Sample records for access cdma techniques

  1. Traffic handling capability of a broadband indoor wireless network using CDMA multiple access

    NASA Astrophysics Data System (ADS)

    Zhang, Chang G.; Hafez, H. M.; Falconer, David D.

    1994-05-01

    CDMA (code division multiple access) may be an attractive technique for wireless access to broadband services because of its multiple access simplicity and other appealing features. In order to investigate traffic handling capabilities of a future network providing a variety of integrated services, this paper presents a study of a broadband indoor wireless network supporting high-speed traffic using CDMA multiple access. The results are obtained through the simulation of an indoor environment and the traffic capabilities of the wireless access to broadband 155.5 MHz ATM-SONET networks using the mm-wave band. A distributed system architecture is employed and the system performance is measured in terms of call blocking probability and dropping probability. The impacts of the base station density, traffic load, average holding time, and variable traffic sources on the system performance are examined. The improvement of system performance by implementing various techniques such as handoff, admission control, power control and sectorization are also investigated.

  2. 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.

  3. Performance, implementation and network management techniques for a European CDMA-based land-mobile satellite system

    NASA Astrophysics Data System (ADS)

    Arenaccio, S.; Vernucci, A.; Padovani, R.; Arcidiacono, A.

    Results of a detailed comparative performance assessment between two candidate access solutions for the provision of land-mobile services, i.e., FDMA and CDMA, for the European Land-Mobile Satellite Services (LMSS) provision are presented. The design of the CDMA access system and the network architecture, system procedures, network control, operation in fading environments, and implementation aspects of the system are described. The CDMA system is shown to yield superior traffic capability, despite the absence of polarization reuse due to payload design, especially in the second-generation era (multiple spot-beams). In this case, the advantage was found to be largely dependent on the traffic distribution across spot beams. Power control techniques are proposed to cope with the geographical disadvantage suffered by mobile stations located at the beam borders to compensate for fadings.

  4. Development of the Average Likelihood Function for Code Division Multiple Access (CDMA) Using BPSK and QPSK Symbols

    DTIC Science & Technology

    2015-01-01

    This research has the purpose to establish a foundation for new classification and estimation of CDMA signals. Keywords: DS / CDMA signals, BPSK, QPSK...DEVELOPMENT OF THE AVERAGE LIKELIHOOD FUNCTION FOR CODE DIVISION MULTIPLE ACCESS ( CDMA ) USING BPSK AND QPSK SYMBOLS JANUARY 2015...To) OCT 2013 – OCT 2014 4. TITLE AND SUBTITLE DEVELOPMENT OF THE AVERAGE LIKELIHOOD FUNCTION FOR CODE DIVISION MULTIPLE ACCESS ( CDMA ) USING BPSK

  5. Average Likelihood Methods for Code Division Multiple Access (CDMA)

    DTIC Science & Technology

    2014-05-01

    lengths in the range of 22 to 213 and possibly higher. Keywords: DS / CDMA signals, classification, balanced CDMA load, synchronous CDMA , decision...likelihood ratio test (ALRT). We begin this classification problem by finding the size of the spreading matrix that generated the DS - CDMA signal. As...Theoretical Background The classification of DS / CDMA signals should not be confused with the problem of multiuser detection. The multiuser detection deals

  6. 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.

  7. 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.

  8. 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

  9. Multiple Access Interference Reduction Using Received Response Code Sequence for DS-CDMA UWB System

    NASA Astrophysics Data System (ADS)

    Toh, Keat Beng; Tachikawa, Shin'ichi

    This paper proposes a combination of novel Received Response (RR) sequence at the transmitter and a Matched Filter-RAKE (MF-RAKE) combining scheme receiver system for the Direct Sequence-Code Division Multiple Access Ultra Wideband (DS-CDMA UWB) multipath channel model. This paper also demonstrates the effectiveness of the RR sequence in Multiple Access Interference (MAI) reduction for the DS-CDMA UWB system. It suggests that by using conventional binary code sequence such as the M sequence or the Gold sequence, there is a possibility of generating extra MAI in the UWB system. Therefore, it is quite difficult to collect the energy efficiently although the RAKE reception method is applied at the receiver. The main purpose of the proposed system is to overcome the performance degradation for UWB transmission due to the occurrence of MAI during multiple accessing in the DS-CDMA UWB system. The proposed system improves the system performance by improving the RAKE reception performance using the RR sequence which can reduce the MAI effect significantly. Simulation results verify that significant improvement can be obtained by the proposed system in the UWB multipath channel models.

  10. Coherent/Noncoherent Detection of Coherent Optical Heterodyne DPSK-CDMA and MFSK-CDMA Signals

    DTIC Science & Technology

    1991-12-01

    AD-A246 215 NAVAL POSTGRADUATE SCHOOL Monterey, Californla DTI THESIS COHERENT/ NONCOHERENT DETECTION OF COHERENT OPTICAL HETERODYNE DPSK-CDMA AND...NO ~ ACCESSION NO 11TILE(ncud S~riy ~a~fiat~r)COHERENT/ NONCOHERENT DETECTION OF COHERENT OPTICAL HETERODYNE DPSK-CDMA AND MFSK-CDMA SIGNALS 12 PERSONAL...early optical fiber communication systems. Gas lasers are also disregarded for practical systems due to size and safety considerations, even though

  11. The Effects of Spatial Diversity and Imperfect Channel Estimation on Wideband MC-DS-CDMA and MC-CDMA

    DTIC Science & Technology

    2009-10-01

    In our previous work, we compared the theoretical bit error rates of multi-carrier direct sequence code division multiple access (MC- DS - CDMA ) and...consider only those cases where MC- CDMA has higher frequency diversity than MC- DS - CDMA . Since increases in diversity yield diminishing gains, we conclude

  12. A narrowband CDMA communications payload for little LEOS applications

    NASA Astrophysics Data System (ADS)

    Michalik, H.; Hävecker, W.; Ginati, A.

    1996-09-01

    In recent years Code Division Multiple Access (CDMA) techniques have been investigated for application in Local Area Networks [J. A. Salehi, IEEE Trans. Commun. 37 (1989)]as well as in Mobile Communications [R. Kohno et al., IEEE Commun. Mag. Jan (1995)]. The main attraction of these techniques is due to potential higher throughput and capacity of such systems under certain conditions compared to conventional multi-access schemes like frequency and time division multiplexing. Mobile communication over a Satellite Link represents in some terms the "worst case" for operating a CDMA-system. Considering e.g. the uplink case from mobile to satellite, the imperfections due to different and time varying channel conditions will add to the well known effects of Multiple Access Interference (MAI) between the simultaneously active users at the satellite receiver. In addition, bandwidth constraints due to the non-availability of large bandwidth channels in the interesting frequency bands, exist for small systems. As a result, for a given service in terms of user data rates, the practical code sequence lengths are limited as well as the available number of codes within a code set. In this paper a communications payload for Small Satellite Applications with CDMA uplink and C/TDMA downlink under the constraint of bandwidth limitations is proposed. To optimise the performance under the above addressed imperfections the system provides ability for power control and synchronisation for the CDMA uplink. The major objectives of this project are studying, development and testing of such a system for educational purposes and technology development at Hochschule Bremen.

  13. Optical CDMA components requirements

    NASA Astrophysics Data System (ADS)

    Chan, James K.

    1998-08-01

    Optical CDMA is a complementary multiple access technology to WDMA. Optical CDMA potentially provides a large number of virtual optical channels for IXC, LEC and CLEC or supports a large number of high-speed users in LAN. In a network, it provides asynchronous, multi-rate, multi-user communication with network scalability, re-configurability (bandwidth on demand), and network security (provided by inherent CDMA coding). However, optical CDMA technology is less mature in comparison to WDMA. The components requirements are also different from WDMA. We have demonstrated a video transport/switching system over a distance of 40 Km using discrete optical components in our laboratory. We are currently pursuing PIC implementation. In this paper, we will describe the optical CDMA concept/features, the demonstration system, and the requirements of some critical optical components such as broadband optical source, broadband optical amplifier, spectral spreading/de- spreading, and fixed/programmable mask.

  14. Asynchronous, Decentralized DS-CDMA Using Feedback-Controlled Spreading Sequences for Time-Dispersive Channels

    NASA Astrophysics Data System (ADS)

    Miyatake, Teruhiko; Chiba, Kazuki; Hamamura, Masanori; Tachikawa, Shin'ichi

    We propose a novel asynchronous direct-sequence codedivision multiple access (DS-CDMA) using feedback-controlled spreading sequences (FCSSs) (FCSS/DS-CDMA). At the receiver of FCSS/DS-CDMA, the code-orthogonalizing filter (COF) produces a spreading sequence, and the receiver returns the spreading sequence to the transmitter. Then the transmitter uses the spreading sequence as its updated version. The performance of FCSS/DS-CDMA is evaluated over time-dispersive channels. The results indicate that FCSS/DS-CDMA greatly suppresses both the intersymbol interference (ISI) and multiple access interference (MAI) over time-invariant channels. FCSS/DS-CDMA is applicable to the decentralized multiple access.

  15. 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.

  16. Adaptive beamforming in a CDMA mobile satellite communications system

    NASA Astrophysics Data System (ADS)

    Munoz-Garcia, Samuel G.

    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.

  17. 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.

  18. 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

  19. Iterative Overlap FDE for Multicode DS-CDMA

    NASA Astrophysics Data System (ADS)

    Takeda, Kazuaki; Tomeba, Hiromichi; Adachi, Fumiyuki

    Recently, a new frequency-domain equalization (FDE) technique, called overlap FDE, that requires no GI insertion was proposed. However, the residual inter/intra-block interference (IBI) cannot completely be removed. In addition to this, for multicode direct sequence code division multiple access (DS-CDMA), the presence of residual interchip interference (ICI) after FDE distorts orthogonality among the spreading codes. In this paper, we propose an iterative overlap FDE for multicode DS-CDMA to suppress both the residual IBI and the residual ICI. In the iterative overlap FDE, joint minimum mean square error (MMSE)-FDE and ICI cancellation is repeated a sufficient number of times. The bit error rate (BER) performance with the iterative overlap FDE is evaluated by computer simulation.

  20. 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.

  1. 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

  2. Adaptive digital beamforming for a CDMA mobile communications payload

    NASA Astrophysics Data System (ADS)

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

    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

  3. 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.

  4. 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.

  5. 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.

  6. A CDMA system implementation with dimming control for visible light communication

    NASA Astrophysics Data System (ADS)

    Chen, Danyang; Wang, Jianping; Jin, Jianli; Lu, Huimin; Feng, Lifang

    2018-04-01

    Visible light communication (VLC), using solid-state lightings to transmit information, has become a complement technology to wireless radio communication. As a realistic multiple access scheme for VLC system, code division multiple access (CDMA) has attracted more and more attentions in recent years. In this paper, we address and implement an improved CDMA scheme for VLC system. The simulation results reveal that the improved CDMA scheme not only supports multi-users' transmission but also maintains dimming value at about 50% and enhances the system efficiency. It can also realize the flexible dimming control by adjusting some parameters of system structure, which rarely affects the system BER performance. A real-time experimental VLC system with improved CDMA scheme is performed based on field programmable gate array (FPGA), reaching a good BER performance.

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

    NASA Astrophysics Data System (ADS)

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

    2004-05-01

    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).

  8. Multiple access techniques and spectrum utilization of the GLOBALSTAR mobile satellite system

    NASA Astrophysics Data System (ADS)

    Louie, Ming; Cohen, Michel; Rouffet, Denis; Gilhousen, Klein S.

    The GLOBALSTAR System is a Low Earth Orbit (LEO) satellite-based mobile communications system that is interoperable with the current and future Public Land Mobile Network (PLMN). The GLOBALSTAR System concept is based upon technological advancement in two key areas: (1) the advancement in LEO satellite technology; (2) the advancement in cellular telephone technology, including the commercial applications of Code Division Multiple Access (CDMA) technologies, and of the most recent progress in Time Division Multiple Access technologies. The GLOBALSTAR System uses elements of CDMA, Frequency Division Multiple Access (FDMA), and Time Division Multiple Access (TDMA) technology, combining with satellite Multiple Beam Antenna (MBA) technology, to arrive at one of the most efficient modulation and multiple access system ever proposed for a satellite communications system. The technology used in GLOBALSTAR exploits the following techniques in obtaining high spectral efficiency and affordable cost per channel, with minimum coordination among different systems: power control, in open and closed loops, voice activation, spot beam satellite antenna for frequency reuse, weighted satellite antenna gain, multiple satellite coverage, and handoff between satellites. The GLOBALSTAR system design will use the following frequency bands: 1610-1626.5 MHz for up-link and 2483.5-2500 MHz for down-link.

  9. Demonstration of the CDMA-mode CAOS smart camera.

    PubMed

    Riza, Nabeel A; Mazhar, Mohsin A

    2017-12-11

    Demonstrated is the code division multiple access (CDMA)-mode coded access optical sensor (CAOS) smart camera suited for bright target scenarios. Deploying a silicon CMOS sensor and a silicon point detector within a digital micro-mirror device (DMD)-based spatially isolating hybrid camera design, this smart imager first engages the DMD starring mode with a controlled factor of 200 high optical attenuation of the scene irradiance to provide a classic unsaturated CMOS sensor-based image for target intelligence gathering. Next, this CMOS sensor provided image data is used to acquire a focused zone more robust un-attenuated true target image using the time-modulated CDMA-mode of the CAOS camera. Using four different bright light test target scenes, successfully demonstrated is a proof-of-concept visible band CAOS smart camera operating in the CDMA-mode using up-to 4096 bits length Walsh design CAOS pixel codes with a maximum 10 KHz code bit rate giving a 0.4096 seconds CAOS frame acquisition time. A 16-bit analog-to-digital converter (ADC) with time domain correlation digital signal processing (DSP) generates the CDMA-mode images with a 3600 CAOS pixel count and a best spatial resolution of one micro-mirror square pixel size of 13.68 μm side. The CDMA-mode of the CAOS smart camera is suited for applications where robust high dynamic range (DR) imaging is needed for un-attenuated un-spoiled bright light spectrally diverse targets.

  10. MAI statistics estimation and analysis in a DS-CDMA system

    NASA Astrophysics Data System (ADS)

    Alami Hassani, A.; Zouak, M.; Mrabti, M.; Abdi, F.

    2018-05-01

    A primary limitation of Direct Sequence Code Division Multiple Access DS-CDMA link performance and system capacity is multiple access interference (MAI). To examine the performance of CDMA systems in the presence of MAI, i.e., in a multiuser environment, several works assumed that the interference can be approximated by a Gaussian random variable. In this paper, we first develop a new and simple approach to characterize the MAI in a multiuser system. In addition to statistically quantifying the MAI power, the paper also proposes a statistical model for both variance and mean of the MAI for synchronous and asynchronous CDMA transmission. We show that the MAI probability density function (PDF) is Gaussian for the equal-received-energy case and validate it by computer simulations.

  11. 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.

  12. Blind information-theoretic multiuser detection algorithms for DS-CDMA and WCDMA downlink systems.

    PubMed

    Waheed, Khuram; Salem, Fathi M

    2005-07-01

    Code division multiple access (CDMA) is based on the spread-spectrum technology and is a dominant air interface for 2.5G, 3G, and future wireless networks. For the CDMA downlink, the transmitted CDMA signals from the base station (BS) propagate through a noisy multipath fading communication channel before arriving at the receiver of the user equipment/mobile station (UE/MS). Classical CDMA single-user detection (SUD) algorithms implemented in the UE/MS receiver do not provide the required performance for modern high data-rate applications. In contrast, multi-user detection (MUD) approaches require a lot of a priori information not available to the UE/MS. In this paper, three promising adaptive Riemannian contra-variant (or natural) gradient based user detection approaches, capable of handling the highly dynamic wireless environments, are proposed. The first approach, blind multiuser detection (BMUD), is the process of simultaneously estimating multiple symbol sequences associated with all the users in the downlink of a CDMA communication system using only the received wireless data and without any knowledge of the user spreading codes. This approach is applicable to CDMA systems with relatively short spreading codes but becomes impractical for systems using long spreading codes. We also propose two other adaptive approaches, namely, RAKE -blind source recovery (RAKE-BSR) and RAKE-principal component analysis (RAKE-PCA) that fuse an adaptive stage into a standard RAKE receiver. This adaptation results in robust user detection algorithms with performance exceeding the linear minimum mean squared error (LMMSE) detectors for both Direct Sequence CDMA (DS-CDMA) and wide-band CDMA (WCDMA) systems under conditions of congestion, imprecise channel estimation and unmodeled multiple access interference (MAI).

  13. Coded DS-CDMA Systems with Iterative Channel Estimation and no Pilot Symbols

    DTIC Science & Technology

    2010-08-01

    ar X iv :1 00 8. 31 96 v1 [ cs .I T ] 1 9 A ug 2 01 0 1 Coded DS - CDMA Systems with Iterative Channel Estimation and no Pilot Symbols Don...sequence code-division multiple-access ( DS - CDMA ) systems with quadriphase-shift keying in which channel estimation, coherent demodulation, and decoding...amplitude, phase, and the interference power spectral density (PSD) due to the combined interference and thermal noise is proposed for DS - CDMA systems

  14. Quadriphase DS-CDMA wireless communication systems employing the generalized detector

    NASA Astrophysics Data System (ADS)

    Tuzlukov, Vyacheslav

    2012-05-01

    Probability of bit-error Per performance of asynchronous direct-sequence code-division multiple-access (DS-CDMA) wireless communication systems employing the generalized detector (GD) constructed based on the generalized approach to signal processing in noise is analyzed. The effects of pulse shaping, quadriphase or direct sequence quadriphase shift keying (DS-QPSK) spreading, aperiodic spreading sequences are considered in DS-CDMA based on GD and compared with the coherent Neyman-Pearson receiver. An exact Per expression and several approximations: one using the characterristic function method, a simplified expression for the improved Gaussian approximation (IGA) and the simplified improved Gaussian approximation are derived. Under conditions typically satisfied in practice and even with a small number of interferers, the standard Gaussian approximation (SGA) for the multiple-access interference component of the GD statistic and Per performance is shown to be accurate. Moreover, the IGA is shown to reduce to the SGA for pulses with zero excess bandwidth. Second, the GD Per performance of quadriphase DS-CDMA is shown to be superior to that of bi-phase DS-CDMA. Numerical examples by Monte Carlo simulation are presented to illustrate the GD Per performance for square-root raised-cosine pulses and spreading factors of moderate to large values. Also, a superiority of GD employment in CDMA systems over the Neyman-Pearson receiver is demonstrated

  15. 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.

  16. Multichannel Baseband Processor for Wideband CDMA

    NASA Astrophysics Data System (ADS)

    Jalloul, Louay M. A.; Lin, Jim

    2005-12-01

    The system architecture of the cellular base station modem engine (CBME) is described. The CBME is a single-chip multichannel transceiver capable of processing and demodulating signals from multiple users simultaneously. It is optimized to process different classes of code-division multiple-access (CDMA) signals. The paper will show that through key functional system partitioning, tightly coupled small digital signal processing cores, and time-sliced reuse architecture, CBME is able to achieve a high degree of algorithmic flexibility while maintaining efficiency. The paper will also highlight the implementation and verification aspects of the CBME chip design. In this paper, wideband CDMA is used as an example to demonstrate the architecture concept.

  17. 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.

  18. Layered video transmission over multirate DS-CDMA wireless systems

    NASA Astrophysics Data System (ADS)

    Kondi, Lisimachos P.; Srinivasan, Deepika; Pados, Dimitris A.; Batalama, Stella N.

    2003-05-01

    n this paper, we consider the transmission of video over wireless direct-sequence code-division multiple access (DS-CDMA) channels. A layered (scalable) video source codec is used and each layer is transmitted over a different CDMA channel. Spreading codes with different lengths are allowed for each CDMA channel (multirate CDMA). Thus, a different number of chips per bit can be used for the transmission of each scalable layer. For a given fixed energy value per chip and chip rate, the selection of a spreading code length affects the transmitted energy per bit and bit rate for each scalable layer. An MPEG-4 source encoder is used to provide a two-layer SNR scalable bitstream. Each of the two layers is channel-coded using Rate-Compatible Punctured Convolutional (RCPC) codes. Then, the data are interleaved, spread, carrier-modulated and transmitted over the wireless channel. A multipath Rayleigh fading channel is assumed. At the other end, we assume the presence of an antenna array receiver. After carrier demodulation, multiple-access-interference suppressing despreading is performed using space-time auxiliary vector (AV) filtering. The choice of the AV receiver is dictated by realistic channel fading rates that limit the data record available for receiver adaptation and redesign. Indeed, AV filter short-data-record estimators have been shown to exhibit superior bit-error-rate performance in comparison with LMS, RLS, SMI, or 'multistage nested Wiener' adaptive filter implementations. Our experimental results demonstrate the effectiveness of multirate DS-CDMA systems for wireless video transmission.

  19. Self-organizing feature maps for dynamic control of radio resources in CDMA microcellular networks

    NASA Astrophysics Data System (ADS)

    Hortos, William S.

    1998-03-01

    The application of artificial neural networks to the channel assignment problem for cellular code-division multiple access (CDMA) cellular networks has previously been investigated. 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. To satisfy the high demands for new services and improved connectivity for mobile communications, microcellular and picocellular systems are being introduced. For these systems, there is a need to develop robust and efficient management procedures for the allocation of power and spectrum to maximize radio capacity. Topology-conserving mappings play an important role in the biological processing of sensory inputs. The same principles underlying Kohonen's self-organizing feature maps (SOFMs) are applied to the adaptive control of radio resources to minimize interference, hence, maximize capacity in direct-sequence (DS) CDMA networks. The approach based on SOFMs is applied to some published examples of both theoretical and empirical models of DS/CDMA microcellular networks in metropolitan areas. The results of the approach for these examples are informally compared to the performance of algorithms, based on Hopfield- Tank neural networks and on genetic algorithms, for the channel assignment problem.

  20. Multimedia transmission in MC-CDMA using adaptive subcarrier power allocation and CFO compensation

    NASA Astrophysics Data System (ADS)

    Chitra, S.; Kumaratharan, N.

    2018-02-01

    Multicarrier code division multiple access (MC-CDMA) system is one of the most effective techniques in fourth-generation (4G) wireless technology, due to its high data rate, high spectral efficiency and resistance to multipath fading. However, MC-CDMA systems are greatly deteriorated by carrier frequency offset (CFO) which is due to Doppler shift and oscillator instabilities. It leads to loss of orthogonality among the subcarriers and causes intercarrier interference (ICI). Water filling algorithm (WFA) is an efficient resource allocation algorithm to solve the power utilisation problems among the subcarriers in time-dispersive channels. The conventional WFA fails to consider the effect of CFO. To perform subcarrier power allocation with reduced CFO and to improve the capacity of MC-CDMA system, residual CFO compensated adaptive subcarrier power allocation algorithm is proposed in this paper. The proposed technique allocates power only to subcarriers with high channel to noise power ratio. The performance of the proposed method is evaluated using random binary data and image as source inputs. Simulation results depict that the bit error rate performance and ICI reduction capability of the proposed modified WFA offered superior performance in both power allocation and image compression for high-quality multimedia transmission in the presence of CFO and imperfect channel state information conditions.

  1. Ultrasonic Array for Obstacle Detection Based on CDMA with Kasami Codes

    PubMed Central

    Diego, Cristina; Hernández, Álvaro; Jiménez, Ana; Álvarez, 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

  2. 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.

  3. Cognitive CDMA Channelization

    DTIC Science & Technology

    2010-03-01

    proposed scheme for power and code allocation for the secondary user is outlined in Fig. 2. V. SIMULATION STUDIES We consider a primary DS - CDMA system...DATES COVERED (From - To) January 2008 – June 2009 4. TITLE AND SUBTITLE COGNITIVE CDMA CHANNELIZATION 5a. CONTRACT NUMBER In-House 5b. GRANT...TELEPHONE NUMBER (Include area code) N/A Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std. Z39.18 Cognitive CDMA Channelization Kanke

  4. 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.

  5. Chaotic CDMA watermarking algorithm for digital image in FRFT domain

    NASA Astrophysics Data System (ADS)

    Liu, Weizhong; Yang, Wentao; Feng, Zhuoming; Zou, Xuecheng

    2007-11-01

    A digital image-watermarking algorithm based on fractional Fourier transform (FRFT) domain is presented by utilizing chaotic CDMA technique in this paper. As a popular and typical transmission technique, CDMA has many advantages such as privacy, anti-jamming and low power spectral density, which can provide robustness against image distortions and malicious attempts to remove or tamper with the watermark. A super-hybrid chaotic map, with good auto-correlation and cross-correlation characteristics, is adopted to produce many quasi-orthogonal codes (QOC) that can replace the periodic PN-code used in traditional CDAM system. The watermarking data is divided into a lot of segments that correspond to different chaotic QOC respectively and are modulated into the CDMA watermarking data embedded into low-frequency amplitude coefficients of FRFT domain of the cover image. During watermark detection, each chaotic QOC extracts its corresponding watermarking segment by calculating correlation coefficients between chaotic QOC and watermarked data of the detected image. The CDMA technique not only can enhance the robustness of watermark but also can compress the data of the modulated watermark. Experimental results show that the watermarking algorithm has good performances in three aspects: better imperceptibility, anti-attack robustness and security.

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

    DOE Office of Scientific and Technical Information (OSTI.GOV)

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

    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.

  7. A Hybrid Path-Oriented Code Assignment CDMA-Based MAC Protocol for Underwater Acoustic Sensor Networks

    PubMed Central

    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

  8. 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

    2013-11-04

    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.

  9. Distributed reservation-based code division multiple access

    NASA Astrophysics Data System (ADS)

    Wieselthier, J. E.; Ephremides, A.

    1984-11-01

    The use of spread spectrum signaling, motivated primarily by its antijamming capabilities in military applications, leads naturally to the use of Code Division Multiple Access (CDMA) techniques that permit the successful simultaneous transmission by a number of users over a wideband channel. In this paper we address some of the major issues that are associated with the design of multiple access protocols for spread spectrum networks. We then propose, analyze, and evaluate a distributed reservation-based multiple access protocol that does in fact exploit CDMA properties. Especially significant is the fact that no acknowledgment or feedback information from the destination is required (thus facilitating communication with a radio-silent mode), nor is any form of coordination among the users necessary.

  10. Support vector machine multiuser receiver for DS-CDMA signals in multipath channels.

    PubMed

    Chen, S; Samingan, A K; Hanzo, L

    2001-01-01

    The problem of constructing an adaptive multiuser detector (MUD) is considered for direct sequence code division multiple access (DS-CDMA) signals transmitted through multipath channels. The emerging learning technique, called support vector machines (SVM), is proposed as a method of obtaining a nonlinear MUD from a relatively small training data block. Computer simulation is used to study this SVM MUD, and the results show that it can closely match the performance of the optimal Bayesian one-shot detector. Comparisons with an adaptive radial basis function (RBF) MUD trained by an unsupervised clustering algorithm are discussed.

  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. 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.

  13. Interference Cancellation Technique Based on Discovery of Spreading Codes of Interference Signals and Maximum Correlation Detection for DS-CDMA System

    NASA Astrophysics Data System (ADS)

    Hettiarachchi, Ranga; Yokoyama, Mitsuo; Uehara, Hideyuki

    This paper presents a novel interference cancellation (IC) scheme for both synchronous and asynchronous direct-sequence code-division multiple-access (DS-CDMA) wireless channels. In the DS-CDMA system, the multiple access interference (MAI) and the near-far problem (NFP) are the two factors which reduce the capacity of the system. In this paper, we propose a new algorithm that is able to detect all interference signals as an individual MAI signal by maximum correlation detection. It is based on the discovery of all the unknowing spreading codes of the interference signals. Then, all possible MAI patterns so called replicas are generated as a summation of interference signals. And the true MAI pattern is found by taking correlation between the received signal and the replicas. Moreover, the receiver executes MAI cancellation in a successive manner, removing all interference signals by single-stage. Numerical results will show that the proposed IC strategy, which alleviates the detrimental effect of the MAI and the near-far problem, can significantly improve the system performance. Especially, we can obtain almost the same receiving characteristics as in the absense of interference for asynchrnous system when received powers are equal. Also, the same performances can be seen under any received power state for synchronous system.

  14. Performance of DS-CDMA with imperfect power control operating over a low earth orbiting satellite link

    NASA Astrophysics Data System (ADS)

    Vojcic, Branimir R.; Pickholtz, Raymond L.; Milstein, Laurence B.

    1994-05-01

    The analysis of both performance and capacity of direct sequence CDMA in terrestrial cellular systems has been addressed in the technical literature. It has been suggested that CDMA be used as a multiple access method for satellite systems as well, in particular for multispot beam Low Earth Orbit Satellites (LEOS). One is tempted to argue that since CDMA works well on terrestrial links, it will nominally work as well on satellite links. However, because there are fundamental differences in the characteristics of the two channels, such as larger time delays from the mobile to the base station and smaller multipath delay spreads on the satellite channels, the performance of CDMA on satellite links cannot always be accurately predicted from its performance on terrestrial channels. In this paper, we analytically derive the performance of a CDMA system which operates over a low earth orbiting satellite channel. We incorporate such effects as imperfect power control and dual-order diversity to obtain the average probability of error of a single user.

  15. Intersystem Interference Reduction for Overlaid HAPS-Terrestrial CDMA System

    NASA Astrophysics Data System (ADS)

    Huang, Jeng-Ji; Wang, Wei-Ting; Li, Mingfu; Shiung, David; Ferng, Huei-Wen

    In this letter, we propose that directional antennas, combined with power management, be incorporated to reduce intersystem interference in a shared band overlaid high altitude platform station (HAPS)-terrestrial code division multiple access (CDMA) system. To eliminate the HAPS to terrestrial interference, the HAPS is accessed only via directional antennas under the proposed scheme. By doing so, the uplink power to the HAPS can accordingly be increased, so that the terrestrial to HAPS interference is also effectively suppressed.

  16. Pilot-Assisted Channel Estimation for Orthogonal Multi-Carrier DS-CDMA with Frequency-Domain Equalization

    NASA Astrophysics Data System (ADS)

    Shima, Tomoyuki; Tomeba, Hiromichi; Adachi, Fumiyuki

    Orthogonal multi-carrier direct sequence code division multiple access (orthogonal MC DS-CDMA) is a combination of time-domain spreading and orthogonal frequency division multiplexing (OFDM). In orthogonal MC DS-CDMA, the frequency diversity gain can be obtained by applying frequency-domain equalization (FDE) based on minimum mean square error (MMSE) criterion to a block of OFDM symbols and can improve the bit error rate (BER) performance in a severe frequency-selective fading channel. FDE requires an accurate estimate of the channel gain. The channel gain can be estimated by removing the pilot modulation in the frequency domain. In this paper, we propose a pilot-assisted channel estimation suitable for orthogonal MC DS-CDMA with FDE and evaluate, by computer simulation, the BER performance in a frequency-selective Rayleigh fading channel.

  17. 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.

  18. 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.

  19. Effects of optical layer impairments on 2.5 Gb/s optical CDMA transmission.

    PubMed

    Feng, H; Mendez, A; Heritage, J; Lennon, W

    2000-07-03

    We conducted a computer simulation study to assess the effects of optical layer impairments on optical CDMA (O-CDMA) transmission of 8 asynchronous users at 2.5 Gb/s each user over a 214-km link. It was found that with group velocity dispersion compensation, two other residual effects, namely, the nonzero chromatic dispersion slope of the single mode fiber (which causes skew) and the non-uniform EDFA gain (which causes interference power level to exceed signal power level of some codes) degrade the signal to multi-access interference (MAI) ratio. In contrast, four wave mixing and modulation due to the Kerr and Raman contributions to the fiber nonlinear refractive index are less important. Current wavelength-division multiplexing (WDM) technologies, including dispersion management, EDFA gain flattening, and 3 rd order dispersion compensation, are sufficient to overcome the impairments to the O-CDMA transmission system that we considered.

  20. Channel coding for underwater acoustic single-carrier CDMA communication system

    NASA Astrophysics Data System (ADS)

    Liu, Lanjun; Zhang, Yonglei; Zhang, Pengcheng; Zhou, Lin; Niu, Jiong

    2017-01-01

    CDMA is an effective multiple access protocol for underwater acoustic networks, and channel coding can effectively reduce the bit error rate (BER) of the underwater acoustic communication system. For the requirements of underwater acoustic mobile networks based on CDMA, an underwater acoustic single-carrier CDMA communication system (UWA/SCCDMA) based on the direct-sequence spread spectrum is proposed, and its channel coding scheme is studied based on convolution, RA, Turbo and LDPC coding respectively. The implementation steps of the Viterbi algorithm of convolutional coding, BP and minimum sum algorithms of RA coding, Log-MAP and SOVA algorithms of Turbo coding, and sum-product algorithm of LDPC coding are given. An UWA/SCCDMA simulation system based on Matlab is designed. Simulation results show that the UWA/SCCDMA based on RA, Turbo and LDPC coding have good performance such that the communication BER is all less than 10-6 in the underwater acoustic channel with low signal to noise ratio (SNR) from -12 dB to -10dB, which is about 2 orders of magnitude lower than that of the convolutional coding. The system based on Turbo coding with Log-MAP algorithm has the best performance.

  1. Downlink Multihop Transmission Technique for Asymmetric Traffic Accommodation in DS-CDMA/FDD Cellular Communications

    NASA Astrophysics Data System (ADS)

    Mori, Kazuo; Naito, Katsuhiro; Kobayashi, Hideo

    This paper proposes an asymmetric traffic accommodation scheme using a multihop transmission technique for CDMA/FDD cellular communication systems. The proposed scheme exploits the multihop transmission to downlink packet transmissions, which require the large transmission power at their single-hop transmissions, in order to increase the downlink capacity. In these multihop transmissions, vacant uplink band is used for the transmissions from relay stations to destination mobile stations, and this leads more capacity enhancement in the downlink communications. The relay route selection method and power control method for the multihop transmissions are also investigated in the proposed scheme. The proposed scheme is evaluated by computer simulation and the results show that the proposed scheme can achieve better system performance.

  2. Performance Analysis of Blind Subspace-Based Signature Estimation Algorithms for DS-CDMA Systems with Unknown Correlated Noise

    NASA Astrophysics Data System (ADS)

    Zarifi, Keyvan; Gershman, Alex B.

    2006-12-01

    We analyze the performance of two popular blind subspace-based signature waveform estimation techniques proposed by Wang and Poor and Buzzi and Poor for direct-sequence code division multiple-access (DS-CDMA) systems with unknown correlated noise. Using the first-order perturbation theory, analytical expressions for the mean-square error (MSE) of these algorithms are derived. We also obtain simple high SNR approximations of the MSE expressions which explicitly clarify how the performance of these techniques depends on the environmental parameters and how it is related to that of the conventional techniques that are based on the standard white noise assumption. Numerical examples further verify the consistency of the obtained analytical results with simulation results.

  3. 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.

  4. Contrast research of CDMA and GSM network optimization

    NASA Astrophysics Data System (ADS)

    Wu, Yanwen; Liu, Zehong; Zhou, Guangyue

    2004-03-01

    With the development of mobile telecommunication network, users of CDMA advanced their request of network service quality. While the operators also change their network management object from signal coverage to performance improvement. In that case, reasonably layout & optimization of mobile telecommunication network, reasonably configuration of network resource, improvement of the service quality, and increase the enterprise's core competition ability, all those have been concerned by the operator companies. This paper firstly looked into the flow of CDMA network optimization. Then it dissertated to some keystones in the CDMA network optimization, like PN code assignment, calculation of soft handover, etc. As GSM is also the similar cellular mobile telecommunication system like CDMA, so this paper also made a contrast research of CDMA and GSM network optimization in details, including the similarity and the different. In conclusion, network optimization is a long time job; it will run through the whole process of network construct. By the adjustment of network hardware (like BTS equipments, RF systems, etc.) and network software (like parameter optimized, configuration optimized, capacity optimized, etc.), network optimization work can improve the performance and service quality of the network.

  5. 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

  6. Adaptive receiver structures for asynchronous CDMA systems

    NASA Astrophysics Data System (ADS)

    Rapajic, Predrag B.; Vucetic, Branka S.

    1994-05-01

    Adaptive linear and decision feedback receiver structures for coherent demodulation in asynchronous code division multiple access (CDMA) systems are considered. It is assumed that the adaptive receiver has no knowledge of the signature waveforms and timing of other users. The receiver is trained by a known training sequence prior to data transmission and continuously adjusted by an adaptive algorithm during data transmission. The proposed linear receiver is as simple as a standard single-user detector receiver consisting of a matched filter with constant coefficients, but achieves essential advantages with respect to timing recovery, multiple access interference elimination, near/far effect, narrowband and frequency-selective fading interference suppression, and user privacy. An adaptive centralized decision feedback receiver has the same advantages of the linear receiver but, in addition, achieves a further improvement in multiple access interference cancellation at the expense of higher complexity. The proposed receiver structures are tested by simulation over a channel with multipath propagation, multiple access interference, narrowband interference, and additive white Gaussian noise.

  7. 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.

  8. A Space-Time Signal Decomposition Algorithm for Downlink MIMO DS-CDMA Receivers

    NASA Astrophysics Data System (ADS)

    Wang, Yung-Yi; Fang, Wen-Hsien; Chen, Jiunn-Tsair

    We propose a dimension reduction algorithm for the receiver of the downlink of direct-sequence code-division multiple access (DS-CDMA) systems in which both the transmitters and the receivers employ antenna arrays of multiple elements. To estimate the high order channel parameters, we develop a layered architecture using dimension-reduced parameter estimation algorithms to estimate the frequency-selective multipath channels. In the proposed architecture, to exploit the space-time geometric characteristics of multipath channels, spatial beamformers and constrained (or unconstrained) temporal filters are adopted for clustered-multipath grouping and path isolation. In conjunction with the multiple access interference (MAI) suppression techniques, the proposed architecture jointly estimates the direction of arrivals, propagation delays, and fading amplitudes of the downlink fading multipaths. With the outputs of the proposed architecture, the signals of interest can then be naturally detected by using path-wise maximum ratio combining. Compared to the traditional techniques, such as the Joint-Angle-and-Delay-Estimation (JADE) algorithm for DOA-delay joint estimation and the space-time minimum mean square error (ST-MMSE) algorithm for signal detection, computer simulations show that the proposed algorithm substantially mitigate the computational complexity at the expense of only slight performance degradation.

  9. On the performance of a code division multiple access scheme with transmit/receive conflicts

    NASA Astrophysics Data System (ADS)

    Silvester, J. A.

    One of the benefits of spread spectrum is that by assigning each user a different orthogonal signal set, multiple transmissions can occur simultaneously. This possibility is utilized in new access schemes called Code Division Multiple Access (CDMA). The present investigation is concerned with a particular CDMA implementation in which the transmit times for each symbol are exactly determined in a distributed manner such that both sender and receiver know them. In connection with a decision whether to transmit or receive, the loss of a symbol in one of the channels results. The system employs thus a coding technique which permits correct decoding of a codeword even if some constituent symbols are missing or in error. The technique used is Reed Solomon coding. The performance of this system is analyzed, and attention is given to the optimum strategy which should be used in deciding whether to receive or transmit.

  10. 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. PMID:27413613

  11. Exploiting Phase Diversity for CDMA2000 1X Smart Antenna Base Stations

    NASA Astrophysics Data System (ADS)

    Kim, Seongdo; Hyeon, Seungheon; Choi, Seungwon

    2004-12-01

    A performance analysis of an access channel decoder is presented which exploits a diversity gain due to the independent magnitude of received signals energy at each of the antenna elements of a smart-antenna base-station transceiver subsystem (BTS) operating in CDMA2000 1X signal environment. The objective is to enhance the data retrieval at cellsite during the access period, for which the optimal weight vector of the smart antenna BTS is not available. It is shown in this paper that the access channel decoder proposed in this paper outperforms the conventional one, which is based on a single antenna channel in terms of detection probability of access probe, access channel failure probability, and Walsh-code demodulation performance.

  12. 2-Step Maximum Likelihood Channel Estimation for Multicode DS-CDMA with Frequency-Domain Equalization

    NASA Astrophysics Data System (ADS)

    Kojima, Yohei; Takeda, Kazuaki; Adachi, Fumiyuki

    Frequency-domain equalization (FDE) based on the minimum mean square error (MMSE) criterion can provide better downlink bit error rate (BER) performance of direct sequence code division multiple access (DS-CDMA) than the conventional rake combining in a frequency-selective fading channel. FDE requires accurate channel estimation. In this paper, we propose a new 2-step maximum likelihood channel estimation (MLCE) for DS-CDMA with FDE in a very slow frequency-selective fading environment. The 1st step uses the conventional pilot-assisted MMSE-CE and the 2nd step carries out the MLCE using decision feedback from the 1st step. The BER performance improvement achieved by 2-step MLCE over pilot assisted MMSE-CE is confirmed by computer simulation.

  13. Joint channel estimation and multi-user detection for multipath fading channels in DS-CDMA systems

    NASA Astrophysics Data System (ADS)

    Wu, Sau-Hsuan; Kuo, C.-C. Jay

    2002-11-01

    The technique of joint blind channel estimation and multiple access interference (MAI) suppression for an asynchronous code-division multiple-access (CDMA) system is investigated in this research. To identify and track dispersive time-varying fading channels and to avoid the phase ambiguity that come with the second-order statistic approaches, a sliding-window scheme using the expectation maximization (EM) algorithm is proposed. The complexity of joint channel equalization and symbol detection for all users increases exponentially with system loading and the channel memory. The situation is exacerbated if strong inter-symbol interference (ISI) exists. To reduce the complexity and the number of samples required for channel estimation, a blind multiuser detector is developed. Together with multi-stage interference cancellation using soft outputs provided by this detector, our algorithm can track fading channels with no phase ambiguity even when channel gains attenuate close to zero.

  14. 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.

  15. 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.

  16. 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.

  17. Interference Canceller Based on Cycle-and-Add Property for Single User Detection in DS-CDMA

    NASA Astrophysics Data System (ADS)

    Hettiarachchi, Ranga; Yokoyama, Mitsuo; Uehara, Hideyuki; Ohira, Takashi

    In this paper, performance of a novel interference cancellation technique for the single user detection in a direct-sequence code-division multiple access (DS-CDMA) system has been investigated. This new algorithm is based on the Cycle-and-Add property of PN (Pseudorandom Noise) sequences and can be applied for both synchronous and asynchronous systems. The proposed strategy provides a simple method that can delete interference signals one by one in spite of the power levels of interferences. Therefore, it is possible to overcome the near-far problem (NFP) in a successive manner without using transmit power control (TPC) techniques. The validity of the proposed procedure is corroborated by computer simulations in additive white Gaussian noise (AWGN) and frequency-nonselective fading channels. Performance results indicate that the proposed receiver outperforms the conventional receiver and, in many cases, it does so with a considerable gain.

  18. 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

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

    PubMed

    Luo, Zhongqiang; Zhu, Lidong

    2015-08-14

    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.

  20. Neurological abnormalities associated with CDMA exposure.

    PubMed

    Hocking, B; Westerman, R

    2001-09-01

    Dysaesthesiae of the scalp and neurological abnormality after mobile phone use have been reported previously, but the roles of the phone per se or the radiations in causing these findings have been questioned. We report finding a neurological abnormality in a patient after accidental exposure of the left side of the face to mobile phone radiation [code division multiple access (CDMA)] from a down-powered mobile phone base station antenna. He had headaches, unilateral left blurred vision and pupil constriction, unilateral altered sensation on the forehead, and abnormalities of current perception thresholds on testing the left trigeminal ophthalmic nerve. His nerve function recovered during 6 months follow-up. His exposure was 0.015-0.06 mW/cm(2) over 1-2 h. The implications regarding health effects of radiofrequency radiation are discussed.

  1. 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.

  2. Quantum internet using code division multiple access

    PubMed Central

    Zhang, Jing; Liu, Yu-xi; Özdemir, Şahin 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

  3. 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.

  4. 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.

  5. 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.

  6. 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

  7. 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

    2015-08-27

    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.

  8. Joint Frequency-Domain Equalization and Despreading for Multi-Code DS-CDMA Using Cyclic Delay Transmit Diversity

    NASA Astrophysics Data System (ADS)

    Yamamoto, Tetsuya; Takeda, Kazuki; Adachi, Fumiyuki

    Frequency-domain equalization (FDE) based on the minimum mean square error (MMSE) criterion can provide a better bit error rate (BER) performance than rake combining. To further improve the BER performance, cyclic delay transmit diversity (CDTD) can be used. CDTD simultaneously transmits the same signal from different antennas after adding different cyclic delays to increase the number of equivalent propagation paths. Although a joint use of CDTD and MMSE-FDE for direct sequence code division multiple access (DS-CDMA) achieves larger frequency diversity gain, the BER performance improvement is limited by the residual inter-chip interference (ICI) after FDE. In this paper, we propose joint FDE and despreading for DS-CDMA using CDTD. Equalization and despreading are simultaneously performed in the frequency-domain to suppress the residual ICI after FDE. A theoretical conditional BER analysis is presented for the given channel condition. The BER analysis is confirmed by computer simulation.

  9. 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.

  10. 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.

  11. Performance of Improved Channel Allocation for Multicarrier CDMA with Adaptive Frequency Hopping and Multiuser Detection

    DTIC Science & Technology

    2008-08-29

    resulting in much larger system capacity than for a non-adaptive MC direct-sequence ( DS )- CDMA system. This conclusion is confirmed for realistic fading...system capacity than for a non-adaptive MC direct-sequence ( DS )- CDMA system. This conclusion is confirmed for realistic fading channels with correlated...transmission method exploits both frequency and multiuser diversity and improves on non-adaptive MC DS - CDMA sys- tems in [6]. In this paper, we focus on the

  12. A Review on Spectral Amplitude Coding Optical Code Division Multiple Access

    NASA Astrophysics Data System (ADS)

    Kaur, Navpreet; Goyal, Rakesh; Rani, Monika

    2017-06-01

    This manuscript deals with analysis of Spectral Amplitude Coding Optical Code Division Multiple Access (SACOCDMA) system. The major noise source in optical CDMA is co-channel interference from other users known as multiple access interference (MAI). The system performance in terms of bit error rate (BER) degrades as a result of increased MAI. It is perceived that number of users and type of codes used for optical system directly decide the performance of system. MAI can be restricted by efficient designing of optical codes and implementing them with unique architecture to accommodate more number of users. Hence, it is a necessity to design a technique like spectral direct detection (SDD) technique with modified double weight code, which can provide better cardinality and good correlation property.

  13. DPLL implementation in carrier acquisition and tracking for burst DS-CDMA receivers.

    PubMed

    Guan, Yun-feng; Zhang, Zhao-yang; Lai, Li-feng

    2003-01-01

    This paper presents the architectures, algorithms, and implementation considerations of the digital phase locked loop (DPLL) used for burst-mode packet DS-CDMA receivers. As we know, carrier offset is a rather challenging problem in CDMA system. According to different applications, different DPLL forms should be adopted to correct different maximum carrier offset in CDMA systems. One classical DPLL and two novel DPLL forms are discussed in the paper. The acquisition range of carrier offset can be widened by using the two novel DPLL forms without any performance degradation such as longer acquisition time or larger variance of the phase error. The maximum acquisition range is 1/(4T), where T is the symbol period. The design can be implemented by FPGA directly.

  14. Fast converging minimum probability of error neural network receivers for DS-CDMA communications.

    PubMed

    Matyjas, John D; Psaromiligkos, Ioannis N; Batalama, Stella N; Medley, Michael J

    2004-03-01

    We consider a multilayer perceptron neural network (NN) receiver architecture for the recovery of the information bits of a direct-sequence code-division-multiple-access (DS-CDMA) user. We develop a fast converging adaptive training algorithm that minimizes the bit-error rate (BER) at the output of the receiver. The adaptive algorithm has three key features: i) it incorporates the BER, i.e., the ultimate performance evaluation measure, directly into the learning process, ii) it utilizes constraints that are derived from the properties of the optimum single-user decision boundary for additive white Gaussian noise (AWGN) multiple-access channels, and iii) it embeds importance sampling (IS) principles directly into the receiver optimization process. Simulation studies illustrate the BER performance of the proposed scheme.

  15. 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.

