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Sample records for access cdma techniques

  1. Use of CDMA access technology in mobile satellite systems

    NASA Technical Reports Server (NTRS)

    Ramasastry, Jay; Wiedeman, Bob

    1995-01-01

    Use of Code Division Multiple Access (CDMA) technology in terrestrial wireless systems is fairly well understood. Similarly, design and operation of Power Control in a CDMA-based system in a terrestrial environment is also well established. Terrestrial multipath characteristics, and optimum design of the CDMA receiver to deal with multipath and fading conditions are reliably established. But the satellite environment is different. When the CDMA technology is adopted to the satellite environment, other design features need to be incorporated (for example; interleaving, open-loop and closed-loop power control design, diversity characteristics) to achieve comparable level of system performance. In fact, the GLOBALSTAR LEO/MSS system has incorporated all these features. Contrary to some published reports, CDMA retains the advantages in the satellite environment that are similar to those achieved in the terrestrial environment. This document gives a description of the CDMA waveform and other design features adopted for mobile satellite applications.

  2. Secure Communications in High Speed Fiber Optical Networks Using Code Division Multiple Access (CDMA) Transmission

    SciTech Connect

    Han, I; Bond, S; Welty, R; Du, Y; Yoo, S; Reinhardt, C; Behymer, E; Sperry, V; Kobayashi, N

    2004-02-12

    This project is focused on the development of advanced components and system technologies for secure data transmission on high-speed fiber optic data systems. This work capitalizes on (1) a strong relationship with outstanding faculty at the University of California-Davis who are experts in high speed fiber-optic networks, (2) the realization that code division multiple access (CDMA) is emerging as a bandwidth enhancing technique for fiber optic networks, (3) the realization that CDMA of sufficient complexity forms the basis for almost unbreakable one-time key transmissions, (4) our concepts for superior components for implementing CDMA, (5) our expertise in semiconductor device processing and (6) our Center for Nano and Microtechnology, which is where the majority of the experimental work was done. Here we present a novel device concept, which will push the limits of current technology, and will simultaneously solve system implementation issues by investigating new state-of-the-art fiber technologies. This will enable the development of secure communication systems for the transmission and reception of messages on deployed commercial fiber optic networks, through the CDMA phase encoding of broad bandwidth pulses. CDMA technology has been developed as a multiplexing technology, much like wavelength division multiplexing (WDM) or time division multiplexing (TDM), to increase the potential number of users on a given communication link. A novel application of the techniques created for CDMA is to generate secure communication through physical layer encoding. Physical layer encoding devices are developed which utilize semiconductor waveguides with fast carrier response times to phase encode spectral components of a secure signal. Current commercial technology, most commonly a spatial light modulator, allows phase codes to be changed at rates of only 10's of Hertz ({approx}25ms response). The use of fast (picosecond to nanosecond) carrier dynamics of semiconductors, as

  3. A CDMA architecture for a Ka-band Personal Access Satellite System

    NASA Technical Reports Server (NTRS)

    Motamedi, Masoud; Sue, Miles K.

    1990-01-01

    A Code Division Multiple Access (CDMA) architecture is currently being studied for use in a Ka-band Personal Access Satellite System (PASS). The complete architecture consisting of block diagrams of the user terminal, the supplier station, the network management center, and the satellite is described along with the access methods and frequency/time plans. The complexity of developing this system using the CDMA architecture is compared to that of a Frequency Division Multiple Access (FDMA) architecture. The inherent advantages and disadvantages of the two architectures are compared and their respective capacities are discussed.

  4. Nonorthogonal CSK/CDMA with Received-Power Adaptive Access Control Scheme

    NASA Astrophysics Data System (ADS)

    Komuro, Nobuyoshi; Habuchi, Hiromasa; Tsuboi, Toshinori

    The measurements for Multiple Access Interference (MAI) problems and the improvement of the data rate are key issues on the advanced wireless networks. In this paper, the nonorthogonal Code Shift Keying Code Division Multiple Access (CSK/CDMA) with received-power adaptive access control scheme is proposed. In our system, a user who is ready to send measures the received power from other users, and then the user decides whether to transmit or refrain from transmission according to the received power and a pre-decided threshold. Not only overcoming the MAI problems, but our system also improve the throughput performance. The throughput performance of the proposed system is evaluated by theoretical analysis. Consequently, the nonorthogonal CSK/CDMA system improves by applying received-power adaptive access control. It was also found that the throughput performance of the nonorthogonal CSK/CDMA system is better than that of the orthogonal CSK/CDMA system at any Eb/N0. We conclude that the nonorthogonal CSK/CDMA system with received-power adaptive access control scheme is expected to be effective in advanced wireless networks.

  5. A satellite mobile communication system based on Band-Limited Quasi-Synchronous Code Division Multiple Access (BLQS-CDMA)

    NASA Technical Reports Server (NTRS)

    Degaudenzi, R.; Elia, C.; Viola, R.

    1990-01-01

    Discussed here is a new approach to code division multiple access applied to a mobile system for voice (and data) services based on Band Limited Quasi Synchronous Code Division Multiple Access (BLQS-CDMA). The system requires users to be chip synchronized to reduce the contribution of self-interference and to make use of voice activation in order to increase the satellite power efficiency. In order to achieve spectral efficiency, Nyquist chip pulse shaping is used with no detection performance impairment. The synchronization problems are solved in the forward link by distributing a master code, whereas carrier forced activation and closed loop control techniques have been adopted in the return link. System performance sensitivity to nonlinear amplification and timing/frequency synchronization errors are analyzed.

  6. High speed OFDM-CDMA optical access network.

    PubMed

    Guo, X; Wang, Q; Zhou, L; Fang, L; Wonfor, A; Penty, R V; White, I H

    2016-04-15

    We demonstrate the feasibility of a 16×3.75  Gb/s (60 Gb/s aggregate) Orthogonal frequency division multiplexing-code division multiple access passive optical network for next-generation access applications. 3.75 Gb/s PON channel transmission over 25 km single-mode fiber shows 0.1 dB dispersion and 0.9 dB crosstalk penalties. Advantages of the system include high capacity, enhanced spectral efficiency, coding gain, and networking functions such as increased security and single-wavelength operation. PMID:27082351

  7. Alternative multiple-access techniques for mobile satellite systems

    NASA Technical Reports Server (NTRS)

    Smith, Patrick O.; Geraniotis, Evaggelos

    1989-01-01

    The use of Code Division Multiple Access (CDMA) to satisfy the diverse requirements of a generic (land, maritime, aeronautical) mobile satellite system (MSS) network design is discussed. Comparisons between CDMA and Frequency Division Multiple Access (FDMA) show that a CDMA network design can support significantly more voice channel allocations than FDMA when relatively simple CDMA correlation receivers are employed, provided that there is sufficient space segment equivalent isotropically radiated power (EIRP). The use of more advanced CDMA receivers can improve the spectral and power efficiency. Although the use of CDMA may not gain immediate and widespread support in the international MSS community, provision for the use of CDMA for a domestic system in the U.S., and possibly for a regional system throughout North America, is likely.

  8. Performance evaluation of multi-access strategies for an integrated voice/data CDMA packet radio network

    NASA Astrophysics Data System (ADS)

    Geraniotis, Evaggelos; Soroushnejad, Mohsen

    1990-11-01

    The problem of voice/data integration in a random-access radio network employing the ALOHA protocol in conjunction with retransmission control is investigated. Channel-access control strategies are introduced that take advantage of the capability of the code-division multiple-access (CDMA) channel to accommodate several voice calls simultaneously, while the data users contend for the remaining (if any) multiple-access capability of that channel. The retransmission probabilities of the backlogged data users are updated based on estimates of data backlog and number of established voice calls, which are obtained from the side information about the state of channel activities. A two-dimensional Markovian model is developed for the voice and data traffic. Based on this model, the voice-call blocking probability, the throughput of both traffic types, and the delay of the data packets are evaluated and the tradeoffs between the parameters of different traffic types are quantified. It is observed that by taking advantage of the multiple-access capability of the CDMA channel in the control of data traffic, we may achieve movable-boundary channel access in the code domain.

  9. System level comparison of FDMA vs. CDMA (under conference guideline constraint)

    NASA Technical Reports Server (NTRS)

    Renshaw, Ken

    1989-01-01

    The margin that is required to mitigate the near-far problem in a Code Division Multiple Access (CDMA) mobile satellite system is determined by the radio-propagation model selected, the distribution of the users in clear and shadowed environments, and implementation techniques. The use of revenue potential as a means of evaluating the relative merits of CDMA and Frequency Division Multiple Access (FDMA) systems is a convenient way to rationalize the performance of systems using high-gain and low-gain antennas. The revenue potential of CDMA is much greater than the revenue potential for FDMA for a particular satellite design considered.

  10. System level comparison of FDMA vs. CDMA (under conference guideline constraint)

    NASA Astrophysics Data System (ADS)

    Renshaw, Ken

    1989-03-01

    The margin that is required to mitigate the near-far problem in a Code Division Multiple Access (CDMA) mobile satellite system is determined by the radio-propagation model selected, the distribution of the users in clear and shadowed environments, and implementation techniques. The use of revenue potential as a means of evaluating the relative merits of CDMA and Frequency Division Multiple Access (FDMA) systems is a convenient way to rationalize the performance of systems using high-gain and low-gain antennas. The revenue potential of CDMA is much greater than the revenue potential for FDMA for a particular satellite design considered.

  11. Optical multiple access techniques for on-board routing

    NASA Technical Reports Server (NTRS)

    Mendez, Antonio J.; Park, Eugene; Gagliardi, Robert M.

    1992-01-01

    The purpose of this research contract was to design and analyze an optical multiple access system, based on Code Division Multiple Access (CDMA) techniques, for on board routing applications on a future communication satellite. The optical multiple access system was to effect the functions of a circuit switch under the control of an autonomous network controller and to serve eight (8) concurrent users at a point to point (port to port) data rate of 180 Mb/s. (At the start of this program, the bit error rate requirement (BER) was undefined, so it was treated as a design variable during the contract effort.) CDMA was selected over other multiple access techniques because it lends itself to bursty, asynchronous, concurrent communication and potentially can be implemented with off the shelf, reliable optical transceivers compatible with long term unattended operations. Temporal, temporal/spatial hybrids and single pulse per row (SPR, sometimes termed 'sonar matrices') matrix types of CDMA designs were considered. The design, analysis, and trade offs required by the statement of work selected a temporal/spatial CDMA scheme which has SPR properties as the preferred solution. This selected design can be implemented for feasibility demonstration with off the shelf components (which are identified in the bill of materials of the contract Final Report). The photonic network architecture of the selected design is based on M(8,4,4) matrix codes. The network requires eight multimode laser transmitters with laser pulses of 0.93 ns operating at 180 Mb/s and 9-13 dBm peak power, and 8 PIN diode receivers with sensitivity of -27 dBm for the 0.93 ns pulses. The wavelength is not critical, but 830 nm technology readily meets the requirements. The passive optical components of the photonic network are all multimode and off the shelf. Bit error rate (BER) computations, based on both electronic noise and intercode crosstalk, predict a raw BER of (10 exp -3) when all eight users are

  12. Throughput of Coded Optical CDMA Systems with AND Detectors

    NASA Astrophysics Data System (ADS)

    Memon, Kehkashan A.; Umrani, Fahim A.; Umrani, A. W.; Umrani, Naveed A.

    2012-09-01

    Conventional detection techniques used in optical code-division multiple access (OCDMA) systems are not optimal and result in poor bit error rate performance. This paper analyzes the coded performance of optical CDMA systems with AND detectors for enhanced throughput efficiencies and improved error rate performance. The results show that the use of AND detectors significantly improve the performance of an optical channel.

  13. Design and Evaluation of a Virtual Quadrant Receiver for 4-ary Pulse Position Modulation/Optical Code Division Multiple Access (4-ary PPM/O-CDMA)

    SciTech Connect

    Mendez, A J; Hernandez, V J; Gagliardi, R M; Bennett, C V

    2006-12-29

    M-ary pulse position modulation (M-ary PPM) is an alternative to on-off-keying (OOK) that transmits multiple bits as a single symbol occupying a frame of M slots. PPM does not require thresholding as in OOK signaling, instead performing a comparison test among all slots in a frame to make the slot decision. Combining PPM with optical code division multiple access (PPM/O-CDMA) adds the benefit of supporting multiple concurrent, asynchronous bursty PPM users. While the advantages of PPM/O-CDMA are well known, implementing a receiver that performs comparison test can be difficult. This paper describes the design of a novel array receiver for M-ary PPM/O-CDMA (M = 4) where the received signal is mapped onto an xy-plane whose quadrants define the PPM slot decision by means of an associated control law. The receiver does not require buffering or nonlinear operations. In this paper we describe a planar lightwave circuit (PLCs) implementation of the receiver. We give detailed numerical simulations that test the concept and investigate the effects of multi-access interference (MAI) and optical beat interference (OBI) on the slot decisions. These simulations provide guidelines for subsequent experimental measurements that will be described.

  14. Computer memory access technique

    NASA Technical Reports Server (NTRS)

    Zottarelli, L. J.

    1967-01-01

    Computer memory access commutator and steering gate configuration produces bipolar current pulses while still employing only the diodes and magnetic cores of the classic commutator, thereby appreciably reducing the complexity of the memory assembly.

  15. Comparison of two underwater acoustic communications techniques for multi-user access

    NASA Astrophysics Data System (ADS)

    Hursky, Paul; Siderius, T. Martin; Kauaiex Group

    2001-05-01

    Frequency hopped frequency shift keying (FHFSK) and code division multiple access (CDMA) are two different modulation techniques for multiple users to communicate with a single receiver simultaneously. In July 2003, these two techniques were tested alongside each other in a shallow water coastal environment off the coast of Kauai. A variety of instruments were used to measure the prevailing oceanography, enabling detailed modeling of the channel. The channel was acoustically probed using LFM waveforms and m-sequences as well. We will present the results of demodulating the FHFSK and CDMA waveforms and discuss modeling the channel for the purpose of predicting multi-user communications performance. a)Michael B. Porter, Paul Hursky, Martin Siderius (SAIC), Mohsen Badiey (UD), Jerald Caruthers (USM), William S. Hodgkiss, Kaustubha Raghukumar (SIO), Dan Rouseff, Warren Fox (APL-UW), Christian de Moustier, Brian Calder, Barbara J. Kraft (UNH), Keyko McDonald (SPAWARSSC), Peter Stein, James K. Lewis, and Subramaniam Rajan (SSI).

  16. Throughput Performance of MC-CDMA HARQ Using ICI Cancellation

    NASA Astrophysics Data System (ADS)

    Fukuda, Kaoru; Nakajima, Akinori; Adachi, Fumiyuki

    Multi-carrier code division multiple access (MC-CDMA) is a promising wireless access technique for the next generation mobile communications systems, in which broadband packet data services will dominate. Hybrid automatic repeat request (HARQ) is an indispensable error control technique for high quality packet data transmission. The HARQ throughput performance of multi-code MC-CDMA degrades due to the presence of residual inter-code interference (ICI) after frequency-domain equalization (FDE). To reduce the residual ICI and improve the throughput performance, a frequency-domain soft interference cancellation (FDSIC) technique can be applied. An important issue is the generation of accurate residual ICI replica for FDSIC. In this paper, low-density parity-check coded (LDPC-coded) MC-CDMA HARQ is considered. We generate the residual ICI replica from a-posteriori log-likelihood ratio (LLR) of LDPC decoder output and evaluate, by computer simulation, the throughput performance in a frequency-selective Rayleigh fading channel. We show that if the residual ICI is removed, MC-CDMA can provide a throughput performance superior to orthogonal frequency division multiplexing (OFDM).

  17. Pilot-Assisted Adaptive Channel Estimation for Coded MC-CDMA with ICI Cancellation

    NASA Astrophysics Data System (ADS)

    Yui, Tatsunori; Tomeba, Hiromichi; Adachi, Fumiyuki

    One of the promising wireless access techniques for the next generation mobile communications systems is multi-carrier code division multiple access (MC-CDMA). MC-CDMA can provide good transmission performance owing to the frequency diversity effect in a severe frequency-selective fading channel. However, the bit error rate (BER) performance of coded MC-CDMA is inferior to that of orthogonal frequency division multiplexing (OFDM) due to the residual inter-code interference (ICI) after frequency-domain equalization (FDE). Recently, we proposed a frequency-domain soft interference cancellation (FDSIC) to reduce the residual ICI and confirmed by computer simulation that the MC-CDMA with FDSIC provides better BER performance than OFDM. However, ideal channel estimation was assumed. In this paper, we propose adaptive decision-feedback channel estimation (ADFCE) and evaluate by computer simulation the average BER and throughput performances of turbo-coded MC-CDMA with FDSIC. We show that even if a practical channel estimation is used, MC-CDMA with FDSIC can still provide better performance than OFDM.

  18. Performance enhancement of MC-CDMA system through novel sensitive bit algorithm aided turbo multi user detection.

    PubMed

    Kumaravel, Rasadurai; Narayanaswamy, Kumaratharan

    2015-01-01

    Multi carrier code division multiple access (MC-CDMA) system is a promising multi carrier modulation (MCM) technique for high data rate wireless communication over frequency selective fading channels. MC-CDMA system is a combination of code division multiple access (CDMA) and orthogonal frequency division multiplexing (OFDM). The OFDM parts reduce multipath fading and inter symbol interference (ISI) and the CDMA part increases spectrum utilization. Advantages of this technique are its robustness in case of multipath propagation and improve security with the minimize ISI. Nevertheless, due to the loss of orthogonality at the receiver in a mobile environment, the multiple access interference (MAI) appears. The MAI is one of the factors that degrade the bit error rate (BER) performance of MC-CDMA system. The multiuser detection (MUD) and turbo coding are the two dominant techniques for enhancing the performance of the MC-CDMA systems in terms of BER as a solution of overcome to MAI effects. In this paper a low complexity iterative soft sensitive bits algorithm (SBA) aided logarithmic-Maximum a-Posteriori algorithm (Log MAP) based turbo MUD is proposed. Simulation results show that the proposed method provides better BER performance with low complexity decoding, by mitigating the detrimental effects of MAI. PMID:25714917

  19. Performance Enhancement of MC-CDMA System through Novel Sensitive Bit Algorithm Aided Turbo Multi User Detection

    PubMed Central

    Kumaravel, Rasadurai; Narayanaswamy, Kumaratharan

    2015-01-01

    Multi carrier code division multiple access (MC-CDMA) system is a promising multi carrier modulation (MCM) technique for high data rate wireless communication over frequency selective fading channels. MC-CDMA system is a combination of code division multiple access (CDMA) and orthogonal frequency division multiplexing (OFDM). The OFDM parts reduce multipath fading and inter symbol interference (ISI) and the CDMA part increases spectrum utilization. Advantages of this technique are its robustness in case of multipath propagation and improve security with the minimize ISI. Nevertheless, due to the loss of orthogonality at the receiver in a mobile environment, the multiple access interference (MAI) appears. The MAI is one of the factors that degrade the bit error rate (BER) performance of MC-CDMA system. The multiuser detection (MUD) and turbo coding are the two dominant techniques for enhancing the performance of the MC-CDMA systems in terms of BER as a solution of overcome to MAI effects. In this paper a low complexity iterative soft sensitive bits algorithm (SBA) aided logarithmic-Maximum a-Posteriori algorithm (Log MAP) based turbo MUD is proposed. Simulation results show that the proposed method provides better BER performance with low complexity decoding, by mitigating the detrimental effects of MAI. PMID:25714917

  20. Design of a Baseband Transceiver for Multicarrier CDMA Communications

    NASA Astrophysics Data System (ADS)

    Tsai, Pei-Yun; Kang, Hsin-Yu; Chiueh, Tzi-Dar

    2005-12-01

    Multicarrier systems have become popular for their spectral efficiency and robustness against frequency-selective fading. Multicarrier code-division multiple access (MC-CDMA) is a technique that combines the advantage of multicarrier modulation with that of code-division multiple access (CDMA) to offer reliable high-data-rate downlink cellular communication services. In this paper, we present the architecture of a downlink baseband transceiver using the MC-CDMA technology under the same bandwidth requirement and channel condition as the third-generation wideband CDMA system. In the transmitter, a scrambling code is applied in order to reduce the peak-to-average power ratio (PAPR) of the transmitter output. In the receiver, we use a joint weighted least-squares (WLS) synchronization error estimation algorithm and a novel channel estimator. Both algorithms greatly enhance the system error-rate performance, as indicated by functional simulation. Simulation results also verify maximum aggregate coded data rates of [InlineEquation not available: see fulltext.] Mbps from 32/64 users in mobile/stationary multipath fading channel with a 3/4 convolutional code, respectively.

  1. Space-Time Coded MC-CDMA: Blind Channel Estimation, Identifiability, and Receiver Design

    NASA Astrophysics Data System (ADS)

    Sun, Wei; Li, Hongbin

    2003-12-01

    Integrating the strengths of multicarrier (MC) modulation and code division multiple access (CDMA), MC-CDMA systems are of great interest for future broadband transmissions. This paper considers the problem of channel identification and signal combining/detection schemes for MC-CDMA systems equipped with multiple transmit antennas and space-time (ST) coding. In particular, a subspace based blind channel identification algorithm is presented. Identifiability conditions are examined and specified which guarantee unique and perfect (up to a scalar) channel estimation when knowledge of the noise subspace is available. Several popular single-user based signal combining schemes, namely the maximum ratio combining (MRC) and the equal gain combining (EGC), which are often utilized in conventional single-transmit-antenna based MC-CDMA systems, are extended to the current ST-coded MC-CDMA (STC-MC-CDMA) system to perform joint combining and decoding. In addition, a linear multiuser minimum mean-squared error (MMSE) detection scheme is also presented, which is shown to outperform the MRC and EGC at some increased computational complexity. Numerical examples are presented to evaluate and compare the proposed channel identification and signal detection/combining techniques.

  2. Proceedings of the Mobile Satellite System Architectures and Multiple Access Techniques Workshop

    NASA Technical Reports Server (NTRS)

    Dessouky, Khaled

    1989-01-01

    The Mobile Satellite System Architectures and Multiple Access Techniques Workshop served as a forum for the debate of system and network architecture issues. Particular emphasis was on those issues relating to the choice of multiple access technique(s) for the Mobile Satellite Service (MSS). These proceedings contain articles that expand upon the 12 presentations given in the workshop. Contrasting views on Frequency Division Multiple Access (FDMA), Code Division Multiple Access (CDMA), and Time Division Multiple Access (TDMA)-based architectures are presented, and system issues relating to signaling, spacecraft design, and network management constraints are addressed. An overview article that summarizes the issues raised in the numerous discussion periods of the workshop is also included.

  3. A performance analysis of DS-CDMA and SCPC VSAT networks

    NASA Technical Reports Server (NTRS)

    Hayes, David P.; Ha, Tri T.

    1990-01-01

    Spread-spectrum and single-channel-per-carrier (SCPC) transmission techniques work well in very small aperture terminal (VSAT) networks for multiple-access purposes while allowing the earth station antennas to remain small. Direct-sequence code-division multiple-access (DS-CDMA) is the simplest spread-spectrum technique to use in a VSAT network since a frequency synthesizer is not required for each terminal. An examination is made of the DS-CDMA and SCPC Ku-band VSAT satellite systems for low-density (64-kb/s or less) communications. A method for improving the standardf link analysis of DS-CDMA satellite-switched networks by including certain losses is developed. The performance of 50-channel full mesh and star network architectures is analyzed. The selection of operating conditions producing optimum performance is demonstrated.

  4. Channel Capacity of MC-CDMA and Impact of Residual ICI

    NASA Astrophysics Data System (ADS)

    Adachi, Koichi; Adachi, Fumiyuki; Nakagawa, Masao

    Orthogonal frequency division multiplexing (OFDM), which uses a number of narrowband orthogonal sub-carriers, is a promising transmission technique. Also multi-carrier code division multi-access (MC-CDMA), which combines OFDM and frequency-domain spreading, has been attracting much attention as a future broadband wireless access. It was shown that MC-CDMA has lower channel capacity than OFDM, due to inter-code interference (ICI) resulting from orthogonality distortion caused by frequency-selective fading. Recently, many ICI cancellers have been proposed to mitigate the effect of ICI. In this paper, we derive a channel capacity expression for MC-CDMA assuming perfect ICI cancellation taking into account both frequency diversity gain and space diversity gain and compare it to that of OFDM. Furthermore, we derive a channel capacity expression for the case of imperfect ICI cancellation to discuss the impact of the residual ICI.

  5. Performance Analysis of SAC Optical PPM-CDMA System-Based Interference Rejection Technique

    NASA Astrophysics Data System (ADS)

    Alsowaidi, N.; Eltaif, Tawfig; Mokhtar, M. R.

    2016-03-01

    In this paper, we aim to theoretically analyse optical code division multiple access (OCDMA) system that based on successive interference cancellation (SIC) using pulse position modulation (PPM), considering the interference between the users, imperfection cancellation occurred during the cancellation process and receiver noises. Spectral amplitude coding (SAC) scheme is used to suppress the overlapping between the users and reduce the receiver noises effect. The theoretical analysis of the multiple access interference (MAI)-limited performance of this approach indicates the influence of the size of M-ary PPM on OCDMA system. The OCDMA system performance improves with increasing M-ary PPM. Therefore, it was found that the SIC/SAC-OCDMA system using PPM technique along with modified prime (MPR) codes used as signature sequence code offers significant improvement over the one without cancellation and it can support up to 103 users at the benchmarking value of bit error rate (BER) = 10-9 with prime number p = 11 while the system without cancellation scheme can support only up to 52 users.

  6. Analysis of multiple access techniques in multi-satellite and multi-spot mobile satellite systems

    NASA Technical Reports Server (NTRS)

    Corazza, Giovanni E.; Ferrarelli, Carlo; Vatalaro, Francesco

    1995-01-01

    In this paper the analysis of mobile satellite systems adopting constellations of multi-spot satellites over non-geostationary orbits is addressed. A link design procedure is outlined, taking into account system spectrum efficiency, probability of bit error and outage probability. A semi-analytic approach to the evaluation of outage probability in the presence of fading and imperfect power control is described, and applied to single channel per carrier (SCPC) and code division multiple access (CDMA) techniques. Some results are shown for the Globalstar, Iridium and Odyssey orbital configurations.

  7. Adaptive digital beamforming for a CDMA mobile communications payload

    NASA Technical Reports Server (NTRS)

    Munoz-Garcia, Samuel G.; Ruiz, Javier Benedicto

    1993-01-01

    In recent years, Spread-Spectrum Code Division Multiple Access (CDMA) has become a very popular access scheme for mobile communications due to a variety of reasons: excellent performance in multipath environments, high scope for frequency reuse, graceful degradation near saturation, etc. In this way, a CDMA system can support simultaneous digital communication among a large community of relatively uncoordinated users sharing a given frequency band. Nevertheless, there are also important problems associated with the use of CDMA. First, in a conventional CDMA scheme, the signature sequences of asynchronous users are not orthogonal and, as the number of active users increases, the self-noise generated by the mutual interference between users considerably degrades the performance, particularly in the return link. Furthermore, when there is a large disparity in received powers - due to differences in slant range or atmospheric attenuation - the non-zero cross-correlation between the signals gives rise to the so-called near-far problem. This leads to an inefficient utilization of the satellite resources and, consequently, to a drastic reduction in capacity. Several techniques were proposed to overcome this problem, such as Synchronized CDMA - in which the signature sequences of the different users are quasi-orthogonal - and power control. At the expense of increased network complexity and user coordination, these techniques enable the system capacity to be restored by equitably sharing the satellite resources among the users. An alternative solution is presented based upon the use of time-reference adaptive digital beamforming on board the satellite. This technique enables a high number of independently steered beams to be generated from a single phased array antenna, which automatically track the desired user signal and null the unwanted interference source. In order to use a time-reference adaptive antenna in a communications system, the main challenge is to obtain a

  8. Adaptive beamforming in a CDMA mobile satellite communications system

    NASA Technical Reports Server (NTRS)

    Munoz-Garcia, Samuel G.

    1993-01-01

    Code-Division Multiple-Access (CDMA) stands out as a strong contender for the choice of multiple access scheme in these future mobile communication systems. This is due to a variety of reasons such as the excellent performance in multipath environments, high scope for frequency reuse and graceful degradation near saturation. However, the capacity of CDMA is limited by the self-interference between the transmissions of the different users in the network. Moreover, the disparity between the received power levels gives rise to the near-far problem, this is, weak signals are severely degraded by the transmissions from other users. In this paper, the use of time-reference adaptive digital beamforming on board the satellite is proposed as a means to overcome the problems associated with CDMA. This technique enables a high number of independently steered beams to be generated from a single phased array antenna, which automatically track the desired user signal and null the unwanted interference sources. Since CDMA is interference limited, the interference protection provided by the antenna converts directly and linearly into an increase in capacity. Furthermore, the proposed concept allows the near-far effect to be mitigated without requiring a tight coordination of the users in terms of power control. A payload architecture will be presented that illustrates the practical implementation of this concept. This digital payload architecture shows that with the advent of high performance CMOS digital processing, the on-board implementation of complex DSP techniques -in particular digital beamforming- has become possible, being most attractive for Mobile Satellite Communications.

  9. Bit Error Rate Analysis for MC-CDMA Systems in Nakagami-[InlineEquation not available: see fulltext.] Fading Channels

    NASA Astrophysics Data System (ADS)

    Li, Zexian; Latva-aho, Matti

    2004-12-01

    Multicarrier code division multiple access (MC-CDMA) is a promising technique that combines orthogonal frequency division multiplexing (OFDM) with CDMA. In this paper, based on an alternative expression for the[InlineEquation not available: see fulltext.]-function, characteristic function and Gaussian approximation, we present a new practical technique for determining the bit error rate (BER) of multiuser MC-CDMA systems in frequency-selective Nakagami-[InlineEquation not available: see fulltext.] fading channels. The results are applicable to systems employing coherent demodulation with maximal ratio combining (MRC) or equal gain combining (EGC). The analysis assumes that different subcarriers experience independent fading channels, which are not necessarily identically distributed. The final average BER is expressed in the form of a single finite range integral and an integrand composed of tabulated functions which can be easily computed numerically. The accuracy of the proposed approach is demonstrated with computer simulations.

  10. Mobile multiple access study

    NASA Technical Reports Server (NTRS)

    1977-01-01

    Multiple access techniques (FDMA, CDMA, TDMA) for the mobile user and attempts to identify the current best technique are discussed. Traffic loading is considered as well as voice and data modulation and spacecraft and system design. Emphasis is placed on developing mobile terminal cost estimates for the selected design. In addition, design examples are presented for the alternative techniques of multiple access in order to compare with the selected technique.

  11. Security Performance of Optical CDMA Against Eavesdropping

    NASA Astrophysics Data System (ADS)

    Shake, Thomas H.

    2005-02-01

    Enhanced security has often been cited as an important benefit of optical CDMA (O-CDMA) signaling. However, the quality and degree of security enhancement has not been closely examined in the literature. This paper examines the degree and types of security that may be provided by O-CDMA encoding. A quantitative analysis of data confidentiality is presented for O-CDMA encoding techniques that use both time spreading and wavelength hopping. The probability of successful data interception is calculated as a function of several parameters, including signal-to-noise ratio and fraction of total available system capacity. For reasonable choices of system and encoding parameters, it is shown that increasing code complexity can increase the signal-to-noise ratio (SNR) required for an eavesdropper to "break" the encoding by only a few dB, while the processing of fewer than 100 bits by an eavesdropper can reduce the SNR required to break the encoding by up to 12 dB. The overall degree of confidentiality obtainable through O-CDMA encoding is also compared with that obtainable through standard cryptography. time-spreading/wavelength-hopping in particular, and O-CDMA in general, are found to provide considerably less data confidentiality than cryptography, and the confidentiality provided is found to be highly dependent on system design and implementation parameters.

  12. A Review on Successive Interference Cancellation Scheme Based on Optical CDMA Network

    NASA Astrophysics Data System (ADS)

    Alsowaidi, N.; Eltaif, T.; Mokhtar, M. R.

    2014-12-01

    Due to various desirable features of optical code division multiple access (OCDMA), it is believed this technique once developed and commercially available will be an integral part of optical access networks. Optical CDMA system suffers from a problem called multiple access interference (MAI) which limits the number of active users, it occurs when number of active users share the same carriers. The aim of this paper is to review successive interference cancellation (SIC) scheme based on optical CDMA system. The paper also reviews the system performance in presence of shot noise, thermal noise, and phase-induced intensity noise (PIIN). A comprehensive review on the mathematical model of SIC scheme using direct detection (DS) and spectral amplitude coding (SAC) were presented in this article.

  13. BER Performance Analysis of MC-CDMA with Overlap-FDE

    NASA Astrophysics Data System (ADS)

    Tomeba, Hiromichi; Takeda, Kazuaki; Adachi, Fumiyuki

    Recently, multi-carrier code division multiple access (MC-CDMA) has been attracting much attention as a broadband wireless access technique for the next generation mobile communication systems. Frequency-domain equalization (FDE) based on the minimum mean square error (MMSE) criterion can take advantage of the channel frequency-selectivity and improve the average bit error rate (BER) performance due to frequency-diversity gain. The conventional FDE requires the insertion of the guard interval (GI) to avoid the inter-block interference (IBI), resulting in the transmission efficiency loss. In this paper, an overlap FDE technique, which requires no GI insertion, is presented for MC-CDMA transmission. An expression for the conditional BER is derived for the given set of channel gains. The average BER performance in a frequency-selective Rayleigh fading channel is evaluated by Monte-Carlo numerical computation method using the derived conditional BER and is confirmed by computer simulation of the signal transmission.

  14. Measurements of Eavesdropping in a Wavelength/Time Optical CDMA (O-CDMA) System, with Data Confidentiality Implications

    SciTech Connect

    Mendez, A J; Hernandez, V J; Bennett, C V; Gagliardi, R M; Lennon, W J

    2005-07-29

    We report measurements on what an eavesdropper ''sees'' when tapping into a wavelength/time O-CDMA system in which 16 of 32 codes are ''lit''. Severe multi-access interference (MAI) provides some data confidentiality.

  15. All-optical code routing in interconnected optical CDMA and WDM ring networks.

    PubMed

    Deng, Yanhua; Fok, Mable P; Prucnal, Paul R; Wang, Ting

    2010-11-01

    We propose an all-optical hybrid network composed of optical code division multiple access (CDMA) rings interconnecting through a reconfigurable wavelength division multiplexing (WDM) metro area ring. This network retains the advantages of both the optical CDMA and WDM techniques, including asynchronous access and differentiated quality of service, while removing the hard limit on the number of subscribers and increasing network flexibility. The all-optical network is enabled by using nonlinear optical loop mirrors in an add/drop router (ADR) that performs code conversion, dropping, and switching asynchronously. We experimentally demonstrate the functionalities of the ADR in the proposed scheme asynchronously and obtain error-free performance. The bit-error rate measurements show acceptable power penalties for different code routes. PMID:21042372

  16. Overloaded Minimum Total Squared Correlation Signatures Based Pilot Aided System for MC-CDMA and STBC MC-CDMA

    NASA Astrophysics Data System (ADS)

    Arifianto, M. S.; Chekima, A.; Hamid, M. Y.; Barukang, L.; Viswacheda, D. V.

    This paper proposes multiple-access schemes based on Overloaded Minimum Total Squared Correlation (TSC) signatures, namely Pilot Aided Multi-Carrier Code-Division Multiple-Access (MC-CDMA) and Pilot Aided Space Time Block Codes (STBC) MC-CDMA. Since overloaded minimum TSC signatures were used as the spreading codes, a number of sub-channels in the MC-CDMA and STBC MC-CDMA schemes were not utilized for data transmission. These empty sub-channels can be exploited for comb-type pilot signaling. To maintain low system complexity, for the pilot sub-channels Least Square (LS) estimation was employed and for interpolating the characteristics of the data sub-channels linear interpolator was applied. The validity of the schemes is confirmed by comparing them with the original MC-CDMA method using Walsh-Hadamard orthogonal codes and also with Walsh-Hadamard based STBC MC-CDMA with block-type pilot. All systems use Equal Gain Combining (EGC) or Maximum Ratio Combining (MRC) in the MC-CDMA block at the receiver. The simulation result shows that although the spreading codes of interest are not fully orthogonal codes, for a low number of users the systems under investigation performed better than their Walsh-Hadamard based counterpart. This will be valuable for Wireless Personal Area Network (PAN) where the number of users is typically low.

  17. Comparison of CDMA and FDMA for the MobileStar(sm) system

    NASA Technical Reports Server (NTRS)

    Jacobs, I. M.; Gilhousen, K. S.; Weaver, L. A.; Renshaw, K.; Murphy, T.

    1988-01-01

    Spread-spectrum code division multiple access (CDMA) and single channel per carrier frequency division multiple access (FDMA) systems are compared for spectrum efficiency. CDMA is shown to have greater maximum throughput than FDMA for the MobileStar(sm) system which uses digital voice activated carriers and directive circularly polarized satellite antennas.

  18. Access Techniques for Document Image Databases.

    ERIC Educational Resources Information Center

    Walker, Frank L.; Thoma, George R.

    1990-01-01

    Describes access and retrieval techniques implemented as part of a research and development program in electronic imaging applied to document storage and retrieval at the National Library of Medicine. Design considerations for large image databases are discussed. (six references) (EAM)

  19. A CDMA synchronisation scheme

    NASA Technical Reports Server (NTRS)

    Soprano, C.

    1993-01-01

    CDMA (Code Division Multiple Access) is known to decrease inter-service interference in Satellite Communication Systems. Its performance is increased by chip quasi-synchronous operation which virtually eliminates the self-noise; however, the theory shows that the time error on the synchronization has to be kept at less than one tenth of a chip which, for 1 Mchip/sec. spreading rate, corresponds to 10(exp -7) sec. This, on the return-link, may only be achieved by means of a closed loop control system which, for mobile communication systems, has to be capable of autonomous operation. Until now some results have been reported on the feasibility of chip quasi-synchronous operation for mobile communication systems only including satellites on GEO (Geostationary Earth Orbit). In what follows, the basic principles are exposed, and results are presented showing how low chip synchronism error may be achieved by means of an autonomous control loop operating through satellites on any Earth orbit.

  20. Code Division Multiple Access system candidate for integrated modular avionics

    NASA Astrophysics Data System (ADS)

    Mendez, Antonio J.; Gagliardi, Robert M.

    1991-02-01

    There are government and industry trends towards avionics modularity and integrated avionics. Key requirements implicit in these trends are suitable data communication concepts compatible with the integration concept. In this paper we explore the use ofCode Division Multiple Access (CDMA) techniques as an alternative to collision detection and collision avoidance multiple access techniques.

  1. The 'SAFARI' Technique Using Retrograde Access Via Peroneal Artery Access

    SciTech Connect

    Zhuang, Kun Da; Tan, Seck Guan; Tay, Kiang Hiong

    2012-08-15

    The 'SAFARI' technique or subintimal arterial flossing with antegrade-retrograde intervention is a method for recanalisation of chronic total occlusions (CTOs) when subintimal angioplasty fails. Retrograde access is usually obtained via the popliteal, distal anterior tibial artery (ATA)/dorsalis pedis (DP), or distal posterior tibial artery (PTA). Distal access via the peroneal artery has not been described and has a risk of continued bleeding, leading to compartment syndrome due to its deep location. We describe our experience in two patients with retrograde access via the peroneal artery and the use of balloon-assisted hemostasis for these retrograde punctures. This approach may potentially give more options for endovascular interventions in lower limb CTOs.

  2. Impairments Computation for Routing Purposes in a Transparent-Access Optical Network Based on Optical CDMA and WDM

    NASA Astrophysics Data System (ADS)

    Musa, Ahmed

    2016-06-01

    Optical access networks are becoming more widespread and the use of multiple services might require a transparent optical network (TON). Multiplexing and privacy could benefit from the combination of wavelength division multiplexing (WDM) and optical coding (OC) and wavelength conversion in optical switches. The routing process needs to be cognizant of different resource types and characteristics such as fiber types, fiber linear impairments such as attenuation, dispersion, etc. as well as fiber nonlinear impairments such as four-wave mixing, cross-phase modulation, etc. Other types of impairments, generated by optical nodes or photonic switches, also affect the signal quality (Q) or the optical signal to noise ratio (OSNR), which is related to the bit error rate (BER). Therefore, both link and switch impairments must be addressed and somehow incorporated into the routing algorithm. However, it is not practical to fully integrate all photonic-specific attributes in the routing process. In this study, new routing parameters and constraints are defined that reflect the distinct characteristics of photonic networking. These constraints are applied to the design phase of TON and expressed as a cost or metric form that will be used in the network routing algorithm.

  3. First satellite mobile communication trials using BLQS-CDMA

    NASA Technical Reports Server (NTRS)

    Luzdemateo, Maria; Johns, Simon; Dothey, Michel; Vanhimbeeck, Carl; Deman, Ivan; Wery, Bruno

    1993-01-01

    In this paper, technical results obtained in the first MSBN Land mobile technical trial are reported. MSBN (Mobile Satellite Business Network) is a new program undertaken by the European Space Agency (ESA) to promote mobile satellite communication in Europe, in particular voice capability. The first phase of the MSBN system implementation plan is an experimental phase. Its purpose is to evaluate through field experiments the performance of the MSBN system prior to finalization of its specifications. Particularly, the objective is to verify in the field and possibly improve the performance of the novel satellite access technique BLQS-CDMA (Band Limited Quasi-Synchronous-Code Division Multiple Access), which is proposed as baseline for the MSBN.

  4. A European mobile satellite system concept exploiting CDMA and OBP

    NASA Technical Reports Server (NTRS)

    Vernucci, A.; Craig, A. D.

    1993-01-01

    This paper describes a novel Land Mobile Satellite System (LMSS) concept applicable to networks allowing access to a large number of gateway stations ('Hubs'), utilizing low-cost Very Small Aperture Terminals (VSAT's). Efficient operation of the Forward-Link (FL) repeater can be achieved by adopting a synchronous Code Division Multiple Access (CDMA) technique, whereby inter-code interference (self-noise) is virtually eliminated by synchronizing orthogonal codes. However, with a transparent FL repeater, the requirements imposed by the highly decentralized ground segment can lead to significant efficiency losses. The adoption of a FL On-Board Processing (OBP) repeater is proposed as a means of largely recovering this efficiency impairment. The paper describes the network architecture, the system design and performance, the OBP functions and impact on implementation. The proposed concept, applicable to a future generation of the European LMSS, was developed in the context of a European Space Agency (ESA) study contract.

  5. Burdick's Technique for Biliary Access Revisited.

    PubMed

    Goenka, Mahesh Kumar; Rai, Vijay Kumar

    2015-01-01

    The precut sphincterotomy is used to facilitate selective biliary access in cases of difficult biliary cannulation. Needle-knife precut papillotomy is the standard of care but is associated with a high rate of complications such as pancreatitis, duodenal perforation, bleeding, etc. Sometimes during bowing of the sphincterotome/cannula and the use of guide wire to facilitate biliary cannulation, inadvertent formation of a false passage occurs in the 10 to 11 o'clock direction. Use of this step to access the bile duct by the intramucosal incision technique was first described by Burdick et al., and since then two more studies have also substantiated the safety and efficacy of this non-needle type of precut sphincterotomy. In this review, we discuss this non-needle technique of precut sphincterotomy and also share our experience using this "Burdick's technique." PMID:25674522

  6. Ultrasonic array for obstacle detection based on CDMA with Kasami codes.

    PubMed

    Diego, Cristina; Hernández, Alvaro; Jiménez, Ana; Alvarez, Fernando J; Sanz, Rebeca; Aparicio, Joaquín

    2011-01-01

    This paper raises the design of an ultrasonic array for obstacle detection based on Phased Array (PA) techniques, which steers the acoustic beam through the environment by electronics rather than mechanical means. The transmission of every element in the array has been encoded, according to Code Division for Multiple Access (CDMA), which allows multiple beams to be transmitted simultaneously. All these features together enable a parallel scanning system which does not only improve the image rate but also achieves longer inspection distances in comparison with conventional PA techniques. PMID:22247675

  7. Why is CDMA the solution for mobile satellite communication

    NASA Technical Reports Server (NTRS)

    Gilhousen, Klein S.; Jacobs, Irwin M.; Padovani, Roberto; Weaver, Lindsay A.

    1989-01-01

    It is demonstrated that spread spectrum Code Division Multiple Access (CDMA) systems provide an economically superior solution to satellite mobile communications by increasing the system maximum capacity with respect to single channel per carrier Frequency Division Multiple Access (FDMA) systems. Following the comparative analysis of CDMA and FDMA systems, the design of a model that was developed to test the feasibility of the approach and the performance of a spread spectrum system in a mobile environment. Results of extensive computer simulations as well as laboratory and field tests results are presented.

  8. Percutaneous Large Arterial Access Closure Techniques.

    PubMed

    McGraw, Charles J; Gandhi, Ripal T; Vatakencherry, Geogy; Baumann, Frederic; Benenati, James F

    2015-06-01

    Endovascular repair has replaced open surgical repair as the standard of care for treatment of abdominal and thoracic aortic aneurysms in appropriately selected patients owing to its decreased morbidity and length of stay and excellent clinical outcomes. Similarly, there is a progressive trend toward total percutaneous repair of the femoral artery using percutaneous suture-mediated closure devices over open surgical repair due to decreased complications and procedure time. This article describes the techniques of closure for large-bore vascular access most commonly used in endovascular treatment of abdominal and thoracic aortic aneurysms, but could similarly be applied to any procedure requiring large-bore arterial access, such as transcatheter aortic valve replacement. PMID:26070624

  9. Blind ICA detection based on second-order cone programming for MC-CDMA systems

    NASA Astrophysics Data System (ADS)

    Jen, Chih-Wei; Jou, Shyh-Jye

    2014-12-01

    The multicarrier code division multiple access (MC-CDMA) technique has received considerable interest for its potential application to future wireless communication systems due to its high data rate. A common problem regarding the blind multiuser detectors used in MC-CDMA systems is that they are extremely sensitive to the complex channel environment. Besides, the perturbation of colored noise may negatively affect the performance of the system. In this paper, a new coherent detection method will be proposed, which utilizes the modified fast independent component analysis (FastICA) algorithm, based on approximate negentropy maximization that is subject to the second-order cone programming (SOCP) constraint. The aim of the proposed coherent detection is to provide robustness against small-to-medium channel estimation mismatch (CEM) that may arise from channel frequency response estimation error in the MC-CDMA system, which is modulated by downlink binary phase-shift keying (BPSK) under colored noise. Noncoherent demodulation schemes are preferable to coherent demodulation schemes, as the latter are difficult to implement over time-varying fading channels. Differential phase-shift keying (DPSK) is therefore the natural choice for an alternative modulation scheme. Furthermore, the new blind differential SOCP-based ICA (SOCP-ICA) detection without channel estimation and compensation will be proposed to combat Doppler spread caused by time-varying fading channels in the DPSK-modulated MC-CDMA system under colored noise. In this paper, numerical simulations are used to illustrate the robustness of the proposed blind coherent SOCP-ICA detector against small-to-medium CEM and to emphasize the advantage of the blind differential SOCP-ICA detector in overcoming Doppler spread.

  10. Performance comparison of modulation techniques for underlay cognitive radio transceivers

    NASA Astrophysics Data System (ADS)

    Khan, Imtiyaz; Singh, Poonam

    2013-01-01

    In this paper, we present a quantitative comparison of two agile modulation techniques employed by cognitive radio transceivers operating in a dynamic spectrum access (DSA) network. One of the modulation techniques is single carrier frequency division multiple access (SC-FDMA). The other modulation technique under study is a variant of multicarrier code division multiple access (MCCDMA). Although several studies comparing conventional OFDM and MC-CDMA has been conducted in literature to justify robust error performance of MC-CDMA, a quantitative performance evaluation of these schemes has not been performed when employed in a DSA network. In this paper we show that their performances can be significantly different from the conventional setup. Analytical expressions for the error probability of an SC-FDMA transceiver have been derived and compared with computer simulation results. The results show that the error robustness of SC-FDMA is relatively better then MC-CDMA in underlay communication.

  11. Optical CDMA system using bacteriorhodopsin for optical data storage

    PubMed

    Bae; Yang; Jin; Lee; Park

    1999-11-01

    An optical CDMA (code division multiple access) system for the optical data storage using bacteriorhodopsin (BR) is reported as an application of the BR materials. The desired signal of multiple input can be recorded and reconstructed by use of orthogonal codes. An experimental setup is proposed and demonstrated. PMID:10585180

  12. Efficient Blind Estimation of MC-CDMA Carrier Frequency Offset

    NASA Astrophysics Data System (ADS)

    Chang, Ann-Chen; Hsu, Chun; Su, Ing-Jiunn

    This letter presents an efficient blind carrier frequency offset (CFO) estimate approach for multicarrier-code division multiple access (MC-CDMA) system. It can reduce the searching grids required and improve the CFO estimating accuracy compared with conventional searching-based algorithms. Simulation results are provided for illustrating the effectiveness of the proposed blind estimate approach.

  13. Fast frequency hopping codes applied to SAC optical CDMA network

    NASA Astrophysics Data System (ADS)

    Tseng, Shin-Pin

    2015-06-01

    This study designed a fast frequency hopping (FFH) code family suitable for application in spectral-amplitude-coding (SAC) optical code-division multiple-access (CDMA) networks. The FFH code family can effectively suppress the effects of multiuser interference and had its origin in the frequency hopping code family. Additional codes were developed as secure codewords for enhancing the security of the network. In considering the system cost and flexibility, simple optical encoders/decoders using fiber Bragg gratings (FBGs) and a set of optical securers using two arrayed-waveguide grating (AWG) demultiplexers (DeMUXs) were also constructed. Based on a Gaussian approximation, expressions for evaluating the bit error rate (BER) and spectral efficiency (SE) of SAC optical CDMA networks are presented. The results indicated that the proposed SAC optical CDMA network exhibited favorable performance.

  14. Iterative Multiuser Detection with Soft Decision-Directed Channel Estimation for MC-IDMA and Performance Comparison with Chip-Interleaved MC-CDMA

    NASA Astrophysics Data System (ADS)

    Suyama, Satoshi; Suzuki, Hiroshi; Fukawa, Kazuhiko; Zhang, Li

    This paper applies iterative multiuser detection employing a new channel estimation scheme to multicarrier interleave-division multiple access (MC-IDMA), called OFDM-IDMA, which is expected to offer improved spectral efficiency in mobile communications. The MC-IDMA transmitter uses both a low-rate channel code and an individual chip interleaver for each user. The MC-IDMA receiver, which this paper focuses upon, repeats the iterative multiuser detection and soft decision-directed channel estimation (SDCE) by exploiting log-likelihood ratios (LLRs) of the coded bits which the maximum a posteriori (MAP)-based channel decoders for all users provide. SDCE estimates channel impulse responses of all users by the least-mean-square (LMS) algorithm, which aims to minimize the mean squared error between the received signal and its replica. This paper investigates the performance of MC-IDMA employing SDCE and compares it with those of three MC-CDMA techniques. Computer simulations demonstrate that MC-IDMA employing SDCE outperforms time-spread MC-CDMA and frequency-spread MC-CDMA, and that it can achieve almost the same bit error rate performance as chip-interleaved MC-CDMA while requiring lower complexity.

  15. Demonstration of Record BER and Number of Users for Optical CDMA (O-CDMA), with Implications to Secure Communications

    SciTech Connect

    Mendez, A J; Hernandez, V J; Bennett, C V; Gagliardi, R M; Lennon, W J

    2005-02-25

    We demonstrate a BER of 10{sup -11} for 16 simultaneous users, using wavelength/time O-CDMA. We show the extent to which severe multi-access interference can be used to mask and/or degrade the signal from an intruder.

  16. Accessibility Techniques for Museum Web Sites.

    ERIC Educational Resources Information Center

    Anable, Susan; Alonzo, Adam

    Like other public institutions, museums strive to make their facilities accessible to people with disabilities, yet these same patrons may be hindered in their use of museum Web sites by electronic accessibility barriers. This presentation demonstrates that access was a primary design factor in the Virtual Museum Tour, part of the Web site of The…

  17. Decision feedback equalization for CDMA in indoor wireless communications

    NASA Astrophysics Data System (ADS)

    Abdulrahman, Majeed; Sheikh, Asrar U. H.; Falconer, David D.

    1994-05-01

    Commercial interest in Code Division Multiple Access (CDMA) systems has risen dramatically in the last few years. It yields a potential increase in capacity over other access schemes, because it provides protection against interference, multipath, fading, and jamming. Recently, several interference cancellation schemes for CDMA have been proposed but they require information about all interfering active users or some channel parameters. In this paper, we present an adaptive fractionally spaced decision feedback equalizer (DFE) for a CDMA system in an indoor wireless Rayleigh fading environment. This system only uses information about the desired user's spreading code and a training sequence. An analysis on the optimum performance of the DFE receiver shows the advantages of this system over others in terms of capacity improvements. A simulation of this system is also presented to study the convergence properties and implementation considerations of the DFE receiver. Effects on the performance because of sudden birth and death of users in the CDMA system and bit error rate performanceof the DFE receiver is also presented. of the DFE receiver is also presented.

  18. BER Performance of Downlink MC-CDMA with ORC in Nakagami-m Fading Channel

    NASA Astrophysics Data System (ADS)

    Lee, Yusung; Kim, Namshik; Park, Hyuncheol

    In this letter, we derive an exact bit error rate (BER) expression for downlink multi-carrier code division multiple access (MC-CDMA) systems with orthogonal restoring combining (ORC) in Nakagami-m fading channel. A simple approximated expression is also provided. For uncoded and coded MC-CDMA systems, the BER expressions are calculated based on the moment generating function (MGF) of the combined fading random variable. The derived analytic expressions are verified by simulation results.

  19. Evaluation of CDMA system capacity for mobile satellite system applications

    NASA Technical Reports Server (NTRS)

    Smith, Partrick O.; Geraniotis, Evaggelos A.

    1988-01-01

    A specific Direct-Sequence/Pseudo-Noise (DS/PN) Code-Division Multiple-Access (CDMA) mobile satellite system (MSAT) architecture is discussed. The performance of this system is evaluated in terms of the maximum number of active MSAT subscribers that can be supported at a given uncoded bit-error probability. The evaluation decouples the analysis of the multiple-access capability (i.e., the number of instantaneous user signals) from the analysis of the multiple-access mutliplier effect allowed by the use of CDMA with burst-modem operation. We combine the results of these two analyses and present numerical results for scenarios of interest to the mobile satellite system community.

  20. Performance Analysis of a New Coded TH-CDMA Scheme in Dispersive Infrared Channel with Additive Gaussian Noise

    NASA Astrophysics Data System (ADS)

    Hamdi, Mazda; Kenari, Masoumeh Nasiri

    2013-06-01

    We consider a time-hopping based multiple access scheme introduced in [1] for communication over dispersive infrared links, and evaluate its performance for correlator and matched filter receivers. In the investigated time-hopping code division multiple access (TH-CDMA) method, the transmitter benefits a low rate convolutional encoder. In this method, the bit interval is divided into Nc chips and the output of the encoder along with a PN sequence assigned to the user determines the position of the chip in which the optical pulse is transmitted. We evaluate the multiple access performance of the system for correlation receiver considering background noise which is modeled as White Gaussian noise due to its large intensity. For the correlation receiver, the results show that for a fixed processing gain, at high transmit power, where the multiple access interference has the dominant effect, the performance improves by the coding gain. But at low transmit power, in which the increase of coding gain leads to the decrease of the chip time, and consequently, to more corruption due to the channel dispersion, there exists an optimum value for the coding gain. However, for the matched filter, the performance always improves by the coding gain. The results show that the matched filter receiver outperforms the correlation receiver in the considered cases. Our results show that, for the same bandwidth and bit rate, the proposed system excels other multiple access techniques, like conventional CDMA and time hopping scheme.

