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Sample records for access cdma based

  1. Use of CDMA access technology in mobile satellite systems

    NASA Technical Reports Server (NTRS)

    Ramasastry, Jay; Wiedeman, Bob

    1995-01-01

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

  2. 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.

  3. Optical fiber-based CDMA networks

    NASA Astrophysics Data System (ADS)

    Gameiro, Atilio M. S.

    1996-01-01

    In this communication we consider the use of an optical fiber based fixed infrastructure for code division multiple access (CDMA) mobile networks. In such a scenario, the base stations are linked to the central station through optical fiber using subcarrier multiplexing (SCM) technology. One of the major problems associated with optical SCM is the nonlinearity of the laser diodes (LD). In this communication we model the LD as a memoryless nonlinearity and evaluate the effect of the nonlinearity on the SCM transmission CDMA signals. We find that the behavior departs significantly from what happens in FDMA and depends critically on the nonlinearity of the LD being a compressing or an expanding one. In the former case significant performance degradation may occur whereas for the latter the degradation is usually not dramatic.

  4. 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.

  5. 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.

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

    SciTech Connect

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

    2004-02-12

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

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

    PubMed

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

    2011-01-01

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

  8. Linear CDMA Detection Algorithm Based on Statistical Neurodynamics and Belief Propagation and the Stability Conditions

    NASA Astrophysics Data System (ADS)

    Shojiguchi, A.; Tanaka, T.; Okada, M.

    Recently a modified algorithm of code-division multiple-access (CDMA) parallel interference canceler (PIC) has been proposed by Tanaka based on statistical neurodynamics. In this paper we apply the modified algorithm to the linear PIC (LPIC) and investigate its stability. We show that the stable (unstable) fixed points of the modified algorithm correspond to the stable (unstable) replica symmetry solutions with the Gaussian prior. We also show the modified algorithm is a special case of Kabashima's belief-propagation algorithm with Gaussian prior.

  9. 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.

  10. Synthesis and demonstration of high speed, bandwidth efficient optical Code Division Multiple Access (CDMA) tested at 1 Gb/s throughput

    NASA Astrophysics Data System (ADS)

    Mendez, Antonio J.; Lambert, James L.; Morookian, John-Michael; Gagliardi, Robert M.

    1994-09-01

    Code division multiple access (CDMA) permits concurrent communication over all virtual channels (in principle), independent of the data rate and the network size. In reality, most CDMA approaches have a bandwidth penalty due to the code length and a loss penalty due to the broadcasting required by CDMA. Both of these penalties can be reduced or ameliorated by means of multi-attribute coding. Matrices constructed from relatively inefficient (0, 1)pulse sequences are suitable multi-attribute non-coherent CDMA codes which are both bandwidth and broadcast efficient. We exhibit a novel approach to synthesizing matrix CDMA codes, develop a 4 x 4 physical model, and demonstrate concurrent communication experimentally at concurrent data rates of 100-, 150-, and 250 Mb/s per port.

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

    NASA Astrophysics Data System (ADS)

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

    2006-03-01

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

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

    NASA Astrophysics Data System (ADS)

    Hortos, William S.

    1996-03-01

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

  13. 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.

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

    PubMed Central

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

    2015-01-01

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

  15. 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.

  16. 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

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

    SciTech Connect

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

    2015-10-26

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

  18. Minimum Kullback-Leibler-Based Turbo Multiuser Detector over Decomposition CDMA Signal

    NASA Astrophysics Data System (ADS)

    Ploysuwan, Tuchsanai; Tantiphanwadi, Sawat; Teekaput, Prasit

    In this paper, we develop a new iterative turbo multiuser detector for direct sequence code-division multiple access (DS-CDMA) systems over unknown frequency-selective channels by decomposing the observation signal into a number of signal components. Virtual trellis model representing the ISI channel for each separating signal user is designed to generate extrinsic probability in term of BCJR algorithm for exchange with a single channel decoder as priori information. Minimum kullback-leibler (MKL) framework is derived to calculate numerical channel estimation and extrinsic probability. In comparison with other similar receiver, simulation results demonstrate that the proposed solution achieves the desirable performance.

  19. An optical CDMA system based on chaotic sequences

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

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

  20. 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.

  1. 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.

  2. SIR-based call admission control for DS-CDMA cellular systems

    NASA Astrophysics Data System (ADS)

    Liu, Zhao; Elzarki, Magda

    1994-05-01

    Signal-to-interference ratio (SIR)-based call admission control (CAC) algorithms are proposed and studied in a DS-CDMA cellular system. Residual capacity is introduced as the additional number of initial calls a base station can accept such that system-wide outage probability will be guaranteed to remain below a certain level. The residual capacity at each cell is updated dynamically according to the reverse-link SIR measurements at the base station. A 2(sup k) factorial experimental design and analysis via computer simulations is used to study the impact of the parameters used in the algorithms. The influence of these parameters on system performance, namely blocking probability and outage probability, is then examined via simulation. The performance of the algorithms is compared together with that of a fixed call admission control scheme (fixed CAC) under both homogeneous and hot spot traffic loadings. The results show that SIR-based CAC always outperforms fixed CAC even under overload situations, which is not the case in FDMA/TDMA cellular systems. The primary benefit of SIR-based CAC in DS-CDMA cellular systems, however, lies in improving the system performance under hot spot traffics.

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

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

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

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

    SciTech Connect

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

    2006-12-29

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

  5. 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.

  6. Influence of Mobile Users' Density Distribution on the CDMA Base Station Power

    NASA Astrophysics Data System (ADS)

    Lebl, Aleksandar; Mitić, Dragan; Popović, Miroslav; Markov, Žarko; Mileusnić, Mladen; Matić, Vladimir

    2016-12-01

    In this paper we analyze the influence of users' density distribution in one cell of CDMA mobile network (ie adjusted power control on the forward link) on base station emission power. This influence is analyzed for different circles radii around base station within which same emission power is generated for all mobile users, and for different values of propagation loss coefficient. It is proved that emission power in this cell must be increased comparing to the similar cell, which uses complete power control. The power increase is greater when greater number of users are situated near base station, and for greater values of propagation loss coefficient. The results are presented, illustrated by numerical examples and verified by simulation for three users' density distributions: uniform, decreasing and increasing density from the base station to the cell rim. The simulation process, which is based on random traffic process, is presented briefly.

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

    NASA Astrophysics Data System (ADS)

    Tseng, Shin-Pin

    2015-06-01

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

  8. 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.

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

    PubMed

    Kumaravel, Rasadurai; Narayanaswamy, Kumaratharan

    2015-01-01

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

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

    DTIC Science & Technology

    2016-05-01

    where the system’s stochastic model is either incomplete or too complex to be described in mathematical terms. Feature based methods often provide an...developing mathematical rules that guarantees optimal performance in noise, i.e., rules that guarantee the lowest error in classification. The method is...suitable in problems where models are available and have low complexity. Its main disadvantage is the development of rules due to the mathematical

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

    PubMed

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

    2006-01-01

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

  12. 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

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

    PubMed

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

    2015-05-18

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

  14. 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

  15. 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

  16. Dispersion Compensation Requirements for Optical CDMA Using WDM Lasers

    SciTech Connect

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

    2001-12-10

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

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

    DTIC Science & Technology

    2008-08-29

    SECURITY CLASSIFICATION OF: Subchannel allocation for the reverse link of multicarrier code-division multiplex-access (MC-CDMA) system with adaptive...Triangle Park, NC 27709-2211 15. SUBJECT TERMS subchannel allocation, fading channels, CDMA Tao Jia, Alexandra Duel-Hallen North Carolina State University... Subchannel allocation for the reverse link of multicarrier code-division multiplex-access (MC-CDMA) system with adaptive frequency hopping (AFH) is

  18. Development of fiber-optic CDMA systems

    NASA Astrophysics Data System (ADS)

    Hassan, Kamel M.

    2005-09-01

    Fiber-Optic code division multiple access communication systems (FO-CDMA) have been given an intensifying interest in the last decade. This is due to several advantages may be offered by this technology, where it offers a promising solution for efficient truly asynchronous multiple access network as well as it has the ability to support variable bit rate and bursty traffic. FO-CDMA system permits an extra high optical signal processing speed compared to electronic signal processing, and there is no need to use wavelength sensitive components which are required in WDMA networks. FO-CDMA may be performed in time domain "t" or in wavelength domain "λ"(spectral amplitude encoding), this strategy is called one dimensional (1-D) optical coding. One of the most serious problems for CDMA is the multiple access interference (MAI), where it produces an asymptotic floor to the error probability, and limits the number of simultaneous users. Developing of FO-CDMA system to increase the number of users as well as to improve the system performance may be done through developing the system structure, choice of the appropriate detection scheme and the proper signature codes, developing the encoders and decoders hardware, use of adequate error correcting codes, incorporating optical amplifiers, use of multidimensional FO-CDMA techniques, and use of MAI cancellation and dispersion compensation techniques. This paper highlights the main directions of system development. The main technological challenges that have to be overcome before a wide spread of this technology have been also investigated. Finally, potential applications of this technology have been discussed.

  19. 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.

  20. An efficient CDMA decoder for correlated information sources

    NASA Astrophysics Data System (ADS)

    Efraim, Hadar; Yacov, Nadav; Shental, Ori; Kanter, Ido

    2009-07-01

    We consider the detection of correlated information sources in the ubiquitous code-division multiple-access (CDMA) scheme. We propose a message-passing based scheme for detecting correlated sources directly, with no need for source coding. The detection is done simultaneously over a block of transmitted binary symbols (word). Simulation results are provided, demonstrating a substantial improvement in bit error rate in comparison with the unmodified detector and the alternative of source compression. The robustness of the error-performance improvement is shown under practical model settings, including wrong estimation of the generating Markov transition matrix and finite-length spreading codes.

  1. 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.

  2. 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.

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

    NASA Astrophysics Data System (ADS)

    Kumar, Pravindra; Srivastava, Anand

    2015-12-01

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

  4. A New Family of 2-D Optical Orthogonal Codes and Analysis of Its Performance in Optical CDMA Access Networks

    NASA Astrophysics Data System (ADS)

    Shurong, Sun; Yin, Hongxi; Wang, Ziyu; Xu, Anshi

    2006-04-01

    A new family of two-dimensional optical orthogonal code (2-D OOC), one-coincidence frequency hop code (OCFHC)/OOC, which employs OCFHC and OOC as wavelengthhopping and time-spreading patterns, respectively, is proposed in this paper. In contrary to previously constructed 2-D OOCs, OCFHC/OOC provides more choices on the number of available wavelengths and its cardinality achieves the upper bound in theory without sacrificing good auto-and-cross correlation properties, i.e., the correlation properties of the code is still ideal. Meanwhile, we utilize a new method, called effective normalized throughput, to compare the performance of diverse codes applicable to optical code division multiple access (OCDMA) systems besides conventional measure bit error rate, and the results indicate that our code performs better than obtained OCDMA codes and is truly applicable to OCDMA networks as multiaccess codes and will greatly facilitate the implementation of OCDMA access networks.

  5. Optical CDMA system using 2-D run-length limited code

    NASA Astrophysics Data System (ADS)

    Liu, Maw-Yang; Jiang, Joe-Air

    2010-10-01

    In this paper, time-spreading wavelength-hopping optical CDMA system using 2-D run-length limited code is investigated. The run-length limited code we use here is predicated upon spatial coding scheme, which can improve system performance significantly. In our proposed system, we employ carrier-hopping prime code and its shifted version as signature sequences. Based on the zero auto-correlation sidelobes property of signature sequence, we propose a two-state trellis coding architecture, which utilizes 2-D parallel detection scheme. The proposed scheme is compact and simple that can be applied to more complicated trellis to further enhance system performance. Multiple access interference is the main deterioration factor in optical CDMA system that affects system performance adversely. Aside from the multiple access interference, some of the adverse impacts of system performance are also taken into consideration, which include thermal noise, shot noise, relative intensity noise, and beat noise.

  6. Delay and throughput characteristics of TH, CDMA, TDMA, and hybrid networks for multipath faded data transmission channels

    NASA Astrophysics Data System (ADS)

    Elhakeem, Ahmed K.; Digirolamo, Rocco; Bdira, Ilyess B.; Talla, M.

    1994-05-01

    The new concepts of adaptive time hopping and variable frame Code Division (CDMA) Multiple Access are introduced. By a unified analysis, the probabilities of bit and packet errors in multipath fading environment for five Time Division (TDMA), Code Division, and Time Hopping (TH) related multiaccess networks are obtained; namely, TDMA, CDMA, CDMA/TDMA, Adaptive CDMA/TH, and variable frame CDMA/TDMA networks. The delay and useful throughputs of the five systems are also evaluated for data and voice traffic. All systems compared have the same channel power and bandwidth and support the same traffic. Though implementation issues are not covered, CDMA systems are put at a disadvantage (compared to cellular-type FDMA networks, for example) by ignoring such inherent advantages as voice silence utilizations and automatic frequency reuse. Nonetheless, two CDMA systems outperform TDMA systems at low and medium input traffics.

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

    DTIC Science & Technology

    2015-01-01

    characterization of signals in terms of the modulation parameters is a field of interest relevant to military and software defined radio . Early modulation...classification algorithms were based on ad-hoc methods. These methods were applied for classifying analog signals such as AM and FM . The methods

  8. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

  10. 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.

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

    PubMed

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

    2012-05-01

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

  12. Simultaneous CDMA and error correction schemes based on wavelet filters in integer quotient rings

    NASA Astrophysics Data System (ADS)

    Lay, Kuen-Tsair; Kong, Lin-Wen; Chen, Jiann-Horng

    2000-04-01

    In the past decade, wavelet filters have been widely applied to signal processing. In effect, wavelet filters are perfect reconstruction filter banks (PRFBs). However, in most researches, the filterbanks and wavelets operate on real- valued or complex-valued signals. In this paper, PRFBs operating over integer quotient rings (IQRs) are introduced. We denote an IQR as Z/(q). Algorithms for constructing such filter banks are proposed. The PRFB design can be carried out either in the time or the frequency domain. We demonstrate that some classical or well known filter tap coefficients can even be transformed into values over Z/(q) in a simple and straightforward way. Here we emphasize that to achieve perfect reconstruction (PR), the filters need not to work on elements in fields. In fact, operating on elements in IQRs can achieve PR with proper choices of a ring and filter tap coefficients. The designed filter banks can be orthogonal or biorthogonal. Based ona PRFB over an IQR, to which we refer as an IQR-PRFB, a perfect reconstruction transmultiplexer (PRTM), to which we refer as an IQR-PRTM, can be derived. Through the utilization of the IQR-PRTM multiplexing and multiple access in a multi-user digital communication system can be realized. The IQR-PRTM effectively decomposes the communication signal space into several orthogonal subspaces, where each multiplexed user sends his message in one of them. If some of the orthogonal subspaces are preserved for parity check, then error correction at the receiving end can be performed. In the proposed schemes, the data to be transmitted must be represented with elements of Z/(q), which can be done easily. A modulation and demodulation/detection scheme, in conjunction with the IQR-PRTM is proposed.

  13. 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.

  14. 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.

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

    SciTech Connect

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

    2005-02-25

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

  16. The lack of histological changes of CDMA cellular phone-based radio frequency on rat testis.

    PubMed

    Lee, Hae-June; Pack, Jeong-Ki; Kim, Tae-Hong; Kim, Nam; Choi, Soo-Yong; Lee, Jae-Seon; Kim, Sung-Ho; Lee, Yun-Sil

    2010-10-01

    We examined the histological changes by radiofrequency (RF) fields on rat testis, specifically with respect to sensitive processes such as spermatogenesis. Male rats were exposed to 848.5 MHz RF for 12 weeks. The RF exposure schedule consisted of two 45-min RF exposure periods, separated by a 15-min interval. The whole-body average specific absorption rate (SAR) of RF was 2.0 W/kg. We then investigated correlates of testicular function such as sperm counts in the cauda epididymis, malondialdehyde concentrations in the testes and epididymis, frequency of spermatogenesis stages, germ cell counts, and appearance of apoptotic cells in the testes. We also performed p53, bcl-2, caspase 3, p21, and PARP immunoblotting of the testes in sham- and RF-exposed animals. Based on these results, we concluded that subchronic exposure to 848.5 MHz with 2.0 W/kg SAR RF did not have any observable adverse effects on rat spermatogenesis.

  17. 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.

  18. 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

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

    PubMed

    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.

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

    SciTech Connect

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

    2006-07-03

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

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

    NASA Astrophysics Data System (ADS)

    Yui, Tatsunori; Tomeba, Hiromichi; Adachi, Fumiyuki

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

  2. Data communications with VSATs - RA/TDMA vs. SS/CDMA

    NASA Astrophysics Data System (ADS)

    Kim, Kap S.

    Random-access TDMA and spread-spectrum CDMA, two of the most predominant hub-VSAT (very-small-aperture terminal) inbound access techniques today, are discussed in relation to the interactive data application environment where the response time is the most critical performance parameter. The system access techniques, access time, channel capacity, and performance comparison are presented. It is concluded that, in general, either RA/TDMA or SS/CDMA can provide cost/performance-effective serivce for interactive applications as compared with terrestrial service alternatives. If the user's data application consists mostly of short message transactions and its inbound aggregated data rate is low (less than 9.6 kb/s), the SS/CDMA system is recommended. The RA/TDMA system is better suited for the user applications which require a mix of interactive and batch processings.

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

    SciTech Connect

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

    2004-07-09

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

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

    SciTech Connect

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

    2005-06-02

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

  5. Code division multiple-access techniques in optical fiber networks. II - Systems performance analysis

    NASA Astrophysics Data System (ADS)

    Salehi, Jawad A.; Brackett, Charles A.

    1989-08-01

    A technique based on optical orthogonal codes was presented by Salehi (1989) to establish a fiber-optic code-division multiple-access (FO-CDMA) communications system. The results are used to derive the bit error rate of the proposed FO-CDMA system as a function of data rate, code length, code weight, number of users, and receiver threshold. The performance characteristics for a variety of system parameters are discussed. A means of reducing the effective multiple-access interference signal by placing an optical hard-limiter at the front end of the desired optical correlator is presented. Performance calculations are shown for the FO-CDMA with an ideal optical hard-limiter, and it is shown that using a optical hard-limiter would, in general, improve system performance.

  6. 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.

  7. Capacity of a spread spectrum CDMA system for cellular mobile radio with consideration of system imperfections

    NASA Astrophysics Data System (ADS)

    Newson, Paul; Heath, Mark R.

    1994-05-01

    There has been much interest in the use of spread spectrum code division multiple access (CDMA) techniques for cellular mobile radio. To date, spread spectrum has been used mainly for military applications, in which the inherent transmission security and immunity to deliberate jamming are important. Spread spectrum systems, however, possess various other features such as multiple access and multipath rejection capability, which make their use attractive within the mobile radio environment. However, the current interest has been principally motivated by recent work in which it is claimed that the CDMA option may offer capacity improvement over more conventional frequency and time division multiple access (FDMA) (TDMA) techniques. Within this paper, the relative capacities of a basic FDMA and CDMA system are examined. It is shown that, in the absence of capacity-enhancing features such as voice activity detection and cell sectorization, the capacity of each system is comparable. The paper then assesses the sensitivity of the CDMA system to typical propagation conditions, power control errors, and realistic antenna patterns and shows that the capacity of a CDMA system may be significantly reduced under nonideal conditions.

  8. 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.

  9. Radio resource management for CDMA systems with interference guard margin (IGM)

    NASA Astrophysics Data System (ADS)

    Chen, Huan; Kumar, Sunil; Kuo, C.-C. Jay

    2001-11-01

    A call admission control (CAC) scheme and a resource reservation estimation (RRE) method suitable for the wide-band code division multiple access (W-CDMA) systems are proposed in this work. The proposed CAC scheme gives preferential treatment to high priority calls, such as handoff calls, by pre-reserving a certain amount of channel margin against the interference effect. It is called the interference guard margin (IGM) scheme. The amount of guard margin is determined by the measurement performed by the RRE module in base stations. Each RRE module dynamically adjusts the level of guard margin by referencing traffic conditions in neighboring cells based upon users' requests. A comprehensive service model is adopted to accommodate the scenario of multiple services supported in the W-CDMA system. The service model of consideration includes not only mobile terminal's service rate (source rate) but also different levels of priorities, mobility and rate adaptivity characteristics. Simulations are conducted with OPNET to study the performance of the proposed scheme in term of the objective function under different traffic conditions.

  10. Alternative multiple-access techniques for mobile satellite systems

    NASA Technical Reports Server (NTRS)

    Smith, Patrick O.; Geraniotis, Evaggelos

    1989-01-01

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

  11. 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.

  12. 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.

  13. 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.

  14. Call admission control for CDMA systems with Interference Guard Margin (IGM)

    NASA Astrophysics Data System (ADS)

    Chen, Huan; Kumar, Sunil; Kuo, C.-C. Jay

    2002-01-01

    A call admission control (CAC) scheme and a resource-reservation estimation (RRE) method suitable for the interference-based wireless system, such as wide-band code division multiple access (W-CDMA), are proposed in this work. The proposed CAC scheme gives preferential treatment to high priority handoff calls by pre-reserving a certain amount of interference margin called the interference guard margin (IGM). The amount of guard margin is determined by the measurement performed by the RRE module in base stations. Each RRE module dynamically adjusts the level of guard margin by considering traffic conditions in neighboring cells based upon handoff requests. A service model is adopted to support multiple services, which includes mobile terminal's data rate, different levels of priorities, mobility and rate adaptivity characteristics. Simulations are conducted with OPNET to study the performance of the proposed scheme in terms of the objective function, blocking probabilities and system utilization under different traffic conditions.

  15. A Novel 2-D OFDM-DS-CDMA Receiver with Frequency-Time Spreading

    NASA Astrophysics Data System (ADS)

    Chen, Joy Iong-Zong

    This paper presents a novel 2-D (2-dimension) receiver that adopts the reception scheme to promote OFDM-DS-CDMA (orthogonal frequency division multiplexing multi-carrier coded-division multiple-access) system performance. The system model includes spread coding and a system block diagram of the 2-D receiver shown graphically with 3-D (three dimensions) plots. The analytical calculation of system performance for an OFDM-DS-CDMA system combined with the proposed receiver equipment is investigated. To evaluate the results from the channel fading effect is considered over the correlated fading environments. The correlated-Nakagami-m statistical distribution is taken into account in the evaluation. The results show that the number of users, the number of subcarriers and the fading channel correlation generally affect OFDM-DS-CDMA systems. The system is also influenced by the Doppler shift and the signal propagation environment (fading parameter).

  16. 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).

  17. Performance of a space-time block coded code division multiple access system over Nakagami-m fading channels

    NASA Astrophysics Data System (ADS)

    Yu, Xiangbin; Dong, Tao; Xu, Dazhuan; Bi, Guangguo

    2010-09-01

    By introducing an orthogonal space-time coding scheme, multiuser code division multiple access (CDMA) systems with different space time codes are given, and corresponding system performance is investigated over a Nakagami-m fading channel. A low-complexity multiuser receiver scheme is developed for space-time block coded CDMA (STBC-CDMA) systems. The scheme can make full use of the complex orthogonality of space-time block coding to simplify the high decoding complexity of the existing scheme. Compared to the existing scheme with exponential decoding complexity, it has linear decoding complexity. Based on the performance analysis and mathematical calculation, the average bit error rate (BER) of the system is derived in detail for integer m and non-integer m, respectively. As a result, a tight closed-form BER expression is obtained for STBC-CDMA with an orthogonal spreading code, and an approximate closed-form BER expression is attained for STBC-CDMA with a quasi-orthogonal spreading code. Simulation results show that the proposed scheme can achieve almost the same performance as the existing scheme with low complexity. Moreover, the simulation results for average BER are consistent with the theoretical analysis.

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

    SciTech Connect

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

    2000-03-16

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

  19. Equalization With Oversampling in Multiuser CDMA Systems

    DTIC Science & Technology

    2007-11-02

    A Mutually-Orthogonal Usercode-Receiver ( AMOUR ) for asynchronous or quasi-synchronous CDMA systems. AMOUR converts a multiuser CDMA system into...of improving the performance of AMOUR systems. They design Fractionally-Spaced AMOUR (FSAMOUR) receivers with integral and rational amounts of...practically guaranteed. They exploit this flexibility in the design of AMOUR and FSAMOUR receivers and achieve noticeable improvements in performance. (11 figures, 23 refs.)

  20. A New TH-CDMA Scheme for Dispersive Infrared Channel and Its Performance Evaluation

    NASA Astrophysics Data System (ADS)

    Hamdi, Mazda; Nasiri-Kenari, Masoumeh

    2011-04-01

    Infrared indoor wireless communications using nondirected links are subject to severe multipath distortion which causes intersymbol interference (ISI). To lessen multipath distortion effect and thereby to improve the system performance, in this paper, we consider a new time-hopping based multiple access scheme for this channel, in which one pulse is transmitted in each bit interval. The position of the pulse is determined based on the output of a low rate error correcting code along with the user's dedicated PN code. We evaluate the multiple access performance of the system for correlation receiver considering background noise, dark current, and thermal noise. We compare the performance of our proposed multiple access scheme with those of the previously introduced code division multiple access schemes for infrared communications, like CDMA and Frame Time Hopping (FTH). Our results show that, for the same bandwidth and bit rate, the proposed system substantially excels the other methods in term of bit error rate, or equivalently the number of the users supported at a fixed bit error rate.

  1. High precision three-dimensional iterative indoor localization algorithm using code division multiple access modulation based on visible light communication

    NASA Astrophysics Data System (ADS)

    Guan, Weipeng; Wu, Yvxiang; Wen, Shangsheng; Yang, Chen; Chen, Hao; Zhang, Zhaoze; Chen, Yingcong

    2016-10-01

    To solve the problem of positioning accuracy affected by mutual interference among multiple reference points in the traditional visible light communication positioning system, an iterative algorithm of received signal strength (RSS) based on code division multiple access (CDMA) coding is proposed. Every light-emitting diode (LED) source broadcasts a unique CDMA modulation identification (ID) code, which is associated with geographic position. The mobile terminal receives a mixed light signal from each LED reference point. By using the orthogonality of the spreading codes, the corresponding ID position information and the intensity attenuation factor of each LED reference point source can be available. According to the ID information and signal attenuation intensity, the location area of each LED and the distance between the receiver end and each LED can be determined. The three-dimensional (3-D) position of the receiver can be obtained by using the iterative algorithm of RSS triangulation. The experimental results show that the proposed algorithm can achieve a positioning accuracy of 5.25 cm in a two-dimensional (2-D) positioning system. And in the 3-D positioning system, the maximum positioning error is 10.27 cm, the minimum positioning error is 0.45 cm, the average positioning error is 3.97 cm, and the proportion of the positioning error exceeding 5 cm is <25%. With a very good positioning accuracy, this system is simple and does not require synchronization processing. What is more, it can be applied to both the 2-D and 3-D localization systems, which has a broad application prospect.

  2. 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.

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

    SciTech Connect

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

    2006-05-25

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

  4. New packet scheduling algorithm in wireless CDMA data networks

    NASA Astrophysics Data System (ADS)

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

    2002-08-01

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

  5. Success with Web-based image access.

    PubMed

    Harrison, Sean W

    2003-01-01

    The University of Mississippi Medical Center in Jackson, Miss., is the only medical school in the state. We performed 235,000 procedures in the 2001-02 fiscal year. All imaging services within the radiology department are networked to a PACS and are filmless. The elimination of film required that we decentralize our traditional file room to allow easy access to our radiology network across the campus. In our facility, there are three levels of image access: Diagnostic Quality, Review Quality and Web Access. Diagnostic Quality requires top-of-the-line workstations and monitors and is the most expensive. Review Quality workstations represent some savings over Diagnostic and are used in the ICU, orthopedics and surgery. Web Access appears to satisfy most areas outside the main diagnostic department. The account set-up procedure is simple because it uses our intranet email system. Images are easily pasted into presentation applications for articles and conferences. However, the main advantage of Web Access is the low cost. The downside of Web Access is that the images are for review only and are limited by the quality of the monitor in use. It is also somewhat cumbersome to retrieve old or comparison images via this method. The Web only holds approximately 45 days of the most recent images, therefore older studies may not be available. The deployment of this Web-based service has aided in our efforts to reduce the amount of film we print and has also been beneficial in improving patient care through faster service.

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

    DTIC Science & Technology

    2009-10-01

    input multiple-output (MIMO) system which employs Alamouti spacetime block coding at each sub-carrier frequency to achieve spatial diversity. We...number of pilot symbols per channel estimate. 13 N/A MC-DS-CDMA, MC-CDMA, Alamouti spacetime block coding, frequency-selective Rayleigh fading

  7. PDA-phone-based instant transmission of radiological images over a CDMA network by combining the PACS screen with a Bluetooth-interfaced local wireless link.

    PubMed

    Kim, Dong Keun; Yoo, Sun K; Park, Jeong Jin; Kim, Sun Ho

    2007-06-01

    Remote teleconsultation by specialists is important for timely, correct, and specialized emergency surgical and medical decision making. In this paper, we designed a new personal digital assistant (PDA)-phone-based emergency teleradiology system by combining cellular communication with Bluetooth-interfaced local wireless links. The mobility and portability resulting from the use of PDAs and wireless communication can provide a more effective means of emergency teleconsultation without requiring the user to be limited to a fixed location. Moreover, it enables synchronized radiological image sharing between the attending physician in the emergency room and the remote specialist on picture archiving and communication system terminals without distorted image acquisition. To enable rapid and fine-quality radiological image transmission over a cellular network in a secure manner, progressive compression and security mechanisms have been incorporated. The proposed system is tested over a code division Multiple Access 1x-Evolution Data-Only network to evaluate the performance and to demonstrate the feasibility of this system in a real-world setting.

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

    NASA Astrophysics Data System (ADS)

    Abolhassani, Bahman

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

  9. Frequency-Domain Equalization for Broadband Single-Carrier Multiple Access

    NASA Astrophysics Data System (ADS)

    Adachi, Fumiyuki; Tomeba, Hiromichi; Takeda, Kazuki

    Single-carrier (SC) multiple access is a promising uplink multiple access technique because of its low peak-to-average power ratio (PAPR) property and high frequency diversity gain that is achievable through simple one-tap frequency-domain equalization (FDE) in a strong frequency-selective channel. The multiple access capability can be obtained by combining either frequency division multiple access (FDMA) or code division multiple access (CDMA) with SC transmission. In this article, we review the recent research on the SC multiple access techniques with one-tap FDE. After introducing the principle of joint FDE/antenna diversity combining, we review various SC multiple access techniques with one-tap FDE, i.e., SC-FDMA, SC-CDMA, block spread CDMA, and delay-time/CDMA.

  10. Performance evaluation of CCI on the forward CDMA channel

    NASA Astrophysics Data System (ADS)

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

    2013-05-01

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

  11. Performance evaluation of CCI on the reverse CDMA channel

    NASA Astrophysics Data System (ADS)

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

    2011-06-01

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

  12. Direct sequence CDMA power control, interleaving, and coding

    NASA Astrophysics Data System (ADS)

    Simpson, Floyd; Holtzman, Jack M.

    1993-09-01

    We develop and analyze models of power control working with other aspects of CDMA systems, such as interleaving and coding on the land/ mobile radio channel. Our orientation is that a power control scheme is keeping the received powers at the base station 'almost equal', and we will be quantifying the performance degradation incurred if the powers are not exactly equal. In doing so, we consider the performance implications of control latency and a maximum speech delay constraint. It turns out that because of positive correlations between the fading channel amplitudes, the effectiveness of the combination of interleaving and coding in combating the effects of power variations due to slow Rayleigh fading is reduced. It is shown however, that power control and interleaving/coding are most effective in complementary parameter regions, thus providing a degree of robustness for both fast and slow Rayleigh fading.

  13. 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.

  14. Modeling mandatory access control in role-based security systems

    SciTech Connect

    Nyanchama, M.; Osborn, S.

    1996-12-31

    This paper discusses the realization of mandatory access control in role-based protection systems. Starting from the basic definitions of roles, their application in security and the basics of the concept of mandatory access control, we develop a scheme of role-based protection that realizes mandatory access control. The basis of this formulation develops from the recognition that roles can be seen as facilitating access to some given information context. By handling each of the role contexts as independent security levels of information, we simulate mandatory access by imposing the requirements of mandatory access control. Among the key considerations, we propose a means of taming Trojan horses by imposing acyclic information flow among contexts in role-based protection systems. The acyclic information flows and suitable access rules incorporate secrecy which is an essential component of mandatory access control.

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

    NASA Astrophysics Data System (ADS)

    Kato, Hiroyuki; Okada, Masato; Miyoshi, Seiji

    2013-07-01

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

  16. 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

  17. 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

  18. A Novel Reference Security Model with the Situation Based Access Policy for Accessing EPHR Data.

    PubMed

    Gope, Prosanta; Amin, Ruhul

    2016-11-01

    Electronic Patient Health Record (EPHR) systems may facilitate a patient not only to share his/her health records securely with healthcare professional but also to control his/her health privacy, in a convenient and easy way even in case of emergency. In order to fulfill these requirements, it is greatly desirable to have the access control mechanism which can efficiently handle every circumstance without negotiating security. However, the existing access control mechanisms used in healthcare to regulate and restrict the disclosure of patient data are often bypassed in case of emergencies. In this article, we propose a way to securely share EPHR data under any situation including break-the-glass (BtG) without compromising its security. In this regard, we design a reference security model, which consists of a multi-level data flow hierarchy, and an efficient access control framework based on the conventional Role-Based Access Control (RBAC) and Mandatory Access Control (MAC) policies.

  19. 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.

  20. Quantum internet using code division multiple access.

    PubMed

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

    2013-01-01

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

  1. Quantum internet using code division multiple access

    NASA Astrophysics Data System (ADS)

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

    2013-07-01

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

  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. A study of multiple access schemes in satellite control network

    NASA Astrophysics Data System (ADS)

    Mo, Zijian; Wang, Zhonghai; Xiang, Xingyu; Wang, Gang; Chen, Genshe; Nguyen, Tien; Pham, Khanh; Blasch, Erik

    2016-05-01

    Satellite Control Networks (SCN) have provided launch control for space lift vehicles; tracking, telemetry and commanding (TTC) for on-orbit satellites; and, test support for space experiments since the 1960s. Currently, SCNs encounter a new challenge: how to maintain the high reliability of services when sharing the spectrum with emerging commercial services. To achieve this goal, the capability of multiple satellites reception is deserved as an update/modernization of SCN in the future. In this paper, we conducts an investigation of multiple access techniques in SCN scenario, e.g., frequency division multiple access (FDMA) and coded division multiple access (CDMA). First, we introduce two upgrade options of SCN based on FDMA and CDMA techniques. Correspondingly, we also provide their performance analysis, especially the system improvement in spectrum efficiency and interference mitigation. Finally, to determine the optimum upgrade option, this work uses CRISP, i.e., Cost, Risk, Installation, Supportability and Performance, as the baseline approach for a comprehensive trade study of these two options. Extensive numerical and simulation results are presented to illustrate the theoretical development.

  4. A Web-Based Remote Access Laboratory Using SCADA

    ERIC Educational Resources Information Center

    Aydogmus, Z.; Aydogmus, O.

    2009-01-01

    The Internet provides an opportunity for students to access laboratories from outside the campus. This paper presents a Web-based remote access real-time laboratory using SCADA (supervisory control and data acquisition) control. The control of an induction motor is used as an example to demonstrate the effectiveness of this remote laboratory,…

  5. Limited Access: The Information Superhighway and Ohio's Neighborhood Based Organizations.

    ERIC Educational Resources Information Center

    Urban Univ. and Neighborhood Network.

    The Urban University and Neighborhood Network, a group dedicated to bringing together Ohio's urban universities and neighborhood-based organizations (NBOs), has been studying NBO access to the Internet. Of 189 Ohio NBOs responding to a survey, only 3 have full access to the Internet. The small size and small budget of many of the state's NBOs…

  6. Unequal error protection codes for wavelet video transmission over W-CDMA, AWGN, and Rayleigh fading channels

    NASA Astrophysics Data System (ADS)

    Le, Minh Hung; Liyana-Pathirana, Ranjith

    2003-06-01

    The unequal error protection (UEP) codes with wavelet-based algorithm for video compression over wide-band code division multiple access (W-CDMA), additive white Gaussian noise (AWGN) and Rayleigh fading channels are analysed. The utilization of Wavelets has come out to be a powerful method for compress video sequence. The wavelet transform compression technique has shown to be more appropriate to high quality video applications, producing better quality output for the compressed frames of video. A spatially scalable video coding framework of MPEG2 in which motion correspondences between successive video frames are exploited in the wavelet transform domain. The basic motivation for our coder is that motion fields are typically smooth that can be efficiently captured through a multiresolutional framework. Wavelet decomposition is applied to video frames and the coefficients at each level are predicted from the coarser level through backward motion compensation. The proposed algorithms of the embedded zero-tree wavelet (EZW) coder and the 2-D wavelet packet transform (2-D WPT) are investigated.

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

    DTIC Science & Technology

    2014-05-01

    AFOSR). Some of the work accomplished was possible by using the AFRL High Performance Computing servers ( Condor HPC). Approved for Public Release...A Matlab implementation of the parameters is shown below. The code was executed using AFRL Condor HPC cluster for calculating the values of

  8. 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.

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

    PubMed

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

    2016-09-01

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

  10. Context-aware access control for pervasive access to process-based healthcare systems.

    PubMed

    Koufi, Vassiliki; Vassilacopoulos, George

    2008-01-01

    Healthcare is an increasingly collaborative enterprise involving a broad range of healthcare services provided by many individuals and organizations. Grid technology has been widely recognized as a means for integrating disparate computing resources in the healthcare field. Moreover, Grid portal applications can be developed on a wireless and mobile infrastructure to execute healthcare processes which, in turn, can provide remote access to Grid database services. Such an environment provides ubiquitous and pervasive access to integrated healthcare services at the point of care, thus improving healthcare quality. In such environments, the ability to provide an effective access control mechanism that meets the requirement of the least privilege principle is essential. Adherence to the least privilege principle requires continuous adjustments of user permissions in order to adapt to the current situation. This paper presents a context-aware access control mechanism for HDGPortal, a Grid portal application which provides access to workflow-based healthcare processes using wireless Personal Digital Assistants. The proposed mechanism builds upon and enhances security mechanisms provided by the Grid Security Infrastructure. It provides tight, just-in-time permissions so that authorized users get access to specific objects according to the current context. These permissions are subject to continuous adjustments triggered by the changing context. Thus, the risk of compromising information integrity during task executions is reduced.

  11. Computationally Efficient Blind Code Synchronization for Asynchronous DS-CDMA Systems with Adaptive Antenna Arrays

    NASA Astrophysics Data System (ADS)

    Hu, Chia-Chang

    2005-12-01

    A novel space-time adaptive near-far robust code-synchronization array detector for asynchronous DS-CDMA systems is developed in this paper. There are the same basic requirements that are needed by the conventional matched filter of an asynchronous DS-CDMA system. For the real-time applicability, a computationally efficient architecture of the proposed detector is developed that is based on the concept of the multistage Wiener filter (MWF) of Goldstein and Reed. This multistage technique results in a self-synchronizing detection criterion that requires no inversion or eigendecomposition of a covariance matrix. As a consequence, this detector achieves a complexity that is only a linear function of the size of antenna array ([InlineEquation not available: see fulltext.]), the rank of the MWF ([InlineEquation not available: see fulltext.]), the system processing gain ([InlineEquation not available: see fulltext.]), and the number of samples in a chip interval ([InlineEquation not available: see fulltext.]), that is,[InlineEquation not available: see fulltext.]. The complexity of the equivalent detector based on the minimum mean-squared error (MMSE) or the subspace-based eigenstructure analysis is a function of[InlineEquation not available: see fulltext.]. Moreover, this multistage scheme provides a rapid adaptive convergence under limited observation-data support. Simulations are conducted to evaluate the performance and convergence behavior of the proposed detector with the size of the[InlineEquation not available: see fulltext.]-element antenna array, the amount of the[InlineEquation not available: see fulltext.]-sample support, and the rank of the[InlineEquation not available: see fulltext.]-stage MWF. The performance advantage of the proposed detector over other DS-CDMA detectors is investigated as well.

  12. Access Control of Web- and Java-Based Applications

    NASA Technical Reports Server (NTRS)

    Tso, Kam S.; Pajevski, Michael J.

    2013-01-01

    Cybersecurity has become a great concern as threats of service interruption, unauthorized access, stealing and altering of information, and spreading of viruses have become more prevalent and serious. Application layer access control of applications is a critical component in the overall security solution that also includes encryption, firewalls, virtual private networks, antivirus, and intrusion detection. An access control solution, based on an open-source access manager augmented with custom software components, was developed to provide protection to both Web-based and Javabased client and server applications. The DISA Security Service (DISA-SS) provides common access control capabilities for AMMOS software applications through a set of application programming interfaces (APIs) and network- accessible security services for authentication, single sign-on, authorization checking, and authorization policy management. The OpenAM access management technology designed for Web applications can be extended to meet the needs of Java thick clients and stand alone servers that are commonly used in the JPL AMMOS environment. The DISA-SS reusable components have greatly reduced the effort for each AMMOS subsystem to develop its own access control strategy. The novelty of this work is that it leverages an open-source access management product that was designed for Webbased applications to provide access control for Java thick clients and Java standalone servers. Thick clients and standalone servers are still commonly used in businesses and government, especially for applications that require rich graphical user interfaces and high-performance visualization that cannot be met by thin clients running on Web browsers

  13. Accessibility

    EPA Pesticide Factsheets

    Federal laws, including Section 508 of the Rehabilitation Act, mandate that people with disabilities have access to the same information that someone without a disability would have. 508 standards cover electronic and information technology (EIT) products.

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

    NASA Technical Reports Server (NTRS)

    Caron, Mario; Hindson, Daniel J.

    1995-01-01

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

  15. Access Control of Web and Java Based Applications

    NASA Technical Reports Server (NTRS)

    Tso, Kam S.; Pajevski, Michael J.; Johnson, Bryan

    2011-01-01

    Cyber security has gained national and international attention as a result of near continuous headlines from financial institutions, retail stores, government offices and universities reporting compromised systems and stolen data. Concerns continue to rise as threats of service interruption, and spreading of viruses become ever more prevalent and serious. Controlling access to application layer resources is a critical component in a layered security solution that includes encryption, firewalls, virtual private networks, antivirus, and intrusion detection. In this paper we discuss the development of an application-level access control solution, based on an open-source access manager augmented with custom software components, to provide protection to both Web-based and Java-based client and server applications.

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

    NASA Astrophysics Data System (ADS)

    Carter, P.; Beach, M. A.

    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. Time-spreading wavelength-hopping optical CDMA system using EWO and TCM

    NASA Astrophysics Data System (ADS)

    Liu, Maw-Yang; Wang, Zhi-Wei

    2011-12-01

    In this paper, time-spreading wavelength-hopping optical CDMA system using trellis coded modulation scheme is investigated. The carrier hopping prime code and its shifted version are employed as signature sequences. Since the carrier hopping prime code is a symmetric code, the out of phase autocorrelation is zero. Applying the orthogonality of the signature sequences, the ternary transmission mechanism can be achieved. The proposed coding scheme is simple in both transmitter and receiver. As the multiple access interference and beat noise are the major deterioration of system performance, using coding scheme is an effective way to reduce the error floor. The numerical results reveal that the proposed coding scheme can significantly improve the system performance.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. Web-based Access to Locally Developed Databases.

    ERIC Educational Resources Information Center

    Mischo, William H.; Schlembach, Mary C.

    1999-01-01

    Describes the Web-based technologies employed by the Grainger Engineering Library Information Center at the University of Illinois, Urbana-Champaign in implementing access to local information resources. Discusses Microsoft Active Server Pages (ASP) technologies and the associated local database structure and format, as well as the general…

  3. Access Control for Agent-based Computing: A Distributed Approach.

    ERIC Educational Resources Information Center

    Antonopoulos, Nick; Koukoumpetsos, Kyriakos; Shafarenko, Alex

    2001-01-01

    Discusses the mobile software agent paradigm that provides a foundation for the development of high performance distributed applications and presents a simple, distributed access control architecture based on the concept of distributed, active authorization entities (lock cells), any combination of which can be referenced by an agent to provide…

  4. Learning at Work: Work-Based Access to Higher Education.

    ERIC Educational Resources Information Center

    Loots, Catriona; Osborne, Michael; Seagraves, Liz

    1998-01-01

    Learning at Work is a Scottish program attempting to widen access to higher education across socioeconomic groups through work-based learning. Factors limiting participation include motivation, employer perceptions of the value of higher education, lack of a learning culture, and economic feasibility. (SK)

  5. Neoplastic transformation in C3H 10T(1/2) cells after exposure to 835.62 MHz FDMA and 847.74 MHz CDMA radiations.

    PubMed

    Roti Roti JL; Malyapa, R S; Bisht, K S; Ahern, E W; Moros, E G; Pickard, W F; Straube, W L

    2001-01-01

    The effect of radiofrequency (RF) radiation in the cellular phone communication range (835.62 MHz frequency division multiple access, FDMA; 847.74 MHz code division multiple access, CDMA) on neoplastic transformation frequency was measured using the in vitro C3H 10T(1/2) cell transformation assay system. To determine if 835.62 MHz FDMA or 847.74 MHz CDMA radiations have any genotoxic effects that induce neoplastic transformation, C3H 10T(1/2) cells were exposed at 37 degrees C to either of the above radiations [each at a specific absorption rate (SAR) of 0.6 W/kg] or sham-exposed at the same time for 7 days. After the culture medium was changed, the cultures were transferred to incubators and refed with fresh growth medium every 7 days. After 42 days, the cells were fixed and stained with Giemsa, and transformed foci were scored. To determine if exposure to 835.62 MHz FDMA or 847.74 MHz CDMA radiation has any epigenetic effects that can promote neoplastic transformation, cells were first exposed to 4.5 Gy of X rays to induce the transformation process and then exposed to the above radiations (SAR = 0.6 W/kg) in temperature-controlled irradiators with weekly refeeding for 42 days. After both the 7-day RF exposure and the 42-day RF exposure after X irradiation, no statistically significant differences in the transformation frequencies were observed between incubator controls, the sham-exposed (maintained in irradiators without power to the antenna), and the 835.62 MHz FDMA or 847.74 MHz CDMA-exposed groups.

  6. 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.

  7. 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.

  8. 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.

  9. Using real-estate-based financing to access capital.

    PubMed

    Tobin, W C; Kryzaniak, L A

    1998-07-01

    One strategy employed by healthcare organizations to increase their market presence is the construction of new facilities. Accessing capital to fund such construction, however, has become more of a challenge. One relatively untapped source of building capital is real-estate-based financing. Nonrecourse mortgages, turnkey net leases, and synthetic leases can provide several advantages to healthcare organizations seeking capital, assuming issues related to building ownership, debt and balance sheet effects, and tax-exempt status have been thoroughly explored first.

  10. 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.

  11. Tag Content Access Control with Identity-based Key Exchange

    NASA Astrophysics Data System (ADS)

    Yan, Liang; Rong, Chunming

    2010-09-01

    Radio Frequency Identification (RFID) technology that used to identify objects and users has been applied to many applications such retail and supply chain recently. How to prevent tag content from unauthorized readout is a core problem of RFID privacy issues. Hash-lock access control protocol can make tag to release its content only to reader who knows the secret key shared between them. However, in order to get this shared secret key required by this protocol, reader needs to communicate with a back end database. In this paper, we propose to use identity-based secret key exchange approach to generate the secret key required for hash-lock access control protocol. With this approach, not only back end database connection is not needed anymore, but also tag cloning problem can be eliminated at the same time.

  12. Development of a statistically based access delay timeline methodology.

    SciTech Connect

    Rivera, W. Gary; Robinson, David Gerald; Wyss, Gregory Dane; Hendrickson, Stacey M. Langfitt

    2013-02-01

    The charter for adversarial delay is to hinder access to critical resources through the use of physical systems increasing an adversarys task time. The traditional method for characterizing access delay has been a simple model focused on accumulating times required to complete each task with little regard to uncertainty, complexity, or decreased efficiency associated with multiple sequential tasks or stress. The delay associated with any given barrier or path is further discounted to worst-case, and often unrealistic, times based on a high-level adversary, resulting in a highly conservative calculation of total delay. This leads to delay systems that require significant funding and personnel resources in order to defend against the assumed threat, which for many sites and applications becomes cost prohibitive. A new methodology has been developed that considers the uncertainties inherent in the problem to develop a realistic timeline distribution for a given adversary path. This new methodology incorporates advanced Bayesian statistical theory and methodologies, taking into account small sample size, expert judgment, human factors and threat uncertainty. The result is an algorithm that can calculate a probability distribution function of delay times directly related to system risk. Through further analysis, the access delay analyst or end user can use the results in making informed decisions while weighing benefits against risks, ultimately resulting in greater system effectiveness with lower cost.

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

    PubMed Central

    Chitra, S.; Kumaratharan, N.

    2015-01-01

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

  14. 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.

  15. Proximity-based access control for context-sensitive information provision in SOA-based systems

    NASA Astrophysics Data System (ADS)

    Rajappan, Gowri; Wang, Xiaofei; Grant, Robert; Paulini, Matthew

    2014-06-01

    Service Oriented Architecture (SOA) has enabled open-architecture integration of applications within an enterprise. For net-centric Command and Control (C2), this elucidates information sharing between applications and users, a critical requirement for mission success. The Information Technology (IT) access control schemes, which arbitrate who gets access to what information, do not yet have the contextual knowledge to dynamically allow this information sharing to happen dynamically. The access control might prevent legitimate users from accessing information relevant to the current mission context, since this context may be very different from the context for which the access privileges were configured. We evaluate a pair of data relevance measures - proximity and risk - and use these as the basis of dynamic access control. Proximity is a measure of the strength of connection between the user and the resource. However, proximity is not sufficient, since some data might have a negative impact, if leaked, which far outweighs importance to the subject's mission. For this, we use a risk measure to quantify the downside of data compromise. Given these contextual measures of proximity and risk, we investigate extending Attribute-Based Access Control (ABAC), which is used by the Department of Defense, and Role-Based Access Control (RBAC), which is widely used in the civilian market, so that these standards-based access control models are given contextual knowledge to enable dynamic information sharing. Furthermore, we consider the use of such a contextual access control scheme in a SOA-based environment, in particular for net-centric C2.

  16. Ontology-Based Federated Data Access to Human Studies Information

    PubMed Central

    Sim, Ida; Carini, Simona; Tu, Samson W.; Detwiler, Landon T.; Brinkley, James; Mollah, Shamim A.; Burke, Karl; Lehmann, Harold P.; Chakraborty, Swati; Wittkowski, Knut M.; Pollock, Brad H.; Johnson, Thomas M.; Huser, Vojtech

    2012-01-01

    Human studies are one of the most valuable sources of knowledge in biomedical research, but data about their design and results are currently widely dispersed in siloed systems. Federation of these data is needed to facilitate large-scale data analysis to realize the goals of evidence-based medicine. The Human Studies Database project has developed an informatics infrastructure for federated query of human studies databases, using a generalizable approach to ontology-based data access. Our approach has three main components. First, the Ontology of Clinical Research (OCRe) provides the reference semantics. Second, a data model, automatically derived from OCRe into XSD, maintains semantic synchrony of the underlying representations while facilitating data acquisition using common XML technologies. Finally, the Query Integrator issues queries distributed over the data, OCRe, and other ontologies such as SNOMED in BioPortal. We report on a demonstration of this infrastructure on data acquired from institutional systems and from ClinicalTrials.gov. PMID:23304360

  17. Coded access optical sensor (CAOS) imager and applications

    NASA Astrophysics Data System (ADS)

    Riza, Nabeel A.

