Science.gov

Sample records for multiple access schemes

  1. 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.

  2. 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.

  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. Quantum Optimal Multiple Assignment Scheme for Realizing General Access Structure of Secret Sharing

    NASA Astrophysics Data System (ADS)

    Matsumoto, Ryutaroh

    The multiple assignment scheme is to assign one or more shares to single participant so that any kind of access structure can be realized by classical secret sharing schemes. We propose its quantum version including ramp secret sharing schemes. Then we propose an integer optimization approach to minimize the average share size.

  5. A signaling and decision scheme with application to multiple-access communication

    NASA Astrophysics Data System (ADS)

    Longwell, B. C.; Arozullah, M.; Black, B. A.

    A decision directed detection method using a quasi-orthogonal set of signaling waveforms for detection-signals in the presence of random access interference is presented. In this method the spectra of a number of users in a random access scheme are allowed to overlap and decision is made by sequential elimination of interference. This method can achieve a larger throughput than that of frequency division multiple access. Performance of this detection scheme is evaluated in terms of probability of error and error propagation. This proposed detector outperforms the optimal linear detector for the same signal set in terms of signal-to-noise ratio needed for a given probability of error and data rate per unit bandwidth. This scheme may have application wherever a number of users need to communicate over a common channel e.g., tactical military communication system.

  6. Color coded multiple access scheme for bidirectional multiuser visible light communications in smart home technologies

    NASA Astrophysics Data System (ADS)

    Tiwari, Samrat Vikramaditya; Sewaiwar, Atul; Chung, Yeon-Ho

    2015-10-01

    In optical wireless communications, multiple channel transmission is an attractive solution to enhancing capacity and system performance. A new modulation scheme called color coded multiple access (CCMA) for bidirectional multiuser visible light communications (VLC) is presented for smart home applications. The proposed scheme uses red, green and blue (RGB) light emitting diodes (LED) for downlink and phosphor based white LED (P-LED) for uplink to establish a bidirectional VLC and also employs orthogonal codes to support multiple users and devices. The downlink transmission for data user devices and smart home devices is provided using red and green colors from the RGB LEDs, respectively, while uplink transmission from both types of devices is performed using the blue color from P-LEDs. Simulations are conducted to verify the performance of the proposed scheme. It is found that the proposed bidirectional multiuser scheme is efficient in terms of data rate and performance. In addition, since the proposed scheme uses RGB signals for downlink data transmission, it provides flicker-free illumination that would lend itself to multiuser VLC system for smart home applications.

  7. 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.

  8. An integrated voice and data multiple-access scheme for a land-mobile satellite system

    NASA Technical Reports Server (NTRS)

    Li, V. O. K.; Yan, T.-Y.

    1984-01-01

    An analytical study is performed of the satellite requirements for a land mobile satellite system (LMSS). The spacecraft (MSAT-X) would be in GEO and would be compatible with multiple access by mobile radios and antennas and fixed stations. The FCC has received a petition from NASA to reserve the 821-825 and 866-870 MHz frequencies for the LMSS, while communications with fixed earth stations would be in the Ku band. MSAT-X transponders would alter the frequencies of signal and do no processing in the original configuration considered. Channel use would be governed by an integrated demand-assigned, multiple access protocol, which would divide channels into reservation and information channels, governed by a network management center. Further analyses will cover tradeoffs between data and voice users, probability of blocking, and the performance impacts of on-board switching and variable bandwidth assignment. Initial calculations indicate that a large traffic volume can be handled with acceptable delays and voice blocking probabilities.

  9. An integrated voice and data multiple-access scheme for a land-mobile satellite system

    NASA Technical Reports Server (NTRS)

    Li, V. O. K.; Yan, T.-Y.

    1984-01-01

    An analytical study is performed of the satellite requirements for a land mobile satellite system (LMSS). The spacecraft (MSAT-X) would be in GEO and would be compatible with multiple access by mobile radios and antennas and fixed stations. The FCC has received a petition from NASA to reserve the 821-825 and 866-870 MHz frequencies for the LMSS, while communications with fixed earth stations would be in the Ku band. MSAT-X transponders would alter the frequencies of signal and do no processing in the original configuration considered. Channel use would be governed by an integrated demand-assigned, multiple access protocol, which would divide channels into reservation and information channels, governed by a network management center. Further analyses will cover tradeoffs between data and voice users, probability of blocking, and the performance impacts of on-board switching and variable bandwidth assignment. Initial calculations indicate that a large traffic volume can be handled with acceptable delays and voice blocking probabilities.

  10. An integrated voice and data multiple-access scheme for a land-mobile satellite system

    NASA Astrophysics Data System (ADS)

    Li, V. O. K.; Yan, T.-Y.

    1984-11-01

    An analytical study is performed of the satellite requirements for a land mobile satellite system (LMSS). The spacecraft (MSAT-X) would be in GEO and would be compatible with multiple access by mobile radios and antennas and fixed stations. The FCC has received a petition from NASA to reserve the 821-825 and 866-870 MHz frequencies for the LMSS, while communications with fixed earth stations would be in the Ku band. MSAT-X transponders would alter the frequencies of signal and do no processing in the original configuration considered. Channel use would be governed by an integrated demand-assigned, multiple access protocol, which would divide channels into reservation and information channels, governed by a network management center. Further analyses will cover tradeoffs between data and voice users, probability of blocking, and the performance impacts of on-board switching and variable bandwidth assignment. Initial calculations indicate that a large traffic volume can be handled with acceptable delays and voice blocking probabilities.

  11. Performance analysis of an adaptive multiple access scheme for the message service of a land mobile satellite experiment (MSAT-X)

    NASA Technical Reports Server (NTRS)

    Yan, T.-Y.; Li, V. O. K.

    1984-01-01

    This paper describes an Adaptive Mobile Access Protocol (AMAP) for the message service of MSAT-X., a proposed experimental mobile satellite communication network. Message lengths generated by the mobiles are assumed to be uniformly distributed. The mobiles are dispersed over a wide geographical area and the channel data rate is limited. AMAP is a reservation based multiple access scheme. The available bandwidth is divided into subchannels, which are divided into reservation and message channels. The ALOHA multiple access scheme is employed in the reservation channels, while the message channels are demand assigned. AMAP adaptively reallocates the reservation and message channels to optimize the total average message delay.

  12. Securing optical code-division multiple-access networks with a postswitching coding scheme of signature reconfiguration

    NASA Astrophysics Data System (ADS)

    Huang, Jen-Fa; Meng, Sheng-Hui; Lin, Ying-Chen

    2014-11-01

    The optical code-division multiple-access (OCDMA) technique is considered a good candidate for providing optical layer security. An enhanced OCDMA network security mechanism with a pseudonoise (PN) random digital signals type of maximal-length sequence (M-sequence) code switching to protect against eavesdropping is presented. Signature codes unique to individual OCDMA-network users are reconfigured according to the register state of the controlling electrical shift registers. Examples of signature reconfiguration following state switching of the controlling shift register for both the network user and the eavesdropper are numerically illustrated. Dynamically changing the PN state of the shift register to reconfigure the user signature sequence is shown; this hinders eavesdroppers' efforts to decode correct data sequences. The proposed scheme increases the probability of eavesdroppers committing errors in decoding and thereby substantially enhances the degree of an OCDMA network's confidentiality.

  13. 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.

  14. Spectrally efficient localized carrier distribution scheme for multiple-user DFT-S OFDM RoF- PON wireless access systems.

    PubMed

    Tao, Li; Yu, Jianjun; Yang, Qi; Luo, Ming; He, Zhixue; Shao, Yufeng; Zhang, Junwen; Chi, Nan

    2012-12-31

    We propose a modified localized carrier distribution scheme based on multi-tone generation to generate 60 GHz mm-wave for different wireless users and it improves the carrier utilization efficiency by 33.3%. The principle of multiple-user discrete Fourier transform spread optical orthogonal frequency-division multiplexing (DFT-S OFDM) Radio-over-fiber (RoF) system is presented. This multiple-user system is applicable to passive optical network (PON). Then we demonstrate a 8 x 4.65 Gb/s multiple-user DFT-S OFDM RoF-PON wireless access system over 40 km fiber link and 60 GHz wireless link using two localized carrier distribution scheme with different spectral efficiency. Compared to conventional OFDM, 2.3 dB reduction of receiver power using DFT-S OFDM modulation scheme and the calculated BER performance for 8 wireless users clearly demonstrates the feasibility of this spectrally efficient multiple-user RoF-PON scheme.

  15. Chaotic communication scheme with multiplication

    NASA Astrophysics Data System (ADS)

    Bobreshov, A. M.; Karavaev, A. A.

    2007-05-01

    A new scheme of data transmission with nonlinear admixing is described, in which the two mutually inverse operations (multiplication and division) ensure multiplicative mixing of the informative and chaotic signals that provides a potentially higher degree of security. A special feature of the proposed scheme is the absence of limitations (related to the division by zero) imposed on the types of informative signals.

  16. Uplink Access Schemes for LTE-Advanced

    NASA Astrophysics Data System (ADS)

    Liu, Le; Inoue, Takamichi; Koyanagi, Kenji; Kakura, Yoshikazu

    The 3GPP LTE-Advanced has been attracting much attention recently, where the channel bandwidth would be beyond the maximum bandwidth of LTE, 20MHz. In LTE, single carrier-frequency division multiple access (SC-FDMA) was accepted as the uplink access scheme due to its advantage of very low cubic metric (CM). For LTE-A wideband transmission, multicarrier access would be more effective than single carrier access to make use of multi-user diversity and can maintain the physical channel structure of LTE, where the control information is transmitted on the edges of each 20MHz. In this paper, we discuss the access schemes in bandwidth under 20MHz as well as over 20MHz. In the case of bandwidth under 20MHz, we propose the access schemes allowing discontinuous resource allocation to enhance average throughput while maintaining cell-edge user throughput, that is, DFT-spread-OFDM with spectrum division control (SDC) and adaptive selection of SC-FDMA and OFDM (SC+OFDM). The number of discontinuous spectrums is denoted as spectrum division (SD). For DFT-S-OFDM, we define a parameter max SD as the upper limit of SD. We evaluate our proposed schemes in bandwidth under 20MHz and find that SC+OFDM as well as SDC with common max SD or UE-specific max SD can improve average throughput while their cell-edge user throughput can approach that of SC-FDMA. In the case of bandwidth over 20MHz, we consider key factors to decide a feasible access scheme for aggregating several 20MHz-wide bands.

  17. Robust rate-adaptive hybrid ARQ scheme for frequency-hopped spread-spectrum multiple-access communication systems

    NASA Astrophysics Data System (ADS)

    Bigloo, Amir M. Y.; Gulliver, T. Aaron; Wang, Q.; Bhargava, Vijay K.

    1994-06-01

    This paper considers the application of rate-adaptive coding (RAC) to a spread spectrum multiple access (SSMA) communication system. Specifically, RAC using a variable rate Reed-Solomon (RS) code with a single decoder is applied to frequency-hopped SSMA. We show that this combination can accommodate a larger number of users compared to that with conventional fixed-rate coding. This increase is a result of a reduction in the channel interference from other users. The penalty for this improvement in most cases is a slight increase in the delay (composed of propagation and decoding delay). The throughput and the undetected error probability for a Q-ary symmetric channel are analyzed, and performance results are presented.

  18. Performance enhancement of successive interference cancellation scheme based on spectral amplitude coding for optical code-division multiple-access systems using Hadamard codes

    NASA Astrophysics Data System (ADS)

    Eltaif, Tawfig; Shalaby, Hossam M. H.; Shaari, Sahbudin; Hamarsheh, Mohammad M. N.

    2009-04-01

    A successive interference cancellation scheme is applied to optical code-division multiple-access (OCDMA) systems with spectral amplitude coding (SAC). A detailed analysis of this system, with Hadamard codes used as signature sequences, is presented. The system can easily remove the effect of the strongest signal at each stage of the cancellation process. In addition, simulation of the prose system is performed in order to validate the theoretical results. The system shows a small bit error rate at a large number of active users compared to the SAC OCDMA system. Our results reveal that the proposed system is efficient in eliminating the effect of the multiple-user interference and in the enhancement of the overall performance.

  19. 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.

  20. Multiple Access Trade Study

    NASA Technical Reports Server (NTRS)

    Motamedi, Masoud

    1990-01-01

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

  1. Access and accounting schemes of wireless broadband

    NASA Astrophysics Data System (ADS)

    Zhang, Jian; Huang, Benxiong; Wang, Yan; Yu, Xing

    2004-04-01

    In this paper, two wireless broadband access and accounting schemes were introduced. There are some differences in the client and the access router module between them. In one scheme, Secure Shell (SSH) protocol is used in the access system. The SSH server makes the authentication based on private key cryptography. The advantage of this scheme is the security of the user's information, and we have sophisticated access control. In the other scheme, Secure Sockets Layer (SSL) protocol is used the access system. It uses the technology of public privacy key. Nowadays, web browser generally combines HTTP and SSL protocol and we use the SSL protocol to implement the encryption of the data between the clients and the access route. The schemes are same in the radius sever part. Remote Authentication Dial in User Service (RADIUS), as a security protocol in the form of Client/Sever, is becoming an authentication/accounting protocol for standard access to the Internet. It will be explained in a flow chart. In our scheme, the access router serves as the client to the radius server.

  2. Fade detector for the FODA-TDMA access scheme

    NASA Astrophysics Data System (ADS)

    Celandroni, Nedo; Ferro, Erina; Marzoli, Antonio

    1989-05-01

    The First in first out Ordered Demand Assignment-Time Division Multiple Access (FODA-TDMA) satellite access scheme designed for simultaneous transmissions of real time data, like packetized voice and slow-scan images (stream traffic) and data coming from standard EDP applications, such as bulk data tansfer, interactive computer access, mailing, data base enquiry and updating (datagram traffic) is described. When deep fades are experienced due to rain attenuation, the system is able to counter the fade. Techniques to detect the fade are presented.

  3. Multiple access mass storage network

    SciTech Connect

    Wentz, D.L. Jr.

    1980-01-01

    The Multi-Access Storage Subnetwork (MASS) is the latest addition to the Octopus computer network at Lawrence Livermore Laboratory. The subnetwork provides shared mass storage for the Laboratory's multiple-host computer configuration. A Control Data Corp. 38500 Mass Storage facility is interfaces by MASS to the large, scientific worker computers to provide an on-line capacity of 1 trillion bits of user-accessible data. The MASS architecture offers a very high performance approach to the management of large data storage, as well as a high degree of reliability needed for operation in the Laboratory's timesharing environment. MASS combines state-of-the-art digital hardware with an innovative system philosophy. The key LLL design features of the subnetwork that contribute to the high performance include the following: a data transmission scheme that provides a 40-Mbit/s channel over distances of up to 1000 ft, a large metal-oxide-semiconductor (MOS) memory buffer controlled by a 24-port memory multiplexer with an aggregate data rate of 280 Mbit/s, and a set of high-speed microprocessor-based controllers driving the commercial mass storage units. Reliability of the system is provided by a completely redundant network, including two control minicomputer systems. Also enhancing reliability is error detection and correction in the MOS memory. A hardware-generated checksum is carried with each file throughout the entire network to ensure integrity of user files. 6 figures, 1 table.

  4. Multiple Access in Ultra-Wideband Communications Using Multiple Pulses

    SciTech Connect

    Nekoogar, F; Dowla, F

    2003-04-11

    Multiple access (MA) in UWB communication is an area of active research. To date several time-division or code-division pulse amplitude modulation (PAM) or pulse position modulation (PPM) schemes have been proposed to separate multiple users in UWB communications. Conventionally, all users employ the same pulse shape and modulate the transmit pulse based on changing amplitude or position. One concern with using the same pulse for all channels is that the multiple access interference (MAI) increases as the number of users increase. This is due to increased cross-correlation between similar pulses of the different channels, raising thus the noise floor in such systems. In this paper we introduce and study the performance of a new MA scheme in the context of multiple orthogonal transmitted-reference (T-R) short duration (nsec) chirp pulses in the presence of multipath and additive white Gaussian noise (AWGN).

  5. Harmonic generation with multiple wiggler schemes

    SciTech Connect

    Bonifacio, R.; De Salvo, L.; Pierini, P.

    1995-02-01

    In this paper the authors give a simple theoretical description of the basic physics of the single pass high gain free electron laser (FEL), describing in some detail the FEL bunching properties and the harmonic generation technique with a multiple-wiggler scheme or a high gain optical klystron configuration.

  6. Multiple access capacity trade-offs for a Ka-band personal access satellite system

    NASA Technical Reports Server (NTRS)

    Dessouky, Khaled; Motamedi, Masoud

    1990-01-01

    System capability is critical to the economic viability of a personal satellite communication system. Ka band has significant potential to support a high capacity multiple access system because of the availability of bandwidth. System design tradeoffs are performed and multiple access schemes are compared with the design goal of achieving the highest capacity and efficiency. Conclusions regarding the efficiency of the different schemes and the achievable capacities are given.

  7. An authentication scheme for secure access to healthcare services.

    PubMed

    Khan, Muhammad Khurram; Kumari, Saru

    2013-08-01

    Last few decades have witnessed boom in the development of information and communication technologies. Health-sector has also been benefitted with this advancement. To ensure secure access to healthcare services some user authentication mechanisms have been proposed. In 2012, Wei et al. proposed a user authentication scheme for telecare medical information system (TMIS). Recently, Zhu pointed out offline password guessing attack on Wei et al.'s scheme and proposed an improved scheme. In this article, we analyze both of these schemes for their effectiveness in TMIS. We show that Wei et al.'s scheme and its improvement proposed by Zhu fail to achieve some important characteristics necessary for secure user authentication. We find that security problems of Wei et al.'s scheme stick with Zhu's scheme; like undetectable online password guessing attack, inefficacy of password change phase, traceability of user's stolen/lost smart card and denial-of-service threat. We also identify that Wei et al.'s scheme lacks forward secrecy and Zhu's scheme lacks session key between user and healthcare server. We therefore propose an authentication scheme for TMIS with forward secrecy which preserves the confidentiality of air messages even if master secret key of healthcare server is compromised. Our scheme retains advantages of Wei et al.'s scheme and Zhu's scheme, and offers additional security. The security analysis and comparison results show the enhanced suitability of our scheme for TMIS.

  8. Secure Dynamic access control scheme of PHR in cloud computing.

    PubMed

    Chen, Tzer-Shyong; Liu, Chia-Hui; Chen, Tzer-Long; Chen, Chin-Sheng; Bau, Jian-Guo; Lin, Tzu-Ching

    2012-12-01

    With the development of information technology and medical technology, medical information has been developed from traditional paper records into electronic medical records, which have now been widely applied. The new-style medical information exchange system "personal health records (PHR)" is gradually developed. PHR is a kind of health records maintained and recorded by individuals. An ideal personal health record could integrate personal medical information from different sources and provide complete and correct personal health and medical summary through the Internet or portable media under the requirements of security and privacy. A lot of personal health records are being utilized. The patient-centered PHR information exchange system allows the public autonomously maintain and manage personal health records. Such management is convenient for storing, accessing, and sharing personal medical records. With the emergence of Cloud computing, PHR service has been transferred to storing data into Cloud servers that the resources could be flexibly utilized and the operation cost can be reduced. Nevertheless, patients would face privacy problem when storing PHR data into Cloud. Besides, it requires a secure protection scheme to encrypt the medical records of each patient for storing PHR into Cloud server. In the encryption process, it would be a challenge to achieve accurately accessing to medical records and corresponding to flexibility and efficiency. A new PHR access control scheme under Cloud computing environments is proposed in this study. With Lagrange interpolation polynomial to establish a secure and effective PHR information access scheme, it allows to accurately access to PHR with security and is suitable for enormous multi-users. Moreover, this scheme also dynamically supports multi-users in Cloud computing environments with personal privacy and offers legal authorities to access to PHR. From security and effectiveness analyses, the proposed PHR access

  9. 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.

  10. Performance of Multiple Pulse Multiple Delay Modulated UWB Signals in a Multiple Access Indoor Wireless Channel

    SciTech Connect

    Nekoogar, F

    2003-06-12

    In this paper, the performance of a two user UWB multiple access (UWB-MA) system based on multiple-pulse multiple-delay (MPMD) modulation scheme in an indoor wireless channel is evaluated by computer simulations. The indoor multipath propagation channel model used in this study is based on the modified statistical Saleh-Valenzuela model proposed by Foerester and Li from Intel. The simulation results indicate that the multipath performance of MPMD modulated signals in a multiple access system outperforms the nonmultipath case as the number of autocorrelation function (ACF) sampling points increases for each user. This is an unusual but important result, since MPMD receiver exploits multipath phenomenon in indoor wireless channels to increase the BER performance, hence the transmission rate in a UWB-MA system.

  11. Implementation of a Cross-Layer Sensing Medium-Access Control Scheme.

    PubMed

    Su, Yishan; Fu, Xiaomei; Han, Guangyao; Xu, Naishen; Jin, Zhigang

    2017-04-10

    In this paper, compressed sensing (CS) theory is utilized in a medium-access control (MAC) scheme for wireless sensor networks (WSNs). We propose a new, cross-layer compressed sensing medium-access control (CL CS-MAC) scheme, combining the physical layer and data link layer, where the wireless transmission in physical layer is considered as a compress process of requested packets in a data link layer according to compressed sensing (CS) theory. We first introduced using compressive complex requests to identify the exact active sensor nodes, which makes the scheme more efficient. Moreover, because the reconstruction process is executed in a complex field of a physical layer, where no bit and frame synchronizations are needed, the asynchronous and random requests scheme can be implemented without synchronization payload. We set up a testbed based on software-defined radio (SDR) to implement the proposed CL CS-MAC scheme practically and to demonstrate the validation. For large-scale WSNs, the simulation results show that the proposed CL CS-MAC scheme provides higher throughput and robustness than the carrier sense multiple access (CSMA) and compressed sensing medium-access control (CS-MAC) schemes.

  12. On board processing for future satellite communications systems: Comparison of FDM, TDM and hybrid accessing schemes

    NASA Technical Reports Server (NTRS)

    Berk, G.; Jean, P. N.; Rotholz, E.

    1982-01-01

    Several satellite uplink and downlink accessing schemes for customer premises service are compared. Four conceptual system designs are presented: satellite-routed frequency division multiple access (FDMA), satellite-switched time division multiple access (TDMA), processor-routed TDMA, and frequency-routed TDMA, operating in the 30/20 GHz band. The designs are compared on the basis of estimated satellite weight, system capacity, power consumption, and cost. The systems are analyzed for fixed multibeam coverage of the continental United States. Analysis shows that the system capacity is limited by the available satellite resources and by the terminal size and cost.

  13. 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.

  14. Distinguishing Schemes and Tasks in Children's Development of Multiplicative Reasoning

    ERIC Educational Resources Information Center

    Tzur, Ron; Johnson, Heather L.; McClintock, Evan; Kenney, Rachael H.; Xin, Yan P.; Si, Luo; Woordward, Jerry; Hord, Casey; Jin, Xianyan

    2013-01-01

    We present a synthesis of findings from constructivist teaching experiments regarding six schemes children construct for reasoning multiplicatively and tasks to promote them. We provide a task-generating platform game, depictions of each scheme, and supporting tasks. Tasks must be distinguished from children's thinking, and learning situations…

  15. An effective and secure key-management scheme for hierarchical access control in E-medicine system.

    PubMed

    Odelu, Vanga; Das, Ashok Kumar; Goswami, Adrijit

    2013-04-01

    Recently several hierarchical access control schemes are proposed in the literature to provide security of e-medicine systems. However, most of them are either insecure against 'man-in-the-middle attack' or they require high storage and computational overheads. Wu and Chen proposed a key management method to solve dynamic access control problems in a user hierarchy based on hybrid cryptosystem. Though their scheme improves computational efficiency over Nikooghadam et al.'s approach, it suffers from large storage space for public parameters in public domain and computational inefficiency due to costly elliptic curve point multiplication. Recently, Nikooghadam and Zakerolhosseini showed that Wu-Chen's scheme is vulnerable to man-in-the-middle attack. In order to remedy this security weakness in Wu-Chen's scheme, they proposed a secure scheme which is again based on ECC (elliptic curve cryptography) and efficient one-way hash function. However, their scheme incurs huge computational cost for providing verification of public information in the public domain as their scheme uses ECC digital signature which is costly when compared to symmetric-key cryptosystem. In this paper, we propose an effective access control scheme in user hierarchy which is only based on symmetric-key cryptosystem and efficient one-way hash function. We show that our scheme reduces significantly the storage space for both public and private domains, and computational complexity when compared to Wu-Chen's scheme, Nikooghadam-Zakerolhosseini's scheme, and other related schemes. Through the informal and formal security analysis, we further show that our scheme is secure against different attacks and also man-in-the-middle attack. Moreover, dynamic access control problems in our scheme are also solved efficiently compared to other related schemes, making our scheme is much suitable for practical applications of e-medicine systems.

  16. A chaos secure communication scheme based on multiplication modulation

    NASA Astrophysics Data System (ADS)

    Fallahi, Kia; Leung, Henry

    2010-02-01

    A secure spread spectrum communication scheme using multiplication modulation is proposed. The proposed system multiplies the message by chaotic signal. The scheme does not need to know the initial condition of the chaotic signals and the receiver is based on an extended Kalman filter (EKF). This signal encryption scheme lends itself to cheap implementation and can therefore be used effectively for ensuring security and privacy in commercial consumer electronics products. To illustrate the effectiveness of the proposed scheme, a numerical example based on Genesio-Tesi system and also Chen dynamical system is presented and the results are compared.

  17. A Hybrid Scheme for Fine-Grained Search and Access Authorization in Fog Computing Environment.

    PubMed

    Xiao, Min; Zhou, Jing; Liu, Xuejiao; Jiang, Mingda

    2017-06-17

    In the fog computing environment, the encrypted sensitive data may be transferred to multiple fog nodes on the edge of a network for low latency; thus, fog nodes need to implement a search over encrypted data as a cloud server. Since the fog nodes tend to provide service for IoT applications often running on resource-constrained end devices, it is necessary to design lightweight solutions. At present, there is little research on this issue. In this paper, we propose a fine-grained owner-forced data search and access authorization scheme spanning user-fog-cloud for resource constrained end users. Compared to existing schemes only supporting either index encryption with search ability or data encryption with fine-grained access control ability, the proposed hybrid scheme supports both abilities simultaneously, and index ciphertext and data ciphertext are constructed based on a single ciphertext-policy attribute based encryption (CP-ABE) primitive and share the same key pair, thus the data access efficiency is significantly improved and the cost of key management is greatly reduced. Moreover, in the proposed scheme, the resource constrained end devices are allowed to rapidly assemble ciphertexts online and securely outsource most of decryption task to fog nodes, and mediated encryption mechanism is also adopted to achieve instantaneous user revocation instead of re-encrypting ciphertexts with many copies in many fog nodes. The security and the performance analysis show that our scheme is suitable for a fog computing environment.

  18. A Hybrid Scheme for Fine-Grained Search and Access Authorization in Fog Computing Environment

    PubMed Central

    Xiao, Min; Zhou, Jing; Liu, Xuejiao; Jiang, Mingda

    2017-01-01

    In the fog computing environment, the encrypted sensitive data may be transferred to multiple fog nodes on the edge of a network for low latency; thus, fog nodes need to implement a search over encrypted data as a cloud server. Since the fog nodes tend to provide service for IoT applications often running on resource-constrained end devices, it is necessary to design lightweight solutions. At present, there is little research on this issue. In this paper, we propose a fine-grained owner-forced data search and access authorization scheme spanning user-fog-cloud for resource constrained end users. Compared to existing schemes only supporting either index encryption with search ability or data encryption with fine-grained access control ability, the proposed hybrid scheme supports both abilities simultaneously, and index ciphertext and data ciphertext are constructed based on a single ciphertext-policy attribute based encryption (CP-ABE) primitive and share the same key pair, thus the data access efficiency is significantly improved and the cost of key management is greatly reduced. Moreover, in the proposed scheme, the resource constrained end devices are allowed to rapidly assemble ciphertexts online and securely outsource most of decryption task to fog nodes, and mediated encryption mechanism is also adopted to achieve instantaneous user revocation instead of re-encrypting ciphertexts with many copies in many fog nodes. The security and the performance analysis show that our scheme is suitable for a fog computing environment. PMID:28629131

  19. An optimized quantum information splitting scheme with multiple controllers

    NASA Astrophysics Data System (ADS)

    Jiang, Min

    2016-12-01

    We propose an efficient scheme for splitting multi-qudit information with cooperative control of multiple agents. Each controller is assigned one controlling qudit, and he can monitor the state sharing of all multi-qudit information. Compared with the existing schemes, our scheme requires less resource consumption and approaches higher communication efficiency. In addition, our proposal involves only generalized Bell-state measurement, single-qudit measurement, one-qudit gates and a unitary-reduction operation, which makes it flexible and achievable for physical implementation.

  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. Multiple-access channels without synchronization

    NASA Technical Reports Server (NTRS)

    Mceliece, R. J.; Posner, E. C.

    1977-01-01

    This paper discusses models for multiple-access communications which take into account the fact that the channel users may not be able to synchronize their transmissions. It is shown that for a broad class of such channels, the capacity region is the same as it would be with user synchronization. Some open problems are discussed.

  4. Suppression of multiple scattering with a CCD camera detection scheme

    NASA Astrophysics Data System (ADS)

    Zakharov, Pavel; Schurtenberger, Peter; Scheffold, Frank

    2005-06-01

    We introduce a CCD camera detection scheme in dynamic light scattering that provides information on the single-scattered auto-correlation function even for fairly turbid samples. Our approach allows access to the extensive range of systems that show low-order scattering by selective detection of the singly scattered light. Model experiments on slowly relaxing suspensions of latex spheres in glycerol were carried out to verify validity range of our approach.

  5. Transparent data service with multiple wireless access

    NASA Technical Reports Server (NTRS)

    Dean, Richard A.; Levesque, Allen H.

    1993-01-01

    The rapid introduction of digital wireless networks is an important part of the emerging digital communications scene. The introduction of Digital Cellular, LEO and GEO Satellites, and Personal Communications Services poses both a challenge and an opportunity for the data user. On the one hand wireless access will introduce significant new portable data services such as personal notebooks, paging, E-mail, and fax that will put the information age in the user's pocket. On the other hand the challenge of creating a seamless and transparent environment for the user in multiple access environments and across multiple network connections is formidable. A summary of the issues associated with developing techniques and standards that can support transparent and seamless data services is presented. The introduction of data services into the radio world represents a unique mix of RF channel problems, data protocol issues, and network issues. These problems require that experts from each of these disciplines fuse the individual technologies to support these services.

  6. Quantum teleportation scheme by selecting one of multiple output ports

    NASA Astrophysics Data System (ADS)

    Ishizaka, Satoshi; Hiroshima, Tohya

    2009-04-01

    The scheme of quantum teleportation, where Bob has multiple (N) output ports and obtains the teleported state by simply selecting one of the N ports, is thoroughly studied. We consider both the deterministic version and probabilistic version of the teleportation scheme aiming to teleport an unknown state of a qubit. Moreover, we consider two cases for each version: (i) the state employed for the teleportation is fixed to a maximally entangled state and (ii) the state is also optimized as well as Alice’s measurement. We analytically determine the optimal protocols for all the four cases and show the corresponding optimal fidelity or optimal success probability. All these protocols can achieve the perfect teleportation in the asymptotic limit of N→∞ . The entanglement properties of the teleportation scheme are also discussed.

  7. Experimental demonstration of block interleaved frequency division multiple access for bidirectional visible light communications

    NASA Astrophysics Data System (ADS)

    Lin, Bangjiang; Yang, Hui; Ye, Weiping; Tang, Xuan; Ghassemlooy, Zabih

    2017-01-01

    We propose a power efficient multiple access scheme for visible light communications (VLC) based on the block interleaved frequency division multiple access (B-IFDMA) which provides large frequency-diversity, flexible bandwidth allocation, low complexity of channel equalization, and user separation. Bidirectional B-IFDMA VLC transmission is experimentally demonstrated to verify its feasibility. The impact of the number of subcarriers per block on the transmission performance under wireless optical channel is investigated.

  8. Performance of random multiple access transmission system

    NASA Technical Reports Server (NTRS)

    Phinainitisart, N.; Wu, W. W.

    1990-01-01

    The performance of the Random Multiple Access (RMA) technique, applied to a direct terminal-to-terminal link with a large number of potential users, is determined. The average signal-to-noise ratio (SNR) is derived. Under Gaussian assumption, the approximation of the probability of error is given. The analysis shows that the system performance is affected by the sequence length, the number of simultaneous users, and the number of cochannel symbols, but is not sensitive to the thermal noise. The performance of using very small aperture antenna for both transmitting and receiving without a hub station is given.

  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. An axisymmetric multiple-relaxation-time lattice Boltzmann scheme

    NASA Astrophysics Data System (ADS)

    Xie, Wenjun

    2015-01-01

    A multiple-relaxation-time (MRT) lattice Boltzmann (LB) scheme developed for axisymmetric flows recovers the complete continuity and Navier-Stokes equations. This scheme follows the strategy of the standard D2Q9 model by using a single particle distribution function and a simple "collision-streaming" updating rule. The extra terms related to axisymmetry in the macroscopic equations are recovered by adding source terms into the LB equation, which are simple and involve no gradients. The compressible effect retained in the Navier-Stokes equations is recovered by introducing a term related to the reversed transformation matrix for MRT collision operator, so as to produce a correct bulk viscosity, making it suitable for compressible flows with high frequency and low Mach number. The validity of the scheme is demonstrated by testing the Hagen-Poiseuille flow and 3D Womersley flow, as well as the standing acoustic waves in a closed cylindrical chamber. The numerical experiments show desirable stability at low viscosities, enabling to simulate a standing ultrasound field in centimeters space.

  12. Multiple time scale based reduction scheme for nonlinear chemical dynamics

    NASA Astrophysics Data System (ADS)

    Das, D.; Ray, D. S.

    2013-07-01

    A chemical reaction is often characterized by multiple time scales governing the kinetics of reactants, products and intermediates. We eliminate the fast relaxing intermediates in autocatalytic reaction by transforming the original system into a new one in which the linearized part is diagonal. This allows us to reduce the dynamical system by identifying the associated time scales and subsequent adiabatic elimination of the fast modes. It has been shown that the reduced system sustains the robust qualitative signatures of the original system and at times the generic form of the return map for the chaotic system from which complex dynamics stems out in the original system can be identified. We illustrate the scheme for a three-variable cubic autocatalytic reaction and four-variable peroxidase-oxidase reaction.

  13. Quality of Recovery Evaluation of the Protection Schemes for Fiber-Wireless Access Networks

    NASA Astrophysics Data System (ADS)

    Fu, Minglei; Chai, Zhicheng; Le, Zichun

    2016-03-01

    With the rapid development of fiber-wireless (FiWi) access network, the protection schemes have got more and more attention due to the risk of huge data loss when failures occur. However, there are few studies on the performance evaluation of the FiWi protection schemes by the unified evaluation criterion. In this paper, quality of recovery (QoR) method was adopted to evaluate the performance of three typical protection schemes (MPMC scheme, OBOF scheme and RPMF scheme) against the segment-level failure in FiWi access network. The QoR models of the three schemes were derived in terms of availability, quality of backup path, recovery time and redundancy. To compare the performance of the three protection schemes comprehensively, five different classes of network services such as emergency service, prioritized elastic service, conversational service, etc. were utilized by means of assigning different QoR weights. Simulation results showed that, for the most service cases, RPMF scheme was proved to be the best solution to enhance the survivability when planning the FiWi access network.

  14. Attitude determination using an adaptive multiple model filtering Scheme

    NASA Technical Reports Server (NTRS)

    Lam, Quang; Ray, Surendra N.

    1995-01-01

    Attitude determination has been considered as a permanent topic of active research and perhaps remaining as a forever-lasting interest for spacecraft system designers. Its role is to provide a reference for controls such as pointing the directional antennas or solar panels, stabilizing the spacecraft or maneuvering the spacecraft to a new orbit. Least Square Estimation (LSE) technique was utilized to provide attitude determination for the Nimbus 6 and G. Despite its poor performance (estimation accuracy consideration), LSE was considered as an effective and practical approach to meet the urgent need and requirement back in the 70's. One reason for this poor performance associated with the LSE scheme is the lack of dynamic filtering or 'compensation'. In other words, the scheme is based totally on the measurements and no attempts were made to model the dynamic equations of motion of the spacecraft. We propose an adaptive filtering approach which employs a bank of Kalman filters to perform robust attitude estimation. The proposed approach, whose architecture is depicted, is essentially based on the latest proof on the interactive multiple model design framework to handle the unknown of the system noise characteristics or statistics. The concept fundamentally employs a bank of Kalman filter or submodel, instead of using fixed values for the system noise statistics for each submodel (per operating condition) as the traditional multiple model approach does, we use an on-line dynamic system noise identifier to 'identify' the system noise level (statistics) and update the filter noise statistics using 'live' information from the sensor model. The advanced noise identifier, whose architecture is also shown, is implemented using an advanced system identifier. To insure the robust performance for the proposed advanced system identifier, it is also further reinforced by a learning system which is implemented (in the outer loop) using neural networks to identify other unknown

  15. 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

  16. 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.

  17. A broadcasting multiple blind signature scheme based on quantum GHZ entanglement

    NASA Astrophysics Data System (ADS)

    Tian, Yuan; Chen, Hong; Gao, Yan; Zhuang, Honglin; Lian, Haigang; Han, Zhengping; Yu, Peng; Kong, Xiangze; Wen, Xiaojun

    2014-09-01

    Using the correlation of the GHZ triplet states, a broadcasting multiple blind signature scheme is proposed. Different from classical multiple signature and current quantum signature schemes, which could only deliver either multiple signature or unconditional security, our scheme guarantees both by adopting quantum key preparation, quantum encryption algorithm and quantum entanglement. Our proposed scheme has the properties of multiple signature, blindness, non-disavowal, non-forgery and traceability. To the best of our knowledge, we are the first to propose the broadcasting multiple blind signature of quantum cryptography.

  18. Improving access to maternity services: an overview of cash transfer and voucher schemes in South Asia.

    PubMed

    Jehan, Kate; Sidney, Kristi; Smith, Helen; de Costa, Ayesha

    2012-06-01

    In Nepal, India, Bangladesh and Pakistan, policy focused on improving access to maternity services has led to measures to reduce cost barriers impeding women's access to care. Specifically, these include cash transfer or voucher schemes designed to stimulate demand for services, including antenatal, delivery and post-partum care. In spite of their popularity, however, little is known about the impact or effectiveness of these schemes. This paper provides an overview of five major interventions: the Aama (Mothers') Programme (cash transfer element) in Nepal; the Janani Suraksha Yojana (Safe Motherhood Scheme) in India; the Chiranjeevi Yojana (Scheme for Long Life) in India; the Maternal Health Voucher Scheme in Bangladesh and the Sehat (Health) Voucher Scheme in Pakistan. It reviews the aims, rationale, implementation challenges, known outcomes, potential and limitations of each scheme based on current available data. Increased use of maternal health services has been reported since the schemes began, though evidence of improvements in maternal health outcomes has not been established due to a lack of controlled studies. Areas for improvement in these schemes, identified in this review, include the need for more efficient operational management, clear guidelines, financial transparency, plans for sustainability, evidence of equity and, above all, proven impact on quality of care and maternal mortality and morbidity.

  19. Contemplation on marking scheme for Type X multiple choice questions, and an illustration of a practically applicable scheme

    PubMed Central

    Siddiqui, Nazeem Ishrat; Bhavsar, Vinayak H.; Bhavsar, Arnav V.; Bose, Sukhwant

    2016-01-01

    Ever since its inception 100 years back, multiple choice items have been widely used as a method of assessment. It has certain inherent limitations such as inability to test higher cognitive skills, element of guesswork while answering, and issues related with marking schemes. Various marking schemes have been proposed in the past but they are not balanced, skewed, and complex, which are based on mathematical calculations which are typically not within the grasp of medical personnel. Type X questions has many advantages being easy to construct, can test multiple concepts/application/facets of a topic, cognitive skill of various level of hierarchy can be tested, and unlike Type K items, they are free from complicated coding. In spite of these advantages, they are not in common use due to complicated marking schemes. This is the reason we explored the aspects of methods of evaluation of multiple correct options multiple choice questions and came up with the simple, practically applicable, nonstringent but logical scoring system for the same. The rationale of the illustrated marking scheme is that it takes into consideration the distracter recognition ability of the examinee rather than relying on the ability only to select the correct response. Thus, examinee's true knowledge is tested, and he is rewarded accordingly for selecting a correct answer and omitting a distracter. The scheme also penalizes for not recognizing a distracter thus controlling guessing behavior. It is emphasized that if the illustrated scoring scheme is adopted, then Type X questions would come in common practice. PMID:27127312

  20. Contemplation on marking scheme for Type X multiple choice questions, and an illustration of a practically applicable scheme.

    PubMed

    Siddiqui, Nazeem Ishrat; Bhavsar, Vinayak H; Bhavsar, Arnav V; Bose, Sukhwant

    2016-01-01

    Ever since its inception 100 years back, multiple choice items have been widely used as a method of assessment. It has certain inherent limitations such as inability to test higher cognitive skills, element of guesswork while answering, and issues related with marking schemes. Various marking schemes have been proposed in the past but they are not balanced, skewed, and complex, which are based on mathematical calculations which are typically not within the grasp of medical personnel. Type X questions has many advantages being easy to construct, can test multiple concepts/application/facets of a topic, cognitive skill of various level of hierarchy can be tested, and unlike Type K items, they are free from complicated coding. In spite of these advantages, they are not in common use due to complicated marking schemes. This is the reason we explored the aspects of methods of evaluation of multiple correct options multiple choice questions and came up with the simple, practically applicable, nonstringent but logical scoring system for the same. The rationale of the illustrated marking scheme is that it takes into consideration the distracter recognition ability of the examinee rather than relying on the ability only to select the correct response. Thus, examinee's true knowledge is tested, and he is rewarded accordingly for selecting a correct answer and omitting a distracter. The scheme also penalizes for not recognizing a distracter thus controlling guessing behavior. It is emphasized that if the illustrated scoring scheme is adopted, then Type X questions would come in common practice.

  1. Spread-spectrum multiple access using wideband noncoherent MFSK

    NASA Technical Reports Server (NTRS)

    Ha, Tri T.; Pratt, Timothy; Maggenti, Mark A.

    1987-01-01

    Two spread-spectrum multiple access systems which use wideband M-ary frequency shift keying (FSK) (MFSK) as the primary modulation are presented. A bit error rate performance analysis is presented and system throughput is calculated for sample C band and Ku band satellite systems. Sample link analyses are included to illustrate power and adjacent satellite interference considerations in practical multiple access systems.

  2. A novel protection scheme for Ethernet PON FTTH access network

    NASA Astrophysics Data System (ADS)

    P'ng, W. T.; Abdullah, M. K.; Khatun, S.; Ahmad-Anas, S. B.; Shaari, S.

    2008-03-01

    Massive deployment of FTTH fiber network causes protection to FTTH network a crucial need. Most FTTH access networks are protected from failure by having redundant network equipments. These are not economical approaches, as the redundant systems are not efficiently utilized by the network. In this paper, the authors propose a protection method where redundant equipments are not required and protection is provided to end user through sharing of bandwidth during the failure time. A protection control unit and an optical switch is employed connecting four Optical Line Terminations (OLTs) with each one serving only 32 Optical Network Units (ONUs). Protection control unit collects information of ONUs served by each OLT and when an OLT fails, it will instruct an active OLT to serve its original ONUs together with the ONUs served by the failed OLT. It also provides information of ONUs served and inform the involved 64 ONUs of their new timeslot allocation. Then, the signal is switched from failed OLT's line to the instructed active OLT. The results show that through sharing of bandwidth, adequate protection is provided without redundant equipment for more than one OLT failure.

  3. Assessment methodology of protection schemes for next generation optical access networks

    NASA Astrophysics Data System (ADS)

    Mas Machuca, Carmen; Wosinska, Lena; Chen, Jiajia

    2015-12-01

    Optical access networks are evolving towards next generation solutions offering much higher bandwidth per end point. Moreover, the uninterrupted access to the network services is becoming crucial and therefore operators are now considering protecting their access networks. However, the cost factor is still very important due to the relatively low cost sharing in access segment. For this purpose, this paper proposes an assessment methodology that can be used to compare different protection schemes and help to identify the suitable solution for a given scenario. The assessment criteria includes some reliability measures such as Failure Impact Factor (FIF) and connection availability, as well as cost parameters such as the investment required in greenfield and brownfield scenarios and the increase in power consumption compared to the unprotected network. The proposed criteria have been used to compare 7 representative protection schemes shown in literature, which differ mainly in the number of protected network elements and the technology used for protection (fiber, wireless, etc.). The considered protection schemes have been applied to a hybrid wavelength division multiplexing/time division multiplexing Passive Optical Network (Hybrid PON) architecture in an urban area. It has been shown that it is difficult to identify the absolute best scheme with respect to all the considered criteria. However, depending on the requirements from the operator regarding the targeted reliability performance in the network, an appropriate protection scheme can be recommended for either a greenfield or a brownfield scenario.

  4. Subcarrier multiplexing multiple-input multiple-output quantum key distribution scheme with orthogonal quantum states

    NASA Astrophysics Data System (ADS)

    Xiao, Hailin; Zhang, Zhongshan

    2017-01-01

    Quantum key distribution (QKD) system is presently being developed for providing high-security transmission in future free-space optical communication links. However, current QKD technique restricts quantum secure communication to a low bit rate. To improve the QKD bit rate, we propose a subcarrier multiplexing multiple-input multiple-output quantum key distribution (SCM-MQKD) scheme with orthogonal quantum states. Specifically, we firstly present SCM-MQKD system model and drive symmetrical SCM-MQKD system into decoherence-free subspaces. We then utilize bipartite Werner and isotropic states to construct multiple parallel single photon with orthogonal quantum states that are invariant for unitary operations. Finally, we derive the density matrix and the capacity of SCM-MQKD system, respectively. Theoretical analysis and numerical results show that the capacity of SCM-MQKD system will increase {log _2}(N^2+1) times than that of single-photon QKD system.

  5. An efficient key-management scheme for hierarchical access control in e-medicine system.

    PubMed

    Wu, Shuhua; Chen, Kefei

    2012-08-01

    In e-medicine system, the sharing of patients' medical histories scattered among medical institutions through the Internet is highly desirable. The most immediate cryptographic need certainly is an efficient key management method to solve dynamic access problems in a user hierarchy. In this paper, we propose a practical solution for dynamic access problem in a user hierarchy based on hybrid cryptosystems. When compared with Nikooghadam et al.'s scheme proposed most recently, the time complexity and the required storage space is reduced significantly. Moreover, it provides provable security, and is easy to implement. Therefore, our scheme is more suitable for e-medicine system.

  6. Parallel implementation of WRF double moment 5-class cloud microphysics scheme on multiple GPUs

    NASA Astrophysics Data System (ADS)

    Huang, Melin; Huang, Bormin; Huang, Allen H.-L.

    2015-05-01

    The Weather Research and Forecast (WRF) Double Moment 5-class (WDM5) mixed ice microphysics scheme predicts the mixing ratio of hydrometeors and their number concentrations for warm rain species including clouds and rain. WDM5 can be computed in parallel in the horizontal domain using multi-core GPUs. In order to obtain a better GPU performance, we manually rewrite the original WDM5 Fortran module into a highly parallel CUDA C program. We explore the usage of coalesced memory access and asynchronous data transfer. Our GPU-based WDM5 module is scalable to run on multiple GPUs. By employing one NVIDIA Tesla K40 GPU, our GPU optimization effort on this scheme achieves a speedup of 252x with respect to its CPU counterpart Fortran code running on one CPU core of Intel Xeon E5-2603, whereas the speedup for one CPU socket (4 cores) with respect to one CPU core is only 4.2x. We can even boost the speedup of this scheme to 468x with respect to one CPU core when two NVIDIA Tesla K40 GPUs are applied.

  7. An EMI-aware prioritized wireless access scheme for e-Health applications in hospital environments.

    PubMed

    Phunchongharn, Phond; Niyato, Dusit; Hossain, Ekram; Camorlinga, Sergio

    2010-09-01

    Wireless communications technologies can support efficient healthcare services in medical and patient-care environments. However, using wireless communications in a healthcare environment raises two crucial issues. First, the RF transmission can cause electromagnetic interference (EMI) to biomedical devices, which could critically malfunction. Second, the different types of electronic health (e-Health) applications require different quality of service (QoS). In this paper, we introduce an innovative wireless access scheme, called EMI-aware prioritized wireless access, to address these issues. First, the system architecture for the proposed scheme is introduced. Then, an EMI-aware handshaking protocol is proposed for e-Health applications in a hospital environment. This protocol provides safety to the biomedical devices from harmful interference by adapting transmit power of wireless devices based on the EMI constraints. A prioritized wireless access scheme is proposed for channel access by two different types of applications with different priorities. A Markov chain model is presented to study the queuing behavior of the proposed system. Then, this queuing model is used to optimize the performance of the system given the QoS requirements. Finally, the performance of the proposed wireless access scheme is evaluated through extensive simulations.

  8. Poll-before-Data Multiple Access

    DTIC Science & Technology

    1999-01-01

    MACA [6], MACAW [1], IEEE 802.11 [5], and FAMA [2], [4] are just a few examples. All of these MAC protocols, and most protocols based on collision...Shenker and L. Zhang, “ MACAW : A Media Access Protocol for Wireless LAN’s” Proc. ACM SIGCOMM 94, London, UK, Aug. 31 - Sep. 2, 1994. [2] C. L. Fullmer and

  9. Simulation and Modeling of a New Medium Access Control Scheme for Multi-Beam Directional Networking

    DTIC Science & Technology

    2017-03-03

    Simulation and Modeling of a New Medium Access Control Scheme for Multi-Beam Directional Networking Brian Proulx, Greg Kuperman, Nathaniel M. Jones...paper, we analyze a new medium access control (MAC) protocol for multi-beam directional network via high- fidelity simulation using a real-time emulator...implement our protocol in both simula- tion and a new Extendable Mobile Ad-hoc Network Emula- tor (EMANE) model that allows for real-time, high fidelity

  10. 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.

  11. One electron-controlled multiple-valued dynamic random-access-memory

    NASA Astrophysics Data System (ADS)

    Kye, H. W.; Song, B. N.; Lee, S. E.; Kim, J. S.; Shin, S. J.; Choi, J. B.; Yu, Y.-S.; Takahashi, Y.

    2016-02-01

    We propose a new architecture for a dynamic random-access-memory (DRAM) capable of storing multiple values by using a single-electron transistor (SET). The gate of a SET is designed to be connected to a plurality of DRAM unit cells that are arrayed at intersections of word lines and bitlines. In this SET-DRAM hybrid scheme, the multiple switching characteristics of SET enables multiple value data stored in a DRAM unit cell, and this increases the storage functionality of the device. Moreover, since refreshing data requires only a small amount of SET driving current, this enables device operating with low standby power consumption.

  12. Design of pulse waveform for waveform division multiple access UWB wireless communication system.

    PubMed

    Yin, Zhendong; Wang, Zhirui; Liu, Xiaohui; Wu, Zhilu

    2014-01-01

    A new multiple access scheme, Waveform Division Multiple Access (WDMA) based on the orthogonal wavelet function, is presented. After studying the correlation properties of different categories of single wavelet functions, the one with the best correlation property will be chosen as the foundation for combined waveform. In the communication system, each user is assigned to different combined orthogonal waveform. Demonstrated by simulation, combined waveform is more suitable than single wavelet function to be a communication medium in WDMA system. Due to the excellent orthogonality, the bit error rate (BER) of multiuser with combined waveforms is so close to that of single user in a synchronous system. That is to say, the multiple access interference (MAI) is almost eliminated. Furthermore, even in an asynchronous system without multiuser detection after matched filters, the result is still pretty ideal and satisfactory by using the third combination mode that will be mentioned in the study.

  13. The Policy Problem: The National Disability Insurance Scheme (NDIS) and Implications for Access to Education

    ERIC Educational Resources Information Center

    Whitburn, Ben; Moss, Julianne; O'Mara, Jo

    2017-01-01

    This paper explores the changing terrain of disability support policy in Australia. Drawing on a critical disability framework of policy sociology, the paper considers the policy problem of access to education for people with disabilities under recent reform by means of the National Disability Insurance Scheme (NDIS), which commenced full roll-out…

  14. Promoting Mathematics Accessibility through Multiple Representations Jigsaws

    ERIC Educational Resources Information Center

    Cleaves, Wendy Pelletier

    2008-01-01

    The ability to examine problems using varied approaches is one of the most important characteristics of good problem solvers. Other characteristics include independence, flexibility in thinking, determination, and a willingness to take risks. By using multiple representations, students are being asked to show the same information in varied ways.…

  15. Promoting Mathematics Accessibility through Multiple Representations Jigsaws

    ERIC Educational Resources Information Center

    Cleaves, Wendy Pelletier

    2008-01-01

    The ability to examine problems using varied approaches is one of the most important characteristics of good problem solvers. Other characteristics include independence, flexibility in thinking, determination, and a willingness to take risks. By using multiple representations, students are being asked to show the same information in varied ways.…

  16. Robust multiple frequency multiple power localization schemes in the presence of multiple jamming attacks

    PubMed Central

    2017-01-01

    Localization of the wireless sensor network is a vital area acquiring an impressive research concern and called upon to expand more with the rising of its applications. As localization is gaining prominence in wireless sensor network, it is vulnerable to jamming attacks. Jamming attacks disrupt communication opportunity among the sender and receiver and deeply impact the localization process, leading to a huge error of the estimated sensor node position. Therefore, detection and elimination of jamming influence are absolutely indispensable. Range-based techniques especially Received Signal Strength (RSS) is facing severe impact of these attacks. This paper proposes algorithms based on Combination Multiple Frequency Multiple Power Localization (C-MFMPL) and Step Function Multiple Frequency Multiple Power Localization (SF-MFMPL). The algorithms have been tested in the presence of multiple types of jamming attacks including capture and replay, random and constant jammers over a log normal shadow fading propagation model. In order to overcome the impact of random and constant jammers, the proposed method uses two sets of frequencies shared by the implemented anchor nodes to obtain the averaged RSS readings all over the transmitted frequencies successfully. In addition, three stages of filters have been used to cope with the replayed beacons caused by the capture and replay jammers. In this paper the localization performance of the proposed algorithms for the ideal case which is defined by without the existence of the jamming attack are compared with the case of jamming attacks. The main contribution of this paper is to achieve robust localization performance in the presence of multiple jamming attacks under log normal shadow fading environment with a different simulation conditions and scenarios. PMID:28493977

  17. Multiple-watermarking scheme based on improved chaotic maps

    NASA Astrophysics Data System (ADS)

    Behnia, S.; Teshnehlab, M.; Ayubi, P.