  1. “Wire-Target” Technique for Precise Vascular Access

    PubMed Central

    Hamzeh, Rabih K.; Danon, Saar; Shah, Sanjay; Levi, Daniel S.; Moore, John W.

    2009-01-01

    Herein, we describe a technique that facilitates percutaneous vascular access when the traditional method of achieving access is unsuccessful. For multiple reasons, gaining access to small vessels in pediatric patients is sometimes difficult. In instances of atrial, ventricular, or great arterial communications, a wire can be positioned from a vein or artery across the communications into an artery or vein to which access needs to be gained. This wire then serves as a target for vascular access. All pediatric patients who underwent cardiac catheterization at Mattel Children's Hospital from July 2003 through June 2006, and at Rady Children's Hospital from July through December 2006, were considered for the wire-target technique when access could not be achieved in vessels of interest via traditional methods. Fifteen wire-target procedures were undertaken in 14 patients (ages, 4 d–11 yr). By use of a directional catheter, a Wholey or 0.014-inch coronary wire was positioned in a vessel to which access was desired. Anterior–posterior and lateral fluoroscopic views were used to target the wire and attain vascular access. The patients' diagnoses, ages, vessels to which access was gained via traditional methods and via the wire-target technique, and wire routes were retrospectively recorded, and outcomes were noted. In all instances, the technique was performed successfully and without complications. In selected pediatric patients in whom percutaneous vascular access is difficult, the wire-target technique may be used safely and effectively to establish arterial, venous, or transhepatic access. PMID:19693307

  2. Joint Transceiver Optimization in MC-CDMA Systems

    NASA Astrophysics Data System (ADS)

    Seo, Kyoungnam; Latchman, Haniph

    Multicarrier code division multiple access (MC-CDMA) systems are well suited for high data rate wireless multimedia services, due to their ability to convert frequency-selective fading channels to distinct flat fading channels with low complexity fast Fourier transform (FFT) devices. However, when multiple users are present, the performance of MC-CDMA systems is degraded by the multiuser interference (MUI) when the channel is frequency-selective. In order to mitigate MUI, we present a joint algorithm that combines transmit power control, antenna array processing and multiuser detection at the receiver. Interestingly, the frequency-selectivity that entails the MUI also provides multipath diversity which can help suppress the MUI. Performance of the algorithm in a number of MC-CDMA system models is evaluated in terms of the average transmit power to achieve the target signal to interference plus noise ratio (SINR). Simulations confirm the outstanding performance of this algorithm compared with the existing ones in MC-CDMA systems.

  3. A hybrid path-oriented code assignment CDMA-based MAC protocol for underwater acoustic sensor networks.

    PubMed

    Chen, Huifang; Fan, Guangyu; Xie, Lei; Cui, Jun-Hong

    2013-01-01

    Due to the characteristics of underwater acoustic channel, media access control (MAC) protocols designed for underwater acoustic sensor networks (UWASNs) are quite different from those for terrestrial wireless sensor networks. Moreover, in a sink-oriented network with event information generation in a sensor field and message forwarding to the sink hop-by-hop, the sensors near the sink have to transmit more packets than those far from the sink, and then a funneling effect occurs, which leads to packet congestion, collisions and losses, especially in UWASNs with long propagation delays. An improved CDMA-based MAC protocol, named path-oriented code assignment (POCA) CDMA MAC (POCA-CDMA-MAC), is proposed for UWASNs in this paper. In the proposed MAC protocol, both the round-robin method and CDMA technology are adopted to make the sink receive packets from multiple paths simultaneously. Since the number of paths for information gathering is much less than that of nodes, the length of the spreading code used in the POCA-CDMA-MAC protocol is shorter greatly than that used in the CDMA-based protocols with transmitter-oriented code assignment (TOCA) or receiver-oriented code assignment (ROCA). Simulation results show that the proposed POCA-CDMA-MAC protocol achieves a higher network throughput and a lower end-to-end delay compared to other CDMA-based MAC protocols. PMID:24193100

  4. MC-CDMA with frequency domain diversity reception for sectored indoor wireless cellular networks

    NASA Astrophysics Data System (ADS)

    Sibanda, Andrew; Dlodlo, Mqhele E.

    2001-07-01

    A Monte Carlo simulation was conducted to assess the performance of Multi-Carrier Code Division Multiple Access (MC-CDMA) in a sectored cell, in an indoor environment. In each sector, terminal schedule packet transmission using slotted p-persistent Inhibit Sense Multiple Access, while the packets themselves are transmitted using MC-CDMA. The simulated bit error rate performance of MC-CDMA with combining strategies maximal ratio combining (MRC) and equal gain combining (EGC) used in the frequency domain are presented. A comparison is made between analytically determined bit error probability for a single user in an additive white Gaussian noise channel using binary phase shift keying (BPSK), and simulated bit error rate for a single user using MC-CDMA with MRC and EGC. The determination of the number of sectors in a cell is also given. MC-CDMA with diversity combining outperforms BPSK in a non-fading AWGN channel. Further, as the user-number increases, EGC performs better than MRC if these combining strategies are used with MC-CDMA. Finally, the results show the basis for determining the number of sectors in a cell. When using slotted p-persistent ISMA, it is envisaged that only a single user will transmit at a time in a sector.

  5. Orthogonal Multi-Carrier DS-CDMA with Frequency-Domain Equalization

    NASA Astrophysics Data System (ADS)

    Tanaka, Ken; Tomeba, Hiromichi; Adachi, Fumiyuki

    Orthogonal multi-carrier direct sequence code division multiple access (orthogonal MC DS-CDMA) is a combination of orthogonal frequency division multiplexing (OFDM) and time-domain spreading, while multi-carrier code division multiple access (MC-CDMA) is a combination of OFDM and frequency-domain spreading. In MC-CDMA, a good bit error rate (BER) performance can be achieved by using frequency-domain equalization (FDE), since the frequency diversity gain is obtained. On the other hand, the conventional orthogonal MC DS-CDMA fails to achieve any frequency diversity gain. In this paper, we propose a new orthogonal MC DS-CDMA that can obtain the frequency diversity gain by applying FDE. The conditional BER analysis is presented. The theoretical average BER performance in a frequency-selective Rayleigh fading channel is evaluated by the Monte-Carlo numerical computation method using the derived conditional BER and is confirmed by computer simulation of the orthogonal MC DS-CDMA signal transmission.

  6. Design of a Virtual Quadrant Receiver for 4-ary Pulse Position Modulation/Optical CDMA (4-ary PPM/O-CDMA)

    SciTech Connect

    Mendez, A J; Gagliardi, R M; Hernandez, V J; Bennett, C V; Lennon, W J

    2006-07-03

    We describe a receiver that performs optical code division multiple access (O-CDMA) decoding followed by pulse position modulation (PPM) symbol detection that behaves like a radar quadrant receiver. Simulations determine the impact of multi-access interference on symbol detection for up to 32 users.

  7. FIR Filter of DS-CDMA UWB Modem Transmitter

    NASA Astrophysics Data System (ADS)

    Kang, Kyu-Min; Cho, Sang-In; Won, Hui-Chul; Choi, Sang-Sung

    This letter presents low-complexity digital pulse shaping filter structures of a direct sequence code division multiple access (DS-CDMA) ultra wide-band (UWB) modem transmitter with a ternary spreading code. The proposed finite impulse response (FIR) filter structures using a look-up table (LUT) have the effect of saving the amount of memory by about 50% to 80% in comparison to the conventional FIR filter structures, and consequently are suitable for a high-speed parallel data process.

  8. A WDM/Optical-CDMA (WDM/O-CDMA) Concept for Avionics Integration

    SciTech Connect

    Mendez, A J; Hernandez, V J; Gagliardi, R M; Braun, S W; Bennett, C V; Lennon, W J

    2005-06-02

    We describe a concept where WDM and O-CDMA share a set of discrete wavelengths and components while using similar modulation formats. O-CDMA acts as a channel multiplier. Experiments show the feasibility of >2X channel multiplication.

  9. Intercarrier Interference Reduction in MC-CDMA System through Second Order Duobinary Coded Phase Rotated Conjugate Cancellation Scheme

    PubMed Central

    Chitra, S.; Kumaratharan, N.

    2015-01-01

    Multi-carrier code division multiple access (MC-CDMA) technique is one of the strong candidates for next generation wireless mobile communication systems. Multi-carrier systems are very much sensitive to carrier frequency offset (CFO) results in intercarrier interference (ICI). To mitigate ICI without any spectral loss, a second order duobinary coded phase rotated conjugate cancellation algorithm is proposed in this paper. In the conventional phase rotated conjugate cancellation (PRCC) technique, one path carries the MC-CDMA signal with a phase spin of ϕ and the other path carries the conjugate of the first path signal with -ϕ phase spin. This artificial phase rotation allows the transmitter to tune the transmitted signals so that the ICI effects could be mutually cancelled at the receiver. Although the PRCC technique reduces the spectral efficiency, the limitation can be overcome by the joint second order duobinary coding scheme with PRCC technique. In the proposed method, the correlative coding between the binary symbols modulated on adjacent subcarriers is used to reduce the ICI without any spectral loss. Simulation results show that the proposed PRCC method provides better carrier to interference ratio (CIR) and bit error rate (BER) performances compared to the conventional conjugate cancellation (CC) technique. PMID:25790029

  10. Intercarrier interference reduction in MC-CDMA system through second order duobinary coded phase rotated conjugate cancellation scheme.

    PubMed

    Chitra, S; Kumaratharan, N

    2015-01-01

    Multi-carrier code division multiple access (MC-CDMA) technique is one of the strong candidates for next generation wireless mobile communication systems. Multi-carrier systems are very much sensitive to carrier frequency offset (CFO) results in intercarrier interference (ICI). To mitigate ICI without any spectral loss, a second order duobinary coded phase rotated conjugate cancellation algorithm is proposed in this paper. In the conventional phase rotated conjugate cancellation (PRCC) technique, one path carries the MC-CDMA signal with a phase spin of ϕ and the other path carries the conjugate of the first path signal with -ϕ phase spin. This artificial phase rotation allows the transmitter to tune the transmitted signals so that the ICI effects could be mutually cancelled at the receiver. Although the PRCC technique reduces the spectral efficiency, the limitation can be overcome by the joint second order duobinary coding scheme with PRCC technique. In the proposed method, the correlative coding between the binary symbols modulated on adjacent subcarriers is used to reduce the ICI without any spectral loss. Simulation results show that the proposed PRCC method provides better carrier to interference ratio (CIR) and bit error rate (BER) performances compared to the conventional conjugate cancellation (CC) technique. PMID:25790029

  11. Generalized Multicarrier CDMA: Unification and Linear Equalization

    NASA Astrophysics Data System (ADS)

    Giannakis, Georgios B.; Anghel, Paul A.; Wang, Zhengdao

    2005-12-01

    Relying on block-symbol spreading and judicious design of user codes, this paper builds on the generalized multicarrier (GMC) quasisynchronous CDMA system that is capable of multiuser interference (MUI) elimination and intersymbol interference (ISI) suppression with guaranteed symbol recovery, regardless of the wireless frequency-selective channels. GMC-CDMA affords an all-digital unifying framework, which encompasses single-carrier and several multicarrier (MC) CDMA systems. Besides the unifying framework, it is shown that GMC-CDMA offers flexibility both in full load (maximum number of users allowed by the available bandwidth) and in reduced load settings. A novel blind channel estimation algorithm is also derived. Analytical evaluation and simulations illustrate the superior error performance and flexibility of uncoded GMC-CDMA over competing MC-CDMA alternatives especially in the presence of uplink multipath channels.

  12. Comparison of FDMA and CDMA for second generation land-mobile satellite communications

    NASA Technical Reports Server (NTRS)

    Yongacoglu, A.; Lyons, R. G.; Mazur, B. A.

    1990-01-01

    Code Division Multiple Access (CDMA) and Frequency Division Multiple Access (FDMA) (both analog and digital) systems capacities are compared on the basis of identical link availabilities and physical propagation models. Parameters are optimized for a bandwidth limited, multibeam environment. For CDMA, the benefits of voice activated carriers, antenna discrimination, polarization reuse, return link power control and multipath suppression are included in the analysis. For FDMA, the advantages of bandwidth efficient modulation/coding combinations, voice activated carriers, polarization reuse, beam placement, and frequency staggering were taken into account.

  13. DS-CDMA satellite diversity reception for personal satellite communication: Downlink performance analysis

    NASA Technical Reports Server (NTRS)

    DeGaudenzi, Riccardo; Giannetti, Filippo

    1995-01-01

    The downlink of a satellite-mobile personal communication system employing power-controlled Direct Sequence Code Division Multiple Access (DS-CDMA) and exploiting satellite-diversity is analyzed and its performance compared with a more traditional communication system utilizing single satellite reception. The analytical model developed has been thoroughly validated by means of extensive Monte Carlo computer simulations. It is shown how the capacity gain provided by diversity reception shrinks considerably in the presence of increasing traffic or in the case of light shadowing conditions. Moreover, the quantitative results tend to indicate that to combat system capacity reduction due to intra-system interference, no more than two satellites shall be active over the same region. To achieve higher system capacity, differently from terrestrial cellular systems, Multi-User Detection (MUD) techniques are likely to be required in the mobile user terminal, thus considerably increasing its complexity.

  14. Model Based Prediction of Uplink Multi-Path Fading Channel Response for Pre-Equalization in Mobile MC-CDMA Systems

    NASA Astrophysics Data System (ADS)

    Mkrtchyan, Gagik; Naito, Katsuhiro; Mori, Kazuo; Kobayashi, Hideo

    Multi-carrier code division multiple access (MC-CDMA) has been considered as one of the promising techniques for the next generation of mobile communication systems because of its efficient bandwidth usage, robustness to the multi-path fading and simple channel-sharing scheme. However, MC-CDMA cannot be employed in the uplink communication where the transmitted signal from each user propagates through the different multi-path fading channel, and the received signals are no longer orthogonal at the base station. As a result, bit error rate (BER) performance in the uplink MC-CDMA communication would be strongly degraded due to the occurrence of multi-user interference (MUI). To solve the MUI problem in the uplink MC-CDMA, the pre-equalization method was proposed in which the uplink signal is pre-equalized at the user terminal by using the channel response estimated from the downlink. Although the pre-equalization method is very effective for the stationary uplink channel with fixed users, it is hard to be employed in the time varying fading channel with mobile users, because there is a big difference in the channel responses between downlink and uplink. For the efficient MUI compensation, each user terminal would be required to predict the future channel conditions based on the current observation. This paper proposes a method for model based uplink channel response prediction by employing the spectral decomposition of the downlink channel impulse response. Computer simulation results show that the proposed method can achieve the accurate prediction of channel response for mobile users during the uplink transmission and allows the effective MUI compensation.

  15. Dispersion Compensation Requirements for Optical CDMA Using WDM Lasers

    SciTech Connect

    Mendez, A J; Hendandez, V J; Feng, H X C; Heritage, J P; Lennon, W J

    2001-12-10

    Optical code division multiple access (O-CDMA) uses very narrow transmission pulses and is thus susceptible to fiber optic link impairments. When the O-CDMA is implemented as wavelength/time (W/T) matrices which use wavelength division multiplexing (WDM) sources such as multi-frequency laser transmitters, the susceptibility may be higher due to: (a) the large bandwidth utilized and (b) the requirement that the various wavelength components of the codes be synchronized at the point of modulation and encoding as well as after (optical) correlation. A computer simulation based on the nonlinear Schroedinger equation, developed to study optical networking on the National Transparent Optical Network (NTON), was modified to characterize the impairments on the propagation and decoding of W/T matrix codes over a link of the NTON. Three critical link impairments were identified by the simulation: group velocity dispersion (GVD); the flatness of the optical amplifier gain; and the slope of the GVD. Subsequently, experiments were carried out on the NTON link to verify and refine the simulations as well as to suggest improvements in the W/T matrix signal processing design. The NTON link measurements quantified the O-CDMA dispersion compensation requirements. Dispersion compensation management is essential to assure the performance of W/T matrix codes.

  16. Optimal Power Distribution Control for Multicode MC-CDMA with Zero-Forcing Successive Interference Cancellation

    NASA Astrophysics Data System (ADS)

    Tan, Mizhou; Ibars, Christian; Bar-Ness, Yeheskel

    2005-12-01

    Multicarrier CDMA (MC-CDMA) has become a promising candidate for future wireless multimedia communications for its robustness to frequency-selective fading and its flexibility for handling multiple data rates. Among different multirate access schemes, multicode MC-CDMA is attractive for its high performance, good flexibility in rate matching, and low complexity. However, its performance is limited by self-interference (SI) and multiuser interference (MUI). In this paper a zero-forcing successive interference cancellation (ZF-SIC) receiver is used to mitigate this problem for multicode MC-CDMA. Furthermore, optimal power distribution control (PDC), which minimizes each user's bit error rate (BER), is considered. Our results show that, in correlated Rayleigh fading channels, the ZF-SIC receiver integrated with the optimal PDC dramatically improves the performance of the multicode MC-CDMA system in comparison to other receivers proposed in the literature. Moreover, the optimal PDC significantly outperforms the PDC based on equal BER criterion, particularly under a short-term transmit power constraint.

  17. Demonstration of high-speed multi-user multi-carrier CDMA visible light communication

    NASA Astrophysics Data System (ADS)

    Yang, Chao; Wang, Yuanquan; Wang, Yiguang; Huang, Xingxing; Chi, Nan

    2015-02-01

    We experimentally demonstrated a high-speed multi-user multi-carrier code-division multiple access (MC-CDMA) visible light communication (VLC) system. By employing a commercially available red light emitting diode (LED) and an avalanche photo diode (APD), we achieved a 16-user VLC system enabled by MC-CDMA, pre- and post-equalization, with an overall bit rate of 750 Mb/s over 1.5 m free-space transmission. The measured bit error ratio (BER) of each user is below the 7% pre-forward-error-correction (pre-FEC) threshold of 3.8×10-3.

  18. Satellite multiple access systems for mobile communication

    NASA Technical Reports Server (NTRS)

    Lewis, J. L.

    1979-01-01

    This paper considers multiple access techniques for a mobile radio system which incorporates a geosynchronous orbiting satellite repeater through which mobile terminals communicate. The communication capacities of FDMA, TDMA and CDMA systems are examined for a 4 MHz bandwidth system to serve up to 10,000 users. An FDMA system with multibeam coverage is analyzed in detail. The system includes an order-wire network for demand-access control and reassignment of satellite channels. Satellite and terminal configurations are developed to a block diagram level and system costs and implementation requirements are discussed.

  19. MC-CDMA for optical wireless communications

    NASA Astrophysics Data System (ADS)

    Luan, Yingzi; Jiang, Guang; Li, Jiandong

    2005-11-01

    MC-CDMA is a spectrum-efficient modulation in RF systems. Here it is used in optical wireless communications. Performance is simulated by using multiuser detection. Spatial Diversity is also considered and analyzed.

  20. Propagation of 2.5 Gb/s Asynchronous, Concurrent, Optical CDMA Signals Through a 214 Kilometer Fiber Optic Link

    SciTech Connect

    Mendez, A.J.; Feng, H.X.C.; Heritage, J.P.; Morookian, J.; Gagliardi, R.M.

    2000-03-16

    The propagation of optical Code Division Multiple Access (CDMA) signals was studied by computer simulation. Group velocity dispersion produces the worst impairment. With dispersion management, the decoder successfully recovers the signals, even in the presence of severe multi-access interference.

  1. Cross-layer optimization for video transmission over multirate GMC-CDMA wireless links.

    PubMed

    Bandyopadhyay, Saurav K; Partasides, George; Kondi, Lisimachos P

    2008-06-01

    In this paper, we consider the problem of video transmission over wireless generalized multicarrier code division multiple access (GMC-CDMA) systems. Such systems offer deterministic elimination of multiple access interference. A scalable video source codec is used and a multirate setup is assumed, i.e., each video user is allowed to occupy more than one GMC-CDMA channels. Furthermore, each of these channels can utilize a different number of subcarriers. We propose a cross-layer optimization method to select the source coding rate, channel coding rate, number of subcarriers per GMC-CDMA channel and transmission power per GMC-CDMA channel given a maximum transmission power for each video user and an available chip rate. Universal rate distortion characteristics (URDC) are used to approximate the expected distortion at the receiver. The proposed algorithm is optimal in the operational rate distortion sense, subject to the specific setup used and the approximation caused by the use of the URDC. Experimental results are presented and conclusions are drawn. PMID:18482895

  2. Multiwavelength optical code-division-multiple-access communication systems

    NASA Astrophysics Data System (ADS)

    Lam, Cedric Fung

    1999-10-01

    There has been tremendous interest in applying spread spectrum and code division multiple access (CDMA) techniques to fiber optic communication systems. In this dissertation, we review the previous work on optical CDMA systems, and we propose and then demonstrate new optical CDMA system designs. The explosive growth in bandwidth demand during the recent years have compelled engineers to achieve one bit per hertz or more bandwidth utilization in optical fibers. We point out that in order to achieve efficient bandwidth utilization, full orthogonality is required in optical CDMA system. At the same time, one would like to avoid having an optical local oscillator, which significantly increases the system complexity. We have studied two spectrally encoded optical CDMA systems, both of which give us full orthogonality. A balanced optical detector, which `computes' the difference between two photodetectors signals, is used to obtain negative outputs from positive-only optical intensity signals, thus achieving full orthogonality in both systems. The first system, complementary spectral intensity encoding, is a fully non-coherent. A novel balanced transmitter has been invented for this system. Unfortunately, the performance of this system is limited by beat noise interference, sometimes called speckle noise. In the second system, spectral phase encoding, a multi-wavelength mode-locked laser source is employed. Spectral phase encoding is applied to various frequency components. By sending the unmodulated carrier along the optical fiber to the receiver, we can achieve the effect of coherent demodulation without using an optical local oscillator. While this system can avoid speckle noise, it is eventually limited by cumulative shot noise. We will show in this dissertation, that cumulative shot noise is unavoidable in all optical CDMA systems. Therefore the ultimate achievable performance of optical CDMA systems under shot noise limitation will be analyzed in this work. Lastly

  3. A Wideband Satcom Based Avionics Network with CDMA Uplink and TDM Downlink

    NASA Technical Reports Server (NTRS)

    Agrawal, D.; Johnson, B. S.; Madhow, U.; Ramchandran, K.; Chun, K. S.

    2000-01-01

    The purpose of this paper is to describe some key technical ideas behind our vision of a future satcom based digital communication network for avionics applications The key features of our design are as follows: (a) Packetized transmission to permit efficient use of system resources for multimedia traffic; (b) A time division multiplexed (TDM) satellite downlink whose physical layer is designed to operate the satellite link at maximum power efficiency. We show how powerful turbo codes (invented originally for linear modulation) can be used with nonlinear constant envelope modulation, thus permitting the satellite amplifier to operate in a power efficient nonlinear regime; (c) A code division multiple access (CDMA) satellite uplink, which permits efficient access to the satellite from multiple asynchronous users. Closed loop power control is difficult for bursty packetized traffic, especially given the large round trip delay to the satellite. We show how adaptive interference suppression techniques can be used to deal with the ensuing near-far problem; (d) Joint source-channel coding techniques are required both at the physical and the data transport layer to optimize the end-to-end performance. We describe a novel approach to multiple description image encoding at the data transport layer in this paper.

  4. Techniques to Access Databases and Integrate Data for Hydrologic Modeling

    SciTech Connect

    Whelan, Gene; Tenney, Nathan D.; Pelton, Mitchell A.; Coleman, Andre M.; Ward, Duane L.; Droppo, James G.; Meyer, Philip D.; Dorow, Kevin E.; Taira, Randal Y.

    2009-06-17

    This document addresses techniques to access and integrate data for defining site-specific conditions and behaviors associated with ground-water and surface-water radionuclide transport applicable to U.S. Nuclear Regulatory Commission reviews. Environmental models typically require input data from multiple internal and external sources that may include, but are not limited to, stream and rainfall gage data, meteorological data, hydrogeological data, habitat data, and biological data. These data may be retrieved from a variety of organizations (e.g., federal, state, and regional) and source types (e.g., HTTP, FTP, and databases). Available data sources relevant to hydrologic analyses for reactor licensing are identified and reviewed. The data sources described can be useful to define model inputs and parameters, including site features (e.g., watershed boundaries, stream locations, reservoirs, site topography), site properties (e.g., surface conditions, subsurface hydraulic properties, water quality), and site boundary conditions, input forcings, and extreme events (e.g., stream discharge, lake levels, precipitation, recharge, flood and drought characteristics). Available software tools for accessing established databases, retrieving the data, and integrating it with models were identified and reviewed. The emphasis in this review was on existing software products with minimal required modifications to enable their use with the FRAMES modeling framework. The ability of four of these tools to access and retrieve the identified data sources was reviewed. These four software tools were the Hydrologic Data Acquisition and Processing System (HDAPS), Integrated Water Resources Modeling System (IWRMS) External Data Harvester, Data for Environmental Modeling Environmental Data Download Tool (D4EM EDDT), and the FRAMES Internet Database Tools. The IWRMS External Data Harvester and the D4EM EDDT were identified as the most promising tools based on their ability to access and

  5. Percutaneous Endovascular Salvage Techniques for Implanted Venous Access Device Dysfunction

    SciTech Connect

    Breault, Stéphane; Glauser, Frédéric; Babaker, Malik Doenz, Francesco Qanadli, Salah Dine

    2015-06-15

    PurposeImplanted venous access devices (IVADs) are often used in patients who require long-term intravenous drug administration. The most common causes of device dysfunction include occlusion by fibrin sheath and/or catheter adherence to the vessel wall. We present percutaneous endovascular salvage techniques to restore function in occluded catheters. The aim of this study was to evaluate the feasibility, safety, and efficacy of these techniques.Methods and MaterialsThrough a femoral or brachial venous access, a snare is used to remove fibrin sheath around the IVAD catheter tip. If device dysfunction is caused by catheter adherences to the vessel wall, a new “mechanical adhesiolysis” maneuver was performed. IVAD salvage procedures performed between 2005 and 2013 were analyzed. Data included clinical background, catheter tip position, success rate, recurrence, and rate of complication.ResultsEighty-eight salvage procedures were performed in 80 patients, mostly women (52.5 %), with a mean age of 54 years. Only a minority (17.5 %) of evaluated catheters were located at an optimal position (i.e., cavoatrial junction ±1 cm). Mechanical adhesiolysis or other additional maneuvers were used in 21 cases (24 %). Overall technical success rate was 93.2 %. Malposition and/or vessel wall adherences were the main cause of technical failure. No complications were noted.ConclusionThese IVAD salvage techniques are safe and efficient. When a catheter is adherent to the vessel wall, mechanical adhesiolysis maneuvers allow catheter mobilization and a greater success rate with no additional risk. In patients who still require long-term use of their IVAD, these procedures can be performed safely to avoid catheter replacement.

  6. Development of Pulse Position Modulation/Optical CDMA (PPM/O-CDMA) for Gb/s Fiber Optic Networking

    SciTech Connect

    Mendez, A J; Hernandez, V J; Gagliardi, R M; Bennett, C V; Lennon, W J

    2006-05-25

    Pulse position modulation (PPM) in lasercom systems is known to provide potential advantages over other modulation schemes. [1]. In PPM, a periodic time frame is established and data is transmitted by placing a pulse in any one of several subintervals (or ''slots'') within each frame. In PPM/O-CDMA all users use the same frame structure and each transmits its unique address code in place of the PPM pulse. The advantage of PPM as a pulsed signal format is that (1) a single pulse can transmit multiple bits during each frame; (2) decoding (determining which subinterval contains the pulse) is by comparison rather than threshold tests (as in on-off-keying); (3) each user transmits in only a small fraction of the frame, hence the multi-access interference (MAI) of any user statistically spreads over the entire frame time, reducing the chance of overlap with any other user; and (4) under an average power constraint, increasing frame time increases the peak pulse power (i.e., PPM trades average power for peak power). The most straightforward approach to implementing PPM/O-CDMA data modulator inserts the PPM pulse modulation first, then imposes the O-CDMA coding. A pulsed PPM modulator converts bits (words) into pulse positions. In the case of wavelength/time (W/T) matrix codes, multi-wavelength pulses are generated at the beginning of each frame, at the frame rate. For M-ary PPM, a block of k bits represents M = 2{sup k} unique interval positions in the frame corresponding to M-l specific time delays (the zero delay is also a position). PPM modulation is achieved by shifting the initial pulse into an interval position with delay D(i) (i=0,1,2,..,M-1). The location of a pulse position (selection of a delay) therefore identifies a unique k-bit word in the frame. At the receiver, determining which delay occurs relative to the frame start time decodes the data word. The probability of pulse overlap between two users decreases with M, which therefore decreases the probability

  7. Improvement of BER performance in MIMO-CDMA systems by using initial-phase optimized gold codes

    NASA Astrophysics Data System (ADS)

    Develi, Ibrahim; Filiz, Meryem

    2013-01-01

    This paper describes a new approach to improve the bit error rate (BER) performance of a multiple-input multiple-output code-division multiple-access (MIMO-CDMA) system over quasi-static Rayleigh fading channels. The system considered employs robust space-time successive interference cancellation detectors and initial-phase optimized Gold codes for the improvement. The results clearly indicate that the use of initial-phase optimized Gold codes can significantly improve the BER performance of the system compared to the performance of a multiuser MIMO-CDMA system with conventional nonoptimized Gold codes. Furthermore, this performance improvement is achieved without any increase in system complexity.

  8. Self-Consistent Signal-to-Noise Analysis of CDMA Multiuser Detection with M-Ary Phase-Shift Keying

    NASA Astrophysics Data System (ADS)

    Kato, Hiroyuki; Okada, Masato; Miyoshi, Seiji

    2013-02-01

    We present a theory of the performance of parallel interference cancellation (PIC) for code division multiple access (CDMA) multiuser detection with M-ary phase-shift keying (M-ary PSK) in the large-system limit. The behavior of PIC is essentially the same as that of the associative memory model. Therefore, we analyze the PIC for CDMA using self-consistent signal-to-noise analysis (SCSNA), which was developed to describe the behavior of the associative memory model. We obtain a quantitative description of the performance of PIC.

  9. A new watermarking approach based on combination of reversible watermarking and CDMA in spatial and DWT domain

    NASA Astrophysics Data System (ADS)

    Bekkouche, S.; Chouarfia, A.

    2011-06-01

    Image watermarking can be defined as a technique that allows insertion of imperceptible and indelible digital data into an image. In addition to its initial application which is the copyright, watermarking can be used in other fields, particularly in the medical field in order to contribute to secure images shared on the network for telemedicine applications. In this report we study some watermarking methods and the comparison result of their combination, the first one is based on the CDMA (Code Division Multiple Access) in DWT and spatial domain and its aim is to verify the image authenticity whereas the second one is the reversible watermarking (the least significant bits LSB and cryptography tools) and the reversible contrast mapping RCM its objective is to check the integrity of the image and to keep the Confidentiality of the patient data. A new scheme of watermarking is the combination of the reversible watermarking method based on LSB and cryptography tools and the method of CDMA in spatial and DWT domain to verify the three security properties Integrity, Authenticity and confidentiality of medical data and patient information .In the end ,we made a comparison between these methods within the parameters of quality of medical images. Initially, an in-depth study on the characteristics of medical images would contribute to improve these methods to mitigate their limits and to optimize the results. Tests were done on IRM kind of medical images and the quality measurements have been done on the watermarked image to verify that this technique does not lead to a wrong diagnostic. The robustness of the watermarked images against attacks has been verified on the parameters of PSNR, SNR, MSE and MAE which the experimental result demonstrated that the proposed algorithm is good and robust in DWT than in spatial domain.

  10. Techniques in distal access of wide-necked giant intracranial aneurysms during treatment with flow diversion

    PubMed Central

    Kan, Peter; Wakhloo, Ajay Kumar; Mokin, Maxim; Puri, Ajit

    2015-01-01

    Background: Accessing the normal distal vessel in treatment of wide-necked giant intracranial aneurysms with flow diversion can be difficult. Case Description: Through illustrative cases, the authors present several useful techniques in distal access of wide-necked giant aneurysms during flow diversion treatment. Obtaining an optimal projection that separates the outflow limb from the aneurysm is most critical. Each of the three techniques described enabled the distal access to giant intracranial aneurysms during treatment with flow diversion. Conclusion: The looped-around technique, balloon-assisted technique, and retrograde access are valuable strategies in crossing the aneurysm if direct distal access cannot be obtained. PMID:26069851

  11. Performance evaluation of CCI on the forward CDMA channel

    NASA Astrophysics Data System (ADS)

    Alam, M. S.; Alsharif, S.; Hossain, A. H. M. Z.

    2013-05-01

    This paper focuses on the performance of cochannel interference (CCI) which is the primary factor to limit the capacity of wireless communication systems. Several cellular network architectures have been proposed in the literature to reduce the cochannel interference, but none of them appears to effectively tackle this problem. Microzoning is the technique, where the cells are further divided into smaller zones. The advantage of this technique is that the cochannel interference in the cellular system is reduced because the cell maintains a particular coverage radius. The objective of this paper is to analyze the performance of cochannel interference on the forward channels of the proposed microzone based CDMA cellular systems operating with perfect power control in an effort to reduce the cochannel interference. Simulation results showed that the proposed technique can effectively minimize cochannel interference and the proposed architecture can be used for practical applications.

  12. New packet scheduling algorithm in wireless CDMA data networks

    NASA Astrophysics Data System (ADS)

    Wang, Yu; Gao, Zhuo; Li, Shaoqian; Li, Lemin

    2002-08-01

    The future 3G/4G wireless communication systems will provide internet access for mobile users. Packet scheduling algorithms are essential for QoS of diversified data traffics and efficient utilization of radio spectrum.This paper firstly presents a new packet scheduling algorithm DSTTF under the assumption of continuous transmission rates and scheduling intervals for CDMA data networks . Then considering the constraints of discrete transmission rates and fixed scheduling intervals imposed by the practical system, P-DSTTF, a modified version of DSTTF, is brought forward. Both scheduling algorithms take into consideration of channel condition, packet size and traffic delay bounds. The extensive simulation results demonstrate that the proposed scheduling algorithms are superior to some typical ones in current research. In addition, both static and dynamic wireless channel model of multi-level link capacity are established. These channel models sketch better the characterizations of wireless channel than two state Markov model widely adopted by the current literature.

  13. Performance Analysis of Direct-Sequence Code-Division Multiple-Access Communications with Asymmetric Quadrature Phase-Shift-Keying Modulation

    NASA Technical Reports Server (NTRS)

    Wang, C.-W.; Stark, W.

    2005-01-01

    This article considers a quaternary direct-sequence code-division multiple-access (DS-CDMA) communication system with asymmetric quadrature phase-shift-keying (AQPSK) modulation for unequal error protection (UEP) capability. Both time synchronous and asynchronous cases are investigated. An expression for the probability distribution of the multiple-access interference is derived. The exact bit-error performance and the approximate performance using a Gaussian approximation and random signature sequences are evaluated by extending the techniques used for uniform quadrature phase-shift-keying (QPSK) and binary phase-shift-keying (BPSK) DS-CDMA systems. Finally, a general system model with unequal user power and the near-far problem is considered and analyzed. The results show that, for a system with UEP capability, the less protected data bits are more sensitive to the near-far effect that occurs in a multiple-access environment than are the more protected bits.

  14. Posterior tibial artery access using transradial techniques: retrograde approach to inaccessible lower extremity lesions.

    PubMed

    Londoño, Juan Carlos; Singh, Vikas; Martinez, Claudia A

    2012-06-01

    Percutaneous intervention of chronic limb ischemia is often limited by vascular access especially in patients with previous surgical interventions. This warrants development of alternative endovascular techniques, particularly for patients in whom traditional ipsilateral antegrade or contralateral retrograde access has failed or is not possible. We describe a novel approach to the posterior tibial artery using retrograde access with transradial techniques including closure devices in two patients with inaccessible antegrade access. PMID:21432983

  15. A cost-effective differential mobility analyzer (cDMA) for multiple DMA column applications

    SciTech Connect

    Mei, F.; Fu, H.; Chen, D.-R.

    2011-05-04

    In aerosol research and applications, a differential mobility analyzer (DMA) is now considered the standard tool for sizing and classifying monodisperse particles in the sub-micrometer and nanometer size ranges. However, DMA application at the pilot or industrial production scale remains infeasible because of the low mass throughput. A simple way to scale up DMA operation is to use multiple DMA columns. The manufacture and maintenance costs of existing DMAs, however, limit such a scale-up. A cost-effective DMA column (named cDMA) has thus been developed in this work to address the above issue. To reduce its manufacturing cost, the prototype was constructed using parts requiring little machining. The cDMA column was also designed for easy maintenance and easy variation of the classification length for any application-specified size range. In this study, prototypes with two particle classification lengths, 1.75 and 4.50 cm, were constructed and their performance was experimentally evaluated at sheath-to-aerosol flowrate ratios of 5:1, 10:1, and 15:1 via the tandem DMA (TDMA) technique. It was concluded that both prototype cDMAs, operated at a sheath/aerosol flowrate ratio less than 15:1 and with a polydisperse aerosol flowrate of 1.0 lpm, achieved sizing resolution comparable to that offered by Nano-DMA. The longer cDMA had comparable transmission efficiency to that of Nano-DMA, and the shorter cDMA exceeded the performance of Nano-DMA. Hence, the cDMA with the shorter (1.75 cm) classification length is better suited for the characterization of macromolecular samples.

  16. The effects of simultaneous combined exposure to CDMA and WCDMA electromagnetic fields on rat testicular function.

    PubMed

    Lee, Hae-June; Jin, Yeung Bae; Kim, Tae-Hong; Pack, Jeong-Ki; Kim, Nam; Choi, Hyung-Do; Lee, Jae-Seon; Lee, Yun-Sil

    2012-05-01

    Wireless mobile phones and other telecommunication devices are used extensively in daily life. We therefore examined the effects of combined exposure to radiofrequency electromagnetic fields (RF-EMF) on rat testicular function, specifically with respect to sensitive processes such as spermatogenesis. Male rats were exposed to single code division multiple access (CDMA) and wideband code division multiple access (WCDMA) RF signals for 12 weeks. The RF exposure schedule comprised 45 min/day, 5 days/week for a total of 12 weeks. The whole-body average specific absorption rate (SAR) of CDMA and WCDMA was 2.0 W/kg each or 4.0 W/kg in total. We then investigated the correlates of testicular function such as sperm count in the cauda epididymis, testosterone concentration in the blood serum, malondialdehyde concentrations in the testes and epididymis, frequency of spermatogenesis stages, and appearance of apoptotic cells in the testes. We also immunoblotted for p53, bcl2, GADD45, cyclin G, and HSP70 in the testes of sham- and combined RF-exposed animals. Based on the results, we concluded that simultaneous exposure to CDMA and WCDMA RF-EMFs at 4.0 W/kg SAR did not have any observable adverse effects on rat spermatogenesis. PMID:22012556

  17. Lack of teratogenicity after combined exposure of pregnant mice to CDMA and WCDMA radiofrequency electromagnetic fields.

    PubMed

    Lee, Hae-June; Lee, Jae-Seon; Pack, Jeong-Ki; Choi, Hyung-Do; Kim, Nam; Kim, Sung-Ho; Lee, Yun-Sil

    2009-11-01

    Concern about the possible adverse effects of radiofrequency (RF)-field exposure on public health has increased because of the extensive use of wireless mobile phones and other telecommunication devices in daily life. The murine fetus is a very sensitive indicator of the effects of stress or stimuli in the environment. Therefore, we investigated the teratogenic effects of multi-signal radiofrequency electromagnetic fields (RF EMFs) on mouse fetuses. Pregnant mice were simultaneously exposed to two types of RF signals, single code division multiple access (CDMA) and wideband code division multiple access (WCDMA). Mice received two 45-min RF-field exposures, separated by a 15-min interval, daily throughout the entire gestation period. The whole-body average specific absorption rate (SAR) of CDMA or WCDMA was 2.0 W/kg. The animals were killed humanely on the 18th day of gestation and fetuses were examined for mortality, growth retardation, changes in head size and other morphological abnormalities. From the results, we report for the first time that simultaneous experimental exposure to CDMA and WCDMA RF EMFs did not cause any observable adverse effects on mouse fetuses. PMID:19883234

  18. Effects of electromagnetic fields emitted from W-CDMA-like mobile phones on sleep in humans.

    PubMed

    Nakatani-Enomoto, Setsu; Furubayashi, Toshiaki; Ushiyama, Akira; Groiss, Stefan Jun; Ueshima, Kazumune; Sokejima, Shigeru; Simba, Ally Y; Wake, Kanako; Watanabe, So-ichi; Nishikawa, Masami; Miyawaki, Kaori; Taki, Masao; Ugawa, Yoshikazu

    2013-12-01

    In this study, we investigated subjective and objective effects of mobile phones using a Wideband Code Division Multiple Access (W-CDMA)-like system on human sleep. Subjects were 19 volunteers. Real or sham electromagnetic field (EMF) exposures for 3 h were performed before their usual sleep time on 3 consecutive days. They were exposed to real EMF on the second or third experimental day in a double-blind design. Sleepiness and sleep insufficiency were evaluated the next morning. Polysomnograms were recorded for analyses of the sleep variables and power spectra of electroencephalograms (EEG). No significant differences were observed between the two conditions in subjective feelings. Sleep parameters including sleep stage percentages and EEG power spectra did not differ significantly between real and sham exposures. We conclude that continuous wave EMF exposure for 3 h from a W-CDMA-like system has no detectable effects on human sleep. PMID:24037832

  19. PAPR reduction in SFBC MIMO MC-CDMA systems via user reservation

    NASA Astrophysics Data System (ADS)

    García-Otero, Mariano; Paredes-Hernández, Luis Alberto

    2011-12-01

    The combination of multicarrier code-division multiple access (MC-CDMA) with multiple-input multiple-output technology is attractive for broadband wireless communications. However, the large values of the peak-to-average power ratio (PAPR) of the signals transmitted on different antennas can lead to nonlinear distortion and a subsequent degradation of the system performance. In this article, we propose a PAPR reduction scheme for space-frequency block coding MC-CDMA downlink transmissions that does not require any processing at the receiver side because it is based on the addition of signals employing the spreading codes of inactive users. As the minimization of the PAPR leads to a second-order cone programming problem that can be too cumbersome for a practical implementation, some strategies to mitigate the complexity of the proposed method are also explored.

  20. Accuracy of dilution techniques for access flow measurement during hemodialysis.

    PubMed

    Krivitski, N M; MacGibbon, D; Gleed, R D; Dobson, A

    1998-03-01

    Access flow is now widely measured by creating artificial recirculation with the dialysis lines reversed and using dilution methods that sense either ultrasound velocity, electrical impedance, optical, or thermal changes. This study identifies and quantifies factors that influence the accuracy of access flow measurements and recommends ways to reduce these errors. Two major sources of access flow measurement error are identified, arising firstly from the second pass of the indicator by recirculation through the cardiopulmonary system (cardiopulmonary recirculation, CPR), and secondly from changes in venous line blood flow (Qb) and vascular access flow induced by the pressure of venous bolus injections. These errors are considered from theory, by direct measurement of access flow in a sheep model, and by analysis of clinical data. Two extremes for the venous introduction of indicator can be considered in access flow measurements, a slow infusion, which perturbs neither the venous line flow nor access flow but increases the error attributable to the second pass of the indicator by recirculation through cardiopulmonary system, or rapid injection, which eases separation of the second pass of the indicator signal but generates changes in the venous flow and access flow. If CPR is not eliminated, the area added to that of the first pass of indicator ranges up to 40%. Good time resolution could permit the separation of the areas generated by the first and second passage of the indicator. In sheep experiments, injections of 5 or 10 mL into a venous port close to the vascular access caused Qb to change by 20% to 40%. Both the animal experiments and analysis of raw data collected during routine clinical dialysis showed that moving the injection site sufficiently far from the patient, before or into the venous bubble trap, reduced the increase in Qb to only approximately 5% during the critical time when the concentration curve is changing for most tubing brands (Baxter, Belco

  1. Space-time adaptive decision feedback neural receivers with data selection for high-data-rate users in DS-CDMA systems.

    PubMed

    de Lamare, Rodrigo C; Sampaio-Neto, Raimundo

    2008-11-01

    A space-time adaptive decision feedback (DF) receiver using recurrent neural networks (RNNs) is proposed for joint equalization and interference suppression in direct-sequence code-division multiple-access (DS-CDMA) systems equipped with antenna arrays. The proposed receiver structure employs dynamically driven RNNs in the feedforward section for equalization and multiaccess interference (MAI) suppression and a finite impulse response (FIR) linear filter in the feedback section for performing interference cancellation. A data selective gradient algorithm, based upon the set-membership (SM) design framework, is proposed for the estimation of the coefficients of RNN structures and is applied to the estimation of the parameters of the proposed neural receiver structure. Simulation results show that the proposed techniques achieve significant performance gains over existing schemes. PMID:18990643

  2. Opportunities for Process Monitoring Techniques at Delayed Access Facilities

    SciTech Connect

    Curtis, Michael M.; Gitau, Ernest TN; Johnson, Shirley J.; Schanfein, Mark; Toomey, Christopher

    2013-09-20

    Except for specific cases where the International Atomic Energy Agency (IAEA) maintains a continuous presence at a facility (such as the Japanese Rokkasho Reprocessing Plant), there is always a period of time or delay between the moment a State is notified or aware of an upcoming inspection, and the time the inspector actually enters the material balance area or facility. Termed by the authors as “delayed access,” this period of time between inspection notice and inspector entrance to a facility poses a concern. Delayed access also has the potential to reduce the effectiveness of measures applied as part of the Safeguards Approach for a facility (such as short-notice inspections). This report investigates the feasibility of using process monitoring to address safeguards challenges posed by delayed access at a subset of facility types.

  3. Static contrast technique for creating transpedal arterial access in patients with tibioperoneal occlusions.

    PubMed

    Chang, John Chien-Hwa; Lin, Lau-Shen; Chiu, Chih-Hung

    2013-10-01

    Transpedal arterial access is a useful but challenging technique for patients with tibioperoneal occlusions. It is associated with a long learning curve, requires the administration of a large amount of contrast media, and exposes patients and interventionists to additional radiation. Here we present a new technique by which it is easier and faster to create a transpedal arterial access. PMID:23769939

  4. The Accessible Pantry: Food Identification Tips, Tools, and Techniques

    ERIC Educational Resources Information Center

    Sokol-McKay, Debra A.; Michels, Dianne

    2006-01-01

    For individuals with visual impairments, poorly designed labels can be barriers to receiving safe and independent access to important information about products in daily use. The authors discuss how organization and proper lighting can reduce the amount of labeling needed on food products and indicate how individuals with visual impairments can…

  5. BER Performance for Downlink MC-CDMA Systems over Rician Fading Channels

    NASA Astrophysics Data System (ADS)

    Hou, Zhihua; Dubey, Vimal K.

    2005-12-01

    We consider downlink multicarrier code-division multiple-access (MC-CDMA) systems using binary phase-shift keying (BPSK) modulation scheme and maximal ratio combining (MRC) in frequency-selective Rician fading channels. A time-domain method to obtain bit error rate (BER) by calculating moment generating function (MGF) of the decision variable for a tapped-delay-line channel model is proposed. This method does not require any assumption regarding the statistical or spectral distribution of multiple access interference (MAI), and it is also not necessary to assume that the fading encountered by the subcarriers is independent of each other. The analytical formula is also verified by simulations.

  6. Peak power minimization in indoor CDMA communications using clusters of antennas

    NASA Astrophysics Data System (ADS)

    Abolhassani, Bahman

    "Battery life" and "cost" constraints are presenting new challenges for the design of wireless networks. The major focus of past research on transmit power control, diversity, modulation and coding techniques has been limited to maximizing coverage and/or capacity for cellular telephone systems. However, for battery powered wireless handsets connected through indoor wireless links, the optimization objective is shifting from link efficiency to battery efficiency and cost. In this thesis, the battery life of handsets and the cost of network are both addressed for an indoor code division multiple access (CDMA) communications system using time division duplex (TDD). A wireless handset needs a large dynamic range transmitter amplifier in order to overcome channel path loss and fading. This makes the amplifier inefficient such that its power consumption becomes proportional to the peak transmit power. Therefore, the amplifier needs a large, heavy and expensive battery which lasts for only a few hours. Indoor wireless users, however, need small, light, low cost handsets with batteries that last for days rather than for a few hours. To achieve a long battery life for handsets, a system architecture is proposed in which each cell uses a central base station along with several radioports. The radioports placed at optimal or near-optimal locations in order to minimize the maximum path loss experienced by handsets. Each radioport may use more than one antenna to combat Rayleigh fading. The central base station selects the radioport that provides the strongest maximally ratio combined signal. An infra-structure cost model is developed for the proposed system, which depends on the peak transmit power capability of handsets and of other system parameters and performances. The number of parameters affecting the network infra-structure cost is high, which makes the cost minimization problematic. To avoid large computation time, a new network planning approach is proposed: its

  7. Space Station multiple access communications system

    NASA Technical Reports Server (NTRS)

    Olson, Nanci A.

    1986-01-01

    The development of a multiple access communications system (MACS) for the space-to-space communications on the Space Station is discussed. The communications capabilities of the FHMA, CDMA, TDMA, SDMA, and FDMA techniques are evaluated; FDMA was selected for the space-to-space communications on the Space Station because of its lower complexity and growth capability. The proposed space-to-space multiple access system for the Space Station is a digitally modulated Ku-band FDMA system with a distributed architecture; this system would transmit on frequencies between 13.4 and 13.7 GHz and receive on frequencies between 14.6 and 14.89 GHz, and the bandwidth will support seven high-data-rate users and 12 low-data-rate users. The IF components and antennas for the MACS are examined. A multiple access breadboard design is described.

  8. Preliminary evaluation of the use of a CDMA-based emergency telemedicine system.

    PubMed

    Kang, Jaemin; Chun, Honggu; Shin, Il Hyung; Shin, Sang Do; Suh, Gil Joon; Kim, Hee Chan

    2006-01-01

    We have conducted a preliminary evaluation of the use of a code division multiple access (CDMA)-based emergency telemedicine system to be used by emergency rescuers providing first-aid treatment for patients. The prototype system included five instrumentation modules for measuring non-invasive arterial blood pressure (NIBP), arterial oxygen saturation (SpO(2)), six-channel electrocardiogram (ECG), blood glucose concentration and body temperature. The patient data were transferred to a doctor's PC through CDMA and TCP/IP networks using an embedded personal digital assistant (PDA) phone. Performance tests in the laboratory showed that the system provided reliable values with error ranges within +/-1% for heart rate, +/-5 mmHg for NIBP, +/-2% for SpO(2) and +/-1% for glucose. The feasibility of the prototype system was then evaluated with 15 real emergency patients on Jeju Island over a two-month period. Measured data were transmitted from a moving ambulance to the emergency medical centre without significant CDMA connection loss or transmission errors. The average transfer time was 8 min. Four emergency doctors and 11 rescuers completed a questionnaire. There were favourable reviews from the users. PMID:17227609

  9. Performance comparison of audio codecs for high-quality color ring-back-tone services over CDMA

    NASA Astrophysics Data System (ADS)

    Lee, Young Han; Kim, Hong Kook; Yu, Jaehwang; Park, SeongSoo; Lee, Dong-Hahk; Woo, Daesic

    2006-10-01

    In this paper, we investigate the use of existing audio codecs for the purpose of a high quality color ring-back- tone service. First of all, we exploit the limitations of the enhanced variable rate codec (EVRC) in a view of music quality because EVRC is a standard speech coder employed in a code division multiple access (CDMA) system. In order to figure it out which current existing audio codec is suitable to deliver music over CDMA or wideband CDMA (W-CDMA), several audio codecs such as two different versions of MPEG AAC and the Enhanced AAC+ codec are reviewed. Next, the music quality of the audio codecs is compared with that of EVRC, where the bit-rates of the audio codecs are set to be around 10 kbit/s because the color ring-back-tone service using one of the audio codecs should be realized by replacing EVRC with it. The quality comparison is performed by an informal listening test as well as an objective quality test. It is shown from the experiments that the audio codecs provide better music quality than EVRC and among them, the Enhance AAC+ codec operated at a bit-rate of 10 kbit/s with a sampling rate of 32 kHz can be considered as a new candidate for the high quality color ring-back-tone service.

  10. A signal processing system of fiber Bragg grating sensor based on code division multiplexing access

    NASA Astrophysics Data System (ADS)

    Li, Wei

    2013-09-01

    A lowcost Fiber Bragg Grating (FBG) Sensing System based on code division multiplexing access (CDMA) technology is proposed. The system using semiconductor optical amplifier and a broadband source is experimented. Without a tunable laser source or electro-optic switch driven, the price of system is very low. CDMA is used to separate each reflected sensor. The experimental results show that theory is correct.

  11. Orthogonal Pilot Channel Using Combination of FDMA and CDMA in Single-Carrier FDMA-Based Evolved UTRA Uplink

    NASA Astrophysics Data System (ADS)

    Kawamura, Teruo; Kishiyama, Yoshihisa; Higuchi, Kenichi; Sawahashi, Mamoru

    In the Evolved UTRA (UMTS Terrestrial Radio Access) uplink, single-carrier frequency division multiple access (SC-FDMA) radio access was adopted owing to its advantageous low peak-to-average power ratio (PAPR) feature, which leads to wide coverage area provisioning with limited peak transmission power of user equipments. This paper proposes orthogonal pilot channel generation using the combination of FDMA and CDMA in the SC-FDMA-based Evolved UTRA uplink. In the proposed method, we employ distributed FDMA transmission for simultaneous accessing users with different transmission bandwidths, and employ CDMA transmission for simultaneous accessing users with identical transmission bandwidth. Moreover, we apply a code sequence with a good auto-correlation property such as a Constant Amplitude Zero Auto-Correlation (CAZAC) sequence employing a cyclic shift to increase the number of sequences. Simulation results show that the average packet error rate performance using an orthogonal pilot channel with the combination of FDMA and CDMA in a six-user environment, i. e., four users each with a 1.25-MHz transmission bandwidth and two users each with a 5-MHz transmission bandwidth, employing turbo coding with the coding r of R=1/2 and QPSK and 16QAM data modulation coincides well with that in a single-user environment with the same transmission bandwidth. We show that the proposed orthogonal pilot channel structure using the combination of distributed FDMA and CDMA transmissions and the application of the CAZAC sequence is effective in the SC-FDMA-based Evolved UTRA uplink.