    2016-04-01

    Starting in 2001, we proposed and extensively demonstrated (using a DMD: Digital Micromirror Device) an agile pixel Spatial Light Modulator (SLM)-based optical imager based on single pixel photo-detection (also called a single pixel camera) that is suited for operations with both coherent and incoherent light across broad spectral bands. This imager design operates with the agile pixels programmed in a limited SNR operations starring time-multiplexed mode where acquisition of image irradiance (i.e., intensity) data is done one agile pixel at a time across the SLM plane where the incident image radiation is present. Motivated by modern day advances in RF wireless, optical wired communications and electronic signal processing technologies and using our prior-art SLM-based optical imager design, described using a surprisingly simple approach is a new imager design called Coded Access Optical Sensor (CAOS) that has the ability to alleviate some of the key prior imager fundamental limitations. The agile pixel in the CAOS imager can operate in different time-frequency coding modes like Frequency Division Multiple Access (FDMA), Code-Division Multiple Access (CDMA), and Time Division Multiple Access (TDMA). Data from a first CAOS camera demonstration is described along with novel designs of CAOS-based optical instruments for various applications.

  18. Improved Channel Allocation for Multicarrier CDMA with Adaptive Frequency Hopping and Multiuser Detection

    DTIC Science & Technology

    2008-08-29

    Areas Commun., vol. 14, pp. 1852-1858, Dec. 1996. [6] Y. H. Kim, I. Song, S. Yoon and S. R. Park, “A multicarrier CDMA system with adaptive subchannel ...J. Li, and Z. Cao, “A near optimal subchannel allocation policy in forward links for multicarrier CDMA system,” Proc. IEEE VTC, 2001-Spring, vol. 2...Rhodes, Greece, 2001, pp. 896-900. [10] T. Jia, and A. Duel-Hallen, “ Subchannel allocation for multicarrier CDMA with adaptive frequency hopping

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

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

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

  20. Comparison of hybrid FDMA/CDMA systems in frequency selective Rayleigh fading

    NASA Astrophysics Data System (ADS)

    Eng, Thomas; Milstein, Laurence B.

    1994-06-01

    A hybrid FDMA/CDMA scheme operating over a frequency selective Rayleigh fading channel is described and analyzed. The performance of the hybrid system is then compared with that of a wideband CDMA system occupying the same total bandwidth. Both coherent and noncoherent modulation formats are investigated; it is found that, for coherent modulation with a RAKE receiver, wideband CDMA has greater capacity than does the hybrid. However, for the noncoherent modulation formats (either DPSK or square-law detected orthogonal signaling), a hybrid system can have a greater capacity if a high channel error rate can be tolerated. Otherwise, a wideband noncoherent system remains optimal.

  1. Amplified CWDM-based Next Generation Broadband Access Networks

    NASA Astrophysics Data System (ADS)

    Peiris, Sasanthi Chamarika

    The explosive growth of both fixed and mobile data-centric traffic along with the inevitable trend towards all-IP/Ethernet transport protocols and packet switched networks will ultimately lead to an all-packet-based converged fixed-mobile optical transport network from the core all the way out to the access network. To address the increasing capacity and speed requirements in the access networks, Wavelength-Division Multiplexed (WDM) and/or Coarse WDM (CWDM)-based Passive Optical Networks (PONs) are expected to emerge as the next-generation optical access infrastructures. However, due to several techno-economic hurdles, CWDM-PONs are still considered an expensive solution and have not yet made any significant inroads into the current access area. One of the key technology hurdles is the scalability of the CWDM-based PONs. Passive component optical insertion losses limit the reach of the network or the number of served optical network units (ONUs). In the recent years, optical amplified CWDM approaches have emerged and new designs of optical amplifiers have been proposed and demonstrated. The critical design parameter for these amplifiers is the very wide optical amplification bandwidth (e.g., 340 nm combined for both directions). The objective of this PhD dissertation work is first to engineer ring and tree-ring based PON architectures that can achieve longer unamplified PON reach and/or provide service to a greater number of ONUs and customers. Secondly is to develop new novel optical amplifier schemes to further address the scalability limitation of the CWDM-based PONs. Specifically, this work proposes and develops novel ultra wide-band hybrid Raman-Optical parametric amplifier (HROPA) schemes that operate over nearly the entire specified CWDM band to provide 340 nm bidirectional optical gain bandwidth over the amplified PON's downstream and upstream CWDM wavelength bands (about 170 nm in each direction). The performance of the proposed HROPA schemes is assessed

  2. Regional Webgis User Access Patterns Based on a Weighted Bipartite Network

    NASA Astrophysics Data System (ADS)

    Li, R.; Shen, Y.; Huang, W.; Wu, H.

    2015-07-01

    With the rapid development of geographic information services, Web Geographic Information Systems (WebGIS) have become an indispensable part of everyday life; correspondingly, map search engines have become extremely popular with users and WebGIS sites receive a massive volume of requests for access. These WebGIS users and the content accessed have regional characteristics; to understand regional patterns, we mined regional WebGIS user access patterns based on a weighted bipartite network. We first established a weighted bipartite network model for regional user access to a WebGIS. Then, based on the massive user WebGIS access logs, we clustered geographic information accessed and thereby identified hot access areas. Finally we quantitatively analyzed the access interests of regional users and the visitation volume characteristics of regional user access to these hot access areas in terms of user access permeability, user usage rate, and user access viscosity. Our research results show that regional user access to WebGIS is spatially aggregated, and the hot access areas that regional users accessed are associated with specific periods of time. Most regional user contact with hot accessed areas is variable and intermittent but for some users, their access to certain areas is continuous as it is associated with ongoing or recurrent objectives. The weighted bipartite network model for regional user WebGIS access provides a valid analysis method for studying user behaviour in WebGIS and the proposed access pattern exhibits access interest of regional user is spatiotemporal aggregated and presents a heavy-tailed distribution. Understanding user access patterns is good for WebGIS providers and supports better operational decision-making, and helpful for developers when optimizing WebGIS system architecture and deployment, so as to improve the user experience and to expand the popularity of WebGIS.

  3. VIALACTEA knowledge base homogenizing access to Milky Way data

    NASA Astrophysics Data System (ADS)

    Molinaro, Marco; Butora, Robert; Bandieramonte, Marilena; Becciani, Ugo; Brescia, Massimo; Cavuoti, Stefano; Costa, Alessandro; Di Giorgio, Anna M.; Elia, Davide; Hajnal, Akos; Gabor, Hermann; Kacsuk, Peter; Liu, Scige J.; Molinari, Sergio; Riccio, Giuseppe; Schisano, Eugenio; Sciacca, Eva; Smareglia, Riccardo; Vitello, Fabio

    2016-08-01

    The VIALACTEA project has a work package dedicated to "Tools and Infrastructure" and, inside it, a task for the "Database and Virtual Observatory Infrastructure". This task aims at providing an infrastructure to store all the resources needed by the, more purposely, scientific work packages of the project itself. This infrastructure includes a combination of: storage facilities, relational databases and web services on top of them, and has taken, as a whole, the name of VIALACTEA Knowledge Base (VLKB). This contribution illustrates the current status of this VLKB. It details the set of data resources put together; describes the database that allows data discovery through VO inspired metadata maintenance; illustrates the discovery, cutout and access services built on top of the former two for the users to exploit the data content.

  4. Diffuse optical tomography based on multiple access coding

    NASA Astrophysics Data System (ADS)

    Wang, Xuefeng; Wang, Yuanqing; Su, Jinshan; Xu, Fan

    2016-04-01

    Diffuse optical tomography (DOT) has the advantages of being a non-invasive, non-radiation emitting and low-cost biological tissue imaging method, and many recent studies have employed this technology. By improving the spatial resolution and developing a new method for constantly improving the flexibility of the experimental device, the system can perform data acquisition rapidly and conveniently. We propose a method for rapid data acquisition based on multiple access coding; it can acquire data in parallel, and the system can greatly improve the temporal resolution of the data acquisition step in diffuse optical tomography thereafter. We simulate the encoding and decoding process of the source-detector pair and successfully isolate the source signal from mixed signals. The DOT image reconstruction highlight the effectiveness of the system.

  5. Interoperability for Individual Learner Centred Accessibility for Web-Based Educational Systems

    ERIC Educational Resources Information Center

    Nevile, Liddy; Treviranus, Jutta

    2006-01-01

    This paper describes the interoperability underpinning a new strategy for delivering accessible computer-based resources to individual learners based on their specified needs and preferences in the circumstances in which they are operating. The new accessibility strategy, known as "AccessForAll," augments the model of universal…

  6. Joint Access Control Based on Access Ratio and Resource Utilization for High-Speed Railway Communications

    NASA Astrophysics Data System (ADS)

    Zhou, Yuzhe; Ai, Bo

    2015-05-01

    The fast development of high-speed rails makes people's life more and more convenient. However, provisioning of quality of service of multimedia applications for users on the high-speed train is a critical task for wireless communications. Therefore, new solutions are desirable to be found to address this kind of problem. Current researches mainly focus on providing seamless broadband wireless access for high-speed mobile terminals. In this paper, an algorithm to calculate the optimal resource reservation fraction of handovers is proposed. A joint access control scheme for high-speed railway communication handover scenario is proposed. Metrics of access ratio and resource utilization ratio are considered jointly in the analysis and the performance evaluation. Simulation results show that the proposed algorithm and the scheme improve quality of service compared with other conventional schemes.

  7. The effect of chronic exposure to 835.62 MHz FDMA or 847.74 MHz CDMA radiofrequency radiation on the incidence of spontaneous tumors in rats.

    PubMed

    La Regina, Marie; Moros, Eduardo G; Pickard, William F; Straube, William L; Baty, Jack; Roti Roti, Joseph L

    2003-08-01

    This study was designed to determine whether chronic exposure to radiofrequency (RF) radiation from cellular phones increased the incidence of spontaneous tumors in F344 rats. Eighty male and 80 female rats were randomly placed in each of three irradiation groups. The sham group received no irradiation; the Frequency Division Multiple Access (FDMA) group was exposed to 835.62 MHz FDMA RF radiation; and the Code Division Multiple Access (CDMA) group was exposed to 847.74 MHz CDMA RF radiation. Rats were irradiated 4 h per day, 5 days per week over 2 years. The nominal time-averaged specific absorption rate (SAR) in the brain for the irradiated animals was 0.85 +/- 0.34 W/kg (mean +/- SD) per time-averaged watt of antenna power. Antennas were driven with a time-averaged power of 1.50 +/- 0.25 W (range). That is, the nominal time-averaged brain SAR was 1.3 +/- 0.5 W/kg (mean +/- SD). This number was an average from several measurement locations inside the brain, and it takes into account changes in animal weight and head position during irradiation. All major organs were evaluated grossly and histologically. The number of tumors, tumor types and incidence of hyperplasia for each organ were recorded. There were no significant differences among final body weights or survival days for either males or females in any group. No significant differences were found between treated and sham-exposed animals for any tumor in any organ. We conclude that chronic exposure to 835.62 MHz FDMA or 847.74 MHz CDMA RF radiation had no significant effect on the incidence of spontaneous tumors in F344 rats.

  8. 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.

  9. A Framework for Context Sensitive Risk-Based Access Control in Medical Information Systems.

    PubMed

    Choi, Donghee; Kim, Dohoon; Park, Seog

    2015-01-01

    Since the access control environment has changed and the threat of insider information leakage has come to the fore, studies on risk-based access control models that decide access permissions dynamically have been conducted vigorously. Medical information systems should protect sensitive data such as medical information from insider threat and enable dynamic access control depending on the context such as life-threatening emergencies. In this paper, we suggest an approach and framework for context sensitive risk-based access control suitable for medical information systems. This approach categorizes context information, estimating and applying risk through context- and treatment-based permission profiling and specifications by expanding the eXtensible Access Control Markup Language (XACML) to apply risk. The proposed framework supports quick responses to medical situations and prevents unnecessary insider data access through dynamic access authorization decisions in accordance with the severity of the context and treatment.

  10. Adolescent health care: improving access by school-based service.

    PubMed

    Gonzales, C; Mulligan, D; Kaufman, A; Davis, S; Hunt, K; Kalishman, N; Wallerstein, N

    1985-10-01

    Participants in this discussion of the potential of school-based health care services for adolescents included family medicine physicians, school health coordinators, a school nurse, and a community worker. It was noted that health care for adolescents tends to be either inaccessible or underutilized, largely because of a lack of sensitivity to adolescent culture and values. An ideal service for adolescents would offer immediate services for crises, strict confidentiality, ready access to prescribed medications, a sliding-scale scheme, and a staff that is tolerant of divergent values and life-styles. School-based pilot adolescent clinics have been established by the University of New Mexico's Department of Family, Community, and Emergency Medicine to test the community-oriented health care model. On-site clinics provide urgent medical care, family planning, pregnancy testing, psychological counseling, alcohol and drug counseling, and classroom health education. Experience with these programs has demonstrated the necessity for an alliance among the health team and the school administration, parents, and students. Financial, ethical, and political factors can serve as constraints to school-based programs. In some cases, school administrators have been resistant to the provision of contraception to students on school grounds and parents have been unwilling to accept the adolescent's right to confidentiality. These problems in part stem from having 2 separate systems, each with its own values, orientation, and responsibilities, housed in 1 facility. In addition, there have been problems generating awareness of the school-based clinic among students. Health education theater groups, peer counseling, and student-run community services have been effective, however, in increasing student participation. It has been helpful to mold clinic services to meet the needs identified by teenagers themselves. There is an interest not only in curative services, but in services focused

  11. Enhanced Access Polynomial Based Self-healing Key Distribution

    NASA Astrophysics Data System (ADS)

    Dutta, Ratna; Mukhopadhyay, Sourav; Dowling, Tom

    A fundamental concern of any secure group communication system is that of key management. Wireless environments create new key management problems and requirements to solve these problems. One such core requirement in these emerging networks is that of self-healing. In systems where users can be offline and miss updates self healing allows a user to recover lost keys and get back into the secure communication without putting extra burden on the group manager. Clearly self healing must be only available to authorized users and this creates more challenges in that we must ensure unauthorized or revoked users cannot, themselves or by means of collusion, avail of self healing. To this end we enhance the one-way key chain based self-healing key distribution of Dutta et al. by introducing a collusion resistance property between the revoked users and the newly joined users. Our scheme is based on the concept of access polynomials. These can be loosely thought of as white lists of authorized users as opposed to the more widely used revocation polynomials or black lists of revoked users. We also allow each user a pre-arranged life cycle distributed by the group manager. Our scheme provides better efficiency in terms of storage, and the communication and computation costs do not increase as the number of sessions grows as compared to most current schemes. We analyze our scheme in an appropriate security model and prove that the proposed scheme is computationally secure and not only achieving forward and backward secrecy, but also resisting collusion between the new joined users and the revoked users. Unlike most existing schemes the new scheme allows temporary revocation. Also unlike existing schemes, our construction does not collapse if the number of revoked users crosses a threshold value. This feature increases resilience against revocation based denial of service (DOS) attacks and thus improves availability of communication channel.

  12. An energy-efficient and elastic optical multiple access system based on coherent interleaved frequency division multiple access.

    PubMed

    Yoshida, Yuki; Maruta, Akihiro; Ishii, Kenji; Akiyama, Yuji; Yoshida, Tsuyoshi; Suzuki, Naoki; Koguchi, Kazuumi; Nakagawa, Junichi; Mizuochi, Takashi; Kitayama, Ken-ichi

    2013-05-20

    This paper proposes a novel bandwidth-elastic and energy-efficient passive optical network (PON) based on the coherent interleaved frequency division multiple access (IFDMA) scheme. We experimentally demonstrate the coherent IFDMA-PON uplink transmission up-to 30 Gbps over a 30 km standard single-mode fiber with 2 × optical network units (ONUs). A low-complexity digital carrier synchronization technique enables multiple access of the ONUs on the basis of 78.1 MHz narrow band orthogonal subcarriers without any guard-bands.

  13. Non-orthogonal optical multicarrier access based on filter bank and SCMA.

    PubMed

    Liu, Bo; Zhang, Lijia; Xin, Xiangjun

    2015-10-19

    This paper proposes a novel non-orthogonal optical multicarrier access system based on filter bank and sparse code multiple access (SCMA). It offers released frequency offset and better spectral efficiency for multicarrier access. An experiment of 73.68 Gb/s filter bank-based multicarrier (FBMC) SCMA system with 60 km single mode fiber link is performed to demonstrate the feasibility. The comparison between fast Fourier transform (FFT) based multicarrier and the proposed scheme is also investigated in the experiment.

  14. Safety management of Ethernet broadband access based on VLAN aggregation

    NASA Astrophysics Data System (ADS)

    Wang, Li

    2004-04-01

    With broadband access network development, the Ethernet technology is more and more applied access network now. It is different from the private network -LAN. The differences lie in four points: customer management, safety management, service management and count-fee management. This paper mainly discusses the safety management related questions. Safety management means that the access network must secure the customer data safety, isolate the broad message which brings the customer private information, such as ARP, DHCP, and protect key equipment from attack. Virtue LAN (VLAN) technology can restrict network broadcast flow. We can config each customer port with a VLAN, so each customer is isolated with others. The IP address bound with VLAN ID can be routed rightly. But this technology brings another question: IP address shortage. VLAN aggregation technology can solve this problem well. Such a mechanism provides several advantages over traditional IPv4 addressing architectures employed in large switched LANs today. With VLAN aggregation technology, we introduce the notion of sub-VLANs and super-VLANs, a much more optimal approach to IP addressing can be realized. This paper will expatiate the VLAN aggregation model and its implementation in Ethernet access network. It is obvious that the customers in different sub-VLANs can not communication to each other because the ARP packet is isolated. Proxy ARP can enable the communication among them. This paper will also expatiate the proxy ARP model and its implementation in Ethernet access network.

  15. Accessing integrated genomic data using GenoBase: A tutorial, Part 1

    SciTech Connect

    Overbeek, R.; Price, M.

    1993-01-01

    GenoBase integrates genomic information from many existing databases, offering convenient access to the curated data. This document is the first part of a two-part tutorial on how to use GenoBase for accessing integrated genomic data.

  16. Browser-Based Accessibility Evaluation Tools for Beginners

    ERIC Educational Resources Information Center

    McHale, Nina

    2011-01-01

    There are hundreds of Web accessibility software options out in the world that serve many different functions. Not surprisingly, many of them are designed for users with a wide range of abilities, with the intent of making the use of computers and the Internet easier for both work and entertainment. There are, however, numerous products available…

  17. Scalable Machine Learning Framework for Behavior-Based Access Control

    DTIC Science & Technology

    2013-08-01

    rules. Dynamic events, such as subversion of credentials (e.g., theft of a Smart Card [3] such as the Common Access Card [4]) or changes in actor... Smart card handbook. Wiley, 2010. [4] DoD ID Card Reference Center, 2013, http://www.cac.mil/ [5] Hearst, Marti A., et al. "Support vector machines

  18. Distributed policy based access to networked heterogeneous ISR data sources

    NASA Astrophysics Data System (ADS)

    Bent, G.; Vyvyan, D.; Wood, David; Zerfos, Petros; Calo, Seraphin

    2010-04-01

    Within a coalition environment, ad hoc Communities of Interest (CoI's) come together, perhaps for only a short time, with different sensors, sensor platforms, data fusion elements, and networks to conduct a task (or set of tasks) with different coalition members taking different roles. In such a coalition, each organization will have its own inherent restrictions on how it will interact with the others. These are usually stated as a set of policies, including security and privacy policies. The capability that we want to enable for a coalition operation is to provide access to information from any coalition partner in conformance with the policies of all. One of the challenges in supporting such ad-hoc coalition operations is that of providing efficient access to distributed sources of data, where the applications requiring the data do not have knowledge of the location of the data within the network. To address this challenge the International Technology Alliance (ITA) program has been developing the concept of a Dynamic Distributed Federated Database (DDFD), also know as a Gaian Database. This type of database provides a means for accessing data across a network of distributed heterogeneous data sources where access to the information is controlled by a mixture of local and global policies. We describe how a network of disparate ISR elements can be expressed as a DDFD and how this approach enables sensor and other information sources to be discovered autonomously or semi-autonomously and/or combined, fused formally defined local and global policies.

  19. VIEWCACHE: An incremental pointer-based access method for autonomous interoperable databases

    NASA Technical Reports Server (NTRS)

    Roussopoulos, N.; Sellis, Timos

    1993-01-01

    One of the biggest problems facing NASA today is to provide scientists efficient access to a large number of distributed databases. Our pointer-based incremental data base access method, VIEWCACHE, provides such an interface for accessing distributed datasets and directories. VIEWCACHE allows database browsing and search performing inter-database cross-referencing with no actual data movement between database sites. This organization and processing is especially suitable for managing Astrophysics databases which are physically distributed all over the world. Once the search is complete, the set of collected pointers pointing to the desired data are cached. VIEWCACHE includes spatial access methods for accessing image datasets, which provide much easier query formulation by referring directly to the image and very efficient search for objects contained within a two-dimensional window. We will develop and optimize a VIEWCACHE External Gateway Access to database management systems to facilitate database search.

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

    PubMed

    Lee, Tong H; Yoo, Sun K

    2008-04-01

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

  1. An Efficient Circulant MIMO Equalizer for CDMA Downlink: Algorithm and VLSI Architecture

    NASA Astrophysics Data System (ADS)

    Guo, Yuanbin; Zhang, Jianzhong(Charlie); McCain, Dennis; Cavallaro, Joseph R.

    2006-12-01

    We present an efficient circulant approximation-based MIMO equalizer architecture for the CDMA downlink. This reduces the direct matrix inverse (DMI) of size[InlineEquation not available: see fulltext.] with[InlineEquation not available: see fulltext.] complexity to some FFT operations with[InlineEquation not available: see fulltext.] complexity and the inverse of some[InlineEquation not available: see fulltext.] submatrices. We then propose parallel and pipelined VLSI architectures with Hermitian optimization and reduced-state FFT for further complexity optimization. Generic VLSI architectures are derived for the[InlineEquation not available: see fulltext.] high-order receiver from partitioned[InlineEquation not available: see fulltext.] submatrices. This leads to more parallel VLSI design with[InlineEquation not available: see fulltext.] further complexity reduction. Comparative study with both the conjugate-gradient and DMI algorithms shows very promising performance/complexity tradeoff. VLSI design space in terms of area/time efficiency is explored extensively for layered parallelism and pipelining with a Catapult C high-level-synthesis methodology.

  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. A contextual role-based access control authorization model for electronic patient record.

    PubMed

    Motta, Gustavo H M B; Furuie, Sergio S

    2003-09-01

    The design of proper models for authorization and access control for electronic patient record (EPR) is essential to a wide scale use of EPR in large health organizations. In this paper, we propose a contextual role-based access control authorization model aiming to increase the patient privacy and the confidentiality of patient data, whereas being flexible enough to consider specific cases. This model regulates user's access to EPR based on organizational roles. It supports a role-tree hierarchy with authorization inheritance; positive and negative authorizations; static and dynamic separation of duties based on weak and strong role conflicts. Contextual authorizations use environmental information available at access time, like user/patient relationship, in order to decide whether a user is allowed to access an EPR resource. This enables the specification of a more flexible and precise authorization policy, where permission is granted or denied according to the right and the need of the user to carry out a particular job function.

  4. Privacy and Access Control for IHE-Based Systems

    NASA Astrophysics Data System (ADS)

    Katt, Basel; Breu, Ruth; Hafner, Micahel; Schabetsberger, Thomas; Mair, Richard; Wozak, Florian

    Electronic Health Record (EHR) is the heart element of any e-health system, which aims at improving the quality and efficiency of healthcare through the use of information and communication technologies. The sensitivity of the data contained in the health record poses a great challenge to security. In this paper we propose a security architecture for EHR systems that are conform with IHE profiles. In this architecture we are tackling the problems of access control and privacy. Furthermore, a prototypical implementation of the proposed model is presented.

  5. Access to Comprehensive School-Based Health Services for Children and Youth, 1995-1998.

    ERIC Educational Resources Information Center

    Access, 1998

    1998-01-01

    This document consists of 11 consecutive issues of the newsletter "Access," published across a four-year period. "Access" presents information on public policy and research of interest to school-based health programs (SBHC) for children and youth. The major topics covered by the newsletters are as follows: (1) a conference,…

  6. Developing Guidelines for Evaluating the Adaptation of Accessible Web-Based Learning Materials

    ERIC Educational Resources Information Center

    Radovan, Marko; Perdih, Mojca

    2016-01-01

    E-learning is a rapidly developing form of education. One of the key characteristics of e-learning is flexibility, which enables easier access to knowledge for everyone. Information and communications technology (ICT), which is e-learning's main component, enables alternative means of accessing the web-based learning materials that comprise the…

  7. Differences in Access to Care among Students Using School-Based Health Centers

    ERIC Educational Resources Information Center

    Parasuraman, Sarika Rane; Shi, Leiyu

    2015-01-01

    Health care reform has changed the landscape for the nation's health safety net, and school-based health centers (SBHCs) remain an important part of this system. However, few large-scale studies have been conducted to assess their impact on access to care. This study investigated differences in access among a nationally representative sample of…

  8. VIEWCACHE: An incremental pointer-based access method for autonomous interoperable databases

    NASA Technical Reports Server (NTRS)

    Roussopoulos, N.; Sellis, Timos

    1992-01-01

    One of biggest problems facing NASA today is to provide scientists efficient access to a large number of distributed databases. Our pointer-based incremental database access method, VIEWCACHE, provides such an interface for accessing distributed data sets and directories. VIEWCACHE allows database browsing and search performing inter-database cross-referencing with no actual data movement between database sites. This organization and processing is especially suitable for managing Astrophysics databases which are physically distributed all over the world. Once the search is complete, the set of collected pointers pointing to the desired data are cached. VIEWCACHE includes spatial access methods for accessing image data sets, which provide much easier query formulation by referring directly to the image and very efficient search for objects contained within a two-dimensional window. We will develop and optimize a VIEWCACHE External Gateway Access to database management systems to facilitate distributed database search.

  9. Discrete Kalman Filter based Sensor Fusion for Robust Accessibility Interfaces

    NASA Astrophysics Data System (ADS)

    Ghersi, I.; Mariño, M.; Miralles, M. T.

    2016-04-01

    Human-machine interfaces have evolved, benefiting from the growing access to devices with superior, embedded signal-processing capabilities, as well as through new sensors that allow the estimation of movements and gestures, resulting in increasingly intuitive interfaces. In this context, sensor fusion for the estimation of the spatial orientation of body segments allows to achieve more robust solutions, overcoming specific disadvantages derived from the use of isolated sensors, such as the sensitivity of magnetic-field sensors to external influences, when used in uncontrolled environments. In this work, a method for the combination of image-processing data and angular-velocity registers from a 3D MEMS gyroscope, through a Discrete-time Kalman Filter, is proposed and deployed as an alternate user interface for mobile devices, in which an on-screen pointer is controlled with head movements. Results concerning general performance of the method are presented, as well as a comparative analysis, under a dedicated test application, with results from a previous version of this system, in which the relative-orientation information was acquired directly from MEMS sensors (3D magnetometer-accelerometer). These results show an improved response for this new version of the pointer, both in terms of precision and response time, while keeping many of the benefits that were highlighted for its predecessor, giving place to a complementary method for signal acquisition that can be used as an alternative-input device, as well as for accessibility solutions.

  10. Materials selection for oxide-based resistive random access memories

    SciTech Connect

    Guo, Yuzheng; Robertson, John

    2014-12-01

    The energies of atomic processes in resistive random access memories (RRAMs) are calculated for four typical oxides, HfO{sub 2}, TiO{sub 2}, Ta{sub 2}O{sub 5}, and Al{sub 2}O{sub 3}, to define a materials selection process. O vacancies have the lowest defect formation energy in the O-poor limit and dominate the processes. A band diagram defines the operating Fermi energy and O chemical potential range. It is shown how the scavenger metal can be used to vary the O vacancy formation energy, via controlling the O chemical potential, and the mean Fermi energy. The high endurance of Ta{sub 2}O{sub 5} RRAM is related to its more stable amorphous phase and the adaptive lattice rearrangements of its O vacancy.

  11. 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.

  12. ACCESSING FEDERAL DATA BASES FOR CONTAMINATED SITE CLEAN-UP TECHNOLOGIES

    EPA Science Inventory

    The Federal Remediation Technologies Roundtable (Roundtable) eveloped this publication to provide information on accessing Federal data bases that contain data on innovative remediation technologies. The Roundtable includes representatives from the Department of Defense (DoD), En...

  13. Access and Completion of a Web-Based Treatment in a Population-Based Sample of Tornado-Affected Adolescents

    PubMed Central

    Price, Matthew; Yuen, Erica; Davidson, Tatiana M.; Hubel, Grace; Ruggiero, Kenneth J.

    2015-01-01

    Although web-based treatments have significant potential to assess and treat difficult to reach populations, such as trauma-exposed adolescents, the extent that such treatments are accessed and used is unclear. The present study evaluated the proportion of adolescents who accessed and completed a web-based treatment for post-disaster mental health symptoms. Correlates of access and completion were examined. A sample of 2,000 adolescents living in tornado-affected communities was assessed via structured telephone interview and invited to a web-based treatment. The modular treatment addressed symptoms of PTSD, depression, and alcohol and tobacco use. Participants were randomized to experimental or control conditions after accessing the site. Overall access for the intervention was 35.8%. Module completion for those who accessed ranged from 52.8% to 85.6%. Adolescents with parents who used the Internet to obtain health-related information were more likely to access the treatment. Adolescent males were less likely to access the treatment. Future work is needed to identify strategies to further increase the reach of web-based treatments to provide clinical services in a post-disaster context. PMID:25622071

  14. Access and completion of a Web-based treatment in a population-based sample of tornado-affected adolescents.

    PubMed

    Price, Matthew; Yuen, Erica K; Davidson, Tatiana M; Hubel, Grace; Ruggiero, Kenneth J

    2015-08-01

    Although Web-based treatments have significant potential to assess and treat difficult-to-reach populations, such as trauma-exposed adolescents, the extent that such treatments are accessed and used is unclear. The present study evaluated the proportion of adolescents who accessed and completed a Web-based treatment for postdisaster mental health symptoms. Correlates of access and completion were examined. A sample of 2,000 adolescents living in tornado-affected communities was assessed via structured telephone interview and invited to a Web-based treatment. The modular treatment addressed symptoms of posttraumatic stress disorder, depression, and alcohol and tobacco use. Participants were randomized to experimental or control conditions after accessing the site. Overall access for the intervention was 35.8%. Module completion for those who accessed ranged from 52.8% to 85.6%. Adolescents with parents who used the Internet to obtain health-related information were more likely to access the treatment. Adolescent males were less likely to access the treatment. Future work is needed to identify strategies to further increase the reach of Web-based treatments to provide clinical services in a postdisaster context.

  15. Accessing technical data bases using STDS: A collection of scenarios

    NASA Technical Reports Server (NTRS)

    Hardgrave, W. T.

    1975-01-01

    A line by line description is given of sessions using the set-theoretic data system (STDS) to interact with technical data bases. The data bases contain data from actual applications at NASA Langley Research Center. The report is meant to be a tutorial document that accompanies set processing in a network environment.

  16. 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.

  17. Gene expression does not change significantly in C3H 10T(1/2) cells after exposure to 847.74 CDMA or 835.62 FDMA radiofrequency radiation.

    PubMed

    Whitehead, T D; Moros, E G; Brownstein, B H; Roti Roti, J L

    2006-06-01

    In vitro experiments with C3H 10T(1/2) mouse cells were performed to determine whether Frequency Division Multiple Access (FDMA) or Code Division Multiple Access (CDMA) modulated radiofrequency (RF) radiations induce changes in gene expression. After the cells were exposed to either modulation for 24 h at a specific absorption rate (SAR) of 5 W/ kg, RNA was extracted from both exposed and sham-exposed cells for gene expression analysis. As a positive control, cells were exposed to 0.68 Gy of X rays and gene expression was evaluated 4 h after exposure. Gene expression was evaluated using the Affymetrix U74Av2 GeneChip to detect changes in mRNA levels. Each exposure condition was repeated three times. The GeneChip data were analyzed using a two-tailed t test, and the expected number of false positives was estimated from t tests on 20 permutations of the six sham RF-field-exposed samples. For the X-ray-treated samples, there were more than 90 probe sets with expression changes greater than 1.3-fold beyond the number of expected false positives. Approximately one-third of these genes had previously been reported in the literature as being responsive to radiation. In contrast, for both CDMA and FDMA radiation, the number of probe sets with an expression change greater than 1.3-fold was less than or equal to the expected number of false positives. Thus the 24-h exposures to FDMA or CDMA RF radiation at 5 W/kg had no statistically significant effect on gene expression.

  18. 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.

  19. Mitigation of timing offset effect in IM/DD based OFDMA-PON uplink multiple access.

    PubMed

    Jung, Sun-Young; Jung, Sang-Min; Park, Hyoung-Joon; Han, Sang-Kook

    2015-06-01

    In orthogonal frequency division multiple access based passive optical network (OFDMA-PON) uplink, synchronization between optical network units (ONUs) is very important to maintain orthogonality. The synchronization among uplink signals is considered as one of the main challenges in OFDMA-PON due to optical path difference. In this paper, the performance degradation according to timing offset between ONUs is experimentally analyzed. And we propose and demonstrate timing offset effect reduction in asynchronous multiple access by using CP extension and filter bank based multicarrier (FBMC) system in intensity modulation/direct detection (IM/DD) based OFDMA-PON uplink transmission.

  20. Spatiotemporal access model based on reputation for the sensing layer of the IoT.

    PubMed

    Guo, Yunchuan; Yin, Lihua; Li, Chao; Qian, Junyan

    2014-01-01

    Access control is a key technology in providing security in the Internet of Things (IoT). The mainstream security approach proposed for the sensing layer of the IoT concentrates only on authentication while ignoring the more general models. Unreliable communications and resource constraints make the traditional access control techniques barely meet the requirements of the sensing layer of the IoT. In this paper, we propose a model that combines space and time with reputation to control access to the information within the sensing layer of the IoT. This model is called spatiotemporal access control based on reputation (STRAC). STRAC uses a lattice-based approach to decrease the size of policy bases. To solve the problem caused by unreliable communications, we propose both nondeterministic authorizations and stochastic authorizations. To more precisely manage the reputation of nodes, we propose two new mechanisms to update the reputation of nodes. These new approaches are the authority-based update mechanism (AUM) and the election-based update mechanism (EUM). We show how the model checker UPPAAL can be used to analyze the spatiotemporal access control model of an application. Finally, we also implement a prototype system to demonstrate the efficiency of our model.

  1. Spatiotemporal Access Model Based on Reputation for the Sensing Layer of the IoT

    PubMed Central

    Guo, Yunchuan; Yin, Lihua; Li, Chao

    2014-01-01

    Access control is a key technology in providing security in the Internet of Things (IoT). The mainstream security approach proposed for the sensing layer of the IoT concentrates only on authentication while ignoring the more general models. Unreliable communications and resource constraints make the traditional access control techniques barely meet the requirements of the sensing layer of the IoT. In this paper, we propose a model that combines space and time with reputation to control access to the information within the sensing layer of the IoT. This model is called spatiotemporal access control based on reputation (STRAC). STRAC uses a lattice-based approach to decrease the size of policy bases. To solve the problem caused by unreliable communications, we propose both nondeterministic authorizations and stochastic authorizations. To more precisely manage the reputation of nodes, we propose two new mechanisms to update the reputation of nodes. These new approaches are the authority-based update mechanism (AUM) and the election-based update mechanism (EUM). We show how the model checker UPPAAL can be used to analyze the spatiotemporal access control model of an application. Finally, we also implement a prototype system to demonstrate the efficiency of our model. PMID:25177731

  2. A multiple access communication network based on adaptive arrays

    NASA Technical Reports Server (NTRS)

    Zohar, S.

    1981-01-01

    A single frequency communication system is considered consisting of K possibly moving users distributed in space simultaneously communicating with a central station equipped with a computationally adapted array of n = or K antennas. Such a configuration could result if K spacecraft were to be simultaneously tracked by a single DSN complex consisting of an n antennas array. The array employs K sets of n weights to segregate the signals received from the K users. The weights are determined by direct computation based on known position information of the K users. Currently known techniques require (for n = K) about (4/3)K to the 4th power computer operations (multiply and add) to perform such computations. A technique that accomplishes this same goal in 8 K to the 3rd power operations, yielding a reduction by a factor K/6, was developed.

  3. The academic, economic and societal impacts of Open Access: an evidence-based review

    PubMed Central

    Tennant, Jonathan P.; Waldner, François; Jacques, Damien C.; Masuzzo, Paola; Collister, Lauren B.; Hartgerink, Chris. H. J.

    2016-01-01

    Ongoing debates surrounding Open Access to the scholarly literature are multifaceted and complicated by disparate and often polarised viewpoints from engaged stakeholders. At the current stage, Open Access has become such a global issue that it is critical for all involved in scholarly publishing, including policymakers, publishers, research funders, governments, learned societies, librarians, and academic communities, to be well-informed on the history, benefits, and pitfalls of Open Access. In spite of this, there is a general lack of consensus regarding the potential pros and cons of Open Access at multiple levels. This review aims to be a resource for current knowledge on the impacts of Open Access by synthesizing important research in three major areas: academic, economic and societal. While there is clearly much scope for additional research, several key trends are identified, including a broad citation advantage for researchers who publish openly, as well as additional benefits to the non-academic dissemination of their work. The economic impact of Open Access is less well-understood, although it is clear that access to the research literature is key for innovative enterprises, and a range of governmental and non-governmental services. Furthermore, Open Access has the potential to save both publishers and research funders considerable amounts of financial resources, and can provide some economic benefits to traditionally subscription-based journals. The societal impact of Open Access is strong, in particular for advancing citizen science initiatives, and leveling the playing field for researchers in developing countries. Open Access supersedes all potential alternative modes of access to the scholarly literature through enabling unrestricted re-use, and long-term stability independent of financial constraints of traditional publishers that impede knowledge sharing. However, Open Access has the potential to become unsustainable for research communities if

  4. The academic, economic and societal impacts of Open Access: an evidence-based review.

    PubMed

    Tennant, Jonathan P; Waldner, François; Jacques, Damien C; Masuzzo, Paola; Collister, Lauren B; Hartgerink, Chris H J

    2016-01-01

    Ongoing debates surrounding Open Access to the scholarly literature are multifaceted and complicated by disparate and often polarised viewpoints from engaged stakeholders. At the current stage, Open Access has become such a global issue that it is critical for all involved in scholarly publishing, including policymakers, publishers, research funders, governments, learned societies, librarians, and academic communities, to be well-informed on the history, benefits, and pitfalls of Open Access. In spite of this, there is a general lack of consensus regarding the potential pros and cons of Open Access at multiple levels. This review aims to be a resource for current knowledge on the impacts of Open Access by synthesizing important research in three major areas: academic, economic and societal. While there is clearly much scope for additional research, several key trends are identified, including a broad citation advantage for researchers who publish openly, as well as additional benefits to the non-academic dissemination of their work. The economic impact of Open Access is less well-understood, although it is clear that access to the research literature is key for innovative enterprises, and a range of governmental and non-governmental services. Furthermore, Open Access has the potential to save both publishers and research funders considerable amounts of financial resources, and can provide some economic benefits to traditionally subscription-based journals. The societal impact of Open Access is strong, in particular for advancing citizen science initiatives, and leveling the playing field for researchers in developing countries. Open Access supersedes all potential alternative modes of access to the scholarly literature through enabling unrestricted re-use, and long-term stability independent of financial constraints of traditional publishers that impede knowledge sharing. However, Open Access has the potential to become unsustainable for research communities if

  5. Web-Based Online Public Access Catalogues of IIT Libraries in India: An Evaluative Study

    ERIC Educational Resources Information Center

    Madhusudhan, Margam; Aggarwal, Shalini

    2011-01-01

    Purpose: The purpose of the paper is to examine the various features and components of web-based online public access catalogues (OPACs) of IIT libraries in India with the help of a specially designed evaluation checklist. Design/methodology/approach: The various features of the web-based OPACs in six IIT libraries (IIT Delhi, IIT Bombay, IIT…

  6. Provider Perspectives on School-Based Mental Health for Urban Minority Youth: Access and Services

    ERIC Educational Resources Information Center

    Gamble, Brandon E.; Lambros, Katina M.

    2014-01-01

    This article provides results from a qualitative study on the efforts of school-based mental health providers (SBMHPs) who serve students in urban, suburban, and ethnically diverse settings to help families access quality mental health services. School-based mental health plays a key role in the provision of direct and indirect intervention…

  7. Area-Based Partnerships in Rural Poland: The Post-Accession Experience

    ERIC Educational Resources Information Center

    Furmankiewicz, Marek; Thompson, Nicola; Zielinska, Marta

    2010-01-01

    The paper examines the characteristics of area-based partnerships in rural Poland. It is based on the study of partnerships created after the accession to the European Union in 2004. Partnership structures have been rapidly adopted in rural Poland due to opportunities provided by the LEADER+ Pilot Programme. However, the research showed that…

  8. Efficient Information Access for Location-Based Services in Mobile Environments

    ERIC Educational Resources Information Center

    Lee, Chi Keung

    2009-01-01

    The demand for pervasive access of location-related information (e.g., local traffic, restaurant locations, navigation maps, weather conditions, pollution index, etc.) fosters a tremendous application base of "Location Based Services (LBSs)". Without loss of generality, we model location-related information as "spatial objects" and the accesses…

  9. NCBI2RDF: enabling full RDF-based access to NCBI databases.

    PubMed

    Anguita, Alberto; García-Remesal, Miguel; de la Iglesia, Diana; Maojo, Victor

    2013-01-01

    RDF has become the standard technology for enabling interoperability among heterogeneous biomedical databases. The NCBI provides access to a large set of life sciences databases through a common interface called Entrez. However, the latter does not provide RDF-based access to such databases, and, therefore, they cannot be integrated with other RDF-compliant databases and accessed via SPARQL query interfaces. This paper presents the NCBI2RDF system, aimed at providing RDF-based access to the complete NCBI data repository. This API creates a virtual endpoint for servicing SPARQL queries over different NCBI repositories and presenting to users the query results in SPARQL results format, thus enabling this data to be integrated and/or stored with other RDF-compliant repositories. SPARQL queries are dynamically resolved, decomposed, and forwarded to the NCBI-provided E-utilities programmatic interface to access the NCBI data. Furthermore, we show how our approach increases the expressiveness of the native NCBI querying system, allowing several databases to be accessed simultaneously. This feature significantly boosts productivity when working with complex queries and saves time and effort to biomedical researchers. Our approach has been validated with a large number of SPARQL queries, thus proving its reliability and enhanced capabilities in biomedical environments.

  10. Increasing Access to Cost Effective Home-Based Rehabilitation for Rural Veteran Stroke Survivors

    PubMed Central

    Housley, SN; Garlow, AR; Ducote, K; Howard, A; Thomas, T; Wu, D; Richards, K; Butler, AJ

    2016-01-01

    Introduction An estimated 750,000 Americans experience a stroke annually. Most stroke survivors require rehabilitation. Limited access to rehabilitation facilities has a pronounced burden on functional outcomes and quality of life. Robotic devices deliver reproducible therapy without the need for real-time human oversight. This study examined the efficacy of using home-based, telerobotic-assisted devices (Hand and Foot Mentor: HM and FM) to improve functional ability and reduce depression symptoms, while improving access and cost savings associated with rehabilitation. Methods Twenty stroke survivors performed three months of home-based rehabilitation using a robotic device, while a therapist remotely monitored progress. Baseline and end of treatment function and depression symptoms were assessed. Satisfaction with the device and access to therapy were determined using qualitative surveys. Cost analysis was performed to compare home-based, robotic-assisted therapy to clinic-based physical therapy. Results Compared to baseline, significant improvement in upper extremity function (30.06%, p= 0.046), clinically significant benefits in gait speed (29.03%), moderate improvement in depressive symptoms (28.44%) and modest improvement in distance walked (30.2%) were observed. Participants indicated satisfaction with the device. Home-based robot therapy expanded access to post-stroke rehabilitation for 35% of the people no longer receiving formal services and increased daily access for the remaining 65%, with a cost savings of $2,352 (64.97%) compared to clinic-based therapy. Conclusion Stroke survivors made significant clinically meaningful improvements in the use of their impaired extremities using a robotic device in the home. Home-based, robotic therapy reduced costs, while expanding access to a rehabilitation modality for people who would not otherwise have received care. PMID:28018979

  11. An Action-Based Fine-Grained Access Control Mechanism for Structured Documents and Its Application

    PubMed Central

    Su, Mang; Li, Fenghua; Tang, Zhi; Yu, Yinyan; Zhou, Bo

    2014-01-01

    This paper presents an action-based fine-grained access control mechanism for structured documents. Firstly, we define a describing model for structured documents and analyze the application scenarios. The describing model could support the permission management on chapters, pages, sections, words, and pictures of structured documents. Secondly, based on the action-based access control (ABAC) model, we propose a fine-grained control protocol for structured documents by introducing temporal state and environmental state. The protocol covering different stages from document creation, to permission specification and usage control are given by using the Z-notation. Finally, we give the implementation of our mechanism and make the comparisons between the existing methods and our mechanism. The result shows that our mechanism could provide the better solution of fine-grained access control for structured documents in complicated networks. Moreover, it is more flexible and practical. PMID:25136651

  12. Trust-Based Access Control Model from Sociological Approach in Dynamic Online Social Network Environment

    PubMed Central

    Kim, Seungjoo

    2014-01-01

    There has been an explosive increase in the population of the OSN (online social network) in recent years. The OSN provides users with many opportunities to communicate among friends and family. Further, it facilitates developing new relationships with previously unknown people having similar beliefs or interests. However, the OSN can expose users to adverse effects such as privacy breaches, the disclosing of uncontrolled material, and the disseminating of false information. Traditional access control models such as MAC, DAC, and RBAC are applied to the OSN to address these problems. However, these models are not suitable for the dynamic OSN environment because user behavior in the OSN is unpredictable and static access control imposes a burden on the users to change the access control rules individually. We propose a dynamic trust-based access control for the OSN to address the problems of the traditional static access control. Moreover, we provide novel criteria to evaluate trust factors such as sociological approach and evaluate a method to calculate the dynamic trust values. The proposed method can monitor negative behavior and modify access permission levels dynamically to prevent the indiscriminate disclosure of information. PMID:25374943

  13. Trust-based access control model from sociological approach in dynamic online social network environment.

    PubMed

    Baek, Seungsoo; Kim, Seungjoo

    2014-01-01

    There has been an explosive increase in the population of the OSN (online social network) in recent years. The OSN provides users with many opportunities to communicate among friends and family. Further, it facilitates developing new relationships with previously unknown people having similar beliefs or interests. However, the OSN can expose users to adverse effects such as privacy breaches, the disclosing of uncontrolled material, and the disseminating of false information. Traditional access control models such as MAC, DAC, and RBAC are applied to the OSN to address these problems. However, these models are not suitable for the dynamic OSN environment because user behavior in the OSN is unpredictable and static access control imposes a burden on the users to change the access control rules individually. We propose a dynamic trust-based access control for the OSN to address the problems of the traditional static access control. Moreover, we provide novel criteria to evaluate trust factors such as sociological approach and evaluate a method to calculate the dynamic trust values. The proposed method can monitor negative behavior and modify access permission levels dynamically to prevent the indiscriminate disclosure of information.

  14. Growth performance of weanling Wistar rats fed on accessions of cooked Colocasia esculenta-based diets.

    PubMed

    Lewu, Muinat N; Yakubu, Toyin M; Adebola, Patrick O; Afolayan, Anthony J

    2011-09-01

    The growth performance of weanling albino rats (Rattus norvegicus) maintained on different accessions (offspring of a variety that was planted/collected at a specific location and time but differing in certain morphologic characteristics) of cooked Colocasia esculenta (cocoyam)-based diets (UFCe1-UFCe7) for 28 days was investigated. Proximate analysis of the formulated diets revealed that UFCe3, UFCe4, UFCe5, UFCe6, and UFCe7 had significantly (P<.05) higher moisture contents than the corn starch-based diet (control). All the accession-based diets of C. esculenta had higher ash contents. Similarly, all the accessions of the C. esculenta-based diet had lower crude lipid content, whereas UFCe3-UFCe7 had significantly lower protein content. Although the crude fiber content was significantly higher in UFCe2, UFCe4, and UFCe5, only UFCe3 had significantly higher carbohydrate content among all the accessions of C. esculenta-based diets. UFCe1, UFCe2, UFCe4, UFCe5, and UFCe6 increased the average weekly water intake, feed consumption, total body weight, liver-body weight ratio, and kidney-body weight ratio of the animals; UFCe3 and UFCe7 decreased these measures. Overall, UFCe1, UFCe2, UFCe4, UFCe5, and UFCe6 are recommended as diets with promise to enhance growth performance in the animals.

  15. Global Location-Based Access to Web Applications Using Atom-Based Automatic Update

    NASA Astrophysics Data System (ADS)

    Singh, Kulwinder; Park, Dong-Won

    We propose an architecture which enables people to enquire about information available in directory services by voice using regular phones. We implement a Virtual User Agent (VUA) which mediates between the human user and a business directory service. The system enables the user to search for the nearest clinic, gas station by price, motel by price, food / coffee, banks/ATM etc. and fix an appointment, or automatically establish a call between the user and the business party if the user prefers. The user also has an option to receive appointment confirmation by phone, SMS, or e-mail. The VUA is accessible by a toll free DID (Direct Inward Dialing) number using a phone by anyone, anywhere, anytime. We use the Euclidean formula for distance measurement. Since, shorter geodesic distances (on the Earth’s surface) correspond to shorter Euclidean distances (measured by a straight line through the Earth). Our proposed architecture uses Atom XML syndication format protocol for data integration, VoiceXML for creating the voice user interface (VUI) and CCXML for controlling the call components. We also provide an efficient algorithm for parsing Atom feeds which provide data to the system. Moreover, we describe a cost-effective way for providing global access to the VUA based on Asterisk (an open source IP-PBX). We also provide some information on how our system can be integrated with GPS for locating the user coordinates and therefore efficiently and spontaneously enhancing the system response. Additionally, the system has a mechanism for validating the phone numbers in its database, and it updates the number and other information such as daily price of gas, motel etc. automatically using an Atom-based feed. Currently, the commercial directory services (Example 411) do not have facilities to update the listing in the database automatically, so that why callers most of the times get out-of-date phone numbers or other information. Our system can be integrated very easily

  16. A Novel Dynamic Spectrum Access Framework Based on Reinforcement Learning for Cognitive Radio Sensor Networks.

    PubMed

    Lin, Yun; Wang, Chao; Wang, Jiaxing; Dou, Zheng

    2016-10-12

    Cognitive radio sensor networks are one of the kinds of application where cognitive techniques can be adopted and have many potential applications, challenges and future research trends. According to the research surveys, dynamic spectrum access is an important and necessary technology for future cognitive sensor networks. Traditional methods of dynamic spectrum access are based on spectrum holes and they have some drawbacks, such as low accessibility and high interruptibility, which negatively affect the transmission performance of the sensor networks. To address this problem, in this paper a new initialization mechanism is proposed to establish a communication link and set up a sensor network without adopting spectrum holes to convey control information. Specifically, firstly a transmission channel model for analyzing the maximum accessible capacity for three different polices in a fading environment is discussed. Secondly, a hybrid spectrum access algorithm based on a reinforcement learning model is proposed for the power allocation problem of both the transmission channel and the control channel. Finally, extensive simulations have been conducted and simulation results show that this new algorithm provides a significant improvement in terms of the tradeoff between the control channel reliability and the efficiency of the transmission channel.

