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Sample records for carrier sense multiple access

  1. A MAC protocol of underwater acoustic sensor networks based on carrier sense multiple access%水声通信网基于载波侦听多路访问的MAC协议

    Institute of Scientific and Technical Information of China (English)

    智纳纳; 刘广钟; 徐明

    2015-01-01

    水下环境的限制,使得水声传感网络具有一些特别的特点。针对已存在的水声通信网络的 MAC 协议的不足,如信道利用率低、时间槽等待空闲时间、时间同步的头部等问题,提出了一种新型的基于载波侦听多路访问/无碰撞的 MAC 协议———CSMA/CF ( Carrier Sense Multiple Access/Collision Free )。该协议通过对网络中的所有节点进行排序,从而使网络中的节点在发送数据帧时具有相同的方向,从而避免冲突。也就是说,按顺序的上一个节点发送完数据之后,该节点立即发送数据,而不必等待一个最大的传输延迟。仿真结果显示,该协议在水声环境中具有较好的网络性能。%Due to limitation of the underwater environment, the underwater acoustic sensor networks(UWASN) has some unique features. Regarding the deficiency of the existing MAC protocol for UWASN, low utilization of channel, the time slot idle time waiting, head of time synchronization and other issues, a MAC protocol of UWASN based on Carrier Sense Multiple Access/Collision Free is raised in this paper. By sorting all station in the network, the station transmits data with the same direction to avoid collision. In other words, after sending data by a sequence of nodes, the nodes send data immediately, instead of waiting for the longest transmission delay. The simulation results show that the protocol in UWASN has better network performance.

  2. Sensing Throughput Optimization in Fading Cognitive Multiple Access Channels With Energy Harvesting Secondary Transmitters

    OpenAIRE

    Biswas, Sinchan; Shirazinia, Amirpasha; Dey, Subhrakanti

    2016-01-01

    The paper investigates the problem of maximizing expected sum throughput in a fading multiple access cognitive radio network when secondary user (SU) transmitters have energy harvesting capability, and perform cooperative spectrum sensing. We formulate the problem as maximization of sum-capacity of the cognitive multiple access network over a finite time horizon subject to a time averaged interference constraint at the primary user (PU) and almost sure energy causality constraints at the SUs....

  3. Performance Analysis of Multiple Access 60 GHz System Using Frequency-shifted Gaussian Pulse and Non-carrier PSWF Pulse

    OpenAIRE

    Hao Zhang; Wei Shi; Tingting Lu; Jingjing Wang; Xinjie Wang

    2013-01-01

    In this paper, a kind of impulse radio (IR) 60 GHz pulse based on Prolate Spheroidal Wave Functions (PSWF) is proposed. The capacity and performance for multiple access 60 GHz communication system based on carrier pulse and impulse radio pulse are analyzed separately. Both frequency-shifted Gaussian pulse and Prolate Spheroidal Wave Functions (PSWF) pulse are considered and devised according to the federal communication commission (FCC) power constraints. Pulse position modulation (PPM) with ...

  4. Performance Analysis of Global Search Algorithm Based Multiuser Detector for Multi Carrier Code Division Multiple Access System under Clipping Noise

    Directory of Open Access Journals (Sweden)

    S. Sivanesskumar

    2011-01-01

    Full Text Available Problem statement: Multi Carrier Code Division Multiple Access (MC-CDMA, a promising technology for the 4G communication systems. The major limitation of MC-CDMA system is the Multiple Access Interference (MAI which is due to near-far effect, frequency offset and nonlinear power amplification due to clipping noise. Approach: The performance of MC-CDMA under clipping noise using Global search algorithm based Multiuser detector in AWGN, Rayleigh and Rician channel is analyzed in this study. Results: The proposed method is simulated using BPSK modulation, Walsh spreading code, number of subcarriers 64 and number of users 16 and clipping noise. Conclusion: By simulation result, BER in AWGN channel outperforms other channels as SNR is increased. The performance of Rician fading channel is better than that of Rayleigh fading channel, because of the LOS path.

  5. Efficient Detection Algorithm for a Multiple-Input and Multiple-Output Multiuser Multi-Carrier Code Division Multiple Access in Time-Varying Channels

    Directory of Open Access Journals (Sweden)

    Fares Sayadi

    2009-01-01

    Full Text Available Problem statement: Maximum Likelihood (ML decoding has been applied for the uplink ofappr a Multi-Carrier Code Division Multiple Access (MC-CDMA system based on Orthogonal Frequency Division Multiplexing (OFDM. Multiple-Input Multiple-Output (MIMO channel from k users, which moves at vehicular speed, to the Base-Station (BS is time-varying. For time-varying channels, Sphere Decoding (SD was introduced to perform ML decoding. Whereas, computational complexity of SD (due to a QR-factorization for each symbol, is nevertheless high. Modified SD had been proposed to achieve near optimum solutions that called Subspace-Sphere Decoder (SPSD. Approach: Proposed algorithm was based on subspace and orthogonal projection with very small dimensionality as robustness scheme in an iterative Multi-User Detection (MUD and Parallel Interference Cancelation (PIC method. Results: This approach had been achieved intense reduction of computational complexity for time-varying channel via one and more than one order of magnitude at channel estimation and multiuser detection respectively. Furthermore, SPSD was robustness to channel estimation error (about 3.8 dB as compared to the representative counterparts in literature. Conclusion: Effectiveness of proposed method was demonstrated by simulations.

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

    Science.gov (United States)

    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.

  7. Carrier sense data highway system

    Science.gov (United States)

    Frankel, Robert

    1984-02-14

    A data transmission system includes a transmission medium which has a certain propagation delay time over its length. A number of data stations are successively coupled to the transmission medium for communicating with one another. Each of the data stations includes a transmitter for originating signals, each signal beginning with a carrier of a duration which is at least the propagation delay time of the transmission medium. Each data station also includes a receiver which receives other signals from other data stations and inhibits operation of the transmitter at the same data station when a carrier of another signal is received.

  8. Study on additional carrier sensing for IEEE 802.15.4 wireless sensor networks.

    Science.gov (United States)

    Lee, Bih-Hwang; Lai, Ruei-Lung; Wu, Huai-Kuei; Wong, Chi-Ming

    2010-01-01

    Wireless sensor networks based on the IEEE 802.15.4 standard are able to achieve low-power transmissions in the guise of low-rate and short-distance wireless personal area networks (WPANs). The slotted carrier sense multiple access with collision avoidance (CSMA/CA) is used for contention mechanism. Sensor nodes perform a backoff process as soon as the clear channel assessment (CCA) detects a busy channel. In doing so they may neglect the implicit information of the failed CCA detection and further cause the redundant sensing. The blind backoff process in the slotted CSMA/CA will cause lower channel utilization. This paper proposes an additional carrier sensing (ACS) algorithm based on IEEE 802.15.4 to enhance the carrier sensing mechanism for the original slotted CSMA/CA. An analytical Markov chain model is developed to evaluate the performance of the ACS algorithm. Both analytical and simulation results show that the proposed algorithm performs better than IEEE 802.15.4, which in turn significantly improves throughput, average medium access control (MAC) delay and power consumption of CCA detection.

  9. Study on Additional Carrier Sensing for IEEE 802.15.4 Wireless Sensor Networks

    Directory of Open Access Journals (Sweden)

    Bih-Hwang Lee

    2010-06-01

    Full Text Available Wireless sensor networks based on the IEEE 802.15.4 standard are able to achieve low-power transmissions in the guise of low-rate and short-distance wireless personal area networks (WPANs. The slotted carrier sense multiple access with collision avoidance (CSMA/CA is used for contention mechanism. Sensor nodes perform a backoff process as soon as the clear channel assessment (CCA detects a busy channel. In doing so they may neglect the implicit information of the failed CCA detection and further cause the redundant sensing. The blind backoff process in the slotted CSMA/CA will cause lower channel utilization. This paper proposes an additional carrier sensing (ACS algorithm based on IEEE 802.15.4 to enhance the carrier sensing mechanism for the original slotted CSMA/CA. An analytical Markov chain model is developed to evaluate the performance of the ACS algorithm. Both analytical and simulation results show that the proposed algorithm performs better than IEEE 802.15.4, which in turn significantly improves throughput, average medium access control (MAC delay and power consumption of CCA detection.

  10. Is CSMA Able to Coordinate Multiple Access in Vehicular Radio Channels Effectively?

    OpenAIRE

    Mittag, J.; Hartenstein, H.

    2012-01-01

    The first generation of inter-vehicle communication networks will most likely be based on the IEEE 802.11p standard. That is, they are going to deploy Carrier Sense Multiple Access (CSMA) to coordinate channel access among neighboring vehicles. Recently, concerns have been raised that fast-fading propagation conditions, i.e. a time- and frequency-selective fading as reported by several measurement campaigns in highway environments, might challenge the effectiveness of CSMA. These concerns als...

  11. Carrier Sense Random Packet CDMA Protocol in Dual-Channel Networks

    Directory of Open Access Journals (Sweden)

    C. Du

    2015-06-01

    Full Text Available Code resource wastage is caused by the reason that many hopping frequency (FH sequences are unused, which occurs under the condition that the number of the actual subnets needed for the tactical network is far smaller than the networking capacity of code division net¬working. Dual-channel network (DCN, consisting of one single control channel and multiple data channels, can solve the code resource wastage effectively. To improve the anti-jamming capability of the control channel of DCN, code division multiple access (CDMA technology was introduced, and a carrier sense random packet (CSRP CDMA protocol based on random packet CDMA (RP-CDMA was proposed. In CSRP-CDMA, we provide a carrier sensing random packet mechanism and a packet-segment acknowledgement policy. Furthermore, an analytical model was developed to evaluate the performance of CSRP-CDMA networks. In this model, the impacts of multi-access interference from both inter-clusters and intra-clusters were analyzed, and the mathematical expressions of packet transmission success probability, normalized network throughput and signal interference to noise ratio, were also derived. Analytical and simulation results demonstrate that the normalized network throughput of CSRP-CDMA outperforms traditional RP-CDMA by 10%, which can guarantee the resource utilization efficiency of the control channel in DCNs.

  12. Blind Estimation of Multiple Carrier Frequency Offsets

    CERN Document Server

    Yu, Yuanning; Poor, H Vincent; Koivunen, Visa

    2007-01-01

    Multiple carrier-frequency offsets (CFO) arise in a distributed antenna system, where data are transmitted simultaneously from multiple antennas. In such systems the received signal contains multiple CFOs due to mismatch between the local oscillators of transmitters and receiver. This results in a time-varying rotation of the data constellation, which needs to be compensated for at the receiver before symbol recovery. This paper proposes a new approach for blind CFO estimation and symbol recovery. The received base-band signal is over-sampled, and its polyphase components are used to formulate a virtual Multiple-Input Multiple-Output (MIMO) problem. By applying blind MIMO system estimation techniques, the system response is estimated and used to subsequently transform the multiple CFOs estimation problem into many independent single CFO estimation problems. Furthermore, an initial estimate of the CFO is obtained from the phase of the MIMO system response. The Cramer-Rao Lower bound is also derived, and the la...

  13. Selective Sensing and Access Strategy to Maximize Throughput in Cognitive Radio Sensor Network

    OpenAIRE

    Weijun Li; Chao Yang; Zhenquan Wu; Beihai Tan; Yuli Fu

    2014-01-01

    This paper presents a selective spectrum sensing and access strategy in a cognitive radio sensor network (CRSN), in order to maximize the throughput of secondary user (SU) system. An SU senses multiple channels simultaneously via wideband spectrum sensing. To maximize the throughput and reduce the sensing energy consumption, not all of the channels are sensed. The SU selects some channels for spectrum sensing and accesses these channels based on the sensing results. The unselected channels ar...

  14. Combating Impairments in Multi-carrier Systems: A Compressed Sensing Approach

    KAUST Repository

    Al-Shuhail, Shamael

    2015-05-01

    Multi-carrier systems suffer from several impairments, and communication system engineers use powerful signal processing tools to combat these impairments and keep up with the capacity/rate demands. Compressed sensing (CS) is one such tool that allows recovering any sparse signal, requiring only a few measurements in a domain that is incoherent with the domain of sparsity. Almost all signals of interest have some degree of sparsity, and in this work we utilize the sparsity of impairments in orthogonal frequency division multiplexing (OFDM) and its variants (i.e., orthogonal frequency division multiplexing access (OFDMA) and single-carrier frequency-division multiple access (SC-FDMA)) to combat them using CS. We start with the problem of peak-to-average power ratio (PAPR) reduction in OFDM. OFDM signals suffer from high PAPR and clipping is the simplest PAPR reduction scheme. However, clipping introduces inband distortions that result in compromised performance and hence needs to be mitigated at the receiver. Due to the high PAPR nature of the OFDM signal, only a few instances are clipped, these clipping distortions can be recovered at the receiver by employing CS. We then extend the proposed clipping recovery scheme to an interleaved OFDMA system. Interleaved OFDMA presents a special structure that result in only self-inflicted clipping distortions. In this work, we prove that distortions do not spread over multiple users (while utilizing interleaved carrier assignment in OFDMA) and construct a CS system that recovers the clipping distortions on each user. Finally, we address the problem of narrowband interference (NBI) in SC-FDMA. Unlike OFDM and OFDMA systems, SC-FDMA does not suffer from high PAPR, but (as the data is encoded in time domain) is seriously vulnerable to information loss owing to NBI. Utilizing the sparse nature of NBI (in frequency domain) we combat its effect on SC-FDMA system by CS recovery.

  15. Open-access microcavities for chemical sensing

    Science.gov (United States)

    Vallance, Claire; Trichet, Aurelien A. P.; James, Dean; Dolan, Philip R.; Smith, Jason M.

    2016-07-01

    The recent development of open-access optical microcavities opens up a number of intriguing possibilities in the realm of chemical sensing. We provide an overview of the different possible sensing modalities, with examples of refractive index sensing, optical absorption measurements, and optical tracking and trapping of nanoparticles. The extremely small mode volumes within an optical microcavity allow very small numbers of molecules to be probed: our current best detection limits for refractive index and absorption sensing are around 105 and 102 molecules, respectively, with scope for further improvements in the future.

  16. Optimality of Multichannel Myopic Sensing in the Presence of Sensing Error for Opportunistic Spectrum Access

    Directory of Open Access Journals (Sweden)

    Xiaofeng Jiang

    2013-01-01

    Full Text Available The optimization problem for the performance of opportunistic spectrum access is considered in this study. A user, with the limited sensing capacity, has opportunistic access to a communication system with multiple channels. The user can only choose several channels to sense and decides whether to access these channels based on the sensing information in each time slot. Meanwhile, the presence of sensing error is considered. A reward is obtained when the user accesses a channel. The objective is to maximize the expected (discounted or average reward accrued over an infinite horizon. This problem can be formulated as a partially observable Markov decision process. This study shows the optimality of the simple and robust myopic policy which focuses on maximizing the immediate reward. The results show that the myopic policy is optimal in the case of practical interest.

  17. A Novel Multiple Access Protocol for Mobile Ad Hoc Network with Smart Antennas

    Institute of Scientific and Technical Information of China (English)

    YANGJun; LIJiandong; ZHOUXiaodong

    2004-01-01

    The approach to employ smart antennas in Mobile ad hoc network (MANET) nodes is presented. An adaptive beamforming-Carrier-Sense multiple access/collison avoidance) (ABF-CSMA/CA) protocol is proposed. In the ABF-CSMA/CA, Request-to-Send/Clear-to-Send (RTS/CTS) dialogue is used to distribute channel reservation information. Training sequences are transmitted just before RTS and CTS packets, so the Temporal reference beamforming (TRB) can be performed by the source node and the destination node.An improved virtual carrier-sense mechanism is also proposed to enhance Collision avoidance (CA) and obtain efficient Space division multiple access (SDMA). In this scheme, every node has two kinds of Network allocation vector (NAV): an oNAV maintains the interval of ongoing transmission of neighbors whose smart antennas operate in omnidirectional mode, and multiple bNAVs maintain those intervals of neighbors whose smart antennas operate in beamforming mode. Theoretical analysis of channel utilization of the proposed protocol is presented. Results show that ABF-CSMA/CA protocol combining with smart antennas can provide higher channel utilization.

  18. Extending the unambiguous velocity range using multiple carrier frequencies

    DEFF Research Database (Denmark)

    Zhang, Z.; Jakobsson, A.; Nikolov, Svetoslav;

    2005-01-01

    Typically, velocity estimators based on the estimation of the Doppler shift will suffer from a limited unambiguous velocity range. Proposed are two novel multiple carrier based velocity estimators extending the velocity range above the Nyquist velocity limit. Numerical simulations indicate...

  19. Generating Functionals of Random Packing Point Processes: From Hard-Core to Carrier Sensing

    CERN Document Server

    Viet, Nguyen Tien

    2012-01-01

    In this paper we study the generating functionals of several models of random packing processes: the classical Mat\\'ern hard-core model; its extensions, the $k$-Mat\\'ern models and the $\\infty$-Mat\\'ern model, which is an example of random sequential packing process. The main new results are: 1) a sufficient condition for the $\\infty$-Mat\\'ern model to be well-defined (unlike the other two, the $\\infty$-Mat\\'ern model may not be well-defined on unbounded spaces); 2) the generating functional of the resulting point process which is given for each of the three models as the solution of a differential equation; 3) series representations and bounds on the generating functional of the packing models; 4) moment measures and other useful properties of the considered packing models which are derived from their generating functionals. These results are applied to various stochastic geometry problems and in particular to the modeling and the analysis of a wireless Carrier Sensing Multiple Access network.

  20. Enhancing Sensing and Channel Access in Cognitive Radio Networks

    KAUST Repository

    Hamza, Doha R.

    2014-06-18

    Cognitive radio technology is a promising technology to solve the wireless spectrum scarcity problem by intelligently allowing secondary, or unlicensed, users access to the primary, licensed, users\\' frequency bands. Cognitive technology involves two main tasks: 1) sensing the wireless medium to assess the presence of the primary users and 2) designing secondary spectrum access techniques that maximize the secondary users\\' benefits while maintaining the primary users\\' privileged status. On the spectrum sensing side, we make two contributions. First, we maximize a utility function representing the secondary throughput while constraining the collision probability with the primary below a certain value. We optimize therein the channel sensing time, the sensing decision threshold, the channel probing time, together with the channel sensing order for wideband primary channels. Second, we design a cooperative spectrum sensing technique termed sensing with equal gain combining whereby cognitive radios simultaneously transmit their sensing results to the fusion center over multipath fading reporting channels. The proposed scheme is shown to outperform orthogonal reporting systems in terms of achievable secondary throughput and to be robust against phase and synchronization errors. On the spectrum access side, we make four contributions. First, we design a secondary scheduling scheme with the goal of minimizing the secondary queueing delay under constraints on the average secondary transmit power and the maximum tolerable primary outage probability. Second, we design another secondary scheduling scheme based on the spectrum sensing results and the primary automatic repeat request feedback. The optimal medium access probabilities are obtained via maximizing the secondary throughput subject to constraints that guarantee quality of service parameters for the primary. Third, we propose a three-message superposition coding scheme to maximize the secondary throughput without

  1. Carrier multiplication in silicon nanocrystals: ab initio results

    Directory of Open Access Journals (Sweden)

    Ivan Marri

    2015-02-01

    Full Text Available One of the most important goals in the field of renewable energy is the development of original solar cell schemes employing new materials to overcome the performance limitations of traditional solar cell devices. Among such innovative materials, nanostructures have emerged as an important class of materials that can be used to realize efficient photovoltaic devices. When these systems are implemented into solar cells, new effects can be exploited to maximize the harvest of solar radiation and to minimize the loss factors. In this context, carrier multiplication seems one promising way to minimize the effects induced by thermalization loss processes thereby significantly increasing the solar cell power conversion. In this work we analyze and quantify different types of carrier multiplication decay dynamics by analyzing systems of isolated and coupled silicon nanocrystals. The effects on carrier multiplication dynamics by energy and charge transfer processes are also discussed.

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

    Science.gov (United States)

    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.

  3. A Review of Packet Reservation Multiple Access

    Directory of Open Access Journals (Sweden)

    Varsha Sharma

    2011-05-01

    Full Text Available The rapid technological advances and innovations of the past few decades have pushed wireless communication from concept to reality. The popularity of wireless communication systems can be seen almost everywhere in the form of cellular networks, WLANs, and WPANs. Packet-switched technology has been demonstrated as effective in cellular radio systems with short propagation delay, not only for data, but also for voice transmission. In fact, packet voice can efficiently exploit speech on-off activity to improve bandwidth utilization over time division multiple access (TDMA. Such an approach has been first suggested in the packet reservation multiple-access (PRMA technique, an adaptation of the reservation ALOHA protocol to the cellular environment. PRMA can be viewed as a combination of TDMA and slotted ALOHA protocols. Recently modified versions of the PRMA protocol have been the subject of extensive research. This paper reviews a number of variations of PRMA protocol in literature.

  4. Cooperation in Carrier Sense Based Wireless Ad Hoc Networks - Part II: Proactive Schemes

    CERN Document Server

    Munari, Andrea; Zorzi, Michele

    2012-01-01

    This work is the second of a two-part series of papers on the effectiveness of cooperative techniques in non-centralized carrier sense-based ad hoc wireless networks. While Part I extensively discussed reactive cooperation, characterized by relayed transmissions triggered by failure events at the intended receiver, Part II investigates in depth proactive solutions, in which the source of a packet exploits channel state information to preemptively coordinate with relays in order to achieve the optimal overall rate to the destination. In particular, this work shows by means of both analysis and simulation that the performance of reactive cooperation is reduced by the intrinsic nature of the considered medium access policy, which biases the distribution of the available relays, locating them in unfavorable positions for rate optimization. Moreover, the highly dynamic nature of interference that characterizes non-infrastructured ad hoc networks is proved to hamper the efficacy and the reliability of preemptively ...

  5. 77 FR 57504 - Special Access for Price Cap Local Exchange Carriers; AT&T Corporation Petition for Rulemaking To...

    Science.gov (United States)

    2012-09-18

    ... COMMISSION 47 CFR Part 1 Special Access for Price Cap Local Exchange Carriers; AT&T Corporation Petition for Rulemaking To Reform Regulation of Incumbent Local Exchange Carrier Rates for Interstate Special Access... access prices and deter anticompetitive practices by price cap local exchange carriers. In the Report...

  6. Multiple-Access Quantum Key Distribution Networks

    CERN Document Server

    Razavi, Mohsen

    2011-01-01

    This paper addresses multi-user quantum key distribution networks, in which any two users can mutually exchange a secret key without trusting any other nodes. The same network also supports conventional classical communications by assigning two different wavelength bands to quantum and classical signals. Time and code division multiple access (CDMA) techniques, within a passive star network, are considered. In the case of CDMA, it turns out that the optimal performance is achieved at a unity code weight. A listen-before-send protocol is then proposed to improve secret key generation rates in this case. Finally, a hybrid setup with wavelength routers and passive optical networks, which can support a large number of users, is considered and analyzed.

  7. Proposition of an Unexploited Multiple Access Technique

    Directory of Open Access Journals (Sweden)

    Sidi Ahmed Djennas

    2012-03-01

    Full Text Available Continual growth in number of telecommunication network users encourages engineers to bring solutions to avoid overload and conflict. The situation is remedied by multiple access techniques and protocols. In fact, several ideas were applied with success to overcome difficulties. Basically, these ideas are based on discrimination in time, frequency, space and modulating code or time management. Within the context, we propose in this paper a new technique which helps us to avoid the conflict between users and manage optimally the information convoy. The basic idea for the new technique, baptized on the occasion by FAT (Fundamentals Agreement Technique, is to develop every signal and to convert it into a form with fundamentals as components. Of course emission and reception parts are in agreement about fundamentals to allow signals recovery later.

  8. Performance of Multi-Carrier Access Schemes with Receiver Impairments in Down Link Indoor Environment

    DEFF Research Database (Denmark)

    Das, Suvra Sekhar; Rao, Raieshwar Kurapati; Prasad, Ramjee

    2006-01-01

    Several multi-carrier spread spectrum (MC SS) access techniques which are based on Orthogonal Frequency Division Multiplexing (OFDM) have been developed till date. Different schemes are expected to perform optimally in different channel conditions. Their performance is also influenced by receiver...... of carrier frequency offset and channel estimation error for sub carrier hopping and non hopping systems. The results presented in this article will prove very important in deciding on a robust access scheme and its relevant parameters for down link indoor wireless local area networks....

  9. Grant-free Rateless Multiple Access: A Novel Massive Access Scheme for Internet of Things

    OpenAIRE

    Zhang, Zhaoyang; Wang, Xianbin; Zhang, Yu; Chen, Yan

    2016-01-01

    Rateless Multiple Access (RMA) is a novel non-orthogonal multiple access framework that is promising for massive access in Internet of Things (IoT) due to its high efficiency and low complexity. In the framework, after certain \\emph{registration}, each active user respectively transmits to the access point (AP) randomly based on an assigned random access control function (RACf) until receiving an acknowledgement (ACK). In this work, by exploiting the intrinsic access pattern of each user, we ...

  10. An optimal probabilistic multiple-access scheme for cognitive radios

    KAUST Repository

    Hamza, Doha R.

    2012-09-01

    We study a time-slotted multiple-access system with a primary user (PU) and a secondary user (SU) sharing the same channel resource. The SU senses the channel at the beginning of the slot. If found free, it transmits with probability 1. If busy, it transmits with a certain access probability that is a function of its queue length and whether it has a new packet arrival. Both users, i.e., the PU and the SU, transmit with a fixed transmission rate by employing a truncated channel inversion power control scheme. We consider the case of erroneous sensing. The goal of the SU is to optimize its transmission scheduling policy to minimize its queueing delay under constraints on its average transmit power and the maximum tolerable primary outage probability caused by the miss detection of the PU. We consider two schemes regarding the secondary\\'s reaction to transmission errors. Under the so-called delay-sensitive (DS) scheme, the packet received in error is removed from the queue to minimize delay, whereas under the delay-tolerant (DT) scheme, the said packet is kept in the buffer and is retransmitted until correct reception. Using the latter scheme, there is a probability of buffer loss that is also constrained to be lower than a certain specified value. We also consider the case when the PU maintains an infinite buffer to store its packets. In the latter case, we modify the SU access scheme to guarantee the stability of the PU queue. We show that the performance significantly changes if the realistic situation of a primary queue is considered. In all cases, although the delay minimization problem is nonconvex, we show that the access policies can be efficiently obtained using linear programming and grid search over one or two parameters. © 1967-2012 IEEE.

  11. Engineered semiconductor nanocrystals with enhanced carrier multiplication yields

    Science.gov (United States)

    Klimov, Victor

    2014-03-01

    Carrier multiplication (CM) is a process whereby absorption of a single photon results in multiple electron-hole pairs (excitons). This process could benefit a number of solar-energy conversion technologies, most notably photocatalysis and photovoltaics. This presentation overviews recent progress in understanding the CM process in semiconductor nanocrystals, motivated by an outstanding challenge in this field - the lack of capability to predict the CM performance of nanocrystals based on their known photophysical properties or documented parameters of parental bulk solids. Here, we present a possible solution to this problem by showing that, using biexciton Auger lifetimes and intraband relaxation rates inferred from ultrafast spectroscopic studies, we can rationalize relative changes in CM yields as a function of nanocrystal composition, size and shape. Further, guided by this model, we demonstrate a two-fold enhancement in multiexciton yields in PbSe nanorods vs. quantum dots attributed to enhanced Coulomb interactions. We also explore the control of competing intra-band cooling for increasing multiexciton production. Specifically, we design a new type of hetero-structured PbSe/CdSe quantum dots with reduced rates of intra-band relaxation and demonstrate a four-fold boost in the multiexciton yield. These studies provide useful guidelines for future efforts to achieve the ultimate, energy-conservation-defined CM efficiencies.

  12. Performance of Joint Spectrum Sensing and MAC Algorithms for Multichannel Opportunistic Spectrum Access Ad Hoc Networks

    CERN Document Server

    Park, Jihoon; Čabrić, Danijela

    2009-01-01

    We present an analytical framework to assess the link layer throughput of multichannel Opportunistic Spectrum Access (OSA) ad hoc networks. Specifically, we focus on analyzing various combinations of collaborative spectrum sensing and Medium Access Control (MAC) protocol abstractions. In analysis we decompose collaborative spectrum sensing into layers, parametrize each layer, classify existing solutions, and propose a new protocol called Truncated Time Division Multiple Access (TTDMA) that supports efficient distribution of sensing results in "k out of N" fusion rule. In case of multichannel MAC protocols we evaluate two main approaches of control channel design with (i) dedicated and (ii) hopping channel. We propose to augment these protocols with options of handling SU connections preempted by PU either by (i) connection buffering until PU departure and (ii) connection switching to a vacant PU channels. By comparing and optimizing different design combinations we show that (i) it is generally better to buff...

  13. Carrier injection engineering in nanowire transistors via dopant and shape monitoring of the access regions

    Energy Technology Data Exchange (ETDEWEB)

    Berrada, Salim, E-mail: s.berrada@insa.ueuromed.org; Bescond, Marc, E-mail: marc.bescond@im2np.fr; Cavassilas, Nicolas; Raymond, Laurent; Lannoo, Michel [IM2NP UMR CNRS 7334, Aix-Marseille Université, Technopôle de Château Gombert, 60 Rue Frédéric Joliot Curie, Bâtiment Néel,13453 Marseille (France)

    2015-10-12

    This work theoretically studies the influence of both the geometry and the discrete nature of dopants of the access regions in ultra-scaled nanowire transistors. By means of self-consistent quantum transport simulations, we show that discrete dopants induce quasi-localized states which govern carrier injection into the channel. Carrier injection can be enhanced by taking advantage of the dielectric confinement occurring in these access regions. We demonstrate that the optimization of access resistance can be obtained by a careful control of shape and dopant position. These results pave the way for contact resistance engineering in forthcoming device generations.

  14. Terahertz study of ultrafast carrier dynamics in InGa/GaN multiple quantum wells

    DEFF Research Database (Denmark)

    Porte, Henrik; Turchinovich, Dmitry; Cooke, David;

    2009-01-01

    Ultrafast carrier dynamics in InGaN/GaN multiple quantum wells is measured by time-resolved terahertz spectroscopy. The built-in piezoelectric field is initially screened by photoexcited, polarized carriers, and is gradullay restored as the carriers recombine. We observe a nonexponential decay...

  15. Optical gas sensing responses in transparent conducting oxides with large free carrier density

    Science.gov (United States)

    Ohodnicki, P. R.; Andio, M.; Wang, C.

    2014-07-01

    Inherent advantages of optical-based sensing devices motivate a need for materials with useful optical responses that can be utilized as thin film functional sensor layers. Transparent conducting metal oxides with large electrical conductivities as typified by Al-doped ZnO (AZO) display attractive properties for high temperature optical gas sensing through strong optical transduction of responses conventionally monitored through changes in measured electrical resistivity. An enhanced optical sensing response in the near-infrared and ultraviolet/visible wavelength ranges is demonstrated experimentally and linked with characteristic modifications to the dielectric constant due to a relatively high concentration of free charge carriers. The impact of light scattering on the magnitude and wavelength dependence of the sensing response is also discussed highlighting the potential for tuning the optical sensing response by controlling the surface roughness of a continuous film or the average particle size of a nanoparticle-based film. The physics underpinning the optical sensing response for AZO films on planar substrates yields significant insight into the measured sensing response for optical fiber-based evanescent wave absorption spectroscopy sensors employing an AZO sensing layer. The physics of optical gas sensing discussed here provides a pathway towards development of sensing materials for extreme temperature optical gas sensing applications. As one example, preliminary results are presented for a Nb-doped TiO2 film with sufficient stability and relatively large sensing responses at sensing temperatures greater than 500 °C.

  16. Spectrum Sensing for Cognitive Radio Based on Multiple Antennas

    DEFF Research Database (Denmark)

    Nguyen, Huan Cong; De Carvalho, Elisabeth; Prasad, Ramjee

    2012-01-01

    Spectrum sensing is a key component for enabling the cognitive radio paradigm. In this paper, we propose a novel totally-blind spectrum sensing technique for cognitive radio device equipped with multiple antennas, namely the Space Frequency Cross Product Sensing (SFCPS) algorithm. Existing...

  17. Passive UHF RFID tag with multiple sensing capabilities.

    Science.gov (United States)

    Fernández-Salmerón, José; Rivadeneyra, Almudena; Martínez-Martí, Fernando; Capitán-Vallvey, Luis Fermín; Palma, Alberto J; Carvajal, Miguel A

    2015-10-22

    This work presents the design, fabrication, and characterization of a printed radio frequency identification tag in the ultra-high frequency band with multiple sensing capabilities. This passive tag is directly screen printed on a cardboard box with the aim of monitoring the packaging conditions during the different stages of the supply chain. This tag includes a commercial force sensor and a printed opening detector. Hence, the force applied to the package can be measured as well as the opening of the box can be detected. The architecture presented is a passive single-chip RFID tag. An electronic switch has been implemented to be able to measure both sensor magnitudes in the same access without including a microcontroller or battery. Moreover, the chip used here integrates a temperature sensor and, therefore, this tag provides three different parameters in every reading.

  18. Passive UHF RFID Tag with Multiple Sensing Capabilities

    Directory of Open Access Journals (Sweden)

    José Fernández-Salmerón

    2015-10-01

    Full Text Available This work presents the design, fabrication, and characterization of a printed radio frequency identification tag in the ultra-high frequency band with multiple sensing capabilities. This passive tag is directly screen printed on a cardboard box with the aim of monitoring the packaging conditions during the different stages of the supply chain. This tag includes a commercial force sensor and a printed opening detector. Hence, the force applied to the package can be measured as well as the opening of the box can be detected. The architecture presented is a passive single-chip RFID tag. An electronic switch has been implemented to be able to measure both sensor magnitudes in the same access without including a microcontroller or battery. Moreover, the chip used here integrates a temperature sensor and, therefore, this tag provides three different parameters in every reading.

  19. Prospective Elementary Teachers Making Sense of Multidigit Multiplication: Leveraging Resources

    Science.gov (United States)

    Whitacre, Ian; Nickerson, Susan D.

    2016-01-01

    This study examines how collective activity related to multiplication evolved over several class sessions in an elementary mathematics content course that was designed to foster prospective elementary teachers' number-sense development. We document how the class drew on as-if-shared ideas to make sense of multidigit multiplication in terms of…

  20. Key issues of multiple access technique for LEO satellite communication systems

    Institute of Scientific and Technical Information of China (English)

    温萍萍; 顾学迈

    2004-01-01

    The large carrier frequency shift caused by the high-speed movement of satellite (Doppler effects) and the propagation delay on the up-down link are very critical issues in an LEO satellite communication system, which affects both the selection and the implementation of a suitable access method. A Doppler based multiple access technique is used here to control the flow and an MPRMA-HS protocol is proposed for the application in LEO satellite communication systems. The extended simulation trials prove that the proposed scheme seems to be a very promising access method.

  1. High integrity carrier phase navigation using multiple civil GPS signals

    Science.gov (United States)

    Jung, Jaewoo

    2000-11-01

    A navigation system should guide users to their destinations accurately and reliably. Among the many available navigation aids, the Global Positioning System stands out due to its unique capabilities. It is a satellite-based navigation system which covers the entire Earth with horizontal accuracy of 20 meters for stand alone civil users. Today, the GPS provides only one civil signal, but two more signals will be available in the near future. GPS will provide a second signal at 1227.60 MHz (L2) and a third signal at 1176.45 MHz (Lc), in addition to the current signal at 1575.42 MHz (L1). The focus of this thesis is exploring the possibility of using beat frequencies of these signals to provide navigation aid to users with high accuracy and integrity. To achieve high accuracy, the carrier phase differential GPS is used. The integer ambiguity is resolved using the Cascade Integer Resolution (CIR), which is defined in this thesis. The CIR is an instantaneous, geometry-free integer resolution method utilizing beat frequencies of GPS signals. To insure high integrity, the probability of incorrect integer ambiguity resolution using the CIR is analyzed. The CIR can immediately resolve the Lc integer ambiguity up to 2.4 km from the reference receiver, the Widelane (L1-L2) integer ambiguity up to 22 km, and the Extra Widelane (L2-Lc) integer ambiguity from there on, with probability of incorrect integer resolution of 10-4 . The optimal use of algebraic combinations of multiple GPS signals are also investigated in this thesis. Finally, the gradient of residual differential ionospheric error is estimated to stimated to increase performance of the CIR.

  2. Optimal Sensing for Opportunistic Spectrum Access in Cognitive Radio

    Directory of Open Access Journals (Sweden)

    Nasrullah Armi

    2010-08-01

    Full Text Available Opportunistic Spectrum Access (OSA brings new research challenges in MAC protocol design. It allows unlicensed users to share licensed spectrum in space and time with no or little interference to Primary Users (PUs. When designing an OSA MAC protocol, one of the most difficult but important problem is how the unlicensed users decide when and which channel they should sense and access without conflicting the communications among PUs. To solve this problem, the unlicensed users should have the ability of adaptively and dynamically seeking and exploiting opportunities in both licensed and unlicensed spectrum and along both the time and the frequency dimensions. Secondary Users (SUs as unlicensed users are required to sense radio frequency band, and when PU are detected, they must vacate the channel immediately within certain amount of time. Due to hardware and energy constraints, full spectrum availability cannot be sensed as well as they do not monitor when there is no data to be transmitted. In this paper, we study MAC protocol design and optimal sensing for OSA in Cognitive Radio (CR ad hoc network under Partially Observable Markov Decision Process (POMDP algorithm that maximizes achievable throughput for SUs with sufficient protection to PUs. Furthermore, we study tractable greedy algorithm to reduce the complexity of POMDP calculation. The derivation of greedy approach proves that sensing problem can be solved either optimally or approximate the optimal solution. Computer simulation is used to evaluate the performances both of optimal and sub optimal strategy.

  3. Optimal Sensing for Opportunistic Spectrum Access in Cognitive Radio

    Directory of Open Access Journals (Sweden)

    Nasrullah Armi, Naufal M. Saad, M. Zuki Yusoff, Muhammad Arshad

    2010-08-01

    Full Text Available One of the most difficult thing but important problem when designing an OSA (Opportunistic Spectrum Access MAC protocol is how the unlicensed users decide when and which channel they should sense and access without conflicting the communications among PUs. To solve this problem, the unlicensed users should have the ability of adaptively and dynamically seeking and exploiting opportunities in both licensed and unlicensed spectrum and along both of the time and the frequency dimensions. Secondary Users (SUs as unlicensed users are required to sense radio frequency band, and when PU are detected, they must vacate the channel immediately within certain amount of time. Due to hardware and energy constraints, full spectrum availability cannot be sensed as well as they do not monitor when there is no data to be transmitted. In this paper, we study MAC protocol design and optimal sensing for OSA in Cognitive Radio (CR ad hoc network under Partially Observable Markov Decision Process (POMDP algorithm that maximizes achievable throughput for SUs with sufficient protection to PUs. The bandwith effect to number of bit transmitted in one slot and tractable greedy algorithm to reduce the complexity of POMDP calculation was studied as well. The derivation of greedy approach proves that sensing problem can be solved either optimally or approximate the optimal solution. Computer simulation is used to evaluate the performances both of optimal and sub optimal strategy.

  4. Spread-spectrum multiple access using wideband noncoherent MFSK

    Science.gov (United States)

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

    1987-11-01

    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.

  5. Enhanced optical oxygen sensing using a newly synthesized ruthenium complex together with oxygen carriers.

    Science.gov (United States)

    Ertekin, Kadriye; Kocak, Suleyman; Sabih Ozer, M; Aycan, Sule; Cetinkaya, Bekir

    2003-11-12

    In this article, an emission based, simple and fast method is proposed for the determination of gaseous oxygen. A newly synthesized fluorophore, dichloro-{2,6-bis[1-(4-dimethylamino-phenylimino) ethyl]pyridine}ruthenium(II) has been used for oxygen sensing together with oxygen carrier perfluorochemicals (PFCs) in silicon matrix. It should be noted that the solubility of oxygen in fluorocarbons is about three to ten times large as that observed in the parent hydrocarbons or in water, respectively. Employed PFCs are chemically and biochemically inert, have high dissolution capacities for oxygen, and, once doped into sensing film, considerably enhance the response of sensing agent. PMID:18969220

  6. On Myopic Sensing for Multi-Channel Opportunistic Access

    CERN Document Server

    Zhao, Qing; Liu, Keqin

    2007-01-01

    We consider a multi-channel opportunistic communication system where the states of these channels evolve as independent and statistically identical Markov chains (the Gilbert-Elliot channel model). A user chooses one channel to sense and access in each slot and collects a reward determined by the state of the chosen channel. The objective is to design a sensing policy for channel selection to maximize the average reward. In this paper, we study the structure, optimality, and performance of the myopic sensing policy. We show that the myopic sensing policy has a simple robust structure that reduces channel selection to a counting procedure and obviates the need for knowing the channel transition probabilities. The optimality of this simple policy is established for the two-channel case and conjectured for the general case based on extensive simulations. The performance of the myopic sensing policy is analyzed, which, based on the optimality of myopic sensing, characterizes the maximum throughput of a multi-chan...

  7. Multiple-input multiple-output symbol rate signal digital predistorter for non-linear multi-carrier satellite channels

    OpenAIRE

    Zenteno, Efrain; Piazza, Roberto; M. R. Bhavani Shankar; Rönnow, Daniel; Ottersten, Björn

    2015-01-01

    A digital predistortion (DPD) scheme is presented for non-linear distortion mitigation in multi-carrier satellite communication channels. The proposed DPD has a multiple-input multiple-output architecture similar to data DPD schemes. However, it enhances the mitigation performance of data DPDs using a multi-rate processing algorithm to achieve spectrum broadening of non-linear operators. Compared to single carrier (single-input single-output) signal (waveform) DPD schemes, the proposed DPD ha...

  8. High power terahertz induced carrier multiplication in Silicon

    DEFF Research Database (Denmark)

    Tarekegne, Abebe Tilahun; Pedersen, Pernille Klarskov; Iwaszczuk, Krzysztof;

    2015-01-01

    The application of an intense THz field results a nonlinear transmission in high resistivity silicon. Upon increasing field strength, the transmission falls from 70% to 62% due to carrier generation through THz-induced impact ionization and subsequent absorption of the THz field by free electrons....

  9. 78 FR 2571 - Special Access for Price Cap Local Exchange Carriers; AT&T Corporation Petition for Rulemaking To...

    Science.gov (United States)

    2013-01-11

    ... January 11, 2013 Part IV Federal Communications Commission 47 CFR Part 69 Special Access for Price Cap Local Exchange Carriers; AT&T Corporation Petition for Rulemaking To Reform Regulation of Incumbent... COMMUNICATIONS COMMISSION 47 CFR Part 69 Special Access for Price Cap Local Exchange Carriers; AT&T...

  10. 78 FR 2600 - Special Access for Price Cap Local Exchange Carriers; AT&T Corporation Petition for Rulemaking To...

    Science.gov (United States)

    2013-01-11

    ... CFR Part 69 Special Access for Price Cap Local Exchange Carriers; AT&T Corporation Petition for Rulemaking To Reform Regulation of Incumbent Local Exchange Carrier Rates for Interstate Special Access... analytic framework capable of assessing whether the Commission's price cap and pricing flexibility...

  11. 78 FR 24683 - Special Access for Price Cap Local Exchange Carriers; AT&T Corporation Petition for Rulemaking To...

    Science.gov (United States)

    2013-04-26

    ... COMMISSION 47 CFR Part 69 Special Access for Price Cap Local Exchange Carriers; AT&T Corporation Petition for Rulemaking To Reform Regulation of Incumbent Local Exchange Carrier Rates for Interstate Special Access.... DATES: The effective date of the Report and Order published on January 11, 2013, at 78 FR 2572,...

  12. 78 FR 67053 - Special Access for Price Cap Local Exchange Carriers; AT&T Corporation Petition for Rulemaking To...

    Science.gov (United States)

    2013-11-08

    ... COMMISSION 47 CFR Part 69 Special Access for Price Cap Local Exchange Carriers; AT&T Corporation Petition for Rulemaking To Reform Regulation of Incumbent Local Exchange Carrier Rates for Interstate Special Access... Collection Order, 78 FR 2571, January 11, 2013, as implemented by this Report and Order, are not...

  13. Ultrafast carrier dynamics in InGaN/GaN multiple quantum wells

    DEFF Research Database (Denmark)

    Porte, Henrik; Turchinovich, Dmitry; Cooke, David;

    We studied the THz conductivity of InGaN/GaN multiple quantum wells (MQWs)by time-resolved terahertz spectroscopy. A nonexponential carrier density decay is observed due to the restoration of a built-in piezoelectric field. Terahertz conductivity spectra show a nonmetallic behavior of the carriers....

  14. Orientation Sensing Using Multiple Passive RFID Tags

    DEFF Research Database (Denmark)

    Krigslund, Rasmus; Popovski, Petar; Pedersen, Gert Frølund

    2012-01-01

    Knowing the inclination of an object can be valuable information in a supply chain application, e.g. when handling orientation sensitive objects. In this work we present a method for sensing the inclination using Radio Frequency IDentification (RFID) technology. The method requires standard RFID...

  15. Impact of sensing errors on the queueing delay and transmit power in cognitive radio access

    KAUST Repository

    Hamza, Doha R.

    2011-03-01

    We study a multiple-access system with a primary user (PU) and a secondary user (SU) utilizing the same frequency band and communicating with a common receiver. Both users transmit with a fixed transmission rate by employing a channel inversion power control scheme. The SU transmits with a certain probability that depends on the sensing outcome, its queue length and whether it has a new packet arrival. We consider the case of erroneous sensing. The goal of the SU is to find the optimal transmission scheduling policy so as to minimize its queueing delay under constraints on its average transmit power and the maximum tolerable primary outage probability caused by miss-detection. The access probabilities are obtained efficiently using linear programming. © 2011 IEEE.

  16. Orthogonal frequency division multiple access fundamentals and applications

    CERN Document Server

    Jiang, Tao; Zhang, Yan

    2010-01-01

    Supported by the expert-level advice of pioneering researchers, Orthogonal Frequency Division Multiple Access Fundamentals and Applications provides a comprehensive and accessible introduction to the foundations and applications of one of the most promising access technologies for current and future wireless networks. It includes authoritative coverage of the history, fundamental principles, key techniques, and critical design issues of OFDM systems. Covering various techniques of effective resource management for OFDM/OFDMA-based wireless communication systems, this cutting-edge reference:Add

  17. High accuracy localization of long term evolution based on a new multiple carrier noise model.

    Science.gov (United States)

    Lee, Wah Ching; Hung, Faan Hei; Tsang, Kim Fung; Wu, Chung Kit; Chi, Hao Ran; Chui, Kwok Tai; Lau, Wing Hong

    2014-01-01

    A high accuracy localization technique using Long Term Evolution (LTE) based on a new and accurate multiple carrier noise model has been developed. In the noise consideration, the LTE multiple carriers phase noise has been incorporated so that a new and accurate noise model is achieved. An experiment was performed to characterize the phase noise of carriers at 2 GHz. The developed noise model was incorporated into LTE localization analysis in a high traffic area in Hong Kong to evaluate the accuracy of localization. The evaluation and analysis reveals that the new localization method achieves an improvement of about 10% accuracy comparing to existing widely adopted schemes. PMID:25436658

  18. High Accuracy Localization of Long Term Evolution Based on a New Multiple Carrier Noise Model

    Directory of Open Access Journals (Sweden)

    Wah Ching Lee

    2014-11-01

    Full Text Available A high accuracy localization technique using Long Term Evolution (LTE based on a new and accurate multiple carrier noise model has been developed. In the noise consideration, the LTE multiple carriers phase noise has been incorporated so that a new and accurate noise model is achieved. An experiment was performed to characterize the phase noise of carriers at 2 GHz. The developed noise model was incorporated into LTE localization analysis in a high traffic area in Hong Kong to evaluate the accuracy of localization. The evaluation and analysis reveals that the new localization method achieves an improvement of about 10% accuracy comparing to existing widely adopted schemes.

  19. Marking sense of students' answers to multiple-choice questions

    Science.gov (United States)

    Dufresne, Robert J.; Leonard, William J.; Gerace, William J.

    2002-03-01

    A detailed example is used to illustrate the difficulties making sense of students' answers to multiple-choice questions. We explore how correct answers can be false indicators of student knowledge and understanding. We caution against excessive reliance on multiple-choice questions for instructional decisions.

  20. Multiple carriers of Q noble gases in primitive meteorites

    CERN Document Server

    Marrocchi, Yves; Estrade, Nicolas

    2015-01-01

    The main carrier of primordial heavy noble gases in chondrites is thought to be an organic phase, known as phase Q, whose precise characterization has resisted decades of investigation. Indirect techniques have revealed that phase Q might be composed of two subphases, one of them associated with sulfide. Here we provide experimental evidence that noble gases trapped within meteoritic sulfides present chemically- and thermally-driven behavior patterns that are similar to Q-gases. We therefore suggest that phase Q is likely composed of two subcomponents: carbonaceous phases and sulfides. In situ decay of iodine at concentrations levels consistent with those reported for meteoritic sulfides can reproduce the 129Xe excess observed for Q-gases relative to fractionated Solar Wind. We suggest that the Q-bearing sulfides formed at high temperature and could have recorded the conditions that prevailed in the chondrule-forming region(s).

  1. Multiple carrier transport in N-face indium nitride

    International Nuclear Information System (INIS)

    We present temperature (20-300 K) dependent multi-carrier measurements of electron species in N-face indium nitride. N-face InN samples were grown to different thicknesses (500-2000 nm) via plasma-assisted molecular beam epitaxy on C-face SiC substrates. Surface and bulk electron transport properties were extracted using a quantitative mobility spectrum analysis. Mobility of both bulk and surface electron species increase with film thickness. The temperature dependence of the mobility of both species differs to that of In-polar samples studied previously, while the mobility of surface electrons is more than twice that of In-polar samples with only a slight corresponding reduction in sheet concentration. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  2. ERP measures of semantic richness: The case of multiple senses

    Directory of Open Access Journals (Sweden)

    Vanessa eTaler

    2013-01-01

    Full Text Available Semantic richness refers to the amount of semantic information that a lexical item possesses. An important measure of semantic richness is the number of related senses that a word has (e.g., TABLE meaning a piece of furniture, a table of contents, to lay aside for future discussion, etc. We measured electrophysiological response to lexical items with many and few related senses in monolingual English-speaking young adults. Participants performed lexical decision on each item. Overall, high-sense words elicited shorter response latencies and smaller N400 amplitudes than low-sense words. These results constitute further evidence of the importance of semantic richness in lexical processing, and provide evidence that processing of multiple related senses begins as early as 200 milliseconds after stimulus onset.

  3. 14 CFR 382.43 - Must information and reservation services of carriers be accessible to individuals with hearing...

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 4 2010-01-01 2010-01-01 false Must information and reservation services... Must information and reservation services of carriers be accessible to individuals with hearing impairments? (a) If, as a carrier, you provide telephone reservation and information service to the...

  4. Optical code division multiple access fundamentals and applications

    CERN Document Server

    Prucnal, Paul R

    2005-01-01

    Code-division multiple access (CDMA) technology has been widely adopted in cell phones. Its astonishing success has led many to evaluate the promise of this technology for optical networks. This field has come to be known as Optical CDMA (OCDMA). Surveying the field from its infancy to the current state, Optical Code Division Multiple Access: Fundamentals and Applications offers the first comprehensive treatment of OCDMA from technology to systems.The book opens with a historical perspective, demonstrating the growth and development of the technologies that would eventually evolve into today's

  5. On Optimality of Myopic Sensing Policy with Imperfect Sensing in Multi-channel Opportunistic Access

    CERN Document Server

    Wang, Kehao; Liu, Quan; Agha, Khaldoun Al

    2012-01-01

    We consider the channel access problem under imperfect sensing of channel state in a multi-channel opportunistic communication system, where the state of each channel evolves as an independent and identically distributed Markov process. The considered problem can be cast into a restless multi-armed bandit (RMAB) problem that is of fundamental importance in decision theory. It is well-known that solving the RMAB problem is PSPACE-hard, with the optimal policy usually intractable due to the exponential computation complexity. A natural alternative is to consider the easily implementable myopic policy that maximizes the immediate reward but ignores the impact of the current strategy on the future reward. In this paper, we perform an analytical study on the optimality of the myopic policy under imperfect sensing for the considered RMAB problem. Specifically, for a family of generic and practically important utility functions, we establish the closed-form conditions under which the myopic policy is guaranteed to b...