  16. Performance Analysis of a De-correlated Modified Code Tracking Loop for Synchronous DS-CDMA System under Multiuser Environment

    NASA Astrophysics Data System (ADS)

    Wu, Ya-Ting; Wong, Wai-Ki; Leung, Shu-Hung; Zhu, Yue-Sheng

    This paper presents the performance analysis of a De-correlated Modified Code Tracking Loop (D-MCTL) for synchronous direct-sequence code-division multiple-access (DS-CDMA) systems under multiuser environment. Previous studies have shown that the imbalance of multiple access interference (MAI) in the time lead and time lag portions of the signal causes tracking bias or instability problem in the traditional correlating tracking loop like delay lock loop (DLL) or modified code tracking loop (MCTL). In this paper, we exploit the de-correlating technique to combat the MAI at the on-time code position of the MCTL. Unlike applying the same technique to DLL which requires an extensive search algorithm to compensate the noise imbalance which may introduce small tracking bias under low signal-to-noise ratio (SNR), the proposed D-MCTL has much lower computational complexity and exhibits zero tracking bias for the whole range of SNR, regardless of the number of interfering users. Furthermore, performance analysis and simulations based on Gold codes show that the proposed scheme has better mean square tracking error, mean-time-to-lose-lock and near-far resistance than the other tracking schemes, including traditional DLL (T-DLL), traditional MCTL (T-MCTL) and modified de-correlated DLL (MD-DLL).

  17. Genetic Local Search for Optimum Multiuser Detection Problem in DS-CDMA Systems

    NASA Astrophysics Data System (ADS)

    Wang, Shaowei; Ji, Xiaoyong

    Optimum multiuser detection (OMD) in direct-sequence code-division multiple access (DS-CDMA) systems is an NP-complete problem. In this paper, we present a genetic local search algorithm, which consists of an evolution strategy framework and a local improvement procedure. The evolution strategy searches the space of feasible, locally optimal solutions only. A fast iterated local search algorithm, which employs the proprietary characteristics of the OMD problem, produces local optima with great efficiency. Computer simulations show the bit error rate (BER) performance of the GLS outperforms other multiuser detectors in all cases discussed. The computation time is polynomial complexity in the number of users.

  18. 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.

  19. A Simple Exact Error Rate Analysis for DS-CDMA with Arbitrary Pulse Shape in Flat Nakagami Fading

    NASA Astrophysics Data System (ADS)

    Rahman, Mohammad Azizur; Sasaki, Shigenobu; Kikuchi, Hisakazu; Harada, Hiroshi; Kato, Shuzo

    A simple exact error rate analysis is presented for random binary direct sequence code division multiple access (DS-CDMA) considering a general pulse shape and flat Nakagami fading channel. First of all, a simple model is developed for the multiple access interference (MAI). Based on this, a simple exact expression of the characteristic function (CF) of MAI is developed in a straight forward manner. Finally, an exact expression of error rate is obtained following the CF method of error rate analysis. The exact error rate so obtained can be much easily evaluated as compared to the only reliable approximate error rate expression currently available, which is based on the Improved Gaussian Approximation (IGA).

  20. 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.

  1. An FPGA-based DS-CDMA multiuser demodulator employing adaptive multistage parallel interference cancellation

    NASA Astrophysics Data System (ADS)

    Li, Xinhua; Song, Zhenyu; Zhan, Yongjie; Wu, Qiongzhi

    2009-12-01

    Since the system capacity is severely limited, reducing the multiple access interfere (MAI) is necessary in the multiuser direct-sequence code division multiple access (DS-CDMA) system which is used in the telecommunication terminals data-transferred link system. In this paper, we adopt an adaptive multistage parallel interference cancellation structure in the demodulator based on the least mean square (LMS) algorithm to eliminate the MAI on the basis of overviewing various of multiuser dectection schemes. Neither a training sequence nor a pilot signal is needed in the proposed scheme, and its implementation complexity can be greatly reduced by a LMS approximate algorithm. The algorithm and its FPGA implementation is then derived. Simulation results of the proposed adaptive PIC can outperform some of the existing interference cancellation methods in AWGN channels. The hardware setup of mutiuser demodulator is described, and the experimental results based on it demonstrate that the simulation results shows large performance gains over the conventional single-user demodulator.

  2. 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.

  3. Sharing possibilities amongst CDMA Mobile Satellite Systems, and impacts of terminal characteristics on sharing

    NASA Astrophysics Data System (ADS)

    Bambace, Luís Antonio Waack; Ceballos, Décio Castilho

    CDMA Mobile Satellite Systems (CDMA MSS) are able to co-directional, co-frequency and co-coverage sharing, and they are strongly interdependent in case of such a sharing. It is also known that the success of any telecommunication project is the use of the correct media to each task. Operators have a clear sight of such a media adequacy in traditional systems, but not necessarily in the case of Mobile Satellite Systems. This creates a risk that a wrong market objective operator causes trouble to other systems. This paper deals with the sharing alternatives for up to four CDMA MSS operating in the same frequency band, and analysts both: satellite to user downlink and user to satellite uplink. The influence of several items in capacity is here treated. The scope includes: downlink power flux density: code availability; single system internal interference; inter-system interference; diversity schemes: average link impairments, margins; user cooperation; terminal specifications and the dependence of the insulation between RHCP and LHCP with fade.

  4. Approximate equiangular tight frames for compressed sensing and CDMA applications

    NASA Astrophysics Data System (ADS)

    Tsiligianni, Evaggelia; Kondi, Lisimachos P.; Katsaggelos, Aggelos K.

    2017-12-01

    Performance guarantees for recovery algorithms employed in sparse representations, and compressed sensing highlights the importance of incoherence. Optimal bounds of incoherence are attained by equiangular unit norm tight frames (ETFs). Although ETFs are important in many applications, they do not exist for all dimensions, while their construction has been proven extremely difficult. In this paper, we construct frames that are close to ETFs. According to results from frame and graph theory, the existence of an ETF depends on the existence of its signature matrix, that is, a symmetric matrix with certain structure and spectrum consisting of two distinct eigenvalues. We view the construction of a signature matrix as an inverse eigenvalue problem and propose a method that produces frames of any dimensions that are close to ETFs. Due to the achieved equiangularity property, the so obtained frames can be employed as spreading sequences in synchronous code-division multiple access (s-CDMA) systems, besides compressed sensing.

  5. System-Level Performance of Antenna Arrays in CDMA-Based Cellular Mobile Radio Systems

    NASA Astrophysics Data System (ADS)

    Czylwik, Andreas; Dekorsy, Armin

    2004-12-01

    Smart antennas exploit the inherent spatial diversity of the mobile radio channel, provide an antenna gain, and also enable spatial interference suppression leading to reduced intracell as well as intercell interference. Especially, for the downlink of future CDMA-based mobile communications systems, transmit beamforming is seen as a well-promising smart antenna technique. The main objective of this paper is to study the performance of diverse antenna array topologies when applied for transmit beamforming in the downlink of CDMA-based networks. In this paper, we focus on uniform linear array (ULA) and uniform circular array (UCA) topologies. For the ULA, we consider three-sector base stations with one linear array per sector. While recent research on downlink beamforming is often restricted to one single cell, this study takes into account the important impact of intercell interference on the performance by evaluating complete networks. Especially, from the operator perspective, system capacity and system coverage are very essential parameters of a cellular system so that there is a clear necessity of intensive system level investigations. Apart from delivering assessments on the performance of the diverse antenna array topologies, in the paper also different antenna array parameters, such as element spacing and beamwidth of the sector antennas, are optimized. Although we focus on the network level, fast channel fluctuations are taken into account by including them analytically into the signal-to-interference calculation.

  6. An Architecture for Enabling Migration of Tactical Networks to Future Flexible Ad Hoc WBWF

    DTIC Science & Technology

    2010-09-01

    Requirements Several multiple access schemes TDMA OFDMA SC-OFDMA, FH- CDMA , DS - CDMA , hybrid access schemes, transitions between them Dynamic...parameters algorithms depend on the multiple access scheme If DS - CDMA : handling of macro-diversity (linked to cooperative routing) TDMA and/of OFDMA...Transport format Ciphering @MAC/RLC level : SCM Physical layer (PHY) : signal processing (mod, FEC, etc) CDMA : macro-diversity CDMA , OFDMA

  7. A General Model for Performance Evaluation in DS-CDMA Systems with Variable Spreading Factors

    NASA Astrophysics Data System (ADS)

    Chiaraluce, Franco; Gambi, Ennio; Righi, Giorgia

    This paper extends previous analytical approaches for the study of CDMA systems to the relevant case of multipath environments where users can operate at different bit rates. This scenario is of interest for the Wideband CDMA strategy employed in UMTS, and the model permits the performance comparison of classic and more innovative spreading signals. The method is based on the characteristic function approach, that allows to model accurately the various kinds of interferences. Some numerical examples are given with reference to the ITU-R M. 1225 Recommendations, but the analysis could be extended to different channel descriptions.

  8. Uplink Packet-Data Scheduling in DS-CDMA Systems

    NASA Astrophysics Data System (ADS)

    Choi, Young Woo; Kim, Seong-Lyun

    In this letter, we consider the uplink packet scheduling for non-real-time data users in a DS-CDMA system. As an effort to jointly optimize throughput and fairness, we formulate a time-span minimization problem incorporating the time-multiplexing of different simultaneous transmission schemes. Based on simple rules, we propose efficient scheduling algorithms and compare them with the optimal solution obtained by linear programming.

  9. Iterative MMSE Detection for MIMO/BLAST DS-CDMA Systems in Frequency Selective Fading Channels - Achieving High Performance in Fully Loaded Systems

    NASA Astrophysics Data System (ADS)

    Silva, João Carlos; Souto, Nuno; Cercas, Francisco; Dinis, Rui

    A MMSE (Minimum Mean Square Error) DS-CDMA (Direct Sequence-Code Division Multiple Access) receiver coupled with a low-complexity iterative interference suppression algorithm was devised for a MIMO/BLAST (Multiple Input, Multiple Output / Bell Laboratories Layered Space Time) system in order to improve system performance, considering frequency selective fading channels. The scheme is compared against the simple MMSE receiver, for both QPSK and 16QAM modulations, under SISO (Single Input, Single Output) and MIMO systems, the latter with 2Tx by 2Rx and 4Tx by 4Rx (MIMO order 2 and 4 respectively) antennas. To assess its performance in an existing system, the uncoded UMTS HSDPA (High Speed Downlink Packet Access) standard was considered.

  10. 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

  11. 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.

  12. Performance Comparison of Orthogonal and Quasi-orthogonal Codes in Quasi-Synchronous Cellular CDMA Communication

    NASA Astrophysics Data System (ADS)

    Jos, Sujit; Kumar, Preetam; Chakrabarti, Saswat

    Orthogonal and quasi-orthogonal codes are integral part of any DS-CDMA based cellular systems. Orthogonal codes are ideal for use in perfectly synchronous scenario like downlink cellular communication. Quasi-orthogonal codes are preferred over orthogonal codes in the uplink communication where perfect synchronization cannot be achieved. In this paper, we attempt to compare orthogonal and quasi-orthogonal codes in presence of timing synchronization error. This will give insight into the synchronization demands in DS-CDMA systems employing the two classes of sequences. The synchronization error considered is smaller than chip duration. Monte-Carlo simulations have been carried out to verify the analytical and numerical results.

  13. Space-Time Processing for Tactical Mobile Ad Hoc Networks

    DTIC Science & Technology

    2010-05-01

    Spatial Diversity and Imperfect Channel Estimation on Wideband MC- DS - CDMA and MC- CDMA " IEEE Transactions on Communications, Vol. 57, No. 10, pp. 2988...include direct sequence code division multiple access ( DS - CDMA ), Frequency Hopped (FH) CDMA and Orthogonal Frequency Division Multiple Access (OFDMA...capability, LPD/LPI, and operability in non-continuous spectrum. In addition, FH- CDMA is robust to the near-far problem, while DS - CDMA requires

  14. 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.

  15. Robust MOE Detector for DS-CDMA Systems with Signature Waveform Mismatch

    NASA Astrophysics Data System (ADS)

    Lin, Tsui-Tsai

    In this letter, a decision-directed MOE detector with excellent robustness against signature waveform mismatch is proposed for DS-CDMA systems. Both the theoretic analysis and computer simulation results demonstrate that the proposed detector can provide better SINR performance than that of conventional detectors.

  16. 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.

  17. The analysis of MAI in large scale MIMO-CDMA system

    NASA Astrophysics Data System (ADS)

    Berceanu, Madalina-Georgiana; Voicu, Carmen; Halunga, Simona

    2016-12-01

    Recently, technological development imposed a rapid growth in the use of data carried by cellular services, which also implies the necessity of higher data rates and lower latency. To meet the users' demands, it was brought into discussion a series of new data processing techniques. In this paper, we approached the MIMO technology that uses multiple antennas at the receiver and transmitter ends. To study the performances obtained by this technology, we proposed a MIMO-CDMA system, where image transmission has been used instead of random data transmission to take benefit of a larger range of quality indicators. In the simulations we increased the number of antennas, we observed how the performances of the system are modified and, based on that, we were able to make a comparison between a conventional MIMO and a Large Scale MIMO system, in terms of BER and MSSIM index, which is a metric that compares the quality of the image before transmission with the received one.

  18. RLS Channel Estimation with Adaptive Forgetting Factor for DS-CDMA Frequency-Domain Equalization

    NASA Astrophysics Data System (ADS)

    Kojima, Yohei; Tomeba, Hiromichi; Takeda, Kazuaki; Adachi, Fumiyuki

    Frequency-domain equalization (FDE) based on the minimum mean square error (MMSE) criterion can increase the downlink bit error rate (BER) performance of DS-CDMA beyond that possible with conventional rake combining in a frequency-selective fading channel. FDE requires accurate channel estimation. Recently, we proposed a pilot-assisted channel estimation (CE) based on the MMSE criterion. Using MMSE-CE, the channel estimation accuracy is almost insensitive to the pilot chip sequence, and a good BER performance is achieved. In this paper, we propose a channel estimation scheme using one-tap recursive least square (RLS) algorithm, where the forgetting factor is adapted to the changing channel condition by the least mean square (LMS)algorithm, for DS-CDMA with FDE. We evaluate the BER performance using RLS-CE with adaptive forgetting factor in a frequency-selective fast Rayleigh fading channel by computer simulation.

  19. Multiuser receiver for DS-CDMA signals in multipath channels: an enhanced multisurface method.

    PubMed

    Mahendra, Chetan; Puthusserypady, Sadasivan

    2006-11-01

    This paper deals with the problem of multiuser detection in direct-sequence code-division multiple-access (DS-CDMA) systems in multipath environments. The existing multiuser detectors can be divided into two categories: (1) low-complexity poor-performance linear detectors and (2) high-complexity good-performance nonlinear detectors. In particular, in channels where the orthogonality of the code sequences is destroyed by multipath, detectors with linear complexity perform much worse than the nonlinear detectors. In this paper, we propose an enhanced multisurface method (EMSM) for multiuser detection in multipath channels. EMSM is an intermediate piecewise linear detection scheme with a run-time complexity linear in the number of users. Its bit error rate performance is compared with existing linear detectors, a nonlinear radial basis function detector trained by the new support vector learning algorithm, and Verdu's optimal detector. Simulations in multipath channels, for both synchronous and asynchronous cases, indicate that it always outperforms all other linear detectors, performing nearly as well as nonlinear detectors.

  20. Optimal lightpath placement on a metropolitan-area network linked with optical CDMA local nets

    NASA Astrophysics Data System (ADS)

    Wang, Yih-Fuh; Huang, Jen-Fa

    2008-01-01

    A flexible optical metropolitan-area network (OMAN) [J.F. Huang, Y.F. Wang, C.Y. Yeh, Optimal configuration of OCDMA-based MAN with multimedia services, in: 23rd Biennial Symposium on Communications, Queen's University, Kingston, Canada, May 29-June 2, 2006, pp. 144-148] structured with OCDMA linkage is proposed to support multimedia services with multi-rate or various qualities of service. To prioritize transmissions in OCDMA, the orthogonal variable spreading factor (OVSF) codes widely used in wireless CDMA are adopted. In addition, for feasible multiplexing, unipolar OCDMA modulation [L. Nguyen, B. Aazhang, J.F. Young, All-optical CDMA with bipolar codes, IEEE Electron. Lett. 31 (6) (1995) 469-470] is used to generate the code selector of multi-rate OMAN, and a flexible fiber-grating-based system is used for the equipment on OCDMA-OVSF code. These enable an OMAN to assign suitable OVSF codes when creating different-rate lightpaths. How to optimally configure a multi-rate OMAN is a challenge because of displaced lightpaths. In this paper, a genetically modified genetic algorithm (GMGA) [L.R. Chen, Flexible fiber Bragg grating encoder/decoder for hybrid wavelength-time optical CDMA, IEEE Photon. Technol. Lett. 13 (11) (2001) 1233-1235] is used to preplan lightpaths in order to optimally configure an OMAN. To evaluate the performance of the GMGA, we compared it with different preplanning optimization algorithms. Simulation results revealed that the GMGA very efficiently solved the problem.

  1. An accurate evaluation of the performance of asynchronous DS-CDMA systems with zero-correlation-zone coding in Rayleigh fading

    NASA Astrophysics Data System (ADS)

    Walker, Ernest; Chen, Xinjia; Cooper, Reginald L.

    2010-04-01

    An arbitrarily accurate approach is used to determine the bit-error rate (BER) performance for generalized asynchronous DS-CDMA systems, in Gaussian noise with Raleigh fading. In this paper, and the sequel, new theoretical work has been contributed which substantially enhances existing performance analysis formulations. Major contributions include: substantial computational complexity reduction, including a priori BER accuracy bounding; an analytical approach that facilitates performance evaluation for systems with arbitrary spectral spreading distributions, with non-uniform transmission delay distributions. Using prior results, augmented by these enhancements, a generalized DS-CDMA system model is constructed and used to evaluated the BER performance, in a variety of scenarios. In this paper, the generalized system modeling was used to evaluate the performance of both Walsh- Hadamard (WH) and Walsh-Hadamard-seeded zero-correlation-zone (WH-ZCZ) coding. The selection of these codes was informed by the observation that WH codes contain N spectral spreading values (0 to N - 1), one for each code sequence; while WH-ZCZ codes contain only two spectral spreading values (N/2 - 1,N/2); where N is the sequence length in chips. Since these codes span the spectral spreading range for DS-CDMA coding, by invoking an induction argument, the generalization of the system model is sufficiently supported. The results in this paper, and the sequel, support the claim that an arbitrary accurate performance analysis for DS-CDMA systems can be evaluated over the full range of binary coding, with minimal computational complexity.

  2. 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.

  3. 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.

  4. Multi-Mode, Multi-Antenna Software Defined Radar for Adaptive Tracking and Identification of Targets in Urban Environments

    DTIC Science & Technology

    2011-10-31

    designs with code division multiple access ( CDMA ). Analog chirp filters were used to produce an up-chirp, which is used as a radar waveform, coupled with...signals. A potential shortcoming of CDMA techniques is that the addition of two signals will result in a non-constant amplitude signal which will be...of low-frequency A/ Ds . As an example for a multiple carrier signal all the received signals from the multiple carriers are aliased onto the

  5. 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.

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

    DOE PAGES

    Garlapati, Shravan; Kuruganti, Teja; Buehrer, Michael R.; ...

    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

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

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zhuang, Kun Da, E-mail: zkunda@gmail.com; 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 givemore » more options for endovascular interventions in lower limb CTOs.« less

  8. 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.

  9. Adaptive Transmission and Channel Modeling for Frequency Hopping Communications

    DTIC Science & Technology

    2009-09-21

    proposed adaptive transmission method has much greater system capacity than conventional non-adaptive MC direct- sequence ( DS )- CDMA system. • We...several mobile radio systems. First, a new improved allocation algorithm was proposed for multicarrier code-division multiple access (MC- CDMA ) system...Multicarrier code-division multiple access (MC- CDMA ) system with adaptive frequency hopping (AFH) has attracted attention of researchers due to its

  10. Spectral shaping of spreading sequences as a mean to address the trade-off between narrowband and multi-access interferences in UWB systems

    NASA Astrophysics Data System (ADS)

    Mangia, Mauro; Pareschi, Fabio; Rovatti, Riccardo; Setti, Gianluca

    This paper presents a way to cope with the need of simultaneously rejecting narrowband interference and multi-access interference in a UWB system based on direct-sequence CDMA. With this aim in mind, we rely on a closed-form expression of the system bit error probability in presence of both effects. By means of such a formula, we evaluate the effect of spectrum shaping techniques applied to the spreading sequences. The availability of a certain number of degrees of freedom in deciding the spectral profile allows us to cope with different configurations depending on the relative interfering power but also on the relative position of the signal center frequency and the narrowband interferer.

  11. Combined Effect of Random Transmit Power Control and Inter-Path Interference Cancellation on DS-CDMA Packet Mobile Communications

    NASA Astrophysics Data System (ADS)

    Kudoh, Eisuke; Ito, Haruki; Wang, Zhisen; Adachi, Fumiyuki

    In mobile communication systems, high speed packet data services are demanded. In the high speed data transmission, throughput degrades severely due to severe inter-path interference (IPI). Recently, we proposed a random transmit power control (TPC) to increase the uplink throughput of DS-CDMA packet mobile communications. In this paper, we apply IPI cancellation in addition to the random TPC. We derive the numerical expression of the received signal-to-interference plus noise power ratio (SINR) and introduce IPI cancellation factor. We also derive the numerical expression of system throughput when IPI is cancelled ideally to compare with the Monte Carlo numerically evaluated system throughput. Then we evaluate, by Monte-Carlo numerical computation method, the combined effect of random TPC and IPI cancellation on the uplink throughput of DS-CDMA packet mobile communications.

  12. 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.

  13. A Novel Design of Reconfigurable Wavelength-Time Optical Codes to Enhance Security in Optical CDMA Networks

    NASA Astrophysics Data System (ADS)

    Nasaruddin; Tsujioka, Tetsuo

    An optical CDMA (OCDMA) system is a flexible technology for future broadband multiple access networks. A secure OCDMA network in broadband optical access technologies is also becoming an issue of great importance. In this paper, we propose novel reconfigurable wavelength-time (W-T) optical codes that lead to secure transmission in OCDMA networks. The proposed W-T optical codes are constructed by using quasigroups (QGs) for wavelength hopping and one-dimensional optical orthogonal codes (OOCs) for time spreading; we call them QGs/OOCs. Both QGs and OOCs are randomly generated by a computer search to ensure that an eavesdropper could not improve its interception performance by making use of the coding structure. Then, the proposed reconfigurable QGs/OOCs can provide more codewords, and many different code set patterns, which differ in both wavelength and time positions for given code parameters. Moreover, the bit error probability of the proposed codes is analyzed numerically. To realize the proposed codes, a secure system is proposed by employing reconfigurable encoders/decoders based on array waveguide gratings (AWGs), which allow the users to change their codeword patterns to protect against eavesdropping. Finally, the probability of breaking a certain codeword in the proposed system is evaluated analytically. The results show that the proposed codes and system can provide a large codeword pattern, and decrease the probability of breaking a certain codeword, to enhance OCDMA network security.

  14. A Joint Optimization Criterion for Blind DS-CDMA Detection

    NASA Astrophysics Data System (ADS)

    Durán-Díaz, Iván; Cruces-Alvarez, Sergio A.

    2006-12-01

    This paper addresses the problem of the blind detection of a desired user in an asynchronous DS-CDMA communications system with multipath propagation channels. Starting from the inverse filter criterion introduced by Tugnait and Li in 2001, we propose to tackle the problem in the context of the blind signal extraction methods for ICA. In order to improve the performance of the detector, we present a criterion based on the joint optimization of several higher-order statistics of the outputs. An algorithm that optimizes the proposed criterion is described, and its improved performance and robustness with respect to the near-far problem are corroborated through simulations. Additionally, a simulation using measurements on a real software-radio platform at 5 GHz has also been performed.

  15. 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. © 2014 Wiley Periodicals, Inc.

  16. Bench-Top Feasibility Testing of a Novel Percutaneous Renal Access Technique: The Laser Direct Alignment Radiation Reduction Technique (DARRT).

    PubMed

    Khater, Nazih; Shen, Jim; Arenas, Javier; Keheila, Mohamed; Alsyouf, Muhannad; Martin, Jacob A; Lightfoot, Michelle A; Li, Roger; Olgin, Gaudencio; Smith, Jason C; Baldwin, D Duane

    2016-11-01

    Traditional techniques for obtaining percutaneous renal access utilize continuous fluoroscopy. In an attempt to minimize radiation exposure, we describe a novel laser direct alignment radiation reduction technique (DARRT) for percutaneous access and test it in a bench-top model. In this randomized-controlled bench-top study, 20 medical personnel obtained renal accesses using both the conventional bullseye technique and the laser DARRT. The primary endpoint was total fluoroscopy time. Secondary endpoints included insertion time, puncture attempts, course corrections, and subjective procedural difficulty. In the laser DARRT, fluoroscopy was used with the C-arm positioned with the laser beam at a 30° angle. The access needle and hub were aligned with the laser beam. Effective caliceal puncture was confirmed with fluoroscopy and direct vision. The Paired samples Wilcoxon signed rank test was used for statistical analysis with significance at p < 0.05. A total of 120 needle placements were recorded. Fluoroscopy time for needle access using the laser DARRT was significantly lower than the bullseye technique in all groups as follows: attendings (7.09 vs 18.51 seconds; p < 0.001), residents (6.55 vs 13.93 seconds; p = 0.001), and medical students (6.69 vs 20.22 seconds; p < 0.001). Students rated the laser DARRT easier to use (2.56 vs 4.89; p < 0.001). No difference was seen in total access time, puncture attempts, or course corrections between techniques. The laser DARRT reduced fluoroscopy time by 63%, compared with the conventional bullseye technique. The least experienced users found the laser DARRT significantly easier to learn. This novel technique is promising and merits additional testing in animal and human models.

  17. Optical digital chaos cryptography

    NASA Astrophysics Data System (ADS)

    Arenas-Pingarrón, Álvaro; González-Marcos, Ana P.; Rivas-Moscoso, José M.; Martín-Pereda, José A.

    2007-10-01

    In this work we present a new way to mask the data in a one-user communication system when direct sequence - code division multiple access (DS-CDMA) techniques are used. The code is generated by a digital chaotic generator, originally proposed by us and previously reported for a chaos cryptographic system. It is demonstrated that if the user's data signal is encoded with a bipolar phase-shift keying (BPSK) technique, usual in DS-CDMA, it can be easily recovered from a time-frequency domain representation. To avoid this situation, a new system is presented in which a previous dispersive stage is applied to the data signal. A time-frequency domain analysis is performed, and the devices required at the transmitter and receiver end, both user-independent, are presented for the optical domain.

  18. 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

  19. Utilizing Spectrum Efficiently (USE)

    DTIC Science & Technology

    2011-02-28

    18 4.8 Space-Time Coded Asynchronous DS - CDMA with Decentralized MAI Suppression: Performance and...numerical results. 4.8 Space-Time Coded Asynchronous DS - CDMA with Decentralized MAI Suppression: Performance and Spectral Efficiency In [60] multiple...supported at a given signal-to-interference ratio in asynchronous direct-sequence code-division multiple-access ( DS - CDMA ) sys- tems was examined. It was

  20. Performance Analysis of Iterative Channel Estimation and Multiuser Detection in Multipath DS-CDMA Channels

    NASA Astrophysics Data System (ADS)

    Li, Husheng; Betz, Sharon M.; Poor, H. Vincent

    2007-05-01

    This paper examines the performance of decision feedback based iterative channel estimation and multiuser detection in channel coded aperiodic DS-CDMA systems operating over multipath fading channels. First, explicit expressions describing the performance of channel estimation and parallel interference cancellation based multiuser detection are developed. These results are then combined to characterize the evolution of the performance of a system that iterates among channel estimation, multiuser detection and channel decoding. Sufficient conditions for convergence of this system to a unique fixed point are developed.

  1. Concept and implementation of the Globalstar mobile satellite system

    NASA Technical Reports Server (NTRS)

    Schindall, Joel

    1995-01-01

    Globalstar is a satellite-based mobile communications system which provides quality wireless communications (voice and/or data) anywhere in the world except the polar regions. The Globalstar system concept is based upon technological advancements in Low Earth Orbit (LEO) satellite technology and in cellular telephone technology, including the commercial application of Code Division Multiple Access (CDMA) technologies. The Globalstar system uses elements of CDMA and Frequency Division Multiple Access (FDMA), combined with satellite Multiple Beam Antenna (MBA) technology and advanced variable-rate vocoder technology to arrive at one of the most efficient modulation and multiple access systems ever proposed for a satellite communications system. The technology used in Globalstar includes the following techniques in obtaining high spectral efficiency and affordable cost per channel: (1) CDMA modulation with efficient power control; (2) high efficiency vocoder with voice activity factor; (3) spot beam antenna for increased gain and frequency reuse; (4) weighted satellite antenna gain for broad geographic coverage; (5) multisatellite user links (diversity) to enhance communications reliability; and (6) soft hand-off between beams and satellites. Initial launch is scheduled in 1997 and the system is scheduled to be operational in 1998. The Globalstar system utilizes frequencies in L-, S- and C-bands which have the potential to offer worldwide availability with authorization by the appropriate regulatory agencies.

  2. 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.

  3. ROSA: Distributed Joint Routing and Dynamic Spectrum Allocation in Cognitive Radio Ad Hoc Networks

    DTIC Science & Technology

    2010-03-01

    Aug. 1999. [20] I. N. Psaromiligkos and S. N. Batalama. Rapid Combined Synchronization/Demodulation Structures for DS - CDMA Systems - Part II: Finite...Medley. Rapid Combined Synchronization/Demodulation Structures for DS - CDMA Systems - Part I: Algorithmic developments. IEEE Transactions on...multiple access ( CDMA ) [21][20] al- low concurrent co-located communications so that a message from node i to node j can be correctly received even if

  4. Mobile satellite business networks: A part of the European mobile system

    NASA Technical Reports Server (NTRS)

    deMateo, M. L.; Jongejans, A.; Loisy, C.; VanHimbeeck, C.; Marchal, J. P.; Borella, A.; Sartori, M.

    1995-01-01

    The European Space Agency (ESA) is presently procuring an L-band payload EMS, to be embarked on the ITALSAT-2 satellite due for launch in early 1996, in order to promote a regional European mobile system. One of the Land Mobile Communication systems supported by EMS is the MSBN (Mobile Satellite Business Network) voice and data system which will offer the services of a business network on a seamless European coverage. This paper will first recall the characteristics of the MSBN system, which is based on quasi-synchronized CDMA (Code Division Multiple Access) techniques in both directions, and then describe the CDMA receivers implementation. Main validation test results will also be reported confirming predicted performances.

  5. Economic effects of access management techniques in North Carolina.

    DOT National Transportation Integrated Search

    2010-12-21

    The NCDOT has made significant strides to reduce collisions and increase capacity along : strategic highway corridors across the state. Efforts have led to the implementation of many : different access management techniques along corridors, such as i...

  6. Comparison of 3 airway access techniques during suspected spine injury management in American football.

    PubMed

    Toler, Julianne D; Petschauer, Meredith A; Mihalik, Jason P; Oyama, Sakiko; Halverson, S Doug; Guskiewicz, Kevin M

    2010-03-01

    To determine how head movement and time to access airway were affected by 3 emergency airway access techniques used in American football. Prospective counterbalanced design. University research laboratory. Eighteen certified athletic trainers (ATCs) and 18 noncertified students (NCSs). Each participant performed 1 trial of each of the 3 after airway access techniques: quick release mechanism (QRM), cordless screwdriver (CSD), and pocket mask insertion (PMI). Time to task completion in seconds, head movement in each plane (sagittal, frontal, and transverse), maximum head movement in each plane, helmet movement in each plane, and maximum helmet movement in each plane. We observed a significant difference between all 3 techniques with respect to time required to achieve airway access (F(2,68) = 263.88; P < 0.001). The PMI allowed for the quickest access followed by the QRM and CSD techniques, respectively. The PMI technique also resulted in significantly less head movement (F(2,68) = 9.06; P = 0.001) and less maximum head movement (F(2,68) = 13.84; P < 0.001) in the frontal plane compared with the QRM and CSD techniques. The PMI technique should be used to gain rapid airway access when managing a football athlete experiencing respiratory arrest in the presence of a suspected cervical spine injury. In the event the athlete does not present with respiratory arrest, the facemask may be removed carefully with a pocket mask ready. Medical professionals must be familiar with differences in equipment and the effects these may have on the management of the spine-injured athlete.

  7. Introduction of a new opto-electrical phase-locked loop in CMOS technology: the PMD-PLL

    NASA Astrophysics Data System (ADS)

    Ringbeck, Thorsten; Schwarte, Rudolf; Buxbaum, Bernd

    1999-12-01

    The huge and increasing need of information in the industrial world demands an enormous potential of bandwidth in telecommunication systems. Optical communication provides all participants with the whole spectrum of digital services like videophone, cable TV, video conferencing and online services. Especially fast and low cost opto-electrical receivers are badly needed in order to expand fiber networks to every home (FTTH--fiber to the home or FTTD--fiber to the desk, respectively). This paper proposes a new receiver structure which is designed to receiver optical data which are encoded by code division multiple access techniques (CDMA). For data recovery in such CDMA networks phase locked loops (PLL) are needed, which synchronize the local oscillator with the incoming clock. In optical code division multiple access networks these PLLs could be realized either with an electrical PLL after opto-electrical converting or directly in the optical path with a pure optical PLL.

  8. Adaptive Digital Signature Design and Short-Data-Record Adaptive Filtering

    DTIC Science & Technology

    2008-04-01

    rate BPSK binary phase shift keying CA − CFAR cell averaging− constant false alarm rate CDMA code − division multiple − access CFAR constant false...Cotae, “Spreading sequence design for multiple cell synchronous DS-CDMA systems under total weighted squared correlation criterion,” EURASIP Journal...415-428, Mar. 2002. [6] P. Cotae, “Spreading sequence design for multiple cell synchronous DS-CDMA systems under total weighted squared correlation

  9. The COMPOSE Project

    NASA Astrophysics Data System (ADS)

    Balletta, P.; Biagini, M.; Gallinaro, G.; Vernucci, A.

    2003-07-01

    This paper provides an overview of the on-going project COMPOSE, an EC co-funded project aiming to define, specify and validate an innovative mobile-services scenario in support of travellers, and to demonstrate the effectiveness of the new proposed location-based value-added services. COMPOSE is supported by organisations belonging to numerous categories covering, as a whole, the entire value-chain of infomobility services provision to the final user. The project team comprises, in addition to the affiliations of the authors, also Teleatlas (NL), ARS T&TT (NL), Alcatel-Bell Space (B), Skysoft (P), Hitech Marketing (A) and MobileGis (IR). The paper describes the services that will be offered to users, encompassing both the pre-trip and the on-trip framework, presents the overall hybrid system architecture also including a via-satellite component based upon the Wideband-CDMA (W-CDMA) technique adopted in UMTS, discusses the access solutions envisaged for that component permitting multiple feeder-link stations to share the CDMA multiplex capacity by directly transmitting their codes to the satellite, and illustrates the results of some computer simulations intended to assess the performance of said access solutions, with regard to the effects of the inevitable up- link frequency errors and transponder non-linearity.

  10. Unconventional signal detection techniques with Gaussian probability mixtures adaptation in non-AWGN channels: full resolution receiver

    NASA Astrophysics Data System (ADS)

    Chabdarov, Shamil M.; Nadeev, Adel F.; Chickrin, Dmitry E.; Faizullin, Rashid R.

    2011-04-01

    In this paper we discuss unconventional detection technique also known as «full resolution receiver». This receiver uses Gaussian probability mixtures for interference structure adaptation. Full resolution receiver is alternative to conventional matched filter receivers in the case of non-Gaussian interferences. For the DS-CDMA forward channel with presence of complex interferences sufficient performance increasing was shown.

  11. The key technique study of a kind of personal navigation oriented LBS system

    NASA Astrophysics Data System (ADS)

    Yan, Lei; Zheng, Jianghua; Zhang, Xin; Peng, Chunhua; He, Lina

    2005-11-01

    With the integration of GIS, IT technology and wireless communication techniques, LBS is fast developing and caused wide concern. Personal navigation is the critical application of LBS. It has higher requirement of data quality, positioning accuracy and multi-model services. The study discusses the key techniques of a personal navigation oriented LBS system. As an example for service platform of China Unicom, NAVISTAR especially emphasizes the importance of spatial data organization. Based-on CDMA1X network, it adopts gpsOne\\MS-Assisted dynamic positioning technique, and puts forward a data organization solution to realize multi-scale representation.

  12. A Code Division Multiple Access Communication System for the Low Frequency Band.

    DTIC Science & Technology

    1983-04-01

    frequency channels spread-spectrum communication / complex sequences, orthogonal codes impulsive noise 20. ABSTRACT (Continue an reverse side It...their transmissions with signature sequences. Our LF/CDMA scheme is different in that each user’s signature sequence set consists of M orthogonal ...signature sequences. Our LF/CDMA scheme is different in that each user’s signature sequence set consists of M orthogonal sequences and thus log 2 M

  13. Wireless Technology

    DTIC Science & Technology

    2009-03-01

    section, we use as an illustration vehicle for the proposed GLRT schemes a packet-data DS - CDMA communication system2. At all times, the GLRT detectors...are imple- 2The combined effect of DS - CDMA multiple access interference (MAI) and AWGN is Gaussian-mixture distributed and not plain Gaussian. It is...closely to the SMI detector in (9) and outperforms all other detectors. DS - CDMA Case-study #2 Asynchronous multipath fading channel: Pilot-assisted

  14. Bi-orthogonal Symbol Mapping and Detection in Optical CDMA Communication System

    NASA Astrophysics Data System (ADS)

    Liu, Maw-Yang

    2017-12-01

    In this paper, the bi-orthogonal symbol mapping and detection scheme is investigated in time-spreading wavelength-hopping optical CDMA communication system. The carrier-hopping prime code is exploited as signature sequence, whose put-of-phase autocorrelation is zero. Based on the orthogonality of carrier-hopping prime code, the equal weight orthogonal signaling scheme can be constructed, and the proposed scheme using bi-orthogonal symbol mapping and detection can be developed. The transmitted binary data bits are mapped into corresponding bi-orthogonal symbols, where the orthogonal matrix code and its complement are utilized. In the receiver, the received bi-orthogonal data symbol is fed into the maximum likelihood decoder for detection. Under such symbol mapping and detection, the proposed scheme can greatly enlarge the Euclidean distance; hence, the system performance can be drastically improved.

  15. Wideband Channel Modeling in Real Atmospheric Environments with Experimental Evaluation

    DTIC Science & Technology

    2013-04-01

    5] D. F. Gingras and P. Gerstoft. 1997. “The Effect of Propagation on Wideband DS - CDMA Systems in the Suburban Environment,” The First IEEE...are commonly used in spread spectrum communication systems such as Code Division Multiple Access ( CDMA ) systems. Narrowband interference mitigation

  16. Cognitive Code-Division Channelization

    DTIC Science & Technology

    2011-04-01

    22] G. N. Karystinos and D. A. Pados, “New bounds on the total squared correlation and optimum design of DS - CDMA binary signature sets,” IEEE Trans...Commun., vol. 51, pp. 48-51, Jan. 2003. [23] C. Ding, M. Golin, and T. Klve, “Meeting the Welch and Karystinos- Pados bounds on DS - CDMA binary...receiver pair coexisting with a primary code-division multiple-access ( CDMA ) system. Our objective is to find the optimum transmitting power and code

  17. Interference Analysis for Highly Directional 60 GHz Mesh Networks: The Case for Rethinking Medium Access Control

    DTIC Science & Technology

    2010-11-24

    Helmken, “Performance analysis of coherent DS - CDMA systems in a Nakagami fading channel with arbitrary parameters,” Vehicular Technology, IEEE...Transactions on, vol. 46, no. 2, pp. 289–297, may 1997. [26] M. Sunay and P. McLane, “Calculating error probabilities for DS - CDMA systems: when not to use

  18. Ultrasound-Guided Renal Access for Percutaneous Nephrolithotomy: A Description of Three Novel Ultrasound-Guided Needle Techniques

    PubMed Central

    Chu, Carissa; Masic, Selma; Usawachintachit, Manint; Hu, Weiguo; Yang, Wenzeng; Stoller, Marshall; Li, Jianxing

    2016-01-01

    Abstract Ultrasound-guided renal access for percutaneous nephrolithotomy (PCNL) is a safe, effective, and low-cost procedure commonly performed worldwide, but a technique underutilized by urologists in the United States. The purpose of this article is to familiarize the practicing urologist with methods for ultrasound guidance for percutaneous renal access. We discuss two alternative techniques for gaining renal access for PCNL under ultrasound guidance. We also describe a novel technique of using the puncture needle to reposition residual stone fragments to avoid additional tract dilation. With appropriate training, ultrasound-guided renal access for PCNL can lead to reduced radiation exposure, accurate renal access, and excellent stone-free success rates and clinical outcomes. PMID:26414304

  19. 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.

  20. UTC Time Transfer for High Frequency Trading Using IS-95 CDMA Base Station Transmissions and IEEE-1588 Precision Time Protocol

    DTIC Science & Technology

    2010-11-01

    CDMA base stations are each synchronized by GPS receivers, they provide an indirect link to GPS system time and UTC time . The major stock...antenna synchronizes the Local Area Network (LAN) to within 10 microseconds of UTC using the IEEE-1588 Precision Time Protocol (PTP). This is an...activities. Understanding and measuring latency on the LAN is key to the success of HFTs. Without precise time synchronization below 1 millisecond

  1. [Thrombosis in vascular accesses for haemodialysis: rescue treatment using invasive vascular radiological techniques].

    PubMed

    García Medina, J; Lacasa Pérez, N; Muray Cases, S; Pérez Garrido, I; García Medina, V

    2009-01-01

    The purpose of this paper is to communicate our experience in the salvage of thrombosed haemodialysis vascular accesses using interventional radiology techniques. In the last four years, we have treated, by radiological means, 101 thrombosed haemodialysis vascular accesses. There were 44 autologous arteriovenous fistulas (43.56%) and 57 PTFE grafts (56.44%). There were 69 men (68.3%) and 32 women (31.7%). The mean age was 67.73 years (range 33-84). The mean vascular access age was 23.79 months (range 1-132). Manual catheter-directed aspiration was used. Fragmented, triturated or pushed the thrombus against the pulmonary circulation was avoided in all cases. 78 accesses were salvaged (77.2%). Autologous fistulas average and PTFE grafts success rate were 84.44% and 71.42% respectively. Angioplasty in one or more lesions after thromboaspiration was performed in all accesses, except six (5.9%). Metallic endoprostheses were implanted in 14 accesses (13.9%). Mean follow-up was 9 months (range 0-44). Primary patency was 42.3% +/- 5 at 6 months and 32% +/- 4 at one year. Autologous fistulas patency was better than PTFE grafts patency (p < or =0,05). Our results suggest thrombosed autologous arteriovenous fistulas salvage is better than PTFE grafts. This justifies interventional radiology techniques in these situations.

  2. Placement of Upper Extremity Arteriovenous Access in Patients with Central Venous Occlusions: A Novel Technique.

    PubMed

    Murga, Allen G; Chiriano, Jason T; Bianchi, Christian; Sheng, Neha; Patel, Sheela; Abou-Zamzam, Ahmed M; Teruya, Theodore H

    2017-07-01

    Central venous occlusion is a common occurrence in patients with end-stage renal disease. Placement of upper extremity arteriovenous access in patients with occlusion of the brachiocephalic veins is often not an option. Avoidance of lower extremity vascular access can decrease morbidity and infection. The central venous lesions were crossed centrally via femoral access. The wire was retrieved in the neck extravascularly. A Hemodialysis Reliable Outflow catheter was then placed in the right atrium and completed with an arterial anastomosis. We describe a novel technique for placing upper extremity arteriovenous access in patients with occlusion of the brachiocephalic veins. This technique was utilized in 3 patients. The technical success was 100%. The placement of upper extremity arteriovenous access in patients with central venous occlusions is technically feasible. Published by Elsevier Inc.

  3. Methodology for assessing the effectiveness of access management techniques : executive summary.

    DOT National Transportation Integrated Search

    1998-09-14

    A methodology for assessing the effectiveness of access management techniques on suburban arterial highways is developed. The methodology is described as a seven-step process as follows: (1) establish the purpose of the analysis (2) establish the mea...

  4. Subxyphoid access of the normal pericardium: a novel drug delivery technique.

    PubMed

    Laham, R J; Simons, M; Hung, D

    1999-05-01

    The pericardial space may potentially serve as a drug delivery reservoir that might be used to deliver therapeutic substances to the heart. This study describes a novel delivery technique that enables safe and rapid percutaneous subxyphoid access of the normal pericardium in a large animal model (49 Yorkshire pigs). An epidural introducer needle (Tuohy-17) is advanced gently under fluoroscopic guidance with a continuous positive pressure of 20-30 mm Hg (achieved by saline infusion using an intraflow system). The positive pressure is intended to push the right ventricle (with a lower pressure) away from the needle's path. Entry of the pericardial space is suspected after an increase in the saline flow through the intraflow system. Access to the pericardial space is confirmed by the injection of 1 ml of diluted contrast under fluoroscopy. A soft floppy-tip 0.025" guidewire is then advanced to the pericardial space and the needle is exchanged for an infusion catheter. Access of the pericardial space was achieved in all animals without any adverse events and without any hemodynamic compromise even with the delivery of fluid volumes as large as 50 ml. Histologic examination in 15 animals 4 weeks after pericardial access did not reveal any delivery-related myocardial damage. The safety, ease, and absence of hemodynamic compromise make this technique a potentially useful method for intrapericardial drug delivery and a good alternative to standard pericardiocentesis in patients with small pericardial effusions at higher risk for complications.

  5. Ultra-Wideband Impulse Radio for Tactical Ad-Hoc Military Communications

    DTIC Science & Technology

    2010-09-02

    Synchronization, Channel Estimation, and Detection for DS - CDMA Impulse-Radio Systems,” IEEE Transactions on Wireless Communications, vol. 4, no. 6, pp...desired user. Complex matrix operations required by other techniques found in the CDMA literature are not required in our suppression process...domain while a frequency-domain procedure for synchronization is studied in [52]. 5 In the CDMA literature, near-far resistant synchronization is studied

  6. Accurate Bit Error Rate Calculation for Asynchronous Chaos-Based DS-CDMA over Multipath Channel

    NASA Astrophysics Data System (ADS)

    Kaddoum, Georges; Roviras, Daniel; Chargé, Pascal; Fournier-Prunaret, Daniele

    2009-12-01

    An accurate approach to compute the bit error rate expression for multiuser chaosbased DS-CDMA system is presented in this paper. For more realistic communication system a slow fading multipath channel is considered. A simple RAKE receiver structure is considered. Based on the bit energy distribution, this approach compared to others computation methods existing in literature gives accurate results with low computation charge. Perfect estimation of the channel coefficients with the associated delays and chaos synchronization is assumed. The bit error rate is derived in terms of the bit energy distribution, the number of paths, the noise variance, and the number of users. Results are illustrated by theoretical calculations and numerical simulations which point out the accuracy of our approach.

  7. Framework for power and activity factor allocation in a multiclass CDMA system

    NASA Astrophysics Data System (ADS)

    Wu, Xinzhou; Srikant, Rayadurgam

    2001-07-01

    We consider a multimedia CDMA uplink where there are multiple classes of users with different Quality-of-Service (QoS) requirements. Each user is modeled as an ON-OFF source, where in the ON state, the user transmits a fixed number of bits in each time slot and in the OFF state, the user is silent. The probability of being in the ON state, known as the activity factor, could be different for different users. Assuming a constant channel gain, we first characterize the set of transmit power levels, activity factors and number of users in each class that can be supported by a system with a given spreading gain under the constraint that each user's QoS requirement must be met. Using this characterization, we then present a utility function-based algorithm for choosing the activity factors of elastic users in the network.

  8. 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.

  9. 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. (c) 2008 Wiley-Liss, Inc.