    2010-09-01

    In this letter a new watermarking scheme for color image is proposed based on a family of the pair-coupled maps. Pair-coupled maps are employed to improve the security of watermarked image, and to encrypt the embedding position of the host image. Another map is also used to determine the pixel bit of host image for the watermark embedding. The purpose of this algorithm is to improve the shortcoming of watermarking such as small key space and low security. Due to the sensitivity to the initial conditions of the introduced pair-coupled maps, the security of the scheme is greatly improved.

  18. Detectability models and waveform design for multiple access Low-Probability-of-Intercept networks

    NASA Astrophysics Data System (ADS)

    Mills, Robert F.

    1994-04-01

    Increased connectivity demands in the tactical battlefield have led to the development of multiple access low probability-of-intercept (LPI) communication networks. Most detectability studies of LPI networks have focused on the individual network links, in which detectability calculations are carried out for a single network emitter. This report, however, presents a different approach to network detectability analysis: it is assumed that the interceptor does not attempt to distinguish one emitter from another, but rather decides only if a network is operating or not. What distinguishes this approach from conventional link intercept analysis is that detection decisions are based on energy received from multiple sources. The following multiple access schemes are considered: frequency division, time division, direct sequence code division, and frequency hop code division. The wideband radiometer and its hybrids, such as the channelized radiometer, are used as potential network intercept receivers.

  19. Molecular Code Division Multiple Access: Gaussian Mixture Modeling

    NASA Astrophysics Data System (ADS)

    Zamiri-Jafarian, Yeganeh

    Communications between nano-devices is an emerging research field in nanotechnology. Molecular Communication (MC), which is a bio-inspired paradigm, is a promising technique for communication in nano-network. In MC, molecules are administered to exchange information among nano-devices. Due to the nature of molecular signals, traditional communication methods can't be directly applied to the MC framework. The objective of this thesis is to present novel diffusion-based MC methods when multi nano-devices communicate with each other in the same environment. A new channel model and detection technique, along with a molecular-based access method, are proposed in here for communication between asynchronous users. In this work, the received molecular signal is modeled as a Gaussian mixture distribution when the MC system undergoes Brownian noise and inter-symbol interference (ISI). This novel approach demonstrates a suitable modeling for diffusion-based MC system. Using the proposed Gaussian mixture model, a simple receiver is designed by minimizing the error probability. To determine an optimum detection threshold, an iterative algorithm is derived which minimizes a linear approximation of the error probability function. Also, a memory-based receiver is proposed to improve the performance of the MC system by considering previously detected symbols in obtaining the threshold value. Numerical evaluations reveal that theoretical analysis of the bit error rate (BER) performance based on the Gaussian mixture model match simulation results very closely. Furthermore, in this thesis, molecular code division multiple access (MCDMA) is proposed to overcome the inter-user interference (IUI) caused by asynchronous users communicating in a shared propagation environment. Based on the selected molecular codes, a chip detection scheme with an adaptable threshold value is developed for the MCDMA system when the proposed Gaussian mixture model is considered. Results indicate that the

  20. A Secure and Verifiable Outsourced Access Control Scheme in Fog-Cloud Computing.

    PubMed

    Fan, Kai; Wang, Junxiong; Wang, Xin; Li, Hui; Yang, Yintang

    2017-07-24

    With the rapid development of big data and Internet of things (IOT), the number of networking devices and data volume are increasing dramatically. Fog computing, which extends cloud computing to the edge of the network can effectively solve the bottleneck problems of data transmission and data storage. However, security and privacy challenges are also arising in the fog-cloud computing environment. Ciphertext-policy attribute-based encryption (CP-ABE) can be adopted to realize data access control in fog-cloud computing systems. In this paper, we propose a verifiable outsourced multi-authority access control scheme, named VO-MAACS. In our construction, most encryption and decryption computations are outsourced to fog devices and the computation results can be verified by using our verification method. Meanwhile, to address the revocation issue, we design an efficient user and attribute revocation method for it. Finally, analysis and simulation results show that our scheme is both secure and highly efficient.

  1. A Secure and Verifiable Outsourced Access Control Scheme in Fog-Cloud Computing

    PubMed Central

    Fan, Kai; Wang, Junxiong; Wang, Xin; Li, Hui; Yang, Yintang

    2017-01-01

    With the rapid development of big data and Internet of things (IOT), the number of networking devices and data volume are increasing dramatically. Fog computing, which extends cloud computing to the edge of the network can effectively solve the bottleneck problems of data transmission and data storage. However, security and privacy challenges are also arising in the fog-cloud computing environment. Ciphertext-policy attribute-based encryption (CP-ABE) can be adopted to realize data access control in fog-cloud computing systems. In this paper, we propose a verifiable outsourced multi-authority access control scheme, named VO-MAACS. In our construction, most encryption and decryption computations are outsourced to fog devices and the computation results can be verified by using our verification method. Meanwhile, to address the revocation issue, we design an efficient user and attribute revocation method for it. Finally, analysis and simulation results show that our scheme is both secure and highly efficient. PMID:28737733

  2. 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).

  3. 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.

  4. Cooperative Interference Alignment for the Multiple Access Channel

    DTIC Science & Technology

    2015-11-01

    1 Cooperative Interference Alignment for the Multiple Access Channel Theodoros Tsiligkaridis, Member, IEEE Abstract—Interference alignment (IA) has...resources for large number of users. To combat these problems, we propose a novel technique for the K-user multiple access (MAC) channel with N receivers...called Cooperative Interference Alignment (C-IA) and derive bounds on the DoF for each user. Assuming K 2 ≤ N ≤ K, we show that C-IA is sum-DoF optimal

  5. Access to Treatment for Diabetes and Hypertension in Rural Cambodia: Performance of Existing Social Health Protection Schemes

    PubMed Central

    Bigdeli, Maryam; Jacobs, Bart; Men, Chean Rithy; Nilsen, Kristine; Van Damme, Wim

    2016-01-01

    Background Non-communicable diseases (NCD) pose challenges to Cambodia’s health system. Medicines for NCD are on the National Essential Medicines List but no clinical guidelines support their utilization. Two social health protection schemes aimed at the informal sector population exist (Health Equity Funds and Insurance) together with two disease-specific interventions (a Peer Educator Network and Chronic Diseases Clinics) targeted at NCD patients. This study examines performance of these various schemes in relation to NCD. Methods Cross-sectional household survey among 709 individuals self-reporting diabetes and/or hypertension in three geographical locations in rural Cambodia using a structured questionnaire investigating diagnostic and treatment pathways, health seeking behaviour, health expenditures, and financial coping mechanisms. Results Two third of respondents with NCD were female and 55% did not belong to any scheme. The majority (59%) were diagnosed in the private sector and only 56% were on allopathic treatment that was mainly sought in the private sector (49%). Outpatient treatment cost was higher in the private sector and when using multiple providers of care. The majority were indebted, 11% due to health-related expenses. Contrary to social health protection schemes, disease-specific interventions offered better access to allopathic treatment and provided medicines in accordance with NEML. Conclusion The benefit packages of existing social health protection schemes and services in the public health sector should be adjusted to cater for the needs of people living with NCD in rural Cambodia. Initiatives that offer active disease management strategies and promote patients and community participation appear more successful in increasing treatment adherence and decreasing the risk of financial hardship. PMID:26815916

  6. Access to Treatment for Diabetes and Hypertension in Rural Cambodia: Performance of Existing Social Health Protection Schemes.

    PubMed

    Bigdeli, Maryam; Jacobs, Bart; Men, Chean Rithy; Nilsen, Kristine; Van Damme, Wim; Dujardin, Bruno

    2016-01-01

    Non-communicable diseases (NCD) pose challenges to Cambodia's health system. Medicines for NCD are on the National Essential Medicines List but no clinical guidelines support their utilization. Two social health protection schemes aimed at the informal sector population exist (Health Equity Funds and Insurance) together with two disease-specific interventions (a Peer Educator Network and Chronic Diseases Clinics) targeted at NCD patients. This study examines performance of these various schemes in relation to NCD. Cross-sectional household survey among 709 individuals self-reporting diabetes and/or hypertension in three geographical locations in rural Cambodia using a structured questionnaire investigating diagnostic and treatment pathways, health seeking behaviour, health expenditures, and financial coping mechanisms. Two third of respondents with NCD were female and 55% did not belong to any scheme. The majority (59%) were diagnosed in the private sector and only 56% were on allopathic treatment that was mainly sought in the private sector (49%). Outpatient treatment cost was higher in the private sector and when using multiple providers of care. The majority were indebted, 11% due to health-related expenses. Contrary to social health protection schemes, disease-specific interventions offered better access to allopathic treatment and provided medicines in accordance with NEML. The benefit packages of existing social health protection schemes and services in the public health sector should be adjusted to cater for the needs of people living with NCD in rural Cambodia. Initiatives that offer active disease management strategies and promote patients and community participation appear more successful in increasing treatment adherence and decreasing the risk of financial hardship.

  7. Multiple-image encryption scheme based on cascaded fractional Fourier transform.

    PubMed

    Kong, Dezhao; Shen, Xueju; Xu, Qinzu; Xin, Wang; Guo, Haiqiong

    2013-04-20

    A multiple-image encryption scheme based on cascaded fractional Fourier transform is proposed. In the scheme, images are successively coded into the amplitude and phase of the input by cascading stages, which ends up with an encrypted image and a series of keys. The scheme takes full advantage of multikeys and the cascaded relationships of all stages, and it not only realizes image encryption but also achieves higher safety and more diverse applications. So multiuser authentication and hierarchical encryption are achieved. Numerical simulation verifies the feasibility of the method and demonstrates the security of the scheme and decryption characteristics. Finally, flexibility and variability of the scheme in application are discussed, and the simple photoelectric mixed devices to realize the scheme are proposed.

  8. Low Density Parity Check Code for the Single Carrier Frequency Division Multiple Access

    NASA Astrophysics Data System (ADS)

    Islam, Mohammad Rakibul; Kim, Jinsang

    A new encoding technique for low density parity check (LDPC) code at the uplink of 3rd Generation Partnership Project Long Term Evolution (3GPP LTE) is proposed. The concept of approximate lower triangulation (ALT) is used where the parity check matrix is preprocessed and encoded in O(n) complexity. This encoding technique is applied in the uplink of LTE system where single carrier frequency division multiple access (SC-FDMA) is used as the multiple access scheme. As the encoding is performed in a O(n) complexity, it will outperform the existing LDPC encoding which is not used in LTE uplink due to its high encoding complexity. The proposed encoding is simulated in the SCFDMA scenario and the BER curve is shown.

  9. High data rate modem simulation for the space station multiple-access communications system

    NASA Technical Reports Server (NTRS)

    Horan, Stephen

    1987-01-01

    The communications system for the space station will require a space based multiple access component to provide communications between the space based program elements and the station. A study was undertaken to investigate two of the concerns of this multiple access system, namely, the issues related to the frequency spectrum utilization and the possibilities for higher order (than QPSK) modulation schemes for use in possible modulators and demodulators (modems). As a result of the investigation, many key questions about the frequency spectrum utilization were raised. At this point, frequency spectrum utilization is seen as an area requiring further work. Simulations were conducted using a computer aided communications system design package to provide a straw man modem structure to be used for both QPSK and 8-PSK channels.

  10. A Temporal Credential-Based Mutual Authentication with Multiple-Password Scheme for Wireless Sensor Networks.

    PubMed

    Liu, Xin; Zhang, Ruisheng; Liu, Qidong

    2017-01-01

    Wireless sensor networks (WSNs), which consist of a large number of sensor nodes, have become among the most important technologies in numerous fields, such as environmental monitoring, military surveillance, control systems in nuclear reactors, vehicle safety systems, and medical monitoring. The most serious drawback for the widespread application of WSNs is the lack of security. Given the resource limitation of WSNs, traditional security schemes are unsuitable. Approaches toward withstanding related attacks with small overhead have thus recently been studied by many researchers. Numerous studies have focused on the authentication scheme for WSNs, but most of these works cannot achieve the security performance and overhead perfectly. Nam et al. proposed a two-factor authentication scheme with lightweight sensor computation for WSNs. In this paper, we review this scheme, emphasize its drawbacks, and propose a temporal credential-based mutual authentication with a multiple-password scheme for WSNs. Our scheme uses multiple passwords to achieve three-factor security performance and generate a session key between user and sensor nodes. The security analysis phase shows that our scheme can withstand related attacks, including a lost password threat, and the comparison phase shows that our scheme involves a relatively small overhead. In the comparison of the overhead phase, the result indicates that more than 95% of the overhead is composed of communication and not computation overhead. Therefore, the result motivates us to pay further attention to communication overhead than computation overhead in future research.

  11. A Temporal Credential-Based Mutual Authentication with Multiple-Password Scheme for Wireless Sensor Networks

    PubMed Central

    Zhang, Ruisheng; Liu, Qidong

    2017-01-01

    Wireless sensor networks (WSNs), which consist of a large number of sensor nodes, have become among the most important technologies in numerous fields, such as environmental monitoring, military surveillance, control systems in nuclear reactors, vehicle safety systems, and medical monitoring. The most serious drawback for the widespread application of WSNs is the lack of security. Given the resource limitation of WSNs, traditional security schemes are unsuitable. Approaches toward withstanding related attacks with small overhead have thus recently been studied by many researchers. Numerous studies have focused on the authentication scheme for WSNs, but most of these works cannot achieve the security performance and overhead perfectly. Nam et al. proposed a two-factor authentication scheme with lightweight sensor computation for WSNs. In this paper, we review this scheme, emphasize its drawbacks, and propose a temporal credential-based mutual authentication with a multiple-password scheme for WSNs. Our scheme uses multiple passwords to achieve three-factor security performance and generate a session key between user and sensor nodes. The security analysis phase shows that our scheme can withstand related attacks, including a lost password threat, and the comparison phase shows that our scheme involves a relatively small overhead. In the comparison of the overhead phase, the result indicates that more than 95% of the overhead is composed of communication and not computation overhead. Therefore, the result motivates us to pay further attention to communication overhead than computation overhead in future research. PMID:28135288

  12. [Innovative patient access schemes for the adoption of new technology: risk-sharing agreements].

    PubMed

    Espín, Jaime; Oliva, Juan; Rodríguez-Barrios, José Manuel

    2010-01-01

    The incorporation of new treatments, procedures and technologies into the services' portfolio of healthcare providers should aim to improve three areas equally: patient access to innovative solutions, the sustainability of the health system and compensation for innovation. However, traditional schemes based on fixed prices that fail to consider the product's appropriate use or its results in terms of effectiveness may lead to inefficient decision-making processes. Recently, risk-sharing agreements have appeared as new access schemes based on results that aim to reduce the uncertainty of the distinct health care players involved in reaching an agreement on new health technology financing and conditions of use. Key elements in the debate on these instruments are the huge variety of instruments available (especially those based on results), the implications for different players involved in their design and supervision, and their possible implementation in Spain. Our main conclusion is that risk-sharing agreements should be used in highly limited cases when standard conditions of access cannot be applied due to uncertainty about long-term effectiveness. These measures are aimed not only at regulating price but also at acting on the appropriate use of new technology. However, because international experience is limited, drawing a solid conclusion on the final results of the application of risk-sharing agreements would be premature. Copyright © 2010 SESPAS. Published by Elsevier Espana. All rights reserved.

  13. Design and Performance Analysis of an ARQ Scheme for Broadband Wireless Access

    NASA Astrophysics Data System (ADS)

    Gürbüz, Özgür

    This paper presents design and analysis of an Automatic Repeat reQuest (ARQ) scheme for enhancing the throughput and reliability of broadband wireless access systems. The impact of ARQ is emphasized in terms of early error recovery, when Internet data applications and the TCP protocol are considered over a point-to-multipoint fixed wireless system. A selective repeat type ARQ scheme is designed and analyzed through extensive, realistic modeling and simulation of the entire network protocol stack and the wireless channel. The system-wide impact of ARQ design is quantified in terms of end-to-end delay, throughput and SNR gain and in all these metrics, significant performance improvement is observed. Enhanced features, namely, Segmentation and Reassembly (SAR) and Bitmap Compression, are proposed and shown to reduce the overhead costs.

  14. Analysis of an FBMC/OQAM scheme for asynchronous access in wireless communications

    NASA Astrophysics Data System (ADS)

    Mattera, Davide; Tanda, Mario; Bellanger, Maurice

    2015-12-01

    The OFDM/OQAM transceiver belongs to the filter-bank-based multicarrier (FBMC) family and, unlike OFDM schemes, it is particularly able to meet the requirements of the physical layer of cognitive radio networks such as high level of adjacent channel leakage ratio and asynchronous communications. The paper proposes and analyzes a new implementation structure, named frequency spreading, for the OFDM/OQAM transceiver. On flat channels, it is equivalent to the standard one in terms of input-output relations, though more complex. On multipath channels, it offers a crucial advantage in terms of equalization, which is performed in the frequency domain, leading to high performance and no additional delay. With its flexibility and level of performance, the analyzed scheme has the potential to outperform OFDM in the asynchronous access context and in cognitive radio networks.

  15. Digital Image Encryption Scheme Based on Multiple Chaotic Systems

    NASA Astrophysics Data System (ADS)

    Abd El-Latif, Ahmed A.; Li, Li; Zhang, Tiejun; Wang, Ning; Song, Xianhua; Niu, Xiamu

    2012-06-01

    Image encryption is a challenging task due to the significant level of sophistication achieved by forgerers and other cybercriminals. Advanced encryption methods for secure transmission, storage, and retrieval of digital images are increasingly needed for a number of military, medical, homeland security, and other applications. In this paper, we introduce a new digital image encryption algorithm. The new algorithm employs multiple chaotic systems and cryptographic primitive operations within the encryption process, which are efficiently implemented on modern processors, and adopts round keys for encryption using a chaotic map. Experiments conducted show that the proposed algorithm possesses robust security features such as fairly uniform distribution, high sensitivity to both keys and plainimages, almost ideal entropy, and the ability to highly de-correlate adjacent pixels in the cipherimages. Furthermore, it has a large key space, which greatly increases its security for image encryption applications.

  16. Improvement of a quantum broadcasting multiple blind signature scheme based on quantum teleportation

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Qiu, Daowen; Zou, Xiangfu

    2016-06-01

    Recently, a broadcasting multiple blind signature scheme based on quantum teleportation has been proposed for the first time. It is claimed to have unconditional security and properties of quantum multiple signature and quantum blind signature. In this paper, we analyze the security of the protocol and show that each signatory can learn the signed message by a single-particle measurement and the signed message can be modified at random by any attacker according to the scheme. Furthermore, there are some participant attacks and external attacks existing in the scheme. Finally, we present an improved scheme and show that it can resist all of the mentioned attacks. Additionally, the secret keys can be used again and again, making it more efficient and practical.

  17. A multi-label image annotation scheme based on improved SVM multiple kernel learning

    NASA Astrophysics Data System (ADS)

    Jin, Cong; Jin, Shu-Wei

    2017-02-01

    Multi-label image annotation (MIA) has been widely studied during recent years and many MIA schemes have been proposed. However, the most existing schemes are not satisfactory. In this paper, an improved multiple kernel learning (IMKL) method of support vector machine (SVM) is proposed to improve the classification accuracy of SVM, then a novel MIA scheme based on IMKL is presented, which uses the discriminant loss to control the number of top semantic labels, and the feature selection approach is also used for improving the performance of MIA. The experiment results show that proposed MIA scheme achieves higher the performance than the existing other MIA schemes, its performance is satisfactory for large image dataset.

  18. The FODA-TDMA satellite access scheme - Presentation, study of the system, and results

    NASA Astrophysics Data System (ADS)

    Celandroni, Nedo; Ferro, Erina

    1991-12-01

    A description is given of FODA-TDMA, a satellite access scheme designed for mixed traffic. The study of the system is presented and the choice of some parameters is justified. A simplified analytic solution is found, describing the steady-state behavior of the system. Some results of the simulation tests for an already existing hardware environment are also presented for the channel speeds of 2 and 8 Mb/s, considering both the stationary and the transient cases. The results of the experimentation at 2 Mb/s on the satellite Eutelsat-F2 are also presented and compared with the results of the simulation.

  19. A novel interacting multiple model based network intrusion detection scheme

    NASA Astrophysics Data System (ADS)

    Xin, Ruichi; Venkatasubramanian, Vijay; Leung, Henry

    2006-04-01

    In today's information age, information and network security are of primary importance to any organization. Network intrusion is a serious threat to security of computers and data networks. In internet protocol (IP) based network, intrusions originate in different kinds of packets/messages contained in the open system interconnection (OSI) layer 3 or higher layers. Network intrusion detection and prevention systems observe the layer 3 packets (or layer 4 to 7 messages) to screen for intrusions and security threats. Signature based methods use a pre-existing database that document intrusion patterns as perceived in the layer 3 to 7 protocol traffics and match the incoming traffic for potential intrusion attacks. Alternately, network traffic data can be modeled and any huge anomaly from the established traffic pattern can be detected as network intrusion. The latter method, also known as anomaly based detection is gaining popularity for its versatility in learning new patterns and discovering new attacks. It is apparent that for a reliable performance, an accurate model of the network data needs to be established. In this paper, we illustrate using collected data that network traffic is seldom stationary. We propose the use of multiple models to accurately represent the traffic data. The improvement in reliability of the proposed model is verified by measuring the detection and false alarm rates on several datasets.

  20. Control packet signaling mechanism using electronic code division multiple access for packet-based networks

    NASA Astrophysics Data System (ADS)

    Nadarajah, Nishaanthan

    2008-10-01

    We propose and experimentally demonstrate the feasibility of a control packet signaling technique using electronic code division multiple access for a wavelength division multiplexing packet-based network, whereby each wavelength channel is assigned a unique electronic code based label on a radio frequency subcarrier. Such a technique allows each wavelength channel to be electronically identified without requiring the use of a WDM demultiplexer. We experimentally demonstrate this technique with two wavelength channels each with 1.25 Gb/s baseband payload data and 10 Mb/s header coded onto an electronic code at 160 Mb/s. A performance study of the electronic code division multiple access based control signaling scheme in a wavelength division multiplexed packet-based access network is also performed in terms of the required power budget to monitor the electronic code division multiple access control signals in the presence of several sources of noise for error-free transmission of both payload data and electronic code division multiple access based control signals. It is shown that the modulation depth of each signal impacts the amount of required optical tap power. As the modulation depth of the electronic code division multiple access based control signal is increased, the required optical tap power is reduced. However, this increases the bit-error-rate for the payload data. Therefore, there lies a maximum and a minimum of the required tap optical power for the successful recovery of both signals. The lower bound of this range is usually determined by the successful recovery of electronic code division multiple access based control signal while the upper bound is determined by the successful recovery of payload data. The required optical tap power is analyzed for different transmission bit rates of the payload data for various receiver architecture scenarios without an optical amplifier at the receiver. The scalability analyses were repeated with an optical

  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. A Comparative Study of Multiplexing Schemes for Next Generation Optical Access Networks

    NASA Astrophysics Data System (ADS)

    Imtiaz, Waqas A.; Khan, Yousaf; Shah, Pir Mehar Ali; Zeeshan, M.

    2014-09-01

    Passive optical network (PON) is a high bandwidth, economical solution which can provide the necessary bandwidth to end-users. Wavelength division multiplexed passive optical networks (WDM PONs) and time division multiplexed passive optical networks (TDM PONs) are considered as an evolutionary step for next-generation optical access (NGOA) networks. However they fail to provide highest transmission capacity, efficient bandwidth access, and robust dispersion tolerance. Thus future PONs are considered on simpler, efficient and potentially scalable, optical code division multiplexed (OCDM) PONs. This paper compares the performance of existing PONs with OCDM PON to determine a suitable scheme for NGOA networks. Two system parameter are used in this paper: fiber length, and bit rate. Performance analysis using Optisystem shows that; for a sufficient system performance parameters i.e. bit error rate (BER) ≤ 10-9, and maximum quality factor (Q) ≥ 6, OCDMA PON efficiently performs upto 50 km with 10 Gbit/s per ONU.

  3. Isolated user security enhancement in optical code division multiple access network against eavesdropping

    NASA Astrophysics Data System (ADS)

    Jyoti, Vishav; Kaler, Rajinder Singh

    2012-09-01

    A novel virtual user system is modeled for enhancing the security of an optical code division multiple access (OCDMA) network. Although the OCDMA system implementing code shift keying (CSK) is secure against a conventional power detector, it is susceptible to differential eavesdropping. An analytical framework is developed for the CSK-OCDMA system to show eavesdropper's code interception performance for a single transmitting user in the presence of a virtual user. It is shown that the eavesdropper's probability of correct bit interception decreases from 7.1×10-1 to 1.85×10-5 with the inclusion of the virtual user. Furthermore, the results confirm that the proposed virtual user scheme increases the confidentiality of the CSK-OCDMA system and outperforms the conventional OCDMA scheme in terms of security.

  4. 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.

  5. Unifications and extensions of the multiple access communications problem

    NASA Astrophysics Data System (ADS)

    Molle, M. L.

    1981-08-01

    Multiple access protocols permit a broadcast communications channel to be shared by a large number of stations under distributed control. It is assumed that only one message at a time can be transmitted successfully over the common channel. A local optimality condition for synchronous multiple access protocols was derived and it is shown that many known protocols are special cases of this condition. A survey of much of the recent work on infinite population tree algorithms that use the history of channel activity to carry out short-range dynamic scheduling is included. An approach is presented for deriving upper bounds on the maximum stable throughput with finite average delay for infinite population protocols.

  6. 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.

  7. Code division multiple access signaling for modulated reflector technology

    DOEpatents

    Briles, Scott D [Los Alamos, NM

    2012-05-01

    A method and apparatus for utilizing code division multiple access in modulated reflectance transmissions comprises the steps of generating a phase-modulated reflectance data bit stream; modifying the modulated reflectance data bit stream; providing the modified modulated reflectance data bit stream to a switch that connects an antenna to an infinite impedance in the event a "+1" is to be sent, or connects the antenna to ground in the event a "0" or a "-1" is to be sent.

  8. Next generation communications satellites: Multiple access and network studies

    NASA Technical Reports Server (NTRS)

    Stern, T. E.; Schwartz, M.; Meadows, H. E.; Ahmadi, H. K.; Gadre, J. G.; Gopal, I. S.; Matsmo, K.

    1980-01-01

    Following an overview of issues involved in the choice of promising system architectures for efficient communication with multiple small inexpensive Earth stations serving hetergeneous user populations, performance evaluation via analysis and simulation for six SS/TDMA (satellite-switched/time-division multiple access) system architectures is discussed. These configurations are chosen to exemplify the essential alternatives available in system design. Although the performance evaluation analyses are of fairly general applicability, whenever possible they are considered in the context of NASA's 30/20 GHz studies. Packet switched systems are considered, with the assumption that only a part of transponder capacit is devoted to packets, the integration of circuit and packet switched traffic being reserved for further study. Three types of station access are distinguished: fixed (FA), demand (DA), and random access (RA). Similarly, switching in the satellite can be assigned on a fixed (FS) or demand (DS) basis, or replaced by a buffered store-and-forward system (SF) onboard the satellite. Since not all access/switching combinations are practical, six systems are analyzed in detail: three FS SYSTEMS, FA/FS, DA/ES, RA/FS; one DS system, DA/DS; and two SF systems, FA/SF, DA/SF. Results are presented primarily in terms of delay-throughput characteristics.

  9. Multitasking for flows about multiple body configurations using the chimera grid scheme

    NASA Technical Reports Server (NTRS)

    Dougherty, F. C.; Morgan, R. L.

    1987-01-01

    The multitasking of a finite-difference scheme using multiple overset meshes is described. In this chimera, or multiple overset mesh approach, a multiple body configuration is mapped using a major grid about the main component of the configuration, with minor overset meshes used to map each additional component. This type of code is well suited to multitasking. Both steady and unsteady two dimensional computations are run on parallel processors on a CRAY-X/MP 48, usually with one mesh per processor. Flow field results are compared with single processor results to demonstrate the feasibility of running multiple mesh codes on parallel processors and to show the increase in efficiency.

  10. Multitasking for flows about multiple body configurations using the chimera grid scheme

    NASA Technical Reports Server (NTRS)

    Dougherty, F. C.; Morgan, R. L.

    1987-01-01

    The multitasking of a finite-difference scheme using multiple overset meshes is described. In this chimera, or multiple overset mesh approach, a multiple body configuration is mapped using a major grid about the main component of the configuration, with minor overset meshes used to map each additional component. This type of code is well suited to multitasking. Both steady and unsteady two dimensional computations are run on parallel processors on a CRAY-X/MP 48, usually with one mesh per processor. Flow field results are compared with single processor results to demonstrate the feasibility of running multiple mesh codes on parallel processors and to show the increase in efficiency.

  11. Efficient storage scheme and algorithms for w-matrix vector multiplication on vector computers

    SciTech Connect

    Huang, H.S.; Lu, C.N. . Dept. of Electrical Engineering)

    1994-05-01

    The W-matrix method has been proposed in many literatures to exploit parallelism in the solution of many power system problems. This paper presents a storage scheme for storing the sparse W-matrix in solving linear equations on vector computers. Based on the proposed storage scheme, several efficient algorithms have been developed to perform the W-matrix vector multiplication for finding linear system solution. In this paper, attention is given to the issues of vector length, data movement between vector registers and memory, and the vector stride. The proposed storage scheme and algorithms are tested on Convex 3840 and Alliant FX/80 vector machines. It is shown that a speedup of two to four times is obtainable as compared to traditional scalar operation. The proposed storage scheme and algorithms can be applied to power system problems that require repeat solutions of linear system, such as load flow, contingency analysis, fast decoupled state estimation and short circuit calculations.

  12. 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

  13. Resident space object tracking using an interacting multiple model mixing scheme

    NASA Astrophysics Data System (ADS)

    Lam, Quang M.

    2014-06-01

    A multiple model estimation scheme is proposed to enhance the robustness of a resident space object (RSO) tracker subject to its maneuverability uncertainties (unplanned or unknown jet firing activities) and other system variations. The concept is based on the Interacting Multiple Model (IMM) estimation scheme. Within the IMM framework, two Extended Kalman Filter (EKF) models: (i) a 6 State (Position and Velocity of a constant orbiting RSO) EKF and (ii) a 9 state (Position, Velocity, and Acceleration of a maneuvering RSO) EKF are designed and implemented to achieve RSO maneuvering detection and enhanced tracking accuracy. The IMM estimation scheme is capable of providing enhanced state vector estimation accuracy and consistent prediction of the RSO maneuvering status, thus offering an attractive design feature for future Space Situational Awareness (SSA) missions. The design concept is illustrated using the Matlab/Based Simulation testing environment.

  14. Multiple-image encryption and authentication in interference-based scheme by aid of space multiplexing

    NASA Astrophysics Data System (ADS)

    Wang, Hongjuan; Qin, Yi; Huang, Yiding; Wang, Zhipeng; Zhang, Yingying

    2017-10-01

    Conventional interference-based encryption (IBE) scheme suffers from the silhouette problem, and its capacity is relatively low. In this paper, we introduce sparse representation and space multiplexing into the IBE scheme and propose a method for multiple-image encryption and authentication. We demonstrate, through space multiplexing, the information of multiple images can be encrypted into two phase only masks. The decrypted images are intended to be authenticated by nonlinear correlation rather than be observed by naked eyes, and because of that, the silhouette problem has been thoroughly suppressed. Moreover, the capacity of the IBE scheme is also extensively enhanced. The feasibility and effectiveness of the proposal have been demonstrated by numerical simulations.

  15. A Novel Multiple-Access Correlation-Delay-Shift-Keying

    NASA Astrophysics Data System (ADS)

    Duan, J. Y.; Jiang, G. P.; Yang, H.

    In Correlation-Delay-Shift-Keying (CDSK), the reference signal and the information-bearing signal are added together during a certain time delay. Because the reference signal is not strictly orthogonal to the information-bearing signal, the cross-correlation between the adjacent chaotic signal (Intra-signal Interference, ISI) will be introduced into the demodulation at the receiver. Therefore, the Bit-Error Ratio (BER) of CDSK is higher than that of Differential-Chaos-Shift-Keying (DCSK). To avoid the ISI component and enhance the BER performance of CDSK in multiuser scenario, Multiple-Access CDSK with No Intra-signal Interference (MA-CDSK-NII) is proposed. By constructing the repeated chaotic generator and applying the Walsh code sequence to modulate the reference signal, in MA-CDSK-NII, the ISI component will be eliminated during the demodulation. Gaussian approximation method is adopted here to obtain the exact performance analysis of MA-CDSK-NII over additive white Gaussian noise (AWGN) channel and Rayleigh multipath fading channels. Results show that, due to no ISI component and lower transmitting power, the BER performance of MA-CDSK-NII can be better than that of multiple-access CDSK and Code-Shifted Differential-Chaos-Shift-Keying (CS-DCSK).

  16. Chip-interleaved optical code division multiple access relying on a photon-counting iterative successive interference canceller for free-space optical channels.

    PubMed

    Zhou, Xiaolin; Zheng, Xiaowei; Zhang, Rong; Hanzo, Lajos

    2013-07-01

    In this paper, we design a novel Poisson photon-counting based iterative successive interference cancellation (SIC) scheme for transmission over free-space optical (FSO) channels in the presence of both multiple access interference (MAI) as well as Gamma-Gamma atmospheric turbulence fading, shot-noise and background light. Our simulation results demonstrate that the proposed scheme exhibits a strong MAI suppression capability. Importantly, an order of magnitude of BER improvements may be achieved compared to the conventional chip-level optical code-division multiple-access (OCDMA) photon-counting detector.

  17. Comparative performance study of one or multiple receivers schemes for FSO links over gamma-gamma turbulence channels

    NASA Astrophysics Data System (ADS)

    Stassinakis, Argyris N.; Nistazakis, Hector E.; Tombras, George S.

    2012-06-01

    Terrestrial free space optical telecommunication systems offer license-free very high bandwidth access characteristics with significantly low installation and operational cost. On the other hand, the performance of such a system depends strongly on the weather conditions in the area between the transmitter and the receiver due to the fact that the transmission media is the atmosphere. A very significant phenomenon which decreases a FSO links' performance is atmospheric turbulence. In order to counterbalance this reduction, in this work, we consider a free space optical system with a multiple receivers' scheme and diversity in space that operates under weak to strong atmospheric turbulence conditions modeled by the gamma-gamma distribution. We derive closed form mathematical expressions for the estimation of the outage probability and the average bit error rate of the multiple receivers' system. Additionally, we compare the performance capabilities of the single point to point link with those of the spatial diversity scheme under the assumption that the total aperture surface of the receivers of the latter is the same as the aperture surface of the single receiver of the former. Moreover, we demonstrate numerical results for a variety of common practical cases for both cases, with and without, spatial diversity.

  18. FODA: a novel efficient multiple access protocol for highly dynamic self-organizing networks

    NASA Astrophysics Data System (ADS)

    Li, Hantao; Liu, Kai; Zhang, Jun

    2005-11-01

    Based on the concept of contention reservation for polling transmission and collision prevention strategy for collision resolution, a fair on-demand access (FODA) protocol for supporting node mobility and multihop architecture in highly dynamic self-organizing networks is proposed. In the protocol, a distributed clustering network architecture formed by self-organizing algorithm and a main idea of reserving channel resources to get polling service are adopted, so that the hidden terminal (HT) and exposed terminal (ET) problems existed in traffic transmission due to multihop architecture and wireless transmission can be eliminated completely. In addition, an improved collision prevention scheme based on binary countdown algorithm (BCA), called fair collision prevention (FCP) algorithm, is proposed to greatly eliminate unfair phenomena existed in contention access of newly active ordinary nodes and completely resolve access collisions. Finally, the performance comparison of the FODA protocol with carrier sense multiple access with collision avoidance (CSMA/CA) and polling protocols by OPNET simulation are presented. Simulation results show that the FODA protocol can overcome the disadvantages of CSMA/CA and polling protocols, and achieve higher throughput, lower average message delay and less average message dropping rate.

  19. 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.

  20. Multiple-image encryption scheme with a single-pixel detector

    NASA Astrophysics Data System (ADS)

    Yuan, Sheng; Liu, Xuemei; Zhou, Xin; Li, Zhongyang

    2016-08-01

    A multiple-image encryption (MIE) scheme with a single-pixel detector has been proposed according to the principle of ghost imaging. In this scheme, each of the spatially coherent laser beams is modified by a set of phase-mask keys and illuminates on a secret image. All of the transmitted lights are recorded together by a single-pixel (bucket) detector to obtain a ciphertext, but anyone of the secret images can be decrypted from the ciphertext independently without any mutually overlapped despite some noise in them. The MIE scheme will bring convenience for data storage and transmission, especially in the case that different secret images need to be distributed to different authorized users, because the ciphertext is a real-valued function and this scheme can effectively avoid the secret images being extracted mutually. The basic principle of the MIE scheme is described theoretically and verified by computer simulations. Finally, the feasibility, robustness and encryption capacity are also tested numerically.

  1. The views of stakeholders on controlled access schemes for high-cost antirheumatic biological medicines in Australia

    PubMed Central

    Lu, Christine Y; Ritchie, Jan; Williams, Ken; Day, Ric

    2007-01-01

    Background In Australia, government-subsidised access to high-cost medicines is "targeted" to particular sub-sets of patients under the Pharmaceutical Benefits Scheme to achieve cost-effective use. In order to determine how this access system could be improved, the opinions of key stakeholders on access to biological agents for rheumatoid arthritis were explored. Methods Thirty-six semi-structured interviews were conducted with persons from relevant stakeholder groups. These were transcribed verbatim, and analysed thematically. Results Controlled access to expensive medicines was considered to be equitable and practical; however, there was disagreement as to the method of defining the target patient populations. Other concerns included timeliness of access, excessive bureaucracy, and the need for additional resources to facilitate the scheme. Collaboration between stakeholders was deemed important because it allows more equitable distribution of limited resources. The majority considered that stakeholder consultation should have been broader. Most wanted increased transparency of the decision-making process, ongoing and timely review of access criteria, and an increased provision of information for patients. More structured communication between stakeholders was proposed. Conclusion The Pharmaceutical Benefit Scheme is adapting to meet the changing needs of patients. Provision of subsidised access to high-cost medicines in a manner that is affordable for individuals and society, and that is equitable and efficiently managed is challenging. The views of stakeholders on targeted access to anti-rheumatic biological medicines in Australia acknowledged this challenge and provided a number of suggestions for modifications. These could serve as a basis to inform the debate on how to change the processes and policies so as to improve the scheme. PMID:18096055

  2. Dynamic Key Management Schemes for Secure Group Access Control Using Hierarchical Clustering in Mobile Ad Hoc Networks

    NASA Astrophysics Data System (ADS)

    Tsaur, Woei-Jiunn; Pai, Haw-Tyng

    2008-11-01

    The applications of group computing and communication motivate the requirement to provide group access control in mobile ad hoc networks (MANETs). The operation in MANETs' groups performs a decentralized manner and accommodated membership dynamically. Moreover, due to lack of centralized control, MANETs' groups are inherently insecure and vulnerable to attacks from both within and outside the groups. Such features make access control more challenging in MANETs. Recently, several researchers have proposed group access control mechanisms in MANETs based on a variety of threshold signatures. However, these mechanisms cannot actually satisfy MANETs' dynamic environments. This is because the threshold-based mechanisms cannot be achieved when the number of members is not up to the threshold value. Hence, by combining the efficient elliptic curve cryptosystem, self-certified public key cryptosystem and secure filter technique, we construct dynamic key management schemes based on hierarchical clustering for securing group access control in MANETs. Specifically, the proposed schemes can constantly accomplish secure group access control only by renewing the secure filters of few cluster heads, when a cluster head joins or leaves a cross-cluster. In such a new way, we can find that the proposed group access control scheme can be very effective for securing practical applications in MANETs.

  3. 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.

  4. 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.

  5. Performance evaluation of an integrated access scheme in a satellite communication channel

    NASA Astrophysics Data System (ADS)

    Suda, T.; Miyahara, H.; Hasegawa, T.

    1983-01-01

    A new integrated access scheme in a satellite communications system containing both bursty terminals and heavily loaded terminals is proposed and analyzed. The method divides the channel frame into two subframes, one for each type of terminal. The subframe for heavily loaded terminals is further divided into a reservation subchannel and a message subchannel. The bursty terminals transmit their packets in their dedicated subframes on the slotted ALOHA protocol. The heavily loaded terminal transmits a reservation packet in a randomly selected small slot of the reservation subchannel to reserve slots in the coming message subchannels. One slot in the same position in each of the succeeding message subchannels is reserved for the terminal until the end-of-use flag is received. Mean transmission delays at both kinds of terminals have been obtained, and it is shown that an optimal frame length exists which minimizes the mean transmission delay at one terminal type while keeping it under some permissible value at the other type.

  6. Assessment of multiple sustainability demands for wastewater treatment alternatives: a refined evaluation scheme and case study.

    PubMed

    Wang, Xu; Liu, Junxin; Ren, Nan-Qi; Yu, Han-Qing; Lee, Duu-Jong; Guo, Xuesong

    2012-05-15

    Current estimation schemes as decision support tools for the selection of wastewater treatment alternatives focus primarily on the treatment efficiency, effluent quality, and environmental consequences for receiving water bodies. However, these schemes generally do not quantify the potential to convert pollutants in wastewater to recoverable resources. This study proposes a refined evaluation scheme for choices of wastewater treatment processes that quantifies not only adverse environmental effects but also bioenergy and nutrient recovery indices. An original means of data processing was established and clear estimate indicators were consequently obtained to allow a smooth overall estimation. An array of wastewater treatment alternatives that meet three effluent limits were used as case studies to demonstrate how the present scheme works, simultaneously, to identify optimum choices. It is concluded in the overall estimation that the lower sustainability of wastewater treatment contributed by increasingly stringent discharge demands was offset and mitigated by the resource-recovery scenarios involved, and the scenario of recovering nutrients via excess-sludge composting was of more benefit. Thus, before tightening wastewater discharge requirements, one should bear in mind the situation of multiple sustainability by setting a goal to achieve not only the greatest reduction in environmental burden but also the maximum resource-recovery benefits.

  7. A novel generation scheme of ultra-short pulse trains with multiple wavelengths

    NASA Astrophysics Data System (ADS)

    Su, Yulong; Hu, Hui; Feng, Huan; Li, Lu; Han, Biao; Wen, Yu; Wang, Yishan; Si, Jinhai; Xie, Xiaoping; Wang, Weiqiang

    2017-04-01

    We demonstrate a novel scheme based on active mode locking combined with four-wave mixing (FWM) to generate ultra-short pulse trains at high repetition rate with multiple wavelengths for applications in various fields. The obtained six wavelengths display high uniformity both in temporal and frequency domain. Pulses at each wavelength are mode locked with pulse duration of 44.37 ps, signal-to-noise ratio (SNR) of 47.89 dB, root-mean-square (RMS) timing jitter of 552.7 fs, and the time-bandwidth product of 0.68 at repetition rate of 1 GHz. The experimental results show this scheme has promising usage in optical communications, optical networks, and fiber sensing.

  8. Designing single- and multiple-shell sampling schemes for diffusion MRI using spherical code.

    PubMed

    Cheng, Jian; Shen, Dinggang; Yap, Pew-Thian

    2014-01-01

    In diffusion MRI (dMRI), determining an appropriate sampling scheme is crucial for acquiring the maximal amount of information for data reconstruction and analysis using the minimal amount of time. For single-shell acquisition, uniform sampling without directional preference is usually favored. To achieve this, a commonly used approach is the Electrostatic Energy Minimization (EEM) method introduced in dMRI by Jones et al. However, the electrostatic energy formulation in EEM is not directly related to the goal of optimal sampling-scheme design, i.e., achieving large angular separation between sampling points. A mathematically more natural approach is to consider the Spherical Code (SC) formulation, which aims to achieve uniform sampling by maximizing the minimal angular difference between sampling points on the unit sphere. Although SC is well studied in the mathematical literature, its current formulation is limited to a single shell and is not applicable to multiple shells. Moreover, SC, or more precisely continuous SC (CSC), currently can only be applied on the continuous unit sphere and hence cannot be used in situations where one or several subsets of sampling points need to be determined from an existing sampling scheme. In this case, discrete SC (DSC) is required. In this paper, we propose novel DSC and CSC methods for designing uniform single-/multi-shell sampling schemes. The DSC and CSC formulations are solved respectively by Mixed Integer Linear Programming (MILP) and a gradient descent approach. A fast greedy incremental solution is also provided for both DSC and CSC. To our knowledge, this is the first work to use SC formulation for designing sampling schemes in dMRI. Experimental results indicate that our methods obtain larger angular separation and better rotational invariance than the generalized EEM (gEEM) method currently used in the Human Connectome Project (HCP).

  9. 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

  10. Analyses and improvement of a broadcasting multiple blind signature scheme based on quantum GHZ entanglement

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Qiu, Daowen; Zou, Xiangfu; Mateus, Paulo

    2017-06-01

    A broadcasting multiple blind signature scheme based on quantum GHZ entanglement has been presented recently. It is said that the scheme's unconditional security is guaranteed by adopting quantum key preparation, quantum encryption algorithm and quantum entanglement. In this paper, we prove that each signatory can get the signed message just by an intercept-resend attack. Then, we show there still exist some participant attacks and external attacks. Specifically, we verify the message sender Alice can impersonate each signatory to sign the message at will, and so is the signature collector Charlie. Also, we demonstrate that the receiver Bob can forge the signature successfully, and with respect to the external attacks, the eavesdropper Eve can modify the signature at random. Besides, we discover Eve can change the signed message at random, and Eve can impersonate Alice as the message sender without being discovered. In particular, we propose an improved scheme based on the original one and show that it is secure against not only the attacks mentioned above but also some collusion attacks.

  11. Fourth Annual International Acquisitions Workshop: Access to Multiple Media Worldwide

    NASA Technical Reports Server (NTRS)

    1994-01-01

    Topics discussed during the workshop include: (1) Multinational-Multiple media collections and activities spanning many countries; (2) Multiple media in North American trade and commerce; (3) African spotlight; (4) Europe-Multiple media in national libraries and services; (5) Scandinavian spotlight; (6) Internet update; (7) Multiple media in US federal agencies; (8) Open-source multiple media in US federal agencies; and (9) Multiple media at US federal technical agencies-NIST and NOAA.

  12. Access to DIII-D data located in multiple files and multiple locations

    SciTech Connect

    McHarg, B.B. Jr.

    1993-10-01

    The General Atomics DIII-D tokamak fusion experiment is now collecting over 80 MB of data per discharge once every 10 min, and that quantity is expected to double within the next year. The size of the data files, even in compressed format, is becoming increasingly difficult to handle. Data is also being acquired now on a variety of UNIX systems as well as MicroVAX and MODCOMP computer systems. The existing computers collect all the data into a single shot file, and this data collection is taking an ever increasing amount of time as the total quantity of data increases. Data is not available to experimenters until it has been collected into the shot file, which is in conflict with the substantial need for data examination on a timely basis between shots. The experimenters are also spread over many different types of computer systems (possibly located at other sites). To improve data availability and handling, software has been developed to allow individual computer systems to create their own shot files locally. The data interface routine PTDATA that is used to access DIII-D data has been modified so that a user`s code on any computer can access data from any computer where that data might be located. This data access is transparent to the user. Breaking up the shot file into separate files in multiple locations also impacts software used for data archiving, data management, and data restoration.

  13. Optical multiple-image authentication scheme based on the phase retrieval algorithm in gyrator domain

    NASA Astrophysics Data System (ADS)

    Sui, Liansheng; Zhang, Xiao; Tian, Ailing

    2017-05-01

    A novel optical multiple-image authentication scheme based on the phase retrieval algorithm is presented in gyrator domain. According to a plain image, only one phase-only mask is obtained as the encrypted result by using the proposed phase retrieval algorithm, which has a fast convergence rate and good performance on mean square error. Afterwards, the sparsely encrypted distribution is extracted from the phase-only mask by selecting a certain percentage of pixels randomly. Different from other multiple-image authentication system based on space multiplexing, all sparsely encrypted distributions of plain images are finally integrated into the ciphertext by making use of the inter-modulation operation of phase masks, where the decryption process can be performed efficiently without any cross-talk noise and the encrypted capacity is nearly unlimited. Only when the secret keys are correct, the content of the plain images can be authenticated, in which the authentication process can be implemented optically by using the architecture of double random phase encoding. Simulation results are given to demonstrate the feasibility and robustness of the proposed scheme.

  14. HiCoDG: a hierarchical data-gathering scheme using cooperative multiple mobile elements.

    PubMed

    Van Le, Duc; Oh, Hoon; Yoon, Seokhoon

    2014-12-17

    In this paper, we study mobile element (ME)-based data-gathering schemes in wireless sensor networks. Due to the physical speed limits of mobile elements, the existing data-gathering schemes that use mobile elements can suffer from high data-gathering latency. In order to address this problem, this paper proposes a new hierarchical and cooperative data-gathering (HiCoDG) scheme that enables multiple mobile elements to cooperate with each other to collect and relay data. In HiCoDG, two types of mobile elements are used: the mobile collector (MC) and the mobile relay (MR). MCs collect data from sensors and forward them to the MR, which will deliver them to the sink. In this work, we also formulated an integer linear programming (ILP) optimization problem to find the optimal trajectories for MCs and the MR, such that the traveling distance of MEs is minimized. Two variants of HiCoDG, intermediate station (IS)-based and cooperative movement scheduling (CMS)-based, are proposed to facilitate cooperative data forwarding from MCs to the MR. An analytical model for estimating the average data-gathering latency in HiCoDG was also designed. Simulations were performed to compare the performance of the IS and CMS variants, as well as a multiple traveling salesman problem (mTSP)-based approach. The simulation results show that HiCoDG outperforms mTSP in terms of latency. The results also show that CMS can achieve the lowest latency with low energy consumption.

  15. HiCoDG: A Hierarchical Data-Gathering Scheme Using Cooperative Multiple Mobile Elements †

    PubMed Central

    Van Le, Duc; Oh, Hoon; Yoon, Seokhoon

    2014-01-01

    In this paper, we study mobile element (ME)-based data-gathering schemes in wireless sensor networks. Due to the physical speed limits of mobile elements, the existing data-gathering schemes that use mobile elements can suffer from high data-gathering latency. In order to address this problem, this paper proposes a new hierarchical and cooperative data-gathering (HiCoDG) scheme that enables multiple mobile elements to cooperate with each other to collect and relay data. In HiCoDG, two types of mobile elements are used: the mobile collector (MC) and the mobile relay (MR). MCs collect data from sensors and forward them to the MR, which will deliver them to the sink. In this work, we also formulated an integer linear programming (ILP) optimization problem to find the optimal trajectories for MCs and the MR, such that the traveling distance of MEs is minimized. Two variants of HiCoDG, intermediate station (IS)-based and cooperative movement scheduling (CMS)-based, are proposed to facilitate cooperative data forwarding from MCs to the MR. An analytical model for estimating the average data-gathering latency in HiCoDG was also designed. Simulations were performed to compare the performance of the IS and CMS variants, as well as a multiple traveling salesman problem (mTSP)-based approach. The simulation results show that HiCoDG outperforms mTSP in terms of latency. The results also show that CMS can achieve the lowest latency with low energy consumption. PMID:25526356

  16. Has the Rajiv Aarogyasri Community Health Insurance Scheme of Andhra Pradesh Addressed the Educational Divide in Accessing Health Care?

    PubMed Central

    Rao, Mala; Singh, Prabal Vikram; Katyal, Anuradha; Samarth, Amit; Bergkvist, Sofi; Renton, Adrian; Netuveli, Gopalakrishnan

    2016-01-01

    Background Equity of access to healthcare remains a major challenge with families continuing to face financial and non-financial barriers to services. Lack of education has been shown to be a key risk factor for 'catastrophic' health expenditure (CHE), in many countries including India. Consequently, ways to address the education divide need to be explored. We aimed to assess whether the innovative state-funded Rajiv Aarogyasri Community Health Insurance Scheme of Andhra Pradesh state launched in 2007, has achieved equity of access to hospital inpatient care among households with varying levels of education. Methods We used the National Sample Survey Organization 2004 survey as our baseline and the same survey design to collect post-intervention data from 8623 households in the state in 2012. Two outcomes, hospitalisation and CHE for inpatient care, were estimated using education as a measure of socio-economic status and transforming levels of education into ridit scores. We derived relative indices of inequality by regressing the outcome measures on education, transformed as a ridit score, using logistic regression models with appropriate weights and accounting for the complex survey design. Findings Between 2004 and 2012, there was a 39% reduction in the likelihood of the most educated person being hospitalised compared to the least educated, with reductions observed in all households as well as those that had used the Aarogyasri. For CHE the inequality disappeared in 2012 in both groups. Sub-group analyses by economic status, social groups and rural-urban residence showed a decrease in relative indices of inequality in most groups. Nevertheless, inequalities in hospitalisation and CHE persisted across most groups. Conclusion During the time of the Aarogyasri scheme implementation inequalities in access to hospital care were substantially reduced but not eliminated across the education divide. Universal access to education and schemes such as Aarogyasri have the

  17. China’s new cooperative medical scheme and equity in access to health care: evidence from a longitudinal household survey

    PubMed Central

    2013-01-01

    Introduction China's New Cooperative Medical Scheme (NCMS) was brought to life in 2003 in response to the deterioration in access to health services in rural areas. Despite its fast expansion, the scheme’s impacts on access to health care have raised growing concerns, in particular regarding whether and to what extent the scheme has reduced inequity in access to health care in rural China. Methods This study examines income-related inequity in access to health care from 2004 (before the national rollout of NCMS) to 2009 (after the expansion of NCMS across the rural China) by estimating Concentration Indices over both formal health care (outpatient care, prevention care) and informal health care use (folk doctor care). Data were drawn from a longitudinal household survey dataset - China Health and Nutrition Survey (CHNS). Results The study suggested that the level of inequity remained the same for outpatient care, and an increased favouring-poor gap in terms of folk doctor care was observed. In terms of preventive care, a favouring-rich inequity was observed both in 2004 and 2009, but the effects of inequity were narrowed. The NCMS had some effects in reducing income-related health inequity in folk doctor care and preventive care, but the contribution was rather small. The study also found that the rural better-off had started to seek for commercial insurance to cover possible financial risks from the burden of diseases. Conclusion The study concludes that the impacts of the NCMS on improving access to formal care for the poor are limited. Without a more comprehensive insurance package that effectively targets the rural poor, the intended equity goals expected from the scheme will be difficult to realize. PMID:23522336

  18. Has the Rajiv Aarogyasri Community Health Insurance Scheme of Andhra Pradesh Addressed the Educational Divide in Accessing Health Care?

