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Sample records for adaptive medium access

  1. Adaptive Medium Access Control Protocol for Wireless Body Area Networks

    Javaid, N.; Ahmad, A.; A. Rahim; Z.A. Khan; M. Ishfaq; Qasim, U.

    2014-01-01

    Wireless Body Area Networks (WBANs) are widely used for applications such as modern health-care systems, where wireless sensors (nodes) monitor the parameter(s) of interest. Nodes are provided with limited battery power and battery power is dependent on radio activity. MAC protocols play a key role in controlling the radio activity. Therefore, we present Adaptive Medium Access Control (A-MAC) protocol for WBANs supported by linear programming models for the minimization of energy consumption ...

  2. Traffic-adaptive, flow-specific medium access for wireless networks

    Walker, T. Owens; Tummala, Murali; McEachen, John

    2009-01-01

    In this report, we formally introduce the novel concept of traffic-adaptive, flow-specific medium access control and show that it outperforms contention, non-contention and hybrid medium access schemes. A traffic-adaptive, flow-specific mechanism is proposed that utilizes flow-specific queue size statistics to select between medium access modes. A general model for traffic adaptive, flow-specific medium access control is developed and it is shown that hybrid medium access as well as traditio...

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

    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....

  4. Design and Analysis of an Attack Resilient and Adaptive Medium access Control Protocol for Computer Networks

    Shukla, Piyush Kumar; Bhadoria, Dr Sarita Singh

    2009-01-01

    The challenge of designing an efficient Medium Access Control (MAC) protocol and analyzing it has been an important research topic for over 30 years. This paper focuses on the performance analysis (through simulation) and modification of a well known MAC protocol CSMA/CD. The existing protocol does not consider the wastage of bandwidth due to unutilized periods of the channel. By considering this fact, performance of MAC protocol can be enhanced. The purpose of this work is to modify the existing protocol by enabling it to adapt according to state of the network. The modified protocol takes appropriate action whenever unutilized periods detected. In this way, to increase the effective bandwidth utilization and determine how it behaves under increasing load, and varying packet sizes. It will also include effects of attacks i.e. Denial of service attacks, Replay Attack, Continuous Channel Access or Exhaustion attack, Flooding attack, Jamming (Radio interference) attack, Selective forwarding attack which degrade...

  5. Efficient Distributed Medium Access

    Shah, Devavrat; Tetali, Prasad

    2011-01-01

    Consider a wireless network of n nodes represented by a graph G=(V, E) where an edge (i,j) models the fact that transmissions of i and j interfere with each other, i.e. simultaneous transmissions of i and j become unsuccessful. Hence it is required that at each time instance a set of non-interfering nodes (corresponding to an independent set in G) access the wireless medium. To utilize wireless resources efficiently, it is required to arbitrate the access of medium among interfering nodes properly. Moreover, to be of practical use, such a mechanism is required to be totally distributed as well as simple. As the main result of this paper, we provide such a medium access algorithm. It is randomized, totally distributed and simple: each node attempts to access medium at each time with probability that is a function of its local information. We establish efficiency of the algorithm by showing that the corresponding network Markov chain is positive recurrent as long as the demand imposed on the network can be supp...

  6. Energy Efficient Medium Access Control Protocol for Clustered Wireless Sensor Networks with Adaptive Cross-Layer Scheduling

    Maria Sefuba

    2015-09-01

    Full Text Available This paper presents an Energy Efficient Medium Access Control (MAC protocol for clustered wireless sensor networks that aims to improve energy efficiency and delay performance. The proposed protocol employs an adaptive cross-layer intra-cluster scheduling and an inter-cluster relay selection diversity. The scheduling is based on available data packets and remaining energy level of the source node (SN. This helps to minimize idle listening on nodes without data to transmit as well as reducing control packet overhead. The relay selection diversity is carried out between clusters, by the cluster head (CH, and the base station (BS. The diversity helps to improve network reliability and prolong the network lifetime. Relay selection is determined based on the communication distance, the remaining energy and the channel quality indicator (CQI for the relay cluster head (RCH. An analytical framework for energy consumption and transmission delay for the proposed MAC protocol is presented in this work. The performance of the proposed MAC protocol is evaluated based on transmission delay, energy consumption, and network lifetime. The results obtained indicate that the proposed MAC protocol provides improved performance than traditional cluster based MAC protocols.

  7. An ultra low-power and traffic-adaptive medium access control protocol for wireless body area network.

    Ullah, Sana; Kwak, Kyung Sup

    2012-06-01

    Wireless Body Area Network (WBAN) consists of low-power, miniaturized, and autonomous wireless sensor nodes that enable physicians to remotely monitor vital signs of patients and provide real-time feedback with medical diagnosis and consultations. It is the most reliable and cheaper way to take care of patients suffering from chronic diseases such as asthma, diabetes and cardiovascular diseases. Some of the most important attributes of WBAN is low-power consumption and delay. This can be achieved by introducing flexible duty cycling techniques on the energy constraint sensor nodes. Stated otherwise, low duty cycle nodes should not receive frequent synchronization and control packets if they have no data to send/receive. In this paper, we introduce a Traffic-adaptive MAC protocol (TaMAC) by taking into account the traffic information of the sensor nodes. The protocol dynamically adjusts the duty cycle of the sensor nodes according to their traffic-patterns, thus solving the idle listening and overhearing problems. The traffic-patterns of all sensor nodes are organized and maintained by the coordinator. The TaMAC protocol is supported by a wakeup radio that is used to accommodate emergency and on-demand events in a reliable manner. The wakeup radio uses a separate control channel along with the data channel and therefore it has considerably low power consumption requirements. Analytical expressions are derived to analyze and compare the performance of the TaMAC protocol with the well-known beacon-enabled IEEE 802.15.4 MAC, WiseMAC, and SMAC protocols. The analytical derivations are further validated by simulation results. It is shown that the TaMAC protocol outperforms all other protocols in terms of power consumption and delay. PMID:20703634

  8. Distributed medium access control in wireless networks

    Wang, Ping

    2013-01-01

    This brief investigates distributed medium access control (MAC) with QoS provisioning for both single- and multi-hop wireless networks including wireless local area networks (WLANs), wireless ad hoc networks, and wireless mesh networks. For WLANs, an efficient MAC scheme and a call admission control algorithm are presented to provide guaranteed QoS for voice traffic and, at the same time, increase the voice capacity significantly compared with the current WLAN standard. In addition, a novel token-based scheduling scheme is proposed to provide great flexibility and facility to the network servi

  9. Scalable Lunar Surface Networks and Adaptive Orbit Access

    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.

  10. Random Access Game and Medium Access Control Design

    Chen, Lijun; Low, Steven H.; Doyle, John C.

    2010-01-01

    Motivated partially by a control-theoretic viewpoint, we propose a game-theoretic model, called random access game, for contention control. We characterize Nash equilibria of random access games, study their dynamics, and propose distributed algorithms (strategy evolutions) to achieve Nash equilibria. This provides a general analytical framework that is capable of modeling a large class of system-wide quality-of-service (QoS) models via the specification of per-node util...

  11. Cater: an Opportunistic Medium Access Control Protocol for Wireless Local Area Networks

    Mullins, Barry E.

    1997-01-01

    An adaptive MAC protocol is developed and analyzed that offers a "best case" scenario by allowing the MAC to control medium parameters thereby fully exploiting the channel of an ad hoc wireless LAN. This new, opportunistic medium access control protocol is called CATER (Code Adapts To Enhance Reliability) and is based on the proposed MAC standard for wireless local area networks (WLAN)-IEEE 802.11 [IEE96]. As currently proposed, IEEE 802.11 uses a fixed pseudo-noise (PN) code for spreading ...

  12. Accessing International Funding for Climate Change Adaptation

    Christiansen, Lars; Ray, Aaron D.; Smith, Joel B.;

    The primary aim of this guidebook is to provide countries participating in the Technology Needs Assessment (TNA) Project with practical guidance that will help them secure financing for adaptation technology transfer project profiles identified in their Technology Action Plans (TAPs). The TNA...... project is being implemented by United Nations Environment Programme (UNEP) on behalf of the Global Environment Facility (GEF). This guidebook provides a number of concrete tools and recommendations that will help TNA countries identify and access funding to implement their TAPs, such as: • An overview of...... eligibility criteria) for developing/ presenting adaptation project ideas to international donors. Using this format when communicating project ideas to international donors and agencies is likely to facilitate greater interest and increase the chances of successfully accessing available funding (Chapter 3...

  13. Evaluating accessible adaptable e-learning

    Douce, Christopher; Porch, Wendy

    2009-01-01

    Two different approaches can increase the accessibility of digital educational materials: content that has been built with the widest possible set of users in mind (universal design), or content that has been designed in such a way that it can be personalised to individual user needs and preferences (personalised design). This paper outlines a number of approaches that could be used to evaluate the provision of learning materials that have been adapted to or chosen for individual learners. A ...

  14. Small and Medium Enterprises` (SMEs) Access to Finance: Philippines

    Aldaba, Rafaelita M.

    2012-01-01

    Based on a survey of 97 firms in the garments, textiles, automotive, electrical and electronics, and food manufacturing industries; the paper highlights the difficulties faced by small and medium enterprises (SMEs) in accessing finance. For both firms with access to finance as well as those that did not make any finance request, financing obstacles posed as one of the top four serious problems for the growth of their businesses. The survey indicates the continued dependence of SMEs on interna...

  15. Efficient medium access control protocol for geostationary satellite systems

    王丽娜; 顾学迈

    2004-01-01

    This paper proposes an efficient medium access control (MAC) protocol based on multifrequency-time division multiple access (MF-TDMA) for geostationary satellite systems deploying multiple spot-beams and onboard processing,which uses a method of random reservation access with movable boundaries to dynamically request the transmission slots and can transmit different types of traffic. The simulation results have shown that our designed MAC protocol can achieve a high bandwidth utilization, while providing the required quality of service (QoS) for each class of service.

  16. Performance analysis of multichannel medium access control algorithms for opportunistic spectrum access

    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

  17. Energy-Efficient Boarder Node Medium Access Control Protocol for Wireless Sensor Networks

    Abdul Razaque; Elleithy, Khaled M.

    2014-01-01

    This paper introduces the design, implementation, and performance analysis of the scalable and mobility-aware hybrid protocol named boarder node medium access control (BN-MAC) for wireless sensor networks (WSNs), which leverages the characteristics of scheduled and contention-based MAC protocols. Like contention-based MAC protocols, BN-MAC achieves high channel utilization, network adaptability under heavy traffic and mobility, and low latency and overhead. Like schedule-based MAC protocols,...

  18. Collision-free prioritized medium access control in wireless networks with hidden nodes

    Andersson, Björn; Pereira, Nuno; Tovar, Eduardo

    2006-01-01

    We propose a collision-free medium access control (MAC) protocol, which implements static-priority scheduling and works in the presence of hidden nodes. The MAC protocol allows multiple masters and is fully distributed; it is an adaptation to a wireless channel of the dominance protocol used in the CAN bus. But unlike that protocol, our protocol does not require a node having the ability to sense the channel while transmitting to the channel. Our protocol is collision-free even in...

  19. Animal Locomotion in Different Mediums: The Adaptations of Wetland Organisms

    2016-06-01

    Wetlands are repositories of unique biodiversity. Wetlandorganisms are well adapted to their habitat, lying at theinterface of aquatic and terrestrial environments. In order tounderstand their adaptations in a better way, it is essential tograsp the basic properties of the medium in which variousorganisms live. This is attempted here by first examining theproperties of the two contrasting environments, terrestrialand aquatic. We focus primarily on locomotion, touchingupon related life processes like respiration, body size andmaintaining body balance by employing basic principles ofbiology and physics.

  20. The impact of energy constraints on the medium access

    Gkatzikis, Lazaros; Koutsopoulos, Iordanis

    2011-01-01

    Contemporary mobile devices are battery powered and due to their shrinking size and increasing complexity operate on a tight energy budget. Thus, energy consumption is becoming one of the major concerns regarding the current and upcoming wireless communication systems. On the other hand, the available bandwidth resources are limited and modern applications are throughput demanding, leading thus to strong competition for the medium. In this direction, we consider a stochastic contention based medium access scheme, where the devices may choose to turn off for some time in order to save energy. We perform an analysis for a slotted ALOHA scenario and we show that the energy constraints, if properly exploited, may reduce contention for the medium. Our results give valuable insights on the energy--throughput tradeoff for any contention based system.

  1. Analyzing Medium Access Techniques in Wireless Body Area Networks

    N. Javaid

    2014-01-01

    Full Text Available This paper presents comparison of Access Techniques used in Medium Access Control (MAC protocol for Wireless Body Area Networks (WBANs. Comparison is performed between Time Division Multiple Access (TDMA, Frequency Division Multiple Access (FDMA, Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA, Pure ALOHA and Slotted ALOHA (S-ALOHA. Performance metrics used for comparison are Throughput (T, Delay (D and Offered Load (G. The main goal for comparison is to show which technique gives highest Throughput and lowest Delay with increase in Load. Energy efficiency is major issue in WBAN that is why there is need to know which technique performs best for energy conservation and also gives minimum delay. Simulations are performed for different scenarios and results are compared for all techniques. We suggest TDMA as best technique to be used in MAC protocol for WBANs due to its high throughput and minimum delay with increase in load. MATLAB is the tool that is used for simulation.

  2. Adapting the Medium: Dynamics of Intermedial Adaptation in Contemporary Japanese Popular Visual Culture

    Pusztai Beáta

    2015-08-01

    Full Text Available With respect to adaptation studies, contemporary Japanese popular culture signifies a unique case, as different types of media (be those textual, auditive, visual or audio-visual are tightly intertwined through the “recycling” of successful characters and stories. As a result, a neatly woven net of intermedial adaptations has been formed - the core of this complex system being the manga-anime-live-action film “adaptational triangle.” On the one hand, the paper addresses the interplay of the various factors by which the very existence of this network is made possible, such as the distinctive cultural attitude to “originality,” the structure of the comics, animation and film industries, and finally, the role of fictitious genealogies of both traditional and contemporary media in the negotiation of national identity. On the other hand, the essay also considers some of the most significant thematic, narrative, and stylistic effects this close interconnectedness has on the individual medium. Special attention is being paid to the nascent trend of merging the adaptive medium with that of the original story (viewing adaptation as integration, apparent in contemporary manga-based live- action comedies, as the extreme case of intermedial adaptation. That is, when the aim of the adaptational process is no longer the transposition of the story but the adaptation (i.e. the incorporation of the medium itself- elevating certain medium-specific devices into transmedial phenomena.

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

    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. Policy Defined Spectrum sharing and medium Access for Cognitive Radios

    Bernhard H. Walke

    2006-04-01

    Full Text Available

    Spectrum regulation will undergo elementary changes in the near future allowing a less restricted and more flexible access to radio spectrum. Intelligent radios, socalled cognitive radios, will realize the dynamic usage of frequency bands on an opportunistic basis, by identifying and using under-utilized spectrum. Such a flexible spectrum usage requires changes in regulation towards a more open spectrum. Policies which determine when spectrum is considered as opportunity and which define the possibilities of using these spectrum opportunities are needed. First, this article discusses an approach that intends to enable distributed QoS support in open spectrum. This algorithm is specified as policy in a machine-understandable policy description language, such that the cognitive radio is capable of reasoning about spectrum usage. Policies that enable a software defined medium access are the second focus of this article. We discuss a step towards the realization of such cognitive radios at the example of the well-known Enhanced Distributed Channel Access of IEEE 802.11e. This channel access protocol is here specified in a machine understandable policy language, instead of lengthy textual description. Such a machine- understandable description of the protocol enables cognitive radios to operate in distributed environments according to the 802.11(e standard.

  5. Medium Access Control for Thermal Energy Harvesting in Advanced Metering Infrastructures

    Vithanage, Madava D.; Fafoutis, Xenofon; Andersen, Claus Bo;

    2013-01-01

    the potential energy that can be harvested from Low Surface Temperature (LST) radiators. The experiments are based on a developed Energy-Harvesting Heat Cost Allocator (EH-HCA) prototype. On the basis of this measured power budget, we model and analytically compare the currently used Medium Access...... Control (MAC) scheme of an industrial case study (IMR+) to a MAC scheme specifically designed for energy harvesting systems (ODMAC). Our analytical comparison shows the efficiency of the latter, as well as its ability to adapt to harvested ambient energy....

  6. Implementing WAI Authoring Tool Accessibility Guidelines in Developing Adaptive Elearning

    Mahieddine Djoudi

    2012-09-01

    Full Text Available Adaptive learning technology allows for the development of more personalized online learning experiences with materials that adapt to student performance and skill level. The term “adaptive” is also used to describe Assistive Technologies that allow the usability of online based courses for learners with disabilities and special needs. Authoring tools can enable, encourage, and assist authors in the creation of elearning content. Because most of the content of the Web based adaptive learning is created using authoring tools, they may be accessible to authors regardless of disability and they may support and encourage the authors in creating accessible elearning content. This paper presents an authoring tool designed for developing accessible adaptive elearning. The authoring tool, dedicated to Algerian universities, is designed to satisfy the W3C/WAI Authoring Tool Accessibility Guidelines (ATAG, and to allow collaboration functionalities among teachers where building elearning courses. After presenting the W3C/WAI accessibility guidelines, the collaborative authoring tool is outlined.

  7. Adaptive Media Access Control for Energy Harvesting - Wireless Sensor Networks

    Fafoutis, Xenofon; Dragoni, Nicola

    2012-01-01

    ODMAC (On-Demand Media Access Control) is a recently proposed MAC protocol designed to support individual duty cycles for Energy Harvesting — Wireless Sensor Networks (EH-WSNs). Individual duty cycles are vital for EH-WSNs, because they allow nodes to adapt their energy consumption to the ever...... three key properties of EH-WSNs: adaptability of energy consumption, distributed energy-aware load balancing and support for different application-specific requirements....

  8. An Efficient Medium Access Control Protocol with Parallel Transmission for Wireless Sensor Networks

    Mitsuji Matsumoto

    2012-08-01

    Full Text Available In this paper, we present a novel low power medium access control protocol for wireless sensor networks (WSNs. The proposed protocol, EP-MAC (Efficient MAC with Parallel Transmission achieves high energy efficiency and high packet delivery ratio under different traffic load. EP-MAC protocol is basically based on the Time Division Multiple Access (TDMA approach. The power of Carrier Sense Multiple Access (CSMA is used in order to offset the fundamental problems that the stand-alone TDMA method suffers from, i.e., problems such as lack of scalability, adaptability to varying situations, etc. The novel idea behind the EP-MAC is that it uses the parallel transmission concept with the TDMA link scheduling. EP-MAC uses the methods for the transmission power adjustment, i.e., uses the minimum level power necessary to reach the intended neighbor within a specified bit error rate [BER] target. This reduces energy consumption, as well as further enhances the scope of parallel transmission of the protocol. The simulation studies support the theoretical results, and validate the efficiency of our proposed EP-MAC protocol.

  9. Sustainable medium access control: Implementation and evaluation of ODMAC

    Fafoutis, Xenofon; Di Mauro, Alessio; Dragoni, Nicola

    2013-01-01

    Harvesting small-scale ambient energy constitutes a promising source of power for wireless embedded devices. Due to the unpredictable nature of the harvested energy, adaptive radio duty cycling can lead to a long-term sustainable operation. In energy constrained conditions, very low duty cycles a...

  10. A survey of medium access control protocols for wireless ad hoc networks

    Elvio João Leonardo; Ailton Akira Shinoda

    2004-01-01

    A number of issues distinguishes Medium Access Control (MAC) protocols for wireless networks from those used in wireline systems. In addition, for ad-hoc networks, the characteristics of the radio channel, the diverse physical-layer technologies available and the range of services envisioned make it a difficult task to design an algorithm to discipline the access to the shared medium that results efficient, fair, power consumption sensitive and delay bound. This article presents the current “...

  11. Energy-Efficient Boarder Node Medium Access Control Protocol for Wireless Sensor Networks

    Abdul Razaque

    2014-03-01

    Full Text Available This paper introduces the design, implementation, and performance analysis of the scalable and mobility-aware hybrid protocol named boarder node medium access control (BN-MAC for wireless sensor networks (WSNs, which leverages the characteristics of scheduled and contention-based MAC protocols. Like contention-based MAC protocols, BN-MAC achieves high channel utilization, network adaptability under heavy traffic and mobility, and low latency and overhead. Like schedule-based MAC protocols, BN-MAC reduces idle listening time, emissions, and collision handling at low cost at one-hop neighbor nodes and achieves high channel utilization under heavy network loads. BN-MAC is particularly designed for region-wise WSNs. Each region is controlled by a boarder node (BN, which is of paramount importance. The BN coordinates with the remaining nodes within and beyond the region. Unlike other hybrid MAC protocols, BN-MAC incorporates three promising models that further reduce the energy consumption, idle listening time, overhearing, and congestion to improve the throughput and reduce the latency. One of the models used with BN-MAC is automatic active and sleep (AAS, which reduces the ideal listening time. When nodes finish their monitoring process, AAS lets them automatically go into the sleep state to avoid the idle listening state. Another model used in BN-MAC is the intelligent decision-making (IDM model, which helps the nodes sense the nature of the environment. Based on the nature of the environment, the nodes decide whether to use the active or passive mode. This decision power of the nodes further reduces energy consumption because the nodes turn off the radio of the transceiver in the passive mode. The third model is the least-distance smart neighboring search (LDSNS, which determines the shortest efficient path to the one-hop neighbor and also provides cross-layering support to handle the mobility of the nodes. The BN-MAC also incorporates a semi

  12. Energy-efficient boarder node medium access control protocol for wireless sensor networks.

    Razaque, Abdul; Elleithy, Khaled M

    2014-01-01

    This paper introduces the design, implementation, and performance analysis of the scalable and mobility-aware hybrid protocol named boarder node medium access control (BN-MAC) for wireless sensor networks (WSNs), which leverages the characteristics of scheduled and contention-based MAC protocols. Like contention-based MAC protocols, BN-MAC achieves high channel utilization, network adaptability under heavy traffic and mobility, and low latency and overhead. Like schedule-based MAC protocols, BN-MAC reduces idle listening time, emissions, and collision handling at low cost at one-hop neighbor nodes and achieves high channel utilization under heavy network loads. BN-MAC is particularly designed for region-wise WSNs. Each region is controlled by a boarder node (BN), which is of paramount importance. The BN coordinates with the remaining nodes within and beyond the region. Unlike other hybrid MAC protocols, BN-MAC incorporates three promising models that further reduce the energy consumption, idle listening time, overhearing, and congestion to improve the throughput and reduce the latency. One of the models used with BN-MAC is automatic active and sleep (AAS), which reduces the ideal listening time. When nodes finish their monitoring process, AAS lets them automatically go into the sleep state to avoid the idle listening state. Another model used in BN-MAC is the intelligent decision-making (IDM) model, which helps the nodes sense the nature of the environment. Based on the nature of the environment, the nodes decide whether to use the active or passive mode. This decision power of the nodes further reduces energy consumption because the nodes turn off the radio of the transceiver in the passive mode. The third model is the least-distance smart neighboring search (LDSNS), which determines the shortest efficient path to the one-hop neighbor and also provides cross-layering support to handle the mobility of the nodes. The BN-MAC also incorporates a semi

  13. A hybrid medium access control for convergence of broadband wireless and wireline ATM networks

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

    2000-01-01

    In this paper, we propose a hybrid medium access control protocol for supporting broadband integrated services in the wireless ATM networks. The integrated services include CBR, VBR and ABR traffic varying from low bit-rate to very high bit-rate. The proposed protocol is an excellent compromise of...... contention, reservation and polling access techniques based on the dynamic TDMA system. Extensive simulation results using realistic data traffic sources, show that the proposed medium access scheme may provide QoS guarantees to different ATM traffic including the realistic MPEG video traces with low cell...

  14. Medium Access Control in Energy Harvesting - Wireless Sensor Networks

    Fafoutis, Xenofon

    Control (MAC) protocols that are following the receiver-initiated paradigm of asynchronous communication. According to the receiver-initiated paradigm the communication is initiated by the receiver that states its availability to receive data through beacons. The sender is passively listening...... to the channel until it receives the beacon of interest. In this context, the dissertation begins with an in-depth survey of all the receiverinitiated MAC protocols and presents their unique optimization features, which deal with several challenges of the link layer such as mitigation of the energy consumption......-efficient features that aim to adapt the consumed energy to match the harvested energy, distribute the load with respect to the harvested energy, decrease the overhead of the communication, address the requirements for collision avoidance, prioritize urgent traffic and secure the system against beacon replay attacks...

  15. Distributed Medium Access Control with SDMA Support for WLANs

    Zhou, Sheng; Niu, Zhisheng

    With simultaneous multi-user transmissions, spatial division multiple access (SDMA) provides substantial throughput gain over the single user transmission. However, its implementation in WLANs with contention-based IEEE 802.11 MAC remains challenging. Problems such as coordinating and synchronizing the multiple users need to be solved in a distributed way. In this paper, we propose a distributed MAC protocol for WLANs with SDMA support. A dual-mode CTS responding mechanism is designed to accomplish the channel estimation and user synchronization required for SDMA. We analytically study the throughput performance of the proposed MAC, and dynamic parameter adjustment is designed to enhance the protocol efficiency. In addition, the proposed MAC protocol does not rely on specific physical layer realizations, and can work on legacy IEEE 802.11 equipment with slight software updates. Simulation results show that the proposed MAC outperforms IEEE 802.11 significantly, and that the dynamic parameter adjustment can effectively track the load variation in the network.