  6. Cooperation in Carrier Sense Based Wireless Ad Hoc Networks - Part I: Reactive Schemes

    CERN Document Server

    Munari, Andrea; Zorzi, Michele

    2012-01-01

    Cooperative techniques have been shown to significantly improve the performance of wireless systems. Despite being a mature technology in single communication link scenarios, their implementation in wider, and practical, networks poses several challenges which have not been fully identified and understood so far. In this two-part paper, the implementation of cooperative communications in non-centralized ad hoc networks with sensing-based channel access is extensively discussed. Both analysis and simulation are employed to provide a clear understanding of the mutual influence between the link layer contention mechanism and collaborative protocols. Part I of this work focuses on reactive cooperation, in which relaying is triggered by packet delivery failure events, while Part II addresses proactive approaches, preemptively initiated by the source based on channel state information. Results show that sensing-based channel access significantly hampers the effectiveness of cooperation by biasing the spatial distri...

  7. A novel Modulation Topology for Power Converters utilizing Multiple Carrier Signals

    DEFF Research Database (Denmark)

    Knott, Arnold; Pfaffinger, Gerhard; Andersen, Michael Andreas E.

    2008-01-01

    Power converters are known to generate spectral components in the range of interest of electromagnetic compatibility measurements. Common approaches to manipulate some selected components in these frequency ranges are shown here. These approaches add components to the input signal of the modulator...... to derive a slightly varied spectrum. To achieve a rectangular output signal, those modulators use a triangular or saw tooth carrier signal. A novel family of modulators is shown here, using more than one carrier signal to obtain a completely changed spectrum while maintaining the rectangular shaped...... waveform at the output. The multiple carriers are fed into multiple comparators and their outputs are intelligently combined by logic gates to get a single signal to drive one power stage of any type of converter. This commutation distinguishes between the four members of the novel family: the first one...

  8. Empirical formulae for excess noise factor with dead space for single carrier multiplication

    KAUST Repository

    Dehwah, Ahmad H.

    2011-09-01

    In this letter, two empirical equations are presented for the calculation of the excess noise factor of an avalanche photodiode for single carrier multiplication including the dead space effect. The first is an equation for calculating the excess noise factor when the multiplication approaches infinity as a function of parameters that describe the degree of the dead space effect. The second equation can be used to find the minimum value of the excess noise factor for any multiplication when the dead space effect is completely dominant, the so called "deterministic" limit. This agrees with the theoretically known equation for multiplications less than or equal to two. © 2011 World Scientific Publishing Company.

  9. A study of multiple access schemes in satellite control network

    Science.gov (United States)

    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.

  10. Block Interleaved Frequency Division Multiple Access for Power Efficiency, Robustness, Flexibility, and Scalability

    Directory of Open Access Journals (Sweden)

    Frank Tobias

    2009-01-01

    Full Text Available The multiple access solution in an IMT-Advanced mobile radio system has to meet challenging requirements such as high throughput, low delays, high flexibility, good robustness, low computational complexity, and a high power efficiency, especially in the uplink. In this paper, a novel multiple access scheme for uplinks denoted as B-IFDMA is presented. We show that this scheme is able to provide equal or better error rate performance than the Single-Carrier Frequency Division Multiple Access (SCFDMA schemes IFDMA and LFDMA, when considering realistic channel estimation performance at the receiver and no reliable channel state information at the transmitter. We also show that B-IFDMA provides better amplifier efficiency than OFDMA and can provide better end-to-end energy efficiency than IFDMA and LFDMA. Moreover, the scheme shows a promisingly high robustness to frequency-offsets and Doppler spread. Thus, this scheme can be regarded as a promising solution for the uplink of future mobile radio systems.

  11. Non-Orthogonal Multiple Access for Visible Light Communications

    Science.gov (United States)

    Marshoud, Hanaa; Kapinas, Vasileios M.; Karagiannidis, George K.; Muhaidat, Sami

    2016-01-01

    The main limitation of visible light communication (VLC) is the narrow modulation bandwidth, which reduces the achievable data rates. In this paper, we apply the non-orthogonal multiple access (NOMA) scheme to enhance the achievable throughput in high-rate VLC downlink networks. We first propose a novel gain ratio power allocation (GRPA) strategy that takes into account the users' channel conditions to ensure efficient and fair power allocation. Our results indicate that GRPA significantly enhances system performance compared to the static power allocation. We also study the effect of tuning the transmission angles of the light emitting diodes (LEDs) and the field of views (FOVs) of the receivers, and demonstrate that these parameters can offer new degrees of freedom to boost NOMA performance. Simulation results reveal that NOMA is a promising multiple access scheme for the downlink of VLC networks.

  12. A Multiple Access Protocol for Multimedia Transmission over Wireless Networks

    CERN Document Server

    Yu, Hong

    2012-01-01

    This paper develops and evaluates the performance of an advanced multiple access protocol for transmission of full complement of multimedia signals consisting of various combinations of voice, video, data, text and images over wireless networks. The protocol is called Advanced Multiple Access Protocol for Multimedia Transmission (AMAPMT) and is to be used in the Data Link Layer of the protocol stack. The principle of operation of the protocol is presented in a number of logical flow charts. The protocol grants permission to transmit to a source on the basis of a priority scheme that takes into account a time-to-live (TTL) parameter of all the transactions, selectable priorities assigned to all the sources and relevant channel state information (CSI) in this order. Performance of the protocol is evaluated in terms of quality of service parameters like packet loss ratio (PLR), mean packet transfer delay (MPTD) and throughput. Using a simulation model based on an OPNET simulation software package does the evalua...

  13. Code division multiple access signaling for modulated reflector technology

    Science.gov (United States)

    Briles, Scott D.

    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.

  14. Accessing Applications from Multiple File Servers in a Computer Network

    OpenAIRE

    J.S.J. Daka; J. S. Isaac

    2005-01-01

    This study proposes a technique of accessing applications from multiple file servers in a computer network that caters for a large user community. The technique is a step towards creating a computer network system that is simple to implement, scalable, easy to manage, transparent to the user and suitable for a university-type environment. The proposed technique has some features of a distributed system, but is not as complex. It is built around a very popular commercial ne...

  15. Modemless Multiple Access Communications over Powerlines for DC Microgrid Control

    OpenAIRE

    Angjelichinoski, Marko; Stefanovic, Cedomir; Popovski, Petar

    2016-01-01

    We present a communication solution tailored specifically for DC microgrids (MGs) that exploits: (i) the communication potential residing in power electronic converters interfacing distributed generators to powerlines and (ii) the multiple access nature of the communication channel presented by powerlines. The communication is achieved by modulating the parameters of the primary control loop implemented by the converters, fostering execution of the upper layer control applications. We present...

  16. Spatially continuous distributed fiber optic sensing using optical carrier based microwave interferometry.

    Science.gov (United States)

    Huang, Jie; Lan, Xinwei; Luo, Ming; Xiao, Hai

    2014-07-28

    This paper reports a spatially continuous distributed fiber optic sensing technique using optical carrier based microwave interferometry (OCMI), in which many optical interferometers with the same or different optical path differences are interrogated in the microwave domain and their locations can be unambiguously determined. The concept is demonstrated using cascaded weak optical reflectors along a single optical fiber, where any two arbitrary reflectors are paired to define a low-finesse Fabry-Perot interferometer. While spatially continuous (i.e., no dark zone), fully distributed strain measurement was used as an example to demonstrate the capability, the proposed concept may also be implemented on other types of waveguide or free-space interferometers and used for distributed measurement of various physical, chemical and biological quantities. PMID:25089493

  17. LINEAR-DISPERSION DIVISION MULTIPLE-ACCESS FOR MIMO SYSTEMS

    Institute of Scientific and Technical Information of China (English)

    Deng Dan; Lv Xingzai; Zhu Jinkang

    2008-01-01

    Comprehensive study on novel Linear-Dispersion Division Multiple-Access (LDDMA) for multi-user uplink Multiple-Input Multiple-Output (MIMO) systems is proposed. In the new multi- plexing scheme, each user's information symbol is dispersed by a User-Specific Matrix (USM) both in space and time domain and linearly combined at base-station side. And a simple random search al- gorithm, based on capacity maximization criteria, is developed to generate a bank of USMs. Simulation results are presented to demonstrate the advantages of LDDMA. When the Bit Error Rate (BER) reaches 10, the performance gains are 3dB and 5dB, compared with Time-Division Linear Dispersion Codes (TD-LDC) and BLAST, respectively.

  18. Subsurface Imaging and Sensing of Charge Carrier Movements in the Earth’s Crust

    Science.gov (United States)

    Dahlgren, R.; Freund, F. T.; Lazarus, M.; Wang, J. S.; Rekenthaler, D.; Peters, R. D.; Duma, G.

    2009-12-01

    The DUSEL facility will enable unique opportunities for field experiments that would otherwise not be possible at surface facilities (Lesko, K.T., TAUP, 2007) and support a host of undergraduate and graduate educational projects. In this presentation, some of the proposed geophysics experiments will be described as part of the subsurface Imaging and Sensing (SIS) project to study charge carrier movement in crustal rock as a function of various perturbations. The electric conductivity of the Earth’s crust is dominated by positive hole charge carriers, e.g. mobile electron vacancy defects (EVD) in the oxygen anion sublattice of minerals that make up the bulk of crustal rocks. We are interested in (i) coupling of fundamental processes linked to the activation of additional EVDs in rocks deep in the crust subjected to tectonic stresses and the outflow of these charge carriers into the surrounding rocks, (ii) their manifestation across the electromagnetic spectrum and other measuands, (iii) induced forces that arise when these charge carriers are subjected to the episodic or daily magnetic field variations coming from geomagnetic storms or from the ionospheric current vortex, and (iv) in the movement of positive holes in the shallow crust when a thunderstorm system drifts overhead, dragging along a charge cloud in the ground. We propose to conduct active rock stressing experiments in situ using expanding grout technique (performing electrical, electromagnetic, and VolksMeter tilt measurements) and to monitor the electric and magnetic field variations penetrating into the Earth’s crust. Additionally optical phenomena will be investigated (anomalous infrared signatures, visible light arising from atomic oxygen and corona discharge, and infrared imaging). If budget permits, measurement of changes of acoustic velocity, evolution of chemical species (H2, O*, Rn, etc) and radar reflectivity as a function of stresses will also be attempted. We propose to study the charge

  19. Remote Sensing Image Feature Extracting Based Multiple Ant Colonies Cooperation

    Directory of Open Access Journals (Sweden)

    Zhang Zhi-long

    2014-02-01

    Full Text Available This paper presents a novel feature extraction method for remote sensing imagery based on the cooperation of multiple ant colonies. First, multiresolution expression of the input remote sensing imagery is created, and two different ant colonies are spread on different resolution images. The ant colony in the low-resolution image uses phase congruency as the inspiration information, whereas that in the high-resolution image uses gradient magnitude. The two ant colonies cooperate to detect features in the image by sharing the same pheromone matrix. Finally, the image features are extracted on the basis of the pheromone matrix threshold. Because a substantial amount of information in the input image is used as inspiration information of the ant colonies, the proposed method shows higher intelligence and acquires more complete and meaningful image features than those of other simple edge detectors.

  20. On Multiuser Power Region of Fading Multiple-Access Channel with Multiple Antennas

    CERN Document Server

    Zhang, Rui; Cioffi, John M

    2008-01-01

    This paper is concerned with the fading MIMO-MAC with multiple receive antennas at the base station (BS) and multiple transmit antennas at each mobile terminal (MT). Two multiple-access techniques are considered for scheduling transmissions from each MT to the BS at the same frequency, which are space-division multiple-access (SDMA) and time-division multiple-access (TDMA). For SDMA, all MTs transmit simultaneously to the BS and their individual signals are resolved at the BS via multiple receive antennas while for TDMA, each MT transmits independently to the BS during mutually orthogonal time slots. It is assumed that the channel-state information (CSI) of the fading channel from each MT to the BS is unknown at each MT transmitter, but is perfectly known at the BS receiver. Thereby, the BS can acquire the long-term channel-distribution information (CDI) for each MT. This paper extends the well-known transmit-covariance feedback scheme for the point-to-point fading MIMO channel to the fading MIMO-MAC, whereby...

  1. Registration and Fusion of Multiple Source Remotely Sensed Image Data

    Science.gov (United States)

    LeMoigne, Jacqueline

    2004-01-01

    Earth and Space Science often involve the comparison, fusion, and integration of multiple types of remotely sensed data at various temporal, radiometric, and spatial resolutions. Results of this integration may be utilized for global change analysis, global coverage of an area at multiple resolutions, map updating or validation of new instruments, as well as integration of data provided by multiple instruments carried on multiple platforms, e.g. in spacecraft constellations or fleets of planetary rovers. Our focus is on developing methods to perform fast, accurate and automatic image registration and fusion. General methods for automatic image registration are being reviewed and evaluated. Various choices for feature extraction, feature matching and similarity measurements are being compared, including wavelet-based algorithms, mutual information and statistically robust techniques. Our work also involves studies related to image fusion and investigates dimension reduction and co-kriging for application-dependent fusion. All methods are being tested using several multi-sensor datasets, acquired at EOS Core Sites, and including multiple sensors such as IKONOS, Landsat-7/ETM+, EO1/ALI and Hyperion, MODIS, and SeaWIFS instruments. Issues related to the coregistration of data from the same platform (i.e., AIRS and MODIS from Aqua) or from several platforms of the A-train (i.e., MLS, HIRDLS, OMI from Aura with AIRS and MODIS from Terra and Aqua) will also be considered.

  2. A Soft Sensing-Based Cognitive Access Scheme Exploiting Primary Feedback

    OpenAIRE

    Arafa Ahmed, M.; Seddik, Karim G.; Sultan Ahmed, K.; Elbatt, Tamer; El-Sherif, Amr

    2012-01-01

    Cognitive Radio International audience In this paper, we examine a cognitive spectrum access scheme in which secondary users exploit the primary feedback information. We consider an overlay secondary network employing a random access scheme in which secondary users access the channel by certain access probabilities that are function of the spectrum sensing metric. In setting our problem, we assume that secondary users can eavesdrop on the primary link's feedback. We study the cognitive ...

  3. Accessing Applications from Multiple File Servers in a Computer Network

    Directory of Open Access Journals (Sweden)

    J. S.J. Daka

    2005-01-01

    Full Text Available This study proposes a technique of accessing applications from multiple file servers in a computer network that caters for a large user community. The technique is a step towards creating a computer network system that is simple to implement, scalable, easy to manage, transparent to the user and suitable for a university-type environment. The proposed technique has some features of a distributed system, but is not as complex. It is built around a very popular commercial network operating system called NetWare.

  4. OVERSAMPLED CHAOTIC BINARY SEQUENCES FOR MULTIPLE ACCESS COMMUNICATION

    Institute of Scientific and Technical Information of China (English)

    Zhang Hongtao; Wang Huiyun; Ding Runtao

    2002-01-01

    Noise interference and multiple access interference are the main impairment to the performance of DS/CDMA communication system. This letter presents that OverSampled Chaotic Map (OSCM) binary sequences are secure as spreading sequences, and based on the optimal quantizing method, the BER performance of the system has been derived in detail, the internal relationships among the number of users, the power of noise and the length of code chips are revealed in mathematical formulae. The performance of the system can be improved by employing these formulae. Numerical results conform the efficiency of discussion in this letter.

  5. Multiple regimes of carrier cooling in photoexcited graphene probed by time-resolved terahertz spectroscopy

    Science.gov (United States)

    Frenzel, A. J.; Gabor, N. M.; Herring, P. K.; Fang, W.; Kong, J.; Jarillo-Herrero, P.; Gedik, N.

    2013-03-01

    Energy relaxation and cooling of photoexcited charge carriers in graphene has recently attracted significant attention due to possible hot carrier effects, large quantum efficiencies, and photovoltaic applications. However, the details of these processes remain poorly understood, with many conflicting interpretations reported. Here we use time-resolved terahertz spectroscopy to explore multiple relaxation and cooling regimes in graphene in order to elucidate the fundamental physical processes which occur upon photoexcitation of charge carriers. We observe a novel negative terahertz photoconductivity that results from the unique linear dispersion and allows us to measure the electron temperature with ultrafast time resolution. Additionally, we present measurements of the relaxation dynamics over a wide range of excitation fluence. By varying the pump photon energy, we demonstrate that cooling dynamics of photoexcited carriers depend on the amount of energy deposited in the graphene system by the pump pulse, not the number of absorbed photons. The data suggest that fundamentally different regimes are encountered for different excitation fluences. These results may provide a unifying framework for reconciling various measurements of energy relaxation and cooling in graphene.

  6. Multiple hot-carrier collection in photo-excited graphene Moiré superlattices

    Science.gov (United States)

    Wu, Sanfeng; Wang, Lei; Lai, You; Shan, Wen-Yu; Aivazian, Grant; Zhang, Xian; Taniguchi, Takashi; Watanabe, Kenji; Xiao, Di; Dean, Cory; Hone, James; Li, Zhiqiang; Xu, Xiaodong

    2016-01-01

    In conventional light-harvesting devices, the absorption of a single photon only excites one electron, which sets the standard limit of power-conversion efficiency, such as the Shockley-Queisser limit. In principle, generating and harnessing multiple carriers per absorbed photon can improve efficiency and possibly overcome this limit. We report the observation of multiple hot-carrier collection in graphene/boron-nitride Moiré superlattice structures. A record-high zero-bias photoresponsivity of 0.3 A/W (equivalently, an external quantum efficiency exceeding 50%) is achieved using graphene’s photo-Nernst effect, which demonstrates a collection of at least five carriers per absorbed photon. We reveal that this effect arises from the enhanced Nernst coefficient through Lifshtiz transition at low-energy Van Hove singularities, which is an emergent phenomenon due to the formation of Moiré minibands. Our observation points to a new means for extremely efficient and flexible optoelectronics based on van der Waals heterostructures.

  7. Some New Results on the Multiple-AccessWiretap Channel

    Directory of Open Access Journals (Sweden)

    Bin Dai

    2014-08-01

    Full Text Available In this paper, some new results on the multiple-access wiretap channel (MAC-WT are provided. Specifically, first, we investigate the degraded MAC-WT, where two users transmit their corresponding confidential messages (no common message to a legitimate receiver via a multiple-access channel (MAC, while a wiretapper wishes to obtain the messages via a physically degraded wiretap channel. The secrecy capacity region of this model is determined for both the discrete memoryless and Gaussian cases. For the Gaussian case, we find that this secrecy capacity region is exactly the same as the achievable secrecy rate region provided by Tekin and Yener, i.e., Tekin–Yener’s achievable region is exactly the secrecy capacity region of the degraded Gaussian MAC-WT. Second, we study a special Gaussian MAC-WT, and find the power control for two kinds of optimal points (max-min point and single user point on the secrecy rate region of this special Gaussian model.

  8. A multiple copyright identification watermarking algorithm based on code division multiple access

    Institute of Scientific and Technical Information of China (English)

    Zhang Fan; Li Jie; Su Yuting; Zhang Chun tian

    2008-01-01

    A multiple watermarking algorithm is presented according to the multiple accessing technique of the code division multiple access (CDMA) system. Multiple watermarks are embedded into digital images in the wavelet transform domain. Each of the watermarks is embedded and extracted independently without impacts to each other. Multiple watermarks are convolution encoded and block interleaved, and the orthogonal Gold sequences are used to spread spectrum of the copyright messages. CDMA encoded watermark messages are embedded into the wavelet sub-bands excluding the wavelet HH1 sub-bands. The embedment amplitude is decided by Watson's perceptual model of wavelet transform domain, and the embedment position in the selected wavelet sub-bands is decided randomly by a pseudo-random noise (PN) sequence. As a blind watermarking algorithm, watermarks are extracted without original image. The watermarking capacity of proposed algorithm is also discussed. When two watermarks are embedded in an image at the same time, the capacity is larger than the capacity when a single watermark is embedded, and is smaller than the sum of the capacity of two separately embedded watermarks. Experimental results show that the proposed algorithm improves the detection bits error rate (BER) observably, and the multiple watermarks have a preferable robustness and invisibility.

  9. Sequential Joint Spectrum Sensing and Channel Estimation for Dynamic Spectrum Access

    OpenAIRE

    Yilmaz, Yasin; Guo, Ziyu; Wang, Xiaodong

    2014-01-01

    Dynamic spectrum access under channel uncertainties is considered. With the goal of maximizing the secondary user (SU) throughput subject to constraints on the primary user (PU) outage probability we formulate a joint problem of spectrum sensing and channel state estimation. The problem is cast into a sequential framework since sensing time minimization is crucial for throughput maximization. In the optimum solution, the sensing decision rule is coupled with the channel estimator, making the ...

  10. Multiple Detectors Based Analytical Performance of Spectrum Sensing

    Directory of Open Access Journals (Sweden)

    S.Taruna

    2014-03-01

    Full Text Available A key challenge in operating cognitive radios (CRs in a self-organizing (ad hoc network is how to adaptively and efficiently utilize spectrum resources keeping in mind that no interference is caused to primary users and also that no spectrum is rendered unused when a secondary user is waiting for access. Detecting the spectrum holes using one detector can be insufficient for increasing secondary users. In the proposed paper, an attempt has been made to implement multiple detectors to improve the probability of detection by increasing the SNR. Multiple detector technique has been implemented using various methods like Selection Combining (SC, Equal Gain Combining (EGC, and Maximum Ratio Combining (MRC, to discover which of these methods provide better increase in SNR as the numbers of detectors are increased.

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

    Science.gov (United States)

    Peng, Wei-Chung; Yang, Chau-Chin

    1990-01-01

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

  12. Remote Sensing Open Access Journal: Leading a New Paradigm in Publishing

    Directory of Open Access Journals (Sweden)

    Prasad S. Thenkabail

    2011-12-01

    Full Text Available Remote Sensing is a pathfinding open access journal providing great opportunities for the growing community of remote sensing and geoscience scientists and practitioners to publish high quality research and practical papers expeditiously. It is a journal keeping up with the changing times we live in: open access, instant access, free access, and global access from whichever precise latitude and longitude you live in on the planet Earth or for that matter anywhere in space as long as we have internet access! So, open access journals are breaking many paradigms and setting forth new ones that will soon become the norm as we advance into the twenty-first century. The days of inordinate delays in publishing good science research articles are fast disappearing with open access journals. In remote sensing and geoscience, Remote Sensing (http://www.mdpi.com/journal/remotesensing/ is one of the pioneers, thanks to the vision of Dr. Shu-Kun Lin, the publisher. It started in the year 2009 with headquarters in Basel, Switzerland and a branch office in Beijing, China. It will soon complete Volume 3 by the end of 2011.

  13. A Frequency—Diversity Spread—Spectrum Multiple Access System with Random Signature Sequences

    Institute of Scientific and Technical Information of China (English)

    CaoYewen; XiangHaige

    1995-01-01

    A new scheme for the spread-spectrum multiple access system named Frequency-Diver-sity Spread-Spectrum Multiple Access(FD-DDMA)system,is proposed.In this FD-SSMA sys-tem,the same information will be modulated on a group of mutually orthogonal frequency compo-nents(carriers)with a random signature sequence at the same time,and it will be demodulated by a coherent receiver for every component and then incorporated (ad if using frequency diversity)on the basis of this random sequence.The spectrum of the modulated signal is very close to that of a white-noise in a wider frequency band due to orthogonality for all frequency components and prop-erty of the random sequence,the system becomes a spread-spectrum one.The (Inverse)Fast Froier Transform(IFFT,FFT)can be applied in the system ,which provides additional flexibility.The performance in an asynchronous mode,such as ability of multiusers,anti-interferences ,is an-alyzed.

  14. Hot carrier multiplication on graphene/TiO2 Schottky nanodiodes

    Science.gov (United States)

    Lee, Young Keun; Choi, Hongkyw; Lee, Hyunsoo; Lee, Changhwan; Choi, Jin Sik; Choi, Choon-Gi; Hwang, Euyheon; Park, Jeong Young

    2016-06-01

    Carrier multiplication (i.e. generation of multiple electron–hole pairs from a single high-energy electron, CM) in graphene has been extensively studied both theoretically and experimentally, but direct application of hot carrier multiplication in graphene has not been reported. Here, taking advantage of efficient CM in graphene, we fabricated graphene/TiO2 Schottky nanodiodes and found CM-driven enhancement of quantum efficiency. The unusual photocurrent behavior was observed and directly compared with Fowler’s law for photoemission on metals. The Fowler’s law exponent for the graphene-based nanodiode is almost twice that of a thin gold film based diode; the graphene-based nanodiode also has a weak dependence on light intensity—both are significant evidence for CM in graphene. Furthermore, doping in graphene significantly modifies the quantum efficiency by changing the Schottky barrier. The CM phenomenon observed on the graphene/TiO2 nanodiodes can lead to intriguing applications of viable graphene-based light harvesting.

  15. Soft, transparent, electronic skin for distributed and multiple pressure sensing.

    Science.gov (United States)

    Levi, Alessandro; Piovanelli, Matteo; Furlan, Silvano; Mazzolai, Barbara; Beccai, Lucia

    2013-01-01

    In this paper we present a new optical, flexible pressure sensor that can be applied as smart skin to a robot or to consumer electronic devices. We describe a mechano-optical transduction principle that can allow the encoding of information related to an externally applied mechanical stimulus, e.g., contact, pressure and shape of contact. The physical embodiment that we present in this work is an electronic skin consisting of eight infrared emitters and eight photo-detectors coupled together and embedded in a planar PDMS waveguide of 5.5 cm diameter. When a contact occurs on the sensing area, the optical signals reaching the peripheral detectors experience a loss because of the Frustrated Total Internal Reflection and deformation of the material. The light signal is converted to electrical signal through an electronic system and a reconstruction algorithm running on a computer reconstructs the pressure map. Pilot experiments are performed to validate the tactile sensing principle by applying external pressures up to 160 kPa. Moreover, the capabilities of the electronic skin to detect contact pressure at multiple subsequent positions, as well as its function on curved surfaces, are validated. A weight sensitivity of 0.193 gr(-1) was recorded, thus making the electronic skin suitable to detect pressures in the order of few grams. PMID:23686140

  16. Soft, Transparent, Electronic Skin for Distributed and Multiple Pressure Sensing

    Directory of Open Access Journals (Sweden)

    Alessandro Levi

    2013-05-01

    Full Text Available In this paper we present a new optical, flexible pressure sensor that can be applied as smart skin to a robot or to consumer electronic devices. We describe a mechano-optical transduction principle that can allow the encoding of information related to an externally applied mechanical stimulus, e.g., contact, pressure and shape of contact. The physical embodiment that we present in this work is an electronic skin consisting of eight infrared emitters and eight photo-detectors coupled together and embedded in a planar PDMS waveguide of 5.5 cm diameter. When a contact occurs on the sensing area, the optical signals reaching the peripheral detectors experience a loss because of the Frustrated Total Internal Reflection and deformation of the material. The light signal is converted to electrical signal through an electronic system and a reconstruction algorithm running on a computer reconstructs the pressure map. Pilot experiments are performed to validate the tactile sensing principle by applying external pressures up to 160 kPa. Moreover, the capabilities of the electronic skin to detect contact pressure at multiple subsequent positions, as well as its function on curved surfaces, are validated. A weight sensitivity of 0.193 gr−1 was recorded, thus making the electronic skin suitable to detect pressures in the order of few grams.

  17. Dynamic Rate Allocation in Fading Multiple-access Channels

    CERN Document Server

    ParandehGheibi, Ali; Ozdaglar, Asuman; Medard, Muriel

    2008-01-01

    We consider the problem of rate allocation in a fading Gaussian multiple-access channel (MAC) with fixed transmission powers. Our goal is to maximize a general concave utility function of transmission rates over the throughput capacity region. In contrast to earlier works in this context that propose solutions where a potentially complex optimization problem must be solved in every decision instant, we propose a low-complexity approximate rate allocation policy and analyze the effect of temporal channel variations on its utility performance. To the best of our knowledge, this is the first work that studies the tracking capabilities of an approximate rate allocation scheme under fading channel conditions. We build on an earlier work to present a new rate allocation policy for a fading MAC that implements a low-complexity approximate gradient projection iteration for each channel measurement, and explicitly characterize the effect of the speed of temporal channel variations on the tracking neighborhood of our p...

  18. Carrier localization effect in polarized InGaN multiple quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Zukauskas, A.; Kazlauskas, K.; Tamulaitis, G.; Mickevicius, J.; Jursenas, S.; Kurilcik, G.; Miasojedovas, S. [Institute of Materials Science and Applied Research, Vilnius University, Sauletekio al. 9, Build. III, 10222 Vilnius (Lithuania); Springis, M.; Tale, I. [Institute of Solid State Physics, University of Latvia, Kengaraga iela 8, Riga 1063 (Latvia); Cheng, Yung-Chen; Wang, Hsiang-Chen; Huang, Chi-Feng; Yang, C.C. [Graduate Institute of Electro-Optical Engineering, National Taiwan University, 1 Roosevelt Road, Sec. 4, Taipei (Taiwan)

    2005-05-01

    Carrier localization effects in polarized InGaN/GaN multiple quantum wells (MQWs) were investigated as a function of well width, d, and In content, x. Using photoreflectance (PR), photoluminescence (PL), PL excitation (PLE), selective excitation of PL, PL excitation power, and time-resolved PL spectroscopy, the dominance of the localization effect against the built-in field effect on carrier recombination dynamics in In{sub x}Ga{sub 1-x}N MQWs of different well width (d = 2.0-4.0 nm, x {approx} 0.15) and In content (x {approx} 0.22-0.27, d = 2.5 nm) was revealed. Based on the modeling of the PL spectra by Monte Carlo simulation of exciton hopping and the spectroscopic reference provided by PR, increased In content and well width were found to increase the band potential fluctuations and carrier localization depth. The density of localized states deduced from the simulation was found to be in a fair agreement with the PLE data. The built-in field strength in InGaN QWs containing 15% of In was estimated to be of 0.5 MV/cm. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  19. A QUANTUM MULTIPLE ACCESS COMMUNICATIONS SCHEME USING ORBITAL ANGULAR MOMENTUM

    Institute of Scientific and Technical Information of China (English)

    Dong Xiaoliang; Zhao Shengmei; Zheng Baoyu

    2013-01-01

    We propose a quantum multiple access communications scheme using Orbital Angular Momentum (OAM) sector states in the paper.In the scheme,each user has an individual modified Poincare Bloch sphere and encodes his information with his own corresponding sector OAM states.A prepared entangled photon pairs are separated at transmitter and receiver.At the transmitter,each user encodes his information with the sector OAM states on the photons and the superposition of the different sector OAM states is carried by the photons.Then the photons are transmitted through quantum noiseless channel to the receiver.At the receiver,each user could retrieve his information by coincidently measuring the transmitted photons with the receiver side photons which are modulated by a special prepared measurement basis.The theoretical analysis and the numerical simulations show that each user could get his information from the superposition state without error.It seems that this scheme provides a novel method for quantum multiple users communications.

  20. Coalitional Games in Partition Form for Joint Spectrum Sensing and Access in Cognitive Radio Networks

    CERN Document Server

    Saad, Walid; Zheng, Rong; Hjørungnes, Are; Başar, Tamer; Poor, H Vincent

    2012-01-01

    Unlicensed secondary users (SUs) in cognitive radio networks are subject to an inherent tradeoff between spectrum sensing and spectrum access. Although each SU has an incentive to sense the primary user (PU) channels for locating spectrum holes, this exploration of the spectrum can come at the expense of a shorter transmission time, and, hence, a possibly smaller capacity for data transmission. This paper investigates the impact of this tradeoff on the cooperative strategies of a network of SUs that seek to cooperate in order to improve their view of the spectrum (sensing), reduce the possibility of interference among each other, and improve their transmission capacity (access). The problem is modeled as a coalitional game in partition form and an algorithm for coalition formation is proposed. Using the proposed algorithm, the SUs can make individual distributed decisions to join or leave a coalition while maximizing their utilities which capture the average time spent for sensing as well as the capacity achi...

  1. Cyclostationary Beacon for Assisting Spectrum Sensing in Opportunistic Spectrum Access

    Directory of Open Access Journals (Sweden)

    Thomas Kaiser

    2011-03-01

    Full Text Available Cognitive radio is a promising solution to the problem of spectrum scarcity by means of allowing secondary radio networks access the spectrum opportunistically. One of the most important issues in cognitive radio is how to detect existing over-the-air signals reliably. Not a few literatures have reported that signals could be detected via their inherent or embedded properties. However, this approach may not be reliable and flexible enough for all kinds of signals with different modulation types. In this paper, we propose a type of multitone beacon signal carrying cyclostationary signatures, which is able to enhance the reliability and efficiency of signal detection at low cost of spectrum overhead. This beacon not only can indicate the presence or absence of user signal but also can reveal some other information helpful to opportunistic spectrum access through the information bits carried on its cyclostationary signatures. It could be applied to device/network identification, indication of spectrum allocation and spectrum rendezvous, both for primary and secondary users. Based on our previous work reported in [1], the generation and detection algorithm of the beacon signal are extended with improved spectral efficiency. Performance is discussed with both computer simulation and testbed validation.

  2. An Enhanced Multiple Random Access Scheme for Satellite Communications

    CERN Document Server

    Bui, Huyen-Chi; Boucheret, Marie-Laure

    2011-01-01

    In this paper, we introduce Multi-Slots Coded ALOHA (MuSCA) as a multiple random access method for satellite communications. This scheme can be considered as a generalization of the Contention Resolution Diversity Slotted Aloha (CRDSA) mechanism. Instead of transmitting replicas, this system replaces them by several parts of a single word of an error correcting code. It is also different from Coded Slotted ALOHA (CSA) as the assumption of destructive collisions is not adopted. In MuSCA, the entity in charge of the decoding mechanism collects all bursts of the same user (including the interfered slots) before decoding and implements a successive interference cancellation (SIC) process to remove successfully decoded signals. Simulations show that for a frame of 100 slots, the achievable total normalized throughput is greater than 1.25 and 1.4 for a frame of 500 slots, resulting in a gain of 80% and 75% with respect to CRDSA and CSA respectively. This paper is a first analysis of the proposed scheme and opens se...

  3. Explicit receivers for pure-interference bosonic multiple access channels

    CERN Document Server

    Wilde, Mark M

    2012-01-01

    The pure-interference bosonic multiple access channel has two senders and one receiver, such that the senders each communicate with a single mode of light and the effect of the channel is to mix their transmissions on a beamsplitter. The receiver then obtains a signal from one of the output ports. In prior work, Yen and Shapiro found the capacity region of this channel if the senders are restricted to coherent-state encodings. Here, we demonstrate how to achieve the Yen-Shapiro region (in some cases) with a sequential decoding strategy, such that the receiver performs binary-outcome quantum measurements for every codeword pair in the senders' codebooks. A crucial component of this scheme is a non-destructive "vacuum-or-not" measurement that projects an n-symbol modulated codeword onto the n-fold vacuum state or its orthogonal complement, such that the post-measurement state is either the n-fold vacuum or has the vacuum removed from the support of the n symbols' joint quantum state. This receiver requires the ...

  4. Multiple Access Techniques for Next Generation Wireless: Recent Advances and Future Perspectives

    Directory of Open Access Journals (Sweden)

    Shree Krishna Sharma

    2016-01-01

    Full Text Available The advances in multiple access techniques has been one of the key drivers in moving from one cellular generation to another. Starting from the first generation, several multiple access techniques have been explored in different generations and various emerging multiplexing/multiple access techniques are being investigated for the next generation of cellular networks. In this context, this paper first provides a detailed review on the existing Space Division Multiple Access (SDMA related works. Subsequently, it highlights the main features and the drawbacks of various existing and emerging multiplexing/multiple access techniques. Finally, we propose a novel concept of clustered orthogonal signature division multiple access for the next generation of cellular networks. The proposed concept envisions to employ joint antenna coding in order to enhance the orthogonality of SDMA beams with the objective of enhancing the spectral efficiency of future cellular networks.

  5. An Acquisition Performance Analysis of DS-MC-CDMA System under Multiple Access Interference Conditions

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Multi-Access Interference's (MAI's) effect on parallel acquisition performance of DS-Multi-carrier CDMA system under the typical indoor radio channel is discussed in the paper. Moreover, a comparison of acquisition performance impairment produced by the MAI in DS-MC-CDMA and DS-Single-carrier CDMA is also made. Results are given in terms of average acquisition time obtained by means of simulations and theory analysis.

  6. Blind Identification of Distributed Antenna Systems with Multiple Carrier Frequency Offsets

    CERN Document Server

    Yu, Yuanning; Poor, H Vincent

    2007-01-01

    In spatially distributed multiuser antenna systems, the received signal contains multiple carrier-frequency offsets (CFOs) arising from mismatch between the oscillators of transmitters and receivers. This results in a time-varying rotation of the data constellation, which needs to be compensated at the receiver before symbol recovery. In this paper, a new approach for blind CFO estimation and symbol recovery is proposed. The received base-band signal is over-sampled, and its polyphase components are used to formulate a virtual Multiple-Input Multiple-Output (MIMO) problem. By applying blind MIMO system estimation techniques, the system response can be estimated and decoupled versions of the user symbols can be recovered, each one of which contains a distinct CFO. By applying a decision feedback Phase Lock Loop (PLL), the CFO can be mitigated and the transmitted symbols can be recovered. The estimated MIMO system response provides information about the CFOs that can be used to initialize the PLL, speed up its ...

  7. Characterisation of multiple carrier transport in indium nitride grown by molecular beam epitaxy

    International Nuclear Information System (INIS)

    Quantitative mobility spectrum analysis (QMSA) was performed on multiple magnetic field Hall effect measurements of indium nitride grown by molecular beam epitaxy. This enables two clearly distinct electron species to be identified, which are attributed to the bulk and a surface accumulation layer. In this material, single magnetic field data corresponds to neither electron species, as both contribute significantly to the total conduction. The bulk electron distribution has an extracted average Hall mobility of 3570 cm2/(Vs) at 300 K with a concentration of 1.5 x 1017 cm-3, while the surface electrons have sheet charge density that is an order of magnitude higher than previously reported surface concentrations. The high quality bulk characteristics revealed emphasise the importance of using multi-carrier analysis when performing transport measurements on InN. (Abstract Copyright [2007], Wiley Periodicals, Inc.)

  8. Enhancing Access to Land Remote Sensing Data through Mainstream Social Media Channels

    Science.gov (United States)

    Sohre, T.; Maiersperger, T.

    2011-12-01

    Social media tools are changing the way that people discover information, communicate, and collaborate. Government agencies supporting the Land Remote Sensing user community have begun taking advantage of standard social media tools and capabilities. National Aeronautics and Space Administration (NASA) Earth Observing System (EOS) data centers have started providing outreach utilizing services including Facebook, Twitter, and YouTube videos. Really Simple Syndication (RSS) Feeds have become more standard means of sharing information, and a DataCasting tool was created as a NASA Technology Infusion effort to make RSS-based technology for accessing Earth Science information available. The United States Geological Survey (USGS) has also started using social media to allow the community access to news feeds and real-time earthquake alerts; listen to podcasts; get updates on new USGS publications, videos, and photographs; and more. Twitter feeds have been implemented in 2011 for the USGS Land Cover and Landsat user communities. In early 2011, the NASA Land Processes Distributed Active Archive Center (LP DAAC) user working group suggested the investigation of concepts for creating and distributing "bundles" of data, which would aggregate theme-based data sets from multiple sources. The LP DAAC is planning to explore the use of standard social bookmarking tools to support community developed bundles through the use of tools such as Delicious, Digg, or StumbleUpon. This concept would allow science users to organize and discover common links to data resources based on community developed tags, or a folksonomy. There are challenges that will need to be addressed such as maintaining the quality of tags but a social bookmarking system may have advantages over traditional search engines or formal ontologies for identifying and labeling various data sets relevant to a theme. As classification is done by the community of scientists who understand the data, the tagged data sets

  9. PERFORMANCE OF OPPORTUNISTIC SPECTRUM ACCESS WITH SENSING ERROR IN COGNITIVE RADIO AD HOC NETWORKS

    Directory of Open Access Journals (Sweden)

    N. ARMI

    2012-04-01

    Full Text Available Sensing in opportunistic spectrum access (OSA has a responsibility to detect the available channel by performing binary hypothesis as busy or idle states. If channel is busy, secondary user (SU cannot access and refrain from data transmission. SU is allowed to access when primary user (PU does not use it (idle states. However, channel is sensed on imperfect communication link. Fading, noise and any obstacles existed can cause sensing errors in PU signal detection. False alarm detects idle states as a busy channel while miss-identification detects busy states as an idle channel. False detection makes SU refrain from transmission and reduces number of bits transmitted. On the other hand, miss-identification causes SU collide to PU transmission. This paper study the performance of OSA based on the greedy approach with sensing errors by the restriction of maximum collision probability allowed (collision threshold by PU network. The throughput of SU and spectrum capacity metric is used to evaluate OSA performance and make comparisons to those ones without sensing error as function of number of slot based on the greedy approach. The relations between throughput and signal to noise ratio (SNR with different collision probability as well as false detection with different SNR are presented. According to the obtained results show that CR users can gain the reward from the previous slot for both of with and without sensing errors. It is indicated by the throughput improvement as slot number increases. However, sensing on imperfect channel with sensing errors can degrade the throughput performance. Subsequently, the throughput of SU and spectrum capacity improves by increasing maximum collision probability allowed by PU network as well. Due to frequent collision with PU, the throughput of SU and spectrum capacity decreases at certain value of collision threshold. Computer simulation is used to evaluate and validate these works.

  10. High-Frequency Link Inverter for Fuel Cells Based on Multiple-Carrier PWM (to continue)

    Institute of Scientific and Technical Information of China (English)

    2004-01-01

    C. Operation of a PWM Cycloconverter The concepts in Section Ⅱ-B, present a progression of solutions to known design difficulties. To incorporate these benefits and eliminate the redundant conversion step shown in Fig. 6, we propose the PWM cycloconverter shown in Fig. 7. It will be shown in Section Ⅲ. that the conventional PWM inverter can be unified through a multiple-carrier PWM framework. The control concept introduced is extended to demonstrate that multiple-carrier PWM methods lead to HF link inverters that are nearly as simple to control as conventional PWM inverters.

  11. Novel Scheme of Carrier Tri-reuse and Distribution Fiber Protection Based on Round Shift Method in Optical Access Network

    Science.gov (United States)

    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.

  12. Scalable Lunar Surface Networks and Adaptive Orbit Access

    Science.gov (United States)

    Wang, Xudong

    2015-01-01

    Teranovi Technologies, Inc., has developed innovative network architecture, protocols, and algorithms for both lunar surface and orbit access networks. A key component of the overall architecture is a medium access control (MAC) protocol that includes a novel mechanism of overlaying time division multiple access (TDMA) and carrier sense multiple access with collision avoidance (CSMA/CA), ensuring scalable throughput and quality of service. The new MAC protocol is compatible with legacy Institute of Electrical and Electronics Engineers (IEEE) 802.11 networks. Advanced features include efficiency power management, adaptive channel width adjustment, and error control capability. A hybrid routing protocol combines the advantages of ad hoc on-demand distance vector (AODV) routing and disruption/delay-tolerant network (DTN) routing. Performance is significantly better than AODV or DTN and will be particularly effective for wireless networks with intermittent links, such as lunar and planetary surface networks and orbit access networks.

  13. Secondary access based on sensing and primary ARQ feedback in spectrum sharing systems

    KAUST Repository

    Hamza, Doha R.

    2012-04-01

    In the context of primary/secondary spectrum sharing, we propose a randomized secondary access strategy with access probabilities that are a function of both the primary automatic repeat request (ARQ) feedback and the spectrum sensing outcome. The primary terminal operates in a time slotted fashion and is active only when it has a packet to send. The primary receiver can send a positive acknowledgment (ACK) when the received packet is decoded correctly. Lack of ARQ feedback is interpreted as erroneous reception or inactivity. We call this the explicit ACK scheme. The primary receiver may also send a negative acknowledgment (NACK) when the packet is received in error. Lack of ARQ feedback is interpreted as an ACK or no-transmission. This is called the explicit NACK scheme. Under both schemes, when the primary feedback is interpreted as a NACK, the secondary user assumes that there will be retransmission in the next slot and accesses the channel with a certain probability. When the primary feedback is interpreted as an ACK, the secondary user accesses the channel with either one of two probabilities based on the sensing outcome. Under these settings, we find the three optimal access probabilities via maximizing the secondary throughput given a constraint on the primary throughput. We compare the performance of the explicit ACK and explicit NACK schemes and contrast them with schemes based on either sensing or primary ARQ feedback only. © 2012 IEEE.

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

    Science.gov (United States)

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

    2014-01-01

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

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

    Directory of Open Access Journals (Sweden)

    Yunchuan Guo

    2014-01-01

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

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

    Science.gov (United States)

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

    2014-01-01

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

  17. A Soft Sensing-Based Cognitive Access Scheme Exploiting Primary Feedback

    CERN Document Server

    Arafa, Ahmed M; Sultan, Ahmed K; ElBatt, Tamer; El-Sherif, Amr A

    2012-01-01

    In this paper, we examine a cognitive spectrum access scheme in which secondary users exploit the primary feedback information. We consider an overlay secondary network employing a random access scheme in which secondary users access the channel by certain access probabilities that are function of the spectrum sensing metric. In setting our problem, we assume that secondary users can eavesdrop on the primary link's feedback. We study the cognitive radio network from a queuing theory point of view. Access probabilities are determined by solving a secondary throughput maximization problem subject to a constraint on the primary queues' stability. First, we formulate our problem which is found to be non-convex. Yet, we solve it efficiently by exploiting the structure of the secondary throughput equation. Our scheme yields improved results in, both, the secondary user throughput and the primary user packet delay. In addition, it comes very close to the optimal genie-aided scheme in which secondary users act upon t...

  18. A 433-MHz Rail-to-Rail Voltage Amplifier with Carrier Sensing Function for Wireless Sensor Networks

    Science.gov (United States)

    Takeuchi, Takashi; Mikami, Shinji; Lee, Hyeokjong; Kawaguchi, Hiroshi; Ohta, Chikara; Yoshimoto, Masahiko

    In this paper we propose a novel functional amplifier suitable for low-power wireless receivers in a wireless sensor network. This amplifier can change input threshold level as carrier sensing level, since it has a minimum input amplitude to be amplified. A simple rail-to-rail output is suitable for a subsequent digital interface. The target frequency is 433MHz, and the maximum voltage gain is 11dB. The standby power is 39.5nW, and the active power is 352µW. The chip area is 82 × 24µm2.

  19. Wide area real time kinematic decimetre positioning with multiple carrier GNSS signals

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    This paper presents the technical basis for wide area real time decimetre positioning services using multiple carrier signals transmitted by future GNSS such as modernized GPS and Compass systems. The first step is to form two ionosphere-reduced extra-widelanes (EWL) that have the minimal total noise levels in cycles, considering the effects of the ionospheric and tropospheric delays, orbital error, and phase noise terms in various observational environments. The proposed three carrier ambiguity resolution approach can determine the integer ambiguities of the selected EWL signals with geometry-free and geometry- based estimations respectively over the distances of typically hundreds of kilometres. With two ambiguity-fixed EWL signals, the kinematic positioning solutions can be achieved in decimetre level accuracy. A semi-simulation method is employed to generate three frequency Compass data to demonstrate the above expected performance for decimetre positioning services. Both theoretical and experimental results have demonstrated the overall 3D root mean square accuracy of better than 15 cm obtained through with a phase smoothing process over 120 epochs. The dominating error factor in this positioning result is the residual tropospheric biases, which would become less correlated as the baselines grow beyond hundreds of kilometres. With respect to dual-frequency based precise point positioning and wide area differential positioning solutions, a major advantage of using the third frequency signals is the convergence time being shorten from tens of minutes to a few minutes. In addition, due to the instant ambiguity resolution capability, phase breaks or cycle slips no longer affect the continuity of the solutions. This reliable decimetre positioning capability introduces a significant improvement to safety-of-life, liability-critical and professional applications.

  20. Accessing and Utilizing Remote Sensing Data for Vectorborne Infectious Diseases Surveillance and Modeling

    Science.gov (United States)

    Kiang, Richard; Adimi, Farida; Kempler, Steven

    2008-01-01

    Background: The transmission of vectorborne infectious diseases is often influenced by environmental, meteorological and climatic parameters, because the vector life cycle depends on these factors. For example, the geophysical parameters relevant to malaria transmission include precipitation, surface temperature, humidity, elevation, and vegetation type. Because these parameters are routinely measured by satellites, remote sensing is an important technological tool for predicting, preventing, and containing a number of vectorborne infectious diseases, such as malaria, dengue, West Nile virus, etc. Methods: A variety of NASA remote sensing data can be used for modeling vectorborne infectious disease transmission. We will discuss both the well known and less known remote sensing data, including Landsat, AVHRR (Advanced Very High Resolution Radiometer), MODIS (Moderate Resolution Imaging Spectroradiometer), TRMM (Tropical Rainfall Measuring Mission), ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer), EO-1 (Earth Observing One) ALI (Advanced Land Imager), and SIESIP (Seasonal to Interannual Earth Science Information Partner) dataset. Giovanni is a Web-based application developed by the NASA Goddard Earth Sciences Data and Information Services Center. It provides a simple and intuitive way to visualize, analyze, and access vast amounts of Earth science remote sensing data. After remote sensing data is obtained, a variety of techniques, including generalized linear models and artificial intelligence oriented methods, t 3 can be used to model the dependency of disease transmission on these parameters. Results: The processes of accessing, visualizing and utilizing precipitation data using Giovanni, and acquiring other data at additional websites are illustrated. Malaria incidence time series for some parts of Thailand and Indonesia are used to demonstrate that malaria incidences are reasonably well modeled with generalized linear models and artificial

  1. Cognitive Spectrum Efficient Multiple Access Technique using Relay Systems

    DEFF Research Database (Denmark)

    Frederiksen, Flemming Bjerge; Prasad, Ramjee

    2007-01-01

    Methods to enhance the use of the frequency spectrum by automatical spectrum sensing plus spectrum sharing in a cognitive radio technology context will be presented and discussed in this paper. Ideas to increase the coverage of cellular systems by relay channels, relay stations and collaborate...... radio will be presented as well....

  2. Adaptive Information Access on Multiple Applications Support Wireless Sensor Networks

    DEFF Research Database (Denmark)

    Tobgay, Sonam; Olsen, Rasmus Løvenstein; Prasad, Ramjee

    2014-01-01

    Accessing information remotely to dynamically changing information elements cannot be avoided and has become a required functionality for various network services. Most applications require up-to-date information which is reliable and accurate. The information reliability in terms of using correct...

  3. Radio Access Sharing Strategies for Multiple Operators in Cellular Networks

    DEFF Research Database (Denmark)

    Popovska Avramova, Andrijana; Iversen, Villy Bæk

    2015-01-01

    Mobile operators are moving towards sharing network capacity in order to reduce capital and operational expenditures, while meeting the increasing demand for mobile broadband data services. Radio access network sharing is a promising technique that leads to reduced number of physical base station...

  4. Pilotless recovery of clipped OFDM signals by compressive sensing over reliable data carriers

    KAUST Repository

    Al-Safadi, Ebrahim B.

    2012-06-01

    In this paper we propose a novel method of clipping mitigation in OFDM using compressive sensing that completely avoids using reserved tones or channel-estimation pilots. The method builds on selecting the most reliable perturbations from the constellation lattice upon decoding at the receiver (in the frequency domain), and performs compressive sensing over these observations in order to completely recover the sparse nonlinear distortion in the time domain. As such, the method provides a practical solution to the problem of initial erroneous decoding decisions in iterative ML methods, and the ability to recover the distorted signal in one shot. © 2012 IEEE.

  5. Pilotless Recovery of Clipped OFDM Signals by Compressive Sensing over Reliable Data Carriers

    CERN Document Server

    Safadi, Ebrahim B Al

    2011-01-01

    In this paper we propose a novel form of clipping mitigation in OFDM using compressive sensing that completely avoids tone reservation and hence rate loss for this purpose. The method builds on selecting the most reliable perturbations from the constellation lattice upon decoding at the receiver, and performs compressive sensing over these observations in order to completely recover the temporally sparse nonlinear distortion. As such, the method provides a unique practical solution to the problem of initial erroneous decoding decisions in iterative ML methods, offering both the ability to augment these techniques and to solely recover the distorted signal in one shot.