  17. A Novel Dynamic Spectrum Access Framework Based on Reinforcement Learning for Cognitive Radio Sensor Networks

    PubMed Central

    Lin, Yun; Wang, Chao; Wang, Jiaxing; Dou, Zheng

    2016-01-01

    Cognitive radio sensor networks are one of the kinds of application where cognitive techniques can be adopted and have many potential applications, challenges and future research trends. According to the research surveys, dynamic spectrum access is an important and necessary technology for future cognitive sensor networks. Traditional methods of dynamic spectrum access are based on spectrum holes and they have some drawbacks, such as low accessibility and high interruptibility, which negatively affect the transmission performance of the sensor networks. To address this problem, in this paper a new initialization mechanism is proposed to establish a communication link and set up a sensor network without adopting spectrum holes to convey control information. Specifically, firstly a transmission channel model for analyzing the maximum accessible capacity for three different polices in a fading environment is discussed. Secondly, a hybrid spectrum access algorithm based on a reinforcement learning model is proposed for the power allocation problem of both the transmission channel and the control channel. Finally, extensive simulations have been conducted and simulation results show that this new algorithm provides a significant improvement in terms of the tradeoff between the control channel reliability and the efficiency of the transmission channel. PMID:27754316

  18. RiBAC: Role Interaction Based Access Control Model for Community Computing

    NASA Astrophysics Data System (ADS)

    Jung, Youna; Masoumzadeh, Amirreza; Joshi, James B. D.; Kim, Minkoo

    Community computing is an agent-based development paradigm for ubiquitous computing systems. In a community computing system, ubiquitous services are provided by cooperation among agents. While agents cooperate, they interact with each other continuously to access data of other agents and/or to execute other agent’s actions. However, in cases of security-critical ubiquitous services such as medical or military services, an access control mechanism is necessary to prevent unauthorized access to critical data or action. In this paper, we propose a family of Role interaction Based Access Control (RiBAC) models for Community Computing, by extending the existing RBAC model to consider role interactions. As a basic model, we propose the core RiBAC model. For the convenience of management and to provide more fine-grained access control, we propose Hierarchical RiBAC (H-RiBAC), Constrained RiBAC (C-RiBAC), and Constrained Hierarchical RiBAC (CH-RiBAC) models. Finally, we extend the existing community computing framework to accommodate the specification and enforcement of RiBAC policies.

  19. 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.

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

    NASA Astrophysics Data System (ADS)

    Fu, Hongliang; Tao, Yong

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

  1. Optimal channel access protocol with multiple reception capacity

    NASA Astrophysics Data System (ADS)

    Chlamtac, Imrica; Farago, Andras

    1994-04-01

    A multiple access packet communication model is analyzed in which the users can receive packets on more than one common channel. For this type of system, a new channel access protocol is presented. We prove that under heavy homogeneous load the protocol guarantees the maximum achievable throughput among all possible protocols. The general model can be applied to different systems, according to various realizations of the logical channels. For example, in packet radio networks the channels can be realized by different carrier frequencies (FDMA) or by different codes (CDMA). The simplicity and optimality of the protocol make it attractive for practical applications.

  2. Adolescents' Willingness to Access School-Based Support for Nonsuicidal Self-Injury

    ERIC Educational Resources Information Center

    Heath, Nancy L.; Baxter, Alyssa L.; Toste, Jessica R.; McLouth, Rusty

    2010-01-01

    Nonsuicidal self-injury (NSSI) is a prevalent behaviour among youth. School is an opportune setting for intervention with this population, but it is unknown how many youth who engage in NSSI would be willing to access school-based support. The current study surveyed 7,126 middle and high school students. Those that indicated that they engaged in…

  3. The TriLab, a Novel ICT Based Triple Access Mode Laboratory Education Model

    ERIC Educational Resources Information Center

    Abdulwahed, Mahmoud; Nagy, Zoltan K.

    2011-01-01

    This paper introduces a novel model of laboratory education, namely the TriLab. The model is based on recent advances in ICT and implements a three access modes to the laboratory experience (virtual, hands-on and remote) in one software package. A review of the three modes is provided with highlights of advantages and disadvantages of each mode.…

  4. Making Web-Based Tables Accessible for Users of Screen Readers.

    ERIC Educational Resources Information Center

    Amtmann, Dagmar; Johnson, Kurt; Cook, Debbie

    2002-01-01

    Summarizes results from a study of problems blind people using screen readers and Web browsers experienced when reading tables on the World Wide Web. Explains accessibility factors including complexity of layout, use of HTML programming, features of screen-reading software, and user variables; and makes recommendations for Web-based tables,…

  5. Perceptions of Personal Well-Being among Youth Accessing Residential or Intensive Home-Based Treatment

    ERIC Educational Resources Information Center

    Preyde, Michele; Watkins, Hanna; Ashbourne, Graham; Lazure, Kelly; Carter, Jeff; Penney, Randy; White, Sara; Frensch, Karen; Cameron, Gary

    2013-01-01

    The outcomes of youth accessing residential treatment or intensive home-based treatment are varied. Understanding youth's perceptions of their well-being may inform service. The purpose of this report was to explore perceptions of youth's mental health, life satisfaction, and outlook for the future. Youth reported ongoing struggles with mental…

  6. Flexible OFDM-based access systems with intrinsic function of chromatic dispersion compensation

    NASA Astrophysics Data System (ADS)

    Konishi, Tsuyoshi; Murakawa, Takuya; Nagashima, Tomotaka; Hasegawa, Makoto; Shimizu, Satoshi; Hattori, Kuninori; Okuno, Masayuki; Mino, Shinji; Himeno, Akira; Uenohara, Hiroyuki; Wada, Naoya; Cincotti, Gabriella

    2015-12-01

    Cost-effective and tunable chromatic dispersion compensation in a fiber link are still an open issue in metro and access networks to cope with increasing costs and power consumption. Intrinsic chromatic dispersion compensation functionality of optical fractional orthogonal frequency division multiplexing is discussed and experimentally demonstrated using dispersion-tunable transmitter and receiver based on wavelength selective switching devices.

  7. Open access of evidence-based publications: the case of the orthopedic and musculoskeletal literature.

    PubMed

    Yammine, Kaissar

    2015-11-01

    The open access model, where researchers can publish their work and make it freely available to the whole medical community, is gaining ground over the traditional type of publication. However, fees are to be paid by either the authors or their institutions. The purpose of this paper is to assess the proportion and type of open access evidence-based articles in the form of systematic reviews and meta-analyses in the field of musculoskeletal disorders and orthopedic surgery. PubMed database was searched and the results showed a maximal number of hits for low back pain and total hip arthroplasty. We demonstrated that despite a 10-fold increase in the number of evidence-based publications in the past 10 years, the rate of free systematic reviews in the general biomedical literature did not change for the last two decades. In addition, the average percentage of free open access systematic reviews and meta-analyses for the commonest painful musculoskeletal conditions and orthopedic procedures was 20% and 18%, respectively. Those results were significantly lower than those of the systematic reviews and meta-analyses in the remaining biomedical research. Such findings could indicate a divergence between the efforts engaged at promoting evidence-based principles and those at disseminating evidence-based findings in the field of musculoskeletal disease and trauma. The high processing fee is thought to be a major limitation when considering open access model for publication.

  8. Rural Older Adults' Access Barriers to In-Home and Community-Based Services

    ERIC Educational Resources Information Center

    Li, Hong

    2006-01-01

    This study identified specific access barriers to seven commonly used in-home and community-based services (CBS) and examined factors that were related to barriers to these services. The data used in this study were extracted from the 1999 National Long Term Care Survey and included 283 dyads of rural older adults and their caregivers. The CBS to…

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

    PubMed

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

    2011-08-01

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

  10. Performance Analysis of a CDMA VSAT System With Convoltional and Reed-Solomon Coding

    DTIC Science & Technology

    2002-09-01

    Error Correction (FEC), Walsh codes and PN sequences are used to generate a CDMA system and FEC is used to further improve the performance. Convolutional and block coding methods are examined and the results are obtained for each different case, including concatenated use of the codes, The performance of the system is given in terms of Bit Error Rate (BER), As observed from the results, the performance is mainly affected by the number of users and the code

  11. 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.

  12. 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.

  13. Inequity of access to ACE inhibitors in Swedish heart failure patients: a register-based study

    PubMed Central

    Lindahl, Bertil; Hanning, Marianne; Westerling, Ragnar

    2016-01-01

    Background Several international studies suggest inequity in access to evidence-based heart failure (HF) care. Specifically, studies of ACE inhibitors (ACEIs) point to reduced ACEI access related to female sex, old age and socioeconomic position. Thus far, most studies have either been rather small, lacking diagnostic data, or lacking the possibility to account for several individual-based sociodemographic factors. Our aim was to investigate differences, which could reflect inequity in access to ACEIs based on sex, age, socioeconomic status or immigration status in Swedish patients with HF. Methods Individually linked register data for all Swedish adults hospitalised for HF in 2005–2010 (n=93 258) were analysed by multivariate regression models to assess the independent risk of female sex, high age, low employment status, low income level, low educational level or foreign country of birth, associated with lack of an ACEI dispensation within 1 year of hospitalisation. Adjustment for possible confounding was made for age, comorbidity, Angiotensin receptor blocker therapy, period and follow-up time. Results Analysis revealed an adjusted OR for no ACEI dispensation for women of 1.31 (95% CI 1.27 to 1.35); for the oldest patients of 2.71 (95% CI 2.53 to 2.91); and for unemployed patients of 1.59 (95% CI 1.46 to 1.73). Conclusions Access to ACEI treatment was reduced in women, older patients and unemployed patients. We conclude that access to ACEIs is inequitable among Swedish patients with HF. Future studies should include clinical data, as well as mortality outcomes in different groups. PMID:26261264

  14. Lack of access and continuity of adult health care: a national population-based survey

    PubMed Central

    Dilélio, Alitéia Santiago; Tomasi, Elaine; Thumé, Elaine; da Silveira, Denise Silva; Siqueira, Fernando Carlos Vinholes; Piccini, Roberto Xavier; Silva, Suele Manjourany; Nunes, Bruno Pereira; Facchini, Luiz Augusto

    2015-01-01

    OBJECTIVE To describe the lack of access and continuity of health care in adults. METHODS A cross-sectional population-based study was performed on a sample of 12,402 adults aged 20 to 59 years in urban areas of 100 municipalities of 23 states in the five Brazilian geopolitical regions. Barriers to the access and continuity of health care and were investigated based on receiving, needing and seeking health care (hospitalization and accident/emergency care in the last 12 months; care provided by a doctor, by other health professional or home care in the last three months). Based on the results obtained by the description of the sample, a projection is provided for adults living in Brazilian urban areas. RESULTS The highest prevalence of lack of access to health services and to provision of care by health professionals was for hospitalization (3.0%), whilst the lowest prevalence was for care provided by a doctor (1.1%). The lack of access to care provided by other health professionals was 2.0%; to accident and emergency services, 2.1%; and to home care, 2.9%. As for prevalences, the greatest absolute lack of access occurred in emergency care (more than 360,000 adults). The main reasons were structural and organizational problems, such as unavailability of hospital beds, of health professionals, of appointments for the type of care needed and charges made for care. CONCLUSIONS The universal right to health care in Brazil has not yet been achieved. These projections can help health care management in scaling the efforts needed to overcome this problem, such as expanding the infrastructure of health services and the workforce. PMID:26061454

  15. The impact of access to health services on prediabetes awareness: A population-based study.

    PubMed

    Campbell, Tonya J; Alberga, Amanda; Rosella, Laura C

    2016-12-01

    Research demonstrates that prediabetes awareness has important implications for participation in diabetes risk-reducing behaviors. We examined the impact of levels of access to health services on prediabetes awareness. In 2016, we conducted an analysis among U.S. adults with prediabetes using cross-sectional data from three cycles (2007-2008, 2009-2010, and 2011-2012) of the National Health and Nutrition Examination Survey. Participants aware and unaware of their prediabetes were classified as having full, partial, or no access to health services based on current health insurance coverage and having a routine place to go for health care. Multivariable logistic regression was used to estimate the association between access to health services and prediabetes awareness. Among a total sample of 2999U.S. adults with prediabetes, an estimated 92.0% were unaware of their prediabetes status. Participants that were unaware of their prediabetes tended to be younger, male, and were less likely to be obese or have a family history of diabetes. Having no access to health services significantly increased the odds of being prediabetes unaware (AOR: 2.65; 95% CI: 1.10-6.38). However, participants with insurance but no place of regular care had the greatest odds of being prediabetes unaware (AOR: 3.21; 95% CI: 1.21-8.55). These findings suggest that access to health services is a key factor for prediabetes awareness. Health policies and interventions should strive to ensure equitable access to health services in order to detect prediabetes, and promote awareness and engagement in risk-reducing behaviors to decrease the incidence of diabetes.

  16. mzServer: web-based programmatic access for mass spectrometry data analysis.

    PubMed

    Askenazi, Manor; Webber, James T; Marto, Jarrod A

    2011-05-01

    Continued progress toward systematic generation of large-scale and comprehensive proteomics data in the context of biomedical research will create project-level data sets of unprecedented size and ultimately overwhelm current practices for results validation that are based on distribution of native or surrogate mass spectrometry files. Moreover, the majority of proteomics studies leverage discovery-mode MS/MS analyses, rendering associated data-reduction efforts incomplete at best, and essentially ensuring future demand for re-analysis of data as new biological and technical information become available. Based on these observations, we propose to move beyond the sharing of interpreted spectra, or even the distribution of data at the individual file or project level, to a system much like that used in high-energy physics and astronomy, whereby raw data are made programmatically accessible at the site of acquisition. Toward this end we have developed a web-based server (mzServer), which exposes our common API (mzAPI) through very intuitive (RESTful) uniform resource locators (URL) and provides remote data access and analysis capabilities to the research community. Our prototype mzServer provides a model for lab-based and community-wide data access and analysis.

  17. 28 CFR 16.82 - Exemption of the National Drug Intelligence Center Data Base-limited access.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... Intelligence Center Data Base-limited access. 16.82 Section 16.82 Judicial Administration DEPARTMENT OF JUSTICE....82 Exemption of the National Drug Intelligence Center Data Base—limited access. (a) The following... Intelligence Center Data Base (JUSTICE/NDIC-001). (2) (b) These exemptions apply only to the extent...

  18. 28 CFR 16.82 - Exemption of the National Drug Intelligence Center Data Base-limited access.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... Intelligence Center Data Base-limited access. 16.82 Section 16.82 Judicial Administration DEPARTMENT OF JUSTICE....82 Exemption of the National Drug Intelligence Center Data Base—limited access. (a) The following... Intelligence Center Data Base (JUSTICE/NDIC-001). (2) (b) These exemptions apply only to the extent...

  19. 28 CFR 16.82 - Exemption of the National Drug Intelligence Center Data Base-limited access.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... Intelligence Center Data Base-limited access. 16.82 Section 16.82 Judicial Administration DEPARTMENT OF JUSTICE....82 Exemption of the National Drug Intelligence Center Data Base—limited access. (a) The following... Intelligence Center Data Base (JUSTICE/NDIC-001). (2) (b) These exemptions apply only to the extent...

  20. SiCOH-based resistive random access memory for backend of line compatible nonvolatile memory application

    NASA Astrophysics Data System (ADS)

    Zheng, Liang; Dai, Ya-Wei; Yu, Lin-Jie; Chen, Lin; Sun, Qing-Qing; Zhang, David Wei

    2017-04-01

    We investigated the resistive switching characteristics of a SiCOH low-k-material-based resistive random access memory (RRAM) in this study. This SiCOH-based RRAM is fully compatible with backend CMOS technology, which is extremely important for its applicability. The device demonstrated here had higher performance characteristics than a conventional SiO2-based RRAM, such as a higher ON/OFF ratio (around 102), and a higher cycling endurance in an ambient environment. Taken together, these characteristics make the device a promising candidate for next-generation nonvolatile applications.

  1. An efficient and secure attribute based signcryption scheme with LSSS access structure.

    PubMed

    Hong, Hanshu; Sun, Zhixin

    2016-01-01

    Attribute based encryption (ABE) and attribute based signature (ABS) provide flexible access control with authentication for data sharing between users, but realizing both functions will bring about too much computation burden. In this paper, we combine the advantages of CP-ABE with ABS and propose a ciphertext policy attribute based signcryption scheme. In our scheme, only legal receivers can decrypt the ciphertext and verify the signature signed by data owner. Furthermore, we use linear secret sharing scheme instead of tree structure to avoid the frequent calls of recursive algorithm. By security and performance analysis, we prove that our scheme is secure as well as gains higher efficiency.

  2. XRootd, disk-based, caching proxy for optimization of data access, data placement and data replication

    NASA Astrophysics Data System (ADS)

    Bauerdick, L. A. T.; Bloom, K.; Bockelman, B.; Bradley, D. C.; Dasu, S.; Dost, J. M.; Sfiligoi, I.; Tadel, A.; Tadel, M.; Wuerthwein, F.; Yagil, A.; Cms Collaboration

    2014-06-01

    Following the success of the XRootd-based US CMS data federation, the AAA project investigated extensions of the federation architecture by developing two sample implementations of an XRootd, disk-based, caching proxy. The first one simply starts fetching a whole file as soon as a file open request is received and is suitable when completely random file access is expected or it is already known that a whole file be read. The second implementation supports on-demand downloading of partial files. Extensions to the Hadoop Distributed File System have been developed to allow for an immediate fallback to network access when local HDFS storage fails to provide the requested block. Both cache implementations are in pre-production testing at UCSD.

  3. Land Based Anti-Ship Missiles: A Complementary Capability for Maintaining Access in an Anti-Access/Area Denial Environment

    DTIC Science & Technology

    2014-12-01

    advantages and prevent access into their “near seas.” This monograph uses two case studies to demonstrate an ability to innovate (1973 Arab -Israeli War...advantages and prevent access into their “near seas.” This monograph uses two case studies to demonstrate an ability to innovate (1973 Arab ...1 Literature Review………..………………………………………………………………………...5 Research Methodology………...…………………………………………………………………18 1973 Arab -Israeli War

  4. One-fifth of nonelderly Californians do not have access to job-based health insurance coverage.

    PubMed

    Lavarreda, Shana Alex; Cabezas, Livier

    2010-11-01

    Lack of job-based health insurance does not affect just workers, but entire families who depend on job-based coverage for their health care. This policy brief shows that in 2007 one-fifth of all Californians ages 0-64 who lived in households where at least one family member was employed did not have access to job-based coverage. Among adults with no access to job-based coverage through their own or a spouse's job, nearly two-thirds remained uninsured. In contrast, the majority of children with no access to health insurance through a parent obtained public health insurance, highlighting the importance of such programs. Low-income, Latino and small business employees were more likely to have no access to job-based insurance. Provisions enacted under national health care reform (the Patient Protection and Affordable Care Act of 2010) will aid some of these populations in accessing health insurance coverage.

  5. Breaking and Fixing Origin-Based Access Control in Hybrid Web/Mobile Application Frameworks

    PubMed Central

    Georgiev, Martin; Jana, Suman; Shmatikov, Vitaly

    2014-01-01

    Hybrid mobile applications (apps) combine the features of Web applications and “native” mobile apps. Like Web applications, they are implemented in portable, platform-independent languages such as HTML and JavaScript. Like native apps, they have direct access to local device resources—file system, location, camera, contacts, etc. Hybrid apps are typically developed using hybrid application frameworks such as PhoneGap. The purpose of the framework is twofold. First, it provides an embedded Web browser (for example, WebView on Android) that executes the app's Web code. Second, it supplies “bridges” that allow Web code to escape the browser and access local resources on the device. We analyze the software stack created by hybrid frameworks and demonstrate that it does not properly compose the access-control policies governing Web code and local code, respectively. Web code is governed by the same origin policy, whereas local code is governed by the access-control policy of the operating system (for example, user-granted permissions in Android). The bridges added by the framework to the browser have the same local access rights as the entire application, but are not correctly protected by the same origin policy. This opens the door to fracking attacks, which allow foreign-origin Web content included into a hybrid app (e.g., ads confined in iframes) to drill through the layers and directly access device resources. Fracking vulnerabilities are generic: they affect all hybrid frameworks, all embedded Web browsers, all bridge mechanisms, and all platforms on which these frameworks are deployed. We study the prevalence of fracking vulnerabilities in free Android apps based on the PhoneGap framework. Each vulnerability exposes sensitive local resources—the ability to read and write contacts list, local files, etc.—to dozens of potentially malicious Web domains. We also analyze the defenses deployed by hybrid frameworks to prevent resource access by foreign

  6. Breaking and Fixing Origin-Based Access Control in Hybrid Web/Mobile Application Frameworks.

    PubMed

    Georgiev, Martin; Jana, Suman; Shmatikov, Vitaly

    2014-02-01

    Hybrid mobile applications (apps) combine the features of Web applications and "native" mobile apps. Like Web applications, they are implemented in portable, platform-independent languages such as HTML and JavaScript. Like native apps, they have direct access to local device resources-file system, location, camera, contacts, etc. Hybrid apps are typically developed using hybrid application frameworks such as PhoneGap. The purpose of the framework is twofold. First, it provides an embedded Web browser (for example, WebView on Android) that executes the app's Web code. Second, it supplies "bridges" that allow Web code to escape the browser and access local resources on the device. We analyze the software stack created by hybrid frameworks and demonstrate that it does not properly compose the access-control policies governing Web code and local code, respectively. Web code is governed by the same origin policy, whereas local code is governed by the access-control policy of the operating system (for example, user-granted permissions in Android). The bridges added by the framework to the browser have the same local access rights as the entire application, but are not correctly protected by the same origin policy. This opens the door to fracking attacks, which allow foreign-origin Web content included into a hybrid app (e.g., ads confined in iframes) to drill through the layers and directly access device resources. Fracking vulnerabilities are generic: they affect all hybrid frameworks, all embedded Web browsers, all bridge mechanisms, and all platforms on which these frameworks are deployed. We study the prevalence of fracking vulnerabilities in free Android apps based on the PhoneGap framework. Each vulnerability exposes sensitive local resources-the ability to read and write contacts list, local files, etc.-to dozens of potentially malicious Web domains. We also analyze the defenses deployed by hybrid frameworks to prevent resource access by foreign-origin Web content

  7. Ethernet access network based on free-space optic deployment technology

    NASA Astrophysics Data System (ADS)

    Gebhart, Michael; Leitgeb, Erich; Birnbacher, Ulla; Schrotter, Peter

    2004-06-01

    The satisfaction of all communication needs from single households and business companies over a single access infrastructure is probably the most challenging topic in communications technology today. But even though the so-called "Last Mile Access Bottleneck" is well known since more than ten years and many distribution technologies have been tried out, the optimal solution has not yet been found and paying commercial access networks offering all service classes are still rare today. Conventional services like telephone, radio and TV, as well as new and emerging services like email, web browsing, online-gaming, video conferences, business data transfer or external data storage can all be transmitted over the well known and cost effective Ethernet networking protocol standard. Key requirements for the deployment technology driven by the different services are high data rates to the single customer, security, moderate deployment costs and good scalability to number and density of users, quick and flexible deployment without legal impediments and high availability, referring to the properties of optical and wireless communication. We demonstrate all elements of an Ethernet Access Network based on Free Space Optic distribution technology. Main physical parts are Central Office, Distribution Network and Customer Equipment. Transmission of different services, as well as configuration, service upgrades and remote control of the network are handled by networking features over one FSO connection. All parts of the network are proven, the latest commercially available technology. The set up is flexible and can be adapted to any more specific need if required.

  8. Indexing the medical open access literature for textual and content-based visual retrieval.

    PubMed

    Eggel, Ivan; Müller, Henning

    2010-01-01

    Over the past few years an increasing amount of scientific journals have been created in an open access format. Particularly in the medical field the number of openly accessible journals is enormous making a wide body of knowledge available for analysis and retrieval. Part of the trend towards open access publications can be linked to funding bodies such as the NIH1 (National Institutes of Health) and the Swiss National Science Foundation (SNF2) requiring funded projects to make all articles of funded research available publicly. This article describes an approach to make part of the knowledge of open access journals available for retrieval including the textual information but also the images contained in the articles. For this goal all articles of 24 journals related to medical informatics and medical imaging were crawled from the web pages of BioMed Central. Text and images of the PDF (Portable Document Format) files were indexed separately and a web-based retrieval interface allows for searching via keyword queries or by visual similarity queries. Starting point for a visual similarity query can be an image on the local hard disk that is uploaded or any image found via the textual search. Search for similar documents is also possible.

  9. Web-Based Geographic Information System Tool for Accessing Hanford Site Environmental Data

    SciTech Connect

    Triplett, Mark B.; Seiple, Timothy E.; Watson, David J.; Charboneau, Briant L.; Morse, John G.

    2014-11-15

    Data volume, complexity, and access issues pose severe challenges for analysts, regulators and stakeholders attempting to efficiently use legacy data to support decision making at the U.S. Department of Energy’s (DOE) Hanford Site. DOE has partnered with the Pacific Northwest National Laboratory (PNNL) on the PHOENIX (PNNL-Hanford Online Environmental Information System) project, which seeks to address data access, transparency, and integration challenges at Hanford to provide effective decision support. PHOENIX is a family of spatially-enabled web applications providing quick access to decades of valuable scientific data and insight through intuitive query, visualization, and analysis tools. PHOENIX realizes broad, public accessibility by relying only on ubiquitous web-browsers, eliminating the need for specialized software. It accommodates a wide range of users with intuitive user interfaces that require little or no training to quickly obtain and visualize data. Currently, PHOENIX is actively hosting three applications focused on groundwater monitoring, groundwater clean-up performance reporting, and in-tank monitoring. PHOENIX-based applications are being used to streamline investigative and analytical processes at Hanford, saving time and money. But more importantly, by integrating previously isolated datasets and developing relevant visualization and analysis tools, PHOENIX applications are enabling DOE to discover new correlations hidden in legacy data, allowing them to more effectively address complex issues at Hanford.

  10. Scalable Authorization in Role-Based Access Control Using Negative Permissions and Remote Authorization

    DTIC Science & Technology

    2003-01-01

    and Hongjie Xin for making this a rewarding team experience. Thanks to Mr. Michael Warres from Sun Microsystems for being prompt and meticulous in our...Windows NT), and security policies based on the Chinese wall model for separation of duties [8]. RBAC simplifies the administration of access...connection check is sort of a first wall of defense against illegitimate users, while the JavaSpace action is more specific to a particular object, known as

  11. A secure WDM ring access network employing silicon micro-ring based remote node

    NASA Astrophysics Data System (ADS)

    Sung, Jiun-Yu; Chow, Chi-Wai; Yeh, Chien-Hung; Xu, Ke; Hsu, Chin-Wei; Su, Hong-Quan; Tsang, Hon-Ki

    2014-08-01

    A secure and scalable wavelength-division-multiplexing (WDM) ring-based access network is proposed and demonstrated using proof-of-concept experiments. In the remote node (RN), wavelength hopping for specific optical networking unit (ONU) is deployed by using silicon micro-ring resonators (SMR). Using silicon-based devices could be cost-effective for the cost-sensitive access network. Hence the optical physical layer security is introduced. The issues of denial of service (DOS) attacks, eavesdropping and masquerading can be made more difficult in the proposed WDM ring-based access network. Besides, the SMRs with different dropped wavelengths can be cascaded, such that the signals pass through the preceding SMRs can be dropped by a succeeding SMR. This can increase the scalability of the RN for supporting more ONUs for future upgrade. Here, error-free 10 Gb/s downlink and 1.25 Gb/s uplink transmission are demonstrated to show the feasibility of the proposed network.

  12. Is Team-Based Primary Care Associated with Less Access Problems and Self-Reported Unmet Need in Canada?

    PubMed

    Zygmunt, Austin; Asada, Yukiko; Burge, Frederick

    2015-07-15

    As in many jurisdictions, the delivery of primary care in Canada is being transformed from solo practice to team-based care. In Canada, team-based primary care involves general practitioners working with nurses or other health care providers, and it is expected to improve equity in access to care. This study examined whether team-based care is associated with fewer access problems and less unmet need and whether socioeconomic gradients in access problems and unmet need are smaller in team-based care than in non-team-based care. Data came from the 2008 Canadian Survey of Experiences with Primary Health Care (sample size: 10,858). We measured primary care type as team-based or non-team-based and socioeconomic status by income and education. We created four access problem variables and four unmet need variables (overall and three specific components). For each, we ran separate logistic regression models to examine their associations with primary care type. We examined socioeconomic gradients in access problems and unmet need stratified by primary care type. Primary care type had no statistically significant, independent associations with access problems or unmet need. Among those with non-team-based care, a statistically significant education gradient for overall access problems existed, whereas among those with team-based care, no statistically significant socioeconomic gradients existed.

  13. Adaptation of AMO-FBMC-OQAM in optical access network for accommodating asynchronous multiple access in OFDM-based uplink transmission

    NASA Astrophysics Data System (ADS)

    Jung, Sun-Young; Jung, Sang-Min; Han, Sang-Kook

    2015-01-01

    Exponentially expanding various applications in company with proliferation of mobile devices make mobile traffic exploded annually. For future access network, bandwidth efficient and asynchronous signals converged transmission technique is required in optical network to meet a huge bandwidth demand, while integrating various services and satisfying multiple access in perceived network resource. Orthogonal frequency division multiplexing (OFDM) is highly bandwidth efficient parallel transmission technique based on orthogonal subcarriers. OFDM has been widely studied in wired-/wireless communication and became a Long term evolution (LTE) standard. Consequently, OFDM also has been actively researched in optical network. However, OFDM is vulnerable frequency and phase offset essentially because of its sinc-shaped side lobes, therefore tight synchronism is necessary to maintain orthogonality. Moreover, redundant cyclic prefix (CP) is required in dispersive channel. Additionally, side lobes act as interference among users in multiple access. Thus, it practically hinders from supporting integration of various services and multiple access based on OFDM optical transmission In this paper, adaptively modulated optical filter bank multicarrier system with offset QAM (AMO-FBMC-OQAM) is introduced and experimentally investigated in uplink optical transmission to relax multiple access interference (MAI), while improving bandwidth efficiency. Side lobes are effectively suppressed by using FBMC, therefore the system becomes robust to path difference and imbalance among optical network units (ONUs), which increase bandwidth efficiency by reducing redundancy. In comparison with OFDM, a signal performance and an efficiency of frequency utilization are improved in the same experimental condition. It enables optical network to effectively support heterogeneous services and multiple access.

  14. Anatomic Suitability for Transcaval Access Based on Computed Tomography.

    PubMed

    Lederman, Robert J; Greenbaum, Adam B; Rogers, Toby; Khan, Jaffar M; Fusari, Melissa; Chen, Marcus Y

    2017-01-09

    Transcaval access has been used successfully for over 200 transcatheter aortic valve replacements, large-bore percutaneous left ventricular assist devices, and thoracic endovascular aortic aneurysm repairs. This review teaches how to plan transcaval access and closure based on computed tomography. The main planning goals are to: 1) identify calcium-free crossing targets in the abdominal aorta along with optimal fluoroscopic projection angles and level with respect to lumbar vertebrae; 2) identify obstacles such as interposed bowel or pedunculated aortic atheroma; 3) plan covered stent bailout; and 4) identify jeopardized vascular branches such as renal arteries that might be obstructed by bailout covered stents if employed. The aorta and inferior vena cava are segmented (sculpted) using an image reconstruction workstation and crossing targets are highlighted. Important measurements such as aortic lumen diameter and target distance from renal arteries, aortoiliac bifurcation, and right femoral vein puncture site are reported to assist the operator. The proposed classification for transcaval feasibility has been revised, making some previously unfavorable candidates now feasible or favorable based on procedural success to date. Transcaval access allows percutaneous introduction of large devices into the aorta despite small or diseased iliofemoral arteries. By following these simplified procedures, both operators and imaging specialists can easily prepare comprehensive treatment plans.

  15. BARTER: Behavior Profile Exchange for Behavior-Based Admission and Access Control in MANETs

    NASA Astrophysics Data System (ADS)

    Frias-Martinez, Vanessa; Stolfo, Salvatore J.; Keromytis, Angelos D.

    Mobile Ad-hoc Networks (MANETs) are very dynamic networks with devices continuously entering and leaving the group. The highly dynamic nature of MANETs renders the manual creation and update of policies associated with the initial incorporation of devices to the MANET (admission control) as well as with anomaly detection during communications among members (access control) a very difficult task. In this paper, we present BARTER, a mechanism that automatically creates and updates admission and access control policies for MANETs based on behavior profiles. BARTER is an adaptation for fully distributed environments of our previously introduced BB-NAC mechanism for NAC technologies. Rather than relying on a centralized NAC enforcer, MANET members initially exchange their behavior profiles and compute individual local definitions of normal network behavior. During admission or access control, each member issues an individual decision based on its definition of normalcy. Individual decisions are then aggregated via a threshold cryptographic infrastructure that requires an agreement among a fixed amount of MANET members to change the status of the network. We present experimental results using content and volumetric behavior profiles computed from the ENRON dataset. In particular, we show that the mechanism achieves true rejection rates of 95% with false rejection rates of 9%.

  16. Access patterns of a clinic-based health information web site for international travelers.

    PubMed

    Licciardone, John C

    2002-01-01

    A large national telephone survey conducted in 2000 by the Pew Internet & American Life Project estimated that 52 million American adults used the Internet to acquire health information. Based on population estimates, these users comprised 25% of all adults. The growth of online health information coupled with increasing Internet access has led to the emergence of consumer informatics as an outbranching from traditional medical informatics. The ease of international communications afforded by the Internet holds great promise for consumers in the realm of travel medicine. For example, an early study found that a Web site hosted by an international travel medicine clinic was accessed by client computers in more than 100 countries. Nevertheless, relatively little research has been conducted on consumer informatics in travel medicine. An important aspect of consumer informatics involves studying consumers' needs for health information. The purpose of this study was to perform a descriptive analysis of overall use and content-specific access patterns for health information provided on a clinic-based Web site for international travelers.

  17. A Computer-Based Method for Teaching Catheter-Access Hemodialysis Management.

    PubMed

    Pun, Sut-Kam; Chiang, Vico Chung-Lim; Choi, Kup-Sze

    2016-10-01

    Patients undergoing hemodialysis are highly susceptible to infections, which could lead to morbidity and mortality. One of the major sources of infections stems from the mishandling of hemodialysis access sites. Although healthcare workers receive training on how to aseptically handle hemodialysis catheters, the increasing number of blood infections associated with dialysis suggests that the conventional approach to training may not be sufficient to ensure a clear understanding of the necessary knowledge and skills. With advancements in digital technology, computer-assisted learning has been gaining popularity as an approach to teaching clinical skills. The purpose of this study was to evaluate the effectiveness of a computer-based training system developed to teach healthcare workers catheter-access hemodialysis management. Forty nurses were recruited and randomly assigned into two groups: the control group, which received conventional training only; and the experimental group, which received both conventional and computer-based training. A knowledge test and a skills competence test were administered to both groups before and after the intervention to evaluate their performance. The results show that the performance of the nurses in the experimental group was significantly better than that in the control group, indicating that the proposed training system is an effective tool for supplementing the learning of catheter-access hemodialysis management.

  18. Fiber-based multiple-access frequency synchronization via 1f-2f dissemination

    NASA Astrophysics Data System (ADS)

    Zhu, Xi; Wang, Bo; Gao, Chao; Wang, Li-Jun

    2016-09-01

    Considering the reference frequency dissemination requirements of the Square Kilometre Array telescope (SKA) project, on the basis of the 1f-2f precision frequency synchronization scheme, we propose and demonstrate a fiber-based multiple-access frequency synchronization scheme. The dissemination reference frequency can be recovered at arbitrary nodes along the entire fiber link. It can be applied to antennas close proximity to the SKA central station, and will lead to a better SKA frequency synchronization network. As a performance test, we recover the disseminated 100-MHz reference frequency at an arbitrary node chosen as being 5 km away from the transmitting site. Relative frequency stabilities of 2.0×10-14/s and 1.6×10-16/104s are obtained. We also experimentally verify the feasibility of a frequency dissemination link with three access points. Project supported by the National Key Scientific Instrument and Equipment Development Project of China (Grant No. 2013YQ09094303).

  19. Open access to technology platforms for InP-based photonic integrated circuits

    NASA Astrophysics Data System (ADS)

    Ławniczuk, Katarzyna; Augustin, Luc M.; Grote, Norbert; Wale, Michael J.; Smit, Meint K.; Williams, Kevin A.

    2015-04-01

    Open access to generic technology platforms for photonic integrated circuit manufacturing enables low-cost development of application-specific photonic chips for novel or improved products. It brings photonic ICs within reach for many industrial users and research institutes, by moving toward a fabless business model. In the current status, InP-based open access manufacturing services are offered through multi-project wafer runs by Fraunhofer Heinrich Hertz Institut, SMART Photonics, and Oclaro. In this paper, we review state-of-the-art InP photonic integration technology platforms, present examples of complex InP photonic ICs developed in the generic technologies, and give a prospect for further development of these photonic integration platforms.

  20. Apparatus, method and system to control accessibility of platform resources based on an integrity level

    DOEpatents

    Jenkins, Chris; Pierson, Lyndon G.

    2016-10-25

    Techniques and mechanism to selectively provide resource access to a functional domain of a platform. In an embodiment, the platform includes both a report domain to monitor the functional domain and a policy domain to identify, based on such monitoring, a transition of the functional domain from a first integrity level to a second integrity level. In response to a change in integrity level, the policy domain may configure the enforcement domain to enforce against the functional domain one or more resource accessibility rules corresponding to the second integrity level. In another embodiment, the policy domain automatically initiates operations in aid of transitioning the platform from the second integrity level to a higher integrity level.

  1. Estimating spatial accessibility to facilities on the regional scale: an extended commuting-based interaction potential model

    PubMed Central

    2011-01-01

    Background There is growing interest in the study of the relationships between individual health-related behaviours (e.g. food intake and physical activity) and measurements of spatial accessibility to the associated facilities (e.g. food outlets and sport facilities). The aim of this study is to propose measurements of spatial accessibility to facilities on the regional scale, using aggregated data. We first used a potential accessibility model that partly makes it possible to overcome the limitations of the most frequently used indices such as the count of opportunities within a given neighbourhood. We then propose an extended model in order to take into account both home and work-based accessibility for a commuting population. Results Potential accessibility estimation provides a very different picture of the accessibility levels experienced by the population than the more classical "number of opportunities per census tract" index. The extended model for commuters increases the overall accessibility levels but this increase differs according to the urbanisation level. Strongest increases are observed in some rural municipalities with initial low accessibility levels. Distance to major urban poles seems to play an essential role. Conclusions Accessibility is a multi-dimensional concept that should integrate some aspects of travel behaviour. Our work supports the evidence that the choice of appropriate accessibility indices including both residential and non-residential environmental features is necessary. Such models have potential implications for providing relevant information to policy-makers in the field of public health. PMID:21219597

  2. The Inter-Regional Inequality of Access to Information and Communication Technology in Turkey Based on PISA 2009 Data

    ERIC Educational Resources Information Center

    Guzeller, Cem Oktay; Akin, Ayca

    2011-01-01

    The purpose of this study was to investigate the extent to which students from Turkey have access to a computer and the internet at school and at home, and differences in ICT accessibility by geographic region based on the data obtained from the PISA 2009. Data collected through the ICT questionnaire were analyzed by descriptive statistical…

  3. Accessibility and Use of Web-Based Electronic Resources by Physicians in a Psychiatric Institution in Nigeria

    ERIC Educational Resources Information Center

    Oduwole, Adebambo Adewale; Oyewumi, Olatundun

    2010-01-01

    Purpose: This study aims to examine the accessibility and use of web-based electronic databases on the Health InterNetwork Access to Research Initiative (HINARI) portal by physicians in the Neuropsychiatric Hospital, Aro--a psychiatry health institution in Nigeria. Design/methodology/approach: Collection of data was through the use of a three-part…

  4. 28 CFR 16.82 - Exemption of the National Drug Intelligence Center Data Base-limited access.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... analyzing information and would impede the development of criminal intelligence necessary for effective law... Intelligence Center Data Base-limited access. 16.82 Section 16.82 Judicial Administration DEPARTMENT OF JUSTICE....82 Exemption of the National Drug Intelligence Center Data Base—limited access. (a) The...

  5. 28 CFR 16.82 - Exemption of the National Drug Intelligence Center Data Base-limited access.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... analyzing information and would impede the development of criminal intelligence necessary for effective law... Intelligence Center Data Base-limited access. 16.82 Section 16.82 Judicial Administration DEPARTMENT OF JUSTICE....82 Exemption of the National Drug Intelligence Center Data Base—limited access. (a) The...

  6. OTIS Basic Index Access System (OBIAS); A System for Retrieval of Information From the ERIC and CIJE Data Bases Utilizing a Direct Access Inverted Index of Descriptors and a Reformatted Direct Access ERIC-CIJE File.

    ERIC Educational Resources Information Center

    Bracken, Paula

    The OTIS Basic Index Access System (OBIAS) for searching the ERIC data base is described. This system offers two advantages over the previous system. First, search time has been halved, reducing the cost per search to an estimated $10 on a batch basis. Second, the "OTIS ERIC Descripter Catalog" which contains all descriptors used in the…

  7. WaveNet: A Web-Based Metocean Data Access, Processing and Analysis Tool; Part 5 - WW3 Database

    DTIC Science & Technology

    2015-02-01

    ERDC/CHL CHETN-IV-103 February 2015 Approved for public release; distribution is unlimited. WaveNet: A Web -Based Metocean Data Access, Processing...modeling and planning missions require metocean data (e.g., winds, waves, tides, water levels). WaveNet is a web -based graphical-user-interface (GUI...AND SUBTITLE WaveNet: A Web -Based Metocean Data Access, Processing and Analysis Tool; Part 5 - WW3 Database 5a. CONTRACT NUMBER 5b. GRANT NUMBER

  8. Improving Inpatient Surveys: Web-Based Computer Adaptive Testing Accessed via Mobile Phone QR Codes

    PubMed Central

    2016-01-01

    Background The National Health Service (NHS) 70-item inpatient questionnaire surveys inpatients on their perceptions of their hospitalization experience. However, it imposes more burden on the patient than other similar surveys. The literature shows that computerized adaptive testing (CAT) based on item response theory can help shorten the item length of a questionnaire without compromising its precision. Objective Our aim was to investigate whether CAT can be (1) efficient with item reduction and (2) used with quick response (QR) codes scanned by mobile phones. Methods After downloading the 2008 inpatient survey data from the Picker Institute Europe website and analyzing the difficulties of this 70-item questionnaire, we used an author-made Excel program using the Rasch partial credit model to simulate 1000 patients’ true scores followed by a standard normal distribution. The CAT was compared to two other scenarios of answering all items (AAI) and the randomized selection method (RSM), as we investigated item length (efficiency) and measurement accuracy. The author-made Web-based CAT program for gathering patient feedback was effectively accessed from mobile phones by scanning the QR code. Results We found that the CAT can be more efficient for patients answering questions (ie, fewer items to respond to) than either AAI or RSM without compromising its measurement accuracy. A Web-based CAT inpatient survey accessed by scanning a QR code on a mobile phone was viable for gathering inpatient satisfaction responses. Conclusions With advances in technology, patients can now be offered alternatives for providing feedback about hospitalization satisfaction. This Web-based CAT is a possible option in health care settings for reducing the number of survey items, as well as offering an innovative QR code access. PMID:26935793

  9. An Effective Massive Sensor Network Data Access Scheme Based on Topology Control for the Internet of Things

    PubMed Central

    Yi, Meng; Chen, Qingkui; Xiong, Neal N.

    2016-01-01

    This paper considers the distributed access and control problem of massive wireless sensor networks’ data access center for the Internet of Things, which is an extension of wireless sensor networks and an element of its topology structure. In the context of the arrival of massive service access requests at a virtual data center, this paper designs a massive sensing data access and control mechanism to improve the access efficiency of service requests and makes full use of the available resources at the data access center for the Internet of things. Firstly, this paper proposes a synergistically distributed buffer access model, which separates the information of resource and location. Secondly, the paper divides the service access requests into multiple virtual groups based on their characteristics and locations using an optimized self-organizing feature map neural network. Furthermore, this paper designs an optimal scheduling algorithm of group migration based on the combination scheme between the artificial bee colony algorithm and chaos searching theory. Finally, the experimental results demonstrate that this mechanism outperforms the existing schemes in terms of enhancing the accessibility of service requests effectively, reducing network delay, and has higher load balancing capacity and higher resource utility rate. PMID:27827878

  10. An Effective Massive Sensor Network Data Access Scheme Based on Topology Control for the Internet of Things.

    PubMed

    Yi, Meng; Chen, Qingkui; Xiong, Neal N

    2016-11-03

    This paper considers the distributed access and control problem of massive wireless sensor networks' data access center for the Internet of Things, which is an extension of wireless sensor networks and an element of its topology structure. In the context of the arrival of massive service access requests at a virtual data center, this paper designs a massive sensing data access and control mechanism to improve the access efficiency of service requests and makes full use of the available resources at the data access center for the Internet of things. Firstly, this paper proposes a synergistically distributed buffer access model, which separates the information of resource and location. Secondly, the paper divides the service access requests into multiple virtual groups based on their characteristics and locations using an optimized self-organizing feature map neural network. Furthermore, this paper designs an optimal scheduling algorithm of group migration based on the combination scheme between the artificial bee colony algorithm and chaos searching theory. Finally, the experimental results demonstrate that this mechanism outperforms the existing schemes in terms of enhancing the accessibility of service requests effectively, reducing network delay, and has higher load balancing capacity and higher resource utility rate.

  11. Prevention literacy: community-based advocacy for access and ownership of the HIV prevention toolkit

    PubMed Central

    Parker, Richard G; Perez-Brumer, Amaya; Garcia, Jonathan; Gavigan, Kelly; Ramirez, Ana; Milnor, Jack; Terto, Veriano

    2016-01-01

    . However, linkages to community advocacy and mobilization efforts are limited and unsustainable. Success of prevention efforts depends on equity of access, community-based ownership, and multilevel support structures to enable usage and sustainability. Conclusions For existing HIV prevention efforts to be effective in “real-world” settings, with limited resources, reflection on historical lessons and contextual realities (i.e. policies, financial constraints, and biomedical patents) indicated the need to extend principles developed for treatment access and treatment literacy, to support prevention literacy and prevention access as an integral part of the global response to HIV. PMID:27702430

  12. Efficient traffic grooming with dynamic ONU grouping for multiple-OLT-based access network

    NASA Astrophysics Data System (ADS)

    Zhang, Shizong; Gu, Rentao; Ji, Yuefeng; Wang, Hongxiang

    2015-12-01

    Fast bandwidth growth urges large-scale high-density access scenarios, where the multiple Passive Optical Networking (PON) system clustered deployment can be adopted as an appropriate solution to fulfill the huge bandwidth demands, especially for a future 5G mobile network. However, the lack of interaction between different optical line terminals (OLTs) results in part of the bandwidth resources waste. To increase the bandwidth efficiency, as well as reduce bandwidth pressure at the edge of a network, we propose a centralized flexible PON architecture based on Time- and Wavelength-Division Multiplexing PON (TWDM PON). It can provide flexible affiliation for optical network units (ONUs) and different OLTs to support access network traffic localization. Specifically, a dynamic ONU grouping algorithm (DGA) is provided to obtain the minimal OLT outbound traffic. Simulation results show that DGA obtains an average 25.23% traffic gain increment under different OLT numbers within a small ONU number situation, and the traffic gain will increase dramatically with the increment of the ONU number. As the DGA can be deployed easily as an application running above the centralized control plane, the proposed architecture can be helpful to improve the network efficiency for future traffic-intensive access scenarios.

  13. SPIDR III: A Web Services Based System for Managing and Accessing Solar Terrestrial Physics Data

    NASA Astrophysics Data System (ADS)

    Redmon, R.; Kihn, E.; Zhizhin, M.

    2005-05-01

    We present SPIDR III, a web based data access, visualization and data management system for the space environment community, allowing a solar terrestrial physics customer to intelligently access and manage historical space physics data for integration with environmental models and space weather forecasts. SPIDR III is the newly redesigned Space Physics Interactive Resource (SPIDR) web application and was redesigned with input from it's user community via an intensive usability study. We will present on SPIDR III's new features, improved use and on lessons learned in usability and federating multi-source data. In 2004, SPIDR II underwent extensive rework yielding a completely redesigned interface for improved user interaction and the addition of many enhanced and complex features. The usability alterations were motivated in large part by a usability study performed by outside professional site reviewers and involving key data managers and current SPIDR II users. SPIDR III is built following the application direct to data archive paradigm, using Web Services both for internal and external exchange of data and information. It is now a framework and application set of Web Services. This application suite is fully open source and is designed to operate as a standalone VO as well as seamlessly integrate with other existing VOs. This extensible and open design yields easy mirroring worldwide for free and open exchange of scientific data and information. Data managed by SPIDR includes Geomagnetic Indices, GOES, Ionospheric, and DMSP which is archived/ingested from many data providers including WDC, IIWG, SAO, HDF, AFCCC, SEC, NASA, and this list is easily extendable. SPIDR III may be accessed via http://spidr.ngdc.noaa.gov/spidr/ A guest login is provided for convenience. Becoming a full access user, is free and only requires completing a short registration form.

  14. Integration of variable-rate OWC with OFDM-PON for hybrid optical access based on adaptive envelope modulation

    NASA Astrophysics Data System (ADS)

    Chen, Chen; Zhong, Wen-De; Wu, Dehao

    2016-12-01

    In this paper, we investigate an integrated optical wireless communication (OWC) and orthogonal frequency division multiplexing based passive optical network (OFDM-PON) system for hybrid wired and wireless optical access, based on an adaptive envelope modulation technique. Both the outdoor and indoor wireless communications are considered in the integrated system. The data for wired access is carried by a conventional OFDM signal, while the data for wireless access is carried by an M-ary pulse amplitude modulation (M-PAM) signal which is modulated onto the envelope of a phase-modulated OFDM signal. By adaptively modulating the wireless M-PAM signal onto the envelope of the wired phase-modulated constant envelope OFDM (CE-OFDM) signal, hybrid wired and wireless optical access can be seamlessly integrated and variable-rate optical wireless transmission can also be achieved. Analytical bit-error-rate (BER) expressions are derived for both the CE-OFDM signal with M-PAM overlay and the overlaid unipolar M-PAM signal, which are verified by Monte Carlo simulations. The BER performances of wired access, indoor OWC wireless access and outdoor OWC wireless access are evaluated. Moreover, variable-rate indoor and outdoor optical wireless access based on the adaptive envelope modulation technique is also discussed.

  15. 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).