  16. Cognitive radio networks medium access control for coexistence of wireless systems

    Bian, Kaigui; Gao, Bo

    2014-01-01

    This book gives a comprehensive overview of the medium access control (MAC) principles in cognitive radio networks, with a specific focus on how such MAC principles enable different wireless systems to coexist in the same spectrum band and carry out spectrum sharing.  From algorithm design to the latest developments in the standards and spectrum policy, readers will benefit from leading-edge knowledge of how cognitive radio systems coexist and share spectrum resources.  Coverage includes cognitive radio rendezvous, spectrum sharing, channel allocation, coexistence in TV white space, and coexistence of heterogeneous wireless systems.   • Provides a comprehensive reference on medium access control (MAC)-related problems in the design of cognitive radio systems and networks; • Includes detailed analysis of various coexistence problems related to medium access control in cognitive radio networks; • Reveals novel techniques for addressing the challenges of coexistence protocol design at a higher level ...

  17. Optimal Medium Access Control in Cognitive Radios: A Sequential Design Approach

    Lai, Lifeng; Jiang, Hai; Poor, H Vincent

    2008-01-01

    The design of medium access control protocols for a cognitive user wishing to opportunistically exploit frequency bands within parts of the radio spectrum having multiple bands is considered. In the scenario under consideration, the availability probability of each channel is unknown a priori to the cognitive user. Hence efficient medium access strategies must strike a balance between exploring the availability of channels and exploiting the opportunities identified thus far. Using a sequential design approach, an optimal medium access strategy is derived. To avoid the prohibitive computational complexity of this optimal strategy, a low complexity asymptotically optimal strategy is also developed. The proposed strategy does not require any prior statistical knowledge about the traffic pattern on the different channels.

  18. A survey of medium access control protocols for wireless ad hoc networks

    Elvio João Leonardo

    2004-01-01

    Full Text Available A number of issues distinguishes Medium Access Control (MAC protocols for wireless networks from those used in wireline systems. In addition, for ad-hoc networks, the characteristics of the radio channel, the diverse physical-layer technologies available and the range of services envisioned make it a difficult task to design an algorithm to discipline the access to the shared medium that results efficient, fair, power consumption sensitive and delay bound. This article presents the current “state-of-art” in this area, including solutions already commercially available as well as those still in study.

  19. Virus spreading in wireless sensor networks with a medium access control mechanism

    In this paper, an extended version of standard susceptible-infected (SI) model is proposed to consider the influence of a medium access control mechanism on virus spreading in wireless sensor networks. Theoretical analysis shows that the medium access control mechanism obviously reduces the density of infected nodes in the networks, which has been ignored in previous studies. It is also found that by increasing the network node density or node communication radius greatly increases the number of infected nodes. The theoretical results are confirmed by numerical simulations. (general)

  20. Does Firm Profile Influence Financial Access among Small and Medium Enterprises in Kenya?

    2013-01-01

    The purpose of this research is to determine whether firm-specific factors influence Small and Medium Enterprises’ (SMEs) ability to access finance. To address the study objectives, data from a sample of 103 SMEs was used in the study. Using multiple regression analysis, we found that, firm profile such as ownership structure; size of the firm; business type; and age of the business indeed influence SMEs’ access to finance.

  1. Strategies for adaptation of mAb-producing CHO cells to serum-free medium

    Costa A; Rodrigues M.; Henriques Mariana; Oliveira Rosário; Azeredo Joana

    2011-01-01

    Large-scale production of biopharmaceuticals commonly requires the use of serum-free medium, for safety and cost reasons. However, serum is essential to most mammalian cells growth, and its removal implies a very time-consuming process for cell adaptation. Thus, the aim of the study was to evaluate different strategies for cell adaptation to serum-free medium. Three cell types were used to assess the impact of transfection on adaptation: one common CHO-K1 cell line and two CHO-K1 cells tr...

  2. Adaptability of the internal business environment of small and medium-sized enterprises in Slovakia

    Misunova Hudakova, Ivana; Misun, Juraj

    2014-01-01

    Companies that are exposed to an uncertain changing business environment must be able to adapt and change in order to achieve some compliance with the subject of business carried out and the objectives with the ambient conditions. Also these conditions can be a source of threats for small and medium-sized enterprises. In this context, we emphasize the adaptability of the enterprise. It is the active joining of resolving the conflict between the business entity and its environment. Signs of th...

  3. An adaptive digital controller for satellite medium power DC/DC converter

    Skup, Konrad R.; Grudziński, Paweł; Orleański, Orleański

    2011-01-01

    In this paper the work concerning an adaptive digital controller for satellite medium power DC/DC converters is presented. The adaptive techniques and methods developed in Space Research Centre allows an implemented in VHDL controller to modify its parameters according to detected changes in operating conditions. Inductor entering from discontinuous to continuous current mode and vice versa or moving sampling instants due to changes in duty time are good examples of varying operation...

  4. Dynamic Cognitive Self-Organized TDMA for Medium Access Control in Real-Time Vehicle to Vehicle Communications

    Mario Manzano

    2013-01-01

    Full Text Available The emergence of intelligent transport systems has brought out a new set of requirements on wireless communication. To cope with these requirements, several proposals are currently under discussion. In this highly mobile environment, the design of a prompt, efficient, flexible, and reliable medium access control, able to cover the specific constraints of the named real-time communications applications, is still unsolved. This paper presents the original proposal integrating Non-Cooperative Cognitive Time Division Multiple Access (NCC-TDMA based on Cognitive Radio (CR techniques to obtain a mechanism which complies with the requirements of real-time communications. Though the proposed MAC uses a slotted channel, it can be adapted to operate on the physical layer of different standards. The authors’ analysis considers the IEEE WAVE and 802.11p as the standards of reference. The mechanism also offers other advantages, such as avoiding signalling and the adaptation capacity to channel conditions and interferences. The solution is applied to the problem of units merging a convoy. Comparison results between NCC-TDMA and Slotted-Aloha are included.

  5. A Combined Solution for Routing and Medium Access Control Layer Attacks in Mobile Ad Hoc Networks

    R. Murugan; Shanmugam, A.

    2010-01-01

    Problem statement: In Mobile Ad hoc Network (MANET), both the routing layer and the Medium Access Control (MAC) layer are vulnerable to several attacks. There are very few techniques to detect and isolate the attacks of both these layers simultaneously. In this study, we developed a combined solution for routing and MAC layer attacks. Approach: Our approach, makes use of three techniques simultaneously which consists of a cumulative frequency based detection technique for&...

  6. A Study of Medium Access Control Protocols for Wireless Body Area Networks

    Ullah, Sana; Shen, Bin; Islam, S.M. Riazul; Khan, Pervez; Saleem, Shahnaz; Kwak, Kyung Sup

    2010-01-01

    The seamless integration of low-power, miniaturised, invasive/non-invasive lightweight sensor nodes have contributed to the development of a proactive and unobtrusive Wireless Body Area Network (WBAN). A WBAN provides long-term health monitoring of a patient without any constraint on his/her normal dailylife activities. This monitoring requires low-power operation of invasive/non-invasive sensor nodes. In other words, a power-efficient Medium Access Control (MAC) protocol is required to satis...

  7. Onboard Interference Prediction for the Cognitive Medium Access in the LEO Satellite Uplink Transmission

    Zhuochen Xie; Huijie Liu; Xuwen Liang

    2014-01-01

    Cognitive radio (CR) is an efficient way to increase spectrum efficiency for the small low earth orbit (LEO) satellite communication system. Due to the implementation difficulties, we focus on the CR in the uplink transmission. In CR, the cognitive medium access (CMA) is designed to enable the coexistence with the interferences from other systems. However, the CMA schemes designed for the terrestrial system cannot deal well with the global history of interferences in our system. Here, we desi...

  8. Cross-layer rate control, medium access control and routing design in cooperative VANET

    Zhou, Liang; Zheng, Baoyu; Geller, Benoit; Wei, Anne; Xu, Shan; Li, Yajun

    2008-01-01

    In this paper, we address the rate control, the Medium Access Control (MAC) and the routing problem for cooperative Vehicular Ad-Hoc Network (VANET) in the framework of cross-layer design. At first, we introduce the cooperative communication conception to VANET, and propose an opportunistic cooperation strategy to improve the system performance. And then, we develop a cross-layer solution which consists of the link capacity detection with adjusting persistence probability at the MAC Layer, th...

  9. Medium access control and hardware prototype designs for low-energy wireless sensor networks

    Kohvakka, M.

    2009-07-01

    A Wireless Sensor Network (WSN) is an emerging technology consisting of small, cheap, and ultra-low energy sensor nodes, which cooperatively monitor physical quantities, actuate, and perform data processing tasks. A deployment may comprise thousands of randomly distributed autonomous nodes, which must self-configure and create a multi-hop network topology.This thesis focuses on low-energy WSNs targeting to long network lifetime. The main research problem is the combination of adaptive and scalable multi-hop networking with constrained energy budget, processing power, and communication bandwidth. The research problem is approached by energy-efficient protocols and low-power sensor node platforms. The main contribution of this thesis is an energy-efficient Medium Access Control (MAC) design for TUTWSN (Tampere University of Technology Wireless Sensor Network). The design comprises channel access and networking mechanisms, which specify data exchange, link synchronization, network self-configuration, and neighbor discovery operations. The second outcome are several low-power sensor node platforms, which have been designed and implemented to evaluate the performance of the MAC design and hardware components in real deployments. The third outcome are the performance models and analysis of several MAC designs including TUTWSN, IEEE 802.15.4, and the most essential research proposals.The results and conclusion of this Thesis indicate that it is possible to implement multi-hop WSNs in harsh and dynamic operation conditions with years of lifetime using current low-cost components and batteries. Energy analysis results indicate that the lowest energy consumption is achieved by using simple and high data-rate transceivers. It is also critical to minimize sleep mode power consumption of all components and to use accurate wake-up timers. However, the selection of components constitutes only a minor part of the solution, and an energy-efficient MAC layer design being able to

  10. Adaptive MAC-layer protocol for multiservice digital access via tree and branch communication networks

    Sriram, Kotikalapudi; Li, Chia-Chang; Magill, Peter; Whitaker, Norman A.; Dail, James E.; Dajer, Miguel A.; Siller, Curtis A.

    1995-11-01

    Described here is an adaptive MAC-layer protocol that supports multiservice (STM and ATM) applications in the context of subscriber access to tree and branch (e.g., fiber-coaxial cable) networks. The protocol adapts to changing demands for a mix of circuit and cell mode applications, and efficiently allocates upstream and downstream bandwidth to a variety of bursty and isochronous traffic sources. In the case of a hybrid fiber-coaxial (HFC) network the protocol resides in customer premises equipment and a common head-end controller. A medium-access control (MAC) processor provides for dividing the time domain for a given digital bitstream into successive frames, each with multiple STM and ATM time slots. Within the STM region of a frame, variable length time slots are allocated to calls (e.g., telephony, video telephony) requiring different amounts of bandwidth. A contention access signaling channel is also provided in this region for call control and set-up requests. Within the ATM region fixed-length time slots accommodate one individual ATM cell. These ATM time slots may be reserved for a user for the duration of a call or burst of successive ATM cells, or shared via a contention process. At least one contention time slot is available for signaling messages related to ATM call control and set-up requests. Further, the fixed-length ATM time slots may be reserved by a user for the duration of a call, or shared through a contention process. This paper describes the MAC-layer protocol, its relation to circuit- and ATM- amenable applications, and its performance with respect to signaling throughput and latency, and bandwidth efficiency for several service scenarios.

  11. Sensory and adaptive access of manufacturing equipment resources in cloud manufacturing

    Liu Mingli

    2015-01-01

    Full Text Available Sensory and adaptive access of manufacturing equipment (ME is the key of physical resources virtualization in cloud manufacturing (CM. Three aspects including status sensory of ME, Internet of Things (IoT and adaptive access of CM service platform were elaborated to analyze the characteristics and to investigate the related technologies. The importance of fiber Bragg grating sensing technology for ME sensory was analyzed. The heterogeneous fusion system and fusion access method as well as device of equipment resources were discussed. The access of ME resources for CM service platform was investigated based on three aspects including information fusion, description and retrieval and service release. Taking the realization of intelligent sensory and adaptive access for typical ME resources as an example, the prototype system, the sensory of ME resources and the realization of IoT of ME resources as well as the adaptive access method for CM service platform were expounded.

  12. Performance analysis of adaptive modulation for cognitive radios with opportunistic access

    Chen, Yunfei

    2011-06-01

    The performance of adaptive modulation for cognitive radio with opportunistic access is analyzed by considering the effects of spectrum sensing and primary user traffic for Nakagami-m fading channels. Both the adaptive continuous rate scheme and the adaptive discrete rate scheme are considered. Numerical results show that spectrum sensing and primary user traffic cause considerable degradation to the bit error rate performance of adaptive modulation in a cognitive radio system with opportunistic access to the licensed channel. They also show that primary user traffic does not affect the link spectral efficiency performance of adaptive modulation, while the spectrum sensing degrades the link spectral efficiency performance. © 2011 IEEE.

  13. Medium Access Control for Thermal Energy Harvesting in Advanced Metering Infrastructures

    Vithanage, Madava D.; Fafoutis, Xenofon; Andersen, Claus Bo; Dragoni, Nicola

    In this paper we investigate the feasibility of powering wireless metering devices, namely heat cost allocators, by thermal energy harvested from radiators. The goal is to take a first step toward the realization of Energy-Harvesting Advanced Metering Infrastructures (EH-AMIs). While traditional...... the potential energy that can be harvested from Low Surface Temperature (LST) radiators. The experiments are based on a developed Energy-Harvesting Heat Cost Allocator (EH-HCA) prototype. On the basis of this measured power budget, we model and analytically compare the currently used Medium Access...

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

    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.

  15. Adaptive scheduling in cellular access, wireless mesh and IP networks

    Nieminen, Johanna

    2011-01-01

    Networking scenarios in the future will be complex and will include fixed networks and hybrid Fourth Generation (4G) networks, consisting of both infrastructure-based and infrastructureless, wireless parts. In such scenarios, adaptive provisioning and management of network resources becomes of critical importance. Adaptive mechanisms are desirable since they enable a self-configurable network that is able to adjust itself to varying traffic and channel conditions. The operation of adaptive me...

  16. ACADA: Access Control-driven Architecture with Dynamic Adaptation

    Pereira, Óscar Narciso Mortágua; Rui L. Aguiar; Santos, Maribel Yasmina

    2012-01-01

    Programmers of relational database applications use software solutions (Hibernate, JDBC, LINQ, ADO.NET) to ease the development process of business tiers. These software solutions were not devised to address access control policies, much less for evolving access control policies, in spite of their unavoidable relevance. Currently, access control policies, whenever implemented, are enforced by independent components leading to a separation between policies and their enf...

  17. A Novel Medium Access Control for Ad hoc Networks Based on OFDM System

    YU Yi-fan; YIN Chang-chuan; YUE Guang-xin

    2005-01-01

    Recently, hosts of Medium Access Control (MAC) protocols for Ad hoc radio networks have been proposed to solve the hidden terminal problem and exposed terminal problem. However most of them take into no account the interactions between physical (PHY) system and MAC protocol. Therefore, the current MAC protocols are either inefficient in the networks with mobile nodes and fading channel or difficult in hardware implementation. In this paper, we present a novel media access control for Ad hoc networks that integrates a media access control protocol termed as Dual Busy Tone Multiple Access (DBTMA) into Orthogonal Frequency Division Multiplexing (OFDM) system proposed in IEEE 802.11a standard. The analysis presented in the paper indicates that the proposed MAC scheme achieves performance improvement over IEEE 802.11 protocol about 25%~80% especially in the environment with high mobility and deep fading. The complexity of the proposed scheme is also lower than other implementation of similar busy tone solution. Furthermore, it is compatible with IEEE 802.11a networks.

  18. Scalable Lunar Surface Networks and Adaptive Orbit Access Project

    National Aeronautics and Space Administration — Innovative network architecture, protocols, and algorithms are proposed for both lunar surface networks and orbit access networks. Firstly, an overlaying...

  19. Needs-Adapted Data Access and Data Presentation

    Bergenholtz, Henning

    2011-01-01

    This paper has two connected topics: 1. access to data in dictionaries, 2. monofunctional dictionaries. The first topic has not been in focus in the theoretical lexicography. It is somehow surprising, because a quick and an easy access to the data giving the user the needed information is the main...

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

    Ray, Surjya Sarathi

    One of the main challenges that prevents the large-scale deployment of Wireless Sensor Networks (WSNs) is providing the applications with the required quality of service (QoS) given the sensor nodes' limited energy supplies. WSNs are an important tool in supporting applications ranging from environmental and industrial monitoring, to battlefield surveillance and traffic control, among others. Most of these applications require sensors to function for long periods of time without human intervention and without battery replacement. Therefore, energy conservation is one of the main goals for protocols for WSNs. Energy conservation can be performed in different layers of the protocol stack. In particular, as the medium access control (MAC) layer can access and control the radio directly, large energy savings is possible through intelligent MAC protocol design. To maximize the network lifetime, MAC protocols for WSNs aim to minimize idle listening of the sensor nodes, packet collisions, and overhearing. Several approaches such as duty cycling and low power listening have been proposed at the MAC layer to achieve energy efficiency. In this thesis, I explore the possibility of further energy savings through the advertisement of data packets in the MAC layer. In the first part of my research, I propose Advertisement-MAC or ADV-MAC, a new MAC protocol for WSNs that utilizes the concept of advertising for data contention. This technique lets nodes listen dynamically to any desired transmission and sleep during transmissions not of interest. This minimizes the energy lost in idle listening and overhearing while maintaining an adaptive duty cycle to handle variable loads. Additionally, ADV-MAC enables energy efficient MAC-level multicasting. An analytical model for the packet delivery ratio and the energy consumption of the protocol is also proposed. The analytical model is verified with simulations and is used to choose an optimal value of the advertisement period

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

    Ray, Surjya Sarathi

    One of the main challenges that prevents the large-scale deployment of Wireless Sensor Networks (WSNs) is providing the applications with the required quality of service (QoS) given the sensor nodes' limited energy supplies. WSNs are an important tool in supporting applications ranging from environmental and industrial monitoring, to battlefield surveillance and traffic control, among others. Most of these applications require sensors to function for long periods of time without human intervention and without battery replacement. Therefore, energy conservation is one of the main goals for protocols for WSNs. Energy conservation can be performed in different layers of the protocol stack. In particular, as the medium access control (MAC) layer can access and control the radio directly, large energy savings is possible through intelligent MAC protocol design. To maximize the network lifetime, MAC protocols for WSNs aim to minimize idle listening of the sensor nodes, packet collisions, and overhearing. Several approaches such as duty cycling and low power listening have been proposed at the MAC layer to achieve energy efficiency. In this thesis, I explore the possibility of further energy savings through the advertisement of data packets in the MAC layer. In the first part of my research, I propose Advertisement-MAC or ADV-MAC, a new MAC protocol for WSNs that utilizes the concept of advertising for data contention. This technique lets nodes listen dynamically to any desired transmission and sleep during transmissions not of interest. This minimizes the energy lost in idle listening and overhearing while maintaining an adaptive duty cycle to handle variable loads. Additionally, ADV-MAC enables energy efficient MAC-level multicasting. An analytical model for the packet delivery ratio and the energy consumption of the protocol is also proposed. The analytical model is verified with simulations and is used to choose an optimal value of the advertisement period

  2. A High Throughput Medium Access Control Implementation Based on IEEE 802.11e Standard

    Huang, Min Li; Lee, Jin; Setiawan, Hendra; Ochi, Hiroshi; Park, Sin-Chong

    With the growing demand for high-performance multimedia applications over wireless channels, we need to develop a Medium Access Control (MAC) system that supports high throughput and quality of service enhancements. This paper presents the standard analysis, design architecture and design issues leading to the implementation of an IEEE 802.11e based MAC system that supports MAC throughput of over 100Mbps. In order to meet the MAC layer timing constraints, a hardware/software co-design approach is adopted. The proposed MAC architecture is implemented on the Xilinx Virtex-II Pro Field-Programmable Gate Array (FPGA) (XC2VP70-5FF1704C) prototype, and connected to a host computer through an external Universal Serial Bus (USB) interface. The total FPGA resource utilization is 11, 508 out of 33, 088 (34%) available slices. The measured MAC throughput is 100.7Mbps and 109.2Mbps for voice and video access categories, transmitted at a data rate of 260Mbps based on IEEE 802.11n Physical Layer (PHY), using the contention-based hybrid coordination function channel access mechanism.

  3. Speed regulating Effects of Incentive-based Intelligent Speed Adaptation in the short and medium term

    Agerholm, Niels

    Speed regulating Effects of Incentive-based Intelligent Speed Adaptation in the short and medium term Despite massive improvements in vehicles’ safety equipment, more information and safer road network, inappropriate road safety is still causing that more than 250 people are killed and several...... fewer speed limit violations. Estimation of safety effects showed various results and the reduction in the number of fatalities was estimated to be as high as 37 to 42% if ISA was fully implemented. Despite convincing effects of ISA in short term, it was found that the effect of ISA decreased over time...... activation of ISA. The effect was studied on the basis of the Danish ISA trial PAYS. Short term means 0-1.5 months after ISA activation, while medium-term means 3-4.5 months after ISA activation. Regarding short-term effects, it was found that the combination of informative and incentive ISA resulted in...

  4. A Cloud-Assisted Random Linear Network Coding Medium Access Control Protocol for Healthcare Applications

    Kartsakli, Elli; Antonopoulos, Angelos; Alonso, Luis; Verikoukis, Christos

    2014-01-01

    Relay sensor networks are often employed in end-to-end healthcare applications to facilitate the information flow between patient worn sensors and the medical data center. Medium access control (MAC) protocols, based on random linear network coding (RLNC), are a novel and suitable approach to efficiently handle data dissemination. However, several challenges arise, such as additional delays introduced by the intermediate relay nodes and decoding failures, due to channel errors. In this paper, we tackle these issues by adopting a cloud architecture where the set of relays is connected to a coordinating entity, called cloud manager. We propose a cloud-assisted RLNC-based MAC protocol (CLNC-MAC) and develop a mathematical model for the calculation of the key performance metrics, namely the system throughput, the mean completion time for data delivery and the energy efficiency. We show the importance of central coordination in fully exploiting the gain of RLNC under error-prone channels. PMID:24618727

  5. Access to finance for small and medium-sized enterprises in North Kosovo

    Ljumović Isidora

    2015-01-01

    Full Text Available The purpose of this paper is to identify the problems small and medium-sized enterprises (SMEs are facing in Serbian municipalities in North Kosovo. The experience and previous researches show that SMEs, especially those in crisis areas, have a greater demand than supply for financial resources. We have created a questionnaire in order to get relevant data from SMEs in North Kosovo and to assess the shortcomings of the system of financing. Results show that access to finance in North Kosovo is extremely limited. Entrepreneurs and SMEs are usually financed with own resources and with a help from friends or family, while the bank loans are not frequent and are very expensive.

  6. A Time Tree Medium Access Control for Energy Efficiency and Collision Avoidance in Wireless Sensor Networks

    Kilhung Lee

    2010-03-01

    Full Text Available This paper presents a medium access control and scheduling scheme for wireless sensor networks. It uses time trees for sending data from the sensor node to the base station. For an energy efficient operation of the sensor networks in a distributed manner, time trees are built in order to reduce the collision probability and to minimize the total energy required to send data to the base station. A time tree is a data gathering tree where the base station is the root and each sensor node is either a relaying or a leaf node of the tree. Each tree operates in a different time schedule with possibly different activation rates. Through the simulation, the proposed scheme that uses time trees shows better characteristics toward burst traffic than the previous energy and data arrival rate scheme.

  7. Cooperative Medium Access Control Protocol for Mobile Ad-hoc Networks using Spatial Diversity

    Tazeem Ahmad Khan

    2013-10-01

    Full Text Available Enhancement the Performance of MANET (Mobile Ad-hoc Network using spatial diversity. Spatial diversity implemented using cooperative transmission technique in Medium access control (MAC layer level protocol. In noisy environment limit the network performance like coverage area, limit number of node, degrade packet transmission rate, increase packet loss rate etc. In this paper enhance the source to destination transmission range, minimize the packet loss, improve packet transmission rate and appropriate end to end delay. When direct link is fail to transmit packet then Cooperative scheme help to transmit packet. Cooperative scheme is to help the packet transmission with five handshakes instead of four. This scheme implemented in MANET network on MAC layer protocol. Cooperative scheme improve the performance with help of intermediate node between sources to destination. We are performance analysis using discrete simulator NS-2 in MANET. Our performance based on MAC layer level with cooperative scheme in IEEE WLAN standard CSMA/CA protocol.

  8. Near-Optimal Deviation-Proof Medium Access Control Designs in Wireless Networks

    Phan, Khoa Tran; van der Schaar, Mihaela

    2010-01-01

    Distributed medium access control (MAC) protocols are essential for the proliferation of low cost, decentralized wireless local area networks (WLANs). Most MAC protocols are designed with the presumption that nodes comply with prescribed rules. However, selfish nodes have natural motives to manipulate protocols in order to improve their own performance. This often degrades the performance of other nodes as well as that of the overall system. In this work, we propose a class of protocols that limit the performance gain which nodes can obtain through selfish manipulation while incurring only a small efficiency loss. The proposed protocols are based on the idea of a review strategy, with which nodes collect signals about the actions of other nodes over a period of time, use a statistical test to infer whether or not other nodes are following the prescribed protocol, and trigger a punishment if a departure from the protocol is perceived. We consider the cases of private and public signals and provide analytical a...