  12. Communication for Inquiry and Access: Teaching Techniques from Discourse Research

    ERIC Educational Resources Information Center

    Staats, Susan; Duranczyk, Irene; Moore, Randy; Hatch, Jay; Jensen, Murray; Somdahl, Charles

    2006-01-01

    Adopting inquiry-based science and mathematics pedagogies changes traditional classroom communication patterns. Linguistic research in science and mathematics classrooms has identified communication techniques that help teachers manage classroom discussions to increase student interaction and a sense of student responsibility for learning. These…

  13. Multiple Access Trade Study

    NASA Technical Reports Server (NTRS)

    Motamedi, Masoud

    1990-01-01

    The Personal Access Satellite System (PASS) strawman design uses a hybrid Time Division Multiple Access (TDMA)/Frequency Division Multiple Access (FDMA) implementation. TDMA is used for the forward direction (from Suppliers to Users), and FDMA for the return direction (from Users to Suppliers). An alternative architecture is proposed that will require minimal real time coordination and yet provide a fast access method by using random access Code Division Multiple Access (CDMA). The CDMA system issues are addressed such as connecting suppliers and users, both of whom may be located anywhere in the CONUS, when the user terminals are constrained in size and weight; and providing efficient traffic routing under highly variable traffic requirements. It is assumed that bandwidth efficiency is not of paramount importance. CDMA or Spread Spectrum Multiple Access (SSMA) communication is a method in which a group of carriers operate at the same nominal center frequency but are separable from each other by the low cross correlation of the spreading codes used. Interference and multipath rejection capability, ease of selective addressing and message screening, low density power spectra for signal hiding and security, and high resolution ranging are among the benefits of spread spectrum communications.

  14. RBF multiuser detector with channel estimation capability in a synchronous MC-CDMA system.

    PubMed

    Ko, K; Choi, S; Kang, C; Hong, D

    2001-01-01

    The authors propose a multiuser detector with channel estimation capability using a radial basis function (RBF) network in a synchronous multicarrier-code division multiple access (MC-CDMA) system. The authors propose to connect an RBF network to the frequency domain to effectively utilize the frequency diversity. Simulations were performed over frequency-selective and multi-path fading channels. These simulations confirmed that the proposed receiver can be used both for the channel estimation and as a multi-user receiver, thus permitting an increase in the number of active users. PMID:18249987

  15. Permanent pacing in patients without upper limb venous access: a review of current techniques

    PubMed Central

    Seow, Swee-Chong; Lim, Toon-Wei; Singh, Devinder; Yeo, Wee-Tiong; Kojodjojo, Pipin

    2014-01-01

    Permanent transvenous cardiac pacing is usually accomplished through the upper limb veins. When these are occluded, several other vascular access options exist which include the internal jugular, external jugular, femoral and iliac veins as well as more proximal access of the subclavian veins. Anterograde and retrograde techniques to restore subclavian venous patency has been described. A review of these approaches is undertaken, with a discussion of their pros and cons. Familiarity with these techniques will enable the implanter to perform transvenous pacing when faced with limited vascular access. PMID:27326197

  16. Performance Evaluation of Virtualization Techniques for Control and Access of Storage Systems in Data Center Applications

    NASA Astrophysics Data System (ADS)

    Ahmadi, Mohammad Reza

    2013-09-01

    Virtualization is a new technology that creates virtual environments based on the existing physical resources. This article evaluates effect of virtualization techniques on control servers and access method in storage systems [1, 2]. In control server virtualization, we have presented a tile based evaluation based on heterogeneous workloads to compare several key parameters and demonstrate effectiveness of virtualization techniques. Moreover, we have evaluated the virtualized model using VMotion techniques and maximum consolidation. In access method, we have prepared three different scenarios using direct, semi-virtual, and virtual attachment models. We have evaluated the proposed models with several workloads including OLTP database, data streaming, file server, web server, etc. Results of evaluation for different criteria confirm that server virtualization technique has high throughput and CPU usage as well as good performance with noticeable agility. Also virtual technique is a successful alternative for accessing to the storage systems especially in large capacity systems. This technique can therefore be an effective solution for expansion of storage area and reduction of access time. Results of different evaluation and measurements demonstrate that the virtualization in control server and full virtual access provide better performance and more agility as well as more utilization in the systems and improve business continuity plan.

  17. Dynamic quality of service differentiation using fixed code weight in optical CDMA networks

    NASA Astrophysics Data System (ADS)

    Kakaee, Majid H.; Essa, Shawnim I.; Abd, Thanaa H.; Seyedzadeh, Saleh

    2015-11-01

    The emergence of network-driven applications, such as internet, video conferencing, and online gaming, brings in the need for a network the environments with capability of providing diverse Quality of Services (QoS). In this paper, a new code family of novel spreading sequences, called a Multi-Service (MS) code, has been constructed to support multiple services in Optical- Code Division Multiple Access (CDMA) system. The proposed method uses fixed weight for all services, however reducing the interfering codewords for the users requiring higher QoS. The performance of the proposed code is demonstrated using mathematical analysis. It shown that the total number of served users with satisfactory BER of 10-9 using NB=2 is 82, while they are only 36 and 10 when NB=3 and 4 respectively. The developed MS code is compared with variable-weight codes such as Variable Weight-Khazani Syed (VW-KS) and Multi-Weight-Random Diagonal (MW-RD). Different numbers of basic users (NB) are used to support triple-play services (audio, data and video) with different QoS requirements. Furthermore, reference to the BER of 10-12, 10-9, and 10-3 for video, data and audio, respectively, the system can support up to 45 total users. Hence, results show that the technique can clearly provide a relative QoS differentiation with lower value of basic users can support larger number of subscribers as well as better performance in terms of acceptable BER of 10-9 at fixed code weight.

  18. Accessibility

    MedlinePlus

    ... www.nlm.nih.gov/medlineplus/accessibility.html MedlinePlus Accessibility To use the sharing features on this page, ... Subscribe to RSS Follow us Disclaimers Copyright Privacy Accessibility Quality Guidelines Viewers & Players MedlinePlus Connect for EHRs ...

  19. Effects of simultaneous combined exposure to CDMA and WCDMA electromagnetic fields on serum hormone levels in rats

    PubMed Central

    Jin, Yeung Bae; Choi, Hyung-Do; Kim, Byung Chan; Pack, Jeong-Ki; Kim, Nam; Lee, Yun-Sil

    2013-01-01

    Despite more than a decade of research on the endocrine system, there have been no published studies about the effects of concurrent exposure of radiofrequency electromagnetic fields (RF-EMF) on this system. The present study investigated the several parameters of the endocrine system including melatonin, thyroid stimulating hormone, stress hormone and sex hormone after code division multiple access (CDMA, 849 MHz) and wideband code division multiple access (WCDMA, 1.95 GHz) signals for simultaneous exposure in rats. Sprague-Dawley rats were exposed to RF-EMF signals for 45 min/day, 5 days/week for up to 8 weeks. The whole-body average specific absorption rate (SAR) of CDMA or WCDMA was 2.0 W/kg (total 4.0 W/kg). At 4 and 8 weeks after the experiment began, each experimental group's 40 rats (male 20, female 20) were autopsied. Exposure for 8 weeks to simultaneous CDMA and WCDMA RF did not affect serum levels in rats of melatonin, thyroid stimulating hormone (TSH), triiodothyronine (T3) and thyroxin (T4), adrenocorticotropic hormone (ACTH) and sex hormones (testosterone and estrogen) as assessed by the ELISA method. PMID:23239176

  20. Effects of simultaneous combined exposure to CDMA and WCDMA electromagnetic fields on serum hormone levels in rats.

    PubMed

    Jin, Yeung Bae; Choi, Hyung-Do; Kim, Byung Chan; Pack, Jeong-Ki; Kim, Nam; Lee, Yun-Sil

    2013-05-01

    Despite more than a decade of research on the endocrine system, there have been no published studies about the effects of concurrent exposure of radiofrequency electromagnetic fields (RF-EMF) on this system. The present study investigated the several parameters of the endocrine system including melatonin, thyroid stimulating hormone, stress hormone and sex hormone after code division multiple access (CDMA, 849 MHz) and wideband code division multiple access (WCDMA, 1.95 GHz) signals for simultaneous exposure in rats. Sprague-Dawley rats were exposed to RF-EMF signals for 45 min/day, 5 days/week for up to 8 weeks. The whole-body average specific absorption rate (SAR) of CDMA or WCDMA was 2.0 W/kg (total 4.0 W/kg). At 4 and 8 weeks after the experiment began, each experimental group's 40 rats (male 20, female 20) were autopsied. Exposure for 8 weeks to simultaneous CDMA and WCDMA RF did not affect serum levels in rats of melatonin, thyroid stimulating hormone (TSH), triiodothyronine (T3) and thyroxin (T4), adrenocorticotropic hormone (ACTH) and sex hormones (testosterone and estrogen) as assessed by the ELISA method. PMID:23239176

  1. Adaptive Channel-Tracking Method and Equalization for MC-CDMA Systems over Rapidly Fading Channel under Colored Noise

    NASA Astrophysics Data System (ADS)

    Yang, Chang-Yi; Chen, Bor-Sen

    2010-12-01

    A recursive maximum-likelihood (RML) algorithm for channel estimation under rapidly fading channel and colored noise in a multicarrier code-division multiple-access (MC-CDMA) system is proposed in this paper. A moving-average model with exogenous input (MAX) is given to describe the transmission channel and colored noise. Based on the pseudoregression method, the proposed RML algorithm can simultaneously estimate the parameters of channel and colored noise. Following the estimation results, these parameters can be used to enhance the minimum mean-square error (MMSE) equalizer. Considering high-speed mobile stations, a one-step linear trend predictor is added to improve symbol detection. Simulation results indicate that the proposed RML estimator can track the channel more precisely than the conventional estimator. Meanwhile, the performance of the proposed enhanced MMSE equalizer is robust to the rapidly Rayleigh fading channel under colored noise in the MC-CDMA systems.

  2. A Brief Survey of Media Access Control, Data Link Layer, and Protocol Technologies for Lunar Surface Communications

    NASA Technical Reports Server (NTRS)

    Wallett, Thomas M.

    2009-01-01

    This paper surveys and describes some of the existing media access control and data link layer technologies for possible application in lunar surface communications and the advanced wideband Direct Sequence Code Division Multiple Access (DSCDMA) conceptual systems utilizing phased-array technology that will evolve in the next decade. Time Domain Multiple Access (TDMA) and Code Division Multiple Access (CDMA) are standard Media Access Control (MAC) techniques that can be incorporated into lunar surface communications architectures. Another novel hybrid technique that is recently being developed for use with smart antenna technology combines the advantages of CDMA with those of TDMA. The relatively new and sundry wireless LAN data link layer protocols that are continually under development offer distinct advantages for lunar surface applications over the legacy protocols which are not wireless. Also several communication transport and routing protocols can be chosen with characteristics commensurate with smart antenna systems to provide spacecraft communications for links exhibiting high capacity on the surface of the Moon. The proper choices depend on the specific communication requirements.

  3. Quantum internet using code division multiple access.

    PubMed

    Zhang, Jing; Liu, Yu-xi; Ozdemir, Sahin Kaya; Wu, Re-Bing; Gao, Feifei; Wang, Xiang-Bin; Yang, Lan; Nori, Franco

    2013-01-01

    A crucial open problem inS large-scale quantum networks is how to efficiently transmit quantum data among many pairs of users via a common data-transmission medium. We propose a solution by developing a quantum code division multiple access (q-CDMA) approach in which quantum information is chaotically encoded to spread its spectral content, and then decoded via chaos synchronization to separate different sender-receiver pairs. In comparison to other existing approaches, such as frequency division multiple access (FDMA), the proposed q-CDMA can greatly increase the information rates per channel used, especially for very noisy quantum channels. PMID:23860488

  4. Quantum internet using code division multiple access

    NASA Astrophysics Data System (ADS)

    Zhang, Jing; Liu, Yu-Xi; Özdemir, Şahin Kaya; Wu, Re-Bing; Gao, Feifei; Wang, Xiang-Bin; Yang, Lan; Nori, Franco

    2013-07-01

    A crucial open problem inS large-scale quantum networks is how to efficiently transmit quantum data among many pairs of users via a common data-transmission medium. We propose a solution by developing a quantum code division multiple access (q-CDMA) approach in which quantum information is chaotically encoded to spread its spectral content, and then decoded via chaos synchronization to separate different sender-receiver pairs. In comparison to other existing approaches, such as frequency division multiple access (FDMA), the proposed q-CDMA can greatly increase the information rates per channel used, especially for very noisy quantum channels.

  5. [Application of ultrasonography in central venous catheterization; access sites and procedure techniques].

    PubMed

    Czyzewska, Dorota; Ustymowicz, Andrzej; Klukowski, Mark

    2016-08-01

    Central venous catheterization is commonly performed in clinical practice. Traditional procedural technique is based on anatomical landmarks, but is associated with a high risk of failure and complications. To decrease their incidence European and American societies recommend application of ultrasonography. Preliminary ultrasonographic examination allows for assessment of local anatomical relations as well as vessel morphology (diameter, patency), while real-time ultrasonography increases chances of successful needle insertion. This paper presents the most common venous access sites and procedure techniques. PMID:27157792

  6. Reaching the Connected Generation: "College Access Marketers" Slow in Adopting New Techniques

    ERIC Educational Resources Information Center

    Gastwirth, David

    2007-01-01

    This author states that "college access marketing" efforts aimed at increasing college attendance and success have been slow to incorporate new techniques such as "buzz marketing," "viral marketing," "product seeding," and "guerrilla marketing." Yet for a "connected generation" of potential college students, these kinds of strategies could be…

  7. CDMA with interference cancellation for multiprobe missions

    NASA Technical Reports Server (NTRS)

    Divsalar, D.; Simon, M. K.

    1995-01-01

    Code division multiple-access spread spectrum has been proposed for use in future multiprobe/multispacecraft missions. This article considers a general parallel interference-cancellation scheme that significantly reduces the degradation effect of probe (user) interference but with a lesser implementation complexity than the maximum-likelihood technique. The scheme operates on the fact that parallel processing simultaneously removes from each probe (user) the total interference produced by the remaining most reliably received probes (users) accessing the channel. The parallel processing can be done in multiple stages. The proposed scheme uses tentative decision devices with different optimum thresholds at the multiple stages to produce the most reliably received data for generation and cancellation of probe/spacecraft interference. The one-stage interference cancellation was analyzed for two types of tentative decision devices, namely, hard and null zone decisions. Simulation results are given for one- and two-stage interference cancellation for equal as well as unequal received power probes.

  8. 2-GHz band CW and W-CDMA modulated radiofrequency fields have no significant effect on cell proliferation and gene expression profile in human cells.

    PubMed

    Sekijima, Masaru; Takeda, Hiroshi; Yasunaga, Katsuaki; Sakuma, Noriko; Hirose, Hideki; Nojima, Toshio; Miyakoshi, Junji

    2010-01-01

    We investigated the mechanisms by which radiofrequency (RF) fields exert their activity, and the changes in both cell proliferation and the gene expression profile in the human cell lines, A172 (glioblastoma), H4 (neuroglioma), and IMR-90 (fibroblasts from normal fetal lung) following exposure to 2.1425 GHz continuous wave (CW) and Wideband Code Division Multiple Access (W-CDMA) RF fields at three field levels. During the incubation phase, cells were exposed at the specific absorption rates (SARs) of 80, 250, or 800 mW/kg with both CW and W-CDMA RF fields for up to 96 h. Heat shock treatment was used as the positive control. No significant differences in cell growth or viability were observed between any test group exposed to W-CDMA or CW radiation and the sham-exposed negative controls. Using the Affymetrix Human Genome Array, only a very small (< 1%) number of available genes (ca. 16,000 to 19,000) exhibited altered expression in each experiment. The results confirm that low-level exposure to 2.1425 GHz CW and W-CDMA RF fields for up to 96 h did not act as an acute cytotoxicant in either cell proliferation or the gene expression profile. These results suggest that RF exposure up to the limit of whole-body average SAR levels as specified in the ICNIRP guidelines is unlikely to elicit a general stress response in the tested cell lines under these conditions. PMID:20215713

  9. Analysis of Jammer Resistant, Spread Spectrum, VSAT Communication Scheme for Maritime Platform Using DS-CDMA

    NASA Astrophysics Data System (ADS)

    Aras, Ersin

    2002-09-01

    In this thesis, a new VSAT (Very Small Aperture Terminal) Communication system is developed using Direct Sequence Code Division Multiple Access (DS-CDMA) for multiple maritime mobile users in the footprints of national communication satellites. The Forward Error Correction (FEC) is implemented by applying convolution encoding with soft decision decoding. The worst case scenario is always considered by placing VSAT system and different types of jammers on the footprint where the minimum signal- to-noise ratio is possible. Using this assumption, the performance of the system is analyzed for different convolution code rates, for a different number of users and for the different jammer powers. The Walsh codes are used to establish an orthogonal cover between CDMA channels in a VSAT. Additionally, spread spectrum is included by PN sequences to ensure as much orthogonal coverage as possible between the VSATs. Also, that spreading is the key to minimizing these hostile jammers effects. After analyzing VSAT system for possible scenario elements, optimum system parameters are introduced for military and civilian applications.

  10. Improving performance of DS-CDMA systems using chaotic complex Bernoulli spreading codes

    NASA Astrophysics Data System (ADS)

    Farzan Sabahi, Mohammad; Dehghanfard, Ali

    2014-12-01

    The most important goal of spreading spectrum communication system is to protect communication signals against interference and exploitation of information by unintended listeners. In fact, low probability of detection and low probability of intercept are two important parameters to increase the performance of the system. In Direct Sequence Code Division Multiple Access (DS-CDMA) systems, these properties are achieved by multiplying the data information in spreading sequences. Chaotic sequences, with their particular properties, have numerous applications in constructing spreading codes. Using one-dimensional Bernoulli chaotic sequence as spreading code is proposed in literature previously. The main feature of this sequence is its negative auto-correlation at lag of 1, which with proper design, leads to increase in efficiency of the communication system based on these codes. On the other hand, employing the complex chaotic sequences as spreading sequence also has been discussed in several papers. In this paper, use of two-dimensional Bernoulli chaotic sequences is proposed as spreading codes. The performance of a multi-user synchronous and asynchronous DS-CDMA system will be evaluated by applying these sequences under Additive White Gaussian Noise (AWGN) and fading channel. Simulation results indicate improvement of the performance in comparison with conventional spreading codes like Gold codes as well as similar complex chaotic spreading sequences. Similar to one-dimensional Bernoulli chaotic sequences, the proposed sequences also have negative auto-correlation. Besides, construction of complex sequences with lower average cross-correlation is possible with the proposed method.

  11. Combinative exposure effect of radio frequency signals from CDMA mobile phones and aphidicolin on DNA integrity.

    PubMed

    Tiwari, R; Lakshmi, N K; Surender, V; Rajesh, A D V; Bhargava, S C; Ahuja, Y R

    2008-01-01

    The aim of present study is to assess DNA integrity on the effect of exposure to a radio frequency (RF) signal from Code Division Multiple Access (CDMA) mobile phones. Whole blood samples from six healthy male individuals were exposed for RF signals from a CDMA mobile phone for 1 h. Alkaline comet assay was performed to assess the DNA damage. The combinative exposure effect of the RF signals and APC at two concentrations on DNA integrity was studied. DNA repair efficiency of the samples was also studied after 2 h of exposure. The RF signals and APC (0.2 microg/ml) alone or in synergism did not have any significant DNA damage as compared to sham exposed. However, univariate analysis showed that DNA damage was significantly different among combinative exposure of RF signals and APC at 0.2 microg/ml (p < 0.05) and at 2 microg/ml (p < 0.02). APC at 2 microg/ml concentration also showed significant damage levels (p < 0.05) when compared to sham exposed. DNA repair efficiency also varied in a significant way in combinative exposure sets (p < 0.05). From these results, it appears that the repair inhibitor APC enhances DNA breaks at 2 microg/ml concentration and that the damage is possibly repairable. Thus, it can be inferred that the in vitro exposure to RF signals induces reversible DNA damage in synergism with APC. PMID:19037791

  12. Analysis of Optical CDMA Signal Transmission: Capacity Limits and Simulation Results

    NASA Astrophysics Data System (ADS)

    Garba, Aminata A.; Yim, Raymond M. H.; Bajcsy, Jan; Chen, Lawrence R.

    2005-12-01

    We present performance limits of the optical code-division multiple-access (OCDMA) networks. In particular, we evaluate the information-theoretical capacity of the OCDMA transmission when single-user detection (SUD) is used by the receiver. First, we model the OCDMA transmission as a discrete memoryless channel, evaluate its capacity when binary modulation is used in the interference-limited (noiseless) case, and extend this analysis to the case when additive white Gaussian noise (AWGN) is corrupting the received signals. Next, we analyze the benefits of using nonbinary signaling for increasing the throughput of optical CDMA transmission. It turns out that up to a fourfold increase in the network throughput can be achieved with practical numbers of modulation levels in comparison to the traditionally considered binary case. Finally, we present BER simulation results for channel coded binary and[InlineEquation not available: see fulltext.]-ary OCDMA transmission systems. In particular, we apply turbo codes concatenated with Reed-Solomon codes so that up to several hundred concurrent optical CDMA users can be supported at low target bit error rates. We observe that unlike conventional OCDMA systems, turbo-empowered OCDMA can allow overloading (more active users than is the length of the spreading sequences) with good bit error rate system performance.

  13. Effects of 1950 MHz W-CDMA-like signal on human spermatozoa.

    PubMed

    Nakatani-Enomoto, Setsu; Okutsu, Miho; Suzuki, Satoshi; Suganuma, Ryota; Groiss, Stefan Jun; Kadowaki, Suguru; Enomoto, Hiroyuki; Fujimori, Keiya; Ugawa, Yoshikazu

    2016-09-01

    There are growing concerns about how electromagnetic waves (EMW) emitted from mobile phones affect human spermatozoa. Several experiments have suggested harmful effects of EMW on human sperm quality, motility, velocity, or the deoxyribonucleic acid (DNA) of spermatozoa. In this study, we analyzed the effects on human spermatozoa (sperm motility and kinetic variables) induced by 1 h of exposure to 1950 MHz Wideband Code Division Multiple Access (W-CDMA)-like EMW with specific absorption rates of either 2.0 or 6.0 W/kg, using a computer-assisted sperm analyzer system. We also measured the percentage of 8-hydroxy-2'-deoxyguanosine (8-OHdG) positive spermatozoa with flow cytometry to evaluate damage to DNA. No significant differences were observed between the EMW exposure and the sham exposure in sperm motility, kinetic variables, or 8-OHdG levels. We conclude that W-CDMA-like exposure for 1 h under temperature-controlled conditions has no detectable effect on normal human spermatozoa. Differences in exposure conditions, humidity, temperature control, baseline sperm characteristics, and age of donors may explain inconsistency of our results with several previous studies. Bioelectromagnetics. 37:373-381, 2016. © 2016 Wiley Periodicals, Inc. PMID:27288295

  14. Image guided portal vein access techniques in TIPS creation and considerations regarding their use

    PubMed Central

    2016-01-01

    Transjugular intrahepatic portosystemic shunt (TIPS) is a difficult procedure to perform and accessing the portal vein is a very challenging step. There are three broad categories of image guided TIPS creation techniques. Each technique has its advantages and disadvantages. TIPS procedure carries some risk of complications regardless of the guidance technique employed. The technology for TIPS has evolved in parallel with the expanding indications for TIPS. Ultrasound guidance technique offers a safe option, particularly for patients with challenging anatomy. Patient safety should always come first and the US guided technique should be more routinely used. Experience is the main factor in the success of TIPS. Other factors to consider in reducing the all-cause morbidity and mortality are patient selection, patient management and the clinical setting. PMID:27385392

  15. Efficient Service Delivery for High-speed Railway Communications Using MIMO and Access Control Technique

    NASA Astrophysics Data System (ADS)

    Zhou, Yuzhe; Ai, Bo

    2014-07-01

    In order to realize the notion of "anytime, anywhere" communication for high-speed train passengers, the Long Term Evolution for Railway is designed to provide broadband accesses and reliable communications for high-speed train passengers. However, with the increase of train speed, the system is subject to high bit error rate, Doppler frequency shift, and call drops. This paper is trying to solve these problems by employing the Multiple-Input Multiple-Output technique and access control schemes. The goal is to provide higher quality of services such as data rate, reliability, and delay for train passengers. Physical layer performance analysis and access control schemes are proposed in a two-hop model. Handovers and service types are also considered. Simulation results show that proposed models and schemes perform better in improving the quality of services.

  16. Preliminary application of a single-port access technique for laparoscopic ovariohysterectomy in dogs

    PubMed Central

    Sánchez-Margallo, F. M.; Tapia-Araya, A.; Díaz-Güemes, I.

    2015-01-01

    Laparoscopic ovariohysterectomy using single-portal access was performed in nine selected owned dogs admitted for elective ovariohysterectomy and the surgical technique and outcomes were detailed. A multiport device (SILS Port, Covidien, USA) was placed at the umbilical area through a single 3 cm incision. Three cannulae were introduced in the multiport device through the access channels and laparoscopic ovariohysterectomy was performed using a 5-mm sealing device, a 5-mm articulating grasper and a 5-mm 30° laparoscope. The mean total operative time was 52.66±15.20 minutes and the mean skin incision during surgery was 3.09±0.20 cm. Of the nine cases examined, in the one with an ovarian tumour, the technique was converted to multiport laparoscopy introducing an additional 5-mm trocar. No surgical complications were encountered and intraoperative blood loss was minimum in all animals. Clashing of the instruments and reduced triangulation were the main limitations of this technique. The combination of articulated and straight instruments facilitated triangulation towards the surgical field and dissection capability. One month after surgery a complete wound healing was observed in all animals. The present data showed that ovariohysterectomy performed with a single-port access is technically feasible in dogs. The unique abdominal incision minimises the abdominal trauma with good cosmetic results. PMID:26568831

  17. Improved CDMA Performance Using Parallel Interference Cancellation

    NASA Technical Reports Server (NTRS)

    Simon, Marvin; Divsalar, Dariush

    1995-01-01

    This report considers a general parallel interference cancellation scheme that significantly reduces the degradation effect of user interference but with a lesser implementation complexity than the maximum-likelihood technique. The scheme operates on the fact that parallel processing simultaneously removes from each user the interference produced by the remaining users accessing the channel in an amount proportional to their reliability. The parallel processing can be done in multiple stages. The proposed scheme uses tentative decision devices with different optimum thresholds at the multiple stages to produce the most reliably received data for generation and cancellation of user interference. The 1-stage interference cancellation is analyzed for three types of tentative decision devices, namely, hard, null zone, and soft decision, and two types of user power distribution, namely, equal and unequal powers. Simulation results are given for a multitude of different situations, in particular, those cases for which the analysis is too complex.

  18. Mechanical thrombectomy with ‘ADAPT’ technique by transcervical access in acute ischemic stroke

    PubMed Central

    Remollo, Sebastian; García, Maria Rosa; Hidalgo, Cristina; Hernández-Perez, Maria; Ciorba, Mihaela

    2015-01-01

    Background The mechanical thrombectomy (MT) for endovascular clot retrieval has dramatically improved successful revascularization and clinical outcome in selected acute stroke patients. MT is typically performed via a transfemoral approach, but catheterization of the occluded vessel can be problematic in cases of extensive vessel tortuosity. We describe a case of MT with the ‘ADAPT’ technique by direct carotid access due to an inability to catheterize the ICA by a transfemoral approach for acute cerebral ischemia in the setting of left MCA occlusion. Excellent angiographic and good clinical results were obtained without any complications. Case report An 80-year-old woman was admitted with a stroke by occlusion of the left MCA, with an NIHSS: 11, and an ASPECT: 7 in the CT. Under sedation a transfemoral angiography was performed, but after multiple attempts, it was impossible to make a stable catheterization of the left CCA. A transcervical approach was pursued. With ultrasound guidance the CCA was catheterized. Using the ‘ADAPT’ technique, we performed a successful MT. Post-procedure angiography (at 14 minutes) demonstrated recanalization of the entire left MCA (TICI: 3), without complications. The carotid access point was closed with a percutaneous closure. Control TC at 24 h showed a slight hypodensity in the left lenticular nucleus, and loss of gray-white matter differentiation in the adjacent cortex. Neurologically, the patient presented with progressive improvement. At discharge, she had an NIHSS: 0, mRS: 0 and Barthel: 100. Conclusions MT by direct carotid access is an effective alternative technique in those cases where it is not accessible by a transfemoral approach. PMID:26443297

  19. The reverse J arteriovenous graft configuration for hemodialysis access: rationale, technique, and outcomes.

    PubMed

    Cull, David L; Carsten, Christopher G; Kalbaugh, Corey A; York, John W; Campbell, Ted R; Cass, Anna L; Taylor, Spence M

    2008-07-01

    The long-term survival of patients on hemodialysis is often limited by the exhaustion of vascular access sites. A fundamental principle of vascular access surgery is that the arteriovenous (AV) access be placed as far distally in the arm as possible. This principle enhances the secondary patency of the AV grafts by preserving the proximal veins for AV graft revision and provides venous outflow for a new AV access to be placed more proximally in the extremity. The standard straight and looped AV graft configurations violate this principle by bypassing long segments of vein in the extremity that could be used for AV graft revision or new AV graft placement. We have developed a novel AV graft configuration that preserves venous outflow and enhances the longevity of each AV access site. The purpose of this review is to describe the reverse J AV graft technique and to report our outcomes with the procedure. Between February 2004 and April 2007, 26 AV grafts were placed using the reverse J configuration. Eighteen (69%) AV grafts were placed in the upper arm, 7 (27%) were placed in the forearm, and 1 (4%) was placed in the thigh. Median follow-up was 320 days. The secondary AV graft patency was 90 per cent at 6 months, 84 per cent at 12 months, and 84 per cent at 18 months. Five AV grafts were subsequently revised to a loop configuration. Overall patient survival was 85 per cent at 6 months, 68 per cent at 12 months, and 62 per cent at 18 months. Compared with the standard straight and looped AV graft configurations, the reverse J AV graft configuration preserves the length of venous outflow in the extremity for AV graft revision or new AV graft placement. Therefore, the reverse J configuration enhances the secondary patency of AV graft patency and AV access site longevity. PMID:18646480

  20. Performance Analysis of New Binary User Codes for DS-CDMA Communication

    NASA Astrophysics Data System (ADS)

    Usha, Kamle; Jaya Sankar, Kottareddygari

    2016-03-01

    This paper analyzes new binary spreading codes through correlation properties and also presents their performance over additive white Gaussian noise (AWGN) channel. The proposed codes are constructed using gray and inverse gray codes. In this paper, a n-bit gray code appended by its n-bit inverse gray code to construct the 2n-length binary user codes are discussed. Like Walsh codes, these binary user codes are available in sizes of power of two and additionally code sets of length 6 and their even multiples are also available. The simple construction technique and generation of code sets of different sizes are the salient features of the proposed codes. Walsh codes and gold codes are considered for comparison in this paper as these are popularly used for synchronous and asynchronous multi user communications respectively. In the current work the auto and cross correlation properties of the proposed codes are compared with those of Walsh codes and gold codes. Performance of the proposed binary user codes for both synchronous and asynchronous direct sequence CDMA communication over AWGN channel is also discussed in this paper. The proposed binary user codes are found to be suitable for both synchronous and asynchronous DS-CDMA communication.

  1. Access technique and its problems in parenteral nutrition – Guidelines on Parenteral Nutrition, Chapter 9

    PubMed Central

    Jauch, K. W.; Schregel, W.; Stanga, Z.; Bischoff, S. C.; Braß, P.; Hartl, W.; Muehlebach, S.; Pscheidl, E.; Thul, P.; Volk, O.

    2009-01-01

    Catheter type, access technique, and the catheter position should be selected considering to the anticipated duration of PN aiming at the lowest complication risks (infectious and non-infectious). Long-term (>7–10 days) parenteral nutrition (PN) requires central venous access whereas for PN <3 weeks percutaneously inserted catheters and for PN >3 weeks subcutaneous tunnelled catheters or port systems are appropriate. CVC (central venous catheter) should be flushed with isotonic NaCl solution before and after PN application and during CVC occlusions. Strict indications are required for central venous access placement and the catheter should be removed as soon as possible if not required any more. Blood samples should not to be taken from the CVC. If catheter infection is suspected, peripheral blood-culture samples and culture samples from each catheter lumen should be taken simultaneously. Removal of the CVC should be carried out immediately if there are pronounced signs of local infection at the insertion site and/or clinical suspicion of catheter-induced sepsis. In case PN is indicated for a short period (max. 7–10 days), a peripheral venous access can be used if no hyperosmolar solutions (>800 mosm/L) or solutions with a high titration acidity or alkalinity are used. A peripheral venous catheter (PVC) can remain in situ for as long as it is clinically required unless there are signs of inflammation at the insertion site. PMID:20049083

  2. Ka-band geostationary satellite spacing requirements and access schemes

    NASA Technical Reports Server (NTRS)

    Caron, Mario; Hindson, Daniel J.

    1995-01-01

    Geostationary satellite systems for wideband personal communications applications have been proposed. This paper looks at the geostationary satellite spacing requirement to meet the ITU-R sharing criterion for FDMA and CDMA access schemes. CDMA capacity equation is first developed. Then the basis for the interference analysis between two systems with an overlapping coverage area is developed for the cases of identical and different access schemes and for bandwidth and power limited systems. An example of an interference analysis between two systems is fully carried out. The paper also points out the inherent problems when comparing systems with different access schemes. It is found that under certain scenarios, CDMA can allow a closer spacing between satellites.

  3. Strict optical orthogonal codes for purely asynchronous code-division multiple-access applications.

    PubMed

    Zhang, J G

    1996-12-10

    Strict optical orthogonal codes are presented for purely asynchronous optical code-division multiple-access (CDMA) applications. The proposed code can strictly guarantee the peaks of its cross-correlation functions and the sidelobes of any of its autocorrelation functions to have a value of 1 in purely asynchronous data communications. The basic theory of the proposed codes is given. An experiment on optical CDMA systems is also demonstrated to verify the characteristics of the proposed code. PMID:21151299

  4. Handover aspects for a Low Earth Orbit (LEO) CDMA Land Mobile Satellite (LMS) system

    NASA Technical Reports Server (NTRS)

    Carter, P.; Beach, M. A.

    1993-01-01

    This paper addresses the problem of handoff in a land mobile satellite (LMS) system between adjacent satellites in a low earth orbit (LEO) constellation. In particular, emphasis is placed on the application of soft handoff in a direct sequence code division multiple access (DS-CDMA) LMS system. Soft handoff is explained in terms of terrestrial macroscopic diversity, in which signals transmitted via several independent fading paths are combined to enhance the link quality. This concept is then reconsidered in the context of a LEO LMS system. A two-state Markov channel model is used to simulate the effects of shadowing on the communications path from the mobile to each satellite during handoff. The results of the channel simulation form a platform for discussion regarding soft handoff, highlighting the potential merits of the scheme when applied in a LEO LMS environment.

  5. DOA estimation for local scattered CDMA signals by particle swarm optimization.

    PubMed

    Chang, Jhih-Chung

    2012-01-01

    This paper deals with the direction-of-arrival (DOA) estimation of local scattered code-division multiple access (CDMA) signals based on a particle swarm optimization (PSO) search. For conventional spectral searching estimators with local scattering, the searching complexity and estimating accuracy strictly depend on the number of search grids used during the search. In order to obtain high-resolution and accurate DOA estimation, a smaller grid size is needed. This is time consuming and it is unclear how to determine the required number of search grids. In this paper, a modified PSO is presented to reduce the required search grids for the conventional spectral searching estimator with the effects of local scattering. Finally, several computer simulations are provided for illustration and comparison. PMID:22737004

  6. CP decomposition approach to blind separation for DS-CDMA system using a new performance index

    NASA Astrophysics Data System (ADS)

    Rouijel, Awatif; Minaoui, Khalid; Comon, Pierre; Aboutajdine, Driss

    2014-12-01

    In this paper, we present a canonical polyadic (CP) tensor decomposition isolating the scaling matrix. This has two major implications: (i) the problem conditioning shows up explicitly and could be controlled through a constraint on the so-called coherences and (ii) a performance criterion concerning the factor matrices can be exactly calculated and is more realistic than performance metrics used in the literature. Two new algorithms optimizing the CP decomposition based on gradient descent are proposed. This decomposition is illustrated by an application to direct-sequence code division multiplexing access (DS-CDMA) systems; computer simulations are provided and demonstrate the good behavior of these algorithms, compared to others in the literature.

  7. A self-learning call admission control scheme for CDMA cellular networks.

    PubMed

    Liu, Derong; Zhang, Yi; Zhang, Huaguang

    2005-09-01

    In the present paper, a call admission control scheme that can learn from the network environment and user behavior is developed for code division multiple access (CDMA) cellular networks that handle both voice and data services. The idea is built upon a novel learning control architecture with only a single module instead of two or three modules in adaptive critic designs (ACDs). The use of adaptive critic approach for call admission control in wireless cellular networks is new. The call admission controller can perform learning in real-time as well as in offline environments and the controller improves its performance as it gains more experience. Another important contribution in the present work is the choice of utility function for the present self-learning control approach which makes the present learning process much more efficient than existing learning control methods. The performance of our algorithm will be shown through computer simulation and compared with existing algorithms. PMID:16252828

  8. Soft-PIC multiuser detection in MC-CDMA uplink system

    NASA Astrophysics Data System (ADS)

    Guo, Li-Li; Yuan, Bing-Bing

    2005-06-01

    It is necessary for an MC-CDMA uplink receiver to employ MUD (multiuser detection) in a frequency selective fading channel. After analyzing the algorithm of PIC (parallel interference cancellation) MUD, a novel MUD scheme, Soft-PIC (soft parallel interference cancellation) is proposed. Based on the reliability of each detected user signal in the former stage, this Soft-PIC detection scheme substitutes a soft decision of the variable for the hard decision in PIC scheme. Compared with the PIC scheme, it can reconstruct the interference signals more accurately and eliminate MAI (multiple access interference) in a more efficient way. PIC is one of the most practical schemes in numerous multiuser detection technologies. However, Soft-PIC as an improved PIC scheme deserves further study.

  9. Efficiency droop effects of GaN-based light-emitting diodes on the performance of code division multiple access visible-light communication system

    NASA Astrophysics Data System (ADS)

    Lu, Huimin; Yan, Chaowen; Gao, Wei; Yu, Tongjun; Wang, Jianping

    2016-02-01

    The physical mechanism in efficiency droop of GaN-based light-emitting diodes (LEDs) was investigated using a modified rate equation model considering inhomogeneous carrier distribution and was compared with the measured result. On this basis, the efficiency droop effect on the performance of a code division multiple access (CDMA) visible-light communication (VLC) system using GaN-based LEDs was also analyzed. The results reveal that the obvious transmitted signal error under the effect of LED efficiency droop leads to performance deterioration of multiuser CDMA VLC systems. Also, the performance of CDMA VLC systems is reduced with the user number increase due to LED efficiency droop. The bit error rate of a CDMA VLC system was further calculated for different branch signal levels and bias currents. It is demonstrated that the efficiency droop effect on the performance of CDMA VLC systems can be alleviated by adjusting the branch signal level and the bias current.

  10. Adaptive Resource Allocation for the PB/MC-CDMA System in Frequency Selective Fading Channels

    NASA Astrophysics Data System (ADS)

    Lee, Kyujin; Lee, Kyesan

    We propose Adaptive Resource Allocation for the Partial Block MC-CDMA (ARA-PB/MC-CDMA) system. The ARA-PB/MC-CDMA system aims to improve total throughput performance and frequency efficiency across various channel conditions. It adaptively changes the number of blocks to improve the throughput performance and frequency efficiency according to the Signal to Interference Ratio (SIR). Therefore, the proposed system supports various Quality of Service (QoS) requirements for various SIR values.

  11. Development of a mobile emergency patient information and imaging communication system based on CDMA-1X EVDO

    NASA Astrophysics Data System (ADS)

    Yang, Keon Ho; Jung, Haijo; Kang, Won-Suk; Jang, Bong Mun; Kim, Joong Il; Han, Dong Hoon; Yoo, Sun-Kook; Yoo, Hyung-Sik; Kim, Hee-Joung

    2006-03-01

    The wireless mobile service with a high bit rate using CDMA-1X EVDO is now widely used in Korea. Mobile devices are also increasingly being used as the conventional communication mechanism. We have developed a web-based mobile system that communicates patient information and images, using CDMA-1X EVDO for emergency diagnosis. It is composed of a Mobile web application system using the Microsoft Windows 2003 server and an internet information service. Also, a mobile web PACS used for a database managing patient information and images was developed by using Microsoft access 2003. A wireless mobile emergency patient information and imaging communication system is developed by using Microsoft Visual Studio.NET, and JPEG 2000 ActiveX control for PDA phone was developed by using the Microsoft Embedded Visual C++. Also, the CDMA-1X EVDO is used for connections between mobile web servers and the PDA phone. This system allows fast access to the patient information database, storing both medical images and patient information anytime and anywhere. Especially, images were compressed into a JPEG2000 format and transmitted from a mobile web PACS inside the hospital to the radiologist using a PDA phone located outside the hospital. Also, this system shows radiological images as well as physiological signal data, including blood pressure, vital signs and so on, in the web browser of the PDA phone so radiologists can diagnose more effectively. Also, we acquired good results using an RW-6100 PDA phone used in the university hospital system of the Sinchon Severance Hospital in Korea.

  12. Application of neural networks to channel assignment for cellular CDMA networks with multiple services and mobile base stations

    NASA Astrophysics Data System (ADS)

    Hortos, William S.

    1996-03-01

    The use of artificial neural networks to the channel assignment problem for cellular code- division multiple access (CDMA) telecommunications systems is considered. CDMA takes advantage of voice activity and spatial isolation because its capacity is only interference limited, unlike time-division multiple access (TDMA) and frequency-division multiple access (FDMA) where capacities are bandwidth limited. Any reduction in interference in CDMA translates linearly into increased capacity. FDMA and TDMA use a frequency reuse pattern as a method to increase capacity, while CDMA reuses the same frequency for all cells and gains a reuse efficiency by means of orthogonal codes. The latter method can improve system capacity by factors of four to six over digital TDMA or FDMA. Cellular carriers are planning to provide multiple communication services using CDMA in the next generation cellular system infrastructure. The approach of this study is the use of neural network methods for automatic and local network control, based on traffic behavior in specific cell cites and demand history. The goal is to address certain problems associated with the management of mobile and personal communication services in a cellular radio communications environment. In planning a cellular radio network, the operator assigns channels to the radio cells so that the probability of the processed carrier-to-interference ratio, CII, exceeding a predefined value is sufficiently low. The RF propagation, determined from the topography and infrastructure in the operating area, is used in conjunction with the densities of expected communications traffic to formulate interference constraints. These constraints state which radio cells may use the same code (channel) or adjacent channels at a time. The traffic loading and the number of service grades can also be used to calculate the number of required channels (codes) for each cell. The general assignment problem is the task of assigning the required number

  13. Multi-Sensor Detection with Particle Swarm Optimization for Time-Frequency Coded Cooperative WSNs Based on MC-CDMA for Underground Coal Mines.

    PubMed

    Xu, Jingjing; Yang, Wei; Zhang, Linyuan; Han, Ruisong; Shao, Xiaotao

    2015-01-01

    In this paper, a wireless sensor network (WSN) technology adapted to underground channel conditions is developed, which has important theoretical and practical value for safety monitoring in underground coal mines. According to the characteristics that the space, time and frequency resources of underground tunnel are open, it is proposed to constitute wireless sensor nodes based on multicarrier code division multiple access (MC-CDMA) to make full use of these resources. To improve the wireless transmission performance of source sensor nodes, it is also proposed to utilize cooperative sensors with good channel conditions from the sink node to assist source sensors with poor channel conditions. Moreover, the total power of the source sensor and its cooperative sensors is allocated on the basis of their channel conditions to increase the energy efficiency of the WSN. To solve the problem that multiple access interference (MAI) arises when multiple source sensors transmit monitoring information simultaneously, a kind of multi-sensor detection (MSD) algorithm with particle swarm optimization (PSO), namely D-PSO, is proposed for the time-frequency coded cooperative MC-CDMA WSN. Simulation results show that the average bit error rate (BER) performance of the proposed WSN in an underground coal mine is improved significantly by using wireless sensor nodes based on MC-CDMA, adopting time-frequency coded cooperative transmission and D-PSO algorithm with particle swarm optimization. PMID:26343660

  14. Multi-Sensor Detection with Particle Swarm Optimization for Time-Frequency Coded Cooperative WSNs Based on MC-CDMA for Underground Coal Mines

    PubMed Central

    Xu, Jingjing; Yang, Wei; Zhang, Linyuan; Han, Ruisong; Shao, Xiaotao

    2015-01-01

    In this paper, a wireless sensor network (WSN) technology adapted to underground channel conditions is developed, which has important theoretical and practical value for safety monitoring in underground coal mines. According to the characteristics that the space, time and frequency resources of underground tunnel are open, it is proposed to constitute wireless sensor nodes based on multicarrier code division multiple access (MC-CDMA) to make full use of these resources. To improve the wireless transmission performance of source sensor nodes, it is also proposed to utilize cooperative sensors with good channel conditions from the sink node to assist source sensors with poor channel conditions. Moreover, the total power of the source sensor and its cooperative sensors is allocated on the basis of their channel conditions to increase the energy efficiency of the WSN. To solve the problem that multiple access interference (MAI) arises when multiple source sensors transmit monitoring information simultaneously, a kind of multi-sensor detection (MSD) algorithm with particle swarm optimization (PSO), namely D-PSO, is proposed for the time-frequency coded cooperative MC-CDMA WSN. Simulation results show that the average bit error rate (BER) performance of the proposed WSN in an underground coal mine is improved significantly by using wireless sensor nodes based on MC-CDMA, adopting time-frequency coded cooperative transmission and D-PSO algorithm with particle swarm optimization. PMID:26343660

  15. Venous Access Ports: Indications, Implantation Technique, Follow-Up, and Complications

    SciTech Connect

    Walser, Eric M.

    2012-08-15

    The subcutaneous venous access device (SVAD or 'port') is a critical component in the care of patients with chronic disease. The modern SVAD provides reliable access for blood withdrawal and medication administration with minimal disruption to a patient's lifestyle. Because of improved materials and catheter technology, today's ports are lighter and stronger and capable of high-pressure injections of contrast for cross-sectional imaging. The majority of SVAD placement occurs in interventional radiology departments due to their ability to provide this service at lower costs, lower, complication rates, and greater volumes. Port-insertion techniques vary depending on the operator, but all consist of catheter placement in the central venous circulation followed by subcutaneous pocket creation and port attachment to the catheter with fixation and closure of the pocket. Venous access challenges occasionally occur in patients with central vein occlusions, necessitating catheterization of collateral veins or port placement in alternate locations. Complications of SVADs include those associated with the procedure as well as short- (<30 days) and long-term problems. Procedural and early complications are quite rare due to the near-universal use of real-time ultrasound guidance for vein puncture, but they can include hematoma, catheter malposition, arrhythmias, and pneumothorax. Late problems include both thrombotic complications (native venous or port-catheter thrombosis) and infections (tunnel or pocket infections or catheter-associated bloodstream infections). Most guidelines suggest that 0.3 infections/1000 catheter days is an appropriate upper threshold for the insertion of SVADs.

  16. Code-division multiple-access multiuser demodulator by using quantum fluctuations

    NASA Astrophysics Data System (ADS)

    Otsubo, Yosuke; Inoue, Jun-ichi; Nagata, Kenji; Okada, Masato

    2014-07-01

    We examine the average-case performance of a code-division multiple-access (CDMA) multiuser demodulator in which quantum fluctuations are utilized to demodulate the original message within the context of Bayesian inference. The quantum fluctuations are built into the system as a transverse field in the infinite-range Ising spin glass model. We evaluate the performance measurements by using statistical mechanics. We confirm that the CDMA multiuser modulator using quantum fluctuations achieve roughly the same performance as the conventional CDMA multiuser modulator through thermal fluctuations on average. We also find that the relationship between the quality of the original information retrieval and the amplitude of the transverse field is somehow a "universal feature" in typical probabilistic information processing, viz., in image restoration, error-correcting codes, and CDMA multiuser demodulation.

  17. Code-division multiple-access multiuser demodulator by using quantum fluctuations.

    PubMed

    Otsubo, Yosuke; Inoue, Jun-Ichi; Nagata, Kenji; Okada, Masato

    2014-07-01

    We examine the average-case performance of a code-division multiple-access (CDMA) multiuser demodulator in which quantum fluctuations are utilized to demodulate the original message within the context of Bayesian inference. The quantum fluctuations are built into the system as a transverse field in the infinite-range Ising spin glass model. We evaluate the performance measurements by using statistical mechanics. We confirm that the CDMA multiuser modulator using quantum fluctuations achieve roughly the same performance as the conventional CDMA multiuser modulator through thermal fluctuations on average. We also find that the relationship between the quality of the original information retrieval and the amplitude of the transverse field is somehow a "universal feature" in typical probabilistic information processing, viz., in image restoration, error-correcting codes, and CDMA multiuser demodulation. PMID:25122270

  18. Theoretical study of use of optical orthogonal codes for compressed video transmission in optical code division multiple access (OCDMA) system

    NASA Astrophysics Data System (ADS)

    Ghosh, Shila; Chatterji, B. N.

    2007-09-01

    A theoretical investigation to evaluate the performance of optical code division multiple access (OCDMA) for compressed video transmission is shown. OCDMA has many advantages than a typical synchronous protocol time division multiple access (TDMA). A pulsed laser transmission of multi channel digital video can be done using various techniques depending on whether the multi channel data are to be synchronous or asynchronous. A typical form of asynchronous digital operation is wavelength division multiplexing (WDM) in which the digital data of each video source are assigned a specific and separate wavelength. A sophisticated hardware such as accurate wavelength control of all lasers and tunable narrow band optical filters at the receivers is required in this case. A major disadvantage with CDMA is the reduction in per channel data rate (relative to the speeds available in the laser itself) that occurs in the insertion of code addressing. Hence optical CDMA for the video transmission application is meaningful when individual channel video bit rates can be significantly reduced and that can be done by compression of video data. In our work for compression of video image standard JPEG is implemented where a compression ratio of about 60 % is obtained without noticeable image degradation. Compared to the other existing techniques JPEG standard achieves higher compression ration with high S/N ratio. Here we demonstrated the auto and cross correlation properties of the codes. We have shown the implementation of bipolar Walsh coding in OCDMA system and their use in transmission of image/video.

  19. Hypersensitivity to RF fields emitted from CDMA cellular phones: a provocation study.

    PubMed

    Nam, Ki Chang; Lee, Ju Hyung; Noh, Hyung Wook; Cha, Eun Jong; Kim, Nam Hyun; Kim, Deok Won

    2009-12-01

    With the number of cellular phone users rapidly increasing, there is a considerable amount of public concern regarding the effects that electromagnetic fields (EMFs) from cellular phones have on health. People with self-attributed electromagnetic hypersensitivity (EHS) complain of subjective symptoms such as headaches, insomnia, and memory loss, and attribute these symptoms to radio frequency (RF) radiation from cellular phones and/or base stations. However, EHS is difficult to diagnose because it relies on a person's subjective judgment. Various provocation studies have been conducted on EHS caused by Global System for Mobile Communications (GSM) phones in which heart rate and blood pressure or subjective symptoms were investigated. However, there have been few sham-controlled provocation studies on EHS with Code Division Multiple Access (CDMA) phones where physiological parameters, subjective symptoms, and perception of RF radiation for EHS and non-EHS groups were simultaneously investigated. In this study, two volunteer groups of 18 self-reported EHS and 19 non-EHS persons were tested for both sham and real RF exposure from CDMA cellular phones with a 300 mW maximum exposure that lasted half an hour. We investigated not only the physiological parameters such as heart rate, respiration rate, and heart rate variability (HRV), but also various subjective symptoms and the perception of EMF. In conclusion, RF exposure did not have any effects on physiological parameters or subjective symptoms in either group. As for EMF perception, there was no evidence that the EHS group better perceived EMF than the non-EHS group. PMID:19551766

  20. Carrier Estimation Using Classic Spectral Estimation Techniques for the Proposed Demand Assignment Multiple Access Service

    NASA Technical Reports Server (NTRS)

    Scaife, Bradley James

    1999-01-01

    In any satellite communication, the Doppler shift associated with the satellite's position and velocity must be calculated in order to determine the carrier frequency. If the satellite state vector is unknown then some estimate must be formed of the Doppler-shifted carrier frequency. One elementary technique is to examine the signal spectrum and base the estimate on the dominant spectral component. If, however, the carrier is spread (as in most satellite communications) this technique may fail unless the chip rate-to-data rate ratio (processing gain) associated with the carrier is small. In this case, there may be enough spectral energy to allow peak detection against a noise background. In this thesis, we present a method to estimate the frequency (without knowledge of the Doppler shift) of a spread-spectrum carrier assuming a small processing gain and binary-phase shift keying (BPSK) modulation. Our method relies on an averaged discrete Fourier transform along with peak detection on spectral match filtered data. We provide theory and simulation results indicating the accuracy of this method. In addition, we will describe an all-digital hardware design based around a Motorola DSP56303 and high-speed A/D which implements this technique in real-time. The hardware design is to be used in NMSU's implementation of NASA's demand assignment, multiple access (DAMA) service.

  1. Percutaneous stone clearance of the gallbladder through an access cholecystostomy. Laparoscopic-guided technique.

    PubMed

    Abd el Ghany, A B; Holley, M P; Cuschieri, A

    1989-01-01

    A laparoscopic-guided technique of percutaneous gallstone fragmentation/removal has been developed in the pig. The procedure entails the creation of a percutaneous access cholecystostomy. The access tract can be safely dilated after 7 days to F16, thereby allowing the introduction of both the Olympus flexible and the Berci-Shore rigid choledochoscopes. Following endoscopic occlusion of the cystic duct by a biliary balloon catheter, stone fragmentation can be conducted under direct visual control. In this particular study, electrohydraulic lithotripsy was performed of human cholesterol and bile-pigment stones inserted into the gallbladder of 16 pigs. The gallstone debris resulting from lithotripsy was then washed out with saline. Larger residual fragments could easily be extracted with the Dormia basket under visual guidance. There was a significant positive correlation between stone size (r = 0.98) and weight (r = 0.96) and the number of pulses needed to achieve satisfactory stone fragmentation. The gross composition of the stones (predominantly cholesterol or pigment) did not influence the number of pulses required. Electrohydraulic lithotripsy caused an explosion effect (the fragments hit the gallbladder wall), causing submucosal haematoma formation. This, however, was not followed by any untoward effect until sacrifice of the animals 10-16 weeks later. Electrohydraulic shocks delivered to the gallbladder wall itself resulted in larger haematoma formation and breach of the gallbladder mucosa with active bleeding into the gallbladder lumen, but again no instance of gallbladder perforation was encountered.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2530642

  2. Virtual queueing techniques for UBR+ service in ATM with fair access and minimum bandwidth guarantee

    SciTech Connect

    Siu, K.Y.; Wu, Y.; Ren, W.

    1998-11-01

    The ATM Forum is currently discussing the need for a new best-effort service called UBR+, which is an enhancement to the existing UBR service, to support data traffic. The objective of the UBR+ service is to provide each user with a minimum service rate guarantee and a fair access to any excess available bandwidth. In this paper, the authors present a new efficient scheme for supporting this service. The key advantage of the scheme is that it employs only FIFO queueing (instead of per-VC queueing) and admits simple implementation in ATM switches. The ideas involve a simple scheduling mechanism that is based on per-VC queueing and incorporate the virtual queueing technique that can efficiently emulate per-VC queueing on a shared FIFO queue. Simulation results are presented to show that the schemes can deliver almost ideal performance for supporting the new service requirements of UBR+.

  3. Double-Step Image Superimposition Technique for Fabricating a Drilling Guide to Access the Abutment Screw in Implant Prostheses.