    PubMed

    Rao, Mala; Singh, Prabal Vikram; Katyal, Anuradha; Samarth, Amit; Bergkvist, Sofi; Renton, Adrian; Netuveli, Gopalakrishnan

    2016-01-01

    Equity of access to healthcare remains a major challenge with families continuing to face financial and non-financial barriers to services. Lack of education has been shown to be a key risk factor for 'catastrophic' health expenditure (CHE), in many countries including India. Consequently, ways to address the education divide need to be explored. We aimed to assess whether the innovative state-funded Rajiv Aarogyasri Community Health Insurance Scheme of Andhra Pradesh state launched in 2007, has achieved equity of access to hospital inpatient care among households with varying levels of education. We used the National Sample Survey Organization 2004 survey as our baseline and the same survey design to collect post-intervention data from 8623 households in the state in 2012. Two outcomes, hospitalisation and CHE for inpatient care, were estimated using education as a measure of socio-economic status and transforming levels of education into ridit scores. We derived relative indices of inequality by regressing the outcome measures on education, transformed as a ridit score, using logistic regression models with appropriate weights and accounting for the complex survey design. Between 2004 and 2012, there was a 39% reduction in the likelihood of the most educated person being hospitalised compared to the least educated, with reductions observed in all households as well as those that had used the Aarogyasri. For CHE the inequality disappeared in 2012 in both groups. Sub-group analyses by economic status, social groups and rural-urban residence showed a decrease in relative indices of inequality in most groups. Nevertheless, inequalities in hospitalisation and CHE persisted across most groups. During the time of the Aarogyasri scheme implementation inequalities in access to hospital care were substantially reduced but not eliminated across the education divide. Universal access to education and schemes such as Aarogyasri have the synergistic potential to achieve equity

  19. Value based pricing, research and development, and patient access schemes. Will the United Kingdom get it right or wrong?

    PubMed

    Towse, Adrian

    2010-09-01

    The National Health Service (NHS) should reward innovation it values. This will enable the NHS and the United Kingdom (UK) economy to benefit and impact positively on the Research and Development (R&D) decision making of companies. The National Institute for Health and Clinical Excellence (NICE) currently seeks to do this on behalf of the NHS. Yet the Office of Fair Trading proposals for Value Based Pricing add price setting powers--initially for the Department of Health (DH) and then for NICE. This introduces an additional substantial uncertainty that will impact on R&D and, conditional on R&D proceeding, on launch (or not) in the UK. Instead of adding to uncertainty the institutional arrangements for assessing value should seek to be predictable and science based, building on NICE's current arrangements. The real challenge is to increase understanding of the underlying cost-effectiveness of the technology itself by collecting evidence alongside use. The 2009 Pharmaceutical Price Regulation Scheme sought to help do this with Flexible Pricing (FP) and Patient Access Schemes (PASs). The PASs to date have increased access to medicines, but no schemes proposed to date have yet helped to tackle outcomes uncertainty. The 2010 Innovation Pass can also be seen as a form of 'coverage with evidence development.' The NHS is understandably concerned about the costs of running such evidence collection schemes. Enabling the NHS to deliver on such schemes will impact favourably on R&D decisions. Increasing the uncertainty in the UK NHS market through government price setting will reduce incentives for R&D and for early UK launch.

  20. Value based pricing, research and development, and patient access schemes. Will the United Kingdom get it right or wrong?

    PubMed Central

    Towse, Adrian

    2010-01-01

    The National Health Service (NHS) should reward innovation it values. This will enable the NHS and the United Kingdom (UK) economy to benefit and impact positively on the Research and Development (R&D) decision making of companies. The National Institute for Health and Clinical Excellence (NICE) currently seeks to do this on behalf of the NHS. Yet the Office of Fair Trading proposals for Value Based Pricing add price setting powers – initially for the Department of Health (DH) and then for NICE. This introduces an additional substantial uncertainty that will impact on R&D and, conditional on R&D proceeding, on launch (or not) in the UK. Instead of adding to uncertainty the institutional arrangements for assessing value should seek to be predictable and science based, building on NICE's current arrangements. The real challenge is to increase understanding of the underlying cost-effectiveness of the technology itself by collecting evidence alongside use. The 2009 Pharmaceutical Price Regulation Scheme sought to help do this with Flexible Pricing (FP) and Patient Access Schemes (PASs). The PASs to date have increased access to medicines, but no schemes proposed to date have yet helped to tackle outcomes uncertainty. The 2010 Innovation Pass can also be seen as a form of ‘coverage with evidence development.’ The NHS is understandably concerned about the costs of running such evidence collection schemes. Enabling the NHS to deliver on such schemes will impact favourably on R&D decisions. Increasing the uncertainty in the UK NHS market through government price setting will reduce incentives for R&D and for early UK launch. PMID:20716236

  1. Design of an image encryption scheme based on a multiple chaotic map

    NASA Astrophysics Data System (ADS)

    Tong, Xiao-Jun

    2013-07-01

    In order to solve the problem that chaos is degenerated in limited computer precision and Cat map is the small key space, this paper presents a chaotic map based on topological conjugacy and the chaotic characteristics are proved by Devaney definition. In order to produce a large key space, a Cat map named block Cat map is also designed for permutation process based on multiple-dimensional chaotic maps. The image encryption algorithm is based on permutation-substitution, and each key is controlled by different chaotic maps. The entropy analysis, differential analysis, weak-keys analysis, statistical analysis, cipher random analysis, and cipher sensibility analysis depending on key and plaintext are introduced to test the security of the new image encryption scheme. Through the comparison to the proposed scheme with AES, DES and Logistic encryption methods, we come to the conclusion that the image encryption method solves the problem of low precision of one dimensional chaotic function and has higher speed and higher security.

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

    NASA Technical Reports Server (NTRS)

    Dessouky, Khaled

    1989-01-01

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

  3. Multiple access techniques and spectrum utilization of the Globalstar mobile satellite system

    NASA Astrophysics Data System (ADS)

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

    1992-03-01

    The Globalstar LEO satellite system is described in terms of the commercial application of multiple-access and other technologies for cellular telephones. Attention is given to the simultaneous spectrum usage in several bands and the use of time-domain duplexing to achieve multiple access in both systems A and B. The efficiency of the code-division multiple-access (CDMA) technique employed is demonstrated in a discussion of the total system capacity for the 24-satellite constellation. CDMA is shown to allow frequency reuse of adjacent beams with marginal isolation, capacity increases by means of the voice-activity factor, and spectrum sharing among different operators. Also employed in the system are frequency- and time-division multiple-access technologies which enhance the efficiency of the modulation and multiple-access system.

  4. Dialysis access in a patient with multiple central venous stenoses.

    PubMed

    Cui, Tianlei; Zhao, Yuliang; Li, Xiao; Zhou, Li; Liu, Fang; Fu, Ping

    2014-01-01

    We report a female patient, with obstructed right femoral and right brachiocephalic vein, narrowed left femoral vein, left brachiocephalic vein and superior vena cava, due to long-term catheterization for dialysis. Angioplasty and synthesized graft transplant were successfully performed. The new access withstood early cannulation only 3 days after the procedure. Angioplasty can ameliorate existing stenosis and enable permanent access creation, while an artificial graft may provide faster maturation than documented.

  5. Performance analysis of commercial multiple-input-multiple-output access point in distributed antenna system.

    PubMed

    Fan, Yuting; Aighobahi, Anthony E; Gomes, Nathan J; Xu, Kun; Li, Jianqiang

    2015-03-23

    In this paper, we experimentally investigate the throughput of IEEE 802.11n 2x2 multiple-input-multiple-output (MIMO) signals in a radio-over-fiber-based distributed antenna system (DAS) with different fiber lengths and power imbalance. Both a MIMO-supported access point (AP) and a spatial-diversity-supported AP were separately employed in the experiments. Throughput measurements were carried out with wireless users at different locations in a typical office environment. For the different fiber length effect, the results indicate that MIMO signals can maintain high throughput when the fiber length difference between the two remote antenna units (RAUs) is under 100 m and falls quickly when the length difference is greater. For the spatial diversity signals, high throughput can be maintained even when the difference is 150 m. On the other hand, the separation of the MIMO antennas allows additional freedom in placing the antennas in strategic locations for overall improved system performance, although it may also lead to received power imbalance problems. The results show that the throughput performance drops in specific positions when the received power imbalance is above around 13 dB. Hence, there is a trade-off between the extent of the wireless coverage for moderate bit-rates and the area over which peak bit-rates can be achieved.

  6. A double-moment multiple-phase four-class bulk ice scheme, Part 1: Description

    NASA Technical Reports Server (NTRS)

    Ferrier, Brad Shoenberg

    1994-01-01

    A detailed ice-phase bulk microphysical scheme has been developed for simulating the hydrometeor distributions of convective and stratiform precipitation in different large-scale environmental conditions. The proposed scheme involves 90 distinct microphysical processes, which predict the mixing ratios and the number concentrations of small ice crystals, snow, graupel, and frozen drops/hail, as well as the mixing ratios of liquid water on wet precipitation ice (snow, graupel, frozen drops). The number of adjustable coefficients has been significantly reduced in comparison with other bulk schemes. Additional improvements have been made to the parameterization in the following areas: (1) representing small ice crystals with nonzero terminal fall velocities and dispersive size distributions, (2) accurate and computationally efficient calculations of precipitation collection processes, (3) reformulating the collection equation to prevent unrealistically large accretion rates, (4) more realistic conversion by riming between different classes of precipitation ice, (5) preventing unrealistically large rates of raindrop freezing and freezing of liquid water on ice, (6) detailed treatment of various rime-splintering ice multiplication mechanisms, (7) a simple representation of the Hobbs-Rangno ice enhancement process, (8) aggregation of small ice crystals and snow, and (9) allowing explicit competition between cloud water condensation and ice deposition rates rather than using saturation adjustment techniques. For the purposes of conserving the higher moments of the particle distributions, preserving the spectral widths (or slopes) of the particle spectra is shown to be more important than strict conservation of particle number concentration when parameterizing changes in ice-particle number concentrations due to melting, vapor transfer processes (sublimation of dry ice, evaporation from wet ice), and conversion between different hydrometeor species. The microphysical scheme

  7. A double-moment multiple-phase four-class bulk ice scheme, Part 1: Description

    NASA Technical Reports Server (NTRS)

    Ferrier, Brad Shoenberg

    1994-01-01

    A detailed ice-phase bulk microphysical scheme has been developed for simulating the hydrometeor distributions of convective and stratiform precipitation in different large-scale environmental conditions. The proposed scheme involves 90 distinct microphysical processes, which predict the mixing ratios and the number concentrations of small ice crystals, snow, graupel, and frozen drops/hail, as well as the mixing ratios of liquid water on wet precipitation ice (snow, graupel, frozen drops). The number of adjustable coefficients has been significantly reduced in comparison with other bulk schemes. Additional improvements have been made to the parameterization in the following areas: (1) representing small ice crystals with nonzero terminal fall velocities and dispersive size distributions, (2) accurate and computationally efficient calculations of precipitation collection processes, (3) reformulating the collection equation to prevent unrealistically large accretion rates, (4) more realistic conversion by riming between different classes of precipitation ice, (5) preventing unrealistically large rates of raindrop freezing and freezing of liquid water on ice, (6) detailed treatment of various rime-splintering ice multiplication mechanisms, (7) a simple representation of the Hobbs-Rangno ice enhancement process, (8) aggregation of small ice crystals and snow, and (9) allowing explicit competition between cloud water condensation and ice deposition rates rather than using saturation adjustment techniques. For the purposes of conserving the higher moments of the particle distributions, preserving the spectral widths (or slopes) of the particle spectra is shown to be more important than strict conservation of particle number concentration when parameterizing changes in ice-particle number concentrations due to melting, vapor transfer processes (sublimation of dry ice, evaporation from wet ice), and conversion between different hydrometeor species. The microphysical scheme

  8. A speed-up scheme based on multiple-instance pruning for pedestrian detection using a support vector machine.

    PubMed

    Yu, Jaehoon; Miyamoto, Ryusuke; Onoye, Takao

    2013-12-01

    In pedestrian detection, as sophisticated feature descriptors are used for improving detection accuracy, its processing speed becomes a critical issue. In this paper, we propose a novel speed-up scheme based on multiple-instance pruning (MIP), one of the soft cascade methods, to enhance the processing speed of support vector machine (SVM) classifiers. Our scheme mainly consists of three steps. First, we regularly split an SVM classifier into multiple parts and build a cascade structure using them. Next, we rearrange the cascade structure for enhancing the rejection rate, and then train the rejection threshold of each stage composing the cascade structure using the MIP. To verify the validity of our scheme, we apply it to a pedestrian classifier using co-occurrence histograms of oriented gradients trained by an SVM, and experimental results show that the processing time for classification of the proposed scheme is as low as one-hundredth of the original classifier without sacrificing detection accuracy.

  9. 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.

  10. Geographic Access Modeling of Emergency Obstetric and Neonatal Care in Kigoma Region, Tanzania: Transportation Schemes and Programmatic Implications

    PubMed Central

    Chen, Yi No; Schmitz, Michelle M; Serbanescu, Florina; Dynes, Michelle M; Maro, Godson; Kramer, Michael R

    2017-01-01

    ABSTRACT Background: Access to transportation is vital to reducing the travel time to emergency obstetric and neonatal care (EmONC) for managing complications and preventing adverse maternal and neonatal outcomes. This study examines the distribution of travel times to EmONC in Kigoma Region, Tanzania, using various transportation schemes, to estimate the proportion of live births (a proxy indicator of women needing delivery care) with poor geographic access to EmONC services. Methods: The 2014 Reproductive Health Survey of Kigoma Region identified 4 primary means of transportation used to travel to health facilities: walking, cycling, motorcycle, and 4-wheeled motor vehicle. A raster-based travel time model was used to map the 2-hour travel time catchment for each mode of transportation. Live birth density distributions were aggregated by travel time catchments, and by administrative council, to estimate the proportion of births with poor access. Results: Of all live births in Kigoma Region, 13% occurred in areas where women can reach EmONC facilities within 2 hours on foot, 33% in areas that can be reached within 2 hours only by motorized vehicles, and 32% where it is impossible to reach EmONC facilities within 2 hours. Over 50% of births in 3 of the 8 administrative councils had poor estimated access. In half the councils, births with poor access could be reduced to no higher than 12% if all female residents had access to motorized vehicles. Conclusion: Significant differences in geographic access to EmONC in Kigoma Region, Tanzania, were observed both by location and by primary transportation type. As most of the population may only have good EmONC access when using mechanized or motorized vehicles, bicycles and motorcycles should be incorporated into the health transportation strategy. Collaboration between private transportation sectors and obstetric service providers could improve access to EmONC services among most populations. In areas where residents may

  11. Geographic Access Modeling of Emergency Obstetric and Neonatal Care in Kigoma Region, Tanzania: Transportation Schemes and Programmatic Implications.

    PubMed

    Chen, Yi No; Schmitz, Michelle M; Serbanescu, Florina; Dynes, Michelle M; Maro, Godson; Kramer, Michael R

    2017-09-27

    Access to transportation is vital to reducing the travel time to emergency obstetric and neonatal care (EmONC) for managing complications and preventing adverse maternal and neonatal outcomes. This study examines the distribution of travel times to EmONC in Kigoma Region, Tanzania, using various transportation schemes, to estimate the proportion of live births (a proxy indicator of women needing delivery care) with poor geographic access to EmONC services. The 2014 Reproductive Health Survey of Kigoma Region identified 4 primary means of transportation used to travel to health facilities: walking, cycling, motorcycle, and 4-wheeled motor vehicle. A raster-based travel time model was used to map the 2-hour travel time catchment for each mode of transportation. Live birth density distributions were aggregated by travel time catchments, and by administrative council, to estimate the proportion of births with poor access. Of all live births in Kigoma Region, 13% occurred in areas where women can reach EmONC facilities within 2 hours on foot, 33% in areas that can be reached within 2 hours only by motorized vehicles, and 32% where it is impossible to reach EmONC facilities within 2 hours. Over 50% of births in 3 of the 8 administrative councils had poor estimated access. In half the councils, births with poor access could be reduced to no higher than 12% if all female residents had access to motorized vehicles. Significant differences in geographic access to EmONC in Kigoma Region, Tanzania, were observed both by location and by primary transportation type. As most of the population may only have good EmONC access when using mechanized or motorized vehicles, bicycles and motorcycles should be incorporated into the health transportation strategy. Collaboration between private transportation sectors and obstetric service providers could improve access to EmONC services among most populations. In areas where residents may not access EmONC facilities within 2 hours

  12. 47 CFR 76.2000 - Exclusive access to multiple dwelling units generally.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 4 2011-10-01 2011-10-01 false Exclusive access to multiple dwelling units... to multiple dwelling units generally. (a) Prohibition. No cable operator or other provider of MVPD... rule, MDU shall include a multiple dwelling unit building (such as an apartment building,...

  13. 47 CFR 76.2000 - Exclusive access to multiple dwelling units generally.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false Exclusive access to multiple dwelling units... to multiple dwelling units generally. (a) Prohibition. No cable operator or other provider of MVPD... rule, MDU shall include a multiple dwelling unit building (such as an apartment building,...

  14. 47 CFR 76.2000 - Exclusive access to multiple dwelling units generally.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 4 2014-10-01 2014-10-01 false Exclusive access to multiple dwelling units... to multiple dwelling units generally. (a) Prohibition. No cable operator or other provider of MVPD... rule, MDU shall include a multiple dwelling unit building (such as an apartment building,...

  15. 47 CFR 76.2000 - Exclusive access to multiple dwelling units generally.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 4 2013-10-01 2013-10-01 false Exclusive access to multiple dwelling units... to multiple dwelling units generally. (a) Prohibition. No cable operator or other provider of MVPD... rule, MDU shall include a multiple dwelling unit building (such as an apartment building,...

  16. 47 CFR 76.2000 - Exclusive access to multiple dwelling units generally.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 4 2012-10-01 2012-10-01 false Exclusive access to multiple dwelling units... to multiple dwelling units generally. (a) Prohibition. No cable operator or other provider of MVPD... rule, MDU shall include a multiple dwelling unit building (such as an apartment building,...

  17. Optical Multiple Access Network (OMAN) for advanced processing satellite applications

    NASA Technical Reports Server (NTRS)

    Mendez, Antonio J.; Gagliardi, Robert M.; Park, Eugene; Ivancic, William D.; Sherman, Bradley D.

    1991-01-01

    An OMAN breadboard for exploring advanced processing satellite circuit switch applications is introduced. Network architecture, hardware trade offs, and multiple user interference issues are presented. The breadboard test set up and experimental results are discussed.

  18. Access Scheme for Controlling Mobile Agents and its Application to Share Medical Information.

    PubMed

    Liao, Yu-Ting; Chen, Tzer-Shyong; Chen, Tzer-Long; Chung, Yu-Fang; Chen, Yu- Xin; Hwang, Jen-Hung; Wang, Huihui; Wei, Wei

    2016-05-01

    This study is showing the advantage of mobile agents to conquer heterogeneous system environments and contribute to a virtual integrated sharing system. Mobile agents will collect medical information from each medical institution as a method to achieve the medical purpose of data sharing. Besides, this research also provides an access control and key management mechanism by adopting Public key cryptography and Lagrange interpolation. The safety analysis of the system is based on a network attacker's perspective. The achievement of this study tries to improve the medical quality, prevent wasting medical resources and make medical resources access to appropriate configuration.

  19. Unreasonable effectiveness of learning neural networks: From accessible states and robust ensembles to basic algorithmic schemes

    PubMed Central

    Borgs, Christian; Chayes, Jennifer T.; Ingrosso, Alessandro; Lucibello, Carlo; Saglietti, Luca; Zecchina, Riccardo

    2016-01-01

    In artificial neural networks, learning from data is a computationally demanding task in which a large number of connection weights are iteratively tuned through stochastic-gradient-based heuristic processes over a cost function. It is not well understood how learning occurs in these systems, in particular how they avoid getting trapped in configurations with poor computational performance. Here, we study the difficult case of networks with discrete weights, where the optimization landscape is very rough even for simple architectures, and provide theoretical and numerical evidence of the existence of rare—but extremely dense and accessible—regions of configurations in the network weight space. We define a measure, the robust ensemble (RE), which suppresses trapping by isolated configurations and amplifies the role of these dense regions. We analytically compute the RE in some exactly solvable models and also provide a general algorithmic scheme that is straightforward to implement: define a cost function given by a sum of a finite number of replicas of the original cost function, with a constraint centering the replicas around a driving assignment. To illustrate this, we derive several powerful algorithms, ranging from Markov Chains to message passing to gradient descent processes, where the algorithms target the robust dense states, resulting in substantial improvements in performance. The weak dependence on the number of precision bits of the weights leads us to conjecture that very similar reasoning applies to more conventional neural networks. Analogous algorithmic schemes can also be applied to other optimization problems. PMID:27856745

  20. GSFC conceptual design study for an inter-satellite Optical Multiple Access communication system

    NASA Technical Reports Server (NTRS)

    Fox, Neil; Maynard, Will; Clarke, Ernest; Bruno, Ronald

    1991-01-01

    System and terminal level specifications for an inter-satellite Optical Multiple Access (OMA) communication system are presented, as well as the resulting hardware designs for both OMA relay and OMA user terminals. The OMA relay terminal design uses a mechanical innovation which moves multiple fiber optic pickups in the focal plane, thereby providing simultaneous links with multiple OMA user terminals via a single telescope. Thus, with such a terminal on a relay satellite, multiple access service can be provided with a minimum of impact on the relay satellite.

  1. GSFC conceptual design study for an inter-satellite Optical Multiple Access communication system

    NASA Technical Reports Server (NTRS)

    Fox, Neil; Maynard, Will; Clarke, Ernest; Bruno, Ronald

    1991-01-01

    System and terminal level specifications for an inter-satellite Optical Multiple Access (OMA) communication system are presented, as well as the resulting hardware designs for both OMA relay and OMA user terminals. The OMA relay terminal design uses a mechanical innovation which moves multiple fiber optic pickups in the focal plane, thereby providing simultaneous links with multiple OMA user terminals via a single telescope. Thus, with such a terminal on a relay satellite, multiple access service can be provided with a minimum of impact on the relay satellite.

  2. An Integrated Approach for Accessing Multiple Datasets through LANCE

    NASA Astrophysics Data System (ADS)

    Murphy, K. J.; Teague, M.; Conover, H.; Regner, K.; Beaumont, B.; Masuoka, E.; Vollmer, B.; Theobald, M.; Durbin, P.; Michael, K.; Boller, R. A.; Schmaltz, J. E.; Davies, D.; Horricks, K.; Ilavajhala, S.; Thompson, C. K.; Bingham, A.

    2011-12-01

    The NASA/GSFC Land Atmospheres Near-real time Capability for EOS (LANCE) provides imagery for approximately 40 data products from MODIS, AIRS, AMSR-E and OMI to support the applications community in the study of a variety of phenomena. Thirty-six of these products are available within 2.5 hours of observation at the spacecraft. The data set includes the population density data provided by the EOSDIS Socio-Economic Data and Applications Center (SEDAC). The purpose of this paper is to describe the variety of tools that have been developed by LANCE to support user access to the imagery. The long-standing Rapid Response system has been integrated into LANCE and is a major vehicle for the distribution of the imagery to end users. There are presently approximately 10,000 anonymous users per month accessing these imagery. The products are grouped into 14 applications categories such as Smoke Plumes, Pollution, Fires, Agriculture and the selection of any category will make relevant subsets of the 40 products available as possible overlays in an interactive Web Client utilizing Web Mapping Service (WMS) to support user investigations (http://lance2.modaps.eosdis.nasa.gov/wms/). For example, selecting Severe Storms will include 6 products for MODIS, OMI, AIRS, and AMSR-E plus the SEDAC population density data. The client and WMS were developed using open-source technologies such as OpenLayers and MapServer and provides a uniform, browser-based access to data products. All overlays are downloadable in PNG, JPEG, or GeoTiff form up to 200MB per request. The WMS was beta-tested with the user community and substantial performance improvements were made through the use of such techniques as tile-caching. LANCE established a partnership with Physical Oceanography Distributed Active Archive Center (PO DAAC) to develop an alternative presentation for the 40 data products known as the State of the Earth (SOTE). This provides a Google Earth-based interface to the products grouped in

  3. Equitable access to health insurance for socially excluded children? The case of the National Health Insurance Scheme (NHIS) in Ghana.

    PubMed

    Williams, Gemma A; Parmar, Divya; Dkhimi, Fahdi; Asante, Felix; Arhinful, Daniel; Mladovsky, Philipa

    2017-08-01

    To help reduce child mortality and reach universal health coverage, Ghana extended free membership of the National Health Insurance Scheme (NHIS) to children (under-18s) in 2008. However, despite the introduction of premium waivers, a substantial proportion of children remain uninsured. Thus far, few studies have explored why enrolment of children in NHIS may remain low, despite the absence of significant financial barriers to membership. In this paper we therefore look beyond economic explanations of access to health insurance to explore additional wider determinants of enrolment in the NHIS. In particular, we investigate whether social exclusion, as measured through a sociocultural, political and economic lens, can explain poor enrolment rates of children. Data were collected from a cross-sectional survey of 4050 representative households conducted in Ghana in 2012. Household indices were created to measure sociocultural, political and economic exclusion, and logistic regressions were conducted to study determinants of enrolment at the individual and household levels. Our results indicate that socioculturally, economically and politically excluded children are less likely to enrol in the NHIS. Furthermore, households excluded in all dimensions were more likely to be non-enrolled or partially-enrolled (i.e. not all children enrolled within the household) than fully-enrolled. These results suggest that equity in access for socially excluded children has not yet been achieved. Efforts should be taken to improve coverage by removing the remaining small, annually renewable registration fee, implementing and publicising the new clause that de-links premium waivers from parental membership, establishing additional scheme administrative offices in remote areas, holding regular registration sessions in schools and conducting outreach sessions and providing registration support to female guardians of children. Ensuring equitable access to NHIS will contribute substantially

  4. Concept for Multiple-Access Free-Space Laser Communications

    NASA Technical Reports Server (NTRS)

    Wilson, Keith

    2004-01-01

    A design concept for a proposed airborne or spaceborne free-space optical-communication terminal provides for simultaneous reception of signals from multiple other opticalcommunication terminals aboard aircraft or spacecraft that carry scientific instruments and fly at lower altitudes. The concept reflects the need for rapid acquisition and tracking of the signals coming from the lower-altitude terminals as they move across the field of view.

  5. A Novel Read Scheme for Large Size One-Resistor Resistive Random Access Memory Array

    PubMed Central

    Zackriya, Mohammed; Kittur, Harish M.; Chin, Albert

    2017-01-01

    The major issue of RRAM is the uneven sneak path that limits the array size. For the first time record large One-Resistor (1R) RRAM array of 128x128 is realized, and the array cells at the worst case still have good Low-/High-Resistive State (LRS/HRS) current difference of 378 nA/16 nA, even without using the selector device. This array has extremely low read current of 9.7 μA due to both low-current RRAM device and circuit interaction, where a novel and simple scheme of a reference point by half selected cell and a differential amplifier (DA) were implemented in the circuit design. PMID:28186147

  6. A Novel Read Scheme for Large Size One-Resistor Resistive Random Access Memory Array

    NASA Astrophysics Data System (ADS)

    Zackriya, Mohammed; Kittur, Harish M.; Chin, Albert

    2017-02-01

    The major issue of RRAM is the uneven sneak path that limits the array size. For the first time record large One-Resistor (1R) RRAM array of 128x128 is realized, and the array cells at the worst case still have good Low-/High-Resistive State (LRS/HRS) current difference of 378 nA/16 nA, even without using the selector device. This array has extremely low read current of 9.7 μA due to both low-current RRAM device and circuit interaction, where a novel and simple scheme of a reference point by half selected cell and a differential amplifier (DA) were implemented in the circuit design.

  7. Transmission access and pricing with multiple separate energy forward markets

    SciTech Connect

    Gribik, P.R.; Angelidis, G.A.; Kovacs, R.R.

    1999-08-01

    California`s congestion management protocols provide comparable access and prices to all users of the transmission system (power exchange and bilateral contract parties). The users implicitly bid for capacity on major transmission paths between zones. The Independent System Operator (ISO) allocates the available transmission capacity on these paths so that it maximizes the value of this capacity as measured by the users` bids. Everyone scheduling flow on a congested path is charged the marginal-cost-based price for using the path. The ISO keeps each party`s portfolio of generation and load individually in balance when adjusting schedules to relieve congestion on interzonal paths. By keeping the portfolios of the different parties separate, the ISO clears its transmission market without arranging energy trades between parties. Parties are responsible for arranging their own trades. The ISO does not become involved in the energy forward markets.

  8. Towards a standard licensing scheme for the access and use of satellite earth observation data for disaster management

    NASA Astrophysics Data System (ADS)

    Clark, Nathan E.

    2017-10-01

    This paper explores from the view of the data recipient and user the complexities of creating a common licensing scheme for the access and use of satellite earth observation (EO) data in international disaster management (DM) activities. EO data contributions in major disaster events often involve numerous data providers with separate licensing mechanisms for controlling the access, uses, and distribution of data by the end users. A lack of standardization among the terminology, wording, and conditions within these licenses creates a complex legal environment for users, and often prevents them from using, sharing and combining datasets in an effective and timely manner. It also creates uncertainty among data providers as to the types of licensing controls that should be applied in disaster scenarios. This paper builds from an ongoing comparative analysis of the common and conflicting conditions among data licenses that must be addressed in order to facilitate easier access and use of EO data within the DM sector and offers recommendations towards the alignment of the structural and technical aspects of licenses among data providers.

  9. Next generation communications satellites: multiple access and network studies

    NASA Technical Reports Server (NTRS)

    Meadows, H. E.; Schwartz, M.; Stern, T. E.; Ganguly, S.; Kraimeche, B.; Matsuo, K.; Gopal, I.

    1982-01-01

    Efficient resource allocation and network design for satellite systems serving heterogeneous user populations with large numbers of small direct-to-user Earth stations are discussed. Focus is on TDMA systems involving a high degree of frequency reuse by means of satellite-switched multiple beams (SSMB) with varying degrees of onboard processing. Algorithms for the efficient utilization of the satellite resources were developed. The effect of skewed traffic, overlapping beams and batched arrivals in packet-switched SSMB systems, integration of stream and bursty traffic, and optimal circuit scheduling in SSMB systems: performance bounds and computational complexity are discussed.

  10. A Fair Contention Access Scheme for Low-Priority Traffic in Wireless Body Area Networks

    PubMed Central

    Sajeel, Muhammad; Bashir, Faisal; Asfand-e-yar, Muhammad; Tauqir, Muhammad

    2017-01-01

    Recently, wireless body area networks (WBANs) have attracted significant consideration in ubiquitous healthcare. A number of medium access control (MAC) protocols, primarily derived from the superframe structure of the IEEE 802.15.4, have been proposed in literature. These MAC protocols aim to provide quality of service (QoS) by prioritizing different traffic types in WBANs. A contention access period (CAP)with high contention in priority-based MAC protocols can result in higher number of collisions and retransmissions. During CAP, traffic classes with higher priority are dominant over low-priority traffic; this has led to starvation of low-priority traffic, thus adversely affecting WBAN throughput, delay, and energy consumption. Hence, this paper proposes a traffic-adaptive priority-based superframe structure that is able to reduce contention in the CAP period, and provides a fair chance for low-priority traffic. Simulation results in ns-3 demonstrate that the proposed MAC protocol, called traffic- adaptive priority-based MAC (TAP-MAC), achieves low energy consumption, high throughput, and low latency compared to the IEEE 802.15.4 standard, and the most recent priority-based MAC protocol, called priority-based MAC protocol (PA-MAC). PMID:28832495

  11. A Fair Contention Access Scheme for Low-Priority Traffic in Wireless Body Area Networks.

    PubMed

    Henna, Shagufta; Sajeel, Muhammad; Bashir, Faisal; Asfand-E-Yar, Muhammad; Tauqir, Muhammad

    2017-08-23

    Recently, wireless body area networks (WBANs) have attracted significant consideration in ubiquitous healthcare. A number of medium access control (MAC) protocols, primarily derived from the superframe structure of the IEEE 802.15.4, have been proposed in literature. These MAC protocols aim to provide quality of service (QoS) by prioritizing different traffic types in WBANs. A contention access period (CAP)with high contention in priority-based MAC protocols can result in higher number of collisions and retransmissions. During CAP, traffic classes with higher priority are dominant over low-priority traffic; this has led to starvation of low-priority traffic, thus adversely affecting WBAN throughput, delay, and energy consumption. Hence, this paper proposes a traffic-adaptive priority-based superframe structure that is able to reduce contention in the CAP period, and provides a fair chance for low-priority traffic. Simulation results in ns-3 demonstrate that the proposed MAC protocol, called traffic- adaptive priority-based MAC (TAP-MAC), achieves low energy consumption, high throughput, and low latency compared to the IEEE 802.15.4 standard, and the most recent priority-based MAC protocol, called priority-based MAC protocol (PA-MAC).

  12. Students' Whole Number Multiplicative Concepts: A Critical Constructive Resource for Fraction Composition Schemes

    ERIC Educational Resources Information Center

    Hackenberg, Amy J.; Tillema, Erik S.

    2009-01-01

    This article reports on the activity of two pairs of sixth grade students who participated in an 8-month teaching experiment that investigated the students' construction of fraction composition schemes. A fraction composition scheme consists of the operations and concepts used to determine, for example, the size of 1/3 of 1/5 of a whole in…

  13. Mof-Tree: A Spatial Access Method To Manipulate Multiple Overlapping Features.

    ERIC Educational Resources Information Center

    Manolopoulos, Yannis; Nardelli, Enrico; Papadopoulos, Apostolos; Proietti, Guido

    1997-01-01

    Investigates the manipulation of large sets of two-dimensional data representing multiple overlapping features, and presents a new access method, the MOF-tree. Analyzes storage requirements and time with respect to window query operations involving multiple features. Examines both the pointer-based and pointerless MOF-tree representations.…

  14. Mof-Tree: A Spatial Access Method To Manipulate Multiple Overlapping Features.

    ERIC Educational Resources Information Center

    Manolopoulos, Yannis; Nardelli, Enrico; Papadopoulos, Apostolos; Proietti, Guido

    1997-01-01

    Investigates the manipulation of large sets of two-dimensional data representing multiple overlapping features, and presents a new access method, the MOF-tree. Analyzes storage requirements and time with respect to window query operations involving multiple features. Examines both the pointer-based and pointerless MOF-tree representations.…

  15. Multiple Access in Ultra-Wideband Communications Using Multiple Pulses and the Use of Least Squares Filters

    SciTech Connect

    Nekoogar, F

    2003-06-19

    Multiple access (MA) in UWB communication has recently been studied in the context of multiple transmitted-reference short duration chirp pulses in the presence of additive white Gaussian noise (AWGN). The transmitted-reference (TR) receiver was extended in previous studies using multiple orthogonal pulses. Improved performance was observed in simulations by sampling the receiver autocorrelation function (ACF) at both zero- and non-zero lags. Sampling of non-zero ACF lags of orthogonal pulses is a novel approach. Method of using least squares filtering techniques for further tolerance against noise and interference for the TR method is proposed.

  16. Cometary cores with multiple structure from the oort cloud and the general scheme of origin of unusually active comets

    SciTech Connect

    Davydov, V.D.

    1986-03-01

    A newly conceived scheme is constructed which synthesizes consistent solutions to several principal problems concerning multiple-core comets: a power mechanism, a place and epoch of formation of the multiple core structure, the qualitative differences between current structure and younger structure, the origin of two types of cometary orbits, and a trigger mechanism for recent ignition of cometary activity of a multiple core. This scheme uses a new explanation of the ejection of dust (including icy dust) from various cometary cores as evidence that the material of multiple-core comets may be collisionally ablated at the expense of the comet-centered orbital energy of a multitude of massive boulders (see Kosm. Issled., No. 6 (1984)). Natural mechanisms are shown which preserve this important feature of multiple cores. The concept consists of the following elements: evolution of a system of satellites of the core toward a colli sionless structure; preservation of internal kinetic energy in the collisionless system over astro nomically lengthy time scales; tidal initiation of a collisional mechanism with the first revolution of the ancient multiple core in the zone of visibility. It is possible that such revoltions correspond to the existence of especially active comets in nearly parabolic orbits. Multiple structure in the core of active short-period comets might be descended from a nearly parabolic comet (if the theory holds on perturbational multistage transformation of near-parabolic orbits into contemporary short-period orbits).

  17. Access to anticancer drugs: many evidence-based treatments are off-label and unfunded by the Pharmaceutical Benefits Scheme.

    PubMed

    Mellor, J D; Van Koeverden, P; Yip, S W K; Thakerar, A; Kirsa, S W; Michael, M

    2012-11-01

    The off-label use of a drug refers to a use outside the terms of its approval by the Therapeutic Goods Administration (TGA). It is also possible to prescribe unlicensed drugs under the TGA's special access scheme. A high rate of off-label prescribing has previously been reported in cancer. Our study aimed to document the disparity between evidence-based clinical guidelines for anticancer therapy, product approval and funding status of these agents within an academic tertiary/quaternary cancer centre. All chemotherapy protocols approved for use in our specialist oncology centre were assessed to determine if the drugs were off-label or unlicensed for that indication based on review of their current product information. The Pharmaceutical Benefits Scheme (PBS) funding status for each protocol was subsequently assessed. A total of 448 protocols containing 82 different drugs across 15 tumour groups was identified. Overall, 189 (42.2%) of protocols were off-label, and three (0.7%) were unlicensed. This resulted in all 192 protocols being unfunded by the PBS. Of the 189 off-label protocols, 132 (69.9%) were based on established evidence-based treatment guidelines, and a further 39 (20.6%) was based on phase II or III clinical trial data. Over 90% of off-label protocols are supported by established treatment guidelines or published peer-reviewed research even though the medications are not approved for that particular use by the TGA. However, these off-label protocols are unfunded by the PBS; this results in a marked inequality of access to appropriate medications for cancer patients across Australia. © 2012 The Authors; Internal Medicine Journal © 2012 Royal Australasian College of Physicians.

  18. A Busy-Tone-Multiple-Access-Type Scheme for Packet-Radio Networks,

    DTIC Science & Technology

    1981-06-01

    is applied in each of the L distinct channels. In addition a node that senses activity on the subchannel Z (where lstL), transmits a signal over a...transmission. From the above description, it is clear that the probability of completed transmission at a node i that uses the subchannel Z for...transmission is given here by : Sm Ps 1- - (12) mCB(i) 11m𔄀 where B(i) is the collection of all nodes in A(i) that use the subchannel I for transmission and 6

  19. A comparison of Frequency Domain Multiple Access (FDMA) and Time Domain Multiple Access (TDMA) approaches to satellite service for low data rate Earth stations

    NASA Technical Reports Server (NTRS)

    Stevens, G.

    1983-01-01

    A technological and economic assessment is made of providing low data rate service to small earth stations by satellite at Ka-band. Various Frequency Domain Multiple Access (FDMA) and Time Domain Multiple Access (TDMA) scenarios are examined and compared on the basis of cost to the end user. Very small stations (1 to 2 meters in diameter) are found not to be viable alternatives to available terrestrial services. However, medium size (3 to 5 meters) earth stations appear to be very competitive if a minimum throughput of about 1.5 Mbs is maintained. This constrains the use of such terminals to large users and shared use by smaller users. No advantage was found to the use of FDMA. TDMA had a slight advantage from a total system viewpoint and a very significant advantage in the space segment (about 1/3 the required payload weight for an equivalent capacity).

  20. Prediction of ligand binding affinity using a multiple-conformations-multiple-protonation scheme: application to estrogen receptor α.

    PubMed

    Mizutani, Miho Y; Takamatsu, Yoshihiro; Ichinose, Tazuko; Itai, Akiko

    2012-01-01

    A fast method that can predict the binding affinities of chemicals to a target protein with a high degree of accuracy will be very useful in drug design and regulatory science. We have been developing a scoring function for affinity prediction, which can be applied to extensive protein systems, and also trying to generate a prediction scheme that specializes in each target protein, with as high a predictive power as possible. In this study, we have constructed a prediction scheme with target-specific scores for estimating ligand-binding affinities to human estrogen receptor α (ERα), considering the major conformational change between agonist- and antagonist-bound forms and the change in protonation states of histidine at the ligand-binding site. The generated scheme calibrated with fewer training compounds (23 for the agonist-bound form, 17 for the antagonist-bound form) demonstrated good predictive power (a predictive r(2) of 0.83 for 154 validation compounds); this was also true for compounds with frameworks that were quite different from those of the training compounds. Our prediction scheme will be useful in drug development targeting ERα and in primary screening of endocrine disruptors, and provides a successful method of affinity prediction considering the major conformational changes in a protein.

  1. Channel access schemes and fiber optic configurations for integrated-services local area networks. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Nassehi, M. Mehdi

    1987-01-01

    Local Area Networks are in common use for data communications and have enjoyed great success. Recently, there is a growing interest in using a single network to support many applications in addition to traditional data traffic. These additional applications introduce new requirements in terms of volume of traffic and real-time delivery of data which are not met by existing networks. To satisfy these requirements, a high-bandwidth tranmission medium, such as fiber optics, and a distributed channel access scheme for the efficient sharing of the bandwidth among the various applications are needed. As far as the throughput-delay requirements of the various application are concerned, a network structure along with a distributed channel access are proposed which incorporate appropriate scheduling policies for the transmission of outstanding messages on the network. A dynamic scheduling policy was devised which outperforms all existing policies in terms of minimizing the expected cost per message. A broadcast mechanism was devised for the efficient dissemination of all relevant information. Fiber optic technology is considered for the high-bandwidth transmisison medium.

  2. Teaching Individuals with Profound Multiple Disabilities to Access Preferred Stimuli with Multiple Microswitches

    ERIC Educational Resources Information Center

    Tam, Gee May; Phillips, Katrina J.; Mudford, Oliver C.

    2011-01-01

    We replicated and extended previous research on microswitch facilitated choice making by individuals with profound multiple disabilities. Following an assessment of stimulus preferences, we taught 6 adults with profound multiple disabilities to emit 2 different responses to activate highly preferred stimuli. All participants learnt to activate…

  3. Study on the energy-efficient scheme based on the interconnection of optical-network-units for next generation optical access network

    NASA Astrophysics Data System (ADS)

    Lv, Yunxin; Jiang, Ning; Qiu, Kun; Xue, Chenpeng

    2014-12-01

    An energy-efficient scheme based on the interconnection of optical network unit (ONU) is introduced, which can significantly reduce the energy consumption of the low-traffic operation. The energy consumption model for the ONU-interconnected optical access network (OAN) based on the electronic switch (ES) technology is established, and the energy efficiency of the proposed scheme is analyzed and compared with that of the OAN using optical switch (OS). The simulation results demonstrate that the ONU-interconnected scheme can efficiently reduce the energy consumption of OAN, and it shows a good energy consumption performance under daily traffic model.

  4. Joint source-channel coding for a quantum multiple access channel

    NASA Astrophysics Data System (ADS)

    Wilde, Mark M.; Savov, Ivan

    2012-11-01

    Suppose that two senders each obtain one share of the output of a classical, bivariate, correlated information source. They would like to transmit the correlated source to a receiver using a quantum multiple access channel. In prior work, Cover, El Gamal and Salehi provided a combined source-channel coding strategy for a classical multiple access channel which outperforms the simpler ‘separation’ strategy where separate codebooks are used for the source coding and the channel coding tasks. In this paper, we prove that a coding strategy similar to the Cover-El Gamal-Salehi strategy and a corresponding quantum simultaneous decoder allow for the reliable transmission of a source over a quantum multiple access channel, as long as a set of information inequalities involving the Holevo quantity hold.

  5. Joint power and multiple access control for wireless mesh network with Rose projection method.

    PubMed

    Tang, Meiqin; Shang, Lili; Xin, Yalin; Liu, Xiaohua; Wei, Xinjiang

    2014-01-01

    This paper investigates the utility maximization problem for the downlink of the multi-interface multichannel wireless mesh network with orthogonal frequency division multiple access. A cross-layer joint power and multiple access control algorithm are proposed. Rosen projection matrix is combined with Solodov projection techniques to build a three-memory gradient Rosen projection method, which is applied to solve this optimization problem. The convergence analysis is given and simulations show that the proposed solution achieves significant throughput compared with existing approaches.

  6. 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.

  7. Joint Power and Multiple Access Control for Wireless Mesh Network with Rose Projection Method

    PubMed Central

    Tang, Meiqin; Shang, Lili; Xin, Yalin; Liu, Xiaohua; Wei, Xinjiang

    2014-01-01

    This paper investigates the utility maximization problem for the downlink of the multi-interface multichannel wireless mesh network with orthogonal frequency division multiple access. A cross-layer joint power and multiple access control algorithm are proposed. Rosen projection matrix is combined with Solodov projection techniques to build a three-memory gradient Rosen projection method, which is applied to solve this optimization problem. The convergence analysis is given and simulations show that the proposed solution achieves significant throughput compared with existing approaches. PMID:24883384

  8. Dynamical downscaling of regional climate over eastern China using RSM with multiple physics scheme ensembles

    NASA Astrophysics Data System (ADS)

    Peishu, Zong; Jianping, Tang; Shuyu, Wang; Lingyun, Xie; Jianwei, Yu; Yunqian, Zhu; Xiaorui, Niu; Chao, Li

    2016-06-01

    The parameterization of physical processes is one of the critical elements to properly simulate the regional climate over eastern China. It is essential to conduct detailed analyses on the effect of physical parameterization schemes on regional climate simulation, to provide more reliable regional climate change information. In this paper, we evaluate the 25-year (1983-2007) summer monsoon climate characteristics of precipitation and surface air temperature by using the regional spectral model (RSM) with different physical schemes. The ensemble results using the reliability ensemble averaging (REA) method are also assessed. The result shows that the RSM model has the capacity to reproduce the spatial patterns, the variations, and the temporal tendency of surface air temperature and precipitation over eastern China. And it tends to predict better climatology characteristics over the Yangtze River basin and the South China. The impact of different physical schemes on RSM simulations is also investigated. Generally, the CLD3 cloud water prediction scheme tends to produce larger precipitation because of its overestimation of the low-level moisture. The systematic biases derived from the KF2 cumulus scheme are larger than those from the RAS scheme. The scale-selective bias correction (SSBC) method improves the simulation of the temporal and spatial characteristics of surface air temperature and precipitation and advances the circulation simulation capacity. The REA ensemble results show significant improvement in simulating temperature and precipitation distribution, which have much higher correlation coefficient and lower root mean square error. The REA result of selected experiments is better than that of nonselected experiments, indicating the necessity of choosing better ensemble samples for ensemble.

  9. Dynamical downscaling of regional climate over eastern China using RSM with multiple physics scheme ensembles

    NASA Astrophysics Data System (ADS)

    Peishu, Zong; Jianping, Tang; Shuyu, Wang; Lingyun, Xie; Jianwei, Yu; Yunqian, Zhu; Xiaorui, Niu; Chao, Li

    2017-08-01

    The parameterization of physical processes is one of the critical elements to properly simulate the regional climate over eastern China. It is essential to conduct detailed analyses on the effect of physical parameterization schemes on regional climate simulation, to provide more reliable regional climate change information. In this paper, we evaluate the 25-year (1983-2007) summer monsoon climate characteristics of precipitation and surface air temperature by using the regional spectral model (RSM) with different physical schemes. The ensemble results using the reliability ensemble averaging (REA) method are also assessed. The result shows that the RSM model has the capacity to reproduce the spatial patterns, the variations, and the temporal tendency of surface air temperature and precipitation over eastern China. And it tends to predict better climatology characteristics over the Yangtze River basin and the South China. The impact of different physical schemes on RSM simulations is also investigated. Generally, the CLD3 cloud water prediction scheme tends to produce larger precipitation because of its overestimation of the low-level moisture. The systematic biases derived from the KF2 cumulus scheme are larger than those from the RAS scheme. The scale-selective bias correction (SSBC) method improves the simulation of the temporal and spatial characteristics of surface air temperature and precipitation and advances the circulation simulation capacity. The REA ensemble results show significant improvement in simulating temperature and precipitation distribution, which have much higher correlation coefficient and lower root mean square error. The REA result of selected experiments is better than that of nonselected experiments, indicating the necessity of choosing better ensemble samples for ensemble.

  10. Multi-pulse multi-delay (MPMD) multiple access modulation for UWB

    DOEpatents

    Dowla, Farid U.; Nekoogar, Faranak

    2007-03-20

    A new modulation scheme in UWB communications is introduced. This modulation technique utilizes multiple orthogonal transmitted-reference pulses for UWB channelization. The proposed UWB receiver samples the second order statistical function at both zero and non-zero lags and matches the samples to stored second order statistical functions, thus sampling and matching the shape of second order statistical functions rather than just the shape of the received pulses.

  11. An Innovative Approach to Scheme Learning Map Considering Tradeoff Multiple Objectives

    ERIC Educational Resources Information Center

    Lin, Yu-Shih; Chang, Yi-Chun; Chu, Chih-Ping

    2016-01-01

    An important issue in personalized learning is to provide learners with customized learning according to their learning characteristics. This paper focused attention on scheming learning map as follows. The learning goal can be achieved via different pathways based on alternative materials, which have the relationships of prerequisite, dependence,…

  12. An Innovative Approach to Scheme Learning Map Considering Tradeoff Multiple Objectives

    ERIC Educational Resources Information Center

    Lin, Yu-Shih; Chang, Yi-Chun; Chu, Chih-Ping

    2016-01-01

    An important issue in personalized learning is to provide learners with customized learning according to their learning characteristics. This paper focused attention on scheming learning map as follows. The learning goal can be achieved via different pathways based on alternative materials, which have the relationships of prerequisite, dependence,…

  13. Simplified Learning Scheme For Analog Neural Network

    NASA Technical Reports Server (NTRS)

    Eberhardt, Silvio P.

    1991-01-01

    Synaptic connections adjusted one at a time in small increments. Simplified gradient-descent learning scheme for electronic neural-network processor less efficient than better-known back-propagation scheme, but offers two advantages: easily implemented in circuitry because data-access circuitry separated from learning circuitry; and independence of data-access circuitry makes possible to implement feedforward as well as feedback networks, including those of multiple-attractor type. Important in such applications as recognition of patterns.

  14. Optical receiver sensitivity analysis for electronic code division multiple access over passive optical network

    NASA Astrophysics Data System (ADS)

    Han, Yamei; Liang, Siyuan; Wang, Liqian; Chen, Xue

    2010-12-01

    Optical receiver sensitivity for electronic code division multiple access over a passive optical network (ECDMA-PON) is analyzed theoretically. Compared with TDM system, ECDMA-PON offers better receiver sensitivity due to coding gain. Fundamental simulation results are provided to show its validity.

  15. A Random-Access Multiple-Program System for the U of M Language Laboratory.

    ERIC Educational Resources Information Center

    Mills, David L.

    1969-01-01

    The operational characteristics of a modern equipment facility (random-access multiple-program system) being planned and constructed for the University of Michigan language laboratory and how it compares with the system it is to replace are summarized in this article. A technical description of the structural makeup of the system precedes an…

  16. Performance analysis of hybrid ARQ protocols in a slotted code division multiple-access network

    NASA Astrophysics Data System (ADS)

    Hanratty, Joseph M.

    1989-08-01

    A link throughput-delay analysis is presented for a slotted direct-sequence spread-spectrum multiple-access packet radio network (PRN) operating in the presence of background noise, multiple-access interference, and pulsed jammer noise. The PRN is comprised of an arbitrary number of full-duplex radio units arranged in a paired-off topology. Slotted ALOHA random access is used in conjunction with CDMA for channel access and a type 1 hybrid ARQ is used for error control. Expression are derived for the link throughput-delay in terms of the channel cutoff rate and capacity. With the friendly objective of maximizing the link throughput, and the enemy objective of minimizing the link throughput, the dependency of the optimal retransmission probability, processing gain, code rate, and jamming fraction on the population size, traffic intensity, bit energy-to-background-noise ratio, is examined in detail. It is shown that properly designed (optimized) PRN using random-access CDMA offers a significantly larger heavy load throughput than a random-access PRN.

  17. A collaborative approach to improving patient access in general practice: impact of three different pilot schemes in 12 general practices in Greenwich

    PubMed Central

    Lawless, Melanie; Wright, Ellen; Davidson, Jackie

    2016-01-01

    Abstract Background With rising patient demand and expectations, many practices are struggling to respond to the demand for appointments. Objective To investigate different approaches to improving access to general practice and assess the impact on (i) patient experience, (ii) practice staff experience and (iii) activity in A&E and walk-in centres. Method Greenwich CCG piloted three approaches in 12 volunteer practices. The schemes were:(1) Systematic GP telephone triage of all appointment requests.(2) Analysis and comparison of practice data including demand and capacity to identify opportunities for improvement.(3) Online consultations. Qualitative and quantitative evaluation was undertaken. Results Overall results were inconclusive and no one pilot scheme was overwhelmingly successful in improving patient experience of access or reducing practice workload. Scheme 1 telephone triage: In some cases, overall demand on clinician time through the day reduced as face-to-face consultations were replaced with shorter telephone consultations. However, in other practices, total consulting time went up when telephone consultations took longer than the suggested average 5 min. Scheme 2 practice analysis and benchmarking: The pilot practices implemented no significant changes. Scheme 3 online consultations: Take up was low, with users as a percentage of total list size dropping significantly to even lower levels in the second half of the pilot – from 3.13% in the first three months to 1.20% in the second three months. Conclusion As the pilots did not improve the overall patient experience of access or practice workload, the pilot schemes were not rolled out by the CCG. From the CCG’s point of view, it was valuable to test out the effect of a scheme before committing further resources. PMID:28250835

  18. Lexical access changes in patients with multiple sclerosis: a two-year follow-up study.

    PubMed

    Sepulcre, Jorge; Peraita, Herminia; Goni, Joaquin; Arrondo, Gonzalo; Martincorena, Inigo; Duque, Beatriz; Velez de Mendizabal, Nieves; Masdeu, Joseph C; Villoslada, Pablo

    2011-02-01

    The aim of the study was to analyze lexical access strategies in patients with multiple sclerosis (MS) and their changes over time. We studied lexical access strategies during semantic and phonemic verbal fluency tests and also confrontation naming in a 2-year prospective cohort of 45 MS patients and 20 healthy controls. At baseline, switching lexical access strategy (both in semantic and in phonemic verbal fluency tests) and confrontation naming were significantly impaired in MS patients compared with controls. After 2 years follow-up, switching score decreased, and cluster size increased over time in semantic verbal fluency tasks, suggesting a failure in the retrieval of lexical information rather than an impairment of the lexical pool. In conclusion, these findings underline the significant presence of lexical access problems in patients with MS and could point out their key role in the alterations of high-level communications abilities in MS.