  6. Generating free charges by carrier multiplication in quantum dots for highly efficient photovoltaics.

    Science.gov (United States)

    Ten Cate, Sybren; Sandeep, C S Suchand; Liu, Yao; Law, Matt; Kinge, Sachin; Houtepen, Arjan J; Schins, Juleon M; Siebbeles, Laurens D A

    2015-02-17

    CONSPECTUS: In a conventional photovoltaic device (solar cell or photodiode) photons are absorbed in a bulk semiconductor layer, leading to excitation of an electron from a valence band to a conduction band. Directly after photoexcitation, the hole in the valence band and the electron in the conduction band have excess energy given by the difference between the photon energy and the semiconductor band gap. In a bulk semiconductor, the initially hot charges rapidly lose their excess energy as heat. This heat loss is the main reason that the theoretical efficiency of a conventional solar cell is limited to the Shockley-Queisser limit of ∼33%. The efficiency of a photovoltaic device can be increased if the excess energy is utilized to excite additional electrons across the band gap. A sufficiently hot charge can produce an electron-hole pair by Coulomb scattering on a valence electron. This process of carrier multiplication (CM) leads to formation of two or more electron-hole pairs for the absorption of one photon. In bulk semiconductors such as silicon, the energetic threshold for CM is too high to be of practical use. However, CM in nanometer sized semiconductor quantum dots (QDs) offers prospects for exploitation in photovoltaics. CM leads to formation of two or more electron-hole pairs that are initially in close proximity. For photovoltaic applications, these charges must escape from recombination. This Account outlines our recent progress in the generation of free mobile charges that result from CM in QDs. Studies of charge carrier photogeneration and mobility were carried out using (ultrafast) time-resolved laser techniques with optical or ac conductivity detection. We found that charges can be extracted from photoexcited PbS QDs by bringing them into contact with organic electron and hole accepting materials. However, charge localization on the QD produces a strong Coulomb attraction to its counter charge in the organic material. This limits the production

  7. Centralized optical-frequency-comb-based RF carrier generator for DWDM fiber-wireless access systems

    DEFF Research Database (Denmark)

    Pang, Xiaodan; Beltran, Marta; Sanchez, Jose;

    2014-01-01

    In this paper, we report on a gigabit capacity fiber-wireless system that enables smooth integration between high-speed wireless networks and dense wavelength-division-multiplexing (DWDM) access networks. By employing a centralized optical frequency comb, both the wireline and the wireless services...

  8. DWDM Fiber-Wireless Access System with Centralized Optical Frequency Comb-based RF Carrier Generation

    DEFF Research Database (Denmark)

    Pang, Xiaodan; Beltrán, Marta; Sánchez, José;

    2013-01-01

    We propose and experimentally demonstrate an optical wireless DWDM system at 60 GHz with optical incoherent heterodyne up-conversion using an optical frequency comb. Multiple users with wireline and wireless services are simultaneously supported....

  9. Adaptive Information Access in Multiple Applications Support Wireless Sensor Network

    DEFF Research Database (Denmark)

    Tobgay, Sonam; Olsen, Rasmus Løvenstein; Prasad, Ramjee

    2012-01-01

    specific WSN considering its resource constraints, neglecting the return-of-investment and usefulness of the system. In this paper, we bring out the WSN scenario which supports multiple applications and study the challenges that would pose in implementation as each specific application has its own specific...

  10. Multiple Access Scheme for Multi-Symbol Encapsulated Orthogonal Frequency Division Multiplexing

    Directory of Open Access Journals (Sweden)

    Biswajit Datta

    2011-11-01

    Full Text Available A new multiple access scheme using Multi-Symbol Encapsulated Orthogonal Frequency Division Multiplexing (MSE-OFDM is proposed. This is basically a time division multiple access (TDMA technique utilizing the MSE-OFDM. The Bit Error Rate (BER performance of the TDMA system using conventional OFDM is slightly better than that of the proposed system. This weakness is compensated as the proposed technique exhibits an improvement in bandwidth efficiency compared to the TDMA using conventional OFDM.

  11. Academic and Non-Profit Accessibility to Commercial Remote Sensing Software

    Science.gov (United States)

    O'Connor, A. S.; Farr, B.

    2013-12-01

    Remote Sensing as a topic of teaching and research at the university and college level continues to increase. As more data is made freely available and software becomes easier to use, more and more academic and non-profits institutions are turning to remote sensing to solve their tough and large spatial scale problems. Exelis Visual Information Solutions (VIS) has been supporting teaching and research endeavors for over 30 years with a special emphasis over the last 5 years with scientifically proven software and accessible training materials. The Exelis VIS academic program extends to US and Canadian 2 year and 4 year colleges and universities with tools for analyzing aerial and satellite multispectral and hyperspectral imagery, airborne LiDAR and Synthetic Aperture Radar. The Exelis VIS academic programs, using the ENVI Platform, enables labs and classrooms to be outfitted with software and makes software accessible to students. The ENVI software provides students hands on experience with remote sensing software, an easy teaching platform for professors and allows researchers scientifically vetted software they can trust. Training materials are provided at no additional cost and can either serve as a basis for course curriculum development or self paced learning. Non-profit organizations like The Nature Conservancy (TNC) and CGIAR have deployed ENVI and IDL enterprise wide licensing allowing researchers all over the world to have cost effective access COTS software for their research. Exelis VIS has also contributed licenses to the NASA DEVELOP program. Exelis VIS is committed to supporting the academic and NGO community with affordable enterprise licensing, access to training materials, and technical expertise to help researchers tackle today's Earth and Planetary science big data challenges.

  12. Optimal Random Access and Random Spectrum Sensing for an Energy Harvesting Cognitive Radio with and without Primary Feedback Leveraging

    Directory of Open Access Journals (Sweden)

    Ahmed El Shafie

    2014-07-01

    Full Text Available We consider a secondary user (SU with energy harvesting capability. We design access schemes for the SU which incorporate random spectrum sensing and random access, and which make use of the primary automatic repeat request (ARQ feedback. We study two problem-formulations. In the first problemformulation, we characterize the stability region of the proposed schemes. The sensing and access probabilities are obtained such that the secondary throughput is maximized under the constraints that both the primary and secondary queues are stable. Whereas in the second problem-formulation, the sensing and access probabilities are obtained such that the secondary throughput is maximized under the stability of the primary queue and that the primary queueing delay is kept lower than a specified value needed to guarantee a certain quality of service (QoS for the primary user (PU. We consider spectrum sensing errors and assume multipacket reception (MPR capabilities. Numerical results show the enhanced performance of our proposed systems.

  13. Redefining nondiscriminatory access to remote sensing imagery and its impact on global transparency

    Science.gov (United States)

    Aten, Michelle L.

    2003-04-01

    Global transparency is founded on the Open Skies philosophy and its precept of non-discriminatory access. Global transparency implies that anyone can have anytime, anyplace access to a wide-array of remotely sensed imagery. The custom of non-discriminatory access requires that datasets of interest must be affordable, usable, and obtainable in a timely fashion devoid of political, economic or technical obstacles. Thus, an assessment of the correlation between the availability of satellite imagery and changes in governmental policies, pricing fluctuations of data, and advances in technology is critical to assessing the viability of global transparency. The Open Skies philosophy was originally proposed at the 1955 Geneva Summit to advocate mutually beneficial aerial reconnaissance missions over the USSR and the US as a verification tool for arms control and non-proliferation agreements. However, due to Cold War tensions, this philosophy and the custom of non-discriminatory were not widely adopted in the civilian remote sensing community until the commissioning of the Landsat Program in 1972. Since this time, commercial high-resolution satellites have drastically changed the circumstances on which the fundamental tenets of this philosophy are based. Since the successful launch of the first of this satellite class, the IKONOS satellite, high-resolution imagery is now available to non-US governments and an unlimited set of non-state actors. As more advanced capabilities are added to the growing assortment of remote sensing satellites, the reality of global transparency will rapidly evolve. This assessment includes an overview of historical precedents and a brief explanation of relevant US policy decisions that define non-discriminatory access with respect to US government and US based corporate assets. It also presents the dynamics of the political, economic, and technical barriers that may dictate or influence the remote sensing community's access to satellite data. In

  14. User—dependent Perfect—scheduling Multiple Access (UPMA) for Wireless Ad Hoc Networ

    Institute of Scientific and Technical Information of China (English)

    LIJiandong; LIWeiying; YANGJiawei; WENGJiwei

    2003-01-01

    A new multiple access protocol for wireless Internet access, called user-dependent perfect-scheduling multiple access (UPMA), is proposed. Packet transmis-sions are scheduled according to the number of active users,packet queue length and round-robin service rule. The proposed self-organizing algorithm is used to determine the number of active users. Users in ad h0c network are divided into clusters by the self-organizing algorithm. In each cluster an independent UPMA is used. UPMA al-gorithms for star and ad hoc wireless network are given.Performance analysis shows that UPMA have stable and very high throughnut.

  15. Optimum Access Analysis of Collaborative Spectrum Sensing in Cognitive Radio Network using MRC

    Directory of Open Access Journals (Sweden)

    Risala Tasin Khan

    2016-07-01

    Full Text Available The performance of cognitive radio network mainly depends on the finest sensing of the presence or absence of Primary User (PU. The throughput of a Secondary User (SU can be reduced because of the false detection of PU which causes an SU from its transmission opportunity. The factorization of the probability of correct decision is a really hard job when the special false alarm is incorporated into it. Previous works focus on collaborative sensing on the normal environment. In this paper, we have proposed a collaborative sensing method in Cognitive radio network for optimal access of PU licensed band by SU. It is shown performance analysis of energy detection through different cognitive users and conducts a clear comparison between local and collaborative sensing. In this paper, the maximal ratio combining diversity technique with energy detection has been employed to reduce the false alarm probability in the collaborative environment. The simulation result shows significant reduction of the probability of misdetection with increasing in the number of collaborative users. We also analyze that MRC scheme exhibits the best detection performance in collaborative environment.

  16. A Multiple-Reception Access Protocol with Interruptions with Mixed Priorities in CDMA Networks

    Institute of Scientific and Technical Information of China (English)

    Lu Xiaowen; Zhu Jinkang

    2003-01-01

    A novel access protocol called Multiple-Reception Access Protocol (MRAP) and its modification MRAP/WI are proposed. In this protocol, all colliding users with a common code can be identified by the base station due to the offset of arrival time Thus they can retransmit access requests under the base station's control. Furthermore new arrivals with higher priority level can interrupt the lower retransmission in order to reduce its access delay although it increases the lower priority's delay. Simulation results of MRAP and MRAP/WI are given in order to highlight the superior performance of the proposed approach.

  17. Performance analysis of spectrum sensing with multiple status changes in primary user traffic

    KAUST Repository

    Tang, Liang

    2012-06-01

    In this letter, the impact of primary user traffic with multiple status changes on the spectrum sensing performance is analyzed. Closed-form expressions for the probabilities of false alarm and detection are derived. Numerical results show that the multiple status changes of the primary user cause considerable degradation in the sensing performance. This degradation depends on the number of changes, the primary user traffic model, the primary user traffic intensity and the signal-to-noise ratio of the received signal. Numerical results also show that the amount of degradation decreases when the number of changes increases, and converges to a minimum sensing performance due to the limited sensing period and primary holding time. © 2012 IEEE.

  18. RF channel performance assessment for a multiple carrier millimeter-wave communication system

    Institute of Scientific and Technical Information of China (English)

    Thomas WONG; Ming YAN

    2004-01-01

    Channel capacity, system versatility and ease of maintenance are factors of prime concern in future generations of wireless communication systems. As a result, millimeter-wave can offer considerable advantages in providing broadband interface. Nonlinearity and noise effects, including parametric fluctuations, are two significant causes for signal degradation in broadband communication systems. Two methods to assess the performance of an RF channel in a multi-carrier system are described. By measuring the forward transfer function from transmitter IF to receiver IF as the frequency is swept across the channel bandwidth, characteristics such as gain flatness, channel dispersion, and saturation effects are revealed. To evaluate the ability of the communication link in preserving the synchronization between two carriers, their heterodyned spectrum at the receiver IF output is studied. Both measurement methods employ standard equipment and have been found to be effective when applied to a multi-carrier millimeter-wave system with over 1 GHz instantaneous bandwidth.

  19. Linear Precoding for the MIMO Multiple Access Channel with Finite Alphabet Inputs and Statistical CSI

    OpenAIRE

    Wu, Yongpeng; Wen, Chao-Kai; Xiao, Chengshan; Gao, Xiqi; Schober, Robert

    2014-01-01

    In this paper, we investigate the design of linear precoders for the multiple-input multiple-output (MIMO) multiple access channel (MAC). We assume that statistical channel state information (CSI) is available at the transmitters and consider the problem under the practical finite alphabet input assumption. First, we derive an asymptotic (in the large system limit) expression for the weighted sum rate (WSR) of the MIMO MAC with finite alphabet inputs and Weichselberger's MIMO channel model. S...

  20. Using Multiple Senses in Tourism Marketing: The Helsinki Expert, Eckero Line and Linnanmaki Amusement Park Cases

    OpenAIRE

    Isacsson, Annica; Alakoski, Leena; Bäck, Asta

    2009-01-01

    In order to create awareness & motivation among future travellers, tourism communication, should, according to our understanding, not only appeal to the visuals, but to all user senses in an inter medial mix. Hence, smell, sound, touch, taste and sight must be touched, in order for communication to be perceived valuable and interesting, as we argue that the activation of multiple senses enhances the feeling of authenticity and experience. If combined with ration and need, in addition to the i...

  1. Multi-channel Opportunistic Access: A Case of Restless Bandits with Multiple Plays

    CERN Document Server

    Ahmad, Sahand Haji Ali

    2009-01-01

    This paper considers the following stochastic control problem that arises in opportunistic spectrum access: a system consists of n channels (Gilbert-Elliot channels)where the state (good or bad) of each channel evolves as independent and identically distributed Markov processes. A user can select exactly k channels to sense and access (based on the sensing result) in each time slot. A reward is obtained whenever the user senses and accesses a good channel. The objective is to design a channel selection policy that maximizes the expected discounted total reward accrued over a finite or infinite horizon. In our previous work we established the optimality of a greedy policy for the special case of k = 1 (i.e., single channel access) under the condition that the channel state transitions are positively correlated over time. In this paper we show under the same condition the greedy policy is optimal for the general case of k >= 1; the methodology introduced here is thus more general. This problem may be viewed as ...

  2. Multiple stimulated emission fluorescence photoacoustic sensing and spectroscopy

    Science.gov (United States)

    Li, Gaoming; Gao, Fei; Qiu, Yishen; Feng, Xiaohua; Zheng, Yuanjin

    2016-07-01

    Multiple stimulated emission fluorescence photoacoustic (MSEF-PA) phenomenon is demonstrated in this letter. Under simultaneous illumination of pumping light and stimulated emission light, the fluorescence emission process is speeded up by the stimulated emission effect. This leads to nonlinear enhancement of photoacoustic signal while the quantity of absorbed photons is more than that of fluorescent molecules illuminated by pumping light. The electronic states' specificity of fluorescent molecular can also be labelled by the MSEF-PA signals, which can potentially be used to obtain fluorescence excitation spectrum in deep scattering tissue with nonlinearly enhanced photoacoustic detection. In this preliminary study, the fluorescence excitation spectrum is reconstructed by MSEF-PA signals through sweeping the wavelength of exciting light, which confirms the theoretical derivation well.

  3. Low-sampling-rate M-ary multiple access UWB communications in multipath channels

    KAUST Repository

    Alkhodary, Mohammad T.

    2015-08-31

    The desirable characteristics of ultra-wideband (UWB) technology are challenged by formidable sampling frequency, performance degradation in the presence of multi-user interference, and complexity of the receiver due to the channel estimation process. In this paper, a low-rate-sampling technique is used to implement M-ary multiple access UWB communications, in both the detection and channel estimation stages. A novel approach is used for multiple-access-interference (MAI) cancelation for the purpose of channel estimation. Results show reasonable performance of the proposed receiver for different number of users operating many times below Nyquist rate.

  4. Prospective Mathematics Teachers' Sense Making of Polynomial Multiplication and Factorization Modeled with Algebra Tiles

    Science.gov (United States)

    Caglayan, Günhan

    2013-01-01

    This study is about prospective secondary mathematics teachers' understanding and sense making of representational quantities generated by algebra tiles, the quantitative units (linear vs. areal) inherent in the nature of these quantities, and the quantitative addition and multiplication operations--referent preserving versus referent…

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

    Energy Technology Data Exchange (ETDEWEB)

    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

  6. AquaUsers: Improving access to remotely sensed data for non-specialists

    Science.gov (United States)

    Clements, Oliver; Walker, Peter; Calton, Ben; Miller, Peter

    2015-04-01

    In recent years more and more complex remotely sensed data have been made available to the public by national and international agencies. These data are also reprocessed by different organisations to produce secondary products that are of specific need to a community. For instance the production of chlorophyll concentration maps from ocean colour data provided by NASA for the marine community. Providing access to such data has normally been focused on simply making the data available with appropriate metadata so that domain specialists can make use of it. One area that has seen significant investment, both of time and money, has been in the production of web based data portals. Primarily these have focused on spatial data. By providing a web map visualisation users are able to quickly assess both spatial coverage and data values. Data portal improvements have been possible thanks to advancements in back end data servers such as Thredds and ncWMS as well as improvements in front-end libraries for data visualisation including OpenLayers and D3. Data portals that make use of these technological advancements have aimed at improving the access and use of data by trained scientific domain specialists. There is now a push to improve access to these systems by non-scientific domain specialists through several European Commission funded projects, including OPEC and AquaUsers. These projects have improved upon an open source web GIS portal created by Plymouth Marine Laboratory [https://github.com/pmlrsg/GISportal]. We will present the latest version of our GIS portal, discuss the designs steps taken to achieve the latest build and share user stories as to how non-domain specialists are now able to utilise the system and get benefits from remotely sensed data. A first version was produced and disseminated to end users for feedback. At this stage the end users included government advisors, fish farmers and scientific groups with no specific GIS training or knowledge. This

  7. Integrated reconfigurable multiple-input–multiple-output antenna system with an ultra-wideband sensing antenna for cognitive radio platforms

    KAUST Repository

    Hussain, Rifaqat

    2015-06-18

    © The Institution of Engineering and Technology 2015. A compact, novel multi-mode, multi-band frequency reconfigurable multiple-input-multiple-output (MIMO) antenna system, integrated with ultra-wideband (UWB) sensing antenna, is presented. The developed model can be used as a complete antenna platform for cognitive radio applications. The antenna system is developed on a single substrate area of dimensions 65 × 120 mm2. The proposed sensing antenna is used to cover a wide range of frequency bands from 710 to 3600 MHz. The frequency reconfigurable dual-element MIMO antenna is integrated with P-type, intrinsic, N-type (PIN) diodes for frequency agility. Different modes of selection are used for the MIMO antenna system reconfigurability to support different wireless system standards. The proposed MIMO antenna configuration is used to cover various frequency bands from 755 to 3450 MHz. The complete system comprising the multi-band reconfigurable MIMO antennas and UWB sensing antenna for cognitive radio applications is proposed with a compact form factor.

  8. Experimental demonstration of 2.5 Gbit/S incoherent two-dimensional optical code division multiple access system

    International Nuclear Information System (INIS)

    We demonstrated error-free operation of 4 simultaneous users in a fast frequency-hopping time-spreading optical code division multiple access system operating at 2.5 Gbit/s a Star architecture. Effective power penalty was ≤0.5dB. Novel optical code division multiple access receiver based on Terahertz Optical Asymmetric Demultiplexer was demonstrated to eliminate multiple access interference (Authors)

  9. Implementation of Multiple Host Nodes in Wireless Sensing Node Network System for Landslide Monitoring

    International Nuclear Information System (INIS)

    This paper proposes multiple host nodes in Wireless Sensing Node Network System (WSNNS) for landslide monitoring. As landslide disasters damage monitoring system easily, one major demand in landslide monitoring is the flexibility and robustness of the system to evaluate the current situation in the monitored area. For various reasons WSNNS can provide an important contribution to reach that aim. In this system, acceleration sensors and GPS are deployed in sensing nodes. Location information by GPS, enable the system to estimate network topology and enable the system to perceive the location in emergency by monitoring the node mode. Acceleration sensors deployment, capacitate this system to detect slow mass movement that can lead to landslide occurrence. Once deployed, sensing nodes self-organize into an autonomous wireless ad hoc network. The measurement parameter data from sensing nodes is transmitted to Host System via host node and ''Cloud'' System. The implementation of multiple host nodes in Local Sensing Node Network System (LSNNS), improve risk- management of the WSNNS for real-time monitoring of landslide disaster

  10. Ultrafast Supercontinuum Spectroscopy of Carrier Multiplication and Biexcitonic Effects in Excited States of PbS Quantum Dots

    Energy Technology Data Exchange (ETDEWEB)

    Sfeir M. Y.; Gesuele, F.; Koh, W.-K.; Murray, C.B.; Heinz, T.F.; Wong, C.W.

    2012-06-01

    We examine the population dynamics of multiple excitons in PbS quantum dots using spectrally resolved ultrafast supercontinuum transient absorption (SC-TA) measurements. We simultaneously probe the first three excitonic transitions. The transient spectra show the presence of bleaching of absorption for the 1S{sub h}-1S{sub e} transition, as well as transients associated with the 1P{sub h}-1P{sub e} transition. We examine signatures of carrier multiplication (multiple excitons arising from a single absorbed photon) from analysis of the bleaching features in the limit of low absorbed photon numbers (multiple-exciton generation is discussed both in terms of the ratio between early- to long-time transient absorption signals and of a broadband global fit to the data. Analysis of the population dynamics shows that bleaching associated with biexciton population is red shifted with respect to the single exciton feature, which is in accordance with a positive binding energy for the biexciton.

  11. Influence of Rapid Thermal Annealing on Carrier Dynamics in GaInNAs/GaAs Multiple Quantum Wells

    Institute of Scientific and Technical Information of China (English)

    ZHOU Wei; YANG Jie; XIA Su-Jing; LI Xiang; TANG Wu

    2011-01-01

    The excitation intensity and time-resolved photoluminescence spectroscopy are used to investigate the impact of annealing on the carrier dynamics in the Ga0.66In0.34N0.013As0.987 /GaAs multiple quantum well structure grown by metalorganic chemical vapor deposition.The measurement of excitation intensity photoluminescence (PL),performed for as-grown and annealed samples at different temperatures,indicates that the localized potential has come down slightly after annealing but does not alter the fact that PL emission at low temperature is dominated by localized exciton recombination.In contrast,free carrier recombination is magnified by post-grown annealing at room temperature.Our results show that the decay times are 0.587 and 0.327ns at 10K for the as-grown and annealed samples,and radiative decay times also shorten significantly after annealing at all temperatures.Hence the improvement of luminescence efficiency after annealing is caused by the reduction of localization and enhancement of radiative recombination rate.The reduction of the density of nonradiative centers is demonstrated indirectly after annealing.Recently,GaInNAs alloys have attracted an increasing amount of attention,driven by not only their potential applications in various electronic and optoelectronics devices but also their intriguing physical properties.[1] It has been demonstrated that the optical quality of GaInNAs/GaAs quantum wells can be improved by rapid thermal annealing (RTA).[2,3]%The excitation intensity and time-resolved photoluminescence spectroscopy are used to investigate the impact of annealing on the carrier dynamics in the Ga0.66ln0.34N0.013As0.987/GaAs multiple quantum well structure grown by metalorganic chemical vapor deposition. The measurement of excitation intensity photoluminescence (PL), performed for as-grown and annealed samples at different temperatures, indicates that the localized potential has come down slightly after annealing but does not alter the fact that PL

  12. OPTIMIZATION OF MULTIPLE-CHANNEL COOPERATIVE SPECTRUM SENSING WITH DATA FUSION RULE IN COGNITIVE RADIO NETWORKS

    Institute of Scientific and Technical Information of China (English)

    Yu Huogen; Tang Wanbin; Li Shaoqian

    2012-01-01

    This paper focuses on multi-channel Cooperative Spectrum Sensing (CSS) where Secondary Users (SUs) are assigned to cooperatively sense multiple channels simultaneously.A multi-channel CSS optimization problem of joint spectrum sensing and SU assignment based on data fusion rule is formulated,which maximizes the total throughput of the Cognitive Radio Network (CRN) subject to the constraints of probabilities of detection and false alarm.To address the optimization problem,a Branch and Bound (BnB) algorithm and a greedy algorithm are proposed to obtain the optimal solutions.Simulation results are presented to demonstrate the effectiveness of our proposed algorithms and show that the throughput improvement is achieved through the joint design.It is also shown that the greedy algorithm with a low complexity achieves the comparable performance to the exhaustive algorithm.

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

    Science.gov (United States)

    Ha, Tri T.; Pratt, Timothy

    1989-05-01

    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.

  14. Knowledge-Based Multiple Access Protocol in Broadband Wireless ATM Networks

    DEFF Research Database (Denmark)

    Liu, Hong; Gliese, Ulrik Bo; Dittmann, Lars

    1999-01-01

    In this paper, we propose a knowledge-based multiple access protocol for the extension of wireline ATM to wireless networks. The objective is to enable effecient transmission of all kinds of ATM traffic in the wireless channel with guaranteed QoS.The proposed protocol utilixes knowledge of the main...... characteristics of the traffic for allocating bandwidth effeciently to CBR, VBR and ABR/UBR connections by a compromise of assignment, contetion, reservation and polling access techniques. Simulation results show that the proposed protocol can achieve a very high channel utilization of 90 % while providing...

  15. Achieving Uniform Carriers Distribution in MBE Grown Compositionally Graded InGaN Multiple-Quantum-Well LEDs

    KAUST Repository

    Mishra, Pawan

    2015-05-06

    We investigated the design and growth of compositionally-graded InGaN multiple quantum wells (MQW) based light-emitting diode (LED) without an electron-blocking layer (EBL). Numerical investigation showed uniform carrier distribution in the active region, and higher radiative recombination rate for the optimized graded-MQW design, i.e. In0→xGa1→(1-x)N / InxGa(1-x)N / Inx→0Ga(1-x)→1N, as compared to the conventional stepped-MQW-LED. The composition-grading schemes, such as linear, parabolic, and Fermi-function profiles were numerically investigated for comparison. The stepped- and graded-MQW-LED were then grown using plasma assisted molecular beam epitaxy (PAMBE) through surface-stoichiometry optimization based on reflection high-energy electron-diffraction (RHEED) in-situ observations. Stepped- and graded-MQW-LED showed efficiency roll over at 160 A/cm2 and 275 A/cm2, respectively. The extended threshold current density roll-over (droop) in graded-MQW-LED is due to the improvement in carrier uniformity and radiative recombination rate, consistent with the numerical simulation.

  16. Adaptive radio resource allocation for multiple traffic OFDMA broadband wireless access system

    Institute of Scientific and Technical Information of China (English)

    LU Yan-hui; LUO Tao; YIN Chang-chuan; YUE Guang-xin

    2006-01-01

    In this article, an adaptive radio resource allocation algorithm applied to multiple traffic orthogonal frequency division multiple access (OFDMA) system is proposed, which distributes subcarriers and bits among users according to their different quality of service requirements and traffic type. By classifying and prioritizing the users based on their traffic characteristic and ensuring resource for higher priority users, the new scheme decreases tremendously the outage probability of the users requiting a real-time transmission without impact on the spectrum efficiency of system, as well as the outage probability of data users is not increased compared with the radio resource allocation methods published.

  17. Resource allocation using time division multiple access over wireless relay networks

    Institute of Scientific and Technical Information of China (English)

    DAI Qin-yun; RONG Lu; HU Hong-lin; SU Gang

    2008-01-01

    This article considers a wireless network consisting of multiple sources that communicate with the corresponding destination utilizing a single half-duplex relay, whereas, the sources use the relay opportunistically. By integrating the information theory with the concept of effective capacity, this article proposes a dynamic time allocation strategy over the wireless relay network that aims at maximizing the relay network throughput, subject to a given delay quality of service (QoS) constraint, where time division multiple access (TDMA) is applied in the relay network. The simulation results show that the proposed allocation strategy can significantly improve the effective capacity as compared to the traditional equal time allocation strategy.

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

    Science.gov (United States)

    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.

  19. Variable-length coding for short packets over a multiple access channel with feedback

    DEFF Research Database (Denmark)

    Trillingsgaard, Kasper Fløe; Popovski, Petar

    2014-01-01

    We consider a two-user discrete memoryless multiple access channel with a common stop-feedback signal from the receiver to both transmitters. The achievable regions are characterized using joint decoding and successive cancellation decoding and, it is shown that the achievable regions are signifi......We consider a two-user discrete memoryless multiple access channel with a common stop-feedback signal from the receiver to both transmitters. The achievable regions are characterized using joint decoding and successive cancellation decoding and, it is shown that the achievable regions...... are significantly larger for variable-length stop-feedback codes compared to fixed-blocklength codes. This is analogous to the result by Polyanskiy et al. (2011) for the point-to-point channel. An important conclusion is the following. In the asymptotic case the capacity region can be achieved by joint decoding...

  20. A distributed Synchronous reservation multiple access control protocol for mobile Ad hoc networks

    Institute of Scientific and Technical Information of China (English)

    ZHANG Yanling; SUN Xianpu; LI Jiandong

    2007-01-01

    This study proposes a new multiple access control protocol named distributed synchronous reservation multiple access control protocol.in which the hidden and exposed terminal problems are solved,and the quality of service(QoS)requirements for real-time traffic are guaranteed.The protocol is founded on time division multiplex address and a different type of traffic is assigned to difierent priority,according to which a node should compete for and reserve the free slots in a different method.Moreover,there is a reservation acknowledgement process before data transmit in each reserved slot,so that the intruded terminal problem is solved.The throughput and average packets drop probability of this protocol are analyzed and simulated in a fully connected network.the results of which indicate that this protocol is efficient enough to support the real-time traffic.and it is more suitable to MANETs.

  1. On Resource Allocation in Fading Multiple Access Channels - An Efficient Approximate Projection Approach

    CERN Document Server

    ParandehGheibi, Ali; Ozdaglar, Asuman; Medard, Muriel

    2008-01-01

    We consider the problem of rate and power allocation in a multiple-access channel. Our objective is to obtain rate and power allocation policies that maximize a general concave utility function of average transmission rates on the information theoretic capacity region of the multiple-access channel. Our policies does not require queue-length information. We consider several different scenarios. First, we address the utility maximization problem in a nonfading channel to obtain the optimal operating rates, and present an iterative gradient projection algorithm that uses approximate projection. By exploiting the polymatroid structure of the capacity region, we show that the approximate projection can be implemented in time polynomial in the number of users. Second, we consider resource allocation in a fading channel. Optimal rate and power allocation policies are presented for the case that power control is possible and channel statistics are available. For the case that transmission power is fixed and channel ...

  2. Space-division multiple access for CDMA multiuser underwater acoustic communications

    Institute of Scientific and Technical Information of China (English)

    Jingwei Yin; Pengyu Du; Guang Yang; Huanling Zhou

    2015-01-01

    Time reversal mirror (TRM) can use the physical cha-racteristics of the underwater acoustic (UWA) channel to focus on the desired user in multi-user UWA communication. The active average sound intensity (AASI) detector can estimate al azimuths of users with the same frequency band at the same time in or-der to achieve directional communication by vector combination. Space-division multiple access (SDMA) based on TRM combined with the AASI detector is proposed in this paper, which can make the capacity of the code division multiple access (CDMA) UWA system significantly increase. The simulation and lake test results show that the 7-user UWA multi-user system can achieve low bit error communication.

  3. Information Theory vs. Queueing Theory for Resource Allocation in Multiple Access Channels

    CERN Document Server

    ParandehGheibi, Ali; Ozdaglar, Asuman; Eryilmaz, Atilla

    2008-01-01

    We consider the problem of rate allocation in a fading Gaussian multiple-access channel with fixed transmission powers. The goal is to maximize a general concave utility function of the expected achieved rates of the users. There are different approaches to this problem in the literature. From an information theoretic point of view, rates are allocated only by using the channel state information. The queueing theory approach utilizes the global queue-length information for rate allocation to guarantee throughput optimality as well as maximizing a utility function of the rates. In this work, we make a connection between these two approaches by showing that the information theoretic capacity region of a multiple-access channel and its stability region are equivalent. Moreover, our numerical results show that a simple greedy policy which does not use the queue-length information can outperform queue-length based policies in terms of convergence rate and fairness.

  4. Data Access Services that Make Remote Sensing Data Easier to Use

    Science.gov (United States)

    Lynnes, Christopher

    2010-01-01

    This slide presentation reviews some of the processes that NASA uses to make the remote sensing data easy to use over the World Wide Web. This work involves much research into data formats, geolocation structures and quality indicators, often to be followed by coding a preprocessing program. Only then are the data usable within the analysis tool of choice. The Goddard Earth Sciences Data and Information Services Center is deploying a variety of data access services that are designed to dramatically shorten the time consumed in the data preparation step. On-the-fly conversion to the standard network Common Data Form (netCDF) format with Climate-Forecast (CF) conventions imposes a standard coordinate system framework that makes data instantly readable through several tools, such as the Integrated Data Viewer, Gridded Analysis and Display System, Panoply and Ferret. A similar benefit is achieved by serving data through the Open Source Project for a Network Data Access Protocol (OPeNDAP), which also provides subsetting. The Data Quality Screening Service goes a step further in filtering out data points based on quality control flags, based on science team recommendations or user-specified criteria. Further still is the Giovanni online analysis system which goes beyond handling formatting and quality to provide visualization and basic statistics of the data. This general approach of automating the preparation steps has the important added benefit of enabling use of the data by non-human users (i.e., computer programs), which often make sub-optimal use of the available data due to the need to hard-code data preparation on the client side.

  5. Throughput Analysis Model for IEEE 802.11e EDCA with Multiple Access Categories

    Directory of Open Access Journals (Sweden)

    Y. Lee

    2013-08-01

    Full Text Available IEEE 802.11e standard has been specified to support differentiated quality of service (QoS, one of the critical issues on the conventional IEEE 802.11 wireless local area networks (WLANs. Enhanced Distributed Channel Access (EDCA is the fundamental and mandatory contention-based channel access method of IEEE 802.11e, and delivers traffic based on differentiated Access Categories (ACs. A general three dimensional Markov chain model of IEEE 802.11e EDCA for performance analysis is proposed in this paper. The analytical model considers multiple stations with an arbitrary number of different ACs. It also differentiates the contention window (CW sizes and the arbitration interframe spaces (AIFSs, and considers virtual collision mechanism. Based on the model, the saturation throughput of EDCA is derived, and the accuracy of the proposed model is validated via simulations.

  6. A Multi-Service Oriented Multiple-Access Scheme For M2M Support in Future LTE

    OpenAIRE

    Ksairi, Nassar; Tomasin, Stefano; Debbah, Mérouane

    2016-01-01

    We propose a novel multiple-access technique to overcome the shortcomings of the current proposals for the future releases of Long-Term Evolution (LTE). We provide a unified radio access system that efficiently and flexibly integrates both traditional cellular services and machine-to-machine (M2M) connections arising from Internet-of-Things (IoT) applications. The proposed solution, referred to as multi-service oriented multiple access (MOMA), is based on a) establishing separate classes of u...

  7. Distributed Joint Source-Channel Coding on a Multiple Access Channel with Side Information

    OpenAIRE

    R. Rajesh; Sharma, Vinod

    2008-01-01

    We consider the problem of transmission of several distributed sources over a multiple access channel (MAC) with side information at the sources and the decoder. Source-channel separation does not hold for this channel. Sufficient conditions are provided for transmission of sources with a given distortion. The source and/or the channel could have continuous alphabets (thus Gaussian sources and Gaussian MACs are special cases). Various previous results are obtained as special cases. We also pr...

  8. Analysis of Coded FHSS Systems with Multiple Access Interference over Generalized Fading Channels

    OpenAIRE

    Zummo SalamA

    2008-01-01

    Abstract We study the effect of interference on the performance of coded FHSS systems. This is achieved by modeling the physical channel in these systems as a block fading channel. In the derivation of the bit error probability over Nakagami fading channels, we use the exact statistics of the multiple access interference (MAI) in FHSS systems. Due to the mathematically intractable expression of the Rician distribution, we use the Gaussian approximation to derive the error probability of coded...

  9. Parity-Check Network Coding for Multiple Access Relay Channel in Wireless Sensor Cooperative Communications

    OpenAIRE

    Bing Du; Jun Zhang

    2010-01-01

    A recently developed theory suggests that network coding is a generalization of source coding and channel coding and thus yields a significant performance improvement in terms of throughput and spatial diversity. This paper proposes a cooperative design of a parity-check network coding scheme in the context of a two-source multiple access relay channel (MARC) model, a common compact model in hierarchical wireless sensor networks (WSNs). The scheme uses Low-Density Parity-Check (LDPC) as the ...

  10. Performance analysis of slotted fiber-optic code-division multiple-access (CDMA) packet networks

    OpenAIRE

    Hsu, CS; Li, VOK

    1997-01-01

    This paper examines code-division multiple-access (CDMA) techniques used in slotted fiber-optic packet networks. Since the inherent properties and signal processing of the conventional communication channels are different from those of the fiber-optic channels, new code sequences must be constructed for fiber-optic applications. The goal of our research is to analyze the performance of fiber-optic CDMA packet networks using code sequences with given orthogonality properties. © 1997 IEEE.

  11. Performance analysis of unslotted fiber-optic code-division multiple-access (CDMA) packet networks

    OpenAIRE

    Hsu, CS; Li, VOK

    1997-01-01

    This paper examines code-division multiple-access (CDMA) techniques used in unslotted fiber-optic packet networks. Since the inherent properties and signal processing of the conventional communication channels are different from those of the fiber-optic channels, new code sequences must be constructed for fiber-optic applications. In unslotted systems, the exact solution is very difficult to obtain. Therefore, two approximation methods are presented to analyze the performance of such systems....

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

    Science.gov (United States)

    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.

  13. Partial Interference and Its Performance Impact on Wireless Multiple Access Networks

    Directory of Open Access Journals (Sweden)

    Lau WingCheong

    2010-01-01

    Full Text Available To determine the capacity of wireless multiple access networks, the interference among the wireless links must be accurately modeled. In this paper, we formalize the notion of the partial interference phenomenon observed in many recent wireless measurement studies and establish analytical models with tractable solutions for various types of wireless multiple access networks. In particular, we characterize the stability region of IEEE 802.11 networks under partial interference with two potentially unsaturated links numerically. We also provide a closed-form solution for the stability region of slotted ALOHA networks under partial interference with two potentially unsaturated links and obtain a partial characterization of the boundary of the stability region for the general M-link case. Finally, we derive a closed-form approximated solution for the stability region for general M-link slotted ALOHA system under partial interference effects. Based on our results, we demonstrate that it is important to model the partial interference effects while analyzing wireless multiple access networks. This is because such considerations can result in not only significant quantitative differences in the predicted system capacity but also fundamental qualitative changes in the shape of the stability region of the systems.

  14. A simple and accessible synthetic lectin for glucose recognition and sensing

    Science.gov (United States)

    Ke, Chenfeng; Destecroix, Harry; Crump, Matthew P.; Davis, Anthony P.

    2012-09-01

    Binding carbohydrates from water is a difficult task, even for the natural carbohydrate-binding proteins known as lectins. The design of synthetic lectin mimics is correspondingly challenging, especially if good selectivities are required. In previous work we showed that success is possible, but only for complex polycyclic architectures that require lengthy and low-yielding syntheses; for example, one glucose-selective system was made in 21 steps and only 0.1% overall yield. Here we report the discovery of a simple monocyclic host that matches the earlier designs, but is far more accessible as it is prepared in just five steps and 23% overall yield. The new synthetic lectin binds glucose with excellent selectivity versus other common monosaccharides (for example, ∼50:1 versus galactose) and sufficient affinity for glucose sensing at the concentrations found in blood. It also features a built-in signalling system in the form of strong and guest-dependent fluorescence emission. The effectiveness and simplicity of this molecule suggests the potential for development into a new methodology for practical glucose monitoring.

  15. ASIC3 Channels Integrate Agmatine and Multiple Inflammatory Signals through the Nonproton Ligand Sensing Domain

    Directory of Open Access Journals (Sweden)

    Cao Hui

    2010-12-01

    Full Text Available Abstract Background Acid-sensing ion channels (ASICs have long been known to sense extracellular protons and contribute to sensory perception. Peripheral ASIC3 channels represent natural sensors of acidic and inflammatory pain. We recently reported the use of a synthetic compound, 2-guanidine-4-methylquinazoline (GMQ, to identify a novel nonproton sensing domain in the ASIC3 channel, and proposed that, based on its structural similarity with GMQ, the arginine metabolite agmatine (AGM may be an endogenous nonproton ligand for ASIC3 channels. Results Here, we present further evidence for the physiological correlation between AGM and ASIC3. Among arginine metabolites, only AGM and its analog arcaine (ARC activated ASIC3 channels at neutral pH in a sustained manner similar to GMQ. In addition to the homomeric ASIC3 channels, AGM also activated heteromeric ASIC3 plus ASIC1b channels, extending its potential physiological relevance. Importantly, the process of activation by AGM was highly sensitive to mild acidosis, hyperosmolarity, arachidonic acid (AA, lactic acid and reduced extracellular Ca2+. AGM-induced ASIC3 channel activation was not through the chelation of extracellular Ca2+ as occurs with increased lactate, but rather through a direct interaction with the newly identified nonproton ligand sensing domain. Finally, AGM cooperated with the multiple inflammatory signals to cause pain-related behaviors in an ASIC3-dependent manner. Conclusions Nonproton ligand sensing domain might represent a novel mechanism for activation or sensitization of ASIC3 channels underlying inflammatory pain-sensing under in vivo conditions.

  16. Dual-mode on-demand droplet routing in multiple microchannels using a magnetic fluid as carrier phase.

    Science.gov (United States)

    Kim, Jitae; Won, June; Song, Simon

    2014-09-01

    We present dual-mode, on-demand droplet routing in a multiple-outlet microfluidic device using an oil-based magnetic fluid. Magnetite (Fe3O4) nanoparticle-contained oleic acid (MNOA) was used as a carrier phase for droplet generation and manipulation. The water-in-MNOA droplets were selectively distributed in a curved microchannel with three branches by utilizing both a hydrodynamic laminar flow pattern and an external magnetic field. Without the applied magnetic field, the droplets travelled along a hydrodynamic centerline that was displaced at each bifurcating junction. However, in the presence of a permanent magnet, they were repelled from the centerline and diverted into the desired channel when the repelled distance exceeded the minimum offset allocated to the channel. The repelled distance, which is proportional to the magnetic field gradient, was manipulated by controlling the magnet's distance from the device. To evaluate routing performance, three different sizes of droplets with diameters of 63, 88, and 102 μm were directed into designated outlets with the magnet positioned at varying distances. The result demonstrated that the 102-μm droplets were sorted with an accuracy of ∼93%. Our technique enables on-demand droplet routing in multiple outlet channels by simply manipulating magnet positions (active mode) as well as size-based droplet separation with a fixed magnet position (passive mode). PMID:25332742

  17. 一种自适应功率控制的信道预约多址接入协议%Channel reservation MAC protocol with adaptive power control mechanism carrier sensing

    Institute of Scientific and Technical Information of China (English)

    袁韵洁; 李波; 闫中江

    2013-01-01

    提出了一种动态调整发送功率和载波侦听门限的信道预约多址接入协议(PC-CRM).该协议将功率控制技术应用于信道预约机制,通过对预约节点发送功率的优化设定和载波侦听门限的动态调整,使得相邻节点可以同时复用信道,从而在增强预约稳定性的基础上,提升了网络容量,降低了节点能耗.仿真结果显示,与IEEE 802.11 DCF和基本信道预约协议相比,PC-CRM协议在网络吞吐率、能量消耗效率和分组延迟抖动方面均有明显优势.%vA channel reservation MAC protocol with the adjustable transmission power and carrier sensing threshold, called PC-CRM, is proposed. PC-CRM solves the problems of poor transmission quality, low network capacity and high energy consumption, which are caused by the distributed contention based channel access scheme in Ad Hoc networks. By employing power control into the channel reservation schemes, PC-CRM adjusts the transmission power and carrier sensing threshold to the optimum values, such that the channel is multiplexed in space. Additionally, PC-CRM is also capable of stabilizing the channel reservation, improving the network capacity, and reducing the energy cost. Simulation results show that, compared with IEEE 802. 11DCF and the basic channel reservation scheme, PC-CRM performs better in terms of the throughput, energy efficiency and delay jitter.

  18. UNAPPROVED ACCESS POINT ELIMINATION IN WLAN USING MULTIPLE AGENTS AND SKEW INTERVALS

    Directory of Open Access Journals (Sweden)

    Prof.S.B.Vanjale

    2012-02-01

    Full Text Available For the Wireless Networks, presence of unapproved access points is becoming the major security issue. If this kind of network threats are not detected and mitigated on time, those will lead to the serious network damage and data loss. There are many researchers proposed solutions to overcome this security problem of WLAN, but those proposed tools having limitations or maybe they not automated to adopt the frequent changes in WLAN. We are into this research to present the new approach based on Master and Slave agents. Thisproposed approach not only looking for fast detection of Rough Access points in the network but also presenting the solution to mitigate the WLAN from them. In short new framework is dealing with detecting as well as eliminating the Unapproved Access Points in the network. In proposed approach, the Master and slave agents are automatically scanning the networks for any unauthorized access points using the skew intervals. This Methodology has the following outstanding properties: (1 it doesn’t require any specialized hardware; (2 the proposed algorithm detects and completely eliminates the unapproved aps from network; (3 it provides a cost-effective solution; (4 due to multiple master agents possibility of network congestion or delaysis reduced. The proposed technique can block unapproved APs as well as remove them from the networks both in form of Unauthorized APs or as a Rogue Clients Acting as APs.

  19. A Fuzzy Logic Based Power Control for Wideband Code Division Multiple Access Wireless Networks

    Directory of Open Access Journals (Sweden)

    T. Ravichandran

    2012-01-01

    Full Text Available Problem statement: Resource management is one of the most important engineering issues in 3G systems where multiple traffic classes are supported each being characterized by its required Quality of Service (QoS parameters. Call Admission Control (CAC is one of the resource management functions, which regulates network access to ensure QoS provisioning. Efficient CAC is necessary for the QoS provisioning in WCDMA environment. The effective functioning of WCDMA systems is influenced by the power control utility. Approach: In this study, we propose to design a fuzzy logic based power control for Wideband Code Division Multiple Access Wireless Networks. This proposed technique is aimed at multiple services like voice, video and data for multiclass users. The fuzzy logic technique is used to estimate the optimal admissible users group inclusive of optimum transmitting power level. This technique reduces the interference level and call rejection rate. Results: By simulation results, we demonstrate that the proposed technique achieve reduced energy consumption for a cell with increased throughput. Conclusion: The proposed technique minimizes the power consumption and call rejection rate.

  20. Near-field wireless sensing of single and multiple open-ended micro coils

    Directory of Open Access Journals (Sweden)

    A. Yousaf

    2013-05-01

    Full Text Available In this work we present near-field wireless sensing of single and multiple open-ended micro coils using an electrically small loop antenna. Wirelessly characterized parameters of open-ended micro coils include its resonance frequency, quality factor and inductance. Moreover a wireless frequency-dependent analytical model was developed. Micro coil inductance was extracted from the wirelessly measured signal using a constraint-based least-squares approach. Wireless measurements and analytical fit of micro coils are in strong agreement which validates the analytical model. Finite element method (FEM simulations of the coupled system were done in COMSOL Multiphysics.

  1. Delay-limited capacity of fading multiple access and broadcast channels in the low power regime

    KAUST Repository

    Rezki, Zouheir

    2015-09-11

    We study delay-limited (also called zero-outage) capacity region of the fading multi-access channel (MAC) with Gaussian noise and perfect channel state information (CSI) at the receiver and at the transmitters (CSI-TR), in the low-power regime. We show that for fading channels where the MAC capacity region is strictly positive, it has a multidimensional rectangle structure and thus is simply characterized by single user capacity points. More specifically, we show that at low power, the boundary surface of the capacity region shrinks to a single point corresponding to the sum-rate maximizer and that the coordinates of this point coincide with single user capacity bounds. Using the duality of the Gaussian MAC and broadcast channels (BC), we show that time-sharing (or time division multiple access (TDMA)) is asymptotically optimal. © 2015 IEEE.

  2. A General Rate Duality of the MIMO Multiple Access Channel and the MIMO Broadcast Channel

    CERN Document Server

    Hunger, Raphael

    2008-01-01

    We present a general rate duality between the multiple access channel (MAC) and the broadcast channel (BC) which is applicable to systems with and without nonlinear interference cancellation. Different to the state-of-the-art rate duality with interference subtraction from Vishwanath et al., the proposed duality is filter-based instead of covariance-based and exploits the arising unitary degree of freedom to decorrelate every point-to-point link. Therefore, it allows for noncooperative stream-wise decoding which reduces complexity and latency. Moreover, the conversion from one domain to the other does not exhibit any dependencies during its computation making it accessible to a parallel implementation instead of a serial one. We additionally derive a rate duality for systems with multi-antenna terminals when linear filtering without interference (pre-)subtraction is applied and the different streams of a single user are not treated as self-interference. Both dualities are based on a framework already applied ...

  3. Gigabit Ethernet signal transmission using asynchronous optical code division multiple access.

    Science.gov (United States)

    Ma, Philip Y; Fok, Mable P; Shastri, Bhavin J; Wu, Ben; Prucnal, Paul R

    2015-12-15

    We propose and experimentally demonstrate a novel architecture for interfacing and transmitting a Gigabit Ethernet (GbE) signal using asynchronous incoherent optical code division multiple access (OCDMA). This is the first such asynchronous incoherent OCDMA system carrying GbE data being demonstrated to be working among multi-users where each user is operating with an independent clock/data rate and is granted random access to the network. Three major components, the GbE interface, the OCDMA transmitter, and the OCDMA receiver are discussed in detail. The performance of the system is studied and characterized through measuring eye diagrams, bit-error rate and packet loss rate in real-time file transfer. Our Letter also addresses the near-far problem and realizes asynchronous transmission and detection of signal.

  4. A passive optical network based on optical code division multiplexing and time division multiple access technology

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A passive optical network (PON) scheme based on optical code division multiplexing (OCDM) for the downstream traffics is proposed and analyzed in detail. In the PON, the downstream traffics are broadcasted by OCDM technology to guarantee the security, while the upstream traffics pass through the same optical fiber by the common time division multiple access (TDMA) technology to decrease the cost.This schemes are denoted as OCDM/TDMA-PON, which can be applied to an optical access network (OAN) with full services on demand, such as Internet protocol, video on demand, tele-presence and high quality audio. The proposed OCDM/TDMA-PON scheme combines advantages of PON, TDMA, and OCDM technology. Simulation results indicate that the designed scheme improves the OAN performance,and enhances flexibility and scalability of the system.

  5. 14 CFR 382.69 - What requirements must carriers meet concerning the accessibility of videos, DVDs, and other...

    Science.gov (United States)

    2010-01-01

    ... concerning the accessibility of videos, DVDs, and other audio-visual presentations shown on-aircraft to... meet concerning the accessibility of videos, DVDs, and other audio-visual presentations shown on... videos, DVDs, and other audio-visual displays played on aircraft for safety purposes, and all such...

  6. Reset-sensing quasi-V2 single-inductor multiple-output buck converter with reduced cross-regulation

    OpenAIRE

    Lee, ATL; Tan, SC; Hui, SYR; Chan, PCH; Sin, JKO

    2015-01-01

    This paper proposes a reset-sensing quasi-V2 single-inductor multiple-output (SIMO) converter with minimal cross-regulation. The conventional quasi-V2 sensing scheme in SIMO converters suffers from serious cross-regulation which is primarily induced by the load differentiation with unbalanced loads. It is shown that the proposed reset-sensing quasi-V2 control scheme can significantly reduce cross-regulation by completely discharging the feed-forward sensing node to zero volts during the idle ...

  7. Rendering Intelligence at Physical Layer for Smart Addressing and Multiple Access

    DEFF Research Database (Denmark)

    Sanyal, Rajarshi; Prasad, Ramjee; Cianca, Ernestina

    2010-01-01

    addressing of a node. For a typical closed user group type of network, we propose a multiple access mechanism and network topology which will not only eliminate the need of intelligent core network equipments in the network area , but to use this intelligent physical layer to directly reach any node over......The primary objective of this work is to propose a technique of wireless communication, where we render intelligence to the physical layer. We aim to realize a physical layer that can take part in some processes which is otherwise confined to higher layer signalling activities, like for example...

  8. Conflict resolution protocols for random multiple-access channels with binary feedback

    Science.gov (United States)

    Berger, T.; Mehravari, N.

    The problem of conflict resolution in a random multiple-access, time-slotted, packet-switched channel with binary feedback is considered. Conflict resolution algorithms (CRA) for two different types of binary feedback which informs the users only about whether or not there was a collision in the previous slot achieves a throughput of 0.442. The CRA proposed for the case in which the feedback informs the users about whether or not the previous slot was empty achieves a throughput of 0.279.