  9. Adapting Building Design to Access by Individuals with Intellectual Disability

    L Castell

    2012-11-01

    Full Text Available Over the last 15 years, since introductionof the Disability Discrimination Act (DDA(Commonwealth Government of Australia,1992, there has been much discussionabout the extent and nature of buildingaccess for the disabled, particularly inresponse to proposed revisions to theBuilding Code of Australia (BCA and theintroduction of a Premises Standardcovering building access. Much of theargument which contributed to the twoyear delay in submitting a final version ofthese documents for government approvalrelated to the extent of access provisionsand the burden of cost. The final versionsubmitted to government by the AustralianBuilding Codes Board (ABCB (notreleased publicly appears to still containinconsistencies between the DDA and theBCA in several areas such as wayfindingand egress.In the debate preceding submission of thefinal version there appears to have beenlittle reference to access requirements forindividuals with intellectual disability (ID.This may be due to a general lack ofresearch on the topic. Consequently, thispaper uses a combination of theknowledge gained from a limited numberof previous wayfinding studies, literaturedescribing general problems faced bythose with ID and the author’s personalexperience observing others with ID tocreate a list of probable difficulties andsuggested solutions. The paperconcludes with a discussion about theassociated cost implications and benefitsin providing the required access.

  10. Adaptive Traffic Control Systems in a medium-sized Scandinavian city

    Agerholm, Niels; Olesen, Anne Vingaard

    2016-01-01

    Adaptive Traffic Control Systems (ATCS) are aimed at reducing congestion. ATCS adapt to approaching traffic to continuously optimise the traffic flows in question. ATCS have been implemented in many locations, including the Scandinavian countries, with various effects. Due to congestion problems......, ATCS were installed in the eight signalised intersections of a 1.7 km stretch of the ring road in the medium-sized Danish city of Aalborg. To measure the effect of ATCS a with/without study was carried out. GPS data from a car following the traffic, recorded transportation times for buses in service...... morning peak and midday off-peak. The effect on crossing and turning traffic was slight, and while reduced transportation time was found in one part of the ring road in another part transportation time was seen to increase. The benefit to the ring road was partly gained at the cost of slightly increased...

  11. Directional Medium Access Control (MAC Protocols in Wireless Ad Hoc and Sensor Networks: A Survey

    David Tung Chong Wong

    2015-06-01

    Full Text Available This survey paper presents the state-of-the-art directional medium access control (MAC protocols in wireless ad hoc and sensor networks (WAHSNs. The key benefits of directional antennas over omni-directional antennas are longer communication range, less multipath interference, more spatial reuse, more secure communications, higher throughput and reduced latency. However, directional antennas lead to single-/multi-channel directional hidden/exposed terminals, deafness and neighborhood, head-of-line blocking, and MAC-layer capture which need to be overcome. Addressing these problems and benefits for directional antennas to MAC protocols leads to many classes of directional MAC protocols in WAHSNs. These classes of directional MAC protocols presented in this survey paper include single-channel, multi-channel, cooperative and cognitive directional MACs. Single-channel directional MAC protocols can be classified as contention-based or non-contention-based or hybrid-based, while multi-channel directional MAC protocols commonly use a common control channel for control packets/tones and one or more data channels for directional data transmissions. Cooperative directional MAC protocols improve throughput in WAHSNs via directional multi-rate/single-relay/multiple-relay/two frequency channels/polarization, while cognitive directional MAC protocols leverage on conventional directional MAC protocols with new twists to address dynamic spectrum access. All of these directional MAC protocols are the pillars for the design of future directional MAC protocols in WAHSNs.

  12. Transparent Adaptable Network Access and Service Content Differentiation

    Senneset, Thomas

    2006-01-01

    Today s most advanced mobile devices support communication through a variety of network technologies; GSM (including GPRS and EDGE), UMTS, WLAN, Bluetooth, and IR. This master thesis characterizes different network technologies and protocols available to mobile devices, phones in particular. In addition, service provisioning capabilities over different types of networks are identified. Internet access till now has been provided over GSM or UMTS, often via a WAP Gateway. With a WAP Gateway, ...

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

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

    2014-01-01

    information is challenged by dynamic nature of information elements. These challenges are more prominent in case of wireless sensor network (WSN) applications, as the information that the sensor node collects are mostly dynamic in nature (say, temperature). Therefore, it is likely that there can be a mismatch...... of information between the one which user uses and the one which is available at the source at the same instant of time. This leads to unreliable information being used by the application user for processing. Information accessing with minimal mismatch is desired by the WSN applications especially when WSN...

  14. Corporate Social Responsibility (CSR) for Global Market Access: A Malaysian Case Study on Small and Medium Enterprises (SMEs)

    Tareq Bin Hossain; Chamhuri Siwar; Mohd Fauzi Mohd Jani; Abul Bashar Bhuiyan

    2013-01-01

    The Corporate Social Responsibility (CSR) is a powerful tool or channel for ensuring greater market access and enables a better engagement in the global market. The study examines how Corporate Social Responsibility (CSR) is contributing to mass access of Small and Medium Enterprises (SMEs) in the global market. The study used cross section primary data from the level of executives of the corporations. Towards the achievement of its objectives this study uses descriptive statistical tools. Th...

  15. On the accessibility of adaptive phenotypes of a bacterial metabolic network.

    Wilfred Ndifon

    2009-08-01

    Full Text Available The mechanisms by which adaptive phenotypes spread within an evolving population after their emergence are understood fairly well. Much less is known about the factors that influence the evolutionary accessibility of such phenotypes, a pre-requisite for their emergence in a population. Here, we investigate the influence of environmental quality on the accessibility of adaptive phenotypes of Escherichia coli's central metabolic network. We used an established flux-balance model of metabolism as the basis for a genotype-phenotype map (GPM. We quantified the effects of seven qualitatively different environments (corresponding to both carbohydrate and gluconeogenic metabolic substrates on the structure of this GPM. We found that the GPM has a more rugged structure in qualitatively poorer environments, suggesting that adaptive phenotypes could be intrinsically less accessible in such environments. Nevertheless, on average approximately 74% of the genotype can be altered by neutral drift, in the environment where the GPM is most rugged; this could allow evolving populations to circumvent such ruggedness. Furthermore, we found that the normalized mutual information (NMI of genotype differences relative to phenotype differences, which measures the GPM's capacity to transmit information about phenotype differences, is positively correlated with (simulation-based estimates of the accessibility of adaptive phenotypes in different environments. These results are consistent with the predictions of a simple analytic theory that makes explicit the relationship between the NMI and the speed of adaptation. The results suggest an intuitive information-theoretic principle for evolutionary adaptation; adaptation could be faster in environments where the GPM has a greater capacity to transmit information about phenotype differences. More generally, our results provide insight into fundamental environment-specific differences in the accessibility of adaptive

  16. Adaptive Hybrid Mobile Agent Protocol for Wireless Multihop Internet Access

    A. Velmurugan

    2006-01-01

    Full Text Available Internet-based Mobile Ad Hoc Networking (MANET is an emerging technology that supports self-organizing mobile networking infrastructures. This is expected to be of great use in commercial applications for the next generation Internet users. A number of technical challenges are faced today due to the heterogeneous, dynamic nature of this hybrid MANET. A new hybrid routing scheme AODV_ALMA is proposed, which act simultaneously combining mobile agents to find path to the gateway to establish connection with Internet host and on-demand distance vector approach to find path in local MANET is one of the unique solution. An adaptive gateway discovery mechanism based on mobile agents making use of pheromone value, pheromone decay time and balance index is used to estimate the path and next hop to the gateway. The mobile nodes automatically configure the address using mobile agents first selecting the gateway and then using the gateway prefix address. The mobile agents are also used to track changes in topology enabling high network connectivity with reduced delay in packet transmission to Internet. The performance tradeoffs and limitations with existing solutions for various mobility conditions are evaluated using simulation."

  17. Medium Access Control Protocols for Wireless Sensor Networks with Energy Harvesting

    Iannello, Fabio; Spagnolini, Umberto

    2011-01-01

    The design of Medium Access Control (MAC) protocols for wireless sensor networks (WSNs) has been conventionally tackled by assuming battery-powered devices and by adopting the network lifetime as the main performance criterion. While WSNs operated by energy-harvesting (EH) devices are not limited by network lifetime, they pose new design challenges due to the uncertain amount of harvestable energy. Novel design criteria are thus required to capture the trade-offs between the potentially infinite network lifetime and the uncertain energy availability. This paper addresses the analysis and design of WSNs with EH devices by focusing on conventional MAC protocols, namely TDMA, Framed-ALOHA (FA) and Dynamic-FA (DFA), and by accounting for the performance trade-offs and design issues arising due to EH. A novel metric, referred to as delivery probability, is introduced to measure the capability of a MAC protocol to deliver the measure of any sensor in the network to the intended destination (or fusion center, FC). T...

  18. A Combined Solution for Routing and Medium Access Control Layer Attacks in Mobile Ad Hoc Networks

    R. Murugan

    2010-01-01

    Full Text Available Problem statement: In Mobile Ad hoc Network (MANET, both the routing layer and the Medium Access Control (MAC layer are vulnerable to several attacks. There are very few techniques to detect and isolate the attacks of both these layers simultaneously. In this study, we developed a combined solution for routing and MAC layer attacks. Approach: Our approach, makes use of three techniques simultaneously which consists of a cumulative frequency based detection technique for detecting MAC layers attacks, data forwarding behavior based detection technique for detecting packet drops and message authentication code based technique for packet modification. Results: Our combined solution presents a reputation value for detecting the malicious nodes and isolates them from further network participation till its revocation. Our approach periodically checks all nodes, including the isolated nodes, at regular time period λ. A node which recovers from its misbehaving condition is revoked to its normal condition after the time period λ. Conclusion/Recommendations: By simulation results, we show that our combined solution provides more security by increased packet delivery ratio and reduced packet drops. We also shown that our approach has less overhead compared to the existing technique.

  19. A Study of Medium Access Control Protocols for Wireless Body Area Networks

    Ullah, Sana; Islam, S M Riazul; Khan, Pervez; Saleem, Shahnaz; Kwak, Kyung Sup; 10.3390/s100100128

    2010-01-01

    The seamless integration of low-power, miniaturised, invasive/non-invasive lightweight sensor nodes have contributed to the development of a proactive and unobtrusive Wireless Body Area Network (WBAN). A WBAN provides long-term health monitoring of a patient without any constraint on his/her normal dailylife activities. This monitoring requires low-power operation of invasive/non-invasive sensor nodes. In other words, a power-efficient Medium Access Control (MAC) protocol is required to satisfy the stringent WBAN requirements, including low-power consumption. In this paper, we first outline the WBAN requirements that are important for the design of a low-power MAC protocol. Then we study low-power MAC protocols proposed/investigated for a WBAN with emphasis on their strengths and weaknesses. We also review different power-efficient mechanisms for a WBAN. In addition, useful suggestions are given to help the MAC designers to develop a low-power MAC protocol that will satisfy the stringent WBAN requirements.

  20. Energy-Efficient Reservation-Based Medium Access Control Protocol for Wireless Sensor Networks

    Kohvakka Mikko

    2010-01-01

    Full Text Available In Wireless Sensor Networks (WSNs, a robust and energy-efficient Medium Access Control (MAC protocol is required for high energy efficiency in harsh operating conditions, where node and link failures are common. This paper presents the design of a novel MAC protocol for low-power WSNs. The developed MAC protocol minimizes the energy overhead of idle time and collisions by strict frame synchronization and slot reservation. It combines a dynamic bandwidth adjustment mechanism, multi-cluster-tree network topology, and a network channel allowing rapid and low-energy neighbor discoveries. The protocol achieves high scalability by employing frequency and time division between clusters. Performance analysis shows that the MAC protocol outperforms current state-of-the-art protocols in energy efficiency, and the energy overhead compared to an ideal MAC protocol is only 2.85% to 27.1%. The high energy efficiency is achieved in both leaf and router nodes. The models and the feasibility of the protocol were verified by simulations and with a full-scale prototype implementation.

  1. Improvement in Medium Access Control protocol based on new contention scheme for wireless ad hoc network

    C.Ellammal

    2012-05-01

    Full Text Available In todays wireless networks, stations using the IEEE 802.11 standard contend for the channel using the Distributed Coordination Function (DCF. Research has shown that DCF€™s performance degrades especially with the large number of stations. This becomes more concerning due to the increasing proliferation of wireless devices. In this paper, we present a Medium Access Control (MAC scheme for wireless LANs and compare its performance to DCF . Our scheme, which attempts to resolve the contention in a constant number of slots (or constant time, is called CONSTI. The contention resolution happens over a predefined number of slots. In a slot, the stations probabilistically send a jam signal on the channel. The stations listening retire if they hear a jam signal. The others continue to the next slot. Over several slots, we aim to have one station remaining in the contention, which will then transmit its data. We find the optimal parameters of CONSTI and present an analysis on its performance.

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

    Coetzer, Alan; Redmond, Janice; Sharafizad, Jalleh

    2012-01-01

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

  3. Underwater acoustic sensor networks: Medium access control, routing and reliable transfer

    Xie, Peng

    Recently there have been growing interests in monitoring aquatic environments for scientific exploration, commercial exploitation and coastline protection. The ideal vehicle for this type of extensive monitoring is a mobile underwater sensor network (M-UWSN), consisting of a large number of low cost underwater sensors that can move with water currents and dispersion. M-UWSNs are significantly different from terrestrial sensor networks: (1) Radio channels do not work well under water. They must be replaced by acoustic channels, which feature long propagation delays, low communication bandwidth and high channel error rates; (2) While most ground sensors are static, underwater sensor nodes may move with water currents (and other underwater activities), as introduces passive sensor mobility. Due to the very different environment properties and the unique characteristics of acoustic channels, the protocols developed for terrestrial sensor networks are not applicable to M-UWSNs, and new research at every level of the protocol suite is demanded. In this dissertation work, we investigate three fundamental networking problems in M-UWSN design: medium access control, multi-hop routing and reliable data transfer. (1) Medium access control (MAC): the long propagation delays and narrow communication bandwidth of acoustic channels pose the major challenges to the energy-efficient MAC design in M-UWSNs. For the first time, we formally investigate the random access and RTS/CTS techniques in networks with long propagation delays and low communication bandwidth (as in M-UWSNs). Based on this study, we propose a novel reservation-based MAC approach, called R-MAC, for dense underwater sensor networks with unevenly distributed (spatially and temporally) traffic. Simulation results show that R-MAC is not only energy efficient but also supports fairness. (2) Multi-hop routing: In M-UWSNs, energy efficiency and mobility handling are the two major concerns for multi-hop routing, which have

  4. Design of an Integrated Role-Based Access Control Infrastructure for Adaptive Workflow Systems

    C Narendra, Nanjangud

    2003-01-01

    With increasing numbers of organizations automating their business processes by using workflow systems, security aspects of workflow systems has become a heavily researched area. Also, most workflow processes nowadays need to be adaptive, i.e., constantly changing, to meet changing business conditions. However, little attention has been paid to integrating Security and Adaptive Workflow. In this paper, we investigate this important research topic, with emphasis on Role Based Access Control (R...

  5. Adaptation of Mycobacterium smegmatis to an Industrial Scale Medium and Isolation of the Mycobacterial PorinMspA

    Wendel, Sebastian O; Perera, Ayomi S; Pfromm, Peter H; Czermak, Peter; Stefan H. Bossmann

    2013-01-01

    The adaptation of the organism to a simple and cost-effective growth medium is mandatory in developing a process for large scale production of the octamericporinMspA, which is isolated from Mycobacterium smegmatis. A fermentation optimization with the minimal nutrients required for growth has been performed. During the fermentation, the iron- and ammonium chloride concentrations in the medium were varied to determine their impact on the observed growth rates and cell mass yields. Common antib...

  6. Adapting Online Learning Resources for All: Planning for Professionalism in Accessibility

    McAndrew, Patrick; Farrow, Robert; Cooper, Martyn

    2012-01-01

    Online resources for education offer opportunities for those with disabilities but also raise challenges on how to best adjust resources to accommodate accessibility. Automated reconfiguration could in principle remove the need for expensive and time-consuming discussions about adaptation. On the other hand, human-based systems provide much needed…

  7. Corporate Social Responsibility (CSR for Global Market Access: A Malaysian Case Study on Small and Medium Enterprises (SMEs

    Tareq Bin Hossain

    2013-01-01

    Full Text Available The Corporate Social Responsibility (CSR is a powerful tool or channel for ensuring greater market access and enables a better engagement in the global market. The study examines how Corporate Social Responsibility (CSR is contributing to mass access of Small and Medium Enterprises (SMEs in the global market. The study used cross section primary data from the level of executives of the corporations. Towards the achievement of its objectives this study uses descriptive statistical tools. The findings of the study revealed that practicing of CSR is playing pivotal role to pick up the brand image and reputation of the Malaysian SMEs to the customers in the global arena.

  8. A Novel Adaptive MAC Protocol for Wireless Internet Access Network with Smart Antennas

    YANGJun; LIJiandong

    2004-01-01

    Employing smart antennas in the Central access point (CAP) of wireless Internet access networks is studied. Based on the characteristics of the networks and smart antennas, a Polling-based Adaptive beamforming multiple access protocol (PB-ABFMA) is proposed. In PB-ABFMA, the CAP requests the corresponding Mobile terminal (MT) to transmit training sequence just before the data packets transmission, so the Temporal reference beamforming (TRB) can be performed by the smart antennas. The CAP schedules packet transmissions based on the polling mechanism and dynamic TDMA, and a mini-slot is used to keep connectivity when an MT is idle, therefore,the access delay is reduced. Meanwhile, a simple and effec-tive access method is proposed to guarantee rapid access of new arrival MTs to the channel. Based on the “requestreply” traffic, which is the main traffic in Internet, the theoretical analysis of channel utilization and mean turnaround delay is presented. Analysis and simulation results show that the proposed PB-ABFMA protocols effectively support the application of smart antennas and provide high channel utilization and low turn-around delay.

  9. Adapting online learning resources for all: planning for professionalism in accessibility

    Patrick McAndrew

    2012-12-01

    Full Text Available Online resources for education offer opportunities for those with disabilities but also raise challenges on how to best adjust resources to accommodate accessibility. Automated reconfiguration could in principle remove the need for expensive and time-consuming discussions about adaptation. On the other hand, human-based systems provide much needed direct support and can help understand options and individual circumstances. A study was carried out within an EU-funded accessibility project at The Open University (OU in parallel with studies at three other European universities. The study combined focus groups, user-testing, management consultation and student survey data to help understand ways forward for accessibility. The results reinforce a holistic view of accessibility, based on three factors: positioning the university as a positive provider to disabled students; developing processes, systems and services to give personal help; and planning online materials which include alternatives. The development of a model that helps organisations incorporate professionalism in accessibility is described, though challenges remain. For example, a recurrent difficulty in providing adequate self-description of accessibility needs implies that a completely automated solution may not be attainable. A more beneficial focus, therefore, may be to develop systems that support the information flow required by the human “in the loop.”

  10. Adaptive coded spreading OFDM signal for dynamic-λ optical access network

    Liu, Bo; Zhang, Lijia; Xin, Xiangjun

    2015-12-01

    This paper proposes and experimentally demonstrates a novel adaptive coded spreading (ACS) orthogonal frequency division multiplexing (OFDM) signal for dynamic distributed optical ring-based access network. The wavelength can be assigned to different remote nodes (RNs) according to the traffic demand of optical network unit (ONU). The ACS can provide dynamic spreading gain to different signals according to the split ratio or transmission length, which offers flexible power budget for the network. A 10×13.12 Gb/s OFDM access with ACS is successfully demonstrated over two RNs and 120 km transmission in the experiment. The demonstrated method may be viewed as one promising for future optical metro access network.

  11. Accessing English and Networks at an English-Medium Multicultural Church in East Canada: An Ethnography

    Han, Huamei

    2014-01-01

    Drawing from a larger ethnography of skilled Chinese immigrants' language learning during settlement in Toronto, this article explores the role of informal interactions in facilitating immigrants learning English as a second language and settlement. Examining various activities and networks available at an English-medium multicultural church,…

  12. Adaptive-Reliable Medium Access Control Protocol for Wireless Body Area Networks

    Rahim, A.; Javaid, N.; M Aslam; Qasim, U.; Khan, Z. A.

    2012-01-01

    Extensive energy is consumed by Transceiver communication operation [1]. Existing research on MAC layer focuses to maximize battery-powered sensor node's life. Bottleneck of MAC layer protocol design for WBAN is to achieve high reliability and energy minimization. Majority of MAC protocols designed for WBANs are based upon TDMA approach. However, a new protocol needs to be defined to achieve high energy efficiency, fairness and avoid extra energy consumption due to synchronization.

  13. Adaptive e-Learning: A Conceptual Solution for the analysis of link between Medium of Instruction and Performance

    Damodaran Venkatesan; RM. Chandrasekaran

    2010-01-01

    e-Learning system emphasizes on the available content to all learners irrespective of their knowledge level and relevance. This paper concentrates on the result oriented investigation of the impact of learner’s primary medium of instruction (MI) at school in understanding the content given to them in English and proposes a design for developing an Adaptive e-Learning (AeL) system personalized to the learner. An appropriate statistical model has been developed to analyze the impact and the res...

  14. An Adaptive Channel Access Method for Dynamic Super Dense Wireless Sensor Networks.

    Lei, Chunyang; Bie, Hongxia; Fang, Gengfa; Zhang, Xuekun

    2015-01-01

    Super dense and distributed wireless sensor networks have become very popular with the development of small cell technology, Internet of Things (IoT), Machine-to-Machine (M2M) communications, Vehicular-to-Vehicular (V2V) communications and public safety networks. While densely deployed wireless networks provide one of the most important and sustainable solutions to improve the accuracy of sensing and spectral efficiency, a new channel access scheme needs to be designed to solve the channel congestion problem introduced by the high dynamics of competing nodes accessing the channel simultaneously. In this paper, we firstly analyzed the channel contention problem using a novel normalized channel contention analysis model which provides information on how to tune the contention window according to the state of channel contention. We then proposed an adaptive channel contention window tuning algorithm in which the contention window tuning rate is set dynamically based on the estimated channel contention level. Simulation results show that our proposed adaptive channel access algorithm based on fast contention window tuning can achieve more than 95 % of the theoretical optimal throughput and 0 . 97 of fairness index especially in dynamic and dense networks. PMID:26633421

  15. An Adaptive Channel Access Method for Dynamic Super Dense Wireless Sensor Networks

    Chunyang Lei

    2015-12-01

    Full Text Available Super dense and distributed wireless sensor networks have become very popular with the development of small cell technology, Internet of Things (IoT, Machine-to-Machine (M2M communications, Vehicular-to-Vehicular (V2V communications and public safety networks. While densely deployed wireless networks provide one of the most important and sustainable solutions to improve the accuracy of sensing and spectral efficiency, a new channel access scheme needs to be designed to solve the channel congestion problem introduced by the high dynamics of competing nodes accessing the channel simultaneously. In this paper, we firstly analyzed the channel contention problem using a novel normalized channel contention analysis model which provides information on how to tune the contention window according to the state of channel contention. We then proposed an adaptive channel contention window tuning algorithm in which the contention window tuning rate is set dynamically based on the estimated channel contention level. Simulation results show that our proposed adaptive channel access algorithm based on fast contention window tuning can achieve more than 95 % of the theoretical optimal throughput and 0 . 97 of fairness index especially in dynamic and dense networks.

  16. Unsynchronized Energy-Efficient Medium Access Control and Routing in Wireless Sensor Networks

    Hurni, Philipp

    This master thesis investigates optimizations on recently proposed fully unsynchronized power saving sensor MAC protocols. In contrast to many other sensor MAC protocols, unsynchronized sensor MAC protocols renounce on any kind of network- or cluster-wide synchronization for channel access coordination and maintenance of a common wake-sleep pattern, because in wireless sensor networks with low traffic requirements, the overhead for maintaining synchronization is likely to exceed the energy spent for the actual data traffic.

  17. The accessing of finance by Small Medium Micro Enterprises in the Mafikeng / Karabo Khiba

    Khiba, Karabo

    2006-01-01

    The research study investigates some of the problems or challenges faced by SMMEs in the Mafikeng and Mmabatho area of the North West province. It strives to find out the extent to which these problems occur and the impact they have on these businesses. The research focuses on a number of major problems considered to be hindering the growth of SMMEs in this area, namely the lack of entrepreneurial management, financial skills, accessing finance and the role played by lack of fi...

  18. Low and medium level radioactive waste repository: the access to information

    The technological option for the nuclear energy and the society welfare must be carried on together. Access to qualified information should be allowed to the ones responsible for the preparation of material related to the project as well as to all the interested parties involved. The aim of this paper is to give some guidelines to be followed during the project implementation to guarantee this access. Complete information should be available to those involved in the project in a common database, a virtual library, where every document might be obtained. Information should be updated continuously, allowing access, through reliable search and storage tools. Every step of the project development should be well documented containing data and any eventual modification. To guarantee an open and participative conduction of the Project, several tools might be employed, according to the development of the project. Some of the suggested strategies refer to: informative and educational materials production; public consulting; interaction groups; meetings with people - mainly residents or inhabitants and specialists and stakeholders. The criteria to identify information to be released should be: novelty, impact and public interest. The rule should be to give information to all interested ones, avoiding hidden intentions. The strategy should be elaborated according to the local inhabitant's profile. Communication should be mainly done in a personal way. The responsibility for providing the information should be under an Informative Committee created specifically for communication of the project, supervised by the General Coordination and the Technical Committees. (author)

  19. Adapt

    Bargatze, L. F.

