.; Grosso-Pilcher, C.; Kim, Y. K.; Krop, D.; Kwang, S.; Lee, H. S.; Paramonov, A. A.; Schmidt, M. A.; Shiraishi, S.; Shochet, M.; Wilbur, S.; Wolfe, C.; Yang, U. K. [Enrico Fermi Institute, University of Chicago, Chicago, Illinois 60637 (United States)] (and others)

    2009-05-01

    We present a measurement of the mass of the top quark using data corresponding to an integrated luminosity of 1.9 fb{sup -1} of pp 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. We reconstruct two observables in each channel and use a nonparametric 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 dilepton channel. We 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 dilepton candidate events, we measure the top quark mass to be M{sub top}=171.9{+-}1.7(stat+JES){+-}1.1(other syst) GeV/c{sup 2}=171.9{+-}2.0 GeV/c{sup 2}.

  1. Implementable wireless access for B3G networks. I. MIMO mimo channel measurement, analysis, and modeling [Topics in Radio Communications

    Microsoft Academic Search

    Mischa Dohler; Stephen McLaughlin; Dave Laurenson; Mark Beach; Chor Min Tan; A. H. Aghvami

    2007-01-01

    Within Mobile VCE, a team of several leading U.K. universities, in dose association with major manufacturers and international telecom operators from the mobile industry, have been addressing the challenging task of designing transceiver structures for beyond 3G networks. Innovative approaches led to a plethora of cross-layer optimized technologies of low complexity and high robustness, allowing for the much promised multimedia-centric

  2. Plasma resistivity profile measurement from an external radio-frequency magnetic coil

    NASA Astrophysics Data System (ADS)

    Slough, John T.; Andreason, Samuel P.; Milroy, Richard D.

    2004-10-01

    Plasma resistivity is obtained by measuring the change in circuit behavior from a simple loop placed externally to the plasma. The loop is part of a series-driven oscillator that can be tuned over a wide range of frequencies with a very low internal impedance. By varying the frequency, and observing both the detuning and loading of this circuit, the location and resistance of the screening currents can be determined. A two-dimensional resistive magnetohydrodynamic code calculation is performed to obtain both the plasma interaction with the oscillating field as well as the effects of nearby conductors. The plasma resistance in the numerical calculations is adjusted to match the data from the experiment and, in this way, obtain a measure of the plasma resistivity profile.

  3. Polarization diversity for urban millimetric mobile radio communications: comparison of initial propagation measurement results with prediction

    Microsoft Academic Search

    H J Thomast; G L Siqueirat; R. S. Cole

    1992-01-01

    An experimental study of the propagation of vertical and horizontal polarized 55-GHz millimeter waves from a fixed transmitter to a mobile receiver in an urban environment is described. Ranges up to 400 m were used and measurements were obtained in the presence of traffic. Components transmitted received on orthogonal polarizations are uncorrelated. Cross coupling components are on average 10-20 dB

  4. Comparison of equatorial electron densities measured by whistlers and by a satellite radio technique

    Microsoft Academic Search

    D. L. Carpenter; R. R. Anderson; T. F. Bell; T. R. Miller

    1981-01-01

    For the first time, data on magnetospheric equatorial electron density from multiple whistler paths have been compared with in situ satellite measurements of electron density along near-equatorial orbits. The whistlers data were recorded at Siple, Antarctica (Lapprox.4.2) on June 28 and July 10, 1978, and at Palmer, Antarctica (Lapprox.2.3) on April 10, 1978. The satellite data were obtained by the

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

    Microsoft Academic Search

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

    2001-01-01

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

  6. Multi-frequency radiowave propagation measurements in the portable radio environment

    Microsoft Academic Search

    D. M. J. Devasirvatham; C. Banerjee; M. J. Krain; D. A. Rappaport

    1990-01-01

    Time-delay-spread and signal-level measurements were made in two dissimilar office buildings at 850 MHz, 1.7 GHz, and 4.0 GHz. No significant statistical difference in time-delay spread was found. The maximum RMS time-delay spread at the three frequencies did not exceed 270 ns at the larger building and 100 ns at the smaller building. Attenuation, although very nearly the same, decreased

  7. Improvement of GPS radio occultation retrieval error of E region electron density: COSMIC measurement and IRI model simulation

    NASA Astrophysics Data System (ADS)