  9. TELEMEDICINE NETWORK BASED ON CODE-DIVISION MULTIPLE ACCESS WIRELESS TECHNOLOGY

    Institute of Scientific and Technical Information of China (English)

    同鸣; 卞正中; 张亮

    2003-01-01

    Objective To satisfy the need of reliable and efficient telemedicine in many mobile and ambulance situations. Methods A practical telemedicine system bases on code-division multiple access (CDMA) wireless communication technology has been developed, which has never been mentioned before. The design scheme for the proposed system is described and detailed analysis of the network protocol stacks and the data flow is presented. Results Experiments on real time transmission of medical images using developed system have demonstrated that the system performance is satisfactory and acceptable. Conclusion The telemedicine system based on CDMA is easy to implement and has high quality of transmitted images. It would be a prospective solution to mobile telemedicine.

  10. Cooperative Transmission in Mobile Wireless Sensor Networks with Multiple Carrier Frequency Offsets: A Double-Differential Approach

    Directory of Open Access Journals (Sweden)

    Kun Zhao

    2014-01-01

    Full Text Available As a result of the rapidly increasing mobility of sensor nodes, mobile wireless sensor networks (MWSNs would be subject to multiple carrier frequency offsets (MCFOs, which result in time-varying channels and drastically degrade the network performance. To enhance the performance of such MWSNs, we propose a relay selection (RS based double-differential (DD cooperative transmission scheme, termed RSDDCT, in which the best relay sensor node is selected to forward the source sensor node’s signals to the destination sensor node with the detect-and-forward (DetF protocol. Assuming a Rayleigh fading environment, first, exact closed-form expressions for the outage probability and average bit error rate (BER of the RSDDCT scheme are derived. Then, simple and informative asymptotic outage probability and average BER expressions at the large signal-to-noise ratio (SNR regime are presented, which reveal that the RSDDCT scheme can achieve full diversity. Furthermore, the optimum power allocation strategy in terms of minimizing the average BER is investigated, and simple analytical solutions are obtained. Simulation results demonstrate that the proposed RSDDCT scheme can achieve excellent performance over fading channels in the presence of unknown random MCFOs. It is also shown that the proposed optimum power allocation strategy offers substantial average BER performance improvement over the equal power allocation strategy.

  11. Achievable Rate of a Cognitive MIMO Multiple Access Channel With Multi-Secondary Users

    KAUST Repository

    Sboui, Lokman

    2015-03-01

    We study the secondary sum-rate of an underlay cognitive multiple access channel consisting of a primary user and multiple secondary users (SUs) communicating with a common destination. We propose a particular linear precoding and SU selection scheme that maximize the cognitive sum-rate. This scheme is based on space alignment strategy allowing SUs to share the spectrum without interfering with each other. We derive the optimal power allocation for each selected SU after applying perfect or imperfect successive interference cancellation. Numerical results show that the proposed scheme provides a significant sum-rate improvement as the number of SUs increases. In addition, it achieves almost the same performance as an exhaustive search selection, mainly in low and high power ranges. © 1997-2012 IEEE.

  12. The Impact of Facebook Access in Creating a Sense of Community in Tourism and Recreation Classes

    Science.gov (United States)

    Tuma, Lorie A.

    2012-01-01

    Previous research has indicated that college students use social networking sites such as Facebook to establish friendships, maintain communication, and foster a sense of community; research also has indicated that many college instructors do not. Many college faculty acknowledge the importance of a sense of community in the classroom but are…

  13. Bit Error Rate Performance Analysis on Modulation Techniques of Wideband Code Division Multiple Access

    CERN Document Server

    Masud, M A; Rahman, M A

    2010-01-01

    In the beginning of 21st century there has been a dramatic shift in the market dynamics of telecommunication services. The transmission from base station to mobile or downlink transmission using M-ary Quadrature Amplitude modulation (QAM) and Quadrature phase shift keying (QPSK) modulation schemes are considered in Wideband-Code Division Multiple Access (W-CDMA) system. We have done the performance analysis of these modulation techniques when the system is subjected to Additive White Gaussian Noise (AWGN) and multipath Rayleigh fading are considered in the channel. The research has been performed by using MATLAB 7.6 for simulation and evaluation of Bit Error Rate (BER) and Signal-To-Noise Ratio (SNR) for W-CDMA system models. It is shows that the analysis of Quadrature phases shift key and 16-ary Quadrature Amplitude modulations which are being used in wideband code division multiple access system, Therefore, the system could go for more suitable modulation technique to suit the channel quality, thus we can d...

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

    Science.gov (United States)

    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.

  15. Multiple origins of hydrogenosomes : functional and phylogenetic evidence from the ADP/ATP carrier of the anaerobic chytrid Neocallimastix sp.

    NARCIS (Netherlands)

    Voncken, F; Boxma, B; Tjaden, J; Akhmanova, A; Huynen, M; Tielens, AGM; Haferkamp, [No Value; Neuhaus, HE; Vogels, G; Veenhuis, M; Hackstein, JHP; Tielens, Aloysius G.M.; Haferkamp, Ilka; Hackstein, Johannes H.P.

    2002-01-01

    A mitochondrial-type ADP/ATP carrier (AAC) has been identified in the hydrogenosomes of the anaerobic chytridiomycete fungus Neocallimastix sp. L2. Biochemical and immunocytochemical studies revealed that this ADP/ATP carrier is an integral component of hydrogenosomal membranes. Expression of the co

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

    Science.gov (United States)

    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.

  17. Understanding droop effect by analysis on carrier density dependence in InGaN/GaN multiple-quantum-well light-emitting diodes

    Science.gov (United States)

    Liu, Wei; Zhao, Degang; Jiang, Desheng; Chen, Ping; Liu, Zongshun; Zhu, Jianjun; Yang, Jing; He, Xiaoguang; Li, Xiaojing; Li, Xiang; Liang, Feng; Liu, Jianping; Zhang, Liqun; Yang, Hui; Zhang, Yuantao; Du, Guotong

    2016-08-01

    The droop behaviors of two InGaN/GaN multiple-quantum-well blue-green light-emitting diodes grown on c-plane sapphires with different In content are investigated. The higher-In-content sample exhibits a lower efficiency, followed by a more significant droop as current increases in comparison with the lower-In-content diode. However, it is found that for both samples their efficiency reduction trend with increasing carrier density is nearly the same. Combining with the recombination rate equations, an analysis reveals that at the same injection current level, the carrier density in the higher-In-content quantum wells which have stronger polarization effect is larger due to the smaller bimolecular recombination coefficient, resulting in a more significant droop with current. Therefore, a study on the dependence of efficiency on carrier density can provide a clear elucidation to the physical mechanism of the efficiency droop behavior.

  18. Optical Properties and Carrier Dynamics of GaAs/GaInAs Multiple-Quantum-Well Shell Grown on GaAs Nanowire by Molecular Beam Epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Park, Kwangwook; Ravindran, Sooraj; Ju, Gun Wu; Min, Jung-Wook; Kang, Seokjin; Myoung, NoSoung; Yim, Sang-Youp; Jo, Yong-Ryun; Kim, Bong-Joong; Lee, Yong Tak

    2016-12-01

    GaAs/GaInAs multiple-quantum-well (MQW) shells having different GaInAs shell width formed on the surface of self-catalyzed GaAs core nanowires (NWs) are grown on (100) Si substrate using molecular beam epitaxy. The photoluminescence emission from GaAs/GaInAs MQW shells and the carrier lifetime could be varied by changing the width of GaInAs shell. Time-resolved photoluminescence measurements showed that the carrier lifetime had a fast and slow decay owing to the mixing of wurtzite and zinc-blende structures of the NWs. Furthermore, strain relaxation caused the carrier lifetime to decrease beyond a certain thickness of GaInAs quantum well shells.

  19. Photoinduced Transformation between Charge Carrier and Spin Carrier in Polymers

    Institute of Scientific and Technical Information of China (English)

    MEI Yuan; ZHAO Chang; SUN Xin

    2006-01-01

    By dynamical simulations, we show a transforming process between neutral soliton (spin carrier) and charged soliton (charge carrier) in polymers via photo-excitation, taking a polaron as the transitional bridge. It is photoinduced transformation between spin carrier and charge carrier. In this way, we demonstrate an access for polymers to be applied to spintronics.

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

    Science.gov (United States)

    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.

  1. Accessing, Utilizing and Visualizing NASA Remote Sensing Data for Malaria Modeling and Surveillance

    Science.gov (United States)

    Kiang, Richard K.; Adimi, Farida; Kempler, Steven

    2007-01-01

    This poster presentation reviews the use of NASA remote sensing data that can be used to extract environmental information for modeling malaria transmission. The authors discuss the remote sensing data from Landsat, Advanced Very High Resolution Radiometer (AVHRR), Moderate Resolution Imaging Spectroradiometer (MODIS), Tropical Rainfall Measuring Mission (TRMM), Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), Earth Observing One (EO-1), Advanced Land Imager (ALI) and Seasonal to Interannual Earth Science Information Partner (SIESIP) dataset.

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

    Science.gov (United States)

    Vijayakumaran, Vineeth

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

  3. Multihop Medium Access Control for WSNs: An Energy Analysis Model

    Directory of Open Access Journals (Sweden)

    Haapola Jussi

    2005-01-01

    Full Text Available We present an energy analysis technique applicable to medium access control (MAC and multihop communications. Furthermore, the technique's application gives insight on using multihop forwarding instead of single-hop communications. Using the technique, we perform an energy analysis of carrier-sense-multiple-access (CSMA- based MAC protocols with sleeping schemes. Power constraints set by battery operation raise energy efficiency as the prime factor for wireless sensor networks. A detailed energy expenditure analysis of the physical, the link, and the network layers together can provide a basis for developing new energy-efficient wireless sensor networks. The presented technique provides a set of analytical tools for accomplishing this. With those tools, the energy impact of radio, MAC, and topology parameters on the network can be investigated. From the analysis, we extract key parameters of selected MAC protocols and show that some traditional mechanisms, such as binary exponential backoff, have inherent problems.

  4. Inter-comparison of multiple angle remotely sensed data across different spatial resolutions and sensors for determination of albedo

    OpenAIRE

    Khavarian Nehzak, Hassan

    2012-01-01

    Surface albedo is one of the critical parameters required by studies of surface energy balance and climate models. Albedo is defined as the ratio of outgoing radiances to incoming irradiances over hemispherical view-illumination geometry. Remotely sensed albedo is usually based on multiple view angle observations and a Bidirectional Reflectance Distribution Function (BRDF) model. The accuracy of remotely sensed albedo depends on a variety of factors of which the main ones are the accuracy of ...

  5. A Low Complexity VCS Method for PAPR Reduction in Multicarrier Code Division Multiple Access

    Institute of Scientific and Technical Information of China (English)

    Si-Si Liu; Yue Xiao; Qing-Song Wen; Shao-Qian Li

    2007-01-01

    This paper investigatesa peak to average power ratio (PAPR) reduction method in multicarrier code division multiple access (MC-CDMA) system. Variable code sets (VCS), a spreading codes selection scheme, can improve the PAPR property of the MC-CDMA signals, but this technique requires an exhaustive search over the combinations of spreading code sets. It is observed that when the number of active users increases, the search complexity will increase exponentially. Based on this fact, we propose a low complexity VCS (LC-VCS) method to reduce the computational complexity. The basic idea of LC-VCS is to derive new signals using the relationship between candidature signals. Simulation results show that the proposed approach can reduce PAPR with lower computational complexity. In addition, it can be blindly received without any side information.

  6. New code match strategy for wideband code division multiple access code tree management

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Orthogonal variable spreading factor channelization codes are widely used to provide variable data rates for supporting different bandwidth requirements in wideband code division multiple access (WCDMA) systems. A new code match scheme for WCDMA code tree management was proposed. The code match scheme is similar to the existing crowed-first scheme. When choosing a code for a user, the code match scheme only compares the one up layer of the allocated codes, unlike the crowed-first scheme which perhaps compares all up layers. So the operation of code match scheme is simple, and the average time delay is decreased by 5.1%. The simulation results also show that the code match strategy can decrease the average code blocking probability by 8.4%.

  7. An asymptotically nonadaptive algorithm for conflict resolution in multiple-access channels

    Science.gov (United States)

    Komlos, J.; Greenberg, A. G.

    1985-03-01

    A basic problem in the decentralized control of a multiple access channel is to resolve the conflicts that arise when several stations transmit simultaneously to the channel. Capetanakis, Hayes, and Tsybakov and Mikhailov found a deterministic tree algorithm that resolves conflicts among k stations from an ensemble of n in time (Theta) /k + k log(n/k)/ in the worst case. In this algorithm, at each step, the choice of which stations to enable to transmit depends crucially on feedback information provided by the channel. It is shown that if k is given a priori then such conflicts can be resolved in time (Theta) /k + k log(n/k)/ using an algorithm in which the corresponding choices do not depend on feedback.

  8. Analysis of Coded FHSS Systems with Multiple Access Interference over Generalized Fading Channels

    Directory of Open Access Journals (Sweden)

    Zummo SalamA

    2008-01-01

    Full Text Available Abstract We study the effect of interference on the performance of coded FHSS systems. This is achieved by modeling the physical channel in these systems as a block fading channel. In the derivation of the bit error probability over Nakagami fading channels, we use the exact statistics of the multiple access interference (MAI in FHSS systems. Due to the mathematically intractable expression of the Rician distribution, we use the Gaussian approximation to derive the error probability of coded FHSS over Rician fading channel. The effect of pilot-aided channel estimation is studied for Rician fading channels using the Gaussian approximation. From this, the optimal hopping rate in coded FHSS is approximated. Results show that the performance loss due to interference increases as the hopping rate decreases.

  9. A Bayesian Game-Theoretic Approach for Distributed Resource Allocation in Fading Multiple Access Channels

    Directory of Open Access Journals (Sweden)

    Gaoning He

    2010-01-01

    Full Text Available A Bayesian game-theoretic model is developed to design and analyze the resource allocation problem in K-user fading multiple access channels (MACs, where the users are assumed to selfishly maximize their average achievable rates with incomplete information about the fading channel gains. In such a game-theoretic study, the central question is whether a Bayesian equilibrium exists, and if so, whether the network operates efficiently at the equilibrium point. We prove that there exists exactly one Bayesian equilibrium in our game. Furthermore, we study the network sum-rate maximization problem by assuming that the users coordinate according to a symmetric strategy profile. This result also serves as an upper bound for the Bayesian equilibrium. Finally, simulation results are provided to show the network efficiency at the unique Bayesian equilibrium and to compare it with other strategies.

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

    Science.gov (United States)

    Zohar, S.

    1982-01-01

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

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

    Science.gov (United States)

    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.

  12. Analysis of Coded FHSS Systems with Multiple Access Interference over Generalized Fading Channels

    Directory of Open Access Journals (Sweden)

    Salam A. Zummo

    2009-02-01

    Full Text Available We study the effect of interference on the performance of coded FHSS systems. This is achieved by modeling the physical channel in these systems as a block fading channel. In the derivation of the bit error probability over Nakagami fading channels, we use the exact statistics of the multiple access interference (MAI in FHSS systems. Due to the mathematically intractable expression of the Rician distribution, we use the Gaussian approximation to derive the error probability of coded FHSS over Rician fading channel. The effect of pilot-aided channel estimation is studied for Rician fading channels using the Gaussian approximation. From this, the optimal hopping rate in coded FHSS is approximated. Results show that the performance loss due to interference increases as the hopping rate decreases.

  13. Optical Shared Memory Computing and Multiple Access Protocols for Photonic Networks

    Science.gov (United States)

    Li, Kuang-Yu.

    In this research we investigate potential applications of optics in massively parallel computer systems, especially focusing on design issues in three-dimensional optical data storage and free-space photonic networks. An optical implementation of a shared memory uses a single photorefractive crystal and can realize the set of memory modules in a digital shared memory computer. A complete instruction set consists of R sc EAD, W sc RITE, S sc ELECTIVE E sc RASE, and R sc EFRESH, which can be applied to any memory module independent of (and in parallel with) instructions to the other memory modules. In addition, a memory module can execute a sequence of R sc EAD operations simultaneously with the execution of a W sc RITE operation to accommodate differences in optical recording and readout times common to optical volume storage media. An experimental shared memory system is demonstrated and its projected performance is analyzed. A multiplexing technique is presented to significantly reduce both grating- and beam-degeneracy crosstalk in volume holographic systems, by incorporating space, angle, and wavelength as the multiplexing parameters. In this approach, each hologram, which results from the interference between a single input node and an object array, partially overlaps with the other holograms in its neighborhood. This technique can offer improved interconnection density, optical throughput, signal fidelity, and space-bandwidth product utilization. Design principles and numerical simulation results are presented. A free-space photonic cellular hypercube parallel computer, with emphasis on the design of a collisionless multiple access protocol, is presented. This design incorporates wavelength-, space-, and time-multiplexing to achieve multiple access, wavelength reuse, dense connectivity, collisionless communications, and a simple control mechanism. Analytic models based on semi-Markov processes are employed to analyze this protocol. The performance of the

  14. A localized cooperative wideband spectrum sensing for dynamic access of TV bands using RF sensor networks

    KAUST Repository

    Mirza, Mohammed

    2011-07-01

    In this paper we address and simulate a Radio Frequency (RF) sensor network for a cooperative spectrum sensing and localization scheme. The proposed method integrates a Wavelet based Multi-Resolution Spectrum Sensing (MRSS), an N-bit hard combination technique for cooperative decision making and a Received Signal Strength (RSS) based localization algorithm to detect the availability of frequency bands and the location of the usable base station. We develop an N-bit hard combination technique and compare its performance to a traditionally used 2-bit hard combination for cooperative sensing. The key idea is to design a novel RF sensor network based cooperative wideband spectrum sensing and localization scheme by using a wavelet based Multi-Resolution Spectrum Sensing (MRSS) and Received Signal Strength (RSS) Localization techniques which were originally proposed for cognitive radio applications. The performance evaluations are also done to show the different detection accuracies for varying parameters such as number of sensor nodes, Signal to Noise Ratios (SNR) and number of averaged Power Spectral Densities (PSD). The proposed scheme improves the problems of shadowing, fading and noise. In addition, the RSS based localization technique was shown to be an acceptable means of estimating the position of the available transmitter. © 2011 IEEE.

  15. An Adaptive Time-Spread Multiple-Access Policy for Wireless Sensor Networks

    Directory of Open Access Journals (Sweden)

    Konstantinos Oikonomou

    2007-05-01

    Full Text Available Sensor networks require a simple and efficient medium access control policy achieving high system throughput with no or limited control overhead in order to increase the network lifetime by minimizing the energy consumed during transmission attempts. Time-spread multiple-access (TSMA policies that have been proposed for ad hoc network environments, can also be employed in sensor networks, since no control overhead is introduced. However, they do not take advantage of any cross-layer information in order to exploit the idiosyncrasies of the particular sensor network environment such as the presence of typically static nodes and a common destination for the forwarded data. An adaptive probabilistic TSMA-based policy, that is proposed and analyzed in this paper, exploits these idiosyncrasies and achieves higher system throughput than the existing TSMA-based policies without any need for extra control overhead. As it is analytically shown in this paper, the proposed policy always outperforms the existing TSMA-based policies, if certain parameter values are properly set; the analysis also provides for these proper values. It is also shown that the proposed policy is characterized by a certain convergence period and that high system throughput is achieved for long convergence periods. The claims and expectations of the provided analysis are supported by simulation results presented in this paper.

  16. Method for Multiple Targets Tracking in Cognitive Radar Based on Compressed Sensing

    Directory of Open Access Journals (Sweden)

    Yang Jun

    2016-02-01

    Full Text Available A multiple targets cognitive radar tracking method based on Compressed Sensing (CS is proposed. In this method, the theory of CS is introduced to the case of cognitive radar tracking process in multiple targets scenario. The echo signal is sparsely expressed. The designs of sparse matrix and measurement matrix are accomplished by expressing the echo signal sparsely, and subsequently, the restruction of measurement signal under the down-sampling condition is realized. On the receiving end, after considering that the problems that traditional particle filter suffers from degeneracy, and require a large number of particles, the particle swarm optimization particle filter is used to track the targets. On the transmitting end, the Posterior Cramér-Rao Bounds (PCRB of the tracking accuracy is deduced, and the radar waveform parameters are further cognitively designed using PCRB. Simulation results show that the proposed method can not only reduce the data quantity, but also provide a better tracking performance compared with traditional method.

  17. Parity-Check Network Coding for Multiple Access Relay Channel in Wireless Sensor Cooperative Communications

    Directory of Open Access Journals (Sweden)

    Du Bing

    2010-01-01

    Full Text Available A recently developed theory suggests that network coding is a generalization of source coding and channel coding and thus yields a significant performance improvement in terms of throughput and spatial diversity. This paper proposes a cooperative design of a parity-check network coding scheme in the context of a two-source multiple access relay channel (MARC model, a common compact model in hierarchical wireless sensor networks (WSNs. The scheme uses Low-Density Parity-Check (LDPC as the surrogate to build up a layered structure which encapsulates the multiple constituent LDPC codes in the source and relay nodes. Specifically, the relay node decodes the messages from two sources, which are used to generate extra parity-check bits by a random network coding procedure to fill up the rate gap between Source-Relay and Source-Destination transmissions. Then, we derived the key algebraic relationships among multidimensional LDPC constituent codes as one of the constraints for code profile optimization. These extra check bits are sent to the destination to realize a cooperative diversity as well as to approach MARC decode-and-forward (DF capacity.

  18. High photo-excited carrier multiplication by charged InAs dots in AlAs/GaAs/AlAs resonant tunneling diode

    OpenAIRE

    Wang, Wangping; Hou, Ying; Xiong, Dayuan; Li, Ning; Lu, Wei

    2007-01-01

    We present an approach for the highly sensitive photon detection based on the quantum dots (QDs) operating at temperature of 77K. The detection structure is based on an AlAs/GaAs/AlAs double barrier resonant tunneling diode combined with a layer of self-assembled InAs QDs (QD-RTD). A photon rate of 115 photons per second had induced 10nA photocurrent in this structure, corresponding to the photo-excited carrier multiplication factor of 10^7. This high multiplication factor is achieved by the ...

  19. Characterization of coded random access with compressive sensing based multi user detection

    DEFF Research Database (Denmark)

    Ji, Yalei; Stefanovic, Cedomir; Bockelmann, Carsten;

    2014-01-01

    and is inherently capable to take advantage of the capture effect from the PHY layer. Furthermore, at the PHY layer, compressive sensing based multi-user detection (CS-MUD) is a novel technique that exploits sparsity in multi-user detection to achieve a joint activity and data detection. In this paper, we combine...

  20. Mapping of government land encroachment in Cameron Highlands using multiple remote sensing datasets

    International Nuclear Information System (INIS)

    The cold and refreshing highland weather is one of the factors that give impact to socio-economic growth in Cameron Highlands. This unique weather of the highland surrounded by tropical rain forest can only be found in a few places in Malaysia. It makes this place a famous tourism attraction and also provides a very suitable temperature for agriculture activities. Thus it makes agriculture such as tea plantation, vegetable, fruits and flowers one of the biggest economic activities in Cameron Highlands. However unauthorized agriculture activities are rampant. The government land, mostly forest area have been encroached by farmers, in many cases indiscriminately cutting down trees and hill slopes. This study is meant to detect and assess this encroachment using multiple remote sensing datasets. The datasets were used together with cadastral parcel data where survey lines describe property boundary, pieces of land are subdivided into lots of government and private. The general maximum likelihood classification method was used on remote sensing image to classify the land-cover in the study area. Ground truth data from field observation were used to assess the accuracy of the classification. Cadastral parcel data was overlaid on the classification map in order to detect the encroachment area. The result of this study shows that there is a land cover change of 93.535 ha in the government land of the study area between years 2001 to 2010, nevertheless almost no encroachment took place in the studied forest reserve area. The result of this study will be useful for the authority in monitoring and managing the forest

  1. Mapping of government land encroachment in Cameron Highlands using multiple remote sensing datasets

    Science.gov (United States)

    Zin, M. H. M.; Ahmad, B.

    2014-02-01

    The cold and refreshing highland weather is one of the factors that give impact to socio-economic growth in Cameron Highlands. This unique weather of the highland surrounded by tropical rain forest can only be found in a few places in Malaysia. It makes this place a famous tourism attraction and also provides a very suitable temperature for agriculture activities. Thus it makes agriculture such as tea plantation, vegetable, fruits and flowers one of the biggest economic activities in Cameron Highlands. However unauthorized agriculture activities are rampant. The government land, mostly forest area have been encroached by farmers, in many cases indiscriminately cutting down trees and hill slopes. This study is meant to detect and assess this encroachment using multiple remote sensing datasets. The datasets were used together with cadastral parcel data where survey lines describe property boundary, pieces of land are subdivided into lots of government and private. The general maximum likelihood classification method was used on remote sensing image to classify the land-cover in the study area. Ground truth data from field observation were used to assess the accuracy of the classification. Cadastral parcel data was overlaid on the classification map in order to detect the encroachment area. The result of this study shows that there is a land cover change of 93.535 ha in the government land of the study area between years 2001 to 2010, nevertheless almost no encroachment took place in the studied forest reserve area. The result of this study will be useful for the authority in monitoring and managing the forest.

  2. Hardware-In-the-Loop Measurements of the Multi-Carrier Compressed Sensing Multi-User Detection (MCSM) System

    OpenAIRE

    Bockelmann, Carsten; Monsees, Fabian; Woltering, Matthias; Dekorsy, Armin

    2015-01-01

    MCSM is a recently proposed novel system concept to solve the massive access problem envisioned in future communication systems like 5G and industry 4.0 systems. This work focuses on the practical verification of the theoretical gains that MCSM provides using a Hardware-In-the-Loop (HIL) measurement setup. We present results in two different scenarios: (i) a LoS lab setup and (ii) a non-LoS machine hall. In both scenarios MCSM shows promising performance in terms of the number of supported us...

  3. Remote sensing image classification based on block feature point density analysis and multiple-feature fusion

    Science.gov (United States)

    Li, Shijin; Jiang, Yaping; Zhang, Yang; Feng, Jun

    2015-10-01

    With the development of remote sensing (RS) and the related technologies, the resolution of RS images is enhancing. Compared with moderate or low resolution images, high-resolution ones can provide more detailed ground information. However, a variety of terrain has complex spatial distribution. The different objectives of high-resolution images have a variety of features. The effectiveness of these features is not the same, but some of them are complementary. Considering the above information and characteristics, a new method is proposed to classify RS images based on hierarchical fusion of multi-features. Firstly, RS images are pre-classified into two categories in terms of whether feature points are uniformly or non-uniformly distributed. Then, the color histogram and Gabor texture feature are extracted from the uniformly-distributed categories, and the linear spatial pyramid matching using sparse coding (ScSPM) feature is obtained from the non-uniformly-distributed categories. Finally, the classification is performed by two support vector machine classifiers. The experimental results on a large RS image database with 2100 images show that the overall classification accuracy is boosted by 10.1% in comparison with the highest accuracy of single feature classification method. Compared with other multiple-feature fusion methods, the proposed method has achieved the highest classification accuracy on this dataset which has reached 90.1%, and the time complexity of the algorithm is also greatly reduced.

  4. Optical Code-Division Multiple-Access and Wavelength Division Multiplexing: Hybrid Scheme Review

    Directory of Open Access Journals (Sweden)

    P. Susthitha Menon

    2012-01-01

    Full Text Available Problem statement: Hybrid Optical Code-Division Multiple-Access (OCDMA and Wavelength-Division Multiplexing (WDM have flourished as successful schemes for expanding the transmission capacity as well as enhancing the security for OCDMA. However, a comprehensive review related to this hybrid system are lacking currently. Approach: The purpose of this paper is to review the literature on OCDMA-WDM overlay systems, including our hybrid approach of one-dimensional coding of SAC OCDMA with WDM signals. In addition, we present an additional review of other categorios of hybrid WDM/OCDMA schemes, where codes of OCDMA can be employed on each WDM wavelength. Furthermore, an essential background of OCDMA, recent coding techniques and security issues are also presented. Results: Our results indicate that the feasibility of transmitting both OCDMA and WDM users on the same spectrum band can be achieved using MQC family code with an acceptable performance as well as good data confidentiality. In addition, the WDM interference signals can be suppressed properly for detection of optical broadband CDMA using notch filters. Conclusion: The paper provides a comprehensive overview of hybrid OCDMA-WDM systems and can be used as a baseline study for other scientists in the similar scope of research.

  5. Entanglement distribution over quantum code-division multiple-access networks

    Science.gov (United States)

    Zhu, Chang-long; Yang, Nan; Liu, Yu-xi; Nori, Franco; Zhang, Jing

    2015-10-01

    We present a method for quantum entanglement distribution over a so-called code-division multiple-access network, in which two pairs of users share the same quantum channel to transmit information. The main idea of this method is to use different broadband chaotic phase shifts, generated by electro-optic modulators and chaotic Colpitts circuits, to encode the information-bearing quantum signals coming from different users and then recover the masked quantum signals at the receiver side by imposing opposite chaotic phase shifts. The chaotic phase shifts given to different pairs of users are almost uncorrelated due to the randomness of chaos and thus the quantum signals from different pair of users can be distinguished even when they are sent via the same quantum channel. It is shown that two maximally entangled states can be generated between two pairs of users by our method mediated by bright coherent lights, which can be more easily implemented in experiments compared with single-photon lights. Our method is robust under the channel noises if only the decay rates of the information-bearing fields induced by the channel noises are not quite high. Our study opens up new perspectives for addressing and transmitting quantum information in future quantum networks.

  6. Primary user localisation and uplink resource allocation in orthogonal frequency division multiple access cognitive radio systems

    KAUST Repository

    Nam, Haewoon

    2015-05-21

    In cognitive radio networks, secondary users (SUs) can share spectrum with primary users (PUs) under the condition that no interference is caused to the PUs. To evaluate the interference imposed to the PUs, the cognitive systems discussed in the literature usually assume that the channel state information (CSI) of the link from a secondary transmitter to a primary receiver (interference link) is known at the secondary transmitter. However, this assumption may often be impractical in cognitive radio systems, since the PUs need to be oblivious to the presence of the SUs. The authors first discuss PU localisation and then introduce an uplink resource allocation algorithm for orthogonal frequency division multiple access-based cognitive radio systems, where relative location information between primary and SUs is used instead of CSI of the interference link to estimate the interference. Numerical and simulation results show that it is indeed effective to use location information as a part of resource allocation and thus a near-optimal capacity is achieved. © The Institution of Engineering and Technology 2015.

  7. Enhanced Seamless Handoff Using Multiple Access Points in Wireless Local Area Network

    Directory of Open Access Journals (Sweden)

    Prabhavathy . G,

    2015-06-01

    Full Text Available The Mobility in wireless cellular communication systems is its backbone so as to enhance the quality of service and maintain the continuous service. Handoff is an important task in maintaining the continuity of call in cellular systems and its failure can result in ongoing call termination. In cellular mobile networks, the coverage region is divided into smaller cells in order to achieve high system capacity. Each cell has a Base-Station (BS, which provides the service to the Mobile Terminals (MTs, i.e. users equipped with phones, within its region. Before a mobile user can communicate with other user(s in the network, a group of the frequency bands or channels should usually be assigned. The MTs is free to move across cells. When the mobile user crossing a cell boundary or by deterioration in quality of the signal in the current channel, handoff process is initiated. The scope of this project is to design 802.11 handoff schemes to solve the handoff problems in closely-spaced WLANs.The major problem in multiple WLANs are so many users trying to use same access point(AP, and interferences from nearby WLAN. The better hand off scheme based on signal strength and velocity of the nodes is proposed. The simulation results show that the proposed handoff scheme significantly reduces packet losses compared with existing handoff schemes.

  8. A USER-DEPENDENT PERFECT-SCHEDULING MULTIPLE ACCESS PROTOCOL FOR VOICE-DATA INTEGRATION IN WIRELESS NETWORKS

    Institute of Scientific and Technical Information of China (English)

    Zhou Yajian; Li Jiandong; Liu Kai

    2002-01-01

    A novel Multiple Access Control (MAC) protocol - User-dependent Perfect-scheduling Multiple Access (UPMA) protocol, which supports joint transmission of voice and data packets,is proposed. By this protocol, the bandwidth can be allocated dynamically to the uplink and downlink traffic with on-demand assignment and the transmission of Mobile Terminals (MTs)can be perfectly scheduled by means of polling. Meanwhile, a unique frame structure is designed to guarantee Quality of Service (QoS) in voice traffic supporting. An effective collision resolution algorithm is also proposed to guarantee rapid channel access for activated MTs. Finally, performance of UPMA protocol is evaluated by simulation and compared with MPRMA protocol.Simulation results show that UPMA protocol has better performance.

  9. A USER-DEPENDENT PERFECT-SCHEDULING MULTIPLE ACCESS PROTOCOL FOR VOICE-DATA INTEGRATION IN WIRELESS NETWORKDS

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A novel Multiple Access Control(MAC) protocol-User-dependent Perfect-scheduling Multiple Access(UPMA) protocol,which supports joint transmission of voice and data packets,is proposed.By this protocol,the bandwidth can be allocated dynamically to the uplink and downlink traffic with on-demand assignment and the transmission of Mobile Terminals(MTs) can be perfectly scheduled by means of polling.Meanwhile.a unique frame stucture is designed to guarantee Quality of Service(QoS) in voice traffic supporting.An effective colision resolution algorthm is also proposed to guarantee rapid channel access for activated MTs.Finally,performance of UPMA protocol is evaluated by simulation and compared with MPRMA protocol.Simulation results show that UPMA protocol has better performance.

  10. Performance Study of Hybrid DS/FFH Spread-Spectrum Systems in the Presence of Frequency-Selective Fading and Multiple-Access Interference

    Energy Technology Data Exchange (ETDEWEB)

    Olama, Mohammed M [ORNL; Smith, Stephen Fulton [ORNL; Kuruganti, Phani Teja [ORNL; Ma, Xiao [ORNL

    2012-01-01

    Hybrid spread-spectrum (HSS) systems have recently received considerable interest in commercial, Smart Grid, and military communication systems because they accommodate high data rates with high link integrity, even in the presence of significant multipath effects and interfering signals. A highly useful form of this modulation scheme is the specific code-related combination of standard direct-sequence spread spectrum (DSSS) with fast frequency-hopping (FFH) spread spectrum, denoted hybrid DS/FFH, wherein multiple frequency hops occur within a single data-bit time. In this paper we perform a simulation-based study of the DS/FFH performance as compared to the existing standard DSSS and FHSS wireless networks. The performance metrics are bit-error probability and multiple-access capability. The parameter space of DS/FFH, including the DS spreading rate, frequency hopping rate, carrier frequencies, and numbers of users, is explored to show its performance under frequency-selective Rayleigh fading environments and multiuser interference. Direct digital synthesizers to achieve fast hopping speeds are also considered in our study.

  11. Web-based interactive access, analysis and comparison of remotely sensed and in situ measured temperature data

    Science.gov (United States)

    Eberle, Jonas; Urban, Marcel; Hüttich, Christian; Schmullius, Christiane

    2014-05-01

    Numerous datasets providing temperature information from meteorological stations or remote sensing satellites are available. However, the challenging issue is to search in the archives and process the time series information for further analysis. These steps can be automated for each individual product, if the pre-conditions are complied, e.g. data access through web services (HTTP, FTP) or legal rights to redistribute the datasets. Therefore a python-based package was developed to provide data access and data processing tools for MODIS Land Surface Temperature (LST) data, which is provided by NASA Land Processed Distributed Active Archive Center (LPDAAC), as well as the Global Surface Summary of the Day (GSOD) and the Global Historical Climatology Network (GHCN) daily datasets provided by NOAA National Climatic Data Center (NCDC). The package to access and process the information is available as web services used by an interactive web portal for simple data access and analysis. Tools for time series analysis were linked to the system, e.g. time series plotting, decomposition, aggregation (monthly, seasonal, etc.), trend analyses, and breakpoint detection. Especially for temperature data a plot was integrated for the comparison of two temperature datasets based on the work by Urban et al. (2013). As a first result, a kernel density plot compares daily MODIS LST from satellites Aqua and Terra with daily means from GSOD and GHCN datasets. Without any data download and data processing, the users can analyze different time series datasets in an easy-to-use web portal. As a first use case, we built up this complimentary system with remotely sensed MODIS data and in situ measurements from meteorological stations for Siberia within the Siberian Earth System Science Cluster (www.sibessc.uni-jena.de). References: Urban, Marcel; Eberle, Jonas; Hüttich, Christian; Schmullius, Christiane; Herold, Martin. 2013. "Comparison of Satellite-Derived Land Surface Temperature and Air

  12. A Bio-Inspired Two-Layer Sensing Structure of Polypeptide and Multiple-Walled Carbon Nanotube to Sense Small Molecular Gases

    Directory of Open Access Journals (Sweden)

    Li-Chun Wang

    2015-03-01

    Full Text Available In this paper, we propose a bio-inspired, two-layer, multiple-walled carbon nanotube (MWCNT-polypeptide composite sensing device. The MWCNT serves as a responsive and conductive layer, and the nonselective polypeptide (40 mer coating the top of the MWCNT acts as a filter into which small molecular gases pass. Instead of using selective peptides to sense specific odorants, we propose using nonselective, peptide-based sensors to monitor various types of volatile organic compounds. In this study, depending on gas interaction and molecular sizes, the randomly selected polypeptide enabled the recognition of certain polar volatile chemical vapors, such as amines, and the improved discernment of low-concentration gases. The results of our investigation demonstrated that the polypeptide-coated sensors can detect ammonia at a level of several hundred ppm and barely responded to triethylamine.

  13. Advanced mobile networking, sensing, and controls.

    Energy Technology Data Exchange (ETDEWEB)

    Feddema, John Todd; Kilman, Dominique Marie; Byrne, Raymond Harry; Young, Joseph G.; Lewis, Christopher L.; Van Leeuwen, Brian P.; Robinett, Rush D. III; Harrington, John J.

    2005-03-01

    This report describes an integrated approach for designing communication, sensing, and control systems for mobile distributed systems. Graph theoretic methods are used to analyze the input/output reachability and structural controllability and observability of a decentralized system. Embedded in each network node, this analysis will automatically reconfigure an ad hoc communication network for the sensing and control task at hand. The graph analysis can also be used to create the optimal communication flow control based upon the spatial distribution of the network nodes. Edge coloring algorithms tell us that the minimum number of time slots in a planar network is equal to either the maximum number of adjacent nodes (or degree) of the undirected graph plus some small number. Therefore, the more spread out that the nodes are, the fewer number of time slots are needed for communication, and the smaller the latency between nodes. In a coupled system, this results in a more responsive sensor network and control system. Network protocols are developed to propagate this information, and distributed algorithms are developed to automatically adjust the number of time slots available for communication. These protocols and algorithms must be extremely efficient and only updated as network nodes move. In addition, queuing theory is used to analyze the delay characteristics of Carrier Sense Multiple Access (CSMA) networks. This report documents the analysis, simulation, and implementation of these algorithms performed under this Laboratory Directed Research and Development (LDRD) effort.

  14. Integrating Multiple Knowledge Sources to Disambiguate Word Sense: An Exemplar-Based Approach

    OpenAIRE

    Ng, Hwee Tou; Lee, Hian Beng

    1996-01-01

    In this paper, we present a new approach for word sense disambiguation (WSD) using an exemplar-based learning algorithm. This approach integrates a diverse set of knowledge sources to disambiguate word sense, including part of speech of neighboring words, morphological form, the unordered set of surrounding words, local collocations, and verb-object syntactic relation. We tested our WSD program, named {\\sc Lexas}, on both a common data set used in previous work, as well as on a large sense-ta...

  15. Integrating Multiple Knowledge Sources to Disambiguate Word Sense An Exemplar-Based Approach

    CERN Document Server

    Ng, H T; Ng, Hwee Tou; Lee, Hian Beng

    1996-01-01

    In this paper, we present a new approach for word sense disambiguation (WSD) using an exemplar-based learning algorithm. This approach integrates a diverse set of knowledge sources to disambiguate word sense, including part of speech of neighboring words, morphological form, the unordered set of surrounding words, local collocations, and verb-object syntactic relation. We tested our WSD program, named {\\sc Lexas}, on both a common data set used in previous work, as well as on a large sense-tagged corpus that we separately constructed. better than the most frequent heuristic on the highly ambiguous words in the large corpus tagged with the refined senses of {\\sc WordNet}.

  16. Compressed sensing of roller bearing fault based on multiple down-sampling strategy

    International Nuclear Information System (INIS)

    Roller bearings are essential components of rotating machinery and are often exposed to complex operating conditions, which can easily lead to their failures. Thus, to ensure normal production and the safety of machine operators, it is essential to detect the failures as soon as possible. However, it is a major challenge to maintain a balance between detection efficiency and big data acquisition given the limitations of sampling theory. To overcome these limitations, we try to preserve the information pertaining to roller bearing failures using a sampling rate far below the Nyquist sampling rate, which can ease the pressure generated by the large-scale data. The big data of a faulty roller bearing’s vibration signals is firstly reduced by a down-sample strategy while preserving the fault features by selecting peaks to represent the data segments in time domain. However, a problem arises in that the fault features may be weaker than before, since the noise may be mistaken for the peaks when the noise is stronger than the vibration signals, which makes the fault features unable to be extracted by commonly-used envelope analysis. Here we employ compressive sensing theory to overcome this problem, which can make a signal enhancement and reduce the sample sizes further. Moreover, it is capable of detecting fault features from a small number of samples based on orthogonal matching pursuit approach, which can overcome the shortcomings of the multiple down-sample algorithm. Experimental results validate the effectiveness of the proposed technique in detecting roller bearing faults. (paper)

  17. Multiple-image encryption by space multiplexing based on compressive sensing and the double-random phase-encoding technique.

    Science.gov (United States)

    Deepan, B; Quan, C; Wang, Y; Tay, C J

    2014-07-10

    In this paper, a new multiple-image encryption and decryption technique that utilizes the compressive sensing (CS) concept along with a double-random phase encryption (DRPE) has been proposed. The space multiplexing method is employed for integrating multiple-image data. The method, which results in a nonlinear encryption system, is able to overcome the vulnerability of classical DRPE. The CS technique and space multiplexing are able to provide additional key space in the proposed method. A numerical experiment of the proposed method is implemented and the results show that the proposed method has good accuracy and is more robust than classical DRPE. The proposed system is also employed against chosen-plaintext attacks and it is found that the inclusion of compressive sensing enhances robustness against the attacks.

  18. Highly accessible Pt nanodots homogeneously decorated on Au nanorods surface for sensing

    International Nuclear Information System (INIS)

    Highlights: • Seed-growth of highly-dispersed catalytic Pt nanodot on Au nanorod (PtND@AuNR). • Good accessibility of catalytic sites was evidenced by its peroxidase-like activity. • Excellent assay performances of H2O2 at PtND@AuNR-based sensor. - Abstract: Some nanostructures are reported to possess enzyme-mimetic activities similar to those of natural enzymes. Herein, highly-dispersed Pt nanodots on Au nanorods (HD- PtNDs@AuNRs) with mimetic peroxidase activity were designed as an active electrode modifier for fabrication of a hydrogen peroxide (H2O2) electrochemical sensor. The HD-PtNDs@AuNRs were synthesized by a seed-mediated growth approach and confirmed by scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, and UV–vis spectroscopy. The electrochemical and catalytical performances of HD-PtNDs@AuNRs towards H2O2 reduction were investigated in detail by cyclic voltammetry and amperometry. The HD-PtNDs@AuNRs modified electrode displayed a high catalytic activity to H2O2 at −0.10 V (versus SCE), a rapid response within 5 s, a wide linear range of 2.0–3800.0 μM, a detection limit of 1.2 μM (S/N = 3), and a high sensitivity of 181 μA mM−1 cm−2. These results suggested a promising potential of fabricating H2O2 electrochemical sensor using HD- PtNDs@AuNRs

  19. Highly accessible Pt nanodots homogeneously decorated on Au nanorods surface for sensing

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Xun [College of Chemistry, Jilin University, Changchun 130012 (China); Li, Xin [College of Electronic Science and Engineering, Jilin University, Changchun 130012 (China); Shi, Hongyan; Huang, Hao [College of Chemistry, Jilin University, Changchun 130012 (China); Wu, Xiaochun [CAS Key Laboratory of Standardization and Measurement for Nanotechnology, National Center for Nanoscience and Technology, Beijing 100190 (China); Song, Wenbo, E-mail: wbsong@jlu.edu.cn [College of Chemistry, Jilin University, Changchun 130012 (China)

    2014-12-10

    Highlights: • Seed-growth of highly-dispersed catalytic Pt nanodot on Au nanorod (PtND@AuNR). • Good accessibility of catalytic sites was evidenced by its peroxidase-like activity. • Excellent assay performances of H{sub 2}O{sub 2} at PtND@AuNR-based sensor. - Abstract: Some nanostructures are reported to possess enzyme-mimetic activities similar to those of natural enzymes. Herein, highly-dispersed Pt nanodots on Au nanorods (HD- PtNDs@AuNRs) with mimetic peroxidase activity were designed as an active electrode modifier for fabrication of a hydrogen peroxide (H{sub 2}O{sub 2}) electrochemical sensor. The HD-PtNDs@AuNRs were synthesized by a seed-mediated growth approach and confirmed by scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, and UV–vis spectroscopy. The electrochemical and catalytical performances of HD-PtNDs@AuNRs towards H{sub 2}O{sub 2} reduction were investigated in detail by cyclic voltammetry and amperometry. The HD-PtNDs@AuNRs modified electrode displayed a high catalytic activity to H{sub 2}O{sub 2} at −0.10 V (versus SCE), a rapid response within 5 s, a wide linear range of 2.0–3800.0 μM, a detection limit of 1.2 μM (S/N = 3), and a high sensitivity of 181 μA mM{sup −1} cm{sup −2}. These results suggested a promising potential of fabricating H{sub 2}O{sub 2} electrochemical sensor using HD- PtNDs@AuNRs.

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

    Science.gov (United States)

    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

  1. Bright Fluorescence and Host-Guest Sensing with a Nanoscale M₄L₆ Tetrahedron Accessed by Self-Assembly of Zinc-Imine Chelate Vertices and Perylene Bisimide Edges.

    Science.gov (United States)

    Frischmann, Peter D; Kunz, Valentin; Würthner, Frank

    2015-06-15

    A highly luminescent Zn4L6 tetrahedron is reported with 3.8 nm perylene bisimide edges and hexadentate Zn(II)-imine chelate vertices. Replacing Fe(II) and monoamines commonly utilized in subcomponent self-assembly with Zn(II) and tris(2-aminoethyl)amine provides access to a metallosupramolecular host with the rare combination of structural integrity at concentrations <10(-7) mol L(-1) and an exceptionally high fluorescence quantum yield of Φ(em) =0.67. Encapsulation of multiple perylene or coronene guest molecules is accompanied by strong luminescence quenching. We anticipate this self-assembly strategy may be generalized to improve access to brightly fluorescent coordination cages tailored for host-guest light-harvesting, photocatalysis, and sensing.

  2. Comparison of a Ring On-Chip Network and a Code-Division Multiple-Access On-Chip Network

    OpenAIRE

    Xin Wang; Jari Nurmi

    2007-01-01

    Two network-on-chip (NoC) designs are examined and compared in this paper. One design applies a bidirectional ring connection scheme, while the other design applies a code-division multiple-access (CDMA) connection scheme. Both of the designs apply globally asynchronous locally synchronous (GALS) scheme in order to deal with the issue of transferring data in a multiple-clock-domain environment of an on-chip system. The two NoC designs are compared with each other by their network structures, ...

  3. ADNP-CSMA Random Multiple Access protocol application with the function of monitoring in Ad Hoc network

    Directory of Open Access Journals (Sweden)

    Zhan Gang

    2016-01-01

    Full Text Available In Ad Hoc networks,the net work of mobile nodes exchange information with their wireless transceiver equipment,the network throughput is in increased,compared to other such multiple hops network.Moreover along with the rapid development of modern information,communication business also will be increase.However,the access and adaptive of previous CSMA protocol are insufficient.According to these properties,this paper presents a kind of adaptive dual clock with monitoring function P-CSMA random multiple access protocol(ADNP-CSMA,and discusses two kinds of P-CSMA.ACK with monitoring function is introduced to maintain the stability of the whole system,and the introduction of dual clock mechanism reduces the channel of idle period.It calculate the system throughput expression through the method of average period,and the simulation results show that the system is constant in the case of high load throughput.

  4. Effect of Yoga Exercise on General Health Status (GHS and Sense of Life in Patients with Multiple Sclerosis

    Directory of Open Access Journals (Sweden)

    SH Najafi doulatabad

    2011-08-01

    Full Text Available Introduction & Objective: Multiple sclerosis (MS is a type of progressing and degenerating disease of myelin membrane of nervous cells in the Central Nervous System (CNS which could cause the incidence of many signs and complications in patients. The disease could affect different aspects of an individual’s life and disturb his/her normal life. This study was carried out in order to survey the effect of yoga exercise on general health status (GHS and sense of life in patients with multiple sclerosis. Materials & Methods: This research was a clinical trial study carried out at Yasouj University of Medical Sciences on 60 female patients with multiple sclerosis from Kohgiloyeh and Boyerahmad province in 2009.The data collecting tool consisted was MSQoL-54 questionnaire contained demographic information of patients. Patients were randomly divided into two control and case groups (30 persons in each group. Then, the general health status (GHS and sense of life of the subjects were evaluated. Yoga therapy was done in the case group for three months and each month included eight sessions of 1-1.5 hours while no intervention was carried out on the control group. One month after Yoga therapy, the general health status (GHS and sense of life for both groups were evaluated and compared with each other. Collected data were analyzed using descriptive tests, statistical independent t-test and paired t-test by the SPSS software. Results: The mean age of samples was 31.6±8.0 with the range of 18-45 years. Forty two (70% of the subjects were married and 18 (30% were single. Forty four (73.3% had high school education and 16 (26.6% had a university degree. Regarding occupation, most of them (63.3% were housewives. Results of the study showed that after Yoga therapy, the mean rate of general health status (GHS and sense of life as a whole had significant statistical difference between two groups (P<0.05. Conclusion: Yoga has improved the general health status

  5. Bit Error Rate Performance for Multicarrier Code Division Multiple Access over Generalized η-μ Fading Environment

    Directory of Open Access Journals (Sweden)

    James Osuru Mark

    2011-01-01

    Full Text Available The multicarrier code division multiple access (MC-CDMA system has received a considerable attention from researchers owing to its great potential in achieving high data rates transmission in wireless communications. Due to the detrimental effects of multipath fading the performance of the system degrades. Similarly, the impact of non-orthogonality of spreading codes can exist and cause interference. This paper addresses the performance of multicarrier code division multiple access system under the influence of frequency selective generalized η-µ  fading channel and multiple access interference caused by other active users to the desired one. We apply Gaussian approximation technique to analyse the performance of the system. The avearge bit error rate is derived and expressed in Gauss hypergeometic functions. Maximal ratio combining diversity technique is utilized to alleviate the deleterious effect of multipath fading. We observed that the system performance improves when the parameter η increase or decreasse in format 1 or format 2 conditions respectively.

  6. Popular Content Distribution in CR-VANETs with Joint Spectrum Sensing and Channel Access using Coalitional Games

    Directory of Open Access Journals (Sweden)

    Tianyu Wang

    2014-07-01

    Full Text Available Driven by both safety concerns and commercial interests, popular content distribution (PCD, as one of the key services offered by vehicular networks, has recently received considerable attention. In this paper, we address the PCD problem in highway scenarios, in which a popular file is distributed to a group of onboard units (OBUs driving through an area of interest (AoI. Due to high speeds of vehicles and deep fading of vehicle-to-roadside (V2R channels, the OBUs may not finish downloading the entire file. Consequently, a peer-to-peer (p2p network should be constructed among the OBUs for completing the file delivery process. Here, we apply the cognitive radio technique for vehicle-to-vehicle communications and propose a cooperative approach based on coalition formation games, which jointly considers the spectrum sensing and channel access performance. Simulation results show that our approach presents a considerable performance improvement compared with the non-cooperative case.

  7. Inhibition of human immunodeficiency virus type 1 multiplication by antisense and sense RNA expression.

    OpenAIRE

    Joshi, S; Van Brunschot, A; Asad, S.; van der Elst, I; Read, S. E.; Bernstein, A

    1991-01-01

    Human immunodeficiency virus type 1 (HIV-1) primarily infects CD4+ lymphocytes and macrophages and causes AIDS in humans. Retroviral vectors allowing neomycin phosphotransferase (npt) gene expression were engineered to express 5' sequences of HIV-1 RNA in the antisense or sense orientation and used to transform the human CD4+ lymphocyte-derived MT4 cell line. Cells expressing antisense or sense RNA to the HIV-1 tat mRNA leader sequence, as part of the 3' untranslated region of the npt mRNA, r...