    PubMed

    Mai, Hang-Nga; Kim, Kyung-Rok; Lee, Du-Hyeong

    2016-01-01

    Limited retrievability is a major disadvantage of cement-retained implant restorations. Despite great progress in locating the abutment screw within crowns, the existing techniques are based on prior data or prefabricated devices and require significant work. This study introduces a new procedure for fabricating a guide template to drill a screw access hole using a double-step superimposition technique that incorporates intraoral optical scanning, cone beam computed tomography, and dental design software. The double-step superimposition technique with computer-aided design/computer-assisted manufacturing technology can enhance the convenience and accuracy of drilling the screw-access hole. PMID:27479352

  4. A Link-Level Simulator of the cdma2000 Reverse-Link Physical Layer

    PubMed Central

    Gharavi, H.; Chin, F.; Ban, K.; Wyatt-Millington, R.

    2003-01-01

    The cdma2000 system is an evolutionary enhancement of the IS-95 standards which support 3G services defined by the International Telecommunications Union (ITU). cdma2000 comes in two phases: 1XRTT and 3XRTT (1X and 3X indicates the number of 1.25 MHz wide radio carrier channels used and RTT stands for Radio Transmission Technology). The cdma2000 1XRTT, which operates within a 1.25 MHz bandwidth, can be utilized in existing IS-95 CDMA channels as it uses the same bandwidth, while 3XRTT requires the commitment of 5 MHz bandwidth to support higher data rates. This paper describes a software model implementation of the cdma2000 reverse link and its application for evaluating the effect of rake receiver design parameters on the system performance under various multipath fading conditions. The cdma2000 models were developed at the National Institute of Standards and Technology (NIST), using SPW (Signal Processing Worksystem) commercial software tools. The model has been developed in a generic manner that includes all the reverse link six radio configurations and their corresponding data rates, according to cdma2000 specifications. After briefly reviewing the traffic channel characteristics of the cdma2000 reverse link (subscriber to base station), the paper discusses the rake receiver implementation including an ideal rake receiver. It then evaluates the performance of each receiver for a Spreading Rate 3 (3XRTT) operation, which is considered as a true “3G” cdma2000 technology. These evaluations are based on the vehicular IMT-2000 (International Mobile Telecommunication 2000) channel model using the link budget defined in cdma2000 specifications for the reverse link.

  5. On the Construction of Orthogonal Spreading Code Groups for MC-CDMA with FDE in a Frequency Selective Channel

    NASA Astrophysics Data System (ADS)

    Adachi, Koichi; Nakagawa, Masao

    The bit error rate (BER) performance of multicode multi-carrier code division multiple access (MC-CDMA) severely degrades due to the inter-code interference (ICI) in a strong frequency-selective channel. Recently a spreading code group construction method was proposed for MC-CDMA. The Walsh-Hadmard (WH) codes are divided into a number of code groups such that the code orthogonality can be maintained within each group even in a strong frequency-selective channel; any code pair taken from different groups is not orthogonal. The number of spreading codes in each group is determined by the maximum time delay difference of the channel. In this paper, we point out that the number of codes in each group is determined by the distribution of time delay differences among the propagation paths of the channel, not the maximum time delay difference. Based on that observation, we show that more orthogonal spreading codes can exist in each code group. The conditional BER is derived taking into account the interference from other code groups and the achievable downlink BER performance using the proposed spreading code group construction is numerically evaluated in a frequency-selective Rayleigh fading channel.

  6. Reducing BER of spectral-amplitude coding optical code-division multiple-access systems by single photodiode detection technique

    NASA Astrophysics Data System (ADS)

    Al-Khafaji, H. M. R.; Aljunid, S. A.; Amphawan, A.; Fadhil, H. A.; Safar, A. M.

    2013-03-01

    In this paper, we present a single photodiode detection (SPD) technique for spectral-amplitude coding optical code-division multiple-access (SAC-OCDMA) systems. The proposed technique eliminates both phase-induced intensity noise (PIIN) and multiple-access interference (MAI) in the optical domain. Analytical results show that for 35 simultaneous users transmitting at data rate of 622 Mbps, the bit-error rate (BER) = 1.4x10^-28 for SPD technique is much better compared to 9.3x10^-6 and 9.6x10^-3 for the modified-AND as well as the AND detection techniques, respectively. Moreover, we verified the improved performance afforded by the proposed technique using data transmission simulations.

  7. Asynchronous detection of optical code division multiple access signals using a bandwidth-efficient and wavelength-aware receiver.

    PubMed

    Fok, Mable P; Deng, Yanhua; Prucnal, Paul R

    2010-04-01

    We experimentally demonstrate what we believe to be a novel detection scheme for interfacing asynchronous optical code division multiple access (CDMA) signals with an electronic clock and data recovery system that operates only at the baseband bandwidth. This allows using a large optical bandwidth expansion factor in which the optical chip rate is much larger than the bandwidth of the optoelectronic receiver. The received optical CDMA signal is launched into a four-wave-mixing-based wavelength-aware all-optical front end that rejects multiaccess interference, followed by an amplitude-noise suppression stage comprised of a semiconductor optical amplifier. The clean signal is then converted into a non-return-to-zero-like signal by a baseband receiver. Using the proposed detection scheme, asynchronous transmission and detection of optical CDMA signals is implemented. With the novel detection scheme, the classic CDMA near-far problem is mitigated, and error-free detection is easily obtained. PMID:20364229

  8. Choice of FDMA/SCPC access technique for aeronautical satellite voice system

    NASA Technical Reports Server (NTRS)

    Smith, G. K.

    1989-01-01

    A worldwide aeronautical mobile satellite system is about to become operational. The system architecture and access methods have been debated extensively, resulting in the selection of Time Division Multiplexing/Time Division Multiple Access (TDM/TDMA) access for packet data, and Single Channel Per Carrier (SCPC) for voice. These have become standards for airline use, and also satisfy the known requirements of ICAO for safety related communications. Voice communications are expected to absorb a high proportion of satellite bandwidth and power in the future. Here, it is explained why INMARSAT selected Frequency Division Multiple Access/SCPC satellite access for this application.

  9. Efficient Management of Multiple Piconets in an MC-CDMA-Based UWB System

    NASA Astrophysics Data System (ADS)

    Gong, Peng; Xue, Peng; Piao, Cheng Jie; Kim, Duk Kyung

    With multiple overlapped piconets, the IEEE 802.15.3 Medium Access Control (MAC) protocol uses a Parent/Child (P/C) or Parent/Neighbor (P/N) configuration to avoid inter-piconet interference. However, the throughput of a P/N or P/C configuration cannot exceed that of a single piconet. In the present paper we propose an efficient means of managing multiple piconets to cooperate with a Multi-Carrier Code Division Multiple Access (MC-CDMA) based UWB system. The proposed management approach uses an Intermediate Device (IDEV) to connect Piconet Coordinators (PNCs). A senior PNC adaptively arranges two simultaneous data transmission links with the proposed spreading matrices in each Channel Time Allocation (CTA) instead of a P/C or P/N configuration, which supports only a single link in each CTA. Simulation results demonstrate the proposed scheme can achieve a higher throughput with an acceptable compromise of link success probability in multiple overlapped piconets.

  10. Direct sequence spread spectrum CDMA in shared spectrum applications

    NASA Technical Reports Server (NTRS)

    Schilling, Donald L.; Milstein, Laurence B.; Pickholtz, Raymond L.; Miller, Frank

    1991-01-01

    Personal Communication Network (PCN) is an entirely wireless communication system with the capability of assessing the wired telephone system to reach anyone processing only a wired telephone. It is expected to compete with the existing mobile cellular system which connects directly to the wired telephone system. While many PCN systems employ TDMA technology, the PCN system described here uses Broadband CDMA (BCDMA(sup SM)) which is capable of sharing the spectrum with other users and which is extremely resistant to fading caused by multipath.

  11. Diversity reception for advanced multi-satellite networks: A CDMA approach

    NASA Technical Reports Server (NTRS)

    Colzi, E.; Degaudenzi, R.; Elia, C.; Giannetti, F.; Viola, R.

    1993-01-01

    Diversity reception for Synchronous CDMA (S-CDMA) is introduced and analyzed. A Gaussian co-channel synchronous and asynchronous interference approximation is derived to evaluate the effects on the system bit error rate. Numerical results are provided for a simple mobile communication system where the signals transmitted by two distinct satellites in visibility are coherently combined by a three fingers Rake receiver. A second example showing performance of an integrated ground/satellite single frequency network for digital audio broadcasting is presented. Results show the capacity advantage of utilizing S-CDMA in combination with diversity reception.

  12. Seldinger Technique for Placement of “Peripheral” Internal Jugular Line: Novel Approach for Emergent Vascular Access

    PubMed Central

    Ash, Adam J.; Raio, Christopher

    2016-01-01

    This is a case report describing the ultrasound-guided placement of a peripheral intravenous catheter into the internal jugular vein of a patient with difficult vascular access. Although this technique has been described in the past, this case is novel in that the Seldinger technique was used to place the catheter. This allows for safer placement of a longer catheter (2.25″) without the need for venous dilation, which is potentially hazardous. PMID:26823937

  13. Promising Rapid Access High-Capacity Mass Storage Technique For Diagnostic Information Utilizing Optical Disc

    NASA Astrophysics Data System (ADS)

    Colby, R. L.; Bartuska, A. J.; Herzog, D. G.

    1982-01-01

    The optical disc has become a new technique for mass digital data storage of X-ray images from examinations and films in todays hospitals. Up to 36,000 X-ray images can be stored on one side of a 12-inch disc by melting holes 0.015 mils in size in an ablative material such as tellerium with a laser beam. This unique characteristic makes the disc suitable for storage and retrieval of X-rays in a record and playback system in either a single disc or multiple disc "jukebox" configuration. Doctors, nurses, technicians and other hospital personnel can call up a particular X-ray in less than 0.6 of a second in an on-line single disc system and up to less than 6 seconds in an on-line "jukebox" system. The jukebox is configured to hold up to 100 discs, thus storing 3,600,000 X-rays in hospitals with a bed size of greater than 500. The estimated exposed films on file in those hospitals is 327,400,000 and the estimated annual X-ray exams are 44,300. Thus, a single disc system could be used for an all electronic X-ray scanning system for annual X-ray exams. The jukebox configuration, which has expansion capability for servicing multiple simultaneous user request, can be applied to large archival mass storage. These systems could store the existing exposed films in hospitals with bed size greater than 500 at record and playback data rates of 50 Mb/s with access times of less than 15 seconds.

  14. Phenotype and seed production among hyacinth bean (Lablab purpureus L. Sweet) accessions rescued using hydroponic techniques

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Hyacinth bean, Lablab purpureus L. (Sweet) is a legume used as a vegetable, forage, and in home gardens as an ornamental plant. Many accessions do not flower during their juvenile period in Byron, GA. Other hyacinth bean accessions produce few seed when regenerated in the field. This study was condu...

  15. Impact of optical hard limiter on the performance of an optical overlapped-code division multiple access system

    NASA Astrophysics Data System (ADS)

    Inaty, Elie; Raad, Robert; Tablieh, Nicole

    2011-08-01

    Throughout this paper, a closed form expression of the multiple access interference (MAI) limited bit error rate (BER) is provided for the multiwavelength optical code-division multiple-access system when the system is working above the nominal transmission rate limit imposed by the passive encoding-decoding operation. This system is known in literature as the optical overlapped code division multiple access (OV-CDMA) system. A unified analytical framework is presented emphasizing the impact of optical hard limiter (OHL) on the BER performance of such a system. Results show that the performance of the OV-CDMA system may be highly improved when using OHL preprocessing at the receiver side.

  16. A Novel Technique Using a Protection Filter During Fibrin Sheath Removal for Implanted Venous Access Device Dysfunction.

    PubMed

    Sotiriadis, Charalampos; Hajdu, Steven David; Degrauwe, Sophie; Barras, Heloise; Qanadli, Salah Dine

    2016-08-01

    With the increased use of implanted venous access devices (IVADs) for continuous long-term venous access, several techniques such as percutaneous endovascular fibrin sheath removal, have been described, to maintain catheter function. Most standard techniques do not capture the stripped fibrin sheath, which is subsequently released in the pulmonary circulation and may lead to symptomatic pulmonary embolism. The presented case describes an endovascular technique which includes stripping, capture, and removal of fibrin sheath using a novel filter device. A 64-year-old woman presented with IVAD dysfunction. Stripping was performed using a co-axial snare to the filter to capture the fibrin sheath. The captured fragment was subsequently removed for visual and pathological verification. No immediate complication was observed and the patient was discharged the day of the procedure. PMID:27016091

  17. Effects of W-CDMA 1950 MHz EMF emitted by mobile phones on regional cerebral blood flow in humans.

    PubMed

    Mizuno, Yoko; Moriguchi, Yoshiya; Hikage, Takashi; Terao, Yasuo; Ohnishi, Takashi; Nojima, Toshio; Ugawa, Yoshikazu

    2009-10-01

    Use of the third generation mobile phone system is increasing worldwide. This is the first study to investigate the effects of the third generation system on regional cerebral blood flow (rCBF) in humans. We compared effects of the electromagnetic field (EMF) emitted from the Wideband Code Division Multiple Access (W-CDMA) cellular system versus sham control exposure on rCBF in humans. Nine healthy male volunteers participated in this study. Positron emission tomography (PET) scans were obtained before, during, and after unilateral 30 min EMF exposure. The subtraction analysis revealed no significant rCBF changes caused by the EMF conditions compared with the sham exposure, suggesting that EMF emitted by a third generation mobile phone does not affect rCBF in humans. PMID:19475648

  18. Image fiber optic space-CDMA parallel transmission experiment using 8 x 8 VCSEL/PD arrays.

    PubMed

    Nakamura, Moriya; Kitayama, Ken-ichi; Igasaki, Yasunori; Shamoto, Naoki; Kaneda, Keiji

    2002-11-10

    We experimentally demonstrate space-code-division multiple access (space-CDMA) based twodimensional (2-D) parallel optical interconnections by using image fibers and 8 x 8 vertical-cavity surface-emitting laser (VCSEL)/photo diode (PD) arrays. Two spatially encoded four-bit (2 x 2) parallel optical signals were emitted fiom 2-D VCSEL arrays and transmitted through image fibers. The encoded signals were multiplexed by an image-fiber coupler and detected by a 2-D PD array on the receiver side. The receiver recovered the intended parallel signal by decoding the signal. The transmission speed was 64 Mbps/ch (total throughput: 512 Mbps). Bit-error-rate (BER) measurement with a laterally misaligned PD array showed the array had a misalignment tolerance of 25 microm for a BER performance of 10(-9). PMID:12440546

  19. A Charrelation Matrix-Based Blind Adaptive Detector for DS-CDMA Systems.

    PubMed

    Luo, Zhongqiang; Zhu, Lidong

    2015-01-01

    In this paper, a blind adaptive detector is proposed for blind separation of user signals and blind estimation of spreading sequences in DS-CDMA systems. The blind separation scheme exploits a charrelation matrix for simple computation and effective extraction of information from observation signal samples. The system model of DS-CDMA signals is modeled as a blind separation framework. The unknown user information and spreading sequence of DS-CDMA systems can be estimated only from the sampled observation signals. Theoretical analysis and simulation results show that the improved performance of the proposed algorithm in comparison with the existing conventional algorithms used in DS-CDMA systems. Especially, the proposed scheme is suitable for when the number of observation samples is less and the signal to noise ratio (SNR) is low. PMID:26287209

  20. Experimental demonstration of interference avoidance protocol (transmission scheduling) in O-CDMA networks.

    PubMed

    Saghari, Poorya; Kamath, P; Arbab, Vahid R; Haghi, Mahta; Willner, Alan E; Bannister, Joe A; Touch, Joe D

    2007-12-10

    We experimentally demonstrate a transmission scheduling algorithm to avoid congestion collapse in O-CDMA networks. Our result shows that transmission scheduling increases the performance of the system by orders of magnitude. PMID:19550934

  1. Bit-Error-Rate Performance of a Gigabit Ethernet O-CDMA Technology Demonstrator (TD)

    SciTech Connect

    Hernandez, V J; Mendez, A J; Bennett, C V; Lennon, W J

    2004-07-09

    An O-CDMA TD based on 2-D (wavelength/time) codes is described, with bit-error-rate (BER) and eye-diagram measurements given for eight users. Simulations indicate that the TD can support 32 asynchronous users.

  2. A Charrelation Matrix-Based Blind Adaptive Detector for DS-CDMA Systems

    PubMed Central

    Luo, Zhongqiang; Zhu, Lidong

    2015-01-01

    In this paper, a blind adaptive detector is proposed for blind separation of user signals and blind estimation of spreading sequences in DS-CDMA systems. The blind separation scheme exploits a charrelation matrix for simple computation and effective extraction of information from observation signal samples. The system model of DS-CDMA signals is modeled as a blind separation framework. The unknown user information and spreading sequence of DS-CDMA systems can be estimated only from the sampled observation signals. Theoretical analysis and simulation results show that the improved performance of the proposed algorithm in comparison with the existing conventional algorithms used in DS-CDMA systems. Especially, the proposed scheme is suitable for when the number of observation samples is less and the signal to noise ratio (SNR) is low. PMID:26287209

  3. An Adaptive User Grouping and Subcarrier Allocation Algorithm for Grouped MC-CDMA Systems

    NASA Astrophysics Data System (ADS)

    Huang, Jinri; Niu, Zhisheng

    In MC-CDMA systems, subcarriers can be shared by different users. In this letter, we exploit the shared nature of subcarriers and propose a user grouping and subcarrier allocation algorithm for grouped MC-CDMA systems. The scheme aims at maximizing the total system throughput while providing bandwidth-fairness among groups. Simulation results are given to demonstrate the performance of the proposed algorithm in terms of sum capacity and per-user throughput.

  4. An information theory criteria based blind method for enumerating active users in DS-CDMA system

    NASA Astrophysics Data System (ADS)

    Samsami Khodadad, Farid; Abed Hodtani, Ghosheh

    2014-11-01

    In this paper, a new and blind algorithm for active user enumeration in asynchronous direct sequence code division multiple access (DS-CDMA) in multipath channel scenario is proposed. The proposed method is based on information theory criteria. There are two main categories of information criteria which are widely used in active user enumeration, Akaike Information Criterion (AIC) and Minimum Description Length (MDL) information theory criteria. The main difference between these two criteria is their penalty functions. Due to this difference, MDL is a consistent enumerator which has better performance in higher signal-to-noise ratios (SNR) but AIC is preferred in lower SNRs. In sequel, we propose a SNR compliance method based on subspace and training genetic algorithm to have the performance of both of them. Moreover, our method uses only a single antenna, in difference to the previous methods which decrease hardware complexity. Simulation results show that the proposed method is capable of estimating the number of active users without any prior knowledge and the efficiency of the method.

  5. Laser noise measurement techniques and applications of femtosecond encoding in the frequency domain

    NASA Astrophysics Data System (ADS)

    Scott, Ryan Patrick

    This dissertation investigates mode-locked laser noise measurement techniques, the concept and measurement of a laser's noise transfer function, and then two applications of spectral encoding of optical pulses. The one application is optical code division multiple access (O-CDMA) and the other is optical arbitrary waveform generation (OAWG). The relationship between source stability, encoding, and overall system performance in O-CDMA is also discussed. Techniques for making sensitive and high-dynamic-range measurements of laser amplitude and envelope phase noise (timing jitter) in the frequency domain at the shot-noise limit are described. The short term stability of a Kerr-lens modelocked (KLM) Ti:sapphire laser is shown to be close to that of the precision crystal oscillators used in its characterization. The amplitude and envelope phase noise of a KLM Ti:sapphire laser are shown to depend directly on the pump laser amplitude stability. The sensitivity of this process is described by a noise transfer function (NTF) which represents the magnitude of the amplitude-to-amplitude modulation and amplitude-to-phase modulation conversion gain of the pump-induced amplitude and phase noise, respectively. A spectral phase-encoded time-spreading (SPECTS) O-CDMA testbed is described. The testbed employs a fiber-pigtailed, bulk-optics arrangement that utilizes a two-dimensional spatial light phase modulator for encoding multiple channels. The time-gated SPECTS O-CDMA receiver is composed of a nonlinear optical loop mirror (NOLM) and a nonlinear thresholder Experimentally measured performance is compared to numerical simulations. Finally, an optical frequency comb with 20-GHz spacing is shaped by an integrated silica arrayed-waveguide grating (AWG) pair to produce optical waveforms with high fidelity. Characterization of both the intensity and phase of the crafted opitical fields is accomplished with cross-correlation frequency-resolved optical gating (XFROG) which has been

  6. Random-access technique for modular bathymetry data storage in a continental shelf wave refraction program

    NASA Technical Reports Server (NTRS)

    Poole, L. R.

    1974-01-01

    A study was conducted of an alternate method for storage and use of bathymetry data in the Langley Research Center and Virginia Institute of Marine Science mid-Atlantic continental-shelf wave-refraction computer program. The regional bathymetry array was divided into 105 indexed modules which can be read individually into memory in a nonsequential manner from a peripheral file using special random-access subroutines. In running a sample refraction case, a 75-percent decrease in program field length was achieved by using the random-access storage method in comparison with the conventional method of total regional array storage. This field-length decrease was accompanied by a comparative 5-percent increase in central processing time and a 477-percent increase in the number of operating-system calls. A comparative Langley Research Center computer system cost savings of 68 percent was achieved by using the random-access storage method.

  7. Techniques to Improve Subject Retrieval in Online Catalogs: Flexible Access to Elements in the Bibliographic Record.

    ERIC Educational Resources Information Center

    Connell, Tschera Harkness

    1991-01-01

    Discussion of improving subject access in online library catalogs focuses on a study that used a book description from "Book Review Digest" to evaluate the information on the bibliographic record found on the OCLC database. Matching by Library of Congress Subject Headings and by keywords in the title are discussed. (22 references) (LRW)

  8. Modern techniques and technologies for unbundled access in the local loop

    NASA Astrophysics Data System (ADS)

    Bacis Vasile, Irina Bristena; Schiopu, Paul; Marghescu, Cristina

    2015-02-01

    The efficient and unbundled use of the existing telecommunications infrastructure represents a major goal for the development of the services offered by telecommunications providers. A major telecommunications operator can provide services to a subscriber using a copper wire pair or part of the frequency spectrum of a copper wire pair, together with other operators, through a process of unbundling access in the local loop. Since access to the vocal band is an already solved problem, concerns turn to the broadband access with xDSL service delivery on ungrouped subscriber loops; besides the legal and economic aspects involved this has become an engineering problem also. The local loop unbundling methods have a substantial technical impact. This impact should be taken into account right from the design stage and then in the standardization stage of broadband systems intended to operate on copper wire pairs in the local loop. These systems are known under the generic term of xDSL and began to be analyzed in the late 90s. xDSL became the dominant solution for providing Internet at a reasonable price for both residential and business subscribers. In this massive development scenario, certain problems will arise from the early stages of deployment, and another type of problems will occur later on when a large number of systems will be installed in a single beam.

  9. A Code Phase Division Multiple Access (CPDMA) technique for VSAT satellite communications

    NASA Technical Reports Server (NTRS)

    Bruno, R.; Mcomber, R.; Weinberg, A.

    1991-01-01

    A reference concept and implementation relevant to the application of Code Phase Division Multiple Access (CPDMA) to a high capacity satellite communication system providing 16 Kbps single hop channels between Very Small Aperture Terminals (VSAT's) is described. The description includes a potential implementation of an onboard CPDMA bulk demodulator/converter utilizing programmable charge coupled device (CCD) technology projected to be available in the early 1990's. A high level description of the system architecture and operations, identification of key functional and performance requirements of the system elements, and analysis results of end-to-end system performance relative to key figures of merit such as spectral efficiency are also provided.

  10. A Low-PAPR Multiplexed MC-CDMA System with Enhanced Data Rate and Link Quality

    NASA Astrophysics Data System (ADS)

    Deng, Juinn-Horng; Hwang, Jeng-Kuang

    Recently, a new multi-carrier CDMA (MC-CDMA) system with cyclic-shift orthogonal keying (CSOK) has been proposed and shown to be more spectral and power efficient than conventional MC-CDMA systems. In this paper, a novel extension called the multiplexed CSOK (MCSOK) MC-CDMA system is proposed to further increase the data rate while maintaining a low peak-to-average power ratio (PAPR). First, the data stream is divided into multiple parallel substreams that are mapped into QPSK-CSOK symbols in terms of cyclic shifted Chu sequences. Second, these sequences are repeated, modulated, summed, and placed on IFFT subcarriers, resulting in a constant-modulus multiplexed signal that preserves the desired orthogonality among substreams. The receiver performs frequency-domain equalization and uses efficient demultiplexing, despreading, and demapping schemes to detect the modulation symbols. Furthermore, an alternate MCSOK system configuration with high link quality is also presented. Simulations show that the proposed MCSOK system attains lower PAPR and BER, as compared to conventional MC-CDMA system using Walsh codes. Under a rich multipath environment, the high link quality configuration exhibits excellent performance with both diversity gain and MCSOK modulation gain.

  11. Immediate endodontic access cavity sealing: fundamentals of a new restorative technique.

    PubMed

    De Rose, Luca; Krejci, I; Bortolotto, T

    2015-09-01

    Endodontic access cavity sealing is conventionally performed after endodontic irrigation, referred to as delayed endodontic sealing (DES). Evidence shows that endodontic irrigation with NaOCl decreases dentinal bond quality and could cause coronal leakage. Access cavity sealing before endodontic irrigation is a new restorative approach, referred to as immediate endodontic sealing (IES). The primary aim of this in vitro study was to investigate whether IES improved internal adaptation. The secondary aim was to investigate the influence of the viscosity of the composite used to seal the dentine, on the internal adaptation in both IES and DES groups. Third molars (n= 40) with fully developed apices were used. The teeth were prepared into standard Class II MO cavities, and divided in 4 groups according to the approach, and composite viscosity was used for sealing. Group 1: IES + low viscosity composite; group 2: IES + high viscosity composite; group 3: DES + low viscosity composite; and group 4: DES + high viscosity composite. Samples were then sectioned axially for observation using scanning electron microscopy. Outcome was evaluated by determining the internal adaptation of the samples, which was judged based on the percentage of a continuous margin at the tooth-composite interface. The results were analyzed using a two-way analysis of variance and Mann-Whitney test. IES groups exhibited significantly greater internal adaptation (p = 0.000) as compared with DES groups. Composite viscosity did not significantly affect internal adaptation in either IES or DES groups (p > 0.005). PMID:25183493

  12. DNA strand breaks are not induced in human cells exposed to 2.1425 GHz band CW and W-CDMA modulated radiofrequency fields allocated to mobile radio base stations.

    PubMed

    Sakuma, N; Komatsubara, Y; Takeda, H; Hirose, H; Sekijima, M; Nojima, T; Miyakoshi, J

    2006-01-01

    We conducted a large-scale in vitro study focused on the effects of low level radiofrequency (RF) fields from mobile radio base stations employing the International Mobile Telecommunication 2000 (IMT-2000) cellular system in order to test the hypothesis that modulated RF fields may act as a DNA damaging agent. First, we evaluated the responses of human cells to microwave exposure at a specific absorption rate (SAR) of 80 mW/kg, which corresponds to the limit of the average whole body SAR for general public exposure defined as a basic restriction in the International Commission on Non-Ionizing Radiation Protection (ICNIRP) guidelines. Second, we investigated whether continuous wave (CW) and Wideband Code Division Multiple Access (W-CDMA) modulated signal RF fields at 2.1425 GHz induced different levels of DNA damage. Human glioblastoma A172 cells and normal human IMR-90 fibroblasts from fetal lungs were exposed to mobile communication frequency radiation to investigate whether such exposure produced DNA strand breaks in cell culture. A172 cells were exposed to W-CDMA radiation at SARs of 80, 250, and 800 mW/kg and CW radiation at 80 mW/kg for 2 and 24 h, while IMR-90 cells were exposed to both W-CDMA and CW radiations at a SAR of 80 mW/kg for the same time periods. Under the same RF field exposure conditions, no significant differences in the DNA strand breaks were observed between the test groups exposed to W-CDMA or CW radiation and the sham exposed negative controls, as evaluated immediately after the exposure periods by alkaline comet assays. Our results confirm that low level exposures do not act as a genotoxicant up to a SAR of 800 mW/kg. PMID:16283663

  13. Advanced techniques and technology for efficient data storage, access, and transfer

    NASA Technical Reports Server (NTRS)

    Rice, Robert F.; Miller, Warner

    1991-01-01

    Advanced techniques for efficiently representing most forms of data are being implemented in practical hardware and software form through the joint efforts of three NASA centers. These techniques adapt to local statistical variations to continually provide near optimum code efficiency when representing data without error. Demonstrated in several earlier space applications, these techniques are the basis of initial NASA data compression standards specifications. Since the techniques clearly apply to most NASA science data, NASA invested in the development of both hardware and software implementations for general use. This investment includes high-speed single-chip very large scale integration (VLSI) coding and decoding modules as well as machine-transferrable software routines. The hardware chips were tested in the laboratory at data rates as high as 700 Mbits/s. A coding module's definition includes a predictive preprocessing stage and a powerful adaptive coding stage. The function of the preprocessor is to optimally process incoming data into a standard form data source that the second stage can handle.The built-in preprocessor of the VLSI coder chips is ideal for high-speed sampled data applications such as imaging and high-quality audio, but additionally, the second stage adaptive coder can be used separately with any source that can be externally preprocessed into the 'standard form'. This generic functionality assures that the applicability of these techniques and their recent high-speed implementations should be equally broad outside of NASA.

  14. Comparison of Venae Sectio vs. modified Seldinger Technique for Totally Implantable Access Ports; Portas-trial [ISRCTN:52368201

    PubMed Central

    Knebel, P; Fröhlich, B; Knaebel, H-P; Kienle, P; Luntz, S; Buchler, MW; Seiler, CM

    2006-01-01

    Background The insertion of a Totally Implantable Access Port (TIAP) is a routinely employed technique in patients who need a safe and permanent venous access. The number of TIAP implantations is increasing constantly mainly due to advanced treatment options for malignant diseases. Therefore it is important to identify the implantation technique which has the optimal benefit/risk ratio for the patient. Study design A single-centre, randomized, controlled superiority trial to compare two different TIAP implantation techniques. Sample size: 160 patients will be included and randomized intra-operatively. Eligibility criteria: Age equal or older than 18 years, patients scheduled for primary elective implantation of a TIAP in local anaesthesia and a signed informed consent. Primary endpoint: Primary success rate of the randomized technique. Intervention: Venae Sectio in combination with the Seldinger Technique (guide wire and a peel away sheath) will be used to place a TIAP. Reference treatment: Conventional Venae Sectio will be used with a direct insertion of the TIAP without guide wire or peel away sheath. Duration of study: Approximately 20 months. Organisation/Responsibility The trial will be conducted in compliance with the protocol and in accordance with the moral, ethical, and scientific principles governing clinical research as set out in the Declaration of Helsinki (1989) and Good Clinical Practice (GCP). The trial will also be carried out in keeping with local and regulatory requirements. The Klinisches Studienzentrum Chirurgie (KSC) – Centre of Clinical Trials in Surgery at the Department of Surgery, University Hospital Heidelberg is responsible for planning and conduction of the trial. Documentation of patient's data will be accomplished via electronical Case Report Files (eCRF) with MACRO®-Software by the KSC. Randomization, data management, monitoring and biometry are provided by the independent Koordinierungszentrum für Klinische Studien (KKS)

  15. A Wide Dynamics and Fast Scan Interrogating Method for a Fiber Bragg Grating Sensor Network Implemented Using Code Division Multiple Access

    PubMed Central

    Kim, Youngbok; Jeon, Sie-Wook; Kwon, Won-Bae; Park, Chang-Soo

    2012-01-01

    We propose and demonstrate a fiber Bragg grating (FBG) sensor network employing the code division multiple access (CDMA) technique to identify information from individual sensors. To detect information without considering time delays between sensors, a sliding correlation method is applied, in which two different signals with the same pseudo-random binary sequence (PRBS) pattern, but slightly different frequencies, are applied to the source and detector sides. Moreover, for time domain detection, a wavelength-to-time conversion technique using a wavelength dispersive medium is introduced. The experimental results show that the proposed sensor network has a wide strain dynamic range of 2,400 με and a low crosstalk of 950:1. PMID:22778619

  16. A wide dynamics and fast scan interrogating method for a fiber Bragg grating sensor network implemented using code division multiple access.

    PubMed

    Kim, Youngbok; Jeon, Sie-Wook; Kwon, Won-Bae; Park, Chang-Soo

    2012-01-01

    We propose and demonstrate a fiber Bragg grating (FBG) sensor network employing the code division multiple access (CDMA) technique to identify information from individual sensors. To detect information without considering time delays between sensors, a sliding correlation method is applied, in which two different signals with the same pseudo-random binary sequence (PRBS) pattern, but slightly different frequencies, are applied to the source and detector sides. Moreover, for time domain detection, a wavelength-to-time conversion technique using a wavelength dispersive medium is introduced. The experimental results show that the proposed sensor network has a wide strain dynamic range of 2,400 με and a low crosstalk of 950:1. PMID:22778619

  17. Delay-bounded semi-reliable vital sign transmission protocol for mobile telemedicine over a CDMA 1x EV-DO network.

    PubMed

    Lee, Tong H; Yoo, Sun K

    2008-04-01

    The reliable and instant transmission of vital signs is important for remote time-critical patient care through a telemedicine system. However, sometimes the reliability and instantaneity conditions cannot be satisfied simultaneously under a high-noise mobile network, because they are reciprocal to each other. In this paper, the vital sign transmission protocol (VSTP) running over a CDMA 1x EVDO (Code Division Multiple Access 1x Evolution Data Only) mobile network is proposed to comply with both the reliability and instantaneity requirements. The switching buffer management scheme is combined with a hybrid error control scheme, consisting of forward error correction (FEC) and automatic repeat request (ARQ). The CDMA 1x EVDO mobile network is modeled by two states using the Markov wireless channel model to test transmission performance under diverse network conditions. Throughout the noisy environment simulation, the performance of the VSTP is compared with the Transmission Control Protocol (TCP) and User Datagram Protocol (UDP) to demonstrate its efficacy over error-prone mobile network. PMID:17561431

  18. Accessing gelling ability of vegetable proteins using rheological and fluorescence techniques.

    PubMed

    Batista, Ana Paula; Portugal, Carla A M; Sousa, Isabel; Crespo, João G; Raymundo, Anabela

    2005-08-01

    This work aims to present a comprehensive study about the macroscopic characteristics of globular vegetable proteins, in terms of their gelling ability, by understanding their molecular behaviour, when submitted to a thermal gelling process. The gels of soy, pea and lupin proteins were characterized by rheological techniques. Gelation kinetics, mechanical spectra, as well as the texture of these gels were analyzed and compared. Additionally, capillary viscometry, steady-state fluorescence and fluorescence anisotropy were used to monitor the structural changes induced by the thermal denaturation, which constitutes the main condition for the formation of a gel structure. Based on these techniques it was possible to establish a relationship between the gelling ability of each protein isolate and their structural resistance to thermal unfolding, enabling us to explain the weakest and the strongest gelling ability observed for lupin and soy proteins isolates, respectively. PMID:15996729

  19. Accessing Interior Vector Magnetic Field Components in Neutron EDM Experiments via Boundary Value Techniques

    NASA Astrophysics Data System (ADS)

    Plaster, Brad

    2012-10-01

    We propose a new technique for the determination and monitoring of the interior vector magnetic field components during the operation of neutron EDM experiments. If a suitable three-dimensional volume surrounding the fiducial volume of an experiment can be defined which contains no interior currents or magnetization, each of the interior vector field components will satisfy the Laplace Equation within this volume. Therefore, if the field components can be measured on the boundary, the interior vector field components can be determined uniquely via numerical solution of the Laplace Equation. We discuss the applicability of this technique to the determination of the magnetic field components and magnetic field gradients in the fiducial volumes of neutron EDM experiments.

  20. Field transients of coherent terahertz synchrotron radiation accessed via time-resolving and correlation techniques

    NASA Astrophysics Data System (ADS)

    Pohl, A.; Semenov, A.; Hübers, H.-W.; Hoehl, A.; Ries, M.; Wüstefeld, G.; Ulm, G.; Ilin, K.; Thoma, P.; Siegel, M.

    2016-03-01

    Decaying oscillations of the electric field in repetitive pulses of coherent synchrotron radiation in the terahertz frequency range was evaluated by means of time-resolving and correlation techniques. Comparative analysis of real-time voltage transients of the electrical response and interferograms, which were obtained with an ultrafast zero-bias Schottky diode detector and a Martin-Puplett interferometer, delivers close values of the pulse duration. Consistent results were obtained via the correlation technique with a pair of Golay Cell detectors and a pair of resonant polarisation-sensitive superconducting detectors integrated on one chip. The duration of terahertz synchrotron pulses does not closely correlate with the duration of single-cycle electric field expected for the varying size of electron bunches. We largely attribute the difference to the charge density oscillations in electron bunches and to the low-frequency spectral cut-off imposed by both the synchrotron beamline and the coupling optics of our detectors.

  1. An investigation of a sterile access technique for the repair and adjustment of sterile spacecraft

    NASA Technical Reports Server (NTRS)

    Farmer, F. H.; Fuller, H. V.; Hueschen, R. M.

    1973-01-01

    A description is presented of a unique system for the sterilization and sterile repair of spacecraft and the results of a test program designed to assess the biological integrity and engineering reliability of the system. This trailer-mounted system, designated the model assembly sterilizer for testing (MAST), is capable of the dry-heat sterilization of spacecraft and/or components less than 2.3 meters in diameter at temperatures up to 433 K and the steam sterilization of components less than 0.724 meter in diameter. Sterile access to spacecraft is provided by two tunnel suits, called the bioisolator suit systems (BISS), which are contiguous with the walls of the sterilization chambers. The test program was designed primarily to verify the biological and engineering reliability of the MAST system by processing simulated space hardware. Each test cycle simulated the initial sterilization of a spacecraft, sterile repair of a failed component, removal of the spacecraft from the MAST for mating with the bus, and a sterile recycle repair.

  2. Optimum and Suboptimum Code Allocation for Peak Power Reduction in Down-Link MC CDMA

    NASA Astrophysics Data System (ADS)

    Choi, Kwonhue; Jin, Jiyu

    We develop an optimum code allocation scheme by investigating the peak to average power ratio (PAPR) characteristic of a down-link multi-carrier (MC)-CDMA system using Walsh-Hadamard code. It is shown that PAPR of a MC-CDMA system is highly dependent upon the selection of code combination. Based on this fact, we develop the allocation method which minimizes PAPR according to the number of active users. In addition, an efficient suboptimum code combination search scheme is also proposed for near minimum PAPR.

  3. Interference cancellation technique of optical AND gate receiver using optical thyristor.

    PubMed

    Kang, Tae-Gu

    2008-09-01

    We demonstrate an interference cancellation technique of optical AND gate receiver using optical thyristor for fiber-optic code division multiple access (FO-CDMA) systems. In particular, we fabricate the optical thyristor operating as optical hard-limiter and evaluate that the optical AND gate receiver using fabricated optical thyristor excludes the peaks of side-lobe and cross-correlation result in the system performance degradation. It found that the optical AND gate receiver using optical thyristor excludes the intensity of interference signal resulting in that the peaks of side-lobe and cross-correlation can be fully eliminated for any two users. Therefore, the optical AND gate receiver using optical thyristor is shown to be effective to accommodate more simultaneous users. PMID:18773033

  4. Small access postaural parotidectomy: an analysis of techniques, feasibility and safety.

    PubMed

    Yuen, Anthony Po-Wing

    2016-07-01

    For cosmetic consideration of parotidectomy, the surgical approaches have evolved from Blair incision through modified facelift incision to postaural-hairline incision. The present study aims at evaluating the feasibility and safety of the new technique of postaural approach. Parotidectomy was performed with a 4-5 cm incision in the postaural sulcus. There were 69 patients who were assessed pre-operatively feasible for consideration of the postaural parotidectomy. There were 56 (81 %) patients who could have the postaural parotidectomy successfully without complications. The minimally invasive postaural approach is a further step in cosmetic consideration of parotidectomy. It is a feasible and safe approach for most small to medium size benign parotid tumors located in the mid and lower pole regions of the parotid gland. PMID:26122398

  5. Kalai-Smorodinsky bargaining solution for optimal resource allocation over wireless DS-CDMA visual sensor networks

    NASA Astrophysics Data System (ADS)

    Pandremmenou, Katerina; Kondi, Lisimachos P.; Parsopoulos, Konstantinos E.

    2012-01-01

    Surveillance applications usually require high levels of video quality, resulting in high power consumption. The existence of a well-behaved scheme to balance video quality and power consumption is crucial for the system's performance. In the present work, we adopt the game-theoretic approach of Kalai-Smorodinsky Bargaining Solution (KSBS) to deal with the problem of optimal resource allocation in a multi-node wireless visual sensor network (VSN). In our setting, the Direct Sequence Code Division Multiple Access (DS-CDMA) method is used for channel access, while a cross-layer optimization design, which employs a central processing server, accounts for the overall system efficacy through all network layers. The task assigned to the central server is the communication with the nodes and the joint determination of their transmission parameters. The KSBS is applied to non-convex utility spaces, efficiently distributing the source coding rate, channel coding rate and transmission powers among the nodes. In the underlying model, the transmission powers assume continuous values, whereas the source and channel coding rates can take only discrete values. Experimental results are reported and discussed to demonstrate the merits of KSBS over competing policies.

  6. Joint Carrier Distribution and Frequency Hopping Scheme for Improving the BER Performance in PB/MC-CDMA Systems

    NASA Astrophysics Data System (ADS)

    Lee, Kyujin; Lee, Kyesan

    In this paper, we propose a novel frequency-hopping scheme in order to improve the BER (Bit Error Rate) performance of the Partial Block MC-CDMA (PB/MC-CDMA) system. The joint carrier distribution and frequency hopping (JDFH) scheme achieves the optimal frequency diversity gain while avoiding interference. By contrast, the conventional FH scheme only avoids interference, and the frequency interleaving scheme achieves only frequency diversity. The JDFH scheme thus performs better than conventional schemes, such as carrier FH, block FH, or frequency interleaving. Through computer simulations, we confirmed the superior performance of the PB/MC-CDMA system when using the JDFH scheme.

  7. A Per-baseline, Delay-spectrum Technique for Accessing the 21 cm Cosmic Reionization Signature

    NASA Astrophysics Data System (ADS)

    Parsons, Aaron R.; Pober, Jonathan C.; Aguirre, James E.; Carilli, Christopher L.; Jacobs, Daniel C.; Moore, David F.

    2012-09-01

    A critical challenge in measuring the power spectrum of 21 cm emission from cosmic reionization is compensating for the frequency dependence of an interferometer's sampling pattern, which can cause smooth-spectrum foregrounds to appear unsmooth and degrade the separation between foregrounds and the target signal. In this paper, we present an approach to foreground removal that explicitly accounts for this frequency dependence. We apply the delay transformation introduced in Parsons & Backer to each baseline of an interferometer to concentrate smooth-spectrum foregrounds within the bounds of the maximum geometric delays physically realizable on that baseline. By focusing on delay modes that correspond to image-domain regions beyond the horizon, we show that it is possible to avoid the bulk of smooth-spectrum foregrounds. We map the point-spread function of delay modes to k-space, showing that delay modes that are uncorrupted by foregrounds also represent samples of the three-dimensional power spectrum, and can be used to constrain cosmic reionization. Because it uses only spectral smoothness to differentiate foregrounds from the targeted 21 cm signature, this per-baseline analysis approach relies on spectrally and spatially smooth instrumental responses for foreground removal. For sufficient levels of instrumental smoothness relative to the brightness of interfering foregrounds, this technique substantially reduces the level of calibration previously thought necessary to detect 21 cm reionization. As a result, this approach places fewer constraints on antenna configuration within an array, and in particular, facilitates the adoption of configurations that are optimized for power-spectrum sensitivity. Under these assumptions, we demonstrate the potential for the Precision Array for Probing the Epoch of Reionization (PAPER) to detect 21 cm reionization at an amplitude of 10 mK2 near k ~ 0.2 h Mpc-1 with 132 dipoles in 7 months of observing.

  8. A PER-BASELINE, DELAY-SPECTRUM TECHNIQUE FOR ACCESSING THE 21 cm COSMIC REIONIZATION SIGNATURE

    SciTech Connect

    Parsons, Aaron R.; Pober, Jonathan C.; Aguirre, James E.; Moore, David F.; Carilli, Christopher L.; Jacobs, Daniel C.

    2012-09-10

    A critical challenge in measuring the power spectrum of 21 cm emission from cosmic reionization is compensating for the frequency dependence of an interferometer's sampling pattern, which can cause smooth-spectrum foregrounds to appear unsmooth and degrade the separation between foregrounds and the target signal. In this paper, we present an approach to foreground removal that explicitly accounts for this frequency dependence. We apply the delay transformation introduced in Parsons and Backer to each baseline of an interferometer to concentrate smooth-spectrum foregrounds within the bounds of the maximum geometric delays physically realizable on that baseline. By focusing on delay modes that correspond to image-domain regions beyond the horizon, we show that it is possible to avoid the bulk of smooth-spectrum foregrounds. We map the point-spread function of delay modes to k-space, showing that delay modes that are uncorrupted by foregrounds also represent samples of the three-dimensional power spectrum, and can be used to constrain cosmic reionization. Because it uses only spectral smoothness to differentiate foregrounds from the targeted 21 cm signature, this per-baseline analysis approach relies on spectrally and spatially smooth instrumental responses for foreground removal. For sufficient levels of instrumental smoothness relative to the brightness of interfering foregrounds, this technique substantially reduces the level of calibration previously thought necessary to detect 21 cm reionization. As a result, this approach places fewer constraints on antenna configuration within an array, and in particular, facilitates the adoption of configurations that are optimized for power-spectrum sensitivity. Under these assumptions, we demonstrate the potential for the Precision Array for Probing the Epoch of Reionization (PAPER) to detect 21 cm reionization at an amplitude of 10 mK{sup 2} near k {approx} 0.2 h Mpc{sup -1} with 132 dipoles in 7 months of observing.

  9. Demonstration of end-to-end cloud-DSL with a PON-based fronthaul supporting 5.76-Gb/s throughput with 48 eCDMA-encoded 1024-QAM discrete multi-tone signals.

    PubMed

    Fang, Liming; Zhou, Lei; Liu, Xiang; Zhang, Xiaofeng; Sui, Meng; Effenberger, Frank; Zhou, Jun

    2015-05-18

    We experimentally demonstrate an end-to-end ultra-broadband cloud-DSL network using passive optical network (PON) based fronthaul with electronic code-division-multiple-access (eCDMA) encoding and decoding. Forty-eight signals that are compliant with the very-high-bit-rate digital subscriber line 2 (VDSL2) standard are transmitted with a record throughput of 5.76 Gb/s over a hybrid link consisting of a 20-km standard single-mode fiber and a 100-m twisted pair. PMID:26074597

  10. Performance of Adaptive Trellis Coded Modulation Applied to MC-CDMA with Bi-orthogonal Keying

    NASA Astrophysics Data System (ADS)

    Tanaka, Hirokazu; Yamasaki, Shoichiro; Haseyama, Miki

    A Generalized Symbol-rate-increased (GSRI) Pragmatic Adaptive Trellis Coded Modulation (ATCM) is applied to a Multi-carrier CDMA (MC-CDMA) system with bi-orthogonal keying is analyzed. The MC-CDMA considered in this paper is that the input sequence of a bi-orthogonal modulator has code selection bit sequence and sign bit sequence. In [9], an efficient error correction code using Reed-Solomon (RS) code for the code selection bit sequence has been proposed. However, since BPSK is employed for the sign bit modulation, no error correction code is applied to it. In order to realize a high speed wireless system, a multi-level modulation scheme (e.g. MPSK, MQAM, etc.) is desired. In this paper, we investigate the performance of the MC-CDMA with bi-orthogonal keying employing GSRI ATCM. GSRI TC-MPSK can arbitrarily set the bandwidth expansion ratio keeping higher coding gain than the conventional pragmatic TCM scheme. By changing the modulation scheme and the bandwidth expansion ratio (coding rate), this scheme can optimize the performance according to the channel conditions. The performance evaluations by simulations on an AWGN channel and multi-path fading channels are presented. It is shown that the proposed scheme has remarkable throughput performance than that of the conventional scheme.

  11. How old is too old? A contribution to the discussion on age limits for assisted reproduction technique access.

    PubMed

    Kocourková, Jiřina; Konečná, Hana; Burcin, Boris; Kučera, Tomáš

    2015-05-01

    In 2012, the Czech Republic established the women's age limit for access to assisted reproduction techniques at age 49 years. In this paper, the acceptability of this age limit from the children's perspective in the Czech Republic is assessed. Although the necessity of balancing the interests of parents and children is acknowledged, little research has taken children's interests into account. We have attempted to map out 'children's interests', asking older children and adolescents (aged 11-25 years) how old they would prefer their parents to be: Czech respondents would prefer to have younger parents. This finding is consistent with the optimal biological childbearing age rather than with the current postponement to a later age. So far, assisted reproduction techniques have been largely regarded as a medical treatment justifying the current women's age limit of 49 years. Had the children's perspective been taken into account, this age limit might have been lower than 49 years. We propose that reproductive health policy should adequately reflect multiple perspectives as an integral part of a multi-layered support system of a society. PMID:25773530

  12. Advanced multiple access concepts in mobile satellite systems

    NASA Technical Reports Server (NTRS)

    Ananasso, Fulvio

    1990-01-01

    Some multiple access strategies for Mobile Satellite Systems (MSS) are discussed. These strategies were investigated in the context of three separate studies conducted for the International Maritime Satellite Organization (INMARSAT) and the European Space Agency (ESA). Satellite-Switched Frequency Division Multiple Access (SS-FDMA), Code Division Multiple Access (CDMA), and Frequency-Addressable Beam architectures are addressed, discussing both system and technology aspects and outlining advantages and drawbacks of either solution with associated relevant hardware issues. An attempt is made to compare the considered option from the standpoint of user terminal/space segment complexity, synchronization requirements, spectral efficiency, and interference rejection.

  13. Access to the carotid artery bifurcation: Cadaveric study with application to nasotracheal intubation as a technique to improve access to a high carotid artery bifurcation.

    PubMed

    Foreman, Paul M; Harrigan, Mark R; Griessenauer, Christoph J; Loukas, Marios; Tubbs, R Shane

    2015-12-01

    Carotid endarterectomy (CEA) is a common and efficacious surgical procedure for the prevention of ischemic stroke due to atherosclerosis of the internal carotid artery (ICA). A high common carotid artery bifurcation can make CEA technically difficult due to limited carotid artery exposure. A cadaveric study was performed to evaluate the efficacy of nasotracheal intubation for improving access to a high carotid artery bifurcation. Based on this study, nasotracheal intubation does not improve access to a high carotid artery bifurcation as compared with orotracheal intubation. PMID:26312946

  14. Optimal power allocation and joint source-channel coding for wireless DS-CDMA visual sensor networks

    NASA Astrophysics Data System (ADS)

    Pandremmenou, Katerina; Kondi, Lisimachos P.; Parsopoulos, Konstantinos E.

    2011-01-01

    In this paper, we propose a scheme for the optimal allocation of power, source coding rate, and channel coding rate for each of the nodes of a wireless Direct Sequence Code Division Multiple Access (DS-CDMA) visual sensor network. The optimization is quality-driven, i.e. the received quality of the video that is transmitted by the nodes is optimized. The scheme takes into account the fact that the sensor nodes may be imaging scenes with varying levels of motion. Nodes that image low-motion scenes will require a lower source coding rate, so they will be able to allocate a greater portion of the total available bit rate to channel coding. Stronger channel coding will mean that such nodes will be able to transmit at lower power. This will both increase battery life and reduce interference to other nodes. Two optimization criteria are considered. One that minimizes the average video distortion of the nodes and one that minimizes the maximum distortion among the nodes. The transmission powers are allowed to take continuous values, whereas the source and channel coding rates can assume only discrete values. Thus, the resulting optimization problem lies in the field of mixed-integer optimization tasks and is solved using Particle Swarm Optimization. Our experimental results show the importance of considering the characteristics of the video sequences when determining the transmission power, source coding rate and channel coding rate for the nodes of the visual sensor network.

  15. Performance of code division multiple access systems

    NASA Technical Reports Server (NTRS)

    Weber, C. L.; Huth, G. K.; Batson, B. H.

    1980-01-01

    The performance of code division multiple-access (CDMA) systems is determined using direct sequence spectral spreading. Under relatively ideal conditions, the degradation in system performance as a function of the number of users is shown to have a threshold effect. This basic limitation in the number of users of the system is further limited if the powers are unequal. For two users, system performance as a function of their power ratio also has a threshold effect. System performance as a function of the amount of spectral spreading is determined. The performance of both coded and uncoded systems is predicted.

  16. A Novel Nonlinear Precoding Detection Algorithm for VBLAST in MIMO-MC-CDMA Downlink System

    NASA Astrophysics Data System (ADS)

    Fu, Hongliang; Tao, Yong

    Considering the error propagation effect and high complexity of the Vertical Bell Labs Layered Space Time (V-BLAST), a novel nonlinear ZF-THP algorithm for VBLAST in MIMO-MC-CDMA downlink system is proposed in this paper. QR decomposition is used for precoding matrix, the nonlinear Tomlinson-Harashima Precoding (THP) is used between the sub-carrier channels of MC-CDMA to eliminate interference from other signals at the transmitter, and can obtain frequency diversity gain and eliminate effectively the error propagation effect. At the receiver, zero forcing criterion is used, and the complexity of the receiver can be reduced. Simulation results show that the proposed algorithm is better than the traditional zero forcing algorithm and the linear precoding algorithm in the system BER.

  17. Lack of promoting effects of chronic exposure to 1.95-GHz W-CDMA signals for IMT-2000 cellular system on development of N-ethylnitrosourea-induced central nervous system tumors in F344 rats.

    PubMed

    Shirai, Tomoyuki; Ichihara, Toshio; Wake, Kanako; Watanabe, So-ichi; Yamanaka, Yukio; Kawabe, Mayumi; Taki, Masao; Fujiwara, Osamu; Wang, Jianqing; Takahashi, Satoru; Tamano, Seiko

    2007-10-01

    The present study was performed to evaluate effects of a 2-year exposure to an electromagnetic near-field (EMF) equivalent to that generated by cellular phones on tumor development in the central nervous system (CNS) of rats. For this purpose, pregnant F344 rats were given a single administration of N-ethylnitrosourea (ENU) on gestational day 18. A total of 500 pups were divided into five groups, each composed of 50 males and 50 females: Group 1, untreated controls; Group 2, ENU alone; Groups 3 to 5, ENU + EMF (sham exposure and two exposure levels). A 1.95-GHz wide-band code division multiple access (W-CDMA) signal, which is a feature of the International Mobile Telecommunication 2000 (IMT-2000) cellular system was employed for exposure of the rat head starting from 5 weeks of age, 90 min a day, 5 days a week, for 104 weeks. Brain average specific absorption rates (SARs) were designed to be .67 and 2.0 W/kg for low and high exposures, respectively. The incidence and numbers of brain tumors in female rats exposed to 1.95-GHz W-CDMA signals showed tendencies to increase but without statistical significance. Overall, no significant increase in incidences or numbers, either in the males or females, was detected in the EMF-exposed groups. In addition, no clear changes in tumor types in the brain were evident. Thus, under the present experimental conditions, exposure of heads of rats to 1.95-GHz W-CDMA signals for IMT-2000 for a 2-year period was not demonstrated to accelerate or otherwise affect ENU-initiated brain tumorigenesis. PMID:17516507

  18. Multigenerational effects of whole body exposure to 2.14 GHz W-CDMA cellular phone signals on brain function in rats.