  10. Central venous access devices: an investigation of oncology nurses' troubleshooting techniques.

    PubMed

    Mason, Tina M; Ferrall, Sheila M; Boyington, Alice R; Reich, Richard R

    2014-08-01

    Experienced oncology nurses use different troubleshooting techniques for clearing occluded central venous access devices (CVADs) with varying degrees of success. The purpose of this study was to explore troubleshooting techniques used for clearing occluded CVADs by experienced oncology RNs and identify the perceived effectiveness of each technique. An invitation for a web-based survey was sent to select RN members of the Oncology Nursing Society. All nurses (N = 224) reported asking patients to raise and/or move their arm. Most nurses asked patients to lie down, cough, and take deep breaths. Respondents considered instilling a thrombolytic agent to be the most effective technique. No associations were found between techniques and respondents' years in oncology nursing, work setting, certification, or academic degree. The findings contribute to knowledge about care of patients with occluded devices and will help formulate direction for additional investigation of CVADs. Establishing the appropriateness of practice-related troubleshooting techniques may eliminate unnecessary steps and save nursing time. Educating nurses on the topic will also help reduce techniques that are not expected to yield results or are contraindicated.

  11. 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.

  12. Popliteal versus tibial retrograde access for subintimal arterial flossing with antegrade-retrograde intervention (SAFARI) technique.

    PubMed

    Hua, W R; Yi, M Q; Min, T L; Feng, S N; Xuan, L Z; Xing, J

    2013-08-01

    This study aimed to ascertain differences in benefit and effectiveness of popliteal versus tibial retrograde access in subintimal arterial flossing with the antegrade-retrograde intervention (SAFARI) technique. This was a retrospective study of SAFARI-assisted stenting for long chronic total occlusion (CTO) of TASC C and D superficial femoral lesions. 38 cases had superficial femoral artery lesions (23 TASC C and 15 TASC D). All 38 cases underwent SAFARI-assisted stenting. The ipsilateral popliteal artery was retrogradely punctured in 17 patients. A distal posterior tibial (PT) or dorsalis pedis (DP) artery was retrogradely punctured in 21 patients, and 16 of them were punctured after open surgical exposure. SAFARI technical success was achieved in all cases. There was no significant difference in 1-year primary patency (75% vs. 78.9%, p = .86), secondary patency (81.2% vs. 84.2%, p = .91) and access complications (p = 1.00) between popliteal and tibial retrograde access. There was statistical difference in operation time between popliteal (140.1 ± 28.4 min) and tibial retrograde access with PT/DP punctures after surgical vessel exposure (120.4 ± 23.0 min, p = .04). The SAFARI technique is a safe and feasible option for patients with infrainguinal CTO (TASC II C and D). The PT or DP as the retrograde access after surgical vessel exposure is a good choice when using the SAFARI technique. Copyright © 2013 European Society for Vascular Surgery. Published by Elsevier Ltd. All rights reserved.

  13. 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

  14. Code-division multiple-access protocol for active RFID systems

    NASA Astrophysics Data System (ADS)

    Mazurek, Gustaw; Szabatin, Jerzy

    2008-01-01

    Most of the Radio Frequency Identification (RFID) systems operating in HF and UHF bands employ narrowband modulations (FSK or ASK) with Manchester coding. However, these simple transmission schemes are vulnerable to narrowband interference (NBI) generated by other radio systems working in the same frequency band, and also suffer from collision problem and need special anti-collision procedures. This becomes especially important when operating in a noisy, crowded industrial environment. In this paper we show the performance of RFID system with DS-CDMA transmission in comparison to a standard system with FSK modulation defined in ISO 18000-7. Our simulation results show that without any bandwidth expansion the immunity against NBI can be improved by 8 dB and the system capacity can be 7 times higher when using DS-CDMA transmission instead of FSK modulation with Manchester coding.

  15. 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…

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

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Breault, Stéphane, E-mail: stephane.breault@chuv.ch; Glauser, Frédéric, E-mail: frederic.glauser@chuv.ch; Babaker, Malik, E-mail: malik.babaker@chuv.ch

    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”more » 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.« less

  17. Multi-Hop Link Capacity of Multi-Route Multi-Hop MRC Diversity for a Virtual Cellular Network

    NASA Astrophysics Data System (ADS)

    Daou, Imane; Kudoh, Eisuke; Adachi, Fumiyuki

    In virtual cellular network (VCN), proposed for high-speed mobile communications, the signal transmitted from a mobile terminal is received by some wireless ports distributed in each virtual cell and relayed to the central port that acts as a gateway to the core network. In this paper, we apply the multi-route MHMRC diversity in order to decrease the transmit power and increase the multi-hop link capacity. The transmit power, the interference power and the link capacity are evaluated for DS-CDMA multi-hop VCN by computer simulation. The multi-route MHMRC diversity can be applied to not only DS-CDMA but also other access schemes (i. e. MC-CDMA, OFDM, etc.).

  18. Vascular Access Type and Patient and Technique Survival in Home Hemodialysis Patients: The Canadian Organ Replacement Register.

    PubMed

    Perl, Jeffrey; Nessim, Sharon J; Moist, Louise M; Wald, Ron; Na, Yingbo; Tennankore, Karthik K; Chan, Christopher T

    2016-02-01

    While central venous catheter (CVC) use has expanded home hemodialysis (HHD) eligibility to many patients who may be unable to self-cannulate an arteriovenous (AV) access, the association between CVC use and mortality has not been directly examined among HHD patients. Registry-based retrospective observational cohort study. Incident HHD patients in The Canadian Organ Replacement Register who had information for vascular access type (CVC vs AV access) within the first year of HHD therapy initiation. Use of a CVC versus an AV access (AV fistula or graft) within the first year of HHD therapy initiation. The composite of all-cause mortality and technique failure (long-term transfer to an alternate dialysis modality). A Cox proportional hazards model was used to evaluate the adjusted composite outcome and each outcome separately. 1,869 patients initiated HHD therapy in Canada in 1996 to 2012, of whom 1,217 had an access type recorded within the first year of HHD therapy initiation. Compared to CVC use (n=523) and during a median follow-up of 513 and 427 days for AV access and CVC patients, respectively, AV access use (n=694) was associated with lower risk for the composite event of death and technique failure (490 events; adjusted HR, 0.78; 95% CI, 0.64-0.94) and lower adjusted all-cause mortality (129 deaths; adjusted HR, 0.63; 95% CI, 0.43-0.91); the risk for technique failure was nominally lower, but this result was not statistically significant (361 events; adjusted HR, 0.84; 95% CI, 0.67-1.05). Results were robust to sensitivity analyses and after missing data imputation. Missing information for vascular access type (n=659[35% of patients]) and lack of information for longitudinal changes in vascular access type. Compared to CVC use, AV access use was associated with superior survival. Minimizing CVC use and maximizing AV access use while addressing barriers to their placement and self-cannulation may improve HHD outcomes. Copyright © 2016 National Kidney

  19. Pigeon chest: comparative analysis of surgical techniques in minimal access repair of pectus carinatum (MARPC).

    PubMed

    Muntean, Ancuta; Stoica, Ionica; Saxena, Amulya K

    2018-02-01

    After minimally invasive repair for pectus excavatum (MIRPE), similar procedures for pectus carinatum were developed. This study aimed to analyse the various published techniques of minimal access repair for pectus carinatum (MARPC) and compare the outcomes. Literature was reviewed on PubMed with the terms "pectus carinatum", "minimal access repair", "thoracoscopy" and "children". Twelve MARPC techniques that included 13 articles and 140 patients with mean age 15.46 years met the inclusion criteria. Success rate of corrections was n = 125, about 89% in cumulative reports, with seven articles reporting 100%. The complication rate was 39.28%. Since the pectus bar is placed over the sternum and has a large contact area, skin irritation was the most frequent morbidity (n = 20, 14.28%). However, within the complication group (n = 55), wire breakage (n = 21, 38.18%) and bar displacement (n = 10, 18.18%) were the most frequent complications. Twenty-two (15.71%) patients required a second procedure. Recurrences have been reported in four of twelve techniques. There were no lethal outcomes. MARPC techniques are not standardized, as MIRPE are, so comparative analysis is difficult as the only common denominator is minimal access. Surgical morbidity is high in MARPC and affects > 2/3rd patients with about 15% requiring surgery for complication management.

  20. On Performance of Linear Multiuser Detectors for Wireless Multimedia Applications

    NASA Astrophysics Data System (ADS)

    Agarwal, Rekha; Reddy, B. V. R.; Bindu, E.; Nayak, Pinki

    In this paper, performance of different multi-rate schemes in DS-CDMA system is evaluated. The analysis of multirate linear multiuser detectors with multiprocessing gain is analyzed for synchronous Code Division Multiple Access (CDMA) systems. Variable data rate is achieved by varying the processing gain. Our conclusion is that bit error rate for multirate and single rate systems can be made same with a tradeoff with number of users in linear multiuser detectors.

  1. Organic Techniques for Protecting Virtual Private Network (VPN) Services from Access Link Flooding Attacks

    DTIC Science & Technology

    2002-01-01

    Submitted to ICN 2002 Organic Techniques for Protecting Virtual Private Network (VPN) Services from Access Link Flooding Attacks1 Ranga S. Ramanujan ...using these techniques is also described. Contact author: Dr. Ranga S. Ramanujan Architecture Technology Corporation 9971 Valley View Road Eden Prairie...OF ABSTRACT 18. NUMBER OF PAGES 15 19a. NAME OF RESPONSIBLE PERSON a. REPORT unclassified b. ABSTRACT unclassified c . THIS PAGE unclassified

  2. 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.

  3. Integration between terrestrial-based and satellite-based land mobile communications systems

    NASA Technical Reports Server (NTRS)

    Arcidiancono, Antonio

    1990-01-01

    A survey is given of several approaches to improving the performance and marketability of mobile satellite systems (MSS). The provision of voice/data services in the future regional European Land Mobile Satellite System (LMSS), network integration between the Digital Cellular Mobile System (GSM) and LMSS, the identification of critical areas for the implementation of integrated GSM/LMSS areas, space segment scenarios, LMSS for digital trunked private mobile radio (PMR) services, and code division multiple access (CDMA) techniques for a terrestrial/satellite system are covered.

  4. Methodology for assessing the effectiveness of access management techniques : final report, September 14, 1998.

    DOT National Transportation Integrated Search

    1998-09-14

    A methodology for assessing the effectiveness of access management techniques on suburban arterial highways is developed. The methodology is described as a seven-step process as follows: (1) establish the purpose of the analysis (2) establish the mea...

  5. Application of Fiber-Optical Techniques in the Access Transmission and Backbone Transport of Mobile Networks

    NASA Astrophysics Data System (ADS)

    Hilt, Attila; Pozsonyi, László

    2012-09-01

    Fixed access networks widely employ fiber-optical techniques due to the extremely wide bandwidth offered to subscribers. In the last decade, there has also been an enormous increase of user data visible in mobile systems. The importance of fiber-optical techniques within the fixed transmission/transport networks of mobile systems is therefore inevitably increasing. This article summarizes a few reasons and gives examples why and how fiber-optic techniques are employed efficiently in second-generation networks.

  6. Biliary access in technically difficult biliary cannulation: the mucosal bridge technique

    PubMed Central

    Thomas, Rebecca; Shah, Suhaila Rizal; Worthley, Christopher S

    2009-01-01

    Background: The use of precut sphincterotomy during endoscopic retrograde cholangiopancreatography (ERCP) facilitates selective bile duct access in difficult procedures. However, it is also associated with high rates of complications. Several techniques for precut sphincterotomy have been described in the literature. This paper reports our experience with a non-needle-knife technique for precut sphincterotomy, namely, the mucosal bridge technique. Methods: We analysed the experience of a single surgical endoscopist at our centre in performing precut sphincterotomies by retrospectively examining information in the database for January 2002 to February 2008, which had been stored prospectively using Endoscribe. Results: The mucosal bridge technique was performed in 16 (3.19%) of 501 patients. Success rates were 75% and 100% after first and second ERCPs, respectively. The failure of initial procedures was caused by bleeding, tissue oedema, poorly visualized papilla or a poorly distensible duodenum and oedematous papilla. There were four cases of complications, which included periductular extravasation of contrast, bleeding, and sepsis in two patients. However, these complications were not a direct consequence of the precut sphincterotomy. Conclusions: The mucosal bridge technique can be used to increase the likelihood of successful bile duct cannulation, thus preventing the need for a second intervention. PMID:19590645

  7. 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.

  8. 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.

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

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Whelan, Gene; Tenney, Nathan D.; Pelton, Mitchell A.

    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.more » 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

  10. Simulated Assessment of Interference Effects in Direct Sequence Spread Spectrum (DSSS) QPSK Receiver

    DTIC Science & Technology

    2014-03-27

    bit error rate BPSK binary phase shift keying CDMA code division multiple access CSI comb spectrum interference CW continuous wave DPSK differential... CDMA ) and GPS systems which is a Gold code. This code is generated by a modulo-2 operation between two different preferred m-sequences. The preferred m...10 SNR Sim (dB) S N R O ut ( dB ) SNR RF SNR DS Figure 3.26: Comparison of input S NRS im and S NROut of the band-pass RF filter (S NRRF) and

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

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Walser, Eric M., E-mail: walser.eric@mayo.edu

    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 ofmore » 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.« less

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

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Miyayama, Shiro; Matsui, Osamu; Taki, Keiichi

    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 performedmore » 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.« less

  13. Quantum key distribution in multicore fibre for secure radio access networks

    NASA Astrophysics Data System (ADS)

    Llorente, Roberto; Provot, Antoine; Morant, Maria

    2018-01-01

    Broadband access in optical domain usually focuses in providing a pervasive cost-effective high bitrate communication in a given area. Nowadays, it is of utmost interest also to be able to provide a secure communication to the costumers in the area. Wireless access networks rely on optical domain for both fronthaul and backhaul of the radio access network (C-RAN). Multicore fiber (MCF) has been proposed as a promising candidate for the optical media of choice in nextgeneration wireless. The capacity demand of next-generation 5G networks makes interesting the use of high-capacity optical solutions as space-division multiplexing of different signals over MCF media. This work addresses secure MCF communication supporting C-RAN architectures. The paper proposes the use of one core in the MCF to transport securely an optical quantum key encoding altogether with end-to-end wireless signal transmitted in the remaining cores in radio-over-fiber (RoF). The RoF wireless signals are suitable for radio access fronthaul and backhaul. The theoretical principle and simulation analysis of quantum key distribution (QKD) are presented in this paper. The potential impact of optical RoF transmission crosstalk impairments is assessed experimentally considering different cellular signals on the remaining optical cores in the MCF. The experimental results report fronthaul performance over a four-core optical fiber with RoF transmission of full-standard CDMA signals providing 3.5G services in one core, HSPA+ signals providing 3.9G services in the second core and 3GPP LTEAdvanced signals providing 4G services in the third core, considering that the QKD signal is allocated in the fourth core.

  14. Hybrid optical CDMA-FSO communications network under spatially correlated gamma-gamma scintillation.

    PubMed

    Jurado-Navas, Antonio; Raddo, Thiago R; Garrido-Balsells, José María; Borges, Ben-Hur V; Olmos, Juan José Vegas; Monroy, Idelfonso Tafur

    2016-07-25

    In this paper, we propose a new hybrid network solution based on asynchronous optical code-division multiple-access (OCDMA) and free-space optical (FSO) technologies for last-mile access networks, where fiber deployment is impractical. The architecture of the proposed hybrid OCDMA-FSO network is thoroughly described. The users access the network in a fully asynchronous manner by means of assigned fast frequency hopping (FFH)-based codes. In the FSO receiver, an equal gain-combining technique is employed along with intensity modulation and direct detection. New analytical formalisms for evaluating the average bit error rate (ABER) performance are also proposed. These formalisms, based on the spatially correlated gamma-gamma statistical model, are derived considering three distinct scenarios, namely, uncorrelated, totally correlated, and partially correlated channels. Numerical results show that users can successfully achieve error-free ABER levels for the three scenarios considered as long as forward error correction (FEC) algorithms are employed. Therefore, OCDMA-FSO networks can be a prospective alternative to deliver high-speed communication services to access networks with deficient fiber infrastructure.

  15. Operational evaluation of a DGPS / SATCOM VTS : final report

    DOT National Transportation Integrated Search

    1996-09-01

    Satellite communications (SATCOM) using code division multiple access(CDMA) modulation and burst messaging, provided a new dimension to communication channel capacity, operating dependability, and area of coverage. This technology, together with diff...

  16. Minimal access portoenterostomy: advantages and disadvantages of standard laparoscopic and robotic techniques.

    PubMed

    Dutta, Sanjeev; Woo, Russell; Albanese, Craig T

    2007-04-01

    Minimal access portoenterostomy (Kasai procedure) for biliary atresia represents a technically challenging operation. The standard laparoscopic approach yields results comparable to the open technique. After an initial experience with standard laparoscopy, we assessed the potentially superior optics and dexterity of a surgical robotic system for performing portoenterostomy. We reviewed our experience with minimal access portoenterostomy to compare the relative advantages and disadvantages of standard laparoscopic and robotic approaches to biliary atresia. We reviewed the charts of all patients who underwent either laparoscopic or robotic portoenterostomy at our institution between October 2002 and October 2005. Outcome measures included the need to convert to laparotomy, complications, functional outcome expressed either as the direct bilirubin at most recent follow-up (> or = 3 months) or age at transplant, and density of adhesions at transplant. Surgeons' impressions of the two minimal access modalities were also reviewed. A total of 10 patients underwent minimal access portoenterostomy (7 standard laparoscopy; 3 robotic-assisted). Mean follow-up was 20 months (range, 1-36 months). There were no conversions to laparotomy and no intraoperative complications. There was one port site infection that resolved with antibiotics. Five patients (4 laparoscopic, 1 robotic) had progressed to transplantation at the time of follow-up. At transplant, one patient had mild adhesions and two had dense adhesions. Adhesions were not noted for 2 patients. We believe both surgical modalities are feasible from a technical point of view. However, the optical and dexterity advantages of the robotic system were offset by the large instrument size and lack of force feedback.

  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. Robotic percutaneous access to the kidney: comparison with standard manual access.

    PubMed

    Su, Li-Ming; Stoianovici, Dan; Jarrett, Thomas W; Patriciu, Alexandru; Roberts, William W; Cadeddu, Jeffrey A; Ramakumar, Sanjay; Solomon, Stephen B; Kavoussi, Louis R

    2002-09-01

    To evaluate the efficiency, accuracy, and safety of robotic percutaneous access to the kidney (PAKY) for percutaneous nephrolithotomy in comparison with conventional manual techniques. We compared the intraoperative access variables (number of access attempts, time to successful access, estimated blood loss, complications) of 23 patients who underwent robotic PAKY with the remote center of motion device (PAKY-RCM) with the same data from a contemporaneous series of 23 patients who underwent conventional manual percutaneous access to the kidney. The PAKY-RCM incorporates a robotic arm and a friction transmission with axial loading system to accurately position and insert a standard 18-gauge needle percutaneously into the kidney. The blood loss during percutaneous access was estimated on a four-point scale (1 = minimal to 4 = large). The color of effluent urine was graded on a four-point scale (1 = clear to 4 = red). The mean target calix width was 13.5 +/- 9.2 mm in the robotic group and 12.2 +/- 4.5 mm in the manual group (P = 0.57). When comparing PAKY-RCM with standard manual techniques, the mean number of attempts was 2.2 +/- 1.6 v 3.2 +/- 2.5 (P = 0.14), time to access was 10.4 +/- 6.5 minutes v 15.1 +/- 8.8 minutes (P = 0.06), estimated blood loss score was 1.3 +/- 0.49 v 1.7 +/- 0.66 (P = 0.14), and color of effluent urine following access was 2.0 +/- 0.90 v 2.1 +/- 0.7 (P = 0.82). The PAKY-RCM was successful in obtaining access in 87% (20 of 23) of cases. The other three patients (13%) required conversion to manual techniques. There were no major intraoperative complications in either group. Robotic PAKY is a feasible, safe, and efficacious method of obtaining renal access for nephrolithotomy. The number of attempts and time to access were comparable to those of standard manual percutaneous access techniques. These findings provide the groundwork for the development of a completely automated robot-assisted percutaneous renal access device.

  19. A New Technique for Femoral Venous Access in Infants Using Arterial Injection Venous Return Guidance

    PubMed Central

    Ebishima, Hironori; Kitano, Masataka; Kurosaki, Kenichi; Shiraishi, Isao

    2017-01-01

    Objectives: Although venography guidance is helpful for central venous catheter placement, it is sometimes difficult to place a peripheral intravenous cannula for enhancement. We designed a new technique for establishing femoral venous access using venography guidance in the return phase of peripheral arteriography. This new technique was named arterial injection venous return guidance. Here we assessed the efficacy and safety of arterial injection venous return guidance. Methods: We reviewed data of 29 infants less than 6 months old undergoing catheter intervention at our institute in 2014. Of the 29 patients, femoral venous cannulation was performed using arterial injection venous return guidance in 5 patients, venography in 20 patients, and the landmark method in 4 patients. The technical success rates and incidence of complications were compared. Results: The overall success rates were 100% in the arterial injection venous return-guided and venography-guided groups. The mean procedure duration and mean contrast material injection time were similar between the groups. The contrast effect on the femoral vein in the arterial injection venous return-guided group was lower than that in the venography-guided group, but adequate for surgery. The overall complication rate was 17%, and obstruction of previously placed intravenous catheters was the most common complication. Conclusions: Therefore, the arterial injection venous return guidance technique was as safe and efficient as venography for establishing venous access. PMID:29034015

  20. Performance improvement of optical CDMA networks with stochastic artificial bee colony optimization technique

    NASA Astrophysics Data System (ADS)

    Panda, Satyasen

    2018-05-01

    This paper proposes a modified artificial bee colony optimization (ABC) algorithm based on levy flight swarm intelligence referred as artificial bee colony levy flight stochastic walk (ABC-LFSW) optimization for optical code division multiple access (OCDMA) network. The ABC-LFSW algorithm is used to solve asset assignment problem based on signal to noise ratio (SNR) optimization in OCDM networks with quality of service constraints. The proposed optimization using ABC-LFSW algorithm provides methods for minimizing various noises and interferences, regulating the transmitted power and optimizing the network design for improving the power efficiency of the optical code path (OCP) from source node to destination node. In this regard, an optical system model is proposed for improving the network performance with optimized input parameters. The detailed discussion and simulation results based on transmitted power allocation and power efficiency of OCPs are included. The experimental results prove the superiority of the proposed network in terms of power efficiency and spectral efficiency in comparison to networks without any power allocation approach.

  1. Receiver Statistics for Cognitive Radios in Dynamic Spectrum Access Networks

    DTIC Science & Technology

    2012-02-28

    SNR) are employed by many protocols and processes in direct-sequence ( DS ) spread-spectrum packet radio networks, including soft-decision decoding...adaptive modulation protocols, and power adjustment protocols. For DS spread spectrum, we have introduced and evaluated SNR estimators that employ...obtained during demodulation in a binary CDMA receiver. We investigated several methods to apply the proposed metric to the demodulator’s soft-decision

  2. Boosting the FM-Index on the GPU: Effective Techniques to Mitigate Random Memory Access.

    PubMed

    Chacón, Alejandro; Marco-Sola, Santiago; Espinosa, Antonio; Ribeca, Paolo; Moure, Juan Carlos

    2015-01-01

    The recent advent of high-throughput sequencing machines producing big amounts of short reads has boosted the interest in efficient string searching techniques. As of today, many mainstream sequence alignment software tools rely on a special data structure, called the FM-index, which allows for fast exact searches in large genomic references. However, such searches translate into a pseudo-random memory access pattern, thus making memory access the limiting factor of all computation-efficient implementations, both on CPUs and GPUs. Here, we show that several strategies can be put in place to remove the memory bottleneck on the GPU: more compact indexes can be implemented by having more threads work cooperatively on larger memory blocks, and a k-step FM-index can be used to further reduce the number of memory accesses. The combination of those and other optimisations yields an implementation that is able to process about two Gbases of queries per second on our test platform, being about 8 × faster than a comparable multi-core CPU version, and about 3 × to 5 × faster than the FM-index implementation on the GPU provided by the recently announced Nvidia NVBIO bioinformatics library.

  3. Does the Implantation Technique for Totally Implantable Venous Access Ports (TIVAPs) Influence Long-Term Outcome?

    PubMed

    Biacchi, Daniele; Sammartino, Paolo; Sibio, Simone; Accarpio, Fabio; Cardi, Maurizio; Sapienza, Paolo; De Cesare, Alessandro; Atta, Joseph Maher Fouad; Impagnatiello, Alessio; Di Giorgio, Angelo

    2016-02-01

    Totally implantable venous access ports (TIVAP) are eventually explanted for various reasons, related or unrelated to the implantation technique used. Having more information on long-term explantation would help improve placement techniques. From a series of 1572 cancer patients who had TIVAPs implanted in our center with the cutdown technique or Seldinger technique, we studied the 542 patients who returned to us to have their TIVAP explanted after 70 days or more. As outcome measures we distinguished between TIVAPs explanted for long-term complications (infection, catheter-, reservoir-, and patient-related complications) and TIVAPs no longer needed. Univariate and multivariate analyses were run to investigate the reasons for explantation and their possible correlation with implantation techniques. The most common reason for explantation was infection (47.6 %), followed by catheter-related (20.8 %), patient-related (14.7 %), and reservoir-related complications (4.7 %). In the remaining 12.2 % of cases, the TIVAP was explanted complication free after the planned treatments ended. Infection correlated closely with longer TIVAP use. Univariate and multivariate analyses identified the Seldinger technique as a major risk factor for venous thrombosis and catheter dislocation. The need for long-term TIVAP explantation in about one-third of cancer patients is related to the implantation techniques used.

  4. Safety evaluation of access management policies and techniques, TechBrief

    DOT National Transportation Integrated Search

    2015-08-01

    Access management is the process that provides (or manages) access to land development while simultaneously preserving the flow of traffic on the surrounding road network for safety, capacity, and speed. Access management provides important benefits ...

  5. User needs for propagation data

    NASA Technical Reports Server (NTRS)

    Sullivan, Thomas M.

    1993-01-01

    New and refined models of radio signal propagation phenomena are needed to support studies of evolving satellite services and systems. Taking an engineering perspective, applications for propagation measurements and models in the context of various types of analyses that are of ongoing interest are reviewed. Problems that were encountered in the signal propagation aspects of these analyses are reviewed, and potential solutions to these problems are discussed. The focus is on propagation measurements and models needed to support design and performance analyses of systems in the Mobile-Satellite Service (MSS) operating in the 1-3 GHz range. These systems may use geostationary or non-geostationary satellites and Frequency Division Multiple Access (FDMA), Time Division Multiple Access Digital (TDMA), or Code Division Multiple Access (CDMA) techniques. Many of the propagation issues raised in relation to MSS are also pertinent to other services such as broadcasting-satellite (sound) at 2310-2360 MHz. In particular, services involving mobile terminals or terminals with low gain antennas are of concern.

  6. Comparison of a novel real-time SonixGPS needle-tracking ultrasound technique with traditional ultrasound for vascular access in a phantom gel model.

    PubMed

    Kopac, Daniel S; Chen, Jerry; Tang, Raymond; Sawka, Andrew; Vaghadia, Himat

    2013-09-01

    Ultrasound-guided percutaneous vascular access for endovascular procedures is well established in surgical practice. Despite this, rates of complications from venous and arterial access procedures remain a significant cause of morbidity. We hypothesized that the use of a new technique of vascular access using an ultrasound with a novel needle-guidance positioning system (GPS) would lead to improved success rates of vascular puncture for both in-plane and out-of-plane techniques compared with traditional ultrasound. A prospective, randomized crossover study of medical students from all years of medical school was conducted using a phantom gel model. Each medical student performed three ultrasound-guided punctures with each of the four modalities (in-plane no GPS, in-plane with GPS, out-of-plane no GPS, out-of-plane with GPS) for a total of 12 attempts. The success or failure was judged by the ability to aspirate a simulated blood solution from the model. The time to successful puncture was also recorded. A poststudy validated NASA Task Load Index workload questionnaire was conducted to assess the student's perceptions of the two different techniques. A total of 30 students completed the study. There was no significant difference seen in the mean times of vascular access for each of the modalities. Higher success rates for vascular access using the GPS for both the in-plane (94% vs 91%) and the out-of-plane (86% vs 70%) views were observed; however, this was not statistically significant. The students perceived the mental demand (median 12.0 vs 14.00; P = .035) and effort to be lower (mean 11.25 vs 14.00; P = .044) as well as the performance to be higher (mean 15.50 vs 14.00; P = .041) for the GPS vs the traditional ultrasound-guided technique. Students also perceived their ability to access vessels increased with the aid of the GPS (7.00 vs 6.50; P = .007). The majority of students expressed a preference for GPS (26/30, 87%) as opposed to the traditional counterpart

  7. Active Spread-Spectrum Steganalysis for Hidden Data Extraction

    DTIC Science & Technology

    2011-09-01

    steganalysis. In particular, we aim to recover blindly se- cret data hidden in image hosts via (multi-signature) direct- sequence SS embedding [18]-[25...access (CDMA) communica- tion systems. Under the assumption that the embedded se- cret messages are independent identically distributed (i.i.d.) random

  8. Coronary and peripheral stenting in aorto-ostial protruding stents: The balloon assisted access to protruding stent technique.

    PubMed

    Helmy, Tarek A; Sanchez, Carlos E; Bailey, Steven R

    2016-03-01

    Treatment of aorto-ostial in-stent restenosis lesions represents a challenge for interventional cardiologists. Excessive protrusion of the stent into the aorta may lead to multiple technical problems, such as difficult catheter reengagement of the vessel ostium or inability to re-wire through the stent lumen in repeat interventions. We describe a balloon assisted access to protruding stent technique in cases where conventional coaxial engagement of an aorto-ostial protruding stent with the guide catheter or passage of the guide wire through the true lumen is not feasible. This technique is applicable both in coronary and peripheral arteries. © 2015 Wiley Periodicals, Inc.

  9. Impact of dynamic rate coding aspects of mobile phone networks on forensic voice comparison.

    PubMed

    Alzqhoul, Esam A S; Nair, Balamurali B T; Guillemin, Bernard J

    2015-09-01

    Previous studies have shown that landline and mobile phone networks are different in their ways of handling the speech signal, and therefore in their impact on it. But the same is also true of the different networks within the mobile phone arena. There are two major mobile phone technologies currently in use today, namely the global system for mobile communications (GSM) and code division multiple access (CDMA) and these are fundamentally different in their design. For example, the quality of the coded speech in the GSM network is a function of channel quality, whereas in the CDMA network it is determined by channel capacity (i.e., the number of users sharing a cell site). This paper examines the impact on the speech signal of a key feature of these networks, namely dynamic rate coding, and its subsequent impact on the task of likelihood-ratio-based forensic voice comparison (FVC). Surprisingly, both FVC accuracy and precision are found to be better for both GSM- and CDMA-coded speech than for uncoded. Intuitively one expects FVC accuracy to increase with increasing coded speech quality. This trend is shown to occur for the CDMA network, but, surprisingly, not for the GSM network. Further, in respect to comparisons between these two networks, FVC accuracy for CDMA-coded speech is shown to be slightly better than for GSM-coded speech, particularly when the coded-speech quality is high, but in terms of FVC precision the two networks are shown to be very similar. Copyright © 2015 The Chartered Society of Forensic Sciences. Published by Elsevier Ireland Ltd. All rights reserved.

  10. 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

  11. Access to destinations : annual accessibility measure for the Twin Cities Metropolitan Region.

    DOT National Transportation Integrated Search

    2012-11-01

    This report summarizes previous phases of the Access to Destinations project and applies the techniques developed : over the course of the project to conduct an evaluation of accessibility in the Twin Cities metropolitan region for : 2010. It describ...

  12. 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.

  13. MAC Protocol for Ad Hoc Networks Using a Genetic Algorithm

    PubMed Central

    Elizarraras, Omar; Panduro, Marco; Méndez, Aldo L.

    2014-01-01

    The problem of obtaining the transmission rate in an ad hoc network consists in adjusting the power of each node to ensure the signal to interference ratio (SIR) and the energy required to transmit from one node to another is obtained at the same time. Therefore, an optimal transmission rate for each node in a medium access control (MAC) protocol based on CSMA-CDMA (carrier sense multiple access-code division multiple access) for ad hoc networks can be obtained using evolutionary optimization. This work proposes a genetic algorithm for the transmission rate election considering a perfect power control, and our proposition achieves improvement of 10% compared with the scheme that handles the handshaking phase to adjust the transmission rate. Furthermore, this paper proposes a genetic algorithm that solves the problem of power combining, interference, data rate, and energy ensuring the signal to interference ratio in an ad hoc network. The result of the proposed genetic algorithm has a better performance (15%) compared to the CSMA-CDMA protocol without optimizing. Therefore, we show by simulation the effectiveness of the proposed protocol in terms of the throughput. PMID:25140339

  14. System access control study

    DOT National Transportation Integrated Search

    1974-06-01

    The report presents a summary of a study conducted for the Transportation Systems Center of promising access control techniques which are applicable to an aeronautical satellite system. Several frequency division multiple access (FDMA) and time divis...

  15. Mini access guide to simplify calyceal access during percutaneous nephrolithotomy: A novel device.

    PubMed

    Chowdhury, Puskar Shyam; Nayak, Prasant; David, Deepak; Mallick, Sujata

    2017-01-01

    A precise puncture of the renal collecting system is the most essential step for percutaneous nephrolithotomy (PCNL). There are many techniques describing this crucial first step in PCNL including the bull's eye technique, triangulation technique, free-hand technique, and gradual descensus technique. We describe a novel puncture guide to assist accurate percutaneous needle placement during bull's eye technique. The mini access guide (MAG) stabilizes the initial puncture needle by mounting it on an adjustable multidirectional carrier fixed to the patient's skin, which aids in achieving the "bull's eye" puncture. It also avoids a direct fluoroscopic exposure of the urologist's hand during the puncture. Sixty consecutive patients with solitary renal calculus were randomized to traditional hand versus MAG puncture during bull's eye technique of puncture and the fluoroscopy time was assessed. The median fluoroscopy screening time for traditional free-hand bull's eye and MAG-guided bull's eye puncture (fluoroscopic screening time for puncture) was 55 versus 21 s ( P = 0.001) and the median time to puncture was 80 versus 55 s ( P = 0.052), respectively. Novice residents also learned puncture technique faster with MAG on simulator. The MAG is a simple, portable, cheap, and novel assistant to achieve successful PCNL puncture. It would be of great help for novices to establish access during their learning phase of PCNL. It would also be an asset toward significantly decreasing the radiation dose during PCNL access.

  16. Laparoscopic access overview: Is there a safest entry method?

    PubMed

    Bianchi, G; Martorana, E; Ghaith, A; Pirola, G M; Rani, M; Bove, P; Porpiglia, F; Manferrari, F; Micali, S

    2016-01-01

    Laparoscopy is a minimally invasive technique to access the abdominal cavity, for diagnostic or therapeutic applications. Optimizing the access technique is an important step for laparoscopic procedures. The aim of this study is to assess the outcomes of different laparoscopic access techniques and to identify the safest one. Laparoscopic access questionnaire was forwarded via e-mail to the 60 centers who are partners in working group for laparoscopic and robotic surgery of the Italian Urological Society (SIU) and their American and European reference centers. The response rate was 68.33%. The total number of procedures considered was 65.636. 61.5% of surgeons use Veress needle to create pneumoperitoneum. Blind trocar technique is the most commonly used, but has the greatest number of complications. Optical trocar technique seems to be the safest, but it's the less commonly used. The 28,2% of surgeons adopt open Hasson's technique. Total intra-operative complications rate was 3.3%. Open conversion rate was 0.33%, transfusion rate was 1.13%, and total post-operative complication rate was 2.53%. Laparoscopic access is a safe technique with low complication rate. Most of complications can be managed conservatively or laparoscopically. The choice of access technique can affect the rate and type of complications and should be planned according to surgeon experience, safety of each technique and patient characteristics. All access types have perioperative complications. According with our study, optical trocar technique seems to be the safest. Copyright © 2016 AEU. Publicado por Elsevier España, S.L.U. All rights reserved.

  17. Information Ubiquity in Austere Locations

    DTIC Science & Technology

    2011-01-01

    are incompatible (e.g., GSM vs. CDMA ), or are insecure for one’s purposes. There might be satellite communi- cations, but its access might be...Ave. Latency (Unloaded) Ave. Latency (Overloaded) Std Dev. (Unloaded) Std Dev. (Overloaded) M ill is ec on ds AOI UAV UAV 1 UAV 2 UAV 3 Joseph

  18. Totally implantable vascular access device (TIVAD) placement: a modified technique that takes post-procedure aesthetic aspects into account.

    PubMed

    Liberale, Gabriel

    2017-04-01

    Major progress has been made in breast cancer reconstruction surgery. The standard technique for totally implanted vascular access device (TIVAD) implantation generally requires an incision for port insertion on the anterior part of the thorax that leaves a scar in the middle of the neckline in patients who have undergone mastectomy with complex breast reconstruction. The aim of this technical note is to report our revised surgical technique for TIVAD placement. In patients with breast cancer, we take a lateralized approach, performing an oblique incision on the lowest part of the deltopectoral groove. This allows us to introduce the port and to place it on the anterolateral part of the thorax, thus avoiding an unaesthetic scar on the anterior part of the thorax. Our modified technique for TIVAD implantation is described.

  19. Benefits of access management.

    DOT National Transportation Integrated Search

    2003-01-01

    This brochure serves as a guide to the major benefits of several : access management techniques in use across the United States. The : purpose of this brochure is to provide a comprehensive and succinct : examination of the benefits of access managem...

  20. Systems implications of L-band fade data statistics for LEO mobile systems

    NASA Astrophysics Data System (ADS)

    Devieux, Carrie L.

    This paper examines and analyzes research data on the role of foliage attenuation in signal fading between a satellite transmitter and a terrestrial vehicle-mounted receiver. The frequency band of measurement, called L-Band, includes the region 1610.0 to 1626.5 MHz. Data from tests involving various combinations of foliage and vehicle movement conditions clearly show evidence of fast fading (in excess of 0.5 dB per millisecond) and fade depths as great or greater than 16 dB. As a result, the design of a communications link power control that provides the level of accuracy necessary for power sensitive systems could be significantly impacted. Specific examples of this include the communications links that employ Code Division Multiple Access (CDMA) as a modulation technique.

  1. Systems implications of L-band fade data statistics for LEO mobile systems

    NASA Technical Reports Server (NTRS)

    Devieux, Carrie L.

    1993-01-01

    This paper examines and analyzes research data on the role of foliage attenuation in signal fading between a satellite transmitter and a terrestrial vehicle-mounted receiver. The frequency band of measurement, called L-Band, includes the region 1610.0 to 1626.5 MHz. Data from tests involving various combinations of foliage and vehicle movement conditions clearly show evidence of fast fading (in excess of 0.5 dB per millisecond) and fade depths as great or greater than 16 dB. As a result, the design of a communications link power control that provides the level of accuracy necessary for power sensitive systems could be significantly impacted. Specific examples of this include the communications links that employ Code Division Multiple Access (CDMA) as a modulation technique.

  2. Interference Rejection and Management

    DTIC Science & Technology

    2009-07-01

    performance of a DS CDMA receiver. And it was shown in [34] that in order to successfully have a CDMA system overlay narrowband users, i.e., to deploy... CDMA transmitters and the CDMA receivers. 9.2.1.2 Multicarrier Direct Sequence In a multicarrier DS system, multiple narrowband DS waveforms, each at...1)] mmax(i−1) m=mmin(i−1) Detection of the (i−1)th path Pi,Di Pi−1,Di−1 channel estimator \\ data detector Fig. 9.1 Low-pass equivalent of the DS / CDMA

  3. Percutaneous Portal Vein Access and Transhepatic Tract Hemostasis

    PubMed Central

    Saad, Wael E. A.; Madoff, David C.

    2012-01-01

    Percutaneous portal vein interventions require minimally invasive access to the portal venous system. Common approaches to the portal vein include transjugular hepatic vein to portal vein access and direct transhepatic portal vein access. A major concern of the transhepatic route is the risk of postprocedural bleeding, which is increased when patients are anticoagulated or receiving pharmaceutical thrombolytic therapy. Thus percutaneous portal vein access and subsequent closure are important technical parts of percutaneous portal vein procedures. At present, various techniques have been used for either portal access or subsequent transhepatic tract closure and hemostasis. Regardless of the method used, meticulous technique is required to achieve the overall safety and effectiveness of portal venous procedures. This article reviews the various techniques of percutaneous transhepatic portal vein access and the various closure and hemostatic methods used to reduce the risk of postprocedural bleeding. PMID:23729976

  4. One-dimensional photonic crystals for code-division multiple access

    NASA Astrophysics Data System (ADS)

    Wang, Shamino Yuanliang

    One-dimensional photonic crystals exhibit reduced group velocity and huge dispersion at their rejection band edge frequencies. Therefore they are natural candidates as optical delay lines, dispersion compensators, and pulse reshapers. Using wavelength tunable pulses spectrally sliced from a mode-locked fiber laser, the transmission mode measurement was performed in the time domain with single picosecond resolution. Group delays and dispersion were measured with an autocorrelator as an ultrafast optical detector and cross-correlator. Our experimental results agree qualitatively with the theoretical and simulation predictions. A maximum group delay of 10 ps for a commercial 3 mm long uniform fiber Bragg grating and that of 22.6 ps for a research laboratory fabricated 1 cm grating were measured, corresponding to a group velocity 66% of the speed of light in bare fiber. We have also demonstrated in the overlap transmission region of a grating pair both gratings contribute to the group delay while the group velocity dispersion was canceled, resulting in additive delay in transmission with minimal pulse reshaping. This compound grating configuration was further expanded as specially designed grating sequence encoders and decoders in matched filter CDMA. The transmitter grating sequence temporally stretched the input pulse into a long time scale low peak intensity pseudorandom noise, while the conjugate grating sequence in the receiver performed pulse reconstruction and data recovery. A temporal FWHM contrast ratio of 2.5 and a peak intensity contrast ratio of 10 between the correctly and incorrectly decoded signals were achieved. Armed with more sophisticated grating designs we believe this would be a powerful solution to CDMA orthogonal code requirements.

  5. Anatomical investigations on intraosseous access in stillborns - Comparison of different devices and techniques.

    PubMed

    Fuchs, Zeynep; Scaal, Martin; Haverkamp, Heinz; Koerber, Friederike; Persigehl, Thorsten; Eifinger, Frank

    2018-06-01

    Intraosseous (IO)-access plays an alternative route during resuscitation. Our study was performed to investigate the successful rate of IO-access in preterm and term stillborns using different devices and techniques. The cadavers used were legal donations. 16 stillborns, median: 29.2 weeks (IQR 27.2-38.4) were investigated. Two different needles (a: Butterfly needle, 21G, Venofix ® Fa.Braun; b: Arrow ® EZ-IO ® 15G, Teleflex, Dublin, Ireland) were used. Needles were inserted i: manually, using a Butterfly needle; ii: manually, using EZ-IO ® needle or iii: using a battery-powered semi-automatic drill (Arrow ® EZ-IO ® ). Spectral-CT's were performed. The diameter of the corticalis was determined from the CT-images. Successful hit rates with 95% confidence intervals (CI) and odds ratios between the three methods were estimated using a generalised linear mixed model (GLMM). Estimated success rate was 61.1% (95%CI:39.7%-78.9%) for the Butterfly needle, 43.0% (95%CI:23.4%-65.0%) for hand-twisted EZ-IO ® screwing and 39.7% (95%CI:24.1-57.7%) for the semi-automatic drill (Arrow ® EZ-IO ® ), all referring to an average diameter of the corticalis of 1.2 mm. The odds of a correct position were 2.4 times higher (95%CI:0.8-7.6) when using the Butterfly needle than with the drill. In contrast, the odds of correct positioning when inserting the needle by hand were not significantly different from using the drill (odds ratio 1.1, 95%CI: 0.4-3.3). Neither of these effects nor the diameter of the corticalis with an odds ratio near one were significant in the model. Median diameter of the bone marrow cavity was 4.0 mm [IQR 3.3-4.7]. Intraosseous access for premature and neonatal infants could be best achieved by using a manually twisted Butterfly needle. Copyright © 2018 Elsevier B.V. All rights reserved.

  6. 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.

  7. 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.

  8. Improving playground surface accessibility

    Treesearch

    Theodore L. Laufenberg

    2004-01-01

    Could accessibility be improved and maintenance be reduced for wood fiber- based playgrounds? In July 2001, the US Access Board asked the Forest Products Laboratory (FPL) for advice and a potential solution. Since that time new product standards have been adopted by ASTM for engineered wood fiber (EWF), new test techniques have been promulgated by RESNA (Rehabilitation...

  9. Non-visual Web Browsing: Beyond Web Accessibility

    PubMed Central

    Ramakrishnan, I.V.; Ashok, Vikas

    2017-01-01

    People with vision impairments typically use screen readers to browse the Web. To facilitate non-visual browsing, web sites must be made accessible to screen readers, i.e., all the visible elements in the web site must be readable by the screen reader. But even if web sites are accessible, screen-reader users may not find them easy to use and/or easy to navigate. For example, they may not be able to locate the desired information without having to listen to a lot of irrelevant contents. These issues go beyond web accessibility and directly impact web usability. Several techniques have been reported in the accessibility literature for making the Web usable for screen reading. This paper is a review of these techniques. Interestingly, the review reveals that understanding the semantics of the web content is the overarching theme that drives these techniques for improving web usability. PMID:29202137

  10. Non-visual Web Browsing: Beyond Web Accessibility.

    PubMed

    Ramakrishnan, I V; Ashok, Vikas; Billah, Syed Masum

    2017-07-01

    People with vision impairments typically use screen readers to browse the Web. To facilitate non-visual browsing, web sites must be made accessible to screen readers, i.e., all the visible elements in the web site must be readable by the screen reader. But even if web sites are accessible, screen-reader users may not find them easy to use and/or easy to navigate. For example, they may not be able to locate the desired information without having to listen to a lot of irrelevant contents. These issues go beyond web accessibility and directly impact web usability. Several techniques have been reported in the accessibility literature for making the Web usable for screen reading. This paper is a review of these techniques. Interestingly, the review reveals that understanding the semantics of the web content is the overarching theme that drives these techniques for improving web usability.

  11. Overview of Sparse Graph for Multiple Access in Future Mobile Networks

    NASA Astrophysics Data System (ADS)

    Lei, Jing; Li, Baoguo; Li, Erbao; Gong, Zhenghui

    2017-10-01

    Multiple access via sparse graph, such as low density signature (LDS) and sparse code multiple access (SCMA), is a promising technique for future wireless communications. This survey presents an overview of the developments in this burgeoning field, including transmitter structures, extrinsic information transform (EXIT) chart analysis and comparisons with existing multiple access techniques. Such technique enables multiple access under overloaded conditions to achieve a satisfactory performance. Message passing algorithm is utilized for multi-user detection in the receiver, and structures of the sparse graph are illustrated in detail. Outlooks and challenges of this technique are also presented.

  12. Measuring Time-of-Flight in an Ultrasonic LPS System Using Generalized Cross-Correlation

    PubMed Central

    Villladangos, José Manuel; Ureña, Jesús; García, Juan Jesús; Mazo, Manuel; Hernández, Álvaro; Jiménez, Ana; Ruíz, Daniel; De Marziani, Carlos

    2011-01-01

    In this article, a time-of-flight detection technique in the frequency domain is described for an ultrasonic Local Positioning System (LPS) based on encoded beacons. Beacon transmissions have been synchronized and become simultaneous by means of the DS-CDMA (Direct-Sequence Code Division Multiple Access) technique. Every beacon has been associated to a 255-bit Kasami code. The detection of signal arrival instant at the receiver, from which the distance to each beacon can be obtained, is based on the application of the Generalized Cross-Correlation (GCC), by using the cross-spectral density between the received signal and the sequence to be detected. Prior filtering to enhance the frequency components around the carrier frequency (40 kHz) has improved estimations when obtaining the correlation function maximum, which implies an improvement in distance measurement precision. Positioning has been achieved by using hyperbolic trilateration, based on the Time Differences of Arrival (TDOA) between a reference beacon and the others. PMID:22346645

  13. Measuring time-of-flight in an ultrasonic LPS system using generalized cross-correlation.

    PubMed

    Villladangos, José Manuel; Ureña, Jesús; García, Juan Jesús; Mazo, Manuel; Hernández, Alvaro; Jiménez, Ana; Ruíz, Daniel; De Marziani, Carlos

    2011-01-01

    In this article, a time-of-flight detection technique in the frequency domain is described for an ultrasonic local positioning system (LPS) based on encoded beacons. Beacon transmissions have been synchronized and become simultaneous by means of the DS-CDMA (direct-sequence code Division multiple access) technique. Every beacon has been associated to a 255-bit Kasami code. The detection of signal arrival instant at the receiver, from which the distance to each beacon can be obtained, is based on the application of the generalized cross-correlation (GCC), by using the cross-spectral density between the received signal and the sequence to be detected. Prior filtering to enhance the frequency components around the carrier frequency (40 kHz) has improved estimations when obtaining the correlation function maximum, which implies an improvement in distance measurement precision. Positioning has been achieved by using hyperbolic trilateration, based on the time differences of arrival (TDOA) between a reference beacon and the others.