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

    NASA Astrophysics Data System (ADS)

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

    2001-05-01

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

  17. TiO2 thin film based transparent flexible resistive switching random access memory

    NASA Astrophysics Data System (ADS)

    Pham, Kim Ngoc; Dung Hoang, Van; Tran, Cao Vinh; Thang Phan, Bach

    2016-03-01

    In our work we have fabricated TiO2 based resistive switching devices both on transparent substrates (ITO, IGZO/glass) and transparent flexible substrate (ITO/PET). All devices demonstrate the reproducibility of forming free bipolar resistive switching with high transparency in the visible light range (∼80% at the wavelength of 550 nm). Particularly, transparent and flexible device exhibits stable resistive switching performance at the initial state (flat) and even after bending state up to 500 times with curvature radius of 10% compared to flat state. The achieved characteristics of resistive switching of TiO2 thin films seem to be promising for transparent flexible random access memory.

  18. Nonvolatile transtance change random access memory based on magnetoelectric P(VDF-TrFE)/Metglas heterostructures

    NASA Astrophysics Data System (ADS)

    Lu, Peipei; Shang, Dashan; Shen, Jianxin; Chai, Yisheng; Yang, Chuansen; Zhai, Kun; Cong, Junzhuang; Shen, Shipeng; Sun, Young

    2016-12-01

    Transtance change random access memory (TCRAM) is a type of nonvolatile memory based on the nonlinear magnetoelectric coupling effects of multiferroics. In this work, ferroelectric P(VDF-TrFE) thin films were prepared on Metglas foil substrates by the sol-gel technique to form multiferroic heterostructures. The magnetoelectric voltage coefficient of the heterostructure can be switched reproducibly to different levels between positive and negative values by applying selective electric-field pulses. Compared with bulk multiferroic heterostructures, the polarization switching voltage was reduced to 7 V. Our facile technological approach enables this organic magnetoelectric heterostructure as a promising candidate for the applications in multilevel TCRAM devices.

  19. 75 FR 1020 - Amendments to the Export Administration Regulations (EAR) Based Upon the Accession of Albania and...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-01-08

    ... Regulations (EAR) Based Upon the Accession of Albania and Croatia to Formal Membership in the North Atlantic... * * * * * * * Albania \\2 3\\ X X ...... X ....... X X X X ...... ...... ...... ...... ...... * * * * * * * Croatia \\3\\...

  20. Comparison of a retrotransposon-based marker with microsatellite markers for discriminating accessions of Vitis vinifera.

    PubMed

    Sant'Ana, G C; Ferreira, J L; Rocha, H S; Borém, A; Pasqual, M; Cançado, G M A

    2012-05-21

    Identification and knowledge concerning genetic diversity are fundamental for efficient management and use of grapevine germplasm. Recently, new types of molecular markers have been developed, such as retrotransposon-based markers. Because of their multilocus pattern, retrotransposon-based markers might be able to differentiate grapevine accessions with just one pair of primers. In order to evaluate the efficiency of this type of marker, we compared retrotransposon marker Tvv1 with seven microsatellite markers frequently used for genotyping of the genus Vitis (VVMD7, VVMD25, VVMD5, VVMD27, VVMD31, VVS2, and VZAG62). The reference population that we used consisted of 26 accessions of Vitis, including seven European varieties of Vitis vinifera, four North American varieties and hybrids of Vitis labrusca, and 15 rootstock hybrids obtained from crosses of several Vitis species. Individually, the Tvv1 and the group of seven SSR markers were capable of distinguishing all accessions except 'White Niagara' compared to 'Red Niagara'. Using the Structure software, the retrotransposon marker Tvv1 generated two clusters: one with V. vinifera plus North American varieties and the other comprising rootstocks. The seven SSR markers generated five clusters: V. vinifera, the North American varieties, and three groups of rootstock hybrids. The percentages of variation explained by the first two components in the principal coordinate analysis were 65.21 (Tvv1) and 50.42 (SSR markers) while the Mantel correlation between the distance matrixes generated by the two types of markers was 42.5%. We conclude that the Tvv1 marker is useful for DNA fingerprinting, but it lacks efficiency for discrimination of structured groups.

  1. Access to HIV prevention services among gender based violence survivors in Tanzania

    PubMed Central

    Mboya, Beati; Temu, Florence; Awadhi, Bayoum; Ngware, Zubeda; Ndyetabura, Elly; Kiondo, Gloria; Maridadi, Janneth

    2012-01-01

    Introduction Currently, Tanzania's HIV prevalence is 5.7%. Gender inequality and Gender Based Violence (GBV) are among factors fuelling the spread of HIV in Tanzania. This study was conducted to assess universal access to HIV prevention services among GBV survivors in Iringa and Dar-es-Salaam where HIV prevalence is as high as 14.7% and 9% respectively compared to a national average of 5.7%. Methods In 2010, a mixed methods study using triangulation model was conducted in Iringa and Dar-es-Salaam regions to represent rural and urban settings respectively. Questionnaires were administered to 283 randomly selected survivors and 37 health providers while 28 in-depth interviews and 16 focus group discussions were conducted among various stakeholders. Quantitative data was analyzed in SPSS by comparing descriptive statistics while qualitative data was analyzed using thematic framework approach. Results Counseling and testing was the most common type of HIV prevention services received by GBV survivors (29%). Obstacles for HIV prevention among GBV survivors included: stigma, male dominance culture and fear of marital separation. Bribery in service delivery points, lack of confidentiality, inadequate GBV knowledge among health providers, and fear of being involved in legal matters were mentioned to be additional obstacles to service accessibility by survivors. Reported consequences of GBV included: psychological problems, physical trauma, chronic illness, HIV infection. Conclusion GBV related stigma and cultural norms are obstacles to HIV services accessibility. Initiation of friendly health services, integration of GBV into HIV services and community based interventions addressing GBV related stigma and cultural norms are recommended. PMID:23467278

  2. A carrier sensed multiple access protocol for high data base rate ring networks

    NASA Technical Reports Server (NTRS)

    Foudriat, E. C.; Maly, Kurt J.; Overstreet, C. Michael; Khanna, S.; Paterra, Frank

    1990-01-01

    The results of the study of a simple but effective media access protocol for high data rate networks are presented. The protocol is based on the fact that at high data rates networks can contain multiple messages simultaneously over their span, and that in a ring, nodes used to detect the presence of a message arriving from the immediate upstream neighbor. When an incoming signal is detected, the node must either abort or truncate a message it is presently sending. Thus, the protocol with local carrier sensing and multiple access is designated CSMA/RN. The performance of CSMA/RN with TTattempt and truncate is studied using analytic and simulation models. Three performance factors, wait or access time, service time and response or end-to-end travel time are presented. The service time is basically a function of the network rate, it changes by a factor of 1 between no load and full load. Wait time, which is zero for no load, remains small for load factors up to 70 percent of full load. Response time, which adds travel time while on the network to wait and service time, is mainly a function of network length, especially for longer distance networks. Simulation results are shown for CSMA/RN where messages are removed at the destination. A wide range of local and metropolitan area network parameters including variations in message size, network length, and node count are studied. Finally, a scaling factor based upon the ratio of message to network length demonstrates that the results, and hence, the CSMA/RN protocol, are applicable to wide area networks.

  3. The storage system of PCM based on random access file system

    NASA Astrophysics Data System (ADS)

    Han, Wenbing; Chen, Xiaogang; Zhou, Mi; Li, Shunfen; Li, Gezi; Song, Zhitang

    2016-10-01

    Emerging memory technologies such as Phase change memory (PCM) tend to offer fast, random access to persistent storage with better scalability. It's a hot topic of academic and industrial research to establish PCM in storage hierarchy to narrow the performance gap. However, the existing file systems do not perform well with the emerging PCM storage, which access storage medium via a slow, block-based interface. In this paper, we propose a novel file system, RAFS, to bring about good performance of PCM, which is built in the embedded platform. We attach PCM chips to the memory bus and build RAFS on the physical address space. In the proposed file system, we simplify traditional system architecture to eliminate block-related operations and layers. Furthermore, we adopt memory mapping and bypassed page cache to reduce copy overhead between the process address space and storage device. XIP mechanisms are also supported in RAFS. To the best of our knowledge, we are among the first to implement file system on real PCM chips. We have analyzed and evaluated its performance with IOZONE benchmark tools. Our experimental results show that the RAFS on PCM outperforms Ext4fs on SDRAM with small record lengths. Based on DRAM, RAFS is significantly faster than Ext4fs by 18% to 250%.

  4. Model Based User's Access Requirement Analysis of E-Governance Systems

    NASA Astrophysics Data System (ADS)

    Saha, Shilpi; Jeon, Seung-Hwan; Robles, Rosslin John; Kim, Tai-Hoon; Bandyopadhyay, Samir Kumar

    The strategic and contemporary importance of e-governance has been recognized across the world. In India too, various ministries of Govt. of India and State Governments have taken e-governance initiatives to provide e-services to citizens and the business they serve. To achieve the mission objectives, and make such e-governance initiatives successful it would be necessary to improve the trust and confidence of the stakeholders. It is assumed that the delivery of government services will share the same public network information that is being used in the community at large. In particular, the Internet will be the principal means by which public access to government and government services will be achieved. To provide the security measures main aim is to identify user's access requirement for the stakeholders and then according to the models of Nath's approach. Based on this analysis, the Govt. can also make standards of security based on the e-governance models. Thus there will be less human errors and bias. This analysis leads to the security architecture of the specific G2C application.

  5. SAHBNET, an Accessible Surface-Based Elastic Network: An Application to Membrane Protein

    PubMed Central

    Dony, Nicolas; Crowet, Jean Marc; Joris, Bernard; Brasseur, Robert; Lins, Laurence

    2013-01-01

    Molecular Dynamics is a method of choice for membrane simulations and the rising of coarse-grained forcefields has opened the way to longer simulations with reduced calculations times. Here, we present an elastic network, SAHBNET (Surface Accessibility Hydrogen-Bonds elastic NETwork), that will maintain the structure of soluble or membrane proteins based on the hydrogen bonds present in the atomistic structure and the proximity between buried residues. This network is applied on the coarse-grained beads defined by the MARTINI model, and was designed to be more physics-based than a simple elastic network. The SAHBNET model is evaluated against atomistic simulations, and compared with ELNEDYN models. The SAHBNET is then used to simulate two membrane proteins inserted in complex lipid bilayers. These bilayers are formed by self-assembly and the use of a modified version of the GROMACS tool genbox (which is accessible through the gcgs.gembloux.ulg.ac.be website). The results show that SAHBNET keeps the structure close to the atomistic one and is successfully used for the simulation of membrane proteins. PMID:23722660

  6. The Accessibility, Usability, and Reliability of Chinese Web-Based Information on HIV/AIDS

    PubMed Central

    Niu, Lu; Luo, Dan; Liu, Ying; Xiao, Shuiyuan

    2016-01-01

    Objective: The present study was designed to assess the quality of Chinese-language Internet-based information on HIV/AIDS. Methods: We entered the following search terms, in Chinese, into Baidu and Sogou: “HIV/AIDS”, “symptoms”, and “treatment”, and evaluated the first 50 hits of each query using the Minervation validation instrument (LIDA tool) and DISCERN instrument. Results: Of the 900 hits identified, 85 websites were included in this study. The overall score of the LIDA tool was 63.7%; the mean score of accessibility, usability, and reliability was 82.2%, 71.5%, and 27.3%, respectively. Of the top 15 sites according to the LIDA score, the mean DISCERN score was calculated at 43.1 (95% confidence intervals (CI) = 37.7–49.5). Noncommercial websites showed higher DISCERN scores than commercial websites; whereas commercial websites were more likely to be found in the first 20 links obtained from each search engine than the noncommercial websites. Conclusions: In general, the HIV/AIDS related Chinese-language websites have poor reliability, although their accessibility and usability are fair. In addition, the treatment information presented on Chinese-language websites is far from sufficient. There is an imperative need for professionals and specialized institutes to improve the comprehensiveness of web-based information related to HIV/AIDS. PMID:27556475

  7. Heterogeneous access and processing of EO-Data on a Cloud based Infrastructure delivering operational Products

    NASA Astrophysics Data System (ADS)

    Niggemann, F.; Appel, F.; Bach, H.; de la Mar, J.; Schirpke, B.; Dutting, K.; Rucker, G.; Leimbach, D.

    2015-04-01

    To address the challenges of effective data handling faced by Small and Medium Sized Enterprises (SMEs) a cloud-based infrastructure for accessing and processing of Earth Observation(EO)-data has been developed within the project APPS4GMES(www.apps4gmes.de). To gain homogenous multi mission data access an Input Data Portal (IDP) been implemented on this infrastructure. The IDP consists of an Open Geospatial Consortium (OGC) conformant catalogue, a consolidation module for format conversion and an OGC-conformant ordering framework. Metadata of various EO-sources and with different standards is harvested and transferred to an OGC conformant Earth Observation Product standard and inserted into the catalogue by a Metadata Harvester. The IDP can be accessed for search and ordering of the harvested datasets by the services implemented on the cloud infrastructure. Different land-surface services have been realised by the project partners, using the implemented IDP and cloud infrastructure. Results of these are customer ready products, as well as pre-products (e.g. atmospheric corrected EO data), serving as a basis for other services. Within the IDP an automated access to ESA's Sentinel-1 Scientific Data Hub has been implemented. Searching and downloading of the SAR data can be performed in an automated way. With the implementation of the Sentinel-1 Toolbox and own software, for processing of the datasets for further use, for example for Vista's snow monitoring, delivering input for the flood forecast services, can also be performed in an automated way. For performance tests of the cloud environment a sophisticated model based atmospheric correction and pre-classification service has been implemented. Tests conducted an automated synchronised processing of one entire Landsat 8 (LS-8) coverage for Germany and performance comparisons to standard desktop systems. Results of these tests, showing a performance improvement by the factor of six, proved the high flexibility and

  8. Bipolar resistive switching characteristics in tantalum nitride-based resistive random access memory devices

    SciTech Connect

    Kim, Myung Ju; Jeon, Dong Su; Park, Ju Hyun; Kim, Tae Geun

    2015-05-18

    This paper reports the bipolar resistive switching characteristics of TaN{sub x}-based resistive random access memory (ReRAM). The conduction mechanism is explained by formation and rupture of conductive filaments caused by migration of nitrogen ions and vacancies; this mechanism is in good agreement with either Ohmic conduction or the Poole-Frenkel emission model. The devices exhibit that the reset voltage varies from −0.82 V to −0.62 V, whereas the set voltage ranges from 1.01 V to 1.30 V for 120 DC sweep cycles. In terms of reliability, the devices exhibit good retention (>10{sup 5 }s) and pulse-switching endurance (>10{sup 6} cycles) properties. These results indicate that TaN{sub x}-based ReRAM devices have a potential for future nonvolatile memory devices.

  9. Characteristics and mechanism study of cerium oxide based random access memories

    SciTech Connect

    Hsieh, Cheng-Chih; Roy, Anupam; Rai, Amritesh; Chang, Yao-Feng; Banerjee, Sanjay K.

    2015-04-27

    In this work, low operating voltage and high resistance ratio of different resistance states of binary transition metal oxide based resistive random access memories (RRAMs) are demonstrated. Binary transition metal oxides with high dielectric constant have been explored for RRAM application for years. However, CeO{sub x} is considered as a relatively new material to other dielectrics. Since research on CeO{sub x} based RRAM is still at preliminary stage, fundamental characteristics of RRAM such as scalability and mechanism studies need to be done before moving further. Here, we show very high operation window and low switching voltage of CeO{sub x} RRAMs and also compare electrical performance of Al/CeO{sub x}/Au system between different thin film deposition methods and discuss characteristics and resistive switching mechanism.

  10. Outline of a multiple-access communication network based on adaptive arrays

    NASA Technical Reports Server (NTRS)

    Zohar, S.

    1982-01-01

    Attention is given to a narrow-band communication system consisting of a central station trying to receive signals simultaneously from K spatially distinct mobile users sharing the same frequencies. One example of such a system is a group of aircraft and ships transmitting messages to a communication satellite. A reasonable approach to such a multiple access system may be based on equipping the central station with an n-element antenna array where n is equal to or greater than K. The array employs K sets of n weights to segregate the signals received from the K users. The weights are determined by direct computation based on position information transmitted by the users. A description is presented of an improved technique which makes it possible to reduce significantly the number of required computer operations in comparison to currently known techniques.

  11. Accessing the third dimension in localization-based super-resolution microscopy.

    PubMed

    Hajj, Bassam; El Beheiry, Mohamed; Izeddin, Ignacio; Darzacq, Xavier; Dahan, Maxime

    2014-08-21

    Only a few years after its inception, localization-based super-resolution microscopy has become widely employed in biological studies. Yet, it is primarily used in two-dimensional imaging and accessing the organization of cellular structures at the nanoscale in three dimensions (3D) still poses important challenges. Here, we review optical and computational techniques that enable the 3D localization of individual emitters and the reconstruction of 3D super-resolution images. These techniques are grouped into three main categories: PSF engineering, multiple plane imaging and interferometric approaches. We provide an overview of their technical implementation as well as commentary on their applicability. Finally, we discuss future trends in 3D localization-based super-resolution microscopy.

  12. The impacts of problem gambling on concerned significant others accessing web-based counselling.

    PubMed

    Dowling, Nicki A; Rodda, Simone N; Lubman, Dan I; Jackson, Alun C

    2014-08-01

    The 'concerned significant others' (CSOs) of people with problem gambling frequently seek professional support. However, there is surprisingly little research investigating the characteristics or help-seeking behaviour of these CSOs, particularly for web-based counselling. The aims of this study were to describe the characteristics of CSOs accessing the web-based counselling service (real time chat) offered by the Australian national gambling web-based counselling site, explore the most commonly reported CSO impacts using a new brief scale (the Problem Gambling Significant Other Impact Scale: PG-SOIS), and identify the factors associated with different types of CSO impact. The sample comprised all 366 CSOs accessing the service over a 21 month period. The findings revealed that the CSOs were most often the intimate partners of problem gamblers and that they were most often females aged under 30 years. All CSOs displayed a similar profile of impact, with emotional distress (97.5%) and impacts on the relationship (95.9%) reported to be the most commonly endorsed impacts, followed by impacts on social life (92.1%) and finances (91.3%). Impacts on employment (83.6%) and physical health (77.3%) were the least commonly endorsed. There were few significant differences in impacts between family members (children, partners, parents, and siblings), but friends consistently reported the lowest impact scores. Only prior counselling experience and Asian cultural background were consistently associated with higher CSO impacts. The findings can serve to inform the development of web-based interventions specifically designed for the CSOs of problem gamblers.

  13. Access to health care: the role of a community based health insurance in Kenya

    PubMed Central

    Mwaura, Judy Wanja; Pongpanich, Sathirakorn

    2012-01-01

    Background Out-of-pocket payments create financial barriers to health care access. There is an increasing interest in the role of community based health insurance schemes in improving equity and access of the poor to essential health care. The aim of this study was to assess the impact of Jamii Bora Health Insurance on access to health care among the urban poor. Methods Data was obtained from the household health interview survey in Kibera and Mathare slums, which consisted of 420 respondents, aged 18 and above who were registered as members of Jamii Bora Trust. The members of Jamii Bora Trust were divided into two groups the insured and the non-insured. Results In total, 17.9% respondents were hospitalized and women (19.6%) were more likely to be admitted than men (14.7%). Those in the poorest quintile had the highest probability of admission (18.1%). Those with secondary school education, large household size, and aged 50 and above also had slightly greater probability of admission (p<0.25). 86% of admissions among the insured respondents were covered JBHI and those in the poorest quintile were more likely to use the JBHI benefit. Results from the logistic regression revealed that the probability of being admitted, whether overall admission or admission covered by the JBHI benefit was determined by the presence of chronic condition (p<0.01). Conclusion Utilization and take up of the JBHI benefits was high. Overall, JBHI favoured the members in the lower income quintiles who were more likely to use health care services covered by the JBHI scheme. PMID:22891093

  14. PANATIKI: a network access control implementation based on PANA for IoT devices.

    PubMed

    Moreno Sanchez, Pedro; Marin Lopez, Rafa; Gomez Skarmeta, Antonio F

    2013-11-01

    Internet of Things (IoT) networks are the pillar of recent novel scenarios, such as smart cities or e-healthcare applications. Among other challenges, these networks cover the deployment and interaction of small devices with constrained capabilities and Internet protocol (IP)-based networking connectivity. These constrained devices usually require connection to the Internet to exchange information (e.g., management or sensing data) or access network services. However, only authenticated and authorized devices can, in general, establish this connection. The so-called authentication, authorization and accounting (AAA) services are in charge of performing these tasks on the Internet. Thus, it is necessary to deploy protocols that allow constrained devices to verify their credentials against AAA infrastructures. The Protocol for Carrying Authentication for Network Access (PANA) has been standardized by the Internet engineering task force (IETF) to carry the Extensible Authentication Protocol (EAP), which provides flexible authentication upon the presence of AAA. To the best of our knowledge, this paper is the first deep study of the feasibility of EAP/PANA for network access control in constrained devices. We provide light-weight versions and implementations of these protocols to fit them into constrained devices. These versions have been designed to reduce the impact in standard specifications. The goal of this work is two-fold: (1) to demonstrate the feasibility of EAP/PANA in IoT devices; (2) to provide the scientific community with the first light-weight interoperable implementation of EAP/PANA for constrained devices in the Contiki operating system (Contiki OS), called PANATIKI. The paper also shows a testbed, simulations and experimental results obtained from real and simulated constrained devices.

  15. PANATIKI: A Network Access Control Implementation Based on PANA for IoT Devices

    PubMed Central

    Sanchez, Pedro Moreno; Lopez, Rafa Marin; Gomez Skarmeta, Antonio F.

    2013-01-01

    Internet of Things (IoT) networks are the pillar of recent novel scenarios, such as smart cities or e-healthcare applications. Among other challenges, these networks cover the deployment and interaction of small devices with constrained capabilities and Internet protocol (IP)-based networking connectivity. These constrained devices usually require connection to the Internet to exchange information (e.g., management or sensing data) or access network services. However, only authenticated and authorized devices can, in general, establish this connection. The so-called authentication, authorization and accounting (AAA) services are in charge of performing these tasks on the Internet. Thus, it is necessary to deploy protocols that allow constrained devices to verify their credentials against AAA infrastructures. The Protocol for Carrying Authentication for Network Access (PANA) has been standardized by the Internet engineering task force (IETF) to carry the Extensible Authentication Protocol (EAP), which provides flexible authentication upon the presence of AAA. To the best of our knowledge, this paper is the first deep study of the feasibility of EAP/PANA for network access control in constrained devices. We provide light-weight versions and implementations of these protocols to fit them into constrained devices. These versions have been designed to reduce the impact in standard specifications. The goal of this work is two-fold: (1) to demonstrate the feasibility of EAP/PANA in IoT devices; (2) to provide the scientific community with the first light-weight interoperable implementation of EAP/PANA for constrained devices in the Contiki operating system (Contiki OS), called PANATIKI. The paper also shows a testbed, simulations and experimental results obtained from real and simulated constrained devices. PMID:24189332

  16. Providing web-based tools for time series access and analysis

    NASA Astrophysics Data System (ADS)

    Eberle, Jonas; Hüttich, Christian; Schmullius, Christiane

    2014-05-01

    Time series information is widely used in environmental change analyses and is also an essential information for stakeholders and governmental agencies. However, a challenging issue is the processing of raw data and the execution of time series analysis. In most cases, data has to be found, downloaded, processed and even converted in the correct data format prior to executing time series analysis tools. Data has to be prepared to use it in different existing software packages. Several packages like TIMESAT (Jönnson & Eklundh, 2004) for phenological studies, BFAST (Verbesselt et al., 2010) for breakpoint detection, and GreenBrown (Forkel et al., 2013) for trend calculations are provided as open-source software and can be executed from the command line. This is needed if data pre-processing and time series analysis is being automated. To bring both parts, automated data access and data analysis, together, a web-based system was developed to provide access to satellite based time series data and access to above mentioned analysis tools. Users of the web portal are able to specify a point or a polygon and an available dataset (e.g., Vegetation Indices and Land Surface Temperature datasets from NASA MODIS). The data is then being processed and provided as a time series CSV file. Afterwards the user can select an analysis tool that is being executed on the server. The final data (CSV, plot images, GeoTIFFs) is visualized in the web portal and can be downloaded for further usage. As a first use case, we built up a complimentary web-based system with NASA MODIS products for Germany and parts of Siberia based on the Earth Observation Monitor (www.earth-observation-monitor.net). The aim of this work is to make time series analysis with existing tools as easy as possible that users can focus on the interpretation of the results. References: Jönnson, P. and L. Eklundh (2004). TIMESAT - a program for analysing time-series of satellite sensor data. Computers and Geosciences 30

  17. Genetic diversity of Capsicum chinensis (Solanaceae) accessions based on molecular markers and morphological and agronomic traits.

    PubMed

    Finger, F L; Lannes, S D; Schuelter, A R; Doege, J; Comerlato, A P; Gonçalves, L S A; Ferreira, F R A; Clovis, L R; Scapim, C A

    2010-09-21

    We estimated the genetic diversity of 49 accessions of the hot pepper species Capsicum chinensis through analyses of 12 physicochemical traits of the fruit, eight multi-categorical variables, and with 32 RAPD primers. Data from the physicochemical traits were submitted to analysis of variance to estimate the genetic parameters, and their means were clustered by the Scott-Knott test. The matrices from the individual and combined distance were estimated by multivariate analyses before applying Tocher's optimization method. All physicochemical traits were examined for genetic variability by analysis of variance. The responses of these traits showed more contribution from genetic than from environmental factors, except the percentage of dry biomass, content of soluble solids and vitamin C level. Total capsaicin had the greatest genetic divergence. Nine clusters were formed from the quantitative data based on the generalized distance of Mahalanobis, using Tocher's method; four were formed from the multi-categorical data using the Cole-Rodgers coefficient, and eight were formed from the molecular data using the Nei and Li coefficient. The accessions were distributed into 14 groups using Tocher's method, and no significant correlation between pungency and origin was detected. Uni- and multivariate analyses permitted the identification of marked genetic diversity and fruit attributes capable of being improved through breeding programs.

  18. Evidence-based psychological treatments for mental disorders: modifiable barriers to access and possible solutions.

    PubMed

    Harvey, Allison G; Gumport, Nicole B

    2015-05-01

    The prevalence of mental disorders is high and appears to be growing, yet the majority of individuals who meet diagnostic criteria for a mental disorder are not able to access an adequate treatment. While evidence-based psychological treatments (EBPTs) are effective single or adjunctive treatments for mental disorders, there is also evidence that access to these treatments is diminishing. We seek to highlight modifiable barriers to these problems at the patient, therapist, treatment, organization and government-levels of analysis. A range of solutions to each set of contributors is offered and domains for future research are highlighted. In particular, we focus on the need to continue to work toward innovation in treatment development while also solving the difficulties relating to the dissemination of EBPTs. Several relatively new concepts in the field will be discussed (implementation cliff, program drift, voltage drop and deployment treatment development) and we contrast America and England as examples of government-level processes that are in the process of major change with respect to EBPTs. We conclude that there is a need for people in our field to become more knowledgeable about, and get involved in, shaping public policy.

  19. Evidence-based psychological treatments for mental disorders: Modifiable barriers to access and possible solutions

    PubMed Central

    Harvey, Allison G.; Gumport, Nicole B.

    2015-01-01

    The prevalence of mental disorders is high and appears to be growing, yet the majority of individuals who meet diagnostic criteria for a mental disorder are not able to access an adequate treatment. While evidence-based psychological treatments (EBPTs) are effective single or adjunctive treatments for mental disorders, there is also evidence that access to these treatments is diminishing. We seek to highlight modifiable barriers to these problems at the patient, therapist, treatment, organization and government-levels of analysis. A range of solutions to each set of contributors is offered and domains for future research are highlighted. In particular, we focus on the need to continue to work toward innovation in treatment development while also solving the difficulties relating to the dissemination of EBPTs. Several relatively new concepts in the field will be discussed (implementation cliff, program drift, voltage drop and deployment treatment development) and we contrast America and England as examples of government-level processes that are in the process of major change with respect to EBPTs. We conclude that there is a need for people in our field to become more knowledgeable about, and get involved in, shaping public policy. PMID:25768982

  20. The new ALICE DQM client: a web access to ROOT-based objects

    NASA Astrophysics Data System (ADS)

    von Haller, B.; Carena, F.; Carena, W.; Chapeland, S.; Chibante Barroso, V.; Costa, F.; Delort, C.; Dénes, E.; Diviá, R.; Fuchs, U.; Niedziela, J.; Simonetti, G.; Soós, C.; Telesca, A.; Vande Vyvre, P.; Wegrzynek, A.

    2015-12-01

    A Large Ion Collider Experiment (ALICE) is the heavy-ion detector designed to study the physics of strongly interacting matter and the quark-gluon plasma at the CERN Large Hadron Collider (LHC). The online Data Quality Monitoring (DQM) plays an essential role in the experiment operation by providing shifters with immediate feedback on the data being recorded in order to quickly identify and overcome problems. An immediate access to the DQM results is needed not only by shifters in the control room but also by detector experts worldwide. As a consequence, a new web application has been developed to dynamically display and manipulate the ROOT-based objects produced by the DQM system in a flexible and user friendly interface. The architecture and design of the tool, its main features and the technologies that were used, both on the server and the client side, are described. In particular, we detail how we took advantage of the most recent ROOT JavaScript I/O and web server library to give interactive access to ROOT objects stored in a database. We describe as well the use of modern web techniques and packages such as AJAX, DHTMLX and jQuery, which has been instrumental in the successful implementation of a reactive and efficient application. We finally present the resulting application and how code quality was ensured. We conclude with a roadmap for future technical and functional developments.

  1. Setting Access Permission through Transitive Relationship in Web-based Social Networks

    NASA Astrophysics Data System (ADS)

    Hong, Dan; Shen, Vincent Y.

    The rising popularity of various social networking websites has created a huge problem on Internet privacy. Although it is easy to post photos, comments, opinions on some events, etc. on the Web, some of these data (such as a person’s location at a particular time, criticisms of a politician, etc.) are private and should not be accessed by unauthorized users. Although social networks facilitate sharing, the fear of sending sensitive data to a third party without knowledge or permission of the data owners discourages people from taking full advantage of some social networking applications. We exploit the existing relationships on social networks and build a ‘‘trust network’’ with transitive relationship to allow controlled data sharing so that the privacy and preferences of data owners are respected. The trust network linking private data owners, private data requesters, and intermediary users is a directed weighted graph. The permission value for each private data requester can be automatically assigned in this network based on the transitive relationship. Experiments were conducted to confirm the feasibility of constructing the trust network from existing social networks, and to assess the validity of permission value assignments in the query process. Since the data owners only need to define the access rights of their closest contacts once, this privacy scheme can make private data sharing easily manageable by social network participants.

  2. Exploring access to scientific literature using content-based image retrieval

    NASA Astrophysics Data System (ADS)

    Deserno, Thomas M.; Antani, Sameer; Long, Rodney

    2007-03-01

    The number of articles published in the scientific medical literature is continuously increasing, and Web access to the journals is becoming common. Databases such as SPIE Digital Library, IEEE Xplore, indices such as PubMed, and search engines such as Google provide the user with sophisticated full-text search capabilities. However, information in images and graphs within these articles is entirely disregarded. In this paper, we quantify the potential impact of using content-based image retrieval (CBIR) to access this non-text data. Based on the Journal Citations Report (JCR), the journal Radiology was selected for this study. In 2005, 734 articles were published electronically in this journal. This included 2,587 figures, which yields a rate of 3.52 figures per article. Furthermore, 56.4% of these figures are composed of several individual panels, i.e. the figure combines different images and/or graphs. According to the Image Cross-Language Evaluation Forum (ImageCLEF), the error rate of automatic identification of medical images is about 15%. Therefore, it is expected that, by applying ImageCLEF-like techniques, already 95.5% of articles could be retrieved by means of CBIR. The challenge for CBIR in scientific literature, however, is the use of local texture properties to analyze individual image panels in composite illustrations. Using local features for content-based image representation, 8.81 images per article are available, and the predicted correctness rate may increase to 98.3%. From this study, we conclude that CBIR may have a high impact in medical literature research and suggest that additional research in this area is warranted.

  3. Access, Use, and Preferences for Technology-Based Perinatal and Breastfeeding Support Among Childbearing Women

    PubMed Central

    Demirci, Jill Radtke; Cohen, Susan M.; Parker, Maris; Holmes, Ashleigh; Bogen, Debra L.

    2016-01-01

    ABSTRACT We surveyed 146 postpartum women who birthed at 34–37 6/7 weeks of gestation and intended to breastfeed about their use of and preferences regarding technology to obtain perinatal and breastfeeding support. Most participants owned smartphones and used technology during pregnancy to track pregnancy data, follow fetal development, address pregnancy concerns, and obtain breastfeeding information. Internet, e-mail, apps, and multiplatform resources were the most popular technologies used and preferred. Demographic differences existed in mobile technology access and preferences for different technologies. In terms of technology-based breastfeeding support, women wanted encouragement, anticipatory guidance, and information about milk production. A nuanced understanding of the technology childbearing women use and desire has the potential to impact clinical care and inform perinatal support interventions. PMID:26848248

  4. Orthogonal frequency-division multiplexing access (OFDMA) based wireless visible light communication (VLC) system

    NASA Astrophysics Data System (ADS)

    Sung, Jiun-Yu; Yeh, Chien-Hung; Chow, Chi-Wai; Lin, Wan-Feng; Liu, Yang

    2015-11-01

    An orthogonal frequency-division multiplexing access (OFDMA) based visible light communication (VLC) system is proposed in this paper. The architecture of the proposed system is divided into several VLC cells, which is defined in this paper. The deployment and upgrade of the system involve only simple combination of the VLC cells. Hence it is economically advantageous. To guarantee smooth communication, nearly equal data rate is provided at every location within the system with no concern on the system scale. The user location monitor strategy is also discussed to solve the region division issues. The characteristics of the proposed system are analyzed in detail in this paper. A one-dimensional experiment was demonstrated with 13.6 Mb/s data rate.

  5. Building secure wireless access point based on certificate authentication and firewall captive portal

    NASA Astrophysics Data System (ADS)

    Soewito, B.; Hirzi

    2014-03-01

    Wireless local area network or WLAN more vulnerability than wired network even though WLAN has many advantages over wired. Wireless networks use radio transmissions to carry data between end users and access point. Therefore, it is possible for someone to sit in your office building's lobby or parking lot or parking lot to eavesdrop on the wireless network communication. This paper discussed securing wires local area network used WPA2 Enterprise based PEAP MS-CHAP and Captive portal firewall. We also divided the network for employer and visitor to increase the level of security. Our experiment showed that the WLAN could be broken using the attacker tool such as airodump, aireply, and aircrack.

  6. Terminology issues in user access to Web-based medical information.

    PubMed Central

    McCray, A. T.; Loane, R. F.; Browne, A. C.; Bangalore, A. K.

    1999-01-01

    We conducted a study of user queries to the National Library of Medicine Web site over a three month period. Our purpose was to study the nature and scope of these queries in order to understand how to improve users' access to the information they are seeking on our site. The results show that the queries are primarily medical in content (94%), with only a small percentage (5.5%) relating to library services, and with a very small percentage (.5%) not being medically relevant at all. We characterize the data set, and conclude with a discussion of our plans to develop a UMLS-based terminology server to assist NLM Web users. Images Figure 1 PMID:10566330

  7. A Time-constrained Network Voronoi Construction and Accessibility Analysis in Location-based Service Technology

    NASA Astrophysics Data System (ADS)

    Yu, W.; Ai, T.

    2014-11-01

    Accessibility analysis usually requires special models of spatial location analysis based on some geometric constructions, such as Voronoi diagram (abbreviated to VD). There are many achievements in classic Voronoi model research, however suffering from the following limitations for location-based services (LBS) applications. (1) It is difficult to objectively reflect the actual service areas of facilities by using traditional planar VDs, because human activities in LBS are usually constrained only to the network portion of the planar space. (2) Although some researchers have adopted network distance to construct VDs, their approaches are used in a static environment, where unrealistic measures of shortest path distance based on assumptions about constant travel speeds through the network were often used. (3) Due to the computational complexity of the shortest-path distance calculating, previous researches tend to be very time consuming, especially for large datasets and if multiple runs are required. To solve the above problems, a novel algorithm is developed in this paper. We apply network-based quadrat system and 1-D sequential expansion to find the corresponding subnetwork for each focus. The idea is inspired by the natural phenomenon that water flow extends along certain linear channels until meets others or arrives at the end of route. In order to accommodate the changes in traffic conditions, the length of network-quadrat is set upon the traffic condition of the corresponding street. The method has the advantage over Dijkstra's algorithm in that the time cost is avoided, and replaced with a linear time operation.

  8. Ship accessibility predictions for the Arctic Ocean based on IPCC CO2 emission scenarios

    NASA Astrophysics Data System (ADS)

    Oh, Jai-Ho; Woo, Sumin; Yang, Sin-Il

    2017-02-01

    Changes in the extent of Arctic sea ice, which have resulted from climate change, offer new opportunities to use the Northern Sea Route (NSR) and Northwest Passage (NWP) for shipping. However, choosing to navigate the Arctic Ocean remains challenging due to the limited accessibility of ships and the balance between economic gain and potential risk. As a result, more precise and detailed information on both weather and sea ice change in the Arctic are required. In this study, a high-resolution global AGCM was used to provide detailed information on the extent and thickness of Arctic sea ice. For this simulation, we have simulated the AMIP-type simulation for the present-day climate during 31 years from 1979 to 2009 with observed SST and Sea Ice concentration. For the future climate projection, we have performed the historical climate during 1979-2005 and subsequently the future climate projection during 2010-2099 with mean of four CMIP5 models due to the two Representative Concentration Pathway scenarios (RCP 8.5 and RCP 4.5). First, the AMIP-type simulation was evaluated by comparison with observations from the Hadley Centre sea-ice and Sea Surface Temperature (HadlSST) dataset. The model reflects the maximum (in March) and minimum (in September) sea ice extent and annual cycle. Based on this validation, the future sea ice extents show the decreasing trend for both the maximum and minimum seasons and RCP 8.5 shows more sharply decreasing patterns of sea ice than RCP 4.5. Under both scenarios, ships classified as Polar Class (PC) 3 and Open-Water (OW) were predicted to have the largest and smallest number of ship-accessible days (in any given year) for the NSR and NWP, respectively. Based on the RCP 8.5 scenario, the projections suggest that after 2070, PC3 and PC6 vessels will have year-round access across to the Arctic Ocean. In contrast, OW vessels will continue to have a seasonal handicap, inhibiting their ability to pass through the NSR and NWP.

  9. Efficient Consistency Achievement of Federated Identity and Access Management Based on a Novel Self-Adaptable Approach

    NASA Astrophysics Data System (ADS)

    Cha, Shi-Cho; Chang, Hsiang-Meng

    Federated identity and access management (FIAM) systems enable a user to access services provided by various organizations seamlessly. In FIAM systems, service providers normally stipulate that their users show assertions issued by allied parties to use their services as well as determine user privileges based on attributes in the assertions. However, the integrity of the attributes is important under certain circumstances. In such a circumstance, all released assertions should reflect modifications made to user attributes. Despite the ability to adopt conventional certification revocation technologies, including CRL or OCSP, to revoke an assertion and request the corresponding user to obtain a new assertion, re-issuing an entirely new assertion if only one attribute, such as user location or other environmental information, is changed would be inefficient. Therefore, this work presents a self-adaptive framework to achieve consistency in federated identity and access management systems (SAFIAM). In SAFIAM, an identity provider (IdP), which authenticates users and provides user attributes, should monitor access probabilities according to user attributes. The IdP can then adopt the most efficient means of ensuring data integrity of attributes based on related access probabilities. While Internet-based services emerge daily that have various access probabilities with respect to their user attributes, the proposed self-adaptive framework significantly contributes to efforts to streamline the use of FIAM systems.

  10. Virtual and Physical Experimentation in Inquiry-Based Science Labs: Attitudes, Performance and Access

    NASA Astrophysics Data System (ADS)

    Pyatt, Kevin; Sims, Rod

    2012-02-01

    This study investigated the learning dimensions that occur in physical and virtual inquiry-based lab investigations, in first-year secondary chemistry classes. This study took place over a 2 year period and utilized an experimental crossover design which consisted of two separate trials of laboratory investigation. Assessment data and attitudinal data were gathered and analyzed to measure the instructional value of physical and virtual lab experiences in terms of student performance and attitudes. Test statistics were conducted for differences of means for assessment data. Student attitudes towards virtual experiences in comparison to physical lab experiences were measured using a newly created Virtual and Physical Experimentation Questionnaire (VPEQ). VPEQ was specifically developed for this study, and included new scales of Usefulness of Lab, and Equipment Usability which measured attitudinal dimensions in virtual and physical lab experiences. A factor analysis was conducted for questionnaire data, and reliability of the scales and internal consistency of items within scales were calculated. The new scales were statistically valid and reliable. The instructional value of physical and virtual lab experiences was comparable in terms of student performance. Students showed preference towards the virtual medium in their lab experiences. Students showed positive attitudes towards physical and virtual experiences, and demonstrated a preference towards inquiry-based experiences, physical or virtual. Students found virtual experiences to have higher equipment usability as well as a higher degree of open-endedness. In regards to student access to inquiry-based lab experiences, virtual and online alternatives were viewed favorably by students.

  11. A Survey of Exemplar Teachers' Perceptions, Use, and Access of Computer-Based Games and Technology for Classroom Instruction

    ERIC Educational Resources Information Center

    Proctor, Michael D.; Marks, Yaela

    2013-01-01

    This research reports and analyzes for archival purposes surveyed perceptions, use, and access by 259 United States based exemplar Primary and Secondary educators of computer-based games and technology for classroom instruction. Participating respondents were considered exemplary as they each won the Milken Educator Award during the 1996-2009…

  12. Can free open access resources strengthen knowledge-based emerging public health priorities, policies and programs in Africa?

    PubMed Central

    Tambo, Ernest; Madjou, Ghislaine; Khayeka-Wandabwa, Christopher; Tekwu, Emmanuel N.; Olalubi, Oluwasogo A.; Midzi, Nicolas; Bengyella, Louis; Adedeji, Ahmed A.; Ngogang, Jeanne Y.

    2016-01-01

    Tackling emerging epidemics and infectious diseases burden in Africa requires increasing unrestricted open access and free use or reuse of regional and global policies reforms as well as timely communication capabilities and strategies. Promoting, scaling up data and information sharing between African researchers and international partners are of vital importance in accelerating open access at no cost. Free Open Access (FOA) health data and information acceptability, uptake tactics and sustainable mechanisms are urgently needed. These are critical in establishing real time and effective knowledge or evidence-based translation, proven and validated approaches, strategies and tools to strengthen and revamp health systems.  As such, early and timely access to needed emerging public health information is meant to be instrumental and valuable for policy-makers, implementers, care providers, researchers, health-related institutions and stakeholders including populations when guiding health financing, and planning contextual programs. PMID:27508058

  13. Organizational interventions improving access to community-based primary health care for vulnerable populations: a scoping review.

    PubMed

    Khanassov, Vladimir; Pluye, Pierre; Descoteaux, Sarah; Haggerty, Jeannie L; Russell, Grant; Gunn, Jane; Levesque, Jean-Frederic

    2016-10-10

    Access to community-based primary health care (hereafter, 'primary care') is a priority in many countries. Health care systems have emphasized policies that help the community 'get the right service in the right place at the right time'. However, little is known about organizational interventions in primary care that are aimed to improve access for populations in situations of vulnerability (e.g., socioeconomically disadvantaged) and how successful they are. The purpose of this scoping review was to map the existing evidence on organizational interventions that improve access to primary care services for vulnerable populations. Scoping review followed an iterative process. Eligibility criteria: organizational interventions in Organisation for Economic Cooperation and Development (OECD) countries; aiming to improve access to primary care for vulnerable populations; all study designs; published from 2000 in English or French; reporting at least one outcome (avoidable hospitalization, emergency department admission, or unmet health care needs).

  14. Dynamic Spectrum Access to the Combined Resource of Commercial and Public Safety Bands Based on a WCDMA Shared Network

    NASA Astrophysics Data System (ADS)

    Jeon, Hyoungsuk; Im, Sooyeol; Kim, Youmin; Kim, Seunghee; Kim, Jinup; Lee, Hyuckjae

    The public safety spectrum is generally under-utilized due to the unique traffic characteristics of bursty and mission critical. This letter considers the application of dynamic spectrum access (DSA) to the combined spectrum of public safety (PS) and commercial (CMR) users in a common shared network that can provide both PS and CMR services. Our scenario includes the 700MHz Public/Private Partnership which was recently issued by the Federal Communications Commission. We first propose an efficient DSA mechanism to coordinate the combined spectrum, and then establish a call admission control that reflects the proposed DSA in a wideband code division multiple access based network. The essentials of our proposed DSA are opportunistic access to the public safety spectrum and priority access to the commercial spectrum. Simulation results show that these schemes are well harmonized in various network environments.

  15. Can free open access resources strengthen knowledge-based emerging public health priorities, policies and programs in Africa?

    PubMed

    Tambo, Ernest; Madjou, Ghislaine; Khayeka-Wandabwa, Christopher; Tekwu, Emmanuel N; Olalubi, Oluwasogo A; Midzi, Nicolas; Bengyella, Louis; Adedeji, Ahmed A; Ngogang, Jeanne Y

    2016-01-01

    Tackling emerging epidemics and infectious diseases burden in Africa requires increasing unrestricted open access and free use or reuse of regional and global policies reforms as well as timely communication capabilities and strategies. Promoting, scaling up data and information sharing between African researchers and international partners are of vital importance in accelerating open access at no cost. Free Open Access (FOA) health data and information acceptability, uptake tactics and sustainable mechanisms are urgently needed. These are critical in establishing real time and effective knowledge or evidence-based translation, proven and validated approaches, strategies and tools to strengthen and revamp health systems.  As such, early and timely access to needed emerging public health information is meant to be instrumental and valuable for policy-makers, implementers, care providers, researchers, health-related institutions and stakeholders including populations when guiding health financing, and planning contextual programs.

  16. Rocket-Based Combined-Cycle Propulsion Technology for Access-to-Space Applications

    NASA Technical Reports Server (NTRS)

    Hueter, Uwe

    1999-01-01

    NASA's Office of Aero-Space Technology (OAST) established three major goals, referred to as, "The Three Pillars for Success". The Advanced Space Transportation Program Office (ASTP) at the NASA's Marshall Space Flight Center (MSFC) in Huntsville, Ala. focuses on future space transportation technologies under the "Access to Space" pillar. One of the main activities over the past three years has been on advancing the hydrogen fueled rocket-based combined cycle (RBCC) technologies. The RBCC effort that was completed early this year was the initial step leading to flight demonstrations of the technology for space launch vehicle propulsion. Aerojet and Boeing-Rocketdyne designed, built and ground tested their RBCC engine concepts. In addition, ASTROX, Georgia Institute of Technology, McKinney Associates, Pennsylvania State University (PSU), and University of Alabama in Huntsville conducted supporting activities. The RBCC activity included ground testing of components (e.g., injectors, thrusters, ejectors and inlets) and integrated flowpaths. Inlet testing was performed at the Lewis Research Center's 1 x 1 wind tunnel. All direct connect and free-jet engine testing were conducted at the GASL facilities on Long Island, New York. Testing spanned the Mach range from sea level static to Mach 8. Testing of the rocket-only mode, simulating the final phase of the ascent mission profile, was also performed. The originally planned work on these contracts was completed in 1999. Follow-on activities have been initiated for both hydrogen and hydrocarbon fueled RBCC concepts. Studies to better understand system level issues with the integration of RBCC propulsion with earth-to-orbit vehicles have also been conducted. This paper describes the status, progress and future plans of the RBCC activities funded by NASA/MSFC with a major focus on the benefits of utilizing air-breathing combined-cycle propulsion in access-to-space applications.

  17. Face Recognition for Access Control Systems Combining Image-Difference Features Based on a Probabilistic Model

    NASA Astrophysics Data System (ADS)

    Miwa, Shotaro; Kage, Hiroshi; Hirai, Takashi; Sumi, Kazuhiko

    We propose a probabilistic face recognition algorithm for Access Control System(ACS)s. Comparing with existing ACSs using low cost IC-cards, face recognition has advantages in usability and security that it doesn't require people to hold cards over scanners and doesn't accept imposters with authorized cards. Therefore face recognition attracts more interests in security markets than IC-cards. But in security markets where low cost ACSs exist, price competition is important, and there is a limitation on the quality of available cameras and image control. Therefore ACSs using face recognition are required to handle much lower quality images, such as defocused and poor gain-controlled images than high security systems, such as immigration control. To tackle with such image quality problems we developed a face recognition algorithm based on a probabilistic model which combines a variety of image-difference features trained by Real AdaBoost with their prior probability distributions. It enables to evaluate and utilize only reliable features among trained ones during each authentication, and achieve high recognition performance rates. The field evaluation using a pseudo Access Control System installed in our office shows that the proposed system achieves a constant high recognition performance rate independent on face image qualities, that is about four times lower EER (Equal Error Rate) under a variety of image conditions than one without any prior probability distributions. On the other hand using image difference features without any prior probabilities are sensitive to image qualities. We also evaluated PCA, and it has worse, but constant performance rates because of its general optimization on overall data. Comparing with PCA, Real AdaBoost without any prior distribution performs twice better under good image conditions, but degrades to a performance as good as PCA under poor image conditions.

  18. MATISSE a web-based tool to access, visualize and analyze high resolution minor bodies observation

    NASA Astrophysics Data System (ADS)

    Zinzi, Angelo; Capria, Maria Teresa; Palomba, Ernesto; Antonelli, Lucio Angelo; Giommi, Paolo

    2016-07-01

    In the recent years planetary exploration missions acquired data from minor bodies (i.e., dwarf planets, asteroid and comets) at a detail level never reached before. Since these objects often present very irregular shapes (as in the case of the comet 67P Churyumov-Gerasimenko target of the ESA Rosetta mission) "classical" bidimensional projections of observations are difficult to understand. With the aim of providing the scientific community a tool to access, visualize and analyze data in a new way, ASI Science Data Center started to develop MATISSE (Multi-purposed Advanced Tool for the Instruments for the Solar System Exploration - http://tools.asdc.asi.it/matisse.jsp) in late 2012. This tool allows 3D web-based visualization of data acquired by planetary exploration missions: the output could either be the straightforward projection of the selected observation over the shape model of the target body or the visualization of a high-order product (average/mosaic, difference, ratio, RGB) computed directly online with MATISSE. Standard outputs of the tool also comprise downloadable files to be used with GIS software (GeoTIFF and ENVI format) and 3D very high-resolution files to be viewed by means of the free software Paraview. During this period the first and most frequent exploitation of the tool has been related to visualization of data acquired by VIRTIS-M instruments onboard Rosetta observing the comet 67P. The success of this task, well represented by the good number of published works that used images made with MATISSE confirmed the need of a different approach to correctly visualize data coming from irregular shaped bodies. In the next future the datasets available to MATISSE are planned to be extended, starting from the addition of VIR-Dawn observations of both Vesta and Ceres and also using standard protocols to access data stored in external repositories, such as NASA ODE and Planetary VO.