    PubMed

    Shirai, Tomoyuki; Imai, Norio; Wang, Jianqing; Takahashi, Satoru; Kawabe, Mayumi; Wake, Kanako; Kawai, Hiroki; Watanabe, So-Ichi; Furukawa, Fumio; Fujiwara, Osamu

    2014-10-01

    The present experimental study was carried out with rats to evaluate the effects of whole body exposure to 2.14 GHz band code division multiple access (W-CDMA) signals for 20 h a day, over three generations. The average specific absorption rate (SAR, in unit of W/kg) for dams was designed at three levels: high (<0.24 W/kg), low (<0.08 W/kg), and 0 (sham exposure). Pregnant mothers (4 rats/group) were exposed from gestational day (GD) 7 to weaning and then their offspring (F1 generation, 4 males and 4 females/dam, respectively) were continuously exposed until 6 weeks of age. The F1 females were mated with F1 males at 11 weeks old, and then starting from GD 7, they were exposed continuously to the electromagnetic field (EMF; one half of the F1 offspring was used for mating, that is, two of each sex per dam and 8 males and 8 females/group, except for all offspring for the functional development tests). This protocol was repeated in the same manner on pregnant F2 females and F3 pups; the latter were killed at 10 weeks of age. No abnormalities were observed in the mother rats (F0 , F1 , and F2 ) and in the offspring (F1 , F2 , and F3 ) in any biological parameters, including neurobehavioral function. Thus, it was concluded that under the experimental conditions applied, multigenerational whole body exposure to 2.14 GHz W-CDMA signals for 20 h/day did not cause any adverse effects on the F1 , F2 , and F3 offspring. PMID:25196377

  19. Single integrated device for optical CDMA code processing in dual-code environment.

    PubMed

    Huang, Yue-Kai; Glesk, Ivan; Greiner, Christoph M; Iazkov, Dmitri; Mossberg, Thomas W; Wang, Ting; Prucnal, Paul R

    2007-06-11

    We report on the design, fabrication and performance of a matching integrated optical CDMA encoder-decoder pair based on holographic Bragg reflector technology. Simultaneous encoding/decoding operation of two multiple wavelength-hopping time-spreading codes was successfully demonstrated and shown to support two error-free OCDMA links at OC-24. A double-pass scheme was employed in the devices to enable the use of longer code length. PMID:19547056

  20. Effects on rat testis of 1.95-GHz W-CDMA for IMT-2000 cellular phones.

    PubMed

    Imai, Norio; Kawabe, Mayumi; Hikage, Takashi; Nojima, Toshio; Takahashi, Satoru; Shirai, Tomoyuki

    2011-08-01

    In recent years concern has arisen whether carrying a cellular phone near the reproductive organs such as the testes may cause dysfunction and particularly decrease in sperm development and production, and thus fertility in men. The present study was performed to investigate the effects of a 1.95 GHz electromagnetic field on testicular function in male Sprague-Dawley rats. Five week old animals were divided into 3 groups of 24 each and a 1.95-GHz wide-band code division multiple access (W-CDMA) signal, which is used for the freedom of mobile multimedia access (FOMA), was employed for whole body exposure for 5 hours per day, 7 days a week for 5 weeks (the period from the age of 5 to 10 weeks, corresponding to reproductive maturation in the rat). Whole-body average specific absorption rates (SAR) for individuals were designed to be 0.4 and 0.08 W/kg respectively. The control group received sham exposure. There were no differences in body weight gain or weights of the testis, epididymis, seminal vesicles, and prostate among the groups. The number of sperm in the testis and epididymis were not decreased in the electromagnetic field (EMF) exposed groups, and, in fact, the testicular sperm count was significantly increased with the 0.4 SAR. Abnormalities of sperm motility or morphology and the histological appearance of seminiferous tubules, including the stage of the spermatogenic cycle, were not observed. Thus, under the present exposure conditions, no testicular toxicity was evident. PMID:21204746

  1. SMAC: A soft MAC to reduce control overhead and latency in CDMA-based AMI networks

    DOE PAGESBeta

    Garlapati, Shravan; Kuruganti, Teja; Buehrer, Michael R.; Reed, Jeffrey H.

    2015-10-26

    The utilization of state-of-the-art 3G cellular CDMA technologies in a utility owned AMI network results in a large amount of control traffic relative to data traffic, increases the average packet delay and hence are not an appropriate choice for smart grid distribution applications. Like the CDG, we consider a utility owned cellular like CDMA network for smart grid distribution applications and classify the distribution smart grid data as scheduled data and random data. Also, we propose SMAC protocol, which changes its mode of operation based on the type of the data being collected to reduce the data collection latency andmore » control overhead when compared to 3G cellular CDMA2000 MAC. The reduction in the data collection latency and control overhead aids in increasing the number of smart meters served by a base station within the periodic data collection interval, which further reduces the number of base stations needed by a utility or reduces the bandwidth needed to collect data from all the smart meters. The reduction in the number of base stations and/or the reduction in the data transmission bandwidth reduces the CAPital EXpenditure (CAPEX) and OPerational EXpenditure (OPEX) of the AMI network. Finally, the proposed SMAC protocol is analyzed using markov chain, analytical expressions for average throughput and average packet delay are derived, and simulation results are also provided to verify the analysis.« less

  2. Performance evaluation of wavelet-based ECG compression algorithms for telecardiology application over CDMA network.

    PubMed

    Kim, Byung S; Yoo, Sun K

    2007-09-01

    The use of wireless networks bears great practical importance in instantaneous transmission of ECG signals during movement. In this paper, three typical wavelet-based ECG compression algorithms, Rajoub (RA), Embedded Zerotree Wavelet (EZ), and Wavelet Transform Higher-Order Statistics Coding (WH), were evaluated to find an appropriate ECG compression algorithm for scalable and reliable wireless tele-cardiology applications, particularly over a CDMA network. The short-term and long-term performance characteristics of the three algorithms were analyzed using normal, abnormal, and measurement noise-contaminated ECG signals from the MIT-BIH database. In addition to the processing delay measurement, compression efficiency and reconstruction sensitivity to error were also evaluated via simulation models including the noise-free channel model, random noise channel model, and CDMA channel model, as well as over an actual CDMA network currently operating in Korea. This study found that the EZ algorithm achieves the best compression efficiency within a low-noise environment, and that the WH algorithm is competitive for use in high-error environments with degraded short-term performance with abnormal or contaminated ECG signals. PMID:17701824

  3. SMAC: A soft MAC to reduce control overhead and latency in CDMA-based AMI networks

    SciTech Connect

    Garlapati, Shravan; Kuruganti, Teja; Buehrer, Michael R.; Reed, Jeffrey H.

    2015-10-26

    The utilization of state-of-the-art 3G cellular CDMA technologies in a utility owned AMI network results in a large amount of control traffic relative to data traffic, increases the average packet delay and hence are not an appropriate choice for smart grid distribution applications. Like the CDG, we consider a utility owned cellular like CDMA network for smart grid distribution applications and classify the distribution smart grid data as scheduled data and random data. Also, we propose SMAC protocol, which changes its mode of operation based on the type of the data being collected to reduce the data collection latency and control overhead when compared to 3G cellular CDMA2000 MAC. The reduction in the data collection latency and control overhead aids in increasing the number of smart meters served by a base station within the periodic data collection interval, which further reduces the number of base stations needed by a utility or reduces the bandwidth needed to collect data from all the smart meters. The reduction in the number of base stations and/or the reduction in the data transmission bandwidth reduces the CAPital EXpenditure (CAPEX) and OPerational EXpenditure (OPEX) of the AMI network. Finally, the proposed SMAC protocol is analyzed using markov chain, analytical expressions for average throughput and average packet delay are derived, and simulation results are also provided to verify the analysis.

  4. Electromagnetic Interference Assessment of CDMA and GSM Wireless Phones to Aircraft Navigation Radios

    NASA Technical Reports Server (NTRS)

    Ely, Jay J.; Nguyen, Truong X.; Koppen, Sandra V.; Salud, M. Theresa

    2002-01-01

    To address the concern for cellular phone electromagnetic interference (EMI) to aircraft radios, a radiated emission measurement process for CDMA (IS-95) and GSM (ETSI GSM 11.22) wireless handsets was developed. Spurious radiated emissions were efficiently characterized from devices tested in either a semi-anechoic or reverberation chamber, in terms of effective isotropic radiated power. Eight representative handsets (4 GSM, 4 CDMA) were commanded to operate while varying their radio transmitter parameters (power, modulation, etc.). This report provides a detailed description of the measurement process and resulting data, which may subsequently be used by others as a basis of consistent evaluation for cellular/PCS phones, Bluetooth, IEEE802.11b, IEEE802.11a, FRS/GMRS radios, and other portable transmitters. Aircraft interference path loss (IPL) and navigation radio interference threshold data from numerous reference documents, standards, and NASA partnerships were compiled. Using this data, a preliminary risk assessment is provided for CDMA and GSM wireless phone interference to aircraft localizer, Glideslope, VOR, and GPS radio receivers on typical transport airplanes. The report identifies where existing data for device emissions, IPL, and navigation radio interference thresholds needs to be extended for an accurate risk assessment for wireless transmitters in aircraft.

  5. Occluded Brescia-Cimino Hemodialysis Fistulas: Endovascular Treatment with Both Brachial Arterial and Venous Access Using the Pull-Through Technique

    SciTech Connect

    Miyayama, Shiro Matsui, Osamu; Taki, Keiichi; Minami, Tetsuya; Shinmura, Rieko; Ito, Chiharu; Takamatsu, Shigeyuki; Kobayashi, Miki; Ushiogi, Yashuyuki

    2005-12-15

    We retrospectively evaluated the usefulness of both arterial and venous access with the pull-through technique in endovascular treatment of totally occluded Brescia-Cimino fistulas. We treated 26 patients (17 men, 9 women; age range 43-82 years, mean age 66 years) with occluded Brescia-Cimino fistulas. First, the occluded segment was traversed from the antegrade brachial arterial access using a microcatheter-guidewire system. Second, the vein was retrogradely punctured after confirmation of all diseased segments, and a 0.014- or 0.016-inch guidewire was pulled through the venous access when the occluded segment was long. All interventions including thrombolysis, thromboaspiration, angioplasty, and stent placement were performed via the venous access. The occlusion was successfully crossed via the brachial arterial access in 23 patients (88%). In 2 patients it was done from the venous approach. In the remaining patient it was not possible to traverse the occluded segment. The pull-through technique was successful in all 19 attempts. Clinical success was achieved in 96%, the primary patency rates at 6, 12, and 18 months were 83%, 78%, and 69%, the primary assisted patency rates were 92%, 92%, and 72%, and the secondary patency rates were 92%, 92%, and 92%, respectively. Minor complications in 5 patients included venous perforation in 2 (8%), venous rupture in 1 (4%), and regional hematoma in 2 (8%). Our study suggests that endovascular treatments with both arterial and venous access using the pull-through technique are highly effective in restoring function in totally occluded Brescia-Cimino fistulas.

  6. Joint Transmitter and Receiver Power Allocation under Minimax MSE Criterion with Perfect and Imperfect CSI for MC-CDMA Transmissions

    NASA Astrophysics Data System (ADS)

    Kotchasarn, Chirawat; Saengudomlert, Poompat

    We investigate the problem of joint transmitter and receiver power allocation with the minimax mean square error (MSE) criterion for uplink transmissions in a multi-carrier code division multiple access (MC-CDMA) system. The objective of power allocation is to minimize the maximum MSE among all users each of which has limited transmit power. This problem is a nonlinear optimization problem. Using the Lagrange multiplier method, we derive the Karush-Kuhn-Tucker (KKT) conditions which are necessary for a power allocation to be optimal. Numerical results indicate that, compared to the minimum total MSE criterion, the minimax MSE criterion yields a higher total MSE but provides a fairer treatment across the users. The advantages of the minimax MSE criterion are more evident when we consider the bit error rate (BER) estimates. Numerical results show that the minimax MSE criterion yields a lower maximum BER and a lower average BER. We also observe that, with the minimax MSE criterion, some users do not transmit at full power. For comparison, with the minimum total MSE criterion, all users transmit at full power. In addition, we investigate robust joint transmitter and receiver power allocation where the channel state information (CSI) is not perfect. The CSI error is assumed to be unknown but bounded by a deterministic value. This problem is formulated as a semidefinite programming (SDP) problem with bilinear matrix inequality (BMI) constraints. Numerical results show that, with imperfect CSI, the minimax MSE criterion also outperforms the minimum total MSE criterion in terms of the maximum and average BERs.

  7. Using the Critical Incident Technique to Research Decision Making regarding Access to Training and Development in Medium-Sized Enterprises

    ERIC Educational Resources Information Center

    Coetzer, Alan; Redmond, Janice; Sharafizad, Jalleh

    2012-01-01

    Employees in small and medium-sized enterprises (SMEs) form part of a "disadvantaged" group within the workforce that receives less access to training and development (T&D) than employees in large firms. Prior research into reasons for the relatively low levels of employee participation in training and development has typically involved surveys of…

  8. Using Commercially Available Techniques to Make Organic Chemistry Representations Tactile and More Accessible to Students with Blindness or Low Vision

    ERIC Educational Resources Information Center

    Supalo, Cary A.; Kennedy, Sean H.

    2014-01-01

    Organic chemistry courses can present major obstacles to access for students with blindness or low vision (BLV). In recent years, efforts have been made to represent organic chemistry concepts in tactile forms for blind students. These methodologies are described in this manuscript. Further work being done at Illinois State University is also…

  9. Totally implantable venous access devices: retrospective analysis of different insertion techniques and predictors of complications in 796 devices implanted in a single institution

    PubMed Central

    2014-01-01

    Background The aim of this study was to assess the efficacy and safety of totally implanted vascular devices (TIVAD) using different techniques of insertion. Methods We performed a retrospective study using a prospective collected database of 796 consecutive oncological patients in which TIVADs were inserted. We focused on early and late complications following different insertion techniques (surgical cutdown, blind and ultrasound guided percutaneous) according to different techniques. Results Ultrasound guided technique was used in 646 cases, cephalic vein cutdown in 102 patients and percutaneous blind technique in 48 patients. The overall complication rate on insertion was 7.2% (57 of 796 cases). Early complications were less frequent using the ultrasound guided technique: arterial puncture (p = 0.009), technical failure (p = 0.009), access site change after first attempt (p = 0.002); pneumothorax occurred in 4 cases, all using the blind percutaneus technique. Late complications occurred in 49 cases (6.1%) which required TIVAD removal in 43 cases and included: sepsis (29 cases), thrombosis (3 cases), dislocation (7 cases), skin dehiscence (3 cases), and severe pain (1 case). Conclusion Ultrasound guided technique is the safest option for TIVAD insertion, with the lowest rates of immediate complications. PMID:24886342

  10. Effects of gestational exposure to 1.95-GHz W-CDMA signals for IMT-2000 cellular phones: Lack of embryotoxicity and teratogenicity in rats.

    PubMed

    Ogawa, Kumiko; Nabae, Kyoko; Wang, Jianqing; Wake, Kanako; Watanabe, So-ichi; Kawabe, Mayumi; Fujiwara, Osamu; Takahashi, Satoru; Ichihara, Toshio; Tamano, Seiko; Shirai, Tomoyuki

    2009-04-01

    The present study was designed to evaluate whether gestational exposure to an EMF targeting the head region, similar to that from cellular phones, might affect embryogenesis in rats. A 1.95-GHz wide-band code division multiple access (W-CDMA) signal, which is one applied for the International Mobile Telecommunication 2000 (IMT-2000) system and used for the freedom of mobile multimedia access (FOMA), was employed for exposure to the heads of four groups of pregnant CD(SD) IGS rats (20 per group) for gestational days 7-17. The exposure was performed for 90 min/day in the morning. The spatial average specific absorption rate (SAR) for individual brains was designed to be 0.67 and 2.0 W/kg with peak brain SARs of 3.1 and 7.0 W/kg for low (group 3) and high (group 4) exposures, respectively, and a whole-body average SAR less than 0.4 W/kg so as not to cause thermal effects due to temperature elevation. Control and sham exposure groups were also included. At gestational day 20, all dams were killed and fetuses were taken out by cesarean section. There were no differences in maternal body weight gain. No adverse effects of EMF exposure were observed on any reproductive and embryotoxic parameters such as number of live (243-271 fetuses), dead or resorbed embryos, placental weights, sex ratios, weights or external, visceral or skeletal abnormalities of live fetuses. PMID:19194858

  11. Capacity enhancement of wavelength/time/space asynchronous optical CDMA with relaxed cross-correlation

    NASA Astrophysics Data System (ADS)

    Singh, Jaswinder

    2013-12-01

    The analysis of a three-dimensional (3-D) wavelength/time/space (W-T-S) asynchronous optical CDMA code family is presented considering MAI only under relaxed cross-correlation (λc ⩾ 1). Based on the code performance, it is shown that for code-limited systems (when W and/or T are non-prime), the number of generated codes and hence the supported users can be significantly increased by relaxing the cross-correlation constraint if a slight degradation in code performance can be tolerated.

  12. Multiple Access Schemes for Lunar Missions

    NASA Technical Reports Server (NTRS)

    Deutsch, Leslie; Hamkins, Jon; Stocklin, Frank J.

    2010-01-01

    Two years ago, the NASA Coding, Modulation, and Link Protocol (CMLP) study was completed. The study, led by the authors of this paper, recommended codes, modulation schemes, and desired attributes of link protocols for all space communication links in NASA's future space architecture. Portions of the NASA CMLP team were reassembled to resolve one open issue: the use of multiple access (MA) communication from the lunar surface. The CMLP-MA team analyzed and simulated two candidate multiple access schemes that were identified in the original CMLP study: Code Division MA (CDMA) and Frequency Division MA (FDMA) based on a bandwidth-efficient Continuous Phase Modulation (CPM) with a superimposed Pseudo-Noise (PN) ranging signal (CPM/PN). This paper summarizes the results of the analysis and simulation of the CMLP-MA study and describes the final recommendations.

  13. A New Approach to Parallel Interference Cancellation for CDMA

    NASA Technical Reports Server (NTRS)

    Divsalar, Dariush; Simon, Martin

    1996-01-01

    This paper introduces an improved nonlinear parallel interference cancellation scheme that significantly reduces the degrading effect of user interference with implementation complexity linear in the number of users. The scheme operates on the fact that parallel processing simultaneously removes from each user a part of the interference produced by the remaining users accessing the channel the amount being proportional to their reliability. The parallel processing can be done in multiple stages. Simulation results are given for a multitude of different situations, in particular those cases for which the analysis is too complex.

  14. An optical CDMA system based on chaotic sequences

    NASA Astrophysics Data System (ADS)

    Liu, Xiao-lei; En, De; Wang, Li-guo

    2014-03-01

    In this paper, a coherent asynchronous optical code division multiple access (OCDMA) system is proposed, whose encoder/decoder is an all-optical generator. This all-optical generator can generate analog and bipolar chaotic sequences satisfying the logistic maps. The formula of bit error rate (BER) is derived, and the relationship of BER and the number of simultaneous transmissions is analyzed. Due to the good property of correlation, this coherent OCDMA system based on these bipolar chaotic sequences can support a large number of simultaneous users, which shows that these chaotic sequences are suitable for asynchronous OCDMA system.

  15. A New Aloha Anti-Collision Algorithm Based on CDMA

    NASA Astrophysics Data System (ADS)

    Bai, Enjian; Feng, Zhu

    The tags' collision is a common problem in RFID (radio frequency identification) system. The problem has affected the integrity of the data transmission during the process of communication in the RFID system. Based on analysis of the existing anti-collision algorithm, a novel anti-collision algorithm is presented. The new algorithm combines the group dynamic frame slotted Aloha algorithm with code division multiple access technology. The algorithm can effectively reduce the collision probability between tags. Under the same number of tags, the algorithm is effective in reducing the reader recognition time and improve overall system throughput rate.

  16. Comparison of superior vena caval and inferior vena caval access using a radioisotope technique during normal perfusion and cardiopulmonary resuscitation

    SciTech Connect

    Dalsey, W.C.; Barsan, W.G.; Joyce, S.M.; Hedges, J.R.; Lukes, S.J.; Doan, L.A.

    1984-10-01

    Recent studies of thoracic pressure changes during external cardiopulmonary resuscitation (CPR) suggest that there may be a significant difference in the rate of delivery of intravenous drugs when they are administered through the extrathoracic inferior vena cava (IVC) rather than the intrathoracic superior vena cava (SVC). Comparison of delivery of a radionuclide given using superior and inferior vena caval access sites was made during normal blood flow and during CPR. Mean times from injection to peak emission count in each ventricle were determined. There were no significant differences between mean peak times for SVC or IVC routes during normal flow or CPR. When peak times were corrected for variations in cardiac output, there were no significant differences between IVC and SVC peak times during normal flow. During CPR, however, mean left ventricular peak time, when corrected for cardiac output, was significantly shorter (P less than .05) when the SVC route was used. The mean time for the counts to reach half the ventricular peak was statistically shorter (P less than .05) in both ventricles with the SVC route during the low flow of CPR. This suggests that during CPR, increased drug dispersion may occur when drugs are infused by the IVC route and thus may modify the anticipated effect of the drug bolus. These results suggest that during CPR, both the cardiac output and the choice of venous access are important variables for drug delivery.

  17. Electrical Spreading Code-Based OFDM Optical Access Networks for Budget Enhancement and Reduced System Bandwidth Requirement

    NASA Astrophysics Data System (ADS)

    Kumar, Pravindra; Srivastava, Anand

    2015-12-01

    Passive optical networks based on orthogonal frequency division multiplexing (OFDM-PON) give better performance in high-speed optical access networks. For further improvement in performance, a new architecture of OFDM-PON based on spreading code in electrical domain is proposed and analytically analyzed in this paper. This approach is referred as hybrid multi-carrier code division multiple access-passive optical network (MC-CDMA-PON). Analytical results show that at bit error rate (BER) of 10-3, there is 9.4 dB and 14.2 dB improvement in optical power budget for downstream and upstream, respectively, with MC-CDMA-PON system as compared to conventional OFDM-PON system for the same number of optical network units (ONUs).

  18. Physical Layer Characteristics and Techniques for Visible Light Communications

    NASA Astrophysics Data System (ADS)

    Cui, Kaiyun

    With the rapid development of semiconductor lighting technologies, the light emitting diodes (LEDs) are promising to eventually replace traditional incandescent and fluorescent lamps for their high energy efficiency, environmental friendliness, and long lifetime. Visible light communication (VLC) utilizing lighting LEDs as transmitters has been an emerging research area since its first proposal. Ubiquitous communication coverage will become possible with wide deployment of lighting LEDs. This thesis studies physical layer characteristics of VLC systems based on either indoor LED lighting or outdoor LED traffic signaling infrastructure. Advanced communication techniques are proposed to cope with LED bandwidth limitations and grant multiple accesses. Their performance is comprehensively analyzed in typical lighting and signaling environments. Firstly, communication link issues are studied. A conversion method from photometric parameters for illumination to radiometric parameters for communication is developed. Two typical VLC links, the line-of-sight (LOS) link and non-line-of-sight (NLOS) diffuse link, are characterized both experimentally and numerically. Some optional reverse link provisions are evaluated for a full duplex system. Different noise sources and background interferences are analyzed, and dominant noises are identified under typical application scenarios. With identified signal propagation and noise characteristics, link performance is then evaluated. Secondly, transceiver design techniques to increase the data rate are proposed, including digital pre-equalization techniques and the optical orthogonal frequency division multiplexing (O-OFDM) whose peak to average power ratio (PAPR) issue is investigated. Thirdly, the capacity of the multiple-input multiple-output (MIMO) VLC system exploring inherent multiple LED transmitters and multiple photodetectors is evaluated. The effects of some system parameters involved in non-imaging and imaging transceivers

  19. Performance Analysis of OCDMA Based on AND Detection in FTTH Access Network Using PIN & APD Photodiodes

    NASA Astrophysics Data System (ADS)

    Aldouri, Muthana; Aljunid, S. A.; Ahmad, R. Badlishah; Fadhil, Hilal A.

    2011-06-01

    In order to comprise between PIN photo detector and avalanche photodiodes in a system used double weight (DW) code to be a performance of the optical spectrum CDMA in FTTH network with point-to-multi-point (P2MP) application. The performance of PIN against APD is compared through simulation by using opt system software version 7. In this paper we used two networks designed as follows one used PIN photo detector and the second using APD photo diode, both two system using with and without erbium doped fiber amplifier (EDFA). It is found that APD photo diode in this system is better than PIN photo detector for all simulation results. The conversion used a Mach-Zehnder interferometer (MZI) wavelength converter. Also we are study, the proposing a detection scheme known as AND subtraction detection technique implemented with fiber Bragg Grating (FBG) act as encoder and decoder. This FBG is used to encode and decode the spectral amplitude coding namely double weight (DW) code in Optical Code Division Multiple Access (OCDMA). The performances are characterized through bit error rate (BER) and bit rate (BR) also the received power at various bit rate.

  20. Electrospray Ionization Mass Spectrometry: A Technique to Access the Information beyond the Molecular Weight of the Analyte

    PubMed Central

    Banerjee, Shibdas; Mazumdar, Shyamalava

    2012-01-01

    The Electrospray Ionization (ESI) is a soft ionization technique extensively used for production of gas phase ions (without fragmentation) of thermally labile large supramolecules. In the present review we have described the development of Electrospray Ionization mass spectrometry (ESI-MS) during the last 25 years in the study of various properties of different types of biological molecules. There have been extensive studies on the mechanism of formation of charged gaseous species by the ESI. Several groups have investigated the origin and implications of the multiple charge states of proteins observed in the ESI-mass spectra of the proteins. The charged analytes produced by ESI can be fragmented by activating them in the gas-phase, and thus tandem mass spectrometry has been developed, which provides very important insights on the structural properties of the molecule. The review will highlight recent developments and emerging directions in this fascinating area of research. PMID:22611397

  1. Phosphorylation and gene expression of p53 are not affected in human cells exposed to 2.1425 GHz band CW or W-CDMA modulated radiation allocated to mobile radio base stations.

    PubMed

    Hirose, H; Sakuma, N; Kaji, N; Suhara, T; Sekijima, M; Nojima, T; Miyakoshi, J

    2006-09-01

    A large-scale in vitro study focusing on low-level radiofrequency (RF) fields from mobile radio base stations employing the International Mobile Telecommunication 2000 (IMT-2000) cellular system was conducted to test the hypothesis that modulated RF fields induce apoptosis or other cellular stress response that activate p53 or the p53-signaling pathway. First, we evaluated the response of human cells to microwave exposure at a specific absorption rate (SAR) of 80 mW/kg, which corresponds to the limit of the average whole-body SAR for general public exposure defined as a basic restriction by the International Commission on Non-Ionizing Radiation Protection (ICNIRP) guidelines. Second, we investigated whether continuous wave (CW) and wideband code division multiple access (W-CDMA) modulated signal RF fields at 2.1425 GHz induced apoptosis or any signs of stress. Human glioblastoma A172 cells were exposed to W-CDMA radiation at SARs of 80, 250, and 800 mW/kg, and CW radiation at 80 mW/kg for 24 or 48 h. Human IMR-90 fibroblasts from fetal lungs were exposed to both W-CDMA and CW radiation at a SAR of 80 mW/kg for 28 h. Under the RF field exposure conditions described above, no significant differences in the percentage of apoptotic cells were observed between the test groups exposed to RF signals and the sham-exposed negative controls, as evaluated by the Annexin V affinity assay. No significant differences in expression levels of phosphorylated p53 at serine 15 or total p53 were observed between the test groups and the negative controls by the bead-based multiplex assay. Moreover, microarray hybridization and real-time RT-PCR analysis showed no noticeable differences in gene expression of the subsequent downstream targets of p53 signaling involved in apoptosis between the test groups and the negative controls. Our results confirm that exposure to low-level RF signals up to 800 mW/kg does not induce p53-dependent apoptosis, DNA damage, or other stress response in human

  2. Adaptive Code Division Multiple Access Protocol for Wireless Network-on-Chip Architectures

    NASA Astrophysics Data System (ADS)

    Vijayakumaran, Vineeth

    Massive levels of integration following Moore's Law ushered in a paradigm shift in the way on-chip interconnections were designed. With higher and higher number of cores on the same die traditional bus based interconnections are no longer a scalable communication infrastructure. On-chip networks were proposed enabled a scalable plug-and-play mechanism for interconnecting hundreds of cores on the same chip. Wired interconnects between the cores in a traditional Network-on-Chip (NoC) system, becomes a bottleneck with increase in the number of cores thereby increasing the latency and energy to transmit signals over them. Hence, there has been many alternative emerging interconnect technologies proposed, namely, 3D, photonic and multi-band RF interconnects. Although they provide better connectivity, higher speed and higher bandwidth compared to wired interconnects; they also face challenges with heat dissipation and manufacturing difficulties. On-chip wireless interconnects is one other alternative proposed which doesn't need physical interconnection layout as data travels over the wireless medium. They are integrated into a hybrid NOC architecture consisting of both wired and wireless links, which provides higher bandwidth, lower latency, lesser area overhead and reduced energy dissipation in communication. However, as the bandwidth of the wireless channels is limited, an efficient media access control (MAC) scheme is required to enhance the utilization of the available bandwidth. This thesis proposes using a multiple access mechanism such as Code Division Multiple Access (CDMA) to enable multiple transmitter-receiver pairs to send data over the wireless channel simultaneously. It will be shown that such a hybrid wireless NoC with an efficient CDMA based MAC protocol can significantly increase the performance of the system while lowering the energy dissipation in data transfer. In this work it is shown that the wireless NoC with the proposed CDMA based MAC protocol

  3. A discussion on mobile satellite system and the myths of CDMA and diversity revealed

    NASA Technical Reports Server (NTRS)

    Hart, Nicholas; Goerke, Thomas; Jahn, Axel

    1995-01-01

    The paper explores the myths and facts surrounding: link margins and constellation designs; the use of satellite diversity in a mobile satellite channel; trade-offs in multiple access technique. Different satellite constellations are presented, which are comparable with those used by the big LEO proponents, with the associated trade-offs in the system design. Propagation data and results from various narrowband and wideband measurement campaigns are used to illustrate the expected differences in service performance.

  4. Long Term Follow-Up of the Endovascular Trans-Vessel Wall Technique for Parenchymal Access in Rabbit with Full Clinical Integration

    PubMed Central

    Lundberg, Johan; Jonsson, Stefan; Holmin, Staffan

    2011-01-01

    Objective Endovascular techniques are providing options to surgical/percutaneous cell transplantation methods. Some cells, e.g. insulin producing cells, are not suitable for intra-luminal transplantation and for such cells, other options must be found. We have constructed a “nanocatheter” with a penetrating tip for vessel perforation, thereby creating a working channel for parenchymal access by endovascular technique. To finish the procedure safely, the distal tip is detached to provide a securing plug in the vessel wall defect. Materials and Methods We have performed interventions with full clinical integration in the superior mesenteric artery (SMA), the subclavian artery and the external carotid artery in rabbits. No hemorrhagic- or thromboembolic events occurred during the procedure. Stenosis formation and distal embolisation were analyzed by angiography and macroscopic inspection during autopsy at five, 30 and 80 days. All animals and implanted devices were also evaluated by micro-dissections and histochemical analysis. Results In this study we show safety data on the trans-vessel wall technique by behavioral, angiographical and histological analysis. No stenosis formation was observed at any of the follow-up time points. No animals or organs have shown any signs of distress due to the intervention. Histological examination showed no signs of hemorrhage, excellent biocompatibility with no inflammation and a very limited fibrous capsule formation around the device, comparable to titanium implants. Further, no histological changes were detected in the endothelia of the vessels subject to intervention. Conclusions The trans-vessel wall technique can be applied for e.g. cell transplantations, local substance administration and tissue sampling with low risk for complications during the procedure and low risk for hemorrhage, stenosis development or adverse tissue reactions with an 80 days follow-up time. The benefit should be greatest in organs that are

  5. Simple nonlinear interferometer-based all-optical thresholder and its applications for optical CDMA.

    PubMed

    Kravtsov, Konstantin; Prucnal, Paul R; Bubnov, Mikhail M

    2007-10-01

    We present an experimental demonstration of an ultrafast all-optical thresholder based on a nonlinear Sagnac interferometer. The proposed design is intended for operation at very small nonlinear phase shifts. Therefore, it requires an in-loop nonlinearity lower than for the classical nonlinear loop mirror scheme. Only 15 meters of conventional (non-holey) silica-based fiber is used as a nonlinear element. The proposed thresholder is polarization insensitive and is good for multi-wavelength operation, meeting all the requirements for autocorrelation detection in various optical CDMA communication systems. The observed cubic transfer function is superior to the quadratic transfer function of second harmonic generation-based thresholders. PMID:19550579

  6. A Study on Channel Estimation Methods for Time-Domain Spreading MC-CDMA Systems

    NASA Astrophysics Data System (ADS)

    Nagate, Atsushi; Fujii, Teruya

    As a candidate for the transmission technology of next generation mobile communication systems, time-domain spreading MC-CDMA systems have begun to attract much attention. In these systems, data and pilot symbols are spread in the time domain and code-multiplexed. To combat fading issues, we need to conduct channel estimation by using the code-multiplexed pilot symbols. Especially in next generation systems, frequency bands higher than those of current systems, which raise the maximum Doppler frequency, are expected to be used, so that a more powerful channel estimation method is expected. Considering this, we propose a channel estimation method for highly accurate channel estimation; it is a combination of a two-dimensional channel estimation method and an impulse response-based channel estimation method. We evaluate the proposed method by computer simulations.

  7. Accessing groundwater quality in lower part of Nagapattinam district, Southern India: using hydrogeochemistry and GIS interpolation techniques

    NASA Astrophysics Data System (ADS)

    Gnanachandrasamy, G.; Ramkumar, T.; Venkatramanan, S.; Vasudevan, S.; Chung, S. Y.; Bagyaraj, M.

    2015-03-01

    The aim of this present study was to evaluate groundwater quality in the lower part of Nagapattinam district, Tamil Nadu, Southern India. A detailed geochemical study of groundwater region is described, and the origin of the chemical composition of groundwater has been qualitatively evaluated, using observations over a period of two seasons premonsoon (June) and monsoon (November) in the year of 2010. To attempt this goal, samples were analysed for various physico-chemical parameters such as temperature, pH, salinity, Na+, Ca2+, K+, Mg2+, Cl-, HCO3 - and SO4 2-. The abundance of major cations concentration in groundwater is as Na > Ca > Mg > K, while that of anions is Cl > SO4 > HCO3. The Piper trilinear diagram indicates Ca-Cl2 facies, and according to USSL diagram, most of the sample exhibits high salinity hazard (C3S1) type in both seasons. It indicates that high salinity (C3) and low sodium (S1) are moderately suitable for irrigation purposes. Gibbs boomerang exhibits most of the samples mainly controlled by evaporation and weathering process sector in both seasons. Irrigation status of the groundwater samples indicates that it was moderately suitable for agricultural purpose. ArcGIS 9.3 software was used for the generation of various thematic maps and the final groundwater quality map. An interpolation technique inverse distance weighting was used to obtain the spatial distribution of groundwater quality parameters. The final map classified the ground quality in the study area. The results of this research show that the development of the management strategies for the aquifer system is vitally necessary.

  8. Replica Analysis of Multiuser Detection for Code Division Multiple Access with M-Ary Phase-Shift Keying

    NASA Astrophysics Data System (ADS)

    Kato, Hiroyuki; Okada, Masato; Miyoshi, Seiji

    2013-07-01

    We analyze the performance of the maximizer of the posterior marginals (MPM) detector for code division multiple access (CDMA) multiuser detection with M-ary phase shift keying (M-ary PSK) in the large system limit by the replica method. The obtained theory agrees with computer simulation reasonably well. We also derive the theory in the case of the large M limit and discuss the dependence of the properties of M-ary PSK CDMA communication on M. We show that the waterfall phenomenon occurs for both the finite and infinite values of M. We also show that a value of M for which the decoded phase information on the original user symbol becomes minimum exists. Furthermore, we discuss the relationship between the theory based on the replica method and that based on self-consistent signal-to-noise analysis (SCSNA).

  9. Multiple fiber Bragg grating sensor network with a rapid response and wide spectral dynamic range using code division multiple access

    NASA Astrophysics Data System (ADS)

    Kim, Youngbok; Jeon, Sie-Wook; Park, Chang-Soo

    2011-05-01

    Fiber Bragg grating (FBG) sensor networks have been intensively researched in optical sensor area and it developed in wavelength division multiplexing (WDM) and time division multiplexing (TDM) technologies which was adopted for its interrogating many optical sensors. In particular, WDM technology can be easily employed to interrogate FBG sensor however, the number of FBG sensors is limited. On the other hand, the TDM technique can extremely expand the number of sensor because the FBG sensors have same center wavelength. However, it suffers from a reduced sensor output power due to low reflectivity of FBG sensor. In this paper, we proposed and demonstrated the FBG sensor network based on code division multiple access (CDMA) with a rapid response and wide spectral dynamic range. The reflected semiconductor optical amplifier (RSOA) as a light source was directly modulated by the generated pseudorandom binary sequence (PRBS) code and the modulated signal is amplified and goes through FBG sensors via circulator. When the modulated optical signal experienced FBG sensor array, the optical signal which was consistent with center wavelength of FBGs is reflected and added from each sensors. The added signal goes into dispersion compensating fiber (DCF) as a dispersion medium. After through the DCF, the optical signal is converted into electrical signal by using photodetector (PD). For separate individual reflected sensor signal, the sliding correlation method was used. The proposed method improves the code interference and it also has advantages such as a large number of sensors, continuously measuring individual sensors, and decreasing the complexity of the sensor network.

  10. Distributed magnetic field positioning system using code division multiple access

    NASA Technical Reports Server (NTRS)

    Prigge, Eric A. (Inventor)

    2003-01-01

    An apparatus and methods for a magnetic field positioning system use a fundamentally different, and advantageous, signal structure and multiple access method, known as Code Division Multiple Access (CDMA). This signal architecture, when combined with processing methods, leads to advantages over the existing technologies, especially when applied to a system with a large number of magnetic field generators (beacons). Beacons at known positions generate coded magnetic fields, and a magnetic sensor measures a sum field and decomposes it into component fields to determine the sensor position and orientation. The apparatus and methods can have a large `building-sized` coverage area. The system allows for numerous beacons to be distributed throughout an area at a number of different locations. A method to estimate position and attitude, with no prior knowledge, uses dipole fields produced by these beacons in different locations.

  11. Effects of Fiber Dispersion on the Performance of Optical CDMA Systems

    NASA Astrophysics Data System (ADS)

    Kharazi, Seyed Mohammad Saleh Seyedzadeh; Mahdiraji, Ghafour Amouzad; Sahbudin, Ratna Kalos Zakiah; Abas, Ahmad Fauzi; Anas, Siti Barirah Ahmad

    2012-12-01

    In recent years, Optical Code Division Multiple Access (OCDMA) system had received great attentions due to its potential to support applications with various data rates and Quality of Service requirements in physical layer. Since the main part of any fiber-based transmission system is the optical fiber itself, OCDMA also suffers from fiber impairments especially dispersion. In this paper, a review of fiber dispersion effects on system performance of different coding techniques is presented, focusing on single mode fiber. The different coding techniques include direct-sequence, spectral amplitude encoding and wavelength hopping/time spreading. In addition, the basic dispersion compensation approaches, which have been proposed in the literature, for these particular coding schemes are also discussed.

  12. Power Assigning Method for Increasing the Number of Users in Time-spreading Optical CDMA Systems

    NASA Astrophysics Data System (ADS)

    Salehi, Mohammad Reza; Abiri, Ebrahim; Kazemi, Keyvan; Dezfouli, Mehran

    2011-04-01

    In this paper, a method for increasing the number of supportable users in a time-spreading Optical code division multiple access (OCDMA) system is proposed. In the presented technique, a unique codeword is assigned to a couple of users instead of just one. Different optical powers are employed for such users in order to distinguish them from each other. Other methods use the frequency or the polarization of the optical signals as an additional coding dimension to increase the number of codewords and hence the number of users in the network. It is proposed to employ nonlinear optical regenerators for separating optical pulses with different powers. A comprehensive design algorithm for such regenerators is presented. In order to evaluate the performance of the designed regenerators a TS-OCDMA system is simulated using OptiSystem software. Results indicate an error free transmission in the system employing the proposed technique.

  13. Performance of Reed-Solomon Coded MC-DS-CDMA with Bi-orthogonal Modulation

    NASA Astrophysics Data System (ADS)

    Tanaka, Hirokazu; Jang, Kyung Woon; Yamasaki, Shoichiro; Haseyama, Miki

    In this paper, an error correction scheme suitable for MC-DS-CDMA system with bi-orthogonal modulation is proposed. The input sequence of a bi-orthogonal modulator consists of n - 1 bit code selection bit sequence and 1 bit sign bit sequence. In order to apply an efficient error correction code, the following points should be considered; (1) if the code selection bits can be protected sufficiently, the sign bit error can also be reduced sufficiently, (2) since a code selection bit sequence consists of n - 1 bits, employing a symbol error correcting code is more effective for encoding code selection bits, (3) the complexity of the error correction encoder and decoder implementations should be minimum. Based on these conditions, we propose to employ Reed-Solomon (RS) code for encoding the code selection bits and no error correction code for the sign bit. Additionally, detection algorithm at the bi-orthogonal demodulator is modified for compensating degradations of the sign bit error rate performance. The performance in an Additive White Gaussian Noise (AWGN) channel is evaluated by both theoretical analysis and computer simulations. The performance evaluations by simulations on multi-path fading channels are also shown. It is shown that the proposed scheme has remarkable improvement.

  14. Four-Channel, 8 x 8 Bit, Two-Dimensional Parallel Transmission by use of Space-Code-Division Multiple-Access Encoder and Decoder Modules.

    PubMed

    Nakamura, M; Kitayama, K; Igasaki, Y; Kaneda, K

    1998-07-10

    We experimentally demonstrate four-channel multiplexing of 64-bit (8 x 8) two-dimensional (2-D) parallel data links on the basis of optical space-code-division multiple access (CDMA) by using new modules of optical spatial encoders and a decoder with a new high-contrast 9-m-long image fiber with 3 x 10(4) cores. Each 8 x 8 bit plane (64-bit parallel data) is optically encoded with an 8 x 8, 2-D optical orthogonal signature pattern. The encoded bit planes are spatially multiplexed and transmitted through an image fiber. A receiver can recover the intended input bit plane by means of an optical decoding process. This result should encourage the application of optical space-CDMA to future high-throughput 2-D parallel data links connecting massively parallel processors. PMID:18285889

  15. A CDMA Spotbeam Architecture for the Next Generation Satellite System (NGSS) for the Aeronautical Telecommunications Network (ATN)

    NASA Technical Reports Server (NTRS)

    Raghavan, Rajesh S.; Shamma, Mohammed A.

    2003-01-01

    This paper will present work being done to model and simulate a CDMA based Mobile Satellite System architecture for providing all or part of the future Air Traffic Management (ATM) services. Such a system, will help in relieving the dependence on ground based networks, if not eliminate it. Additionally such an architecture can be used in parallel or as a supplementary service along with ground based links to help alleviate any capacity bottlenecks, or in areas where such services are difficult to make available such as in oceanic, remote areas outside the jet highways, or in developing countries where ground services are less available.

  16. High security chaotic multiple access scheme for visible light communication systems with advanced encryption standard interleaving

    NASA Astrophysics Data System (ADS)

    Qiu, Junchao; Zhang, Lin; Li, Diyang; Liu, Xingcheng

    2016-06-01

    Chaotic sequences can be applied to realize multiple user access and improve the system security for a visible light communication (VLC) system. However, since the map patterns of chaotic sequences are usually well known, eavesdroppers can possibly derive the key parameters of chaotic sequences and subsequently retrieve the information. We design an advanced encryption standard (AES) interleaving aided multiple user access scheme to enhance the security of a chaotic code division multiple access-based visible light communication (C-CDMA-VLC) system. We propose to spread the information with chaotic sequences, and then the spread information is interleaved by an AES algorithm and transmitted over VLC channels. Since the computation complexity of performing inverse operations to deinterleave the information is high, the eavesdroppers in a high speed VLC system cannot retrieve the information in real time; thus, the system security will be enhanced. Moreover, we build a mathematical model for the AES-aided VLC system and derive the theoretical information leakage to analyze the system security. The simulations are performed over VLC channels, and the results demonstrate the effectiveness and high security of our presented AES interleaving aided chaotic CDMA-VLC system.

  17. Blind multiuser detector for chaos-based CDMA using support vector machine.

    PubMed

    Kao, Johnny Wei-Hsun; Berber, Stevan Mirko; Kecman, Vojislav

    2010-08-01

    The algorithm and the results of a blind multiuser detector using a machine learning technique called support vector machine (SVM) on a chaos-based code division multiple access system is presented in this paper. Simulation results showed that the performance achieved by using SVM is comparable to existing minimum mean square error (MMSE) detector under both additive white Gaussian noise (AWGN) and Rayleigh fading conditions. However, unlike the MMSE detector, the SVM detector does not require the knowledge of spreading codes of other users in the system or the estimate of the channel noise variance. The optimization of this algorithm is considered in this paper and its complexity is compared with the MMSE detector. This detector is much more suitable to work in the forward link than MMSE. In addition, original theoretical bit-error rate expressions for the SVM detector under both AWGN and Rayleigh fading are derived to verify the simulation results. PMID:20570769

  18. Performance improvement of FSO/CDMA systems over dispersive turbulence channel using multi-wavelength PPM signaling.

    PubMed

    Dang, Ngoc T; Pham, Anh T

    2012-11-19

    Previous studies show that, compared to on-off keying (OOK) signaling, pulse-position modulation (PPM) is favorable in FSO/CDMA systems thanks to its energy efficiency and simple detection. Nevertheless, when the system bit rate increases and the transmission distance is far, the FSO/CDMA systems using PPM signaling critically suffer from the impact of pulse broadening caused by dispersion, especially when the modulation level is high. In this paper, we therefore propose to use multi-wavelength PPM (MWPPM) signaling to overcome the limitation of PPM. To further improve the system performance, avalanche photodiode (APD) is also used. The performance of the proposed system is theoretically analyzed using a realistic model of Gaussian pulse propagation. To model the impact of intensity fluctuation caused by the atmospheric turbulence, the log-normal channel is used. We find that, by using MWPPM, the effects of both intensity fluctuation and pulse broadening are mitigated, the BER is therefore significantly improved. Additionally, we quantitatively show that the system performance is further improved by using APD, especially when the average APD gain is chosen properly. PMID:23187533

  19. Decision Making Regarding Access to Training and Development in Medium-Sized Enterprises: An Exploratory Study Using the Critical Incident Technique

    ERIC Educational Resources Information Center

    Coetzer, Alan; Redmond, Janice; Sharafizad, Jalleh

    2012-01-01

    Purpose: The purpose of this paper is to develop an understanding of factors that impinge on managerial decision-making processes regarding employee access to structured training and development (T&D) opportunities that are at least partially funded by the firm. Design/methodology/approach: Semi-structured interviews incorporating the Critical…

  20. PAPR reduction in synchronous CI/MC-CDMA uplink system using genetic algorithms

    NASA Astrophysics Data System (ADS)

    Hati, Sumanta; Maity, Santi P.

    2013-01-01

    Main disadvantage of a multicarrier communication system is high peak to average power ratio (PAPR) of the transmitted signal. The high PAPR causes the performance degradation due to nonlinear distortion in the high power amplifier (HPA). PAPR value is closely depends on transmitted power and correlation properties of the user's spreading code. High peak and low average value of the transmitted power increases the PAPR. On the other side high auto correlation function (ACF) value and low cross correlation function (CCF) value of the spreading code also increases the PAPR. But to eliminate the multiple access interference (MAI) in receiver end, ACF should be peak and CCF should be posses zero for all time shifts. So, there is a conflicting nature of PAPR and bit error rate (BER). That's why an exhaustive effort has been made in this paper for proper distribution of transmitted power within an acceptable range of peak transmitted power and evaluates the new spreading codes using Genetic Algorithms (GA). In general, to obtain optimum PAPR reduction using GA, total searching time to find out the proper amplitude and phase parameters must be accomplished. Simulation results show that PAPR and BER performance using this proposed technique is better than conventional network.

  1. Design of a search and rescue terminal based on the dual-mode satellite and CDMA network

    NASA Astrophysics Data System (ADS)

    Zhao, Junping; Zhang, Xuan; Zheng, Bing; Zhou, Yubin; Song, Hao; Song, Wei; Zhang, Meikui; Liu, Tongze; Zhou, Li

    2010-12-01

    The current goal is to create a set of portable terminals with GPS/BD2 dual-mode satellite positioning, vital signs monitoring and wireless transmission functions. The terminal depends on an ARM processor to collect and combine data related to vital signs and GPS/BD2 location information, and sends the message to headquarters through the military CDMA network. It integrates multiple functions as a whole. The satellite positioning and wireless transmission capabilities are integrated into the motherboard, and the vital signs sensors used in the form of belts communicate with the board through Bluetooth. It can be adjusted according to the headquarters' instructions. This kind of device is of great practical significance for operations during disaster relief, search and rescue of the wounded in wartime, non-war military operations and other special circumstances.

  2. Web Accessibility and Accessibility Instruction

    ERIC Educational Resources Information Center

    Green, Ravonne A.; Huprich, Julia

    2009-01-01

    Section 508 of the Americans with Disabilities Act (ADA) mandates that programs and services be accessible to people with disabilities. While schools of library and information science (SLIS*) and university libraries should model accessible Web sites, this may not be the case. This article examines previous studies about the Web accessibility of…

  3. Open Access

    ERIC Educational Resources Information Center

    Suber, Peter

    2012-01-01

    The Internet lets us share perfect copies of our work with a worldwide audience at virtually no cost. We take advantage of this revolutionary opportunity when we make our work "open access": digital, online, free of charge, and free of most copyright and licensing restrictions. Open access is made possible by the Internet and copyright-holder…

  4. Access Denied

    ERIC Educational Resources Information Center

    Villano, Matt

    2008-01-01

    Building access control (BAC)--a catchall phrase to describe the systems that control access to facilities across campus--has traditionally been handled with remarkably low-tech solutions: (1) manual locks; (2) electronic locks; and (3) ID cards with magnetic strips. Recent improvements have included smart cards and keyless solutions that make use…

  5. A Unified Framework of the Performance Evaluation of Optical Time-Wavelength Code-Division Multiple-Access Systems

    NASA Astrophysics Data System (ADS)

    Inaty, Elie

    In this paper, we provide an analysis to the performance of optical time-wavelength code-division multiple-access (OTW-CDMA) network when the system is working above the nominal transmission rate limit imposed by the passive encoding-decoding operation. We address the problem of overlapping in such a system and how it can directly affect the bit error rate (BER). A unified mathematical framework is presented under the assumption of one coincidence sequences with non-repeating wavelengths. A closed form expression of the multiple access interference limited BER is provided as a function of different system parameters. Results show that the performance of OTW-CDMA system may be critically affected when working above the nominal limit; an event that may happen when the network operates at high transmission rate. In addition, the impact of the derived error probability on the performance of two newly proposed MAC protocols, the S-ALOHA and the R3T, is also investigated. It is shown that for low transmission rates, the S-ALOHA is better than the R3T; while the R3T is better at very high transmission rates. However, in general it is postulated that the R3T protocol suffers a higher delay mainly because of the presence of additional modes.

  6. A traffic-depended multi-buffer node architecture and an effective access technique under symmetric and asymmetric IP traffic scenarios for unslotted ring WDM MANs

    NASA Astrophysics Data System (ADS)

    Baziana, Peristera A.

    2016-09-01

    This study aims to put forward an extensive discussion about the increasing demand for available bandwidth to serve the multiple types of traffic in modern wavelength division multiplexing (WDM) metropolitan area networks (MANs). A traffic-depended multi-buffer node architecture in conjunction with an efficient asynchronous transmission WDM access (WDMA) protocol to serve the variable size Internet packets in ring MANs is proposed. The structure of the multi-buffer node architecture is determined by the probability distribution of each packet size category in the MAN traffic, providing storage and dropping events equity among the nodes. The adopted WDMA algorithm satisfies the requirement for high performance efficiency especially under high offered load, by taking care to optimally face the bandwidth fragmentation problem and to maximize the bandwidth exploitation, while it effectively avoids both the packets collisions over the wavelengths and the destination conflicts. Numerical results prove that the proposed network model achieves throughput improvement up to 334% as compared with the relative study of Pranggono and Elmirghani (2011). An analytical framework is developed for the protocol throughput predictions under both symmetric and asymmetric IP traffic scenarios. Also, the proposed protocol performance is thoroughly investigated through simulation results based on Poisson and self-similar traffic model statistics, for both traffic scenarios.

  7. A novel 2D wavelength-time chaos code in optical CDMA system

    NASA Astrophysics Data System (ADS)

    Zhang, Qi; Xin, Xiangjun; Wang, Yongjun; Zhang, Lijia; Yu, Chongxiu; Meng, Nan; Wang, Houtian

    2012-11-01

    Two-dimensional wavelength-time chaos code is proposed and constructed for a synchronous optical code division multiple access system. The access performance is compared between one-dimensional chaos code, WDM/chaos code and the proposed code. Comparison shows that two-dimensional wavelength-time chaos code possesses larger capacity, better spectral efficiency and bit-error ratio than WDM/chaos combinations and one-dimensional chaos code.

  8. Computed Tomography-Guided Access to the Cisterna Chyli: Introduction of a Technique for Direct Lymphangiography to Evaluate and Treat Chylothorax

    SciTech Connect

    Schoellnast, Helmut; Maybody, Majid; Getrajdman, George I.; Bains, Manjit S.; Finley, David J.; Solomon, Stephen B.

    2011-02-15

    The purpose of this report is to introduce a technique of direct lymphangiography to enable chylothorax treatment. Using a hybrid computed tomography (CT) and fluoroscopy imaging system, a 21-gauge needle was placed under CT guidance into the cisterna chyli to allow contrast lymphangiography and CT lymphangiography in two patients with presumed postoperative chylothorax. Water-soluble contrast media injection demonstrated the thoracic duct anatomy in both patients. Further successful needle disruption of the cisterna chyli was performed in one patient to interrupt lymph flow and stop the chylous leak, with subsequent resolution of the chylothorax.