  14. Ultra-processed food product brands on Facebook pages: highly accessed by Brazilians through their marketing techniques.

    PubMed

    Horta, Paula M; Rodrigues, Fernanda T; Dos Santos, Luana C

    2018-06-01

    To analyse the content and extent of marketing of ultra-processed food products (UPP) and their brand pages on Facebook, which are highly accessed by Brazilians. Descriptive. Sixteen UPP brand pages on Facebook were selected from 250 pages that were the most liked by Brazilians in October 2015. We analysed the frequency of 'likes' and members 'talking about' each one of the pages, in addition to fifteen marketing techniques used in the previous year (September 2014 to October 2015). The number of posts, likes, 'shares' and 'commentaries', and the mean number of likes, shares and commentaries per post, were collected for one month, from 23 September to 23 October 2015. The two most liked pages were: Coke® (93 673 979 likes) and McDonald's® (59 749 819 likes). Regarding the number of people talking about the pages, McDonald's led with 555 891 commentaries, followed by Coke (287 274), Burger King® (246 148) and Kibon® (244 523). All pages used marketing techniques, which included photos, user conversations, presence of brand elements and links. Videos were observed on 93·8 % of the pages; promotions on 68·8 %; and celebrities on 62·5 %. In one month, Garoto®, Outback® and Coke were brands that published more than one post per day. Kibon achieved the highest ratio of likes per post (285 845·50) and Burger King had the highest mean shares per post (10 083·93), including commentaries per post (7958·13). UPP marketing is extensively used on Facebook pages and is highly accessed by Brazilians, with UPP companies employing a diversity of marketing strategies.

  15. 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

  16. Survey of Airport Access Analysis Techniques - Models, Data and a Research Program

    DOT National Transportation Integrated Search

    1972-06-01

    The report points up the differences and similarities between airport access travel and general urban trip making. Models and surveys developed for, or applicable, to airport access planning are reviewed. A research program is proposed which would ge...

  17. Central venous access: techniques and indications in oncology.

    PubMed

    Marcy, Pierre-Yves

    2008-10-01

    Long lines can be inserted centrally or peripherally through patent veins into the central venous system down to the atrial caval junction. Traditionally surgeons, anesthetists, cardiologists and more recently interventional radiologists have been placing them using vein cutdown or percutaneous needle puncture techniques. Typical candidates for implanted venous catheters are cancer patients undergoing long-term chemotherapy. The most important issues, in addition to the patency of central veins and the history of previous indwelling catheters, pacewires or venous thrombosis, are the patient's performance status, body mass index, medical history and respiratory status, and the relevant technique. The present article will give an overview of the radiological and surgical implantation techniques and will highlight the impact of imaging means on the technical feasibility, assessment and treatment of device-related complications.

  18. Self-taught axillary vein access without venography for pacemaker implantation: prospective randomized comparison with the cephalic vein access.

    PubMed

    Squara, Fabien; Tomi, Julien; Scarlatti, Didier; Theodore, Guillaume; Moceri, Pamela; Ferrari, Emile

    2017-12-01

    Axillary vein access for pacemaker implantation is uncommon in many centres because of the lack of training in this technique. We assessed whether the introduction of the axillary vein technique was safe and efficient as compared with cephalic vein access, in a centre where no operators had any previous experience in axillary vein puncture. Patients undergoing pacemaker implantation were randomized to axillary or cephalic vein access. All three operators had no experience nor training in axillary vein puncture, and self-learned the technique by reading a published review. Axillary vein puncture was fluoroscopy-guided without contrast venography. Cephalic access was performed by dissection of delto-pectoral groove. Venous access success, venous access duration (from skin incision to guidewire or lead in superior vena cava), procedure duration, X-ray exposure, and peri-procedural (1 month) complications were recorded. results We randomized 74 consecutive patients to axillary (n = 37) or cephalic vein access (n = 37). Axillary vein was successfully accessed in 30/37 (81.1%) patients vs. 28/37 (75.7%) of cephalic veins (P = 0.57). Venous access time was shorter in axillary group than in cephalic group [5.7 (4.4-8.3) vs. 12.2 (10.5-14.8) min, P < 0.001], as well as procedure duration [34.8 (30.6-38.4) vs. 42.0 (39.1-46.6) min, P = 0.043]. X-ray exposure and peri-procedural overall complications were comparable in both groups. Axillary puncture was safe and faster than cephalic access even for the five first procedures performed by each operator. Self-taught axillary vein puncture for pacemaker implantation seems immediately safe and faster than cephalic vein access, when performed by electrophysiologists trained to pacemaker implantation but not to axillary vein puncture. Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2017. For Permissions, please email: journals.permissions@oup.com.

  19. 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…

  20. Unbundling in Current Broadband and Next-Generation Ultra-Broadband Access Networks

    NASA Astrophysics Data System (ADS)

    Gaudino, Roberto; Giuliano, Romeo; Mazzenga, Franco; Valcarenghi, Luca; Vatalaro, Francesco

    2014-05-01

    This article overviews the methods that are currently under investigation for implementing multi-operator open-access/shared-access techniques in next-generation access ultra-broadband architectures, starting from the traditional "unbundling-of-the-local-loop" techniques implemented in legacy twisted-pair digital subscriber line access networks. A straightforward replication of these copper-based unbundling-of-the-local-loop techniques is usually not feasible on next-generation access networks, including fiber-to-the-home point-to-multipoint passive optical networks. To investigate this issue, the article first gives a concise description of traditional copper-based unbundling-of-the-local-loop solutions, then focalizes on both next-generation access hybrid fiber-copper digital subscriber line fiber-to-the-cabinet scenarios and on fiber to the home by accounting for the mix of regulatory and technological reasons driving the next-generation access migration path, focusing mostly on the European situation.

  1. Land Development and Subdivision Regulations that Support Access Management

    DOT National Transportation Integrated Search

    1993-01-01

    This report examines the role of the comprehensive plan in developing an access : management program, aspects of current regulatory practice that contribute to : access problems, and regulatory techniques that support access management : principles. ...

  2. Space-Time Joint Interference Cancellation Using Fuzzy-Inference-Based Adaptive Filtering Techniques in Frequency-Selective Multipath Channels

    NASA Astrophysics Data System (ADS)

    Hu, Chia-Chang; Lin, Hsuan-Yu; Chen, Yu-Fan; Wen, Jyh-Horng

    2006-12-01

    An adaptive minimum mean-square error (MMSE) array receiver based on the fuzzy-logic recursive least-squares (RLS) algorithm is developed for asynchronous DS-CDMA interference suppression in the presence of frequency-selective multipath fading. This receiver employs a fuzzy-logic control mechanism to perform the nonlinear mapping of the squared error and squared error variation, denoted by ([InlineEquation not available: see fulltext.],[InlineEquation not available: see fulltext.]), into a forgetting factor[InlineEquation not available: see fulltext.]. For the real-time applicability, a computationally efficient version of the proposed receiver is derived based on the least-mean-square (LMS) algorithm using the fuzzy-inference-controlled step-size[InlineEquation not available: see fulltext.]. This receiver is capable of providing both fast convergence/tracking capability as well as small steady-state misadjustment as compared with conventional LMS- and RLS-based MMSE DS-CDMA receivers. Simulations show that the fuzzy-logic LMS and RLS algorithms outperform, respectively, other variable step-size LMS (VSS-LMS) and variable forgetting factor RLS (VFF-RLS) algorithms at least 3 dB and 1.5 dB in bit-error-rate (BER) for multipath fading channels.

  3. Interference-Assisted Techniques for Transmission and Multiple Access in Optical Communications

    NASA Astrophysics Data System (ADS)

    Guan, Xun

    communication (VLC) by adopting PNC, with a newly proposed phase-aligning method. PNC could improve the throughput at the bottlenecking relay node in a VLC system, and the proposed phase aligning method can improve the BER performance. The second part of this thesis discusses another interference-assisted technology in communication, that is, non-orthogonal multiple access (NOMA). NOMA multiplexes signals from multiple users in another dimension: power domain, with a non-orthogonal multiplexing in other dimensions such as time, frequency and code. Three schemes are proposed in this part. The first and the second schemes both realize NOMA in VLC, with different multiuser detection (MUD) techniques and a proposed phase pre-distortion method. Although both can decrease the system BER compared to conventional NOMA, the scheme using joint detection (JD) outperforms the one using successive interference cancellation (SIC). The third scheme investigated in this part is a combination of NOMA and a multicarrier precoding (MP) technology based on an orthogonal circulant transform matrix (OCT). This combination can avoid the complicated adaptive bit loading or electronic equalization, making NOMA more attractive in a practical system.

  4. Advanced Techniques for Deploying Reliable and Efficient Access Control: Application to E-healthcare.

    PubMed

    Jaïdi, Faouzi; Labbene-Ayachi, Faten; Bouhoula, Adel

    2016-12-01

    Nowadays, e-healthcare is a main advancement and upcoming technology in healthcare industry that contributes to setting up automated and efficient healthcare infrastructures. Unfortunately, several security aspects remain as main challenges towards secure and privacy-preserving e-healthcare systems. From the access control perspective, e-healthcare systems face several issues due to the necessity of defining (at the same time) rigorous and flexible access control solutions. This delicate and irregular balance between flexibility and robustness has an immediate impact on the compliance of the deployed access control policy. To address this issue, the paper defines a general framework to organize thinking about verifying, validating and monitoring the compliance of access control policies in the context of e-healthcare databases. We study the problem of the conformity of low level policies within relational databases and we particularly focus on the case of a medical-records management database defined in the context of a Medical Information System. We propose an advanced solution for deploying reliable and efficient access control policies. Our solution extends the traditional lifecycle of an access control policy and allows mainly managing the compliance of the policy. We refer to an example to illustrate the relevance of our proposal.

  5. Forming a Cyber Coalition

    DTIC Science & Technology

    2012-04-06

    Estonia 6 :  98% of Estonian‟s territory was covered with Internet access: fixed line, broadband, WiMax, WiFi , and CDMA21 mobile wireless Internet...The hacked homepage displayed a prominent image of Bashar al-Assad, the President of Syria, with a text proclaiming “Syrian Electronic Army Were...update and harmonize their criminal laws against hacking , infringements on copyrights, computer facilitated fraud, child pornography, and other illicit

  6. American Thyroid Association Statement on Remote-Access Thyroid Surgery.

    PubMed

    Berber, Eren; Bernet, Victor; Fahey, Thomas J; Kebebew, Electron; Shaha, Ashok; Stack, Brendan C; Stang, Michael; Steward, David L; Terris, David J

    2016-03-01

    Remote-access techniques have been described over the recent years as a method of removing the thyroid gland without an incision in the neck. However, there is confusion related to the number of techniques available and the ideal patient selection criteria for a given technique. The aims of this review were to develop a simple classification of these approaches, describe the optimal patient selection criteria, evaluate the outcomes objectively, and define the barriers to adoption. A review of the literature was performed to identify the described techniques. A simple classification was developed. Technical details, outcomes, and the learning curve were described. Expert opinion consensus was formulated regarding recommendations for patient selection and performance of remote-access thyroid surgery. Remote-access thyroid procedures can be categorized into endoscopic or robotic breast, bilateral axillo-breast, axillary, and facelift approaches. The experience in the United States involves the latter two techniques. The limited data in the literature suggest long operative times, a steep learning curve, and higher costs with remote-access thyroid surgery compared with conventional thyroidectomy. Nevertheless, a consensus was reached that, in appropriate hands, it can be a viable option for patients with unilateral small nodules who wish to avoid a neck incision. Remote-access thyroidectomy has a role in a small group of patients who fit strict selection criteria. These approaches require an additional level of expertise, and therefore should be done by surgeons performing a high volume of thyroid and robotic surgery.

  7. Design and realization of an automatic weather station at island

    NASA Astrophysics Data System (ADS)

    Chen, Yong-hua; Li, Si-ren

    2011-10-01

    In this paper, the design and development of an automatic weather station monitoring is described. The proposed system consists of a set of sensors for measuring meteorological parameters (temperature, wind speed & direction, rain fall, visibility, etc.). To increase the reliability of the system, wind speed & direction are measured redundantly with duplicate sensors. The sensor signals are collected by the data logger CR1000 at several analog and digital inputs. The CR1000 and the sensors form a completely autonomous system which works with the other systems installed in the container. Communication with the master PC is accomplished over the method of Code Division Multiple Access (CDMA) with the Compact Caimore6550P CDMA DTU. The data are finally stored in tables on the CPU as well as on the CF-Card. The weather station was built as an efficient autonomous system which operates with the other systems to provide the required data for a fully automatic measurement system.

  8. American Thyroid Association Statement on Remote-Access Thyroid Surgery

    PubMed Central

    Bernet, Victor; Fahey, Thomas J.; Kebebew, Electron; Shaha, Ashok; Stack, Brendan C.; Stang, Michael; Steward, David L.; Terris, David J.

    2016-01-01

    Background: Remote-access techniques have been described over the recent years as a method of removing the thyroid gland without an incision in the neck. However, there is confusion related to the number of techniques available and the ideal patient selection criteria for a given technique. The aims of this review were to develop a simple classification of these approaches, describe the optimal patient selection criteria, evaluate the outcomes objectively, and define the barriers to adoption. Methods: A review of the literature was performed to identify the described techniques. A simple classification was developed. Technical details, outcomes, and the learning curve were described. Expert opinion consensus was formulated regarding recommendations for patient selection and performance of remote-access thyroid surgery. Results: Remote-access thyroid procedures can be categorized into endoscopic or robotic breast, bilateral axillo-breast, axillary, and facelift approaches. The experience in the United States involves the latter two techniques. The limited data in the literature suggest long operative times, a steep learning curve, and higher costs with remote-access thyroid surgery compared with conventional thyroidectomy. Nevertheless, a consensus was reached that, in appropriate hands, it can be a viable option for patients with unilateral small nodules who wish to avoid a neck incision. Conclusions: Remote-access thyroidectomy has a role in a small group of patients who fit strict selection criteria. These approaches require an additional level of expertise, and therefore should be done by surgeons performing a high volume of thyroid and robotic surgery. PMID:26858014

  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. Average Likelihood Methods of Classification of Code Division Multiple Access (CDMA)

    DTIC Science & Technology

    2016-05-01

    case of cognitive radio applications. Modulation classification is part of a broader problem known as blind or uncooperative demodulation the goal of...Introduction 2 2.1 Modulation Classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 2.2 Research Objectives...6 3 Modulation Classification Methods 7 3.0.1 Ad Hoc

  11. Proceedings of the Fourth International Mobile Satellite Conference (IMSC 1995)

    NASA Technical Reports Server (NTRS)

    Rigley, Jack R. (Compiler); Estabrook, Polly (Compiler); Reekie, D. Hugh M. (Editor)

    1995-01-01

    The theme to the 1995 International Mobile Satellite Conference was 'Mobile Satcom Comes of Age'. The sessions included Modulation, Coding, and Multiple Access; Hybrid Networks - 1; Spacecraft Technology; propagation; Applications and Experiments - 1; Advanced System Concepts and Analysis; Aeronautical Mobile Satellite Communications; Mobile Terminal Antennas; Mobile Terminal Technology; Current and Planned Systems; Direct Broadcast Satellite; The Use of CDMA for LEO and ICO Mobile Satellite Systems; Hybrid Networks - 2; and Applications and Experiments - 2.

  12. Utility of Intravascular US-Guided Portal Vein Access during Transjugular Intrahepatic Portosystemic Shunt Creation: Retrospective Comparison with Conventional Technique in 109 Patients.

    PubMed

    Pillai, Anil K; Andring, Brice; Faulconer, Nicholas; Reis, Stephen P; Xi, Yin; Iyamu, Ikponmwosa; Suthpin, Patrick D; Kalva, Sanjeeva P

    2016-08-01

    To compare safety and effectiveness of intravascular ultrasound (US)-guided portal vein access during transjugular intrahepatic portosystemic shunt (TIPS) creation with conventional TIPS technique. In this retrospective study, TIPS creation using intravascular US guidance in 55 patients was compared with conventional TIPS creation in 54 patients by 10 operators over a 3-year period. Operators were classified as experienced if they had performed ≥ 20 TIPS procedures at the beginning of the study period. Time to portal vein access, total radiation dose, and needle pass-related capsular perforation were recorded. Baseline demographic characteristics of patients were similar (P > .05). Mean time to portal venous access was 46 minutes ± 37 for conventional TIPS and 31 minutes ± 19 for intravascular US-guided TIPS (P = .007). Intravascular US guidance allowed significantly shorter times (48 min ± 30 vs 28 min ± 16; P = .01) to portal vein access among operators (n = 5) with limited experience but failed to achieve any significant time savings (44 min ± 43 vs 34 min ± 22; P = .89) among experienced operators (n = 5). Needle pass-related capsular perforation occurred in 17/54 (34%) patients with conventional TIPS and 5/55 (9%) patients with intravascular US-guided TIPS (P = .004). Radiation dose was 2,376 mGy ± 1,816 for conventional TIPS and 1,592 mGy ± 1,263 for intravascular US-guided TIPS (P = .004). Intravascular US-guided portal vein access during TIPS creation is associated with shorter portal vein access times, decreased needle pass-related capsular perforations, and reduced radiation dose. Copyright © 2016 SIR. Published by Elsevier Inc. All rights reserved.

  13. Three-Dimensional Printing: An Aid to Epidural Access for Neuromodulation.

    PubMed

    Taverner, Murray G; Monagle, John P

    2017-08-01

    The case report details to use of three-dimensional (3D) printing as an aid to neuromodulation. A patient is described in whom previous attempts at spinal neuromodulation had failed due to lack of epidural or intrathecal access, and the use of a 3D printed model allowed for improved planning and ultimately, success. Successful spinal cord stimulation was achieved with the plan developed by access to a 3D model of the patient's spine. Neuromodulation techniques can provide the optimal analgesic techniques for individual patients. At times these can fail due to lack of access to the site for intervention, in this case epidural access. 3D printing may provide additional information to improve the likelihood of access when anatomy is distorted and standard approaches prove difficult. © 2017 International Neuromodulation Society.

  14. 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.

  15. Secure Web-Site Access with Tickets and Message-Dependent Digests

    USGS Publications Warehouse

    Donato, David I.

    2008-01-01

    Although there are various methods for restricting access to documents stored on a World Wide Web (WWW) site (a Web site), none of the widely used methods is completely suitable for restricting access to Web applications hosted on an otherwise publicly accessible Web site. A new technique, however, provides a mix of features well suited for restricting Web-site or Web-application access to authorized users, including the following: secure user authentication, tamper-resistant sessions, simple access to user state variables by server-side applications, and clean session terminations. This technique, called message-dependent digests with tickets, or MDDT, maintains secure user sessions by passing single-use nonces (tickets) and message-dependent digests of user credentials back and forth between client and server. Appendix 2 provides a working implementation of MDDT with PHP server-side code and JavaScript client-side code.

  16. 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,…

  17. Public Safety Broadband Network Architecture Description

    DTIC Science & Technology

    2013-08-01

    could be used to add an in-app purchase to the user’s mobile phone bill. Major operators , such as AT& T , Deutsche Telekom, Orange, Telefonica and...3GPP technologies such as CDMA2000 and WiMAX networks. MME Mobility Managemen t Entity The MME is the key control-node for the LTE access-network... operator ( operator -managed small cells, etc.) or provides sufficient security (authentication, encryption, etc.). See Figure D3. Figure D3: ITU- T

  18. Empowering Learners with Mobile Open-Access Learning Initiatives

    ERIC Educational Resources Information Center

    Mills, Michael, Ed.; Wake, Donna, Ed.

    2017-01-01

    Education has been progressing at a rapid pace ever since educators have been able to harness the power of mobile technology. Open-access learning techniques provide more students with the opportunity to engage in educational opportunities that may have been previously restricted. "Empowering Learners with Mobile Open-Access Learning…

  19. Minimal access treatment of pectus carinatum: a preliminary report.

    PubMed

    Hock, András

    2009-04-01

    Unlike the minimal access repair of pectus excavatum (PE), a minimal access repair of pectus carinatum (PC) has not been established. This initial experience reports the correction of PC using a minimal access technique in five patients. The procedure was performed by insertion of a pectus bar through either bilateral or only left midaxillary incision. The pectus bar was placed so that the elevated sternum could be depressed. Thoracoscopy was not employed during the procedures and no stabiliser plates were used. On completion of the procedure, a chest tube was inserted into the thoracic cavity to evacuate the air from the thoracic cavity followed by wound closure. The operation time ranged from 75 to 110 min. The chest tube was removed on the second postoperative day and the patients were discharged between the fifth and seventh postoperative day. There was one dislocation in which the bar was finally removed, and in three patients a prolapse of the end of the strut through intercostal space necessitated refixation using wires. Despite a small series, this method offers a minimal access repair of PC, which is comparable to the technique used for PE. The invasiveness of our method is obviously far less, than of those different open surgical techniques performed worldwide presently. Our postoperative results warrant the application of this technique in patients with PC.

  20. Superior Recess Access of the Lumbar Facet Joint.

    PubMed

    Demir-Deviren, Sibel; Singh, Sukhminder; Hanelin, Joshua

    2017-04-01

    Descriptive approach to accessing the lumbar facet joint by superior recess. This study is aimed to describe an approach to accessing the lumbar facet joint through targeting the superior recess during lumbar facet joint injections. Lumbar facet joint injections are routinely performed for both the diagnosis and treatment of chronic low back pain. Previous studies either did not specify which part of the joint to target, or recommended targeting the inferior aspect of the joint to access the inferior recess. One study did mention the superior recess as an alternative to injecting the inferior recess, but none has focused on description of the technique. This is the first time this technique has been described. The records and fluoroscopic images were reviewed for all patients over a period of 9 months (January-September 2012) using the proposed technique. This resulted in a total of 48 patients; 15 men, 29 women, and a total of 117 facet joint intra-articular injections. Among these 48 patients, injections were repeated in total of 4 cases. The average time of injections among 4 repeat cases was 121 days. The success of the procedure was confirmed with an arthrogram demonstrating contrast flowing from the superior recess inferiorly through the joint space. Successful access of the lumbar facet joint through puncture of the superior recess was seen in 114 cases, with 3 unsuccessful attempts to enter facet joints due to osteophytes at involved levels. There were no complications observed during the procedure. We find this approach to be highly successful, safe, and well tolerated by the patient and recommend it as a technique for access of the lumbar facet joint in those patients in whom direct puncture of the inferior recess is difficult.

  1. An easy access to retrieve dental implants displaced into the maxillary sinus: the bony window technique.

    PubMed

    Biglioli, Federico; Chiapasco, Matteo

    2014-12-01

    To present the authors' experience concerning the removal of dental implants displaced in the maxillary sinus via an intraoral approach consisting of the creation of a bony window pedicled to the maxillary sinus membrane. Thirty-six systemically healthy patients, presenting with oral implants displaced into the maxillary sinus, but with no signs of acute or chronic sinusitis, were consecutively treated between 2002 and 2012 via an intraoral approach with the bony window technique. Removal of oral implants from the maxillary sinus was achieved in all patients, and postoperative recovery was uneventful in all of them. Computed tomographies performed after surgery showed no signs of residual sinus infection in all patients and a complete ossification of the bony window margins. Twelve of the 36 treated patients were treated with a sinus grafting procedure 12-18 months after in the same areas previously treated with the bone lid technique. Seventeen implants were placed in the grafted areas 6-9 months later and, after a further waiting period needed for osseointegration, the treated patients were rehabilitated with implant-supported prostheses. The survival rate of implants was 100%, and no complications related to the sinuses and implants were recorded. Results from this study seem to demonstrate that the bony window technique is a safe and easy way to remove oral implants from the maxillary sinus under local anesthesia. The surgical access is hardly visible 6-12 months after surgery, and maxillary sinuses appeared free from residual pathology in all treated patients. Finally, this procedure allows a second-stage sinus grafting procedure via a lateral approach as in a previously untreated maxillary sinus, thus allowing an implant-supported prosthetic restoration. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  2. IDMA-Based MAC Protocol for Satellite Networks with Consideration on Channel Quality

    PubMed Central

    2014-01-01

    In order to overcome the shortcomings of existing medium access control (MAC) protocols based on TDMA or CDMA in satellite networks, interleave division multiple access (IDMA) technique is introduced into satellite communication networks. Therefore, a novel wide-band IDMA MAC protocol based on channel quality is proposed in this paper, consisting of a dynamic power allocation algorithm, a rate adaptation algorithm, and a call admission control (CAC) scheme. Firstly, the power allocation algorithm combining the technique of IDMA SINR-evolution and channel quality prediction is developed to guarantee high power efficiency even in terrible channel conditions. Secondly, the effective rate adaptation algorithm, based on accurate channel information per timeslot and by the means of rate degradation, can be realized. What is more, based on channel quality prediction, the CAC scheme, combining the new power allocation algorithm, rate scheduling, and buffering strategies together, is proposed for the emerging IDMA systems, which can support a variety of traffic types, and offering quality of service (QoS) requirements corresponding to different priority levels. Simulation results show that the new wide-band IDMA MAC protocol can make accurate estimation of available resource considering the effect of multiuser detection (MUD) and QoS requirements of multimedia traffic, leading to low outage probability as well as high overall system throughput. PMID:25126592

  3. Mobile phone base station-emitted radiation does not induce phosphorylation of Hsp27.

    PubMed

    Hirose, H; Sakuma, N; Kaji, N; Nakayama, K; Inoue, K; Sekijima, M; Nojima, T; Miyakoshi, J

    2007-02-01

    An in vitro study focusing on the effects of 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 act to induce phosphorylation and overexpression of heat shock protein hsp27. 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 activation or gene expression of hsp27 and other heat shock proteins (hsps). Human glioblastoma A172 cells were exposed to W-CDMA radiation at SARs of 80 and 800 mW/kg for 2-48 h, and CW radiation at 80 mW/kg for 24 h. Human IMR-90 fibroblasts from fetal lungs were exposed to W-CDMA at 80 and 800 mW/kg for 2 or 28 h, and CW at 80 mW/kg for 28 h. Under the RF field exposure conditions described above, no significant differences in the expression levels of phosphorylated hsp27 at serine 82 (hsp27[pS82]) were observed between the test groups exposed to W-CDMA or CW signal and the sham-exposed negative controls, as evaluated immediately after the exposure periods by bead-based multiplex assays. Moreover, no noticeable differences in the gene expression of hsps were observed between the test groups and the negative controls by DNA Chip analysis. Our results confirm that exposure to low-level RF field up to 800 mW/kg does not induce phosphorylation of hsp27 or expression of hsp gene family.

  4. Signal Classification in Fading Channels Using Cyclic Spectral Analysis

    DTIC Science & Technology

    2009-07-01

    Classifier Design The proposed classifier is designed to classify AM, BFSK, OFDM, DS - CDMA , 4-ASK, 8-ASK, BPSK, QPSK, 8-PSK, 16-PSK, 16-QAM, and 64-QAM...five independent neural networks, each trained to classify a signal as either AM, BFSK, DS - CDMA , or a linear modulation scheme with a real-valued...in an SOF image that resembles those of QAM and PSK signals. Additionally, the DS - CDMA scheme can be thought to look like a BPSK signal. However, due

  5. Cognitive Airborne Networking: Self-Aware Communications via Sensing, Adaptation, and Cross-Layer Optimization

    DTIC Science & Technology

    2011-03-01

    Karystinos and D. A. Pados, “New bounds on the total squared correlation and optimum design of DS - CDMA binary signature sets,” IEEE Trans. Commun...vol. 51, pp. 48-51, Jan. 2003. [99] C. Ding, M. Golin, and T. Klφve, “Meeting the Welch and Karystinos-Pados bounds on DS - CDMA binary signature sets...Designs, Codes and Cryptography, vol. 30, pp. 73-84, Aug. 2003. [100] V. P. Ipatov, “On the Karystinos-Pados bounds and optimal binary DS - CDMA

  6. The maxillary molar endodontic access opening: A microscope-based approach

    PubMed Central

    Mamoun, John Sami

    2016-01-01

    This article reviews the basic clinical techniques of performing a maxillary molar endodontic access opening, starting from the initial access opening into the pulp chamber, to the point where a size #10 file has been advanced to the apices of all three or four (or more) canals. The article explains how the use of the dental surgical operating microscope or microscope-level loupes magnification of ×6–8 or greater, combined with head-mounted or coaxial illumination, improve the ability of a dentist to identify microscopic root canal orifices, which facilitates the efficient creation of conservative access openings with adequate straight-line access in maxillary molars. Magnified photos illustrate various microscopic anatomical structures or landmarks of the initial access opening. Techniques are explored for implementing an access opening for teeth with vital versus necrotic pulpal tissues. The article also explores the use of piezoelectric or ultrasonic instruments for revealing root canal orifices and for removing pulp stones or calcified pulpal tissue inside the pulp chamber. PMID:27403069

  7. A novel PON based UMTS broadband wireless access network architecture with an algorithm to guarantee end to end QoS

    NASA Astrophysics Data System (ADS)

    Sana, Ajaz; Hussain, Shahab; Ali, Mohammed A.; Ahmed, Samir

    2007-09-01

    In this paper we proposes a novel Passive Optical Network (PON) based broadband wireless access network architecture to provide multimedia services (video telephony, video streaming, mobile TV, mobile emails etc) to mobile users. In the conventional wireless access networks, the base stations (Node B) and Radio Network Controllers (RNC) are connected by point to point T1/E1 lines (Iub interface). The T1/E1 lines are expensive and add up to operating costs. Also the resources (transceivers and T1/E1) are designed for peak hours traffic, so most of the time the dedicated resources are idle and wasted. Further more the T1/E1 lines are not capable of supporting bandwidth (BW) required by next generation wireless multimedia services proposed by High Speed Packet Access (HSPA, Rel.5) for Universal Mobile Telecommunications System (UMTS) and Evolution Data only (EV-DO) for Code Division Multiple Access 2000 (CDMA2000). The proposed PON based back haul can provide Giga bit data rates and Iub interface can be dynamically shared by Node Bs. The BW is dynamically allocated and the unused BW from lightly loaded Node Bs is assigned to heavily loaded Node Bs. We also propose a novel algorithm to provide end to end Quality of Service (QoS) (between RNC and user equipment).The algorithm provides QoS bounds in the wired domain as well as in wireless domain with compensation for wireless link errors. Because of the air interface there can be certain times when the user equipment (UE) is unable to communicate with Node B (usually referred to as link error). Since the link errors are bursty and location dependent. For a proposed approach, the scheduler at the Node B maps priorities and weights for QoS into wireless MAC. The compensations for errored links is provided by the swapping of services between the active users and the user data is divided into flows, with flows allowed to lag or lead. The algorithm guarantees (1)delay and throughput for error-free flows,(2)short term fairness

  8. Reduced cost alternatives to premise wiring using ATM and microcellular technologies

    NASA Technical Reports Server (NTRS)

    Gejji, Raghvendra R.

    1993-01-01

    The cost of premises wiring keeps increasing due to personnel moves, new equipment, capacity upgrades etc. It would be desirable to have a wireless interface from the workstations to the fixed network, so as to minimize the wiring changes needed. New technologies such as microcellular personal communication systems are promising to bring down the cost of wireless communication. Another promising technology is Code Division Multiple Access (CDMA), which could dramatically increase the bandwidth available for wireless connections. In addition, Asynchronous Transfer Mode (ATM) technology is emerging as a technique for integrated management of voice, data, and video traffic on a single network. The focus of this investigation will be to assess the future utility of these new technologies for reducing the premise wiring cost at KSC. One of the issues to be studied is the cost comparison of 'old' versus 'new,' especially as time and technology progress. An additional issue for closer study is a feasible time-line for progress in technological capability.

  9. A novel wireless local positioning system for airport (indoor) security

    NASA Astrophysics Data System (ADS)

    Zekavat, Seyed A.; Tong, Hui; Tan, Jindong

    2004-09-01

    A novel wireless local positioning system (WLPS) for airport (or indoor) security is introduced. This system is used by airport (indoor) security guards to locate all of, or a group of airport employees or passengers within the airport area. WLPS consists of two main parts: (1) a base station that is carried by security personnel; hence, introducing dynamic base station (DBS), and (2) a transponder (TRX) that is mounted on all people (including security personnel) present at the airport; thus, introducing them as active targets. In this paper, we (a) draw a futuristic view of the airport security systems, and the flow of information at the airports, (b) investigate the techniques of extending WLPS coverage area beyond the line-of-sight (LoS), and (c) study the performance of this system via standard transceivers, and direct sequence code division multiple access (DS-CDMA) systems with and without antenna arrays and conventional beamforming (BF).

  10. New Bounds on the Total-Squared-Correlation of Quaternary Signature Sets and Optimal Designs

    DTIC Science & Technology

    2010-03-01

    2004. [8] G. S. Rajappan and M. L. Honig, “Signature sequence adaptation for DS - CDMA with multipath,” IEEE Journal on Selected Areas in Commun., vol...vol. 51, pp. 1900-1907, May 2005. [10] G. N. Karystinos and D. A. Pados, “New bounds on the total squared correlation and optimum design of DS - CDMA ...Pados bounds on DS - CDMA binary signature sets,” Des., Codes Cryp- togr., vol. 30, pp. 73-84, Aug. 2003. [12] V. P. Ipatov, “On the Karystinos-Pados bounds

  11. Minimum Total-Squared-Correlation Quaternary Signature Sets: New Bounds and Optimal Designs

    DTIC Science & Technology

    2009-12-01

    50, pp. 2433-2440, Oct. 2004. [11] G. S. Rajappan and M. L. Honig, “Signature sequence adaptation for DS - CDMA with multipath," IEEE J. Sel. Areas...OPTIMAL DESIGNS 3671 [14] C. Ding, M. Golin, and T. Kløve, “Meeting the Welch and Karystinos- Pados bounds on DS - CDMA binary signature sets," Des., Codes...Cryp- togr., vol. 30, pp. 73-84, Aug. 2003. [15] V. P. Ipatov, “On the Karystinos-Pados bounds and optimal binary DS - CDMA signature ensembles," IEEE

  12. Insertion, Detection, and Extraction of Messages Hidden by Optimal Multi-Signature Spread Spectrum Means

    DTIC Science & Technology

    2015-07-09

    49, pp. 873-885, Apr. 2003. [23] G. N. Karystinos and D. A. Pados, “New bounds on the total squared correlation and optimum design of DS - CDMA binary...bounds on DS - CDMA binary signature sets,” Designs, Codes and Cryptography, vol. 30, pp. 73-84, Aug. 2003. [25] V. P. Ipatov, “On the Karystinos-Pados...bounds and optimal binary DS - CDMA signature ensembles,” IEEE Commun. Letters, vol. 8, pp. 81-83, Feb. 2004. [26] G. N. Karystinos and D. A. Pados

  13. 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…

  14. 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

  15. Wireless visual sensor network resource allocation using cross-layer optimization

    NASA Astrophysics Data System (ADS)

    Bentley, Elizabeth S.; Matyjas, John D.; Medley, Michael J.; Kondi, Lisimachos P.

    2009-01-01

    In this paper, we propose an approach to manage network resources for a Direct Sequence Code Division Multiple Access (DS-CDMA) visual sensor network where nodes monitor scenes with varying levels of motion. It uses cross-layer optimization across the physical layer, the link layer and the application layer. Our technique simultaneously assigns a source coding rate, a channel coding rate, and a power level to all nodes in the network based on one of two criteria that maximize the quality of video of the entire network as a whole, subject to a constraint on the total chip rate. One criterion results in the minimal average end-to-end distortion amongst all nodes, while the other criterion minimizes the maximum distortion of the network. Our approach allows one to determine the capacity of the visual sensor network based on the number of nodes and the quality of video that must be transmitted. For bandwidth-limited applications, one can also determine the minimum bandwidth needed to accommodate a number of nodes with a specific target chip rate. Video captured by a sensor node camera is encoded and decoded using the H.264 video codec by a centralized control unit at the network layer. To reduce the computational complexity of the solution, Universal Rate-Distortion Characteristics (URDCs) are obtained experimentally to relate bit error probabilities to the distortion of corrupted video. Bit error rates are found first by using Viterbi's upper bounds on the bit error probability and second, by simulating nodes transmitting data spread by Total Square Correlation (TSC) codes over a Rayleigh-faded DS-CDMA channel and receiving that data using Auxiliary Vector (AV) filtering.

  16. Quantum secret sharing for a general quantum access structure

    NASA Astrophysics Data System (ADS)

    Bai, Chen-Ming; Li, Zhi-Hui; Si, Meng-Meng; Li, Yong-Ming

    2017-10-01

    Quantum secret sharing is a procedure for sharing a secret among a number of participants such that only certain subsets of participants can collaboratively reconstruct it, which are called authorized sets. The quantum access structure of a secret sharing is a family of all authorized sets. Firstly, in this paper, we propose the concept of decomposition of quantum access structure to design a quantum secret sharing scheme. Secondly, based on a maximal quantum access structure (MQAS) [D. Gottesman, Phys. Rev. A 61, 042311 (2000)], we propose an algorithm to improve a MQAS and obtain an improved maximal quantum access structure (IMQAS). Then, we present a sufficient and necessary condition about IMQAS, which shows the relationship between the minimal authorized sets and the players. In accordance with properties, we construct an efficient quantum secret sharing scheme with a decomposition and IMQAS. A major advantage of these techniques is that it allows us to construct a method to realize a general quantum access structure. Finally, we present two kinds of quantum secret sharing schemes via the thought of concatenation or a decomposition of quantum access structure. As a consequence, we find that the application of these techniques allows us to save more quantum shares and reduces more cost than the existing scheme.

  17. 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. © 2015 S. Karger AG, Basel.

  18. 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. Copyright 2008 Wiley-Liss, Inc.

  19. Transcolonic Perirectal NOTES Access (PNA): A feasibility study with survival in swine model.

    PubMed

    Oliveira, André L A; Zorron, Ricardo; Oliveira, Flavio M M DE; Santos, Marcelo B Dos; Scheffer, Jussara P; Rios, Marcelo; Antunes, Fernanda

    2017-05-01

    Transrectal access still has some unsolved issues such as spatial orientation, infection, access and site closure. This study presents a simple technique to perform transcolonic access with survival in a swine model series. A new technique for NOTES perirectal access to perform retroperitoneoscopy, peritoneoscopy, liver and lymphnode biopsies was performed in 6 pigs, using Totally NOTES technique. The specimens were extracted transanally. The flexible endoscope was inserted through a posterior transmural incision and the retrorectal space. Cultures of bacteria were documented for the retroperitoneal space and intra abdominal cavity after 14 days. Rectal site was closed using non-absorbable sutures. There was no bowel cleansing, nor preoperative fasting. The procedures were performed in 6 pigs through transcolonic natural orifice access using available endoscopic flexible instruments. All animals survived 14 days without complications, and cultures were negative. Histopathologic examination of the rectal closure site showed adequate healing of suture line and no micro abscesses. The results of feasibility and safety of experimental Transcolonic NOTES potentially brings new frontiers and future wider applications for minimally invasive surgery. The treatment of colorectal, abdominal and retroperitoneal diseases through a flexible Perirectal NOTES Access (PNA) is a promising new approach.

  20. Treatment of hand ischemia following angioaccess surgery using the distal revascularization interval-ligation technique with preservation of vascular access: description of an 18-case series.

    PubMed

    Sessa, Carmine; Riehl, Gregory; Porcu, Paolo; Pichot, Olivier; Palacin, Pedro; Maghlaoua, Mohamed; Magne, Jean-Luc

    2004-11-01

    Hand ischemia is a rare complication of angioaccess surgery for hemodialysis. Management usually requires ligation of the arteriovenous fistula (AVF). The purpose of this report is to describe our experience with the use of the distal revascularization interval-ligation (DRIL) technique for treatment of ischemia without ligation of the AVF. From January 1999 to September 2002, the DRIL technique was used to treat 18 patients (10 men, 8 women, 10 diabetic patients) with severe paresthesia of the hand (n = 9) and finger necrosis (n = 10). The AVF was located at the elbow in 16 patients and at the wrist in 2 patients. Mean flow distal to the AVF was less than 10 mL in 5 patients, less than 5 mL in 10, and unmeasurable in 3. The conduit used for all DRIL arterial bypasses, including 15 brachiobrachial bypasses, 1 axillobrachial bypass, 1 brachioradial bypass, and 1 radioradial bypass, was the great saphenous vein graft. Trophic manifestations required finger amputation in five patients, pulpar necrosis resection in four, and transmetacarpal amputation of the index finger in one patient. Symptoms disappeared in 13 patients (73%) and improved in 5 (27%). The time required for healing of finger amputations and trophic manifestations ranged from 15 days to 2 months. Mean arterial flow through the DRIL bypass was 50 mL/min (range, 20-90 mL/min). With a mean follow-up interval of 16 months (range, 5-48 months), primary patency of the DRIL artery bypass and AVF was 94% and the limb salvage rate was 100%. The DRIL technique is the most effective procedure for treatment of angioaccess-induced hand ischemia. This technique can be used to achieve persistent relief of symptoms with continued access patency. The DRIL artery bypass improves vacularization of the hand, and ligature of the artery stops the vascular steal without affecting hemodialysis access. The DRIL technique should be proposed as first-line treatment for hand ischemia due to AVF for hemodialysis.

  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. 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…

  3. 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.

  4. SAW devices for consumer communication applications.

    PubMed

    Ruppel, C W; Dill, R; Fischerauer, A; Fischerauer, G; Gawlik, A; Machui, J; Muller, F; Reindl, L; Ruile, W; Scholl, G; Schropp, I; Wagner, K C

    1993-01-01

    An overview of surface acoustic wave (SAW) filter techniques available for different applications is given. Techniques for TV IF applications are outlined, and typical structures are presented. This is followed by a discussion of applications for SAW resonators. Low-loss devices for mobile communication systems and pager applications are examined. Tapped delay lines (matched filters) and convolvers for code-division multiaccess (CDMA) systems are also covered. Although simulation procedures are not considered, for many devices the theoretical frequency response is presented along with the measurement curve.

  5. Comparing the performance of FA, DFA and DMA using different synthetic long-range correlated time series

    PubMed Central

    Shao, Ying-Hui; Gu, Gao-Feng; Jiang, Zhi-Qiang; Zhou, Wei-Xing; Sornette, Didier

    2012-01-01

    Notwithstanding the significant efforts to develop estimators of long-range correlations (LRC) and to compare their performance, no clear consensus exists on what is the best method and under which conditions. In addition, synthetic tests suggest that the performance of LRC estimators varies when using different generators of LRC time series. Here, we compare the performances of four estimators [Fluctuation Analysis (FA), Detrended Fluctuation Analysis (DFA), Backward Detrending Moving Average (BDMA), and Centred Detrending Moving Average (CDMA)]. We use three different generators [Fractional Gaussian Noises, and two ways of generating Fractional Brownian Motions]. We find that CDMA has the best performance and DFA is only slightly worse in some situations, while FA performs the worst. In addition, CDMA and DFA are less sensitive to the scaling range than FA. Hence, CDMA and DFA remain “The Methods of Choice” in determining the Hurst index of time series. PMID:23150785

  6. 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…

  7. 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.

  8. Diffusion accessibility as a method for visualizing macromolecular surface geometry.

    PubMed

    Tsai, Yingssu; Holton, Thomas; Yeates, Todd O

    2015-10-01

    Important three-dimensional spatial features such as depth and surface concavity can be difficult to convey clearly in the context of two-dimensional images. In the area of macromolecular visualization, the computer graphics technique of ray-tracing can be helpful, but further techniques for emphasizing surface concavity can give clearer perceptions of depth. The notion of diffusion accessibility is well-suited for emphasizing such features of macromolecular surfaces, but a method for calculating diffusion accessibility has not been made widely available. Here we make available a web-based platform that performs the necessary calculation by solving the Laplace equation for steady state diffusion, and produces scripts for visualization that emphasize surface depth by coloring according to diffusion accessibility. The URL is http://services.mbi.ucla.edu/DiffAcc/. © 2015 The Protein Society.

  9. [Intraosseous infusion. An important technique also for paediatric anaesthesia].

    PubMed

    Weiss, M; Henze, G; Eich, C; Neuhaus, D

    2009-09-01

    Timely establishment of venous access in infants and toddlers can prove a particularly challenging task. Since the 1940s the technique of intraosseous infusion has established itself as a valuable alternative means for rapid, efficient and safe delivery of drugs and fluids to critically ill children. Whereas international guidelines for paediatric emergency medical care have assigned intraosseous infusion a high priority, most anaesthetists utilize this well-proven technique with great reluctance. This article describes the technique of intraosseous infusion, introduces two different cannulation systems, and discusses its potential indications in paediatric anaesthesia, based on current emergency medical care guidelines as well as some of our own case studies. In particular, children with acutely life-threatening conditions, such as circulatory arrest, laryngospasm, acute airway haemorrhage, hypovolaemic shock or hypothermia secondary to extensive burns, should receive an intraosseous cannula if intravenous access cannot be rapidly established. Future discussion may reveal whether a transiently inserted intraosseous infusion would also be indicated if the child with difficult or impossible venous access presents without acute life-threatening conditions for anaesthesia. Successful application of the intraosseous infusion technique requires immediate access to the necessary equipment, intensive education, continuous training and clear guidelines for its application in an anaesthesia department.

  10. Laparoscopic access with a visualizing trocar.

    PubMed

    Wolf, J S

    1997-01-01

    Although useful in most situations, there are several inherent disadvantages of the standard laparoscopic access techniques of Veress needle insertion and Hasson-type cannula placement. Veress needle placement may be hazardous in patients at high risk for intraabdominal adhesions and difficult in patients who are obese. The usual alternative, the Hasson-type cannula, often does not provide a good gas seal. As another option, the use of a visualizing trocar (OPTIVIEW) has proven to be effective in the initial experience at the University of Michigan. The inner trocar of the visualizing trocar is hollow except for a clear plastic conical tip with two external ridges. The trocar-cannula assembly is passed through tissue layers to enter the operative space under direct vision from a 10-mm zero-degree laparoscope placed into the trocar. Results suggest that this technique is an excellent alternative to Veress needle placement when laparoscopic access is likely to be hazardous or difficult.

  11. 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

  12. Evaluation of ultrasound-guided vascular access in dogs.

    PubMed

    Chamberlin, Scott C; Sullivan, Lauren A; Morley, Paul S; Boscan, Pedro

    2013-01-01

    To describe the technique and determine the feasibility, success rate, perceived difficulty, and time to vascular access using ultrasound guidance for jugular vein catheterization in a cardiac arrest dog model. Prospective descriptive study. University teaching hospital. Nine Walker hounds. A total of 27 jugular catheterizations were performed postcardiac arrest using ultrasound guidance. Catheterizations were recorded based on the order in which they were performed and presence/absence of a hematoma around the vein. Time (minutes) until successful vascular access and perceived difficulty in achieving vascular access (scale of 1 = easy to 10 = difficult) were recorded for each catheterization. Mean time to vascular access was 1.9 minutes (95% confidence interval, 1.1-3.4 min) for catheterizations without hematoma, versus 4.3 minutes (1.8-10.1 min) for catheterizations with hematoma (P = 0.1). Median perceived difficulty was 2 of 10 (range 1-7) for catheterizations without hematoma, versus 2 of 10 (range 1-8) for catheterizations with hematoma (P = 0.3). A learning curve was evaluated by comparing mean time to vascular access and perceived difficulty in initial versus subsequent catheterizations. Mean time to vascular access was 2.5 minutes (1.0-6.4 min) in the initial 13 catheterizations versus 3.3 minutes (1.5-7.5 min) in the subsequent 14 catheterizations (P = 0.6). Median perceived difficulty in the first 13 catheterizations (3, range 1-8) was significantly greater (P = 0.049) than median perceived difficulty in the subsequent 14 catheterizations (2, range 1-6). Ultrasound-guided jugular catheterization is associated with a learning curve but is successful in obtaining rapid vascular access in dogs. Further prospective studies are warranted to confirm the utility of this technique in a clinical setting. © Veterinary Emergency and Critical Care Society 2013.