    2015-12-01

    Active Data Archive Product Tracking (ADAPT) is a collection of software routines that permits one to generate XML metadata files to describe and register data products in support of the NASA Heliophysics Virtual Observatory VxO effort. ADAPT is also a philosophy. The ADAPT concept is to use any and all available metadata associated with scientific data to produce XML metadata descriptions in a consistent, uniform, and organized fashion to provide blanket access to the full complement of data stored on a targeted data server. In this poster, we present an application of ADAPT to describe all of the data products that are stored by using the Common Data File (CDF) format served out by the CDAWEB and SPDF data servers hosted at the NASA Goddard Space Flight Center. These data servers are the primary repositories for NASA Heliophysics data. For this purpose, the ADAPT routines have been used to generate data resource descriptions by using an XML schema named Space Physics Archive, Search, and Extract (SPASE). SPASE is the designated standard for documenting Heliophysics data products, as adopted by the Heliophysics Data and Model Consortium. The set of SPASE XML resource descriptions produced by ADAPT includes high-level descriptions of numerical data products, display data products, or catalogs and also includes low-level "Granule" descriptions. A SPASE Granule is effectively a universal access metadata resource; a Granule associates an individual data file (e.g. a CDF file) with a "parent" high-level data resource description, assigns a resource identifier to the file, and lists the corresponding assess URL(s). The CDAWEB and SPDF file systems were queried to provide the input required by the ADAPT software to create an initial set of SPASE metadata resource descriptions. Then, the CDAWEB and SPDF data repositories were queried subsequently on a nightly basis and the CDF file lists were checked for any changes such as the occurrence of new, modified, or deleted

  20. Multiobjective adaptive feedback control of two-photon absorption coupled with propagation through a dispersive medium

    This work uses shaped femtosecond laser pulses to control the two-photon absorption (TPA) of coumarin 153 in a dispersive toluene medium. The dispersive medium reshapes the pulse along the optical path, and management of this effect is used to achieve spatial localization of TPA. Other control objectives were successfully implemented, including dual localization and high resolution local optimization of TPA. The solutions to these objectives were explored by means of evolutionary single- and multi-objective algorithms within a laboratory feedback loop.

  1. Adaptation of Mycobacterium smegmatis to an Industrial Scale Medium and Isolation of the Mycobacterial PorinMspA.

    Wendel, Sebastian O; Perera, Ayomi S; Pfromm, Peter H; Czermak, Peter; Bossmann, Stefan H

    2013-01-01

    The adaptation of the organism to a simple and cost-effective growth medium is mandatory in developing a process for large scale production of the octamericporinMspA, which is isolated from Mycobacterium smegmatis. A fermentation optimization with the minimal nutrients required for growth has been performed. During the fermentation, the iron- and ammonium chloride concentrations in the medium were varied to determine their impact on the observed growth rates and cell mass yields. Common antibiotics to control contamination were eliminated in favor of copper sulfate to reduce costs. MspA has been successfully isolated from the harvested M. smegmatisusing aqueous nOPOE (n-octyloligooxyethylene) at 65°C. Because of the extraordinary stability of MspA, it is possible to denature and precipitate virtually all other proteins and contaminants by following this approach. To further purify the product, acetone is used for precipitation. Gel electrophoresis confirmed the presence and purity of MspA. A maximum of 840µg (via Bradford assay) of pure MspA per liter of the optimized simple growth medium has been obtained. This is a 40% increase with respect to the previously reported culture medium for MspA. PMID:23802026

  2. Cross-Cultural adaptation of an instrument to computer accessibility evaluation for students with cerebral palsy

    Gerusa Ferreira Lourenço

    2015-03-01

    Full Text Available The specific literature indicates that the successful education of children with cerebral palsy may require the implementation of appropriate assistive technology resources, allowing students to improve their performance and complete everyday tasks more efficiently and independently. To this end, these resources must be selected properly, emphasizing the importance of an appropriate initial assessment of the child and the possibilities of the resources available. The present study aimed to translate and adapt theoretically an American instrument that evaluates computer accessibility for people with cerebral palsy, in order to contextualize it for applicability to Brazilian students with cerebral palsy. The methodology involved the steps of translation and cross-cultural adaptation of this instrument, as well as the construction of a supplementary script for additional use of that instrument in the educational context. Translation procedures, theoretical and technical adaptation of the American instrument and theoretical analysis (content and semantics were carried out with the participation of professional experts of the special education area as adjudicators. The results pointed to the relevance of the proposal of the translated instrument in conjunction with the script built to the reality of professionals involved with the education of children with cerebral palsy, such as occupational therapists and special educators.

  3. Energy-Efficient Medium Access Control Protocols for Wireless Sensor Networks

    Ren Qingchun

    2006-01-01

    Full Text Available A key challenge for wireless sensor networks is how to extend network lifetime with dynamic power management on energy-constraint sensor nodes. In this paper, we propose two energy-efficient MAC protocols: asynchronous MAC (A-MAC protocol and asynchronous schedule-based MAC (ASMAC protocol. A-MAC and ASMAC protocols are attractive due to their suitabilities for multihop networks and capabilities of removing accumulative clock-drifts without any network synchronization. Moreover, we build a traffic-strength- and network-density-based model to adjust essential algorithm parameters adaptively. Simulation results show that our algorithms can successfully acquire the optimum values of power-on/off duration, schedule-broadcast interval, as well as super-time-slot size and order. These algorithm parameters can ensure adequate successful transmission rate, short waiting time, and high energy utilization. Therefore, not only the performance of network is improved but also its lifetime is extended when A-MAC or ASMAC is used.

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

    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

  5. The HARNESS Workbench: Unified and Adaptive Access to Diverse HPC Platforms

    Sunderam, Vaidy S.

    2012-03-20

    The primary goal of the Harness WorkBench (HWB) project is to investigate innovative software environments that will help enhance the overall productivity of applications science on diverse HPC platforms. Two complementary frameworks were designed: one, a virtualized command toolkit for application building, deployment, and execution, that provides a common view across diverse HPC systems, in particular the DOE leadership computing platforms (Cray, IBM, SGI, and clusters); and two, a unified runtime environment that consolidates access to runtime services via an adaptive framework for execution-time and post processing activities. A prototype of the first was developed based on the concept of a 'system-call virtual machine' (SCVM), to enhance portability of the HPC application deployment process across heterogeneous high-end machines. The SCVM approach to portable builds is based on the insertion of toolkit-interpretable directives into original application build scripts. Modifications resulting from these directives preserve the semantics of the original build instruction flow. The execution of the build script is controlled by our toolkit that intercepts build script commands in a manner transparent to the end-user. We have applied this approach to a scientific production code (Gamess-US) on the Cray-XT5 machine. The second facet, termed Unibus, aims to facilitate provisioning and aggregation of multifaceted resources from resource providers and end-users perspectives. To achieve that, Unibus proposes a Capability Model and mediators (resource drivers) to virtualize access to diverse resources, and soft and successive conditioning to enable automatic and user-transparent resource provisioning. A proof of concept implementation has demonstrated the viability of this approach on high end machines, grid systems and computing clouds.

  6. Innovation, adaptability, and collaboration: Keys to success for small and medium sized reactors. Cairo, 27 May 2001

    Small and medium sized reactors, within a power output of less than 700 MW(e), are receiving increased consideration in the effort to meet changing market requirements. Smaller plants allow a more incremental investment, which can be used to hedge against demand uncertainty. They are more suitable for standardization and prefabrication, which in turn encourages enhanced quality control and stimulates rapid development of expertise and shorter construction schedules. They provide a better match to grid capacity in developing countries. And they are more easily adapted to a broad range of industrial settings and applications, such as district heating, heavy oil recovery, or the production of hydrogen and other chemical fuels. Sea water desalination is an application for which smaller reactors hold a particular advantage. Nuclear powered desalination is a proven technology. Clearly, we live in an era in which our society faces many difficult economic, environmental and social issues associated with sustainable development and energy demand. Against that backdrop, nuclear power is a mature technology that deserves careful consideration as a contributor to solving some of these issues. The development of innovative small and medium sized reactors will play a key role in helping to match state-of-the-art technology to user needs. An exchange of information and ideas is a step towards further progress

  7. Landscape Influences on Fisher Success: Adaptation Strategies in Closed and Open Access Fisheries in Southern Chile

    Tracy Van Holt

    2012-03-01

    Full Text Available Determinants of fisher success in southern Chile's loco (Concholepas concholepas fishery are examined by comparing fisher success in exclusive access territories that vary in relationship to tree-plantation development, which can affect shellfish quality. The relative importance of fishers' experience and capture technology (traditional measures of fisher success are evaluated against environmental and geospatial characteristics. While knowledge and technology explained variation in catches, this did not translate into higher prices or profit. Fishers succeeded (gained higher prices for locos and had higher monthly incomes from their management areas when they harvested shellfish from closed (exclusive nearshore management areas where the environmental condition produced high quality locos regardless of their fishing experience, technology, and the geospatial features of management areas. Experienced fishers who worked in management areas near tree plantations that fail to produce resources of sufficient quality shifted to offshore fisheries where their experience counted. Offshore fishers working in the congrio (Genypterus chilensis fishery likely exposed themselves to more risk and benefited from their experience and available technology; environmental condition and geospatial factors played little role in their success (price. Closed management areas provided resources to harvest, but may reduce a fisher's ability to adapt to environmental change because success depends on environmental factors outside of a fisher's control. Fishers were not financially rewarded for their experience or their technology in the loco fishery.

  8. Energy-Efficiency Analysis of a Distributed Queuing Medium Access Control Protocol for Biomedical Wireless Sensor Networks in Saturation Conditions

    Christos Verikoukis

    2011-01-01

    Full Text Available The aging population and the high quality of life expectations in our society lead to the need of more efficient and affordable healthcare solutions. For this reason, this paper aims for the optimization of Medium Access Control (MAC protocols for biomedical wireless sensor networks or wireless Body Sensor Networks (BSNs. The hereby presented schemes always have in mind the efficient management of channel resources and the overall minimization of sensors’ energy consumption in order to prolong sensors’ battery life. The fact that the IEEE 802.15.4 MAC does not fully satisfy BSN requirements highlights the need for the design of new scalable MAC solutions, which guarantee low-power consumption to the maximum number of body sensors in high density areas (i.e., in saturation conditions. In order to emphasize IEEE 802.15.4 MAC limitations, this article presents a detailed overview of this de facto standard for Wireless Sensor Networks (WSNs, which serves as a link for the introduction and initial description of our here proposed Distributed Queuing (DQ MAC protocol for BSN scenarios. Within this framework, an extensive DQ MAC energy-consumption analysis in saturation conditions is presented to be able to evaluate its performance in relation to IEEE 802.5.4 MAC in highly dense BSNs. The obtained results show that the proposed scheme outperforms IEEE 802.15.4 MAC in average energy consumption per information bit, thus providing a better overall performance that scales appropriately to BSNs under high traffic conditions. These benefits are obtained by eliminating back-off periods and collisions in data packet transmissions, while minimizing the control overhead.

  9. Medium-Range Predictability of Contrail-Cirrus Demonstrated during Experiments Ml-Cirrus and Access-Ii

    Schumann, U.

    2015-12-01

    The Contrail Cirrus Prediction model CoCiP (doi:10.5194/gmd-5-543-2012) has been applied quasi operationally to predict contrails for flight planning of ML-CIRRUS (C. Voigt, DLR, et al.) in Europe and for ACCESS II in California (B. Anderson, NASA, et al.) in March-May 2014. The model uses NWP data from ECMWF and past airtraffic data (actual traffic data are used for analysis). The forecasts provided a sequence of hourly forecast maps of contrail cirrus optical depth for 3.5 days, every 12 h. CoCiP has been compared to observations before, e.g. within a global climate-aerosol-contrail model (Schumann, Penner et al., ACPD, 2015, doi:10.5194/acpd-15-19553-2015). Good predictions would allow for climate optimal routing (see, e.g., US patent by Mannstein and Schumann, US 2012/0173147 A1). The predictions are tested by: 1) Local eyewitness reports and photos, 2) satellite observed cloudiness, 3) autocorrelation analysis of predictions for various forecast periods, 4) comparisons of computed with observed optical depth from COCS (doi:10.5194/amt-7-3233-2014, 2014) by IR METEOSAT-SEVIRI observations over Europe. The results demonstrate medium-range predictability of contrail cirrus to a useful degree for given traffic, soot emissions, and high-quality NWP data. A growing set of satellite, Lidar, and in-situ data from ML-CIRRUS and ACCENT are becoming available and will be used to further test the forecast quality. The autocorrelation of optical depth predictions is near 70% for 3-d forecasts for Europe (outside times with high Sahara dust loads), and only slightly smaller for continental USA. Contrail cirrus is abundant over Europe and USA. More than 1/3 of all cirrus measured with the research aircraft HALO during ML-CIRRUS was impacted by contrails. The radiative forcing (RF) is strongly daytime and ambience dependent. The net annual mean RF, based on our global studies, may reach up to 0.08 W/m2 globally, and may well exceed 1 W/m2 regionally, with maximum over Europe

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

    Radovan, Marko; Perdih, Mojca

    2016-01-01

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

  11. Reduced-complexity adaptive multi-channel assignment for shared access points in over-loaded small-cell networks

    Radaydeh, Redha Mahmoud

    2013-06-01

    This paper proposes a reduced-complexity downlink multi-channel assignment scheme when feedback links are capacity-limited. The system model treats the case when multiple access points are allocated to serve scheduled users in over-loaded (i.e. dense) pico/femtocell networks. It assumes that the deployed access points can be shared simultaneously and employ isotropic antenna arrays of arbitrary sizes. Moreover, they transmit their data on a common physical channel and can not coordinate their transmissions. On the other hand, each scheduled user can be served by single transmit channel from each active access point at a time, and it lacks coordination with concurrent active users. The scheme operates according to the occupancy of available transmit channels, wherein extensively occupied access points are avoided adaptively, while reducing the load of processing. The operation is linked to a target performance via controlling the observed aggregate interference from the projected set of serving points. Through the analysis, results for the scheduled user outage performance, and the average number of active access points are presented. Numerical and simulations studies clarify the gains of the proposed scheme for different operating conditions. © 2013 IEEE.

  12. Adaptive MPI Multirail Tuning for Non-Uniform Input/Output Access

    Moreaud, Stéphanie; Goglin, Brice; Namyst, Raymond

    2010-01-01

    Multicore processors have not only reintroduced Non-Uniform Memory Access (NUMA) architectures in nowadays parallel computers, but they are also responsible for non-uniform access times with respect to Input/Output devices (NUIOA). In clusters of multicore machines equipped with several Network Interfaces, performance of communication between processes thus depends on which cores these processes are scheduled on, and on their distance to the Network Interface Cards involved. We propose a tech...

  13. Intelligent Voice-Based Door Access Control System Using Adaptive-Network-based Fuzzy Inference Systems (ANFIS for Building Security

    Wahyudi

    2007-01-01

    Full Text Available Secure buildings are currently protected from unauthorized access by a variety of devices. Even though there are many kinds of devices to guarantee the system safety such as PIN pads, keys both conventional and electronic, identity cards, cryptographic and dual control procedures, the people voice can also be used. The ability to verify the identity of a speaker by analyzing speech, or speaker verification, is an attractive and relatively unobtrusive means of providing security for admission into an important or secured place. An individual’s voice cannot be stolen, lost, forgotten, guessed, or impersonated with accuracy. Due to these advantages, this paper describes design and prototyping a voice-based door access control system for building security. In the proposed system, the access may be authorized simply by means of an enrolled user speaking into a microphone attached to the system. The proposed system then will decide whether to accept or reject the user’s identity claim or possibly to report insufficient confidence and request additional input before making the decision. Furthermore, intelligent system approach is used to develop authorized person models based on theirs voice. Particularly Adaptive-Network-based Fuzzy Inference Systems is used in the proposed system to identify the authorized and unauthorized people. Experimental result confirms the effectiveness of the proposed intelligent voice-based door access control system based on the false acceptance rate and false rejection rate.

  14. Adaptive Technology that Provides Access to Computers. DO-IT Program.

    Washington Univ., Seattle.

    This brochure describes the different types of barriers individuals with mobility impairments, blindness, low vision, hearing impairments, and specific learning disabilities face in providing computer input, interpreting output, and reading documentation. The adaptive hardware and software that has been developed to provide functional alternatives…

  15. Analysis of Educational Web Pattern Using Adaptive Markov Chain For Next Page Access Prediction

    Harish Kumar; Anil Kumar Solanki

    2011-01-01

    The Internet grows at an amazing rate as an information gateway and as a medium for business and education industry. Universities with web education rely on web usage analysis to obtain students behavior for web marketing. Web Usage Mining (WUM) integrates the techniques of two popular research fields – Data Mining and the Internet. Web usage mining attempts to discover useful knowledge from the secondary data (Web logs). These useful data pattern are use to analyze visitors activities in the...

  16. Spectral Efficiency of Multiple Access Fading Channels with Adaptive Interference Cancellation

    Shakya, Indu L

    2012-01-01

    Reliable estimation of users' channels and data in rapidly time varying fading environments is a very challenging task of multiuser detection (MUD) techniques that promise impressive capacity gains for interference limited systems such as non-orthogonal CDMA and spatial multiplexing MIMO based LTE. This paper analyzes relative channel estimation error performances of conventional single user and multiuser receivers for an uplink of DS-CDMA and shows their impact on output signal to interference and noise ratio (SINR) performances. Mean squared error (MSE) of channel estimation and achievable spectral efficiencies of these receivers obtained from the output SINR calculations are then compared with that achieved with new adaptive interference canceling receivers. It is shown that the adaptive receivers using successive (SIC) and parallel interference cancellation (PIC) methods offer much improved channel estimation and SINR performances, and hence significant increase in achievable sum date rates.

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

    Chien, Tsair-Wei; Lin, Weir-Sen

    2016-01-01

    Background The National Health Service (NHS) 70-item inpatient questionnaire surveys inpatients on their perceptions of their hospitalization experience. However, it imposes more burden on the patient than other similar surveys. The literature shows that computerized adaptive testing (CAT) based on item response theory can help shorten the item length of a questionnaire without compromising its precision. Objective Our aim was to investigate whether CAT can be (1) efficient with item reductio...

  18. Achieving Capacity of Bi-Directional Tandem Collision Network by Joint Medium-Access Control and Channel-Network Coding

    Shum, Kenneth W

    2009-01-01

    In ALOHA-type packetized network, the transmission times of packets follow a stochastic process. In this paper, we advocate a deterministic approach for channel multiple-access. Each user is statically assigned a periodic protocol signal, which takes value either zero or one, and transmit packets whenever the value of the protocol signal is equal to one. On top of this multiple-access protocol, efficient channel coding and network coding schemes are devised. We illustrate the idea by constructing a transmission scheme for the tandem collision network, for both slot-synchronous and slot-asynchronous systems. This cross-layer approach is able to achieve the capacity region when the network is bi-directional.

  19. The design-by-adaptation approach to universal access: learning from videogame technology

    Shepherd, Ifan D. H.; Bleasdale-Shepherd, Iestyn D.

    2010-01-01

    This paper proposes an alternative approach to the design of universally accessible interfaces to that provided by formal design frameworks applied ab initio to the development of new software. This approach, design-byadaptation, involves the transfer of interface technology and/or design principles from one application domain to another, in situations where the recipient domain is similar to the host domain in terms of modelled systems, tasks and users. Using the example of interaction in 3D...

  20. An Adaptive Channel Access Method for Dynamic Super Dense Wireless Sensor Networks

    Chunyang Lei; Hongxia Bie; Gengfa Fang; Xuekun Zhang

    2015-01-01

    Super dense and distributed wireless sensor networks have become very popular with the development of small cell technology, Internet of Things (IoT), Machine-to-Machine (M2M) communications, Vehicular-to-Vehicular (V2V) communications and public safety networks. While densely deployed wireless networks provide one of the most important and sustainable solutions to improve the accuracy of sensing and spectral efficiency, a new channel access scheme needs to be designed to solve the channel co...

  1. THE ACCESS OF SMALL AND MEDIUM SIZE ENTERPRISES TO BANKING FINANCING AND CURRENT CHALLANGES: THE CASE OF EU COUNTRIES

    Roman Angela; Rusu Valentina Diana

    2012-01-01

    Bank loans are a vital resource for SMEs financing because of the reducedpossibilities of these firms to find alternative sources of financing. In the context of the currentcrisis, the access to loans for SMEs has deteriorated significantly due to lower availability of bankloans, that can hamper the exit from the crisis of these firms and the relaunch of the nationaleconomies. Moreover, the adoption of the new banking regulations by Basel III Accord raisesconcerns about their possible negativ...

  2. Integration of Intercultural Competence in the Processes of Enterprise Internationalization: Possibilities of the Adaptation of the Model in the Operation of Small and Medium Enterprises

    Jolita Vveinhardt

    2015-05-01

    Full Text Available The article briefly presents the problems identified during the studies carried out by the authors previously, i.e. the problems of intercultural competence and its integration in the processes of internationalization are disclosed. On the basis of the researches carried out the model of integration of intercultural competence in the internationalization processes is adapted, preparing the plan of development of intercultural competence in enterprises. At the end of the article the guidelines for the application of the model for development of internationalization of small and medium enterprises is presented.

  3. An Energy-efficient Rate Adaptive Media Access Protocol (RA-MAC for Long-lived Sensor Networks

    Wen Hu

    2010-06-01

    Full Text Available We introduce an energy-efficient Rate Adaptive Media Access Control (RA-MAC algorithm for long-lived Wireless Sensor Networks (WSNs. Previous research shows that the dynamic and lossy nature of wireless communications is one of the major challenges to reliable data delivery in WSNs. RA-MAC achieves high link reliability in such situations by dynamically trading off data rate for channel gain. The extra gain that can be achieved reduces the packet loss rate which contributes to reduced energy expenditure through a reduced numbers of retransmissions. We achieve this at the expense of raw bit rate which generally far exceeds the application’s link requirement. To minimize communication energy consumption, RA-MAC selects the optimal data rate based on the estimated link quality at each data rate and an analytical model of the energy consumption. Our model shows how the selected data rate depends on different channel conditions in order to minimize energy consumption. We have implemented RA-MAC in TinyOS for an off-the-shelf sensor platform (the TinyNode on top of a state-of-the-art WSN Media Access Control Protocol, SCP-MAC, and evaluated its performance by comparing our implementation with the original SCP-MAC using both simulation and experiment.

  4. An energy-efficient rate adaptive media access protocol (RA-MAC) for long-lived sensor networks.

    Hu, Wen; Chen, Quanjun; Corke, Peter; O'Rourke, Damien

    2010-01-01

    We introduce an energy-efficient Rate Adaptive Media Access Control (RA-MAC) algorithm for long-lived Wireless Sensor Networks (WSNs). Previous research shows that the dynamic and lossy nature of wireless communications is one of the major challenges to reliable data delivery in WSNs. RA-MAC achieves high link reliability in such situations by dynamically trading off data rate for channel gain. The extra gain that can be achieved reduces the packet loss rate which contributes to reduced energy expenditure through a reduced numbers of retransmissions. We achieve this at the expense of raw bit rate which generally far exceeds the application's link requirement. To minimize communication energy consumption, RA-MAC selects the optimal data rate based on the estimated link quality at each data rate and an analytical model of the energy consumption. Our model shows how the selected data rate depends on different channel conditions in order to minimize energy consumption. We have implemented RA-MAC in TinyOS for an off-the-shelf sensor platform (the TinyNode) on top of a state-of-the-art WSN Media Access Control Protocol, SCP-MAC, and evaluated its performance by comparing our implementation with the original SCP-MAC using both simulation and experiment. PMID:22219675

  5. Adaptive interference-aware multichannel assignment for shared overloaded small-cell access points under limited feedback

    Radaydeh, Redha Mahmoud

    2014-02-01

    This paper proposes a reduced-complexity multichannel assignment scheme for short-range cellular systems. It treats the scenario when a number of small-cell (e.g., femtocell) access points (APs) can be shared to serve active scheduled users. The APs employ isotropic antenna arrays and operate using an open-access control strategy. To improve the reuse ratio of physical resources, the APs are assumed to occupy a single physical channel, wherein coordination among them is infeasible. On the other hand, to improve the spatial coverage, a scheduled user can be served by a single transmit channel from an AP at a time. For the case of overloaded APs and when the feedback links are capacity limited, the scheme attempts to identify the suitable transmit channels from the deployed APs in an adaptive manner such that certain performance and/or processing load limits are satisfied. The effects of some system and design parameters on the outcomes of the scheme are thoroughly discussed. Novel results for the statistics of the resulting interference power are presented, from which results for some performance measures and processing loads are obtained. Numerical and simulations results are provided to clarify the achieved gains, as compared with related models under different operating conditions. © 2013 IEEE.

  6. An Adaptive Gateway Discovery Algorithm to support QoS When Providing Internet Access to Mobile Ad Hoc Networks

    Mari Carmen Domingo

    2007-04-01

    Full Text Available When a node in an ad hoc network wants Internet access, it needs to obtain information about the available gateways and it should select the most appropriate of them. In this work we propose a new gateway discovery scheme suitable for real-time applications that adjusts the frequency of gateway advertisements dynamically. This adjustment is related to the percentage of real-time sources that have quality of service problems because of excessive end-to-end delays. The optimal values for the configuration parameters (time interval and threshold of the proposed adaptive gateway discovery mechanism for the selected network conditions have been studied with the aid of simulations. The scalability of the proposed scheme with respect to mobility as well as the impact of best-effort traffic load have been analyzed. Simulation results indicate that the proposed scheme significantly improves the average end-to-end delay, jitter and packet delivery ratio of real-time flows; the routing overhead is also reduced and there is no starvation of best-effort traffic.