  9. Unique Access to Learning

    ERIC Educational Resources Information Center

    Goble, Don

    2009-01-01

    This article describes the many learning opportunities that broadcast technology students at Ladue Horton Watkins High School in St. Louis, Missouri, experience because of their unique access to technology and methods of learning. Through scaffolding, stepladder techniques, and trial by fire, students learn to produce multiple television programs,…

  10. SU-E-T-603: Analysis of Optical Tracked Head Inter-Fraction Movements Within Masks to Access Intracranial Immobilization Techniques in Proton Therapy

    SciTech Connect

    Hsi, W; Zeidan, O

    2014-06-01

    Purpose: We present a quantitative methodology utilizing an optical tracking system for monitoring head inter-fraction movements within brain masks to assess the effectiveness of two intracranial immobilization techniques. Methods and Materials: A 3-point-tracking method was developed to measure the mask location for a treatment field at each fraction. Measured displacement of mask location to its location at first fraction is equivalent to the head movement within the mask. Head movements for each of treatment fields were measured over about 10 fractions at each patient for seven patients; five treated in supine and two treated in prone. The Q-fix Base-of-Skull head frame was used in supine while the CIVCO uni-frame baseplate was used in prone. Displacements of recoded couch position of each field post imaging at each fraction were extracted for those seven patients. Standard deviation (S.D.) of head movements and couch displacements was scored for statistical analysis. Results: The accuracy of 3PtTrack method was within 1.0 mm by phantom measurements. Patterns of head movement and couch displacement were similar for patients treated in either supine or prone. In superior-inferior direction, mean value of scored standard deviations over seven patients were 1.6 mm and 3.4 mm for the head movement and the couch displacement, respectively. The result indicated that the head movement combined with a loose fixation between the mask-to-head frame results large couch displacements for each patient, and also large variation between patients. However, the head movement is the main cause for the couch displacement with similar magnitude of around 1.0 mm in anterior-posterior and lateral directions. Conclusions: Optical-tracking methodology independently quantifying head movements could improve immobilization devices by correctly acting on causes for head motions within mask. A confidence in the quality of intracranial immobilization techniques could be more efficient by

  11. Overview of techniques for mitigation of fading and shadowing in the direct broadcast satellite radio environment

    NASA Technical Reports Server (NTRS)

    Bell, David; Gevargiz, John; Vaisnys, Arvydas; Julian, David

    1995-01-01

    The DBS radio propagation environment is divided into three sub-environments, indoor, rural-suburban mobile and urban mobile. Indoor propagation effects are in a large part determined by construction material. Non-metallic materials afford direct, albeit attenuated penetration of the satellite signal with a minimum of multipath signal scattering. Signal penetration into structures using significant metallic materials is often indirect, through openings such as doors and windows and propagation will involve significant multipath components. Even so, delay spread in many situations is on the order of 10's of nanoseconds resulting in relatively flat fading. Thus frequency diversity techniques such as Orthogonal Frequency Division Multiplex (OFDM) and Code Division Multiple Access (CDMA) or equalization techniques do not realize their intended performance enhancement. Antenna diversity, directivity and placement are key mitigation techniques for the indoor environment. In the Rural-Suburban mobile environment with elevation angles greater than 20 deg, multipath components from the satellite signal are 15-20 dB below the line-of-sight signal level and often originate from nearby reflectors. Thus shadowing is the dominant signal impairment and fading effects are again found to be relatively flat for a large fading margin. Because receiver motion induces rapid variations in the signal level, temporal diversity techniques such as interleaving, channel coding and retransmission can be used to combat short intermittent fading events. Antenna diversity and directivity techniques are again useful in this environment. Finally, in the Urban mobile environment, slower vehicle speeds and blockage by buildings causes signal fades that are too long and too deep to combat with signal margin or time diversity. Land-based signal boosters are needed to fill in the coverage gaps of the satellite only broadcast scheme. On frequency boosters are suggested to conserve bandwidth yet these

  12. Hemodialysis access - self care

    MedlinePlus

    Kidney failure - chronic-hemodialysis access; Renal failure - chronic-hemodialysis access; Chronic renal insufficiency - hemodialysis access; Chronic kidney failure - hemodialysis access; Chronic renal failure - hemodialysis access; dialysis - hemodialysis access

  13. Hemodialysis access - self care

    MedlinePlus

    Kidney failure - chronic-hemodialysis access; Renal failure - chronic-hemodialysis access; Chronic renal insufficiency - hemodialysis access; Chronic kidney failure - hemodialysis access; Chronic renal failure - ...

  14. Expanding Access

    ERIC Educational Resources Information Center

    Roach, Ronald

    2007-01-01

    There is no question that the United States lags behind most industrialized nations in consumer access to broadband Internet service. For many policy makers and activists, this shortfall marks the latest phase in the struggle to overcome the digital divide. To remedy this lack of broadband affordability and availability, one start-up firm--with…

  15. Access Denied

    ERIC Educational Resources Information Center

    Raths, David

    2012-01-01

    As faculty members add online and multimedia elements to their courses, colleges and universities across the country are realizing that there is a lot of work to be done to ensure that disabled students (and employees) have equal access to course material and university websites. Unfortunately, far too few schools consider the task a top priority.…

  16. Easy Access

    ERIC Educational Resources Information Center

    Gettelman, Alan

    2009-01-01

    School and university restrooms, locker and shower rooms have specific ADA accessibility requirements that serve the needs of staff, students and campus visitors who are disabled as a result of injury, illness or age. Taking good care of them is good for the reputation of a sensitive community institution, and fosters positive public relations.…

  17. Probability of error analysis for FHSS/CDMA communications in the presence of fading

    NASA Astrophysics Data System (ADS)

    Wickert, Mark A.; Turcotte, Randy L.

    1992-04-01

    Expressions are found for the error probability of a slow frequency-hopped spread-spectrum (FHSS) M-ary FSK multiple-access system in the presence of slow-nonselective Rayleigh or single-term Rician fading. The approach is general enough to allow for the consideration of independent power levels; that is to say, the power levels of the interfering signals can be varied with respect to the power level of the desired signal. The exact analysis is carried out for one and two multiple-access interferers using BFSK modulation. The analysis is general enough for the consideration of the near/far problem under the specified channel conditions. Comparisons between the error expressions developed here and previously published upper bounds (Geraniotis and Pursley, 1982) show that, under certain conditions, the previous upper bounds on the error probability may exceed the true error probability by an order of magnitude.

  18. A novel method for performance improvement of optical CDMA system using alterable concatenated code

    NASA Astrophysics Data System (ADS)

    Qiu, Kun; Zhang, Chongfu

    2007-04-01

    A novel method using alterable concatenated code to pre-encode is proposed to reduce the impact of system impairment and multiple access interference (MAI) in optical code division multiple access (OCDMA) system, comprehensive comparisons between different concatenated code type and forward error correcting (FEC) scheme are studied by simulation. In the scheme, we apply concatenated coding to the embedded modulation scheme, and optical orthogonal code (OOC) is employed as address sequence code, an avalanche photodiode (APD) is selected as the system receiver. The bit error rate (BER) performance is derived taking into account the effect of some noises, dispersion power penalty and the MAI. From both theoretical analysis and numerical results, we can show that the proposed system has good performance at a BER of 10 -9 with a gain of 6.4 dB improvement achieved using the concatenated code as the pre-code, and this scheme permits implementation of a cost effective OCDMA system.

  19. S-band multiple-access interference study for advanced tracking and data relay satellite systems

    NASA Technical Reports Server (NTRS)

    Peng, Wei-Chung; Yang, Chau-Chin

    1990-01-01

    The results of a study on the effect of mutual interference among S-band multiple access (SMA) system users of advanced tracking and data relay satellite system (ATDRSS) are presented. In the ATDRSS era, the SMA system is required to support data rates ranging from 10 kb/s to 3 Mb/s. The system will consist of four advanced tracking and data relay satellites (ATDRS) each supporting up to five telemetry links. All users have 10 MHz bandwidth with their carrier frequency equal to 2.2875 GHz. A hybrid SDMA/CDMA scheme is used to mitigate the effect of the interference among system users. SMA system interference probability is evaluated with CLASS software. User link margin degradation due to mutual interference between two users is evaluated. System interference probability is evaluated for the projected 1996 mission model, a reference mission model, and a modified reference mission model.

  20. Investigation of in-band transmission of both spectral amplitude coding/optical code division multiple-access and wavelength division multiplexing signals

    NASA Astrophysics Data System (ADS)

    Ashour, Isaac A. M.; Shaari, Sahbudin; Shalaby, Hossam M. H.; Menon, P. Susthitha

    2011-06-01

    The transmission of both optical code division multiple-access (OCDMA) and wavelength division multiplexing (WDM) users on the same band is investigated. Code pulses of spectral amplitude coding (SAC)/optical code division multiple-access (CDMA) are overlaid onto a multichannel WDM system. Notch filters are utilized in order to suppress the WDM interference signals for detection of optical broadband CDMA signals. Modified quadratic congruence (MQC) codes are used as the signature codes for the SAC/OCDMA system. The proposed system is simulated and its performance in terms of both the bit-error rate and Q-factor are determined. In addition, eavesdropper probability of error-free code detection is evaluated. Our results are compared to traditional nonhybrid systems. It is concluded that the proposed hybrid scheme still achieves acceptable performance. In addition, it provides enhanced data confidentiality as compared to the scheme with SAC/OCDMA only. It is also shown that the performance of the proposed system is limited by the interference of the WDM signals. Furthermore, the simulation illustrates the tradeoff between the performance and confidentiality for authorized users.

  1. Hemodialysis access procedures

    MedlinePlus

    Kidney failure - chronic-dialysis access; Renal failure - chronic-dialysis access; Chronic renal insufficiency-dialysis access; Chronic kidney failure-dialysis access; Chronic renal failure-dialysis access

  2. Data Access Performance Through Parallelization and Vectored Access: Some Results

    SciTech Connect

    Furano, Fabrizio; Hanushevsky, Andrew; /SLAC

    2011-11-10

    High Energy Physics data processing and analysis applications typically deal with the problem of accessing and processing data at high speed. Recent studies, development and test work have shown that the latencies due to data access can often be hidden by parallelizing them with the data processing, thus giving the ability to have applications which process remote data with a high level of efficiency. Techniques and algorithms able to reach this result have been implemented in the client side of the Scalla/xrootd system, and in this contribution we describe the results of some tests done in order to compare their performance and characteristics. These techniques, if used together with multiple streams data access, can also be effective in allowing to efficiently and transparently deal with data repositories accessible via a Wide Area Network.

  3. Add/drop multiplexing and TDM signal transmission in an optical CDMA ring network

    NASA Astrophysics Data System (ADS)

    Chen, Biao; Guo, Changjian; Chen, Jiajia; Zhang, Linjian; Jiang, Qiong; He, Sailing

    2007-08-01

    It is shown that a ring topology is better than a star topology for an optical-code-division multiple access (OCDMA) network as an optical metropolitan or local area network in terms of security and capacity. Each node in an OCDMA ring network requires an OCDMA add/drop multiplexer. We present what we believe to be a novel OCDMA add/drop multiplexer that can simultaneously add and drop multiple code channels, and a proof-of-feasibility experiment is demonstrated. An OCDMA ring may also adapt code channels for time domain multiplexing and other digital signal transmission systems. An experiment for the synchronized digital hierarchy (SDH) signal over a OCDMA link is demonstrated.

  4. Successive Interference Cancellation for DS-Optical PPM-CDMA Systems

    NASA Astrophysics Data System (ADS)

    Alsowaidi, N.; Eltaif, Tawfig; Mokhtar, M. R.

    2016-06-01

    In this paper we introduce a successive interference cancellation (SIC) scheme for direct sequence optical code division multiple access (DS-OCDMA) systems using pulse position modulation (PPM). Considering double-padded modified prime code (DPMPC) as a signature sequence code, results show that the system has better performance in terms of both capacity and bit error rate (BER) as compared to the one without cancellation scheme, where the system with SIC scheme can support up to 88 users while the system without SIC scheme can support only 38 users at similar BER=10-9. Although the receiver sensitivity is affected by the overlapping between users, which limits the system performance, the theoretical analysis of this issue indicates the influence of the size of M-ary PPM on OCDMA system. Hence, the BER value is still sufficient for good system performance.

  5. Development of a New Class of Zero Cross Correlation Codes for Optical CDMA Systems

    NASA Astrophysics Data System (ADS)

    Rashidi, Che Bin Mohd; Aljunid, S. A.; Ghani, F.; Anuar, M. S.

    2012-03-01

    The paper presents a method for the development of a new class of zero cross correlation optical code for Optical Code Division Multiple Access (OCDMA) system using Spectral Amplitude Coding. The proposed code is called Modified Zero Cross Correlation Code (MZCC). The code has minimum length and can be constructed quite simply for any number of users and for any code weights. The code has better spectrum slicing properties and noise performance in term of Bit Error Rate. The Modified Zero Cross Correlation Code will be demonstrated in simulation using OptiSys. 6.0 to observe noise performance which is better as compared to the existing Zero Cross Correlation Code.

  6. Remote access thyroid surgery

    PubMed Central

    Bhatia, Parisha; Mohamed, Hossam Eldin; Kadi, Abida; Walvekar, Rohan R.

    2015-01-01

    Robot assisted thyroid surgery has been the latest advance in the evolution of thyroid surgery after endoscopy assisted procedures. The advantage of a superior field vision and technical advancements of robotic technology have permitted novel remote access (trans-axillary and retro-auricular) surgical approaches. Interestingly, several remote access surgical ports using robot surgical system and endoscopic technique have been customized to avoid the social stigma of a visible scar. Current literature has displayed their various advantages in terms of post-operative outcomes; however, the associated financial burden and also additional training and expertise necessary hinder its widespread adoption into endocrine surgery practices. These approaches offer excellent cosmesis, with a shorter learning curve and reduce discomfort to surgeons operating ergonomically through a robotic console. This review aims to provide details of various remote access techniques that are being offered for thyroid resection. Though these have been reported to be safe and feasible approaches for thyroid surgery, further evaluation for their efficacy still remains. PMID:26425450

  7. A new blind nulling algorithm for CDMA mobile satellite communication systems

    NASA Astrophysics Data System (ADS)

    Liu, Yunzhi; Wang, Huali; Wang, Zhihui

    2007-11-01

    A new anti-jamming method is proposed combining adaptive array with direct sequence spread spectrum (DSSS) techniques in mobile satellite communication system. Different with the conventional depreading process, the proposed method modifies DSSS despreador, in which the output data are blindly processed. It overcomes the problem that DSSS signal often has very lower SNR, which is difficult to be captured in constant modulus array processing, especially when strong interference/jamming signals exist coincidentally.

  8. Intraosseous access and adults in the emergency department.

    PubMed

    Lowther, Ashleigh

    This article examines the use of the intraosseous route for obtaining vascular access in adults. It discusses indications for intraosseous access, the techniques and devices used, and contraindications. PMID:21901968

  9. United States Access Board

    MedlinePlus

    ... disabilities through leadership in accessible design and the development of accessibility guidelines and standards for the built environment, transportation, communication, medical diagnostic equipment, and information technology. ...

  10. A Theory of Access

    ERIC Educational Resources Information Center

    Ribot, Jesse C.; Peluso, Nancy Lee

    2003-01-01

    The term "access" is frequently used by property and natural resource analysts without adequate definition. In this paper we develop a concept of access and examine a broad set of factors that differentiate access from property. We define access as "the "ability" to derive benefits from things," broadening from property's classical definition as…

  11. Multi-static networked 3D ladar for surveillance and access control

    NASA Astrophysics Data System (ADS)

    Wang, Y.; Ogirala, S. S. R.; Hu, B.; Le, Han Q.

    2007-04-01

    A theoretical design and simulation of a 3D ladar system concept for surveillance, intrusion detection, and access control is described. It is a non-conventional system architecture that consists of: i) multi-static configuration with an arbitrarily scalable number of transmitters (Tx's) and receivers (Rx's) that form an optical wireless code-division-multiple-access (CDMA) network, and ii) flexible system architecture with modular plug-and-play components that can be deployed for any facility with arbitrary topology. Affordability is a driving consideration; and a key feature for low cost is an asymmetric use of many inexpensive Rx's in conjunction with fewer Tx's, which are generally more expensive. The Rx's are spatially distributed close to the surveyed area for large coverage, and capable of receiving signals from multiple Tx's with moderate laser power. The system produces sensing information that scales as NxM, where N, M are the number of Tx's and Rx's, as opposed to linear scaling ~N in non-network system. Also, for target positioning, besides laser pointing direction and time-of-flight, the algorithm includes multiple point-of-view image fusion and triangulation for enhanced accuracy, which is not applicable to non-networked monostatic ladars. Simulation and scaled model experiments on some aspects of this concept are discussed.

  12. Introduction: Access to fertility care.

    PubMed

    Davis, Owen K; Sokol, Rebecca Z

    2016-05-01

    Given that only an estimated 24% of infertile couples in the United States can fully engage in the medical care required to successfully conceive, the American Society for Reproductive Medicine (ASRM) has incorporated improved access to the full gamut of fertility therapies as an integral component of the Society's strategic plan that was launched in 2014. Toward this end, the ASRM hosted a two-day summit held in Washington D.C. in September 2015 that attracted thought leaders, both speakers and attendees, from around the world. This issue's Views and Reviews focuses on several key areas integral to this effort: an appreciation of the economic challenges to access, as well as the impact and interplay of racial, ethnic, emotional and gender-specific issues in the treatment of infertility. The potential to broaden access to care through modification of existing assisted reproductive techniques is also explored. PMID:27054311

  13. Surveillance and Monitoring of Dialysis Access

    PubMed Central

    Kumbar, Lalathaksha; Karim, Jariatul; Besarab, Anatole

    2012-01-01

    Vascular access is the lifeline of a hemodialysis patient. Currently arteriovenous fistula and graft are considered the permanent options for vascular access. Monitoring and surveillance of vascular access are an integral part of the care of hemodialysis patient. Although different techniques and methods are available for identifying access dysfunction, the scientific evidence for the optimal methodology is lacking. A small number of randomized controlled trials have been performed evaluating different surveillance techniques. We performed a study of the recent literature published in the PUBMED, to review the scientific evidence on different methodologies currently being used for surveillance and monitoring and their impact on the care of the dialysis access. The limited randomized studies especially involving fistulae and small sample size of the published studies with conflicting results highlight the need for a larger multicentered randomized study with hard clinical end points to evaluate the optimal surveillance strategy for both fistula and graft. PMID:22164333

  14. World Wide Access: Accessible Web Design.

    ERIC Educational Resources Information Center

    Washington Univ., Seattle.

    This brief paper considers the application of "universal design" principles to Web page design in order to increase accessibility for people with disabilities. Suggestions are based on the World Wide Web Consortium's accessibility initiative, which has proposed guidelines for all Web authors and federal government standards. Seven guidelines for…

  15. Exact probability of error analysis for FHSS/CDMA communications in the presence of single term Rician fading

    NASA Astrophysics Data System (ADS)

    Turcotte, Randy L.; Wickert, Mark A.

    An exact expression is found for the probability of bit error of an FHSS-BFSK (frequency-hopping spread-spectrum/binary-frequency-shift-keying) multiple-access system in the presence of slow, nonselective, 'single-term' Rician fading. The effects of multiple-access interference and/or continuous tone jamming are considered. Comparisons are made between the error expressions developed here and previously published upper bounds. It is found that under certain channel conditions the upper bounds on the probability of bit error may exceed the actual probability of error by an order of magnitude.

  16. Hemodialysis access procedures

    MedlinePlus

    National Kidney and Urologic Diseases Information Clearinghouse. Vascular Access for Hemodialysis . Updated July 23, 2014. Available at: kidney.niddk.nih.gov/kudiseases/pubs/vascularaccess/index.aspx. Accessed: February 9, 2015. ...

  17. Making Online Information Accessible to Students with Disabilities, Part II.

    ERIC Educational Resources Information Center

    Robertson, Janna Siegel; Harris, James Wallace

    2003-01-01

    Focuses on the major HTML coding techniques used when making Web pages and online courses accessible to students with disabilities. Examples of accessibility features provided are not difficult for most Web authors to incorporate into their Web pages. With a few adaptations, Web page developers can make online information accessible to students…

  18. [Accessible Rural Housing.

    ERIC Educational Resources Information Center

    Baker, Nick, Ed.

    1995-01-01

    This issue of the quarterly newsletter "Rural Exchange" provides information and resources on accessible rural housing for the disabled. "Accessible Manufactured Housing Could Increase Rural Home Supply" (Nick Baker) suggests that incorporation of access features such as lever door handles and no-step entries into manufactured housing could help…

  19. Open Access Alternatives

    ERIC Educational Resources Information Center

    Tenopir, Carol

    2004-01-01

    Open access publishing is a hot topic today. But open access publishing can have many different definitions, and pros and cons vary with the definitions. Open access publishing is especially attractive to companies and small colleges or universities that are likely to have many more readers than authors. A downside is that a membership fee sounds…

  20. Demystifying Remote Access

    ERIC Educational Resources Information Center

    Howe, Grant

    2009-01-01

    With money tight, more and more districts are considering remote access as a way to reduce expenses and budget information technology costs more effectively. Remote access allows staff members to work with a hosted software application from any school campus without being tied to a specific physical location. Each school can access critical…

  1. Open Access and beyond.

    PubMed

    Mathur, Shawn; Schmidt, Christian; Das, Chhaya; Tucker, Philip W

    2006-01-01

    Uncensored exchange of scientific results hastens progress. Open Access does not stop at the removal of price and permission barriers; still, censorship and reading disabilities, to name a few, hamper access to information. Here, we invite the scientific community and the public to discuss new methods to distribute, store and manage literature in order to achieve unfettered access to literature. PMID:16956402

  2. Reflective Database Access Control

    ERIC Educational Resources Information Center

    Olson, Lars E.

    2009-01-01

    "Reflective Database Access Control" (RDBAC) is a model in which a database privilege is expressed as a database query itself, rather than as a static privilege contained in an access control list. RDBAC aids the management of database access controls by improving the expressiveness of policies. However, such policies introduce new interactions…

  3. A Novel Scheme of Fast-frequency Hopping Optical CDMA System with No-hit-zone Sequence

    NASA Astrophysics Data System (ADS)

    Ji, Jianhua; liu, Ling; Wang, Ke; Zhang, Zhipeng; Xu, Ming

    2013-09-01

    In traditional fast frequency-hopping OCDMA (FFH-OCDMA) system, beat noise and multiple-access interference are the main performance limitations, and complicated power control must be employed to eliminate the near-far effect. In this paper, a novel scheme of FFH-OCDMA with no-hit-zone sequence is proposed, which is named NHZ FFH-OCDMA. In NHZ FFH-OCDMA, the synchronization among users can be controlled within permissible time delay, and the code cross-correlation for different users equals zero. Therefore, near-far effect can be eliminated. Furthermore, beat noise and multiple-access interference also can be removed. Simulation of eight simultaneous users with dada rate 100 Mbit/s is demonstrated, where the fiber link consists of 50 km single-mode fiber, plus 5 km dispersion compensating fiber. Simulation results show that the near-far problem of NHZ FFH-OCDMA can be eliminated, and complicated power control can be removed. Therefore, this scheme is a good candidate for optical access network.

  4. Mobile access control vestibule

    NASA Astrophysics Data System (ADS)

    DePoy, Jennifer M.

    1998-12-01

    The mobile access control vestibule (MACV) is an adaptation of techniques developed for mobile military command centers. The overall configuration of modules acts as an entry control/screening facility or transportable command center. The system would provide the following capabilities: (1) A key element for force protection, rapid deployment units sent to areas having no prepositioned equipment or where there has been a degradation of that equipment as a result of natural disasters or civil unrest. (2) A rapidly deployable security control center to upgrade the security at nonmilitary sites (e.g., diplomatic or humanitarian organizations). (3) Personnel screening, package screening, badge/identification card production for authorized personnel, centralized monitoring of deployed perimeter sensors, and centralized communications for law enforcement personnel. (4) Self-contained screening and threat detection systems, including explosives detection using the system developed by Sandia National Laboratories for the FAA. When coupled with transportable electric generators, the system is self-sufficient. The communication system for the MACV would be a combination of physically wired and wireless communication units that supports by ad hoc networking.

  5. Education in vascular access.

    PubMed

    Moist, Louise M; Lee, Timmy C; Lok, Charmaine E; Al-Jaishi, Ahmed; Xi, Wang; Campbell, Vern; Graham, Janet; Wilson, Barb; Vachharajani, Tushar J

    2013-01-01

    The successful creation and use of an arteriovenous vascular access (VA) requires a coordinated, educated multidisciplinary team to ensure an optimal VA for each patient. Patient education programs on VA are associated with increased arteriovenous VA use at dialysis initiation. Education should be tailored to patient goals and preferences with the understanding that experiential education from patient to patient is far more influential than that provided by the healthcare professional. VA education for the nephrologist should focus on addressing the systematic and patient-level barriers in achieving a functional VA, with specific components relating to VA creation, maturation, and cannulation that consider patient goals and preferences. A deficit in nursing skills in the area of assessment and cannulation can have devastating consequences for hemodialysis patients. Delivery of an integrated education program increases nurses' knowledge of VA and development of simulation programs or constructs to assist in cannulation of the VA will greatly facilitate the much needed skill transfer. Adequate VA surgical training and experience are critical to the creation and outcomes of VA. Simulations can benefit nephrologists, dialysis nurses surgeons, and interventionalists though aiding in surgical creation, understanding of the physiology and anatomy of a dysfunctional VA, and practicing cannulation techniques. All future educational initiatives must emphasize the importance of multidisciplinary care to attain successful VA outcomes. PMID:23432319

  6. [Permanent vascular access for haemodialysis].

    PubMed

    Manafov, E N; Batrashov, V A; Sergeev, O G; Yudaev, S S

    2015-01-01

    The presence of a permanent vascular access (PVA) is the pledge of successful treatment of patients being on chronic haemodialysis (CD). Creation and maintenance of a functioning PVA is the priority task of vascular and endovascular surgeons, nephrologists and specialists of haemodialysis departments. According to the KDOQI guidelines, the most preferable type of PVA is a native arteriovenous fistula (AVF). As an alternative it is possible to use a synthetic prosthesis for creating an arteriovenous shunt (AVS) or implantation of a central venous catheter (CVC). Various complications of vascular accesses leading to their loss create the necessity of forming just another PVA, thus negatively influencing the life span and quality of life of this cohort of patients. Improving surgical technique and approaches to treatment, as well as carrying out dynamic monitoring of the condition of the created PVA make it possible to considerably decrease the incidence rate of such complications and to improve the quality of medical care rendered. PMID:26451410

  7. Single Port Access (SPA™) Minimal Access Surgery Through a Single Incision.

    PubMed

    Curcillo, Paul G; King, Stephanie A; Podolsky, Erica R; Rottman, Steven J

    2009-04-01

    The practice of surgical techniques is constantly improving and evolving. In the last two decades, minimally invasive surgery has gained widespread acceptance. Virtually all procedures can now be performed laparoscopically. This trend not only provides better cosmesis, but offers decreased recovery times as well. The initial trend from open to laparoscopic surgery was to use smaller incisions. The natural continuation of this is to now decrease the number of incisions necessary to perform minimal access surgery. To this end, the authors have seen a constantly evolving stream of technology and instrumentation in laparoscopy. New venues, such as robotics and Natural Orifice. Transluminal Endoscopic Surgery (NOTES), have developed as well. As part of this evolution, the authors developed Single Port Access (SPA™) surgery in April 2007 as a novel and innovative platform of minimal access surgery. Its acceptance through our training programs, as well as the subsequent development of modified Single Port techniques, demonstrates the potential to develop a new platform of minimal access surgery. The SPA™ technique is a method of abdominal entry for a wide spectrum of laparoscopic procedures performed by multiple surgical specialties. Using the access techniques we developed, the authors have performed nearly 200 general surgical and gynecologic procedures through a single incision, often <2 cm in length and hidden within the umbilicus. In addition, the development of SPA™ surgery has been focused on using current and standard instrumentation, as well as currently practiced surgical techniques already familiar to surgeons in standard multiport laparoscopy. The "Independence of Motion" attained in this access technique, without the need for any new access or operative devices, allows up to four instruments to be place through a single incision<2 cm in length. We have striven to maintain safety principles of multiport laparoscopy, as well, and have continued to improve

  8. Effects of short-term W-CDMA mobile phone base station exposure on women with or without mobile phone related symptoms.

    PubMed

    Furubayashi, Toshiaki; Ushiyama, Akira; Terao, Yasuo; Mizuno, Yoko; Shirasawa, Kei; Pongpaibool, Pornanong; Simba, Ally Y; Wake, Kanako; Nishikawa, Masami; Miyawaki, Kaori; Yasuda, Asako; Uchiyama, Mitsunori; Yamashita, Hitomi Kobayashi; Masuda, Hiroshi; Hirota, Shogo; Takahashi, Miyuki; Okano, Tomoko; Inomata-Terada, Satomi; Sokejima, Shigeru; Maruyama, Eiji; Watanabe, Soichi; Taki, Masao; Ohkubo, Chiyoji; Ugawa, Yoshikazu

    2009-02-01

    To investigate possible health effects of mobile phone use, we conducted a double-blind, cross-over provocation study to confirm whether subjects with mobile phone related symptoms (MPRS) are more susceptible than control subjects to the effect of electromagnetic fields (EMF) emitted from base stations. We sent questionnaires to 5,000 women and obtained 2,472 valid responses from possible candidates; from these, we recruited 11 subjects with MPRS and 43 controls. There were four EMF exposure conditions, each of which lasted 30 min: continuous, intermittent, and sham exposure with and without noise. Subjects were exposed to EMF of 2.14 GHz, 10 V/m (W-CDMA), in a shielded room to simulate whole-body exposure to EMF from base stations, although the exposure strength we used was higher than that commonly received from base stations. We measured several psychological and cognitive parameters pre- and post-exposure, and monitored autonomic functions. Subjects were asked to report on their perception of EMF and level of discomfort during the experiment. The MPRS group did not differ from the controls in their ability to detect exposure to EMF; nevertheless they consistently experienced more discomfort, regardless of whether or not they were actually exposed to EMF, and despite the lack of significant changes in their autonomic functions. Thus, the two groups did not differ in their responses to real or sham EMF exposure according to any psychological, cognitive or autonomic assessment. In conclusion, we found no evidence of any causal link between hypersensitivity symptoms and exposure to EMF from base stations. PMID:18780296

  9. Performance of asynchronous fiber-optic code division multiple access system based on three-dimensional wavelength/time/space codes and its link analysis.

    PubMed

    Singh, Jaswinder

    2010-03-10

    A novel family of three-dimensional (3-D) wavelength/time/space codes for asynchronous optical code-division-multiple-access (CDMA) systems with "zero" off-peak autocorrelation and "unity" cross correlation is reported. Antipodal signaling and differential detection is employed in the system. A maximum of [(W x T+1) x W] codes are generated for unity cross correlation, where W and T are the number of wavelengths and time chips used in the code and are prime. The conditions for violation of the cross-correlation constraint are discussed. The expressions for number of generated codes are determined for various code dimensions. It is found that the maximum number of codes are generated for S < or = min(W,T), where W and T are prime and S is the number of space channels. The performance of these codes is compared to the earlier reported two-dimensional (2-D)/3-D codes for asynchronous systems. The codes have a code-set-size to code-size ratio greater than W/S. For instance, with a code size of 2065 (59 x 7 x 5), a total of 12,213 users can be supported, and 130 simultaneous users at a bit-error rate (BER) of 10(-9). An arrayed-waveguide-grating-based reconfigurable encoder/decoder design for 2-D implementation for the 3-D codes is presented so that the need for multiple star couplers and fiber ribbons is eliminated. The hardware requirements of the coders used for various modulation/detection schemes are given. The effect of insertion loss in the coders is shown to be significantly reduced with loss compensation by using an amplifier after encoding. An optical CDMA system for four users is simulated and the results presented show the improvement in performance with the use of loss compensation. PMID:20220892

  10. Demystifying Open Access

    SciTech Connect

    Mele, Salvatore

    2007-05-14

    The tenets of Open Access are to grant anyone, anywhere and anytime free access to the results of scientific research. HEP spearheaded the Open Access dissemination of scientific results with the mass mailing of preprints in the pre-WWW era and with the launch of the arXiv preprint system at the dawn of the '90s. The HEP community is now ready for a further push to Open Access while retaining all the advantages of the peer-review system and, at the same time, bring the spiralling cost of journal subscriptions under control. I will present a possible plan for the conversion to Open Access of HEP peer-reviewed journals, through a consortium of HEP funding agencies, laboratories and libraries: SCOAP3 (Sponsoring Consortium for Open Access Publishing in Particle Physics). SCOAP3 will engage with scientific publishers towards building a sustainable model for Open Access publishing, which is as transparent as possible for HEP authors. The current system in which journals income comes from subscription fees is replaced with a scheme where SCOAP3 compensates publishers for the costs incurred to organise the peer-review service and give Open Access to the final version of articles. SCOAP3 will be funded by all countries active in HEP under a 'fair share' scenario, according to their production of HEP articles. In this talk I will present a short overview of the history of Open Access in HEP, the details of the SCOAP3 model and the outlook for its implementation.

  11. Demystifying Open Access

    SciTech Connect

    Mele, Salvatore

    2007-05-14

    The tenets of Open Access are to grant anyone, anywhere and anytime free access to the results of scientific research. HEP spearheaded the Open Access dissemination of scientific results with the mass mailing of preprints in the pre-WWW era and with the launch of the arXiv preprint system at the dawn of the '90s. The HEP community is now ready for a further push to Open Access while retaining all the advantages of the peer-review system and, at the same time, bring the spiralling cost of journal subscriptions under control. I will present a possible plan for the conversion to Open Access of HEP peer-reviewed journals, through a consortium of HEP funding agencies, laboratories and libraries: SCOAP3 (Sponsoring Consortium for Open Access Publishing in Particle Physics). SCOAP3 will engage with scientific publishers towards building a sustainable model for Open Access publishing, which is as transparent as possible for HEP authors. The current system in which journals income comes from subscription fees is replaced with a scheme where SCOAP3 compensates publishers for the costs incurred to organise the peer-review service and give Open Access to the final version of articles. SCOAP3 will be funded by all countries active in HEP under a "fair share" scenario, according to their production of HEP articles. In this talk I will present a short overview of the history of Open Access in HEP, the details of the SCOAP3 model and the outlook for its implementation.

  12. Access Interface Strategies

    PubMed Central

    Fager, Susan; Beukelman, David R.; Fried-Oken, Melanie; Jakobs, Tom; Baker, John

    2013-01-01

    Individuals who rely on augmentative and alternative communication (AAC) devices to support their communication often have physical movement challenges that require alternative methods of access. Technology that supports access, particularly for those with the most severe movement deficits, have expanded substantially over the years. The purposes of this article are to review the state of the science of access technologies that interface with augmentative and alternative communication devices and to propose a future research and development agenda that will enhance access options for people with limited movement capability due to developmental and acquired conditions. PMID:22590797

  13. Optical Access Networks

    NASA Astrophysics Data System (ADS)

    Zheng, Jun; Ansari, Nirwan

    2005-05-01

    Call for Papers: Optical Access Networks With the wide deployment of fiber-optic technology over the past two decades, we have witnessed a tremendous growth of bandwidth capacity in the backbone networks of today's telecommunications infrastructure. However, access networks, which cover the "last-mile" areas and serve numerous residential and small business users, have not been scaled up commensurately. The local subscriber lines for telephone and cable television are still using twisted pairs and coaxial cables. Most residential connections to the Internet are still through dial-up modems operating at a low speed on twisted pairs. As the demand for access bandwidth increases with emerging high-bandwidth applications, such as distance learning, high-definition television (HDTV), and video on demand (VoD), the last-mile access networks have become a bandwidth bottleneck in today's telecommunications infrastructure. To ease this bottleneck, it is imperative to provide sufficient bandwidth capacity in the access networks to open the bottleneck and thus present more opportunities for the provisioning of multiservices. Optical access solutions promise huge bandwidth to service providers and low-cost high-bandwidth services to end users and are therefore widely considered the technology of choice for next-generation access networks. To realize the vision of optical access networks, however, many key issues still need to be addressed, such as network architectures, signaling protocols, and implementation standards. The major challenges lie in the fact that an optical solution must be not only robust, scalable, and flexible, but also implemented at a low cost comparable to that of existing access solutions in order to increase the economic viability of many potential high-bandwidth applications. In recent years, optical access networks have been receiving tremendous attention from both academia and industry. A large number of research activities have been carried out or

  14. Optical Access Networks

    NASA Astrophysics Data System (ADS)

    Zheng, Jun; Ansari, Nirwan; Jersey Inst Ansari, New; Jersey Inst, New

    2005-04-01

    Call for Papers: Optical Access Networks With the wide deployment of fiber-optic technology over the past two decades, we have witnessed a tremendous growth of bandwidth capacity in the backbone networks of today's telecommunications infrastructure. However, access networks, which cover the "last-mile" areas and serve numerous residential and small business users, have not been scaled up commensurately. The local subscriber lines for telephone and cable television are still using twisted pairs and coaxial cables. Most residential connections to the Internet are still through dial-up modems operating at a low speed on twisted pairs. As the demand for access bandwidth increases with emerging high-bandwidth applications, such as distance learning, high-definition television (HDTV), and video on demand (VoD), the last-mile access networks have become a bandwidth bottleneck in today's telecommunications infrastructure. To ease this bottleneck, it is imperative to provide sufficient bandwidth capacity in the access networks to open the bottleneck and thus present more opportunities for the provisioning of multiservices. Optical access solutions promise huge bandwidth to service providers and low-cost high-bandwidth services to end users and are therefore widely considered the technology of choice for next-generation access networks. To realize the vision of optical access networks, however, many key issues still need to be addressed, such as network architectures, signaling protocols, and implementation standards. The major challenges lie in the fact that an optical solution must be not only robust, scalable, and flexible, but also implemented at a low cost comparable to that of existing access solutions in order to increase the economic viability of many potential high-bandwidth applications. In recent years, optical access networks have been receiving tremendous attention from both academia and industry. A large number of research activities have been carried out or

  15. Optical Access Networks

    NASA Astrophysics Data System (ADS)

    Zheng, Jun; Ansari, Nirwan

    2005-06-01

    Call for Papers: Optical Access Networks With the wide deployment of fiber-optic technology over the past two decades, we have witnessed a tremendous growth of bandwidth capacity in the backbone networks of today's telecommunications infrastructure. However, access networks, which cover the "last-mile" areas and serve numerous residential and small business users, have not been scaled up commensurately. The local subscriber lines for telephone and cable television are still using twisted pairs and coaxial cables. Most residential connections to the Internet are still through dial-up modems operating at a low speed on twisted pairs. As the demand for access bandwidth increases with emerging high-bandwidth applications, such as distance learning, high-definition television (HDTV), and video on demand (VoD), the last-mile access networks have become a bandwidth bottleneck in today's telecommunications infrastructure. To ease this bottleneck, it is imperative to provide sufficient bandwidth capacity in the access networks to open the bottleneck and thus present more opportunities for the provisioning of multiservices. Optical access solutions promise huge bandwidth to service providers and low-cost high-bandwidth services to end users and are therefore widely considered the technology of choice for next-generation access networks. To realize the vision of optical access networks, however, many key issues still need to be addressed, such as network architectures, signaling protocols, and implementation standards. The major challenges lie in the fact that an optical solution must be not only robust, scalable, and flexible, but also implemented at a low cost comparable to that of existing access solutions in order to increase the economic viability of many potential high-bandwidth applications. In recent years, optical access networks have been receiving tremendous attention from both academia and industry. A large number of research activities have been carried out or

  16. A Summarization on PAPR Techniques for OFDM Systems

    NASA Astrophysics Data System (ADS)

    Elavarasan, Parthasarathy; Nagarajan, G.

    2015-12-01

    Communication is one of the main aspects of life. With the advancement in age and its growing demands, there has been rapid growth in the field of communications. Signals, which were initially sent in the analog domain, are being sent in the digital domain. For better transmission, still the single carrier waves are being replaced by multi carriers. Multi carrier systems like CDMA and OFDM are now a day being implemented normally. In the OFDM system, orthogonally placed sub carriers are used to carry the data from the transmitter end to the receiver end. Presence of guard band in this system deals with the problem of ISI and noise is minimized by larger number of sub carriers. But the large peak to average power ratio (PAPR) of these signal have some undesirable effects on the system. This paper focuses on presenting the basics of an OFDM system and various methods to reduce the PAPR. High peak to average power ratio of the transmit signal is a major drawback of multicarrier transmission in OFDM. This article describes some of the important PAPR reduction techniques for multicarrier transmission including amplitude clipping and filtering, coding, partial transmit sequence, selected mapping, interleaving, tone reservation, tone injection and active constellation extension. Finally the criterion for PAPR reduction technique selection has been discussed.

  17. Accessing the Microform Publication.

    ERIC Educational Resources Information Center

    Schindler, Stan

    1985-01-01

    Characterizes types of indexing programs used by Research Publications, Inc. and describes provision of access to four major projects: "The Official Washington Post Index" (provides access to newspaper and microfilm edition); "The Eighteenth Century"; "The Declassified Documents Reference System" (ongoing fiche project abstracted and indexed…

  18. ACCESS Pointing Control System

    NASA Technical Reports Server (NTRS)

    Brugarolas, Paul; Alexander, James; Trauger, John; Moody, Dwight; Egerman, Robert; Vallone, Phillip; Elias, Jason; Hejal, Reem; Camelo, Vanessa; Bronowicki, Allen; O'Connor, David; Partrick, Richard; Orzechowski, Pawel; Spitter, Connie; Lillie, Chuck

    2010-01-01

    ACCESS (Actively-Corrected Coronograph for Exoplanet System Studies) was one of four medium-class exoplanet concepts selected for the NASA Astrophysics Strategic Mission Concept Study (ASMCS) program in 2008/2009. The ACCESS study evaluated four major coronograph concepts under a common space observatory. This paper describes the high precision pointing control system (PCS) baselined for this observatory.

  19. Access to Higher Education

    ERIC Educational Resources Information Center

    Briscoe, Felecia; De Oliver, Miguel

    2006-01-01

    This case study researches the degree to which the location and services offered by a multicampus university, geographically situated consistent with the commercial principles of a large mass-market enterprise, facilitate access for educationally underserved groups. First, the necessity of democratizing educational access to an underprivileged…

  20. Intellectual Access to Images.

    ERIC Educational Resources Information Center

    Chen, Hsin-Liang; Rasmussen, Edie M.

    1999-01-01

    The increased availability of digital images is accompanied by a need for solutions to the problems inherent in indexing them for retrieval. Problems in image description and access are discussed, with a perspective on traditional and new solutions. Recent developments in intellectual access to images are surveyed and contrasted with…

  1. The Universal Access System.

    ERIC Educational Resources Information Center

    Scott, Neil G.

    This final report discusses the outcomes of a project that created a Universal Access System (UAS), a system that gives students with disabilities access to the same computers as their classmates. The project developed a new approach in which the needs of the individual with disabilities are handled separately from the computers and other devices…

  2. MedlinePlus: Accessibility

    MedlinePlus

    ... Tools Español You Are Here: Home → MedlinePlus Accessibility URL of this page: https://medlineplus.gov/accessibility.html ... or (301) 594-5983 and provide the address (URL) of the page on which you need assistance, ...

  3. Access and Technology

    ERIC Educational Resources Information Center

    Watson, Lemuel W.

    2004-01-01

    Community colleges are well positioned to provide underserved student populations with access to computer technology. This chapter explores the issues of access and technology from multiple perspectives in the community college, and explains how community colleges can develop a foundation for their technology plan.

  4. Improving School Access Control

    ERIC Educational Resources Information Center

    National Clearinghouse for Educational Facilities, 2008

    2008-01-01

    Few things are more important for school safety and security than controlling access to buildings and grounds. It is relatively easy to incorporate effective access control measures in new school designs but more difficult in existing schools, where most building and site features cannot be readily altered or reconfigured. The National…

  5. Clinical review: Vascular access for fluid infusion in children

    PubMed Central

    Haas, Nikolaus A

    2004-01-01

    The current literature on venous access in infants and children for acute intravascular access in the routine situation and in emergency or intensive care settings is reviewed. The various techniques for facilitating venous cannulation, such as application of local warmth, transillumination techniques and epidermal nitroglycerine, are described. Preferred sites for central venous access in infants and children are the external and internal jugular veins, the subclavian and axillary veins, and the femoral vein. The femoral venous cannulation appears to be the most safe and reliable technique in children of all ages, with a high success and low complication rates. Evidence from the reviewed literature strongly supports the use of real-time ultrasound techniques for venous cannulation in infants and children. Additionally, in emergency situations the intraosseous access has almost completly replaced saphenous cutdown procedures in children and has decreased the need for immediate central venous access. PMID:15566619

  6. Optical Access Networks

    NASA Astrophysics Data System (ADS)

    Zheng, Jun; Ansari, Nirwan

    2005-03-01

    Call for Papers: Optical Access Networks With the wide deployment of fiber-optic technology over the past two decades, we have witnessed a tremendous growth of bandwidth capacity in the backbone networks of today's telecommunications infrastructure. However, access networks, which cover the "last-mile" areas and serve numerous residential and small business users, have not been scaled up commensurately. The local subscriber lines for telephone and cable television are still using twisted pairs and coaxial cables. Most residential connections to the Internet are still through dial-up modems operating at a low speed on twisted pairs. As the demand for access bandwidth increases with emerging high-bandwidth applications, such as distance learning, high-definition television (HDTV), and video on demand (VoD), the last-mile access networks have become a bandwidth bottleneck in today's telecommunications infrastructure. To ease this bottleneck, it is imperative to provide sufficient bandwidth capacity in the access networks to open the bottleneck and thus present more opportunities for the provisioning of multiservices. Optical access solutions promise huge bandwidth to service providers and low-cost high-bandwidth services to end users and are therefore widely considered the technology of choice for next-generation access networks. To realize the vision of optical access networks, however, many key issues still need to be addressed, such as network architectures, signaling protocols, and implementation standards. The major challenges lie in the fact that an optical solution must be not only robust, scalable, and flexible, but also implemented at a low cost comparable to that of existing access solutions in order to increase the economic viability of many potential high-bandwidth applications. In recent years, optical access networks have been receiving tremendous attention from both academia and industry. A large number of research activities have been carried out or

  7. Rising Expectations: Access to Biomedical Information

    PubMed Central

    Lindberg, D. A. B.; Humphreys, B. L.

    2008-01-01

    Summary Objective To provide an overview of the expansion in public access to electronic biomedical information over the past two decades, with an emphasis on developments to which the U.S. National Library of Medicine contributed. Methods Review of the increasingly broad spectrum of web-accessible genomic data, biomedical literature, consumer health information, clinical trials data, and images. Results The amount of publicly available electronic biomedical information has increased dramatically over the past twenty years. Rising expectations regarding access to biomedical information were stimulated by the spread of the Internet, the World Wide Web, advanced searching and linking techniques. These informatics advances simplified and improved access to electronic information and reduced costs, which enabled inter-organizational collaborations to build and maintain large international information resources and also aided outreach and education efforts The demonstrated benefits of free access to electronic biomedical information encouraged the development of public policies that further increase the amount of information available. Conclusions Continuing rapid growth of publicly accessible electronic biomedical information presents tremendous opportunities and challenges, including the need to ensure uninterrupted access during disasters or emergencies and to manage digital resources so they remain available for future generations. PMID:18587496

  8. Optical Access Networks

    NASA Astrophysics Data System (ADS)

    Zheng, Jun; Ansari, Nirwan

    2005-01-01

    Call for Papers: Optical Access Networks

    Guest Editors Jun Zheng, University of Ottawa Nirwan Ansari, New Jersey Institute of Technology

    Submission Deadline: 1 June 2005

    Background

    With the wide deployment of fiber-optic technology over the past two decades, we have witnessed a tremendous growth of bandwidth capacity in the backbone networks of today's telecommunications infrastructure. However, access networks, which cover the "last-mile" areas and serve numerous residential and small business users, have not been scaled up commensurately. The local subscriber lines for telephone and cable television are still using twisted pairs and coaxial cables. Most residential connections to the Internet are still through dial-up modems operating at a low speed on twisted pairs. As the demand for access bandwidth increases with emerging high-bandwidth applications, such as distance learning, high-definition television (HDTV), and video on demand (VoD), the last-mile access networks have become a bandwidth bottleneck in today's telecommunications infrastructure. To ease this bottleneck, it is imperative to provide sufficient bandwidth capacity in the access networks to open the bottleneck and thus present more opportunities for the provisioning of multiservices. Optical access solutions promise huge bandwidth to service providers and low-cost high-bandwidth services to end users and are therefore widely considered the technology of choice for next-generation access networks. To realize the vision of optical access networks, however, many key issues still need to be addressed, such as network architectures, signaling protocols, and implementation standards. The major challenges lie in the fact that an optical solution must be not only robust, scalable, and flexible, but also implemented at a low cost comparable to that of existing access solutions in order to increase the

  9. Multiple-Access Quantum-Classical Networks

    NASA Astrophysics Data System (ADS)

    Razavi, Mohsen

    2011-10-01

    A multi-user network that supports both classical and quantum communication is proposed. By relying on optical code-division multiple access techniques, this system offers simultaneous key exchange between multiple pairs of network users. A lower bound on the secure key generation rate will be derived for decoy-state quantum key distribution protocols.

  10. Computer Access for the Visually Impaired.

    ERIC Educational Resources Information Center

    Krolick, Bettye

    1984-01-01

    Provides information on and evaluation of microcomputer equipment modifications for improving accessibility to the visually impaired. Equipment discussed includes input and visual output modification techniques and devices, software designed for visually impaired users, and braille output peripherals. Lists sources for available peripherals,…

  11. HRP Data Accessibility 2009

    NASA Video Gallery

    Dr. Clarence Sams spoke at the 2009 Human Research Program's Investigators Workshop on the current status of Data Accessibility. In this presentation he discusses the content of the Human Life Scie...

  12. Critical Access Hospitals (CAH)

    MedlinePlus

    ... CAH Conditions of Participation . What are the location requirements for CAH status? Critical Access Hospitals must be ... clinic that does not meet the CAH distance requirements? As of January 1, 2008, all CAHs, including ...

  13. Adapting Web Browsers for Accessibility.

    ERIC Educational Resources Information Center

    Hendrix, Paul; Birkmire, Mike

    This paper examines ways to make World Wide Web browsers accessible for individuals with disabilities, and through them, gain access to the information on the Web. It discusses which browsers can be made more accessible and evaluates different types of input. Mouse access, keyboard access, and voice input are reviewed. Processing aids, such as…

  14. Optical Access Networks

    NASA Astrophysics Data System (ADS)

    Zheng, Jun; Ansari, Nirwan

    2005-02-01

    Call for Papers: Optical Access Networks With the wide deployment of fiber-optic technology over the past two decades, we have witnessed a tremendous growth of bandwidth capacity in the backbone networks of today's telecommunications infrastructure. However, access networks, which cover the "last-mile" areas and serve numerous residential and small business users, have not been scaled up commensurately. The local subscriber lines for telephone and cable television are still using twisted pairs and coaxial cables. Most residential connections to the Internet are still through dial-up modems operating at a low speed on twisted pairs. As the demand for access bandwidth increases with emerging high-bandwidth applications, such as distance learning, high-definition television (HDTV), and video on demand (VoD), the last-mile access networks have become a bandwidth bottleneck in today's telecommunications infrastructure. To ease this bottleneck, it is imperative to provide sufficient bandwidth capacity in the access networks to open the bottleneck and thus present more opportunities for the provisioning of multiservices. Optical access solutions promise huge bandwidth to service providers and low-cost high-bandwidth services to end users and are therefore widely considered the technology of choice for next-generation access networks. To realize the vision of optical access networks, however, many key issues still need to be addressed, such as network architectures, signaling protocols, and implementation standards. The major challenges lie in the fact that an optical solution must be not only robust, scalable, and flexible, but also implemented at a low cost comparable to that of existing access solutions in order to increase the economic viability of many potential high-bandwidth applications. In recent years, optical access networks have been receiving tremendous attention from both academia and industry. A large number of research activities have been carried out or

  15. Vascular Access in Children

    SciTech Connect

    Krishnamurthy, Ganesh Keller, Marc S.

    2011-02-15

    Establishment of stable vascular access is one of the essential and most challenging procedures in a pediatric hospital. Many clinical specialties provide vascular service in a pediatric hospital. At the top of the 'expert procedural pyramid' is the pediatric interventional radiologist, who is best suited and trained to deliver this service. Growing awareness regarding the safety and high success rate of vascular access using image guidance has led to increased demand from clinicians to provide around-the-clock vascular access service by pediatric interventional radiologists. Hence, the success of a vascular access program, with the pediatric interventional radiologist as the key provider, is challenging, and a coordinated multidisciplinary team effort is essential for success. However, there are few dedicated pediatric interventional radiologists across the globe, and also only a couple of training programs exist for pediatric interventions. This article gives an overview of the technical aspects of pediatric vascular access and provides useful tips for obtaining vascular access in children safely and successfully using image guidance.

  16. Access to health care

    PubMed Central

    Fortin, Martin; Maltais, Danielle; Hudon, Catherine; Lapointe, Lise; Ntetu, Antoine Lutumba

    2005-01-01

    OBJECTIVE To explore access to health care for patients presenting with multiple chronic conditions and to identify barriers and factors conducive to access. DESIGN Qualitative study with focus groups. SETTING Family practice unit in Chicoutimi (Saguenay), Que. PARTICIPANTS Twenty-five male and female adult patients with at least four chronic conditions but no cognitive disorders or decompensating conditions. METHODS For this pilot study, only three focus group discussions were held. MAIN FINDINGS The main barriers to accessing follow-up appointments included long waits on the telephone, automated telephone-answering systems, and needing to attend at specific times to obtain appointments. The main barriers to specialized care were long waiting times and the need to get prescriptions and referrals from family physicians. Factors reported conducive to access included systematic callbacks and the personal involvement of family physicians. Good communication between family physicians and specialists was also perceived to be an important factor in access. CONCLUSION Systematic callbacks, family physicians’ personal efforts to obtain follow-up visits, and better physician-specialist communication were all suggested as ways to improve access to care for patients with multiple chronic conditions. PMID:16926944

  17. Advanced access appointments

    PubMed Central

    Hudec, John C.; MacDougall, Steven; Rankin, Elaine

    2010-01-01

    ABSTRACT OBJECTIVE To examine the effects of advanced access (same-day physician appointments) on patient and provider satisfaction and to determine its association with other variables such as physician income and patient emergency department use. DESIGN Patient satisfaction survey and semistructured interviews with physicians and support staff; analysis of physician medical insurance billings and patient emergency department visits. SETTING Cape Breton, NS. PARTICIPANTS Patients, physicians, and support staff of 3 comparable family physician practices that had not implemented advanced access and an established advanced access practice. MAIN OUTCOME MEASURES Self-reported provider and patient satisfaction, physician office income, and patients’ emergency department use. RESULTS The key benefits of implementation of advanced access were an increase in provider and patient satisfaction levels, same or greater physician office income, and fewer less urgent (triage level 4) and nonurgent (triage level 5) emergency department visits by patients. CONCLUSION Currently within the Central Cape Breton Region, 33% of patients wait 4 or more days for urgent appointments. Findings from this study can be used to enhance primary care physician practice redesign. This research supports many benefits of transitioning to an advanced access model of patient booking. PMID:20944024

  18. Technology Resources: Mathematics Accessibility for All Not Accommodation for Some

    ERIC Educational Resources Information Center

    Duranczyk, Irene M.

    2009-01-01

    When faculty and learning assistance staff create teaching documents and web pages envisioning the widest range of users they can save time while achieving access for all. There are tools and techniques available to make mathematics visual, orally, and dynamically more accessible through multimodal presentation forms. Resources from Design…

  19. The Subject Access Problem--Opportunities for Solution: A Workshop.

    ERIC Educational Resources Information Center

    Committee for the Coordination of National Bibliographic Control, Washington, DC.

    This report presents the recommendations of 35 workshops participants, drawn from a variety of backgrounds and information environments, which was organized to: (1) highlight the role of subject access with the emphasis on the needs of the information seeker; (2) compare techniques for subject access now being used in the library and the…

  20. Geographic Accessibility to Higher Education on the Island of Ireland

    ERIC Educational Resources Information Center

    Walsh, Sharon; Flannery, Darragh; Cullinan, John

    2015-01-01

    This paper presents, for the first time, comprehensive measures of geographic accessibility to higher education both within and between the Republic of Ireland and Northern Ireland. Using geographic information system techniques, we find high levels of geographic accessibility to higher education in both jurisdictions. However, when we…

  1. Binary Coded Web Access Pattern Tree in Education Domain

    ERIC Educational Resources Information Center

    Gomathi, C.; Moorthi, M.; Duraiswamy, K.