  19. A Study on Railway Signal System to Apply CDMA-QAM Method

    NASA Astrophysics Data System (ADS)

    Mochizuki, Hiroshi; Asano, Akira; Sano, Minoru; Takahashi, Sei; Nakamura, Hideo

    Recently, QAM (Quadrature Amplitude Modulation) transmission is paid to attention in digital modulation method, and it has been used for wireless LAN and digital broadcasting. QAM is a modulation method that puts information on carrier amplitude and phase. So QAM can achieve high-capacity data transmission that the use efficiency of frequency band is good. But QAM has a bad characteristic that is weak to the noise and the interference because distance between each symbol is short. Then we propose the method that not transmission data but CDMA signal, obtained after transmission data is modulated by spread code and multiplexed, is given to each symbol of QAM. And we studied about railway signal system on track circuit as a sample to apply this method. As result of computer simulations, we verified to be able to achieve the improvement of signal to noise ratio by optimizing the constellation map of QAM. We report with the method of a synchronous acquisition.

  20. Design and Implementation of Uniform Data Access Platform based on JSON

    NASA Astrophysics Data System (ADS)

    Ding, Chen-Lu; Wang, Fang-Xiao; Wang, Jun

    There are lots of heterogeneous data sources which reside in many information systems, it is very difficult to for users to access the data sources through the study of existing SOA technology. In this paper, the design and implementation of a unified implementation of structured, unstructured data access platform, through the use of JSON as the data exchange technology. The platform will realize efficient interaction between data and resource requestors to improve the data access service management and efficiency of customization.

  1. Smartphone-based system to improve transportation access for the cognitively impaired.

    PubMed

    Anderson, Shane M; Riehle, Timothy H; Lichter, Patrick A; Brown, Allen W; Panescu, Dorin

    2015-01-01

    This project developed and evaluated a smartphone-based system to improve mobility and transportation access for the cognitively impaired. The proposed system is intended to allow the cognitively impaired to use public transportation systems, community transportation and dedicated transportation services for the disabled with greater ease and safety. Individuals with cognitive disabilities are often unable to operate an automobile, or may require a prolonged recovery period before resuming driving. Public transportation systems represent a significant means to allow these individuals to maintain independence. Yet public transportation systems can pose significant challenges to individuals with cognitive impairment. The goal of this project is to develop a system to reduce these barriers via a technological solution consisting of components developed both for the cognitively impaired user and their caregiver or family member. The first component consists of a cognitive prosthetic device featuring traditional memory cueing and reminders as well as custom location-based transportation specific functions. This cognitive mobility assistant will leverage the computing power and GPS location determination capabilities of inexpensive, powerful smart phones. The second component consists of a management application which offers caregivers the ability to configure and program the reminder and transit functions remotely via the Internet. Following completion of the prototype system a pilot human test was performed with cognitively disabled individuals and family members or caregivers to assess the usability and acceptability of both system components.

  2. An Ultrasonic Multiple-Access Ranging Core Based on Frequency Shift Keying Towards Indoor Localization.

    PubMed

    Segers, Laurent; Van Bavegem, David; De Winne, Sam; Braeken, An; Touhafi, Abdellah; Steenhaut, Kris

    2015-07-30

    This paper describes a new approach and implementation methodology for indoor ranging based on the time difference of arrival using code division multiple access with ultrasound signals. A novel implementation based on a field programmable gate array using finite impulse response filters and an optimized correlation demodulator implementation for ultrasound orthogonal signals is developed. Orthogonal codes are modulated onto ultrasound signals using frequency shift keying with carrier frequencies of 24.5 kHz and 26 kHz. This implementation enhances the possibilities for real-time, embedded and low-power tracking of several simultaneous transmitters. Due to the high degree of parallelism offered by field programmable gate arrays, up to four transmitters can be tracked simultaneously. The implementation requires at most 30% of the available logic gates of a Spartan-6 XC6SLX45 device and is evaluated on accuracy and precision through several ranging topologies. In the first topology, the distance between one transmitter and one receiver is evaluated. Afterwards, ranging analyses are applied between two simultaneous transmitters and one receiver. Ultimately, the position of the receiver against four transmitters using trilateration is also demonstrated. Results show enhanced distance measurements with distances ranging from a few centimeters up to 17 m, while keeping a centimeter-level accuracy.

  3. Genetic diversity among melon accessions (Cucumis melo) from Turkey based on SSR markers.

    PubMed

    Kaçar, Y A; Simsek, O; Solmaz, I; Sari, N; Mendi, Y Y

    2012-12-19

    Melon (Cucumis melo) is an important vegetable crop in Turkey, where it is grown in many regions; the most widely planted lines are local winter types belonging to the var. inodorous. We examined 81 melon genotypes collected from different provinces of Turkey, compared with 15 reference melon genotypes obtained from INRA/France, to determine genetic diversity among Turkish melons. Twenty polymorphic primers were used to generate the SSR markers. PCR amplification was performed and electrophoresis was conducted. SSR data were used to generate a binary matrix. For cluster analysis, UPGMA was employed to construct a clustering dendrogram based on the genetic distance matrix. The cophenetic correlation was compared with the similarity matrix using the Mantel matrix correspondence test to evaluate the representativeness of the dendrogram. A total of 123 alleles were amplified using the 20 SSR primer sets. The number of alleles detected by a single primer set ranged from 2 to 12, with an average of 6.15. The similarity ranged from 0.22 to 1.00 in the dendrogram developed from microsatellite analysis. Based on this molecular data, we concluded that genetic diversity among these Turkish accessions is relatively high.

  4. An Ultrasonic Multiple-Access Ranging Core Based on Frequency Shift Keying Towards Indoor Localization

    PubMed Central

    Segers, Laurent; Van Bavegem, David; De Winne, Sam; Braeken, An; Touhafi, Abdellah; Steenhaut, Kris

    2015-01-01

    This paper describes a new approach and implementation methodology for indoor ranging based on the time difference of arrival using code division multiple access with ultrasound signals. A novel implementation based on a field programmable gate array using finite impulse response filters and an optimized correlation demodulator implementation for ultrasound orthogonal signals is developed. Orthogonal codes are modulated onto ultrasound signals using frequency shift keying with carrier frequencies of 24.5 kHz and 26 kHz. This implementation enhances the possibilities for real-time, embedded and low-power tracking of several simultaneous transmitters. Due to the high degree of parallelism offered by field programmable gate arrays, up to four transmitters can be tracked simultaneously. The implementation requires at most 30% of the available logic gates of a Spartan-6 XC6SLX45 device and is evaluated on accuracy and precision through several ranging topologies. In the first topology, the distance between one transmitter and one receiver is evaluated. Afterwards, ranging analyses are applied between two simultaneous transmitters and one receiver. Ultimately, the position of the receiver against four transmitters using trilateration is also demonstrated. Results show enhanced distance measurements with distances ranging from a few centimeters up to 17 m, while keeping a centimeter-level accuracy. PMID:26263986

  5. Metal oxide resistive random access memory based synaptic devices for brain-inspired computing

    NASA Astrophysics Data System (ADS)

    Gao, Bin; Kang, Jinfeng; Zhou, Zheng; Chen, Zhe; Huang, Peng; Liu, Lifeng; Liu, Xiaoyan

    2016-04-01

    The traditional Boolean computing paradigm based on the von Neumann architecture is facing great challenges for future information technology applications such as big data, the Internet of Things (IoT), and wearable devices, due to the limited processing capability issues such as binary data storage and computing, non-parallel data processing, and the buses requirement between memory units and logic units. The brain-inspired neuromorphic computing paradigm is believed to be one of the promising solutions for realizing more complex functions with a lower cost. To perform such brain-inspired computing with a low cost and low power consumption, novel devices for use as electronic synapses are needed. Metal oxide resistive random access memory (ReRAM) devices have emerged as the leading candidate for electronic synapses. This paper comprehensively addresses the recent work on the design and optimization of metal oxide ReRAM-based synaptic devices. A performance enhancement methodology and optimized operation scheme to achieve analog resistive switching and low-energy training behavior are provided. A three-dimensional vertical synapse network architecture is proposed for high-density integration and low-cost fabrication. The impacts of the ReRAM synaptic device features on the performances of neuromorphic systems are also discussed on the basis of a constructed neuromorphic visual system with a pattern recognition function. Possible solutions to achieve the high recognition accuracy and efficiency of neuromorphic systems are presented.

  6. Toward a Computer Vision-based Wayfinding Aid for Blind Persons to Access Unfamiliar Indoor Environments.

    PubMed

    Tian, Yingli; Yang, Xiaodong; Yi, Chucai; Arditi, Aries

    2013-04-01

    Independent travel is a well known challenge for blind and visually impaired persons. In this paper, we propose a proof-of-concept computer vision-based wayfinding aid for blind people to independently access unfamiliar indoor environments. In order to find different rooms (e.g. an office, a lab, or a bathroom) and other building amenities (e.g. an exit or an elevator), we incorporate object detection with text recognition. First we develop a robust and efficient algorithm to detect doors, elevators, and cabinets based on their general geometric shape, by combining edges and corners. The algorithm is general enough to handle large intra-class variations of objects with different appearances among different indoor environments, as well as small inter-class differences between different objects such as doors and door-like cabinets. Next, in order to distinguish intra-class objects (e.g. an office door from a bathroom door), we extract and recognize text information associated with the detected objects. For text recognition, we first extract text regions from signs with multiple colors and possibly complex backgrounds, and then apply character localization and topological analysis to filter out background interference. The extracted text is recognized using off-the-shelf optical character recognition (OCR) software products. The object type, orientation, location, and text information are presented to the blind traveler as speech.

  7. Animacy-Based Accessibility and Competition in Relative Clause Production in Hindi and Malayalam.

    PubMed

    Perera, C K; Srivastava, A K

    2016-08-01

    Two studies investigated interaction of animacy-based accessibility and competition processes with language specific constraints in shaping production preferences. Relative clause elicitation tasks (Gennari et al. in Cogn Psychol 65:141-176, 2012) were performed by two groups with 40 participants in each. Significantly more passives were produced with animate question/focus and assigned subject function to them in Malayalam, while the difference was insignificant in Hindi with animacy not equating with grammatical function assignment. Both languages produced active objects with OSV order significantly more with animate question/focus. This indicates animacy effect on word order. Animacy also influenced the expression of the agent phase in both languages as a tendency was found to omit the agent by-phase or to delay its appearance, when the two animate nouns entering into the structure are highly similar. The results point to language specific constraints in relative clause production and variability in the role of animacy-based retrieval order across languages.

  8. Toward a Computer Vision-based Wayfinding Aid for Blind Persons to Access Unfamiliar Indoor Environments

    PubMed Central

    Tian, YingLi; Yang, Xiaodong; Yi, Chucai; Arditi, Aries

    2012-01-01

    Independent travel is a well known challenge for blind and visually impaired persons. In this paper, we propose a proof-of-concept computer vision-based wayfinding aid for blind people to independently access unfamiliar indoor environments. In order to find different rooms (e.g. an office, a lab, or a bathroom) and other building amenities (e.g. an exit or an elevator), we incorporate object detection with text recognition. First we develop a robust and efficient algorithm to detect doors, elevators, and cabinets based on their general geometric shape, by combining edges and corners. The algorithm is general enough to handle large intra-class variations of objects with different appearances among different indoor environments, as well as small inter-class differences between different objects such as doors and door-like cabinets. Next, in order to distinguish intra-class objects (e.g. an office door from a bathroom door), we extract and recognize text information associated with the detected objects. For text recognition, we first extract text regions from signs with multiple colors and possibly complex backgrounds, and then apply character localization and topological analysis to filter out background interference. The extracted text is recognized using off-the-shelf optical character recognition (OCR) software products. The object type, orientation, location, and text information are presented to the blind traveler as speech. PMID:23630409

  9. Lunar archive panoramas: modern image processing and access to the historic data based on spatial context

    NASA Astrophysics Data System (ADS)

    Kozlova, Natalia; Kokhanov, Alexander; Oberst, Jürgen; Zubarev, Anatoliy; Nadezhdina, Irina; Patraty, Vyacheslav; Karachevtseva, Irina; Garov, Andrey; Matveev, Evgeniy

    The objectives of our work are to fully exploit the historic Soviet Lunokhod data and use the results for scientific and public purposes. Unfortunately, many of the relevant operational parameters of the Lunokhods missions are lost. Modern photogrammetry is a key to solving these issues, providing analysis techniques, not available at the time of the early lunar missions. For this purpose we use special developed software, GIS tools and high-resolution LRO data [1]. Results of new image processing of historic data are part of PRoViDE project (Planetary Robotics Vision Data Exploitation) which aims to assemble a major portion of the imaging data gathered from different vehicles and probes on planetary surfaces into a unique database, bringing them into a spatial context and providing access to a complete set of 3D vision products (http://www.provide-space.eu/). Our technology of archive panorama processing allows us to recover lost information of Soviet lunar missions and study lunar landing site imagery by state-of-the-art photogrammetric techniques. Our main task is to perform lunar panoramas in measurement form based on photogrammetry and geoanalyses methods, and then involve them in more detailed morphometric analyses [2] and 3D-modeling of lunar surface based on LROC NAC image processing [3]. The results of our work are various types of new products: panoramas in different projections, updated metadata with recovering parameters, and ortho-panoramas, which can be used for quantitative geomorphology assessment based on spatial tools [4]. All data products obtained as a result of the study are to be placed into Planetary data storage which is developing as Geodesy and Cartography Node [5]. Access to archive lunar data will be organized via Geo-portal (http://cartsrv.mexlab.ru/geoportal/) using authorization service, which provided data security and user control. Planetary spatial information system can integrate various types of data for planets and their

  10. Electro-optical time gating based on Mach-Zehnder modulator for multiple access interference elimination in optical code-division multiple access networks

    NASA Astrophysics Data System (ADS)

    Chen, Yinfang; Wang, Rong; Fang, Tao; Pu, Tao; Xiang, Peng; Zheng, Jilin; Zhu, Huatao

    2014-05-01

    An electro-optical time gating technique, which is based on an electrical return-to-zero (RZ) pulse driven Mach-Zehnder modulator (MZM) for eliminating multiple access interference (MAI) in optical code-division multiple access (OCDMA) networks is proposed. This technique is successfully simulated in an eight-user two-dimensional wavelength-hopping time-spreading system, as well as in a three-user temporal phase encoding system. Results show that in both systems the MAI noise is efficiently removed and the average received power penalty improved. Both achieve error-free transmissions at a bit rate of 2.5 Gb/s. In addition, we also individually discuss effects of parameters in two systems, such as the extinction ratio of the MZM, the duty cycle of the driven RZ pulse, and the time misalignment between the driven pulse and the decoded autocorrelation peak, on the output bit error rate performance. Our work shows that employing a common MZM as a thresholder provides another probability and an interesting cost-effective choice for a smart size, low energy, and less complex thresholding technique for integrated detection in OCDMA networks.

  11. Language Access Toolkit: An Organizing and Advocacy Resource for Community-Based Youth Programs

    ERIC Educational Resources Information Center

    Beyersdorf, Mark Ro

    2013-01-01

    Asian American Legal Defense and Education Fund (AALDEF) developed this language access toolkit to share the expertise and experiences of National Asian American Education Advocates Network (NAAEA) member organizations with other community organizations interested in developing language access campaigns. This toolkit includes an overview of…

  12. The Cybermobile: A Gateway for Public Access to Network-Based Information.

    ERIC Educational Resources Information Center

    Drumm, John E.; Groom, Frank M.

    1997-01-01

    Though the bookmobile has fallen on hard times, the cybermobile, a technology platform combining personal computing, CD-ROMs, fiber network, and wireless access to the Internet, may be the next step in mobile library services. Discusses standard vehicle, computer hardware, software, wireless access, and alliances with users, vendors, and community…

  13. Community Based Mathematics Project: Conceptualizing Access through Locally Relevant Mathematics Curricula

    ERIC Educational Resources Information Center

    Ebby, Caroline; Lim, Vivian; Reinke, Luke; Remillard, Janine; Magee, Emily; Hoe, Nina; Cyrus, Maya

    2011-01-01

    In this article, the authors describe a conceptual framework for using locally relevant mathematics curricula to increase access to mathematics for marginalized youth. Drawing on different strands of research on equity in mathematics education, the authors propose that there are three kinds of access that are afforded by the use of contexts that…

  14. Efficient Streaming Mass Spatio-Temporal Vehicle Data Access in Urban Sensor Networks Based on Apache Storm.

    PubMed

    Zhou, Lianjie; Chen, Nengcheng; Chen, Zeqiang

    2017-04-10

    The efficient data access of streaming vehicle data is the foundation of analyzing, using and mining vehicle data in smart cities, which is an approach to understand traffic environments. However, the number of vehicles in urban cities has grown rapidly, reaching hundreds of thousands in number. Accessing the mass streaming data of vehicles is hard and takes a long time due to limited computation capability and backward modes. We propose an efficient streaming spatio-temporal data access based on Apache Storm (ESDAS) to achieve real-time streaming data access and data cleaning. As a popular streaming data processing tool, Apache Storm can be applied to streaming mass data access and real time data cleaning. By designing the Spout/bolt workflow of topology in ESDAS and by developing the speeding bolt and other bolts, Apache Storm can achieve the prospective aim. In our experiments, Taiyuan BeiDou bus location data is selected as the mass spatio-temporal data source. In the experiments, the data access results with different bolts are shown in map form, and the filtered buses' aggregation forms are different. In terms of performance evaluation, the consumption time in ESDAS for ten thousand records per second for a speeding bolt is approximately 300 milliseconds, and that for MongoDB is approximately 1300 milliseconds. The efficiency of ESDAS is approximately three times higher than that of MongoDB.

  15. Access to Primary Care and Visits to Emergency Departments in England: A Cross-Sectional, Population-Based Study

    PubMed Central

    Cowling, Thomas E.; Cecil, Elizabeth V.; Soljak, Michael A.; Lee, John Tayu; Millett, Christopher; Majeed, Azeem; Wachter, Robert M.; Harris, Matthew J.

    2013-01-01

    Background The number of visits to hospital emergency departments (EDs) in England has increased by 20% since 2007-08, placing unsustainable pressure on the National Health Service (NHS). Some patients attend EDs because they are unable to access primary care services. This study examined the association between access to primary care and ED visits in England. Methods A cross-sectional, population-based analysis of patients registered with 7,856 general practices in England was conducted, for the time period April 2010 to March 2011. The outcome measure was the number of self-referred discharged ED visits by the registered population of a general practice. The predictor variables were measures of patient-reported access to general practice services; these were entered into a negative binomial regression model with variables to control for the characteristics of patient populations, supply of general practitioners and travel times to health services. Main Result and Conclusion General practices providing more timely access to primary care had fewer self-referred discharged ED visits per registered patient (for the most accessible quintile of practices, RR = 0.898; P<0.001). Policy makers should consider improving timely access to primary care when developing plans to reduce ED utilisation. PMID:23776694

  16. Spatial Access to Emergency Services in Low- and Middle-Income Countries: A GIS-Based Analysis

    PubMed Central

    Tansley, Gavin; Schuurman, Nadine; Amram, Ofer; Yanchar, Natalie

    2015-01-01

    Injury is a leading cause of the global disease burden, accounting for 10 percent of all deaths worldwide. Despite 90 percent of these deaths occurring in low and middle-income countries (LMICs), the majority of trauma research and infrastructure development has taken place in high-income settings. Furthermore, although accessible services are of central importance to a mature trauma system, there remains a paucity of literature describing the spatial accessibility of emergency services in LMICs. Using data from the Service Provision Assessment component of the Demographic and Health Surveys of Namibia and Haiti we defined the capabilities of healthcare facilities in each country in terms of their preparedness to provide emergency services. A Geographic Information System-based network analysis method was used to define 5- 10- and 50-kilometer catchment areas for all facilities capable of providing 24-hour care, higher-level resuscitative services or tertiary care. The proportion of a country’s population with access to each level of service was obtained by amalgamating the catchment areas with a population layer. A significant proportion of the population of both countries had poor spatial access to lower level services with 25% of the population of Haiti and 51% of the population of Namibia living further than 50 kilometers from a facility capable of providing 24-hour care. Spatial access to tertiary care was considerably lower with 51% of Haitians and 72% of Namibians having no access to these higher-level services within 50 kilometers. These results demonstrate a significant disparity in potential spatial access to emergency services in two LMICs compared to analogous estimates from high-income settings, and suggest that strengthening the capabilities of existing facilities may improve the equity of emergency services in these countries. Routine collection of georeferenced patient and facility data in LMICs will be important to understanding how spatial

  17. User-access-frequency statistics based hotspot adjustment in all-optically interconnected metro-embedded datacenters

    NASA Astrophysics Data System (ADS)

    Chen, Gang; Guo, Hongxiang; Zhang, Dongxu; Wu, Jian; Cao, Xiaoyuan; Yoshikane, Noboru; Tsuritani, Takehiro; Morita, Itsuro

    2016-12-01

    Traditional datacenters are typically deployed with highly clustered resources and built-in remote areas far away from users, requiring huge floor space and power consumption. The proposed metro-embedded datacenter architecture with distributed resources spreading across the metro area close to users could be a promising solution, which exhibits lower access latency and more flexibility for service orchestration. Based on metro-embedded datacenter, we propose the conception of "follow the user" with user access location aware dynamic hotspots adjustments. By enabling service hotspots adjustment according to user access frequency statistics, the quality of service can be significantly improved in terms of reduced latency. Finally, we experimentally demonstrate low-latency service provisioning based on the proposed principle.

  18. Single-Carrier Based Multiplexing of Layer 1/Layer 2 Control Signals in Evolved UTRA Uplink Using DFT-Spread OFDM

    NASA Astrophysics Data System (ADS)

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

    This paper proposes efficient single-carrier (SC) based multiplexing schemes for Layer 1 (L1)/Layer 2 (L2) control signals in SC-FDMA radio access using DFT-Spread OFDM in the Evolved UTRA uplink. L1/L2 control signals are necessary for key packet access techniques such as downlink scheduling, link adaptation, hybrid automatic repeat request (ARQ) with soft combining, and for uplink feedback control signals. We first propose a SC-based multiplexing scheme for L1/L2 control signals within a shared data channel for a set of user equipment (UE) that transmits both an uplink shared data channel and L1/L2 control signals within the same subframe. We also propose a multiplexing scheme for L1/L2 control signals without uplink data transmission that takes advantage of intra-subframe frequency hopping (FH) using multiple exclusively-assigned time-frequency resource blocks (RBs) to obtain a frequency diversity gain. Furthermore, we propose an orthogonal CDMA-based multiplexing scheme using cyclic shifts of a constant amplitude zero auto-correlation (CAZAC) sequence for L1/L2 control signals from different UEs within the same narrowband time-frequency RB. Computer simulation results show that the proposed SC-based multiplexing scheme for the L1/L2 control signals within the shared data channel achieves a higher user throughput than a multicarrier-based multiplexing scheme. The results also show that the proposed multiplexing scheme for the L1/L2 control signals that takes advantage of the intra-subframe FH for the UE without uplink data transmission achieves high quality reception through large frequency diversity gain. Furthermore, we show that the proposed cyclic-shift based orthogonal CDMA multiplexing is effective in the multiplexing of multiple L1/L2 control signals from different UEs within the same RB.

  19. Prediction of highly expressed genes in microbes based on chromatin accessibility

    PubMed Central

    Willenbrock, Hanni; Ussery, David W

    2007-01-01

    Background It is well known that gene expression is dependent on chromatin structure in eukaryotes and it is likely that chromatin can play a role in bacterial gene expression as well. Here, we use a nucleosomal position preference measure of anisotropic DNA flexibility to predict highly expressed genes in microbial genomes. We compare these predictions with those based on codon adaptation index (CAI) values, and also with experimental data for 6 different microbial genomes, with a particular interest in experimental data from Escherichia coli. Moreover, position preference is examined further in 328 sequenced microbial genomes. Results We find that absolute gene expression levels are correlated with the position preference in many microbial genomes. It is postulated that in these regions, the DNA may be more accessible to the transcriptional machinery. Moreover, ribosomal proteins and ribosomal RNA are encoded by DNA having significantly lower position preference values than other genes in fast-replicating microbes. Conclusion This insight into DNA structure-dependent gene expression in microbes may be exploited for predicting the expression of non-translated genes such as non-coding RNAs that may not be predicted by any of the conventional codon usage bias approaches. PMID:17295928

  20. Measurement-based management of mental health quality and access in VHA: SAIL mental health domain.

    PubMed

    Lemke, Sonne; Boden, Matthew Tyler; Kearney, Lisa K; Krahn, Dean D; Neuman, Matthew J; Schmidt, Eric M; Trafton, Jodie A

    2017-02-01

    We outline the development of a Mental Health Domain to track accessibility and quality of mental health care in the United States Veterans Health Administration (VHA) as part of a broad-based performance measurement system. This domain adds an important element to national performance improvement efforts by targeting regional and facility leadership and providing them a concise yet comprehensive measure to identify facilities facing challenges in their mental health programs. We present the conceptual framework and rationale behind measure selection and development. The Mental Health Domain covers three important aspects of mental health treatment: Population Coverage, Continuity of Care, and Experience of Care. Each component is a composite of existing and newly adapted measures with moderate to high internal consistency; components are statistically independent or moderately related. Development and dissemination of the Mental Health Domain involved a variety of approaches and benefited from close collaboration between local, regional, and national leadership and from coordination with existing quality-improvement initiatives. During the first year of use, facilities varied in the direction and extent of change. These patterns of change were generally consistent with qualitative information, providing support for the validity of the domain and its component measures. Measure maintenance remains an iterative process as the VHA mental health system and potential data resources continue to evolve. Lessons learned may be helpful to the broader mental health-provider community as mental health care consolidates and becomes increasingly integrated within healthcare systems. (PsycINFO Database Record

  1. A web-accessible content-based cervicographic image retrieval system

    NASA Astrophysics Data System (ADS)

    Xue, Zhiyun; Long, L. Rodney; Antani, Sameer; Jeronimo, Jose; Thoma, George R.

    2008-03-01

    Content-based image retrieval (CBIR) is the process of retrieving images by directly using image visual characteristics. In this paper, we present a prototype system implemented for CBIR for a uterine cervix image (cervigram) database. This cervigram database is a part of data collected in a multi-year longitudinal effort by the National Cancer Institute (NCI), and archived by the National Library of Medicine (NLM), for the study of the origins of, and factors related to, cervical precancer/cancer. Users may access the system with any Web browser. The system is built with a distributed architecture which is modular and expandable; the user interface is decoupled from the core indexing and retrieving algorithms, and uses open communication standards and open source software. The system tries to bridge the gap between a user's semantic understanding and image feature representation, by incorporating the user's knowledge. Given a user-specified query region, the system returns the most similar regions from the database, with respect to attributes of color, texture, and size. Experimental evaluation of the retrieval performance of the system on "groundtruth" test data illustrates its feasibility to serve as a possible research tool to aid the study of the visual characteristics of cervical neoplasia.

  2. PKI-based secure mobile access to electronic health services and data.

    PubMed

    Kambourakis, G; Maglogiannis, I; Rouskas, A

    2005-01-01

    Recent research works examine the potential employment of public-key cryptography schemes in e-health environments. In such systems, where a Public Key Infrastructure (PKI) is established beforehand, Attribute Certificates (ACs) and public key enabled protocols like TLS, can provide the appropriate mechanisms to effectively support authentication, authorization and confidentiality services. In other words, mutual trust and secure communications between all the stakeholders, namely physicians, patients and e-health service providers, can be successfully established and maintained. Furthermore, as the recently introduced mobile devices with access to computer-based patient record systems are expanding, the need of physicians and nurses to interact increasingly with such systems arises. Considering public key infrastructure requirements for mobile online health networks, this paper discusses the potential use of Attribute Certificates (ACs) in an anticipated trust model. Typical trust interactions among doctors, patients and e-health providers are presented, indicating that resourceful security mechanisms and trust control can be obtained and implemented. The application of attribute certificates to support medical mobile service provision along with the utilization of the de-facto TLS protocol to offer competent confidentiality and authorization services is also presented and evaluated through experimentation, using both the 802.11 WLAN and General Packet Radio Service (GPRS) networks.

  3. Providing universal access. Malvar, province of Batangas. Community-based RH / FP.

    PubMed

    Villegas, P M

    1998-01-01

    Health development is a priority objective in Malvar, a town of 27,800 people, as of 1996, in the province of Batangas. Malvar's population lives in 4633 households. The Japanese Organization for International Cooperation in Family Planning (JOICFP)-supported Sustainable Community-based Reproductive Health (RH)/Family Planning (FP) Project Emphasizing Quality of Care is very important to the people of Malvar. The project is managed by the Interagency Community Organizing Committee (ICOC) established in December 1993. The author describes the many ways in which the RH/FP project has contributed to Malvar's goal of providing universal access to various services, including family planning information and services and reproductive health services. The project has increased the acceptance of family planning and resulted in an increase in the contraceptive prevalence rate from 13.3% in 1993 to 61.0% in 1997. Over the same period, the infant mortality rate per 1000 live births has fallen from 39.4 to 14.1.

  4. Evidence-based consensus on the insertion of central venous access devices: definition of minimal requirements for training.

    PubMed

    Moureau, N; Lamperti, M; Kelly, L J; Dawson, R; Elbarbary, M; van Boxtel, A J H; Pittiruti, M

    2013-03-01

    There is a lack of standard minimal requirements for the training of insertion techniques and maintenance of central venous access devices (CVADs). An international evidence-based consensus task force was established through the World Congress of Vascular Access (WoCoVA) to provide definitions and recommendations for training and insertion of CVADs. Medical literature published from February 1971 to April 2012 regarding 'central vascular access', 'training', 'competency', 'simulation', and 'ultrasound' was reviewed on Pubmed, BioMed Central, ScienceDirect, and Scopus databases. The GRADE and the GRADE-RAND methods were utilized to develop recommendations. Out of 156 papers initially identified, 83 papers described training for central vascular access placement. Sixteen recommendations are proposed by this task force, each with an evidence level, degree of consensus, and recommendation grade. These recommendations suggest central venous access education include didactic or web-based teaching with insertion procedure, infection prevention, complications, care, and maintenance of devices, along with laboratory models and tools for simulation practice incorporating ultrasound. Clinical competence should be determined by observation during clinical practice using a global rating scale rather than by the number of procedures performed. Ensuring safe insertion and management of central venous devices requires standardized education, simulation practice, and supervised insertions.

  5. Generation-based memory synchronization in a multiprocessor system with weakly consistent memory accesses

    DOEpatents

    Ohmacht, Martin

    2014-09-09

    In a multiprocessor system, a central memory synchronization module coordinates memory synchronization requests responsive to memory access requests in flight, a generation counter, and a reclaim pointer. The central module communicates via point-to-point communication. The module includes a global OR reduce tree for each memory access requesting device, for detecting memory access requests in flight. An interface unit is implemented associated with each processor requesting synchronization. The interface unit includes multiple generation completion detectors. The generation count and reclaim pointer do not pass one another.

  6. A Promising Practicum Pilot--Exploring Associate Teachers' Access and Interactions with a Web-Based Learning Tool

    ERIC Educational Resources Information Center

    Petrarca, Diana

    2013-01-01

    This paper explores how a small group of associate teachers (i.e., the classroom teachers who host, supervise, and mentor teacher candidates during practicum placements) accessed and interacted with the Associate Teacher Learning Tool (ATLT), a web-based learning tool created specifically for this new group of users. The ATLT is grounded in…

  7. Bases and spaces: resources on the web for accessing the draft human genome - II - After publication of the draft

    PubMed Central

    Semple, Colin AM

    2001-01-01

    The volume of human genome sequence and the variety of web-based tools to access it continue to grow at an impressive rate, but a working knowledge of certain key resources can be sufficient to get the most from your genome. This article provides an update to Genome Biology 2000, 1(4):reviews2001.1-2001.5. PMID:11423014

  8. Designing a Competence-Based Syllabus for Turkish Speaking Learners of English in Terms of Accessibility to Universal Grammar

    ERIC Educational Resources Information Center

    Seker, Emrullah

    2016-01-01

    This study focuses on designing an English grammar syllabus for Turkish speaking English learners, which is based on the assumption that learning English grammar will be simpler and easier for Turkish speaking learners if it is introduced in a way by which they can achieve accessibility to Universal Grammar. In this study, I analyze almost all…

  9. Toward a New Model for Promoting Urban Children's Mental Health: Accessible, Effective, and Sustainable School-Based Mental Health Services

    ERIC Educational Resources Information Center

    Atkins, Marc S.; Graczyk, Patricia A.; Frazier, Stacy L.; Abdul-Adil, Jaleel

    2003-01-01

    A program of research related to school-based models for urban children's mental health is described, with a particular focus on improving access to services, promoting children's functioning, and providing for program sustainability. The first study in this series responded to the urgent need to engage more families in mental health services, and…

  10. Awareness of Accessibility Barriers in Computer-Based Instructional Materials and Faculty Demographics at South Dakota Public Universities

    ERIC Educational Resources Information Center

    Olson, Christopher

    2013-01-01

    Advances in technology and course delivery methods have enabled persons with disabilities to enroll in higher education at an increasing rate. Federal regulations state persons with disabilities must be granted equal access to the information contained in computer-based instructional materials, but faculty at the six public universities in South…

  11. Advertisement-Based Energy Efficient Medium Access Protocols for Wireless Sensor Networks

    NASA Astrophysics Data System (ADS)

    Ray, Surjya Sarathi

    . Simulations show that the optimized ADV-MAC provides substantial energy gains (50% to 70% less than other MAC protocols for WSNs such as T-MAC and S-MAC for the scenarios investigated) while faring as well as T-MAC in terms of packet delivery ratio and latency. Although ADV-MAC provides substantial energy gains over S-MAC and T-MAC, it is not optimal in terms of energy savings because contention is done twice -- once in the Advertisement Period and once in the Data Period. In the next part of my research, the second contention in the Data Period is eliminated and the advantages of contention-based and TDMA-based protocols are combined to form Advertisement based Time-division Multiple Access (ATMA), a distributed TDMA-based MAC protocol for WSNs. ATMA utilizes the bursty nature of the traffic to prevent energy waste through advertisements and reservations for data slots. Extensive simulations and qualitative analysis show that with bursty traffic, ATMA outperforms contention-based protocols (S-MAC, T-MAC and ADV-MAC), a TDMA based protocol (TRAMA) and hybrid protocols (Z-MAC and IEEE 802.15.4). ATMA provides energy reductions of up to 80%, while providing the best packet delivery ratio (close to 100%) and latency among all the investigated protocols. Simulations alone cannot reflect many of the challenges faced by real implementations of MAC protocols, such as clock-drift, synchronization, imperfect physical layers, and irregular interference from other transmissions. Such issues may cripple a protocol that otherwise performs very well in software simulations. Hence, to validate my research, I conclude with a hardware implementation of the ATMA protocol on SORA (Software Radio), developed by Microsoft Research Asia. SORA is a reprogrammable Software Defined Radio (SDR) platform that satisfies the throughput and timing requirements of modern wireless protocols while utilizing the rich general purpose PC development environment. Experimental results obtained from the hardware

  12. 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

  13. 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.

  14. Investigation of Inter-Node B Macro Diversity for Single-Carrier Based Radio Access in Evolved UTRA Uplink

    NASA Astrophysics Data System (ADS)

    Kawai, Hiroyuki; Morimoto, Akihito; Higuchi, Kenichi; Sawahashi, Mamoru

    This paper investigates the gain of inter-Node B macro diversity for a scheduled-based shared channel using single-carrier FDMA radio access in the Evolved UTRA (UMTS Terrestrial Radio Access) uplink based on system-level simulations. More specifically, we clarify the gain of inter-Node B soft handover (SHO) with selection combining at the radio frame length level (=10msec) compared to that for hard handover (HHO) for a scheduled-based shared data channel, considering the gains of key packet-specific techniques including channel-dependent scheduling, adaptive modulation and coding (AMC), hybrid automatic repeat request (ARQ) with packet combining, and slow transmission power control (TPC). Simulation results show that the inter-Node B SHO increases the user throughput at the cell edge by approximately 10% for a short cell radius such as 100-300m due to the diversity gain from a sudden change in other-cell interference, which is a feature specific to full scheduled-based packet access. However, it is also shown that the gain of inter-Node B SHO compared to that for HHO is small in a macrocell environment when the cell radius is longer than approximately 500m due to the gains from hybrid ARQ with packet combining, slow TPC, and proportional fairness based channel-dependent scheduling.

  15. Lumpy - an interactive Lumped Parameter Modeling code based on MS Access and MS Excel.

    NASA Astrophysics Data System (ADS)

    Suckow, A.

    2012-04-01

    Several tracers for dating groundwater (18O/2H, 3H, CFCs, SF6, 85Kr) need lumped parameter modeling (LPM) to convert measured values into numbers with unit time. Other tracers (T/3He, 39Ar, 14C, 81Kr) allow the computation of apparent ages with a mathematical formula using radioactive decay without defining the age mixture that any groundwater sample represents. Also interpretation of the latter profits significantly from LPM tools that allow forward modeling of input time series to measurable output values assuming different age distributions and mixtures in the sample. This talk presents a Lumped Parameter Modeling code, Lumpy, combining up to two LPMs in parallel. The code is standalone and freeware. It is based on MS Access and Access Basic (AB) and allows using any number of measurements for both input time series and output measurements, with any, not necessarily constant, time resolution. Several tracers, also comprising very different timescales like e.g. the combination of 18O, CFCs and 14C, can be modeled, displayed and fitted simultaneously. Lumpy allows for each of the two parallel models the choice of the following age distributions: Exponential Piston flow Model (EPM), Linear Piston flow Model (LPM), Dispersion Model (DM), Piston flow Model (PM) and Gamma Model (GM). Concerning input functions, Lumpy allows delaying (passage through the unsaturated zone) shifting by a constant value (converting 18O data from a GNIP station to a different altitude), multiplying by a constant value (geochemical reduction of initial 14C) and the definition of a constant input value prior to the input time series (pre-bomb tritium). Lumpy also allows underground tracer production (4He or 39Ar) and the computation of a daughter product (tritiugenic 3He) as well as partial loss of the daughter product (partial re-equilibration of 3He). These additional parameters and the input functions can be defined independently for the two sub-LPMs to represent two different recharge

  16. Measuring Land Uses Accessibility by Using Fuzzy Majority Gis-Based Multicriteria Decision Analysis Case Study: Malayer City

    NASA Astrophysics Data System (ADS)

    Taravat, A.; Yari, A.; Rajaei, M.; Mousavian, R.

    2014-10-01

    Public spaces accessibility has become one of the important factors in urban planning. Therefore, considerable attention has been given to measure accessibility to public spaces on the UK, US and Canada, but there are few studies outside the anglophone world especially in developing countries such as Iran. In this study an attempt has been made to measure objective accessibility to public spaces (parks, school, library and administrative) using fuzzy majority GIS-based multicriteria decision analysis. This method is for defining the priority for distribution of urban facilities and utilities as the first step towards elimination of social justice. In order to test and demonstrate the presented model, the comprehensive plan of Malayer city has been considered for ranking in three objectives and properties in view of index per capital (Green space, sport facilities and major cultural centers like library and access index). The results can be used to inform the local planning process and the GIS approach can be expanded into other local authority domains. The results shows that the distribution of facilities in Malayer city has followed on the base of cost benefit law and the human aspect of resource allocation programming of facilities (from centre to suburbs of the city).

  17. Giving office-based physicians electronic access to patients' prior imaging and lab results did not deter ordering of tests.

    PubMed

    McCormick, Danny; Bor, David H; Woolhandler, Stephanie; Himmelstein, David U

    2012-03-01

    Policy-based incentives for health care providers to adopt health information technology are predicated on the assumption that, among other things, electronic access to patient test results and medical records will reduce diagnostic testing and save money. To test the generalizability of findings that support this assumption, we analyzed the records of 28,741 patient visits to a nationally representative sample of 1,187 office-based physicians in 2008. Physicians' access to computerized imaging results (sometimes, but not necessarily, through an electronic health record) was associated with a 40-70 percent greater likelihood of an imaging test being ordered. The electronic availability of lab test results was also associated with ordering of additional blood tests. The availability of an electronic health record in itself had no apparent impact on ordering; the electronic access to test results appears to have been the key. These findings raise the possibility that, as currently implemented, electronic access does not decrease test ordering in the office setting and may even increase it, possibly because of system features that are enticements to ordering. We conclude that use of these health information technologies, whatever their other benefits, remains unproven as an effective cost-control strategy with respect to reducing the ordering of unnecessary tests.

  18. Labour and residential accessibility: a Bayesian analysis based on Poisson gravity models with spatial effects

    NASA Astrophysics Data System (ADS)

    Alonso, M. P.; Beamonte, M. A.; Gargallo, P.; Salvador, M. J.

    2014-10-01

    In this study, we measure jointly the labour and the residential accessibility of a basic spatial unit using a Bayesian Poisson gravity model with spatial effects. The accessibility measures are broken down into two components: the attractiveness component, which is related to its socio-economic and demographic characteristics, and the impedance component, which reflects the ease of communication within and between basic spatial units. For illustration purposes, the methodology is applied to a data set containing information about commuters from the Spanish region of Aragón. We identify the areas with better labour and residential accessibility, and we also analyse the attractiveness and the impedance components of a set of chosen localities which allows us to better understand their mobility patterns.

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

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

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

  20. Steganography-based access control to medical data hidden in electrocardiogram.

    PubMed

    Mai, Vu; Khalil, Ibrahim; Ibaida, Ayman

    2013-01-01

    Steganographic techniques allow secret data to be embedded inside another host data such as an image or a text file without significant changes to the quality of the host data. In this research, we demonstrate how steganography can be used as the main mechanism to build an access control model that gives data owners complete control to their sensitive cardiac health information hidden in their own Electrocardiograms. Our access control model is able to protect the privacy of users, the confidentiality of medical data, reduce storage space and make it more efficient to upload and download large amount of data.

  1. Community knowledge of law at the end of life: availability and accessibility of web-based resources.

    PubMed

    White, Ben; Willmott, Lindy; Tilse, Cheryl; Wilson, Jill; Lawson, Deborah; Pearce, Angela; Dunn, Jeffrey; Aitken, Joanne F; Feeney, Rachel; Jowett, Stephanie

    2017-03-30

    Objective The aim of the present study was to identify online resources community members may access to inform themselves about their legal duties and rights in end-of-life decision making.Methods Resource mapping identified online resources that members of the public in New South Wales, Victoria and Queensland are likely to identify, and assessed the ease or difficulty in locating them. Resources were then critically analysed for accessibility of language and format using the Patient Education Materials Assessment Tool (PEMAT).Results Identified resources differed considerably based on whether search terms identified by community members or experts were used. Most resources focused on advance directives, enduring powers of attorney and substitute decision making. Relatively few provided information about legal duties (e.g. powers and responsibilities of substitute decision makers) or resolving conflict with health practitioners. Accessibility (understandability and actionability) of resource content varied.Conclusions Although numerous resources on end-of-life law are available online, community members may not be able to identify relevant resources or find resource content accessible.What is known about the topic? Research on participation by patients in decision making about their treatment has focused primarily on medical rather than legal knowledge.What does this paper add? The present study investigated which online resources community members may access to inform themselves about the law on end-of-life decision making. The resources identified were analysed for ease of location and content accessibility.What are the implications for practitioners? Authors of online resources on end-of-life decision making should consider whether their resources can be: (1) identified by search terms used by the public; (2) understood by a general audience; and (3) readily used to promote reader action.

  2. WWC Review of the Report "Looking beyond Enrollment: The Causal Effect of Need-Based Grants on College Access, Persistence, and Graduation." What Works Clearinghouse Single Study Review

    ERIC Educational Resources Information Center

    What Works Clearinghouse, 2014

    2014-01-01

    The 2013 study, "Looking Beyond Enrollment: The Causal Effect of Need-Based Grants on College Access, Persistence, and Graduation," examined whether eligibility for the Florida Student Access Grant (FSAG), a need-based grant for low-income students in Florida, affects college enrollment, credit accumulation, persistence over time in…

  3. Multi-component access to a community-based weight loss program: 12 week results

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The current study examined weight loss between a comprehensive lifestyle modification program (Weight Watchers PointsPlus program) that included three ways to access and a self-help (SH) condition. A total of 293 participants were randomized to either a Weight Watchers condition (WW) (n=148) or a SH...

  4. A Model for Trust-based Access Control and Delegation in Mobile Clouds (Post Print)

    DTIC Science & Technology

    2013-10-01

    Qing-Guo, Z., Rong, L.: An Access Control Model for Ubiquitous Computing Application. In: Proceedings of the 2nd International Conference on Mobile ... Technology , Applications and Systems, Guangzhou, China (November 2005) 22. Baracaldo, N., Joshi, J.B.D.: A Trust-and-Risk Aware RBAC Framework: Tackling

  5. How accessible are coral reefs to people? A global assessment based on travel time.

    PubMed

    Maire, Eva; Cinner, Joshua; Velez, Laure; Huchery, Cindy; Mora, Camilo; Dagata, Stephanie; Vigliola, Laurent; Wantiez, Laurent; Kulbicki, Michel; Mouillot, David

    2016-04-01

    The depletion of natural resources has become a major issue in many parts of the world, with the most accessible resources being most at risk. In the terrestrial realm, resource depletion has classically been related to accessibility through road networks. In contrast, in the marine realm, the impact on living resources is often framed into the Malthusian theory of human density around ecosystems. Here, we develop a new framework to estimate the accessibility of global coral reefs using potential travel time from the nearest human settlement or market. We show that 58% of coral reefs are located < 30 min from the nearest human settlement. We use a case study from New Caledonia to demonstrate that travel time from the market is a strong predictor of fish biomass on coral reefs. We also highlight a relative deficit of protection on coral reef areas near people, with disproportional protection on reefs far from people. This suggests that conservation efforts are targeting low-conflict reefs or places that may already be receiving de facto protection due to their isolation. Our global assessment of accessibility in the marine realm is a critical step to better understand the interplay between humans and resources.

  6. Access to the Albanian VET System: Social, Individual and School-Based Barriers

    ERIC Educational Resources Information Center

    Xhumari, Merita; Dibra, Sidita

    2016-01-01

    This article analyses the determinants of access to the VET system in Albania and its impact on the inclusion of young people and vulnerable groups. The VET system often attracts students who have completed the compulsory levels of education with weak academic results. Many come from families with a low level of income and a low education level.…

  7. The Effects of a State Need-based Access Grant on Traditional and Nontraditional Student Persistence

    ERIC Educational Resources Information Center

    Davidson, J. Cody

    2015-01-01

    In 2011-2012, more than 236.7 billion dollars of student financial aid was disbursed to undergraduate and graduate students at postsecondary institutions in the United States. Today, many groups and organizations are advocating for financial aid to increase student access and success as well as to assist the neediest students. The purpose of this…

  8. Pilot Evaluation of a Web-Based Intervention Targeting Sexual Health Service Access

    ERIC Educational Resources Information Center

    Brown, K. E.; Newby, K.; Caley, M.; Danahay, A.; Kehal, I.

    2016-01-01

    Sexual health service access is fundamental to good sexual health, yet interventions designed to address this have rarely been implemented or evaluated. In this article, pilot evaluation findings for a targeted public health behavior change intervention, delivered via a website and web-app, aiming to increase uptake of sexual health services among…

  9. On2broker: Semantic-Based Access to Information Sources at the WWW.

    ERIC Educational Resources Information Center

    Fensel, Dieter; Angele, Jurgen; Decker, Stefan; Erdmann, Michael; Schnurr, Hans-Peter; Staab, Steffen; Studer, Rudi; Witt, Andreas

    On2broker provides brokering services to improve access to heterogeneous, distributed, and semistructured information sources as they are presented in the World Wide Web. It relies on the use of ontologies to make explicit the semantics of Web pages. This paper discusses the general architecture and main components (i.e., query engine, information…

  10. Success with ACCESS: Use of Community-Based Participatory Research for Implementation

    ERIC Educational Resources Information Center

    Eilola, Carolyn; Fishman, Kathryn; Greenburg, Arielle; Moore, Crystal Dea; Schrijver, Andrew; Totino, Jamin

    2011-01-01

    The Assessment of Campus Climate to Enhance Student Success survey (ACCESS) is a set of four questionnaires designed to elicit feedback from five campus constituencies including faculty, administration, staff, students with disabilities, and students without disabilities "to use in planning and garnering support for meaningful activities and…

  11. The University of Minnesota's Internet Gopher System: A Tool for Accessing Network-Based Electronic Information.

    ERIC Educational Resources Information Center

    Wiggins, Rich

    1993-01-01

    Describes the Gopher system developed at the University of Minnesota for accessing information on the Internet. Highlights include the need for navigation tools; Gopher clients; FTP (File Transfer Protocol); campuswide information systems; navigational enhancements; privacy and security issues; electronic publishing; multimedia; and future…

  12. Partners on the Net: FDLP Partnering to Coordinate Remote Access to Internet-Based Government Information.

    ERIC Educational Resources Information Center

    Aldrich, Duncan

    1998-01-01

    Discusses the Government Printing Office (GPO) plan for the transition to an electronic Federal Depository Library Program (FDLP) that, through a network of partnerships comprised of the GPO, the National Archives and Records Administration, federal agencies, and FDLP libraries, will increase public access to government information. (JAK)

  13. Market-Based Higher Education: Does Colorado's Voucher Model Improve Higher Education Access and Efficiency?

    ERIC Educational Resources Information Center

    Hillman, Nicholas W.; Tandberg, David A.; Gross, Jacob P. K.

    2014-01-01

    In 2004, Colorado introduced the nation's first voucher model for financing public higher education. With state appropriations now allocated to students, rather than institutions, state officials expect this model to create cost efficiencies while also expanding college access. Using difference-in-difference regression analysis, we find limited…

  14. Impact of Improving Community-Based Access to Malaria Diagnosis and Treatment on Household Costs

    PubMed Central

    Castellani, Joëlle; Nsungwa-Sabiiti, Jesca; Mihaylova, Borislava; Ajayi, IkeOluwapo O.; Siribié, Mohamadou; Afonne, Chinenye; Balyeku, Andrew; Sermé, Luc; Sanou, Armande K.; Sombié, Benjamin S.; Tiono, Alfred B.; Sirima, Sodiomon B.; Kabarungi, Vanessa; Falade, Catherine O.; Kyaligonza, Josephine; Evers, Silvia M. A. A.; Paulus, Aggie T. G.; Petzold, Max; Singlovic, Jan; Gomes, Melba

    2016-01-01

    Background. Community health workers (CHWs) were trained in Burkina Faso, Nigeria, and Uganda to diagnose febrile children using malaria rapid diagnostic tests, and treat positive malaria cases with artemisinin-based combination therapy (ACT) and those who could not take oral medicines with rectal artesunate. We quantified the impact of this intervention on private household costs for childhood febrile illness. Methods. Households with recent febrile illness in a young child in previous 2 weeks were selected randomly before and during the intervention and data obtained on household costs for the illness episode. Household costs included consultation fees, registration costs, user fees, diagnosis, bed, drugs, food, and transport costs. Private household costs per episode before and during the intervention were compared. The intervention's impact on household costs per episode was calculated and projected to districtwide impacts on household costs. Results. Use of CHWs increased from 35% of illness episodes before the intervention to 50% during the intervention (P < .0001), and total household costs per episode decreased significantly in each country: from US Dollars (USD) $4.36 to USD $1.54 in Burkina Faso, from USD $3.90 to USD $2.04 in Nigeria, and from USD $4.46 to USD $1.42 in Uganda (all P < .0001). There was no difference in the time used by the child's caregiver to care for a sick child (59% before intervention vs 51% during intervention spent ≤2 days). Using the most recent population figures for each study district, we estimate that the intervention could save households a total of USD $29 965, USD $254 268, and USD $303 467, respectively, in the study districts in Burkina Faso, Nigeria, and Uganda. Conclusions. Improving access to malaria diagnostics and treatments in malaria-endemic areas substantially reduces private household costs. The key challenge is to develop and strengthen community human resources to deliver the intervention, and ensure

  15. Multi-service small-cell cloud wired/wireless access network based on tunable optical frequency comb

    NASA Astrophysics Data System (ADS)

    Xiang, Yu; Zhou, Kun; Yang, Liu; Pan, Lei; Liao, Zhen-wan; Zhang, Qiang

    2015-11-01

    In this paper, we demonstrate a novel multi-service wired/wireless integrated access architecture of cloud radio access network (C-RAN) based on radio-over-fiber passive optical network (RoF-PON) system, which utilizes scalable multiple- frequency millimeter-wave (MF-MMW) generation based on tunable optical frequency comb (TOFC). In the baseband unit (BBU) pool, the generated optical comb lines are modulated into wired, RoF and WiFi/WiMAX signals, respectively. The multi-frequency RoF signals are generated by beating the optical comb line pairs in the small cell. The WiFi/WiMAX signals are demodulated after passing through the band pass filter (BPF) and band stop filter (BSF), respectively, whereas the wired signal can be received directly. The feasibility and scalability of the proposed multi-service wired/wireless integrated C-RAN are confirmed by the simulations.