    Wu, Kang-Hung; Su, Ching-Lun; Chu, Yen-Hsyang

    2015-03-01

    In this article, we use the International Reference Ionosphere (IRI) model to simulate temporal and spatial distributions of global E region electron densities retrieved by the FORMOSAT-3/COSMIC satellites by means of GPS radio occultation (RO) technique. Despite regional discrepancies in the magnitudes of the E region electron density, the IRI model simulations can, on the whole, describe the COSMIC measurements in quality and quantity. On the basis of global ionosonde network and the IRI model, the retrieval errors of the global COSMIC-measured E region peak electron density (NmE) from July 2006 to July 2011 are examined and simulated. The COSMIC measurement and the IRI model simulation both reveal that the magnitudes of the percentage error (PE) and root mean-square-error (RMSE) of the relative RO retrieval errors of the NmE values are dependent on local time (LT) and geomagnetic latitude, with minimum in the early morning and at high latitudes and maximum in the afternoon and at middle latitudes. In addition, the seasonal variation of PE and RMSE values seems to be latitude dependent. After removing the IRI model-simulated GPS RO retrieval errors from the original COSMIC measurements, the average values of the annual and monthly mean percentage errors of the RO retrieval errors of the COSMIC-measured E region electron density are, respectively, substantially reduced by a factor of about 2.95 and 3.35, and the corresponding root-mean-square errors show averaged decreases of 15.6% and 15.4%, respectively. It is found that, with this process, the largest reduction in the PE and RMSE of the COSMIC-measured NmE occurs at the equatorial anomaly latitudes 10°N-30°N in the afternoon from 14 to 18 LT, with a factor of 25 and 2, respectively. Statistics show that the residual errors that remained in the corrected COSMIC-measured NmE vary in a range of -20% to 38%, which are comparable to or larger than the percentage errors of the IRI-predicted NmE fluctuating in a range of -6.5% to 20%.

  8. Measuring and evaluating the role of ATP-sensitive K+ channels in cardiac muscle.

    PubMed

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

    2012-03-01

    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 1980s 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 an electrophysiological laboratory. The focus is on the K(ATP) channel, but many of the techniques described are also used to study other ion channels. PMID:22245446

  9. Emissions of SO2, NOx, and CO2 from the Houston Ship Channel Measured by the NOAA WP-3

    NASA Astrophysics Data System (ADS)

    Washenfelder, R. A.; Brock, C. A.; Frost, G. J.; Holloway, J. S.; Peischl, J. W.; Ryerson, T. B.; Trainer, M.; Fehsenfeld, F. C.

    2007-12-01

    The Port of Houston is made up of the Houston Ship Channel and Galveston Bay. Together these comprise a 25- mile long complex of diversified public and private facilities, including a petrochemical complex that is among the largest in the world. The Houston Ship Channel is a major source of industrial pollution, emitting sulfur dioxide (SO2), nitrogen oxides (NOx), carbon monoxide (CO), carbon dioxide (CO2), and volatile organic compounds (VOC). Unlike a single large power plant, the Houston Ship Channel consists of numerous sources that can be difficult to quantify in inventories. In order to evaluate and predict air quality in the Houston area, it is important to understand the magnitude and variability of sources in the Houston Ship Channel, and how these sources are evolving over time. We examine fluxes of SO2, NOx, and CO2 from the Houston Ship Channel observed onboard the NOAA WP-3 during September - October 2006. We report the magnitude of these sources, and compare these results to aircraft measurements from 2000 to identify trends.

  10. Downscaling of radio brightness measurements for soil moisture estimation: A four-dimensional variational data assimilation approach

    NASA Astrophysics Data System (ADS)

    Reichle, Rolf H.; Entekhabi, Dara; McLaughlin, Dennis B.