  13. Evaluation of a simplified augmented reality device for ultrasound-guided vascular access in a vascular phantom.

    PubMed

    Jeon, Yunseok; Choi, Seungpyo; Kim, Heechan

    2014-09-01

    To investigate whether a novel ultrasound device may be used with a simplified augmented reality technique, and to compare this device with conventional techniques during vascular access using a vascular phantom. Prospective, randomized study. Anesthesiology and Pain Medicine departments of a university-affiliated hospital. 20 physicians with no experience with ultrasound-guided techniques. All participants performed the vascular access technique on the vascular phantom model using both a conventional device and the new ultrasound device. Time and the number of redirections of the needle until aspiration of dye into a vessel of the vascular phantom were measured. The median/interquartile range of time was 39.5/41.7 seconds versus 18.6/10.0 seconds (P < 0.001) and number of redirections was 3/3.5 versus 1/0 (P < 0.001) for the conventional and novel ultrasound devices, respectively. During vascular access in a vascular phantom model, the novel device decreased the time and the number of redirections significantly. The device successfully improved the efficiency of the ultrasound-guided vascular access technique. Copyright © 2014 Elsevier Inc. All rights reserved.

  14. Optimizing tertiary storage organization and access for spatio-temporal datasets

    NASA Technical Reports Server (NTRS)

    Chen, Ling Tony; Rotem, Doron; Shoshani, Arie; Drach, Bob; Louis, Steve; Keating, Meridith

    1994-01-01

    We address in this paper data management techniques for efficiently retrieving requested subsets of large datasets stored on mass storage devices. This problem represents a major bottleneck that can negate the benefits of fast networks, because the time to access a subset from a large dataset stored on a mass storage system is much greater that the time to transmit that subset over a network. This paper focuses on very large spatial and temporal datasets generated by simulation programs in the area of climate modeling, but the techniques developed can be applied to other applications that deal with large multidimensional datasets. The main requirement we have addressed is the efficient access of subsets of information contained within much larger datasets, for the purpose of analysis and interactive visualization. We have developed data partitioning techniques that partition datasets into 'clusters' based on analysis of data access patterns and storage device characteristics. The goal is to minimize the number of clusters read from mass storage systems when subsets are requested. We emphasize in this paper proposed enhancements to current storage server protocols to permit control over physical placement of data on storage devices. We also discuss in some detail the aspects of the interface between the application programs and the mass storage system, as well as a workbench to help scientists to design the best reorganization of a dataset for anticipated access patterns.

  15. Full-band TDM-OPDMA for OBI-reduced simultaneous multiple access in a single-wavelength optical access network.

    PubMed

    Jung, Sun-Young; Kim, Chang-Hun; Han, Sang-Kook

    2018-05-14

    Simultaneous multiple access (MA) within a single wavelength can increase the data rate and split ratio in a passive optical network while optical beat interference (OBI) becomes serious in the uplink. Previous techniques to reduce OBI were limited by their complexity and lack of extendibility; as well, bandwidth allocation among MA signals is needed for single photo diode (PD) detection. We proposed and experimentally demonstrated full-band optical pulse division multiplexing-based MA (OPDMA) in an optical access network, which can effectively reduce OBI with extendibility and fully utilize frequency resources of optical modulator without bandwidth allocation in a single-wavelength MA.

  16. Emergency intraosseous access in a helicopter emergency medical service: a retrospective study.

    PubMed

    Sunde, Geir A; Heradstveit, Bård E; Vikenes, Bjarne H; Heltne, Jon K

    2010-10-07

    Intraosseous access (IO) is a method for providing vascular access in out-of-hospital resuscitation of critically ill and injured patients when traditional intravenous access is difficult or impossible. Different intraosseous techniques have been used by our Helicopter Emergency Medical Services (HEMS) since 2003. Few articles document IO use by HEMS physicians. The aim of this study was to evaluate the use of intraosseous access in pre-hospital emergency situations handled by our HEMS. We reviewed all medical records from the period May 2003 to April 2010, and compared three different techniques: Bone Injection Gun (B.I.G® - Waismed), manual bone marrow aspiration needle (Inter V - Medical Device Technologies) and EZ-IO® (Vidacare), used on both adults and paediatric patients. During this seven-year period, 78 insertion attempts were made on 70 patients. Overall success rates were 50% using the manual needle, 55% using the Bone Injection Gun, and 96% using the EZ-IO®. Rates of success on first attempt were significantly higher using the EZ-IO® compared to the manual needle/Bone Injection Gun (p < 0.01/p < 0.001). Fifteen failures were due to insertion-related problems (19.2%), with four technical problems (5.1%) and three extravasations (3.8%) being the most frequent causes. Intraosseous access was primarily used in connection with 53 patients in cardiac arrest (75.7%), including traumatic arrest, drowning and SIDS. Other diagnoses were seven patients with multi-trauma (10.0%), five with seizures/epilepsy (7.1%), three with respiratory failure (4.3%) and two others (2.9%). Nearly one third of all insertions (n = 22) were made in patients younger than two years. No cases of osteomyelitis or other serious complications were documented on the follow-up. Newer intraosseous techniques may enable faster and more reliable vascular access, and this can lower the threshold for intraosseous access on both adult and paediatric patients in critical situations. We believe

  17. Emergency intraosseous access in a helicopter emergency medical service: a retrospective study

    PubMed Central

    2010-01-01

    Background Intraosseous access (IO) is a method for providing vascular access in out-of-hospital resuscitation of critically ill and injured patients when traditional intravenous access is difficult or impossible. Different intraosseous techniques have been used by our Helicopter Emergency Medical Services (HEMS) since 2003. Few articles document IO use by HEMS physicians. The aim of this study was to evaluate the use of intraosseous access in pre-hospital emergency situations handled by our HEMS. Methods We reviewed all medical records from the period May 2003 to April 2010, and compared three different techniques: Bone Injection Gun (B.I.G® - Waismed), manual bone marrow aspiration needle (Inter V - Medical Device Technologies) and EZ-IO® (Vidacare), used on both adults and paediatric patients. Results During this seven-year period, 78 insertion attempts were made on 70 patients. Overall success rates were 50% using the manual needle, 55% using the Bone Injection Gun, and 96% using the EZ-IO®. Rates of success on first attempt were significantly higher using the EZ-IO® compared to the manual needle/Bone Injection Gun (p < 0.01/p < 0.001). Fifteen failures were due to insertion-related problems (19.2%), with four technical problems (5.1%) and three extravasations (3.8%) being the most frequent causes. Intraosseous access was primarily used in connection with 53 patients in cardiac arrest (75.7%), including traumatic arrest, drowning and SIDS. Other diagnoses were seven patients with multi-trauma (10.0%), five with seizures/epilepsy (7.1%), three with respiratory failure (4.3%) and two others (2.9%). Nearly one third of all insertions (n = 22) were made in patients younger than two years. No cases of osteomyelitis or other serious complications were documented on the follow-up. Conclusions Newer intraosseous techniques may enable faster and more reliable vascular access, and this can lower the threshold for intraosseous access on both adult and paediatric

  18. Comparison of external catheters with subcutaneous vascular access ports for chronic vascular access in a porcine model.

    PubMed

    Chuang, Marc; Orvieto, Marcelo; Laven, Brett; Gerber, Glenn; Wardrip, Craig; Ritch, Chad; Shalhav, Arieh

    2005-03-01

    We sought to compare the outcomes of two chronic vascular access techniques, the externalized catheter and the subcutaneous vascular access port, in pigs. Female farm pigs (n = 30) underwent placement of a chronic vascular access device in the jugular vein for a research protocol: 18 of the animals underwent placement of a tunneled Hickman catheter (THC), and the remaining 12 animals underwent placement of a subcutaneous vascular access port (VAP) without external components. After placement of the devices, animals underwent serial blood sampling. All animals were given identical antibiotic prophylaxis. VAP access required the use of a restraint sling for Huber needle insertion, whereas THC access required no additional equipment. Animals were euthanatized 1 month after placement of the device. In the VAP group, the port was retrieved, cleaned, and steam-autoclaved for reuse. In the THC group, 13 (72%) animals developed infectious complications, and blood and wound cultures were often polymicrobial. One animal was euthanatized secondary to overwhelming sepsis. In addition, three (17%) animals developed thromboembolic complications. In contrast, no thromboembolic complications were noted in the VAP group, and only one animal developed a transient fever which resolved spontaneously; no septic complications or abscesses developed. Blood draws with no anesthesia were successful in both groups. We conclude that subcutaneous vascular access ports are a safe and efficient method for obtaining reliable chronic vascular access for a 1-month period in pigs. The subcutaneous devices were associated with low morbidity. In contrast, externalized catheters can be associated with considerable morbidity.

  19. 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.

  20. Portal-endocrine and gastric-exocrine drainage technique of pancreas transplantation provides an easy access for evaluation of pancreatic allograft dysfunction: six-year experience at a single center.

    PubMed

    Zibari, Gazi B; Fallahzadeh, Mohammad Kazem; Hamidian Jahromi, Alireza; Zakhary, Joseph; Dies, David; Wellman, Greg; Singh, Neeraj; Shokouh-Amiri, Hosein

    2014-01-01

    The aim of this study is to report our six-year experience with portal-endocrine and gastric-exocrine drainage technique of pancreatic transplantation, which was first developed and implemented at our center in 2007. In this study, the outcomes of all patients at our center who had pancreas transplantation with portal-endocrine and gastric-exocrine drainage technique were evaluated. From October 2007 to November 2013, 38 patients had pancreas transplantation with this technique - 31 simultaneous kidney pancreas and seven pancreas alone. Median duration of follow-up was 3.8 years. One-, three-, and five-year patient and graft survival rates were 94%, 87%, 70% and 83%, 65%, 49%, respectively. For pancreas allograft dysfunction evaluation, 51 upper endoscopies were performed in 14 patients; donor duodenal biopsies were successfully obtained in 45 (88%). We detected nine episodes of acute rejection (eight patients) and seven episodes of cytomegalovirus (CMV) duodenitis (six patients). No patient developed any complication due to upper endoscopy. Portal-endocrine and gastric-exocrine drainage technique of pancreas transplantation provides lifelong easy access to the transplanted duodenum for evaluation of pancreatic allograft dysfunction.

  1. Artificial intelligence applications of fast optical memory access

    NASA Astrophysics Data System (ADS)

    Henshaw, P. D.; Todtenkopf, A. B.

    The operating principles and performance of rapid laser beam-steering (LBS) techniques are reviewed and illustrated with diagrams; their applicability to fast optical-memory (disk) access is evaluated; and the implications of fast access for the design of expert systems are discussed. LBS methods examined include analog deflection (source motion, wavefront tilt, and phased arrays), digital deflection (polarization modulation, reflectivity modulation, interferometric switching, and waveguide deflection), and photorefractive LBS. The disk-access problem is considered, and typical LBS requirements are listed as 38,000 beam positions, rotational latency 25 ms, one-sector rotation time 1.5 ms, and intersector space 87 microsec. The value of rapid access for increasing the power of expert systems (by permitting better organization of blocks of information) is illustrated by summarizing the learning process of the MVP-FORTH system (Park, 1983).

  2. 2D Presentation Techniques of Mind-maps for Blind Meeting Participants.

    PubMed

    Pölzer, Stephan; Miesenberger, Klaus

    2015-01-01

    Mind-maps, used as ideation technique in co-located meetings (e.g. in brainstorming sessions), which meet with increased importance in business and education, show considerably accessibility challenges for blind meeting participants. Besides an overview of general aspects of accessibility issues in co-located meetings, this paper focuses on the design and development of alternative non-visual presentation techniques for mind-maps. The different aspects of serialized presentation techniques (e.g. treeview) for Braille and audio rendering and two dimensional presentation techniques (e.g. tactile two dimensional array matrix and edge-projection method [1]) are discussed based on the user feedback gathered in intermediate tests following a user centered design approach.

  3. Balloon Blocking Technique (BBT) for Superselective Catheterization of Inaccessible Arteries with Conventional and Modified Techniques

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Morishita, Hiroyuki, E-mail: hmorif@koto.kpu-m.ac.jp, E-mail: mori-h33@xa2.so-net.ne.jp; Takeuchi, Yoshito, E-mail: yotake62@qg8.so-net.ne.jp; Ito, Takaaki, E-mail: takaaki@koto.kpu-m.ac.jp

    2016-06-15

    PurposeThe purpose of the study was to retrospectively evaluate the efficacy and safety of the balloon blocking technique (BBT).Materials and MethodsThe BBT was performed in six patients (all males, mean 73.5 years) in whom superselective catheterization for transcatheter arterial embolization by the conventional microcatheter techniques had failed due to anatomical difficulty, including targeted arteries originating steeply or hooked from parent arteries. All BBT procedures were performed using Seldinger’s transfemoral method. Occlusive balloons were deployed and inflated at the distal side of the target artery branching site in the parent artery via transfemoral access. A microcatheter was delivered from a 5-F cathetermore » via another femoral access and was advanced over the microguidewire into the target artery, under balloon blockage of advancement of the microguidewire into non-target branches. After the balloon catheter was deflated and withdrawn, optimal interventions were performed through the microcatheter.ResultsAfter success of accessing the targeted artery by BBT, optimal interventions were accomplished in all patients with no complications other than vasovagal hypotension, which responded to nominal therapy.ConclusionThe BBT may be useful in superselective catheterization of inaccessible arteries due to anatomical difficulties.« less

  4. Minimal access surgery of pediatric inguinal hernias: a review.

    PubMed

    Saranga Bharathi, Ramanathan; Arora, Manu; Baskaran, Vasudevan

    2008-08-01

    Inguinal hernia is a common problem among children, and herniotomy has been its standard of care. Laparoscopy, which gained a toehold initially in the management of pediatric inguinal hernia (PIH), has managed to steer world opinion against routine contralateral groin exploration by precise detection of contralateral patencies. Besides detection, its ability to repair simultaneously all forms of inguinal hernias (indirect, direct, combined, recurrent, and incarcerated) together with contralateral patencies has cemented its role as a viable alternative to conventional repair. Numerous minimally invasive techniques for addressing PIH have mushroomed in the past two decades. These techniques vary considerably in their approaches to the internal ring (intraperitoneal, extraperitoneal), use of ports (three, two, one), endoscopic instruments (two, one, or none), sutures (absorbable, nonabsorbable), and techniques of knotting (intracorporeal, extracorporeal). In addition to the surgeons' experience and the merits/limitations of individual techniques, it is the nature of the defect that should govern the choice of technique. The emerging techniques show a trend toward increasing use of extracorporeal knotting and diminishing use of working ports and endoscopic instruments. These favor wider adoption of minimal access surgery in addressing PIH by surgeons, irrespective of their laparoscopic skills and experience. Growing experience, wider adoption, decreasing complications, and increasing advantages favor emergence of minimal access surgery as the gold standard for the treatment of PIH in the future. This article comprehensively reviews the laparoscopic techniques of addressing PIH.

  5. European Mobile Satellite Services (EMSS): A regional system for Europe

    NASA Technical Reports Server (NTRS)

    Loisy, C.; Edin, P.; Benedicto, F. J.

    1995-01-01

    The European Space Agency is presently procuring two L-band payloads in order to promote a regional system for the provision of European Mobile Satellite Services (EMSS). These are the EMS payload on the Italsat I-F2 satellite and the LLM payload on the ARTEMIS satellite. Telecommunication system studies have been concentrating on mobile applications where full European geographical coverage is required. Potential applications include high priority Private Mobile Radio networks requiring national or European coverage, such as civil security, fire brigades, police and health services, as well as a dedicated system for provision of Air Traffic Services to the civil aviation community. A typical application is an intelligent road traffic management system combining a geographically selective traffic data collection service based on probe vehicles with a geographically selective traffic information broadcast service. Network architectures and bearer services have been developed both for data only and voice/data services. Vehicle mounted mobile transceivers using CDMA access techniques have been developed. The EMSS operational phase will start with the EMS payload in orbit in 1996 and continue with the LLM payload in 1997.

  6. Access control for electronic patient records.

    PubMed

    Glagola, M J

    1998-01-01

    The transition from hardcopy records to electronic records is in the forefront for healthcare today. For healthcare facilities, a major issue is determining who can access patients' medical information and how access to this information can be controlled. There are three components to access control: identification, authentication and authorization. Checking proof of identity is a means of authenticating someone--through a driver's license, passport or their fingerprints. Similar processes are needed in a computer environment, through the use of passwords, one-time passwords or smartcards, encryption and kerberos, and call-back procedures. New in the area of access control are biometric devices, which are hardware/software combinations that digitize a physical characteristic and compare the sample with previously stored samples. Fingerprints, voiceprints and facial features are examples. Their cost is currently prohibitive, but in time, they may become more common. Digital certificates and certification authorities are other means used to authenticate identify. When a system challenges a user's identity at log on, the user provides a certification that tells the system to go to the issuing certification authority and find proof the user's claim is valid. Low-level certifications offer little value for sensitive data, but high-level certification is now being introduced. It requires more specific, detailed information on the applicant. Authorization, the final component of access control, establishes what a specific user can and cannot access. To have effective access control, transaction logging and system monitoring are needed to ensure the various techniques are being used and performing properly.

  7. 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.

  8. Controlling user access to electronic resources without password

    DOEpatents

    Smith, Fred Hewitt

    2017-08-22

    Described herein are devices and techniques for remotely controlling user access to a restricted computer resource. The process includes obtaining an image from a communication device of a user. An individual and a landmark are identified within the image. Determinations are made that the individual is the user and that the landmark is a predetermined landmark. Access to a restricted computing resource is granted based on the determining that the individual is the user and that the landmark is the predetermined landmark. Other embodiments are disclosed.

  9. Insurance + Access ≠ Health Care: Typology of Barriers to Health Care Access for Low-Income Families

    PubMed Central

    DeVoe, Jennifer E.; Baez, Alia; Angier, Heather; Krois, Lisa; Edlund, Christine; Carney, Patricia A.

    2007-01-01

    PURPOSE Public health insurance programs have expanded coverage for the poor, and family physicians provide essential services to these vulnerable populations. Despite these efforts, many Americans do not have access to basic medical care. This study was designed to identify barriers faced by low-income parents when accessing health care for their children and how insurance status affects their reporting of these barriers. METHODS A mixed methods analysis was undertaken using 722 responses to an open-ended question on a health care access survey instrument that asked low-income Oregon families, “Is there anything else you would like to tell us?” Themes were identified using immersion/crystallization techniques. Pertinent demographic attributes were used to conduct matrix coded queries. RESULTS Families reported 3 major barriers: lack of insurance coverage, poor access to services, and unaffordable costs. Disproportionate reporting of these themes was most notable based on insurance status. A higher percentage of uninsured parents (87%) reported experiencing difficulties obtaining insurance coverage compared with 40% of those with insurance. Few of the uninsured expressed concerns about access to services or health care costs (19%). Access concerns were the most common among publicly insured families, and costs were more often mentioned by families with private insurance. Families made a clear distinction between insurance and access, and having one or both elements did not assure care. Our analyses uncovered a 3-part typology of barriers to health care for low-income families. CONCLUSIONS Barriers to health care can be insurmountable for low-income families, even those with insurance coverage. Patients who do not seek care in a family medicine clinic are not necessarily getting their care elsewhere. PMID:18025488

  10. The Implications of Lowering the Cost to Access Space on Airpower

    DTIC Science & Technology

    2017-06-01

    1 The Implications of Lowering the Cost to Access Space on Airpower Major Gabe Arrington School of Advanced Air and Space Studies...2017 DISTRIBUTION A: Approved for public release: distribution unlimited 2 Disclaimer Opinions, conclusions, and recommendations...implications that lowering the cost to access space will have on Airpower. The research conducted used predominantly qualitative research techniques to

  11. Evaluations of cellulose accessibilities of lignocelluloses by solute exclusion and protein adsorption techniques

    Treesearch

    Q.Q. Wang; Z. He; Z. Zhu; Y.-H.P. Zhang; Y. Ni; X.L. Luo; J.Y. Zhu

    2012-01-01

    Cellulose accessibilities of a set of hornified lignocellulosic substrates derived by drying the never dried pretreated sample and a set of differently pretreated lodgepople pine substrates, were evaluated using solute exclusion and protein adsorption methods. Direct measurements of cellulase adsorption onto cellulose surface of the set of pretreated substrates were...

  12. Vascular access in critical limb ischemia.

    PubMed

    Kang, Won Yu; Campia, Umberto; Ota, Hideaki; Didier, Romain J; Negi, Smita I; Kiramijyan, Sarkis; Koifman, Edward; Baker, Nevin C; Magalhaes, Marco A; Lipinski, Michael J; Escarcega, Ricardo O; Torguson, Rebecca; Waksman, Ron; Bernardo, Nelson L

    2016-01-01

    Currently, percutaneous endovascular intervention is considered a first line of therapy for treating patients with critical limb ischemia. As the result of remarkable development of techniques and technologies, percutaneous endovascular intervention has led to rates of limb salvage comparable to those achieved with bypass surgery, with fewer complications, even in the presence of lower rates of long-term patency. Currently, interventionalists have a multiplicity of access routes including smaller arteries, with both antegrade and retrograde approaches. Therefore, the choice of the optimal access site has become an integral part of the success of the percutaneous intervention. By understanding the technical aspects, as well as the advantages and limitations of each approach, the interventionalists can improve clinical outcomes in patients with severe peripheral arterial disease. This article reviews the access routes in critical limb ischemia, their advantages and disadvantages, and the clinical outcomes of each. Copyright © 2016 Elsevier Inc. All rights reserved.

  13. Controlling user access to electronic resources without password

    DOEpatents

    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.

  14. 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)

  15. Patient privacy protection using anonymous access control techniques.

    PubMed

    Weerasinghe, D; Rajarajan, M; Elmufti, K; Rakocevic, V

    2008-01-01

    The objective of this study is to develop a solution to preserve security and privacy in a healthcare environment where health-sensitive information will be accessed by many parties and stored in various distributed databases. The solution should maintain anonymous medical records and it should be able to link anonymous medical information in distributed databases into a single patient medical record with the patient identity. In this paper we present a protocol that can be used to authenticate and authorize patients to healthcare services without providing the patient identification. Healthcare service can identify the patient using separate temporary identities in each identification session and medical records are linked to these temporary identities. Temporary identities can be used to enable record linkage and reverse track real patient identity in critical medical situations. The proposed protocol provides main security and privacy services such as user anonymity, message privacy, message confidentiality, user authentication, user authorization and message replay attacks. The medical environment validates the patient at the healthcare service as a real and registered patient for the medical services. Using the proposed protocol, the patient anonymous medical records at different healthcare services can be linked into one single report and it is possible to securely reverse track anonymous patient into the real identity. The protocol protects the patient privacy with a secure anonymous authentication to healthcare services and medical record registries according to the European and the UK legislations, where the patient real identity is not disclosed with the distributed patient medical records.

  16. A microlagoon technique for the culture of mammalian cells

    NASA Technical Reports Server (NTRS)

    Cone, C. D., Jr.; Peddrew, K. H.

    1968-01-01

    Technique obtains micropartitioning in a simple and reproducible manner by forming a field of tiny ponds or lagoons on the surface of a suitable culturing vessel. The technique allows free access of the common culture to all parts of the field.

  17. 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…

  18. Accessibility, Textbooks, and Access Services

    ERIC Educational Resources Information Center

    Kahler, Janice E.

    2017-01-01

    Putting access in Access Services is the goal. The Course Reserves unit is the place. Textbooks are the focus. Electronic technologies are the future. Patron-centric services will be our standard. Access to textbooks by all patrons will be the achievement. Course Reserves located in Library West at the University of Florida George A. Smathers…

  19. Complications of the access during aortic valve implantation through transfemoral access.

    PubMed

    Alsac, Jean-Marc; Zegdi, Rachid; Blanchard, Didier; Achouh, Paul; Cholley, Bernard; Berrebi, Alain; Julia, Pierre; Fabiani, Jean-Noël

    2011-08-01

    Aortic valve implantation (AVI) is a booming therapeutic option in high-risk patients with calcific aortic stenosis. Retrograde femoral approach drawbacks include vascular complications owing to the size of the introduction system (22- and 24-F).The aim of this study was to retrospectively analyze the incidence and the treatment of vascular complications in the first 2 years of transfemoral AVI experience with the first generation of Edwards SAPIEN transcatheter heart valves. Since December 2007, AVI has been performed in 71 patients, 21 times by the transapical route and 50 times by the transfemoral route through an inguinal approach with the first generation of Edwards SAPIEN transcatheter heart valves (23 and 26 mm). The incidence and the treatment of vascular complications were evaluated as main criteria for transfemoral AVI. All the procedures could be successfully performed by a femoral route, except for three cases when the introducing device could not be fixed on the thoracic aorta because of vascular access problems. Vascular access-related complications occurred in nine patients (18%), including three iliac dissections, two aortic dissections, three femoral lesions, and one thoracic aorta rupture. These complications were treated either in a conservative way (n = 2), or in an endovascular way using a contralateral approach (n = 3), or surgically through an inguinal approach (n = 3). A traumatic rupture of the thoracic aorta resulted in the death of a female patient. In our experience, transfemoral AVI gives a satisfying technical success rate in the selected patients. The incidence of complications involving the vascular access remains an important limitation of this new technique. Although a conservative or endovascular treatment can be applied in most cases, improving the introduction devices is highly expected because it would reduce the complications rate of vascular access. Copyright © 2011 Annals of Vascular Surgery Inc. Published by Elsevier Inc

  20. Optical fiber cabling technologies for flexible access network

    NASA Astrophysics Data System (ADS)

    Tanji, Hisashi

    2008-07-01

    Fiber-to-the-home (FTTH) outside plant infrastructure should be so designed and constructed as to flexibly deal with increasing subscribers and system evolution to be expected in the future, taking minimization of total cost (CAPEX and OPEX) into consideration. With this in mind, fiber access architectures are reviewed and key technologies on optical fiber and cable for supporting flexible access network are presented. Low loss over wide wavelength (low water peak) and bend-insensitive single mode fiber is a future proof solution. Enhanced separable ribbon facilitates mid-span access to individual fibers in a cable installed, improving fiber utilizing efficiency and flexibility of distribution design. It also contributes to an excellent low PMD characteristic which could be required for video RF overlay system or high capacity long reach metro-access convergence network in the future. Bend-insensitive fiber based cabling technique including field installable connector greatly improves fiber/cable handling in installation and maintenance work.

  1. Scrubbing technique for needleless connectors to minimize contamination risk.

    PubMed

    Satou, K; Kusanagi, R; Nishizawa, A; Hori, S

    2018-03-21

    This study aimed to investigate the appropriate scrubbing technique for needleless connectors to minimize contamination risk. To demonstrate a highly effective scrubbing technique to physically eliminate bacteria, needleless connectors were contaminated with Geobacillus stearothermophilus spores and then scrubbed. The study showed that the highest bacterial elimination rate was achieved by scrubbing an access port in a straight line with an alcohol cotton swab, applying a force that was almost equal to an arterial compression haemostasis to the access port, and repeating this procedure once using a new alcohol cotton swab. Copyright © 2018 The Author(s). Published by Elsevier Ltd.. All rights reserved.

  2. A comparison of Percutaneous femoral access in Endovascular Repair versus Open femoral access (PiERO): study protocol for a randomized controlled trial.

    PubMed

    Vierhout, Bastiaan P; Saleem, Ben R; Ott, Alewijn; van Dijl, Jan Maarten; de Kempenaer, Ties D van Andringa; Pierie, Maurice E N; Bottema, Jan T; Zeebregts, Clark J

    2015-09-14

    Access for endovascular repair of abdominal aortic aneurysms (EVAR) is obtained through surgical cutdown or percutaneously. The only devices suitable for percutaneous closure of the 20 French arteriotomies of the common femoral artery (CFA) are the Prostar(™) and Proglide(™) devices (Abbott Vascular). Positive effects of these devices seem to consist of a lower infection rate, and shorter operation time and hospital stay. This conclusion was published in previous reports comparing techniques in patients in two different groups (cohort or randomized). Access techniques were never compared in one and the same patient; this research simplifies comparison because patient characteristics will be similar in both groups. Percutaneous access of the CFA is compared to surgical cutdown in a single patient; in EVAR surgery, access is necessary in both groins in each patient. Randomization is performed on the introduction site of the larger main device of the endoprosthesis. The contralateral device of the endoprosthesis is smaller. When we use this type of randomization, both groups will contain a similar number of main and contralateral devices. Preoperative nose cultures and perineal cultures are obtained, to compare colonization with postoperative wound cultures (in case of a surgical site infection). Furthermore, patient comfort will be considered, using VAS-scores (Visual analog scale). Punch biopsies of the groin will be harvested to retrospectively compare skin of patients who suffered a surgical site infection (SSI) to patients who did not have an SSI. The PiERO trial is a multicenter randomized controlled clinical trial designed to show the consequences of using percutaneous access in EVAR surgery and focuses on the occurrence of surgical site infections. NTR4257 10 November 2013, NL44578.042.13.

  3. 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.

  4. 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…

  5. A Portable Farmland Information Collection System with Multiple Sensors.

    PubMed

    Zhang, Jianfeng; Hu, Jinyang; Huang, Lvwen; Zhang, Zhiyong; Ma, Yimian

    2016-10-22

    Precision agriculture is the trend of modern agriculture, and it is also one of the important ways to realize the sustainable development of agriculture. In order to meet the production requirements of precision agriculture-efficient use of agricultural resources, and improving the crop yields and quality-some necessary field information in crop growth environment needs to be collected and monitored. In this paper, a farmland information collection system is developed, which includes a portable farmland information collection device based on STM32 (a 32-bit comprehensive range of microcontrollers based on ARM Crotex-M3), a remote server and a mobile phone APP. The device realizes the function of portable and mobile collecting of multiple parameters farmland information, such as chlorophyll content of crop leaves, air temperature, air humidity, and light intensity. UM220-III (Unicore Communication Inc., Beijing, China) is used to realize the positioning based on BDS/GPS (BeiDou Navigation Satellite System, BDS/Global Positioning System, GPS) dual-mode navigation and positioning system, and the CDMA (Code Division Multiple Access, CDMA) wireless communication module is adopted to realize the real-time remote transmission. The portable multi-function farmland information collection system is real-time, accurate, and easy to use to collect farmland information and multiple information parameters of crops.

  6. A Portable Farmland Information Collection System with Multiple Sensors

    PubMed Central

    Zhang, Jianfeng; Hu, Jinyang; Huang, Lvwen; Zhang, Zhiyong; Ma, Yimian

    2016-01-01

    Precision agriculture is the trend of modern agriculture, and it is also one of the important ways to realize the sustainable development of agriculture. In order to meet the production requirements of precision agriculture—efficient use of agricultural resources, and improving the crop yields and quality—some necessary field information in crop growth environment needs to be collected and monitored. In this paper, a farmland information collection system is developed, which includes a portable farmland information collection device based on STM32 (a 32-bit comprehensive range of microcontrollers based on ARM Crotex-M3), a remote server and a mobile phone APP. The device realizes the function of portable and mobile collecting of multiple parameters farmland information, such as chlorophyll content of crop leaves, air temperature, air humidity, and light intensity. UM220-III (Unicore Communication Inc., Beijing, China) is used to realize the positioning based on BDS/GPS (BeiDou Navigation Satellite System, BDS/Global Positioning System, GPS) dual-mode navigation and positioning system, and the CDMA (Code Division Multiple Access, CDMA) wireless communication module is adopted to realize the real-time remote transmission. The portable multi-function farmland information collection system is real-time, accurate, and easy to use to collect farmland information and multiple information parameters of crops. PMID:27782076

  7. Tibiopedal access for lower extremity arterial intervention: when to use and how to perform.

    PubMed

    Wiechmann, Bret N

    2014-09-01

    Tibiopedal artery access is being used with increasing frequency as an alternative access to facilitate procedural success in lower extremity arterial intervention. This technique is usually employed in the setting of critical limb ischemia and tibial artery intervention, but it may offer potential practical advantages for popliteal artery and even superficial femoral artery intervention in unique situations. As in all cases of lower extremity arterial intervention, consideration of access is important not only for initial approach to any obstructing lesion but also for exit strategy. The dorsalis pedis artery and posterior tibial artery can be readily accessed if necessary owing to their relatively superficial position in the foot or the ankle, yet their normal diameter and the presence of significant calcification (a common finding in patients with tibial occlusive disease and critical limb ischemia) can pose difficulties as well. In addition, the peroneal artery in the lower leg can be accessed percutaneously; however, its size and depth may present additional challenges. Meticulous attention to detail is paramount in avoiding complications in what may be the only distal vessel supplying the foot. This article describes common techniques in using tibiopedal artery access as a means of alternative access for successful infrainguinal intervention. Copyright © 2014 Elsevier Inc. All rights reserved.

  8. The Use of Ultrasound to Improve Axillary Vein Access and Minimize Complications during Pacemaker Implantation.

    PubMed

    Esmaiel, Abdullah; Hassan, Jeremy; Blenkhorn, Fay; Mardigyan, Vartan

    2016-05-01

    The Agency for Healthcare Research and Quality in the United States recommends the use of ultrasound (US) for central venous access to improve patient outcomes. However, in a recent publication, US is still underutilized for axillary vein access during pacemaker implantation. We sought to describe a technique for US-guided axillary vein access during pacemaker implantation and to report complication rates and success rate. Retrospective data collection included success rate and complications on all pacemaker implants by one operator since implementing the systematic use of US at our institution, from November 2012 to January 2015. For the last 59 cases, data were collected prospectively to include time of venous access and number of attempts. A total of 403 consecutive patients were included in the analysis. Two leads were implanted in 255 cases and one lead was implanted in 148 cases. The rate of successful US-guided access was 99.25%. There were no access-related complications. The average number of venipuncture attempts was 1.18 per patient. The average time to obtain venous access was 2.24 minutes including the time to apply the sterile US sleeve. The described technique has the potential to improve the success rate of axillary vein access and minimize complications during pacemaker implantation. ©2016 Wiley Periodicals, Inc.

  9. Multiuser TOA Estimation Algorithm in DS-CDMA Sparse Channel for Radiolocation

    NASA Astrophysics Data System (ADS)

    Kim, Sunwoo

    This letter considers multiuser time delay estimation in a sparse channel environment for radiolocation. The generalized successive interference cancellation (GSIC) algorithm is used to eliminate the multiple access interference (MAI). To adapt GSIC to sparse channels the alternating maximization (AM) algorithm is considered, and the continuous time delay of each path is estimated without requiring a priori known data sequences.

  10. Use of an angiographic catheter to facilitate fluoroscopy-guided percutaneous renal access in cases with diffuse contrast extravasation.

    PubMed

    Giannakopoulos, Stilianos; Bantis, Athanasios; Kalaitzis, Christos; Touloupidis, Stavros

    2010-10-01

    Occasionally during percutaneous surgery, significant contrast extravasation obscures the field, making fluoroscopic access no longer feasible. Herein, we describe a salvage technique. The cystoscopically placed, open-end ureteral catheter is exchanged with an angled-tip angiographic catheter. With the aid of a guidewire and under fluoroscopic guidance, the tip of the catheter is placed in a posterior calix. The "bull's eye" technique is then applied to direct the needle into the tip of the catheter. This technique was used in four cases over a 7-year period. Successful access was accomplished in all cases through a middle or upper calix. The catheter serves as a target for providing access to the renal collecting system and facilitates final tract dilatation.

  11. Energy-efficient process-stacking multiplexing access for 60-GHz mm-wave wireless personal area networks.

    PubMed

    Estevez, Claudio; Kailas, Aravind

    2012-01-01

    Millimeter-wave technology shows high potential for future wireless personal area networks, reaching over 1 Gbps transmissions using simple modulation techniques. Current specifications consider dividing the spectrum into effortlessly separable spectrum ranges. These low requirements open a research area in time and space multiplexing techniques for millimeter-waves. In this work a process-stacking multiplexing access algorithm is designed for single channel operation. The concept is intuitive, but its implementation is not trivial. The key to stacking single channel events is to operate while simultaneously obtaining and handling a-posteriori time-frame information of scheduled events. This information is used to shift a global time pointer that the wireless access point manages and uses to synchronize all serviced nodes. The performance of the proposed multiplexing access technique is lower bounded by the performance of legacy TDMA and can significantly improve the effective throughput. Work is validated by simulation results.

  12. Insurance + access not equal to health care: typology of barriers to health care access for low-income families.

    PubMed

    Devoe, Jennifer E; Baez, Alia; Angier, Heather; Krois, Lisa; Edlund, Christine; Carney, Patricia A

    2007-01-01

    Public health insurance programs have expanded coverage for the poor, and family physicians provide essential services to these vulnerable populations. Despite these efforts, many Americans do not have access to basic medical care. This study was designed to identify barriers faced by low-income parents when accessing health care for their children and how insurance status affects their reporting of these barriers. A mixed methods analysis was undertaken using 722 responses to an open-ended question on a health care access survey instrument that asked low-income Oregon families, "Is there anything else you would like to tell us?" Themes were identified using immersion/crystallization techniques. Pertinent demographic attributes were used to conduct matrix coded queries. Families reported 3 major barriers: lack of insurance coverage, poor access to services, and unaffordable costs. Disproportionate reporting of these themes was most notable based on insurance status. A higher percentage of uninsured parents (87%) reported experiencing difficulties obtaining insurance coverage compared with 40% of those with insurance. Few of the uninsured expressed concerns about access to services or health care costs (19%). Access concerns were the most common among publicly insured families, and costs were more often mentioned by families with private insurance. Families made a clear distinction between insurance and access, and having one or both elements did not assure care. Our analyses uncovered a 3-part typology of barriers to health care for low-income families. Barriers to health care can be insurmountable for low-income families, even those with insurance coverage. Patients who do not seek care in a family medicine clinic are not necessarily getting their care elsewhere.

  13. Evaluation of spatial accessibility to primary healthcare using GIS

    NASA Astrophysics Data System (ADS)

    Jamtsho, S.; Corner, R. J.

    2014-11-01

    Primary health care is considered to be one of the most important aspects of the health care system in any country, which directly helps in improving the health of the population. Potential spatial accessibility is a very important component of the primary health care system. One technique for studying spatial accessibility is by computing a gravity-based measure within a geographic information system (GIS) framework. In this study, straight-line distances between the associated population clusters and the health facilities and the provider-to-population ratio were used to compute the spatial accessibility of the population clusters for the whole country. Bhutan has been chosen as the case study area because it is quite easy to acquire and process data for the whole country due to its small size and population. The spatial accessibility measure of the 203 sub-districts shows noticeable disparities in health care accessibility in this country with about only 19 sub-districts achieving good health accessibility ranking. This study also examines a number of different health accessibility policy scenarios which can assist in identifying the most effective health policy from amongst many probable planning scenarios. Such a health accessibility measuring system can be incorporated into an existing spatial health system in developing countries to facilitate the proper planning and equitable distribution of health resources.

  14. ACCESS: The Arizona-CfA-Catolica Exoplanet Spectroscopy Survey

    NASA Astrophysics Data System (ADS)

    Lopez-Morales, Mercedes; Apai, Daniel; Jordan, Andres; Espinoza, Nestor; Rackham, Benjamin; Fraine, Jonathan D.; Rodler, Florian; Lewis, Nikole; Fortney, Jonathan J.; Osip, David J.

    2014-06-01

    The Arizona-CfA-Catolica Exoplanet Spectroscopy Survey (ACCESS) is an international, multi-institutional consortium with members from the Harvard-Smithsonian CfA, the University of Arizona, Pontificia Universidad Catolica in Chile, MIT and UC Santa Cruz and the Carnegie Institution. ACCESS' goal is to observe about two dozen planets covering a wide range of mass, radius, atmospheric temperatures and energy irradiation levels, with two main scientific goals: 1) to obtain, for the first time, a uniform sample of visible transmission spectra of exoplanets, allowing the study of their atmospheric characteristics as a statistically significant sample, and 2) to mature the technique of ground-based observations of exoplanetary atmospheres for future observations of small planets. Here we describe ACCESS and its first science results.

  15. Peritoneal Dialysis Access Revision in Children: Causes, Interventions, and Outcomes.

    PubMed

    Borzych-Duzalka, Dagmara; Aki, T Fazil; Azocar, Marta; White, Colin; Harvey, Elizabeth; Mir, Sevgi; Adragna, Marta; Serdaroglu, Erkin; Sinha, Rajiv; Samaille, Charlotte; Vanegas, Juan Jose; Kari, Jameela; Barbosa, Lorena; Bagga, Arvind; Galanti, Monica; Yavascan, Onder; Leozappa, Giovanna; Szczepanska, Maria; Vondrak, Karel; Tse, Kei-Chiu; Schaefer, Franz; Warady, Bradley A

    2017-01-06

    Little published information is available about access failure in children undergoing chronic peritoneal dialysis. Our objectives were to evaluate frequency, risk factors, interventions, and outcome of peritoneal dialysis access revision. Data were derived from 824 incident and 1629 prevalent patients from 105 pediatric nephrology centers enrolled in the International Pediatric Peritoneal Dialysis Network Registry between 2007 and 2015. In total, 452 access revisions were recorded in 321 (13%) of 2453 patients over 3134 patient-years of follow-up, resulting in an overall access revision rate of 0.14 per treatment year. Among 824 incident patients, 186 (22.6%) underwent 188 access revisions over 1066 patient-years, yielding an access revision rate of 0.17 per treatment year; 83% of access revisions in incident patients were reported within the first year of peritoneal dialysis treatment. Catheter survival rates in incident patients were 84%, 80%, 77%, and 73% at 12, 24, 36, and 48 months, respectively. By multivariate logistic regression analysis, risk of access revision was associated with younger age (odds ratio, 0.93; 95% confidence interval, 0.92 to 0.95; P<0.001), diagnosis of congenital anomalies of the kidney and urinary tract (odds ratio, 1.28; 95% confidence interval, 1.03 to 1.59; P=0.02), coexisting ostomies (odds ratio, 1.42; 95% confidence interval, 1.07 to 1.87; P=0.01), presence of swan neck tunnel with curled intraperitoneal portion (odds ratio, 1.30; 95% confidence interval, 1.04 to 1.63; P=0.02), and high gross national income (odds ratio, 1.10; 95% confidence interval, 1.02 to 1.19; P=0.01). Main reasons for access revisions included mechanical malfunction (60%), peritonitis (16%), exit site infection (12%), and leakage (6%). Need for access revision increased the risk of peritoneal dialysis technique failure or death (hazard ratio, 1.35; 95% confidence interval, 1.10 to 1.65; P=0.003). Access dysfunction due to mechanical causes doubled the risk

  16. Peritoneal Dialysis Access Revision in Children: Causes, Interventions, and Outcomes

    PubMed Central

    Aki, T. Fazil; Azocar, Marta; White, Colin; Harvey, Elizabeth; Mir, Sevgi; Adragna, Marta; Serdaroglu, Erkin; Sinha, Rajiv; Samaille, Charlotte; Vanegas, Juan Jose; Kari, Jameela; Barbosa, Lorena; Bagga, Arvind; Galanti, Monica; Yavascan, Onder; Leozappa, Giovanna; Szczepanska, Maria; Vondrak, Karel; Tse, Kei-Chiu; Schaefer, Franz; Warady, Bradley A.

    2017-01-01

    Background and objectives Little published information is available about access failure in children undergoing chronic peritoneal dialysis. Our objectives were to evaluate frequency, risk factors, interventions, and outcome of peritoneal dialysis access revision. Design, setting, participants, & measurements Data were derived from 824 incident and 1629 prevalent patients from 105 pediatric nephrology centers enrolled in the International Pediatric Peritoneal Dialysis Network Registry between 2007 and 2015. Results In total, 452 access revisions were recorded in 321 (13%) of 2453 patients over 3134 patient-years of follow-up, resulting in an overall access revision rate of 0.14 per treatment year. Among 824 incident patients, 186 (22.6%) underwent 188 access revisions over 1066 patient-years, yielding an access revision rate of 0.17 per treatment year; 83% of access revisions in incident patients were reported within the first year of peritoneal dialysis treatment. Catheter survival rates in incident patients were 84%, 80%, 77%, and 73% at 12, 24, 36, and 48 months, respectively. By multivariate logistic regression analysis, risk of access revision was associated with younger age (odds ratio, 0.93; 95% confidence interval, 0.92 to 0.95; P<0.001), diagnosis of congenital anomalies of the kidney and urinary tract (odds ratio, 1.28; 95% confidence interval, 1.03 to 1.59; P=0.02), coexisting ostomies (odds ratio, 1.42; 95% confidence interval, 1.07 to 1.87; P=0.01), presence of swan neck tunnel with curled intraperitoneal portion (odds ratio, 1.30; 95% confidence interval, 1.04 to 1.63; P=0.02), and high gross national income (odds ratio, 1.10; 95% confidence interval, 1.02 to 1.19; P=0.01). Main reasons for access revisions included mechanical malfunction (60%), peritonitis (16%), exit site infection (12%), and leakage (6%). Need for access revision increased the risk of peritoneal dialysis technique failure or death (hazard ratio, 1.35; 95% confidence interval, 1

  17. 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.

  18. Central venous access in children: indications, devices, and risks.

    PubMed

    Ares, Guillermo; Hunter, Catherine J

    2017-06-01

    Central venous catheters (CVCs) have a prominent role in the diagnostic and therapy of neonates and children. Herein, we describe the multiple indications for CVC use and the different devices available for central venous access. Given the prevalent use of CVCs, healthcare systems are focused on reducing complications from their use, particularly central line-associated bloodstream infections (CLABSIs). The most up-to-date information available sheds light on best practices and future areas of investigation. Large systematic reviews of randomized trials suggest that ultrasound guidance for placement of CVCs in children is safer than using blind technique, at least for internal jugular vein access. Appropriate catheter tip placement is associated with decreased complications. Furthermore, the prophylactic use of ethanol lock between cycles of parenteral nutrition administration has reduced the rates of CLABSI. A recent randomized trial in pediatric CVCs showed a benefit with antibiotic-coated CVCs. Based on the available evidence, multiple techniques for CVC placement are still valid, including the landmark technique based on practitioner experience, but ultrasound guidance has been shown to decrease complications from line placement. Adherence to CVC care protocols is essential in reducing infectious complications.

  19. The versatility of intraosseous vascular access in perioperative medicine: a case series.

    PubMed

    Anson, Jonathan A; Sinz, Elizabeth H; Swick, John T

    2015-02-01

    Intraosseous vascular access is a time-tested procedure that is reemerging in popularity. This is primarily a result of the emphasis on intraosseous access in the American Heart Association Guidelines for Cardiopulmonary Resuscitation and Advanced Cardiac Life Support. Modern intraosseous insertion devices are easy to learn and use, suggesting the possibility of use beyond the resuscitation setting. We present a case series of recent intraosseous insertions for a variety of indications by anesthesiologists at our institution to demonstrate the potential utility of this alternative access technique. Copyright © 2014 Elsevier Inc. All rights reserved.

  20. Is Accessibility an Issue in the Knowledge Society? Modern Web Applications in the Light of Accessibility

    NASA Astrophysics Data System (ADS)

    Bártek, Luděk; Ošlejšek, Radek; Pitner, Tomáš

    Recent development in Web shows a significant trend towards more user participation, massive use of new devices including portables, and high interactivity. The user participation goes hand in hand with inclusion of all potential user groups - also with special needs. However, we claim that albeit all the effort towards accessibility, it has not yet found an appopriate reflection among stakeholders of the "Top Web Applications" nor their users. This leads to undesired causes - the business-driven Web without all user participation is not a really democratic medium and, actually, does not comply with the original characteristics of Web 2.0. The paper tries to identify perspectives of further development including standardization processes and technical obstacles behind. It also shows ways and techniques to cope with the challenge based on our own research and development in accessible graphics and dialog-based systems.