  16. A comprehensive school-based/linked dental program: an essential piece of the California access to care puzzle.

    PubMed

    Fine, Jared I; Isman, Robert E; Grant, Catherine B

    2012-03-01

    California children suffer more from dental disease than any other chronic childhood disease. Disparities in access and oral health are disproportionately represented among children from minority and low-income families. A comprehensive school-based/linked dental program is one essential ingredient in addressing these problems. Described here are the goals, program elements, and challenges of building a seamless dental services system that could reduce barriers care, maximize resources, and employ best practices to improve oral health.

  17. 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.

  18. North Carolina physician-based preventive oral health services improve access and use among young Medicaid enrollees.

    PubMed

    Kranz, Ashley M; Lee, Jessica; Divaris, Kimon; Baker, A Diane; Vann, William

    2014-12-01

    To combat disparities in oral health and access to dental care among infants and toddlers, most state Medicaid programs now reimburse physician-based preventive oral health services such as fluoride varnish applications. We used geospatial data to examine the distribution of dental and medical Medicaid providers of pediatric oral health services throughout North Carolina to determine if these services have improved access to care for Medicaid enrollees younger than age three. We then used claims data to examine the association between distance from these practices and use of dental services for a cohort of approximately 1,000 young children. Among one hundred counties, four counties had no physician-based preventive oral health services, and nine counties had no dental practice. While children who lived farther from the nearest dental practice were less likely to make dental visits, distance from physician-based preventive oral health services did not predict utilization. For young Medicaid enrollees, oral health services provided in medical offices can improve access and increase utilization.

  19. Evidence-based practice in the management of vascular access devices for home parenteral nutrition therapy.

    PubMed

    Ryder, Marcia

    2006-01-01

    Catheter-related bloodstream infection and catheter occlusion are potential significant complications of parenteral nutrition therapy. The increased incidence and associated morbidity, mortality, increased costs, and quality-of-life issues experienced with these adverse events necessitate specialized management of vascular access devices. The host coagulation response to biomaterials and the associated development of biofilm on vascular devices are complex phenomena. Multiple interventions are required to prevent access of bacteria to both intraluminal and extraluminal catheter surfaces, and the occurrence of catheter occlusion. The discovery of the biofilm form of microbial life and the associated recalcitrance of biofilm bacteria to antimicrobials has provided insight into the failure of current prevention, diagnostic, and treatment protocols. Critical interventions are presented correlating current evidence with new discoveries in pathogenesis.

  20. Composable Distributed Access Control and Integrity Policies for Query-Based Wireless Sensor Networks

    DTIC Science & Technology

    2008-03-01

    multiple WSN policies. The construction, hybridization, and composition of well–known models is demonstrated to preserve security, sustaining...confidentiality in Bell–LaPadula’s model , integrity in Biba’s strict integrity model , and conflict of interest avoidance in the Chinese Wall. Using WASL, a multi...as defined by the security model . It is also be more flexible in that a policy file update is all that is required to modify the accesses permitted

  1. Intensity distribution based space and time division multiple access technique for hybrid-LOS indoor optical wireless communication

    NASA Astrophysics Data System (ADS)

    Miyamoto, Shinichi; Kawamoto, Kenji; Sampei, Seiichi

    2010-02-01

    This paper proposes a space division and time division multiple access (SD/TDMA) technique based on intensity distributions for hybrid line-of-sight (hybrid-LOS) indoor optical wireless communication system. At first, a novel signal discrimination scheme for the spatially multiplexed optical signals is proposed and it is applied to a space division multiple access (SDMA) in hybrid-LOS system. In the proposed scheme, multiple terminals simultaneously transmit their optical signals to access point (AP) using on-off-keying (OOK) modulation, and the spatially multiplexed optical signals are received by a photodetectors array (PD-array), where multiple PDs are disposed to observe the spatial intensity distribution of optical signals. Because the terminals transmit their data using OOK modulation, the spatial intensity distribution observed by the AP equipped with PD-array is subject to the data transmitted from individual terminals, and the AP can identify the terminals transmitting the optical signal by determining the transmitted intensity distribution. Of course, the transmitted intensity distributions are not orthogonal signal and the discriminability of transmitted intensity distributions is much related to the differences of intensity distributions. This implies that the number of terminals that can simultaneously access to the AP will be limited and it is determined by the differences of the candidate intensity distributions. In order to enhance the discriminability of the transmitted intensity distributions, the proposed signal discrimination scheme is further applied to the SD/TDMA. In the SD/TDMA, the discriminability required to enable SDMA is ensured by introducing a scheduling algorithm in which terminals with higher discriminatory of transmitted intensity distributions are allocated to the same time slot. Numerical results show that SD/TDMA using proposed signal discrimination scheme increases the throughput and the number of terminals that can access to

  2. An interaction-based access control model (IBAC) for collaborative services

    SciTech Connect

    Altunay, Mine; Byrd, Gregory T.; Brown, Doug E.; Dean, Ralph A.; /North Carolina State U.

    2008-04-01

    A collaboration is a collection of services that work together to achieve a common goal. Although collaborations help when tackling difficult problems, they lead to security issues. First, a collaboration is often performed by services that are drawn from different security domains. Second, a service interacts with multiple peer services during the collaboration. These interactions are not isolated from one another--e.g., data may flow through a sequence of different services. As a result, a service is exposed to multiple peer services in varying degrees, leading to different security threats. We identify the types of interactions that can be present in collaborations, and discuss the security threats due to each type. We propose a model for representing the collaboration context so that a service can be made aware of the existing interactions. We provide an access control model for a service participating in a collaboration. We couple our access control model with a policy model, so that the access requirements from collaborations can be expressed and evaluated.

  3. DMD-based random-access optical-resolution photoacoustic microscopy

    NASA Astrophysics Data System (ADS)

    Liang, Jinyang; Zhou, Yong; Winkler, Amy W.; Wang, Lidai; Maslov, Konstantin I.; Li, Chiye; Wang, Lihong V.

    2014-03-01

    The scanning mechanism is a major technical focus in optical-resolution photoacoustic microscopy. Flexible scanning access with fast scanning speed is desired to monitor biological and physiological dynamics with high temporal resolution. We developed random-access optical-resolution photoacoustic microscopy (RA-OR-PAM) using a digital micromirror device (DMD). Each micromirror on the DMD can be independently controlled, allowing imaging of regions of interest with arbitrary user-selected shapes without extraneous information. A global structural image is first acquired, and the regions of interest are selected. The laser beam then scans these regions exclusively, resulting in a faster frame rate than in a conventional raster scan. This system can rapidly scan arbitrarily shaped regions of interest with a lateral resolution of 3.6 μm within a 40×40 μm2 imaging area, a size comparable to the focal spot size of a 50 MHz ultrasound transducer. We demonstrated the random-access ability of RA-OR-PAM by imaging a monolayer of red blood cells. This system was then used to monitor blood flow in vivo within user-selected capillaries in a mouse ear. By imaging only the capillary of interest, the frame rate was increased by up to 13.3 times.

  4. The effect of 835.62 MHz FDMA or 847.74 MHz CDMA modulated radiofrequency radiation on the induction of micronuclei in C3H 10T(1/2) cells.

    PubMed

    Bisht, Kheem S; Moros, Eduardo G; Straube, William L; Baty, Jack D; Roti Roti, Joseph L

    2002-05-01

    To determine if radiofrequency (RF) radiation induces the formation of micronuclei, C3H 10T(1/2) cells were exposed to 835.62 MHz frequency division multiple access (FDMA) or 847.74 MHz code division multiple access (CDMA) modulated RF radiation. After the exposure to RF radiation, the micronucleus assay was performed by the cytokinesis block method using cytochalasin B treatment. The micronuclei appearing after mitosis were scored in binucleated cells using acridine orange staining. The frequency of micronuclei was scored both as the percentage of binucleated cells with micronuclei and as the number of micronuclei per 100 binucleated cells. Treatment of cells with cytochalasin B at a concentration of 2 microg/ml for 22 h was found to yield the maximum number of binucleated cells in C3H 10T(1/2) cells. The method used for the micronucleus assay in the present study detected a highly significant dose response for both indices of micronucleus production in the dose range of 0.1-1.2 Gy and it was sensitive enough to detect a significant (P > 0.05) increase in micronuclei after doses of 0.3 Gy in exponentially growing cells and after 0.9 Gy in plateau-phase cells. Exponentially growing cells or plateau-phase cells were exposed to CDMA (3.2 or 4.8 W/kg) or FDMA (3.2 or 5.1 W/kg) RF radiation for 3, 8, 16 or 24 h. In three repeat experiments, no exposure condition was found by analysis of variance to result in a significant increase relative to sham-exposed cells either in the percentage of binucleated cells with micronuclei or in the number of micronuclei per 100 binucleated cells. In this study, data from cells exposed to different RF signals at two SARs were compared to a common sham-exposed sample. We used the Dunnett's test, which is specifically designed for this purpose, and found no significant exposure-related differences for either plateau-phase cells or exponentially growing cells. Thus the results of this study are not consistent with the possibility that

  5. Using NASA's Giovanni Web Portal to Access and Visualize Satellite-based Earth Science Data in the Classroom

    NASA Technical Reports Server (NTRS)

    Lloyd, Steven; Acker, James G.; Prados, Ana I.; Leptoukh, Gregory G.

    2008-01-01

    One of the biggest obstacles for the average Earth science student today is locating and obtaining satellite-based remote sensing data sets in a format that is accessible and optimal for their data analysis needs. At the Goddard Earth Sciences Data and Information Services Center (GES-DISC) alone, on the order of hundreds of Terabytes of data are available for distribution to scientists, students and the general public. The single biggest and time-consuming hurdle for most students when they begin their study of the various datasets is how to slog through this mountain of data to arrive at a properly sub-setted and manageable data set to answer their science question(s). The GES DISC provides a number of tools for data access and visualization, including the Google-like Mirador search engine and the powerful GES-DISC Interactive Online Visualization ANd aNalysis Infrastructure (Giovanni) web interface.

  6. International dissemination of evidence-based practice, open access and the IACAPAP textbook of child and adolescent mental health.

    PubMed

    Rey, Joseph M; Omigbodun, Olayinka Olusola

    2015-01-01

    Dramatic changes have occurred in both publishing and teaching in the last 20 years stemming from the digital and Internet revolutions. Such changes are likely to grow exponentially in the near future aided by the trend to open access publishing. This revolution has challenged traditional publishing and teaching methods that-largely but not exclusively due to cost-are particularly relevant to professionals in low and middle income countries. The digital medium and the Internet offer boundless opportunities for teaching and training to people in disadvantaged regions. This article describes the development of the IACAPAP eTextbook of child and adolescent mental health, its use, accessibility, and potential impact on the international dissemination of evidence-based practice.

  7. A new tool for modeling dune field evolution based on an accessible, GUI version of the Werner dune model

    NASA Astrophysics Data System (ADS)

    Barchyn, Thomas E.; Hugenholtz, Chris H.

    2012-02-01

    Research into aeolian dune form and dynamics has benefited from simple and abstract cellular automata computer models. Many of these models are based upon a seminal framework proposed by Werner (1995). Unfortunately, most versions of this model are not publicly available or are not provided in a format that promotes widespread use. In our view, this hinders progress in linking model simulations to empirical data (and vice versa). To this end, we introduce an accessible, graphical user interface (GUI) version of the Werner model. The novelty of this contribution is that it provides a simple interface and detailed instructions that encourage widespread use and extension of the Werner dune model for research and training purposes. By lowering barriers for researchers to develop and test hypotheses about aeolian dune and dune field patterns, this release addresses recent calls to improve access to earth surface models.

  8. Effect of accessions of Colocasia esculenta-based diets on the hepatic and renal functional indices of weanling Wistar rats.

    PubMed

    Lewu, Muinat N; Yakubu, Musa T; Adebola, Patrick O; Afolayan, Anthony J

    2010-10-01

    The liver and kidney functional indices of weanling albino rats (Rattus norvegicus) maintained on different accessions (offspring of a variety planted/collected at a specific location and time but differing in certain morphological characteristics) of cooked Colocasia esculenta (cocoyam)-based diets (UFCe1-UFCe7) for 28 days were investigated. All the accessions of C. esculenta-based diets did not significantly (P > .05) alter the serum levels of albumin, globulin, inorganic phosphorus, calcium, magnesium, and uric acid of the animals.The total protein and total bilirubin levels decreased only in the UFCe3- and UFCe4-fed animals, respectively. Whereas UFCe1 and UFCe2 significantly decreased the conjugated bilirubin levels, UFCe3 and UFCe6 increased it. While all the accessions of C. esculenta-based diet decreased the serum alkaline phosphatase activity, γ-glutamyl transferase activity was increased. UFCe1 and UFCe5 increased the serum alanine aminotransferase activity, whereas UFCe4 decreased the activity of the enzyme. Again, UFCe3 and UFCe1 increased the serum creatinine and aspartate aminotransferase activity of the animals. Furthermore, the computed blood urea nitrogen:creatinine ratio was higher in animals maintained on UFCe1-, UFCe3-, UFCe4-, and UFCe5-based diets. Whereas UFCe6 and UFCe7 increased the level of sodium in the serum of the animals, UFCe4 and UFCe5 decreased the chloride level. The serum urea level was decreased by UFCe1, UFCe3, UFCe4, and UFCe5, whereas the potassium level increased in the UFCe4-, UFCe6-, and UFCe7-fed animals. Overall, the results revealed that all the accessions of C. esculenta produced selective effects on the hepatic and renal functional indices of the weanling rats. The highest alterations were produced by UFCe4, whereas the least was from UFCe2. These alterations may have consequential effects on the normal functioning of the liver and kidney of the animals. UFCe2 exhibited the least toxicity risk among the

  9. World Wide Access: Accessible Web Design.

    ERIC Educational Resources Information Center

    Washington Univ., Seattle.

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

  10. Arteriovenous Access

    PubMed Central

    MacRae, Jennifer M.; Dipchand, Christine; Oliver, Matthew; Moist, Louise; Yilmaz, Serdar; Lok, Charmaine; Leung, Kelvin; Clark, Edward; Hiremath, Swapnil; Kappel, Joanne; Kiaii, Mercedeh; Luscombe, Rick; Miller, Lisa M.

    2016-01-01

    Complications of vascular access lead to morbidity and may reduce quality of life. In this module, we review both infectious and noninfectious arteriovenous access complications including neuropathy, aneurysm, and high-output access. For the challenging patients who have developed many complications and are now nearing their last vascular access, we highlight some potentially novel approaches. PMID:28270919

  11. Circulating Tumor Cells: Clinically Relevant Molecular Access Based on a Novel CTC Flow Cell

    PubMed Central

    Winer-Jones, Jessamine P.; Vahidi, Behrad; Arquilevich, Norma; Fang, Cong; Ferguson, Samuel; Harkins, Darren; Hill, Cory; Klem, Erich; Pagano, Paul C.; Peasley, Chrissy; Romero, Juan; Shartle, Robert; Vasko, Robert C.; Strauss, William M.; Dempsey, Paul W.

    2014-01-01

    Background Contemporary cancer diagnostics are becoming increasing reliant upon sophisticated new molecular methods for analyzing genetic information. Limiting the scope of these new technologies is the lack of adequate solid tumor tissue samples. Patients may present with tumors that are not accessible to biopsy or adequate for longitudinal monitoring. One attractive alternate source is cancer cells in the peripheral blood. These rare circulating tumor cells (CTC) require enrichment and isolation before molecular analysis can be performed. Current CTC platforms lack either the throughput or reliability to use in a clinical setting or they provide CTC samples at purities that restrict molecular access by limiting the molecular tools available. Methodology/Principal Findings Recent advances in magetophoresis and microfluidics have been employed to produce an automated platform called LiquidBiopsy®. This platform uses high throughput sheath flow microfluidics for the positive selection of CTC populations. Furthermore the platform quantitatively isolates cells useful for molecular methods such as detection of mutations. CTC recovery was characterized and validated with an accuracy (<20% error) and a precision (CV<25%) down to at least 9 CTC/ml. Using anti-EpCAM antibodies as the capture agent, the platform recovers 78% of MCF7 cells within the linear range. Non specific recovery of background cells is independent of target cell density and averages 55 cells/mL. 10% purity can be achieved with as low as 6 CTCs/mL and better than 1% purity can be achieved with 1 CTC/mL. Conclusions/Significance The LiquidBiopsy platform is an automated validated platform that provides high throughput molecular access to the CTC population. It can be validated and integrated into the lab flow enabling CTC enumeration as well as recovery of consistently high purity samples for molecular analysis such as quantitative PCR and Next Generation Sequencing. This tool opens the way for

  12. 44% efficiency operation of power heterojunction FET at near pinch-off for 3.5 V wide-band CDMA cellular phones

    NASA Astrophysics Data System (ADS)

    Nishimura, T. B.; Iwata, N.; Bito, Y.; Hau, G.

    1999-08-01

    This paper describes 1.95 GHz power performance of a double-doped AlGaAs/InGaAs/AlGaAs heterojunction FET (HJFET) operated at 3.5 V drain bias voltage for Wide-band CDMA (W-CDMA) cellular phone systems. An HJFET with a novel multilayer cap and a narrow recess structure showed a low on-resistance ( Ron) of 1.4 ohm mm. With an optimum output impedance matching at a reduced quiescent drain current of 80 mA (less than 1% of the maximum drain current), the HJFET exhibited a high power added efficiency (PAE) of 44.2% with an output power of 600 mW (28.0 dBm) and an adjacent channel leakage power ratio (ACPR) of -43 dBc at 5 MHz off-center frequency. This high PAE obtained was ascribed to an ACPR dip behavior with respect to the input power at around the W-CDMA criteria. Through an ACPR simulation with measured AM-AM and AM-PM conversion characteristics, the AM-AM conversion characteristic was found to dominate the W-CDMA ACPR rather than the AM-PM conversion.

  13. FeTRAM. An organic ferroelectric material based novel random access memory cell.

    PubMed

    Das, Saptarshi; Appenzeller, Joerg

    2011-09-14

    Science and technology in the electronics area have always been driven by the development of materials with unique properties and their integration into novel device concepts with the ultimate goal to enable new functionalities in innovative circuit architectures. In particular, a shift in paradigm requires a synergistic approach that combines materials, devices and circuit aspects simultaneously. Here we report the experimental implementation of a novel nonvolatile memory cell that combines silicon nanowires with an organic ferroelectric polymer-PVDF-TrFE-into a new ferroelectric transistor architecture. Our new cell, the ferroelectric transistor random access memory (FeTRAM) exhibits similarities with state-of-the-art ferroelectric random access memories (FeRAMs) in that it utilizes a ferroelectric material to store information in a nonvolatile (NV) fashion but with the added advantage of allowing for nondestructive readout. This nondestructive readout is a result of information being stored in our cell using a ferroelectric transistor instead of a capacitor-the scheme commonly employed in conventional FeRAMs.

  14. Gis-Based Accessibility Analysis of Urban Emergency Shelters: the Case of Adana City

    NASA Astrophysics Data System (ADS)

    Unal, M.; Uslu, C.

    2016-10-01

    Accessibility analysis of urban emergency shelters can help support urban disaster prevention planning. Pre-disaster emergency evacuation zoning has become a significant topic on disaster prevention and mitigation research. In this study, we assessed the level of serviceability of urban emergency shelters within maximum capacity, usability, sufficiency and a certain walking time limit by employing spatial analysis techniques of GIS-Network Analyst. The methodology included the following aspects: the distribution analysis of emergency evacuation demands, the calculation of shelter space accessibility and the optimization of evacuation destinations. This methodology was applied to Adana, a city in Turkey, which is located within the Alpine-Himalayan orogenic system, the second major earthquake belt after the Pacific-Belt. It was found that the proposed methodology could be useful in aiding to understand the spatial distribution of urban emergency shelters more accurately and establish effective future urban disaster prevention planning. Additionally, this research provided a feasible way for supporting emergency management in terms of shelter construction, pre-disaster evacuation drills and rescue operations.

  15. Community-based dental partnerships: improving access to dental care for persons living with HIV/AIDS.

    PubMed

    Mofidi, Mahyar; Gambrell, Alan

    2009-11-01

    Access to oral health care for persons living with HIV/AIDS is limited. Academic dental institutions can play a significant role in addressing the problem. The purpose of this article is to describe the design and impact of the Community-Based Dental Partnership Program (CBDPP), a federal program created to reduce dental care access disparities for persons living with HIV/AIDS through education and training of students and residents in underserved communities. CBDPP forms collaborations between participating dental education programs and community health organizations. Data for this report were drawn and analyzed from site visits, site visit reports, focus groups, and program data reports. In 2007, 4,745 individuals received oral health services through this program, an increase of 47 percent from 2004, the first year of full program operations. The number of dental providers who delivered oral health services grew from 766 in 2004 to 1,474 in 2007. Providers acquired skills, developed self-confidence, and overcame stereotypes in managing the oral health needs of persons living with HIV/AIDS. Community partners reported expanded dental care capacity to meet the unmet oral health needs of their service populations. CBDPP has had a positive impact on access to dental care and training of providers in HIV and oral health.

  16. Analysis of single nucleotide polymorphisms based on RNA sequencing data of diverse bio-geographical accessions in barley

    PubMed Central

    Takahagi, Kotaro; Uehara-Yamaguchi, Yukiko; Yoshida, Takuhiro; Sakurai, Tetsuya; Shinozaki, Kazuo; Mochida, Keiichi; Saisho, Daisuke

    2016-01-01

    Barley is one of the founder crops of Old world agriculture and has become the fourth most important cereal worldwide. Information on genome-scale DNA polymorphisms allows elucidating the evolutionary history behind domestication, as well as discovering and isolating useful genes for molecular breeding. Deep transcriptome sequencing enables the exploration of sequence variations in transcribed sequences; such analysis is particularly useful for species with large and complex genomes, such as barley. In this study, we performed RNA sequencing of 20 barley accessions, comprising representatives of several biogeographic regions and a wild ancestor. We identified 38,729 to 79,949 SNPs in the 19 domesticated accessions and 55,403 SNPs in the wild barley and revealed their genome-wide distribution using a reference genome. Genome-scale comparisons among accessions showed a clear differentiation between oriental and occidental barley populations. The results based on population structure analyses provide genome-scale properties of sub-populations grouped to oriental, occidental and marginal groups in barley. Our findings suggest that the oriental population of domesticated barley has genomic variations distinct from those in occidental groups, which might have contributed to barley’s domestication. PMID:27616653

  17. Military Personnel: Visibility over Junior Enlisted Servicemember Access to Services on Bases Could Be Enhanced

    DTIC Science & Technology

    2015-05-01

    and (3) Randolph Air Force Base. In addition, Camp Bullis is solely a training facility that is also considered a part of Joint Base San Antonio...Sam Houston, (2) Lackland Air Force Base, and (3) Randolph Air Force Base. In addition, Camp Bullis is solely a training facility that also

  18. Interactive Web-based Access and Analysis Tools for the Western Climate Mapping Initiative (WestMap)

    NASA Astrophysics Data System (ADS)

    Comrie, A. C.; Redmond, K.; Glueck, M. F.; Reinbold, H.

    2006-12-01

    The Western Climate Mapping Consortium (WestMap) has developed a prototype web-based interactive access and resource interface to optimize public dissemination and usage of fine-scale spatial climate time series for the western United States. The western U.S. focus reflects the complex climate interactions and diverse geography that make resource management, policy considerations, and climate research challenging in this region. WestMap was conceived by a consortium comprised of the University of Arizona/CLIMAS, the Western Regional Climate Center (WRCC)/Desert Research Institute, and the PRISM group at Oregon State University, along with collaborators at Scripps Institute of Oceanography/California Applications Project, NOAA Climate Diagnostics Center, and the USDA Natural Resource Conservation Service. WestMap evolved in direct response to a multitude of requests to the WRCC and the RISAs from public and private stakeholder communities for lengthy time series of fine-scale spatial climate aggregated to user-specified domains, and related user-friendly web-based access and analysis tools. The WestMap interface is designed to link three stakeholder-driven components, 1) climate data development and operations (access, maintenance); 2) error assessment, data analysis, diagnostics, and related tools; and (3) data access, visualization, and educational resources. The 100-year PRISM 4km monthly temperature and precipitation series serve as the initial data archive, updating automatically once in operational mode. Operational user components are being designed to allow direct stakeholder access to user-specified data and resources most relevant to current needs in a timely manner. Requested resources currently in development and limited testing stages include clickable maps, regional aggregate capabilities, basic statistical analysis, time series visualization, error assessment, and download/print capability. Phased prototype testing, currently underway internally, will

  19. Architecture and implementation for a system enabling smartphones to access smart card based healthcare records.

    PubMed

    Karampelas, Vasilios; Pallikarakis, Nicholas; Mantas, John

    2013-01-01

    The healthcare researchers', academics' and practitioners' interest concerning the development of Healthcare Information Systems has been on a steady rise for the last decades. Fueling this steady rise has been the healthcare professional need of quality information, in every healthcare provision incident, whenever and wherever this incident may take place. In order to address this need a truly mobile health care system is required, one that will be able to provide a healthcare provider with accurate patient-related information regardless of the time and place that healthcare is provided. In order to fulfill this role the present study proposes the architecture for a Healthcare Smartcard system, which provides authenticated healthcare professionals with remote mobile access to a Patient's Healthcare Record, through their Smartphone. Furthermore the research proceeds to develop a working prototype system.

  20. Based on asynchronous communication protocol of geographic space information service access mechanism research

    NASA Astrophysics Data System (ADS)

    Chen, G.; Zhao, J.; Gu, M.; Li, D.

    2014-04-01

    At present, the traditional way of accessing to classified network in geographic spatial information services is using network gatekeeper and firewall etc. to ensure public and classified network communications links. However, the physical isolation between classified network and public network is crossed, which is bound to cause classified network potential security hazard. In Yunnan province space Land dynamic monitoring integration project, it proposed the point to point text message communication protocol and asynchronous transmission mechanism. Using geo-spatial information encryption processing and data compression processing method, it reduced the risk of data sensitivity and monitored, namely to ensure data security, which realized geographic spatial information services data communication effectively between classified network and public network in the rigid field conditions.

  1. Paving the Way to Novel Phosphorus-Based Architectures: A Noncatalyzed Protocol to Access Six-Membered Heterocycles.

    PubMed

    Romero-Nieto, Carlos; López-Andarias, Alicia; Egler-Lucas, Carolina; Gebert, Florian; Neus, Jens-Peter; Pilgram, Oliver

    2015-12-21

    Phosphorus-based heterocycles provide access to materials with properties that are inaccessible from all-carbon architectures. The unique hybridization of phosphorus gives rise to electron-accepting capacities, a large variety of coordination reactions, and the possibility of controlling the electronic properties through phosphorus postfunctionalization. Herein, we describe a new noncatalyzed synthetic protocol to prepare fused six-membered phosphorus heterocycles. In particular, we report the synthesis of novel phosphaphenalenes. These fused systems exhibit the benefits of both five- and six-membered phosphorus heterocycles and enable a series of versatile postfunctionalization reactions. This work thus opens up new horizons in the field of conjugated materials.

  2. Using NASA's Giovanni Web Portal to Access and Visualize Satellite-Based Earth Science Data in the Classroom

    NASA Astrophysics Data System (ADS)

    Lloyd, S. A.; Acker, J. G.; Prados, A. I.; Leptoukh, G. G.

    2008-12-01

    One of the biggest obstacles for the average Earth science student today is locating and obtaining satellite- based remote sensing datasets in a format that is accessible and optimal for their data analysis needs. At the Goddard Earth Sciences Data and Information Services Center (GES-DISC) alone, on the order of hundreds of Terabytes of data are available for distribution to scientists, students and the general public. The single biggest and time-consuming hurdle for most students when they begin their study of the various datasets is how to slog through this mountain of data to arrive at a properly sub-setted and manageable dataset to answer their science question(s). The GES DISC provides a number of tools for data access and visualization, including the Google-like Mirador search engine and the powerful GES-DISC Interactive Online Visualization ANd aNalysis Infrastructure (Giovanni) web interface. Giovanni provides a simple way to visualize, analyze and access vast amounts of satellite-based Earth science data. Giovanni's features and practical examples of its use will be demonstrated, with an emphasis on how satellite remote sensing can help students understand recent events in the atmosphere and biosphere. Giovanni is actually a series of sixteen similar web-based data interfaces, each of which covers a single satellite dataset (such as TRMM, TOMS, OMI, AIRS, MLS, HALOE, etc.) or a group of related datasets (such as MODIS and MISR for aerosols, SeaWIFS and MODIS for ocean color, and the suite of A-Train observations co-located along the CloudSat orbital path). Recently, ground-based datasets have been included in Giovanni, including the Northern Eurasian Earth Science Partnership Initiative (NEESPI), and EPA fine particulate matter (PM2.5) for air quality. Model data such as the Goddard GOCART model and MERRA meteorological reanalyses (in process) are being increasingly incorporated into Giovanni to facilitate model- data intercomparison. A full suite of data

  3. Artificial intelligence models for predicting iron deficiency anemia and iron serum level based on accessible laboratory data.

    PubMed

    Azarkhish, Iman; Raoufy, Mohammad Reza; Gharibzadeh, Shahriar

    2012-06-01

    Iron deficiency anemia (IDA) is the most common nutritional deficiency worldwide. Measuring serum iron is time consuming, expensive and not available in most hospitals. In this study, based on four accessible laboratory data (MCV, MCH, MCHC, Hb/RBC), we developed an artificial neural network (ANN) and an adaptive neuro-fuzzy inference system (ANFIS) to diagnose the IDA and to predict serum iron level. Our results represent that the neural network analysis is superior to ANFIS and logistic regression models in diagnosing IDA. Moreover, the results show that the ANN is likely to provide an accurate test for predicting serum iron levels with high accuracy and acceptable precision.

  4. Overcoming access barriers to health services through membership-based microfinance organizations: a review of evidence from South Asia.

    PubMed

    Saha, Somen; Annear, Peter Leslie

    2014-06-30

    It is a challenge for the poor to overcome the barriers to accessing health services. Membership-based microfinance with associated health programmes can improve health outcomes for the poor. This study reviewed the evidence published between 1993 and 2013 on the role of membership-based microfinance with associated health programmes in improving health outcomes for the poor in South Asia. A total of 661 papers were identified and 26 selected for inclusion, based on the relevance and rigour of the research methods. Of these 26, five were evidence reviews. Of the remaining 21 papers, 12 were from India, seven from Bangladesh, and one each from Sri Lanka and Indonesia. Three papers addressed more than one theme. Five key themes emerged from the review: (i) the impact of microfinance programmes on the social and economic situation of the poor; (ii) the impact of microfinance programmes on community health; (iii) the impact of integrated microfinance health programmes on raising client awareness; (iv) the impact of integrated microfinance health programmes on financing health care; and (v) the impact of integrated microfinance health programmes on affordable health-care products and services. The review provides new evidence on the pathways through which microfinance helps to improve population health and value for money for such programmes. Among countries with large populations in the informal sector, there is a strong case for policy-makers to support these groups in providing access to life-saving health care among the poor.

  5. Overcoming access barriers to health services through membership-based microfinance organizations: a review of evidence from South Asia

    PubMed Central

    Saha, Somen; Annear, Peter Leslie

    2015-01-01

    It is a challenge for the poor to overcome the barriers to accessing health services. Membership-based microfinance with associated health programmes can improve health outcomes for the poor. This study reviewed the evidence published between 1993 and 2013 on the role of membership-based microfinance with associated health programmes in improving health outcomes for the poor in South Asia. A total of 661 papers were identified and 26 selected for inclusion, based on the relevance and rigour of the research methods. Of these 26, five were evidence reviews. Of the remaining 21 papers, 12 were from India, seven from Bangladesh, and one each from Sri Lanka and Indonesia. Three papers addressed more than one theme. Five key themes emerged from the review: (i) the impact of microfinance programmes on the social and economic situation of the poor; (ii) the impact of microfinance programmes on community health; (iii) the impact of integrated microfinance health programmes on raising client awareness; (iv) the impact of integrated microfinance health programmes on financing health care; and (v) the impact of integrated microfinance health programmes on affordable health-care products and services. The review provides new evidence on the pathways through which microfinance helps to improve population health and value for money for such programmes. Among countries with large populations in the informal sector, there is a strong case for policy-makers to support these groups in providing access to life-saving health care among the poor. PMID:25685728

  6. People living with HIV travel farther to access healthcare: a population-based geographic analysis from rural Uganda

    PubMed Central

    Akullian, Adam N; Mukose, Aggrey; Levine, Gillian A; Babigumira, Joseph B

    2016-01-01

    Introduction The availability of specialized HIV services is limited in rural areas of sub-Saharan Africa where the need is the greatest. Where HIV services are available, people living with HIV (PLHIV) must overcome large geographic, economic and social barriers to access healthcare. The objective of this study was to understand the unique barriers PLHIV face when accessing healthcare compared with those not living with HIV in a rural area of sub-Saharan Africa with limited availability of healthcare infrastructure. Methods We conducted a population-based cross-sectional study of 447 heads of household on Bugala Island, Uganda. Multiple linear regression models were used to compare travel time, cost and distance to access healthcare, and log binomial models were used to test for associations between HIV status and access to nearby health services. Results PLHIV travelled an additional 1.9 km (95% CI (0.6, 3.2 km), p=0.004) to access healthcare compared with those not living with HIV, and they were 56% less likely to access healthcare at the nearest health facility to their residence, so long as that facility lacked antiretroviral therapy (ART) services (aRR=0.44, 95% CI (0.24 to 0.83), p=0.011). We found no evidence that PLHIV travelled further for care if the nearest facility supplies ART services (aRR=0.95, 95% CI (0.86 to 1.05), p=0.328). Among those who reported uptake of care at one of two facilities on the island that provides ART (81% of PLHIV and 68% of HIV-negative individuals), PLHIV tended to seek care at a higher tiered facility that provides ART, even when this facility was not their closest facility (30% of PLHIV travelled further than the closest ART facility compared with 16% of HIV-negative individuals), and travelled an additional 2.2 km (p=0.001) to access that facility, relative to HIV-negative individuals (aRR=1.91, 95% CI (1.00 to 3.65), p=0.05). Among PLHIV, residential distance was associated with access to facilities providing ART (RR=0

  7. On the Choice of Access Point Selection Criterion and Other Position Estimation Characteristics for WLAN-Based Indoor Positioning

    PubMed Central

    Laitinen, Elina; Lohan, Elena Simona

    2016-01-01

    The positioning based on Wireless Local Area Networks (WLAN) is one of the most promising technologies for indoor location-based services, generally using the information carried by Received Signal Strengths (RSS). One challenge, however, is the huge amount of data in the radiomap database due to the enormous number of hearable Access Points (AP) that could make the positioning system very complex. This paper concentrates on WLAN-based indoor location by comparing fingerprinting, path loss and weighted centroid based positioning approaches in terms of complexity and performance and studying the effects of grid size and AP reduction with several choices for appropriate selection criterion. All results are based on real field measurements in three multi-floor buildings. We validate our earlier findings concerning several different AP selection criteria and conclude that the best results are obtained with a maximum RSS-based criterion, which also proved to be the most consistent among the different investigated approaches. We show that the weighted centroid based low-complexity method is very sensitive to AP reduction, while the path loss-based method is also very robust to high percentage removals. Indeed, for fingerprinting, 50% of the APs can be removed safely with a properly chosen removal criterion without increasing the positioning error much. PMID:27213395

  8. Web-based interactive access, analysis and comparison of remotely sensed and in situ measured temperature data

    NASA Astrophysics Data System (ADS)

    Eberle, Jonas; Urban, Marcel; Hüttich, Christian; Schmullius, Christiane

    2014-05-01

    Numerous datasets providing temperature information from meteorological stations or remote sensing satellites are available. However, the challenging issue is to search in the archives and process the time series information for further analysis. These steps can be automated for each individual product, if the pre-conditions are complied, e.g. data access through web services (HTTP, FTP) or legal rights to redistribute the datasets. Therefore a python-based package was developed to provide data access and data processing tools for MODIS Land Surface Temperature (LST) data, which is provided by NASA Land Processed Distributed Active Archive Center (LPDAAC), as well as the Global Surface Summary of the Day (GSOD) and the Global Historical Climatology Network (GHCN) daily datasets provided by NOAA National Climatic Data Center (NCDC). The package to access and process the information is available as web services used by an interactive web portal for simple data access and analysis. Tools for time series analysis were linked to the system, e.g. time series plotting, decomposition, aggregation (monthly, seasonal, etc.), trend analyses, and breakpoint detection. Especially for temperature data a plot was integrated for the comparison of two temperature datasets based on the work by Urban et al. (2013). As a first result, a kernel density plot compares daily MODIS LST from satellites Aqua and Terra with daily means from GSOD and GHCN datasets. Without any data download and data processing, the users can analyze different time series datasets in an easy-to-use web portal. As a first use case, we built up this complimentary system with remotely sensed MODIS data and in situ measurements from meteorological stations for Siberia within the Siberian Earth System Science Cluster (www.sibessc.uni-jena.de). References: Urban, Marcel; Eberle, Jonas; Hüttich, Christian; Schmullius, Christiane; Herold, Martin. 2013. "Comparison of Satellite-Derived Land Surface Temperature and Air

  9. 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

  10. Prototype and Evaluation of AutoHelp: A Case-based, Web-accessible Help Desk System for EOSDIS

    NASA Technical Reports Server (NTRS)

    Mitchell, Christine M.; Thurman, David A.

    1999-01-01

    AutoHelp is a case-based, Web-accessible help desk for users of the EOSDIS. Its uses a combination of advanced computer and Web technologies, knowledge-based systems tools, and cognitive engineering to offload the current, person-intensive, help desk facilities at the DAACs. As a case-based system, AutoHelp starts with an organized database of previous help requests (questions and answers) indexed by a hierarchical category structure that facilitates recognition by persons seeking assistance. As an initial proof-of-concept demonstration, a month of email help requests to the Goddard DAAC were analyzed and partially organized into help request cases. These cases were then categorized to create a preliminary case indexing system, or category structure. This category structure allows potential users to identify or recognize categories of questions, responses, and sample cases similar to their needs. Year one of this research project focused on the development of a technology demonstration. User assistance 'cases' are stored in an Oracle database in a combination of tables linking prototypical questions with responses and detailed examples from the email help requests analyzed to date. When a potential user accesses the AutoHelp system, a Web server provides a Java applet that displays the category structure of the help case base organized by the needs of previous users. When the user identifies or requests a particular type of assistance, the applet uses Java database connectivity (JDBC) software to access the database and extract the relevant cases. The demonstration will include an on-line presentation of how AutoHelp is currently structured. We will show how a user might request assistance via the Web interface and how the AutoHelp case base provides assistance. The presentation will describe the DAAC data collection, case definition, and organization to date, as well as the AutoHelp architecture. It will conclude with the year 2 proposal to more fully develop the

  11. Guy's Stone Score (GSS) Based on Intravenous Pyelogram (IVP) Findings Predicting Upper Pole Access Percutaneous Nephrolithotomy (PCNL) Outcomes

    PubMed Central

    Rod-Ong, Pattara; Kitirattrakarn, Pruit; Chongruksut, Wilaiwan

    2016-01-01

    Objective. To predict the success rate and complications following percutaneous nephrolithotomy via the upper pole using the Guy's Stone Score (GSS) based on the findings of a preoperative intravenous pyelogram (IVP). Patients and Methods. Two hundred and twenty-seven renal operations, which were carried out using PCNL via the upper pole, were classified according to the GSS assigned. Any complications were classified according to the Clavien classification. The success rates and incidence of any complications were compared between each GSS. Results. The immediate success rates were 87.50% of GSS1, 71.43% of GSS2, 53.62% of GSS3, and 38.46% of GSS4, P < 0.01. There were statistically significant differences between the groups in stone size, overall immediate success rate, operative time, number of access tracts, and frequency of tubeless PCNL. Major complications (a Clavien score of 3–5) were significantly higher in the cases with a higher GSS. Conclusion. A GSS based on an IVP is a simple and reliable tool in predicting the success rate and possible complications following upper pole access PCNL. PMID:28003822

  12. POD-based analysis of combustion images in optically accessible engines

    SciTech Connect

    Bizon, K.; Continillo, G.; Mancaruso, E.; Merola, S.S.; Vaglieco, B.M.

    2010-04-15

    This paper reports on 2D images of combustion-related luminosity taken in two optically accessible automobile engines of the most recent generation. The results are discussed to elucidate physical phenomena in the combustion chambers. Then, proper orthogonal decomposition (POD) is applied to the acquired images. The coefficients of the orthogonal modes are then used for the analysis of cycle variability, along with data of dynamic in-cylinder pressure and rate of heat release. The advantage is that statistical analysis can be run on a small number of scalar coefficients rather than on the full data set of pixel luminosity values. Statistics of the POD coefficients provide information on cycle variations of the luminosity field. POD modes are then discriminated by means of normality tests, to separate the mean from the coherent and the incoherent parts of the fluctuation of the luminosity field, in a non-truncated representation of the data. The morphology of the fluctuation components can finally be reconstructed by grouping coherent and incoherent modes. The structure of the incoherent component of the fluctuation is consistent with the underlying turbulent field. (author)

  13. Access Nets: Modeling Access to Physical Spaces

    NASA Astrophysics Data System (ADS)

    Frohardt, Robert; Chang, Bor-Yuh Evan; Sankaranarayanan, Sriram

    Electronic, software-managed mechanisms using, for example, radio-frequency identification (RFID) cards, enable great flexibility in specifying access control policies to physical spaces. For example, access rights may vary based on time of day or could differ in normal versus emergency situations. With such fine-grained control, understanding and reasoning about what a policy permits becomes surprisingly difficult requiring knowledge of permission levels, spatial layout, and time. In this paper, we present a formal modeling framework, called AccessNets, suitable for describing a combination of access permissions, physical spaces, and temporal constraints. Furthermore, we provide evidence that model checking techniques are effective in reasoning about physical access control policies. We describe our results from a tool that uses reachability analysis to validate security policies.

  14. The On-Line Uv/Vis Spectra Data Base An Example For Interactive Access To Scientific Information

    NASA Astrophysics Data System (ADS)

    Noelle, A.; Hartmann, G.; Richter, A.

    2003-04-01

    The basic concept of the on-line "UV/Vis Spectra Data Base" is to provide useful information to the scientific community on a proper basis, especially in times where scientific information becomes more and more a commercial product and is therefore often not within the financial means of those people who actually generated the information. Besides the EGS activities in peer reviewed open access e-publishing (e.g. the journal "Atmopheric Chemistry and Physics", ACP) this concept can help the community to reduce the "digital divide" for scientific and technical information. The on-line data base is maintained by a team consisting of the data base providers, the data producer and its users. The long-term scienctific success depends on the close cooperation of this team. Therefore all scientists are encouraged to join this cooperative effort and support the data base either actively or passively. Active support means the provision of missing or newly measured validated spectral data for inclusion in the data base. Although there is a moderate annual maintenance fee for the data base utilization, those scientists who actively support the data base can use the data base free-of-charge. There is also the possibility to support the data base passively by subscription to the data base. Even those scienctists who do not support the data base can benefit from the "Literature Service" which is free-of-charge. This data base concept differs from other commercial activities on this area and matches the philosophy of Copernicus.

  15. Proto-Examples of Data Access and Visualization Components of a Potential Cloud-Based GEOSS-AI System

    NASA Astrophysics Data System (ADS)

    Teng, W. L.; Lynnes, C.

    2014-12-01

    Once a research or application problem has been identified, one logical next step is to search for available relevant data products. Thus, an early component of a potential GEOSS-AI system, in the continuum between observations and end point research, applications, and decision making, would be one that enables transparent data discovery and access by users. Such a component might be effected via the system's "data agents." Presumably, some kind of data cataloging has already been implemented, e.g., in the GEOSS Common Infrastructure (GCI). Both the agents and cataloging could also leverage existing resources external to the system. The system would have some means to accept and integrate user-contributed agents. The need or desirability for some data format internal to the system should be evaluated. Another early component would be one that facilitates browsing/visualization of the data, as well as some basic analyses. Three ongoing projects at the NASA Goddard Earth Sciences Data and Information Services Center (GES DISC) provide possible proto-examples of potential data access and visualization components of a cloud-based GEOSS-AI system. Reorganizing data archived as time-step arrays to point-time series ("data rods"), as well as leveraging the NASA Simple Subset Wizard (SSW), to significantly increase the number of data products available, at multiple NASA data centers, for production as on-the-fly (virtual) data rods. SSW's data discovery is based on OpenSearch. Both pre-generated and virtual data rods are accessible via Web services. Developing Web Feature Services to publish the metadata, and expose the locations, of pre-generated and virtual data rods in the GEOSS Portal and enable direct access of the data via Web services. SSW is also leveraged to increase the availability of both NASA and non-NASA data. Federating NASA Giovanni (Geospatial Interactive Online Visualization and Analysis Interface), for multi-sensor data exploration, that would allow each

  16. Proto-Examples of Data Access and Visualization Components of a Potential Cloud-Based GEOSS-AI System

    NASA Technical Reports Server (NTRS)

    Teng, William; Lynnes, Christopher

    2014-01-01

    Once a research or application problem has been identified, one logical next step is to search for available relevant data products. Thus, an early component of a potential GEOSS-AI system, in the continuum between observations and end point research, applications, and decision making, would be one that enables transparent data discovery and access by users. Such a component might be effected via the systems data agents. Presumably, some kind of data cataloging has already been implemented, e.g., in the GEOSS Common Infrastructure (GCI). Both the agents and cataloging could also leverage existing resources external to the system. The system would have some means to accept and integrate user-contributed agents. The need or desirability for some data format internal to the system should be evaluated. Another early component would be one that facilitates browsing visualization of the data, as well as some basic analyses.Three ongoing projects at the NASA Goddard Earth Sciences Data and Information Services Center (GES DISC) provide possible proto-examples of potential data access and visualization components of a cloud-based GEOSS-AI system. 1. Reorganizing data archived as time-step arrays to point-time series (data rods), as well as leveraging the NASA Simple Subset Wizard (SSW), to significantly increase the number of data products available, at multiple NASA data centers, for production as on-the-fly (virtual) data rods. SSWs data discovery is based on OpenSearch. Both pre-generated and virtual data rods are accessible via Web services. 2. Developing Web Feature Services to publish the metadata, and expose the locations, of pre-generated and virtual data rods in the GEOSS Portal and enable direct access of the data via Web services. SSW is also leveraged to increase the availability of both NASA and non-NASA data.3.Federating NASA Giovanni (Geospatial Interactive Online Visualization and Analysis Interface), for multi-sensor data exploration, that would allow each

  17. A novel base-induced isomerization gives access to unprecedented (E)-exo-glycals.

    PubMed

    Eppe, Guillaume; Dumitrescu, Lidia; Pierrot, Olivier; Li, Tianlei; Pan, Weidong; Vincent, Stéphane P

    2013-08-26

    Bump the base: This study reports the discovery of the base-induced Z-to-E isomerization of exo-glycals bearing an electron-withdrawing group (EWG). The scope of this novel transformation regarding the carbohydrate unit is also discussed. After elucidating the mechanism, preparation of novel (E)-exo- glycals was performed (TBS = tert-butyldimethylsilyl).

  18. Activity Based Learning as Self-Accessing Strategy to Promote Learners' Autonomy

    ERIC Educational Resources Information Center

    Ravi, R.; Xavier, P.

    2007-01-01

    The Activity Based Learning (ABL) is unique and effective to attract out-of -school children to schools. It facilitates readiness for learning, instruction, reinforcement and evaluation. ABL has transformed the classrooms into hubs of activities and meaningful learning. Activity-based learning, naturally leads to cooperative learning. Since group…

  19. Placement of Base Stations in Broadband Power Line Communications Access Networks by Means of Multi-criteria Optimization

    NASA Astrophysics Data System (ADS)

    Haidine, Abdelfatteh; Lehnert, Ralf

    Broadband Power Line Communications (B-PLC) technology is an alternative for broadband access networks, allowing bit rates up to currently 200Mbps. This technique uses the wiring of the low-voltage grid in order to offer to the users the telecommunications services, such as Internet, VoIP, VoD, etc. The B-PLC design process is sub-divided into two parts: the Generalized Base Station Placement (GBSP) problem and the PLC Channel Allocation Problem (P-CAP). This paper focuses on GBSP that is modeled as multi-criteria combinatorial optimization problem. Based on our published mathematical modeling, this paper supplies more numerical experiments for the evaluation of Multi-Objective Evolutionary Algorithms (MOEAs) in solving GBSP. Their performance is compared with the single-objective optimization.

  20. Enhancing Accessibility and Engagement in Evidence-Based Parenting Programs to Reduce Maltreatment: Conversations With Vulnerable Parents

    PubMed Central

    Sanders, Matthew R.; Metzler, Carol W.; Prinz, Ronald J.; Kast, Elizabeth Z.

    2013-01-01

    11 focus groups (N = 160) of high-risk parents in Los Angeles County were asked to assess the value of social media to deliver an evidence-based parenting program, Triple P—Positive Parenting Program, to reduce child maltreatment. For feasibility, (N = 238) parents were surveyed regarding their internet use. Parents responded enthusiastically to the online program, and expressed the importance of a sense of community and learning through the experiences of others. 78% of the young, high-poverty, minority parents used the internet. An online evidence-based parenting program delivered in social media could enhance accessibility and engagement of high-risk parents – a powerful tool to reduce child maltreatment. PMID:23710156

  1. Novel Scheme of Carrier Tri-reuse and Distribution Fiber Protection Based on Round Shift Method in Optical Access Network

    NASA Astrophysics Data System (ADS)

    Chen, Haibin; Gan, Chaoqin; Yin, Maojun; Ni, Cuiping

    2015-06-01

    A novel architecture of optical access network based on round shift method is proposed. Round shift method is composed by round service mode of carriers and cycle characteristic of 2×N arrayed waveguide grating (AWG). By utilizing the round service mode, every carrier is tri-reused to provide service for three different optical network units. Besides, in remote node, the 2×3N AWG can be replaced by three 2×N AWGs and AWGs' channel spacing is increased. So, the demand on RN's AWGs is decreased. Furthermore, based on the cycle characteristic of 2×N AWG, a 1+1 protection scheme is presented to provide independent protection for distribution fibers. Simulation and analysis show the proposed scheme works well.