    2008-01-01

    Web Access Pattern (WAP), which is the sequence of accesses pursued by users frequently, is a kind of interesting and useful knowledge in practice. Sequential Pattern mining is the process of applying data mining techniques to a sequential database for the purposes of discovering the correlation relationships that exist among an ordered list of…

  2. Ureteric access sheath aided insertion of resonance metal ureteric stent

    PubMed Central

    Winter, Matthew; Strahan, Stephen; Wines, Michael

    2014-01-01

    Ureteral obstruction caused by malignancy is a challenging and often complicated problem for urologists. We present a novel technique of ureteric access sheath aided insertion of a Resonance metal ureteric stent in the setting of a difficult obstruction. PMID:24879725

  3. Dismantling techniques

    SciTech Connect

    Wiese, E.

    1998-03-13

    Most of the dismantling techniques used in a Decontamination and Dismantlement (D and D) project are taken from conventional demolition practices. Some modifications to the techniques are made to limit exposure to the workers or to lessen the spread of contamination to the work area. When working on a D and D project, it is best to keep the dismantling techniques and tools as simple as possible. The workers will be more efficient and safer using techniques that are familiar to them. Prior experience with the technique or use of mock-ups is the best way to keep workers safe and to keep the project on schedule.

  4. ISDC Data Access Layer

    NASA Astrophysics Data System (ADS)

    Jennings, D.; Borkowski, J.; Contessi, T.; Lock, T.; Rohlfs, R.; Walter, R.

    The ISDC Data Access Layer (DAL) is an ANSI C and \\fortran 90 compatible library under development in support of the ESA INTEGRAL mission data analysis software. DALs primary purpose is to isolate the analysis software from the specifics of the data formats while at the same time providing new data abstraction and access capabilities. DAL supports the creation and manipulation of hierarchical data sets which may span multiple files and, in theory, multiple computer systems. A number of Application Programming Interfaces (APIs) are supported by DAL that allow software to view and access data at different levels of complexity. DAL also allows data sets to reside on disk, in conventional memory or in shared memory in a way that is transparent to the user/application.

  5. Data access for scientific problem solving

    NASA Technical Reports Server (NTRS)

    Brown, James W.

    1987-01-01

    An essential ingredient in scientific work is data. In disciplines such as Oceanography, data sources are many and volumes are formidable. The full value of large stores of data cannot be realized unless careful thought is given to data access. JPL has developed the Pilot Ocean Data System to investigate techniques for archiving and accessing ocean data obtained from space. These include efficient storage and rapid retrieval of satellite data, an easy-to-use user interface, and a variety of output products which, taken together, permit researchers to extract and use data rapidly and conveniently.

  6. Access to space studies

    NASA Technical Reports Server (NTRS)

    Martin, James A.

    1993-01-01

    The National Aeronautics and Space Administration is currently considering possible directions in Earth-to-orbit vehicle development under a study called 'Access to Space.' This agency-wide study is considering commercial launch vehicles, human transportation, space station logistics, and other space transportation requirements over the next 40 years. Three options are being considered for human transportation: continued use of the Space Shuttle; development of a small personnel carrier (personnel logistics system (PLS)); or development of an advanced vehicle such as a single-stage-to-orbit (SSTO). Several studies related to the overall Access to Space study are reported in this document.

  7. Accessibility | Smokefree.gov

    Cancer.gov

    Smokefree.gov is committed to providing access to all individuals—disabled or not—who are seeking information on its Web sites. To provide this information, the smokefree.gov Web site has been designed to comply with Section 508 of the Rehabilitation Act (as amended). Section 508 requires that all individuals with disabilities (whether they are federal government employees or members of the general public) have access to and use of information and data comparable to that provided to individuals without disabilities, unless an undue burden would be imposed.

  8. Migrants' access to healthcare.

    PubMed

    Norredam, Marie

    2011-10-01

    There are strong pragmatic and moral reasons for receiving societies to address access to healthcare for migrants. Receiving societies have a pragmatic interest in sustaining migrants' health to facilitate integration; they also have a moral obligation to ensure migrants' access to healthcare according to international human rights principles. The intention of this thesis is to increase the understanding of migrants' access to healthcare by exploring two study aims: 1) Are there differences in migrants' access to healthcare compared to that of non-migrants? (substudy I and II); and 2) Why are there possible differences in migrants' access to healthcare compared to that of non-migrants? (substudy III and IV). The thesis builds on different methodological approaches using both register-based retrospective cohort design, cross-sectional design and survey methods. Two different measures of access were used to explore differences: 1) cancer stage at diagnosis as a clinical outcome and 2) emergency room (ER) contacts as a utilisation measure. Both informal and formal barriers to access were studied to explore why possible differences existed including: 1) motivation for using ER; and 2) asylum seekers' healthcare entitlements. Different definitions of migration and ethnicity were investigated including: country of birth and residence status. Substudy I showed a tendency towards more advanced stage at diagnosis or unknown stage among most subgroups of migrant women with a history of cancer compared to non-migrant women. Sub-study II found that some migrants (those born in Somalia, Turkey and Ex-Yugoslavia) use ER services more frequently than do non-migrants whereas others have the same or lower utilisation levels. As a consequence, substudy III was undertaken, which documented that more migrant within all subgroups had considered contacting a primary caregiver before visiting the ER compared to non-migrants, but that migrants experienced communication problems herein

  9. Digital Scholarship and Open Access

    ERIC Educational Resources Information Center

    Losoff, Barbara; Pence, Harry E.

    2010-01-01

    Open access publications provide scholars with unrestricted access to the "conversation" that is the basis for the advancement of knowledge. The large number of open access journals, archives, and depositories already in existence demonstrates the technical and economic viability of providing unrestricted access to the literature that is the…

  10. Internet 2 Access Grid.

    ERIC Educational Resources Information Center

    Simco, Greg

    2002-01-01

    Discussion of the Internet 2 Initiative, which is based on collaboration among universities, businesses, and government, focuses on the Access Grid, a Computational Grid that includes interactive multimedia within high-speed networks to provide resources to enable remote collaboration among the research community. (Author/LRW)

  11. A matter of access

    PubMed Central

    Hu, Zheng; Chen, Kaifu; Li, Wei; Tyler, Jessica K

    2014-01-01

    The mechanism whereby transcriptional activators facilitate transcription activation has been debated. Our recent genome-wide profiling of gene expression during aging, where nucleosomes are depleted, indicates that the function of seemingly all transcriptional activators is to trigger nucleosome disassembly from promoters to allow the general transcription machinery access to the DNA. PMID:25764221

  12. Serving up Access

    ERIC Educational Resources Information Center

    Rich, Sarah

    2011-01-01

    When low-income students returned to Chicago public schools this fall, many had better access to technology, thanks to a public-private partnership. Chicago families with children enrolled in the National School Lunch Program are eligible for subsidized computers and Internet connections through an agreement between the city and telecom giant…

  13. ACCESS PENNSYLVANIA Curriculum Guide.

    ERIC Educational Resources Information Center

    Pennsylvania State Library, Harrisburg.

    This curriculum guide was prepared as a tool for teaching students the purpose and function of the ACCESS PENNSYLVANIA database in the total concept of information literacy. The database on compact laser disc contains information about the holdings of hundreds of school, public, academic, and special use libraries. The database can be searched at…

  14. Accessibility Standards, Illustrated.

    ERIC Educational Resources Information Center

    Jones, Michael A.

    The book sets forth Illinois environmental accessibility standards for disabled persons based on observation and interview data. Photographs, drawings, and detailed floor plans are included in sections dealing with human data (including space requirements for maneuvering wheelchairs, color blindness, incontinence, and severe auditory or visual…

  15. College Access Marketing

    ERIC Educational Resources Information Center

    Tremblay, Christopher W.

    2011-01-01

    College Access Marketing (CAM) is a relatively new phenomenon that seeks to positively influence the college-going rate. This report defines CAM, describes CAM examples, and discusses how CAM seeks to counter barriers to college. It explores four main elements of CAM: information, marketing, advocacy, and social mobilization. Further, it…

  16. Partners: Promoting Accessible Recreation.

    ERIC Educational Resources Information Center

    Sable, Janet; Gravink, Jill

    1995-01-01

    The Promoting Accessible Recreation through Networking, Education, Resources and Services (PARTNERS) Project, a partnership between Northeast Passage, the University of New Hampshire, and Granite State Independent Living Foundation, helps create barrier-free recreation for individuals with physical disabilities. The paper describes PARTNERS and…

  17. Uniform Federal Accessibility Standards.

    ERIC Educational Resources Information Center

    Department of Housing and Urban Development, Washington, DC.

    The document presents uniform standards for facility accessibility by physically handicapped persons for Federal and federally funded facilities. The standards are to be applied during the design, construction, and alteration of buildings and facilities to the extent required by the Architectural Barriers Act of 1968, as amended. Technical…

  18. Improved Access to Learning.

    ERIC Educational Resources Information Center

    Miller, Sandra; Simkins, Michael

    2002-01-01

    Describes efforts by principal of the Willow Elementary School in the Charter Oak Unified School District (California) to provide students with technology-enhanced access to information and learning resources to improve reading and mathematics skills. Includes list of the Web addresses for the skills software used at the school. (PKP)

  19. CAS. Controlled Access Security

    SciTech Connect

    Martinez, B.; Pomeroy, G.

    1989-12-01

    The Security Alarm System is a data acquisition and control system which collects data from intrusion sensors and displays the information in a real-time environment for operators. The Access Control System monitors and controls the movement of personnel with the use of card readers and biometrics hand readers.

  20. ACCESS Project: Final Report

    SciTech Connect

    Weller, Heiko

    2015-04-01

    The ACCESS project addressed the development, testing, and demonstration of the proposed advanced technologies and the associated emission and fuel economy improvement at an engine dynamometer and on a full-scale vehicle. Improve fuel economy by 25% with minimum performance penalties Achieve SULEV level emissions with gasoline Demonstrate multi-mode combustion engine management system

  1. Strategies for Improving Access.

    ERIC Educational Resources Information Center

    Hore, Terry; Barwood, Bryan

    1989-01-01

    The development of the varied strategies that have been introduced in order to improve access for disadvantaged groups at Monash University is discussed. The Junior University Programme, the Monash Orientation Scheme for Aborigines, the Mature Age Special Admission Scheme, Special Entry Scheme, and the Schools Link Programme are described. (MLW)

  2. Access to Success

    ERIC Educational Resources Information Center

    Brunken, Anna; Delly, Pamela

    2011-01-01

    Changes to education in Australia have seen new government legislations increasing educational pathways so students can more easily enter university, the aim being to increase participation. Now, many domestic students utilise various pathways to access university. Some have undertaken basic Further Education Diplomas, received subject credits,…

  3. Fixed Access Network Sharing

    NASA Astrophysics Data System (ADS)

    Cornaglia, Bruno; Young, Gavin; Marchetta, Antonio

    2015-12-01

    Fixed broadband network deployments are moving inexorably to the use of Next Generation Access (NGA) technologies and architectures. These NGA deployments involve building fiber infrastructure increasingly closer to the customer in order to increase the proportion of fiber on the customer's access connection (Fibre-To-The-Home/Building/Door/Cabinet… i.e. FTTx). This increases the speed of services that can be sold and will be increasingly required to meet the demands of new generations of video services as we evolve from HDTV to "Ultra-HD TV" with 4k and 8k lines of video resolution. However, building fiber access networks is a costly endeavor. It requires significant capital in order to cover any significant geographic coverage. Hence many companies are forming partnerships and joint-ventures in order to share the NGA network construction costs. One form of such a partnership involves two companies agreeing to each build to cover a certain geographic area and then "cross-selling" NGA products to each other in order to access customers within their partner's footprint (NGA coverage area). This is tantamount to a bi-lateral wholesale partnership. The concept of Fixed Access Network Sharing (FANS) is to address the possibility of sharing infrastructure with a high degree of flexibility for all network operators involved. By providing greater configuration control over the NGA network infrastructure, the service provider has a greater ability to define the network and hence to define their product capabilities at the active layer. This gives the service provider partners greater product development autonomy plus the ability to differentiate from each other at the active network layer.

  4. NOAA Enterprise Archive Access Tool

    NASA Astrophysics Data System (ADS)

    Rank, R. H.; McCormick, S.; Cremidis, C.

    2010-12-01

    A challenge for any consumer of National Oceanic and Atmospheric Administration (NOAA) environmental data archives is that the disparate nature of these archives makes it difficult for consumers to access data in a unified manner. If it were possible for consumers to have seamless access to these archives, they would be able to better utilize the data and thus maximize the return on investment for NOAA’s archival program. When unified data access is coupled with sophisticated data querying and discovery techniques, it will be possible to provide consumers with access to richer data sets and services that extend the use of key NOAA data. Theoretically, there are two ways that unified archive access may be achieved. The first approach is to develop a single archive or archiving standard that would replace the current NOAA archives. However, the development of such an archive would pose significant technical and administrative challenges. The second approach is to develop a middleware application that would provide seamless access to all existing archives, in effect allowing each archive to exist “as is” but providing a translation service for the consumer. This approach is deemed more feasible from an administrative and technical standpoint; however, it still presents unique technical challenges due to the disparate architectures that exist across NOAA archives. NOAA has begun developing the NEAAT. The purpose of NEAAT is to provide a middleware and a simple standardized API between NOAA archives and data consumers. It is important to note that NEAAT serves two main purposes: 1) To provide a single application programming interface (API) that enables designated consumers to write their own custom applications capable of searching and acquiring data seamlessly from multiple NOAA archives. 2) To allow archive managers to expose their data to consumers in conjunction with other NOAA resources without modifying their archiving systems or way of presenting data

  5. An isoflux antenna for a low earth orbit satellite mobile communication system

    NASA Astrophysics Data System (ADS)

    Tsao, C.-H. A.; Jung, P.; Raguenet, G.

    1992-03-01

    In this paper a satellite antenna for a low earth orbit satellite mobile communication system is described. The proposed communication system employs TDD-FD-CDMA (time division duplexing-frequency division-code division multiple access) technique which imposes certain constraints on the antenna design. The antenna discussed in this paper employs six spot beams in conjunction with the CDMA technology to allow the frequency spectrum reuse. The antenna radiation pattern in each beam is shaped to compensate for the path loss differences caused by the slant range differences from the spacecraft to different points on earth. This design provides an isometric radiation flux density on earth within each beam to mitigate the potential near/far problems in a CDMA system. Additional constraints on the antenna design include low profile, light weight and easy deployment to meet the requirements of small satellite implementation of the system.

  6. Accessing Space Weather Information

    NASA Astrophysics Data System (ADS)

    Morrison, D.; Weiss, M.; Immer, E. A.; Patrone, D.; Potter, M.; Barnes, R. J.; Colclough, C.; Holder, R.

    2009-12-01

    To meet the needs of our technology based society, space weather forecasting needs to be advanced and this will entail collaboration amongst research, military and commercial communities to find new ways to understand, characterize, and forecast. In this presentation VITMO, the Virtual Ionosphere-Thermosphere-Mesosphere Observatory will be used as a prototype for a generalized system as a means to bring together a set of tools to access data, models and online collaboration tools to enable rapid progress. VITMO, available at http://vitmo.jhuapl.edu/, currently provides a data access portal for researchers and scientists to enable finding data products as well as access to tools and models. To further the needs of space weather forecasters, the existing VITMO data holdings need to be expanded to provide additional datasets as well as integrating relevant models and model output. VITMO can easily be adapted for the Space Weather domain in its entirety. In this presentation, we will demonstrate how VITMO and the VITMO architecture can be utilized as a prototype in support of integration of Space Weather forecasting tools, models and data.

  7. Working Concept of Accessibility

    PubMed Central

    Schroeder, Bastian J.; Rouphail, Nagui M.; Hughes, Ronald G.

    2010-01-01

    This research presents an analysis framework and associated performance measures for quantifying the accessibility of pedestrian crossings at modern roundabouts for pedestrians who are blind. The measures, developed under two ongoing national research projects, NCHRP Project 3-78A and a bioengineering research grant from the National Institutes of Health–National Eye Institute, attempt to isolate the components of the crossing task for a blind pedestrian into computable and replicable quantities that allow the comparison of accessibility across individuals or sites. The framework differentiates between crossing opportunities in the form of yields and crossable gaps and the utilization of these opportunities by the pedestrian. It further accounts for the amount of delay and risk involved in the crossing. The analysis framework and measures are demonstrated for two single-lane roundabouts in North Carolina evaluated under the aforementioned research projects. The application shows that the accessibility of a pedestrian crossing to a blind pedestrian is characterized by a combination of different measures and further depends on crossing geometry, traffic volume, driver behavior, and the travel skills and risk-taking behavior of the individual. With successful demonstration at roundabout crosswalks, the analysis framework is hypothesized to have broader application to unsignalized pedestrian crossings, including midblock locations. PMID:20664802

  8. Digital imaging access library

    NASA Astrophysics Data System (ADS)

    Cook, Jay F.; Hansen, Mark; Francoise, James J.; Leckie, Robert G.; Smith, Donald V.

    1994-05-01

    The ability to access a vast array of radiological and pathologic diagnoses through computer searches of local medical facility databases is a by-product of the continued development of filmless imaging systems. The Department of Defense (DoD) Medical Diagnostic Imaging Support initiative is expanding through the addition of on-line systems at several DoD health care facilities. Madigan Army Medical Center, as the initial site, will soon be 90% filmless, with over one million images archived. Multiple other DoD medical centers are under installation. The eventual goal is an interconnected network of PACS systems of DoD medical centers and their supported medical facilities throughout the United States. To access this potential pool of medical information requires a centralized database capable of acting as a diagnostic index system. The establishment of a multi-center film library index begins with an initial analysis of issues regarding data storage and access, indexing, cross-coding with pathological files, communication formats, cost sharing, and patient confidentiality. In initiating these first steps to developing this telecommunications library these issues and their implications are discussed. The final implementation of this system will facilitate markedly improved research and teaching capabilities in both radiological and pathological fields.

  9. User-Centered Indexing for Adaptive Information Access

    NASA Technical Reports Server (NTRS)

    Chen, James R.; Mathe, Nathalie

    1996-01-01

    We are focusing on information access tasks characterized by large volume of hypermedia connected technical documents, a need for rapid and effective access to familiar information, and long-term interaction with evolving information. The problem for technical users is to build and maintain a personalized task-oriented model of the information to quickly access relevant information. We propose a solution which provides user-centered adaptive information retrieval and navigation. This solution supports users in customizing information access over time. It is complementary to information discovery methods which provide access to new information, since it lets users customize future access to previously found information. It relies on a technique, called Adaptive Relevance Network, which creates and maintains a complex indexing structure to represent personal user's information access maps organized by concepts. This technique is integrated within the Adaptive HyperMan system, which helps NASA Space Shuttle flight controllers organize and access large amount of information. It allows users to select and mark any part of a document as interesting, and to index that part with user-defined concepts. Users can then do subsequent retrieval of marked portions of documents. This functionality allows users to define and access personal collections of information, which are dynamically computed. The system also supports collaborative review by letting users share group access maps. The adaptive relevance network provides long-term adaptation based both on usage and on explicit user input. The indexing structure is dynamic and evolves over time. Leading and generalization support flexible retrieval of information under similar concepts. The network is geared towards more recent information access, and automatically manages its size in order to maintain rapid access when scaling up to large hypermedia space. We present results of simulated learning experiments.

  10. After Access: Underrepresented Students' Postmatriculation Perceptions of College Access Capital

    ERIC Educational Resources Information Center

    Means, Darris R.; Pyne, Kimberly B.

    2016-01-01

    This qualitative study explores the perceived impact of college-going capital gained during participation in a college access program. In three, semistructured interviews spanning the first-year college experience, 10 first-year college students who participated in a college access program articulate the value of access programming and also raise…

  11. Stapedectomy technique.

    PubMed

    House, J W

    1993-06-01

    This article reviews the evolution of the author's stapedectomy technique from total footplate removal with single loop wire prosthesis and Gelfoam seal to small fenestra stapedectomy with platinum ribbon piston prosthesis and blood seal. The author concludes that the microdrill is effective, safe, and cost effective for performing this procedure. Since using this technique, the author has had no cases of sensorineural hearing loss and few complaints of dizziness or vertigo. PMID:8341570

  12. Spatial Techniques

    NASA Astrophysics Data System (ADS)

    Jabeur, Nafaa; Sahli, Nabil

    The environment, including the Earth and the immense space, is recognized to be the main source of useful information for human beings. During several decades, the acquisition of data from this environment was constrained by tools and techniques with limited capabilities. However, thanks to continuous technological advances,spatial data are available in huge quantities for different applications. The technological advances have been achieved in terms of hardware and software as well. They are allowing for better accuracy and availability, which in turn improves the quality and quantity of useful knowledge that can be extracted from the environment. They have been applied to geography, resulting in geospatial techniques. Applied to both science and technology, geospatial techniques resulted in areas of expertise, such as land surveying, cartography, navigation, remote sensing, Geographic Infor-mation Systems (GISs), and Global Positioning Systems (GPSs). They had evolved quickly with advances in computing, satellite technology and a growing demand to understand our global environment. In this chapter, we will discuss three important techniques that are widely used in spatial data acquisition and analysis: GPS and remote sensing techniques that are used to collect spatial data and a GIS that is used to store, manipulate, analyze, and visualize spatial data. Later in this book, we will discuss the techniques that are currently available for spatial knowledge discovery.

  13. Network acceleration techniques

    NASA Technical Reports Server (NTRS)

    Crowley, Patricia (Inventor); Awrach, James Michael (Inventor); Maccabe, Arthur Barney (Inventor)

    2012-01-01

    Splintered offloading techniques with receive batch processing are described for network acceleration. Such techniques offload specific functionality to a NIC while maintaining the bulk of the protocol processing in the host operating system ("OS"). The resulting protocol implementation allows the application to bypass the protocol processing of the received data. Such can be accomplished this by moving data from the NIC directly to the application through direct memory access ("DMA") and batch processing the receive headers in the host OS when the host OS is interrupted to perform other work. Batch processing receive headers allows the data path to be separated from the control path. Unlike operating system bypass, however, the operating system still fully manages the network resource and has relevant feedback about traffic and flows. Embodiments of the present disclosure can therefore address the challenges of networks with extreme bandwidth delay products (BWDP).

  14. History of the Buttonhole Technique.

    PubMed

    Misra, Madhukar

    2015-01-01

    The constant side method of access cannulation in hemodialysis, popularly known as the 'buttonhole' method, has an interesting history. Dr. Zbylut J. Twardowski, a Polish nephrologist, discovered this technique by pure serendipity in 1972. A patient with a complicated vascular access history and limited options for cannulation was repeatedly 'stuck' at the same sites by a nurse. Soon it was noticed that the cannulation at the same spot became easier with time. Since the needles were being reused, the sharpness of the needles decreased with time and the bluntness of the needle seemed to minimize the damage to the cannulation tract (another serendipity!). This method soon became popular among patients, and many patients started using this technique. This chapter traces the invention of this technique and its subsequent development following Dr. Twardowski's emigration to the USA. PMID:26283554

  15. Chemists, Access, Statistics

    NASA Astrophysics Data System (ADS)

    Holmes, Jon L.

    2000-06-01

    New JCE Internet Feature at JCE Online Biographical Snapshots of Famous Chemists is a new JCE Internet feature on JCE Online. Edited by Barbara Burke, this feature provides biographical information on leading chemists, especially women and minority chemists, fostering the attitude that the practitioners of chemistry are as human as those who endeavor to learn about it. Currently, the column features biographical "snapshots" of 30 chemists. Each snapshot includes keywords and bibliography and several contain links to additional online information about the chemist. More biographical snapshots will appear in future installments. In addition, a database listing over 140 women and minority chemists is being compiled and will be made available online with the snapshots in the near future. The database includes the years of birth and death, gender and ethnicity, major and minor discipline, keywords to facilitate searching, and references to additional biographical information. We welcome your input into what we think is a very worthwhile resource. If you would like to provide additional biographical snapshots, see additional chemists added to the database, or know of additional references for those that are already in the database, please contact JCE Online or the feature editor. Your feedback is welcome and appreciated. You can find Biographical Snapshots of Famous Chemists starting from the JCE Online home page-- click the Features item under JCE Internet and then the Chemist Bios item. Access JCE Online without Name and Password We have recently been swamped by libraries requesting IP-number access to JCE Online. With the great benefit IP-number authentication gives to librarians (no user names and passwords to administer) and to their patrons (no need to remember and enter valid names and passwords) this is not surprising. If you would like access to JCE Online without the need to remember and enter a user name and password, you should tell your librarian about our

  16. Decomposition techniques

    USGS Publications Warehouse

    Chao, T.T.; Sanzolone, R.F.

    1992-01-01

    Sample decomposition is a fundamental and integral step in the procedure of geochemical analysis. It is often the limiting factor to sample throughput, especially with the recent application of the fast and modern multi-element measurement instrumentation. The complexity of geological materials makes it necessary to choose the sample decomposition technique that is compatible with the specific objective of the analysis. When selecting a decomposition technique, consideration should be given to the chemical and mineralogical characteristics of the sample, elements to be determined, precision and accuracy requirements, sample throughput, technical capability of personnel, and time constraints. This paper addresses these concerns and discusses the attributes and limitations of many techniques of sample decomposition along with examples of their application to geochemical analysis. The chemical properties of reagents as to their function as decomposition agents are also reviewed. The section on acid dissolution techniques addresses the various inorganic acids that are used individually or in combination in both open and closed systems. Fluxes used in sample fusion are discussed. The promising microwave-oven technology and the emerging field of automation are also examined. A section on applications highlights the use of decomposition techniques for the determination of Au, platinum group elements (PGEs), Hg, U, hydride-forming elements, rare earth elements (REEs), and multi-elements in geological materials. Partial dissolution techniques used for geochemical exploration which have been treated in detail elsewhere are not discussed here; nor are fire-assaying for noble metals and decomposition techniques for X-ray fluorescence or nuclear methods be discussed. ?? 1992.

  17. Web Site Accessibility and Usability: Towards More Functional Sites for All

    ERIC Educational Resources Information Center

    Yates, Ross

    2005-01-01

    Purpose: The purpose of this paper is to explore both accessibility and usability and examine the inhibitors and methods to evaluate site accessibility. Design techniques which improve end-user access and site interactivity, demonstrated by practical examples, are also studied. Design/methodology/approach: Assesses various web sites for…

  18. Tracer Technique

    NASA Astrophysics Data System (ADS)

    Haba, H.; Motomura, S.; Kamino, S.; Enomoto, S.

    In radioactive tracer technique, radioactive nuclides are used to follow the behavior of elements or chemical species in chemical and other processes. This is realized by means of radioactivity measurement. In 1913, Hevesy and Paneth succeeded in determining the extremely low solubility of lead salts by using naturally occurring 210Pb as a radioactive tracer. As various radioactive nuclides became artificially available, this technique has been widely employed in studies of chemical equilibrium and reactions as well as in chemical analysis. It is also an essential technique in biochemical, biological, medical, geological, and environmental studies. Medical diagnosis and industrial process control are the fields of its most important practical application. In this chapter, fundamental ideas concerning radioactive tracers will be described followed by their application with typical examples. Detailed description on their application to life sciences and medicine is given in Vol. 4.

  19. Access to legal abortion.

    PubMed

    1993-10-01

    Countries are grouped by the nature and extent of access to legal abortion. The categories include abortion on demand, for social reasons, for health reasons, for rape or incest or to save a mother's life, and only to save a mother's life. Abortion on demand is available for about 40% of the world's population and may have restrictions, such as parental consent or approval of state committees or physicians. There are 22 countries in Europe, 12 in the former Soviet Union, four in Asia, four in the Americas, one in the Middle East (Turkey), and one in Africa (Tunisia) which provide access to early abortion on demand. Abortion for social and economic reasons is available to 21% of the world's population in five countries in Asia, three in Europe (Great Britain, Finland, and Hungary), and one in Africa (Zambia). Abortion for health reasons is available to 16% of the world's population located in 21 countries in Africa, eight in the Americas, seven in Asia, five in Europe, and four in the Middle East. Laws governing about 5% of the world's population permit abortion only in the case of rape, incest, or when a mother's life is in danger (Brazil, Mexico, and Sudan). 18% of the world's population is covered by laws which permit an abortion only when a mother's life is in danger; this includes 19 countries in Africa, 11 in the Americas, nine in Asia, seven in the Middle East, and one in Europe (Ireland). PMID:12287145

  20. Accessible magnetic resonance imaging.

    PubMed

    Kaufman, L; Arakawa, M; Hale, J; Rothschild, P; Carlson, J; Hake, K; Kramer, D; Lu, W; Van Heteren, J

    1989-10-01

    The cost of magnetic resonance imaging (MRI) is driven by magnetic field strength. Misperceptions as to the impact of field strength on performance have led to systems that are more expensive than they need to be. Careful analysis of all the factors that affect diagnostic quality lead to the conclusion that field strength per se is not a strong determinant of system performance. Freed from the constraints imposed by high-field operation, it is possible to exploit a varied set of opportunities afforded by low-field operation. In addition to lower costs and easier siting, we can take advantage of shortened T1 times, higher contrast, reduced sensitivity to motion, and reduced radiofrequency power deposition. These conceptual advantages can be made to coalesce onto practical imaging systems. We describe a low-cost MRI system that utilizes a permanent magnet of open design. Careful optimization of receiving antennas and acquisition sequences permit performance levels consistent with those needed for an effective diagnostic unit. Ancillary advantages include easy access to the patient, reduced claustrophobia, quiet and comfortable operation, and absence of a missile effect. The system can be sited in 350 sq ft and consumes a modest amount of electricity. MRI equipment of this kind can widen the population base than can access this powerful and beneficial diagnostic modality. PMID:2640910

  1. Miscellaneous Techniques

    NASA Astrophysics Data System (ADS)

    Jha, Shyam N.

    Nondestructive way of determining the food quality is the need of the hour. Till now major methods such as colour measurements and their modeling; machine vision systems; X-ray, CT and MRI; NIR spectroscopy; electronic nose and tongue; and ultrasonic technology have been discussed in detail. These techniques, in general, are considered to be sophisticated and costly, and therefore probably are not being adopted as fast as it should be. I am however of the reverse opinion. While going through these techniques, it has been seen that majority of quality parameters have been measured and correlated with the signals obtained using different equipment.

  2. Evaluating Web accessibility at different processing phases

    NASA Astrophysics Data System (ADS)

    Fernandes, N.; Lopes, R.; Carriço, L.

    2012-09-01

    Modern Web sites use several techniques (e.g. DOM manipulation) that allow for the injection of new content into their Web pages (e.g. AJAX), as well as manipulation of the HTML DOM tree. This has the consequence that the Web pages that are presented to users (i.e. after browser processing) are different from the original structure and content that is transmitted through HTTP communication (i.e. after browser processing). This poses a series of challenges for Web accessibility evaluation, especially on automated evaluation software. This article details an experimental study designed to understand the differences posed by accessibility evaluation after Web browser processing. We implemented a Javascript-based evaluator, QualWeb, that can perform WCAG 2.0 based accessibility evaluations in the two phases of browser processing. Our study shows that, in fact, there are considerable differences between the HTML DOM trees in both phases, which have the consequence of having distinct evaluation results. We discuss the impact of these results in the light of the potential problems that these differences can pose to designers and developers that use accessibility evaluators that function before browser processing.

  3. Technical Note [cmUse of a Snare Wire to Perform Nephrostomy Access in the Presence of Obstructive Staghorn Calculi

    SciTech Connect

    Nosher, John L.; Siegel, Randall L.; Bodner, Leonard J.

    1996-05-15

    We describe a technique for gaining access to the central collecting system via a chosen calyx, utilizing an alternative entry point to that calyx. An Amplatz nitinol loop snare is then used to convert this access to a traditional approach.

  4. Broadening Access to Virtual Observatories

    NASA Astrophysics Data System (ADS)

    Bentley, R. D.; Brooke, J.; Fox, P. A.

    2011-12-01

    The HELIO project is developing infrastructure to support the study of heliophysics, a relatively new, cross-disciplinary science. The project is providing integrated access to data from a number of disciplines - solar and heliospheric physics, geophysics (magnetospheric and ionospheric) and planetary environments (in-situ data). There are still relatively few scientists that possess the knowledge to work comfortably in all the domains involved and we are investigating ways in which to improve this situation. If some of the ideas that we are looking at prove successfully, a bi-product could be that the technique can be tuned to the audience that you are trying to address, including the public. We will describe some of the ideas that we are working on and suggest how they may be useful in the wider community. Some of this work is being done in conjunction with the CASSIS project that is trying to encourage the adoption of standards to increase the interoperability between domains. The HELIO and CASSIS projects are funded under the European Commission's Seventh Framework Programme (FP7).

  5. Agriculture: access to technology limited.

    PubMed

    1997-01-01

    From country to country and even regionally, the roles of women in agriculture vary, but most of their labor is in unpaid subsistence production and their contributions tend to be underestimated, according to the results of the [UN] Secretary-General's report. Depending on circumstances, they have complementary roles with men, sharing or dividing tasks in the production of crops, care of animals, and forestry management. In sub-Saharan Africa, for example, women contribute 60-80% of labor in food production for both household consumption and sale, while in Malaysia the women account for only 35% of the agricultural labor force, and in Ireland the participation rate is only 10.4%. Although women make this important amount of labor contributions to agricultural production, "development policies tend to favor export crops to earn foreign exchange and the agricultural research tends to address the improvement of production and technologies for commercial production". This results in limited access for women to technical knowledge and innovations, including irrigation, machinery, farming techniques and extension services. This is strengthened by the fact that most of the extension services target farmers who own land and can obtain credit to invest in input and technology. PMID:12293737

  6. Remote access astronomy

    NASA Astrophysics Data System (ADS)

    Beare, Richard; Bowdley, David; Newsam, Andrew; Roche, Paul

    2003-05-01

    There is still nothing to beat the excitement and fulfilment that you can get from observing celestial bodies on a clear dark night, in a remote location away from the seemingly ever increasing light pollution from cities. However, it is also the specific requirements for good observing that can sometimes prevent teachers from offering this opportunity to their students. Compromises for a town-based school or college might be to view only bright objects such as planets, or stars of magnitude 4 or brighter because of light pollution, but you would still require a knowledgeable teacher or astronomer and equipment to take outside with the students. Remote access astronomy using robotic telescopes can partly provide a solution to these problems and also opens up the doors to exciting projects that may otherwise be inaccessible to schools and colleges.

  7. Titration Techniques

    NASA Astrophysics Data System (ADS)

    Jacobsen, Jerrold J.; Houston Jetzer, Kelly; Patani, Néha; Zimmerman, John; Zweerink, Gerald

    1995-07-01

    Significant attention is paid to the proper technique for reading a meniscus. Video shows meniscus-viewing techniques for colorless and dark liquids and the consequences of not reading a meniscus at eye level. Lessons are provided on approaching the end point, focusing on end point colors produced via different commonly used indicators. The concept of a titration curve is illustrated by means of a pH meter. Carefully recorded images of the entire range of meniscus values in a buret, pipet, and graduated cylinder are included so that you can show your students, in lecture or pre-lab discussion, any meniscus and discuss how to read the buret properly. These buret meniscus values are very carefully recorded at the rate of one video frame per hundredth of a milliliter, so that an image showing any given meniscus value can be obtained. These images can be easily incorporated into a computer-based multimedia environment for testing or meniscus-reading exercises. Two of the authors have used this technique and found the exercise to be very well received by their students. Video on side two shows nearly 100 "bloopers", demonstrating both the right way and wrong ways to do tasks associated with titration. This material can be used in a variety of situations: to show students the correct way to do something; to test students by asking them "What is this person doing wrong?"; or to develop multimedia, computer-based lessons. The contents of Titration Techniques are listed below: Side 1 Titration: what it is. A simple titration; Acid-base titration animation; A brief redox titration; Redox titration animation; A complete acid-base titration. Titration techniques. Hand technique variations; Stopcock; Using a buret to measure liquid volumes; Wait before reading meniscus; Dirty and clean burets; Read meniscus at eye level (see Fig. 1); Meniscus viewing techniques--light colored liquids; Meniscus viewing techniques--dark liquids; Using a magnetic stirrer; Rough titration

  8. Electrochemical Techniques

    SciTech Connect

    Chen, Gang; Lin, Yuehe

    2008-07-20

    Sensitive and selective detection techniques are of crucial importance for capillary electrophoresis (CE), microfluidic chips, and other microfluidic systems. Electrochemical detectors have attracted considerable interest for microfluidic systems with features that include high sensitivity, inherent miniaturization of both the detection and control instrumentation, low cost and power demands, and high compatibility with microfabrication technology. The commonly used electrochemical detectors can be classified into three general modes: conductimetry, potentiometry, and amperometry.

  9. Public Access and Open Access: Is There a Difference? | Poster

    Cancer.gov

    By Robin Meckley, Contributing Writer, and Tracie Frederick, Guest Writer Open access and public access—are they different concepts or are they the same? What do they mean for the researchers at NCI at Frederick? “Open-access (OA) literature is digital, online, free of charge, and free of most copyright and licensing restrictions. What makes it possible is the Internet and the consent of the author or copyright-holder,” according to an open access website maintained by Peter Suber, director, Harvard Open Access Project.

  10. Transparent data service with multiple wireless access

    NASA Technical Reports Server (NTRS)

    Dean, Richard A.; Levesque, Allen H.

    1993-01-01

    The rapid introduction of digital wireless networks is an important part of the emerging digital communications scene. The introduction of Digital Cellular, LEO and GEO Satellites, and Personal Communications Services poses both a challenge and an opportunity for the data user. On the one hand wireless access will introduce significant new portable data services such as personal notebooks, paging, E-mail, and fax that will put the information age in the user's pocket. On the other hand the challenge of creating a seamless and transparent environment for the user in multiple access environments and across multiple network connections is formidable. A summary of the issues associated with developing techniques and standards that can support transparent and seamless data services is presented. The introduction of data services into the radio world represents a unique mix of RF channel problems, data protocol issues, and network issues. These problems require that experts from each of these disciplines fuse the individual technologies to support these services.

  11. National Radiobiology Archives distributed access programmer's guide

    SciTech Connect

    Prather, J. C.; Smith, S. K.; Watson, C. R.

    1991-12-01

    The National Radiobiology Archives is a comprehensive effort to gather, organize, and catalog original data, representative specimens, and supporting materials related to significant radiobiology studies. This provides researchers with information for analyses which compare or combine results of these and other studies and with materials for analysis by advanced molecular biology techniques. This Programmer's Guide document describes the database access software, NRADEMO, and the subset loading script NRADEMO/MAINT/MAINTAIN, which comprise the National Laboratory Archives Distributed Access Package. The guide is intended for use by an experienced database management specialist. It contains information about the physical and logical organization of the software and data files. It also contains printouts of all the scripts and associated batch processing files. It is part of a suite of documents published by the National Radiobiology Archives.

  12. Fade detector for the FODA-TDMA access scheme

    NASA Astrophysics Data System (ADS)

    Celandroni, Nedo; Ferro, Erina; Marzoli, Antonio

    1989-05-01

    The First in first out Ordered Demand Assignment-Time Division Multiple Access (FODA-TDMA) satellite access scheme designed for simultaneous transmissions of real time data, like packetized voice and slow-scan images (stream traffic) and data coming from standard EDP applications, such as bulk data tansfer, interactive computer access, mailing, data base enquiry and updating (datagram traffic) is described. When deep fades are experienced due to rain attenuation, the system is able to counter the fade. Techniques to detect the fade are presented.

  13. [Intraosseous vascular access, a technic previously underestimated in France].

    PubMed

    Oriot, D; Cardona, J; Berthier, M; Nasimi, A; Boussemart, T

    1994-07-01

    Intraosseous vascular access is a simple and very efficient technique for fluid and drug administration in any pediatric emergencies where the intravenous route is impossible or inadequate. Yet it remains unrecognized in France. Its pharmacokinetics is close to that of peripheral intravenous route, but it allows much greater infusion flow rates. In pediatric resuscitation it must be considered as the number one technique of intravascular access in infants, and rapidly as the first alternative after failure of attempt of intravenous route in children under 6. Provided that the technique is performed with careful asepsis, the risk of infectious complications is very low. However the intraosseous route must remain a transitory vascular access, and has to be stopped as soon as possible, its use never exceeding 24 hours. PMID:7987470

  14. Phylogenetic diversity of fungal communities in areas accessible and not accessible to tourists in Naracoorte Caves.

    PubMed

    Adetutu, Eric M; Thorpe, Krystal; Bourne, Steven; Cao, Xiangsheng; Shahsavari, Esmaeil; Kirby, Greg; Ball, Andrew S

    2011-01-01

    The fungal diversity in areas accessible and not accessible to tourists at UNESCO World Heritage-listed Naracoorte Caves was investigated with culture-dependent and culture-independent techniques for assistance in cave management protocol development. The caves were selected based on tourist numbers and configurations: Stick Tomato (open, high numbers), Alexandra (lockable openings, high numbers) and Strawhaven (control; no access). Culture-based survey revealed Ascomycota dominance irrespective of sampling area with Microascales (Trichurus sp.) being most frequently isolated. Some Hypocreales-like sequences belonging to Fusarium sp., Trichoderma sp. and Neonectria sp. (Stick Tomato) were cultured only from areas not accessible to tourists. These orders also were detected by DGGE assay irrespective of sampling area. The predominance of Ascomycota (especially Microascales) suggested their important ecological roles in these caves. Culture-independent analysis showed higher Shannon fungal diversity values (from ITS-based DGGE profiles) in tourist-accessible areas of these caves than in inaccessible areas with the fungal community banding patterns being substantially different in Stick Tomato Cave. Further investigations are needed to determine the cause of the differences in the fungal communities of Stick Tomato Cave, although cave-related factors such as use, configuration and sediment heterogeneity might have contributed to these differences. PMID:21642344

  15. Remote Data Access with IDL

    NASA Technical Reports Server (NTRS)

    Galloy, Michael

    2013-01-01

    A tool based on IDL (Interactive Data Language) and DAP (Data Access Protocol) has been developed for user-friendly remote data access. A difficulty for many NASA researchers using IDL is that often the data to analyze are located remotely and are too large to transfer for local analysis. Researchers have developed a protocol for accessing remote data, DAP, which is used for both SOHO and STEREO data sets. Server-side side analysis via IDL routine is available through DAP.

  16. 28 CFR 17.44 - Access eligibility.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... Judicial Administration DEPARTMENT OF JUSTICE CLASSIFIED NATIONAL SECURITY INFORMATION AND ACCESS TO CLASSIFIED INFORMATION Access to Classified Information § 17.44 Access eligibility. (a) Determinations of eligibility for access to classified information are separate from suitability determinations with respect...

  17. 28 CFR 17.44 - Access eligibility.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... Judicial Administration DEPARTMENT OF JUSTICE CLASSIFIED NATIONAL SECURITY INFORMATION AND ACCESS TO CLASSIFIED INFORMATION Access to Classified Information § 17.44 Access eligibility. (a) Determinations of eligibility for access to classified information are separate from suitability determinations with respect...

  18. Vehicle barrier with access delay

    DOEpatents

    Swahlan, David J; Wilke, Jason

    2013-09-03

    An access delay vehicle barrier for stopping unauthorized entry into secure areas by a vehicle ramming attack includes access delay features for preventing and/or delaying an adversary from defeating or compromising the barrier. A horizontally deployed barrier member can include an exterior steel casing, an interior steel reinforcing member and access delay members disposed within the casing and between the casing and the interior reinforcing member. Access delay members can include wooden structural lumber, concrete and/or polymeric members that in combination with the exterior casing and interior reinforcing member act cooperatively to impair an adversarial attach by thermal, mechanical and/or explosive tools.

  19. Atomic memory access hardware implementations

    SciTech Connect

    Ahn, Jung Ho; Erez, Mattan; Dally, William J

    2015-02-17

    Atomic memory access requests are handled using a variety of systems and methods. According to one example method, a data-processing circuit having an address-request generator that issues requests to a common memory implements a method of processing the requests using a memory-access intervention circuit coupled between the generator and the common memory. The method identifies a current atomic-memory access request from a plurality of memory access requests. A data set is stored that corresponds to the current atomic-memory access request in a data storage circuit within the intervention circuit. It is determined whether the current atomic-memory access request corresponds to at least one previously-stored atomic-memory access request. In response to determining correspondence, the current request is implemented by retrieving data from the common memory. The data is modified in response to the current request and at least one other access request in the memory-access intervention circuit.

  20. [Tracheostomy techniques].

    PubMed

    Mieth, M; Schellhaaß, A; Hüttner, F J; Larmann, J; Weigand, M A; Büchler, M W

    2016-01-01

    Due to the comprehensive establishment of modern techniques, tracheostomy has become a routine procedure in intensive care units (ICU). The negative effects of prolonged translaryngeal intubation on the laryngeal and tracheal mucosa up to tracheal stenosis can be reduced by tracheostomy. Furthermore, long-term ventilation is facilitated; however, there is no clear evidence on the optimal timing of tracheostomy in critically ill patients. The specific indications and contraindications of surgical as well as percutaneous tracheostomy must be strictly observed for a safe and successful intervention. Exchanging the tracheostomy tube may lead to potentially dangerous situations especially after percutaneous tracheostomy. A standardized and structured approach is therefore recommended. PMID:26643155

  1. Separation techniques.

    PubMed

    Duke, T

    1998-10-01

    The past two years have seen continued development of capillary electrophoresis methods. The separation performance of flowable sieving media now equals, and in some respects exceeds, that provided by gels. The application of microfabrication techniques to separation science is gaining pace. There is a continuing trend towards miniaturization and integration of separation with preparative or analytical steps. Innovative separation methods based on microfabrication technology include electrophoresis in purpose-designed molecular sieves, dielectric, trapping using microelectrodes, and force-free motion in Brownian ratchets. PMID:9818184

  2. Nonvolatile random access memory

    NASA Technical Reports Server (NTRS)

    Wu, Jiin-Chuan (Inventor); Stadler, Henry L. (Inventor); Katti, Romney R. (Inventor)

    1994-01-01

    A nonvolatile magnetic random access memory can be achieved by an array of magnet-Hall effect (M-H) elements. The storage function is realized with a rectangular thin-film ferromagnetic material having an in-plane, uniaxial anisotropy and inplane bipolar remanent magnetization states. The thin-film magnetic element is magnetized by a local applied field, whose direction is used to form either a 0 or 1 state. The element remains in the 0 or 1 state until a switching field is applied to change its state. The stored information is detcted by a Hall-effect sensor which senses the fringing field from the magnetic storage element. The circuit design for addressing each cell includes transistor switches for providing a current of selected polarity to store a binary digit through a separate conductor overlying the magnetic element of the cell. To read out a stored binary digit, transistor switches are employed to provide a current through a row of Hall-effect sensors connected in series and enabling a differential voltage amplifier connected to all Hall-effect sensors of a column in series. To avoid read-out voltage errors due to shunt currents through resistive loads of the Hall-effect sensors of other cells in the same column, at least one transistor switch is provided between every pair of adjacent cells in every row which are not turned on except in the row of the selected cell.

  3. ACCESS: Detector Performance

    NASA Astrophysics Data System (ADS)

    Morris, Matthew J.; Kaiser, M.; Rauscher, B. J.; Kimble, R. A.; Kruk, J. W.; Mott, D. B.; Wen, Y.; Foltz, R.; McCandliss, S. R.; Pelton, R. S.; Wright, E. L.; Feldman, P. D.; Moos, H. W.; Riess, A. G.; Benford, D. J.; Gardner, J. P.; Woodgate, B. E.; Bohlin, R.; Deustua, S. E.; Dixon, W. V.; Sahnow, D. J.; Kurucz, R. L.; Lampton, M.; Perlmutter, S.

    2013-01-01

    ACCESS, Absolute Color Calibration Experiment for Standard Stars, is a series of rocket-borne sub-orbital missions and ground-based experiments that will enable improvements in the precision of the astrophysical flux scale through the transfer of absolute laboratory detector standards from the National Institute of Standards and Technology (NIST) to a network of stellar standards with a calibration accuracy of 1% and a spectral resolving power of 500 across the 0.35 to 1.7 micron bandpass (overview Kaiser et al.). The flight detector and detector spare have been integrated with their electronics and flight mount. The controller electronics have been flight qualified. Vibration testing to launch loads and thermal vacuum testing of the detector, mount, and housing have been performed. The flight detector controller boards have been installed into a ruggedized flight housing. They have been successfully vacuum tested for periods significantly longer than the flight length, and components have been heat-sunk and reinforced as necessary. Thermal stability tests have been performed, and results will be presented. Goddard Space Flight Center’s Detector Characterization Lab (DCL) executed initial characterization tests for the flight detector in 2007. These were repeated in 2012, to ensure and establish baseline performance. Current lab characterization tests at Johns Hopkins are ongoing, and results will be presented. NASA sounding rocket grant NNX08AI65G supports this work.

  4. Access to space study

    NASA Technical Reports Server (NTRS)

    1994-01-01

    This report summarizes the results of a comprehensive NASA in-house study to identify and assess alternate approaches to access to space through the year 2030, and to select and recommend a preferred cause of action. The goals of the study were to identify the best vehicles and transportation architectures to make major reductions in the cost of space transportation (at least 50%), while at the same time increasing safety for flight crews by at least an order of magnitude. In addition, vehicle reliability was to exceed 0.98 percent, and, as important, the robustness, pad time, turnaround time, and other aspects of operability were to be vastly improved. This study examined three major optional architectures: (1) retain and upgrade the Space Shuttle and expendable launch vehicles; (2) develop new expendable vehicles using conventional technologies and transition from current vehicles beginning in 2005; and (3) develop new reusable vehicles using advanced technology, and transition from current vehicles beginning in 2008. The launch-needs, mission model utilized for for the study was based upon today's projection of civil, defense, and commercial mission payload requirements.

  5. A quantum access network.

    PubMed

    Fröhlich, Bernd; Dynes, James F; Lucamarini, Marco; Sharpe, Andrew W; Yuan, Zhiliang; Shields, Andrew J

    2013-09-01

    The theoretically proven security of quantum key distribution (QKD) could revolutionize the way in which information exchange is protected in the future. Several field tests of QKD have proven it to be a reliable technology for cryptographic key exchange and have demonstrated nodal networks of point-to-point links. However, until now no convincing answer has been given to the question of how to extend the scope of QKD beyond niche applications in dedicated high security networks. Here we introduce and experimentally demonstrate the concept of a 'quantum access network': based on simple and cost-effective telecommunication technologies, the scheme can greatly expand the number of users in quantum networks and therefore vastly broaden their appeal. We show that a high-speed single-photon detector positioned at a network node can be shared between up to 64 users for exchanging secret keys with the node, thereby significantly reducing the hardware requirements for each user added to the network. This point-to-multipoint architecture removes one of the main obstacles restricting the widespread application of QKD. It presents a viable method for realizing multi-user QKD networks with efficient use of resources, and brings QKD closer to becoming a widespread technology. PMID:24005413

  6. Making Astronomy Accessible

    NASA Astrophysics Data System (ADS)

    Grice, Noreen A.

    2011-05-01

    A new semester begins, and your students enter the classroom for the first time. You notice a student sitting in a wheelchair or walking with assistance from a cane. Maybe you see a student with a guide dog or carrying a Braille computer. Another student gestures "hello” but then continues hand motions, and you realize the person is actually signing. You wonder why another student is using an electronic device to speak. Think this can't happen in your class? According to the U.S. Census, one out of every five Americans has a disability. And some disabilities, such as autism, dyslexia and arthritis, are considered "invisible” disabilities. This means you have a high probability that one of your students will have a disability. As an astronomy instructor, you have the opportunity to reach a wide variety of learners by using creative teaching strategies. I will share some suggestions on how to make astronomy and your part of the universe more accessible for everyone.

  7. Remote direct memory access

    DOEpatents

    Archer, Charles J.; Blocksome, Michael A.

    2012-12-11

    Methods, parallel computers, and computer program products are disclosed for remote direct memory access. Embodiments include transmitting, from an origin DMA engine on an origin compute node to a plurality target DMA engines on target compute nodes, a request to send message, the request to send message specifying a data to be transferred from the origin DMA engine to data storage on each target compute node; receiving, by each target DMA engine on each target compute node, the request to send message; preparing, by each target DMA engine, to store data according to the data storage reference and the data length, including assigning a base storage address for the data storage reference; sending, by one or more of the target DMA engines, an acknowledgment message acknowledging that all the target DMA engines are prepared to receive a data transmission from the origin DMA engine; receiving, by the origin DMA engine, the acknowledgement message from the one or more of the target DMA engines; and transferring, by the origin DMA engine, data to data storage on each of the target compute nodes according to the data storage reference using a single direct put operation.

  8. Ferroelectric random access memories.

    PubMed

    Ishiwara, Hiroshi

    2012-10-01

    Ferroelectric random access memory (FeRAM) is a nonvolatile memory, in which data are stored using hysteretic P-E (polarization vs. electric field) characteristics in a ferroelectric film. In this review, history and characteristics of FeRAMs are first introduced. It is described that there are two types of FeRAMs, capacitor-type and FET-type, and that only the capacitor-type FeRAM is now commercially available. In chapter 2, properties of ferroelectric films are discussed from a viewpoint of FeRAM application, in which particular attention is paid to those of Pb(Zr,Ti)O3, SrBi2Ta2O9, and BiFeO3. Then, cell structures and operation principle of the capacitor-type FeRAMs are discussed in chapter 3. It is described that the stacked technology of ferroelectric capacitors and development of new materials with large remanent polarization are important for fabricating high-density memories. Finally, in chapter 4, the optimized gate structure in ferroelectric-gate field-effect transistors is discussed and experimental results showing excellent data retention characteristics are presented. PMID:23421123

  9. Is Your Church Accessible? Houses of Worship: Physical Accessibility Checklist.

    ERIC Educational Resources Information Center

    Ensign, Arselia, Ed.

    1991-01-01

    This checklist is intended to help churches evaluate the accessibility of their facilities to those with physical disabilities. Categories covered are: basic accessibility, parking lots, walks, ramps, entrances/exits, doors and doorways, stairs and steps, floors, worship space, rest rooms, controls, water fountains, identification, warning…

  10. Access to Public Educational Facilities under the Equal Access Act.

    ERIC Educational Resources Information Center

    Wood, R. Craig; Goldblatt, Steven M.

    1988-01-01

    Discussion centers on the legal bases by which school administrators permit access to public educational facilities by religiously and politically oriented student organizations. It concludes that access should be granted to students whose purposes do not disrupt teaching and learning. (JAM)

  11. Self-Access Centers: Maximizing Learners' Access to Center Resources

    ERIC Educational Resources Information Center

    McMurry, Benjamin L.; Tanner, Mark W.; Anderson, Neil J.

    2009-01-01

    Although some students have discovered how to use self-access centers effectively, the majority appear to be unaware of available resources. A website and database of materials were created to help students locate materials and use the Self-Access Study Center (SASC) at Brigham Young University's English Language Center (ELC) more effectively.…

  12. Making Diabetes Education Accessible For People With Visual Impairment

    PubMed Central

    Williams, Ann S.