  1. Single-port access laparoscopic hysterectomy: a new dimension of minimally invasive surgery.

    PubMed

    Liliana, Mereu; Alessandro, Pontis; Giada, Carri; Luca, Mencaglia

    2011-01-01

    The fundamental idea is to have all of the laparoscopic working ports entering the abdominal wall through the same incision. Single-incision laparoscopic surgery is an alternative to conventional multiport laparoscopy. Single-access laparoscopy using a transumbilical port affords maximum cosmetic benefits because the surgical incision is hidden in the umbilicus and reduces morbidity of minimally invasive surgery. The advantages of single-access laparoscopic surgery may include less bleeding, infection, and hernia formation and better cosmetic outcome and less pain. The disadvantages and limitations include longer surgery time, difficulty in learning the technique, and the need for specialized instruments. This review summarizes the history of SPAL hysterectomy (single-port access laparoscopy), and emphasizes nomenclature, surgical technique, instrumentation, and perioperative outcomes. Specific gynecological applications of single-port hysterectomy to date are summarized. Using the PubMed database, the English-language literature was reviewed for the past 40 years. Keyword searches included scarless, scar free, single-port/trocar/incision, single-port access laparoscopic hysterectomy. Within the bibliography of selected references, additional sources were retrieved. The purpose of the present article was to review the development and current status of SPAL hysterectomy and highlight important advances associated with this innovative approach.

  2. Sustaining change: the imperative for patient access strategies.

    PubMed

    Glynn, Peter A R

    2006-01-01

    The paper by Trypuc, MacLeod and Hudson provides a timely and important overview of methods to sustain provincial wait time strategies. The emphasis on accountability for patient access to timely care throughout the healthcare system comes through strongly--as it should. These accountabilities are made "real" through purchase service agreements. Physician-hospital relationships are a fundamental aspect of this accountability. This commentary suggests the inclusion of two additional supporting tools in addition to those cited by the authors of the lead paper--quality monitoring and the use of industrial engineering techniques for queue management and patient flow analysis. Strong and persistent leadership of patient access strategies will ensure sustainable change.

  3. Physical and Visual Accessibilities in Intensive Care Units: A Comparative Study of Open-Plan and Racetrack Units.

    PubMed

    Rashid, Mahbub; Khan, Nayma; Jones, Belinda

    2016-01-01

    This study compared physical and visual accessibilities and their associations with staff perception and interaction behaviors in 2 intensive care units (ICUs) with open-plan and racetrack layouts. For the study, physical and visual accessibilities were measured using the spatial analysis techniques of Space Syntax. Data on staff perception were collected from 81 clinicians using a questionnaire survey. The locations of 2233 interactions, and the location and length of another 339 interactions in these units were collected using systematic field observation techniques. According to the study, physical and visual accessibilities were different in the 2 ICUs, and clinicians' primary workspaces were physically and visually more accessible in the open-plan ICU. Physical and visual accessibilities affected how well clinicians' knew their peers and where their peers were located in these units. Physical and visual accessibilities also affected clinicians' perception of interaction and communication and of teamwork and collaboration in these units. Additionally, physical and visual accessibilities showed significant positive associations with interaction behaviors in these units, with the open-plan ICU showing stronger associations. However, physical accessibilities were less important than visual accessibilities in relation to interaction behaviors in these ICUs. The implications of these findings for ICU design are discussed.

  4. Barriers and facilitators to intraosseous access in adult resuscitations when peripheral intravenous access is not achievable.

    PubMed

    James Cheung, Warren; Rosenberg, Hans; Vaillancourt, Christian

    2014-03-01

    care, and was associated with a low complication rate. Conversely, the perception that nurses are not familiar or supportive of IO access and a lack of physician confidence regarding the appropriate indications for IO access were barriers to use. These data are an important step in the knowledge-to-action process, as they identify specific factors associated with physician use of IO access. Interventions addressing these actionable facilitators and barriers are likely to have a positive effect on increasing the appropriate physician use of this potentially life-saving technique in adult patients requiring emergent vascular access. © 2014 by the Society for Academic Emergency Medicine.

  5. Transradial access: lessons learned from cardiology.

    PubMed

    Snelling, Brian M; Sur, Samir; Shah, Sumedh Subodh; Marlow, Megan M; Cohen, Mauricio G; Peterson, Eric C

    2018-05-01

    Innovations in interventional cardiology historically predate those in neuro-intervention. As such, studying trends in interventional cardiology can be useful in exploring avenues to optimise neuro-interventional techniques. One such cardiology innovation has been the steady conversion of arterial puncture sites from transfemoral access (TFA) to transradial access (TRA), a paradigm shift supported by safety benefits for patients. While neuro-intervention has unique anatomical challenges, the access itself is identical. As such, examining the extensive cardiology literature on the radial approach has the potential to offer valuable lessons for the neuro-interventionalist audience who may be unfamiliar with this body of work. Therefore, we present here a report, particularly for neuro-interventionalists, regarding the best practices for TRA by reviewing the relevant cardiology literature. We focused our review on the data most relevant to our audience, namely that surrounding the access itself. By reviewing the cardiology literature on metrics such as safety profiles, cost and patient satisfaction differences between TFA and TRA, as well as examining the technical nuances of the procedure and post-procedural care, we hope to give physicians treating complex cerebrovascular disease a broader data-driven understanding of TRA. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

  6. The Oxford Probe: an open access five-hole probe for aerodynamic measurements

    NASA Astrophysics Data System (ADS)

    Hall, B. F.; Povey, T.

    2017-03-01

    The Oxford Probe is an open access five-hole probe designed for experimental aerodynamic measurements. The open access probe can be manufactured by the end user via additive manufacturing (metal or plastic). The probe geometry, drawings, calibration maps, and software are available under a creative commons license. The purpose is to widen access to aerodynamic measurement techniques in education and research environments. There are many situations in which the open access probe will allow results of comparable accuracy to a well-calibrated commercial probe. We discuss the applications and limitations of the probe, and compare the calibration maps for 16 probes manufactured in different materials and at different scales, but with the same geometrical design.

  7. Centralized light-source optical access network based on polarization multiplexing.

    PubMed

    Grassi, Fulvio; Mora, José; Ortega, Beatriz; Capmany, José

    2010-03-01

    This paper presents and demonstrates a centralized light source optical access network based on optical polarization multiplexing technique. By using two optical sources emitting light orthogonally polarized in the Central Node for downstream and upstream operations, the Remote Node is kept source-free. EVM values below telecommunication standard requirements have been measured experimentally when bidirectional digital signals have been transmitted over 10 km of SMF employing subcarrier multiplexing technique in the electrical domain.

  8. Retroperitoneal access for robotic renal surgery.

    PubMed

    Anderson, Barrett G; Wright, Alec J; Potretzke, Aaron M; Figenshau, R Sherburne

    2018-01-01

    Retroperitoneal access for robotic renal surgery is an effective alternative to the commonly used transperitoneal approach. We describe our contemporary experience and technique for attaining retroperitoneal access. We outline our institutional approach to retroperitoneal access for the instruction of urologists at the beginning of the learning curve. The patient is placed in the lateral decubitus position. The first incision is made just inferior to the tip of the twelfth rib as described by Hsu, et al. After the lumbodorsal fascia is traversed, the retroperitoneal space is dilated with a round 10 millimeter AutoSutureTM (Covidien, Mansfield, MA) balloon access device. The following trocars are used: A 130 millimeter KiiR balloon trocar (Applied Medical, Rancho Santa Margarita, CA), three robotic, and one assistant. Key landmarks for the access and dissection are detailed. 177 patients underwent a retroperitoneal robotic procedure from 2007 to 2015. Procedures performed include 158 partial nephrectomies, 16 pyeloplasties, and three radical nephrectomies. The robotic fourth arm was utilized in all cases. When compared with the transperitoneal approach, the retroperitoneal approach was associated with shorter operative times and decreased length of stay (1). Selection bias and surgeon preference accounted for the higher proportion of patients who underwent partial nephrectomy off-camp via the retroperitoneal approach. Retroperitoneal robotic surgery may confer several advantages. In patients with previous abdominal surgery or intra-abdominal conditions, the retroperitoneum can be safely accessed while avoiding intraperitoneal injuries. The retroperitoneum also provides a confined space that may minimize the sequelae of potential complications including urine leak. Moreover, at our institution, retroperitoneal robotic surgery is associated with shorter operative times and a decreased length of stay when compared with the transperitoneal approach (2). In selected

  9. Optical protocols for terabit networks

    NASA Technical Reports Server (NTRS)

    Chua, P. L.; Lambert, J. L.; Morookian, J. M.; Bergman, L. A.

    1991-01-01

    This paper describes a new fiber-optic local area network technology providing 100X improvement over current technology, has full crossbar funtionality, and inherent data security. Based on optical code-division multiple access (CDMA), using spectral phase encoding/decoding of optical pulses, networking protocols are implemented entirely in the optical domain and thus conventional networking bottlenecks are avoided. Component and system issues for a proof-of-concept demonstration are discussed, as well as issues for a more practical and commercially exploitable system. Possible terrestrial and aerospace applications of this technology, and its impact on other technologies are explored. Some initial results toward realization of this concept are also included.

  10. A Symptom-Focused Hypnotic Approach to Accessing and Processing Previously Repressed/Dissociated Memories.

    ERIC Educational Resources Information Center

    Ratican, Kathleen L.

    1996-01-01

    The kinesthetic track back technique accesses the origins of current symptoms and may uncover previously repressed/dissociated material, if such material exists in the client's unconscious mind, is relevant to the symptoms, and is ready to be processed consciously. Case examples are given to illustrate proper use of this technique. (LSR)

  11. Empower: access to medicine - working towards early access.

    PubMed

    Pearson, Jennifer Bryant; Turgoose, James; Hargrave, James

    2015-01-01

    Empower: Access to Medicine's contribution will document the founding of Empower: Access to Medicine and tactics used to create a lobbying campaign designed to facilitate the debate around barriers to medical innovation and patient access to medicines. The article will detail the evolution of the campaign's goals and the potential solutions to an expensive and slow system. Specifically the submission will look at the influence that Empower: Access to Medicine had on the Government's thinking and development of an early access scheme.

  12. The Future of Accessibility in International Higher Education

    ERIC Educational Resources Information Center

    Alphin, Henry C., Jr., Ed.; Chan, Roy Y., Ed.; Lavine, Jennie, Ed.

    2017-01-01

    Education is the foundation to almost all successful lives, and it is important that a high level of schooling be available on a global scale. Studying the trends in accessibility in education will allow educators to improve their own teaching techniques, as well as expand their influence to more remote areas in the world. "The Future of…

  13. Spatial Access to Primary Care Providers in Appalachia

    PubMed Central

    Donohoe, Joseph; Marshall, Vince; Tan, Xi; Camacho, Fabian T.; Anderson, Roger T.; Balkrishnan, Rajesh

    2016-01-01

    Purpose: The goal of this research was to examine spatial access to primary care physicians in Appalachia using both traditional access measures and the 2-step floating catchment area (2SFCA) method. Spatial access to care was compared between urban and rural regions of Appalachia. Methods: The study region included Appalachia counties of Pennsylvania, Ohio, Kentucky, and North Carolina. Primary care physicians during 2008 and total census block group populations were geocoded into GIS software. Ratios of county physicians to population, driving time to nearest primary care physician, and various 2SFCA approaches were compared. Results: Urban areas of the study region had shorter travel times to their closest primary care physician. Provider to population ratios produced results that varied widely from one county to another because of strict geographic boundaries. The 2SFCA method produced varied results depending on the distance decay weight and variable catchment size techniques chose. 2SFCA scores showed greater access to care in urban areas of Pennsylvania, Ohio, and North Carolina. Conclusion: The different parameters of the 2SFCA method—distance decay weights and variable catchment sizes—have a large impact on the resulting spatial access to primary care scores. The findings of this study suggest that using a relative 2SFCA approach, the spatial access ratio method, when detailed patient travel data are unavailable. The 2SFCA method shows promise for measuring access to care in Appalachia, but more research on patient travel preferences is needed to inform implementation. PMID:26906524

  14. Intermodal Ground Access to Airports: A Planning Guide - A Good Start

    DOT National Transportation Integrated Search

    1997-01-01

    This Guide is designed to provide policy guidance, rules of thumb, data, and analytical techniques related to airport access. It has been prepared to help airport operator, local governments, metropolitan planning organizations, consultants and other...

  15. Collaborative Indoor Access Point Localization Using Autonomous Mobile Robot Swarm

    PubMed Central

    Awad, Fahed; Naserllah, Muhammad; Omar, Ammar; Abu-Hantash, Alaa; Al-Taj, Abrar

    2018-01-01

    Localization of access points has become an important research problem due to the wide range of applications it addresses such as dismantling critical security threats caused by rogue access points or optimizing wireless coverage of access points within a service area. Existing proposed solutions have mostly relied on theoretical hypotheses or computer simulation to demonstrate the efficiency of their methods. The techniques that rely on estimating the distance using samples of the received signal strength usually assume prior knowledge of the signal propagation characteristics of the indoor environment in hand and tend to take a relatively large number of uniformly distributed random samples. This paper presents an efficient and practical collaborative approach to detect the location of an access point in an indoor environment without any prior knowledge of the environment. The proposed approach comprises a swarm of wirelessly connected mobile robots that collaboratively and autonomously collect a relatively small number of non-uniformly distributed random samples of the access point’s received signal strength. These samples are used to efficiently and accurately estimate the location of the access point. The experimental testing verified that the proposed approach can identify the location of the access point in an accurate and efficient manner. PMID:29385042

  16. Collaborative Indoor Access Point Localization Using Autonomous Mobile Robot Swarm.

    PubMed

    Awad, Fahed; Naserllah, Muhammad; Omar, Ammar; Abu-Hantash, Alaa; Al-Taj, Abrar

    2018-01-31

    Localization of access points has become an important research problem due to the wide range of applications it addresses such as dismantling critical security threats caused by rogue access points or optimizing wireless coverage of access points within a service area. Existing proposed solutions have mostly relied on theoretical hypotheses or computer simulation to demonstrate the efficiency of their methods. The techniques that rely on estimating the distance using samples of the received signal strength usually assume prior knowledge of the signal propagation characteristics of the indoor environment in hand and tend to take a relatively large number of uniformly distributed random samples. This paper presents an efficient and practical collaborative approach to detect the location of an access point in an indoor environment without any prior knowledge of the environment. The proposed approach comprises a swarm of wirelessly connected mobile robots that collaboratively and autonomously collect a relatively small number of non-uniformly distributed random samples of the access point's received signal strength. These samples are used to efficiently and accurately estimate the location of the access point. The experimental testing verified that the proposed approach can identify the location of the access point in an accurate and efficient manner.

  17. An alternative and inexpensive percutaneous access needle in pediatric patients.

    PubMed

    Penbegul, Necmettin; Soylemez, Haluk; Bozkurt, Yasar; Sancaktutar, Ahmet Ali; Bodakci, Mehmet Nuri; Hatipoglu, Namik Kemal; Atar, Murat; Yildirim, Kadir

    2012-10-01

    The most important factor that increases the cost of percutaneous surgery is the disposable instruments used for the surgery. In this study we present the advantages of using an intravenous cannula instead of a percutaneous access needle for renal access. Recently, percutaneous stone surgery has grown in use in pediatric cases and is considered a minimally invasive surgery. The most important step in this surgery is access to the renal collecting systems. Although fluoroscopy has been used frequently at this stage, the use of ultrasound has recently increased. During percutaneous accesses under all types of imaging techniques, disposable 11- to 15-cm-long 18-ga needles are used. In pediatric cases, these longer needles are difficult to use. Using disposable materials in percutaneous nephrolithotomy increases the cost of the procedure. Therefore, we asserted that percutaneous access especially in pediatric cases could be performed using a 16-ga intravenous cannula (angiocath). Indeed, percutaneous access was performed successfully, especially in pediatric preschool patients. Shorter needle length, easy skin entry, comfort of manipulation, clear visualization of the metal needle on ultrasound, and wide availability can be considered advantages of this method. The angiocath is also less expensive than a percutaneous access needle. Angiocath is inexpensive, easily available, and practical, and it is the shortest needle to perform percutaneous access in pediatric patients. Copyright © 2012 Elsevier Inc. All rights reserved.

  18. Single-port access laparoscopic reversal of Hartmann operation.

    PubMed

    Borowski, D W; Kanakala, V; Agarwal, A K; Tabaqchali, M A; Garg, D K; Gill, T S

    2011-08-01

    Single-port access offers cosmetic advantages in addition to the well-recognized benefits of standard multiport laparoscopic surgery, and can be performed with the use of standard straight instruments. We describe a technique of single-port access reversal of Hartmann colostomy by use of the colostomy site for access. After routine skin preparation and laparoscopic setup, the colostomy is mobilized from its mucocutaneous border, and the anvil of a circular stapler is secured to the distal lumen. By the use of a GelPoint system with 3 or 4 trocars, the intra-abdominal adhesions are divided and the splenic flexure is mobilized to achieve sufficient access to the abdominal and pelvic cavities and proximal colonic mobility. The rectal stump is mobilized to the mid rectum, starting from the posterior mesorectal fascia around to the anterior rectal wall. A tension-free colorectal anastomosis is secured with a standard circular stapling device inserted transanally, and leak tested. The colostomy wound is closed in standard fashion. Five patients underwent single-port access reversal of Hartmann resection (4 diverticular perforations and 1 pT3N0 colon cancer), with a mean operating time of 155 (range, 137-187) minutes and a median length of stay of 3 (range, 2-11) days. There were no conversions, major surgical morbidity, or deaths. Single-port access reversal of Hartmann colostomy through the stoma site is safe, and it offers additional cosmetic advantages with no apparent additional morbidity in comparison with standard multiport surgery.

  19. Microfluidic CODES: a scalable multiplexed electronic sensor for orthogonal detection of particles in microfluidic channels.

    PubMed

    Liu, Ruxiu; Wang, Ningquan; Kamili, Farhan; Sarioglu, A Fatih

    2016-04-21

    Numerous biophysical and biochemical assays rely on spatial manipulation of particles/cells as they are processed on lab-on-a-chip devices. Analysis of spatially distributed particles on these devices typically requires microscopy negating the cost and size advantages of microfluidic assays. In this paper, we introduce a scalable electronic sensor technology, called microfluidic CODES, that utilizes resistive pulse sensing to orthogonally detect particles in multiple microfluidic channels from a single electrical output. Combining the techniques from telecommunications and microfluidics, we route three coplanar electrodes on a glass substrate to create multiple Coulter counters producing distinct orthogonal digital codes when they detect particles. We specifically design a digital code set using the mathematical principles of Code Division Multiple Access (CDMA) telecommunication networks and can decode signals from different microfluidic channels with >90% accuracy through computation even if these signals overlap. As a proof of principle, we use this technology to detect human ovarian cancer cells in four different microfluidic channels fabricated using soft lithography. Microfluidic CODES offers a simple, all-electronic interface that is well suited to create integrated, low-cost lab-on-a-chip devices for cell- or particle-based assays in resource-limited settings.

  20. Impacts of extension access and cooperative membership on technology adoption and household welfare.

    PubMed

    Wossen, Tesfamicheal; Abdoulaye, Tahirou; Alene, Arega; Haile, Mekbib G; Feleke, Shiferaw; Olanrewaju, Adetunji; Manyong, Victor

    2017-08-01

    This paper examines the impacts of access to extension services and cooperative membership on technology adoption, asset ownership and poverty using household-level data from rural Nigeria. Using different matching techniques and endogenous switching regression approach, we find that both extension access and cooperative membership have a positive and statistically significant effect on technology adoption and household welfare. Moreover, we find that both extension access and cooperative membership have heterogeneous impacts. In particular, we find evidence of a positive selection as the average treatment effects of extension access and cooperative membership are higher for farmers with the highest propensity to access extension and cooperative services. The impact of extension services on poverty reduction and of cooperatives on technology adoption is significantly stronger for smallholders with access to formal credit than for those without access. This implies that expanding rural financial markets can maximize the potential positive impacts of extension and cooperative services on farmers' productivity and welfare.

  1. An incremental database access method for autonomous interoperable databases

    NASA Technical Reports Server (NTRS)

    Roussopoulos, Nicholas; Sellis, Timos

    1994-01-01

    We investigated a number of design and performance issues of interoperable database management systems (DBMS's). The major results of our investigation were obtained in the areas of client-server database architectures for heterogeneous DBMS's, incremental computation models, buffer management techniques, and query optimization. We finished a prototype of an advanced client-server workstation-based DBMS which allows access to multiple heterogeneous commercial DBMS's. Experiments and simulations were then run to compare its performance with the standard client-server architectures. The focus of this research was on adaptive optimization methods of heterogeneous database systems. Adaptive buffer management accounts for the random and object-oriented access methods for which no known characterization of the access patterns exists. Adaptive query optimization means that value distributions and selectives, which play the most significant role in query plan evaluation, are continuously refined to reflect the actual values as opposed to static ones that are computed off-line. Query feedback is a concept that was first introduced to the literature by our group. We employed query feedback for both adaptive buffer management and for computing value distributions and selectivities. For adaptive buffer management, we use the page faults of prior executions to achieve more 'informed' management decisions. For the estimation of the distributions of the selectivities, we use curve-fitting techniques, such as least squares and splines, for regressing on these values.

  2. Port-Access cardiac surgery: from a learning process to the standard.

    PubMed

    Greco, Ernesto; Barriuso, Clemente; Castro, Miguel Angel; Fita, Guillermina; Pomar, José L

    2002-01-01

    Port-Access surgery has been one of the most innovative and controversial methods in the spectrum of minimally invasive techniques for cardiac operations and has been widely used for the treatment of several cardiac diseases. The technique was introduced in our center to evaluate its efficacy in reproducing standardized results without an additional risk. Endovascular cardiopulmonary bypass (CPB) through femoral access and endoluminal aortic occlusion were used in 129 patients for a variety of surgical procedures, all of which were video-assisted. A minimal (4-6 cm) anterior thoracotomy through the fourth intercostal space was used in all cases as the surgical approach. More than 96% of the planned cases concluded as true Port-Access procedures. Mean CBP and crossclamp times were 87.2 min. +/- 51.2 (range of 10-457) and 54.9 min. +/- 30.6 (range of 10-190), respectively. Hospital mortality for the overall group was 1.5%, and mitral valve surgery had a 2.2% hospital death rate. The incidence of early neurological events was 0.7%. Mean extubation time, ICU stay, and total length of hospital stay were 5 hours +/- 6 hrs. (range of 2-32), 12 hours +/- 11.8 hrs. (range of 5-78), and 7 days +/- 7.03 days (range of 1-72), respectively. Our experience indicates that the Port- Access technique is safe and permits reproduction of standardized results with the use of a very limited surgical approach. We are convinced that this is a superior procedure for certain types of surgery, including isolated primary or redo mitral surgery, repair of a variety of atrial septal defects (ASDs), and atrial tumors. It is especially useful in high-risk patients, such as elderly patients or those requiring reoperation. Simplification of the procedure is nevertheless desirable in order to further reduce the time of operation and to address other drawbacks.

  3. Percutaneous management of vascular access in transfemoral transcatheter aortic valve implantation

    PubMed Central

    Dato, Ilaria; Burzotta, Francesco; Trani, Carlo; Crea, Filippo; Ussia, Gian Paolo

    2014-01-01

    Transcatheter aortic valve implantation (TAVI) using stent-based bioprostheses has recently emerged as a promising alternative to surgical valve replacement in selected patients. The main route for TAVI is retrograde access from the femoral artery using large sheaths (16-24 F). Vascular access complications are a clinically relevant issue in TAVI procedures since they are reported to occur in up to one fourth of patients and are strongly associated with adverse outcomes. In the present paper, we review the different types of vascular access site complications associated with transfemoral TAVI. Moreover, we discuss the possible optimal management strategies with particular attention to the relevance of early diagnosis and prompt treatment using endovascular techniques. PMID:25228962

  4. Advanced intellect-augmentation techniques

    NASA Technical Reports Server (NTRS)

    Engelbart, D. C.

    1972-01-01

    User experience in applying our augmentation tools and techniques to various normal working tasks within our center is described so as to convey a subjective impression of what it is like to work in an augmented environment. It is concluded that working-support, computer-aid systems for augmenting individuals and teams, are undoubtedly going to be widely developed and used. A very special role in this development is seen for multi-access computer networks.

  5. A wireless laser displacement sensor node for structural health monitoring.

    PubMed

    Park, Hyo Seon; Kim, Jong Moon; Choi, Se Woon; Kim, Yousok

    2013-09-30

    This study describes a wireless laser displacement sensor node that measures displacement as a representative damage index for structural health monitoring (SHM). The proposed measurement system consists of a laser displacement sensor (LDS) and a customized wireless sensor node. Wireless communication is enabled by a sensor node that consists of a sensor module, a code division multiple access (CDMA) communication module, a processor, and a power module. An LDS with a long measurement distance is chosen to increase field applicability. For a wireless sensor node driven by a battery, we use a power control module with a low-power processor, which facilitates switching between the sleep and active modes, thus maximizing the power consumption efficiency during non-measurement and non-transfer periods. The CDMA mode is also used to overcome the limitation of communication distance, which is a challenge for wireless sensor networks and wireless communication. To evaluate the reliability and field applicability of the proposed wireless displacement measurement system, the system is tested onsite to obtain the required vertical displacement measurements during the construction of mega-trusses and an edge truss, which are the primary structural members in a large-scale irregular building currently under construction. The measurement values confirm the validity of the proposed wireless displacement measurement system and its potential for use in safety evaluations of structural elements.

  6. Retroperitoneal versus direct femoral artery approach for thoracic endovascular aortic repair access: a case-control study.

    PubMed

    Etezadi, Vahid; Katzen, Barry T; Benenati, James F; Alehashemi, Sara; Tsoukas, Athanassios I; Puente, Orlando A

    2011-04-01

    Many individuals who are candidates for thoracic endovascular aortic repair (TEVAR) are found to have iliac artery anatomy and/or disease that preclude transfemoral endovascular access and require retroperitoneal surgical approach through more proximal arteries. This relatively more invasive technique could potentially affect the procedural outcomes. This study compares the retroperitoneal with transfemoral access used for TEVAR in a single center. In this study, 133 consecutive patients (96 men; mean age ± SD: 69.5 ± 14.7 years) who underwent TEVAR between 1994 and 2009 in a single center were retrospectively evaluated. The type of endovascular access was identified in all the patients. The basic demographics, access method, endograft type, 30-day morbidity and mortality rates, as well as procedure recordings including fluoroscopic and procedure duration, estimated blood loss, and duration of hospitalization were compared between the TEVAR procedures performed using a surgical retroperitoneal approach and those using the standard femoral access. Retroperitoneal access was used in 19 (14.3%; 13 women; mean age ± SD: 71 ± 12.2 years) and direct femoral access in 114 (85.7%; 24 women; mean age ± SD: 69 ± 15.4 years) patients. Two of the retroperitoneal accesses were obtained after failure of femoral approach. Techniques that were used included iliac artery conduit (seven patients), aortic artery conduit (eight patients), aortobifemoral artery graft conduit (one patient), and direct sheath introduction through the distal aorta (two patients) or common iliac artery (one patient). Retroperitoneal approach was used more frequently in women (35%) as compared with men (6%) (p = 0.0001). In all, 79% of the retroperitoneal approaches were associated with use of delivery sheath sizes larger than 24F (p = 0.049). TEVAR technical success was 100% with retroperitoneal and 97.3% with femoral access (p > 0.05). Thirty-day mortality rates were 0% and 8.8% and the rates of

  7. Lateral access to the holes of photonic crystal fibers selective filling and sensing applications

    NASA Astrophysics Data System (ADS)

    Cordeiro, Cristiano M. B.; Dos Santos, Eliane M.; Brito Cruz, C. H.; de Matos, Christiano J.; Ferreiira, Daniel S.

    2006-09-01

    A new, simple, technique is demonstrated to laterally access the cladding holes of solid-core photonic crystal fibers (PCFs) or the central hole of hollow-core PCFs by blowing a hole through the fiber wall (using a fusion splicer and the application of pressure). For both fiber types material was subsequently and successfully inserted into the holes. The proposed method compares favorably with other reported selective filling techniques in terms of simplicity and reproducibility. Also, since the holes are laterally filled, simultaneous optical access to the PCFs is possible, which can prove useful for practical sensing applications. As a proof-of-concept experiment, Rhodamine fluorescence measurements are shown.

  8. Common Femoral Artery Access on YouTube: What Practices are Being Shown and Who is Delivering the Message?

    PubMed

    Pitcher, Grayson S; Newton, Daniel H; Amendola, Michael F

    Novice learners are increasingly turning to YouTube as a learning resource for surgical procedures. One example of such a procedure is common femoral artery puncture and sheath placement. Practitioners in several specialties perform this procedure to access the arterial system for angiography and intervention. We set forth to compare the techniques demonstrated on YouTube by the various specialists, as well as compare each specialty׳s prevalence on this website. YouTube (www.youtube.com) was accessed in December 2015 at multiple time points with a cleared-cache web browser for the keyword search categories: "femoral artery access," "femoral access," and "angiography access." The top 500 videos from each of these keyword searches were analyzed. Videos were categorized by practitioner specialty, technique, duration of video, age of video, and total views. Videos with clear demonstration of femoral artery access were included in the analysis. All industry videos were excluded from the analysis. Categorical variables were compared using Fisher׳s exact test, and continuous variables were compared with the Student׳s t-test. A total of 2460, 4680 and 1800 videos were found for each keyword search, respectively. Of these, 33 videos clearly demonstrated femoral artery access technique. Vascular specialists, compared to interventional cardiology and radiology, had fewer videos (n = 4 vs. 14) and older videos (3.5 ± 2.1y vs. 2.25 ± 0.5y, p < 0.05). The vascular specialists demonstrated ultrasound-guided access, while interventional cardiology predominantly demonstrated landmark-guided access (p < 0.05). Although YouTube and other online resources are being used by novice learners, vascular specialists are underrepresented for femoral artery access, a foundational vascular procedure. Other practitioners demonstrate videos with landmark-guided access and rarely demonstrate ultrasound use. As recognized vascular experts, vascular surgeons should improve their visibility in

  9. Planning/scheduling techniques for VQ-based image compression

    NASA Technical Reports Server (NTRS)

    Short, Nicholas M., Jr.; Manohar, Mareboyana; Tilton, James C.

    1994-01-01

    The enormous size of the data holding and the complexity of the information system resulting from the EOS system pose several challenges to computer scientists, one of which is data archival and dissemination. More than ninety percent of the data holdings of NASA is in the form of images which will be accessed by users across the computer networks. Accessing the image data in its full resolution creates data traffic problems. Image browsing using a lossy compression reduces this data traffic, as well as storage by factor of 30-40. Of the several image compression techniques, VQ is most appropriate for this application since the decompression of the VQ compressed images is a table lookup process which makes minimal additional demands on the user's computational resources. Lossy compression of image data needs expert level knowledge in general and is not straightforward to use. This is especially true in the case of VQ. It involves the selection of appropriate codebooks for a given data set and vector dimensions for each compression ratio, etc. A planning and scheduling system is described for using the VQ compression technique in the data access and ingest of raw satellite data.

  10. Novel Method for Exchange of Impella Circulatory Assist Catheter: The "Trojan Horse" Technique.

    PubMed

    Phillips, Colin T; Tamez, Hector; Tu, Thomas M; Yeh, Robert W; Pinto, Duane S

    2017-07-01

    Patients with an indwelling Impella may require escalation of hemodynamic support or exchange to another circulatory assistance platform. As such, preservation of vascular access is preferable in cases where anticoagulation cannot be discontinued or to facilitate exchange to an alternative catheter or closure device. Challenges exist in avoiding bleeding and loss of wire access in these situations. We describe a single-access "Trojan Horse" technique that minimizes bleeding while maintaining arterial access for rapid exchange of this percutaneous ventricular assist device.

  11. Novel Use of a Pneumatic Compression Device for Haemostasis of Haemodialysis Fistula Access Catheterisation Sites

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    O’Reilly, Michael K., E-mail: moreilly1@mater.ie; Ryan, David; Sugrue, Gavin

    PurposeTransradial pneumatic compression devices can be used to achieve haemostasis following radial artery puncture. This article describes a novel technique for acquiring haemostasis of arterio-venous haemodialysis fistula access sites without the need for suture placement using one such compression device.Materials and MethodsA retrospective review of fistulograms with or without angioplasty/thrombectomy in a single institution was performed. 20 procedures performed on 12 patients who underwent percutaneous intervention of failing or thrombosed arterio-venous fistulas (AVF) had 27 puncture sites. Haemostasis was achieved using a pneumatic compression device at all access sites. Procedure details including size of access sheath, heparin administration and complicationsmore » were recorded.ResultsTwo diagnostic fistulograms, 14 fistulograms and angioplasties and four thrombectomies were performed via access sheaths with an average size (±SD) of 6 Fr (±1.12). IV unfractionated heparin was administered in 11 of 20 procedures. Haemostasis was achieved in 26 of 27 access sites following 15–20 min of compression using the pneumatic compression device. One case experienced limited bleeding from an inflow access site that was successfully treated with reinflation of the device for a further 5 min. No other complication was recorded.ConclusionsHaemostasis of arterio-venous haemodialysis fistula access sites can be safely and effectively achieved using a pneumatic compression device. This is a technically simple, safe and sutureless technique for acquiring haemostasis after AVF intervention.« less

  12. High-performance and high-reliability SOT-6 packaged diplexer based on advanced IPD fabrication techniques

    NASA Astrophysics Data System (ADS)

    Qiang, Tian; Wang, Cong; Kim, Nam-Young

    2017-08-01

    A diplexer offering the advantages of compact size, high performance, and high reliability is proposed on the basis of advanced integrated passive device (IPD) fabrication techniques. The proposed diplexer is developed by combining a third-order low-pass filter (LPF) and a third-order high-pass filter (HPF), which are designed on the basis of the elliptic function prototype low-pass filter. Primary components, such as inductors and capacitors, are designed and fabricated with high Q-factor and appropriate values, and they are subsequently used to construct a compact diplexer having a chip area of 900 μm × 1100 μm (0.009 λ0 × 0.011 λ0, where λ0 is the guided wavelength). In addition, a small-outline transistor (SOT-6) packaging method is adopted, and reliability tests (including temperature, humidity, vibration, and pressure) are conducted to guarantee long-term stability and commercial success. The packaged measurement results indicate excellent RF performance with insertion losses of 1.39 dB and 0.75 dB at operation bands of 0.9 GHz and 1.8 GHz, respectively. The return loss is lower than 10 dB from 0.5 GHz to 4.0 GHz, while the isolation is higher than 15 dB from 0.5 GHz to 3.0 GHz. Thus, it can be concluded that the proposed SOT-6 packaged diplexer is a promising candidate for GSM/CDMA applications. Synthetic solution of diplexer design, RF performance optimization, fabrication process, packaging, RF response measurement, and reliability test is particularly explained and analyzed in this work.

  13. A Novel Technique to Detect Code for SAC-OCDMA System

    NASA Astrophysics Data System (ADS)

    Bharti, Manisha; Kumar, Manoj; Sharma, Ajay K.

    2018-04-01

    The main task of optical code division multiple access (OCDMA) system is the detection of code used by a user in presence of multiple access interference (MAI). In this paper, new method of detection known as XOR subtraction detection for spectral amplitude coding OCDMA (SAC-OCDMA) based on double weight codes has been proposed and presented. As MAI is the main source of performance deterioration in OCDMA system, therefore, SAC technique is used in this paper to eliminate the effect of MAI up to a large extent. A comparative analysis is then made between the proposed scheme and other conventional detection schemes used like complimentary subtraction detection, AND subtraction detection and NAND subtraction detection. The system performance is characterized by Q-factor, BER and received optical power (ROP) with respect to input laser power and fiber length. The theoretical and simulation investigations reveal that the proposed detection technique provides better quality factor, security and received power in comparison to other conventional techniques. The wide opening of eye in case of proposed technique also proves its robustness.

  14. 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…

  15. An alternative gallbladder extraction technique in laparoscopic cholecystectomy.

    PubMed

    Tang, C N; Wong, D C T

    2006-05-01

    In this era of minimally invasive surgery, the challenge remains in finding techniques to reduce access trauma in terms of fewer and smaller size trocar ports. Our new described technique will allow a smaller subxiphoid port to be used to achieve extraction of the gallbladder without the need to change to a 5 mm laparoscope. We believe this method is easy to learn, safe and with no observable complications from our experience.

  16. Simulating GPS radio signal to synchronize network--a new technique for redundant timing.

    PubMed

    Shan, Qingxiao; Jun, Yang; Le Floch, Jean-Michel; Fan, Yaohui; Ivanov, Eugene N; Tobar, Michael E

    2014-07-01

    Currently, many distributed systems such as 3G mobile communications and power systems are time synchronized with a Global Positioning System (GPS) signal. If there is a GPS failure, it is difficult to realize redundant timing, and thus time-synchronized devices may fail. In this work, we develop time transfer by simulating GPS signals, which promises no extra modification to original GPS-synchronized devices. This is achieved by applying a simplified GPS simulator for synchronization purposes only. Navigation data are calculated based on a pre-assigned time at a fixed position. Pseudo-range data which describes the distance change between the space vehicle (SV) and users are calculated. Because real-time simulation requires heavy-duty computations, we use self-developed software optimized on a PC to generate data, and save the data onto memory disks while the simulator is operating. The radio signal generation is similar to the SV at an initial position, and the frequency synthesis of the simulator is locked to a pre-assigned time. A filtering group technique is used to simulate the signal transmission delay corresponding to the SV displacement. Each SV generates a digital baseband signal, where a unique identifying code is added to the signal and up-converted to generate the output radio signal at the centered frequency of 1575.42 MHz (L1 band). A prototype with a field-programmable gate array (FPGA) has been built and experiments have been conducted to prove that we can realize time transfer. The prototype has been applied to the CDMA network for a three-month long experiment. Its precision has been verified and can meet the requirements of most telecommunication systems.

  17. The blind pushing technique for peripherally inserted central catheter placement through brachial vein puncture.

    PubMed

    Lee, Jae Myeong; Cho, Young Kwon; Kim, Han Myun; Song, Myung Gyu; Song, Soon-Young; Yeon, Jae Woo; Yoon, Dae Young; Lee, Sam Yeol

    2018-03-01

    The objective of this study was to conduct a prospective clinical trial evaluating the technical feasibility and short-term clinical outcome of the blind pushing technique for placement of pretrimmed peripherally inserted central catheters (PICCs) through brachial vein access. Patients requiring PICC placement at any of the three participating institutions were prospectively enrolled between January and December 2016. The review boards of all participating institutions approved this study, and informed consent was obtained from all patients. PICC placement was performed using the blind pushing technique and primary brachial vein access. The following data were collected from unified case report forms: access vein, obstacles during PICC advancement, procedure time, and postprocedural complications. During the 12-month study period, 1380 PICCs were placed in 1043 patients. Of these, 1092 PICCs placed in 837 patients were enrolled, with 834 PICCs (76%) and 258 PICCs (34%) placed through brachial vein and nonbrachial vein access, respectively. In both arms, obstacles were most commonly noted in the subclavian veins (n = 220) and axillary veins (n = 94). Successful puncture of the access vein was achieved at first try in 1028 PICCs (94%). The technical success rate was 99%, with 1055 PICCs (97%) placed within 120 seconds of procedure time and 1088 PICCs (99%) having the tip located at the ideal position. Follow-up Doppler ultrasound detected catheter-associated upper extremity deep venous thrombosis (UEDVT) for 18 PICCs in 16 patients and late symptomatic UEDVT for 16 PICCs in 16 patients (3.1%). Catheter-associated UEDVT was noted for 28 PICCs (82%) and 6 PICCs (18%) placed through brachial vein and nonbrachial vein access, respectively. The incidence of obstacles and the procedure time (<120 seconds) differed significantly between brachial vein and nonbrachial vein access (P = .001). There was no statistically significant difference between brachial vein and

  18. Developing a Virtual Teach-To-Goal™ Inhaler Technique Learning Module: A Mixed Methods Approach.

    PubMed

    Wu, Meng; Woodrick, Nicole M; Arora, Vineet M; Farnan, Jeanne M; Press, Valerie G

    Most hospitalized patients with asthma or chronic obstructive pulmonary disease misuse respiratory inhalers. An in-person educational strategy, teach-to-goal (TTG), improves inpatients' inhaler technique. To develop an effective, portable education intervention that remains accessible to hospitalized patients postdischarge for reinforcement of proper inhaler technique. A mixed methods approach at an urban academic hospital was used to iteratively develop, modify, and test a virtual teach-to-goal ™ (V-TTG ™ ) educational intervention using patient end-user feedback. A survey examined access and willingness to use technology for self-management education. Focus groups evaluated patients' feedback on access, functionality, and quality of V-TTG ™ . Forty-eight participants completed the survey, with most reporting having Internet access; 77% used the Internet at home and 82% used the Internet at least once every few weeks. More than 80% reported that they were somewhat or very likely to use V-TTG ™ to gain skills to improve their health. Most participants reported smartphone access (73%); half owned laptop computers (52%). Participants with asthma versus chronic obstructive pulmonary disease were more likely to own a smartphone, have a data plan, and have daily Internet use (P < .05). Nine focus groups (n = 25) identified themes for each domain: access-platform and delivery, Internet access, and technological literacy; functionality-usefulness, content, and teaching strategy; and quality-clarity, ease of use, length, and likability. V-TTG ™ is a promising educational tool for improving patients' inhaler technique, iteratively developed and refined with patient input. Patients in our urban, academic hospital overwhelmingly reported access to platforms and willingness to use V-TTG ™ for health education. Copyright © 2017 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.

  19. Providing end-to-end QoS for multimedia applications in 3G wireless networks

    NASA Astrophysics Data System (ADS)

    Guo, Katherine; Rangarajan, Samapth; Siddiqui, M. A.; Paul, Sanjoy

    2003-11-01

    As the usage of wireless packet data services increases, wireless carriers today are faced with the challenge of offering multimedia applications with QoS requirements within current 3G data networks. End-to-end QoS requires support at the application, network, link and medium access control (MAC) layers. We discuss existing CDMA2000 network architecture and show its shortcomings that prevent supporting multiple classes of traffic at the Radio Access Network (RAN). We then propose changes in RAN within the standards framework that enable support for multiple traffic classes. In addition, we discuss how Session Initiation Protocol (SIP) can be augmented with QoS signaling for supporting end-to-end QoS. We also review state of the art scheduling algorithms at the base station and provide possible extensions to these algorithms to support different classes of traffic as well as different classes of users.

  20. Structural proteomics: Topology and relative accessibility of plant lipid droplet associated proteins.

    PubMed

    Jolivet, Pascale; Aymé, Laure; Giuliani, Alexandre; Wien, Frank; Chardot, Thierry; Gohon, Yann

    2017-10-03

    Lipid droplets are the major stock of lipids in oleaginous plant seeds. Despite their economic importance for oil production and biotechnological issues (biofuels, lubricants and plasticizers), numerous questions about their formation, structure and regulation are still unresolved. To determine water accessible domains of protein coating at lipid droplets surface, a structural proteomic approach has been performed. This technique relies on the millisecond timescale production of hydroxyl radicals by the radiolysis of water using Synchrotron X-ray white beam. Thanks to the evolution of mass spectrometry analysis techniques this approach allows the creation of a map of the solvent accessibility for proteins difficult to study by other means. Using these results, a S3 oleosin water accessibility map is proposed. This is the first time that such a map on an oleosin co-purified with plant lipid droplets and other associated protein is presented. Lipid droplet associated proteins function is linked to stability, structure and probably formation and lipid mobilization of droplets. Structure of these proteins in their native environment, at the interface between bulk water and the lipidic core of these organelles is only based on hydrophobicity plot. Using hydroxyl radical footprinting and proteomics approaches we studied water accessibility of one major protein in these droplets: S3 oleosin of Arabidopsis thaliana seeds. Copyright © 2017 Elsevier B.V. All rights reserved.

  1. SSR-based genetic diversity and structure of garlic accessions from Brazil.

    PubMed

    da Cunha, Camila Pinto; Resende, Francisco Vilela; Zucchi, Maria Imaculada; Pinheiro, José Baldin

    2014-10-01

    Garlic is a spice and a medicinal plant; hence, there is an increasing interest in 'developing' new varieties with different culinary properties or with high content of nutraceutical compounds. Phenotypic traits and dominant molecular markers are predominantly used to evaluate the genetic diversity of garlic clones. However, 24 SSR markers (codominant) specific for garlic are available in the literature, fostering germplasm researches. In this study, we genotyped 130 garlic accessions from Brazil and abroad using 17 polymorphic SSR markers to assess the genetic diversity and structure. This is the first attempt to evaluate a large set of accessions maintained by Brazilian institutions. A high level of redundancy was detected in the collection (50 % of the accessions represented eight haplotypes). However, non-redundant accessions presented high genetic diversity. We detected on average five alleles per locus, Shannon index of 1.2, HO of 0.5, and HE of 0.6. A core collection was set with 17 accessions, covering 100 % of the alleles with minimum redundancy. Overall FST and D values indicate a strong genetic structure within accessions. Two major groups identified by both model-based (Bayesian approach) and hierarchical clustering (UPGMA dendrogram) techniques were coherent with the classification of accessions according to maturity time (growth cycle): early-late and midseason accessions. Assessing genetic diversity and structure of garlic collections is the first step towards an efficient management and conservation of accessions in genebanks, as well as to advance future genetic studies and improvement of garlic worldwide.

  2. MARSnet: Mission-aware Autonomous Radar Sensor Network for Future Combat Systems

    DTIC Science & Technology

    2009-03-23

    15 , , L x(s)x*(s) ds WdB = lOlog Jo Y ; ; (19) In addition, the sidelobe structure is changed because of the Dop])ler shift...Synchro- nous CDMA Systems.’’ IEICE Trans.Fundamentals. E832A(11): 1 16, 2000. 24 [10] P. Z. Fan. "New Direction in Spreading Sequence Design and the...Suehiro , N Kuroyanagi and P Z Fan. "Two types of polyphase sequence set. for approximately synchronized CDMA systems." IEICE Trans. Fundamentals. E862A

  3. How to start a minimal access mitral valve program.

    PubMed

    Hunter, Steven

    2013-11-01

    The seven pillars of governance established by the National Health Service in the United Kingdom provide a useful framework for the process of introducing new procedures to a hospital. Drawing from local experience, the author present guidance for institutions considering establishing a minimal access mitral valve program. The seven pillars of governance apply to the practice of minimally invasive mitral valve surgery, based on the principle of patient-centred practice. The author delineate the benefits of minimally invasive mitral valve surgery in terms of: "clinical effectiveness", including reduced length of hospital stay, "risk management effectiveness", including conversion to sternotomy and aortic dissection, "patient experience" including improved cosmesis and quicker recovery, and the effectiveness of communication, resources and strategies in the implementation of minimally invasive mitral valve surgery. Finally, the author have identified seven learning curves experienced by surgeons involved in introducing a minimal access mitral valve program. The learning curves are defined as: techniques of mitral valve repair, Transoesophageal Echocardiography-guided cannulation, incisions, instruments, visualization, aortic occlusion and cardiopulmonary bypass strategies. From local experience, the author provide advice on how to reduce the learning curves, such as practising with the specialised instruments and visualization techniques during sternotomy cases. Underpinning the NHS pillars are the principles of systems awareness, teamwork, communication, ownership and leadership, all of which are paramount to performing any surgery but more so with minimal access surgery, as will be highlighted throughout this paper.