  8. Local charge neutrality condition, Fermi level and majority carrier density of a semiconductor with multiple localized multi-level intrinsic/impurity defects

    Institute of Scientific and Technical Information of China (English)

    Ken K. Chin

    2011-01-01

    For semiconductors with localized intrinsic/impurity defects,intentionally doped or unintentionally incorporated,that have multiple transition energy levels among charge states,the general formulation of the local charge neutrality condition is given for the determination of the Fermi level and the majority carrier density.A graphical method is used to illustrate the solution of the problem.Relations among the transition energy levels of the multi-level defect are derived using the graphical method.Numerical examples are given for p-doping of the CdTe thin film used in solar panels and semi-insulating Si to illustrate the relevance and importance of the issues discussed in this work.

  9. Multiple Perspectives on the Accessibility of E-Learning in Canadian Colleges and Universities

    Science.gov (United States)

    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…

  10. Multiple access protocol for supporting multimedia services in wireless ATM networks

    DEFF Research Database (Denmark)

    Liu, Hong; Dittmann, Lars; Gliese, Ulrik Bo;

    1999-01-01

    The furture broadband wireless asynchronous transfer mode (ATM) networks must provide seamless extension of multimedia services from the wireline ATM networks. This requires an effecient wireless access protocol to fulfill varying Quality-og-Service (QoS) requirements for multimedia applications...

  11. Architecture of Wireless Sensor Networks with Mobile Sinks: Multiple Access Case

    OpenAIRE

    Liang Song; Dimitrios Hatzinakos

    2007-01-01

    We propose to develop Wireless Sensor Networks with Mobile Sinks (MSSN), under high sensor node density, where multiple sensor nodes need to share one single communication channel in the node-to-sink transmission. By exploiting the tradeoff between the successful information retrieval probability and the nodes energy consumption, a number of multiple nodes transmission scheduling algorithms are proposed. Both optimal and suboptimal algorithms, which exhibit exponential and linear complexity r...

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

    CERN Document Server

    Bock, Nicolas; Sałek, Paweł; Niklasson, Anders M N; Challacombe, Matt

    2008-01-01

    We investigate effects of ordering in blocked matrix--matrix multiplication. We find that submatrices do not have to be stored contiguously in memory to achieve near optimal performance. Instead it is the choice of multiplication ordering that leads to a speedup of up to four times for small block sizes. This is in contrast to results for single matrix elements showing that contiguous memory allocation quickly becomes irrelevant as the blocksize increases.

  13. 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

    Science.gov (United States)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  15. Interpolated Compressed Sensing for 2D Multiple Slice Fast MR Imaging

    OpenAIRE

    Yong Pang; Xiaoliang Zhang

    2013-01-01

    Sparse MRI has been introduced to reduce the acquisition time and raw data size by undersampling the k-space data. However, the image quality, particularly the contrast to noise ratio (CNR), decreases with the undersampling rate. In this work, we proposed an interpolated Compressed Sensing (iCS) method to further enhance the imaging speed or reduce data size without significant sacrifice of image quality and CNR for multi-slice two-dimensional sparse MR imaging in humans. This method utilizes...

  16. Road Extraction from High-resolution Remote Sensing Images Based on Multiple Information Fusion

    Directory of Open Access Journals (Sweden)

    LI Xiao-feng

    2016-02-01

    Full Text Available Road extraction from high-resolution remote sensing images has been considered to be a significant but very difficult task.Especially the spectrum of some buildings is similar with that of roads,which makes the surfaces being connect with each other after classification and difficult to be distinguished.Based on the cooperation between road surfaces and edges,this paper presents an approach to purify roads from high-resolution remote sensing images.Firstly,we try to improve the extraction accuracy of road surfaces and edges respectively.The logic cooperation between these two binary images is used to separate road and non-road objects.Then the road objects are confirmed by the cooperation between surfaces and edges.And the effective shape indices(e.g.polar moment of inertia and narrow extent index are applied to eliminate non-road objects.So the road information is refined.The experiments indicate that the proposed approach is efficient for eliminating non-road information and extracting road information from high-resolution remote sensing image.

  17. A New Performance Analysis Method of Optical Code Division Multiple Access Systems with An Optical Hard-Limiter

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A new performance analysis method of Optical Code Division Multiple Access (OCDMA) systems with an optical hard-limiter is studied. The bit error probability of the OCDMA system is derived, and the numerical results of the system with and without an ideal optical hard-limiter are analyzed respectively. The results show that although the derived expression is different from the one derived by J A Salehi[1], the numerical results are the same as those analyzed by J A Salehi, and the numerical result can be easily achieved in this expression.

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

    Science.gov (United States)

    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.

  19. Multiple Temperature-Sensing Behavior of Green and Red Upconversion Emissions from Stark Sublevels of Er3+

    Directory of Open Access Journals (Sweden)

    Baosheng Cao

    2015-12-01

    Full Text Available Upconversion luminescence properties from the emissions of Stark sublevels of Er3+ were investigated in Er3+-Yb3+-Mo6+-codoped TiO2 phosphors in this study. According to the energy levels split from Er3+, green and red emissions from the transitions of four coupled energy levels, 2H11/2(I/2H11/2(II, 4S3/2(I/4S3/2(II, 4F9/2(I/4F9/2(II, and 2H11/2(I + 2H11/2(II/4S3/2(I + 4S3/2(II, were observed under 976 nm laser diode excitation. By utilizing the fluorescence intensity ratio (FIR technique, temperature-dependent upconversion emissions from these four coupled energy levels were analyzed at length. The optical temperature-sensing behaviors of sensing sensitivity, measurement error, and operating temperature for the four coupled energy levels are discussed, all of which are closely related to the energy gap of the coupled energy levels, FIR value, and luminescence intensity. Experimental results suggest that Er3+-Yb3+-Mo6+-codoped TiO2 phosphor with four pairs of energy levels coupled by Stark sublevels provides a new and effective route to realize multiple optical temperature-sensing through a wide range of temperatures in an independent system.

  20. Multiple choice exams of medical knowledge with open books and web access? A validity study

    DEFF Research Database (Denmark)

    O'Neill, Lotte; Simonsen, Eivind Ortind; Knudsen, Ulla Breth;

    2015-01-01

    Background: Open book tests have been suggested to lower test anxiety and promote deeper learning strategies. In the Aarhus University medical program, ¼ of the curriculum assess students’ medical knowledge with ‘open book, open web’ (OBOW) multiple choice examinations. We found little existing...

  1. Embedding multiple self-organisation functionalities in future radio access networks

    NARCIS (Netherlands)

    Jansen, T.; Amirijoo, M.; Türke, U.; Jorguseski, L.; Zetterberg, K.; Nascimento, J.R.V. do; Schmelz, L.C.; Turk, J.; Balan, I.

    2009-01-01

    Wireless network operators today allocate considerable manual effort in managing their networks. A viable solution for lowering the manual effort is to introduce self-organisation functionalities. In this paper we discuss the challenges that are encountered when embedding multiple self-organisation

  2. Oceanographic profile data collected aboard multiple platforms worldwide from 1959-05-26 to 2012-06-03 (NCEI Accession 0098794)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NODC Accession 0098794 contains physical and chemical oceanographic profile data collected aboard multiple ships worldwide from 1959-05-26 to 2012-06-03. These data...

  3. Radiative recombination mechanism of carriers in InGaN/AlInGaN multiple quantum wells with varying aluminum content

    International Nuclear Information System (INIS)

    Highlights: • Structural and optical properties of In GaN/AlxInyGa1−x−yN MQWs were investigated. • The existence of In-rich clusters has been verified by Raman spectra. • The degree of localization effect increase with increasing Al content in barriers. • The origin of the deep localized states could be assigned to the larger QCSE. • Recombination mechanism of carriers with increasing temperature has been proposed. - Abstract: The structural and optical properties of In0.20Ga0.80N/AlxInyGa1−x−yN multiple quantum wells samples with varying Al content in barrier layers grown on sapphire substrates by metalorganic chemical vapor deposition have been investigated by means of high-resolution X-ray diffraction, Raman scattering measurements and temperature-dependent photoluminescence. Raman measurements verified the existence of In-rich clusters in ternary and quaternary layers. At 10 K and 300 K, the PL spectrum of each sample is dominated by a sharp emission peak arising from In0.20Ga0.80N well layers. The anomalous temperature-dependent S-shaped behaviors of emission energies have been observed, indicating the presence of localized states induced by the potential fluctuations in the quantum wells due to the inhomogeneous distribution of In-rich clusters. The degree of the localization effect and the transition temperatures between different temperature regions can be enhanced by increasing Al content in barrier layers. The improvement of the localized states emission has been observed at the lower energy side of band gap emission of quantum wells with increasing Al content. The origin of the deep localized states could be attributed to the larger quantum-confined Stark effect in the quantum wells with higher Al content. The recombination mechanism of carriers between band edge and localized states was proposed for interpreting of the emission characteristics

  4. Performance Analysis of Ultra Wideband Multiple Access Time Hopping – Pulse Shape Modulation in Presence of Timing Jitter

    Directory of Open Access Journals (Sweden)

    D. Adhikari

    2014-09-01

    Full Text Available In short-range networks such as wireless personal area networks (WPAN, multiple user wireless connectivity for surveillance would require a wireless technology that supports multiple streams of high-speed data and consumes very little power. Ultra wideband (UWB technology enables wireless connectivity across multiple devices (users addressing the need for high-speed WPAN. Apart from having a distinct advantage of higher data rate over Bluetooth v4.0 (24 Mbps, the UWB technology is also found to be tolerant to frequency-selective multipath fading. In this paper authors discuss a time-hopping pulse shape modulation UWB signalling scheme for ad-hoc high bit rate wireless connectivity for defence applications. Authors analyse multiple access interference for both Gaussian channel and frequency selective multipath fading channel to compare the effects of timing jitter on two types of pulse shapes, namely modified Hermite pulse (MHP and prolate spheroidal wave functions (PSWF. Authors make a comparative analysis of the system performance with respect to PSWF and MHP to ascertain robustness to timing jitter. In the process, authors introduced a new metric of decision factor in timing jitter analysis.Defence Science Journal, Vol. 64, No. 5, September 2014, pp.464-470, DOI:http://dx.doi.org/10.14429/dsj.64.5787

  5. 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

    OpenAIRE

    Tuyet-Hanh, Tran Thi; Lee, Jong-Koo; Oh, Juhwan; Van Minh, Hoang; Lee, Chul Ou; 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 Clu...

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

    Directory of Open Access Journals (Sweden)

    Laurent Segers

    2014-02-01

    Full Text Available 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.

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

    Science.gov (United States)

    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.

  8. Transmission Analysis of Optical Code Division Multiple Access Communication Systems in the Presence of Noise in Local Area Network Applications

    Directory of Open Access Journals (Sweden)

    Ahmed Nabih Zaki Rashed

    2013-04-01

    Full Text Available OCDMA is an essential part of the digital communication system now days for long haul, high speed networks. The biggest challenge with Optical CDMA system is to maintain the performance of the system and offer high bandwidth in case of higher number of users at minimum cost. As the number of users increase, the input requirements i.e. transmitted power, bit rate etc start increasing sharply which contribute to the additional cost. It has recently attracted significant research interest because of the advantages it offers in terms of the flexibility in the management of the system resources. We have taken into account the system design parameters are determined such as BER (bit error rate, signal to noise ratio (SNR, transmission bit rates, and optical received power for different code lengths. The Optical CDMA systems suffer from the problem of multiple access interference (MAI.As the number of users increase the BER error rate degrades because the effect of MAI (multiple access interference increases. So, there is a limitation in number of users, as the number of users increase SNR decrease and probability of error increases.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

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

    Directory of Open Access Journals (Sweden)

    Kyriakos Souliotis

    2016-02-01

    Full Text Available Background While there is currently no cure for multiple sclerosis (MS, treatment with biologic diseasemodifying 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.

  11. Change Analysis of Antarctic Ice Shelves Based on Multiple Remote Sensing Products

    Science.gov (United States)

    Tian, Yixiang; Weng, Hexia; Lv, Da; Tong, Xiaohua; Li, Rongxing

    2016-06-01

    The Antarctic ice sheet is well known as the most sensitive and key issue in the global climate change research and is playing a more and more important role for the global sea level change. Measurement of changes in area and mass of the Antarctic ice sheet is critically important and has been made by using different remote sensing technologies and ground exploration data. Sequential mapping of Antarctic boundaries provides a simple and direct method for measuring the area and volume if ice sheet or ice shelves advances or retreats in the Antarctic coasts. Our results show that the total ice shelf area is retreated between 1963 and 2009. However, the trend for each ice shelf is quite different.

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

    Science.gov (United States)

    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…

  13. On Low-Complexity Full-diversity Detection In Multi-User MIMO Multiple-Access Channels

    KAUST Repository

    Ismail, Amr

    2014-01-28

    Multiple-input multiple-output (MIMO) techniques are becoming commonplace in recent wireless communication standards. This newly introduced dimension (i.e., space) can be efficiently used to mitigate the interference in the multi-user MIMO context. In this paper, we focus on the uplink of a MIMO multiple access channel (MAC) where perfect channel state information (CSI) is only available at the destination. We provide new sufficient conditions for a wide range of space-time block codes (STBC)s to achieve full-diversity under partial interference cancellation group decoding (PICGD) with or without successive interference cancellation (SIC) for completely blind users. Interference cancellation (IC) schemes for two and three users are then provided and shown to satisfy the full-diversity criteria. Beside the complexity reduction due to the fact that PICGD enables separate decoding of distinct users without sacrificing the diversity gain, further reduction of the decoding complexity may be obtained. In fact, thanks to the structure of the proposed schemes, the real and imaginary parts of each user\\'s symbols may be decoupled without any loss of performance. Our new IC scheme is shown to outperform recently proposed two-user IC scheme especially for high spectral efficiency while requiring significantly less decoding complexity.

  14. Uncorrelated multiple conductive filament nucleation and rupture in ultra-thin high-κ dielectric based resistive random access memory

    KAUST Repository

    Wu, Xing

    2011-08-29

    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 dielectricresistive 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.

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

    Science.gov (United States)

    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. PMID:26452016

  16. Carrier Localization Effects in InGaN/GaN Multiple-Quantum-Wells LED Nanowires: Luminescence Quantum Efficiency Improvement and “Negative” Thermal Activation Energy

    Science.gov (United States)

    Bao, Wei; Su, Zhicheng; Zheng, Changcheng; Ning, Jiqiang; Xu, Shijie

    2016-01-01

    Two-dimensional InGaN/GaN multiple-quantum-wells (MQW) LED structure was nanotextured into quasi-one-dimensional nanowires (NWs) with different average diameters with a combination approach of Ni nanoislands as mask + dry etching. Such nanotexturing bring out several appealing effects including deeper localization of carriers and significant improvement in quantum efficiency (e.g., from 4.76% of the planar MQW structure to 12.5% of the 160 nm MQW NWs) of light emission in the whole interested temperature range from 4 K to 300 K. With the aid of localized-state ensemble (LSE) luminescence model, the photoluminescence spectra of the samples are quantitatively interpreted in the entire temperature range. In terms of distinctive temperature dependence of photoluminescence from these samples, a concept of “negative” thermal activation energy is tentatively proposed for the MQW NWs samples. These findings could lead to a deeper insight into the physical nature of localization and luminescence mechanism of excitons in InGaN/GaN nanowires. PMID:27686154

  17. Social Representations Of Violence Against Rural Women: Unveiling Senses In Multiple Views

    Directory of Open Access Journals (Sweden)

    Marta Cocco Costa

    2014-04-01

    Full Text Available We analyze the social representations of violence against women from the perspective of city managers, professionals and health workers in rural settings of the southern half of Rio Grande do Sul. The study has a qualitative approach and adds a theoretical/methodological perspective of social representations. The data were generated by means of the associative method, question-stimulus of words and expressions emergence. The analysis of word association was performed with EVOC software, considering frequency and order of association with inducing terms. Participants recognize violence against women as gender destination that induces consent, resignation, guilt and fear, and results in naturalization and trivialization of this social phenomenon. We highlight the need to produce ruptures in established and traditional forms of health care, in the conservative and stereotypical views of violence, favoring access to friendly service and avoiding the reproduction of gender inequalities.

  18. An Aligned-Gap and Centered-Gap Rectangular Multiple Split Ring Resonator for Dielectric Sensing Applications

    Directory of Open Access Journals (Sweden)

    Izyani Mat Rusni

    2014-07-01

    Full Text Available This paper presents the design and development of a planar Aligned-Gap and Centered-Gap Rectangular Multiple Split Ring Resonator (SRR for microwave sensors that operates at a resonance frequency around 5 GHz. The sensor consists of a microstrip transmission line loaded with two elements of rectangular SRR on both sides. The proposed metamaterial sensors were designed and fabricated on Rogers RT5880 substrate having dielectric constant of 2.2 and thickness of 0.787 mm. The final dimension of the proposed sensor was measured at 35 × 14 mm2. Measured results show good agreement with simulated ones as well as exhibiting high Q-factor for use in sensing application. A remarkably shift of resonance frequency is observed upon introduction of several sample with different dielectric value.

  19. Classification of hyperspectral remote sensing images based on simulated annealing genetic algorithm and multiple instance learning

    Institute of Scientific and Technical Information of China (English)

    高红民; 周惠; 徐立中; 石爱业

    2014-01-01

    A hybrid feature selection and classification strategy was proposed based on the simulated annealing genetic algorithm and multiple instance learning (MIL). The band selection method was proposed from subspace decomposition, which combines the simulated annealing algorithm with the genetic algorithm in choosing different cross-over and mutation probabilities, as well as mutation individuals. Then MIL was combined with image segmentation, clustering and support vector machine algorithms to classify hyperspectral image. The experimental results show that this proposed method can get high classification accuracy of 93.13%at small training samples and the weaknesses of the conventional methods are overcome.

  20. Interpolated compressed sensing for 2D multiple slice fast MR imaging.

    Directory of Open Access Journals (Sweden)

    Yong Pang

    Full Text Available Sparse MRI has been introduced to reduce the acquisition time and raw data size by undersampling the k-space data. However, the image quality, particularly the contrast to noise ratio (CNR, decreases with the undersampling rate. In this work, we proposed an interpolated Compressed Sensing (iCS method to further enhance the imaging speed or reduce data size without significant sacrifice of image quality and CNR for multi-slice two-dimensional sparse MR imaging in humans. This method utilizes the k-space data of the neighboring slice in the multi-slice acquisition. The missing k-space data of a highly undersampled slice are estimated by using the raw data of its neighboring slice multiplied by a weighting function generated from low resolution full k-space reference images. In-vivo MR imaging in human feet has been used to investigate the feasibility and the performance of the proposed iCS method. The results show that by using the proposed iCS reconstruction method, the average image error can be reduced and the average CNR can be improved, compared with the conventional sparse MRI reconstruction at the same undersampling rate.

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

    Science.gov (United States)

    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

  2. ECOHAB: Culver_M- NOAA CSC/Coastal Remote Sensing West Florida Coast Cruise, April 1999 (NODC Accession 0000535)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Abstract: The Coastal Services Center's (CSC) Coastal Remote Sensing (CRS) program is involved with programs to validate satellite algorithms for ocean properties....

  3. Radionuclide carriers

    International Nuclear Information System (INIS)

    A new carrier for radionuclide technetium 99m has been prepared for scintiscanning purposes. The new preparate consists of physiologically acceptable water-insoluble Tcsup(99m)-carrier containing from 0.2 to 0.8 weight percent of stannic ion as reductor, bound to an anionic starch derivative with about 1-20% of phosphate substituents. (EG)

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

    Science.gov (United States)

    Han, Junkai; Shen, Yongtao; Feng, Wei

    2016-08-01

    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. PMID:27378190

  5. Optimal Throughput and Energy Efficiency for Wireless Sensor Networks: Multiple Access and Multipacket Reception

    Directory of Open Access Journals (Sweden)

    Li Wenjun

    2005-01-01

    Full Text Available We investigate two important aspects in sensor network design—the throughput and the energy efficiency. We consider the uplink reachback problem where the receiver is equipped with multiple antennas and linear multiuser detectors. We first assume Rayleigh flat-fading, and analyze two MAC schemes: round-robin and slotted-ALOHA. We optimize the average number of transmissions per slot and the transmission power for two purposes: maximizing the throughput, or minimizing the effective energy (defined as the average energy consumption per successfully received packet subject to a throughput constraint. For each MAC scheme with a given linear detector, we derive the maximum asymptotic throughput as the signal-to-noise ratio goes to infinity. It is shown that the minimum effective energy grows rapidly as the throughput constraint approaches the maximum asymptotic throughput. By comparing the optimal performance of different MAC schemes equipped with different detectors, we draw important tradeoffs involved in the sensor network design. Finally, we show that multiuser scheduling greatly enhances system performance in a shadow fading environment.

  6. A design of a wavelength-hopping time-spreading incoherent optical code division multiple access system

    International Nuclear Information System (INIS)

    We present the architecture and code design for a highly scalable, 2.5 Gb/s per user optical code division multiple access (OCDMA) system. The system is scalable to 100 potential and more than 10 simultaneous users, each with a bit error rate (BER) of less than 10-9. The system architecture uses a fast wavelength-hopping, time-spreading codes. Unlike frequency and phase sensitive coherent OCDMA systems, this architecture utilizes standard on off keyed optical pulses allocated in the time and wavelength dimensions. This incoherent OCDMA approach is compatible with existing WDM optical networks and utilizes off the shelf components. We discuss the novel optical subsystem design for encoders and decoders that enable the realization of a highly scalable incoherent OCDMA system with rapid reconfigurability. A detailed analysis of the scalability of the two dimensional code is presented and select network deployment architectures for OCDMA are discussed (Authors)

  7. Chemosensors — Welcome to a New Open Access Journal Intended to Cover All Aspects of Chemical Sensing

    OpenAIRE

    Medintz, Igor L.

    2012-01-01

    It gives me great pleasure to welcome you to Chemosensors, a new online-only journal established by the Multidisciplinary Digital Publishing Institute (MDPI, Basel, Switzerland) with the intent of covering all aspects of chemical sensing. The ability to sense or detect/identify and quantitate a chemical entity, and in particular accomplish this through the use of chemical means, has never been a more important part of our society. Chemosensing permeates diverse fields including healthcare (e....

  8. Ultrafast carrier relaxation in GaN, In_(0.05)Ga_(0.95)N and an In_(0.05)Ga_(0.95)/In_(0.15)Ga_(0.85)N Multiple Quantum Well

    OpenAIRE

    Ozgur, Umit; Everitt, Henry O.

    2002-01-01

    Room temperature, wavelength non-degenerate ultrafast pump/probe measurements were performed on GaN and InGaN epilayers and an InGaN multiple quantum well structure. Carrier relaxation dynamics were investigated as a function of excitation wavelength and intensity. Spectrally-resolved sub-picosecond relaxation due to carrier redistribution and QW capture was found to depend sensitively on the wavelength of pump excitation. Moreover, for pump intensities above a threshold of 100 microJ/cm2, al...

  9. A Sensing Error Aware MAC Protocol for Cognitive Radio Networks

    CERN Document Server

    Hu, Donglin

    2011-01-01

    Cognitive radios (CR) are intelligent radio devices that can sense the radio environment and adapt to changes in the radio environment. Spectrum sensing and spectrum access are the two key CR functions. In this paper, we present a spectrum sensing error aware MAC protocol for a CR network collocated with multiple primary networks. We explicitly consider both types of sensing errors in the CR MAC design, since such errors are inevitable for practical spectrum sensors and more important, such errors could have significant impact on the performance of the CR MAC protocol. Two spectrum sensing polices are presented, with which secondary users collaboratively sense the licensed channels. The sensing policies are then incorporated into p-Persistent CSMA to coordinate opportunistic spectrum access for CR network users. We present an analysis of the interference and throughput performance of the proposed CR MAC, and find the analysis highly accurate in our simulation studies. The proposed sensing error aware CR MAC p...

  10. Mapping Woody Plant Encroachment in Grassland Using Multiple Source Remote Sensing images: Case Study in Oklahoma

    Science.gov (United States)

    Wang, J.; Xiao, X.; Qin, Y.; Dong, J.; Zhang, G.; Zhang, Y.; Zou, Z.; Zhou, Y.; Wu, X.; Bajgain, R.

    2015-12-01

    Woody plant encroachment (mainly Juniperus virginiana, a coniferous evergreen tree) in the native grassland has been rapidly increasing in the U.S. Southern Great Plains, largely triggered by overgrazing domestic livestock, fire suppression, and changing rainfall regimes. Increasing dense woody plants have significant implications for local grassland ecosystem dynamics, such as carbon storage, soil nutrient availability, herbaceous forage production, livestock, watershed hydrology and wildlife habitats. However, very limited data are available about the spatio-temporal dynamics of woody plant encroachment to the native grassland at regional scale. Data from remotes sensing could potentially provide relevant information and improve the conversion of native grassland to woody plant encroachment. Previous studies on woody detection in grassland mainly conducted at rangeland scale using airborne or high resolution images, which is sufficient to monitor the dynamics of woody plant encroachment in local grassland. This study examined the potential of medium resolution images to detect the woody encroachment in tallgrass prairie. We selected Cleveland county, Oklahoma, US. as case study area, where eastern area has higher woody coverage than does the western area. A 25-m Phased Array Type L-band Synthetic Aperture Radar (PALSAR, N36W98) image was used to map the trees distributed in the grassland. Then, maximum enhanced vegetation index (EVI) and normalized difference vegetation index (NDVI) in the winter calculated from time-series Landsat images was used to identify the invaded woody species (Juniperus virginiana) through phenology-based algorithm. The resulting woody plant encroachment map was compared with the results extracted from the high resolution images provided by the National Agriculture Imagery Program (NAIP). Field photos were also used to validate the accuracy. These results showed that integrating PALSAR and Landsat had good performance to identify the

  11. Mixing stream and datagram traffic on satellite: A FIFO Order-based Demand Assignment (FODA) Time Division Multiple Access (TDMA) scheme

    Science.gov (United States)

    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.

  12. Aircraft Carriers

    DEFF Research Database (Denmark)

    Nødskov, Kim; Kværnø, Ole

    in Asia and will balance the carrier acquisitions of the United States, the United Kingdom, Russia and India. China’s current military strategy is predominantly defensive, its offensive elements being mainly focused on Taiwan. If China decides to acquire a large carrier with offensive capabilities......, then the country will also acquire the capability to project military power into the region beyond Taiwan, which it does not possess today. In this way, China will have the military capability to permit a change of strategy from the mainly defensive, mainland, Taiwan-based strategy to a more assertive strategy...... to acquire a carrier, they can either buy one or build it themselves. The easiest way would be to buy a carrier, and if that is the chosen option, then Russia would be the most likely country to build it. Technologically, it will be a major challenge for them to build one themselves and it is likely...

  13. VCSEL-based gigabit IR-UWB link for converged communication and sensing applications in optical metro-access networks

    DEFF Research Database (Denmark)

    Pham, Tien Thang; Gibbon, Timothy Braidwood; Tafur Monroy, Idelfonso

    2012-01-01

    We report on experimental demonstration of an impulse radio ultrawideband (IR-UWB) based converged communication and sensing system. A 1550-nm VCSEL-generated IR-UWB signal is used for 2-Gbps wireless data distribution over 800-m and 50-km single mode fiber links which present short-range in...

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

    Science.gov (United States)

    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.

  15. Quantum Multiple Access Channel

    Institute of Scientific and Technical Information of China (English)

    侯广; 黄民信; 张永德

    2002-01-01

    We consider the transmission of classical information over a quantum channel by many senders, which is a generalization of the two-sender case. The channel capacity region is shown to be a convex hull bound by the yon Neumann entropy and the conditional yon Neumann entropies. The result allows a reasonable distribution of channel capacity over the senders.

  16. Circulation in the southern Great Barrier Reef studied through an integration of multiple remote sensing and in situ measurements

    Science.gov (United States)

    Mao, Yadan; Luick, John L.

    2014-03-01

    New mechanisms for stratification and upwelling in the southern Great Barrier Reef (GBR) are identified, and dynamic details of Capricorn Eddy, a transient feature located off the shelf at the southern extremity of the GBR, are revealed using the newly available surface current from High Frequency (HF) radar combined with other remote sensing and mooring data. The HF radar surface currents were used for tidal harmonic analysis and current-wind correlation analysis. These analyses, combined with Sea Surface Temperature (SST) data, mooring data, and altimetry-based geostrophic currents, enabled the effects of forcing from the large-scale oceanic currents (including the East Australian Current (EAC)), wind, and tides in a topographically complex flow regime to be separately identified. Within the indentation region where the width of the shelf abruptly narrows, current is strongly coupled with the EAC. Here strong residual flows, identified on current maps and SST images, fall into three patterns: southward flow, northwestward flow, and an eddy. Multiple data sets shed light on the prerequisite for the formation of the eddy, the reasons for its geometric variation, and its evolution with time. Intrusions of the eddy onto the shelf result in stratification characterized by a significant increase of surface temperature. Upwelling driven by wind or oceanic inflow is shown to cause stratification of previously well-mixed shelf water. The upwelling appears to be associated with equatorward-traveling coastal-trapped waves. The integrative method of analysis embodied here is applicable to other coastal regions with complex circulation.

  17. Chemosensors — Welcome to a New Open Access Journal Intended to Cover All Aspects of Chemical Sensing

    Directory of Open Access Journals (Sweden)

    Igor L. Medintz

    2012-12-01

    Full Text Available It gives me great pleasure to welcome you to Chemosensors, a new online-only journal established by the Multidisciplinary Digital Publishing Institute (MDPI, Basel, Switzerland with the intent of covering all aspects of chemical sensing. The ability to sense or detect/identify and quantitate a chemical entity, and in particular accomplish this through the use of chemical means, has never been a more important part of our society. Chemosensing permeates diverse fields including healthcare (e.g., blood chemistry analysis, food safety (e.g., detecting contamination and spoilage, environmental monitoring (e.g., air and water quality, product and manufacturing assurance (e.g., purity and efficacy, household safety (e.g., smoke detection, forensics (e.g., drug analysis, and biological research (e.g., quantitating DNA or monitoring intracellular homeostasis, to name but a paltry few areas. Indeed, the application of chemosensing has become such an integrated aspect of modern society that trying to compile a comprehensive list of where it is utilized or relied on is almost impossible. Equally daunting is trying to compile a comprehensive list of all the different sensing techniques, types of analysis, modes of signal transduction, instruments and similar type aspects. The pace of new developments in this field is both remarkable and continuously accelerating with new products and applications being developed on an almost unceasing basis. [...

  18. Strategies of Building a Stronger Sense of Community for Sustainable Neighborhoods: Comparing Neighborhood Accessibility with Community Empowerment Programs

    Directory of Open Access Journals (Sweden)

    Te-I Albert Tsai

    2014-05-01

    Full Text Available New Urbanist development in the U.S. aims at enhancing a sense of community and seeks to return to the design of early transitional neighborhoods which have pedestrian-oriented environments with retail shops and services within walking distances of housing. Meanwhile, 6000 of Taiwan’s community associations have been running community empowerment programs supported by the Council for Cultural Affairs that have helped many neighborhoods to rebuild so-called community cohesion. This research attempts to evaluate whether neighborhoods with facilities near housing and shorter travel distances within a neighborhood would promote stronger social interactions and form a better community attachment than neighborhoods that have various opportunities for residents to participate in either formal or informal social gatherings. After interviewing and surveying residents from 19 neighborhoods in Taipei’s Beitou District, and correlating the psychological sense of community with inner neighborhood’s daily travel distances and numbers of participatory activities held by community organizations under empowerment programs together with frequencies of regular individual visits and casual meetings, statistical evidence yielded that placing public facilities near residential locations is more effective than providing various programs for elevating a sense of community.

  19. Energy-Based Cooperative Spectrum Sensing of SC-FDMA Systems

    Directory of Open Access Journals (Sweden)

    Fucheng Yang

    2014-07-01

    Full Text Available In this paper, we propose a frequency-hopping M-ary frequency-shift keying spectrum sensing network (FH/MFSK SSN for identifying the on/off states of the users supported by a single-carrier frequency-division multiple assess (SC-FDMA primary radio (PR system. Specifically, the spectrums of an uplink interleaved frequency-division multiple access (IFDMA PR system are monitored by a number of cognitive radio sensing nodes (CRSNs. These CRSNs distributedly detect the on/off states of users based on one of the three energy detection schemes. After the local spectrum sensing, the CRSNs transmit their detected states to a fusion centre (FC with the aid of FH/MFSK techniques. At the FC, the on/off states of the users supported the IFDMA PR system are finally classified according to either the conventional equal-gain combining (EGC scheme or the novel erasure-supported EGC (ES-EGC scheme. In this way, the on/off information about the spectrums occupied by an IFDMA PR systemcan be obtained, so that they can be exploited by a cognitive radio (CR system. For local spectrum sensing, in this paper, we consider four synchronisation scenarios concerning the synchronisation between the received IFDMA signals and the CRSNs. The performance of the FH/MFSK SSN associated with various schemes is investigated by simulations. Our studies show that the FH/MFSK SSN constitutes one of the highly reliable spectrum sensing schemes, which are capable of exploiting both the space diversity provided by local CRSNs and the frequency diversity provided by the subcarriers of IFDMA system.

  20. Accessibility, Demography and Protection: Drivers of Forest Stability and Change at Multiple Scales in the Cauvery Basin, India

    Directory of Open Access Journals (Sweden)

    Jane Southworth

    2010-01-01

    Full Text Available The Cauvery basin of Karnataka State encompasses a range of land cover types, from dense forest areas and plantations in the Western Ghats hills, to fertile agricultural lands in the river valley. Recent demographic changes, rapid economic development and urbanization have led to the conversion of vast stretches of forested land into plantations and permanent agriculture. We examine the human drivers of forest cover change between 2001 and 2006, using MODIS 250 m data at multiple spatial scales of nested administrative units i.e., districts and taluks. Population density does not emerge as a major driver of forest distribution or deforestation. Protected areas and landscape accessibility play a major role in driving the distribution of stable forest cover at different spatial scales. The availability of forested land for further clearing emerges as a major factor impacting the distribution of deforestation, with new deforestation taking place in regions with challenging topography. This research highlights the importance of using a regional approach to study land cover change, and indicates that the drivers of forest change may be very different in long settled landscapes, for which little is known in comparison to frontier forests.

  1. A multiple regrowth process for monolithically-integrated InP-based mode-locked laser diodes with uni-travelling carrier absorber

    Science.gov (United States)

    Lohe, Hans-Jörg; Scollo, Riccardo; Vogt, Werner; Gini, Emilio; Robin, Franck; Erni, Daniel; Harbers, Rik; Jäckel, Heinz

    2006-04-01

    Progress in photonics by monolithic integration for higher functional density, performance and reduced cost faces challenging hurdles due to technological and functional heterogeneities. Advanced local material growth techniques are enabling concepts towards high-density photonic integration, unprecedented performance and multi-functionality and ultimately optical systems-on-a-chip. For example mode-locked laser diodes (MLLDs) are key devices for ultra-short pulse generation for all-optical Tbit/s communication networks. MLLDs suffer from material compromises and will benefit from the possibility to design the gain, absorber and passive-waveguiding sections independently. We have proposed and demonstrated the integration of a saturable absorber with a fast absorption recovery time based on an InP/InGaAsP uni-traveling-carrier structure (UTC) to achieve pulses below 1 ps with repetition rates up to 40 GHz. The use of the UTC absorber instead of the commonly employed reverse-biased gain material requires however the heterogeneous growth of multiple layer stacks on the same chip with the butt-coupled regrowth technique.Critical for the MLLD performance are the reflections and the optical coupling between the different monolithic integrated layer structures of passive, absorbing and amplifying sections. 2D FDTD simulations of the optical waveguides demonstrate that to minimize reflections an angled interface between the different structures is preferable and can lead to reflection coefficients as low as 10^-6. To obtain an angled interface we used a wet chemical etching process sequence of selective and non-selective etchants, which is sensitive to crystal orientation and yields a 55° tilted interface. In addition we can conclude from our simulations that in order to minimize both, insertion loss and reflections, a bending of the light guiding layers has to be prevented. Bendings can lead to measured losses of 5-7 dB per interface whereas correctly aligned light

  2. Multi-User Interference Cancellation Scheme(s) for Muliple Carrier Frequency Offset Compensation in Uplink OFDMA

    DEFF Research Database (Denmark)

    Nguyen, Huan Cong; Carvalho, Elisabeth De; Prasad, Ramjee

    2006-01-01

    We consider the uplink of an Orthogonal Frequency Division Multiple Access (OFDMA)-based system, where each Mobile Station (MS) experiences a different Carrier Frequency Offset (CFO). Uncorrected CFO destroy the orthogonality among subcarriers, which could cause severe Inter-Carrier Interference...... (ICI) and degrade the system performance considerably. In this paper, we propose a novel Multi-User Interference (MUI) cancellation scheme for uplink OFDMA, which utilizes multiple OFDM-demodulators architecture to correct and then compensate the negative effects of multiple CFOs at the receiver's side...

  3. 一种基于子载波侦听的宽带无线网络接入控制策略%A Subcarrier-Sensing-Based Medium Access Control Scheme in Wireless Broadband Networks

    Institute of Scientific and Technical Information of China (English)

    尹杰晨; 毛玉明; 冷鹏

    2014-01-01

    In the orthogonal frequency division multiple access (OFDMA)wireless broadband networks ,the efficiency of ran-dom access can be improved by distributing contention onto multiple channels .However ,due to the multichannel property ,the tradi-tional systems based on request-to-send (RTS )control frame have to encounter the idleness of subchannel ,the extension of RTS transmission time and the complex synchronization of uplink communication .To solve these problems ,in our scheme ,the users send signals on random subcarrier to request transmission opportunity .The access point senses these request signals ,and determines which user is permitted to access channel according to the busy state of the subcarriers .The theoretical analysis and simulation results both show that our scheme outperforms the traditional RTS-based schemes in term of the throughput .%在基于正交频分多址技术的宽带网络中,通过把竞争分散到多个子信道能有效改善随机接入的性能。然而多信道特性也会使传统基于Request-To-Send (RTS )控制帧的随机接入协议面临子信道空闲、RTS传输时间延长、上行复杂的问题。针对这些问题,在本文所提出的接入方法中,用户在没有被分配到资源时通过在随机子载波上发送信号来请求传输机会,与此同时,接入点对这些信号侦听,并根据子载波忙闲状态确定哪些用户可以接入。理论分析及仿真结果表明,相比传统依靠RTS的接入方法,采用子载波侦听,系统将获得更高的吞吐量。

  4. Multi-channel Dual Clocks three-dimensional probability Random Multiple Access protocol for Wireless Public Bus Networks based on RTS/CTS mechanism

    Directory of Open Access Journals (Sweden)

    Zhou Sheng Jie

    2016-01-01

    Full Text Available A MAC protocol for public bus networks, called Bus MAC protocol, designed to provide high quality Internet service for bus passengers. The paper proposed a multi-channel dual clocks three-demission probability random multiple access protocol based on RTS/CTS mechanism, decreasing collisions caused by multiple access from multiple passengers. Use the RTS/CTS mechanism increases the reliability and stability of the system, reducing the collision possibility of the information packets to a certain extent, improves the channel utilization; use the multi-channel mechanism, not only enables the channel load balancing, but also solves the problem of the hidden terminal and exposed terminal. Use the dual clocks mechanism, reducing the system idle time. At last, the different selection of the three-dimensional probabilities can make the system throughput adapt to the network load which could realize the maximum of the system throughput.

  5. Analysis of tumor template from multiple compartments in a blood sample provides complementary access to peripheral tumor biomarkers.

    Science.gov (United States)

    Strauss, William M; Carter, Chris; Simmons, Jill; Klem, Erich; Goodman, Nathan; Vahidi, Behrad; Romero, Juan; Masterman-Smith, Michael; O'Regan, Ruth; Gogineni, Keerthi; Schwartzberg, Lee; Austin, Laura K; Dempsey, Paul W; Cristofanilli, Massimo

    2016-05-01

    Targeted cancer therapeutics are promised to have a major impact on cancer treatment and survival. Successful application of these novel treatments requires a molecular definition of a patient's disease typically achieved through the use of tissue biopsies. Alternatively, allowing longitudinal monitoring, biomarkers derived from blood, isolated either from circulating tumor cell derived DNA (ctcDNA) or circulating cell-free tumor DNA (ccfDNA) may be evaluated. In order to use blood derived templates for mutational profiling in clinical decisions, it is essential to understand the different template qualities and how they compare to biopsy derived template DNA as both blood-based templates are rare and distinct from the gold-standard. Using a next generation re-sequencing strategy, concordance of the mutational spectrum was evaluated in 32 patient-matched ctcDNA and ccfDNA templates with comparison to tissue biopsy derived DNA template. Different CTC antibody capture systems for DNA isolation from patient blood samples were also compared. Significant overlap was observed between ctcDNA, ccfDNA and tissue derived templates. Interestingly, if the results of ctcDNA and ccfDNA template sequencing were combined, productive samples showed similar detection frequency (56% vs 58%), were temporally flexible, and were complementary both to each other and the gold standard. These observations justify the use of a multiple template approach to the liquid biopsy, where germline, ctcDNA, and ccfDNA templates are employed for clinical diagnostic purposes and open a path to comprehensive blood derived biomarker access. PMID:27049831

  6. Volcanic eruptions, hazardous ash clouds and visualization tools for accessing real-time infrared remote sensing data

    Science.gov (United States)

    Webley, P.; Dehn, J.; Dean, K. G.; Macfarlane, S.

    2010-12-01

    Volcanic eruptions are a global hazard, affecting local infrastructure, impacting airports and hindering the aviation community, as seen in Europe during Spring 2010 from the Eyjafjallajokull eruption in Iceland. Here, we show how remote sensing data is used through web-based interfaces for monitoring volcanic activity, both ground based thermal signals and airborne ash clouds. These ‘web tools’, http://avo.images.alaska.edu/, provide timely availability of polar orbiting and geostationary data from US National Aeronautics and Space Administration, National Oceanic and Atmosphere Administration and Japanese Meteorological Agency satellites for the North Pacific (NOPAC) region. This data is used operationally by the Alaska Volcano Observatory (AVO) for monitoring volcanic activity, especially at remote volcanoes and generates ‘alarms’ of any detected volcanic activity and ash clouds. The webtools allow the remote sensing team of AVO to easily perform their twice daily monitoring shifts. The web tools also assist the National Weather Service, Alaska and Kamchatkan Volcanic Emergency Response Team, Russia in their operational duties. Users are able to detect ash clouds, measure the distance from the source, area and signal strength. Within the web tools, there are 40 x 40 km datasets centered on each volcano and a searchable database of all acquired data from 1993 until present with the ability to produce time series data per volcano. Additionally, a data center illustrates the acquired data across the NOPAC within the last 48 hours, http://avo.images.alaska.edu/tools/datacenter/. We will illustrate new visualization tools allowing users to display the satellite imagery within Google Earth/Maps, and ArcGIS Explorer both as static maps and time-animated imagery. We will show these tools in real-time as well as examples of past large volcanic eruptions. In the future, we will develop the tools to produce real-time ash retrievals, run volcanic ash dispersion

  7. System and method for determination of the reflection wavelength of multiple low-reflectivity bragg gratings in a sensing optical fiber

    Science.gov (United States)

    Moore, Jason P. (Inventor)

    2009-01-01

    A system and method for determining a reflection wavelength of multiple Bragg gratings in a sensing optical fiber comprise: (1) a source laser; (2) an optical detector configured to detect a reflected signal from the sensing optical fiber; (3) a plurality of frequency generators configured to generate a signal having a frequency corresponding to an interferometer frequency of a different one of the plurality of Bragg gratings; (4) a plurality of demodulation elements, each demodulation element configured to combine the signal produced by a different one of the plurality of frequency generators with the detected signal from the sensing optical fiber; (5) a plurality of peak detectors, each peak detector configured to detect a peak of the combined signal from a different one of the demodulation elements; and (6) a laser wavenumber detection element configured to determine a wavenumber of the laser when any of the peak detectors detects a peak.

  8. Structure Tuning of Cationic Oligospermine-siRNA Conjugates for Carrier-Free Gene Silencing.

    Science.gov (United States)

    Nothisen, Marc; Bagilet, Jérémy; Behr, Jean-Paul; Remy, Jean-Serge; Kotera, Mitsuharu

    2016-08-01

    Oligospermine-siRNA conjugates are able to induce efficient luciferase gene silencing upon carrier-free transfection. These conjugates are readily accessible by a versatile automated chemistry that we developed using a DMT-spermine phosphoramidite reagent. In this article, we used this chemistry to study a wide range of structural modifications of the oligospermine-siRNA conjugates, i.e., variation of conjugate positions and introduction of chemical modifications to increase nuclease resistance. At first we examined gene silencing activity of a series of siRNA-tris(spermine) conjugates with and without chemical modifications in standard carrier assisted conditions. The three spermine units attached at one of the two ends of the sense strand or at the 3'-end of the antisense strand are compatible with gene silencing activity whereas attachment of spermine units at the 5'-end of the antisense strand abolished the activity. 2'-O-Methylated nucleotides introduced in the sense strand are compatible while not in the antisense strand. Thiophosphate links could be used without activity loss at the 3'-end of both strands and at the 5'-end of the sense strand to conjugate oligospermine. Consequently a series of oligospermine-siRNA conjugates containing 15 to 45 spermines units in various configurations were chosen, prepared, and examined in carrier-free conditions. Attachment of 30 spermine units singly at the 5'-end of the sense strand provides the most potent carrier-free siRNA. Longevity of luciferase gene silencing was studied using oligospermine-siRNA conjugates. Five day long efficiency with more than 80% gene expression knockdown was observed upon transfection without vector. Oligospermine-siRNA conjugates targeting cell-constitutive natural lamin A/C gene were prepared. Efficient gene silencing was observed upon carrier-free transfection of siRNA conjugates containing 20 or 30 spermine residues grafted at the 5'-end of the sense strand. PMID:27398779

  9. 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

    Directory of Open Access Journals (Sweden)

    Tran Thi Tuyet-Hanh

    2016-02-01

    Full Text Available 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

  10. Structuring waveguide-grating-based wavelength-division multiplexing/optical code division multiple access network codecs over topology of concentric circles

    Science.gov (United States)

    Huang, Jen-Fa; Nieh, Ta-Chun; Chen, Kai-Sheng

    2013-01-01

    The cyclic period and free spectral range of arrayed-waveguide gratings (AWG) in a wavelength-division multiplexing/optical code division multiple access optical code division multiple access network are exploited. The total optical network unit (ONU) of network capacity is partitioned into groups of different wavelength in accordance with the geographical location of subscribers based on the radial distance of the ONU to the optical line terminal. Combining concentric circles round by round for ONU groups enables a fixed round-trip time in the data transmission and a significant increase in system performance. Using AWG router, the proposed topology of concentric circles retains signature orthogonality and minimizes wavelength collisions on the photo-detector. Furthermore, the adoption of extended M-sequence codes corresponding to the AWG codec provides a simpler, more efficient coding procedure and accommodates more users in a single group.

  11. Intestinal sensing of nutrients.

    Science.gov (United States)

    Tolhurst, Gwen; Reimann, Frank; Gribble, Fiona M

    2012-01-01

    Ingestion of a meal triggers a range of physiological responses both within and outside the gut, and results in the remote modulation of appetite and glucose homeostasis. Luminal contents are sensed by specialised chemosensitive cells scattered throughout the intestinal epithelium. These enteroendocrine and tuft cells make direct contact with the gut lumen and release a range of chemical mediators, which can either act in a paracrine fashion interacting with neighbouring cells and nerve endings or as classical circulating hormones. At the molecular level, the chemosensory machinery involves multiple and complex signalling pathways including activation of G-protein-coupled receptors and solute carrier transporters. This chapter will discuss our current knowledge of the molecular mechanisms underlying intestinal chemosensation with a particular focus on the relatively well-characterised nutrient-triggered secretion from the enteroendocrine system. PMID:22249821

  12. Preconception Carrier Screening

    Science.gov (United States)

    ... Events Advocacy For Patients About ACOG Preconception Carrier Screening Home For Patients Search FAQs Preconception Carrier Screening ... Screening FAQ179, August 2012 PDF Format Preconception Carrier Screening Pregnancy What is preconception carrier screening? What is ...

  13. Conceptual Learning with Multiple Graphical Representations: Intelligent Tutoring Systems Support for Sense-Making and Fluency-Building Processes

    Science.gov (United States)

    Rau, Martina A.

    2013-01-01

    Most learning environments in the STEM disciplines use multiple graphical representations along with textual descriptions and symbolic representations. Multiple graphical representations are powerful learning tools because they can emphasize complementary aspects of complex learning contents. However, to benefit from multiple graphical…

  14. Responsible implementation of expanded carrier screening

    Science.gov (United States)

    Henneman, Lidewij; Borry, Pascal; Chokoshvili, Davit; Cornel, Martina C; van El, Carla G; Forzano, Francesca; Hall, Alison; Howard, Heidi C; Janssens, Sandra; Kayserili, Hülya; Lakeman, Phillis; Lucassen, Anneke; Metcalfe, Sylvia A; Vidmar, Lovro; de Wert, Guido; Dondorp, Wybo J; Peterlin, Borut

    2016-01-01

    This document of the European Society of Human Genetics contains recommendations regarding responsible implementation of expanded carrier screening. Carrier screening is defined here as the detection of carrier status of recessive diseases in couples or persons who do not have an a priori increased risk of being a carrier based on their or their partners' personal or family history. Expanded carrier screening offers carrier screening for multiple autosomal and X-linked recessive disorders, facilitated by new genetic testing technologies, and allows testing of individuals regardless of ancestry or geographic origin. Carrier screening aims to identify couples who have an increased risk of having an affected child in order to facilitate informed reproductive decision making. In previous decades, carrier screening was typically performed for one or few relatively common recessive disorders associated with significant morbidity, reduced life-expectancy and often because of a considerable higher carrier frequency in a specific population for certain diseases. New genetic testing technologies enable the expansion of screening to multiple conditions, genes or sequence variants. Expanded carrier screening panels that have been introduced to date have been advertised and offered to health care professionals and the public on a commercial basis. This document discusses the challenges that expanded carrier screening might pose in the context of the lessons learnt from decades of population-based carrier screening and in the context of existing screening criteria. It aims to contribute to the public and professional discussion and to arrive at better clinical and laboratory practice guidelines. PMID:26980105

  15. A point-wise fiber Bragg grating displacement sensing system and its application for active vibration suppression of a smart cantilever beam subjected to multiple impact loadings

    International Nuclear Information System (INIS)

    In this work, active vibration suppression of a smart cantilever beam subjected to disturbances from multiple impact loadings is investigated with a point-wise fiber Bragg grating (FBG) displacement sensing system. An FBG demodulator is employed in the proposed fiber sensing system to dynamically demodulate the responses obtained by the FBG displacement sensor with high sensitivity. To investigate the ability of the proposed FBG displacement sensor as a feedback sensor, velocity feedback control and delay control are employed to suppress the vibrations of the first three bending modes of the smart cantilever beam. To improve the control performance for the first bending mode when the cantilever beam is subjected to an impact loading, we improve the conventional velocity feedback controller by tuning the control gain online with the aid of information from a higher vibration mode. Finally, active control of vibrations induced by multiple impact loadings due to a plastic ball is performed with the improved velocity feedback control. The experimental results show that active vibration control of smart structures subjected to disturbances such as impact loadings can be achieved by employing the proposed FBG sensing system to feed back out-of-plane point-wise displacement responses with high sensitivity. (paper)

  16. Theoretical analysis and simulation of a code division multiple access system (cdma for secure signal transmission in wideband channels

    Directory of Open Access Journals (Sweden)

    Stevan M. Berber

    2014-06-01

    Code Division Multiple Access (CDMA technique which allows communications of multiple users in the same communication system. This is achieved in such a way that each user is assigned a unique code sequence, which is used at the receiver side to discover the information dedicated to that user. These systems belong to the group of communication systems for direct sequence spread spectrum systems. Traditionally, CDMA systems use binary orthogonal spreading codes. In this paper, a mathematical model and simulation of a CDMA system based on the application of non-binary, precisely speaking, chaotic spreading sequences. In their nature, these sequences belong to random sequences with infinite periodicity, and due to that they are appropriate for applications in the systems that provide enhanced security against interception and secrecy in signal transmission. Numerous papers are dedicated to the development of CDMA systems in flat fading channels. This paper presents the results of these systems analysis for the case when frequency selective fading is present in the channel. In addition, the paper investigates a possibility of using interleaving techniques to mitigate fading in a wideband channel with the frequency selective fading. Basic structure of a CDMA communication system and its operation In this paper, a CDMA system block schematic is ppresented and the function of all blocks is explained. Notation  to be used in the paper is introduced. Chaotic sequences are defined and explained in accordance with the method of their generation. A wideband channel with frequency selective fading is defined by its impulse response function. Theoretical analysis of a CDMA system with flat fading in a narrowband channel A narrowband channel and flat fading are defined. A mathematical analysis of the system is conducted by presenting the signal expressions at vital points in the transmitter and receiver. The expression of the signal at the output of the sequence correlator is

  17. Comparing near-earth and satellite remote sensing based phenophase estimates: an analysis using multiple webcams and MODIS (Invited)

    Science.gov (United States)

    Hufkens, K.; Richardson, A. D.; Migliavacca, M.; Frolking, S. E.; Braswell, B. H.; Milliman, T.; Friedl, M. A.