  7. Optimal Policy of Cross-Layer Design for Channel Access and Transmission Rate Adaptation in Cognitive Radio Networks

    Jiang Zhu

    2010-01-01

    Full Text Available In this paper, we investigate the cross-layer design of joint channel access and transmission rate adaptation in CR networks with multiple channels for both centralized and decentralized cases. Our target is to maximize the throughput of CR network under transmission power constraint by taking spectrum sensing errors into account. In centralized case, this problem is formulated as a special constrained Markov decision process (CMDP, which can be solved by standard linear programming (LP method. As the complexity of finding the optimal policy by LP increases exponentially with the size of action space and state space, we further apply action set reduction and state aggregation to reduce the complexity without loss of optimality. Meanwhile, for the convenience of implementation, we also consider the pure policy design and analyze the corresponding characteristics. In decentralized case, where only local information is available and there is no coordination among the CR users, we prove the existence of the constrained Nash equilibrium and obtain the optimal decentralized policy. Finally, in the case that the traffic load parameters of the licensed users are unknown for the CR users, we propose two methods to estimate the parameters for two different cases. Numerical results validate the theoretic analysis.

  8. Accessible bioprinting: adaptation of a low-cost 3D-printer for precise cell placement and stem cell differentiation.

    Reid, John A; Mollica, Peter A; Johnson, Garett D; Ogle, Roy C; Bruno, Robert D; Sachs, Patrick C

    2016-01-01

    The precision and repeatability offered by computer-aided design and computer-numerically controlled techniques in biofabrication processes is quickly becoming an industry standard. However, many hurdles still exist before these techniques can be used in research laboratories for cellular and molecular biology applications. Extrusion-based bioprinting systems have been characterized by high development costs, injector clogging, difficulty achieving small cell number deposits, decreased cell viability, and altered cell function post-printing. To circumvent the high-price barrier to entry of conventional bioprinters, we designed and 3D printed components for the adaptation of an inexpensive 'off-the-shelf' commercially available 3D printer. We also demonstrate via goal based computer simulations that the needle geometries of conventional commercially standardized, 'luer-lock' syringe-needle systems cause many of the issues plaguing conventional bioprinters. To address these performance limitations we optimized flow within several microneedle geometries, which revealed a short tapered injector design with minimal cylindrical needle length was ideal to minimize cell strain and accretion. We then experimentally quantified these geometries using pulled glass microcapillary pipettes and our modified, low-cost 3D printer. This systems performance validated our models exhibiting: reduced clogging, single cell print resolution, and maintenance of cell viability without the use of a sacrificial vehicle. Using this system we show the successful printing of human induced pluripotent stem cells (hiPSCs) into Geltrex and note their retention of a pluripotent state 7 d post printing. We also show embryoid body differentiation of hiPSC by injection into differentiation conducive environments, wherein we observed continuous growth, emergence of various evaginations, and post-printing gene expression indicative of the presence of all three germ layers. These data demonstrate an

  9. A methodology for the valuation and selection of adaptable technology portfolios and its application to small and medium airports

    Pinon, Olivia J.

    The increase in the types of airspace users (large aircraft, small and regional jets, very light jets, unmanned aerial vehicles, etc.), as well as the very limited number of future new airport development projects are some of the factors that will characterize the next decades in air transportation. These factors, associated with a persistent growth in air traffic will worsen the current gridlock situation experienced at some major airports. As airports are becoming the major capacity bottleneck to continued growth in air traffic, it is therefore primordial to make the most efficient use of the current, and very often, underutilized airport infrastructure. This research thus proposes to address the increase in air traffic demand and resulting capacity issues by considering the implementation of operational concepts and technologies at underutilized airports. However, there are many challenges associated with sustaining the development of this type of airports. First, the need to synchronize evolving technologies with airports’ needs and investment capabilities is paramount. Additionally, it was observed that the evolution of secondary airports, and their needs, is tightly linked to the environment in which they operate. In particular, sensitivity of airports to changes in the dynamics of their environment is important, therefore requiring that the factors that drive the need for technology acquisition be identified and characterized. Finally, the difficulty to evaluate risk and make financially viable decisions, particularly when investing in new technologies, cannot be ignored. This research provides a methodology that addresses these challenges and ensures the sustainability of airport capacity-enhancement investments in a continuously changing environment. In particular, it is articulated around the need to provide decision makers with the capability to valuate and select adaptable technology portfolios to ensure airport financial viability. Hence, the four

  10. A Semantic-Oriented Architecture of a Functional Module for Personalized and Adaptive Access to the Knowledge in a Multimedia Digital Library

    Paneva-Marinova, Desislava

    2008-01-01

    This article presents the principal results of the doctoral thesis “Semantic-oriented Architecture and Models for Personalized and Adaptive Access to the Knowledge in Multimedia Digital Library” by Desislava Ivanova Paneva-Marinova (Institute of Mathematics and Informatics), successfully defended before the Specialised Academic Council for Informatics and Mathematical Modelling on 27 October, 2008. This paper presents dissertation work on semantic-oriented architectures and...

  11. A new PON system for LAN and medium/high-speed Internet access%一种适用于LAN及 中高速Internet接入的PON系统

    冯先成; 韵湘; 胡煌球

    2001-01-01

    一种适用于中高速计算机通信的共享接入的新型PON系统,将使多个ONU公平共享一条高速宽带通道,从而提供经济有效的中高速Internet接入.%A new shared-access system suitable for medium/high-speed Internet access has been developed. This system is based on PON system. By using the new shared-access technologies, where a high-speed path for computer communication is shared equally by multiple OUNs, high-speed path for Internet access can be provided economically.

  12. Study on a compact and adaptable Thomson Spectrometer for laser-initiated 11B(p,α)8Be reactions and low-medium energy particle detection

    Consoli, F.; De Angelis, R.; Bonasera, A.; Sura, J.; Andreoli, P.; Cristofari, G.; Cipriani, M.; Di Giorgio, G.; Ingenito, F.; Barbarino, M.; Labaune, C.; Baccou, C.; Depierreux, S.; Goyon, C.; Yahia, V.

    2016-05-01

    Thomson Spectrometers are of primary importance in the discrimination of particles produced by laser-plasma interaction, according to their energy and charge-mass ratio. We describe here a detailed study on a set of Thomson Spectrometers, adaptable to different experimental situations, with the aim of being placed directly within the experimental chamber, rather than in additional extensions, in order to increase the solid angle of observation. These instruments are suitable for detection of low-medium energy particles and can be effectively employed in laser-plasma experiments of 11B(p,α)8Be fusion. They are provided with permanent magnets, have small dimensions and compact design. In these small configurations electric and magnetic fringing fields play a primary role for particle deflection, and their accurate characterization is required. It was accomplished by means of COMSOL electromagnetic solver coupled to an effective analytical model, very suitable for practical use of the spectrometers. Data from experimental measurements of the magnetic fields have been also used. We describe the application of the spectrometers to an experiment of laser-plasma interaction, coupled to Imaging Plate detectors. Data analysis for spectrum and yield of the detected radiation is discussed in detail.

  13. Catalase activity is stimulated by H2O2 in rich culture medium and is required for H2O2 resistance and adaptation in yeast

    Dorival Martins

    2014-01-01

    Full Text Available Catalases are efficient scavengers of H2O2 and protect cells against H2O2 stress. Examination of the H2O2 stimulon in Saccharomyces cerevisiae revealed that the cytosolic catalase T (Ctt1 protein level increases 15-fold on H2O2 challenge in synthetic complete media although previous work revealed that deletion of the CCT1 or CTA1 genes (encoding peroxisomal/mitochondrial catalase A does not increase the H2O2 sensitivity of yeast challenged in phosphate buffer (pH 7.4. This we attributed to our observation that catalase activity is depressed when yeast are challenged with H2O2 in nutrient-poor media. Hence, we performed a systematic comparison of catalase activity and cell viability of wild-type yeast and of the single catalase knockouts, ctt1∆ and cta1∆, following H2O2 challenge in nutrient-rich medium (YPD and in phosphate buffer (pH 7.4. Ctt1 but not Cta1 activity is strongly induced by H2O2 when cells are challenged in YPD but suppressed when cells are challenged in buffer. Consistent with the activity results, exponentially growing ctt1∆ cells in YPD are more sensitive to H2O2 than wild-type or cta1∆ cells, whereas in buffer all three strains exhibit comparable H2O2 hypersensitivity. Furthermore, catalase activity is increased during adaptation to sublethal H2O2 concentrations in YPD but not in buffer. We conclude that induction of cytosolic Ctt1 activity is vital in protecting yeast against exogenous H2O2 but this activity is inhibited by H2O2 when cells are challenged in nutrient-free media.

  14. The resilience activation framework: a conceptual model of how access to social resources promotes adaptation and rapid recovery in post-disaster settings.

    Abramson, David M; Grattan, Lynn M; Mayer, Brian; Colten, Craig E; Arosemena, Farah A; Bedimo-Rung, Ariane; Lichtveld, Maureen

    2015-01-01

    A number of governmental agencies have called for enhancing citizens' resilience as a means of preparing populations in advance of disasters, and as a counterbalance to social and individual vulnerabilities. This increasing scholarly, policy, and programmatic interest in promoting individual and communal resilience presents a challenge to the research and practice communities: to develop a translational framework that can accommodate multidisciplinary scientific perspectives into a single, applied model. The Resilience Activation Framework provides a basis for testing how access to social resources, such as formal and informal social support and help, promotes positive adaptation or reduced psychopathology among individuals and communities exposed to the acute collective stressors associated with disasters, whether human-made, natural, or technological in origin. Articulating the mechanisms by which access to social resources activate and sustain resilience capacities for optimal mental health outcomes post-disaster can lead to the development of effective preventive and early intervention programs. PMID:24870399

  15. High Speed, Low Cost Telemetry Access from Space Development Update on Programmable Ultra Lightweight System Adaptable Radio (PULSAR)

    Simms, William Herbert, III; Varnavas, Kosta; Eberly, Eric

    2014-01-01

    Software Defined Radio (SDR) technology has been proven in the commercial sector since the early 1990's. Today's rapid advancement in mobile telephone reliability and power management capabilities exemplifies the effectiveness of the SDR technology for the modern communications market. In contrast, the foundations of transponder technology presently qualified for satellite applications were developed during the early space program of the 1960's. Conventional transponders are built to a specific platform and must be redesigned for every new bus while the SDR is adaptive in nature and can fit numerous applications with no hardware modifications. A SDR uses a minimum amount of analog / Radio Frequency (RF) components to up/down-convert the RF signal to/from a digital format. Once the signal is digitized, all processing is performed using hardware or software logic. Typical SDR digital processes include; filtering, modulation, up/down converting and demodulation. NASA Marshall Space Flight Center (MSFC) Programmable Ultra Lightweight System Adaptable Radio (PULSAR) leverages existing MSFC SDR designs and commercial sector enhanced capabilities to provide a path to a radiation tolerant SDR transponder. These innovations (1) reduce the cost of NASA Low Earth Orbit (LEO) and Deep Space standard transponders, (2) decrease power requirements, and (3) commensurately reduce volume. A second pay-off is the increased SDR flexibility by allowing the same hardware to implement multiple transponder types simply by altering hardware logic - no change of hardware is required - all of which will ultimately be accomplished in orbit. Development of SDR technology for space applications will provide a highly capable, low cost transponder to programs of all sizes. The MSFC PULSAR Project results in a Technology Readiness Level (TRL) 7 low-cost telemetry system available to Smallsat and CubeSat missions, as well as other platforms. This paper documents the continued development and

  16. RED for PMTCT: an adaptation of immunization's Reaching Every District approach increases coverage, access, and utilization of PMTCT care in Bondo District, Kenya.

    Kanyuuru, Lynn; Kabue, Mark; Ashengo, Tigistu A; Ruparelia, Chandrakant; Mokaya, Evans; Malonza, Isaac

    2015-06-01

    Gaps exist in coverage, early access, and utilization of prevention of mother-to-child transmission of HIV (PMTCT) services in Kenya. The Maternal and Child Health Integrated Program, led by Jhpiego, piloted an adaptation of immunization's Reaching Every District (RED) approach in Bondo District as a way of improving PMTCT care. Routine district-level monthly summary service delivery pre- and post-implementation data were analyzed. Marked improvements resulted in the proportion of HIV-infected and non-infected pregnant women completing four focused prenatal care visits, from 25% to 41%, and the proportion of HIV-exposed infants (HEIs) tested at six weeks, from 27% to 78% (PHIV infection at 12months was 52%, while 77% of HEIs were issued antiretroviral prophylaxis by the end of the pilot. Implementation of RED for PMTCT demonstrated that PMTCT services can be delivered effectively in the context of the existing community strategy and resulted in increased coverage, access, and utilization of care for HIV-positive pregnant women and their children. PMID:26115861

  17. Programmable Ultra Lightweight System Adaptable Radio (PULSAR) Low Cost Telemetry - Access from Space Advanced Technologies or Down the Middle

    Sims. Herb; Varnavas, Kosta; Eberly, Eric

    2013-01-01

    Software Defined Radio (SDR) technology has been proven in the commercial sector since the early 1990's. Today's rapid advancement in mobile telephone reliability and power management capabilities exemplifies the effectiveness of the SDR technology for the modern communications market. In contrast, presently qualified satellite transponder applications were developed during the early 1960's space program. Programmable Ultra Lightweight System Adaptable Radio (PULSAR, NASA-MSFC SDR) technology revolutionizes satellite transponder technology by increasing data through-put capability by, at least, an order of magnitude. PULSAR leverages existing Marshall Space Flight Center SDR designs and commercially enhanced capabilities to provide a path to a radiation tolerant SDR transponder. These innovations will (1) reduce the cost of NASA Low Earth Orbit (LEO) and Deep Space transponders, (2) decrease power requirements, and (3) a commensurate volume reduction. Also, PULSAR increases flexibility to implement multiple transponder types by utilizing the same hardware with altered logic - no analog hardware change is required - all of which can be accomplished in orbit. This provides high capability, low cost, transponders to programs of all sizes. The final project outcome would be the introduction of a Technology Readiness Level (TRL) 7 low-cost CubeSat to SmallSat telemetry system into the NASA Portfolio.

  18. 面向普适计算的自适应模糊访问控制方法%Adaptive fuzzy access control method for pervasive computing

    张立臣; 王小明; 窦文阳

    2012-01-01

    普适环境中的上下文信息是普适访问控制的关键因素,对主体的授权和对主体使用权限过程的控制具有决定性影响.系统安全强度和安全策略应随上下文的变化而动态改变.传统访问控制模型均未考虑上下文对安全强度和安全策略的动态影响,不适合普适计算环境.提出了普适环境下安全强度和安全策略随上下文动态变化的思想,基于区间值模糊集合理论建立了上下文信息相关的产生式规则,设计了一种简单高效的区间值模糊访问控制方法,以提高普适计算系统中安全强度和安全策略的自适应性,更符合普适环境.%Context information is one of the key factors in pervasive access control systems, and produces the decisive influence on authorization and permission control on the subjects in pervasive computing environments. The security threshold intensity and the security policies should rectify according to the changes of context information, which has not been taken into consideration by traditional access control models, not fitting for the pervasive computing environment. In order to deeply adapt to the pervasive computing environment, the idea of security threshold intensity and security policies adjusted according to the changes of context information is proposed. A context related production rules based on the interval-valued fuzzy theory are produced, and a simple efficient interval value fuzzy access control method is designed to improve the adaptivity of the security threshold intensity and security policies in pervasive computing systems.

  19. Multiuser Medium Access Algorithm Research in Distributed Cognitive Network%分布式认知网络中多用户频谱接入算法研究

    黄丽; 朱光喜; 方红斌; 王德胜

    2012-01-01

    认知频谱接入技术通过感知侦测并伺机接入空闲频带,大大缓解了频谱资源稀缺和利用率低下的矛盾.在未知信道占用信息情况下,认知用户如何快速找到最优空闲信道,并避免相互之间的冲突,是认知接入算法的难点和关键技术.本文中提出一种低复杂度的分布式认知接入算法,通过学习物理层的感知结果和链路层的发送确认信息,同时获取主用户的信道占用概率和从用户之间的冲突概率,能快速选择感知信道,并有效避免了从用户之间的竞争.仿真结果表明,该算法在未知信道占用概率信息的情况下,网络平均吞吐量明显优于贪婪等算法,很好地解决了认知网络中多个从用户频谱共享问题,同时收敛速度较快.%Cognitive medium access, built on sensing and accessing idle frequency bands, greatly releases the confliction between the frequency scarcity and the low utilization of a precious radio resource. How to quickly probe and optimally exploit multiple vacant channels with unknown parameters as well as to avoid the competition among cognitive users, is key to the cognitive access strategy. This paper proposed a low complexity and efficient distributed access strategy based on joint design of sensing results in physical layer and acknowledgment information in medium access layer, which not only learned from primary time-varying traffic information but also considered spectrum-sharing among competitive cognitive users. Finally, numerical results show that the algorithm can gain higher average throughout compared with greedy strategy etc. without a prior transition probability of each channel and has faster convergence.

  20. Body surface area adapted iopromide 300 mg/ml versus 370 mg/ml contrast medium injection protocol: Influence on quantitative and clinical assessment in combined PET/CT

    Verburg, Frederik A., E-mail: fverburg@ukaachen.de [RWTH Aachen University Hospital, Department of Nuclear Medicine, Pauwelsstraße 30, 52074 Aachen (Germany); Maastricht University Medical Center, Department of Nuclear Medicine, P. Debyelaan 25, 6229 HX Maastricht (Netherlands); Apitzsch, Jonas [RWTH Aachen University Hospital, Department of Diagnostic and Interventional Radiology, Pauwelsstraße 30, 52074 Aachen (Germany); Lensing, Carina [RWTH Aachen University Hospital, Department of Nuclear Medicine, Pauwelsstraße 30, 52074 Aachen (Germany); Kuhl, Christiane K. [RWTH Aachen University Hospital, Department of Diagnostic and Interventional Radiology, Pauwelsstraße 30, 52074 Aachen (Germany); Pietsch, Hubertus [Bayer Pharma AG, Müllerstrasse 178, 13353 Berlin (Germany); Mottaghy, Felix M. [RWTH Aachen University Hospital, Department of Nuclear Medicine, Pauwelsstraße 30, 52074 Aachen (Germany); Maastricht University Medical Center, Department of Nuclear Medicine, P. Debyelaan 25, 6229 HX Maastricht (Netherlands); Behrendt, Florian F. [RWTH Aachen University Hospital, Department of Nuclear Medicine, Pauwelsstraße 30, 52074 Aachen (Germany)

    2013-12-01

    Purpose: To investigate the quantitative and qualitative differences between combined positron emission tomography and computed X-ray tomography (PET/CT) enhanced with contrast medium with either an iodine concentration 300 mg/ml or 370 mg/ml. Materials and methods: 120 consecutive patients scheduled for F-18-Fluorodeoxyglucose (FDG) PET/CT were included. The first (second) 60 patients received contrast medium with 300 (370) mg iodine/ml. Intravenous injection protocols were adapted for an identical iodine delivery rate (1.3 mg/s) and body surface area (BSA) adapted iodine dose (22.26 g I/m{sup 2}). Maximum and mean standardized uptake values (SUV{sub max}; SUV{sub mean}) and contrast enhancement (HU) were determined in the ascending aorta, the abdominal aorta, the inferior vena cava, the portal vein, the liver and the right kidney in the venous contrast medium phase. PET data were evaluated visually for the presence of malignancy and image quality. Results: Both media caused significantly higher values for HU, SUV{sub mean} and SUV{sub max} for the enhanced PET/CT than the non-enhanced one (all p < 0.01). There were no significant differences in the degree of increase of HU, SUV{sub mean} and SUV{sub max} between the two contrast media at any anatomic site (all p > 0.05). Visual evaluation of lesions showed no differences between contrast and non-contrast PET/CT or between the two different contrast media (p = 0.77). Conclusion: When using a constant iodine delivery rate and total iodine dose in a BSA adapted injection protocol, there are no quantitative or qualitative differences in either CT or PET between contrast media with an iodine concentration of 300 mg/ml and 370 mg/ml, respectively.

  1. Body surface area adapted iopromide 300 mg/ml versus 370 mg/ml contrast medium injection protocol: Influence on quantitative and clinical assessment in combined PET/CT

    Purpose: To investigate the quantitative and qualitative differences between combined positron emission tomography and computed X-ray tomography (PET/CT) enhanced with contrast medium with either an iodine concentration 300 mg/ml or 370 mg/ml. Materials and methods: 120 consecutive patients scheduled for F-18-Fluorodeoxyglucose (FDG) PET/CT were included. The first (second) 60 patients received contrast medium with 300 (370) mg iodine/ml. Intravenous injection protocols were adapted for an identical iodine delivery rate (1.3 mg/s) and body surface area (BSA) adapted iodine dose (22.26 g I/m2). Maximum and mean standardized uptake values (SUVmax; SUVmean) and contrast enhancement (HU) were determined in the ascending aorta, the abdominal aorta, the inferior vena cava, the portal vein, the liver and the right kidney in the venous contrast medium phase. PET data were evaluated visually for the presence of malignancy and image quality. Results: Both media caused significantly higher values for HU, SUVmean and SUVmax for the enhanced PET/CT than the non-enhanced one (all p < 0.01). There were no significant differences in the degree of increase of HU, SUVmean and SUVmax between the two contrast media at any anatomic site (all p > 0.05). Visual evaluation of lesions showed no differences between contrast and non-contrast PET/CT or between the two different contrast media (p = 0.77). Conclusion: When using a constant iodine delivery rate and total iodine dose in a BSA adapted injection protocol, there are no quantitative or qualitative differences in either CT or PET between contrast media with an iodine concentration of 300 mg/ml and 370 mg/ml, respectively

  2. Effects of feed access after hatch and inclusion of fish oil and medium chain fatty acids in a pre-starter diet on broiler chicken growth performance and humoral immunity.

    Lamot, D M; van der Klein, S A S; van de Linde, I B; Wijtten, P J A; Kemp, B; van den Brand, H; Lammers, A

    2016-09-01

    Delayed feed and water access is known to impair growth performance of day old broiler chickens. Although effects of feed access on growth performance and immune function of broilers have been examined before, effects of dietary composition and its potential interaction with feed access are hardly investigated. This experiment aimed to determine whether moment of first feed and water access after hatch and pre-starter composition (0 to 7 days) affect growth rate and humoral immune function in broiler chickens. Direct fed chickens received feed and water directly after placement in the grow-out facility, whilst delayed fed chickens only after 48 h. Direct and delayed fed chickens received a control pre-starter diet, or a diet containing medium chain fatty acids (MCFA) or fish oil. At 21 days, chickens were immunized by injection of sheep red blood cells. The mortality rate depended on an interaction between feed access and pre-starter composition (P=0.014). Chickens with direct feed access fed the control pre-starter diet had a higher risk for mortality than chickens with delayed feed access fed the control pre-starter diet (16.4% v. 4.2%) whereas the other treatment groups were in-between. BW gain and feed intake till 25 days in direct fed chickens were higher compared with delayed fed chickens, whilst gain to feed ratio was lower. Within the direct fed chickens, the control pre-starter diet resulted in the highest BW at 28 days and the MCFA pre-starter diet the lowest (Δ=2.4%), whereas this was opposite for delayed fed chickens (Δ=3.0%; P=0.033). Provision of MCFA resulted in a 4.6% higher BW gain and a higher gain to feed ratio compared with other pre-starter diets, but only during the period it was provided (2 to 7 days). Minor treatment effects were found for humoral immune response by measuring immunoglobulins, agglutination titers, interferon gamma (IFN- γ ), and complement activity. Concluding, current inclusion levels of fish oil (5 g/kg) and MCFA (30 g

  3. Medium Access Control of Non Uniformly Distributed Multi Hop Network Communication Node%非均匀分布多跳网络通信节点介质访问控制

    杨志忠

    2015-01-01

    在非均匀分布多跳网络中,需要对通信节点进行介质访问控制设计,提高网络通信节点的吞吐性和安全性.传统方法采用多路复用器输出端口信号检测方法进行非均匀分布多跳网络通信节点的介质访问控制,产生强烈的信道畸变,节点的通信控制性能不好.提出一种基于协同调度的混合协议激振算法的非均匀分布多跳网络通信节点介质访问控制方法.将非均匀分布多跳网络通信节点分簇模型的服务器网络接收端和发送端数据的信息熵作为信道传递向量函数,构建协同调度混合协议服务器模型,求得非均匀分布多跳网络时延扩展与信道特性测量均衡后的频谱,可以有效提高信息传输的保真度.仿真结果表明,采用该算法可以有效提高对多跳网络的通信节点介质访问控制性能,提高了通信节点的吞吐性能,降低重复传输次数,保证非均匀分布多跳网络通信的安全性和保真性.%In the non uniform distribution in multi hop networks, the need for access control design of node communication medium, to increase the throughput and security of network communication node. The traditional method is using the detec-tion method of the multiplexer output port signals are non uniformly distributed multi hop network communication node me-dium access control, produce the channel distortion strongly, node communication control performance is not good. This pa-per proposes a hybrid protocol excitation algorithm based on collaborative scheduling non-uniform distribution of multi hop network communication node medium access control method. Non uniform distribution of multi hop network communication node clustering model information entropy server network receiver and transmitter data as the channel transfer vector func-tion, construction of the collaborative scheduling hybrid protocol server model, obtain the non uniformly distributed multi hop network delay spread and

  4. 计算机辅助器具适配方法与挑战%Computer Access Assessment and Adaptation:Methods and Challenges (review)

    魏晨婧; 孙利宁; 赖卿; 李高峰

    2015-01-01

    The computer access, such as special mouse keyboard, software of the voice input and the magnified or reading screen, etc., can facilitate the people with disabilities to use the computer more efficiently. The computer access adaption should be evaluated to meet the users' needs, their function and the circumstances in which they live. The products should be easily designed, remade, and used for the cus-tomers and the prices should be available. For China, it is important to form professional teams, establish the good service process, achieve more supports, especially financial support, to research and develop more varieties of products.%计算机辅具,如特制的鼠标键盘、语音输入、读屏放大软件等,可以帮助功能障碍者更有效率地使用计算机,是他们获得全面康复的重要手段.计算机辅具适配需要根据使用者的需求、所处环境、身体功能等进行评估,遵循由简到繁原则,购买、改造或设计安全易用、经济易得的产品.我国计算机辅具适配服务刚刚起步,急需建立专业评估团队,设立科学的服务流程,研发多样的产品,引发各界关注,寻求更多的经费支持.