  4. How to start a minimal access mitral valve program

    PubMed Central

    2013-01-01

    The seven pillars of governance established by the National Health Service in the United Kingdom provide a useful framework for the process of introducing new procedures to a hospital. Drawing from local experience, the author present guidance for institutions considering establishing a minimal access mitral valve program. The seven pillars of governance apply to the practice of minimally invasive mitral valve surgery, based on the principle of patient-centred practice. The author delineate the benefits of minimally invasive mitral valve surgery in terms of: “clinical effectiveness”, including reduced length of hospital stay, “risk management effectiveness”, including conversion to sternotomy and aortic dissection, “patient experience” including improved cosmesis and quicker recovery, and the effectiveness of communication, resources and strategies in the implementation of minimally invasive mitral valve surgery. Finally, the author have identified seven learning curves experienced by surgeons involved in introducing a minimal access mitral valve program. The learning curves are defined as: techniques of mitral valve repair, Transoesophageal Echocardiography-guided cannulation, incisions, instruments, visualization, aortic occlusion and cardiopulmonary bypass strategies. From local experience, the author provide advice on how to reduce the learning curves, such as practising with the specialised instruments and visualization techniques during sternotomy cases. Underpinning the NHS pillars are the principles of systems awareness, teamwork, communication, ownership and leadership, all of which are paramount to performing any surgery but more so with minimal access surgery, as will be highlighted throughout this paper. PMID:24349981

  5. Reinforced aneurysmorrhaphy for true aneurysmal haemodialysis vascular access.

    PubMed

    Rokošný, S; Baláž, P; Wohlfahrt, P; Palouš, D; Janoušek, L

    2014-04-01

    In 2008, a new technique of reinforced aneurysmorrhaphy with a polyester mesh tube for salvaging true aneurysmal arteriovenous (AV) haemodialysis access was described by us. In this study, the long-term patency and complication rates associated with this procedure were analysed, and the effect of reinforced aneurysmorrhaphy on high-flow vascular access was assessed. This was a retrospective non-randomised study with prospectively collected data performed at a single centre. Patients with true aneurysmal haemodialysis AV access who underwent aneurysmorrhaphy with external mesh prosthesis between March 2007 and October 2012 were included. Clinical assessment and duplex ultrasound were performed preoperatively, 1, 3, and 12 months postoperatively, and annually thereafter. Data from 62 patients (median age 60 years, range 28-81 years; 63% men) were analysed. The commonest indication was high-flow vascular access associated with the risk of high output cardiac failure (24 patients, 39%). The mean follow-up time was 14.66 ± 12.80 months. Primary patency rates at 6 and 12 months were 86% and 79% respectively. Assisted primary patency rates at 6 and 12 months were 89% and 80% respectively. In 23 patients (96%) operated on for high-flow vascular access, decreased vascular access flow was observed after the procedure. The average flow reduction after aneurysmorrhaphy was 2,197 mL/minute. Postoperative bleeding and infection necessitating surgical revision occurred in three (4.8%) and three (4.8%) patients respectively. Reinforced aneurysmorrhaphy with an external mesh prosthesis is an effective method for treating true aneurysmal haemodialysis AV access, with excellent long-term patency and minimal complications due to infection. Copyright © 2014 European Society for Vascular Surgery. Published by Elsevier Ltd. All rights reserved.

  6. Current Developments in Machine Learning Techniques in Biological Data Mining.

    PubMed

    Dumancas, Gerard G; Adrianto, Indra; Bello, Ghalib; Dozmorov, Mikhail

    2017-01-01

    This supplement is intended to focus on the use of machine learning techniques to generate meaningful information on biological data. This supplement under Bioinformatics and Biology Insights aims to provide scientists and researchers working in this rapid and evolving field with online, open-access articles authored by leading international experts in this field. Advances in the field of biology have generated massive opportunities to allow the implementation of modern computational and statistical techniques. Machine learning methods in particular, a subfield of computer science, have evolved as an indispensable tool applied to a wide spectrum of bioinformatics applications. Thus, it is broadly used to investigate the underlying mechanisms leading to a specific disease, as well as the biomarker discovery process. With a growth in this specific area of science comes the need to access up-to-date, high-quality scholarly articles that will leverage the knowledge of scientists and researchers in the various applications of machine learning techniques in mining biological data.

  7. Retropinacol/Cross-pinacol Coupling Reactions - A Catalytic Access to 1,2-Unsymmetrical Diols

    PubMed Central

    Scheffler, Ulf; Mahrwald, Rainer

    2014-01-01

    Unsymmetrical 1,2-diols are hardly accessible by reductive pinacol coupling processes. A successful execution of such a transformation is bound to a clear recognition and strict differentiation of two similar carbonyl compounds (aldehydes → secondary 1,2-diols or ketones → tertiary 1,2-diols). This fine-tuning is still a challenge and an unsolved problem for an organic chemist. There exist several reports on successful execution of this transformation but they cannot be generalized. Herein we describe a catalytic direct pinacol coupling process which proceeds via a retropinacol/cross-pinacol coupling sequence. Thus, unsymmetrical substituted 1,2-diols can be accessed with almost quantitative yields by means of an operationally simple performance under very mild conditions. Artificial techniques, such as syringe-pump techniques or delayed additions of reactants are not necessary. The procedure we describe provides a very rapid access to cross-pinacol products (1,2-diols, vicinal diols). A further extension of this new process, e.g. an enantioselective performance could provide a very useful tool for the synthesis of unsymmetrical chiral 1,2-diols. PMID:24747370

  8. Network acceleration techniques

    NASA Technical Reports Server (NTRS)

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

  9. Genetic diversity and relationship analysis of Gossypium arboreum accessions.

    PubMed

    Liu, F; Zhou, Z L; Wang, C Y; Wang, Y H; Cai, X Y; Wang, X X; Zhang, Z S; Wang, K B

    2015-11-19

    Simple sequence repeat techniques were used to identify the genetic diversity of 101 Gossypium arboreum accessions collected from India, Vietnam, and the southwest of China (Guizhou, Guangxi, and Yunnan provinces). Twenty-six pairs of SSR primers produced a total of 103 polymorphic loci with an average of 3.96 polymorphic loci per primer. The average of the effective number of alleles, Nei's gene diversity, and Shannon's information index were 0.59, 0.2835, and 0.4361, respectively. The diversity varied among different geographic regions. The result of principal component analysis was consistent with that of unweighted pair group method with arithmetic mean clustering analysis. The 101 G. arboreum accessions were clustered into 2 groups.

  10. Standardized technique for single port laparoscopic ileostomy and colostomy.

    PubMed

    Shah, A; Moftah, M; Hadi Nahar Al-Furaji, H; Cahill, R A

    2014-07-01

    Single site laparoscopic techniques and technology exploit maximum usefulness from confined incisions. The formation of an ileostomy or colostomy seems very applicable for this modality as the stoma occupies the solitary incision obviating any additional wounds. Here we detail the principles of our approach to defunctioning loop stoma formation using single port laparoscopic access in a stepwise and standardized fashion along with the salient specifics of five illustrative patients. No specialized instrumentation is required and the single access platform is established table-side using the 'glove port' technique. The approach has the intra-operative advantage of excellent visualization of the correct intestinal segment for exteriorization along with direct visual control of its extraction to avoid twisting. Postoperatively, abdominal wall trauma has been minimal allowing convalescence and stoma care education with only one parietal incision. Single incision stoma siting proves a ready, robust and reliable technique for diversion ileostomy and colostomy with a minimum of operative trauma for the patient. Colorectal Disease © 2014 The Association of Coloproctology of Great Britain and Ireland.

  11. Optical protocols for advanced spacecraft networks

    NASA Technical Reports Server (NTRS)

    Bergman, Larry A.

    1991-01-01

    Most present day fiber optic networks are in fact extensions of copper wire networks. As a result, their speed is still limited by electronics even though optics is capable of running three orders of magnitude faster. Also, the fact that photons do not interact with one another (as electrons do) provides optical communication systems with some unique properties or new functionality that is not readily taken advantage of with conventional approaches. Some of the motivation for implementing network protocols in the optical domain, a few possible approaches including optical code-division multiple-access (CDMA), and how this class of networks can extend the technology life cycle of the Space Station Freedom (SSF) with increased performance and functionality are described.

  12. Simultaneous sampling technique for two spectral sources

    NASA Technical Reports Server (NTRS)

    Jarrett, Olin, Jr.

    1987-01-01

    A technique is described that uses a bundle of fiber optics to simultaneously sample a dye laser and a spectral lamp. By the use of a real-time display with this technique, the two signals can be superimposed, and the effect of any spectral adjustments can be immediately accessed. In the NASA's CARS system used for combustion diagnostics, the dye laser mixes with a simultaneously pulsed Nd:YAG laser at 532 nm to probe the vibrational levels of nitrogen. An illustration of the oscilloscopic display of the system is presented.

  13. Vital Business Educators' Perceptions about the Usefulness of Business Education Periodicals: Making the Relevant Literature More Accessible

    ERIC Educational Resources Information Center

    Scott, James Calvert; Blaszczynski, Carol; Green, Diana J.; Fagerheim, Britt Anna

    2008-01-01

    Problem: The business education literature isn't accessible. Research Questions: Which business education periodicals do vital business educators perceive to be more useful? In which databases and/or indices are they found? How much literature is fugitive? What strategies might increase literature accessibility? Research Method: Delphi technique.…

  14. Design of a memory-access controller with 3.71-times-enhanced energy efficiency for Internet-of-Things-oriented nonvolatile microcontroller unit

    NASA Astrophysics Data System (ADS)

    Natsui, Masanori; Hanyu, Takahiro

    2018-04-01

    In realizing a nonvolatile microcontroller unit (MCU) for sensor nodes in Internet-of-Things (IoT) applications, it is important to solve the data-transfer bottleneck between the central processing unit (CPU) and the nonvolatile memory constituting the MCU. As one circuit-oriented approach to solving this problem, we propose a memory access minimization technique for magnetoresistive-random-access-memory (MRAM)-embedded nonvolatile MCUs. In addition to multiplexing and prefetching of memory access, the proposed technique realizes efficient instruction fetch by eliminating redundant memory access while considering the code length of the instruction to be fetched and the transition of the memory address to be accessed. As a result, the performance of the MCU can be improved while relaxing the performance requirement for the embedded MRAM, and compact and low-power implementation can be performed as compared with the conventional cache-based one. Through the evaluation using a system consisting of a general purpose 32-bit CPU and embedded MRAM, it is demonstrated that the proposed technique increases the peak efficiency of the system up to 3.71 times, while a 2.29-fold area reduction is achieved compared with the cache-based one.

  15. Water accessibility in a membrane-inserting peptide comparing Overhauser DNP and pulse EPR methods.

    PubMed

    Segawa, Takuya F; Doppelbauer, Maximilian; Garbuio, Luca; Doll, Andrin; Polyhach, Yevhen O; Jeschke, Gunnar

    2016-05-21

    Water accessibility is a key parameter for the understanding of the structure of biomolecules, especially membrane proteins. Several experimental techniques based on the combination of electron paramagnetic resonance (EPR) spectroscopy with site-directed spin labeling are currently available. Among those, we compare relaxation time measurements and electron spin echo envelope modulation (ESEEM) experiments using pulse EPR with Overhauser dynamic nuclear polarization (DNP) at X-band frequency and a magnetic field of 0.33 T. Overhauser DNP transfers the electron spin polarization to nuclear spins via cross-relaxation. The change in the intensity of the (1)H NMR spectrum of H2O at a Larmor frequency of 14 MHz under a continuous-wave microwave irradiation of the nitroxide spin label contains information on the water accessibility of the labeled site. As a model system for a membrane protein, we use the hydrophobic α-helical peptide WALP23 in unilamellar liposomes of DOPC. Water accessibility measurements with all techniques are conducted for eight peptides with different spin label positions and low radical concentrations (10-20 μM). Consistently in all experiments, the water accessibility appears to be very low, even for labels positioned near the end of the helix. The best profile is obtained by Overhauser DNP, which is the only technique that succeeds in discriminating neighboring positions in WALP23. Since the concentration of the spin-labeled peptides varied, we normalized the DNP parameter ϵ, being the relative change of the NMR intensity, by the electron spin concentration, which was determined from a continuous-wave EPR spectrum.

  16. 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…

  17. Direct Percutaneous Left Ventricular Access and Port Closure

    PubMed Central

    Barbash, Israel M.; Saikus, Christina E.; Faranesh, Anthony Z.; Ratnayaka, Kanishka; Kocaturk, Ozgur; Chen, Marcus Y.; Bell, Jamie A.; Virmani, Renu; Schenke, William H.; Hansen, Michael S.; Slack, Michael C.; Lederman, Robert J.

    2012-01-01

    Objectives This study sought to evaluate feasibility of nonsurgical transthoracic catheter-based left ventricular (LV) access and closure. Background Implanting large devices, such as mitral or aortic valve prostheses, into the heart requires surgical exposure and repair. Reliable percutaneous direct transthoracic LV access and closure would allow new nonsurgical therapeutic procedures. Methods Percutaneous direct LV access was performed in 19 swine using real-time magnetic resonance imaging (MRI) and an “active” MRI needle antenna to deliver an 18-F introducer sheath. The LV access ports were closed percutaneously using a commercial ventricular septal defect occluder and an “active” MRI delivery cable for enhanced visibility. We used “permissive pericardial tamponade” (temporary fluid instillation to separate the 2 pericardial layers) to avoid pericardial entrapment by the epicardial disk. Techniques were developed in 8 animals, and 11 more were followed up to 3 months by MRI and histopathology. Results Imaging guidance allowed 18-F sheath access and closure with appropriate positioning of the occluder inside the transmyocardial tunnel. Of the survival cohort, immediate hemostasis was achieved in 8 of 11 patients. Failure modes included pericardial entrapment by the epicardial occluder disk (n = 2) and a true-apex entry site that prevented hemostatic apposition of the endocardial disk (n = 1). Reactive pericardial effusion (192 ± 118 ml) accumulated 5 ± 1 days after the procedure, requiring 1-time drainage. At 3 months, LV function was preserved, and the device was endothelialized. Conclusions Direct percutaneous LV access and closure is feasible using real-time MRI. A commercial occluder achieved hemostasis without evident deleterious effects on the LV. Having established the concept, further clinical development of this approach appears realistic. PMID:22192372

  18. Multi terabits/s optical access transport technologies

    NASA Astrophysics Data System (ADS)

    Binh, Le Nguyen; Wang Tao, Thomas; Livshits, Daniil; Gubenko, Alexey; Karinou, Fotini; Liu Ning, Gordon; Shkolnik, Alexey

    2016-02-01

    Tremendous efforts have been developed for multi-Tbps over ultra-long distance and metro and access optical networks. With the exponential increase demand on data transmission, storage and serving, especially the 5G wireless access scenarios, the optical Internet networking has evolved to data-center based optical networks pressuring on novel and economical access transmission systems. This paper reports (1) Experimental platforms and transmission techniques employing band-limited optical components operating at 10G for 100G based at 28G baud. Advanced modulation formats such as PAM-4, DMT, duo-binary etc are reported and their advantages and disadvantages are analyzed so as to achieve multi-Tbps optical transmission systems for access inter- and intra- data-centered-based networks; (2) Integrated multi-Tbps combining comb laser sources and micro-ring modulators meeting the required performance for access systems are reported. Ten-sub-carrier quantum dot com lasers are employed in association with wideband optical intensity modulators to demonstrate the feasibility of such sources and integrated micro-ring modulators acting as a combined function of demultiplexing/multiplexing and modulation, hence compactness and economy scale. Under the use of multi-level modulation and direct detection at 56 GBd an aggregate of higher than 2Tbps and even 3Tbps can be achieved by interleaved two comb lasers of 16 sub-carrier lines; (3) Finally the fundamental designs of ultra-compacts flexible filters and switching integrated components based on Si photonics for multi Tera-bps active interconnection are presented. Experimental results on multi-channels transmissions and performances of optical switching matrices and effects on that of data channels are proposed.

  19. The transferability of safety-driven access management models for application to other sites.

    DOT National Transportation Integrated Search

    2001-01-01

    Several research studies have produced mathematical models that predict the safety impacts of selected access management techniques. Since new models require substantial resources to construct, this study evaluated five existing models with regard to...

  20. Towards ubiquitous access of computer-assisted surgery systems.

    PubMed

    Liu, Hui; Lufei, Hanping; Shi, Weishong; Chaudhary, Vipin

    2006-01-01

    Traditional stand-alone computer-assisted surgery (CAS) systems impede the ubiquitous and simultaneous access by multiple users. With advances in computing and networking technologies, ubiquitous access to CAS systems becomes possible and promising. Based on our preliminary work, CASMIL, a stand-alone CAS server developed at Wayne State University, we propose a novel mobile CAS system, UbiCAS, which allows surgeons to retrieve, review and interpret multimodal medical images, and to perform some critical neurosurgical procedures on heterogeneous devices from anywhere at anytime. Furthermore, various optimization techniques, including caching, prefetching, pseudo-streaming-model, and compression, are used to guarantee the QoS of the UbiCAS system. UbiCAS enables doctors at remote locations to actively participate remote surgeries, share patient information in real time before, during, and after the surgery.

  1. Methodological proceedings to evaluate the physical accessibility in urban historic sites.

    PubMed

    Ribeiro, Gabriela Sousa; Martins, Laura Bezerra; Monteiro, Circe Maria Gama

    2012-01-01

    Historic urban sites are set by cultural and social diversities, generating multiple activities and use and access to these sites should be available to all people including those with disabilities. Taking into consideration that using the same methodology that was used in different historic sites researches with positive results facilitates replication, we aimed to develop methodological procedures that identify conditions of physical accessibility in open public spaces and access to public buildings in historic urban sites to support proposals about design requirements for improvements to the problems diagnosed and control inadequacies of the physical environment. The study methods and techniques from different areas of knowledge culminated in a proposal built with an emphasis on user participation that could be applied with low cost and in relatively short period of time.

  2. Technical Note [cmUse of a Snare Wire to Perform Nephrostomy Access in the Presence of Obstructive Staghorn Calculi

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    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.

  3. Intravascular US-Guided Portal Vein Access: Improved Procedural Metrics during TIPS Creation.

    PubMed

    Gipson, Matthew G; Smith, Mitchell T; Durham, Janette D; Brown, Anthony; Johnson, Thor; Ray, Charles E; Gupta, Rajan K; Kondo, Kimi L; Rochon, Paul J; Ryu, Robert K

    2016-08-01

    To evaluate transjugular intrahepatic portosystemic shunt (TIPS) outcomes and procedure metrics with the use of three different image guidance techniques for portal vein (PV) access during TIPS creation. A retrospective review of consecutive patients who underwent TIPS procedures for a range of indications during a 28-month study period identified a population of 68 patients. This was stratified by PV access techniques: fluoroscopic guidance with or without portography (n = 26), PV marker wire guidance (n = 18), or intravascular ultrasound (US) guidance (n = 24). Procedural outcomes and procedural metrics, including radiation exposure, contrast agent volume used, procedure duration, and PV access time, were analyzed. No differences in demographic or procedural characteristics were found among the three groups. Technical success, technical success of the primary planned approach, hemodynamic success, portosystemic gradient, and procedure-related complications were not significantly different among groups. Fluoroscopy time (P = .003), air kerma (P = .01), contrast agent volume (P = .003), and total procedural time (P = .02) were reduced with intravascular US guidance compared with fluoroscopic guidance. Fluoroscopy time (P = .01) and contrast agent volume (P = .02) were reduced with intravascular US guidance compared with marker wire guidance. Intravascular US guidance of PV access during TIPS creation not only facilitates successful TIPS creation in patients with challenging anatomy, as suggested by previous investigations, but also reduces important procedure metrics including radiation exposure, contrast agent volume, and overall procedure duration compared with fluoroscopically guided TIPS creation. Copyright © 2016 SIR. Published by Elsevier Inc. All rights reserved.

  4. 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

  5. Commissurotomy for improving access to the oral cavity of the wombat.

    PubMed

    Wilson, G J; Gillett, A

    2010-07-01

    Wombats are a grazing marsupial with a diet rich in silicates, which is highly abrasive and results in a higher rate of tooth attrition than in other grazing marsupials such as kangaroos. Any interference in the natural wear process, such as malocclusion or loss of teeth, causes overgrowth of teeth. The small mouth opening of the wombat makes access to the caudal mouth difficult and overgrowth of cheek teeth can be difficult to treat effectively. This case report describes a technique that greatly improves access to allow dental treatment of all overgrown teeth with minimal complications.

  6. Compression technique for large statistical data bases

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Eggers, S.J.; Olken, F.; Shoshani, A.

    1981-03-01

    The compression of large statistical databases is explored and are proposed for organizing the compressed data, such that the time required to access the data is logarithmic. The techniques exploit special characteristics of statistical databases, namely, variation in the space required for the natural encoding of integer attributes, a prevalence of a few repeating values or constants, and the clustering of both data of the same length and constants in long, separate series. The techniques are variations of run-length encoding, in which modified run-lengths for the series are extracted from the data stream and stored in a header, which ismore » used to form the base level of a B-tree index into the database. The run-lengths are cumulative, and therefore the access time of the data is logarithmic in the size of the header. The details of the compression scheme and its implementation are discussed, several special cases are presented, and an analysis is given of the relative performance of the various versions.« less

  7. Exploring accessibility of pretreated poplar cell walls by measuring dynamics of fluorescent probes.

    PubMed

    Paës, Gabriel; Habrant, Anouck; Ossemond, Jordane; Chabbert, Brigitte

    2017-01-01

    The lignocellulosic cell wall network is resistant to enzymatic degradation due to the complex chemical and structural features. Pretreatments are thus commonly used to overcome natural recalcitrance of lignocellulose. Characterization of their impact on architecture requires combinatory approaches. However, the accessibility of the lignocellulosic cell walls still needs further insights to provide relevant information. Poplar specimens were pretreated using different conditions. Chemical, spectral, microscopic and immunolabeling analysis revealed that poplar cell walls were more altered by sodium chlorite-acetic acid and hydrothermal pretreatments but weakly modified by soaking in aqueous ammonium. In order to evaluate the accessibility of the pretreated poplar samples, two fluorescent probes (rhodamine B-isothiocyanate-dextrans of 20 and 70 kDa) were selected, and their mobility was measured by using the fluorescence recovery after photobleaching (FRAP) technique in a full factorial experiment. The mobility of the probes was dependent on the pretreatment type, the cell wall localization (secondary cell wall and cell corner middle lamella) and the probe size. Overall, combinatory analysis of pretreated poplar samples showed that even the partial removal of hemicellulose contributed to facilitate the accessibility to the fluorescent probes. On the contrary, nearly complete removal of lignin was detrimental to accessibility due to the possible cellulose-hemicellulose collapse. Evaluation of plant cell wall accessibility through FRAP measurement brings further insights into the impact of physicochemical pretreatments on lignocellulosic samples in combination with chemical and histochemical analysis. This technique thus represents a relevant approach to better understand the effect of pretreatments on lignocellulose architecture, while considering different limitations as non-specific interactions and enzyme efficiency.

  8. A Parent-Focused Early Intervention Program for Autism: Who Gets Access?

    ERIC Educational Resources Information Center

    Birkin, Christina; Anderson, Angelika; Seymour, Fred; Moore, Dennis W.

    2008-01-01

    Background: The EarlyBird program is a psycho-educational early intervention program for parents of children with autistic spectrum disorder (ASD). It aims to provide parents with skills to increase their child's communication and manage challenging behaviour using behavioural techniques. Method: Two interlinked studies examined access to the…

  9. [Public control and equity of access to hospitals under non-State public administration].

    PubMed

    Carneiro Junior, Nivaldo; Elias, Paulo Eduardo

    2006-10-01

    To analyze social health organizations in the light of public control and the guarantee of equity of access to health services. Utilizing the case study technique, two social health organizations in the metropolitan region of São Paulo were selected. The analytical categories were equity of access and public control, and these were based on interviews with key informants and technical-administrative reports. It was observed that the overall funding and administrative control of the social health organizations are functions of the state administrator. The presence of a local administrator is important for ensuring equity of access. Public control is expressed through supervisory actions, by means of accounting and financial procedures. Equity of access and public control are not taken into consideration in the administration of these organizations. The central question lies in the capacity of the public authorities to have a presence in implementing this model at the local level, thereby ensuring equity of access and taking public control into consideration.

  10. Flexible single-incision surgery: a fusion technique.

    PubMed

    Noguera, José F; Dolz, Carlos; Cuadrado, Angel; Olea, José; García, Juan

    2013-06-01

    The development of natural orifice transluminal endoscopic surgery has led to other techniques, such as single-incision surgery. The use of the flexible endoscope for single-incision surgery paves the way for further refinement of both surgical methods. To describe a new, single-incision surgical technique, namely, flexible single-incision surgery. Assessment of the safety and effectiveness of endoscopic cholecystectomy in a series of 30 patients. This technique consists of a single umbilical incision through which a flexible endoscope is introduced and consists of 2 parallel entry ports that provide access to nonarticulated laparoscopic instruments. The technique was applied in all patients for whom it was prescribed. No general or surgical wound complications were noted. Surgical time was no longer than usual for single-port surgery. Flexible single-incision surgery is a new single-site surgical technique offering the same level of patient safety, with additional advantages for the surgeon at minimal cost.

  11. Water accessibility in a membrane-inserting peptide comparing Overhauser DNP and pulse EPR methods

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Segawa, Takuya F., E-mail: takuya.segawa@alumni.ethz.ch; Doppelbauer, Maximilian; Garbuio, Luca

    2016-05-21

    Water accessibility is a key parameter for the understanding of the structure of biomolecules, especially membrane proteins. Several experimental techniques based on the combination of electron paramagnetic resonance (EPR) spectroscopy with site-directed spin labeling are currently available. Among those, we compare relaxation time measurements and electron spin echo envelope modulation (ESEEM) experiments using pulse EPR with Overhauser dynamic nuclear polarization (DNP) at X-band frequency and a magnetic field of 0.33 T. Overhauser DNP transfers the electron spin polarization to nuclear spins via cross-relaxation. The change in the intensity of the {sup 1}H NMR spectrum of H{sub 2}O at a Larmormore » frequency of 14 MHz under a continuous-wave microwave irradiation of the nitroxide spin label contains information on the water accessibility of the labeled site. As a model system for a membrane protein, we use the hydrophobic α-helical peptide WALP23 in unilamellar liposomes of DOPC. Water accessibility measurements with all techniques are conducted for eight peptides with different spin label positions and low radical concentrations (10–20 μM). Consistently in all experiments, the water accessibility appears to be very low, even for labels positioned near the end of the helix. The best profile is obtained by Overhauser DNP, which is the only technique that succeeds in discriminating neighboring positions in WALP23. Since the concentration of the spin-labeled peptides varied, we normalized the DNP parameter ϵ, being the relative change of the NMR intensity, by the electron spin concentration, which was determined from a continuous-wave EPR spectrum.« less

  12. A Rewritable, Random-Access DNA-Based Storage System.

    PubMed

    Yazdi, S M Hossein Tabatabaei; Yuan, Yongbo; Ma, Jian; Zhao, Huimin; Milenkovic, Olgica

    2015-09-18

    We describe the first DNA-based storage architecture that enables random access to data blocks and rewriting of information stored at arbitrary locations within the blocks. The newly developed architecture overcomes drawbacks of existing read-only methods that require decoding the whole file in order to read one data fragment. Our system is based on new constrained coding techniques and accompanying DNA editing methods that ensure data reliability, specificity and sensitivity of access, and at the same time provide exceptionally high data storage capacity. As a proof of concept, we encoded parts of the Wikipedia pages of six universities in the USA, and selected and edited parts of the text written in DNA corresponding to three of these schools. The results suggest that DNA is a versatile media suitable for both ultrahigh density archival and rewritable storage applications.

  13. A Rewritable, Random-Access DNA-Based Storage System

    NASA Astrophysics Data System (ADS)

    Tabatabaei Yazdi, S. M. Hossein; Yuan, Yongbo; Ma, Jian; Zhao, Huimin; Milenkovic, Olgica

    2015-09-01

    We describe the first DNA-based storage architecture that enables random access to data blocks and rewriting of information stored at arbitrary locations within the blocks. The newly developed architecture overcomes drawbacks of existing read-only methods that require decoding the whole file in order to read one data fragment. Our system is based on new constrained coding techniques and accompanying DNA editing methods that ensure data reliability, specificity and sensitivity of access, and at the same time provide exceptionally high data storage capacity. As a proof of concept, we encoded parts of the Wikipedia pages of six universities in the USA, and selected and edited parts of the text written in DNA corresponding to three of these schools. The results suggest that DNA is a versatile media suitable for both ultrahigh density archival and rewritable storage applications.

  14. Design of an Efficient CAC for a Broadband DVB-S/DVB-RCS Satellite Access Network

    NASA Astrophysics Data System (ADS)

    Inzerilli, Tiziano; Montozzi, Simone

    2003-07-01

    This paper deals with efficient utilization of network resources in an advanced broadband satellite access system. It proposes a technique for admission control of IP streams with guaranteed QoS which does not interfere with the particular BoD (Bandwidth on Demand) algorithm that handles access to uplink bandwidth, an essential part of a DVB- RCS architecture. This feature of the admission control greatly simplify its integration in the satellite network. The purpose of this admission control algorithm in particular is to suitably and dynamically configure the overall traffic control parameters, in the access terminal of the user and service segment, with a simple approach which does not introduces limitations and/or constraints to the BoD algorithm. Performance of the proposed algorithm is evaluated thorugh Opnet simulations using an ad-hoc platform modeling DVB-based satellite access.The results presented in this paper were obtained within SATIP6 project, which is sponsored within the 5th EU Research Programme, IST. The aims of the project are to evaluate and demonstrate key issues of the integration of satellite-based access networks into the Internet in order to support multimedia services over wide areas. The satellite link layer is based on DVB-S on the forward link and DVB-RCS on the return link. Adaptation and optimization of the DVB-RCS access standard in order to support QoS provision are central issues of the project. They are handled through an integration of Connection Admission Control (CAC), Traffic Shaping and Policing techniques.

  15. 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.

  16. Promoting open access to science through effective communication

    NASA Astrophysics Data System (ADS)

    Egger, A. E.

    2006-12-01

    Geology is a difficult subject to communicate effectively. Many people associate geology with memorizing rock and mineral names and not with dynamic earth processes. Even more challenging for the non-geologist is the concept of deep time, and why processes that happened millions of years ago are important to us today. Additionally, many people view science itself as inaccessible and difficult. And yet, geology is a naturally accessible subject, as it is all around us. In order to communicate effectively, geologists must convince others that their work is both accessible and relevant, even though it may not directly generate economic benefits or lend insight into solutions for our modern problems like climate change. As scientists, we know the connections are there, but convincing others requires creating face-to-face, positive interactions through the use of active techniques to help bring the audience to an understanding of the process of science in addition to the subject matter itself. My overarching motive for creating and participating in communication activities with a broad audience is thus to demonstrate that science is accessible to everyone, that a scientific way of thinking can be both fun and useful, and that a little knowledge about geology can give you a new perspective on the world. Using this motivation as a guiding principle regardless of the specific audience, two techniques are important to make the communication effective. First, whenever possible, I conduct activities in the field (broadly speaking), or at least bring the field into the talk, and model the scientific process by asking for participation. This allows the audience to fully understand how geologic work is done, including the mundane and the mistakes. Second, I take my audience seriously, including all questions and observations, in order to build confidence in everyone that they are able to contribute to and understand both geology and the scientific process in general. Despite the

  17. Accelerated Peer-Review Journal Usage Technique for Undergraduates

    ERIC Educational Resources Information Center

    Wallace, J. D.

    2008-01-01

    The internet has given undergraduate students ever-increasing access to academic journals via search engines and online databases. However, students typically do not have the ability to use these journals effectively. This often poses a dilemma for instructors. The accelerated peer-review journal usage (APJU) technique provides a way for…

  18. Soft errors in commercial off-the-shelf static random access memories

    NASA Astrophysics Data System (ADS)

    Dilillo, L.; Tsiligiannis, G.; Gupta, V.; Bosser, A.; Saigne, F.; Wrobel, F.

    2017-01-01

    This article reviews state-of-the-art techniques for the evaluation of the effect of radiation on static random access memory (SRAM). We detailed irradiation test techniques and results from irradiation experiments with several types of particles. Two commercial SRAMs, in 90 and 65 nm technology nodes, were considered as case studies. Besides the basic static and dynamic test modes, advanced stimuli for the irradiation tests were introduced, as well as statistical post-processing techniques allowing for deeper analysis of the correlations between bit-flip cross-sections and design/architectural characteristics of the memory device. Further insight is provided on the response of irradiated stacked layer devices and on the use of characterized SRAM devices as particle detectors.

  19. Techniques Used by Bearded Capuchin Monkeys (Sapajus libidinosus) to Access Water in a Semi-Arid Environment of North-Eastern Brazil.

    PubMed

    Castro, Shalana Cássia do Nascimento; Souto, Antonio da Silva; Schiel, Nicola; Biondi, Luiz Matos; Caselli, Christini B

    2017-01-01

    The exploratory behaviour and the ability of capuchin monkeys to use tools allows them to thrive at times and places of limited food and water abundance, such as in semi-arid environments. Here, we report the behaviours employed by individuals belonging to a wild group of bearded capuchin monkeys (Sapajus libidinosus) to access natural water sources in a dry forest of north-eastern Brazil. An adult female employed a twig as a tool and her tail to gain access to accumulated rainwater in a tree hole, and other individuals used their hands and mouth to manipulate orchids' pseudobulbs and the liquid endosperm of palm nuts. The behaviour of wild Sapajus to access water from non-food sources may enable them to circumvent the risk of dehydration in environments with reduced availability of fleshy fruits and with ephemeral and rare water sources. Our findings contribute to the still scarce but accumulating reports on primate drinking behaviour and to the knowledge of tool use in wild populations of capuchin monkeys, enriching our understanding of primate strategies to gain access to a vital resource under challenging conditions. © 2017 S. Karger AG, Basel.

  20. Learning Relational Policies from Electronic Health Record Access Logs

    PubMed Central

    Malin, Bradley; Nyemba, Steve; Paulett, John

    2011-01-01

    Modern healthcare organizations (HCOs) are composed of complex dynamic teams to ensure clinical operations are executed in a quick and competent manner. At the same time, the fluid nature of such environments hinders administrators' efforts to define access control policies that appropriately balance patient privacy and healthcare functions. Manual efforts to define these policies are labor-intensive and error-prone, often resulting in systems that endow certain care providers with overly broad access to patients' medical records while restricting other providers from legitimate and timely use. In this work, we propose an alternative method to generate these policies by automatically mining usage patterns from electronic health record (EHR) systems. EHR systems are increasingly being integrated into clinical environments and our approach is designed to be generalizable across HCOs, thus assisting in the design and evaluation of local access control policies. Our technique, which is grounded in data mining and social network analysis theory, extracts a statistical model of the organization from the access logs of its EHRs. In doing so, our approach enables the review of predefined policies, as well as the discovery of unknown behaviors. We evaluate our approach with five months of access logs from the Vanderbilt University Medical Center and confirm the existence of stable social structures and intuitive business operations. Additionally, we demonstrate that there is significant turnover in the interactions between users in the HCO and that policies learned at the department level afford greater stability over time. PMID:21277996

  1. Cellulase digestibility of pretreated biomass is limited by cellulose accessibility.

    PubMed

    Jeoh, Tina; Ishizawa, Claudia I; Davis, Mark F; Himmel, Michael E; Adney, William S; Johnson, David K

    2007-09-01

    Attempts to correlate the physical and chemical properties of biomass to its susceptibility to enzyme digestion are often inconclusive or contradictory depending on variables such as the type of substrate, the pretreatment conditions and measurement techniques. In this study, we present a direct method for measuring the key factors governing cellulose digestibility in a biomass sample by directly probing cellulase binding and activity using a purified cellobiohydrolase (Cel7A) from Trichoderma reesei. Fluorescence-labeled T. reesei Cel7A was used to assay pretreated corn stover samples and pure cellulosic substrates to identify barriers to accessibility by this important component of cellulase preparations. The results showed cellulose conversion improved when T. reesei Cel7A bound in higher concentrations, indicating that the enzyme had greater access to the substrate. Factors such as the pretreatment severity, drying after pretreatment, and cellulose crystallinity were found to directly impact enzyme accessibility. This study provides direct evidence to support the notion that the best pretreatment schemes for rendering biomass more digestible to cellobiohydrolase enzymes are those that improve access to the cellulose in biomass cell walls, as well as those able to reduce the crystallinity of cell wall cellulose.

  2. Matrix Management in Practice in Access Services at the NCSU Libraries

    ERIC Educational Resources Information Center

    Harris, Colleen S.

    2010-01-01

    The former Associate Head of Access and Delivery Services of the North Carolina State University Libraries reports on successful use of matrix management techniques for the Circulation and Reserves unit of the department. Despite their having fallen out of favor in much of the management literature, matrix management principles are useful for…

  3. A Novel Qualitative Method to Improve Access, Elicitation, and Sample Diversification for Enhanced Transferability Applied to Studying Chemistry Outreach

    ERIC Educational Resources Information Center

    Pratt, Justin M.; Yezierski, Ellen J.

    2018-01-01

    Conducting qualitative research in any discipline warrants two actions: accessing participants and eliciting their ideas. In chemistry education research (CER), survey techniques have been used to increase access to participants and diversify samples. Interview tasks (such as card sorting, using demonstrations, and using simulations) have been…

  4. Pendulum Exercises After Hip Arthroscopy: A Video Technique.

    PubMed

    Sauber, Ryan; Saborio, George; Nickel, Beth M; Kivlan, Benjamin R; Christoforetti, John J

    2016-08-01

    Advanced hip joint-preserving arthroscopic techniques have been shown to improve patient-reported functional outcomes with low rates of postoperative complications. Prior work has shown that formation of adhesive scar is a potential source of persistent pain and cause for revision surgery. As resources for postoperative in-studio physical therapy become scarce, a home-based strategy to avoid scar formation without adding formal therapy cost may be beneficial. The purpose of this technical note is to introduce a patient-centered educational video technique for home-caregiver delivery of manual hip pendulum exercises in the postoperative setting. This video technique offers access to our method for pendulum exercise as part of early recovery after advanced hip arthroscopy.

  5. A new slit lamp-based technique for anterior chamber angle estimation.

    PubMed

    Gispets, Joan; Cardona, Genís; Tomàs, Núria; Fusté, Cèlia; Binns, Alison; Fortes, Miguel A

    2014-06-01

    To design and test a new noninvasive method for anterior chamber angle (ACA) estimation based on the slit lamp that is accessible to all eye-care professionals. A new technique (slit lamp anterior chamber estimation [SLACE]) that aims to overcome some of the limitations of the van Herick procedure was designed. The technique, which only requires a slit lamp, was applied to estimate the ACA of 50 participants (100 eyes) using two different slit lamp models, and results were compared with gonioscopy as the clinical standard. The Spearman nonparametric correlation between ACA values as determined by gonioscopy and SLACE were 0.81 (p < 0.001) and 0.79 (p < 0.001) for each slit lamp. Sensitivity values of 100 and 87.5% and specificity values of 75 and 81.2%, depending on the slit lamp used, were obtained for the SLACE technique as compared with gonioscopy (Spaeth classification). The SLACE technique, when compared with gonioscopy, displayed good accuracy in the detection of narrow angles, and it may be useful for eye-care clinicians without access to expensive alternative equipment or those who cannot perform gonioscopy because of legal constraints regarding the use of diagnostic drugs.

  6. Measuring geographical accessibility to rural and remote health care services: Challenges and considerations.

    PubMed

    Shah, Tayyab Ikram; Milosavljevic, Stephan; Bath, Brenna

    2017-06-01

    This research is focused on methodological challenges and considerations associated with the estimation of the geographical aspects of access to healthcare with a focus on rural and remote areas. With the assumption that GIS-based accessibility measures for rural healthcare services will vary across geographic units of analysis and estimation techniques, which could influence the interpretation of spatial access to rural healthcare services. Estimations of geographical accessibility depend on variations of the following three parameters: 1) quality of input data; 2) accessibility method; and 3) geographical area. This research investigated the spatial distributions of physiotherapists (PTs) in comparison to family physicians (FPs) across Saskatchewan, Canada. The three-steps floating catchment areas (3SFCA) method was applied to calculate the accessibility scores for both PT and FP services at two different geographical units. A comparison of accessibility scores to simple healthcare provider-to-population ratios was also calculated. The results vary considerably depending on the accessibility methods used and the choice of geographical area unit for measuring geographical accessibility for both FP and PT services. These findings raise intriguing questions regarding the nature and extent of technical issues and methodological considerations that can affect GIS-based measures in health services research and planning. This study demonstrates how the selection of geographical areal units and different methods for measuring geographical accessibility could affect the distribution of healthcare resources in rural areas. These methodological issues have implications for determining where there is reduced access that will ultimately impact health human resource priorities and policies. Copyright © 2017 Elsevier Ltd. All rights reserved.

  7. Distributed Storage Algorithm for Geospatial Image Data Based on Data Access Patterns.

    PubMed

    Pan, Shaoming; Li, Yongkai; Xu, Zhengquan; Chong, Yanwen

    2015-01-01

    Declustering techniques are widely used in distributed environments to reduce query response time through parallel I/O by splitting large files into several small blocks and then distributing those blocks among multiple storage nodes. Unfortunately, however, many small geospatial image data files cannot be further split for distributed storage. In this paper, we propose a complete theoretical system for the distributed storage of small geospatial image data files based on mining the access patterns of geospatial image data using their historical access log information. First, an algorithm is developed to construct an access correlation matrix based on the analysis of the log information, which reveals the patterns of access to the geospatial image data. Then, a practical heuristic algorithm is developed to determine a reasonable solution based on the access correlation matrix. Finally, a number of comparative experiments are presented, demonstrating that our algorithm displays a higher total parallel access probability than those of other algorithms by approximately 10-15% and that the performance can be further improved by more than 20% by simultaneously applying a copy storage strategy. These experiments show that the algorithm can be applied in distributed environments to help realize parallel I/O and thereby improve system performance.

  8. Emerging technologies and web accessibility: research challenges and opportunities focussing on vision issues.

    PubMed

    Harper, Simon; Yesilada, Yeliz

    2012-01-01

    This is a technological review paper focussed on identifying both the research challenges and opportunities for further investigation arising from emerging technologies, and it does not aim to propose any recommendation or standard. It is focussed on blind and partially sighted World Wide Web (Web) users along with others who use assistive technologies. The Web is a fast moving interdisciplinary domain in which new technologies, techniques and research is in perpetual development. It is often difficult to maintain a holistic view of new developments within the multiple domains which together make up the Web. This suggests that knowledge of the current developments and predictions of future developments are additionally important for the accessibility community. Web accessibility has previously been characterised by the correction of our past mistakes to make the current Web fulfil the original vision of access for all. New technologies were not designed with accessibility in mind and technologies that could be useful for addressing accessibility issues were not identified or adopted by the accessibility community. We wish to enable the research community to undertake preventative measures and proactively address challenges, while recognising opportunities, before they become unpreventable or require retrospective technological enhancement. This article then reviews emerging trends within the Web and Web Accessibility domains.

  9. 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

  10. 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

  11. 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

  12. Demonstration of an SOA-assisted open metro-access infrastructure for heterogeneous services.

    PubMed

    Schmuck, H; Bonk, R; Poehlmann, W; Haslach, C; Kuebart, W; Karnick, D; Meyer, J; Fritzsche, D; Weis, E; Becker, J; Freude, W; Pfeiffer, T

    2014-01-13

    An open converged metro-access network approach allows for sharing optical layer resources like fibers and optical spectrum among different services and operators. We demonstrated experimentally the feasibility of such a concept by the simultaneous operation of multiple services showing different modulation formats and multiplexing techniques. Flexible access nodes are implemented including semiconductor optical amplifiers to create a transparent and reconfigurable optical ring network. The impact of cascaded optical amplifiers on the signal quality is studied along the ring. In addition, the influence of high power rival signals in the same waveband and in the same fiber is analyzed.

  13. 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.

  14. Moving toward a universally accessible web: Web accessibility and education.

    PubMed

    Kurt, Serhat

    2017-12-08

    The World Wide Web is an extremely powerful source of information, inspiration, ideas, and opportunities. As such, it has become an integral part of daily life for a great majority of people. Yet, for a significant number of others, the internet offers only limited value due to the existence of barriers which make accessing the Web difficult, if not impossible. This article illustrates some of the reasons that achieving equality of access to the online world of education is so critical, explores the current status of Web accessibility, discusses evaluative tools and methods that can help identify accessibility issues in educational websites, and provides practical recommendations and guidelines for resolving some of the obstacles that currently hinder the achievability of the goal of universal Web access.

  15. Gaining Access to Economically Marginalized Rural Populations: Lessons Learned from Nonprobability Sampling

    ERIC Educational Resources Information Center

    Mammen, Sheila; Sano, Yoshie

    2012-01-01

    Poverty is a significant problem in rural America. Gaining access to economically marginalized rural populations in order to recruit individuals to participate in a research study, however, is often a challenge. This article compares three different nonprobability sampling techniques that have been used to recruit rural, low-income…

  16. Indoor high precision three-dimensional positioning system based on visible light communication using modified genetic algorithm

    NASA Astrophysics Data System (ADS)

    Chen, Hao; Guan, Weipeng; Li, Simin; Wu, Yuxiang

    2018-04-01

    To improve the precision of indoor positioning and actualize three-dimensional positioning, a reversed indoor positioning system based on visible light communication (VLC) using genetic algorithm (GA) is proposed. In order to solve the problem of interference between signal sources, CDMA modulation is used. Each light-emitting diode (LED) in the system broadcasts a unique identity (ID) code using CDMA modulation. Receiver receives mixed signal from every LED reference point, by the orthogonality of spreading code in CDMA modulation, ID information and intensity attenuation information from every LED can be obtained. According to positioning principle of received signal strength (RSS), the coordinate of the receiver can be determined. Due to system noise and imperfection of device utilized in the system, distance between receiver and transmitters will deviate from the real value resulting in positioning error. By introducing error correction factors to global parallel search of genetic algorithm, coordinates of the receiver in three-dimensional space can be determined precisely. Both simulation results and experimental results show that in practical application scenarios, the proposed positioning system can realize high precision positioning service.

  17. Fluorescence correlation spectroscopy: novel variations of an established technique.

    PubMed

    Haustein, Elke; Schwille, Petra

    2007-01-01

    Fluorescence correlation spectroscopy (FCS) is one of the major biophysical techniques used for unraveling molecular interactions in vitro and in vivo. It allows minimally invasive study of dynamic processes in biological specimens with extremely high temporal and spatial resolution. By recording and correlating the fluorescence fluctuations of single labeled molecules through the exciting laser beam, FCS gives information on molecular mobility and photophysical and photochemical reactions. By using dual-color fluorescence cross-correlation, highly specific binding studies can be performed. These have been extended to four reaction partners accessible by multicolor applications. Alternative detection schemes shift accessible time frames to slower processes (e.g., scanning FCS) or higher concentrations (e.g., TIR-FCS). Despite its long tradition, FCS is by no means dated. Rather, it has proven to be a highly versatile technique that can easily be adapted to solve specific biological questions, and it continues to find exciting applications in biology and medicine.

  18. Non-Orthogonal Multiple Access for Ubiquitous Wireless Sensor Networks.

    PubMed

    Anwar, Asim; Seet, Boon-Chong; Ding, Zhiguo

    2018-02-08

    Ubiquitous wireless sensor networks (UWSNs) have become a critical technology for enabling smart cities and other ubiquitous monitoring applications. Their deployment, however, can be seriously hampered by the spectrum available to the sheer number of sensors for communication. To support the communication needs of UWSNs without requiring more spectrum resources, the power-domain non-orthogonal multiple access (NOMA) technique originally proposed for 5th Generation (5G) cellular networks is investigated for UWSNs for the first time in this paper. However, unlike 5G networks that operate in the licensed spectrum, UWSNs mostly operate in unlicensed spectrum where sensors also experience cross-technology interferences from other devices sharing the same spectrum. In this paper, we model the interferences from various sources at the sensors using stochastic geometry framework. To evaluate the performance, we derive a theorem and present new closed form expression for the outage probability of the sensors in a downlink scenario under interference limited environment. In addition, diversity analysis for the ordered NOMA users is performed. Based on the derived outage probability, we evaluate the average link throughput and energy consumption efficiency of NOMA against conventional orthogonal multiple access (OMA) technique in UWSNs. Further, the required computational complexity for the NOMA users is presented.

  19. Multi-modal two-step floating catchment area analysis of primary health care accessibility.

    PubMed

    Langford, Mitchel; Higgs, Gary; Fry, Richard

    2016-03-01

    Two-step floating catchment area (2SFCA) techniques are popular for measuring potential geographical accessibility to health care services. This paper proposes methodological enhancements to increase the sophistication of the 2SFCA methodology by incorporating both public and private transport modes using dedicated network datasets. The proposed model yields separate accessibility scores for each modal group at each demand point to better reflect the differential accessibility levels experienced by each cohort. An empirical study of primary health care facilities in South Wales, UK, is used to illustrate the approach. Outcomes suggest the bus-riding cohort of each census tract experience much lower accessibility levels than those estimated by an undifferentiated (car-only) model. Car drivers' accessibility may also be misrepresented in an undifferentiated model because they potentially profit from the lower demand placed upon service provision points by bus riders. The ability to specify independent catchment sizes for each cohort in the multi-modal model allows aspects of preparedness to travel to be investigated. Copyright © 2016. Published by Elsevier Ltd.