    2010-01-01

    Purpose The purpose of this study was to identify changes needed to make the diabetes education materials and programs of the Diabetes Association of Greater Cleveland (DAGC) accessible for people who have visual impairment and diabetes (PVID). Methods Using the principles and techniques of participatory action research (PAR), five PVID and four staff members of a local diabetes association met once a month for a year to plan, implement, and evaluate progress towards full accessibility of all diabetes education materials and programs. The researcher served as facilitator. Results Four “transformational moments” are presented through which the PAR process enabled PVID and diabetes professionals to learn to understand and trust each other. Changes made to increase accessibility included: production of two recordings for providing access to print information about diabetes; planning public education program publicity and locations for access; development of guidelines to help speakers make their diabetes education presentations accessible for people who cannot see slides and gestures. and presentation of an inservice for the entire staff of the diabetes association, including information about how they live with visual impairment, and common courtesies that make communication with PVID more effective Implications Diabetes education programs should include planning for full accessibility for PVID. Diabetes organizations should publish teaching materials in accessible format. PMID:19417119

  13. The Table Access Protocol: Providing standard access to astronomical data

    NASA Astrophysics Data System (ADS)

    Nandrekar-Heinis, D.; Michel, L.; Louys, M.; Bonnarel, F.

    2014-11-01

    In the upcoming era of large scale, geographically distributed, varied sources of astronomical data, a standard, simple and flexible way to access this data is necessary and useful for astronomers across the globe. Most of the modern surveys such as the Sloan Digital Sky Survey (SDSS) are available in well organized tabular formats. The Table Access Protocol (TAP) supports a standard web interface to access this kind of tabular data. Predefined queries and results formats help different data providers to implement these services. TAP also helps various software tools to access data and perform cross-matches seamlessly across different data sources. It is then possible to access data in tools that consume TAP web services. This supports further detailed data analysis on a queried slice of data. This document describes TAP and its utility for astronomers and data scientists. It also provides information on the protocol for data providers and developers.

  14. Optimizing the TRD design for ACCESS

    SciTech Connect

    Cherry, M. L.; Guzik, T. G.; Isbert, J.; Wefel, J. P.

    1999-01-22

    The present ACCESS design combines an ionization calorimeter with a transition radiation detector (TRD) to measure the cosmic ray composition and energy spectrum from H to Fe at energies above 1 TeV/nucleon to the 'knee' in the all particle spectrum. We are in the process of optimizing the TRD design to extend the range of the technique to as high an energy as possible given the constraints of the International Space Station mission and the need to coexist with the calorimeter. The current status of the design effort and preliminary results will be presented.

  15. An access alternative for mobile satellite networks

    NASA Technical Reports Server (NTRS)

    Wu, W. W.

    1988-01-01

    Conceptually, this paper discusses strategies of digital satellite communication networks for a very large number of low density traffic stations. These stations can be either aeronautical, land mobile, or maritime. The techniques can be applied to international, domestic, regional, and special purpose satellite networks. The applications can be commercial, scientific, military, emergency, navigational or educational. The key strategy is the use of a non-orthogonal access method, which tolerates overlapping signals. With n being either time or frequency partitions, and with a single overlapping signal allowed, a low cost mobile satellite system can be designed with n squared (n squared + n + 1) number of terminals.

  16. Internet Access to Spacecraft

    NASA Technical Reports Server (NTRS)

    Rash, James; Parise, Ron; Hogie, Keith; Criscuolo, Ed; Langston, Jim; Jackson, Chris; Price, Harold; Powers, Edward I. (Technical Monitor)

    2000-01-01

    The Operating Missions as Nodes on the Internet (OMNI) project at NASA's Goddard Space flight Center (GSFC), is demonstrating the use of standard Internet protocols for spacecraft communication systems. This year, demonstrations of Internet access to a flying spacecraft have been performed with the UoSAT-12 spacecraft owned and operated by Surrey Satellite Technology Ltd. (SSTL). Previously, demonstrations were performed using a ground satellite simulator and NASA's Tracking and Data Relay Satellite System (TDRSS). These activities are part of NASA's Space Operations Management Office (SOMO) Technology Program, The work is focused on defining the communication architecture for future NASA missions to support both NASA's "faster, better, cheaper" concept and to enable new types of collaborative science. The use of standard Internet communication technology for spacecraft simplifies design, supports initial integration and test across an IP based network, and enables direct communication between scientists and instruments as well as between different spacecraft, The most recent demonstrations consisted of uploading an Internet Protocol (IP) software stack to the UoSAT- 12 spacecraft, simple modifications to the SSTL ground station, and a series of tests to measure performance of various Internet applications. The spacecraft was reconfigured on orbit at very low cost. The total period between concept and the first tests was only 3 months. The tests included basic network connectivity (PING), automated clock synchronization (NTP), and reliable file transfers (FTP). Future tests are planned to include additional protocols such as Mobile IP, e-mail, and virtual private networks (VPN) to enable automated, operational spacecraft communication networks. The work performed and results of the initial phase of tests are summarized in this paper. This work is funded and directed by NASA/GSFC with technical leadership by CSC in arrangement with SSTL, and Vytek Wireless.

  17. Accessing the Internet Via Satellite.

    ERIC Educational Resources Information Center

    Jackson, Lisa M.

    1998-01-01

    Discusses the use of satellite technology as an option for public schools to access the Internet. Examines costs and available technology. Presents two examples of school-satellite usage, including its use by the Navajo Nation to provide Internet access for its students who are spread out across 26,000 square miles. (GR)

  18. Money, Equity, and College Access.

    ERIC Educational Resources Information Center

    Orfield, Gary

    1992-01-01

    Three decades after massive government commitment to financial aid, minority and low income access is declining and aid going to middle class students. Policies and political deadlock have worsened the situation of those in need, and hard choices must be made if college access is to be restored without greater expenditures. (SK)

  19. Bibliographic Access and Control System.

    ERIC Educational Resources Information Center

    Kelly, Betsy; And Others

    1982-01-01

    Presents a brief summary of the functions of the Bibliographic Access & Control System (BACS) implemented at the Washington University School of Medicine Library, and outlines the design, development, and uses of the system. Bibliographic control of books and serials and user access to the system are also discussed. (Author/JL)

  20. Advanced Placement: Access Not Exclusion.

    ERIC Educational Resources Information Center

    Camara, Wayne; Dorans, Neil J.; Morgan, Rick; Myford, Carol

    2000-01-01

    Refutes the assertion by W. Lichten (2000) that increased access to advanced placement (AP) courses in high school has led to a decline in AP quality. Suggests that increased access exposes students to college-level course material, encourages teachers to expand their knowledge domains, increases curriculum rigor, and give students new challenges.…

  1. ERIC Data Access System (EDAS).

    ERIC Educational Resources Information Center

    Rao, Pal V.

    The ERIC Data Access System (EDAS) is an information retrieval system developed at Eastern Illinois University to access the Educational Resources Information Center (ERIC) database and make it available to Eastern faculty and students in a convenient and timely fashion. This paper describes briefly why and how Eastern developed and implemented…

  2. Editorial: Next Generation Access Networks

    NASA Astrophysics Data System (ADS)

    Ruffini, Marco; Cincotti, Gabriella; Pizzinat, Anna; Vetter, Peter

    2015-12-01

    Over the past decade we have seen an increasing number of operators deploying Fibre-to-the-home (FTTH) solutions in access networks, in order to provide home users with a much needed network access upgrade, to support higher peak rates, higher sustained rates and a better and more uniform broadband coverage of the territory.

  3. Distributed Access to Administrative Systems.

    ERIC Educational Resources Information Center

    Carson, Eugene

    1987-01-01

    Administrators, faculty, and staff should have electronic access to records needed to perform their jobs, and students should have access to their own records--course registration and addresses. User-directed analysis and reporting are discussed and the security and audit issues are examined. (Author/MLW)

  4. Internet Accessibility in Latin America.

    ERIC Educational Resources Information Center

    Haymond, Ruel

    1998-01-01

    Addresses the problems that prohibit expanded Internet access and possible solutions to these problems, particularly with respect to the country of Chile. The three main problems that block Internet usage in Latin America are high demand and poor infrastructure; high costs for Internet access; and high preliminary costs for computers, modems, and…

  5. Accessibility on the Hudson River

    ERIC Educational Resources Information Center

    Exceptional Parent, 2010

    2010-01-01

    This article describes how Beverly and Martin Ryfa, working with an architect who specializes in accessible design, were able to build a house that is handicap accessible for their 9-year-old daughter, Danielle, who suffered an intraventricular hemorrhage when she was three days old. The article describes the features of their house that make…

  6. Accessible Multimedia for the Web.

    ERIC Educational Resources Information Center

    Zaparyniuk, Nicholas; Code, Jillianne

    With the Internet taking a dominant role in corporate training, education, retail, and customer based product exploration, authors of Web-based information need to ensure that the media they deliver is accessible to the widest possible audience. Whether users have a visual, auditory, physical, or developmental disability, accessible multimedia can…

  7. Open access: a closed shop?

    NASA Astrophysics Data System (ADS)

    Bradford, Rick

    2013-01-01

    Your December 2012 issue contains both a short news article on the progress of the open-access movement ("UK open access gains ground", p11) and a lengthy feature about the visionary Irish physicist Edward Hutchinson Synge ("Unknown genius", pp26-29). I find the combination of these articles ironic.

  8. Minority Access to Higher Education

    ERIC Educational Resources Information Center

    Jackson, Nathaniel

    2012-01-01

    Blacks, Hispanics, Native Americans, and Asian Americans are entitled to equal access to all institutions of higher education. Ensuring greater access and participation by minorities in higher education is one of the most practical ways of moving America closer to the ideal of equal opportunity, which is the actualization of the American dream.…

  9. Cochlear implant simulator for surgical technique analysis

    NASA Astrophysics Data System (ADS)

    Turok, Rebecca L.; Labadie, Robert F.; Wanna, George B.; Dawant, Benoit M.; Noble, Jack H.

    2014-03-01

    Cochlear Implant (CI) surgery is a procedure in which an electrode array is inserted into the cochlea. The electrode array is used to stimulate auditory nerve fibers and restore hearing for people with severe to profound hearing loss. The primary goals when placing the electrode array are to fully insert the array into the cochlea while minimizing trauma to the cochlea. Studying the relationship between surgical outcome and various surgical techniques has been difficult since trauma and electrode placement are generally unknown without histology. Our group has created a CI placement simulator that combines an interactive 3D visualization environment with a haptic-feedback-enabled controller. Surgical techniques and patient anatomy can be varied between simulations so that outcomes can be studied under varied conditions. With this system, we envision that through numerous trials we will be able to statistically analyze how outcomes relate to surgical techniques. As a first test of this system, in this work, we have designed an experiment in which we compare the spatial distribution of forces imparted to the cochlea in the array insertion procedure when using two different but commonly used surgical techniques for cochlear access, called round window and cochleostomy access. Our results suggest that CIs implanted using round window access may cause less trauma to deeper intracochlear structures than cochleostomy techniques. This result is of interest because it challenges traditional thinking in the otological community but might offer an explanation for recent anecdotal evidence that suggests that round window access techniques lead to better outcomes.

  10. Preserved saphenous vein allografts for vascular access.

    PubMed

    Piccone, V A; Sika, J; Ahmed, N; LeVeen, H H; DiScala, V

    1978-09-01

    Preserved venous allografts were used as an alternate access procedure in 70 patients receiving dialysis during a three year period. The clinical experience with allograft fistulas revealed an extremely high initial patency rate; absence of infection postoperatively and during three years of dialysis; suitability for dialysis a week after implantation, thus greatly obviating the need for Silastic shunts; a low long term thrombosis rate and the weakly antigenic allograft veins produced no accelerated rejection of subsequently transplanted kidneys. Surviving patients average 172 dialysis treatments per allograft. Allograft fistulas constituted 45 per cent of the last 100 vascular procedures, an indication of the extent of usage. Microscopic examination of grafts retrieved from patients who died during the late follow-up period demonstrated that structural components of the wall of the vein were still identifiable. Allograft venous fistulas offer dependable, safe vascular access, especially in the infection prone patient with diabetes who is receiving dialysis treatment. The clinical results of allograft fistulas suggests a major role for this technique in vascular access operations. PMID:684591

  11. New techniques

    NASA Astrophysics Data System (ADS)

    Pisacane, V. L.

    1983-04-01

    Equipment, operations, calibration, and accuracy of existing positioning, geodetic, and gravimetric equipment are explored. Radio navigation and positioning systems now include OMEGA, LORAN, VOR, DME, TACAN, and LONAR. Dedicated positioning satellites comprise the Transit and Navstar systems, with positioning accuracies of 8 m available with the GPS. Missile tracking, particularly for submarine launched rockets, is accomplished with the Satrack satellite, which furnishes position and velocity accuracy to within 40 ft and 0.08 ft/sec, respectively. VLBI techniques permit sighting of astronomical objects to obtain 20 cm accuracy for pole positioning and 1 m/sec for earth rotation speeds. Methods have been devised to use portable equipment which compensates for refraction when using lasers and masers in ranging trials. NASA has established a fixed and mobile global laser tracking network to provide a ranging accuracy of 100 cm when employed with satellite and lunar reflectors. Lasers are also used for terrain contouring, aircraft ranging, and satellite altimetry. A free-fall gravimeter has been developed which involves dropping one reflector of a two-beam Michelson interferometer, yielding an accuracy of 10 microgal. It is noted that new standards are needed for the NASA Deep Space Network.

  12. Success Factors for Open Access

    PubMed Central

    2003-01-01

    Open access to the peer-reviewed primary research literature would greatly facilitate knowledge transfer between the creators and the users of the results of research and scholarship. Criteria are needed to assess the impact of recent initiatives, such as the Budapest Open Access Initiative. For example, how many open-access research journals exist within a given field, and what is the reputation of each one? And, how many openly-accessible institutional e-print archives have been created and how many are actually are being used by researchers and scholars? A simple approach to an assessment of the open-access portion of the medical literature is described, and some preliminary results are summarized. These preliminary results point to the need for incentives to foster the implementation of initiatives such as the Budapest Open Access Initiative. An example of an incentive model is proposed, where an agency or foundation that provides peer-reviewed grants-in-aid to researchers establishes an e-print archive. Only current grantees of the agency would be eligible to post reports about the results of research projects or programs that have been supported by the agency. Some advantages and implications of this particular model are outlined. It is suggested that incentive models of this kind are needed to increase the likelihood that open access to the primary medical research literature will soon reach a "tipping point" and move quickly toward wide acceptance. PMID:12746206

  13. Success factors for open access.

    PubMed

    Till, James E

    2003-01-01

    Open access to the peer-reviewed primary research literature would greatly facilitate knowledge transfer between the creators and the users of the results of research and scholarship. Criteria are needed to assess the impact of recent initiatives, such as the Budapest Open Access Initiative. For example, how many open-access research journals exist within a given field, and what is the reputation of each one? And, how many openly-accessible institutional e-print archives have been created and how many are actually are being used by researchers and scholars? A simple approach to an assessment of the open-access portion of the medical literature is described, and some preliminary results are summarized. These preliminary results point to the need for incentives to foster the implementation of initiatives such as the Budapest Open Access Initiative. An example of an incentive model is proposed, where an agency or foundation that provides peer-reviewed grants-in-aid to researchers establishes an e-print archive. Only current grantees of the agency would be eligible to post reports about the results of research projects or programs that have been supported by the agency. Some advantages and implications of this particular model are outlined. It is suggested that incentive models of this kind are needed to increase the likelihood that open access to the primary medical research literature will soon reach a "tipping point" and move quickly toward wide acceptance. PMID:12746206

  14. Transgluteal CT-Guided Percutaneous Renal Access for Percutaneous Nephrolithotomy in a Pelvic Horseshoe Kidney

    PubMed Central

    Mullins, Ryan J.; Dauw, Casey A.; Borofsky, Michael S.; York, Nadya; Patel, Aashish A.

    2015-01-01

    Abstract CT-guided percutaneous renal access has been described as a safe and effective access technique in patients with complex anatomy, including ectopic kidney, retrorenal colon, spinal dysraphism, hepatomegaly, and splenomegaly. In comparison to conventional intraoperative fluoroscopic-guided access, CT imaging allows for delineation of surrounding structures that are at risk for injury during percutaneous access. However, previous reports indicate that pelvic kidneys might be inaccessible percutaneously without laparoscopic assistance. Herein, we present a novel transgluteal route to renal access for percutaneous nephrolithotomy (PCNL) in a patient with a pelvic horseshoe kidney and severe spinal deformity.

  15. Database Access Integration Services (DAIS)

    SciTech Connect

    Mitchell, P. . Sensor and System Development Center); Nordell, D. )

    1992-12-01

    The Database Access Integration Services (DAIS) is a collection of services that facilitate access to data among diverse data systems in an electric utility communications network. DAIS provides access to data in distributed, heterogeneous data systems that include relational database management systems, other database management systems, control systems, file systems, and application systems. It also provides a common method for describing data, common data access operations and essential support services including a data dictionary, a data directory and distributed data access management capabilities. The DAIS project has developed specifications intended for vendor and third-party implementation. The software developed is only to implement a data access integration demonstration. These specifications can serve as a basis for influencing industry standards development. One important consequence of this strategy is that most actual software development will be performed by vendors, not utilities. DAIS is a tool to support data access. It is policy neutral regarding issues such as local or central administration of data or standardization of information model contents (e.g., EPRI Plant Information Network). As a tool, it can be used to help realize such policies. The DAIS does not provide data storage facilities, schema integration, distributed query processing, distributed applications or cooperative processing. Rather, DAIS is complementary to these functions and can be used with other software that does provide these functions. This project documented the requirements for the DAIS. These requirements are the basis for design of the DAIS specifications. The key requirements for a DAIS are: Uniform access to heterogeneous utility data systems, remote update; coexistence with local data systems; local autonomy ; Security and access restriction enforcement; OSI compatibility; open architecture and extensibility; and operating platform independence.

  16. Time division multiplexed orbital angular momentum access system

    NASA Astrophysics Data System (ADS)

    Shi, Jianyang; Fang, Yuan; Chi, Nan

    2016-03-01

    We propose and experimentally demonstrate time division multiplexed orbital angular momentum (OAM) access system to increase transmission capacity and spectral efficiency. In this system, data carried on different time tributaries share the same OAM mode. Multiple time division multiplexed OAM modes are multiplexed to realize two-dimensional (time dimension and OAM dimension) multiplexing. Therefore, the capacity and spectral efficiency of the access system will increase. The orthogonality between optical time division multiplexing (OTDM) and OAM techniques is also verified in our experiment. In a proof-of-concept experiment, 2×5-Gbps return-to-zero signal over OAM mode +4 is transmitted and investigated. The bit error ratio performance after transmission in this system can be smaller than 1×10-9. Results show that the proposed time division multiplexed OAM access system is suitable for future broadband access network.

  17. How to prolong the patency of vascular access.

    PubMed

    Glazer, Sidney; Saint, Lindsey; Shenoy, Surendra

    2015-01-01

    Prolonging the patency and limiting the complications of a functioning hemodialysis (HD) access require a multidisciplinary approach. It begins with careful access planning that is executed and continually reinforced by physicians and facility staff encouraging active patient participation. Vascular access (VA) dysfunctions identified by regular monitoring and surveillance need further evaluation. Color duplex ultrasound is evolving as the primary tool to evaluate functional implication of the structural problems in the VA. While ease of scheduling makes endovascular management attractive, definitive surgical management provides better longevity and should be used when indicated. Timing of intervention and selection of technique depend on optimal use of available expertise and the nature of the problem. Avoiding a bridging HD catheter should be a priority while prolonging access patency and improving patient safety. PMID:25676299

  18. Controlling user access to electronic resources without password

    SciTech Connect

    Smith, Fred Hewitt

    2015-06-16

    Described herein are devices and techniques for remotely controlling user access to a restricted computer resource. The process includes pre-determining an association of the restricted computer resource and computer-resource-proximal environmental information. Indicia of user-proximal environmental information are received from a user requesting access to the restricted computer resource. Received indicia of user-proximal environmental information are compared to associated computer-resource-proximal environmental information. User access to the restricted computer resource is selectively granted responsive to a favorable comparison in which the user-proximal environmental information is sufficiently similar to the computer-resource proximal environmental information. In at least some embodiments, the process further includes comparing user-supplied biometric measure and comparing it with a predetermined association of at least one biometric measure of an authorized user. Access to the restricted computer resource is granted in response to a favorable comparison.

  19. Perceived accessibility versus actual physical accessibility of healthcare facilities.

    PubMed

    Sanchez, J; Byfield, G; Brown, T T; LaFavor, K; Murphy, D; Laud, P

    2000-01-01

    This study addressed how healthcare clinics perceive themselves in regard to accessibility for persons with spinal cord injuries (SCI). All 40 of the clinics surveyed reported that they were wheelchair accessible; however, there was significant variability in the number of sites that actually met the guidelines of the Americans with Disability Act. In general, a person using a wheelchair could enter the building, the examination room, and the bathroom. The majority of sites did not have an examination table that could be lowered to wheelchair level. Most reported limited experience in working with persons with (SCI), yet they claimed to be able to assist with difficult transfers. Only one site knew about autonomic dysreflexia. Problems of accessibility appeared to be seriously compounded by the clinics' perception of how they met physical accessibility guidelines without consideration of the actual needs of persons with SCI. This study addressed the perception of accessibility as reported by clinic managers versus actual accessibility in healthcare clinics in a Midwestern metropolitan area for persons using wheelchairs. PMID:10754921

  20. Crossroads: Modern Interactive Intersections and Accessible Pedestrian Signals

    ERIC Educational Resources Information Center

    Barlow, Janet M.; Franck, Lukas

    2005-01-01

    This article discusses the interactive nature of modern actuated intersections and the effect of that interface on pedestrians who are visually impaired. Information is provided about accessible pedestrian signals (APS), the role of blindness professionals in APS installation decisions, and techniques for crossing streets with APS.

  1. Multisensory Public Access Catalogs on CD-ROM.

    ERIC Educational Resources Information Center

    Harrison, Nancy; Murphy, Brower

    1987-01-01

    BiblioFile Intelligent Catalog is a CD-ROM-based public access catalog system which incorporates graphics and sound to provide a multisensory interface and artificial intelligence techniques to increase search precision. The system can be updated frequently and inexpensively by linking hard disk drives to CD-ROM optical drives. (MES)

  2. Accessing Social Capital through the Academic Mentoring Process

    ERIC Educational Resources Information Center

    Smith, Buffy

    2007-01-01

    This article explores how mentors and mentees create and maintain social capital during the mentoring process. I employ a sociological conceptual framework and rigorous qualitative analytical techniques to examine how students of color and first-generation college students access social capital through mentoring relationships. The findings…

  3. Open Access Publishing in Astronomy

    NASA Astrophysics Data System (ADS)

    Grothkopf, U.; Meakins, S.

    2012-08-01

    Open Access (OA) in scholarly literature means the "immediate, free availability on the public internet, permitting any users to read, download, copy, distribute, print, search or link to the full text of these articles". The Open Access movement has been made possible thanks to the wide-spread availability of internet access and has received increasing interest since the 1990s, mostly due to the fast rising journal subscription prices. This presentation will review the current situation of Open Access in astronomy. It will answer the question why it makes sense to publish in an OA journal and will provide criteria to judge the quality of OA journals and publishers, along with suggestions how to identify so-called predatory publishers.

  4. Astronauts Access Web from Space

    NASA Video Gallery

    Aboard the International Space Station, Expedition 22 Commander Jeff Williams and Flight Engineers Soichi Noguchi and T.J. Creamer share their thoughts about Internet access from space and post a r...

  5. Computer Security Systems Enable Access.

    ERIC Educational Resources Information Center

    Riggen, Gary

    1989-01-01

    A good security system enables access and protects information from damage or tampering, but the most important aspects of a security system aren't technical. A security procedures manual addresses the human element of computer security. (MLW)

  6. Computer access security code system

    NASA Technical Reports Server (NTRS)

    Collins, Earl R., Jr. (Inventor)

    1990-01-01

    A security code system for controlling access to computer and computer-controlled entry situations comprises a plurality of subsets of alpha-numeric characters disposed in random order in matrices of at least two dimensions forming theoretical rectangles, cubes, etc., such that when access is desired, at least one pair of previously unused character subsets not found in the same row or column of the matrix is chosen at random and transmitted by the computer. The proper response to gain access is transmittal of subsets which complete the rectangle, and/or a parallelepiped whose opposite corners were defined by first groups of code. Once used, subsets are not used again to absolutely defeat unauthorized access by eavesdropping, and the like.

  7. UK to support open access

    NASA Astrophysics Data System (ADS)

    Banks, Michael

    2012-08-01

    The UK government has "widely accepted" the recommendations of a major report into open-access publishing that was released in June by a 15-strong working group led by the British sociologist Janet Finch.

  8. Just the Facts: Vascular Access

    MedlinePlus

    ... vein thicker so it can be used for dialysis. A fistula is often the longest-lasting access. ... Artery Graft Illustration from Core Curriculum for the Dialysis Technician , 1998 Vein A catheter is a plastic ...

  9. 10 CFR 1017.19 - Access limitations.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... INFORMATION Access to Unclassified Controlled Nuclear Information § 1017.19 Access limitations. A person may only have access to UCNI if he or she has been granted routine access by an Authorized Individual (see... 10 Energy 4 2010-01-01 2010-01-01 false Access limitations. 1017.19 Section 1017.19...

  10. 47 CFR 76.702 - Public access.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false Public access. 76.702 Section 76.702... CABLE TELEVISION SERVICE Cable Television Access § 76.702 Public access. A cable operator may refuse to transmit any public access program or portion of a public access program that the operator...

  11. 10 CFR 1017.21 - Limited access.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... INFORMATION Access to Unclassified Controlled Nuclear Information § 1017.21 Limited access. (a) A person who is not eligible for routine access to specific UCNI under § 1017.20 may request limited access to... 10 Energy 4 2010-01-01 2010-01-01 false Limited access. 1017.21 Section 1017.21 Energy...

  12. 32 CFR 154.49 - Granting access.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... SECURITY PROGRAM REGULATION Issuing Clearance and Granting Access § 154.49 Granting access. (a) Access to classified information shall be granted to persons whose official duties require such access and who have the... 32 National Defense 1 2011-07-01 2011-07-01 false Granting access. 154.49 Section 154.49...

  13. 47 CFR 76.702 - Public access.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 4 2011-10-01 2011-10-01 false Public access. 76.702 Section 76.702... CABLE TELEVISION SERVICE Cable Television Access § 76.702 Public access. A cable operator may refuse to transmit any public access program or portion of a public access program that the operator...

  14. 32 CFR 154.49 - Granting access.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... SECURITY PROGRAM REGULATION Issuing Clearance and Granting Access § 154.49 Granting access. (a) Access to classified information shall be granted to persons whose official duties require such access and who have the... 32 National Defense 1 2010-07-01 2010-07-01 false Granting access. 154.49 Section 154.49...

  15. 10 CFR 1017.21 - Limited access.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... INFORMATION Access to Unclassified Controlled Nuclear Information § 1017.21 Limited access. (a) A person who is not eligible for routine access to specific UCNI under § 1017.20 may request limited access to... 10 Energy 4 2011-01-01 2011-01-01 false Limited access. 1017.21 Section 1017.21 Energy...

  16. 10 CFR 1017.19 - Access limitations.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... INFORMATION Access to Unclassified Controlled Nuclear Information § 1017.19 Access limitations. A person may only have access to UCNI if he or she has been granted routine access by an Authorized Individual (see... 10 Energy 4 2011-01-01 2011-01-01 false Access limitations. 1017.19 Section 1017.19...

  17. 32 CFR 154.49 - Granting access.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 32 National Defense 1 2013-07-01 2013-07-01 false Granting access. 154.49 Section 154.49 National... SECURITY PROGRAM REGULATION Issuing Clearance and Granting Access § 154.49 Granting access. (a) Access to classified information shall be granted to persons whose official duties require such access and who have...

  18. 32 CFR 154.49 - Granting access.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 32 National Defense 1 2012-07-01 2012-07-01 false Granting access. 154.49 Section 154.49 National... SECURITY PROGRAM REGULATION Issuing Clearance and Granting Access § 154.49 Granting access. (a) Access to classified information shall be granted to persons whose official duties require such access and who have...

  19. 5 CFR 2606.203 - Granting access.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 5 Administrative Personnel 3 2010-01-01 2010-01-01 false Granting access. 2606.203 Section 2606... Access to Records and Accounting of Disclosures § 2606.203 Granting access. (a) The methods for allowing access to records, when such access has been granted by OGE or the other agency concerned are:...

  20. 5 CFR 2606.203 - Granting access.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 5 Administrative Personnel 3 2011-01-01 2011-01-01 false Granting access. 2606.203 Section 2606... Access to Records and Accounting of Disclosures § 2606.203 Granting access. (a) The methods for allowing access to records, when such access has been granted by OGE or the other agency concerned are:...

  1. 5 CFR 2606.203 - Granting access.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 5 Administrative Personnel 3 2012-01-01 2012-01-01 false Granting access. 2606.203 Section 2606... Access to Records and Accounting of Disclosures § 2606.203 Granting access. (a) The methods for allowing access to records, when such access has been granted by OGE or the other agency concerned are:...

  2. 5 CFR 2606.203 - Granting access.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 5 Administrative Personnel 3 2014-01-01 2014-01-01 false Granting access. 2606.203 Section 2606... Access to Records and Accounting of Disclosures § 2606.203 Granting access. (a) The methods for allowing access to records, when such access has been granted by OGE or the other agency concerned are:...

  3. 32 CFR 154.49 - Granting access.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 32 National Defense 1 2014-07-01 2014-07-01 false Granting access. 154.49 Section 154.49 National... SECURITY PROGRAM REGULATION Issuing Clearance and Granting Access § 154.49 Granting access. (a) Access to classified information shall be granted to persons whose official duties require such access and who have...

  4. Preparing for the New Remote Access.

    ERIC Educational Resources Information Center

    Taylor, William E.

    1997-01-01

    Integrated remote access servers support many different types of access. Remote access has been integrated as a strategic tool as application developers build remote access capabilities into their software. Discusses demands of using remote access as a strategic component and management matters. (AEF)

  5. 47 CFR 76.702 - Public access.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 4 2013-10-01 2013-10-01 false Public access. 76.702 Section 76.702... CABLE TELEVISION SERVICE Cable Television Access § 76.702 Public access. A cable operator may refuse to transmit any public access program or portion of a public access program that the operator...

  6. 47 CFR 76.702 - Public access.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 4 2014-10-01 2014-10-01 false Public access. 76.702 Section 76.702... CABLE TELEVISION SERVICE Cable Television Access § 76.702 Public access. A cable operator may refuse to transmit any public access program or portion of a public access program that the operator...

  7. Holistic Approaches to E-Learning Accessibility

    ERIC Educational Resources Information Center

    Phipps, Lawrie; Kelly, Brian

    2006-01-01

    The importance of accessibility to digital e-learning resources is widely acknowledged. The World Wide Web Consortium Web Accessibility Initiative has played a leading role in promoting the importance of accessibility and developing guidelines that can help when developing accessible web resources. The accessibility of e-learning resources…

  8. Accessible solitons of fractional dimension

    NASA Astrophysics Data System (ADS)

    Zhong, Wei-Ping; Belić, Milivoj; Zhang, Yiqi

    2016-05-01

    We demonstrate that accessible solitons described by an extended Schrödinger equation with the Laplacian of fractional dimension can exist in strongly nonlocal nonlinear media. The soliton solutions of the model are constructed by two special functions, the associated Legendre polynomials and the Laguerre polynomials in the fraction-dimensional space. Our results show that these fractional accessible solitons form a soliton family which includes crescent solitons, and asymmetric single-layer and multi-layer necklace solitons.

  9. [The concepts of health access].

    PubMed

    Sanchez, Raquel Maia; Ciconelli, Rozana Mesquita

    2012-03-01

    This article describes four dimensions of health access-availability, acceptability, ability to pay and information-correlating these dimensions to indicators and discussing the complexity of the concept of access. For a study of these four dimensions, searches were conducted using the PubMed/MEDLINE, LILACS, SciELO, and World Health Organization Library & Information Networks for Knowledge (WHOLIS) databases. Large-circulation media vehicles, such as The Economist, The Washington Post, and the BBC network were also searched. The concept of health access has become more complex with time. The first analyses, carried out in the 1970s, suggested a strong emphasis on geographical (availability) and financial (ability to pay) aspects. More recently, the literature has focused on less tangible aspects, such as cultural, educational, and socioeconomic issues, incorporating the element of acceptability into the notion of health access. The literature also shows that information provides the starting point for access to health, in association with health empowerment and literacy for health care decision-making. The study concludes that improvements in access to health and the guarantee of equity will not be achieved by initiatives focusing on health care systems alone, but rather will depend on intersectoral actions and social and economic policies aimed at eliminating income and education differences. PMID:22569702

  10. Memory availability and referential access

    PubMed Central

    Johns, Clinton L.; Gordon, Peter C.; Long, Debra L.; Swaab, Tamara Y.

    2013-01-01

    Most theories of coreference specify linguistic factors that modulate antecedent accessibility in memory; however, whether non-linguistic factors also affect coreferential access is unknown. Here we examined the impact of a non-linguistic generation task (letter transposition) on the repeated-name penalty, a processing difficulty observed when coreferential repeated names refer to syntactically prominent (and thus more accessible) antecedents. In Experiment 1, generation improved online (event-related potentials) and offline (recognition memory) accessibility of names in word lists. In Experiment 2, we manipulated generation and syntactic prominence of antecedent names in sentences; both improved online and offline accessibility, but only syntactic prominence elicited a repeated-name penalty. Our results have three important implications: first, the form of a referential expression interacts with an antecedent’s status in the discourse model during coreference; second, availability in memory and referential accessibility are separable; and finally, theories of coreference must better integrate known properties of the human memory system. PMID:24443621

  11. Translaminar lumbar epidural endoscopy: anatomy, technique, and indications.

    PubMed

    De Antoni, D J; Claro, M L; Poehling, G G; Hughes, S S

    1996-06-01

    This article describes a new technique to achieve access to the epidural space via a direct posterior portal. This minimally invasive technique allows treatment of disc protrusions and extrusions with full visualization and minimal dissection of the paraspinal musculature. Hemostasis, visualization, and triangulation is performed with standard arthroscopic instrumentation. The anatomy of, indications for, and advantages of this techniques are described. PMID:8783828

  12. Safety and Efficacy of Laparoscopic Access in a Surgical Training Program.

    PubMed

    Johnson, Timothy G; Hooks, William B; Adams, Ashley; Hope, William W

    2016-02-01

    Our study evaluated outcomes of laparoscopic access in a surgical residency program and identified variables associated with adverse outcomes. Following IRB approval, we reviewed prospectively collected data from consecutive laparoscopic surgeries from a single surgeon August 2008 to November 2011. Descriptive statistics were generated, and successful and unsuccessful access techniques were compared using the t test, Fisher exact test, and χ test of independence, with P<0.05 considered significant. Five hundred consecutive laparoscopic surgeries were evaluated; the average patient age was 47 years and 55% of patients were female. The most common procedures included laparoscopic cholecystectomy (29%), laparoscopic ventral hernia (15%), laparoscopic appendectomy (12%), laparoscopic colon/small bowel (11%), and laparoscopic inguinal hernia (10%). Successful laparoscopic access was obtained in 98% of patients. The most common access techniques were umbilical stalk technique (57%) and Veress followed by optical trocar technique (29%). The complication rate was 7% and included multiple access attempts in 3.4%, attending physician having to take over access in 1.6%, bleeding/solid organ injury in 0.8%, insufflating peritoneum in 0.6%, and bowel injury in 0.2%. There was a significant relationship between entry technique and failure rate. Open cutdown away from umbilicus had a higher failure rate than other techniques (P=0.0002). There was also a significant relationship between type of surgery and failure rate of technique, with laparoscopic ventral hernia and laparoscopic small bowel cases having the highest failure rate (P=0.005). We observed no difference in success rate based on age, sex, race, previous surgery, and resident training level (P>0.05). Laparoscopic access using appropriate techniques can be safely performed in a residency training program. Laparoscopic ventral hernia and small bowel procedures for obstruction can be difficult cases to obtain access, and

  13. Biomass accessibility analysis using electron tomography

    SciTech Connect

    Hinkle, Jacob D.; Ciesielski, Peter N.; Gruchalla, Kenny; Munch, Kristin R.; Donohoe, Bryon S.

    2015-12-25

    Substrate accessibility to catalysts has been a dominant theme in theories of biomass deconstruction. Furthermore, current methods of quantifying accessibility do not elucidate mechanisms for increased accessibility due to changes in microstructure following pretreatment.

  14. 36 CFR 9.32 - Access.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... CFR 2.17. (d) No access to a site outside a unit will be permitted across unit lands unless such access is by foot, pack animal, or designated road. Persons using designated roads for access to such...

  15. 36 CFR 9.32 - Access.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... CFR 2.17. (d) No access to a site outside a unit will be permitted across unit lands unless such access is by foot, pack animal, or designated road. Persons using designated roads for access to such...

  16. 36 CFR 9.32 - Access.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... CFR 2.17. (d) No access to a site outside a unit will be permitted across unit lands unless such access is by foot, pack animal, or designated road. Persons using designated roads for access to such...

  17. 36 CFR 9.32 - Access.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... CFR 2.17. (d) No access to a site outside a unit will be permitted across unit lands unless such access is by foot, pack animal, or designated road. Persons using designated roads for access to such...

  18. Abridged Technique for Precise Implant Angulation.

    PubMed

    Perumal, Praveen; Chander, Gopi Naveen; Viswanathan, Anitha Kuttae; Reddy, Ramesh; Muthukumar, B

    2015-12-01

    Enormous scientific knowledge with evidence and clinical dexterity impart definitive ground for success in implant dentistry. Nevertheless, the unfeasibility to access the inner bone tissue makes the situation altogether more demanding. Presently the advent of numerous imaging techniques and associated surgical guide templates are documented for evaluation of implant angulation. However, they are not cost effective and consume more time to plan and design the structure. This article describes a simple concise technique for precise implant angulation. PMID:26816997

  19. Abridged Technique for Precise Implant Angulation

    PubMed Central

    Perumal, Praveen; Chander, Gopi Naveen; Reddy, Ramesh; Muthukumar, B.

    2015-01-01

    Enormous scientific knowledge with evidence and clinical dexterity impart definitive ground for success in implant dentistry. Nevertheless, the unfeasibility to access the inner bone tissue makes the situation altogether more demanding. Presently the advent of numerous imaging techniques and associated surgical guide templates are documented for evaluation of implant angulation. However, they are not cost effective and consume more time to plan and design the structure. This article describes a simple concise technique for precise implant angulation. PMID:26816997

  20. Oversize Color Images Project, 1994-1995. A Report to the Commission on Preservation and Access.

    ERIC Educational Resources Information Center

    Gertz, Janet

    This report provides results of the first phase of a project to identify acceptable preservation and digital access techniques for dealing with oversize, color images associated with text. The goal of Phase I was to provide a preservation-quality photographic archival copy, a digital version for online access, and paper printouts. Five maps from…

  1. Fiber-wireless (FiWi) access networks for a green video-dominated future internet

    NASA Astrophysics Data System (ADS)

    Maier, Martin

    2010-12-01

    We report on our ongoing research activities on integrated EPON and WLAN-based wireless mesh networks with a focus on reducing the CO2 footprint and improving the bandwidth-efficient video transport of fiber-wireless (FiWi) access networks. Various power saving techniques and mechanisms for efficient video transport in FiWi access networks are discussed.

  2. WWW--Wealth, Weariness or Waste. Controlled Vocabulary and Thesauri in Support of Online Information Access.

    ERIC Educational Resources Information Center

    Batty, David

    1998-01-01

    Discusses the problems of access to information in a machine-sensible environment, and the potential of modern library techniques to help in solving them. Explains how authors and publishers can make information more accessible by providing indexing information that uses controlled vocabulary, terms from a thesaurus, or other linguistic assistance…

  3. Defining Reading Proficiency for Accessible Large-Scale Assessments: Some Guiding Principles and Issues

    ERIC Educational Resources Information Center

    National Accessible Reading Assessment Projects, 2006

    2006-01-01

    The National Accessible Reading Assessment Projects (NARAP) is a collaboration of two projects funded by the U.S. Department of Education to conduct research and development on accessible reading assessments for students with disabilities that affect reading. The goal of these projects is to produce research findings and assessment techniques that…

  4. United States Federal Health Care Websites: A Multimethod Evaluation of Website Accessibility for Individuals with Disabilities

    ERIC Educational Resources Information Center

    Brobst, John L.

    2012-01-01

    The problem addressed by this study is the observed low levels of compliance with federal policy on website accessibility. The study examines the two key federal policies that promote website accessibility, using a side-by-side policy analysis technique. The analysis examines the Americans with Disabilities Act of 1990 and Section 508 of the…

  5. Using Motion Planning to Determine the Existence of an Accessible Route in a CAD Environment

    ERIC Educational Resources Information Center

    Pan, Xiaoshan; Han, Charles S.; Law, Kincho H.

    2010-01-01

    We describe an algorithm based on motion-planning techniques to determine the existence of an accessible route through a facility for a wheeled mobility device. The algorithm is based on LaValle's work on rapidly exploring random trees and is enhanced to take into consideration the particularities of the accessible route domain. Specifically, the…

  6. [Intraosseous access in adults--an alternative if conventional vascular access is difficult?].

    PubMed

    Isbye, Dan Lou; Nielsen, Søren Loumann

    2006-08-21

    Intraosseous infusion is widely used in children, but its use in adults is much less common. This is probably because another vascular access can usually be achieved, and also because of lack of knowledge of the technique. Placement in adults is a quick procedure with a high rate of success. Drugs and fluids do not change the pharmacodynamics or pharmacokinetics of intraosseous administration, and anything can be given. Infusion rates have been achieved that in part make fluid resuscitation possible. Its uses are many and the contraindications few; complications are rare when simple guidelines are followed. PMID:16942698

  7. Fluoroscopy guided percutaneous renal access in prone position

    PubMed Central

    Sharma, Gyanendra R; Maheshwari, Pankaj N; Sharma, Anshu G; Maheshwari, Reeta P; Heda, Ritwik S; Maheshwari, Sakshi P

    2015-01-01

    Percutaneous nephrolithotomy is a very commonly done procedure for management of renal calculus disease. Establishing a good access is the first and probably the most crucial step of this procedure. A proper access is the gateway to success. However, this crucial step has the steepest learning curve for, in a fluoroscopy guided access, it involves visualizing a three dimensional anatomy on a two dimensional fluoroscopy screen. This review describes the anatomical basis of the renal access. It provides a literature review of all aspects of percutaneous renal access along with the advances that have taken place in this field over the years. The article describes a technique to determine the site of skin puncture, the angle and depth of puncture using a simple mathematical principle. It also reviews the common problems faced during the process of puncture and dilatation and describes the ways to overcome them. The aim of this article is to provide the reader a step by step guide for percutaneous renal access. PMID:25789297

  8. Fluoroscopy guided percutaneous renal access in prone position.

    PubMed

    Sharma, Gyanendra R; Maheshwari, Pankaj N; Sharma, Anshu G; Maheshwari, Reeta P; Heda, Ritwik S; Maheshwari, Sakshi P

    2015-03-16

    Percutaneous nephrolithotomy is a very commonly done procedure for management of renal calculus disease. Establishing a good access is the first and probably the most crucial step of this procedure. A proper access is the gateway to success. However, this crucial step has the steepest learning curve for, in a fluoroscopy guided access, it involves visualizing a three dimensional anatomy on a two dimensional fluoroscopy screen. This review describes the anatomical basis of the renal access. It provides a literature review of all aspects of percutaneous renal access along with the advances that have taken place in this field over the years. The article describes a technique to determine the site of skin puncture, the angle and depth of puncture using a simple mathematical principle. It also reviews the common problems faced during the process of puncture and dilatation and describes the ways to overcome them. The aim of this article is to provide the reader a step by step guide for percutaneous renal access. PMID:25789297

  9. Emergency access authorization for personally controlled online health care data.

    PubMed

    Chen, Tingting; Zhong, Sheng

    2012-02-01

    Personally controlled health records (PCHR) systems have emerged to allow patients to control their own medical data. In a PCHR system, all the access privileges to a patient's data are granted by the patient. However, in many emergency cases, it is impossible for the patient to participate in access authorization on site when immediate medical treatment is needed. To solve the emergency access authorization problem in the absence of patients, we consider two cases: a) the requester is already in the PCHR system but has not obtained the access privilege of the patient's health records, and b) the requester does not even have an account in the PCHR system to submit its request. For each of the two cases, we present a method for emergency access authorization, utilizing the weighted voting and source authentication cryptographic techniques. Our methods provide an effective, secure and private solution for emergency access authorization, that makes the existing PCHR system frameworks more practical and thus improves the patients' experiences of health care when using PCHR systems. We have implemented a prototype system as a proof of concept. PMID:20703719

  10. Three essays on access pricing

    NASA Astrophysics Data System (ADS)

    Sydee, Ahmed Nasim

    In the first essay, a theoretical model is developed to determine the time path of optimal access price in the telecommunications industry. Determining the optimal access price is an important issue in the economics of telecommunications. Setting a high access price discourages potential entrants; a low access price, on the other hand, amounts to confiscation of private property because the infrastructure already built by the incumbent is sunk. Furthermore, a low access price does not give the incumbent incentives to maintain the current network and to invest in new infrastructures. Much of the existing literature on access pricing suffers either from the limitations of a static framework or from the assumption that all costs are avoidable. The telecommunications industry is subject to high stranded costs and, therefore, to address this issue a dynamic model is imperative. This essay presents a dynamic model of one-way access pricing in which the compensation involved in deregulatory taking is formalized and then analyzed. The short run adjustment after deregulatory taking has occurred is carried out and discussed. The long run equilibrium is also analyzed. A time path for the Ramsey price is shown as the correct dynamic price of access. In the second essay, a theoretical model is developed to determine the time path of optimal access price for an infrastructure that is characterized by congestion and lumpy investment. Much of the theoretical literature on access pricing of infrastructure prescribes that the access price be set at the marginal cost of the infrastructure. In proposing this rule of access pricing, the conventional analysis assumes that infrastructure investments are infinitely divisible so that it makes sense to talk about the marginal cost of investment. Often it is the case that investments in infrastructure are lumpy and can only be made in large chunks, and this renders the marginal cost concept meaningless. In this essay, we formalize a model of

  11. Efficient Multi Secret Sharing with Generalized Access Structures

    NASA Astrophysics Data System (ADS)

    VP, Binu; A, Sreekumar

    2014-03-01

    Multi-secret sharing is an extension of secret sharing technique where several secrets are shared between the participants, each according to a specified access structure. The secrets can be reconstructed according to the access structure by participants using their private shares.Each participant has to hold a single share, additional information are made available in a public bulletin board.The scheme is computationally efficient and also each participant can verify the shares of the other participants and also the reconstructed secret.The scheme does not need any secure channel also.

  12. Mechanisms that improve referential access.

    PubMed

    Gernsbacher, M A

    1989-07-01

    Two mechanisms, suppression and enhancement, are proposed to improve referential access. Enhancement improves the accessibility of previously mentioned concepts by increasing or boosting their activation; suppression improves concepts' accessibility by decreasing or dampening the activation of other concepts. Presumably, these mechanisms are triggered by the informational content of anaphors. Six experiments investigated this proposal by manipulating whether an anaphoric reference was made with a very explicit, repeated name anaphor or a less explicit pronoun. Subjects read sentences that introduced two participants in their first clauses, for example, "Ann predicted that Pam would lose the track race," and the sentences referred to one of the two participants in their second clauses, "but Pam/she came in first very easily." While subjects read each sentence, the activation level of the two participants was measured by a probe verification task. The first two experiments demonstrated that explicit, repeated name anaphors immediately trigger the enhancement of their own antecedents and immediately trigger the suppression of other (nonantecedent) participants. The third experiment demonstrated that less explicit, pronoun anaphors also trigger the suppression of other nonantecedents, but they do so less quickly--even when, as in the fourth experiment, the semantic information to identify their antecedents occurs prior to the pronouns (e.g., "Ann predicted that Pam would lose the track race. But after winning the race, she..."). The fifth experiment demonstrated that more explicit pronouns--pronouns that match the gender of only one participant-trigger suppression more powerfully. A final experiment demonstrated that it is not only rementioned participants who improve their referential access by triggering the suppression of other participants; newly introduced participants do so too (e.g., "Ann predicted that Pam would lose the track race, but Kim..."). Thus, both

  13. ACCESSING HDF DATA VIA OPENDAP

    NASA Astrophysics Data System (ADS)

    Yang, M.; Lee, H.; Folk, M. J.

    2009-12-01

    HDF is a set of data formats and software libraries for storing scientific data with an emphasis on standards, storage, and I/O efficiency. The HDF-EOS version 2 (HDF-EOS2) profile and library, built on top of HDF version 4 (HDF4), define and implement the standard data format for the NASA Earth Science Data and Information System (ESDIS). Since the launch of Terra in 1999, the EOS Data and Information System (EOSDIS) has produced more than three terabytes of EOS earth science data daily. More than five hundred data products in NASA data centers are stored in HDF4. HDF5 is a newer data format. It has been embraced as an important data format for Earth science, HDF-EOS5, which is built on top of HDF5, is the primary data format for data from the Aura satellite. HDF5 is being used as the data format for data products produced from the National Polar Orbiting Environmental Satellite System (NPOESS). The newer version of netCDF, netCDF-4, is built on top of HDF5. The OPeNDAP Data Access Protocol (DAP) and its related software (servers and clients) have emerged as important components of the earth science data system infrastructure. The OPeNDAP protocol is widely used to remotely access earth science data. Several third-party visualization and analysis tools that can read data from OPeNDAP servers, such as IDV, GrADS, Ferret, NCL, MATLAB, and IDL, are widely used by many earth scientists, researchers, and educators to access HDF earth science data. Ensuring easy access to HDF4, HDF5 and HDF-EOS data via the above tools through OPeNDAP will reduce the time for HDF users to visualize the data in their favorite way and improve their working efficiencies accordingly. In the past two years, under the support of NASA ESDIS and ACCESS projects, The HDF Group implemented the HDF5-OPeNDAP data handler so that some NASA HDF-EOS5 Aura Swath and Grid data can be accessed by widely used visualization and analysis tools such as IDV, GrADS, Ferret, NCL and IDL via OPeNDAP. The HDF

  14. PDA-phone-based instant transmission of radiological images over a CDMA network by combining the PACS screen with a Bluetooth-interfaced local wireless link.

    PubMed

    Kim, Dong Keun; Yoo, Sun K; Park, Jeong Jin; Kim, Sun Ho

    2007-06-01

    Remote teleconsultation by specialists is important for timely, correct, and specialized emergency surgical and medical decision making. In this paper, we designed a new personal digital assistant (PDA)-phone-based emergency teleradiology system by combining cellular communication with Bluetooth-interfaced local wireless links. The mobility and portability resulting from the use of PDAs and wireless communication can provide a more effective means of emergency teleconsultation without requiring the user to be limited to a fixed location. Moreover, it enables synchronized radiological image sharing between the attending physician in the emergency room and the remote specialist on picture archiving and communication system terminals without distorted image acquisition. To enable rapid and fine-quality radiological image transmission over a cellular network in a secure manner, progressive compression and security mechanisms have been incorporated. The proposed system is tested over a code division Multiple Access 1x-Evolution Data-Only network to evaluate the performance and to demonstrate the feasibility of this system in a real-world setting. PMID:17505870

  15. Single port access holographic particle image velocimetry

    SciTech Connect

    Woodruff, S.D.; Richards, G.A.; Cha, D.J.

    1995-07-01

    An optical system, which requires only a single optical window mounted on a test volume, is proposed for holographic particle image velocimetry (HPIV). The optical system is a derivative of the double-exposure, double-reference-beam, off-axis HPIV system, but the innovative idea behind the system is to use back scattered light from the particles as the object wave. A 45{degree} beam splitter inserted in front of the window serves to admit the illuminating beam and extract the back scattered light. This concept can be of great engineering interest because optical access is often limited to one window in practical devices. The preliminary results of the technique appear quite promising, with current studies aimed at defining the optical resolution capabilities.

  16. An open access thyroid ultrasound image database

    NASA Astrophysics Data System (ADS)

    Pedraza, Lina; Vargas, Carlos; Narváez, Fabián.; Durán, Oscar; Muñoz, Emma; Romero, Eduardo

    2015-01-01

    Computer aided diagnosis systems (CAD) have been developed to assist radiologists in the detection and diagnosis of abnormalities and a large number of pattern recognition techniques have been proposed to obtain a second opinion. Most of these strategies have been evaluated using different datasets making their performance incomparable. In this work, an open access database of thyroid ultrasound images is presented. The dataset consists of a set of B-mode Ultrasound images, including a complete annotation and diagnostic description of suspicious thyroid lesions by expert radiologists. Several types of lesions as thyroiditis, cystic nodules, adenomas and thyroid cancers were included while an accurate lesion delineation is provided in XML format. The diagnostic description of malignant lesions was confirmed by biopsy. The proposed new database is expected to be a resource for the community to assess different CAD systems.

  17. Access to Vocational Education. A Planning System for Local Secondary and Post-Secondary Program and Facility Accessibility. Step 3: Generating Strategies.

    ERIC Educational Resources Information Center

    Rice, Eric; And Others

    This guidebook focuses on the third of five steps included in a planning system for improving local secondary and postsecondary program and facilities accessibility: generating strategies. The guidebook is comprised of four sections, each describing a specific technique for generating strategies. Techniques presented are (1) nominal group…

  18. An energy-efficient and elastic optical multiple access system based on coherent interleaved frequency division multiple access.

    PubMed

    Yoshida, Yuki; Maruta, Akihiro; Ishii, Kenji; Akiyama, Yuji; Yoshida, Tsuyoshi; Suzuki, Naoki; Koguchi, Kazuumi; Nakagawa, Junichi; Mizuochi, Takashi; Kitayama, Ken-ichi

    2013-05-20

    This paper proposes a novel bandwidth-elastic and energy-efficient passive optical network (PON) based on the coherent interleaved frequency division multiple access (IFDMA) scheme. We experimentally demonstrate the coherent IFDMA-PON uplink transmission up-to 30 Gbps over a 30 km standard single-mode fiber with 2 × optical network units (ONUs). A low-complexity digital carrier synchronization technique enables multiple access of the ONUs on the basis of 78.1 MHz narrow band orthogonal subcarriers without any guard-bands. PMID:23736447

  19. Progress of solid-phase microextraction coatings and coating techniques.

    PubMed

    Jiang, Guibin; Huang, Minjia; Cai, Yaqi; Lv, Jianxia; Zhao, Zongshan

    2006-07-01

    Solid-phase microextraction (SPME) has been popular as an environmentally friendly sample pretreatment technique to extract a very wide range of analytes. This is partly owing to the development of SPME coatings. One of the key factors affecting the extraction performances, such as the sensitivity, selectivity, and reproducibility, is the properties of the coatings on SPME fibers. This paper classifies the materials used as SPME coatings and introduces some common preparation techniques of SPME coating in detail, such as sol-gel technique, electrochemical polymerization technique, particle direct pasting technique, restricted access matrix SPME technique, and molecularly imprinted SPME technique. PMID:16884587

  20. 32 CFR 2400.25 - Access.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... § 2400.25 Access. (a) A person is eligible for access to classified information provided that a... established by the head of each office to prevent access to classified information before a personnel security clearance has been granted. The number of people cleared and granted access to classified information...