  19. 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.

  20. Turbulence mitigation scheme based on multiple-user detection in an orbital-angular-momentum multiplexed system

    NASA Astrophysics Data System (ADS)

    Zou, Li; Wang, Le; Zhao, Sheng-Mei; Chen, Han-Wu

    2016-11-01

    Atmospheric turbulence (AT) induced crosstalk can significantly impair the performance of a free-space optical (FSO) communication link using orbital angular momentum (OAM) multiplexing. In this paper, we propose a multiple-user detection (MUD) turbulence mitigation scheme in an OAM-multiplexed FSO communication link. First, we present a MUD equivalent communication model for an OAM-multiplexed FSO communication link under AT. In the equivalent model, each input bit stream represents one user’s information. The deformed OAM spatial modes caused by AT, instead of the pure OAM spatial modes, are used as information carriers, and the overlapping between the deformed OAM spatial modes are computed as the correlation coefficients between the users. Then, we present a turbulence mitigation scheme based on MUD idea to enhance AT tolerance of the OAM-multiplexed FSO communication link. In the proposed scheme, the crosstalk caused by AT is used as a useful component to deduce users’ information. The numerical results show that the performance of the OAM-multiplexed communication link has greatly improved by the proposed scheme. When the turbulence strength is 1 × 10-15 m-2/3, the transmission distance is 1000 m and the channel signal-to-noise ratio (SNR) is 26 dB, the bit-error-rate (BER) performance of four spatial multiplexed OAM modes lm = +1,+2,+3,+4 are all close to 10-5, and there is a 2-3 fold increase in the BER performance in comparison with those results without the proposed scheme. In addition, the proposed scheme is more effective for an OAM-multiplexed FSO communication link with a larger OAM mode topological charge interval. The proposed scheme is a promising direction for compensating the interference caused by AT in the OAM-multiplexed FSO communication link. Project supported by the National Natural Science Foundation of China (Grant Nos. 61271238 and 61475075), the Open Research Fund of Key Lab of Broadband Wireless Communication and Sensor Network

  1. Persons with Multiple Disabilities Exercise Adaptive Response Schemes with the Help of Technology-Based Programs: Three Single-Case Studies

    ERIC Educational Resources Information Center

    Lancioni, Giulio E.; Singh, Nirbhay N.; O'Reilly, Mark F.; Sigafoos, Jeff; Oliva, Doretta; Campodonico, Francesca; Lang, Russell

    2012-01-01

    The present three single-case studies assessed the effectiveness of technology-based programs to help three persons with multiple disabilities exercise adaptive response schemes independently. The response schemes included (a) left and right head movements for a man who kept his head increasingly static on his wheelchair's headrest (Study I), (b)…

  2. Persons with Multiple Disabilities Exercise Adaptive Response Schemes with the Help of Technology-Based Programs: Three Single-Case Studies

    ERIC Educational Resources Information Center

    Lancioni, Giulio E.; Singh, Nirbhay N.; O'Reilly, Mark F.; Sigafoos, Jeff; Oliva, Doretta; Campodonico, Francesca; Lang, Russell

    2012-01-01

    The present three single-case studies assessed the effectiveness of technology-based programs to help three persons with multiple disabilities exercise adaptive response schemes independently. The response schemes included (a) left and right head movements for a man who kept his head increasingly static on his wheelchair's headrest (Study I), (b)…

  3. Transitory flow in a complex hydroelectric scheme with multiple intakes and water tanks

    NASA Astrophysics Data System (ADS)

    Bucur, D. M.; Ghergu, C. M.; Tănase, N. O.; Isbăşoiu, E. C.

    2010-08-01

    This paper analyzes the free surface level variation in the surge tank and in the secondary shafts of a complex hydro electrical scheme with two headraces and four secondary intakes. An analysis of the transient operating regimes of the hydropower plant must take in account the complex flow in the surge tank and in all the secondary catchments. Important operation restrictions and different transport capacities of the headraces must be considered. The study is completed with the mathematical model of the phenomenon and with the numerical simulation of the regimes. It is pointed out which are the operating regimes and the maneuvers that can cause malfunctions or undesirable incidents.

  4. Study of spread spectrum multiple access systems for satellite communications with overlay on current services

    NASA Technical Reports Server (NTRS)

    Ha, Tri T.; Pratt, Timothy

    1989-01-01

    The feasibility of using spread spectrum techniques to provide a low-cost multiple access system for a very large number of low data terminals was investigated. Two applications of spread spectrum technology to very small aperture terminal (VSAT) satellite communication networks are presented. Two spread spectrum multiple access systems which use a form of noncoherent M-ary FSK (MFSK) as the primary modulation are described and the throughput analyzed. The analysis considers such factors as satellite power constraints and adjacent satellite interference. Also considered is the effect of on-board processing on the multiple access efficiency and the feasibility of overlaying low data rate spread spectrum signals on existing satellite traffic as a form of frequency reuse is investigated. The use of chirp is examined for spread spectrum communications. In a chirp communication system, each data bit is converted into one or more up or down sweeps of frequency, which spread the RF energy across a broad range of frequencies. Several different forms of chirp communication systems are considered, and a multiple-chirp coded system is proposed for overlay service. The mutual interference problem is examined in detail and a performance analysis undertaken for the case of a chirp data channel overlaid on a video channel.

  5. Coherent beam combining and optical space-time division multiple access

    NASA Astrophysics Data System (ADS)

    Miniscalco, William; Lane, Steven A.; Fisher, Kirk; Waite, Stephanie; Howlett, Michael; Smith, Irl

    2010-08-01

    We have developed an approach to multiple-access lasercom that adopts the commercial paradigm of sharing the most expensive terminal resources among all users. Space-time division multiple access (STDMA), analogous to an optical space-time switch, hops the transmit beam and receive direction among multiple users and exchanges data while the beam dwells on a user. A key enabler of STDMA is electronic beam steering using liquid crystal optical phased arrays, which provides fast, precise, and agile beam re-pointing. We have built the first optical STDMA terminal, combining beam hopping between remote terminals with coherent combining of both transmit and receive apertures, which is an effective means for increasing antenna gain in systems for which large aperture components are impractical. Coherent beam combining provided the expected increase in antenna gain, and the terminal was found to re-point the beam among users quickly and precisely enough to suffer only minor throughput degradation. Communications test were performed using 10 Gb/s Ethernet for a single-aperture configuration. Performance is presented as a function of angle scan speed and STDMA dwell time per remote terminal. The results suggest that STDMA is a viable technology for supporting multiple-access space-based laser communication.

  6. MSACompro: protein multiple sequence alignment using predicted secondary structure, solvent accessibility, and residue-residue contacts.

    PubMed

    Deng, Xin; Cheng, Jianlin

    2011-12-14

    Multiple Sequence Alignment (MSA) is a basic tool for bioinformatics research and analysis. It has been used essentially in almost all bioinformatics tasks such as protein structure modeling, gene and protein function prediction, DNA motif recognition, and phylogenetic analysis. Therefore, improving the accuracy of multiple sequence alignment is important for advancing many bioinformatics fields. We designed and developed a new method, MSACompro, to synergistically incorporate predicted secondary structure, relative solvent accessibility, and residue-residue contact information into the currently most accurate posterior probability-based MSA methods to improve the accuracy of multiple sequence alignments. The method is different from the multiple sequence alignment methods (e.g. 3D-Coffee) that use the tertiary structure information of some sequences since the structural information of our method is fully predicted from sequences. To the best of our knowledge, applying predicted relative solvent accessibility and contact map to multiple sequence alignment is novel. The rigorous benchmarking of our method to the standard benchmarks (i.e. BAliBASE, SABmark and OXBENCH) clearly demonstrated that incorporating predicted protein structural information improves the multiple sequence alignment accuracy over the leading multiple protein sequence alignment tools without using this information, such as MSAProbs, ProbCons, Probalign, T-coffee, MAFFT and MUSCLE. And the performance of the method is comparable to the state-of-the-art method PROMALS of using structural features and additional homologous sequences by slightly lower scores. MSACompro is an efficient and reliable multiple protein sequence alignment tool that can effectively incorporate predicted protein structural information into multiple sequence alignment. The software is available at http://sysbio.rnet.missouri.edu/multicom_toolbox/.

  7. Solvable biological evolution models with general fitness functions and multiple mutations in parallel mutation-selection scheme

    NASA Astrophysics Data System (ADS)

    Saakian, David B.; Hu, Chin-Kun; Khachatryan, H.

    2004-10-01

    In a recent paper [Phys. Rev. E 69, 046121 (2004)], we used the Suzuki-Trottere formalism to study a quasispecies biological evolution model in a parallel mutation-selection scheme with a single-peak fitness function and a point mutation. In the present paper, we extend such a study to evolution models with more general fitness functions or multiple mutations in the parallel mutation-selection scheme. We give some analytical equations to define the error thresholds for some general cases of mean-field-like or symmetric mutation schemes and fitness functions. We derive some equations for the dynamics in the case of a point mutation and polynomial fitness functions. We derive exact dynamics for two-point mutations, asymmetric mutations, and the four-value spin model with a single-peak fitness function. The same method is applied for the model with a royal road fitness function. We derive the steady-state distribution for the single-peak fitness function.

  8. Pentagraph image fusion scheme for motion blur prevention using multiple monochromatic images.

    PubMed

    Volfman, Alon A; Mendlovic, David; Raz, Ariel

    2016-04-10

    This paper introduces the pentagraph image fusion (PIF) scheme for motion-related blur prevention in images. The PIF algorithm processes five monochromatic images into a single, low-noise, no-blur color image. The images are acquired using a new photography scheme, sequential filter photography (SFP), where instead of using a stationary Bayer pattern color filter array in front of the image sensor, a tunable color filter array is used. Using this approach, several monochromatic images are captured one by one and later fused into one color image. The SFP introduces various advantages such as higher resolution, better SNR, and the ability to control both exposure time and color filter separately for each image. The PIF algorithm harnesses all the advantages of SFP for the first time, to the best of our knowledge, in the field of blur-free image acquisition. Five images are taken with controllable exposure time and color filter, three images for the color bands, and two high-signal panchromatic images. These images are fused together to be a single, low-noise, no-blur color image. The algorithm presents a generic approach of dealing with both local and global motion blur and does not require any user intervention.

  9. Optical multiple-image encryption in diffractive-imaging-based scheme using spectral fusion and nonlinear operation.

    PubMed

    Qin, Yi; Gong, Qiong; Wang, Zhipeng; Wang, Hongjuan

    2016-11-14

    We report a new method for multiple-image encryption in diffractive-imaging-based encryption (DIBE) scheme. The discrete cosine transformation (DCT) spectra of the primary images are extracted, compacted and then nonlinear-transformed before being sent to the DIBE, where they are encoded into a single intensity pattern. With the help of a suggested phase retrieval algorithm, the original images can be recovered with high quality. Furthermore, due to the introduction of the nonlinear operation, the proposal is demonstrated to be robust to the currently available cryptographic attacks. The proposal probes a new way for multiple-image encryption in DIBE, and its effectiveness and feasibility have been supported by numerical simulations.

  10. The rigorous stochastic matrix multiplication scheme for the calculations of reduced equilibrium density matrices of open multilevel quantum systems

    NASA Astrophysics Data System (ADS)

    Chen, Xin

    2014-04-01

    Understanding the roles of the temporary and spatial structures of quantum functional noise in open multilevel quantum molecular systems attracts a lot of theoretical interests. I want to establish a rigorous and general framework for functional quantum noises from the constructive and computational perspectives, i.e., how to generate the random trajectories to reproduce the kernel and path ordering of the influence functional with effective Monte Carlo methods for arbitrary spectral densities. This construction approach aims to unify the existing stochastic models to rigorously describe the temporary and spatial structure of Gaussian quantum noises. In this paper, I review the Euclidean imaginary time influence functional and propose the stochastic matrix multiplication scheme to calculate reduced equilibrium density matrices (REDM). In addition, I review and discuss the Feynman-Vernon influence functional according to the Gaussian quadratic integral, particularly its imaginary part which is critical to the rigorous description of the quantum detailed balance. As a result, I establish the conditions under which the influence functional can be interpreted as the average of exponential functional operator over real-valued Gaussian processes for open multilevel quantum systems. I also show the difference between the local and nonlocal phonons within this framework. With the stochastic matrix multiplication scheme, I compare the normalized REDM with the Boltzmann equilibrium distribution for open multilevel quantum systems.

  11. The rigorous stochastic matrix multiplication scheme for the calculations of reduced equilibrium density matrices of open multilevel quantum systems

    SciTech Connect

    Chen, Xin

    2014-04-21

    Understanding the roles of the temporary and spatial structures of quantum functional noise in open multilevel quantum molecular systems attracts a lot of theoretical interests. I want to establish a rigorous and general framework for functional quantum noises from the constructive and computational perspectives, i.e., how to generate the random trajectories to reproduce the kernel and path ordering of the influence functional with effective Monte Carlo methods for arbitrary spectral densities. This construction approach aims to unify the existing stochastic models to rigorously describe the temporary and spatial structure of Gaussian quantum noises. In this paper, I review the Euclidean imaginary time influence functional and propose the stochastic matrix multiplication scheme to calculate reduced equilibrium density matrices (REDM). In addition, I review and discuss the Feynman-Vernon influence functional according to the Gaussian quadratic integral, particularly its imaginary part which is critical to the rigorous description of the quantum detailed balance. As a result, I establish the conditions under which the influence functional can be interpreted as the average of exponential functional operator over real-valued Gaussian processes for open multilevel quantum systems. I also show the difference between the local and nonlocal phonons within this framework. With the stochastic matrix multiplication scheme, I compare the normalized REDM with the Boltzmann equilibrium distribution for open multilevel quantum systems.

  12. Energy-Efficient Deadline-Aware Data-Gathering Scheme Using Multiple Mobile Data Collectors.

    PubMed

    Dasgupta, Rumpa; Yoon, Seokhoon

    2017-04-01

    In wireless sensor networks, the data collected by sensors are usually forwarded to the sink through multi-hop forwarding. However, multi-hop forwarding can be inefficient due to the energy hole problem and high communications overhead. Moreover, when the monitored area is large and the number of sensors is small, sensors cannot send the data via multi-hop forwarding due to the lack of network connectivity. In order to address those problems of multi-hop forwarding, in this paper, we consider a data collection scheme that uses mobile data collectors (MDCs), which visit sensors and collect data from them. Due to the recent breakthroughs in wireless power transfer technology, MDCs can also be used to recharge the sensors to keep them from draining their energy. In MDC-based data-gathering schemes, a big challenge is how to find the MDCs' traveling paths in a balanced way, such that their energy consumption is minimized and the packet-delay constraint is satisfied. Therefore, in this paper, we aim at finding the MDCs' paths, taking energy efficiency and delay constraints into account. We first define an optimization problem, named the delay-constrained energy minimization (DCEM) problem, to find the paths for MDCs. An integer linear programming problem is formulated to find the optimal solution. We also propose a two-phase path-selection algorithm to efficiently solve the DCEM problem. Simulations are performed to compare the performance of the proposed algorithms with two heuristics algorithms for the vehicle routing problem under various scenarios. The simulation results show that the proposed algorithms can outperform existing algorithms in terms of energy efficiency and packet delay.

  13. Energy-Efficient Deadline-Aware Data-Gathering Scheme Using Multiple Mobile Data Collectors

    PubMed Central

    Dasgupta, Rumpa; Yoon, Seokhoon

    2017-01-01

    In wireless sensor networks, the data collected by sensors are usually forwarded to the sink through multi-hop forwarding. However, multi-hop forwarding can be inefficient due to the energy hole problem and high communications overhead. Moreover, when the monitored area is large and the number of sensors is small, sensors cannot send the data via multi-hop forwarding due to the lack of network connectivity. In order to address those problems of multi-hop forwarding, in this paper, we consider a data collection scheme that uses mobile data collectors (MDCs), which visit sensors and collect data from them. Due to the recent breakthroughs in wireless power transfer technology, MDCs can also be used to recharge the sensors to keep them from draining their energy. In MDC-based data-gathering schemes, a big challenge is how to find the MDCs’ traveling paths in a balanced way, such that their energy consumption is minimized and the packet-delay constraint is satisfied. Therefore, in this paper, we aim at finding the MDCs’ paths, taking energy efficiency and delay constraints into account. We first define an optimization problem, named the delay-constrained energy minimization (DCEM) problem, to find the paths for MDCs. An integer linear programming problem is formulated to find the optimal solution. We also propose a two-phase path-selection algorithm to efficiently solve the DCEM problem. Simulations are performed to compare the performance of the proposed algorithms with two heuristics algorithms for the vehicle routing problem under various scenarios. The simulation results show that the proposed algorithms can outperform existing algorithms in terms of energy efficiency and packet delay. PMID:28368300

  14. Multiple-access phased array antenna simulator for a digital beam-forming system investigation

    NASA Technical Reports Server (NTRS)

    Kerczewski, Robert J.; Yu, John; Walton, Joanne C.; Perl, Thomas D.; Andro, Monty; Alexovich, Robert E.

    1992-01-01

    Future versions of data relay satellite systems are currently being planned by NASA. Being given consideration for implementation are on-board digital beamforming techniques which will allow multiple users to simultaneously access a single S-band phased array antenna system. To investigate the potential performance of such a system, a laboratory simulator has been developed at NASA's Lewis Research Center. This paper describes the system simulator, and in particular, the requirements, design and performance of a key subsystem, the phased array antenna simulator, which provides realistic inputs to the digital processor including multiple signals, noise, and nonlinearities.

  15. Multiple-access phased array antenna simulator for a digital beam forming system investigation

    NASA Technical Reports Server (NTRS)

    Kerczewski, Robert J.; Yu, John; Walton, Joanne C.; Perl, Thomas D.; Andro, Monty; Alexovich, Robert E.

    1992-01-01

    Future versions of data relay satellite systems are currently being planned by NASA. Being given consideration for implementation are on-board digital beamforming techniques which will allow multiple users to simultaneously access a single S-band phased array antenna system. To investigate the potential performance of such a system, a laboratory simulator has been developed at NASA's Lewis Research Center. This paper describes the system simulator, and in particular, the requirements, design, and performance of a key subsystem, the phased array antenna simulator, which provides realistic inputs to the digital processor including multiple signals, noise, and nonlinearities.

  16. Fairness for Non-Orthogonal Multiple Access in 5G Systems

    NASA Astrophysics Data System (ADS)

    Timotheou, Stelios; Krikidis, Ioannis

    2015-10-01

    In non-orthogonal multiple access (NOMA) downlink, multiple data flows are superimposed in the power domain and user decoding is based on successive interference cancellation. NOMA's performance highly depends on the power split among the data flows and the associated power allocation (PA) problem. In this letter, we study NOMA from a fairness standpoint and we investigate PA techniques that ensure fairness for the downlink users under i) instantaneous channel state information (CSI) at the transmitter, and ii) average CSI. Although the formulated problems are non-convex, we have developed low-complexity polynomial algorithms that yield the optimal solution in both cases considered.

  17. 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.

  18. 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.

  19. Study of optoelectronic switch for satellite-switched time-division multiple access

    NASA Technical Reports Server (NTRS)

    Su, Shing-Fong; Jou, Liz; Lenart, Joe

    1987-01-01

    The use of optoelectronic switching for satellite switched time division multiple access will improve the isolation and reduce the crosstalk of an IF switch matrix. The results are presented of a study on optoelectronic switching. Tasks include literature search, system requirements study, candidate switching architecture analysis, and switch model optimization. The results show that the power divided and crossbar switching architectures are good candidates for an IF switch matrix.

  20. Error correction coding for frequency-hopping multiple-access spread spectrum communication systems

    NASA Technical Reports Server (NTRS)

    Healy, T. J.

    1982-01-01

    A communication system which would effect channel coding for frequency-hopped multiple-access is described. It is shown that in theory coding can increase the spectrum utilization efficiency of a system with mutual interference to 100 percent. Various coding strategies are discussed and some initial comparisons are given. Some of the problems associated with implementing the type of system described here are discussed.

  1. Field of view extension using frequency division multiple access technique: numerical analysis

    NASA Astrophysics Data System (ADS)

    Kavehvash, Zahra; Mehrany, Khashayar; Bagheri, Saeed

    2011-06-01

    Integral imaging could be considered as one of the prospective methods for recording and displaying 3D images based on its distinct features. Some of the most important challenges with this approach are the field of view and resolution limitation. In this work we investigate using frequency division multiple access (FDMA) idea for solving this problem. Simulation results show an increase of more than ten percent in the performance of the 3D reconstructed images using the proposed method.

  2. Coherent direct sequence optical code multiple access encoding-decoding efficiency versus wavelength detuning.

    PubMed

    Pastor, D; Amaya, W; García-Olcina, R; Sales, S

    2007-07-01

    We present a simple theoretical model of and the experimental verification for vanishing of the autocorrelation peak due to wavelength detuning on the coding-decoding process of coherent direct sequence optical code multiple access systems based on a superstructured fiber Bragg grating. Moreover, the detuning vanishing effect has been explored to take advantage of this effect and to provide an additional degree of multiplexing and/or optical code tuning.

  3. Utility of the Beta-Multinomial Distribution in Multiple Classification Scheme.

    ERIC Educational Resources Information Center

    Peng, Chao-Ying Joanne

    This study is an attempt to answer the following research question: can the reliability of a criterion-referenced test be accurately determined according to a multiple classification of the student's performance? Specifically, the study pursues the beta-multinomial model, which postulates the probability distribution of an examinee's degree of…

  4. MSAIndelFR: a scheme for multiple protein sequence alignment using information on indel flanking regions.

    PubMed

    Al-Shatnawi, Mufleh; Ahmad, M Omair; Swamy, M N S

    2015-11-23

    The alignment of multiple protein sequences is one of the most commonly performed tasks in bioinformatics. In spite of considerable research and efforts that have been recently deployed for improving the performance of multiple sequence alignment (MSA) algorithms, finding a highly accurate alignment between multiple protein sequences is still a challenging problem. We propose a novel and efficient algorithm called, MSAIndelFR, for multiple sequence alignment using the information on the predicted locations of IndelFRs and the computed average log-loss values obtained from IndelFR predictors, each of which is designed for a different protein fold. We demonstrate that the introduction of a new variable gap penalty function based on the predicted locations of the IndelFRs and the computed average log-loss values into the proposed algorithm substantially improves the protein alignment accuracy. This is illustrated by evaluating the performance of the algorithm in aligning sequences belonging to the protein folds for which the IndelFR predictors already exist and by using the reference alignments of the four popular benchmarks, BAliBASE 3.0, OXBENCH, PREFAB 4.0, and SABRE (SABmark 1.65). We have proposed a novel and efficient algorithm, the MSAIndelFR algorithm, for multiple protein sequence alignment incorporating a new variable gap penalty function. It is shown that the performance of the proposed algorithm is superior to that of the most-widely used alignment algorithms, Clustal W2, Clustal Omega, Kalign2, MSAProbs, MAFFT, MUSCLE, ProbCons and Probalign, in terms of both the sum-of-pairs and total column metrics.

  5. An efficient sparse matrix multiplication scheme for the CYBER 205 computer

    NASA Technical Reports Server (NTRS)

    Lambiotte, Jules J., Jr.

    1988-01-01

    This paper describes the development of an efficient algorithm for computing the product of a matrix and vector on a CYBER 205 vector computer. The desire to provide software which allows the user to choose between the often conflicting goals of minimizing central processing unit (CPU) time or storage requirements has led to a diagonal-based algorithm in which one of four types of storage is selected for each diagonal. The candidate storage types employed were chosen to be efficient on the CYBER 205 for diagonals which have nonzero structure which is dense, moderately sparse, very sparse and short, or very sparse and long; however, for many densities, no diagonal type is most efficient with respect to both resource requirements, and a trade-off must be made. For each diagonal, an initialization subroutine estimates the CPU time and storage required for each storage type based on results from previously performed numerical experimentation. These requirements are adjusted by weights provided by the user which reflect the relative importance the user places on the two resources. The adjusted resource requirements are then compared to select the most efficient storage and computational scheme.

  6. Effectiveness of Space-Division Multiple-Access in MIMO Communication Systems with Parallel Data Transmission

    NASA Astrophysics Data System (ADS)

    Ermolayev, V. T.; Flaksman, A. G.; Averin, I. M.; Gribov, D. V.

    2004-02-01

    We consider multiple-input multiple-output (MIMO) cellular communication systems with antenna arrays at both link ends and data transmission via parallel eigenchannels matched with a random spatial channel. We analyze the effectiveness of the space-division multiple-access (SDMA) method, which does not require estimation of signal-arrival directions and is based on orthogonalization of the parallel channels of all users. We obtained approximate analytical expressions for the mean ratio of the signal power to the noise power and the MIMO system capacity, which are derived for the case of Rayleigh fading of signals. Although the obtained formulas are much simpler than the exact ones, they ensure high accuracy for an arbitrary number of transmitting and receiving antennas and an arbitrary power of transmitter. Our results demonstrate the high effectiveness of the proposed SDMA method.

  7. 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.

  8. 39% access time improvement, 11% energy reduction, 32 kbit 1-read/1-write 2-port static random-access memory using two-stage read boost and write-boost after read sensing scheme

    NASA Astrophysics Data System (ADS)

    Yamamoto, Yasue; Moriwaki, Shinichi; Kawasumi, Atsushi; Miyano, Shinji; Shinohara, Hirofumi

    2016-04-01

    We propose novel circuit techniques for 1 clock (1CLK) 1 read/1 write (1R/1W) 2-port static random-access memories (SRAMs) to improve read access time (tAC) and write margins at low voltages. Two-stage read boost (TSR-BST) and write word line boost (WWL-BST) after the read sensing schemes have been proposed. TSR-BST reduces the worst read bit line (RBL) delay by 61% and RBL amplitude by 10% at V DD = 0.5 V, which improves tAC by 39% and reduces energy dissipation by 11% at V DD = 0.55 V. WWL-BST after read sensing scheme improves minimum operating voltage (V min) by 140 mV. A 32 kbit 1CLK 1R/1W 2-port SRAM with TSR-BST and WWL-BST has been developed using a 40 nm CMOS.

  9. A high capacity multiple watermarking scheme based on Fourier descriptor and Sudoku

    NASA Astrophysics Data System (ADS)

    Zhang, Li; Zheng, Huimin

    2015-12-01

    Digital watermark is a type of technology to hide some significant information which is mainly used to protect digital data. A high capacity multiple watermarking method is proposed, which adapts the Fourier descriptor to pre-process the watermarks, while a Sudoku puzzle is used as a reference matrix in embedding process and a key in extraction process. It can dramatically reduce the required capacity by applying Fourier descriptor. Meanwhile, the security of watermarks can be guaranteed due to the Sudoku puzzle. Unlike previous algorithms applying Sudoku puzzle in spatial domain, the proposed algorithm works in transformed domain by applying LWT2.In addition, the proposed algorithm can detect the temper location accurately. The experimental results demonstrated that the goals mentioned above have been achieved.

  10. Spatial-phase code-division multiple-access system with multiplexed Fourier holography switching for reconfigurable optical interconnection.

    PubMed

    Takasago, K; Takekawa, M; Shirakawa, A; Kannari, F

    2000-05-10

    A new, to our knowledge, space-variant optical interconnection system based on a spatial-phase code-division multiple-access technique with multiplexed Fourier holography is described. In this technique a signal beam is spread over wide spatial frequencies by an M-sequence pseudorandom phase code. At a receiver side a selected signal beam is properly decoded, and at the same time its spatial pattern is shaped with a Fourier hologram, which is recorded by light that is encoded with the same M-sequence phase mask as the desired signal beam and by light whose spatial beam pattern is shaped to a signal routing pattern. Using the multiplexed holography, we can simultaneously route multisignal flows into individually specified receiver elements. The routing pattern can also be varied by means of switching the encoding phase code or replacing the hologram. We demonstrated a proof-of-principle experiment with a doubly multiplexed hologram that enables simultaneous routing of two signal beams. Using a numerical model, we showed that the proposed scheme can manage more than 250 routing patterns for one signal flow with one multiplexed hologram at a signal-to-noise ratio of ~5.

  11. Access to Electronic Personal Health Records Among Patients With Multiple Chronic Conditions: A Secondary Data Analysis.

    PubMed

    Greenberg, Alexandra J; Falisi, Angela L; Finney Rutten, Lila J; Chou, Wen-Ying Sylvia; Patel, Vaishali; Moser, Richard P; Hesse, Bradford W

    2017-06-02

    In the United States, national incentives for offering access to electronic personal health records (ePHRs) through electronic means are geared toward creating a culture of patient engagement. One group of patients who stand to benefit from online access to ePHRs is the growing population with multiple chronic conditions (MCC). However, little is known about the current availability and use of ePHRs and patient portals among those managing MCC. The aim was to determine the associations between number of chronic conditions and sociodemographic characteristics and usage of ePHRs, and to assess how the public's use of ePHRs varies across subpopulations, including those with MCC. This study used data collected from the 2014 Health Information National Trends Survey (HINTS), and assessed differences in use of ePHRs between those with and without MCC (N=3497) using multiple logistic regression techniques. Variables associated with health care systems (insurance status, having a regular provider) and patient-reported self-efficacy were included in the statistical models. Those with MCC (n=1555) had significantly higher odds of accessing their records three or more times in the past year compared to those reporting no chronic conditions (n=1050; OR 2.46, 95% CI 1.37-4.45), but the overall percentage of those with MCC using ePHRs remained low (371 of 1529 item respondents, 25.63% weighted). No difference in odds of accessing their records was found between those reporting one chronic condition (n=892) and those reporting none (n=1050; OR 1.02, 95% CI 0.66-1.58). Significant differences in odds of accessing ePHRs were seen between income and age groups (P<.001 and P=.05, respectively), and by whether respondents had a regular provider (P=.03). We conclude that ePHRs provide a unique opportunity to enhance MCC patient self-management, but additional effort is needed to ensure that these patients are able to access their ePHRs. An increase in availability of patient access to

  12. Multiple number and letter comparison: directionality and accessibility in numeric and alphabetic memories.

    PubMed

    Jou, Jerwen

    2003-01-01

    In 3 experiments, subjects made comparativejudgments on a set of 2 numbers or letters, 3 numbers or letters, or 5 numbers or letters. Numeric and alphabetic serial order memories were contrasted. Three aspects of serial order memory processes were identified: computational complexity, directionality, and accessibility. Computational complexity is the number of algorithmic steps involved in identifying a target. Directional bias is measured as the speed differences in identifying serial targets of equal computational complexity in a stimulus array. Memory accessibility is measured as the numeric and alphabetic serial position effects. Subjects had a slight directional bias favoring backward ordering for single digits but no bias in 2-digit number ordering, in contrast to a strong forward directional advantage in letter ordering. The speed of number access was found to steadily and evenly decrease along the numeric scale, in contrast to a systematic pattern of variations in alphabet access along the alphabetic scale. Finally, the middle item effect (the middle item in a multi-item array is identified most slowly) found in Jou's (1997) multiple-letter comparison study was generalized to numbers.

  13. An establishment of vascular access through superior vena cava for a patient with multiple central venous stenosis or occlusion.

    PubMed

    Diao, Yong Shu; Feng, Yan Huan; Liu, Chun Cheng; Cui, Tian Lei; Fu, Ping

    2016-05-01

    The patency of vascular access is of vital importance to dialysis patients. Access dysfunction is largely caused by vessel stenosis and thrombosis. Nephrologists usually find themselves helpless when all treatments fail and the vascular access seems to have exhausted. Here we report a successful establishment of vascular access through superior vena cava for a critical patient with multiple central venous stenosis or occlusion. To our knowledge, it is the first case ever reported on the successful establishment of vascular access through superior vena cava under such a complicated condition of vascular exhaustion.

  14. A Creative Helicobacter pylori Diagnosis Scheme Based on Multiple Genetic Analysis System: Qualification and Quantitation.

    PubMed

    Zhou, Lifang; Zhao, Fuju; Hu, Binjie; Fang, Yi; Miao, Yingxin; Huang, Yiqin; Ji, Da'nian; Zhang, Jinghao; Xu, Lingli; Zhang, Yanmei; Bao, Zhijun; Zhao, Hu

    2015-10-01

    Currently, several diagnostic assays for Helicobacter pylori (H. pylori) are available, but each has some limitations. Further, a high-flux quantitative assay is required to assist clinical diagnosis and monitor the effectiveness of therapy and novel vaccine candidates. Three hundred and eighty-seven adult patients [nonulcer dyspepsia (NUD) 295, peptic ulcer disease (PUD) 77, gastric cancer (GC) 15] were enrolled for gastrointestinal endoscopies. Three biopsy samples from gastric antrum were collected for the following tests: culture, rapid urease test (RUT), histopathology, conventional polymerase chain reaction (PCR), and Multiple Genetic Analysis System (MGAS). The diagnostic capability of H. pylori for all methods was evaluated through the receiver operating characteristic (ROC) curves. Based on the gold standard, the sensitivity and specificity of MGAS were 92.9 and 92.4%, and positive predict value (PPV) and negative predict value (NPV) were 96.0 and 87.1%, respectively. All the above parameters of MGAS were higher than that of culture (except its specificity), RUT and histopathology, and nearly closed to that of conventional PCR. The area under curve (AUC) was 0.7575 (Culture), 0.8870 (RUT), 0.9000 (Histopathology), 0.9496 (Conventional PCR), and 0.9277 (MGAS). No significant statistical difference was observed for the H. pylori DNA load in different disease groups (p = .067). In contrast, a statistically significant difference in the H. pylori DNA copy number was observed based on age (p = .043) and gender (p = .021). The data showed that MGAS performed well in detecting H. pylori infection. Furthermore, the quantitative analysis showed that the load of H. pylori was significantly different within both age and gender groups. These results suggested that MGAS could be a potential alternative method for clinical detection and monitoring of the effectiveness of H. pylori therapy. © 2015 John Wiley & Sons Ltd.

  15. Design and performance evaluation of a wideband FM spread-spectrum multiple-access system

    NASA Technical Reports Server (NTRS)

    Wachsman, R. H.; Ghais, A. F.

    1971-01-01

    The system described performs the tracking and communications functions of a tracking and data relay satellite system (TDRS). The spread-spectrum signal format is achieved through wide deviation FM by a sinusoidal subcarrier unique to each multiple-access user. A compound phase-locked loop tracks carrier and subcarrier and demodulates data and ranging signals. Design parameters of user and ground terminals for TDRS are given. Acquisition procedures are described. Performance analyses are presented including the effects of noise, RFI, multipath and other users.

  16. 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.

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

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

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

  18. Visit to general practitioners as a proxy for accessing chronic benefits by members of medical schemes, South Africa

    PubMed Central

    Gantsho, Monwabisi

    2012-01-01

    Abstract Background Prescribed Minimum Benefits is a list of conditions that all medical schemes need to cover in full, and includes a select of chronic conditions. Chronic conditions affect people's lifestyles and require ongoing management over a period of years for long-term survival. Objectives This study examined the association between prevalence of selected chronic diseases and health service use, in particular visits to general practitioners (GPs) by medical scheme members. Method This was a retrospective study on medical schemes data. The median imputation method was employed to deal with missing and unreported chronic diseases prevalence. Multivariate logistic regression analysis was employed to assess effects of chronic disease prevalence, age stratum and scheme size on GP visits per annum. Results The study showed that prevalence of asthma was significantly associated with more than three GP visits (OR = 1.081; 95% CI = 1.008–1.159), as was prevalence of type 2 diabetes (OR = 1.087; 95% CI = 1.027–1.152), whilst prevalence of hyperlipidaemia (OR = 0.92; 95% CI = 0.875–0.97) was more likely to be associated with less than three GP visits. Prevalence of hypertension was associated with more than three GP visits per year (OR = 1.132; 95% CI = 1.017–1.26). Conclusion This study shows that scheme size, prevalence of chronic diseases such as asthma, type 2 diabetes, hyperlipidaemia and hypertension are related to GP visits. GPs and managed care programmes employed by schemes should give special attention to certain disease states with high prevalence rates in an effort to better manage them.

  19. The Effects of Noncontingent Access to Single-versus Multiple-Stimulus Sets on Self-Injurious Behavior.

    ERIC Educational Resources Information Center

    DeLeon, Iser G.; Anders, Bonita M.; Rodriguez-Catter, Vanessa; Neidert, Pamela L.

    2000-01-01

    The automatically reinforced self-injury of a girl (age 11) with autism was treated by providing noncontingent access to a single set of preferred toys during 30-minute sessions. Rotating toy sets after 10 minutes or providing access to multiple toy sets resulted in reductions that lasted the entire 30 minutes. (Contains four references.)…

  20. The Effects of Noncontingent Access to Single-versus Multiple-Stimulus Sets on Self-Injurious Behavior.

    ERIC Educational Resources Information Center

    DeLeon, Iser G.; Anders, Bonita M.; Rodriguez-Catter, Vanessa; Neidert, Pamela L.

    2000-01-01

    The automatically reinforced self-injury of a girl (age 11) with autism was treated by providing noncontingent access to a single set of preferred toys during 30-minute sessions. Rotating toy sets after 10 minutes or providing access to multiple toy sets resulted in reductions that lasted the entire 30 minutes. (Contains four references.)…

  1. Spreading and Interleaving Design for Synchronous Interleave-Division Multiple-Access

    NASA Astrophysics Data System (ADS)

    Song, Guanghui; Cheng, Jun; Watanabe, Yoichiro

    A K-user interleave-division multiple-access (IDMA) system with symbol-synchronous and equal-power users is considered. In this IDMA system, the spreading, interleaving, and multiple-access channel (MAC) are jointly considered as an equivalent channel, referred to as an IDMA channel. Given channel signal-to-noise ratio (SNR), the sum capacity of the IDMA channel is only determined by a K-user spread-interleave (SI) matrix. First, it is shown that to maximize the sum capacity of the IDMA channel, rows or columns of its K-user SI matrix should be pairwise orthogonal. The optimal K-user SI matrix is constructed. Second, for the IDMA system with each user employing the same spreading sequence followed by random interleaving, it is shown that, as the number of users approaches infinity, the sum capacity of the IDMA channel converges to a determinate value, which is achieved by a balanced spreading sequence. Moreover, when both the number of users and the data length approach infinity, this determinate value of sum capacity is achieved by an arbitrary spreading sequence. Furthermore, for a finite number of users, an optimal spreading sequence is derived by minimizing an expected column correlation of the K-user SI matrix. It shows that this optimal spreading sequence provides the maximum ergodic sum capacity.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. UK multiple sclerosis risk-sharing scheme: a new natural history dataset and an improved Markov model

    PubMed Central

    Palace, Jacqueline; Bregenzer, Thomas; Tremlett, Helen; Oger, Joel; Zhu, Fheng; Boggild, Mike; Duddy, Martin; Dobson, Charles

    2014-01-01

    Objectives In 2002, the UK's National Institute for Health and Care Excellence concluded that the multiple sclerosis (MS) disease modifying therapies; interferon-β and glatiramer acetate, were not cost effective over the short term but recognised that reducing disability over the longer term might dramatically improve the cost effectiveness. The UK Risk-sharing Scheme (RSS) was established to ensure cost-effective provision by prospectively collecting disability-related data from UK-treated patients with MS and comparing findings to a natural history (untreated) cohort. However, deficiencies were found in the originally selected untreated cohort and the resulting analytical approach. This study aims to identify a more suitable natural history cohort and to develop a robust analytical approach using the new cohort. Design The Scientific Advisory Group, recommended the British Columbia Multiple Sclerosis (BCMS) database, Canada, as providing a more suitable natural history comparator cohort. Transition probabilities were derived and different Markov models (discrete and continuous) with and without baseline covariates were applied. Setting MS clinics in Canada and the UK. Participants From the BCMS database, 898 ‘untreated’ patients with MS considered eligible for drug treatment based on the UK's Association of British Neurologists criteria. Outcome measure The predicted Expanded Disability Status Scale (EDSS) score was collected and assessed for goodness of fit when compared with actual outcome. Results The BCMS untreated cohort contributed 7335 EDSS scores over a median 6.4 years (6357 EDSS ‘transitions’ recorded at consecutive visits) during the period 1980–1995. A continuous Markov model with ‘onset age’ as a binary covariate was deemed the most suitable model for future RSS analysis. Conclusions A new untreated MS cohort from British Columbia has been selected and will be modelled using a continuous Markov model with onset age as a baseline

  7. A Decentralized Event-Triggered Dissipative Control Scheme for Systems With Multiple Sensors to Sample the System Outputs.

    PubMed

    Zhang, Xian-Ming; Han, Qing-Long

    2016-12-01

    This paper is concerned with decentralized event-triggered dissipative control for systems with the entries of the system outputs having different physical properties. Depending on these different physical properties, the entries of the system outputs are grouped into multiple nodes. A number of sensors are used to sample the signals from different nodes. A decentralized event-triggering scheme is introduced to select those necessary sampled-data packets to be transmitted so that communication resources can be saved significantly while preserving the prescribed closed-loop performance. First, in order to organize the decentralized data packets transmitted from the sensor nodes, a data packet processor (DPP) is used to generate a new signal to be held by the zero-order-hold once the signal stored by the DPP is updated at some time instant. Second, under the mechanism of the DPP, the resulting closed-loop system is modeled as a linear system with an interval time-varying delay. A sufficient condition is derived such that the closed-loop system is asymptotically stable and strictly (Q0,S0,R0) -dissipative, where Q0,S0 , and R0 are real matrices of appropriate dimensions with Q0 and R0 symmetric. Third, suitable output-based controllers can be designed based on solutions to a set of a linear matrix inequality. Finally, two examples are given to demonstrate the effectiveness of the proposed method.

  8. Satellite-matrix-switched, time-division-multiple-access network simulator

    NASA Technical Reports Server (NTRS)

    Ivancic, William D.; Andro, Monty; Nagy, Lawrence A.; Budinger, James M.; Shalkhauser, Mary JO

    1990-01-01

    A versatile experimental Ka-band network simulator has been implemented at the NASA Lewis Research Center to demonstrate and evaluate a satellite-matrix-switched, time-division-multiple-access (SMS-TDMA) network and to evaluate future digital ground terminals and radiofrequency (RF) components. The simulator was implemented by using proof-of-concept RF components developed under NASA contracts and digital ground terminal and link simulation hardware developed at Lewis. This simulator provides many unique capabilities such as satellite range delay and variation simulation and rain fade simulation. All network parameters (e.g., signal-to-noise ratio, satellite range variation rate, burst density, and rain fade) are controlled and monitored by a central computer. The simulator is presently configured as a three-ground-terminal SMS-TDMA network.

  9. 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.

  10. Satellite-matrix-switched, time-division-multiple-access network simulator

    NASA Technical Reports Server (NTRS)

    Ivancic, William D.; Andro, Monty; Nagy, Lawrence A.; Budinger, James M.; Shalkhauser, Mary JO

    1989-01-01

    A versatile experimental Ka-band network simulator has been implemented at the NASA Lewis Research Center to demonstrate and evaluate a satellite-matrix-switched, time-division-multiple-access (SMS-TDMA) network and to evaluate future digital ground terminals and radiofrequency (RF) components. The simulator was implemented by using proof-of-concept RF components developed under NASA contracts and digital ground terminal and link simulation hardware developed at Lewis. This simulator provides many unique capabilities such as satellite range delay and variation simulation and rain fade simulation. All network parameters (e.g., signal-to-noise ratio, satellite range variation rate, burst density, and rain fade) are controlled and monitored by a central computer. The simulator is presently configured as a three-ground-terminal SMS-TDMA network.

  11. Multiple user access and testing for PreNotiS: a fast mobile event reporting solution

    NASA Astrophysics Data System (ADS)

    Chan, Michael; Kumar, Abhinav; Akopian, David; Agaian, Sos S.

    2011-06-01

    The PreNotiS (preventive notification system) was proposed to address the current lack in consumer prevention and disaster informatics systems. The underscore of this letter is to propose PreNotiS as a provision of trusted proxies of information sourcing to be integral to the disaster informatics framework. To promote loose coupling among subsystems, PreNotiS has evolved into a model-view-controller (MVC) architecture via object-oriented incremental prototyping. The MVC specifies how all subsystems and how they interact with each other. A testing framework is also proposed for the PreNotiS to verify multiple concurrent user access which might be observable during disasters. The framework relies on conceptually similar self-test modules to help with serviceability.

  12. System and method for integrating and accessing multiple data sources within a data warehouse architecture

    DOEpatents

    Musick, Charles R.; Critchlow, Terence; Ganesh, Madhaven; Slezak, Tom; Fidelis, Krzysztof

    2006-12-19

    A system and method is disclosed for integrating and accessing multiple data sources within a data warehouse architecture. The metadata formed by the present method provide a way to declaratively present domain specific knowledge, obtained by analyzing data sources, in a consistent and useable way. Four types of information are represented by the metadata: abstract concepts, databases, transformations and mappings. A mediator generator automatically generates data management computer code based on the metadata. The resulting code defines a translation library and a mediator class. The translation library provides a data representation for domain specific knowledge represented in a data warehouse, including "get" and "set" methods for attributes that call transformation methods and derive a value of an attribute if it is missing. The mediator class defines methods that take "distinguished" high-level objects as input and traverse their data structures and enter information into the data warehouse.

  13. 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.

  14. Analysis of the TDRS multiple access system for possible use as an attitude control system sensor

    NASA Technical Reports Server (NTRS)

    Blevins, Bruce Allyn; Sank, Victor J.

    1993-01-01

    A member of the constellation of TDR satellites (TDRS) has experienced a failure of its prime earth sensor. Failure of the remaining earth sensor could result in the inability of the satellite to control its attitude and provide user services. Loss of the satellite would be a serious event. The multiple access (MA) antenna array on the TDRS has been proposed for use as a backup sensor for the attitude control system. This paper describes our analysis of the performance of the MA array as an interferometer used for accurate attitude determination. A least squares fit of a plane to the MA phase information appears to represent the TDRS body roll and pitch within about 0.1 deg. This is sufficient for SGL pointing and MA and SSA user services. Analytic improvements that include ionospheric correction may yield sufficient accuracy for KSA user services.

  15. Multiple carcinomas in the hemodialysis access induced ischemic hand of a renal transplant patient.

    PubMed

    Van Hoek, Frank; Van Tits, Herm W; Van Lijnschoten, Ineke; De Haas, Boudewijn D; Scheltinga, Marc R

    2010-01-01

    Long term immunosuppression following organ transplantation promotes the onset of skin cancers. A renal transplant patient developed multiple hyperkeratotic nodi in the left hand and digital pain following prolonged immunosuppression. Several skin abnormalities were observed in an ischemic and atrophic left hand in the presence of a patent Cimino-Brescia arteriovenous fistula previously used for hemodialysis. Severe hand ischemia was confirmed by digital plethysmography. Pathological examination of all 7 excised skin lesions indicated manifestations of well differentiated squamous cell carcinomas (SCC). Severe loco-regional ischemia due to an intact hemodialysis access may enhance the toxic effects of chronic immunosuppressive medication. Oxidative stress may act as a co-carcinogenic factor for the development of SCC in renal transplant patients receiving immunosuppressive agents.

  16. Multiple access system configurations for a data relay satellite using phased array antennas

    NASA Astrophysics Data System (ADS)

    Losquadro, G.

    1990-03-01

    Two configurations of a multiple access link in an intersatellite Tracking and Data Relay System are proposed which are suitable for supporting a small number of LEO user spacecraft. The advantages of one of these systems, which operates at S band with onboard implemented phased array (OPIBA), over NASA's TDRS MA system are discussed. The other configuration uses the Ka band with OPIBA and can provide two or more agile scanning beams for the forward link and for the return link, avoiding heavy moving parts aboard the DRS satellite and offering wide transmission capacity. A novel compact beam-forming network is proposed for an application using optical techniques and fiber optics jointly with an active array antenna.

  17. Non-orthogonal multiple access with phase pre-distortion in visible light communication.

    PubMed

    Guan, Xun; Yang, Qing; Hong, Yang; Chan, Calvin Chun-Kit

    2016-10-31

    Non-orthogonal multiple access (NOMA) offers a good balance between throughput and fairness for visible light communication (VLC). This work presents a phase pre-distortion method to improve the symbol error rate performance of NOMA uplink with successive interference cancellation (SIC) decoding in VLC. Both theoretical analysis and experimental evaluation have shown that the proposed phase pre-distortion method improves the bit-error-rate (BER) performance for NOMA under both low and high relative power ratios. Specifically, at low relative power ratios, the proposed method can eliminate the possible BER floors and alleviate the power ratio requirement by 2 dB at the BER of 3.8 × 10-3.

  18. 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.

  19. Multiple Coaxial Catheter System for Reliable Access in Interventional Stroke Therapy

    SciTech Connect

    Kulcsar, Zsolt Yilmaz, Hasan; Bonvin, Christophe; Lovblad, Karl O.; Ruefenacht, Daniel A.

    2010-12-15

    In some patients with acute cerebral vessel occlusion, navigating mechanical thrombectomy systems is difficult due to tortuous anatomy of the aortic arch, carotid arteries, or vertebral arteries. Our purpose was to describe a multiple coaxial catheter system used for mechanical revascularization that helps navigation and manipulations in tortuous vessels. A triple or quadruple coaxial catheter system was built in 28 consecutive cases presenting with acute ischemic stroke. All cases were treated by mechanical thrombectomy with the Penumbra System. In cases of unsuccessful thrombo-aspiration, additional thrombolysis or angioplasty with stent placement was used for improving recanalization. The catheter system consisted of an outermost 8-Fr and an intermediate 6-Fr guiding catheter, containing the inner Penumbra reperfusion catheters. The largest, 4.1-Fr, reperfusion catheter was navigated over a Prowler Select Plus microcatheter. The catheter system provided access to reach the cerebral lesions and provided stability for the mechanically demanding manipulations of thromboaspiration and stent navigation in all cases. Apart from their mechanical role, the specific parts of the system could also provide access to different types of interventions, like carotid stenting through the 8-Fr guiding catheter and intracranial stenting and thrombolysis through the Prowler Select Plus microcatheter. In this series, there were no complications related to the catheter system. In conclusion, building up a triple or quadruple coaxial system proved to be safe and efficient in our experience for the mechanical thrombectomy treatment of acute ischemic stroke.

  20. Suppression of optical beat interference-noise in orthogonal frequency division multiple access-passive optical network link using self-homodyne balanced detection

    NASA Astrophysics Data System (ADS)

    Won, Yong-Yuk; Jung, Sang-Min; Han, Sang-Kook

    2014-08-01

    A new technique, which reduces optical beat interference (OBI) noise in orthogonal frequency division multiple access-passive optical network (OFDMA-PON) links, is proposed. A self-homodyne balanced detection, which uses a single laser for the optical line terminal (OLT) as well as for the optical network unit (ONU), reduces OBI noise and also improves the signal to noise ratio (SNR) of the discrete multi-tone (DMT) signal. The proposed scheme is verified by transmitting quadrature phase shift keying (QPSK)-modulated DMT signal over a 20-km single mode fiber. The optical signal to noise ratio (OSNR), that is required for BER of 10-5, is reduced by 2 dB in the balanced detection compared with a single channel due to the cancellation of OBI noise in conjunction with the local laser.

  1. The impact of changing the land surface scheme in ACCESS(v1.0/1.1) on the surface climatology

    NASA Astrophysics Data System (ADS)

    Kowalczyk, Eva A.; Stevens, Lauren E.; Law, Rachel M.; Harman, Ian N.; Dix, Martin; Franklin, Charmaine N.; Wang, Ying-Ping

    2016-08-01

    The Community Atmosphere Biosphere Land Exchange (CABLE) model has been coupled to the UK Met Office Unified Model (UM) within the existing framework of the Australian Community Climate and Earth System Simulator (ACCESS), replacing the Met Office Surface Exchange Scheme (MOSES). Here we investigate how features of the CABLE model impact on present-day surface climate using ACCESS atmosphere-only simulations. The main differences attributed to CABLE include a warmer winter and a cooler summer in the Northern Hemisphere (NH), earlier NH spring runoff from snowmelt, and smaller seasonal and diurnal temperature ranges. The cooler NH summer temperatures in canopy-covered regions are more consistent with observations and are attributed to two factors. Firstly, CABLE accounts for aerodynamic and radiative interactions between the canopy and the ground below; this placement of the canopy above the ground eliminates the need for a separate bare ground tile in canopy-covered areas. Secondly, CABLE simulates larger evapotranspiration fluxes and a slightly larger daytime cloud cover fraction. Warmer NH winter temperatures result from the parameterization of cold climate processes in CABLE in snow-covered areas. In particular, prognostic snow density increases through the winter and lowers the diurnally resolved snow albedo; variable snow thermal conductivity prevents early winter heat loss but allows more heat to enter the ground as the snow season progresses; liquid precipitation freezing within the snowpack delays the building of the snowpack in autumn and accelerates snow melting in spring. Overall we find that the ACCESS simulation of surface air temperature benefits from the specific representation of the turbulent transport within and just above the canopy in the roughness sublayer as well as the more complex snow scheme in CABLE relative to MOSES.

  2. The impact of changing the land surface scheme in ACCESS(v1.0/1.1) on the surface climatology

    SciTech Connect

    Kowalczyk, Eva A.; Stevens, Lauren E.; Law, Rachel M.; Harman, Ian N.; Dix, Martin; Franklin, Charmaine N.; Wang, Ying -Ping

    2016-08-23

    The Community Atmosphere Biosphere Land Exchange (CABLE) model has been coupled to the UK Met Office Unified Model (UM) within the existing framework of the Australian Community Climate and Earth System Simulator (ACCESS), replacing the Met Office Surface Exchange Scheme (MOSES). Here we investigate how features of the CABLE model impact on present-day surface climate using ACCESS atmosphere-only simulations. The main differences attributed to CABLE include a warmer winter and a cooler summer in the Northern Hemisphere (NH), earlier NH spring runoff from snowmelt, and smaller seasonal and diurnal temperature ranges. The cooler NH summer temperatures in canopy-covered regions are more consistent with observations and are attributed to two factors. Firstly, CABLE accounts for aerodynamic and radiative interactions between the canopy and the ground below; this placement of the canopy above the ground eliminates the need for a separate bare ground tile in canopy-covered areas. Secondly, CABLE simulates larger evapotranspiration fluxes and a slightly larger daytime cloud cover fraction. Warmer NH winter temperatures result from the parameterization of cold climate processes in CABLE in snow-covered areas. In particular, prognostic snow density increases through the winter and lowers the diurnally resolved snow albedo; variable snow thermal conductivity prevents early winter heat loss but allows more heat to enter the ground as the snow season progresses; liquid precipitation freezing within the snowpack delays the building of the snowpack in autumn and accelerates snow melting in spring. Altogether we find that the ACCESS simulation of surface air temperature benefits from the specific representation of the turbulent transport within and just above the canopy in the roughness sublayer as well as the more complex snow scheme in CABLE relative to MOSES.