  5. Use of Adaptive Laboratory Evolution To Discover Key Mutations Enabling Rapid Growth of Escherichia coli K-12 MG1655 on Glucose Minimal Medium

    LaCroix, Ryan A.; Sandberg, Troy E.; O'Brien, Edward J.;

    2015-01-01

    Adaptive laboratory evolution (ALE) has emerged as an effective tool for scientific discovery and addressing biotechnological needs. Much of ALE's utility is derived from reproducibly obtained fitness increases. Identifying causal genetic changes and their combinatorial effects is challenging and...... exponential growth, fitness increases up to 1.6-fold were obtained compared to the wild type. These increases are comparable to previously reported maximum growth rates in similar conditions but were obtained over a shorter time frame. Across the eight replicate ALE experiments performed, causal mutations...... were identified using three approaches: identifying mutations in the same gene/region across replicate experiments, sequencing strains before and after computationally determined fitness jumps, and allelic replacement coupled with targeted ALE of reconstructed strains. Three genetic regions were most...

  6. Metabolic and proteomic adaptation of Lactobacillus rhamnosus strains during growth under cheese-like environmental conditions compared to de Man, Rogosa, and Sharpe medium.

    Bove, Claudio Giorgio; De Angelis, Maria; Gatti, Monica; Calasso, Maria; Neviani, Erasmo; Gobbetti, Marco

    2012-11-01

    The aim of this study was to demonstrate the metabolic and proteomic adaptation of Lactobacillus rhamnosus strains, which were isolated at different stages of Parmigiano Reggiano cheese ripening. Compared to de Man, Rogosa, and Sharpe (MRS) broth, cultivation under cheese-like conditions (cheese broth, CB) increased the number of free amino acids used as carbon sources. Compared with growth on MRS or pasteurized and microfiltrated milk, all strains cultivated in CB showed a low synthesis of d,l-lactic acid and elevated levels of acetic acid. The proteomic maps of the five representative strains, showing different metabolic traits, were comparatively determined after growth on MRS and CB media. The amount of intracellular and cell-associated proteins was affected by culture conditions and diversity between strains, depending on their time of isolation. Protein spots showing decreased (62 spots) or increased (59 spot) amounts during growth on CB were identified using MALDI-TOF-MS/MS or LC-nano-ESI-MS/MS. Compared with cultivation on MRS broth, the L. rhamnosus strains cultivated under cheese-like conditions had modified amounts of some proteins responsible for protein biosynthesis, nucleotide, and carbohydrate metabolisms, the glycolysis pathway, proteolytic activity, cell wall, and exopolysaccharide biosynthesis, cell regulation, amino acid, and citrate metabolism, oxidation/reduction processes, and stress responses. PMID:22965658

  7. Pre-stack reverse-time migration based on the time–space domain adaptive high-order finite-difference method in acoustic VTI medium

    With the increment of seismic exploration precision requirement, it is significant to develop the anisotropic migration methods. Pre-stack reverse-time migration (RTM) is performed based on acoustic vertical transversely isotropic (VTI) wave equations, and the accuracy and efficiency of RTM strongly depend on the algorithms used for wave equation numerical solution. Finite-difference (FD) methods have been widely used in numerical solution of wave equations. The conventional FD method derives spatial FD coefficients from the space domain dispersion relation, and it is difficult to satisfy the time–space domain dispersion relation of the wave equation exactly. In this paper, we adopt a time–space domain FD method to solve acoustic VTI wave equations. Dispersion analysis and numerical modelling results demonstrate that the time–space domain FD method has greater accuracy than the conventional FD method under the same discretizations. The time–space domain high-order FD method is also applied in the wavefield extrapolation of acoustic VTI pre-stack RTM. The model tests demonstrate that the acoustic VTI pre-stack RTM based on the time–space domain FD method can obtain better images than that based on the conventional FD method, and the processing results show that the imaging quality of the acoustic VTI RTM is clearer and more correct than that of acoustic isotropic RTM. Meanwhile, in the process of wavefield forward and backward extrapolation, we employ adaptive variable-length spatial operators to compute spatial derivatives to improve the computational efficiency effectively almost without reducing the imaging accuracy. (paper)

  8. Cross-layer combining of power control and adaptive modulation with truncated ARQ for cognitive radios

    CHENG Shi-lun; YANG Zhen

    2008-01-01

    To maximize throughput and to satisfy users' requirements in cognitive radios, a cross-layer optimization problem combining adaptive modulation and power control at the physical layer and truncated automatic repeat request at the medium access control layer is proposed. Simulation results show the combination of power control, adaptive modulation, and truncated automatic repeat request can regulate transmitter powers and increase the total throughput effectively.

  9. CORELA: A cooperative relaying enhanced link adaptation algorithm for IEEE 802.11 WLANs

    Li, L.; Kaleshi, D; Zhong, Fan

    2011-01-01

    One of the key challenges for cooperative relaying multi-rate wireless networks is the integration and interaction of relaying with link adaptation algorithms, in particular under incomplete and/or imprecise channel state information conditions. In this paper we propose a practical cooperative relaying link adaptation medium access protocol that considers the historical link quality to enable the relay terminal to adjust its transmission relaying rate by estimating the error probability based...

  10. Decentralised Learning MACs for Collision-free Access in WLANs

    Fang, Minyu; Duffy, Ken R; Leith, Douglas J

    2010-01-01

    By combining the features of CSMA and TDMA, fully decentralised WLAN MAC schemes have recently been proposed that converge to collision-free schedules. In this paper we describe a MAC with optimal long-run throughput that is almost decentralised. We then design two scheme that are practically realisable, decentralised approximations of this optimal scheme and operate with different amounts of sensing information. We achieve this by (1) introducing learning algorithms that can substantially speed up convergence to collision free operation; (2) developing a decentralised schedule length adaptation scheme that provides long-run fair (uniform) access to the medium while maintaining collision-free access for arbitrary numbers of stations.

  11. Adapting an evidence-based intervention for HIV to avail access to testing and risk-reduction counseling for female victims of sexual violence in post-earthquake Haiti.

    Rahill, Guitele J; Joshi, Manisha; Hernandez, Anthony

    2016-01-01

    Haiti has the highest prevalence of HIV/AIDS in the Caribbean. Before the 2010 earthquake, Haitian women bore a disproportionate burden of HIV/AIDS, had lower HIV knowledge, less capacity to negotiate for safer sex, and limited access to HIV testing and risk-reduction (RR) counseling. Since 2010, there has been an increase in sexual violence against women, characterized by deliberate vaginal injuries by non-intimate partners, increasing victims' risk of sexually transmitted infections including HIV/AIDS. Needed is an adaptation of evidence-based interventions for HIV that include HIV testing and counseling for this stigmatized population. We reviewed several features of Centers for Disease Control and Prevention's 103 evidence-based interventions for HIV (e.g., measures used, participant risk characteristics, theoretical framework, outcome variables, and evidence tier) in an attempt to seek a feasibly adaptable evidence-based intervention for HIV that could be used for victims of sexual violence (VOSV). RESPECT, one of the reviewed evidence-based HIV interventions, comprises of one-on-one, client-focused HIV prevention/RR counseling, and RAPID HIV testing. Adapting RESPECT can enhance access to testing for Haitian VOSV and can influence their perceptions of HIV risk, and establishment of RR goals for future consensual intimate relations. Adapting and implementing RESPECT can increase uptake of evidence-based HIV interventions among Haitians and positively affect a region with high HIV prevalence and increased rates of sexual violence. PMID:26278002

  12. Is the adapted Household Food Insecurity Access Scale (HFIAS) developed internationally to measure food insecurity valid in urban and rural households of Ethiopia?

    Gebreyesus, Seifu H; Lunde, Torleif; Mariam, Damen H.; Woldehanna, Tassew; Lindtjørn, Bernt

    2015-01-01

    Background The concept of food insecurity encompasses three dimensions. One of these dimensions, the access component of household food insecurity is measured through the use of the Household Food Insecurity Access Scale (HFIAS). Despite its application in Ethiopia and other similar developing countries, its performance is still poorly explored. Our study aims to evaluate the validity of the HFIAS in Ethiopia. Methods We conducted repeated cross-sectional studies in urban and rural villages o...

  13. Expressing Adaptation Strategies Using Adaptation Patterns

    Zemirline, N.; Bourda, Y.; Reynaud, C.

    2012-01-01

    Today, there is a real challenge to enable personalized access to information. Several systems have been proposed to address this challenge including Adaptive Hypermedia Systems (AHSs). However, the specification of adaptation strategies remains a difficult task for creators of such systems. In this paper, we consider the problem of the definition…

  14. The Medium is the Message

    Ørum, Tania

    2016-01-01

    Danish avant-garde artists did not have the access to professional sound studios and public radio open to their colleagues in Swede, but they were equally interested in working with sound as a medium and in gaining acces to the electronic mass media. This essay examines one of the few experimental...

  15. 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

    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。

  16. Adaptive ethnography

    Berth, Mette

    2005-01-01

    This paper focuses on the use of an adaptive ethnography when studying such phenomena as young people's use of mobile media in a learning perspective. Mobile media such as PDAs and mobile phones have a number of affordances which make them potential tools for learning. However, before we begin to...... design and develop educational materials for mobile media platforms we must first understand everyday use and behaviour with a medium such as a mobile phone. The paper outlines the research design for a PhD project on mobile learning which focuses on mobile phones as a way to bridge the gap between...... formal and informal learning contexts. The paper also proposes several adaptive methodological techniques for studying young people's interaction with mobiles....

  17. 接入技术与基础网络设施之适应性研究%The Research on Adaptabilities of Access Technologies to the Network Infrastructure

    周强; 张文生

    2015-01-01

    在中国国内各地的有线电视网络上,充斥着多种接入网技术,太多技术难免造成“选择性困惑”。本文作者构建了“周氏平面”,并利用该平面形象地描述了各种接入技术与基础网络设施之间的适应性关系,从而对运营商的技术选择和未来的技术演进提供了有益的帮助。%Variety of access technologies already existed in those cable networks around China. So many technol-ogies often make operators dropped in the"selectivity confusion”. This article will start from the most basic hierarchy of cable television network&applications, discusses the intrinsic connections between those various layers. Especially, the author created a kind of "Zhou Chart" to describe the relations between access technologies layer and network infrastructure layer. With this chart, the adaptability of various access technologies to the different network infrastruc-tures (i.e. matching) can be understood very easily and graphically, thus such a chart can be helps for operators how to select technology correctly and future network evolution path.

  18. Adipose tissue partitioning of limit-fed beef cattle and beef cattle with ad libitum access to feed differing in adaptation to heat.

    Sprinkle, J E; Ferrell, C L; Holloway, J W; Warrington, B G; Greene, L W; Wu, G; Stuth, J W

    1998-03-01

    We compared fat distribution and lipoprotein lipase (LPL) activity in steers differing in adaptability to the subtropics. Steers were fed a grain diet (3.13 Mcal ME/kg DM) at limited (150 kcal ME x kg[-.75] x d[-1]; .23 kg ADG) or ad libitum levels for 140 d, then slaughtered. Sixteen British- (8 Angus, 8 Hereford; S), 16 Boran- (R), 16 Brahman- (B), and 16 Tuli- (T) cross steers from MARC III composite cows were used. Adipose tissue samples from perirenal, omental, and subcutaneous depots were analyzed for LPL activity. Carcass measurements including omental, external, and seam fat trim from 1/ 2 of the carcass were measured. Subcutaneous fat had greater (P .05) in fat distribution for steers fed at limited levels. Means for ADG, slaughter weights, carcass weights, yield grades, and carcass lipid weights for S and B fed for ad libitum intake were greater (P .05) for the other breeds with ad libitum intake. Factor analysis of fat depots for animals with ad libitum intake indicated that Bos taurus cattle differing in adaptation to heat deposited fat differently; S deposited greater (P < .05) proportions of carcass fat and T deposited greater (P < .05) proportions of internal fat. It seems that accumulation of internal fat is detrimental for ADG for Bos taurus cattle. PMID:9535321

  19. Genotipagem de polimorfismos associados com sistemas de macho-esterilidade em acessos de cebola adaptados ao Brasil Genotyping of polymorphisms associated with male-sterility systems in onion accessions adapted for cultivation in Brazil

    Carlos Francisco Ragassi

    2012-09-01

    Full Text Available A produção em escala comercial de sementes híbridas de cebola (Allium cepa tem sido conduzida com o emprego de dois sistemas de macho-esterilidade do tipo genética-citoplasmática (CMS-S e CMS-T em associação ao citoplasma normal (macho-fértil. No entanto, a análise molecular desses diferentes tipos citoplasmáticos ainda não está disponível para um grande número de acessos de cebola adaptados para cultivo em regiões tropicais. Além de adaptação às condições edafoclimáticas do Brasil, muitos desses acessos apresentam tolerância a doenças, sendo de potencial valor como genitores de híbridos. O presente trabalho visou identificar os tipos citoplasmáticos de acessos de cebola de diferentes grupos morfoagronômicos de interesse para o melhoramento genético no Brasil, usando a reação da polimerase em cadeia (PCR com 'primers' específicos para regiões polimórficas do genoma mitocondrial de cebola. Foi observada, nos 66 acessos amostrados, a presença dos três principais tipos de citoplasma descritos para cebola (S, N e T. Foi constatada maior frequência do citoplasma S (56% seguido do citoplasma T (25,8%. Em 18,2% das amostras, foi encontrado exclusivamente o citoplasma N. Essa caracterização pode ser útil para guiar a escolha de materiais genéticos dentro dos programas de melhoramento com objetivo de desenvolver cultivares híbridas adaptadas às condições tropicais.The synthesis of onion (Allium cepa hybrids relies upon the use of two genetic-cytoplasmic male-sterility systems, CMS-S and CMS-T, in association to the normal male-fertile (N cytoplasm. However, the molecular phenotyping of male-sterility-inducing and normal cytoplasms of many onion accessions adapted for cultivation under tropical conditions is not available. Some of these accessions were reported as presenting tolerance to diseases and adaptation to tropical and subtropical regions. Therefore, these accessions are potential sources of parental

  20. MAC Protocols for Optimal Information Retrieval Pattern in Sensor Networks with Mobile Access

    Yang Zhiyu

    2005-01-01

    Full Text Available In signal field reconstruction applications of sensor network, the locations where the measurements are retrieved from affect the reconstruction performance. In this paper, we consider the design of medium access control (MAC protocols in sensor networks with mobile access for the desirable information retrieval pattern to minimize the reconstruction distortion. Taking both performance and implementation complexity into consideration, besides the optimal centralized scheduler, we propose three decentralized MAC protocols, namely, decentralized scheduling through carrier sensing, Aloha scheduling, and adaptive Aloha scheduling. Design parameters for the proposed protocols are optimized. Finally, performance comparison among these protocols is provided via simulations.

  1. Knowledge unbound selected writings on Open Access, 2002-2011

    Suber, Peter

    2016-01-01

    Peter Suber has been a leading advocate for open access since 2001 and has worked full time on issues of open access since 2003. As a professor of philosophy during the early days of the internet, he realized its power and potential as a medium for scholarship. As he writes now, "it was like an asteroid crash, fundamentally changing the environment, challenging dinosaurs to adapt, and challenging all of us to figure out whether we were dinosaurs." When Suber began putting his writings and course materials online for anyone to use for any purpose, he soon experienced the benefits of that wider exposure. In 2001, he started a newsletter -- the Free Online Scholarship Newsletter, which later became the SPARC Open Access Newsletter -- in which he explored the implications of open access for research and scholarship. This book offers a selection of some of Suber's most significant and influential writings on open access from 2002 to 2010. In these texts, Suber makes the case for open access to research; answers c...

  2. An Environment-Adaptive Role-Based Access Control Model%一个环境适应的基于角色的访问控制模型

    吴新松; 贺也平; 周洲仪; 梁洪亮

    2011-01-01

    大型网络应用如疫情报告系统需要访问控制系统根据环境变化调整访问控制策略,而现有的访问控制模型缺乏灵活性,难以适应环境动态变化的需要.通过对RBAC模型进行扩展,提出了一个环境适应的基于角色的访问控制模型EA-RBAC.该模型相对于传统RBAC模型,增加了事件触发、基于事件的状态等价类迁移、环境角色和虚拟域等机制.通过事件触发机制和状态等价类迁移实现了系统对环境变化的感知和随环境变化的状态迁移.通过环境角色和虚拟域的概念,实现了环境角色的动态调整和用户授权的按状态调整.该模型能够根据环境变化,在不失安全性的前提下为大型网络应用灵活实施访问控制策略.作为示例,给出了模型在疫情报告系统中的适用性分析.%Large scale network-based applications, such as infectious diseases reporting system,require that access control policy can be changed according to environment alternation. However,existing access control models are inflexible and can not be adapted to environment alternation because they are lack of mechanisms to capture environment alternation and to change access control policy. In this paper, we analyze the access control requirements of infectious diseases reporting system. Based on the analysis, we extract the general access control requirements of large scale network-based applications. Through extending RBAC model, we design the components of the environmentadaptive role-based access control model called EA-RBAC and give the formal definition of the model.Compared with traditional RBAC models, EA-RBAC model adds event-trigger, event-based equivalent states transition, environment role and virtual domain mechanisms. Through event-trigger and equivalent states transition, the system can perceive environment alternation and transit state based on environment alternation. Through environment role and virtual domains, the system can

  3. Technology transfer for adaptation

    Biagini, Bonizella; Kuhl, Laura; Gallagher, Kelly Sims; Ortiz, Claudia

    2014-09-01

    Technology alone will not be able to solve adaptation challenges, but it is likely to play an important role. As a result of the role of technology in adaptation and the importance of international collaboration for climate change, technology transfer for adaptation is a critical but understudied issue. Through an analysis of Global Environment Facility-managed adaptation projects, we find there is significantly more technology transfer occurring in adaptation projects than might be expected given the pessimistic rhetoric surrounding technology transfer for adaptation. Most projects focused on demonstration and early deployment/niche formation for existing technologies rather than earlier stages of innovation, which is understandable considering the pilot nature of the projects. Key challenges for the transfer process, including technology selection and appropriateness under climate change, markets and access to technology, and diffusion strategies are discussed in more detail.

  4. Cooperative Energy Harvesting-Adaptive MAC Protocol for WBANs

    Esteves, Volker; Antonopoulos, Angelos; Kartsakli, Elli; Puig-Vidal, Manel; Miribel-Català, Pere; Verikoukis, Christos

    2015-01-01

    In this paper, we introduce a cooperative medium access control (MAC) protocol, named cooperative energy harvesting (CEH)-MAC, that adapts its operation to the energy harvesting (EH) conditions in wireless body area networks (WBANs). In particular, the proposed protocol exploits the EH information in order to set an idle time that allows the relay nodes to charge their batteries and complete the cooperation phase successfully. Extensive simulations have shown that CEH-MAC significantly improves the network performance in terms of throughput, delay and energy efficiency compared to the cooperative operation of the baseline IEEE 802.15.6 standard. PMID:26029950

  5. 自适应商品属性变化的商品库设计与访问研究%Adaptive changes in product attribute database design and access of goods

    孙仁鹏

    2011-01-01

    为了使系统能够适应因商品种类的变化而带来的商品属性的变化,提出了动态生成自适应的商品表和动态生成数据访问SQL语句的设计思路.在深入研究江苏苏泽电子商务业务需求的基础上,将不同种类商品表的具体设计交给用户完成,系统只需提供统一的商品表结构设计的客户端界面,而商品数据录入界面将根据对应表结构动态生成,软件与具体的商品表结构相分离,不会因为商品属性的变化而需要进行系统的维护,相对通用.对商品表的访问采用动态SQL语句,所需的主要参数从界面和用户数据字典中提取.该研究在实践中得到良好的应用,节省了大量后期维护成本.%In order to make system adapt the change for commodity characteristic caused by the type, design ideas about dynamically generated commodity list and dynamic adaptive data access SQL statement are presented. A depth study is made in accordance with the e-commerce business requirements for Jiangsu Suze Co., Ltd. Detailed design about different commodity can be finished by user, and client interface shall be provided by the system, yet inputting data interface for commodity property can be dynamically generated in accordance with corresponding database structure, thus software and detailed database structure are divided, and system needn' t be maintained if there is any change for commodity property because of its relatively general function. The dynamic SQL statement is used for database access, and the required parameters can be got from user' s data dictionary. This research has been successfully put into service, and lots of post-maintenance costs are reduced.

  6. 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

    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。

  7. Chemically defined medium and Caenorhabditis elegans

    Szewczyk, Nathaniel J.; Kozak, Elena; Conley, Catharine A.

    2003-01-01

    BACKGROUND: C. elegans has been established as a powerful genetic system. Use of a chemically defined medium (C. elegans Maintenance Medium (CeMM)) now allows standardization and systematic manipulation of the nutrients that animals receive. Liquid cultivation allows automated culturing and experimentation and should be of use in large-scale growth and screening of animals. RESULTS: We find that CeMM is versatile and culturing is simple. CeMM can be used in a solid or liquid state, it can be stored unused for at least a year, unattended actively growing cultures may be maintained longer than with standard techniques, and standard C. elegans protocols work well with animals grown in defined medium. We also find that there are caveats to using defined medium. Animals in defined medium grow more slowly than on standard medium, appear to display adaptation to the defined medium, and display altered growth rates as they change the composition of the defined medium. CONCLUSIONS: As was suggested with the introduction of C. elegans as a potential genetic system, use of defined medium with C. elegans should prove a powerful tool.

  8. Adaptation of Lactobacillus plantarum IMDO 130201, a Wheat Sourdough Isolate, to Growth in Wheat Sourdough Simulation Medium at Different pH Values through Differential Gene Expression ▿ †

    Vrancken, Gino; De Vuyst, Luc; Rimaux, Tom; Allemeersch, Joke; Weckx, Stefan

    2011-01-01

    Sourdough is a very competitive and challenging environment for microorganisms. Usually, a stable microbiota composed of lactic acid bacteria (LAB) and yeasts dominates this ecosystem. Although sourdough is rich in carbohydrates, thus providing an ideal environment for microorganisms to grow, its low pH presents a particular challenge. The nature of the adaptation to this low pH was investigated for Lactobacillus plantarum IMDO 130201, an isolate from a laboratory wheat sourdough fermentation...

  9. Open access

    Dorch, Bertil Fabricius; Demaio, Alessandro; Hersch, Fred

    2012-01-01

    This week, we celebrate open access week – an event aimed at bringing attention to this rapidly emerging form of scientific publication and its ethical imperatives. Traditionally, knowledge breakthroughs and scientific discoveries are shared through publication in academic journals. Peer...... ideas, break down barriers to science and make knowledge accessible to the masses – but this is not actually the case....

  10. Open Access

    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…

  11. Accessible Website Content Guidelines for Users with Intellectual Disabilities

    Karreman, Joyce; van der Geest, Thea; Buursink, Esmee

    2007-01-01

    Background: The W3C Web Accessibility Initiative has issued guidelines for making websites better and easier to access for people with various disabilities (W3C Web Accessibility Initiative guidelines 1999). Method: The usability of two versions of a website (a non-adapted site and a site that was adapted on the basis of easy-to-read guidelines)…

  12. Media Access Control for Wireless Sensor and Actuator Networks

    Nabi, Muaz Un

    2012-01-01

    In a wireless network, the medium is a shared resource. The nodes in the network negotiate access of the shared resource using the Medium Access Control (MAC) protocol. The design of a MAC protocol for a sensor node is not the same as that for a wireless transceiver. Due to the transceiver characteristics, the MAC protocol design is limited in terms of medium access methods. However, in most cases, the protocols rely on simple access methods i.e. Time Division Multiple Access (TDMA) or Carrie...

  13. Optimizing Channel Access for Event-Driven Wireless Sensor Networks: Analysis and Enhancements

    Shakya, Rajeev K; Verma, Nishchal K

    2012-01-01

    We study the problem of medium access control in domain of event-driven wireless sensor networks (WSN). In this kind of WSN, sensor nodes send data to sink node only when an event occurs in the monitoring area. The nodes in this kind of WSN encounter correlated traffic as a subset of nodes start sending data by sensing a common event simultaneously. We wish to rethink of medium access control (MAC) for this type of traffic characteristics. For WSN, many existing MAC protocols utilize the basic CSMA strategies like 802.11 that uses Binary Exponential Backoff (BEB) algorithm to handle the collisions among packets when more than one node want to access the channel. We show that this BEB algorithm does not work well without incurring access delay or performance degradation due to increased number of collisions and retransmissions when nodes encounter correlated traffic. In this paper, we investigate on how to minimize the access delay and improve throughput by setting contention window (CW) size adaptively accord...