  20. Influence of operator experience and PCI volume on transfemoral access techniques: A collaboration of international cardiovascular societies.

    PubMed

    Nelson, Daniel W; Damluji, Abdulla A; Patel, Nish; Valgimigli, Marco; Windecker, Stephan; Byrne, Robert; Nolan, James; Patel, Tejas; Brilakis, Emmanouil; Banerjee, Subhash; Mayol, Jorge; Cantor, Warren J; Alfonso, Carlos E; Rao, Sunil V; Moscucci, Mauro; Cohen, Mauricio G

    2018-03-01

    Transfemoral access (TFA) is widely used for coronary angiography and percutaneous coronary intervention (PCI). The influence of operator age, gender, experience, and procedural volume on performance of femoral arterial access has not been studied. A survey instrument was developed and distributed via e-mail from professional societies to interventional cardiologists worldwide from March to December 2016. A total of 988 physicians from 88 countries responded to the survey. TFA is the preferred approach for patients with cardiogenic shock, left main or bifurcation PCI, and procedures with mechanical circulatory support. Older (<50years: 56.4%; ≥50years: 66.8%, p<0.0039) and high PCI volume operators (<100 PCI: 57.3%; 100-299 PCI: 58.7%; ≥300 PCI: 64.3%, p<0.134) preferred palpation only without imaging (fluoroscopy or ultrasound (US)) for TFA. Most respondents preferred not to use micropuncture needle to puncture the femoral artery. Older (≥50years: 64.4%; <50years: 71.5%, p<0.04) and high PCI volume operators (≥300 PCI: 64.1%; 100-299 PCI: 72.6%; <100 PCI: 67.9%, p<0.072) tended not to perform femoral angiography (FA). Of those performing FA, the majority opted to do it at the end of the procedure. Despite best practice guideline recommendations, older and high PCI volume interventional cardiologists prefer not to use imaging for femoral access or perform femoral angiography during TF procedures. These data highlight opportunities to further reduce TFA complications. Copyright © 2017 Elsevier Inc. All rights reserved.

  1. 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…

  2. Comparative study of electromechanical impedance and Lamb wave techniques for fatigue crack detection and monitoring in metallic structures

    NASA Astrophysics Data System (ADS)

    Lim, Say Ian; Liu, Yu; Soh, Chee Kiong

    2012-04-01

    Fatigue cracks often initiate at the weld toes of welded steel connections. Usually, these cracks cannot be identified by the naked eyes. Existing identification methods like dye-penetration test and alternating current potential drop (ACPD) may be useful for detecting fatigue cracks at the weld toes. To apply these non-destructive evaluation (NDE) techniques, the potential sites have to be accessible during inspection. Therefore, there is a need to explore other detection and monitoring techniques for fatigue cracks especially when their locations are inaccessible or cost of access is uneconomical. Electro-mechanical Impedance (EMI) and Lamb wave techniques are two fast growing techniques in the Structural Health Monitoring (SHM) community. These techniques use piezoelectric ceramics (PZT) for actuation and sensing. Since the monitoring site is only needed to be accessed once for the instrumentation of the transducers, remote monitoring is made possible. The permanent locations of these transducers also translate to having consistent measurement for monitoring. The main focus of this study is to conduct a comparative investigation on the effectiveness and efficiency of the EMI technique and the Lamb wave technique for successful fatigue crack identification and monitoring of welded steel connections using piezoelectric transducers. A laboratory-sized non-load carrying fillet weld specimen is used in this study. The specimen is subjected to cyclic tensile load and data for both techniques are acquired at stipulated intervals. It can be concluded that the EMI technique is sensitive to the crack initiation phase while the Lamb wave technique correlates well with the crack propagation phase.

  3. Architectural Considerations of Fiber-Radio Millimeter-Wave Wireless Access Systems

    NASA Astrophysics Data System (ADS)

    Kitayama, Ken-Ichi

    The architecture of fiber-radio mm-wave wireless access systems critically depends upon the optical mm-wave generation and transport techniques. Four optical mm-wave generation and transport techniques: 1) optical self-heterodyning, 2) external modulation, 3) up- and downconversion, and 4) optical transceiver, will be assessed. From the technical viewpoints, their advantages and disadvantages are discussed. The economical assessment, focusing on the cost of a base station BS ( ), will suggest that the optical transceiver looks the most promising in the long run, but in the near future, however, the external modulation will be cost-effective. The experimental results of 60 GHz testbeds using the external modulation will support the conclusion.

  4. Using ICT techniques for improving mechatronic systems' dependability

    NASA Astrophysics Data System (ADS)

    Miron, Emanuel; Silva, João P. M. A.; Machado, José; Olaru, Dumitru; Prisacaru, Gheorghe

    2013-10-01

    The use of analysis techniques for industrial controller's analysis, such as Simulation and Formal Verification, is complex on industrial context. This complexity is due to the fact that such techniques require sometimes high investment in specific skilled human resources that have sufficient theoretical knowledge in those domains. This paper aims, mainly, to show that it is possible to obtain a timed automata model for formal verification purposes, considering the CAD model of a mechanical component. This systematic approach can be used, by companies, for the analysis of industrial controllers programs. For this purpose, it is discussed, in the paper, the best way to systematize these procedures, and this paper describes, only, the first step of a complex process and promotes a discussion of the main difficulties that can be found and a possibility for handle those difficulties. A library for formal verification purposes is obtained from original 3D CAD models using Software as a Service platform (SaaS) that, nowadays, has become a common deliverable model for many applications, because SaaS is typically accessed by users via internet access.

  5. Four-point injection technique for lip augmentation.

    PubMed

    Sahan, Ali; Funda, Tamer

    2018-06-01

    Lip augmentation procedures with hyaluronic acid dermal fillers have become increasingly popular worldwide because full lips are often considered beautiful and youthful. The goal of a lip augmentation procedure is to create smooth lips with adequate volume and a natural appearance. Various techniques for lip augmentation have been utilized and described. In the four-point injection technique, the lips were divided equally into right side and left side. Four entry points were made above the vermilion border for the upper lip and below the vermilion border for the lower lip. The filler was administered with a fanning technique through each entry point. Between January 2017 and November 2017, 50 female patients underwent a nonsurgical lip augmentation procedure with injectable fillers using this technique. Forty-five patients (90%) reported that they were satisfied or extremely satisfied with their lip enhancement procedure. No serious complications were observed. The advantages of this technique are reducing the risk of complications like erythema, edema, and vascular injuries, and providing easy access to injection sites.

  6. Single-cell epigenomics: techniques and emerging applications.

    PubMed

    Schwartzman, Omer; Tanay, Amos

    2015-12-01

    Epigenomics is the study of the physical modifications, associations and conformations of genomic DNA sequences, with the aim of linking these with epigenetic memory, cellular identity and tissue-specific functions. While current techniques in the field are characterizing the average epigenomic features across large cell ensembles, the increasing interest in the epigenetics within complex and heterogeneous tissues is driving the development of single-cell epigenomics. We review emerging single-cell methods for capturing DNA methylation, chromatin accessibility, histone modifications, chromosome conformation and replication dynamics. Together, these techniques are rapidly becoming a powerful tool in studies of cellular plasticity and diversity, as seen in stem cells and cancer.

  7. Intuitive tactile zooming for graphics accessed by individuals who are blind and visually impaired.

    PubMed

    Rastogi, Ravi; Pawluk, T V Dianne; Ketchum, Jessica

    2013-07-01

    One possibility of providing access to visual graphics for those who are visually impaired is to present them tactually: unfortunately, details easily available to vision need to be magnified to be accessible through touch. For this, we propose an "intuitive" zooming algorithm to solve potential problems with directly applying visual zooming techniques to haptic displays that sense the current location of a user on a virtual diagram with a position sensor and, then, provide the appropriate local information either through force or tactile feedback. Our technique works by determining and then traversing the levels of an object tree hierarchy of a diagram. In this manner, the zoom steps adjust to the content to be viewed, avoid clipping and do not zoom when no object is present. The algorithm was tested using a small, "mouse-like" display with tactile feedback on pictures representing houses in a community and boats on a lake. We asked the users to answer questions related to details in the pictures. Comparing our technique to linear and logarithmic step zooming, we found a significant increase in the correctness of the responses (odds ratios of 2.64:1 and 2.31:1, respectively) and usability (differences of 36% and 19%, respectively) using our "intuitive" zooming technique.

  8. 10 CFR 25.15 - Access permitted under “Q” or “L” access authorization.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 10 Energy 1 2013-01-01 2013-01-01 false Access permitted under âQâ or âLâ access authorization. 25.15 Section 25.15 Energy NUCLEAR REGULATORY COMMISSION ACCESS AUTHORIZATION Access Authorizations § 25.15 Access permitted under “Q” or “L” access authorization. (a) A “Q” access authorization permits an...

  9. 10 CFR 25.15 - Access permitted under “Q” or “L” access authorization.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 10 Energy 1 2012-01-01 2012-01-01 false Access permitted under âQâ or âLâ access authorization. 25.15 Section 25.15 Energy NUCLEAR REGULATORY COMMISSION ACCESS AUTHORIZATION Access Authorizations § 25.15 Access permitted under “Q” or “L” access authorization. (a) A “Q” access authorization permits an...

  10. 10 CFR 25.15 - Access permitted under “Q” or “L” access authorization.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 10 Energy 1 2011-01-01 2011-01-01 false Access permitted under âQâ or âLâ access authorization. 25.15 Section 25.15 Energy NUCLEAR REGULATORY COMMISSION ACCESS AUTHORIZATION Access Authorizations § 25.15 Access permitted under “Q” or “L” access authorization. (a) A “Q” access authorization permits an...

  11. 10 CFR 25.15 - Access permitted under “Q” or “L” access authorization.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 10 Energy 1 2014-01-01 2014-01-01 false Access permitted under âQâ or âLâ access authorization. 25.15 Section 25.15 Energy NUCLEAR REGULATORY COMMISSION ACCESS AUTHORIZATION Access Authorizations § 25.15 Access permitted under “Q” or “L” access authorization. (a) A “Q” access authorization permits an...

  12. 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

  13. 7 CFR 54.13 - Accessibility and refrigeration of products; access to establishments.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 3 2010-01-01 2010-01-01 false Accessibility and refrigeration of products; access to establishments. 54.13 Section 54.13 Agriculture Regulations of the Department of Agriculture (Continued...) Regulations Service § 54.13 Accessibility and refrigeration of products; access to establishments. (a) The...

  14. 7 CFR 54.13 - Accessibility and refrigeration of products; access to establishments.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 3 2011-01-01 2011-01-01 false Accessibility and refrigeration of products; access to establishments. 54.13 Section 54.13 Agriculture Regulations of the Department of Agriculture (Continued...) Regulations Service § 54.13 Accessibility and refrigeration of products; access to establishments. (a) The...

  15. 7 CFR 54.13 - Accessibility and refrigeration of products; access to establishments.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 3 2012-01-01 2012-01-01 false Accessibility and refrigeration of products; access to establishments. 54.13 Section 54.13 Agriculture Regulations of the Department of Agriculture (Continued...) Regulations Service § 54.13 Accessibility and refrigeration of products; access to establishments. (a) The...

  16. 7 CFR 54.13 - Accessibility and refrigeration of products; access to establishments.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 3 2013-01-01 2013-01-01 false Accessibility and refrigeration of products; access to establishments. 54.13 Section 54.13 Agriculture Regulations of the Department of Agriculture (Continued...) Regulations Service § 54.13 Accessibility and refrigeration of products; access to establishments. (a) The...

  17. 7 CFR 54.13 - Accessibility and refrigeration of products; access to establishments.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 3 2014-01-01 2014-01-01 false Accessibility and refrigeration of products; access to establishments. 54.13 Section 54.13 Agriculture Regulations of the Department of Agriculture (Continued...) Regulations Service § 54.13 Accessibility and refrigeration of products; access to establishments. (a) The...

  18. 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

  19. The International Year of Astronomy 2009 (IYA2009): Making Astronomy Accessible to Differently-Abled Individuals

    NASA Astrophysics Data System (ADS)

    Venner, L.

    2008-12-01

    The US Goal for the IYA2009 is: To offer an engaging astronomy experience to every person in the country, nurture existing partnerships, and build new connections to sustain public interest. NASAís commitment to the IYA2009 US goal is demonstrated by their support of accessible programming and materials developed to reach every person in the country including differently-abled individuals. The members of NASAís Jet Propulsion Laboratory Solar System Ambassador Program have been utilizing these accessible programs and materials in schools and science centers in addition to offering accessible star parties to the public. This paper will present some of the materials and techniques used by Ambassadors to bring astronomy to every person. Accessible programming will ensure that the next generation of explorers will include diverse individuals from all walks of life.

  20. Assessment method of accessibility conditions: how to make public buildings accessible?

    PubMed

    Andrade, Isabela Fernandes; Ely, e Vera Helena Moro Bins

    2012-01-01

    The enforcement of accessibility today has faced several difficulties, such as intervention in historic buildings that now house public services and cultural activities, such as town halls, museums and theaters and should allow access, on equal terms to all people. The paper presents the application of a method for evaluating the spatial accessibility conditions and their results. For this, we sought to support the theoretical foundation about the main issue involved and legislation. From the method used--guided walks--it was possible to identify the main barriers to accessibility in historic buildings. From the identified barriers, possible solutions are presented according to the four components of accessibility: spatial orientation, displacement, use and communication. It is hoped also that the knowledge gained in this research contributes to an improvement of accessibility legislation in relation to the listed items.

  1. Access to safe legal abortion in Malaysia: women's insights and health sector response.

    PubMed

    Low, Wah-Yun; Tong, Wen-Ting; Wong, Yut-Lin; Jegasothy, Ravindran; Choong, Sim-Poey

    2015-01-01

    Malaysia has an abortion law, which permits termination of pregnancy to save a woman's life and to preserve her physical and mental health (Penal Code Section 312, amended in 1989). However, lack of clear interpretation and understanding of the law results in women facing difficulties in accessing abortion information and services. Some health care providers were unaware of the legalities of abortion in Malaysia and influenced by their personal beliefs with regard to provision of abortion services. Accessibility to safer abortion techniques is also an issue. The development of the 2012 Guidelines on Termination of Pregnancy and Guidelines for Management of Sexual and Reproductive Health among Adolescents in Health Clinics by the Ministry of Health, Malaysia, is a step forward toward increasing women's accessibility to safe abortion services in Malaysia. This article provides an account of women's accessibility to abortion in Malaysia and the health sector response in addressing the barriers. © 2014 APJPH.

  2. 34 CFR 98.3 - Access to instructional material used in a research or experimentation program.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... RIGHTS IN RESEARCH, EXPERIMENTAL PROGRAMS, AND TESTING § 98.3 Access to instructional material used in a... designed to explore or develop new or unproven teaching methods or techniques. (c) For the purpose of the...

  3. 34 CFR 98.3 - Access to instructional material used in a research or experimentation program.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... RIGHTS IN RESEARCH, EXPERIMENTAL PROGRAMS, AND TESTING § 98.3 Access to instructional material used in a... designed to explore or develop new or unproven teaching methods or techniques. (c) For the purpose of the...

  4. 34 CFR 98.3 - Access to instructional material used in a research or experimentation program.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... RIGHTS IN RESEARCH, EXPERIMENTAL PROGRAMS, AND TESTING § 98.3 Access to instructional material used in a... designed to explore or develop new or unproven teaching methods or techniques. (c) For the purpose of the...

  5. 34 CFR 98.3 - Access to instructional material used in a research or experimentation program.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... RIGHTS IN RESEARCH, EXPERIMENTAL PROGRAMS, AND TESTING § 98.3 Access to instructional material used in a... designed to explore or develop new or unproven teaching methods or techniques. (c) For the purpose of the...

  6. 34 CFR 98.3 - Access to instructional material used in a research or experimentation program.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... RIGHTS IN RESEARCH, EXPERIMENTAL PROGRAMS, AND TESTING § 98.3 Access to instructional material used in a... designed to explore or develop new or unproven teaching methods or techniques. (c) For the purpose of the...

  7. Calibrating and training of neutron based NSA techniques with less SNM standards

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Geist, William H; Swinhoe, Martyn T; Bracken, David S

    2010-01-01

    Accessing special nuclear material (SNM) standards for the calibration of and training on nondestructive assay (NDA) instruments has become increasingly difficult in light of enhanced safeguards and security regulations. Limited or nonexistent access to SNM has affected neutron based NDA techniques more than gamma ray techniques because the effects of multiplication require a range of masses to accurately measure the detector response. Neutron based NDA techniques can also be greatly affected by the matrix and impurity characteristics of the item. The safeguards community has been developing techniques for calibrating instrumentation and training personnel with dwindling numbers of SNM standards. Montemore » Carlo methods have become increasingly important for design and calibration of instrumentation. Monte Carlo techniques have the ability to accurately predict the detector response for passive techniques. The Monte Carlo results are usually benchmarked to neutron source measurements such as californium. For active techniques, the modeling becomes more difficult because of the interaction of the interrogation source with the detector and nuclear material; and the results cannot be simply benchmarked with neutron sources. A Monte Carlo calculated calibration curve for a training course in Indonesia of material test reactor (MTR) fuel elements assayed with an active well coincidence counter (AWCC) will be presented as an example. Performing training activities with reduced amounts of nuclear material makes it difficult to demonstrate how the multiplication and matrix properties of the item affects the detector response and limits the knowledge that can be obtained with hands-on training. A neutron pulse simulator (NPS) has been developed that can produce a pulse stream representative of a real pulse stream output from a detector measuring SNM. The NPS has been used by the International Atomic Energy Agency (IAEA) for detector testing and training applications at

  8. Arthroscopic Talar Dome Access Using a Standard Versus Wire-Based Traction Method for Ankle Joint Distraction.

    PubMed

    Barg, Alexej; Saltzman, Charles L; Beals, Timothy C; Bachus, Kent N; Blankenhorn, Brad D; Nickisch, Florian

    2016-07-01

    To evaluate the accessibility of the talar dome through anterior and posterior portals for ankle arthroscopy with the standard noninvasive distraction versus wire-based longitudinal distraction using a tensioned wire placed transversely through the calcaneal tuberosity. Seven matched pairs of thigh-to-foot specimens underwent ankle arthroscopy with 1 of 2 methods of distraction: a standard noninvasive strapping technique or a calcaneal tuberosity wire-based technique. The order of the arthroscopic approach and use of a distraction method was randomly determined. The areas accessed from both 2-portal anterior and 2-portal posterior approaches were determined by using a molded translucent grid. The mean talar surface accessible by anterior ankle arthroscopy was comparable with noninvasive versus calcaneal wire distraction with 57.8% ± 17.2% (range, 32.9% to 75.7%) versus 61.5% ± 15.2% (range, 38.5% to 79.1%) of the talar dome, respectively (P = .590). The use of calcaneal wire distraction significantly improved posterior talar dome accessibility compared with noninvasive distraction, with 56.4% ± 20.0% (range, 14.4% to 78.0%) versus 39.8% ± 14.9% (range, 20.0% to 57.6%) of the talar dome, respectively (P = .031). Under the conditions studied, our cadaveric model showed equivalent talar dome access with 2-portal anterior arthroscopy of calcaneal wire-based distraction versus noninvasive strap distraction, but improved access for 2-portal posterior arthroscopy with calcaneal wire-based distraction versus noninvasive strap distraction. The posterior 40% of the talar dome is difficult to access via anterior ankle arthroscopy. Posterior calcaneal tuberosity wire-based longitudinal distraction improved arthroscopic access to the centro-posterior talar dome with a posterior arthroscopic approach. Published by Elsevier Inc.

  9. 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

  10. Accessing Electronic Journals.

    ERIC Educational Resources Information Center

    McKay, Sharon Cline

    1999-01-01

    Discusses issues librarians need to consider when providing access to electronic journals. Topics include gateways; index and abstract services; validation and pay-per-view; title selection; integration with OPACs (online public access catalogs)or Web sites; paper availability; ownership versus access; usage restrictions; and services offered…

  11. Universal accessibility of "accessible" fitness and recreational facilities for persons with mobility disabilities.

    PubMed

    Arbour-Nicitopoulos, Kelly P; Ginis, Kathleen A Martin

    2011-01-01

    This study descriptively measured the universal accessibility of "accessible" fitness and recreational facilities for Ontarians living with mobility disabilities. The physical and social environments of 44 fitness and recreational facilities that identified as "accessible" were assessed using a modified version of the AIMFREE. None of the 44 facilities were completely accessible. Mean accessibility ratings ranged between 31 and 63 out of a possible 100. Overall, recreational facilities had higher accessibility scores than fitness centers, with significant differences found on professional support and training, entrance areas, and parking lot. A modest correlation was found between the availability of fitness programming and the overall accessibility of fitness-center specific facility areas. Overall, the physical and social environments of the 44 fitness and recreational facilities assessed were limited in their accessibility for persons with mobility disabilities. Future efforts should be directed at establishing and meeting universal accessibility guidelines for Canadian physical activity facilities.

  12. Accessing memory

    DOEpatents

    Yoon, Doe Hyun; Muralimanohar, Naveen; Chang, Jichuan; Ranganthan, Parthasarathy

    2017-09-26

    A disclosed example method involves performing simultaneous data accesses on at least first and second independently selectable logical sub-ranks to access first data via a wide internal data bus in a memory device. The memory device includes a translation buffer chip, memory chips in independently selectable logical sub-ranks, a narrow external data bus to connect the translation buffer chip to a memory controller, and the wide internal data bus between the translation buffer chip and the memory chips. A data access is performed on only the first independently selectable logical sub-rank to access second data via the wide internal data bus. The example method also involves locating a first portion of the first data, a second portion of the first data, and the second data on the narrow external data bus during separate data transfers.

  13. Third Annual Foreign Acquisitions Workshop: Improving Access to Foreign Gray Literature

    NASA Technical Reports Server (NTRS)

    1993-01-01

    The theme of the Third Annual Foreign Acquisitions Workshop was the acquisition of and access to foreign (non-U.S.) gray literature. Individual presentations addressed general topics related to the value and scope of gray literature, specialized and foreign gray-literature sources, intellectual property issues, and U.S. Federal Agency activities. Additional topics focused on electronic access and evaluation techniques and the current and potential uses of networking technology. The workshop papers are presented in their entirety or in abstract or outline form. Appendices include a listing of databases that include foreign gray literature, a bibliography, and a report on U.S.-Japan cooperation in the use of scientific and technical information.

  14. Training for percutaneous renal access on a virtual reality simulator.

    PubMed

    Zhang, Yi; Yu, Cheng-fan; Liu, Jin-shun; Wang, Gang; Zhu, He; Na, Yan-qun

    2013-01-01

    The need to develop new methods of surgical training combined with advances in computing has led to the development of virtual reality surgical simulators. The PERC Mentor(TM) is designed to train the user in percutaneous renal collecting system access puncture. This study aimed to validate the use of this kind of simulator, in percutaneous renal access training. Twenty-one urologists were enrolled as trainees to learn a fluoroscopy-guided percutaneous renal accessing technique. An assigned percutaneous renal access procedure was immediately performed on the PERC Mentor(TM) after watching instruction video and an analog operation. Objective parameters were recorded by the simulator and subjective global rating scale (GRS) score were determined. Simulation training followed and consisted of 2 hours daily training sessions for 2 consecutive days. Twenty-four hours after the training session, trainees were evaluated performing the same procedure. The post-training evaluation was compared to the evaluation of the initial attempt. During the initial attempt, none of the trainees could complete the appointed procedure due to the lack of experience in fluoroscopy-guided percutaneous renal access. After the short-term training, all trainees were able to independently complete the procedure. Of the 21 trainees, 10 had primitive experience in ultrasound-guided percutaneous nephrolithotomy. Trainees were thus categorized into the group of primitive experience and inexperience. The total operating time and amount of contrast material used were significantly lower in the group of primitive experience versus the inexperience group (P = 0.03 and 0.02, respectively). The training on the virtual reality simulator, PERC Mentor(TM), can help trainees with no previous experience of fluoroscopy-guided percutaneous renal access to complete the virtual manipulation of the procedure independently. This virtual reality simulator may become an important training and evaluation tool in

  15. AEROSAT Access Control Summary

    DOT National Transportation Integrated Search

    1976-10-01

    The report consists of three basic sections. Section 2 is a discussion of the communications concepts germane to AEROSAT access control. It defines and reviews the principles of multiplexing, multiple access, demand access, and access control and rel...

  16. Aerosat Access Control Summary

    DOT National Transportation Integrated Search

    1976-10-01

    The report consists of three basic sections. Section 2 is a discussion of the communications concepts germane to AEROSAT access control. It defines and reviews the principles of multiplexing, multiple access, demand access, and access control and rel...

  17. Transparency of Biobank Access in Canada: An Assessment of Industry Access and the Availability of Information on Access Policies and Resulting Research.

    PubMed

    Gibson, Shannon G; Axler, Renata E; Lemmens, Trudo

    2017-12-01

    A key issue impacting public trust in biobanks is how these resources are utilized, including who is given access to biobank data and samples. To assess the conditions under which researchers are given access to Canadian biobanks, we reviewed websites and contacted Canadian biobanks to determine the availability of information on access policies and procedures; research resulting from access biobank data and samples; and conditions on private industry access to biobanks. We also conducted expert interviews with key Canadian stakeholders ( n = 11) to obtain their perspectives on biobank transparency and access policies. Among 21 Canadian biobanks, there was wide variation in the access information made publicly available, and the majority of these allowed access by industry applicants. Biobanks should be governed by the principles of transparency, accountability, and accessibility, and attention must be given to the conditions around the commercialization of biobank-based research.

  18. Integration of EGA secure data access into Galaxy.

    PubMed

    Hoogstrate, Youri; Zhang, Chao; Senf, Alexander; Bijlard, Jochem; Hiltemann, Saskia; van Enckevort, David; Repo, Susanna; Heringa, Jaap; Jenster, Guido; J A Fijneman, Remond; Boiten, Jan-Willem; A Meijer, Gerrit; Stubbs, Andrew; Rambla, Jordi; Spalding, Dylan; Abeln, Sanne

    2016-01-01

    High-throughput molecular profiling techniques are routinely generating vast amounts of data for translational medicine studies. Secure access controlled systems are needed to manage, store, transfer and distribute these data due to its personally identifiable nature. The European Genome-phenome Archive (EGA) was created to facilitate access and management to long-term archival of bio-molecular data. Each data provider is responsible for ensuring a Data Access Committee is in place to grant access to data stored in the EGA. Moreover, the transfer of data during upload and download is encrypted. ELIXIR, a European research infrastructure for life-science data, initiated a project (2016 Human Data Implementation Study) to understand and document the ELIXIR requirements for secure management of controlled-access data. As part of this project, a full ecosystem was designed to connect archived raw experimental molecular profiling data with interpreted data and the computational workflows, using the CTMM Translational Research IT (CTMM-TraIT) infrastructure http://www.ctmm-trait.nl as an example. Here we present the first outcomes of this project, a framework to enable the download of EGA data to a Galaxy server in a secure way. Galaxy provides an intuitive user interface for molecular biologists and bioinformaticians to run and design data analysis workflows. More specifically, we developed a tool -- ega_download_streamer - that can download data securely from EGA into a Galaxy server, which can subsequently be further processed. This tool will allow a user within the browser to run an entire analysis containing sensitive data from EGA, and to make this analysis available for other researchers in a reproducible manner, as shown with a proof of concept study.  The tool ega_download_streamer is available in the Galaxy tool shed: https://toolshed.g2.bx.psu.edu/view/yhoogstrate/ega_download_streamer.

  19. Integration of EGA secure data access into Galaxy

    PubMed Central

    Hoogstrate, Youri; Zhang, Chao; Senf, Alexander; Bijlard, Jochem; Hiltemann, Saskia; van Enckevort, David; Repo, Susanna; Heringa, Jaap; Jenster, Guido; Fijneman, Remond J.A.; Boiten, Jan-Willem; A. Meijer, Gerrit; Stubbs, Andrew; Rambla, Jordi; Spalding, Dylan; Abeln, Sanne

    2016-01-01

    High-throughput molecular profiling techniques are routinely generating vast amounts of data for translational medicine studies. Secure access controlled systems are needed to manage, store, transfer and distribute these data due to its personally identifiable nature. The European Genome-phenome Archive (EGA) was created to facilitate access and management to long-term archival of bio-molecular data. Each data provider is responsible for ensuring a Data Access Committee is in place to grant access to data stored in the EGA. Moreover, the transfer of data during upload and download is encrypted. ELIXIR, a European research infrastructure for life-science data, initiated a project (2016 Human Data Implementation Study) to understand and document the ELIXIR requirements for secure management of controlled-access data. As part of this project, a full ecosystem was designed to connect archived raw experimental molecular profiling data with interpreted data and the computational workflows, using the CTMM Translational Research IT (CTMM-TraIT) infrastructure http://www.ctmm-trait.nl as an example. Here we present the first outcomes of this project, a framework to enable the download of EGA data to a Galaxy server in a secure way. Galaxy provides an intuitive user interface for molecular biologists and bioinformaticians to run and design data analysis workflows. More specifically, we developed a tool -- ega_download_streamer - that can download data securely from EGA into a Galaxy server, which can subsequently be further processed. This tool will allow a user within the browser to run an entire analysis containing sensitive data from EGA, and to make this analysis available for other researchers in a reproducible manner, as shown with a proof of concept study.  The tool ega_download_streamer is available in the Galaxy tool shed: https://toolshed.g2.bx.psu.edu/view/yhoogstrate/ega_download_streamer. PMID:28232859

  20. [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…

  1. Advanced Stent Graft Treatment of Venous Stenosis Affecting Hemodialysis Vascular Access: Case Illustrations

    PubMed Central

    Patel, Darshan; Ray, Charles E.; Lokken, R. Peter; Bui, James T.; Lipnik, Andrew J.; Gaba, Ron C.

    2016-01-01

    Surgically placed dialysis access is an important component of dialysis replacement therapy. The vast majority of patients undergoing dialysis will have surgically placed accesses at some point in the course of their disease, and for many patients these accesses may represent their definitive renal replacement option. Most, if not all, arteriovenous fistulae and grafts will require interventions at some point in time. Percutaneous angioplasty is the typical first treatment performed for venous stenoses, with stents and stent grafts being reserved for patients in whom angioplasty and surgical options are exhausted. In some salvage situations, stent graft placement may be the only or best option for patients. This article describes, using case illustrations, placement of stent grafts in such patients; a focus will also be made on the techniques utilized in such salvage situations. PMID:27011426

  2. Polyphenolic Composition and Antioxidant Activities of 6 New Turmeric (Curcuma Longa L.) Accessions.

    PubMed

    Chinedum, Eleazu; Kate, Eleazu; Sonia, Chukwuma; Ironkwe, Adanma; Andrew, Igwe

    2015-01-01

    The phytochemical composition and antioxidant capacities of 6 new NRCRI turmeric (Curcuma longa L.) accessions (39, 35, 60, 30, 50 and 41) were determined using standard techniques. The moisture contents of the tumeric samples ranged from 15.75 to 47.80% and the curcumin contents of the turmeric samples fell within the range of curcumin obtained from turmeric in other countries of the world. Furthermore, the turmeric accessions contained considerable amounts of antioxidants (measured using 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical and reducing power assays), alkaloids, flavonoids, anthocyanins, and phenolics. There was significant correlation between the anthocyanin contents of the tumeric accessions versus their alkaloid (0.744) and flavonoid contents (0.986) suggesting an additive effect between the anthocyanins and alkaloids in turmeric; significant correlation between the inhibition of the turmeric accessions on DPPH radical versus their flavonoid (0.892) and anthocyanin (0.949) contents and significant correlation between the reducing power of the turmeric accessions versus their flavonoid (0.973) and anthocyanin (0.974) contents suggesting that anthocyanins as flavonoids largely contribute to the antioxidant activities of turmeric. The positive regression recorded between inhibition of DPPH radical by the turmeric accessions and quercetin versus reducing power (R2 = 0.852) suggest that any of these methods could be used to assess the antioxidant activities of tumeric. Finally, the study indicated the potentials of the turmeric accessions especially accessions 30 and 50 as promising sources of antioxidants.

  3. Delivering accessible fieldwork: preliminary findings from a collaborative international study

    NASA Astrophysics Data System (ADS)

    Stokes, Alison; Atchison, Christopher; Feig, Anthony; Gilley, Brett

    2017-04-01

    Students with disabilities are commonly excluded from full participation in geoscience programs, and encounter significant barriers when accessing field-learning experiences. In order to increase talent and diversity in the geoscience workforce, more inclusive learning experiences must be developed that will enable all students to complete the requirements of undergraduate degree programs, including fieldwork. We discuss the outcomes of a completely accessible field course developed through the collaborative effort of geoscience education practitioners from the US, Canada and the UK. This unique field workshop has brought together current geoscience academics and students with disabilities to share perspectives on commonly-encountered barriers to learning in the field, and explore methods and techniques for overcoming them. While the student participants had the opportunity to learn about Earth processes while situated in the natural environment, participating geoscience instructors began to identify how to improve the design of field courses, making them fully inclusive of learners with disabilities. The outcomes from this experience will be used to develop guidelines to facilitate future development and delivery of accessible geoscience fieldwork.

  4. Application of holographic optical techniques to bulk memory.

    NASA Technical Reports Server (NTRS)

    Anderson, L. K.

    1971-01-01

    Current efforts to exploit the spatial redundancy and built-in imaging of holographic optical techniques to provide high information densities without critical alignment and tight mechanical tolerances are reviewed. Read-write-erase in situ operation is possible but is presently impractical because of limitations in available recording media. As these are overcome, it should prove feasible to build holographic bulk memories with mechanically replaceable hologram plates featuring very fast (less than 2 microsec) random access to large (greater than 100 million bit) data blocks and very high throughput (greater than 500 Mbit/sec). Using volume holographic storage it may eventually be possible to realize random-access mass memories which require no mechanical motion and yet provide very high capacity.

  5. 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…

  6. New Insights into Dialysis Vascular Access: What Is the Optimal Vascular Access Type and Timing of Access Creation in CKD and Dialysis Patients?

    PubMed

    Woo, Karen; Lok, Charmaine E

    2016-08-08

    Optimal vascular access planning begins when the patient is in the predialysis stages of CKD. The choice of optimal vascular access for an individual patient and determining timing of access creation are dependent on a multitude of factors that can vary widely with each patient, including demographics, comorbidities, anatomy, and personal preferences. It is important to consider every patient's ESRD life plan (hence, their overall dialysis access life plan for every vascular access creation or placement). Optimal access type and timing of access creation are also influenced by factors external to the patient, such as surgeon experience and processes of care. In this review, we will discuss the key determinants in optimal access type and timing of access creation for upper extremity arteriovenous fistulas and grafts. Copyright © 2016 by the American Society of Nephrology.

  7. An Adaptive OFDMA-Based MAC Protocol for Underwater Acoustic Wireless Sensor Networks

    PubMed Central

    Khalil, Issa M.; Gadallah, Yasser; Hayajneh, Mohammad; Khreishah, Abdallah

    2012-01-01

    Underwater acoustic wireless sensor networks (UAWSNs) have many applications across various civilian and military domains. However, they suffer from the limited available bandwidth of acoustic signals and harsh underwater conditions. In this work, we present an Orthogonal Frequency Division Multiple Access (OFDMA)-based Media Access Control (MAC) protocol that is configurable to suit the operating requirements of the underwater sensor network. The protocol has three modes of operation, namely random, equal opportunity and energy-conscious modes of operation. Our MAC design approach exploits the multi-path characteristics of a fading acoustic channel to convert it into parallel independent acoustic sub-channels that undergo flat fading. Communication between node pairs within the network is done using subsets of these sub-channels, depending on the configurations of the active mode of operation. Thus, the available limited bandwidth gets fully utilized while completely avoiding interference. We derive the mathematical model for optimal power loading and subcarrier selection, which is used as basis for all modes of operation of the protocol. We also conduct many simulation experiments to evaluate and compare our protocol with other Code Division Multiple Access (CDMA)-based MAC protocols. PMID:23012517

  8. An adaptive OFDMA-based MAC protocol for underwater acoustic wireless sensor networks.

    PubMed

    Khalil, Issa M; Gadallah, Yasser; Hayajneh, Mohammad; Khreishah, Abdallah

    2012-01-01

    Underwater acoustic wireless sensor networks (UAWSNs) have many applications across various civilian and military domains. However, they suffer from the limited available bandwidth of acoustic signals and harsh underwater conditions. In this work, we present an Orthogonal Frequency Division Multiple Access (OFDMA)-based Media Access Control (MAC) protocol that is configurable to suit the operating requirements of the underwater sensor network. The protocol has three modes of operation, namely random, equal opportunity and energy-conscious modes of operation. Our MAC design approach exploits the multi-path characteristics of a fading acoustic channel to convert it into parallel independent acoustic sub-channels that undergo flat fading. Communication between node pairs within the network is done using subsets of these sub-channels, depending on the configurations of the active mode of operation. Thus, the available limited bandwidth gets fully utilized while completely avoiding interference. We derive the mathematical model for optimal power loading and subcarrier selection, which is used as basis for all modes of operation of the protocol. We also conduct many simulation experiments to evaluate and compare our protocol with other Code Division Multiple Access (CDMA)-based MAC protocols.

  9. User Practices in Keyword and Boolean Searching on an Online Public Access Catalog.

    ERIC Educational Resources Information Center

    Ensor, Pat

    1992-01-01

    Discussion of keyword and Boolean searching techniques in online public access catalogs (OPACs) focuses on a study conducted at Indiana State University that examined users' attitudes toward searching on NOTIS (Northwestern Online Total Integrated System). Relevant literature is reviewed, and implications for library instruction are suggested. (17…

  10. Technique of after-loading interstitial implants.

    PubMed

    Syed, A M; Feder, B H

    1977-01-01

    Interstitial implants are either removable or permanent (and occasionally a combination of both). Permanent implants are generally utilized where tumors are not accessible enough to permit easy removal of sources or where accurate source distribution is less critical. They are useful for cancers of the lung, pancreas, prostate, bladder, lymph nodes, etc. Radon and gold-198 have been largely replaced by iodine-125. Our major interests are in the removable after-loading iridium-192 implant techniques. Template (steel guide) and non-template (plastic tube) techniques are utilized. Templates are preferred where the tumor volume can only be approached from one side and where accurate positioning of sources would otherwise be difficult. They are useful for cancers of the cervix, vagina, urethra, and rectum. Non-template (plastic tube) techniques are preferred where the tumor volume can be approached from at least two sides and where templates are either not feasible or not essential for accurate positioning of sources. The single needle non-template approach is useful for cancers of lip, nodes, and breast (plastic button) and for cancers of the oral cavity and oropharynx (gold button). The paired needle non-template approach is useful for cancers of the gum, retromolar trigone, and base of tongue (loop technique) and for cancers of the palate (arch technique). Procedures for each technique are described in detail.

  11. Determination of the genetic diversity among accessions of Senna spectabilis (canafístula) by using RAPD markers.

    PubMed

    Santos, M F; Araújo Neto, R B; Nascimento, M P S B C; Lima, P S C

    2013-12-02

    Senna spectabilis (DC.) H.S. Irwin & Barneby (Fabaceae; Caesalpinioideae), commonly known as "canafístula" or "cassia", is widely used in the semi-arid region of northeastern Brazil as a source of forage and timber. The plant presents a high nutritional content in comparison with other forage species that are native to the Brazilian Caatinga; thus, it represents a valuable resource during periods of drought. The aim of this study was to evaluate the genetic variability among eight accessions of S. spectabilis available in the forage germplasm collection of Embrapa Meio-Norte using the random-amplified polymorphic DNA technique. The 15 primers selected for use in the analysis produced 107 bands, including 59 (55.14%) that were polymorphic. A similarity matrix was generated on the basis of Jaccard coefficients, and a dendrogram was constructed using the unweighted pair group method with arithmetic mean clustering technique. The mean value of the similarity coefficients was 0.73, and the cophenetic correlation coefficient was 83.76%. Accessions CAN. 4 and CAN. 5 presented the greatest genetic similarity, while CAN. 6 and CAN. 8 were the most divergent. The S. spectabilis accessions were classified into two main groups with group I including accessions CAN. 1, CAN. 2, CAN. 4, CAN. 5, CAN. 7, CAN. 8, and CAN. 9, and group II comprising the single accession CAN. 6. The results presented herein revealed that, although the germplasm collection is presently limited, there is sufficient genetic variability among the accessions to permit future breeding programs.

  12. Prototype for Automatable, Dielectrophoretically-Accessed Intracellular Membrane–Potential Measurements by Metal Electrodes

    PubMed Central

    Sukhorukov, Vladimir L.; Zimmermann, Dirk

    2013-01-01

    Abstract Functional access to membrane proteins, for example, ion channels, of individual cells is an important prerequisite in drug discovery studies. The highly sophisticated patch-clamp method is widely used for electrogenic membrane proteins, but is demanding for the operator, and its automation remains challenging. The dielectrophoretically-accessed, intracellular membrane–potential measurement (DAIMM) method is a new technique showing high potential for automation of electrophysiological data recording in the whole-cell configuration. A cell suspension is brought between a mm-scaled planar electrode and a μm-scaled tip electrode, placed opposite to each other. Due to the asymmetric electrode configuration, the application of alternating electric fields (1–5 MHz) provokes a dielectrophoretic force acting on the target cell. As a consequence, the cell is accelerated and pierced by the tip electrode, hence functioning as the internal (working) electrode. We used the light-gated cation channel Channelrhodopsin-2 as a reporter protein expressed in HEK293 cells to characterize the DAIMM method in comparison with the patch-clamp technique. PMID:22994967

  13. Trans-Splenic Portal Vein Embolization: A Technique to Avoid Damage to the Future Liver Remnant

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sarwar, Ammar, E-mail: asarwar@bidmc.harvard.edu; Brook, Olga R.; Weinstein, Jeffrey L.

    2016-10-15

    Portal vein embolization (PVE) induces hypertrophy of the future liver remnant (FLR) in patients undergoing extensive hepatic resection. Portal vein access for PVE via the ipsilateral hepatic lobe (designated for resection) places veins targeted for embolization at acute angles to the access site requiring reverse curve catheters for access. This approach also involves access close to tumors in the ipsilateral lobe and requires care to avoid traversing tumor. Alternatively, a contralateral approach (through the FLR) risks damage to the FLR due to iatrogenic trauma or non-target embolization. Two patients successfully underwent PVE via trans-splenic portal vein access, allowing easy accessmore » to the ipsilateral portal veins and eliminating risk of damage to FLR. Technique and advantages of trans-splenic portal vein access to perform PVE are described.« less

  14. Where to go? Strategic modelling of access to emergency shelters in Mozambique.

    PubMed

    Gall, Melanie

    2004-03-01

    This paper, through spatial-analysis techniques, examines the accessibility of emergency shelters for vulnerable populations, and outlines the benefits of an extended and permanently established shelter network in central Mozambique. The raster-based modelling approach considers data on land cover, locations of accommodation centres in 2000, settlements and infrastructure. The shelter analysis is a two-step process determining access for vulnerable communities first, followed by a suitability analysis for additional emergency shelter sites. The results indicate the need for both retrofitting existing infrastructure (schools, health posts) to function as shelters during an emergency, and constructing new facilities - at best multi-purpose facilities that can serve as social infrastructure and shelter. Besides assessing the current situation in terms of availability and accessibility of emergency shelters, this paper provides an example of evaluating the effectiveness of humanitarian assistance without conventional mechanisms like food tonnage and number of beneficiaries.

  15. 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…

  16. Accessibility | NREL

    Science.gov Websites

    electronic and information technologies accessible to individuals with disabilities in accordance with Section 508 of the Rehabilitation Act (29 U.S.C. 794d), as amended in 1998. Contact us with feedback or concerns related to the accessibility of this website.

  17. Internet Access and Usage by Secondary School Students in Morogoro Municipality, Tanzania

    ERIC Educational Resources Information Center

    Tarimo, Ronald; Kavishe, George

    2017-01-01

    The purpose of this paper was to report results of a study on the investigation of the Internet access and usage by secondary school students in Morogoro municipality in Tanzania. A simple random sampling technique was used to select 120 students from six schools. The data was collected through a questionnaire. A quantitative approach using the…

  18. Aneurysms in vascular access: state of the art and future developments.

    PubMed

    Inston, Nicholas; Mistry, Hiren; Gilbert, James; Kingsmore, David; Raza, Zahid; Tozzi, Matteo; Azizzadeh, Ali; Jones, Robert; Deane, Colin; Wilkins, Jason; Davidson, Ingemar; Ross, John; Gibbs, Paul; Huang, Dean; Valenti, Domenico

    2017-11-17

    A master class was held at the Vascular Access at Charing Cross (VA@CX2017) conference in April 2017 with invited experts and active audience participation to discuss arteriovenous (AV) vascular access aneurysms, a serious and common complication of vascular access (VA). The natural history of aneurysms in VA is poorly defined, and although classifications exist they are not uniformly applied in studies or clinical practice. True and pseudo aneurysms of AV access occur. Whilst an AV fistula by definition is an abnormal dilatation of a blood vessel, an agreed definition of 18 mm, or 3 times accepted maturation diameter, is proposed. The mechanism of aneurysmal dilatation is unknown but appears to be a combination of excessive external remodeling, wall changes due to injury, and obstruction of outflow. Diagnosis of AV aneurysms is based on physical examination and ultrasound. Venography and cross-sectional imaging may assist and be required for the investigation of outflow stenosis. Treatment of pseudo aneurysms and true aneurysms of VA (AVA) is not evidence-based, but relies on clinical experience and available facilities. In many AVA, a conservative approach with surveillance is suitable, although intervals and modalities are unclear. Avoidance of rupture is imperative and preemptive treatment should aim for access preservation, ideally with avoidance of prosthetic materials. Different techniques of aneurysmorrhaphy are described with good results in published series. Although endovascular approaches and stenting are described with good short-term results, issues with cannulation of stented areas occur and, while possible, this is not recommended, and long-term access revision is recommended.

  19. Anomaly and signature filtering improve classifier performance for detection of suspicious access to EHRs.

    PubMed

    Kim, Jihoon; Grillo, Janice M; Boxwala, Aziz A; Jiang, Xiaoqian; Mandelbaum, Rose B; Patel, Bhakti A; Mikels, Debra; Vinterbo, Staal A; Ohno-Machado, Lucila

    2011-01-01

    Our objective is to facilitate semi-automated detection of suspicious access to EHRs. Previously we have shown that a machine learning method can play a role in identifying potentially inappropriate access to EHRs. However, the problem of sampling informative instances to build a classifier still remained. We developed an integrated filtering method leveraging both anomaly detection based on symbolic clustering and signature detection, a rule-based technique. We applied the integrated filtering to 25.5 million access records in an intervention arm, and compared this with 8.6 million access records in a control arm where no filtering was applied. On the training set with cross-validation, the AUC was 0.960 in the control arm and 0.998 in the intervention arm. The difference in false negative rates on the independent test set was significant, P=1.6×10(-6). Our study suggests that utilization of integrated filtering strategies to facilitate the construction of classifiers can be helpful.

  20. Anomaly and Signature Filtering Improve Classifier Performance For Detection Of Suspicious Access To EHRs

    PubMed Central

    Kim, Jihoon; Grillo, Janice M; Boxwala, Aziz A; Jiang, Xiaoqian; Mandelbaum, Rose B; Patel, Bhakti A; Mikels, Debra; Vinterbo, Staal A; Ohno-Machado, Lucila

    2011-01-01

    Our objective is to facilitate semi-automated detection of suspicious access to EHRs. Previously we have shown that a machine learning method can play a role in identifying potentially inappropriate access to EHRs. However, the problem of sampling informative instances to build a classifier still remained. We developed an integrated filtering method leveraging both anomaly detection based on symbolic clustering and signature detection, a rule-based technique. We applied the integrated filtering to 25.5 million access records in an intervention arm, and compared this with 8.6 million access records in a control arm where no filtering was applied. On the training set with cross-validation, the AUC was 0.960 in the control arm and 0.998 in the intervention arm. The difference in false negative rates on the independent test set was significant, P=1.6×10−6. Our study suggests that utilization of integrated filtering strategies to facilitate the construction of classifiers can be helpful. PMID:22195129