  3. The impact of changing the land surface scheme in ACCESS(v1.0/1.1) on the surface climatology

    DOE PAGES

    Kowalczyk, Eva A.; Stevens, Lauren E.; Law, Rachel M.; ...

    2016-08-23

    The Community Atmosphere Biosphere Land Exchange (CABLE) model has been coupled to the UK Met Office Unified Model (UM) within the existing framework of the Australian Community Climate and Earth System Simulator (ACCESS), replacing the Met Office Surface Exchange Scheme (MOSES). Here we investigate how features of the CABLE model impact on present-day surface climate using ACCESS atmosphere-only simulations. The main differences attributed to CABLE include a warmer winter and a cooler summer in the Northern Hemisphere (NH), earlier NH spring runoff from snowmelt, and smaller seasonal and diurnal temperature ranges. The cooler NH summer temperatures in canopy-covered regions aremore » more consistent with observations and are attributed to two factors. Firstly, CABLE accounts for aerodynamic and radiative interactions between the canopy and the ground below; this placement of the canopy above the ground eliminates the need for a separate bare ground tile in canopy-covered areas. Secondly, CABLE simulates larger evapotranspiration fluxes and a slightly larger daytime cloud cover fraction. Warmer NH winter temperatures result from the parameterization of cold climate processes in CABLE in snow-covered areas. In particular, prognostic snow density increases through the winter and lowers the diurnally resolved snow albedo; variable snow thermal conductivity prevents early winter heat loss but allows more heat to enter the ground as the snow season progresses; liquid precipitation freezing within the snowpack delays the building of the snowpack in autumn and accelerates snow melting in spring. Altogether we find that the ACCESS simulation of surface air temperature benefits from the specific representation of the turbulent transport within and just above the canopy in the roughness sublayer as well as the more complex snow scheme in CABLE relative to MOSES.« less

  4. Massive MIMO for Wireless Sensing With a Coherent Multiple Access Channel

    NASA Astrophysics Data System (ADS)

    Jiang, Feng; Chen, Jie; Swindlehurst, A. Lee; Lopez-Salcedo, Jose A.

    2015-06-01

    We consider the detection and estimation of a zero-mean Gaussian signal in a wireless sensor network with a coherent multiple access channel, when the fusion center (FC) is configured with a large number of antennas and the wireless channels between the sensor nodes and FC experience Rayleigh fading. For the detection problem, we study the Neyman-Pearson (NP) Detector and Energy Detector (ED), and find optimal values for the sensor transmission gains. For the NP detector which requires channel state information (CSI), we show that detection performance remains asymptotically constant with the number of FC antennas if the sensor transmit power decreases proportionally with the increase in the number of antennas. Performance bounds show that the benefit of multiple antennas at the FC disappears as the transmit power grows. The results of the NP detector are also generalized to the linear minimum mean squared error estimator. For the ED which does not require CSI, we derive optimal gains that maximize the deflection coefficient of the detector, and we show that a constant deflection can be asymptotically achieved if the sensor transmit power scales as the inverse square root of the number of FC antennas. Unlike the NP detector, for high sensor power the multi-antenna ED is observed to empirically have significantly better performance than the single-antenna implementation. A number of simulation results are included to validate the analysis.

  5. Does China's new cooperative medical scheme promote rural elders' access to healthcare services in relation to chronic conditions?

    PubMed Central

    Dai, Baozhen

    2015-01-01

    Background This study examined use of healthcare services by elderly people with a long-term condition living in rural China and participating in that country's New Cooperative Medical Scheme (NCMS). Methods Data were taken from the 2009 China Health and Nutrition Survey. Results The study results showed that education level and annual income were low among rural elders (aged ≥65 years); the illiteracy rate was 58.0% (200/345) and 67.6% (92/136) had an annual income of less than 5000 Chinese yuan renminbi. The elders had low rates of treatment and use of preventive healthcare services while the prevalence of chronic disease was highest among them when compared to other age groups. Among the few elders who received preventive healthcare, most received it at village clinics. Conclusions Preventive healthcare services and chronic disease management are urgently needed by rural elders in China. NCMS should initiate payments to township health centers to enable them to undertake community outreach and education campaigns among rural residents, and train village doctors in standard chronic condition management and prevention, with prioritization of the provision of prevention and management of chronic conditions by village clinics. PMID:25091022

  6. Helping members of a community-based health insurance scheme access quality inpatient care through development of a preferred provider system in rural Gujarat.

    PubMed

    Ranson, M Kent; Sinha, Tara; Gandhi, Fenil; Jayswal, Rupal; Mills, Anne J

    2006-01-01

    We describe and analyse the experience of piloting a preferred provider system (PPS) for rural members of Vimo SEWA, a fixed-indemnity, community-based health insurance (CBHI) scheme run by the Self-Employed Women's Association (SEWA). The objectives of the PPS were (i) to facilitate access to hospitalization by providing financial benefits at the time of service utilization; (ii) to shift the burden of compiling a claim away from members and towards Vimo SEWA staff; and (iii) to direct members to inpatient facilities of acceptable quality. The PPS was launched between August and October 2004, in 8 subdistricts covering 15,000 insured. The impact of the scheme was analysed using data from a household survey of claimants and qualitative data from in-depth interviews and focus group discussions. The PPS appears to have been successful in terms of two of the three primary objectives--it has transferred much of the burden of compiling a health Insurance claim onto Vimo SEWA staff, and it has directed members to inpatient facilities with acceptable levels of technical quality (defined in terms of structural Indicators). However, even under the PPS, user fees pose a financial barrier, as the insured have to mobilize funds to cover the costs of medicines, supplies, registration fee, etc. before receipt of cash payment from Vimo SEWA. Other barriers to the success of the PPS were the geographic Inaccessibility of some of the selected hospitals, lack of awareness about the PPS among members and a variety of administrative problems. This pilot project provides useful lessons relating to strategic purchasing by CBHI schemes and, more broadly, managed care in India. In particular, the pragmatic approach taken to assessing hospitals and identifying preferred providers is likely to be useful elsewhere.

  7. Helping members of a community-based health insurance scheme access quality inpatient care through development of a preferred provider system in rural Gujarat

    PubMed Central

    RANSON, M. KENT; SINHA, TARA; GANDHI, FENIL; JAYSWAL, RUPAL; MILLS, ANNE J.

    2007-01-01

    We describe and analyse the experience of piloting a preferred provider system (PPS) for rural members of Vimo SEWA, a fixed-indemnity, community-based health insurance (CBHI) scheme run by the Self-Employed Women’s Association (SEWA). The objectives of the PPS were (i) to facilitate access to hospitalization by providing financial benefits at the time of service utilization; (ii) to shift the burden of compiling a claim away from members and towards Vimo SEWA staff; and (iii) to direct members to inpatient facilities of acceptable quality. The PPS was launched between August and October 2004, in 8 subdistricts covering 15 000 insured. The impact of the scheme was analysed using data from a household survey of claimants and qualitative data from in-depth interviews and focus group discussions. The PPS appears to have been successful in terms of two of the three primary objectives—it has transferred much of the burden of compiling a health insurance claim onto Vimo SEWA staff, and it has directed members to inpatient facilities with acceptable levels of technical quality (defined in terms of structural indicators). However, even under the PPS, user fees pose a financial barrier, as the insured have to mobilize funds to cover the costs of medicines, supplies, registration fee, etc. before receipt of cash payment from Vimo SEWA. Other barriers to the success of the PPS were the geographic inaccessibility of some of the selected hospitals, lack of awareness about the PPS among members and a variety of administrative problems. This pilot project provides useful lessons relating to strategic purchasing by CBHI schemes and, more broadly, managed care in India. In particular, the pragmatic approach taken to assessing hospitals and identifying preferred providers is likely to be useful elsewhere. PMID:17203684

  8. A Seamless Handoff Scheme with Access Point Load Balance for Real-Time Services Support in 802.11 Wireless LANs

    NASA Astrophysics Data System (ADS)

    Manodham, Thavisak; Loyola, Luis; Miki, Tetsuya

    IEEE 802.11 wirelesses LANs (WLANs) have been rapidly deployed in enterprises, public areas, and households. Voice-over-IP (VoIP) and similar applications are now commonly used in mobile devices over wireless networks. Recent works have improved the quality of service (QoS) offering higher data rates to support various kinds of real-time applications. However, besides the need for higher data rates, seamless handoff and load balancing among APs are key issues that must be addressed in order to continue supporting real-time services across wireless LANs and providing fair services to all users. In this paper, we introduce a novel access point (AP) with two transceivers that improves network efficiency by supporting seamless handoff and traffic load balancing in a wireless network. In our proposed scheme, the novel AP uses the second transceiver to scan and find neighboring STAs in the transmission range and then sends the results to neighboring APs, which compare and analyze whether or not the STA should perform a handoff. The initial results from our simulations show that the novel AP module is more effective than the conventional scheme and a related work in terms of providing a handoff process with low latency and sharing traffic load with neighbor APs.

  9. Persons with multiple disabilities exercise adaptive response schemes with the help of technology-based programs: three single-case studies.

    PubMed

    Lancioni, Giulio E; Singh, Nirbhay N; O'Reilly, Mark F; Sigafoos, Jeff; Oliva, Doretta; Campodonico, Francesca; Lang, Russell

    2012-01-01

    The present three single-case studies assessed the effectiveness of technology-based programs to help three persons with multiple disabilities exercise adaptive response schemes independently. The response schemes included (a) left and right head movements for a man who kept his head increasingly static on his wheelchair's headrest (Study I), (b) left- and right-arm movements for a woman who tended to hold both arms/hands tight against her body (Study II), and (c) touching object cues on a computer screen for a girl who rarely used her residual vision for orienting/guiding her hand responses. The technology involved microswitches/sensors to detect the response schemes and a computer/control system to record their occurrences and activate preferred stimuli contingent on them. Results showed large increases in the response schemes targeted for each of the three participants during the intervention phases of the studies. The importance of using technology-based programs as tools for enabling persons with profound and multiple disabilities to practice relevant responses independently was discussed.

  10. Satellite range delay simulator for a matrix-switched time division multiple-access network simulator

    NASA Technical Reports Server (NTRS)

    Nagy, Lawrence A.

    1989-01-01

    The Systems Integration, Test, and Evaluation (SITE) facility at NASA Lewis Research Center is presently configured as a satellite-switched time division multiple access (SS-TDMA) network simulator. The purpose of SITE is to demonstrate and evaluate advanced communication satellite technologies, presently embodied by POC components developed under NASA contracts in addition to other hardware, such as ground terminals, designed and built in-house at NASA Lewis. Each ground terminal in a satellite communications system will experience a different aspect of the satellite's motion due mainly to daily tidal effects and station keeping, hence a different duration and rate of variation in the range delay. As a result of this and other effects such as local oscillator instability, each ground terminal must constantly adjust its transmit burst timing so that data bursts from separate ground terminals arrive at the satellite in their assigned time slots, preventing overlap and keeping the system in synchronism. On the receiving end, ground terminals must synchronize their local clocks using reference transmissions received through the satellite link. A feature of the SITE facility is its capability to simulate the varying propagation delays and associated Doppler frequency shifts that the ground terminals in the network have to cope with. Delay is achieved by means of two NASA Lewis designed and built range delay simulator (RDS) systems, each independently controlled locally with front panel switches or remotely by an experiment control and monitor (EC/M) computer.

  11. Interference suppression for code-division multiple-access communications in an underwater acoustic channel.

    PubMed

    Yang, T C; Yang, Wen-Bin

    2009-07-01

    In a code-division multiple-access communications network, the signal from a nearby user often creates a strong interference for the signal from a distant user. This is known as the near-far problem. Power control of source levels is ineffective in an underwater acoustic channel due to the slow sound speed. Interference rejection based on code orthogonality is ineffective using matched-filter processing due to the fact that multipath arrivals effectively destroy the code orthogonality and that the signal arrival times between different users are not synchronized. An algorithm, called hyperspace cancellation by coordinate zeroing, is used in this paper to remove/suppress interference. Using a fast Walsh-Hadamard transform (FWHT) based on the interferer's code sequence, the interference signal is enhanced and removed by coordinate zeroing. The residual signal is transformed back using an inverse FWHT. The filtered data, with the interference signal largely removed, are processed using the desired signal code sequence. Two methods previously developed for direct-sequence spread-spectrum communications in an underwater channel are used to extract the transmitted symbols. Low bit error rate (<10(-2)) is found with the at-sea data for signal-to-interference ratio as low as -8 to -11 dB.

  12. 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.

  13. Accessing the genomic information of unculturable oceanic picoeukaryotes by combining multiple single cells

    PubMed Central

    Mangot, Jean-François; Logares, Ramiro; Sánchez, Pablo; Latorre, Fran; Seeleuthner, Yoann; Mondy, Samuel; Sieracki, Michael E.; Jaillon, Olivier; Wincker, Patrick; Vargas, Colomban de; Massana, Ramon

    2017-01-01

    Pico-sized eukaryotes play key roles in the functioning of marine ecosystems, but we still have a limited knowledge on their ecology and evolution. The MAST-4 lineage is of particular interest, since it is widespread in surface oceans, presents ecotypic differentiation and has defied culturing efforts so far. Single cell genomics (SCG) are promising tools to retrieve genomic information from these uncultured organisms. However, SCG are based on whole genome amplification, which normally introduces amplification biases that limit the amount of genomic data retrieved from a single cell. Here, we increase the recovery of genomic information from two MAST-4 lineages by co-assembling short reads from multiple Single Amplified Genomes (SAGs) belonging to evolutionary closely related cells. We found that complementary genomic information is retrieved from different SAGs, generating co-assembly that features >74% of genome recovery, against about 20% when assembled individually. Even though this approach is not aimed at generating high-quality draft genomes, it allows accessing to the genomic information of microbes that would otherwise remain unreachable. Since most of the picoeukaryotes still remain uncultured, our work serves as a proof-of-concept that can be applied to other taxa in order to extract genomic data and address new ecological and evolutionary questions. PMID:28128359

  14. 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

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

    NASA Technical Reports Server (NTRS)

    Scaife, Bradley James

    1999-01-01

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

  16. Accessing the genomic information of unculturable oceanic picoeukaryotes by combining multiple single cells.

    PubMed

    Mangot, Jean-François; Logares, Ramiro; Sánchez, Pablo; Latorre, Fran; Seeleuthner, Yoann; Mondy, Samuel; Sieracki, Michael E; Jaillon, Olivier; Wincker, Patrick; Vargas, Colomban de; Massana, Ramon

    2017-01-27

    Pico-sized eukaryotes play key roles in the functioning of marine ecosystems, but we still have a limited knowledge on their ecology and evolution. The MAST-4 lineage is of particular interest, since it is widespread in surface oceans, presents ecotypic differentiation and has defied culturing efforts so far. Single cell genomics (SCG) are promising tools to retrieve genomic information from these uncultured organisms. However, SCG are based on whole genome amplification, which normally introduces amplification biases that limit the amount of genomic data retrieved from a single cell. Here, we increase the recovery of genomic information from two MAST-4 lineages by co-assembling short reads from multiple Single Amplified Genomes (SAGs) belonging to evolutionary closely related cells. We found that complementary genomic information is retrieved from different SAGs, generating co-assembly that features >74% of genome recovery, against about 20% when assembled individually. Even though this approach is not aimed at generating high-quality draft genomes, it allows accessing to the genomic information of microbes that would otherwise remain unreachable. Since most of the picoeukaryotes still remain uncultured, our work serves as a proof-of-concept that can be applied to other taxa in order to extract genomic data and address new ecological and evolutionary questions.

  17. Persons with Multiple Disabilities Use Forehead and Smile Responses to Access or Choose among Technology-Aided Stimulation Events

    ERIC Educational Resources Information Center

    Lancioni, Giulio E.; Singh, Nirbhay N.; O'Reilly, Mark F.; Sigafoos, Jeff; Alberti, Gloria; Bellini, Domencio; Oliva, Doretta; Boccasini, Adele; La Martire, Maria L.; Signorino, Mario

    2013-01-01

    A variety of technology-aided programs have been developed to help persons with congenital or acquired multiple disabilities access preferred stimuli or choose among stimulus options. The application of those programs may pose problems when the participants have very limited behavior repertoires and are unable to use conventional responses and…

  18. System and Method for Detecting Unauthorized Device Access by Comparing Multiple Independent Spatial-Time Data Sets from Other Devices

    NASA Technical Reports Server (NTRS)

    Krage, Frederick J. (Inventor); Westmeyer, Paul A. (Inventor); Wertenberg, Russell F. (Inventor); Riegel, Jack F. (Inventor)

    2017-01-01

    An authentication procedure utilizes multiple independent sources of data to determine whether usage of a device, such as a desktop computer, is authorized. When a comparison indicates an anomaly from the base-line usage data, the system, provides a notice that access of the first device is not authorized.

  19. Persons with Multiple Disabilities Use Forehead and Smile Responses to Access or Choose among Technology-Aided Stimulation Events

    ERIC Educational Resources Information Center

    Lancioni, Giulio E.; Singh, Nirbhay N.; O'Reilly, Mark F.; Sigafoos, Jeff; Alberti, Gloria; Bellini, Domencio; Oliva, Doretta; Boccasini, Adele; La Martire, Maria L.; Signorino, Mario

    2013-01-01

    A variety of technology-aided programs have been developed to help persons with congenital or acquired multiple disabilities access preferred stimuli or choose among stimulus options. The application of those programs may pose problems when the participants have very limited behavior repertoires and are unable to use conventional responses and…

  20. Multiple Intimate Partner Violence Experiences: Knowledge, Access, Utilization and Barriers to Utilization of Resources by Women of the African Diaspora

    PubMed Central

    Sabri, Bushra; Huerta, Julia; Alexander, Kamila A.; St.Vil, Noelle M.; Campbell, Jacquelyn C.; Callwood, Gloria B.

    2016-01-01

    Objective This study examined knowledge, access, utilization, and barriers to use of resources among Black women exposed to multiple types of intimate partner violence in Baltimore, Maryland and the U.S. Virgin Islands (USVI). Methods We analyzed quantitative survey data collected by 163 women recruited from primary care, prenatal or family planning clinics in Baltimore and the USVI. In addition we analyzed qualitative data from in-depth interviews with 11 women. Quantitative data were analyzed using descriptive statistics and qualitative data were analyzed using thematic analysis. Results A substantial proportion of Black women with multiple types of violence experiences lacked knowledge of, did not have access to, and did not use resources. Barriers to resource use were identified at the individual, relationship, and community levels. Conclusion There is need for programs to develop awareness, promote access and utilization of resources, and eliminate barriers to resource use among abused Black women. PMID:26548679

  1. Signal extraction in a power-recycled michelson interferometer with fabry-perot arm cavities by use of a multiple-carrier frontal modulation scheme.

    PubMed

    Sigg, D; Mavalvala, N; Giaime, J; Fritschel, P; Shoemaker, D

    1998-08-20

    We present a signal extraction scheme for longitudinal sensing and control of an interferometric gravitational-wave detector based on a multiple-frequency heterodyne detection technique. Gravitational-wave detectors use multiple-mirror resonant optical systems where resonance conditions must be satisfied for multiple degrees of freedom that are optically coupled. The multiple-carrier longitudinal-sensing technique provides sensitive signals for all interferometric lengths to be controlled and successfully decouples them. The feasibility of the technique is demonstrated on a tabletop-scale power-recycled Michelson interferometer with Fabry-Perot arm cavities, and the experimentally measured values of the length-sensing signals are in good agreement with theoretical calculations.

  2. Multiple perspectives on the accessibility of e-learning in Canadian colleges and universities.

    PubMed

    Asuncion, Jennison V; Fichten, Catherine S; Ferraro, Vittoria; Chwojka, Caroline; Barile, Maria; Nguyen, Mai Nhu; Wolforth, Joan

    2010-01-01

    An exploratory study identified and compared the views of 77 campus disability service providers, 38 professors, and 45 e-learning professionals from Canadian colleges and universities regarding their experiences with e-learning and its accessibility to students with disabilities. Findings indicate that all groups saw benefit in having someone who makes e-learning accessible to students with disabilities on campus and that problems related to e-learning accessibility were most likely to go to campus disability service providers and least likely to e-learning professionals. Only half of the participants indicated that professors are taught about e-learning accessibility, that there is someone on campus who makes e-learning accessible, that accessibility is a criterion for selecting new types of e-learning, and that their school has e-learning accessibility guidelines or policies. These findings suggest that important e-learning accessibility problems remain. Recommendations for colleges and universities on how to increase e-learning accessibility are provided.

  3. Improved Iterative Decoding of Network-Channel Codes for Multiple-Access Relay Channel

    PubMed Central

    Majumder, Saikat; Verma, Shrish

    2015-01-01

    Cooperative communication using relay nodes is one of the most effective means of exploiting space diversity for low cost nodes in wireless network. In cooperative communication, users, besides communicating their own information, also relay the information of other users. In this paper we investigate a scheme where cooperation is achieved using a common relay node which performs network coding to provide space diversity for two information nodes transmitting to a base station. We propose a scheme which uses Reed-Solomon error correcting code for encoding the information bit at the user nodes and convolutional code as network code, instead of XOR based network coding. Based on this encoder, we propose iterative soft decoding of joint network-channel code by treating it as a concatenated Reed-Solomon convolutional code. Simulation results show significant improvement in performance compared to existing scheme based on compound codes. PMID:27347526

  4. Improved Iterative Decoding of Network-Channel Codes for Multiple-Access Relay Channel.

    PubMed

    Majumder, Saikat; Verma, Shrish

    2015-01-01

    Cooperative communication using relay nodes is one of the most effective means of exploiting space diversity for low cost nodes in wireless network. In cooperative communication, users, besides communicating their own information, also relay the information of other users. In this paper we investigate a scheme where cooperation is achieved using a common relay node which performs network coding to provide space diversity for two information nodes transmitting to a base station. We propose a scheme which uses Reed-Solomon error correcting code for encoding the information bit at the user nodes and convolutional code as network code, instead of XOR based network coding. Based on this encoder, we propose iterative soft decoding of joint network-channel code by treating it as a concatenated Reed-Solomon convolutional code. Simulation results show significant improvement in performance compared to existing scheme based on compound codes.

  5. Ultra Wide Band Multiple Access Performance Using TH-PPM and DS-BPSK Modulations

    DTIC Science & Technology

    2003-03-01

    communications for In- ternet applications is gaining popularity. Current technologies such as IEEE 802.11, Bluetooth , and the European HiperLAN...schemes, heterodyning provides frequency translation for typical narrow band radios or wireless communication schemes such as Bluetooth and IEEE...Systems/Area Radius of Area Spatial Capacity IEEE802.11b 11 Mbps 3 100 meters 1,000 b s·m2 Bluetooth 1 Mbps 10 10 meters 30,000 b s·m2 IEEE802.11a 54

  6. Public Funding and Open Access to Research: A Review of Canadian Multiple Sclerosis Research

    PubMed Central

    Stephenson, Carol; Stephenson, Erin; Chaves, Debbie

    2017-01-01

    Background Multiple sclerosis (MS), a progressive demyelinating disease of the brain and spinal cord, is the leading cause of nontraumatic neurological damage in young adults. Canada has one of the highest reported incidents of MS, with estimates between 55 and 240 per 100,000 individuals. Between 2009 and 2014, the MS Society of Canada provided over Can $90 million to researchers and, since 2013, has encouraged researchers to make both current and previous research products openly available. Objective The goal of the study was to determine the open access (OA) cost implications and repository policies of journals frequently used by a sample of MS researchers. This study benchmarked current publishing preferences by MS Society of Canada researchers by examining the OA full-text availability of journal articles written by researchers funded between 2009 and 2014. Methods Researchers were identified from the 2009 to 2014 annual MS Society of Canada Research Summaries. Articles were identified through searches in Web of Science, Scopus, Medline and Embase (both via OVID). Journal level analysis included comparison of OA policies, including article processing charges (APCs) and repository policies. Data were analyzed using descriptive statistics. Results There were 758 articles analyzed in this study, of which 288 (38.0%) were OA articles. The majority of authors were still relying on journal policies for deposit in PubMed Central or availability on publisher websites for OA. Gold OA journals accounted for 10.2% of the journals in this study and were associated with significantly lower APCs (US $1900) than in hybrid journals (US $3000). Review of the journal self-archiving options highlighted the complexity of stipulations that authors would have to navigate to legally deposit a version of their article. Conclusions This study found that there are currently researcher- and publisher-imposed barriers to both the gold and green roads to OA. These results provide a

  7. Data Management for Flexible Access - Implementation and Lessons Learned from work with Multiple User Communities

    NASA Astrophysics Data System (ADS)

    Benedict, K. K.; Scott, S.; Hudspeth, W. B.

    2012-12-01

    There is no shortage of community-specific and generic data discovery and download platforms and protocols (e.g. CUAHSI HIS, DataONE, GeoNetwork Open Source, GeoPortal, OGC CSW, OAI PMH), documentation standards (e.g. FGDC, ISO 19115, EML, Dublin Core), data access and visualization standards and models (e.g. OGC WxS, OpenDAP), and general-purpose web service models (i.e. REST & SOAP) upon which Geo-informatics cyberinfrastructure (CI) may be built. When attempting to develop a robust platform that may service a wide variety of users and use cases the challenge is one of identifying which existing platform (if any) may support those current needs while also allowing for future expansion for additional capabilities. In the case of the implementation of a data storage, discovery and delivery platform to support the multiple projects at the Earth Data Analysis Center at UNM, no single platform or protocol met the joint requirements of two initial applications (the New Mexico Resource Geographic Information System [http://rgis.unm.edu] and the New Mexico EPSCoR Data Portal [http://nmepscor.org/dataportal]) and furthermore none met anticipated additional requirements as new applications of the platform emerged. As a result of this assessment three years ago EDAC embarked on the development of the Geographic Storage, Transformation, and Retrieval Engine (GSToRE) platform as a general purpose platform upon which n-tiered geospatially enabled data intensive applications could be built. When initially released in 2010 the focus was on the publication of dynamically generated Open Geospatial Consortium services based upon a PostgreSQL/PostGIS backend database. The identification of additional service interface requirements (implementation of the DataONE API and CUAHSI WaterML services), use cases provided by the NM EPSCoR education working group, and expanded metadata publication needs have led to a significant update to the underlying data management tier for GSToRE - the

  8. 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

  9. Interval-Searching Algorithms for Multiple-Access Contention Resolution: Delay and Throughput

    NASA Astrophysics Data System (ADS)

    Huang, Jian-Cheng

    Message contention is inevitable in any random multiple-access communication system. In order to achieve a high percentage of successful transmissions, the behavior of users must be governed by a contention resolution algorithm (CRA). A CRA is characterized by its throughput rate, transmission delay and stability. A challenging design problem consists of making the best trade-off among these characteristics subject to additional restrictions imposed by distributed processing requirements. We study a class of highly efficient CRA's called interval-searching algorithms (ISA) which segment the message transmissions into consecutive sessions so as to achieve high throughput rate and low average delay while maintaining stability. At the initiation of an ISA session, a time interval is enabled. The messages that arrived before a certain threshold in that interval are resolved during this session. Next, the algorithm enables a new interval immediately adjacent to the resolved portion of the one enabled previously. Three efficient ISA's are discussed in this thesis. The Gallager-Massey-Tsybadov-Ruget, or "0.487", CRA is the most efficient one known with ternary feedback. A modified version of this algorithm is thoroughly analyzed. An ergodicity theorem for a quantity called transmission lag, which is intimately related to the message delay, is deduced and rigorously proved. By bounding the kernal in the integral equation for the probability density function of the steady -state transmission lag, we derive both upper and lower bounds on the rate-delay characteristic and compare them to simulation results. A new class of ISA's, called multibit feedback algorithms (MFA), is proposed and analyzed. In MFA's an m-bit subfield is added to each message packet which provides the users with a partition of the initial contention group into m subgroups and ensures that no empty slots occur during the resolution session. MFA's prove to be highly efficient, very fast and absolutely

  10. Public Funding and Open Access to Research: A Review of Canadian Multiple Sclerosis Research.

    PubMed

    Bakker, Caitlin; Stephenson, Carol; Stephenson, Erin; Chaves, Debbie

    2017-02-27

    Multiple sclerosis (MS), a progressive demyelinating disease of the brain and spinal cord, is the leading cause of nontraumatic neurological damage in young adults. Canada has one of the highest reported incidents of MS, with estimates between 55 and 240 per 100,000 individuals. Between 2009 and 2014, the MS Society of Canada provided over Can $90 million to researchers and, since 2013, has encouraged researchers to make both current and previous research products openly available. The goal of the study was to determine the open access (OA) cost implications and repository policies of journals frequently used by a sample of MS researchers. This study benchmarked current publishing preferences by MS Society of Canada researchers by examining the OA full-text availability of journal articles written by researchers funded between 2009 and 2014. Researchers were identified from the 2009 to 2014 annual MS Society of Canada Research Summaries. Articles were identified through searches in Web of Science, Scopus, Medline and Embase (both via OVID). Journal level analysis included comparison of OA policies, including article processing charges (APCs) and repository policies. Data were analyzed using descriptive statistics. There were 758 articles analyzed in this study, of which 288 (38.0%) were OA articles. The majority of authors were still relying on journal policies for deposit in PubMed Central or availability on publisher websites for OA. Gold OA journals accounted for 10.2% of the journals in this study and were associated with significantly lower APCs (US $1900) than in hybrid journals (US $3000). Review of the journal self-archiving options highlighted the complexity of stipulations that authors would have to navigate to legally deposit a version of their article. This study found that there are currently researcher- and publisher-imposed barriers to both the gold and green roads to OA. These results provide a current benchmark against which efforts to enhance

  11. Bedside computer access for an individual with severe and multiple disabilities: a case study.

    PubMed

    Blain, Stefanie; McKeever, Patricia; Chau, Tom

    2010-01-01

    This case study documents the process of designing a custom-tailored bedside computer access solution for a 20-year old individual with quadriplegia and reports the effects of computer access on her participation in life activities. We adopted a person-focused approach to match the individual to an access solution. Two months after the access solution's introduction, we measured its impact using a 2-dimensional Fitt's Law test and questionnaire from the ISO 9241-9 standards document, typing tests, a usage log and a semi-structured interview. The Canadian Occupational Performance Measure was also administered pre- and post- access, focusing on the client's perceived ability to use the computer. After 2 months, the individual was spending an average of 8.4 h per day on the computer, engaging in electronic communication, recreational, and educational activities. She learned single-switch typing with a throughput of 1.03 bits/s and targeting accuracy of 87.5%. The questionnaire revealed that the client was thoroughly satisfied with the interface. These results were interpreted as positive gains in the International Classification of Functioning, Disability and Health domains of communication and social interaction. By addressing individual goals, abilities and relevant environmental factors, a bedside computer access solution can be developed for individuals in long-term care. The introduction of a computer access solution augmented the participant's communication, leisure and educational activities, as well as perceived independence.

  12. 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.

  13. Nonadditivity of quantum and classical capacities for entanglement breaking multiple-access channels and the butterfly network

    SciTech Connect

    Grudka, Andrzej; Horodecki, Pawel

    2010-06-15

    We analyze quantum network primitives which are entanglement breaking. We show superadditivity of quantum and classical capacity regions for quantum multiple-access channels and the quantum butterfly network. Since the effects are especially visible at high noise they suggest that quantum information effects may be particularly helpful in the case of the networks with occasional high noise rates. The present effects provide a qualitative borderline between superadditivities of bipartite and multipartite systems.

  14. A no-key-exchange secure image sharing scheme based on Shamir's three-pass cryptography protocol and the multiple-parameter fractional Fourier transform.

    PubMed

    Lang, Jun

    2012-01-30

    In this paper, we propose a novel secure image sharing scheme based on Shamir's three-pass protocol and the multiple-parameter fractional Fourier transform (MPFRFT), which can safely exchange information with no advance distribution of either secret keys or public keys between users. The image is encrypted directly by the MPFRFT spectrum without the use of phase keys, and information can be shared by transmitting the encrypted image (or message) three times between users. Numerical simulation results are given to verify the performance of the proposed algorithm.

  15. A chimera grid scheme. [multiple overset body-conforming mesh system for finite difference adaptation to complex aircraft configurations

    NASA Technical Reports Server (NTRS)

    Steger, J. L.; Dougherty, F. C.; Benek, J. A.

    1983-01-01

    A mesh system composed of multiple overset body-conforming grids is described for adapting finite-difference procedures to complex aircraft configurations. In this so-called 'chimera mesh,' a major grid is generated about a main component of the configuration and overset minor grids are used to resolve all other features. Methods for connecting overset multiple grids and modifications of flow-simulation algorithms are discussed. Computational tests in two dimensions indicate that the use of multiple overset grids can simplify the task of grid generation without an adverse effect on flow-field algorithms and computer code complexity.

  16. A New Improving Quantum Secret Sharing Scheme

    NASA Astrophysics Data System (ADS)

    Xu, Ting-Ting; Li, Zhi-Hui; Bai, Chen-Ming; Ma, Min

    2017-01-01

    An improving quantum secret sharing scheme (IQSS scheme) was introduced by Nascimento et al. (Phys. Rev. A 64, 042311 (2001)), which was analyzed by the improved quantum access structure. In this paper, we propose a new improving quantum secret sharing scheme, and more quantum access structures can be realized by this scheme than the previous one. For example, we prove that any threshold and hypercycle quantum access structures can be realized by the new scheme.

  17. A New Improving Quantum Secret Sharing Scheme

    NASA Astrophysics Data System (ADS)

    Xu, Ting-Ting; Li, Zhi-Hui; Bai, Chen-Ming; Ma, Min

    2017-04-01

    An improving quantum secret sharing scheme (IQSS scheme) was introduced by Nascimento et al. (Phys. Rev. A 64, 042311 (2001)), which was analyzed by the improved quantum access structure. In this paper, we propose a new improving quantum secret sharing scheme, and more quantum access structures can be realized by this scheme than the previous one. For example, we prove that any threshold and hypercycle quantum access structures can be realized by the new scheme.

  18. Weighted sum-rate maximization for multi-user SIMO multiple access channels in cognitive radio networks

    NASA Astrophysics Data System (ADS)

    He, Peter; Zhao, Lian; Lu, Jianhua

    2013-12-01

    In this article, an efficient distributed and parallel algorithm is proposed to maximize the sum-rate and optimize the input distribution policy for the multi-user single input multiple output multiple access channel (MU-SIMO MAC) system with concurrent access within a cognitive radio (CR) network. The single input means that every user has a single antenna and multiple output means that base station(s) has multiple antennas. The main features are: (i) the power distribution for the users is updated by using variable scale factors which effectively and efficiently maximize the objective function at each iteration; (ii) distributed and parallel computation is employed to expedite convergence of the proposed distributed algorithm; and (iii) a novel water-filling with mixed constraints is investigated, and used as a fundamental block of the proposed algorithm. Due to sufficiently exploiting the structure of the proposed model, the proposed algorithm owns fast convergence. Numerical results verify that the proposed algorithm is effective and fast convergent. Using the proposed approach, for the simulated range, the required number of iterations for convergence is two and this number is not sensitive to the increase of the number of users. This feature is quite desirable for large scale systems with dense active users. In addition, it is also worth noting that the proposed algorithm is a monotonic feasible operator to the iteration. Thus, the stop criterion for computation could be easily set up.

  19. MSA-PAD: DNA multiple sequence alignment framework based on PFAM accessed domain information.

    PubMed

    Balech, Bachir; Vicario, Saverio; Donvito, Giacinto; Monaco, Alfonso; Notarangelo, Pasquale; Pesole, Graziano

    2015-08-01

    Here we present the MSA-PAD application, a DNA multiple sequence alignment framework that uses PFAM protein domain information to align DNA sequences encoding either single or multiple protein domains. MSA-PAD has two alignment options: gene and genome mode.

  20. Hop-Reservation Multiple Access (HRMA) for Ad-Hoc Networks

    DTIC Science & Technology

    1999-01-01

    5] and MACAW [6]. III. CORRECTNESS OF HRMA The following theorem proves that HRMA eliminates hidden- terminal interference problems. To prove this...Bharghavan, A. Demers, S. Shenker, and L. Zhang, “ MACAW : A Me- dia Access Protocol for Wireless LAN’s,” in Proc. ACM SIGCOMM ’94, pp. 212–25, London

  1. Multi-pulse frequency shifted (MPFS) multiple access modulation for ultra wideband

    DOEpatents

    Nekoogar, Faranak [San Ramon, CA; Dowla, Farid U [Castro Valley, CA

    2012-01-24

    The multi-pulse frequency shifted technique uses mutually orthogonal short duration pulses o transmit and receive information in a UWB multiuser communication system. The multiuser system uses the same pulse shape with different frequencies for the reference and data for each user. Different users have a different pulse shape (mutually orthogonal to each other) and different transmit and reference frequencies. At the receiver, the reference pulse is frequency shifted to match the data pulse and a correlation scheme followed by a hard decision block detects the data.

  2. A licence to vape: Is it time to trial of a nicotine licensing scheme to allow Australian adults controlled access to electronic cigarettes devices and refill solutions containing nicotine?

    PubMed

    Gartner, Coral; Hall, Wayne

    2015-06-01

    Australia has some of the most restrictive laws concerning use of nicotine in e-cigarettes. The only current legal option for Australians to legally possess and use nicotine for vaping is with a medical prescription and domestic supply is limited to compounding pharmacies that prepare medicines for specific patients. An alternative regulatory option that could be implemented under current drugs and poisons regulations is a 'nicotine licensing' scheme utilising current provisions for 'dangerous poisons'. This commentary discusses how such a scheme could be used to trial access to nicotine solutions for vaping outside of a 'medicines framework' in Australia. Copyright © 2015 Elsevier B.V. All rights reserved.

  3. Hybrid bidirectional radio-over-fiber-based orthogonal frequency division multiple access-passive optical network supporting 60/120 GHz using offset quadrate phase shift keying

    NASA Astrophysics Data System (ADS)

    Zhang, Chongfu; Chen, Chen; Qiu, Kun

    2015-09-01

    A hybrid bidirectional orthogonal frequency division multiple access-passive optical network (OFDMA-PON) based on offset quadrate phase shift keying (OQPSK) to support 60- and 120-GHz radio-over-fiber system is proposed. The system can support wired/wireless applications and enable the dynamic bandwidth allocation according to a subscriber's application. It is successfully achieved by using the millimeter waves (MMWs) generation and the carrier-reuse technique. In the proposed scheme, the MMW bands used for downlink (DL) and uplink transmissions are generated at the optical line terminal by the dual-arm Mach-Zehnder modulators. Both 60- and 120-GHz MMWs are obtained for the transmission of the high bit-rate services in source-free optical network units (ONUs), only using a single 15-GHz sinusoidal wave source. The Rayleigh backscattering effect is considered in the proposed OQPSK-based OFDMA-PON. For DL transmission over a 30-km single-mode fiber, the power penalties are less than 0.8 and 1 dB for the OQPSK-OFDM wired data at 10 Gb/s and the OQPSK-OFDM wireless data at 5 Gb/s, respectively.

  4. Demonstration of a lexical access deficit in relapsing-remitting and secondary progressive forms of multiple sclerosis.

    PubMed

    Joly, H; Cohen, M; Lebrun, C

    2014-01-01

    The commonly used test to evaluate naming ability in multiple sclerosis (MS) is the Boston Naming Test (BNT). In previous studies the BNP has not shown any specific deficit in MS patients. The BNT score is obtained by adding spontaneously correct answers to correct answers obtained after semantic and phonological clues are given. Our hypothesis was that due to a lexical access deficit based on executive dysfunction, MS patients would need more clues than control subjects to normalize their performances,. Fifteen relapsing-remitting (RR) and 17 secondary progressive (SP) MS patients, and 32 controls matched for sex, age, and educational level, took the BNT. The 32 MS patients also took the BCCog (Short French battery used in MS to evaluate cognitive functions) in order to evaluate their executive functions. MS patients needed significantly more clues than matched controls to normalize their performances (P<0.001). This lexical access deficit was more frequent in the SP than in the RR group (P<0.05). A lexical access deficit inducing a denomination problem has thus been shown in MS patients. Further research should aim to better evaluate the executive functions of patients with a lexical access deficit.

  5. Resolving the problem of multiple accessions of the same transcript deposited across various public databases.

    PubMed

    Weirick, Tyler; John, David; Uchida, Shizuka

    2017-03-01

    Maintaining the consistency of genomic annotations is an increasingly complex task because of the iterative and dynamic nature of assembly and annotation, growing numbers of biological databases and insufficient integration of annotations across databases. As information exchange among databases is poor, a 'novel' sequence from one reference annotation could be annotated in another. Furthermore, relationships to nearby or overlapping annotated transcripts are even more complicated when using different genome assemblies. To better understand these problems, we surveyed current and previous versions of genomic assemblies and annotations across a number of public databases containing long noncoding RNA. We identified numerous discrepancies of transcripts regarding their genomic locations, transcript lengths and identifiers. Further investigation showed that the positional differences between reference annotations of essentially the same transcript could lead to differences in its measured expression at the RNA level. To aid in resolving these problems, we present the algorithm 'Universal Genomic Accession Hash (UGAHash)' and created an open source web tool to encourage the usage of the UGAHash algorithm. The UGAHash web tool (http://ugahash.uni-frankfurt.de) can be accessed freely without registration. The web tool allows researchers to generate Universal Genomic Accessions for genomic features or to explore annotations deposited in the public databases of the past and present versions. We anticipate that the UGAHash web tool will be a valuable tool to check for the existence of transcripts before judging the newly discovered transcripts as novel. © The Author 2016. Published by Oxford University Press. For Permissions, please email: journals.permissions@oup.com.

  6. BioZoom: Exploiting Source-Capability Information for Integrated Access to Multiple Bioinformatics Data Sources

    SciTech Connect

    Liu, L; Buttler, D; Critchlow, T J; Han, W; Paques, H; Pu, C; Rocco, D

    2003-01-09

    Modern Bioinformatics data sources are widely used by molecular biologists for homology searching and new drug discovery. User-friendly and yet responsive access is one of the most desirable properties for integrated access to the rapidly growing, heterogeneous, and distributed collection of data sources. The increasing volume and diversity of digital information related to bioinformatics (such as genomes, protein sequences, protein structures, etc.) have led to a growing problem that conventional data management systems do not have, namely finding which information sources out of many candidate choices are the most relevant and most accessible to answer a given user query. We refer to this problem as the query routing problem. In this paper we introduce the notation and issues of query routing, and present a practical solution for designing a scalable query routing system based on multi-level progressive pruning strategies. The key idea is to create and maintain source-capability profiles independently, and to provide algorithms that can dynamically discover relevant information sources for a given query through the smart use of source profiles. Compared to the keyword-based indexing techniques adopted in most of the search engines and software, our approach offers fine-granularity of interest matching, thus it is more powerful and effective for handling queries with complex conditions.

  7. BioZone Exploting Source-Capability Information for Integrated Access to Multiple Bioinformatics Data Sources

    SciTech Connect

    Liu, L; Buttler, D; Paques, H; Pu, C; Critchlow

    2002-01-28

    Modern Bioinformatics data sources are widely used by molecular biologists for homology searching and new drug discovery. User-friendly and yet responsive access is one of the most desirable properties for integrated access to the rapidly growing, heterogeneous, and distributed collection of data sources. The increasing volume and diversity of digital information related to bioinformatics (such as genomes, protein sequences, protein structures, etc.) have led to a growing problem that conventional data management systems do not have, namely finding which information sources out of many candidate choices are the most relevant and most accessible to answer a given user query. We refer to this problem as the query routing problem. In this paper we introduce the notation and issues of query routing, and present a practical solution for designing a scalable query routing system based on multi-level progressive pruning strategies. The key idea is to create and maintain source-capability profiles independently, and to provide algorithms that can dynamically discover relevant information sources for a given query through the smart use of source profiles. Compared to the keyword-based indexing techniques adopted in most of the search engines and software, our approach offers fine-granularity of interest matching, thus it is more powerful and effective for handling queries with complex conditions.

  8. Simultaneous measurements of multiple parameters at elevated temperature using a frequency-division multiplexing scheme with tunable diode lasers.

    PubMed

    Cai, Tingdong; Gao, Guangzhen; Liu, Ying

    2012-10-01

    A multiplexed diode-laser sensor system based on second harmonic detection of wavelength modulation spectroscopy (WMS) is developed for application at elevated temperatures with two near-infrared diode lasers multiplexed using a frequency-division multiplexing scheme. One laser is tuned over a H(2)O line pair near 7079.176 and 7079.855 cm(-1), and another laser is tuned over a pair of CO(2) and CO lines near 6361.250 and 6361.344 cm(-1). Temperature and concentrations of H(2)O, CO(2), and CO could be measured simultaneously by this system. In order to remove the need for calibration and correct for transmission variation due to beam steering, mechanical misalignments, soot, and windows fouling, the WMS-1f normalized 2f method is used. Demonstration experiments are conducted in a heated static cell. The precision of temperature and the concentrations for H(2)O, CO(2), and CO are found to be 1.57%, 3.87%, 3.01%, and 3.58%, respectively. These results illustrate the potential of this sensor for applications at high temperatures.

  9. Increasing Access to Clinical Trials and Innovative Therapy for Teenagers and Young Adults with Cancer - A Multiple Stakeholders and Multiple Steps Process.

    PubMed

    Gaspar, Nathalie; Fern, Lorna

    2016-01-01

    The inclusion of teenagers and young adults (TYAs) in cancer clinical trials is focal point for many countries with a specific TYA program. This objective has arisen from data which suggests that lower trial entry may, in part, contribute to lesser survival gains observed in this group when compared to children and some older adult cancers. In this chapter, we discuss obstacles to clinical trials and innovative therapies for TYA. Limited clinical trial availability is discussed in the context of the rarity of TYA cancers and our limited understanding of cancer biology in this group, other obstacles include inappropriate age eligibility criteria, limited accessibility to available trials, a lack of physicians and patients awareness and poor acceptability of trial design. We propose several strategies which could be applied to overcome these obstacles, some ready for implementation and others which require further exploration. Strengthening pediatric and adult oncology collaboration at the individual level and through oncology societies will undoubtedly positively impact accrual to trials for TYA, as will abolishing the use of age as a barrier to drug and trial access. This will allow us to create biologically driven trials and facilitate early new drug access and the creation of biobank collections to drive our understanding of the biology of cancers in this age group. Involving multiple stakeholders in trial design will facilitate acceptable trials to both healthcare professionals and young people themselves. The support of the multidisciplinary TYA team and a culture of research embedded within this are the keys to improving access and participation of TYA in cancer trials. © 2016 S. Karger AG, Basel.

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

    NASA Astrophysics Data System (ADS)

    Mazurek, Gustaw; Szabatin, Jerzy

    2008-01-01

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

  11. On the Performance of Non-Orthogonal Multiple Access in 5G Systems with Randomly Deployed Users

    NASA Astrophysics Data System (ADS)

    Ding, Zhiguo; Yang, Zheng; Fan, Pingzhi; Poor, H. Vincent

    2014-12-01

    In this letter, the performance of non-orthogonal multiple access (NOMA) is investigated in a cellular downlink scenario with randomly deployed users. The developed analytical results show that NOMA can achieve superior performance in terms of ergodic sum rates; however, the outage performance of NOMA depends critically on the choices of the users' targeted data rates and allocated power. In particular, a wrong choice of the targeted data rates and allocated power can lead to a situation in which the user's outage probability is always one, i.e. the user's targeted quality of service will never be met.

  12. Cache oblivious storage and access heuristics for blocked matrix-matrix multiplication

    SciTech Connect

    Bock, Nicolas; Rubensson, Emanuel H; Niklasson, Anders M N; Challacombe, Matt; Salek, Pawel

    2008-01-01

    The authors investigate effects of ordering in blocked matrix-matrix multiplication. They find that submatrices do not have to be stored contiguously in memory in order to achieve near optimal performance. They also find a good choice of execution order of submatrix operations can lead to a speedup of up to four times for small block sizes.

  13. Multiple Providers and Access to Primary Education: The Case of Bangladesh

    ERIC Educational Resources Information Center

    Zia-Us-Sabur; Ahmed, Manzoor

    2010-01-01

    Even though most children in Bangladesh are enrolled in school, the country faces enormous challenges in ensuring that children complete primary education, and learn an acceptable amount. Multiple providers--state, quasi-state, and non-state--have helped to raise the initial enrolment rate and improve the gender balance. The critical question is…

  14. Access to environmental stimulation via eyelid responses for persons with acquired brain injury and multiple disabilities: a new microswitch arrangement.

    PubMed

    Lancioni, Giulio E; Singh, Nirbhay N; O'Reilly, Mark F; Sigafoos, Jeff; Ricci, Irene; Buonocunto, Francesca; Sacco, Valentina

    2012-04-01

    This study assessed a new microswitch arrangement for eyelid responses using an optic sensor placed above the cheekbone and a small sticker on the person's eyelid. This new arrangement, which was designed to avoid interference of the microswitch with the person's visual functioning, was tested on three adults with acquired brain injury and multiple (consciousness, communication, and motor) disabilities. The study was carried out according to a non-concurrent multiple baseline design across participants. Data showed the new microswitch arrangement was suitable for all three participants, who increased their responding during the intervention phase of the study when their responses allowed them to access preferred stimulation. Practical implications of the findings are discussed.

  15. An experimental investigation of an air cooling scheme for the multichip modules of the multiplicity and vertex detector

    SciTech Connect

    Bernardin, J.D.; Bosze, E.; Boissevain, J.; Simon-Gillo, J.

    1997-07-01

    This report presents a summary of an experimental investigation of an electronics air cooling system for the multiplicity and vertex detector (MVD), a device used to determine and characterize the collision location of two accelerated heavy ions. Measurements of the flow rates of the cooling air and the temperatures of the air and electronic components were used to assess and optimize the performance of the proposed air cooling system, identify potential assembly problems and system limitations, and provide the necessary information for designing and sizing the final MVD cooling system components.

  16. The reduced multiplication scheme of the Rys quadrature and new recurrence relations for auxiliary function based two-electron integral evaluation

    NASA Astrophysics Data System (ADS)

    Lindh, R.; Ryu, U.; Liu, B.

    1991-10-01

    The reduced multiplication scheme of the Rys quadrature is presented. The method is based on new ways in which the Rys quadrature can be developed if it is implemented together with the transfer equation applied to the contracted integrals. In parallel to the new scheme of the Rys quadrature improvements are suggested to the auxiliary function based algorithms. The two new methods have very favorable theoretical floating point operation (FLOP) counts as compared to other methods. It is noted that the only significant difference in performance of the two new methods is due to the vectorizability of the presented algorithms. In order to exhibit this, both methods were implemented in the integral program seward. Timings are presented for comparisons with other implemenations. Finally, it is demonstrated how the transfer equation in connection with the use of spherical harmonic Gaussians offers a very attractive path to compute the two-electron integrals of such basis functions. It is demonstrated both theoretically and with actual performance that the use of spherical harmonic Gaussians offers a clear advantage over the traditional evaluation of the two-electron integrals in the Cartesian Gaussian basis.

  17. Ultrasonic Multiple-Access Ranging System Using Spread Spectrum and MEMS Technology for Indoor Localization

    PubMed Central

    Segers, Laurent; Tiete, Jelmer; Braeken, An; Touhafi, Abdellah

    2014-01-01

    Indoor localization of persons and objects poses a great engineering challenge. Previously developed localization systems demonstrate the use of wideband techniques in ultrasound ranging systems. Direct sequence and frequency hopping spread spectrum ultrasound signals have been proven to achieve a high level of accuracy. A novel ranging method using the frequency hopping spread spectrum with finite impulse response filtering will be investigated and compared against the direct sequence spread spectrum. In the first setup, distances are estimated in a single-access environment, while in the second setup, two senders and one receiver are used. During the experiments, the micro-electromechanical systems are used as ultrasonic sensors, while the senders were implemented using field programmable gate arrays. Results show that in a single-access environment, the direct sequence spread spectrum method offers slightly better accuracy and precision performance compared to the frequency hopping spread spectrum. When two senders are used, measurements point out that the frequency hopping spread spectrum is more robust to near-far effects than the direct sequence spread spectrum. PMID:24553084

  18. 40 GHz AlGaInAs Multiple-Quantum-Well Integrated Electroabsorption Modulator/Distributed Feedback Laser Based on Identical Epitaxial Layer Scheme

    NASA Astrophysics Data System (ADS)

    Luo, Yi; Xiong, Bing; Wang, Jian; Cai, Pengfei; Sun, Changzheng

    2006-10-01

    An AlGaInAs multiple-quantum-well (MQW) distributed feedback (DFB) laser is monolithically integrated with a lumped-electrode electroabsorption (EA) modulator based on an identical epitaxial layer integration scheme. The device exhibits a threshold current of 12 mA and an extinction ratio of higher than 13 dB under a 3 V reverse bias. By adopting a dry-etched high-mesa ridge waveguide and planar electrode structures, the capacitance of the modulator is reduced to about 0.11 pF and a 3 dBe modulation bandwidth of over 40 GHz has been demonstrated. To our knowledge, this is the first report on a 40 GHz operation of AlGaInAs integrated light sources.

  19. Performance of a Frequency-Hopped Real-Time Remote Control System in a Multiple Access Scenario

    NASA Astrophysics Data System (ADS)

    Cervantes, Frank

    A recent trend is observed in the context of the radio-controlled aircrafts and automobiles within the hobby grade category and Unmanned Aerial Vehicles (UAV) applications moving to the well-known Industrial, Scientific and Medical (ISM) band. Based on this technological fact, the present thesis evaluates an individual user performance by featuring a multiple-user scenario where several point-to-point co-located real-time Remote Control (RC) applications operate using Frequency Hopping Spread Spectrum (FHSS) as a medium access technique in order to handle interference efficiently. Commercial-off-the-shelf wireless transceivers ready to operate in the ISM band are considered as the operational platform supporting the above-mentioned applications. The impact of channel impairments and of different critical system engineering issues, such as working with real clock oscillators and variable packet duty cycle, are considered. Based on the previous, simulation results allowed us to evaluate the range of variation for those parameters for an acceptable system performance under Multiple Access (MA) environments.