    2010-12-01

    In recent years several studies have used digital cameras and webcams to monitor green leaf phenology. Such "near-surface" remote sensing has been shown to be a cost effective means of accurately capturing phenology. Specifically, it allows for accurate tracking of intra- and inter-annual phenological dynamics at high temporal frequency and over broad spatial scales compared to visual observations or tower-based fAPAR and broadband NDVI measurements. Near surface remote sensing measurements therefore show promise for bridging the gap between traditional in-situ measurements of phenology and satellite remote sensing data. For this work, we examined the relationship between phenophase estimates derived from satellite remote sensing (MODIS) and near-earth remote sensing derived from webcams for a select set of sites with high-quality webcam data. A logistic model was used to characterize phenophases for both the webcam and MODIS data. We documented model fit accuracy, phenophase estimates, and model biases for both data sources. Our results show that different vegetation indices (VI's) derived from MODIS produce significantly different phenophase estimates compared to corresponding estimates derived from webcam data. Different VI's showed markedly different radiometric properties, and as a result, influenced phenophase estimates. The study shows that phenophase estimates are not only highly dependent on the algorithm used but also depend on the VI used by the phenology retrieval algorithm. These results highlight the need for a better understanding of how near-earth and satellite remote data relate to eco-physiological and canopy changes during different parts of the growing season.

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

    Science.gov (United States)

    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.…

  19. Multiple scattering effects with cyclical terms in active remote sensing of vegetated surface using vector radiative transfer theory

    Science.gov (United States)

    The energy transport in a vegetated (corn) surface layer is examined by solving the vector radiative transfer equation using a numerical iterative approach. This approach allows a higher order that includes the multiple scattering effects. Multiple scattering effects are important when the optical t...

  20. A Silicon Micromachined Gyroscope Driven by the Rotating Carrier Self

    Institute of Scientific and Technical Information of China (English)

    Fuxue Zhang; Xu Mao; Yu Liu; Nan Zhang; Wei Zhang

    2006-01-01

    This paper reported a silicon micromachined gyroscope which is driven by the rotating carrier's angular velocity, the silicon was manufactured by anisotropy etching. The design, fabrication and packing of the sensing element were introduced in the paper. The imitation experimentation and performance test have certificated that the principle of the gyroscope is correct and the gyroscope can be used to sense yawing or pitching angular velocity of the rotating carrier, and the angular velocity of the rotating carrier itself.

  1. Blastocystis Isolates from Patients with Irritable Bowel Syndrome and from Asymptomatic Carriers Exhibit Similar Parasitological Loads, but Significantly Different Generation Times and Genetic Variability across Multiple Subtypes.

    Directory of Open Access Journals (Sweden)

    Gie-Bele Vargas-Sanchez

    Full Text Available Blastocystis spp is a common intestinal parasite of humans and animals that has been associated to the etiology of irritable bowel syndrome (IBS; however, some studies have not found this association. Furthermore, many biological features of Blastocystis are little known. The objective of present study was to assess the generation times of Blastocystis cultures, from IBS patients and from asymptomatic carriers. A total of 100 isolates were obtained from 50 IBS patients and from 50 asymptomatic carriers. Up to 50 mg of feces from each participant were cultured in Barret's and in Pavlova's media during 48 h. Initial and final parasitological load were measured by microscopy and by quantitative PCR. Amplicons were purified, sequenced and submitted to GenBank; sequences were analysed for genetic diversity and a Bayesian inference allowed identifying genetic subtypes (ST. Generation times for Blastocystis isolates in both media, based on microscopic measures and molecular assays, were calculated. The clinical symptoms of IBS patients and distribution of Blastocystis ST 1, 2 and 3 in both groups was comparable to previous reports. Interestingly, the group of cases showed scarce mean nucleotide diversity (π as compared to the control group (0.011±0.016 and 0.118±0.177, respectively, whilst high gene flow and small genetic differentiation indexes between different ST were found. Besides, Tajima's D test showed negative values for ST1-ST3. No statistical differences regarding parasitological load between cases and controls in both media, as searched by microscopy and by qPCR, were detected except that parasites grew faster in Barret's than in Pavlova's medium. Interestingly, slow growth of isolates recovered from cases in comparison to those of controls was observed (p<0.05. We propose that generation times of Blastocystis might be easily affected by intestinal environmental changes due to IBS probably because virulent strains with slow growth may be

  2. Maximizing System Throughput by Cooperative Sensing in Cognitive Radio Networks

    OpenAIRE

    Li, Shuang; Zheng, Zizhan; Ekici, Eylem; Shroff, Ness

    2011-01-01

    Cognitive Radio Networks allow unlicensed users to opportunistically access the licensed spectrum without causing disruptive interference to the primary users (PUs). One of the main challenges in CRNs is the ability to detect PU transmissions. Recent works have suggested the use of secondary user (SU) cooperation over individual sensing to improve sensing accuracy. In this paper, we consider a CRN consisting of a single PU and multiple SUs to study the problem of maximizing the total expected...

  3. Accessibility and sensory experiences

    DEFF Research Database (Denmark)

    Ryhl, Camilla

    2010-01-01

    This article introduces a new design concept; sensory accessibility. While acknowledging the importance of sensory experiences in architectural quality, as well as the importance of accommodating user needs the concept combines three equally important factors; architecture, the senses...... and accessibility. Sensory accessibility accommodates aspects of a sensory disability and describes architectural design requirements needed to ensure access to architectural experiences. In the context of architecture accessibility has become a design concept of its own. It is generally described as ensuring...

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

    Directory of Open Access Journals (Sweden)

    Arku Godwin

    2011-05-01

    Full Text Available Abstract 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

  5. Novel wavelength division multiplex-radio over fiber-passive optical network architecture for multiple access points based on multitone generation and triple sextupling frequency

    Science.gov (United States)

    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.

  6. Carrier Frequency Offset Compensation for an Interleaved OFDMA Uplink

    Institute of Scientific and Technical Information of China (English)

    FAN Da; CAO Zhigang

    2008-01-01

    This paper reports an investigation of the carrier frequency offset (CFO) compensation in the up-link of the orthogonal frequency division multiple access (OFDMA) system with interleaved subcarrier as-signment. The presence of CFOs between the transmitters and the uplink receiver will destroy the orthogo-nality among the different subcarriers, resulting in inter-carrier interference and multiuser interference. This paper proposes a pseudoinverse CFO compensation method based on the signal structure. The proposed method can compensate the CFOs of all users simultaneously and isolate the signals from all users at the same time. Compared with the existing CFO compensation methods, the new method provides a consider-able signal-to-noise ratio gain on the bit error rate performance and has a relatively low implementation complexity.

  7. Optimized Sharable-Slot Allocation Using Multiple Channels to Reduce Data-Gathering Delay in Wireless Sensor Networks.

    Science.gov (United States)

    Van Vinh, Phan; Oh, Hoon

    2016-01-01

    The demand for event-driven real-time applications for timely and reliable data acquisition is growing in industrial sectors. However, it is challenging to satisfy the requirements since constraints such as limited available energy and bandwidth are inherent in a wireless sensor network. To deal with timely delivery, one desirable approach is to improve network throughput so that more real-time applications with tighter time constraints can be satisfied in any given network. To deal with reliable delivery, the use of a carrier sense multiple access mechanism for data transmission is preferred, along with the use of a sharable slot within which multiple nodes compete to send data. Thus, we present a method of using multiple channels and a way to optimize the size of the sharable slot. The proposed channel-slot-scheduling algorithm tries to optimize the size of a sharable slot when multiple channels are used. The algorithm also deals with situations where nodes generate multiple data packets in each round of a data-gathering period. It is shown through simulation that our approach greatly outperforms others on some selected metrics. PMID:27070619

  8. Inducible operation of the erythropoietin 3' enhancer in multiple cell lines: evidence for a widespread oxygen-sensing mechanism.

    OpenAIRE

    Maxwell, P H; Pugh, C. W.; Ratcliffe, P. J.

    1993-01-01

    Adaptive responses to hypoxia occur in many biological systems. A well-characterized example is the hypoxic induction of the synthesis of erythropoietin, a hormone which regulates erythropoiesis and hence blood oxygen content. The restricted expression of the erythropoietin gene in subsets of cells within kidney and liver has suggested that this specific oxygen-sensing mechanism is restricted to specialized cells in those organs. Using transient transfection of reporter genes coupled to a tra...

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

    OpenAIRE

    Arku Godwin; Gilliland Jason A; Sadler Richard C

    2011-01-01

    Abstract 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 ma...

  10. In Situ Live Cell Sensing of Multiple Nucleotides Exploiting DNA/RNA Aptamers and Graphene Oxide Nanosheets

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Ying; Li, Zhaohui; Weber, Thomas J.; Hu, Dehong; Lin, Chiann Tso; Li, Jinghong; Lin, Yuehe

    2013-07-23

    Adenosine-5’-triphosphate (ATP) and guanosine-5’-triphosphate (GTP) are primary energy resources and function coordinately for numerous reactions such as microtubule assembly, insulin secretion and ion channel regulation. We have developed a novel DNA/RNA aptamer- graphene oxide nanosheet (GO-nS) sensing platform that can selectively and simultaneously detect ATP and GTP in live cells. A fluorescent tag is covalently attached to aptamers and fluorescence is quenched upon binding of aptamer to the GO-nS. Fluorescently tagged aptamers that selectively bind ATP or GTP were isolated from an aptamer library and were adsorbed onto GO-nS. Upon incubation with targets (ATP and/or GTP), the aptamers readily dissociated from GO-nS and the fluorescent signal was recovered. By covalently attaching fluorophores, both ATP and GTP sensing aptamers could be exploited to simultaneously visualize aptamer dissociation in live cells. In addition, the GO-nS appear to be biocompatible and protect the adsorbed DNA/RNA aptamers from enzymatic cleavage. Our results support the application of aptamer/GO-nS as a sensing platform for nucleotides in living cells and have implications for the development of additional sensor platforms for other bio-molecules that show selective interactions with aptamers and other biomarkers.

  11. Carriers of the astronomical 2175 ? extinction feature

    Energy Technology Data Exchange (ETDEWEB)

    Bradley, J; Dai, Z; Ernie, R; Browning, N; Graham, G; Weber, P; Smith, J; Hutcheon, I; Ishii, H; Bajt, S; Floss, C; Stadermann, F

    2004-07-20

    The 2175 {angstrom} extinction feature is by far the strongest spectral signature of interstellar dust observed by astronomers. Forty years after its discovery the origin of the feature and the nature of the carrier remain controversial. The feature is enigmatic because although its central wavelength is almost invariant its bandwidth varies strongly from one sightline to another, suggesting multiple carriers or a single carrier with variable properties. Using a monochromated transmission electron microscope and valence electron energy-loss spectroscopy we have detected a 5.7 eV (2175 {angstrom}) feature in submicrometer-sized interstellar grains within interplanetary dust particles (IDPs) collected in the stratosphere. The carriers are organic carbon and amorphous silicates that are abundant and closely associated with one another both in IDPs and in the interstellar medium. Multiple carriers rather than a single carrier may explain the invariant central wavelength and variable bandwidth of the astronomical 2175 {angstrom} feature.

  12. Somatic mutations of the RET proto-oncogene are not required for tumor development in multiple endocrine neoplasia type 2 (MEN 2) gene carriers

    NARCIS (Netherlands)

    Landsvater, RM; deWit, MJ; Zewald, RA; Hofstra, RMW; Buys, CHCM; vanAmstel, HKP; Hoppener, JWM; Lips, CJM

    1996-01-01

    Germ line mutations in one allele of the RET proto-oncogene predispose to the multiple endocrine neoplasia type 2 (MEN 2) syndromes, To investigate whether these inherited mutations alone can cause the development of tumors in vivo (oncogene model) or whether somatic mutations in the homologous RET

  13. What Is Carrier Screening?

    Science.gov (United States)

    ... you want to learn. Search form Search Carrier screening You are here Home Testing & Services Testing for ... help you make the decision. What Is Carrier Screening? Carrier screening checks if a person is a " ...

  14. Investigation of code reconfigurable fibre Bragg gratings for Optical Code Division Multiple Access (OCDMA) and Optical Packet Switching (OPS) Networks

    OpenAIRE

    Tian, Chun

    2009-01-01

    This thesis documents my work in the telecommunication system laboratory at the Optoelectronics Research Centre, towards the implementation of code reconfigurable OCDMA and all-optical packet switching nodes based on fibre Bragg grating (FBG) technology. My research work involves characterizing the performance of various gratings, specifically high reflectivity, short chip duration, long code sequences, multiple phase level and tunable superstructured fiber Bragg gratings (SSFBGs), by using t...

  15. Performance of MMSE Receiver based Multi Input Multi Output-Interleave Division Multiple-Access System with Multi-user Detection over Frequency Selective Wireless Communication Channel

    Directory of Open Access Journals (Sweden)

    Kuttathatti S. Vishvaksenan

    2011-01-01

    Full Text Available Problem statement: This study presents the performance analysis of turbo assisted Interleave Division Multiple-Access (IDMA system with Multi Input Multi Output (MIMO support for multi user scenario over correlated frequency selective and uncorrelated frequency selective channel. Approach: The key principle of IDMA is that interleaver unique which distinguishes the users in contrast to spreading sequence in Code Division Multiple Access System (CDMA. Results: In this work, we assume that Interleavers are generated independently and randomly. At the receiver, we employed Ordered SIC (OSIC technique using ZF and MMSE criterion to combat Inter Antenna Interference (IAI and Multi User Interference (MUI problem along with iterative decoding to improve the performance in terms of BER. The performance of system has been discussed for different channel conditions with realistic channel model using extensive simulation runs based on Monte Carlo simulation trials. We have exhibited the flexibility and robustness provided by MIMO-IDMA. Conclusion/Recommendations: It has been proved from the results that IDMA principle can be applied to realize many potential performance gains highlighted by information theory, including coding gain multiplexing gain and multiuser gain. Simulation results presented to demonstrate the benefits of IDMA with MUD and iterative decoding. It is discerned that IDMA performs better than CDMA in frequency selective channel for high load conditions which is assessed through computer simulation results.

  16. Layers of Identity: Multiple Psychological Senses of Community Within a Community Setting Niveles de la Identidad: Múltiples Sentidos Psicológicos de Comunidad en un Entorno Comunitario

    Directory of Open Access Journals (Sweden)

    Anne E Brodsky

    2004-11-01

    Full Text Available This article explores psychological sense of community (PSOC, a feeling of belonging to, importance of, and identification with a community. In much of the research on PSOC, there has been a focus on identifying a single PSOC for an individual in a setting. Qualitative and quantitative data are used here to investigate the presence and operation of multiple psychological senses of community for individuals. These multiple PSOCs are explored in two macro, territorial settings and a subcommunity of one of these settings: a job training and education center for underserved women in Baltimore City. Exploration of multiple PSOCs at the macro- and subcommunity levels expands our conceptualization of the operation of PSOC and has real-life implications for fostering positive outcomes in multicultural communities. © 2001 John Wiley & Sons, Inc.El presente artículo explora el sentido psicológico de comunidad (PSOC, un sentimiento de pertenencia, importancia e identificación con la comunidad. Gran parte de la investigación realizada sobre el PSOC se ha focalizado en identificar un único sentido de comunidad para un individuo en un contexto determinado. Datos cualitativos y cuantitativos son usados aquí para investigar la presencia de múltiples sentidos psicológicos de comunidad para los individuos. Estos múltiples PSOCs son explorados en dos contextos territoriales a nivel macro, y en una subcomunidad de uno de estos contextos: un centro de capacitación laboral y educación para mujeres de escasos recursos en la ciudad de Baltimore. La exploración de múltiples PSOCs en los niveles macro y subcomunitario expande nuestra conceptualización del funcionamiento del PSOC y tiene implicancias en la vida real, para promover resultados positivos en comunidades multiculturales.

  17. Beyond simple point sets to the indistinguishable point-set tensorial limits of R-W algebras: multiple G-invariants and the carrier-map-based quantal-basis completeness of uniform NMR spin systems

    International Nuclear Information System (INIS)

    Augmented quasiparticle (QP) mappings, as applied to indistinguishable point sets of (Liouvillian) democratic-recoupled (DR) tensors, provide for a 1:1 invariant labelling of the underlying (disjoint) dual projective map carrier subspaces, where the Liouville pattern basis set is defined via superboson unit-tensor actions on a null space, | )). The co-operative-action Liouville algebras described here imply parallel limitations to Jucys graph recoupling and its related Racah-Wigner (R-W) algebras once DR indistinguishable point tensorial sets are involved, as in non-SR Sn,n>=4 dominant (NMR) spin symmetry. The importance of Sn G-invariants, as labels for disjoint carrier subspaces in such automorphic spin symmetries, arises from their essential role in defining the quantal-completeness of indistinguishable point sets. From the established properties of augmented-QPs as super-bosons (Temme 2002 Int. J. Quantum Chem. 89 429) (i.e., beyond the earlier Hilbert-space-based Louck and Biedenharn boson pattern views), insight into Atiyah and Sutcliffe's (A-S) assertions (Atiyah and Sutcliffe 2002 Proc. R. Soc. A 458 1089) on the limitations of graph recoupling theory to distinct point sets is obtained. This clarifies the wider analytic intractible of automorphic DR spin systems-beyond the Levi-Civita cyclic-commutation (R-W) approach (Levy-Leblond and Levy-Nahas 1965 J. Math. Phys. 6 1372) which holds for a mono-invariant problem. For (rotating-frame) density matrix approaches to [A]n, [A]n(X) and [AX]n(SU(2) x Sn) (dual) NMR systems, the focus is necessarily on the specialized nature of indistinguishable point sets within multiple invariant-theoretic-based, dynamical spin physics. Here, the GI(s) (GI-cardinality) constitute an important part of the dual irrep set, {Dk(U-tilde) x Γ-tilde[λ](v-tilde)(P)}, with combinatorics, as a central facet of invariant theory, playing a crucial role in the concept of 'quantal completeness' and the impact of A-S's assertion on the

  18. Cooperation Scheme For Distributed Spectrum Sensing In Cognitive Radio Networks

    Directory of Open Access Journals (Sweden)

    Ying Dai

    2014-09-01

    Full Text Available Spectrum sensing is an essential phase in cognitive radio networks (CRNs. It enables secondary users (SUs to access licensed spectrum, which is temporarily not occupied by the primary users (PUs. The widely used scheme of spectrum sensing is cooperative sensing, in which an SU shares its sensing results with other SUs to improve the overall sensing performance, while maximizing its throughput. For a single SU, if its sensing results are shared early, it would have more time for data transmission, which improves the throughput. However, when multiple SUs send their sensing results early, they are more likely to send out their sensing results simultaneously over the same signaling channel. Under these conditions, conflicts would likely happen. Then, both the sensing performance and throughput would be affected. Therefore, it is important to take when-to-share into account. We model the spectrum sensing as an evolutionary game. Different from previous works, the strategy set for each player in our game model contains not only whether to share its sensing results, but also when to share. The payoff for each player is defined based on the throughput, which considers the influence of the time spent both on sensing and sharing. We prove the existence of the evolutionarily stable strategy (ESS. In addition, we propose a practical algorithm for each secondary user to converge to the ESS. We conduct experiments on our testbed consisting of 4 USRP N200s. The experimental results verify for our model, including the convergence to the ESS.

  19. On the capacity of multiple access and broadcast fading Channels with full channel state information at low power regime

    KAUST Repository

    Rezki, Zouheir

    2013-07-01

    We study the throughput capacity region of the Gaussian multi-access (MAC) fading channel with perfect channel state information (CSI) at the receiver and at the transmitters (CSI-TR), at low power regime. We show that it has a multidimensional rectangle structure and thus is simply characterized by single user capacity points. More specifically, we show that at low power regime, the boundary surface of the capacity region shrinks to a single point corresponding to the sum-rate maximizer and that the coordinates of this point coincide with single user capacity bounds. Using the duality of Gaussian MAC and broadcast channels (BC), we provide a simple characterization of the BC capacity region at low power regime. © 2013 IEEE.

  20. Evaluation of Kolmogorov - Smirnov Test and Energy Detector Techniques for Cooperative Spectrum Sensing in Real Channel Conditions

    OpenAIRE

    D. Lekomtcev; R. Marsalek

    2015-01-01

    The cognitive radio technology allows solving one of the main issues of current wireless communication technologies, namely a deficit of vacant spectrum. A dynamic spectrum access used in the cognitive radio networks (CRN) gives an ability to access an unused spectrum in real time. Cooperative spectrum sensing is the most effective method for spectrum holes detecting. It combines sensing information of multiple cognitive radio users. In this paper, an experimental evaluation of spectrum sensi...

  1. GSR-TDMA: A Geometric Spatial Reuse-Time Division Multiple Access MAC Protocol for Multihop Underwater Acoustic Sensor Networks

    Directory of Open Access Journals (Sweden)

    Changho Yun

    2016-01-01

    Full Text Available The nonnegligible propagation delay of acoustic signals causes spatiotemporal uncertainty that occasionally enables simultaneous, collision-free packet transmission among underwater nodes (UNs. These transmissions can be handled by efficiently managing the channel access of the UNs in the data-link layer. To this end, Geometric Spatial Reuse-TDMA (GSR-TDMA, a new TDMA-based MAC protocol, is designed for use in centralized, multihop underwater acoustic sensor networks (UASNs, and in this case all UNs are periodically scheduled after determining a geometric map according to the information on their location. The scheduling strategy increases the number of UNs that send packets coincidentally via two subscheduling configurations (i.e., interhop and intrahop scheduling. Extensive simulations are used to investigate the reception success rate (RSR and the multihop delay (MHD of GSR-TDMA, and the results are compared to those of previous approaches, including C-MAC and HSR-TDMA. GSR-TDMA outperforms C-MAC; the RSR of GSR-TDMA is 15% higher than that of C-MAC, and the MHD of GSR-TDMA is 30% lower than that of C-MAC at the most. In addition, GSR-TDMA provides even better performance improvements over HSR-TDMA; the RSR of GSR-TDMA is 50% higher than that of HSR-TDMA, and the MHD of GSR-TDMA is an order of 102 lower than that of HSR-TDMA at the most.

  2. On the capacity of multiple access and broadcast fading channels with full channel state information at low SNR

    KAUST Repository

    Rezki, Zouheir

    2014-01-01

    We study the throughput capacity region of the Gaussian multi-access (MAC) fading channel with perfect channel state information (CSI) at the receiver and at the transmitters, at low power regime. We show that it has a multidimensional rectangle structure and thus is simply characterized by single user capacity points.More specifically, we show that at low power regime, the boundary surface of the capacity region shrinks to a single point corresponding to the sum rate maximizer and that the coordinates of this point coincide with single user capacity bounds. Inspired from this result, we propose an on-off scheme, compute its achievable rate, and show that this scheme achieves single user capacity bounds of the MAC channel for a wide class of fading channels at asymptotically low power regime. We argue that this class of fading encompasses all known wireless channels for which the capacity region of the MAC channel has even a simpler expression in terms of users\\' average power constraints only. Using the duality of Gaussian MAC and broadcast channels (BC), we deduce a simple characterization of the BC capacity region at low power regime and show that for a class of fading channels (including Rayleigh fading), time-sharing is asymptotically optimal. © 2014 IEEE.

  3. Active sensing: An innovative tool for evaluating grain yield and nitrogen use efficiency of multiple wheat genotypes

    Science.gov (United States)

    Naser, Mohammed Abdulridha

    Precision agricultural practices have significantly contributed to the improvement of crop productivity and profitability. Remote sensing based indices, such as Normalized Difference Vegetative Index (NDVI) have been used to obtain crop information. It is used to monitor crop development and to provide rapid and nondestructive estimates of plant biomass, nitrogen (N) content and grain yield. Remote sensing tools are helping improve nitrogen use efficiency (NUE) through nitrogen management and could also be useful for high NUE genotype selection. The objectives of this study were: (i) to determine if active sensor based NDVI readings can differentiate wheat genotypes, (ii) to determine if NDVI readings can be used to classify wheat genotypes into grain yield productivity classes, (iii) to identify and quantify the main sources of variation in NUE across wheat genotypes, and (iv) to determine if normalized difference vegetation index (NDVI) could characterize variability in NUE across wheat genotypes. This study was conducted in north eastern Colorado for two years, 2010 and 2011. The NDVI readings were taken weekly during the winter wheat growing season from March to late June, in 2010 and 2011 and NUE were calculated as partial factor productivity and as partial nitrogen balance at the end of the season. For objectives i and ii, the correlation between NDVI and grain yield was determined using Pearson's product-moment correlation coefficient (r) and linear regression analysis was used to explain the relationship between NDVI and grain yield. The K-means clustering algorithm was used to classify mean NDVI and mean grain yield into three classes. For objectives iii and iv, the parameters related to NUE were also calculated to measure their relative importance in genotypic variation of NUE and power regression analysis between NDVI and NUE was used to characterize the relationship between NDVI and NUE. The results indicate more consistent association between grain

  4. A Sensing Error Aware MAC Protocol for Cognitive Radio Networks

    Directory of Open Access Journals (Sweden)

    Donglin Hu

    2012-08-01

    Full Text Available Cognitive radios (CR are intelligent radio devices that can sense the radio environment and adapt to changes in the radio environment. Spectrum sensing and spectrum access are the two key CR functions. In this paper, we present a spectrum sensing error aware MAC protocol for a CR network collocated with multiple primary networks. We explicitly consider both types of sensing errors in the CR MAC design, since such errors are inevitable for practical spectrum sensors and more importantly, such errors could have significant impact on the performance of the CR MAC protocol. Two spectrum sensing polices are presented, with which secondary users collaboratively sense the licensed channels. The sensing policies are then incorporated into p-Persistent CSMA to coordinate opportunistic spectrum access for CR network users.We present an analysis of the interference and throughput performance of the proposed CR MAC, and find the analysis highly accurate in our simulation studies. The proposed sensing error aware CR MAC protocol outperforms two existing approaches with considerable margins in our simulations, which justify the importance of considering spectrum sensing errors in CR MAC design.

  5. Airborne multispectral and thermal remote sensing for detecting the onset of crop stress caused by multiple factors

    Science.gov (United States)

    Huang, Yanbo; Thomson, Steven J.

    2010-10-01

    Remote sensing technology has been developed and applied to provide spatiotemporal information on crop stress for precision management. A series of multispectral images over a field planted cotton, corn and soybean were obtained by a Geospatial Systems MS4100 camera mounted on an Air Tractor 402B airplane equipped with Camera Link in a Magma converter box triggered by Terraverde Dragonfly® flight navigation and imaging control software. The field crops were intentionally stressed by applying glyphosate herbicide via aircraft and allowing it to drift near-field. Aerial multispectral images in the visible and near-infrared bands were manipulated to produce vegetation indices, which were used to quantify the onset of herbicide induced crop stress. The vegetation indices normalized difference vegetation index (NDVI) and soil adjusted vegetation index (SAVI) showed the ability to monitor crop response to herbicide-induced injury by revealing stress at different phenological stages. Two other fields were managed with irrigated versus nonirrigated treatments, and those fields were imaged with both the multispectral system and an Electrophysics PV-320T thermal imaging camera on board an Air Tractor 402B aircraft. Thermal imagery indicated water stress due to deficits in soil moisture, and a proposed method of determining crop cover percentage using thermal imagery was compared with a multispectral imaging method. Development of an image fusion scheme may be necessary to provide synergy and improve overall water stress detection ability.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

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

    2012-01-01

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

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

    Directory of Open Access Journals (Sweden)

    Chang-Soo Park

    2012-05-01

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

  9. Optical multidimensional multiple access(O-MDMA): a new concept for free-space laser communication based on photonic mixer devices

    Science.gov (United States)

    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.

  10. Variable Delay With Directly-Modulated R-SOA and Optical Filters for Adaptive Antenna Radio-Fiber Access

    DEFF Research Database (Denmark)

    Prince, Kamau; Presi, Marco; Chiuchiarelli, Andrea;

    2009-01-01

    types of signals defined in IEEE 802.16 (WiMAX) standard for wireless networks: a 90 Mbps single-carrier signal (64-QAM at 2.4 GHz) and a 78 Mbps multitone orthogonal frequency-division multiple access (OFDMA) signal. The power budget of this configuration supports a 4-element antenna array....

  11. Lipid Nanoparticles with Accessible Nickel as a Vaccine Delivery System for Single and Multiple His-tagged HIV Antigens.

    Science.gov (United States)

    Yan, Weili; Jain, Anekant; O'Carra, Ronan; Woodward, Jerold G; Li, Wenxue; Li, Guanhan; Nath, Avindra; Mumper, Russell J

    2009-07-01

    Lipid-based nanoparticles (NPs) with a small amount of surface-chelated nickel (Ni-NPs) were developed to easily formulate the HIV his-tagged Tat protein, as well as to formulate and co-deliver two HIV antigens (his-p24 and his-Nef) on one particle. Female BALB/c mice were immunized by s.c. injection with his-Tat/Ni-NP formulation (1.5 μg Tat-his/mouse) and control formulations on day 0 and 14. The day 28 anti-Tat specific IgG titer with his-Tat/Ni-NP was significantly greater than that with Alum/his-Tat. Furthermore, splenocytes from his-Tat/Ni-NP immunized mice secreted significantly higher IFN-γ than those from mice immunized with Alum/his-Tat. Although Ni-NPs did not show better adjuvant activity than Tat-coated anionic NPs made with sodium dodecyl sulfate (SDS/NPs), they were less toxic than SDS/NPs. The initial results indicated that co-immunization of mice using his-p24/his-Nef/Ni-NP induced greater antibody response compared to using Alum/his-p24/his-Nef. Co-delivery of two antigens using Ni-NPs also increased the immunogenicity of individual antigens compared to delivery of a single antigen by Ni-NPs. In conclusion, Ni-NPs are an efficient delivery system for HIV vaccines including both single antigen delivery and multiple antigen co-delivery. PMID:21966230

  12. Terahertz carrier dynamics in graphene and graphene nanostructures

    DEFF Research Database (Denmark)

    Jensen, Søren A.; Turchinovich, Dmitry; Tielrooij, Klaas Jan;

    2014-01-01

    Photoexcited charge carriers in 2D graphene and in 1D graphene nanostructures were studied with optical pump-THz probe spectroscopy. We find efficient hot-carrier multiplication in 2D graphene, and predominantly free carrier early time response in 1D nanostructures. © 2014 OSA....

  13. A genetic polymorphism (rs17251221 in the calcium-sensing receptor gene (CASR is associated with stone multiplicity in calcium nephrolithiasis.

    Directory of Open Access Journals (Sweden)

    Yii-Her Chou

    Full Text Available Calcium nephrolithiasis is one of the most common causes of renal stones. While the prevalence of this disease has increased steadily over the last 3 decades, its pathogenesis is still unclear. Previous studies have indicated that a genetic polymorphism (rs17251221 in the calcium-sensing receptor gene (CASR is associated with the total serum calcium levels. In this study, we collected DNA samples from 480 Taiwanese subjects (189 calcium nephrolithiasis patients and 291 controls for genotyping the CASR gene. Our results indicated no significant association between the CASR polymorphism (rs17251221 and the susceptibility of calcium nephrolithiasis. However, we found a significant association between rs17251221 and stone multiplicity. The risk of stone multiplicity was higher in patients with the GG+GA genotype than in those with the AA genotype (chi-square test: P = 0.008; odds ratio  =  4.79; 95% confidence interval, 1.44-15.92; Yates' correction for chi-square test: P = 0.013. In conclusion, our results provide evidence supporting the genetic effects of CASR on the pathogenesis of calcium nephrolithiasis.

  14. Multiple Defects of Cell Cycle Checkpoints in U937-ASPI3K, an U937 Cell Mutant Stably Expressing Anti-Sense ATM Gene cDNA

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    (Ataxia-telangiectasia mutated gene (ATM) functions in control of cell cycle checkpoints in responding to DNA damage and protects cells from undergoing apoptosis. Knock-out within tumor cells of endogenous ATM will achieve therapeutic benefits and nable a better understanding of the decisive mechanisms of cell death or survival in response to DNA damaging agents. ) In present paper, we sought to characterize the cell cycle checkpoint profiles in U937-ASPI3K, a U937 cell mutant that was previously established with endogenous ATM knock-out phenotype. Synchronized U937-ASPI3K was exposed to 137Cs irradiation, G1, S, G2/M cell cycle checkpoint profiles were evaluated by determining cell cycle kinetics, p53/p21 protein, cyclin dependent kinase 2 (CDK2) and p34CDC2 kinase activity in response to irradiation. U937-ASPI3K exhibited multiple defects in cell cycle checkpoints as defined by failing to arrest cells upon irradiation. The accumulation of cellular p53/p21 protein and inhibition of CDK kinase was also abolished in U937-ASPI3K. It was concluded that the stable expression of anti-sense PI3K cDNA fragment completely abolished multiple cell cycle checkpoints in U937-ASPI3K, and hence U937-ASPI3K with an AT-like phenotype could serves as a valuable model system for investigating the signal transduction pathway in responding to DNA damaging-based cancer therapy.

  15. NODC Standard Format Coastal Ocean Wave and Current (F181) Data from the Atlantic Remote Sensing Land/Ocean Experiment (ARSLOE) (1980) (NODC Accession 0014202)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains time series coastal ocean wave and current data collected during the Atlantic Remote Sensing Land/Ocean Experiment (ARSLOE). ARSLOE was...

  16. A Waterline Extraction Method from Remote Sensing Image Based on Quad-tree and Multiple Active Contour Model

    Directory of Open Access Journals (Sweden)

    YU Jintao

    2016-09-01

    Full Text Available After the characteristics of geodesic active contour model (GAC, Chan-Vese model(CV and local binary fitting model(LBF are analyzed, and the active contour model based on regions and edges is combined with image segmentation method based on quad-tree, a waterline extraction method based on quad-tree and multiple active contour model is proposed in this paper. Firstly, the method provides an initial contour according to quad-tree segmentation. Secondly, a new signed pressure force(SPF function based on global image statistics information of CV model and local image statistics information of LBF model has been defined, and then ,the edge stopping function(ESF is replaced by the proposed SPF function, which solves the problem such as evolution stopped in advance and excessive evolution. Finally, the selective binary and Gaussian filtering level set method is used to avoid reinitializing and regularization to improve the evolution efficiency. The experimental results show that this method can effectively extract the weak edges and serious concave edges, and owns some properties such as sub-pixel accuracy, high efficiency and reliability for waterline extraction.

  17. Dedicated Carrier Deployment in Heterogeneous Networks with Inter-site Carrier Aggregation

    DEFF Research Database (Denmark)

    Wang, Hua; Rosa, Claudio; Pedersen, Klaus I.

    2013-01-01

    ) or picos with dedicated carrier deployment. Collaborative inter-site carrier aggregation (CA) is proposed in scenarios with macro+RRH deployment to make an efficient use of the fragmented spectrum from multiple cells. While in scenarios with macro+pico deployment, UEs can only connect to either...

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

    Science.gov (United States)

    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.

  19. Multi-user interference cancellation schemes for carrier frequency offset compensation in uplink OFDMA

    DEFF Research Database (Denmark)

    Nguyen, Huan Cong; De Carvalho, Elisabeth; Prasad, Ramjee

    2014-01-01

    Each user in the uplink of an Orthogonal Frequency Division Multiple Access (OFDMA) system may experience a different carrier frequency offset (CFO). These uncorrected CFOs destroy the orthogonality among subcarriers, causing inter-carrier interference and multi-user interference, which degrade...... receiver and a reference frequency-domain multi-user interference cancellation scheme. In a particular scenario, a maximum CFO of up to 40% of the subcarrier spacing can be tolerated, and the CFO-free performance is maintained in the OFDMA uplink. The proposed schemes outperform the multi-user interference...... the system performance severely. In this paper, novel time-domain multi-user interference cancellation schemes for OFDMA uplink are proposed. They employ an architecture with multiple and numerical evaluations show that the proposed schemes achieve a significant performance gain compared to the conventional...

  20. Attack Prevention for Collaborative Spectrum Sensing in Cognitive Radio Networks

    CERN Document Server

    Duan, Lingjie; Huang, Jianwei; Shin, Kang G

    2011-01-01

    Collaborative spectrum sensing can significantly improve the detection performance of secondary unlicensed users (SUs). However, the performance of collaborative sensing is vulnerable to sensing data falsification attacks, where malicious SUs (attackers) submit manipulated sensing reports to mislead the fusion center's decision on spectrum occupancy. Moreover, attackers may not follow the fusion center's decision regarding their spectrum access. This paper considers a challenging attack scenario where multiple rational attackers overhear all honest SUs' sensing reports and cooperatively maximize attackers' aggregate spectrum utilization. We show that, without attack-prevention mechanisms, honest SUs are unable to transmit over the licensed spectrum, and they may further be penalized by the primary user for collisions due to attackers' aggressive transmissions. To prevent such attacks, we propose two novel attack-prevention mechanisms with direct and indirect punishments. The key idea is to identify collisions...

  1. Nitrogen-doped multiple graphene aerogel/gold nanostar as the electrochemical sensing platform for ultrasensitive detection of circulating free DNA in human serum.

    Science.gov (United States)

    Ruiyi, Li; Ling, Liu; Hongxia, Bei; Zaijun, Li

    2016-05-15

    Graphene aerogel has attracted increasing attention due to its large specific surface area, high-conductivity and electronic interaction. The paper reported a facile synthesis of nitrogen-doped multiple graphene aerogel/gold nanostar (termed as N-doped MGA/GNS) and its use as the electrochemical sensing platform for detection of double stranded (dsDNA). On the one hand, the N-doped MGA offers a much better electrochemical performance compared with classical graphene aerogel. Interestingly, the performance can be enhanced by only increasing the cycle number of graphene oxide gelation. On the other hand, the hybridization with GNS further enhances the electrocatalytic activity towards Fe(CN)6(3-/4-). In addition, the N-doped MGA/GNS provides a well-defined three-dimensional architecture. The unique structure make it is easy to combine with dsDNA to form the electroactive bioconjugate. The integration not only triggers an ultrafast DNA electron and charge transfer, but also realizes a significant synergy between N-doped MGA, GNS and dsDNA. As a result, the electrochemical sensor based on the hybrid exhibits highly sensitive differential pulse voltammetric response (DPV) towards dsDNA. The DPV signal linearly increases with the increase of dsDNA concentration in the range from 1.0×10(-)(21) g ml(-)(1) to 1.0×10(-16) g ml(-1) with the detection limit of 3.9×10(-22) g ml(-1) (S/N=3). The sensitivity is much more than that of all reported DNA sensors. The analytical method was successfully applied in the electrochemical detection of circulating free DNA in human serum. The study also opens a window on the electrical properties of multiple graphene aerogel and DNA as well their hybrids to meet the needs of further applications as special nanoelectronics in molecule diagnosis, bioanalysis and catalysis. PMID:26745792

  2. Nitrogen-doped multiple graphene aerogel/gold nanostar as the electrochemical sensing platform for ultrasensitive detection of circulating free DNA in human serum.

    Science.gov (United States)

    Ruiyi, Li; Ling, Liu; Hongxia, Bei; Zaijun, Li

    2016-05-15

    Graphene aerogel has attracted increasing attention due to its large specific surface area, high-conductivity and electronic interaction. The paper reported a facile synthesis of nitrogen-doped multiple graphene aerogel/gold nanostar (termed as N-doped MGA/GNS) and its use as the electrochemical sensing platform for detection of double stranded (dsDNA). On the one hand, the N-doped MGA offers a much better electrochemical performance compared with classical graphene aerogel. Interestingly, the performance can be enhanced by only increasing the cycle number of graphene oxide gelation. On the other hand, the hybridization with GNS further enhances the electrocatalytic activity towards Fe(CN)6(3-/4-). In addition, the N-doped MGA/GNS provides a well-defined three-dimensional architecture. The unique structure make it is easy to combine with dsDNA to form the electroactive bioconjugate. The integration not only triggers an ultrafast DNA electron and charge transfer, but also realizes a significant synergy between N-doped MGA, GNS and dsDNA. As a result, the electrochemical sensor based on the hybrid exhibits highly sensitive differential pulse voltammetric response (DPV) towards dsDNA. The DPV signal linearly increases with the increase of dsDNA concentration in the range from 1.0×10(-)(21) g ml(-)(1) to 1.0×10(-16) g ml(-1) with the detection limit of 3.9×10(-22) g ml(-1) (S/N=3). The sensitivity is much more than that of all reported DNA sensors. The analytical method was successfully applied in the electrochemical detection of circulating free DNA in human serum. The study also opens a window on the electrical properties of multiple graphene aerogel and DNA as well their hybrids to meet the needs of further applications as special nanoelectronics in molecule diagnosis, bioanalysis and catalysis.

  3. 多预约信息转发的协作信道预约多址接入协议%A Multiple Access Control Protocol with Multiple Reservation Information Relay and Cooperative Channel Reservation

    Institute of Scientific and Technical Information of China (English)

    袁韵洁; 李波

    2012-01-01

    针对Ad Hoc网络中实时业务在背景业务繁重时信道接入效率低的问题,提出一种邻节点协作转发信道预约信息(CRI)的多址接入协议(M-CCRM).节点在发送数据分组前,选取多条CRI作为其数据开销,在控制该开销不超过预先设定门限的基础上,将这些CRI随分组一起发送;收到数据分组的邻节点提取其携带的CRI,记录下那些自己位于其预约范围内的CRI,避免在这些CRI的预约时段内接入信道.M-CCRM协议扩大了CRI的覆盖范围,解决了由于信道衰落和(或)分组冲突导致的CRI丢失问题,提高了实时业务的信道接入效率.仿真结果表明,当开销门限为0.02时,M-CCRM协议的实时业务发送失败概率比基本信道预约协议和基本协作预约协议分别降低了31%和20%.%A new multiple access control (MAC) protocol called M-CCRM is proposed to solve the problem of poor channel access efficiency for real-time traffic in Ad Hoc networks with heavy background traffic loads. The proposed protocol bases on the idea of distributing channel reservation information (CRI) through cooperative relays of neighboring nodes. Before a node transmits a packet, multiple CRIs are carefully selected and piggy-backed with the packet so as to limit the corresponding overheads caused by carrying CRIs to be lower than a predefined threshold. By o-verhearing the packet, neighboring nodes record some of the CRIs as long as they are within the channel reservation distance of the CRIs, and then avoid to access the channel while the traffic indicated by the CRIs are carrying on. The proposed MAC protocol enlarges the coverage area of the announced CRIs, and avoids the possible missing of CRIs caused by channel fading and (or) packet collisions. Therefore, the channel access efficiency for real-time traffic is significantly increased. Simulations and comparisons with the basic channel reservation protocol and the basic cooperative channel reservation

  4. AntiJam: Efficient Medium Access despite Adaptive and Reactive Jamming

    CERN Document Server

    Richa, Andrea; Schmid, Stefan; Zhang, Jin

    2010-01-01

    Intentional interference constitutes a major threat for communication networks operating over a shared medium and where availability is imperative. Jamming attacks are often simple and cheap to implement. In particular, today's jammers can perform physical carrier sensing in order to disrupt communication more efficiently, specially in a network of simple wireless devices such as sensor nodes, which usually operate over a single frequency (or a limited frequency band) and which cannot benefit from the use of spread spectrum or other more advanced technologies. This paper proposes the medium access (MAC) protocol \\textsc{AntiJam} that is provably robust against a powerful reactive adversary who can jam a $(1-\\epsilon)$-portion of the time steps, where $\\epsilon$ is an arbitrary constant. The adversary uses carrier sensing to make informed decisions on when it is most harmful to disrupt communications; moreover, we allow the adversary to be adaptive and to have complete knowledge of the entire protocol history....

  5. Research of Mobile Radio Access Networking which Based on Optical Coherent Modulation Technique to Realize Base Station Carrier Remote via Optical Fiber%基于光学相干调制技术实现基站载波光纤拉远的无线移动接入网络研究与设计

    Institute of Scientific and Technical Information of China (English)

    李广

    2014-01-01

    分析了目前数字基带射频拉远组网架构的优势与弊端,提出了基于光学相干调制技术实现基站载波光纤拉远的无线移动接入网络架构,分析了其组网架构的优越性,给出了该接入网的具体实施方式。%In the paper,we analysed the advantages and disadvantages of the current? radio access networking architecture-dig-ital based band remote via optical fiber. We proposed a mobile radio access networking architecture which based on optical co-herent modulation technique to realize base station carrier remote via optical fiber.

  6. Joint Iterative Carrier Synchronization and Signal Detection Employing Expectation Maximization

    DEFF Research Database (Denmark)

    Zibar, Darko; de Carvalho, Luis Henrique Hecker; Estaran Tolosa, Jose Manuel;

    2014-01-01

    In this paper, joint estimation of carrier frequency, phase, signal means and noise variance, in a maximum likelihood sense, is performed iteratively by employing expectation maximization. The parameter estimation is soft decision driven and allows joint carrier synchronization and data detection...... and nonlinear phase noise, compared to digital phase-locked loop (PLL) followed by hard decisions. Additionally, soft decision driven joint carrier synchronization and detection offers an improvement of 0.5 dB in terms of input power compared to hard decision digital PLL based carrier synchronization...

  7. Quality of service modeling and analysis for carrier ethernet

    NARCIS (Netherlands)

    Malhotra, R.

    2008-01-01

    Today, Ethernet is moving into the mainstream evolving into a carrier grade technology. Termed as Carrier Ethernet it is expected to overcome most of the shortcomings of native Ethernet. It is envisioned to carry services end-to-end serving corporate data networking and broadband access demands as w

  8. A TDM/FDMA+Token Ring Hybrid Satellite Multiple Access Protocol for High Dynamic Platforms%适用于高动态平台的TDM/FDMA+令牌环卫星混合多址接入协议

    Institute of Scientific and Technical Information of China (English)

    夏晓巍

    2013-01-01

    Basic multiple access techniques in satellite communication are compared. A hybrid satellite multiple access protocol based on Fix Allocation Multiple Access( FAMA) and Free Allocation( FA) is de-signed for satellite communication system, and specifications and performance are analyzed. Test result shows the proposed protocol is featured by easy accessing, efficient bandwidth utilization and it is applica-ble for high dynamic mobile platform satellite communication. The research in this papaer has reference val-ue for engineering applications.%对卫星通信中比较常用的多址接入方式进行了比较,提出了一种固定分配与自由分配相结合的卫星混合多址接入协议,对指标性能进行了分析。试验结果表明,该协议具有业务接入灵活、卫星频带利用率高、系统实现简单等特点,适用于高动态平台卫星通信。研究内容对相关工程应用具有一定的参考价值。

  9. Asymmetric Carrier Random PWM

    DEFF Research Database (Denmark)

    Mathe, Laszlo; Lungeanu, Florin; Rasmussen, Peter Omand;

    2010-01-01

    This paper presents a new fixed carrier frequency random PWM method, where a new type of carrier wave is proposed for modulation. Based on the measurements, it is shown that the spread effect of the discrete components from the motor current spectra is very effective independent of the modulation...

  10. Peptide-Carrier Conjugation

    DEFF Research Database (Denmark)

    Hansen, Paul Robert

    2015-01-01

    To produce antibodies against synthetic peptides it is necessary to couple them to a protein carrier. This chapter provides a nonspecialist overview of peptide-carrier conjugation. Furthermore, a protocol for coupling cysteine-containing peptides to bovine serum albumin is outlined....

  11. SOARAN: A Service-oriented Architecture for Radio Access Network Sharing in Evolving Mobile Networks

    OpenAIRE

    He, Jun; Song, Wei

    2015-01-01

    Mobile networks are undergoing fast evolution to software-defined networking (SDN) infrastructure in order to accommodate the ever-growing mobile traffic and overcome the network management nightmares caused by unremitting acceleration in technology innovations and evolution of the service market.Enabled by virtualized network functionalities, evolving carrier wireless networks tend to share radio access network (RAN) among multiple (virtual) network operators so as to increase network capaci...

  12. Make electricity a complete and efficient carrier for energy accessibility - Hydro-Quebec strategic R & D; Faire de l'electricite un vecteur complet et efficace pour l'accessibilite de l'energie - La R&D strategique a Hydro-Quebec

    Energy Technology Data Exchange (ETDEWEB)

    Naggar, Raouf

    2010-09-15

    In an energy context dominated by the evolution of needs, the availability of resources and the respect of the environment, electricity will play a role increasingly important in order to make accessible most of the energy resources that are harnessed in real time and not already existing as a portable and storable form. However, to become a complete and efficient accessibility carrier, it will still have to rise to many more challenges in development, exploitation, maintenance and commercial exchanges. The Hydro Quebec research institute (IREQ) has begun several strategic R&D projects to raise to these challenges. [French] Dans un contexte energetique domine par l'evolution des besoins, la disponibilite des ressources et le respect de l'environnement, l'electricite jouera un role de plus en plus important pour rendre accessibles la plupart des ressources energetiques qui sont captees en temps reel et qui ne sont pas deja sous une forme stockable et transportable. Cependant, pour devenir un vecteur d'accessibilite complet et efficace, elle devra encore relever plusieurs defis au niveau du developpement, de l'exploitation, de la maintenance et des echanges commerciaux. L'institut de recherche d'Hydro-Quebec (IREQ) a entrepris plusieurs projets de R&D strategique visant a relever ces defis.

  13. Distributed and adaptive access mechanism supporting multiple-priority levels of throughput%支持优先等级的分布式自适应接入方案

    Institute of Scientific and Technical Information of China (English)

    石春; 何书前; 邓正杰; 张洁

    2015-01-01

    By studying the adjustment rules and ranges of access parameters ,a distributed and adaptive access mechanism was proposed based on channel status information .By sensing and counting channel busy status ,a node adjusting contention window linearly according to different access categories was designed ,which separated the adjustment rules of parameters from the status of data transmissions and alleviated the effect of fixed ranges of contention window on performance .The simulation results demonstrate the validity and scalability of the proposed access mechanism .%对接入参数调整策略和参数范围进行研究,基于信道状态信息,提出支持不同优先等级业务类型的分布式自适应接入方案。通过感知并统计信道状态数据,设计适合不同业务类型的线性调整竞争窗口的方法,解决接入参数调整对于数据传输状态的依赖和固定竞争窗口范围对性能的影响。仿真结果验证了该算法的有效性和良好的可扩展性能。

  14. 共价固定芘衍生物荧光载体制备呋喃妥因传感器%A Pyrene Derivative as Fluorescent Carrier with Covalently Immobilized on Sensing Membrane for Nitrofurantoin

    Institute of Scientific and Technical Information of China (English)

    焦晨旭; 韩媛媛; 邢宝研

    2012-01-01

    A pyrene derivative fluorescent carrier with a terminal double bond, methylacryloylam-idepyrene (MAAP) was synthesized. With the carrier molecules immobilized on the quartz slides via light copolymerization, a new fluorescent sensor was fabricated for the determination of nitrofurantoin based on the fluorescence quenching of MAAP. The quenching mechanism was discussed. The sensor exhibited excellent stability, sufficient repeatability, good selectivity and long lifetime due to the prevention from leaching out of fluorescent carrier. The sensor showed linear responses toward nitrofurantoin in the concentration range of 8. 0 × 10-7 ~ 1. 0× 10 - 4 mol/L with a detection limit of 6. 0 × 10 -7 mol/L. The recovery for the determination of nitrofurantoin in water samples ranged from 96. 0% to 104. 0%.%合成了一种端基双键的芘衍生物荧光载体甲基丙烯酰胺基芘.基于光聚合反应将该荧光载体共聚固定于玻片表面,利用呋喃妥因对共价固定膜甲基丙烯酰胺基芘的猝灭作用,研制了一种测定呋喃妥因的荧光传感器.传感器避免了荧光载体的泄漏,具有较好的稳定性、重现性和选择性,使用寿命长.呋喃妥因测定的线性范围为8.0×10-7~1.0×10-4mol/L,检测限为6.0×10-7mol/L.将传感器用于水样中呋喃妥因的直接测定,回收率为96.0%~ 104.0%.