  2. South Florida Information Access (SOFIA) metadata for the U.S. Geological Survey Greater Everglades place-based studies

    USGS Publications Warehouse

    Stapleton, Jo Anne; Sonenshein, Roy

    2004-01-01

    Beginning in 1995 the U.S. Geological Survey (USGS) funded scientific research to support the restoration of the Greater Everglades area and to supply decision makers and resource mangers with sound data on which to base their actions. However, none of the research and resulting data is useful if it can?t be discovered, can?t be assessed for utility in an application, can?t be accessed, or is in an undetermined format. The decision was made early in the USGS Place-Based Studies (PBS) program to create a ?one-stop? entry for information and data about USGS research results. To facilitate the discovery process some mechanism was needed to allow standardized queries about data. The FGDC metadata standard has been used to document the South Florida PBS data from the beginning.

  3. Usage and Effectiveness of a Fully Automated, Open-Access, Spanish Web-Based Smoking Cessation Program: Randomized Controlled Trial

    PubMed Central

    2014-01-01

    Background The Internet is an optimal setting to provide massive access to tobacco treatments. To evaluate open-access Web-based smoking cessation programs in a real-world setting, adherence and retention data should be taken into account as much as abstinence rate. Objective The objective was to analyze the usage and effectiveness of a fully automated, open-access, Web-based smoking cessation program by comparing interactive versus noninteractive versions. Methods Participants were randomly assigned either to the interactive or noninteractive version of the program, both with identical content divided into 4 interdependent modules. At baseline, we collected demographic, psychological, and smoking characteristics of the smokers self-enrolled in the Web-based program of Universidad Nacional de Educación a Distancia (National Distance Education University; UNED) in Madrid, Spain. The following questionnaires were administered: the anxiety and depression subscales from the Symptom Checklist-90-Revised, the 4-item Perceived Stress Scale, and the Heaviness of Smoking Index. At 3 months, we analyzed dropout rates, module completion, user satisfaction, follow-up response rate, and self-assessed smoking abstinence. Results A total of 23,213 smokers were registered, 50.06% (11,620/23,213) women and 49.94% (11,593/23,213) men, with a mean age of 39.5 years (SD 10.3). Of these, 46.10% (10,701/23,213) were married and 34.43% (7992/23,213) were single, 46.03% (10,686/23,213) had university education, and 78.73% (18,275/23,213) were employed. Participants smoked an average of 19.4 cigarettes per day (SD 10.3). Of the 11,861 smokers randomly assigned to the interactive version, 2720 (22.93%) completed the first module, 1052 (8.87%) the second, 624 (5.26%) the third, and 355 (2.99%) the fourth. Completion data was not available for the noninteractive version (no way to record it automatically). The 3-month follow-up questionnaire was completed by 1085 of 23,213 enrolled smokers

  4. ECOMS-UDG. A User-friendly Data access Gateway to seasonal forecast datasets allowing R-based remote data access, visualization-validation, bias correction and downscaling

    NASA Astrophysics Data System (ADS)

    Santiago Cofiño, Antonio; Gutiérrez, José Manuel; Fernández, Jesús; Bedia, Joaquín; Vega, Manuel; Herrera, Sixto; Frías, María Dolores; Iturbide, Maialen; Magariño, Maria Eugenia; Manzanas, Rodrigo

    2016-04-01

    Seasonal forecasting data from state-or-the-art forecasting systems (e.g. NCEP/CFSv2 or ECMWF/System4) can be obtained directly from the data providers, but the resulting formats, aggregations and vocabularies may not be homogeneous across datasets, requiring some post processing. Moreover, different data policies hold for the various datasets - which are freely available only in some cases - and therefore data access may not be straightforward. Thus, obtaining seasonal climate forecast data is typically a time consuming task. The ECOMS-UDG (User Data Gateway for the ECOMS initiative) has been developed building in the ​User Data Gateway (UDG, http://meteo.unican.es/udg-wiki) in order to facilitate seasonal (re)forecast data access to end users. The required variables have been downloaded from data providers and stored locally in a THREDDS data server implementing fine-grained user authorization. Thus, users can efficiently retrieve the subsets that best suits their particular research aims (typically surface variables for certain regions, periods and/or ensemble members) from a large volume of information. Moreover, an interface layer developed in R allows remote data exploration, access (including homogenization, collocation and sub-setting) and the integration of ECOMS-UDG with a number of R packages developed in the framework of ECOMS for forecast visualization, validation, bias correction and downscaling. This unique framework oriented to climate services allows users from different sectors to easily access seasonal forecasting data (typically surface variables), calibrating and/or downscaling (using upper air information from large scale predictors) this data at local level and validating the different results (using observations). The documentation delivered with the packages includes worked examples showing that the whole visualization, bias correction and/or downscaling tasks requires only a few lines of code and are fully reproducible and adaptable to

  5. 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…

  6. GUI-Based Document Access via SATCOMMS: Online Electronic Document Retrieval at the European Telecommunications Satellite Organization EUTELSAT.

    ERIC Educational Resources Information Center

    Burton, Adrian P.

    1995-01-01

    Discusses accessing online electronic documents at the European Telecommunications Satellite Organization (EUTELSAT). Highlights include off-site paper document storage, the document management system, benefits, the EUTELSAT Standard IBM Access software, implementation, the development process, and future enhancements. (AEF)

  7. HIV/AIDS and access to water: A case study of home-based care in Ngamiland, Botswana

    NASA Astrophysics Data System (ADS)

    Ngwenya, B. N.; Kgathi, D. L.

    This case study investigates access to potable water in HIV/AIDS related home-based care households in five rural communities in Ngamiland, Botswana. Primary data collected from five villages consisted of two parts. The first survey collected household data on demographic and rural livelihood features and impacts of HIV/AIDS. A total of 129 households were selected using a two-stage stratified random sampling method. In the second survey, a total of 39 family primary and community care givers of continuously ill, bed-ridden or non-bed-ridden HIV/AIDS patients were interviewed. A detailed questionnaire, with closed and open-ended questions, was used to collect household data. In addition to using the questionnaire, data were also collected through participant observation, informal interviews and secondary sources. The study revealed that there are several sources of water for communities in Ngamiland such as off-plot, outdoor (communal) and on-plot outdoor and/or indoor (private) water connections, as well as other sources such as bowsed water, well-points, boreholes and open perennial/ephemeral water from river channels and pans. There was a serious problem of unreliable water supply caused by, among other things, the breakdown of diesel-powered water pumps, high frequency of HIV/AIDS related absenteeism, and the failure of timely delivery of diesel fuel. Some villages experienced chronic supply disruptions while others experienced seasonal or occasional water shortages. Strategies for coping with unreliability of water supply included economizing on water, reserve storage, buying water, and collection from river/dug wells or other alternative sources such as rain harvesting tanks in government institutions. The unreliability of water supply resulted in an increase in the use of water of poor quality and other practices of poor hygiene as well as a high opportunity cost of water collection. In such instances, bathing of patients was cut from twice daily to once or

  8. Students with multiple disabilities using technology-based programs to choose and access stimulus events alone or with caregiver participation.

    PubMed

    Lancioni, Giulio E; Singh, Nirbhay N; O'Reilly, Mark F; Sigafoos, Jeff; Oliva, Doretta; Cingolani, Eleonora

    2009-01-01

    The first of these two studies extended preliminary evidence on the use of technology-based programs for enabling students with severe and profound multiple disabilities to choose and access environmental stimuli on their own. Each of the three participants had two microswitches linked to specific sets of stimuli through a computer system. The activation of one of the microswitches triggered the computer system to present a sample of one of the stimuli. If the student chose it, the computer system turned it on for a specific time interval. The second study tested a new technology that allowed the students to choose and access the chosen stimuli with the involvement of the caregiver. The two participants had three microswitches linked to a computer system. The participants' choice of a stimulus alerted the caregiver who then got involved in the stimulation process. The results of both studies showed that the participants learned to activate the basic microswitches consistently, had high percentages of choice for the stimulus samples presented by the computer but with wide differences across stimuli, and largely maintained this performance at a 2-month post-intervention check. These findings were analyzed in terms of the usability of the two types of programs, the role they may play within educational and living contexts, and their innovative technical dimensions.

  9. Closing the digital divide in HIV/AIDS care: development of a theory-based intervention to increase Internet access.

    PubMed

    Kalichman, S C; Weinhardt, L; Benotsch, E; Cherry, C

    2002-08-01

    Advances in information technology are revolutionizing medical patient education and the Internet is becoming a major source of information for people with chronic medical conditions, including HIV/AIDS. However, many AIDS patients do not have equal access to the Internet and are therefore at an information disadvantage, particularly minorities, persons of low-income levels and individuals with limited education. This paper describes the development and pilot testing of a workshop-style intervention designed to close the digital divide in AIDS care. Grounded in the Information-Motivation-Behavioral Skills (IMB) model of health behaviour change, we developed an intervention for persons with no prior history of using the Internet. The intervention included instruction in using hardware and search engines, motivational enhancement to increase interest and perceived relevance of the Internet, and skills for critically evaluating and using health information accessed via the Internet. Participants were also introduced to communication and support functions of the Internet including e-mail, newsgroups and chat groups. Pilot testing demonstrated feasibility, acceptability and promise for closing the digital divide in HIV/AIDS care using a relatively brief and intensive theory-based intervention that could be implemented in community settings.

  10. In situ observation of nickel as an oxidizable electrode material for the solid-electrolyte-based resistive random access memory

    SciTech Connect

    Sun, Jun; Wu, Xing; Xu, Feng; Xu, Tao; Sun, Litao; Liu, Qi; Xie, Hongwei; Long, Shibing; Lv, Hangbing; Li, Yingtao; Liu, Ming

    2013-02-04

    In this letter, we dynamically investigate the resistive switching characteristics and physical mechanism of the Ni/ZrO{sub 2}/Pt device. The device shows stable bipolar resistive switching behaviors after forming process, which is similar to the Ag/ZrO{sub 2}/Pt and Cu/ZrO{sub 2}/Pt devices. Using in situ transmission electron microscopy, we observe in real time that several conductive filaments are formed across the ZrO{sub 2} layer between Ni and Pt electrodes after forming. Energy-dispersive X-ray spectroscopy results confirm that Ni is the main composition of the conductive filaments. The ON-state resistance increases with increasing temperature, exhibiting the feature of metallic conduction. In addition, the calculated resistance temperature coefficient is equal to that of the 10-30 nm diameter Ni nanowire, further indicating that the nanoscale Ni conductive bridge is the physical origin of the observed conductive filaments. The resistive switching characteristics and the conductive filament's component of Ni/ZrO{sub 2}/Pt device are consistent with the characteristics of the typical solid-electrolyte-based resistive random access memory. Therefore, aside from Cu and Ag, Ni can also be used as an oxidizable electrode material for resistive random access memory applications.

  11. 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

  12. IDMA-based MAC protocol for satellite networks with consideration on channel quality.

    PubMed

    Liu, Gongliang; Fang, Xinrui; Kang, Wenjing

    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.

  13. Evaluation of an Access Route to Higher Education through a Work-Based Assessment Strategy

    ERIC Educational Resources Information Center

    Harvey, Morag; Slaughter, Tim

    2007-01-01

    The Open University (OU) is the UK's largest university, with over 200,000 people studying, part time and at a distance, a range of undergraduate and postgraduate courses and packs. Research and development carried out at the OU's Centre for Outcomes-Based Education (COBE), has provided a new way of enabling students to be accredited at higher…

  14. GLONASS-R: GNSS reflectometry with a Frequency Division Multiple Access-based satellite navigation system

    NASA Astrophysics Data System (ADS)

    Hobiger, T.; Haas, R.; Löfgren, J. S.

    2014-04-01

    The information from reflected Global Navigation Satellite System (GNSS) signals can become a valuable data source, from which geophysical properties can be deduced. This approach, called GNSS Reflectometry (GNSS-R), can be used to develop instruments that act like an altimeter when arrival times of direct and reflected signals are compared. Current GNSS-R systems usually entirely rely on signals from the Global Positioning Service (GPS), and field experiments could demonstrate that information from such systems can measure sea level with an accuracy of a few centimeters. However, the usage of the Russian GLONASS system has the potential to simplify the processing scheme and to allow handling of direct and reflected signals like a bistatic radar. Thus, such a system has been developed and deployed for test purposes at the Onsala Space Observatory, Sweden, that has an operational GPS-based GNSS-R system. Over a period of 2 weeks in October 2013, GPS-based GNSS-R sea level monitoring and measurements with the newly developed GLONASS-R system were carried out in parallel. In addition, data from colocated tide gauge measurements were available for comparison. It can be shown that precision and accuracy of the GLONASS-based GNSS-R system is comparable to, or even better than, conventional GPS-based GNSS-R solutions. Moreover, the simplicity of the newly developed GLONASS-R system allows to make it a cheap and valuable tool for various remote sensing applications.

  15. Virtual and Physical Experimentation in Inquiry-Based Science Labs: Attitudes, Performance and Access

    ERIC Educational Resources Information Center

    Pyatt, Kevin; Sims, Rod

    2012-01-01

    This study investigated the learning dimensions that occur in physical and virtual inquiry-based lab investigations, in first-year secondary chemistry classes. This study took place over a 2 year period and utilized an experimental crossover design which consisted of two separate trials of laboratory investigation. Assessment data and attitudinal…

  16. Channel Access in Erlang

    SciTech Connect

    Nicklaus, Dennis J.

    2013-10-13

    We have developed an Erlang language implementation of the Channel Access protocol. Included are low-level functions for encoding and decoding Channel Access protocol network packets as well as higher level functions for monitoring or setting EPICS process variables. This provides access to EPICS process variables for the Fermilab Acnet control system via our Erlang-based front-end architecture without having to interface to C/C++ programs and libraries. Erlang is a functional programming language originally developed for real-time telecommunications applications. Its network programming features and list management functions make it particularly well-suited for the task of managing multiple Channel Access circuits and PV monitors.

  17. Mixing stream and datagram traffic on satellite: A FIFO Order-based Demand Assignment (FODA) Time Division Multiple Access (TDMA) scheme

    NASA Astrophysics Data System (ADS)

    Beltrame, R.; Bonito, A. B.; Celandroni, N.; Ferro, E.

    1985-11-01

    A FIFO Order based Demand Assignment (FODA) access scheme was designed to handle packetized data and voice traffic in a multiple access satellite broadcast channel of Mbits band. The channel is shared by as many as 64 simultaneously active stations in a range of 255 addressable stations. A sophisticated traffic environment is assumed, including different types of service requirements and an arbitrary load distribution among the stations. The results of 2Mbit/sec simulation tests for an existing hardware environment are presented.

  18. Catalytic Coupling of Carbon Dioxide with Terpene Scaffolds: Access to Challenging Bio-Based Organic Carbonates.

    PubMed

    Fiorani, Giulia; Stuck, Moritz; Martín, Carmen; Belmonte, Marta Martínez; Martin, Eddy; Escudero-Adán, Eduardo C; Kleij, Arjan W

    2016-06-08

    The challenging coupling of highly substituted terpene oxides and carbon dioxide into bio-based cyclic organic carbonates catalyzed by Al(aminotriphenolate) complexes is reported. Both acyclic as well as cyclic terpene oxides were used as coupling partners, showing distinct reactivity/selectivity behavior. Whereas cyclic terpene oxides showed excellent chemoselectivity towards the organic carbonate product, acyclic substrates exhibited poorer selectivities owing to concomitant epoxide rearrangement reactions and the formation of undesired oligo/polyether side products. Considering the challenging nature of these coupling reactions, the isolated yields of the targeted bio-carbonates are reasonable and in most cases in the range 50-60 %. The first crystal structures of tri-substituted terpene based cyclic carbonates are reported and their stereoconnectivity suggests that their formation proceeds through a double inversion pathway.

  19. Facile access to unnatural dipeptide-alcohols based on cis-2,5-disubstituted pyrrolidines.

    PubMed

    Jia, Yan-Yan; Li, Xiao-Ye; Wang, Ping-An; Wen, Ai-Dong

    2015-02-11

    Well-defined unnatural dipeptide-alcohols based on a cis-2,5-disubstitued pyrrolidine backbone were synthesized from commercially available starting materials meso-diethyl-2,5-dibromoadipate, (S)-(-)-1-phenylethylamine, and phenylalaninol. The structures of these unnatural dipeptide-alcohols are supported by HRMS, 1H- and 13C-NMR spectroscopy. These unnatural dipeptide-alcohols can act as building blocks for peptidomimetics.

  20. www.mydrugdealer.com: Ethics and legal implications of Internet-based access to substances of abuse.

    PubMed

    Klein, Carolina A; Kandel, Surendra

    2011-01-01

    The Internet has increasingly become an intrinsic part of everyday life, offering countless possibilities for education, services, recreation, and more. In fact, an entire virtual life within the digitalized World Wide Web is possible and common among many Internet users. Today's psychiatrists must therefore incorporate this dimension of human life into clinical practice, to achieve an adequate assessment of the tools and risks available to the patient. We focus on the Internet as a portal for the trade of and access to substances of abuse. We review the legal regulations that may inform care and standards of practice and analyze the difficulties that arise in assessment and monitoring of the current situation. We consider the potential impact of Internet-based narcotics trade on addiction morbidities and the practice of clinical psychiatry, as well as on the potential legal implications that the forensic expert may face.

  1. Towards 5G: A Photonic Based Millimeter Wave Signal Generation for Applying in 5G Access Fronthaul

    PubMed Central

    Alavi, S. E.; Soltanian, M. R. K.; Amiri, I. S.; Khalily, M.; Supa’at, A. S. M.; Ahmad, H.

    2016-01-01

    5G communications require a multi Gb/s data transmission in its small cells. For this purpose millimeter wave (mm-wave) RF signals are the best solutions to be utilized for high speed data transmission. Generation of these high frequency RF signals is challenging in electrical domain therefore photonic generation of these signals is more studied. In this work, a photonic based simple and robust method for generating millimeter waves applicable in 5G access fronthaul is presented. Besides generating of the mm-wave signal in the 60 GHz frequency band the radio over fiber (RoF) system for transmission of orthogonal frequency division multiplexing (OFDM) with 5 GHz bandwidth is presented. For the purpose of wireless transmission for 5G application the required antenna is designed and developed. The total system performance in one small cell was studied and the error vector magnitude (EVM) of the system was evaluated. PMID:26814621

  2. Improved characteristics of amorphous indium-gallium-zinc-oxide-based resistive random access memory using hydrogen post-annealing

    NASA Astrophysics Data System (ADS)

    Kang, Dae Yun; Lee, Tae-Ho; Kim, Tae Geun

    2016-08-01

    The authors report an improvement in resistive switching (RS) characteristics of amorphous indium-gallium-zinc-oxide (a-IGZO)-based resistive random access memory devices using hydrogen post-annealing. Because this a-IGZO thin film has oxygen off-stoichiometry in the form of deficient and excessive oxygen sites, the film properties can be improved by introducing hydrogen atoms through the annealing process. After hydrogen post-annealing, the device exhibited a stable bipolar RS, low-voltage set and reset operation, long retention (>105 s), good endurance (>106 cycles), and a narrow distribution in each current state. The effect of hydrogen post-annealing is also investigated by analyzing the sample surface using X-ray photon spectroscopy and atomic force microscopy.

  3. Towards 5G: A Photonic Based Millimeter Wave Signal Generation for Applying in 5G Access Fronthaul

    NASA Astrophysics Data System (ADS)

    Alavi, S. E.; Soltanian, M. R. K.; Amiri, I. S.; Khalily, M.; Supa’At, A. S. M.; Ahmad, H.

    2016-01-01

    5G communications require a multi Gb/s data transmission in its small cells. For this purpose millimeter wave (mm-wave) RF signals are the best solutions to be utilized for high speed data transmission. Generation of these high frequency RF signals is challenging in electrical domain therefore photonic generation of these signals is more studied. In this work, a photonic based simple and robust method for generating millimeter waves applicable in 5G access fronthaul is presented. Besides generating of the mm-wave signal in the 60 GHz frequency band the radio over fiber (RoF) system for transmission of orthogonal frequency division multiplexing (OFDM) with 5 GHz bandwidth is presented. For the purpose of wireless transmission for 5G application the required antenna is designed and developed. The total system performance in one small cell was studied and the error vector magnitude (EVM) of the system was evaluated.

  4. Towards 5G: A Photonic Based Millimeter Wave Signal Generation for Applying in 5G Access Fronthaul.

    PubMed

    Alavi, S E; Soltanian, M R K; Amiri, I S; Khalily, M; Supa'at, A S M; Ahmad, H

    2016-01-27

    5G communications require a multi Gb/s data transmission in its small cells. For this purpose millimeter wave (mm-wave) RF signals are the best solutions to be utilized for high speed data transmission. Generation of these high frequency RF signals is challenging in electrical domain therefore photonic generation of these signals is more studied. In this work, a photonic based simple and robust method for generating millimeter waves applicable in 5G access fronthaul is presented. Besides generating of the mm-wave signal in the 60 GHz frequency band the radio over fiber (RoF) system for transmission of orthogonal frequency division multiplexing (OFDM) with 5 GHz bandwidth is presented. For the purpose of wireless transmission for 5G application the required antenna is designed and developed. The total system performance in one small cell was studied and the error vector magnitude (EVM) of the system was evaluated.

  5. Wavelet-based compression with ROI coding support for mobile access to DICOM images over heterogeneous radio networks.

    PubMed

    Maglogiannis, Ilias; Doukas, Charalampos; Kormentzas, George; Pliakas, Thomas

    2009-07-01

    Most of the commercial medical image viewers do not provide scalability in image compression and/or region of interest (ROI) encoding/decoding. Furthermore, these viewers do not take into consideration the special requirements and needs of a heterogeneous radio setting that is constituted by different access technologies [e.g., general packet radio services (GPRS)/ universal mobile telecommunications system (UMTS), wireless local area network (WLAN), and digital video broadcasting (DVB-H)]. This paper discusses a medical application that contains a viewer for digital imaging and communications in medicine (DICOM) images as a core module. The proposed application enables scalable wavelet-based compression, retrieval, and decompression of DICOM medical images and also supports ROI coding/decoding. Furthermore, the presented application is appropriate for use by mobile devices activating in heterogeneous radio settings. In this context, performance issues regarding the usage of the proposed application in the case of a prototype heterogeneous system setup are also discussed.

  6. Creating community-based access to primary healthcare for the uninsured through strategic alliances and restructuring local health department programs.

    PubMed

    Scotten, E Shirin L; Absher, Ann C

    2006-01-01

    In 2003, the Wilkes County Health Department joined with county healthcare providers to develop the HealthCare Connection, a coordinated and continuous system of low-cost quality care for uninsured and low-income working poor. Through this program, local providers of primary and specialty care donate specialty care or ancillary services not provided by the Health Department, which provides case management for the program. Basing their methods on business models learned through the UNC Management Academy for Public Health, planners investigated the best practices for extending healthcare coverage to the underinsured and uninsured, analyzed operational costs, discovered underutilized local resources, and built capacity within the organization. The HealthCare Connection is an example of how a rural community can join together in a common business practice to improve healthcare access for uninsured and/or low-income adults.

  7. Capacity allocation mechanism based on differentiated QoS in 60 GHz radio-over-fiber local access network

    NASA Astrophysics Data System (ADS)

    Kou, Yanbin; Liu, Siming; Zhang, Weiheng; Shen, Guansheng; Tian, Huiping

    2017-03-01

    We present a dynamic capacity allocation mechanism based on the Quality of Service (QoS) for different mobile users (MU) in 60 GHz radio-over-fiber (RoF) local access networks. The proposed mechanism is capable for collecting the request information of MUs to build a full list of MU capacity demands and service types at the Central Office (CO). A hybrid algorithm is introduced to implement the capacity allocation which can satisfy the requirements of different MUs at different network traffic loads. Compared with the weight dynamic frames assignment (WDFA) scheme, the Hybrid scheme can keep high priority MUs in low delay and maintain the packet loss rate less than 1% simultaneously. At the same time, low priority MUs have a relatively better performance.

  8. An information theory based search for homogeneity on the largest accessible scale

    NASA Astrophysics Data System (ADS)

    Sarkar, Suman; Pandey, Biswajit

    2016-11-01

    We analyse the Sloan Digital Sky Survey Data Release 12 quasar catalogue to test the large-scale smoothness in the quasar distribution. We quantify the degree of inhomogeneity in the quasar distribution using information theory based measures and find that the degree of inhomogeneity diminishes with increasing length scales which finally reach a plateau at ˜250 h-1 Mpc. The residual inhomogeneity at the plateau is consistent with that expected for a Poisson point process. Our results indicate that the quasar distribution is homogeneous beyond length scales of 250 h-1 Mpc.

  9. Silanol-based surfactants: synthetic access and properties of an innovative class of environmentally benign detergents.

    PubMed

    Hurkes, Natascha; Ehmann, Heike M A; List, Martina; Spirk, Stefan; Bussiek, Malte; Belaj, Ferdinand; Pietschnig, Rudolf

    2014-07-21

    Herein, environmentally friendly surfactants based on new silanols as substitutes for the isoelectronic phosphonates were explored. Surface tensions of aqueous solutions are significantly reduced, particularly with those silanols that feature a high ratio of organic moiety to silanol. Besides their use as surfactants, their potential as coating agents for hydrophilic oxide surfaces was investigated for the example of glass substrates. In the solid-state sheet structures with silanol, double layers are present, in which the sheet spacing varies with the alkyl-chain length.

  10. Spin-based single-photon transistor, dynamic random access memory, diodes, and routers in semiconductors

    NASA Astrophysics Data System (ADS)

    Hu, C. Y.

    2016-12-01

    The realization of quantum computers and quantum Internet requires not only quantum gates and quantum memories, but also transistors at single-photon levels to control the flow of information encoded on single photons. Single-photon transistor (SPT) is an optical transistor in the quantum limit, which uses a single photon to open or block a photonic channel. In sharp contrast to all previous SPT proposals which are based on single-photon nonlinearities, here I present a design for a high-gain and high-speed (up to THz) SPT based on a linear optical effect: giant circular birefringence induced by a single spin in a double-sided optical microcavity. A gate photon sets the spin state via projective measurement and controls the light propagation in the optical channel. This spin-cavity transistor can be directly configured as diodes, routers, DRAM units, switches, modulators, etc. Due to the duality as quantum gate and transistor, the spin-cavity unit provides a solid-state platform ideal for future Internet: a mixture of all-optical Internet with quantum Internet.

  11. Water quality laboratories in Colombia: a GIS-based study of urban and rural accessibility.

    PubMed

    Wright, Jim; Liu, Jing; Bain, Robert; Perez, Andrea; Crocker, Jonny; Bartram, Jamie; Gundry, Stephen

    2014-07-01

    The objective of this study was to quantify sample transportation times associated with mandated microbiological monitoring of drinking-water in Colombia. World Health Organization Guidelines for Drinking-Water Quality recommend that samples spend no more than 6h between collection and analysis in a laboratory. Census data were used to estimate the minimum number of operational and surveillance samples required from piped water supplies under national regulations. Drive-times were then computed from each supply system to the nearest accredited laboratory and translated into sample holding times based on likely daily monitoring patterns. Of 62,502 surveillance samples required annually, 5694 (9.1%) were found to be more than 6 h from the nearest of 278 accredited laboratories. 612 samples (1.0%) were more than 24 hours' drive from the nearest accredited laboratory, the maximum sample holding time recommended by the World Health Organization. An estimated 30% of required rural samples would have to be stored for more than 6 h before reaching a laboratory. The analysis demonstrates the difficulty of undertaking microbiological monitoring in rural areas and small towns from a fixed laboratory network. Our GIS-based approach could be adapted to optimise monitoring strategies and support planning of testing and transportation infra-structure development. It could also be used to estimate sample transport and holding times in other countries.

  12. [Novel access to indazoles based on palladium-catalyzed amination chemistry].

    PubMed

    Inamoto, Kiyofumi

    2008-07-01

    Two efficient methods to construct the indazole nucleus have been developed, both of which utilize palladium-catalyzed intramolecular carbon-nitrogen bond formation. One is based on intramolecular Buchwald-Hartwig amination reaction of 2-halobenzophenone tosylhydrazones. The catalyst system we developed for this reaction allows the cyclization to proceed under very mild conditions and thus could be applied to a wide range of substrates with acid- or base-sensitive functional groups. Furthermore, this methodology could be applied for the construction of benzoisoxazole ring system. In addition, catalytic C-H activation with palladium followed by intramolecular amination of benzophenone tosylhydrazones was also accomplished with the aid of the catalyst system such as Pd(OAc)(2)/Cu(OAc)(2)/AgOCOCF(3), which gave another route to indazoles. Using this combination, indazoles with various functional groups could be obtained in good to high yields, especially in the case of substrates having electron donating group such as methoxy group on benzene ring. Interesting chemo- and regioselectivity were also observed in this reaction.

  13. Internet accessibility and usage among urban adolescents in Southern California: implications for web-based health research.

    PubMed

    Sun, Ping; Unger, Jennifer B; Palmer, Paula H; Gallaher, Peggy; Chou, Chih-Ping; Baezconde-Garbanati, Lourdes; Sussman, Steve; Johnson, C Anderson

    2005-10-01

    The World Wide Web (WWW) poses a distinct capability to offer interventions tailored to the individual's characteristics. To fine tune the tailoring process, studies are needed to explore how Internet accessibility and usage are related to demographic, psychosocial, behavioral, and other health related characteristics. This study was based on a cross-sectional survey conducted on 2373 7th grade students of various ethnic groups in Southern California. Measures of Internet use included Internet use at school or at home, Email use, chat-room use, and Internet favoring. Logistic regressions were conducted to assess the associations between Internet uses with selected demographic, psychosocial, behavioral variables and self-reported health statuses. The proportion of students who could access the Internet at school or home was 90% and 40%, separately. Nearly all (99%) of the respondents could access the Internet either at school or at home. Higher SES and Asian ethnicity were associated with higher internet use. Among those who could access the Internet and after adjusting for the selected demographic and psychosocial variables, depression was positively related with chat-room use and using the Internet longer than 1 hour per day at home, and hostility was positively related with Internet favoring (All ORs = 1.2 for +1 STD, p < 0.05). Less parental monitoring and more unsupervised time were positively related to email use, chat-room use, and at home Internet use (ORs for +1 STD ranged from 1.2 to 2.0, all p < 0.05), but not related to at school Internet use. Substance use was positively related to email use, chat-room use, and at home Internet use (OR for "used" vs. "not used" ranged from 1.2 to 4.0, p < 0.05). Self-reported health problems were associated with higher levels of Internet use at home but lower levels of Internet use at school. More physical activity was related to more email use (OR = 1.3 for +1 STD), chat room use (OR = 1.2 for +1 STD), and at school

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

    NASA Astrophysics Data System (ADS)

    Kaur, Navpreet; Goyal, Rakesh; Rani, Monika

    2017-03-01

    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.

  15. Effect of screw access hole preparation on fracture load of implant-supported zirconia-based crowns: an in vitro study

    PubMed Central

    Mokhtarpour, Hadi; Eftekhar Ashtiani, Reza; Mahshid, Minoo; Tabatabaian, Farhad; Alikhasi, Marzieh

    2016-01-01

    Background. Fracture load of implant-supported restorations is an important factor in clinical success. This study evaluated the effect of two techniques for screw access hole preparation on the fracture load of cement-screw-retained implant-supported zirconia-based crowns. Methods. Thirty similar cement-screw-retained implant-supported zirconia-based maxillary central incisor crowns were evaluated in three groups of 10. Group NH: with no screw access holes for the control; Group HBS: with screw access holes prepared with a machine before zirconia sintering; Group HAS: with screw access holes prepared manually after zirconia sintering. In group HBS, the access holes were virtually designed and prepared by a computer-assisted design/computer-assisted manufacturing system. In group HAS, the access holes were manually prepared after zirconia sintering using a diamond bur. The dimensions of the screw access holes were equal in both groups. The crowns were cemented onto same-size abutments and were then subjected to thermocycling. The fracture load values of the crowns were measured using a universal testing machine. Data were analyzed with ANOVA and Tukey test (P < 0.05). Results. The mean fracture load value for the group NH was 888.37 ± 228.92 N, which was the highest among the groups, with a significant difference (P < 0.0001). The fracture load values were 610.48 ± 125.02 N and 496.74 ± 104.10 Nin the HBS and HAS groups, respectively, with no significant differences (P = 0.44). Conclusion. Both techniques used for preparation of screw access holes in implant-supported zirconia-based crowns decreased the fracture load. PMID:27651885

  16. Effect of screw access hole preparation on fracture load of implant-supported zirconia-based crowns: an in vitro study.

    PubMed

    Mokhtarpour, Hadi; Eftekhar Ashtiani, Reza; Mahshid, Minoo; Tabatabaian, Farhad; Alikhasi, Marzieh

    2016-01-01

    Background. Fracture load of implant-supported restorations is an important factor in clinical success. This study evaluated the effect of two techniques for screw access hole preparation on the fracture load of cement-screw-retained implant-supported zirconia-based crowns. Methods. Thirty similar cement-screw-retained implant-supported zirconia-based maxillary central incisor crowns were evaluated in three groups of 10. Group NH: with no screw access holes for the control; Group HBS: with screw access holes prepared with a machine before zirconia sintering; Group HAS: with screw access holes prepared manually after zirconia sintering. In group HBS, the access holes were virtually designed and prepared by a computer-assisted design/computer-assisted manufacturing system. In group HAS, the access holes were manually prepared after zirconia sintering using a diamond bur. The dimensions of the screw access holes were equal in both groups. The crowns were cemented onto same-size abutments and were then subjected to thermocycling. The fracture load values of the crowns were measured using a universal testing machine. Data were analyzed with ANOVA and Tukey test (P < 0.05). Results. The mean fracture load value for the group NH was 888.37 ± 228.92 N, which was the highest among the groups, with a significant difference (P < 0.0001). The fracture load values were 610.48 ± 125.02 N and 496.74 ± 104.10 Nin the HBS and HAS groups, respectively, with no significant differences (P = 0.44). Conclusion. Both techniques used for preparation of screw access holes in implant-supported zirconia-based crowns decreased the fracture load.

  17. Comparing the quality of accessing medical literature using content-based visual and textual information retrieval

    NASA Astrophysics Data System (ADS)

    Müller, Henning; Kalpathy-Cramer, Jayashree; Kahn, Charles E., Jr.; Hersh, William

    2009-02-01

    Content-based visual information (or image) retrieval (CBIR) has been an extremely active research domain within medical imaging over the past ten years, with the goal of improving the management of visual medical information. Many technical solutions have been proposed, and application scenarios for image retrieval as well as image classification have been set up. However, in contrast to medical information retrieval using textual methods, visual retrieval has only rarely been applied in clinical practice. This is despite the large amount and variety of visual information produced in hospitals every day. This information overload imposes a significant burden upon clinicians, and CBIR technologies have the potential to help the situation. However, in order for CBIR to become an accepted clinical tool, it must demonstrate a higher level of technical maturity than it has to date. Since 2004, the ImageCLEF benchmark has included a task for the comparison of visual information retrieval algorithms for medical applications. In 2005, a task for medical image classification was introduced and both tasks have been run successfully for the past four years. These benchmarks allow an annual comparison of visual retrieval techniques based on the same data sets and the same query tasks, enabling the meaningful comparison of various retrieval techniques. The datasets used from 2004-2007 contained images and annotations from medical teaching files. In 2008, however, the dataset used was made up of 67,000 images (along with their associated figure captions and the full text of their corresponding articles) from two Radiological Society of North America (RSNA) scientific journals. This article describes the results of the medical image retrieval task of the ImageCLEF 2008 evaluation campaign. We compare the retrieval results of both visual and textual information retrieval systems from 15 research groups on the aforementioned data set. The results show clearly that, currently

  18. Methodology of determining the uncertainty in the accessible geothermal resource base of identified hydrothermal convection systems

    USGS Publications Warehouse

    Nathenson, Manuel

    1978-01-01

    In order to quantify the uncertainty of estimates of the geothermal resource base in identified hydrothermal convection systems, a methodology is presented for combining estimates with uncertainties for temperature, area, and thickness of a geothermal reservoir into an estimate of the stored energy with uncertainty. Probability density functions for temperature, area, and thickness are assumed to be triangular in form. In order to calculate the probability distribution function for the stored energy in a single system or in many systems, a computer program for aggregating the input distribution functions using the Monte-Carlo method has been developed. To calculate the probability distribution of stored energy in a single system, an analytical expression is also obtained that is useful for calibrating the Monte Carlo approximation. For the probability distributions of stored energy in a single and in many systems, the central limit approximation is shown to give results ranging from good to poor.

  19. General access to taiwaniaquinoids based on a hypothetical abietane C7-C8 cleavage biogenetic pathway.

    PubMed

    Tapia, Rubén; Guardia, Juan J; Alvarez, Esteban; Haidöur, Ali; Ramos, Jose M; Alvarez-Manzaneda, Ramón; Chahboun, Rachid; Alvarez-Manzaneda, Enrique

    2012-01-06

    A new strategy for synthesizing taiwaniaquinoids, a group of terpenoids with an unusual rearranged 5(6→7) or 6-nor-5(6→7)abeo-abietane skeleton, which exhibit promising biological activities, is reported. The procedure, based on the cleavage of the C7-C8 double bond of abietane diterpenes, is the only one yet reported for synthesizing C(20) taiwaniaquinoids bearing a carbon function on the cyclopentane B ring; it is also applicable to the synthesis of the wide variety of existing taiwaniaquinoids. Utilizing this, (-)-taiwaniaquinone A, F, G, and H, (-)-taiwaniaquinol B, and (-)-dichroanone have been synthesized from (+)-abietic acid. The versatility of this strategy allows us to propose the abietane C7-C8 cleavage as a possible biosynthetic pathway to this type of rearranged diterpenes; this proposal seems to be supported by phytochemical evidence.

  20. Thin Co/Ni-based bottom pinned spin-transfer torque magnetic random access memory stacks with high annealing tolerance

    NASA Astrophysics Data System (ADS)

    Tomczak, Y.; Swerts, J.; Mertens, S.; Lin, T.; Couet, S.; Liu, E.; Sankaran, K.; Pourtois, G.; Kim, W.; Souriau, L.; Van Elshocht, S.; Kar, G.; Furnemont, A.

    2016-01-01

    Spin-transfer torque magnetic random access memory (STT-MRAM) is considered as a replacement for next generation embedded and stand-alone memory applications. One of the main challenges in the STT-MRAM stack development is the compatibility of the stack with CMOS process flows in which thermal budgets up to 400 °C are applied. In this letter, we report on a perpendicularly magnetized MgO-based tunnel junction (p-MTJ) on a thin Co/Ni perpendicular synthetic antiferromagnetic layer with high annealing tolerance. Tunnel magneto resistance (TMR) loss after annealing occurs when the reference layer loses its perpendicular magnetic anisotropy due to reduction of the CoFeB/MgO interfacial anisotropy. A stable Co/Ni based p-MTJ stack with TMR values of 130% at resistance-area products of 9 Ω μm2 after 400 °C anneal is achieved via moment control of the Co/Ta/CoFeB reference layer. Thinning of the CoFeB polarizing layer down to 0.8 nm is the key enabler to achieve 400 °C compatibility with limited TMR loss. Thinning the Co below 0.6 nm leads to a loss of the antiferromagnetic interlayer exchange coupling strength through Ru. Insight into the thickness and moment engineering of the reference layer is displayed to obtain the best magnetic properties and high thermal stability for thin Co/Ni SAF-based STT-MRAM stacks.

  1. Access Denied

    ERIC Educational Resources Information Center

    Villano, Matt

    2008-01-01

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

  2. Open Access

    ERIC Educational Resources Information Center

    Suber, Peter

    2012-01-01

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

  3. Health Care: School-Based Health Centers Can Expand Access for Children. Report to the Chairman, Committee on Government Operations, House of Representatives.

    ERIC Educational Resources Information Center

    General Accounting Office, Washington, DC. Health, Education, and Human Services Div.

    This report reviews the role of school-based health centers (SBHCs) in expanding children's access to health care, and examines financial and other obstacles SBHCs must overcome. The report is based on a literature review; interviews with officials; and case studies conducted at eight SBHCs in California, New Mexico, and New York. The study found…

  4. Accessible Genetics Research Ethics Education (AGREE): A Web-Based Program for IRBs and Investigators

    SciTech Connect

    Sugarman, Jeremy; Lee, Linda

    2006-03-31

    The primary objective of this project was to design and evaluate a series of web-based educational modules on genetics research ethics for members of Institutional Review Boards and investigators to facilitate the development and oversight of important research that is sensitive to the relevant ethical, legal and social issues. After a needs assessment was completed in March of 2003, five online educational modules on the ethics of research in genetics were developed, tested, and made available through a host website for AGREE: http://agree.mc.duke.edu/index.html. The 5 modules are: (1) Ethics and Genetics Research in Populations; (2) Ethics in Behavioral Genetics Research; (3) Ethical Issues in Research on Gene-Environment Interactions; (4) Ethical Issues in Reproductive Genetics Research; and (5) Ethical Issues in Diagnostic and Therapeutic Research. The development process adopted a tested approach used at Duke University School of Medicine in providing education for researchers and IRB members, supplementing it with expert input and a rigorous evaluation. The host website also included a description of the AGREE; short bios on the AGREE Investigators and Expert Advisory Panel; streaming media of selected presentations from a conference, Working at the Frontiers of Law and Science: Applications of the Human Genome held October 2-3, 2003, at the University of North Carolina at Chapel Hill; and links to online resources in genomics, research ethics, ethics in genomics research, and related organizations. The web site was active beginning with the posting of the first module and was maintained throughout the project period. We have also secured agreement to keep the site active an additional year beyond the project period. AGREE met its primary objective of creating web-based educational modules related to the ethical issues in genetics research. The modules have been disseminated widely. While it is clearly easier to judge the quality of the educational experience

  5. CMOS Interface Circuits for Spin Tunneling Junction Based Magnetic Random Access Memories

    SciTech Connect

    Saripalli, Ganesh

    2002-01-01

    Magneto resistive memories (MRAM) are non-volatile memories which use magnetic instead of electrical structures to store data. These memories, apart from being non-volatile, offer a possibility to achieve densities better than DRAMs and speeds faster than SRAMs. MRAMs could potentially replace all computer memory RAM technologies in use today, leading to future applications like instan-on computers and longer battery life for pervasive devices. Such rapid development was made possible due to the recent discovery of large magnetoresistance in Spin tunneling junction devices. Spin tunneling junctions (STJ) are composite structures consisting of a thin insulating layer sandwiched between two magnetic layers. This thesis research is targeted towards these spin tunneling junction based Magnetic memories. In any memory, some kind of an interface circuit is needed to read the logic states. In this thesis, four such circuits are proposed and designed for Magnetic memories (MRAM). These circuits interface to the Spin tunneling junctions and act as sense amplifiers to read their magnetic states. The physical structure and functional characteristics of these circuits are discussed in this thesis. Mismatch effects on the circuits and proper design techniques are also presented. To demonstrate the functionality of these interface structures, test circuits were designed and fabricated in TSMC 0.35μ CMOS process. Also circuits to characterize the process mismatches were fabricated and tested. These results were then used in Matlab programs to aid in design process and to predict interface circuit's yields.

  6. Who Gets Prompt Access to Artemisinin-Based Combination Therapy? A Prospective Community-Based Study in Children from Rural Kilosa, Tanzania

    PubMed Central

    Simba, Daudi O.; Warsame, Marian; Kakoko, Deodatus; Mrango, Zakayo; Tomson, Goran; Premji, Zul; Petzold, Max

    2010-01-01

    Background Effective and timely case management remains one of the fundamental pillars for control of malaria. Tanzania introduced artemisinin-combination therapy [ACT] for uncomplicated malaria; however, the policy change is challenged by limited availability of ACTs due to high cost. This study aimed to determine factors influencing prompt access to ACTs among febrile children in rural Kilosa, Tanzania. Methods and Findings In a community-based study, 1,235 randomly selected children under five were followed up weekly for six months, in 2008. Using a structured questionnaire, children's caretakers were asked about the child's febrile history in the last seven days, and treatment actions including timing, medicines used and source of care. Caretakers' knowledge about malaria and socioeconomic and demographic data were also obtained. About half of followed-up children had at least one episode of fever. Less than half (44.8%) of febrile children were taken to government facilities. Almost one-third (37.6%; 95% CI 33.1–42.1) of febrile children had prompt access to ACT. Care-seeking from a government facility was the overriding factor, increasing the likelihood of prompt access to an ACT 18 times (OR 17.7; 95% CI 10.55–29.54; adjusted OR 16.9; 95% CI 10.06–28.28). Caretakers from the better-off household (3rd–5th quintiles) were more likely to seek care from government facilities (OR 3.66; 95% CI 2.56–5.24; adjusted OR 1.80; 95% CI 1.18–2.76). The majority of antimalarials accessed by the poor were ineffective [86.0%; 295/343], however, they paid more for them (median Tsh 500) compared to the better-offs (median Tsh 0). Conclusions Prompt access to ACT among febrile children was unacceptably low, due mainly to limited availability of subsidised ACT at the location where most caretakers sought care. There is urgent need to accelerate implementation of strategies that will ensure availability of ACT at an affordable price in remote rural areas, where the

  7. Economic approaches to improving access to evidence-based and recovery-oriented services for people with severe mental illness.

    PubMed

    Latimer, Eric A; Bond, Gary R; Drake, Robert E

    2011-09-01

    During the past 3 decades, research has identified several psychosocial evidence-based practices (EBPs) for people with severe mental illness (SMI). Starting from a different origin, the recovery movement has influenced perceptions of how EBPs and other services should be delivered, and also emphasized the value of peer supports. We now know much more than 30 years ago about the kinds of services that help people with SMI live satisfying lives in the community. Evidence-based and recovery-oriented services require additional resources but use them sparingly: they are highly individualized, often result in reductions in costs of other mental health services, such as hospitalizations, and favour reliance on and integration into community settings rather than mental health services. Nevertheless, access to such services remains very limited. During the same period, the place of medications in the services system has become a source of growing concern, and there are several reasons to believe that current spending on medications is excessive. Inadequate housing and community supports that increase lengths of stay unnecessarily and spending on ineffective, nonrecovery-oriented vocational services are only 2 additional forms of misallocation of resources. Devolving control over medication budgets to regional or local health authorities, introducing program budgeting and marginal analysis, and implementing individual budgets to give more control to service users (in addition to promoting shared decision making) merit further investigation as potential strategies to improve outcomes for people with SMI in Canada in the context of limited budgets.

  8. Hanford Borehole Geologic Information System (HBGIS) Updated User’s Guide for Web-based Data Access and Export

    SciTech Connect

    Mackley, Rob D.; Last, George V.; Allwardt, Craig H.

    2008-09-24

    The Hanford Borehole Geologic Information System (HBGIS) is a prototype web-based graphical user interface (GUI) for viewing and downloading borehole geologic data. The HBGIS is being developed as part of the Remediation Decision Support function of the Soil and Groundwater Remediation Project, managed by Fluor Hanford, Inc., Richland, Washington. Recent efforts have focused on improving the functionality of the HBGIS website in order to allow more efficient access and exportation of available data in HBGIS. Users will benefit from enhancements such as a dynamic browsing, user-driven forms, and multi-select options for selecting borehole geologic data for export. The need for translating borehole geologic data into electronic form within the HBGIS continues to increase, and efforts to populate the database continue at an increasing rate. These new web-based tools should help the end user quickly visualize what data are available in HBGIS, select from among these data, and download the borehole geologic data into a consistent and reproducible tabular form. This revised user’s guide supersedes the previous user’s guide (PNNL-15362) for viewing and downloading data from HBGIS. It contains an updated data dictionary for tables and fields containing borehole geologic data as well as instructions for viewing and downloading borehole geologic data.

  9. Atomic Layer Deposited Oxide-Based Nanocomposite Structures with Embedded CoPtx Nanocrystals for Resistive Random Access Memory Applications.

    PubMed

    Wang, Lai-Guo; Cao, Zheng-Yi; Qian, Xu; Zhu, Lin; Cui, Da-Peng; Li, Ai-Dong; Wu, Di

    2017-02-22

    Al2O3- or HfO2-based nanocomposite structures with embedded CoPtx nanocrystals (NCs) on TiN-coated Si substrates have been prepared by combination of thermal atomic layer deposition (ALD) and plasma-enhanced ALD for resistive random access memory (RRAM) applications. The impact of CoPtx NCs and their average size/density on the resistive switching properties has been explored. Compared to the control sample without CoPtx NCs, ALD-derived Pt/oxide/100 cycle-CoPtx NCs/TiN/SiO2/Si exhibits a typical bipolar, reliable, and reproducible resistive switching behavior, such as sharp distribution of RRAM parameters, smaller set/reset voltages, stable resistance ratio (≥10(2)) of OFF/ON states, better switching endurance up to 10(4) cycles, and longer data retention over 10(5) s. The possible resistive switching mechanism based on nanocomposite structures of oxide/CoPtx NCs has been proposed. The dominant conduction mechanisms in low- and high-resistance states of oxide-based device units with embedded CoPtx NCs are Ohmic behavior and space-charge-limited current, respectively. The insertion of CoPtx NCs can effectively improve the formation of conducting filaments due to the CoPtx NC-enhanced electric field intensity. Besides excellent resistive switching performances, the nanocomposite structures also simultaneously present ferromagnetic property. This work provides a flexible pathway by combining PEALD and TALD compatible with state-of-the-art Si-based technology for multifunctional electronic devices applications containing RRAM.

  10. Equal Access.

    ERIC Educational Resources Information Center

    De Patta, Joe

    2003-01-01

    Presents an interview with Stephen McCarthy, co-partner and president of Equal Access ADA Consulting Architects of San Diego, California, about designing schools to naturally integrate compliance with the Americans with Disabilities Act (ADA). (EV)

  11. CUAHSI-HIS: an Internet based system to facilitate public discovery, access, and exploration of different water science data sources

    NASA Astrophysics Data System (ADS)

    Arrigo, J. S.; Hooper, R. P.; Choi, Y.; Ames, D. P.; Kadlec, J.; Whiteaker, T.

    2011-12-01

    "Water is everywhere." This sentiment underscores the importance of instilling hydrologic and earth science literacy in educators, students, and the general public, but also presents challenges for water scientists and educators. Scientific data about water is collected and distributed by several different sources, from federal agencies to scientific investigators to citizen scientists. As competition for limited water resources increase, increasing access to and understanding of the wealth of information about the nation's and the world's water will be critical. The CUAHSI-HIS system is a web based system for sharing hydrologic data that can help address this need. HydroDesktop is a free, open source application for finding, getting, analyzing and using hydrologic data from the CUAHSI-HIS system. It works with HydroCatalog which indexes the data to find out what data exists and where it is, and then it retrieves the data from HydroServers where it is stored communicating using WaterOneFlow web services. Currently, there are over 65 services registered in HydroCatalog providing central discovery of water data from several federal and state agencies, university projects, and other sources. HydroDesktop provides a simplified GIS that allows users to incorporate spatial data, and simple analysis tools to facilitate graphing and visualization. HydroDesktop is designed to be useful for a number of different groups of users with a wide variety of needs and skill levels including university faculty, graduate and undergraduate students, K-12 students, engineering and scientific consultants, and others. This presentation will highlight some of the features of HydroDesktop and the CUAHSI-HIS system that make it particularly appropriate for use in educational and public outreach settings, and will present examples of educational use. The incorporation of "real data," localization to an area of interest, and problem-based learning are all recognized as effective strategies for

  12. Thin Co/Ni-based bottom pinned spin-transfer torque magnetic random access memory stacks with high annealing tolerance

    SciTech Connect

    Tomczak, Y.; Swerts, J.; Mertens, S.; Lin, T.; Couet, S.; Sankaran, K.; Pourtois, G.; Kim, W.; Souriau, L.; Van Elshocht, S.; Kar, G.; Furnemont, A.; Liu, E.