  20. 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.

  1. Simultaneous detection of multiple debris via a cascade of numerical evaluations and a voting scheme for lines in an image sequence

    NASA Astrophysics Data System (ADS)

    Fujita, Koki; Ichimura, Naoyuki; Hanada, Toshiya

    2017-04-01

    This paper presents a novel method to simultaneously detect multiple trajectories of space debris in an observation image sequence to establish a reliable model for space debris environment in Geosynchronous Earth Orbit (GEO). The debris in GEO often appear faintly in image sequences due to the high altitude. A simple but steady way to detect such faint debris is to decrease a threshold value of binarization applied to an image sequence during preprocessing. However, a low threshold value of binarization leads to extracting a large number of objects other than debris that become obstacles to detect debris trajectories. In order to detect debris from binarized image frames with massive obstacles, this work proposes a method that utilizes a cascade of numerical evaluations and a voting scheme to evaluate characteristics of the line segments obtained by connecting two image objects in different image frames, which are the candidates of debris trajectories. In the proposed method, the line segments corresponding to objects other than debris are filtered out using three types of characteristics, namely displacement, direction, and continuity. First, the displacement and direction of debris motion are evaluated to remove irrelevant trajectories. Then, the continuity of the remaining line segments is checked to find debris by counting the number of image objects appearing on or close to the line segments. Since checking the continuity can be regarded as a voting scheme, the proposed cascade algorithm can take advantage of the properties of voting method such as the Hough transform, i.e., the robustness against heavy noises and clutters, and ability of detecting multiple trajectories simultaneously. The experimental tests using real image sequences obtained in a past observation campaign demonstrate the effectiveness of the proposed method.

  2. ECR Browser: A Tool For Visualizing And Accessing Data From Comparisons Of Multiple Vertebrate Genomes

    SciTech Connect

    Loots, G G; Ovcharenko, I; Stubbs, L; Nobrega, M A

    2004-01-06

    The increasing number of vertebrate genomes being sequenced in draft or finished form provide a unique opportunity to study and decode the language of DNA sequence through comparative genome alignments. However, novel tools and strategies are required to accommodate this increasing volume of genomic information and to facilitate experimental annotation of genome function. Here we present the ECR Browser, a tool that provides an easy and dynamic access to whole genome alignments of human, mouse, rat and fish sequences. This web-based tool (http://ecrbrowser.dcode.org) provides the starting point for discovery of novel genes, identification of distant gene regulatory elements and prediction of transcription factor binding sites. The genome alignment portal of the ECR Browser also permits fast and automated alignment of any user-submitted sequence to the genome of choice. The interconnection of the ECR browser with other DNA sequence analysis tools creates a unique portal for studying and exploring vertebrate genomes.

  3. Access to Care for Multiple Sclerosis in Times of Economic Crisis in Greece--the HOPE II Study.

    PubMed

    Souliotis, Kyriakos; Alexopoulou, Elena; Papageorgiou, Manto; Politi, Anastasia; Litsa, Panagiota; Contiades, Xenophon

    2015-09-27

    While there is currently no cure for multiple sclerosis (MS), treatment with biologic disease-modifying drugs (bDMDs) can reduce the impact of the condition on the lives of patients. In Greece, the regulatory change in the distribution system of bDMDs, limited their administration through the designated pharmacies of the National Organization for Healthcare Services Provision (EOPYY) or the National Health System (ESY) hospitals, thus potentially impacting access to MS treatment. In this context, the aim of this paper was to assess the barriers to bDMDs, by recording MS patients' experiences. A survey research was conducted between January and February 2014 in Athens and 5 other major Greek cities with the methods of personal and telephone interview. A structured questionnaire was used to elicit socio-economic and medical information, information related to obstacles in accessing bDMDs and medical treatment, from MS patients that visited EOPYY pharmacies during the study period. During the last year 69% of 179 participants reported that the distribution system of bDMDs has improved. Thirteen percent of participants encountered problems in accessing their medication, and 16.9% of participants in accessing their physician, with the obstacles being more pronounced for non-Athens residents. Frequent obstacles to bDMDs were the distance from EOPYY pharmacies and difficulties in obtaining a diagnosis from an EOPYY/ESY physician, while obstacles to medical care were delays in appointment booking and travel difficulties. Even though the major weaknesses of the distribution system of bDMDs have improved, further amelioration of the system could be achieved through the home delivery of medicines to patients living in remote areas, and through the development of a national MS registry. © 2016 by Kerman University of Medical Sciences.

  4. Access to Care for Multiple Sclerosis in Times of Economic Crisis in Greece – the HOPE II Study

    PubMed Central

    Souliotis, Kyriakos; Alexopoulou, Elena; Papageorgiou, Manto; Politi, Anastasia; Litsa, Panagiota; Contiades, Xenophon

    2016-01-01

    Background: While there is currently no cure for multiple sclerosis (MS), treatment with biologic disease-modifying drugs (bDMDs) can reduce the impact of the condition on the lives of patients. In Greece, the regulatory change in the distribution system of bDMDs, limited their administration through the designated pharmacies of the National Organization for Healthcare Services Provision (EOPYY) or the National Health System (ESY) hospitals, thus potentially impacting access to MS treatment. In this context, the aim of this paper was to assess the barriers to bDMDs, by recording MS patients’ experiences. Methods: A survey research was conducted between January and February 2014 in Athens and 5 other major Greek cities with the methods of personal and telephone interview. A structured questionnaire was used to elicit socio-economic and medical information, information related to obstacles in accessing bDMDs and medical treatment, from MS patients that visited EOPYY pharmacies during the study period. Results: During the last year 69% of 179 participants reported that the distribution system of bDMDs has improved. Thirteen percent of participants encountered problems in accessing their medication, and 16.9% of participants in accessing their physician, with the obstacles being more pronounced for non-Athens residents. Frequent obstacles to bDMDs were the distance from EOPYY pharmacies and difficulties in obtaining a diagnosis from an EOPYY/ESY physician, while obstacles to medical care were delays in appointment booking and travel difficulties. Conclusion: Even though the major weaknesses of the distribution system of bDMDs have improved, further amelioration of the system could be achieved through the home delivery of medicines to patients living in remote areas, and through the development of a national MS registry. PMID:26927393

  5. Simulation scheme of dusk scene using piece-wise multiple regression based on time-series color-block images

    NASA Astrophysics Data System (ADS)

    Liu, Chen-Chung; Yang, Chih-Chao

    2010-09-01

    Dusk and dawn are usually the most beautiful moments of the day, and are almost always too short for busy people nowadays to witness their coming. In this work, an efficient strategy for simulating a dusk scene of an outdoor scene image taken at other times before the sunset is presented. The strategy is a hybrid approach combining the piece-wise multiple regression (PMR) of data, discrete cosine transformation (DCT), and a look-up table algorithm. The process begins using a series of color-block images taken in the afternoon of a day. The best fitting functions of PMR for these color block images exist on separate planes (red, green, and blue) in the DCT domain individually. The reference databases of the DCT coefficients varying with respect to time are then established according to the best fitting functions of PMR. Finally, the dusk scene of an outdoor scene taken in the afternoon is synthesized by querying the reference database. The experiment results show that the presented algorithm can precisely simulate the desired dusk scene from a scene image taken in the afternoon.

  6. Locally accessible conformations of proteins: multiple molecular dynamics simulations of crambin.

    PubMed Central

    Caves, L. S.; Evanseck, J. D.; Karplus, M.

    1998-01-01

    Multiple molecular dynamics (MD) simulations of crambin with different initial atomic velocities are used to sample conformations in the vicinity of the native structure. Individual trajectories of length up to 5 ns sample only a fraction of the conformational distribution generated by ten independent 120 ps trajectories at 300 K. The backbone atom conformational space distribution is analyzed using principal components analysis (PCA). Four different major conformational regions are found. In general, a trajectory samples only one region and few transitions between the regions are observed. Consequently, the averages of structural and dynamic properties over the ten trajectories differ significantly from those obtained from individual trajectories. The nature of the conformational sampling has important consequences for the utilization of MD simulations for a wide range of problems, such as comparisons with X-ray or NMR data. The overall average structure is significantly closer to the X-ray structure than any of the individual trajectory average structures. The high frequency (less than 10 ps) atomic fluctuations from the ten trajectories tend to be similar, but the lower frequency (100 ps) motions are different. To improve conformational sampling in molecular dynamics simulations of proteins, as in nucleic acids, multiple trajectories with different initial conditions should be used rather than a single long trajectory. PMID:9541397

  7. A BER analysis of a space-time signal processing scheme that combines transmitter diversity with beamforming

    NASA Astrophysics Data System (ADS)

    Kim, Ilhan; Chun, Joohwan

    2003-12-01

    We introduce a new space-time signal processing scheme that uses both transmitter diversity technique and beamforming technique for code-division multiple access (CDMA) systems. The introduced scheme achieves the diversity gain over Rayleigh fading channel through the transmitter diversity technique, and the signal-to-noise ratio (SNR) gain by the beamforming technique. Bit error rate (BER) analyses are given each of the three cases in which the transmitter diversity, beamforming and introduced combined scheme are used, in the frequency-flat Rayleigh fading channel. The analytic results are shown to coincide with the Monte-Carlo simulation results. We show that the combined scheme is more robust to the channel correlation and the speed of mobile than the diversity and beamforming scheme. Furthermore, the combined scheme gives a reduced multiple-access-interference because of its beamforming capability.

  8. Post-Coma Persons with Extensive Multiple Disabilities Use Microswitch Technology to Access Selected Stimulus Events or Operate a Radio Device

    ERIC Educational Resources Information Center

    Lancioni, Giulio E.; Singh, Nirbhay N.; O'Reilly, Mark F.; Sigafoos, Jeff; Alberti, Gloria; Oliva, Doretta; Megna, Gianfranco; Iliceto, Carla; Damiani, Sabino; Ricci, Irene; Spica, Antonella

    2011-01-01

    The present two studies extended research evidence on the use of microswitch technology by post-coma persons with multiple disabilities. Specifically, Study I examined whether three adults with a diagnosis of minimally conscious state and multiple disabilities could use microswitches as tools to access brief, selected stimulus events. Study II…

  9. Post-Coma Persons with Extensive Multiple Disabilities Use Microswitch Technology to Access Selected Stimulus Events or Operate a Radio Device

    ERIC Educational Resources Information Center

    Lancioni, Giulio E.; Singh, Nirbhay N.; O'Reilly, Mark F.; Sigafoos, Jeff; Alberti, Gloria; Oliva, Doretta; Megna, Gianfranco; Iliceto, Carla; Damiani, Sabino; Ricci, Irene; Spica, Antonella

    2011-01-01

    The present two studies extended research evidence on the use of microswitch technology by post-coma persons with multiple disabilities. Specifically, Study I examined whether three adults with a diagnosis of minimally conscious state and multiple disabilities could use microswitches as tools to access brief, selected stimulus events. Study II…

  10. 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.

  11. Multiple social identities and stereotype threat: imbalance, accessibility, and working memory.

    PubMed

    Rydell, Robert J; McConnell, Allen R; Beilock, Sian L

    2009-05-01

    In 4 experiments, the authors showed that concurrently making positive and negative self-relevant stereotypes available about performance in the same ability domain can eliminate stereotype threat effects. Replicating past work, the authors demonstrated that introducing negative stereotypes about women's math performance activated participants' female social identity and hurt their math performance (i.e., stereotype threat) by reducing working memory. Moving beyond past work, it was also demonstrated that concomitantly presenting a positive self-relevant stereotype (e.g., college students are good at math) increased the relative accessibility of females' college student identity and inhibited their gender identity, eliminating attendant working memory deficits and contingent math performance decrements. Furthermore, subtle manipulations in questions presented in the demographic section of a math test eliminated stereotype threat effects that result from women reporting their gender before completing the test. This work identifies the motivated processes through which people's social identities became active in situations in which self-relevant stereotypes about a stigmatized group membership and a nonstigmatized group membership were available. In addition, it demonstrates the downstream consequences of this pattern of activation on working memory and performance.

  12. IPAT: a freely accessible software tool for analyzing multiple patent documents with inbuilt landscape visualizer.

    PubMed

    Ajay, Dara; Gangwal, Rahul P; Sangamwar, Abhay T

    2015-01-01

    Intelligent Patent Analysis Tool (IPAT) is an online data retrieval tool, operated based on text mining algorithm to extract specific patent information in a predetermined pattern into an Excel sheet. The software is designed and developed to retrieve and analyze technology information from multiple patent documents and generate various patent landscape graphs and charts. The software is C# coded in visual studio 2010, which extracts the publicly available patent information from the web pages like Google Patent and simultaneously study the various technology trends based on user-defined parameters. In other words, IPAT combined with the manual categorization will act as an excellent technology assessment tool in competitive intelligence and due diligence for predicting the future R&D forecast.

  13. Using multiple hydrogen bonding cross-linkers to access reversibly responsive three dimensional graphene oxide architecture

    NASA Astrophysics Data System (ADS)

    Han, Junkai; Shen, Yongtao; Feng, Wei

    2016-07-01

    Three-dimensional (3D) graphene materials have attracted a lot of attention for efficiently utilizing inherent properties of graphene sheets. However, 3D graphene materials reported in the previous literature are constructed through covalent or weak non-covalent interactions, causing permanent structure/property changes. In this paper, a novel 3D graphene material of dynamic interactions between lamellas with 2-ureido-4[1H]-pyrimidinone as a supra-molecular motif has been synthesized. This 3D graphene material shows enhanced sheet interactions while the cross-linking takes place. With proper solvent stimulation, the integrated 3D graphene material can disassemble as isolated sheets. The driving force for the 3D structure assembly or disassembly is considered to be the forming or breaking of the multiple hydrogen bonding pairs. Furthermore, the 3D material is used as an intelligent dye adsorber to adsorb methylene blue and release it. The controllable and reversible characteristic of this 3D graphene material may open an avenue to the synthesis and application of novel intelligent materials.Three-dimensional (3D) graphene materials have attracted a lot of attention for efficiently utilizing inherent properties of graphene sheets. However, 3D graphene materials reported in the previous literature are constructed through covalent or weak non-covalent interactions, causing permanent structure/property changes. In this paper, a novel 3D graphene material of dynamic interactions between lamellas with 2-ureido-4[1H]-pyrimidinone as a supra-molecular motif has been synthesized. This 3D graphene material shows enhanced sheet interactions while the cross-linking takes place. With proper solvent stimulation, the integrated 3D graphene material can disassemble as isolated sheets. The driving force for the 3D structure assembly or disassembly is considered to be the forming or breaking of the multiple hydrogen bonding pairs. Furthermore, the 3D material is used as an

  14. Habit formation and multiple means to goal attainment: repeated retrieval of target means causes inhibited access to competitors.

    PubMed

    Danner, Unna N; Aarts, Henk; de Vries, Nanne K

    2007-10-01

    Three studies examined the cognitive processes underlying the formation of goal-directed habits in a multiple means context. Repeated retrieval of target means upon goal activation was expected to result in inhibition of competing means for the same goal. In all studies, participants studied goal-means combinations and subsequently practiced the retrieval of certain means to attain the goals in a retrieval paradigm. Study 1 tested accessibility of the different means in a goal-means verification task and showed that competing means were not inhibited after a single retrieval but only upon repeated retrieval (three or nine times). Studies 2 and 3 extended these findings in a means-recognition task and demonstrated that inhibition occurred in the absence of explicit intent or instructions to suppress the competitors. These inhibitory effects of competing means are discussed against the background of current social cognition research on the processes underlying goal-means networks and the formation of habits.

  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. A novel IPTV program multiplex access system to EPON

    NASA Astrophysics Data System (ADS)

    Xu, Xian; Liu, Deming; He, Wei; Lu, Xi

    2007-11-01

    With the rapid development of high speed networks, such as Ethernet Passive Optical Network (EPON), traffic patterns in access networks have evolved from traditional text-oriented service to the mixed text-, voice- and video- based services, leading to so called "Triple Play". For supporting IPTV service in EPON access network infrastructure, in this article we propose a novel IPTV program multiplex access system to EPON, which enables multiple IPTV program source servers to seamlessly access to IPTV service access port of optical line terminal (OLT) in EPON. There are two multiplex schemes, namely static multiplex scheme and dynamic multiplex scheme, in implementing the program multiplexing. Static multiplex scheme is to multiplex all the IPTV programs and forward them to the OLT, regardless of the need of end-users. While dynamic multiplex scheme can dynamically multiplex and forward IPTV programs according to what the end-users actually demand and those watched by no end-user would not be multiplexed. By comparing these two schemes, a reduced traffic of EPON can be achieved by using dynamic multiplex scheme, especially when most end-users are watching the same few IPTV programs. Both schemes are implemented in our system, with their hardware and software designs described.

  17. 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.

  18. Persons with multiple disabilities use forehead and smile responses to access or choose among technology-aided stimulation events.

    PubMed

    Lancioni, Giulio E; Singh, Nirbhay N; O'Reilly, Mark F; Sigafoos, Jeff; Alberti, Gloria; Bellini, Domenico; Oliva, Doretta; Boccasini, Adele; La Martire, Maria L; Signorino, Mario

    2013-05-01

    A variety of technology-aided programs have been developed to help persons with congenital or acquired multiple disabilities access preferred stimuli or choose among stimulus options. The application of those programs may pose problems when the participants have very limited behavior repertoires and are unable to use conventional responses and microswitches. The present two studies assessed non-conventional response-microswitch solutions for three of those participants. Study I included two participants who were exposed to a program in which forehead skin movement was the response required to access preferred stimulation. The microswitch was an optic sensor combined with a small black sticker on the forehead. Study II included one participant who was exposed to a program in which a smile response was required to choose among stimuli. The microswitch for monitoring the smile was a new camera-based technology. The results of the two studies showed that the response-microswitch solutions were suitable for the participants and enabled them to perform successfully. Implications of the studies for people with limited motor behavior and issues for future research were discussed.

  19. The Oxford clinical intranet: providing clinicians with access to patient records and multiple knowledge bases with internet technology.

    PubMed

    Kay, Jonathan D S; Nurse, Dave; Bountis, Christos; Paddon, Kevin

    2004-01-01

    The Oxford Clinical Intranet provides clinicians in primary and secondary care across Oxfordshire with: Access to information about their patients held on multiple remote disparate computer systems, including admissions and episodes, Laboratory Medicine reports, Radiology reports and hospital discharge letters. The patient records are managed using CSW Case Notes. Access to support and advisory information, developed both within the organization and collected from other sites and projects, a wide range of internal handbooks, directories and guidelines and links to external resources, including evidence-based resources, the Cochrane Collaboration and the NHS National electronic Library of Health. Automated retrieval and presentation of the support information that is contextually appropriate to the task being carried out by the clinician and the information held about the patient. For example laboratory reports are linked to handbooks and other reference sources using eLABook, a web-interfaced database subsystem. Internet technology has been used throughout, thus providing a thin-client architecture with cross-platform ability. Appropriate data standards have been used across the communicating systems and the intranet is compliant with the UK eGovernment Interoperability Framework. The intranet was developed at low cost and is now in routine use. This approach appears to be transferable across systems and organisations.

  20. A secure double-image sharing scheme based on Shamir's three-pass protocol and 2D Sine Logistic modulation map in discrete multiple-parameter fractional angular transform domain

    NASA Astrophysics Data System (ADS)

    Sui, Liansheng; Duan, Kuaikuai; Liang, Junli

    2016-05-01

    A secure double-image sharing scheme is proposed by using the Shamir's three-pass protocol in the discrete multiple-parameter fractional angular transform domain. First, an enlarged image is formed by assembling two plain images successively in the horizontal direction and scrambled in the chaotic permutation process, in which the sequences of chaotic pairs are generated by the two-dimensional Sine Logistic modulation map. Second, the scrambled image is divided into two components which are used to constitute a complex image. One component is normalized and regarded as the phase part of the complex image as well as other is considered as the amplitude part. Finally, the complex image is shared between the sender and the receiver by using the Shamir's three-pass protocol, in which the discrete multiple-parameter fractional angular transform is used as the encryption function due to its commutative property. The proposed double-image sharing scheme has an obvious advantage that the key management is convenient without distributing the random phase mask keys in advance. Moreover, the security of the image sharing scheme is enhanced with the help of extra parameters of the discrete multiple-parameter fractional angular transform. To the best of our knowledge, this is the first report on integrating the Shamir's three-pass protocol with double-image sharing scheme in the information security field. Simulation results and security analysis verify the feasibility and effectiveness of the proposed scheme.

  1. Libraries and the Pickle (PCLE) of Content Management Schemes: Survey of Pending Copyright Policy Battles and Their Implications for School Libraries, Free Speech, Access to Information, and Democracy.

    ERIC Educational Resources Information Center

    Minow, Mary; Wilson, Cicely Reed

    2003-01-01

    Explains the copyright policy battles now pending in Congress and the courts, with a discussion of what they mean for free speech, access to information, and democratic culture in school libraries. (MES)

  2. Libraries and the Pickle (PCLE) of Content Management Schemes: Survey of Pending Copyright Policy Battles and Their Implications for School Libraries, Free Speech, Access to Information, and Democracy.

    ERIC Educational Resources Information Center

    Minow, Mary; Wilson, Cicely Reed

    2003-01-01

    Explains the copyright policy battles now pending in Congress and the courts, with a discussion of what they mean for free speech, access to information, and democratic culture in school libraries. (MES)

  3. PWM-switching pattern-based diagnosis scheme for single and multiple open-switch damages in VSI-fed induction motor drives.

    PubMed

    Trabelsi, Mohamed; Boussak, Mohamed; Gossa, Moncef

    2012-03-01

    This paper deals with a fault detection technique for insulated-gate bipolar transistors (IGBTs) open-circuit faults in voltage source inverter (VSI)-fed induction motor drives. The novelty of this idea consists in analyzing the pulse-width modulation (PWM) switching signals and the line-to-line voltage levels during the switching times, under both healthy and faulty operating conditions. The proposed method requires line-to-line voltage measurement, which provides information about switching states and is not affected by the load. The fault diagnosis scheme is achieved using simple hardware and can be included in the existing inverter system without any difficulty. In addition, it allows not only accurate single and multiple faults diagnosis but also minimization of the fault detection time to a maximum of one switching period (T(c)). Simulated and experimental results on a 3-kW squirrel-cage induction motor drive are displayed to validate the feasibility and the effectiveness of the proposed strategy. Crown Copyright © 2011. Published by Elsevier Ltd. All rights reserved.

  4. Comparison of nutrient intakes from two selected diet plans considered healthful versus the cutoff points for green lights as defined by the UK's multiple traffic light scheme.

    PubMed

    Green, H; Fern, E

    2016-02-01

    This study compared nutrient intakes from 7-day menus for the US MyPlate and DASH Eating Plan versus the cutoff points for green lights defined by the UK's multiple traffic light (MTL) scheme. For both diets, the foods achieved green lights for saturated fat and salt, and for beverages for total fat, saturated fat and salt. The other nutrients achieved amber lights but were within the range of the two diets. By contrast, the MTL threshold for salt in beverages was outside the range of the diets. The values for salt in beverages in the MyPlate and Dash diet plans were 0.06±0.07 and 0.19±0.01 (s.d.) g/100 ml, which are both considerably lower compared with the cutoff of 0.3 g/100 ml for an MTL green light. Adjusting the green MTL threshold values to the median values for a healthful diet could help make MTL labelling a more valid way of helping consumers choose a healthful diet.

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

    NASA Technical Reports Server (NTRS)

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

    2005-01-01

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

  6. Searchable attribute-based encryption scheme with attribute revocation in cloud storage.

    PubMed

    Wang, Shangping; Zhao, Duqiao; Zhang, Yaling

    2017-01-01

    Attribute based encryption (ABE) is a good way to achieve flexible and secure access control to data, and attribute revocation is the extension of the attribute-based encryption, and the keyword search is an indispensable part for cloud storage. The combination of both has an important application in the cloud storage. In this paper, we construct a searchable attribute-based encryption scheme with attribute revocation in cloud storage, the keyword search in our scheme is attribute based with access control, when the search succeeds, the cloud server returns the corresponding cipher text to user and the user can decrypt the cipher text definitely. Besides, our scheme supports multiple keywords search, which makes the scheme more practical. Under the assumption of decisional bilinear Diffie-Hellman exponent (q-BDHE) and decisional Diffie-Hellman (DDH) in the selective security model, we prove that our scheme is secure.

  7. 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.

  8. Satellite range delay simulator for a matrix-switched time division multiple-access network simulation system

    NASA Technical Reports Server (NTRS)

    Nagy, Lawrence A.

    1990-01-01

    The Systems Integration, Test, and Evaluation (SITE) facility at NASA Lewis Research Center is presently configured as a satellite-switched time division multiple access (SS-TDMA) network simulator. The purpose of SITE is to demonstrate and evaluate advanced communication satellite technologies, presently embodied by POC components developed under NASA contracts in addition to other hardware, such as ground terminals, designed and built in-house at NASA Lewis. Each ground terminal in a satellite communications system will experience a different aspect of the satellite's motion due mainly to daily tidal effects and station keeping, hence a different duration and rate of variation in the range delay. As a result of this and other effects such as local oscillator instability, each ground terminal must constantly adjust its transmit burst timing so that data bursts from separate ground terminals arrive at the satellite in their assigned time slots, preventing overlap and keeping the system in synchronism. On the receiving end, ground terminals must synchronize their local clocks using reference transmissions received through the satellite link. A feature of the SITE facility is its capability to simulate the varying propagation delays and associated Doppler frequency shifts that the ground terminals in the network have to cope with. Delay is ahcieved by means of two NASA Lewis designed and built range delay simulator (RDS) systems, each independently controlled locally with front panel switches or remotely by an experiment control and monitor (EC/M) computer.

  9. Variable weight Khazani-Syed code using hybrid fixed-dynamic technique for optical code division multiple access system

    NASA Astrophysics Data System (ADS)

    Anas, Siti Barirah Ahmad; Seyedzadeh, Saleh; Mokhtar, Makhfudzah; Sahbudin, Ratna Kalos Zakiah

    2016-10-01

    Future Internet consists of a wide spectrum of applications with different bit rates and quality of service (QoS) requirements. Prioritizing the services is essential to ensure that the delivery of information is at its best. Existing technologies have demonstrated how service differentiation techniques can be implemented in optical networks using data link and network layer operations. However, a physical layer approach can further improve system performance at a prescribed received signal quality by applying control at the bit level. This paper proposes a coding algorithm to support optical domain service differentiation using spectral amplitude coding techniques within an optical code division multiple access (OCDMA) scenario. A particular user or service has a varying weight applied to obtain the desired signal quality. The properties of the new code are compared with other OCDMA codes proposed for service differentiation. In addition, a mathematical model is developed for performance evaluation of the proposed code using two different detection techniques, namely direct decoding and complementary subtraction.

  10. Delay Analysis for TDMA Schemes with Packet Recombining

    NASA Astrophysics Data System (ADS)

    Pereira, Miguel; Bernardo, Luís; Dinis, Rui; Oliveira, Rodolfo; Carvalho, Paulo; Pinto, Paulo

    This paper considers the use of SC modulations (Single-Carrier) with FDE (Frequency-Domain Equalization) with low-complexity soft combining ARQ schemes (Automatic Repeat reQuest). With our technique, packets associated to different transmission attempts are combined in a soft way, allowing improved performances. Its low complexity makes it particularly interesting for the uplink of wireless systems. This paper proposes an accurate analytical model for a TDMA (Time Division Multiple Access) scheme where packet combining ARQ is applied. It evaluates the uplink non-saturated packet delay for a generic message arrival process. Our analytical results are validated using physical and MAC layer simulations.

  11. Persons with Multiple Disabilities Accessing Stimulation and Requesting Social Contact via Microswitch and VOCA Devices: New Research Evaluation and Social Validation

    ERIC Educational Resources Information Center

    Lancioni, Giulio E.; O'Reilly, Mark F.; Singh, Nirbhay N.; Sigafoos, Jeff; Didden, Robert; Oliva, Doretta; Campodonico, Francesca; de Pace, Claudia; Chiapparino, Claudia; Groeneweg, Jop

    2009-01-01

    The first of these two studies assessed whether 11 participants with multiple disabilities of 5.3-18.2 (M = 10.7) years of age would succeed in combining a microswitch for accessing preferred environmental stimuli and a Voice Output Communication Aid (VOCA) for requesting social contact. The second study conducted a social validation assessment of…

  12. Efficient access of compressed data

    SciTech Connect

    Eggers, S.J.; Shoshani, A.

    1980-06-01

    A compression technique is presented that allows a high degree of compression but requires only logarithmic access time. The technique is a constant suppression scheme, and is most applicable to stable databases whose distribution of constants is fairly clustered. Furthermore, the repeated use of the technique permits the suppression of a multiple number of different constants. Of particular interest is the application of the constant suppression technique to databases the composite key of which is made up of an incomplete cross product of several attribute domains. The scheme for compressing the full cross product composite key is well known. This paper, however, also handles the general, incomplete case by applying the constant suppression technique in conjunction with a composite key suppression scheme.

  13. Multiple boron-boron bonds in neutral molecules: an insight from the extended transition state method and the natural orbitals for chemical valence scheme.

    PubMed

    Mitoraj, Mariusz P; Michalak, Artur

    2011-03-21

    We have analyzed the character of B═B and B≡B bonds in the neutral molecules of general form: LHB═BHL (2-L) and LB≡BL (3-L), for various ancillary ligands L attached to the boron center, based on a recently developed method that combines the extended transition state scheme with the theory of natural orbitals for chemical valence (ETS-NOCV). In the case of molecules with the B═B bond, 2-L, we have included L = PMe(3), PF(3), PCl(3), PH(3), C(3)H(4)N(2)═C(NHCH)(2), whereas for molecules containing the B≡B connection, 3-L, the following ligands were considered L = CO, PMe(3), PCl(3), (Me(2)NCH(2)CH(2)O)(2)Ge. The results led us to conclude that use of phosphorus ligands leads to strengthening of the B═B bond by 6.4 kcal/mol (for 2-PMe(3)), by 4.4 (for 2-PF(3)) and by 9.2 (for 2-PH(3)), when compared to a molecule developed on the experimental basis, 2-C(3)H(4)N(2) (ΔE(total) = -118.3 kcal/mol). The ETS scheme has shown that all contributions, that is, (i) orbital interaction ΔE(orb), (ii) Pauli repulsion ΔE(Pauli), and (iii) electrostatic stabilization ΔE(elstat), are important in determining the trend in the B═B bond energies, ΔE(total). ETS-NOCV results revealed that both σ(B═B) and π(B═B) contributions are responsible for the changes in ΔE(orb) values. All considered molecules of the type LB≡BL, 3-L, exhibit a stronger B≡B bond when compared to a double B═B connection in 2-L (|ΔE(total)| is lower by 11.8-42.5 kcal/mol, depending on the molecule). The main reason is a lower Pauli repulsion contribution noted for 3-CO, 3-PMe(3), and 3-PCl(3) molecules. In addition, in the case of 3-PMe(3) and 3-PCl(3), the orbital interaction term is more stabilizing; however, the effect is less pronounced compared to the drop in the Pauli repulsion term. In all of the systems with double and triple boron-boron bonds, the electronic factor (ΔE(orb)) dominates over the electrostatic contribution (ΔE(elstat)). Finally, the strongest B

  14. Post-coma persons with extensive multiple disabilities use microswitch technology to access selected stimulus events or operate a radio device.

    PubMed

    Lancioni, Giulio E; Singh, Nirbhay N; O'Reilly, Mark F; Sigafoos, Jeff; Alberti, Gloria; Oliva, Doretta; Megna, Gianfranco; Iliceto, Carla; Damiani, Sabino; Ricci, Irene; Spica, Antonella

    2011-01-01

    The present two studies extended research evidence on the use of microswitch technology by post-coma persons with multiple disabilities. Specifically, Study I examined whether three adults with a diagnosis of minimally conscious state and multiple disabilities could use microswitches as tools to access brief, selected stimulus events. Study II assessed whether an adult, who had emerged from a minimally conscious state but was affected by multiple disabilities, could manage the use of a radio device via a microswitch-aided program. Results showed that the participants of Study I had a significant increase of microswitch responding during the intervention phases. The participant of Study II learned to change radio stations and seemed to spend different amounts of session time on the different stations available (suggesting preferences among the programs characterizing them). The importance of microswitch technology for assisting post-coma persons with multiple disabilities to positively engage with their environment was discussed. Copyright © 2011 Elsevier Ltd. All rights reserved.

  15. Household trends in access to improved water sources and sanitation facilities in Vietnam and associated factors: findings from the Multiple Indicator Cluster Surveys, 2000-2011.

    PubMed

    Tuyet-Hanh, Tran Thi; Lee, Jong-Koo; Oh, Juhwan; Van Minh, Hoang; Ou Lee, Chul; Hoan, Le Thi; Nam, You-Seon; Long, Tran Khanh

    2016-01-01

    Background Despite progress made by the Millennium Development Goal (MDG) number 7.C, Vietnam still faces challenges with regard to the provision of access to safe drinking water and basic sanitation. Objective This paper describes household trends in access to improved water sources and sanitation facilities separately, and analyses factors associated with access to improved water sources and sanitation facilities in combination. Design Secondary data from the Vietnam Multiple Indicator Cluster Survey in 2000, 2006, and 2011 were analyzed. Descriptive statistics and tests of significance describe trends over time in access to water and sanitation by location, demographic and socio-economic factors. Binary logistic regressions (2000, 2006, and 2011) describe associations between access to water and sanitation, and geographic, demographic, and socio-economic factors. Results There have been some outstanding developments in access to improved water sources and sanitation facilities from 2000 to 2011. In 2011, the proportion of households with access to improved water sources and sanitation facilities reached 90% and 77%, respectively, meeting the 2015 MDG targets for safe drinking water and basic sanitation set at 88% and 75%, respectively. However, despite these achievements, in 2011, only 74% of households overall had access to combined improved drinking water and sanitation facilities. There were also stark differences between regions. In 2011, only 47% of households had access to both improved water and sanitation facilities in the Mekong River Delta compared with 94% in the Red River Delta. In 2011, households in urban compared to rural areas were more than twice as likely (odds ratio [OR]: 2.2; 95% confidence interval [CI]: 1.9-2.5) to have access to improved water and sanitation facilities in combination, and households in the highest compared with the lowest wealth quintile were over 40 times more likely (OR: 42.3; 95% CI: 29.8-60.0). Conclusions More efforts

  16. Household trends in access to improved water sources and sanitation facilities in Vietnam and associated factors: findings from the Multiple Indicator Cluster Surveys, 2000-2011.

    PubMed

    Tuyet-Hanh, Tran Thi; Lee, Jong-Koo; Oh, Juhwan; Van Minh, Hoang; Ou Lee, Chul; Hoan, Le Thi; Nam, You-Seon; Long, Tran Khanh

    2016-01-01

    Despite progress made by the Millennium Development Goal (MDG) number 7.C, Vietnam still faces challenges with regard to the provision of access to safe drinking water and basic sanitation. This paper describes household trends in access to improved water sources and sanitation facilities separately, and analyses factors associated with access to improved water sources and sanitation facilities in combination. Secondary data from the Vietnam Multiple Indicator Cluster Survey in 2000, 2006, and 2011 were analyzed. Descriptive statistics and tests of significance describe trends over time in access to water and sanitation by location, demographic and socio-economic factors. Binary logistic regressions (2000, 2006, and 2011) describe associations between access to water and sanitation, and geographic, demographic, and socio-economic factors. There have been some outstanding developments in access to improved water sources and sanitation facilities from 2000 to 2011. In 2011, the proportion of households with access to improved water sources and sanitation facilities reached 90% and 77%, respectively, meeting the 2015 MDG targets for safe drinking water and basic sanitation set at 88% and 75%, respectively. However, despite these achievements, in 2011, only 74% of households overall had access to combined improved drinking water and sanitation facilities. There were also stark differences between regions. In 2011, only 47% of households had access to both improved water and sanitation facilities in the Mekong River Delta compared with 94% in the Red River Delta. In 2011, households in urban compared to rural areas were more than twice as likely (odds ratio [OR]: 2.2; 95% confidence interval [CI]: 1.9-2.5) to have access to improved water and sanitation facilities in combination, and households in the highest compared with the lowest wealth quintile were over 40 times more likely (OR: 42.3; 95% CI: 29.8-60.0). More efforts are required to increase household access to

  17. Household trends in access to improved water sources and sanitation facilities in Vietnam and associated factors: findings from the Multiple Indicator Cluster Surveys, 2000–2011

    PubMed Central

    Tuyet-Hanh, Tran Thi; Lee, Jong-Koo; Oh, Juhwan; Van Minh, Hoang; Ou Lee, Chul; Hoan, Le Thi; Nam, You-Seon; Long, Tran Khanh

    2016-01-01

    Background Despite progress made by the Millennium Development Goal (MDG) number 7.C, Vietnam still faces challenges with regard to the provision of access to safe drinking water and basic sanitation. Objective This paper describes household trends in access to improved water sources and sanitation facilities separately, and analyses factors associated with access to improved water sources and sanitation facilities in combination. Design Secondary data from the Vietnam Multiple Indicator Cluster Survey in 2000, 2006, and 2011 were analyzed. Descriptive statistics and tests of significance describe trends over time in access to water and sanitation by location, demographic and socio-economic factors. Binary logistic regressions (2000, 2006, and 2011) describe associations between access to water and sanitation, and geographic, demographic, and socio-economic factors. Results There have been some outstanding developments in access to improved water sources and sanitation facilities from 2000 to 2011. In 2011, the proportion of households with access to improved water sources and sanitation facilities reached 90% and 77%, respectively, meeting the 2015 MDG targets for safe drinking water and basic sanitation set at 88% and 75%, respectively. However, despite these achievements, in 2011, only 74% of households overall had access to combined improved drinking water and sanitation facilities. There were also stark differences between regions. In 2011, only 47% of households had access to both improved water and sanitation facilities in the Mekong River Delta compared with 94% in the Red River Delta. In 2011, households in urban compared to rural areas were more than twice as likely (odds ratio [OR]: 2.2; 95% confidence interval [CI]: 1.9–2.5) to have access to improved water and sanitation facilities in combination, and households in the highest compared with the lowest wealth quintile were over 40 times more likely (OR: 42.3; 95% CI: 29.8–60.0). Conclusions More

  18. Accessibility, availability and affordability of anti-malarials in a rural district in Kenya after implementation of a national subsidy scheme.

    PubMed

    Smith, Nathan; Obala, Andrew; Simiyu, Chrispinus; Menya, Diana; Khwa-Otsyula, Barasa; O'Meara, Wendy Prudhomme

    2011-10-26

    Poor access to prompt and effective treatment for malaria contributes to high mortality and severe morbidity. In Kenya, it is estimated that only 12% of children receive anti-malarials for their fever within 24 hours. The first point of care for many fevers is a local medicine retailer, such as a pharmacy or chemist. The role of the medicine retailer as an important distribution point for malaria medicines has been recognized and several different strategies have been used to improve the services that these retailers provide. Despite these efforts, many mothers still purchase ineffective drugs because they are less expensive than effective artemisinin combination therapy (ACT). One strategy that is being piloted in several countries is an international subsidy targeted at anti-malarials supplied through the retail sector. The goal of this strategy is to make ACT as affordable as ineffective alternatives. The programme, called the Affordable Medicines Facility - malaria was rolled out in Kenya in August 2010. In December 2010, the affordability and accessibility of malaria medicines in a rural district in Kenya were evaluated using a complete census of all public and private facilities, chemists, pharmacists, and other malaria medicine retailers within the Webuye Demographic Surveillance Area. Availability, types, and prices of anti-malarials were assessed. There are 13 public or mission facilities and 97 medicine retailers (registered and unregistered). The average distance from a home to the nearest public health facility is 2 km, but the average distance to the nearest medicine retailer is half that. Quinine is the most frequently stocked anti-malarial (61% of retailers). More medicine retailers stocked sulphadoxine-pyramethamine (SP; 57%) than ACT (44%). Eleven percent of retailers stocked AMFm subsidized artemether-lumefantrine (AL). No retailers had chloroquine in stock and only five were selling artemisinin monotherapy. The mean price of any brand of AL, the

  19. An energy-efficient SIMD DSP with multiple VLIW configurations and an advanced memory access unit for LTE-A modem LSIs

    NASA Astrophysics Data System (ADS)

    Tomono, Mitsuru; Ito, Makiko; Nomura, Yoshitaka; Mouri, Makoto; Hirose, Yoshio

    2015-12-01

    Energy efficiency is the most important factor in the design of wireless modem LSIs for mobile handset systems. We have developed an energy-efficient SIMD DSP for LTE-A modem LSIs. Our DSP has mainly two hardware features in order to reduce energy consumption. The first one is multiple VLIW configurations to minimize accesses to instruction memories. The second one is an advanced memory access unit to realize complex memory accesses required for wireless baseband processing. With these features, performance of our DSP is about 1.7 times faster than a base DSP on average for standard LTE-A Libraries. Our DSP achieves about 20% improvement in energy efficiency compared to a base DSP for LTE-A modem LSIs.

  20. Multiplicity

    DTIC Science & Technology

    1991-04-01

    practice as a "[descent] into that inner circle of the Inferno where the damned endlessly degate multiplicity for sentencing." United States v. Barnard...select the charges to be brought in a particular case"). 19 Brown v. Ohio, 432 U.S. 161, 165 (1977). 20 Whalen v. United States, 445 U.S. at 689. 21...parte Lange, 8-5 U.S. (19 Wall.) 163 (1874). Cf. Brown v. Ohio, 432 U.S. at 165 ("once the legislature has acted courts may not impose more than one

  1. Compact Spreader Schemes

    SciTech Connect

    Placidi, M.; Jung, J. -Y.; Ratti, A.; Sun, C.

    2014-07-25

    This paper describes beam distribution schemes adopting a novel implementation based on low amplitude vertical deflections combined with horizontal ones generated by Lambertson-type septum magnets. This scheme offers substantial compactness in the longitudinal layouts of the beam lines and increased flexibility for beam delivery of multiple beam lines on a shot-to-shot basis. Fast kickers (FK) or transverse electric field RF Deflectors (RFD) provide the low amplitude deflections. Initially proposed at the Stanford Linear Accelerator Center (SLAC) as tools for beam diagnostics and more recently adopted for multiline beam pattern schemes, RFDs offer repetition capabilities and a likely better amplitude reproducibility when compared to FKs, which, in turn, offer more modest financial involvements both in construction and operation. Both solutions represent an ideal approach for the design of compact beam distribution systems resulting in space and cost savings while preserving flexibility and beam quality.

  2. Compact spreader schemes

    NASA Astrophysics Data System (ADS)

    Placidi, M.; Jung, J.-Y.; Ratti, A.; Sun, C.

    2014-12-01

    This paper describes beam distribution schemes adopting a novel implementation based on low amplitude vertical deflections combined with horizontal ones generated by Lambertson-type septum magnets. This scheme offers substantial compactness in the longitudinal layouts of the beam lines and increased flexibility for beam delivery of multiple beam lines on a shot-to-shot basis. Fast kickers (FK) or transverse electric field RF Deflectors (RFD) provide the low amplitude deflections. Initially proposed at the Stanford Linear Accelerator Center (SLAC) as tools for beam diagnostics and more recently adopted for multiline beam pattern schemes, RFDs offer repetition capabilities and a likely better amplitude reproducibility when compared to FKs, which, in turn, offer more modest financial involvements both in construction and operation. Both solutions represent an ideal approach for the design of compact beam distribution systems resulting in space and cost savings while preserving flexibility and beam quality.

  3. Security enhanced anonymous multiserver authenticated key agreement scheme using smart cards and biometrics.

    PubMed

    Choi, Younsung; Nam, Junghyun; Lee, Donghoon; Kim, Jiye; Jung, Jaewook; Won, Dongho

    2014-01-01

    An anonymous user authentication scheme allows a user, who wants to access a remote application server, to achieve mutual authentication and session key establishment with the server in an anonymous manner. To enhance the security of such authentication schemes, recent researches combined user's biometrics with a password. However, these authentication schemes are designed for single server environment. So when a user wants to access different application servers, the user has to register many times. To solve this problem, Chuang and Chen proposed an anonymous multiserver authenticated key agreement scheme using smart cards together with passwords and biometrics. Chuang and Chen claimed that their scheme not only supports multiple servers but also achieves various security requirements. However, we show that this scheme is vulnerable to a masquerade attack, a smart card attack, a user impersonation attack, and a DoS attack and does not achieve perfect forward secrecy. We also propose a security enhanced anonymous multiserver authenticated key agreement scheme which addresses all the weaknesses identified in Chuang and Chen's scheme.

  4. Security Enhanced Anonymous Multiserver Authenticated Key Agreement Scheme Using Smart Cards and Biometrics

    PubMed Central

    Choi, Younsung; Nam, Junghyun; Lee, Donghoon; Kim, Jiye; Jung, Jaewook; Won, Dongho

    2014-01-01

    An anonymous user authentication scheme allows a user, who wants to access a remote application server, to achieve mutual authentication and session key establishment with the server in an anonymous manner. To enhance the security of such authentication schemes, recent researches combined user's biometrics with a password. However, these authentication schemes are designed for single server environment. So when a user wants to access different application servers, the user has to register many times. To solve this problem, Chuang and Chen proposed an anonymous multiserver authenticated key agreement scheme using smart cards together with passwords and biometrics. Chuang and Chen claimed that their scheme not only supports multiple servers but also achieves various security requirements. However, we show that this scheme is vulnerable to a masquerade attack, a smart card attack, a user impersonation attack, and a DoS attack and does not achieve perfect forward secrecy. We also propose a security enhanced anonymous multiserver authenticated key agreement scheme which addresses all the weaknesses identified in Chuang and Chen's scheme. PMID:25276847

  5. 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.

  6. SkyDOT: a publicly accessible variability database, containing multiple sky surveys and real-time data

    SciTech Connect

    Starr, D. L.; Wozniak, P. R.; Vestrand, W. T.

    2002-01-01

    SkyDOT (Sky Database for Objects in Time-Domain) is a Virtual Observatory currently comprised of data from the RAPTOR, ROTSE I, and OGLE I1 survey projects. This makes it a very large time domain database. In addition, the RAPTOR project provides SkyDOT with real-time variability data as well as stereoscopic information. With its web interface, we believe SkyDOT will be a very useful tool for both astronomers, and the public. Our main task has been to construct an efficient relational database containing all existing data, while handling a real-time inflow of data. We also provide a useful web interface allowing easy access to both astronomers and the public. Initially, this server will allow common searches, specific queries, and access to light curves. In the future we will include machine learning classification tools and access to spectral information.

  7. Access roads for RAG-ged terrains: control of T cell receptor gene rearrangement at multiple levels.

    PubMed

    Livák, Ferenc; Petrie, Howard T

    2002-10-01

    Antigen-specific immune response requires the generation of a diverse antigen (Ag)-receptor repertoire. The primary repertoire is generated through somatic gene rearrangement and molded by subsequent cellular selection. Constraints during gene recombination influence the ultimate shape of the repertoire. One major control mechanism of gene rearrangement, investigated for many years, is exerted through regulated chromosomal accessibility of the recombinase to the antigen receptor loci. More recent studies began to explore the role of interactions between the recombinase and its cognate recognition DNA sequences. The emerging results suggest that formation of the primary repertoire is controlled by two, partially independent factors: chromosomal accessibility and direct recombinase-DNA interactions.

  8. 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.

  9. Multiple Motives, Conflicting Conceptions: Parsing the Contexts of Differentiated Access to Scientific Information in the Federal Government

    ERIC Educational Resources Information Center

    Oltmann, Shannon M.

    2012-01-01

    Scientific information, used by the U.S. federal government to formulate public policy in many arenas, is frequently contested and sometimes altered, blocked from publication, deleted from reports, or restricted in some way. This dissertation examines how and why restricted access to science policy (RASP) occurs through a comparative case study.…

  10. Use of Multiple Parallel Interface Strategies To Create a Seamless Accessible Interface for Next-Generation Information Systems.

    ERIC Educational Resources Information Center

    Vanderheiden, Gregg C.

    Information systems in public places such as community centers and libraries require some means to provide access to individuals with physical, visual, and, if sound is involved, hearing impairments. This paper proposes a seamless adaptable human interface protocol that would allow users to incrementally modify the command and presentation aspects…

  11. Multiple Motives, Conflicting Conceptions: Parsing the Contexts of Differentiated Access to Scientific Information in the Federal Government

    ERIC Educational Resources Information Center

    Oltmann, Shannon M.

    2012-01-01

    Scientific information, used by the U.S. federal government to formulate public policy in many arenas, is frequently contested and sometimes altered, blocked from publication, deleted from reports, or restricted in some way. This dissertation examines how and why restricted access to science policy (RASP) occurs through a comparative case study.…

  12. Evaluating multiple dimensions of visitors' tradeoffs between access and crowding at Arches National Park using indifference curve analysis

    Treesearch

    Steven R. Lawson; Robert E. Manning

    2001-01-01

    Tradeoffs are an inherent part of many of the decisions faced by outdoor recreation managers. For example, decisions concerning the social carrying capacity of popular attraction sites involve tradeoffs between limiting visitor use to ensure a high quality experience and allowing high levels of visitor use to ensure that large numbers of visitors retain access to park...

  13. Design and Performance of Overlap FFT Filter-Bank for Dynamic Spectrum Access Applications

    NASA Astrophysics Data System (ADS)

    Tanabe, Motohiro; Umehira, Masahiro

    An OFDMA-based (Orthogonal Frequency Division Multiple Access-based) channel access scheme for dynamic spectrum access has the drawbacks of large PAPR (Peak to Average Power Ratio) and large ACI (Adjacent Channel Interference). To solve these problems, a flexible channel access scheme using an overlap FFT filter-bank was proposed based on single carrier modulation for dynamic spectrum access. In order to apply the overlap FFT filter-bank for dynamic spectrum access, it is necessary to clarify the performance of the overlap FFT filter-bank according to the design parameters since its frequency characteristics are critical for dynamic spectrum access applications. This paper analyzes the overlap FFT filter-bank and evaluates its performance such as frequency characteristics and ACI performance according to the design parameters.

  14. An application of the edge effect in measuring accessibility to multiple food retailer types in Southwestern Ontario, Canada

    PubMed Central

    2011-01-01

    Background Trends in food retailing associated with the consolidation of smaller-format retailers into fewer, larger-format supercentres have left some rural areas with fewer sources of nutritious, affordable food. Access to nutritious, affordable food is essential for good dietary habits and combating health issues such as type-2 diabetes, obesity, and cardiovascular disease. Many studies on food environments use inaccurate or incomplete methods for locating food retailers, which may be responsible for mischaracterising food deserts. This study uses databases of every residence in and every food retailer in and around Middlesex County, Ontario, Canada. Residences were geocoded to their precise address, and network analysis techniques were performed in a geographic information system (GIS) to determine distances between every residence and different types of food retailers (grocery stores, fast food, fruit and vegetable sources, grocery stores plus fruit and vegetable sources, variety stores), both when considering and neglecting facilities outside the area of study, to account for a deficiency in analysis termed the 'edge effect'. Results Analysis of household accessibility to food outlets by neighbourhood socioeconomic distress level indicated that residents in the most distressed neighbourhoods tended to have better accessibility to all types of food retailers. In the most distressed neighbourhoods, 79 percent of residences were within walking distance of a grocery store, compared to only 10 percent in the least distressed neighbourhoods. When the edge effect was neglected, 37 percent of distance estimates proved inaccurate. Average accessibility to all food retailer types improved dramatically when food outlets adjacent to the study area were considered, thereby controlling for the edge effect. Conclusion By neglecting to consider food retailers just outside study area boundaries, previous studies may significantly over-report the actual distance necessary to

  15. An application of the edge effect in measuring accessibility to multiple food retailer types in southwestern Ontario, Canada.

    PubMed

    Sadler, Richard C; Gilliland, Jason A; Arku, Godwin

    2011-05-15

    Trends in food retailing associated with the consolidation of smaller-format retailers into fewer, larger-format supercentres have left some rural areas with fewer sources of nutritious, affordable food. Access to nutritious, affordable food is essential for good dietary habits and combating health issues such as type-2 diabetes, obesity, and cardiovascular disease. Many studies on food environments use inaccurate or incomplete methods for locating food retailers, which may be responsible for mischaracterising food deserts. This study uses databases of every residence in and every food retailer in and around Middlesex County, Ontario, Canada. Residences were geocoded to their precise address, and network analysis techniques were performed in a geographic information system (GIS) to determine distances between every residence and different types of food retailers (grocery stores, fast food, fruit and vegetable sources, grocery stores plus fruit and vegetable sources, variety stores), both when considering and neglecting facilities outside the area of study, to account for a deficiency in analysis termed the 'edge effect'. Analysis of household accessibility to food outlets by neighbourhood socioeconomic distress level indicated that residents in the most distressed neighbourhoods tended to have better accessibility to all types of food retailers. In the most distressed neighbourhoods, 79 percent of residences were within walking distance of a grocery store, compared to only 10 percent in the least distressed neighbourhoods. When the edge effect was neglected, 37 percent of distance estimates proved inaccurate. Average accessibility to all food retailer types improved dramatically when food outlets adjacent to the study area were considered, thereby controlling for the edge effect. By neglecting to consider food retailers just outside study area boundaries, previous studies may significantly over-report the actual distance necessary to travel for food. Research on

  16. 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.

  17. Design and evaluation of a virtual quadrant receiver for 4-ary pulse position modulation/optical code division multiple access (4-ary PPM/O-CDMA)

    NASA Astrophysics Data System (ADS)

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

    2007-02-01

    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 the 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.

  18. Novel wavelength division multiplex-radio over fiber-passive optical network architecture for multiple access points based on multitone generation and triple sextupling frequency

    NASA Astrophysics Data System (ADS)

    Cheng, Guangming; Guo, Banghong; Liu, Songhao; Huang, Xuguang

    2014-01-01

    An innovative wavelength division multiplex-radio over fiber-passive optical network architecture for multiple access points (AP) based on multitone generation and triple sextupling frequency is proposed and demonstrated. A dual-drive Mach-Zehnder modulator (DD-MZM) is utilized to realize the multitone generation. Even sidebands are suppressed to make the adjacent frequency separation twice the frequency of the local oscillator by adjusting the modulation voltage of the DD-MZM. Due to adopting three fiber Bragg gratings to reflect the unmodulated sidebands for uplink communications source free at optical network unit (ONU), is achieved. The system can support at least three APs at one ONU simultaneously with a 30 km single-mode fiber (SMF) transmission and 5 Gb/s data rate both for uplink and downlink communications. The theoretical analysis and simulation results show the architecture has an excellent performance and will be a promising candidate in future hybrid access networks.