  15. Near-Infrared Resonance Energy Transfer Glucose Biosensors in Hybrid Microcapsule Carriers

    Directory of Open Access Journals (Sweden)

    Mike McShane

    2008-09-01

    Full Text Available Fluorescence-based sensing systems offer potential for noninvasive monitoring with implantable devices, but require carrier technologies that provide suitable immobilization, accessibility, and biocompatibility. Recent developments towards this goal include a competitive binding assay for glucose that has been encapsulated in semipermeable microcapsule carriers. This paper describes an extension of this work to increase the applicability to in vivo monitoring, wherein two significant developments are described: (1 a near-infrared resonance energy transfer system for transducing glucose concentration, and (2 novel hybrid organic-inorganic crosslinked microcapsules as carriers. The quenching-based assay is a competitive binding (CB system based on apo-glucose oxidase (AG as the receptor and dextran as the competitive ligand. The encapsulated quencher-labeled dextran and near infrared donor-labeled glucose receptor showed a stable and reversible response with tunable sensitivity of 1–5%/mM over the physiological range, making these transducers attractive for continuous monitoring for biomedical applications.

  16. Structural and bioinformatic characterization of an Acinetobacter baumannii type II carrier protein

    Energy Technology Data Exchange (ETDEWEB)

    Allen, C. Leigh; Gulick, Andrew M., E-mail: gulick@hwi.buffalo.edu [University at Buffalo, Buffalo, NY 14203 (United States)

    2014-06-01

    The high-resolution crystal structure of a free-standing carrier protein from Acinetobacter baumannii that belongs to a larger NRPS-containing operon, encoded by the ABBFA-003406–ABBFA-003399 genes of A. baumannii strain AB307-0294, that has been implicated in A. baumannii motility, quorum sensing and biofilm formation, is presented. Microorganisms produce a variety of natural products via secondary metabolic biosynthetic pathways. Two of these types of synthetic systems, the nonribosomal peptide synthetases (NRPSs) and polyketide synthases (PKSs), use large modular enzymes containing multiple catalytic domains in a single protein. These multidomain enzymes use an integrated carrier protein domain to transport the growing, covalently bound natural product to the neighboring catalytic domains for each step in the synthesis. Interestingly, some PKS and NRPS clusters contain free-standing domains that interact intermolecularly with other proteins. Being expressed outside the architecture of a multi-domain protein, these so-called type II proteins present challenges to understand the precise role they play. Additional structures of individual and multi-domain components of the NRPS enzymes will therefore provide a better understanding of the features that govern the domain interactions in these interesting enzyme systems. The high-resolution crystal structure of a free-standing carrier protein from Acinetobacter baumannii that belongs to a larger NRPS-containing operon, encoded by the ABBFA-003406–ABBFA-003399 genes of A. baumannii strain AB307-0294, that has been implicated in A. baumannii motility, quorum sensing and biofilm formation, is presented here. Comparison with the closest structural homologs of other carrier proteins identifies the requirements for a conserved glycine residue and additional important sequence and structural requirements within the regions that interact with partner proteins.

  17. Compressive Sensing for Spread Spectrum Receivers

    DEFF Research Database (Denmark)

    Fyhn, Karsten; Jensen, Tobias Lindstrøm; Larsen, Torben;

    2013-01-01

    to a decrease in the two design parameters. This paper investigates the use of Compressive Sensing (CS) in a general Code Division Multiple Access (CDMA) receiver. We show that when using spread spectrum codes in the signal domain, the CS measurement matrix may be simplified. This measurement scheme, named...... Compressive Spread Spectrum (CSS), allows for a simple, effective receiver design. Furthermore, we numerically evaluate the proposed receiver in terms of bit error rate under different signal to noise ratio conditions and compare it with other receiver structures. These numerical experiments show that though......With the advent of ubiquitous computing there are two design parameters of wireless communication devices that become very important: power efficiency and production cost. Compressive sensing enables the receiver in such devices to sample below the Shannon-Nyquist sampling rate, which may lead...

  18. 社会实践:大学生社会责任感培养的重要载体%Social practice:the important carrier of cultivating the students' sense of social responsibility

    Institute of Scientific and Technical Information of China (English)

    赵曙光

    2013-01-01

    The contemporary college students social responsibility in the mainstream is healthy and positive, but there are also some problems that can not be ignored. Mainly displays in: pay attention to self value, despise social value; social responsibility consciousness and behavior are not unified;pay attention to protect their own rights and obligations, desalination. Carry out social practice can strengthen the students' sense of social responsibility cognition, improve the ability of students to fulfill their social responsibilities, fostering and enhancing the effectiveness of college students' sense of social responsibility.%  当代大学生社会责任感主流是健康的、积极向上的,但是也存在着一些不容忽视的问题。主要表现在:注重自我价值,轻视社会价值;社会责任意识与行为表现不统一;注重维护自身权利,淡化应该履行的义务。深入开展社会实践能强化大学生社会责任感认知,提高大学生履行社会责任的能力,增强培养大学生社会责任感的实效性。

  19. Electroactive polymers for sensing.

    Science.gov (United States)

    Wang, Tiesheng; Farajollahi, Meisam; Choi, Yeon Sik; Lin, I-Ting; Marshall, Jean E; Thompson, Noel M; Kar-Narayan, Sohini; Madden, John D W; Smoukov, Stoyan K

    2016-08-01

    Electromechanical coupling in electroactive polymers (EAPs) has been widely applied for actuation and is also being increasingly investigated for sensing chemical and mechanical stimuli. EAPs are a unique class of materials, with low-moduli high-strain capabilities and the ability to conform to surfaces of different shapes. These features make them attractive for applications such as wearable sensors and interfacing with soft tissues. Here, we review the major types of EAPs and their sensing mechanisms. These are divided into two classes depending on the main type of charge carrier: ionic EAPs (such as conducting polymers and ionic polymer-metal composites) and electronic EAPs (such as dielectric elastomers, liquid-crystal polymers and piezoelectric polymers). This review is intended to serve as an introduction to the mechanisms of these materials and as a first step in material selection for both researchers and designers of flexible/bendable devices, biocompatible sensors or even robotic tactile sensing units. PMID:27499846

  20. Electroactive polymers for sensing

    Science.gov (United States)

    2016-01-01

    Electromechanical coupling in electroactive polymers (EAPs) has been widely applied for actuation and is also being increasingly investigated for sensing chemical and mechanical stimuli. EAPs are a unique class of materials, with low-moduli high-strain capabilities and the ability to conform to surfaces of different shapes. These features make them attractive for applications such as wearable sensors and interfacing with soft tissues. Here, we review the major types of EAPs and their sensing mechanisms. These are divided into two classes depending on the main type of charge carrier: ionic EAPs (such as conducting polymers and ionic polymer–metal composites) and electronic EAPs (such as dielectric elastomers, liquid-crystal polymers and piezoelectric polymers). This review is intended to serve as an introduction to the mechanisms of these materials and as a first step in material selection for both researchers and designers of flexible/bendable devices, biocompatible sensors or even robotic tactile sensing units. PMID:27499846

  1. The value of energy carriers

    NARCIS (Netherlands)

    Gool, W. van

    1987-01-01

    The value of energy carriers can be described thermodynamically by the amount of heat (enthalpy method) or work (exergy or availability method) that can be obtained from the carriers. Prices for energy carriers are used in economics to express their values. The prices for energy carriers are often r

  2. A Comparative Study on Evaluating the Service Quality Attributes based on Kano Model: A Case of Low-cost Carrier and Full-service Carrier

    OpenAIRE

    Byun Hyojeong; Lee Byeongcheol; Rye Jaehee

    2014-01-01

    The emergence and development of low-cost carriers(LCC) with competitive price is heating up the competition in the aviation market more, especially between low-cost carriers(LCC) and full-service carriers(FSC). Therefore, it became more important than ever to implement service differentiation strategies of each airline for securing customers and competitiveness. In this sense, the purpose of this study is to compare and assess the different expectations of the customers for airline service a...

  3. Arctic phytoplankton and zooplankton abundance, temperature and salinity measurements collected from multiple platforms from 1903-02-22 to 1970-09-30 (NODC Accession 0069178)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Arctic phytoplankton and zooplankton abundance, temperature and salinity measurements collected from multiple platforms from 1903-02-22 to 1970-09-30 by Zoological...

  4. Temperature profiles from MBT casts from a World-Wide distribution from MULTIPLE PLATFORMS from 08 April 1948 to 14 December 1968 (NODC Accession 9300131)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Temperature profile data were collected from MBT casts from a World-Wide distribution. Data were collected from MULTIPLE PLATFORMS from 08 April 1948 to 14 Decmeber...

  5. Temperature profiles from XBT casts from a World-Wide distribution from MULTIPLE PLATFORMS from 03 June 1979 to 27 May 1988 (NODC Accession 8800182)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Temperature profiles were collected from XBT casts from a World-Wide distribution. Data were collected from MULTIPLE PLATFORMS from 03 June 1979 to 27 May 1988....

  6. Temperature profile data from XBT casts from MULTIPLE PLATFORMS from a World-Wide distribution from 02 January 1990 to 31 December 1995 (NODC Accession 0001268)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — XBT data were collected from MULTIPLE PLATFORMS from a World-Wide distribution from 02 January 1990 to 31 December 1995. Data were submitted by the UK Hydrographic...

  7. Duchenne muscular dystrophy carriers

    International Nuclear Information System (INIS)

    By means of magnetic resonance imaging (MRI), the proton spin-lattice relaxation times (T1 values) of the skeletal muscles were measured in Duchenne muscular dystrophy (DMD) carriers and normal controls. The bound water fraction (BWF) was calculated from the T1 values obtained, according to the fast proton diffusion model. In the DMD carriers, T1 values of the gluteus maximus and quadriceps femoris muscles were significantly higher, and BWFs of these muscles were significantly lower than in normal control. Degenerative muscular changes accompanied by interstitial edema were presumed responsible for this abnormality. No correlation was observed between the muscle T1 and serum creatine kinase values. The present study showed that MRI could be a useful method for studying the dynamic state of water in both normal and pathological skeletal muscles. Its possible utility for DMD carrier detection was discussed briefly. (orig.)

  8. The value of energy carriers

    OpenAIRE

    Gool, W. van

    1987-01-01

    The value of energy carriers can be described thermodynamically by the amount of heat (enthalpy method) or work (exergy or availability method) that can be obtained from the carriers. Prices for energy carriers are used in economics to express their values. The prices for energy carriers are often related to their enthalpies when other properties and conditions are equivalent. However, it has been suggested that the exergy of the energy carriers is the proper quantity to establish their value...

  9. Remote sensing; Fernerkundung

    Energy Technology Data Exchange (ETDEWEB)

    Glaessler, C.

    2001-07-01

    The potential of different multitemporal and multispectral airborne and spaceborne remote sensing methods for assessment and monitoring of the lignite open-cast mining areas are discussed in this chapter. Emphasis is placed on the successful use of different remote sensing data in variable vegetation structures for dumped sediments with different mineralogical and geochemical properties and for hydrochemical properties of the residual lakes. Multiple remote sensing data are a cost and time efficient tool for the assessment of environmental impacts, supervising of reclamation activities as well as for long term monitoring of the mining area. The airborne data are well suited for large scale detailed research and mapping in smaller sites and the satellite data for the overview scale 1:50 000. An integrated remote sensing-GIS-system including all field and lab data, DTM and other graphical data, improve the results of the remote sensing data classification for the lignite mining region in Central Germany and the Lausitz. (orig.)

  10. Mucosal genetic immunization through microsphere–based oral carriers

    OpenAIRE

    Rosli, Rozita; Nograles, Nadine; Hanafi, Aimi; Nor Shamsudin, Mariana; Abdullah, Syahril

    2013-01-01

    Polymeric carriers in the form of cellulose acetate phthalate (CAP) and alginate (ALG) microspheres were used for encapsulation of plasmid DNA for oral mucosal immunization. Access into the intestinal mucosa by pVAX1 eukaryotic expression plasmid vectors carrying gene-coding sequences, either for the cholera enterotoxin B subunit (ctxB) immunostimulatory antigen or the green fluorescent protein (GFP), delivered from both types of microsphere carriers were examined in orally immunized BALB/c m...

  11. Information and Its Carriers.

    Science.gov (United States)

    Herrmann, F.; And Others

    1985-01-01

    Describes: (1) the structure of a data transmission source, carrier, and receiver; (2) a quantitative measure for the amount of data, followed by some quantitative examples of data transmission processes; (3) the concept of data current; (4) data containers; and (5) how this information can be used to structure physics courses. (JN)

  12. Carrier-interleaved orthogonal multi-electrode multi-carrier resistivity-measurement tool

    Science.gov (United States)

    Cai, Yu; Sha, Shuang

    2016-09-01

    This paper proposes a new carrier-interleaved orthogonal multi-electrode multi-carrier resistivity-measurement tool used in a cylindrical borehole environment during oil-based mud drilling processes. The new tool is an orthogonal frequency division multiplexing access-based contactless multi-measurand detection tool. The tool can measure formation resistivity in different azimuthal angles and elevational depths. It can measure many more measurands simultaneously in a specified bandwidth than the legacy frequency division multiplexing multi-measurand tool without a channel-select filter while avoiding inter-carrier interference. The paper also shows that formation resistivity is not sensitive to frequency in certain frequency bands. The average resistivity collected from N subcarriers can increase the measurement of the signal-to-noise ratio (SNR) by N times given no amplitude clipping in the current-injection electrode. If the clipping limit is taken into account, with the phase rotation of each single carrier, the amplitude peak-to-average ratio can be reduced by 3 times, and the SNR can achieve a 9/N times gain over the single-carrier system. The carrier-interleaving technique is also introduced to counter the carrier frequency offset (CFO) effect, where the CFO will cause inter-pad interference. A qualitative analysis and simulations demonstrate that block-interleaving performs better than tone-interleaving when coping with a large CFO. The theoretical analysis also suggests that increasing the subcarrier number can increase the measurement speed or enhance elevational resolution without sacrificing receiver performance. The complex orthogonal multi-pad multi-carrier resistivity logging tool, in which all subcarriers are complex signals, can provide a larger available subcarrier pool than other types of transceivers.

  13. Multiple symmetric lipomas with high levels of mtDNA with the tRNA(Lys) A-->G(8344) mutation as the only manifestation of disease in a carrier of myoclonus epilepsy and ragged-red fibers (MERRF) syndrome.

    OpenAIRE

    Holme, E; Larsson, N G; Oldfors, A; Tulinius, M; Sahlin, P; Stenman, G

    1993-01-01

    We have investigated the morphology, cytogenetics, and the fraction of mtDNA with the tRNA(Lys) A-->G(8344) mutation in three lipomas in a carrier of this mutation. The son of the patient had myoclonus epilepsy and ragged-red fibers syndrome. The fraction of mtDNA with the tRNA(Lys) mutation varied between 62% and 80% in cultured skin fibroblasts, lymphocytes, normal adipose tissue, and muscle. In the three lipomas the mean fraction of mutated mtDNA was 90%, 94%, and 94%. Ultrastructural exam...

  14. Estudio del protooncogen Ret en neoplasia endocrina multiple 2A y en carcinoma medular en tiroides familiar: Hallazgos clínico-patológicos en portadores asintomáticos Analysis of the RET protooncogene in multiple endocrine neoplasia 2A and in familial medullary thyroid carcinoma: Clinical-pathological findings in asymptomatic carriers

    Directory of Open Access Journals (Sweden)

    S. Belli

    2003-01-01

    Full Text Available El 25% de los carcinomas medulares de tiroides son hereditarios. Se presentan en forma de familiar (CMTF 5% o como neoplasia endocrina múltiple (MEN tipo 2A (17% o 2B (3%, y comparten la herencia, autosómica dominante, de una mutación germinal en el protooncogen RET en uno de 12 codones conocidos. Estudiamos 7 familias (5 CMTF y 2 MEN 2A con el objeto de detectar la mutación familiar e identificar a los portadores asintomáticos. Seis de las siete mutaciones (4 CMTF y 2 MEN 2A fueron en el codón más frecuente, el 634, y una familia con CMTF presentó una mutación germinal novel: una transición T>C en el codón 630, resultando el cambio C630A. De los 57 individuos estudiados, 25 (43.85 % fueron portadores de la mutación, 7 de éstos (28% eran portadores asintomáticos de los cuales 5 eran niños, con una edad X-=11±3.2 años y fueron tiroidectomizados. Presentaron hiperplasia de células C y focos de microcarcinoma en ambos lóbulos tiroideos aun cuando la calcitonina basal o estimulada con pentagastrina fueron normales. En conclusión, describimos una mutación germinal novel en el protooncogen RET: C630A y el hallazgo de enfermedad de la célula C en los portadores asintomáticos, que enfatiza la importancia de la tiroidectomía profiláctica tan pronto como se confirma el diagnóstico molecular.Twenty five percent of the medullary thyroid carcinoma (MTC is hereditary and 5% is familiar (FMTC, or considered as multiple endocrine neoplasia (MEN type 2A (17% or 2B (3%. These diseases are the result of the autosomic dominant inheritance of a mutation in the RET protooncogene, in one out of 12 different known codons. We analyzed 7 families (2 MEN 2A and 5 FMTC. Six mutations were detected in the most frequent codon, 634 (2 MEN 2A y 4 FMTC and one family with FMTC presented a novel mutation: a transition T>C at codon 630, resulting a C630A change. Among 57 individuals studied, 25 (43.85% presented the mutation. Seven (28% were asymptomatic

  15. Intestinal solute carriers

    DEFF Research Database (Denmark)

    Steffansen, Bente; Nielsen, Carsten Uhd; Brodin, Birger;

    2004-01-01

    membrane transporters in the small intestine in order to increase oral bioavailabilities of drug or prodrug, the major influence on in vivo pharmacokinetics is suggested to be dose-dependent increase in bioavailability as well as prolonged blood circulation due to large capacity facilitated absorption......A large amount of absorptive intestinal membrane transporters play an important part in absorption and distribution of several nutrients, drugs and prodrugs. The present paper gives a general overview on intestinal solute carriers as well as on trends and strategies for targeting drugs and....../or prodrugs to these carriers in order to increasing oral bioavailability and distribution. A number of absorptive intestinal transporters are described in terms of gene and protein classification, driving forces, substrate specificities and cellular localization. When targeting absorptive large capacity...

  16. Performance Analysis of Multi-user Multi Input Multi Output- Interleave-Division Multiple-Access System Employing Turbo Coding with Multi-User Detection over Frequency-Selective Wireless Communication Channel

    Directory of Open Access Journals (Sweden)

    Kuttathatti S. Vishvaksenan

    2011-01-01

    Full Text Available Problem statement: This study presents the performance analysis of multi-user Multi Input Multi Output (MIMO assisted interleave based multiple-access system. In IDMA, different interleavers are used to distinguish users as against different signature sequence in a conventional code-Division Multiple-Access (CDMA scheme. Approach: The basic principle of IDMA is that the interleaver is unique for the users. Results: In this study, we consider that Interleavers are generated independently and randomly. Also the IDMA technique is extended to multi user MIMO IDMA with multi-user detection. At the receiver, OSIC detector is realized using ZF for frequency fading channel to combat MAI and MUI problem. The performance of the system is analyzed for different channel conditions using extensive simulation runs based on Monte Carlo simulation trials. Conclusion: It is shown that the IDMA scheme can achieve near single user performance in situations with very large numbers of users while maintaining very low receiver complexity. It is discerned from the computer simulation results that IDMA outperforms CDMA in frequency selective channel for high load conditions.

  17. Hungarian students’ carrier aspirations

    Directory of Open Access Journals (Sweden)

    A.S. Gubik

    2014-06-01

    Full Text Available The article analyzes the students’ carrier aspiration, right after their graduation and five years after their studies. It examines the differences arising from the students’ family business background and their most important social variables (gender, age. Then the study highlights the effects of study field on the students’ intention. The direct effect of education on starting an enterprise is undiscovered in the literature, the paper deals with the influence of availability and services use, offered by higher institutions.

  18. Single Carrier Cyclic Prefix-Assisted CDMA System with Frequency Domain Equalization for High Data Rate Transmission

    Directory of Open Access Journals (Sweden)

    Madhukumar A. S.

    2004-01-01

    Full Text Available Multiple-access interference and interfinger interference limit the capacity of conventional single-carrier DS-CDMA systems. Even though multicarrier CDMA posses the advantages of conventional CDMA and OFDM, it suffers from two major implementation difficulties such as peak-to-average power ratio and high sensitivity to frequency offset and RF phase noise. A novel approach based on single-carrier cyclic prefix-assisted CDMA has been proposed to overcome the disadvantages of single-carrier CDMA and multicarrier modulation. The usefulness of the proposed approach for high-speed packet access with simplified channel estimation procedures are investigated in this paper. The paper also proposes a data-dependent pilot structure for the downlink transmission of the proposed system for enhancing pilot-assisted channel estimation in frequency domain. The performance of the proposed pilot structure is compared against the data-independent common pilot structure. The proposed system is extensively simulated for different channel parameters with different channel estimation and equalization methods and the results are compared against conventional multicarrier CDMA systems with identical system specifications.

  19. Carrier transport uphill. I. General

    DEFF Research Database (Denmark)

    Rosenberg, T; Wilbrandt, W

    1963-01-01

    A quantitative treatment of a carrier pump operating with two carrier forms C and Z is presented. Asymmetric metabolic reactions are assumed to transform Z into C on one and C into Z on the other side of the membrane, establishing a carrier cycle. The kinetical consequences of this mechanism...

  20. Optimisation and common sense

    International Nuclear Information System (INIS)

    This note builds on recent articles about the development of new ICRP recommendations by supporting the use of common sense in optimisation; use of an additional criterion relating to technology-based principles is suggested to support utility- and equity-based criteria. This is taken forward by use of authoritative good practice safety precautions and a need to consider safety in an integrated manner. It is noted that use of common sense in ALARP or ALARA decisions is liable to rely on access to information and training. (author)

  1. 76 FR 38267 - The Federal Motor Carrier Safety Administration's 2011-2016 Strategic Plan: Raising the Safety Bar

    Science.gov (United States)

    2011-06-29

    ... FR 3316) at http://edocket.access.gpo.gov/2008/pdf/E8-785.pdf . FOR FURTHER INFORMATION CONTACT: Ms... Federal Motor Carrier Safety Administration The Federal Motor Carrier Safety Administration's 2011-2016 Strategic Plan: Raising the Safety Bar AGENCY: Federal Motor Carrier Safety Administration (FMCSA),...

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

    CERN Document Server

    Shokri-Ghadikolaei, Hossein; Nasiri-Kenari, Masoumeh

    2012-01-01

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

  3. Remote Sensing

    CERN Document Server

    Khorram, Siamak; Koch, Frank H; van der Wiele, Cynthia F

    2012-01-01

    Remote Sensing provides information on how remote sensing relates to the natural resources inventory, management, and monitoring, as well as environmental concerns. It explains the role of this new technology in current global challenges. "Remote Sensing" will discuss remotely sensed data application payloads and platforms, along with the methodologies involving image processing techniques as applied to remotely sensed data. This title provides information on image classification techniques and image registration, data integration, and data fusion techniques. How this technology applies to natural resources and environmental concerns will also be discussed.

  4. Multiple Perspectives / Multiple Readings

    Directory of Open Access Journals (Sweden)

    Simon Biggs

    2005-01-01

    Full Text Available People experience things from their own physical point of view. What they see is usually a function of where they are and what physical attitude they adopt relative to the subject. With augmented vision (periscopes, mirrors, remote cameras, etc we are able to see things from places where we are not present. With time-shifting technologies, such as the video recorder, we can also see things from the past; a time and a place we may never have visited.In recent artistic work I have been exploring the implications of digital technology, interactivity and internet connectivity that allow people to not so much space/time-shift their visual experience of things but rather see what happens when everybody is simultaneously able to see what everybody else can see. This is extrapolated through the remote networking of sites that are actual installation spaces; where the physical movements of viewers in the space generate multiple perspectives, linked to other similar sites at remote locations or to other viewers entering the shared data-space through a web based version of the work.This text explores the processes involved in such a practice and reflects on related questions regarding the non-singularity of being and the sense of self as linked to time and place.

  5. Maintainable substrate carrier for electroplating

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Chen-An; Abas, Emmanuel Chua; Divino, Edmundo Anida; Ermita, Jake Randal G.; Capulong, Jose Francisco S.; Castillo, Arnold Villamor; Ma, Diana Xiaobing

    2016-08-02

    One embodiment relates to a substrate carrier for use in electroplating a plurality of substrates. The carrier includes a non-conductive carrier body on which the substrates are placed and conductive lines embedded within the carrier body. A plurality of conductive clip attachment parts are attached in a permanent manner to the conductive lines embedded within the carrier body. A plurality of contact clips are attached in a removable manner to the clip attachment parts. The contact clips hold the substrates in place and conductively connecting the substrates with the conductive lines. Other embodiments, aspects and features are also disclosed.

  6. A parallel-pipelined architecture for a multi carrier demodulator

    Science.gov (United States)

    Kwatra, S. C.; Jamali, M. M.; Eugene, Linus P.

    1991-03-01

    Analog devices have been used for processing the information on board the satellites. Presently, digital devices are being used because they are economical and flexible as compared to their analog counterparts. Several schemes of digital transmission can be used depending on the data rate requirement of the user. An economical scheme of transmission for small earth stations uses single channel per carrier/frequency division multiple access (SCPC/FDMA) on the uplink and time division multiplexing (TDM) on the downlink. This is a typical communication service offered to low data rate users in commercial mass market. These channels usually pertain to either voice or data transmission. An efficient digital demodulator architecture is provided for a large number of law data rate users. A demodulator primarily consists of carrier, clock, and data recovery modules. This design uses principles of parallel processing, pipelining, and time sharing schemes to process large numbers of voice or data channels. It maintains the optimum throughput which is derived from the designed architecture and from the use of high speed components. The design is optimized for reduced power and area requirements. This is essential for satellite applications. The design is also flexible in processing a group of a varying number of channels. The algorithms that are used are verified by the use of a computer aided software engineering (CASE) tool called the Block Oriented System Simulator. The data flow, control circuitry, and interface of the hardware design is simulated in C language. Also, a multiprocessor approach is provided to map, model, and simulate the demodulation algorithms mainly from a speed view point. A hypercude based architecture implementation is provided for such a scheme of operation. The hypercube structure and the demodulation models on hypercubes are simulated in Ada.

  7. Online Remote Sensing Interface

    Science.gov (United States)

    Lawhead, Joel

    2007-01-01

    BasinTools Module 1 processes remotely sensed raster data, including multi- and hyper-spectral data products, via a Web site with no downloads and no plug-ins required. The interface provides standardized algorithms designed so that a user with little or no remote-sensing experience can use the site. This Web-based approach reduces the amount of software, hardware, and computing power necessary to perform the specified analyses. Access to imagery and derived products is enterprise-level and controlled. Because the user never takes possession of the imagery, the licensing of the data is greatly simplified. BasinTools takes the "just-in-time" inventory control model from commercial manufacturing and applies it to remotely-sensed data. Products are created and delivered on-the-fly with no human intervention, even for casual users. Well-defined procedures can be combined in different ways to extend verified and validated methods in order to derive new remote-sensing products, which improves efficiency in any well-defined geospatial domain. Remote-sensing products produced in BasinTools are self-documenting, allowing procedures to be independently verified or peer-reviewed. The software can be used enterprise-wide to conduct low-level remote sensing, viewing, sharing, and manipulating of image data without the need for desktop applications.

  8. Participatory sensing as an enabler for self-organisation in future cellular networks

    International Nuclear Information System (INIS)

    In this short review paper we summarise the emerging challenges in the field of participatory sensing for the self-organisation of the next generation of wireless cellular networks. We identify the potential of participatory sensing in enabling the self-organisation, deployment optimisation and radio resource management of wireless cellular networks. We also highlight how this approach can meet the future goals for the next generation of cellular system in terms of infrastructure sharing, management of multiple radio access techniques, flexible usage of spectrum and efficient management of very small data cells

  9. The plant mitochondrial carrier family: functional and evolutionary aspects

    OpenAIRE

    Ilka eHaferkamp; Stephan eSchmitz-Esser

    2012-01-01

    Mitochondria play a key role in respiration and energy production and are involved in multiple eukaryotic but also in several plant specific metabolic pathways. Solute carriers in the inner mitochondrial membrane connect the internal metabolism with that of the surrounding cell. Because of their common basic structure, these transport proteins affiliate to the mitochondrial carrier family (MCF). Generally, MCF proteins consist of six membrane-spanning helices, exhibit typical conserved domain...

  10. Decision feedback loop for tracking a polyphase modulated carrier

    Science.gov (United States)

    Simon, M. K. (Inventor)

    1974-01-01

    A multiple phase modulated carrier tracking loop for use in a frequency shift keying system is described in which carrier tracking efficiency is improved by making use of the decision signals made on the data phase transmitted in each T-second interval. The decision signal is used to produce a pair of decision-feedback quadrature signals for enhancing the loop's performance in developing a loop phase error signal.

  11. Living in a 'fat swamp': exposure to multiple sources of accessible, cheap, energy-dense fast foods in a deprived community.

    Science.gov (United States)

    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. PMID:25885785

  12. Flexible access control for dynamic collaborative environments

    NARCIS (Netherlands)

    Dekker, Mari Antonius Cornelis

    2009-01-01

    Access control is used in computer systems to control access to confidential data. In this thesis we focus on access control for dynamic collaborative environments where multiple users and systems access and exchange data in an ad hoc manner. In such environments it is difficult to protect confident

  13. Equal gain combining for cooperative spectrum sensing in cognitive radio networks

    KAUST Repository

    Hamza, Doha R.

    2014-08-01

    Sensing with equal gain combining (SEGC), a novel cooperative spectrum sensing technique for cognitive radio networks, is proposed. Cognitive radios simultaneously transmit their sensing results to the fusion center (FC) over multipath fading reporting channels. The cognitive radios estimate the phases of the reporting channels and use those estimates for coherent combining of the sensing results at the FC. A global decision is made at the FC by comparing the received signal with a threshold. We obtain the global detection probabilities and secondary throughput exactly through a moment generating function approach. We verify our solution via system simulation and demonstrate that the Chernoff bound and central limit theory approximation are not tight. The cases of hard sensing and soft sensing are considered and we provide examples in which hard sensing is advantageous to soft sensing. We contrast the performance of SEGC with maximum ratio combining of the sensors\\' results and provide examples where the former is superior. Furthermore, we evaluate the performance of SEGC against existing orthogonal reporting techniques such as time division multiple access (TDMA). SEGC performance always dominates that of TDMA in terms of secondary throughput. We also study the impact of phase and synchronization errors and demonstrate the robustness of the SEGC technique against such imperfections. © 2002-2012 IEEE.

  14. Glucose Sensing

    CERN Document Server

    Geddes, Chris D

    2006-01-01

    Topics in Fluorescence Spectroscopy, Glucose Sensing is the eleventh volume in the popular series Topics in Fluorescence Spectroscopy, edited by Drs. Chris D. Geddes and Joseph R. Lakowicz. This volume incorporates authoritative analytical fluorescence-based glucose sensing reviews specialized enough to be attractive to professional researchers, yet also appealing to the wider audience of scientists in related disciplines of fluorescence. Glucose Sensing is an essential reference for any lab working in the analytical fluorescence glucose sensing field. All academics, bench scientists, and industry professionals wishing to take advantage of the latest and greatest in the continuously emerging field of glucose sensing, and diabetes care & management, will find this volume an invaluable resource. Topics in Fluorescence Spectroscopy Volume 11, Glucose Sensing Chapters include: Implantable Sensors for Interstitial Fluid Smart Tattoo Glucose Sensors Optical Enzyme-based Glucose Biosensors Plasmonic Glucose Sens...

  15. "I'm Healthy, It's Not Going To Be Me": Exploring experiences of carriers identified through a population reproductive genetic carrier screening panel in Australia.

    Science.gov (United States)

    Beard, Catherine A; Amor, David J; Di Pietro, Louisa; Archibald, Alison D

    2016-08-01

    Advancing genetic testing technologies mean that population-based carrier screening for multiple inherited conditions is now available. As the number of genetic conditions being screened increases, there is a need for research into how people experience these screening programs. This research aimed to explore how women experience simultaneous carrier screening for three inherited conditions: cystic fibrosis (CF), spinal muscular atrophy (SMA), and fragile X syndrome (FXS). A qualitative approach was adopted using in-depth semi-structured interviews to explore the experiences of ten female participants: five SMA carriers, three CF carriers, and two FXS premutation carriers. Eight participants were pregnant when offered screening by their general practitioner or obstetrician and the decision to have screening was described as straightforward. Participants reported experiencing emotional responses such as anxiety and stress while waiting for either their partner's carrier screen result (CF or SMA carriers) or the pregnancy's CVS result (FXS carrier) and sought additional information about the relevant condition during this time. Most participants were in favor of population carrier screening for these conditions, preferably prior to conception. Genetic counselors played an essential role in supporting couples after they received a carrier result given the variable consent processes undertaken when screening was offered. Further research should focus on the development of reliable online information tailored to people receiving carrier results and strategies for raising awareness of the availability of population carrier screening within the community. © 2016 Wiley Periodicals, Inc. PMID:27150953

  16. Force sensing

    OpenAIRE

    Sanders, David

    2007-01-01

    A young child can explore and learn and compensate for unknown dynamics by prodding, pushing, touching, grasping and feeling. Force sensing and software research could soon allow artificial mechanisms to do the same. Force sensing has its roots in strain gauges, piezoelectrics, Wheatstone bridges, automation, robotics, grippers and virtual reality. That force sensing research has now become commonplace and has expanded from those roots to include so much more: video games, athletic equipment,...

  17. Fundamental Analysis of the Linear Multiple Regression Technique for Quantification of Water Quality Parameters from Remote Sensing Data. Ph.D. Thesis - Old Dominion Univ.

    Science.gov (United States)

    Whitlock, C. H., III

    1977-01-01

    Constituents with linear radiance gradients with concentration may be quantified from signals which contain nonlinear atmospheric and surface reflection effects for both homogeneous and non-homogeneous water bodies provided accurate data can be obtained and nonlinearities are constant with wavelength. Statistical parameters must be used which give an indication of bias as well as total squared error to insure that an equation with an optimum combination of bands is selected. It is concluded that the effect of error in upwelled radiance measurements is to reduce the accuracy of the least square fitting process and to increase the number of points required to obtain a satisfactory fit. The problem of obtaining a multiple regression equation that is extremely sensitive to error is discussed.

  18. Evaluating habitat associations of a fish assemblage at multiple spatial scales in a minimally disturbed stream using low-cost remote sensing

    Science.gov (United States)

    Cheek, Brandon D.; Grabowski, Timothy B.; Bean, Preston T.; Groeschel, Jillian R.; Magnelia, Stephan J.

    2016-01-01

    Habitat heterogeneity at multiple scales is a major factor affecting fish assemblage structure. However, assessments that examine these relationships at multiple scales concurrently are lacking. The lack of assessments at these scales is a critical gap in understanding as conservation and restoration efforts typically work at these levels.A combination of low-cost side-scan sonar surveys, aerial imagery using an unmanned aerial vehicle, and fish collections were used to evaluate the relationship between physicochemical and landscape variables at various spatial scales (e.g. micro-mesohabitat, mesohabitat, channel unit, stream reach) and stream–fish assemblage structure and habitat associations in the South Llano River, a spring-fed second-order stream on the Edwards Plateau in central Texas during 2012–2013.Low-cost side-scan sonar surveys have not typically been used to generate data for riverscape assessments of assemblage structure, thus the secondary objective was to assess the efficacy of this approach.The finest spatial scale (micro-mesohabitat) and the intermediate scale (channel unit) had the greatest explanatory power for variation in fish assemblage structure.Many of the fish endemic to the Edwards Plateau showed similar associations with physicochemical and landscape variables suggesting that conservation and restoration actions targeting a single endemic species may provide benefits to a large proportion of the endemic species in this system.Low-cost side-scan sonar proved to be a cost-effective means of acquiring information on the habitat availability of the entire river length and allowed the assessment of how a full suite of riverscape-level variables influenced local fish assemblage structure.

  19. Broadband Wireline Provider Service: Optical Carrier - Fiber to the End User; BBRI_fiber12

    Data.gov (United States)

    University of Rhode Island Geospatial Extension Program — This dataset represents the availability of wireline broadband Internet access in Rhode Island via "Optical Carrier - Fiber to the End User" technology. Broadband...

  20. Cognitive Self-Scheduled Mechanism for Access Control in Noisy Vehicular Ad Hoc Networks

    Directory of Open Access Journals (Sweden)

    Mario Manzano

    2015-01-01

    Full Text Available Within the challenging environment of intelligent transportation systems (ITS, networked control systems such as platooning guidance of autonomous vehicles require innovative mechanisms to provide real-time communications. Although several proposals are currently under discussion, the design of a rapid, efficient, flexible, and reliable medium access control mechanism which meets the specific constraints of such real-time communications applications remains unsolved in this highly dynamic environment. However, cognitive radio (CR combines the capacity to sense the radio spectrum with the flexibility to adapt to transmission parameters in order to maximize system performance and has thus become an effective approach for the design of dynamic spectrum access (DSA mechanisms. This paper presents the enhanced noncooperative cognitive division multiple access (ENCCMA proposal combining time division multiple access (TDMA and frequency division multiple access (FDMA schemes with CR techniques to obtain a mechanism fulfilling the requirements of real-time communications. The analysis presented here considers the IEEE WAVE and 802.11p as reference standards; however, the proposed medium access control (MAC mechanism can be adapted to operate on the physical layer of different standards. The mechanism also offers the advantage of avoiding signaling, thus enhancing system autonomy as well as behavior in adverse scenarios.

  1. Cooperatively active sensing system

    International Nuclear Information System (INIS)

    Aiming at development of a strong and flexible sensing system, a study on a sensing technology prepared with cooperativity, activity, and real time workability has been promoted. In the former period, together with preparation of plural moving robot group with real time processing capacity of a lot of sensor informations composing of platform, a parallel object direction language Eus Lisp effectively capable of describing and executing cooperative processing and action therewith was developed. And, it was also shown that capacity to adaptively act even at dynamic environment could be learnt experientially. And, on processing of individual sensor information, application of a photographing system with multiple resolution property similar to human visual sense property was attempted. In the latter period, together with intending of upgrading on adaptability of sensing function, by using moving robot group in center of a moving robot loaded with active visual sense, a cooperative active sensing prototype system was constructed to show effectiveness of this study through evaluation experiment of patrolling inspection at plant simulating environment. (G.K.)

  2. Autonomous component carrier selection

    DEFF Research Database (Denmark)

    Garcia, Luis Guilherme Uzeda; Pedersen, Klaus; Mogensen, Preben

    2009-01-01

    in local areas, basing our study case on LTE-Advanced. We present extensive network simulation results to demonstrate that a simple and robust interference management scheme, called autonomous component carrier selection allows each cell to select the most attractive frequency configuration; improving......Low-power base stations such as e.g. Femto-cells are one of the candidates for high data rate provisioning in local areas, such as residences, apartment complexes, business offices and outdoor hotspot scenarios. Unfortunately, the benefits are not without new challenges in terms of interference...... management and efficient system operation. Due to the expected large number of user-deployed cells, centralized network planning becomes unpractical and new scalable alternatives must be sought. In this article, we propose a fully distributed and scalable solution to the interference management problem...

  3. Enhancing Carrier-To-Noise Ratio In Optical Cdma-Based Fiber Radio Networks

    Directory of Open Access Journals (Sweden)

    Surya.R

    2013-06-01

    Full Text Available A Bi-Directional fiber radio networks based on spectral Amplitude Coding (SAC optical Code Division Multiple Access (OCDMA with interference elimination is proposed. Here in this scheme hybrid ring/star topology is used with partial self healing ability and its key feature is to eliminate addition of direct current signal before the optical encoding process. As compared to previous SAC- based fiber radio network the proposed scheme improves both power efficiency and Carrier-to –noise ratio at the decoder. Adding to these improvement simple encoding / decoding structures with small sizes in the control base station is proposed to reduce the cost of the today’s mobile radio networks with large number of remote base stations.

  4. Health Participatory Sensing Networks

    Directory of Open Access Journals (Sweden)

    Andrew Clarke

    2014-01-01

    Full Text Available The use of participatory sensing in relation to the capture of health-related data is rapidly becoming a possibility due to the widespread consumer adoption of emerging mobile computing technologies and sensing platforms. This has the potential to revolutionize data collection for population health, aspects of epidemiology, and health-related e-Science applications and as we will describe, provide new public health intervention capabilities, with the classifications and capabilities of such participatory sensing platforms only just beginning to be explored. Such a development will have important benefits for access to near real-time, large-scale, up to population-scale data collection. However, there are also numerous issues to be addressed first: provision of stringent anonymity and privacy within these methodologies, user interface issues, and the related issue of how to incentivize participants and address barriers/concerns over participation. To provide a step towards describing these aspects, in this paper we present a first classification of health participatory sensing models, a novel contribution to the literature, and provide a conceptual reference architecture for health participatory sensing networks (HPSNs and user interaction example case study.

  5. Remote Sensing.

    Science.gov (United States)

    Williams, Richard S., Jr.; Southworth, C. Scott

    1983-01-01

    The Landsat Program became the major event of 1982 in geological remote sensing with the successful launch of Landsat 4. Other 1982 remote sensing accomplishments, research, publications, (including a set of Landsat worldwide reference system index maps), and conferences are highlighted. (JN)

  6. Decision Analysis of Dynamic Spectrum Access Rules

    Energy Technology Data Exchange (ETDEWEB)

    Juan D. Deaton; Luiz A. DaSilva; Christian Wernz

    2011-12-01

    A current trend in spectrum regulation is to incorporate spectrum sharing through the design of spectrum access rules that support Dynamic Spectrum Access (DSA). This paper develops a decision-theoretic framework for regulators to assess the impacts of different decision rules on both primary and secondary operators. We analyze access rules based on sensing and exclusion areas, which in practice can be enforced through geolocation databases. Our results show that receiver-only sensing provides insufficient protection for primary and co-existing secondary users and overall low social welfare. On the other hand, using sensing information between the transmitter and receiver of a communication link, provides dramatic increases in system performance. The performance of using these link end points is relatively close to that of using many cooperative sensing nodes associated to the same access point and large link exclusion areas. These results are useful to regulators and network developers in understanding in developing rules for future DSA regulation.

  7. Access Denied

    Science.gov (United States)

    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…

  8. Evaluation of Kolmogorov - Smirnov Test and Energy Detector Techniques for Cooperative Spectrum Sensing in Real Channel Conditions

    Directory of Open Access Journals (Sweden)

    D. Lekomtcev

    2015-06-01

    Full Text Available The cognitive radio technology allows solving one of the main issues of current wireless communication technologies, namely a deficit of vacant spectrum. A dynamic spectrum access used in the cognitive radio networks (CRN gives an ability to access an unused spectrum in real time. Cooperative spectrum sensing is the most effective method for spectrum holes detecting. It combines sensing information of multiple cognitive radio users. In this paper, an experimental evaluation of spectrum sensing methods based on the Kolmogorov - Smirnov statistical test and Energy Detector using the Universal Software Radio Peripheral (USRP devices synchronized through a MIMO cable and with further processing in the GNU Radio and Matlab software are presented. Three hard decision fusion schemes are analyzed. Simulation comparison between these rules is presented via Receiver Operating Characteristic (ROC curves. The influence of real channel with interferences is compared in contrast to commonly assumed AWGN channel model of vacant channel noise.

  9. Channel access delay and buffer distribution of two-user opportunistic scheduling schemes in wireless networks

    KAUST Repository

    Hossain, Md Jahangir

    2010-07-01

    In our earlier works, we proposed rate adaptive hierarchical modulation-assisted two-best user opportunistic scheduling (TBS) and hybrid two-user scheduling (HTS) schemes. The proposed schemes are innovative in the sense that they include a second user in the transmission opportunistically using hierarchical modulations. As such the frequency of information access of the users increases without any degradation of the system spectral efficiency (SSE) compared to the classical opportunistic scheduling scheme. In this paper, we analyze channel access delay of an incoming packet at the base station (BS) buffer when our proposed TBS and HTS schemes are employed at the BS. Specifically, using a queuing analytic model we derive channel access delay as well as buffer distribution of the packets that wait at BS buffer for down-link (DL) transmission. We compare performance of the TBS and HTS schemes with that of the classical single user opportunistic schemes namely, absolute carrier-to-noise ratio (CNR)-based single user scheduling (ASS) and normalized CNR-based single user scheduling (NSS). For an independent and identically distributed (i.i.d.) fading environment, our proposed scheme can improve packet\\'s access delay performance compared to the ASS. Selected numerical results in an independent but non-identically distributed (i.n.d.) fading environment show that our proposed HTS achieves overall good channel access delay performance. © 2010 IEEE.

  10. 基于多示例学习的高分辨率遥感影像面向对象分类%Object Oriented High Resolution Remote Sensing Image Classification Based on Multiple Instance Learning

    Institute of Scientific and Technical Information of China (English)

    阿里木·赛买提; 杜培军

    2012-01-01

    多示例学习以示例组成的包作为训练样本,学习的目的是预测新包的类型.从分类角度上,处理问题的策略类似于以均质对象为基本处理单元的面向对象影像分类.针对两者之间理论和方法相似性,将多样性密度多示例学习算法与面向对泉方法相结合用于高分辨率遥感图像分类.以图像分割方法获取均值对象作为示例,利用多样性密度算法对样本包进行学习获取最大多样性密度示例,最后根据相似性最大准则对单示例包或是经聚类算法得到的新包进行类别标记,以获取最终分类结果.通过与SVM分类器的比较,发现多样性密度算法的平均分类精度都在70%以上,最高可达96%左右,且对小样本问题学习能力更强,结果表明多示例学习在遥感图像分类中有着广泛应用前景.%In multiple instance learning) the bags are used as training samples,and the goal of learning is predict the label of new bags. The idea of multiple instance learning is quite similar to the object-oriented image classification,which takes homogeneous object as basic processing unit, so it is feasible to combine multiple instance learning with object-oriented way to classify the high resolution remote sensing image. In this paper, Diverse Oensity(DD) algorithm is used to classify the high resolution remote sensing image according to the object oriented image classification paradigm. Homogeneous objects are generated by image segmentation method first,and then objects used as instances,get the maximum diverse density instance by training bags with DD,so the label of new bags which single instance considered as a bag or obtained by clustering method can be determined by the distance similarity criterion. Compared with the advanced SVM classifier,the classification approach consisting of diverse density algorithm and object oriented can get higher classification accuracy,average accuracy is higher than 70% ,the highest

  11. Cell carriers for oncolytic viruses: current challenges and future directions.

    Science.gov (United States)

    Roy, Dominic G; Bell, John C

    2013-01-01

    The optimal route for clinical delivery of oncolytic viruses is thought to be systemic intravenous injection; however, the immune system is armed with several highly efficient mechanisms to remove pathogens from the circulatory system. To overcome the challenges faced in trying to delivery oncolytic viruses specifically to tumors via the bloodstream, carrier cells have been investigated to determine their suitability as delivery vehicles for systemic administration of oncolytic viruses. Cell carriers protect viruses from neutralization, one of the most limiting aspects of oncolytic virus interaction with the immune system. Cell carriers can also possess inherent tumor tropism, thus directing the delivery of the virus more specifically to a tumor. With preclinical studies already demonstrating the success and feasibility of this approach with multiple oncolytic viruses, clinical evaluation of cell-mediated delivery of viruses is on the horizon. Meanwhile, ongoing preclinical studies are aimed at identifying new cellular vehicles for oncolytic viruses and improving current promising cell carrier platforms. PMID:27512657

  12. Satellite Remote Sensing of Harmful Algal Blooms (HABs and a Potential Synthesized Framework

    Directory of Open Access Journals (Sweden)

    Xulin Guo

    2012-06-01

    Full Text Available Harmful algal blooms (HABs are severe ecological disasters threatening aquatic systems throughout the World, which necessitate scientific efforts in detecting and monitoring them. Compared with traditional in situ point observations, satellite remote sensing is considered as a promising technique for studying HABs due to its advantages of large-scale, real-time, and long-term monitoring. The present review summarizes the suitability of current satellite data sources and different algorithms for detecting HABs. It also discusses the spatial scale issue of HABs. Based on the major problems identified from previous literature, including the unsystematic understanding of HABs, the insufficient incorporation of satellite remote sensing, and a lack of multiple oceanographic explanations of the mechanisms causing HABs, this review also attempts to provide a comprehensive understanding of the complicated mechanism of HABs impacted by multiple oceanographic factors. A potential synthesized framework can be established by combining multiple accessible satellite remote sensing approaches including visual interpretation, spectra analysis, parameters retrieval and spatial-temporal pattern analysis. This framework aims to lead to a systematic and comprehensive monitoring of HABs based on satellite remote sensing from multiple oceanographic perspectives.

  13. Satellite remote sensing of harmful algal blooms (HABs) and a potential synthesized framework.

    Science.gov (United States)

    Shen, Li; Xu, Huiping; Guo, Xulin

    2012-01-01

    Harmful algal blooms (HABs) are severe ecological disasters threatening aquatic systems throughout the World, which necessitate scientific efforts in detecting and monitoring them. Compared with traditional in situ point observations, satellite remote sensing is considered as a promising technique for studying HABs due to its advantages of large-scale, real-time, and long-term monitoring. The present review summarizes the suitability of current satellite data sources and different algorithms for detecting HABs. It also discusses the spatial scale issue of HABs. Based on the major problems identified from previous literature, including the unsystematic understanding of HABs, the insufficient incorporation of satellite remote sensing, and a lack of multiple oceanographic explanations of the mechanisms causing HABs, this review also attempts to provide a comprehensive understanding of the complicated mechanism of HABs impacted by multiple oceanographic factors. A potential synthesized framework can be established by combining multiple accessible satellite remote sensing approaches including visual interpretation, spectra analysis, parameters retrieval and spatial-temporal pattern analysis. This framework aims to lead to a systematic and comprehensive monitoring of HABs based on satellite remote sensing from multiple oceanographic perspectives. PMID:22969372

  14. 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.

    Directory of Open Access Journals (Sweden)

    Georgios Hadjigeorgiou

    Full Text Available 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.

  15. 基于时分同步码多址的无线数据传输方案%Wireless data transmission scheme based on time division-synchronous code division multiple access

    Institute of Scientific and Technical Information of China (English)

    雷文君; 张会业; 崔燕

    2012-01-01

    为了在嵌入式系统中整合无线通信技术进行数据传输,提出一种基于嵌入式的无线数据传输设备的设计方案。无线数据传输设备以三星的S3C2440为中央处理器,时分同步码多址(TD-SCDMA)模块LC6311为网络接入部分。实际测试结果表明,设计方案可确保无线数据的远程传输,实时性好,运行可靠,既能提高网络传输质量,还能降低频谱监测中的隐患,故可应用于频谱远程监控领域。%To integrate wireless communication technique for data transmission in embedded system,an embedded based designing scheme for wireless data transmission is proposed.The wireless data transmission device uses the S3C2440 of Samsung as its central processing unit and time division-synchronous code division multiple access module LC6311 as the part of network access.The testing result indicates that the design of the scheme can ensure long-distance transmission of wireless data,and has got good real-time performance and reliable operation.It not only improves the quality of network transmission,but also greatly reduces the hidden dangers of Spectrum Monitoring,thus the scheme can be applied in the long-distance of spectrum monitoring.

  16. Compressive sensing with a microwave photonic filter

    DEFF Research Database (Denmark)

    Chen, Ying; Yu, Xianbin; Chi, Hao;

    2015-01-01

    In this letter, we present a novel approach to realizing photonics-assisted compressive sensing (CS) with the technique of microwave photonic fi ltering. In the proposed system, an input spectrally sparse signal to be captured and a random sequence are modulated on an optical carrier via two Mach...

  17. 47 CFR 1.1403 - Duty to provide access; modifications; notice of removal, increase or modification; petition for...

    Science.gov (United States)

    2010-10-01

    ... and information relate to a denial of access for reasons of lack of capacity, safety, reliability or... a cable television system or any telecommunications carrier with nondiscriminatory access to any... utility may deny a cable television system or any telecommunications carrier access to its poles,...