    2016-01-25

    Spin-transfer torque magnetic random access memory (STT-MRAM) is considered as a replacement for next generation embedded and stand-alone memory applications. One of the main challenges in the STT-MRAM stack development is the compatibility of the stack with CMOS process flows in which thermal budgets up to 400 °C are applied. In this letter, we report on a perpendicularly magnetized MgO-based tunnel junction (p-MTJ) on a thin Co/Ni perpendicular synthetic antiferromagnetic layer with high annealing tolerance. Tunnel magneto resistance (TMR) loss after annealing occurs when the reference layer loses its perpendicular magnetic anisotropy due to reduction of the CoFeB/MgO interfacial anisotropy. A stable Co/Ni based p-MTJ stack with TMR values of 130% at resistance-area products of 9 Ω μm{sup 2} after 400 °C anneal is achieved via moment control of the Co/Ta/CoFeB reference layer. Thinning of the CoFeB polarizing layer down to 0.8 nm is the key enabler to achieve 400 °C compatibility with limited TMR loss. Thinning the Co below 0.6 nm leads to a loss of the antiferromagnetic interlayer exchange coupling strength through Ru. Insight into the thickness and moment engineering of the reference layer is displayed to obtain the best magnetic properties and high thermal stability for thin Co/Ni SAF-based STT-MRAM stacks.

  13. An extended aqueous solvation model based on atom-weighted solvent accessible surface areas: SAWSA v2.0 model.

    PubMed

    Hou, Tingjun; Zhang, Wei; Huang, Qin; Xu, Xiaojie

    2005-02-01

    A new method is proposed for calculating aqueous solvation free energy based on atom-weighted solvent accessible surface areas. The method, SAWSA v2.0, gives the aqueous solvation free energy by summing the contributions of component atoms and a correction factor. We applied two different sets of atom typing rules and fitting processes for small organic molecules and proteins, respectively. For small organic molecules, the model classified the atoms in organic molecules into 65 basic types and additionally. For small organic molecules we proposed a correction factor of "hydrophobic carbon" to account for the aggregation of hydrocarbons and compounds with long hydrophobic aliphatic chains. The contributions for each atom type and correction factor were derived by multivariate regression analysis of 379 neutral molecules and 39 ions with known experimental aqueous solvation free energies. Based on the new atom typing rules, the correlation coefficient (r) for fitting the whole neutral organic molecules is 0.984, and the absolute mean error is 0.40 kcal mol(-1), which is much better than those of the model proposed by Wang et al. and the SAWSA model previously proposed by us. Furthermore, the SAWSA v2.0 model was compared with the simple atom-additive model based on the number of atom types (NA). The calculated results show that for small organic molecules, the predictions from the SAWSA v2.0 model are slightly better than those from the atom-additive model based on NA. However, for macromolecules such as proteins, due to the connection between their molecular conformation and their molecular surface area, the atom-additive model based on the number of atom types has little predictive power. In order to investigate the predictive power of our model, a systematic comparison was performed on seven solvation models including SAWSA v2.0, GB/SA_1, GB/SA_2, PB/SA_1, PB/SA_2, AM1/SM5.2R and SM5.0R. The results showed that for organic molecules the SAWSA v2.0 model is better

  14. KEGG orthology-based annotation of the predicted proteome of Acropora digitifera: ZoophyteBase - an open access and searchable database of a coral genome

    PubMed Central

    2013-01-01

    Background Contemporary coral reef research has firmly established that a genomic approach is urgently needed to better understand the effects of anthropogenic environmental stress and global climate change on coral holobiont interactions. Here we present KEGG orthology-based annotation of the complete genome sequence of the scleractinian coral Acropora digitifera and provide the first comprehensive view of the genome of a reef-building coral by applying advanced bioinformatics. Description Sequences from the KEGG database of protein function were used to construct hidden Markov models. These models were used to search the predicted proteome of A. digitifera to establish complete genomic annotation. The annotated dataset is published in ZoophyteBase, an open access format with different options for searching the data. A particularly useful feature is the ability to use a Google-like search engine that links query words to protein attributes. We present features of the annotation that underpin the molecular structure of key processes of coral physiology that include (1) regulatory proteins of symbiosis, (2) planula and early developmental proteins, (3) neural messengers, receptors and sensory proteins, (4) calcification and Ca2+-signalling proteins, (5) plant-derived proteins, (6) proteins of nitrogen metabolism, (7) DNA repair proteins, (8) stress response proteins, (9) antioxidant and redox-protective proteins, (10) proteins of cellular apoptosis, (11) microbial symbioses and pathogenicity proteins, (12) proteins of viral pathogenicity, (13) toxins and venom, (14) proteins of the chemical defensome and (15) coral epigenetics. Conclusions We advocate that providing annotation in an open-access searchable database available to the public domain will give an unprecedented foundation to interrogate the fundamental molecular structure and interactions of coral symbiosis and allow critical questions to be addressed at the genomic level based on combined aspects of

  15. Uncorrelated multiple conductive filament nucleation and rupture in ultra-thin high-κ dielectric based resistive random access memory

    NASA Astrophysics Data System (ADS)

    Wu, Xing; Li, Kun; Raghavan, Nagarajan; Bosman, Michel; Wang, Qing-Xiao; Cha, Dongkyu; Zhang, Xi-Xiang; Pey, Kin-Leong

    2011-08-01

    Resistive switching in transition metal oxides could form the basis for next-generation non-volatile memory (NVM). It has been reported that the current in the high-conductivity state of several technologically relevant oxide materials flows through localized filaments, but these filaments have been characterized only individually, limiting our understanding of the possibility of multiple conductive filaments nucleation and rupture and the correlation kinetics of their evolution. In this study, direct visualization of uncorrelated multiple conductive filaments in ultra-thin HfO2-based high-κ dielectric resistive random access memory (RRAM) device has been achieved by high-resolution transmission electron microscopy (HRTEM), along with electron energy loss spectroscopy (EELS), for nanoscale chemical analysis. The locations of these multiple filaments are found to be spatially uncorrelated. The evolution of these microstructural changes and chemical properties of these filaments will provide a fundamental understanding of the switching mechanism for RRAM in thin oxide films and pave way for the investigation into improving the stability and scalability of switching memory devices.

  16. Auxiliary graph based protection for survivable Fiber-Wireless (FiWi) access network considering different levels of failures

    NASA Astrophysics Data System (ADS)

    Liu, Yejun; Guo, Lei; Ma, Rui; Hou, Weigang

    2012-12-01

    Survivability is one of the key issues in Fiber-Wireless (FiWi) access network because network component failures may cause huge data loss, especially when the failures in optical back-end. According to the failure severity, we categorize the failures in optical back-end into two levels, that is, Optical-Network-Unit (ONU)-level failure and segment-level failure. In this paper, instead of the expensive fiber duplication approach traditionally, we propose a novel protection approach for FiWi against ONU-level failure by assigning each ONU several alternate ONUs in the same segment and against the segment-level failure by deploying backup fibers among different segments. On one hand, we optimize the assignment of alternate ONUs, aiming to maximize the amount of protected traffic and minimize the number of wireless hops. On the other hand, we optimize the deployment of backup fibers, aiming to maximize the amount of protected traffic and minimize the length of backup fibers. We mathematically formulate these two objectives as Maximum Protection and Minimum Hops Number (MPMHN) problem and the Maximum Protection and Minimum backup Fibers Length (MPMFL) problem, respectively. An efficient algorithm called Auxiliary Graph based Protection (AGP) is proposed to solve the MPMHN and MPMFL problems. In the simulation, we investigate the performance of AGP in various scenarios and demonstrate the cost-efficiency of the proposed protection approach.

  17. Feasibility of a neutron detector-dosemeter based on single-event upsets in dynamic random-access memories.

    PubMed

    Phillips, G W; August, R A; Campbell, A B; Nelson, M E; Price, J L; Guardala, N A; Moscovitch, M

    2002-01-01

    The feasibility was investigated of a solid-state neutron detector/dosemeter based on single-event upset (SEU) effects in dynamic random-access memories (DRAMs), commonly used in computer memories. Such a device, which uses a neutron converter material to produce a charged particle capable of causing an upset, would be light-weight, low-power, and could be read simply by polling the memory for bit flips. It would have significant advantages over standard solid-state neutron dosemeters which require off-line processing for track etching and analysis. Previous efforts at developing an SEU neutron detector/dosemeter have suffered from poor response, which can be greatly enhanced by selecting a modern high-density DRAM chip for SEU sensitivity and by using a thin 10B film as a converter. Past attempts to use 10B were not successful because the average alpha particle energy was insufficient to penetrate to the sensitive region of the memory. This can be overcome by removing the surface passivation layer before depositing the 10B film or by implanting 10B directly into the chip. Previous experimental data show a 10(3) increase in neutron sensitivity by chips containing borosilicate glass, which could be used in an SEU detector. The results are presented of simulations showing that the absolute efficiency of an SEU neutron dosemeter can be increased by at least a factor of 1000 over earlier designs.

  18. Effect of embedded metal nanocrystals on the resistive switching characteristics in NiN-based resistive random access memory cells

    SciTech Connect

    Yun, Min Ju; Kim, Hee-Dong; Man Hong, Seok; Hyun Park, Ju; Su Jeon, Dong; Geun Kim, Tae

    2014-03-07

    The metal nanocrystals (NCs) embedded-NiN-based resistive random access memory cells are demonstrated using several metal NCs (i.e., Pt, Ni, and Ti) with different physical parameters in order to investigate the metal NC's dependence on resistive switching (RS) characteristics. First, depending on the electronegativity of metal, the size of metal NCs is determined and this affects the operating current of memory cells. If metal NCs with high electronegativity are incorporated, the size of the NCs is reduced; hence, the operating current is reduced owing to the reduced density of the electric field around the metal NCs. Second, the potential wells are formed by the difference of work function between the metal NCs and active layer, and the barrier height of the potential wells affects the level of operating voltage as well as the conduction mechanism of metal NCs embedded memory cells. Therefore, by understanding these correlations between the active layer and embedded metal NCs, we can optimize the RS properties of metal NCs embedded memory cells as well as predict their conduction mechanisms.

  19. AccessAbility @ Cleveland Public Library.

    ERIC Educational Resources Information Center

    Mates, Barbara T.

    2003-01-01

    Describes several programs that were developed by staff at the Cleveland (Ohio) Public Library to be accessible to users with disabilities. Highlights include a Braille reading program; sensory garden; poetry club; book club based on talking books; wheelchair athletics; touching museum artifacts; and a mobile library for users who could not visit…

  20. Comparison of Trial Participants and Open Access Users of a Web-Based Physical Activity Intervention Regarding Adherence, Attrition, and Repeated Participation

    PubMed Central

    Martin-Diener, Eva; Bauer, Georg; Braun-Fahrländer, Charlotte; Martin, Brian W

    2010-01-01

    Background Web-based interventions are popular for promoting healthy lifestyles such as physical activity. However, little is known about user characteristics, adherence, attrition, and predictors of repeated participation on open access physical activity websites. Objective The focus of this study was Active-online, a Web-based individually tailored physical activity intervention. The aims were (1) to assess and compare user characteristics and adherence to the website (a) in the open access context over time from 2003 to 2009, and (b) between trial participants and open access users; and (2) to analyze attrition and predictors of repeated use among participants in a randomized controlled trial compared with registered open access users. Methods Data routinely recorded in the Active-online user database were used. Adherence was defined as: the number of pages viewed, the proportion of visits during which a tailored module was begun, the proportion of visits during which tailored feedback was received, and the time spent in the tailored modules. Adherence was analyzed according to six one-year periods (2003-2009) and according to the context (trial or open access) based on first visits and longest visits. Attrition and predictors of repeated participation were compared between trial participants and open access users. Results The number of recorded visits per year on Active-online decreased from 42,626 in 2003-2004 to 8343 in 2008-2009 (each of six one-year time periods ran from April 23 to April 22 of the following year). The mean age of users was between 38.4 and 43.1 years in all time periods and both contexts. The proportion of women increased from 49.5% in 2003-2004 to 61.3% in 2008-2009 (P< .001). There were differences but no consistent time trends in adherence to Active-online. The mean age of trial participants was 43.1 years, and 74.9% were women. Comparing contexts, adherence was highest for registered open access users. For open access users, adherence

  1. Overcoming inertia: increasing public health departments' access to evidence-based information and promoting usage to inform practice.

    PubMed

    LaPelle, Nancy R; Dahlen, Karen; Gabella, Barbara A; Juhl, Ashley L; Martin, Elaine

    2014-01-01

    In 2010, the New England Region-National Network of Libraries of Medicine at University of Massachusetts Medical School received funding to improve information access for public health departments in 6 New England states and Colorado. Public health departments were provided with desktop digital access to licensed e-resources available through special pricing. In January through mid-April 2012, we evaluated the effectiveness of providing access to and training for using e-resources to public health department staff to motivate usage in practice. We found that additional strategies are needed to accomplish this.

  2. NASA Access Mechanism (NAM)

    NASA Technical Reports Server (NTRS)

    Hunter, Judy

    1993-01-01

    A 1991 user survey indicated that NASA users want (1) access to diverse sources of information; (2) an intuitive approach to system use; (3) avoidance of system query languages; (4) access to peers and other informal sources of information; and (5) simplified and enhanced presentation of search results. Based on these requirements and the use of an intelligent gateway processor, the NASA Access Mechanism (NAM) is being developed to provide the users with the semblance of a one stop shopping environment for information management.

  3. Bryophytes for Beginners: The Usability of a Printed Dichotomous Key versus a Multi-Access Computer-Based Key for Bryophyte Identification

    ERIC Educational Resources Information Center

    Stagg, Bethan C.; Donkin, Maria E.; Smith, Alison M.

    2015-01-01

    Bryophytes are a rewarding study group in field biology and the UK bryophyte flora has international importance to biodiversity conservation. We designed an identification key to common woodland moss species and compared the usability of two formats, web-based multi-access and printed dichotomous key, with undergraduate students. The rate of…

  4. What Works Clearinghouse Quick Review: "Looking Beyond Enrollment: The Causal Effect of Need-Based Grants on College Access, Persistence, and Graduation"

    ERIC Educational Resources Information Center

    What Works Clearinghouse, 2013

    2013-01-01

    This study examined whether eligibility for the Florida Student Access Grant, a need-based grant for low-income students in Florida, affects college enrollment, credit accumulation, persistence over time in college, and, eventually, graduation. The sample for this study included seniors in Florida public high schools in 1999-2000 who submitted a…

  5. Effects of Selected Cultural, Financial, and School-Based Factors on Girl-Child's Educational Access and Socioeconomic Development in Sarkish Flower Farm, Nakuru County, Kenya

    ERIC Educational Resources Information Center

    Ronoh, T. K.; Sang, A. K.; Sisungo, Z. W.; Mumiukha, C. K.; Ayub, M. J.

    2015-01-01

    This paper sought to establish the effects of selected cultural, financial, and school-based factors on the girl-child's access to educational and socioeconomic development in Kenya. It is arguably observed that various local and international conventions, treaties, commissions, and state actors have strived to promote the development of…

  6. The Electronic Journal of Information Technology in Construction (ITcon): An Open Access Journal Using an Un-Paid, Volunteer-Based Organization

    ERIC Educational Resources Information Center

    Björk, Bo-Christer; Turk, Žiga

    2006-01-01

    Introduction: This case study is based on the experiences with the Electronic Journal of Information Technology in Construction (ITcon), founded in 1995. Development: This journal is an example of a particular category of open access journals, which use neither author charges nor subscriptions to finance their operations, but rely largely on…

  7. Quercetin, kaempferol, myricetin, and fatty acid content among several Hibiscus sabdariffa accession calyces based on maturity in a greenhouse

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Flavonols including quercetin, kaempferol, myricetin, and fatty acids in plants have many useful health attributes including antioxidants, cholesterol lowering, and cancer prevention. Six accessions of roselle, Hibiscus sabdariffa calyces were evaluated for quercetin, kaempferol, and myricetin conte...

  8. BPO crude oil analysis data base user`s guide: Methods, publications, computer access correlations, uses, availability

    SciTech Connect

    Sellers, C.; Fox, B.; Paulz, J.

    1996-03-01

    The Department of Energy (DOE) has one of the largest and most complete collections of information on crude oil composition that is available to the public. The computer program that manages this database of crude oil analyses has recently been rewritten to allow easier access to this information. This report describes how the new system can be accessed and how the information contained in the Crude Oil Analysis Data Bank can be obtained.

  9. ScienceCentral: open access full-text archive of scientific journals based on Journal Article Tag Suite regardless of their languages.

    PubMed

    Huh, Sun

    2013-01-01

    ScienceCentral, a free or open access, full-text archive of scientific journal literature at the Korean Federation of Science and Technology Societies, was under test in September 2013. Since it is a Journal Article Tag Suite-based full text database, extensible markup language files of all languages can be presented, according to Unicode Transformation Format 8-bit encoding. It is comparable to PubMed Central: however, there are two distinct differences. First, its scope comprises all science fields; second, it accepts all language journals. Launching ScienceCentral is the first step for free access or open access academic scientific journals of all languages to leap to the world, including scientific journals from Croatia.

  10. A Novel Application of Agent-based Modeling: Projecting Water Access and Availability Using a Coupled Hydrologic Agent-based Model in the Nzoia Basin, Kenya

    NASA Astrophysics Data System (ADS)

    Le, A.; Pricope, N. G.

    2015-12-01

    Projections indicate that increasing population density, food production, and urbanization in conjunction with changing climate conditions will place stress on water resource availability. As a result, a holistic understanding of current and future water resource distribution is necessary for creating strategies to identify the most sustainable means of accessing this resource. Currently, most water resource management strategies rely on the application of global climate predictions to physically based hydrologic models to understand potential changes in water availability. However, the need to focus on understanding community-level social behaviors that determine individual water usage is becoming increasingly evident, as predictions derived only from hydrologic models cannot accurately represent the coevolution of basin hydrology and human water and land usage. Models that are better equipped to represent the complexity and heterogeneity of human systems and satellite-derived products in place of or in conjunction with historic data significantly improve preexisting hydrologic model accuracy and application outcomes. We used a novel agent-based sociotechnical model that combines the Soil and Water Assessment Tool (SWAT) and Agent Analyst and applied it in the Nzoia Basin, an area in western Kenya that is becoming rapidly urbanized and industrialized. Informed by a combination of satellite-derived products and over 150 household surveys, the combined sociotechnical model provided unique insight into how populations self-organize and make decisions based on water availability. In addition, the model depicted how population organization and current management alter water availability currently and in the future.

  11. MO-E-18C-01: Open Access Web-Based Peer-To-Peer Training and Education in Radiotherapy

    SciTech Connect

    Pawlicki, T; Brown, D; Dunscombe, P; Mutic, S

    2014-06-15

    Purpose: Current training and education delivery models have limitations which result in gaps in clinical proficiency with equipment, procedures, and techniques. Educational and training opportunities offered by vendors and professional societies are by their nature not available at point of need or for the life of clinical systems. The objective of this work is to leverage modern communications technology to provide peer-to-peer training and education for radiotherapy professionals, in the clinic and on demand, as they undertake their clinical duties. Methods: We have developed a free of charge web site ( https://i.treatsafely.org ) using the Google App Engine and datastore (NDB, GQL), Python with AJAX-RPC, and Javascript. The site is a radiotherapy-specific hosting service to which user-created videos illustrating clinical or physics processes and other relevant educational material can be uploaded. Efficient navigation to the material of interest is provided through several RT specific search tools and videos can be scored by users, thus providing comprehensive peer review of the site content. The site also supports multilingual narration\\translation of videos, a quiz function for competence assessment and a library function allowing groups or institutions to define their standard operating procedures based on the video content. Results: The website went live in August 2013 and currently has over 680 registered users from 55 countries; 27.2% from the United States, 9.8% from India, 8.3% from the United Kingdom, 7.3% from Brazil, and 47.5% from other countries. The users include physicists (57.4%), Oncologists (12.5%), therapists (8.2%) and dosimetrists (4.8%). There are 75 videos to date including English, Portuguese, Mandarin, and Thai. Conclusion: Based on the initial acceptance of the site, we conclude that this open access web-based peer-to-peer tool is fulfilling an important need in radiotherapy training and education. Site functionality should expand in

  12. Web-Based Access to Positive Airway Pressure Usage with or without an Initial Financial Incentive Improves Treatment Use in Patients with Obstructive Sleep Apnea

    PubMed Central

    Kuna, Samuel T.; Shuttleworth, David; Chi, Luqi; Schutte-Rodin, Sharon; Friedman, Eliot; Guo, Hengyi; Dhand, Sandeep; Yang, Lin; Zhu, Jingsan; Bellamy, Scarlett L.; Volpp, Kevin G.; Asch, David A.

    2015-01-01

    Study Objectives: We tested whether providing adults with obstructive sleep apnea (OSA) with daily Web-based access to their positive airway pressure (PAP) usage over 3 mo with or without a financial incentive in the first week improves adherence and functional outcomes. Setting: Academic- and community-based sleep centers. Participants: One hundred thirty-eight adults with newly diagnosed OSA starting PAP treatment. Interventions: Participants were randomized to: usual care, usual care with access to PAP usage, or usual care with access to PAP usage and a financial incentive. PAP data were transmitted daily by wireless modem from the participants' PAP unit to a website where hours of usage were displayed. Participants in the financial incentive group could earn up to $30/day in the first week for objective PAP use ≥ 4 h/day. Measurements and Results: Mean hours of daily PAP use in the two groups with access to PAP usage data did not differ from each other but was significantly greater than that in the usual care group in the first week and over 3 mo (P < 0.0001). Average daily use (mean ± standard deviation) during the first week of PAP intervention was 4.7 ± 3.3 h in the usual care group, and 5.9 ± 2.5 h and 6.3 ± 2.5 h in the Web access groups with and without financial incentive respectively. Adherence over the 3-mo intervention decreased at a relatively constant rate in all three groups. Functional Outcomes of Sleep Questionnaire change scores at 3 mo improved within each group (P < 0.0001) but change scores of the two groups with Web access to PAP data were not different than those in the control group (P > 0.124). Conclusions: Positive airway pressure adherence is significantly improved by giving patients Web access to information about their use of the treatment. Inclusion of a financial incentive in the first week had no additive effect in improving adherence. Citation: Kuna ST, Shuttleworth D, Chi L, Schutte-Rodin S, Friedman E, Guo H, Dhand S, Yang

  13. Community-based interventions for enhancing access to or consumption of fruit and vegetables among five to 18-year olds: a scoping review

    PubMed Central

    2012-01-01

    Background Low fruit and vegetable ( FV) consumption is a key risk factor for morbidity and mortality. Consumption of FV is limited by a lack of access to FV. Enhanced understanding of interventions and their impact on both access to and consumption of FV can provide guidance to public health decision-makers. The purpose of this scoping review is to identify and map literature that has evaluated effects of community-based interventions designed to increase FV access or consumption among five to 18-year olds. Methods The search included 21 electronic bibliographic databases, grey literature, targeted organization websites, and 15 key journals for relevant studies published up to May 2011. Retrieved citations were screened in duplicate for relevance. Data extracted from included studies covered: year, country, study design, target audience, intervention setting, intervention strategies, interventionists, and reported outcomes. Results The search located 19,607 unique citations. Full text relevance screening was conducted on 1,908 studies. The final 289 unique studies included 30 knowledge syntheses, 27 randomized controlled trials, 55 quasi-experimental studies, 113 cluster controlled studies, 60 before-after studies, one mixed method study, and three controlled time series studies. Of these studies, 46 included access outcomes and 278 included consumption outcomes. In terms of target population, 110 studies focused on five to seven year olds, 175 targeted eight to 10 year olds, 192 targeted 11 to 14 year olds, 73 targeted 15 to 18 year olds, 55 targeted parents, and 30 targeted teachers, other service providers, or the general public. The most common intervention locations included schools, communities or community centres, and homes. Most studies implemented multi-faceted intervention strategies to increase FV access or consumption. Conclusions While consumption measures were commonly reported, this review identified a small yet important subset of literature

  14. Use of Drop-In Clinic Versus Appointment-Based Care for LGBT Youth: Influences on the Likelihood to Access Different Health-Care Structures.

    PubMed

    Newman, Bernie S; Passidomo, Kim; Gormley, Kate; Manley, Alecia

    2014-06-01

    The structure of health-care service delivery can address barriers that make it difficult for lesbian, gay, bisexual, and transgender (LGBT) adolescents to use health services. This study explores the differences among youth who access care in one of two service delivery structures in an LGBT health-care center: the drop-in clinic or the traditional appointment-based model. Analysis of 578 records of LGBT and straight youth (aged 14-24) who accessed health care either through a drop-in clinic or appointment-based care within the first year of offering the drop-in clinic reveals patterns of use when both models are available. We studied demographic variables previously shown to be associated with general health-care access to determine how each correlated with a tendency to use the drop-in structure versus routine appointments. Once the covariates were identified, we conducted a logistic regression analysis to identify its association with likelihood of using the drop-in clinic. Insurance status, housing stability, education, race, and gender identity were most strongly associated with the type of clinic used. Youth who relied on Medicaid, those in unstable housing, and African Americans were most likely to use the drop-in clinic. Transgender youth and those with higher education were more likely to use the appointment-based clinic. Although sexual orientation and HIV status were not related to type of clinic used, youth who were HIV positive used the appointment-based clinic more frequently. Both routes to health care served distinct populations who often experience barriers to accessible, affordable, and knowledgeable care. Further study of the factors related to accessing health care may clarify the extent to which drop-in hours in a youth-friendly context may increase the use of health care by the most socially marginalized youth.

  15. Expanding Access

    ERIC Educational Resources Information Center

    Roach, Ronald

    2007-01-01

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

  16. Easy Access

    ERIC Educational Resources Information Center

    Gettelman, Alan

    2009-01-01

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

  17. Access Denied

    ERIC Educational Resources Information Center

    Raths, David

    2012-01-01

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

  18. The experiences of working carers of older people regarding access to a web-based family care support network offered by a municipality.

    PubMed

    Andersson, Stefan; Erlingsson, Christen; Magnusson, Lennart; Hanson, Elizabeth

    2016-08-01

    Policy makers in Sweden and other European Member States pay increasing attention as to how best support working carers; carers juggling providing unpaid family care for older family members while performing paid work. Exploring perceived benefits and challenges with web-based information and communication technologies as a means of supporting working carers' in their caregiving role, this paper draws on findings from a qualitative study. The study aimed to describe working carers' experiences of having access to the web-based family care support network 'A good place' (AGP) provided by the municipality to support those caring for an older family member. Content analysis of interviews with nine working carers revealed three themes: A support hub, connections to peers, personnel and knowledge; Experiencing ICT support as relevant in changing life circumstances; and Upholding one's personal firewall. Findings indicate that the web-based family care support network AGP is an accessible, complementary means of support. Utilising support while balancing caregiving, work obligations and responsibilities was made easier with access to AGP; enabling working carers to access information, psychosocial support and learning opportunities. In particular, it provided channels for carers to share experiences with others, to be informed, and to gain insights into medical and care issues. This reinforced working carers' sense of competence, helping them meet caregiving demands and see positive aspects in their situation. Carers' low levels of digital skills and anxieties about using computer-based support were barriers to utilising web-based support and could lead to deprioritising of this support. However, to help carers overcome these barriers and to better match web-based support to working carers' preferences and situations, web-based support must be introduced in a timely manner and must more accurately meet each working carer's unique caregiving needs.

  19. Genetic Diversity of Cowpea (Vigna unguiculata (L.) Walp.) Accession in Kenya Gene Bank Based on Simple Sequence Repeat Markers

    PubMed Central

    Muoma, John

    2016-01-01

    Increased agricultural production is an urgent issue. Projected global population is 9 million people by mid of this century. Estimation projects death of 1 million people for lack of food quality (micronutrient deficit) and quantity (protein deficit). Majority of these people will be living in developing countries. Other global challenges include shrinking cultivable lands, salinity, and flooding due to climate changes, new emerging pathogens, and pests. These affect crop production. Furthermore, they are major threats to crop genetic resources and food security. Genetic diversity in cultivated crops indicates gene pool richness. It is the greatest resource for plant breeders to select lines that enhance food security. This study was conducted by Masinde Muliro University to evaluate genetic diversity in 19 cowpea accessions from Kenya national gene bank. Accessions clustered into two major groups. High divergence was observed between accessions from Ethiopia and Australia and those from Western Kenya. Upper Volta accessions were closely related to those from Western Kenya. Low variation was observed between accessions from Eastern and Rift Valley than those from Western and Coastal regions of Kenya. Diversity obtained in this study can further be exploited for the improvement of cowpea in Kenya as a measure of food security. PMID:28003997

  20. Genetic Diversity of Cowpea (Vigna unguiculata (L.) Walp.) Accession in Kenya Gene Bank Based on Simple Sequence Repeat Markers.

    PubMed

    Wamalwa, Emily N; Muoma, John; Wekesa, Clabe

    2016-01-01

    Increased agricultural production is an urgent issue. Projected global population is 9 million people by mid of this century. Estimation projects death of 1 million people for lack of food quality (micronutrient deficit) and quantity (protein deficit). Majority of these people will be living in developing countries. Other global challenges include shrinking cultivable lands, salinity, and flooding due to climate changes, new emerging pathogens, and pests. These affect crop production. Furthermore, they are major threats to crop genetic resources and food security. Genetic diversity in cultivated crops indicates gene pool richness. It is the greatest resource for plant breeders to select lines that enhance food security. This study was conducted by Masinde Muliro University to evaluate genetic diversity in 19 cowpea accessions from Kenya national gene bank. Accessions clustered into two major groups. High divergence was observed between accessions from Ethiopia and Australia and those from Western Kenya. Upper Volta accessions were closely related to those from Western Kenya. Low variation was observed between accessions from Eastern and Rift Valley than those from Western and Coastal regions of Kenya. Diversity obtained in this study can further be exploited for the improvement of cowpea in Kenya as a measure of food security.

  1. Influence of Internet Accessibility and Demographic factors on utilization of Web-based Health Information Resources by Resident Doctors in Nigeria

    PubMed Central

    Ajuwon, GA; Popoola, SO

    2015-01-01

    Background The internet is a huge library with avalanche of information resources including healthcare information. There are numerous studies on use of electronic resources by healthcare providers including medical practitioners however, there is a dearth of information on the patterns of use of web-based health information resource by resident doctors in Nigeria. This study therefore investigates the influence of internet accessibility and demographic factors on utilization of web-based health information resources by resident doctors in tertiary healthcare institutions in Nigeria. Methods Descriptive survey design was adopted for this study. The population of study consisted of medical doctors undergoing residency training in 13 tertiary healthcare institutions in South-West Nigeria. The tertiary healthcare institutions were Federal Medical Centres, University Teaching Hospitals and Specialist Hospitals (Neuropsychiatric and Orthopaedic). A pre-tested, self-administered questionnaire was used for data collection. The Statistical Package for the Social Sciences (SPSS) was used for data analysis. Data were analyzed using descriptive statistics, Pearson Product Moment correlation and multiple regression analysis. Results The mean age of the respondents was 34 years and males were in the majority (69.0%). A total of 96.1% respondents had access to the Internet. E-mail (X̄=5.40, SD=0.91), Google (X̄=5.26, SD=1.38), Yahoo (X̄=5.15, SD=4.44) were used weekly by the respondents. Preparation for Seminar/Grand Round presentation (X̄=8.4, SD=1.92), research (X̄=7.8, SD=2.70) and communication (X̄=7.6, SD=2.60) were ranked high as purposes for use of web-based information resources. There is a strong, positive and significant relationship between internet accessibility and utilization of web-based health information resources (r=0.628, p<0.05). Internet accessibility (B=0.911) and demographic factors: gender (B=−2.027), designation (B=−0.343) educational

  2. Exposing USGS sample collections for broader discovery and access: collaboration between ScienceBase, IEDA:SESAR, and Paleobiology Database

    NASA Astrophysics Data System (ADS)

    Hsu, L.; Bristol, S.; Lehnert, K. A.; Arko, R. A.; Peters, S. E.; Uhen, M. D.; Song, L.

    2014-12-01

    The U.S. Geological Survey (USGS) is an exemplar of the need for improved cyberinfrastructure for its vast holdings of invaluable physical geoscience data. Millions of discrete paleobiological and geological specimens lie in USGS warehouses and at the Smithsonian Institution. These specimens serve as the basis for many geologic maps and geochemical databases, and are a potential treasure trove of new scientific knowledge. The extent of this treasure is virtually unknown and inaccessible outside a small group of paleogeoscientists and geochemists. A team from the USGS, the Integrated Earth Data Applications (IEDA) facility, and the Paleobiology Database (PBDB) are working to expose information on paleontological and geochemical specimens for discovery by scientists and citizens. This project uses existing infrastructure of the System for Earth Sample Registration (SESAR) and PBDB, which already contains much of the fundamental data schemas that are necessary to accommodate USGS records. The project is also developing a new Linked Data interface for the USGS National Geochemical Database (NGDB). The International Geo Sample Number (IGSN) is the identifier that links samples between all systems. For paleontological specimens, SESAR and PBDB will be the primary repositories for USGS records, with a data syncing process to archive records within the USGS ScienceBase system. The process began with mapping the metadata fields necessary for USGS collections to the existing SESAR and PBDB data structures, while aligning them with the Observations & Measurements and Darwin Core standards. New functionality needed in SESAR included links to a USGS locality registry, fossil classifications, a spatial qualifier attribution for samples with sensitive locations, and acknowledgement of data and metadata licensing. The team is developing a harvesting mechanism to periodically transfer USGS records from within PBDB and SESAR to ScienceBase. For the NGDB, the samples are being

  3. Full duplex fiber link for alternative wired and wireless access based on SSB optical millimeter-wave with 4-PAM signal

    NASA Astrophysics Data System (ADS)

    Ma, Jianxin; Zhang, Junjie

    2015-03-01

    A novel full-duplex fiber-wireless link based on single sideband (SSB) optical millimeter (mm)-wave with 10 Gbit/s 4-pulse amplitude modulation (PAM) signal is proposed to provide alternative wired and 40 GHz wireless accesses for the user terminals. The SSB optical mm-wave with 4-PAM signal consists of two tones: one bears the 4-PAM signal and the other is unmodulated with high power. After transmission over the fiber to the hybrid optical network unit (HONU), the SSB optical mm-wave signal can be decomposed by fiber Bragg gratings (FBGs) as the SSB optical mm-wave signal with reduced carrier-to-sideband ratio (the baseband 4-PAM optical signal) and the uplink optical carrier for the wireless (wired) access. This makes the HONU free from the laser source. For the uplink, since the wireless access signal is converted to the baseband by power detection, both the transmitter in the HONU and the receiver in optical line terminal (OLT) are co-shared for both wireless and wired accesses, which makes the full duplex link much simpler. In our scheme, the optical electrical field of the square-root increment level 4-PAM signal assures an equal level spacing receiving for both the downlink wired and wireless accesses. Since the downlink wireless signal is down-converted to the baseband by power detection, RF local oscillator is unnecessary. To confirm the feasibility of our proposed scheme, a simulation full duplex link with 40 GHz SSB optical mm-wave with 10 Gbit/s 4-PAM signal is built. The simulation results show that both down- and up-links for either wired or wireless access can keep good performance even if the link length of the SSMF is extended to 40 km.

  4. Access to Healthcare in Urban Family Physician Reform from Physicians and Patients’ Perspective: a survey-based project in two pilot provinces in Iran

    PubMed Central

    Jahromi, Vahid Kohpeima; Dehnavieh, Reza; Mehrolhassani, Mohammad Hossein; Anari, Hosain Saberi

    2017-01-01

    Introduction Iran introduced the urban family physician reform, based on the primary healthcare (PHC) approach, in 2012. The reform is restricted to two pilot provinces, which are Fars and Mazandaran and its policymakers request evidence of the reform progress. The study aimed to determine the accessibility of health care in the two pilot sites. Methods A cross-sectional study using Primary Care Evaluation Tool (PCET) questionnaires was performed with a multistage stratified cluster sample of the family physicians (n=141) and patients (n=710) in the two provinces between September 2015 and March 2016. The questionnaires contained essential dimensions of health accessibility: organizational, financial, geographical, and cultural access. The data were analyzed by IBM-SPSS software and the descriptive statistics. Results With an average population of 2,332, the main daily task for family physicians was patient visits (n=39). Most patients were satisfied with the current hours (80%) but visiting a family physician on holidays or after working hours were only rarely possible. The co-payment was an inconvenience to access health services in getting medicines, getting paraclinic exams and a visiting specialist. At least 70% of patients could receive their preferred healthcare facilities within 40 minutes. The majority of FPs (64%) believed there were some cultural characteristics in the population that made a limited role for providing better health services. Conclusion In the reform the providers were geographically well distributed and some features of the organizational access were relatively high. However there were some difficulties in the financial, cultural, and other features of organizational access. PMID:28243420

  5. Anatomical features of skull base and oral cavity: a pilot study to determine the accessibility of the sella by transoral robotic-assisted surgery.

    PubMed

    Amelot, Aymeric; Trunet, Stephanie; Degos, Vincent; André, Olivier; Dionnet, Aurore; Cornu, Philippe; Hans, Stéphane; Chauvet, Dorian

    2015-10-01

    The role of transoral robotic surgery (TORS) in the skull base emerges and represents the natural progression toward miniinvasive resections in confined spaces. The accessibility of the sella via TORS has been recently described on fresh human cadavers. An anatomic study is mandatory to know if this approach would be feasible in the majority of patients regardless of their oral morphological features. From 30 skull base CT scans from patients who were asked to open their mouth as wide as they can, we measured specific dimensions of the oral cavity and the skull base, such as length of the palate, mouth opening and distance from the sella to the palate. All data were acquired on a sagittal midline plane and on a 25° rotation plane, which simulated the axis of the robotic instruments. Looking at the projection of the dental palatine line on the sella, we studied possible predictive factors of sellar accessibility and tried to bring objective data for surgical feasibility. We also proposed an angle α to study the working angle at the skull base. We observed that the maximal mouth opening was a good predictive factor of sellar accessibility by TORS (p < 0.05). The mouth aperture threshold value for a good sensitivity, over 80 %, was comparable to the mean value of mouth opening in our series, 38.9 and 39.4 mm respectively. Moreover, we showed a statistically significant increase of the working angle α at the skull base comparing the lateral access to the midline one (p < 0.05). This seemed to quantitatively demonstrate that the robotic arms placed at the labial commissure of the mouth can reach the sella. From these anatomical features and previous cadaveric dissections, we assume that TORS may be feasible on a majority of patients to remove pituitary adenomas.

  6. Effects of Systematically Depriving Access to Computer-Based Stimuli on Choice Responding with Individuals with Intellectual Disabilities

    ERIC Educational Resources Information Center

    Reyer, Howard S.; Sturmey, Peter

    2009-01-01

    Three adults with intellectual disabilities participated to investigate the effects of reinforcer deprivation on choice responding. The experimenter identified the most preferred audio-visual (A-V) stimulus and the least preferred visual-only stimulus for each participant. Participants did not have access to the A-V stimulus for 5 min, 5 and 24 h.…

  7. Analysis and Simulation of Traffic Control for Resource Management in DVB-Based Broadband Satellite Access Networks

    NASA Astrophysics Data System (ADS)

    Impemba, Ernesto; Inzerilli, Tiziano

    2003-07-01

    Integration of satellite access networks with the Internet is seen as a strategic goal to achieve in order to provide ubiquitous broadband access to Internet services in Next Generation Networks (NGNs). One of the main interworking aspects which has been most studied is an efficient management of satellite resources, i.e. bandwidth and buffer space, in order to satisfy most demanding application requirements as to delay control and bandwidth assurance. In this context, resource management in DVB-S/DVB-RCS satellite technologies, emerging technologies for broadband satellite access and transport of IP applications, is a research issue largely investigated as a means to provide efficient bi-directional communications across satellites. This is in particular one of the principal goals of the SATIP6 project, sponsored within the 5th EU Research Programme Framework, i.e. IST. In this paper we present a possible approach to efficiently exploit bandwidth, the most critical resource in a broadband satellite access network, while pursuing satisfaction of delay and bandwidth requirements for applications with guaranteed QoS through a traffic control architecture to be implemented in ground terminals. Performance of this approach is assessed in terms of efficient exploitation of the uplink bandwidth and differentiation and minimization of queuing delays for most demanding applications over a time-varying capacity. Opnet simulations is used as analysis tool.

  8. Access Matters: Meeting the Nation's College Completion Goals Requires Large Increases in Need-Based Grant Aid

    ERIC Educational Resources Information Center

    Advisory Committee on Student Financial Assistance, 2013

    2013-01-01

    This document addresses the status of equality in access to higher education. Some of the motivating factors behind this presentation include: (1) College completion rates including rates of bachelor's degree completion are falling today, particularly among young Americans; (2) Reversing the current trend and increasing college completion has…

  9. Body Functions and Structures Pertinent to Infrared Thermography-Based Access for Clients with Severe Motor Disabilities

    ERIC Educational Resources Information Center

    Memarian, Negar; Venetsanopoulos, Anastasios N.; Chau, Tom

    2011-01-01

    Infrared thermography has been recently proposed as an access technology for individuals with disabilities, but body functions and structures pertinent to its use have not been documented. Seven clients (2 adults, 5 youth) with severe disabilities and their primary caregivers participated in this study. All clients had a Gross Motor Functional…

  10. An Intelligent Information Access System Assisting a Case Based Learning Methodology Evaluated in Higher Education with Medical Students

    ERIC Educational Resources Information Center

    Aparicio, Fernando; De Buenaga, Manuel; Rubio, Margarita; Hernando, Asuncion

    2012-01-01

    In recent years there has been a shift in educational methodologies toward a student-centered approach, one which increasingly emphasizes the integration of computer tools and intelligent systems adopting different roles. In this paper we describe in detail the development of an Intelligent Information Access system used as the basis for producing…

  11. Gaining Access to Late French-Immersion Programs: Class-Based Perspectives of Canadian Students in an Ottawa High School

    ERIC Educational Resources Information Center

    Makropoulos, Josee

    2009-01-01

    The question of access to French-immersion programs has become a timely subject in Canada as a result of shifting political priorities, cutbacks, and growing concern around finding the most efficient way to teach French as a second language (FSL). While drawing on social selection and identity perspectives on school choice, this article presents…

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

    NASA Astrophysics Data System (ADS)

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

    2011-06-01

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

  13. Rainwater Harvesting-based Safe Water Access in Diarrhea-endemic Coastal Communities of Bangladesh under Threats of Climate Change

    NASA Astrophysics Data System (ADS)

    Akanda, A. S.; Redwan, A. M.; Ali, M. A.; Alam, M.; Jutla, A.; Colwell, R. R.

    2014-12-01

    The highly populated coastal floodplains of the Bengal Delta have a long history of water-related natural calamities such as droughts, floods, and cyclones. Population centers along the floodplain corridors of the GBM (Ganges-Brahmaputra-Meghna) river system remain vulnerable to such natural hazards and waterborne epidemic outbreaks due to increasing intensity and changing frequency of extreme events over many areas in the delta region. Such changes in hydrologic extremes and resulting environmental conditions would likely lengthen the transmission seasons of prevalent waterborne diseases and alter their geographic range as well as seasonality. In addition, the combination of changing upstream precipitation and temperature, and coastal sea-level rise are exposing a vast area in Southwestern Bangladesh to increased diarrheal disease outbreaks due to higher salinity and water scarcity in the dry season as well as coastal flooding and water resources contamination in the wet season. It is thus essential to establish sustainable safe water access practices in these regions for the rural communities of low-income people. The impact of climate change in the recent past on the people of coastal rural areas of Bangladesh has been severe, and the water sector is one of its biggest victims. Previously, pond and groundwater sources were considered dependable, but salinity intrusion in both water resources have left the vulnerable people with only a few scarce ponds and forced them to depend more on rainwater than before. The poorest group is suffering the most for this crisis even though paying more of the percentage of their income especially in the dry season (December-March). As rainwater is their most preferred and dependable option during this part of the year, outbreaks of waterborne diseases can be minimized by installing rainwater harvesting systems with effective disinfection system at both household and community levels. In this study, we explore the technical

  14. Extrapolating Ground-Based Aircraft Engine Exhaust Emissions to Cruise Conditions: Lessons From the 2013 ACCESS Chase Plane Experiment

    NASA Astrophysics Data System (ADS)

    Moore, R.; Shook, M.; Thornhill, K. L.; Winstead, E.; Anderson, B. E.

    2011-12-01

    Aircraft engine emissions constitute a tiny fraction of the global black carbon mass, but can have a disproportionate climatic impact because they are emitted high in the troposphere and in remote regions with otherwise low aerosol concentrations. Consequently, these particles are likely to strongly influence cirrus and contrail formation by acting as ice nuclei (IN). However, the ice nucleating properties of aircraft exhaust at relevant atmospheric conditions are not well known, and thus, the overall impact of aviation on cloud formation remains very uncertain. While a number of aircraft engine emissions studies have previously been conducted at sea level temperature and pressure (e.g., APEX, AAFEX-1 and 2), it unclear the extent to which exhaust emissions on the ground translate to emissions at cruise conditions with much lower inlet gas temperatures and pressures. To address this need, the NASA Alternative Fuel Effects on Contrails and Cruise Emissions (ACCESS) was conducted in February-April, 2013 to examine the aerosol and gas emissions from the NASA DC-8 under a variety of different fuel types, engine power, and altitude/meteorological conditions. Two different fuel types were studied: a traditional JP-8 fuel and a 50:50 blend of JP-8 and a camelina-based hydro-treated renewable jet (HRJ) fuel. Emissions were sampled using a comprehensive suite of gas- and aerosol-phase instrumentation integrated on an HU-25 Falcon jet that was positioned in the DC-8 exhaust plume at approximately 100-500m distance behind the engines. In addition, a four-hour ground test was carried out with sample probes positioned at 30 m behind each of the inboard engines. Measurements of aerosol concentration, size distribution, soot mass, and hygroscopicity were carried out along with trace gas measurements of CO2, NO, NO2, O3, and water vapor. NOx emissions were reconciled by employing the well-established Boeing method for normalizing engine fuel flow rates to STP; however, comparison

  15. Extrapolating Ground-Based Aircraft Engine Exhaust Emissions to Cruise Conditions: Lessons From the 2013 ACCESS Chase Plane Experiment

    NASA Astrophysics Data System (ADS)

    Moore, R.; Shook, M.; Thornhill, K. L.; Winstead, E.; Anderson, B. E.

    2013-12-01

    Aircraft engine emissions constitute a tiny fraction of the global black carbon mass, but can have a disproportionate climatic impact because they are emitted high in the troposphere and in remote regions with otherwise low aerosol concentrations. Consequently, these particles are likely to strongly influence cirrus and contrail formation by acting as ice nuclei (IN). However, the ice nucleating properties of aircraft exhaust at relevant atmospheric conditions are not well known, and thus, the overall impact of aviation on cloud formation remains very uncertain. While a number of aircraft engine emissions studies have previously been conducted at sea level temperature and pressure (e.g., APEX, AAFEX-1 and 2), it unclear the extent to which exhaust emissions on the ground translate to emissions at cruise conditions with much lower inlet gas temperatures and pressures. To address this need, the NASA Alternative Fuel Effects on Contrails and Cruise Emissions (ACCESS) was conducted in February-April, 2013 to examine the aerosol and gas emissions from the NASA DC-8 under a variety of different fuel types, engine power, and altitude/meteorological conditions. Two different fuel types were studied: a traditional JP-8 fuel and a 50:50 blend of JP-8 and a camelina-based hydro-treated renewable jet (HRJ) fuel. Emissions were sampled using a comprehensive suite of gas- and aerosol-phase instrumentation integrated on an HU-25 Falcon jet that was positioned in the DC-8 exhaust plume at approximately 100-500m distance behind the engines. In addition, a four-hour ground test was carried out with sample probes positioned at 30 m behind each of the inboard engines. Measurements of aerosol concentration, size distribution, soot mass, and hygroscopicity were carried out along with trace gas measurements of CO2, NO, NO2, O3, and water vapor. NOx emissions were reconciled by employing the well-established Boeing method for normalizing engine fuel flow rates to STP; however, comparison

  16. 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 ...

  17. Accessible Multimedia for the Web.

    ERIC Educational Resources Information Center

    Zaparyniuk, Nicholas; Code, Jillianne

    With the Internet taking a dominant role in corporate training, education, retail, and customer based product exploration, authors of Web-based information need to ensure that the media they deliver is accessible to the widest possible audience. Whether users have a visual, auditory, physical, or developmental disability, accessible multimedia can…

  18. Quantitative determination of cellulose accessibility to cellulase based on adsorption of a nonhydrolytic fusion protein containing CBM and GFP with its applications.

    PubMed

    Hong, Jiong; Ye, Xinhao; Zhang, Y-H Percival

    2007-12-04

    Heterogeneous cellulose accessibility is an important substrate characteristic, but all methods for determining cellulose accessibility to the large-size cellulase molecule have some limitations. Characterization of cellulose accessibility to cellulase (CAC) is vital for better understanding of the enzymatic cellulose hydrolysis mechanism (Zhang and Lynd, Biotechnol. Bioeng. 2004, 88, 797-824; 2006, 94, 888-898). Quantitative determination of cellulose accessibility to cellulase (m2/g of cellulose) was established based on the Langmuir adsorption of the fusion protein containing a cellulose-binding module (CBM) and a green fluorescent protein (GFP). One molecule of the recombinant fusion protein occupied 21.2 cellobiose lattices on the 110 face of bacterial cellulose nanofibers. The CAC values of several cellulosic materials -- regenerated amorphous cellulose (RAC), bacterial microcrystalline cellulose (BMCC), Whatman No. 1 filter paper, fibrous cellulose powder (CF1), and microcrystalline cellulose (Avicel) -- were 41.9, 33.5, 9.76, 4.53, and 2.38 m2/g, respectively. The CAC value of amorphous cellulose made from Avicel was 17.6-fold larger than that of crystalline cellulose - Avicel. Avicel enzymatic hydrolysis proceeded with a transition from substrate excess to substrate limited. The declining hydrolysis rates over conversion are mainly attributed to a combination of substrate consumption and a decrease in substrate reactivity. Declining heterogeneous cellulose reactivity is significantly attributed to a loss of CAC where the easily hydrolyzed cellulose fraction is digested first.

  19. Educational Access in Ghana. Country Policy Brief

    ERIC Educational Resources Information Center

    Akyeampong, K.; Djangmah, J.; Oduro, A.; Seidu, A.; Hunt, F.

    2008-01-01

    This Policy Brief describes and explains patterns of access to schools in Ghana. It outlines policy and legislation on access to education and provides an analysis of access, vulnerability and exclusion. It is based on findings from the Country Analytic Report on Access to Basic Education in Ghana (Akyeampong et al, 2007) [ED508809] which can be…

  20. Educational Access in India. Country Policy Brief

    ERIC Educational Resources Information Center

    Online Submission, 2009

    2009-01-01

    This Policy Brief describes and explains patterns of access to schools in India. It outlines policy and legislation on access to education and provides an analysis of access, vulnerability and exclusion. The quantitative data is supported by a review of research which explains the patterns of access and exclusion. It is based on findings from the…