  19. New LNG process scheme

    SciTech Connect

    Foglietta, J.H.

    1999-07-01

    A new LNG cycle has been developed for base load liquefaction facilities. This new design offers a different technical and economical solution comparing in efficiency with the classical technologies. The new LNG scheme could offer attractive business opportunities to oil and gas companies that are trying to find paths to monetize gas sources more effectively; particularly for remote or offshore locations where smaller scale LNG facilities might be applicable. This design offers also an alternative route to classic LNG projects, as well as alternative fuel sources. Conceived to offer simplicity and access to industry standard equipment, This design is a hybrid result of combining a standard refrigeration system and turboexpander technology.

  20. Microsatellite analysis of Damask rose (Rosa damascena Mill.) accessions from various regions in Iran reveals multiple genotypes.

    PubMed

    Babaei, Alireza; Tabaei-Aghdaei, Seyed Reza; Khosh-Khui, Morteza; Omidbaigi, Reza; Naghavi, Mohammad Reza; Esselink, Gerhard D; Smulders, Marinus J M

    2007-03-08

    Damask roses (Rosa damascena Mill.) are mainly used for essential oil production. Previous studies have indicated that all production material in Bulgaria and Turkey consists of only one genotype. Nine polymorphic microsatellite markers were used to analyze the genetic diversity of 40 accessions of R. damascena collected across major and minor rose oil production areas in Iran. All microsatellite markers showed a high level of polymorphism (5-15 alleles per microsatellite marker, with an average of 9.11 alleles per locus). Cluster analysis of genetic similarities revealed that these microsatellites identified a total of nine different genotypes. The genotype from Isfahan province, which is the major production area, was by far the most common genotype (27/40 accessions). It was identical to the Bulgarian genotype. Other genotypes (each represented by 1-4 accessions) were collected from minor production areas in several provinces, notably in the mountainous Northwest of Iran. This is the first study that uncovered genetic diversity within Damask rose. Our results will guide new collection activities to establish larger collections and manage the Iranian Damask rose genetic resources. The genotypes identified here may be directly useful for breeding.

  1. Microsatellite analysis of Damask rose (Rosa damascena Mill.) accessions from various regions in Iran reveals multiple genotypes

    PubMed Central

    Babaei, Alireza; Tabaei-Aghdaei, Seyed Reza; Khosh-Khui, Morteza; Omidbaigi, Reza; Naghavi, Mohammad Reza; Esselink, Gerhard D; Smulders, Marinus JM

    2007-01-01

    Background Damask roses (Rosa damascena Mill.) are mainly used for essential oil production. Previous studies have indicated that all production material in Bulgaria and Turkey consists of only one genotype. Nine polymorphic microsatellite markers were used to analyze the genetic diversity of 40 accessions of R. damascena collected across major and minor rose oil production areas in Iran. Results All microsatellite markers showed a high level of polymorphism (5–15 alleles per microsatellite marker, with an average of 9.11 alleles per locus). Cluster analysis of genetic similarities revealed that these microsatellites identified a total of nine different genotypes. The genotype from Isfahan province, which is the major production area, was by far the most common genotype (27/40 accessions). It was identical to the Bulgarian genotype. Other genotypes (each represented by 1–4 accessions) were collected from minor production areas in several provinces, notably in the mountainous Northwest of Iran. Conclusion This is the first study that uncovered genetic diversity within Damask rose. Our results will guide new collection activities to establish larger collections and manage the Iranian Damask rose genetic resources. The genotypes identified here may be directly useful for breeding. PMID:17346330

  2. Performance analyses and improvements for the IEEE 802.15.4 CSMA/CA scheme with heterogeneous buffered conditions.

    PubMed

    Zhu, Jianping; Tao, Zhengsu; Lv, Chunfeng

    2012-01-01

    Studies of the IEEE 802.15.4 Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) scheme have been received considerable attention recently, with most of these studies focusing on homogeneous or saturated traffic. Two novel transmission schemes-OSTS/BSTS (One Service a Time Scheme/Bulk Service a Time Scheme)-are proposed in this paper to improve the behaviors of time-critical buffered networks with heterogeneous unsaturated traffic. First, we propose a model which contains two modified semi-Markov chains and a macro-Markov chain combined with the theory of M/G/1/K queues to evaluate the characteristics of these two improved CSMA/CA schemes, in which traffic arrivals and accessing packets are bestowed with non-preemptive priority over each other, instead of prioritization. Then, throughput, packet delay and energy consumption of unsaturated, unacknowledged IEEE 802.15.4 beacon-enabled networks are predicted based on the overall point of view which takes the dependent interactions of different types of nodes into account. Moreover, performance comparisons of these two schemes with other non-priority schemes are also proposed. Analysis and simulation results show that delay and fairness of our schemes are superior to those of other schemes, while throughput and energy efficiency are superior to others in more heterogeneous situations. Comprehensive simulations demonstrate that the analysis results of these models match well with the simulation results.

  3. Can front-of-pack labelling schemes guide healthier food choices? Australian shoppers' responses to seven labelling formats.

    PubMed

    Watson, Wendy L; Kelly, Bridget; Hector, Debra; Hughes, Clare; King, Lesley; Crawford, Jennifer; Sergeant, John; Chapman, Kathy

    2014-01-01

    There is evidence that easily accessible, comprehensible and consistent nutrient information on the front of packaged foods could assist shoppers to make healthier food choices. This study used an online questionnaire of 4357 grocery shoppers to examine Australian shoppers' ability to use a range of front-of-pack labels to identify healthier food products. Seven different front-of-pack labelling schemes comprising variants of the Traffic Light labelling scheme and the Percentage Daily Intake scheme, and a star rating scheme, were applied to nine pairs of commonly purchased food products. Participants could also access a nutrition information panel for each product. Participants were able to identify the healthier product in each comparison over 80% of the time using any of the five schemes that provided information on multiple nutrients. No individual scheme performed significantly better in terms of shoppers' ability to determine the healthier product, shopper reliance on the 'back-of-pack' nutrition information panel, and speed of use. The scheme that provided information about energy only and a scheme with limited numerical information of nutrient type or content performed poorly, as did the nutrition information panel alone (control). Further consumer testing is necessary to determine the optimal format and content of an interpretive front-of-pack nutrition labelling scheme.

  4. Zadoff-Chu sequence-based hitless ranging scheme for OFDMA-PON configured 5G fronthaul uplinks

    NASA Astrophysics Data System (ADS)

    Reza, Ahmed Galib; Rhee, June-Koo Kevin

    2017-05-01

    A Zadoff-Chu (ZC) sequence-based low-complexity hitless upstream time synchronization scheme is proposed for an orthogonal frequency division multiple access passive optical network configured cloud radio access network fronthaul. The algorithm is based on gradual loading of the ZC sequences, where the phase discontinuity due to the cyclic prefix is alleviated by a frequency domain phase precoder, eliminating the requirements of guard bands to mitigate intersymbol interference and inter-carrier interference. Simulation results for uncontrolled-wavelength asynchronous transmissions from four concurrent transmitting optical network units are presented to demonstrate the effectiveness of the proposed scheme.

  5. Matroids and quantum-secret-sharing schemes

    SciTech Connect

    Sarvepalli, Pradeep; Raussendorf, Robert

    2010-05-15

    A secret-sharing scheme is a cryptographic protocol to distribute a secret state in an encoded form among a group of players such that only authorized subsets of the players can reconstruct the secret. Classically, efficient secret-sharing schemes have been shown to be induced by matroids. Furthermore, access structures of such schemes can be characterized by an excluded minor relation. No such relations are known for quantum secret-sharing schemes. In this paper we take the first steps toward a matroidal characterization of quantum-secret-sharing schemes. In addition to providing a new perspective on quantum-secret-sharing schemes, this characterization has important benefits. While previous work has shown how to construct quantum-secret-sharing schemes for general access structures, these schemes are not claimed to be efficient. In this context the present results prove to be useful; they enable us to construct efficient quantum-secret-sharing schemes for many general access structures. More precisely, we show that an identically self-dual matroid that is representable over a finite field induces a pure-state quantum-secret-sharing scheme with information rate 1.

  6. Towards a physiological signal-based access solution for a non-verbal adolescent with severe and multiple disabilities.

    PubMed

    Memarian, Negar; Blain-Moraes, Stefanie; Chau, Tom

    2014-08-01

    To find physiologically arousing stimuli and labile physiological channels in a non-verbal adolescent with severe and multiple congenital disabilities, who did not have a reliable means of communication. The client was repeatedly presented with visual and audiovisual stimuli, representing variations of six contextual factors over three sessions in a one month period. For each stimulus, reactions were detected in the client's four peripheral autonomic nervous system signals using a rule-based classification algorithm. During the presentation of audiovisual stimuli, the number of physiological reactions significantly differed from that observed in baseline (χ(2) = 3.93, p = 0.0476). Aural stimuli articulated in an unfamiliar voice, and aural stimuli containing anticipatory patterns were also physiologically arousing. Fingertip temperature was the client's most labile physiological signal. The results of this case study suggest that physiological data may complement caregiver acumen in deciphering the reactions of non-verbal clients with severe and multiple disabilities.

  7. A robust and novel dynamic-ID-based authentication scheme for care team collaboration with smart cards.

    PubMed

    Chang, Ya-Fen; Chen, Chia-Chen; Chang, Pei-Yu

    2013-04-01

    Nowadays, users/patients may gain desired medical services on-line because of the rapid development of computer network technologies. Conventional healthcare services are provided by a single server. However, care team collaboration by integrating services is the key to improve financial and clinical performance. How a user/patient accesses desired medical services provided by multiple servers becomes a challenge to realize care team collaboration. User authentication plays an important role to protect resources or services from being accessed by unauthorized users. In this paper, we first discuss the perceived security drawbacks of pervasive smart-card-based remote user authentication schemes. Then, we propose a novel dynamic-ID-based user authentication scheme based on elliptic curve cryptosystem (ECC) for multi-server environment with smart cards. The proposed scheme ensures user anonymity and computational efficiency and complies with essential requirements of a secure smart-card-based authentication scheme for multi-server environment to enable care team collaboration.

  8. An analysis of delay-locked loop tracking binary Markovian sequence in the presence of multiple access interference and channel noise

    NASA Astrophysics Data System (ADS)

    Nagata, Keisuke; Fujisaka, Hisato; Kamio, Takeshi; Haeiwa, Kazuhisa

    This paper presents an analysis of delay-locked loops in direct spreading code division multiple access systems with Markovian spreading sequences. The established analysis with piecewise constant approximation is similar to the mean field analysis which estimates macroscopic characteristics of a spatially-distributed probabilistic system from the local interaction between the elements of the system with low computational complexity. The low complexity makes it possible to analyze the behavior of not only second-order archetype delay-locked loops but also higher-order non-coherent delay-locked loops in the presence of both multiple access interference and channel noise. It is found from the presented analysis that replacing i.i.d. spreading sequences with Markovian spreading sequences with non-vanishing negative autocorrelation reduces the phase tracking error of a non-coherent 1Δ delay-locked loop. The time spent for estimating the error by the presented method is about 1/1000 compared with that by the path integral method.

  9. High-resolution 2D NMR spectra in inhomogeneous fields based on intermolecular multiple-quantum coherences with efficient acquisition schemes

    NASA Astrophysics Data System (ADS)

    Lin, Meijin; Huang, Yuqing; Chen, Xi; Cai, Shuhui; Chen, Zhong

    2011-01-01

    High-resolution 2D NMR spectra in inhomogeneous fields can be achieved by the use of intermolecular multiple-quantum coherences and shearing reconstruction of 3D data. However, the long acquisition time of 3D spectral data is generally unbearable for invivo applications. To overcome this problem, two pulse sequences dubbed as iDH-COSY and iDH-JRES were proposed in this paper. Although 3D acquisition is still required for the new sequences, the high-resolution 2D spectra can be obtained with a relatively short scanning time utilizing the manipulation of indirect evolution period and sparse sampling. The intermolecular multiple-quantum coherence treatment combined with the raising and lowering operators was applied to derive analytical signal expressions for the new sequences. And the experimental observations agree with the theoretical predictions. Our results show that the new sequences possess bright perspective in the applications on invivo localized NMR spectroscopy.

  10. Secret Sharing Schemes from Linear Codes over Finite Rings

    NASA Astrophysics Data System (ADS)

    Qian, Jianfa; Ma, Wenping

    An important concept in secret sharing scheme is the access structure. However, determining the access structure of the secret sharing scheme based on a linear code is a very difficult problem. In this work, we provide a method to construct a class of two-weight linear codes over finite rings. Based on the two-weight codes, we present an access structure of a secret sharing scheme.

  11. A simple wavelength-locking scheme of a tunable three-electrode distributed Bragg reflector laser for multiple ITU channel application in C band

    NASA Astrophysics Data System (ADS)

    Ye, Nan; Liu, Yang; Zhao, Ling-Juan

    2010-11-01

    In this paper, a simple wavelength-locking scheme for a tunable distributed Bragg reflector laser is presented. A 1*2 wide band fiber coupler as the function of beam splitter forms two optical paths with evenly separated power, one for wavelength monitoring and the other for power reference. For wavelength monitoring, two single mode fiber collimators- one as a transmitter and the other as a receiver-form a collimated light path for laser beam and a highly stable air-paced Etalon inserted between them is used as an optical frequency discriminator to lock the laser wavelengths to several ITU channels maintain 100GHz or 0.8 nm channel spacing in C band. Meanwhile, a photodetector connected with receiving collimator by a FC/PC connector turns the optical signal into electronic signal. For power reference, one of the coupler output pots is directly connected with a similar photodetector. Then wavelength shifting signal proportional to the power differences between two optical paths could be feed backed to the phase region or DBR region for stabilizing the laser output wavelength.

  12. Resource Allocation Scheme in MIMO-OFDMA System for User's Different Data Throughput Requirements

    NASA Astrophysics Data System (ADS)

    Sann Maw, Maung; Sasase, Iwao

    In the subcarrier and power allocation schemes in Multi-Input Multi-Output and Orthogonal Frequency Division Multiple Access (MIMO-OFDMA) systems, only equal fairness among users has been considered and no scheme for proportional data rate fairness has been considered. In this paper, a subcarrier, bit and power allocation scheme is proposed to maximize the total throughput under the constraints of total power and proportional data rate fairness among users. In the proposed scheme, joint subchannel allocation and adaptive bit loading is firstly performed by using singular value decomposition (SVD) of channel matrix under the constraint of users' data throughput requirements, and then adaptive power loading is applied. Simulation results show that effective performance of the system has been improved as well as each throughput is proportionally distributed among users in MIMO-OFDMA systems.

  13. Performance Analyses and Improvements for the IEEE 802.15.4 CSMA/CA Scheme with Heterogeneous Buffered Conditions

    PubMed Central

    Zhu, Jianping; Tao, Zhengsu; Lv, Chunfeng

    2012-01-01

    Studies of the IEEE 802.15.4 Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) scheme have been received considerable attention recently, with most of these studies focusing on homogeneous or saturated traffic. Two novel transmission schemes—OSTS/BSTS (One Service a Time Scheme/Bulk Service a Time Scheme)—are proposed in this paper to improve the behaviors of time-critical buffered networks with heterogeneous unsaturated traffic. First, we propose a model which contains two modified semi-Markov chains and a macro-Markov chain combined with the theory of M/G/1/K queues to evaluate the characteristics of these two improved CSMA/CA schemes, in which traffic arrivals and accessing packets are bestowed with non-preemptive priority over each other, instead of prioritization. Then, throughput, packet delay and energy consumption of unsaturated, unacknowledged IEEE 802.15.4 beacon-enabled networks are predicted based on the overall point of view which takes the dependent interactions of different types of nodes into account. Moreover, performance comparisons of these two schemes with other non-priority schemes are also proposed. Analysis and simulation results show that delay and fairness of our schemes are superior to those of other schemes, while throughput and energy efficiency are superior to others in more heterogeneous situations. Comprehensive simulations demonstrate that the analysis results of these models match well with the simulation results. PMID:22666076

  14. Development of a multiple-locus variable-number tandem-repeat typing scheme for genetic fingerprinting of Burkholderia cenocepacia and application to nationwide epidemiological analysis.

    PubMed

    Segonds, Christine; Thouverez, Michelle; Barthe, Antoine; Bossuet-Greif, Nadège; Tisseyre, Lenka; Plésiat, Patrick; Vergnaud, Gilles; Chabanon, Gérard; Pourcel, Christine

    2015-02-01

    Organisms of the Burkholderia cepacia complex are especially important pathogens in cystic fibrosis (CF), with a propensity for patient-to-patient spread and long-term respiratory colonization. B. cenocepacia and Burkholderia multivorans account for the majority of infections in CF, and major epidemic clones have been recognized throughout the world. The aim of the present study was to develop and evaluate a multilocus variable-number tandem-repeat (VNTR) analysis (MLVA) scheme for B. cenocepacia. Potential VNTR loci were identified upon analysis of the annotated genome sequences of B. cenocepacia strains AU1054, J2315, and MCO-3, and 10 of them were selected on the basis of polymorphisms and size. A collection of 100 B. cenocepacia strains, including epidemiologically related and unrelated strains, as well as representatives of the major epidemic lineages, was used to evaluate typeability, epidemiological concordance, and the discriminatory power of MLVA-10 compared with those of pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Longitudinal stability was assessed by testing 39 successive isolates from 14 patients. Typeability ranged from 0.91 to 1, except for that of one marker, which was not amplified in 53% of the B. cenocepacia IIIA strains. The MLVA types were shown to be stable in chronically colonized patients and within outbreak-related strains, with excellent epidemiological concordance. Epidemic and/or globally distributed lineages (epidemic Edinburgh-Toronto electrophoretic type 12 [ET-12], sequence type 32 [ST-32], ST-122, ST-234, and ST-241) were successfully identified. Conversely, the discriminatory power of MLVA was lower than that of PFGE or MLST, although PFGE variations within the epidemic lineages sometimes masked their genetic relatedness. In conclusion, MLVA represents a promising cost-effective first-line tool in B. cenocepacia surveillance.

  15. A new multiple scattering scheme for the FLAIR forest radiative transfer model: Application to biochemical and biophysical parameter retrieval using hyperspectral data

    NASA Astrophysics Data System (ADS)

    Omari, Khalid

    This thesis investigated the development and assessment of a simple parameterization of the multiple scattering within canopies assuming the single scattering field is known and the background beneath the canopy is completely absorbing. The parameterization is based on the concept of spectral invariants related to recollision and escape probabilities from vegetation canopies. The simplified approach is evaluated against detailed 3-D ray tracing model, PARCINOPY, as well as reference datasets from the Radiation Modelling Intercomparison Experiment On-Line Checker. Comparison with homogenous canopies simulated with PARCINOPY showed that the model's performance is best in both the solar principal and perpendicular planes at low and mid LAI levels for all solar zenith angles. The comparison to the On-line Checker datasets shows also that the model is a suitable approach to describe the multiple scattering components of physically based models. This simple parameterization is then incorporated into the Four Scale Linear Model for Anisotropie Reflectance (FLAIR) canopy radiative transfer model to enhance the description of the spectrally dependant multiple scattered radiation field of a forest canopy. The contribution of the multiply scattered radiation between the canopy and the background is also added to the parameterization of the multiple scattering component. The validation of the new version of the FLAIR model was performed using the multi-angular data sets obtained by the airborne sensor POLarization and Directionality of the Earth's Reflectances (POLDER) during the BOReal Ecosystem-Atmosphere Study (BOREAS) campaign of 1994. The results indicate that this approach is well suited to the FLAIR model. It is also demonstrated that the multiple scattering problem can be parameterized by a limited number of architectural parameters and the leaf scattering coefficient. Finally, the combined canopy-leaf PROFLAIR (PROSPECT + FLAIR) model is used to investigate the

  16. The use of multiple indices of physiological activity to access viability in chlorine disinfected Escherichia coli O157:H7

    NASA Technical Reports Server (NTRS)

    Lisle, J. T.; Pyle, B. H.; McFeters, G. A.

    1999-01-01

    A suite of fluorescent intracellular stains and probes was used, in conjunction with viable plate counts, to assess the effect of chlorine disinfection on membrane potential (rhodamine 123; Rh123 and bis-(1,3-dibutylbarbituric acid) trimethine oxonol; DiBAC4(3)), membrane integrity (LIVE/DEAD BacLight kit), respiratory activity (5-cyano-2,3-ditolyl tetrazolium chloride; CTC) and substrate responsiveness (direct viable counts; DVC) in the commensal pathogen Escherichia coli O157:H7. After a 5 min exposure to the disinfectant, physiological indices were affected in the following order: viable plate counts > substrate responsiveness > membrane potential > respiratory activity > membrane integrity. In situ assessment of physiological activity by examining multiple targets, as demonstrated in this study, permits a more comprehensive determination of the site and extent of injury in bacterial cells following sublethal disinfection with chlorine. This approach to assessing altered bacterial physiology has application in various fields where detection of stressed bacteria is of interest.

  17. The use of multiple indices of physiological activity to access viability in chlorine disinfected Escherichia coli O157:H7

    NASA Technical Reports Server (NTRS)

    Lisle, J. T.; Pyle, B. H.; McFeters, G. A.

    1999-01-01

    A suite of fluorescent intracellular stains and probes was used, in conjunction with viable plate counts, to assess the effect of chlorine disinfection on membrane potential (rhodamine 123; Rh123 and bis-(1,3-dibutylbarbituric acid) trimethine oxonol; DiBAC4(3)), membrane integrity (LIVE/DEAD BacLight kit), respiratory activity (5-cyano-2,3-ditolyl tetrazolium chloride; CTC) and substrate responsiveness (direct viable counts; DVC) in the commensal pathogen Escherichia coli O157:H7. After a 5 min exposure to the disinfectant, physiological indices were affected in the following order: viable plate counts > substrate responsiveness > membrane potential > respiratory activity > membrane integrity. In situ assessment of physiological activity by examining multiple targets, as demonstrated in this study, permits a more comprehensive determination of the site and extent of injury in bacterial cells following sublethal disinfection with chlorine. This approach to assessing altered bacterial physiology has application in various fields where detection of stressed bacteria is of interest.

  18. Solar energy harvesting scheme using syringe-like ZnO nanorod arrays for InGaN/GaN multiple quantum well solar cells.

    PubMed

    Lin, G J; Lai, K Y; Lin, C A; He, J H

    2012-01-01

    Syringe-like ZnO nanorod arrays (NRAs) synthesized by a hydrothermal method were applied as the light-harvesting layer on InGaN-based multiple quantum well (MQW) solar cells. Theoretical calculations show that the NRAs with an abrupt shrinkage of tip diameter can further suppress surface reflectance in comparison with the flat NRAs. InGaN-based MQW solar cells with the syringe-like NRAs exhibit greatly improved conversion efficiencies by 36%. These results are attributed to the improved flatness of the refractive index profile at the air/device interface, which results in enhanced light trapping effect on the device surface. © 2012 Optical Society of America

  19. 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.

  20. Optical multidimensional multiple access(O-MDMA): a new concept for free-space laser communication based on photonic mixer devices

    NASA Astrophysics Data System (ADS)

    Hess, Holger; Albrecht, Martin; Grothof, Markus; Hussmann, Stephan; Schwarte, Rudolf

    2004-01-01

    Working on optical distance measurement a new optical correlator was developed at the Institute for Data Processing of the University of Siegen in the last years. The so called Photonic Mixer Device (PMD), to be meant originally for laser ranging systems, offers a lot of advantages for wireless optical data communication like high speed spatial light demodulation up to the GHz range and inherent backlight suppression. This contribution describes the application of such PMDs in a free space interconnect based on the principle of Multi Dimensional Multiple Access (MDMA) and the advantages of this new approach, starting from the MDMA principle and followed by the fundamental functionality of PMDs. After that an Optical MDMA (O-MDMA) demonstrator and first measurement results will be presented.

  1. Performance analysis of hybrid ARQ protocols in a slotted direct-sequence code-division multiple-access network - Jamming analysis

    NASA Astrophysics Data System (ADS)

    Hanratty, Joseph M.; Stuber, Gordon L.

    1990-05-01

    An examination is made of the performance of type-I hybrid ARQ (automatic repeat request) protocols in a slotted direct-sequence CDMA (code-division multiple access) network operating in a hostile jamming environment. The network consists of an arbitrary number of transceivers arranged in a paired-off topology. The traffic arrival process is derived by means of a Markov model. Throughput-delay expressions are derived in terms of the channel cutoff rate and capacity. The effects of jammer state information are discussed. Network design parameters are identified and their dependency on system parameters is examined in detail. It is shown that, for a given population size, traffic intensity, and bit energy/jammer noise ratio, there is an optimal probability of retransmission, code rate, and processing gain that maximizes network performance in the presence of worst-case pulse jamming.

  2. Experimental demonstration of a DSP-based cross-channel interference cancellation technique for application in digital filter multiple access PONs.

    PubMed

    Al-Rawachy, E; Giddings, R P; Tang, J M

    2017-02-20

    A DSP-based cross-channel interference cancellation (CCIC) technique with initial condition-free, fast convergence and signal modulation format independence, is experimentally demonstrated in a two-channel point-to-point digital filter multiple access (DFMA) PON system based on intensity-modulation and direct-detection (IMDD). The CCIC-induced transmission performance improvements under various system conditions are fully investigated for the first time. It is shown that with one iteration only the CCIC technique can achieve a reduction in individual OFDM subcarrier BERs of more than 1000 times, an increase in transmission capacity by as much as 19 times and an increase in optical power budget by as much as 3.5dB. The CCIC technique thus has the potential to drastically improve the transmission performance of DFMA PONs.

  3. 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.

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

    PubMed

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

    2015-01-01

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

  5. The new efficient multi-beamforming method based on multiple-access register block on a post-fractional filtering architecture

    NASA Astrophysics Data System (ADS)

    Kang, Jeeun; Kim, Giduck; Yoon, Changhan; Yoo, Yangmo; Song, Tai-Kyong

    2011-03-01

    In medical ultrasound imaging, a multi-beamforming (MBF) method is used for supporting high frame rate imaging or functional imaging where multiple scanlines are reconstructed from a single excitation event. For efficient MBF, a time-sharing technique (i.e., MBF-TS) can be applied. However, the MBF-TS could degrade image quality due to the decreased beamforming frequency. In this paper, the multi-access register-based MBF (MBF-MAR) method running on the post-fractional filtering (PFF) architecture is presented. In PFF-MBF-MAR, instead of lowering beamforming frequency, a multi-access register at each channel is utilized for generating multiple scanlines simultaneously. To evaluate the performance of the proposed PFF-MBF-MAR method, the phantom experiment was conducted where 64- channel pre-beamformed radio-frequency (RF) data were captured from a tissue mimicking phantom by using a modified commercial ultrasound system (SONOLINE G40, Siemens Inc., USA) using a 3-MHz phased array probe. From the phantom experiment, the PFF-MBF-MAR method showed 4.7 dB and 0.6 improvements in the signal-to-noise ratio (SNR) and the contrast-to-noise ratio (CNR), respectively, compared to the PFF-MBF-TS method, while slightly increasing the hardware complexity (<5.2%). The similar results were achieved with the in vivo thyroid data. These results indicate that the proposed PFF-MBF-MAR method can be used for high frame rate imaging or functional imaging without sacrificing image quality while slightly increasing the hardware complexity.

  6. An orthogonal wavelet division multiple-access processor architecture for LTE-advanced wireless/radio-over-fiber systems over heterogeneous networks

    NASA Astrophysics Data System (ADS)

    Mahapatra, Chinmaya; Leung, Victor CM; Stouraitis, Thanos

    2014-12-01

    The increase in internet traffic, number of users, and availability of mobile devices poses a challenge to wireless technologies. In long-term evolution (LTE) advanced system, heterogeneous networks (HetNet) using centralized coordinated multipoint (CoMP) transmitting radio over optical fibers (LTE A-ROF) have provided a feasible way of satisfying user demands. In this paper, an orthogonal wavelet division multiple-access (OWDMA) processor architecture is proposed, which is shown to be better suited to LTE advanced systems as compared to orthogonal frequency division multiple access (OFDMA) as in LTE systems 3GPP rel.8 (3GPP, http://www.3gpp.org/DynaReport/36300.htm). ROF systems are a viable alternative to satisfy large data demands; hence, the performance in ROF systems is also evaluated. To validate the architecture, the circuit is designed and synthesized on a Xilinx vertex-6 field-programmable gate array (FPGA). The synthesis results show that the circuit performs with a clock period as short as 7.036 ns (i.e., a maximum clock frequency of 142.13 MHz) for transform size of 512. A pipelined version of the architecture reduces the power consumption by approximately 89%. We compare our architecture with similar available architectures for resource utilization and timing and provide performance comparison with OFDMA systems for various quality metrics of communication systems. The OWDMA architecture is found to perform better than OFDMA for bit error rate (BER) performance versus signal-to-noise ratio (SNR) in wireless channel as well as ROF media. It also gives higher throughput and mitigates the bad effect of peak-to-average-power ratio (PAPR).

  7. Subchannel Access and Rate Assignment for Multicarrier Multi-Cell Networks

    NASA Astrophysics Data System (ADS)

    Wang, Jui Teng

    We study in this paper the subchannel access and the rate assignment for the multicarrier multi-cell networks. For subchannel access, we show from theoretic results and simulation results that the scheme with only one user per cell in each subchannel outperforms the scheme with multiple users per cell in each subchannel. For rate assignment, a distributed rate assignment is proposed to assign the rate for all subchannels. The proposed rate assignment need not measure the channel gains and uses only local information to iteratively adjust the transmitting power and data rate. We prove that the aggregate rate can be increased by increasing the number of iterations in the proposed rate assignment.

  8. A Selective Group Authentication Scheme for IoT-Based Medical Information System.

    PubMed

    Park, YoHan; Park, YoungHo

    2017-04-01

    The technology of IoT combined with medical systems is expected to support advanced medical services. However, unsolved security problems, such as misuse of medical devices, illegal access to the medical server and so on, make IoT-based medical systems not be applied widely. In addition, users have a high burden of computation to access Things for the explosive growth of IoT devices. Because medical information is critical and important, but users have a restricted computing power, IoT-based medical systems are required to provide secure and efficient authentication for users. In this paper, we propose a selective group authentication scheme using Shamir's threshold technique. The property of selectivity gives the right of choice to users to form a group which consists of things users select and access. And users can get an access authority for those Things at a time. Thus, our scheme provides an efficient user authentication for multiple Things and conditional access authority for safe IoT-based medical information system. To the best of our knowledge, our proposed scheme is the first in which selectivity is combined with group authentication in IoT environments.

  9. Fairness issues in resource allocation schemes for wireless visual sensor networks

    NASA Astrophysics Data System (ADS)

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

    2013-02-01

    This work addresses the problem of fairness and efficiency evaluation of various resource allocation schemes for wireless visual sensor networks (VSNs). These schemes are used to optimally allocate the source coding rates, channel coding rates, and power levels among the nodes of a wireless direct sequence code division multiple access (DS-CDMA) VSN. All of the considered schemes optimize a function of the video qualities of the nodes. However, there is no single scheme that maximizes the video quality of each node simultaneously. In fact, all presented schemes are able to provide a Pareto-optimal solution, meaning that there is no other solution that is simultaneously preferred by all nodes. Thus, it is not clear which scheme results in the best resource allocation for the whole network. To handle the resulting tradeoffs, in this study we examine four metrics that investigate fairness and efficiency under different perspectives. Specifically, we apply a metric that considers both fairness and performance issues, and another metric that measures the "equality" of a resource allocation (equal utilities for the nodes). The third metric computes the total system utility, while the last metric computes the total power consumption of the nodes. Ideally, a desirable scheme would achieve high total utility while being equally fair to all nodes and requiring low amounts of power.

  10. Research on an uplink carrier sense multiple access algorithm of large indoor visible light communication networks based on an optical hard core point process.

    PubMed

    Nan, Zhufen; Chi, Xuefen

    2016-12-20

    The IEEE 802.15.7 protocol suggests that it could coordinate the channel access process based on the competitive method of carrier sensing. However, the directionality of light and randomness of diffuse reflection would give rise to a serious imperfect carrier sense (ICS) problem [e.g., hidden node (HN) problem and exposed node (EN) problem], which brings great challenges in realizing the optical carrier sense multiple access (CSMA) mechanism. In this paper, the carrier sense process implemented by diffuse reflection light is modeled as the choice of independent sets. We establish an ICS model with the presence of ENs and HNs for the multi-point to multi-point visible light communication (VLC) uplink communications system. Considering the severe optical ICS problem, an optical hard core point process (OHCPP) is developed, which characterizes the optical CSMA for the indoor VLC uplink communications system. Due to the limited coverage of the transmitted optical signal, in our OHCPP, the ENs within the transmitters' carrier sense region could be retained provided that they could not corrupt the ongoing communications. Moreover, because of the directionality of both light emitting diode (LED) transmitters and receivers, theoretical analysis of the HN problem becomes difficult. In this paper, we derive the closed-form expression for approximating the outage probability and transmission capacity of VLC networks with the presence of HNs and ENs. Simulation results validate the analysis and also show the existence of an optimal physical carrier-sensing threshold that maximizes the transmission capacity for a given emission angle of LED.

  11. Fundamental Issues of Multiple Accessing

    DTIC Science & Technology

    1983-11-01

    Ngai Hui, submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology ...Foundation under Grant NSF/ECS-79-19880. 72.. -o ’.’i Laboratory for Information and Decision Systems Massachusetts Institute of Technology Cambridge...PROJECT. TASKA*EA S WoAK uNiT NUMOERS Massachusetts Institute of Technology Program Code No. 5T10 Laboratory for Information and Decisions Systems ONR

  12. Nonlinearly stable compact schemes for shock calculations

    NASA Technical Reports Server (NTRS)

    Cockburn, Bernardo; Shu, Chi-Wang

    1992-01-01

    The applications of high-order, compact finite difference methods in shock calculations are discussed. The main concern is to define a local mean which will serve as a reference for introducing a local nonlinear limiting to control spurious numerical oscillations while maintaining the formal accuracy of the scheme. For scalar conservation laws, the resulting schemes can be proven total-variation stable in one space dimension and maximum-norm stable in multiple space dimensions. Numerical examples are shown to verify accuracy and stability of such schemes for problems containing shocks. These ideas can also be applied to other implicit schemes such as the continuous Galerkin finite element methods.

  13. Effect of whole-body exposure to the 848.5 MHz code division multiple access (CDMA) electromagnetic field on adult neurogenesis in the young, healthy rat brain.

    PubMed

    Kim, Hye Sun; Kim, Yeon Ju; Lee, Yu Hee; Lee, Yun-Sil; Choi, Hyung Do; Pack, Jeong-Ki; Kim, Nam; Ahn, Young Hwan

    2015-04-01

    Whether exposure to the 848.5 MHz code division multiple access (CDMA) signal affects adult neurogenesis is unclear. An animal experiment was performed with a reverberation chamber designed as a whole-body CDMA exposure system. Male Sprague-Dawley rats were assigned to three groups (n = 6 per group): Cage-control, sham-exposed, and CDMA-exposed groups. Rats in the CDMA-exposed group were exposed to the CDMA signal at a 2 W/kg whole-body specific absorption rate (SAR) for 1 or 8 h daily, 5 days per week, for 2 weeks. Rats received a single intraperitoneal injection of Bromodeoxyuridine (BrdU) to label proliferative cells daily for the last five consecutive days of CDMA signal exposure. An unbiased stereological method was used to estimate the number of BrdU(+) cells in the subventricular zone (SVZ) and dentate gyrus (DG). We found no significant changes in the number of BrdU(+) cells in the SVZ or DG in the CDMA-exposed rats, compared with rats in the cage-control and sham-exposed groups (p > 0.05). Our results suggest that exposure to the CDMA signal does not affect neurogenesis in the adult rat brain, at least under our experimental conditions.

  14. Plerixafor and G-CSF for autologous stem cell mobilization in patients with NHL, Hodgkin's lymphoma and multiple myeloma: results from the expanded access program.

    PubMed

    Shaughnessy, P; Uberti, J; Devine, S; Maziarz, R T; Vose, J; Micallef, I; Jacobsen, E; McCarty, J; Stiff, P; Artz, A; Ball, E D; Berryman, R; Dugan, M; Joyce, R; Hsu, F J; Johns, D; McSweeney, P

    2013-06-01

    Before US regulatory approval, an expanded access program provided plerixafor to patients with non-Hodgkin's lymphoma (NHL), Hodgkin's lymphoma (HD) or multiple myeloma (MM) who had not previously failed mobilization and were otherwise candidates for auto-SCT. Patients received granulocyte-CSF (G-CSF) 10 mcg/kg daily and plerixafor 0.24 mg/kg starting on day 4 with apheresis on day 5; all repeated daily until collection was complete. Overall, 104 patients received 1 dose of plerixafor. The addition of plerixafor to G-CSF resulted in a median threefold increase in peripheral blood CD34+ cell count between days 4 and 5. Among 43 NHL patients, 74% met the target of 5 × 10(6) CD34+ cells/kg (median, 1 day apheresis, range 1-5 days); among 7 HD patients, 57% met the target of 5 × 10(6) CD34+ cells/kg (median, 2 days apheresis, range 1-3); and among 54 MM patients, 89% met the target of 6 × 10(6) CD34+ cells/kg (median, 1 day apheresis, range 1-4). Overall, 93% of patients had 2 × 10(6) CD34+ cells/kg collected within 1-3 days. Plerixafor-related toxicities were minimal. Engraftment kinetics, graft durability and transplant outcomes demonstrated no unexpected outcomes. Efficacy and safety results were similar to results in phase II and III clinical trials.

  15. MDTri: robust and efficient global mixed integer search of spaces of multiple ternary alloys: A DIRECT-inspired optimization algorithm for experimentally accessible computational material design

    DOE PAGES

    Graf, Peter A.; Billups, Stephen

    2017-07-24

    Computational materials design has suffered from a lack of algorithms formulated in terms of experimentally accessible variables. Here we formulate the problem of (ternary) alloy optimization at the level of choice of atoms and their composition that is normal for synthesists. Mathematically, this is a mixed integer problem where a candidate solution consists of a choice of three elements, and how much of each of them to use. This space has the natural structure of a set of equilateral triangles. We solve this problem by introducing a novel version of the DIRECT algorithm that (1) operates on equilateral triangles insteadmore » of rectangles and (2) works across multiple triangles. We demonstrate on a test case that the algorithm is both robust and efficient. Lastly, we offer an explanation of the efficacy of DIRECT -- specifically, its balance of global and local search -- by showing that 'potentially optimal rectangles' of the original algorithm are akin to the Pareto front of the 'multi-component optimization' of global and local search.« less

  16. A High-Efficiency CMOS Class-B Push-Pull Power Amplifier for Code-Division-Multiple-Access Cellular System

    NASA Astrophysics Data System (ADS)

    Yokoyama, Michio; Saito, Tetsuya; Tachibana, Ryoichi; Morimoto, Akihiro; Masu, Kazuya; Tsubouchi, Kazuo

    2000-04-01

    A silicon Class-B complementary push-pull power amplifier for a code-division-multiple-access IS-95 cellular system has been proposed for the first time. 0.8-μm complementary metal-oxide-semiconductor (CMOS) devices are fabricated and evaluated using RF measurement and simulation. The RF-CMOS balanced design between n- and p-MOS devices has been investigated. From RF simulation, a power-added efficiency (PAE) of over 60% at an input power of 5 dBm and an adjacent-channel-power-ratio of {-}42 dBc are obtained. It is found that both high efficiency and high linearity are obtained using the RF-CMOS balanced design with optimized channel length and width. Furthermore, drain voltage control for IS-95 criteria has been proposed in addition to the balanced design. The overall PAE, which is defined as the PAE multiplied by the probability distribution function of the used power-level and integrated over the entire used power range, has been improved up to 49%.

  17. A Microstrip Patch-Fed Short Backfire Antenna for the Tracking and Data Relay Satellite System-Continuation (TDRSS-C) Multiple Access (MA) Array

    NASA Technical Reports Server (NTRS)

    Nessel, James A.; Kory, Carol L.; Lambert, Kevin M.; Acosta, Roberto J.

    2006-01-01

    Short Backfire Antennas (SBAs) are widely utilized for mobile satellite communications, tracking, telemetry, and wireless local area network (WLAN) applications due to their compact structure and excellent radiation characteristics [1-3]. Typically, these SBA s consist of an excitation element (i.e., a half-wavelength dipole), a reflective bottom plane, a planar sub-reflector located above the "exciter", and an outer circular rim. This configuration is capable of achieving gains on the order of 13-15 dBi, but with relatively narrow bandwidths (approx.3%-5%), making it incompatible with the requirements of the next generation enhanced Tracking and Data Relay Satellite System-Continuation (TDRSS-C) Multiple Access (MA) array [1]. Several attempts have been made to enhance the bandwidth performance of the common dipole-fed SBA by employing various other feeding mechanisms (e.g., waveguide, slot) with moderate success [4-5]. In this paper, a novel method of using a microstrip patch is employed for the first time to excite an SBA. The patch element is fed via two H-shaped slots electromagnetically coupled to a broadband hybrid coupler to maintain a wide bandwidth, as well as provide for dual circular polarization capabilities.

  18. Efficient hop by hop buffer class flow control schemes

    NASA Astrophysics Data System (ADS)

    Chen, Moo-Song; Kadaba, Bharath; Grover, George

    Design issues of hop-by-hop buffer class flow-control schemes are discussed. They are: (1) good window size for high-speed and large-propagation-delay environments and (2) the concept of congestion and access fairness. Schemes are proposed for buffer classification and window-size adjustment. A novel buffer classification, the path-based scheme, has the same fairness property but fewer classes than the route-based scheme. The window adjustment shceme, the quasistatic scheme, has similar or slightly worse performance to, but requires much less complexity than, dynamic schemes.

  19. A Query Result Merging Scheme for Providing Energy Efficiency in Underwater Sensor Networks

    PubMed Central

    Kim, Yunsung; Park, Soo-Hyun

    2011-01-01

    Underwater sensor networks are emerging as a promising distributed data management system for various applications in underwater environments, despite their limited accessibility and restricted energy capacity. With the aid of recent developments in ubiquitous data computing, an increasing number of users are expected to overcome low accessibility by applying queries to underwater sensor networks. However, when multiple users send queries to an underwater sensor network in a disorganized manner, it may incur lethal energy waste and problematic network traffic. The current query management mechanisms cannot effectively deal with this matter due to their limited applicability and unrealistic assumptions. In this paper, a novel query management scheme involving query result merging is proposed for underwater sensor networks. The mechanism is based on a relational database model and is adjusted to the practical restrictions affecting underwater communication environments. Network simulations will prove that the scheme becomes more efficient with a greater number of queries and a smaller period range. PMID:22247695

  20. Asynchronous Communication Scheme For Hypercube Computer

    NASA Technical Reports Server (NTRS)

    Madan, Herb S.

    1988-01-01

    Scheme devised for asynchronous-message communication system for Mark III hypercube concurrent-processor network. Network consists of up to 1,024 processing elements connected electrically as though were at corners of 10-dimensional cube. Each node contains two Motorola 68020 processors along with Motorola 68881 floating-point processor utilizing up to 4 megabytes of shared dynamic random-access memory. Scheme intended to support applications requiring passage of both polled or solicited and unsolicited messages.

  1. Subranging scheme for SQUID sensors

    NASA Technical Reports Server (NTRS)

    Penanen, Konstantin I. (Inventor)

    2008-01-01

    A readout scheme for measuring the output from a SQUID-based sensor-array using an improved subranging architecture that includes multiple resolution channels (such as a coarse resolution channel and a fine resolution channel). The scheme employs a flux sensing circuit with a sensing coil connected in series to multiple input coils, each input coil being coupled to a corresponding SQUID detection circuit having a high-resolution SQUID device with independent linearizing feedback. A two-resolution configuration (course and fine) is illustrated with a primary SQUID detection circuit for generating a fine readout, and a secondary SQUID detection circuit for generating a course readout, both having feedback current coupled to the respective SQUID devices via feedback/modulation coils. The primary and secondary SQUID detection circuits function and derive independent feedback. Thus, the SQUID devices may be monitored independently of each other (and read simultaneously) to dramatically increase slew rates and dynamic range.

  2. Effectiveness and cost-effectiveness of interferon beta and glatiramer acetate in the UK Multiple Sclerosis Risk Sharing Scheme at 6 years: a clinical cohort study with natural history comparator.

    PubMed

    Palace, Jacqueline; Duddy, Martin; Bregenzer, Thomas; Lawton, Michael; Zhu, Feng; Boggild, Mike; Piske, Benjamin; Robertson, Neil P; Oger, Joel; Tremlett, Helen; Tilling, Kate; Ben-Shlomo, Yoav; Dobson, Charles

    2015-05-01

    In 2002, the UK's National Institute for Clinical Excellence (NICE) concluded that interferon beta and glatiramer acetate would be cost effective as disease-modifying therapies (DMTs) for multiple sclerosis only if the short-term disability benefits reported in clinical trials were maintained. The UK Multiple Sclerosis Risk Sharing Scheme (RSS) was established to assess whether disability progression was consistent with a cost-effectiveness target of £36 000 per quality-adjusted life-year projected over 20 years. We aimed to evaluate the long-term effectiveness and cost-effectiveness of these DMTs by comparing a cohort of patients with relapsing-remitting multiple sclerosis enrolled in the UK RSS with a natural history cohort from British Columbia, Canada. In our clinical cohort we included patients starting a DMT who were enrolled in the UK RSS who had relapsing multiple sclerosis at baseline and had at least one further clinical assessment. In our control cohort we included patients in the British Columbia multiple sclerosis database (BCMS; data collection 1980-96) who met the same eligibility criteria as for the RSS cohort. We compared disability progression at 6 years for RSS patients with untreated progression modelled from BCMS patients using continuous Markov and multilevel models. The primary outcomes were the progression ratio (treated vs untreated) measured both in Expanded Disability Status Scale (EDSS) score and utility. A ratio of less than 100% for EDSS implied slower than expected progression on treatment compared with off treatment; a utility ratio of 62% or less implied that the DMTs were cost effective. 5610 patients starting a DMT were enrolled in the UK RSS between Jan 14, 2002, and July 13, 2005 (72 sites), of whom 4137 were included in our clinical cohort. We included 898 BCMS patients in the control cohort who met the RSS inclusion criteria and had at least one EDSS score after baseline. RSS patients had a mean follow-up of 5·1 years (SD 1

  3. Ureteral access strategies: pro-access sheath.

    PubMed

    Vanlangendonck, Richard; Landman, Jaime

    2004-02-01

    Routine use of the ureteral access sheath during flexible ureteroscopic procedures provides consistent, reliable, and unencumbered access to the upper tracts. The ureteral access sheath can be reliably and easily deployed if used properly and requires no special training. As such, it can be easily adopted into current urologic practice. Not only does the access sheath facilitate rapid, repeated, and atraumatic access to the upper tracts, but it also avoids back-loading over a superstiff guidewire, which may incur costly damage to the ureteroscope. The access sheath reduces overall costs and decreases operative times. Furthermore, application of a ureteral access sheath reduces the frustration associated with complex and some routine ureteroscopic procedures by optimizing irrigant flow to improve the surgeon's endoscopic vision while minimizing the intrarenal pressures that the kidney must tolerate. There is no evidence that the access sheath results in clinically significant ureteral ischemia, and extensive clinical use of the access sheath for long procedures has not resulted in increased stricture formation. Finally, the ureteral access sheath is useful for other procedures, such as PCNL, by improving visualization and minimizing the requirement for multiple percutaneous access sites. Winston Churchill said it best: "Give us the tools and we will finish the job." Industry has provided urologists with the tools in the form of advanced flexible ureteroscopes, the holmium laser, nitinol baskets, and the ureteral access sheath. Now it is up to urologists to finish the job.

  4. A New Privacy-Preserving Handover Authentication Scheme for Wireless Networks

    PubMed Central

    Wang, Changji; Yuan, Yuan; Wu, Jiayuan

    2017-01-01

    Handover authentication is a critical issue in wireless networks, which is being used to ensure mobile nodes wander over multiple access points securely and seamlessly. A variety of handover authentication schemes for wireless networks have been proposed in the literature. Unfortunately, existing handover authentication schemes are vulnerable to a few security attacks, or incur high communication and computation costs. Recently, He et al. proposed a handover authentication scheme PairHand and claimed it can resist various attacks without rigorous security proofs. In this paper, we show that PairHand does not meet forward secrecy and strong anonymity. More seriously, it is vulnerable to key compromise attack, where an adversary can recover the private key of any mobile node. Then, we propose a new efficient and provably secure handover authentication scheme for wireless networks based on elliptic curve cryptography. Compared with existing schemes, our proposed scheme can resist key compromise attack, and achieves forward secrecy and strong anonymity. Moreover, it is more efficient in terms of computation and communication. PMID:28632171

  5. Evaluation of practical schemes for correcting multiple scattering effects on gap fraction measurements by plant canopy analyzer LAI-2000/2200: implications for hemispherical photography and terrestrial laser scanners

    NASA Astrophysics Data System (ADS)

    Pisek, J.; Kobayashi, H.; Kuusk, A.

    2016-12-01

    Correct estimates of gap fraction are essential for quantifying canopy architectural variables, such as leaf area and clumping indices, which modify land-atmosphere interactions. The plant canopy analyzer (PCA) LAI-2000/2200 has been in use for the non-destructive determination of leaf area index (LAI), and other structural attributes of vegetative canopies for over 25 years (Li-Cor, 1989). The instrument is considered the world standard for indirect LAI measurements (Li-Cor, 2014). The PCA uses the gap fraction technique for calculation of LAI and mean inclination angle of foliage. However, gap fraction measurements from optical sensors are contaminated by radiation that is scattered by plant elements and ground surfaces. Three proposed alternative schemes for correcting multiple scattering effects on gap fraction measurements by PCA are evaluated: 1) Leblanc and Chen, 2001. Agric. For. Meteorol. 110, 125-139; 2) Kobayashi et al.., 2013. Agric. For. Meteorol. 174-175, 170-183; and 3) Kuusk, 2016. Agric. For. Meteorol. 221, 242-247. Collectively these methods provide suggestions for the correction of LAI estimates from measurements under wide range of illumination conditions. The PCA measurements were taken at two different RAMI (RAdiation transfer Model Intercomparison) stands in Järvselja, Estonia. All three schemes agreed reasonably well in the sparse and homogeneous RAMI Scots pine stand; the effective LAI would be underestimated by up to 13% if the corrections are not implemented. The proposed corrections varied from 7% (method by Kobayashi et al., 2013) up to 23% (method by Leblanc and Chen, 2001) in denser and heterogeneous RAMI birch stand. The role of scattered sky radiation in the estimation of gap fraction in vegetation canopies using passive optical techniques should be clearly accounted for even in case of perfectly overcast sky. The PCA measurements are considered a reference in developing methods of the estimation of gap fraction from hemispherical

  6. Cross-ontological analytics for alignment of different classification schemes

    DOEpatents

    Posse, Christian; Sanfilippo, Antonio P; Gopalan, Banu; Riensche, Roderick M; Baddeley, Robert L

    2010-09-28

    Quantification of the similarity between nodes in multiple electronic classification schemes is provided by automatically identifying relationships and similarities between nodes within and across the electronic classification schemes. Quantifying the similarity between a first node in a first electronic classification scheme and a second node in a second electronic classification scheme involves finding a third node in the first electronic classification scheme, wherein a first product value of an inter-scheme similarity value between the second and third nodes and an intra-scheme similarity value between the first and third nodes is a maximum. A fourth node in the second electronic classification scheme can be found, wherein a second product value of an inter-scheme similarity value between the first and fourth nodes and an intra-scheme similarity value between the second and fourth nodes is a maximum. The maximum between the first and second product values represents a measure of similarity between the first and second nodes.

  7. A Broadcast Scheme for MIMO Systems with Channel State Information at the Transmitter

    NASA Astrophysics Data System (ADS)

    Hwang, Insoo; You, Cheolwoo; Kim, Dongho; Kim, Yungsoo; Tarokh, Vahid

    We propose a new broadcast strategy for a multiple-input multiple-output (MIMO) system with N transmit antennas at the transmitter and M≤N single antenna receivers. The proposed method, based on dirty-paper coding (DPC), spatially separates the M users but does not suffer from the power loss of classical spatial division multiple access (SDMA). For the special case of M=N=2 and when the two single antenna receivers are assumed to be co-located, the proposed scheme produces a 2 transmit, 2 receiver antenna MIMO transmission system that doubles the symbol rate of MIMO space-time block code (STBC) systems from one to two symbol per transmission time. It is proved theoretically and experimentally that the proposed scheme provides the same performance level as that of MIMO STBC systems (i. e., the Alamouti scheme) for the first symbol, and the same performance as the Bell labs layered space-time (BLAST) system for the second symbol. When compared to the BLAST system, the proposed scheme has the same symbol rate, but achieves significantly better performance, since it provides 2 level diversity per symbol on the first symbol while the BLAST system does not provide any diversity.

  8. Access, delivery and perceived efficacy of physiotherapy and use of complementary and alternative therapies by people with progressive multiple sclerosis in the United Kingdom: An online survey.

    PubMed

    Campbell, Evan; Coulter, Elaine; Mattison, Paul; McFadyen, Angus; Miller, Linda; Paul, Lorna

    2017-02-01

    All people with progressive MS in the United Kingdom should have access to physiotherapy through the National Health Service (NHS). However levels of access and delivery are unknown. Furthermore there is no research on perceived efficacy of physiotherapy or the use of complementary and alternative medicine in people with progressive MS in the United Kingdom. An online survey was carried out via the UK MS Register. Inclusion criteria were diagnosis of progressive MS, a member of UK MS Register and 18 years or older. The survey asked participants regarding access and delivery of physiotherapy; perceived efficacy of physiotherapy and interventions received; barriers to accessing physiotherapy and use of complementary and alternative medicine. The following additional data were supplied from the UK MS Register: demographics, EQ5D, MSIS-29 physical and psychological sub-scales and geographical data. Total number of respondents was 1,298 from an identified 2,538 potential registrants: 87% could access physiotherapy services, 77% received physiotherapy from the NHS and 32% were currently receiving physiotherapy. The most common interventions received were home exercise programme (86%), exercises with a physiotherapist (74%) and advice/education (67%). 40% had recently used complementary and alternative medicine. Perceived efficacy of physiotherapy was high with 70% reporting it to be either 'beneficial' or 'very beneficial'. Main barriers to accessing physiotherapy were mobility, fatigue, continence, transport issues, requiring someone to go with them and pain. Access to physiotherapy was high with most people reporting it as beneficial. However 13% reported not having access indicating a gap in accessibility. Considering some of the barriers reported may allow physiotherapy services to address this gap in accessibility. Copyright © 2017 Elsevier B.V. All rights reserved.