  18. Multi Carrier Modulator for Switch-Mode Audio Power Amplifiers

    DEFF Research Database (Denmark)

    Knott, Arnold; Pfaffinger, Gerhard; Andersen, Michael Andreas E.

    2008-01-01

    -mode audio power amplifiers while keeping the performance measures to excellent levels is therefore of high general interest. A modulator utilizing multiple carrier signals to generate a two level pulse train will be shown in this paper. The performance of the modulator will be compared in simulation...

  19. Nanostructured Lipid Carriers: A potential drug carrier for cancer chemotherapy

    Directory of Open Access Journals (Sweden)

    Selvamuthukumar Subramanian

    2012-11-01

    Full Text Available Abstract Nanotechnology having developed exponentially, the aim has been on therapeutic undertaking, particularly for cancerous disease chemotherapy. Nanostructured lipid carriers have attracted expanding scientific and commercial vigilance in the last couple of years as alternate carriers for the pharmaceutical consignment, particularly anticancer pharmaceuticals. Shortcomings often came across with anticancer mixtures, such as poor solubility, normal tissue toxicity, poor specificity and steadiness, as well as the high incidence rate of pharmaceutical resistance and the rapid degradation, need of large-scale output procedures, a fast release of the pharmaceutical from its carrier scheme, steadiness troubles, the residues of the organic solvents utilized in the output method and the toxicity from the polymer with esteem to the carrier scheme are anticipated to be overcome through use of the Nanostructured Lipid Carrier. In this review the benefits, types, drug release modulations, steadiness and output techniques of NLCs are discussed. In supplement, the function of NLC in cancer chemotherapy is presented and hotspots in research are emphasized. It is foreseen that, in the beside future, nanostructured lipid carriers will be further advanced to consign cytotoxic anticancer compounds in a more efficient, exact and protected manner.

  20. Basic Stand Alone Carrier Line Items PUF

    Data.gov (United States)

    U.S. Department of Health & Human Services — This release contains the Basic Stand Alone (BSA) Carrier Line Items Public Use Files (PUF) with information from Medicare Carrier claims. The CMS BSA Carrier Line...

  1. Hyperdatabase: A schema for browsing multiple databases

    International Nuclear Information System (INIS)

    In order to insure effective information retrieval, a user may need to search multiple databases on multiple systems. Although front end systems have been developed to assist the user in accessing different systems, they access one retrieval system at a time and the search has to be repeated for each required database on each retrieval system. More importantly, the user interacts with the results as independent sessions. This paper models multiple bibliographic databases distributed over one or more retrieval systems as a hyperdatabase, i.e., a single virtual database. The hyperdatabase is viewed as a hypergraph in which each node represents a bibliographic item and the links among nodes represent relations among the items. In the response to a query, bibliographic items are extracted from the hyperdatabase and linked together to form a transient hypergraph. This hypergraph is transient in the sense that it is ''created'' in response to a query and only ''exists'' for the duration of the query session. A hypertext interface permits the user to browse the transient hypergraph in a nonlinear manner. The technology to implement a system based on this model is available now, consisting of powerful workstation, distributed processing, high-speed communications, and CD-ROMs. As the technology advances and costs decrease such systems should be generally available. (author). 13 refs, 5 figs

  2. Miniaturized RF Remote Sensing Instruments

    OpenAIRE

    Brady, James; McEachron, Greg

    1995-01-01

    Until recently, miniaturization of RF remote sensing instruments has not been cost effective. Aperture size has governed launch vehicle selection and spacecraft mass has been well within margins. However, as technologies improve for miniature spacecraft, multiple spacecraft can fit within small launch vehicle shrouds. Down-sizing payloads is now advantageous. E-Systems is applying state-of the- art technologies to significantly reduce the size and weight of RF remote sensing payload electroni...

  3. Accessible Knowledge - Knowledge on Accessibility

    DEFF Research Database (Denmark)

    Kirkeby, Inge Mette

    2015-01-01

    Although serious efforts are made internationally and nationally, it is a slow process to make our physical environment accessible. In the actual design process, architects play a major role. But what kinds of knowledge, including research-based knowledge, do practicing architects make use of when...... designing accessible environments? The answer to the question is crucially important since it affects how knowledge is distributed and how accessibility can be ensured. In order to get first-hand knowledge about the design process and the sources from which they gain knowledge, 11 qualitative interviews...... were conducted with architects with experience of designing for accessibility. The analysis draws on two theoretical distinctions. The first is research-based knowledge versus knowledge used by architects. The second is context-independent knowledge versus context-dependent knowledge. The practitioners...

  4. 3D temperature field reconstruction using ultrasound sensing system

    Science.gov (United States)

    Liu, Yuqian; Ma, Tong; Cao, Chengyu; Wang, Xingwei

    2016-04-01

    3D temperature field reconstruction is of practical interest to the power, transportation and aviation industries and it also opens up opportunities for real time control or optimization of high temperature fluid or combustion process. In our paper, a new distributed optical fiber sensing system consisting of a series of elements will be used to generate and receive acoustic signals. This system is the first active temperature field sensing system that features the advantages of the optical fiber sensors (distributed sensing capability) and the acoustic sensors (non-contact measurement). Signals along multiple paths will be measured simultaneously enabled by a code division multiple access (CDMA) technique. Then a proposed Gaussian Radial Basis Functions (GRBF)-based approach can approximate the temperature field as a finite summation of space-dependent basis functions and time-dependent coefficients. The travel time of the acoustic signals depends on the temperature of the media. On this basis, the Gaussian functions are integrated along a number of paths which are determined by the number and distribution of sensors. The inversion problem to estimate the unknown parameters of the Gaussian functions can be solved with the measured times-of-flight (ToF) of acoustic waves and the length of propagation paths using the recursive least square method (RLS). The simulation results show an approximation error less than 2% in 2D and 5% in 3D respectively. It demonstrates the availability and efficiency of our proposed 3D temperature field reconstruction mechanism.

  5. Access Request Trustworthiness in Weighted Access Control Framework

    Institute of Scientific and Technical Information of China (English)

    WANG Lun-wei; LIAO Xiang-ke; WANG Huai-min

    2005-01-01

    Weighted factor is given to access control policies to express the importance of policy and its effect on access control decision. According to this weighted access control framework, a trustworthiness model for access request is also given. In this model, we give the measure of trustworthiness factor to access request, by using some idea of uncertainty reasoning of expert system, present and prove the parallel propagation formula of request trustworthiness factor among multiple policies, and get the final trustworthiness factor to decide whether authorizing. In this model, authorization decision is given according to the calculation of request trustworthiness factor, which is more understandable, more suitable for real requirement and more powerful for security enhancement than traditional methods. Meanwhile the finer access control granularity is another advantage.

  6. Open access

    CERN Document Server

    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 consent, and many authors, musicians, filmmakers, and other creators who depend on royalties are understandably unwilling to give their consent. But for 350 years, scholars have written peer-reviewed journal articles for impact, not for money, and are free to consent to open access without losing revenue. In this concise introduction, Peter Suber tells us what open access is and isn't, how it benefits authors and readers of research, how we pay for it, how it avoids copyright problems, how it has moved from the periphery to the mainstream, and what its future may hold. Distilling a decade of Suber's influential writing and thinking about open access, this is the indispe...

  7. An Efficient MAC Protocol With Selective Grouping and Cooperative Sensing in Cognitive Radio Networks

    OpenAIRE

    Liu, Yi; Xie, Shengli; Yu, Rong; Zhang, Yan; Yuen, Chau

    2013-01-01

    In cognitive radio networks, spectrum sensing is a crucial technique to discover spectrum opportunities for the Secondary Users (SUs). The quality of spectrum sensing is evaluated by both sensing accuracy and sensing efficiency. Here, sensing accuracy is represented by the false alarm probability and the detection probability while sensing efficiency is represented by the sensing overhead and network throughput. In this paper, we propose a group-based cooperative Medium Access Control (MAC) p...

  8. Multiple Payload Ejector for Education, Science and Technology Experiments

    Science.gov (United States)

    Lechworth, Gary

    2005-01-01

    The education research community no longer has a means of being manifested on Space Shuttle flights, and small orbital payload carriers must be flown as secondary payloads on ELV flights, as their launch schedule, secondary payload volume and mass permits. This has resulted in a backlog of small payloads, schedule and cost problems, and an inability for the small payloads community to achieve routine, low-cost access to orbit. This paper will discuss Goddard's Wallops Flight Facility funded effort to leverage its core competencies in small payloads, sounding rockets, balloons and range services to develop a low cost, multiple payload ejector (MPE) carrier for orbital experiments. The goal of the MPE is to provide a low-cost carrier intended primarily for educational flight research experiments. MPE can also be used by academia and industry for science, technology development and Exploration experiments. The MPE carrier will take advantage of the DARPAI NASA partnership to perform flight testing of DARPA s Falcon small, demonstration launch vehicle. The Falcon is similar to MPE fiom the standpoint of focusing on a low-cost, responsive system. Therefore, MPE and Falcon complement each other for the desired long-term goal of providing the small payloads community with a low-cost ride to orbit. The readiness dates of Falcon and MPE are complementary, also. MPE is being developed and readied for flight within 18 months by a small design team. Currently, MPE is preparing for Critical Design Review in fall 2005, payloads are being manifested on the first mission, and the carrier will be ready for flight on the first Falcon demonstration flight in summer, 2006. The MPE and attached experiments can weigh up to 900 lb. to be compatible with Falcon demonstration vehicle lift capabilities fiom Wallops, and will be delivered to the Falcon demonstration orbit - 100 nautical mile circular altitude.

  9. Architecture for the senses

    DEFF Research Database (Denmark)

    Ryhl, Camilla

    2009-01-01

    Accommodating sensory disabilities in architectural design requires specific design considerations. These are different from the ones included by the existing design concept 'accessibility', which primarily accommodates physical disabilites. Hence a new design concept 'sensory accessbility......' is presented as a parallel and complementary concept to the existing one. Sensory accessiblity accommodates sensory disabilities and describes architectural design requirements needed to ensure access to to the sensory experiences and architectural quality of a given space. The article is based on research...... findings from the PhD thesis 'A House for the Senses' by the author, a study of architectural requirements in housing design implied by a sensory impairment. The empirical research project is based on qualitative interviews and 1:1 testing in existing housing with participants who were either blind, deaf...

  10. Mobile and Accessible Learning for MOOCs

    Science.gov (United States)

    Sharples, Mike; Kloos, Carlos Delgado; Dimitriadis, Yannis; Garlatti, Serge; Specht, Marcus

    2015-01-01

    Many modern web-based systems provide a "responsive" design that allows material and services to be accessed on mobile and desktop devices, with the aim of providing "ubiquitous access." Besides offering access to learning materials such as podcasts and videos across multiple locations, mobile, wearable and ubiquitous…

  11. Hemodialysis access - self care

    Science.gov (United States)

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

  12. Ultrafast carrier dynamics in Landau-quantized graphene

    Directory of Open Access Journals (Sweden)

    Wendler Florian

    2015-01-01

    Full Text Available In an external magnetic field, the energy of massless charge carriers in graphene is quantized into non-equidistant degenerate Landau levels including a zero-energy level. This extraordinary electronic dispersion gives rise to a fundamentally new dynamics of optically excited carriers. Here, we review the state of the art of the relaxation dynamics in Landau-quantized graphene focusing on microscopic insights into possible many-particle relaxation channels.We investigate optical excitation into a non equilibrium distribution followed by ultrafast carrier- carrier and carrier-phonon scattering processes. We reveal that surprisingly the Auger scattering dominates the relaxation dynamics in spite of the non-equidistant Landau quantization in graphene. Furthermore, we demonstrate how technologically relevant carrier multiplication can be achieved and discuss the possibility of optical gain in Landau-quantized graphene. The provided microscopic view on elementary many-particle processes can guide future experimental studies aiming at the design of novel graphene-based optoelectronic devices, such as highly efficient photodetectors, solar cells, and spectrally broad Landau level lasers.

  13. Access French

    CERN Document Server

    Grosz, Bernard

    2014-01-01

    Access is the major new language series designed with the needs of today's generation of students firmly in mind. Whether learning for leisure or business purposes or working towards a curriculum qualification, Access French is specially designed for adults of all ages and gives students a thorough grounding in all the skills required to understand, speak, read and write contemporary French from scratch. The coursebook consists of 10 units covering different topic areas, each of which includes Language Focus panels explaining the structures covered and a comprehensive glossary. Learning tips

  14. Carrier Aggregation for LTE-Advanced

    DEFF Research Database (Denmark)

    Pedersen, Klaus Ingemann; Frederiksen, Frank; Rosa, Claudio;

    2011-01-01

    aggregated. This paper presents a summary of the supported CA scenarios as well as an overview of the CA functionality for LTE-Advanced with special emphasis on the basic concept, control mechanisms, and performance aspects. The discussion includes definitions of the new terms primary cell (PCell) and......Carrier aggregation (CA) is one of the key features for LTE-Advanced. By means of CA, users gain access to a total bandwidth of up to 100 MHz in order to meet the IMT-Advanced requirements. The system bandwidth may be contiguous, or composed of several non-contiguous bandwidth chunks, which are...... secondary cell (SCell), mechanisms for activation and deactivation of CCs, and the new cross-CC scheduling functionality for improved control channel optimizations. We also demonstrate how CA can be used as an enabler for simple yet effective frequency domain interference management schemes. In particular...

  15. Downlink Performance of a Multi-Carrier MIMO System in a Bursty Traffic Cellular Network

    DEFF Research Database (Denmark)

    Nguyen, Hung Tuan; Kovacs, Istvan; Wang, Yuanye;

    2011-01-01

    In this paper we analyse the downlink performance of a rank adaptive multiple input multiple output (MIMO) system in a busty traffic cellular network. A LTE-Advanced system with multiple component carriers was selected as a study case. To highlight the advantage of using MIMO techniques, we used...

  16. Compressed sensing based joint-compensation of power amplifier's distortions in OFDMA cognitive radio systems

    KAUST Repository

    Ali, Anum Z.

    2013-12-01

    Linearization of user equipment power amplifiers driven by orthogonal frequency division multiplexing signals is addressed in this paper. Particular attention is paid to the power efficient operation of an orthogonal frequency division multiple access cognitive radio system and realization of such a system using compressed sensing. Specifically, precompensated overdriven amplifiers are employed at the mobile terminal. Over-driven amplifiers result in in-band distortions and out of band interference. Out of band interference mostly occupies the spectrum of inactive users, whereas the in-band distortions are mitigated using compressed sensing at the receiver. It is also shown that the performance of the proposed scheme can be further enhanced using multiple measurements of the distortion signal in single-input multi-output systems. Numerical results verify the ability of the proposed setup to improve error vector magnitude, bit error rate, outage capacity and mean squared error. © 2011 IEEE.

  17. Performance Analysis on the Coexistence of Multiple Cognitive Radio Networks

    Directory of Open Access Journals (Sweden)

    Lijun Qian

    2015-05-01

    Full Text Available The demand for wireless services is growing on a daily basis while spectral resources to support this growth are static. Therefore, there is need for the adoption of a new spectrum sharing paradigm. Cognitive Radio (CR is a revolutionary technology aiming to increase spectrum utilization through dynamic spectrum access, as well as mitigating interference among multiple coexisting wireless networks. In many practical scenarios, multiple CR networks may coexist in the same geographical area, and they may interfere with each other and also have to yield to the primary user (PU. In this study, we investigate how much throughput a node in a CR network can achieve in the presence of another CR network and a PU. The results of this study illustrate how the transmission probability and sensing performance affect the achievable throughput of a node in coexisting CR networks. In addition, these results may serve as guidance for the deployment of multiple CR networks.

  18. Dynamics of unidirectional phonon-assisted transport of photoexcited carriers in step-graded In-x(Al0.17Ga0.83)(1-x)As/Al0.17Ga0.83As multiple quantum wells

    DEFF Research Database (Denmark)

    Machida, S.; Matsuo, M.; Fujiwara, K.;

    2003-01-01

    carriers is possible via phonon-assisted activation above the barrier band-edge state. We have directly measured this perpendicular motion of photoexcited carriers by monitoring the transient PL signals from the different wells, which are spectrally separated. A rate equation analysis rigorously explains...... the dynamical changes of the PL signal intensities from the quantum wells as a function of lattice temperature. Our study of PL dynamics proves the asymmetric perpendicular flow of photoexcited carriers and the capture by the deeper quantum wells, providing firm evidence for the dynamical carrier flow...... and capture processes in the novel heterostructure....

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

    Directory of Open Access Journals (Sweden)

    Meng Yi

    2016-11-01

    Full Text Available 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.

  20. Open Access Publishing in Astronomy

    Science.gov (United States)

    Grothkopf, U.; Meakins, S.

    2012-08-01

    Open Access (OA) in scholarly literature means the "immediate, free availability on the public internet, permitting any users to read, download, copy, distribute, print, search or link to the full text of these articles". The Open Access movement has been made possible thanks to the wide-spread availability of internet access and has received increasing interest since the 1990s, mostly due to the fast rising journal subscription prices. This presentation will review the current situation of Open Access in astronomy. It will answer the question why it makes sense to publish in an OA journal and will provide criteria to judge the quality of OA journals and publishers, along with suggestions how to identify so-called predatory publishers.

  1. Genotyping of Staphylococcus aureus strains isolated from healthy persistent carriers.

    Science.gov (United States)

    Grzegorczyk, Agnieszka; Malm, Anna

    2014-07-01

    The paper presents results on the relatedness of Staphylococcus aureus strains colonizing the upper respiratory tract isolated from healthy persistent carriers. Genotyping was carried out using two methods--multiple-locus variable-number tandem-repeat fingerprinting (MLVF) and pulsed-field gel electrophoresis (PFGE). By comparison of the results obtained by both methods, good correlations between MLVF and PFGE genotyping of strains isolated from the asymptomatic carriers were observed. Further studies are needed to evaluate methods useful for genotyping of S. aureus strains circulating in the community. PMID:24488811

  2. Non Sense

    DEFF Research Database (Denmark)

    Hjort, Katrin

    2010-01-01

    ’t make sense but appeared extremely complicated and contradictionary. This article studies the school reform through the filter of discourse analysis. The reform represents an advances version of liberal management and is construed as an alliance between 4 conflicting regimes of practice. Consequently...

  3. Video key frame extraction based on multiple compressive sensing and distances′computing%基于多重压缩感知和距离计算的视频关键帧提取

    Institute of Scientific and Technical Information of China (English)

    潘磊; 束鑫; 张静; 祁云嵩

    2015-01-01

    Key frame extraction is considered as the key issue of content-based video retrieval.An algorithm based on multiple compressive sensing and distances′computing is proposed.In the first step, each frame in one shot is segmented into several disjoint blocks, high dimensional features of which are generated by filtering. Then, multiple different sparse matrices that satisfy restricted isometry property are employed to sample the high dimensional feature of each block, and the mean value of sampling is calculated as the low dimensional feature of each block.Several different distances are used to compute differences between corresponding blocks of neigh-boring frames to conduct sub-shot segmentation.The frame nearest to the average content of each sub-shot is se-lected as the key frame.Experimental results demonstrate that key frames extracted by the proposed algorithm can describe the main content of shot accurately.%关键帧提取是基于内容的视频检索技术的关键问题.文中提出一种基于多重压缩感知和距离计算的关键帧提取算法,首先将镜头内的各帧图像分割为若干不相交的块,通过滤波器生成块的高维特征;然后利用多个不同的、具有有限等距性质的稀疏矩阵对块高维特征进行采样,将采样的均值作为块的低维特征;采用多种距离计算相邻帧对应块之间的差异,完成子镜头的分割操作,在每个子镜头内部,选取与该子镜头平均内容最接近的帧作为关键帧.实验表明,该算法提取出的关键帧能够准确描述镜头的主要内容.

  4. A Fine-Grained Data Access Control System in Wireless Sensor Network

    Directory of Open Access Journals (Sweden)

    Boniface K. Alese

    2015-12-01

    Full Text Available The evolving realities of Wireless Sensor Network (WSN deployed to various terrain of life require serving multiple applications. As large amount of sensed data are distributed and stored in individual sensors nodes, the illegal access to these sensitive data can be devastating. Consequently, data insecurity becomes a big concern. This study, therefore, proposes a fine-grained access control system which only requires the right set of users to access a particular data, based on their access privileges in the sensor networks. It is designed using Priccess Protocol with Access policy formulation adopting the principle of Bell Lapadula model as well as Attribute-Based Encryption (ABE to control access to sensor data. The functionality of the proposed system is simulated using Netbeans. The performance analysis of the proposed system using execution time and size of the key show that the higher the key size, the harder it becomes for the attacker to hack the system. Additionally, the time taken for the proposed work is lesser which makes the work faster than the existing work. Consequently, a well secure interactive web-based application that could facilitates the field officers access to stored data in safe and secure manner is developed.

  5. Imaging ultrafast carrier transport in nanoscale devices using femtosecond photocurrent microscopy

    CERN Document Server

    Son, B H; Hong, J T; Park, Ji-Yong; Lee, Soonil; Ahn, Y H

    2014-01-01

    One-dimensional nanoscale devices, such as semiconductor nanowires (NWs) and single- walled carbon nanotubes (SWNTs), have been intensively investigated because of their potential application of future high-speed electronic, optoelectronic, and sensing devices. To overcome current limitations on the speed of contemporary devices, investigation of charge carrier dynamics with an ultrashort time scale is one of the primary steps necessary for developing high-speed devices. In the present study, we visualize ultrafast carrier dynamics in nanoscale devices using a combination of scanning photocurrent microscopy and time- resolved pump-probe techniques. We investigate transit times of carriers that are generated near one metallic electrode and subsequently transported toward the opposite electrode based on drift and diffusion motions. Carrier dynamics have been measured for various working conditions. In particular, the carrier velocities extracted from transit times increase for a larger negative gate bias, becau...

  6. Straddle carrier radiation portal monitoring

    Science.gov (United States)

    Andersen, Eric S.; Samuel, Todd J.; Mullen, O. Dennis

    2005-05-01

    U.S. Customs and Border Protection (CBP) is the primary enforcement agency protecting the nation"s ports of entry. CBP is enhancing its capability to interdict the illicit import of nuclear and radiological materials and devices that may be used by terrorists. Pacific Northwest National Laboratory (PNNL) is providing scientific and technical support to CBP in their goal to enable rapid deployment of nuclear and radiation detection systems at U. S. ports of entry to monitor 100% of the incoming international traffic and cargo while not adversely impacting the operations or throughput of the ports. The U.S. ports of entry include the following vectors: land border crossings, seaports, airports, rail crossings, and mail and express consignment courier facilities. U.S. Customs and Border Protection (CBP) determined that a screening solution was needed for Seaport cargo containers being transported by Straddle Carriers (straddle carriers). A stationary Radiation Portal Monitor (RPM) for Straddle Carriers (SCRPM) is needed so that cargo containers can be scanned while in transit under a Straddle Carrier. The Straddle Carrier Portal operational impacts were minimized by conducting a time-motion study at the Port, and adaptation of a Remotely Operated RPM (RO-RPM) booth concept that uses logical lighting schemes for traffic control, cameras, Optical Character Recognition, and wireless technology.

  7. Impact of carriers in oral absorption

    DEFF Research Database (Denmark)

    Gram, Luise Kvisgaard; Rist, Gerda Marie; Lennernäs, Hans;

    2009-01-01

    Carriers may mediate the permeation across enterocytes for drug substances being organic anions. Carrier mediated permeation for the organic anions estrone-3-sulfate (ES) and glipizide across Caco-2 cells were investigated kinetically, and interactions on involved carriers evaluated. Initial......(APP) was not described by carrier kinetics. However, glipizide is affecting exsorption for ES, due to interactions on basolateral carrier. The study confirms that estrone-3-sulfate can be used to characterize anionic carrier kinetics. Furthermore it is suggested that estrone-3-sulfate may be used to identify compounds...... which may interact on anionic carriers....

  8. A new access scheme in OFDMA systems

    Institute of Scientific and Technical Information of China (English)

    GU Xue-lin; YAN Wei; TIAN Hui; ZHANG Ping

    2006-01-01

    This article presents a dynamic random access scheme for orthogonal frequency division multiple access (OFDMA) systems. The key features of the proposed scheme are:it is a combination of both the distributed and the centralized schemes, it can accommodate several delay sensitivity classes,and it can adjust the number of random access channels in a media access control (MAC) frame and the access probability according to the outcome of Mobile Terminals access attempts in previous MAC frames. For floating populated packet-based networks, the proposed scheme possibly leads to high average user satisfaction.

  9. Multiple snapshot compressive beamforming

    DEFF Research Database (Denmark)

    Gerstoft, Peter; Xenaki, Angeliki; Mecklenbrauker, Christoph F.;

    2015-01-01

    For sound fields observed on an array, compressive sensing (CS) reconstructs the multiple source signals at unknown directions-of-arrival (DOAs) using a sparsity constraint. The DOA estimation is posed as an underdetermined problem expressing the field at each sensor as a phase-lagged superposition...

  10. J-Earth: Remote Sensing Analysis Made Easy

    Science.gov (United States)

    Dickenshied, S.; Christensen, P. R.; Prashad, L. C.; Noss, D.; Anwar, S.; Cheeseman, S.; Dunn, S.; Rupp, J.

    2011-12-01

    A wealth of terrestrial remote sensing data has been collected and made public over the years from a variety of missions, but accessing this data and performing analysis on it has often been a time consuming and problematic task. J-Earth is a geospatial application that provides a quick and consistent means of accessing many terrestrial datasets which can then be analyzed and compared with each other. In addition to providing direct access to a number of preprocessed products based off of MODIS, ASTER, and TIMS datasets, J-Earth also makes it easy for a user to import their own data and work with it in an identical fashion. Users can easily work with both graphical and numeric datasets as well as vector/shapefile data. Numeric data can be viewed for a particular location through multiple datasets or plotted across an arbitrary profile line. Shapes can be used to find intersections with other shapefiles or to perform analytical calculations (mean, max, min, etc) upon numeric data within the bounds of a shape. These tools allow a user to quickly assess the geologic parameters of the area, including mineralogy, chemistry, surface temperature, topography and elevation. Additionally, J-Earth allows for temporal comparisons of regions for instruments which have repeat coverage over multiple years. J-Earth is part of the JMARS (Java Mission-planning and Analysis for Remote Sensing) suite of geospatial applications developed by the Mars Space Flight Facility at Arizona State University. This suite of software is used for mission planning and scientific data analysis by active NASA missions to Mars, the Moon, and Vesta. It is used by scientists, researchers and students of all ages from more than 40 countries around the world.

  11. Performance analysis of multichannel medium access control algorithms for opportunistic spectrum access

    NARCIS (Netherlands)

    Pawelczak, P.; Pollin, S.; So, H.-S.W.; Bahai, A.R.S.; Prasad, R.V.; Hekmat, R.

    2009-01-01

    In this paper, different control channel (CC) implementations for multichannel medium access control (MAC) algorithms are compared and analyzed in the context of opportunistic spectrum access (OSA) as a function of spectrum-sensing performance and licensed user activity. The analysis is based on a d

  12. Localized charge carriers in graphene nanodevices

    Energy Technology Data Exchange (ETDEWEB)

    Bischoff, D., E-mail: dominikb@phys.ethz.ch; Varlet, A.; Simonet, P.; Eich, M.; Overweg, H. C.; Ihn, T.; Ensslin, K. [Solid State Physics Laboratory, ETH Zurich, 8093 Zurich (Switzerland)

    2015-09-15

    Graphene—two-dimensional carbon—is a material with unique mechanical, optical, chemical, and electronic properties. Its use in a wide range of applications was therefore suggested. From an electronic point of view, nanostructured graphene is of great interest due to the potential opening of a band gap, applications in quantum devices, and investigations of physical phenomena. Narrow graphene stripes called “nanoribbons” show clearly different electronical transport properties than micron-sized graphene devices. The conductivity is generally reduced and around the charge neutrality point, the conductance is nearly completely suppressed. While various mechanisms can lead to this observed suppression of conductance, disordered edges resulting in localized charge carriers are likely the main cause in a large number of experiments. Localized charge carriers manifest themselves in transport experiments by the appearance of Coulomb blockade diamonds. This review focuses on the mechanisms responsible for this charge localization, on interpreting the transport details, and on discussing the consequences for physics and applications. Effects such as multiple coupled sites of localized charge, cotunneling processes, and excited states are discussed. Also, different geometries of quantum devices are compared. Finally, an outlook is provided, where open questions are addressed.

  13. 49 CFR 1544.219 - Carriage of accessible weapons.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 9 2010-10-01 2010-10-01 false Carriage of accessible weapons. 1544.219 Section...: AIR CARRIERS AND COMMERCIAL OPERATORS Operations § 1544.219 Carriage of accessible weapons. (a... weapons, do not apply to a law enforcement officer (LEO) aboard a flight for which screening is...

  14. 47 CFR 36.213 - Network access services revenues.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 2 2010-10-01 2010-10-01 false Network access services revenues. 36.213 Section 36.213 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES... Income Accounts Operating Revenues § 36.213 Network access services revenues. (a) End User...

  15. HORIZON SENSING

    Energy Technology Data Exchange (ETDEWEB)

    Larry G. Stolarczyk, Sc.D.

    2002-07-31

    Real-time horizon sensing (HS) on continuous mining (CM) machines is becoming an industry tool. Installation and testing of production-grade HS systems has been ongoing this quarter at Oxbow Mining Company, Monterey Coal Company (EXXON), FMC Trona, Twentymile Coal Company (RAG America), and SASOL Coal. Detailed monitoring of system function, user experience, and mining benefits is ongoing. All horizon sensor components have finished MSHA (United States) and IEC (International) certification.

  16. Hemodialysis access procedures

    Science.gov (United States)

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

  17. Get the right access rights!

    CERN Multimedia

    Rosaria Marraffino

    2015-01-01

    On 11 May, a major change concerning the requirements to access the CERN beam facilities was put in place and implemented in ADaMS in order to reduce the number of courses that people who need access to multiple installations have to follow. This revision includes dedicated safety training courses that replace, in particular, the “Safety during LS1” e-learning course, which is now to be considered obsolete.   CERN’s Access Distribution and Management System (ADaMS). As of 11 May, an important improvement was implemented in ADaMS (CERN’s Access Distribution and Management System) regarding the requisites to access safety zones. This change is closely related to the introduction of a generic e-learning course ("CERN Beam Facilities") covering the common risks and systems present in CERN's beam facilities. Two e-learning courses are no longer valid, nor available on the SIR (Safety Information Registration) catalogue: the &ld...

  18. Optimal Joint Allocation of MultiSlot Spectrum Sensing and Transfer Power in MultiChannel Cognitive Radio

    Directory of Open Access Journals (Sweden)

    Xin Liu

    2014-01-01

    Full Text Available In multichannel, cognitive radio (CR, the secondary user (SU is allowed to utilize multiple subaltern frequency bands of the primary user (PU, when these bands, namely, subchannels are not currently being used. To support this spectrum reuse functionality, the SU is required to sense each subchannel, and only the subchannels wherein the PU is inactive are available for the spectrum access of the SU. In this paper, a multislot spectrum sensing and transfer scheme for multichannel CR is proposed, whose sensing stage is divided into several time slots allocated to the subchannels for spectrum sensing. While guaranteeing the spectrum sensing performance on each subchannel and limiting the interference to the PU, we formulate an optimization problem that maximizes the SU’s aggregate throughput by jointly allocating the optimal number of sensing time slots and the optimal transfer power to each subchannel. Theoretical analysis is given to prove the feasibility of the proposed optimization problem and simulation results are presented to show the notable improvement on the SU’s throughput when the sensing time slots and the transfer power are both optimized by the proposed scheme.

  19. 49 CFR 1548.15 - Access to cargo: Security threat assessments for individuals having unescorted access to cargo.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 9 2010-10-01 2010-10-01 false Access to cargo: Security threat assessments for... SECURITY CIVIL AVIATION SECURITY INDIRECT AIR CARRIER SECURITY § 1548.15 Access to cargo: Security threat... must successfully complete a security threat assessment or comparable security threat...

  20. Making Your Website More Accessible. Tips

    Science.gov (United States)

    Arnone, Marilyn

    2007-01-01

    Employing Universal Design for Learning (UDL) principles, such as multiple means of representation (of content), multiple means of engagement (motivation) and multiple means of expression (sharing the results of research, for example), will put one on the right path toward increasing accessibility for all learners. In this article, the author…

  1. Harmony Search Algorithm for Word Sense Disambiguation

    OpenAIRE

    Saad Adnan Abed; Sabrina Tiun; Nazlia Omar

    2015-01-01

    Word Sense Disambiguation (WSD) is the task of determining which sense of an ambiguous word (word with multiple meanings) is chosen in a particular use of that word, by considering its context. A sentence is considered ambiguous if it contains ambiguous word(s). Practically, any sentence that has been classified as ambiguous usually has multiple interpretations, but just one of them presents the correct interpretation. We propose an unsupervised method that exploits knowledge based approaches...

  2. Cell carriers for oncolytic viruses: current challenges and future directions

    Directory of Open Access Journals (Sweden)

    Roy DG

    2013-10-01

    Full Text Available Dominic G Roy,1,2 John C Bell1–31Centre for Innovative Cancer Therapeutics, Ottawa Hospital Research Institute, 2Department of Biochemistry, Immunology and Microbiology, 3Department of Medicine, University of Ottawa, Ottawa, ON, CanadaAbstract: The optimal route for clinical delivery of oncolytic viruses is thought to be systemic intravenous injection; however, the immune system is armed with several highly efficient mechanisms to remove pathogens from the circulatory system. To overcome the challenges faced in trying to delivery oncolytic viruses specifically to tumors via the bloodstream, carrier cells have been investigated to determine their suitability as delivery vehicles for systemic administration of oncolytic viruses. Cell carriers protect viruses from neutralization, one of the most limiting aspects of oncolytic virus interaction with the immune system. Cell carriers can also possess inherent tumor tropism, thus directing the delivery of the virus more specifically to a tumor. With preclinical studies already demonstrating the success and feasibility of this approach with multiple oncolytic viruses, clinical evaluation of cell-mediated delivery of viruses is on the horizon. Meanwhile, ongoing preclinical studies are aimed at identifying new cellular vehicles for oncolytic viruses and improving current promising cell carrier platforms.Keywords: oncolytic virus, cell carrier, systemic delivery, tumor targeting, cancer

  3. Hot carrier degradation in semiconductor devices

    CERN Document Server

    2015-01-01

    This book provides readers with a variety of tools to address the challenges posed by hot carrier degradation, one of today’s most complicated reliability issues in semiconductor devices.  Coverage includes an explanation of carrier transport within devices and book-keeping of how they acquire energy (“become hot”), interaction of an ensemble of colder and hotter carriers with defect precursors, which eventually leads to the creation of a defect, and a description of how these defects interact with the device, degrading its performance. • Describes the intricacies of hot carrier degradation in modern semiconductor technologies; • Covers the entire hot carrier degradation phenomenon, including topics such as characterization, carrier transport, carrier-defect interaction, technological impact, circuit impact, etc.; • Enables detailed understanding of carrier transport, interaction of the carrier ensemble with the defect precursors, and an accurate assessment of how the newly created defects imp...

  4. Autonomous Component Carrier Selection for 4G Femtocells

    DEFF Research Database (Denmark)

    Garcia, Luis Guilherme Uzeda; Kovacs, Istvan; Pedersen, Klaus;

    2012-01-01

    This paper addresses the interference management problem in the context of LTE-Advanced femtocells. Due to the expected large number of user-deployed cells, centralized network planning becomes increasingly less viable. Consequently, we consider an architecture of autonomous decision makers. Our...... main contribution in this paper, denominated Generalized Autonomous Component Carrier Selection (G-ACCS), is a distributed carrier-based inter-cell interference coordination scheme that represents one step towards cognitive radio networks. The algorithm relies on expected rather than sensed...... reuse strategy. The encouraging simulation results demonstrate that G-ACCS achieves an efficient and fair distribution of resources in all considered traffic and deployment conditions. More importantly, this is attained in a truly autonomous fashion, without any explicit parametrization....

  5. Visual Tracking with Multiple Instance Learning Based on Compressive Sensing%基于压缩感知的在线多示例学习目标追踪

    Institute of Scientific and Technical Information of China (English)

    韩亚颖; 王元全

    2014-01-01

    近年来提出的多示例学习算法在一定程度上能够克服模板漂移问题。然而,在线学习需要获取足够多的有用数据才能达到稳定的追踪效果,但是这却增加了算法的复杂度。为了解决这一问题,在压缩感知理论的基础上,运用随机观测的方法对多尺度图像特征进行降维,提取的这些低维特征中包含大量的有用信息。因此,我们提出的算法是先利用压缩感知理论提取目标特征之后,再使用在线多示例学习算法分类器对这些特征进行分类从而实现目标的稳定跟踪。通过对不同的图像序列进行实验,结果表明基于压缩感知的在线多示例学习算法对实时的目标追踪有很好的适应性。%Visual tracking is one of the most popular research topics in the domain of computer vision.It is a challenging task to develop an effective and efficient tracking algorithm because of template drift prob-lems.To alleviate the drift,the multiple instance learning (MIL)method has been applied to target track-ing.However,there must be a sufficient amount of useful data for online MIL to learn at the outset, which actually increases the computational complexity.In this paper,an effective tracking algorithm is proposed which uses an online MIL based on the compressed appearance model to accomplish obj ect track-ing.In order to decrease the computational complexity and obtain sufficient data for online learning adap-tive appearance model,Features are extracted by non-adaptive random proj ections of the multi-scale image feature space based on compressive sensing theories.The experimental results on various videos show that the proposed method has a satisfactory performance in real-time obj ect tracking.

  6. HORIZON SENSING

    Energy Technology Data Exchange (ETDEWEB)

    Larry G. Stolarczyk

    2003-03-18

    With the aid of a DOE grant (No. DE-FC26-01NT41050), Stolar Research Corporation (Stolar) developed the Horizon Sensor (HS) to distinguish between the different layers of a coal seam. Mounted on mining machine cutter drums, HS units can detect or sense the horizon between the coal seam and the roof and floor rock, providing the opportunity to accurately mine the section of the seam most desired. HS also enables accurate cutting of minimum height if that is the operator's objective. Often when cutting is done out-of-seam, the head-positioning function facilitates a fixed mining height to minimize dilution. With this technology, miners can still be at a remote location, yet cut only the clean coal, resulting in a much more efficient overall process. The objectives of this project were to demonstrate the feasibility of horizon sensing on mining machines and demonstrate that Horizon Sensing can allow coal to be cut cleaner and more efficiently. Stolar's primary goal was to develop the Horizon Sensor (HS) into an enabling technology for full or partial automation or ''agile mining''. This technical innovation (R&D 100 Award Winner) is quickly demonstrating improvements in productivity and miner safety at several prominent coal mines in the United States. In addition, the HS system can enable the cutting of cleaner coal. Stolar has driven the HS program on the philosophy that cutting cleaner coal means burning cleaner coal. The sensor, located inches from the cutting bits, is based upon the physics principles of a Resonant Microstrip Patch Antenna (RMPA). When it is in proximity of the rock-coal interface, the RMPA impedance varies depending on the thickness of uncut coal. The impedance is measured by the computer-controlled electronics and then sent by radio waves to the mining machine. The worker at the machine can read the data via a Graphical User Interface, displaying a color-coded image of the coal being cut, and direct the machine

  7. Developing an On-Demand Cloud-Based Sensing-as-a-Service System for Internet of Things

    Directory of Open Access Journals (Sweden)

    Mihui Kim

    2016-01-01

    Full Text Available The increasing number of Internet of Things (IoT devices with various sensors has resulted in a focus on Cloud-based sensing-as-a-service (CSaaS as a new value-added service, for example, providing temperature-sensing data via a cloud computing system. However, the industry encounters various challenges in the dynamic provisioning of on-demand CSaaS on diverse sensor networks. We require a system that will provide users with standardized access to various sensor networks and a level of abstraction that hides the underlying complexity. In this study, we aim to develop a cloud-based solution to address the challenges mentioned earlier. Our solution, SenseCloud, includes a sensor virtualization mechanism that interfaces with diverse sensor networks, a multitenancy mechanism that grants multiple users access to virtualized sensor networks while sharing the same underlying infrastructure, and a dynamic provisioning mechanism to allow the users to leverage the vast pool of resources on demand and on a pay-per-use basis. We implement a prototype of SenseCloud by using real sensors and verify the feasibility of our system and its performance. SenseCloud bridges the gap between sensor providers and sensor data consumers who wish to utilize sensor data.

  8. Ultrafast Probe of Carrier Diffusion and Nongeminate Processes in a Single CdSSe Nanowire

    Directory of Open Access Journals (Sweden)

    Peter S. Eldridge

    2015-01-01

    Full Text Available We measure ultrafast carrier dynamics in a single CdSSe nanowire at different excitation fluences using an ultrafast Kerr-gated microscope. The time-resolved emission exhibits a dependence on excitation fluence, with the onset of the emission varying on the picosecond time scale with increasing laser power. By fitting the emission to a model for amplified spontaneous emission (ASE, we are able to extract the nonradiative carrier recombination lifetime and nongeminate recombination constant. The extracted nongeminate recombination constant suggests that our measurement technique allows the access to the nondiffusion limited recombination regime in nanowires with low carrier mobility.

  9. 三时隙分布式电力调度时分多址自动化控制%Automatic Scheduling Control of Power with Efficient Time Division Multiple Access Method Based on Three Slot Time Distributions

    Institute of Scientific and Technical Information of China (English)

    王俊士

    2014-01-01

    An intelligent distributed power scheduling system was proposed based on collaborative scheduling, the three slot time distributions concept was proposed for the management, and the efficient tome division multiple access method was introduced to collect the consumption information, considering the load capacity of the entire grid, each node of the in-telligent power distribution was set, and the feedback system was used to adjust the resume continuously for optimum power supply state. A series of nodes were used to test the ability, the result shows that the distributed cooperative scheduling algo-rithm has better scheduling efficient in the system, with the same load conditions, the average efficiency of the system was improved 15%, it can be used widely in the power management application.%提出一种智能分布式电力调度系统的协同调度方法,采用三类时隙,即前导时隙、若干中断时隙和大量分配时隙分布式管理的思想,采用高效时分多址协议对每个电网节点的耗电信息进行收集,然后采用协调调度,综合考虑整个电网的负载能力,对每个节点的供电进行智能化的分配,并且采用反馈系统不断调整,达到最优供电状态;采用一组节点进行实际的供电管理实验,结果显示,分布式协同调度算法能够更加高效的调度系统电力,相同载荷情况下,平均效率高出约15%,在电力管理系统中具有广泛应用的价值。

  10. Plasmonic sensing

    DEFF Research Database (Denmark)

    Mogensen, Klaus Bo

    2015-01-01

    that cannot be obtained by traditional refractive index sensing, without the use of bioprobes. A simple modified Drude model is used to account for shifts in the plasmon band position due to electrical charging. Here, a screening parameter is introduced in the expression for the free electron density...... particle ensemble, thereby overcoming typical variations due to differences between samples. For small particle sizes, charge displacement/transfer processes at the particle surface can change the material properties and morphology of the NPs dramatically, resulting in, e.g., a decrease of and a blue shift...

  11. A Robust Cooperative Spectrum Sensing-Assisted Multiuser Resource Allocation Scheme

    Directory of Open Access Journals (Sweden)

    Jun Du

    2015-01-01

    Full Text Available Cognitive radio (CR, which is proposed as a solution for spectrum scarcity, imposes some threats to the network. One severe attack to cognitive radio network is the primary user emulation attack (PUEA, in which an attacker may transmit its signal with high power or mimic specific features of the primary user’s signal to prevent secondary users from accessing the licensed spectrum. In this paper, we study a subcarrier and power allocation problem for orthogonal frequency division multiple access-(OFDMA- based CR systems in the presence of PUEA. To maximize the system throughput while keeping the interference introduced to the primary user (PU below given thresholds with a certain probability, a joint design of a robust cooperative spectrum sensing and a resource allocation scheme is proposed. In the proposed scheme, the inaccurate classification of PU signals and PUEA signals provided by robust cooperative spectrum sensing is utilized by resource scheduling module. To further exploit the underutilized spectrum bands, we also evaluate the performance of the proposed scheme in the hybrid overlay/underlay spectrum access mechanism. Numerical results demonstrate the effectiveness of the proposed scheme compared to conventional scheme regardless of the number of SUs or the kind of spectrum access mechanism being used.

  12. Clipping Noise Cancellation for OFDM and OFDMA Systems Using Compressed Sensing

    CERN Document Server

    Kim, Kee-Hoon; No, Jong-Seon; Chung, Habong

    2011-01-01

    In this paper, we propose clipping noise cancellation scheme using compressed sensing (CS) for orthogonal frequency division multiplexing (OFDM) systems. In the proposed scheme, only the data tones with high reliability are exploited in reconstructing the clipping noise instead of the whole data tones. For reconstructing the clipping noise using a fraction of the data tones at the receiver, the CS technique is applied. The proposed scheme is also applicable to interleaved orthogonal frequency division multiple access (OFDMA) systems due to the decomposition of fast Fourier transform (FFT) structure. Numerical analysis shows that the proposed scheme performs well for clipping noise cancellation of both OFDM and OFDMA systems.

  13. Accessing the exceptional points of parity-time symmetric acoustics

    Science.gov (United States)

    Shi, Chengzhi; Dubois, Marc; Chen, Yun; Cheng, Lei; Ramezani, Hamidreza; Wang, Yuan; Zhang, Xiang

    2016-03-01

    Parity-time (PT) symmetric systems experience phase transition between PT exact and broken phases at exceptional point. These PT phase transitions contribute significantly to the design of single mode lasers, coherent perfect absorbers, isolators, and diodes. However, such exceptional points are extremely difficult to access in practice because of the dispersive behaviour of most loss and gain materials required in PT symmetric systems. Here we introduce a method to systematically tame these exceptional points and control PT phases. Our experimental demonstration hinges on an active acoustic element that realizes a complex-valued potential and simultaneously controls the multiple interference in the structure. The manipulation of exceptional points offers new routes to broaden applications for PT symmetric physics in acoustics, optics, microwaves and electronics, which are essential for sensing, communication and imaging.

  14. Protein carriers of conjugate vaccines: characteristics, development, and clinical trials.

    Science.gov (United States)

    Pichichero, Michael E

    2013-12-01

    The immunogenicity of polysaccharides as human vaccines was enhanced by coupling to protein carriers. Conjugation transformed the T cell-independent polysaccharide vaccines of the past to T cell-dependent antigenic vaccines that were much more immunogenic and launched a renaissance in vaccinology. This review discusses the conjugate vaccines for prevention of infections caused by Hemophilus influenzae type b, Streptococcus pneumoniae, and Neisseria meningitidis. Specifically, the characteristics of the proteins used in the construction of the vaccines including CRM, tetanus toxoid, diphtheria toxoid, Neisseria meningitidis outer membrane complex, and Hemophilus influenzae protein D are discussed. The studies that established differences among and key features of conjugate vaccines including immunologic memory induction, reduction of nasopharyngeal colonization and herd immunity, and antibody avidity and avidity maturation are presented. Studies of dose, schedule, response to boosters, of single protein carriers with single and multiple polysaccharides, of multiple protein carriers with multiple polysaccharides and conjugate vaccines administered concurrently with other vaccines are discussed along with undesirable consequences of conjugate vaccines. The clear benefits of conjugate vaccines in improving the protective responses of the immature immune systems of young infants and the senescent immune systems of the elderly have been made clear and opened the way to development of additional vaccines using this technology for future vaccine products. PMID:23955057

  15. 47 CFR 51.321 - Methods of obtaining interconnection and access to unbundled elements under section 251 of the Act.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 3 2010-10-01 2010-10-01 false Methods of obtaining interconnection and access... COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES (CONTINUED) INTERCONNECTION Additional Obligations of Incumbent Local Exchange Carriers § 51.321 Methods of obtaining interconnection and access...

  16. Fatigue reliability for LNG carrier

    Institute of Scientific and Technical Information of China (English)

    Xiao Taoyun; Zhang Qin; Jin Wulei; Xu Shuai

    2011-01-01

    The procedure of reliability-based fatigue analysis of liquefied natural gas (LNG) carrier of membrane type under wave loads is presented. The stress responses of the hotspots in regular waves with different wave heading angles and wave lengths are evaluated by global ship finite element method (FEM). Based on the probabilistic distribution function of hotspots' short-term stress-range using spectral-based analysis, Weibull distribution is adopted and discussed for fitting the long-term probabilistic distribution of stress-range. Based on linear cumulative damage theory, fatigue damage is characterized by an S-N relationship, and limit state function is established. Structural fatigue damage behavior of several typical hotspots of LNG middle ship section is clarified and reliability analysis is performed. It is believed that the presented results and conclusions can be of use in calibration for practical design and initial fatigue safety evaluation for membrane type LNG carrier.

  17. Gemini surfactants as gene carriers

    Directory of Open Access Journals (Sweden)

    Teresa Piskorska

    2010-03-01

    Full Text Available Gemini surfactants are a new class of amphiphilic compounds built from two classic surfactant moieties bound together by a special spacer group. These compounds appear to be excellent for creating complexes with DNA and are effective in mediating transfection. Thanks to their construction, DNA carrier molecules built from gemini surfactants are able to deliver genes to cells of almost any DNA molecule size, unattainable when using viral gene delivery systems. Moreover, they are much safer for living organisms.

  18. Intelligent card access keys

    International Nuclear Information System (INIS)

    A newly developed access control technology allows information about users to be stored on key-like EEPROM devices. The keys store encrypted information about the user and his or her authorized access activity. Specially developed key readers scan, decrypt, and process the key data, and make the decision whether entry should be granted or denied. The key readers can function as complete, stand-alone facility management systems, incorporating access control, security monitoring, and remote control. In this configuration, the key readers provide anti-passback protection and other special features without requiring any data lines between readers. The key readers also feature sophisticated algorithmic processing for performing complex operations such as two-man control or cross zoned security annunciation. Key readers can also be interconnected with an MCM-1000 Multiples Monitoring System to form a distributed processing local area network. In such a configuration, changes in key reader status can be uploaded to the MCM-1000, and programming changes and operator commands can be downloaded to the key readers

  19. Preventative maintenance of straddle carriers

    Directory of Open Access Journals (Sweden)

    Si Li

    2015-02-01

    Full Text Available Background: Robotic vehicles such as straddle carriers represent a popular form of cargo handling amongst container terminal operators.Objectives: The purpose of this industry-driven study is to model preventative maintenance (PM influences on the operational effectiveness of straddle carriers.Method: The study employs historical data consisting of 21 273 work orders covering a 27-month period. Two models are developed, both of which forecast influences of PM regimes for different types of carrier.Results: The findings of the study suggest that the reliability of the straddle fleet decreases with increased intervals of PM services. The study also finds that three factors – namely resources, number of new straddles, and the number of new lifting work centres – influence the performances of straddles.Conclusion: The authors argue that this collaborative research exercise makes a significant contribution to existing supply chain management literature, particularly in the area of operations efficiency. The study also serves as an avenue to enhance relevant management practice.

  20. Remote Sensing Training for Middle School through the Center of Excellence in Remote Sensing Education

    Science.gov (United States)

    Hayden, L. B.; Johnson, D.; Baltrop, J.

    2012-12-01

    Remote sensing has steadily become an integral part of multiple disciplines, research, and education. Remote sensing can be defined as the process of acquiring information about an object or area of interest without physical contact. As remote sensing becomes a necessity in solving real world problems and scientific questions an important question to consider is why remote sensing training is significant to education and is it relevant to training students in this discipline. What has been discovered is the interest in Science, Technology, Engineering and Mathematics (STEM) fields, specifically remote sensing, has declined in our youth. The Center of Excellence in Remote Sensing Education and Research (CERSER) continuously strives to provide education and research opportunities on ice sheet, coastal, ocean, and marine science. One of those continued outreach efforts are Center for Remote Sensing of Ice Sheets (CReSIS) Middle School Program. Sponsored by the National Science Foundation CReSIS Middle School Program offers hands on experience for middle school students. CERSER and NSF offer students the opportunity to study and learn about remote sensing and its vital role in today's society as it relate to climate change and real world problems. The CReSIS Middle School Program is an annual two-week effort that offers middle school students experience with remote sensing and its applications. Specifically, participants received training with Global Positioning Systems (GPS) where the students learned the tools, mechanisms, and applications of a Garmin 60 GPS. As a part of the program the students were required to complete a fieldwork assignment where several longitude and latitude points were given throughout campus. The students had to then enter the longitude and latitude points into the Garmin 60 GPS, navigate their way to each location while also accurately reading the GPS to make sure travel was in the right direction. Upon completion of GPS training the