    2001-09-01

    This paper investigates the feasibility of estimating large-scale soil moisture profiles and related land surface variables from 1.4 GHz (L-band) passive microwave measurements, using variational data assimilation. Our four-dimensional assimilation algorithm takes into account both model and measurement uncertainties and provides dynamically consistent interpolation and extrapolation of remote sensing data over space and time. The land surface hydrologic model which forms the heart of the variational algorithm was expressly designed for data assimilation purposes. This model captures key physical processes while remaining computationally efficient. We test our algorithm with a series of synthetic experiments based on the Southern Great Plains 1997 Hydrology Experiment. These experiments provide insights about three issues that are crucial to the design of an operational soil moisture assimilation system. Our first synthetic experiment shows that soil moisture can be satisfactorily estimated at scales finer than the resolution of the brightness images. This downscaling experiment indicates that brightness images with a resolution of tens of kilometers can yield soil moisture profile estimates on a scale of a few kilometers, provided that micrometeorological, soil texture, and land cover inputs are available at the finer scale. In our second synthetic experiment we show that adequate soil moisture estimates can be obtained even if quantitative precipitation data are not available. Model error terms estimated from radio brightness measurements are able to account in an aggregate way for the effects of precipitation events. In our third experiment we show that reductions in estimation performance resulting from a decrease in the length of the assimilation time interval are offset by a substantial improvement in computational efficiency.

  11. Radio range measurements of coronal electron densities at 13 and 3.6 centimeter wavelengths during the 1988 solar conjunction of Voyager 2

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

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

  12. Measurement and modeling of auroral absorption of HF radio waves using a single receiver

    NASA Astrophysics Data System (ADS)

    Greenberg, E. M.; LaBelle, J.

    2002-03-01

    We develop a new method of measuring auroral absorption using only a single passive HF receiver detecting a large number of existing HF transmissions. Although the locations, strengths, and timetables of these sources are not known, their large number allows them to be treated statistically. Modeling the distribution of the sources and using the Foppiano and Bradley [1983] model for the propagation of the waves leads to a simulated pattern of received signals at the receiver as a function of time of day which agrees well with the observed pattern.

  13. Radio path length correction using water vapour radiometry

    E-print Network

    R. J. Sault; G. J. Carrad; P. J. Hall; J. Crofts

    2006-12-31

    Path length changes through the atmosphere cause significant errors for astronomical radio interferometry at high frequencies (e.g. 100 GHz). Path length differences typically give rise to a differential excess path of 1mm for antennas separated by 1km, and have fluctuation time scales of greater than 10 seconds. To measure these fluctuations, we are building a four-channel radiometer centred on the 22 GHz water line. By sensing the water vapour emission, the excess path can be deduced and corrected. Multiple channels give us robustness against various systematic errors, but gain stability of the radiometer of 1 pair in 10^4 is still required.

  14. Multiplexing of Radio-Frequency Single Electron Transistors

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

    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.

  15. Radio-Frequency Illuminated Superconductive Disks: Reverse Josephson Effects and Implications for Precise Measuring of Proposed Gravity Effects

    NASA Technical Reports Server (NTRS)

    Noever, David A.; Koczor, Ronald J.

    1998-01-01

    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.

  16. Radio Astronomy

    NSDL National Science Digital Library

    Tenenbaum, David

    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.

  17. End-to-end throughput improvement for single radio multi-channel multi-path wireless mesh networks: a cross layer design

    Microsoft Academic Search

    Cao Trong Hieu; Sungwon Lee; Choong Seon Hong

    2010-01-01

    The distinguished feature of fixed backbone nodes in the wireless mesh networks (WMNs) can be utilized to design an efficient\\u000a cross layer which cooperates routing and scheduling schemes for increasing end-to-end throughput. With only single radio nodes,\\u000a by well designing the scheduling and routing schemes for multiple paths, we show that WMN can gain more throughput and reduce\\u000a communication interference.

  18. Measurement of flow in a microfluidic channel in response to application of voltage

    E-print Network

    Soukup, Elizabeth A

    2014-01-01

    This thesis explores two methods of calculating the flow of Electrorheological fluid in a microfluidic channel in response to a gradient in an electric field: MATLAB simulation and microscopy experiments. Electrorheological ...

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

    E-print Network

    Banerjee, Arindam

    2006-10-30

    A novel gas channel experiment was constructed to study the development of high Atwood number Rayleigh-Taylor mixing. Two gas streams, one containing air and the other containing helium-air mixture, flow parallel to each ...

  20. Deformation in the Santa Barbara Channel from GPS measurements 1987-1991

    NASA Technical Reports Server (NTRS)

    Larson, Kristine M.; Webb, Frank H.

    1992-01-01

    An analysis of GPS data over the period 1987-91 confirms geologic and seismic evidence that the Santa Barbara Channel is a complicated actively deforming region. The data indicate north-south compression in the eastern channel, with little deformation in the west. Rotation may also be an important deformation mechanism. An analysis of strain rate variation over periods of 4.5, 17, and 100 yr suggests that deformation is nonuniform.