  14. Hadrons in medium

    U Mosel

    2006-04-01

    In these lectures I first give the motivation for investigations of in-medium properties of hadrons. I discuss the relevant symmetries of QCD and how they might affect the observed hadron properties. I then discuss at length the observable consequences of in-medium changes of hadronic properties in reactions with elementary probes, and in particular photons, on nuclei. Here I put an emphasis on new experiments on changes of the - and -mesons in medium.

  15. Adaptive Lighting

    Petersen, Kjell Yngve; Søndergaard, Karin; Kongshaug, Jesper

    2015-01-01

    Adaptive LightingAdaptive lighting is based on a partial automation of the possibilities to adjust the colour tone and brightness levels of light in order to adapt to people’s needs and desires. IT support is key to the technical developments that afford adaptive control systems. The possibilities offered by adaptive lighting control are created by the ways that the system components, the network and data flow can be coordinated through software so that the dynamic variations are controlled i...

  16. Accessible Knowledge - Knowledge on Accessibility

    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...

  17. LAMAN: Load Adaptable MAC for Ad Hoc Networks

    Realp Marc

    2005-01-01

    Full Text Available In mobile ad hoc radio networks, mechanisms on how to access the radio channel are extremely important in order to improve network efficiency. In this paper, the load adaptable medium access control for ad hoc networks (LAMAN protocol is described. LAMAN is a novel decentralized multipacket MAC protocol designed following a cross-layer approach. Basically, this protocol is a hybrid CDMA-TDMA-based protocol that aims at throughput maximization in multipacket communication environments by efficiently combining contention and conflict-free protocol components. Such combination of components is used to adapt the nodes' access priority to changes on the traffic load while, at the same time, accounting for the multipacket reception (MPR capability of the receivers. A theoretical analysis of the system is developed presenting closed expressions of network throughput and packet delay. By simulations the validity of our analysis is shown and the performances of a LAMAN-based system and an Aloha-CDMA-based one are compared.

  18. Open access

    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...

  19. Access French

    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

  20. Enabling Adaptive Rate and Relay Selection for 802.11 Mobile Ad Hoc Networks

    Mehta, Neil; Wang, Wenye

    2011-01-01

    Mobile ad hoc networks (MANETs) are self-configuring wireless networks that lack permanent infrastructure and are formed among mobile nodes on demand. Rapid node mobility results in dramatic channel variation, or fading, that degrades MANET performance. Employing channel state information (CSI) at the transmitter can improve the throughput of routing and medium access control (MAC) protocols for mobile ad hoc networks. Several routing algorithms in the literature explicitly incorporate the fading signal strength into the routing metric, thus selecting the routes with strong channel conditions. While these studies show that adaptation to the time-variant channel gain is beneficial in MANETs, they do not address the effect of the outdated fading CSI at the transmitter. For realistic mobile node speeds, the channel gain is rapidly varying, and becomes quickly outdated due the feedback delay. We analyze the link throughput of joint rate adaptation and adaptive relay selection in the presence of imperfect CSI. Mor...

  1. Adaptive skills

    Staša Stropnik; Jana Kodrič

    2013-01-01

    Adaptive skills are defined as a collection of conceptual, social and practical skills that are learned by people in order to function in their everyday lives. They include an individual's ability to adapt to and manage her or his surroundings to effectively function and meet social or community expectations. Good adaptive skills promote individual's independence in different environments, whereas poorly developed adaptive skills are connected to individual's dependency and with g...

  2. Organophilic clay suspension medium

    Dixon, G.G.; Parlman, R.M.; Stewart, W.

    1989-10-24

    This patent describes an improved liquid suspension medium for particulate solids. The suspension medium having been formed by admixing an organophilic clay wherein the clay is selected from the group consisting of bentonite, attapulgite, sepiolite and hectorite and admixtures thereof present in the quantity of about 0.5-8 weight percent with a liquid hydrocarbon present in the quantity of about 99-70 weight percent and at least one activator selected from the group consisting of phenyl hydroxyalkyl ethers.

  3. Concept medium programme

    Bjerrum, Peter

    The present essay is an attempt to determine the architectural project of the 21st century in relation to a modern conception of space as the medium of architecture, and of sociality as its program......The present essay is an attempt to determine the architectural project of the 21st century in relation to a modern conception of space as the medium of architecture, and of sociality as its program...

  4. Fundamentals of Medium Access Control Design for Millimeter Wave Networks

    Shokri, Hossein

    2015-01-01

    In current wireless communication systems, demands for extremely high data rates, along with spectrum scarcity at the microwave bands, make the millimeter wave (mmWave) band very appealing to provide these extremely high data rates even for a massive number of wireless devices. MmWave communications exhibit severe attenuation, vulnerability to obstacles (called blockage), and sparse-scattering environments. Moreover, mmWave signals have small wavelengths that allow the incorporation of many a...

  5. Development of comprehensive medium for micropropagation of cultivated Cassava accessions

    Cassava is one of the most important foods in the human diet in the tropics, where it ranks fifth as a source of energy, after rice, sugar cane, and maize. Since it is a vegetative propagated crop, the use of in vitro propagation is very important to preserve germplasm free of pest and diseases. M...

  6. Sustainable medium access control: Implementation and evaluation of ODMAC

    Fafoutis, Xenofon; Di Mauro, Alessio; Dragoni, Nicola

    vital to guarantee the sustainability of the system; whereas, in the opposite case, the system should use the energy surplus to increase the application performance. In this paper, we implement and evaluate On-Demand MAC (ODMAC), the first receiver-initiated MAC protocol specifically designed for energy...... harvesting applications. In particular, we provide a basic yet fully operational implementation of ODMAC for the Texas Instruments' MSP430 microprocessor family. Furthermore, we verify the theoretical results of our previous work by achieving sustainable operation of an energy harvesting node in various...

  7. Adaptive Lighting

    Petersen, Kjell Yngve; Søndergaard, Karin; Kongshaug, Jesper

    2015-01-01

    Adaptive Lighting Adaptive lighting is based on a partial automation of the possibilities to adjust the colour tone and brightness levels of light in order to adapt to people’s needs and desires. IT support is key to the technical developments that afford adaptive control systems. The possibilities...... offered by adaptive lighting control are created by the ways that the system components, the network and data flow can be coordinated through software so that the dynamic variations are controlled in ways that meaningfully adapt according to people’s situations and design intentions. This book discusses...... distributed differently into an architectural body. We also examine what might occur when light is dynamic and able to change colour, intensity and direction, and when it is adaptive and can be brought into interaction with its surroundings. In short, what happens to an architectural space when artificial...

  8. Características do acesso e utilização de serviços odontológicos em municípios de médio porte Characteristics of the access and utilization of public dental services in medium-sized cities

    Sônia Cristina Lima Chaves

    2012-11-01

    Full Text Available Este estudo de corte transversal descreve as principais características de acesso e utilização de serviços odontológicos básicos e especializados em dois municípios de médio porte da Bahia com 100% de cobertura da Estratégia de Saúde da Família. Realizou-se um inquérito com 2.539 indivíduos de idade acima de 15 anos em 952 domicílios. As principais variáveis analisadas foram a necessidade de saúde bucal percebida, a procura pelo serviço, a barreira de acesso organizacional e o tipo de serviço e o procedimento utilizado. A utilização de serviços públicos odontológicos especializados foi de 11,7% e básicos de 26%. No município com maior utilização de serviços públicos odontológicos, foi menor o uso de serviços privados. A principal barreira de acesso situou-se na AP (Atenção Primária, entre 5,0% e 15,2%. Observou-se pouca interface da atenção secundária com a AP já que apenas 16,6% dos usuários retornaram a esse nível de atenção. Pode-se concluir que a principal barreira de acesso, em municípios com realidades organizacionais e geográficas específicas parece se situar na AP. Ações preventivas individuais foram pouco relatadas. Recomenda-se a redução de barreiras de acesso na AP, bem como a instituição de um protocolo que estimule a longitudinalidade do cuidado nesse nível.This cross-sectional study sought to describe the main characteristics of access and utilization of primary and specialized public dental services in two medium-sized cities in Bahia with 100% coverage of the Family Health Program. A survey of 952 households and 2.539 individuals aged over 15 years was conducted. The main variables analyzed were: perceived oral health needs, demand for the service, barriers of organizational access and the type of service and procedure utilized. The use of specialized public dental services was of 11.7% and primary care was 26%. In the city where there was greater use of public dental services

  9. Engineering Adaptive Web Applications

    Dolog, Peter

    2007-01-01

    Information and services on the web are accessible for everyone. Users of the web differ in their background, culture, political and social environment, interests and so on. Ambient intelligence was envisioned as a concept for systems which are able to adapt to user actions and needs....... With the growing amount of information and services, the web applications become natural candidates to adopt the concepts of ambient intelligence. Such applications can deal with divers user intentions and actions based on the user profile and can suggest the combination of information content and services which...... suit the user profile the most. This paper summarizes the domain engineering framework for such adaptive web applications. The framework provides guidelines to develop adaptive web applications as members of a family. It suggests how to utilize the design artifacts as knowledge which can be used...

  10. Code division controlled-MAC in wireless sensor network by adaptive binary signature design

    Wei, Lili; Batalama, Stella N.; Pados, Dimitris A.; Suter, Bruce

    2007-04-01

    We consider the problem of signature waveform design for code division medium-access-control (MAC) of wireless sensor networks (WSN). In contract to conventional randomly chosen orthogonal codes, an adaptive signature design strategy is developed under the maximum pre-detection SINR (signal to interference plus noise ratio) criterion. The proposed algorithm utilizes slowest descent cords of the optimization surface to move toward the optimum solution and exhibits, upon eigenvector decomposition, linear computational complexity with respect to signature length. Numerical and simulation studies demonstrate the performance of the proposed method and offer comparisons with conventional signature code sets.

  11. The Interstellar Medium

    Lequeux, James

    2005-01-01

    Describing interstellar matter in our galaxy in all of its various forms, this book also considers the physical and chemical processes that are occurring within this matter. The first seven chapters present the various components making up the interstellar matter and detail the ways that we are able to study them. The following seven chapters are devoted to the physical, chemical and dynamical processes that control the behaviour of interstellar matter. These include the instabilities and cloud collapse processes that lead to the formation of stars. The last chapter summarizes the transformations that can occur between the different phases of the interstellar medium. Emphasizing methods over results, "The Interstellar Medium" is written for graduate students, for young astronomers, and also for any researchers who have developed an interest in the interstellar medium.

  12. Adaptive Lighting

    Petersen, Kjell Yngve; Søndergaard, Karin; Kongshaug, Jesper

    2015-01-01

    Adaptive Lighting Adaptive lighting is based on a partial automation of the possibilities to adjust the colour tone and brightness levels of light in order to adapt to people’s needs and desires. IT support is key to the technical developments that afford adaptive control systems. The possibilities...... offered by adaptive lighting control are created by the ways that the system components, the network and data flow can be coordinated through software so that the dynamic variations are controlled in ways that meaningfully adapt according to people’s situations and design intentions. This book discusses...... the investigations of lighting scenarios carried out in two test installations: White Cube and White Box. The test installations are discussed as large-scale experiential instruments. In these test installations we examine what could potentially occur when light using LED technology is integrated and...

  13. An Access Control Framework for Reflective Middleware

    Gang Huang; Lian-Shan Sun

    2008-01-01

    Reflective middleware opens up the implementation details of middleware platform and applications at runtime for improving the adaptability of middleware-based systems. However, such openness brings new challenges to access control of the middleware-based systems.Some users can access the system via reflective entities, which sometimes cannot be protected by access control mechanisms of traditional middleware. To deliver high adaptability securely, reflective middleware should be equipped with proper access control mechanisms for potential access control holes induced by reflection. One reason of integrating these mechanisms in reflective middleware is that one goal of reflective middleware is to equip applications with reflection capabilities as transparent as possible. This paper studies how to design a reflective J2EE middlewarePKUAS with access control in mind. At first, a computation model of reflective system is built to identify all possible access control points induced by reflection. Then a set of access control mechanisms, including the wrapper of MBeans and a hierarchy of Java class loaders, are equipped for controlling the identified access control points. These mechanisms together with J2EE access control mechanism form the access control framework for PKUAS. The paper evaluates the security and the performance overheads of the framework in quality and quantity.

  14. Adaptive skills

    Staša Stropnik

    2013-02-01

    Full Text Available Adaptive skills are defined as a collection of conceptual, social and practical skills that are learned by people in order to function in their everyday lives. They include an individual's ability to adapt to and manage her or his surroundings to effectively function and meet social or community expectations. Good adaptive skills promote individual's independence in different environments, whereas poorly developed adaptive skills are connected to individual's dependency and with greater need for control and help with everyday tasks. Assessment of adaptive skills is often connected to assessment of intellectual disability, due to the reason that the diagnosis of intellectual disability includes lower levels of achievements on standardized tests of intellectual abilities as well as important deficits in adaptive skills. Assessment of adaptive behavior is a part of standard assessment battery with children and adults with different problems, disorders or disabilities that affect their everyday functioning. This contribution also presents psychometric tools most regularly used for assessment of adaptive skills and characteristics of adaptive skills with individual clinical groups.

  15. ADAPT Dataset

    National Aeronautics and Space Administration — Advanced Diagnostics and Prognostics Testbed (ADAPT) Project Lead: Scott Poll Subject Fault diagnosis in electrical power systems Description The Advanced...

  16. Adapting to changing user expectations

    Poland, Jean

    2004-01-01

    Results of user surveys indicate that science and technology library user needs differ from those of humanists and social scientists and are changing rapidly. Science and technology libraries are taking the lead in adapting the public services model accordingly. Science and technology library users are most interested in easy-to-use access tools and library Web sites that enable them to find information on their own as well as easy access to materials from home and office. Their expectations ...

  17. Overview of medium heterogeneity and transport processes

    Medium heterogeneity can have significant impact on the behavior of solute transport. Tracer breakthrough curves from transport in a heterogeneous medium are distinctly different from that in a homogeneous porous medium. Usually the shape of the breakthrough curves are highly non-symmetrical with a fast rise at early times and very long tail at late times, and often, they consist of multiple peaks. Moreover, unlike transport in a homogeneous medium where the same transport parameters describe the entire medium, transport through heterogeneous media gives rise to breakthrough curves which have strong spatial dependence. These inherent characteristics of transport in heterogeneous medium present special challenge to the performance assessment of a potential high level nuclear waste repository with respect to the possible release of radio nuclides to the accessible environment. Since an inherently desirable site characteristic for a waste repository is that flow and transport should be slow, then transport measurements in site characterization efforts will necessarily be spatially small and temporally short compare to the scales which are of relevance to performance assessment predictions. In this paper we discuss the role of medium heterogeneity in site characterization and performance assessment. Our discussion will be based on a specific example of a 3D heterogeneous stochastic model of a site generally similar to, the Aespoe Island, the site of the Hard Rock Laboratory in Southern Sweden. For our study, alternative 3D stochastic fields of hydraulic conductivities conditioned on ''point'' measurements shall be generated. Results of stochastic flow and transport simulations would be used to address the issues of (1) the relationship of tracer breakthrough with the structure of heterogeneity, and (2) the inference from small scale testing results to large scale and long term predictions

  18. Radon in geological medium

    The paper presented deals with behavior of the radon in geological medium and with some results of the radon survey in Bratislava and Kosice regions. 1) The av has been detected in the holes 0.80 m deep. The density of observations - 3 reference areas (one represents 20 stations) per 1 km2. The radon risk maps in 1:25000 and 1:50000 scales have been compiled. The 56.8% of the project area lies in low radon risk, 37.6% in medium radon risk and 5.6% in high radon risk. Follow-up monitoring of the equivalent volume radon activity (EVRA) at the flats, located in the areas with high radon risk of the surface layer, has showed values several times higher than Slovak limits (Marianka, Raca, Vajnory). The evidence that neotectonic is excellent medium for rising up emanation to the subsurface layer, is shown on the map. The tectonic zone of Liscie udolie in Bratislava-Karlova Ves area has been clearly detected by profile radon survey (av > 50 kBq/m3). 2) At present, northern half of the area of Kosice in question was covered by radon survey. The low and medium radon risks have been observed here, while localities with high radon risk are small in extent. The part of radon risk and soil permeability map from northern Kosice area is shown. (J.K.) 3 figs., 2 refs

  19. When Is Open Access Not Open Access?

    MacCallum, Catriona J.

    2007-01-01

    As open access grows in prominence, so too has confusion about what open access means; such confusion arises from a genuine misunderstanding of open access by funders, authors, editors, and publishers alike.

  20. The Local Interstellar Medium

    Redfield, S

    2006-01-01

    The Local Interstellar Medium (LISM) is a unique environment that presents an opportunity to study general interstellar phenomena in great detail and in three dimensions. In particular, high resolution optical and ultraviolet spectroscopy have proven to be powerful tools for addressing fundamental questions concerning the physical conditions and three-dimensional (3D) morphology of this local material. After reviewing our current understanding of the structure of gas in the solar neighborhood, I will discuss the influence that the LISM can have on stellar and planetary systems, including LISM dust deposition onto planetary atmospheres and the modulation of galactic cosmic rays through the astrosphere - the balancing interface between the outward pressure of the magnetized stellar wind and the inward pressure of the surrounding interstellar medium. On Earth, galactic cosmic rays may play a role as contributors to ozone layer chemistry, planetary electrical discharge frequency, biological mutation rates, and cl...

  1. Medium of Blood

    Eddie Glenn

    2012-06-01

    Full Text Available Blood quantum, the measurement of American Indian ancestry possessed by members of America’s Indigenous nations, is most often considered a rubric utilized by the federal government in an oppressive form, or by tribal nations themselves as standards of tribal citizenship requirements. In this essay, the authors recontextualize blood as a medium of national identity within the context of the Cherokee Nation of Oklahoma. Such decentering, as presented here, illuminates Cherokee nationhood in ways that have significant political import.

  2. The Local Interstellar Medium

    Ferlet, R.

    2006-01-01

    The Local Interstellar Medium (LISM) is a unique environment that presents an opportunity to study general interstellar phenomena in great detail and in three dimensions. In particular, high resolution optical and ultraviolet spectroscopy have proven to be powerful tools for addressing fundamental questions concerning the physical conditions and three-dimensional (3D) morphology of this local material. After reviewing our current understanding of the structure of gas in the solar neighborhood...

  3. Concept medium program

    Bjerrum, Peter

    The present essays is an attempt to dertermine the architecural project of the 21st century in realation to a modern conception of space as the medium of architecture, and of society as its program. This attempt adopts the internal point of view of an architect in describing a modern architectural...... project within the framework: concept - program, these notions being concieved as spatial representations primarily and immediately "given" to architecture....

  4. Accessible Website Content Guidelines for Users with Intellectual Disabilities

    Karreman, Joyce; Geest, van der Thea; Buursink, Esmee

    2007-01-01

    Background: The W3C Web Accessibility Initiative has issued guidelines for making websites better and easier to access for people with various disabilities (W3C Web Accessibility Initiative guidelines 1999). - Method: The usability of two versions of a website (a non-adapted site and a site that wa

  5. SMES' SECTOR ACCESS TO FINANCE: AN OVERVIEW

    Roman Angela

    2011-01-01

    Through their contribution to the creation of added value and new jobs, the small and medium enterprises (SMEs) have a significant role in the economic and social development of a country. However, these enterprises are facing numerous obstacles that limit their performance, growth and development. Among the difficulties faced by SMEs, the access to finance is often reported as a major obstacle to the deployment and expansion of their activity. The access to finance is crucial for efficient a...

  6. Ambiguous Adaptation

    Møller Larsen, Marcus; Lyngsie, Jacob

    We investigate why some exchange relationships terminate prematurely. We argue that investments in informal governance structures induce premature termination in relationships already governed by formal contracts. The formalized adaptive behavior of formal governance structures and the flexible and...... reciprocal adaptation of informal governance structure create ambiguity in situations of contingencies, which, subsequently, increases the likelihood of premature relationship termination. Using a large sample of exchange relationships in the global service provider industry, we find support for a hypothesis...

  7. Strategic Adaptation

    Andersen, Torben Juul

    2015-01-01

    This article provides an overview of theoretical contributions that have influenced the discourse around strategic adaptation including contingency perspectives, strategic fit reasoning, decision structure, information processing, corporate entrepreneurship, and strategy process. The related...... concepts of strategic renewal, dynamic managerial capabilities, dynamic capabilities, and strategic response capabilities are discussed and contextualized against strategic responsiveness. The insights derived from this article are used to outline the contours of a dynamic process of strategic adaptation...

  8. Supernova Feedback in an Inhomogeneous Interstellar Medium

    Martizzi, Davide; Quataert, Eliot

    2014-01-01

    Supernova (SN) feedback is one of the key processes shaping the interstellar medium (ISM) of galaxies. SNe contribute to (and in some cases may dominate) driving turbulence in the ISM and accelerating galactic winds. Modern cosmological simulations have sufficient resolution to capture the main structures in the ISM of galaxies, but are typically still not capable of explicitly resolving all of the small-scale stellar feedback processes, including the expansion of supernova remnants (SNRs). We perform a series of controlled three-dimensional hydrodynamic (adaptive mesh refinement, AMR) simulations of single SNRs expanding in an inhomogeneous density field with statistics motivated by those of the turbulent ISM. We use these to quantify the momentum and thermal energy injection from SNe as a function of spatial scale and the density, metallicity, and structure of the ambient medium. Using these results, we develop an analytic sub-resolution model for SN feedback for use in galaxy formation simulations. We then...

  9. Engineering Adaptive Applications

    Dolog, Peter

    Applications on the Web are accessible for users with different background, technical environment used, political, social environment where they reside, interests, goals and so on. The different user types have slightly different requirements for features which such Web applications should have....... The different requirements might be satisfied by different variants of features maintained and provided by Web applications. An adaptive Web application can be seen as a family of Web applications where application instances are those generated for particular user based on his characteristics relevant...... for a domain.In this book, we propose a new domain engineering framework which extends a development process of Web applications with techniques required when designing such adaptive customizable Web applications. The framework is provided with design abstractions which deal separately with...

  10. Chemically Defined Medium and Caenorhabditis elegans: A Powerful Approach

    Szewczyk, N. J.; Kozak, E.; Conley, C. A.

    2003-01-01

    C. elegans has been established as a powerful genetic system. Growth in a chemically defined medium (C. elegans Maintenance Medium (CeMM)) now allows standardization and systematic manipulation of the nutrients that animals receive. Liquid cultivation allows automated culturing and experimentation and should be of me in large-scale growth and screening of animals. Here we present our initial results from developing culture systems with CeMM. We find that CeMM is versatile and culturing is simple. CeMM can be used in a solid or liquid state, it can be stored unused for at least a year, unattended actively growing cultures may be maintained longer than with standard techniques, and standard C. elegans protocols work well with animals grown in defined medium. We also find that there are caveats of using defined medium. Animals in defined medium grow more slowly than on standard medium, appear to display adaptation to the defined medium, and display altered growth rates as they change defined medium composition. As was suggested with the introduction of C. elegans as a potential genetic system, use of defined medium with C. elegans should prove a powerful tool.

  11. On adaptation to the effect of ionizing radiation

    Determination of the notion adaptation and its application in biology and medicine where this notion is understood as accomodation which does not result from pathological consequences (physiological adaptation) is considered. Reactions to influence of those medium factors. Which have no receptors in the organims and those which are destructive at any structural level of the organism should not be called adaptation reactions. 18 refs

  12. Communal farming, climate change adaptation and the media in Zimbabwe

    Mthokozisi P. Ndhlovu

    2016-03-01

    Full Text Available Climate change is destroying Zimbabwean communal farmers’ agricultural activities – a source of living for most people. As communal farmers struggle to adapt, the media is expected to assume a fundamental theoretical role of educating and informing them about the appropriate adaptation techniques. Located in Umguza District in Matabeleland North Province, the study explored how communal farmers created meaning out of climate change media content and its influence on their agricultural practices from October 2014 to April 2015. In doing so, the study used the Two-Step Flow theory and Hall’s Encoding and Decoding Model. Entrenched in pragmatism, the study embedded quantitative techniques at different stages. Multistage sampling combining Simple Random Sampling (SRS, purposive and systematic sampling techniques was used to identify the 263 households for semi structured questionnaires, direct observations and in-depth interviews. The findings were analysed using Statistical Package for the Social Sciences (SPSS, thematic analysis and pattern matching. The results show that personal observations; print, broadcast and online media; and opinion leaders were the main sources of climate change information. The radio was the most used medium in communicating climate change adaptation though it was the second most accessed after mobile phones. Conservation Agriculture and planting of drought-resistant crops were some of the adaptation techniques communicated in the media. When interacting with media content, communal farmers create their own meaning influenced by their cultural values, resulting in some adopting, rejecting or modifying certain adaptation techniques. The study concludes that opinion leaders are fundamental in communal farmers’ interaction with media but their influence must not be overestimated.