  9. Improving the secrecy rate by turning foes to allies: An auction scheme

    NASA Astrophysics Data System (ADS)

    Ma, Ya-Yan; Wang, Bao-Yun

    2015-09-01

    Security against eavesdroppers is a critical issue in cognitive radio networks (CRNs). In this paper, a scenario consisting of one primary pair and multiple secondary pairs is considered. The secondary transmitters (STs) work in half-duplex mode and they are potential eavesdroppers on the primary transmission unless they are allowed to simultaneously transmit with the primary transmitter (PT). A modified second-price sealed-bid auction scheme is employed to model the interaction between the PT and STs. With the proposed auction scheme, the hostile relationship between the PT and STs is transformed into a cooperative relationship. An iterative algorithm based on the max-min criteria is proposed to find the optimal bidding power of the STs for an access chance in the presence of multiple eavesdroppers. Numerical results show that the proposed auction scheme not only improves the PT’s security but also increases the access opportunities of the STs. Project supported by the National Natural Science Foundation of China (Grant Nos. 61271232 and 61372126) and the University Postgraduate Research and Innovation Project in Jiangsu Province, China (Grant No. CXZZ12-0472).

  10. Adaptive mobile access protocol (AMAP) for the message service of a land mobile satellite experiment (MSAT-X)

    NASA Technical Reports Server (NTRS)

    Li, V. O. K.; Yan, T.-Y.

    1984-01-01

    This paper describes a feasibility study of the adaptive mobile access protocol (AMAP) for MSATA-X, a proposed experimental mobile satellite communication network. The mobiles are dispersed over a wide geographical area and the channel data rate is limited due to the size and cost limitations of mobile antennas. AMAP is a reservation based multiple-access scheme. The available bandwidth is divided into subchannels, which are divided into reservation and message channels. The ALOHA multiple-access scheme is employed in the reservation channels, while the message channels are demand assigned. AMAP adaptively reallocates the reservation and message channels to optimize system performance. It has been shown that if messages are generated at a rate of one message per hour, AMAP can support approximately 2000 active users per 2400 bit/s channel with an average delay of 1.4 s.

  11. Demystifying Open Access

    SciTech Connect

    Mele, Salvatore

    2007-05-14

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

  12. Demystifying Open Access

    SciTech Connect

    Mele, Salvatore

    2007-05-14

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

  13. A power-efficient ZF precoding scheme for multi-user indoor visible light communication systems

    NASA Astrophysics Data System (ADS)

    Zhao, Qiong; Fan, Yangyu; Deng, Lijun; Kang, Bochao

    2017-02-01

    In this study, we propose a power-efficient ZF precoding scheme for visible light communication (VLC) downlink multi-user multiple-input-single-output (MU-MISO) systems, which incorporates the zero-forcing (ZF) and the characteristics of VLC systems. The main idea of this scheme is that the channel matrix used to perform pseudoinverse comes from the set of optical Access Points (APs) shared by more than one user, instead of the set of all involved serving APs as the existing ZF precoding schemes often used. By doing this, the waste of power, which is caused by the transmission of one user's data in the un-serving APs, can be avoided. In addition, the size of the channel matrix needs to perform pseudoinverse becomes smaller, which helps to reduce the computation complexity. Simulation results in two scenarios show that the proposed ZF precoding scheme has higher power efficiency, better bit error rate (BER) performance and lower computation complexity compared with traditional ZF precoding schemes.

  14. Novel secure and bandwidth efficient optical code division multiplexed system for future access networks

    NASA Astrophysics Data System (ADS)

    Singh, Simranjit

    2016-12-01

    In this paper, a spectrally coded optical code division multiple access (OCDMA) system using a hybrid modulation scheme has been investigated. The idea is to propose an effective approach for simultaneous improvement of the system capacity and security. Data formats, NRZ (non-return to zero), DQPSK (differential quadrature phase shift keying), and PoISk (polarisation shift keying) are used to get the orthogonal modulated signal. It is observed that the proposed hybrid modulation provides efficient utilisation of bandwidth, increases the data capacity and enhances the data confidentiality over existing OCDMA systems. Further, the proposed system performance is compared with the current state-of-the-art OCDMA schemes.

  15. Efficiently sphere-decodable physical layer transmission schemes for wireless storage networks

    NASA Astrophysics Data System (ADS)

    Lu, Hsiao-Feng Francis; Barreal, Amaro; Karpuk, David; Hollanti, Camilla

    2016-12-01

    Three transmission schemes over a new type of multiple-access channel (MAC) model with inter-source communication links are proposed and investigated in this paper. This new channel model is well motivated by, e.g., wireless distributed storage networks, where communication to repair a lost node takes place from helper nodes to a repairing node over a wireless channel. Since in many wireless networks nodes can come and go in an arbitrary manner, there must be an inherent capability of inter-node communication between every pair of nodes. Assuming that communication is possible between every pair of helper nodes, the newly proposed schemes are based on various smart time-sharing and relaying strategies. In other words, certain helper nodes will be regarded as relays, thereby converting the conventional uncooperative multiple-access channel to a multiple-access relay channel (MARC). The diversity-multiplexing gain tradeoff (DMT) of the system together with efficient sphere-decodability and low structural complexity in terms of the number of antennas required at each end is used as the main design objectives. While the optimal DMT for the new channel model is fully open, it is shown that the proposed schemes outperform the DMT of the simple time-sharing protocol and, in some cases, even the optimal uncooperative MAC DMT. While using a wireless distributed storage network as a motivating example throughout the paper, the MAC transmission techniques proposed here are completely general and as such applicable to any MAC communication with inter-source communication links.

  16. Spatial dimming scheme for optical OFDM based visible light communication.

    PubMed

    Yang, Yang; Zeng, Zhimin; Cheng, Julian; Guo, Caili

    2016-12-26

    A new dimming control scheme termed spatial dimming orthogonal frequency division multiplexing (SD-OFDM) is proposed for multiple-input and multiple output OFDM based visible light communication. The basic idea of SD-OFDM is that the illumination can be represented by the number of glared light emitting diodes (LEDs) in an LED lamp. As the biasing level of LEDs does not adjust to represent the required illumination level, the proposed scheme can significantly mitigate the clipping noise compared to analogue dimming schemes. Furthermore, unlike digital dimming schemes that control illumination levels by setting different duty cycles of pulse width modulation, the proposed scheme is always in the "on-state" for varied illumination levels. Both analytical and simulation results indicate that the proposed scheme is an efficient and feasible dimmable scheme.

  17. Recirculating photonic filter: A wavelength-selective true-time-delay device for optically controlled phased array sensors and wavelength code-division multiple access

    NASA Astrophysics Data System (ADS)

    Yegnanarayanan, Sivasubramaniam

    1999-10-01

    In this dissertation we propose a novel wavelength- selective photonic time-delay filter. This device consists of an optical phased-array waveguide grating in a recirculating feedback configuration: This all-optical tunable optical delay line device permits several novel applications in the optical processing of high frequency signals. The first application is as a true-time-delay generator for squint-free beam steering in optically-controlled microwave phased-array antennas where the optical carrier wavelength is used to select a desired time delay for the microwave signal. Time-delay beam steering ensure wide instantaneous bandwidth operation. The mapping of optical wavelength to the microwave beam direction permits a hardware compressive architecture for the optical control unit that can easily scale to large aperture antenna arrays. Prototype integrated optical chips consisting of optical filters and precision delay lines have demonstrated picosecond resolution time delays. Hybrid devices permit longer time-delays of several tens of nanoseconds through external fiber delay lines. Extension to optically controlled two-dimensional array beam steering using optical wavelength conversion between azimuth and elevation beam steering units is also explored. This overcomes optical/electrical/optical conversion losses in cascading individual beam steering units. A 2-element X-band optically controlled phased array transmitter is assembled in a compact test range to verify the wide bandwidth beam steering system. Such wavelength selective time delay filter devices can also transform optical pulses with wide spectral bandwidth into simultaneous wavelength and time coded waveforms. One application of such hybrid coded waveforms is in optical code-division multiple access (CDMA) communication. Their perfect delta-function autocorrelation and small cross-correlation properties result in significant improvements in the number of orthogonal codes and the number of simultaneous

  18. 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.

  19. A CDMA synchronisation scheme

    NASA Technical Reports Server (NTRS)

    Soprano, C.

    1993-01-01

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

  20. Twin Signature Schemes, Revisited

    NASA Astrophysics Data System (ADS)

    Schäge, Sven

    In this paper, we revisit the twin signature scheme by Naccache, Pointcheval and Stern from CCS 2001 that is secure under the Strong RSA (SRSA) assumption and improve its efficiency in several ways. First, we present a new twin signature scheme that is based on the Strong Diffie-Hellman (SDH) assumption in bilinear groups and allows for very short signatures and key material. A big advantage of this scheme is that, in contrast to the original scheme, it does not require a computationally expensive function for mapping messages to primes. We prove this new scheme secure under adaptive chosen message attacks. Second, we present a modification that allows to significantly increase efficiency when signing long messages. This construction uses collision-resistant hash functions as its basis. As a result, our improvements make the signature length independent of the message size. Our construction deviates from the standard hash-and-sign approach in which the hash value of the message is signed in place of the message itself. We show that in the case of twin signatures, one can exploit the properties of the hash function as an integral part of the signature scheme. This improvement can be applied to both the SRSA based and SDH based twin signature scheme.

  1. How the Pharmaceutical Benefits Scheme began.

    PubMed

    Goddard, Martyn S

    2014-07-07

    Seventy years ago, the Curtin wartime government introduced legislation for a Pharmaceutical Benefits Scheme (PBS). It was a response to the need to provide access to a wave of antibiotic drugs - sulfonamides, streptomycin, penicillin - to the whole population, not only to the minority able to afford them. The scheme was immediately and successfully opposed by doctors and the conservative opposition, which saw in universal health care an underhand plan to nationalise medicine. There were two High Court challenges, two referendums and a constitutional amendment; but it was not until 1960 that Australians had the comprehensive PBS envisaged by Curtin in 1944.

  2. Power consumption analysis of priority-based service differentiation scheme for LR-WPANs

    NASA Astrophysics Data System (ADS)

    Kim, Meejoung; Hwang, Eenjun

    2016-06-01

    In this paper, we investigate the effect of service differentiation on the power consumption in contention period of IEEE 802.15.4 sensor networks. Power consumption is analysed for two different service differentiation schemes under non-saturation condition. The two service differentiation schemes are the differentiation by the backoff exponent (BED) and differentiation by the contention window (CWD), which provide multilevel differentiated services in beacon-enabled mode with slotted carrier sense multiple access/collision avoidance (CSMA/CA) algorithm. The analysis is based on the stationary probabilities of a discrete-time Markov chain, which is a model of CSMA/CA describing the state of a head packet of a device. Numerical results show that CWD uses the power more efficiently and performs better in terms of throughput, while BED more differentiates the service.

  3. Hybrid scheme for color dithering

    NASA Astrophysics Data System (ADS)

    Sloan, Kenneth R., Jr.

    1990-10-01

    This paper presents a hybrid color dithering scheme suitable for rendering continuous tone color images on a CRT display with a small number (on the order of 16-256) of distinct colors. Monochrome (especially bi-level) dithering techniques are well studied. Which of these techniques extend naturally to color? We look at four classes of monochrome dithering techniques and attempt to generalize each one, first to multiple gray-level (but still monochrome) inks and then to a multiple color pallette. In the monochrome case, we discover that texture introduced by the dithering process can significantly affect the appearance of the image. We develop a scheme by which the user can control these texture effects. The primary tradeoff is between very fine grained textures which depend critically on the local gray level and relatively coarser, more obvious, textures which appear uniform across the entire image. In the color case, we have the further complication of choosing a color pallette. We deal primarily with the case where there are a small number of available colors, and where the color pallette is not optimized separately for each image.

  4. 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

  5. Plotting and Scheming

    NASA Technical Reports Server (NTRS)

    2004-01-01

    [figure removed for brevity, see original site] Figure 1 [figure removed for brevity, see original site] Figure 2 Click for larger view

    These two graphics are planning tools used by Mars Exploration Rover engineers to plot and scheme the perfect location to place the rock abrasion tool on the rock collection dubbed 'El Capitan' near Opportunity's landing site. 'El Capitan' is located within a larger outcrop nicknamed 'Opportunity Ledge.'

    The rover visualization team from NASA Ames Research Center, Moffett Field, Calif., initiated the graphics by putting two panoramic camera images of the 'El Capitan' area into their three-dimensional model. The rock abrasion tool team from Honeybee Robotics then used the visualization tool to help target and orient their instrument on the safest and most scientifically interesting locations. The blue circle represents one of two current targets of interest, chosen because of its size, lack of dust, and most of all its distinct and intriguing geologic features. To see the second target location, see the image titled 'Plotting and Scheming.'

    The rock abrasion tool is sensitive to the shape and texture of a rock, and must safely sit within the 'footprint' indicated by the blue circles. The rock area must be large enough to fit the contact sensor and grounding mechanism within the area of the outer blue circle, and the rock must be smooth enough to get an even grind within the abrasion area of the inner blue circle. If the rock abrasion tool were not grounded by its support mechanism or if the surface were uneven, it could 'run away' from its target. The rock abrasion tool is location on the rover's instrument deployment device, or arm.

    Over the next few martian days, or sols, the rover team will use these and newer, similar graphics created with more recent, higher-resolution panoramic camera images and super-spectral data from the miniature thermal emission spectrometer. These data will be used to pick the best

  6. Tabled Execution in Scheme

    SciTech Connect

    Willcock, J J; Lumsdaine, A; Quinlan, D J

    2008-08-19

    Tabled execution is a generalization of memorization developed by the logic programming community. It not only saves results from tabled predicates, but also stores the set of currently active calls to them; tabled execution can thus provide meaningful semantics for programs that seemingly contain infinite recursions with the same arguments. In logic programming, tabled execution is used for many purposes, both for improving the efficiency of programs, and making tasks simpler and more direct to express than with normal logic programs. However, tabled execution is only infrequently applied in mainstream functional languages such as Scheme. We demonstrate an elegant implementation of tabled execution in Scheme, using a mix of continuation-passing style and mutable data. We also show the use of tabled execution in Scheme for a problem in formal language and automata theory, demonstrating that tabled execution can be a valuable tool for Scheme users.

  7. A secure biometrics-based authentication scheme for telecare medicine information systems.

    PubMed

    Yan, Xiaopeng; Li, Weiheng; Li, Ping; Wang, Jiantao; Hao, Xinhong; Gong, Peng

    2013-10-01

    The telecare medicine information system (TMIS) allows patients and doctors to access medical services or medical information at remote sites. Therefore, it could bring us very big convenient. To safeguard patients' privacy, authentication schemes for the TMIS attracted wide attention. Recently, Tan proposed an efficient biometrics-based authentication scheme for the TMIS and claimed their scheme could withstand various attacks. However, in this paper, we point out that Tan's scheme is vulnerable to the Denial-of-Service attack. To enhance security, we also propose an improved scheme based on Tan's work. Security and performance analysis shows our scheme not only could overcome weakness in Tan's scheme but also has better performance.

  8. Multiple bit differential detection of offset QPSK

    NASA Technical Reports Server (NTRS)

    Simon, M.

    2003-01-01

    Analogous to multiple symbol differential detection of quadrature phase-shift-keying, a multiple bit differential detection scheme is described for offset QPSK that also exhibits continuous improvement in performance with increasing observation interval. Being derived from maximum-likelihood (ML) considerations, the proposed scheme is purported to be the most power efficient scheme for such a modulation and detection method.

  9. Development of a generic system for real-time data access and remote control of multiple in-situ water quality monitoring instruments

    NASA Astrophysics Data System (ADS)

    Wright, S. A.; Bennett, G. E.; Andrews, T.; Melis, T. S.; Topping, D. J.

    2005-05-01

    Currently, in-situ monitoring of water quality parameters (e.g. water temperature, conductivity, turbidity) in the Colorado River ecosystem typically consists of deploying instruments in the river, retrieving them at a later date, downloading the datalogger, then examining the data; an arduous process in the remote settings of Grand Canyon. Under this protocol, data is not available real-time and there is no way to detect problems with the instrumentation until after retrieval. The next obvious stage in the development of in-situ monitoring in Grand Canyon was the advent of one-way telemetry, i.e. streaming data in real-time from the instrument to the office and/or the world-wide-web. This protocol allows for real-time access to data and the identification of instrumentation problems, but still requires a site visit to address instrument malfunctions, i.e. the user does not have the ability to remotely control the instrument. At some field sites, such as the Colorado River in Grand Canyon, site visitation is restricted by remoteness and lack of traditional access routes (i.e. roads). Even at less remote sites, it may still be desirable to have two-way communication with instruments in order to, for example, diagnose and potentially fix instrumentation problems, change sampling parameters to save battery power, etc., without having to visit the site. To this end, the U.S. Geological Survey, Grand Canyon Monitoring and Research Center, is currently developing and testing a high-speed, two-way communication system that allows for real-time data access and remote control of instrumentation. The approach tested relies on internet access and may be especially useful in areas where land-line or cellular connections are unavailable. The system is composed of off-the-shelf products, uses a commercial broadband satellite service, and is designed in a generic way such that any instrument that communicates through RS-232 communication (i.e. a serial port) is compatible with

  10. Robust anonymous authentication scheme for telecare medical information systems.

    PubMed

    Xie, Qi; Zhang, Jun; Dong, Na

    2013-04-01

    Patient can obtain sorts of health-care delivery services via Telecare Medical Information Systems (TMIS). Authentication, security, patient's privacy protection and data confidentiality are important for patient or doctor accessing to Electronic Medical Records (EMR). In 2012, Chen et al. showed that Khan et al.'s dynamic ID-based authentication scheme has some weaknesses and proposed an improved scheme, and they claimed that their scheme is more suitable for TMIS. However, we show that Chen et al.'s scheme also has some weaknesses. In particular, Chen et al.'s scheme does not provide user's privacy protection and perfect forward secrecy, is vulnerable to off-line password guessing attack and impersonation attack once user's smart card is compromised. Further, we propose a secure anonymity authentication scheme to overcome their weaknesses even an adversary can know all information stored in smart card.

  11. An Efficient Remote Authentication Scheme for Wireless Body Area Network.

    PubMed

    Omala, Anyembe Andrew; Kibiwott, Kittur P; Li, Fagen

    2017-02-01

    Wireless body area network (WBAN) provide a mechanism of transmitting a persons physiological data to application providers e.g. hospital. Given the limited range of connectivity associated with WBAN, an intermediate portable device e.g. smartphone, placed within WBAN's connectivity, forwards the data to a remote server. This data, if not protected from an unauthorized access and modification may be lead to poor diagnosis. In order to ensure security and privacy between WBAN and a server at the application provider, several authentication schemes have been proposed. Recently, Wang and Zhang proposed an authentication scheme for WBAN using bilinear pairing. However, in their scheme, an application provider could easily impersonate a client. In order to overcome this weakness, we propose an efficient remote authentication scheme for WBAN. In terms of performance, our scheme can not only provide a malicious insider security, but also reduce running time of WBAN (client) by 51 % as compared to Wang and Zhang scheme.

  12. Accessibility | FNLCR

    Cancer.gov

    The Frederick National Laboratory for Cancer Research campus is making every effort to ensure that the information available on our website is accessible to all. If you use special adaptive equipment to access the web and encounter problems when usin

  13. Access to Medications for Cardiovascular Diseases in Low- and Middle-Income Countries.

    PubMed

    Wirtz, Veronika J; Kaplan, Warren A; Kwan, Gene F; Laing, Richard O

    2016-05-24

    Cardiovascular diseases (CVD) represent the highest burden of disease globally. Medicines are a critical intervention used to prevent and treat CVD. This review describes access to medication for CVD from a health system perspective and strategies that have been used to promote access, including providing medicines at lower cost, improving medication supply, ensuring medicine quality, promoting appropriate use, and managing intellectual property issues. Using key evidence in published and gray literature and systematic reviews, we summarize advances in access to cardiovascular medicines using the 5 health system dimensions of access: availability, affordability, accessibility, acceptability, and quality of medicines. There are multiple barriers to access of CVD medicines, particularly in low- and middle-income countries. Low availability of CVD medicines has been reported in public and private healthcare facilities. When patients lack insurance and pay out of pocket to purchase medicines, medicines can be unaffordable. Accessibility and acceptability are low for medicines used in secondary prevention; increasing use is positively related to country income. Fixed-dose combinations have shown a positive effect on adherence and intermediate outcome measures such as blood pressure and cholesterol. We have a new opportunity to improve access to CVD medicines by using strategies such as efficient procurement of low-cost, quality-assured generic medicines, development of fixed-dose combination medicines, and promotion of adherence through insurance schemes that waive copayment for long-term medications. Monitoring progress at all levels, institutional, regional, national, and international, is vital to identifying gaps in access and implementing adequate policies.

  14. Check-Digit Schemes.

    ERIC Educational Resources Information Center

    Wheeler, Mary L.

    1994-01-01

    Discusses the study of identification codes and check-digit schemes as a way to show students a practical application of mathematics and introduce them to coding theory. Examples include postal service money orders, parcel tracking numbers, ISBN codes, bank identification numbers, and UPC codes. (MKR)

  15. Massive Access Control Aided by Knowledge-Extraction for Co-Existing Periodic and Random Services over Wireless Clinical Networks.

    PubMed

    Du, Qinghe; Zhao, Weidong; Li, Weimin; Zhang, Xuelin; Sun, Bo; Song, Houbing; Ren, Pinyi; Sun, Li; Wang, Yichen

    2016-07-01

    The prosperity of e-health is boosted by fast development of medical devices with wireless communications capability such as wearable devices, tiny sensors, monitoring equipments, etc., which are randomly distributed in clinic environments. The drastically-increasing population of such devices imposes new challenges on the limited wireless resources. To relieve this problem, key knowledge needs to be extracted from massive connection attempts dispersed in the air towards efficient access control. In this paper, a hybrid periodic-random massive access (HPRMA) scheme for wireless clinical networks employing ultra-narrow band (UNB) techniques is proposed. In particular, the proposed scheme towards accommodating a large population of devices include the following new features. On one hand, it can dynamically adjust the resource allocated for coexisting periodic and random services based on the traffic load learned from signal collision status. On the other hand, the resource allocation within periodic services is thoroughly designed to simultaneously align with the timing requests of differentiated services. Abundant simulation results are also presented to demonstrate the superiority of the proposed HPRMA scheme over baseline schemes including time-division multiple access (TDMA) and random access approach, in terms of channel utilization efficiency, packet drop ratio, etc., for the support of massive devices' services.

  16. Verifier-based three-party authentication schemes using extended chaotic maps for data exchange in telecare medicine information systems.

    PubMed

    Lee, Tian-Fu

    2014-12-01

    Telecare medicine information systems provide a communicating platform for accessing remote medical resources through public networks, and help health care workers and medical personnel to rapidly making correct clinical decisions and treatments. An authentication scheme for data exchange in telecare medicine information systems enables legal users in hospitals and medical institutes to establish a secure channel and exchange electronic medical records or electronic health records securely and efficiently. This investigation develops an efficient and secure verified-based three-party authentication scheme by using extended chaotic maps for data exchange in telecare medicine information systems. The proposed scheme does not require server's public keys and avoids time-consuming modular exponential computations and scalar multiplications on elliptic curve used in previous related approaches. Additionally, the proposed scheme is proven secure in the random oracle model, and realizes the lower bounds of messages and rounds in communications. Compared to related verified-based approaches, the proposed scheme not only possesses higher security, but also has lower computational cost and fewer transmissions.

  17. A Double-Moment Multiple-Phase Four-Class Bulk Ice Scheme. Part II: Simulations of Convective Storms in Different Large-Scale Environments and Comparisons with other Bulk Parameterizations.

    NASA Astrophysics Data System (ADS)

    Schoenberg Ferrier, Brad; Tao, Wei-Kuo; Simpson, Joanne

    1995-04-01

    Part I of this study described a detailed four-class bulk ice scheme (4ICE) developed to simulate the hydro-meteor profiles of convective and stratiform precipitation associated with mesoscale convective systems. In Part II, the 4ICE scheme is incorporated into the Goddard Cumulus Ensemble (GCE) model and applied without any `tuning' to two squall lines occurring in widely different environments, namely, one over the `Pica) ocean in the Global Atmospheric Research Program's (GARP) Atlantic Tropical Experiment (GATE) and the other over a midlatitude continent in the Cooperative Huntsville Meteorological Experiment (COHMEX). Comparisons were made both with earlier three-class ice formulations and with observations. In both cases, the 4ICE scheme interacted with the dynamics so as to resemble the observations much more closely than did the model runs with either of the three-class ice parameterizations. The following features were well simulated in the COHMEX case: a lack of stratiform rain at the surface ahead of the storm, reflectivity maxima near 60 dBZ in the vicinity of the melting level, and intense radar echoes up to near the tropopause. These features were in strong contrast with the GATE simulation, which showed extensive trailing stratiform precipitation containing a horizontally oriented radar bright band. Peak reflectivities were below the melting level, rarely exceeding 50 dBz, with a steady decrease in reflectivity with height above. With the other bulk formulations, the large stratiform rain areas were not reproduced in the GATE conditions.The microphysical structure of the model clouds in both environments were more realistic than that of earlier modeling efforts. Number concentrations of ice of O(100 L1) occurred above 6 km in the GATE model clouds as a result of ice enhancement and rime splintering in the 4ICE runs. These processes were more effective in the GATE simulation, because near the freezing level the weaker updrafts were comparable in

  18. 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…

  19. 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…

  20. Accessibility, Textbooks, and Access Services

    ERIC Educational Resources Information Center

    Kahler, Janice E.

    2017-01-01

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

  1. Living in a 'fat swamp': exposure to multiple sources of accessible, cheap, energy-dense fast foods in a deprived community.

    PubMed

    Saunders, Patrick; Saunders, Annie; Middleton, John

    2015-06-14

    This study assesses the levels of fats, including trans-fatty acids, and salt in common takeaway fast foods in a deprived urban municipality in the West Midlands, England, and implications in the context of the spatial distribution of fast food takeaways. The results of the compositional analysis of over 250 take-out foods were compared with established and derived standards. About 70% of products exceeded the recommendation that a meal should contain less than 30% of a Guideline Daily Amount (GDA). More than half of them exceeded 50% GDA for at least one metric, including 81% of all analyses for SFA. And 17% of samples exceeded the GDA for SFA, including each of two meals that contained about twice the GDA. Over 30% samples exceeded the children's GDA for total fat or SFA. 27% of salt analyses exceeded the GDA. People in Sandwell are exposed to large portion sizes and high levels of fats and salt in takeaway foods, with levels in some foods having increased since 2010. Given this population's limited options to break out of a highly compromising environment of living simultaneously in a 'swamp' of unhealthy, readily accessible and cheap takeaways, and a 'desert' of healthy options, an immediate and innovative package of interventions is required.

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

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

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

  3. Implicit schemes and parallel computing in unstructured grid CFD

    NASA Technical Reports Server (NTRS)

    Venkatakrishnam, V.

    1995-01-01

    The development of implicit schemes for obtaining steady state solutions to the Euler and Navier-Stokes equations on unstructured grids is outlined. Applications are presented that compare the convergence characteristics of various implicit methods. Next, the development of explicit and implicit schemes to compute unsteady flows on unstructured grids is discussed. Next, the issues involved in parallelizing finite volume schemes on unstructured meshes in an MIMD (multiple instruction/multiple data stream) fashion are outlined. Techniques for partitioning unstructured grids among processors and for extracting parallelism in explicit and implicit solvers are discussed. Finally, some dynamic load balancing ideas, which are useful in adaptive transient computations, are presented.

  4. Unique Access to Learning

    ERIC Educational Resources Information Center

    Goble, Don

    2009-01-01

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

  5. Unique Access to Learning

    ERIC Educational Resources Information Center

    Goble, Don

    2009-01-01

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

  6. ISDC Data Access Layer

    NASA Astrophysics Data System (ADS)

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

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

  7. Technical flaws in multiple-choice questions in the access exam to medical specialties ("examen MIR") in Spain (2009-2013).

    PubMed

    Rodríguez-Díez, María Cristina; Alegre, Manuel; Díez, Nieves; Arbea, Leire; Ferrer, Marta

    2016-02-03

    The main factor that determines the selection of a medical specialty in Spain after obtaining a medical degree is the MIR ("médico interno residente", internal medical resident) exam. This exam consists of 235 multiple-choice questions with five options, some of which include images provided in a separate booklet. The aim of this study was to analyze the technical quality of the multiple-choice questions included in the MIR exam over the last five years. All the questions included in the exams from 2009 to 2013 were analyzed. We studied the proportion of questions including clinical vignettes, the number of items related to an image and the presence of technical flaws in the questions. For the analysis of technical flaws, we adapted the National Board of Medical Examiners (NBME) guidelines. We looked for 18 different issues included in the manual, grouped into two categories: issues related to testwiseness and issues related to irrelevant difficulties. The final number of questions analyzed was 1,143. The percentage of items based on clinical vignettes increased from 50% in 2009 to 56-58% in the following years (2010-2013). The percentage of items based on an image increased progressively from 10% in 2009 to 15% in 2012 and 2013. The percentage of items with at least one technical flaw varied between 68 and 72%. We observed a decrease in the percentage of items with flaws related to testwiseness, from 30% in 2009 to 20% in 2012 and 2013. While most of these issues decreased dramatically or even disappeared (such as the imbalance in the correct option numbers), the presence of non-plausible options remained frequent. With regard to technical flaws related to irrelevant difficulties, no improvement was observed; this is especially true with respect to negative stem questions and "hinged" questions. The formal quality of the MIR exam items has improved over the last five years with regard to testwiseness. A more detailed revision of the items submitted, checking

  8. Hybridization schemes for clusters

    NASA Astrophysics Data System (ADS)

    Wales, David J.

    The concept of an optimum hybridization scheme for cluster compounds is developed with particular reference to electron counting. The prediction of electron counts for clusters and the interpretation of the bonding is shown to depend critically upon the presumed hybridization pattern of the cluster vertex atoms. This fact has not been properly appreciated in previous work, particularly in applications of Stone's tensor surface harmonic (TSH) theory, but is found to be a useful tool when dealt with directly. A quantitative definition is suggested for the optimum cluster hybridization pattern based directly upon the ease of interpretation of the molecular orbitals, and results are given for a range of species. The relationship of this scheme to the detailed cluster geometry is described using Löwdin's partitioned perturbation theory, and the success and range of application of TSH theory are discussed.

  9. Efficient Unrestricted Identity-Based Aggregate Signature Scheme

    PubMed Central

    Yuan, Yumin; Zhan, Qian; Huang, Hua

    2014-01-01

    An aggregate signature scheme allows anyone to compress multiple individual signatures from various users into a single compact signature. The main objective of such a scheme is to reduce the costs on storage, communication and computation. However, among existing aggregate signature schemes in the identity-based setting, some of them fail to achieve constant-length aggregate signature or require a large amount of pairing operations which grows linearly with the number of signers, while others have some limitations on the aggregated signatures. The main challenge in building efficient aggregate signature scheme is to compress signatures into a compact, constant-length signature without any restriction. To address the above drawbacks, by using the bilinear pairings, we propose an efficient unrestricted identity-based aggregate signature. Our scheme achieves both full aggregation and constant pairing computation. We prove that our scheme has existential unforgeability under the computational Diffie-Hellman assumption. PMID:25329777

  10. Efficient unrestricted identity-based aggregate signature scheme.

    PubMed

    Yuan, Yumin; Zhan, Qian; Huang, Hua

    2014-01-01

    An aggregate signature scheme allows anyone to compress multiple individual signatures from various users into a single compact signature. The main objective of such a scheme is to reduce the costs on storage, communication and computation. However, among existing aggregate signature schemes in the identity-based setting, some of them fail to achieve constant-length aggregate signature or require a large amount of pairing operations which grows linearly with the number of signers, while others have some limitations on the aggregated signatures. The main challenge in building efficient aggregate signature scheme is to compress signatures into a compact, constant-length signature without any restriction. To address the above drawbacks, by using the bilinear pairings, we propose an efficient unrestricted identity-based aggregate signature. Our scheme achieves both full aggregation and constant pairing computation. We prove that our scheme has existential unforgeability under the computational Diffie-Hellman assumption.

  11. A generalized well management scheme for reservoir simulation

    SciTech Connect

    Fang, W.Y.; Lo, K.K.

    1995-12-31

    A new generalized well management scheme has been formulated to maximize oil production under multiple facility constraints. The scheme integrates reserve performance, wellbore hydraulics, surface facility constraints and lift-gas allocation o maximize oil production. It predicts well performance based on up-to-date hydraulics and reservoir conditions. The scheme has been implemented in a black oil simulator by using Separable programming and Simplex algorithm. This production optimization scheme has been applied to two full-field models. The oil production of these two full-field models is limited by water, gas and liquid haling limits at both field- and flow station-levels. The gas production is limited by injectivity as well as gas handling limits. For a 12-year production forecast on Field A, the new scheme increased oil production by 3 to 9%. For a 12-year production forecast on field B, the new scheme increased oil production by 7 to 9%.

  12. Leaf water storage increases with salinity and aridity in the mangrove Avicennia marina: integration of leaf structure, osmotic adjustment, and access to multiple water sources.

    PubMed

    Nguyen, Hoa T; Meir, Patrick; Sack, Lawren; Evans, John R; Oliveira, Rafael S; Ball, Marilyn C

    2017-04-05

    Leaf structure and water relations were studied in a temperate population of Avicennia marina subsp. australasica along a natural salinity gradient (28 to 49 parts per thousand (ppt)) and compared with two subspecies grown naturally in similar soil salinities to those of subsp. australasica but under different climates: subsp. eucalyptifolia (salinity 30 ppt, wet tropics) and subsp. marina (salinity 46 ppt, arid tropics). Leaf thickness, leaf dry mass per area, and water content increased with salinity and aridity. Turgor loss point declined with increase in soil salinity, driven mainly by differences in osmotic potential at full turgor. Nevertheless, a high modulus of elasticity (ε) contributed to maintenance of high cell hydration at turgor loss point. Despite similarity among leaves in leaf water storage capacitance, total leaf water storage increased with increasing salinity and aridity. The time that stored water alone could sustain an evaporation rate of 1 mmol m(-2) s(-1) ranged from 77 to 126 min from subspecies eucalyptifolia to ssp. marina, respectively. Achieving full leaf hydration or turgor would require water from sources other than the roots, emphasizing the importance of multiple water sources to growth and survival of Avicennia marina across gradients in salinity and aridity.

  13. Optical Access Networks

    NASA Astrophysics Data System (ADS)

    Zheng, Jun; Ansari, Nirwan

    2005-05-01

    are now underway this hot area. The purpose of this feature issue is to expose the networking community to the latest research breakthroughs and progresses in the area of optical access networks. This feature issue aims to present a collection of papers that focus on the state-of-the-art research in various networking aspects of optical access networks. Original papers are solicited from all researchers involved in area of optical access networks. Topics of interest include but not limited to: Optical access network architectures and protocols Passive optical networks (BPON, EPON, GPON, etc.) Active optical networks Multiple access control Multiservices and QoS provisioning Network survivability Field trials and standards Performance modeling and analysis

  14. Optical Access Networks

    NASA Astrophysics Data System (ADS)

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

    2005-04-01

    are now underway this hot area. The purpose of this feature issue is to expose the networking community to the latest research breakthroughs and progresses in the area of optical access networks. This feature issue aims to present a collection of papers that focus on the state-of-the-art research in various networking aspects of optical access networks. Original papers are solicited from all researchers involved in area of optical access networks. Topics of interest include but not limited to: Optical access network architectures and protocols Passive optical networks (BPON, EPON, GPON, etc.) Active optical networks Multiple access control Multiservices and QoS provisioning Network survivability Field trials and standards Performance modeling and analysis

  15. Optical Access Networks

    NASA Astrophysics Data System (ADS)

    Zheng, Jun; Ansari, Nirwan

    2005-06-01

    are now underway this hot area. The purpose of this feature issue is to expose the networking community to the latest research breakthroughs and progresses in the area of optical access networks. This feature issue aims to present a collection of papers that focus on the state-of-the-art research in various networking aspects of optical access networks. Original papers are solicited from all researchers involved in area of optical access networks. Topics of interest include but not limited to: Optical access network architectures and protocols Passive optical networks (BPON, EPON, GPON, etc.) Active optical networks Multiple access control Multiservices and QoS provisioning Network survivability Field trials and standards Performance modeling and analysis

  16. A New Era of Open Access?

    ERIC Educational Resources Information Center

    Mercieca, Paul; Macauley, Peter

    2008-01-01

    There has been a push for open access journals for more than a decade in a higher education and research environment in which the "publish or perish" syndrome is as dominant as ever. This article examines the success, or otherwise, of open access schemes in light of the Excellence in Research for Australia (ERA) initiative. It compares…

  17. A New Era of Open Access?

    ERIC Educational Resources Information Center

    Mercieca, Paul; Macauley, Peter

    2008-01-01

    There has been a push for open access journals for more than a decade in a higher education and research environment in which the "publish or perish" syndrome is as dominant as ever. This article examines the success, or otherwise, of open access schemes in light of the Excellence in Research for Australia (ERA) initiative. It compares…

  18. Scalable Nonlinear Compact Schemes

    SciTech Connect

    Ghosh, Debojyoti; Constantinescu, Emil M.; Brown, Jed

    2014-04-01

    In this work, we focus on compact schemes resulting in tridiagonal systems of equations, specifically the fifth-order CRWENO scheme. We propose a scalable implementation of the nonlinear compact schemes by implementing a parallel tridiagonal solver based on the partitioning/substructuring approach. We use an iterative solver for the reduced system of equations; however, we solve this system to machine zero accuracy to ensure that no parallelization errors are introduced. It is possible to achieve machine-zero convergence with few iterations because of the diagonal dominance of the system. The number of iterations is specified a priori instead of a norm-based exit criterion, and collective communications are avoided. The overall algorithm thus involves only point-to-point communication between neighboring processors. Our implementation of the tridiagonal solver differs from and avoids the drawbacks of past efforts in the following ways: it introduces no parallelization-related approximations (multiprocessor solutions are exactly identical to uniprocessor ones), it involves minimal communication, the mathematical complexity is similar to that of the Thomas algorithm on a single processor, and it does not require any communication and computation scheduling.

  19. A privacy enhanced authentication scheme for telecare medical information systems.

    PubMed

    Jiang, Qi; Ma, Jianfeng; Ma, Zhuo; Li, Guangsong

    2013-02-01

    The telecare medical information system (TMIS) aims to establish telecare services and enable the public to access medical services or medical information at remote sites. Authentication and key agreement is essential to ensure data integrity, confidentiality, and availability for TMIS. Most recently, Chen et al. proposed an efficient and secure dynamic ID-based authentication scheme for TMIS, and claimed that their scheme achieves user anonymity. However, we observe that Chen et al.'s scheme achieves neither anonymity nor untraceability, and is subject to the identity guessing attack and tracking attack. In order to protect user privacy, we propose an enhanced authentication scheme which achieves user anonymity and untraceablity. It is a secure and efficient authentication scheme with user privacy preservation which is practical for TMIS.

  20. Performance of hashed cache data migration schemes on multicomputers

    NASA Technical Reports Server (NTRS)

    Hiranandani, Seema; Saltz, Joel; Mehrotra, Piyush; Berryman, Harry

    1991-01-01

    After conducting an examination of several data-migration mechanisms which permit an explicit and controlled mapping of data to memory, a set of schemes for storage and retrieval of off-processor array elements is experimentally evaluated and modeled. All schemes considered have their basis in the use of hash tables for efficient access of nonlocal data. The techniques in question are those of hashed cache, partial enumeration, and full enumeration; in these, nonlocal data are stored in hash tables, so that the operative difference lies in the amount of memory used by each scheme and in the retrieval mechanism used for nonlocal data.

  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. 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…

  3. Open Access

    ERIC Educational Resources Information Center

    Suber, Peter

    2012-01-01

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

  4. 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…

  5. Social capital and active membership in the Ghana National Health Insurance Scheme - a mixed method study.

    PubMed

    Fenenga, Christine J; Nketiah-Amponsah, Edward; Ogink, Alice; Arhinful, Daniel K; Poortinga, Wouter; Hutter, Inge

    2015-11-02

    People's decision to enroll in a health insurance scheme is determined by socio-cultural and socio-economic factors. On request of the National health Insurance Authority (NHIA) in Ghana, our study explores the influence of social relationships on people's perceptions, behavior and decision making to enroll in the National Health Insurance Scheme. This social scheme, initiated in 2003, aims to realize accessible quality healthcare services for the entire population of Ghana. We look at relationships of trust and reciprocity between individuals in the communities (so called horizontal social capital) and between individuals and formal health institutions (called vertical social capital) in order to determine whether these two forms of social capital inhibit or facilitate enrolment of clients in the scheme. Results can support the NHIA in exploiting social capital to reach their objective and strengthen their policy and practice. We conducted 20 individual- and seven key-informant interviews, 22 focus group discussions, two stakeholder meetings and a household survey, using a random sample of 1903 households from the catchment area of 64 primary healthcare facilities. The study took place in Greater Accra Region and Western Regions in Ghana between June 2011 and March 2012. While social developments and increased heterogeneity seem to reduce community solidarity in Ghana, social networks remain common in Ghana and are valued for their multiple benefits (i.e. reciprocal trust and support, information sharing, motivation, risk sharing). Trusting relations with healthcare and insurance providers are, according healthcare clients, based on providers' clear communication, attitude, devotion, encouragement and reliability of services. Active membership of the NHIS is positive associated with community trust, trust in healthcare providers and trust in the NHIS (p-values are .009, .000 and .000 respectively). Social capital can motivate clients to enroll in health insurance

  6. Massive momentum-subtraction scheme

    NASA Astrophysics Data System (ADS)

    Boyle, Peter; Del Debbio, Luigi; Khamseh, Ava

    2017-03-01

    A new renormalization scheme is defined for fermion bilinears in QCD at nonvanishing quark masses. This new scheme, denoted RI/mSMOM, preserves the benefits of the nonexceptional momenta introduced in the RI/SMOM scheme and allows a definition of renormalized composite fields away from the chiral limit. Some properties of the scheme are investigated by performing explicit one-loop computation in dimensional regularization.

  7. ESCAP mobile training scheme.

    PubMed

    Yasas, F M

    1977-01-01

    In response to a United Nations resolution, the Mobile Training Scheme (MTS) was set up to provide training to the trainers of national cadres engaged in frontline and supervisory tasks in social welfare and rural development. The training is innovative in its being based on an analysis of field realities. The MTS team consisted of a leader, an expert on teaching methods and materials, and an expert on action research and evaluation. The country's trainers from different departments were sent to villages to work for a short period and to report their problems in fulfilling their roles. From these grass roots experiences, they made an analysis of the job, determining what knowledge, attitude and skills it required. Analysis of daily incidents and problems were used to produce indigenous teaching materials drawn from actual field practice. How to consider the problems encountered through government structures for policy making and decisions was also learned. Tasks of the students were to identify the skills needed for role performance by job analysis, daily diaries and project histories; to analyze the particular community by village profiles; to produce indigenous teaching materials; and to practice the role skills by actual role performance. The MTS scheme was tried in Nepal in 1974-75; 3 training programs trained 25 trainers and 51 frontline workers; indigenous teaching materials were created; technical papers written; and consultations were provided. In Afghanistan the scheme was used in 1975-76; 45 participants completed the training; seminars were held; and an ongoing Council was created. It is hoped that the training program will be expanded to other countries.

  8. Convering ARQ schemes

    NASA Astrophysics Data System (ADS)

    Arazi, B.; Hsieh, J.

    1985-04-01

    The parity check matrix of an (n, k, t) linear error-correcting code provides a unique mapping between binary vectors of length n, whose Hamming weight does not exceed t, and binary vectors of length (n-k) which are the syndrome obtained by multiplying the vector of length n by the parity check matrix. This enables the 'compression' of binary vectors having a limited Hamming weight. It is shown in the paper how this principle can be applied in ARQ schemes, where, upon detection of an error in a received message, further retransmitted messages can be made shorter from one retransmission to the next.

  9. Grading Scheme, Test Difficulty, and the Immediate Feedback Assessment Technique

    ERIC Educational Resources Information Center

    DiBattista, David; Gosse, Leanne; Sinnige-Egger, Jo-Anne; Candale, Bela; Sargeson, Kim

    2009-01-01

    The authors examined how the grading scheme affects learning and students' reactions to the Immediate Feedback Assessment Technique (IFAT), an answer form providing immediate feedback on multiple-choice questions. Undergraduate students (N = 141) took a general-knowledge multiple-choice test of low, medium, or high difficulty. They used the IFAT…

  10. GC-based dynamic QoS priority handoff scheme in multimedia cellular systems

    NASA Astrophysics Data System (ADS)

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

    2001-03-01

    A dynamic call admission control (CAC) and its associated resource reservation (RR) schemes are proposed in this research based on the guard channel (GC) concept for a wireless cellular system supporting multiple QoS classes. A comprehensive service model is developed, which includes not only mobile terminals' bandwidth requirements but also their different levels of priorities, rate adaptivity and mobility. The proposed CAC policy selects the resource access thresold according to the estimated number of incoming call requests of different QoS classes. The amount of resources to be reserved is dynamically adjusted by considering neighboring-cell higher-priority calls which are likely to handoff. The handoff interaction between adjacent cells is estimated by using radio propagation in terms of the signal-to-noise ratio (SNR) and the distance of each active call in neighboring cells. Experiments are conducted by using the OPNET simulator to study the performance of the proposed scheme under various traffic conditions. It is shown that better QoS guarantees can be provided by the proposed CAC and RR schemes.

  11. A scalable key management scheme with minimizing rekey cost for secure multicast over satellite networks

    NASA Astrophysics Data System (ADS)

    Gao, Junwei; Yang, Zongkai; Xie, Haitao

    2007-11-01

    Satellite networks are playing a more and more important role in network infrastructure. They are useful in providing broadband connectivity to remote locations which are harder to reach through terrestrial infrastructure. Data confidentiality and integrity are two critical issues for satellite networks. The multicast traffic should be accessible only to subscribers, this requires security and efficient methods to generate, distribute and update the keys. Access control can be achieved by data encryption, such as end to end security mechanisms----IPSec. Due to the high rekeying cost, most current key management protocols do not scale well for secure multicast over satellite networks. In this article we proposed a scalable key management scheme to provide secure communication in satellite networks with minimal key management overhead. The principle of this approach is to break up IPSec encryption into multiple encryption zones on a single packet and encrypts different regions of the IP packet using different keys. All of those keys are composed into just only one multi group key tree for secure multicast over satellite networks. The proposed scheme can reduce the communication and storage overhead significantly. In addition, the proposed key graph is scalable well.

  12. 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)

  13. 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)

  14. Proposal for a Small Scheme Implementation.

    DTIC Science & Technology

    1984-10-01

    5,-s Accession For ...- NTIS GRA&I DTIC TAB Unannounced ,,-- ,.. Justification By Avaii1," lit-- .c-des Dist j Sp-cio 0U . 8STD S. / Un~lasmiffied P’O...8217 IS[CUNITY CLASLSIICATIO#4 O P THIS PA O6I(I~ . 0.1. Eatoure ) Proposal for a Small Scheme Implementation, by "" Richard Schooler and James W...built.in routines. The garbage collector also needs to distinguish pointers from immediate data. To simplify ~.- "’ p . ’.s garbage collection and permit

  15. 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.

  16. Outcome-based health equity across different social health insurance schemes for the elderly in China.

    PubMed

    Liu, Xiaoting; Wong, Hung; Liu, Kai

    2016-01-14

    Against the achievement of nearly universal coverage for social health insurance for the elderly in China, a problem of inequity among different insurance schemes on health outcomes is still a big challenge for the health care system. Whether various health insurance schemes have divergent effects on health outcome is still a puzzle. Empirical evidence will be investigated in this study. This study employs a nationally representative survey database, the National Survey of the Aged Population in Urban/Rural China, to compare the changes of health outcomes among the elderly before and after the reform. A one-way ANOVA is utilized to detect disparities in health care expenditures and health status among different health insurance schemes. Multiple Linear Regression is applied later to examine the further effects of different insurance plans on health outcomes while controlling for other social determinants. The one-way ANOVA result illustrates that although the gaps in insurance reimbursements between the Urban Employee Basic Medical Insurance (UEBMI) and the other schemes, the New Rural Cooperative Medical Scheme (NCMS) and Urban Residents Basic Medical Insurance (URBMI) decreased, out-of-pocket spending accounts for a larger proportion of total health care expenditures, and the disparities among different insurances enlarged. Results of the Multiple Linear Regression suggest that UEBMI participants have better self-reported health status, physical functions and psychological wellbeing than URBMI and NCMS participants, and those uninsured. URBMI participants report better self-reported health than NCMS ones and uninsured people, while having worse psychological wellbeing compared with their NCMS counterparts. This research contributes to a transformation in health insurance studies from an emphasis on the opportunity-oriented health equity measured by coverage and healthcare accessibility to concern with outcome-based equity composed of health expenditure and health

  17. Experimental Evaluation of LIDAR Data Visualization Schemes

    NASA Astrophysics Data System (ADS)

    Ghosh, S.; Lohan, B.

    2012-07-01

    LiDAR (Light Detection and Ranging) has attained the status of an industry standard method of data collection for gathering three dimensional topographic information. Datasets captured through LiDAR are dense, redundant and are perceivable from multiple directions, which is unlike other geospatial datasets collected through conventional methods. This three dimensional information has triggered an interest in the scientific community to develop methods for visualizing LiDAR datasets and value added products. Elementary schemes of visualization use point clouds with intensity or colour, triangulation and tetrahedralization based terrain models draped with texture. Newer methods use feature extraction either through the process of classification or segmentation. In this paper, the authors have conducted a visualization experience survey where 60 participants respond to a questionnaire. The questionnaire poses six different questions on the qualities of feature perception and depth for 12 visualization schemes. The answers to these questions are obtained on a scale of 1 to 10. Results are thus presented using the non-parametric Friedman's test, using post-hoc analysis for hypothetically ranking the visualization schemes based on the rating received and finally confirming the rankings through the Page's trend test. Results show that a heuristic based visualization scheme, which has been developed by Ghosh and Lohani (2011) performs the best in terms of feature and depth perception.

  18. An Energy Efficient Cooperative Hierarchical MIMO Clustering Scheme for Wireless Sensor Networks

    PubMed Central

    Nasim, Mehwish; Qaisar, Saad; Lee, Sungyoung

    2012-01-01

    In this work, we present an energy efficient hierarchical cooperative clustering scheme for wireless sensor networks. Communication cost is a crucial factor in depleting the energy of sensor nodes. In the proposed scheme, nodes cooperate to form clusters at each level of network hierarchy ensuring maximal coverage and minimal energy expenditure with relatively uniform distribution of load within the network. Performance is enhanced by cooperative multiple-input multiple-output (MIMO) communication ensuring energy efficiency for WSN deployments over large geographical areas. We test our scheme using TOSSIM and compare the proposed scheme with cooperative multiple-input multiple-output (CMIMO) clustering scheme and traditional multihop Single-Input-Single-Output (SISO) routing approach. Performance is evaluated on the basis of number of clusters, number of hops, energy consumption and network lifetime. Experimental results show significant energy conservation and increase in network lifetime as compared to existing schemes. PMID:22368459

  19. An energy efficient cooperative hierarchical MIMO clustering scheme for wireless sensor networks.

    PubMed

    Nasim, Mehwish; Qaisar, Saad; Lee, Sungyoung

    2012-01-01

    In this work, we present an energy efficient hierarchical cooperative clustering scheme for wireless sensor networks. Communication cost is a crucial factor in depleting the energy of sensor nodes. In the proposed scheme, nodes cooperate to form clusters at each level of network hierarchy ensuring maximal coverage and minimal energy expenditure with relatively uniform distribution of load within the network. Performance is enhanced by cooperative multiple-input multiple-output (MIMO) communication ensuring energy efficiency for WSN deployments over large geographical areas. We test our scheme using TOSSIM and compare the proposed scheme with cooperative multiple-input multiple-output (CMIMO) clustering scheme and traditional multihop Single-Input-Single-Output (SISO) routing approach. Performance is evaluated on the basis of number of clusters, number of hops, energy consumption and network lifetime. Experimental results show significant energy conservation and increase in network lifetime as compared to existing schemes.

  20. Observational Study Assessing Demographic, Economic and Clinical Factors Associated with Access and Utilization of Health Care Services of Patients with Multiple Sclerosis under Treatment with Interferon Beta-1b (EXTAVIA)

    PubMed Central

    Tsivgoulis, Georgios; Doskas, Triantafyllos; Petrou, Damianos; Makris, Nikolaos; Vlaikidis, Nikolaos; Thomaidis, Thomas; Kyritsis, Athanasios; Fakas, Nikolaos; Treska, Xoulietta; Karageorgiou, Clementine; Sotirli, Stefania; Giannoulis, Christos; Papadimitriou, Dimitra; Mylonas, Ioannis; Kouremenos, Evaggelos; Vlachos, Georgios; Georgiopoulos, Dimitrios; Mademtzoglou, Despoina; Vikelis, Michalis; Zintzaras, Elias

    2014-01-01

    Multiple sclerosis (MS) results in an extensive use of the health care system, even within the first years of diagnosis. The effectiveness and accessibility of the health care system may affect patients' quality of life. The aim of the present study was to evaluate the health care resource use of MS patients under interferon beta-1b (EXTAVIA) treatment in Greece, the demographic or clinical factors that may affect this use and also patient satisfaction with the health care system. Structured interviews were conducted for data collection. In total, 204 patients (74.02% females, mean age (SD) 43.58 (11.42) years) were enrolled in the study. Analysis of the reported data revealed that during the previous year patients made extensive use of health services in particular neurologists (71.08% visited neurologists in public hospitals, 66.67% in private offices and 48.53% in insurance institutes) and physiotherapists. However, the majority of the patients (52.45%) chose as their treating doctor private practice neurologists, which may reflect accessibility barriers or low quality health services in the public health system. Patients seemed to be generally satisfied with the received health care, support and information on MS (84.81% were satisfied from the information provided to them). Patients' health status (as denoted by disease duration, disability status and hospitalization needs) and insurance institute were found to influence their visits to neurologists. Good adherence (up to 70.1%) to the study medication was reported. Patients' feedback on currently provided health services could direct these services towards the patients' expectations. PMID:25419842