  13. Is adaptation. Truly an adaptation? Is adaptation. Truly an adaptation?

    Thais Flores Nogueira Diniz

    2008-04-01

    Full Text Available The article begins by historicizing film adaptation from the arrival of cinema, pointing out the many theoretical approaches under which the process has been seen: from the concept of “the same story told in a different medium” to a comprehensible definition such as “the process through which works can be transformed, forming an intersection of textual surfaces, quotations, conflations and inversions of other texts”. To illustrate this new concept, the article discusses Spike Jonze’s film Adaptation. according to James Naremore’s proposal which considers the study of adaptation as part of a general theory of repetition, joined with the study of recycling, remaking, and every form of retelling. The film deals with the attempt by the scriptwriter Charles Kaufman, cast by Nicholas Cage, to adapt/translate a non-fictional book to the cinema, but ends up with a kind of film which is by no means what it intended to be: a film of action in the model of Hollywood productions. During the process of creation, Charles and his twin brother, Donald, undergo a series of adventures involving some real persons from the world of film, the author and the protagonist of the book, all of them turning into fictional characters in the film. In the film, adaptation then signifies something different from itstraditional meaning. The article begins by historicizing film adaptation from the arrival of cinema, pointing out the many theoretical approaches under which the process has been seen: from the concept of “the same story told in a different medium” to a comprehensible definition such as “the process through which works can be transformed, forming an intersection of textual surfaces, quotations, conflations and inversions of other texts”. To illustrate this new concept, the article discusses Spike Jonze’s film Adaptation. according to James Naremore’s proposal which considers the study of adaptation as part of a general theory of repetition

  14. Analysis of an Adaptive P-Persistent MAC Scheme for WLAN Providing Delay Fairness

    Yen, Chih-Ming; Chang, Chung-Ju; Chen, Yih-Shen; Huang, Ching Yao

    The paper proposes and analyzes an adaptive p-persistent-based (APP) medium access control (MAC) scheme for IEEE 802.11 WLAN. The APP MAC scheme intends to support delay fairness for every station in each access, denoting small delay variance. It differentiates permission probabilities of transmission for stations which are incurred with various packet delays. This permission probability is designed as a function of the numbers of retransmissions and re-backoffs so that stations with larger packet delay are endowed with higher permission probability. Also, the scheme is analyzed by a Markov-chain analysis, where the collision probability, the system throughput, and the average delay are successfully obtained. Numerical results show that the proposed APP MAC scheme can attain lower mean delay and higher mean throughput. In the mean time, simulation results are given to justify the validity of the analysis, and also show that the APP MAC scheme can achieve more delay fairness than conventional algorithms.

  15. Nuclear medium effects in $\

    Haider, H; Athar, M Sajjad; Vacas, M J Vicente

    2011-01-01

    We study the nuclear medium effects in the weak structure functions $F_2(x,Q^2)$ and $F_3(x,Q^2)$ in the deep inelastic neutrino/antineutrino reactions in nuclei. We use a theoretical model for the nuclear spectral functions which incorporates the conventional nuclear effects, such as Fermi motion, binding and nucleon correlations. We also consider the pion and rho meson cloud contributions calculated from a microscopic model for meson-nucleus self-energies. The calculations have been performed using relativistic nuclear spectral functions which include nucleon correlations. Our results are compared with the experimental data of NuTeV and CDHSW.

  16. Leadership in Romanian Small to Medium Enterprises

    Liliana Crăciun

    2015-04-01

    Full Text Available We have conducted a broad statistical research on Romanian small to medium enterprises (SMEs, with the goal of better understanding: (1 the incipient organizational culture of a recently-opened East European market; and (2 the role of leadership in increasing the competitiveness of SMEs. The paper studies the perceived characteristics of a leader and their influence on the organization’s results (as seen by employees, and it tries to reveal the subliminal inter-correlations among these characteristics. The method is factor analysis (implemented in SPSS, for a questionnaire with 23 items, answered by 930 subjects on a five-point Likert scale. The six factors identified by our analysis were: adaptability; cooperation; authority; charisma; confidence; motivation. By highlighting these basic components, our study aims both at increasing competitiveness in Romanian enterprises and at designing better training programs for managers and entrepreneurs acting on East European markets, adapted to the real characteristics of these young economic environments.

  17. Route to nonlocality and observation of accessible solitons

    Conti, Claudio; Peccianti, Marco; Assanto, Gaetano

    2003-01-01

    We develop a general theory of spatial solitons in a liquid crystalline medium exhibiting a nonlinearity with an arbitrary degree of effective nonlocality. The model accounts the observability of "accessible solitons" and establishes an important link with parametric solitons.

  18. Hot interstellar medium

    In view of that the diffuse component of soft X-rays is emitted mainly by extended supernova remnants and the hot interstellar medium produced thereby, the following three points are discussed. (1.) In the early stage of supernova remnants expanding in low density media, neither the equipartition of energy between electrons and ions nor the ionization equilibrium holds. The shock structure is modified by the pressure of hot plasma. X-ray features of the North Polar Spur are interpreted by taking these points into account. (2.) Several compilations of X-ray line emission are compared. Those by Kato and by Raymond and Smith are different in the equilibrium ion abundances and the collisional excitation rates for some important lines. The origins of differences are shown for some examples. It is demonstrated how the difference affects astrophysical interpretations. (3.) The solar system is surrounded by a hot, tenuous interstellar medium extended in the direction of 1 -- 1500 in the northern hemisphere. In other directions X-rays emitted farther than absorbing clouds are appreciable. (author)

  19. The Local Interstellar Medium

    Redfield, S.

    2006-09-01

    The Local Interstellar Medium (LISM) is a unique environment that presents an opportunity to study general interstellar phenomena in great detail and in three dimensions. In particular, high resolution optical and ultraviolet spectroscopy have proven to be powerful tools for addressing fundamental questions concerning the physical conditions and three-dimensional (3D) morphology of this local material. After reviewing our current understanding of the structure of gas in the solar neighborhood, I will discuss the influence that the LISM can have on stellar and planetary systems, including LISM dust deposition onto planetary atmospheres and the modulation of galactic cosmic rays through the astrosphere --- the balancing interface between the outward pressure of the magnetized stellar wind and the inward pressure of the surrounding interstellar medium. On Earth, galactic cosmic rays may play a role as contributors to ozone layer chemistry, planetary electrical discharge frequency, biological mutation rates, and climate. Since the LISM shares the same volume as practically all known extrasolar planets, the prototypical debris disks systems, and nearby low-mass star-formation sites, it will be important to understand the structures of the LISM and how they may influence planetary atmospheres.

  20. DENSE MEDIUM CYCLONE OPTIMIZATON

    Gerald H. Luttrell; Chris J. Barbee; Peter J. Bethell; Chris J. Wood

    2005-06-30

    Dense medium cyclones (DMCs) are known to be efficient, high-tonnage devices suitable for upgrading particles in the 50 to 0.5 mm size range. This versatile separator, which uses centrifugal forces to enhance the separation of fine particles that cannot be upgraded in static dense medium separators, can be found in most modern coal plants and in a variety of mineral plants treating iron ore, dolomite, diamonds, potash and lead-zinc ores. Due to the high tonnage, a small increase in DMC efficiency can have a large impact on plant profitability. Unfortunately, the knowledge base required to properly design and operate DMCs has been seriously eroded during the past several decades. In an attempt to correct this problem, a set of engineering tools have been developed to allow producers to improve the efficiency of their DMC circuits. These tools include (1) low-cost density tracers that can be used by plant operators to rapidly assess DMC performance, (2) mathematical process models that can be used to predict the influence of changes in operating and design variables on DMC performance, and (3) an expert advisor system that provides plant operators with a user-friendly interface for evaluating, optimizing and trouble-shooting DMC circuits. The field data required to develop these tools was collected by conducting detailed sampling and evaluation programs at several industrial plant sites. These data were used to demonstrate the technical, economic and environmental benefits that can be realized through the application of these engineering tools.

  1. What drives individuals to access the internet mostly using a cell phone?

    Yook, Seungyun; Jung, Yumi

    2012-01-01

    Mobile Internet users can access content, applications, and services using their cell phones. Recent PEW Internet research shows that more than half of U.S. cell phone owners have smartphones. Among them, some people have adopted a mobile phone and use it as a major Internet access medium; they may use other devices such as a desktop computer, notebook, netbook, or tablet PC, but those are not included in their Internet access medium repertoire. This paper examines who accesses the Internet m...

  2. Open Access and its effect on scholarly publication, academic community and library

    R. Vohra; Kumar, S.

    2008-01-01

    Open access is a rising phenomenon that seeks to make scholarly research findings freely accessible to public. This paper discusses the effect of open access on publishers, libraries, users, scholarly societies, indexing services, and resource sharing. There are many supporters for open access throughout the world. Open access is becoming a strong medium for scholarly information exchange among the academicians. Users and libraries benefit in numerous ways and are advocating open access revol...

  3. Implementation considerations of IPsec VPN for small and medium-sized companies

    Hossain, A.S.M. MIR

    2015-01-01

    Security threats threaten online networks. The threats are targeting enterprise networks, personal networks or other networks by accessing or altering important data. Secure-less networks give authorization of access to data in a network. Network administrators need strong network security for preventing unauthorized access, misuse or modification, of the network’s accessible resources. Mostly small or medium-sized enterprises use a firewall, antivirus and anti-spam software for network ...

  4. Adaptive test

    Kjeldsen, Lars Peter; Eriksen, Mette Rose

    2010-01-01

    Artikelen er en evaluering af de adaptive tests, som blev indført i folkeskolen. Artiklen sætter særligt fokus på evaluering i folkeskolen, herunder bidrager den med vejledning til evaluering, evalueringsværktøjer og fagspecifkt evalueringsmateriale.......Artikelen er en evaluering af de adaptive tests, som blev indført i folkeskolen. Artiklen sætter særligt fokus på evaluering i folkeskolen, herunder bidrager den med vejledning til evaluering, evalueringsværktøjer og fagspecifkt evalueringsmateriale....

  5. Small- and Medium-Size Enterprise Financing in Eastern Europe

    Leora F. Klapper; Sarria-Allende, Virginia; Sulla, Victor

    2002-01-01

    There is currently a large interest in understanding firms' access to finance, particularly in the financing of small- and medium-size enterprises (SMEs). But the financing patterns of SMEs across countries is not well understood. For example, little is known about the relative importance of equity, debt, and inter-firm financing for SMEs across countries. The authors use the Amadeus datab...

  6. Perfect Dispersive Medium

    Gupta, Shulabh

    2015-01-01

    Dispersion is at the heart of all ultrafast real-time signal processing systems across the entire electromagnetic spectrum ranging from radio-frequencies to optics. However, following Kramer-Kronig relations, these signal processing systems have been plagued with the parasitic amplitude distortions due to frequency dependent, and non-flat amplitude transmission of naturally dispersive media. This issue puts a serious limitation on the applicability and performance of these signal processing systems. To solve the above mentioned issue, a perfect dispersive medium is proposed in this work, which artificially violates the Kramer-Kronig relations, while satisfying all causality requirements. The proposed dispersive metamaterial is based on loss-gain metasurface pairs and exhibit a perfectly flat transmission response along with arbitrary dispersion in a broad bandwidth, thereby solving a seemingly unavoidable issue in all ultrafast signal processing systems. Such a metamaterial is further shown using sub-waveleng...

  7. Nuclear medium effects in $\

    Haider, H; Athar, M Sajjad; Vacas, M J Vicente

    2011-01-01

    Nuclear medium effects in the weak structure functions $F_2(x,Q^2)$ and $F_3(x,Q^2)$ have been studied for deep inelastic neutrino/antineutrino reactions in iron nucleus by taking into account Fermi motion, binding, pion and rho meson cloud contributions, target mass correction, shadowing and anti-shadowing corrections. The calculations have been performed in a local density approximation using relativistic nuclear spectral functions which include nucleon correlations. Using these structure functions we have obtained the ratio $R_{F2,F3}^A(x,Q^2)= \\frac{2F_{2,3}^A(x,Q^2)}{AF_{2,3}^D(x,Q^2)}$, the differential scattering cross section $\\frac{1}{E}\\frac{d^2\\sigma}{dxdy}$ and the total scattering cross section $\\sigma$. The results of our numerical calculations in $^{56}Fe$ are compared with the experimental results of NuTeV and CDHSW collaborations.

  8. Spiegel. Medium. Kunst

    Kacunko, Slavko

    to human talent, came the millennia of untiring labours and the play of art and science and thought. The human love-affair with reflection (to cite Mark Pendergast’s subtitle - Mirror/Mirror: A History of the Human Love Affair with Reflection [New York 2003]) has always been a platonic one and I hold...... that this is what has assured its multifarious prolongation in art, the humanities, the sciences. This affair was definitely also a narcissistic one, but notwithstanding, that aspect does not constitute the major subject of this book for various reasons. Investigation of the mirror phenomenon in humanities research...... has hitherto focussed on the generation of the sense of self and of ‘consciousness’ – explicitly and primarily so. As a medium of self-knowledge, the mirror’s self-reference set the limit to its scholarly apprehension – self-reference as the great subject of all psycho-analytically informed approaches...

  9. HARVESTED ENERGY-ADAPTIVE MAC PROTOCOL FOR ENERGY HARVESTING IOT NETWORKS

    Hyeong-Kyu Lee

    2015-12-01

    Full Text Available In energy harvesting IoT networks, an energy queue state of an IoT device will change dynamically and the number of IoT devices that transmit data to the IoT AP will vary in a frame. So we need a MAC protocol to adjust the frame length taking the amount of energy of IoT devices into consideration. Since the existing Framed slotted ALOHA (F-ALOHA Medium Access Control (MAC protocol utilizes the fixed frame size, the resource efficiency can be reduced. In this paper, we propose a Harvested Energy-adaptive Medium Access Control (HEMAC protocol where an IoT Access Point (AP allocates slots in accordance with the number of IoT devices that try to transmit data in a frame. The proposed HE-MAC protocol improves the resource efficiency of the F-ALOHA MAC protocol. We show that the resource efficiency of the HE-MAC protocol is superior to those of the F-ALOHA MAC protocol through simulations.

  10. Network-adaptive HD MPEG-2 video streaming with cross-layered channel monitoring in WLAN

    PARK Sanghoon; YOON Hayoung; KIM Jongwon

    2006-01-01

    In this paper, we propose a practical design and implementation of network-adaptive high definition (HD) MPEG-2video streaming combined with cross-layered channel monitoring (CLM) over the IEEE 802.1 la wireless local area network (WLAN). For wireless channel monitoring, we adopt a cross-layered approach, where an access point (AP) periodically measures lower layers such as medium access control (MAC) and physical (PHY) transmission information (e.g., MAC layer loss rate) and then sends the monitored information to the streaming server application. The adaptive streaming server with the CLM scheme reacts more quickly and efficiently to the fluctuating wireless channel than the end-to-end application-layer monitoring (E2EM)scheme. The streaming server dynamically performs priority-based frame dropping to adjust the sending rate according to the measured wireless channel condition. For this purpose, the proposed streaming system nicely provides frame-based prioritized packetization by using a real-time stream parsing module. Various evaluation results over an IEEE 802.1 la WLAN testbed are provided to verify the intended Quality of Service (QoS) adaptation capability. Experimental results showed that the proposed system can mitigate the quality degradation of video streaming due to the fluctuations of time-varying channel.

  11. The Intergalactic Medium

    Madau, P

    2000-01-01

    About half a million years after the Big Bang, the ever-fading cosmic blackbody radiation cooled below 3000 K and shifted first into the infrared and then into the radio, and the smooth baryonic plasma that filled the Universe became neutral. The Universe then entered a ``dark age'' which persisted until the first cosmic structures collapsed into gravitationally-bound systems, and evolved into stars, galaxies, and black holes that lit up the Universe again. Some time between redshift of 7 and 15, stars within protogalaxies created the first heavy elements; these systems, together perhaps with an early population of quasars, generated the ultraviolet radiation that reheated and reionized the cosmos. The history of the Universe during and soon after these crucial formative stages is recorded in the all-pervading intergalactic medium (IGM), which is believed to contain most of the ordinary baryonic material left over from the Big Bang. Throughout the epoch of structure formation, the IGM becomes clumpy and acqui...

  12. Adaptation Laboratory

    Huq, Saleemul

    2011-11-15

    Efforts to help the world's poor will face crises in coming decades as climate change radically alters conditions. Action Research for Community Adapation in Bangladesh (ARCAB) is an action-research programme on responding to climate change impacts through community-based adaptation. Set in Bangladesh at 20 sites that are vulnerable to floods, droughts, cyclones and sea level rise, ARCAB will follow impacts and adaptation as they evolve over half a century or more. National and international 'research partners', collaborating with ten NGO 'action partners' with global reach, seek knowledge and solutions applicable worldwide. After a year setting up ARCAB, we share lessons on the programme's design and move into our first research cycle.

  13. Hedonic "adaptation"

    Paul Rozin

    2008-02-01

    Full Text Available People live in a world in which they are surrounded by potential disgust elicitors such as ``used'' chairs, air, silverware, and money as well as excretory activities. People function in this world by ignoring most of these, by active avoidance, reframing, or adaptation. The issue is particularly striking for professions, such as morticians, surgeons, or sanitation workers, in which there is frequent contact with major disgust elicitors. In this study, we study the ``adaptation'' process to dead bodies as disgust elicitors, by measuring specific types of disgust sensitivity in medical students before and after they have spent a few months dissecting a cadaver. Using the Disgust Scale, we find a significant reduction in disgust responses to death and body envelope violation elicitors, but no significant change in any other specific type of disgust. There is a clear reduction in discomfort at touching a cold dead body, but not in touching a human body which is still warm after death.

  14. Adaptable positioner

    This paper describes the circuits and programs in assembly language, developed to control the two DC motors that give mobility to a mechanical arm with two degrees of freedom. As a whole, the system is based in a adaptable regulator designed around a 8 bit microprocessor that, starting from a mode of regulation based in the successive approximation method, evolve to another mode through which, only one approximation is sufficient to get the right position of each motor. (Author) 22 fig. 6 ref

  15. Adaptive positioner

    This paper describes the circuits and programs in assembly language, developed to control the two DC motors that give mobility to a mechanical arm with two degrees of freedom. As a whole, the system is based in a adaptable regulator designed around a 8 bit microprocessor that, starting from a mode of regulation based in the successive approximation method, evolve to another mode through which, only one approximation is sufficient to get the right position of each motor. (Author) 6 refs

  16. Adaptive noise

    Viney, Mark; Reece, Sarah E.

    2013-01-01

    In biology, noise implies error and disorder and is therefore something which organisms may seek to minimize and mitigate against. We argue that such noise can be adaptive. Recent studies have shown that gene expression can be noisy, noise can be genetically controlled, genes and gene networks vary in how noisy they are and noise generates phenotypic differences among genetically identical cells. Such phenotypic differences can have fitness benefits, suggesting that evolution can shape noise ...

  17. Adaptation funding and development assistance: some FAQs

    Ayers, Jessica; Huq, Saleemul

    2008-11-15

    It's becoming ever clearer that development and climate change are intertwined issues. Unsustainable development drives climate change; sustainable development can reduce vulnerability to it. Development issues can constrain capacity to adapt to climate change; climate impacts can be a barrier to development. So adaptation to climate impacts is increasingly seen as part of good development practice – and development to improve the lives and resource access of people facing climate challenges is viewed as a prerequisite for successful adaptation. But when it comes to adaptation funding, confusion and contention remain over the role development institutions play.

  18. JISC Open Access Briefing Paper

    Swan, Alma

    2005-01-01

    What Open Access is. What Open Access is not. How is Open Access provided? Open Access archives or repositories. Open Access journals. Why should authors provide Open Access to their work? Further information and resources

  19. IMPLEMENTING SMALL AND MEDIUM IT PROJECTS IN SMALL AND MEDIUM ENERPRISES

    Felix DUMITRESCU

    2014-06-01

    Full Text Available Information technology is essential nowadays for all companies. Small enterprises are an important part of the economy and this article aims at providing some useful insight in implementing modern IT projects to their benefit. Due to the limited funding available for the IT infrastructure in most start-ups and small businesses, the projects should be adapted to fulfill the needs of the company for the lowest cost. The paper will start by defining small and medium project management theory and outlining the target of the study, small and medium sized companies. Next it will show a number of case studies of IT projects implemented in different types of small companies in Romania. Based on these implementations the article will draw some conclusions relevant to most small companies which need to design or improve their IT infrastructure.

  20. Impact of EU Enlargement on Business Environment of Small and Medium-Sized Enterprises in Slovakia

    Ján Vravec; Marián Gál; Tomás Sabol

    2005-01-01

    The paper discusses the impact of EU enlargement on business environment in the Slovak Republic. Integration of Slovakia into EU has significantly influenced operating conditions for small and medium enterprises. Prosperity of small and medium enterprises depends mainly on their ability to adapt themselves to these new conditions.

  1. Electron density measurements for plasma adaptive optics

    Neiswander, Brian; Matlis, Eric; Corke, Thomas

    2014-01-01

    This study investigates the feasibility of using plasma as an adaptive optical medium for applications such as beam steering, wavefront control, and adaptive filtering. The optical path length of light propagating through plasma depends on the plasma electron density, which may be controlled via the prescribed voltage, frequency, pressure, gas, and electrode geometry. Accurate control of the optical path length requires characterization of the electron density over all operating conditions. E...

  2. A multimodal end-2-end approach to accessible computing

    Biswas, Pradipta; Langdon, Patrick; Almeida, Luis; Jung, Christoph

    2013-01-01

    This book surveys the phases of delivering accessible products and services through design, development, deployment and maintenance. Examines user models for inclusive design, adaptable multimodal system development for digital TV and ubiquitous devices.

  3. A Selective Medium for Quantitative Reisolation of Trichoderma harzianum from Agaricus bisporus Compost

    Williams, Josie; Clarkson, John M.; Mills, Peter R.; Cooper, Richard M

    2003-01-01

    We adapted a selective medium, previously developed for reisolation of Trichoderma spp. from soil, for quantitative determination of growth of T. harzianum from commercial Agaricus bisporus composts. This medium enables comparisons of aggressive (sensu inhibition of A. bisporus yield) with nonaggressive T. harzianum groups. The resulting medium contains the antimicrobials chloramphenicol, streptomycin, quintozene, and propamocarb and was highly selective, allowing the recovery of T. harzianum...

  4. Accessing OSI Managed Objects from ANSAware

    Genilloud, Guy; Gay, David

    1995-01-01

    This paper presents a mechanism allowing an ODP compliant distributed system, ANSA, to access OSI network management objects as if they were ANSA objects. It defines a mapping from the OSI object model to the ANSA object model, and it specifies how an adapter implements this mapping.

  5. Accessibility in the elementary schools of a municipality west of São Paulo

    José Médice

    2015-09-01

    Full Text Available This study aimed to identify and describe the architectural barriers in elementary schools, before and after the Law of Guidelines and Bases (LDB. It is a cross-sectional, descriptive research to map the architectural conditions of access in fourteen elementary schools in the municipal schools network in a medium-sized city in the western region of the state of São Paulo. The environments were visited and data collection was performed using a standardized protocol. Data was compared to those established by ABNT-9050 and categorized into appropriate and inappropriate. It was observed that 100% of schools before and after LDB, had no anti-slip flooring, tactile warning and directional; accesses, ramps and stairs had no guides and guideposts; dimensions, grip and slip handrails were inadequate, the toilets had no transition area, mirrors and sinks were not adapted; there was no outside furniture such as drinkers and tailored service counters and adapted libraries. Therefore, this study also has shown that schools installed, pre and post LDB presented several inappropriate items to the ABNT (Brazilian Association of Technical Standards standards.

  6. High Speed Downlink Packet Access in UMTS Network

    Vladimir Psenak

    2005-01-01

    Full Text Available High speed downlink packet access added to UMTS network provides to users data speed up to 10 Mbit/s. The achievement of high data speed is possible due to new link management and link control, and also due to change from power adaptation to modulation and coding adaptation. The most important benefit is an accessing of data services, which request big downlink data flow.

  7. Accessible Interface for Multimedia Presentation in Inclusive Education

    Moreno, Lourdes; Martínez, Paloma; Ruiz-Mezcua, Belén; Iglesias, Ana

    2007-01-01

    Among the technological solutions to achieve an inclusive education, the educative electronic accessible resources providing content adaptability is an alternative which reduces discrimination. It also favors the inclusion with right equalities which can be used by students regardless of their specific need and use contexts. Following this line of adaptability of contents on the web, a practical case [1] has been launched: an accessible interface of a multimedia resource with caption and audi...

  8. Mesons in the nuclear Medium

    Kotulla, Martin

    2006-01-01

    We discuss recent experimental results on the modification of hadron properties in a nuclear medium. Particular emphasis is placed on an $\\omega$ production experiment performed by the CBELSA/TAPS collaboration at the ELSA accelerator. The data shows a smaller $\\omega$ meson mass together with a significant increase of its width in the nuclear medium.

  9. Upper medium segment cooling down

    2008-01-01

    <正>The sluggish growth of the passenger car market in top provinces was also reflected in a depression of the upper medium segment. In Jan-Apr, 2008, the top 3 upper medium models accounting for nearly 40% of this segment performed poorly, with the Passat-Lingyu and the Accord decreasing. The Camry also saw a decrease in three top provinces: Guangdong,

  10. CERN Access Cards and Access Authorisations

    2003-01-01

    From the 01/05/2003, all problems relating to access cards and refusal of access to any zone, building or experiment within CERN must be addressed to the Centrale de Surveillance des Accès (CSA building 120) on 78877 or send an e-mail to Access.Surveillance@cern.ch. The responsibles for CERN access control have put into place a procedure with the CSA, Service Enregistrement and the Technical Control Room, to make sure that all problems get resolved in a proper and timely manner.